Introduction to Process Technology

Introduction to Process Technology Third Edition

Charles E. Thomas

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Preface ...........................................................................................................................xi Chapter 1 History of the Chemical Processing Industry ..........................1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Key Terms ..............................................................................................................2 History of the Chemical Processing Industry .........................................................3 Current Issues and Trends ...................................................................................14 Working in the Chemical Processing Industry .....................................................17 College Programs for Process Technology ..........................................................20 Your Career as a Process Technician ..................................................................24 Careers in the Chemical Processing Industry......................................................26 Roles and Responsibilities of a Process Technician ............................................29 Regulatory Agencies............................................................................................34 The Work Environment.........................................................................................37 Summary..............................................................................................................38 Chapter 1 Review Questions ...............................................................................40

Chapter 2 Introduction to Process Technology ..........................................41 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Key Terms ............................................................................................................42 Introduction to Process Technology .....................................................................43 Safety, Health, and Environment..........................................................................47 The Principles of Quality Control .........................................................................50 Instrumentation and Process Control...................................................................51 Process Equipment ..............................................................................................53 Process Systems .................................................................................................55 Process Operations..............................................................................................57 Troubleshooting....................................................................................................60 iii

Contents 2.9 Applied General Chemistry and Physics..............................................................63 2.10 College Math ........................................................................................................65 Summary..............................................................................................................66 Chapter 2 Review Questions ...............................................................................68

Chapter 3 Safety, Health, and Environment ................................................69 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18

Key Terms ............................................................................................................70 Safety, Health, and Environment Overview ..........................................................71 Basic Safety Principles.........................................................................................72 Occupational Safety and Health Act ....................................................................73 The PSM Standard ..............................................................................................74 The Hazard Communication Program..................................................................74 Safe Handling, Storage, and Transportation of Hazardous Chemicals ................77 Physical Hazards Associated with Chemicals......................................................77 Health Hazards Associated with Chemicals ........................................................78 Material Safety Data Sheets ................................................................................79 Toxicology.............................................................................................................79 Respiratory Protection Programs .........................................................................79 Personal Protective Equipment ............................................................................80 Emergency Response..........................................................................................80 Plant Permit System.............................................................................................81 Classification of Fires and Fire Extinguishers ......................................................82 HAZWOPER ........................................................................................................82 Hearing Conservation and Industrial Noise .........................................................83 Department of Transportation ..............................................................................84 Summary..............................................................................................................84 Chapter 3 Review Questions ...............................................................................86

Chapter 4 Applied Physics One ........................................................................87 4.1 4.2 4.3 4.4

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Key Terms ............................................................................................................88 Basic Principles of Pressure ................................................................................89 Heat, Heat Transfer, and Temperature .................................................................99 Fluid Flow...........................................................................................................100 Basic Math for Process Technicians...................................................................104 Summary............................................................................................................109 Chapter 4 Review Questions .............................................................................112

Contents

Chapter 5 Equipment One .................................................................................113 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10

Key Terms ..........................................................................................................114 Basic Hand Tools ...............................................................................................114 Valves.................................................................................................................115 Piping and Storage Tanks ..................................................................................121 Pumps ................................................................................................................124 Compressors......................................................................................................129 Steam Turbines ..................................................................................................132 Gas Turbines ......................................................................................................133 Electricity and Motors.........................................................................................134 Equipment Lubrication, Bearings, and Seals .....................................................135 Steam Traps .......................................................................................................137 Summary............................................................................................................138 Chapter 5 Review Questions .............................................................................139

Chapter 6 Equipment Two ..................................................................................141 6.1 6.2 6.3 6.4 6.5 6.6 6.7

Key Terms ..........................................................................................................142 Heat Exchangers ...............................................................................................142 Cooling Towers...................................................................................................147 Boilers (Steam Generation)................................................................................149 Furnaces ............................................................................................................151 Reactors.............................................................................................................154 Distillation...........................................................................................................157 Separators..........................................................................................................161 Summary............................................................................................................162 Chapter 6 Review Questions .............................................................................165

Chapter 7 Process Instrumentation One ....................................................167 7.1 7.2 7.3 7.4 7.5

Key Terms ..........................................................................................................168 Introduction to Process Instruments ..................................................................168 Symbols and Diagrams ......................................................................................173 Process Diagrams..............................................................................................182 Interlocks and Permissives ................................................................................184 P&ID Components .............................................................................................186 Summary............................................................................................................191 Chapter 7 Review Questions .............................................................................192

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Contents

Chapter 8 Process Instrumentation Two .....................................................193 8.1 8.2 8.3 8.4 8.5 8.6

Key Terms ..........................................................................................................194 Basic Elements of a Control Loop......................................................................195 Process Variables and Control Loops ................................................................196 Primary Elements and Sensors .........................................................................197 Transmitters and Control Loops .........................................................................197 Controllers and Control Modes ..........................................................................200 Final Control Elements and Control Loops ........................................................202 Summary............................................................................................................203 Chapter 8 Review Questions .............................................................................205

Chapter 9 Process Technology—Systems One ........................................207 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9

Key Terms ..........................................................................................................208 Pump System.....................................................................................................208 Compressor System ..........................................................................................208 Electrical System ...............................................................................................212 Lubrication System ............................................................................................213 Hydraulic System ...............................................................................................213 Heat Exchanger System ....................................................................................214 Cooling-Tower System .......................................................................................214 Steam-Generation System (Boilers) ..................................................................216 Furnace System.................................................................................................218 Summary............................................................................................................221 Chapter 9 Review Questions .............................................................................223

Chapter 10 Process Technology—Systems Two ......................................225 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8

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Key Terms ..........................................................................................................226 Reactor System .................................................................................................227 Distillation System..............................................................................................228 Separation System.............................................................................................234 Pressure Relief Equipment and Flare System ...................................................235 Plastics System..................................................................................................236 Refrigeration System .........................................................................................241 Water Treatment System....................................................................................242 Utilities ...............................................................................................................243 Summary............................................................................................................243 Chapter 10 Review Questions ...........................................................................245

Contents

Chapter 11 Industrial Processes ....................................................................247 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.12 11.13 11.14 11.15 11.16 11.17 11.18 11.19 11.20

Key Terms ..........................................................................................................248 Common Industrial Processes ...........................................................................248 Petrochemical Processes...................................................................................251 Benzene .............................................................................................................251 BTX Aromatics ...................................................................................................252 Ethylbenzene .....................................................................................................253 Ethylene Glycols ................................................................................................253 Mixed Xylenes....................................................................................................253 Olefins ................................................................................................................255 Paraxylenes .......................................................................................................255 Polyethylene.......................................................................................................255 Xylene Isomerization..........................................................................................255 Ethylene .............................................................................................................256 Refining Processes ............................................................................................256 Alkylation............................................................................................................256 Fluid Catalytic Cracking .....................................................................................257 Hydrodesulfurization ..........................................................................................258 Hydrocracking ....................................................................................................259 Fluid Coking .......................................................................................................260 Catalytic Reforming............................................................................................260 Crude Distillation................................................................................................260 Summary............................................................................................................262 Chapter 11 Review Questions ...........................................................................264

Chapter 12 Process Technology Operations .............................................265 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8

Key Terms ..........................................................................................................266 Overview of Process ..........................................................................................266 Pilot Plant Operations ........................................................................................266 Process Control Instrumentation........................................................................272 Safety and Quality Control .................................................................................274 Bench-Top Operations .......................................................................................276 Operating Procedures ........................................................................................276 Self-Directed Work Teams..................................................................................278 Walk-Through Qualification................................................................................278 Summary............................................................................................................278 Chapter 12 Review Questions............................................................................280 vii

Contents

Chapter 13 Applied General Chemistry ......................................................281 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8

Key Terms ..........................................................................................................282 Fundamental Principles of Chemistry ................................................................283 Chemical Equations and the Periodic Table .......................................................286 Chemical Reactions ...........................................................................................291 Material Balance ................................................................................................293 Percent-by-Weight Solutions..............................................................................295 Measurements of pH..........................................................................................295 Hydrocarbons.....................................................................................................296 Applied Concepts in Chemical Processing ........................................................298 Summary............................................................................................................300 Chapter 13 Review Questions ...........................................................................303

Chapter 14 Applied Physics Two ....................................................................305 14.1 14.2 14.3 14.4 14.5

Key Terms ..........................................................................................................306 Fundamental Concepts ......................................................................................306 Density and Specific Gravity ..............................................................................308 Pressure in Fluids ..............................................................................................312 Complex and Simple Machines..........................................................................319 Electricity............................................................................................................323 Summary............................................................................................................328 Chapter 14 Review Questions ...........................................................................331

Chapter 15 Environmental Standards ..........................................................333 15.1 15.2 15.3 15.4 15.5 15.6

Key Terms...........................................................................................................334 Air Pollution Control ...........................................................................................335 Water Pollution Control ......................................................................................336 Solid Waste Control............................................................................................336 Toxic Substances Control...................................................................................337 Emergency Response........................................................................................338 Community Right-to-Know .................................................................................338 Summary............................................................................................................339 Chapter 15 Review Questions ...........................................................................340

Chapter 16 Quality Control ...............................................................................341 Key Terms ..........................................................................................................342 16.1 Principles of Continuous Quality Improvement ..................................................342 16.2 Quality Improvement Cycle ................................................................................343 viii

Contents 16.3 16.4 16.5 16.6 16.7 16.8 16.9 16.10 16.11 16.12 16.13

Supplier-Customer Relationship.........................................................................344 Quality Tools.......................................................................................................344 Statistical Process Control .................................................................................344 Flowcharts..........................................................................................................346 Run Charts.........................................................................................................348 Cause-and-Effect (Fishbone) .............................................................................348 Pareto Charts .....................................................................................................350 Planned Experimentation...................................................................................350 Histograms or Frequency Plots ..........................................................................351 Forms for Collecting Data ..................................................................................351 Scatter Plots.......................................................................................................352 Summary............................................................................................................352 Chapter 16 Review Questions............................................................................354

Chapter 17 Process Troubleshooting ............................................................355 17.1 17.2 17.3 17.4 17.5 17.6 17.7 17.8 17.9 17.10 17.11 17.12 17.13 17.14 17.15

Key Terms ..........................................................................................................356 Troubleshooting Methods ...................................................................................356 Troubleshooting Models .....................................................................................360 Basic Equipment Troubleshooting ......................................................................362 Process Control Instrumentation........................................................................362 Pump Model .......................................................................................................363 Compressor Model.............................................................................................365 Heat Exchanger Model.......................................................................................365 Cooling-Tower Model .........................................................................................367 Boiler Model .......................................................................................................369 Furnace Model ...................................................................................................371 Reactor Model....................................................................................................374 Absorption and Stripping Model.........................................................................376 Distillation Model ................................................................................................377 Separation Model ...............................................................................................379 Multivariable Model ............................................................................................381 Summary............................................................................................................381 Chapter 17 Review Questions............................................................................384

Chapter 18 Self-Directed Job Search ...........................................................385 Key Terms ..........................................................................................................386 18.1 The Job Search..................................................................................................386 18.2 Preemployment Testing......................................................................................392 ix

Contents 18.3 Work Experience................................................................................................392 Summary............................................................................................................393 Chapter 18 Review Questions............................................................................394

Chapter 19 Applied General Chemistry Two .............................................395 19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8

Key Terms...........................................................................................................396 Fundamentals of Chemistry ...............................................................................396 The Periodic Table and Chemical Bonding.........................................................400 Organic Chemistry .............................................................................................403 Balancing Equations ..........................................................................................403 Petroleum Refining: Distillation...........................................................................405 Aromatic Hydrocarbons......................................................................................408 Alkenes and Alkynes..........................................................................................408 Alcohols..............................................................................................................411 Summary............................................................................................................413 Chapter 19 Review Questions............................................................................416

Chapter 20 Chemical Process Industry Overview ...................................417 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9

Key Terms ..........................................................................................................418 Industrial Processes...........................................................................................418 Chemical Manufacturing Petroleum Refining .....................................................419 Exploration and Production ................................................................................420 Power Generation ..............................................................................................423 Water and Wastewater Treatment ......................................................................424 Mining and Mineral Processing ..........................................................................426 Food and Beverage Processing .........................................................................427 Pharmaceutical Manufacturing...........................................................................428 Pulp and Paper Processing................................................................................430 Summary............................................................................................................431 Chapter 20 Review Questions............................................................................434

Glossary .....................................................................................................................435 Index ............................................................................................................................451

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The origin and standardization of the process technology program can be traced back to a series of activities and meetings in 1996–1998, organized by educators in the Gulf Coast area and supported by industry. The meetings were designed to officially standardize the process technology curriculum at the state level in Texas. The original process technology pioneers developed eight core courses and a series of physics and chemistry classes that are the foundation for most current process technology programs. The first course identified in this process was “Introduction to Process Technology”; the original vision of this group was to develop it as a survey or overview of each course in the process technology program. This text, Introduction to Process Technology, holds to the original vision of these pioneers and is the only work that reflects the principles they articulated. The course is designed to provide the apprentice technician with the foundation that future classes will build upon.This text devotes a chapter to each of these courses and provides key objectives that instructors can use to develop lesson plans and enhance their instruction. Each chapter includes objectives, key terms, photographs and line drawings, lecture material, summaries, and review questions. An instructor guide is available; however, the author strongly encourages each teacher to develop his or her own tests and learning activities. These activities can be linked to instructional videos, lab exercises, or field trips. Key topics covered in this text include:

• • • • • • • • • •

Introduction to process technology Safety, health, and environment Process instrumentation Process equipment Process systems Quality control Troubleshooting Process operations Applied general chemistry Physics

This textbook is divided into 20 chapters, with the more difficult concepts spread over more than one chapter. Each chapter is intended to cover the key objectives found in individual xi

Preface courses, but at a less intense level that is appropriate to the overview nature of the introductory course. Over the past 15 years, process technology has become one of the most popular programs in community colleges and universities located in heavily industrialized areas. A variety of programs appeared virtually overnight in response to government, industry, and community needs. As defined in the regionally accredited process curriculum, process technology is the study and application of the scientific principles (math, physics, chemistry) associated with the operation (instruments, equipment, systems, troubleshooting) and maintenance (safety, quality) of the chemical processing industry. Process technicians can be found working in petrochemical and refinery operations, the pharmaceutical industry, food processing, paper and pulp manufacturing, and many other areas. This group represents the fourth largest U.S. manufacturing segment. The chemical processing industry (CPI) is currently experiencing severe shortages in skilled technicians to operate plants. As the large Baby-Boomer group reaches retirement age, the CPI braces for a 70% to 80% employee turnover. The next three to seven years will bring massive changes as education levels in the United States continue to drop. The CPI is painfully aware of the changing requirements for process technicians. New technology, rightsizing, and redistribution of technical skills have created a new profile for this group. The term “gold collar” is being applied to the field of process technology, which can command incomes in the six-figure realm. The process technician of the future will have a one-year, state-approved certificate or a two-year AAS degree in process technology. The education needed to achieve that certification or degree will include instruction in modern manufacturing, engineering principles, math, physics, chemistry, unit operations, safety, equipment checking, sampling, data collection, data organization, data analysis, troubleshooting, and operation of new process control computer systems—among other things. These new apprentice technicians will need good interpersonal skills, strong technical and problem-solving skills, the ability to assimilate cutting-edge technologies quickly, and the ability to apply innovative ideas. In addition to these skills, a process technician will need to be able to handle conflict, look at a complex situation and see the overall picture, and communicate effectively. Exposure to these areas and experience will be gained both within technical and academic classes and on the job. The author would like to express his thanks to those individuals who have been involved in the development of the process technology program.

Charles E. Thomas, Ph.D.

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History of the Chemical Processing Industry After studying this chapter, the student will be able to: • • • • • • • • • • • • • • • •

Explain the history and development of the chemical processing industry. Define key terms used in process technology. List alternative fuel sources that will be used in the future. Identify the roles and responsibilities of a process technician. Describe batch operations, thermal cracking, fractional distillation, and catalytic cracking. Describe current issues and trends in the petroleum industry. Explain the future of oil, the “Big Rollover,” and the Hubbert peak theory. Contrast the development of the hydrocarbon industry with advances in modern society. List the skills required to work in the chemical industry. Describe college programs in process technology. Explain skills and techniques used by successful college students. Discuss the key elements of working in a diverse workforce. Define sexual harassment. Describe the chemical processing industry and future trends. Explain the responsibilities of various regulatory agencies. Describe the process technician’s work environment.

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History of the Chemical Processing Industry

Key Terms Batch process—order of work in which all ingredients are added to the process up front. Big Rollover—point at which global oil production peaks and then begins to decline. Biogenic theory—describes how natural gas and crude oil were formed using pressure or compression and heat on ancient organic material. Catalytic cracking—process that uses a catalyst to separate hydrocarbons. Chemical processing industry (CPI)—business segment composed of refinery, petrochemical, paper and pulp, power generation, and food processing companies and technicians. College programs in process technology—state-approved and regionally accredited programs that include courses such as Introduction to Process Technology; Safety, Health, and Environment; Process Instrumentation; Process Technology 1—Equipment, PT 2—Systems, and PT 3— Operations; Process Troubleshooting; Principles of Quality; and applied chemistry, physics, and basic math. Diversity training—identifies and reduces hidden biases between people with differences. Estimated ultimately recoverable (EUR)—technical term describing the total amount of crude oil that will ultimately be recovered. This number is difficult to calculate and fluctuates frequently. Oil reserves are typically underestimated and are adjusted as additional information and new technology become available. Most experts believe that 1.2 trillion barrels (without oil sands) and 3.74 trillion barrels (with oil sands) reflect the world’s total endowment of oil. Fractionating column—the central piece of equipment in a distillation system. Fractionating columns separate hydrocarbons by their individual boiling points. Future hiring trends—directions in employment; large numbers of retiring “baby boomers” will have to be replaced in the chemical processing industry. Goal setting—establishment of reasonable, specific, measurable objectives that lead toward the successful achievement of a goal. Gold collar—term used to describe process technicians. Housekeeping—maintenance of cleanliness and order; closely associated with safety in the chemical processing industry. Process technicians are required to keep their immediate areas clean. Hubbert peak theory—describes how future world petroleum production will peak and then begin the process of global decline. This decline will closely match the former rate of increase, as known oil reservoirs move to exhaustion. Industry training programs—programs whose primary focus is on mandatory safety training and on-the-job training; however, a number of employers’ programs still include some of the topics covered by college process technology courses. Lifelong learning—ongoing process of learning about new technologies and equipment. Global competition requires companies to adopt new and innovative techniques. Process technicians will come into contact with learning opportunities that cannot be found anywhere else. 2

1.1 History of the Chemical Processing Industry

Predicted model of shared responsibilities—forecast that the process technician of the future will take over tasks and job responsibilities presently performed by engineers and chemists. Process technician—a person who operates and maintains the complex equipment, systems, and technologies found in the chemical processing industry. Because these people work closely with specific pieces of equipment or processes, they are commonly called boiler operators, compressor technicians, distillation technicians, refinery technicians, or wastewater operators. Process technology—the study and application of the scientific principles (math, physics, chemistry) associated with the operation (instruments, equipment, systems, troubleshooting) and maintenance (safety, quality) of the chemical processing industry. Sexual harassment—behavior that constitutes unwelcome sexual advances; could take the form of verbal or physical abuse or unwelcome requests for sexual favors. The behavior may involve persons of the opposite sex or of the same sex; the offending conduct may run from supervisor to employee, student to student, employee to employee, teacher to student, and so on. (For further information on sexual harassment, see Title VII of the Civil Rights Act of 1964.) Thermal cracking—process that uses heat and pressure to separate small hydrocarbons from large ones. Time management—a structured system that arranges an individual’s study according to principles governing use of time.

1.1 History of the Chemical Processing Industry The lifeblood of modern society is found in petroleum products. Cars, planes, trains, ships, and farm equipment all require petroleum products to operate. Approximately 85% of all hydrocarbons manufactured are converted into gasoline, jet fuel, diesel, heating oils, and liquefied petroleum. The remaining 15% provides the foundation (feedstock) for fertilizers, pesticides, pharmaceuticals, solvents, plastics, and many other products. It is difficult to look around our world and not see the results of modern petroleum manufacturing. Before 1800, though, few people recognized the value or potential of hydrocarbon processing.

Petroleum The term petroleum combines two Latin words, petra (rock) and oleum (oil). It was first used by a German mineralogist named Georg Bauer (also known as Georgius Agricola) in 1556. Petroleum is a natural resource that took millions of years to develop and is traditionally found in porous rock formations in the Earth’s upper strata. The most dominant view, called the biogenic theory, describes how natural gas and crude oil were formed using pressure or compression and heat on ancient organic material. The biogenic theory hypothesizes that crude oil is made up of the remains of small ocean animals and plants that died, dropped to the bottom of the shallow ocean floor, and were covered by sediment. Over a long period, the tremendous weight of the sediment, combined with a low oxygen content and sustained temperatures around 150 degrees, formed the oil. Under these conditions, a chemical reaction occurs as carbohydrates, proteins, and other compounds are converted to crude oil. Natural gas forms under these same conditions if the temperature is maintained near 200 degrees. As the land masses shifted, the oil was forced by water into cracks, openings, and porous rocks. Crude oil normally varies from dark brown to black, although it occasionally appears to be green or yellowish. 3

Chapter 1

History of the Chemical Processing Industry

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Crude oil is a mixture of hydrocarbons that vary in molecular structure and weight from region to geographic region. It is mostly composed of alkanes, aromatic hydrocarbons, and cycloalkanes. The balance of the compound includes nitrogen, oxygen, iron, nickel, copper, vanadium, and sulfur. Molecular composition also varies depending on geographic location. Typical crude oil compositions include:

• • • • • •

Hydrogen Carbon Sulfur Nitrogen Oxygen Metals

10–14% 83–87% 0.5–6% 0.1–2% 0.1–1.5% <1000 parts per million (ppm)

Modern manufacturers separate these components through the distillation process. Distillation separates the various components in a mixture by boiling point. An astronomer named Thomas Gold used the research of a Russian, Nikolai Kudryavtsev (who worked in the 1800s), to develop the “abiogenic theory.” Gold believed that purely inorganic hydrocarbons exist naturally in the Earth, and that over time these hydrocarbons migrated upward through long fracture networks into oil reservoirs. Gold discounted the biological markers found in the hydrocarbon and attributed their presence to stone-dwelling microbial life-forms. Only a small minority of scientists hold to this theory today. It should be mentioned, though, that modern manufacturers have developed methods to produce hydrocarbons from inorganic materials.

Petroleum Products Some examples of petroleum products are asphalt (for paving), gasoline, kerosene, plastic products, carpet material, baby diapers, aspirin, lubricating oils, butane, propane, detergents, cosmetics, insecticides, fertilizers, wax, milk cartons, and toothpaste. It is difficult to see our culture at its present level of technology without petroleum; however, most experts estimate that the earth’s entire oil reserves are about 1.2 trillion (short-scale) barrels without oil sands and 3.74 trillion barrels with oil sands. Present global consumption is 84.6 million barrels a day, or 30.7 billion barrels per year.The United States produces 4.9 billion barrels per year and refines more than 8.5 billion barrels per year, while importing more than 16 billion barrels per year for commercial needs. The total population of the United States constitutes only 4% of the world’s population, but we use more oil than any other country. These reserves cannot be replaced once they are used, and some projections indicate that, at our present rate of consumption, our oil reserves will be depleted during the next 38.8 years to 122.2 years. Process technicians will find themselves operating processes that use alternate fuel sources such as biofuels, coal, oil shale, and tar sands, nuclear energy, wind power, and hydrogen fuel cells, along with operating new technologies. Huge reserves have been located in Canada, Utah, Wyoming, and Colorado. New conservation strategies, better oil reserve projections, alternate fuel sources, and new technologies can help to extend our supply of energy. In April 2008, the United States Geological Survey released reports of a 3–4.5 billion barrel oil find in Montana and North Dakota. The United States has the world’s largest known deposits of oil shale, which could potentially add 110 years to our reserves. However, significant commercial operations have yet to be implemented, and thus these potential resources do not meet the standard for “proven reserves.” During the past 14 years, advances in technology and massive oil finds in Russia, Colombia, and Africa have added to global reserves. New offshore drilling techniques allow the oil industry to drill 4

1.1 History of the Chemical Processing Industry at depths previously considered impossible. An offshore platform in the Gulf of Mexico called the “Genesis” extends 2,600 feet to the sea floor. The surface rig extends over two and one-half football fields. The Genesis produces more than 55,000 barrels of oil and 72 million standard cubic feet of natural gas. Although this is impressive, a consortium of oil companies led by Chevron recently set a well in the Gulf of Mexico in waters 7,718 feet deep. Technological advances in converting natural gas into oil could add 1.6 trillion barrels to our reserves. This figure represents more oil than we could use in 60 years. At present, natural gas is used for home heating, cooking, and generating electricity. The technology exists to convert natural gas to gasoline, kerosene, diesel, and lubricating oils, but it is still impossible to produce heavy bottom products such as asphalt from natural gas. Modern natural gas plants can be constructed for $10 billion and produce a barrel of oil for less than $20. In 2005, the cost of a barrel of oil was between $50 and $60. By 2008, the price of a barrel of crude oil had skyrocketed to more than $145, with some economists projecting that it would continue to rise. By the late summer of 2008, the price of a barrel of oil had dropped to $98 per barrel, though fluctuations were occurring weekly and even daily. Table 1–1 illustrates how oil prices have historically performed.

Table 1–1 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1986 1985 1982–1985 1984 1983 1982 1981 1978

Illinois Basin Crude Oil Prices $140 $64.20 $58.30 $49.81 $37.41 $27.69 $22.81 $23.00 $27.40 $16.55 $11.91 $18.97 $20.46 $16.75 $15.66 $16.74 $19.25 $20.19 $23.19 $18.33 $14.87 $14.64 $26.50 $28.00 $27.50 $29.00 $31.55 $35.00 $14.00

Iraq war Iraq war Lebanon/Israel conflict; Iraq war Iraq war Iraq war Iraq war 9/11 terrorist attack on United States Cutbacks on imports; reformulated gas & taxes Asian financial crisis

Gulf war

Oil price crash OPEC attempted to set production quotas

Iran/Iraq war

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History of the Chemical Processing Industry

The procedure for using natural gas to create gasoline starts by passing methane and oxygen over a heated catalyst. This releases the hydrogen from the carbon atom and allows it to bond with the oxygen.This reaction produces carbon monoxide and hydrogen called syn-gas, the building blocks for the conversion process. In step two, chains of eight or more carbons are combined to form gasoline. Products produced from natural gas burn cleaner because they do not contain sulfur, nitrogen, or molecular carbon ring arrangements.

Early Contributions The history of the chemical processing industry (CPI) can be traced back thousands of years. The Bible reports that Noah used pitch as a building material for the Ark. In 374 CE, the ancient Chinese connected more than 800 feet of bamboo poles to pipe oil into containers where it was burned to produce salt. Ancient Chinese and Japanese illustrations and records indicate the application and use of natural gas for heating and lighting. Pitch was also used to build the streets and walls of ancient Babylon. Before the first European set foot on the North or South American continents, aboriginal Indians used crude oil for medicine and fuel. Around 600 CE, temples built near Baku, Azerbaijan, had eternal flames that burned continuously and were a source of awe for worshippers.

Jan Baptista van Helmont and John Clayton. Manufactured gas was first discovered in 1609 by Jan Baptista van Helmont, a Belgian physician and chemist. Helmont noticed that when coal is heated, it produces fumes he called “gas.” Almost a century later, an Englishman named John Clayton captured the escaping gas from heated coal in an animal bladder. Clayton continued his experiment by sealing the bladder, then puncturing a small hole in its side and igniting the escaping gas. This demonstrated a variety of new applications for natural gas.

William Murdock. In 1792, a British engineer named William Murdock used the gases from heated coal to light his home. From 1802 to 1804, Murdock installed more than 900 gaslights in local cotton mills. This earned him the title “father of the gas industry.” Large-scale operations adopted Murdock’s process and began to expand. The United States did not adopt this technology until 1817, when Baltimore, Maryland, decided to light up its streets.

William Aaron Hart. In 1821, the first natural gas well in the United States was drilled in Fredonia, New York, by a gunsmith named William Aaron Hart. Hart piped the gas from a 27-foot well to nearby buildings for use as a lighting fuel. Between 1821 and 1865, more than 300 natural gas companies were established. In 1859, crude oil was discovered in Titusville, Pennsylvania; with this discovery, natural gas research and production took a serious downturn from which the industry would not rebound until 1920. Today, natural gas is frequently used for cooking, industrial and residential heating, and as an alternative fuel source.

Abraham Gesner. One of the most significant technological improvements in the petroleum industry occurred in 1840 when Abraham Gesner, a Canadian geologist, discovered how to produce kerosene from coal. Kerosene provided a cheap fuel source for heating and lighting and laid the foundation for the beginning of the chemical processing industry. Unfortunately, because communications and documentation were very crude, Gesner’s discovery was not widely promoted or known, so Samuel Kier and J. C. Booth would repeat this experiment in 1851.

James Young and Samuel Kier. By the mid-1800s, a number of chemists, educators, and inventors were working on useful applications for coal, shale, and crude distillation. In 1847, James 6

1.1 History of the Chemical Processing Industry Young of Scotland found a way to distill coal oil from coal and shale. Around 1851, Samuel M. Kier, a Pittsburgh pharmacist, enlisted the support of J. C. Booth, a chemist, to see if kerosene or coal oil could be distilled from crude oil. The experiments were a success and found immediate application in the kerosene market. Kier also believed that oil was a cure for many illnesses.

Benjamin Sillman, Jr. In 1854, a Yale University professor named Benjamin Sillman, Jr., was asked to analyze a barrel of salt-skimmed crude oil. Sillman suspected that each component in the mixture had a different boiling point, and theorized that the various components of the crude mixture could be separated by distilling at different temperatures. During his experiments, Professor Sillman distilled gasoline, kerosene, and a thick, dark, waxy oil.

Ignacy Lukasiewicz. A Russian named Ignacy Lukasiewicz was the first person to create a process for refining kerosene from crude oil; he did so in 1852 by improving on Gesner’s coalkerosene process. Lukasiewicz used an abundant “rock oil” resource found in the seeps near Krosno. The first Russian refinery, built in 1861 near the productive oil fields of Baku, produced 90% of the world’s oil. Edwin Drake. In 1859, Colonel Edwin L. Drake adapted an old steam engine to fit a drill. Drake selected a spot near Titusville, Pennsylvania, to drill for oil. Drake drilled a 69-foot well that produced 15 barrels to 25 barrels a day; after this success, other oil drillers set down wells. The beautiful Pennsylvania landscape was transformed into an industrial community of wooden derricks, roughnecks, carpenters, and unskilled labor. Oil was shipped out on wagons to waiting river barges for transportation to a handful of East Coast refineries. (It should be noted, though, that the first commercial oil well in North America was drilled by James Miller Williams at Oil Springs, Ontario, Canada, in 1858.) Figure 1–1 shows an early wooden storage tank and piping.

Figure 1–1 Early Chemical Processing 7

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Production was initially limited by product transportation problems and the limited number of refineries. The railroad attempted to offset the transportation problem by laying track down to a point within five miles of the oil fields; however, wagons were still used to transport the product from the derricks to the railroad. The transport bottleneck was not relieved until 1865, when the first oil pipeline was built between the oil fields and the railroad station.

The Batch Process Refinery operation developed overnight as new oil wells were discovered. In 1860, the first refinery was built by William Abbott and William Barnsdall at Oil Creek. Over the next 10 years, a hundred refineries would spring up. The basic operation could be described as a batch process (Figure 1–2). Process technicians charged crude oil to a vessel, and the temperature was raised in steps, from 180 degrees Fahrenheit (°F) to 1,000°F. The products yielded by this process included gasoline, naphtha, kerosene, and bottom residuum. It was a common practice to treat the kerosene with caustic soda, sulfuric acid, and a water bath. The gasoline and naphtha were discarded, and the bottom product was treated and used as a lubricant. Process technicians treated the residuum with acid and naphtha, blended it with steam-refined feedstock, and then ran it through the distillation process again. This final product was blended with brightstock and chilled. The chilled product was stored in canvas bags so that the lighter fractions could escape. Heavy petroleum greases were made by combining the chilled bottom product with fatty oils and wax. Early refiners were able to produce 11 barrels of gas from every 100 barrels of crude oil. Because of this low 11% yield, the entire industry began to look for ways to increase gasoline production without increasing the amounts of less profitable products. Over the next 50 years, refiners increased yields to 20%. Modern refiners are able to convert 45% of a barrel of crude oil into gasoline using cracking processes and combining processes. Cracking processes fall into two categories: thermal and catalytic. Combining processes include alkylation, polymerization, and reforming. Near the beginning of the 20th century, technology took a large step forward. Two inventions were about to change the world we live in forever: the automobile and the light bulb. In 1879, Thomas A. Edison invented the electric light bulb, which slowly replaced the kerosene lamp and natural gas. Natural gas found a market in cooking and heating uses, while kerosene found a market in Condenser

Vapor Liquid

Drum

Tar

Heat

Figure 1–2 Simple Batch Process—1860 8

1.1 History of the Chemical Processing Industry the infant aviation field. The second invention was the automobile. As the automobile industry exploded, the need for gasoline increased dramatically. In contrast, at the beginning of the 20th century, gasoline was considered a worthless by-product of kerosene production and was often dumped on the ground or in local rivers and streams. During this time, a useful application was found for the residuum or bottom product of crude distillation, which could be used to produce a new product called asphalt. Asphalt was being produced in large quantities as crude oil production increased. Both the immensely popular bicycles and the newly available automobiles required bigger, better, smoother roads to travel on, and asphalt filled the bill nicely as a paving material. Soon, government-sponsored road building projects were springing up in every state. On January 10, 1901, the chemical processing industry struck the first oil gusher in North America. Located near Beaumont, Texas, the Spindletop oil field instantly gave the CPI an unlimited oil supply. Other wells were soon discovered in Louisiana and Oklahoma.

Thermal Cracking The Burton Process: 1913–1920. Two of the early problems with the batch process were the poor yield of gasoline (8.4 gallons from a 42-gallon barrel of crude oil) and the residuum that was left over after each run. Early technicians were required to climb into the vessels and chip it out by hand. This procedure was dangerous, inefficient, difficult, costly, and time consuming. Dr. William Burton was a Standard Oil of Indiana chemist who developed a process for the thermal cracking of hydrocarbons using high pressure. Cracking process is a general term used to describe how lighter hydrocarbons are separated (cracked ) from heavier hydrocarbons using conventional methods and higher pressure. Dr. Burton was aware of some experimental studies in England that had produced good results using higher operating pressures. Unfortunately, the process had been conducted in a laboratory and not on a large commercial level. Boilermakers did not have the modern welding technology we use today; instead, the tank seams were filled with molten metal and beaten into place. Thus, it was difficult to find a large vessel that could withstand the higher pressures needed for thermal cracking. Burton’s process produced greater yields: 70% distillates, half of which was gasoline (14.7 gallons). Although the yields improved, the vessels still had to be cleaned out after each run. In the Burton process (Figure 1–3), process technicians charged the vessel with 200 barrels of crude oil and slowly heated it to 700°F.

Fractionating Columns In 1877, the United States Patent Office granted Ernest Solvay a patent for a trayed ammonia distillation column. Over the next 50 years, significant improvements were made in hydrocarbon technology. The first commercial fractionating column, introduced in 1917, featured a “still upon a still” design (Figure 1–4). Fractional distillation relies on Raoult’s law and Dalton’s law. Raoult’s law states that a single chemical component in a mixture will contribute to the overall vapor pressure in relation to the percentage of that component in the total mixture. In contrast, Dalton’s law states that the total vapor pressure of a mixture will be the sum of each partial pressure. As the heated crude oil flowed into the column, a fraction of the feedstock would vaporize and rise up through the upper stills. The heavier components would flow through the lower stills to the bottom of the column. A liquid seal that allowed the hot vapors to pass through was established on the bottom of each still. This process allowed each component in the crude oil mixture to find its place 9

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History of the Chemical Processing Industry Reflux Condenser

Vapor Liquid 3 bbl gasoline per day

750° F 200 barrels Coal

Tar

Firebox Stoker

Flue Stack

Increased Pressure System

Figure 1–3 Thermal Cracking—1913 Overhead

Vapors

Side Stream Feed Liquids

Bottoms

Figure 1–4 Fractionation Column—1917

in the column, where it could then be removed from the liquid seal and stored. Early fractionating columns were linked together in groups of nine, with a common feed line.

Catalytic Cracking The Houdry Process: 1936–. Eugene J. Houdry was the heir apparent to a French structural steel firm. During World War I, he distinguished himself as a hero. If a catalyst could be found to enhance the cracking process, a higher yield could be obtained from a barrel of crude oil. As the impending war closed in, Houdry experimented with a variety of catalysts, which are materials designed to speed up a reaction without becoming part of the reaction. In catalytic cracking, a catalyst is used to enhance the reactions that separate hydrocarbons. 10

1.1 History of the Chemical Processing Industry Using a series of bench-top units, Houdry attempted to find a catalyst that would enhance the cracking process. He also needed to develop a procedure to burn off the carbon that formed on the catalyst during the reaction (Figure 1–5). Three years after the experiment started, Houdry found one of his reactors operating within design specifications. The reactor was filled with aluminum silicate.

Gas

Steam Air

Aviation Fuel RX 1

RX 2

RX 3 Naphtha

Air Compressor Steam Furnace Recycle Stock Boiler Distillation Column

Feed

Figure 1–5 Catalytic Cracking—1936 (The Houdry Process)

Important Events 1500

Hieronymus Braunschweig publishes The Book of the Art of Distillation.

1651

John French publishes The Art of Distillation.

1800

French scientists develop modern process techniques called feed preheating and reflux.

1830

Aeneas Coffey (Great Britain) is awarded a patent for a continuous-operated distillation column (without trays) for whisky.

1859

Colonel Edwin L. Drake adapts an old steam engine to fit a drill and begins drilling for oil near Titusville, Pennsylvania.

1860

Batch operation: The first refinery is built by William Abbott and William Barnsdall at Oil Creek. Crude oil is charged to a vessel, and the temperature is raised in steps, from 180°F to 1,000°F. The products of this process include gasoline, naphtha, kerosene, and bottom residuum. (continued )

11

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Important Events (continued )

12

1870

John D. Rockefeller consolidates control of the oil industry and founds Standard Oil Company.

1877

Ernest Solvay is granted a U.S. patent for a trayed distillation column.

1879

Thomas A. Edison invents the electric light bulb.

1896

Henry Ford designs a gasoline engine.

1901

First oil gusher: The Spindletop, Texas, oil gusher draws thousands on January 10.

1908

Middle East oil: Large oil reserves are found in Masjed Soleyman, Persia.

1913

Thermal cracking: Dr. William Burton, a Standard Oil of Indiana chemist, develops a process for cracking hydrocarbons using high pressure and heat.

1917

The first fractionating column is introduced.

1920

Gas stations open in the United States.

1936

Catalytic cracking: Eugene J. Houdry finds a catalyst, alumina silicate, that enhances the cracking process and gives higher yields from a barrel of crude oil.

1941

Oil embargo is placed on Japan by the United States, Britain, and the Netherlands. Japan bombs Pearl Harbor in December.

1944

Germans create a new technology to convert natural gas into oil.

1969

Santa Barbara, California, oil spill sparks an early environmental movement.

1973

Arab oil embargo: United States faces gas lines for the first time since World War II.

1977

Alaskan pipeline opens.

1979

Iranian revolution: Gasoline price tops $1.00 per gallon. More gas lines.

1984

Bhopal, India, vapor release at Union Carbide plant: Thousands are injured and killed.

1989

Exxon Valdez oil release at Prince William Sound.

1989

Phillips explosion in Houston, Texas, kills 23 technicians.

1990

ARCO explosion in Houston, Texas, kills 17.

1990

Kuwait is invaded by Iraq and the first Gulf war starts; oil fields are burned.

1999

Gas prices plummet below $0.80, then rebound to more than $2.00 per gallon.

2001

The United States is attacked; war on terrorism starts.

2004

Average cost of a barrel of oil exceeds $50.

2005

BP explosion in Texas City, Texas, kills 15 and injures 180.

2006

Many economists believe that the Big Rollover occurred, as worldwide production rates peak at 85 million barrels a day

2008

Average cost of a barrel of crude oil exceeds $145.

1.1 History of the Chemical Processing Industry

Gas

3

2

4

5

6

7

8

9

Feed 235°F

Steam

290

410°F

320

490

385

510

540

580

540

540

540

550

615

645

665

680

Figure 1–6 Fractional Distillation

Modern Fractional Distillation Modern refineries and chemical plants are a lot more efficient than their counterparts from 100 years ago. Today, the process goes through different phases: the separation process, the conversion process, and the treatment process (Figure 1–6).

Separation Process. When crude oil is pumped out of the ground, it is desalted, treated, and sent on for additional processing. This material is heated in a large industrial furnace to 385 degrees Celsius (725°F) and pumped to a fractional distillation column. Hot vapors rise in the column and condense on the various trays while hot liquids drop down the column until they gain enough energy to vaporize or separate from lighter components and congregate on their designated trays. This step is referred to as the separation process. Conversion Process. The conversion process includes vapor recovery and alkylation on the overhead light gases and gasoline lines. Reforming and aromatic recovery are used on the kerosene line. The industrial-fuels midsection of the column is still sent to the catalytic cracking section to squeeze out every drop of light product. The bottom lines used in the production of lubricating oils, greases, and asphalt traditionally go through solvent recovery and the crystallization process.

Treatment Process. During the treatment process, each product stream is treated and blended for product purity. The modern distillation column produces high-octane gasoline, gasoline, jet fuel, kerosene, heating oil, diesel oil, industrial fuels, waxes, lubricating oils, greases, and asphalt. Figure 1–7 is a photograph of a series of columns used in modern distillation. 13

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Figure 1–7 Modern Distillation System

1.2 Current Issues and Trends As the cost of a barrel of oil crosses the $145 threshold, many economists believe the future will see the end of cheap oil and major volatility in the oil market. Each year the production rate at the world’s existing oil reserves drops by approximately 7%. These losses must constantly be made up through new reserve finds and new technology. Oil prices will probably drop back to $60–$70 a barrel before rising again and stabilizing between $130–$150 a barrel over the next 5 years. A number of issues and trends are anticipated to occur over the next 10 years. These include:

• •

14

The Big Rollover (when global oil production peaks, and begins to decline). Many economists believe the peak occurred in 2006 or 2007 at 85 million barrels per day (mbpd). Others believe production can go as high as 110 mbpd in the near future. The Hubbert peak theory (when global petroleum production will peak and decline). The peak occurred in 2006 or 2007. It may be possible to increase production, but the existing global oil powers do not intend to mount an effort to increase production. Some experts believe we could increase our daily production rate from 85 to 90 million barrels.

1.2 Current Issues and Trends

• • • • • • • • • • • •

Rapid industrialization in China and India. Oil supply disruptions in the Middle East, Venezuela, and Nigeria. High-tech future offshore oil exploration. The Bakken formation in Eastern Montana and Western North Dakota. How much oil is there? 413 billion barrels or 4 billion barrels? Wind turbine technology increasingly used in United States. Gas combining operations convert natural gas to heavier hydrocarbons. Rapid change to nonhydrocarbon solutions. Educational program advancements; AAS and BS in Process Technology become sought-after degrees. Many Baby Boomers retire over next 10 years and are replaced by younger workforce. Iraq war and problems with Iran. Worldwide push for development and use of alternative fuel sources. Tremendous variability in price of oil, from $200 per barrel $110 per barrel.

The primary issue involves the point in time when global oil production peaks out and begins to decline. Many oil experts believe the peak has already occurred, and predict that within the next 5 to 10 years it will start to decline. New oil discoveries have declined significantly over the past few years even with significant improvements in exploration technology. According to the Oil Depletion Analysis Centre, 16 new oil fields were discovered in 2000, 8 in 2001, 3 in 2002, and none in 2003. Nevertheless, a number of positive oil-field discoveries have occurred that indicate new resources. These include:

• • • • • •

Geological research on the Bakken formation in Montana and North Dakota (2009) Sixty miles off coast of Florida Brazil oilfield (2007) South Australia (2007) Gulf of Mexico near New Orleans (2006) Brazil oilfield (2005)

The Hubbert peak theory describes how future world petroleum production will peak and then start the process of global decline. This decline will closely match the rate of former increase, as known oil reservoirs move to exhaustion. This theory also describes a method to calculate the peak using discovery and production rates, in combination with known oil reserves. The Big Rollover is another theory that predicts how global oil production will soon peak, and worldwide production will begin to decline. There are two basic theories about the future of global petroleum resources and supplies. Some experts argue that we are not running out of oil; rather, we are running into it. The evidence for supporting or rejecting this stance can be analyzed by the 5- and 20-year trends of oil exploration productivity and the U.S. oil recoverable reserves market. Most experts believe it is not a question of if we will run out, but when. A bright spot in the identification and recovery of reserves is the large offshore regions of Texas and Louisiana. A fundamental question remains: How much oil is there? The estimated ultimately recoverable (EUR) refers to the total amount of crude oil that will ultimately be recovered. This number is difficult to calculate and fluctuates frequently. Oil reserves are typically underestimated and the numbers are adjusted as additional information and new technology become available. Most 15

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History of the Chemical Processing Industry Oil production in billions of barrels

3500

35 World s Total Endowment of Crude Oil

3000

30 Production

2500

25

Crude Oil

2000

20

1500

15

1000

10

500

5 Empty

0

0 1850

1950

2050

2150

Global consumption 30.7 billion barrels per year

Figure 1–8 The History of Crude Oil Consumption experts believe that the world’s total endowment of oil comes to about 1.2 trillion barrels. The world currently consumes 30.7 billion barrels per year. By the end of 2008, the world had consumed more than 1.12 trillion barrels. Figure 1–8 shows the history of crude oil consumption. To extend our natural resources, modern manufacturers will need to look at alternative fuel sources and technologies. Some of these alternative sources include converting natural gas into oil, recovering oil from tar sands, recovering oil from shale, using Antrim shale to produce natural gas, and using coal to produce syn-gas. New technologies with tension-leg platforms for deepwater exploration may open up new oil fields. It is entirely possible that the future may find a way to recycle, recover, combine, and shift our dependence to new technologies and resources. The following chart shows estimated 2008 world reserves.

Country

Reserves (109bbl)

USA

21

4.9

12

Canada

179

2.7

182

Mexico

12

3.2

10

260

8.8

81

99

2.5

108

115

3.7

101

United Arab Emirates

97

2.5

107

Russia

60

9.5

17

Saudi Arabia Kuwait Iraq

16

Production (106bbl/d)

Reserve Life (years)

1.3 Working in the Chemical Processing Industry

Country Iran

Reserves (109bbl)

Production (106bbl/d)

Reserve Life (years)

105

2.2

143

80

2.4

91

Libya

41.5

1.8

63

Nigeria

36.2

2.3

43

?

?

?

Venezuela

China

Many countries have decided that disclosure of their actual reserves is a matter of national security and refuse to provide accurate data—or any information at all. It is also difficult to estimate how much oil can be removed from a reservoir, especially ones in undeveloped countries. It is clear from the preceding chart many countries are not represented, meaning that their reserves have not been calculated.

1.3 Working in the Chemical Processing Industry Preparation and Basic Skills Preparation for work in the chemical processing industry starts early for a process technician. Students should take classes in high school that will prepare them for the fast-paced processes and technologies they will encounter in industry. A solid core curriculum would include microcomputers, communications, math, and science. Some high schools have programs that offer dual credit for process technology classes. These classes give graduating seniors an advantage over other students entering two-year community college programs. Jobs in the chemical processing industry are usually high paying and offer full benefit packages. Because of advances in process control, though, fewer positions are available for job seekers. These rapid changes in technology have been integrated into the competitive global structure of the chemical processing industry. Job descriptions for process technicians require a two-year degree in process technology, good scores on preemployment tests and interviews, and passage of a medical examination.

Reading. To do well on most plant entry exams, above-average reading skills are needed. Operators must read and interpret operating procedures, training procedures, quality and environmental guidelines, customer requests, and many other technical documents. Writing. Process technicians are required to document most of their activities on the job. These documents include logbook entries, lock-out, tag-out, process samples, training procedures, operational procedures, permits, shift relief, work orders, and quality control charts. Technicians must also be able to communicate clearly and accurately in writing with other industry members. Listening. Effective listening skills are helpful to process technicians during equipment malfunctions, troubleshooting, shift relief, training, and team meetings.

Interpersonal Skills and Communication. Interpersonal skills can be enhanced with proper coaching and study inside a normal process technology program. Most people develop basic skills years before entering their occupation, but may find that they need to improve for their jobs. 17

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●

Computer Technology. Process technicians interface with their equipment through advanced instrumentation and electronic networks. The computer console, which is a window to the process, is becoming the central focus of the control room. Technicians need to know how to use personal computers. Skills required in this area include using word processors, spreadsheets, databases, and graphics programs; networking with other sites; using electronic mail; accessing operating procedures; accessing material safety data sheets (MSDS); understanding computer architecture; and applying new technology as it is developed. Math. To pass a typical preemployment exam, a process technician needs a sound understanding of addition, subtraction, division, multiplication, fractions, percentages, decimals, and measurement metrics. The technician of the future will need a much stronger understanding of applied mathematics, including: basic math, algebra, geometry, applied college algebra, trigonometry, physics, and calculus.These foundational courses can enhance a technician’s ability to perform chemical calculations, to control and troubleshoot unit operations, and to interface with unit chemists and engineers. Science. Process technologies are based on the principles of general science, chemistry, and physics. Advanced technology combines raw materials to create useful end products. The science behind this technology is impressive but is usually transparent to the technician. The depth of the technology provides a lifelong learning opportunity for the operator. Industrial manufacturers usually upgrade technology frequently in order to compete in the global economy. Most technicians are exposed to cutting-edge technology throughout their careers. It is important to understand what is happening as raw materials are combined to form new products. Operators do not open and close valves blindly. They carefully study and prepare prior to operating the unit. Successful plant operation requires theoretical knowledge and observational knowledge. Typically, the engineering staff is trained in theory, whereas operators control the observational area. An operator who possesses both theoretical and observational skills will be a valuable asset to the company. Corporate rightsizing and restructuring should require technicians of the future to perform more challenging and technical job functions. Key scientific principles used by technicians include:

• • • • • • •

Fundamentals of chemistry—atoms, elements, atomic structure, hydrocarbons, states of matter, gases, solutions Physics—fluids, temperature, pressure, heat transfer, work, and energy Math and statistics Basic equipment and technology Computer literacy skills Communication skills On-the-job skills

Punctuality. Most companies terminate trainees after several unexcused “tardies.” Punctuality is considered very important to shift workers. Other key characteristics the chemical processing industry looks at are fighting, lack of teamwork, drug abuse, safety violations, and excessive absences. Studies indicate that job satisfaction is linked directly to low instances of these sorts of infractions. 18

1.3 Working in the Chemical Processing Industry

Multitasking. Process technicians typically have many things going on at the same time. Being able to control several work tasks at once is important. Process operators commonly carry small notebooks around the unit with them to simultaneously document and keep up with a variety of tasks. Problem Solving. Your ability to solve problems will improve as you become more familiar with the equipment. The trick is to know your equipment and process. It will help you to be familiar with basic problem-solving techniques so that you can identify the symptom, the problem, and the solution.

Safety Awareness. Safety awareness is taught from the first moment you step into a plant. Statistics indicate that you are safer in the plant than at home, yet every year a large number of work-related fatalities and disabling injuries occur in the chemical industry. Evidence indicates that a well-managed safety program drastically reduces occupational illnesses and injuries. Safety statistics are important to an industrial manufacturer, and extreme pressure is applied to each employee to work safely.

Quality Awareness. The new global economy has introduced a competitive way of doing business. Industrial manufacturers use advanced quality techniques to stay ahead of the competition. These techniques are taught openly and used by the entire company. Technicians should be aware of these quality techniques, which include flowcharts, control charts, statistical process control, scatter plots, histograms, Pareto charts, run charts, ISO-9000 criteria/certification, and training.

Environmental Awareness. Technicians should be aware of the impact they can have on the environment. Industry refers to these programs as air pollution, water pollution, solid waste disposal, toxic waste disposal, emergency response, community right-to-know, and spill release guidelines (Figure 1–9).

Phone

DO I STOP THE SPILL OR CALL FIRST?

Figure 1–9 Spill Releases 19

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1.4 College Programs for Process Technology From the early 1960s to the present, community colleges have attempted to work with industry to help with operator training. In 1990, a number of colleges began to establish process technician training classes. These classes were placed in the continuing education department and did not offer regional credit. In these humble beginnings, the original process technology core curriculum did not exist; however, some similarities did begin to develop among the courses offered. By 1994, a larger number of schools began the process of curriculum development for the newly emerging process technology program. A variety of rubrics and course descriptions could be found at these different colleges, and variations between colleges were significant. In 1995, the first state-approved certificate was offered in the state of Texas. This was quickly followed by a number of other colleges that launched process technology degrees and one-year certificates (see Figure 1–10). In 1997 and 1998, educators worked together to develop a standardized curriculum. In the fall of 2000, educators and industry launched the first standardized process technology program, also in the state of Texas. Other states quickly followed this pattern: Louisiana, New Jersey, California, Alaska, Montana, North Dakota, Alabama, New Mexico, Utah, Wyoming, and Oklahoma. Eight core classes were approved by the states, carried regional credit, and were listed in the college catalogs. Although some variations still exist in these degree programs, each includes the eight core classes.

High School to College Transition The transition between high school and college can be difficult for many students. Process technology students come from a wide array of backgrounds and experiences. College classes are typically diverse and composed of women and men between the ages of 16 and 60. A significant number of these students have college degrees or have completed college classes; however, the largest block of students have never enrolled in a college course. Making the adjustment between high school and college is easier if a student is aware of the differences and given the tools to succeed. Figure 1–11 illustrates the differences between college and high school. High school is vastly different from college. Perhaps the biggest difference between high school and college is in the area of freedom. Most high school programs are structured with rules that dictate how personal time is spent. College students are considered to be adults who are allowed to establish their own rules. In high school, the teacher was primarily responsible for selecting and presenting the material. College students are given the opportunity to decide what is important to them and when they will study it. Because of this freedom, the onus of learning is shifted from the instructor to the student: College instructors place the responsibility for learning on the student. Emphasis should be on learning application, not memorization! Technical instructors use a hands-on approach to learning that is similar to the simple practice exams used by high school teachers. Unlike high school, the college student makes a significant financial investment in his or her education. This sacrifice buys a specific product and a huge educational responsibility. College instructors cover a much larger volume of material than high school instructors. Tests are taken from class lectures, reading assignments, structured experiments, bench-top labs, pilot units, videos, computer programs, and standardized tests. 20

1.4 College Programs for Process Technology

APPRENTICE TRAINING PROGRAMS PROCESS TECHNOLOGY

8. COLLEGE AND INDUSTRY TRAINING PARTNERSHIP 9. HANDS-ON AND CLASSROOM INSTRUCTION

1. STATE-APPROVED CERTIFICATE 2. STATE-APPROVED AAS DEGREE 3. NEW RULES AND REGULATIONS (More Difficult) — IS THE EMPLOYEE QUALIFIED? — IS THE TRAINER QUALIFIED TO TEACH? 4. PROVIDE INDUSTRY WITH QUALIFIED APPLICANTS 5. UNIONS ARE NO LONGER TRAINING PEOPLE 6. SAVE INDUSTRY TRAINING COST 7. INDEPENDENT CERTIFICATION & RECERTIFICATION

INDUSTRY AND COMMUNITY COLLEGES HAVE ENTERED INTO A TRAINING PARTNERSHIP

WHAT NEW RULES AND REGULATIONS?

WHAT ABOUT JOB PLACEMENT? CAN I GET A JOB WITHOUT THE CERTIFICATE?

HOW MUCH DOES IT COST?

HOW LONG DOES IT TAKE TO FINISH?

Figure 1–10 Process Technology Programs

21

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Topic

College

High School

Freedom

Controlled by student

Controlled by administration

Cost

Paid by student

Paid by parents (taxes)

Learning

Student responsibility

Teacher responsibility

Resources

Vast and confusing

Limited

Job

High % work

Low % work

Married

High % married

Low % married

Reward

High paying career

High school diploma

Good students

Sometimes struggle because they do not know how to apply what they have learned

As and Bs, good GPA

Curriculum

Selected by student

Selected by administration

Designed by industry, education, and government

Designed by education

Direct job application

Not directly applied to career tasks (e.g., history, social studies)

Figure 1–11 Differences between College and High School Tools to Succeed in College Understanding the college system Goal setting Time management Applied learning Attitude and participation Figure 1–12 Keys to Success

Tools for Success in College When new process technology students enter college for the first time, they can use a number of tools that have been proven to enhance college performance. Figure 1–12 provides a list of mental tools used by successful college students.

Understanding the College System A new process technology student should be able to quickly decode and understand the educational methodology and administrative requirements that exist in a college. The first step is to get the college catalog and review the rules, procedures, policies, course descriptions, degree

22

1.4 College Programs for Process Technology programs, and faculty. The second step is to set your college course schedule. Fall, spring, and summer course schedules will provide you with a detailed listing of classes, locations, instructors, and times. To start school, you will need to complete a third step: register with the college, provide identification, agree to have your high school send transcripts, and take a series of minor tests for placement purposes. The process technology degree program will require a student to take between 18 to 22 classes. Full-time students will take 5 or 6 classes over a 16-week period and spend an average of 21 hours per week in the classroom or laboratory. College instructors usually provide students with a syllabus that contains information on course description, performance objectives, standards, grading policy, attendance policy, textbooks and supplies, disability assistance, and scheduled exams. Process instructors typically provide students with class outlines. Outlines can be used to prepare for upcoming tests and applied learning activities. The degree program provided by your school will list the required courses to complete the program. Do not get off the path and take classes that will not help you graduate. College process technology programs award either a one-year certificate or a two-year degree. Certificates require a minimum of 30 semester hours and two-year degrees require a minimum of 60 hours. Typical course topics include:

• • • • • • • • • • •

Introduction to Process Technology Process Technology 1—Equipment Process Technology 2—Systems Process Instrumentation Safety, Health, and Environment Process Technology 3—Operations Quality Control Troubleshooting Chemistry and Physics Math Academic core classes

During the educational process, a number of snares and traps can damage a student’s ability to progress. Be prepared to drop a class before the scheduled deadline if any of the following situations arises:

• • • •

You are hopelessly lost and have a D or an F Instructor-student problems Work schedule conflict Family tragedy

Goal Setting Goal setting is a college-level activity used by successful students. Goals should be specific, measurable, and realistic. Short-term goals should be distinguished from long-term goals. The process technology degree program should be broken down into manageable pieces and linked to weekly, monthly, and yearly goals. Job-search activities are typically more effective when you use this structured approach.

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Time Management Time management combines a student’s knowledge of his or her personal study needs with a structured system. The typical time management system includes:

• • • • • •

To-do list and weekly schedule Specific study times Self-discipline Adequate sleep periods (don’t burn the candle at both ends, and don’t sleep too long.) Moving to the next action item when time has expired Mechanism for relaxing

Applied Learning Typical instructional techniques approach learning through a progression from simple to more complex. The process technology program presents the theory of process technology in modular blocks before applied techniques are introduced. As the program builds, the learner is exposed to laboratory equipment and hands-on activities. In the classroom, students may be introduced to the theoretical concepts of pressure, heat transfer, fluid flow, and distillation; in the laboratory, they are asked to apply these concepts. The ability to transition between the book and the lab is a fundamental requirement for success in the PT program. Students who perform well in the classroom may struggle on the bench-top, computer simulator, or pilot plant. Other students may perform well in the lab but do poorly in the classroom.

Attendance and Participation Students who decide early to attend every class and participate in classroom discussion have a tremendous edge over those who do not. Instructors learn the names of these students faster and identify their individual needs more quickly. Participation and attendance are essential elements in the applied learning process.

1.5 Your Career as a Process Technician Successful job applicants are notified by telephone or mail/email and given a starting date. The first few weeks include orientation, paperwork, safety training, tours, and apprentice training. Key individuals in the organization are given the opportunity to speak to the new process technicians. New employees also spend time getting sized for flame-retardant clothing, safety glasses, and work boots, as well as being introduced to coworkers.

Training Industrial training programs vary from one company to another. Some are certified by the U.S. Department of Labor. This certification requires a specific number of on-the-job training hours and scheduled classroom hours. These programs can run from one to five years and usually are correlated with pay increases. Key elements of apprentice training programs include:

• • 24

Orientation, followed by one to eight weeks of industrial classroom training Mandatory safety training before being allowed to go to the unit

1.5 Your Career as a Process Technician

• •

Meeting with the supervisor and training coordinator, and planning work and training activities Meeting with the trainer and supervisor to plan on-the-job training and a new job assignment

After the introductory period, the process technician is assigned to a unit and a trainer. During this time, the new technician reports through the formal chain of command, to the trainer and the unit supervisor. After meeting with the supervisor, the trainer knows the specific area and responsibilities of the trainee. Trainees are typically watched very closely during the first year of employment. Training on the unit includes tracing lines, catching samples, filling out paperwork, housekeeping, checking equipment, making line-ups, starting and stopping equipment, and so on. This process continues until the trainer feels comfortable with the trainee’s progress. During this time frame, the new technician works shift work. This can be a very difficult transition for an individual who has never worked rotating shifts. Most companies provide formal apprentice training for new employees regardless of what type of experience or training those employees have received previously. Portable credentials (an AAS degree or a certificate) are needed to address the CPI’s apprentice training and experiencedtechnician retraining problems. These programs provide prospective employers with a list of qualified candidates who have already completed key elements of the government-required training. Portable credentials could save companies as much as 700 classroom hours.

Diversity, Sexual Harassment, Stress, and Conflict Handling stress, conflict, cultural diversity, and sexual harassment are all important aspects of a process technician’s job.The people who make up the workforce within a plant are typically diverse and well educated. Diversity training identifies and reduces hidden biases between people with differences. Work relationships can be expected to last as long as 35 to 40 years, so it is important to fit in on your unit. Understanding your assignments, multiple roles, and responsibilities and contributing to the overall team effort is important to a successful work career. Sexual harassment is defined as behavior that constitutes unwelcome sexual advances. The behavior could take the form of verbal or physical abuse or unwelcome requests for sexual favors. This behavior may involve persons of the opposite sex or of the same sex, and may involve supervisor–employee behavior, or employee–employee behavior. In addition to being illegal, sexual harassment creates tremendous stress and conflict within the workplace. New technicians describe entering a chemical processing plant as an unusual experience similar to being transplanted into a foreign environment with pipes, tanks, strange equipment, noises, smells, and advanced computer technology. This initial experience is very stressful for the new technician. Each plant has a variety of techniques for reducing the stress on a new technician. Some of these techniques include:

• • •

Systematic, competency-based training Trainer–trainee on-the-job training Job shadowing on-the-job training

Stress levels will drop as the new technician qualifies on a job post and becomes more familiar with the environment. 25

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Conflicts will naturally occur during the work career of most technicians. How these conflicts are handled can be used to determine retention rates, evaluations, promotions, absenteeism, and job satisfaction. Conflicts must be handled professionally and through the proper channels. New technicians sometimes feel they are being singled out and asked to do the most routine, dirtiest jobs. However, training is typically structured like college work, progressing from the simple to the more complex. As you learn and qualify on additional job posts, further responsibilities and the respect of your peers will increase. It is important to remember that during the first 12 months of employment, the apprentice technician should not:

• • • • •

Miss work or come in late Sleep on the job Use illegal drugs or alcohol Fight on the job Be caught in the control room with his or her feet up

During the first year of employment, new technicians are expected to be on their best behavior. You have not yet established a track record, so every activity—positive or negative—counts.

Organizational Structure Chemical plants and refineries are divided into major sections or divisions that make the best sense for the overall operation of the plant. Each section appears to run independently of the others, and each has a designated section head. Process section heads report directly to the plant manager. Plant managers, section heads, and second-line supervisors typically have engineering degrees. The chemical processing industry follows a pyramid-type management structure that includes the plant manager, section head, second-line supervisors, first-line supervisors, and process technicians. A variety of management structures are available; however, large, pyramid-type organizations rarely diverge from the original design. Work teams vary in size from 5 to 20 technicians.

Inside and Outside Operators Process technicians can be classified as inside or outside operators. Inside operators are typically experienced technicians who are familiar with the outside functions of their unit. As the name implies, inside operators spend most of their time inside a control room monitoring and controlling process variables, filling out unit logbooks, and working with the outside operator. The majority of process technicians are outside operators who inspect equipment, perform unit start-ups and shutdowns, troubleshoot problems, perform routine housekeeping, catch readings, and collect samples.

1.6 Careers in the Chemical Processing Industry Electricians, instrument technicians, lab/research technicians, machinists, mechanical craftsmen, and process technicians work as a team to control the operations of a plant (see Figure 1–13). They work with chemists, engineers, secretarial and clerical staff, attorneys, legal assistants, computer specialists, industrial hygienists, and human resource analysts. Each of these occupations starts at different pay rates. The primary financial difference among the four craft occupations and process is shift differential and overtime. Most operating facilities run between 20% and 25% 26

1.6 Careers in the Chemical Processing Industry

Secretarial Clerical Process Technician Research Technician Laboratory Technician

Financial Analyst

Chemical Engineer Mechanical Engineer Electrical Engineer Chemist Plant Management

Patent Attorney Legal Assistants Human Resource Analyst

Computer Science Analyst

Electrician Instrument Technician Mechanical Craftsman Machinist

Figure 1–13 Careers in Industry

overtime for process technicians. In the gulf coast area (Texas and Louisiana), in 2005, a typical starting rate was $22 to $26 per hour for a 12-hour shift, with a top-out rate of around $34. Depending on the amount of overtime worked, new technicians will earn between $62,920 and $74,360 during their first year (2008–2009 Gulf Coast area). Top-out rates in the chemical processing industry are presently between $28 and $38 per hour. Time and a half can add up to as much as $57 per hour for a senior technician working overtime. A typical year will include 2,080 scheduled work hours plus about 25% (520 hours) of overtime.

Process, Research, and Chemical Technicians Process Technician. Start: $22 to $34 per hour; $62,920 to $74,360 per year with 25% overtime. Certificate, AAS degree, or three years’ experience. Maintain unit operations: check equipment, catch samples, take readings, make rounds, troubleshoot, fill out quality charts, operate computer systems, and do housekeeping. Must have strong technical and problem-solving skills, ability to assimilate cutting-edge technologies quickly, and ability to apply innovative ideas. In addition to these skills, a process technician needs to be able to handle conflict, look at a complex situation and see the overall picture, and communicate effectively.

Research Technician. Start: $22 to $34 per hour; $62,920 to $74,360 per year with 25% overtime. Certificate, AAS degree, or three years’ experience. Same as process technician plus: operate bench-top units and pilot plants. Special emphasis on technical and problem-solving skills, ability to assimilate cutting-edge technologies quickly, and ability to apply innovative ideas. 27

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Lab Technician. Start: $22 to $34 per hour; $62,920 to $74,360 per year with 25% overtime. (Note: Overtime is typically lower than 25% for this occupation.) Certificate, AAS degree, or three years’ experience. Degree must include two to three classes in chemistry, math, and physics. Perform quality control tests. Mechanical Crafts Electrician. Start: $19 to $31 per hour; $39,520 per year to start. AC/DC voltage hook-ups, circuit testing, troubleshooting, electrical controls.

Instrument Technician. Start: $19 to $31 per hour; $39,520 per year. Work on level, fluid flow, pressure, and temperature instruments and control loops; troubleshoot; maintain operations.

Machinist. Start: $21 to $34 per hour; $43,680 per year. Maintain mechanical equipment, check rotating equipment alignments. Mechanical Craftsman. Start: $19 to $32 per hour; $39,520 per year. Includes pipe fitting and welding, equipment maintenance, troubleshooting.

Engineering and Chemists Contact Engineer. Start: $34 per hour; $70,720 per year. Bachelor of Science in Chemical Engineering (BSCE) degree. Assigned to operations unit for technical support.

Design Engineer. Start: $32.55 per hour; $67,704 per year. Bachelor of Science in Mechanical Engineering (BSME) degree. Troubleshoot equipment and machinery problems.

Chemist. Start: $43.65 per hour; $90,792 per year. PhD in chemistry. High grade-point average and experience.

Administrative Support Staff Secretarial, Clerical, and Legal Assistant. Start: $18.12 per hour; $37,689 per year. Word processing, computer literacy, and communication skills. Type reports, memos, and letters; do legal research and analysis; perform special services for attorneys.

Computers Computer Science Analyst. Start: $29.30 per hour; $60,944 per year. Bachelor of Science in Computer Science. Maintain plant computer systems.

Personnel Human Resources Analyst. Start: $35.73 per hour; $74,318 per year. Master’s degree in Industrial Relations. Recruiting, labor relations, training, equal employment opportunity (EEO) compliance.

Safety Industrial Hygienist. Start: $30.58 per hour; $63,606 per year. Bachelor’s degree in Environmental Engineering. Ensure compliance with OSHA; help employees to recognize, control, and evaluate occupational hazards.

Other Financial Analyst. Start: $35.73 per hour; $74,318 per year. Master’s Degree in Business Administration (MBA). Develop budgets, analyze costs, monitor expenses. 28

1.7 Roles and Responsibilities of a Process Technician

Patent Attorney. Start: $31.44 per hour; $65,395 per year. Bachelor of Science degree, law degree (Juris Doctor). Protect company inventions, patents, contracts, license agreements.

1.7 Roles and Responsibilities of a Process Technician At present, the chemical processing industry is predicting a severe shortage of skilled technicians to operate their plants. Figure 1–14 shows the “Baby Boom” group in the chemical processing industry that will soon reach retirement age. Over the next 7 to 12 years, the CPI will be forced to replace 70% to 80% of the existing workforce. Future hiring trends indicate that educational levels will continue to drop across the United States. At the same time, advanced technology has captured the CPI and been distributed to the existing workforce. Much of this cutting-edge technology is so expensive and new that local colleges and universities have not had time to integrate it into their curricula. Records indicate that 70% of high school students in the United States do not have the basic skills required to work in the chemical processing industry. Educators and local industry have formed alliances to help develop a standardized curriculum for the technician of the future. The term gold collar is being used to describe the occupation of a process technician. Currently, two models are emerging as the dominant theories concerning what process technicians will be doing in the next century. The American Chemical Society (ACS) believes that the roles of process technicians, engineers, and chemists will overlap more in the future, with technicians taking on job responsibilities and tasks typically performed by engineers and chemists. The second model forecasts that process technicians will take on more of the responsibilities now typically reserved for instrumentation, electrical, and maintenance workers. This second model is popular in nonunion areas; however, union plants are not likely to adopt it.

Ages 19-61

Ages 19-48 BABY BOOMERS Born: 1943-1960

Generation(s) X & Y Ages 49-61

Born: 1961-1981 Born: 1982-2001

35%

2009 100% 65%

500,000

JOBS

325,000

JOBS

This group will retire over the next 12 years

175,000

JOBS

Figure 1–14 Typical Age Distribution 29

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History of the Chemical Processing Industry MODEL ONE 2005

2015 Chemists

Engineering

Engineering

Process Technicians

Chemists

Process Technicians

Overlap indicates shared responsibilities

Figure 1–15 Predicted Model Figure 1–15 shows the most popular model supported by the ACS, the predicted model of shared responsibilities.

Process Technicians in the 21st Century The standard roles and responsibilities of process technicians include understanding and mastery of basic equipment, design, operation, and maintenance. New process technicians will learn about valves, pumps, compressors, steam turbines, instrumentation, heat exchangers, cooling towers, boilers, furnaces, reactors, and distillation columns. In addition to this, technicians will learn how the equipment operates and specific maintenance procedures. Key scientific principles such as heat transfer, compressibility, pressure, and fluid flow will be discussed in relation to the equipment. The technicians of the future must have strong technical and problem-solving skills, the ability to assimilate cutting-edge technologies quickly, and the ability to apply innovative ideas. In addition to these skills, a process technician needs to be able to handle conflict, look at a complex situation and see the overall picture, communicate effectively, and use and understand modern process control. Operators are also responsible for relieving other technicians working a job post, performing shift tasks, making rounds, catching samples, taking readings, troubleshooting unit problems, and filling out control documentation. Process technicians are responsible for maintaining and monitoring equipment, inspecting equipment, placing equipment in service, removing equipment from service, and responding to emergency situations. Additional responsibilities include unit and community safety, maintenance of regulatory and environmental standards, accident prevention, fire prevention, production, housekeeping, and product quality.

The American Chemical Society In 1994, the American Chemical Society sponsored a project called “Foundations for Excellence in the Chemical Process Industries.” The goal of the project was to develop voluntary industry standards for chemical process industry technical workers (laboratory and process technicians). The ACS has been supported in this research by a wide array of community, industrial, and educational institutions. The standards developed under this project were designed to assist educators in curriculum development, instructional strategies, and chemical and process technology program design. 30

1.7 Roles and Responsibilities of a Process Technician The standards developed by the ACS identify the knowledge and skills that process technicians need when they begin work in a manufacturing environment. This identification of standards is part of a much larger grassroots movement toward the development of two structured professions: laboratory and process technician. These two professions have developed in response to the technology revolution.

Training Programs In the past, very little formal training was required prior to taking a job in the chemical processing industry (CPI). Industrial manufacturers relied on preemployment screening and in-house training programs to educate and recertify their employees. Nationally, this method for training is changing. Because of intense competition in the global community, the CPI is evaluating whether a company’s focus should be on training or producing products. When a company identifies a part of its day-to-day operation that could better be operated by an outside organization and hires or uses this organization, this is called outsourcing. Outsourcing of training is becoming a very popular option for industrial manufacturers. Formal industry training programs have been established in local community colleges and universities nationwide. At present, these college programs in process technology are limited to three or four geographic regions across the United States. Students can attend these institutions and receive state-approved certification and two-year degrees in laboratory or process technology. These programs relieve the employer’s burden of typical apprentice training and allow industrial trainers to focus on higher-level, site-specific training. Graduates from these types of programs provide a much larger pool of qualified applicants from which the CPI can choose. In time, preemployment tests will evolve from the typical math and mechanical aptitude tests into a more comprehensive exam covering the entry-level skills discussed in this text. Another popular option being discussed is to waive the preemployment test and use the candidate’s college transcripts. This method appears to work well for other occupations, such as engineering, law, medicine, and chemistry.

New Hiring Standards Employers are requiring prospective employees to have one or more of the following: (1) formal training, (2) state-approved certification, (3) a technical degree, (4) experience, (5) satisfactory scores on a preemployment test, or (6) a combination of these attributes. The chemical processing industry and various educational institutions have entered into formal partnerships to facilitate the technical training of employees.

Program Justification The key reasons driving the development of these technical programs are: (1) rapid advances in technology, (2) desire to eliminate accidents in the workplace, (3) potential catastrophic risks, and (4) new regulations and guidelines from the government. The Occupational Safety and Health Administration (OSHA) recently enacted a process safety management (PSM) standard that requires employers to train their employees on process fundamentals. This standard applies to initial certification and recertification of employees. (See Chapter 2 for more details on the PSM standard.)

Workforce Development According to the ACS, more than 240,000 chemical laboratory technicians and 500,000 plant technical operators are employed in the United States. This group makes up the fourth largest U.S. manufacturing industry. Studies of workforce development indicate that much of the existing 31

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Figure 1–16 Chemical Processing Industry workforce is comprised of the “Baby Boom” generation and is mature. In the near future, this large group will “boom out” or retire, leaving a significant number of vacancies. Measures must be taken soon to stop the loss of technical expertise from this generation, to capture it in the form of technical programs, and to assimilate it into the modern U.S. workforce. Figure 1–16 shows the development of the chemical processing industry, as illustrated by this large chemical processing plant. The ACS has taken significant steps toward the development of a practical, technical foundation. The ACS standards need to be used in the development of future technology programs. Many of the objectives listed in the ACS’s major categories are found in the body of this text. A report on the project, Foundations for Excellence in the Chemical Process Industries, can be obtained by writing to the American Chemical Society, 1155 Sixteenth Street NW, Washington, DC 20036; (202) 872-8734. The standards identified by the group for laboratory and process technicians follow.

Employability Performance-Based Skills Math and Statistics

32

(22 Lab Objectives)

(13 Process Objectives)

Computer literacy

(19L)

(12P)

Communication

(31L)

(14P)

Workplace

(25L)

(19P)

General plant and lab

(32L)

(16P)

1.7 Roles and Responsibilities of a Process Technician Critical Job Functions: Laboratory

• • • • • •

Maintain a safe and clean laboratory adhering to environmental/health and safety regulations (34L). Sample and handle chemical materials (31L). Conduct physical tests (20L). Perform chemical analysis (37L). Perform instrumental analysis (38L). Plan and design experiments; synthesize compounds (53L).

Critical Job Functions: Process

• • • • • •

Maintain safety, health, and environmental standards in the plant (30P). Handle, store, and transport chemical materials (33P). Operate, monitor, and control continuous processes (27P). Operate, monitor, and control batch processes (33P). Provide routine and preventative maintenance and service to processes, equipment, and instrumentation (32P). Analyze plant materials (36P).

Basic process equipment and technology standards are covered at the beginning of each chapter in this book. The subject matter covered in this text is designed to closely resemble current information found in a typical apprentice training program. Industrial manufacturers spend millions of dollars on equipment and technology to produce their products. These same manufacturers employ process technicians to operate and maintain their plants. Taking care of the equipment and operation is the primary responsibility of a process technician. Process technicians maintain and operate the equipment 24 hours a day, 7 days a week. Because of this unique relationship, process technicians become the hub of everyday operations. Operators are responsible for:

• •

• • •

Knowing the basic equipment, design, and operation Equipment operation and specific maintenance procedures – Making relief – Performing shift tasks – Making rounds – Troubleshooting unit problems – Filling out control documentation – Maintaining and monitoring equipment – Inspecting equipment – Placing equipment in service – Removing equipment from service – Responding to emergency situations Safety, health, and environment The principles of quality Strong technical and problem-solving skills, with the ability to adopt and assimilate cutting-edge technologies quickly and apply innovative ideas 33

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• •

Ability to handle conflict, look at a complex situation and see the overall picture, communicate effectively, and use and understand modern process control Ability to understand basic chemistry, physics, and math

Modern manufacturing plants are comprised of complex networks that work closely with each other. The people who operate and maintain these networks include:

• • • • • • • •

Process, research, and laboratory technicians Maintenance technicians: instrument technicians, electricians, mechanics, and machinists Engineers and chemists Administrative, human resources, legal, and financial analysts Computer analysts Safety and industrial hygienists Janitorial technicians Construction: brick, carpentry, structural steel, concrete, and rigging workers

1.8 Regulatory Agencies A number of regulatory agencies work closely with and periodically monitor specific activities in the chemical processing industry. At the federal level, some of these agencies include the Environmental Protection Agency (EPA), the Occupational Safety and Health Administration (OSHA), the Department of Transportation (DOT), and the Nuclear Regulatory Commission (NRC).

Nuclear Regulatory Commission The U.S. Nuclear Regulatory Commission was established by the Energy Reorganization Act of 1974 to regulate nonmilitary use of nuclear materials. The NRC is an independent agency that:

• • • •

Ensures public safety Protects the environment Promotes national security and defense Regulates civilian use of nuclear materials

Process technicians working at nuclear power generation plants will follow guidelines established by the NRC in reactor operation, use of nuclear materials, and waste disposal. The NRC regulates the industry through a four-step approach: (1) regulations and guidance, (2) licensing and certification, (3) oversight, and (4) operational experience. Each of these four areas is supported by research activities, advisory activities, and adjudication. Figure 1–17 illustrates how this process works. Under the first step, regulations and guidance, the NRC develops and amends regulations for licensure or certification, develops and revises guides, reviews plans, and updates the NRC inspection manual. The NRC sends updates and information to new applicants and licensees. 34

1.8 Regulatory Agencies

1. Regulations and Guidance • • • •

Standards Development Rules Guidance Communications

2. Licensing and Certification • •

Certification Licensing

3. Oversight • Inspections • Investigations • Assessment • Enforcement • Allegations

4. Operational Experience • Assessment • Generic Issues

Figure 1–17 How the NRC Regulates Industry 35

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Standards development is a cooperative agreement between the NRC and industry for areas concerning equipment, systems, and raw materials. Nuclear reactors use and produce materials that are carefully regulated. Special nuclear materials include uranium-233, uranium-235, enriched uranium, and plutonium. Source materials include natural uranium, thorium, and depleted uranium that cannot be used as reactor fuel. By-product material is generated from nuclear materials; these by-products include any radioactive material or waste products produced by the reactor system. In 2004, there were approximately 104 nuclear facilities in the United States; the majority of these systems are located in states east of the Mississippi River. Only 19 nuclear reactors are operated west of the Mississippi.

Department of Transportation Raw materials that enter the plant from public roads and highways, railroads, maritime channels, or air are regulated by the U.S. Department of Transportation. Process technicians responsible for shipping out raw materials and products will receive specialized training that will clearly identify and explain specific rules, regulations, and procedures. The DOT system includes the use of labels, signs, and placards. Chapter 3 contains additional information on the DOT. The DOT umbrella covers a wide array of organizations, including:

• • • • • • • • • • • •

Office of the Secretary—the Secretary of Transportation is the principal advisor and is assisted by the deputy secretary in overseeing formulation of the national transportation policy Bureau of Transportation Statistics Federal Aviation Administration Federal Highway Administration Federal Motor Carrier Safety Administration Federal Railroad Administration Federal Transit Administration Maritime Administration National Highway Traffic Safety Administration Research and Special Programs Administration Saint Lawrence Seaway Development Corporation Surface Transportation Board

Environmental Protection Agency The Environmental Protection Agency employs more than 18,000 people across the United States. More than 50% of these individuals are engineers, chemists, or scientists. The President of the United States appoints the administrator of the EPA and carefully monitors all major activities. Established in 1970 to protect human health and the American environment, the EPA works for cleaner water, air, and land. This is accomplished as the EPA heads up the country’s environmental research, science, assessment, and educational process. Understanding the role of the EPA is important for a process technician. The EPA is charged with enforcing the laws enacted by Congress, and does so by designing, developing, and enforcing regulations. Its mission statement applies to a variety of environmental programs. 36

1.9 The Work Environment

Occupational Safety and Health Administration Another regulatory agency that works closely with the chemical processing industry is the Occupational Safety and Health Administration . Three groups were created by the Occupational Safety and Health Act of 1970: OSHA, the Occupational Safety and Health Review Commission (OSHRC), and the National Institute for Occupational Safety and Health (NIOSH).

1.9 The Work Environment It is important to discuss the work environment that a process technician will be asked to perform in. Each chemical plant or refinery is a city within a city that has its own political structure and living environment. This includes the equipment, systems, processes, and people that are unique to the industry. The chemical processing industry operates with a variety of work shifts that include 8- and12-hour rotating shifts. Some smaller facilities shut down over the weekend or even at night; however, the most common work schedule is 24 hours a day, 7 days a week. Process technicians work in an all-weather work environment; that is, they must complete work assignments during a variety of weather conditions. Operational work crews are required to work in a drug- and alcohol-free work environment. The chemical processing industry is an environment that is constantly changing. Team structures are frequently directed internally on the off shift. Shift work has a variety of side effects that should be considered prior to committing to the educational requirements and preparation needed to qualify for a position. Rotating shifts confuse a number of biological functions. Sleep patterns may become erratic and mental fatigue may create problems with job effectiveness. Eating habits are also affected by rotating shift work. This may result in rapid weight loss or increase, or a combination of both that stimulates wide weight swings. This can put serious stress on the primary organs, including the heart. A large problem each new technician faces is integrating into the work team. New teams go through a series of stages, including forming, storming, norming, and performing. However, process teams are typically well developed and mature, and these stages are long settled. Team dynamics are affected by a complex assortment of human attributes. The corporate culture inside the chemical industry generates specific triggers that are designed to create synergy to accomplish organized goals. When the key individuals of a team combine to accomplish organizational goals, synergy is formed. When the organization fails to convince each member of the team to work toward company goals, a series of factors associated with team failures is initiated and synergy declines. Refineries and chemical plants make a significant impact on the community and other industries. Large plants provide jobs and are a major source of manufacturing. These organizations purchase raw materials, both locally and internationally. Local resources include food, water, electricity, compressed gases, education, and so on. The CPI provides serious tax revenues for local schools and colleges. Chemical plants and refineries are typically built in close proximity to each other so that raw materials and products can be exchanged. Community features that will attract global industries include an educated workforce, inexpensive raw materials, central location, and high-quality local shipping lanes, railroads, pipelines, and roads. 37

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Summary The lifeblood of modern society is found in petroleum products. Cars, planes, trains, ships, and farm equipment all require petroleum products to operate. Crude oil is a mixture of hydrocarbons that vary in molecular structure and weight. Modern manufacturers separate these components through the distillation process. In 1859, Edwin L. Drake began drilling for oil near Titusville, Pennsylvania. Almost immediately, Drake’s well produced oil, and this success encouraged other oil drillers to set down wells. In 1860, the first refinery was built by William Abbott and William Barnsdall at Oil Creek. Their batch operation produced gasoline, naphtha, kerosene, and bottom residuum. Early refiners were able to produce only 11 barrels of gas from every 100 barrels of crude oil. Because of this low yield, the industry began to look for ways to increase gasoline production without increasing the reserves of less profitable products. Modern refiners are able to convert 45% of a barrel of crude oil into gasoline, using thermal and catalytic methods. Combining processes include alkylation, polymerization, and reforming. The first fractionating column was introduced in 1917. In the “still upon a still” design, as the heated crude oil flowed into the column, a fraction of the feedstock vaporized and rose up through the upper stills. The heavier components flowed through the lower stills to the bottom of the column. A number of trends are anticipated in oil production in the next 20 years, including the Big Rollover (when oil production peaks, and begins to decline). Many oil experts believe this will occur within the next 10 to 15 years. Most experts agree that the earth’s estimated ultimately recoverable oil reserves are about 1.2 trillion (short-scale) barrels without oil sands and 3.74 trillion barrels with oil sands. Present global consumption is 84.6 million barrels a day or 30.7 billion barrels per year. The United States produces 4.9 billion barrels per year and refines more than 8.5 billion barrels per year, while importing more than 16 billion barrels per year for commercial needs. These reserves cannot be replaced once they are used, and some projections indicate that, at our present rate of consumption, our oil reserves will be depleted during the next 38.8 years to 122.2 years. At the end of 2008, the world had consumed 1.12 trillion barrels. Each year, production from the world’s existing oil reserves drops by approximately 7%. These losses must constantly be made up through new reserve finds and new technology. The standard roles and responsibilities of process technicians include understanding and mastery of basic equipment, design, operation, and maintenance. Process technicians are also responsible for relieving other technicians and working a job post, performing shift tasks, making rounds, catching samples, taking readings, troubleshooting unit problems, filling out control documentation, maintaining and monitoring equipment, inspecting equipment, placing equipment in service, removing equipment from service, and responding to emergency situations. The chemical processing industry and various educational institutions have entered into formal partnerships to facilitate the technical training of employees. The key reasons driving these programs are rapid technological advances, the desire to eliminate workplace accidents, potential catastrophic risks, and government guidelines, including the recently enacted process safety management standard. 38

Summary Preparation for work in the chemical processing industry starts in high school with interpersonal skills, microcomputers, communications, math, and science. College students are given an opportunity to complete courses developed by education and industry, structured according to a set of nationally accepted objectives, and taught by people with years of industrial experience. College PT classes focus on the equipment found in the chemical processing industry. The initial course goes into some depth about the various areas. The second course presents various systems in which equipment is commonly used. The last core course allows a process technician to operate one or more of the systems found in the chemical processing industry. A number of regulatory agencies work closely with and periodically monitor specific activities in the chemical industry. These agencies include the Environmental Protection Agency, the Occupational Safety and Health Administration, the Department of Transportation, and the Nuclear Regulatory Commission. A process technician must be able to integrate well with existing employees and learn to handle workplace stresses and challenges successfully. The chemical processing industry operates with a variety of work shifts, including that include 8- and12-hour rotating shifts. Rotating shift work has biological side effects that must be considered and dealt with. The work environment in this industry is constantly changing.

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Chapter 1 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 40

Describe process technology training programs. What skills do technicians need for success? Describe a typical apprentice training program. List three differences between high school and college. What is your motivation for pursuing a career in process technology? What is time management? What is diversity? Define sexual harassment. List five significant events in the history and development of the chemical processing industry. Describe the primary issue in oil production today. What tools must a student acquire and use to be successful in a process technology program? What is process technology? List all process technology classes offered at your school. Calculate the gross income of a first-year technician. Calculate the gross income of a senior technician at top rate. Use the standard of 2,080 hours plus 1,000 overtime hours at time and a half. Describe batch operation. Contrast thermal and catalytic cracking. Identify two inventions that revolutionized the chemical processing industry. Who was called the “father of the gas industry”? What event took place in 1859 that changed the chemical processing industry? Describe fractional distillation. What are the primary responsibilities of a process operator? Identify the future trends that have been predicted for the process industry. Explain the function of regulatory agencies by describing one such agency and its responsibilities. Describe how shift work can affect the process technician. What are the five basic skills of equipment training? Describe the “Big Rollover” and the Hubbert peak theory. Describe the biogenic theory. Describe the typical molecular composition of crude oil. List some specific products manufactured from petroleum.

Introduction to Process Technology After studying this chapter, the student will be able to: • Describe the process technology curriculum and Associate of Applied Science degree plan. • List the key principles of safety, health, and environment. • Describe the influence of the PSM standard on the process technology curriculum. • Describe the content of a course on the basic principles of quality control. • Describe the content of a course on principles of instrumentation and modern process control. • Describe the content of initial and advanced process equipment courses, including systems and process operations. • Describe the various systems found in the chemical processing industry. • Describe a college-level troubleshooting course, including models and methods that may be taught as part of this course. • Describe how science courses prepare the student to apply the principles of chemistry and physics in the chemical processing industry. • Explain how the process technology curriculum is used to prepare a student for employment in the CPI.

