No title

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007 CURRENT PROBLEMS RUSSIAN ENVIRONMENTALLY CLEAN DIESEL...

Author: Rassadiu V.G. | Durov O.V. | Vasil'ev G.G.

82 downloads 563 Views 564KB Size Report

This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!

Report copyright / DMCA form

DOWNLOAD PDF

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

CURRENT PROBLEMS

RUSSIAN ENVIRONMENTALLY CLEAN DIESEL FUELS OF EUROPEAN QUALITY V. G. Rassadin, O. V. Durov, G. G. Vasil’ev, N. G. Gavrilov,

UDC 665.753

O. Yu. Shlygin, and N. M. Likhterova

The results of screening tests of foreign catalysts from Criterion, Haldor Topsoe, and Akzo Nobel for production of EN–590 (Euro–2, Euro–3) diesel fuels are examined. The effectiveness of revamping the LCh–24/2000 unit for processing these fuels using the Akzo Nobel catalyst package was demonstrated. The physicochemical characteristics of the diesel fuel with additives that satisfies the requirements of GOST R 52368-2005 for fuel with a residual sulfur content of less than 50 ppm are reported. The high price of crude oil all over the world allowed diversifying the processing schemes for domestic oil refineries (OR) at the beginning of 2000 to increase the competitiveness of their products on world markets. The tendency to produce petroleum products of European quality at Russian OR became irreversible after the advent of the law on “Technical Regulation” (June 26, 2003). Revamping and retooling of motor fuel production units are now being conducted at almost all Russian OR [1–10]. The leading oil companies have perfected technologies for production of high–quality motor fuels in two directions. TNC and Angara Oil Company have primarily attempted to fully utilize domestic developments in the area of technology, catalysts, and equipment in developing a strategy for retooling and revamping existing fuel production plants. LUKOIL has taken into account world experience, including purchase of licenses for the most promising technologies, equipment, and catalysts from the leading firms in the USA and Western Europe. Guarantees of the reliability of operation and high quality of the equipment and catalysts allowed organizing production of export products of European quality at OR in record times, which expanded the amount of investments for further development of their refineries combined with the high crude oil prices. ____________________________________________________________________________________________________ LUKOIL OJSC-Nizhegorodnefteorgsintez. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 3 – 9, January – February, 2007. 0009-3092/07/4301–0001 © 2007 Springer Science+Business Media, Inc.

1

Table 1

Hydrogenation product obtained on catalyst 448 T@ with beads with diameter of, mm GKD-300

837

828

829

828

829

830

832

10200 83

9700 97

100

600

170

500

1300

540

70,1

74,2

76

79,4

77,4

74

0,93 22,9

1,06 22

1,4 21,6

1,23 21,1

1,08 23,2

0,8 27,5

1,02 32,5

53

55

50

54

54

54

52

0,26 aromatic (including thiophene derivatives) 32,5 Cetane number 51

424 T@

839

TK-554

GM-85 Co

Density at 20°C, kg/m3 Content total sulfur, ppm nitrogen, ppm hydrocarbons, wt. % unsaturated

GKD-300

Indexes

TK-554, 424 T@, 448 T@, GM-85 Co

Feedstock for certification of catalysts

1.3

2.5

The strategy for developing production of high–quality diesel fuels created at LUKOIL includes four stages: • hydrorefining of straight–run diesel cuts on high–efficiency foreign catalysts that allow obtaining products with a residual sulfur content of less than 350 (version I) and less than 50 (version II) ppm in existing hydrorefining units; • combining hydrorefining and hydroisomerization of straight–run diesel cuts with a residual total sulfur content of less than 10 ppm and less than 11% polycyclic aromatic hydrocarbons in newly constructed hydrotreating units based on licenses from the leading foreign firms in this sector; • combining desulfurizing, denitration, and hydrodearomatization of catalytic gasoils, coking, visbreaking in complexes for exhaustive refining of crude oil using catalysts and technologies from the leading foreign companies; • hydrocracking of vacuum straight–run and secondary gasoils with a mandatory system for removal of high–molecular–weight polycyclic aromatic hydrocarbons [11]. Within the framework of this strategy, LUKOIL is the developer of national standards for production of EN–228 automotive gasolines (GOST R 51866–2002), domestic Jet A–1 fuel (GOST R 52050–2003), and EN–590 diesel fuel (GOST R 52368–2005). Development of national standards for motor fuels of European quality corresponds to the requirements of the law on “Technical Regulation” and is totally harmonized with the text of the draft special technical regulation “Requirements for Gasolines, Diesel Fuel, and Individual Fuel–Lubricant Materials.” The latter has been approved and will become a Federal law in 12 months after the date of official publication. LUKOIL is thus successively implementing diversification of oil refinery technology in view of world trends. According to the strategy developed, the first stage of diversification of diesel fuel production technology is being implemented at LUKOIL–Nizhnegorodnefteorgsintez Co. User demand in internal and external markets for 2

Table 2

Feedstock for testing KF–757 catalyst

Hydrogenation product on KF–757 catalyst

IBP 10 % 50 %

111 183 277

164 242 313

90 %

358 404

368 412

15289

10**

Indexes Distillation, °C

EP Content*, ppm total sulfur methylthiophenes C2–C4 thiophenes

49

Not detected

2524

same

benzothiophenes C1–C5 benzothiophenes

340

same

8088

same

4287 972

217

43.5

44.5

C1–C5 dibenzothiophenes nitrogen Cetane index Notes.

* Determined by atomic–emission analysis

** Determined by XFA

the products manufactured by the company is being evaluated to determine the niche in sales markets to 2014. In conducting the market analysis, the following hypotheses were advanced concerning the development of internal and external markets: • the increase in the real earnings of the population will be up to 6% a year; • the passenger car fleet will increase by 40% by 2010; • production of passenger cars will increase to 2–2.5 million units by 2010 and imports will crease to 400,000 units; • the increase in demand for motor fuels in Russia will be determined by the growth rate of the Russian GDP, slightly exceeding it; • exports of gasoline to Europe will be limited except perhaps for a small amount of high–octane gasoline to Baltic countries; • the demand for diesel fuel for internal and external markets will increase. According to market studies, potential annual sales volumes for the basic petroleum products for LUKOIL–Nizhegorodnefteorgsintez by 2014 are projected at, in millions of tons: 2.8–2.9 for gasoline; 1–1.5 for jet fuel; 4–5 for diesel fuel; 2.5–3 for boiler fuel. Based on an analysis of sales markets and the status of the available production capacities for hydrorefining of middle–distillate fuel cuts at the company, the LCh–24/2000 unit with output of 2 million tons/year in feedstock started up in 1993 was selected for revamping. The unit includes the following blocks: reactor, hydrogen product stabilization; treatment of circulating hydrogen–containing gas (CHCG) and hydrocarbon gas to remove hydrogen sulfide, ammonia, and water with a solution of monoethanolamine (MEA); regeneration of MEA. Before beginning revamping, a bid for selecting the catalyst for hydrotreating of diesel cuts to obtain EN–590 fuel was conducted between the licensing companies Criterion, Haldor Topsoe, Axens, and Akzo Nobel.

3

Sulfur content, ppm

Sulfur content, ppm

Temperature,°C

Temperature,°C

Fig. 1. Sulfur content in hydrogenation product as a function of the temperature in the reactor for catalysts: a) TK–554; b) 424T@; c) 448 T@ with granules 1.3 mm (curve 1) and 2.5 mm in diameter (curve 2); d) GKD–300 (curve 1) and GM–85 Co (curve 2); e) STARS series KF–757. The

foreign

catalysts

TK–554

(Haldor

To p s o e ) ,

424T@,

448

T@

(Criterion),

and STARS series KF–757 (Akzo Nobel) in comparison to the domestic catalysts GM–85 Co (VNIIOS NK [All–Russian Scientific–Research Institute of Organic Synthesis Oil Co.]) and GKD–300 (VNII NP [ All–Russian Scientific–Research Institute of the Petroleum Industry]). The tests were conducted at pressure of 3 MPa, feedstock space velocity of 4 h –1 , CHCG to sulfur ratio of 250 nm 3/m 3. The domestic catalyst GKD–300 was tested in more severe conditions: pressure of 4 MPa, feedstock space velocity of 3 h –1 . To obtain hydrogenation products with a residual sulfur content of less than 50 ppm, the feedstock space velocity did not exceed 2–2.5 h –1 . The physicochemical properties of the feedstock used in certification of the catalysts are reported in Tables 1 and 2. In testing KF–757 catalyst on a wide middle–distillate cut that included heavy naphtha cuts (IBP–10%), kerosene and diesel cuts with a high (404°C) end point by atomic emission analysis, we were able to follow the degree of removal of thiophene derivatives of different molecular weight. 4

Content, wt. %

TK–554 424T@ 448 T@ 448 T@ GM–85 Co GKD–300 1.3 2.5 Fig. 2. Coke (1) and sulfur (2) content on catalysts after testing at 380°C. The dependences of the total sulfur content in the hydrogenation products on the temperature in the reactor were established during the experiments (Fig. 1). The residual sulfur content in the hydrogenates was determined by x–ray fluorescence analysis (XFA). The data obtained show that KF–757 catalyst exhibits the highest activity in reactions of hydrogenolysis of sulfur compounds. The physicochemical properties of the hydrogenation products with a minimum content of sulfur compounds obtained in testing the catalysts are reported in Tables 1 and 2. The coke and sulfur content was determined after completion of the experiments at a temperature of 380 on the domestic catalysts and Criterion and Haldor Topsoe catalysts. As the data show (Fig. 2), the domestic catalysts have a high tendency to form coke deposits while GM–85 Co catalyst is also characterized by a low degree of sulfiding. As a result of testing the catalysts and generalizing the licensing company data, preference was given to Akzo Nobel. This company’s catalyst package was purchased and loaded in 2003: KG–55, KF–542, KF–841, KF–757. The characteristics of these catalysts are reported in Table 3. The total volume loaded was 77 m 3. The loading diagram is shown in Fig. 3. Before loading the catalyst system, partial revamping of reactor R–201 and individual units in the installation was conducted to increase its efficiency: • a new DUPLEX distribution tray from Akzo Nobel was installed in the reactor; • the heat–exchange conditions were improved in the lower part of tower K–205 in the MEA regeneration block to reduce the concentration of hydrogen sulfide in CHCG; • defects in feeding MEA to tower K–205 were identified and eliminated; • discharge of treated diesel fuel into the PLC system; • the vapor cooling conditions in stabilization tower K–201 were improved and the possibility of fuel entering the circulating water supply system was eliminated; • the efficiency of operation of furnace P–201 was increased; • a separate line was installed for taking environmentally clean diesel fuel (less than 350 and less than 50 ppm sulfur) off the unit. Installation of new lines for taking stable hydrogenation product off the unit was caused by the high dissolving power of the hydrogenation product with respect to deposits in the pipelines that previously transported hydrogenation products with a higher content of sulfur compounds and resins. These data were obtained as a result of many years of domestic experience in production of thermostable RT and T–6 jet fuels. KF–757 catalyst was delivered in oxide form and impregnated with a special composition that fixes the position of the active sites on the support. In this respect, sulfiding was allowed only by the feedstock. Sulfiding 5

Hose

STARS series KF-757-3Q

same

KF-841-2E

Leak-proof

same

KF-542-5R

STARS series KF-757-1.5E

Hose

Loading method

KG-55

Catalyst

Volume loaded in reactor, m3 1.02

64.13

8.16

2.04

1.53

CoO/ MoO3

CoO/MoO3 on Al2O3

Ni/Mo on Al2O3

MoO3/NiO/CoO on Al2O3

SiO2/Al2O3

Chemical composition

in laboratory determination 750

780

780

670

880

668

694

686

596

—

in hose loading

Bulk density, kg/m3

772

803

803

—

—

in leak-proof loading

Table 3

647

795

686

637

647

real

6 Ring

19.2 × 9.5

6×3

2.6 × 5.1

1.4 × 3.5

Quadrilobe

same

Cylinder

Segmented ring

2.1×4.5

Granule shape

Granule size, mm

same

Protective layer to trap particulate contaminants and pollution, slowing increase in pressure drop Hydrogenation of unsaturated compounds, trapping of particulate contaminants (has a high volume of free space), improving feedstock stream distribution Exhaustive denitration and hydrogenation, trapping of metals, improving feedstock stream distribution Exhaustive hydrotreating of middle distillates to 50 ppm sulfur content

Application

15

15

10

5

–

Required sulfur content, %

was conducted according to the company’s recommendations for straight–run diesel cut with a 0.9 wt. % sulfur content. After sulfiding of the catalyst and entry of the unit into normal operation, a fixed run in two regimes that ensured production of diesel fuel with a residual sulfur content of less than 350 ppm (version I) and less than 50 ppm (version II) was conducted. The results of the two versions of runs (Table 4) correspond to Akzo Nobel recommendations primarily with respect to the sulfur content. In charging feedstock at 310 m 3/h, the sulfur content in the product was on

Layer number

Catalyst brand

Layer height, mm

Layer volume, m3

Beads with diameter of, mm 1

16 – 20

690

–

2

10

50

–

3 4

6 KF-757-3Q

90 100

– 1.02

5

KF-757-1.5E

6250

64.13

6

KF-841-2E

795

8.16

7

KF-542-5R

200

2.04

8

KG-55

150

1.53

8325

76.88

Total

Fig. 3. Diagram of loading Akzo Nobel catalyst in reactor 201 (internal diameter of 3616 mm, height of 11.192 mm, volume of 114.9 m3). 7

average 310 ppm, and the mean weighted temperature in the catalyst bed was 334°C, which is 16°C lower than the temperature predicted by the company. At feedstock input of 230 m 3/hk (guaranteed input of 210 m3/h), the residual sulfur content was 31 ppm and the weighted mean temperature in the catalyst bed was 10° lower than expected. D u r i n g t h e r u n , i t was not possible to maintain the concentration of hydrogen in the CHCG at 80 vol. % (contract data) due to the low hydrogen content (76 vol. % on average) in the fresh HCG entering the unit. It was only 69 vol. %, which decreased the partial hydrogen pressure at the reactor inlet from 2.4 (initial data) to 1.9 MPa. This negatively affected the work of the catalyst system and increased the rate of coke formation on the catalyst. D u r i n g t h e c o n t r o l r u n i n l o a d i n g f e e d s t o c k a t 3 1 0 m 3/ h , t h e p r e s s u r e d r o p i n t h e r e a c t o r was 0.31 MPa, i.e., slightly higher than predicted (0.24 MPa), which was due to the following causes: increasing the total volume of actually charged catalyst from 70 to 77 m 3 ; a low hydrogen content (69–70 vol. %) in the circulating gas, which increased the viscosity of the gas and the CHCT flow velocity to 86–96,000 nm 3/h (according to calculated data, 75,000 nm3/h at an 80 vol. % concentration of hydrogen). All of these factors caused a significant increase in the pressure loss in the catalyst bed and an increase in the pressure differential. After completion of the fixed run, HCG began to be fed from the reforming unit Recovery Place block to the LCh–24/2000 unit with continuous regeneration of the catalyst. The concentration of hydrogen in the HCG from this unit was 90–91 vol. %, which allowed reducing consumption of hydrogen and blowing off HCG. Table 4

Data from fixed run according to version Indexes

I

II

programmed

real

programmed

real

1.6 (max) <350

0.95 300

1.6 (max) <50

1 31/8*

310

310

210

230

75000

84000

7500

94000

Pressure at reactor inlet, MPa

3.25

3.28

3.25

3.28

Pressure drop in reactor, MPa

0.24

0.31

0.19

0.27

80

69.6

80

69.6

hydrogen sulfide

<0.1

Abs.

<0.1

Abs.

Partial hydrogen pressure, MPa

2.4

1.96

2.4

1.96

340

328

353

348

356

337

369

355

350

334

363

353

Sulfur content in feedstock, wt. % in product, ppm Flow rate, m3/h feedstock CHCG (in normal conditions)

Concentration in HCG, vol. % hydrogen

Temperature of catalyst layer, °C at beginning of cycle at reactor inlet at reactor outlet mean weighted Note.

*In the numerator – residual sulfur content in stable hydrogenation product, determined by energy–disperse

X–ray fluorescence spectrometry; in the numerator – determined by X–ray spectrometry. 8

Table 5 Fixed run producing hydrogenation product with a sulfur content of, wt. % <0.035 <0.05

Feedstock, products

Taken, wt. % Feedstock HCG

100.0 2.3

100.0 2.3

102.3

102.3

Stable hydrogenation product Distillate

98.0 1.8

97.5 2.2

Hydrogen sulfide Hydrocarbon gas Losses

0.7 1.6 0.2

0.7 1.7 0.2

102.3

102.3

Total Obtained, wt. %

Total

Table 6

Standards for mild climate Indexes A

B

C

D

E

F

Cetane number Cetane index Density at 15°C, kg/m Content

min 46 820—845

3

polycyclic aromatics, wt. %

max 11

sulfur, ppm

max 350

water, mg/kg

max 200

Flash point (closed cup), °C Carbon residue of 10% residue, wt. %

max 0.30

Ash content, wt. %

max 0.01

min 55

Total contamination, mg/kg

max 24

Corrosiveness (copper, 3 h, 50°C) Oxidative stability, g/m3

class 1 max 25

Lubricity: corrected wear scar diameter (WSD 1.4) at 60°C, μm 2

Viscosity at 40°C, mm /sec Distillation, vol. % under 250°C under 350°C 95 vol. % Distillation temperature, °C Limiting filterability temperature, °C, max

+5

0

Diesel fuel, version II Sample Sample 1 2 55 54 52.6

52.2

835.8

836.4

– 31

– 40 Abs.

70 0.012

70 0.011 Abs.

1

1 class 1

max 460

3.1 533

3.1 534

2.0 – 4.5

3.03

3.03

max 65

33

33

min 85

95

95

max 360

350

350

-7

-7

-5

-10 -15 -20

The nitrogen content and cetane number of the hydrogenation product were determined during the run together with the sulfur content in the feedstock and products. In production of diesel fuel with a sulfur content of less than 350 ppm, the nitrogen content decreased from 132 to 95 ppm and the cetane number was 55 points. 9

Table 7

Indexes

Operation of LCh–24/2000 unit on GKD–300, GKD–205 on KF–757 catalyst catalyst system

Consumption 0.358

0.417

12000 – 13600

17200 – 22400

in fresh HCG in CHCG, nm3/h

78 – 80 77 – 78

77 – 78 73

Emission of HCG, nm3/h

4000

9000

of 100% hydrogen to reaction, wt. % in feedstock 3

fresh HCG, nm /h Concentration of hydrogen, vol. %

Table 8

Electric power, kwh/month

Data from operation of LCh– 24/2000 on GKD–300 on Akzo Nobel catalyst package catalyst real planned real planned 12.5 12.5 11.6 11.6

Steam, thousands of kJ/month

77.93

94.28

67.46

67.46

Fuel, kg equiv. fuel/month

7.6

7.6

7.3

7.3

MEA (over 6 months), kg

0.006

0.013

0.01

0.01

7

7

–

–

KG-55 (protective layer)

–

–

0.15

0.15

KF-542-5R (hydrogenation of unsaturated compounds, improved distribution) KF-841-2E (denitration, hydrogenation, improved distribution)

– –

– –

0.2 0.86

0.2 0.86

KF-757-1.5E (exhaustive hydrotreating)

–

–

7.84

7.84

KF-757-3Q (exhaustive hydrotreating)

–

–

0.1

0.1

Consumption indexes per 1 ton feedstock

Losses, g catalyst over 6 months catalyst package over 1 month

In production of diesel with a sulfur content of less than 350 and less than 50 ppm, the decrease in the density of the product in comparison to the density of the feedstock was 6–8 and 10–11 kg/m 3 , respectively. Despite the very low partial hydrogen pressure, the catalyst system had high hydrogenating activity with respect to polycyclic aromatic hydrocarbons. The increase in the partial hydrogen pressure in the system to the calculated values additionally decreased the density and increased the cetane number of the product as a result of hydrogenation of aromatic structures. The material balances of the fixed runs of the LCh–24/2000 unit with the Akzo Nobel catalyst package are reported in Table 5. It follows from these data that an increase in the degree of removal of sulfur compounds decreases the yield of stable hydrogenation product and increases the yield of cuts that distill below the boiling point of the feedstock, as well as an increase in the yield of hydrocarbon gases. This is due to intensified degradation of the hydrocarbons in the feedstock as a result of the increase in the temperature in the reaction zone (see Table 4). In refining fuel according to version II, the temperature in the reaction zone should be increased by almost 20°C. Revamping the unit and replacing the GKD–300 and GKD–205 domestic catalysts by the Akzo Nobel catalyst package ensured obtaining diesel fuel with a residual sulfur content of less than 350 and less than 50 ppm. 10

Diesel fuel with a residual sulfur content of less than 2000 ppm was previously refined in the LCh–24/2000 unit. At the minimum reactor temperature (320–322°C at the inlet and 330–333°C at the outlet), the sulfur content in the stable hydrogenation product was 400–500 ppm. This allowed increasing the volume of production of fuel with a sulfur content of less than 2000 ppm by 60 m 3/h by mixing the stable hydrogenation product with the straight–run diesel cut. In the course of the version II fixed run, pilot–industrial lots of diesel fuel of environmental classes 3 and 4 were obtained. The physicochemical properties of the class 4 fuel are reported in Table 6. This fuel totally satisfies the requirements of GOST R 52368-2005. To increase the lubricity, Lubrisol 539 M antiwear additive in the concentration of 50 ppm was added to the diesel fuel with a 50 ppm sulfur content. After the fixed runs, the hydrogen consumption and specific standards for consumption of electric power, heat carriers, reagents, and catalysts were compared with the same indexes for operation of the LCh–24/2000 on the domestic catalyst GKD–300. The comparison showed that the total consumption of hydrogen increased and the proportion of blown CHCG increased significantly in using highly active catalytic systems (Table 7).. On the contrary, the specific standards for consumption of electric power, fuel, and steam decreased (Table 8). Due to the decrease in fuel consumption, for example, the economic effectiveness of operating the P–201 furnace was 770,051 rubles/year. Since the draft specifications provide for introduction of environmental requirements for classes 3 and 45 diesel fuels as a federal law from 01.01.2009 and 01.01.2010, the diversification of production of diesel fuel allowed LUKOIL”Nizhegorodnefteorgsintez to assume a leading position among RF oil refineries and to make additional profits for a long time from offering high–quality diesel fuels on internal and external markets. REFERENCES 1. V. N. Chistyakov and D. A. Pidzhakov, Neftepererab. Neftekhim. No. 7, 7–11 (2004). 2. 3.

A. I. Emilin, G. P. Grishanov, V. A. Mikishev, et al., Ibid., No. 8, 23–31 (2003). S. A. Logino, B. P. Lebedev, V. M. Kapustin, et al., Ibid., No. 11, 67–74 (2001).

4. 5.

S. A. Loginov, V. M. Kapustin, A. I. Lugovskoi, et al., Ibid., No. 8, 11–13. S. A. Logino, V. M. Kapustin, A. I. Lugovskoi, et al., Ibid., No. 11, 57–61.

