Научная статья на тему 'EXPERIMENTAL RESEARCH OF THE SURFACE TENSION OF PETROLEUM PRODUCTS IN A WIDE TEMPERATURE RANGE'

EXPERIMENTAL RESEARCH OF THE SURFACE TENSION OF PETROLEUM PRODUCTS IN A WIDE TEMPERATURE RANGE Текст научной статьи по специальности «Электротехника, электронная техника, информационные технологии»

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Ключевые слова
PETROLEUM PRODUCTS / CAPILLARY CONSTANT / SURFACE TENSION / PSEUDOCRITICAL TEMPERATURE / SURFACE ENERGY

Аннотация научной статьи по электротехнике, электронной технике, информационным технологиям, автор научной работы — Nemzer B.V., Malofeev V.A., Grigoryev B.A.

This article presents the results of an experimental research of the surface tension σ of fractions of the Mangyshlak (Uzen oil field) and Samotlor oils obtained earlier in the Industrial Thermal Physics Laboratory of the Grozny Oil Institute. For measurements, a differential method of capillary rise was used with five calibrated glass capillaries of various diameters, the inhomogeneity of the inner diameter of which did not exceed 0,04 % of the average value. The temperature of the measuring cell was maintained with an accuracy of ±0,02 K and was measured with reference-grade platinum resistance thermometer PTS-10. Visual observation of the level of meniscus fluid in the capillaries was carried out using a KM-6 cathetometer. The maximum error in measuring the capillary constant in the specified temperature range was 0,5 %. The total error of an individual measurement of σ, depending on the value of the reduced temperature, varied from 0,5…0,8 % in the range of 233…423 K to 1,0…1,2 % in the range of 423…573 K.The article presents the experimental values of the capillary constant and surface tension of the investigated fractions of the Mangyshlak and Samotlor oils as well as their smoothed values. The data obtained allowed to describe the surface tension of the investigated petroleum products, depending on their physicochemical characteristics, by various approximation equations with a sufficient degree of accuracy. The specific excess entropies and energies of the surface layer were also calculated for the fractions of Samotlor oil.A generalized dependence has been obtained using the theory of corresponding states, which gives the opportunity to calculate with high accuracy the surface tension of fractions of Mangyshlak oil in the entire investigated temperature range. The possibility of using the van der Waals equation with a constant exponent is shown to describe the temperature dependence of the surface tension of the Mangyshlak oil fractions.

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Текст научной работы на тему «EXPERIMENTAL RESEARCH OF THE SURFACE TENSION OF PETROLEUM PRODUCTS IN A WIDE TEMPERATURE RANGE»

UDC [553.981+553.982]:532.612

Experimental research of the surface tension of petroleum products in a wide temperature range

B.V. Nemzer1*, V.A. Malofeev2, B.A. Grigoryev3

1 University of Illinois at Urbana-Champaign, Bld. 52, East Gregory Drive, Champaign, IL 61820, Illinois, United States

2 Grozny State Oil Technical University, Bld. 100, Isaeva av., Grozny, 364024, Russian Federation

3 Gazprom VNIIGAZ LLC, Bld. 1, Estate 15, Proyektiruemyy proezd no. 5537, Razvilka village, Leninskiy urban district, Moscow Region, 142717, Russian Federation

* E-mail: bnemzer@futureceuticals.com

Abstract. This article presents the results of an experimental research of the surface tension c of fractions of the Mangyshlak (Uzen oil field) and Samotlor oils obtained earlier in the Industrial Thermal Physics Laboratory of the Grozny Oil Institute. For measurements, a differential method of capillary rise was used with five calibrated glass capillaries of various diameters, the inhomogeneity of the inner diameter of which did not exceed 0,04 % of the average value. The temperature of the measuring cell was maintained with an accuracy of ±0,02 K and was measured with reference-grade platinum resistance thermometer PTS-10. Visual observation of the level of meniscus fluid in the capillaries was carried out using a KM-6 cathetometer. The maximum error in measuring the capillary constant in the specified temperature range was 0,5 %. The total error of an individual measurement of c, depending on the value of the reduced temperature, varied from 0,5...0,8 % in the range of 233.. .423 K to 1,0.. .1,2 % in the range of 423.. .573 K.

The article presents the experimental values of the capillary constant and surface tension of the investigated fractions of the Mangyshlak and Samotlor oils as well as their smoothed values. The data obtained allowed to describe the surface tension of the investigated petroleum products, depending on their physicochemical characteristics, by various approximation equations with a sufficient degree of accuracy. The specific excess entropies and energies of the surface layer were also calculated for the fractions of Samotlor oil.

A generalized dependence has been obtained using the theory of corresponding states, which gives the opportunity to calculate with high accuracy the surface tension of fractions of Mangyshlak oil in the entire investigated temperature range. The possibility of using the van der Waals equation with a constant exponent is shown to describe the temperature dependence of the surface tension of the Mangyshlak oil fractions.

Keywords:

petroleum products, capillary constant, surface tension, pseudocritical temperature, surface energy.

Experimental data on the surface tension c of petroleum products are scarce and scattered. In the Industrial Thermal Physics Laboratory of the Grozny Oil Institute, this property has been intensively studied in the last years of its existence. This article presents the experimental data on c for fractions of two oils - Mangyshlak (Uzen oil field, 13 fractions) and Samotlor (12 fractions).