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Key Terms Applied General Chemistry—study of the general concepts of chemistry with an emphasis on industrial applications. Students measure physical properties of matter, perform chemical calculations, describe atomic and molecular structures, distinguish periodic relationships of elements, name and write inorganic formulas, write equations for chemical reactions, demonstrate stoichiometric relationships, and demonstrate basic laboratory skills. Applied Math for Process Technicians—variations in this area include studies in two or more of the following areas; basic mathematics, technical algebra, math with applications, college algebra, statistics, trigonometry, statistics, applied or academic physics. Faculty expectations—college faculty’s assumption that process technology students will be responsible for their own learning, setting goals, managing their time, participating in class activities, and attending scheduled class meetings. Introduction to Process Technology—a survey course of all the courses found in the regionally accredited process technology program. Occupational Safety and Health Administration (OSHA)—Federal agency created by the Occupational Safety and Health Act; composed of three division: the Occupational Safety and Health Administration, the National Institute for Occupational Safety and Health, and the Occupational Safety and Health Review Commission. Principles of Quality—course covering the background and application of quality concepts. Topics include team skills, quality tools, statistics, economics, and continuous improvement. Focuses on the application of statistics, statistical process control, math, and quality tools to process systems and operations. Process—a collection of equipment systems that work together to produce products (e.g., crude distillation). Process Instrumentation—course for study of the instruments and instrument systems used in the chemical processing industry; includes terminology, primary variables, symbology, control loops, and basic troubleshooting. The purpose of this class is to provide students with an understanding of the basic instrumentation and modern process control used in the chemical processing industry. Process technicians—Process technicians have advanced training in the equipment, technology, and scientific principles associated with modern manufacturing. Process technicians typically have college degrees and can be found operating and troubleshooting the complex systems found in the chemical processing industry. Process Technology—as defined in the regionally accredited process curriculum, course for study and application of the scientific principles (math, physics, chemistry) associated with the operation (instruments, equipment, systems, troubleshooting) and maintenance (safety, quality) of the chemical processing industry. Process Technology 1—Equipment—instruction in the use of common process equipment, including basic components and related scientific principles. Includes a study of valves, pipes and tanks, pumps, compressors, motors and turbines, heat exchangers, cooling towers, boilers, furnaces, distillation columns, reactors, and separators. 42

2.1 Introduction to Process Technology

Process Technology 2—Systems—study of common process systems found in the chemical process industry, including related scientific principles. Includes study of pump and compressor systems, heat exchangers and cooling tower systems, boilers and furnace systems, distillation systems, reaction systems, utility system, separation systems, plastics systems, instrument systems, water treatment, and extraction systems. Computer console operation is often included in systems training. Emphasizes scale-up from laboratory (glassware) bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation, reaction, and fluid flow principles. Process Technology 3—Operations—combines process systems into operational processes with emphasis on operations under various conditions. Topics include typical duties of an operator. Instruction focuses on the principles of modern manufacturing technology and process equipment. Emphasizes scale-up from laboratory bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation and fluid flow principles. The purpose of this class is to provide adult learners with the opportunity to work in a self-directed work team, operate a complex operational system, collect and analyze data, start and stop process equipment, follow and write operational procedures. The course is advanced and requires the learner to apply classroom skills to real-life operational activities. Students are required to qualify and operate a process unit. Process Troubleshooting—instruction in the different types of troubleshooting techniques, methods, and models used to solve process problems. Topics include application of data collection and analysis, cause-effect relationships, and reasoning. Emphasizes application of troubleshooting methods to scale-up from laboratory bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation and fluid flow principles. PSM standard—a governmental process safety management standard designed to prevent the catastrophic release of toxic, hazardous, or flammable materials that could lead to a fire, explosion, or asphyxiation. Safety, Health, and Environment—course in which students gain knowledge and skills to reinforce the attitudes and behaviors required for safe and environmentally sound work habits. Emphasizes safety, health, and environmental issues in the performance of all job tasks, and covers regulatory compliance issues. System—a collection of equipment designed to perform a specific function (e.g., refrigeration system).

2.1 Introduction to Process Technology Process technology, as defined in the regionally accredited process curriculum, is the study and application of the scientific principles (math, physics, chemistry) associated with the operation (instruments, equipment, systems, troubleshooting) and maintenance (safety, quality) of the chemical processing industry. The term process technology was first created in the communitycollege environment to describe a new program being designed to train process technicians. Two program descriptions were developed at the same time: process technology and chemical technology. Originally the rubrics were PTEC and CTEC. Chemical technology is used to train laboratory technicians. Figure 2–1 shows campus facilities used to prepare adult learners for employment in the chemical processing industry (process or laboratory). This could include research pharmaceutical, food processing, power generation, operator, or process technicians. 43

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Figure 2–1 The Community College

A process technology student is required to study the equipment and technology common to most industrial processes and to understand the relationships they share. For example, piping, valves, pumps, and tanks share a unique relationship common to many processes. In a process technology program or course of study for the Associate of Applied Science degree, a student will learn the principles of modern process control and troubleshooting. Most programs start this process using the five elements of a control loop as a guide. Because new governmental guidelines require process technicians to understand the chemistry of the processes they are operating, a solid foundation in applied math, physics, and chemistry is required. Calculating product transfers; mixing raw materials to form new products; and dealing with pressure, level, flow, and temperature problems are all areas to which the math/science foundation is commonly applied. During the program, a student will be exposed to advanced quality control techniques, safety training from a process technician’s view, and human relations. The knowledge and skills learned in the process technology degree program can be directly applied to a number of hands-on learning activities at the educational institution before being applied on the job. 44

2.1 Introduction to Process Technology When students enroll in a process technology program, faculty expectations are that the students will have the skills to complete a regimented curriculum (Figure 2–2) that has been developed by education, industry, and governmental agencies. Successful completion of a regionally accredited program requires a student to demonstrate the following skills:

• • • • • • • •

Self-directed study habits—attendance, participation, critical thinking, troubleshooting, goal setting, time management, motivation, reading and study, homework, self-directed work ethic Interpersonal skills—listening, communication, diversity awareness, using quality tools, honesty, integrity, working with supervision Safety awareness—safety, health, and environmental considerations Application of the principles of quality control to process operations Use of complex instrumentation systems Basic understanding of the equipment and technology—computer literacy, basic math and science, mechanical aptitude, assimilation of skills, hands-on operation Recognition and operation of various process systems Troubleshooting of typical process problems

Figure 2–2 College Classroom 45

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Introduction to Process Technology is the first course taken in the process technology program. It is specifically designed to provide the adult learner with a general overview of the entire program. Process technology programs include eight core classes:

• • • • • • • •

Introduction to Process Technology Safety, Health, and Environment Process Instrumentation The Principles of Quality PT 1—Equipment PT 2—Systems PT 3—Operations Process Troubleshooting

Additional courses may include:

• • • • • • • • • •

Math (one or two classes) Applied General Chemistry and Physics College Physics General or Organic Chemistry English Composition 1 and 2 Speech Social Behavioral Science Computer Literacy Humanities/Fine Arts Other technical electives

This chapter focuses on the typical courses found in process technology programs around the world and provides a foundation upon which future students and educators can build. Course Description: “Introduction to Process Technology” is a survey of all the courses found in the process technology curriculum.

Introduction to Process Technology Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 46

History of the Chemical Processing Industry Introduction to Process Technology Safety, Health, and Environment Applied Physics 1 Equipment 1 Equipment 2 Process Instrumentation 1 Process Instrumentation 2 Process Technology (PT) Systems 1 Process Technology Systems 2 Industrial Processes Process Technology Operations Applied General Chemistry 1 Applied Physics 2 Environmental Standards

2.2 Safety, Health, and Environment 16. 17. 18. 19. 20.

Quality Control Process Troubleshooting Self-Directed Job Search Applied General Chemistry 2 Chemical Process Industry Overview

2.2 Safety, Health, and Environment Process safety refers to the application of engineering, science, and human factors to the design and operation of chemical processes and systems. The primary purpose of process safety is to prevent injuries, fatalities, fires, explosions, and unexpected releases of hazardous materials. Process safety focuses on the individual chemical processes and operational procedures associated with these systems. A process safety analysis is used to establish safe operating parameters, instrument interlocks, alarms, process design, and start-up, shutdown, and emergency procedures. Process safety programs cannot completely eliminate risk; they can only control or reduce those risks. Safety, Health, and Environment courses for process technicians deal with items such as personal protective equipment, hazard communication, permit systems, fire extinguishers, hazardous materials and emergency response, following procedures, general safety rules, and equipment and operation hazards. Safety training is designed to keep employees safe and productive, protect the community and environment, and protect equipment and physical facilities. Safety Course Description: Development of knowledge and skills to reinforce the attitudes and behaviors required for safe and environmentally sound work habits. Emphasis on safety, health, and environmental issues in the performance of all job tasks and regulatory compliance issues. The student will list components of a typical plant safety and environmental program; describe the role of a process technician in relation to safety, health, and environment; and identify and describe safety, health, and environmental equipment uses.

Typical Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Introduction to Process Safety Hazard Classification Routes of Entry and Environmental Effects Gases, Vapors, Particulates, and Toxic Metals Hazards of Liquids Hazardous Chemical Identification: HAZCOM, Toxicology, DOT Fire and Explosion Electrical, Noise, Heat, Radiation, Ergonomic, and Biological Hazards Operating Hazards: Permits, Emergency Response, HAZWOPER Personal Protective Equipment (PPE) Engineering Controls Administrative Controls Regulatory Overview: OSHA, PSM, EPA

Over the past 30 years, a number of incidents have occurred that have quietly changed the chemical processing industry forever. Incidents such as those in Bhopal, Alaska (the Exxon Valdez oil spill), and Texas City (involving BP) have made us aware of the potential for catastrophic events 47

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that exists in our modern manufacturing environment. Technological advances in modern manufacturing are so rapid that many technologies are outdated a few months after they are installed. Process technicians use this technology to control many of their processes. A single operator can remotely control a manufacturing complex from a single control room. Figure 2–3 shows a process technician monitoring process conditions.

(a)

(b) Figure 2–3 Process Control Room 48

2.2 Safety, Health, and Environment In 1992, after years of research and investigation into the causes of industrial explosions, fires, and vapor releases, the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) released the Process Safety Management Standard. This PSM standard was the government’s response to a number of incidents that had alarmed the chemical processing industry, communities and the public at large, and government. Key elements of the standard include employee participation, process safety information, operations procedures, process hazard analysis, employee training, emergency response, and hot work permitting. OSHA and the EPA believe that the key to preventing catastrophic emergencies in the chemical processing industry is adequate employee training. This was the conclusion of the governmental groups that investigated the Phillips Chemical and ARCO vapor release and explosions. The employee training aspect of the PSM standard includes seven sections:

• • • • • • •

Process overview Training records and method used to administer training (documentation of attendance and competency achieved is required) Identification of chemicals used in the process Control of access to and egress from the process unit Training materials (must reflect current work practices) Refresher training Contract labor requirements for informing, training, and documenting

Within months of the release of the PSM standard, industry joined with education to form a number of industrial partnerships. These early partnerships initiated the development of a new two-year degree program, “Process Technology.” The key considerations driving the development of this program were (1) rapid advances in technology, (2) desire to eliminate accidents in the workplace, (3) potential catastrophic risks, (4) new regulations and guidelines from the government, and (5) loss of the Baby Boomer workforce. Safety programs have a rich tradition inside the chemical processing industry. The CPI has been very receptive to establishment and adoption of sound safety principles and government regulations. Process technicians must undergo a wide variety of government-mandated training and are subject to numerous regulations. The following are 10 of the most common safety training issues: process safety management (29 C.F.R. §1910.119); OSHA; hazard communication (29 C.F.R. §1910.1200); HAZWOPER (29 C.F.R. §1910.120); fire fighting (29 C.F.R. §1910.157); permit system; environmental awareness; departments of transportation; respiratory protection (29 C.F.R. §1910.134); and personal protective equipment (29 C.F.R. §§1910.133, 1910.135). The hazard communication standard is a central feature in the safe operation of the chemical processing industry. HAZCOM ensures that process technicians can safely handle, transport, and store chemicals.The standard covers chemical lists, material safety data sheets (MSDS), personal protective equipment, physical and health hazards, toxicology, hazardous chemicals and operations, manufacturer’s information, and warning labels. Permit systems are designed to protect workers from hazardous energy, hot work, opening and blinding, confined-space entry, and cold work. A good permit system can easily be integrated into normal operations to enhance protection of employees, equipment, and the environment. Fire protection, prevention, and control are principles relating to industrial fires. Process technicians are required to participate in yearly training using fire extinguishers, monitors, and hoses. During 49

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these exercises, each member of the team aggressively attacks and extinguishes a variety of fires. Fire prevention educates technicians about fire hazards and steps to take to eliminate them.

2.3 The Principles of Quality Control During the early 1980s, U.S. industry was taught a valuable lesson in the area of quality improvement. Using advanced quality practices, the Japanese captured major economic markets from U.S. counterparts. A decade earlier, American business had refused to listen to several leading quality thinkers. This lack of vision cost the stockholders of these companies dearly, as Dr. W. Edwards Deming, Joseph M. Juran, and others took their message to the Japanese. By 1985, all of the leading oil and automotive giants were listening very closely to what these “quality gurus” had to say. A basic principle of quality control states that each process has a range that it naturally moves through. For example, the normal temperature range for your home may fluctuate between 70 and 80 degrees; your desired setpoint may be 75 degrees. Before statistical process control (SPC), an adjustment was made each time the process variable rose above or fell below the setpoint (Figure 2–4). If natural variation is not taken into consideration, the process could be driven completely out of control by the well-intentioned but overreactive adjustments. SPC allows a process to operate within its own variation by making adjustments only after a number of out-of-limit samples have been caught. In the Principles of Quality course, students use advanced statistics and mathematics to work with operational data. Process technicians collect, organize, and analyze data during routine operations. The statistical approach works well with statistical process control and control charts. A variety of processes can easily be adapted to fit these quality tools. Examples of these include equipment and quality variables; process variables include pressure, temperature, flow, level, and analytical parameters. Principles of Quality Course Description: Study of the background and application of quality concepts. Topics include team skills, quality tools, statistics, economics, and continuous improvement. The focus of the course is on the application of statistics, statistical process control, math, and quality tools to process systems and operations.

Typical Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 50

The Quality Gurus Total Quality Management (TQM) Quality Tools 1 Statistics 1 Statistical Process Control Control Charts Quality Tools 2 Statistics 2 Variation in Processes Customer Satisfaction The Economics of Quality Communication—The Critical Skill International Standards Organization (ISO) Teamwork and Personal Effectiveness

2.4 Instrumentation and Process Control NORMAL VARIATION

Temperature 90 85 80 Target

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16:00

Back in control. Minor adjustment to 87˚F

Figure 2–4 Temperature Control Before SPC

2.4 Instrumentation and Process Control Process Instrumentation is a core class designed to teach the process technology student the basic principles for reading process blueprints, the primary function of instruments, and how instruments work together to automatically control a process. Process instruments fall into five different groups: (1) primary elements and sensors, (2) transmitters, (3) controllers, (4) transducers, and (5) final control elements. Figure 2–5 shows various instruments used in the processing industry. 51

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Figure 2–5 Process Instruments Each part found in a plant has an equivalent plan symbol or diagram and a specific relationship to other pieces of equipment. Examples of such relationships include:

• • • • • • •

Transmitters and controllers Piping, tanks, and valves Pumps and compressors Motors and steam turbines Heat exchangers and cooling towers Fired heaters and boilers Distillation columns and reactors

Process Instrumentation Course Description: Study of the instruments and instrument systems used in the chemical processing industry; includes terminology, primary variables, symbols and diagrams, control loops, and basic troubleshooting.The purpose of this class is to provide students with an understanding of basic instrumentation and modern process control used in the chemical processing industry. Process instrumentation is taught from the concept of the control loop in relation to how a process technician runs a unit. (Process instrumentation is one of the eight core 52

2.5 Process Equipment classes required by the State of Texas for process technology majors.) In process instrumentation classes, students learn to describe the basic instrumentation used in modern process control; draw and label each of the control loops used in industry (flow, level, pressure, temperature, and analytical); draw a cascade control loop; describe manual, automatic, and cascade controls; draw a process flow diagram; and create a piping and instrumentation drawing.

Process Instrumentation Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Symbols and Diagrams Process Flow Diagrams (PFD) Basic Instrumentation 1 Basic Instrumentation 2 Control Loops 1 Control Loops 2—Controllers and Control Modes Modern Process Control—Application and Console Operations Piping and Instrumentation Drawing 1 Piping and Instrumentation Drawing 2

2.5 Process Equipment Process training for operators includes an in-depth study of the basic equipment found in the chemical processing industry (Figure 2–6). This knowledge forms a basis for future site-specific training activities. Not all of the equipment reviewed in the training program will be found on the unit you will be assigned to, of course. However, the odds indicate that at some time in your work career you will come in contact with all of the equipment that you initially study in this course—and much more. Equipment training focuses on five basic skills: (1) familiarity with the equipment and basic components, (2) understanding of how the device operates (scientific principles and technology), (3) equipment relationships within a system, (4) preventive maintenance and troubleshooting, and (5) operation of the equipment. Process technicians are not required to become mechanical, instrument, or electrical technicians; however, they are required to have a sound understanding of the equipment that makes up a particular process. These five basic skills allow a technician to understand the process and communicate effectively with maintenance and engineering. Most entry-level training programs cover the following types of equipment:

• • • • • • • • • •

Valves, piping, and vessels Pumps, compressors, fans, and blowers Steam turbines and motors Heat exchangers and cooling towers Boilers and furnaces Reactors and distillation columns Instrumentation Basic hand tools Lubrication, bearings, and seals Flares, mixers, and steam traps 53

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Introduction to Process Technology Heat Exchanger

Furnace

Distillation Column

Pump Valve

Figure 2–6 Equipment

Process Technology (PT) 1—Equipment Course Description: Instruction in the use of common process equipment.

Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 54

Introduction to Process Equipment Valves Piping and Vessels Pumps Compressors Turbines and Motors Heat Exchangers Cooling Towers Boilers Furnaces Reactors Distillation Columns

2.6 Process Systems

2.6 Process Systems Process Technology 2—Systems is a study of the common industrial processes broken down into smaller components called systems. A system includes an arrangement of equipment engineered to perform a specific function. A system can also be characterized as a collection of equipment that works together to produce a product. An example of this is a pump system that includes pipes, valves, instruments, a pump, and a tank. The purpose of this system is to transfer a liquid from one place to another. This grouping of equipment can be used in a wide variety of systems. Although a large number of systems and equipment exist, most college programs focus on the equipment most commonly used in their geographic area. Until 1990, systems training was left up to the chemical processing industry, as site-specific, on-the-job training. An average, full-time, working process technician would spend several years studying the different systems in his or her plant. Process systems take their specific characteristics from the equipment that makes up the process unit. Some of the basic systems found in the chemical processing industry include:

• • • • • • • • • • • • •

Pump-around system Compressor (air or gases) system Heat exchanger and cooling tower system Lubrication system Electrical system Furnace system Plastics system Reactor system Steam generation system Distillation system Refrigeration system Water treatment system Process control system

Modern manufacturing plants are comprised of complex networks that work closely with each other. The people who operate and maintain these networks include process technicians, maintenance technicians, instrument technicians, electricians, computer, laboratory technicians, chemists, and engineers. PT 2—Systems Course Description: Study of common process systems found in the chemical process industry, including related scientific principles. Includes the study of pumps and compressor systems, heat exchangers and cooling towers, boilers and furnace systems, distillation systems, reaction systems, utility systems, separation systems, plastics systems, instrument systems, water treatment systems, and extraction systems. A hands-on lab gives students an opportunity to work with glass bench-top distillation units, start up and shut down a debutanizer unit from a computer console, and operate a distillation pilot plant.

Typical Course Outline: 1. Instrumentation and Process Control Systems 2. Pump and Compressor Systems 55

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Introduction to Process Technology SP PV OP%

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2.7 Process Operations 3. 4. 5. 6. 7. 8. 9. 10.

Heat Exchanger and Cooling Tower Systems Boiler and Furnace Systems Distillation Systems Reactor Systems Utility Systems Extraction and Other Separation Systems Plastics Systems Other Systems

Heat transfer is an important process used in the chemical processing industry. A heat exchanger is a device used to transfer heat energy from a hotter fluid to a cooler fluid. Heat exchangers come in a variety of designs, including shell and tube, air-cooled, spiral, and plate. Heat exchangers use the principles of conductive and convective heat transfer. A shell-and-tube heat exchanger system consists of shell in and out piping; tube in and out piping; valves; instruments; flow, temperature, analytical, and pressure control loops; and two separate pump systems. Figure 2–7 illustrates the basic components of a heat exchanger system. A distillation process is a complex arrangement of systems that includes: cooling tower system, pump and feed system, heat exchanger system, product storage system, compressed air system, steam generation system, and complex instrument control system (see Figure 2–8). Each of these systems is designed to support a specific part of the distillation process. Distillation is a process that separates the various components in a mixture based on the differences in their volatilities (each chemical substance has a unique boiling point). In this type of system, a distillation column is the central piece of equipment. College faculty focus on how to operate these systems with modern process control, using various labs and hands-on teaching opportunities.

2.7 Process Operations Process Technology 3—Operations is an applied learning course that allows a technician to operate a working unit. These working units come in a variety of shapes and designs depending on the college or university. The key is the application of classroom skills to process equipment and systems. Process technicians collect, organize, and analyze data by catching samples and monitoring operating equipment. PT 3—Operations is an advanced course that provides a series of challenges to adult learners, such as working in a self-directed work team, troubleshooting problems, starting up and shutting down equipment, following safety procedures, and developing operational procedures. Ideally, the operations course students have access to an operating unit either at the college or a local industry. The class is designed to closely represent the first three months of working in the chemical processing industry. For example, Figure 2–9 illustrates the components found in a simple reactor operation. PT 3—Operations Course Description: This course combines systems into operational processes with emphasis on operation under various conditions. Topics include typical duties of an operator. Instruction focuses on the principles of chemical engineering and process equipment. Emphasis on scale-up from laboratory bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation and fluid flow principles. The purpose of this class is to provide adult learners with the opportunity to work in a self-directed work team, operate a complex distillation system, collect and analyze data, 57

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• • • • • • • 58

Orientation to and overview of the operating unit Safety, health, and environment review On-the-job training in drawing process flow diagrams Develop and use standard operational procedures Work in self-directed teams Complete operational assignments Collect, organize, and analyze data

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• • •

Troubleshoot process problems Complete the qualification process and a written exam Operate the process unit (required), including start-up and shut-down

Typical Course Outline: 1. Orientation and Overview of Unit (includes all safety aspects) 2. Draw Simple Process Flow Diagrams of Operating Unit (includes listing primary equipment, flows, and instrumentation) 3. Complete Line Tracing and Initial Training 4. Complete Basic Equipment, Instruments, and Flows Assessment Exam 5. Work in Team Assignments by Initial Assessment Ranking 59

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6. Complete Team Assignments – Write start-up procedures – Write and develop a team checklist – Record daily activity in technical notebook – Complete operational directives 7. Complete Individual Walk-Through Checklist with Instructor 8. Complete Final Exam and Turn in Technical Notebook

2.8 Troubleshooting Process Troubleshooting is an important part of a technician’s job description. This course is advanced and has a high degree of analytical difficulty. A process technician’s role can be compared to that of a jet fighter pilot. The pilot not only needs to be familiar with the aircraft, but must also be able to use it in a variety of combat situations. The skills needed to make a good fighter pilot are the same skills required to make a good process technician. Troubleshooting skills vary significantly between technicians. Some technicians are content with simply knowing about the equipment and systems they operate and how to start them up and shut them down. Other technicians have the rare ability to move far beyond simply operating the unit: they quickly identify problems and apply corrections. These few technicians are highly valued by their employers because they are a critical component in keeping the unit running safely and efficiently. Troubleshooting the operation of process equipment requires a good understanding of complex operations and how the equipment and systems operate. Equipment used in modern manufacturing is run 24 hours a day, 7 days a week, 52 weeks a year. Routine maintenance is performed on this equipment during scheduled maintenance times. Process technicians should attempt to uncover as much information as possible about the equipment in their units. Much of this information can be found in technical manuals, checksheets, SPC charts, or the operating manuals. Manufacturer information is typically included in the engineering specifications, drawings, and equipment descriptions.

Process Troubleshooting Models One of the highest levels a process technician can achieve is the ability to clearly see the process and sequentially break down, identify, and resolve process problems. Process troubleshooting has traditionally been considered the area of senior technicians, although some people believe that successful techniques can be taught to all technicians. Experience has proven over time to be the best teacher on equipment that is manually operated; however, new computer technology provides advanced control instrumentation that can be used to quickly and methodically track down process problems. It is well known that a single problem can have a cascading effect on all surrounding equipment and instrumentation. This phenomenon is commonly associated with both primary problems and secondary problems. Troubleshooting models are attached to equipment and systems presently being studied at every community college and university that teaches process technology. The 10 models commonly used to teach process troubleshooting include:

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Distillation model Reaction model Separation model

2.8 Troubleshooting

• • • • • • •

Pump and tank model Compressor model Heat exchanger model Cooling tower model Boiler model Furnace model Multiple-variable (multi-variable) model

These 10 models provide the hardware or framework within which the various troubleshooting methodologies are applied. Each model has a complete set of process control instrumentation and equipment arrangements. A complete range of troubleshooting scenarios has been developed and is typically included with these models. Other models used include stripping and adsorption, decanting, and gas and oil recovery. Figure 2–10 is an example of a multiple-variable process model.

Troubleshooting Methods A number of troubleshooting methods can be used with these models. Methods vary depending on individual educational faculty, consultants, and industry. The basic approach to most methods includes the development of a good educational foundation. 1. Method One: Educational (Completed in College Program) • Gain basic knowledge of the equipment and technology • Understand the math, physics, and chemistry associated with the equipment • Study equipment arrangements in systems • Study process control instrumentation • Operate equipment in complex arrangements • Troubleshoot process problems 2. Method Two: Instrumental (Completed in College Program) • Gain basic understanding of process control instrumentation • Gain basic understanding of the unit process flow plan • Advanced training in controller operation (PLC (programmable logic controller) and DCS (distributed control system)) • Troubleshoot process problems 3. Method Three: Experiential (Completed on the Job) • Experience operating specific equipment and system • Gain familiarity with past problems and solutions • Develop ability to think outside the box and innovate • Apply critical thinking; identify and challenge assumptions • Evaluate, monitor, measure, and test alternatives • Troubleshoot process problems 4. Method Four: Scientific (Requires Engineering Technology, Process Technology, Experience, and High Aptitude) • Have good grounding in principles of mathematics, physics, and chemistry • Understand theory-based operations • Have good understanding of equipment design and operation • View the problem from the outside in • Use outside information and expertise and reflective thinking • Generate alternatives, do brainstorming, and rank alternatives • Troubleshoot process problems 61

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2.9 Applied General Chemistry and Physics

Statistics, Statistical Process Control, and Quality Tools Data collection, organization, and analysis are another approach that can be used to troubleshoot process problems. Check-sheets are used to collect large quantities of data. This quantitative data can be organized into graphics or trends to plot process variation or changes. Data analysis utilizes a variety of quality techniques to put all of the parts in place. Control charts are frequently used to assist process technicians in operating a complicated process. Quality tools include a variety of methods designed to improve product quality. Troubleshooting Course Description: Instruction in the different types of troubleshooting techniques, methods, and models used to solve process problems. Topics include application of data collection and analysis, cause-effect relationships, and reasoning.

Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Introduction to Process Instrumentation and Troubleshooting Process Symbols and Diagrams Understanding Process Equipment Relationships Introduction to Control Loops Statistics, Quality Tools, and Troubleshooting Control Charts Introduction to Process Troubleshooting Pump Model Compressor Model Heat Exchanger Model Cooling Tower Model Boiler Model Furnace Model Distillation Model Reactor Model Separation Model Multiple-variable Plant

2.9 Applied General Chemistry and Physics Applied general chemistry and physics are two fundamental courses that have been recommended by industry for inclusion in process technology programs. It is clear that information contained in academic chemistry and physics courses does not address key topics required by the occupation. Also, the process safety management standard requires that process technicians have an understanding of the chemistry and physics associated with the processes they are operating. Figure 2–11 demonstrates how adult learners can use hands-on bench-top operations to understand the science associated with difficult topics. Process technicians frequently mix chemicals together under a variety of conditions to produce new products. These chemical mixtures may be heated, cooled, blended, passed over a catalyst, or distilled. The chemistry associated with these processes may be simple, or may be quite complex. Documentation associated with these mixtures should be designed so that a new technician will be able to understand the basic chemistry. 63

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Figure 2–11 Bench-top Operation

Common chemistry and physics topics include:

• • • • • • • • • • • • • • 64

Pressure Temperature Fluid flow Heat transfer Heat and energy Density Viscosity Specific gravity Reactors Atoms and elements Bonding Molecules Compounds Solutions

2.10 College Math

• • • •

Mixtures Hydrocarbons Distillation Matter

Process technicians need to understand the chemistry and physics of the operations and processes they work with. Associated with each piece of equipment or system is a series of scientific principles. These principles include, among other things, fluid flow, reactions, heat transfer, temperature, distillation, gas laws, pressure, electricity, mechanical rotation, material balance, pH measurements, density, specific gravity, the periodic table of elements, and organic chemistry. The full list is much longer than this; the more technicians know, the better the product they will produce and the safer their work environment will be. It is difficult to separate chemistry and physics. Some colleges combine applied chemistry and physics into one course; others have two separate courses. Almost all require either a natural science chemistry or physics course as a prerequisite; a few require both. Completion of these courses helps round out a technician’s academic and technical training. Completion of these courses also makes it easier for process technicians and engineers to communicate effectively. Applied General Chemistry Course Description: Study of the general concepts of chemistry with an emphasis on industrial applications. Student will measure physical properties of matter, perform chemical calculations, describe atomic and molecular structures, distinguish periodic relationships of elements; name and write inorganic formulas; write equations for chemical reactions; demonstrate stoichiometric relationships; and demonstrate basic laboratory skills.

Course Outline: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Pressure and Characteristics of Fluids Temperature, Heat Transfer, and Associated Math Fundamentals of Chemistry and the Periodic Table Chemical Reactions, Material Balance, % by Weight, pH Fundamental Concepts of Physics; Density, Specific Gravity, Pressure Complex and Simple Machines, Electricity, Magnetism Advanced Concepts of Chemistry—Distillation Chemical Bonds, Fluid Flow, Gas Laws, and Heat Organic Chemistry—Alkanes, Chemical Etymology – Carbon and hydrogen, chemical equations – Alkenes and alkynes, aromatic – Alcohols, phenols, esters, halides, aldehydes – Ketones, carboxylic acids, amines, amides

2.10 College Math Math requirements vary from college to college, but a standard exists between institutions. The majority of community colleges require only one or two math courses. Most universities require students to take at least one math course beyond college algebra. Manufacturing engineering technology, a field closely related to process technology, requires three to five math courses. Typically, process technology programs include one applied or academic math course; one applied 65

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general chemistry course or one applied physics course; and one natural science course, either physics or chemistry. The courses commonly used to fulfill these requirements include:

• • • •

Basic Mathematics and Pre-Algebra (depending on student preparation) Technical Algebra or College Algebra – Optional: Technical Math 2 or Academic Math Applied General Chemistry or Physics Academic Physics or Chemistry – Optional: Statistics (typically covered in principles of quality)

Summary “Introduction to Process Technology” is a survey course that covers all of the courses found in the process technology curriculum and degree. This course is designed as an overview and short synopsis of common elements found in each course. Process safety is described as the application of engineering, science, and human factors to the design and operation of chemical processes and systems. Safety courses for process technicians deal with use of safety equipment, process safety analysis, and the prevention of injuries, fatalities, fires, explosions, or unexpected releases of hazardous materials. Safety training is designed to keep employees safe and productive, protect the community, environment, and protect equipment and physical facilities. In a “Principles of Quality” course, process technicians collect, organize, and analyze data during routine operations, and study the background and application of quality concepts. Topics include team skills, quality tools, statistics, economics, and continuous improvement. The focus is on the application of statistics, statistical process control, math, and quality tools to process systems and operations. Process training for operators includes an in-depth study of the basic equipment found in the chemical processing industry. Equipment training focuses on five basic skills: (1) familiarity with the equipment and basic components, (2) understanding the operation of the device (scientific principles and technology), (3) equipment relationships within a system, (4) preventive maintenance and troubleshooting, and (5) operating the equipment. A process is a collection of equipment that works together to produce a product. Some of the basic systems found in the chemical processing industry include the pump-around system, compressor system, heat exchanger and cooling tower system, boiler and furnace, distillation, separations and reactions. Process technology operations is an applied learning course that allows a technician to operate a working unit. It provides a series of challenges to adult learners, such as working in a self-directed work team, troubleshooting problems, starting up and shutting down equipment, following safety procedures, and developing operational procedures. Process instruments fall into five different groups: (1) primary elements and sensors, (2) transmitters, (3) controllers, (4) transducers, and (5) final control elements.

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Summary Process troubleshooting, which is an important part of a process technician’s job description, incorporates three basic components: knowledge of the equipment, instrumentation, and technology; understanding of the scientific principles associated with your unit; and an understanding of a basic troubleshooting system. The basic tools used in troubleshooting include checklists, control loops, data collection, SPC charts, flow charts, brainstorming, systems knowledge, and scientific principles. Ten common models are used to teach process troubleshooting: distillation model, reaction model, separation model, pump and tank model, compressor model, heat exchanger model, cooling tower model, boiler model, furnace model, and multi-variable model. These models provide the hardware or framework within which the various troubleshooting methods are applied. Common chemistry and physics topics include pressure, heat transfer, viscosity, atoms and elements, compounds, hydrocarbons, temperature, heat and energy, specific gravity, bonding, solutions, distillation, fluid flow, density, reactions, molecules, compounds, mixtures, and matter. College mathematics courses for process technicians typically focus on common applied operations. Variations on basic math, algebra, trigonometry, physics, chemistry, and statistics are woven into the daily technician routines.

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Introduction to Process Technology

Chapter 2 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9.

List the basic concepts of modern quality control. List the basic concepts taught in safety, health, and environment courses. List three basic systems found in the chemical processing industry. List the basic concepts taught in process operations courses. List the basic concepts taught in process instrumentation courses. List the basic concepts taught in process troubleshooting courses. Describe how science and chemistry are related to the other process classes. Explain why a good mathematical foundation is important to a process technician. List the basic concepts taught in introduction to process technology courses.

10. List the basic concepts taught in the process equipment course. 11. Describe the process technology curriculum and Associate of Applied Science degree plan at your school.

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Safety, Health, and Environment After studying this chapter, the student will be able to: • • • • • • • • • • • • • •

Explain the basic principles of safety, health, and environment. Describe the general safety rules used by chemical processing plants. Discuss the process safety management (PSM) standard. Describe the hazard communication standard. Discuss physical and health hazards. Explain toxicology and the terms associated with it. Describe air-purifying and air-supplying respirators. Describe personal protective equipment and the four levels of PPE. Describe typical plant permit systems. Describe the principles of fire prevention, protection, and control. Evaluate the different types of fire extinguishers. Describe HAZWOPER. Explain the principles of hearing protection. Describe the sections of the DOT.

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Safety, Health, and Environment

Key Terms Air-purifying respirator—breathing device that mechanically filters or absorbs airborne contaminants. Air-supplying respirator—breathing device that provides the user with a contaminant-free air source. Department of Transportation (DOT)—governmental agency empowered to regulate the transportation of goods on public roads and highways. Emergency response—how specific individuals act during an emergency situation; the employer must have a written plan setting out and documenting these actions. First responder—person who undertakes the first two levels of emergency response as described by HAZWOPER (29 C.F.R. §1910.120). The first responder awareness and operations levels set out a series of structured responsibilities. The awareness level teaches a technician how to recognize a hazardous chemical release, the hazards associated with the release, and how to initiate the emergency response procedure. The operations level teaches a technician how to safely respond to a release and prevent its spread. Hazard communication (HAZCOM) standard—known as “workers’ right to know,” ensures that process technicians can safely handle, transport, and store chemicals. HAZWOPER—hazardous waste operations and emergency response. Lock-out/tag-out—term used to describe a procedure for shutting down and making unavailable for use equipment that falls under the control of hazardous energy regulations (29 C.F.R. §1910.147). Permit system—a regulated system that requires a variety of permits for various applications. The most common applications are cold work, hot work, confined space entry, opening/blinding, permit to enter, and lock-out/tag-out. Personal protective equipment (PPE)—gear used to protect a technician from hazards found in a plant. OSHA and EPA have identified four levels of PPE that could be required during an emergency situation. Level A provides the most protection; level D provides the least. Physical hazard—name for a chemical that statistically falls into one of the following categories: combustible liquid, compressed gas, explosive or flammable, organic peroxide, oxidizer, pyrophoric, unstable, or water reactive. Process safety management (PSM) standard—governmentally set rules designed to prevent the catastrophic release of toxic, hazardous, or flammable materials that could lead to a fire, explosion, or asphyxiation. Respiratory protection—a standard or program designed to protect employees from airborne contaminants.

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3.1 Safety, Health, and Environment Overview

3.1 Safety, Health, and Environment Overview In the past few decades, a number of occurrences have changed the chemical processing industry (CPI) forever. Incidents like those in India, Texas, and Alaska have made us aware of the potential for catastrophic events that exists in our modern manufacturing environment. The rapid advances in technology mean that a single process technician may be remotely controlling a company’s vast equipment resources from a single control room, even if he or she is not yet thoroughly acquainted with the new equipment being used in the plant’s systems. In 1992, the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) jointly released a process safety management (PSM) standard. The PSM standard was developed in response to a number of incidents that had alarmed the chemical processing industry, community, and government, and was based on years of research and investigation into the causes of industrial explosions, fires, and vapor releases. Key elements of the standard include employee participation, process safety information, operations procedures, process hazard analysis, employee training, emergency response, and hot work permitting. Both OSHA and the EPA believe that the key to preventing catastrophic emergencies inside the chemical processing industry is adequate employee training. This was the conclusion of the governmental groups that investigated the Phillips Chemical Company and ARCO vapor release and explosions. The employee training aspect of the PSM standard includes seven sections:

• • • • • • •

Process overview Training records and method used to administer training (attendance and competency achieved must be documented) Identification of chemicals used in the process Control of access to and from the process unit Requirements that training materials reflect current work practices Refresher training Contract labor requirements (contract labor must inform, train, and document that training)

Within months of the release of the PSM standard, industry joined with education to form a number of industrial partnerships. These early partnerships led to the development of a new two-year degree program in “Process Technology.” The key reasons driving the development of this program were: (1) rapid advances in technology, (2) desire to eliminate accidents in the workplace, (3) potential catastrophic risks, (4) new regulations and guidelines from the government, and (5) loss of the Baby Boom workforce. Safety programs have a rich tradition inside the chemical processing industry, and the CPI has been very receptive to adopting sound safety principles and government regulations. Process technicians are subject to a wide variety of government-mandated training and regulations. The following are 10 of the most common safety training issues:

• • • •

Process safety management (29 C.F.R. §1910.119) OSHA Hazard communication (29 C.F.R. §1910.1200) HAZWOPER (29 C.F.R. §1910.120)

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• • • • • •

Firefighting (29 C.F.R. §1910.157) Permit system Environmental awareness Department of Transportation Respiratory protection (29 C.F.R. §1910.134) Personal protective equipment (29 C.F.R. §§1910.133 and 1910.135)

The hazard communication (HAZCOM) standard is a central feature in the safe operation of the chemical processing industry. HAZCOM ensures that process technicians can safely handle, transport, and store chemicals.The standard mandates that workers have access to chemical lists, material safety data sheets, information on physical and health hazards, toxicology, hazardous chemicals and operations, manufacturers’ information, and warning labels. It also sets requirements for availability and use of personal protective equipment. Permit systems are designed to protect workers from dangers involved in hazardous energy, hot work, opening and blinding, confined-space entry, and cold work. A good permit system can easily be integrated into normal operations to protect employees, equipment, and the environment. The principles of fire protection, prevention, and control are designed to provide protection from industrial fires. Process technicians are required to participate in yearly training during which technicians are educated about fire hazards and the steps to take to eliminate them. These training sessions also include hands-on practice in extinguishing fires.

3.2 Basic Safety Principles The philosophy behind most modern safety programs involves the prevention of accidents. Successful accident prevention depends on three basic elements: safe working environments, safe working practices, and effective leadership. Safety programs for process technicians usually include elements of the following topics:

• • • • • • • • • • • •

HAZCOM—workers’ right to know about the chemicals they use HAZWOPER—hazardous waste operations and emergency response Respiratory protection Permit system Process safety management Personal protective equipment Hearing conservation Fire prevention and protection Department of Transportation (DOT) rules and regulations Environmental standards Basic principles of safety and contractor safety Lock-out, tag-out, and confined-space awareness

General safety rules are designed to protect human life, the environment, and physical equipment or facilities. Before a new technician even enters a refinery or chemical plant, a simple overview of the general plant safety rules is conducted. These rules include: 72

3.3 Occupational Safety and Health Act 1. Do not go to a fire, explosion, accident, or vapor release scene unless you have specific duties or responsibilities there. 2. Obey all traffic rules. 3. Do not park in designated fire lanes. 4. Report injuries immediately. 5. Stay clear of suspended loads. 6. Smoking and matches are not permitted in most sections of a plant. 7. Drink only from designated water fountains and potable water outlets. 8. Use the right tool for the right job. 9. Report to the designated equipment owner before entering an operating area. Stay in your assigned area. 10. Illegal drugs and alcohol are not permitted in the plant. 11. Firearms and cameras are not allowed in the plant. 12. Take steps to remove hazardous conditions. 13. Review and follow all safety rules and procedures, including those relating to: • personal protective equipment • hazard communication • respiratory protection • permit system • hazardous waste operations and emergency response • housekeeping • fire prevention 14. Know and understand the alarms and rules associated with: • vapor release • fire or explosion • evacuation • all-clear notifications

3.3 Occupational Safety and Health Act In 1970, a landmark piece of legislation was passed that made safety and health on the job in the chemical processing industry a matter of federal law. The Occupational Safety and Health Act (OSHA) brought in sweeping changes that affected 4 million American businesses and, more importantly, 57 million employees and their families. Why was this legislation needed? In 1969, 2.5 million disabling injuries and 14,000 deaths were directly linked to safety and health violations. The purpose of OSHA is (1) to remove known hazards from the workplace that could lead to serious injury or death, and (2) to ensure safe and healthful working conditions for American workers. The scope and coverage of the legislation are extensive. The Occupational Safety and Health Act applies to four broad categories: agriculture, construction, general industry, and maritime. Three primary agencies are responsible for administration of the Occupational Safety and Health Act (see Figure 3–1): 1. National Institute for Occupational Safety and Health (NIOSH) 2. Occupational Safety and Health Administration (OSHA) 3. Occupational Safety and Health Review Commission (OSHRC) 73

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OSHA OCCUPATIONAL SAFETY & HEALTH ACT

NIOSH National Institute for Occupational Safety & Health ●

Safety & Health Research

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Recommends New Standards

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OSHA

OSHRC

Occupational Safety & Health Administration

Occupational Safety & Health Review Commission

Investigates Catastrophies & Fatalities Establishes Standards & Penalties Inspects Workplaces

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Independent Agency Conducts Hearings on Contested Issues Assesses Penalties, Conducts Investigations, Supports or Modifies or Overturns OSHA

Figure 3–1 OSHA

3.4 The PSM Standard After the ARCO and Phillips plant explosions in 1989 and 1990, OSHA and the EPA went to work on a new standard that would limit the possibility of such problems happening again. After years of research and investigation into the causes of industrial explosions, fires, and vapor releases, the government issued the process safety management (PSM) standard. Figure 3–2 illustrates the key elements of the standard.

3.5 The Hazard Communication Program Government Mandate: Hazard Communication (29 C.F.R. §1910.1200) A fundamental principle of the chemical hazard communication (HAZCOM) program is that informed people are less likely to be injured by chemicals and chemical processes than uninformed people. According to the standard, all of the chemical inventories and processes within a chemical plant or refinery must be evaluated for potential hazards and risks. Where a risk is found, essential information and training are required for all people affected. A chemical HAZCOM program is composed of two essential parts: the written program (which addresses chemical manufacturers) and employee training (Figure 3–3).

Requirements of the Standard (Documentation) Because the chemical processing industry manufactures chemicals and employs technicians, the CPI is responsible for both sections of the OSHA standard that addresses chemical manufacturers’ employer requirements and user responsibilities. Chemical manufacturers are required by the HAZCOM standard to: • Analyze and assess the hazards associated with each chemical, and develop written procedures for evaluating chemicals. • Document the hazard, and develop material safety data sheets (MSDS) and warning labels. 74

3.5 The Hazard Communication Program

EMPLOYEE PARTICIPATION ● ●

Written program How employees will access ihazard identification system — identify hazards — gather information — communication system

PROCESS SAFETY ● ●

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Process flow diagram Equipment, process description, limitations Consequences of deviation Safety and relief devices Electrical classifications Characteristics of chemicals Process chemistry Mixing chemicals

PROCESS HAZARD ANALYSIS ● SOP, safety, training up front ● Identify unit hazards ● Identify causes and consequences — fires — vapor releases — explosions

INCIDENT INVESTIGATION For catastrophic events: ● Assemble team within 48 hours ● Address all findings ● Correct action items

OPERATIONS PROCEDURES ● ● ● ● ● ●

Operations and maintenance Reflect current work practices Process properties Hazards Start-up, shutdown Change of chemicals

EMPLOYEE TRAINING ● ● ● ●

● ● ●

Process overview Training records and methods Attendance and competency Training materials reflect current work practices Control access to unit Refresher training Contractors must inform and train their employees and document that training

HOT WORK PERMIT Protect from fires and explosions ● Specific procedures for hot work ● Defined as welding, cutting, spark producing ●

EMERGENCY PLANNING Emergency response plan — designated meeting points — key contacts ● Emergency response - roles and responsibilities ● Written action plans ●

Figure 3–2 Process Safety Management

• •

Disseminate the information to affected individuals. Label, tag, and attach warning documentation to chemicals leaving the workplace.

Employers are responsible for the development of a written hazard communication program, a hazardous chemical inventory list, and associated material safety data sheets. This written program should be designed so that it is given to the new employee upon initial assignment. The materials should be site specific, readily accessible by plant personnel, and include an evergreen feature that will keep it up to date. Employers are also required to provide training to employees 75

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HAZCOM

HAZCOM PROGRAM must include: ● Container labeling and warnings ● MSDS ● Employee training

29 C.F.R. §1910.1200 OSHA

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WRITTEN PROGRAM (Documentation)

EMPLOYEE TRAINING

Chemical Manufacturers

Physical Hazards

Analyze Chemical Hazards Develop Written Procedures for Evaluating Chemicals Document Hazards Develop MSDS & Warning Labels Disseminate Information Label, Tag, Attach Documentation to Chemicals Leaving Workplace

● ● ● ●

Combustible Flammable Explosive Compressed

Chemical Lists ● ● ●

Plant Chemical Inventory List Provided to All Employees Toxicology

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Material Safety Data Sheets

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Chemical Hazards Physical Hazards Product Identification PPE Storage & Handling Reactivity

Carcinogen Mutagen Teratogen Asphyxiation

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Hazardous Chemicals Hazardous Operations

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Corrosive Toxic Neurotoxic Target Organ Effects

Hard Hat Safety Glasses FRC Monogoggles

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Respirators Gloves Safety Shoes Radio

Release Detection ●

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Methods Used to Detect the Release of Hazardous Chemicals Human Senses Detectors

Figure 3–3 HAZCOM

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Oxidizer Pyrophoric Unstable Water Reactive

Personal Protective Equipment

Target Critical Operations ●

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Chemical Hazards

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●

●

3.7 Physical Hazards Associated with Chemicals about the hazards of the chemicals they will be working with, how to read an MSDS, how to select and use personal protective equipment, and how to read and use one of the three standard labeling systems: Department of Transportation (DOT), Hazardous Materials Identification System (HMIS), and National Fire Protection Association (NFPA).

Delivery of the Standard to Employees The HAZCOM standard requires an employer to provide information or training to employees about their plant’s hazard communication program. Fundamental information that must be given to a process technician includes: the key elements of the HAZCOM standard; the plant’s written hazard communication program; a detailed hazardous chemical inventory list; and associated material safety data sheets, along with warning labels, tags, and signs. Information should be included on how to access the HAZCOM system, chemical inventory list, and MSDS 24 hours a day, 7 days a week. Employers are required by law to provide open access to HAZCOM materials. This is why the HAZCOM standard is frequently referred to as the “workers’ right to know act.” The chemical processing industry initiates the delivery of HAZCOM training when a technician is first assigned to the plant. Training focuses on the physical and health hazards associated with exposure to chemicals. Additional information is provided on toxicology, physical properties of the chemicals, and hazards associated with handling, storing, and transporting chemicals. New technicians are required to review company procedures used to protect employees from hazardous chemicals, and specific operations are identified that may expose an employee to a chemical. The training section also includes the selection and use of personal protective equipment and the methods and observations used to detect the release of hazardous chemicals.

3.6 Safe Handling, Storage, and Transportation of Hazardous Chemicals Process technicians who transport, store, and handle chemicals must understand the systems, equipment, and technology they are working with; the physical hazards associated with chemicals in their facility; the health hazards associated with chemicals in their facility; chemical routes of entry into the human body; use of the material safety data sheets; and proper usage of labeling, signs, and tags.

3.7 Physical Hazards Associated with Chemicals A physical hazard is defined as a chemical that falls into one of the following categories: • Combustible liquid—has a flash point between 100°F (38.8°C) and 200°F (93°C) • Compressed gas—has a gauge pressure of 40 psig at 70°F (21.1C°) • Explosive—a chemical characterized by the sudden release of pressure, gas, and heat when it is exposed to pressure, high temperature, or sudden shock • Flammable gas—forms a flammable mixture with air at ambient temperature • Flammable liquid—has a flash point below 100°F (37°C) • Organic peroxide—explodes when temperature exceeds a specified point

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• • • •

Oxidizer—a chemical that promotes combustion in other materials through the rapid release of oxygen, usually resulting in a fire Pyrophoric—a chemical that ignites spontaneously with air at temperatures below 130°F (54.4°C) Unstable—a chemical that will react (condense, decompose, polymerize, or become self-reactive) when it is exposed to temperature, pressure, or shock Water reactive—a chemical that reacts with water to form a flammable or hazardous gas

3.8 Health Hazards Associated with Chemicals One or more of the following health hazards may be associated with chemicals that the process technician works with:

• • • • • • • • • • • • • •

Carcinogen—known cancer-causing substance Mutagen—a chemical that is suspected to have the properties required to change or alter the genetic structure of a living cell Teratogen—a substance that is suspected to have an adverse effect on the development of a human fetus Reproductive toxin—a chemical that inhibits the ability of a person to have children; chemicals are routinely tested for this property Asphyxiation—occurs when oxygen is removed or displaced by a chemical or when a chemical blocks or impedes the ability of a person’s body to use oxygen Anesthetic—dulls the senses (e.g., alcohol) Neurotoxin—slows down brain function (e.g., lead and mercury) Allergic response—a negative reaction to a chemical that triggers a physical response of discomfort, injury, or death Irritant—chemical that causes temporary discomfort when it comes into contact with human tissue Sensitizer—a chemical that affects the nerves (e.g., phenol is absorbed through the skin and will sensitize the affected area) Corrosive—a chemical that causes severe damage to human tissue (e.g., sulfuric acid) Toxic—a chemical that has been determined to have an adverse health impact Highly toxic—a chemical of which only a small amount is lethal Target organ effects—a chemical that contacts the body at one location (e.g., a hand) and is transferred to another area of the body where it has an adverse effect on a specific organ

Hazardous chemicals can enter the human body through: • Inhalation • Absorption (skin contact) • Ingestion • Injection Physical hazards and health hazards in a chemical plant or refinery must be quickly recognizable to process technicians. Recognizing a hazard and knowing how to respond are key elements of a technician’s training. Figure 3–4 illustrates this. 78

3.11 Respiratory Protection Programs

TOX IC

DANGER

HAZARD

Figure 3–4 Hazard Recognition

3.9 Material Safety Data Sheets It has been estimated that one out of every four workers in the United States handles a chemical. Development of the material safety data sheet (MSDS) for each chemical is the responsibility of the chemical manufacturer. A typical material safety data sheet has nine or ten sections, as follows: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Product Identification and Emergency Information Hazardous Ingredients Health Information and Protection or Hazards Identification Fire and Explosion Hazard Physical Data and Chemical Properties Spill Control Procedure Regulatory Information Reactivity Data Storage and Handling Personal Protective Equipment

3.10

Toxicology

Toxicology is the science that studies the noxious or harmful effects of chemicals on living substances. The fundamentals of toxicology include a relationship between dose and response. Dose is the amount of chemical entering or being administered to a subject. Response is the toxic effect the dose has on the subject.

3.11

Respiratory Protection Programs

The Occupational Safety and Health Administration requires employers who use and issue respirators to develop a written respiratory protection program. Employees must receive proper training in respiratory protection. Process technicians use two basic types of respirators: (1) air purifying, and (2) air supplying. 79

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Air-Purifying Respirators Air-purifying respirators are either half-face or full-face. Half-face air-purifying respirators are designed to cover the mouth and nose. In contrast, full-face respirators form a positive seal around the eyes, nose, and mouth. These respirators are designed to remove specific contaminants or organic vapors from the air. Concentrations of these contaminants may range from 5 to 50 times the normal exposure limit allowed by law.

Air-Supplying Respirators Air-supplying respirators are either self-contained breathing apparatus (SCBA) or hose-line respirators. These respirators are designed to be used in oxygen-deficient atmospheres.

3.12 Personal Protective Equipment Each human being has more than 19 square feet of surface area and breathes more than 3,000 gallons of air per day. Because chemical exposure comes through inhalation, ingestion, injection, and skin contact, protective measures have to be in place. Personal protective equipment (PPE) is an effective means of protecting technicians from hazardous situations. Engineering and environmental controls provide another layer of protection. The primary purpose of PPE is to prevent exposure to hazards when engineering or environmental controls cannot be used. Typical outerwear worn by process technicians includes: • Safety hat • Safety glasses • Fire-retardant clothing • Safety shoes • Hearing protection • Gloves • Face shield • Chemical monogoggles • Slicker suit • Radio • Respirator • Chemical suit • Totally encapsulating chemical protective suit

3.13 Emergency Response The chemical manufacturing industry defines an emergency as a loss of containment of a chemical or the potential for loss of containment that results in an emergency situation requiring an immediate response. Examples of emergency response situations include fires, explosions, vapor releases, and reportable-quantity chemical spills.

80

3.14 Plant Permit System The levels of response for a first responder have been determined by the chemical processing industry to be: • First responder awareness level—individuals are trained to respond to a hazardous substance release, initiate an emergency response, evacuate the area, and notify proper authorities • First responder operations level—individuals are trained to respond with an aggressive posture during a chemical release by going to the point of the release and attempting to contain or stop it

Emergency Response PPE Levels Emergency response uses four levels of personal protective equipment, according to the Environmental Protection Agency and the Occupational Safety and Health Administration. 1. Level A mandates the highest level of PPE protection by requiring a technician to don a totally encapsulating chemical protective suit. 2. Level B deals with chemical exposures that are not considered to be extremely toxic unless they are absorbed through the skin. In this case, a non-airtight chemical protective suit may be worn. Typically, the openings on a non-airtight chemical suit are taped to limit exposure. 3. Level C is used when the hazard is determined not to adversely affect exposed skin. 4. Level D provides the least amount of protection to a process technician. Level D protection is determined by individual companies, because the standard personal protective equipment is the work uniform.

3.14 Plant Permit System The plant permit system is a regulated system that uses a variety of permits for various applications. The types of permits used in the chemical processing industry include:

• • • • • • •

Cold work permit—routine maintenance and mechanical work Hot work permit—any maintenance procedure that produces a spark, excessive heat, or requires welding or burning Opening/blinding permit—removing blinds, installing blinds, or opening vessels, lines, and equipment Permit to enter—designed to protect employees from oxygen deficient atmospheres, hazardous conditions, power-driven equipment, and toxic and flammable materials Unplugging permit—barricades area, clears lines for unplugging, informs personnel, issues opening/blinding permit, issues unplugging permit Energy isolation procedure—isolates potentially hazardous forms of energy, such as electricity, pressurized gases and liquids, gravity, and spring tension Lock-out/tag-out procedure—a standard according to which technicians shut down a piece of equipment at the local start/stop switch, turn the main breaker off, attach a lock-out adapter and process padlock, try to start the equipment, and tag it as being out of service (tag-out) and record the incident in a lock-out logbook

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●

3.15 Classification of Fires and Fire Extinguishers The fire classification system is designed to simplify the selection of firefighting techniques and equipment.

• • • •

Class A fires involve the burning of combustible materials such as wood, paper, plastic, cloth fibers, and rubber. Class B fires involve combustible and flammable gases and liquids and grease. Class C fires are categorized as electrical fires. They involve energized equipment and class A, B, and D materials that are located near the fire. Class D fires involve combustible metals such as aluminum, magnesium, potassium, sodium, titanium, and zirconium.

The five types of fire extinguishers most commonly found in the chemical processing industry, and their range of effectiveness, are as follows: 1. Carbon dioxide (CO2) extinguishers are effective on class B and C fires because they cool and displace oxygen. 2. Dry chemical fire extinguishers are effective on class A, B, and C fires because they displace oxygen. 3. Foam fire extinguishers are used to control flammable liquid fires. The foam forms an effective barrier between the flammable liquid and the oxygen needed for combustion. Foam extinguishers are effective on class A and B fires. 4. Halon fire extinguishers are designed for use on class A, B, and C fires. 5. Water fire extinguishers are designed for use on class A fires only. Figure 3–5 shows some common fire extinguishers.

3.16

HAZWOPER

The term HAZWOPER is used to describe OSHA’s hazardous waste operations and emergency response standard. HAZWOPER is broken down into the following areas:

• • •

82

Emergency response—first responder awareness level, first responder operations level Hazardous waste operations—incident command system, scene safety and control, spill control and containment, decontamination procedures, emergency termination or all-clear notification Hazard protection, prevention, and control – terms and definitions – PPE levels – identification of hazardous materials – hazards initiating an emergency response – avoiding hazards – entry of hazardous materials into the body – unit monitors and field survey instruments

3.17 Hearing Conservation and Industrial Noise

Discharge Lever Pin Carrying Handle Carbon Dioxide Discharge Horn

Fuel Heat

Oxygen Pick-up Tube

Discharge Lever

Discharge Lever

Carrying Handle

Cap

Puncturing Lever

Handle Pick-up Tube

CO2 Nozzle

Dry Chemical

Dry Chemical

Figure 3–5 Fire Extinguishers

3.17 Hearing Conservation and Industrial Noise When OSHA was enacted in 1970, federal regulations for controlling noise in the workplace were implemented. This new standard has two major components: (1) maximum noise exposure, and (2) actions that employers must take if the limits are exceeded. Under this standard, employers must:

• • •

Reduce noise using engineering and administrative controls. Provide hearing protection for employees. Implement a hearing conservation program (HCP): – monitor sound levels – conduct audiometric tests – provide hearing protection – provide training 83

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3.18 Department of Transportation Shipments of hazardous materials are regulated by the U.S. Department of Transportation (DOT) (Figure 3–6). The DOT regulations contain specific information on how hazardous materials are to be identified, placarded, documented, labeled, marked, and packaged. Hazardous material shipments that are not in compliance with federal regulations will be delayed, and noncompliance can result in severe penalties. In civil cases, marking the wrong name on a container can incur fines of up to $25,000 per violation. In criminal cases, fines of up to $500,000 and five years in jail can be imposed for intentionally shipping a hazardous chemical and attaching the wrong MSDS. Materials are classified for transportation using nine different categories: 1. Explosive 6. Poisonous and Infectious Materials 2. Gases 7. Radioactive Materials 3. Flammable Liquids 8. Corrosive Materials 4. Self Reactive 9. Miscellaneous Hazardous Materials 5. Oxides and Peroxides

Summary Safety, health, and environment training includes initial and continuous training and the employment of safety systems that are carefully integrated into everyday operation. Some of these systems include permits, personal protective equipment, firefighting, hazard communication, HAZWOPER, and process safety management. OSHA and the EPA developed the process safety management (PSM) standard to prevent the catastrophic release of toxic, hazardous, or flammable materials that could lead to a fire, explosion, or asphyxiation. Several critical elements of the PSM standard include employee training, operations procedures, process safety, employee participation, and hot work. A fundamental principle of the chemical hazard communication (HAZCOM) program is that informed people are less likely to be injured by chemicals and chemical processes than uninformed people. A chemical hazard communication program is composed of both information and training. Chemical exposure comes from inhalation, ingestion, injection, and/or absorption (skin contact). Personal protective equipment provides an effective means for protecting technicians from hazardous situations. Engineering and environmental controls provide another layer of protection. The primary purpose of PPE is to prevent exposure to hazards when engineering or environmental controls cannot be used. Process technicians use two basic types of respirators: air purifying and air supplying. Hearing conservation regulations have two major components: maximum noise exposure and actions employers must take if the limits are exceeded. The types of permits used in the chemical processing industry include cold work permits, hot work permits, opening/blinding permits, permits to enter, unplugging permits, energy isolation procedures, and lock-out, tag-out procedures. Fires are classified as Class A, B, C, or D. The most common fire extinguishers found in industry are CO2, dry chemical, foam, halon, and water fire extinguishers. 84

Summary

POISON GAS 2

OXYGEN

FLAMMABLE GAS 2

2

NON-FLAMMABLE GAS

ORGANIC PEROXIDE

5

2

PLACARDS POISON

COMBUSTIBLE

FLAMMABLE

CORROSIVE

OXIDIZER

8

5

6 3

3

NFPA DIAMOND

4

HEALTH HAZARD

SHIPPING PAPERS

3

SHIPPER'S DECLARATION FOR DANGEROUS GOODS Shipper

2 W

Air Waybill No. Bigg Chemical Co. 4500 Baker Drive Baytown, TX 77520

SPECIFIC HAZARD

Page 1 of 1

FIRE HAZARD

REACTIVITY HAZARD

Consignee

HMIS SYSTEM

Mr. John Doe 1987 Macbeth Salt Lake City, UT 84501

Chemical Name WARNING Failure to Comply in all respects with the applicable Dangerous goods Regulations may be a breach of the applicable law, subject to legal penalties.

Transport Details Passenger and Cargo

Cargo Aircraft only

Shipment Type

Airport of Destination

NON-RADIOACTIVE

HEALTH

2

FLAMMABILITY

0

REACTIVITY

1

PERSONAL PROTECTION

E

RADIOACTIVE

PROPER SHIPPING NAME CLASS

ID

SubRisk

QUANTITY TYPE OF PACKING

PACKING INSTRUCT

AUTHORIZATION

THE DOT SYSTEM ADDITIONAL HANDLING INFORMATION

Name/ Title I hereby declare that the contents of the consignment are fully and accurately described above by proper shipping name and are classified, packed, marked and labelled, and are in all respects in the proper condition for transport by air according to the National Regulations.

Place & Date

1. 2. 3. 4. 5.

Material Classification Shipping Papers Labeling Placarding Emergency Response

Signature

Figure 3–6 DOT Labels, Signs, and Placards

The term HAZWOPER describes OSHA’s hazardous waste operations and emergency response standard. HAZWOPER covers the areas of emergency response; hazardous waste operations; and hazard protection, prevention, and control. Shipments of hazardous materials are regulated by the U.S. Department of Transportation. DOT regulations contain specific information on how hazardous materials are identified, placarded, documented, labeled, marked, and packaged. 85

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Chapter 3 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

86

Describe the basic principles of process safety management. Describe the important features of the HAZCOM program. Describe the important features of HAZWOPER. What personal protective equipment does a process technician typically wear? What is the respiratory protection standard? What three agencies are primarily responsible for administration of the Occupational Safety and Health Act? What is the Occupational Safety and Health Administration? Describe the major features of the PSM standard and explain its importance. What is emergency response? What is toxicology, and how are dose and response important? Describe the role of the DOT in ensuring the safety of hazardous materials. What is a physical hazard? Identify the physical properties of and hazards associated with handling, storing, and transporting chemicals. What is a fundamental principle of the chemical hazard communication program? What are the two basic types of air-purifying respirators? What are the basic types of air respirators? Describe the key elements of the permit system. What do you think are the 10 most important general safety rules for a chemical plant? What are the critical elements of hearing conservation, including the employer’s responsibilities? What do you think is the most important safety rule?

Applied Physics One After studying this chapter, the student will be able to: • • • • •

Describe key terms and definitions used in basic process principles. Describe and apply the basic principles of pressure. Perform pressure calculations. Analyze the scientific principles of heat, heat transfer, and temperature. Perform simple temperature conversions between the Fahrenheit, Celsius, Kelvin, and Rankine scales. • Examine and apply the principles of fluid flow in process equipment. • Solve basic mathematical problems encountered in industry.

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Key Terms Absorbed heat—transferred heat; effects include increase in volume and temperature, change of state, electrical transfer, and chemical change. Algebra—a branch of mathematics that uses letters to represent numbers and signs to represent operations. It is a kind of universal arithmetic or, more simply, mathematics using letters. Bernoulli’s principle—states that in a closed process with a constant flow rate, changes in fluid velocity (kinetic energy) decrease or increase pressure; kinetic-energy and pressure-energy changes correspond to pipe-size changes; pipe-diameter changes cause velocity changes; and pressure-energy, kinetic-energy (fluid velocity), and pipe-diameter changes are related. Boyle’s law—at a constant temperature, the volume of a gas is inversely proportional to its pressure. V1 P  2 V2 P1

P1 V1  P2 V2

or

Charles’s law—at a constant pressure, the volume of a gas is proportional to its absolute temperature. V1 T1  V2 T2

or

V1 ___ T1

V T2

 ___2

Dalton’s law—states that the total pressure of a gas mixture is the sum of the pressures of the individual gases: Ptotal  P1  P2  P3 Fluid flow—flow characterized by fluid particle movements (e.g., laminar or turbulent). Heat—a form of energy caused by increased molecular activity. Heat transfer—transmission of heat through conduction (heat energy transferred through a solid object; e.g., a heat exchanger), convection (heat transferred by fluid currents from a heat source; e.g., the convection section of a furnace or the economizer section of a boiler), or radiation (heat energy transferred through space by means of electromagnetic waves; e.g., the sun). Ideal gas law—combination of Boyle’s and Charles’s laws, expressed as: P1V1 PV  2 2 T1 T2 Liquid pressure—the pressure exerted by a confined fluid. Liquid pressure is exerted equally and perpendicularly to all surfaces confining the fluid. Mathematics—field dealing with numbers and number operations. Process technicians use a variety of mathematical and scientific functions to perform their jobs. Some of the terms used in this area include: • addition—a term applied to a mathematical operation for combining numbers. • conversion tables—charts that display equivalent units of measure. 88

4.1 Basic Principles of Pressure

• decimal point—the period or “dot” between whole numbers and fractional numbers. • denominator—the bottom number in a fraction. • dimensional analysis—conversion within one system of units or to another system of units. Example: changing English-system feet to International System (SI) meters. • division—a mathematical operation for determining how many times one number or quantity is contained in another number or quantity. • divisor—the number by which one is dividing. • fraction—a part of a whole amount. • grouping symbols—signs used to separate functions in an equation. • lowest common denominator (LCD)—the smallest whole number that can be used to divide two or more denominators. • mixed number—a whole number and a fraction. • multiplication—the process of adding a number to itself a specified number of times. • numerator—the top number in a fraction. • percent—a fractional amount expressed in terms of parts per one hundred. • subtraction—a mathematical operation in which one number is deducted from another. Pascal’s law—pressure in a fluid is transmitted equally in all directions, molecules in liquids move freely, and molecules are close together in a liquid. Pressure—force or weight per unit area (Force  Area  Pressure); measured in pounds per square inch. Temperature—the hotness or coldness of a substance.

4.1 Basic Principles of Pressure Pressure is defined as force or weight per unit area (Force  Area  Pressure). The term pressure is typically applied to gases or liquids. Pressure is measured in pounds per square inch (psi). Atmospheric pressure is produced by the weight of the atmosphere as it presses down on an object resting on the surface of the earth. “The earth is surrounded by a fluid consisting of 78% nitrogen and 21% oxygen. Pressure at the top of this fluid, “air” is measured at zero psia and 14.7 psia (1.3 kPa) at sea level. Figure 4–1 illustrates this point. The higher the atmosphere, or gas, or liquid, the greater the pressure at the bottom. In a liquid, pressure is not dependent upon the shape or size of the vessel or pipe. Figure 4–2 illustrates this point. Pressure is equal to the force divided by the area. A simple equation can be used to calculate pressure in a process system. Height  .433  specific gravity  pressure. Any additional pressure or force above the liquid must be added to the answer. Vapor pressure, nitrogen blankets, or control pressures are examples of variables that should be added into the total pressure. The factor of .433 was developed using the equation P  F  A. Figure 4–3 illustrates how this factor was developed. Specific gravity for a substance is also calculated using the water standard. For example: 1 gallon of water weighs approximately 8.33 pounds. 8.33  8.33  1. The specific gravity of water is 1. Other substances have different weights. For example, if 1 gallon of a substance weighs 6.5 pounds, it’s specific gravity can be calculated by dividing 6.5 pounds by 8.33 pounds  .78. The specific gravity of this new substance is .78. Using this simple approach the specific gravity of any substances can be calculated. 89

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Applied Physics One Vacuum of Space 0 psi

Atmospheric Pressure

Atmosphere 78% Nitrogen

14.7 psi

21% Oxygen

Figure 4–1 Atmospheric Pressure

Liquid Level

Pi

Pi

Pi

Pi

Pi

Pi

Figure 4–2 Shape vs. Pressure Figure 4–4 illustrates how a simple pressure calculation is performed by a technician. Two of the most common types of pressure are atmospheric and hydrostatic. Atmospheric pressure is the force exerted on the earth by the weight of gases that surround it. Pressure decreases with altitude because of the reduced height (weight) of the gas. Hydrostatic pressure is the pressure exerted on a contained liquid and is determined by the depth of the liquid. Even a novice swimmer is familiar with pressure differences between the surface of the water and bottom of the pool. This pressure difference is what causes your ears to pop as you drive over a mountain in Colorado (atmospheric) or swim to the bottom of a 10’ pool (hydrostatic).

Boiling Point and Vapor Pressure The boiling point of a substance is the temperature at which the vapor pressure exceeds atmospheric pressure, bubbles become visible in the liquid, and vaporization begins. 90

4.1 Basic Principles of Pressure

(Force) Weight = 62.4 lbs 1 cubic foot of water

P=F÷A

Area 12" X 12" = 144"

12" 12" P = 62.4 lbs. 144 P = .433. Figure 4–3 Pressure Equation Molecular motion in water vapor produces pressure; both motion and pressure increase as heat is added to the liquid. The vapor pressure of a substance is directly linked to the strength of the molecular bonds of a substance. The stronger the bonds or molecular attraction, the lower the vapor pressure. If a substance has a low vapor pressure, it will have a high boiling point. For example, gold changes from a solid to a liquid at 1,947°F (1,064°C) and boils when the temperature reaches 5,084°F (2,807°C). Water changes from a solid to a liquid at 32°F (0°C ) and boils when the temperature reaches 212°F (100°C). Liquids need not reach their boiling points to begin the process of evaporation. For example, a pan of water placed outside on a hot summer day (98°F [36.66°C]) will evaporate over time. The sun increases the molecular activity of the water vapor, and some of the molecules escape into the atmosphere.Wind currents enhance the process of evaporation by sweeping away water molecules in vapor that are replaced by other water molecules.

Pressure Impact on Boiling Pressure directly affects the boiling point of a substance. As the pressure increases:

• • • •

The boiling point increases The escape of molecules from the surface of the liquid is reduced The gas or vapor molecules are forced closer together The vapor phase above a liquid could be forced back into solution 91

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height X .433 x specific gravity = 45’ X .433 x .69 = 13.4 psi + 12 psi = 25.4 psi PIC

I

P

12 psi Flare FC

FE I

I P

P

FIC

FT

FT

PT

FIC

PE 0

0 0

0 0 0

0

0 0 0

0

0

0

0

0

0

0 0

Specific Gravity .69

30’-0” 15’-0”

Pi

30’-0”

Pi

Pump

Figure 4–4 Simple Pressure Calculation

These are important facts for a process technician to understand. A change in pressure shifts the boiling points of raw materials and products. Pressure problems are common in industrial manufacturing environments and must be controlled.

Vacuum Atmospheric pressure is 14.7 psi. Any pressure below this is referred to as a vacuum, even if the pressure is not completely absent (zero). Vacuum affects the boiling point of a substance in the opposite way that positive pressure does. 92

4.1 Basic Principles of Pressure Vacuum systems:

• • • • •

Lower the boiling point of a substance Enhance the molecular escape of a liquid Reduce energy costs Reduce molecular damage due to overheating Reduce equipment damage

Pascal’s Law Blaise Pascal was a French scientist who discovered that pressure in a fluid is transmitted equally in all directions. Pascal successfully described the effects of pressure in a liquid and established the scientific foundation for hydraulics. Key facts for process technicians to remember in regard to Pascal’s law are that pressure in a fluid is transmitted equally in all directions, molecules in liquids move freely, and molecules are close together in a liquid.

Boyle’s Law Robert Boyle was an Irish scientist who developed the law that describes how the volume of a gas responds to pressure changes. Key facts for process technicians to remember in regard to Boyle’s law are that pressure decreases volume and moves gas molecules closer together; the higher the pressure, the smaller the volume; and gas volume decreases by one-half when pressure doubles. Boyle’s law can be written as: P1V1  P2V2.

Determining Pressures Produced by Liquids The pressure a liquid exerts on a container is determined by the height (amount) and density of the fluid. The pressure exerted by a 20-foot (ft) column of mercury would be more than that exerted by a 20-foot column of water, because the specific gravity of mercury (Hg) is much higher than that of water.

Pressure Problems Pressure problems can be correctly calculated by using the following formula: Pressure  Force  Area EXAMPLE 1: Stone Calculate the pressure produced by a 1,000-pound (lb.) stone block (see Figure 4–5) that is 20 inches long and 20 inches wide.

20 in.

1,000 lb 20 in. 20 in.

Figure 4–5 Stone Block 93

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Solution:

The area occupied by the stone 20-in. length  20-in. width Pressure  1,000  400 The psi at the base of the stone

   

400 sq in. 400 sq in. 2.5 psi 2.5 psi

EXAMPLE 2: Water Calculate the pressure produced by one cubic foot of water (62.4 lb) in a vessel that is 1 foot high, 1 foot long, and 1 foot wide. Solution:

1-ft length  1-ft width  1-ft height  1 sq ft or 144 sq in.  62.4 lb H2O 1-ft3 H2O Pressure  62.4  144  0.433 psi

Note: Each additional foot of water will add 0.433 psi. A common formula used to figure pressure is: Height  0.433  Specific Gravity  Pressure EXAMPLE 3: Gasoline Calculate the pressure produced by 1 cubic foot of gasoline (0.75 specific gravity [sg]) in a vessel that is 1 foot long, 1 foot high, and 1 foot wide. Solution:

1-ft length  1-ft width  1-ft height  1 sq ft or 144 sq in.  62.4 lb H2O  0.75 sg Pressure  47  144  0.327 psi

Note: Each additional foot of gasoline will add 0.327 psi. EXAMPLE 4: Water Calculate the pressure produced by water (62.4 lb) in a 6-ft high vessel. Solution:

Now try:

1 sq ft or 144 sq in.  62.4 lb H2O 62.4 lb  6 ft  144 sq in.  2.6 psi Height  0.433  Specific Gravity  Pressure 6 ft  0.433  1  2.6 psi

EXAMPLE 5: Water Calculate the pressure produced by water (62.4 lb) in a 200-ft-high vessel. Solution:

200 ft  0.433  1  86.6 psi

EXAMPLE 6: Gasoline Calculate the pressure exerted on the bottom of a 20-ft distillation column filled with gasoline. Add 100 psi to the column, giving a top gauge reading of 100 psi. What will be the bottom gauge reading in psi? Solution:

To calculate the bottom pressure of the distillation column, two variables must be considered: The pressure of the gasoline  20 ft  0.433  0.75  6.5 psi Plus the pressure added to the column: 100 psi. The answer is 6.5 psi  100 psi  106.5 psi.

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4.1 Basic Principles of Pressure

4.33 3.46 2.6 1.732 0.866

Density 62.4 lb cu ft

Density 840.7 lb cu ft

Density 47 lb cu ft

12 11 10 9 8 7 6 5 4 3 2 1

12 11 10 9 8 7 6 5 4 3 2 1

12 11 10 9 8 7 6 5 4 3 2 1

3.9 3.03 2.17 1.299 0.433 psi per ft

WATER

59 psi

29.5 psi

5.9 psi

MERCURY

3.27 psi

1.64 psi

P R E S S U R E

0.327 psi

GASOLINE

Figure 4–6 Liquid Pressure Principles 1, 2, 3

EXAMPLE 7: Gasoline Calculate the pressure exerted on a 20-ft column filled with 10 ft of gasoline. The vapor pressure of gasoline at 100°F is 12 psi. Solution:

10 ft  0.433  0.75  3.25 psi 3.25  12 psi  15.25 psi The answer is 15.25 psi.

Principles of Liquid Pressure The principles of liquid pressure are (see Figures 4–6 and 4–7): 1. 2. 3. 4. 5. 6.

Liquid pressure is directly proportional to the density of the liquid. Liquid pressure is proportional to the height (amount) of the liquid. Liquid pressure is exerted in a perpendicular direction on the walls of a vessel. Liquid pressure is exerted equally in all directions. Liquid pressure at the base of a tank is not affected by the size or shape of the tank. Liquid pressure transmits applied force equally, without loss, inside an enclosed container.

Absolute, Vacuum, and Gauge Pressure Three different types of pressure gauges can be found in industrial environments: absolute (psia), gauge (psig), and vacuum (psiv) (see Figure 4–8). Absolute pressure is equal to gauge pressure plus local atmospheric pressure (at sea level, 14.7 psi). Gauge pressure is equal to the absolute pressure minus the local atmospheric pressure (at sea level, 14.7 psi). Vacuum is measured typically in inches of mercury (in. Hg). Any pressure below atmospheric pressure (14.7 psi) is referred to as vacuum.

Gases and Pressure Liquids typically are considered to be noncompressible even though a 10% decrease in volume can be observed when a pressure of 65,000 psi is applied. Gases behave much differently than liquids. Gases are very compressible. The volume of a gas is determined by the shape of the 95

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30 ft

30 ft

30 ft

WATER 13 psi

WATER 13 psi

WATER 13 psi

Applied force transmitted equally without loss

30 ft

Pressure exerted equally in all directions

WATER

Figure 4–7 Liquid Pressure Principles 4, 5, 6 GAUGE

ABSOLUTE

PSIG = PSIA - 14.7

PSIA = PSIG + 14.7

5 0

10 15 20

PSIG

5 0

VACUUM

10 15 20

PSIA

0 15

10 30 30 PSIV

Figure 4–8 PSIA–PSIG–PSIV vessel containing it, the temperature, and the pressure. Operators use these three factors in the control and storage of gases.

Gas Laws Dalton’s law (Ptotal  P1  P2  P3) states that the total pressure of a gas mixture is the sum of the pressures of the individual gases. In the distillation process, Dalton’s law can be applied by a process technician to each individual tray in a plate column system. Distillation is a process that separates the components in a mixture by their individual volatilities or boiling points. The larger the difference between the partial pressures, the easier it is to separate the fractions by boiling point. Each tray in a distillation column has a different molecular structure and the vapors above the liquid will be composed of the vaporized fractions moving up the column. Lighter components will exert a higher pressure. According to Dalton’s law, each tray will have a different pressure. These pressures can be 96

4.1 Basic Principles of Pressure

ºF ºF %

SP PV OP% TE

TT

DPT

Dalton’s Law Partial Pressures

Tray #10

TIC TE Tray #9

FIC

I

PI

TE

P

Tray #8

FIC

FT TE

FE

FT

Feed Tray #7 FO

Feed Mix Benzene 50% Hexane 25% Heptane 25%

Vapor Pressure @ 175ºF 14.7 psia @ 175ºF 20.6 psia @ 175ºF 8.8 psia @ 175ºF

175ºF

TE

Benzene 50% Hexane 35% Heptane 15%

Benzene 50% 14.7 X .05 = 7.35 psia Hexane 25% 20.6 psia X .25 = 5.15 psiaF Heptane 25% 8.8 psia X .25 = 2.2 psia

Tray #6

Ptotal = 7.35 + 5.15 + 2.2 Ptotal = 14.7 psia

Figure 4–9 Dalton’s Law of Partial Pressures calculated if we know the original feedstock composition and the vapor pressures of the individual components at a set temperature. For example, a feedstock containing 25% hexane, 50% benzene, and 25% heptane will exert partial pressures at different temperatures that can be added up to give the total pressure. The equation (Ptotal  P1  P2  P3) can be used to identify what the total pressure is on tray #6 in Figure 4–9. One of the primary components in the mixture, benzene, is represented in Figure 4–10. Benzene is the most common aromatic hydrocarbon. It has six carbon atoms connected in a ring; each carbon atom has four carbon bonds, three used and one free. Substance

Vapor Pressure @ 175°F in PSIA

Hexane

20.6 PSIA  .25  5.15 PSIA

Benzene

14.7 PSIA  .50  7.35 PSIA

Heptane

8.8 PSIA  .25  2.2 PSIA

14.7 PSIA (Ptotal)  5.15 (P1)  7.35 (P2)  2.2 (P3) Original

BP

Hexane C6H14

5.15  14.7  .35  100  35%

25%

69°C

Benzene C6H6

7.35  14.7  .5  100  50%

50%

?

Heptane C7H16

2.2  14.7  .15  100  15%

15%

98°C 97

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H

H

H

H

H H

H

C

H

C

C

C

C H

H H

Benzene- a total of six electrons can be found in the donut-shaped clouds.

C H

Figure 4–10 True Benzene Ring

Charles’s law states that a constant pressure, the volume of a gas is proportional to its absolute temperature. (At a constant pressure the volume will increase as the temperature increases, or decrease as the temperature decreases.)

V1 T1  V2 T2

or

V1  V 2 ___ ___ T1 T2

Charles’s law and Boyle’s law can be combined into a single formula called the ideal gas law (PV  nRT ), which calculates the pressure, temperature, volume, or moles of any gas.

P  pressure of the gas V  volume n  moles of gas T  temperature in Kelvins (K) R  ideal gas constant (0.08206 L  atm/mol  K) The combined gas law calculates changes in a gaseous substance from one condition to another and is expressed as:

P1V1 PV  2 2 T1 T2 As an example of Charles’s law, let us start by blowing up a balloon to a volume of 1 liter at 28°C and then cool the balloon to 10°C. What is the volume of the balloon when the gas cools? The problem can be solved using the same kind of ratio used with Boyle’s law. Since V1  k  T1 and V2  k  T2, the relationship is expressed as:

V2 T2  V1 T1 98

4.2 Heat, Heat Transfer, and Temperature

T1 is calculated by converting 28°C to K. 28°C  273  301K. T2 is 10°C  273  283K. V2 283K  1L 301K V2  1L  283/301  .94L  940mL According to Charles’s law and the kinetic molecular theory of gases, a gas held at a steady pressure will increase in volume as the temperature increases or will decrease in volume as the temperature decreases.

4.2 Heat, Heat Transfer, and Temperature Heat is a form of energy caused by increased molecular activity. A basic principle of heat states that it cannot be created or destroyed, only transferred from one substance to another. Heat moves from warmer areas to colder areas, transferring energy as it goes. This process continues until the heat energy has been equally distributed. A stone thrown into a still pool of water sends ripples out in all directions; heat energy moves in a similar pattern. Heat is measured in energy units called British thermal units (Btus). A Btu is the amount of heat needed to raise one pound of water one degree Fahrenheit. Another common unit used in industrial manufacturing is the calorie. One calorie is roughly equal to the heat energy required to raise the temperature of one gram of water one degree Celsius. The effects of absorbed heat are: • Increase in volume • Increase in temperature • Change of state (solid, liquid, gas) • Chemical change (matches) • Electrical transfer (thermocouple) Heat comes in a variety of forms: • Sensible heat—heat that can be sensed or measured; increase or decrease in temperature Latent heat—hidden heat that does not cause a temperature change • • Latent heat of fusion—heat required to melt a substance; heat removed to freeze a substance • Latent heat of vaporization—heat required to change a liquid to gas • Latent heat of condensation—heat removed to condense a gas • Specific heat—the Btus required to raise one pound of a specific substance by 1°F. Heat transfer occurs in different ways. Heat is transmitted through:

• • •

Conduction—occurs when heat energy is transferred through a solid object (e.g., a boiler) Convection—occurs when fluid currents transfer heat from a heat source (e.g., upper convection section of a furnace) Radiation—occurs when heat energy is transferred through space by means of electromagnetic waves (e.g., the sun) 99

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˚F

˚R 672˚R

K

˚C

212˚F

100˚C

373 K

Water boils

492˚R

32˚F

273 K

0 ˚C

Water freezes

0˚R

-460˚F

-273˚C

0K

ABSOLUTE ZERO Fahrenheit = F Rankine = R Celsius = C Kelvin = K

Figure 4–11 Temperature Scales Temperature By measuring the hotness or coldness of a substance, we determine temperature. Process operators use a variety of temperature scales (see Figure 4–11). The four most common systems are described here: Scale

Water Boils

Water Freezes

Conversion Formula

Kelvin (K)

373 K

273 K

K  °C  273

Celsius (°C)

100°C

0°C

°C  (°F  32)  1.8

Fahrenheit (°F)

212°F

32°F

°F  1.8°C  32

Rankine (°R)

672°R

492°R

°R  °F  460

Key Points to Remember

• • • •

Heat is a form of energy caused by increased molecular activity; it cannot be created or destroyed, only transferred from one substance to another. The hotness or coldness of a substance determines the temperature. Heat is measured in Btus; temperature is measured by one of the temperature scales (e.g., K, C, F, or R). Temperature and heat are not the same.

4.3 Fluid Flow Modern industrial process plants are connected by a complex network of pipes, valves, pumps, and tanks. Centrifugal and positive displacement pumps are used to transfer fluids from place to 100

4.3 Fluid Flow place inside and outside the plant. The combination of pumps and pipes closely resembles the way the human heart pumps fluid into arteries and veins. Fluids assume the shape of the container they occupy. A fluid can be a liquid or a gas. When a liquid is in motion, it remains in motion until it reaches its own level or is stopped. Fluid flow is a critical concept used in the day-to-day operation of all plants. Flow rate  Volume  Time Example: FR  6.0 gallons  2.5 minutes FR  2.4 gpm

Bernoulli’s Principle The Swiss scientist Daniel Bernoulli developed a key scientific principle for fluid flow. Bernoulli’s principle states that in a closed process with a constant flow rate, changes in fluid velocity (kinetic energy) decrease or increase pressure; kinetic-energy and pressure-energy changes correspond to pipe-size changes; pipe-diameter changes cause velocity changes; and pressure-energy, kinetic-energy (or “fluid velocity”), and pipe-diameter changes are related. Reynolds Number 

(Velocity of Fluid) (Inside Diameter of Pipe) (Density of Fluid) (Absolute Viscosity of Fluid)

Viscosity Another term commonly used in industry to describe the flow characteristics of a substance is viscosity (see Figure 4–12). Viscosity is defined as a fluid’s resistance to flow.

Density Industry uses four different ways to express a fluid’s heaviness: density, specific gravity, baume gravity, and API gravity.

Water

Lube Oil

Figure 4–12 Viscosity 101

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The density of a fluid is defined as the mass of a substance per unit volume. Density measurements are used to determine heaviness. For example, one gallon of water weighs 8.33 lb, one gallon of crude oil weighs 7.20 lb, and one gallon of gasoline weighs 6.15 lb.

Specific Gravity Specific gravity (sg) is defined as the ratio of a fluid’s density (liquid or gas) to the density of water or air. It is common for operators to confuse specific gravity with density. This mistake is easy to understand, because specific gravity is a method for determining the heaviness of a fluid. Density is the heaviness of a substance. Specific gravity compares this heaviness to a standard and then calculates a new ratio. Most hydrocarbons have a specific gravity below 1.0.

Key Points to Remember

• • • • •

Density is calculated by weighing unit volumes of a fluid at 60°F (15.55°C). The density of one gallon of water is 8.33 lb/gal. The density of air is 0.08 lb/cu ft. The specific gravity of water is 8.33 lb/gal  8.33  1.0. The specific gravity of gasoline is 6.15 lb/gal  8.33  0.738.

Baume Gravity Baume gravity is the standard used by industrial manufacturers to measure nonhydrocarbon heaviness.

API Gravity The American Petroleum Institute (API) applies gravity standards to measure the heaviness of a hydrocarbon. A specially designed hydrometer, marked in units API, is used to determine the heaviness or density of a hydrocarbon. High API readings indicate low fluid gravity.

Turbulent and Laminar Flow Two major classifications of fluid flow are laminar and turbulent (see Figure 4–13). Laminar flow, or streamline flow, moves through a system in thin cylindrical sheets of liquid flowing inside one another. This type of flow has little, if any, turbulence in it. Laminar flow usually exists at lower flow rates. As flows increase, the laminar flow pattern breaks into turbulent flow. Turbulent flow is the random movement or mixing of fluids. Once turbulent flow is initiated, molecular activity speeds up until the fluid is uniformly turbulent. Turbulent flow allows molecules of fluid to mix more readily and absorb heat. Laminar flow promotes the development of static film, which acts as an insulator.Turbulent flow decreases the thickness of static film.

Forms of Liquid Energy Liquid energy may take the form of kinetic energy (fluid motion), pressure and potential energy (stored energy, liquid head, internal pressure), or heat energy (fluid friction).

102

4.3 Fluid Flow

Laminar flow

Turbulent flow

Laminar flow Restrictions and bends create turbulence Static flow

Figure 4–13 Laminar and turbulent flow

Fluid Energy Conversions

• • • • •

Steam turbine—steam-pressure energy is converted to kinetic energy; kinetic energy is converted to rotational or mechanical energy. Boiler—heat energy is transferred to water; water boils, creating steam energy. Steam energy creates pressure energy. Steam and pressure energy are used in distillation, heat exchangers, reactors, laminating, extrusion, and steam turbines. Furnace—heat energy is transferred to the charge. Distillation tower—heat energy is transferred to a feed, which separates the individual components by boiling point. Condensation and vaporization occur along the temperature gradient of the tower. Energy is converted into kinetic energy. As fluid slows, it is converted into pressure energy.

Measuring Flow Rate Flow rate (in gallons per minute or gpm) equals volume per unit of time. Velocity (in feet per second or fps, feet per minute or fpm, feet per hour or fph) equals distance per unit of time.

Flow of Solids A variety of gases are used to transfer solids from one location to another: nitrogen, air, chlorine, and hydrogen. When properly fluidized, solids respond like fluids. Solid transfer requires small, granular, porous solids that respond positively to aeration. Several examples of industry processes that use this procedure are modern plastics manufacturing (granules, powder, flakes), catalytic cracking units, and vacuum systems.

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4.4 Basic Math for Process Technicians Basic mathematics is typically encountered on the preemployment tests administered by most plants. Inability to handle simple mathematics functions appears to be the primary disqualifier for potential applicants. The widespread use of calculators and the years elapsed since eighth-grade mathematics require most people to review these rusty skills or risk being eliminated from the pool of applicants being invited to interview. Process technicians use a variety of mathematical and scientific functions to perform their normal job responsibilities. Some of these functions include:

Phase 1: Preemployment Skills Required

• • • • • • • • • • • • • • • • •

Addition Subtraction Multiplication Division Fractions (addition, subtraction, multiplication, and division) Decimals (addition, subtraction, multiplication, and division) Percents and percentages Averaging Mechanical aptitude Equations (algebraic expressions) Canceling Ratios Proportions (direct and inverse) Constants and variables Factors and factoring Exponents Grouping

Phase 2: On-the-Job Skills Required

• • • • • • • • • •

• • 104

Area Volume Volumetric flow rate X-Y graphs Bar graphs Pie graphs Strip charts Trends Word problems Pressure in fluids: – Force  Area  Height  Density – Pressure  Force  Area – Pressure  Height  Density Specific weight of liquid: – Weight of liquid  Weight of water Work, force, and distance: – W  Force  Density

4.4 Basic Math for Process Technicians

• • • • •

Mechanical advantage: – MA  Resistance  Effort Levers Boyle’s law: – P1V1  P2V2 Motion of bodies: – vst – s  vt Heat transfer

Phase 1: Preemployment Skills Mathematics is an important part of operating a process unit. Flow rates must be calculated, filling ratios checked, conversion tables used, additive recipes blended, and special equations applied to industrial processes. The following is a review of some basic mathematical skills and operations. 1.

1,545  2,000 3,545

2.

1,245  456 789

3. 8,768  234  37.47 4. Calculate the mean average of the following numbers: 125,678 2,345 234 1,429 STEP 1 125,678 2,345 234  1,429 129,686 STEP 2 129,686  4  32,421.5 5. 467,897  34  15,908,498 6. 0.4568  9,457  4,319.96 7. Convert 39 to a mixed number. 19 Divide 39 by 19; the answer is 2 1 . 19 105

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8. Convert 1 4 to a fraction. 8 1  8  4  the numerator 12  the numerator Put 12 over eight. The answer is 12. 8 9. 4  9 7 8 STEP 1 When adding or subtracting fractions, first find the lowest common denominator (LCD). Find a number that both 7 and 8 can divide into: 7  8  56 STEP 2 Write equivalent fractions with a common denominator. 4  32 9  63 7 56 8 56

STEP 3 Add the numerators.