6. 7.

S. A. Loginov, V. M. Kapustin, A. I. Lugovskoi, et al., Ibid., No. 10, 8–11. A. I. Lugovskoi, S. A. Loginov, K. B. Rudyak, et al., Khim. Tekhnol. Topliv Masel, No. 5, 35–37 (2000).

8. 9.

V. K. Smirnov, K. N. Irisova, E. L. Talisman, et al., Ibid., No. 4, 37–41 (2004). L. N. Osipov, V. A. Khavkin, B. L. Lebedev, et al., in : Proceedings of the Annual Scientific and Technical Conference “The Current State of Oil Refining Processes” [in Russian], GUP “INKhP”, OAO Bashneftekhim, Ufa (2004), pp. 142–144.

10. 11.

V. P. Kostyuchenko, Ibid., pp. 145–155. V. P. Bazhenov, InfoTEK: Statistika, Dokumenty, Fakty, No. 11, 83–90 (2002).

11

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

TECHNOLOGY

EXPERIENCE IN OPERATING FUEL-CUT HYDROTREATING UNITS G. G. Vasil’ev, O. V. Durov, V. G. Rassadin, N. G. Gavrilov, O. Yu. Shlygin, and N. M. Likhterova

UDC 665.753

The data on use of the GKD-205 and GKD-300 catalyst system in the L-24/7 unit are generalized. These catalysts lose activity during each regeneration, which negatively affects the unit’s operating conditions. In refining diesel fuel of environmental class 2 (Euro-2), the output in feedstock decreases sharply and the temperature in the reactor increases. In addition, they are characterized by low mechanical strength: losses from wear are greater than 10 wt. %. It is recommended that they be replaced by highly effective catalysts with improved operating properties. The development of a comprehensive systems program for retooling and developing the oil refinery without fail includes an analysis of the current state of active plants. Revealing the cause-effect correlations in unsatisfactory operation of units in production of higher quality products is the basis for developing substantiated solutions in improving the technical and technological states of existing and newly constructed units. A comprehensive inspection of fuel cut hydrorefining units to detect problems in their operation was conducted in 2000-2002 at LUKOIL–Nizhegorodnefteorgsintez. The results of the inspection of the L-24/7 hydrotreating unit in operation on the system of GKD-205 and GKD-300 domestic catalysts are reported here. Diesel fuels with a residual sulfur content of less than 0.2 wt. % have been produced according to GOST 305 in this unit since 1996. However, after converting the unit to production of diesel fuel with a residual sulfur content of less than 0.05 wt. %, significant worsening of the activity of the catalyst system was noted, especially after regeneration. This was manifested by a decrease in the output of the unit in feedstock, an increase in the temperature at the reactor inlet, and a pressure drop in the reactors of both blocks (Tables 1 and 2). For example, the temperature at the inlet to reactor R-1 increased significantly – to 355°C (345°C before regeneration) and the pressure drop also increased to 1.2 MPa in unit I (see Table 1) 3 months after the first regeneration of GKD-205 catalyst. ____________________________________________________________________________________________________ LUKOIL–Nizhegorodnefteorgsintez OJSC. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 10 – 12, January – February, 2007. 12

0009-3092/07/4301–0012 © 2007 Springer Science+Business Media, Inc.

13

4.7 4.8 2.1 2.7 2.9 3.06 2.7 2.8 2.9 2.9 4.5 2.9

120 110

40 80 110 80 110 85 140 70 137

145

148 65 85 90 95 85 88 90 90 140 90

10

1 4

14

21 22 23

20

18 19

8

7

6

40 110 130

8

1.3 2.6 3.5 2.6 3.5 2.7 4.5 2.3 4.4

3.8 3.5

1.3 3.5 4.1

3.8 4.3

120 135

27

space velocity, h-1

feedstock consumption, m3/h

Duration of run, months

Table 1

368 367 367 370 370 365 367 374 374 370 370

374 372 372 375 375 377 370 374 380 380 382 373

379

3.8/3 3.6/2.7 4.1/3.3 4.2/3.4 4.4/3.4 4.1/3.3 4.1/3.35 4.1/3.3 3.4/3.1 3.7/3.3 3.45/3.1

3.8/3.1

3/2.9 2.7/2.5 3.3/3 3.4/3 3.4/3.1 3.3/3.1 3.35/3.05 3.3/3.3 3.1/3 3.3/3.2 3.1/3

3.1/3

0.9 1.1 1.1 1.2 1.2 1 1.05 0.8 0.4 0.5 0.45

0.8

Block I operating indexes temperature (°C) at reactor pressure (MPa) in reactor inlet R-1 R-2 overall R-1 R-2 (inlet/outlet) (inlet/outlet) differential On GKD-205 catalyst fresh 340 340 3.6/3.1 3.1/3 0.6 345 348 3.8/3.3 3.3/3.2 0.6 after regeneration 230 232 3.1/3.1 3.1/3 0.1 355 357 3.8/3.4 3.4/2.6 1.2 371 378 4.5/3.8 3.8/3 1.5 after recharging and screening 360 365 3.6/3.5 3.5/3.5 0.1 361 366 4.4/3.8 3.8/3.3 1.1 On fresh GKD-300 catalyst 235 237 3.6/3.5 3.5/3.4 0.2 345 347 2.85/2.8 2.8/2.6 0.25 360 364 2.9/2.75 2.75/2.6 0.3 350 353 2.9/2.65 2.65/2.5 0.4 370 374 3.25/3 3/2.8 0.45 355 358 3.1/2.8 2.8/2.7 0.4 374 376 3.5/3.1 3.1/2.9 0.6 361 363 3.3/3 3/2.8 0.5 375 378 3.5/3 3/2.9 0.6 Kerosene 1 1.04 1.25 1.3 1.26 1.23 0.97 1.15 1.1 (tEP. – 350°С) 1 0.95 0.8 0.85 0.81 0.91 0.86 0.94 0.79 0.93 0.92

1.21 1.17

Kerosene 0.94 1.4

0.63 1.13

in feedstock

0.18 0.049 0.036 0.047 0.05 0.035 0.049 0.03 0.026 0.11 0.03

0.11

Kerosene 0.17 0.18 0.16 0.18 0.13 0.16 0.03 0.13

0.2 0.13

Kerosene 0.2 0.19

0.09 0.18

in hydrogenation product

sulfur content, wt. %

14

feedstock consumption, m 3 /h

110 100

105 120 110

100 125 100 60

Duration of run, months

25

17

0 6 18 26

Table 2

3.4 4.2 3.3 2

3.2 3.5 3.2

3.4 3.1

space velocity, h -1

355 375 358 378

355 365 380

335 355

R-3

R-3 (inlet/outlet)

359 378 360 380 3.7/3.5 3.4/3.3 3.2/2.9 3.4/3.1

3.5/3.4 3.3/3.2 2.9/2.7 3.1/3

3.8/3.7 3.7/3.5 3.3/3.1

3.5/3.3 3.6/3.5

R-4 (inlet/outlet)

0.3 0.2 0.5 0.4

0.4 0.5 0.5

0.2 0.5

overall differential

pressure (MPa) in reactor

On GKD-300 catalyst fresh 337 3.5/3.5 358 4/3.6 after first regeneration 357 4.1/3.8 370 4/3.7 385 3.6/3.3 after second regeneration

R-4

temperature (°C) at reactor inlet

Block I operating indexes

1.07 1.04 0.88 0.91

1 0.9 1.17

0.6 1.22

in feedstock

0.18 0.17 0.2 0.04

0.2 0.15 0.1

0.095 0.16

in hydrogenation product

sulfur content, wt. %

Important loss of activity after each regeneration was also noted for GKD-300 catalyst in block II (see Table 2). After the first regeneration of the catalyst, the temperature at the reactor inlet was 350-357°C (versus 335-337°C on fresh catalyst) in loading the block in feedstock at 105 m 3 /h (100 m 3/h after regeneration). After the second regeneration 17 months later, the temperature at the reactor inlet increased to 355-359°C, and the block charge in feedstock decreased to 100 m 3/h. Refining fuel with a residual sulfur content of less than 0.2 wt. % with an increase in the output of the block to 130 m 3/h (feedstock space velocity of 4.3 h -1 ) became possible only when the reactor inlet temperature increased to 378-380°C. Production of diesel fuel with a residual sulfur content of less than 0.05 wt . % on GKD-300 catalyst in block I (see Table 1) was characterized by an increase in the pressure drop to 1.0-1.2 MPa and the reactor inlet temperature to 370-380°C for a feedstock space velocity of 2.7-2.9 h -1. In refining diesel fuel of environmental class 2 in block II (Euro-2) with a sulfur content of less than 0.05 wt. %, the reactor inlet temperature was 378-380°C for a feedstock space velocity of 2.0-2.1 h -1 and a pressure drop in the system of 0.4-0.5 MPa (see Table 2). The data in Table 3 also confirm the decrease in the activity of GKD-300 catalyst as a result of regeneration. After regeneration, the pore volume and specific surface area of the catalyst decreased by 42 and 38%, respectively. Table 3

GKD-300 catalyst (block II)

Indexes

fresh

Content, wt. % dust and grit coke

0.03 —

sulfur

after passivation from reactor

after regeneration at catalyst plant (Ufa) According to LUKOIL–Nizhegorodnefteorgsintez data

according to catalyst plant data

R-3

R-4

0.19 3.54

0.15 2.56

0.21 0.07

– 0.12

0.03

3.59

3.69

0.037

0.8

iron Specific surface area, m2/g

0.01 240

0.054 131

0.045 124

0.014 140*

– 193.1

Pore volume, cm3/g

0.74

0.34

0.3

0.46

–

Note.

2

*According to data from Nizhegorodskie Sorbenty, 160 m /g.

Table 4

Content, wt. %

Catalyst

coke

sulfur

iron

Block I GKD-205 from reactor R-1

4.29

11.1

3.43

R-2

2.18

12.07

5.09

3.5

6.75

2.25

1.54

6.54

1.72

Block II GKD -300 from reactor R-3 R-4

15

The increase in the pressure differential in the reactor systems of blocks I and II during operation of the unit is due to abrasion of the catalyst granules and clogging of its pore structure with products of corrosion. The compositions of the catalyst dust and grit, determined in discharging the catalysts after passivation, are reported in Table 4. As follows from the data reported, GKD-205 catalyst has a high tendency to form coke deposits and low hydrogenating power. The high concentration of sulfur in the grit of this catalyst indicates participation of feedstock sulfur compounds in condensation of high-molecular-weight hydrocarbons and resinous compounds. GKD-300 catalyst grit i8s characterized by a lower iron content, which is probably the case of the high porosity of the bed of this catalyst, caused by the high mechanical strength of its granules. It is thus necessary to replace the traditionally used catalysts by high-efficiency catalytic systems characterized by improved performance properties in order to produce diesel fuels of European quality in existing units.

16

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

REVAMPING THE EXTRACTION BLOCKS IN VACUUM RESID DEASPHALTING UNITS

K. G. Ziganshin, A. A. Osintsev, G. K. Ziganshin, A. I. Elshin, I. V. Pavlov, L. A. Ponyaev, O. A. Chekenev, S. Yu. Tvorogov, A. A. Rytsev,

UDC 665.637.6:665.662.3

A. V. Pastukhov, S. V. Kuznetsov, S. P. Yanbaev, Zh. Yu. Gusakova, and A. L. Samoshkin

Deasphalting of vacuum resid with liquefied propane is usually conducted in extraction towers of the gravity type. Standard towers (Fig. 1a) have a small (~7 m) height of the propane and vacuum resid reaction zone and are equipped with baffle trays that consist of metal trays 353 mm wide and 6 mm thick with a step of 68 mm positioned at a 45° angle. This design of the internals insignificantly increases the time the phases are held in the tower and causes formation of “coke” deposits, which are high-melting asphaltite, on the trays. The extraction tower with baffle trays is close to the spray tower in efficiency. Table 1 Refractive index at 50°C for deasphalted product from tower

Deasphalted product takeoff Year in first block

in second block

in 36/2M unit

K-1

K-2

Vacuum resid quality indexes nominal [Engler] viscosity at 80°C, sec

flash point (closed cup), °C

—

—

Before revamping 36/2M unit 2003

—

—

37.0

Standard max of 1.5050

After revamping of first extraction block 2004

41.0

37.3

39.3

1.5027

1.5035

19.2

195

2005*

41.2

36.5

38.9

1.5023

1.5030

19.7

200

22

210

After revamping of second extraction block 2005 Note.

41.8

41.2

41.5

1.5027

1.5034

*For January–September, 2005.

____________________________________________________________________________________________________ IMPA Engineering Ltd.; Angara Petrochemical Company. Neftekhimmash Co. Prommet Ltd. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 13 – 16, January – February, 2007. 0009-3092/07/4301–0017 © 2007 Springer Science+Business Media, Inc.

17

a

IV

IV

b

V

V

V

V I

V

V 3

I

1 2

II

III

II

III

Fig. 1. Diagram of the vacuum resid deasphalting extraction tower: a) before revamping; b) after revamping; 1) baffle trays; 2) IMPA Engineering packing; 3) mixer; I) vacuum resid; II) propane; III) asphalt solution; IV) solution of deasphalted product; V) steam. To increase the deasphalting efficiency, a combined technical solution is proposed: use of contact devices from IMPA Engineering [1] combined with the vacuum resid preparation scheme in [2, 3]. The reaction of the phases on the catalyst systems is potentiated inside the tower and additional reaction of the phases in a special mixer in the feedstock preparation unit takes place outside the tower (Fig. 1b). This solution was implemented in the 36/2M unit for deasphalting vacuum resid with liquid propane at the Angara Petrochemical Co.’s Oil Refinery. The unit has two parallelly operating extraction blocks with separate blocks for regenerating the deasphalted solution, which allows obtaining two deasphalting products. The first extraction block was revamped in 2004, then the indexes of operation of the two extractors – the first with IMPA Engineering contact devices and a vacuum resid preparation unit, and the second, with baffle trays. The towers (3 m in diameter, 19.7 m high) operated on the same feedstock. In 2005, after revamping the second block, the operating indexes obtained for the entire unit were generalized. 18

Table 2

Vacuum resid Indexes

after revamping of

before revamping*

first block**

second block***

967 – 993/977

993

–

closed-cup

180 – 206/194

175 – 210/206

180 – 210/207

open-cup

–

250

250

Concentration of chlorides, mg/dm3, max

–

5 – 9/7

9 – 12/11

Carbon residue, %

–

14 – 15/14.4

13 – 15/13.7

13 – 28/19.3

16 – 28/21.6

15 – 23/19

–

10 – 20/16

13 – 19/16

Density at 20°C, kg/m Flash point, °C

Nominal [Engler] viscosity at 80°C, sec Concentration of alkali, g/ton Note.

In the numerator: limiting values; in the denominator: average value.

*For January–October, 2003. **For September–October, 2005. ***For November–December, 2005. Table 3

Deasphalted product Indexes

before revamping

after revamping of first block

second block

18 – 24/21

18 – 24/21.5

19 – 24/21.7

1.5000 – 1.5050/1.5028

1.4990 – 1.5050/1.5021

1.5000 – 1.5050/1.5026

5.5 – 6.5/6

5 – 7.5/6

5.5 – 6/6

Carbon residue, %

0.82 – 1.1/0.93

0.72 – 1.1/0.93

0.8 – 1.1/0.95

Density at 20°C, kg/m3

914 – 923/920

908 – 922/917

913 – 922/918

Viscosity at 100°C, mm2/sec Refractive index at 50°C Color, CST units

Note.

In the numerator: limiting values; in the denominator: average value.

* For January–October, 2003. ** For September–October, 2005. *** For November–December, 2005.

Both projects were executed in brief times due to the coordinated work of all participating organizations: Angara Petrochemical Company, IMPA Engineering, Neftekhimmash Co., and Prommet Ltd. IMPA Engineering, which specializes in improving extraction processes, won the bid for the projects. It developed the revamping projects, procured the packages for internals and mixers, and supervised installation of the equipment. The advantages of the proposed conclusion include the effective phase reaction on contact devices. This is done by increasing the active interface, varying the distribution of the contacting phases over the section of the tower, and creating a film of solid phase with a two-sided working surface due to the hydrodynamically permeable film-forming surfaces. Their assigned position forms a periodic phase collection and redistribution system. A number of factors that reduce “coking” of he packing is also characteristic of the IMPA contact devices: optimum stream hydrodynamics and nonmagnetic packing material – stainless steel. Stainless steel is used because high-melting asphaltite, which has polar properties, forms “coking” foci that subsequently enlarge on ordinary carbon steel. The trays are also designed for simple and fast assembly/disassembly. The feedstock preparation unit, where the vacuum resid is mixed with propane in its special mixer, allows: • developing the phase contact surface before the feedstock enters the tower; 19

Table 4

Content, % Components

Extraction coefficient

in deasphalted product

in vacuum resid

DA-1

DA-2

DA-1

DA-2

Hydrocarbons paraffins and naphthenes

9.4

27.5

23.8

2.93

2.54

aromatics

59.1

68

70.8

1.15

1.2

Resins

22.9

4.5

5.3

0.19

0.23

Asphaltenes

8.6

Abs.

Abs.

0

0

Notations.

DA-1, DA-2 – deasphalted products from first (with contact devices) and second (with baffle trays) blocks.

Table 5

Indexes

Project 1

Project 2

Discount rate, %

10

10

Payback period, months

9.5

7

Discounted payback period, months

10.5

8

Accounting rate of return, %

231

313

1,391,058

2,017,370

Investment profitability index

7.7

10.2

Internal profit rate, %

130

160

Net present value, US$

NPV, million US dollars

2.25 1.75 2 1.25 1 0.75 0.25 −0.25

2004 2006

2008

2010 Year

2012

2014 2016

Fig. 2. Change in net present value NPV by years after revamping of 36/2M unit: 1) according to project 1; 2) according to project 2. • bringing the feedstock and solvent entering the unit to a state of phase equilibrium and obtaining up to one additional theoretical contact stage as a result; • significantly improving phase distribution over the tower section and enhancing heat and mass exchange in the extractor due to the decrease in the viscosity of the vacuum resid previously saturated with the solvent. This technical solution allowed significantly improving the operating indexes of the 36/2M unit. The results of monitoring operation of the two extraction blocks after revamping the first block are reported in Table 1. The average monthly takeoff of deasphalted product in the first unit was 3-8% higher and the average annual takeoff was 3.8-4.8% higher with stable product quality (Tables 2 and 3). The increase in the efficiency of the first

20

extraction unit allowed obtaining deasphalted product of better group composition (Table 4). After revamping the second extraction block in October, 2005, takeoff of deasphalted product in the unit increased by 4% and more. According to estimations of the economic efficiency of revamping the extraction blocks in the 36/2M unit, the net present value of the investment projects is US$3.4 million for a discounted payback time of less than one year (Table 5, Fig. 2). The calculated investment period (duration of designing, delivery of equipment, construction, and startup) is 12 months, and the period for calculation of the efficiency was set at 10 years. The average sector values of the cost of the base oil and profitability of production were used in the calculation. Mandatory payments and taxes were calculated in accordance with active legislation. The results of revamping demonstrate the possibilities of increasing the profitability of production of deasphalted product s feedstock for manufacture of high-quality base oils or catalytic cracking feedstock and the possibilities for reducing power consumption in existing units. REFERENCES 1. K. G. Ziganshin, A. A. Osintsev, G. K. Zaganshin, et al., in: Catalog of Proceedings of the III I n t e r n a t i o n a l C o n f e re n c e “ E x t r a c t i o n o f O rg a n i c C o m p o u n d s ” – E O S - 2 0 0 5 , Vo ro n e z h , October 17-21, 2005 [in Russian], Izd. VITA, Voronezh (2005). 2. 3.

RF Patent No. 1281586. G. K. Ziganshin,. Doctoral Dissertation, Ufa State Petroleum Engineering University, Ufa (1999).

21

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

PULSED-MIXING CRYSTALLIZERS IN DEWAXING UNITS. BASIC RESULTS OF INTRODUCTION

A. N. Polyakov, A. V. Tarasov, N. I. Suzdal’tsev, and S. P. Yakovlev

UDC 665.772

The results of introducing pulsed-mixing crystallizers in dewaxing units at Novokuibyshevsk Lube Oil and Additives Plant Ltd. are analyzed. Introduction of these units significantly increased the technical and economic effectiveness of production of base oils and solid waxes. A pulsed-mixing crystallizer (PMC) on the 39/4 dewaxing unit was started up at Novokuibyshevsk Lube Oil and Additives Plant in January, 2006. The feedstock treated was raffinates of 340-430 and 370-500°C vacuum distillates and residual. The basic physicochemical properties of the feedstock are reported in Table 1. The manufacturing flow chart after inclusion of the PMC is shown in Fig. 1. In processing the residual feedstock, the unit operates in a two-stage dewaxing mode and in a three-stage mode in processing distillate feedstock. Feedstock I enters pulsed-mixing crystallizer 2 and is mixed under the pulsing effect of a compressed inert gas (created by pulser I) with wet solvent II fed into the lower collector of the crystallizer, cooled in block 9 for utilization of the cold of filtrate III from the first stage. Dry solvent IV, fed for dilution and washing of sediments in the filtration section, is cooled in the same block with the filtrate from the first stage. Table 1

Raffinate Indexes Density at 20°C, kg/m3 Melting point, °C Cut points, °C Refractive index 2

Viscosity at 100 °C, mm /sec

vacuum distillate

residual

340 – 430°С

370 – 500°С

845 – 850

863 – 874

880 – 884

27 – 30

40 – 42

49 – 52

330 – 440

370 – 520

360 – 540

1.4689 – 1.4695

1.4710 – 1.4740

1.4790 – 1.4840

4 – 4.6

6.63 – 8.2

15.91 – 16.91

____________________________________________________________________________________________________ Novokuibyshevsk Lube Oil and Additives Plant Ltd. VOKSTEK Ltd. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 17 – 19, January – February, 2007. 22

0009-3092/07/4301–0022 © 2007 Springer Science+Business Media, Inc.

VIII

2*

IV

1* VII

6

3*

7

8 IX

5 4* V III II

9 II IV

IV I

VI

III

Fig. 1. Diagram of including a pulsed-mixing crystallizer in 39/4 and 39/8 units: 1) pulser; 2) pulsed crystallizer; 3) tank; 4) pump; 5) evaporative crystallizers; 6, 7, 8) filters for first, second, and third stages; 9) block for utilization of cold from firststage filtration; I) feedstock; II) wet solvent; III) first-stage filtrate; IV) dry solvent; V, VI, VII) second- and third-stage filtrates and mixture of both; VIII) suspension from pulsed-mixing crystallizer; IX) wax residue; the new equipment is indicated by the asterisk.

In processing distillate feedstock, a coolant – mixture VII of filtrates V and VI from the second and third stages – is fed into the upper collector of the PMC. Filtrate V from the second stage is fed into the same collector in processing residual raffinate. Suspension VIII obtained in the PMC enters tank 3 by gravity feed and is pumped by pump 4 to ammonia scraper crystallizers 5. Wax residue (petrolatum) IX enters the solvent regeneration block after three (two) filtration stages. It is not necessary to dry the wet solvent to obtain one of the coolants with the required low-temperature potential in the unit operating in the dewaxing mode. This is because the temperature of the second-stage filtrate or mixture of second- and third-stage filtrates used as one of the coolants allows obtaining a suspension at the PMC outlet with a temperature of 2-5°C. This temperature totally satisfies the assigned conditions and corresponds to the temperatures of suspensions obtained in regenerative crystallizers. The basic results of a fixed run of the unit from January 1 to February 14, 2006, when raffinate of the 370-500°C cut was primarily processed, are reported in Table 2. After introduction of the pulsed-mixing crystallizer, the oil content in the slack wax decreased from 16-18 to 2-5 wt. % with a 4-5 wt. % increase in takeoff of dewaxed oil. One pulsed-mixing crystallizer in the unit replaced six previously used regenerative scraper crystallizers, which eliminated the operating costs of maintaining and servicing them. Only ammonia scraper crystallizers, where the suspension entering from the PMC is cooled to the filtration temperature, operate in the crystallization mode. Some regenerative crystallizers with detached scraper shaft drives are used as heat exchangers for cooling the wet solvent with the first-stage filtrate. Introduction of the pulsed-mixing crystallizer in production of wax suspensions thus demonstrated the high efficiency of this apparatus and confirmed the previously obtained results in [1-4]. However, the operating life of the 39/4 unit with the PMC is still insufficient for fully assessing the technical and economic effect of introducing the new equipment. 23

Table 2

Indexes

Dewaxed oil

Wax (slack wax) from deoiling stage

With pulsed-mixing crystallizer Solid point, °C

max -15

–

Oil content, wt. %

–

2–5

Melting point, °C

–

58 – 59

81 – 82

–

Yield of dewaxed oil, wt. %

With regenerative scraper crystallizers Solid point, °C

max -15

–

Oil content, wt. %

–

16 – 18

Melting point, °C

–

54 – 56

77 – 78

–

Yield of dewaxed oil, wt. % Table 3

Indexes

39/8 Unit before installation of after installation of PMC PMC

Yield of dewaxed oil, (wt. %) in vacuum distillate raffinate II III

77 – 78

83 – 84

74 – 75

82 – 83

Oil content (wt. %) in slack wax (wax) from vacuum distillate raffinate II III

12 – 14

under 2.3

16 – 19

under 5

This estimation was performed with the results of operating the 39/8 unit in 2004-2005, where the PMC was installed in November, 2004. The unit operates in three dewaxing stages – the second- and third-stage filtrates are fed for dilution of the feedstock suspension after mixing before the first filtration stage (see Fig. 1). Some time was necessary for selecting the optimum operating conditions for the PMC, crystallization, and filtration sections, since stable feedstock quality was not ensured [4]: raffinates of distillates from AVT-9 and AVT-11 units (lube oil and fuel) entered almost haphazardly. As a result, it was possible to stably process slack wax with an oil content of less than 5 wt. % – an analog of brand Ns wax – from vacuum distillate raffinate II and slack wax with an oil content of less than 10 wt. % from vacuum distillate raffinate III [4]. After debugging the operating conditions for the PMC and filtration section on the 39/8 unit, delivery of vacuum distillate raffinates II and III of stable quality was organized. As a result, it was possible to go from processing wax with an oil content of less than 2.3 wt. % (brand T2 wax base) and slack wax with an oil content of less than 5 wt. % (analog of brand Ns wax). Takeoff of dewaxed oil increased by 6 wt. %. The basic indexes of operation of the 39/8 unit before and after installation of the PMC are reported in Table 3. The economic effect of introduction of the pulsed-mixing crystallizer in the 39/8 unit was calculated from the condition of increasing processing of dewaxed lube oils and increasing the quality of the waxes and slack waxes obtained. The cost of implementing the project, including the costs for manufacture and delivery of the basic and additional equipment (crystallizer with pulser, tank, working and reserve pumps), and the costs for 24

assembling the pulsed-mixing crystallizer block (with consideration of the cost of the materials, cut-off and regulating equipment, control and measuring instruments) were 16,240,600 rubles. The following data were additionally used for the technical and economic calculations: 6 detached scraper shaft drives in regenerative crystallizers; 7 kW scraper shaft drive power, 132 kW for additionally included N-101 (N-101A) pump; electric power cost of 1.05 ruble/kwh; annual costs for servicing one regenerative crystallizer: for overhaul, 40,000 rubles; for one scraper shaft assembly, 510,000 rubles. The results of the technical and economic calculations are reported below:* Lifetime of project, years Tax, %

10

on profit on assets

24 2.2

VAT Discount rate, %

18 10

Cost of project, thousands of rubles with VAT

16,240.6

without VAT Reduction in operating expenses, thousands of rubles with VAT without VAT

13,763 2283.2 1935.2

Increase in commercial products, thousands of rubles with VAT

52,594.7

without VAT Increase in profits, thousands of rubles

44,572 56,506.9

Depreciation deductions for year, thousands of rubles Net present value (NPV), thousands of rubles

1376 205,952.4

Payback time, months 4 After adjusting the operating conditions of the 39/8 unit with a pulsed-mixing crystallizer and organization of delivery of feedstock of the required quality, the increase in profits from introducing the PCM in comparison to the basic version (use of regenerative crystallizers) was 46,506,900 rubles a year for a payback time of all outlays of no more than 4 months. The pulsed-mixing crystallizer was not washed even once for a year. No significant pressure differences were observed in the lower part of the PCM and the temperature profile in the apparatus, which indicates the absence of wax deposits in the sections of the crystallizer. The crystallizer, pulser, and coolant production and feed system exhibited the required reliability in operation. Due to the hermetic sealing of the pulsed-mixing crystallizer (absence of sealing of scraper mechanism shafts), losses of selective solvents decreases and the environmental safety of production increases. The operating expenses for repairs and servicing the regenerative scraper crystallizers are eliminated. REFERENCES 1.

S. P. Yakovlev, E. D. Radchenko, N. N. Khvostenko, et al., Nauka Tekhnol. Uglevodorodov, No. 2, 4145 (1999).

*These indexes can be corrected in consideration of the volume and cost of research and design-construction work determined in each concrete case. 25

2. 3.

S. P. Yakovlev, E. D. Radchenko, V. F. Blokhina, et al., Khim. Tekhnol. Topl. Masel, No. 4, 12-15 (2000). S. P. Yakovlev, E. D. Radchenko, V. F. Blokhinov, et al., Ibid., No. 2, 16-17 (2002).

4.

S. P. Yakovlev, Ibid., No. 4, 12-15 (2005).

26

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

EQUIPMENT

MODERN COMPRESSOR EQUIPMENT S. L. Utyushev, Yu. N. Bobrov, V. V. Yashin, and V. N. Kosogorov

UDC 665.63.048:665.531

Penzkompressormash Co. is one of the leading domestic and compressor-building companies. With more than half a century of history behind it, it has supplied approximately 23,000 air and gas compressors to different sectors of industry in Russia and abroad. These are basically piston compressors on a 5G horizontal base and M10 opposite base with output of 14-220 m 3 /min and final pressure of 0.22-40 MPa. In addition, 4400 special compressors have been manufactured for the petrochemical, metallurgical, and air and space industries. The equipment is distinguished by good quality and high reliability. Many compressors (5G-100/8, 5G-600/42-60, 5G-125/13-60, VN120) made more than 40 years ago continue to be used in oil refineries and other plants. At present, Penzkompressormash Co. is manufacturing piston compressors on a M10 base, both general purpose and special purpose, equipped with a microprocessor automation system without lubrication of cylinders and gaskets. Special compressors on this base for compression of hydrogen-containing gases are being s u c c e s s f u l l y u s e d i n f u e l h y d r o t r e a t i n g u n i t s a t o i l r e f i n e r i e s i n P e r m ’ , U k h t a , Ya r o s l a v l ’ , a n d Komsomol’sk-na-Amure. Manufacture of MKZ-50U1 monoblock modules of the container type for compressor filling stations where vehicles are filled with natural gas as motor fuel has been mastered. The demand for improved modules of types MKZSA-50, MKZSA-100U1, MKZSA-100/20-250, and MKZSA-100/6-250 with automated filling control is increasing. They are supplied with a heated operator module. In 1992, due to a decrease in the demand for piston compressors, Penzkompressormash Co. began to master mass production of screw air compressors (such compressors were previously manufactured in small quantities and without noise-insulating housing). A decision was immediately made to create compressor units with competitive advantages different from those manufactured by Kazan’ Compressor and Chita Machine-Building Plants. Screw compressors began to be supplied in the monoblock version in noise-insulating housing for the first time in Russia. All of the mechanisms and units, including the oil trap, gas and oil cooler, and automation ____________________________________________________________________________________________________ Penkyhkompressormash OJSC. Prommashinvest TIC. Ob’edinenie “Kompressor” Ltd. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 20 – 21, January – February, 2007. 0009-3092/07/4301–0027 © 2007 Springer Science+Business Media, Inc.

27

system, which provides continuous regulation of output from 100 to 10% as a function of the demand for compressed air. The assortment began to expand with the increase in the demand for these compressors. In addition to water-cooled units, air-cooled compressors, most in demand by the market, were rapidly mastered. The assortment of air screw compressor units now includes 24 types and modifications with output of 4 to 40 m 3 /min. The company takes a rigorous approach to ensuring the quality of the screw compressor units. A laboratory with test benches was created in a short time. Each compressor manufactured is tested under the working load and all technical characteristics are checked. The company certified the compressors manufactured at the NASTKhOL Certification Center (Moscow) and certified the testing laboratory. By constantly keeping up with recent advances in compressor construction and considering the comments and wishes of user sites, designers, and process engineers, the companies are continuously improving their products. All design changes are usually only undertaken after tests on plant benches and in critical cases, on compressors from the plant’s compressor facilities. Penzkompressormash Co. was the first Russian compressor manufacturer to be certified in the Russian marine navigation register by activating a quality system at the plant for satisfying international standards ISO 9001:1994 and then also ISO 9001:2000. The plant management conducted a reorganization directed toward optimizing the production areas and plant management structure. Large investments were simultaneously made to acquire advanced imported equipment. Plant specialists and management were trained in England. Great attention is being focused on borrowing the leading advances in foreign screw compressor construction. Several units of the latest constituents of screw compressor units, software for shaping the rotors, and thermodynamic and geometric modeling of screw compressors have been acquired. Combined with the English gear-milling machines and Holroyd precision milling cutter sharpening machines, this allowed designing and manufacturing the most up-to-date compressor stages for screw compressor units with output of 1 to 100 m 3/min. One such base stage which has no analogs in Russian compressor building has been designed, manufactured, and is undergoing factory tests. A great deal of work was done in 2004-2005 to increase the reliability and technical level of mass-produced compressor units with output of 6, 20, 30, and 40 m 3 /min. Water-cooled screw compressors 1VV-20/9 and air-cooled compressor 1VV-20/9M1 were improved significantly, so that their technical level and reliability were much higher. In 2005, air-cooled 1VV-30/9 and air-cooled 1VV-30/9M1 compressors were updated. A modification of the 1VV-30/9M1PCh air screw unit was created with a frequency converter and the most economical method of regulating output: by changing the rotor rotation rate of the electric motor in the range from 100 to 30% and maintaining the pressure established with accuracy of 0.02 MPa. These compressors correspond to the foreign analogs on the technical level. They are equipped with updated compressor stages with N progressive profile rotors, and an automation system based on a microprocessor controller is used in them and provides for network connections with a complex compressor station automation and control system based on a RS-485 interface. The experience gained in creating screw compressor units, the modern production capacities, and the competent personnel allowed the plant to set a new strategic goal in 2005 – to become the basic supplier of reliable and efficient screw compressor aggregates for Russian Railways Co. (RR) traction-traveling brake systems. A series of experimental samples of such aggregates was designed, manufactured and tested in the same year. In the course of prolonged experimental design work and testing, compact compressor stages and many original units

28

were carefully worked out. In 2006, the plant began mass production of such compressor aggregates with output of 2-4.5 m 3/min and delivered them to Transmashholding locomotive construction companies. Production of general-purpose industrial screw compressor units with output of 2 to 9 m 3 /min, including the most up-to-date unit using an aggregate compact compressor module which has no analog in domestic compressor construction, was parallelly mastered based on these compressor aggregates. Having mastered new kinds of compressor and associated equipment and satisfactorily reorganized in complicated market conditions, Penzkompressormash Co. will continue to be one of the most reliable partners for many Russian users by filling their orders in the optimum times and with the proper quality.

29

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

CHEMMOTOLOGY

CRITERIA FOR LIMITING CONTAMINATION OF MOTOR OIL BY FUEL Yu. A. Gur’yanov

UDC 621.836:681.518.54(04)

The change in the service properties of modern motor oils in contamination by fuel was examined. It was experimentally shown that mineral and synthetic oils can totally lose their working capacity when contaminated by fuel. The dependences of the properties of oils on the mechanical and thermal loads in the friction unit and the degree of contamination of the oil by the fuel were obtained. The limiting and damaging concentrations of fuel in oils of different quality were substantiated. Recommendations were made for determining the limiting concentrations. Increasing the efficiency of internal combustion engines (ICE) is associated with stiffening of the operating conditions of their assemblies and units. Increasingly severe requirements are being imposed on lube oil for this reason. A valuable and irreplaceable constructive element in the current stage of development of technology, lube oil, together with other ICE elements, ensure their breakdown-free and long-term operation. Tribologists say that any difference in the brand or quality of the lube oil will ineluctably be reflected in the reliability of the machine, especially in its most complicated and highly loaded aggregate – the ICE [1]. An efficient lube oil ensures standard friction conditions in the joints of parts and rational use of the lifetime of the unit. Lube oil which partially or totally loses its working capacity becomes the cause of high wear of the friction surfaces of parts and this causes premature failure of the engine. We know that lube oil can lose working capacity for a short time due to malfunctions of such ICE systems as the cooling, air cleaning, oil, and fuel supply systems. Observation of the real state of motor oils in ICE [2] suggests that contamination by fuel is the most probable cause of loss of working capacity by the oil. In winter, lube oil is contaminated with fuel in an amount higher than the acceptable amount in 90% of gasoline ICE on average. Contamination of motor oil by fuel (diesel or gasoline) worsens its basic performance properties: neutralizing (antioxidant and anticorrosion) and viscosity. ____________________________________________________________________________________________________ Chelyabinsk State Agroengineering University. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 22 – 26, January – February, 2007. 30

0009-3092/07/4301–0030 © 2007 Springer Science+Business Media, Inc.

P 1

Rb

N

N

2

3

dr

Fig. 1. Diagram of friction of parts of the “ball

b

– ring” type: 1) ball; 2) ring sample;

3) antifriction layer; P – load on friction unit given by the machine’s weighting system; b – working width of ring edge; R b – ball radius; d r – average ring edge diameter; N

– normal force acting in friction zone.

The neutralizing properties of lube oil contaminated with fuel are worsened by heavy fuel cuts. It has been experimentally shown that cuts that distill at temperatures above 340°C are the most harmful [3]. Under the effect of the operating temperature of ICE, light cuts evaporate, and heavy cuts accumulate in the lube oil. As a result of worsening of the antioxidant and anticorrosion properties, the intensity of formation of oilsoluble products increases by 1.5 times and by 2 times for insoluble products, and the induction period of formation of sludge also decreases by 2 times [3]. These changes in the quality of the lube oil cause more intensive aging of the oil, reduced oil filter lifetimes, increased contamination of parts with varnish and carbon deposits, and coking of piston rings. The decrease in the viscosity of oil contaminated with fuel makes the friction conditions much more severe and causes a corresponding increase in the intensity of wear of working surfaces [4]. When the viscosity of the oil decreases by one class, the wear intensity increases by 2-3 times. However, this was established in studies of the previous generation of lube oils. We evaluated the effect of fuel on the lubricating properties of modern motor oils and substantiated the limiting values of fuel contamination of lube oils of different quality. The effect of fuel on the service properties of modern motor oils was investigated with a MAST-1 machine for assessing antifriction properties. LUKOIL motor oils were tested: Standart mineral (SAE 10W-40, API SF/CC), semisynthetic Super and Lyuks (SAE 5W-40, API SJ/CF), synthetic Sintetik (SAE 5W-40, API SL/CJ). Each oil was contaminated with winter diesel fuel in concentrations of 1, 3, 5, and 7 vol. % before testing. The ring sample (Fig. 1) was made from the bearing liner of an ICE crankshaft with an aluminum antifriction layer. A ball 12 mm in diameter from a standard bearing with surface hardness of the same order as the hardness of the crankshaft neck was used as the top sample. The friction moments of clean and contaminated oil samples were determined at oil temperatures of 24 to 120°C and mechanical loads from 50 to 184 N, which corresponds to the conditions of operation of ICE sliding bearings. • Results of Assessing the Antifriction Properties of Clean Lube Oils The lube oils were comparatively evaluated with the friction coefficient and friction moment at an oil temperature of 80°C. The friction coefficient for Sintetik synthetic oil was much lower than for Standart mineral 31

0.4 34

a

0.35 2 0.3 1 0.25 0.2 260 b 220 1

180 140

4 3

2

100 60 40

70

100

130

160 190

Fig. 2. Friction coefficient f (a) and moment M (b) vs. mechanical load P at 80°C in the volume of fresh all-season motor oil: 1) Sintetik; 2) Lyuks; 3) Standart; 4) Super. and Lyuks and Super semisynthetic oils, by 0.05-0.07 on average (Fig. 2a). The mineral and semisynthetic Super oils gave approximately the same friction coefficient, while the Lyuks oil was in the middle. A decrease (by – 0.02) in the friction coefficient with an increase in the load was observed for all of the oils. The curves of the friction moment dependences are positioned in the same order (Fig. 2b) as the curves for the friction coefficient. Let us consider the dependences of the friction moment on the load at different bulk oil temperatures. For the uncontaminated synthetic oil, the friction moment is almost independent of the temperature in the oil gap (Fig. 3a). This indicates that the given lube oil ensures stable lubrication and thus friction conditions. No breaks were observed in the oil film in the mechanical load and temperatures ranges examined, except at the maximum mechanical load of 184 N and low temperatures, 26 and 60°C. The carrying capacity of an uncontaminated mineral oil film (Fig. 3b) was much lower than for the synthetic oil. At oil temperatures from 60 to 120°C, the maximum load at which the integrity of the oil film was preserved did not exceed 90 N. At 120°C, the oil lost the ability to ensure standard friction of the working surfaces. This caused passage into a friction regime over the modified layers, indicated by the horizontal segment on the curve in the 90110 N load range. % Results of Evaluating the Antifriction Properties of Lube Oils Contaminated with Fuel When synthetic oil was contaminated with 1% diesel fuel, the minimum carrying capacity of the oil film was 150 N at 60°C and the maximum carrying capacity was 184 N at 100 and 120°C (Fig. 4a). As a result of contamination of the oil with this amount of fuel, the carrying capacity of the oil film decreased by 20 N (11%) at 60°C and by 14 N (8%) at 80°C. The oil retained temperature invariance in the entire range of mechanical loads. The initial and final values of the friction moment did not change. 32

In contamination of the synthetic oil with 3% fuel, the dependences of the friction moment at 26 and 120°C and 90 N mechanical load and higher changed significantly (Fig. 4b). The appearance on the curve of segments with a smaller slope in the 90-110 N load range indicates the inability of oil in such a diluted state to ensure friction of working surfaces by adsorption layers. This causes an adhesive reaction of the friction surfaces. The antiscuff additive is activated as a result and ensures operation of the friction unit by modified layers and thus decreases the friction coefficient. The carrying capacity of the film at 80 and 100°C for this oil, in comparison to the oil contaminated with 1% fuel, decreased from 170 to 150 N (by 18%) and from 184 to 170 N at 120°C (by 11%). This reduction was due to the extremely important decrease in the film thickness caused by dilution of the oil by the fuel and as a result, onset of the initial stage of adhesive reaction of the friction surfaces. The temperature in the contact zone is insufficient to trigger activity of the antiscuff additive. The signs of deterioration of the synthetic oil contaminated with 7% fuel were pronounced (Fig. 4c): at low temperatures (60 and 80°C), the friction moment increased by 20 N×m, attaining the maximum value of 260 N×m characteristic of overheated lube oils. At higher temperatures, friction took place over the modified layers beginning with almost the minimum load, 50 N. The chemical modification mode was activated, confirmed by the decrease in the friction moment by approximately 20 N×m in the region of high mechanical loads at 120°C. In comparison to the oil contaminated with 3% fuel, the carrying capacity of the film of this oil did not change, which was also due to an increase in the antiscuff additive’s activity in such severe friction conditions.

260 a 220 180 140 100 60 260 b 220 180 140 100 60 40

70

100

130

160 190

Fig. 3. Friction moment M vs. mechanical load P at different temperatures in the bulk of Sintetik synthetic (a) and Standart mineral oils (b): – 26°C; – 60°C ; Δ – 100°C; × – 120°C.

c

– 80°C;

33

At an oil temperature of 26°C and consequently low antiscuff activity, the carrying capacity of the film decreased from 170 to 150 N. In contamination with 1% fuel, the lubricating properties of the mineral oil worsened significantly (Fig. 4d). In comparison to clean oil (Fig. 3b), the maximum increase in the friction moment was 30 N×m at 60 and 80°C and 20 N×m at 26°C. Chemical modification of the oil strengthened significantly at 120°C, confirmed by the increase in the carrying capacity of the modified layers to 150 N at a relatively low friction moment, 235 N×m.