STEP 4 Convert to a mixed number.

32  63  63 56 56 56

95  139 56 56

10. 9  9 2 4 STEP 1 When dividing fractions, invert the divisor. 9 inverted is 4. 4 9 STEP 2 Multiply. 9  4  36  2 2 6 18 STEP 3 Convert to a whole number. 36  2 18 11. 18  32  612  51  25 1 12 2 24 2 2 12. 4  3 3 9

106

STEP 1 Write equivalent fractions with a common denominator.

STEP 2 Subtract the numerators and convert.

12 4 3  9

12 3 9 9  9 9

4.4 Basic Math for Process Technicians 3 3 9  9

9 9 1

13. 123.678  0.0043  123.68 14. 454.67  12.34  36.85 15. A tank has a 1,400-lb mixture of water and salt in it. Of the mixture, 18% is salt. How many pounds of salt are in it? 1,400  0.18  252 lb of salt 16. Product Tank 1403 has a total capacity of 400,000 gal. At 1:00 AM, Tank 1403 has 60,000 gal in it. Your product pump is filling the tank at 2.2 gal/minute. How many hours (h) do you have before the tank runs over? STEP 1 400,000

STEP 2 2.2

STEP 3 340,000  132  2,575.75 h

17. (102)2  (10  10  100)2, 100  100  10,000 18. Convert 0.45 to a percentage. The answer is 45%. 19. Convert 115% to a decimal. The answer is 1.15. Algebra is used to solve many simple problems encountered by process technicians. Basic mathematics is useful but inadequate for all process problems. Algebra uses letters and symbols to represent variables that are known and unknown. This form of mathematics allows unknown variables to be identified by following well-defined principles.

Principle 1. An algebraic equation is structured like a balance scale. The products on the left equal the products on the right. For example: Solution:

6x  30 or 6 (?)  30 x5

Principle 2. When solving for unknowns, the opposite function must be used. Addition and subtraction are opposites, and multiplication and division are opposites. Solve for x: x52 x  5  5  2  5 (the opposite of addition is subtraction) x  3 The following are some practice problems for you to work through. 20. Solve for x: 4x  20 4x  20 4 4 x5 107

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21. Solve for x: x  10  14  3 x  10  10  11  10 x  21 22. Solve for x: 2x  8  x 2x  x  8  x  x x8 23. Solve for x: x  28 x 2282 x  10 24. Solve for x: x  14  16 x  14  14  16  14 x2 25. Solve for x: 3  6 (2  x)  45 3  12  6x  45 15  6x  45 15  15  6x  45  15 6x  30 6x  30 6 6 x  5

Phase 2: On-the-Job Skills A process technician has to deal with many volume issues on the job. The formulas in Figure 4–14 are used extensively in the CPI.

Height

di Ra

us

Radius

Width Length Volume = LWH

Volume =

4 3

πr 3

Figure 4–14 Volume Formulas 108

Volume =

πr 2h

Height

Summary 26. A rectangular tank is 30 ft long, 16 ft tall, and 6 ft wide. What is the volume of this tank?

V  LWH 30  16  6  2,880 27. A vertical tank is 30 ft tall with a diameter of 10 ft. Product level is 15 ft. What is the volume of the product?

V  4/3 r 2h V  3.1416  52  15 ft V  1,178.1 28. The product level in Drum 1201 was 950 cubic feet at 4:00 AM. At 8:00 AM, D-1201 has 1,950 cu ft of product. No fluid was removed from the drum. Calculate the flow rate into D-1201. (Refer to the volume formulas in Figure 4–14.)

Vin 

Vf  Vi t

1950  950  250 4

Summary Pressure is defined as force or weight per unit area (Force  Area  Pressure). The term is typically applied to gases or liquids. Pressure is measured in pounds per square inch. Pressure is directly proportional to amount: the more of the atmosphere, gas, or liquid, the greater the pressure. At sea level, atmospheric pressure equals 14.7 pounds per square inch. The boiling point of a substance is the temperature at which the vapor pressure exceeds atmospheric pressure, bubbles become visible in the liquid, and vaporization begins. Vapor pressure, which is the weight of a liquid’s vapor, is directly related to the strength of the molecular bonds of a substance. The stronger the bonds or molecular attraction, the lower the vapor pressure. If a substance has a low vapor pressure, it will have a high boiling point. As the pressure increases, the boiling point increases and the escape of molecules from the surface of the liquid is reduced proportionally. The vapor phase above a liquid could be forced back into solution. Any pressure below atmospheric pressure (14.7 psi) is referred to as a vacuum. Vacuum lowers the boiling point of a substance; enhances molecular escape of liquid; and reduces energy costs, molecular damage due to overheating, and equipment damage. Robert Boyle, an Irish scientist, developed the law that describes how the volume of a gas responds to pressure changes. The basic principles of Boyle’s law are: Pressure decreases volume and moves gas molecules closer together; the higher the pressure, the smaller the volume; and gas volume decreases by one-half when pressure doubles. Pascal’s law states that pressure in a fluid is transmitted equally in all directions, molecules in liquids move freely, and molecules are close together in a liquid. The pressure a liquid exerts on a 109

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container is determined by the height and the weight of the fluid (Height  0.433  Specific Gravity  Pressure). The principles of liquid pressure are: • Liquid pressure is directly proportional to the density of the substance. • Liquid pressure is proportional to the amount of the liquid. • Liquid pressure is exerted in a perpendicular direction on the walls of a vessel. • Liquid pressure is exerted equally in all directions. • Liquid pressure at the base of a tank is not affected by the size or shape of the tank. • Liquid pressure transmits applied force equally, without loss, inside an enclosed container. Three different types of pressure gauges are used in industrial environments: absolute (psia), gauge (psig), and vacuum (psiv). Absolute pressure is equal to gauge pressure plus local atmospheric pressure (14.7 psi). Gauge pressure is equal to the absolute pressure minus the local atmospheric pressure (14.7 psi). Vacuum is typically measured in inches of mercury. Any pressure below atmospheric pressure (14.7 psi) is called vacuum. Liquids are considered to be noncompressible; gases are very compressible. Dalton’s law (Ptotal  P1  P2  P3) states that the total pressure of a gas mixture is the sum of the pressures of the individual gases. Heat is a form of energy caused by increased molecular activity. A basic principle of heat is that it cannot be created or destroyed, only transferred from one substance to another. Heat moves from hot areas to cold areas, transferring energy as it goes. Heat is measured in energy units called British thermal units (Btus). A Btu is the amount of heat needed to raise one pound of water one degree Fahrenheit. The effects of absorbed heat are: • Increase in volume • Increase in temperature • Change of state (solid, liquid, or gas) • Chemical change (matches) • Electrical transfer (thermocouple) Heat comes in a variety of forms. Sensible heat can be sensed or measured. Temperature can be increased or decreased. Latent heat is hidden heat that does not cause a temperature change. Latent heat of fusion is required to melt a substance. Heat is removed to freeze a substance. Latent heat of vaporization is required to change a liquid to gas. Latent heat of condensation is required to condense a gas. Specific heat is the Btus needed to raise one pound of a specific substance one degree Fahrenheit. Heat is transmitted through conduction (transfer through a solid object), convection (transfer from a heat source through fluid currents), and radiation (transfer of energy through space by means of electromagnetic waves).

110

Summary By measuring the hotness or coldness of a substance, we determine temperature. Process operators use a variety of temperature systems. The four most common are Kelvin (K), Celsius (C), Fahrenheit (F), and Rankine (R). Temperature conversion formulas are available to be used by process technicians. A fluid can be classified as a liquid or a gas. When a liquid is in motion, it remains in motion until it reaches its own level or is stopped. Bernoulli’s principle states that in a closed process with a constant flow rate, changes in fluid velocity (kinetic energy) decrease or increase pressure; kinetic-energy and pressure-energy changes correspond to pipe-size changes; pipe-diameter changes cause velocity changes; and pressure-energy, kinetic-energy (fluid velocity), and pipe-diameter changes are related. Industry commonly uses the term viscosity to describe the flow characteristics of a substance. Viscosity is defined as a fluid’s resistance to flow. Process technicians use four different ways to express a fluid’s heaviness: density (the mass of a substance per unit volume), specific gravity (the ratio of a fluid’s density to the density of water or air), baume gravity (the standard used by industrial manufacturers to measure nonhydrocarbon heaviness), and API gravity (based on the American Petroleum Institute’s standards for measuring the heaviness of a hydrocarbon using API’s specially designed hydrometer; high API readings indicate low fluid gravity). Operators commonly confuse specific gravity with density. Density is the heaviness of a substance, whereas specific gravity compares this heaviness to a standard and then calculates a new ratio. Most hydrocarbons have a specific gravity below 1.0. Two major classifications of fluid flow are laminar and turbulent. Laminar or streamline flow moves through a system in thin cylindrical sheets of liquid flowing inside one another. Turbulent flow is the random movement or mixing of fluids. Turbulent flow allows molecules of fluid to mix more readily and absorb heat. Laminar flow promotes the development of static film, which acts as an insulator. Turbulent flow decreases the thickness of static film. Industrial forms of liquid energy include kinetic energy (fluid motion), pressure and potential energy (stored energy, liquid head, internal pressure), and heat energy (fluid friction). Process technicians use a variety of mathematical and scientific functions to perform their normal job responsibilities.

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Chapter 4 Review Questions 1. Bernoulli’s principle states that in a closed process with a constant flow rate: a. changes in fluid velocity (kinetic energy) decrease or increase pressure. b. kinetic-energy and pressure-energy changes correspond to pipe-size changes. c. pipe-diameter changes cause velocity changes. d. all of the above. 2. As the pressure increases inside a confined space: a. the boiling point increases. b. the escape of molecules from the surface of the liquid is increased proportionally. c. the gas or vapor molecules are forced closer together. d. a and c. 3. Solve for y: 62  13y  3 4. Solve for x : 2x  9 5. Pressure is directly proportional to: a. amount (height). c. specific gravity. b. sound. d. mathematics. 6. Atmospheric pressure is: a. 14.3 psi. c. 14.7 psi. b. 14.5 psi. d. 15.7 psi. 7. True or false? Heat and temperature are basically the same thing. 8. An example of fluid flow is: a. turbulent. c. kinetic. b. gravity. d. potential. 9. Boyle’s law describes how: a. the volume of a gas responds to pressure changes. b. pressure in a fluid is transmitted equally in all directions. c. the volume of a liquid responds to pressure changes. d. kinetic-energy and pressure-energy changes correspond to pipe-size changes. 10. True or false? A liquid need not reach its boiling point to begin the process of evaporation. 11. Calculate the pressure produced by a 2,000-lb stone block, 12-in. length  12-in. width  12-in. height Pressure  Force (weight)  Area 12. Calculate the pressure exerted on a 26-ft column filled with 13 ft of gasoline. The vapor pressure of gasoline at 100°F is 12 psi.

112

Equipment One After studying this chapter, the student will be able to: • Describe the basic hand tools used in industry. • Identify and describe the valves used in industry. • Describe the various types of storage and piping used in the chemical processing industry. • Identify the operation and primary components of centrifugal and axial pumps. • Explain the operation and types of positive displacement pumps. • Describe dynamic and positive displacement compressors. • Describe how a steam turbine works. • Describe the purpose of seals, bearings, and lubrication.

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Equipment One

Key Terms Basic hand tools—term used to describe the typical tools that process technicians use to perform their job activities. Compressor—a device designed to accelerate or compress gases. Compressors come in two basic designs: (1) positive displacement (rotary and reciprocating), and (2) dynamic (axial and centrifugal). Cyclone—a device used to remove solids from a gas stream. Demineralizer—a filtering-type device that removes dissolved substances from a fluid. Filter—device that removes solids from fluids. Lubrication system—system that includes a lubricant reservoir, pump, valves, heat exchanger, and piping. Piping—used in industry to safely contain and transport chemicals; composed of a variety of materials and configured in a variety of shapes and designs. Pumps—used primarily to move liquids from one place to another. Pumps come in two basic designs: (1) positive displacement (rotary and reciprocating), and (2) centrifugal. Steam trap—a device used to remove condensate from steam systems. Steam turbine—energy-conversion device that converts steam energy (kinetic energy) to useful mechanical energy. Steam turbines come in two basic designs: (1) condensing and (2) noncondensing. They are used as drivers to turn pumps, compressors, electric generators, and propeller shafts (e.g., on naval vessels). Strainer—a device used to remove solids from a process before they can enter a pump and damage it. Tanks—vessels that store and contain fluids. Tank designs include spherical, open-top, floating-roof, drum, and closed styles. Valve—a device designed to control (stop, start, or direct) the flow of fluids.

5.1 Basic Hand Tools Basic hand tools are the usual tools that process technicians typically use to perform their job activities (Figure 5–1). Union plants may have limitations on the type of work a process technician may perform. In these plants, the process technician may not be allowed to cross crafts and use hand tools except on a limited basis. In nonunion plants, hand tool usage plays only a minor role, as skilled craftspersons are available for complex jobs. However, process technicians are required to perform routine maintenance on their units, since most mechanical craftspersons work the day shift and leave the evening and night shifts open for callouts. When a callout is required, the company typically pays time and a half, so it gets expensive. Also, in addition to the money issue, it takes time for the maintenance staff to return to the work site. Because of these facts, many companies require routine maintenance on the off shift(s) to be 114

5.2 Valves

Flat head screwdriver (plain slotted) Pliers

Phillips screwdriver

Crescent wrench

Channel locks

Open end wrench

Open

Box Needle nose pliers

Pipe wrench

Figure 5–1 Basic Hand Tools handled by process technicians. In some cases, a little minor maintenance can prevent major equipment damage. Here is a list of some basic hand tools: Pliers Wire cutters Needle-nose pliers Channel locks Vice grips Phillips screwdriver Flat-head screwdriver Pipe wrench Crescent wrench Ratchet and socket sets Hammer Utility knife Chisels File Wire brush Hacksaw Level Allen wrenches Wrenches—metric, English, open, box, combination

5.2 Valves A valve is a device designed to control the flow of fluid through process piping. Following are some of the different types of valves that are used in industry. 115

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Gate Valves A gate valve places a movable metal gate in the path of a process flow in a pipeline. Gate valves come in two designs: (1) rising stem and (2) nonrising stem. Located at the top of a closed gate valve is the hand wheel. The hand wheel is attached to a threaded stem. As the hand wheel is turned counterclockwise, the stem in the center of the hand wheel begins to rise. This lifts the gate out of the valve body and allows product to flow. Another type of rising-stem valve is threaded at the bottom of the stem. In this type of valve, the hand wheel is firmly attached to the stem and rises with it as the valve is opened. A nonrising-stem gate valve has a collar that keeps the stem from moving up or down. The hand wheel is firmly attached to the stem of a nonrising gate. Turning the hand wheel screws the stem into or out of the gate. The basic components of a gate valve are illustrated in Figure 5–2.

Globe Valves A globe valve places a movable metal disc in the path of a process flow. This type of valve is the most common used for throttling service. The disc is designed to fit snugly into the seat and stop flow. Process fluid enters the globe valve and is directed through a 90-degree turn to the bottom of the seat and disc. As the fluid passes by the disc, it is evenly dispersed. Globe valves are designed to be installed in high-use areas. If a globe valve is installed in a lowuse area, it tends to plug up even if it has a self-cleaning design. Globe valves come in the following designs: typical globe valve with ball, plug, or composition element; needle valve; and angle valve. Globe valves and gate valves have very similar components, as illustrated in Figure 5–3.

Ball Valves Ball valves (see Figure 5–4) take their name from the ball-shaped, movable element in the center of the valve. Unlike a gate or globe valve, a ball valve does not lift the flow control device out of the process stream; instead, the hollow ball rotates into the open or closed position. Ball valves offer very little restriction to flow. Most can be opened 100% with a quarter turn of the valve handle,

Handwheel Yoke Bushing

Gland Bolt Bonnet Bonnet Bolt Nut Bonnet Bolt Body

Stem Bonnet Gasket Wedge Pin

Wedge

Seat Ring Gate

Figure 5–2 Gate Valve 116

Packing Stuffing Box

5.2 Valves

Hand Wheel Yoke Sleeve Stem Gland Flange Gland Bolt

Packing Gland

Stuffing Box

Packing Bonnet

Gasket

Body Disc Nut Disc

Inlet

Seat

Figure 5–3 Globe Valve

Joint Bolt

Washer Gland Bolt

Lever

Packing Stem

Washer Body

Seat

Ball Ball

Inlet Seat

Figure 5–4 Ball Valve although some larger valves require hand wheels and gearboxes for opening. In the closed position, the port is turned away from the process flow. In the open position, the port lines up perfectly with the inner diameter of the pipe.

Plug Valves Quick-opening, one-quarter-turn plug valves are very popular in the manufacturing industry. The plug valve takes its name from the plug-shaped flow control element it uses to regulate flow. Plug valves provide very little restriction on flow, and can be opened 100% with a quarter turn of the valve handle. In the closed position, the port is turned away from the process flow. In the open position, the port lines up perfectly with the inner diameter of the pipe. 117

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Equipment One

●

Bonnet Bolt

Bonnet

Bonnet

Gasket

Bonnet Nut Body

Guide Body

Ball Flow

Disc Flow Seat

Ball Check Valve

Lift Check Valve

Cover Nut Bonnet Gasket

Hinge Pin

Body

Flow

Disc Flow

Discharge

Stop Check Valve

Swing Check Valve

Figure 5–5 Check Valves

Check Valves A check valve (see Figure 5–5) is a type of automatic valve designed to control flow direction and prevent possible contamination or damage to equipment. The check valve will prevent backflow as long as the device is operating properly. Check valves come in a variety of designs and applications. Typical designs include:

• •

•

118

Swing check, which has a hinged disk that slams shut when flow reverses. Flow lifts the disc and keeps it lifted until flow stops or reverses. The body of the check valve has a cap for easy access to the flow control element. Lift check, which has a disc that rests on the seat when flow is idle and lifts when flow is active. Special guides keep the disc in place. Like the swing check, it is designed to close when flow reverses. Lift checks are ideal for systems where flow rates fluctuate. The lift check is more durable than a swing check. Ball check, which has a ball-shaped disc that rests on a beveled, round seat. The ball is down when flow is idle and up when flow is active. Special guides keep the ball disc in place. Like the swing check, it is designed to close when flow reverses. Ball checks are ideal for systems where flow rates fluctuate. The ball check is as durable as a lift check and more durable than a swing check.

5.2 Valves

•

Stop check, which combines design characteristics of both a lift check and a globe valve. In the closed position, the stop check disc is firmly seated. In the open position, the stem rises out of the body of the flow control element and acts like a guide for the disc. In the open position, the stop check valve functions like a lift check valve with one exception: The degree of lift can be controlled.

Butterfly Valve A valve commonly used for throttling and on-off service is a butterfly valve. The body of this type of valve is relatively small compared to other valves, and therefore it occupies much less space in a pipeline. The flow control element closely resembles a well-worn catcher’s mitt. A metal shaft extends through the center of the “mitt” and allows the disc to rotate one-quarter turn. A quarter turn is all it takes to open the valve 100%.

Diaphragm Valve In a chemical plant, a variety of corrosive or sticky substances is transferred from place to place. Standard valves would have a difficult time with this type of product, but diaphragm valves are specifically designed for the job. Diaphragm valves use a flexible diaphragm and seat to regulate flow. The hand wheel on this type of valve operates just like that on a gate or globe valve. The stem is attached to the center of a flexible diaphragm. The diaphragm rests on the seat. The internal parts of the valve never come into contact with the process. The diaphragm forms a seal and holds the seal until the process pressure overcomes the control pressure. Diaphragm valves are typically used in low-pressure applications. Diaphragm valves come in two designs:

• •

Weir diaphragm valve—has a weir located in the body of the valve. Flow must go over the top of the weir and lift the compressor to exit. There is a large pressure drop across the body of the valve. This valve uses thicker, more durable diaphragm material. Straight-through diaphragm valve—flexible diaphragm extends across the pipe. There is very little pressure drop across this type of valve.

Diaphragm valves handle corrosive fluids, have good throttling capability, and are used in lowpressure applications. These valves are used in operations that have moderate temperature and pressure fluctuations.

Relief Valves Relief valves are designed to respond automatically to sudden increases in pressure. A relief valve opens at a predetermined pressure. In a relief valve, a disc is held in place by a spring that will not open until system pressure exceeds its operating limits. Tremendous pressures can be generated in process units. When a system overpressurizes, safety valves respond to allow excess pressure to be vented to the flare header or atmosphere. This prevents damage to equipment and personnel. Relief valves are designed to open slowly, and thus are best for pressurized liquid service. They do not respond well in gas service, where quicker pressure reduction is needed.

Safety Valve Safety valves are considered to be a process system’s last line of defense. They are designed to respond quickly to excess vapor or gas pressure. This type of valve is very similar in design to a relief valve. The three major differences between a relief valve and a safety valve are (1) liquid versus gas service, (2) pressure response time, and (3) size of exhaust port. Relief valves are designed to lift slowly, whereas safety valves tend to pop off. Because the exhaust port is much larger 119

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Equipment One Adjustment Screw

Cap Release Lever

Lock Nut

Washer Stem or Spindle

Spring

Outlet

Huddling Chamber

Disc or Feather Seat

Body

Inlet

Figure 5–6 Safety Valve in a safety valve, it can release more flow at much lower velocities. This keeps the trim from being damaged. Figure 5–6 is an illustration of a safety valve.

Automatic Valves The chemical processing industry uses a complex network of automated systems to control its processes. The smallest unit in this network is called a control loop. Control loops usually have (1) a sensing device, (2) a transmitter, (3) a controller, (4) a transducer, and (5) an automatic valve. Automatic valves (see Figure 5–7) can be controlled from remote locations, making them

Air to Close

Actuator

Heavy Spring

Gland Flange Packing Gland

Gland Bolt Pin Stuffing Box

Wire Coil

Packing Bonnet

Gasket

Armature

Body Flow

Disc

Automatic Valve

Figure 5–7 Automatic Valves 120

Solenoid Valve

5.3 Piping and Storage Tanks invaluable in modern processing. Any of the valves described in this chapter can be automated. To automate a valve, a device known as an actuator is installed. The actuator controls the position of the flow control element by moving and controlling the position of the valve stem. Actuators can be classified as pneumatic, hydraulic, or electric.

5.3 Piping and Storage Tanks Industrial piping is composed of a variety of metals and other materials, and is configured in a variety of shapes and designs to safely contain and transport chemicals. The engineering design team carefully selects the types of materials that are compatible with the chemicals and operational conditions. Piping can be composed of stainless steel, carbon steel, iron, plastic, or specialty metals. Individual joints can be threaded on each end, flanged, welded, or glued. A wide array of fittings are used to connect piping. The various types of fittings include couplings, unions, elbows, tees, nipples, plugs, caps, and bushings. Figure 5–8 illustrates the various types of fittings and piping. The chemical processing industry uses a variety of tanks, drums, bins, and spheres to store chemicals. The most popular designs are shown in Figure 5–9. The materials used in these designs include carbon steel, stainless steel, iron, specialty metals, and plastic. Each vessel includes a code stamp that indicates high-pressure and temperature ratings, manufacturer, date, type of metal, storage capacity, and special precautions. Most vessels include strapping tables that allow a technician access to data that can be used to identify capacity. Aboveground storage vessels that have pressures greater than 15 psig are governed by the ASME Code, Section V111. Common storage designs include spheres, spheroids, horizontal cylindrical tanks (drums), bins, and fixed- and floating-roof tanks. Tanks, drums, and vessels are typically classified as low pressure, high pressure, liquid service, gas service, insulated, steam traced, or water cooled. Wall thickness and shape often determine the service for a stationary vessel. Some tanks are designed with internal or external floating roofs, double walls, dome or cone

90˚

Nipple

Tee

Elbow

Cap

45˚ Elbow

Bell Reducer

Bushing

Flange

Coupling

Plug

Union

Strainer

Figure 5–8 Pipe Fittings 121

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Equipment One

Spherical Storage Tank

Dome Roof Tank Open Top Tank

Sphere

Tank

Internal Floating Roof Tank

Horizontal Cylindrical Vessel

Drum

Double Wall Tank

Cone Roof Tank External Floating Roof

Bin

Tank

Figure 5–9 Tank Designs roofs, or open tops. Earthen or concrete dikes often surround a tank and are designed for containment in the event of a spill. Spherical and spheroidal storage tanks are designed to store gases or pressures above 5 psi. Spheroid tanks are flatter than spherical tanks. Figure 5–9 illustrates each of these designs. Horizontal cylindrical tanks or drums can be used for pressures between 15 and 1,000⫹ psig. Floatingroof storage tanks are used for materials near atmospheric pressure. In the basic design, a void forms between the floating roof and the product, forming a constant seal. The primary purpose of a floating roof is to reduce vapor losses and contain stored fluids. In areas of heavy snowfall, an internal floating roof is used in combination with an external roof, because the weight of the snow would affect the seal. Nitrogen blankets are also used to put pressure on the surface of a liquid and make the atmosphere inert. Vapor recovery systems are used to prevent hydrocarbons from escaping into the atmosphere. Process technicians often inspect their stationary vessels using the following methods: listen, touch, look, feel, and smell. An experienced technician can identify a problem by listening for abnormal sounds and vibrations. Touching the equipment allows a technician to identify unusual heat patterns. Visually inspecting tanks through the gauge hatch and sump levels allows a technician to look at a questionable tank and determine corrective action. Figure 5–10 shows a typical tank arrangement.

Filters The chemical processing industry has adopted the practice of using surface water for industrial applications instead of well water. When large quantities of water are pulled out of the ground, the upper layers of soil drop. Some residences in heavily industrialized areas have seen the ground 122

5.3 Piping and Storage Tanks

Figure 5–10 Tank Storage Raw Water

Freeboard Cullsan P Cullcite

Cullsan A

Two Layers Underbedding

Cullsan G50 Cullsan U Cullsan Medium

Filtered water

Figure 5–11 Filter level reduced so rapidly that their homes and businesses have been dropped below sea level and flooded. In higher locations, this process can cause foundations to shift or crack, damaging the overall structure. Because of this problem, chemical manufacturers bring water in from local rivers and lakes. The water is initially brought into a large water basin where sediments are allowed to settle. Several large pumps take suction off the basin and transfer the water to filters designed to remove suspended solids. Figure 5–11 illustrates a typical industrial filter.

Strainers, Cyclones, and Demineralizers A strainer removes solids from a process before they can enter a pump and damage it. A cyclone is used to remove solids from a gas stream. A typical cyclone is shaped like a V-bottomed tank with a port in the top, bottom, and upper side. Gases and solids enter the top upper side of the tank and are swirled around the tank. Solids drop to the bottom of the cone while gases escape out the top of the tank. Demineralizers remove dissolved substances from a fluid. 123

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5.4 Pumps The chemical processing industry uses pumps to move liquids from one place to another. Pumps come in a variety of shapes and designs and operate under two very different principles. Dynamic and positive displacement. Dynamic pumps include centrifugal and axial models. A centrifugal pump uses the principle of centrifugal force to add energy to a liquid. The primary principle involves spinning the liquid in a circular rotation that propels it outward and into a discharge chute known as a volute. Centrifugal force and the design of the volute add energy or velocity to the liquid. As the liquid leaves the volute, it begins to slow down, creating pressure. Fluid pressure moves the process through the pipes. Axial pumps use a propeller to spin the liquid axially along the rotating shaft in order to move the liquid. In each of these pumps, the rotating element is designed to accelerate the flow of liquid. Positive displacement pumps can be classified as rotary or reciprocating. These types of pumps are designed to displace liquid with each stroke or rotation of the moving element. Because liquids are essentially noncompressible at most operating pressures, severe damage can occur to equipment or personnel if the pump is not lined up correctly. New process technicians are given careful instruction on the design and operation of pumps. The first centrifugal pump was designed in 1600 by a Frenchman named Denis Papin. The design was improved in 1851 by an Englishman named John Appold, who replaced the straight vane with a curved vane impeller. The basic components of a centrifugal pump include: casing, suction eye, volute, wear rings, rotating shaft connected to the impeller, motor, coupling, bearings and seals, discharge nozzle, gearbox, lubrication system, suction and discharge pressure gauges, and isolation valves. Figure 5–12 shows the basic components of a single-stage, horizontally mounted centrifugal pump. Liquid is pushed into the suction eye as the liquid level in the feed tank is carefully adjusted

Coupling Discharge

Motor

Casing Impeller Wear Rings

Rotating Shaft Packing Gland Suction Eye

Packing Volute

Figure 5–12 Centrifugal Pump 124

5.4 Pumps

Figure 5–13 (a) Horizontal Centrifugal Pump (b) Vertical Centrifugal Pump to provide the proper net positive suction head (NPSH). A pump curve is used to set up the correct operating condition for a centrifugal pump. Efficiency curves include multiple values: gallons per minute (gpm) and differential head (discharge head minus suction head). Centrifugal pumps can be classified as horizontally mounted or vertically mounted, single stage or multistage (more than one impeller). Operating problems associated with centrifugal pumps include cavitation and vapor lock. Cavitation occurs when air pockets form and collapse inside the volute; actually, the liquid in the pumping chamber is boiling. The phenomenon of rapid expansion and collapse wreaks havoc on the internal parts surrounding the suction eye. When a pump cavitates, it sounds like marbles being blended in a high-speed mixer. Vapor lock occurs when an air pocket forms inside the pump, preventing the intake and discharge of liquid. Centrifugal pumps are designed to run only when full of liquid, and cannot tolerate air pockets. Figure 5–13 shows both vertically and horizontally mounted centrifugal pumps. Suction and discharge pressures must be carefully controlled if these pumps are to operate correctly. Most of these factors are taken into consideration during the engineering design; however, liquid levels and line-ups are variables that can change. Figure 5–14 shows a typical family tree for the dynamic pump family. Centrifugal pumps are often used in jet pump systems. A jet pump uses a unique design on the suction side of the pump to create a venturi effect as a portion of the discharge is pushed down the casing and back into the suction line. This process provides the lift needed to raise liquid levels that are lower than 40 feet. Single-stage centrifugal pumps can operate for short periods of time with the discharge closed because of the principle of internal slip. Internal slip is the percentage of fluid that leaks or slips past the internal clearances of a pump over a given time. Because the impeller does not physically come into contact with the casing, the liquid slips between the fixed and moving parts. It is a common practice to “press up” a line by closing a discharge valve down the line in a pipeline; however, large multistage centrifugal pumps can be damaged by this procedure. 125

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Equipment One

DYNAMIC

AXIAL

CENTRIFUGAL

Vertical Horizontal Single Stage Multistage

Figure 5–14 Dynamic Pump Family Tree Thrust and Radial Bearings Propeller Driver

Mechanical Seal

Coupling

Figure 5–15 Axial Pump Axial pumps are composed of a motor, coupling, bearings, seals, propeller, and shaft. As the propeller turns, fluids are propelled axially along the shaft. This feature operates in a manner similar to the way a ceiling fan moves air around a room. Other examples include a boat propeller and a box fan. Figure 5–15 shows the basic components of an axial pump.

Positive Displacement Pumps Pumps that operate by displacing fluid positively are classified as positive displacement (PD) pumps. The two primary designs are rotary and reciprocating. It is important for the process technician to understand, before use, how any piece of equipment operates; this is especially true with PD pumps, which are not as forgiving as centrifugal pumps. Correct alignment of a PD pump is critical in operation, because these pumps are designed to positively displace liquid on each stroke or rotation. Inside an enclosed vessel, a liquid transfers pressure instantly equally in all directions. For this reason, liquids should be considered noncompressible. Process technicians must never leave a valve closed on the discharge side of the pump, or serious consequences will result.

Rotary Pumps. Rotary pumps are characterized by a rotary movement; types include screw, lobe, vane, and gear. Figures 5–16 and 5–17 illustrate rotary-type pumps. Rotary pumps displace liquid with gears, vanes, screws, or other rotating elements. The common thread between these two groups is the positive displacement action of the device. Centrifugal pumps are often mistakenly 126

5.4 Pumps Cooling Water Jacket Power Gear

Suction

Discharge

Suction

Discharge

Vanes

Suction

Discharge

Casing

Off-Center Rotor Base

Idler Gear

Lobe Pump

External Gear Pump

Sliding Vane Pump

Figure 5–16 Rotary Pumps

Power Gear

Suction

Discharge

Idler Gear External Gear Pump

Figure 5–17 External Gear Pump considered rotary designs; however, although the impeller on a centrifugal pump does rotate, the liquid is not positively displaced. This is the primary distinction between rotary and centrifugal pumps. Rotary pumps include single-screw, twin-screw, or three-screw pump operation. Vane pump designs include flexible-vane and sliding-vane types. Gear pumps include internal and external gear pumps. Lobe pumps have moving elements that resemble twin-turning lobes that use timing gears to keep them from coming into contact with each other. The positive displacement pump family tree in Figure 5–18 shows some of the differences between these pumps.

Reciprocating Pumps Reciprocating pumps include piston, plunger, and diaphragm designs. This type of pump draws a specific volume of liquid into a chamber on the intake stroke and positively displaces this volume with a piston, plunger, or diaphragm on the discharge stroke. Typically, a series of flow-regulating check valves are used on the inlet and outlet lines. Reciprocating pumps are characterized by a back-and-forth movement, similar to the pumping action of an oldfashioned, hand-operated water pump. Figures 5–19 and 5–20 show examples of reciprocating pumps. The basic components of a reciprocating pump include a connecting rod, piston/plunger or diaphragm, seals, check valves, motor, cylinder or pumping chamber, casing, and bearings. 127

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Equipment One Progressive Cavity Single !.0 Screw Pump

Timed

Multiple

Untimed 2.0 External Gear

Spur Helical Herringbone

Timed Untimed

No Crescent 3.0 Internal Gear

Crescent

ROTARY 4.0 Sliding Vane POSITIVE DISPLACEMENT 5.0 Flexible Vane

6.0 Lobe Pump

Blade, Bucket Roller, Slipper

Vane in Rotor Vane in Stator

Tube, Vane, Liner Single Multiple 1.0 Piston

RECIPROCATING

2.0 Plunger 3.0 Diaphragm

Figure 5–18 Positive Displacement Pump Family Tree

Operation of a Positive Displacement Pump The correct operation of a PD pump includes correctly lining up the pump from the suction tank to the discharge tank. This includes opening all the suction and discharge valves on the flow path to the destination tank and closing any valve that is not on that flow path. Adequate liquid level is required on the suction side to operate the pump, and space should be available in the destination tank. A positive displacement pump is not dependent on NPSH or liquid level; however, adequate suction is required. Vented and nonvented tanks respond differently during product transfers and should be carefully monitored. Positive displacement pumps are not supposed to be throttled or regulated on the discharge side. After the line has been walked and every valve has been checked, the pump can be started. Suction and pressure gauges should be carefully monitored, and flow rates tracked. Flow control loops are typically not used with PD pumps unless a series of relief valves and pressure control devices is used. A simple calculation should be made on how fast the tank will fill and how fast the suction tank will empty. Careful monitoring of liquid levels is important. Samples are frequently caught on the product lines and sent to the lab for quality checks. Some PD pumps are designed to be run liquid full at all times, whereas others can be run empty for short periods of time. 128

5.5 Compressors

Discharge

Packing

Check Valve

XXXXX

Piston

XXXXX

Piston Rings

Packing Gland

Suction Piston Pump

Figure 5–20 Piston Pump

Figure 5–19 Reciprocating Pumps

5.5 Compressors The operation and design of a compressor can usually be classified into one of two groups: positive displacement or dynamic. Dynamic compressors operate by accelerating the gas and converting the energy to pressure. This type of compressor can be either centrifugal or axial. Centrifugal compressors (see Figure 5–21) operate by adding centrifugal force to the product Discharge

Impeller Diffuser Plates Wear Rings

Shaft Gland

Casing Suction Eye

Figure 5–21 Centrifugal Compressor 129

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Equipment One

Figure 5–22 Blower stream. The design and application of centrifugal compressors accelerate the velocity of the gases. This velocity or kinetic energy is converted to pressure as the gas flow leaves the volute and enters the discharge pipe. Centrifugal compressors can deliver much higher flow rates than positive displacement compressors. The basic components of a centrifugal compressor include the casing, motor or driver, coupling, volute, suction eye or inlet, impellers, wear rings, seals, bearings, discharge port, suction gauge, and discharge gauge. An axial flow compressor is composed of a rotor that has rows of fan-like blades. Unlike centrifugal compressors, axial compressors do not use centrifugal force to increase gas velocity. Instead, airflow is moved axially along the shaft. Rotating blades attached to a shaft push gases over stationary blades called stators. The stators are mounted or attached to the casing. As the gas velocity is increased by the rotating blades, the stator blades slow it down. As the gas slows, kinetic energy is released in the form of pressure. Gas velocity increases as it moves from stage to stage until it reaches the discharge port. Figure 5–22 shows a single-stage centrifugal blower.

Positive Displacement Compressors Positive displacement compressors (see Figure 5–23) operate by trapping a specific amount of gas and forcing it into a smaller volume. They are classified as rotary or reciprocating. Positive displacement compressors and positive displacement pumps operate in a similar fashion. The primary difference is that compressors are designed to transfer gases and pumps are designed to move liquids. A rotary compressor design includes a rotary screw, sliding vane, lobe, and liquid ring. A reciprocating compressor includes a piston (Figure 5–24) and diaphragm. 130

5.5 Compressors Discharge Line Piston Cylinder Piston Rings

Driver

Connecting Rod Crankshaft

Seals and Shaft

Crank Pin and Main Bearings

Suction Line

Valves Connecting Rod

Counterweights

Foundation

Piston

Piston Compressor

Figure 5–23 Positive Displacement (PD) Compressor

Figure 5–24 Piston Compressor 131

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5.6 Steam Turbines A steam turbine is a device “driver” that converts kinetic energy (steam energy of movement) to mechanical energy. Steam turbines have a specially designed rotor that rotates as steam strikes it. This rotation is used to operate a variety of shaft-driven equipment. The steam used to operate a steam turbine is produced in a boiler. Boilers produce steam that can enter a turbine at temperatures as high as 1,000°F, and pressures as high as 3,500 psi inlet and 200 psi outlet. High-pressure steam is slowly admitted into a turbine to warm it up and remove the condensate. Steam enters a turbine through the steam chest. The steam chest typically has a strainer on the inlet side to remove solids. Inside the steam chest is a device called the governor valve. The governor valve opens and closes to admit steam into the turbine. A governor system controls the position of the governor valve. An overspeed trip mechanism is attached to the rotor and will shut off the flow of steam into the turbine when it reaches 115% of its design limit. The shutoff valve is typically located in front of the governor valve. As steam leaves the steam chest, it is directed into the nozzle block. The nozzle directs the steam onto the blading, which is attached to the shaft. The blading and shaft make up the rotor. Impulse or reaction movement occurs as the steam strikes the rotor, converting the steam energy into mechanical energy. Each stage consists of a set of moving and stationary blades. The curved blades of each stage are designed so the spaces between the blading act like the nozzle to increase steam velocity. As the steam zigzags between the stationary and moving blades, it expands to as much as 1,000 times its original volume. Modern turbine design increases the size of each stage, giving the turbine a conical shape. Steam turbines are typically classified as condensing, noncondensing, impulse, or reactive. In the condensing design, a heat exchanger is used to condense the steam. In contrast, the noncondensing design utilizes the exhaust as low-pressure steam. Impulse and reactive movement describe how the steam acts upon the rotor. In the reactive design, the nozzle is mounted on the rotor, whereas the impulse design allows the steam to blow against the rotor. Reactive movement is a reactive response to the release of steam. Steam turbines are used primarily as drivers for pumps, compressors, and generation of electric power. Figure 5–25 illustrates the internal components of an impulse steam turbine. Fixed Blades

Moving Blades

Casing

Radial Bearings

Rotating Shaft Thrust Bearings Coupling

Governor System

Labyrinth Seals Slinger Ring Carbon Rings

Steam Inlet Governor Valve

Rotor Nozzle Block Steam Outlet

Figure 5–25 Steam Turbine 132

5.7 Gas Turbines

5.7 Gas Turbines The basic components of a gas turbine system (Figure 5–26) fall into four primary areas: the compressor, combustion chamber, gas turbine, and load. Each of these areas has a number of critical components and is linked by a common axle (Figure 5–27). Each part of the gas turbine system is an integral part of the whole unit. Axial flow compressors have replaced most other compressor designs because of the large volume this design can handle. The combustion chamber combines two feed components to produce a continuous, high-pressure flow into the turbine. The gas turbine has a number of stages that increase in size to accommodate the expanding hot gases that jet through the moving turbine wheels and stationary blades. Part 1—Compressor • Compressor rotor assembly • Stator blades, rotor blades • Compressor case assembly • Air inlet filter assembly • Bearings and seals • Compressor diffuser assembly Part 2—Combustion Chamber • Fuel injector • Combustor housing assembly • Gas fuel manifold • Bleed air valve • Ignitor

Spark Plug

Air In

Exhaust

Fuel L Workload L Air Compressor

Combustion Chamber

Gas Turbine

Figure 5–26 Gas Turbine 133

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Equipment One

Combustion Chamber

Combustor Assembly

Gas Turbine

Air Compressor Air In

Fuel Injector

Spark Plug

Exhaust

L Workload

Axle L Diffuser Turbine Rotor Compressor Rotor Stationary Blades Figure 5–27 Gas Turbine Internals

Part 3—Gas Turbine • Gas producer turbine rotor assembly • Power turbine rotor assembly • Moving turbine wheels and stationary blades • Nozzle case and assembly • Turbine exhaust diffuser • Exhaust collector Part 4—Workload • Driven shaft • Driven device

5.8 Electricity and Motors The majority of electrical power produced in the world is alternating current (AC). Alternating current is defined as current that reverses direction at regular intervals. Most industrial motors use alternating current. Alternating current can be transformed using a step-down or step-up transformer. Voltage can be increased for the purpose of transmission and then stepped down as it nears the electrical equipment. Voltages between 69 kilovolts (kV), 138 kV, and 345 kV are frequently used. Direct current (DC) does not change flow direction, and thus cannot be used in the same way as alternating current. 134

5.9 Equipment Lubrication, Bearings, and Seals Frame Stator Bearing Oil

Revolving Magnetic Poles Rotor

Fan

Seals

Bearing

Load

Revolving Magnetic Flux Wave Bearing Electric Power

Figure 5–28 Typical Motor During the 1904 World’s Fair, Thomas Edison attempted to demonstrate that low-voltage direct current could light the fair more economically than the alternating current advocated by George Westinghouse and Nikola Tesla. Under Edison’s plan, it would have cost $1.00 for every light bulb, versus Westinghouse’s bid of 25 cents per light bulb. Alternating current easily won the contest and has remained the most popular option. The chemical processing industry uses three-phase motors to operate pumps, compressors, fans, blowers, and other electrically driven equipment. Three-phase motors come in three basic designs: squirrel-cage induction motors, wound-rotor induction motors, and synchronous motors. The primary difference is in the rotor. The direction of rotation in a motor is determined by strong magnetic fields. A typical motor is composed of stator windings, rotor and shaft, bearings and seals, conduit box, frame, fan, lubrication system, and shroud. Figure 5–28 illustrates the location of these components. Figure 5–29 shows an AC motor.

5.9 Equipment Lubrication, Bearings, and Seals One of the primary functions a process technician performs is periodic checks of the equipment system. During these routine checks, equipment oil levels and operating conditions are closely inspected. High temperatures, unusual noises or smells, and erratic flows are all signs that a problem has developed.

Lubrication To ensure the good operation of process equipment, proper lubrication must be maintained. A lubrication system protects the moving parts of equipment by placing a thin film of protection between surfaces that come into contact with each other (Figure 5–30). Under a microscope, the smooth surface of a gear may appear very rough. Without lubrication, a tremendous amount of friction would develop. Lubrication helps remove heat generated by friction and provides a fluid barrier between the metal parts to reduce friction. Loss of lubrication causes severe damage to compressors, steam turbines, pumps, generators, and engines. Most rotary equipment requires some type of lubrication. 135

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Equipment One

Figure 5–29 AC Motor

Pump Bearings

Gearbox

Fluid Reservoir

Compressor Bearings

Figure 5–30 Lubrication System Bearings Radial and axial bearings can be found in most rotating equipment, and require lubrication to operate properly. Radial bearings are designed to prevent vertical (up-and-down) and horizontal (side-to-side) movement of the rotating shaft. Axial bearings are designed to prevent back-andforth movement of the shaft. Radial bearings come in a variety of designs, including ball bearings, friction or sleeve bearings, rolling-element bearings, and shielded bearings.

Seals Shaft seals are designed to prevent leakage between internal compartments in a rotating piece of equipment. Shaft seals come in a variety of shapes and designs. Typical designs include labyrinth seals, carbon seals, packing seals, and mechanical seals. Labyrinth seals trap lubrication and fluids between a maze of ridges. Segmental carbon seals are mounted in a ring-shaped design around the rotating shaft. A spring holds the soft graphite seal in place and allows it to wear evenly. Mechanical 136

5.10 Steam Traps

Bottle Oiler

Radial Movement

Oil Oil

Ball Bearing

Retainer Cage

Shaft Outside Ring

Inside Ring Thrust Bearing

Friction Bearing

Shaft Seals Radial Bearing

Thrust or Axial Movement

Figure 5–31 Seals and Bearings seals come in a modular kit that is slid into place as one unit. Mechanical seals provide a stationary seat and a moving seal face. Mechanical seals are designed to withstand high pressure; carbon seals and labyrinth seals cannot. Shaft seals minimize air leakage into and out of the equipment; keep dirt, chemicals, and water out of the lubricant; and keep the clean lubricant in the chamber where the bearings and moving components are located. Seals and bearings are illustrated in Figure 5–31.

5.10 Steam Traps Steam traps are used to eliminate condensate from industrial steam systems. Condensate can cause a lot of serious problems as it flows with the steam. Slugs of water can damage equipment and lead to a condition known as water hammer. To eliminate this problem, steam traps are used to remove condensate. Steam traps are classified as either mechanical or thermostatic. Figure 5–32 Outlet

Cap

Valve

Air Vent

Contracted

Steam Bucket Condensate Bucket Weight

Expanded Inlet Bucket Trap

Bellows

Figure 5–32 Steam Traps 137

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illustrates two different steam-trap designs. Mechanical steam traps include floats and inverted buckets. Thermostatic traps include bellows-type traps.

Summary Basic hand tools are the typical tools that process technicians use to perform their job activities. These include tools such as pliers, screwdrivers, wrenches, and channel locks. Process technicians are required to perform routine maintenance on their units. A little minor maintenance can often prevent major equipment damage. Tanks and pipes store and contain fluids. Tank designs vary depending upon their service. Pipe size and design determine flow rates, pump and valve sizes, turbulent or laminar flow, instrument type, and automation. Valves control the flow of fluids. Valves come in a variety of shapes, sizes, and designs that throttle, stop, or start flow. Common valve designs are gate, globe, ball, plug, check, and butterfly. Filters remove solids from fluids. Strainers remove solids from a process before the solids can enter a pump and damage it. A cyclone is used to remove solids from a gas stream. A typical cyclone is shaped like a V-bottomed tank with ports in the top, bottom, and upper side. Gases and solids enter the top upper side of the tank and are swirled around the tank. Solids drop to the bottom of the cone while gases escape out the top of the tank. Demineralizers remove dissolved substances from a fluid. Pumps are primarily used to move liquids from one place to another. The two basic designs are positive displacement and dynamic. Positive displacement pumps can be classified as rotary or reciprocating. Reciprocating pumps are characterized by a back-and-forth motion, whereas rotary pumps move in a circular fashion. Dynamic pumps can be classified as centrifugal or axial. The centrifugal pump uses centrifugal force to move liquids; axial pumps push liquids along a straight line. Compressors are closely related to pumps. They come in two basic designs: positive displacement (rotary and reciprocating) or dynamic (axial or centrifugal). A compressor is designed to accelerate or compress gases. Steam turbines are used as drivers to turn pumps, compressors, and electric generators. Highpressure steam is directed into buckets designed to turn a rotor and provide rotational energy. Steam turbines serve the same function as electric motors. A typical motor is composed of stator windings, rotor and shaft, bearings and seals, conduit box, frame, fan, lubrication system, and shroud. Steam turbines and motors are two of the most popular devices used by industry as drivers. Shaft seals are designed to prevent leakage between internal compartments in a rotating piece of equipment. Typical shaft seal designs include labyrinth seals, carbon seals, packing seals, and mechanical seals. Radial and axial bearings can be found in most rotating equipment and require lubrication to operate properly. Radial bearings are designed to prevent up-and-down and side-toside movement of the rotating shaft; axial bearings are designed to prevent back-and-forth movement of the shaft.

138

Chapter 5 Review Questions

Chapter 5 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Draw a gate valve and label its parts. Draw a centrifugal pump and label its parts. What is the primary difference between a pump and a compressor? Describe how a steam turbine works. Sketch a simple drawing if needed. Describe alternating current. Draw a rotary pump and label its parts. Show rotation. Explain the purpose of bearings and seals. What are the basic components of an electrical motor? List the basic hand tools used by process technicians. Describe how a steam trap operates. Draw a globe valve and label its parts. What is the primary purpose of a floating roof? List the standard pipe fittings used to connect pipe. What types of materials are used in the manufacture of storage tanks? How much pressure can a typical horizontal cylindrical tank hold? Draw the type of valve used to relieve pressure, and label its parts. Describe how an industrial motor works. Describe centrifugal movement. Draw a reciprocating pump and label its parts. Show rotation. Explain the importance of lubrication for a pump, compressor, or turbine.

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Equipment Two After studying this chapter, the student will be able to: • • • • • • • • •

Describe the purpose and components of different types of heat exchangers. Describe the key components and operation of a cooling tower. List the primary components of a fire-tube boiler and a water-tube boiler. Describe the primary components and operation of cabin, cylindrical, and box furnaces. Identify the purpose and components of a reactor. Describe the different types of catalysts: adsorption, intermediate, inhibitor, and poisoned. Compare and contrast the various types of chemical reactions: exothermic, endothermic, replacement, and neutralization. Describe the purpose and components of plate and packed distillation columns. Explain the purpose and components of a typical separator.

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Key Terms Boilers—devices primarily designed to boil water and generate steam for industrial applications. Boilers are classified as either water tube or fire tube. Steam generation systems produce high-, medium-, and low-pressure steam for industrial use. Catalyst—a chemical that can increase or decrease a reaction rate without becoming part of the product. Catalysts are classified as adsorption, intermediate, inhibitor, or poisoned. Chemical reactions—interactions between two or more chemicals in which a new substance is formed; types include exothermic, endothermic, replacement, and neutralization. Cooling towers—devices used by industry to remove heat from water. In a typical tower, a boxshaped collection of multilayered slats and louvers directs airflow and breaks up water as it cascades from the top of the water distribution system. Cooling towers are classified by the way they produce airflow and by the way the air moves in relation to the downward flow of water. Basic designs include atmospheric, natural, forced, and induced draft. Distillation column—a collection of stills stacked one on top of another; separates chemical mixtures by boiling points. Distillation columns fall into two distinct classes: plate and packed. Fire-tube heaters—furnaces consisting of a battery of tubes that pass through a firebox. Fired heaters or furnaces are commercially used to heat large volumes of crude oil or hydrocarbons. Basic designs include cylindrical, cabin, and box. Fluid flow—movement of fluid particles; can be described as laminar, turbulent, parallel, series, counterflow, or cross-flow. Heat—a form of energy caused by increased molecular activity. Forms include sensible heat and latent heat. Heat exchanger—an energy-transfer device designed to convey heat from one substance to another. Basic designs include pipe coil, shell-and-tube, air-cooled, plate-and-frame, and spiral. Heat transfer—movement of heat energy; methods include conduction, convection, and radiant. Reactor—device used to convert raw materials into useful products through chemical reactions. A reactor combines raw materials, heat, pressure, and catalysts in the right proportions. Five reactor designs are commonly used: stirred, fixed-bed, fluidized-bed, tubular, and furnace.

6.1 Heat Exchangers Heat exchangers transfer energy, in the form of heat, between two fluids without the fluids coming into physical contact with each other. A typical shell-and-tube heat exchanger has a tube-side flow and a shell-side flow. Heat energy is transferred to the cooler stream as the streams pass each other in the exchanger. A standard exchanger has a shell, tubes, tube sheet, shell inlet and outlet, tube inlet and outlet, and baffles. Heat exchangers fall into the following categories:

• • 142

Simple pipe-coil Shell-and-tube

6.1 Heat Exchangers

• • •

Plate-and-frame Spiral Air-cooled

Shell-and-tube heat exchangers can be broken down into: (1) pipe-coil; (2) double-pipe; (3) fixedhead, single-pass; (4) fixed-head, multipass; (5) floating-head, multipass (U-tube); (6) kettle reboiler; (7) thermosyphon reboiler; and (8) shell nomenclature. These devices can be mounted vertically or horizontally. The problems associated with shell-and-tube heat exchanger operation (see Figures 6–1 and 6–2) include fouling, corrosion, tube rupture, shell leaks, gasket leaks, pressure problems related to blockage, product contamination, fires, and explosions. Although these problems are rare, a heat exchanger is still a simple device that can be turned into a bomb by accidentally closing the wrong valve. When a heat source is allowed to flow over trapped liquid, problems can develop quickly. Process technicians should carefully monitor inlet and outlet pressures and temperatures. These indicators can rapidly identify impending problems. Tube leakage can typically be identified in product samples. The transfer of heat (heat transfer) between two fluid streams is an important process in the chemical processing industry. The simplest type of heat exchanger is a pipe coil. Copper tubes, which are easily bent to form, are submerged in water or sprayed with water. This process is very effective in low-volume, low-heat-load operations; however, larger processes require more complex devices. Pipe-coil heat transfer devices evolved into a double-pipe design that provided better temperature control and became the first true shell-and-tube heat exchanger. A double-pipe heat exchanger has a pipe (tube) within a pipe (shell) design. Fins can be added to the tubes to provide greater surface area and higher heat transfer rates. Thin metal fins conduct heat energy from hot areas to colder areas. A simple double-pipe design is the hair-pin exchanger. Figures 6–3 and 6–4 show a simple pipe-coil heat exchanger and a hair-pin heat exchanger. Another type of heat exchanger is a kettle reboiler. Reboilers are energy-balance devices attached to distillation columns to help control temperature. Reboilers have two basic designs: Shell Nozzle Inlet Tube Nozzle Inlet

Transverse Baffles

Shell Flange

Floating Head Backing Device

Shell Floating Head Cover Channel Cover and Head

Floating Tubesheet Shell Cover

Tubes Pass Partition Tube Nozzle Outlet

Fixed Tubesheet

Shell Nozzle Outlet

Support Saddle

Floating Head

Figure 6–1 Shell-and-Tube Heat Exchanger 143

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Figure 6–2 Shell-and-Tube Heat Exchanger Tube Outlet

Tube Inlet Figure 6–3 Pipe-Coil Heat Exchanger thermosyphon and kettle. Thermosyphon reboilers are typically single-pass, shell-and-tube heat exchangers. Kettle reboilers have a specially designed vapor-disengaging cavity that removes the lighter components of the bottom stream. These lighter fractions are returned to the bottom of the column. Process technicians monitor and control the temperature at both the bottom and the top of the column. Kettle reboilers have five connections, two on the tube side and three on the shell side. Steam or hot oil flows through the tube side and provides the heat source. Flow rate is carefully controlled and frequently linked to the bottom temperature control system. The higher the flow rate, the hotter the bottom product. The shell side has three nozzles: one liquid-product feed line, one vapor-return line to the column, and one heavy-liquid-out product line. A kettle reboiler can be used to (1) control the liquid level on the bottom of the column, (2) control the temperature of the column, and (3) help control product purity in the bottom of the column. Figure 6-5 shows what a kettle reboiler looks like, and Figure 6–6 shows two thermosyphon and one kettle reboiler arrangements on a distillation column. 144

6.1 Heat Exchangers Finned Center Tube

Shell Inlet Shell Tube Inlet Tube Outlet

Shell Outlet Shell Inlet

Tube Inlet

Tube Outlet

Shell Outlet

Figure 6–4 Double-Pipe Heat Exchanger Vapor

Shell Nozzle Outlet Shell (Steam) Tube Inlet

Vapor Disengaging Cavity Liquid Head

(Liquid) Shell Outlet (Condensate)Tube Outlet Feed In

Figure 6–5 Kettle Reboiler Along with maintaining the energy balance on a distillation column, a heat exchanger can be used to preheat the feed. In this type of design, two or more exchangers may be used. As feed enters the first heat exchanger, the transfer of energy occurs. This process gradually raises the temperature of the feed before it enters the second exchanger. As the temperature of the feed increases, 145

6.2 Cooling Towers

Condenser

EX Heater

Feed

Hot Oil

EX Reboiler Feed Hot Oil

EX

Figure 6–7 Three Types of Heat Exchangers Tube Inlet Nozzle Air Stationary Tubesheet

Finned Tubes Head

Channel Head Fan Tube Inlet Nozzle

Figure 6–8 Air-Cooled Heat Exchanger exchangers, like fouling and corrosion. These simple devices are easy to construct and have a low operating cost. Figure 6–8 shows what a typical air-cooled heat exchanger looks like.

6.2 Cooling Towers A cooling tower is a simple device used by industry to remove heat from water. Hot water transfers heat to cooler air as it passes through the internal components of the tower. This type of heat is called sensible heat; sensible heat can be measured or felt. Sensible heat accounts for only 10% 147

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Kettle Reboiler Horizontal EX

EX

EX

Heating Fluid

Figure 6–6 Reboiler Designs pressure increases, and the confined liquid moves toward the column. Temperature is an important process variable that can influence the operation of the entire system. Many of the processes found in industry produce vaporized products or partially vaporized products. Heat exchangers called condensers or coolers are designed to change the vapor into a more useful form. Liquid products are easier to transfer and control than vaporized materials. A good example of this process is a distillation system. As lighter components in the feed mixture vaporize and move up the column, the flow is directed out the overhead line and into a condenser. A cooling-tower system provides cooling water to the overhead condenser at specific flow rates. Air-cooled heat exchangers are also frequently used in this type of system. Figure 6–7 shows a heat exchanger used as a heater, a kettle reboiler, and a condenser.

Air-cooled heat exchangers are similar in design to shell-and-tube heat exchangers, but do not use a shell. Air-cooled devices such as car radiators work to remove heat generated by a combustion engine. Air-cooled heat exchangers or fin fans are designed to condense or partially condense hot vapors from a distillation system. These heat transfer devices are very effective and are widely used across the process industry. An air-cooled heat exchanger is composed of an inlet channel head and a return head, a series of plain or finned tubes, two tube sheets, and a fan. The fan can be positioned in a forced-draft or induced-draft position over/under the tubes. Air-cooled heat exchangers have none of the operational problems associated with shell-and-tube 146

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to 20% of the heat transfer in a cooling tower. Most of the heat stripping from a tower is caused by evaporation. Evaporation accounts for 80% to 90% of the heat transfer in a cooling tower. When water changes to vapor, it takes heat energy with it, leaving behind the cooler liquid. The principle of evaporation is the most critical factor in cooling-tower efficiency. A cooling tower is a large rectangular or box-shaped device filled with wooden or plastic slats and louvers that direct airflow and break up water as it falls from the top of the water distribution header. The internal design of the tower ensures good air and water contact. Cooling towers are classified by (1) how they produce airflow, and (2) the direction the airflow takes in relation to the downward flow of water. Airflow may be produced naturally or mechanically. Mechanical drafts are created by fans located on the side or top of the cooling tower. Flow direction into a tower is either cross flow or counterflow. Cross flow goes horizontally across the downward flow of water before exiting the system. When the air is forced to move vertically upward, against the downward flow of water, it is referred to as counterflow. Cooling towers come in the following designs: Natural Drafts • Atmospheric—simple counterflow • Hyperbolic (chimney towers)—counterflow or cross-flow Mechanical Drafts • Forced draft—counterflow • Induced draft—counterflow or cross-flow The basic components of a cooling tower include a water basin, pump, and water make-up system at the base of the cooling tower. The internal frame is made of pressure-treated wood or plastic and is designed to support the internal components of the tower. Some of these components include the fill or splash boards and drift eliminators. The fill or splash boards enhance liquid air contact, while the drift eliminators reduce the amount of water lost from the tower because of excess airflow. Louvers on the side of the cooling water tower admit air into the device. A hot-water distribution system is typically located on the top of the cooling tower fill. A fan may be used to enhance airflow through the cooling tower. Fan location determines whether airflow is induced (drawn in) or forced (pushed in). Figures 6–9 and 6–10 show typical cooling towers. Additional information about cooling towers can be found in Chapter 9. (See Figure 6–11.) Water Distribution System

Hot Water Header

Fan

Return Line

V

Air In

V

V

V

V

V V

V

V

V

V

V V

V

V

V

V

V

V

V

V V

V

V V

V

V V

V

V

V V

V

Fill V

V

V

V

V

V

Drift Eliminators

V

V

V

Louvers Air In

V

To Process

Cold Water Basin Make-up Water

Pump

Figure 6–9 Induced-Draft Cooling Tower 148

6.3 Boilers (Steam Generation) Water Distribution System Drift Eliminators

Hot Water Return

EX Solid Walls

EX Fan EX Make-up Water

Water Basin Cold Water Out

Figure 6–10 Forced-Draft Cooling Tower

Figure 6–11 Cooling Tower

6.3 Boilers (Steam Generation) Steam generators, commonly called boilers, are used by industrial manufacturers to produce steam. Steam is used to drive turbines and provide heat to process equipment. Steam generators are classified as fire-tube or water-tube boilers. High-pressure, medium-pressure, and low-pressure steam is 149

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Hot Combustion Gases

Steam Out Safety

Steam Burner

Natural Gas Tubes Water In

Combustion Tube

Figure 6–12 Fire-Tube Boiler circulated and used in numerous applications within a typical plant. Water-tube boilers are typically designed for large industrial applications; fire-tube boilers are used in smaller systems and processes.

Fire-Tube Boilers Fire-tube boilers contain the combustion gases in tubes that occupy a small percentage of the overall volume of the heater. The heated tubes run through a shell that contains the heated medium (water). A fire-tube boiler resembles a multipass shell-and-tube heat exchanger. This type of boiler is composed of a shell and a series of steel tubes designed to transfer heat through the combustion chamber (tube) into the horizontal fire tubes. Exhaust fumes exit through a chamber similar to an exchanger head and pass safely out of the boiler. The water level in the boiler shell is maintained above the tubes to protect them from overheating. The term fire tube comes from the way the boiler is constructed. The basic components of a fire-tube boiler include a large shell that surrounds a horizontal series of tubes. A large, lower combustion tube is attached to a burner that admits heat into the tubes. The upper tubes transfer hot combustion gases through the system and out the stack. Airflow is closely controlled with the inlet air louvers and the stack damper. Water level in the shell is maintained slightly above the tubes. As heat energy is transferred into the water, the temperature rises until the fluid boils. A pressure control valve maintains the correct operating pressure on the vessel. Every fire-tube boiler is equipped with a pressure relief system. A series of safety valves may be located on the discharge side of the shell. Low-pressure steam is discharged into a common steam header that is connected to various locations in the facility. A condensate return line admits the condensed steam into a deaerator drum and the water make-up system. Figure 6–12 illustrates the basic components of a fire-tube boiler.

Water-Tube Boilers The chemical processing industry also uses large industrial boilers commonly called water-tube boilers (see Figure 6–13). A water-tube boiler consists of an upper steam-generating drum and a 150

6.4 Furnaces

Desuperheated Steam Damper

Steam-Generating Drum

Economizer Section

Superheated Steam

Downcomer Heat Air In

Stack

Water In

Riser

SteamGenerating Tubes

Mud Drum Furnace

Figure 6–13 Water-Tube Boiler

lower mud drum connected by three types of tubes: downcomers, risers, and steam-generating tubes. These drums and tubes are surrounded by a furnace and a series of specially designed burners. The lower mud drum and water tubes are completely filled with water, whereas the upper steam-generating drum is only partially full. This vapor cavity allows steam pressure to build, collect, and pass out of the header. Water is carried through tubes that flow near and around the burners. As heat is applied to the water-generating tubes and drums, the water circulates around the boiler, down the downcomer tube, into the lower drum, and back up the riser tube and steamgenerating tubes of the furnace. During normal operation, high-pressure steam is superheated and sent to the main steam header. Lost water in the boiler is replaced by the make-up water line. Additional information about boilers can be found in Chapter 9.

6.4 Furnaces A fired heater or furnace is a device used primarily to heat large quantities of hydrocarbons. These systems are very expensive and complex and require a well-trained and dedicated staff. A process technician assigned to these units studies the basic components of the system, traces out each major flow path, and works closely with senior technicians until he or she is qualified to operate the equipment. Modern control instrumentation and high-tech control rooms are designed to monitor and control all vital processes. 151

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Furnaces are classified as direct fired or indirect fired. Direct-fired furnaces can be identified by the amount of volume the combustion gases occupy inside the furnace. Fired heaters are used in many processes, including distillation, reactor processes, olefin production, and hydrocracking. Furnaces heat raw materials to produce products like gasoline, oil, kerosene, plastic, and rubber. Fired heaters consist essentially of a battery of pipes or tubes that pass through a firebox. These tubes run along the inside walls and roof of a furnace. The heat released by the burners is transferred through the tubes and into the process fluid. The fluid remains in the furnace just long enough to reach operating conditions before exiting and being shipped to the processing unit. As with most industrial applications, fired heaters come in a wide variety of designs. Typical furnace designs include: • Cabin—direct fired • Cylindrical—direct fired • Box—direct fired • A-frame—direct fired • Fire-tube—indirect fired A furnace or fired heater can be classified as natural, induced, forced, or balanced draft. The pressure inside a warm furnace is typically lower because of buoyancy differences in the cooler outside air. A natural-draft furnace can operate using this approach; however, when fans are used to push or pull the air through the furnace, greater heat transfer rates can be achieved. A naturaldraft fired heater is severely limited in contrast to these systems. The types of problems a fired heater or furnace system typically encounters include: flame impingement on tubes, coke buildup inside the tubes, hot spots inside the furnace, fuel composition changes, burner flameout, control-valve failure, and feed-pump failure.

Cabin-Fired Heaters The basic components of a cabin-fired heater include a tough metal shell that surrounds a firebox, convection section, and stack. The inside of the furnace is lined with a special refractory material (brick, blocks, peep stones, gunite) that is designed to reflect heat. A battery of tubes passes through the convection and radiant sections and into a common insulated header that passes out of the furnace. A series of burners is located on the bottom of the furnace or on the sides. Fluid flow is carefully balanced through the tubes to prevent equipment or product damage. Airflow and oxygen content are controlled through primary, secondary, and damper adjustments. Figure 6–14 illustrates the basic layout of a cabin furnace.

Cylindrical-Fired Heaters Cylindrical furnaces use a small footprint and a tube-shaped firebox to transfer heat energy into a moving liquid. Tubes are arranged in a helical or spiral pattern around the outside wall of the cylinder. The burner is traditionally located in the center so the flames do not come into contact with the radiant tubes, refractory material, or shell. The primary source of heat transfer is radiant and convective; however, conductive heat transfer occurs as energy passes through the tubes. Cylindrical furnace designs may include a small convection section, similar to the type found in a cabin furnace.

152

6.4 Furnaces

Stack

Charge in Damper Convection Section

Shock bank Co

nve

c

e Tub n tio

s

Radiant Section

Refractory

Shell

Fuel

Fire Box

s ube T t n dia Cha Ra

rge

out

Burners

Figure 6–14 Cabin Furnace

The basic components of a cylindrical furnace are the same as found in a cabin furnace, with the addition of a cone located between the radiant and convection sections. The cone evenly distributes the heat as it moves up. Dampers are not typically used in this type of system. Figure 6–15 shows a cylindrical furnace with a helical coil.

Box Furnaces A box furnace design is commonly used in the chemical processing industry for a variety of applications and processes. This type of furnace closely resembles a box and has the same standard components as a cabin furnace. The burners may be arranged on the bottom or on the sidewall; the tube arrangement depends on how the burners line up. Several simple designs are shown in Figure 6–16, along with their various operational components.

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Stack

Convection Tubes No Convection X X X X X X X X X

Cone

X X X

Cylindrical All Radiant Radiant Section

Burner

Helical Coil

Burner

Figure 6–15 Cylindrical Furnace

6.5 Reactors A reactor is a device used to convert raw materials into useful products through chemical reactions. These devices combine raw materials with catalyst, gases, pressure, or heat; reactors are designed to operate under a variety of conditions. The shape and design of a reactor are dictated by the application it will be used in. Five reactor designs are commonly used in the chemical processing industry: stirred reactors, fixed-bed reactors, fluidized-bed reactors, tubular reactors, and furnace reactors. Nuclear reactors are also used to produce steam for power generation. Reactors are used in a variety of processes and systems: • Alkylation • Fluid coking • Fluid catalytic cracking • Chemical synthesis • Fixed- and fluidized-bed reactions • Batch and continuous processes • Hydrodesulfurization • Hydrocracking 154

6.5 Reactors

Damper Convection Section

Radiant Section

Stack Firebox Burner

Radiant Section

Bridgewall

Feed In

Air Preheat for Burner Feed In Convection Section

Firebox

Burner

Figure 6–16 Box Furnaces The basic components of a reactor include a shell, a heating or cooling device, two or more product inlet ports, and one outlet port. A mixer may be used to blend the materials together. Figure 6–17 is an illustration of a simple mixing reactor. A number of critical process variables associated with reactor operation include temperature, pressure, concentration of reactants, catalysts, and time. As the temperature increases, molecular activity increases. Because a chemical reactor is designed to make chemical bonds, break chemical bonds, or make and break chemical bonds, temperature is carefully controlled. By increasing the pressure, molecules are moved closer together. When this process is combined with heat, a higher number of molecular collisions can be achieved. The more collisions, the more chemical reactions occur within a specific amount of time. The speed at which two or more chemicals react doubles for each 10°C increase in temperature. The concentration of reactants in the reactor has a significant impact on how fast a reaction will occur. Stirred reactors are designed to enhance molecular contact. Reaction time can also provide the contact that reactants need to produce the desired products. In some cases a catalyst may be used to speed up the reaction. A catalyst is a chemical that can increase or decrease a reaction 155

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PIC

I

P Fi

Stirred Reactor

Vapor Product

FC

Reactant #1 SIC

AT FC

PE I

FIC

P

Reactant #2

FT

Mixer

PT

FE

I

ST

FC

P

FT

Heat or Cooling

FIC

LE LT

I

P

AIC TIC

TE

TT AT Pi

FC

LIC Pi

I

AE

Liquid Product

P

Pump

Figure 6–17 Stirred Reactor rate without becoming part of the product. Catalysts can be classified as adsorption, intermediate, inhibitor, or poisoned. Chemical reactions are classified as exothermic, endothermic, replacement, or neutralization. Exothermic reactions produce heat, whereas endothermic reactions require heat. A combustion reaction is an exothermic reaction. The reaction that causes Jell-O pudding to thicken is an endothermic reaction. Another critical factor in reactor operation is material balance of reactants. Industrial chemists know exactly how much of one chemical will react with another chemical. Chemical and mechanical engineers carefully design reactor systems to ensure that flow rates and times are as productive as possible. When process technicians allow flow rates, pressures, temperatures, time, or any number of variables to deviate from the specifications (move off-spec), significant revenue can be lost. Figure 6–18 shows several reactor designs. 156

6.6 Distillation

FIC Feed to RX

FIC

Fixed Bed (Converter) Reactor

Feed to RX

Fixed Bed Catalyst

EX

FIC Pump Feed to RX

FIC 2 FIC 1

Feed to RX

FIC 1

Feed to RX

FIC 2

Flue Gas Heat Out

Heat In

Recycle RX

Heat In

Burner Direct Fired RX

Jacketed RX

Figure 6–18 Reactor Designs

6.6 Distillation A distillation column is a series of stills placed one on top of another. As vaporization occurs, the lighter components of the mixture move up the tower and are distributed on the various trays. The lightest component goes out the top of the column in a vapor state and is passed over the cooling coils of a shell-and-tube condenser. As the hot vapor comes into contact with the coils, it condenses and is collected in the overhead accumulator. Part of this product is sent to storage; the rest is returned to the tower as reflux.

Distillation is a process that separates substances from a mixture by the various boiling points of the substances. During the distillation process, a mixture is heated until it vaporizes; then the vapor is condensed on the trays or at various stages of the column where it is drawn off and collected in a variety of overhead, side-stream, and bottom receivers. The condensed liquid is referred to as the distillate; the liquid that does not vaporize in a column is called the residue. During tower operation, raw materials are pumped to a feed tank and mixed thoroughly. Mixing is usually accomplished with a pump-around loop or a mixer. This mixture is pumped to a feed preheater or furnace where the temperature of the fluid mixture is brought up to operating conditions. Preheaters are usually shell-and-tube heat exchangers or fired furnaces. This preheated fluid then enters the feed tray or section in the tower. Part of the mixture vaporizes as it enters the column, while the rest begins to drop into the lower sections of the tower. Heat balance on the tower is maintained by a device known as a reboiler. Reboilers take suction off the bottom of the tower. The heaviest components of the tower are pulled into the reboiler and 157

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stripped of smaller molecules. The stripped vapors are returned to the column and allowed to separate in the tower. Distillation columns come in two basic designs: plate and packed.

Plate Column The basic components of a plate distillation column include: a feed line, feed tray, rectifying or enriching section, stripping section, downcomer, reflux line, energy-balance system, overhead cooling system, condenser, preheater, reboiler, accumulator, feed tank, product tanks, bottom line, top line, side stream, and an advanced instrument control system. Plate columns hold trays that may be bubble-cap, valve, or sieve. Figure 6–19 shows the basic components of a plate distillation column.

Packed Column The basic components of a packed distillation column include: a feed line, feed distributors, shell, hold-down grids, random or structured packing, packing support grids, bed limiters, bottom outlet, top vapor outlet, instrumentation, and an energy-balance system. Packed columns are filled with packing to enhance vapor liquid contact. The most common types of packing are: sulzer, rasching ring, flexiring, pall ring, intalox saddle, berl saddle, metal intalox, teller rosette, and mini-ring. Packing can be random or structured.

FIC

CTW In

Condenser

R E C T I F Y I N G

TIC casc

AT #1 FIC Hot Oil In

S T R I P P I N G

PIC

LIC FIC

Accumulator Pump

Feed Tray

Feed

CTW Out

Reflux

Downcomer

TIC casc

AT #2

Hot Vapor FIC

Steam In Bottom LIC

AT #3

Figure 6–19 Distillation Column—Plate Design 158

6.6 Distillation Packed columns are designed for pressure drops between 0.20 and 0.60 inches of water per foot of packing material. The vertical alignment of a packed distillation column is very important because for each degree of inclination, 5% to 10% efficiency is lost. When the column is tilted, dry sections form in the column and liquid channeling occurs. Figures 6–20 and 6–21 illustrate the basic components of a packed column.

Vapor Outlet Hatch Reflux Liquid Distributor Structured Packing

X X X X X X XX X

XX X

X XXX X z Zn n z X X X X Zn Z X X X NZnz N Znz N Znz NX X X X X X X X X X X X XX X X XX X X X X X X X X X X X X X XX X X X X X X X X X X X Zn X X X X X XX X z n zN X X X X X Zn Z Znz N Znz N Znz N

Hold-Down Grid

Support Grid

Liquid Collector Liquid Feed Line

Ringed Channel X X

X

X

X

X X

X

X

X

Hold-Down Grid Random Ring Packing

Support Plates Hatch

Vapor Feed

Random Saddle Packing

Structured Grid XX XX XXXXXXXXXXXXXXXXXXX XXX X XXXXXXXXXXX

Reboiler Return

Bottom Line

Figure 6–20 Distillation Column—Packed Design 159

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Equipment Two

Vapor Outlet Reflux

Xxxxxxxxxxxxxx

Bed Limiter

Random Saddle Packing X X

X X

X X X X X X X X X X X X X X X X X

Cone Support

Liquid Feed Line

Xxxxxxxxxxxxxx

Hatch

Sight Glass

Saddle Packing X X

X X

X X X X X X X X X X X X X X X X X

Cone Support

Reboiler Return

Bottom Line

Figure 6–21 Distillation column—Packed random saddle design

160

6.7 Separators

6.7 Separators One of the problems most frequently encountered in chemical process operations is that of separating two materials from a mixture or a solution. Distillation is one way of making such a separation, and it is perhaps the most frequently used method. Another useful separation method is extraction. Extraction is a process for separating two materials in a mixture by introducing a third material that will dissolve one of the first two materials but not the other. In liquid-liquid extraction, all four materials are liquids, and the mixture is separated by allowing them to separate into layers (layer out) by weight or density. In many cases, it is impractical to separate two chemicals by distillation because the boiling points of the materials are too close together. In such a case it is frequently possible to find a third chemical that will dissolve only one of the two chemicals. In this situation, extraction is a better method of making the separation than distillation. Many chemicals are sensitive to heat and will degrade or decompose if raised to a temperature high enough for distillation. For these chemicals, extraction, which can usually be carried out at normal temperatures, is a practical alternative. Often, one of the materials to be separated is present only in very small amounts. It might be possible to recover such a material by distillation, but it is usually much easier and more economical to do so by extraction. The key requirement of any commercial process is that it be economical. In situations in which several alternative means of separating two chemicals could be used, the one that is the most economical (cost-effective) is chosen. Because many relatively inexpensive solvents are available, and because the equipment required for an extraction operation is relatively simple, economic considerations often favor liquid-liquid extraction. There are basically three steps in the liquid-liquid extraction process: (1) contact the solvent with the feed solution; (2) separate the raffinate from the extract; (3) separate the solvent from the solute. Step 3, recovery of the solvent and solute, is usually done by some other process, such as distillation. In liquid-liquid extraction, the feed is the original solution. The feed solution, containing the solute (the material that will be dissolved), is fed to the lower portion of the extraction column. The solvent (the material that dissolves the solute) is added near the top. Because of density differences, the lighter feed solution tends to rise to the top while the heavier solvent sinks to the bottom. As the two streams mix, the solvent dissolves the solute. Thus, the solute, which was originally rising with the feed solution, actually reverses its direction of flow and goes out with the solvent through the bottom of the column. This new solution, consisting of solvent and solute, is called the extract. The other chemical in the feed stream, now free of the solute, goes out the top as the raffinate. The raffinate and extract streams are not soluble in each other and will layer out. Figure 6–22 shows the basic flow path and equipment and instruments associated with the separator. The solvent must be able to dissolve the solute, but it should not be a substance that will dissolve the raffinate or contaminate it. It also must be insoluble, so that it will layer out. The density of the solvent should vary sufficiently from the density of the raffinate so that they can be layered out by the effects of gravity. The solvent must be a substance that can be separated from the solute. It should be inexpensive and readily available, and it should not be hazardous or corrosive.

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Fi

I

PIC

Feed Pi

P

PT PE

I

TIC

P

Separator Light LIC

TT

I

LIC

LE

Temperature Control

LT

LE

Heavy

LT

Light

I

P

P

Pi

AT

AT

Fi

TE LCV

LCV

Pi Pi

Pi

Pump

Pump

Figure 6–22 Separator

Summary Heat exchangers transfer energy, in the form of heat, between two fluids that do not physically contact each other. A standard exchanger has a shell, tubes, tube sheet, shell inlet and outlet, tube inlet and outlet, and baffles. Heat exchanger designs include simple pipe-coil, shell-and-tube, plate-and-frame, spiral, and air-cooled. Shell-and-tube heat exchangers fall into one of eight design types: pipe-coil; double-pipe; fixed-head, single-pass; fixed-head, multipass; floating-head, multipass (U-tube); kettle reboiler; thermosyphon reboiler; and shell nomenclature. These devices can be vertically or horizontally mounted. A typical shell-and-tube heat exchanger has a tube-side flow and a shellside flow. Heat energy is transferred to the cooler stream as the flows pass each other in the exchanger. The simplest type of heat exchanger is a pipe coil, in which tubes are bent to form and then submerged in water or sprayed with water. This process is very effective in low-volume, low-heat-load operations. A double-pipe heat exchanger, which has a pipe-within-a-pipe design, provides better temperature control. Reboilers are energy-balance devices attached to distillation columns to help control the temperature. Reboilers have two basic designs: thermosyphon and kettle. 162

Summary Air-cooled heat exchangers are similar in design to shell-and-tube heat exchangers, but without the shell. Air-cooled devices like car radiators remove heat generated by a combustion engine. Aircooled heat exchangers or fin fans are designed to condense or partially condense hot vapors from a distillation system. An air-cooled heat exchanger is composed of an inlet channel head and a return head, a series of plain or finned tubes, two tube sheets, and a fan. A cooling tower is a simple device used to remove heat from water. Heat exchangers and cooling towers typically work together to remove heat from a variety of industrial applications. A cooling tower is a box-shaped collection of multilayered slats and louvers that direct airflow and break up water as it cascades from the top of the tower or water distribution system. The internal design of the tower ensures good air and water contact. Hot water transfers heat to cooler air as it passes in the tower. Sensible heat accounts for 10–20% of the heat transfer in a cooling tower; evaporation accomplishes 80–90% of the heat transfer. The principle of evaporation is the most critical factor in cooling tower efficiency. Cooling towers are classified by how they produce airflow and the direction the airflow takes in relation to the downward flow of water. Airflow into and through a tower, which is produced naturally or mechanically, is either cross flow or counterflow. Cooling tower designs may be: (1) natural drafts, which include atmospheric (simple counterflow) and hyperbolic (chimney towers, either counterflow or cross flow); and (2) mechanical drafts, including forced draft (counterflow) and induced draft (counterflow or cross flow). The basic components of a cooling tower include a water basin, pump, and water make-up system at the base of the cooling tower. Louvers on the side of the cooling water tower admit air into the device. A fan may be used to enhance airflow through the cooling tower. Steam generators, commonly called boilers, are used to produce steam at various pressures that drives turbines and provides heat to process equipment. Water-tube boilers are typically designed for large industrial applications; fire-tube boilers are used in smaller systems and processes. Fire-tube heaters contain the combustion gases in tubes that occupy a small percentage of the overall volume of the heater. The basic components of a fire-tube boiler include a large shell that surrounds a horizontal series of tubes. A large, lower combustion tube is attached to a burner that admits heat into the tubes. The upper tubes transfer hot combustion gases through the system and out the stack. Airflow is closely controlled with the inlet air louvers and the stack damper. Water level in the shell is maintained slightly above the tubes. A water-tube boiler consists of an upper steam-generating drum and a lower mud drum connected by three sets of tubes: downcomers, risers, and steam-generating tubes. A furnace surrounds and provides heat to the drums and tubes. As heat is applied to the water-generating tubes and drums, the water circulates around the boiler, down the downcomer tube, into the mud drum, and back up the riser tube and steam-generating tubes of the furnace. The energy in steam can easily be transformed into mechanical or heat energy upon condensation. A steam-generation system is designed to safely return cooled condensate to the boiler. A device called a steam trap is used to collect and transfer this material. Low points in the steam system are used to capture cooled condensate before it can damage the piping or equipment. The chemical processing industry uses fired heaters or furnaces to heat large quantities of crude oil and other hydrocarbons up to operating temperature for processing. As the heated feed leaves 163

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the furnace, it is transported to a wide assortment of chemical processes. Fired heaters consist of a battery of tubes that pass through a firebox. Typical furnace designs include: cabin, cylindrical, box, and A-frame (direct fired), plus fire-tube (indirect fired). Cabin fired heaters include a tough metal shell that surrounds a firebox, convection section, and stack. Cylindrical furnaces use a tube-shaped firebox to transfer heat energy into a moving liquid. A box furnace has the same standard components as a cabin furnace.The burners can be arranged on the bottom or on the sidewall. The tube arrangement depends on how the burners line up. A reactor converts raw materials into useful products through chemical reactions. Reactors are designed to operate under a variety of conditions to combine raw materials with catalyst, gases, pressure, or heat. The shape and design of a reactor are dictated by the application it will be used in. Five reactor designs are commonly used in the chemical processing industry: stirred, fixed-bed, fluidizedbed, tubular, and furnace. Nuclear reactors are also used to produce steam for power generation. The basic components of a reactor include a shell, a heating or cooling device, two or more product inlet ports, and one outlet port. A mixer may be used to blend the materials together. A number of critical process variables are associated with reactor operation, including temperature, pressure, concentration of reactants, catalysts, and time. Distillation is a process that separates a substance from a mixture by using the boiling point of the substance. During the distillation process, a mixture is heated until it vaporizes, then is condensed on trays or at various stages of the column where it is drawn off and collected in a variety of overhead, side stream, and bottom receivers. A distillation column is a series of stills stacked vertically: As vaporization occurs, the lighter components of the mixture move up the tower and are distributed on the various trays. The lightest component goes out the top of the column in a vapor state, is passed over the cooling coils of a condenser, and is collected as condensate in an overhead accumulator. Heat balance on the tower is maintained by reboilers, which take suction off the bottom of the tower. Distillation columns come in two basic designs: plate and packed. One of the most frequently encountered problems in chemical process operations is that of separating two materials from a mixture or a solution. Distillation is the most frequently used method of making such a separation. Another useful separation method is extraction, a process that separates two materials in a mixture by introducing a third material that will dissolve one of the first two materials but not the other. In liquid-liquid extraction, all four materials are liquids, and the mixture is separated by allowing them to layer out by weight or density. There are basically three steps in the liquid-liquid extraction process: (1) contact the solvent with the feed solution; (2) separate the raffinate from the extract; and (3) separate the solvent from the solute. The solvent must be able to dissolve the solute but not the raffinate; must be insoluble so that it will layer out; must be separable from the solute; should be inexpensive and readily available; and should not be hazardous or corrosive.

164

Chapter 6 Review Questions

Chapter 6 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Draw a shell-and-tube heat exchanger. Label and show flows with a red pen. Draw a cooling tower and label its parts. Label and show flows with a red pen. Compare heat transfer in a cooling tower and a heat exchanger. Draw a box furnace with an air preheater system and label its parts. Label and show flows with a red pen. Draw a water-tube boiler and label its parts. Illustrate flows with a red pen. Compare water-tube and fire-tube boilers. List the four basic furnace designs discussed in this chapter. List four different types of fired heater burners. Explain how a furnace supports the various processes found in the chemical processing industry. Compare a kettle reboiler with a thermosyphon reboiler. Explain how each works and the primary differences between them. What are the primary differences between a forced-draft and an induced-draft cooling tower? List each type of heat exchanger and describe the basic operation of each type.

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Process Instrumentation One After studying this chapter, the student will be able to: • List and describe the basic instruments associated with temperature, flow, level, pressure, and analytical measurement. • Draw the basic symbols for equipment used in the chemical processing industry. • Identify and draw standard instrument symbols. • Draw typical line symbols used in industry. • Draw a simple process flow diagram (PFD). • Draw a complex piping and instrument drawing (P&ID). • Describe process legends and foundation, elevation, electrical, and equipment location drawings. • Describe how interlocks and permissives work.

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Key Terms Electrical drawings—graphical representations that use symbols and diagrams to depict an electrical process system. Elevation drawings—graphical representations showing the location of process equipment in relation to existing structures and ground level. Equipment location drawings—show the exact floor plan location of equipment in relationship to the plant’s physical boundaries. Flow diagram—a simplified diagram that uses process symbols to describe the primary flow path through a unit. Foundation drawings—diagrams containing concrete, wire mesh, and steel specifications that identify width, depth, and thickness of footings, support beams, and foundation. Legends—used to describe symbol meanings, abbreviations, prefixes, and other specialized equipment; function like the key of a map. Piping and instrumentation drawing (P&ID)—a complex diagram that uses process symbols to describe a process unit. Process equipment—piping, tanks, valves, pumps, compressors, steam turbines, heat exchangers, cooling towers, furnaces, boilers, reactors, distillation towers, and so on; all the primary machines and devices used in a process. Process flow diagram (PFD)—chart used to outline or explain the complex flow, equipment, instrumentation, electronics, elevations, footings, and foundations that exist in a process unit. Process instrumentation—transmitters, controllers, transducers, primary elements and sensors, and so on; all the measurement and control devices used to monitor and control a process. Process symbols—images that graphically depict process equipment, piping, and instrumentation.

7.1 Introduction to Process Instruments The primary variables that a process technician works with and controls are pressure, temperature, flow, level, and analytical or composition. Various instruments are designed to help facilitate this critical aspect of process work. Some of these instruments include computers, gauges, recorders, transmitters, controllers, transducers, primary elements and sensors, switches, and control valves. Process technicians use instruments to control complex industrial processes. Thirty years ago, most operators controlled the processes in their plant manually. This type of process was “valve intensive”; in other words, it required the technician to open and close line-ups manually. Basic process instruments have improved as the era of automation has been ushered in. A single process technician can monitor and control a much larger process from a single control center. 168

7.1 Introduction to Process Instruments

Pressure The scientific principles associated with pressure are invaluable in modern chemical processing, and they are used and applied constantly. (In Chapter 4, we discussed how pressure is equal to force divided by area.) A variety of instruments is used to measure and indicate pressure. Some of the more common ones include pressure indicators that use manometers, bourdon tubes, or helical, spiral, or bellows-shaped tubes. The movement created when these devices expand or contract is used to indicate pressure. Pressure transmitters are used with control loops that are designed to control the pressure in a specific system. They use a flexible diaphragm to measure changes in pressure. Pressure gauges are typically located on the suction and discharge of a pump, on the inlet and outlet of a heat exchanger, on the bottom of a tank, or on a compressor system. Figure 7–1 illustrates the various components of these different devices. Operators frequently walk through the unit and review various pressure gauges. Console operators closely monitor pressure variables and respond to any alarms. Pressure readings are typically measured in psia or psig.

Bellows

20 10 C-Type Bourdon Tube 40 30 Mechanical Linkage

100

40 50

50 60

20

70

10

80 0

0

0

30

Slack Diaphragm

90

200

LBS PER SQ. IN. PNEUMATIC CONTROLLER

Pressure Transmitter

Spiral H

L

Process Tubing

Figure 7–1 Pressure Devices 169

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Temperature During routine operations, the temperature of each process is carefully controlled by a small group of instruments. Common examples of these instruments include thermocouples, RTDs, capillary tubing, thermometers, thermal bulbs, thermistors, and bimetallic detectors. Figure 7–2 shows examples of these different devices. Temperature changes are measured in Fahrenheit, Rankine, Celsius, and/or Kelvin. Water freezes at 32 degrees Fahrenheit and 0 degrees Celsius and boils at 212 degrees Fahrenheit and 100 degrees Celsius. Rankine and Kelvin are absolute measurement scales. Degrees Kelvin ⫽ degrees Celsius ⫹ 273, and degrees Rankine ⫽ degrees Fahrenheit ⫹ 459.7.

Thermocouples are composed of two dissimilar metals that expand at different rates. This type of device converts heat to electricity; that is, a thermocouple generates an electric signal in response to heat intensity. This signal can be converted into a temperature measurement.