260

a 220

180

140

100 60 260

b 220

180

140

100 60 260

220

180

140

100 60 40

70

100

130

160

190 40

70

100

130

160

190

Fig. 4. Friction moment M vs. load P at different levels of contamination with diesel fuel and temperatures of synthetic Sintetik (a-c) and mineral Standart (d-f) oils; a, d – 1%; b, e – 3%, c, f – 7%; – 26°C; – 60°C ; c – 80°C; Δ – 100°C; × – 120°C 34

In addition, the lube oil lost its ability to provide for friction over adsorption layers at 100°C. For this reason, passage to a friction regime over modified layers began at mechanical loads of 90-110 N. Contamination of mineral oil with 3% fuel (Fig. 4e) sharply worsened its lubricating properties. The appearance of segments on the curves with a smaller slope in the 90-110 N load range at temperatures of 80 to 120°C indicates activation of the antiscuff additive. In comparison to clean oil (see Fig. 3b), the maximum increase in the friction moment at 60, 80, and 100°C was approximately 30 N×m (14%) and at 26°C, 20 N×m (10%). This indicates a transitional state where standard friction conditions are lost and the antiscuff additive’s activity is still inadequate. At 100 and 120°C, chemical modification of the lube oil is significantly activated: the carrying capacity of the modified layers increased to 150 and 170 N for a friction moment equal to 265 N×m. The initial friction moment at 50 N and high temperatures in comparison to clean lube oil (Fig. 3b) decreased to 100 N×m, which indicates the effect of the antiscuff additive and loss of the ability to ensure standard friction conditions by the oil. In contamination of the mineral oil by 7% fuel, its basic service properties that ensure minimum wear of working surfaces and friction by adsorption layers were totally lost (Fig. 4f). As a result, the character of the dependences of the friction moment on the load and temperature of the lube oil changed to linear and the inflection of the curves (see Fig. 3b and 4e) with the 90 N load disappeared. This is due to attaining hazardous dilution of the oil by the fuel. Regardless of the mechanical load and the temperature, with this dilution the oil cannot ensure friction of the working surfaces in standard conditions in physical adsorption of surfactant molecules. In this case, friction is only ensured by chemical reaction of the antiscuff additive with the working surfaces of the friction unit. As indicated in [1, 5], the friction coefficient is almost the same in relative movement of working surfaces over adsorption and modified layers. However, the intensity of wear in the last case is two to three orders of magnitude higher than in friction over adsorption layers, i.e., than in standard functioning of friction units. As a consequence, the level of fuel contamination of the oil that causes transition of friction from the standard conditions to friction over modified layers to begin is the criterion of the limiting state of motor oil with respect to fuel contamination. In view of the above, we note: standard lubricating conditions are characteristic of uncontaminated synthetic oil (see Fig. 3a) at all mechanical and heat loads; for oil contaminated with 1% fuel (see Fig. 4a), standard lubricating conditions are also realized at all mechanical and heat loads; an exception is the regime at 120°C and a mechanical load in the range of 110-184 N, where a clear decrease in the friction moment is observed relative to other conditions, which indicates activation of the antiscuff additive; at this contamination, the oil can be considered totally efficient if its temperature in bulk is no higher than 100°C. In synthetic oil contaminated with 3% fuel (see Fig. 4b), the antiscuff additive starts working at a mechanical load of 90 N and higher and temperatures of 26 and 120°C, which indicates loss of a significant part of the service properties by the oil. As a consequence, contamination of synthetic oil with 3% winter diesel fuel can be considered limiting. Standard lubrication conditions are characteristic of uncontaminated mineral oil (see Fig. 3b) at all mechanical and heat loads. However, at an oil temperature of 120°C and mechanical load of 90 N and higher, there is a clear transition from standard friction conditions to friction conditions over modified layers. As a consequence, when this oil is sued to ensure standard lubricating conditions, its temperature should not exceed 100°C. The presence of 1% fuel in the mineral oil caused the friction moment to increase by 15% at temperatures of 60 and 80°C, which indicates breakdown of adsorption layers, and at 100 and 120°C, manifest activation of the

35

antiscuff additive. As a consequence, contamination of the mineral oil with 1% winter diesel fuel can be considered limiting. In the case of mineral oil contaminated with 3% fuel, the standard lubrication conditions are lost and a modified-layer friction regime is realized at a mechanical load of 90 N and higher and temperature in the 80-120°C range (see Fig. 4e). This finding indicates degradation of the service properties of the oil at this level of contamination, which causes wear of friction units two to three orders of magnitude higher in further operation of the ICE in comparison to wear in the standard regime, and inefficient use of engine life as a result. The mineral oil contaminated with 7% fuel on the contrary, like the synthetic oil but to a lesser degree, reaches a hazardous state where all of its service properties (except for one) are lost and only the transport function is fulfilled “ delivery of the antiscuff additive to the zone of actual contact of the friction surfaces. In this period, the maximum consumption of this additive is attained, since the standard friction coefficient is ensured by maximum activity of the corrosion-mechanical process. This explains the overlap of the two curves in Fig. 4f. As soon as the additive reserve begins to be depleted, breakdown inevitably takes place, despite the fact that the external conditions of ICE operation do not differ from the standard conditions. Gasoline has approximately the same negative effect on the properties of motor oil, but its diluting power is one order of magnitude higher than the power of winter diesel fuel. Fuel in motor oil can thus cause total loss of its service properties and as a result, very rapid depletion of the service life of the ICE. According to our observations, the real operating time of ICE between overhauls is usually 15-100,000 km. To ensure rational use of the service life in designing and manufacturing ICE, it is useful to not allow a concentration of diesel fuel greater than 2-3% in synthetic oil and greater than 1% in mineral oil. Such fuel quantities cannot be detected in working lube oil by organoleptic methods. For this reason, instrumental methods are used to monitor oil quality. In production conditions, portable instruments based on fast methods of assessing the quality of fresh and working oils are preferred. Instruments that do not use glass instruments and vessels and chemical reagents are most convenient. One such instrument is the portable machine diagnostics kit based on the parameters of working oils – KDMP-3 – which allows assessing the quality of working oil with ten and fresh oil with seven basic service properties in field and stationary conditions [6, 7]. REFERENCES 1. A. V. Chichinadze (ed.), Friction, Wear, and Lubrication (Tribology and Triboengineering) [in Russian], 2.

Mashinostroenie, Moscow (2003). N. I. Skinder and Yu. a. Gur’yanov, Khim. Tekhnol. Topl. Masel, No. 5, 28-30 (2003).

3. 4.

V. B. Polyakova, Ibid., No. 3, 31-32 (1990). V. I. Vorozhikhina, L. S. Ryaznov, E. P. Vol’skii, et al., Ibid., No. 2, 42-44 (1985).

5.

R. Baltenas, S. A. Safonov, A. I. Ushakov, et al., Motor Oils [in Russian], Al’fa-Lab, Moscow”St. Petersburg (2000).

6. 7.

N. I. Skinder and Yu. A. Gur’yanov, Khim. Tekhnol. Topl. Masel, No. 1, 38-40 (2001). P. I. Tarasov and Yu. A. Gur’yanov, Gorn. Promyshl., No. 1, 57-61 (2005).

36

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

SEMILIQUID GREASES FOR REDUCING GEARS FOR GENERAL MACHINE-BUILDING PURPOSES

A. A. Sirotenko, L. V. Pakina, and L. A. Savel’eva

UDC 621.892.261

Plastic greases with a penetration index at 25°C above 380 according to GOST 5346–78, ultimate strength according to GOST 7143–73 of less than 100 Pa, and whose viscosity in a wide temperature range is a function of the strain rate gradient, are usually semiliquid. Because of these properties, these greases can be used together with gear-case oils in the gears in gear boxes for general machine building. However, in comparison to gear-case oils, semiliquid plastic greases require more power for moving the gear at temperatures above 20°C, eliminate heat from the gear transmission worse, and restrict the speed of a transmission wheel of larger diameter – maximum of 3 m/sec. When the grease is replaced by fresh grease, it is usually necessary to disassemble the reducing gear. However, the presence of a soap thickener in the structure of the semiliquid grease broadens the temperature range of operation of the reducing gear and makes it possible to start up at 10-30°C below the solid point of the oil that acts as the dispersion medium for the grease. The use of semiliquid greases in industrial reducing gears is most frequently due to the desire to reduce consumption of lubricant irreversibly lost through shaft collars, labyrinth seals, and slots in the reducing gear body assembly. In the USSR, the assortment of semiliquid greases was very limited. Transol-100, Transol-200, and TsIATIM-208 greases were basically used in industrial reducing gears. Transol-100 grease, developed for screw reducing gears at the end of the 1970s at MASMA SIA [1], was manufactured at Berdyansk Experimental Petroleum and Oil Refinery according to TU 38.USSSR 201352–84 and was widely used in different climatic zones in the country. This grease ensured prolonged operation of worm reducing gears with an interaxial distance of less than 100 mm at ambient temperatures from –30 to +50C. 12-Hydroxystearic acid soap and a polymer were used as the thickener and a mixture of mineral and synthetic oils was used as the dispersion medium. The synthetic oil prevented catastrophic wear of the material of the worm wheel (basically bronze Br OF10). ____________________________________________________________________________________________________ Shaumyan Plant CJSC. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp.27 – 29, January – February, 2007. 0009-3092/07/4301–0037 © 2007 Springer Science+Business Media, Inc.

37

38

Note.

Indexes added to TU 0254-015-56194358 – 2005.

Free organic acid content according to GOST 6707 – 76, % in terms of oleic acid

Saponification number according to GOST21749 – 76*, mg KOH/g

Volatility (100, 1 h) according to GOST 9566–74, %

>100 Weakly basic

<1.5

<1200

<100

at –30°C and 10 sec-1

according to GOST 7163 – 84 at –30°C and 10 sec-1

3–5

at +50°C and 10 sec-1

Effective viscosity, Pa⋅ sec according to GOST 26581 – 85*

<35

Colloidal stability according to GOST 7142 – 74, % pressed oil

Standard

>150

Indexes

Drop point according to GOST 6793 – 74, °C

Table 1

0.1

45.3

4.2

3.1 Solidified at –20°C 774.4

38.2

0.57

45.2

–

–

–

2.6

37.4

AZMOL-Transol-100 before after testing testing 188 176

0.43

145.4

1.24

774

58.5

4.1

33.4

148.8 Weakly basic

–

–

–

6.7

28.3

Transol-100-PSh before after testing testing 178 178

Semiliquid grease

Transol-100 grease is now manufactured by AZMOL Co. (Berdyansk, Ukraine) under the trade name AZMOL-Transol-100 (TU U 23.2-00152365-181–2003). It virtually does not enter the RF due not only to the fall of the USSR but also to a greater degree to halting of synthetic oil production in the territory of the former USSR. The quality of the semiliquid grease of the Transol-100 type supplied to consumers through middlemen does not always correspond to the standards for AZMOL-Transol-100 grease not only with respect to the individual standards indexes but also with respect to the temperature range of utilization of the grease given in the standards. There are data on the impossibility of running reducing gears serviced with a semiliquid grease of the Transol-100 type with no load at an ambient temperature below –20C. Reduktor NTTs Co. (St. Petersburg) turned to Shaumyan Plant Co. (St. Petersburg) to solve the problem of manufacturing their own semiliquid grease of the Transol-100 type of the required quality and in the required amount. The plant manufactures lubricating materials (motor and industrial oils, plastic greases, and LCPM) for railroads, marine and river fleets, and for motor transport and industrial enterprises. In 1997-2002, it went through three stages of bankruptcy, but retained its own capabilities and prospects. The plant is now manufacturing marine oils, including oils for modern boosted ship diesels and diesel generators, and new brands of oils: helicopter and motor for diesel engines. Shaumyan Plant Co. has been manufacturing semiliquid greases for more than 20 years: • in 1984 in collaboration with MASMA SIA, SKP-M grease (TU 0254-318-00148820–97) for medium- and high-load gear (cylindrical and conical) reduction units and engine reduction units with a crankcase lubrication system by dipping; • in 1995, LZ-PZhL-00 grease (TU 0254-312-00148820–96) for joints of equal angular velocities of the secondary shaft of the BAZ 212213 auto was developed at the request of AvtoVAZ Co.; • in 1999, in collaboration with VNIITransmash, a new grease, Redusma (TU 0254-324-00148820–99), was m a n u f a c t u r e d f o r t w o - s t a g e r e d u c i n g g e a r s i n s t a l l e d i n s e r i e s L M - 6 8 a n d LV S - 8 6 s t r e e t c a r s u s e d by Go4elektrotrans GUP (St. Petersburg) and the new streetcars manufactured by Petersburg Streetcar-Mechanical Plant. Table 2 Duration of test,* h

Note.

Temperature (°C) of grease in reducing gear

Load, %

AZMOL-Transol-100

Transol-100-PSh

5

72

68

50

8

101

102

100

10

104

103

100

15

91

103

100

20

91

98

100

25

95

92

100

30

90

96

100

35

93

84

100

40

91

86

100

45

90

86

100

50

80

86

100

55

83

82

100

56

89

86

100

*The tests were performed at an ambient temperature of 20°C by N. V. Vasil’ev

39

A number of additional testing methods were used in developing the formula and technology for manufacturing the semiliquid grease of the Transol-100 type, and they were then taken into consideration in TU 0254-015-56194358–2005 for Transol-100-PSh grease. In comparison to AZMOL-Transol-100 grease, the following indexes are additionally determined for this grease: • e f f e c t i v e v i s c o s i t y a t + 5 0 a n d – 3 0 ° C a n d s t r a i n r a t e g r a d i e n t o f 1 0 s e c -1 a c c o r d i n g to GOST 26581–85 – for controlling the structure and low-temperature properties; • saponification number according to GOST 21749–76 – for controlling the amount and quality of synthetic oil in the finished grease; • open-cup flash point according to GOST 4333–87 – for controlling the quality of the dispersion medium. These indexes were primarily incorporated in TU 0254-015-56194358–2005 for the following reasons. The Rheotest 2 rotary viscometer and its modifications produce more stable results than instruments for determining Table 3

AZMOL-Transol-200 (TU U 23.2-00152365-181–2003)

Transol-200 (TU 0254-016-05766706–98)

Transol-200-PSh (TU 0254-018-56194358–2005)

Grease

>150

169

161

168

–

420

385

410

400 – 430

425

370

415

≤1400

1629

1388

711

3–6

5.2

11,8

5

welding

>2800

3286

2325

3090

critical

>700

785

981

785

>390

500

441

491

Indexes

Standard

Drop point, °C Penetration at 25°C without stirring with stirring Effective viscosity, Pa⋅sec according to GOST 7163 – 84 (–30°C, 10 sec-1) -1

according to GOST 26581 – 85 (+50°C, 10 sec ) Lubricant properties (Four-ball friction tester, according to GOST 9490–75 load, N

scoring index, N Corrosive effect on copper M01 (100°C, 3 h)

Passed

Flash point (open cup), °C

170

174

130

178

Volatility (100°C, 1 h), %

≤0.8

0.5

1

0.75

Content free alkali free organic acids, % oleic acid Colloidal stability, %

40

≤1

Abs.

max 1.0

0.54

0.28

0.8

max 30

20.4

36.3

14.9

the penetration index for analyzing semiliquid greases at a temperature of +50°C. In our opinion, the penetration index (over 380) in the subsequent revisions of the standard for semiliquid greases should be optional or it should not be determined with a full-size cone according to GOST 1440–78 but with a micropenetrometer with a half- or one-fourth-sized cone [2]. In studying the different semiliquid greases, we repeatedly encountered samples of greases from unknown manufacturers. These greases contained some highly volatile fractions of petroleum oil components to improve the low-temperature properties. Mechanisms cannot operate in such surrogate greases in nominal loading conditions for a long time. It was possible to detect the adulterant with the saponification number of the grease and the flash point according to GOST 4333–87. However, for greases of the Transol type which contain lithium 12-hydroxystearate, melting of the soap prevents correct determination of the flash point. For this reason, the rate of heating the grease in determining the flash point in the given case should be no greater than 2°C/min. Comparative tests of Transol-100-PSh experimental semiliquid grease and AZMOL-Transol-100 commercial grease manufactured by AZMOL Co. (Berdyansk) were conducted on the bench at Reduktor NTTs Co. This bench is a screw reducing gear with an electric motor installed in a rigid frame. A system for creating the necessary load is placed on the shaft of the reducing gear. The power consumption, torque on the reducing gear shaft, and temperature of the grease in the reducing gear were monitored in the tests. The indexes for the properties of Transol-100-PSh and AZMOL-Transol-100 greases before and after testing are reported in Table 1, and the experimental data on the dependence of the temperature of the grease in the Table 4

Transol-100-PSh

Transol-200-PSh

Redusma

SKP-M

LZ-PZhL-00

Semiliquid plastic grease

Li-soap

Li-soap

Na- soap

Li-soap

Li-soap

150

150

120

140

160

400 – 430

400 – 430

380 – 430

380 – 450

400 – 440

100

250

70

3–6

3–7

welding

1780

critical

Indexes

Type of thickener Oil base

semisynthetic

Drop point, °C, min Penetration at

petroleum

Effective viscosity (GOST 26581–85, 10 sec-1), Pa⋅sec at –30°C, max at +50°C Lubricant properties (four-ball friction tester, GOST 9490–75) load, N, min

scoring index, N, min Corrosive effect on metal (100°C, 3 h)

4–8

100 (at 0°С) –

5–8

2800

1648

1740

3200

700

700

700

820

780

350

400

380

380

490

steel 20

steel 20

steel 20

–

Passed copper М01 copper М01

Flash point (open cup), °C, min

170

170

160

245

150

Colloidal stability, % pressed oil, max

35

30

35

30

35

41

reducing gear on the duration of operation of the reducing gear on the bench are reported in Table 2. The results of the tests confirmed the possibility of using Transol-100-PSh grease instead of AZMOL-Transol-100 grease in single and multistage screw reducing gears. Transol-200 grease, like Transol-100 grease, was developed at MASMA SIA [1]. It is intended for use in cylindrical and planetary reducing gears. 12-hydroxystearic acid lithium soap and a polymer are used as the thickener in it, and a mixture of mineral oils with addition of an additive package to improve the lubricant properties is used as the dispersion medium. This type of grease is supplied to the user under the brands AZMOL-Transol-200 (AZMOL Co., Berdyansk, Ukraine); Transol-200 (RIKOS Co., Rostov-on-Don), and Transol-200-PSh (Shaumyan Plant Co., St. Petersburg). The results of tests of commercial samples of these greases supplied to consumers in 2005 are reported in Table 3. In comparison to ordinary plastic greases, it is not very easy to obtain stability of their “colloidal stability” and “penetration” indexes. Not only the quality of manufacture and storage conditions of the product by the manufacturer but also, to a greater degree, the conditions of storage and delivery of the goods to the middleman, as well as the conditions of storage and use (i.e., conditions of delivery of the semiliquid grease to the reducing gear and use) by the consumer can play the main role here. The assortment and quality indexes of the semiliquid greases for reducing gears for different applications manufactured by Shaumyan Plant Co. are reported in Table 4. We would like to thank the General Director of Reduktor NTTs Co., V. I. Parubets, for collaborating in testing Transol-100-PSh grease and for providing samples of AZMOL Co. and RIKOS Co. commercial greases, and T. G. Malyshevaya for scientific and methodological assistance in developing the semiliquid grease technology. REFERENCES 1.

V. M. Shkol’nikov (ed.), Fuels, Lubricants, and Industrial Fluids. Assortment and Use. A Handbook [in Russian], 2 nd ed., Tekhinform, Moscow (1999).

2.

V. V. Sinitsyn, Plastic Greases and Evaluation of Their Quality (Foreign Standards and Specifications) [in Russian], Izd. Standartov, Moscow (1975), p. 192.

42

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

RESEARCH

EFFECT OF SHOCK-WAVE PROCESSES ON THE PHYSICOCHEMICAL PROPERTIES OF CRUDE OIL

A. F. Maksimenko

UDC 622.279.72+621.039

The effect of a shock wave on the physicochemical properties of crude oils was experimentally studied. The complicated character of this effect on complex organic compounds was demonstrated. The rheological properties and group composition of the crudes were changed by the shock wave. The interest in the behavior of substances in unusual conditions has existed over entire historical epochs. Until the beginning of the 20 th century, the temperature and active medium were the basic factors that acted on a substance. Bridgeman’s classic studies stimulated the development of research on the effect of high static pressure on different substances. In the mid-1950s, studies of the effect of dynamic loads and shock waves were published. Shock-wave loading of organic substances is complicated in nature. It is accompanied by heating of the substance and an increase in its entropy. The heating temperature progressively increases with an increase in the amplitude of the compression wave. Since unloading of the substance is isentropic, removing the pressure decreases the temperature of the substance, significantly in some cases. As a result of these factors and rearrangement of molecules in the phase transition, the properties of organic substances can be varied within wide limits. Polymerization of organic monomers on passage of shock waves was discovered* in 1964 at the Institute of Chemical Physics, Russian Academy of Sciences. This discovery launched a new area of organic chemistry – the shock-wave area. In conducting the first experiments, it was found that different reactions can take place in organic compounds on passage of a shock wave: degradation, substitution, isomerization, etc. As a result of studies of two large groups of organic compounds – aromatics and olefins, it was shown that shock-wave degradation of aromatic compounds differs from their degradation at a constant temperature. According ____________________________________________________________________________________________________ I. M. Gubkin Russian State University of Oil and Gas. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 34 – 35, January – February, 2007. 0009-3092/07/4301–0043 © 2007 Springer Science+Business Media, Inc.

43

Table 1

Structures Aromatics benzenes

Content (%) in Vasyugan crude before shock-wave after shock-wave compression compression 35.24 35.40 5.82

6.91

monocyclics

6.49

8.99

substituted polycyclics

22.93

19.50

Paraffins Naphthenes

29.27 19.22

38.95 13.37

Unsaturateds

16.27

12.28

to the data of Block and Weir,* benzene does not undergo chemical changes at static pressure of 4000 MPa and temperature of 600°C. However, in shock-wave loading, such changes take place for a pressure jump to 1100-1500 MPa on the shock wave front, and the yield of reaction products is 0.4-1%. Due to the development of effective new methods of processing hydrocarbon feedstock, the urgency of investigating the changes in the physicochemical properties after shock compression increased. The results of an IR-spectroscopic study of the group composition of different crude oils before and after shock-wave compression are reported here. The analysis of the IR absorption spectra of crude from the Yarega field showed that its group composition before and after shock compression was qualitatively identical. However, some changes were observed in the quantitative ratio of hydrocarbon structures. After shock compression, the paraffin content decreased by 2%, but the naphthene and aromatic hydrocarbon content increased by the same amount. These at first glance insignificant changes led to a 11% decrease in the kinematic viscosity of the crude at 22°C: from 2970 to 2643.3 mm 2/sec. The character of the changes in crudes from Tuimazy and Grachev fields was similar. The group composition of crude from the Vasugyan field was almost unchanged after shock compression (Table 1). The total content of aromatic structures remained unchanged, but the ratio of short and long alkyl radicals in them and their branching changed. The content of paraffin structures increased by almost 10% due to a decrease in the content of naphthenes and unsaturated hydrocarbons. The content of benzene and monocyclic substituted structures increased in aromatic structures due to a decrease in the content of polycyclics. The viscosity of the crude at 22°C decreased by 17.3%, from 153 to 126.6 mm 2/sec. The content of hydrocarbon structures in crude from the Zolotukhino field is reported in Table 2. New structural groups did not form in this crude as a result of shock-wave compression, but the ratio of existing hydrocarbon structures changed. Zolotukhino crude is aromatic with a high content of polycyclic structures which gives it relatively high viscosity. After shock compression, the content of paraffinic and naphthenic structures decreased, but the content of aromatics increased. The amount of benzene structures in the latter almost did not change, but the amount of monocyclic substituted structures increased due to a decrease in the amount of polycyclics. The kinematic viscosity of the crude at 22°C decreased by 12.5%. Crude from the Borovichi field is very inhomogeneous in consistency: the more fluid phase contains very viscous amorphous inclusions. This crude is paraffinic-aromatic. It also contains up to 16% naphthenic and approximately 7% unsaturated hydrocarbons. Its viscosity at 72°C is 336 mm 2 /sec. *A. N. Dremin and L. V. Babar, Shock-Wave Chemistry of Organic Substances [in Russian], Nauka, Moscow (1984). 44

Table 2

Structures Paraffins Naphthenes Aromatics

Content (%) in Zolotukhino crude before shock-wave after shock-wave compression compression 34.78 26.48 22.02 43.20

16.52 57.00

After shock-wave loading, the same structural groups are present in the crude. However, the sharp decrease in the absorption band characteristic of intermolecular hydrogen bonds in its IR spectrum indicates rupture of these bonds. A slight decrease in the amount of aromatic structures is observed due to an increase in the amount of paraffinic structures with reduced branching of these structures. The content of monocyclic substituted structures increased in the aromatic structures due to a decrease in the content of polycyclic structures. The component composition of the crude changed: the proportion of asphaltenes and alcohol–benzene resins increased due to a decrease in the proportion of benzene resins. As a result, the kinematic viscosity of the crude at 72°C decreased by 17%. It should be noted that in studying the changes in the component composition of gas condensate caused by shock compression, formation of a naphtha cut – up to 12 wt. % per sample, a 9-12 wt. % increase in low-boiling cuts, and a 2.5-3 wt. % decrease in heavy resids were observed. All of these changes in shock-wave loading cannot be explained by the effect of pressure and temperature alone. Macromolecular chain breaking under the effect of the mechanical energy of the shock wave is the basic event in mechanochemical degradation, and critical local overloads that exceed the strength of chemical bonds arise as a result of uneven distribution of energy in the molecular chain. The effect of pulsed loads on a substance can differ as a function of their source, and it is only effective when it corresponds to the physical properties of the substance and creates the maximum concentration of energy per unit of volume. As we know, degradation, accompanied by breaking of chemical bonds, develops under the effect of instantaneous force concentrated on small surfaces of macromolecular compounds in regions of intensive loads, together with the appearance of fluidity due to the appearance of very large stresses. These processes do not develop in the entire area of the intensive loads simultaneously, but are successively propagated at a very high rate. As a consequence, the initial stages of phase transitions – the appearance and growth of supramolecular structures – are of important theoretical and practical significance. Due to the complexity of their composition caused by the content of organic and inorganic compounds of different molecular weight and natural surfactants (carboxylic acids, gums, asphaltenes, etc.), complex structural units consisting of a nucleus and an adsorptionsolvate layer arise in crude oil, gas condensate, and petroleum residues in ordinary conditions under the effect of intermolecular interactions. Effects of redistribution of hydrocarbons between phases arise under the effect of a shock pulse as a result of a directed change in the geometric dimensions of disperse formations and the interfacial layer. In the final analysis, this affects the physicochemical properties of natural organic compounds and the yield and quality of the products of refining hydrocarbon feedstock. For this reason, shock-wave technologies can be used to enhance refining of this feedstock.