RTD

THERMOCOUPLE

200 0

200 0

400 C

400

Rankin

Fahrenheit

R

C

672 R

Celsius

Kelvin

°F

°C

K

212°F

100°C

373 K

Water boils

Electronic Circuit 492 R

32°F

Water freezes

0°C

273 K

Water freezes

Thermal Well 0 R

-460°F

ABSOLUTE ZERO

Different Metals

Metal Wire Platinum or Nickel

200

Thermal Bulb

0 200 0

400 C

400 C

Thermally Reactive Metal Thermally Stable Metal Bonding Metal

Bimetallic

x x

x

x

Capillary Tubing

Figure 7–2 Temperature Measurement Devices 170

-273°C

0K

7.1 Introduction to Process Instruments

Level For level measurement, technicians use sight glasses, floats, displacement devices, conductivity probes, and differential pressure transmitters. Sight glasses are attached to the process equipment or tank being measured. An open and vented sight glass allows the liquid level in the tank to rise to its correct level. This allows a technician to visually check the level under any operating condition. Floats and displacement devices can be attached to mechanical arms, rods, tapes, or chains that move indicators. These same devices can also be attached to transmitters and can relay an electric, electronic, or pneumatic signal. Conductivity probes can be used as high- and low-level alarms. These devices use electricity to complete or break a circuit. Differential pressure (DP) transmitters are used to detect pressure changes in liquid level. Because the height (amount) of a liquid is directly proportional to the pressure exerted by the liquid, a DP transmitter can accurately calculate and transmit this signal to a distant point. Figure 7–3 illustrates each of these devices. In addition to the level-measurement devices illustrated in Figure 7–3, there are air bubbler systems for level detection, ultrasonic level detectors, and radiation level detectors. Ultrasonic and

High Level Alarm

Capacitance Probe 0%

50% 100

LIC 202

TK-202

I

Transmitter

P Rod

0%

50% 100

Transducer

Displacer

Fail Open

Level Controller

Transducer I P

Sight glass Fail Open

High Control Valve

Low

Differential Pressure Transmitter

Figure 7–3 Level Measurement 171

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radiation detectors are classified as noncontacting. Ultrasonic detectors emit a pulsed frequency signal from the top of the vessel down. This standardized wave velocity allows the device to actually determine how much material is not in the vessel.The detector must be positioned so the pulse wave strikes the perpendicular surface of the liquid. Radiation level detectors have two basic parts: a radiation transmitter and a radiation detector. These devices are positioned on opposite sides of the vessel. When a gamma wave is emitted from the transmitter, it is absorbed by the liquid and a comparison is made between the energy emitted and the energy received.

Flow Flow rate is typically measured in gallons per minute (gpm) or gallons per hour (gph). A variety of devices can be used to accomplish flow measurement. Common examples of flow measurement devices are orifice plates, venturi nozzles, nutating disc meters, turbine flow meters, oval gear meters, rotameters, pitot tubes, weir and flume, and flow transmitters. Figure 7–4 shows a few examples of flow-measurement devices.

Motor

Turbine Flow Meter 29347

Flow In Oval Gear Meter Flow Controller 0

25

Flow In

50

90

GPM

80 70 60

Rotameter

Transducer

50 40

I

30

P

20 10

Control Valve

Orifice Plate

Flow In

Figure 7–4 Flow Measurement 172

7.2 Symbols and Diagrams Orifice 10 15 20 PSIG

5 0

200 0

400

C

Pressure Gauge

Recorder Controller

0

150

300

FAHRENHEIT TEMPERATURE TRANSMITTER

Thermocouple Temperature Controller

H Control Valve

L

P Cell Transmitter

Figure 7–5 Basic Instruments

Orifice plates are flat plates with holes that are typically smaller than the inside diameter of the pipe. The intent is to place the device between two flanges and restrict flow so that an artificial high- and low-pressure zone is created on each side of the orifice. A transmitter is used to calculate the differential and calculate a flow rate. The venturi flow nozzle uses the same principle as the orifice plate. Rotameters have a glass tube with a flow element trapped between the measurement grid. This type of device provides direct contact between the measurement element and the fluid. Flow typically enters at the bottom of the rotameter and lifts the flow element. Oval gear meters and turbine flow meters displace a specific amount of liquid on each rotation. This is used to calculate total flow rate through the system. Pitot tubes are positioned perpendicular to flow. As the liquid enters the tube, precision-machined sensing vents determine flow rate.

Analytical Analytical variables are associated with devices designed to measure the composition of a substance. For example, process technicians use analyzers to determine the percentage of a substance in a process stream. Analyzers come in a variety of shapes and designs, and can measure the concentration of a specific chemical or element. Other examples of analytical process variables include pH or parts per million (ppm). These variables are frequently tracked on a cooling water system. Plastic plant technicians check for melt flow, color, and the concentration of special additives. Figure 7–5 shows an assortment of basic instruments used in the chemical processing industry.

7.2 Symbols and Diagrams One of the more difficult tasks a new process technician is faced with is memorizing the hundreds of symbols and diagrams associated with the process industry. These process symbols form the 173

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written flow language necessary for understanding how a specific process operates. This learning process should be taken one step at a time, building from simple symbols to more complex processes. Learning and recognizing these symbols is the key to moving to the next step of a very good career. Symbols and diagrams can be broken down into four primary parts: • Process equipment symbols • Process instrument symbols • Process flow diagrams (PFDs) • Piping and instrumentation drawings (P&IDs) Symbols and diagrams have been developed for most pieces of industrial equipment, process flows, and instrumentation.The symbols covered in this chapter include those typically used with valves, piping, tanks, pumps, compressors, steam turbines, motors, heat exchangers, cooling towers, furnaces, boilers, distillation columns, and reactors. Figure 7–6 shows many of the basic symbols for valves. GATE VALVES

Manually Operated

Gate

Pneumatic

GLOBE VALVES

Globe

Pneumatic

M

H

Motor

Hydraulic

M

H

Motor

Hydraulic

Bleeder Bleeder

M

Angle

Needle Pneumatic

BALL VALVES

Ball

PLUG VALVES

H

Ball

Butterfly

M

Plug

Motor or Hydraulic

BUTTERFLY VALVES

Motor

Motor or Hydraulic

Plug

M Butterfly

S

Motor or Hydraulic

DIAPHRAGM VALVES

Solenoid CLOSED

Pneumatically Operated

CHECK VALVES M

Diaphragm SAFETY (Gases)

Knife Valve

Check

Motor RELIEF (Liquids)

Four-Way Valve

Three-Way Valve

Pinch Valve Gauge

Figure 7–6 Valve Symbols 174

Stop Check

Rotameter

Orifice

7.2 Symbols and Diagrams

Piping Symbols Each plant will have a file of its standardized piping symbols. Process technicians should carefully review these piping symbols for major and minor flows, and for electric, pneumatic, capillary, hydraulic, and future equipment. The major flow path through a unit illustrates the critical areas a new technician should concentrate on. Some of the devices used in piping are strainers, filters, flanges, spool pieces, and steam traps. A variety of piping symbols can be found in Figure 7–7.

Pumps and Tank Symbols Pumps and tanks come in a variety of designs and shapes. Some of these designs include centrifugal and positive displacement pumps. Centrifugal pumps can be mounted vertically and horizontally in the field. Special symbols are used to distinguish each of these. A common symbol

Y-Type Strainer

RS

Removable Spool Flexible Hose

Duplex Strainer

Expansion Joint Basket Strainer XXX

Breather

D

Detonation Arrestor

Vent Cover

F

Flame Arrestor

In-Line Mixer

S

In-Line Silencer S

T

Vent Silencer

Diverter Valve

Steam Trap Desuperheater

DS

Rotary Valve

Ejector / Eductor

Pulsation Dampener

Exhaust Head Flange Future Equipment Major Process Minor Process

Nonconnecting Line

Hydraulic X

Capillary Tubing

• • • •

Mechanical Link

X

X

X

Electric Connecting Line

Pneumatic L L L

Electromagnetic, Sonic Optical, Nuclear

Nonconnecting Line Jacketed or Double Containment Software or Data Link

Figure 7–7 Piping Symbols 175

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CENTRIFUGAL PUMPS

POSITIVE DISPLACEMENT PUMPS Positive Displacement

Positive Displacement Vertical

Horizontal

Progressive Cavity

Gear Pump

Screw Pump Vertical Screw Pump Sump Pump

Vertical

Vertical Can Pump

Vacuum Pump

Reciprocating Pump

STORAGE SYMBOLS

Dome Roof Tank Bin

Open Top Tank Tank

Tank

Internal Floating Roof Tank

Double Wall Tank

Cone Roof Tank

Drum Sphere

Onion Tank

External Floating Roof

Figure 7–8 Pump and Tank Symbols

used to describe a positive displacement pump looks like a set of stairs. This illustrates how pressure builds on each rotation or stroke of the flow elements. Positive displacement pumps can be classified as rotary or reciprocating. Special symbols are used to describe each of these devices, including screw pumps, gear pumps, and reciprocating pumps. A variety of symbols are used to illustrate the different type of tanks and vessels found in the chemical processing industry, including bins, drums, and dome, cone, open-top, floating-roof, and spherical tanks. Process symbols are designed to graphically display the vessel as it appears in the field. Common pump and tank symbols are shown in Figure 7–8.

Compressor and Pump Symbols Compressors and pumps share a common set of operating principles. The dynamic and positive displacement families share common categories. Therefore, the symbols for compressors may closely resemble those for pumps. In most cases, the symbol is slightly larger in the compressor symbol file. For a multistage, centrifugal compressor, the symbol clearly describes how the gas is 176

7.2 Symbols and Diagrams

CENTRIFUGAL COMPRESSORS

POSITIVE DISPLACEMENT COMPRESSORS

T Centrifugal Compressor

Centrifugal Compressor (Turbine Driven)

Reciprocating Compressor Rotary Compressor

Centrifugal Compressor Centrifugal Blower

Rotory Compressor & Silencers

Rotary Screw Compressor

Liquid Ring Vacuum

Positive Displacement Blower Reciprocating Compressor

Axial Compressor

STEAM TURBINES

Agitator or Mixer

Motor Turbine Driver

Doubleflow Turbine Diesel Motor

Figure 7–9 Compressor, Steam Turbine, and Motor Symbols

compressed prior to being released. This is in sharp contrast to the steam turbine symbol, which illustrates the opposite effect as the steam expands while passing over the rotor. Modern piping and instrumentation drawings show the motor symbol connected to the driven equipment. This equipment may be a pump, compressor, mixer, fan, conveyor, or generator. Figure 7–9 illustrates the standardized symbols for compressors, steam turbines, and motors.

Heat Exchanger and Cooling Tower Symbols Heat exchangers and cooling towers are two types of industrial equipment that share a unique relationship. A heat exchanger is a device used to transfer heat energy between two process flows. The cooling tower performs a similar function; however, cooling towers and heat exchangers operate according to different scientific principles. Heat exchangers transfer heat energy through conductive and convective heat transfer methods, whereas cooling towers transfer heat energy to the outside air through the principle of evaporation. Figures 7–10 and 7–11 illustrate the standard symbols used for heat exchangers and cooling towers. The symbol for a heat exchanger clearly illustrates the flows through the device. It is important for a process technician to be able to see the shell inlet and outlet and the tube inlet and outlet flow 177

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Plate and Frame Heat Exchanger Hairpin Exchanger

Air-Cooled Exchanger (Louvers Optional)

Double-Pipe Heat Exchanger

U-Tube Heat Exchanger

Single Pass Heat Exchanger

C

C

Spiral Heat Exchanger

Heater

Condenser

Shell & Tube Heat Exchanger

Figure 7–10 Heat Exchanger Symbols

INDUCED DRAFT Cross Flow

HYPERBOLIC Chimney Tower

FORCED DRAFT Counterflow

NATURAL DRAFT Counterflow

Figure 7–11 Cooling-Tower Symbols 178

Reboiler

7.2 Symbols and Diagrams paths. A heat exchanger with an arrow drawn through the body illustrates whether the device is being used to heat or cool a product. The downward direction indicates heating; the upward direction illustrates cooling. Heat exchanger types include shell-and-tube, plate-and-frame, spiral, and air-cooled. Shell-andtube heat exchangers are the most common and complex. For example, a shell-and-tube heat exchanger can be drawn as a single-pass, fixed-head, multipass, double-pipe with fins, U-tube, or kettle reboiler. The symbol for each device is unique and helps identify how the device is being used and how to safely operate it. Spiral and plate-and-frame heat exchangers are widely used; however, they are not as common as shell-and-tube devices. Air-cooled heat exchangers are often referred to as fin fans. Actually, the tubes can be plain or finned depending on system requirements. Finned tubes transfer heat more effectively. Devices of this sort are used to condense overhead vapors from a distillation system. The symbols used for these devices distinguish the differences between them. The symbol for a cooling tower is designed to resemble the actual device in the process unit. Cooled product flows out of the bottom of the tower and to the processing units, while hot water returns to a point located above the fill. The primary purpose of a cooling tower is to cool water. A cooling tower has a box or rectangular shape that rests on a concrete water basin. It is filled with a matrix of boards or slats that are positioned to break up the downward flow of water. Air passes between the downward flow of water and out the top as the air rises naturally or is drawn in mechanically. The primary mechanism of heat transfer is through evaporation. This principle accounts for 80% to 90% of the cooling process. (Sensible heat accounts for the rest.) A pump takes suction off the basin, sends it to a heat exchanger system, and then returns it to the cooling tower. Hot water enters the top of the cooling tower and is distributed using the water distribution system. A mechanical fan may be used to draw in or expel air through a set of air louvers located on the sides of the cooling tower. The water basin has a water make-up system designed to maintain water level. Periodically, the water in the basin is blown down to reduce suspended solids in the process stream.

Boiler and Furnace Symbols A steam generator or boiler is used by industry to boil water and produce high-, medium-, or lowpressure steam. The symbol for a boiler closely resembles that for a large water-tube boiler. Boilers are composed of an upper steam-generating drum, a lower mud drum, downcomer tubes, riser tubes, steam-generating tubes, an economizer section, a water make-up system, a stack, a fan, and burners. All of these devices are neatly enclosed inside a refractory-lined shell designed to reflect heat back into the furnace. Boilers can be classified as water tube (direct fired) or fire tube (indirect fired), depending on the internal design of the device. Fire-tube boilers are used in small commercial operations and typically do not have the range or capacity of water-tube boilers. A fired heater or furnace is used to heat large quantities of hydrocarbons for industrial use in a distillation system or reactor. Fired heaters are characterized by three basic designs: cabin, cylindrical, and box. The basic components of a furnace include shell, refractory lining, burners, radiant tubes, convective tubes, damper, stack, and firebox. Air and fuel are proportionally balanced as temperatures in the furnace are held constant. Figure 7–12 shows the two standard symbols used for a fired heater or furnace and a boiler. 179

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Furnace

Boiler

Figure 7–12 Boiler and Furnace Symbols Distillation Symbols On a typical flow diagram, distillation columns, reactors, boilers, and furnaces are drawn as they visually appear in the plant. If a proprietary process includes several types of equipment not typically found on a standard symbol file, the designer will draw the device as it visually appears in the unit.

Distillation is a process that separates the components in a mixture by boiling point. At the heart of a distillation system is the column. Distillation columns come in two basic designs: plate and packed. Flow arrangements vary from process to process. The symbols allow the technician to identify primary and secondary flow paths. The two standard symbols for distillation columns are shown in Figure 7–13. A distillation system is a complex arrangement of equipment and instruments. In most cases, all of the equipment covered in this text could be found in service within a distillation system. The symbol used on a diagram for a plate column should indicate the type of tray used in the system: bubble-cap, valve, or sieve. The first distillation column was invented in 1917. Today, a number of modifications allow modern process technicians to operate much more efficiently. The design, however, still includes the original still-on-top-of-a-still approach. The basic components of a plate distillation column are a feed line; feed tray; stripping section below the feed line; enriching or rectifying section above the feed line; overhead vapor outlet, side-stream outlet, and bottom outlet; reboiler; instrumentation for level, temperature, flow, pressure, and composition control; outer shell; and a top reflux line. Packed columns are designed to enhance vapor-liquid contact as hot vapors rise up the column and liquids condense and drop down the column. In this type of system, packing is used to create the surface area for this contact, as liquids and vapors compete for access through the same passages. Various packing designs include saddle, ring, and sulzer packing.The basic components of a packed column include a feed line; structured or unstructured packing; liquid distributor; shell; overhead vapor outlet, side-stream outlet, and bottom outlet; packing supports; bed limiters; reboiler; instrumentation for level, temperature, flow, pressure, and composition control; and a top reflux line.

Reactor Symbols Modern process manufacturing utilizes all of our advanced knowledge about chemistry and chemical reactions to form and create new products. The primary people involved in this industry 180

7.2 Symbols and Diagrams

PLATE TOWER Bubble-Cap, Sieve, Valve

PACKED TOWER Saddle, Ring, Sulzer, Rosette

Single Pass Demister Spray Nozzle Chimney Two Pass Packed Section

Draw Off Generic Tray

Manway

Vortex Breaker

Figure 7–13 Distillation Symbols

are chemical engineers, chemists, mechanical engineers, and process chemical technicians. While much of the chemistry is transparent to the technician, understanding the complex concepts is important to being able to operate modern reactor systems. There are six basic reactor designs: stirred-tank, fixed-bed, fluidized-bed, tubular, furnace, and nuclear. The primary reaction variables include temperature, pressure, flow, concentration of reactants, catalysts, and time. Chemical reactions may be exothermic (produce heat), endothermic (require heat), replacement, and neutralization. Reactors are stationary vessels that are classified as batch, semi-batch, or continuous. Some reactors use mixers to blend the individual components. Reactor design depends on the type of service the reactor will be used in. Some of the reactor processes (among many others) include alkylation, catcracking, hydrodesulfurization, hydrocracking, fluid coking, reforming, polyethylene, and mixed-xylene. Figure 7–14 shows the standard symbols for reactors. 181

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Hydrocracking

Fluid Catalytic Cracking

Hydrodesulfurization

Fluid Coking

Mixing Reactor

Tubular Reactor

Reformer

Fluidized Reactor

Alkylation

Figure 7–14 Reactor Symbols

7.3 Process Diagrams Process diagrams can be broken down into two major categories: process flow diagrams and piping and instrumentation drawings. A flow diagram is a simplified illustration that uses process symbols to describe the primary flow path through a unit. A piping and instrumentation drawing is a complex diagram that uses process symbols to describe an entire process unit. Process flow diagrams (PFDs) are used to outline or explain the complex flows, equipment, instrumentation, electronics, elevations, footings, and foundations that exist in a process unit. New technicians are required to study a simple flow diagram of their assigned unit. Process flow diagrams typically include the major equipment and piping path the process takes through the unit. As operators learn more about symbols and diagrams, they graduate to the much more complex piping and instrumentation drawings. Some symbols are common between plants, whereas others change depending on the company. In other words, two different symbols may be used to identify a centrifugal pump or a valve, for example. Some standardization of process symbols and diagrams is taking place, but the process technician must learn what symbols his or her employer uses. The symbols shown in this chapter reflect a wide variety of petrochemical and refinery operations. 182

7.3 Process Diagrams A piping and instrumentation drawing (P&ID) is a complex representation of the various units found in a plant. While the simple process flow diagram is typically used to describe the primary flow path through a unit, a P&ID, like a road map, can show intricate details of a unit that cannot easily be noticed during a walk-through. Process technicians are expected to be able to read simple flow diagrams within hours of starting their initial training. Technicians will graduate to reading and using complex P&IDs over the course of their training. To read a P&ID, you need to understand process equipment, process instrumentation, and process technology. Some of this equipment includes piping, valves, pumps, tanks, compressors, steam turbines, process instrumentation, heat exchangers, cooling towers, furnaces, boilers, reactors, and distillation columns. The next step in using a P&ID is to memorize your plant’s process symbol list. This information can be found on the process legend. Process and instrumentation drawings have a variety of elements, including flow diagrams, equipment layouts, elevation plans, electrical layouts, title blocks and legends, and footings and foundation drawings. Figure 7–15 shows the basic relationships and flow paths found in a process unit. It is easier to understand a simple flow diagram if it is broken down into four different sections: feed, preheating, the process, and the final products (see Figure 7–16).This simple left-to-right approach allows a technician to identify where the process starts and where it will eventually end.The feed section includes the feed

Cooling Tower

Vacuum Pump Product Tank 1 Drum

Furnace Feed Tank

Column Reactors

Product Tank 2

Bottom Tank

Boiler

Figure 7–15 Process Flow Diagram (PFD) 183

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Process Instrumentation One

Cooling Tower

TK-2

Column Blending Tank Mixing Reactor TK 3

EX-1

TK 4

TK-1 Furnace

TK 5

TK 6

Boiler Feed Section

Preheating

The Process

Products

Figure 7–16 Four-Section Flow Diagram tanks, mixers, piping, and valves. In the second section/step, the process flow is gradually heated up for processing; this section includes heat exchangers and furnaces. In the third section, the process is detailed.The process area is a complex collection of equipment pieces that work together in a system. The process is designed to create products that will be sent to the final section.Typical process-section components are distillation and reaction. The final section shows the final product(s). Instrumentation symbols are shown on a P&ID as a circle, inside which information is included that tells the process technician what type of instrument is represented. Figure 7–17 shows examples of typical instrument symbols.

7.4 Interlocks and Permissives An interlock is a device designed to prevent damage to equipment and personnel. It accomplishes this by stopping or preventing the start of certain equipment functions unless a preset condition has been met. There are two types of interlocks: softwire and hardwire. Softwire interlocks are contained within the logic of the control computer software. Hardwire interlocks are a physical arrangement. A hardwire interlock usually involves electrical relays that operate independently of the control computer. In many cases they run side by side with the computer interlocks. However, hardwire interlocks cannot be bypassed. They must be satisfied before the process they are part of can take place. A permissive is a special type of interlock that controls a set of conditions that must be satisfied before a piece of equipment can be started. Permissives deal with start-up items, whereas hardwire interlocks deal with shutdown items. A permissive is an interlock controlled by the distributive control system (DCS). This type of interlock will not necessarily shut down the equipment if one or more of its conditions are not met. It will, however, keep the equipment from starting up. 184

7.4 Interlocks and Permissives

Ti

Temp Indicator

Fi

Flow Indicator

TT

Temp Transmitter

FT

Flow Transmitter

I P

Transducer

PIC 105

Pressure Indicating Controller

Flow Recorder

PRC 40

Pressure Recording Controller Level Alarm

Temp Recorder

TC

Temp. Controller

FC

Flow Controller

LA 25

Li

Level Indicator

Pi

Pressure Indicator

FE

Flow Element

LT 65

Level Transmitter

PT 55

Pressure Transmitter

TE

Temperature Element

LR 65

Level Recorder

PR 55

Pressure Recorder

LG

Level Gauge

LC 65

Level Controller

PC 55

Pressure Controller

PG

Press. Gauge

PA 25

Press. Alarm (Remote Location)

LAH 2

Level Alarm High (Remote Location)

Thermowell

LAL 2

Level Alarm Low (Remote Location)

PSIA

Pounds Per Square Inch Absolute

Flow Nozzle

FA 25

Flow Alarm (Remote Location)

PSID

Pounds Per Square Inch Differential

PSIG

TW

Pounds Per Square Inch Gauge

Venturi

Fi

AT TY E

Rotameter

Pitot Tube

Restriction Orifice

PIC

PS*

Level Indicating Controller PLC (Remote Loc.) Press. Indicating Controller DCS (Remote Loc.) Press. Indicating Controller PLC (Remote Loc.) Pressure Switch * = H/L

Transducer (Converter)

Pounds Per Square Inch Vacuum

AT 101

AIC 101

In-Line Pressure Element

Analyzer Transmitter

Transducer (Converter) P Elec to Pneumatic)

PSIV

Averaging Pitot Tube

PE Ultrasonic

FT In-Line Flow Element

FE

FS*

Flow Switch * = H/L

AS*

Analytical Switch * = H/L

LS*

Level Switch * = H/L

AE 101

Vortex Meter Sight Flow Indicator

PIC

Level Indicating Controller DCS (Remote Loc.)

PT

Flow Conditioning Devices

FO

LIC

4

TR

FR

LIC 15

Wedge Meter

Turbine Meter

Flume Duplex Strainer

Weir

Basket Strainer

Target Positive Displacement

What it does M

Variable being measured

Instrument

Magnetic Orifice

FT

FIC

In-Line Flow Element with Integral Transmitter. Ex. Mass, Coriolis, Thermal, Int. Orifice

55 Field mounted Control loop

Remote location (board mounted)

Remote location (behind control panel)

Figure 7–17 Instrument Symbols 185

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7.5 P&ID Components The piping and instrumentation drawing includes a graphic representation of the equipment, piping, and instrumentation (see Figure 7–18). Modern process control is vividly illustrated in this type of drawing. Process technicians can look at their process and see how the engineering department has automated their unit. Pressure, temperature, flow, level, and analytical control loops are all included on the unit P&ID. The basic components of a piping and instrumentation drawing are the process legend, foundation, elevation, electrical, equipment location drawings, simple flow diagram, piping, and instrumentation.

Simple Flow Diagram A simple flow diagram provides a quick snapshot or overview of the operating unit. Flow diagrams include all primary equipment, flows, and numbers. A technician can use this document to trace the primary flow of chemicals through the unit. Secondary or minor flows are not included. Complex control loops and instrumentation are not included. The flow diagram is used for visitor information and new employee training.

Process Legends The process legend (see Figure 7–19) provides the information needed to interpret and read the P&ID. Process legends are found at the front of the P&ID. The legend includes information about piping, instrument, and equipment symbols; abbreviations; title block; drawing number; revision number; approvals; and company prefixes. At present, symbol and diagram standardization is not complete or uniformly accepted. Many companies use their own symbols file for display on unit drawings. Unique and unusual equipment will also require a modified symbols file.

P-12 CT-105

V-2

V-3

PC

PCV

PT

D-105

TK-10

LC

I/P

TK-12

V-4

C-105

RX-105

V-5 I/P TT

FT

V-1

LT

P-14

F-105

FC

P-13

I/P

FCV P-10

V-6

TK-14

TC LT

TE

TT

TC

I/P

RX-106

I/P

P-15

LC I/P

EX-105

TK-16 P-11

V-7

B-105

Figure 7–18 Piping and Instrumentation Drawing (P&ID) 186

7.5 P&ID Components

VALVE SYMBOLS Ball

Gate Valve

Bleeder Valves

Minor Process Pneumatic

Pneumatic

Angle Globe Valve

Future Equipment Major Process

Manually Operated Valve

Pneumatic

Plug

Knife Valve

SAFETY (Gases)

Four-Way Valve

Diaphragm

Pinch Valve

Relief Valve

Solenoid Valve CLOSED

Hydraulic

INDUCED DRAFT Cross Flow

Butterfly S

Check Valve

LINE SYMBOLS

EQUIPMENT CONT.

X

Mechanical Link

• • • •

X

X

X

Electromagnetic, Sonic Optical, Nuclear Electric

Stop Check

Three-Way Valve

EQUIPMENT SYMBOLS

L L L

Capillary Tubing

Connecting Line

NATURAL DRAFT Counterflow

Nonconnecting Line Nonconnecting Line Jacketed or Double Containment

Vacuum Pump

Horizontal

Software or Data Link

Vertical

INSTRUMENT SYMBOLS Sump Pump

BOILER

Orifice

TI

Temp Indicator

FI

Flow Indicator

Centrifugal Rotameter

Gear Pump

Positive Displacement

FURNACE

Rotary Screw Compressor

TT

Temp Transmitter

FT

Flow Transmitter

TR

Temp Recorder

FR

Flow Recorder

TC

Temp. Controller

FC

Flow Controller

LI

Pressure Indicator

Gauge

Reciprocating Pump

Single Pass

Demister

Screw Pump Chimney

Progressive Cavity Two Pass

Spray Nozzle Packed Section

Level Indicator

PI

LT 65

Level Transmitter

PT 55

Pressure Transmitter

LR 65

Level Recorder

PR 55

Pressure Recorder

LC 65

Level Controller

PC 55

Pressure Controller

I

Transducer

FE

Flow Element

TE

Temperature Element PIC 105

LG

Level Gauge

AT

Analyzer Transmitter

P

Draw Off

C

Double-Pipe Heat Exchanger

C

Spiral Heat Exchanger

Generic Tray

Manway

Plate and Frame Heat Exchanger Vortex Breaker

PRC 40 LA 25

Pressure Indicating Controller Pressure Recording Controller Level Alarm

P Air Cooled Exchanger (Louvers Optional)

C

E

Drum APPROVED

Dome Roof Tank

Sphere

10-6-99

DATE GENERAL LEGEND

Condenser

DISTILLATION UNIT Cone Roof Tank

Internal Floating Roof Tank

DRAWING NUMBER

OO6543 REVISION 1

PAGE 1 OF 30

Heater

ABBREVIATIONS

PREFIXES CW- cooling water MU- make-up FW- feed water SE- sewer

RX- reactor UT- utilities CA- chemical addition IA- instrument air

D- drum C- column CT- cooling tower

TK-tank F- furnace EX- exchanger

P- pump V- valve

Figure 7–19 Process Legend 187

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Process Instrumentation One S

4"

18"

W

E

Remesh

12"

N

2' x 64' x 18" load bearing beam

Rebar in all beams

32'-0" Remesh over plastic

Remesh

6-8-10 Method

6'-0" 10'-0"

28'-0"

90

8'-0" 28'-0" 64'-0"

Estimating Materials:

cu yds =

width x length x thickness 27

Figure 7–20 Foundation Foundation Foundation drawings (see Figure 7–20) are used by the construction crew pouring the footers, beams, and foundation. Concrete and steel specifications are designed to support equipment, integrate underground piping, and provide support for exterior and interior walls. Foundation drawings are typically not used by process technicians; however, they are useful when questions arise about piping that disappears under the ground and when new equipment is added.

Elevation Elevation drawings are graphical representations that show the location of process equipment in relation to existing structures and ground level. In a multistory structure, the elevation drawing provides the technician with information about equipment operation and location. The drawing closely resembles a process that removes the outside wall of the building and draws the exposed equipment. This information is important for making rounds, doing equipment checks, developing checklists, catching samples, and performing start-ups and shutdowns. The elevation plan in Figure 7–21 illustrates equipment and structure locations.

Electrical Electrical drawings include symbols and diagrams that depict an electrical process system. Electrical drawings show unit electricians where power transmission lines run and places where it is stepped down or up for operational purposes. A complex P&ID is designed to be used by a variety of crafts.The primary users of the document after plant start-up are process technicians, instrument and electrical, mechanical, safety, and engineering. 188

7.5 P&ID Components

RX-300

C-300

TK-300

EL 40'-0

D-56

EL 28'-0"

RX-105

EL 16'-0"

TK-105

TK-200

RX-106

Figure 7–21 Elevation

A process technician typically traces power to the unit from a motor control center (MCC). The primary components of an electrical system are the MCC, motors, transformers, breakers, fuses, switch gears, starters, and switches. Specific safety rules apply to the operation of electrical systems. The primary safety system is the isolation of hazardous energy through lock-out/tag-out measures. Process technicians are required to have training in this area. Figure 7–22 shows the basic symbols and flow path associated with an electrical drawing. Electrical lines are typically run in cable trays to switches, motors, ammeters, substations, and control rooms. A transformer is a device used by industry to convert high voltage to low voltage. Problems with transformers are always handled by the electrical department. Electrical breakers are designed to interrupt current flow if design conditions are exceeded. Breakers are not switches and should not be turned on or off. If a tripping problem occurs, the technician should call for an electrician. Fuses are devices designed to protect equipment from excess current. A thin strip of metal within the fuse will melt if design specifications are exceeded. During operational rounds, technicians check the ammeters inside the MCC for current flow to their electrical systems. Voltmeters, electrical devices used to monitor voltage in an electrical system, are also checked during routine rounds.

Equipment Location Drawings Equipment location drawings show the exact floor plan location of equipment in relationship to the plant’s physical boundaries. Figure 7–23 illustrates this layout. Location drawings provide benefits similar to those of elevation drawings. The entire P&ID provides a three-dimensional look at the unit. 189

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Process Instrumentation One 69,000 Volts 69 kV

MAIN TRANSFORMER

V As

A

51

Vs 27

13.2 kV 13.8 kV 2.3 kV

480 V BUS MAIN POWER DISTRIBUTION

Generator

BOILER

13,200 V 13,800 V 2,300 V

Steam Turbine

MCC #1

2.3 kV or 480 Volts

Motor Starter

ELECTRIC POWER PLANT

Motor Starter

M

M

Motor

Fuse

M

Motor

V

Voltmeter—measures voltage

27

Under Voltage Relay

A

Ammeter—measures electric current

V s

MCC

Motor Control Center

Voltmeter Switch Current Transformer—reduces high voltage to instrumentation

As

Ammeter Switch

50

Transformer Overcurrent Relay (Instantaneous)

Potential Transforming Symbol

51

Transformer Overcurrent Relay (Time delay)

Power Transformer—reduces high voltage

Circuit Breaker—a protective device that interrupts current flow through an electric circuit

Switch

Figure 7–22 Electrical

190

On Off

Motor Circuit Contacts

Summary

TK-2

TK-3

TK-4

8'-0"

TK-1

P-200A

TK-100

TK-200

P-500A

20'-0"

8'-0" EX-600

6'-0"

D-500

18'-0"

C-600

10'-0"

8'-0"

TK-300

P-300A

20'-0"

20'-0"

20'-0"

6'-0"

P-100A

P-600A

20'-0"

TK-400

P-400A

16'-0"

Figure 7–23 Equipment Location

Summary The primary variables that a process technician works with and controls include pressure, temperature, flow, level, and analytical or composition.Various instruments are designed to help facilitate this critical aspect of process work. Some of these instruments include computers, gauges, recorders, transmitters, controllers, transducers, primary elements and sensors, switches, and control valves. Symbols and diagrams have been developed for most pieces of industrial equipment, process flows, and instrumentation. The symbols covered in this chapter include those typically used with valves, piping, tanks, pumps, compressors, steam turbines, motors, heat exchangers, cooling towers, furnaces, boilers, distillation columns, and reactors. These symbols are used in process symbols to describe a process unit. Process diagrams are used to outline or explain the complex flows, equipment, instrumentation, electronics, elevations, footings, and foundations that exist in and make up a process unit.These diagrams can be broken down into two major categories: process flow diagrams and piping and instrumentation drawings.The PFD is typically a simplified illustration that describes the primary flow path through a unit, whereas the P&ID is a complex representation of the various units found in a plant. An interlock is a device designed to prevent damage to equipment and personnel by stopping or preventing the start of certain equipment functions unless a preset condition has been met. A permissive is a special type of interlock that controls a set of conditions that must be satisfied before a piece of equipment can be started. Permissives deal with start-up items, whereas hardwire interlocks deal with shutdown items. A permissive interlock will not necessarily shut down the equipment if one or more of its conditions are not met, but it will keep the equipment from starting up. 191

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Chapter 7 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

16. 17. 18. 19. 20.

192

Describe a process flow diagram. Describe a piping and instrumentation drawing. How are instrumentation symbols shown on a P&ID? Draw the symbols for a gate valve and a globe valve. Draw the symbols for a centrifugal pump and a positive displacement pump. Draw the symbols for a blower and a reciprocating compressor. Draw the symbol for a steam turbine. Draw the symbol for a heat exchanger. Draw the symbol for a cooling tower. Draw the symbol for a packed column. Draw the symbol for a plate column. Draw the symbol for a furnace. Draw the symbol for a boiler. Draw the symbol for a manually operated valve. Draw a simple flow diagram. Include piping, pumps, two tanks, and six different valves. Provide a way to circulate and blend the material using the pumps-piping-valves relationship. Draw a simple P&ID. Do not copy the example from the book. Be original. List and describe the instruments associated with flow measurement. List and describe the instruments associated with temperature measurement. List and describe the instruments associated with level measurement. List and describe the instruments associated with pressure measurement.

Process Instrumentation Two After studying this chapter, the student will be able to: • • • • • • • •

Define the term control loop, and identify the five elements of a control loop. Draw a level control loop. Draw a pressure control loop. Draw a flow control loop. Draw a temperature control loop. Discuss the function of transmitters. Describe manual, automatic, and cascade control features. Describe the various controller modes, rate modes, reset modes, and proportional bands and how each complements the other. • Describe a programmable logic controller. • Describe a distributive control system. • Understand the purpose and functioning of automatic valves.

193

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Process Instrumentation Two

Key Terms Automatic/manual control—term describing two modes in which controllers can be operated. During plant start-up, the controller is typically placed in the manual position. In this mode, only manual control affects the position of the control valve; it does not respond to process load changes. After the process is stable, the operator places the controller in automatic mode, which allows the controller to supervise the control loop function. At this point, the controller will automatically open and close the control valve to maintain the setpoint. Cascade control—a term describing how one control loop controls or overrides the instructions of another control loop to achieve a desired setpoint. Control loop—a collection of instruments that work together to automatically control a process. A loop includes a primary element or sensor, a transmitter, a controller, a transducer, and a final control element. Controller—device the primary purpose of which is to receive a signal from a transmitter, compare this signal to a setpoint, and adjust the (final control element) process to stay within the range of the setpoint. Controllers come in three basic designs: pneumatic, electronic, and electric. Controller modes—settings and functions that include proportional (P), proportional plus integral (PI), proportional plus derivative (PD), and proportional-integral-derivative (PID). Proportional control is primarily used to provide gain where little or no load change typically occurs in the process. Proportional plus integral is used to eliminate offset between the setpoint and process variables; PI works best where large changes occur slowly. Proportional plus derivative is designed to correct fast-changing errors and avoid overshooting the setpoint; PD works best when frequent small changes are required. Proportional-integral-derivative is applied where massive, rapid load changes occur; PID reduces the amount of swing between the process variable and the setpoint. Proportional band—on a controller, describes the scaling factor used to take a controller from 0% to 100% output. Range—the portion of the process controlled by the controller. For example, the temperature range for a controller may be limited from 80°F to 140°F. Rate (or derivative) mode—enhances controller output by increasing the output in relationship to the changing process variable. As the process variable approaches the setpoint, the rate or derivative mode relaxes, providing a braking action that prevents overshooting of the setpoint. The rate responds aggressively to rapid changes and passively to smaller changes in the process variable. Reset (or integral) mode—designed to reduce the difference between the setpoint and process variable by adjusting the controller output continuously until the offset is eliminated. The reset or integral mode responds proportionally to the size of the error, the length of time that it lasts, and the integral gain setting. Span—the difference between the upper and lower range limits.

194

8.1 Basic Elements of a Control Loop

8.1 Basic Elements of a Control Loop Process technicians use instrumentation to control a variety of automated processes. The key component of automatic control is the control loop, a group of instruments that work together to control a process (see Figure 8–1). These instruments typically include a transmitter coupled with a sensing device or primary element, a controller, a transducer, and a control valve. Process plants are composed of hundreds of control loops. These control loops are used to maintain pressure, temperature, flow, level, and analytical process variables. The basic elements of a control loop are: 1. Measurement device—primary elements and sensors • Flow—orifice plate, flow nozzle • Level—float, displacer • Pressure—helix, spiral, bellows • Temperature—thermocouple, thermal and resistance bulb 2. Transmitter—a device designed to convert a measurement into a signal. This signal is transmitted to another instrument. • Pressure transmitter—tubing to process • Temperature transmitter—tubing to process • Flow transmitter—DP cell, high/low pressure taps • Level transmitter—hooked to float or displacer 3. Controller—a device designed to compare a signal to a setpoint and transmit a signal to a final control element. • Recording • Indicating • Blind • Strip chart • Vertical and scale 4. Transducer—a device designed to convert an air signal to an electric signal or an electric signal to a pneumatic signal. Sometimes referred to as an I to P or a converter. • Air signal to an electric signal • Electric signal to a pneumatic signal 5. Final control element—the part of a control loop that actually makes the change to control the process. • Control valve • Motor on a pump or compressor UNIT FEED PUMP 150 GPM @ 300 PSIG

Controller FC

Pi

Pi

Pi

Pi

Transmitter

I/P Transducer

FT

P&ID DWG Primary Element

Final Control Element

Figure 8–1 Typical Control Loop 195

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8.2 Process Variables and Control Loops Process variables typically fall into five different groups: pressure, temperature, flow, level, and analytical variables. Each control loop is specifically designed to work with a selected variable. Process technicians monitor many control process variables. Figure 8–2 shows an example of a flow control loop. Flow loops are typically designed so that a measurement of the flow rate is taken first and then the flow is interrupted or controlled downstream. Flow control loops start at the primary element. Flow control primary elements may include orifice plates, venturi tubes, flow nozzles, nutating disks, oval gears, or turbine meters. The most common primary element is the orifice plate, which artificially creates a high-pressure/lowpressure situation that can be measured by the transmitter. Primary elements are typically used in conjunction with a transmitter. Although it appears that the primary element is interrupting the flow, this is not the case. Increased velocity across the orifice plate compensates for the restriction. The transmitted signal is sent to a controller that compares the incoming signal with the desired setpoint. If a change is required, the controller sends a signal to a final control element. Control loop design uses the five elements of the control loop. The one area that changes consistently is the first: primary elements and sensors. Pressure control loops use devices to detect pressure changes. These primary elements are typically expansion-type devices. Primary pressure elements include bourdon, helical, spiral, bellows, pressure capsule, and diaphragm. Figure 8–3 shows a pressure transmitter, controller, transducer, and control valve. Figure 8–4 is a simple layout for a temperature control loop. In large fired furnaces, a temperature measurement is taken at the furnace or from the exiting charge. The primary sensors used to detect temperature are thermocouples or RTDs, often called temperature elements. Like primary elements, temperature elements are linked to transmitters. A 4- to 20-milliamp (mA) signal is sent to a controller that compares it to a setpoint. Controllers may be located in the field near the equipment or in a remote location. The controller sends an electric signal to a transducer, which is typically located near the valve to eliminate process lag. The transducer converts the electric signal to a pneumatic signal of 3 to 15 psi. The control valve (see Figure 8–4) opens and closes according to the signal. Temperature is controlled by reducing or increasing fuel flow to the burners. Level control loops use floats, displacers, or differential pressure transmitters. Figure 8–5 shows a differential pressure (ΔP) cell to detect level changes. The primary element or sensor is inside

Controller

Transducer FC

I/P

Transmitter Final Control Element

FT

Flow Primary Element

Bypass Loop

Figure 8–2 Flow Control Loop 196

8.4 Transmitters and Control Loops

Controller PIC

I

P

Transducer

Transmitter

PT

Sensor

PE

PCV

Final Control Element

PRESSURE

Figure 8–3 Pressure Control Loop

Sensor

Transmitter TE TT

Controller TC

Transducer

I/P

Fuel Gas Final Control Element

Figure 8–4 Temperature Control Loop the transmitter. These two devices couple up to detect changes and send a signal to a level controller. A transducer converts the signal and opens or closes the control valve.

8.3 Primary Elements and Sensors Figure 8–6 shows the primary elements and sensors for flow, level, pressure, and temperature.

8.4 Transmitters and Control Loops Differential pressure or ΔP cell transmitters come in two basic designs: pneumatic or electronic. Controllers are typically mounted between 400 feet (closed loop) and 1,000 feet (open loop) from the transmitter. The signal from an electronic transmitter is proportional to the difference in the highand low-pressure legs. Standard output signals are 4 to 20 mA, 10 to 50 mA, and 1 to 5 volts (V). 197

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LEVEL

LE

LT LIC

I

Controller

P

Transducer

Final Control Element Figure 8–5 Level Control Loop

Primary Element

Sensor

Flow

Orifice plate, flow nozzle, ΔP cell ΔP cell (diaphragm)

Level

Float, displacer, ΔP cell (diaphragm)

Pressure

Helix, spiral, bellows, bourdon tube, ΔP cell ΔP cell

Temperature

Capillary tubing, thermal & resistance Thermocouple, RTD bulb

ΔP cell

Figure 8–6 Primary Elements Chart 198

8.4 Transmitters and Control Loops The 10–50 mA transmitter is becoming very popular because it has a higher tolerance to outside interference. Pneumatic transmitters require a 20-psig air supply in order to run the standard 3- to 15-psig output. (See Figure 8–7.) Differential pressure cells function by running a high- and low-pressure tap to each side of an internal twin-diaphragm capsule. Pressure changes cause the diaphragms to move. This process increases or decreases the signal to the controller. Figure 8–8 illustrates how a ΔP transmitter operates.

Smart transmitters are frequently found in the chemical processing industry. This type of transmitter is very reliable and does not need constant attention. Smart transmitters have an internal diagnostic system that warns the operator if a problem is about to occur. This type of transmitter can be used to monitor liquid or gas service, pressure, viscosity, temperature, flow, or level. Several advantageous features of the smart transmitter include speed, reliability, internal diagnostics capability, strong digital signal, and remote calibration capabilities.

Air-to-Open psi

4–20 mA

Valve Position

10–50 mA

1–5 V

3

4

Closed

10

1

6

8

25%

20

2

9

12

50%

30

3

12

16

75%

40

4

15

20

100%

50

5

Figure 8–7 Pneumatic Electric Comparison Chart

Δ

P Cell Transmitter Delta

H

Flow in

L

Low Pressure

High Pressure

Orifice Plate

Figure 8–8

ΔP Cell Transmitter 199

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8.5 Controllers and Control Modes The primary purpose of a controller (see Figure 8–9) is to receive a signal from a transmitter, compare this signal to a setpoint, and adjust the process (via the final control element) to stay within the range of the setpoint. Controllers come in three basic designs: pneumatic, electronic, and electric. Electronic controllers were first introduced in the early 1960s. Before then, only pneumatic controllers were used. Pneumatic controllers require a clean air supply pressure of 20 psig. Several of the more attractive features of electronic controllers are the reduction of lag time in process changes, low installation expense, and ease of installation. As use of the personal computer (PC) became widespread, a number of applications were found for controller use. Distributed control systems (DCSs) began to replace the older pneumatic and

Figure 8–9 Controller 200

8.5 Controllers and Control Modes electronic controllers. The primary reason was the ease with which a DCS could be installed and the relatively few wires required to do it. Most modern plants are still a combination of all three systems—pneumatic, electronic, and electric. It is almost impossible to identify from the control loop function what type of controller (pneumatic, electronic, or DCS) is being used. Controllers can be operated in manual, automatic, or cascade control. During plant start-up, the controller is typically placed in the manual position and left there until the process has lined out. This process initiates a setpoint on the final control element; however, it does not utilize a controlling function. It only opens the valve 50% or 25% and keeps it there until the technician changes the mode. This keeps the process from swinging up and down during start-up. After the process is stable, the operator places the controller on automatic and allows it to supervise the control loop function. At this point, the controller will open and close the control valve to maintain the setpoint. Cascade control describes how one control loop controls or overrides the instructions of another control loop in order to achieve a desired setpoint. In this case, a control loop’s controller may use all five elements of another control loop as its final control element.

Proportional Band The proportional band on a controller describes the scaling factor used to take a controller from 0% to 100% output. For example, if the proportional band is set at 50% and the amount of lift the final control element (in this case a globe valve) has off the seat is 4 inches, the control valve will open 2 inches. Range is the portion of the process controlled by the controller. For example, the temperature range for a controller may be limited to 80°F to 140°F. Span is the difference (Δ) between the upper and lower range limits. This value is always recorded as a single number. For example, the difference between 80 and 140 is 60, so the span is 60.

Controller Modes Controller modes include proportional (P), proportional plus integral (PI), proportional plus derivative (PD), and proportional-integral-derivative (PID). Proportional control is primarily used to provide gain where little or no load change typically occurs in the process. Proportional plus integral is used to eliminate offset between the setpoint and process variables; PI works best where large changes occur slowly. Proportional plus derivative is designed to correct fast-changing errors and avoid overshooting the setpoint; PD works best when frequent small changes are required. Proportional-integral-derivative is applied where massive, rapid load changes occur; PID reduces the amount of swing between the process variable and the setpoint.

Rate Mode The rate (or derivative) mode enhances controller output by increasing the output in relationship to the changing process variable. As the process variable approaches the setpoint, the rate or derivative mode relaxes, providing a braking action that prevents overshooting of the setpoint. The rate responds aggressively to rapid changes and passively to smaller changes in the process variable.

Reset Mode The reset (or integral) mode is designed to reduce the difference between the setpoint and the process variable by adjusting the controller output continuously until the offset is eliminated. The reset mode responds proportionally to the size of the error, the length of time that it lasts, and the integral gain setting. 201

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Tuning Controllers Tuning controllers: • Turn rate action off • Set integral (reset) action to minimum • Establish arbitrary gain • Set controller to AUTO mode – reduce gain if process swings – increase gain if process response is too slow A graph of the process should be a straight line when the process is in control.

Programmable Logic Controllers A programmable logic controller is a modern control system that combines microprocessor features with software-configurable controllers. The basic components of this system include processor CPU (central processing unit) module; mounting rack; power supply; user-defined, plug-in input/output modules; and communication interface module. This type of system requires minimal space, is extremely reliable, is reprogrammable, and has high computational ability. Another attractive feature is that laptop computers can interface with and program the system.

Distributive Control Systems Distributive control systems combine some of the most innovative technologies into an interactive network of intelligent microprocessors, application software, and communication networks. The hardware for a DCS includes a host CPU or programmable logic controller (PLC), intelligent field devices (transmitters, controllers, and control valves), remote CPU, and keyboard. This type of system offers the highest level of operator interaction.

8.6 Final Control Elements and Control Loops Automatic Valves Final control elements are typically automated valves; however, motors or other electrical devices can be used. The final control element is the last link in the modern control loop and is the device that actually makes the change in the process. Automatic valves open or close to regulate the process. Control loops usually have (1) a sensing device, (2) a transmitter, (3) a controller, (4) a transducer, and (5) an automatic valve. Automatic valves can be controlled from remote locations, making them invaluable in modern processing. To automate a valve, a device known as an actuator is installed. The actuator controls the position of the flow control element by moving and controlling the position of the valve stem. Actuators come in three basic designs: 1. Pneumatically (air) operated—This is the most common type of actuator. Pneumatic actuators convert air pressure to mechanical energy and can be found in three designs: (1) diaphragm, (2) piston, and (3) vane. 1. Diaphragm—The diaphragm actuator is a dome-shaped device that has a flexible diaphragm running through the center. It is typically mounted on the top of the valve. The center of the diaphragm in the dome is attached to the stem. The valve position (on or off)

202

Summary is held in place by a powerful spring. When air enters the dome on one side of the flexible diaphragm, it opens, closes, or throttles the valve, depending on the valve design. 2. Piston—The piston actuator, which uses an airtight cylinder and piston to move or position the stem, is commonly used in combination with automated gate valves or slide valves. It is also used where a lot of stem travel is needed. 3. Vane—Vane actuators direct air against paddles or vanes. 2. Electrically operated—This actuator converts electricity to mechanical energy. Examples are the solenoid valve and the motor-driven actuator. • Solenoid valves are designed for on-off service. The internal structure of a solenoid resembles a globe valve. The disc rests in the seat, stopping flow. The stem is attached to a metal core or armature that is held in place by a spring. A wire coil surrounds the upper spring and stem. When the wire coil is energized, a magnetic field is created, causing the armature to lift and compressing the spring. The armature is held in place until the current stops. • A motor-driven actuator is attached to the stem of a valve by a set of gears. Gear movement controls the position of the stem. 3. Hydraulically operated—This type of actuator converts liquid pressure to mechanical energy. The hydraulic actuator uses a liquid-tight cylinder and piston to move or position the stem. These are commonly used in combination with automated gate valves or slide valves, and are also used where a lot of stem travel is needed. Common terminology for actuators includes: • Air to open, spring to close—fails in the closed position if air system goes down. Air line is typically located on the bottom of the dome. • Air to close, spring to open—fails in the open position if air system goes down. Air line is typically located on the top of the dome. • Double-acting, no spring—air lines located on both sides of the dome. The most common type of automated valve is a globe valve, because of its versatile, on-off or throttling feature. Control loops use on-off or throttling-type valves to regulate the flow of fluid in and out of a system. Automatic valves can be used to control pressure, temperature, flow, or level. Automatic valves fall into the following categories: 1. Control valve—air-operated, electrically operated, hydraulically operated. 2. Spring- or weight-operated—hold the flow control element in place until pressure from under the disk grows strong enough to lift the element from the seat (e.g., check valve).

Summary A control loop is a group of instruments that work together to control a process. These instruments typically include a transmitter coupled with a sensing device or primary element, a controller, a transducer, and a control valve. There are five typical process variables: pressure, temperature, flow, level, and analytical. Control loops are specifically designed to work with a selected variable. The primary purpose of a controller is to receive a signal from a transmitter, compare this signal to a setpoint, and adjust the process (using a final control element) to stay within the range of the setpoint. Controllers come in three basic designs: pneumatic, electronic, and electric.

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A programmable logic controller is a modern control system that combines microprocessor features with software-configurable controllers. The basic components of this system include processor CPU module, mounting rack, power supply, user-defined plug-in input/output modules, and communication interface module. Distributive control systems combine some of the most innovative technologies into an interactive network of intelligent microprocessors, application software, and communication networks. The hardware for a DCS includes a host CPU or PLC, intelligent field devices (transmitters, controllers, and control valves), remote CPU, and keyboard. Final control elements are typically automated valves; however, motors or other electrical devices can be used. The final control element is the last link in the modern control loop and is the device that actually makes the change in the process. Actuators for control valves come in three basic designs: pneumatic, electric, and hydraulic. Pneumatic actuators, which convert air pressure to mechanical energy, use three designs: diaphragm, piston, and vane. Electrically operated actuators convert electricity to mechanical energy. Common examples include solenoid valves and motor-driven actuators. Hydraulically operated actuators convert liquid pressure to mechanical energy. The hydraulic actuator uses a liquid-tight cylinder and piston to move or position the valve stem.

204

Chapter 8 Review Questions

Chapter 8 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

List the three basic designs for valve actuators. Describe the system designated by the terms “air to open” and “air to close.” Define proportional control. Describe rate and reset. List the primary elements and sensors associated with flow. List the primary elements and sensors associated with level. List the primary elements and sensors associated with pressure. List the primary elements and sensors associated with temperature. List the five elements of a control loop. Draw a pressure control loop and label its parts. Draw a flow control loop and label its parts. Draw a level control loop and label its parts. Draw a temperature control loop and label its parts. Describe how proportional control works with reset. Describe how proportional control works with rate. Describe a programmable logic controller. Describe a distributive control system. Describe how a 3–15 psi pneumatic signal relates to a 4–20 mA electric signal. What is a smart transmitter, and what are some of its advantages?

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Process Technology— Systems One After studying this chapter, the student will be able to: • • • • • • • • • • •

Describe a simple pump-around system. Identify the key components of a compressor system. Describe common turbines and a gas turbine system. Identify the key components of an electrical system. Describe a simple lubrication system. Identify the key components of a hydraulic system. Identify the basic components of a heat exchanger system. Identify the primary components of a cooling-tower system. Describe the basic components of a steam-generation system. Describe the important aspects of a fired heater or furnace system. Explain the relationship between cooling towers and heat exchangers.

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Key Terms Compressor system—key elements of this system include piping, valves, a compressor, a receiver, heat exchangers, dryers, back pressure regulators, gauges, and moisture removal equipment. Cooling-tower system—includes a cooling-tower and pipe system to transfer cooled water to the unit and back to the cooling-tower water-distribution system. The cooling tower has a series of complex instrument systems to control ppm, pH, level, temperature, fan speed, and flow rate. Electrical system—system composed of a boiler, a steam turbine, a main substation with transformers, a motor control center, and electrically powered equipment. Furnace system—typically used to heat up large quantities of hydrocarbons or chemicals. The basic equipment in a furnace system includes a furnace, advanced process control systems and instruments, pump systems, compressor systems, and fuel systems. Heat exchanger system—consists of shell in/out piping; tube in/out piping; valves; instruments; flow, temperature, analytical, and pressure control loops; and two separate pump systems. Pump-around system—consists of a series of piping, storage tank(s), valves, gauges, and a pump. Steam-generation system—a complex arrangement of boiler systems designed to convert water to steam. These include pump-around systems, advanced process control systems and instruments, fuel systems, and compressor systems.

9.1 Pump System New technicians have difficulty determining which pieces of industrial equipment go together when asked to develop a simple flow diagram. Figure 9–1 illustrates the basic equipment found in a typical pump-around system. Using a simple pump-around system, technicians can learn how to perform equipment line-ups, start-ups, operational checks, and shutdowns. A key question that apprentice technicians need to answer is how to redirect flow from an operating pump, whether dynamic or positive displacement. The key elements of a pump-around system include process piping, storage tank(s), valves, gauges, and a pump. Scientific principles associated with pumps include fluid flow characteristics, pressure, temperature, heat transfer, electricity, rotation, and kinetic energy.

9.2 Compressor System A compressor system is a simple arrangement of equipment designed to produce clean, dry, compressed air or gas for industrial applications. Compressors are also used to transfer or compress light hydrocarbon gases, nitrogen, hydrogen, carbon dioxide, chlorine, and a large variety of specialty gases. Compressors are used at pipe-line lift stations to add energy to compressed feedstocks. Compressor systems are also used to transfer granular and flake polymer and additives 208

9.2 Compressor System Pressure Relief To Flare LA

Hi 85% Lo 65%

LIC

FR 202

FIC FIC

I

I

P

P

FT FT

(Feed Tank) LT

LE Ti

NPDH

Pi NPSH

Pi

Centrifugal Pump A Pi Pi

Centrifugal Pump B

Figure 9–1 Pump-Around System and small plastic pellets from one place to another. In natural gas plants, compressors are used to establish feed-gas process pressures. A compressor system typically includes process piping, valves, a compressor, a receiver, heat exchangers, dryers, back pressure regulators, gauges, and moisture removal equipment. The sequence and equipment arrangement is illustrated in Figure 9–2. Additional information about compressor systems can be found in Chapter 5. Scientific principles associated with compressors include fluid flow characteristics, pressure, temperature, heat transfer, electricity, rotation, and kinetic energy.

Typical Compressor System In a refinery or chemical plant, compressors are used to compress gases like nitrogen, hydrogen, carbon dioxide, and chlorine. These gases are sent to headers from which they are distributed to a variety of applications. Compressors also provide clean, dry air for instruments and control 209

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PIC

PT

Pi

PE

Instrument Air Header

Air inlet

Steam

I

P

Dryers

Pi

Pi

ON OFF

Pi

M

Centrifugal Compressor (Multi-Stage)

Receiver

Figure 9–2 Compressor System devices. When compressors are used in a process system, a wide assortment of supporting equipment is required. A small sample of this list could include the compressor, receiver, safety valves, heat exchangers, motor, lubrication systems, control instruments, valves, dryers, demister, regulators, and pipe header.

Typical Turbine Systems Turbines are classified according to their principle of operation and the type of fluid that turns them. All turbines respond to impulse or reaction movement. The four main types of turbines are steam turbines, gas turbines, wind turbines, and water turbines. The primary function of a turbine is to convert steam, gas, wind, or water energy into mechanical energy that can be used to drive rotating equipment.

Gas Turbine System (Industrial Driver) A gas turbine is a device that uses high-pressure combustion gases to turn a series of turbine wheels to provide rotational energy to a driven device. Gas turbines are used to operate electric generators, ships, and racing cars, and as a primary component of jet aircraft engines. The gas turbine does this by providing the rotational energy needed to turn an axle or shaft. There are three primary parts of a gas turbine system: an axial compressor, a combustion chamber, and a gas 210

9.2 Compressor System

Air inlet

Pi

Pi L

L

Fire Water Pump

Jet Engine Combustor Assembly L

Nozzle

Axle

Air In

Tailpipe L

Compressor

Fuel Injector

Exhaust Gases Turbine

Spark Plug

Figure 9–3 Gas Turbine System turbine. The gas turbine system mixes compressed air with fuel in a combustion chamber. A spark plug ignites the mixture, which is directed into the suction side of the gas turbine. The hot combustion gases rush into the gas turbine, causing the turbine wheels to turn. Hot exhaust gases are discharged from the body of the gas turbine. The air compressor and the gas turbine are mounted to the same axle, which is connected to the workload (Figure 9–3). When an air compressor and a combustion chamber are used in combination with each other, it is frequently referred to as a gas generator. During operation, a fraction of the power generated by the turbine is used to run the compressor. When the air compressor pulls air into the system, it increases the pressure. When the compressed air mixes with the fuel and is ignited, the higher pressure allows the mixture to burn better. The fuel used to operate a gas turbine is natural gas or oil. The hot combustion gases produced by the gas or oil is used in the same way a steam turbine 211

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uses steam to turn the rotor. The air for combustion is generally filtered through a bag-house arrangement to remove airborne contaminants, which would settle on turbine components.

9.3 Electrical System An electrical system is designed to provide electricity to operate motors, lights, electric plugs, fans, computer equipment, control instrumentation, cameras, motor control centers, and many other instruments and areas. Electricity is generated by an electric generator. Typically, boilers provide steam that turns a steam turbine, which in turn rotates the electric generator, producing electricity. Electrical systems (see Figure 9–4) are a collection of complex processes that include a boiler to generate steam, a steam turbine, an electric generator to produce electricity and create the load for commercial distribution, insulated wiring, a main substation with transformers to reduce the electrical output, a motor control center (MCC) to centralize local power distribution, and electrically powered equipment that is run by the electrical system. Process technicians are not trained as electrical technicians; however, safely operating a system that uses electricity requires a comprehensive education. Only qualified electricians work on industrial electrical systems that can have very high voltages. Typically, two electricians work on

69,000 Volts 69 kV Transformer Main Substation

Generator

Boiler Steam Turbine

13,200 V 13, 800 V 2,300 V

Voltmeter

13.2 kV 13.8 kV 2.3 kV

MCC Motor Iron Core Rotor

SSSSSSSS SS S S S S S S S S S S S S SS SSSSSSSS

On Off

2.3 kV or 480 Volts

Stator Windings Stator Core

Rotating Magnetic + (Cause Rotation)

Bearings

Figure 9–4 Electrical System 212

MCC

9.5 Hydraulic System

I I

PIC

P

P

TIC

PT Pump Bearings

PE

TT Gearbox TE Fluid Reservoir

Compressor Bearings

Figure 9–5 Lubrication System projects together to ensure personal safety. Process technicians closely monitor substation variables and electrical equipment operations.Worn belts on motor systems, exposed wiring, smoking motors, fires, arcing, or strange electrical smells are reported immediately.

9.4 Lubrication System Lubrication systems provide a constant source of clean oil to pump and compressor bearings, gearboxes, steam turbines, and rotating or moving equipment. A typical lubrication system includes a lubricant reservoir, pump, valves, heat exchanger, and piping. Figure 9–5 illustrates how an industrial lubrication system operates.

9.5 Hydraulic System Process technicians use hydraulic systems (see Figure 9–6) to open or close valves, lift heavy objects, run hydraulic motors, and stop the rotation of a rotary or reciprocating device. A hydraulic system is a collection of equipment designed to apply pressure on a confined liquid in order to perform work. A similar process is used in the brake systems of most cars and trucks. A hydraulic system is composed of a fluid reservoir, strainer, pump, piping, flow control valve, pressure control valve, four-way directional control valve, and actuator (cylinder, piston). 213

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Process Technology—Systems One Flow Control Valve

Pressure Control Valve

Directional Control Valve

Pump

XXX

Fluid Reservoir Actuator

Strainer

Figure 9–6 Hydraulic System

9.6 Heat Exchanger System Heat transfer is an important process in the chemical processing industry. A heat exchanger is a device used to transfer heat energy from a hotter fluid to a cooler fluid. Heat exchangers come in a variety of designs, including shell-and-tube, air-cooled, spiral, and plate. Heat exchangers use the principles of conductive and convective heat transfer. A heat exchanger system consists of shell in/out piping; tube in/out piping; valves; flow, temperature, analytical, and pressure control loops and instruments; and two separate pump systems. A heat exchanger system typically includes two, three, four, or more heat exchangers working together in series or parallel operation. These systems can appear very complicated for a new technician, because each exchanger has a separate tube inlet and outlet system and shell inlet and outlet system. Steam, hot oil, or a previously heated process stream can be used as the heating medium. As heat energy is transferred between process flows, process variables are closely observed. Figure 9–7 shows what a typical heat exchanger system looks like.

9.7 Cooling-Tower System A cooling-tower system includes a cooling tower and pipe system to transfer cooled water to the unit and back to the cooling-tower water-distribution system. The cooling tower uses a series of complex instrument systems to control ppm, pH, level, temperature, fan speed, and flow rate. Cooling-tower systems are very complex and can be challenging for new technicians to master. As the water flows from the cooling tower to the operational processes, it picks up heat and suspended solids. As this heated water is returned to the cooling tower, these suspended solids begin to accumulate in the basin and on the internal components of the tower. These suspended and dissolved solids can change the pH and conductivity of the water system. 214

9.7 Cooling-Tower System

FR

FIC 225 GPM

P

TIC

TT

180ºF

Fi

TE

FO

TAH

Ti

195ºF

180.5 ºF

625 GPM

P

FT

TR I

I

Pi

Ti

35 psig

225 ºF

Heat Exchanger Hot Oil Insulated Tank

Bypass

Ti

Pump

200 ºF

Ti

Ti

173ºF

115ºF

Pi

Heat Exchanger

130 psig

Bypass

Pi

135 psig

Tube Inlet 222ºF Liquid

AT

Pi

Pi

Ti

135 psig

80ºF

40 psig

Shell Inlet 80ºF Liquid

Pump

Figure 9–7 Heat Exchanger System

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Process Technology—Systems One TR 125ºF

COOLING TOWER

On Off

TIC

SIC

125ºF

1250RPM

ST

TT

SE

515gpm

Fi TE

I

P

Pi

Ti

45 psig

160ºF

Ti 75ºF

Heat Exchanger “Condenser”

Pi 50 psig

Ti LIC 75%

LT

P

130ºF

LA Hi

Low I

Ti 85ºF

Pump

AE

AA

Hi Low

AT

AIC

AE

AE

I

AT

AT

AIC

Blowdown

FT

TIC 60ºF

FIC

I

P

525gpm

Low Pressure Steam 30 PPM

I

P

FE

AIC

4.5

7.8 pH

I

P

TE TT

P

I

P

Figure 9–8 Cooling-Tower System Figure 9–8 illustrates what a cooling-tower system looks like. A cooling-tower system also includes the following control features: basin level control, basin pH control, chemical additive control, parts per million (ppm) control, temperature control, flow control, and fan speed control.

Heat Exchangers and Cooling Towers Heat exchangers and cooling towers are often paired in industrial cooling systems. The system consists of a cooling tower, heat exchanger, and pump. During operation, cooling water is pumped into the shell side of a heat exchanger and returned (much hotter) to the top of the cooling tower. As the hot water goes into the top of the cooling tower, it enters a water-distribution header where it is sprayed over the internal components (fill ) of the tower (Figure 9–9). As the water falls on the splash bars, contact occurs between cooler air and the water. Ten to 20% of the sensible heat is removed by this process. Another 80% to 90% of the heat energy is removed through evaporation. The cooled water collects in a basin at the foot of the cooling tower, where a recirculation pump sends it back to the heat exchanger.

9.8 Steam-Generation System (Boilers) The production of steam is very important to the operation of an industrial facility. Steam is used in a variety of operations, including heating and temperature control, steam turbines, steam tracing, heat exchangers, reboilers, stripping, and distillation. The energy in steam can easily be 216

9.8 Steam-Generation System (Boilers) TR 125ºF

COOLING TOWER

On Off

TIC

SIC

125ºF

1250RPM

ST

TT

SE

515gpm

Fi TE

Ti 160ºF

Pi 45 psig

I

P

Ti 75ºF Ex

Ti 145ºF

Pi

Heat Exchanger “Series Flow”

50 psig

LIC

LT

75%

P

Parallel Flow

Ti

Low I

Ti 85ºF

Pump

LA Hi

AE

AA

Hi Low

AT

AIC

AE

AE

I

AT

AT

AIC

Blowdown

TT

FT

130ºF FIC

I

P

525gpm

Low Pressure Steam 30 PPM

I

P

TIC 60ºF

FE

AIC

4.5

7.8 pH

I

P

TE

P

I

P

Figure 9–9 Cooling Tower and Heat Exchanger System transformed into mechanical or heat energy upon condensation. A typical steam-generation system includes super-high-pressure (SHP) steam generation and distribution, high-pressure (HP) steam (400–800 psig), medium-pressure (MP) steam (200 psig), and low-pressure (LP) steam (50 psig). SHP steam can be as high as 1,200 psig. The heat value for steam is easily calculated, because it generally corresponds to the pressure. The following are some typical steam temperature and pressure relationships: 274°F @ 30 psig 298°F @ 50 psig 338°F @ 100 psig 388°F @ 200 psig 421°F @ 300 psig 448°F @ 400 psig 470°F @ 500 psig 489°F @ 600 psig A steam-generation system is designed to safely return cooled condensate to the boiler. A device called a steam trap is used to collect and transfer this material. Low points in the steam system are used to capture cooled condensate before it can damage the piping or equipment. Water can expand to many times its original volume when vaporized, so the condensate return header is a 217

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HIGH

T

To Units

400–800 psig

T

T To Condensate Tank MEDIUM

Boiler 180–200 psig

To Units

To T T T Condensate Tank Condensate Return

Feed Tank Water Make-Up Vent

Flash Tank

Deaerator

LOW 50 psig

T BFW Pump

To Units T

T

T

Low Pressure Condensate Condensate Tank Figure 9–10 Steam-Generation System critical part of the system. Water is also basically noncompressible, and at high velocities can seriously damage equipment. Figure 9–10 shows the many applications in which steam is used. The heart of a steam-generation system is the boiler that produces steam for the high, medium, and low steam systems. A condensate return system captures and returns condensate to the boiler. Figure 9–11 shows how each part in the steam generation system works.

9.9 Furnace System The chemical processing industry uses fired heaters to heat large quantities of crude oil and other hydrocarbon feedstocks up to operating temperatures for processing. For this reason, the furnace 218

9.9 Furnace System Boiler System 60 psig

305ºF TE

LAL

450ºF

50%

LAL

Pi -.02

I

# per hour of steam required at full load.

P

120 psig

LE

-.02

LIC

PR

FIC

50%

50% BA

on/off

LP Steam LT

To Header

PE

PIC

350ºF

LT

Pi

Treated water

LIC

Superheated

TR

35%

LR

Ti

100 psig

PA Low

PT

Vent

I

150 psig Hi

TE

Desuperheated Steam

Stack

P

Pi

350ºF PA Hi 75 psig Low 50 psig

I

FT

Deaerator

LE

P

FE

o PIC -.05

35%

LR

I

PT PE

Burner(s)

TE

P

TE

600ºF

Fan

º

500ºF

o

Ai AA Hi

Fan

P

I

FIC

155 psig Pi

Low 0-10% Oxygen 150 GPM

I

Natural Gas Tank

P

FIC

60 psig

50%

Pi FT

FE

FE

FT

Pump

Figure 9–11 Steam-Generation System: How Each Part Works

system supports a number of other major processes, including raw material transportation and storage, utilities, distillation, and reaction systems. The furnace system itself is a collection of other systems linked together to produce a specific result. The furnace is composed of a firebox, outer shell, lower radiant section, upper convection section, insulation, refractory material, convection tubes, radiant tubes, stack, damper, and burners. A typical furnace system (see Figure 9–12) includes an established raw-material storage system. This system includes storage tanks, pumps, pipes, and valves that work together in a complex network. Raw materials are brought in by pipeline, ship, barges, and trucks. Raw materials are typically prepared for introduction into the furnace through processes such as desalting, heating, blending, or the addition of special chemicals or additives. As the heated feed leaves the furnace, it is transported to a wide assortment of chemical processes. Furnace systems play a vital role in modern manufacturing. Typical systems supported by a furnace system include:

• • • • •

Steam generation Utilities and steam production Distillation and mixture separations Reactors and chemical reactions Electric power generation 219

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Heat Exchanger Charge In Pump

Furnace Fuel Oil Tank 1

2

3

4

Charge Out

Pump Heat Exchanger Steam Pilot Fuel

Figure 9–12 Furnace (Fired Heater) System

Furnace Operation During operation, a furnace technician carefully observes and reacts to the amount of oxygen in the system. Draft gauges and O2 analyzers are used to determine the correct oxygen percentages for optimal operation. Snuffing or purging steam or nitrogen is used to purge oxygen and fuel out of the system in the event of a flameout or equipment failure. Purging steam is also used to preheat the furnace, remove coke from lines, and protect the furnace during various emergency situations. A recent study indicated that the majority of plants are spending more money on the refurbishment of existing furnace systems than on the purchase of new fired heaters. It is a common practice to add air preheaters and modern instrumentation to improve operation.

Furnace Classifications A furnace can be classified as natural, induced, forced, or balanced draft. The pressure inside a warm furnace is typically lower because of buoyancy differences between air inside the furnace and the cooler outside air. A natural-draft furnace can operate using this approach; however, when fans are used to push or pull air through the furnace, greater heat transfer rates can be achieved. A natural-draft fired heater is severely limited in contrast to these systems. Figure 9–13 shows the four different systems used to control airflow.

Burners and Fuel Heat Values The fuel typically used in modern fired heater design is natural gas. Fuel heat values are important variables in economic operation of a furnace system. Heat value refers to the known differences in the heat energy released when different fuels burn. Natural gas has a heat value of 909 Btu/ft3. 220

Summary

Fan

Fan

Air

Air

Induced Draft

Natural Draft

Fan

Preheated Air

Forced Draft

Fan

Preheated Air

Balanced Draft

Figure 9–13 Fired Heater Draft Designs

A number of older fired heaters burn oil and require a number of auxiliary systems to operate. The types of burners used in fired heaters include premix, combination, raw gas, and gas or oil. Many systems use steam to help atomize the heated fuel at the point of ignition. Primary air provides oxygen to the fuel mixture. Primary air is located at the point on the burner where air and fuel mix, whereas secondary air registers are located on the bottom and sides of the burner. Flame patterns are important to an experienced technician and can provide an indication of how the system is working. Visual checks are possible at different points on the fired heater.

Furnace Problems During normal operations, checklists and samples are collected as advanced instrumentation monitors the process. The types of problems a fired heater or furnace system typically encounter include: flame impingement on tubes, coke buildup inside the tubes, hot spots inside the furnace, fuel composition changes, burner flameout, control valve failure, and feed-pump failure. Other problems may include incorrect temperature indicator readings, failure of oxygen analyzers, oxygen leaks on the furnace, and the unexpected shutdown of downstream equipment. A fired heater system is designed to run almost continuously, 24 hours a day, 7 days a week. The operational team is in place to ensure that the equipment and systems operate safely, effectively, and produce a quality product that meets or exceeds customer expectations.

Summary New technicians often have difficulty determining which pieces of industrial equipment go together when asked to develop a simple flow diagram. Using a simple pump-around system, technicians can learn how to perform equipment line-ups, start-ups, operational checks, and shutdowns. The 221

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key elements of a pump-around system include process piping, storage tank(s), valves, gauges, and a pump. A compressor system, which is a simple arrangement of equipment designed to produce clean, dry, compressed air or gas for industrial applications, typically includes process piping, valves, a compressor, a receiver, heat exchangers, dryers, back pressure regulators, gauges, and moisture removal equipment. Electrical systems are a collection of complex processes that generate steam, produce electricity, reduce electrical output, centralize local power distribution, and run electrically powered equipment. Lubrication systems provide a constant source of clean oil to pump and compressor bearings, gearboxes, steam turbines, and rotating or moving equipment. Hydraulic systems, which are designed to apply pressure on a confined liquid in order to perform work, are used to open and close valves, lift heavy objects, run hydraulic motors, and stop the rotation of a rotary or reciprocating device. A typical steam-generation system includes generation and distribution of super-high-pressure steam (up to 1,200 psig), high-pressure steam (400–800 psig), medium-pressure steam (200 psig), and low-pressure steam (50 psig). The heat value for steam generally corresponds to the pressure.

222

Chapter 9 Review Questions

Chapter 9 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Identify the equipment used in a pump-around system. Identify the equipment used in a compressor system. Identify the equipment used in a lubrication system. Identify the equipment used in an electrical system. Identify the equipment used in a hydraulic system. Describe the primary equipment and components found in a steam-generation system. Describe the primary equipment and components found in a furnace system. Draw a simple pump-around system. Explain how a heat exchanger system operates. List the basic components of a gas turbine system.

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Process Technology— Systems Two After studying this chapter, the student will be able to: • Describe the different type of reactors used in the chemical processing industry. • List the unique characteristics of a reactor system and explain how it is different from other industrial processes. • List the critical process variables associated with reactor operation. • List the primary components of a distillation system. • Compare and contrast absorber columns and adsorption columns. • Describe how a scrubber operates. • Compare and contrast separation and distillation systems. • Describe the basic equipment used in pressure relief systems. • Describe the various equipment pieces found in a flare system and how it operates. • Describe typical plastics plant equipment. • Explain how an extruder operates. • Explain how a refrigeration system works. • Identify the basic equipment used in a refrigeration system. • Describe how a water treatment system works. • Identify the basic equipment used in a water treatment system. • Describe the various systems found in utility sections of process plants. • Explain the functions and typical components of a utility system in a refinery or chemical plant.

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Key Terms Absorber—device used to remove selected components from a gas stream by contacting the stream with a gas or liquid. Adsorber—device (such as a reactor or a dryer) filled with porous solid designed to remove gases and liquids from a mixture. Demineralizer—a filtering-type device that removes dissolved substances from a fluid. Extract—composed of the solute and the heavier solvent; will layer out or naturally separate from the lighter raffinate. The heavier extract does not flow over the weir; rather, it goes out the extract discharge port. Extruder—a complex piece of equipment composed of a heated jacket, a set of screws or a screw, a heated die, a large motor, a gearbox, and a pelletizer. An extruder converts raw plastic material into pelletized plastics ready for further processing into finished products. Most extruders use a single- or twin-screw design surrounded by a heated barrel. The molten polymer is forced or pumped through a die. Flare system—safely burns excess hydrocarbons. A flare system is composed of a flare, knockout drum, flare header, fan optional, steam line and steam ring, fuel line, and burner. Layer out—a process in which two liquids that are not soluble separate naturally from each other (example: oil and water). Packed distillation column—system filled with packing to enhance vapor-liquid contact to separate the components in a mixture by boiling point. The most common types of packing include sulzer, rasching ring, flexiring, pall ring, intalox saddle, berl saddle, metal intalox, teller rosette, and mini-ring packing. The basic components of a packed column include a feed line, feed distributors, a shell, hold-down grids, random or structured packing, packing support grids, bed limiters, a bottom outlet, a top vapor outlet, instrumentation, and an energy balance system. Packed columns are designed for pressure drops between 0.20 and 0.60 inches of water per foot of packing material. Plate distillation column system—has trays that are designed to enhance vapor-liquid contact in the distillation process. Plate columns may be bubble-cap, valve tray, or sieve tray. The basic components of a plate distillation column include a feed line, feed tray, rectifying or enriching section, stripping section, downcomer, shell, reflux line, energy balance system, overhead cooling system, condenser, preheater, reboiler, accumulator, feed tank, product tanks, bottom line, top line, side stream, and advanced instrument control system. Pressure relief system—safety system that includes relief valves, safety valves, rupture discs, piping, drums, vent stacks, pressure indicators, pressure alarms, pressure control loops, and flare systems. Raffinate—the lighter material in the feedstock that is free of the solute or material being dissolved; flows over the weir in the separator. Refrigeration system—used to provide cooling (e.g., air conditioning) to industrial applications. Refrigeration units are composed of a compressor (high-pressure refrigeration gas), heat exchanger–cooling tower combination, receiver, expansion valve (low-pressure refrigeration liquid), and heat exchanger (evaporator)–low-pressure refrigerant gas unit. 226

10.1 Reactor System

Scrubber—device used to remove chemicals and solids from process gases. Solute—material that is dissolved in liquid–liquid extraction. Solvent—chemical that will dissolve another chemical. Separation system—designed to separate two liquids from each other by density differences; typically, a solvent is introduced that will dissolve one of the components in the mixture, enhancing the separation process. A separator has a shell, weir, vapor cavity, feed inlet, extract port and pump, and raffinate port and pump. Stirred reactor—typically includes a vessel, a mixer, valves, piping, two or more inlet ports, and a single outlet port. Reactors are complex analytical devices that have control features for a wide array of process variables and come in a variety of shapes and designs.

10.1 Reactor System Reactor System Heated or cooled chemicals can be sent to reactors that are designed to combine chemicals and form new products. Reactors come in a variety of shapes and designs, such as stirred, fluidized, fixed-bed, and tubular (Figure 10–1). Reaction technology can be described as batch, semi-batch, or continuous operation. Reactors are vessels designed to allow a reaction to occur as two or more FIC Feed to RX

FIC

Fixed Bed (Converter) Reactor

Feed to RX

Fixed Bed Catalyst

EX

FIC Pump Feed to RX

FIC 2 FIC 1

Feed to RX

FIC 1

Feed to RX

FIC 2

Flue Gas Heat Out

Heat In

Recycle RX

Heat In

Burner Direct Fired RX

Jacketed RX

Figure 10–1 Reactor Designs 227

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Feed

PIC

C LIC

Flare A

FIC FIC

Feed LIC

B

B C B B C C A B A B A C

Hot Oil

Catalyst Distillation Column

TIC

TIC

B

FIC LIC

Stirred Reactor

A B C

Pump

TIC

LIC

C

Figure 10–2 Typical Reactor System flows are exposed to each other under a variety of conditions; variables include heat, cold, pressure, concentration, time, or presence of a catalyst. A typical stirred reactor is composed of a vessel, a mixer, valves, piping, two or more inlet ports, and a single outlet port. Figure 10–2 shows a reactor system with a distillation column being used to separate the various components in the mixture. The central feature of this process is a stirred reactor that has a controlled flow rate of reactant B and a controlled catalyst flow rate of C. Reaction time is enhanced by the agitation of the stirred reactor. Reactant B and catalyst C combine to form product A. The reaction does not convert 100% of reactant B and catalyst C; however, a significant amount of product A exits from the reactor. The distillation column is designed to separate components A, B, and C from the mixture by their unique boiling points. The distillation column does not change the molecular structure of the feed. The scientific principle underlying this process rests firmly on the reactor system and the chemical reaction between reactant B and catalyst C.

10.2 Distillation System A distillation process uses a complex arrangement of systems that includes a cooling-tower system, pump-and-feed system, preheat system, product storage system, compressed-air system, steam-generation system, and complex instrument control system. (See Figure 10–3.) Each of these stand-alone systems is designed to support a specific part of the distillation process. Each 228

10.2 Distillation System Flow Diagram Process Unit

Cooling Tower

Vacuum Pump

Product Tank 1

Drum

Furnace Feed Tank Column

Reactors

Product Tank 2

Instrument Air Header

Dryers Boiler

Bottom Tank

T To Boiler Compressor (Turbine Driven)

Figure 10–3 Distillation System chemical substance has a unique boiling point. The distillation process was developed to take advantage of this principle, in that it separates the various components in a mixture by the differences in their volatilities. In this type of system, a distillation column is the central piece of equipment. Distillation columns use either a plate or a packed design. Distillation systems are used in a wide variety of applications, including: • Separating salt water from sea water to create distilled water • Separating crude oil into various fractions, such as gasoline, jet fuel, diesel, lubricants, etc. • Separating air into oxygen, nitrogen, and argon • Separating and concentrating higher alcohol concentration in fermented solutions Products made by distillation include natural gas, propane, butane, gasoline, kerosene, jet fuel, light oil, and heavy oil. These products can be used to make plastic, synthetic rubber, medicine, chemicals, and many other useful compounds and components. 229

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Chemical engineering emerged as a discipline in the 1890s, as a science that employed empirical methods. However, the “new” discipline had a long history. The first distillation system (apparatus) was used by Babylonian alchemists in Iraq (Mesopotamia) in 2000 BCE. Large-scale (spirits) distillation was practiced by Greek alchemists in 100 AD. Detailed instructions for a distillation process were written by an Alexandrian named Zosimos in the fourth century CE. Other significant contributions included those of:

•

• • • • • • •

Jabir ibn Hayyan (Geber), a Persian, 800 AD, who was the first to use alembics and retorts or multiple chemical apparatus. An alembic (feed flask) and retort (accumulator) are glassware vessels; the apparatus has a long tapering neck that slopes downward. The distance between the alembic and the retort acts as a type of air-cooled condenser. al-Razi (Rhazes), a Persian, 900 AD, who was the first to distill petroleum for the purpose of separating kerosene. Avicenna, 1100 AD, who invented steam distillation. Hieronymus Braunschweig, a German, 1500 AD, who published The Book of the Art of Distillation. John French, 1651, who published The Art of Distillation. This book, which included diagrams and illustrations, used Braunschweig’s book as a resource. A French scientist in the early 1800s who developed modern process techniques called feed preheating and reflux. Aeneas Coffey, who was issued a British patent in 1830 for his continuous-operated distillation column (for whisky). Ernest Solvay, who was granted a U.S. patent for a trayed ammonia distillation column in 1877.

During the distillation process, hydrocarbon feed is stored in a feed tank. Before the feed is sent to the column, it is tested to ensure that it meets quality specifications. Some blending may occur at this point to ensure feed uniformity. Before the charge can be sent to the column, it must be heated up to operating temperatures. This part of the process involves sending the feed through a series of heat exchangers or a fired furnace. Feedstock temperatures are gradually stepped up as the flow moves through the system. As the heated charge leaves the furnace and enters the distillation column, a fraction of the feed vaporizes and rises up the column, while the heavier components (still in liquid state) drop down the column. This initiates the process of separation by boiling point. Because the energy in the process stream begins to dissipate immediately, a reboiler or heating source is attached to the column. This allows the separation process to continue. Some distillation columns are steam traced to ensure even temperature control. The distillation process is represented by four distinct systems and one super system: • Utilities super system—boiler system, compressor systems, cooling-tower system, electrical system, water system • Feed system—tanks, piping, valves, pumps • Preheating and heating system—heat exchangers and furnace • Process—distillation column or reactor, for example • Products system—tanks, piping, valves, pumps Figure 10–4 illustrates the complexity of a distillation system. 230

10.2 Distillation System

Fi

To Flare

Separator

Ti

Condenser Ti Pump

Pump

Cooling Tower

AIC

Pump

o

Furnace

AT

To Flare Fi

Drum Tank

Stirred Reactor

Pump

Distillation Column

Pi

AT

Fi

Ti

Tank

o

Pump

Fi

FO

Ti Heat Exchanger Hot Oil Tank

Pi Pi

Ti

Ti

Kettle Reboiler DPT

T

Feed Tank

Ti Pi

Boiler

Pi

AT

Fi Pump

Deaerator

AT o

Pump

Tank

START

Pump

Air Header

Ti Pump

Steam

Tank

Dryers Air inlet

Receiver

Pump

Compressor (Multi-Stage)

Figure 10–4 Multivariable Unit 231

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Absorption, Stripping, and Scrubbing Columns An absorber column is a device used to remove selected components from a gas stream by contacting the stream with a gas or liquid. A typical gas absorber is a plate distillation column or packed distillation column that ensures intimate contact between raw natural gas and an absorption medium. Absorption can roughly be compared to fractionation, although absorption columns work differently than typical fractionators because during the process the vapor and liquid do not vaporize to any degree. Figure 10–5 illustrates the scientific principles involved in absorption. Product exchange takes place in one direction, vapor phase to liquid phase. The absorption oil gently tugs the pentanes, butanes, and so on out of the vapor. In an absorber, the gas is brought into the bottom of the column while lean oil is pumped into the top of the column. As the lean oil moves down the column, it absorbs elements from the rich gas. As the raw, rich gas moves up the column, it is robbed of specific hydrocarbons and exits as lean gas.

Stripping columns are used with absorption columns to remove liquid hydrocarbons from the absorption oil. To the untrained eye, stripping and absorption columns are identical. As rich oil leaves the bottom of the absorber, it is pumped into the midsection of a stripping column. Figure 10–5 illustrates how steam is injected directly into the bottom of the stripper, allowing for 100% conversion of Btus. As the hydrocarbons break free from the absorption oil, they move up the column, while the lean oil is recycled back to the absorber.

Lean Gas Product

Rich Oil

Rich Gas Steam Lean Oil ABSORPTION COLUMN The liquid phase removes lighter components from the vapor phase. One direction component removal.

STRIPPING COLUMN Reverses absorption process. Strips out hydrocarbons from absorption oil.

Figure 10–5 Absorption and Stripping Column 232

10.2 Distillation System

Adsorption During the adsorption process, a device (reactor, dryer, etc.) is filled with a porous solid designed to remove gases or liquids from a mixture. Typically the process is run in parallel with a primary and secondary vessel. The adsorber can be activated alumina or charcoal. A variety of adsorption materials can be used. The adsorption material has selective properties that will remove specific components of the mixture as it passes over the adsorber. A stripping gas is used to remove the stripped components from the adsorption material. During the adsorption process, the mixture to be separated is passed over the fixed-bed medium (adsorbent) in the primary device. Figure 10–6 illustrates this process. At the conclusion of the cycle, the process flow is transferred to the secondary device; then a stripping gas is admitted into the primary device. The stripping gas is designed to remove or separate the selected chemical from the adsorption material. At the end of this cycle, the stripping gas stops as the process switches back and repeats.

Scrubber A scrubber is a device used to remove chemicals and solids from process gases, to protect and enhance environmental quality. Scrubbers are cylindrical in shape and can be filled with packing material or left empty. As dirty gases enter the lower section of a scrubber, they begin to rise. As these dirty vapors rise, they encounter a liquid chemical wash that is being sprayed downward. As the vapors and liquid come into contact, the undesirable products entrained in the stream are removed. As dirty materials are absorbed into the liquid medium, they fall to the bottom of the scrubber, where they are mechanically removed. Clean gases flow out the top of the scrubber and move on for further processing. Figure 10–7 is an illustration of a simple scrubber.

Stripping Gas

Stripping Gas

Packed Tower Activated Alumina or Charcoal

Figure 10–6 Adsorption System 233

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Berl Saddle Packing Gas In

Caustic Soda Pump

Drain

Figure 10–7 Scrubber System

Solvent

Raffinate

Feed

Extract

Figure 10–8 Chemical Separations

10.3 Separation System Chemical separation (Figure 10–8) is an alternative to distillation. At the heart of a separation system is a separator, a device that is designed to separate two liquids from each other by density differences. Typically, a solvent is introduced that will dissolve one of the components in the mixture, thereby enhancing the separation process. After the solvent is introduced into the feedstock, it is blended in and then allowed to layer out. The heavier solvent tends to drop to the bottom of the separator, because its density differs from that of the solute. As the solvent mixes with and dissolves the solute, it reverses direction and sinks. This new material—the solvent-and-solute combination—is called the extract. Meanwhile, the lighter material, free from the solute, rises to the top and flows over the weir. The raffinate and extract are not soluble and will naturally layer out. This process actually changes the direction of the flow: Lighter materials float to the top, while 234

10.4 Pressure Relief Equipment and Flare System

Fi

I

PIC

Feed Pi

P

PT PE

I

TIC

P

Separator Light LIC

TT

I

LIC

LE

Temperature Control

LT

LE

Heavy

LT

Light

I

P

P

Pi

AT

AT

Fi

TE LCV

LCV

Pi Pi

Pump

Pi

Pump

Figure 10–9 Chemical Separation System the heavier component sinks to the bottom. A separator has a shell, a weir, a vapor cavity, a feed inlet, an extract pump, and a raffinate pump. In addition to this equipment, a separator system includes temperature, level, flow, pressure, and analytical control instrumentation; two different outlet points, with separate pump systems for the extract and raffinate; and storage facilities. Figure 10–9 shows the major equipment found in a separation process. A number of key terms associated with separation include: • Liquid-liquid extraction—separates two materials in a chemical mixture by introducing a third chemical that will dissolve one of the other two chemicals. Feedstock —the original solution fed to the separator. • • Layering out—a process in which two liquids that are not soluble separate naturally from each other (layer out) over a specific time. • Solute—the material that is dissolved in the separation process. • Solvent—substance that is specifically designed to dissolve a certain chemical.

10.4 Pressure Relief Equipment and Flare System Pressure relief equipment includes relief valves, safety valves, rupture discs, piping, drums, vent stacks, pressure indicators, pressure alarms, pressure control loops, and flare systems. Process equipment is typically rated for specific pressure and temperature ranges. Engineering specifications 235

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allow equipment systems to run within these specified conditions. Pressure control devices are designed to ensure that these conditions and operating parameters are not exceeded. Pressure relief devices can be placed on pumps, compressors, tanks, piping, reactors, distillation columns, refrigeration systems, and many other kinds of equipment. Many materials cannot be released to the atmosphere. These types of chemicals can be recycled back to the system, or sent to a scrubber or flare system. The discharge from all safety valves, pressure relief regulators, and operating vents and blowdown valves in hydrocarbon service is collected in a closed piping system and sent to a flare stack. Steam, air, and nitrogen vapors discharge to the atmosphere. Steam safety valves discharge harmless gases through tail pipes at a safe distance above grade or above the nearest operating platform. Flare systems are used to safely remove excess hydrocarbons from a variety of plant processes. Flare systems are connected by a complex network of pipes and headers to a knockout drum and flare. Governmental laws and regulations require the flare to be located a safe distance from the operating units and populated areas. Figure 10–10 shows a diagram and photograph of a typical flare system. Flare systems are part of a plant’s safety system. Most process units are aligned to safety relief valves that lift when specified pressures are exceeded. These safety valves discharge into the flare header. Unexpected process upsets are dumped to the flare system as a last course of action. A typical flare system includes:

• • • • • •

Flare—a long narrow pipe mounted vertically Steam ring—mounted at the top of the flare; used to disperse hydrocarbon vapors Ignition source—located at the top of the flare Fan—mounted at the base of the flare and used for forced-draft operation Knockout drum with water seal Flare header

10.5 Plastics System A simple plastics system includes equipment that performs extrusion, molding, casting, laminating, and calendering (see Figure 10–11). Injection molding, compression molding, and blow molding are processes that resemble the way we make waffles for breakfast: Molten polymer is squeezed into a mold to produce a product. Examples of products manufactured by this process include tableware, plastic toys, and baby bottles.

Extrusion is a process that takes molten polymer and squeezes it down a barrel. This process is comparable to squeezing shampoo out of a plastic bottle. Examples of products made from the plastic pellets produced by extruders are: baby diapers, washing machine parts, and car parts. The laminating process takes aluminum foil, paper, or cloth and coats it with melted resin. This process is similar to building a sandwich. Examples of laminated products include motherboards and electronic circuits.

Casting is a process that most closely reflects baking a cake. Just like cake batter is poured into a pan, molten polymer is poured into a mold. This process yields items such as eyeglass lenses. 236

10.5 Plastics System Flame Arrestor

Typical Flare Seal Water and Knockout Pot

Enriched Flare Gas Natural Gas

Two-Speed Fan

Figure 10–10 (a)

Flare System

Figure 10–10 (b)

Flare System 237

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Blender

Blender Air System Feed Tank

Scalping Box Feeders Dryer Classifier Pellet Water Slurry

Homogenizer Screen Pac Main Drive Motor

Gear Box

Extruder Die

Desch Coupling

Pelletizer Chamber

Figure 10–11

Pellet Water

Water Tank

Plastics System

The last process, calendering, closely resembles spreading butter over hot pancakes. During the calendering process, rollers spread molten resins over thin sheets of paper or cloth. Calendering is used to make playing cards, for example. The initial process for creating plastic is very complex. Plastic is made from synthetic resins. The atoms that make up the molecules of synthetic resins are composed of carbon, hydrogen, oxygen, and nitrogen. Process technicians make synthetic resins by combining chemical compounds such as ammonia, benzene, hexamethylenetetramine, or a variety of other hard-to-pronounce chemicals. The reaction that takes place creates synthetic links between molecules called monomers. 238

10.5 Plastics System From Homogenizer

Melt Divert Valve

Feed In

Screen Pack

Degas Vent Gearbox and Motor

Pellet Water Out Pelletizer

Die Melt Divert Valve to Mat Pellet Water In

Figure 10–12

Plastics Extruder

This process creates long-chain molecules called polymers. Industrial manufacturers refer to this process as polymerization. Key elements found in a plastics system include: • Polymerization section—reactor, distillation • Feed and transfer section—valves, piping, tanks, solids feeders, compressor • Blending section—additive blenders, homogenizer • Extrusion section—extruder, pelletizer, pipes, valves, pumps • Drying section—dryer, classifier • Products section—solids feeders, compressor, pipes, valves, storage tanks • Packing and transportation section—bags, boxes, railroad, truck An extruder is a complex device composed of a heated jacket, a set of screws or a single screw, a heated die, a large motor, a gearbox, and a pelletizer. The purpose of the extruder is to melt the polypropylene granule mixture, quickly quench it, and cut it into small pellets that are easier to handle. In its granular form, the molecular weight distribution and swell are too broad; various additives, such as peroxide, help narrow this down. Melting the granules encapsulates the additives in the polypropylene. Customers will not accept raw granules because of the danger of dust explosions. Figure 10–12 illustrates a plastics extruder.

Solids feeders are composed of single or multiple screws that rotate inside a sleeve. Granules and additives from the feed and additive tanks are conveyed to the homogenizer by the feeders. Most solids feeders are single screws that deliver solids at a specific rate. Granules leave the feed tank continuously when the extruder is in operation. Figure 10–13 illustrates how a solids feeder operates. Some solids feeders have a two-stage design that allows granules to drop into a variable-speed screw mounted on a scale. From the scale, a constant-speed screw delivers granules to a discharge line. The speed of the first screw is adjusted to maintain a constant scale weight. The result is a feed that is constant by weight. 239

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Feed Tank

Slide Valve

Variable Speed First Stage Continuous Feeder Second Stage Scale

Figure 10–13

Solids Feeder

Pellet Slurry Scalping Bars Filters

Trash Helix and Screen

Pellet Divert Valve Dryer

Classifier

Scrap Pan

Water

Figure 10–14

Scrap Box

Pellets

Classifier

The classifier is a vibrating tub with screens in two stages that permit the desired size of pellets to pass through. Larger pellets or clumps that have managed to pass through the scalping box are eliminated from the product flow here. Between the two screens is a cleaning kit that is used to prevent pellets from lodging in the individual holes of the classifier. Figure 10–14 shows what this device looks like. 240

10.6 Refrigeration System

10.6 Refrigeration System Heating and cooling are two important aspects of modern process control. Refrigeration systems (see Figure 10–15) are used to provide cooling to industrial applications like air conditioning. Refrigeration units are composed of:

• • • • •

Compressor—high-pressure refrigeration gas Heat exchanger–cooling tower combination Receiver Expansion valve—low-pressure refrigeration liquid Heat exchanger (evaporator)—low-pressure refrigerant gas

In the refrigeration process, low-pressure refrigerant gas is drawn into a compressor, converted into high-pressure refrigeration gas, and pushed into a shell-and-tube heat exchanger. The compression process generates a tremendous amount of heat that must be removed by the exchanger. During the cooling process, the gas condenses into liquid phase and is collected in a receiver. From the receiver, the high-pressure liquid refrigerant is pushed through a small opening in an expansion valve. As the liquid expands, it changes phase. Because the boiling point of the

Rotary Screw Compressor

Oil Separator

1

HOT High Pressure Gas Refrigerant

Slide Valve

COLD Evaporator

Condenser

4

2 Expansion

Low Pressure Liquid Refrigerant

Figure 10–15 (a)

3

High Pressure Liquid Refrigerant

Two-Step Refrigeration System 241

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Pump INDUCED DRAFT Cross Flow High Pressure Gas (Refrigerant) Hot Oil Separator

1

Low Pressure Vapor

Rotary Screw Compressor

C O L D

Slide Valve Evaporator

4

2

Expansion Device (Orifice)

Pump To Fan Coil Units (Finned Coils)

High Pressure Gas (Refrigerant)

Low Pressure Liquid Refrigerant

3

Condenser

High Pressure Liquid Refrigerant

Chilled Water

Thermal Storage Tank Ice Covered Tubes Pump Ice Water Supply

Plate and Frame Exchange Pump

Figure 10–15 (b)

Glycol

Two-Step Refrigeration System

refrigerant is low, a cooling effect occurs in the evaporator. As the low-pressure refrigerant leaves the evaporator, it enters the suction side of the compressor and the process begins again.

10.7 Water Treatment System Twenty years ago, the chemical processing industry pumped a tremendous amount of water out of the ground for industrial applications. This practice was stopped after it was discovered that as the water table dropped, so did the surrounding countryside. The CPI now uses surface water for most industrial applications. Surface water is defined as water that is drawn in for industrial applications from lakes, rivers, and oceans. As water enters the plant, it is stored in large holding basins and allowed to settle out (Figure 10–16). A series of large pumps take suction off the basin and send water to a series of filters for additional purification. Chemicals are added to control pH and remove suspended or dissolved solids. Some filtered water is sent to demineralizers for additional treatment to remove dissolved impurities. 242

Summary

Pump

Filter

Cooling Tower Settling Basin

Figure 10–16

Water Treatment System

10.8 Utilities Utility System A refinery or chemical plant is supported by a utility section that provides steam, air, nitrogen, natural gas, water, cooling systems, compressed gases, and a variety of other things. In many facilities, water treatment and power distribution are located in the utility section. New technicians often get their first start in utilities. Steam is generated in a boiler system. Compressed gases are brought in by truck, cylinder, or pipeline, or may be compressed on site using existing compressor systems. Surface water is brought in and treated for industrial and domestic uses; this process includes filtering and demineralizing. In the water treatment process, all of the sewers in the plant are directed toward the environmental control system. Rainwater and chemicals are carefully treated before being released into the environment. Cooling towers control the temperature of industrial water used in heat exchanger systems. Electricity may be generated in house using boilers, turbines, and electric generators, or may be purchased from local power companies. Electricity is stepped down and sent to local motor control centers located throughout the plant. Furnaces produce the steam to heat cooling-tower basins and to support hundreds of applications in the plant. Process plants have utility sections that specialize in water treatment, steam generation, cooling, and gas compression. Process utilities are typically defined as water and compressed gases. Plant water can be classified as boiler feed water, drinking water, firewater, cooling-tower water, potable water, and wastewater. Compressed gases include air, nitrogen, hydrogen, chlorine, and others.

Summary Reactors are used to combine raw materials, heat, pressure, and catalysts in the right proportions. Five reactor designs are commonly used in the chemical processing industry: stirred reactors, fixed-bed reactors, fluidized-bed reactors, tubular reactors, and furnace reactors. The basic components of a reactor include a shell, a heating or cooling device, two or more product inlet ports, and one outlet port. Critical process variables in reactor operation include temperature, pressure, concentration of reactants, catalysts, and time. 243

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A distillation process consists of a complex arrangement of systems that includes cooling-tower system, pump-and-feed system, preheat system, product storage system, compressed-air system, steam-generation system, and complex instrument control system. Distillation columns separate chemical mixtures by the boiling points of the mixture components. Distillation columns are either plate or packed designs. Distillation was used long before the evolution of the modern chemical engineering discipline. An absorber is used to remove selected components from a gas stream by contacting the stream with a gas or liquid. Stripping columns are used with absorption columns to remove liquid hydrocarbons from the absorption oil. An adsorber is a device filled with a porous solid designed to remove gases and liquids from a mixture. A scrubber is used to protect and enhance environmental quality by removing chemicals and solids from process gases. In contrast to distillation, which uses boiling point to separate chemicals, a separation system uses density differences to achieve the separation. Pressure relief equipment includes relief valves, safety valves, rupture discs, piping, drums, vent stacks, pressure indicators, pressure alarms, pressure control loops, and flare systems. Pressure relief devices can be placed on pumps, compressors, tanks, piping, reactors, distillation columns, refrigeration systems, and many other kinds of equipment. Materials that cannot be released to the atmosphere are recycled back to the system, or sent to a scrubber or flare system. The discharge from pressure relief equipment is collected in a closed piping system and sent to a flare stack. Harmless gases are discharged at a safe distance from plant operations areas. Flare systems are designed to safely burn excess hydrocarbons. A flare system is composed of a flare, knockout drum, flare header, fan (optional), steam line and steam ring, fuel line, and burner. A flare is a tall pipe located a specified distance from the facility. An extruder is a complex device used in plastics plants. It is composed of a heated jacket, set of screws or screw, heated die, large motor, gearbox, and pelletizer. The extruder melts a polypropylene granule mixture to encapsulate additives, quickly quenches it, and cuts it into small pellets that are easier to handle. A simple plastics system includes equipment for extrusion, molding, casting, laminating, and calendering. In the refrigeration process, low-pressure refrigerant gas is drawn into a compressor, converted into high-pressure refrigeration gas, and pushed into a shell-and-tube heat exchanger. The heat generated by the compression process must be removed by the exchanger. During the cooling process, the gas condenses into liquid phase and is collected in a receiver. From the receiver, the high-pressure liquid refrigerant is pushed through a small opening in an expansion valve. As the liquid expands, it changes phase and creates a cooling effect in the evaporator.The low-pressure refrigerant leaves the evaporator and enters the suction side of the compressor so the process can begin again. The chemical processing industry uses surface water, drawn in from lakes, rivers, and oceans, for most industrial applications. As water enters the plant, it is stored in large holding basins and allowed to settle. A series of large pumps send water to a series of filters for additional purification. Chemicals are added to control pH and suspended or dissolved solids. Some filtered water is sent to demineralizers for additional treatment to remove dissolved impurities. Process plants have utility sections that specialize in water treatment, steam generation, cooling, and gas compression. 244

Chapter 10 Review Questions

Chapter 10 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Describe how a distillation column works. What is the primary function of a reactor? Draw a simple flare system. List the basic equipment found in a distillation system. List the equipment found in utility systems. Describe the basic equipment found in a stirred reactor system. Describe the equipment found in an extrusion system. Describe a scrubber’s primary function. Compare and contrast an absorption column with an adsorption system. List the basic equipment used in a refrigeration system. List the basic equipment found in a water treatment system. Describe the purpose and operation of a pressure relief system and flare system. Describe how a refrigeration system works. What kinds of systems are found in a plant’s utility section? List the various sections found in a plastics plant.

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Industrial Processes After studying this chapter, the student will be able to: • • • • • • • •

Define terms related to common industrial processes. Explain and contrast petrochemical processes. Describe the benzene, BTX aromatics, and ethylbenzene processes. Describe the ethylene glycols, mixed xylenes, and olefins processes. Describe the paraxylene, polyethylene, and xylene isomerization processes. Describe the alkylation and fluid catalytic cracking processes. Describe hydrodesulfurization, hydrocracking, and fluid coking Describe the catalytic reforming and crude distillation processes.

247

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Industrial Processes

Key Terms Alkylation—uses a reactor to make one large molecule out of two small molecules. Alkylation unit—uses a reactor filled with catalyst to cause a chemical reaction that produces the desired product. Catcracker—uses a fixed-bed catalyst to separate smaller hydrocarbons from larger ones. Distillation tower—a series of stills arranged so the vapor and liquid products from each tray flow countercurrently to each other. Fixed-bed reactor—device in which the fixed medium remains in place as raw materials pass over it. Fluid catalytic cracking—a process that uses a reactor to split large gas oil molecules into smaller, more useful ones. Fluid coking—a process that uses a reactor to scrape the bottom of the barrel and squeeze light products out of the residue. Fluidized-bed reactor—suspends solids within the reactor by countercurrent flow of gas. Particle segregation occurs over time as heavier components fall to the bottom and lighter ones move to the top. Hydrocracking—uses a multistage reactor system to boost yields of gasoline from crude oil. Hydrodesulfurization unit—sweetens products by removing sulfur. Reactor—a device used to convert raw materials into useful products through chemical reactions. It combines raw materials, heat, pressure, and catalysts in the right proportions to initiate reactions and form products. Reboiler—a heat exchanger used to maintain the heat balance on a distillation tower. Reformer—a reactor filled with a catalyst designed to break large molecules into smaller ones through chemical reactions that remove hydrogen atoms. Regenerator—used to recycle or regenerate contaminated catalyst.

11.1 Common Industrial Processes During World War I (1914 to 1918), oil production became as important as ammunition production. Oil was used to operate ships, airplanes, tanks, automobiles, motorcycles, and other motorized equipment. As technology improved, so did farming techniques around the world: Tractor technology and other motorized farming implements increased productivity. The increased productivity enabled by gasoline led to a new revenue-generating source for the government (the gas tax). Another byproduct of gas production was asphalt.This new material enabled the federal government, along with state and local authorities, to upgrade existing road systems and launch new road-building ventures. During World War II (1939 to 1945), technology took a few more steps forward. New process equipment was tested on naval vessels, submarines, aircraft, and land vehicles and in communications. 248

11.1 Common Industrial Processes American oil companies demonstrated the ability to adapt quickly to wartime needs, and ended up producing more than 80% of the aviation fuel used by the Allies. Huge quantities of oil and new specialty chemicals were needed during the war. For example, butadiene was used to make synthetic rubber; toluene is a major ingredient in medicinal oils and the explosive TNT. The World War II period saw significant improvements in the industrial processes of alkylation and catalytic cracking. These two processes greatly enhanced the production of high-octane aviation gasoline. Postwar years saw another tremendous increase in oil consumption. Process technicians could easily find lifelong jobs at many of the large refineries. In the early 1950s, a Humble Oil (now Exxon) company employee could get a car loan in the Baytown, Texas, area simply by showing the salesperson an employee badge. This experience was common in cities where oil refining, gas processing, and petrochemicals pumped huge amounts of money into the local economy. From 1950 to 1972, the government continued to draft large numbers of process technicians into the military. Most companies worked with employees who had been drafted and allowed them to return to their jobs after their tours of duty. Some companies counted an employee’s service time in the military as uninterrupted company service time. This group of employees greatly influenced the development of the military-type environment found in the chemical processing industry.

Workforce Trends 1960–1980 As the complexity of industrial processes increased, a significant change occurred in the make-up of the technical workforce. Starting in the 1960s and building into the 1970s, the chemical processing industry began to employ large numbers of engineers. As this fact became known, engineering programs around the United States began to draw students. Colleges started turning out record numbers of:

• • • • • •

Electrical engineers Chemical engineers Mechanical engineers Petroleum engineers Industrial engineers Nuclear engineers

Engineers were employed in the chemical processing industry as technical support to the operations groups. This relationship was not new; engineers, chemists, and technicians had worked together as a team for many years. The increased numbers, however, were new.

Common Processes Industrial processes fall into three basic groups: refining (19 processes), gas processing (15 processes), and petrochemical processing (40 processes). The oldest and best-established group is refining processing. The most common industrial processes in the refining and petrochemical areas include: Petrochemical Processes

Refining Processes

Alkylbenzene, linear

Alkylation (4)

Amines, methyl

Benzene reduction

Ammonia (5)

Benzene saturation

Benzene

Catalytic reforming (3) 249

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Industrial Processes Petrochemical Processes (continued) Bisphenol-A (2)

Coking (4)

BTX aromatics (3)

Cracking

Butadiene

Catalytic

Butanediol, 1,4-

Deep catalytic

Butyraldehyde, n and i

Fluid catalytic (6)

Caprolactam

Hydrocracking (6)

Cumene (3)

Residual catalytic

Dimethyl terephthalate (2)

Crude distillation

EDC via oxychlorination

Deasphalting (3)

Ethanolamines

Electrical desalting

Ethylbenzene (3)

Ethers (7)

Ethylene (6)

Hydrogenation

Ethylene glycols

Hydrotreating (7)

Ethylene oxide

Isomerization (6)

Formaldehyde

Treating

Maleic anhydride

Visbreaking (3)

Methanol (4) Olefins (3) Paraxylene (2) Phenol (2) Phthalic anhydride Polycaproamide Polyethylene (5) Polyethylene terephthalate (PET) Polyethylene, LDPE-EVA Polypropylene (3) Propylene (3) PVC (suspension) (2) Styrene (2) Terephthalic acid Urea Vinyl chloride Vinyl chloride monomer Xylene isomerization Xylene isomers Xylenes, mixed 250

Refining Processes (continued)

11.3 Benzene The numbers in parentheses indicate the number of registered processes or ways to manufacture the chemical.

11.2 Petrochemical Processes Gas processing springs directly from the refining process. Since 1960, rapid developments have occurred in the petrochemical area. Currently, there are hundreds of petrochemical processes, and many of them can be accomplished in more than one way. Petrochemical processes are far more numerous than the basic core refinery processes. This chapter lists many of the primary processes found throughout the country. A process technician working in ethylene production could have to deal with more than five different operational arrangements. In addition to new processes, a tremendous surge in the development of small, specialty chemical companies is anticipated in the next 10 to 20 years.

11.3 Benzene The benzene process is designed to produce high-purity benzene and heavy aromatics from a mixture of toluene and heavier aromatics (Figure 11–1). Heated hydrogen and feedstock are (1) passed over a special catalyst bed that reacts to form a mixture of benzene, unreacted toluene, xylene, and heavy aromatics. This mixture is (2) condensed in a drum and (3) stabilized. Stabilized bottoms are sent to a fixed-bed clay treater for acid wash color specifications and then (4) distilled to separate benzene, xylenes, toluene, and C9⫹ aromatics. The yields are 99 mol% aromatic yield of fresh toluene. Typical production yields for xylenes and benzene are: Wt% Feedstock

Benzene

Xylene

Nonaromatics

3.2

2.3

Benzene

0

Toluene

47.3 Recycle Hydrogen

H2 Make-Up

Furnace

11.3 0.7

Fuel Gas

Benzene

C7 Aromatics Start Xylenes

Recycle Toluene and C9 aromatics

Figure 11–1 Benzene Process 251

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49.5

0.3

0

85.4

100%

100%

75.7

36.9

0

37.7

Wt% Products Benzene C8 aromatics

11.4 BTX Aromatics BTX aromatics (Figure 11–2) are derived using a process based on extractive distillation. The process is designed to produce yields of benzene, toluene hydrogen, xylenes, and C5⫹. The BTX process starts with a feedstock composed of paraffins 57%, naphthenes 37%, and aromatics 6% being fed into a series of moving fluidized-bed reactors 1 through 4. The feed flows downward over the special catalyst bed and out the lower section of the number 1 reactor; the process is then repeated with reactors 2, 3, and 4. The catalyst and feed mixtures are designed to flow from reactors 1 through 4. Because solids and liquids have different flow characteristics, a unique gas-lift transfer process is required to move the solid catalyst from one reactor to the next. The gas-lifted catalyst is “series-fed” into each reactor’s feed hopper until it reaches reactor 4. As the catalyst moves between reactors, it accumulates coke deposits. To eliminate the coke deposits, the fourth reactor transfers the catalyst to a regenerator where the coke is removed. The regenerated catalyst is gas-lifted back to the feed-hopper section on reactor 1 where the process starts over.

Paraffins Naphthenes Aromatics START

Feed Regenerator

Moving-Bed Reactors 1–4

RX 1

RX 2

Catalyst Gas-Lift System

RX 3

RX 4

Aromizate to Separator H2, C5, Benzene, Toluene, Xylenes

Figure 11–2 BTX Aromatics Process 252

11.7 Mixed Xylenes

PEB Column

Ethylbenzene Column

Benzene Column

Transalkylation Reactor

Alkylation Reactor

EB

Ethylene Recycle Benzene

Start Benzene

Heavy Ends Polyethylbenzenes

Figure 11–3 Ethylbenzene Process

11.5 Ethylbenzene One of the more common ways to manufacture ethylbenzene (Figure 11–3) is to use a fixed-bed reactor filled with a special catalyst, a series of distillation columns, and a special process for alkylation of benzene/ethylene.

11.6 Ethylene Glycols The raw feedstock for an ethylene glycols unit includes refined ethylene oxide and pure water. A mixture of ethylene oxide and recycled pure water is (1) pumped to a feed tank, where it is blended and heated prior to being (2) sent to the glycol reactor. Residence times in the reactor are long enough to allow all of the ethylene oxide to react. After the reaction is complete, the water/glycol mixture is pumped to a multistage evaporator. A thermosyphon reboiler is used to maintain temperature on the column. A total of six glycol columns is utilized to purify and separate the various components of the process streams. The glycol/water mixture flows from one column to the next, encountering successively lower pressures in each column. The last four columns operate under a vacuum. The plant process is designed to produce purified monoethylene glycol (EB); however, a number of secondary products, such as triethylene glycol (TEG) and diethylene glycol (DEG), are also formed. Figure 11–4 illustrates the ethylene glycol process.

11.7 Mixed Xylenes The mixed xylenes process (Figure 11–5) selectively converts toluene to high-purity benzene, mixed xylenes, C9⫹ aromatics, and C5⫺. The feedstock is composed of dry toluene, C9 aromatics, and hydrogen-rich recycle gas. The raw feedstock is introduced to the unit by being passed through a heat exchanger and a fired heater, and into a reactor. Mixed xylenes and benzene are produced during toluene disproportionation in the vapor phase. Products from the reactor are pumped to a separator where hydrogen-rich gas is recycled to the reactor and primary bottom products are pumped into a series of fractionation columns for product separation. 253

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Industrial Processes Make-Up Water Start EO Hydration Reactor

Water Recycle

Figure 11–4 Ethylene Glycol Process

H2 Recycle

H2

Fuel System CW

CW Stabilizer Start Toluene

Steam Reactor

Separator

Furnace

To Fractionation System

Figure 11–5 Mixed Xylenes Process

Reactor Wt% Yields

Feed

C5 and lighter

1.3

C9⫹ aromatics

1.8

Benzene Toluene Ethylbenzene

254

Product

19.8 100

52.0 0.6

m-Xylene

12.8

o-Xylene

5.4

p-Xylene

6.3

11.11 Xylene Isomerization

11.8 Olefins Three processes are associated with production of olefins. One process is designed to convert natural gas or raw methanol to ethylene, propylene, and butane. The second process is designed to produce isobutylene and isoamylene feedstocks from hydrocarbon feedstock. This material is used in production of ethers, polymerization, and linear olefins for alkylation. The third process selectively converts gas oil feedstocks into high-octane gasoline and distillate, and C2–C5 olefins.

11.9 Paraxylenes The paraxylene process (Figure 11–6) takes mixed xylenes from reformers or steam crackers to produce high-purity paraxylene. Feedstock is pumped to a feed rerun column that removes C9 (and heavier) materials out the bottom and mixed xylenes out the top. The overhead product is sent to a set of adsorption columns where paraxylene is removed and purified to 99.9%. A series of distillation columns is used to separate or recycle the rest of the products.

11.10 Polyethylene A variety of polyethylene processes exist and are popular with industrial manufacturers (Figure 11–7). These applications can be used to produce high- or low-density polyethylene, linear polyethylene, or linear low-density polyethylene.

11.11 Xylene Isomerization Xylene isomerization takes depleted paraxylene and orthoxylene streams from the paraxylene unit and passes them over a dual fixed-bed catalyst. As the process flow moves through the reactor and over the catalyst, it is combined with hydrogen-rich recycle gas. The upper section of the reactor is utilized for EB dealkylation, and the lower section is optimized for xylene isomerization. EB conversion rates are typically in excess of 65%, whereas paraxylene concentrations are typically 102% greater than equilibrium. PX Unit Cool Single-Stage Crystallizer

Heat Feed Start Pure p-Xylene

Figure 11–6 Paraxylene Process 255

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Industrial Processes Fresh Diluent

Catalyst

Ethylene Recovery

M

Compressor 1 Fractionator Recycle

M

Recycle Diluent

5

Flash Chamber

M

To Flare

2 Start Ethylene

3

Loop Reactors

4

Comonomer

Purge Column

Nitrogen To Extruder

Figure 11–7 Polyethylene Process

11.12 Ethylene Industrial manufacturers use six popular methods to produce ethylene. The Lummus method is used to produce more than 45% of the ethylene sold in the world. This process produces 99.95 vol.% polymer-grade ethylene. Some of the by-products created during this process are propylene, butadiene-rich C4s, aromatic-rich C6–C8 pyrolysis gasoline, and pure-grade hydrogen.

11.13 Refining Processes Industrial manufacturers use 19 common refining processes. Refining processes are typically linked to the large branches of the crude oil tree. The global economy has allowed the chemical processing industry to diversify into a variety of business ventures. During the 1960s and 1970s, a large number of petrochemical processes were developed; each of these processes had its roots in the refinery operation. The refining group has the oldest set of processes. Products from the refinery are typically used as feedstocks for modern petrochemical processes.

11.14 Alkylation Alkylation units take two small molecules of isobutane and olefin (propylene, butylenes, or pentylenes) and combine them into one large molecule of high-octane liquid called alkylate. This alkylation combining process (Figure 11–8) takes place inside a reactor filled with an acid catalyst. Alkylate is a superior antiknock product that is used in blending unleaded gasoline. 256

11.15 Fluid Catalytic Cracking

Hydrocarbon Treated with Caustic

Acid Settler Isobutane and Refrigerant Recycle to Reactor

Isobutane and Propane Propane

Plate Tower

Recycled Acid

Plate Tower

Reactor Isobutane Olefin Feed (propylene, butylenes, or pentylenes) Alkylate

Figure 11–8 Alkylation

After the reaction, a number of products are formed that require further processing to separate and clean the desired chemical streams. A separator and an alkaline substance are used to remove (strip) the acid. The stripped acid is sent back to the reactor, while the remaining reactor products are sent to a distillation tower. Alkylate, isobutane, and propane gas are fractionally separated in the tower. Isobutane is returned to the alkylation reactor for further processing. Alkylate is sent on to the gasoline blending unit.

11.15 Fluid Catalytic Cracking When crude oil comes into a refinery, it is processed in an atmospheric pipe still. The side stream of the pipe still is rich with light gas oil. Fluid catalytic cracking units, or catcrackers, split this gas oil into smaller, more useful molecules (Figure 11–9). Fluid catalytic cracking units use the following equipment during operation:

• • •

Catalyst regenerator Reactor Fractionating tower

During operation, gas oil enters the reactor and is mixed with a superheated powdered catalyst (the cat in catcracking). The term cracking is appropriate for this process because, during vaporization, the molecules literally split; they are then sent to a fractionation tower for further processing. The chemical reaction between the catalyst and light gas oil produces a solid carbon (coke) deposit. This deposit forms on the powdered catalyst and deactivates it. The spent catalyst 257

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Industrial Processes Cracked Gas Cracked Molecules Gas and Heat for Steam Production

Naphtha Plate Tower

Heating Oil

Regenerator Light Gas Oil

Reactor

Gas Oil Mixes with Powdered Catalyst Regenerated Catalyst

Coke Catalyst Recycles to Regenerator

Heavy Gas Oil

Spent Catalyst Recycled Liquids

Figure 11–9 Catcracking is drawn off and sent to the regenerator where the coke is burned off. Catalyst regeneration is a continuous process during operation. In the fractionation tower, the light gas oil is separated into five different cuts: 1. 2. 3. 4. 5.

Cat-cracked gas Cat-cracked naphtha Cat-cracked heating oil Light gas oil Residue

11.16 Hydrodesulfurization Crude oil is a mixture of hydrocarbons, clay, water, and sulfur. Some crude mixtures have higher concentrations of sulfur than others; these mixtures are referred to as sour feed. Hydrodesulfurization (Figure 11–10) is a process used by industrial manufacturers to “sweeten” or remove the sulfur. Hydrodesulfurization units use the following equipment during operation:

• • •

Fired heater Separator Reactor

During operation, sour feed is mixed with hydrogen and heated in a fired furnace. The heated mixture is sent to a reactor where the hydrogen combines with the sulfur to form hydrogen sulfide. When the temperature is lowered slightly, the sweet crude condenses, leaving the hydrogen sulfide in a vapor state.This vapor-and-liquid mixture is sent to a separator where the low-sulfur sweet 258

11.17 Hydrocracking

Feed with Sulfur

Furnace

Separator Charge Out

1

2

3

4

Mixture of Hydrogen Sulfide, Hydrogen, and Product Is Cooled

Low Sulfur Product

Recycled H2

Figure 11–10

Reactor

Hydrodesulfurization

feed is removed. The hydrogen sulfide and hydrogen are sent for further processing during which the hydrogen is separated and returned to the original system.

11.17 Hydrocracking Hydrocracking is a process that industrial manufacturers use to boost gasoline yields (see Figure 11–11). The process splits heavy gas oil molecules into smaller, lighter molecules called hydrocrackate. Hydrocracking units use the following equipment during operation:

• • •

First- and second-stage reactors Separator drum Fractionating tower

The hydrocracking process mixes heavy gas oil feed with hydrogen before sending it to the firststage reactor. The reactor is filled with a fixed bed of catalyst. As process flow moves from the top of the reactor to the bottom, the cracking reaction takes place. First-stage hydrocrackate is sent to a separator drum where the hydrogen is reclaimed and the hydrocrackate is moved to a fractionation tower. In the fractionation tower, the hydrocrackate is separated into five different cuts: 1. 2. 3. 4. 5.

Butane Light hydrocrackate Heavy hydrocrackate Heating oil Heavy bottom

The heavy bottom is mixed with hydrogen and sent to the second-stage reactor for further processing. The second-stage reactor reclaims as much of the hydrocrackate as possible before sending it to the separator and tower. 259

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Plate Tower

H2 Recycle Separator Drum

Light Hydrocrackate

Hydrogen Heavy Hydrocrackate

1st stage Reactor and Catalyst

Heating Oil 2nd Stage Reactor and Catalyst

Heavy Bottom

Figure 11–11

Hydrocracking

11.18 Fluid Coking Fluid coking (Figure 11–12) is a process used by industrial manufacturers to squeeze every last useful molecule out of heavy residues. Residue from other processes flows into a specially designed, high-temperature reactor. Light products vaporize and flow to a fractionation column. The remaining material is sent to a burner where further processing takes place. The burner produces three separate products: 1. Coker gas for use in the plant 2. Product coke for sale 3. Recycled coke for the reactors

11.19 Catalytic Reforming The catalytic reforming process (Figure 11–13) utilizes refinery naphtha to produce high-octane reformate. The advanced design utilizes a set of four moving-bed reactors and one regenerator. The process is similar to that used for BTX aromatics. The design employs continuous catalyst regeneration, continuous liquid flow, and solid flow movements between reactors.

11.20 Crude Distillation In a crude distillation process (Figure 11–14), the various fractions of crude oil are separated by their boiling points. During the distillation process, crude oil goes through a number of phases. The initial charge is heated and desalted. This heating process is gradual; the charge moves through 260

11.20 Crude Distillation Liquid Products to Fractionation

Scrubber Separates and Recycles Heavy Hydrocarbons from Light Gases

Reactor

Coker Gas

Burner

Product Coke

Residue Feed

Hot Coke Recycled

Air and Steam

Coke to Burner

Figure 11–12

Fluid Coking

Reactor with Catalyst

Hydrogen

Separator Furnace

1

2

3

4

High Octane Naphtha

RX

Heat Exchanger

Figure 11–13

Reforming

a series of heat exchangers before it enters the fired furnace. In the furnace, the charge splits into a number of passes that are combined when the feedstock exits the furnace. A typical inlet temperature for a fired furnace is 550°F; the outlet temperature varies between 675°F and 725°F. The heated charge is pumped to a distillation column where a fraction of the feed vaporizes and moves up the column. (The distillation column incorporates a still-upon-a-still design.) Vapors rise up the column while liquids drop down. Molecular distribution is different on each tray in the distillation column. A typical distillation column has one feed line, one overhead line, one reflux line, 261

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Column

Feed Tank

Heat Exchanger Furnace

Figure 11–14

Reboiler

Crude Distillation

four side streams, and one bottom line. Different products exit at each point on the column. Crude distillation columns produce flash gas, light and heavy naphtha, kerosene, diesel, cracker feed, gas oils, and asphalt.

Summary Industrial processes can be broken into three basic groups: refining (19 processes), gas processing (15 processes), and petrochemical processing (40 processes). The oldest and best established group is refining processing; gas processing springs directly from the refining process. During the past 30 to 40 years, the gas processing and petrochemical areas have experienced rapid technological advances and significant workforce shifts. The refining processes discussed in this chapter included alkylation, fluid catalytic cracking, hydrodesulfurization, hydrocracking, fluid coking, catalytic reforming, and crude distillation. Alkylation takes two small molecules of isobutane and olefin and combines them into one large molecule called alkylate. Fluid catalytic cracking uses a heated catalyst to break large gas oil molecules into smaller ones. Hydrodesulfurization removes sulfur from a process stream. Hydrocracking uses a multistage reactor system to boost yields of gasoline from crude oil. Fluid coking is applied to heavy residues to remove or break loose usable products. Catalytic reforming uses a reactor/catalyst approach to break hydrogen loose from high-octane naphtha. Crude distillation separates the various components in crude oil by their boiling points. The petrochemical processes covered in this chapter include those that use or produce benzene, BTX aromatics, ethylbenzene, ethylene glycol, mixed xylenes, olefins, paraxylene, polyethylene, xylene isomerization, and ethylene. The benzene process uses heated hydrogen, toluene, and heavy aromatic feedstock to produce high-purity benzene and heavier aromatics by passing it over a fixed catalyst bed. The BTX aromatics process passes a feedstock composed of paraffin, napthenes, and aromatics through a series of fluidized-bed reactors. Ethylbenzene manufacturing

262

Summary uses a fixed-bed reactor filled with catalyst, a feedstock of ethylene and benzene, and a series of distillation columns to produce product. Ethylene glycol is commonly used as antifreeze in automobiles. The feedstock includes pure water and refined ethylene oxide. This system combines a blending feed tank, glycol reactor, and a series of distillation columns. Olefin manufacturing includes three major processes: the first converts natural gas to ethylene, propylene, or butane; the second produces isobutylene and isoamylene from hydrocarbon feedstocks; the third converts gas oil feedstocks into high-octane gasoline, distillates, and C2–C5 olefins. Plastics manufacturing employs a number of polymer processes that handle polyethylene, polypropylene, and butyl polymers.

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Chapter 11 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

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What is the primary difference between petrochemical and refinery processes? List the significant industry events that occurred between 1914 and 1960. Describe the evolution of the refinery process to petrochemical processes. Describe the benzene process. Describe the BTX aromatics process. Sketch the ethylbenzene process. Describe ethylene glycols operations. Describe mixed xylenes operations. Describe olefins operations. Describe the paraxylene process. Draw a simple sketch of the polyethylene process. Describe xylene isomerization operations. Describe the ethylene process. Explain the basic refining process. Explain alkylation. Describe fluid catalytic cracking, catalytic reforming, and hydrocracking. Describe the hydrodesulfurization process. Explain the principles of crude distillation. Explain fluid coking.

Process Technology Operations After studying this chapter, the student will be able to: • Describe and operate the feed and preheat system. • Identify the basic components of the distillation system. • Describe and operate the overhead and bottom systems on the distillation column. • Describe and control the various process variables in the distillation system. • Collect operational data and process samples. • Know and apply safety and quality control rules and procedures. • Use an operating procedure to start up and shut down the distillation process. • Establish setpoints on each control loop and monitor operation. • Work in a self-directed team. • Complete the post-job walk-through with the instructor. • Qualify to operate the pilot plant. • Troubleshoot and analyze operational problems on the pilot plant.

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Key Terms Feed system—composed of a variety of equipment systems, including feed tanks, valves, piping, instruments, and pumps. Process instruments—devices that control processes and provide information about pressure, temperature, levels, flow, and analytical variables. Process Technology 3—Operations—a college-level course, designed to be the capstone experience, that includes all the elements covered in a process technology two-year degree program. Trainee—an unqualified technician recently assigned to an operating unit. Trainer—a qualified technician assigned to mentor a trainee.

12.1 Overview of Process Process technology programs include traditional coursework and hands-on training. Theory courses cover safety, quality, process equipment, physics, chemistry, and instrumentation. The hands-on component emphasizes process systems, troubleshooting, and operations. These classes include console training, bench-top operations, and pilot plant operations. Process Technology 3—Operations is a college-level course designed to be a hands-on experience. This course includes all the elements covered in a process technology two-year degree program and may be used as the capstone experience of that program. The pilot plant equipment and systems will vary from one college to the next. Donations from local industry and grants are typically used to purchase or secure expensive process equipment. Although the equipment and systems available to each college are different, the objectives remain constant: The goal of these programs is to prepare graduates to take entry-level positions in the chemical processing industry. Technicians should consider this class to be the single most important course they will take prior to entering the workforce.

12.2 Pilot Plant Operations This chapter is an overview of a simple distillation process used by a number of educational programs to teach operations. Primary equipment and systems are designed to simulate this process. Trainers usually require that new trainees receive an overview of the pilot plant process. The feedstock simulated in this process is a binary mixture of butane (40%) and pentane (60%). Most educational programs use propylene glycol, water, or red dye to simulate these feed mixtures. Flow rates are controlled to the distillation column at 200 gallons per minute (gpm) or hour (gph). Three butane analyzers are located on the unit to analyze the feed, overhead stream, and bottom stream. Feed-tank levels are controlled at 50% by level control loops. The distillation column 266

12.2 Pilot Plant Operations separates the components in the mixture by boiling point; however, some overlap of the butane and pentane still takes place in both the overhead and bottom streams. The distillation column has an enriching or rectifying section, a feed section, and a stripping section. A distillation system, however, also includes a large assortment of equipment and systems that support the process: feed section, preheat section, distillation column, overhead section, bottom section, and product storage. The quality system provides the mathematical foundation that standardizes plant operations. A unit checklist is designed to collect a wide variety of operational information.

Feed System The feed system is composed of a variety of equipment systems, including feed tank, valves, piping, instruments, and pumps. Inside the feed system, the composition of the feedstock is closely monitored. Flow rates, pressures, temperatures, and levels are carefully maintained. Figure 12–1 shows the basic equipment found in a distillation feed system. Compressed air or nitrogen systems are also used in the feed system. Nitrogen is an inert gas that provides protection from fire or explosion. Compressed air is used to open, close, or throttle control valves. Basic instrument systems used in the feed system include indicators, control loops, recorders, and analyzers.

Preheat System Before feed can be sent to the distillation column, it must be preheated to a temperature range that will allow the separation process to occur. The pilot plant uses heat exchanger 101 to heat up the feed. Heating the feed initiates the distillation process, as the various components in the mixture respond differently. Figure 12–2 illustrates what the preheat system looks like on this unit. As the feed is heated, pressure increases inside the pipe as the lighter components attempt to escape from the liquid. (Heat increases molecular movement within the liquid.) A temperature control loop maintains unit specifications. As the heated feed exits the heat exchanger, a temperature element and transmitter send a signal to TIC 101. The controller compares the signal to the setpoint and makes adjustments to the temperature control valve. The control valve regulates the flow of hot oil through the heat exchanger. Pump 101 is a centrifugal pump designed to pump feed to the column through the tube side of heat exchanger 100.

V-4

V-5

AT

CV-10

TK-100 V-3 Pi

Pi

FEED TANK

V-2 V-1

P-101

Figure 12–1 Distillation Feed System 267

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FIC 100 185°F 25 psi Ti

23 psi

Pi

278°F

Pi

Ti

I/P 200 gpm

FT

EX-100 TE

CV-10

TE Flow CV-9

I/P

TIC 101

P-101 350°F HOT OIL IN

Figure 12–2 Preheat System

Distillation Column After the feed has been blended and preheated, it is sent to the distillation column (see Figure 12–3). A flow control loop regulates the flow of feed at 200 gallons per minute. An orifice plate and flow transmitter send a signal to FIC 100. The controller compares this signal to the setpoint and adjusts the feed by opening or closing control valve 10. In a plate column, the heated feed enters on the feed tray. The part of the column above the feed line is called the rectifying or enriching section. The part of the distillation column below the feed line is referred to as the stripping section. As the heated feed enters the column, part of it vaporizes and moves up the column. The heavier part of the mixture flows down the column through devices called downcomers. Each tray in the column forms a liquid seal that provides good vapor–liquid contact. Theoretically, each tray in the column would have a different molecular structure, ranging from heavier components in the bottom to lighter components in the top. The lighter fractions exert a higher vapor pressure. Typically, the temperatures are higher in the bottom of the column and lower at the top. This is referred to as a temperature gradient. Two scientific principles must be balanced on a distillation column: energy and mass. Heat is returned to the system using a kettle reboiler connected to the bottom of the distillation column. (A reboiler is a heat transfer device designed to add energy to the bottom fractions.) The heavier bottom product is still rich with lighter components that need help breaking free from the larger molecules. As the heated fluid passes through the reboiler, the lighter components vaporize and flow into the column under the bottom tray. The space below the bottom tray allows the liquid to free-roll and boil. As feed flows into the column through a single feed source, the rate is carefully monitored. The various fractions in the mixture can flow out the overhead, side, or bottom. The old saying that “what flows into the column must flow out ” is still true. 268

12.2 Pilot Plant Operations Heat Exchanger (Overhead Condenser)

Pi

EX-101

FIC Pi

TIC CV-11 Tray 8

Pi

Tray 7

FIC 100 AT

Ti

Enriching Section

Reflux

Pi

D-100

Tray 6

100

CV-12

Flare

LIC 100

Fi

Tray 5

I/P

CV-14 Tray 4

FT

Flow Feed Analyzer #1

PIC

Overhead Accumulator

FIC

CV-13 AT

Ti

P-103

Feed Tray

CV-10

Feed Analyzer #2 Tray 2

Stripping Section

Tray 1

TIC Hot Vapor

C-100

CV-15 Steam In Pi

Pi

Ti

FIC

Kettle Reboiler

102

Distillation Column

EX-102 LIC 102 Feed Analyzer #3 AT

To Boiler

Fi CV-16

P-104

Figure 12–3 Distillation Column The overhead system is specifically designed to condense the lighter fractions and send them to product storage and back to the top tray in the column. The cooled, condensed product that flows back to the column is called reflux. The system is specifically designed to control product purity and control temperature in the top of the column. The overhead system includes a condenser, accumulator, pump, and piping. Figure 12–4 shows an overhead system. The bottom product is sent to the tank farm for storage. (Figure 12–5 shows a bottom system.) The tank farm has a number of product and off-spec tanks. The overhead stream is sent to the tank farm, tested, and—if approved—shipped to the customer.

Variations in Feed Composition In a binary mixture, two components are separated from the feedstock. In this example, our distillation system has a 40/60 mixture of butane (water) and pentane (propylene glycol and red dye). Three butane analyzers are used to monitor the concentration of butane in the various streams. 269

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Flow Controller PV SP 400 OP%

Heat Exchanger (Overhead Condenser)

I/P

Temp/Controller PV SP 160 OP% Tray 8

FIC 105 FT

Pressure Controller PIC 101

I/P

PV SP 100 OP%

PT

TE TT

PE

Tray 7

LE LT

D-100

LIC

Tray 6

102 I/P

Tray 5

Fi

Tray 4

P-103

PV SP 50 OP%

TIC 103

I/P

AT 2

FIC 102

Level Controller

FT

Fi

Flow Controller PV SP 130 OP%

Figure 12–4 Overhead System

Feed composition, overhead product, and bottom product should be found in the following concentrations:

270

Overhead

98.5% butane, 1.5% pentane

Bottom

8% butane, 92% pentane

Feedstock

40% butane, 60% pentane

12.2 Pilot Plant Operations

Temperature Controller

Flow Controller PV SP 12 OP%

TIC 102

Tray 4

PV 220 SP OP%

Tray 3

FIC 104

I/P

FT

Steam In

Tray 2 Tray 1 Hot Vapor C-100

TE TT LE LT LIC

103

Kettle Reboiler

To Boiler

Level Controller PV SP 50 OP%

I/P Fi

P-104

Bottom Product

Figure 12–5 Bottom System

Variations in product composition are carefully monitored and controlled. To do this, a variety of modern control features are incorporated into the system, including temperature, pressure, level, and flow control loops. Product variation is the enemy of any chemical process. When product specifications are not met, customers will take their business elsewhere.

Data Collection Data collection gathers information about feed composition, overhead purity, and bottom purity. Three analyzers are placed in each of these streams to allow each process technician on shift to monitor and record the process. Figure 12–6 shows information collected from the overhead line. In addition to the product lines, data is collected continuously on each control loop, and alarms are located on key equipment. A unit checklist is filled out during every shift as part of the data collection process concerning unit variables.

Control Charts Controlling the overhead butane concentration is an important quality aspect of process control on a distillation system. This is accomplished by carefully monitoring the analyzer on the overhead reflux stream and recording the lab results from each shift. The three daily 271

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Sample

Date X1

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

5-1-06 5-2-06 5-3-06 5-4-06 5-5-06 5-6-06 5-7-06 5-8-06 5-9-06 5-10-06 5-11-06 5-12-06

98.6 99.1 98.3 99 97.8 98.3 96.9 97.8 99 97.9 98.1 98.3

Flow (gpm) X2 X3 98.7 98.7 98.6 98.7 97.5 98 97.5 98.4 99.1 98.1 98.5 98.8

99 98.5 99.1 98.2 98 98.8 98.1 98.6 98.7 98.6 99.2 99

∑X

X-Bar

R

296 296 296 295 293 295 292 295 297 295 296 296

98.76 98.76 98.66 98.63 97.77 98.37 97.5 98.26 98.93 98.2 98.6 98.7

.4 .6 .8 .8 .5 .8 1.2 .8 .7 .7 1.1 .7

98.43

X Chart UCL  X-bar  (A2  R) LCL  X-bar  (A2  R)

98.43  (1.023  .758)  99.2 98.43  (1.023  .758)  97.66

Range Chart UCL  R  D4 LCL  R  D3

.758  2.575  1.95 .758  0  0

.758

Figure 12–6 Distillation—Overhead Purity

results are averaged and included on the control chart. The range is calculated by subtracting the lowest reading from the highest. Using the equations for the X-bar chart (Figure 12–7) and the R-bar chart (Figure 12–8), the upper and lower control limits can be calculated. The average of the three daily results and the range between the variables allow us to develop the control chart.

12.3 Process Control Instrumentation A number of variables in a distillation process are controlled by the process instruments, including pressure, temperature, level, flow, and analytical variables. The composition of the overhead stream is only one of a large number of variables. The three analyzers on the unit are primary targets for a quality system. Figure 12–9 shows the typical variables found on this system. 272

12.3 Process Control Instrumentation

% of Butane in Reflux 99.46 99.2

UCLX

= 99.2

98.95 98.69 Target

98.43

X = 98.43

98.17 97.9 97.66

LCLX = 97.66

97.40 97.14 2

0

4

6 Sample

8

12

10

Figure 12–7 Butane Overhead Control X-Bar Chart

2.0

Range UCLR = 1.95

1.8 1.6 1.4 1.2 1.0 Target

0.8 R = 0.758 0.6 0.4 LCLR 0

2

4

6

8

10

=0

12

Sample

Figure 12–8 Butane Overhead Control R-Bar Chart 273

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Tag#

Description

Setpoint

AT-1 AT-2 AT-3 TIC-101 TIC-102 TIC-103 PIC-101 FIC-100 FIC-102 FIC-103 FIC-104 FIC-105 FI-102B LIC-101 LIC-102 LIC-103 LIC

Butane Feed Analyzer Butane Overhead Analyzer Butane Bottom Analyzer Preheater Hot Oil Column Bottom Tray #1 Column Top Tray #8 Column Top Pressure Unit Feed Reflux Flow Rate Bottom Flow Rate Steam to Reboiler Cooling Water to Overhead Condenser Overhead Flow to Tank Farm Feed Tank Level Overhead Accumulator Level Reboiler Level All Product Tank Levels

40% 98.5% 8% 278°F 220°F 160°F 100 psig 200 gpm 130 gpm 135 gpm 12 mlb/hr 400 gpm 65 gpm 50% 50% 50% 50%

Figure 12–9 Distillation—Typical Process Variables

12.4 Safety and Quality Control Pilot plant operation includes specialized studies in all areas of safety training. This includes wearing personal protective equipment, reviewing a chemical inventory list, and discussing safe handling and transportation of products. Hazards associated with heat, temperature, and pressure are carefully reviewed with new technicians. There are a number of general safety rules for the pilot plant. Permit systems are designed to protect workers from hazardous energy, hot work, opening and blinding, confined-space entry, and cold work. A good permit system can easily be integrated into normal operations to protect employees, equipment, and the environment. The key to preventing catastrophic emergencies inside the pilot plant is adequate technician training. The employee training aspect of the program includes the following sections:

• • • • • 274

Process overview Training records Identification of chemicals used in the process Control of access to and from the process unit Training materials that reflect current work practices

12.4 Safety and Quality Control General safety rules are designed to protect human life, the environment, and physical equipment or facilities. Before entering the pilot plant, a simple overview of the general plant safety rules is conducted. These rules include: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14.

Respond to a fire, explosion, accident, or vapor release. Obey all college traffic rules. Do not park in designated fire lanes. Report injuries to the instructor immediately. Stay clear of suspended loads. Smoking and matches are not permitted in the pilot plant. Drink only from designated water fountains and potable water outlets. Use the right tool for the right job. Report to the designated equipment owner before entering an operating area. Stay in your assigned area. Illegal drugs and alcohol are not permitted in the plant. Firearms are not allowed in the plant. Take steps to remove hazardous conditions. Review and follow all safety rules and procedures, including: • personal protective equipment • hazard communication • respiratory protection • permit system • hazardous waste operations and emergency response • housekeeping • fire prevention Know and understand the alarms and rules associated with: • vapor release • fire or explosion • evacuation • all clear

Statistical process control (SPC) allows a process to operate within its own variation by making adjustments only after a number of samples have been taken (caught ). The quality system on the pilot unit is linked to the customer’s specifications on the overhead and bottom streams.

Data Collection and Data Organization A large number of operating variables are checked each shift. These variables include, at the least, pressure, temperature, level, flow, and compositional data. Each variable is checked to see if it is within operational specifications. This data is carefully organized using a variety of quality tools and techniques, including:

• • • • • •

Flowchart of start-up and operation Checksheet for variables Scatter diagram comparing overhead and bottom or feed Histogram on product data (variation) Run chart on temperature data—upper/lower Control chart for color, and X-bar and R-bar charts

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Analyzing the Data Data analysis is a continuous process that process technicians carefully monitor. The following questions should help:

• • • • • • • • •

What is the purity of the overhead stream? What is the purity of the bottom stream? What is the feed composition? What is the energy output on the reboiler? What is the energy output on the hot oil system? Do product flow rates match operational and customer expectations? Are pressure readings on pumps and equipment within guidelines? Was the quality different at start-up? If so, did it improve or worsen? Can the purity be controlled using the X-bar/R-chart system?

12.5 Bench-Top Operations The pilot plant is supported by a bench-top unit designed to simulate actual operation. The glass distillation unit includes most of the key equipment found on the unit. Figure 12–10 illustrates what a simple bench-top unit might look like. The process flow diagram (PFD) includes: operational data, such as how many milliliters (mL) the three-neck flask holds; measurements of the unit; average flow rate for the overhead line, measured in minutes; temperature scale in degrees Fahrenheit or Celsius; feedstock composition; quantity; and so on.

12.6 Operating Procedures Writing operational procedures is a process that uses the expertise of the equipment manufacturers, engineers, and operating staff. Typically, action words are used to identify each step of the procedure. A start-up and shutdown procedure for each operating system should be written. This process documentation should be in place before the equipment is started. A start-up procedure is characterized by a series of action-related items:

• • • • • • • • • • • • • • 276

Collect 1,000 mL feedstock sample. Ensure that area is clean. Review safety procedure. Check feedstock composition. Pour feedstock into flask. Take cold readings on bottom temp/top temp. Set controller on 50%. Review start-up procedure. Ensure that unit is not dead-headed. Turn on heating mantle and record time. Catch temperature readings every five minutes. Turn condenser on when upper temp reaches 150°F. Record observations from visual checks of system. Catch first overhead sample 10 minutes after upper temp reaches 210°F.

12.6 Operating Procedures

Temperature Data

TI

DISTILLATION EXPERIMENT

VAPOR

V A P O R

Collect Data

Water Out

Water In

L I Q U I D

Organize Data —Pareto —Cause and effect —Check sheets —PFD —Scatter diagram —Histogram —Run chart —Planned experimentation —TPM

CONDENSER

PACKED COLUMN

V A P O R

Analyze Data

Temperature Data

Quality Data (COLOR)

L I Q U I D

TI Red Dye HEATING MANTLE

Figure 12–10

Sample

3 NECK FLASK TC

50% Max.

Plate Distillation Column (Bench-Top Unit)

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• •

Record quantity of upper sample. Record temp delta between upper and lower and time lag between bottom and top (i.e., how much time expired between the bottom boiling and top temperature moving to match). Composite overhead sample. Catch fresh overhead sample.

• •

The objective of experimental design in bench-top operations is to determine which variables in the process or product are the critical parameters and their setpoint values. By using formal experimental techniques, the effect of many variables can be studied at one time.

12.7 Self-Directed Work Teams College operational classes have a limited amount of time to train and qualify technicians: between 12 and 16 weeks. During the fourth or fifth week, new technicians take an assessment test on all equipment and technology associated with the pilot plant. This exam is designed for operational shift placement. Before operating the unit, each technician spends hours tracing lines, identifying equipment, preparing checklists, and developing start-up and shutdown procedures. A technical notebook is used to collect and organize all this material. Immediately following the assessment exam, each operational shift is organized with a shift leader and lead operator. Each team is given specific operational assignments.The instructor initially assumes the trainer role; however, this quickly changes as the team takes on more individual responsibility. Teams are given more challenging operational assignments as they progress through the semester. The instructor makes careful observations of each team and carefully monitors individual work behaviors.

12.8 Walk-Through Qualification Near the end of the semester, each new trainee is required to complete a unit walk-through with the instructor. During this process, a standardized checklist is used to record each student’s level of competency. At the final exam, trainees are required to draw and identify each part of the pilot unit. These exams are typically extensive and require significant effort, since operational and troubleshooting data are included. The technical notebook reflects the sum of the student’s efforts during the semester and is turned in on the last day.

Summary Process technology programs include traditional coursework and hands-on training. Theory courses cover safety, quality, process equipment, physics, chemistry, and instrumentation. The hands-on component includes process systems, troubleshooting, and operations. These classes include console training, bench-top operations, and pilot plant operations. The goal of these programs is to prepare graduates to take entry-level positions in the chemical processing industry. Process Technology 3—Operations is a college-level course designed to be the capstone experience of a process technology two-year degree program.

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Summary A pilot unit includes feed section, preheat system, distillation column, overhead system, bottom system, and product storage. The feed system is composed of a variety of equipment systems, including feed tank, valves, piping, instruments, and pumps. Before feed can be sent to the distillation column, it needs to be preheated using a heat exchanger. After the feed has been blended and preheated, it is sent to the distillation column. In a plate column, the heated feed enters on the feed tray. As the heated feed enters the column, part of it vaporizes and moves up the column. The heavier part of the mixture flows down the column through devices called downcomers. The overhead system is specifically designed to condense the lighter fractions and send them to product storage and back to the top tray in the column. The cooled, condensed product that flows back to the column is called reflux. The system is specifically designed to control product purity and control temperature in the top of the column. The overhead system includes a condenser, accumulator, pump, and piping. The bottom product is sent to the tank farm for storage. The overhead stream is sent to the tank farm, tested, and shipped to the customer. A unit checklist is filled out on every shift as part of the data collection process regarding unit variables. A large number of operating variables are checked each shift to see whether they are within operational specifications. These data are carefully organized using a variety of quality tools and techniques, including flowcharts, checksheets, scatter diagrams, histograms, run charts, and control charts. New technicians take an assessment test on all equipment and technology associated with the pilot plant during the fourth or fifth week of a college operational class to determine operational shift placement. Shifts are then organized with a shift leader and lead operator. Near the end of the semester, each new trainee is required to complete a unit walk-through with the instructor. Each student keeps a technical notebook throughout the semester in which information is collected and organized; this notebook is turned in on the last day.

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Chapter 12 Review Questions 1. Describe the significance of the operations class. 2. Compare theory-related topics with the hands-on topics covered in the unit operations class. 3. Describe the feed and preheat systems. 4. Identify the major equipment found in the distillation system. 5. What is the primary difference between a trainer and a trainee? 6. Define the term bench-top operations and describe the purposes of a bench-top unit. 7. Explain the key elements covered on the assessment exam. 8. Explain the importance of operating procedures. 9. Describe the key elements of the walk-through qualification. 10. Describe the importance of control instrumentation in the pilot plant process.

280

Applied General Chemistry After studying this chapter, the student will be able to: • • • •

• • • • •

Describe the fundamental principles of chemistry. Define fundamental chemistry terms. Describe and use chemical equations and the periodic table. Describe these chemical reactions: exothermic endothermic replacement neutralization combustion heat and pressure catalytic Perform a material balance. Perform a percent-by-weight calculation. Describe pH measurements. Describe hydrocarbons. Review applied concepts of chemical processing.

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Key Terms Acid—a chemical compound that has a pH value below 7.0, changes blue litmus to red, yields hydrogen ions in water, and has a high concentration of hydrogen ions. Atom—the smallest particle of a chemical element that still retains the properties of the element. An atom is composed of protons and neutrons in a central nucleus surrounded by electrons. Nearly all of an atom’s mass is located in the nucleus. Atomic mass unit (AMU)—the sum of the masses in the nucleus of an atom. Atomic number—identifies the position of the element on the periodic table and the total number of protons in the atom. Balanced equation—axiom that the sum of the reactants (atoms) equals the sum of the products (atoms). Base—a chemical compound that has a soapy feel and a pH value above 7.0. It turns red litmus paper blue and yields hydroxyl ions. Catalyst—a chemical that can increase or decrease reaction rate without becoming part of the product. Catcracking—a process designed to increase the yield of desirable products from a barrel of crude oil; uses a catalyst to accelerate the separation process. Chemical bonding (covalent)—occurs when elements react with each other by sharing electrons. This forms an electrically neutral molecule. Chemical bonding (ionic)—occurs when positively charged elements react with negatively charged elements to form ionic bonds through the transfer of valence electrons. Ionic bonds have higher melting points and are held together by electrostatic attraction. Chemical equation—numbers and symbols that represent a description of a chemical reaction. Chemical reaction—a term used to describe the breaking, forming, or breaking and forming of chemical bonds. Types include exothermic, endothermic, replacement, and neutralization. Chemistry—the science and laws that deal with the characteristics or structure of elements and the changes that take place when elements combine to form other substances. Combustion reaction—an exothermic reaction that requires fuel, oxygen, and heat to occur. In this type of reaction, oxygen reacts with another material so rapidly that fire is created. Compound—a substance formed by the chemical combination of two or more substances in definite proportions by weight. Electron—a negatively charged particle that orbits the nucleus of an atom. Element—matter composed of identical atoms. Endothermic reaction—a reaction that requires external heat or energy to take place. Exothermic reaction—a reaction that produces heat or energy.

282

13.1 Fundamental Principles of Chemistry

Fractional distillation—a process that separates the components in a mixture by their individual boiling points. Hydrocarbons—a class of chemical compounds that contain hydrogen and carbon. Hydrogen ion—positively charged hydrogen particle. Hydroxyl ion—negatively charged OH particle. Ion—electrically charged atom. Material balancing—a method for calculating reactant amounts versus product target rates. Matter—anything that occupies space and has mass. Mixture—composed of two or more substances that are only physically combined. Mixtures can be separated through physical means such as boiling or magnetic attraction. Molecule—the smallest particle that retains the properties of the compound. Neutralization reaction—a reaction designed to remove hydrogen ions or hydroxyl ions from a liquid. Neutron—a neutral particle in the nucleus of an atom. Percent-by-weight solution—representation in which the concentration of the solute is expressed as a percentage of the total weight of the solution. Periodic table—chart arranged by atomic number that provides information about all known elements (e.g., atomic mass, symbol, atomic number, boiling point). pH—a measurement system/scale used to determine the acidity or alkalinity of a solution. Products—manufactured materials made from reactants combined in specific proportions. Proton—a positively charged particle in the nucleus of an atom. Reactants—raw materials that are combined in specific proportions to form finished products. Reaction rate—the amount of time it takes a given amount of reactants to form a product. Replacement reaction—a reaction designed to break a bond and form a new bond by replacing one or more of the components of the original compound. Solute—the material dissolved in a solution. Solution—a homogenous mixture.

13.1 Fundamental Principles of Chemistry Chemistry is the study of the characteristics or structure of elements and the changes that take place when elements combine to form other substances. Process operators play a major role in the production and manufacturing of finished products from raw materials. Modern chemistry is an essential part of the process environment and for this reason is a vital part in the initial training of most technicians.

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Matter is anything that occupies space and has mass. The four physical states of matter are solid, liquid, gas, and plasma (the latter can be found in powerful magnetic fields).

Elements The purest form of matter is called an element. Elements cannot be broken down or changed by chemical or physical means. An element is composed of identical components called atoms. A list of all of the known elements, both natural and synthetic, can be found on the chemical element chart (periodic table). The periodic table provides information about all known elements, such as atomic mass, symbol, atomic number, and boiling point.

Atoms An atom is the smallest particle of an element that still retains the characteristics of that element. Atoms are composed of positively charged particles called protons, an equal number of neutral particles called neutrons, and negatively charged particles called electrons (Figure 13–1). Protons and neutrons make up the majority of the mass of an atom and reside in a central area referred to as the nucleus. The sum of the masses in the nucleus (protons and neutrons) is called the atomic mass unit (AMU).

Atomic Number The atomic number of an element is determined by the number of protons in its nucleus. The atomic number is used to locate the element in its proper place on the periodic table.

Electrons Orbiting the nucleus are negatively charged particles known as electrons. Electrons and protons are equally balanced in an atom. This is important because it ensures that each atom is electrically neutral.

Valence Electrons The electrons that reside in the outermost shell of an atom are referred to as valence electrons. Valence electrons are important to chemistry because they provide the links by which PROTON

+ Nucleus NEUTRON

N

-

Valence Shell

N + +N+ N N + N+ + N

ELECTRON

-

-

Shell

Valence Electrons CARBON ATOM 4E 2E 6 P, 6 N

Figure 13–1 Carbon Atom

284

13.1 Fundamental Principles of Chemistry virtually every chemical reaction occurs. Atoms share their valence electrons to form chemical bonds.

Chemical Bonding—Covalent and Ionic The two most common models for chemical bonding are covalent and ionic. Covalent bonds occur when elements react with each other by sharing electrons. This forms an electrically neutral molecule because the protons and electrons electrically balance each other. If an atom has unequal numbers of protons or electrons, it is called an ion. Ions are electrically charged atoms (positive or negative). Ionic chemical bonding occurs when positively charged elements react with negatively charged elements to form ionic bonds through the sharing or lending of electrons. Substances with ionic bonds have higher melting points and are held together by electrostatic attraction.

Molecules and Compounds Compounds are the products of chemical reactions (Figure 13–2). A compound is a substance formed by the chemical combination of two or more substances in definite proportions by weight. A molecule is the smallest particle that retains the properties of the compound.

Solutions Solutions are a type of homogenous mixture. The term homogenous signifies that the components of the solution are evenly mixed or distributed. A common example of a homogenous solution is a drink mix. As the powdered drink substance is mixed with water, it becomes evenly dispersed throughout the water, creating a solution.

Mixtures Mixtures do not have a definite composition. A mixture is composed of two or more substances that are only mixed physically. Because a mixture is not chemically combined, it can be separated through physical means, such as boiling or magnetic attraction.

OXYGEN ATOM 6E 2E 8 P, 8 N - -

N + N +N+ N + + N +N+N + N

H

-

H

- -

WATER a covalent compound

Figure 13–2

Compound

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Vapor Recovery

Alkylation Petrochemicals

Reforming

Aromatic Recovery

Treating Blending

High Octane Gas

Treating Blending

Jet Fuel & Gasoline

Treating Blending Treating Blending

Catalytic Cracking

Kerosene Diesel Oil Heating Oil Industrial Fuels

Feed Solvent Extraction

Waxes

Crystallization

Treating Blending

Lubricating Oils

Treating Blending

Greases

Asphalt

Figure 13–3 Crude Oil Distillation

Crude oil is a simple example of a mixture (Figure 13–3). It is composed of hundreds of different hydrocarbons. Process operators separate the different components in the crude oil by heating it to the boiling point in a distillation column.

13.2 Chemical Equations and the Periodic Table The most common chemical substances are elements. Chemical elements are the building blocks of all substances. Each element is composed of atoms of only one kind. Chemists describe elements with letters from the alphabet. The letter symbol for hydrogen is H. The letter symbol for carbon is C (Figure 13–4). A periodic table or chemical element chart (Figure 13–5) lists all known chemical elements, with their symbols and other information. A good understanding of the chemical element chart helps a technician better understand chemical equations. A chemical reaction can be described by associated numbers and symbols. The chemical number identifies how many protons are in an atom, and the atomic mass unit identifies how many units of an element are present. 286

13.2 Chemical Equations and the Periodic Table

Atomic Number

6

Atomic Weight

12.011

C CARBON

Symbol

Element

Figure 13–4 Periodic Table Information Box

GROUP 1A 1 1.0079

V111 2 4.002

H

He 11A

HYDROGEN

6.941

3

Li LITHIUM

4

V11B HELIUM VB V1B 111B 1VB 5 10.81 6 12.01 7 14.006 8 15.99 9 18.99 10 20.18

9.0126

Be

B

BERYLLIUM

BORON

22.9912 24.30

11

Na

13 26.98 14

Mg

Al

111A 1VA VA V1A V11A V111A 19 39.09 20 40.08 21 44.95 22 47.9 23 50.94 24 51.99 25 54.93 26 55.84 27 58.93 28 SODIUM

K POTASSIUM

37

85.46

Rb RUBIDIUM

MAGNESIUM

Ca CALCIUM

Sc SCANDIUM

38 87.62 39

Sr

88.9

Y VITRIUM

STRONTIUM

Ti TITANIUM

40

Ba

CESIUM

BARLUM

87

223

88

226

Fr

Ra

FRANCIUM

RADIUM

La LANTHANUM

89

227

V

Cr Mn

VANADIUM

CHROMIUM MANGANESE

91.22 41 92.9

Zr ZIRCONIUM

55 132.90 56 137.3357 138.9 72

Cs

C CARBON

42

Nb NIOBIUM

Ta

HAFNIUM

TANTALUM

104

105

43

Mo

98

Tc

IRON

44

101

74

183

75

106

Ni

Cu

NICKEL

COPPER

102.9 46 106.4

76

190

RHODIUM

77

192

47

PALLADIUM

78

195

Os

Ir

Pt

RHENIUM

OSMIUM

IRIDIUM

PLATINUM

Zn Ga ZINC

GALLIUM

107.8 48 112.4 49 114.8

Pd Ag

Re

W TUNGSTEN

186

Co 45

Si

15

O

F

OXYGEN

FLUORINE

30.97 16 32.0617 35.45

P

S

Cl

Ne NEON

18

39.94

Ar

1B 11B ALUMINUM SILICON PHOSPHORUS SULFUR CHLORINE ARGON 29 63.54 30 65.38 31 69.72 32 72.59 33 74.92 34 78.96 35 79.90 36 83.8

COBALT

Ru Rh

MOLYBDENUM TECHNETIUM RUTHENIUM

178.4 73 180.9

Hf

95.9

Fe

58.7

28.08

N NITROGEN

SILVER

Cd CADIUM

79 196.9 80

200.6

Au Hg GOLD

MERCURY

In INDIUM

Ge

TI

Se SELENIUM

Br BROMINE

Kr KRYPTON

50 118.6 51 121.7 52 127.6 53 126.9 54 131.3

Sn TIN

81 204.3 82

THALLIUM

As

GERMANIUM ARSENIC

Sb ANTIMONY

207

Pb LEAD

Te

I

TELLURIUM

IODINE

83 208.9 84

Bi BISMUTH

209

85

210

Po

At

POLONIUM

ASTATINE

Xe XENON

86

222

Rn RADON

Ac Unq Unp Unh ACTINIUM

Figure 13–5 Periodic Table

In a chemical equation, the raw materials or reactants are placed on the left side. As the reactants are mixed together, they yield predictable products. A yield sign or arrow immediately follows the reactants. The products are placed on the right side of the equation. Because atoms cannot be created or destroyed, a common rule of thumb is “what goes into a chemical equation must come out.” The sum of the reactants must equal the sum of the products. EXAMPLE: C ⫹ O2 1 carbon 2 oxygen (reactants)

(yields) ⫽ ⫽

CO2 1 carbon 2 oxygen (products) 287

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Remember, what goes in must come out! CuSO4 ⫹ H2

Cu ⫹ H2SO4 1 copper 2 hydrogen 1 sulfur 4 oxygen

1 copper 2 hydrogen 1 sulfur 4 oxygen

4NH3 ⫹ 3O2

2N2 ⫹ 6H2O

4 nitrogen 12 hydrogen 6 oxygen

4 nitrogen 12 hydrogen 6 oxygen

Mass Relationships—Chemical Equations To work out mass relationships, you need to have a good understanding of the chemical element chart. Certain elements combine to form chemicals that you will recognize easily; for example, water (H2O) or carbon dioxide (CO2). The elements and atomic mass units are listed on the periodic table. EXAMPLE: H3PO4 ⫹ 3NaOH

Na3PO4 ⫹ 3H2O

Phosphoric acid and sodium hydroxide react to form sodium phosphate and water. What is the product’s total molecular weight? Phosphoric acid (H3PO4) Sodium hydroxide (NaOH) Sodium phosphate (Na3PO4) Water (H2O)

⫽ ⫽ ⫽ ⫽

1 molecule 1 molecule 1 molecule 1 molecule

(molecular weight?) (molecular weight?) (molecular weight?) (molecular weight?)

H3PO4—Reactant 3 hydrogen ⫽ 3 ⫻ 1.008 AMU ⫽ 3.024 1 phosphorus ⫽ 1 ⫻ 30.98 AMU ⫽ 30.98 4 oxygen ⫽ 4 ⫻ 16.00 AMU ⫽ 64.00 98.00 grams, pounds, or tons 3NaOH—Reactant 3 sodium ⫽ 3 ⫻ 23.00 AMU ⫽ 69.00 3 oxygen ⫽ 3 ⫻ 16.00 AMU ⫽ 48.00 3 hydrogen ⫽ 3 ⫻ 1.008 AMU ⫽ 3.024 120.02 grams, pounds, or tons 98.00 ⫹ 120.02 ⫽ 218.02 Reactant’s total molecular weight ⫽ 218 grams, pound, or tons

288

13.2 Chemical Equations and the Periodic Table Na3PO4—Product 3 sodium ⫽ 3 ⫻ 23.00 AMU ⫽ 69.00 1 phosphorus ⫽ 1 ⫻ 30.98 AMU ⫽ 30.98 4 oxygen ⫽ 4 ⫻ 16.00 AMU ⫽ 64.00 163.98 grams, pounds, or tons 3H2O—Product 6 hydrogen 3 oxygen

⫽ 6 ⫻ 1.008 AMU ⫽ 6.048 ⫽ 3 ⫻ 16.00 AMU ⫽ 48.000 54.050 grams, pounds, or tons

163.98 ⫹ 54.05 ⫽ 218.03 Product’s total molecular weight ⫽ 218 grams, pounds, or tons EXAMPLE: 4H2O 4H2 ⫹ 2O2 Four volumes of hydrogen react with two volumes of oxygen to produce four volumes of water vapor. What is the product’s total molecular weight? Hydrogen (2H2) ⫽ 1 molecule (molecular weight?) Oxygen (O2) ⫽ 1 molecule (molecular weight?) 2H2—Reactant 8 hydrogen

⫽ 8 ⫻ 1.008 AMU ⫽

O2—Reactant 4 oxygen

⫽ 4 ⫻ 16 AMU

8.064 grams, pounds, or tons

⫽ 64.00 grams, pounds, or tons

8.064 ⫹ 64.00 ⫽ 72.064 Reactant’s total molecular weight ⫽ 72.06 grams, pounds, or tons 4H2O—Product 8 hydrogen 4 oxygen

⫽ 8 ⫻ 1.008 AMU ⫽ 8.064 ⫽ 4 ⫻ 16.00 AMU ⫽ 64.00 72.06 grams, pounds, or tons

Product’s total molecular weight

⫽ 72.06 grams, pounds, or tons

Solve: Given the chemical equation: H3PO4 ⫹ 3NaOH 18 tons 10 tons

Na3PO4 ⫹ 3H2O (28 total tons)

a. Change H3PO4 (18 tons) to 1,800 tons. b. What must the (3NaOH) weight be to balance the equation?

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Solution: The first thing to remember in this type of problem is to identify the relative weight and the actual weight. The relative weight in this problem is 1,800 tons. The actual weight is 18 tons. Now, divide the relative weight by the actual weight. 1,800 ⫼ 18 ⫽ 100 Use this new factor to adjust the 10 tons of 3NaOH. 10 tons ⫻ 100 ⫽ 1,000 tons 1,000 tons balances the 3NaOH equation. Solve: Given the chemical equation: H3PO4 ⫹ 3NaOH

Na3PO4 ⫹ 3H2O

If you are told to add 25 lb of phosphoric acid (H3PO4) to the previous equation, how many pounds do you need to add to the sodium hydroxide (NaOH) to keep the equation balanced? Solution: The first thing to remember in this type of problem is to identify the relative weight and the actual weight. The relative weight in this problem is 25 lb. The actual weight is the total AMU of H3PO4, which is 98 AMUs. (This can be in pounds or tons.) Now, divide the relative weight by the actual weight. 25 ⫼ 98 ⫽ 0.255 H3PO4 (phosphoric acid) H3 P O4

⫽ ⫽ ⫽

3 ⫻ 1.0079 1 ⫻ 31 4 ⫻ 16

TOTAL

3NaOH (sodium hydroxide) ⫽ 3.0237 ⫽ 31 ⫽ 64 98

3Na 3O 3H TOTAL

Use this new factor to adjust the 120 AMUs of 3NaOH. 0.255 ⫻ 120 ⫽ 30.6 lb 30.6 lb balances the 3NaOH equation. Solve: ⫹

N2 120 lb ? lb 420 lb

3H2 39 lb ? lb 136.5 lb

2NH3 159 lb 556 lb

Solution: The relative weight is 556 lb. The actual is 159 lb. 556 ⫼ 159 ⫽ 3.5 3.5 3.5 290

⫻ ⫻

120 39

⫽ 420 ⫽ 136.5

⫽ ⫽ ⫽

3 ⫻ 23 3 ⫻ 16 3⫻1

⫽ ⫽ ⫽

69 48 3 120

13.3 Chemical Reactions Solve: + CH4 1,600 lb

2O2 ?

CO2 ?

+

2H2O ?

Solution: The relative weight is 1,600 lb. The actual weight is CH4 (16 AMUs). 1C 1 ⫻ 12 ⫽ 12 4H 4 ⫻ 1 ⫽ 4 16

4O2

4 ⫻ 16 ⫽ 64

1C 1 ⫻ 12 ⫽ 12 2O2 2 ⫻ 16 ⫽ 32 44

4H 4 ⫻ 1 ⫽ 4 2O2 2 ⫻ 16 ⫽ 32 36

1,600 ⫼ 16 = 100 CH4 2O2 CO2 2H2O

100 ⫻ 16 100 ⫻ 64 100 ⫻ 44 100 ⫻ 36

⫽ ⫽ ⫽ ⫽

1,600 lb 6,400 lb 4,400 lb 3,600 lb

13.3 Chemical Reactions Exothermic Exothermic reactions are chemical reactions characterized by the liberation of heat. As the reaction rate increases, the evolution of heat energy increases. Exothermic reactions can be moderated by controlling reactant flow rates, removing heat, or providing cooling.

Endothermic Endothermic reactions must absorb energy in order to proceed.

Replacement Industrial manufacturers use replacement reactions to remove dissolved mineral ions from process water. A number of dissolved minerals can be found in process fluids; for example, a compound commonly found in process water is calcium chloride. Calcium chloride (CaCl2) forms positive calcium (Ca⫹) ions and negative chloride (Cl2⫺) ions when it is dissolved in water. A replacement reaction can remove the Ca⫹ ions and the Cl2⫺ ions using synthetic resins. Resins are plastic strands rolled into balls and charged with ions. An H⫹ ion on a resin ball is replaced by the Ca⫹ ion as the process fluid moves through the resin bed. The replacement reaction will take place until all of the Ca⫹ ions are removed from the fluid or the H⫹ ions from the resin balls are used up. Resin balls used for replacement reactions can be treated with either positively or negatively charged ions. For example, resin balls charged with hydroxyl ions (OH⫺) can be used to replace the chloride ion (Cl⫺).

Neutralization Neutralization reactions remove hydrogen ions (acid) or hydroxyl ions (base) from a liquid. Neutralization reactions are designed to reduce or eliminate the acidity or alkalinity of a solution. Hydrogen ions (acid) and hydroxyl ions (base) neutralize each other. 291

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Combustion Combustion reactions are exothermic reactions that require fuel, oxygen, and heat to occur. In this type of reaction, oxygen reacts with another material so rapidly that fire is created. A fired furnace or a boiler is an example of a device that uses combustion reaction. Natural methane gas is pumped to the burner, mixed with oxygen, and ignited. This type of reaction can be represented by the following chemical equation: CH4 ⫹ 2O2

CO2 ⫹ 2H2O

In this equation, one molecule of methane (CH4) chemically reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.

Heat and Pressure For a chemical reaction to occur, the atoms of the reactants must collide with each other. The addition of heat to a process increases reactant molecular activity.The addition of heat energy thus affects a process by increasing molecular activity, increasing the number of atomic collisions, and enhancing the formation of chemical bonds. This increased activity ensures a much higher rate of energy transfer between molecules as they collide with each other. Reaction rates double with every 10 degrees of heat added. Note: High temperatures can cause undesirable products to form. Process temperatures are closely monitored during operation to ensure smooth and efficient reaction rates. Another important factor in a chemical reaction is pressure. Pressure has its greatest impact on gases, which are much easier to compress than liquids. Pressure can change the boiling point of a liquid and slow down molecular activity. As pressure builds, it pushes the gas molecules closer together and back into the liquid. More heat is required to boil the liquid, which wastes time and money. (See Figure 13–6.) Reaction rates are affected by:

• • • • • •

Heat—molecular activity increases, atomic collisions increase, and the formation of chemical bonds is enhanced Surface area—solids Concentration—liquid and gas reactants Pressure Flow rates—reactants and products Catalyst presence

Catalyst A catalyst is a chemical that increases or decreases the reaction rate without becoming part of the product. Types of catalysts include:

•

292

Adsorption-type catalyst—a solid that attracts and holds reactant molecules so that a higher number of collisions can occur. It also stretches the bonds of the reactants it is holding, weakening the bonds so that less energy is required to break them and rebond.

13.4 Material Balance 150 psig

150 psig

400°F 400°F

Heat Exchanger HOT Steam In Feed

150 psig

Steam LT

Heat speeds up molecular activity. Pressure pushes molecules closer together.

Figure 13–6 Heat and Pressure

• • •

Intermediate-type catalyst—forms an intermediate product by attaching to the reactant and slowing it down so collisions can occur. This type of catalyst does not become part of the final product. Inhibitor-type catalyst—decreases reaction rate. Poisoned catalyst—no longer functions; used up.

13.4 Material Balance Material balancing is a method technicians use to determine the exact amount of reactants needed to produce the specified products. This method is used when two or more substances are combined in a chemical process. Reactants must be mixed in the proper proportions to avoid waste. Material balancing provides an operator with the correct reactant ratio. The steps in checking a material balance are: 1. determine the weight of each molecule, 2. ensure that reactant total weight is equal to product total weight, and 3. determine relative numbers of reactant atoms or ions. 293

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Relative and Actual Weights H⫹ ⫹ OH⫺ H2O ⫹ ⫺ H (1 AMU) ⫹ OH (17 AMU)

Step 1 Step 2

H2O (18 AMU)

Note: The relationship between AMUs and other units is 1 AMU ⫽ 1 gram, pound, or ton. Step 3

H2O (18 g) H⫹ (1 g) ⫹ OH⫺ (17 g) Add 10 grams of hydrogen ions and balance the equation.

Step 4

H⫹ (10 ⫻ 1 g) ⫹ OH⫺ (10 ⫻ 17 g)

Step 5

H⫹ (10 g) ⫹ OH⫺ (170 g)

H2O (? g) H2O (180 g)

EXAMPLE 1 Solve: Na2O ⫹ 2HOCl

2NaOCl ⫹ H2O

List the reactant elements. List the product elements. Is this chemical equation balanced? Na2O ⫹ 2HOCl 2Na 3O 2Cl 2H

2NaOCl ⫹ H2O 2Na 3O 2Cl 2H

Yes, this chemical equation is a balanced equation.

EXAMPLE 2 Solve: 2H3PO4

H2O ⫹ H4P2O8

List the reactant elements. Is this chemical equation balanced? 2H3PO4 6H 2P 8O

H2O ⫹ H4P2O8 6H 2P 9O

No, this chemical equation is not balanced.

294

13.6 Measurement of pH

13.5 Percent-by-Weight Solutions Percent-by-weight solutions are expressed as a percentage of the weight of the total solution. In other words, the weight of the solute (material being dissolved) is taken in relationship to the weight of the entire solution. In a weight-percent problem, the amount of the solute and solvent can be calculated. For example, a 400-lb barrel has a 6% catalyst solution. The weight of the catalyst can be determined by multiplying the weight of the solution by the percent of the solute. Weight of Solution 400 pounds

⫻ ⫻

Percent of Solute 6% or 0.06

⫽ ⫽

Weight of Solute 24 lb

Figure 13–7 is an example of a solution.

13.6 Measurement of pH The term pH refers to a measurement system used to determine the acidity or alkalinity of a solution. An acid is a chemical compound that has a pH value below 7.0. It changes blue litmus to red and yields hydrogen ions in water. An acid has a high concentration of hydrogen ions.

FEED STOCK SOLUTION A HOMOGENOUS MIXTURE

Condenser 2 R E C T I F Y I N G

1. Methane 2. Ethane 3. Propane 4. Butane 5. Pentane 6. Hexane 7. Octane 8. Nonane 9. Decane 10. Residue

3 4

Vacuum Pump Pump 1

5 6 7 8 9

Heat Exchanger

LT

S T R I P P Bottom I Residual N G

Hot Vapor Line Steam Reboiler

10 Bottom

Figure 13–7 Solution

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A base is a chemical compound that has a soapy feel and a pH value above 7.0. It turns red litmus paper blue and yields hydroxyl ions. The methods for determining pH include:

• • •

pH comparator—an indicator solution is added to the fluid to be checked. The color of the resulting solution is compared to the pH comparator standards. pH paper—red or blue litmus is impregnated with an indicator that causes a color change to occur in the presence of an acid or base. pH meter—directly measures the concentration of hydrogen ions in a solution.

13.7 Hydrocarbons A hydrocarbon is a chemical compound that contains hydrogen and carbon. One of the bestknown hydrocarbons is crude oil. Crude oil is a mixture of hydrocarbons that vary from simple to complex. Industrial manufacturers separate the various components of crude oil by boiling or distilling it. The lighter carbon molecules have different boiling points than the heavier molecules. The simplest hydrocarbon is methane or natural gas. Methane has one carbon atom and four hydrogen atoms. Close examination of the atomic structure of methane indicates that the outer valence electrons tend to couple in pairs. Compounds made up of carbon atoms have four possible bonds on each atom. The four arms (valence electrons) on each carbon atom bond with a hydrogen or another carbon atom. Each slot on the carbon atom must be filled. There are millions of possible combinations for these carbon atoms. Chemists have divided these hydrocarbons into two very large families: alkanes and olefins.

Alkanes Figure 13–8 shows the composition of some alkanes. The First 10 Alkanes Name Molecular Formula 1. Methane

CH4

2. Ethane

C2H6

3. Propane

C3H8

4. Butane

C4H10

5. Pentane

C5H12

6. Hexane

C6H14

7. Heptane

C7H16

8. Octane

C8H18

9. Nonane

C9H20

10. Decane

296

C10H22

13.7 Hydrocarbons Methane H H

C

H

H

H

H

H

Propane

Ethane H H C

C

H

H

H

H

H

Pentane H H H

H

C

C

C

C

C

H

H

H

H

H

H

H

Heptane H H H

H

H

C

C

C

C

C

C

C

H

H

H

H

H

H

H

H

H

H

C

C

C

H

H

H

H

H

H

n-Butane

H

H

H

H

H

H

C

C

C

C

H

H

H

H

H

H

Hexane H H H

C

C

C

C

C

C

H

H

H

H

H

H

H

H

Octane H H H

H

H

H

C

C

C

C

C

H

H

H

H

H

H

H

H

H

C

C

C

H

H

H

H

Figure 13–8 Alkanes

Chain Length Effects on Boiling Point Molecular Boiling Weight Point

Alkane

Structure

Methane

CH4

16

–164°C

Ethane

CH3—CH3

30

–89°C

Propane

CH3—CH2—CH3

44

–42°C

Butane

CH3—CH2—CH2—CH3

58

–0.5°C

Pentane

CH3—CH2—CH2—CH2—CH3

72

36°C

Hexane

CH3—CH2—CH2—CH2—CH2—CH3

86

69°C

Heptane

CH3—CH2—CH2—CH2—CH2—CH2—CH3

100

98°C

Octane

CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH3

114

126°C

Nonane

CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH3

128

151°C

Decane

CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH3

142

174°C

Olefins Olefins (Figure 13–9) do not occur naturally in crude oil. Olefins are created by a manmade process called cracking. Each molecule of an olefin has at least one double bond.

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Applied General Chemistry Ethylene C 2 H4 H

H

Propylene C H 3 6 H H H

C

C

H

H

H

C

C

H

BP = –155°F

Butylene C4 H 8 H H H H

C

C

H

H

BP = –54°F

C

C

C

H

H

H

BP = 21°F

Butadiene C4 H6 H H H H C H

C

C

C H

Figure 13–9 Olefins

13.8 Applied Concepts in Chemical Processing Distillation A number of fractions (components) are obtained from the distillation of petroleum. Distillation is defined as the separation of the various fractions in a mixture by individual boiling points. Hydrocarbon fractions obtained from petroleum include straight-run gasoline, kerosene, heating oil, diesel, jet fuel, lubricating oil, paraffin wax, asphalt, and tar (Figure 13–10). Additional processes can be applied to these different fractions to create other products. Boiling Range Below 200°C 150–275°C 175–350°C 350–550°C Residue

Carbons 4–12 10–14 12–20 20–36 36+ C1

Fraction straight-run gasoline kerosene heating oil, diesel, jet fuel lubricating oil, paraffin wax asphalt, tar

C4 Gases

CRUDE OIL

Feed

C 4

C 12

Gasoline

C 10

C 14

Kerosene

C12

C20 Heating Oil

C20

C36

C 36 +

Figure 13–10 298

Lube Oil

Asphalt–Tar

Hydrocarbon Fractions

13.8 Applied Concepts in Chemical Processing A distillation tower is a series of stills placed one on top of the other. As vaporization occurs, the lighter components of the mixture move up the tower and are distributed on the various trays. The lightest component goes out the top of the tower in a vapor state and is passed over the cooling coils of a shell-and-tube condenser. As the hot vapor comes into contact with the coils, it condenses and is collected in the overhead accumulator. Part of this product is sent to storage, while the rest is returned to the tower as reflux. Heat balance on the tower is maintained by a device known as a reboiler. Reboilers take suction off the bottom of the tower. The heaviest components of the tower are pulled into the reboiler and stripped of smaller molecules. The stripped vapors are returned to the column and allowed to separate in the tower.

Reactors Process technicians play a major role in the production and manufacturing of chemicals: They operate and maintain the systems that combine raw materials and modern reaction technology to form new products. The foundation upon which this industry rests is modern chemistry. As noted earlier in this chapter, chemistry is the study of the characteristics or structure of elements and the changes that take place when they combine to form other substances. A reactor is designed to make or break chemical bonds, thereby changing the molecular structure of raw materials. In short, a reactor is a device used to convert raw materials into useful products through chemical reactions. Process operators are responsible for the safe and efficient operation of the reactor and its associated equipment.