45

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

STRUCTURAL FEATURES OF INDUSTRIAL WATER-CRUDE OIL EMULSIONS. MICROWAVE STUDIES

I. N. Evdokimov and M. A. Novikov

UDC 665.7.033.28

The thermal properties and structural features of industrial water-oil emulsions were investigated with microwave treatment. The critical concentrations of water at which abrupt structural changes take place were determined. The effect of the mass fraction of water in the emulsion on its heating rate and the efficiency of demulsification was studied. A 15-20 or 60-65% water content is recommended for breaking down emulsions. Demulsification takes place with minimum power consumption and with the highest efficiency. The performance and user properties of crude oils and many petroleum products – fuel, viscous oils, and greases – are to a great degree determined by the presence of water in them [1, 2]. The formation of emulsions of water with fuel can cause engines to break down, and formation of emulsions with lube oil in the crankcase ventilation system can diminish the protective properties of the lube oil. One negative factor in crude production is its flooding, which causes problems related to formation of stable water–crude oil emulsions. Water also enters crude oil when steam is pumped into the stratum and during desalting in electric desalting units (EDU). Petroleum emulsions are easily formed in turbulent streams of a water-crude mixture when the pressure in the pore channels changes and during movement through throttle plugs and different valves in pipeline systems. An increase in the viscosity of the crude can increase the pumping costs due to higher power consumption. The presence of emulsions intensifies corrosive wear of the equipment. Typical natural emulsions are water in crude oil [3]. Crude oil contains surfactants (SF) such as asphaltenes, naphthenic acids, and solid organic and inorganic particles. According to the Bancroft rule, a liquid containing SF becomes a continuous phase [4]. In migrating to the phase boundary, SF form elastic protective films around drops of water [1]. Modern methods of breaking down water–crude emulsions are based on using contact heating methods or chemical additives (demulsifiers). Excessively high power consumption is characteristic of the first, and ____________________________________________________________________________________________________ I. M. Gubkin Russian State University of Oil and Gas. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 36 – 38, January – February, 2007. 46

0009-3092/07/4301–0046 © 2007 Springer Science+Business Media, Inc.

45 1 40 3 35 2 30

25 20

Fig. 1. Sample temperature T vs. microwave exposure time t : 1) pure water; 2) pure crude ; 3) water–crude emulsion with 30% water. contamination of wastewaters and oil refining products is characteristic of the second method. Contactless microwave demulsification, patented more than two decades ago, is an alternative to these methods [5]. Microwaves have high penetrating power and act selectively on water, crude, and interfacial films, ensuring separate energy input. As a result, the phase separation rate increases significantly in comparison to ordinary heating methods and power consumption decreases [6-9]. Detailed information on the structural properties of the emulsions are necessary for controlling and increasing the efficiency of demulsification [10]. Our studies provided new information on the character of the structural changes in natural water–crude emulsions and revealed the features of their breakdown by microwave treatment. Emulsions based on crude oil taken from well No. 624 (Bobrikov stratum) in the Kuroki field in Volgograd oblast were investigated. The degassed crude had a density of 832 kg/m 3 at 20°C and a solid point below –18°C, and1% asphaltene, 8% resin, and 2% paraffin content. The aqueous phase was a double distillate (pH=5.5) obtained according to GOST 6709–92 and stored in air. All preliminary procedures were conducted in a thermally controlled cabinet at a temperature of 20°C. Water in proportions of 0 to 100 wt. % (with a 5% step) was mixed with the crude oil with a mixer (~2000 ppm) for 8-10 min. Samples of the emulsions weighing 70±0.5 g were placed in 100-ml glass vessels for microwave treatment. The type of emulsion (water in crude or crude in water) was determined by the drop test method [9]. All emulsions with a water content of up to 80% (inclusively) were of the water in crude type. An Elenberg Microwave Oven MS-1700M (2.45 GHz, 700 W) operating in the minimum (17%) output power range was used as the microwave source in the experiments. In each experiment, the vessel with the emulsion (initial temperature of 20±0.1°C) was placed in the center of the microwave oven and exposed to microwave treatment for the assigned time (accuracy of determination of ±0.5 sec). The temperature of the emulsion was measured with a calibrated thermocouple placed on the axis of the sample at a depth of 10 mm from the surface of the emulsion. In addition, the heating time t d at which the beginning of demulsification was visually observed was recorded: appearance of the first drops of water on the bottom/walls of the vessel containing the emulsion or formation of a layer of pure crude on the surface. The effectiveness of demulsification was defined as 1/t d.

47

2.0

dT/dt

1.6 1.2 0.8 0.4

0

0,2

0.4

0.6

0.8

1.0

c, mass portion Fig. 2. Water–crude emulsion heating rate dT/dt vs. water content c. Typical curves of heating the samples with pure water, pure crude, and a water–crude emulsion with a 30% water content are shown in Fig. 1. As expected, they were almost linear for water, and heating took place at a constant rate dT/dt which corresponded to absorbed energy of 5.8 W/cm 3 . For the crude oil sample, linearity persisted at the beginning of heating to the temperature of 28°C with absorbed energy of 1.2 W/cm 3 . Slowing of the heating rate on the 29-30°C segment indicates the appearance of endothermic processes perhaps related to decomposition of colloidal aggregates of SF or melting of wax microcrystals. At higher temperatures, the heating curve again became linear, and the absorbed energy was 1 W/cm 3. The insignificant decrease in the heating level could be due to an increase in heat losses at high temperatures. The water–crude emulsion heating curve has an even more complex shape. Its most distinctive feature is the sharp increase in the heating rate at 35°C. The cause of this increase is the onset of demulsification, visually detected by the appearance of layers of free pure crude and/or pure water. The constancy of the absorbed energy in the first stage (0-6 sec) of microwave heating indicates preservation of the initial internal structure of the emulsion, of which quantity dT/dt could be a characteristic. The essentially nonmonotonic dependence of the initial heating rate dT/dt on the content of water in the emulsion, which indicates sharp changes in the structure of the emulsion, is shown in Fig. 2. Such an effect of the water content on the properties of an emulsion undergoing microwave treatment have not been published previously. Our previous experiments [10] demonstrated the nonmonotonic effect of the water content on the viscosity and density of natural water–crude emulsions. These effects were attributed to the characteristic formations of the emulsion structure only observed in model microemulsions [11]. By analogy with the results in [10], the specific dependence in Fig. 2 can be identified with the appearance of the same structural effects. Freshly prepared emulsions with a low water content can be regarded as suspensions of individual, noninteracting drops of water [10, 11]. The initial heating rates of such emulsions are lower than for pure crude due to the well-known predominant absorption of microwave energy by water. As a result, the energy absorbed by the basic (by mass) crude phase decreases, and the low thermal conductivity of the crude prevents rapid heat transfer from the water drops. We attribute the sharp increase in the initial heating rate in mass fractions of water close to 0.2 (volume fraction of ~0.17) to the appearance of percolation. This event has been well investigated in model microemulsions, but rarely discussed with respect to the behavior of natural water–crude emulsions. As a result of percolation, the

48

0.09

1/td, sec −1

0.08

0.06

0.04

0.02

0,05

0.20

0.35 0.50 c, mass portion

0.65

0.80

Fig. 3. Effectiveness 1/t d of demulsification vs. water content c in emulsion. water drops form extensive “chains” that facilitate energy transfer over great distances and increase the conductivity of the sample [3, 11, 12]. The experimental percolation thresholds in model emulsions with different SF were observed in the range of 0.16-0.28 volume fractions of water [12, 13], which is close to the value of 0.17 in our experiments (see Fig. 2). Consolidation of the protective layers of SF around the water drops caused by percolation can cause formation of a new (bicontinuous) structure in natural water–crude emulsions [10]. Actually, it was hypothesized more than four decades ago that the presence of an elastic protective layer which acts as a barrier to coalescence of the drops could be the cause of the stability of water–crude emulsions. It was recently shown in [13, 14] that this layer can have a very complex composition. For example, it can include liquid-crystalline naphthenic acid structures, molecular aggregates of asphaltenes, and solid particles. Such boundary layers are essentially a special “third phase” of water–crude emulsions. In the case of the approximate equality of the proportions of water and crude, a “third phase” of thermodynamically unstable natural emulsions can form transitional bicontinuous structures that externally resemble the stable bicontinuous structures in model microemulsions [11, 12]. We previously [10] discovered the appearance of special bicontinuous structures in industrial water–crude emulsions with a 0.4-0.6 (wt.) fraction of water by density and viscosity measurements. In view of the results obtained, we correlated the appearance of the local heating rate minimum in Fig. 2 for a mass fraction of water close to 0.4 (volume fraction of 0.37) with the onset of formation of such transitional structures. The probable mechanism of the appearance of the minimum is a decrease in interfacial heat exchange in the bicontinuous structure in comparison to the drop structure for the same water content in the case of contraction of the total water–crude contact area. The rapid increase in the initial heating rate observed in Fig. 2 for a water content greater than 0.4 could be attributed to the appearance of important polydispersion of the aqueous phase after decomposition of the bicontinuous structures. Actually, previous studies [10] showed that at this water content in water–crude emulsions, the distribution of water drops by size becomes bimodal. Large water drops constitute an “ordinary” aqueous phase, and closely packed drops less than 7-8 mm in size constitute a “third phase.” Such closely packed disperse structures stabilized by small drops of water are

49

characterized by extremely high dielectric losses in comparison to a continuous aqueous phase. As a consequence, the specific properties of the “third phase” can be responsible for the increase in the heating rate observed in Fig. 2 for 0.55-0.7 mass fractions of water (0.5-0.66 volume fractions). Finally, it follows from Fig. 2 that for a mass fraction of water greater than 0.65, the heating rate will decrease to values close to those observed for pure water. In consideration of the absence of phase inversion in the investigated samples up to a mass fraction of water of 0.8, such behavior can be assigned to the onset of formation of “close packing” of the water drops. The value of 0.65 is close to the known mass fraction of disperse phase in “arbitrary close packing” of identical drops (volume fraction of 0.637, mass fraction of 0.66). The change in the heating rate can be attributed to the fact that additional pressure on the “third phase” arises in “close packing” of large drops of water when they touch each other, and enlargement of the smallest drops of water begins in this phase. For this reason, the “third phase” loses its high energy-absorbing properties and the overall heating rate decreases. The dependence of the effectiveness of demulsification on the fraction of water in the emulsion is shown in Fig. 3. It is clear that the highest efficiency is attained for mass fractions of water close to 0.2 and 0.6, corresponding to the formation of the special states of the structure of water–crude emulsions described above. The concentrations of water in an emulsion at which the structure of the disperse phase changes markedly, causing a sharp change in the thermal properties of the emulsions, were thus found as a result of studying industrial mixtures of crude oil and water. The heating rate and demulsification efficiency are maximum in emulsions with approximately 20 and 60% concentrations of water. Maintaining the fraction of water near these values can minimize power consumption and accelerate microwave demulsification processes. REFERENCES 1. G. N. Poznyshev, Stabilization and Breaking of Emulsions [in Russian], Nedra, Moscow (1982). 2. 3.

N. M. Likhterova, V. P. Kovalenko, and V. V. Lebedev, Khim. Tekhnol. Topl. Masel, No. 4, 24-28 (2003). W. Clayton, Theory of Emulsions and Technical Applications [Russian translation], Izdatinlit, Moscow

4.

(1950). W. D. Bancroft, J. Phys. Chem., 17, 501 (1913).

5. 6.

US Patent No. 4 582 629. J.-H. Hong, B.-S. Kim, and D.-C. Kim, Korean Chem. Eng. Res., 42, No. 6, 662-668 (2004).

7. 8.

C. S. Fang, B. K. L. Chang, P. M. C. Lai, et al., Chem. Eng. Commun., 73, No. 1, 227-239 (1988). L.-X. Xia, S.-W. Lu, and G. Cao, Ibid., 191, No. 8, 1053-1063 (2004).

9. 10.

C.-C. Chan and Y.-C. Chen, Separation Sci. Technol., 37, No. 15, 3407-3420 (2002). I. N. Evdokimov, N. Yu. Eliseev, and V. A. Iktisanov, Khim. Tekhnol. Topl. Masel, No. 4, 37-39 (2005).

11. 12.

P. Sherman, Emulsion Science, Academic Press, New York (1968). G. C. Bye et. al., in: Microemulsions: Structure and Dynamics, S. E. Friberg and P. Bothorel (eds.),

13.

CRC Press, Boca Raton, Florida (1987). S. I. Borisov, M. V. Kateev, E. S. Kalinin, et al., Neft. Khozyaistvo, No. 4, 74-77 (2004).

14.

T. F. Kosmacheva and F. R. Bugaidulin, Ibid., No. 12, 114-118 (2005).

50

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

REFORMING OF n-HEXADECANE ON MODIFIED ALUMINOSILICATES

Ali Busenna, O. Zamumi, I. M. Kolesnikov, and Le Tu An’

UDC 66.023.66.007

Catalysts containing amorphous aluminosilicate and crystalline zeolite phases are widely used for industrial cracking of petroleum cuts. These catalysts also exhibit high activity in cracking of individual hydrocarbons. The activity and selectivity of the amorphous aluminosilicate phase can be increased by modifying it with metal oxides, creating additional ensembles of tetrahedrons of the type (AlO 4⋅SiO 4⋅MeO 4) or ensembles of polyhedrons of another composition: (AlO 6 ⋅SiO 4⋅MeO4 ) or (AlO 4⋅SiO4 ⋅MeO 6) in the lattice. These ensembles are randomly positioned in the lattice, which also reflects the amorphous structure of metal silicates. In special conditions – in liquid medium (water) at high pressure, metal silicates crystallize with formation of zeolites. When incorporated in the amorphous phase, zeolites serve as active catalytic components. Cobalt or zirconium compounds which also attack the aluminosilicate structure, changing the activity and selectivity of the catalysts, can also be added to the amorphous phase. New data on the activity of metal aluminosilicate catalysts containing these compounds in a fixed amount are reported here. The catalysts were Table 1

Catalyst (arbitrary designation) К1

Note.

Chemical composition,* wt. %

pH of sol in synthesis

Sio2

Al2O3

CaO

ZrO2

10.5

92

–

7.84

–

К2

4.5

92.2

–

7.74

–

К3

4.5

89.75

8.5

1.22

–

К4

10.5

90.8

6.97

1.38

–

К5

10.5

87.7

9.06

–

2.18

К6

4.5

86.9

11

–

1.38

* Remainder – sodium oxide

____________________________________________________________________________________________________ M. Bucher University of Hydrocarbons and Chemistry, Algiers. I. M. Gubkin Russian State University of Oil and Gas. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 39 – 41, January – February, 2007. 0009-3092/07/4301–0051 © 2007 Springer Science+Business Media, Inc.

51

Table 2

Unit cell size, nm

Compound

a

b

c

Co2SiO4

0.4781

1.0296

0.5998

CoSiO2

1.8296

0.8923

0.5204

Table 3

Catalyst (see Table 1)

Pore volume (cm3/g) after heating at, °C

Average pore radius (nm) after heating at, °C

500

700

900

500

700

900

К1

0.63

0.51

0.46

0.832

0.904

1.312

К2

0.64

0.55

0.23

0.447

0.954

1.162

К3

0.24

0.14

0.05

0.910

0.900

1.020

К4

0.65

0.47

0.19

0.388

0.821

1.594

К5

0.29

0.16

0.13

1.450

2.250

4.090

К6

0.24

0.17

0.16

1.970

2.430

4.300

used for conversion of n-hexadecane to reveal the basic types of reactions (cracking, reforming, isomerization, etc.) that determine the composition of the catalyzate and hydrocarbon gases. Aluminosilicate catalysts modified with cobalt and zirconium compounds were synthesized in a continuous unit by feeding aqueous solutions of Al 2(SO 4)⋅18H2 O, Co(NO 3) 2 ⋅8H 2 O, and ZrOCl⋅8H 2 O salts and an aqueous solution of liquid glass, Na 2SiO 3, in the corresponding ratios, in the mixing unit. In mixing the solutions at 10°C and pH 4.5 or 10.5 (to establish the effect of the pH on the properties and activity of the catalyst), a metal aluminosilicate sol was obtained. The sol stream in the form of microdrops was passed through a grooved divider into a lower container filled with transformer oil. In passing from the surface of the oil to the bottom of the vessel, the sol droplets solidified into gel beads. The beads formed were placed in a separate container, washed with distilled water, and underwent syneresis for 8 h at 40°C in the mother liquor separated from them. The mother liquor was displaced from the container with an activating aqueous solution of (NH 4) 2 SO 4 and the gel was activated at 50°C for 24 h. Substitution of Na + ions by NH +4 ions took place in bulk and on the surface of the hydrogel particles in activation. Activation continued until the Na + ions were totally substituted, determined by the absence of these ions in the hydrogel particles. The activated hydrogel was washed with distilled water until the SO2-4 ions in the washing water totally disappeared. The gel was separated from the moisture on a filter, placed in an oven, and dried at 110°C to a constant weight, then calcined in an air stream at 500, 700, and 900°C for 6 h. After calcination, the catalysts were stored in a desiccator to prevent sorption of moisture and organic compounds from the environment. The chemical composition was determined, the IR and x-ray structural spectra were recorded, and the acidity, external appearance, specific surface area, volume, and average pore radius were determined for the catalysts calcined at 500°C. The chemical composition and acidity of the external surface of the modified catalysts are reported in Table 1. The basic components are SiO 2 and Al 2O 3 , CoO, and ZrO2 , which play the role of modifiers. The x-ray structural analysis showed that the modified and initial aluminosilicates are x-ray amorphous structures, while the cobalt silicate has a crystal lattice with an orthorhombic unit cell whose size is shown in Table 2 for the two compounds identified.

52

Table 4

Catalyst (see Table 1)

Specific surface area (m2/g) after heating at, °C 500

700

900

К1

151

113

56

К2

271

260

151

К3

228

113

99

К4

335

295

67

К5

253

194

166

К6

246

168

161

Table 5

Catalyst (see Table 1)

Acidity (meq H+/g) after heating at, °C 500

700

900

К1

2.45

2.35

2.3

К2

3.76

2.7

2.35

К3

4.8

2.85

2.75

К4

2.8

2.4

2.2

К5

3.45

2.3

2.15

К6

3.8

2.8

2.4

The absorption bands at 730-780 cm -1 in the IR spectra of the modified aluminosilicates were assigned to vibrations of the bonds in island ensembles of {AlO 4Table 3⋅SiO 4} tetrahedrons, those at 500-600 cm -1 were a s s i g n e d t o p o l y m e r i z a t i o n e n s e m b l e s o f { M e O 6⋅ S i O 4} t e t r a h e d r o n s , t h o s e a t 1 6 0 0 - 1 7 0 0 c m -1 t o h y d r o x y l a t e d > A l O 6H ⋅ S i O 4} p o l y h e d r o n s , a n d t h o s e a t 3 4 5 2 c m -1 t o h y d r a t e d s i l i c o n o x i d e tetrahedrons {SiO 4⋅SiO 4}H 2O. The texture of the catalysts was determined by adsorption of nitrogen. The average radius and pore volume characterizing it are reported in Table 3. The pore volume decreased and the average radius increased when the sample heating temperature increased from 500 to 900°C. The increase in the average radius is due to destruction of blind pores joined by narrow pores into wider pores due to the effect of water vapor and a decrease in the number of winding pores. These three causes of the change in texture reflect an overall change in the physical properties of the catalysts. The wider-pore catalysts were synthesized in basic medium. T h e c a l c u l a t e d s p e c i f i c s u r f a c e a r e a s o f t h e i n v e s t i g a t e d c a t a l y s t s a r e r e p o r t e d i n Ta b l e 4 . Catalyst K 4 , synthesized at pH 10.5, has a higher specific surface area than the other catalysts. The specific surface area of the catalysts decreased with an increase in the calcination temperature as a result of an increase in the average pore radius. The acidity was investigated by titration of suspensions of the samples in benzene with a solution of n-butylamine to determine the nature of the activity of the modified catalysts in reforming and cracking of n-hexadecane. The acidity of the accessible active ensembles of tetrahedrons containing or not containing hydroxyl groups was determined in titration. The results of the experiments are reported in Table 5. Catalysts K 2, K 3, and K 6 , synthesized from sol at pH 4.5, had higher acidity. Moreover, their specific surface was lower than for catalysts K 1, K 4, and K 5, synthesized at pH 10.5. As a consequence, the activity of the catalysts is not directly correlated with the acidity of their surface. It can be explained by the premises of the theory of catalysis by polyhedrons in [1, 2].