Catalytic Cracking Crude oil comes into a refinery and is processed in a fractionating tower. The side stream of the column is rich with light gas oil. Fluid catalytic cracking units split this gas oil into smaller, more useful molecules. Generally, only 20% of a barrel of crude oil can be used to produce gasoline. Fluid catalytic cracking is a process that uses a reactor to split large, covalent gas oil molecules into smaller, more useful ones. For instance, cracking a C12 kerosene molecule yields two C6 molecules (hexane and hexene). Figure 13–11 illustrates this process.The catalytic process increases yields from 20% to 50% by splitting the kerosene and heating oil fractions of the crude. H

H

H

H

H

H

H

H

H

H

H

H

H - C - C - C - C - C - C - C - C - C - C - C - C - H H

H

H

H

H

H

H

H

H

H

H

H

C 12 H 26 H

H

H

H

H

H - C - C - C - C - C - C -- H H

H

H H C H 6 14

H

H

H

+

H

H

H

H

H

H

C - C - C - C - C - C -- H H

H H C 6 H 12

H

H

1-Hexene

Hexane

Figure 13–11

Cracking 299

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A typical fluid catalytic cracking unit includes a catalyst regenerator, reactor, and fractionating tower. During operation, gas oil enters the reactor and is mixed with a superheated powdered catalyst. The term cracking or catcracking is applied to the process because during vaporization the molecules literally split; they are then sent to a fractionation tower for further processing. The chemical reaction between the catalyst and light gas oil produces a solid carbon deposit (coke) that collects on the powdered catalyst and eventually deactivates it. The spent catalyst is drawn off and sent to the regenerator where the coke is burned off. Catalyst regeneration is a continuous process during operation. In the fractional distillation tower, the light gas oil is separated into five different “cuts”: catcracked gas, catcracked naphtha, catcracked heating oil, light gas oil, and residue.

Hydrocracking Hydrocracking is a process that industrial manufacturers use to boost gasoline yields. During this process, heavy gas oil molecules are split into smaller, lighter molecules called hydrocrackate. Heavy gas oil feed is mixed with hydrogen before being sent to a first-stage reactor, which is filled with a fixed bed of catalyst. As process flow moves from the top of the reactor to the bottom, the cracking reaction takes place. First-stage hydrocrackate is sent to a separator drum where the hydrogen is reclaimed; the hydrocrackate is then moved on to a fractionating tower. In the fractionation tower, the hydrocrackate is separated into five different cuts: butane, light hydrocrackate, heavy hydrocrackate, heating oil, and heavy bottom. The heavy bottom is mixed with hydrogen and sent to a second-stage reactor for further processing. The second-stage reactor reclaims as much of the hydrocrackate as possible before sending it to the separator and tower.

Alkylation Alkylation uses a reactor to make one large molecule out of two small molecules. Alkylation units take two small molecules of isobutane and olefin (propylene, butylenes, or pentylenes) and combine them into one large molecule of high-octane liquid called alkylate. (Alkylate is a superior antiknock product that is used in blending unleaded gasoline.) This combining process takes place inside a reactor filled with an acid catalyst. After the reaction, a number of products are formed that require further processing to separate and clean the desired chemical streams. A separator and an alkaline substance are used to remove (strip) the acid.The stripped acid is sent back to the reactor while the remaining reactor products are sent to a distillation tower. Alkylate, isobutane, and propane gas are fractionally separated in the tower. Isobutane is returned to the alkylation reactor for further processing. Alkylate is sent on to the gasoline blending unit.

Summary Chemistry is the study of the characteristics or structure of elements and the changes that take place when they combine to form other substances. Process operators play a major role in converting raw materials into finished products. Modern chemistry is an essential part of the process environment and thus is a vital part of technician training. 300

Summary The four physical states of matter are solid, liquid, gas, and plasma. The purest form of matter is an element, which is composed of identical components called atoms. Elements cannot be broken down or changed by chemical or physical means. The periodic table (chemical element chart) lists information about all known elements, including atomic mass, symbol, atomic number, and boiling point. An atom is the smallest particle of an element that still retains the characteristics of that element. Atoms are composed of positively charged particles called protons, an equal number of neutral particles called neutrons, and negatively charged particles called electrons. Protons and neutrons make up the majority of the mass in an atom and reside in an area referred to as the nucleus. The sum of the masses in the nucleus (protons and neutrons) is called the atomic mass unit (AMU). The atomic number of an element is determined by the number of protons in its nucleus. Orbiting the nucleus are negatively charged electrons. Electrons and protons are equally balanced in an atom, so each atom is electrically neutral. The electrons that reside in the outermost shell of an atom are called valence electrons; they act as the links in virtually every chemical reaction. Atoms share their valence electrons to form chemical bonds. The two most common chemical bonds are covalent and ionic. Covalent bonds occur when elements react with each other by sharing electrons, and ionic bonds occur when positively charged elements react with negatively charged elements to form ionic bonds through the sharing or lending of electrons. Compounds are the products of chemical reactions. A compound is a substance formed by the chemical combination of two or more substances in definite proportions by weight. A molecule is the smallest particle that retains the properties of the compound. Solutions are a type of homogenous mixture. The term homogenous indicates that the solution components are evenly distributed throughout the mixture. Mixtures do not have a definite composition. A mixture is composed of two or more substances that are only physically mixed, not chemically combined. Thus, the components of a mixture can be separated through physical means, such as boiling or magnetic processes. Elements are identified by letters of the alphabet. A periodic table lists the symbols for all known elements. A chemical reaction can be described by using associated numbers and symbols. In a chemical equation, the raw materials or reactants are placed on the left side, a yield sign or arrow immediately follows the reactants, and the products are placed on the right side. Because atoms cannot be created or destroyed, a common rule of thumb is that the sum of the reactants must equal the sum of the products. Exothermic reactions are accompanied by the liberation of heat. Endothermic reactions must absorb energy to proceed. Replacement reactions can be used to remove undesired products and replace them with desired ones. Neutralization reactions remove hydrogen ions (acid) or hydroxyl ions (base) from a liquid to reduce or eliminate the acidity or alkalinity of a solution. Hydrogen ions (acid) and hydroxyl ions (base) neutralize each other. 301

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Combustion reactions are exothermic reactions that require fuel, oxygen, and heat to occur. A fired furnace or a boiler uses a combustion reaction. For a chemical reaction to occur, the atoms of the reactants must collide with each other. The addition of heat to a process will increase reactant molecular activity, which ensures a much higher rate of energy transfer between molecules as they collide with each other. Reaction rates double with every 10 degrees of heat and are affected by heat, surface area, concentration, pressure, flow rates, and the presence of catalysts. Material balancing is a method technicians use to determine the exact amount of reactants needed to produce the specified products. Percent-by-weight solutions are expressed as a percentage of the weight of the solute in relationship to the weight of the entire solution. The term pH refers to the acidity or alkalinity of a solution. A hydrocarbon is a chemical compound that contains hydrocarbon and carbon. Crude oil is a mixture of hydrocarbons that vary in size and structure from simple to complex. Much modern manufacturing is based on separating the various components in crude oil by their individual boiling points. Important applied concepts of chemical processing include distillation, catalytic cracking, hydrocracking, and alkylation.

302

Chapter 13 Review Questions

Chapter 13 Review Questions 1. What is chemistry? Why is it important to a process technician? 2. What is matter? List the four states of matter. 3. Describe an atom. What is a proton, electron, valence electron, neutron, AMU, and atomic number? 4. What is an element? 5. What is the function of the periodic table? Describe element symbols. 6. Define the terms ion and atom. 7. Define the terms covalent bond and ionic bond. 8. Describe the differences between mixtures and compounds. 9. What is a chemical equation? Describe reactants and products in an equation. What does the yield sign mean? 10. H2 ⫹ O H2O. Is this chemical equation balanced? List the reactant elements and the product elements. 11. 8NH3 ⫹ 6O2 4N2 ⫹ 12H2O. Is this chemical equation balanced? List the reactant elements and the product elements. 12. Determine whether this chemical equation is balanced: H3PO4 ⫹ 3NaOH Na3PO4 ⫹ 3H2O. List the reactant elements and AMUs. List the product elements and AMUs. 13. You are given the chemical equation H3PO4 ⫹ 3NaOH Na3PO4 ⫹ 3H2O. If you are told to add 15 lb of phosphoric acid (H3PO4) to this equation, how many pounds will you need to add to the sodium hydroxide (NaOH) to keep the equation balanced? 14. What is an exothermic reaction? How do you control it? 15. List and describe the different types of chemical reactions. 16. How do heat and pressure affect a chemical reaction? 17. What affects reaction rates? 18. List the different types of catalysts. 19. A 500-lb barrel contains a 10% catalyst solution. What is the weight of the catalyst? 20. Contrast an acid and a base. 21. Describe crude oil distillation.

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Applied Physics Two After studying this chapter, the student will be able to: • • • • • • • • • • •

Describe the fundamental concepts of physics. Define key terms used in process physics. Contrast and compare density and specific gravity. Describe the principle of pressure in fluids. Convert inches of water to pounds per square inch gauge. Convert inches of mercury (Hg) to inches of water. Describe the relationship between temperature and pressure. Describe the scientific principles underlying simple and complex machines. Describe the basic principles of electricity. Use gas-law formulas to solve simple problems. Solve simple fluid flow problems.

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Key Terms API gravity—standard by which to measure the heaviness or density of a hydrocarbon; a specially designed hydrometer marked in units API is used. Atmospheric pressure—the combined weight of all the gases exerted on the surface of the earth. At sea level, the total mass is estimated at 5.5  1015 tons, or 760 mmHg, or 14.7 psi, or one atmosphere. Barometer—an instrument to measure atmospheric pressure; invented by Evangelista Torricelli in 1643. Baumé gravity—the standard used by industrial manufacturers to measure nonhydrocarbon heaviness. Density—the heaviness of a substance. Energy—anything that causes matter to change and does not have the properties of matter. Inertia—a principle that explains a body’s ability to resist motion. Kinetic energy—the energy of motion or velocity. Mass—the quantity of matter in an object. Matter—anything that occupies space and has mass or volume. Potential energy—stored energy. Specific gravity—a measurement of the heaviness of a fluid. Specific gravity equals the mass of a substance divided by the mass of an equal volume of water. The specific gravity of gasoline is 6.15 lb/gal  8.33  0.738. Weight—the force of molecular gravitation.

14.1 Fundamental Concepts Matter and Energy Physics is the study of matter and energy. Matter is anything that occupies space and has mass or volume. Energy is anything that causes matter to change and does not have the properties of matter. Energy takes the form of heat (Btu; causes matter to expand), electricity (kilowatt hour), potential (height, foot-pound), kinetic (moving, foot-pound), light (produces chemical changes in film), magnetism (creates motion in certain materials), and mechanical work (horsepower hour). There are two basic states of matter: potential and kinetic. Potential energy is stored energy. Kinetic energy is the energy of motion or velocity.

Specific Properties of Matter One of the key principles associated with matter is that of attraction or gravitation. All molecules are attracted to each other. The force of molecular gravitation is called weight. Weight is closely related to mass. If the weight of two bodies is the same, the mass of these bodies is the same. 306

14.1 Fundamental Concepts Gravitational force between two objects is dependent upon the weight of the bodies and the distance between them: The larger the body, the greater the attraction. Force is inversely proportional to the square of the distance. When the distance between two attracted objects is doubled, the force is only one-fourth as great. The mass of an object is identified as the quantity of matter. The measure of a body’s mass is often identified by its weight. Inertia is a principle used to explain a body’s ability to resist motion. A force must be exerted to move a body that is at rest. To change the speed or direction of a moving object, a force must be applied. All matter has inertia. The total amount of inertia a body contains depends on the total mass in the body.

Volume is the space occupied by a body. See Figures 14–1, 14–2, and 14–3 for volume formulas for a sphere, cylinder, and rectangular solid. A fundamental principle of matter is that it cannot be created or destroyed, only changed from one state to another. This principle of indestructibility holds true for energy as well. It can only be transformed from one form to another.

Porosity or particle structure is a principle of matter that deals with the vast amounts of space that exist between molecules. This principle helps explain why mixtures of gases, liquids, or solids can occupy a smaller volume than the original components.

s iu

d Ra

Volume =

4 3 πr 3

Figure 14–1 Volume Formula: Sphere

Height Radius

Height

Width Length Volume = πr 2h

Figure 14–2 Volume Formula: Cylinder

Volume = lwh

Figure 14–3 Volume Formula: Rectangular Solid 307

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800 mL 500 mL

Figure 14–4 Displacement

Archimedes’ Principle Archimedes’ principle applies to specific weight of solids denser than water. The principle states that: • A submerged object will displace its own volume of water. (See Figure 14–4.) • Weight loss of the object equals the weight of the water displaced. EXAMPLE: A chunk of metal weighs 1,000 g in air and 650 g in water. What is its specific weight? Solution: Specific weight metal



Weight of metal in air 1,000  (1,000 – 650) Loss of weight in water

 2.85

14.2 Density and Specific Gravity Because the density of liquids and solids varies so much, it is convenient to have a standard to compare them to. The standard used to compare densities is water. Water weighs 62.5 lb per cubic foot or one gram per cubic centimeter. The terms specific gravity and specific weight are used to compare the density of water to another substance. Hydrocarbons are typically lighter than water. Their specific gravities will be less than one, whereas substances heavier than water have specific gravities of greater than one. Specific gravity is defined as the comparison of a fluid (liquid or gas) to the density of water or air. It is a common mistake for operators to confuse specific gravity with density. This confusion is understandable, because specific gravity is a method for determining the heaviness of a fluid. Density is the heaviness of a substance, whereas specific gravity compares this heaviness to a standard and then calculates a new ratio. Most hydrocarbons have specific gravities below 1.0. Key points to remember: • The specific gravity of water is 8.33 lb/gal  8.33  1.0 • The specific gravity of gasoline is 6.15 lb/gal  8.33  0.738 308

14.2 Density and Specific Gravity

• • •

The density of water is 8.33 lb/gal The density of air is 0.08 lb per cubic foot Density is calculated by weighing unit volumes of a fluid at 60 degrees Fahrenheit (15.5 degrees Celsius).

Determining Specific Gravity Specific gravity is determined by comparing the weight of a volume of material with the weight of the same volume of water. There are two methods for determining specific gravity: Specific gravity 

Weight of definite volume of given material Weight of the same volume of water

Specific gravity of a sinking solid 

Weight of the object in air Loss of weight in water

Density Industry uses four different ways to express the heaviness of a fluid: • Density—(Density  Weight  Volume). The density of water is 8.33 lb/gal. The density of a fluid is defined as the mass of a substance per unit volume. Density measurements are used to determine heaviness. D  8.33 lb  1 gal. This equation can also be expressed as W  D  V or as V  W  D. Specific gravity—The specific gravity of water is 8.33  8.33  1. The specific gravity • of gasoline is 6.15 lb/gal  8.33  0.738. • Baumé gravity—This is the standard used by industrial manufacturers to measure nonhydrocarbon heaviness. • API gravity—The American Petroleum Institute applies API gravity standards to measure the heaviness of a hydrocarbon. A specially designed hydrometer marked in units API is used to determine the heaviness or density of a hydrocarbon. High API readings indicate low fluid gravity. The density of a fluid is defined as the mass of a substance per unit volume. Density measurements are used to determine heaviness. For example, one gallon of: water  8.33 lb crude oil  7.20 lb gasoline  6.15 lb

Viscosity Another term commonly used in industry to describe the flow characteristics of a substance is viscosity. Viscosity is defined as a fluid’s resistance to flow. Weight  Volume  Density Density of water    

1 g per cubic centimeter 62.5 lb per cubic foot 1687.5 lb per cubic yard 16.41 g per cubic inch 309

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EXAMPLE 1 Find the density of helium gas: 20 liters of the gas weighs 3.4 grams. Solution:

D  W V D  3.5 g  0.17 gl 20L EXAMPLE 2 Find the volume of a granite object with a density of 2.6 g per cubic centimeter and a weight of 1,280 g. Solution:

V  W D 3 V  1.280 g 3  1.280 (g  cm )  492 cm3 2.6 g 2.6 g/cm

Elasticity Elasticity refers to the tendency of a substance to return to its original shape after a distorting force is removed. Substances such as iron and steel have a high degree of elasticity, whereas substances such as clay or putty have a very low elasticity rating. Steel can be subjected to a force of thousands of pounds per square inch and yet return to its original shape when the distorting force is removed. The term strain is used to describe the total distortion that occurs after the distorting force is removed. Robert Hooke’s law states that strain is proportional to stress if the stress remains within the elastic limit of the material. The elastic limit of a substance is the maximum force a substance can withstand without breaking or becoming permanently deformed. A spring device can be used to demonstrate Hooke’s law. Distorting forces can be classified as compressing, stretching, tearing, twisting, and bending.

Hardness The hardness of a substance is determined by its ability to scratch or mark another substance. Diamond is the hardest natural substance known; gold is very soft.

Tenacity Tenacity is the ability of a substance to resist being pulled or torn apart. Tenacity per unit area is called tensile strength. Tensile strength is measured in pounds per square inch.

310

14.2 Density and Specific Gravity

Ductility Ductility is a material’s ability to be drawn into fine threads. Copper and aluminum, both of which can be made into wire, are good examples of materials with high ductility.

Malleability Malleability describes the ability of a substance to be beaten or rolled into thin sheets. For example, gold is extremely malleable: it can be rolled out to a sheet about 1/300,000 inch thick.

Adhesion Dissimilar molecules carry very powerful attractive forces, referred to as adhesion. Examples of materials with great adhesion include concrete and glue.

Surface Tension Surface tension is the result of molecular attraction in a liquid that is stronger along the outer perimeter and weaker toward the middle. The liquid acts like a stretched sheet of rubber. Surface forces vary from those found deeper in the liquid, because there are no upward forces.

Capillary Action When a liquid comes in contact with the outside of its container, it experiences two forces: cohesive force and adhesion. The adhesive force is the result of the attractive forces between the walls of the container and the fluid; the cohesive force is related to the internal characteristics of the liquid. When the adhesive forces of the system are greater than the cohesive internal forces of the liquid, the liquid tends to cling to the sides of the container. This tendency of a liquid to cling to and climb up the walls of the container is called wetting. Mercury is so dense that it has the opposite reaction as most liquids. Wetting does not occur; instead, the adhesive forces dome up the mercury near the wall of the container. The density of the liquid and the size of the tube determine how high or low a liquid will move inside a container.

Temperature and Cohesive Force When the temperature inside a process system is increased, the cohesive forces between molecules are reduced. EXAMPLE 1 What is the density of a cube of iron, 15 cm on an edge, that weighs 9.6 kg? Solution:

D  W V D  9.6 kg3  2.84 g/cm3 15cm 9,600  3,375  2.84 g/cm3 Answer: 2.84 g/cm3

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EXAMPLE 2 How many liters of alcohol will weigh 30 kg? (Density of alcohol  0.8 g/cm3) Solution: Liters of alcohol  37,500 grams  1,000 grams  37.5 L

V  W D V 

30 g  37,500 0.8 g/cm3

Answer: 37.5 L Note: 1 kg  1,000 g

Practical Exercises 1. A beam of cedar wood 20 ft long, 2 ft wide, and 6 in. thick weighs 150 lb. Calculate its density. Show your work! 2. A cylinder 4 cm in diameter and 40 cm long is made of brass (density  8.5 g/cm3). Calculate its weight. Show your work! 3. What is the weight of a rectangular steel bar 15 ft long, 1 ft wide, and 2 in. thick? (Density of steel  461 lb/ft3.) Show your work! Note: W  D  V

14.3 Pressure in Fluids At sea level, the atmosphere that surrounds the Earth is composed of 78.1% nitrogen, 20.9% oxygen, 0.9% argon, and 0.03% carbon dioxide, as measured in dry air. The remaining components, in decreasing proportion, include neon, helium, methane, krypton, hydrogen, oxides of nitrogen, and xenon. It should be noted that humid air contains higher percentages of water vapor, which lowers the percentages of the other gases. The area immediately above the surface of the Earth, which sustains life and produces our weather, is called the troposphere. In this thin, six-mile-high band, we find rain, clouds, wind, ice, and snow. The temperature of the atmosphere decreases rapidly as we ascend through the troposphere and into the stratosphere where the ozone layer is found. The stratosphere extends from 6 miles to 31 miles above the surface of the Earth. The thin, dry air in the middle of the stratosphere is very cold, averaging 55C. From 31 miles to 50 miles above the Earth, we find the mesosphere. The ionosphere is a region of ionized gases that exists above the mesosphere. Temperature variations in this band rapidly rise and fall. The ionosphere extends from 50 miles to approximately 93 miles above the surface of the Earth. Atmospheric pressure is the combined weight of all the gases exerted on the surface of the Earth. At sea level, the total mass is estimated at 5.5  1015 tons, or 760 mmHg, or 14.7 psi, or one atmosphere. In 1643, Evangelista Torricelli was able to prove his atmospheric theory using a device called a barometer. Barometer is a combination of Greek words, baros meaning pressure or weight, and metros, meaning measure. Variations in the density of atmospheric gases form high 312

14.3 Pressure in Fluids and low atmospheric pressures. As atmospheric pressure increases, our weather improves; as it decreases, a cloudy, rainy forecast is issued. Note: 1 psi  27.7 inches of water  2.04 inches of mercury (Hg) Problem: Convert 8” of Hg to inches of water 8 inches of Hg  27.7 inches of water  2.04 inches of Hg  108.627 inches of water Inches of water can be converted to psig using the following equation: height of liquid  27.7. Inches of mercury (Hg) can be converted to psig using the following equation: height of liquid  2.04.

Force and Pressure Force is a push or a pull that is used to change the direction, speed, or shape of a body. Gravitational force in liquids and pressure in fluids share a unique relationship. Pressure is the total force divided by the area. Force is measured in units of weight: P (pressure)  F (force)  A (area)

EXAMPLE 1 A rectangular tank 10 ft square and 8 ft deep is filled with water. The volume of the tank is 800 ft3. Water weighs 62.5 lb/ft. Calculate the total force exerted by the water against the bottom of the tank. Solution: Total Force F F

  

Area A 10 ft2

  

Height H 8 ft

  

Density D 62.5 lb/ft3



50,000 lb

Answer: The total force exerted by the water against the bottom of the tank is 50,000 lb. Pressure (P)  Force (weight)  Area

EXAMPLE 2 Calculate the pressure produced by a 2,000-lb stone block, 40 in. length  20 in. width. The height is not required to solve this problem. Solution: The area occupied by the stone  800 in.2 40 in. length  20 in. wide  800 in.2 P  2,000  800  2.5 psi Answer: The pressure at the base of the stone  2.5 psi. 313

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EXAMPLE 3 Calculate the pressure produced by a 10-ft onion tank filled with a hydrocarbon fluid (0.72 sg). Vapor pressure is 200. Add 45 psi N2 to the total. What is the final pressure? Solution: Height  0.433  Specific Gravity  Pressure 10 ft  0.433  0.72 sg  3.1 psi 3.1 psi  200  45 psi  248.1 psi Answer: 248.1 psi

Practical Exercises 1. Calculate the pressure produced by a 456-lb granite block, 10 in. length  15 in. width  72 in. height. 2. Calculate the pressure produced by a 40-ft onion tank filled with 17.5 ft of a hydrocarbon fluid (0.54 sg). Vapor pressure is 300 psi. Add 15 psi N2 to the total. What is the final pressure? 3. Calculate the pressure produced by water in a 14.5-ft-high vessel. 4. Calculate the pressure exerted on the bottom of a 69-ft distillation column by a 10-ft hydrocarbon level. Specific gravity is 0.67. Vapor pressure at 240 degrees Fahrenheit (115.5 degrees Celsius) is 236. One hundred psi is added to the column, giving a top gauge reading of ____________ psi and a bottom gauge reading of ____________ psi. 5. What pressure, in pounds per square inch, is a scuba diver subjected to when descending to an ocean depth of 125 ft? 6. A rectangular vessel 10 ft wide, 20 ft long, and 12 ft deep is filled with mercury (specific gravity  13.5). Answer the following questions using the pressure equation P  FA: a. What is the pressure on the bottom of the tank? b. Identify the pressure on one side of the vessel at the 6-foot mark. c. What is the total force on the bottom of the tank? d. Identify the pressure at the top of the tank.

Flow Rate Calculations Another common problem encountered by process technicians is the calculation of flow rate. Figure 14–5 shows the various components found in a simple pump system: valves, piping, a flow control loop, and a pump. The simple equation used to calculate flow rate is: FR  Volume  Time Sample Problem: Calculate the flow rate (FR) of the following pump-around system. FR ? Volume  600 gallons Time  3 minutes FR  600 gallons  3 minutes FR  200 GPM

Pressure/Temperature Relationships In larger commercial operations, a distillation system has a complex feed and storage system, which includes a series of tanks that are used to provide a steady flow of raw materials to the 314

14.3 Pressure in Fluids

FIC

I

200 GPM

P

FT

NPDH

Flow Rate =

Pi NPSH

FR =

Pi

Volume Time

600 gallons 3 minutes

FR = 200 gallons

M

Centrifugal Pump

Figure 14–5 Flow Rate Calculation column, and a system of tanks for new product storage. Process technicians operating these systems should be aware of the science and physics associated with this equipment. Charles’s law and the ideal gas law illustrate the close relationship between temperature and pressure inside an enclosed vessel. In the system shown in Figure 14–6, a hot liquid (200F) is allowed to cool overnight in an enclosed vessel to 78F. We can see the relationship between temperature and pressure using the following formula: P2  P1  T2  T1 P2  ? P1  24.7 psia T1  200F  460  660R T2  78F  460  538R 24.7 psia  538R  13288.6  660R  20 psia P2  20 psia Compressors come in a variety of styles and designs; the most common being dynamic and positive displacement. Each of these designs is governed by standard scientific principles that should be well understood by process technicians assigned to these areas. Because compressors are so widely used, almost every process technician will come into contact with a compressor system. The compression of gases and vapors in the process industry is very important and is used in the following applications:

• • • • •

air nitrogen natural gases and hydrocarbons hydrogen, carbon dioxide, carbon monoxide, chlorine, helium, argon other vapors and gases 315

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P1 = 24.7 psia T1 = 200ºF + 460 = 660ºR T2 = 78ºF + 460 = 538ºR P2 = P1 T 2 T1 (24.7 psia) (538ºR) 660ºR

FIC

P2 = 20 psia

I

P

FT 24.7 psia

20 psia

P

1

P

2

200ºF

T

1

78ºF

NPDH

T

Pi

Differential Pressure 4.7 psi

2

Pi

NPSH

M Closed

Closed

Centrifugal Pump

Figure 14–6 Enclosed Tank When a gas is compressed, the molecules that make up the gas are moved closer together. This increases the chances of molecular collisions that produce heat and increase the pressure beyond the normal calculated compression ratio. Figure 14–7 shows a typical compressor system, illustrating the various components and process variables associated with the system as it is started up. The scientific comparison is between the initial conditions or process variables and the operating variables. (This figure does not show an inner-cooler or an after-cooler, to illustrate what happens when these systems are not used.) The starting pressure is 14.7 psia and final pressure is 35 psia. Using the formula: T2  P2  T1  P1, it is possible to observe the operation of the scientific laws that takes place when the compressor is started up. As the pressure increases, so does the temperature. Formula: T2  P2  T1  P1 P1  14.7 psia T1  70F  460  530R T2  ? P2  35 psia Formula: T2  P2  T1  P1 35 psia  530R  14.7 psia  ? 1262R  460  802F T2  802F 316

14.3 Pressure in Fluids

T2 =

Air inlet

P2 T1 P1

Pi

Pi

?

35 PSIA

T2

P2

T1

P1

Start: 14.7 psia

Pi

End: 35 psia

70ºF

14.7 PSIA

M

Centrifugal Compressor (Multi-Stage)

Receiver

Figure 14–7 Compressor System

Heat Exchangers: Temperature vs. Pressure A heat exchanger is an energy transfer device, however, a number of scientific principles govern what happens inside this unusual device. Some of these principles include the laws of heat transfer, thermal expansion, pressure, and fluid flow, among others. The operation of a heat exchanger presents a number of hazardous situations. It is possible, for instance, to create a bomb by closing the wrong valves. In this example, we will look at how isolating an exchanger could create a vacuum that may damage or collapse the shell. In Figure 14–8, the shell inlet and outlet are blocked and the hot liquid (350F) is allowed to cool down to a temperature of 33F in an enclosed shell. Formula: P2  P1  T2  T1 P2  ? P1  19.7 psia T1  350F  460  810R T2  33F  460  493R 19.7 psia  493R  9712  810R  12 psia P2  12 psia The shell will be under a vacuum as the materials cool down to 33F. Most industrial equipment is designed to handle pressure from the inside out, not from the outside in. 317

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Closed Hot Oil

P2 =

350ºF 19.7 PSIA Closed

T1

P1

T2

P2

33ºF

?

Heat Exchanger

P1 T2 T1

Closed Pi

Pump

Figure 14–8 Heat Exchanger—Temperature vs. Pressure 1

In the next example, the heat exchange moves in the opposite direction. In most heat exchangers, the shell is able to handle higher temperatures and pressures; in Figure 14–9, however, we see how the tubes can be damaged by a technician who is unfamiliar with the scientific principles associated with operating a heat exchanger. In the past, many senior technicians simply taught new technicians which valves to open and which sequence to do it in. Very little discussion was had concerning the science of what was taking place inside the device. Modern technicians are required to understand the science and technology associated with modern process control. In the following example, the tubes are rated at 50 psia @ 800F. If these limits are exceeded, hazardous conditions will be created, under which the tubes could rupture. Because the tubes are hidden in the shell, it is difficult for a new technician to immediately recognize that a serious problem has occured. Formula: P2  P1  T2  T1 P2  ? P1  30 psia T1  350F  460  810R T2  1000F  460  1460R 30 psia  1460R  43,800  810R  54 psia P2  54 psia 318

14.4 Complex and Simple Machines 350ºF 30 PSIA Closed Hot Oil

P1

T1

Closed Heat Exchanger

P2 =

P1 T2 T1

T2

P2

1000ºF

?

Closed Pi

Pump

P2 =

(30 psia) (1460ºR) 810ºR

P2 =

54 psia

Figure 14–9 Heat Exchanger—Temperature vs. Pressure 2

14.4 Complex and Simple Machines Work Work is the process of overcoming the downward pull of gravity and moving a body that has been at rest. When you attempt to lift a body at rest, work is not accomplished unless the object is lifted. Work is equal to force times distance.

W  FD EXAMPLE Calculate how much work is done when a force of 50 lb is applied to push a wagon 20 ft. Solution: To solve this problem, multiply the applied force (50 lb) by the distance through which the force acts (20 ft). 319

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Work  W  

Force  Distance F  D 50 lb  20 ft

 1,000 ft-lb

Answer: 1,000 ft-lb.

Practical Exercises 1. Calculate the amount of work accomplished by a 3-ft table holding up a 2-lb book. 2. Calculate the amount of work accomplished when a weight is lifted 240 ft by a force of 600 lb. (Work  Force  Distance) 3. A man weighing 190 lb climbs a 35-ft staircase in 25 sec. Calculate how much work was performed.

Mechanical Advantage Mechanical advantage (MA) is the ratio between resistance overcome and effort applied. When determining the mechanical advantage of a system, the resistance is divided by the effort. For example, when a 100-lb force moves a resistance force of 400 lb, the machine has a mechanical advantage of 4. Actual MA is calculated using the following equation:

MA  Resistance  R Effort E Inclined Plane When an object is rolled or slid up a ramp, the scientific principle of the inclined plane comes into play. Inclined planes are very useful when one must move large, heavy objects from one level to another. Other examples of application of this principle include stairways, ramps, inclined roads, and inclined tracks. In the inclined plane principle, ideal MA is calculated by using the resistance force (gravity) that overcomes the vertical height of the plane and the effort force (length) that acts through the entire length of the plane. For example:

Ideal MA  De  Length of plane Dr Height of plane EXAMPLE A 24-ft-long inclined ramp extends from the ground to a height of 8 ft. A force of 180 lb is required to roll a 420-lb cart up the ramp. • Calculate the actual MA. • Calculate the ideal MA. • Calculate the efficiency. • Calculate how much work is accomplished against gravity. • Calculate how much work is done in overcoming friction. Solutions:

Actual MA  R  420 lb  2.33 E 180 lb 320

14.4 Complex and Simple Machines

Ideal MA  De  24 ft  3.0 Dr 8 ft Efficiency  Actual MA  2.33  77% Ideal MA 3 Work output  R  Dr  420 lb  8 ft  3,360 ft-lb Work to overcome traction  Work input  Work output  (E  De)  (R  Dr)  (180 lb  24 ft)  (420 lb  8 ft)  960 ft-lb

The Principle of Moments and Levers The principle of moments and levers can be illustrated using an ordinary playground seesaw. A seesaw is designed to operate like a balanced lever. Two arms of equal length extend across the fulcrum. When a force acts upon the lever arm, it causes a reaction. The lever will remain balanced only if the two forces acting on the seesaw are distributed equally. The point along the lever where the force is applied is important to this distribution concept. The moment of a force is equal to the product of the force and the perpendicular distance from the fulcrum. EXAMPLE 1 Do the total clockwise moments balance the total counterclockwise moments in Figure 14–10? Solution: Counterclockwise Force  Distance 50 lb  6 ft 12 lb  4 ft CCW Moments

   

Clockwise Force  60 lb  4 lb  CW Moments

Moment 300 ft-lb 48 ft-lb 348 ft-lb

Distance  Moment 5 ft  300 ft-lb 12 ft  48 ft-lb  348 ft-lb

If the force and distance are perpendicular to each other, no work is accomplished. When a lever is in equilibrium, the total counterclockwise and clockwise forces are equal.

60 lb

50 lb 12 lb

4 lb 4 ft-0 in. 6 ft-0 in.

Figure 14–10

5 ft-0 in. 12 ft-0 in.

Law of Moments 1 321

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EXAMPLE 2 A balanced lever arm rests on a fulcrum at its center. A 200-lb force is applied 5 ft from the fulcrum. To maintain equilibrium, how far from the fulcrum, on the other lever arm, should a 100-lb force be applied? Solution: CCW moments  200 lb  5 ft  x  Answer: 10 ft

CW moments 100 lb  x ft 10 ft

EXAMPLE 3 A 200-lb weight and a 100-lb weight rest 8 ft and 6 ft from the fulcrum. A 200-lb weight rests on the opposite side. How many feet from the fulcrum must the weight be placed to establish equilibrium? Solution: (200 lb  8 ft)  (100 lb  6 ft)  200 lb  x ft

x

 1,600  600 200

 11 ft

Answer: 11 ft EXAMPLE 4 A balanced lever arm rests on a fulcrum at its center. A 600-lb force is applied 5 ft from the fulcrum (Figure 14–11). To maintain equilibrium, how far from the fulcrum, on the other lever arm, should a 1200-lb force be applied?

1200 lbs. 600 lbs. 5‘

Figure 14–11 322

?‘

Law of Moments 2

14.5 Electricity Solution: CCW moments 600 lb  5 ft 3000  1200 x

   

CW moments 1200 lb  x ft 2.5 2.5 ft

Answer: 2.5 ft

14.5 Electricity Electricity is a primary part of modern industrial operation. It is used to operate motors that provide the rotational energy for pumps, compressors, fans, mixers, conveyors, generators, extruders, and many other critical pieces of equipment. It is also used for lighting, air conditioning, electrical outlets, and modern process control. Without electricity the world would be a very different place, void of many of the comforts we take for granted. To operate a plant efficiently, a process technician needs to have a basic understanding of electricity and the equipment it operates.

Electric current is defined as electrons in motion. Electricity is often defined as the movement of electrons from one point to another. Nearly all of the electrical energy in the world is delivered by alternating current (AC); this form of electricity cannot be produced by batteries, but must be generated by strong magnetic fields. Alternating current is a flow of electrons that reverses direction at regular intervals. The term alternating current cycle really means a circle. An AC generator is a rotating machine that converts mechanical energy into electrical energy or alternating current. Another form of electrical energy is direct current, defined as the flow of electrons in one direction. A battery can generate direct current (DC). An example of this is a battery connected to a light connected to a switch connected to a battery. Figure 14–12 illustrates the key components of a DC circuit. Electricity is produced by a series of processes that should be very familiar to most process technicians. A steam-generation system or boiler provides useful steam to drive a steam turbine that is connected to an electric generator. The electric generator sends (11,000V) current to a step-up transformer that delivers this load to high-voltage power lines. These step-up transformers step the voltage up 25 times to 275,000 volts. The ability to use the transformer for step-up or step-down purposes is the primary advantage of alternating current over direct current. These power lines are used to distribute electricity across a wide network. The high-voltage power lines (275,000V) are connected to a step-down transformer. This type of transformer is designed to reduce the current to useable voltages like 110V and 220V.

Ohm’s Law The relationship between current, resistance, and electric potential was first discovered and described by a German scientist named George S. Ohm (1784–1854). Ohm’s law describes how the amount of current that flows through a wire depends on the resistance it must overcome and the electrical pressure or voltage that is pushing the electrons.The greater the voltage, the greater the current; conversely, the greater the resistance, the less the current.

Resistance: The Ohm. Different substances have different resistances to the flow of electricity. Metals are typically good conductors of electrons; silver and copper are two of the best conductors. 323

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Light

Switch

Battery

+_ Figure 14–12

Direct-Current Circuit

Glass, rubber, and sulfur offer very high resistance and therefore are good insulators. Resistance is affected by the length of the substance in the direction of current flow: The longer the distance, the greater the resistance. Resistance is also affected by the temperature of the substance. In electrical formulas, the capital letter R stands for resistance, and the capital Greek letter omega () is the symbol for ohm. For example, resistance equals 50 ohms is expressed as R  50 .

The Ampere. The unit for electric current is the ampere (A). One ampere is equal to a flow of 1 coulomb per second. In applications or equations where the ampere is too large, milliampere (mA) is used. A milliamp is a thousandth (0.001) of an amp. In an electrical formula, the capital letter I represents current. Thirty amperes would be represented as I  30A.

Electric Potential: The Volt. An electric generator or battery provides a constant source of electric potential. The unit of electric potential (E) is the volt (V). For example, the electric potential of a 12-volt battery could be written as E  12V. One volt will cause one ampere of current to flow through a resistance of one ohm. V  voltage (also expressed as E  electric potential in V) I  current in A R  resistance in  Depending on the value needed, Ohm’s law can be expressed algebraically in three ways: 1. V  IR (used to find the voltage when current and resistance are specified) 2. I  VR (used to find current when voltage and resistance are known) 3. R  VI (used to find resistance when voltage and current are specified) 324

14.5 Electricity EXAMPLE 1 What current, in amps, will flow through a conductor with a resistance of 20 ohms if the potential difference is 240 volts? Solution: IVR  240 volts  20 ohms  12 amps EXAMPLE 2 An electric device uses 8 amps of current on a 120-volt circuit. What is the resistance? Solution: IVR RVI  120 volts  8 amps  15 ohms EXAMPLE 3 An electric motor on a centrifugal pump has a total resistance of 6 ohms. If the motor uses 19 amps of current, what voltage does the motor need? Solution: IVR V  IR  19 amps  6 ohms  114 volts

Steam Turbine and Heat Rate Equation A steam turbine is a device used to create useful rotational energy for the purpose of operating any number of rotational devices. These devices include pumps; compressors; electric generators; turbo-electric locomotives; rotating shafts on submarines, ships, automobiles; fans; and a wide assortment of other devices used in industry and our society. In a steam turbine, high-pressure steam is directed against a set of rotating and fixed blades. The design of the blading creates a very productive pumping action as the steam moves from rotating to fixed to rotating blading. Modern steam turbine design may have as many as 50 or more stages linked along a horizontal shaft. Each shaft consists of a set of moving and stationary blades. The curved blades of each stage are designed so that the spaces between the blades act as nozzles that increase steam velocity. The rotating blades are precision-mounted to a rotating shaft, making it appear to be one seamless unit. The fixed blades are half-crescent devices mounted to the lower casing. Because steam expands as it enters the turbine, the blades gradually increase in diameter within the body of the device, creating a conical shape. In modern steam turbines, the steam used to operate the device enters at temperatures as high as 538C and pressures as high as 3,500 psi at the nozzle block and 200 psi at the exhaust port. 325

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The basic components of a steam turbine are: • rotor • fixed blades and moving blades • steam chest • strainer • governor valve • overspeed trip • nozzle blocks • governor system • steam inlet and outlet • casing • seals and bearings Process technicians perform simple calculations associated with the operation of a steam turbine system. Figure 14–13 shows the typical variables on a steam turbine. Heat rate  steam flow  specific heat capacity  temperature difference. The heat-rate formula is:

Rh  Ws  c  T Rh  heat rate in btu/hr Ws  steam flow in lb/hr c  specific heat capacity in btu/lb F T  change in temperature in F

412ºF

Ti

NPDH

Pi

NPSH

Pi

Steam: 600 ibs per hr.

Steam Turbine Centrifugal Pump

212ºF

Ti

Figure 14–13 326

Specific Heat Capacity for Steam c = 0.48

Steam Turbine

14.5 Electricity EXAMPLE 1 Determine the heat rate. Steam enters a turbine at 412F at atmospheric pressure. Steam at 600 lb flows through the turbine each hour during normal operation. Rh  ? Ws  600 lbs/hr c  0.48 Tin  412F Tout  212F T  412F  212F  200F Formula: Rh  Ws  c  T 600  0.48  200F  57,600 btu/hr Note: 57,600 btu/hr is the amount of heat turned into useful work each hour. EXAMPLE 2 Calculate the horsepower (HP) output. Formula: HP  heat rate  0.000393 HP  ? Rh  57,600 btu/hr HP  57,600 btu/hr  0.000393  22.6 HP EXAMPLE 3 Identify the steam turbine’s thermal efficiency. Formula: e  (Tin  Tout)  Tin First, convert F to C to K C 412F 212F e e

     

(F  32)  1.8 211C  273  484K 100C  273  373K (Tin  Tout)  Tin  100  484K 373K  111K  484K .23  100  23% 23% thermal efficiency

Note: This information is very useful in identifying correct pipe sizes and equipment sizes.

Heat Exchanger and Thermal Efficiency A heat exchanger is an energy transfer device that is designed to transfer heat energy between separate streams without physically mixing the streams. Heat transfer takes place primarily through conduction and convection. A heat exchanger has a series of tubes that are surrounded by a shell and attached to an inlet head and in some models an out head. A typical heat exchanger has a shell 327

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Ti 400ºF

T in

Steam In

Heat Exchanger T in - T out e

=

T in

Ti

T out

180ºF

Figure 14–14

Heat Exchanger and Thermal Efficiency

inlet and outlet, a tube inlet and outlet, a shell, and tubes.These heat transfer devices are very common and are used in numerous applications. In the following example, steam enters the upper shell inlet at 400F and exits at 180F. During normal operation, approximately 600 lb of steam flows through the shell per hour. An impingement baffle is located on the shell inlet to deflect and reduce any damage to the tubes. In solving the following problem, refer to Figure 14–14. EXAMPLE 1 Determine the thermal efficiency of the heat exchanger. Formula: e  (Tin  Tout)  Tin First, convert F to C to K. (400F  32)  1.8  204C  273  477K (180F  32)  1.8  82C  273  355K e  (477K  355K)  477K  100  26%

Summary Physics is the study of matter and energy. Matter is anything that occupies space and has mass or volume. The specific properties of matter are weight, mass, inertia, volume, indestructibility, and porosity. Energy is anything that causes matter to change and does not have the properties of matter. Forms of energy include heat, electricity, potential, kinetic, light, magnetic, and mechanical. There 328

Summary are two basic states of energy: potential and kinetic. Potential energy is stored energy, and kinetic energy is the energy of motion or velocity. Because the density of liquids and solids varies so much, we use a standard to which to compare them. The standard used to compare densities is water. Water weighs 62.5 lb per cubic foot or one gram per cubic centimeter. Specific gravity is the comparison of a fluid (liquid or gas) to the density of water or air; it is a method for determining the heaviness of a fluid. Density is the heaviness of a substance. Most hydrocarbons have specific gravities below 1.0 (that is, they are typically lighter than water). Specific gravity is determined by comparing the weight of a volume of material with the weight of the same volume of water. Industry uses four different ways to express a fluid’s heaviness: density, specific gravity, Baumé gravity, and API gravity. The density of a fluid is the mass of a substance per unit volume. The term used by industry to describe a fluid’s resistance to flow is viscosity. Elasticity refers to the tendency of a substance to return to its original shape after a distorting force is removed. Strain is the total distortion that occurs after the distorting force is removed. Robert Hooke’s law states that strain is proportional to stress if the stress remains within the elastic limit of the material. Distorting forces take the form of compressing, stretching, tearing, twisting, and bending. The elastic limit of a substance is the maximum force that substance can withstand without breaking or becoming permanently deformed. The hardness of a substance is determined by its ability to scratch or mark another substance. Tenacity is the ability of a substance to resist being pulled or torn apart. Tenacity per unit area is called tensile strength and is measured in pounds per square inch. Ductility is a material’s ability to be drawn into fine threads. Malleability refers to the ability of a substance to be beaten or rolled into thin sheets. Dissimilar molecules carry very powerful attractive forces referred to as adhesion. Surface tension is the result of molecular attraction in fluids, which is stronger along the outer perimeter and weaker toward the middle. Surface forces vary from those found deeper in the liquid because there are no upward forces. When a liquid comes in contact with the outside of its container, it experiences both cohesive force and adhesion. The adhesive force is the result of the attractive forces between the walls of the container and the fluid, and cohesive force is related to the internal characteristics of the liquid. The density of the liquid and the size of the tube determine how high or low a liquid will move inside a container. When the temperature inside a process system is increased, the cohesive forces between molecules are reduced. Force is defined as a push or a pull that is used to change the direction, speed, or shape of a body. Gravitational force in liquids and pressure in fluids share a unique relationship. Pressure is the total force divided by the area. Force is measured in units of weight. Work is the process of overcoming the downward pull of gravity and moving a body that has been at rest. It is equal to force times distance (W  FD). 329

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Mechanical advantage is the ratio between resistance overcome and effort applied. When determining the mechanical advantage of a system, the resistance is divided by the effort. The moment of a force is equal to the product of the force and the perpendicular distance from the fulcrum. If the force and distance are perpendicular to each other, no work is accomplished. Ohm’s law states that the amount of current that flows through a wire depends on the resistance it must overcome and the electrical pressure or voltage that is pushing the electrons. The greater the voltage, the greater the current; conversely, the greater the resistance, the less the current. Ohm’s law is used to describe the relationship between current, voltage and resistance.

330

Chapter 14 Review Questions

Chapter 14 Review Questions 1. What is the volume of a rectangular object 4 ft long, 3 ft wide, and 10 ft high? 2. What is the volume of a cylinder that has a 15-ft diameter and stands 22 ft tall? 3. Find the density of hydrogen gas: Forty liters of the gas weighs 3.3 g. 4. Find the volume of a metal object with a density of 4.6 g per cubic centimeter and a weight of 4,280 grams. 5. What is the density of a cube of iron, 25 cm on an edge, that weighs 16.5 kg? 6. How many liters of alcohol will weigh 80 kg? (Density of alcohol  0.8 g/cm3) 7. A beam of cedar wood 43 ft long, 3 ft wide, and 6 in. thick weighs 350 lb. Calculate its density. 8. A cylinder 6 cm in diameter and 30 cm long is made of brass (density  8.5 g/cm3). Calculate its weight. 9. What is the weight of a rectangular steel bar 10 ft long, 2 ft wide, and 2 in. thick? (Density of steel  461 lb/ft3.) 10. Calculate the pressure produced by a 3,500-lb stone block, 60 in. length  20 in. width  72 in. height. 11. Calculate the pressure produced by a 956-lb granite block, 110 in. length  15 in. width  72 in. height. 12. Calculate the pressure produced by a 22-ft onion tank filled with a hydrocarbon fluid (0.72 sg). Vapor pressure is 430. Add 55 psi N2 to the total. What is the final pressure? 13. Calculate the pressure produced by water in a 19.5-ft-high vessel. 14. Contrast density and specific gravity. 15. Calculate the pressure exerted on the bottom of a 79-ft distillation column by a 10-ft hydrocarbon level. Specific gravity is 0.67. Vapor pressure at 240 degrees Fahrenheit (115.5 degrees Celsius) is 236. One hundred psi is added to the column, giving a top gauge reading of ______________ psi and a bottom gauge reading of ______________ psi. 16. What pressure, in pounds per square inch, is a scuba diver subjected to when descending to an ocean depth of 105 ft? 17. A chunk of rock weighs 1,000 g in air and 350 g in water. What is its specific weight? 18. Calculate how much work is done when a force of 50 lb is applied to push a wagon 20 ft. To solve this problem, multiply the applied force (50 lb) by the distance through which the force acts (20 ft). 19. Calculate the amount of work accomplished by a 2-ft table holding up a 2-lb book. 20. Calculate the amount of work accomplished when a weight is lifted 140 ft by a force of 300 lb. 21. A man weighing 150 lb climbs a 35-ft staircase in 15 seconds. Calculate how much work was performed. 331

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22. A 20-ft-long inclined ramp extends from the ground to a height of 6 ft. A force of 190 lb is required to roll a 520-lb cart up the ramp. a. Calculate the actual MA. b. Calculate the ideal MA. c. Calculate the efficiency. d. Calculate how much work is accomplished against gravity. e. Calculate how much work is done in overcoming friction. 23. A 1,600-lb weight and a 400-lb weight rest 8 ft and 6 ft from the fulcrum. A 700-lb weight rests on the opposite side. How many feet from the fulcrum must the weight be placed to establish equilibrium? 24. What current, in amps, will flow through a conductor with a resistance of 20 ohms if the potential difference is 120 volts? (I  V  R) 25. An electric motor on a centrifugal pump has a total resistance of 6 ohms. If the motor uses 21 amps of current, what voltage does the motor need? (V  IR)

332

Environmental Standards After studying this chapter, the student will be able to: • • • • • • •

Define the key terms associated with environmental awareness training. Describe air pollution control. Discuss water pollution control. Explain solid waste control. Describe toxic substances control. Explain emergency response. Discuss the community right-to-know principle.

333

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Key Terms Air permits—government-granted licenses that must be obtained for any project that has the possibility of producing air pollutants. Air pollution—contamination of the air, especially by industrial waste gases, fuel exhausts, or smoke. Community Awareness and Emergency Response (CAER)—a program designed to inform the community surrounding a plant of potentially hazardous situations and of hazardous chemicals found in the plant, to work with the community to develop emergency response programs, and to open the lines of communication between industry and the community. Clean Air Act—legislation intended to enhance the quality of the nation’s air, accelerate a national research and development program to prevent air pollution, provide technical and financial assistance to state and local governments, and develop a regional air pollution control program. Clean Water Act of 1972—legislation adopting the best available technology (BAT) strategy for all cleanups. Community right-to-know—a principle holding that a community should be aware of the chemicals manufactured or used by local chemical plants and business. Legislation, regulations, and programs based on this principle are intended to involve the community in emergency response plans, improve communication and understanding between industry and the surrounding community, improve local emergency response planning, and identify potential hazards. Emergency response—actions taken when an emergency occurs in an industrial environment; follows a specific set of standards. Drills are carefully planned and include preparations for worst-case scenarios (e.g., vapor releases, chemical spills, explosions, fires, equipment failures, hurricanes, high winds, loss of power, and bomb threats or bombings). Environmental Protection Agency (EPA)—a federal agency with authority to make and enforce environmental policy. Resource Conservation and Recovery Act (RCRA)—federal law enacted in 1976 to protect human health and the environment. A secondary goal is to conserve natural resources. It attains these goals by regulating all aspects of hazardous waste management, including generation, storage, treatment, and disposal. This concept is referred to as “cradle to grave” management. Solid waste—a by-product of modern technology; technically defined as a discarded solid, liquid, or containerized gas. This definition includes materials that have been recycled or abandoned through disposal, burning or incineration, accumulation, storage, or treatment. Toxic Substances Control Act of 1976 (TSCA)—federal legislation intended to protect human health and the environment, and to regulate commerce by requiring testing and imposing restrictions on certain chemical substances. The TSCA applies to all manufacturers, exporters, importers, processors, distributors, and disposers of chemical substances in the United States. Water permit—government-granted license issued as part of efforts to control water pollution. Water pollution—contamination of the water, especially by industrial wastes. 334

15.1 Air Pollution Control

15.1 Air Pollution Control Modern technology produces a variety of useful products. This same technology produces by-products that can harm the environment. Because of the potential hazards that accompany technology, environmental laws and regulations have been passed to protect our future.The purpose of the Clean Air Act is to enhance the quality of the nation’s air; accelerate a national research and development (R&D) program to prevent air pollution; provide technical and financial assistance to state and local governments for dealing with air pollution; and develop a regional air pollution control program.

Air Pollution Control In 1955, the original Clean Air Act was passed to fight air pollution. Over the years, a number of modifications have been made to that act: 1960 amendment—directed Surgeon General to study vehicle pollution 1963 amendment—directed research into fuel desulfurization and development of air quality criteria 1965 amendment—mandate to study new sources of pollution 1967—Quality Air Act 1970—Clean Air Amendment 1977 amendment—the Clean Air Act for emission standards 1990—reauthorization of federal Clean Air Act

• • • • • • • • • •

Air toxins Acid deposition Job training for workers laid off because of Clean Air Act requirements Air quality standards Permits Stratospheric ozone and global climate protection Provisions for enforcement Acid rain and air monitoring research Provision to improve air quality and visibility near national parks Provisions relating to mobile sources

Agencies The Environmental Protection Agency (EPA) was established in 1970. The EPA is an independent agency of the United States government whose primary purpose is to protect the environment from pollution. The EPA has authority to develop and enforce environmental policy. The Air Pollution Control Board maintains numerous regional offices throughout each state. Each location receives public complaints, coordinates investigations, documents violations, and recommends enforcement actions.

Air Permitting Air permits must be obtained for any project that has the possibility of producing air pollutants. The Air Control Board (ACB) takes about three to eight months to complete the permitting process. After the ACB issues a permit, which will place limits on emissions, a yearly inspection is scheduled. 335

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Penalties for civil and criminal abuses of the Clean Air Act range from $25,000 a day to $250,000 and 2 to 15 years in jail. For example, smoking flares in excess of 5 minutes must be reported. Failure to report results in severe penalties.

15.2 Water Pollution Control The federal Clean Water Act was passed in 1898 to fight water pollution. Fifty years later, Congress provided funds for the construction of municipal wastewater treatment facilities. The Water Control Act of 1965 took a “water quality” approach and initiated close examination of receiving waters. States were required to establish standards for water quality. The Clean Water Act of 1972 adopted the best available technology (BAT) strategy for all cleanups. Under the 1987 amendments to this act, states are required to identify waters that are not expected to meet quality standards.

Water Pollution Standards and Regulations The Clean Water Act regulates wastewater. Wastewater standards are applied to: • Process wastewater—process contact water; contaminated water from vessels and equipment, tanks, slab cleanup, and so on • Rainwater—sewer system releases • Once-through cooling water—cooling-tower blowdown or boiler blowdown The federal Clean Water Act is designed to protect U.S. water quality. The EPA, state water commissions, the Army Corps of Engineers, state Parks and Wildlife departments, and the U.S. Department of Fisheries and Wildlife help enforce the Clean Water Act.

National Water Quality Standards National Water Quality Standards state that: • All U.S. waters shall be fishable and swimmable. • No discharge of toxic pollutants in toxic quantities will be allowed. • Technology must be developed to eliminate pollutant discharge.

Water Permitting The Clean Water Act requires a company to have a water permit, similar to an air permit. In some states, a two-permit system exists.

15.3 Solid Waste Control Solid waste is a by-product of modern technology. Solid waste is technically defined as a discarded solid, liquid, or containerized gas. This definition includes materials that have been recycled or abandoned through disposal, burning or incineration, accumulation, storage, or treatment. 336

15.4 Toxic Substances Control The Resource Conservation and Recovery Act (RCRA) was enacted as public law in 1976. The purpose of RCRA is to protect human health and the environment. A secondary goal is to conserve our country’s natural resources. The RCRA attains these goals by regulating all aspects of hazardous waste management: generation, storage, treatment, and disposal. This concept is referred to as “cradle to grave” waste management. Solid waste is categorized as: Class One, Hazardous: ignitable, reactive, corrosive, toxic Class One, Nonhazardous: RCRA regulations do not apply Class Two Examples include garbage, cured epoxy resin, biopond filter solids Class Three Examples include uncontaminated or inert material, “wood”

Laws The RCRA establishes these penalties: civil penalty of $25,000 a day; criminal penalty for knowing endangerment, $250,000 and 15 years in jail ($1 million for a company). Liability extends to any person involved in breaking the law. State water commissions have been organized in each state to regulate and control the solid waste generated within their boundaries.

Permitting Storage of a hazardous chemical for more than 90 days requires a permit. An ideal facility includes:

• • • •

A covered facility to prevent rainwater contamination No contact with soil Containment for all equipment Raised equipment to permit inspection for leaks

15.4 Toxic Substances Control The Toxic Substances Control Act of 1976 (TSCA) is a federal law that was intended to protect human health and the environment. The TSCA was also designed to regulate commerce by requiring testing and imposing restrictions on certain chemical substances. The TSCA requirements apply to all manufacturers, exporters, importers, processors, distributors, and disposers of chemical substances in the United States.

Controls The TSCA inventory (a list of 70,000 toxic chemicals) was established to record all products manufactured, imported, sold, processed, or used for commercial purposes. Exemptions include R&D chemicals and by-products without commercial purpose. The TSCA also controls premanufacture review of new chemical substances, risk assessment by testing and information gathering, recordkeeping and reporting on health and environmental effects associated with chemical substances, and restrictions on known hazardous chemicals. The Toxic Substances Control Act establishes severe penalties for those who break the law. Currently, yearly penalties for violations are estimated at more than $40 million. The EPA is the primary agency charged with enforcing toxic substance control. 337

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15.5 Emergency Response In an industrial environment, responding to an emergency is done according to a specific set of standards. Emergency response drills are carefully planned and include preparations for worstcase scenarios: for example, vapor releases, chemical spills, explosions, fires, equipment failure, hurricane, high winds, loss of power, and bomb threats or actual bombings. Programs such as Community Awareness and Emergency Response (CAER) are designed to work with the community while industry utilizes and implements:

• • • •

Action plans Emergency response coordinators and teams Site-specific drills Incident reports

15.6 Community Right-to-Know The community right-to-know principle holds that a community should be aware of the chemicals manufactured or used by local chemical plants and business. Legislation, regulations, and programs based on this principle are intended to involve the community in emergency response plans, improve communication and understanding between industry and the surrounding community, improve local emergency response planning, and identify potential hazards. The Comprehensive Environmental Response Compensation and Liability Act (CERCLA) holds generators and disposers of hazardous waste liable for past practices, and established the “Superfund” of $1.6 billion to pay for cleanup operations at abandoned hazardous waste sites. It also mandated that the public be informed of these sites and the known hazards. Community rightto-know and CAER programs work with CERCLA to protect the community. The following employ the community right-to-know principle: • CERCLA • Emergency planning and community right-to-know programs • Superfund Amendments and Reauthorization Act (SARA) • Hazard Communication Act (HAZCOM) • OSHA Hazard Communication Act (OSHA HAZCOM) • Material Safety Data Sheets (MSDSs) Agencies involved include: • Department of Health • State water commission • U.S. Environmental Protection Agency The goal of all these laws and programs is, very simply, to protect citizens.

Quality Standards Industry believes that reducing and recycling wastes at their source are the first priority of responsible waste management. Industry has put in place environmental management systems 338

Summary to make, use, handle, and dispose of its products safely. Industry is committed to making major expenditures in environmental technology to reduce emissions and protect the environment.

Summary Air pollution is the contamination of the air, especially by industrial waste gases, fuel exhausts, and smoke. Water pollution is the contamination of the water, especially by industrial wastes. Solid waste is a by-product of modern technology and is technically defined as a discarded solid, liquid, or containerized gas. This definition includes materials that have been recycled or abandoned through disposal, burning or incineration, accumulation, storage, or treatment. In an industrial environment, responding to an emergency is done according to a specific set of standards. Emergency response drills include practice for worst-case scenarios. Legislation, regulations, and programs based on the community right-to-know principle are intended to increase community awareness of the chemicals manufactured or used by local chemical plants and business, involve the community in emergency response plans, improve communication and understanding, improve local emergency response planning, and identify potential hazards. The purpose of the Resource Conservation and Recovery Act, enacted in 1976, is to protect human health and the environment and to conserve our country’s natural resources by regulating all aspects of hazardous waste management, including generation, storage, treatment, and disposal. This concept is referred to as “cradle to grave” management. The Toxic Substances Control Act, a federal law enacted in 1976, was intended to protect human health and the environment. The TSCA was also designed to regulate commerce by requiring testing and imposing restrictions on certain chemical substances. The TSCA requirements apply to all manufacturers, exporters, importers, processors, distributors, and disposers of chemical substances in the United States.

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Chapter 15 Review Questions 1. Solid waste is technically defined as: a. a discarded solid, liquid, or containerized gas. b. materials recycled or abandoned through disposal, burning (incineration), accumulation, storage, or treatment. c. a material composed of 2% hydrocarbons. d. a and b. 2. The community right-to-know principle: (select all correct responses) a. increases community awareness of the chemicals manufactured or used by local chemical plants and business. b. identifies potential hazards. c. improves communication and understanding. d. improves local emergency response planning. e. involves the community in emergency response plans. 3. The purpose of the RCRA is to protect: a. human health and the environment. b. industrial equipment. c. industrial manufacturers from liability lawsuits. d. a and c. 4. “Cradle to grave” is part of which act? a. Resource Conservation and Recovery Act b. Clean Air Act c. Clean Water Act d. Toxic Substances Control Act 5. Smoking flares in excess of _________ minutes should be reported. a. 3 b. 10 c. 5 d. none of these 6. Vapor releases, chemical spills, explosions, fires, equipment failures, hurricanes, high winds, loss of power, and bomb threats fall under which main program? 7. What must be obtained for any project that has the possibility of producing air pollutants?

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Quality Control After studying this chapter, the student will be able to: • Define quality control principles and terms. • Describe the principles of continuous quality improvement. • Explain the four phases of the quality improvement cycle (plan, observe and analyze, learn, and act). • Describe the supplier-customer relationship. • Identify and describe quality tools used in the industry. • Describe statistical process control. • Use flowcharts, run charts, cause-and-effect (fishbone) diagrams, and Pareto charts. • Describe planned experimentation. • Explain and use histograms or frequency plots. • Describe forms for collecting data. • Describe scatter plots.

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Key Terms Cause-and-effect (C&E) diagram (fishbone diagram)—a method for summarizing available knowledge about the causes of process variation. Control charts (SPC charts)—statistical tools used to determine and control process variations. Flowchart—a picture of the activities that take place in a process. Forms for collecting data—can vary from notes jotted down on a napkin to complex, preprinted documentation tools. Histogram (frequency plot)—a graphical tool used to understand variability. The chart is constructed with a block of data separated into 5 to 12 bars or sections from low number to high number. The vertical axis is the frequency and the horizontal axis is the “scale of characteristics.” The finished chart resembles a bell if the data is in control. Improvement cycle—a four-phase system for quality improvement: plan, observe and analyze, learn, and act. Pareto chart—a simple bar graph with classifications along the horizontal and vertical axes. The vertical axis is usually the number of occurrences, cost, or time. The horizontal axis orders the bars from the most frequent to the least frequent. Planned experimentation—a tool used to test and implement changes to a process (aimed at reducing variation) and to understand the causes of variation (process problems). Run chart—a graphical record of a process variable measured over time. Scatter plot—chart used to indicate relationships between two variables or pairs of data. Statistical process control (SPC)—statistical control methodology applied to a process.

16.1 Principles of Continuous Quality Improvement This section discusses the technology that provides the foundation for quality improvement. Process technicians use this technology as a valuable component of the continuous quality improvement team. The principles of continuous quality improvement include: • Innovate and improve services, products, and processes • Integrate suppliers and customers into the quality process • Use quality tools – Statistical process control – Flowcharts – Cause-and-effect diagrams (fishbone diagrams) – Pareto charts – Run charts – Control charts – Planned experimentation 342

16.2 Quality Improvement Cycle

• • • •

– Histograms or frequency plots – Forms for collecting data – Scatter plots Audit and evaluate Provide continuous quality improvement training to all employees Make an unrelenting commitment to quality and involve all levels in the organization Document what you do, and do what you say

16.2 Quality Improvement Cycle The quality improvement cycle consists of four phases that are continuously re-implemented: plan, observe and analyze, learn, and act (Figure 16–1).

Phase 1: Plan The first step in the improvement cycle is to increase current knowledge of the process. The more the team knows about the process, the more likely it is that changes submitted by the team will improve quality. Phase 1 takes a significant amount of time to complete. The planning phase should address specific objectives and questions, make predictions, and propose a plan for testing. At the conclusion of Phase 1, the plan that is developed should consider methods, resources, schedules, and people.

Phase 2: Observe and Analyze Phase 2 implements the data collection process. The data collected is used to address the questions from Phase 1. Data analysis can reveal what is actually happening, and lead to refinement of or changes in the initial questions in Phase 3.

Phase 3: Learn This phase combines Phase 1 and Phase 2 activities. The results of the data analysis are compared to current knowledge and theories to see if contradictions exist.

Phase 4: Act The results from Phase 3 are used to decide whether a change to the process is required. If a change is required, a modified brainstorming session should be conducted to determine what changes to the process would result in improvement. These changes should be stated clearly.

ACT Phase 4 Phase 3

LEARN

PLAN Phase 1 Phase 2

OBSERVE and ANALYZE

Figure 16–1 Improvement Cycle 343

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16.3 Supplier-Customer Relationship Industrial manufacturers buy raw materials from suppliers to make products for their customers. Companies depend on suppliers to provide them with quality raw materials. Customers depend on companies to provide them with quality products. In today’s global economy, a new relationship exists between suppliers, companies, and customers. Each is dependent on the other for financial success. Companies are becoming more and more involved with customers and suppliers. Both raw materials and products are tracked from inception. Documentation, quality charts, and external audits follow products and raw materials from cradle to grave. Customers are providing more information about their needs to companies.

16.4 Quality Tools Process operators use a number of analytical quality tools to perform their jobs, including: • Flowcharts • Cause-and-effect diagrams (fishbone diagrams) • Pareto charts • Run charts • Control charts • Planned experimentation • Histograms or frequency plots • Forms for collecting data • Scatter plots

16.5 Statistical Process Control Statistical process control (SPC) is a quality tool based on the principles of statistical mathematics and applied to a process to control product quality. The theory of SPC is based on some complex mathematics, but you need not be a mathematician to understand how to use the system. In any process, a certain amount of variability occurs. Variability is defined as the tendency to vary or change. For example, process equipment does not heat up to 450.5⬚F and stay at exactly 450.5⬚F. Instead, it tends to move a bit lower and higher. These variations occur with temperature, pressure, flows, and levels. Each process has its own variability and ability to tolerate change. SPC identifies this variability and enhances an operator’s ability to control the process by setting limits on the variability. In the past, operators would adjust their equipment based on current readings. If the reading is taken when the normal variation of a process is in a low cycle, the operator’s adjustment will swing the process variable high. Adjustments made without SPC methodology tend to create or exaggerate these natural high and low swings. Customers identify the key target setpoints for the products they require. In-house engineers identify other process variables, such as temperatures, flows, levels, and pressures, that support the ability of the process to produce the desired products. SPC allows normal equipment and process fluctuations to be considered over a longer period of time. To warrant adjustment, sample results must demonstrate a downward or upward trend away from the key target setpoints. 344

16.5 Statistical Process Control

Product Directives Most companies use a product directive or recipe for each product they make. Product directives detail operating parameters and control points such as:

• • • • •

Correct feed Temperature and pressure profile Equipment speed Additive setpoint Level and flow setpoints

Sample Types Raw materials normally are sampled before and during a process run. However, when troubleshooting problems, it is advisable to catch samples frequently.

Additives. Additives are sampled for purity and conformation to specifications when received at the warehouse. When troubleshooting control problems, additional samples are taken (caught) from containers being used at the time problems occurred. Products. Products are sampled for customer specifications. Sampling is performed to confirm that the process is in control, but sample results also can be a flag for unseen problems. Typical Sample Tag. A blue tag is used for samples to be processed by the laboratory according to the usual procedures. A green tag indicates to the laboratory that this sample should be given high priority. Figure 16–2 shows sample tags. PT774-0001

PLASTICS UNIT

549-7200A

FINISHING SAMPLE Date Time Extruder Grade Submitted by Lot # TEST

HIGH PRIORITY START-UP SAMPLE

REASON FOR PRIORITY

Results

MFR Color PPG Calcium Stearate BHT Ir-1010 Ultranox 626

SAMPLE TIME

DATE

GRADE CHANGE

CHANGE OF FEED

EXTRUDER START UP

OTHER (LIST BELOW)

GRADE

EXTRUDER

SUBMITTED BY

TEST MELT FLOW RATE @

PU AND CPL TO RECORD SEPARATELY

C

230

TIME SAMPLE IN LAB TIME RESULTS RELEASED

Remarks Remarks

Blue (Normal) Sample Tag

Green (High Priority) Sample Tag

Figure 16–2 Sample Tags 345

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Quality Control EXTRUDER GRADE DATE LOT TIME VALUE

PP0001 2/20/98 99546789 16 2.2

3r 2r r x -r -2r -3r

2.5 QUALITY LIMITS

1.8

18 2.11

20 2.2

22 2.17

0

R 0.156

3r 2r r QUALITY x LIMITS -r -2r 0.083 -3r PELLET SIZE COLOR TEST BIN REC BLENDER

4

6

8

10

= 2.36 = 2.29 = 2.22 = 2.15 = 2.08 = 2.01 = 1.94

VALUE 0.167

2

0.120

0.120 0.116 0.156

KEY ADDITIVE- IR-1010 0.134

= 0.143 = 0.137 = 0.131 = 0.125 = 0.119 = 0.113 = 0.107 35 MIN 2 MAX

#1

3-301

COMMENTS: #1 No apparent assignable cause; made no adjustment (possibly end of mix—higher concentration of IR-1010?)

COMPOSITES RESULTS DATE/TIME

MFR

ADDITIVE

Figure 16–3 Quality Control Run Chart (Melt Flow Rate)

Control Charts Statistical process control charts (SPC charts) are used to plot quality parameter points from samples taken at different times during a run. Even if all of the points are within specifications, when they are plotted on a graph you may see quite clearly that there is a trend that in time will result in off-specification material unless an adjustment is made. An upset or out-of-control situation is both vividly revealed and documented by such a chart (see Figure 16–3).

SPC Guidelines SPC guidelines account for normal process deviations and process upsets. (See Figure 16–4.)

16.6 Flowcharts A flowchart is a picture of the key activities that take place in a process (Figure 16–5). Flowcharts describe how the process is actually working today. One of the common mistakes people make when flowcharting is to add too much information to the chart. Flowcharts should include action or step boxes and yes/no decision diamonds.

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16.6 Flowcharts Evaluation

Action

Seven in a row on one side of the target.

Action is usually a small setpoint change. Usually indicates a process shift. Using the average of the last two results, adjust according to the product directive.

Three results in a row or three out of four results The three-out-of-four case scenario keeps one above yellow (+1 sigma) or below yellow isolated plot point from upsetting the process. (-1 sigma). Using the average of the last two results, make adjustments according to the product directive. Two results in a row or two out of three results Using the average of the last two results, make above orange (+2 sigma) or below orange adjustments according to the product directive. (-2 sigma). One result above/below red (+3 or -3 sigma).

A red plot point requires immediate evaluation. Check process trends to see if a significant step change occurred. If a shift in the normal process is identified, make adjustments according to the product directive. If the change does not look reasonable (no visible change in operating conditions), resample and send a green tag to the laboratory. If the green tag result is in control, disregard the questionable result and follow normal procedures. If the resample confirms the previous result, take the appropriate action and resample after 30 minutes. If the green tag result is above quality limits, divert to off test until the process is back in control.

One result crosses 4 sigma lines.

A four-sigma jump requires immediate investigation. Check process trends to see if a significant step change occurred. If a shift in the normal process is identified, make (+3 or -3 sigma) product directive adjustments. If the change does not look reasonable (no visible change in operating conditions), resample and send a green tag to the laboratory. If the green tag result is in control, disregard the questionable result and follow normal procedures. If the resample confirms the previous result, take the appropriate action and resample after 30 minutes. If the green tag result is above quality limits, divert to off test until the process is back in control.

Figure 16–4 Statistical Process Control Guidelines

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Activities in Process

Start Distillation System

Start Feed System

Decision

Take Samples

Good

Activities in Process

Start Pre-Heat System

Line-up Column

Decision

Take Samples

Send To Column #2

Fill Tank

Hold-up Re-Test

Bad Line-up Side Stream

Pre-Heat Feed

Line-up Bottom

Decision

Take Samples

Hold-up Re-Test

? Bad Good Go to Product Tank

Decision

Hold

To Customers (END)

Line-up Overhead

Move to Reactor System

Add Chemical XXX

Make Correction

To Storage

Take Samples

Bad

Hold-up Re-Test

Good Bad Good

Figure 16–5 Flowchart

16.7 Run Charts One of the quality tools most commonly used in industry is a run chart (Figure 16–6). Run charts are very powerful tools that show a graphical record of a process variable measured over time. The following steps should be used when building a run chart:

• • •

Estimate the expected range of data points. Develop a vertical scale for the data that uses 50% to 70% of the overall range so the chart is not too narrow or too wide. Plot the data over time.

16.8 Cause-and-Effect (Fishbone) Diagrams Another important quality tool is a cause-and-effect (C&E) diagram, also called a fishbone diagram (Figure 16–7). Cause-and-effect diagrams organize the causes of variation into general 348

16.8 Cause-and-Effect (Fishbone)

250 240 200 Target 180 0.160 0.140 0.120 0.100

Time

Figure 16–6 Run Chart

PROCEDURES (METHODS)

FEEDSTOCK BAD (MATERIALS)

Feed concentration bad Training Product too pure Trainee Additive not available New job Warehouse delays Procedures Did not follow procedure Weekend Busy Wrong procedure PROBLEM Instrument air lost transmitter failed Equipment pump failed exchanger leak EQUIPMENT FAILURE (MACHINES)

Inattentive Tired Drugs Upset with Co-worker Angry with management Family problems

TECHNICIAN ERROR (PEOPLE)

Figure 16–7 Fishbone Diagram

categories: (1) methods, (2) materials, (3) equipment (machines), and (4) human. Each of these four sections summarizes available knowledge about the causes of process variation. C&E diagrams were developed by Kaoru Ishikawa in 1943. 349

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16.9 Pareto Charts A Pareto chart is a simple bar graph with classifications along the horizontal and vertical axes (Figure 16–8). The vertical axis is usually the number of occurrences, cost, or time. The horizontal axis orders the bars from the most frequent to the least frequent. This type of chart takes its name from a man named Vilfredo Pareto, who pioneered income distribution studies.

16.10 Planned Experimentation Planned experimentation is a tool used to test and implement changes to a process (aimed at reducing variation) and understand the causes of variation (process problems). (See Figure 16–9.) Global pressures are forcing organizations to meet customer needs, reduce costs, and improve

Number of Occurrences

B

A

C

F

H

D

E

G

I

J

L

K

Figure 16–8 Pareto Chart

R E S P O N S E

X

X

X X

X2

X3

X

X X

X1

TEST

X2 -

R E S P O N S E

X2 +

_

X1

X2 X3

X2 +

EFFECTS

Figure 16–9 Planned Experimentation 350

X3

16.12 Forms for Collecting Data productivity. Planned experimentation is part of the continuous improvement process. Principles for design and analysis of planned experiments include:

• • • • • •

designing new systems that vary from current practices developing and implementing change effective changes rate and extent of product improvement process improvement linking systems to change

The principles associated with planned experimentation require change, however, some changes do not improve the system. Questions generated by planned experimentation include:

• •

which single condition or parameter do we test first. how will we recognize if the change is correct.

Changes that create improvement require the use of statistical process experimentation and observation. This is of course followed up by analysis, design, development, implementation, and evaluation of the change or changes made.

16.11 Histograms or Frequency Plots Histograms or frequency plots are graphical tools used to understand variability (Figure 16–10). The chart is constructed with a block of data separated into 5 to 12 bars or sections from low number to high number. The vertical axis is the frequency and the horizontal axis is the “scale of characteristics.” The finished chart resembles a bell if the data is in control.

16.12 Forms for Collecting Data The forms used for data collection can range from notes jotted down on a napkin or scrap of paper to complex, preprinted checklists. Forms are very helpful in collecting and organizing raw data. Most operators carry around small notebooks to record information collected during routine rounds. Figure 16–11 shows a sample form for collecting data. 9

6 X X X X X

X X X X X X

X X X X X X X

50

54

58

Frequency 3

0

30

X

X X

X X X

34

38

42

X X X X 46

X X X X X X X X

X X X X X X X X X

X X X X X X X X

62

66

70

Scale of the Characteristic

Figure 16–10

Histograms 351

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Setpoint

Checklist Unit 1

Figure 16–11

Actual

Form for Collecting Data

Y

X

Figure 16–12

Scatter Plots

16.13 Scatter Plots Scatter plots are used to indicate relationships between two variables or pairs of data (Figure 16–12). The easiest way to determine if a cause-and-effect relationship exists between two variables is to use a scatterplot.Variables such as flow rate and temperature can be used in a scatter diagram. In this relationship, temperature may increase or decrease as flow rate fluctuates. This response would show up on a scatterplot diagram on the x- or y-axis.The independent variable is typically controllable, while the dependent variable is located on the opposite axis. The steps in setting up a scatterplot include collecting data in ordered pairs. The cause or independent variable and the effect or dependent variable are placed side-by-side in ordered pairs. A common example of this relationship can be found using miles per hour versus miles per gallon. By increasing the MPH and comparing it to MPG the scatterplot data can be collected. When placed on the chart it becomes clear that as MPH increase, MPG decreases.

Summary The principles of continuous quality improvement include innovation and improvement of services, products, and processes; integration of suppliers and customers into the quality process; use of quality tools; audit and evaluation; provision of continuous quality improvement training to all employees, unrelenting commitment to quality and involvement of all levels in the organization; and documentation. The four phases of quality improvement are plan, observe and analyze, learn, and act. The first step in the improvement cycle is to increase current knowledge of the process and develop a plan 352

Summary for improvement. Phase 2 implements the data collection process. In Phase 3, the results of the data analysis are compared to current knowledge to see if contradictions exist. In Phase 4, the results are used to decide whether a change to the process is required. Companies are becoming more and more involved with customers and suppliers. Both products and raw materials are tracked from cradle to grave. Customers are providing more information about their needs to companies. Process technicians use quality tools during normal operations. Statistical process control is a quality tool based on the principles of statistical mathematics. Control charts are used to plot quality parameter points from samples taken at different times during a run. A flowchart is a picture of the key activities that take place in a process and describes how the process actually works today. Run charts are powerful tools that show a graphical record of a process variable measured over time. Cause-and-effect diagrams organize the causes of variation into general categories: methods, materials, equipment, and human. Pareto charts, planned experimentation, forms for collecting data, and scatter plots are other tools used in quality improvement.

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Chapter 16 Review Questions 1. 2. 3. 4.

5.

6. 7.

8. 9. 10.

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List five quality tools. Describe the improvement cycle. What type of quality chart is a picture of activities that take place in a process? The principles of quality improvement include all of the following except: a. quality tools b. contingency perspective c. audits and evaluations d. innovation and improvement of services and products Which of the following is not a quality chart? a. control b. flow c. Pareto d. Gantt What do the initials SPC stand for? Which chart uses quality methodology to control a process? a. flow b. Pareto c. run d. SPC Name four charts that work with process variation. What is another name for a fishbone chart? Planned experimentation is: a. a tool used to test and implement changes in a process. b. a tool designed to reduce variation. c. a tool designed to help operators understand process variability. d. all of the above.

Process Troubleshooting After studying this chapter, the student will be able to: • • • • • • • • • • •

Describe the various troubleshooting methods. Identify and describe the various troubleshooting models. Describe how different variables affect each other. Explain how problems with process equipment affect other systems. Analyze process problems and provide solutions. Troubleshoot specific operational scenarios. Describe the varied instrumentation used to troubleshoot process problems. Distinguish between primary and secondary problems. Collect, organize, and analyze data. Respond to alarms and control systems that are outside operational guidelines. Compare troubleshooting methods and models.

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Key Terms Control loop—system consisting of a collection of instruments that work together to control pressure, temperature, level, flow, and analytical variables. Information from control loops is invaluable in the troubleshooting process. Equipment failure—occurrence when equipment has broken, ruptured, or is no longer responding to its design specifications. Fail open/fail closed—term used in troubleshooting that describes how a control valve ceases to work (fails): in the open or the closed position. Primary operational problem—term for the first issue (problem) that created a process upset. Process flow diagram (PFD)—graphic chart used in troubleshooting to quickly identify the primary flow path and the control instrumentation being used in the process. Process variables—changeable conditions (variables) that can be detected by instruments and that provide clues to what is occurring within the “big picture” of the entire process. Secondary operational problems—issues created or responded to during a process upset other than the primary problem. Troubleshooting methods—means of diagnosing process problems; include educational, instrumental, experiential, and scientific. Troubleshooting models—tools used to teach troubleshooting techniques. Basic models include distillation, reaction, and absorption and stripping, or combinations of these three.

17.1 Troubleshooting Methods Troubleshooting the operation of process equipment requires a good understanding of basic components and how the equipment operates. Equipment used in modern manufacturing is run 24 hours a day, 7 days a week, 52 weeks a year. Routine maintenance is performed on this equipment during scheduled maintenance times. Plants that build redundancy into their processes provide backup systems for critical equipment. For example, pumps and compressors typically have two or three backups. Process technicians should attempt to uncover as much information as possible about the equipment used in their units. Much of this information can be found in technical manuals or the operating manuals. Manufacturer information is typically included in the engineering specifications, drawings, and equipment descriptions. Data collection, organization, and analysis can be used to troubleshoot process problems. Checksheets are used to collect large quantities of data. This quantitative data can be organized into graphics or plotted as trends to discover process variation or changes. Data analysis utilizes a variety of quality techniques to put all of the parts in place. 356

17.1 Troubleshooting Methods A number of troubleshooting methods can be used with any of the troubleshooting models. Methods employed vary depending on the individual educational faculty, consultants, and industry. The basic approach to most methods includes the development of a good educational foundation.

Method One: Educational To do competent troubleshooting, a process technician should have: • Basic knowledge of the equipment and technology • Understanding of the math, physics, and chemistry associated with the equipment • Studied equipment arrangements in systems • Studied process control instrumentation • Operated equipment in complex arrangements • Studied troubleshooting of process problems Troubleshooting is a process that requires a wide array of skills and techniques. The primary goal is to control variables such as temperature, pressure, flow, level, and analytical variables. This requires the use of modern control instrumentation such as indicators, alarms, transmitters, controllers, control valves, transducers, analyzers, interlocks, and so on. With these instruments, it is possible to control large, complex processes from a single room. In these types of systems, process setpoints and process variables on controllers should be clearly related and reflect each other. Process problems are quickly identified when these two do not align. For example, if the flow rate is set at 200 gpm and the process variable is 175 gpm, a 25-gpm difference exists. This could indicate a serious problem.

Method Two: Instrumental The instrumental method of process troubleshooting involves: • Basic understanding of process control instrumentation • Basic understanding of the unit process flow plan • Advanced training in controller operation (PLC and DCS) • Knowledge of process-problem troubleshooting

Method Three: Experiential The experiential method of process troubleshooting involves: • Experience in operating specific equipment and systems • Familiarity with past problems and solutions • Ability to think “outside the box” (use creativity and imagination) • Critical thinking, especially in identifying and challenging assumptions • Evaluating, monitoring, measuring, and testing alternatives

Method Four: Scientific Scientific methods of process troubleshooting are grounded in principles of mathematics, physics, and chemistry; they apply scientific theory to operations. A scientific method:

• •

Requires a good understanding of equipment design and operation Views the problem from the outside in 357

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• •

Uses outside information and expertise and reflective thinking Generates alternatives, does brainstorming, and ranks alternatives

Troubleshooting Process Problems 1. In Figure 17–1, what will happen if P-104 fails and cannot be restarted? a. Steam flow will b. Bottom flow rate will Increase Increase Decrease Decrease Stay the same Stay the same c. Bottom temperature will Increase Decrease Stay the same

d. Bottom level will Increase Decrease Stay the same

The questions that are developed for troubleshooting scenarios can vary from equipment failure to instrument failure. Each of these simulated failures provides good experience for the new technician. Collecting and organizing these scenarios is a difficult process that takes time and effort. In Figure 17–1, the steam flow will increase, the bottom flow rate will decrease, the bottom temperature will decrease, and the bottom level will increase. Why?

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Figure 17–1 Basic Troubleshooting 1

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17.1 Troubleshooting Methods 2. In Figure 17–2, what will happen if the reflux control valve fails to close? a. Column pressure will b. Reflux flow rate will Increase Increase Decrease Decrease Stay the same Stay the same c. Column top temperature will Increase Decrease Stay the same

d. Level in D-100 will Increase Decrease Stay the same Flow Controller PV SP 400 OP% FIC 105

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Figure 17–2 Basic Troubleshooting 2

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In Figure 17–2, the column pressure will stay the same, the reflux flow rate will increase, the column top temperature will go down, and the level in D-100 will decrease. Technicians should study these problems and ask why a specific control loop responds in a certain way. Note that controllers in AUTO (automatic), MAN (manual), and Cascade modes will respond differently in operation.

Systematic Approach to Teaching Troubleshooting To troubleshoot effectively, a technician needs to know whether a control valve fails open (FO) or fails closed (FC). When an automated valve is installed in a unit or process, the engineers take into account whether that valve should fail open or fail closed. Each valve operates differently; for example, when a valve is designed to fail closed, a heavy spring causes the flow control element to move to the closed position. It takes instrument air to open the valve. A fail-closed valve would assume the following positions: Fail Closed (FC) 0%

Closed

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50%

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When a valve is designed to fail in the open position, like an emergency water system, the valve will respond as follows: Fail Open (FO) 0%

100% open

25%

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50%

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75%

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100%

closed

Figure 17–3 compares these two systems—fail open/fail closed—and illustrates how each works.

17.2 Troubleshooting Models One of the highest levels a process technician can achieve is the ability to clearly see the process and sequentially break down, identify, and resolve process problems. Process troubleshooting has traditionally been considered the domain of senior technicians; however, some people believe that successful techniques can be taught to all technicians. Experience has proven over time to be the best teacher on equipment that is manually operated, although new computer technology provides advanced control instrumentation that can be used to quickly and methodically track down process problems. It is well known that a single problem can have a cascading effect on all surrounding equipment and instrumentation. This phenomenon is commonly associated with primary and secondary operational problems. 360

17.2 Troubleshooting Models

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Troubleshooting models are literal, physical demonstrations of the equipment and systems presently being taught in community colleges and universities. Some of these models are the reaction model, the absorption and stripping model, the separation model, and the distillation model. These models are completely outfitted with alarms, analyzers, interlocks, permissives, video trends, recorders, and control instrumentation. Process problems can be simulated using these models. A good college curriculum includes the use of advanced computer system software that closely simulates console operations. Software companies like Advanced Training Resources (ATR®) are leading the way in the development of this type of software and computer systems. Some college 361

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training systems have modern control instrumentation mounted on operational pilot units. Students using these types of systems receive true hands-on experience. The 11 models used to teach process troubleshooting are: • Pump and tank model • Compressor model • Heat exchanger model • Cooling-tower model • Steam-generation model • Furnace model • Distillation model • Reaction model • Separation model • Absorption and stripping model • Combination of the preceding models These 11 models provide the hardware to which, or framework within which, the various troubleshooting methodologies are applied. Each model has a complete set of process control instrumentation and equipment arrangements. A complete range of troubleshooting scenarios has been developed for educators and typically accompanies these models. It should be noted that these models are only the more common used by educators. Many other models can be used, depending upon the background and experience of the educators and the resources available to the educational program or facility.

17.3 Basic Equipment Troubleshooting Troubleshooting the operation of process equipment requires a good understanding of basic components and how the equipment operates. Knowledge of the routine maintenance schedule, the redundancies built into the process, and the location of information about the process is essential for effective troubleshooting. Data collection, organization, and analysis are equally important parts of troubleshooting process problems. Process flow diagrams (PFDs) are used to quickly identify the primary flow path and the control instrumentation being used in the process. Checksheets are used to collect data that can be graphically organized or charted to show trends and reveal process variation or changes. Data analysis utilizes a variety of quality techniques to pinpoint process problems and potential issues.

17.4 Process Control Instrumentation Figure 17–4 shows process control instrumentation being used to control each process variable on a column. The level in the bottom of the column and the overhead accumulator must be controlled at 50%. The thermosyphon reboiler maintains the energy balance on the column at a set temperature. The bottom and the top temperatures form a gradient. Flow to the column and reflux lines allows the system to operate in automatic mode. Pressure is held at specified values on the 362

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Figure 17–4 Control Loops

overhead accumulator. This has an effect on the entire distillation column even though pressures and temperatures will vary slightly throughout the column. Figure 17–4 shows how all of these control loops would be located in the system. Process technicians can monitor the response of these systems from the control console. The various types of instruments and control loops allow process technicians to operate larger and more complex processes.

17.5 Pump Model The primary purpose of a pump system is to move a product from one place to another. Moving liquids is a common practice in the chemical processing industry, and new process technicians are given detailed instruction on the basic components found in a pump system. This includes 363

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training in the basic types of pumps and their individual components, types of valves and components, piping, various tanks and vessels, and heat exchanger identification. Unfortunately, it is far more difficult to teach apprentice technicians how to perform complex pump line-ups, troubleshoot pump problems, switch pumps on the fly, change line-ups while the pump is on line, and identify potential problems from operational data. Using the pump model as a training tool, a college professor has a much larger platform to work from. The basic equipment components found in a pump system include: • Two pumps—one primary and one backup • Piping and valves • Feed tank • Process control instrumentation—control loops, analyzers, instruments Figure 17–5 shows the basic components of a pump model. A variety of troubleshooting scenarios can be applied to this simple model.Variations depend on the instructor’s experience and questions generated by the students.

closed

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17.7 Heat Exchanger Model

17.6 Compressor Model The compressor system is critical to modern process control. Air systems provide clean, dry air that is used to open valves and control the flow rate of liquids and gases in the process industry. Compressors are also used to transfer nitrogen, hydrogen, argon, natural gas and other hydrocarbon gases, chlorine, carbon monoxide, carbon dioxide, helium, pure oxygen, and many other specialty gases. In the plastics industry, compressors are critical in the transfer of solids, such as granules, flakes, powder, and additives. The primary purpose of a compressor is to compress gases to create energy to transfer the gas from one place to another. Apprentice technicians typically study the various compressors found in industry and should be able to identify critical components. Included in this study are discussions on the scientific principles associated with the operation of a compressor, however, operating a compressor system is a much more complex undertaking. Very few colleges actually have a complete compressor system on which each apprentice technician has an opportunity to train and qualify for start-up, maintenance, data collection, troubleshooting, and shutdown. This is a gap in the system, but the troubleshooting model allows instructors some flexibility to discuss and illustrate operational techniques. The basic equipment components found in a compressor model include: • Compressor and receiver • Piping and valves • Dryers • Process control instrumentation Figure 17–6 shows the basic components of a compressor model. A variety of troubleshooting scenarios can be applied to this simple model. Variations depend on the instructor’s experience and questions generated by the students.

17.7 Heat Exchanger Model The primary purpose of heat exchangers in the chemical processing industry is to heat or cool process flows. Heat energy flows from hotter areas to colder areas and moves via conductive and convective heat transfer. A shell-and-tube heat exchanger has a cylindrical shell that surrounds a tube bundle. Fluid flow through the exchanger is referred to as either tube-side flow or shell-side flow. A series of baffles supports the tubes, directs flow, decreases tube vibration, increases velocity, creates pressure drops, and protects the tubes. This enhances the heat transfer process. Differences in baffle arrangement produce a variety of fluid flow patterns, mostly turbulent. Fluid flow in heat exchangers is often described as cross flow, counter flow, or parallel flow. Heat exchangers are used in almost every process facility. Heat exchangers are classified as: • Shell-and-tube – pipe-coil – double-pipe – hair-pin

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Figure 17–6 Compressor Model

– – – – • • •

fixed-head or floating-head single-pass or multipass u-tube reboilers—thermosyphon or kettle Plate and frame Spiral Air-cooled (fin fans)

Process technicians carefully review the various designs and components associated with heat exchanger systems. Work with heat exchangers carries serious responsibilities, because an incorrectly aligned heat exchanger can turn into a bomb. Most college programs spend significant time working with apprentice technicians as a group; unfortunately, individual, one-on-one, hands-on training is not possible. However, the heat exchanger model allows college professors to individually review and evaluate apprentice technicians on complex line-ups and troubleshooting scenarios. 366

17.8 Cooling-Tower Model The key scientific principles associated with the operation of a heat exchanger system include: • Temperature—preheat, condenser, reboiler, conversions • Heat transfer—conductive, convective • Tube growth—expansion • Pressure—delta, inlet, outlet • Fouling • Boiling points • pH of water • Fluid flow—turbulent, laminar, parallel, cross-flow, counter-flow • Flow rates • Electricity for pumps and instruments • Modern process control • Chemical properties The primary equipment components in a heat exchanger system include: • Multiple pumps—shell inflows and shell outflows • Piping and valves • One or two heat exchangers • Process control instrumentation Figure 17–7 shows the basic components of a heat exchanger model. A variety of troubleshooting scenarios can be applied to this simple model. Variations depend on the instructor’s experience and questions generated by the students.

17.8 Cooling-Tower Model The primary purpose of a cooling tower is to cool water. This accomplished primarily through evaporation or convective heat transfer. As water is pumped into the plant, it picks up heat energy. Hot water is routed to the cooling tower so that it can be cooled and returned to the operating units. Cooling towers are classified by how they produce airflow, and how they produce airflow in relation to the downward flow of water. A cooling tower can produce airflow mechanically or naturally. After airflow enters the cooling tower, it can cross the downward flow of water or run counter to the downward flow of water. Cooling towers are classified as: • Atmospheric-draft • Natural-draft • Forced-draft, counter-flow • Induced-draft, cross-flow The key scientific principles associated with the operation of a cooling tower include: • Evaporation • Heat transfer and temperature • Relative humidity • pH of water • Fluid flow of water and air • Parts per million (ppm) and coagulants—water quality 367

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Figure 17–7 Heat Exchanger Model

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• • • • •

Pressure Biocides and algaecides—prevent biological growth Draft—induced, forced, atmospheric, natural Electricity Modern process control

The study of cooling towers takes place primarily in the classroom. Students focus on the different designs and various components found there. Hands-on experience is difficult to come by in the college instructional setting. Some classrooms have small models that have been automated for process control; however, this is the exception to the rule. Most college systems have small cooling towers that are used with the temperature control systems. Students are allowed to view and tour these devices, but it is not possible for students to operate these devices because they are in operational service. For this reason, the cooling-tower model offers students and professors opportunities to memorize start-up procedures and setpoints, operate the model, and troubleshoot process problems. The scope of the instruction on troubleshooting coolingtower processes is limited only by the time allowed to cover the topic and the background of the faculty. It should be noted that a cooling-tower system includes a number of inherent safety hazards, including hot water, chemical additives, slipping hazards, rotating equipment, and electrical hazards. The basic components of a cooling tower include: • Concrete water basin • Splash bars or fill • Pump • Make-up water • Water distribution system • Air louvers • Drift eliminators • Support structure—plastic or pressure-treated • Fan and motor (optional) • Piping • Heat exchangers • Hot-water return header • Blow-down • Chemical additive controls • Modern process control instrumentation and control loops Figure 17–8 shows the basic components of a cooling-tower model. A variety of troubleshooting scenarios can be applied to this simple model. Variations depend on the instructor’s experience and questions generated by the students.

17.9 Boiler Model A steam-generation system is a complex arrangement of equipment and subsystems designed to produce clean, dry steam for industrial applications. The industrial steam produced from boilers

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Figure 17–8 Cooling-Tower Model

has hundreds of applications in the processing industry. Steam is typically produced in high, medium, and low pressures. When the burners are lit in a boiler, hot combustion gases begin to flow over the steam-generating tubes, riser tubes, downcomer tubes, and drums. Radiant, conductive, and convective heat transfer begins to take place. Hot combustion gases flow out of the firebox, into the economizer section, and out the stack. Fans provide airflow through the furnace, creating a negative draft. (Because the furnace is hotter than the outside air, significant density differences exist.) Water temperature increases at controlled rates as pressure builds inside the large upper steam generating drum. As the temperature of the water inside the generating and riser tubes increases, the density of water decreases and natural circulation is established. Bubbles form, break loose, and rise through the tubes, picking up additional heat energy through kinetic motion, conduction, and radiant heat transfer. When the pressure increases to slightly above the system pressure setpoint, steam will flow to the header. Inside the upper steamgenerating drum, steam and water come into physical contact, saturating the steam. This wet steam exits the steam drum and is directed through tubes back into the furnace where the temperature is significantly increased. This process, called superheating, dries out the steam and increases the pressure. The relationship between steam pressure and temperature can be found in a steam table.

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17.10 Furnace Model A number of hazards are associated with the operation of a boiler system. Some of these hazards include:

• • • • • • • • • • • •

Hazards associated with high temperature steam, “burns” Hazards associated with using natural gas Hazards associated with leaks Instrument failures Confined Space Entry permit Opening blinding permits Isolation of Hazardous Energy permit “Lock-out, Tag-out” Routine work Hazards associated with lighting burners Exceeding boiler temperatures or pressures Hazards associated with using water treatment chemicals Error with valve line up resulting in explosion or fire

Many other potential hazards exist beyond those in the preceding list; this is why careful training is required for all new technicians assigned to utilities. The focus in the classroom is on the various types of steam-generation systems and the hundreds of components that make up any steamgeneration system. College faculty use videotapes and other instructional materials, and conduct plant tours to show students what these systems look like. Unfortunately, the same problem that exists with the other major areas exists with steam-generating systems as well: Hands-on opportunities are rare and limited and are not available to all of the students in the program. The boiler model offers a systematic approach to learning that gives apprentice technicians and faculty the opportunity to discuss the very complex operational and troubleshooting scenarios that arise with a steam-generating system. Figure 17–9 shows the basic components of a steam-generation (boiler) model. A variety of troubleshooting scenarios can be applied to this simple model. Variations depend on faculty experience and questions generated by apprentice technicians.

17.10 Furnace Model A furnace, or fired heater, is a device used to heat up chemicals or chemical mixtures. Furnaces consist essentially of a battery of fluid-filled tubes that pass through a heated oven. These devices provide a critical function in the daily operation of the chemical processing industry. Process heaters are more technically defined as combustion devices designed to transfer convective and radiant heat energy to chemicals or chemical mixtures.These heaters are typically associated with reactors or distillation systems. Process heaters come in a wide variety of shapes and designs, but the basic styles include cabin, box, and cylindrical.The various parts of a process heater include a radiant section and burners, a bridgewall section, a convection section and shock bank, and a stack with damper control. Modern control instrumentation is used to maintain these rather large and elaborate systems. The primary means of heat transfer in a fired heater are radiant, conduction, and convection. Radiant heat transfer accounts for 60% to 70% of the total heat energy picked up by the charge in the furnace. Convective heat transfer accounts for about 30% to 40% of the total heat energy

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Figure 17–9 Steam-Generation (Boiler) Model picked up in the furnace. Conductive heat transfer processes occur in each of these areas; however, it is easier to measure temperature differences in the actual charge than to calculate the conductive heat transfer coefficients. For heat transfer in the firebox or radiant section, the greatest efficiency is obtained when maximum furnace temperatures are achieved. Decreasing excess air in the furnace maximizes radiant heat transfer. Therefore, controlling excess oxygen in the furnace is the single most important variable affecting efficiency. Excess airflow will decrease furnace temperatures around the burners and force the automatic controls to increase natural-gas flow rates to the burner, wasting supplies and money. As hot combustion gases rise, cooler air is entrained, causing the temperature to decrease. Excess air enhances this process. When excess air enters the burner through the primary and secondary air registers, a temperature shift occurs as heat is moved away from the burners. Higher temperatures are created in the upper section of the firebox due to the reduced heat transfer in the lower section. Temperatures in the convection section and stack will also rise significantly. This will reduce the amount of heat available for heating the hot oil and more fuel will have to be burned to maintain process specifications. The basic components of a furnace system include: • Firebox and refractory material • Radiant and convection tubes • Soot blower 372

17.10 Furnace Model

• • • • • • • • • • • •

Stack damper Burners Bridgewall section Fuel system Forced-draft process heater Shell Radiant section Convection section Stack Fans Primary and secondary air Advanced process control instrumentation and control loops

Figure 17–10 shows the basic components of a furnace model. A variety of troubleshooting scenarios can be applied to this simple model. Variations depend on faculty experience and questions generated by apprentice technicians.

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Slight Negative

Pi

Hi 365ºF Low 335ºF

BA

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AT 25% SP PV OP% 25%

PA

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-.05

TV AV

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TV 800 gpm AV

Cu Ft/min

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AIC I

I

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low NOx Burner

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TR

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I

TV AV

I

o

I

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TV 0.5 in H2O AV

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I PT FC

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Figure 17–10

P

PIC Steam

SP 35 PSIG PV 0% OP%

FT

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Furnace Model 373

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17.11 Reactor Model The purpose of a reactor is to make, break, or make and break chemical bonds to form new products. A reactor is a vessel in which a controlled chemical reaction takes place. The things that have an effect on a chemical reaction are called reaction variables. The design and operation of a reactor enhance molecular contact between four reactants: pentane, butane, liquid catalyst, and solvent. Feed to the reactor is controlled at 36.5 gpm. The composition of feed from the column is 38% liquid catalyst, 61% butane, and 1% pentane. Solvent feed to the reactor is controlled at 68 gpm. The materials in the reactor are chilled to 120⬚F at 85 psig. The reactants are designed to form a new product with an excess of pure butane. The concentration of reactants in the reactor has a major effect on how fast the reaction will take place, what products will be produced, and how much heat will have to be added to or taken away from the reaction. A separator is used to remove the new products and isolate the butane for storage. The reactor model (Figure 17–11) provides a framework on which to develop a series of troubleshooting scenarios. Problems presented develop from simple to complex as students learn one section and move to the next. Educators use this model to teach one part of a much larger process; it is possible to create a multiprocess plant within the walls of the classroom to be used for study. Troubleshooting a reactor system requires the student to become familiar with the typical operation of the unit. As equipment and instrumentation fails, the student sees the cascading effect a single problem can have on the unit. A single problem can create a series of other problems, so students must learn to identify the primary problem that started the system failure(s). Some of the scientific principles associated with the operation of a stirred reactor include: • Pressure • Heat transfer and temperatures • Fundamental chemistry • Chemical reactions and chemical bonds – exothermic, endothermic, replacement, neutralization – chemical equations – mass relationships • Fluid flow – controlled flow rates of solvent, reactants, catalysts, and products • Mixtures, compounds, solutions • Agitation • Catalysts • Electricity—motors and instrumentation • Modern process control Process variable alarms can be activated by analytical (composition), pressure, temperature, flow, level, and time variables. Rotational speed on the agitator may be fixed or variable. A series of interlocks, permissives, and alarms will engage during operation and will provide a support network for the technician. A series of process video trends will be displayed to track each of the critical variables. Samples are taken frequently to ensure product quality. Stirred reactors are connected to off-specification (off-test) systems that allow flexibility in switching between prime and off-test 374

17.11 Reactor Model SP 85 psig PV 85 psig OP% 25% Hi-100psig

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Lo-110ºF

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AT

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To Separator 104.5 GPM

Figure 17–11

Reactor Model

operations. An automatic shutdown allows a technician to push one button and shut down the system in the event of a runaway reaction or emergency. The reactor has a stainless-steel shell designed to withstand temperatures in excess of 500 psig at 650⬚F. A dimpled water jacket is used to maintain the temperature at 120⬚F to maximize reaction rates. Product agitation is maintained by a mixer at 250 rpm. The composition of the feed to the reactor is 1% pentane, 38% liquid catalyst, and 61% butane. A solvent (toluene, C7H8) is introduced to the reactor and blended with the column feed. Unlike other processes, the solvent 375

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(toluene) and liquid catalyst react with the butane and pentane to form a new product that is separated in the separator. The liquid catalyst enhances the separation of butane and pentane in the column and is easily separated on a tray; however, once the liquid catalyst is exposed to the butane and pentane feed, it is slightly modified at the molecular level. The operating conditions in the reactor also promote this process. The agitation process in the reactor is a critical variable responsible for the reaction that forms a new product. Problems associated with operation of a reactor include: • Feed composition changes • Concentration increase—increases reaction factors • Agitation problems—will reduce reaction • Loss of cooling water—temperature will increase • Loss of level control • Instrument problems • Loss of pressure control—increase or decrease • Reaction time in reactor—reaction incomplete • Column and solvent flow rates • Temperature increase—doubles reaction rate for every 10⬚C increase • Loss of catalyst—reaction will stop

17.12 Absorption and Stripping Model The absorption and stripping model (Figure 17–12) uses two plate distillation columns to separate vaporized catalyst and return it to the reactor. This feedstock is a vapor by-product of the stirred reactor. An absorbent enters the top of the absorption column and flows down through the trays, becoming rich in catalyst. This enriched material is pumped out of the bottom of the absorber and into the stripping column. The stripper separates the catalyst and absorbent as the vaporized catalyst moves up the column and out to the reactor system. The lean absorbent is pumped out of the bottom of the stripper and into the top of the absorption column. The physical properties of the absorbent allow it to gently tug the catalysts out of the absorber and then release them when exposed to higher temperatures in the stripper. Catalyst-free waste gases flow out the top of the absorber and into the vapor recovery system. The purpose of the absorption and stripping model is to illustrate to apprentice technicians how distillation columns can be used to separate a specific component and feed it back into the system. The principles of distillation can be used in a varaiety of ways. The basic components of the absorption and stripping model include:

• • • • • • • • • 376

Distillation column used for absorption Distillation column used for stripping Two heat exchangers for cooling Two heat exchangers for heating Stirred reactor Four pumps Modern process control instrumentation Vapor recovery system and flare Separator

17.13 Distillation Model

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Absorbent

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AT To Separator 1. Product 2. Waste 3. Catalyst

Figure 17–12

Absorption and Stripping Model

17.13 Distillation Model Distillation is a method used to separate chemical substances in a boiling mixture based upon individual variations in the volatilities of those substances. Distillation is used to separate crude oil into various fractions; separate salt from water; separate oxygen, nitrogen, and argon from air; and distill beverages for higher alcohol content. A variety of distillation models can be used with the various troubleshooting methods. A distillation system includes a well-defined feed system, an overhead system, a bottom system, and a column system overview. Plate columns and packed columns offer a different variety of process troubleshooting scenarios. In Figure 17–13, a binary mixture is heated and sent to an eight-tray distillation column. The feed system uses a flow control, 377

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Figure 17–13

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Distillation Model

P

17.14 Separation Model temperature control, and primary-variable indicators. Changes can be made to one or more of these variables and observations recorded by individual learners. Software from a number of companies supports these changes and responses. Sample problems on the feed system can be paper-based or electronic. These same problems can be plugged into the overhead and bottom systems. In a distillation system, the following variables are directly related to each other:

• • • • • •

Pressure and boiling point Temperature and pressure Composition changes in feed to column Level in accumulator, reboiler, tanks, tray flooding Flow rate Time

17.14 Separation Model A separator is a device that is designed to separate two liquids from each other through density differences; typically, a solvent is introduced that will dissolve one of the components in the mixture and thereby enhance the separation process. A separator has a shell, a weir, a vapor cavity, a feed inlet, an extract pump, and a raffinate pump. One of the problems most frequently encountered in chemical process operations is that of separating two materials from a mixture or a solution. Distillation is perhaps the most frequently used method of making such a separation, but extraction is also useful. In an extraction process, two materials in a mixture are separated by introducing a third material that will dissolve one of the two materials but not the other. In liquid-liquid extraction, all four materials are liquids, and the mixture is separated by allowing them to layer out by weight or density. Many chemicals are sensitive to heat and will degrade or decompose if raised to a temperature high enough for distillation. In these cases, extraction, which can usually be carried out at normal temperatures, is a practical alternative. Because many relatively inexpensive solvents are available, and because the equipment required for an extraction operation is relatively simple, economic considerations often favor liquid-liquid extraction. There are basically three steps in the liquid-liquid extraction process: (1) contact the solvent with the feed solution; (2) separate the raffinate from the extract; (3) separate the solvent from the solute. Step 3, recovery of the solvent and solute, is left to be done by some other process, such as distillation. In liquid-liquid extraction, the feed solution, containing the solute (the material that will be dissolved), is fed to the lower portion of the extraction column. The solvent (the material that dissolves the solute) is added near the top. Because of density differences, the lighter feed solution tends to rise to the top while the heavier solvent sinks to the bottom. As the two streams mix, the solvent dissolves the solute. Thus, the solute, which was originally rising with the feed solution, actually reverses its direction of flow and goes out with the solvent through the bottom of the column. This new solution, consisting of solvent and solute, is called the extract. The other chemical in the feed stream, now free of the solute, goes out the top as the raffinate. The raffinate and extract streams are not soluble in each other and will layer out. 379

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The solvent must be able to dissolve the solute, but it should not dissolve the raffinate or contaminate it. It also must be insoluble, so that it will layer out. The density of the solvent should vary sufficiently from the density of the raffinate so that they can layer out by the effects of gravity. The solvent must be a substance that can be separated from the solute. It should be inexpensive and readily available, and it should not be hazardous or corrosive. Common separation problems include: • Feed composition changes • Unreacted feed • Loss of cooling water • Loss of level control • Instrument problems • Loss of pressure control • Equipment failures—example pump TV 104.5 gpm AV

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Figure 17–14 380

TV 15 gpm AV

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Raffinate

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Summary Figure 17–14 shows the basic flow path and equipment and instruments associated with the separator system.

17.15 Multivariable Model The purpose of the multiple-variable model is to provide an apprentice technician with a comprehensive view of the large scope of operations he or she will be exposed to in the chemical processing industry. When all of the equipment pieces are combined into a full-scale plant, it is easier to see how each system operates and the potential problems that troubleshooters will encounter. Nine of the troubleshooting models have been combined to make the multivariable model shown in Figure 17–15.

Summary The ability to clearly see the process and sequentially break down, identify, and resolve process problems signals that a technician has reached one of the highest levels of learning. Experience is a proven teacher, although new computer technology can be used to quickly and methodically track down process problems. A single problem can have a cascading effect on all surrounding equipment and instrumentation. Troubleshooting models include the reaction model, the absorption and stripping model, the separation model, and the distillation model. These models constitute the equipment and systems presently being used for instruction in community colleges and universities. These models are completely outfitted with alarms, analyzers, interlocks, permissives, video trends, recorders, and control instrumentation. Process problems can be simulated using these models. A college curriculum includes the use of advanced computer system software that closely simulates console operations. Some college training systems have modern control instrumentation mounted on operational pilot units. Students using these types of systems receive true hands-on experience. The four models used to teach process troubleshooting are the distillation model, the reaction and separation model, the absorption and stripping model, and the combination model. Each model has a complete set of process control instrumentation and equipment arrangements. Various troubleshooting methodologies are applied to these four models. A complete range of troubleshooting scenarios has been developed and is typically included with these models. Troubleshooting methods vary depending on the individual educational faculty, consultants, and industry. These methods include educational, instrumental, experiential, and scientific. The troubleshooting process requires a wide array of skills and techniques. The primary goal is to control variables such as temperature, pressure, flow, level, and analytical. With modern control instrumentation, such as indicators, alarms, transmitters, controllers, control valves, transducers, analyzers, interlocks, and so on, it is possible to control large, complex processes from a single room. 381

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Fi

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Figure 17–15 382

Multivariable Model

Dryer-101

Summary Data collection, organization, and analysis are another part of troubleshooting process problems. Data analysis utilizes a variety of quality techniques to put all of the parts in place. Process flow diagrams are used to identify the primary flow path and control instrumentation being used in the process. Checksheets are used to collect large amounts of quantitative data that can be organized into graphics or trends to plot process variation or changes.

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Chapter 17 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

384

List the various troubleshooting models. Compare and contrast troubleshooting methods with troubleshooting models. Describe the term process troubleshooting. Explain how control loops are used in process troubleshooting. Compare and contrast primary and secondary problems on an operating system. How are checklists used to troubleshoot problems? List the various instruments used in troubleshooting. In Figure 17–11, what would happen if the heat was lost? Draw a pressure and level control chart. In Figure 17–2, what would happen if the pressure increased 50 psi? In Figure 17–1, what happens when the steam flow increases?

Self-Directed Job Search After studying this chapter, the student will be able to: • • • • • •

Explain how to conduct a successful job search. Write an effective cover letter. Write an effective process technology resume. Obtain job lists from local chambers of commerce. Describe the kinds of preemployment tests that are given to job applicants. Compare the benefits of work experience and education.

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Key Terms Educational credentials—job qualifications earned through school study; include a one-year certificate or a two-year AAS degree. Certificates may be level one or level two. Job lists—information about potential employers; contain contact name, address, telephone number, and size of company. They can be obtained from the local chamber of commerce (a small fee may apply). Job search—requires four to six months, a good resume and cover letter, a certificate or degree, good investigative skills (to identify who is hiring and who to contact), knowledge of application methods, interest cards, tests, and so on. Job searches are very difficult and require serious dedication, time, and a “thick skin.” Preemployment tests—examinations administered by potential employers to determine applicants’ job qualifications and readiness; examples include the Bennett Mechanical Comprehension Test (BMCT) by George K. Bennett (S & T version); the Richardson, Bellows, Henry & Company “Test of Chemical Comprehension” (S & T version, 1970); and the California Math Test. Types include reading comprehension, accuracy checking, block counting, and tests developed in-house. Resume—a one-page document designed to sum up a job applicant’s skills, work history, hobbies, and education.

18.1 The Job Search Understanding the job market is very important in conducting a successful job search. Although statistics indicate that a large number of process technician positions will become available over the next 10 years, the chemical processing industry is very cyclical in nature. Employment opportunities may surface only once a year. Each company has different hiring needs and different mechanisms for granting interviews. It is the responsibility of each job applicant to become familiar with the hiring practices of the companies in the area or in which he or she is interested. A list of companies that are potential employers can be obtained at the chamber of commerce (sometimes a small fee is charged). A telephone call to the company can also provide an applicant with invaluable information. As a new job applicant, you will be competing against a large number of people for a select few jobs. Only a small fraction of process technician job seekers are truly qualified to work in the chemical processing industry. A job applicant whose educational credentials include a one-year certificate in process technology is much better prepared than applicants without job-specific education. It has been statistically proven that graduates of process technology programs complete mandatory training and job post-training more quickly than non-graduates, and have a very low dropout rate after starting a new job. The truth is that it is very difficult to compete with new graduates—if they can find their way through the mass of unqualified candidates and secure interviews. Job Market Facts: • Job lists can be picked up at local chambers of commerce. • Hiring practices are cyclical.

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18.1 The Job Search

• • • • • • • • •

A job search can take four to six months. The majority of process technician job applicants are not qualified for the job. Each company has its own hiring practices and procedures for prospective employees. Preemployment testing procedures vary by company. The process technician degree is valuable. Finding a job is your responsibility. Networking yields more job opportunities. Newspaper ads have poor placement rates. A good resume and cover letter are important.

Now that you have enrolled in the process technology degree program, there are a number of things you should know so you can position yourself as the top candidate. To be a top candidate, you will need to be better at searching for a job than other people. High grade-point averages (GPAs) and test scores do not indicate how successful you will be in a job search. The truth is, most people are not very good at looking for work. A number of critical elements determine job search success:

• • • • • • • •

• •

•

Job searching is your responsibility—do not believe that someone else will find you a job. Develop a job search plan. Narrow your search—Houston area, Salt Lake City, near your home. Interview—this is a numbers game. The more interviews, the better your chances. Learn to network—75% of all jobs come from networking. Do not rely heavily on newspaper ads; the placement rate from these widely disseminated ads is poor. Use placement agencies—Certified Personnel; Manpower, Inc.; Skillmaster; Kelly Scientific Services; Allstates Personnel; Staffing Professionals; college job placement services; and so on. Become a private investigator: – contact employers – call hot lines – write sales letters – visit human resources (HR) departments – find out hiring procedures Write a good resume. Develop good interview skills: – research the company – make a positive first impression: solid handshake, appropriate dress – state your strengths; develop rapport (“chemistry”) with interviewers – practice answering hard questions Follow up.

Resume and Cover Letter A successful job search requires a cover letter and a resume. The resume is a summary of your life experiences, presented in a positive, concise, and job-relevant manner. A variety of formats are

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available (the Internet has a number of good resources for resumes); select a style based on your individual preference. Elements of a resume include:

• • • • • • •

Your name Address Telephone number(s) E-mail address PTEC education Work experience Reference(s)

Figure 18–1 shows a sample resume. It is important for you to write your own resume. Do not have a friend or relative write it for you; they may include things about you that would be difficult to explain in an interview. Complete your resume before you write the cover letter. A good cover letter should introduce you to the company, highlight important points of your resume, and make an interviewer want to talk to you. Elements of a cover letter include:

• • • • • • • •

Your address Date Name and address of the person you are contacting Greeting Paragraph 1—a brief explanation of why you are writing and how you found out about the company Paragraphs 2–3—a description of how your education and skills would benefit the organization Last paragraph—request for a reply; tell the reader how to reach you Complimentary closing

Figure 18–2 shows an example of a cover letter.

The Selection Process and Interviews During the selection process, a job placement officer sees literally hundreds of resumes. Recruiting is an important feature of good business, and most companies take it very seriously. Job interviewers carefully screen for the best applicants. In a job search, aggressive, professional marketing will give you an edge over competing applicants. The next step can be summed up as: “It’s how you package the product.” A well-written, clean resume and cover letter can go a long way toward getting you an interview. During the selection process, resumes and job applications are typically separated into three stacks: AAS degree—process technology, one-year certificate, and uneducated. A company may use a preemployment test to select resumes to investigate further. Process experience is another important variable used to determine second-phase recruiting or who will get an interview. Companies select employees based upon a wide array of needs. Attrition rates and new plant expansions create opportunities for process technicians. Companies will attempt to hire the best 388

18.1 The Job Search

GLENDA RAMIREZ 75 East Payton St. Houston, TX 77409 Home 555-456-1234 Cell 936-776-0123 [email protected]

OBJECTIVE

To obtain an entry-level position as a process technician.

EDUCATION

In 2009 I graduated from technical college with an Associate of Applied Science (AAS) degree in Process Technology. My course of studies included the operation and maintenance of a full-scale pilot plant, console operation, bench-top operation, process equipment and systems instrumentation, chemistry, math, and physics. Additional topics of study included safety, quality control, troubleshooting, and the academic core.

EMPLOYMENT 06/07–Present

REFERENCES

True Value Hardware, Baytown, Texas Supervisor: Bill Johnson, 555-425-1234 Performed general maintenance, stocking, sales. My Favorite Instructor—Process Technology Process Technical College P.O. Box 848, Baytown, TX 77522-0818

Figure 18–1 Resume Example 389

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75 East Payton St. Houston, TX 77409 June 5, 2009 Ms. S. Johnson Human Resource Manager Texas Refinery and Chemical Company Inc. Baytown, TX 77522 Dear Ms. Johnson: I am writing in response to your classified ad for a process technician placed in the Baytown Sun and Houston Chronicle on June 4. Enclosed you will find my resume, which describes my educational background and work experience. On May 15, 2009, I graduated with an Associate of Applied Science degree in Process Technology from Process Technical College. As my enclosed resume indicates, I have taken courses that have prepared me to take an entry-level position as a process technician at your company. I look forward to meeting with you for an interview. If you have any additional questions, please call 555-456-1234 after 3:00 p.m., or my cell 936-776-0123. I can also be contacted at [email protected].

Sincerely,

Glenda Ramirez

Figure 18–2 Cover Letter Example 390

18.1 The Job Search possible candidate based on company needs, equal employment opportunity (EEO) requirements, and personal relationships. Typical interview questions asked by employers include: • Tell us about yourself. Why should we hire you? • Why do you want to leave your present position? • Why did you leave your last job? • Tell me what you have learned in your college classes. • Tell me about the different types of pumps you have studied. • What is distillation? What is reflux and what is its purpose? • List the elements of a control loop. • Do you have any hands-on experience? • Tell me how to put a distillation system online. • What do you know about our company? • What are your personal goals in this job for the next year? The next five years? The next ten years? • How do you handle stress? • If you were asked to perform an unsafe act by your supervisor, how would you respond? • Why did you choose to be a process technician? • Do you have plans to continue your education? Questions asked by job applicants might include: • Can you tell me about your safety program? • What specific responsibilities of the position do you consider the most important? • How are process technicians evaluated at your company? • What would you expect me to accomplish during my first six months? The first year? Two years? • What long- and short-term problems will I face as a new technician at your company? The following are some suggestions for job searching by process technology students: • Get a one-year certificate in process technology. • Get a two-year degree in process technology. • Prepare for preemployment tests, and sign up for placement agency tests. • Improve your skills in math, reading comprehension, and communications. • Develop a network (friends, instructors); get references; gather documents; prepare for interviews; research companies; develop a job search plan. • Prepare a resume, target companies you want to work for, mail out resumes, follow up on job leads, get jobline numbers. • Dress appropriately—jeans, long-sleeved shirt, work boots, little makeup, toned-down jewelry. • Be accessible—allocate time; get an answering machine; check your e-mail frequently. • Sign up with your state’s workforce commission and placement agencies. • Identify your strengths and weaknesses. • Don’t get discouraged; find healthy ways to deal with stress. • Go to chambers of commerce and get job lists. • Go to companies and develop relationships. • Check out www.twc.state.us (process Internet site for Texas). • Improve your appearance. 391

Chapter 18

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Self-Directed Job Search

18.2 Preemployment Testing At present, a variety of preemployment tests are given to job applicants. The most common types of preemployment tests include mechanical aptitude, chemical comprehension, reading comprehension, basic math, psychological, and block-counting exams. Some companies spend thousands of dollars developing their own tests; others use standardized exams. Mechanical aptitude tests are administered frequently to individuals wishing to work in the chemical processing industry. Mechanical aptitude reveals your ability to predict which way an object will move when influenced by an outside set of forces. The most common form is the Bennett Mechanical Comprehension Test (BMCT) by George K. Bennett. The BMCT uses an S-and-T (science and technology) format that includes 68 questions. Another mechanical aptitude test that can be purchased at local bookstores is the ARCO book on mechanical aptitude and spatial relationships. There are a number of good texts that will help new technicians improve their ability to work out mechanical aptitude problems. In 1970, Richardson, Bellows, Henry & Company developed the “Test of Chemical Comprehension.” This test comes in a 50-question, S-and-T format. Questions on the test were developed from information that should be learned in a high school science class. Most preemployment tests have a math section that covers addition, subtraction, multiplication, division of fractions and whole numbers, decimals, averaging, percentages, and low-level algebra. Block-counting tests ask the job applicant to look at a three-dimensional drawing and identify the total number of blocks. Because some of the blocks are hidden, this test can be tricky; carelessly rushing through this section of the test is a mistake. The block-counting test is designed to screen for observational accuracy. Reading comprehension is a common testing practice that screens for how well a technician can read a paragraph or two and then answer or respond to specific instructions or questions. People who read and comprehend quickly should not be concerned about this type of testing. If you like to read instructions carefully before you respond, you will need to develop a system that increases your speed, as all of these tests are timed.

18.3 Work Experience Industrial employers have traditionally valued prospective employees who have experience in industry. Some companies require five years of experience before they will even initiate the interview process. Industrial experience provides a track record of a person’s stability, ability to work rotating shifts, and exposure to industrial processes and the environment. One might argue that experience or exposure to all industrial processes is impossible to obtain, since more than 40 petrochemical processes and 19 refinery processes can be identified (and this does not include the gas processes). The only common thread between these facilities is the equipment and technology used, although it appears in different arrangements. A prospective employee with strong science and math backgrounds, good mechanical aptitude and troubleshooting skills, and a process technology degree provides prospective employers with an informed trainee who is well prepared to start site-specific training. With the availability of such education, experience does not carry the weight that it used to. Since 1989, the government and industrial manufacturers have been raising the bar for process technicians. Displaced process operators are being required to go back to school and obtain a certificate 392

Summary or degree before they can return to their occupation. This added level of education is designed to protect the process technician, community, and industrial manufacturers from inability to handle rapid advances in technology. Experienced technicians have a number of negative issues and concerns to address, including:

• • • •

Why did you leave your last job? – Bad habits? – Trained incorrectly? Do you have a two-year degree in process technology? What industrial processes have you been exposed to? Did you complete a Department of Labor-approved apprentice training program?

Do not let a lack of experience discourage you. The bottom line in job seeking is to get a good education, develop your foundational skills, and “sell yourself” with a good resume, cover letter, and interview responses.

Summary A successful job search requires four to six months, a good resume and cover letter, a certificate or degree, and good investigative skills to identify who is hiring, who to contact, the application method, and so on. Job searches are very difficult and require serious dedication, time, and persistence. A variety of preemployment tests are given to job applicants in the chemical processing industry, including the Bennett Mechanical Comprehension Test and the “Test of Chemical Comprehension.” Tests may focus on mechanical aptitude, reading comprehension, and/or basic math skills. Industrial work experience provides a track record of a person’s stability, ability to work rotating shifts, and exposure to industrial processes and the environment. Experience is not as important as it used to be, however, now that more than 40 petrochemical processes and 19 refinery processes are in operation. A prospective employee with strong science and math backgrounds, good mechanical aptitude, troubleshooting skills, and a process technology degree provides prospective employers with an informed trainee who is well prepared to start site-specific training.

393

Chapter 18

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Self-Directed Job Search

Chapter 18 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

394

List the key elements of a resume. Write a resume. List the key elements of a cover letter. Write a cover letter. Tell us about yourself. Why should we hire you? Why do you want to leave your present position? Why did you leave your last job? Tell me what you have learned at Process Technical College. Tell me about the different types of pumps you have studied. What is distillation? What is reflux and what is its purpose? List the elements of a control loop. Do you have any hands-on experience? Tell me how to put a distillation system online. How do you find information about a company? What are your personal goals in this job for the next year? The next five years? The next ten years? How do you handle stress? If you were asked to perform an unsafe act by your supervisor, how would you respond? Why did you choose to be a process technician? Do you have plans to continue your education? Select an ad from the paper and apply for a process job.

Applied General Chemistry Two After studying this chapter, the student will be able to: • • • • • • • • • • • • • •

Describe the basic steps of the scientific method. Describe the concept of a mole. Solve simple exponential notation problems. Understand the nature of elements and compounds. Read and use the periodic table. Describe the principles associated with electron configuration. Recognize and interpret the formulas for organic chemicals. Balance simple chemical equations. Describe the principles of distillation. Solve simple problems using Dalton’s law of partial pressures. Describe aromatic hydrocarbons. Identify the basic concepts associated with chemical bonding. Describe alkanes, alkenes, alkynes, and cycloalkanes. Describe the basic characteristics of an alcohol.

395

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Applied General Chemistry Two

Key Terms Alkane group—family of hydrocarbons that are composed of carbon and hydrogen held together by single covalent bonds. Benzene—the most common aromatic hydrocarbon. The benzene molecule has six carbon atoms connected in a ring. Each carbon atom has four bonding sites available; in benzene, three are used and one is free. The three bonds are covalent; the fourth can be shared by all six carbon atoms. This creates a donut-shaped cloud or aromatic ring. Reactions with benzene are substitution and not addition. Covalent bonding—the mechanism of electron sharing that holds atoms together to form molecules. In a covalent bond, atoms share a pair of electrons. Cycloalkane family—group of hydrocarbons characterized by the presence of a ring or cycle of carbons from three methylene groups located on the apex of the equilateral triangle. Dalton’s law of partial pressures—states that the total pressure of a gas mixture is the sum of the pressures of the individual gases (their partial pressures); Ptotal  P1  P2  P3. Distillation—a process used to separate the components in a mixture by their volatilities in a boiling liquid mixture. Dmitri Mendeleev—(1834–1907); a Russian professor of chemistry who devised the first periodic table of elements. Exponential (scientific) notation—a number system based on powers of 10 (exponents), designed to make it easier to work with very large numbers. Ionic bonding—magnetic-type bonds. In ionic bonding, one or more electrons transfer from one or more atoms to another, creating a positive ion and negative ion that attract and hold each other. These bonds are extremely strong. Mole—the molecular formula weight of any substance expressed in grams. Organic chemistry—the study of compounds that contain carbon. Saturated hydrocarbon—contains the maximum number of hydrogen atoms and contains single covalent bonds. An unsaturated hydrocarbon can still accept an additional hydrogen atom. Science—a way of knowing and understanding the universe and the world we live in. The Latin word for science is scire, which means “to know.” Scientific method—the systematic process or framework by which science operates.

19.1 Fundamentals of Chemistry Science is a way of knowing and understanding the universe and the world we live in. The Latin word for science is scire, which means “to know.” Science operates by asking questions, observing, analyzing observations, and communicating observations. This type of procedure raises a never-ending supply of questions. Scientific inquiry uses theories and hypotheses to explain

396

19.1 Fundamentals of Chemistry phenomena. A theory is best described as a firmly grounded interpretation of confirmed observations. A hypotheses is a tentative explanation of a small set of observations. Process technicians spend a great amount of time making observations and collecting, organizing, and analyzing the data from those observations. As active observers and participants in operating a wide variety of chemical processes, technicians need to have a good understanding of science and the scientific method. The scientific method is the process or framework by which and within which science operates. Collectively, this method of learning is very powerful. Key steps in the scientific method include: using a systematic, fact-based approach; asking questions; observing; analyzing observations; and communicating observations. Most of the manufacturing processes in the world use or require a chemical reaction. Plants are set up to provide the conditions that are most favorable for the desired reaction(s). However, to initiate these processes correctly, a certain amount of starting materials (reactants) is needed to begin a chemical reaction. These amounts vary depending on the substances used and the reaction desired, but the amounts must be both sufficient and correct. Thus, we need to know formula weights. We can calculate this by simply adding up the molecular weights of each element in a compound. For example, the formula weight of urea, (NH2)2CO, is 60 AMU: N (nitrogen)

 14  2  28

H (hydrogen) 

14 

4

C (carbon)

 12  1  12

O (oxygen)

 16  1  16 60 AMU

The Mole The mole is often referred to as a chemist’s unit of quantity. Counting atoms is a difficult process and beyond the scope of most calculators, but measuring the mass of a sample is easy when we can relate the number of atoms in a sample to its mass. This is the unique purpose of the mole. A mole of any substance is its molecular formula weight expressed in grams. Avogadro’s number is a universal constant that states the number of molecules in a mole: N0  6.023  1023 molecules/mole. One mole (abbreviated mol) of any element (chemical compound) has the same number of chemical particles as one mole of another element (chemical compound). In other words, 1 mole of any compound contains 6.02  1023 molecules. Review the following problem using the mole concept. EXAMPLE A single aspirin tablet contains 0.36 g aspirin. The molecular formula of aspirin is C9H8O4. Identify how many aspirin molecules a single tablet contains. Step 1

The formula weight of aspirin is: C (carbon)  12  9  108 H (hydrogen)  1  8  8 O (oxygen)  16  4  64 180 AMU

397

Chapter 19

Step 2

●

Applied General Chemistry Two 0.36 g aspirin  1 mole aspirin 180 g aspirin  0.0020 mole aspirin or 2.0  103 mol aspirin

Note: 1 mole of any compound contains 6.02  1023 molecules. Step 3

2.0  103 mole (6.02  1023 molecules)  1.2  1021 molecules mole

Answer: 1.2  10 21 molecules of aspirin (C9H8O4).

Exponential Notation In chemistry and physics, it is often necessary to work with very large numbers. An easy way to handle these large numbers is called exponential notation, a system based on the powers of 10. Exponential notation is also referred to as scientific notation. For example, 57,500 can be expressed as 5.75  104. We generate the exponential notation by moving the decimal point four places to the left and inserting the multiplier of the correct power of 10: 57,500  5.75  104. We can do the same thing with a number like 0.0000575 by moving the decimal point five places to the right to express it as 5.75  105. When it is necessary to add, subtract, divide, and multiply numbers in exponential notation, there are a number of rules that must be followed. To add or subtract, the exponents must be the same. For example: 4.5  103  8.2  103 12.7  103

or

0.0127  1.27  102

If the exponents are different, a correction must be made to one of the variables. For example, to add 5.95  102 and 1.8  103, we would have to adjust the expression as follows: 5.95  102  0.18  102 6.13  102 The same principle holds true when we subtract exponents. For example, to subtract 5.21  104 from 1.77  105, the expression would be adjusted to: 1.77  105 .521  105 1.25  105

398

19.1 Fundamentals of Chemistry When it is necessary to multiply numbers in exponential notation, we multiply the numerical coefficients and algebraically add the exponents. For example, to multiply 5.5  105 by 2.25  109, we would use the following expression: 5.5  2.25  12.375 105  109  1059  1014 Answer: 12.4  1014  1.24  1015 When it is necessary to divide numbers in exponential notation, we divide the numerical coefficients and algebraically subtract the exponents. For example: 9.5  108 3.1  1010 9.5  3.1  3.06 108  1010  10810  102 Answer: 3.06  102 Examples of Exponential Notation 0.001  103 0.01  102 0.1  101 10  101 100  102 1000  103

Elements and Compounds Elements are composed of identical atoms; they are the fundamental substances of chemistry and the process industry. Elements cannot be converted into other elements. Today we recognize 116 different elements. Some of these elements include carbon and hydrogen, which are the primary building blocks of materials for the chemical and refining industry. Process technicians also commonly use other elements, such as oxygen, nitrogen, sodium, magnesium, potassium, chlorine, helium, iron, copper, titanium, gold, platinum, mercury, aluminum, and argon. Compounds are composed of two or more elements in well-defined ratios. Sugar is a compound formed by three elements—carbon, hydrogen, and oxygen—in specific ratios. Sodium chloride (table salt) is a compound formed from the combination of two elements, chlorine and sodium, in specific ratios. Other common compounds include water (H2O), sodium (23 AMU) chloride (35.5 AMU), and hydrogen peroxide.

399

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Applied General Chemistry Two

19.2 The Periodic Table and Chemical Bonding Three factors affect the properties of an atom or ion: atomic number, mass number, and electron configuration. Process technicians are primarily concerned with the electron configuration and the valence shell. The outermost shell in an atom is referred to as the valence shell. The atoms of elements have different arrangements and they tend to react in an effort to fill the valence shell. The electrons in the valence shell are referred to as valence electrons.

Periodic Table Dmitri Mendeleev, a popular Russian professor of chemistry who lived from 1834 to 1907, devised the first periodic table of elements. During his studies, Mendeleev recognized repetitions in the properties of elements; that is, properties and similarities that repeated over and over again. This recurrence is referred to as periodicity or periodic. The periodic table is organized in sequence of increasing atomic number rather than by atomic weight (Figure 19–1). The elements tend to fall into rows so that elements in the same vertical column or group have similar properties. Boiling points and melting points tend to increase as we move down a column. For example, the elements in column 18 are gases at room temperature and tend not to react and form compounds; only a few exceptions can be found. After some thought, Mendeleev numbered the columns with Roman numerals, some with the letter “A” and some with the letter “B.” This system was used virtually unchanged until quite recently, when minor variation between U.S. and European chemists (A/B variation) forced the international chemistry organization to recommend a column numbering system from 1–18, moving from left to right. In columns 1, 2, and 13–18, a number of elements extend above the rest. These elements are referred to as representative elements. The elements found in columns 3–12 are classified as transition elements. At the bottom of the periodic table are two rows that appear to be separated from the main body of the table. This is for convenience only. Elements 58–71 and 90–103 are called inner transition elements and actually fit between columns 3 and 4. The elements on the periodic table can be classified as metals, nonmetals, metalloids, or noble gases. Metals tend to be shiny and have atoms that give up electrons. Metals are malleable and tend to be excellent conductors of heat and electricity. By nature, nonmetals do not conduct electricity and have atoms that do not naturally give up electrons; however, they do tend to accept electrons. The metalloid elements are located along the heavy black stair-step line on the right-hand side of the periodic table. Boron, silicon, germanium, arsenic, antimony, tellurium, polonium, and astatine are classified as metalloids. Helium, neon, argon, krypton, xenon, and radon are classified as inert or noble gases. These six elements have unique properties that are different from those of the other nonmetals. These inert or noble gases refuse to accept or give electrons. The rest of the nonmetals include hydrogen, carbon, nitrogen, oxygen, fluorine, phosphorus, sulfur, chlorine, selenium, bromine, and iodine.These 11 elements are critical in the study of organic chemistry.

400

19.2 The Periodic Table and Chemical Bonding Inert or Noble Gases

PERIODIC TABLE OF ELEMENTS

THOMAS 1 Period 1

18

GROUP 1A 1 1.0079

H

20.3 14 .09

H - gas

1s

2A

HYDROGEN

6.941

3 2

Be

3A 5

2 2

3

BERYLLIUM

5

4

6

22.99 12 24.30

11 1156 371 .97

2 8 1

1363 922 1.74

Na Mg

7

10

9

8

2793 933 2.7

8B 3B 4B 7B 5B 6B SODIUM MAGNESIUM 19 39.092 20 40.08 21 44.95 22 47.9 23 50.94 24 51.99 25 54.93 26 55.84 27 58.93 28

K

1032 336 .86

8 8 1

4s

POTASSIUM

5

Rb 5s

2 8 18 8 1

RUBIDIUM

6

Sc 3d

SCANDIUM

38 87.622 39 1650 1041 2.6

2 8 9 2

3104 1812 3

Sr

3611 1799 4.5

8 18 5s 82 STRONTIUM

Y

Ti 3d

944 302 1.9

Cs 6s

CESIUM

Ba

2171 1002 3.5

8 8 18 18 18 6s 18 8 8 1 BARLUM 2

2 8 18 9 2

YITRIUM

88 8

223 2

Fr

18 32 7s 18 8 FRANCIUM 1 950 300

226 2

8 18 32 18 7s 8 RADIUM 2

Ra

1809 973 5

3730 1193 6.7

40

La

227 2

3682 2175 5.8

V 3d

2 8 11 2

VANADIUM

91.22 41 92.9

2 8 18 10 4d 2 ZIRCONIUM

Zr

4682 2125 6.49

Nb 4d

NIOBIUM

Hf

104

2 8 5731 18 3287 32 16.6 5d 10 2 TANTALUM

Ta

Fe

3135 1809 7.86

CHROMIUM

2 8 3d 13 2 MANGANESE

42

43

44

3d

95.9 2 8 18 13 1

Mo 4d

MOLYBDENUM

74

106

2335 1517 7.43

4538 2473 11.5

98

Tc 4d

263

75

186

2 8 18 32 5d 13 RHENIUM 2

5869 3453 21

Re

107

262

IRON

Bohrium

Co

3201 1768 8.9

3d

45

190

2 8 18 32 5d 14 OSMIUM 2

Os

5285 3300 22.4

108

3d

2 8 16 2

4d RHODIUM

192

2 8 18 18 4d 0 PALLADIUM

Pd

3237 1825 12

78

195

2 2 8 4100 8 18 2045 18 21.4 32 5d 32 5d 17 17 IRIDIUM 0 PLATINUM 1

4701 2716 22.5

2 3

Ir

Pt

Al

2 8 3

C

2 4

CARBON

Si

N

2 8 4

Cu

2836 1358 8.25

47

3d

2 8 18 1

1180 693 7.14

Zn 3d

2 8 18 2

Ga

2478 303 5.91

4p

Ge

2 3107 1210 8 5.32 18 3

4d

2 8 18 18 1

Cd 4d

CADIUM

SILVER

79 196.9 80 3130 1338 19.2

Au 5d

GOLD

2 8 18 18 2

1040 594 8.65

200.6

2 630 8 234 18 13.53 32 5d 18 1 MERCURY

Hg

In

2346 430 7.31

5p

4p

2 8 18 4

GERMANIUM

GALLIUM

ZINC

107.8 48 112.4 49 114.8

Ag 2436 1234 10.5

Meitnerium

Rg

6d

6d

6d Hassium

Ds

Mt

O

F

85 53.5 1.7

2 6

2 7

P

550 317 1.82

3p

20.18

Ne

27.1 24.6 .90

FLUORINE

OXYGEN

2 8

NEON

30.97 16 32.0617 35.45

15

10

2p

2p

2 8 5

718 388.4 2.07

2 8 18 18 3

2 8 18 5

958 494 4.8

S

239 172 3.17

2 8 6

Cl

39.94

18

Ar

2 8 7

87.3 83.8 1.784

2 8 18 7

119.8 115.78 3.74

2 8 8

Sn 5p

8 18 18 4

ARSENIC

2023 601 11.4

Sb

1860 904 6.68

8 18 18 5

5p

ANTIMONY

TIN

INDIUM

Tl

4p

6d

Se

332 266 3.12

2 8 18 8 SELENIUM

Br

4p

4p

BROMINE

Kr 4p

2 8 18 8

KRYPTON

50 118.62 51 121.72 52 127.62 53 126.9 54 131.3 2

2876 505 7.3

81 204.3 82

2 2 8 1746 8 577 18 11.85 18 32 32 6p 18 18 2 THALLIUM 3

As

876 1081 5.72

207

Pb 6p

LEAD

2 8 18 32 18 4

Te

458 387 4.92

1261 723 6.24

8 18 5p 18 6 TELLURIUM

83 208.92 84

IODINE

209

114 115 113 Discovered1999 2004 2004 1996

8 18 18 7

210

85

2 8 18 32 6p 18 ASTATINE 7

Po

Bi

I

5p

2 8 8 1235 527 18 18 9.4 32 32 6p 18 6p 18 BISMUTH 5 POLONIUM 7

1837 545 9.8

265 109 266 110 271 111 272112

Hs

90.18 50.35 1.43

2

1s

HELIUM

15.99 9 18.99

8

2 5

NITROGEN

28.08

3540 1685 2.33

14.006

4.2 .95 .1787

7A

6A

7 77.35 63.14 1.25

He

17

3p 1B 2B ALUMINUM 3pSILICON PHOSPHORUS SULFUR CHLORINE 3p ARGON 29 63.54 30 65.38 31 69.72 32 72.59 33 74.92 34 78.96 35 79.90 36 83.8

COPPER

NICKEL 2 8 18 18 1

3970 2236 12.4

77

58.7

Ni

3187 1726 8.9

102.9 46 106.4

Ru Rh

76

2 8 15 2

COBALT

101

2 8 18 15 4d 1 RUTHENIUM 4423 2523 12.2

6d

6d Seaborgium

2 8 14 2

3d

Bh

Sg

Db

2 8 18 14 1

TECHNETIUM

183

W

261 105 263

Rf

2 8 13 1

2 2 8 8 5828 3680 18 18 19.3 32 32 5d 12 11 2 TUNGSTEN 2

8 18 32 18 6d 9 6d 6d ACTINIUM 2 Rutherfordium Dubnium

Ac

3473 1323 10.07

Cr Mn

2945 2130 7.19

2 4912 8 2890 18 10.2 12 1

5017 274 0 8.55

178.4 73 180.9

8 4876 18 2500 18 13.1 5d 5d 9 LANTHANUM 2 HAFNIUM

89

2 8 10 2

TITANIUM

88.9

4d

3562 1943 4.5

55 132.90 56 137.33 57 138.92 72 2 2

87 7

2 8 8 2

CALCIUM

85.46

37 961 313 1.53

Ca

1757 1112 1.55

12.01

4470 4100 2.62

13 26.98 14

3s

4

B

6

BORON

Transition Elements

2 8 2

5A

4A

10.81

2p

12

11

Nonmetals 15 16

14

13

4275 2300 2.34

2s

LITHIUM

3

9.0126

4

2745 2 1560 1 1.9

Li

1615 454 .53

Fr - liquid Na - solid

2

1

V111A 2 4.002

610 575

At

165 161.4 5.89

Xe 5p

XENON

86

2 8 18 18 8

222

2 8 18 32 6p 18 RADON 8

Rn

211 202 9.91

116 1999

Darmstadtium Roentgenium

Inner Transition Elements 58 Lanthanides 4f

140.115

3699 1071 6.78

Ce

Cerium

5f

Actinides

90

1 2 3 4 5 6 7 8

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p 8s

3785 1204 6.77

144.24

2 8 18 21 3341 8 1289 2 7.0

Pr Nd

2 8 18 22 8 2

Praseodymium Neodymium

91

232.04

Th

5061 2028 11.7

Thorium

Electron Placement

59140.9076 60

2 8 18 20 8 2

2 8 18 32 18 10 2

------15.4

231.03

Pa

2 8 18 32 20 9 2

Protactinium

Prefixes 1. mono 2. di 3. tri 4. tetra 5. penta 6. hexa 7. hepta 8. octa 9. nona 10. deca

92 4407 1405 18.9

238.03

U

Uranium

2 8 18 32 21 9 2

61

144.91 2 8 18 23 8 2

62

150.36 2 8 18 24 8 2

Pm Sm 3785 1204 6.5

Promethium

93

237.05

Np ---910 20.4

2 8 18 32 22 9 2

Neptunium

2064 1345 7.54

Samarium

94

244.66

2 8 18 25 8 2

157.25

Eu Gd

1870 1090 5.26

Europium

95

3539 1585 7.89

2 8 18 25 9 2

Gadolinium

243.06 2 8 18 32 25 8 2

96

247.07 2 8 18 32 25 9 2

65 158.9253 66

Tb

3496 1630 8.27

3503 913 19.8

Plutonium

2880 1268 13.6

Americium

---1340 13.5

Curium

____ ____ ____

162.5

Dy

2835 1682 8.54

2 8 18 28 8 2

Dysprosium

247.07 2 8 18 32 26 9 2

Berkelium

Common Positive Valences

Fe 2, 3 Ni 2 Cu 1, 2 Zn 2 Al 3 Ag 1 Cd 2 Sn 2, 4 Au 1 Hg 1, 2 Pb 2, 4

2 8 18 27 8 2

Terbium

97

Pu Am Cm Bk

Diatomic Elements

1. Bromine 2. Chlorine 3. Fluorine 4. Hydrogen 5. Iodine 6. Nitrogen 7. Oxygen

2 8 18 32 23 9 2

63 151.965 64

98

251.08

Cf

____ 900 ____

2 8 18 32 27 9 2

Californium

67164.9303 68

Ho

2968 1743 8.8

Holmium

99

2 8 18 29 8 2

252.08 2 8 18 32 28 9 2

167.26

Er

3136 1795 9.05

Erbium

100

Einsteinium

____ ____ ____

Fermium

69168.9342 70

2 8 18 32 29 9 2

173.04

Tm Yb 2 8 18 31 8 2

2220 1818 9.33

1467 1097 6.98

Thulium

257.1

Es Fm

____ ____ ____

2 8 18 30 8 2

101

Ytterbium

258.1

Md ____ ____ ____

2 8 18 32 30 9 2

102

259.1

No

____ ____ ____

Nobelium

Mendelevium

2 8 18 32 8 2

2 8 18 32 31 9 2

71

174.967 2 8 18 32 9 Lutetium 2 262.1

Lu

3668 1936 9.84

103

Lr

____ ____ ____

2 8 18 32 32 9 2

Lawrencium

Multivalent Metals Iron Lead Tin Mercury Copper

Fe Pb Sn Hg Cu

Ferrum Plumbum Stannum Mercurum Cuprum

Atomic Number 6 4470 Boiling Point(K) 4100 Melting Point (K) Density @ 300K (g/cm3) 2.62

12.011

C

2 4

2p

CARBON Element

(ous) +2 +2 +2 +1 +1

(ic) +3 +4 +4 +2 +2

Atomic Weight electrons in shells Symbol Electron Placement

Figure 19–1 Thomas Periodic Table

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Electron Configuration Element

EC

Atomic #

Hydrogen

1s1

1

2

Helium

2

1s

Lithium

2

1s 2s

1

3

2

2

4

Beryllium

1s 2s

Boron

1s22s22p1

5

2

2

2

6

2

2

3

7

Oxygen

2

2

1s 2s 2p

4

8

Fluorine

1s22s22p5

9

Carbon Nitrogen

1s 2s 2p 1s 2s 2p

2

2

6

2

2

6

2

3

2

2

6

2

6

1s 2s 2p

Neon Phosphorus

10

1s 2s 2p 3s 3p

15 2

Calcium

1s 2s 2p 3s 3p 4s

Manganese

1s22s22p63s23p64s23d5 2

2

6

2

6

2

10

2

2

6

2

6

2

10

1s 2s 2p 3s 3p 4s 3d

Zinc Bromine

20

1s 2s 2p 3s 3p 4s 3d 4p

25 30 5

35

Covalent Bonding Covalent bonding is the mechanism of electron sharing that binds atoms together to form molecules. In covalent bonding, a bond is made of a pair of electrons shared by two atoms. More complex electron structures may share one, two, or three electron pairs between atoms. Examples of this include:

• • •

Hydrogen (H2) has one bond between the hydrogen atoms H - H Oxygen (O2) has two bonds between the oxygen atoms O  O Nitrogen (N2) has three bonds between the nitrogen atoms N  N

Covalent bonds have unique properties, one of which is that they are not limited to atoms of the same element or to only two atoms for each molecule. Common examples include water (H2O), ammonia (NH3), carbon dioxide (CO2), and methane (CH4). In the water molecule, the oxygen atom forms two covalent bonds with the hydrogen. In the ammonia molecule, three bonds are shared with the nitrogen. One of the most useful covalent bonds is found with the element carbon. Carbon atoms tend to form four covalent bonds because there are four electrons in the outer shell; this leaves the outer shell in the carbon atom four electrons short. Because of the numerous opportunities for bonding, some carbon compounds are made of tens of thousands of atoms. Crude oil is a good example of how hydrogen and carbon link together to form a variety of hydrocarbon chains: methane, ethane, propane, butane, pentane, octane, decane, and much larger hydrocarbons. Other common hydrocarbons include kerosene, gasoline, jet fuel, light oil, heavy oil, and asphalt. 402

19.4 Balancing Equations Another type of bonding is called ionic bonding. Ionic bonds are best described as magnetic-type bonds. In this process, one or more electrons transfer from one or more atoms to another atom, creating a positive ion and a negative ion that attract or hold to each other. These type of bonds are very strong. An example of a compound with ionic bonding is sodium chloride (NaCl). To better understand ionic bonds, spend some time reviewing ions and how they are formed. Most molecular bonds are covalent. However, in solids there are four bonding entities or mechanisms: ionic, covalent, metallic, and van der Waals.

19.3 Organic Chemistry Organic chemistry is frequently described as the study of compounds that contain carbon. Life as we understand it depends on water and on the compounds of carbon. Water is the fluid of life and combines with carbon compounds to form covalent entities; in combination with hydrogen, oxygen, nitrogen, sulfur, and phosphorus atoms, these form the building blocks of life. Crude oil is composed of things that were once living on the face of the earth. Carbon compounds can be found in all living things. Simply put, organic chemistry is the chemistry of carbon compounds.

Methane is a simple hydrocarbon (a compound made of carbon and hydrogen) and is described as tetravalent because it has four valence electrons that form covalent bonds. The alkane group includes methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), pentane (C5H12), hexane (C6H14), heptane (C7H16), octane (C8H18), nonane (C9H18), decane (C10H22), undecane (C11H24), dodecane (C12H26), tridecane (C13H28), tetradecane (C14H30), pentadecane (C15H32), hexadecane (C16H34), heptadecane (C17H36), octadecane (C18H38), nonadecane (C19H40), eicosane (C20H42), triacontane (C30H62), and undecahectane (C111H224). Alkanes are chemical compounds that consist of atoms of carbon and hydrogen linked together by a single bond. These compounds are essential in the chemical processing industry. Formulas for hydrocarbon compounds may be expressed with a type of shorthand notation. For example, propane has a shorthand formula CH3-CH2-CH3 that is more accurately called a condensed structural formula. When using the shorthand formula, it is important to remember that the real compound and the three carbons are not in a straight line; rather, they are connected at a 110-degree angle.

19.4 Balancing Equations Being able to balance a simple equation is an important part of working in the chemical industry. The raw materials that go into the development of new products on a commercial scale are very expensive. Balancing equations allows a technician to accurately determine the amount of reactants needed or products to be made. An unbalanced equation may include:

• • •

Initial reactants Final products Process conditions (heat, temperature, pressure, analytical variables) 403

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An unbalanced chemical equation will not yield the correct quantities. The law of conservation of matter is satisfied only when an equation is balanced. The total amount of reactants must equal the total amount of products; in other words, “what goes in must come out.” Correct proportions are involved at every step of a chemical process. When looking at a chemical equation, the number immediately to the left of the chemical determines the molecules or mole units. For example, 2H2O indicates that there are two water molecules. Another common equation found in the chemical processing industry is CH4  2O2 → CO2  2H2O In this equation, methane (CH4) burns and consumes oxygen (O2) while producing carbon dioxide (CO2) and water (H2O). In this balanced equation, one methane molecule reacts with two oxygen molecules to produce one carbon dioxide molecule and two water molecules. Another similar equation involves propane instead of methane: CH3-CH2-CH3  O2 → CO2  H2O We can clearly see that the equation is not balanced. To balance the two sides, we would need to make the following adjustment: CH3-CH2-CH3  5O2 → 3CO2  4H2O After this adjustment, the chemical equation for oxidation of propane to carbon dioxide and water is balanced. When balancing an equation, the following principles are very helpful:

• • • • • •

Determine if the equation is balanced or not. Never touch the subscripts. For example, in H2O, leave the subscript 2 alone; a change will alter the composition of the compound and the substance itself. Focus on the coefficients to balance an equation. Work from one side to the other. Typically it is easiest to start with one side and then balance the other. Most operations move left to right, trial and error. Ensure that you have accounted for each source of a particular element that you are attempting to balance. It is possible that two or more molecules contain the same element. Adjust the coefficient of monoatomic elements last. Adjust the coefficient of polyatomic ions that are acting as a group in self-contained groups on both sides of the equation.

EXAMPLE Not balanced (NH4)2CO3 → NH3  CO2  H2O Balanced (NH4)2CO3 → 2NH3  CO2  H2O

Reactants

404

Products

Nitrogen  2

Nitrogen  2

Hydrogen  8

Hydrogen  8

Carbon  1

Carbon  1

Oxygen  3

Oxygen  3

19.5 Petroleum Refining: Distillation Each reaction will present its own mystery and problem, but most can be solved using the inspection method used here.

Practice Problems Balance the following equations:

1. Sn  Cl2 → SnCl4 Answer: Sn  2Cl2 → SnCl4

2. Fe  O2 → Fe2O3 Answer: 4Fe  3O2 → 2Fe2O3

3. CaO  HCl → CaCl2  H2O Answer: CaO  2HCl → CaCl2  H2O 4. Balance the following butane combustion equation. C4H10  O2 → CO2  H2O Answer: 2CH3-CH2-CH2-CH3  13O2 → 8CO2  10H2O

19.5 Petroleum Refining: Distillation Converting raw materials into useful products such as gasoline, diesel, jet fuel, or light oils is known as petroleum refining. Refining is done on crude oil—the substance whose price has fluctuated widely recently and caused tremendous and volatile swings in the economy as a whole. Because so many products begin with crude oil, or depend on it for manufacturing processes or transportation, high oil prices mean high prices at the gasoline pump and higher prices on almost everything we purchase. An essential part of petroleum refining is distillation. Distillation is a process used to separate the components in a mixture by their volatilities in a boiling liquid mixture. Typically, distillation is part of a much larger chemical or refining process. Distillation can be used to:

• • • •

Separate salt from sea water Separate oxygen, nitrogen, and argon from air Produce higher alcohol content in fermented solutions Separate various components in crude oil

In a laboratory environment, distillation glassware is used to conduct bench-top operations. On a small scale, these operations can be carefully controlled and provide relevant data applicable to a large-scale commercial unit. The feedstock is placed in the bottom flask and heated up to operational conditions. As the feed heats up, the separation process begins. Initially, bubbles form and then begin to break the surface of the liquid. The lighter components in the mixture have the higher volatility; thus, they will overcome atmospheric pressure first and escape the rapidly moving molecules in the liquid. The initial boiling point of the mixture is quite different from the final boiling point. As the vapors initially move up the distillation column, they come into contact with the cooler glass 405

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surfaces of the trays and return to the liquid state, transferring heat to the trays, downcomers, and shell. As the liquids begin to accumulate on the trays, the rising vapors gently lift the liquid, creating good liquid-vapor contact as the liquids drop down the column and the vapors rise. Heat energy is transferred from areas of hot to cold as the vapors continue to rise from the lower trays to the top of the column. Each tray has a permeable liquid seal on the bottom. The downcomer’s lower tip is submerged in the liquid, forming a liquid seal through which vapor must pass in order to move up the column. Each tray acts as an individual still. Over time, each tray in the column will collect a substance with a different molecular structure, with the lighter molecules in the top and the heavier ones in the bottom. At some time in the distillation process, the majority of the lighter components will vaporize, flow out the top of the column, and be condensed in the overhead condenser. At this point, the component with the next highest volatility will start to vaporize. As the initial boiling point gradually moves toward the final boiling point, the level in the bottom flask begins to decrease. During some operations, the vapor appears to pulse upward one to three trays at a time. It is also possible to see one or two dry trays in the column while the other sections have a good liquid level above the tray. If the column is being pushed too hard, the upper trays may flood and cause problems in the lower section of the column. It is also possible to see the transfer of heat energy in the condenser as fluid passes in opposite directions. In a glass distillation bench-top operation, it is easy to observe occurrences and record data that are not visible on a large-scale operation. The equipment in a bench-top setup includes:

• • • • •

Bottom flask and temperature indicator Bottom flask heating mantle Distillation column Overhead condenser and cooling water Overhead flask

Dalton’s law of partial pressures (Ptotal  P1  P2  P3) can be applied to a distillation system. Dalton’s law states that the total pressure of a gas mixture is the sum of the pressures of the individual gases (the partial pressures). A distillation system is by nature designed to separate the components in a mixture. As the mixture is heated in a heat exchanger or fired heater, the piping keeps the liquid confined as it expands, artificially shifting the boiling point. The feed rate to the column is carefully controlled. The heated mixture enters the column on the feed tray and rapidly expands, with the lighter components vaporizing and the heavier liquids cascading down the internals of the column until they gain enough heat energy to flash or vaporize. The different trays in the column are filled with vapors and liquids. If you know the vapor pressure exerted by a specific chemical, you can calculate its partial pressure on the various trays. Figure 19–2 illustrates the partial pressure principle. For example, a mixture of hexane 25%, benzene 50%, and heptane 25% will exert a specific pressure at 175F. To calculate the partial pressure, use the formula: Partial pressure  vapor pressure  percent of fraction Substance

406

Vapor pressure @175°F Psia.

Percent

Hexane

20.6 psia

25%

Benzene

14.7 psia

50%

Heptane

8.8 psia

25%

19.5 Petroleum Refining: Distillation

ºF ºF %

SP PV OP% TE

TT

DPT

Dalton’s Law Partial Pressures

Tray #10

TIC TE Tray #9

FIC

I

PI

TE

P

Tray #8

FIC

FT TE

FE

Feed Tray #7

FT

FO

Feed Mix Benzene 50% Hexane 25% Heptane 25%

Vapor Pressure @ 175ºF 14.7 psia @ 175ºF 20.6 psia @ 175ºF 8.8 psia @ 175ºF

175ºF

TE

Benzene 50% Hexane 35% Heptane 15% Tray #6

Benzene 50% 14.7 X .05 = 7.35 psia Hexane 25% 20.6 psia X .25 = 5.15 psiaF Heptane 25% 8.8 psia X .25 = 2.2 psia

Ptotal = 7.35 + 5.15 + 2.2 Ptotal = 14.7 psia

Figure 19–2 Dalton’s Law of Partial Pressures

Hexane  20.6 psia  0.25  5.15 psia Benzene  14.7 psia  0.50  7.35 psia Heptane  8.8 psia  0.25  2.20 psia Total pressure  14.70 psia Using this information, we can calculate the total pressure on tray 9 by adding up the partial pressures. This information also illustrates that the chemical with the highest volatility is hexane (C6H14), which has a boiling point of 69C. Heptane has a boiling point of 98C and at 175F (79.4C) it represents the lowest percentage of the three components in vapor state above the tray. The larger the difference between the partial pressures, the easier it is to separate the fractions by boiling point. Original Feed %

BP

5.15  14.7  .35  100  35%

25%

69C

Heptane, C7H16

2.2  14.7  .15  100  15%

25%

98C

Benzene, C6H6

7.35  14.7  .5  100  50%

50%

Hexane, C6H14

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19.6 Aromatic Hydrocarbons Benzene is the most common aromatic hydrocarbon. Chemists have determined that aromatic compounds include both hydrocarbons and compounds that cannot be classified as hydrocarbons. The benzene molecule has six carbon atoms connected in a ring. Each carbon atom has four bonding sites available; however, in benzene, three are used and one is free. The three bonds are covalent; the fourth can be shared by all six carbon atoms. This creates a donut-shaped cloud or aromatic ring. Figure 19–3 shows the true benzene ring. The benzene ring may have some of its six hydrogens replaced by other groups. (Reactions with benzene are by substitution and not addition.) These compounds are found in Figure 19–4 and should be memorized. The groups within the hydrocarbon family include:

• • • • •

Alkane—Single covalent bonds Alkene—Double bonds Alkyne—Triple bonds Cycloalkane—Contains a ring or cycle of carbons Aromatic—Contains at least one highly unsaturated six-carbon ring

H

H

H

H

H H

H

C

H

C

C

C

C H

H

Benzene- a total of six electrons can be found in the donut-shaped clouds.

H

C H

Figure 19–3 True Benzene Ring

19.7 Alkenes and Alkynes The suffix “-ene” is used to describe carbon-carbon double bonds. Let’s build on the foundation of the alkane family: We have seen that these compounds fit the general formula CnH2n2. For example, ethane (C2H6) uses n as 2 and 2n  2 is 6. However, alkanes can combine with a variety of carbon and hydrogen proportions. Using ethane as a model, we remove two hydrogen atoms, one from each methyl group. This process removes the proton and electrons, allowing the hydrogen atoms to combine to form a diatomic molecule held together by a covalent bond. What is the fate of the two unpaired electrons that remain on the carbons we removed the hydrogen from? Figure 19–5 shows what the process looks like. It is possible for these two electrons to pair up and form a second covalent carbon-carbon bond. Hydrocarbons that have carbon-to-carbon double bonds are known as alkenes. 408

19.7 Alkenes and Alkynes NH 2 C

CH 3 Toluene

Benzoic Acid

Phenol

Aniline

OH

O

HO

CH 2 CH 3

Bromobenzene

Nitrobenzene Cl

NO 2

Br

Chlorobenzene

Ethylbenzene

Formulas that Represent Benzene as an aromatic (sextet) of Electrons

H H

H

H

C C

C

H

H

C

C H

H

C C

C

C

H

C H

C

C

H

H

Benzene Represented using Lewis Structure (Must Draw Two Lewis Structures to be Correct)

Figure 19–4 Nomenclature of Benzene Derivatives The alkene group closely resembles the alkane family. Ethylene (CH2CH2) is the first member of the alkene or olefin family.The next alkene is propene (C3H6), for which the shorthand formula is CH2CHCH3. By removing two hydrogens from any alkane, we can create an alkene. In molecules that have 409

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Ethane H H

: : : :

H H H :C : C : H H H

H C C

H

H H

Ethene or Ethylene H

:

:

:

:

H H C:: C H H

H

H C C H

Figure 19–5 Ethane to Ethene two or three carbon atoms, the double bond can be on the first or second carbon. In the case of butene, if the double bond is between the first and second carbon, it is called 1-butene: CH2CH-CH2-CH3  H2. If it is between the second and third carbon, it is called 2-butene: CH3-CHCH-CH3  H2. If a carbon chain has four or more carbon-carbon bonds, we number the position of the double bond using the lower available number. Compounds with two or more double bonds take the suffix “-diene” or “triene.” For example, 1,3 butadiene is shown as CH2CH-CHCH2. Ethylene and propylene currently rank fourth and fifth in industrial chemical tonnage, just behind three inorganic chemicals (sulfuric acid, nitrogen, and oxygen). Compounds in the alkynes family contain carbon-carbon triple bonds.The first member of this family is acetylene: HCCH. Acetylene is the only alkyne that has widespread industrial usage; it is a fuel for the oxyacetylene torch and welding applications. Unlike the alkane family, the first members of the alkene and alkyne families have a range of odors, from slightly sweet to sharp and pungent. As previously mentioned, alkenes and alkynes are organic compounds containing double and triple bonds and are referred to as unsaturated. Alkanes have single bonds and are classified as saturated. A saturated hydrocarbon contains the maximum number of hydrogen atoms and contains single covalent bonds. An unsaturated hydrocarbon can still accept an additional hydrogen. Another group that should be discussed is the cycloalkane family. This group is characterized with a ring or cycle of carbons from three methylene groups located on the apex of the equilateral triangle. Figure 19–6 illustrates this family. Examples of this group include:

410

cyclopropane, C3H6 (triangle)

3

cyclobutane, C4H8 (square)

4

cyclopentane, C5H10 (pentagon)

5

cyclohexane, C6H12 (hexagon)

6

19.8 Alcohols

C4 H8

C3 H 6

H2 C

H2 C

H 2C

C5 H10

CH 2

H 2C

CH 2

H 2C

CH 2

Cyclopropane

Cyclobutane

CH 2

H 2C H 2C

CH 2

Cyclopentane

C6 H12

H2 C H 2C

CH 2

H 2C

CH 2 C H2 Cyclohexane

Figure 19–6 The Cycloalkane Family

19.8 Alcohols Alcohols are compounds that contain OH groups connected to an alkyl carbon. Phenols are similar, but have an OH group connected directly to an aromatic ring. The terms primary, secondary, and tertiary are used to describe alcohols. In a primary alcohol, a carbon can be connected to one or no other carbon atoms; example: CH3-OH, methyl alcohol. A secondary is connected to two carbons; example: isopropyl alcohol. Tertiary describes connections to three other carbons; example: tert-butyl alcohol (Figure 19–7). Classify the alcohols in Figure 19–8 as primary, secondary, or tertiary, using the previous examples as a guide. Alcohols can be characterized as neutral compounds. When dissolved in pure water, the pH remains neutral or 7. When an alcohol is combined with sulfuric or phosphoric acid and heated, it loses an 411

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Common Name: sec-Butyl alcohol

Common Name: Methyl alcohol

CH 3 CH 2 CH 3

CH

CH 3

OH OH

Classification: Primary

Classification: Secondary

Common Name: tert-Butyl alcohol CH 3 CH 3

C

OH

CH 3 Classification: Tertiary

Figure 19–7 Primary, Secondary, and Tertiary Alcohols

CH3-CH2-CH2-CH2-OH

Figure 19–8 (a)

Primary Alcohol CH 3

CH 3 CH 2

CH

CH 3 CH 3

CH 2

C

OH

OH CH 3 Classification: Secondary

Figure 19–8 (b) 412

Secondary Alcohol

Classification: Tertiary

Figure 19–8 (c)

Tertiary Alcohol

Summary OH group and a hydrogen atom on the adjacent carbon to form an alkene. This is possible in alcohols that have at least one hydrogen atom on the adjacent carbon. Sodium hydroxide (NaOH) is classified as a metallic hydroxide or base and produces OH ions in water. Alcohols do not respond this way because the OH group in an alcohol is connected to the carbon atom by a covalent bond.

Ethanol Ethanol, CH3CH2OH, is often referred to as grain alcohol, because it has traditionally been produced through a fermentation process using grains such as corn, rye, and wheat. Other stocks used to produce ethanol include molasses from sugar cane, grapes, and potatoes. During the fermentation process, sugars (C6H12O6) are converted to ethanol and CO2 using enzymes that are present in yeast cells. Wine contains between 10 and 13% ethanol. Pure ethanol (95%  5% water) is classified as absolute alcohol. Recently ethanol has become popular as a gasoline additive. Denatured alcohol (ethanol) has small quantities of methanol or benzene added. Both of these chemicals are poisonous and are designed to make the ethanol unfit for drinking, thus avoiding any use or taxation as liquor. The chemical additives do not affect the laboratory use of denatured alcohol.

Methanol Methanol, CH3OH, is sometimes referred to as wood alcohol, because at one time methanol was made from wood. Modern manufacturers produce methanol by subjecting hydrogen and CO3 to extremely high temperatures and pressures in the presence of a catalyst. Methanol is a toxic liquid used as a solvent for paints, varnishes, and the production of formaldehyde.

Ethylene Glycol Ethylene glycol, HO-CH2CH2-OH, was commonly used as antifreeze in radiators, because of its unique ability to lower the freezing point of water. Ethylene glycol also has a higher boiling point than water and provides additional protection from high and low temperature variations during operation. Because ethylene glycol is toxic when ingested, other products such as propylene glycol are now being used in its place.

Isopropyl Alcohol Isopropyl alcohol or rubbing alcohol is used:

• • • •

to cool the skin by rapid evaporation (fever reduction) to disinfect cuts and scrapes as an astringent, to decrease pore size, limit secretions, and harden skin as a cosmetic solvent

Summary Science is a way of knowing and understanding the world we live in. The scientific method is described as the process by which or framework within which science operates. Key steps in the scientific method include a systematic, fact-based approach; asking questions; observing; analyzing observations, and communicating observations. Scientists propose theories and hypotheses to explain phenomena. A theory is a firmly grounded interpretation of confirmed observations. A hypotheses is a tentative explanation of a small set of observations. 413

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A mole is used to measure the mass of a sample by relating the number of atoms in a sample to its mass. A mole of any substance is its molecular formula weight expressed in grams. Avogadro’s number is a universal constant that states the number of molecules in a mole: N0  6.023  1023 molecules/mole. An easy way to handle large numbers is exponential (scientific) notation, a system based on the powers of 10. Elements are composed of identical atoms. Elements cannot be converted into other elements. Today we recognize 116 different elements. Carbon and hydrogen are the primary building blocks of the chemical and refining industry. Compounds are composed of two or more elements in welldefined ratios. Three properties of an atom or ion are the atomic number, mass number, and electron configuration. The outermost shell in an atom is the valence shell. The electrons in the valence shell are called valence electrons. Elements have different arrangements and tend to react in an effort to fill the valence shell. Dmitri Mendeleev devised the first periodic table of elements, arranged by repetitions he recognized in the properties of elements. The current periodic table is organized in sequence of increasing atomic number. Elements in the same vertical column or group have similar properties. In columns 1, 2, and 13–18, representative elements extend above the rest. The elements found in columns 3–12 are transition elements. Elements 58–71 and 90–103 are inner transition elements. The elements on the periodic table are classified as metals, nonmetals, metalloids, or noble gases. Metals have atoms that give up electrons, are malleable, and tend to be excellent conductors of heat and electricity. Nonmetals do not conduct electricity and have atoms that tend to accept electrons. Inert or noble gases gases refuse to accept or give electrons. Covalent bonding is the mechanism of electron sharing that holds atoms together to form molecules. In a covalent bond, atoms share a pair of electrons. More complex electron structures may have one, two, or three shared electron pairs between atoms. Covalent bonds are not limited to atoms of the same element or to only two atoms for each molecule. Carbon atoms tend to form four covalent bonds because there are only four electrons in the outer shell. In ionic bonding, magnetic-type bonds form between ions with opposite charges. In this process, one or more electrons transfer from one or more atoms to another, creating a positive ion and negative ion that attract or hold to each other. Solids may be bonded by one of four types: ionic, covalent, metallic, and van der Waals. Being able to balance equations allows a technician to accurately determine the correct amount of reactants or products. The total amount of reactants must equal the total amount of products. An unbalanced equation may include initial reactants, final products, process conditions, and heat, temperature, pressure, and analytical variables, but it will not include the correct quantities. In a chemical equation, the number immediately to the left of the chemical determines the molecules or mole units. Use the following principles when balancing an equation:

414

Summary

• • • • • •

Determine if the equation is balanced or not. Never touch the subscripts. Focus on the coefficients, working from one side of the equation to the other. Ensure that you have included each source for a particular element that you are attempting to balance. Adjust the coefficient of monoatomic elements last. Adjust the coefficient of polyatomic ions that are acting as a group in self-contained groups on both sides of the equation.

Petroleum refining converts raw materials into useful products. Distillation, a process used to separate the components in a mixture by their volatilities in a boiling liquid mixture, is often used in refining. Dalton’s law of partial pressures (Ptotal  P1  P2  P3) can be applied to a distillation system. Organic chemistry is the study of compounds that contain carbon. Life as we know it depends on water and on the compounds of carbon; in combination with hydrogen, oxygen, nitrogen, sulfur, and phosphorus, carbon atoms form the building blocks of life. Crude oil is composed of things that were once living on the face of the earth. The hydrocarbon family includes alkanes (single covalent bonds), alkenes (double bonds), alkynes (triple bonds), cycloalkanes (contain a ring or cycle of carbons), and aromatics (contain at least one highly unsaturated six-carbon ring). Alkanes are chemical compounds that consist of carbon and hydrogen atoms linked together by a single bond. Methane is a tetravalent simple hydrocarbon or carbon compound. The suffix “-ene” is used to describe the double bonds formed in alkenes. The alkene group closely resembles the alkane family. By removing two hydrogens from any alkane, we can create an alkene. In molecules that have two or three carbon atoms, the double bond can be on the first or second carbon. In the case of butene, if the double bond is between the first and second carbon, it is referred to as 1-butene. Compounds in the alkynes family contain carbon-carbon triple bonds. Acetylene is the only alkyne that has widespread industrial usage. The cycloalkane family is characterized by a ring or cycle of carbons from three methylene groups located on the apex of an equilateral triangle. Alcohols are neutral compounds: When dissolved in pure water, the pH remains neutral or 7. When an alcohol is combined with sulfuric or phosphoric acid and heated, it loses an OH group and a hydrogen atom on the adjacent carbon to form an alkene. Alcohols that are commonly used in industry include ethanol, methanol, ethylene glycol, and isopropyl alcohol.

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Chapter 19 Review Questions 1. What is the formula weight of aspirin (C9H8O4)? 2. Describe the special characteristics of the alkane family. 3. List the first four members of the cycloalkane family and the distinguishing characteristics of this group. 4. Describe the special characteristics of the alkene family. 5. Describe the special characteristics of the alkyne family. 6. Identify the classification and special characteristics of benzene. 7. Draw the benzene ring. 8. List the key steps in balancing a chemical equation. 9. Balance: CaO  HCl → CaCl2  H2O 10. Balance: NaOH  SO2 → Na2SO3  H2O 11. What is the molecular weight of (NH2)2CO? 12. How much does one mole of H2O weigh? 13. List the electron configuration for bromine. 14. List four different applications for distillation. 15. Cyclopropane is characterized by what shape?

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Chemical Process Industry Overview After studying this chapter, the student will be able to: • • • • •

Describe industrial processes and systems. Describe the economic impact of the U.S. chemical manufacturing industry. Explain the importance of oil and gas exploration and production. Identify the basic equipment used in power generation. Describe the “life cycle” of wastewater—where it comes from and how it is treated. • Explain the operation concepts associated with the mining and mineral, food and beverage, pharmaceutical, and pulp and paper processing industries.

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Key Terms Food and beverage processing—industry segment that includes bakeries, breweries, dairies, meat packaging, shellfish processing, and the fishing industry. Mining and mineral processing—industry segment that involves technicians in underground mining and open-pit mining. Mining is the systematic extraction of minerals from beneath the surface or inside the pit. This process is also applied to nonmetallic minerals and rocks (e.g., coal mining). Nuclear generators—reactors that produce an unlimited amount of heat that can be used to produce steam, which can in turn be used to produce electricity or in a number of other useful applications. Oil and natural gas exploration and production—location and extraction of hydrocarbon resources; the first step in providing aviation fuel, gasoline for motorized vehicles, light and heat for homes, and raw materials for industry to support the production of materials that make up our modern society. Pharmaceutical industry—industry segment that maintains a close relationship with research, chemists, engineers, doctors, and the medical profession. The manufacturing side of this industry employs cutting-edge technologies associated with reactions, filtering, drying, and distillation. Power generation companies—transport low-cost alternating current across great distances using power transformers to step down high voltages. Power transformation—the conversion of energy into electricity. Methods for transforming power into electrical power include: (1) steam turbines, (2) gas turbines, (3) wind turbines, (4) water turbines, and (5) diesel engines. These devices are connected to electric generators, where fuel cells produce electricity. Pulp and paper industry—industry segment consisting of pulp and paper mills and converting operations. Pulp is made by chemically or mechanically separating wood fibers from nonfibrous material. Sewage—water that contains 0.1% solid waste matter produced by human beings. Sewage is frequently referred to as wastewater. More than 80% of the sewage produced in the United States comes from industrial sources. U.S. chemical manufacturing industry—economic bloc that produced more than $460 billion of export goods in 2003.

20.1 Industrial Processes Industrial processes are categorized as petrochemical, refinery, environmental, or gas processes. At present, hundreds of different processes exist and are used in industry. Recently, the petrochemical and environmental areas have significantly added to this overall total. The more common

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20.2 Chemical Manufacturing Petroleum Refining petrochemical processes handle ethylene, olefins, benzene, ammonia, and aromatics. Popular refinery operations include traditional crude distillation, reforming, cracking, isomerization coking, and alkylation. Since the early 1980s, environmental issues have been in the forefront of public and industry consciousness. Much-used environmental systems are applied to water treatment, air pollution, solid waste, and toxic waste.

20.2 Chemical Manufacturing Petroleum Refining The U.S. chemical manufacturing industry (see Figure 20–1) produced more than $460 billion worth of export goods in 2003. Chemical exports alone for 2003 were in excess of $91 billion. The second-ranked industry is motor vehicles, with more than $61 billion in sales. Chemical plants and refineries are a complex array of systems and operations designed to produce specific products associated with the hydrocarbon family. The term chemical manufacturing petroleum refining is directly associated with refinery and chemical plant operation. Modern manufacturing includes the use of equipment and technology directly related to this industry. This industry segment is primarily responsible for the design and development of the original process technology program. As the program has expanded, a much larger family has been included: natural gas and oil exploration and production, power generation, water and wastewater treatment, mining and mineral processing, food and beverage processing, pharmaceutical manufacturing, and paper and pulp manufacturing. A much closer relationship now exists in

Figure 20–1 Chemical Manufacturing Industry

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college programs between manufacturing engineering technology, engineering technology, and process technology. Refineries are designed to separate the various fractions found in crude oil into useful products, such as naphtha, gasoline, kerosene, light oils, heavy oils, and natural gases. Each of these products is essential for keeping our global economy moving. Refineries receive crude oil and chemical from pipelines, ships, barges, rail cars, and trucks. These devices are used to transport materials from oil fields and markets around the world. Chemical plants use the raw materials produced in the refinery to make the chemicals that are the basis of products like plastics and synthetic rubber. Chemicals made by these processes are used in the clothing and textile industry, automobile industry, pharmaceutical and medical industry, computer and electronic appliance industry, and in paint, fertilizers, and so on. Chemical plants specialize in the large-scale production of chemical feedstocks and products made from the everversatile hydrocarbons. Technicians may work inside a chemical plant manufacturing a specific chemical and be totally unaware of how and where that chemical product is being used in our complex modern society.

20.3 Exploration and Production Oil and natural gas exploration and production are the first step in providing aviation fuel, gasoline for motorized vehicles, lights and heat for homes, and raw materials for industry to support the production of the myriad materials that make up our modern society. This includes plastics, fertilizers, medicines, and synthetic rubber. Our modern computer and information age would not exist without these products. Our present educational systems do not eloquently describe the importance of exploration and production, which include both offshore and onshore drilling. Currently, approximately 25% of U.S. oil and natural gas production comes from offshore drilling rigs and facilities. Alaska is responsible for 18% of the U.S. oil and gas market. The government owns a bit more than one-third of the property in the United States. More than half of this land is set aside as protected areas, national parks, and wilderness areas. When oil and gas manufacturers develop hydrocarbon facilities on government lands, they are required to pay a royalty to the government. Oil and gas manufacturers pay billions in taxes to individual states and the federal government. Many new technicians are curious about how the industry explores for oil and natural gas. Between 1859 and the early 1900s, finding oil was a matter of luck; however, today we have the technology to “see” what lies beneath the ground. Geologists look for a number of clues in rocks that suggest the presence of oil. Oil is a fossil fuel that began forming more than 10 million years ago in shallow seas, as tiny plants and animals called plankton died and sank into the mud and sand. Over time, the remains of these organisms formed into sedimentary layers that contained little oxygen. In this environment, tiny microorganisms broke the fractions into carbon-rich compounds. The heat and pressure of the built-up layers distilled the resulting organic “soup” into crude oil and natural gas. Drilling rigs are set in place after geologists have identified and evaluated a spot with potential to yield oil (see Figure 20–2). 420

20.3 Exploration and Production

Hoisting System

Derrick

Swivel

Kelly Pipe

Turntable

Engine

Electric Generator

Casing

Blowout Preventer

Mud Pit Drill String Drill Collar Bit

Figure 20–2 Oil Rig Modern geologists look at surface rocks and terrain. They also use satellite images, seismology, sniffers, and magnetometers to find oil. These modern methods have a 10% success rate. Global positioning satellites may assist in locating and marking potential drilling sites. (See Figure 20–3.) Technicians involved in exploration and drilling use a variety of equipment, including:

• • • • • • •

Large diesel engines or electric generators Hoisting systems or turntables Rotating equipment—swivel, kelly, turntable, drill string (drill pipe, collars) Casing Circulation system—pipes, valves, pumps, mud-return line, shale shaker, shale slide, mud mixing hopper, mud pits, reserve pit Derrick Blowout preventer 421

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Figure 20–3 Oil Recovery

Offshore Structures A drilling rig is, essentially, a structure designed to house equipment and technology that can be used to explore for, drill for, and extract natural gas or oil from underground reservoirs. This activity may be a land-based operation or a marine-based operation. An offshore drilling rig is more correctly identified as a platform. Platforms that have a producing well are called production platforms. Operations whose primary purpose is drilling rest on floating rigs or semisubmersible rigs. It has been estimated that more than 4,000 offshore production facilities exist on the outer continental shelf (OCS). These exploration wells can be drilled to depths of around 10,000 feet. Most production systems are designed to operate at depths of 6,000 feet. Oil and gas product pipeline networks extend well off the continental slope. Offshore production rigs and drilling and production platforms can be classified as onshore platforms, fixed platforms, jackup rigs, semisubmersibles, drill ships, and tension-leg platforms. Fixed platforms are built of concrete and steel and are firmly anchored to the sea bed for long-term production drilling. A semisubmersible platform has hollow legs that can be used as displacement tanks to raise, lower, or stabilize the platform. This type of platform is movable and typically is anchored to the sea floor by cables. Jackup platforms have movable legs that can be raised or 422

20.4 Power Generation lowered; this type of platform can be moved from one location to another. Drill-ship rigs use global positioning systems (GPS) to drill for natural gas or oil. Tension-leg platforms allow deep-water drilling by anchoring to the sea floor and virtually stopping any vertical movement. Offshore structures are relatively self-sufficient; they provide electrical generators, water desalinators, sleeping facilities, communication stations, and modern amenities. Production platforms are connected by pipelines or floating storage units to onshore operations. Key process elements of oil and gas recovery include: wellhead, production manifold, production separator, water injection pumps, gas compressors, glycol process to dry gas, oil and gas export metering, and main oil-line pumps.