53

80 K6 60 x, wt. %

K3 K4 40 K5 20

0 200

250

300 t, °C

350

400

Fig. 1. Degree of conversion x of n-hexadecane vs. temperature t on catalysts modified with zirconium oxide (solid curves) and cobalt oxide (dashed curves). According to this theory, amorphous lattices with a higher content of ensembles of tetrahedrons of the {AlO 4⋅SiO 4}, {SiO4⋅ZrO4⋅AlO 4}, {SiO4⋅AlO 4⋅SiO 4}, and {CoO43⋅SiO 4⋅AlO 4} type are obtained from the sol in acid medium. This is confirmed by the IR spectra of the catalysts synthesized from sols at pH 4.5 and 10.5. After the physicochemical properties, composition, structure, and acidity of catalysts K 1-K 6, their activity in cracking and reforming of liquid n-hexadecane was investigated. The reactions were conducted in a continuous unit in the gas phase in conditions of ideal displacement of the vapor phase over the catalyst bed. The reactor was charged with 40 cm 3 of bead or grain catalyst, and it was heated in a stream of dried air with impurities removed at 500°C for 3 h. Conversion of n-hexadecane took place in the 350-400°C temperature range at a feed rate of 1 cm 3/(cm 3⋅h) for 1 h. At the end of the process, the degree of conversion of the feedstock and content of four classes of hydrocarbons in the catalyzate: paraffins, olefins, naphthenes, and aromatics, were determined. The increase in the degree of conversion with an increase in the temperature in the catalyst bed (Fig. 1) is due to both activation of the hydrocarbon molecules in the feedstock and to electron promotion (or electron respiration) of tetrahedron ensembles. Catalysts K 3 and K 5 synthesized at pH 4.5 and modified with cobalt and zirconium compounds exhibited high acidity and consequently higher activity. Catalyzate was obtained on catalyst K 6 that distills within 30-165°C and has the following hydrocarbon composition, wt. %: 10.05 n-paraffins; 9.21 olefins; 18.50 naphthenes; 38.12 isoparaffins; and 23.49 aromatics. The octane number (motor) of the catalyzate was 79.3. Based on these data, we note that the n-hexadecane molecules undergo cracking and reforming reactions in the presence of the zirconium aluminosilicate catalyst. The yield of gaseous hydrocarbons increased from 0.9 to 4.5 wt. % with an increase in the temperature. The presence of C 1-C 15 hydrocarbons in the products of conversion indicate catalytic cracking processes. Hexadecane is present in the catalyzate both in the initial and in isomeric forms. Unsaturated hydrocarbons and aromatics – benzene and alkylbenzenes with a shorter alkyl radical – are formed in cracking reactions. The presence of isoparaffins, naphthenes, and aromatic hydrocarbons in the catalyzate indicates reforming of n-hexadecane. Isoparaffins are formed by isomerization of n-paraffins on ensembles of tetrahedrons. Reactions of dehydrocyclization of molecules of unsaturated hydrocarbons take place on the same ensembles with formation of aromatics. Naphthenes can be synthesized in several reactions: Diels–Adler,

54

100

V, vol. %

80

40

0 40

80

120 tdis, °C

160

Fig. 2. Curve of distillation of liquid reformate into narrow cuts (V, t dis – distillation volume and temperature).

cyclization of olefins with formation of cyclohexane and decalin, whose dehydrogenation yields benzene and naphthalene, respectively. This approach to explaining the chemistry of conversion of n-hexadecane on modified aluminosilicate catalysts, i.e., with separation of cracking and reforming processes, will allow more clearly elucidating the quality of the catalyzate obtained. The liquid catalyzate was distilled from an Engler flask into narrow cuts to determine its motor properties. The distillation curve obtained (Fig. 2) is characteristic of the commercial naphtha cut, 50 vol. % of which distills at a temperature no higher than 120°C. As a consequence, a high-octane component as an additional additive for commercial gasoline can be obtained in conversion of n-paraffins in low-octane naphtha cuts on cobalt- and zirconium-modified aluminosilicate catalysts. REFERENCES 1. I. M. Kolesnikov, G. I. Vyakhirev, M. Yu. Kil’yanov, et all, Solid Catalysts, Their Structure, Composition, 2.

and Catalytic Activity [in Russian], Neft’ i Gaz, Moscow (2000). I. M. Kolesnikov, Catalysis and Catalyst Production [in Russian], Tekhnika, Moscow (2004).

55

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

EFFECT OF A COPOLYMER MODIFIER ON DEWAXING OF LUBE DISTILLATES

I. K. Veliev

UDC 665.547.391

Dewaxing with selective solvents in production of lube oils from paraffin-base crudes requires large investments and operating expenses. Up to 40% of all expenses are for this process. For this reason, searching for ways to enhance it is a pressing problem [1]. Use of modifiers is the most effective and simplest method of increasing the efficiency of dewaxing of lube distillates with selective solvents. The efficiency of Paragel, Hightech E-603, Viscoplex, and N-500 pour-point depressants, which are products of condensation of chloroparaffin with naphthalene and methacrylic acid ester and aliphatic alcohol polymers in three-stage dewaxing of raffinates obtained from mixing crudes at Pleven Oil Refinery (Bulgaria), was demonstrated in [2]. On addition of 0.2 wt. % of these additives, the yield of dewaxed oil increased by 2-3 wt. % and the filtration rate of the suspension in all stages increased by 2-4 times. Table 1

Raffinate from selective treatment wit phenol Indexes

Density at 20°C, kg/m3

from Ufa OR distillate I-20 oil I-40 oil (distillate III) (distillate IV) 866.7 881.3

from Novo-Gor’kovsky OR I-40 distillate oil MS-20 residual oil (distillate IV) 884.3 893.8

Viscosity at 100°C, mm2/sec

4.43

7

7.02

17.6

Flash point, °C

210

230

226

282

Melting point, °C

+21

+36

+36

+40

Color, CNT units

2.5

4

3

5

12.86

13.49

16.36

13.06

Solid paraffin content, wt. %

____________________________________________________________________________________________________ Yu. G. Mamedaliev Institute of Petrochemical Processes, National Academy of Sciences of Azerbaidzhan. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 42 – 43, January – February, 2007. 56

0009-3092/07/4301–0056 © 2007 Springer Science+Business Media, Inc.

Table 2 Dewaxing Indexes

of distillate raffinates of I-20 (distillate III) and I-40 (distillate IV) lube oils at Ufa OR

at Novo-Gor’kovsky OR I-40 oil distillate raffinate

MS-20 oil residual raffinate

Solvent composition, wt. % methyl ethyl ketone

60

60

50

toluene

40

40

50

for feedstock dilution

280

300

420

for washing residue

100

100

100

Filtration temperature, °C

-25

-25

-25

Solution cooling rate, deg/h

180

120

120

Amount of solvent, wt. %

Approximately 40 pilot industrial products were tested as modifiers to enhance dewaxing at the Institute of Petrochemical Processes (IPCP), Azerbaidzhan National Academy of Sciences [3-5]. DN-MA additive, an alkyl methacrylate copolymer, was the most effective. It is stable during storage and in solutions of slack wax and petrolatum in dewaxing. We found that the optimum amount is 0.15 wt. % in raffinate in dewaxing of distillate and residual raffinates from furfural treatment of Baku paraffin-base crudes. We investigated the mechanism of action of this additive in distillate and residual raffinates. The increase in the effectiveness of the process was due to a decrease in the viscosity of the cooled solution as a result of formation of a primary coagulation structure. This improved diffusion of wax crystals to the crystallization center and prevented formation of an extensive wax lattice during crystallization. A correlation was established between the effectiveness of the additive and its dielectric constant, which can be used as a criterion of the suitability of the modifier. It was 2.9600 for DN-MA versus 2.6933 for AzNII and 2.5314 for PMA “D”, for example [3] The use of DN-MA modifier additive has advantages over MAX-Dewax technology [6]. Due to the increase in production of high wax crudes, increasing the efficiency of dewaxing with selective solvents has become very urgent. We investigated the effect of DN-MA additive on the effectiveness of dewaxing raffinates from selective treatment of medium-sulfur crudes. Distillate raffinates of I-20 and I-40 lube oils from Ufa OR and I-40 oil distillate raffinate and MS-20 oil residual raffinate from Novo-Gor’kovsky OR were dewaxed. The quality indexes of these raffinates are reported in Table 1, the dewaxing conditions used at these OR are shown in Table 2, and the results of dewaxing with no additives and with DN-MA additive are reported in Table 3. As Table 3 shows, when the amount of DN-MA is increased from 0.1 to 0.2 wt. %, the yield of dewaxed oil and the suspension filtration rate increase in dewaxing of distillate and residual raffinates, while the solid point of the oil remains unchanged, the viscosity index increases, and the oil content in slack wax and petrolatum decreases. The greatest effect is obtained with 0.15 wt. % additive. Increasing the amount from 0.15 to 0.2 wt. % insignificantly affected the results. As a result of using DN-MA additive in the optimum amount (0.15 wt. %), it was possible to obtain dewaxed lube oil with a high yield and improved physicochemical properties, reduce the oil content in slack wax by 2.5 times, and increase the filtration rate of the cooled solution by 2-4.8 times. 57

58

20.3 19.1 17.7 17.4

82.8

79.7 80.9

82.3 82.6

0.2

0 0.1 0.15 0.2

21 19.5

79 80.5

81.2

0.2 18.8

(31.5)

14.8 14.4

85.2 85.6

68.5

21 17.8

79 82.2

0 0.1 0.15

0 0.1 0.15 0.2

18.2 17.4

81.8 82.6 17.2

18.8

81.2

lube oil

slack wax (petrolatum)

Yield, wt. %

0 0.1 0.15

Amount of DN-MA additive, wt. %

Table 3

480

266 480

100

310 312

100 200

895.7

20.2

20.3 20.2

92

91 92

90

MS-20 oil residual raffinate [5] 897.9 20.5 897.1 896.9

92 92

91 91

at Novo-Gor’kovsky OR raffinate (distilalte IV) 885.6 7.02 884.6 7.65 884 7.49 883.8 7.45

dewaxed lube oil viscosity at density at viscosity 10°C, 3 20°C, kg/m index mm2/sec DEWAXING at Ufa OR I-20 oil medium-viscosity distillate raffinate (distillate III) 100 878.2 4.43 100 200 877.8 4.81 101 300 869.6 4.75 104 312 868.9 4.69 104 I-40 oil viscous distillate raffinate (distillate IV) 100 887.8 7 90 150 886.5 7.63 92 200 886.4 7.5 94 250 886.1 7.45 94 Filtration rate, %

-15

-15 -15

-15

-15 -15

-15 -15

-20 -20

-20 -20

-19

-19 -19

-19

solid point, °C

Physicochemical properties

64

63 64

(62)

55 55

52 54

54 54

53 54

54

54 54

52

melting point, °C

5.2

10 5.6

(32.8)

9.1 8.9

21 14.2

8.4 8.2

20.8 13.5

8.2

20 11.5 8.5

oil content, wt. %

slack wax (petrolatum)

This additive is a universal modifier: it is equally effective in dewaxing of both distillate and residual raffinates from phenol and furfural treatment obtained from both medium-sulfur and from low-sulfur crudes. REFERENCES 1.

L. P. Kazakova and S. E. Krein, Physicochemical Principles of Petroleum Oil Production [in Russian], Khimiya, Moscow (1978).

2. 3.

P. G. Furnadzhieva, G. P. Abrashov, A. Atanosov, et al., Neft’ Khimiya (Sofiya), No. 11, 191-198 (1973). I. K. Veliev, Candidate Dissertation, Institute of Petroleum Chemistry, AzerbSSR Academy of Sciences,

4.

Baku (1982). R. Sh. Kuliev, F. R. Shirinov, and I. K. Veliev, Azerbaidzh. Neft. Khozyaistvo, No. 3, 25-27 (1997).

5. 6.

R. Sh. Kuliev, F. R. Shirinov, and I. K. Veliev, Khim. Tekhnol. Topl. Masel, No. 3, 13-14 (1998). R. Sh. Kuliev, I. K. Veliev, and S. R. Kulieva, Ibid., No. 6, 11-13 (2003).

59

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

METHODS OF ANALYSIS

A PIEZORESONANCE SENSOR SYSTEM FOR RAPID EVALUATION OF THE QUALITY OF GASOLINES

A. V. Kalach and V. F. Selemenev

UDC 543.662.6

The urgency of the problem of supplying the country’s growing auto fleet with high–quality motor fuel with improved environmental characteristics is primarily due to entry of important amounts of harmful substances contained in adulterated liquid fuel into the environment. Of all aspects of the overall environmental picture, the problem of atmospheric pollution by harmful products of oil refining, primarily those released in use of gasolines and diesel fuels in motor vehicles, has received the most attention [1]. Motor vehicles are responsible for more than 60% of the total volume of pollutants in most large cities. Since adulteration of automotive fuel in Russia has become massive, it is urgent and necessary to develop and use modern methods of quality control. One of the most intensively developing branches of science “ sensors “ allows quickly obtaining reliable information on product quality. We developed a new method for fast evaluation of the quality of commercial gasolines using piezoresonance sensor systems. Commercial A–76 and AI–92 gasolines purchased at service stations in Voronezh were selected for the study. The studies were conducted with AL–cut quartz resonators (nominal oscillation frequency: 8–10 MHz) manufactured at P’ezo Co. (Moscow). Polymethylphenyl silicone (PMPS) and squalane (Sq) were used as the sorbent modifiers for the piezoresonance sensors (PrS). These sorbents were selected because of the stability of the PrS analytical signal obtained. The sorbent (25 mg) for modification of the PrS was placed in a 25–cm 3 graduated flask and the volume was brought to the mark with the corresponding solvent (in our case, chloroform for PMPS and hexane for Sq). The sorbent solution was applied to both electrodes of the quartz crystal with a microsyringe. The modified crystal was held in the temperature range whose upper limit corresponded to the boiling point of the solvent. The shift of the PrS oscillation frequency was only established after this. ____________________________________________________________________________________________________ Institute of RF Ministry of Internal Affairs. Voronezh State University. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 44 – 45, January – February, 2007. 60

0009-3092/07/4301–0060 © 2007 Springer Science+Business Media, Inc.

The decrease in the working oscillation frequency of the PrS was calculated with the Sauerbrei equation [2, 3]:

Δf = -2.3 ⋅ 10 -6 f 02 Δm / A w h e r e Δ f i s t h e c h a n g e i n t h e r e s o n a t o r f r e q u e n c y, H z ; f 0 i s t h e r e s o n a n c e f r e q u e n c y o f t h e piezosensor, MHz; Δm is the mass of the modifier, g; A is the surface area of the modifier (set equal to the area of the electrodes), cm 2. The original piezoresonance sensor system described in detail in [4] was used for analyzing the gasoline samples. The analysis of the published data showed that the principle of fabrication of adulterated gasoline frequently consists of bringing the octane number of the blend to the required value [1]. As practice shows, this can be conveniently done by adding an adulterant to the gasoline “ gas condensate or ethanol. However, such additives increase the octane number of the gasoline only for a short time, after which the auto continues to operate on gasoline of lower quality which unconditionally leads to early wear of the internal parts of the engine. The complex implementation, use of a large number of chemical reagents, duration of the analysis, for example with the PIANO method [5], are serious drawbacks of existing methods of assessing the quality of gasolines in our opinion. Taking into account the overall tendency of both researchers and consumers to assess the quality of a product with rapid, simple, and economically expedient methods and instruments, attention should be focused on developing portable instruments, test methods, and operative screening methods [6, 7]. We took into consideration the wide distribution of methods that allow assessing the integral (generalized) indexes of the sample analyzed in developing a new method of assessing the real quality of commercial gasolines [7]. It totally does not follow from the octane number of gasoline determined by some method, which, for example, would be equal to 76, that the investigated gasoline will correspond to brand A–76. The results of the analysis only show its octane number and this frequently means the version of assessing the quality of commercial gasoline is not acceptable. To establish the correspondence of a product to a real commercial brand and concrete standard, not to speak of the manufacturer, it is necessary to determine so many indexes that the cost and time for solving this problem in a large stream of samples would end at an impasse for both manufacturer and researcher. Multisensor systems formed from nonselective sensors have been widely used in practice [8–10]. Identifying the odor of the material and establishing the concentration of substances contained in the sample if possible is the main problem that can be solved with such systems. This is due to processing the data and identifying the multidimensional picture of the sensor signals: “odor pattern,” “visual impression.” Sensors are usually characterized by cross sensitivity so that an important number of them complicates processing of the results of the measurement in most cases. For this reason, reducing the size of the measurement space by isolating the most informative sensor elements is justified. The proposed method is based on use of a multisensor system formed of six piezoresonance sensors modified with squalane and polymethylphenyl silicone, which allows rapidly evaluating the quality of commercial gasolines in a maximum of 3 min [11]. Profile analysis was used for constructing the overall signal of the system, the so–called “visual imprint.” This method is based on unifying the individual olfactory and other parameters of gasoline to obtain a qualitatively new characteristic of the product. After statistical processing, the results can be represented graphically in the form of the complete circumference profile (see Fig. 1).

61

200 1

400 1 200

2

2

0

100 3

200 1

0

3

500 1 2

2

100 0

3

0

3

Fig. 1. “Visual imprints” of samples of gasoline acquired at two Tyumen Petroleum Company filling stations: A, C) A–76; B, D) AI–92.

The most informative piezoresonance sensors and an algorithm for identifying their signals in pairs of analyzed gasolines that ensure obtaining different “visual imprints” of the products were distinguished. A multisensor system for analysis of the investigated gasolines was formulated based on the PrS signals selected for maximum recognition of analytes that differ significantly with respect to the overall response (“visual imprint”). Optimizing the algorithm for forming matrix responses of six and more sensors allows obtaining the “visual imprints” of analytes that differ significantly from each other. By comparing these imprints, it is possible to: distinguish the characteristic geometric samples “ the “visual imprints” for all commercial gasolines studied; rapidly order the sensors by maximum and minimum sensitivity to vapors of the investigated gasolines. Using piezoresonance sensors with close affinity to the components of the gasolines increases the degree of difference of the “visual imprints”. As Fig. 1 shows, A–76 and AI–92 commercial gasolines at two different filling stations (samples A, B and C, D) unfortunately differ significantly with respect to the “visual imprints.” This probably cannot be due to different manufacturing technology alone. This finding once more confirms the necessity of developing portable fast methods of quality control for petroleum products (on the example of gasolines) and the applicability of our method for evaluating the quality of purchased commercial gasolines. The method is characterized by simplicity and availability to users. It will allow gasoline manufacturers to monitor the manufacturing process and filling station owners to monitor shipments. The results obtained allow recommending the method for fast evaluation of commercial gasolines. In our opinion, this method can be used for evaluating the quality of any petroleum products. As a consequence, manufacturers of liquid fuel can operatively control the manufacturing process and act on it by attaining the required indexes at minimal cost. However, it should be remembered that no fast analysis replaces the umpire laboratory method of assessing product quality.

62

REFERENCES 1. A. S. Safonov, A. I. Ushakov, and I. V. Chechkenev, Automotive Fuels: Chemmotology. Performance 2.

Properties. Assortment [in Russian], NPIKTs, St. Petersburg (2002). V. V. Malov, Piezoresonance Sensors [in Russian], Energoatomizdat, Moscow (1989).

3. 4.

L. M. Dorozhkin, V. S. Doroshenko, Yu. I. Krasilov, et al., Zh. Anal. Khim., 50, No. 9, 979–982 (1995). A. V. Kalach, Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 47, No. 9, 146–148 (2004).

5.

V. I. Vershinin, B. G. Derendyaev, and K. S. Lebedev, Computer Identification of Organic Compounds [in Russian], Akademkniga, Moscow (2002).

6. 7.

Yu. A. Zolotov, Zavod. Lab. Diagnost. Mater., 68, No. 1, 14–21 (2002). Yu. A. Zolotov, Zh. Anal. Khim., 59, No. 7, 677 (2004).

8.

I. V. Kruglenko, B. A. Snopok, Yu. M. Shirshov, et al., in: Proceedings of the Conference “Sensor”2000. Sensors and Microsystems,” St. Petersburg, June 21–23, 2000 [in Russian], St. Petersburg (2000), p.

9.

110. A. V. Kalach, Ya. I. Korenman, and S. I. Niftaliev, Man–made Neuronal Networks “ Yesterday, Today,

10.

Tomorrow [in Russian], Voronezh State Technol. Acad., Voronezh (2002). A. V. Kalach, in: Proceedings of the All–Russian Conference “Russian Analysts”, Moscow, September

11.

27–October 1, 2004 [in Russian], Moscow (2004), p. 104. RF Patent No. 2248571.

63

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

QUALITY CONTROL OF PETROLEUM OILS WITH ADDITIVES

K. V. Kovalenko, S. V. Krivokhizha, and G. V. Rakaeva

UDC 665.765.03

The performance properties of the initial components and finished product were evaluated during fabrication of models of commercial lube oils by scattered light correlation spectroscopy. This method allows determining the size and average radius of colloidal formations and the stability of colloidal solutions against separation. Using the data obtained, changes can be made in the manufacturing technology and formula of the oils by changing the mixing temperature and parameters of the initial components: the indexes of the base, the sequence of incorporating the additives, and the concentration and composition of the additives. Many petroleum oils contain surfactants (SF) – additives that improve their performance properties: colloidal stability against separation, chemical stability against oxidation, lubricity, detergent, anticorrosion, demulsifying, and antifoaming properties [1, 2]. In high enough concentrations, these additives form micellar solutions. The formation and properties of these solutions, the reaction of additives of different types in them and consequently, the effectiveness of the additives are described by the laws of colloid chemistry, physical chemistry, and physics [3, 4]. These laws are frequently used in selecting and increasing the effectiveness of additives to lube oils and fuels, which in turn allows reducing consumption of power and the most important petroleum products in modern industry [5, 6]. Selection of the base oil – the bases in production of commercial lube oil – is determined by both the required functional properties of the oil and the economic indexes of its production and use. Petroleum base oils are the most high-volume. Additives are incorporated in them to enhance certain performance properties [7, 8]. One method of selecting additives for lube oils is to apply the principles of nanotechnology, to wit, to create a stable structure (dispersion) of colloidal formations (CF) of nano dimensions in commercial oils. Nanosystems, according to the classification used in colloid chemistry, are ultradisperse colloidal systems with a particle size falling in the range of 1 to 100 nm [9-11]. ____________________________________________________________________________________________________ P. N. Lebedev Physics Institute. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 46 – 49, January – February, 2007. 64

0009-3092/07/4301–0064 © 2007 Springer Science+Business Media, Inc.