20.4 Power Generation Electricity generation is the first step in delivering power to consumers and the local community. Three important aspects of power generation include: electric power transmission, electricity distribution, and electricity retailing (see Figure 20–4). Power generation requires the use of large industrial boilers to produce steam. Steam generators, or boilers as they are commonly called, are used by industrial manufacturers to produce steam. Boilers use natural gas as fuel to operate the burners. Steam is used to turn steam turbines that are used as the primary driver for large commercial electric generators. Steam generators are part of a complex network that also

Figure 20–4 Power Generation 423

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includes valves, pipes, storage tanks, pumps, compressors, motors, steam and gas turbines, heat exchangers, cooling towers, instrumentation, and advanced computer technology. In addition, a large assortment of electrical equipment, transformers, breakers, and wiring is also part of this network. Electricity can be as hazardous as the most lethal chemical, so safety training and safe operating practices are carefully embedded in the training program. Electricity provides light, heat, and power for a variety of activities. Power generation companies transport low-cost alternating current across great distances using power transformers to step down high voltages. Power generation plants use natural gas, oil, coal, hydroelectric, nuclear, wind, solar, tidal harness, or hydrogen as sources to produce heat or mechanical (rotational) energy. The power transformation methods used to convert heat or mechanical power into electrical power include:

• • • • •

Steam turbines Gas turbines Wind turbines Water turbines Diesel engines

These devices are connected to electric generators, where fuel cells produce electricity. Nuclear generators produce an unlimited amount of heat that can be used to produce steam that can be used to produce electricity or in a number of other useful applications. Cogeneration is a process that combines the generation of electricity and heat, using fossil fuels, syngas, biogas, or solar power as fuel sources. Power generation and electric companies can be found in strategic locations all around the world. This opens up many employment opportunities.

20.5 Water and Wastewater Treatment Process technicians work in water and wastewater treatment facilities located around the world. (See Figure 20–5.) City water supplies require employees with strong backgrounds in process equipment and technology. Special licenses and certifications are required to work in these areas. Whether their jobs deal with safe drinking water supplies, wastewater treatment, or another part of the water system, technicians should receive highly specialized training. Public water supplies are regulated and tested frequently for purity. Surface waters, rivers, streams, and lakes may be used as the original feed source. Depending on the specific characteristics of the water, a wide variety of purification techniques can be used, including settling, filtration, chlorination, demineralization, and mineral removal. The need for safe loading, storage, inspection, treatment, and transportation within the public water system means that this field comprises a very complex set of processes. (See Figure 20–6.) Wastewater treatment is an extremely important service-related industry that is carefully integrated into our society. Sewage is defined as water that contains one-tenth of 1% (0.1%) solid waste matter produced by human beings. Sewage is frequently referred to as wastewater. Wastewater comes from sinks and toilets of homes, factories, offices, and restaurants. Sewage contains harmful chemicals and disease-producing bacteria. Without processing, this harmful material 424

20.5 Water and Wastewater Treatment

Pump Filter Cooling Tower

Settling Basin

Figure 20–5 Wastewater Treatment

Figure 20–6 Water Treatment would eventually find its way into our lakes, rivers, and oceans. Industry converts this harmful material into a semi-clear, harmless liquid called effluent. More than 80% of the sewage produced in the United States comes from industrial sources. Primary treatment removes 50% of the heaviest solid material from the sewage. Secondary 425

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treatment removes 85%–90% of the remaining solids; this step may use the activated sludge process or the trickling filtration process. The third step, called tertiary treatment, may include chemical treatment, radiation treatment, microscopic treatment, or discharge of effluent into lagoons. Water treatment technicians work with a variety of process systems to improve water quality before it is discharged into public water systems.

20.6 Mining and Mineral Processing Mining and mineral processing technicians are involved in both underground mining and open-pit mining. Mining is the systematic extraction of ore from beneath the ground surface or inside a pit. This process is also applied to nonmetallic minerals and rocks (e.g., coal mining). Underground mining (Figure 20–7) requires large capital investments in equipment and structured mining systems. Entry into underground mines is by shafts, adits, spiral ramps, or inclines. Developmental workings consist of mine levels and sublevels dug into the deposits. These passageways are called drifts when they follow the deposits, and cross-cuts when they are driven across the mineralization. Developmental workings on successive mine levels are connected by passageways called raises when driven upward, and winzes when driven downward. Mining technicians use conveyors, drills, hand tools, pumps, pipes, valves, elevators, heavy equipment, and personal protective equipment. Exploration and development combine to form the preproduction stage of underground mining. During the exploration phase, newly

Shaft Collar Winze Incline

Cross-Cut Loading Pocket

Adit Ore Pass

Sump Figure 20–7 Mining Methods 426

20.7

Food and Beverage Processing

discovered mineral deposits are evaluated for total tonnage and grade, suitability for mining, and metallurgical recovery characteristics. Mine development starts if the initial evaluation indicates that sufficient quantities of quality deposits can be accessed in a cost-effective manner. The mining methods used depend on the strength of the ore and wall rock. These methods include:

• • • • • • • • • • •

Open stoping Sublevel stoping Vertical crater retreat Room-and-pillar mining Shrinkage stoping Cut-and-fill stoping Square-set stoping Longwall mining Top-slice stoping Sublevel caving Block caving

20.7 Food and Beverage Processing The food and beverage processing industry (see Figure 20–8) is another important segment of the chemical processing industry. College programs prepare students to take entry-level positions in a wide variety of areas. Food and beverage processing workers are found in bakeries, breweries, dairies, meat packaging, shellfish processing, and the fishing industry. Half of the tasks are completed with automated equipment, with the balance being done manually. Work may include loading and unloading cartons on conveyors or rolling racks, packing boxes, keeping the area clean, and doing equipment and system checks. Operation of advanced automation requires skills, knowledge, and training beyond those received by typical workers. Computers and control systems that change temperatures, pressures, tank levels, flows, and compositional values are part of the food and beverage manufacturing system. Many of the automated systems are unique and require hours of on-the-job training before a technician can work unsupervised. Modern food and beverage manufacturers use equipment and technology currently being taught by PTEC programs in local community colleges and universities. In addition to working with these systems, technicians are required to use advanced quality principles and safety techniques. Quality control includes the use and application of information presently being taught in local process technology programs. Employers look for technicians who are team players, display a willingness to work and learn the job, and work well in diverse work groups. As for other areas in the CPI, technicians must be dependable and committed to safe work practices. Safety, health, and environment include training in principles that have direct application to the food and beverage industry. The work in the food and beverage industry is physically demanding and has a lower pay structure than for technicians working in the hydrocarbon processing industry. Many food and beverage companies work rotating shifts and use self-directed work teams. 427

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Figure 20–8 Food and Beverage Processing

20.8 Pharmaceutical Manufacturing Pharmaceutical manufacturers employ three techniques covered in local process technology programs: bench-top operations, pilot plant operations, and full-scale manufacturing. The pharmaceutical industry maintains a close relationship with researchers, chemists, engineers, doctors, and the medical profession. The manufacturing side of this industry employs cutting-edge technologies associated with reactions, filtering, drying, and distillation. Advanced instrumentation and computer technology are found at every level of this operation. Technicians employed in this field are required to have advanced training and college degrees in process technology, chemistry, and/or engineering. Pharmaceutical manufacturing (see Figure 20–9) is an exciting career that can be pursued in many parts of the world. The work is considered high tech and cutting edge and in many aspects is very challenging. Pharmaceutical plants are multipurpose, DEA-certified, and FDA-registered, with a complete spectrum of active pharmaceutical ingredient (API) production capabilities. These typically include drying, process development, chemical synthesis, advanced micronization with state-of-the-art jet mills, and dosage-form manufacturing suites. Pharmaceutical manufacturers develop high-purity, sophisticated chemicals in weights from gram quantities to hundreds of kilos. The equipment and technology associated with pharmaceutical manufacturing include areas and topics covered in process technology AAS degree programs. A special emphasis is placed on: 428

20.8 Pharmaceutical Manufacturing

Abbott Aventis

Cipla

GlaxoSmithKline

Merck

Johnson & Johnson

AstraZeneca Janssen

Solvay

Ranbaxy Pfizer OHM

Figure 20–9 Major Pharmaceutical Manufacturers

• • • • • • • • • • • • • • • • •

Cryogenic reactions (to ⫺80⬚C) Cryogenic volatile organic compound (VOC) condensers (to ⫺73⬚C) High-vacuum distillation Monel reactors (50 gallon) Stainless-steel reactors (200 to 1,500 gallon) Glass-lined/Hastelloy reactors (50 to 2,000 gallon) Plate columns (1,500 gallon) Packed columns (2,000 gallon) Hastelloy centrifuges Reactor/drying systems Filter-dryers for API manufacturing of high-purity, ultra-high-quality products Temperature ranges from –80⬚C to 280⬚C Solids processing systems Hydrogenation to 35 bar Mass spectrometers Liquid and gas chromatographs Infrared (IR) and ultraviolet (UV) spectrometers

Chemical reactions used in pharmaceutical manufacturing include: • Acetylenic chemistry • Aldol condensation • Ammonia reactions 429

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• • • • • • •

Chiral chemistry Cryogenic reactions Epichlorohydrin chemistry Hydrogenization Optical resolution Hydride reduction Sulfoxidation

Technicians working in the pharmaceutical industry will be in a competitive, well-paying, stable environment. Job movement tends to be from one pharmaceutical company to another with higher pay. Job transfers and promotions are possible within companies. New advancements in equipment, technology, and pharmaceuticals will create an environment of lifelong learning and constant change. The research side of pharmaceuticals is constantly investing in computing technology and three-dimensional (3-D) molecular modeling to streamline drug creation and accelerate regulatory compliance and approvals. Computers are also extensively used to predict biologically active compounds and to load and analyze raw data from clinical trials.

20.9 Pulp and Paper Processing A number of process technology programs are working with the pulp and paper industry to add specific tasks relating to the desired skill sets for this field. Many of the core skills are covered in the existing program, and with a few minor additions the program can be adapted to fit this industry segment. A paper and pulp industry operation is typically located in an area with abundant raw materials. These facilities spread out over many acres and closely resemble the scope of large chemical plants (Figure 20–10). This industry is composed of two sections: mills and converting operations. Pulp and paper mills produce chemical, mechanical, and thermomechanical pulps to form paper, building papers, and form paper. Pulp is made by chemically or mechanically separating wood fibers from nonfibrous material. The typical process uses sodium hydroxide and sodium sulfide to dissolve the nonfibrous material. Chlorine gas, hydrogen peroxide, chlorine dioxide, and sodium peroxide can be used to bleach the paper. Pulpwood is brought into the paper mill from local forests by truck. Raw wood is sent to a device called a barker before it is sent to the chipper. Bark is removed from the trees in the barker, and the stripped wood is then broken up into smaller chunks in the chipper. A screen ensures that uniform wood chips are fed into the continuous digester, where chemicals are added, recovered, and added again. This slurry is then sent to the bleaching section. From this point, the paper pulp is sent to a section that includes a refiner, jordan, and cleaner. The cleaner has two separate flows: a wet side and a dry side. On the wet side, the water is removed from the treated pulp. A device called the Fourdriner machine prepares the pulp before it enters the presses. From the presses, the material enters a series of dryers before going to a size press. Paper is rolled up using a device called a roll winder. On the dry side of the cleaners, the pulp goes to a cylinder machine before going to the presses and dryers. As you can tell from this brief description, the paper manufacturing industry uses specialized equipment to produce paper products; however, much of the equipment and technology discussion and education in local process technology programs can be applied in this industry. 430

Summary

Continuous Digester Chemical Recovery and Regeneration Screen Chipper Barker Blow Tank

Pulpwood

Cleaners

Jordan

Pi

Washing

Bleaching

Refiner

Ti

Presses Roll Winder Cylinder Machine

Coaters

Calenders

Dryers Roll Winder

Wet End Fourdriner Presses

Figure 20–10

Dryers

Coaters

Calenders

Paper and Pulp Manufacturing

Summary Chemical manufacturing petroleum refining, once associated directly with refinery and chemical plant operation, has come to include natural gas and oil exploration and production, power generation, water and wastewater treatment, mining and mineral processing, food and beverage processing, pharmaceutical manufacturing, and paper and pulp manufacturing. Refineries separate the various fractions found in crude oil into useful products, and chemical plants use those raw materials to make chemicals used in the processes of the clothing and textile industry, the automobile industry, the pharmaceutical and medical industries, the computer and electronic appliance industry, and in paint, fertilizers, and so on. Refineries are designed to separate the various fractions found in crude oil into useful products. Each of these products is essential for keeping our global economy moving. Refineries receive crude oil and chemical from pipelines, ships, barges, rail cars, and trucks, which transport materials from oil fields and markets around the world. 431

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Chemical plants use the raw materials produced in the refinery to make chemicals that are in turn used to make products such as plastics and synthetic rubber. Chemical plants specialize in the largescale production of chemical feedstocks and products made from ever-versatile hydrocarbons. Industrial processes are categorized as petrochemical, refinery, environmental, or gas processes. There are hundreds of different processes, and the overall total has been expanded significantly by the petrochemical and environmental. The more common petrochemical processes use ethylene, olefins, benzene, ammonia, and aromatics. Refinery operations include traditional crude distillation, reforming, cracking, isomerization coking, and alkylation. Environmental systems are applied to water treatment, air pollution, solid waste, and toxic waste. Oil and natural gas exploration and production is the first step in providing aviation fuel, gasoline for vehicles, light and heat, and raw materials for industry to support the production of the many materials that our modern society uses. This includes plastics, fertilizers, medicines, and synthetic rubber. Exploration and production include offshore drilling and onshore drilling. Three important aspects of power generation include: electric power transmission, electricity distribution, and electricity retailing. Power generation requires the use of large industrial boilers to produce steam. Public water supplies are regulated and tested frequently for purity. Surface waters, rivers, streams, and lakes may be used as the original feed source. Depending on the specific characteristics of the water, a wide variety of purification techniques may be used, including settling, filtration, chlorination, demineralization, and mineral removal. Technicians working with water supplies or wastewater treatment should receive highly specialized training; also, special licenses and certifications are required to work in these areas. Mining and mineral processing technicians are involved in underground mining and open-pit mining, processes that systematically extract ore from beneath the surface of the ground or the inside of a pit. This process is also applied to nonmetallic minerals and rocks (e.g., coal mining). Underground mining requires large capital investments in equipment and structured mining systems. The food and beverage processing industry is another important part of the chemical processing industry. College programs prepare students to take a wide variety of entry-level positions in bakeries, breweries, dairies, meat packaging, shellfish processing, and the fishing industry. Although some tasks are completed with automated equipment, the balance are done manually. Tasks may include loading and unloading conveyors or rolling racks, packing boxes, keeping the area clean, and doing equipment and system checks. Pharmaceutical manufacturers used three techniques being taught in local process technology programs: bench-top operations, pilot plant operations, and full-scale manufacturing. The pharmaceutical industry maintains a close relationship with researchers, chemists, engineers, doctors, and the medical profession. The manufacturing side of this industry employs the use of cuttingedge technologies for reactions, filtering, drying, and distillation. Advanced instrumentation and computer technology are used at every level of this operation. Technicians employed in this area are required to have advanced training and college degrees in process technology, chemistry, and/or engineering.

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Summary Paper and pulp industry operations are typically located in areas with abundant raw materials. This industry is composed of two sections: mills and converting operations. Pulp and paper mills produce chemical, mechanical, and thermomechanical pulps to form paper and building papers. Pulp is made by chemically or mechanically separating the wood fibers from nonfibrous material. These large facilities spread out over many acres and closely resemble large chemical plants.

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Chapter 20 Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

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Describe three petrochemical processes. Describe three refinery processes. Describe how wood is turned into paper products. Explain the close relationship between pharmaceutical manufacturing and the chemical processing industry. Describe the food and beverage processing industry. Describe the different aspects of mining and mineral processing. Explain the roles and responsibilities of water and wastewater treatment workers. List the equipment that is used in both power generation and process technology. Describe the importance of oil and gas exploration and production. Describe the importance of wastewater treatment and water treatment.

Absorbed heat—transferred heat; effects include increase in volume and temperature, change of state, electrical transfer, and chemical change. Absorber—device used to remove selected components from a gas stream by contacting the stream with a gas or liquid. Acid—a chemical compound that has a pH value below 7.0, changes blue litmus to red, yields hydrogen ions in water, and has a high concentration of hydrogen ions. Adsorber—device (such as a reactor or a dryer) filled with porous solid designed to remove gases and liquids from a mixture. Air permits—government-granted licenses that must be obtained for any project that has the possibility of producing air pollutants. Air pollution—contamination of the air, especially by industrial waste gases, fuel exhausts, or smoke. Air-purifying respirator—breathing device that mechanically filters or absorbs airborne contaminants. Air-supplying respirator—breathing device that provides the user with a contaminant-free air source. Algebra—a branch of mathematics that uses letters to represent numbers and signs to represent

operations. It is a kind of universal arithmetic or, more simply, mathematics using letters. Alkane group—family of hydrocarbons that are composed of carbon and hydrogen held together by single covalent bonds. Alkylation—uses a reactor to make one large molecule out of two small molecules. Alkylation unit—uses a reactor filled with catalyst to cause a chemical reaction that produces the desired product. AMU—see atomic mass unit. API gravity—standard by which to measure the heaviness or density of a hydrocarbon; a specially designed hydrometer marked in units API is used. Applied General Chemistry—study of the general concepts of chemistry with an emphasis on industrial applications. Students measure physical properties of matter, perform chemical calculations, describe atomic and molecular structures, distinguish periodic relationships of elements, name and write inorganic formulas, write equations for chemical reactions, demonstrate stoichiometric relationships, and demonstrate basic laboratory skills. Applied Math for Process Technicians—variations in this area include studies in two or more of the following areas; basic mathematics, technical algebra, math with applications, college algebra,

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Glossary statistics, trigonometry, statistics, applied or academic physics.

Batch process—order of work in which all ingredients are added to the process up front.

Atmospheric pressure—the combined weight of all the gases exerted on the surface of the earth. At sea level, the total mass is estimated at 5.5 ⫻ 1015 tons, or 760 mmHg, or 14.7 psi, or one atmosphere.

Baume´ gravity—the standard used by industrial manufacturers to measure nonhydrocarbon heaviness.

Atom—the smallest particle of a chemical element that still retains the properties of the element. An atom is composed of protons and neutrons in a central nucleus surrounded by electrons. Nearly all of an atom’s mass is located in the nucleus. Atomic mass unit (AMU)—the sum of the masses in the nucleus of an atom. Atomic number—identifies the position of the element on the periodic table and the total number of protons in the atom. Automatic/manual control—term describing two modes in which controllers can be operated. During plant start-up, the controller is typically placed in the manual position. In this mode, only manual control affects the position of the control valve; it does not respond to process load changes. After the process is stable, the operator places the controller in automatic mode, which allows the controller to supervise the control loop function. At this point, the controller will automatically open and close the control valve to maintain the setpoint. Balanced equation—axiom that the sum of the reactants (atoms) equals the sum of the products (atoms). Barometer—an instrument to measure atmospheric pressure; invented by Evangelista Torricelli in 1643. Base—a chemical compound that has a soapy feel and a pH value above 7.0. It turns red litmus paper blue and yields hydroxyl ions.

Benzene—the most common aromatic hydrocarbon. The benzene molecule has six carbon atoms connected in a ring. Each carbon atom has four bonding sites available; in benzene, three are used and one is free. The three bonds are covalent; the fourth can be shared by all six carbon atoms. This creates a donutshaped cloud or aromatic ring. Reactions with benzene are substitution and not addition. Bernoulli’s principle—states that in a closed process with a constant flow rate, changes in fluid velocity (kinetic energy) decrease or increase pressure; kinetic-energy and pressure-energy changes correspond to pipe-size changes; pipe-diameter changes cause velocity changes; and pressureenergy, kinetic-energy (fluid velocity), and pipediameter changes are related. Big Rollover—point at which global oil production peaks and then begins to decline. Biogenic theory—describes how natural gas and crude oil were formed using pressure or compression and heat on ancient organic material. Boilers—devices primarily designed to boil water and generate steam for industrial applications. Boilers are classified as either water tube or fire tube. Steam generation systems produce high-, medium-, and low-pressure steam for industrial use. Boyle’s law—at a constant temperature, the volume of a gas is inversely proportional to its pressure. V P —1 ⫽ —2 or P1V1 ⫽ P2V2 V2 P1 C&E diagram—see cause-and-effect diagram.

Basic hand tools—term used to describe the typical tools that process technicians use to perform their job activities.

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CAER—see Community Awareness and Emergency Response.

Glossary Cascade control—a term describing how one control loop controls or overrides the instructions of another control loop to achieve a desired setpoint. Catalyst—a chemical that can increase or decrease a reaction rate without becoming part of the product. Catalysts are classified as adsorption, intermediate, inhibitor, or poisoned. Catalytic cracking—process that uses a catalyst to separate hydrocarbons. Catcracker—uses a fixed-bed catalyst to separate smaller hydrocarbons from larger ones. Catcracking—a process designed to increase the yield of desirable products from a barrel of crude oil; uses a catalyst to accelerate the separation process. Cause-and-effect (C&E) diagram (fishbone diagram)—a method for summarizing available knowledge about the causes of process variation. Charles’s law—at a constant pressure, the volume of a gas is proportional to its absolute temperature. V T V V —1 ⫽ —1 or —1 ⫽ —2 V2 T2 T1 T2 Chemical bonding (covalent)—occurs when elements react with each other by sharing electrons. This forms an electrically neutral molecule. Chemical bonding (ionic)—occurs when positively charged elements react with negatively charged elements to form ionic bonds through the transfer of valence electrons. Ionic bonds have higher melting points and are held together by electrostatic attraction. Chemical equation—numbers and symbols that represent a description of a chemical reaction. Chemical processing industry (CPI)—business segment composed of refinery, petrochemical, paper and pulp, power generation, and food processing companies and technicians. Chemical reaction—interactions between two or more chemicals in which a new substance is formed;

a term used to describe the breaking, forming, or breaking and forming of chemical bonds. Types include exothermic, endothermic, replacement, and neutralization. Chemistry—the science and laws that deal with the characteristics or structure of elements and the changes that take place when elements combine to form other substances. Clean Air Act—legislation intended to enhance the quality of the nation’s air, accelerate a national research and development program to prevent air pollution, provide technical and financial assistance to state and local governments, and develop a regional air pollution control program. Clean Water Act of 1972—legislation adopting the best available technology (BAT) strategy for all cleanups. College programs in process technology—stateapproved and regionally accredited programs that include courses such as Introduction to Process Technology; Safety, Health, and Environment; Process Instrumentation; Process Technology 1— Equipment, PT 2—Systems, and PT 3—Operations; Process Troubleshooting; Principles of Quality; and applied chemistry, physics, and basic math. Combustion reaction—an exothermic reaction that requires fuel, oxygen, and heat to occur. In this type of reaction, oxygen reacts with another material so rapidly that fire is created. Community Awareness and Emergency Response (CAER)—a program designed to inform the community surrounding a plant of potentially hazardous situations and of hazardous chemicals found in the plant, to work with the community to develop emergency response programs, and to open the lines of communication between industry and the community. Community right-to-know—a principle holding that a community should be aware of the chemicals manufactured or used by local chemical plants and business. Legislation, regulations, and programs

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Glossary based on this principle are intended to involve the community in emergency response plans, improve communication and understanding between industry and the surrounding community, improve local emergency response planning, and identify potential hazards. Compound—a substance formed by the chemical combination of two or more substances in definite proportions by weight. Compressor—a device designed to accelerate or compress gases. Compressors come in two basic designs: (1) positive displacement (rotary and reciprocating), and (2) dynamic (axial and centrifugal). Compressor system—key elements of this system include piping, valves, a compressor, a receiver, heat exchangers, dryers, back pressure regulators, gauges, and moisture removal equipment. Control charts (SPC charts)—statistical tools used to determine and control process variations. Control loop—a collection of instruments that work together to automatically control a process (such as pressure, temperature, level, flow, or analytical variables). A loop includes a primary element or sensor, a transmitter, a controller, a transducer, and a final control element. Information from control loops is invaluable in the troubleshooting process. Controller—device the primary purpose of which is to receive a signal from a transmitter, compare this signal to a setpoint, and adjust the (final control element) process to stay within the range of the setpoint. Controllers come in three basic designs: pneumatic, electronic, and electric. Controller modes—settings and functions that include proportional (P), proportional plus integral (PI), proportional plus derivative (PD), and proportionalintegral-derivative (PID). Proportional control is primarily used to provide gain where little or no load change typically occurs in the process. Proportional plus integral is used to eliminate offset between the setpoint and process variables; PI works best where

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large changes occur slowly. Proportional plus derivative is designed to correct fast-changing errors and avoid overshooting the setpoint; PD works best when frequent small changes are required. Proportional-integral-derivative is applied where massive, rapid load changes occur; PID reduces the amount of swing between the process variable and the setpoint. Cooling tower—device used by industry to remove heat from water. In a typical tower, a box-shaped collection of multilayered slats and louvers directs airflow and breaks up water as it cascades from the top of the water distribution system. Cooling towers are classified by the way they produce airflow and by the way the air moves in relation to the downward flow of water. Basic designs include atmospheric, natural, forced, and induced draft. Cooling-tower system—includes a cooling-tower and pipe system to transfer cooled water to the unit and back to the cooling-tower water-distribution system. The cooling tower has a series of complex instrument systems to control ppm, pH, level, temperature, fan speed, and flow rate. Covalent bonding—the mechanism of electron sharing that holds atoms together to form molecules. In a covalent bond, atoms share a pair of electrons. CPI—see chemical processing industry. Cycloalkane family—group of hydrocarbons characterized by the presence of a ring or cycle of carbons from three methylene groups located on the apex of the equilateral triangle. Cyclone—a device used to remove solids from a gas stream. Dalton’s law of partial pressures—states that the total pressure of a gas mixture is the sum of the pressures of the individual gases (their partial pressures); Ptotal ⫽ P1 ⫹ P2 ⫹ P3. Demineralizer—a filtering-type device that removes dissolved substances from a fluid.

Glossary Density—the heaviness of a substance. Department of Transportation (DOT)—governmental agency empowered to regulate the transportation of goods on public roads and highways. Derivative mode—see rate mode. Distillation—a process used to separate the components in a mixture by their volatilities in a boiling liquid mixture. Distillation column—a collection of stills stacked one on top of another; separates chemical mixtures by boiling points. Distillation columns fall into two distinct classes: plate and packed. Distillation tower—a series of stills arranged so the vapor and liquid products from each tray flow countercurrently to each other. Diversity training—identifies and reduces hidden biases between people with differences. Dmitri Mendeleev—(1834–1907); a Russian professor of chemistry who devised the first periodic table of elements. DOT—see Department of Transportation. Educational credentials—job qualifications earned through school study; include a one-year certificate or a two-year AAS degree. Certificates may be level one or level two. Electrical drawings—graphical representations that use symbols and diagrams to depict an electrical process system. Electrical system—system composed of a boiler, a steam turbine, a main substation with transformers, a motor control center, and electrically powered equipment. Electron—a negatively charged particle that orbits the nucleus of an atom. Element—matter composed of identical atoms.

Elevation drawings—graphical representations showing the location of process equipment in relation to existing structures and ground level. Emergency response—actions taken when an emergency occurs in an industrial environment; how specific individuals act during an emergency situation. The employer must have a written plan, setting out and documenting these actions, that follows a specific set of standards. Drills are carefully planned and include preparations for worstcase scenarios (e.g., vapor releases, chemical spills, explosions, fires, equipment failures, hurricanes, high winds, loss of power, and bomb threats or bombings). Endothermic reaction—a reaction that requires external heat or energy to take place. Energy—anything that causes matter to change and does not have the properties of matter. Environmental Protection Agency (EPA)—a federal agency with authority to make and enforce environmental policy. Equipment failure—occurrence when equipment has broken, ruptured, or is no longer responding to its design specifications. Equipment location drawings—show the exact floor plan location of equipment in relationship to the plant’s physical boundaries. Estimated ultimately recoverable (EUR)— technical term describing the total amount of crude oil that will ultimately be recovered. This number is difficult to calculate and fluctuates frequently. Oil reserves are typically underestimated and are adjusted as additional information and new technology become available. Most experts believe that 1.2 trillion barrels (without oil sands) and 3.74 trillion barrels (with oil sands) reflect the world’s total endowment of oil. Exothermic reaction—a reaction that produces heat or energy.

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Glossary Exponential (scientific) notation—a number system based on powers of 10 (exponents), designed to make it easier to work with very large numbers. Extract—composed of the solute and the heavier solvent; will layer out or naturally separate from the lighter raffinate. The heavier extract does not flow over the weir; rather, it goes out the extract discharge port. Extruder—a complex piece of equipment composed of a heated jacket, a set of screws or a screw, a heated die, a large motor, a gearbox, and a pelletizer. An extruder converts raw plastic material into pelletized plastics ready for further processing into finished products. Most extruders use a single- or twin-screw design surrounded by a heated barrel. The molten polymer is forced or pumped through a die. Faculty expectations—college faculty’s assumption that process technology students will be responsible for their own learning, setting goals, managing their time, participating in class activities, and attending scheduled class meetings.

level teaches a technician how to recognize a hazardous chemical release, the hazards associated with the release, and how to initiate the emergency response procedure. The operations level teaches a technician how to safely respond to a release and prevent its spread. Fixed-bed reactor—device in which the fixed medium remains in place as raw materials pass over it. Flare system—safely burns excess hydrocarbons. A flare system is composed of a flare, knock-out drum, flare header, fan optional, steam line and steam ring, fuel line, and burner. Flow diagram—a simplified diagram that uses process symbols to describe the primary flow path through a unit. Flowchart—a picture of the activities that take place in a process. Fluid catalytic cracking—a process that uses a reactor to split large gas oil molecules into smaller, more useful ones.

Fail open/fail closed—term used in troubleshooting that describes how a control valve ceases to work (fails): in the open or the closed position.

Fluid coking—a process that uses a reactor to scrape the bottom of the barrel and squeeze light products out of the residue.

Feed system—composed of a variety of equipment systems, including feed tanks, valves, piping, instruments, and pumps.

Fluid flow—movement of fluid particles; can be described as laminar, turbulent, parallel, series, counterflow, or cross-flow.

Filter—device that removes solids from fluids.

Fluidized-bed reactor—suspends solids within the reactor by countercurrent flow of gas. Particle segregation occurs over time as heavier components fall to the bottom and lighter ones move to the top.

Fire-tube heaters—furnaces consisting of a battery of tubes that pass through a firebox. Fired heaters or furnaces are commercially used to heat large volumes of crude oil or hydrocarbons. Basic designs include cylindrical, cabin, and box. First responder—person who undertakes the first two levels of emergency response as described by HAZWOPER (29 C.F.R. §1910.120). The first responder awareness and operations levels set out a series of structured responsibilities. The awareness

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Food and beverage processing—industry segment that includes bakeries, breweries, dairies, meat packaging, shellfish processing, and the fishing industry. Forms for collecting data—can vary from notes jotted down on a napkin to complex, preprinted documentation tools.

Glossary Foundation drawings—diagrams containing concrete, wire mesh, and steel specifications that identify width, depth, and thickness of footings, support beams, and foundation. Fractional distillation—a process that separates the components in a mixture by their individual boiling points. Fractionating column—the central piece of equipment in a distillation system. Fractionating columns separate hydrocarbons by their individual boiling points. Frequency plot—see histogram. Furnace system—typically used to heat up large quantities of hydrocarbons or chemicals. The basic equipment in a furnace system includes a furnace, advanced process control systems and instruments, pump systems, compressor systems, and fuel systems. Future hiring trends—directions in employment; large numbers of retiring “baby boomers” will have to be replaced in the chemical processing industry. Goal setting—establishment of reasonable, specific, measurable objectives that lead toward the successful achievement of a goal. Gold collar—term used to describe process technicians. Hazard communication (HAZCOM) standard— known as “workers’ right to know,” ensures that process technicians can safely handle, transport, and store chemicals. HAZWOPER—hazardous waste operations and emergency response.

another. Basic designs include pipe coil, shell-andtube, air-cooled, plate-and-frame, and spiral. Heat exchanger system—consists of shell in/out piping; tube in/out piping; valves; instruments; flow, temperature, analytical, and pressure control loops; and two separate pump systems. Heat transfer—transmission of heat (movement of heat energy) through conduction (heat energy transferred through a solid object; e.g., a heat exchanger), convection (heat transferred by fluid currents from a heat source; e.g., the convection section of a furnace or the economizer section of a boiler), or radiation (heat energy transferred through space by means of electromagnetic waves; e.g., the sun). Histogram (frequency plot)—a graphical tool used to understand variability. The chart is constructed with a block of data separated into 5 to 12 bars or sections from low number to high number. The vertical axis is the frequency and the horizontal axis is the “scale of characteristics.” The finished chart resembles a bell if the data is in control. Housekeeping—maintenance of cleanliness and order; closely associated with safety in the chemical processing industry. Process technicians are required to keep their immediate areas clean. Hubbert peak theory—describes how future world petroleum production will peak and then begin the process of global decline. This decline will closely match the former rate of increase, as known oil reservoirs move to exhaustion. Hydrocarbons—a class of chemical compounds that contain hydrogen and carbon. Hydrocracking—uses a multistage reactor system to boost yields of gasoline from crude oil.

Heat—a form of energy caused by increased molecular activity. Forms include sensible heat and latent heat.

Hydrodesulfurization unit—sweetens products by removing sulfur.

Heat exchanger—an energy-transfer device designed to convey heat from one substance to

Hydrogen particle.

ion—positively

charged

hydrogen

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Glossary Hydroxyl ion—negatively charged OH particle. Ideal gas law—combination of Boyle’s and Charles’s laws, expressed as:

P1V1 P1V2 ⫽ T1 T2 Improvement cycle—a four-phase system for quality improvement: plan, observe and analyze, learn, and act. Industry training programs—programs whose primary focus is on mandatory safety training and onthe-job training; however, a number of employers’ programs still include some of the topics covered by college process technology courses. Inertia—a principle that explains a body’s ability to resist motion. Integral mode—see reset mode. Introduction to Process Technology—a survey course of all the courses found in the regionally accredited process technology program. Ion—electrically charged atom. Ionic bonding—magnetic-type bonds. In ionic bonding, one or more electrons transfer from one or more atoms to another, creating a positive ion and negative ion that attract and hold each other. These bonds are extremely strong. Job lists—information about potential employers; contain contact name, address, telephone number, and size of company. They can be obtained from the local chamber of commerce (a small fee may apply). Job search—requires four to six months, a good resume and cover letter, a certificate or degree, good investigative skills (to identify who is hiring and who to contact), knowledge of application methods, interest cards, tests, and so on. Job searches are very difficult and require serious dedication, time, and a “thick skin.”

Layer out—a process in which two liquids that are not soluble separate naturally from each other (example: oil and water). Legends—used to describe symbol meanings, abbreviations, prefixes, and other specialized equipment; function like the key of a map. Lifelong learning—ongoing process of learning about new technologies and equipment. Global competition requires companies to adopt new and innovative techniques. Process technicians will come into contact with learning opportunities that cannot be found anywhere else. Liquid pressure—the pressure exerted by a confined fluid. Liquid pressure is exerted equally and perpendicularly to all surfaces confining the fluid. Lock-out/tag-out—term used to describe a procedure for shutting down and making unavailable for use equipment that falls under the control of hazardous energy regulations (29 C.F.R. §1910.147). Lubrication system—system that includes a lubricant reservoir, pump, valves, heat exchanger, and piping. Mass—the quantity of matter in an object. Material balancing—a method for calculating reactant amounts versus product target rates. Mathematics—field dealing with numbers and number operations. Process technicians use a variety of mathematical and scientific functions to perform their jobs. Some of the terms used in this area include:

• • • •

Kinetic energy—the energy of motion or velocity.

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addition—a term applied to a mathematical operation for combining numbers. conversion tables—charts that display equivalent units of measure. decimal point—the period or “dot” between whole numbers and fractional numbers. denominator—the bottom number in a fraction.

Glossary

•

•

• • • • • • • • •

dimensional analysis—conversion within one system of units or to another system of units. Example: changing Englishsystem feet to International System (SI) meters. division—a mathematical operation for determining how many times one number or quantity is contained in another number or quantity. divisor—the number by which one is dividing. fraction—a part of a whole amount. grouping symbols—signs used to separate functions in an equation. lowest common denominator (LCD)—the smallest whole number that can be used to divide two or more denominators. mixed number—a whole number and a fraction. multiplication—the process of adding a number to itself a specified number of times. numerator—the top number in a fraction. percent—a fractional amount expressed in terms of parts per one hundred. subtraction—a mathematical operation in which one number is deducted from another.

Matter—anything that occupies space and has mass or volume. Mendeleev, Dmitri—see Dmitri Mendeleev. Mining and mineral processing—industry segment that involves technicians in underground mining and open-pit mining. Mining is the systematic extraction of minerals from beneath the surface or inside the pit. This process is also applied to nonmetallic minerals and rocks (e.g., coal mining). Mixture—composed of two or more substances that are only physically combined. Mixtures can be separated through physical means such as boiling or magnetic attraction. Mole—the molecular formula weight of any substance expressed in grams.

Molecule—the smallest particle that retains the properties of the compound. Neutralization reaction—a reaction designed to remove hydrogen ions or hydroxyl ions from a liquid. Neutron—a neutral particle in the nucleus of an atom. Nuclear generators—reactors that produce an unlimited amount of heat that can be used to produce steam, which can in turn be used to produce electricity or in a number of other useful applications. Occupational Safety and Health Administration (OSHA)—Federal agency created by the Occupational Safety and Health Act; composed of three division: the Occupational Safety and Health Administration, the National Institute for Occupational Safety and Health, and the Occupational Safety and Health Review Commission. Oil and natural gas exploration and production— location and extraction of hydrocarbon resources; the first step in providing aviation fuel, gasoline for motorized vehicles, light and heat for homes, and raw materials for industry to support the production of materials that make up our modern society. Organic chemistry—the study of compounds that contain carbon. OSHA—see Occupational Safety and Health Administration. P&ID—see piping and instrumentation drawing. Packed distillation column—system filled with packing to enhance vapor-liquid contact to separate the components in a mixture by boiling point. The most common types of packing include sulzer, rasching ring, flexiring, pall ring, intalox saddle, berl saddle, metal intalox, teller rosette, and mini-ring packing. The basic components of a packed column include a feed line, feed distributors, a shell, holddown grids, random or structured packing, packing support grids, bed limiters, a bottom outlet, a top

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Glossary vapor outlet, instrumentation, and an energy balance system. Packed columns are designed for pressure drops between 0.20 and 0.60 inches of water per foot of packing material. Pareto chart—a simple bar graph with classifications along the horizontal and vertical axes. The vertical axis is usually the number of occurrences, cost, or time. The horizontal axis orders the bars from the most frequent to the least frequent. Pascal’s law—pressure in a fluid is transmitted equally in all directions, molecules in liquids move freely, and molecules are close together in a liquid. Percent-by-weight solution—representation in which the concentration of the solute is expressed as a percentage of the total weight of the solution. Periodic table—chart arranged by atomic number that provides information about all known elements (e.g., atomic mass, symbol, atomic number, boiling point). Permit system—a regulated system that requires a variety of permits for various applications. The most common applications are cold work, hot work, confined space entry, opening/blinding, permit to enter, and lock-out/tag-out. Personal protective equipment (PPE)—gear used to protect a technician from hazards found in a plant. OSHA and EPA have identified four levels of PPE that could be required during an emergency situation. Level A provides the most protection; level D provides the least.

employs cutting-edge technologies associated with reactions, filtering, drying, and distillation. Physical hazard—name for a chemical that statistically falls into one of the following categories: combustible liquid, compressed gas, explosive or flammable, organic peroxide, oxidizer, pyrophoric, unstable, or water reactive. Piping—used in industry to safely contain and transport chemicals; composed of a variety of materials and configured in a variety of shapes and designs. Piping and instrumentation drawing (P&ID)—a complex diagram that uses process symbols to describe a process unit. Planned experimentation—a tool used to test and implement changes to a process (aimed at reducing variation) and to understand the causes of variation (process problems). Plate distillation column system—has trays that are designed to enhance vapor-liquid contact in the distillation process. Plate columns may be bubblecap, valve tray, or sieve tray. The basic components of a plate distillation column include a feed line, feed tray, rectifying or enriching section, stripping section, downcomer, shell, reflux line, energy balance system, overhead cooling system, condenser, preheater, reboiler, accumulator, feed tank, product tanks, bottom line, top line, side stream, and advanced instrument control system. Potential energy—stored energy. Power generation companies—transport lowcost alternating current across great distances using power transformers to step down high voltages.

PFD—see process flow diagram. pH—a measurement system/scale used to determine the acidity or alkalinity of a solution. Pharmaceutical industry—industry segment that maintains a close relationship with research, chemists, engineers, doctors, and the medical profession. The manufacturing side of this industry

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Power transformation—the conversion of energy into electricity. Methods for transforming power into electrical power include: (1) steam turbines, (2) gas turbines, (3) wind turbines, (4) water turbines, and (5) diesel engines. These devices are connected to electric generators, where fuel cells produce electricity. PPE—see personal protective equipment.

Glossary Predicted model of shared responsibilities— forecast that the process technician of the future will take over tasks and job responsibilities presently performed by engineers and chemists. Preemployment tests—examinations administered by potential employers to determine applicants’ job qualifications and readiness; examples include the Bennett Mechanical Comprehension Test (BMCT) by George K. Bennett (S & T version); the Richardson, Bellows, Henry & Company “Test of Chemical Comprehension” (S & T version, 1970); and the California Math Test. Types include reading comprehension, accuracy checking, block counting, and tests developed in-house. Pressure—force or weight per unit area (Force ⫼ Area ⫽ Pressure); measured in pounds per square inch. Pressure relief system—safety system that includes relief valves, safety valves, rupture discs, piping, drums, vent stacks, pressure indicators, pressure alarms, pressure control loops, and flare systems. Primary operational problem—term for the first issue (problem) that created a process upset. Principles of Quality—course covering the background and application of quality concepts.Topics include team skills, quality tools, statistics, economics, and continuous improvement. Focuses on the application of statistics, statistical process control, math, and quality tools to process systems and operations. Process—a collection of equipment systems that work together to produce products (e.g., crude distillation). Process equipment—piping, tanks, valves, pumps, compressors, steam turbines, heat exchangers, cooling towers, furnaces, boilers, reactors, distillation towers, and so on; all the primary machines and devices used in a process. Process flow diagram (PFD)—chart used to outline or explain the complex flow, equipment,

instrumentation, electronics, elevations, footings, and foundations that exist in a process unit; used in troubleshooting to quickly identify the primary flow path and the control instrumentation being used in the process. Process instrumentation—transmitters, controllers, transducers, primary elements and sensors, and so on; all the measurement and control devices used to monitor and control a process. Process Instrumentation—course for study of the instruments and instrument systems used in the chemical processing industry; includes terminology, primary variables, symbology, control loops, and basic troubleshooting. The purpose of this class is to provide students with an understanding of the basic instrumentation and modern process control used in the chemical processing industry. Process instruments—devices that control processes and provide information about pressure, temperature, levels, flow, and analytical variables. Process safety management (PSM) standard— governmentally set rules (a governmental process safety management standard) designed to prevent the catastrophic release of toxic, hazardous, or flammable materials that could lead to a fire, explosion, or asphyxiation. Process symbols—images that graphically depict process equipment, piping, and instrumentation. Process technician—a person who operates and maintains the complex equipment, systems, and technologies found in the chemical processing industry. Process technicians have advanced training in the equipment, technology, and scientific principles associated with modern manufacturing. Process technicians typically have college degrees and can be found operating and troubleshooting the complex systems found in the chemical processing industry. Because these people work closely with specific pieces of equipment or processes, they are commonly called boiler operators, compressor technicians, distillation technicians, refinery technicians, or wastewater operators.

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Glossary Process Technology—as defined in the regionally accredited process curriculum, course for study and application of the scientific principles (math, physics, chemistry) associated with the operation (instruments, equipment, systems, troubleshooting) and maintenance (safety, quality) of the chemical processing industry. Process Technology 1—Equipment—instruction in the use of common process equipment, including basic components and related scientific principles. Includes a study of valves, pipes and tanks, pumps, compressors, motors and turbines, heat exchangers, cooling towers, boilers, furnaces, distillation columns, reactors, and separators. Process Technology 2—Systems—study of common process systems found in the chemical process industry, including related scientific principles. Includes study of pump and compressor systems, heat exchangers and cooling tower systems, boilers and furnace systems, distillation systems, reaction systems, utility system, separation systems, plastics systems, instrument systems, water treatment, and extraction systems. Computer console operation is often included in systems training. Emphasizes scale-up from laboratory (glassware) bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation, reaction, and fluid flow principles. Process Technology 3—Operations—a collegelevel course, designed to be the capstone experience, that includes all the elements covered in a process technology two-year degree program. Combines process systems into operational processes with emphasis on operations under various conditions.Topics include typical duties of an operator. Instruction focuses on the principles of modern manufacturing technology and process equipment. Emphasizes scale-up from laboratory bench to pilot unit. The purpose of this class is to provide adult learners with the opportunity to work in a self-directed work team, operate a complex operational system, collect and

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analyze data, start and stop process equipment, follow and write operational procedures. Process Troubleshooting—instruction in the different types of troubleshooting techniques, methods, and models used to solve process problems. Topics include application of data collection and analysis, cause-effect relationships, and reasoning. Emphasizes application of troubleshooting methods to scale-up from laboratory bench to pilot unit. Describe unit operation concepts; solve elementary chemical mass/energy balance problems; interpret analytical data; and apply distillation and fluid flow principles. Process variables—changeable conditions (variables) that can be detected by instruments and that provide clues to what is occurring within the “big picture” of the entire process. Products—manufactured materials made from reactants combined in specific proportions. Proportional band—on a controller, describes the scaling factor used to take a controller from 0% to 100% output. Proton—a positively charged particle in the nucleus of an atom. PSM standard—see process safety management standard. Pulp and paper industry—industry segment consisting of pulp and paper mills and converting operations. Pulp is made by chemically or mechanically separating wood fibers from nonfibrous material. Pump-around system—consists of a series of piping, storage tank(s), valves, gauges, and a pump. Pumps—used primarily to move liquids from one place to another. Pumps come in two basic designs: (1) positive displacement (rotary and reciprocating), and (2) centrifugal.

Glossary Raffinate—the lighter material in the feedstock that is free of the solute or material being dissolved; flows over the weir in the separator. Range—the portion of the process controlled by the controller. For example, the temperature range for a controller may be limited from 80⬚F to 140⬚F. Rate (or derivative) mode—enhances controller output by increasing the output in relationship to the changing process variable. As the process variable approaches the setpoint, the rate or derivative mode relaxes, providing a braking action that prevents overshooting of the setpoint. The rate responds aggressively to rapid changes and passively to smaller changes in the process variable. RCRA—see Resource Recovery Act.

Conservation

and

Reactants—raw materials that are combined in specific proportions to form finished products. Reaction rate—the amount of time it takes a given amount of reactants to form a product. Reactor—device used to convert raw materials into useful products through chemical reactions. It combines raw materials, heat, pressure, and catalysts in the right proportions to initiate reactions and form products. Five reactor designs are commonly used: stirred, fixed-bed, fluidized-bed, tubular, and furnace. Reboiler—a heat exchanger used to maintain the heat balance on a distillation tower. Reformer—a reactor filled with a catalyst designed to break large molecules into smaller ones through chemical reactions that remove hydrogen atoms. Refrigeration system—used to provide cooling (e.g., air conditioning) to industrial applications. Refrigeration units are composed of a compressor (high-pressure refrigeration gas), heat exchanger– cooling tower combination, receiver, expansion valve (low-pressure refrigeration liquid), and heat

exchanger (evaporator)–low-pressure refrigerant gas unit. Regenerator—used to recycle or regenerate contaminated catalyst. Replacement reaction—a reaction designed to break a bond and form a new bond by replacing one or more of the components of the original compound. Reset (or integral) mode—designed to reduce the difference between the setpoint and process variable by adjusting the controller output continuously until the offset is eliminated. The reset or integral mode responds proportionally to the size of the error, the length of time that it lasts, and the integral gain setting. Resource Conservation and Recovery Act (RCRA)—federal law enacted in 1976 to protect human health and the environment. A secondary goal is to conserve natural resources. It attains these goals by regulating all aspects of hazardous waste management, including generation, storage, treatment, and disposal. This concept is referred to as “cradle to grave” management. Respiratory protection—a standard or program designed to protect employees from airborne contaminants. Resume—a one-page document designed to sum up a job applicant’s skills, work history, hobbies, and education. Run chart—a graphical record of a process variable measured over time. Safety, Health, and Environment—course in which students gain knowledge and skills to reinforce the attitudes and behaviors required for safe and environmentally sound work habits. Emphasizes safety, health, and environmental issues in the performance of all job tasks, and covers regulatory compliance issues.

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Glossary Saturated hydrocarbon—contains the maximum number of hydrogen atoms and contains single covalent bonds. An unsaturated hydrocarbon can still accept an additional hydrogen atom. Scatter plot—chart used to indicate relationships between two variables or pairs of data. Science—a way of knowing and understanding the universe and the world we live in. The Latin word for science is scire, which means “to know.”

Solid waste—a by-product of modern technology; technically defined as a discarded solid, liquid, or containerized gas. This definition includes materials that have been recycled or abandoned through disposal, burning or incineration, accumulation, storage, or treatment. Solute—material that is dissolved in liquid-liquid extraction; the material dissolved in a solution. Solution—a homogenous mixture.

Scientific method—the systematic process or framework by which science operates.

Solvent—chemical that will dissolve another chemical.

Scientific notation—see exponential notation.

Span—the difference between the upper and lower range limits.

Scrubber—device used to remove chemicals and solids from process gases.

SPC—see statistical process control.

Secondary operational problems—issues created or responded to during a process upset other than the primary problem. Separation system—designed to separate two liquids from each other by density differences; typically, a solvent is introduced that will dissolve one of the components in the mixture, enhancing the separation process. A separator has a shell, weir, vapor cavity, feed inlet, extract port and pump, and raffinate port and pump. Sewage—water that contains 0.1% solid waste matter produced by human beings. Sewage is frequently referred to as wastewater. More than 80% of the sewage produced in the United States comes from industrial sources. Sexual harassment—behavior that constitutes unwelcome sexual advances; could take the form of verbal or physical abuse or unwelcome requests for sexual favors. The behavior may involve persons of the opposite sex or of the same sex; the offending conduct may run from supervisor to employee, student to student, employee to employee, teacher to student, and so on. (For further information on sexual harassment, see Title VII of the Civil Rights Act of 1964.)

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Specific gravity—a measurement of the heaviness of a fluid. Specific gravity equals the mass of a substance divided by the mass of an equal volume of water. The specific gravity of gasoline is 6.15 lb/gal ⫼ 8.33 ⫽ 0.738. Statistical process control (SPC)—statistical control methodology applied to a process. Steam-generation system—a complex arrangement of boiler systems designed to convert water to steam. These include pump-around systems, advanced process control systems and instruments, fuel systems, and compressor systems. Steam trap—a device used to remove condensate from steam systems. Steam turbine—energy-conversion device that converts steam energy (kinetic energy) to useful mechanical energy. Steam turbines come in two basic designs: (1) condensing and (2) noncondensing. They are used as drivers to turn pumps, compressors, electric generators, and propeller shafts (e.g., on naval vessels). Stirred reactor—typically includes a vessel, a mixer, valves, piping, two or more inlet ports, and a single outlet port. Reactors are complex analytical

Glossary devices that have control features for a wide array of process variables and come in a variety of shapes and designs. Strainer—a device used to remove solids from a process before they can enter a pump and damage it. System—a collection of equipment designed to perform a specific function (e.g., refrigeration system).

Trainee—an unqualified technician recently assigned to an operating unit. Trainer—a qualified technician assigned to mentor a trainee. Troubleshooting methods—means of diagnosing process problems; include educational, instrumental, experiential, and scientific.

Tanks—vessels that store and contain fluids. Tank designs include spherical, open-top, floating-roof, drum, and closed styles.

Troubleshooting models—tools used to teach troubleshooting techniques. Basic models include distillation, reaction, and absorption and stripping, or combinations of these three.

Temperature—the hotness or coldness of a substance.

TSCA—see Toxic Substances Control Act of 1976.

Thermal cracking—process that uses heat and pressure to separate small hydrocarbons from large ones.

U.S. chemical manufacturing industry—economic bloc that produced more than $460 billion of export goods in 2003.

Time management—a structured system that arranges an individual’s study according to principles governing use of time.

Valve—a device designed to control (stop, start, or direct) the flow of fluids.

Toxic Substances Control Act of 1976 (TSCA)— federal legislation intended to protect human health and the environment, and to regulate commerce by requiring testing and imposing restrictions on certain chemical substances. The TSCA applies to all manufacturers, exporters, importers, processors, distributors, and disposers of chemical substances in the United States.

Water permit—government-granted license issued as part of efforts to control water pollution. Water pollution—contamination of the water, especially by industrial wastes. Weight—the force of molecular gravitation.

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A Abbott, William, 8 Abiogenic theory, 4 Absolute pressure (psia), 95 Absorbed heat, 88 Absorber columns, 226, 232, 376–377 AC (alternating current), 134–135, 323 ACB (Air Control Board), 335–336 Acids, 282, 291, 295–296 ACS (American Chemical Society), 29, 30–31 Activated charcoal, 233 Actuators, 202–203 Adhesion, 311 Adsorber, 226, 233 Air, density, 102 Air, respirators, 70, 79–80 Air bubbler systems, 171–172 Air Control Board (ACB), 335–336 Air-cooled heat exchangers, 146–147, 178–179 Airflow, 148, 178–179, 372 Air pollution, 334, 335–336 Air pressure, mechanical energy and, 202–203 Alcohols, 411–413 Alkalinity, 291, 295–296 Alkanes, 296–297, 396, 403, 408 Alkenes, 408–411 Alkylate, 300 Alkylation, 8, 248, 256–257, 300 Alkynes, 408–411 Allergic responses, 78

Alternative fuel sources, 4, 16 American Chemical Society (ACS), 29, 30–31 American Petroleum Institute (API), 102 Ampere, 324 Analytical control loops, 186–191 Analytical variables, measures of, 173, 196–197 Anesthetic chemicals, 78 Aniline, 409 API gravity, 102, 306, 309 Archimedes’ principle, 308 Argicola, Georgius, 3 Argon, 315–316 Aromatic hydrocarbons, 251–252, 408 Asphalt, 9, 262, 298–300 Asphyxiation, 78 Associate of Applied Science degree, 44 Atmospheric pressure, 89–90, 306, 312–313 Atomic mass unit (amu), 282, 284, 288–291 Atomic number, 282, 284 Atoms, 282, 284 Automatic controls, 194, 195, 201 Automatic valves, 120–121, 202–203 Avogadro’s number, 397 Axial bearings, 136 Axial compressors, 130 Axial pumps, 124, 126

Alternating current (AC), 134–135, 323

Ball valves, 116–117, 118, 174

B Backup systems, 356 Balanced equations, 282

451

Index Barnsdall, William, 8 Barometer, 306, 312–313 Bases, 282, 291, 295–296 Batch process, 2, 8–9 Bauer, Georg, 3 Baumé gravity, 102, 306, 309 Bearings, 135–137 Bench-top operations, 276 Bennett Mechanical Comprehension Test (BMCT), 392 Benzene, 97, 251–252, 396, 408 Benzoic acid, 409 Bernoulli’s principle, 88, 101 Big Rollover, 2, 14–17 Biofuels, 4 Biogenic theory, 2, 3–4 Blinding permit, 81 Block-counting tests, 392 Blow molding, 236, 238–240 Boilers defined, 142 downcomer tubes, 268 electrical systems and, 212–213, 230–231 overview, 103, 149–151 physics of, 323 reactions in, 292 steam-generation systems, 216–218, 423–424 symbols, 179–180 troubleshooting, 369–371, 372 Boiling point chemical reactions and, 90–92, 292, 400 distillation systems, 229, 298–300 hydrocarbons, 296–298 Box furnaces, 153, 155 Boyle’s law, 88, 93, 98 Breakers, electrical, 189 British thermal units (BTUs), 99 Bromobenzene, 409 BTUs (British thermal units), 99 BTX aromatics, 252

C Cabin-fired heaters, 152, 153 CAER (Community Awareness and Emergency Response), 334, 338 Calendering, plastics, 236, 238–240 Calories, 99 Capillary action, 311 Carbon. See Hydrocarbons Carbon dioxide, 208–212, 315–316 Carbon monoxide, 315–316 Carbon seals, 136 Carcinogens, 78 Cascade controls, 194, 201 Casting, plastics, 236, 238–240 Catalysts, 282 defined, 142 reactors, 155–156 regenerators, 257–258 types of, 292–293 Catalytic cracking (catcracking) chemistry of, 282, 299–300 process development, 2, 8, 10–11 process of, 257–258 Catalytic reforming, 260, 261 Cause-and-effect (C&E) diagram, 342, 348–349 Cavitation, 125 Celcius (°C), 100, 170 Centrifugal compressors, 129–131, 177 Centrifugal pumps, 124, 125, 176 CERCLA (Comprehensive Environmental Compensation and Liability Act), 338–339 Charcoal, 233 Charles’ law, 88, 98–99, 315 Check valves, 118, 174 Chemical bonding, 285

Burton, William, 9

Chemical manufacturing, 419–420

452

Burton Process, 9 Butane, 255, 296–297 Butterfly valves, 119, 174 Butylenes, 256–257

Index Chemical processing industry (CPI), 2 current trends and issues, 14–17 history of, 3–14 work environment, 37 Chemicals, hazardous, 77–78. See also HAZCOM (hazard communication standard); HAZWOPER (hazardous waste operations and emergency response) Chemistry, 42 alcohols, 411–413 alkenes, 408–411 alkynes, 408–411 aromatic hydrocarbons, 408 chemical bonds, 282, 400–403 definitions, 282 distillation, 298–300 education and training, 63–65 equations and periodic table, 286–291, 403–405 fundamental principles, 283–285, 396–399 hydrocarbons, 296–298 material balance, 293–294 organic, 396, 403 percent-by-weight solutions, 295 periodic table, 400–403 petroleum refining, 405–407 pH measurement, 295–296 reactions, 142, 156, 285 reaction types, 291–293 Chemists, 28 Chimney tower, 178 Chlorine, compression systems, 208–212, 315–316 Chlorobenzene, 409 Classifier, 240 Clayton, John, 6 Clean Air Act (1972), 334, 335 Clean Water Act (1972), 334, 336 Coal, 4, 16 Cogeneration, 424 Cohesive force, 311–312 Coke deposits, 252

Cold work permit, 81 College programs, process technology, 20–24, 31 Combustible liquids, 77–78 Combustion reactions, 156, 282, 292 Community Awareness and Emergency Response (CAER), 334, 338 Community right-to-know, 334, 338–339 Compounds, chemical, 285, 399 Comprehensive Environmental Compensation and Liability Act (CERCLA), 338–339 Compressed-air systems, 228–234 Compressed gases, 77–78, 208–212 Compression molding, 236, 238–240 Compressors, 114, 129–131 physics of, 315–316, 325–327 refrigeration, 241–242 symbols, 176–177 troubleshooting, 365 Compressor systems, 208–212, 230–231 Computer software, 184, 361–362 Condensation, latent heat of, 99 Condensers, 146–147 Conduction, 99, 372 Conductivity probes, 171–172 Contact Engineer, 28 Control charts, 271–272, 273, 342, 346 Controllers, 194, 200–202 Control loops automatic valves, 120–121 basic elements, 195 controllers and control modes, 200–202 defined, 194, 356 final control elements, 202–203 pressure, 235–236 process variables, 196–197 transmitters, 197–199 troubleshooting, 363 Control modes, 200–202 Control valves, 203 Convection, 99, 152–153, 371–373 Coolers, 146–147

453

Index Cooling towers defined, 142, 208 distillation systems, 228–234 overview, 147–149, 214, 216 symbols, 177–179 troubleshooting, 367, 369 utility systems, 243 Corrosive chemicals, 78 Counterflow, airflow, 148, 178 Covalent bonds, 282, 285, 396, 402 Cover letters, 387–390 Cracker feed, 262 Cracking processes, 8–9, 297 catalytic cracking, 2, 10–11 fluid catalytic cracking, 257–258 thermal cracking, 9, 10 Cross flow, airflow, 148, 178 Crude oil. See also Oil refining batch processing, 8–9 biogenic theory, 3–4 chemical makeup, 296–298 consumption, 4 current trends and issues, 14–17 density, 309 distillation, 260, 262, 286 exploration and production, 418 Customer relationships, 344 Cycloalkanes, 396, 408, 410–411 Cyclones, 114, 123 Cylindrical-fired heaters, 152–153, 154 D Dalton’s law, 9, 88, 96–97, 396, 406–407 Data collection/analysis pilot plant, 271, 272 quality control, 275–276, 344–352 safety, 63 types of, 342 DC (direct current), 134–135, 323 DCS (distributive control system), 184, 200–201, 202

454

Decane, 296–297 Demineralizers, 114, 123, 226, 242–243 Density, 101–102, 306, 308–312 Department of Transportation (DOT). See DOT (Department of Transportation) Derivative mode, controllers, 194, 201 Diagrams overview, 173–174 piping and instrumentation drawings (P&ID), 183–184, 186–191 process flow diagrams (PFDs), 182–184 process symbols, 175–182 Diaphragm actuator, 202–203 Diaphragm valve, 119 Diaphragm valves, 174 Diesel, 262 distillation of, 298–300 Diesel engines, 424 Differential pressure (DP), 196–197 transmitters, 197–199 Differential pressure transmitters, 171–172 Direct current (DC), 134–135, 323 Direct-fired furnaces, 152–154 Discharge pressure, 125 Displacement, 308 Displacement devices, 171–172 Distillate, 157 Distillation, 157–160, 232, 396 chemistry of, 298–300 crude oil, 286 petroleum, 405–407 pilot plant operation, 266–272 symbols, 180, 181 troubleshooting, 377–379, 379–381 Distillation column, 157–160, 180, 181 defined, 142 packed, 226 pilot plant operation, 268–269 plate, 226 reactor systems, 228 troubleshooting, 376–377

Index Distillation columns crude distillate, 261 Distillation process, 4, 57, 58 Dalton’s law, 96–97 Distillation system, 146–147 Distillation systems overview, 228–234 Distillation towers, 103 alkylation, 257 chemistry in, 299 defined, 248 Distributive control system (DCS), 184, 200–201, 202 Diversity training, 2, 25 Documentation HAZCOM, 74–77 DOT (Department of Transportation) labeling, 84, 85 overview, 36, 70 warning labels, 77 Double-pipe heat exchangers, 143–147 Downcomer tubes, boilers, 151, 268 Drafts, airflow, 148, 178 Drake, Edwin, 7 Drilling rigs, 422 Ductility, 311 Dynamic compressors, 129–131, 315–316 E Education and training, 17–24 ACS standards, 31–32 chemistry and physics, 63–65 instrumentation and process control, 51–53 job search, 386–397 math, 65–66 process equipment, 53–54 process operations, 57–60 process systems, 55–57 process technology programs, 43–47 quality control principles, 50–51 safety, health and environment, 47–50

statistics, 63 troubleshooting, 60–63 Efficiency curves, 125 Effluent, 424–426 Elasticity, 310 Electrical breakers, 189 Electrical drawings, 168, 188–189, 190 Electrical systems, 208, 212–213, 230–231 Electricians, 28 Electricity, 134–135 generation of, 212–213, 325–327, 423–424 physics of, 323–328 thermocouples, 170 utility systems, 243 Electronic controllers, 200–202 Electronic transmitters, 197–199 Electrons, 282, 284, 402 Elements, chemical, 282, 284, 288–291, 399 Elements, control loops, 197, 198 Elevation drawings, 168, 188 Emergency response, 70, 80–83, 334, 338 Employee training, 74–77, 274–275 Employment in chemical processing ACS hiring standards, 31 education and training, 17–24 job search, 386–393 overview, 24–29 preemployment testing, 392 Endothermic reactions, 156, 282, 291 Energy defined, 306 fluid energy conversions, 103 isolation procedure, 81 liquid, 102 mechanical, 202–203 rotational, 210–212, 325–327 Engineers, 28 Enriching, 268 Entry permit, 81 Environmental hazards, 47–50, 71–72

455

Index Environmental Protection Agency (EPA), 36, 49–50, 71–72, 334, 335–336 Environmental quality, 233 Environmental standards air pollution control, 335–336 community right-to-know, 338–339 emergency response, 338 solid waste control, 336–337 toxic substances, 337 water pollution, 336 EPA (Environmental Protection Agency), 36, 49–50, 71–72, 334, 335–336 Equipment education and training, 51–54 failure, 356 operating procedures, 276, 278 safety training, 47–50 troubleshooting, 60–63, 356, 360 Equipment location drawings, 168, 189, 191 Estimated ultimately recoverable (EUR) oil, 2, 15 Ethane, 296–297 Ethanol, 413 Ethers, 255 Ethylbenzene, 253, 409 Ethylene, 255, 256 Ethylene glycols, 253, 254, 413 Evaporation, cooling towers, 148 Exothermic reactions, 156, 282, 291 Expansion valve, 241 Experimentation, planned, 342, 350–351 Explosive materials, 77–78 Exponential notation, 396, 398 Extraction, separators, 161, 234–235, 379–381 Extracts, 161, 226, 234–235, 379 Extrusion, 226, 236, 238–240 F Fahrenheit (°F), 100, 170 Fail open/fail closed, 356 Feed systems, 161, 230–231, 266, 267, 269–271

456

Filters, 114, 122–123 Fin fans, 146–147, 178–179 Fire control, 49–50, 72, 82 Fired heaters (furnaces) control loops, 196 distillation systems, 230–231, 261 energy conversion, 103 overview, 151–154, 155 reactions in, 292 symbols, 179–180 troubleshooting, 371–373 Fired heater systems, 208, 218–221 Fire extinguishers, 82 Fire prevention, 49–50, 72 Fire protection, 49–50, 72 Fire-tube boilers, 150, 179–180 Fire-tube heaters, 142 First responder, 70, 81 Fishbone diagram, 342, 348–349 Fittings, pipes, 121–123 Fixed-bed reactors, 154–157, 181–182, 227–228, 248, 253 Fixed-head heat exchangers, 143–147 Fixed platforms, drilling rigs, 422–423 Flammable gases, 77–78 Flammable liquids, 77–78 Flare system, 226, 236–237 Flash gas, 262 Floating-head, multipass (U-tube), 143–147 Floats, 171–172 Flow. See also Fluid flow control loops, 196–197 data collection, 275–276 rate calculations, 103, 172–173, 314 symbols, 177–179 Flowcharts, 342, 346, 348 Flow diagrams, 168, 186–191 Flow of solids, 103 Fluid catalytic cracking, 248, 257–258 Fluid coking, 248, 260 Fluid energy conversions, 103

Index Fluid flow, 88, 100–103 cabin-fired heaters, 152 defined, 142 physics of, 317–319 Fluidized-bed reactors, 154–157, 181–182, 227–228, 248, 252 Fluids. See also Fluid flow pressure in, 312–319 specific gravity, 308–312 Food and beverage processing, 418, 427 Force, 313–314, 319–323 Formula weights, 397 Foundation drawings, 168, 188 Foundations for Excellence in the Chemical Process Industries (ACS, 1994), 30–31, 32 Fractional distillation, 2, 9–10, 13, 257–258, 283, 298–300 Frequency plots, 342 Friction, 135–137 Fuel heat values, 220–221 Furnace reactors, 154–157, 181–182 reactions in, 292 Furnaces control loops, 196 distillation systems, 230–231, 261 energy conversion, 103 overview, 151–154, 155 reactions in, 192 symbols, 179–180 troubleshooting, 371–373 Furnace systems, 218–221 defined, 208 Fuses, 189 Fusion latent heat of, 99 G Gases Charles’ law, 88, 98–99 compressed, 77–78 compressor systems, 208–212, 315–316 flammable, 77–78

ideal gas law, 88, 98–99 Noble, 400 pressure, 89–90, 95–99 Gas generator, 211 Gas oils, 262 Gasoline batch processing, 8 cracking, 300 density, 309 distillation of, 298–300 olefins, 255 specific gravity, 102 Gas turbines, 133–134, 210–212, 424 Gate valves, 116, 174 Gauge pressure (psig), 95 Generators, electric, 325–327 Gesner, Abraham, 6 Globe valves, 116 Glove valves, 174, 203 Gold, Thomas, 4 Gold collar, 2, 29 Governor valves, 132 Gravitational force, 307 H Hair-pin heat exchanger, 143–147 Hand tools, 114–115 Hardness, 310 Hardwire interlocks, 184 Hart, William Aaron, 6 Hazard communication standard. See HAZCOM (hazard communication standard) Hazardous chemicals, 77–78. See also HAZCOM (hazard communication standard); HAZWOPER (hazardous waste operations and emergency response) Hazardous chemicals, safety of, 77–78 Hazardous Materials Identification System (HMIS), 77 Hazardous waste operations, 82–83 HAZCOM (hazard communication standard), 49–50, 70, 72, 74–77, 338

457

Index HAZWOPER (hazardous waste operations and emergency response), 70, 82–83 Health hazards chemical, 78 education and training, 47–50 overview, 71–72 Hearing conservation program (HCP), 83 Heat. See also Heat transfer chemical reactions and, 292 defined, 142 physics of, 99–100 rate, calculating, 327 thermocouples, 170 Heaters. See Fired heaters (furnaces) Heat exchangers distillations, 230–231 physics of, 317–319, 327–328 refrigeration, 241–242 symbols, 177–179 troubleshooting, 365–367, 368 Heat exchanger systems, 56–57, 142–147, 208, 214–216 Heating oil, 298–300 Heat transfer, 56–57, 88 convective, 152–153 defined, 142 heat exchangers, 143–147 physics of, 99–100, 317–319 Heat values, fuel, 220–221 Helium, 315–316 Heptane, 296–297 Hexane, 296–297, 299–300 Hexene, 299–300 High-pressure (HP) steam, 217 Histograms, 342, 351 History chemical processing industry, 3–14 distillation systems, 230 industrial processes, 248–251 HMIS (Hazardous Materials Identification System), 77 Hooke’s law, 310

458

Horsepower (HP), 327 Hot work permit, 81 Houdry process, 10–11 HP (high-pressure) steam, 217 HP (horsepower), 327 Hubbert peak theory, 2, 14–17 Hydraulically operated actuator, 203 Hydraulic systems, 213–214 Hydrocarbons aromatic, 408 chains, 402 chemistry of, 296–298 compression of, 315–316 defined, 283 distillation fractions, 298–300 saturated, 396, 410 specific gravity, 308 Hydrocrackate, 300 Hydrocracking, 248, 259–260, 300 Hydrodesulfurization, 248, 258–259 Hydrogen acid-base reactions, 291 compressor systems, 208–212, 315–316 in crude oil, 4 defined, 283 pH measurement, 295–296 Hydrogen fuel cells, 4 Hydrostatic pressure, 90 Hydroxyl ion, 283, 291 I Ideal gas law, 88, 98–99, 315 Improvement cycles, 342 Inclined planes, 320 Industrial fires, 49–50, 72, 82 Industrial hygienist, 28 Industrial noise, 83 Industrial processes chemical manufacturing, 419–420 development of, 248–251 food and beverage industry, 427

Index mining and mineral processes, 426–427 oil and natural gas exploration and production, 420–423 overview, 418–419 petrochemical, 251–256 petroleum refining, 256–262, 419–420 pharmaceutical manufacturing, 428–430 power generation, 423–424 pulp and paper processing, 430–431 water and wastewater treatment, 424–426 Inert gases, 400 Inertia, 306, 307 Injection molding, 236, 238–240 Inner transition elements, 400 Instrumentation distillation systems, 228–234 education and training, 51–53 piping and instrumentation drawings (P&ID), 168, 183–184, 186–191 process control, 272, 274 separator systems, 235 symbols, 184, 185 Instrument technicians, 28 Integral mode, controllers, 194, 201 Interlocks, 184 Internal slip, 125 Interviews, employment, 388–391 Ionic bonds, 282, 285, 396, 403 Ions, 283, 285 Irritants, 78 Isobutane, 256–257, 300 Isopropyl alcohol, 413

batch processing, 8 catalytic cracking, 299–300 distillation of, 298–300 Kettle reboiler heat exchangers, 143–147, 178–179 Kier, Samuel, 6–7 Kinetic energy, 306

K Kelvin (K), 100, 170

L Labels DOT, 77, 84, 85 HAZCOM, 76 warning, 49–50 Lab technician, 28 Labyrinth seals, 136 Laminar flow, 102 Laminating, plastics, 236, 238–240 Latent heat, 99 Layer out process, 226, 235 Legislation. See also Environmental standards air pollution control, 335–336 community right-to-know, 338–339 emergency response, 338 safety, 71–74 solid waste control, 336–337 toxic substances, 337 water pollution, 336 Level measurements, 171–172 control loops, 196–197 data collection, 275–276 piping and instrumentation drawings (P&ID), 186–191 Liability. See Environmental standards Lift check valve, 118 Liquid energy, 102 Liquid-liquid extraction process, 161, 235, 379–381 Liquids pressure, 88, 89–90, 93, 95 Liquids, flammable, 77–78 Litmus paper, 295–296

Kerosene, 262

Lobe pumps, 127

J Jackup platforms, 422–423 Jet fuel, 298–300 Jet pump systems, 125 Jobs. See Employment in chemical processing

459

Index Lock-out/tab-out procedure, 70, 81, 189 Logic controllers, programmable, 202 LP (low-pressure) steam, 217 Lubricating oil, distillation of, 298–300 Lubrication systems, 114, 135–137, 213 Lukasiewicz, Ignacy, 7 Lummus method, 256 M Machines, 319–323 Machinists, 28 Malleability, 311 Manual controls, 194, 201 Manufacturer’s information, 49–50 Mass, 306, 307 Material balancing, 283 Material safety data sheets. See MSDS (material safety data sheets) Math, applied, 42, 65–66, 104–109 Matter, 306 MCC (motor control center), 189, 212–213 Mechanical advantage, 320 Mechanical craftsmen, 28 Mechanical drafts, airflow, 148 Mechanical energy, 202–203 Mechanical seals, 136–137 Mechanical steam traps, 138 Medium-pressure (MP) steam, 217 Melting point, 400 Mendeleev, Dmitri, 396, 400 Mercury, 311 Metalloids, 400 Metals, 400 Methane, 296–297 Methanol, 255, 413 Mineral ions, 291 Mineral processing, 418, 426–427 Mining, 418, 426–427 Mixtures, 283, 285 Mole, 396, 397 Molecules, 283, 285. See also Chemistry

460

Moments and levers, principle of, 321–323 Motor control center (MCC), 189, 212–213 Motor-driven actuators, 203 Motors, 134–135, 177 MP (medium-pressure) steam, 217 MSDS (material safety data sheets), 49–50, 76–77, 79, 338 Mud drums, boilers, 151 Multiple-variable process model, 62 Murdock, William, 6 Mutagens, 78 N Naphtha, 8, 262 National Fire Protection Association (NFPA), 77 National Institute for Occupational Safety and Health (NIOSH), 37, 73–74 Natural drafts, airflow, 148 Natural gas biogenic theory, 3–4 chemical makeup, 296 compression, 315–316 conversion to oil, 5 exploration and production, 418, 420–423 heat value, 220–221 olefins, 255 Neurotoxins, 78 Neutralization reactions, 283, 291 Neutrons, 283, 284 NFPA (National Fire Protection Association), 77 NIOSH (National Institute for Occupational Safety and Health), 37, 73–74 Nitrobenzene, 409 Nitrogen, 4, 208–212, 315–316 Noble gases, 400 Noise, 83 Nonane, 296–297 Nonmetals, 400 NRC (Nuclear Regulatory Commission), 34–36 Nuclear reactors, 4, 34–36, 154–157, 181–182, 418, 424 Nuclear Regulatory Commission (NRC), 34–36

Index O Occupational Safety and Health Administration (OSHA), 37, 42, 49–50, 71–74, 338 Occupational Safety and Health Review Commission (OSHRC), 37, 72–74 Occupations. See Employment in chemical processing Octane, 296–297 Offshore drilling, 4–5, 422–423 Ohm’s law, 323–324 Oil current trends and issues, 14–17 exploration and production, 420–423 refining, distillation, 405–407, 419–420 refining, history, 3–14 Oil Depletion Analysis Centre, 15 Oil shale, 4, 16 Olefins, 255, 256–257, 296–298, 300, 409 Opening/blinding permit, 81 Operations, equipment education and training, 53–54 procedures, 276, 278 safety training, 47–50 troubleshooting, 356, 360 Operations, process, 57–60 Organic chemistry, 396, 403 Organic peroxide, 77–78 Orifice plates, 173, 196 OSHA (Occupational Safety and Health Administration), 37, 42, 49–50, 71–74, 338 OSHRC (Occupational Safety and Health Review Commission), 37, 72–74 Overhead systems, 269 Oxidizers, 78 Oxygen, 4 P Packed distillation column, 158–160, 180, 181, 226, 232 Paper industry, 418 Paraffin, 298–300 Paraxylenes, 255

Pareto chart, 342, 350 Pascal’s law, 89, 93 PD (positive displacement) pumps, 124, 126–128, 176 PD (proportional plus derivative) controllers, 194, 201 Pentane, 296–297 Pentylenes, 256–257 Percent-by-weight, 283 Periodic table, 283, 284, 286–291, 400–403 Permissives, 184 Permit systems, 70, 81, 274 air permits, 335–336 overview, 72 water, 334, 336 Permit to enter, 81 Peroxide, 77–78 Personal protective equipment (PPE), 70, 80, 81 Petrochemical processes, 251–256 Petroleum. See also oil overview, 3–4 products from, 4–6 refining, distillation, 405–407, 419–420 PFD (process flow diagrams), 168, 173–174, 182–184, 356 pH, 283, 295–296 Pharmaceutical industry, 418, 428–430 Phenol, 409, 411–413 Physical hazards, 49–50, 70, 77–78 Physics education and training, 63–65 electricity, 323–328 fundamental concepts, 306–308 machines, complex and simple, 319–323 pressure in fluids, 312–319 P&ID (piping and instrumentation drawings), 168, 173–175, 183–184, 186–191 PID (proportional-integral-derivative) controllers, 194, 201 Pilot plant operation, 266–276 Pipe-coil heat exchangers, 143–147

461

Index Pipes/piping, 114, 121–123, 173–175. See also Piping and instrumentation drawings (P&ID) Piping and instrumentation drawings (P&ID), 168, 173–175, 183–184, 186–191 PI (proportional plus integral) controllers, 194, 201 Piston actuator, 203 Piston compressor, 131 Planned experimentation, 342, 350–351 Plant permit system, 81 Plastics system, 236, 238–240 Plate-and-frame heat exchangers, 178–179 Plate distillation absorption, 232 defined, 226 overview, 158 symbols for, 180, 181 troubleshooting, 376–377 Platform, drilling rigs, 422–423 Plug valves, 117, 174 Pneumatic actuators, 202–203 Pneumatic controllers, 200–202 Pneumatic transmitters, 197–199 Pollution control. See Environmental standards Polyethylene, 255, 256 Polymerization, 8, 239 Porosity, 307 Positive displacement compressors, 130–131, 177, 315–316 Positive displacement pumps, 124, 126–128, 176 Potential energy, 306 Power generation, 418, 423–424 Power transformation, 418, 423–424 PPE (personal protective equipment), 49–50, 70, 80, 81 P (proportional) controller, 194 Preheat systems, 228–234, 267 Pressure absolute, 95 boiling point and, 90–92 Boyle’s law, 88, 93, 98 Charles’ law, 88, 98–99 chemical reactions and, 292

462

control loops, 196–197 conversion to mechanical energy, 202–203 Dalton’s law, 88, 96–97, 396, 406–407 data collection, 275–276 differential pressure transmitters, 171–172 discharge, 125 in fluids, 312–319 gases, 89–90, 95–99 gauges and instruments, 95169 ideal gas law, 88, 98–99 liquid pressure, 88, 89–90, 95 overview, 89–90 Pascal’s law, 89, 93 piping and instrumentation drawings (P&ID), 186–191 problems, 93–95 relief systems, 150 steam, 217 suction, 125 temperature and, 314–319 transmitters, 197–199 vacuum, 92–93, 95 Pressure relief system, 226, 235–236 Primary operational problems, 356, 360 Principle of moments and levers, 321–323 Procedures, operating, 276, 278 Process, defined, 42 Process diagrams. See Process flow diagrams (PFDs) Process flow diagrams (PFDs), 168, 173–174, 182–184, 356 Process heaters, 371–373 Process instrumentation defined, 266 definition, 42 distillation, 272, 274 level measurements, 171–172 overview, 51–53, 168 pressure, 169, 171–172, 186–191 symbols, 173–174, 185–187 temperature, 170 troubleshooting, 362–363

Index Process legend, 183, 186–187 Process operations, 57–60 Process Safety Management (PSM) standard, 43, 49–50, 70–72, 74 Process symbols, 168. See also Piping and instrumentation drawings (P&ID); Process flow diagrams (PFD) boiler and furnace systems, 179–180 compressors and pumps, 176–177 distillation, 180, 181 heat exchangers and cooling towers, 177–179 instruments, 185–187 overview, 173–174 piping, 175 pumps and tank systems, 175–176 reactors, 180–182 Process technician careers in, overview, 24–29, 31 defined, 3, 42 education and training, 17–24 job description, 27 roles and responsibilities, 29–34 Process technology defined, 3, 42 education and training, 43–47 Process variables, 196–197, 356. See also Quality control Product directives, 345 Products, chemical reactions, 287 Product storage systems, 228–234 Product variation, 271, 344–346. See also Quality control Programmable logic controllers, 202 Propane, 296–297 Proportional band, controllers, 194, 201 Proportional-integral-derivative (PID) controllers, 194, 201 Proportional (P) controllers, 194 Proportional plus derivative (PD) controllers, 194, 201 Proportional plus integral (PI) controllers, 194, 201

Protective equipment, 49–50, 70, 80, 81 Protons, 284 psia (absolute pressure), 95, 169 psig (gauge pressure), 95, 169, 217 PSM standard (Process Safety Management), 43, 49–50, 70, 71–72, 74 Pulp and paper industry, 418 Pump-and-feed systems, 228–234 Pump-around systems, 208, 209 Pump curve, 125 Pumps, 114, 124–129 physics of, 325–327 symbols, 175–177 troubleshooting, 363–364 Pyrophoric, 78

Propylene, 255, 256–257

Range, 194

Q Quality control cause-and-effect (C&E) diagrams, 342, 348–349 data collection forms, 351 education and training, 50–51 flowcharts, 346, 348 histograms, 351 improvement cycle, 343 Pareto chart, 350 pilot distillation plant, 274–276 planned experimentation, 342, 350–351 principles of, 42, 342–343 run charts, 342, 348 scatter plots, 342, 352 statistical process control (SPC), 342, 344–346 supplier-customer relationships, 344 tools, 344 waste management, 338–339 R Radial bearings, 136 Radiant heat transfer, 152–153, 371–373 Radiation, 99 Radiation level detectors, 171–172 Raffinate, extractions, 161, 226, 234–235, 379

463

Index Rankine (°R), 100, 170 Raoult’s law, 9 Rate mode, controllers, 194, 201 Raw materials, 219, 345 RCRA (Resource Conservation and Recovery Act), 334, 337 Reactants, 283, 287, 293–294, 397 Reaction rate, 155–156, 283, 292 Reaction variables, 374 Reactors, 154–157 BTX aromatics, 252 chemistry in, 299 defined, 142, 248 fluid catalytic cracking, 257–258 nuclear, 4, 34–36, 154–157, 181–182, 418, 424 overview, 59 symbols, 180–182 systems, 227–228 troubleshooting, 374–376 Reading comprehension tests, 392 Reboiler, distillation, 157–158, 230, 248, 268, 299 Reciprocating compressors, 130–131 Reciprocating pumps, 127 Rectifying, 268 Redundancy, 356 Refining processes, 8–9, 249–250, 256–262, 419–420 Reflux, 157–160, 268 Reformer, 248, 255 Refrigeration systems, 226, 241–242 Regenerators, 248, 252 Regulations. See Legislation Regulatory agencies, 34–37 Relief valves, 119, 174 Remote controlled valves, 202–203 Replacement reactions, 283, 291 Representative elements, 400 Reproductive toxins, 78 Research technician, 27 Reset mode, controllers, 194, 201 Residue, distillation, 157

464

Residuum, batch processing, 8 Resins, 291 Resistance, electrical, 323–324 Resource Conservation and Recovery Act (RCRA), 334, 337 Respiratory protection, 70, 79–80 Resume, 387–390 Reynold’s number, 101 Riser tubes, boilers, 151 Rotameters, 173 Rotary compressors, 130–131 Rotary pumps, 126–127 Rotational energy, 210–212, 325–327 Rotor, 132 Run chart, 342, 348 S Safety basic principles, 72–73 cooling towers, 369 education and training, 47–50 electrical drawings, 189 hazardous chemicals, 77–78 interlocks and permissives, 184 overview, 71–72 pilot distillation plant, 274–276 pressure relief, 150, 226, 235–236 Safety valves, 119–120, 150, 174 Salaries, 27–29 Samples, quality control, 345 Saturated hydrocarbons, 396, 410 Scatter plots, 342, 352 Scientific method, 397 Scientific notation, 396, 398 Scrubbers, 227, 233 Seals, 135–137 Secondary operational problems, 356, 360 Sensible heat, 99, 147–148 Sensitizers, 78 Sensors, control loops, 197 Separation systems, 161, 227, 234–235, 379–381

Index Sewage treatment, 418, 424–426 Shale, 4, 16 Shell-and-tube condensers, 299 Shell-and-tube heat exchangers, 143–147, 178–179, 365–367, 368 Shell heat exchangers, 143–147 SHP (super-high-pressure) steam, 217 Shutdown items, 184, 276, 278 Sight glasses, 171–172 Sillman, Benjamin Jr., 7 Simulations, 361–362 Single-pass heat exchangers, 143–147 Sliding vane pumps, 127 Smart transmitters, 199 Software, simulations, 361–362 Softwire interlocks, 184 Solenoid valves, 203 Solids, 103, 239–240 Solid waste, 334, 336–337 Solutes, 161, 227, 235 Solutions, 285 Solvay, Ernest, 9 Solvents, 161, 227, 235 Sour feed, 258 SPC (statistical process control), 50, 63, 342, 344–346 Specifications, product, 271 Specific gravity, 102, 306, 308–312 Specific heat, 99 Specific weight, 308–312 Spiral heat exchangers, 178–179 Spring valves, 203 Start-up items, 184, 201, 276, 278 Statistical process control (SPC), 50, 63, 275, 342, 344–346 Steam generation systems, 149–151, 208, 216–218, 228–234, 323, 423–424 Steam traps, 114, 137–138, 217 Steam turbines, 103, 114, 132, 424 electrical systems and, 212–213 physics of, 325–327 symbols, 177

Stirred reactors, 154–157, 156, 227–228 Stirred-tank reactors, 181–182 Stop check valve, 118–119 Storage hazardous chemicals, 77–78 symbols, 175–176 tanks, 121–123 Straight-through diaphragm valve, 119 Strain, 310 Strainers, 114, 123 Streamline flow, 102 Stripping columns, 232, 268, 376–377 Suction pressure, 125 Sulfur, crude oil, 4 Superfund Amendments and Reauthorization Act, 338 Superheating, steam, 371 Super-high-pressure steam (SHP), 217 Supplier-customer relationships, 344 Surface tension, 311 Swing check valves, 118 Symbols, process, 168. See also Piping and instrumentation drawings (P&ID); Process flow diagrams (PFD) boiler and furnace systems, 179–180 compressors and pumps, 176–177 distillation, 180, 181 heat exchangers and cooling towers, 177–179 instruments, 185–187 overview, 173–174 piping, 175 pumps and tank systems, 175–176 reactors, 180–182 Syn-gas, 6, 16 Synthetic resins, 238 T Tag-out procedures, 70, 81 Tanks, storage, 114, 121–123, 175–176 Tar, 298–300 Target organ effects, 78 Tar sands, 4, 16

465

Index Temperature cohesive force and, 311–312 control loops, 196–197 data collection, 275–276 distillation systems, 230, 268 gauges and instruments, 170 physics of, 99–100 piping and instrumentation drawings (P&ID), 186–191 pressure and, 314–319 Tenacity, 310 Tensile strength, 310 Tension-leg platforms, 423 Teratogens, 78 Test of Chemical Comprehension, 392 Thermal cracking, 3, 8, 9, 10 Thermal efficiency, 327–328 Thermal expansion, 317–319 Thermocouples, 170 Thermostatic traps, 138 Thermosyphon reboiler, 143–147, 362–363 Three-phase motor, 135 Toluene, 251–252, 409 Tools hand tools, 114–115 quality control, 344–352 Toxic chemicals, 78, 334, 337 Toxicology, 49–50, 79 Toxic Substances Control Act (1976), 334, 337 Training programs, 17–24 ACS standards, 31 HAZCOM, 74–77 safety, 274–275 Transformers, 189 Transition elements, 400 Transmitters, control loops, 197–199 Transportation, hazardous chemicals, 77–78 Troubleshooting absorption and stripping model, 376–377 boiler model, 369–371, 372 compressor model, 365

466

cooling tower model, 367, 369 distillation model, 377–379 education and training for, 60–63 equipment, 362 furnaces, 221, 371–373 heat exchanger model, 365–367, 368 instrumentation, 362–363 methods, 356–360 models, 360–362 multivariable model, 381, 382 pump model, 363–364 reactor model, 374–376 separation model, 379–381 TSCA (Toxic Substances Control Act 1976), 334, 337 Tubular reactors, 154–157, 181–182, 227–228 Tuning controllers, 202 Turbines, 114, 132, 133–134, 424 Turbine systems, 210–212 Turbulent flow, 102 U Ultrasonic level detectors, 171–172 Unplugging permit, 81 Unsaturated hydrocarbons, 410 Unstable chemicals, 78 Utility systems, 243 U-tube heat exchangers, 143–147, 178–179 V Vacuum, pressure (psiv), 92–93, 95, 317–319 Valence electrons, 284–285 Valves, 114 automatic, 203 control, 203 expansion, 241 governor, 132 pressure relief, boilers, 150 pressure relief systems, 235–236 symbols, 174 types of, 115–121

Index Vane actuator, 203 van Helmont, Jan Baptista, 6 Vaporization distillation, 157–160, 299 heat exchanger, 146–147 latent heat, 99 Vapor lock, 125 Vapor pressure, 90–92, 97, 406–407 Vapors, compression and, 315–316 Variation, product, 271, 344–346. See also Quality control Venturi flow nozzles, 173 Viscosity, 101, 309–310 Voltage, 134–135, 324 Voltmeters, 189 Volume, 307 Volute, 124 W Wages, chemical processing industry, 27–29 Warning labels DOT, 77, 84, 85 HAZCOM, 76 overview, 49–50 Waste management, 338–339

Water density, 102, 309 permits, 334, 336 pollution, 334, 336 sources of, 122–123 specific gravity, 102 treatment of, 242–243 Water hammer, 137–138 Water reactive chemicals, 78 Water treatment systems, 242–243, 424–426 Water-tube boilers, 150–151, 179–180 Water turbines, 424 Weight, defined, 306 Weight-operated valves, 203 Weir diaphragm valve, 119 Wetting, 311 Wind power, 4, 424 Work, physics, 319–323 Work teams, 278 X Xylenes, 251–255 Y Young, James, 6–7

467