This size range corresponds to the limiting degree of dispersion at which a colloidal system still retains one of its most important properties – heterogeneity. According to the estimations in [12], the minimum size of phase disperse particles is approximately 1 nm (3-5 molecular diameters). The goal of our study* was to develop principles for energy-saving, environmentally clean technology for manufacturing petroleum oils with additives that have assigned performance properties. The method of correlation spectroscopy was used here for the first time to study intermolecular interactions of additives in lube oils under the effect of UHF radiation. The possibility of optimizing the manufacturing processes for production of industrial oils was demonstrated by the new method of UHF-radiation treatment. Theoretical substantiation of the principles of the mechanism of the reaction of additives and their selection to ensure the assigned performance properties of commercial petroleum products was proposed previously in [13]. Correlation spectroscopy was used in [13, 14] to study the intermolecular interaction of additives and their models and compositions to determine the colloidal stability of commercial oils. A hypothetical mechanism of the intermolecular interactions of SF in low-polarity media was given in these studies. A correlation was established between the average effective radius of colloidal formations, heating temperature, and time elapsing since the oil composition was made up. The possibility of developing a new, highly sensitive, economical, and effective method of evaluating the performance properties of petroleum products was demonstrated. A method for objectively substantiating the stability and performance characteristics of commercial oils based on the size of the CF in the additives and the purposeful alteration of the size was substantiated. It was found in [13, 14] that on one hand, CF form and enlarge on prolonged heating of a solution of additives in a base oil, i.e., during the final stage of fabrication of commercial oils. On the other hand, according to the data in [15, 16], the absorption spectrum of this solution in the infrared region changes in the same way both on heating and in treatment of the solution with UHF radiation, i.e., microwave radiation with a frequency of 2.45 GHz and tunable power of up to 750 W. It is logical to hypothesize that in exposure of a solution of additives in base oil to UHF radiation, like heating it, CF will form and enlarge. I-20A base oil (SAE 10) manufactured by Tektron Ltd. (Moscow oblast) was used as the base for the model compositions. Fenom from Tribotechnology Co. (Zelenograd), added in concentrations of 3.54 and 5 wt. %, was used as the additive in the model compositions. The viscosity of the base was measured with a Höppler viscometer. It was equal to 52.7 mPa⋅sec at 25°C and 6.91 mPa⋅sec at 80°C. The refractive index was 1.4833 for I-20A oil and 1.4997 for the additive. The samples were carefully dedusted before the measurements since light scattering on dust is much stronger than on the CF in the additive. Immediately after mixing, the same composition was filtered simultaneously into a cuvette with a metal collar – for measurement of the size of CF on heating in a thermostat – and into a cuvette with a caprolon collar – for treatment in the UHF-radiation chamber. The cylindrical cuvettes were fixed with these collars in the center of a cylindrical immersion vessel during the measurements, which facilitated adjustment, eliminated the problem of flashing, and improved the accuracy of the measurements. Treatment with UHF radiation was conducted in a 20-liter chamber, and the frequency of the radiation was 2.45 GHz with emitter power of 600 W. The temperature of the oil varied by no more than 1.5°. The size of the CF in the additives in the oils was measured by light-scattering correlation spectroscopy [17]. The width and shape of the central polarized Rayleigh line of light scattered by the solution of *Conducted with the participation of L. L. Chaikov. 65

the additive in the oil were experimentally determined with this method. The average radius of the CF and if necessary, the degree of their polydispersion as a function of the time the sample was heated or the exposure to the UHF radiation was found with the width of this line. The signal from the PEM (photoelectron multiplier) operating in the one-electron mode passed through an amplifier-discriminator and entered a digital correlator. In [14], this was a correlator from Malvern Instruments, Ltd. (England). We used a modern Fotokor correlator from Anteks-97 Ltd. (Moscow). The setup is described in detail in [18]. For monodisperse suspensions of CF particles, the central polarized Rayleigh line of scattered light had the shape of a Lorentzian with half-width G at half-height equal to:

G = Dq 2 = kTq 2 / 6πηr where D is the particle diffusion coefficient;

(1)

q = q S − ql = (4π sin θ / 2 / λ ) ; q S, q L are the wave vectors of

scattered and laser light; n is the refractive index of the oil; è is the scattering angle; l is the wavelength of the light; k is the Boltzmann constant; T is the absolute temperature; h is the viscosity of the base; r is the radius of the CF. For polydisperse systems containing CF with different radii, the spectrum consists of several superimposed Lorentzians with a common center at zero frequency (based on the number of particles with different sizes). In this case, the correlation function obtained is the sum of the same number of exponentials where each one has a characteristic fall time equal to 1/G 1, 1/G 2, …. The amplitudes of these exponentials are proportional to the intensity I of light scattering on CF with a radius corresponding to G 1 , G 2, …. We used three methods to process the correlation function. The results of earlier measurements, some of which are reported in [14], were processed as follows. A complex function having the form of the sum of several exponentials was approximated by one exponential and based on the value of G 1 obtained, the average effective radius of CF, by which we will subsequently mean radius r measured by the method, was determined. Due to improved processing of the intensity in plotting the correlation function, the modern Fotokor correlator can be used to obtain a complex function in undistorted form, and its software can be used to perform an initial analysis of the function obtained for polydispersion by two methods: the method of moments and the Tikhonov regularization method. The regularization method is very complicated and is beyond the scope of the study. We only note that it makes it possible to plot a histogram of the distribution of the scattering particles by size. The method of moments consists of the following. The dependence of the logarithm of the correlation function on time t, which is linear in the case of a monodisperse sample and is curved in the presence of polydispersion, and is distributed in series by degrees of time:

[

]

ln G (τ ) / I 2 − 1 = G2τ + C 2τ 2 + C 3τ 3

(2)

where coefficient G2 for the first degree of time gives an average particle radius r determined from Eq. (1), coefficient C 2 gives information on the width of the particle distribution by size, and coefficient C 3 gives information on the asymmetry of this distribution. The function processing program is available in the software for the Fotokor correlator. The particle radius obtained in this way is basically used in discussing the results of a study. We will call it the average radius of colloidal formations (ARCF).

66

60 I

II

50 R, nm

2 40 30 1 20 10

0.2 0.4 0.6 1

2

4 6 10 20 lnτ (τ, minutes)

40 60100

Fig. 1. Average radius r of CF vs. logarithm of UHF radiation exposure time ln τ for a composition of I-20A base oil with Fenom additive in the concentration: 1) 3.54 wt. %; 2) 5 wt. %; I) region of an increase in the size of CF; II) region of stability of the size of CF. The dependences of the size of CF on the duration of exposure to UHF radiation (Fig. 1) and the sample heating time (Fig. 2) were obtained with the data from the measurements. As Fig. 1 shows, ARCF is also a function of the concentration of SF. We can draw the following conclusions from the data obtained. • Formation and enlargement of CF in additives in lube oils under the effect of UHF radiation were found for the first time by correlation spectroscopy. • Formation and probably further enlargement of associates take place both in holding the solution at high temperature (see Fig. 2) and in treating the solution with UHF radiation (see Fig. 1). The results obtained confirm the hypothesis that when a solution of additives in base oil is treated with UHF radiation, as in heating this solution, the CF in the additives form and enlarge [14, 16], mixing of the additives in the base oil in exposure to a UHF field is almost independent of the initial and final temperatures of the mixed components. • We see from a comparison of the dependences of ARCF on the time of exposure to the UHF radiation for composites with a different concentration of additives (see Fig. 1) that when the concentration increases, the exposure time necessary for formation and growth of CF decreases sharply. For obtaining stable colloidal solutions at a 3.54% concentration of additive, 15 min of exposure to UHF radiation is required, and for a 5% concentration, 5 min is sufficient. Interruption of the time scale means that the sample was held for 12 h at room temperature without exposure to UHF radiation.. The exposure time for each composition with a different concentration of additive should be experimentally evaluated separately. The results obtained show that ARCF is a function of the concentration of additive and stability of the colloidal solutions is attained with the duration of heating and/or exposure to the UHF radiation (segment II in Figs. 1 and 2). In addition, exposure to UHF radiation is preferable, since 15 min is required for obtaining the required CF size in this case, while 20 h is required for heating. Important fluctuations in the scattering intensity with characteristic times of the order of several and even tens of minutes were observed during the measurements. This effect could be due to either the rapid formation of very large (of the order of 200 nm) individual particles which then decomposed into smaller particles, or to nonuniformity of the rate of formation and enlargement of CF over the cuvette volume. The last hypothesis is in agreement with the dependence of the duration of UHF radiation on the sample volume obtained in [16]. 67

220 80

r, nm

60

40

20 I

II

0 4

8.25 14 19 28.538.5 lnτ (τ, h)

Fig. 2. Average radius r of CF vs. logarithm of heating time at 80°C ln τ for composition of I-20A base oil with 3.54 wt. % Fenom additive. See Fig. 1 for designations. This effect can be used in low-tonnage production of commercial petroleum products. Commercial lube oil differs from the initial solution by the presence of stable CF formed [7, 13, 14]. The structure and concentration of these formations are a function of the concentration and composition of the additives, as well as of the oil base [8, 14]. We can hypothesize that an external electromagnetic UHF field will alter the state of the solvation shells of CF and accelerate their coagulation, bringing the commercial product to a stable colloidal state. Formation (structuring) of disperse phase CF in the dispersion medium takes place in uniform distribution of the mixed components in the total volume as a result of heating or exposure to UHF radiation, and this allows obtaining a final product in a stable colloidal state with the necessary properties. • Strong polydispersion of the solutions containing CF was found in the measurements. In addition to particles whose size was close to or larger than the ARCF, the histogram analysis of the measured correlation functions showed (after prolonged accumulation) the presence of 3-15-nm particles characteristic of micelles. This confirms the hypothesis concerning the possible mechanism of formation and enlargement of CF, initially related to formation and then aggregation of micelles of the additive [1]. The impossibility of reliably determining the amount of additive concentrated in the CF also indicates the inhomogeneity of the process. This question is important from the point of view of both manufacture and ensuring the colloidal stability of the oils. The selected improved method of determining ARCF in colloidal solutions with the data from scatteredlight correlation spectroscopy demonstrates the possibility of using additives and their compositions in commercial oils. It also allows assessing the effect of the reaction of the additives on the size of their CF (in the 0.01-100 mm range) and the performance properties of commercial products. This can be used in developing scientific principles for selecting additive compositions for commercial oils to increase their colloidal stability based on optimization of process and formula factors in regulation of intermolecular interactions of SF in low-polarity media. This method can be used in technology for production and use of petroleum products: fuels, lubricants, and industrial fluids. It can also be used in ecology for analysis of disperse pollutants and quality control of manufactured commercial products. 68

REFERENCES 1. G. I. Fuks, Colloid Chemistry of Crude Oil and Petroleum Products [in Russian], Znanie, Moscow (1984). 2.

I. G. Fuks, G. I. Fuks, and G. V. Rakaeva, in: Tribomechanics – Machine Building [in Russian], Mashinostroenie, Moscow (1983), p. 26.

3. 4.

G. I. Fuks, G. V. Rakaeva, V. P. Tikhonov, et al., Koll. Zh., 45, No. 3, 515-519 (1983). G. V. Rakaeva, E. K. Kozlova, S. B. Shibryaev, et al., in: Increasing the Reliability of Lubricated Friction Units in Aviation Engineering Based on Improving the Technology for Using and Unifying Lubricating Materials [in Russian], TsNIITEneftekhim, Moscow (1983), pp. 35-36.

5.

A. A. Chesnokov, O. N. Nikol’skaya, I. G. Fuks, et al., in: Industrial Purity of Working Fluids in Hydraulic Systems and Filtration [in Russian], NATI, Chelyabinsk (1983), pp. 71-72.

6. 7.

G. V. Rakaeva, G. I. Fuks, I. G. Fuks, et al., Khim. Tekhnol. Topl. Masel, No. 7, 35-37 (1984). USSR Inventor’s Certificate No. 1453887.

8. 9.

G. N. Bakakin, G. V. Rakaeva, S. V. Kharitonov, et al., Khim. Tekhnol. Topl. Masel, No. 5, 15-16 (1991). P. A. Rebinder and G. I. Fuks, Advances in Colloid Chemistry [in Russian], Nauka, Moscow (1973), pp. 5-

10.

8. D. H. Everett, Basic Principles of Colloid Science, Royal Society of Chemistry, London (1988).

11. 12.

J. Israelashvili, Intermolecular and Surface Forces, Academic Press, London (1994). P. A. Rebinder, Selected Works. Surface Phenomena in Disperse Systems. Colloid Chemistry [in Russian],

13.

Nauka, Moscow (1979). G. V. Rakaeva, Candidate Dissertation, I. M. Gubkin Moscow Institute of Petrochemistry and Gas Processing,

14.

Moscow (1984). A. M. Kapustin, S. V. Krivokhizha, G. V. Rakaeva, et al., Khim. Tekhnol. Topliv Masel, No. 1, 26-28 (1995).

15. 16.

RF Patent No. 2158175. A. A. Rukhadze, U. Yusupaliev, Yu. M. Egorov, et al., Kratk. Soobshch. Fiz. FIAN, No. 8, 23-26 (2001).

17.

E. Jackman, in: Photon Correlation and Light Beating Spectroscopy, H. Z. Cummins and E. R. Pike (eds.), Plenum, New York and London (1974).

18.

L. L. Chaikov, Trudy Fiz. Inst. Akad. Nauk SSSR, 207, 84-152 (1991).

69

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

ECOLOGY

KINETICS OF CORROSION OF STEEL St3 IN WATER UNSATURATED WITH CALCIUM CARBONATE. EFFECT OF EQUILIBRIUM SOLUBILITY OF IRON HYDROXIDE

V. F. Sorochenko

UDC 543.3.32:620.193.3

The possibility of decreasing the rate of deep penetration of corrosion in St3 steel in Dnepr water unsaturated with calcium carbonate with pH 6.63 was theoretically substantiated and experimentally confirmed. As indicated in [1, 2], in natural and circulating water with pH 8.2-8.4, carbonic acid is in the form of HCO-3 ions. Water is considered aggressive or corrosive if its pH, measured with a pH-meter, is equal to the calculated value of pH s of water saturated with calcium carbonate, or less than this value [3-5]:

pH ≤ pH S

(1)

In such water, the concentration of carbon dioxide is higher than or equal to its equilibrium concentration with calcium carbonate at pH s. The tendency of natural water toward a deposit-free process when used in continuous systems or reuse without intermediate cooling is determined by the difference between pH and pH s , called the stability index I:

I = pH − pH s

(2)

____________________________________________________________________________________________________ National Technical University of Ukraine. Kiev Polytechnic Institute. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 50 – 51, January – February, 2007. 70

0009-3092/07/4301–0070 © 2007 Springer Science+Business Media, Inc.

According to [1], this index can only serve as a qualitative index of the properties of water, which are a function of the presence of carbonic acid. The reliability of determination of these properties by the given method decreases if the circulating water contains alkaline substances. According to other concepts [6, 7] concerning the corrosiveness of water, the corrosion resistance of iron in it almost does not change at pH 4-9. In comparing these views, we can draw a conclusion concerning the “indeterminacy” of the value of the pH in inequality (1). From our point of view, the value of the pH in this inequality can be found by considering the thermodynamic features of formation of solid compounds of iron with oxygen. According to the potential–pH diagram of the iron–water system at 25°C [8], the thermodynamic conditions of formation of a protective layer of iron hydroxide on the surface of iron are found from the solubility product of the latter: 2 SPFe (OH )2 = aOH = 1.8 ⋅10 −15 mole 3 / dm 9 −a Fe 2 + sat

(3)

2+ 2 + are the equilibrium activity of OH and Fe where aOH − , a Fe sat ions, mole/dm 3.

Since

(

)

a Fe 2 + = SPFe (OH )2 / K H2 2O a H2 + sat

(where

K H 2O is the dissociation constant of water at 25°C, equal to 1⋅10 -14 mole 2 /dm6 ; a H + is the equilibrium

3 2 + = 1 mole/dm : activity of H + ions, mole/dm 3), we find from Eq. (3) at a Fe (OH )2 sat = a Fe sat

lg a H + = pH 6.63 Substituting this pH in inequality (1), we obtain:

6.63 ≤ pH ≤ pH S For I £ 0, we find from Eq. (2) and Fig. 1 the boundaries of the high thermodynamic stability of Fe(OH) 2:

6.63 ≤ pH ≤ 8.4

(4)

According to our hypothesis, inequality (4) can be extended to the class of hydrocarbonate feed water (the object investigated) of water cycles (WC) in the presence of free carbonic acid in return water. At pH 7, from Eq. (3) a Fe 2+ =1.8 ⋅ 10 -1 mole/dm 3. As a consequence, the relation r of Fe 2+ ion activities at pH 6.63 and pH 7 (for example) is equal to:

r = a Fe 2+

sat ( pH6.63 )

/ a Fe 2 +

sat ( pH7 )

= 1 / 0.18 = 5.5

(5)

71

100

0.25 1

80

0.2

60

0.15

40

0.1

20

0.05 3

2 0 4

5

6 6.63 7 pH

8 8.4

.

9

CP, mm/year

N, %

4

0

Fig. 1. Molar concentrations N for CO2 (1), HCO3 - (2), CO 32- (3), and rate CP of deep penetration of corrosion in steel St3 (4) as a function of the pH of the water. Iron(II)-hydroxide equilibrium at

a Fe (OH )2 sat = a Fe 2+ = 1 mole/dm 3 corresponds sat

to pH 6.63; the boundary of the equilibrium existence of carbon dioxide in the water corresponds to pH 8.4. Such a thermodynamically substantiated sharp decrease in the equilibrium activity of iron(II) hydroxide ca determine the novelty of the view on the zero-waste environmental increase in the chemical resistance of carbon steel to corrosive processes (object of investigation) in natural water of the hydrocarbonate type in the pH range of 6.63-8.4. The goal of this study was to reveal the high corrosion resistance of carbon steel in water unsaturated with calcium carbonate in the region of the thermodynamic existence of the solid phase of iron hydroxide at pH ≥ 6.63 . The corrosion studies were conducted in Dnepr water with pH 8.05 from Kremenchusk Reservoir, which had the following composition (mg/dm 3): 36.4 Ca 2+; 5.8 Mg2+; 75.2 HCO 3-; 5 Na + + K +; 8.6 SO 42-; 3.1 Cl -. The quality of the water was evaluated with the methods in [9]. The rate of deep penetration of corrosion in samples of steel St3 in aerated unmixed medium at 55±2°C for 20 days (GOST 9.502–82) was determined by mass spectrometry. The hydrogen index was measured with a pH-meter. The given pH values were ensured by adding 0.1 N cp hydrochloric acid to the river water. The effect of the pH of Dnepr water on the rate CP of deep penetration of corrosion in samples of steel St3 is shown in Fig. 2. The maximum values of CP were observed on the first-second and tenth days of the corrosion tests, and the minimum values were observed on the fifth-seventh and twentieth days. When the pH of the river water decreased from 7 to 6.5, 5.5, and 4.5, CP increased from 0.089 to 0.220, 0.186 and 0.197 mm/year, i.e., by 2-2.5 times [7]. This confirms the validity of inequality (4) (see Fig. 1) and the theoretical relation r = 5.5 (5). The same tendency toward a decrease in CP (by 2 and 1.74 times) in going from pH 6.5 to 7 in the presence of 1 mg/dm 3 of natural LST complexone was demonstrated in [10]. Based on the traditional concepts in [8] concerning the solubility of iron hydroxide from the potential–pH diagrams of the iron–water system at 25°C, the well-known concepts in [6, 7] concerning the stabilization of the corrosion resistance of iron in return water at pH 4-9 and simultaneously the concepts concerning

72

0.35

0.30

CP, mm/year

4.5 0.25

0.20 5.5

6.5 0.15

7.0 8.2 0.10 0

5

10 τ, days

15

20

Fig. 2. Rate CP of deep penetration of corrosion in steel St3 in Dnepr water with different pH (see figures on curves) as a function of duration t of test.

the high corrosiveness of return water unsaturated with calcium carbonate at

pH ≤ pH S (8.2 − 8.4) were thus

refined [1-5]. The physicochemical principles of the effect of the equilibrium solubility of iron hydroxide on slowing corrosion of steel St3 in water from the Dnepr River unsaturated with CaCO 3 were elaborated and their extension to WC used at return water pH within the following limits was recommended:

6.63 ≤ pH ≤ pH S (8.2 − 8.4) Use of WC at return water pH of

≤ 6.63 is undesirable due to the increase in the rate of deep penetration of

corrosion in St3 steel by 2-2.5 times. REFERENCES 1. A. F. Shabalin, Return Water Supply of Industrial Enterprises [in Russian], Stroiizdat, Moscow (1972). 2.

A. P. Shut’ko, V. F. Sorochenko, Ya. B. Kozlikovskii, et al., Treatment of Water with Basic Aluminum Chlorides [in Russian], Tekhnika, Kiev (1984).

3. 4.

I. L. Rozenfel’d, Corrosion Inhibitors [in Russian], Khimiya, Moscow (1977). A. P. Askol’zin and A. P. Zhukov, Oxygen Corrosion of Equipment in Chemical Plants [in Russian],

5.

Khimiya, Moscow (1985). SNiP 2.04.02–84, Water Supply. External Mains and Equipment [in Russian], Stroiizdat, Moscow

6.

(1985). L. P. Lyublinskii, What Do We Have to Know about Corrosion? [in Russian], Lenizdat, Leningrad

7.

(1980). M. A. Sukhotin, A. V. Shreider, and Yu. I. Archakov (eds.), Corrosion and Protection of Chemical Equipment [in Russian], Vol. 9, Khimiya, Leningrad (1974). 73

8.

Helmut Kaesche, Korrosion der Metalle—Physikalisch-chemische Prinzipien und aktuelle Probleme, Springer-Verlag, Berlin-Heidelberg-New York (1966).

9.

Methodological Handbook on Analysis of Wastewaters in Oil Refineries and Petrochemical Plants [in Russian], MNKhP SSSR, Moscow (1977).

10.

V. F. Sorochenko, Khim. Tekhnol. Topl. Masel, No. 1, 14-16 (1995).

74

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 1, 2007

REVIEWS

PHYSICOCHEMICAL ASPECTS OF MANUFACTURE OF THREE-PHASE COLLOIDAL FUELS

S. L. Khil’ko and E. V. Titov

UDC 622.75.552.57

The basic physicochemical characteristics of fabrication of three-phase colloidal fuels were analyzed. The effect of the nature and content of solid and liquid phases, type of chemical additives (plasticizers, emulsifiers, and stabilizers), and the basic methods of obtaining three-phase systems from bituminous coals and brown coals were examined. The search for an alternative to traditional liquid fuels is one of the most pressing problems in energetics. In countries experiencing a shortage of fuel and energy resources, the problem of the rational use of energy carriers has become especially acute. Beginning in the 1970s, great attention has been focused on creation of new technologies for man-made liquid fuels based on colloidal systems – suspensions and emulsions – in all developed countries. In 1975, The European Economic Community created a program based on production of synthetic liquid fuels for development of research and industrial studies, proposing replacement of more than 30% of petroleum fuels by man-made fuels [1]. Three-phase colloidal fuels based on finely ground coal, petroleum hydrocarbons, water, and chemical additives can be one alternative type of liquid energy carrier for heat and power plants. The basic physicochemical properties of such fuels are determined by: the nature and concentration of the solid phase; the nature and content of the liquid phase; the type of chemical additives (plasticizers, emulsifiers, and stabilizers); the method of obtaining the three-phase systems. Preparation of colloidal fuels involves solving a wide range of problems in physical chemistry and physicochemical mechanics of disperse systems. As indicated in [2, 3], disperse systems of the solid–liquid type ____________________________________________________________________________________________________ I. M. Litvinenko Institute of Physical Organic Chemistry and Carbon Chemistry. National Academy of Sciences of Ukraine. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, January – February, 2007. 0009-3092/07/4301–0075 © 2007 Springer Science+Business Media, Inc.

pp. 52 – 56,

75

are three-dimensional structures of particles of the solid (disperse) phase. Such structures are characterized by certain mechanical properties, and the most important ones are viscosity, plasticity, elasticity, and strength. These properties are due to reaction of particles of the disperse phase with the liquid dispersion medium and with each other. In contrast to molecular systems, the concept of stability, meaning the constancy of the properties of these systems in time, exists for disperse systems. According to Deryagin, the three kinds of stability of disperse systems differ [4]: • phase – resistance to separation, where a new system with a different concentration of particles capable of coexisting with the initial concentration arises; • aggregate – stability caused by the fact that the forces of interaction between disperse particles are much greater than the intermolecular interactions and are differently dependent on the radius of their effect; in the interaction of disperse particles, aggregates of two, three, and more particles can form (coagulation); • resistance to a change in dispersion, i.e., invariability of the particle distribution by size. Spontaneous adhesion of particles and formation of three-dimensional structures (structure formation) from them through very thin layers of liquid phase is the manifestation of a combination of forces of attraction and repulsion of the particles. Structure formation is primarily determined by the nature of the surface, shape, and size distribution of particles of the solid phase, (granulometric composition), and the nature of the liquid phase, type of chemical additives, etc. The colloidal fuels obtained in the form of disperse systems should satisfy the following requirements [5]: • have a high heat value – the concentration of combustible components in them should be 65-75%; • h a v e a l o w v i s c o s i t y l e v e l ; t h e e f f e c t i v e v i s c o s i t y η ef a t a s h e a r r a t e o f ε ≈ 1 0 s e c - 1 are the most important rheological characteristics – the pumps for pumping fuel in fuel preparation systems and the initial shear stress or dynamic yield point s 0 are usually calculated for this shear rate, and its value determines the yield point of the structural network; these parameters should be within the following limits: ηef = 1-2.5 Pa⋅sec, σ0 = 5-15 Pa; • be sedimentation- and aggregate-stable. Let us consider the basic factors that affect the physicochemical properties of three-phase colloidal fuels. Nature of the solid phase. Solid fuel of different types, primarily energy-producing bituminous coals, is used as the disperse phase in colloidal fuels. Brown coals and peat can also be used. Use of solid residues from processing coal and crude oil, coke, coal tar, shale and coke tars is also known [6]. The surface properties of dispersions of bituminous coals are primarily determined by the degree of metamorphism of the latter. Bituminous coals of different degrees of metamorphism are characterized by a mosaic surface with a defined hydrophilic-hydrophobic balance, i.e., ratio of hydrophilic groups, for example, COOH, CO, OH, NH 2, etc., and hydrophobic fragments [7]. Highly metamorphized coals (grades T, A, TA bituminous coals) are characterized by a low oxygen content in the surface layer. For this reason, on the whole they have a hydrophobic surface, are poorly wet by water, do not form a developed hydrated layer around particles, and the colloidal fuels containing them as the solid phase do not have a pronounced capacity for formation of structural skeletons in the system, i.e., they have some aggregate stability. However, systems with such a solid phase have weak sedimentation stability [8]. The coal particles in low stages of metamorphism (subbituminous coals, grades D, G, DG) are characterized by high surface hydrophilicity‘. For this reason, they have a pronounced ability to form developed hydrate layers around themselves and thus strong structural skeletons in colloidal fuel systems. Such systems are characterized by pronounced sedimentation stability [8, 9].

76

The manifest hydrophilicity of the surface of brown coal and peat particles is due to the high content of oxygen-containing functional groups. In addition, high porosity and the presence of water are characteristic of the surface of these particles, and this creates difficulties in using brown coals and peat as fuel. Nature of the liquid phase. The maximum concentration of combustible components in colloidal fuels can b e a t t a i n e d b y i n c o r p o r a t i n g a t h i r d p h a s e b a s e d o n l i q u i d c o m b u s t i b l e h y d r o c a r b o n s . Wa t e r a n d hydrocarbons are usually the liquid phase. Light and middle distillate crude oil cuts can be used as the hydrocarbons [10, 11]. However, heavy crude cuts – different grades of atmospheric resids [6, 12, 13] or crude oil [6, 14] – are most frequently used. Three versions of the simultaneous existence of a water and oil phase in the system are possible. First, in the form of an emulsion. As a function of the nature of the oil phase, the oil–water phase ratio, the type of chemical additives, and the consumer properties of the fuel, both oil-in-water (drops of oil uniformly distributed in water – O/W) and water-in-oil (drops of water in oil – W/O) emulsions can be obtained. The other two versions of coexistence of the oil phase and water can be obtained by mixing one kind of liquid with a solid phase and formation of a dispersion medium by addition of a second liquid. Nature of chemical additives. Chemical additives in three-phase colloidal fuel systems perform different functions. To obtain systems with sedimentation and aggregate stability and a low viscosity level, they must have pronounced plasticizing, stabilizing, and emulsifying properties. Surfactants (SF) of different types: ionogenic [15], nonionogenic [16], and polymers [17] and inorganic substances [18] can be used to stabilize water-containing coal-oil systems. Using mixtures of different additives, each with its own function, is the most acceptable version for giving three-phase colloidal fuel systems the required properties. Different combinations of chemical additives that give such systems the necessary properties are described in the literature [19]. Ionogenic SF, usually sulfonates, play the role of plasticizing (dispersing, diluting) additives. Nonionogenic SF (polyalkylene oxides, for example) and polymers (polysaccharides, dextrins, gelatin, casein, etc.) fulfill the functions of stabilizers and emulsifiers. Combinations of high- and low-molecular-weight SF are most frequently used in chemical additives. High-molecular-weight SF and polymers can ensure elevated stability for disperse systems by creating a mechanically strong adsorption layer (“colloidal shield”) on the surface of particles [2, 3]. Low-molecular-weight SF can significantly decrease the surface tension between phases and exhibit plasticizing (diluting) properties in disperse systems. U)sing SF with a wide molecular-weight distribution as additives that improve the structural and mechanical properties is a promising direction in solving the problem of fabricating colloidal fuels. High- and low-molecular-weight fractions of SF of the same kind can fulfill different functions in disperse systems. Such substances include some natural SF and products of their modification, for example, lignosulfonates and humates. Industrial lignosulfonates are products of complex transformations for which the initial raw material is wood lignin. They are obtained by dissolving the noncellulose components of wood in production of paper with sulfite technology. Industrial lignosulfonates as products based on natural raw material are distinguished by wide polydispersity, and their molecular weight varies from several hundred to several tens of thousands of units [20]. For this reason, they can perform different functions in disperse systems. The high-molecular-weight fractions of these compounds in coal-based disperse systems exhibit pronounced stabilizing properties, while the low-molecular-weight fractions are effective diluents [21, 22]. Humic acids obtained from brown coals and peat are another type of multifunctional SF. These compounds are also distinguished by wide molecular-weight distribution, which can vary from 4000-8000 to 30,000-40,000 units [23]. Humate additive fractions of different molecular weight can be used in disperse systems for fulfilling different functions. The high-molecular-weight fractions of these compounds can 77

exhibit stabilizing and emulsifying properties, while the low-molecular weight fractions can act as effective plasticizers and dispersants. We have accumulated extensive data on use of native (natural) and modified (sulfonated) humic acid salts as plasticizers for fuel suspensions [24-28], emulsifiers, and stabilizers of fuel emulsions [29, 30], etc. Due to the above, it is evident that use of additives of one kind with a broad spectrum of action is promising in production of three-phase colloidal fuel systems both from process and from economic points of view. Method of fabricating three-phase fuel systems. The physicochemical properties of three-phase colloidal fuels are a function of the method of fabrication (i.e., method of combining three phases) to a significant degree. Different methods are described in the literature. The type of solid fuel is the determining factor for selecting the method, since the surface properties of bituminous and brown coals differ significantly. Bituminous coals. An oil phase based on petroleum refining products is added to bituminous coal suspension fuels to increase the heat value. Adding it to a water–coal suspension (WCS) is most acceptable from a process point of view [31-34]. Water–oil–coal suspensions (WOCS) are obtained in two stages. WCS with plasticizers, emulsifiers, and stabilizers are prepared in the first stage, usually by “wet grinding.” The coal is ground into particles of the required size in aqueous medium together with the chemical additives. With this grinding method, power consumption is much less than in “dry” grinding (Rebinder effect [3]). The concentration of coal in the suspension must be lower than the maximum possible concentration, which allows regulating its rheological parameters on addition of the oil phase. In the second stage, a petroleum component, atmospheric resid, for example, is added to the WCS and stirred intensively until a homogeneous suspension is obtained. Let us consider some drawbacks of this method of obtaining WOCS. Addition of the petroleum component to WCS implies obtaining an emulsion containing some portion of the water from the WCS. Chemical additives previously incorporated in the WCS should regulate the properties of the emulsion. It is impossible to obtain an emulsion of the desired composition with the assigned optimum properties without changing the granulometric composition of the solid phase and properties of the WCS. This is due to the comparability of the energy expended for obtaining the emulsion with the energy required for dispersing the solid phase. Repeated dispersion of the entire system for obtaining the emulsion together with coal previously ground to particles of the required size can lead to overgrinding of the coal and perturbation of the granulometric composition of the solid phase. In addition, the chemical additives previously incorporated in the WCS adsorbed on the surface of the solid phase cannot have the required regulating effect on the properties of the emulsion obtained. As a result, the physicochemical properties of the final product (colloidal fuel based on WOCS) can be inconstant or can vary in time. WOCS without the required stability, i.e., not suitable for storage, can be considered as an alternative fuel if they are used immediately after preparation. Another method of preparing WOCS consists of fabricating an emulsion of the petroleum product, water, and chemical additive followed by incorporation of finely ground coal powder in it [16, 17]. In this case, WOCS are also prepared in two stages. The emulsion is prepared in the first stage. The optimum physicochemical properties, primarily the particle size and stability, are ensured by selecting an appropriate disperser and the type and concentration of the chemical additives (emulsifiers and stabilizers). Finely ground coal powder together with plasticizers are added to the emulsion and mixed until a homogeneous system is obtained in the second stage. In mixing, the size of the particles in the emulsion will not change, since the energy of preparing the emulsion will be much greater than the energy of mixing for blending the mixtures [2, 3].

78

With this method, it is possible to obtain sufficiently stable WOCS with constant physicochemical properties. The colloidal fuel based on such systems can be used in boiler units both immediately after preparation and after storage for some time. We developed this method of fabricating three-phase colloidal systems and investigated their rheological properties. Subbituminous coal from the Donbas with particles with an average size of less than 20 mm was used as the solid phase. The liquid phase was an O/W emulsion of diesel fuel in water with stabilizer additives (sodium sulfohumate) made in an UZDN-A ultrasound disintegrator with treatment with ultrasound with a frequency of 22 kHz for 3 min [30, 35]. These three-component systems remain fluid only at a rigorously determined content c o of oil phase in the emulsion and a given concentration c so of solid phase. Addition of oil phase above the acceptable limit will cause it to aggregate and sharply increase the rheological parameters. As follows from Table 1, when the ratios between solid and oil phases are respected, stable suspensions with industrially acceptable values of the effective viscosity h ef and dynamic yield point σ 0 . It was shown in [30, 35] that production of WOCS from bituminous coals and emulsion liquid phase with optimum physicochemical properties is only possible as a result of compromising on the combination of concentrations of all components of the system. Such a combination can be attained by studying the rheological properties of these systems. The third method of preparation of WOCS consists of combined dispersion of all three phases – coal, petroleum product, and water, with addition of chemical additives [17, 36]. This method is technically the simplest. However, it is impossible to obtain a dispersion with the required solid-phase and emulsion particle size and with the optimum physicochemical properties with this method: the probability of the appearance of different uncontrollable processes, which can cause irreversible coagulation and aggregation, for example, is high, and this negatively affects the properties of the final product. Brown coals and peat. The use of these kinds of raw material involves certain difficulties, primarily caused by their high natural moisture content, which attains 40-60%. Moisture is stably retained in the structure of the coal due to its developed surface and the high content of oxygen-containing groups in its structure that form hydrogen bonds with molecules of water. In addition, brown coals tend to spontaneously ignite, which makes them difficult to store and ship. However, the comparatively low cost (approximately $10 per ton) and large natural reserves of brown coal make the problem of rationally using this kind of hydrocarbon feedstock as fuel very pressing. One possible way of utilizing brown coals in energetics in which these drawbacks are eliminated to a significant degree can be to make a liquid energy carrier from them – WOCS. Several methods of fabricating a suspension fuel based on brown coals and peat are described in the literature. One of them consists of grinding brown coal (or peat) with a high natural moisture content with addition of a small amount of water to obtain WCS followed by addition of the petroleum product and homogenization of the entire mixture [37-39]. This method differs little from the method of obtaining WOCS from bituminous coals examined above. Table 1

cso, wt. %

co, vol. %

50

30

ηef at ε = 9 sec-1, Pa⋅sec 0.84

55

20

60

10

σ0, Pa

Stability, days

7.98

>30

1.02

10.96

>30

1.32

15.56

>30

79

Table 2

cso, wt. %

ηef at ε = 9 sec-1, Pa⋅sec

σ0, Pa

r

43.5

0.24

1.87

0.991

46

0.43

3.51

0.997

48

0.86

5.14

0.998

49

1.42

10.91

0.997

50

2.19

15.79

0.996

According to another method, brown coal or peat is first dried and then a suspension fuel is made from it. Different methods are used to reduce the natural moisture content of brown coals. One of several methods widely used in heat and power engineering is to dry the coal at a low temperature (100-160°C) in an atmosphere of waste stack gases with simultaneous grinding to obtain a dispersion for powder combustion. The residual moisture content of the product obtained is 10-20% (“cake”) [40, 41]. There are technologies for more exhaustive treatment of brown coal, for example, Hot Water Drying (HWD) [42] and its analogs [43-46]. Exhaustive drying is conducted in closed vessels in conditions of high temperatures (240-400°C) and pressures of the liberated gases. In addition to elimination of water, carboxyl groups decompose with liberation of carbon dioxide from the structure of the coal and resinous substances and oils. These components are strongly retained on the surface of the coal in micropores and make it hydrophobic. After such treatment, brown coal becomes similar to bituminous coals in the character of the surface and heat value and suitable for manufacturing suspension fuel. The essence of our method of obtaining WOCS from brown coal [28, 47, 48] consists of increasing the degree of surface hydrophoby by blocking some of the oxygen-containing surface groups in application of liquid hydrocarbons (diesel fuel, GOST 1667–68) to the surface of the solid hydrocarbons and subsequent addition of an aqueous solution of a chemical additive – sodium sulfohumate. The mixture is mixed with a mechanical stirrer in the intensively turbulent mode (rotation rate of 1500 min -1). Brown coal (“cake”) from the Aleksandriisk deposit (Ukraine) prepared for powder combustion at Aleksandriisk TEPP-3 was used for fabricating the suspensions. Addition of petroleum hydrocarbons to the fuel composition increases its heat value. This method also allows increasing the degree of hydrophoby of brown coal powder as a result of addition of oil phase and attaining the surface hydrophilic-hydrophobic balance required for formation of coagulation structures in the suspensions. Optimizing their composition, i.e., searching for the ratios of components at which the physicochemical ratios of components best satisfy the process requirements, is an important stage in preparation of industrial suspensions. Production of WOCS includes determination of the region of optimum concentrations of the chemical additive, oil, and solid phases. In addition, a search is conducted for the granulometric composition of the disperse phase at which the best rheological parameters of the suspensions are attained. The regions of optimum concentrations of each component were determined as a result of studying the rheological properties of WOCS in subsequent variation of the concentration of each of the three components [28]. The rheological characteristics of brown-coal WOCS as a function of the concentration c so of solid phase at the optimum concentrations of the suspension found (9% oil phase, 0.275% sodium sulfohumate) and the optimum granulometric composition of the solid phase: maximum average particle size of 80 mm, are reported in Table 2. The effectiveness of the plasticizing effect of chemical additives in suspension fuels was evaluated based on the ability of the SF to ensure viscoplastic flow of the suspension [26]. The values of correlation coefficient

80

r in the equation of viscoplastic flow: σ = σ 0 + η efε, are reported in Table 2. The high values indicate the correspondence of the chemical additive used – sodium sulfohumate – to the effectiveness criterion. There are published examples of preparation of suspensions from soft brown coals previously treated by HWD or similar technologies that attain an approximately 60% concentration of combustible components in the system. The suspensions contain SF that improve their stability and fluidity [42-46]. Using the proposed method of obtaining a suspension and sodium sulfohumate as chemical additive, concentrations of solid phase (in terms of dry combustible mass) equal to 50 wt. % and rheological parameters that satisfy the requirements of the technology can be attained: η ef = 2.19 Pa⋅sec; σ = 15.8 Pa; sedimentation stability for more than 30 days; resistance to formation of aggregates. The total combustible hydrocarbon content – coal and oil phase – reaches 59%. One possible method of preparing three-phase colloidal fuels from brown coals can thus be to modify their hydrophilic and highly porous surface by incorporating an oil phase with addition of sodium sulfohumate (SF) as a regulator of the rheological properties of the suspension. A fuel system can be obtained with industrially acceptable physicochemical parameters and a concentration of combustible components of the same order as in using HWD and analogous technologies, but with much lower power consumption for exhaustive drying of wet brown coals. In conclusion, we note that the problem of preparing colloidal types of fuel is solved individually and often empirically in each concrete case. The properties of such fuels can be predicted and regulated only by knowing the mechanisms of physicochemical processes in heterogeneous systems. REFERENCES 1. A. L. Lapidus and A. Yu. Krylov, Coal and Natural Gas – Sources for Production of Man-made 2.

Liquid Fuel and Chemical Products [in Russian], Znanie, Moscow (1986). Yu. G. Frolov, Course in Colloid Chemistry. Surface Phenomena and Disperse Systems [in Russian],

3.

Khimiya, Moscow (1982). P. A. Rebinder, Surface Phenomena in Disperse Systems. Physicochemical Mechanics. Selected

4.

Works [in Russian], Khimiya, Moscow (1979). V. N. Deryagin, Usp. Khim., No. 4, 675-721 (1979).

5.

N. B. Ur’ev, Physicochemical Principles of the Technology of Disperse Systems and Materials [in Russian], Khimiya, Moscow (1988).

6. 7.

USA Patent No. 4560391. I. A. Tarkovskaya, Oxidized Coal [in Russian], Naukova Dumka, Kiev (1981).

8. 9.

I. K. Srymanaki and N. A. Mansour, Fuel Sci. Technol. Int., 5, No. 1, 63-76 (1987). S. Watanabe and K. Katabe, in: 6 th Int. Symp. Coal Slurr. Combust. Technol., Pittsburgh (1984),

10.

pp. 467-478. J. Dooher, R. Genberg, R. Lippman, et al., Mech. Eng., 98, No. 11, 36-41 (1976).

11. 12.

L. Bartha, N. Nemes, N. Kriko, et al., Hung. J. Ind. Chem., 16, No. 4, 407-417 (1988). H. Terada, F. Koda, and T. Hishinuma, Inst. Chem. Eng. Symp. Ser., No. 95, 413-426 (1985).

13. 14.

P. Fournier, J. Bertrand, and J. P. Couduc, Chem. Eng. J., 31, No. 3, 175-185 (19850. Japanese Patent Application No. 53-16007.

15. 16.

Japanese Patent Application No. 53-50202 and 53-82811. US Patent No. 4130401.

17. 18.

US Patent Nos. 4153421 and 4744797. US Patent No. 4670019 and GDR Patent No. 232837.

19.

US Patents Nos. 4162143, 4171957, and 4713086. 81

20. 21.

M. I. Chudakov, Industrial Use of Lignin [in Russian], Lesnaya Promyshlennost’, Moscow (1983). V. V. Vasil’ev, T. D. Degtyarenko, V. Yu. Tretinnik, et al., Khim. Tverd. Topl., No. 2, 123-127 (1988).

22. 23.

A. S. Makarov, E. P. Olofinskii, and T. D. Degtyarenko, Vestn. Akad. Nauk USSR, No. 2, 66-75 (1989). I. I. Lishtvan, N. N. Kruglitskii, and V. Yu. Tretinnik, Physicochemical Mechanics of Humic Substances

24.

[in Russian], Nauka i Tekhnika, Minsk (1975). USSR Inventor’s Certificate No. 1829390.

25. 26.

Ukraine Patent No. 5583. S. L. Khil’ko, E. V. Titov, A. F. Popov, et al., Khim. Promyshl. Ukr., No. 4 (33), 7-10 (1999).

27. 28.

S. L. Khil’ko, E. V. Titov, A. F. Popov, et al., Khim. Promyshl. Ukr., No. 4 (33), 7-10 (1999). S. L. Khil’ko and E. V. Titov, Khim. Tverd. Topl., No. 1, 78-87 (2001).

29. 30.

S. L. Khil’ko and E. V. Titov, Zh. Prikl. Khim., No. 8, 1383-1386 (2000). S. L. Khil’ko and E. V. Titov, Neft. Gaz. Promyshl. (Kiev), No. 2, 56-59 (2001).

31. 32.

French Patent Application No. 2363621. F. Pascale, Doctoral Thesis, Ing. Inst. Nat. Polytechn., Toulouse (1985).

33.

K. Fu, D. Guo, and L. Yang, in: Coal Utilization & Fuel Systems, 21 st Int. Technic. Conf., Marth, Clearwater (1996), p. 259.

34. 35.

French Patent Application No. 2595711. S. L. Khil’ko and E. V. Titov, in: Vibrotechnology-2003 Scientific Works [in Russian], NPO BOTUM,

36.

Odessa (2003), pp. 89-90. US Patent No. 4780110.

37. 38.

Japanese Patent Application No. 57-195797. Japanese Patent Application No. 54-68804.

39. 40.

V. I. Ugursal and G. D. Mackay, Int. J. Energy Res., 15, 637-652 (1991). D. Böcker and H. Krensing, Braunkohle, 34, No. 1, 1-5 (1982).

41. 42.

K. Hamerak, Techn. Heute, No. 7, 16-25 (1980). Andrew Gaved, World Coal, No. 2, 19-28 (1995).

43. 44.

J. Kempe and M. Herzog, Erdol Köhle-Erdgas-Petrochem., 45, No. 12, 472-474 (1992). Austrian Patent No. 366405.

45. 46.

E. G. Gorlov, G. S. Golovin, and O. V. Zotova, Khim. Tverd. Topl., No. 6, 117-125 (1994). G. N. Delyagin, E. I. Rukin, and T. P. Gorskaya, Ibid., No. 4, 133-136 (1977).

47. 48.

Ukraine Patent No. 35787. S. L. Khil’ko and E. V. Titov, in: Anthology of Studies on Industrial Chemistry [in Russian], Ministerstvo Promyshlennosti Ukrainy, Kiev (1997), pp. 258-261.

82

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

No title

Recommend Documents