Experiment

To measure the surface tension, researchers used a differential method of capillary rise with five calibrated glass capillaries of various diameters, the inhomogeneity of the inner diameter of which did not exceed 0,04 % of the average value. Thermostating of the measuring cell was carried out with an accuracy of ±0,02 °C, the temperature was measured with reference-grade platinum resistance thermometer PTS-10. Visual observation of the level of meniscus fluid in the capillaries was carried out using a KM-6 cathetometer. A detailed description of the experimental apparatus and the experimental method is given earlier [1-3]. The maximum error in measuring the capillary constant a2 in the specified temperature range was 0,5 %.

Results and discussion

Table 1 shows the experimental values of the capillary constant a2 of the investigated fractions of Mangyshlak oil.

Table 1

Experimental values of the capillary constant for the Mangyshlak oil fractions:

T - temperature; IBP - initial boiling point

T, K a2, mm2 T, K a2, mm2 T, K a2, mm2 T, K a2, mm2

Fraction: IBP...335 K

241,35 6,849 294,33 5,468 372,98 3,426 417,69 2,169

256,11 6,458 305,49 5,181 381,34 3,202 431,42 1,754

263,49 6,266 324,72 4,689 393,03 2,878 438,12 1,545

282,05 5,784 359,14 3,795 408,51 2,438 440,23 1,479

Fraction: 335.358 K

239,12 7,091 283,41 6,051 342,53 4,700 426,55 2,702

247,34 6,894 297,64 5,724 369,01 4,092 448,48 2,129

261,74 6,554 314,96 5,328 382,16 3,784 473,03 1,874

269,15 6,381 329,83 4,990 397,67 3,415 492,84 1,513

Fraction: 358.378 K

243,16 6,348 317,36 4,904 389,32 3,529 468,54 1,876

264,17 5,930 342,41 4,428 397,76 3,363 481,11 1,584

281,94 5,583 349,54 4,293 425,69 2,801 499,03 1,152

297,04 5,292 371,84 3,867 461,71 2,030 506,42 1,014

Fraction: IBP...453 K

233,17 7,846 299,87 6,373 399,61 4,251 481,97 2,346

249,32 7,480 324,62 5,845 414,57 3,924 501,44 1,942

261,05 7,219 338,16 5,559 443,81 3,265 536,18 1,247

273,18 6,951 365,21 4,967 468,02 2,691 541,23 1,130

294,47 6,489 388,33 4,494 - - - -

Fraction: 453.513 K

251,03 7,417 343,18 5,851 432,76 4,412 539,32 2,557

284,47 6,838 369,19 5,439 466,29 3,859 552,84 2,295

298,61 6,599 387,51 5,144 481,54 3,599 571,27 1,921

316,84 6,294 396,48 4,999 513,64 3,035 - -

Fraction: 453.463 K

251,03 7,460 338,43 5,965 419,71 4,635 489,11 3,462

279,18 6,966 352,18 5,783 431,54 4,440 501,43 3,243

292,33 6,740 372,94 5,399 458,16 3,995 533,49 2,648

307,45 6,483 398,06 4,989 471,03 3,776 558,67 2,150

316,52 6,330 — - - - - -

Fraction: 463.473 K

253,06 7,423 356,73 5,704 450,98 4,200 506,88 3,262

278,21 6,992 389,19 5,187 469,74 3,892 533,49 2,786

296,35 6,685 396,02 5,079 482,24 3,684 554,01 2,474

323,48 6,241 411,53 4,832 - - - -

Fraction: 473.483 K

264,02 7,279 339,65 6,071 441,15 4,516 506,31 3,486

278,19 7,047 361,54 5,732 478,68 3,931 527,49 3,131

293,33 6,802 392,19 5,264 491,52 3,726 561,82 2,525

308,71 6,557 422,28 4,805 - - - -

Fraction: 483.493 K

261,04 7,352 341,72 6,079 456,17 4,350 516,84 3,393

283,29 6,992 374,64 5,579 481,19 3,964 541,08 2,986

301,02 6,711 391,02 5,333 498,71 3,687 571,35 2,447

334,58 6,188 418,96 4,913 - - - -

Fraction: 493.503 K

256,14 7,456 345,64 6,036 443,51 4,554 539,41 3,024

274,52 7,092 379,19 5,525 469,28 4,159 561,07 2,645

291,66 6,879 392,58 5,263 492,19 3,800 572,19 2,444

313,98 6,526 421,08 4,894 514,74 3,436 - -

T, K a2, mm2 T, K a2, mm2 T, K a2, mm2 T, K a2, mm2

Fraction: 503...513 K

271,15 7,349 349,50 6,140 441,88 4,774 530,11 3,428

298,02 6,926 372,23 5,801 472,39 4,320 542,26 3,231

313,27 6,690 396,82 5,437 486,16 4,113 569,38 2,774

336,31 6,339 420,01 5,096 502,76 3,858 - -

Fraction: 513.553 K

276,30 7,291 319,47 6,580 418,02 5,027 519,03 3,391

284,46 7,155 342,88 6,205 439,13 4,696 548,21 2,878

301,48 6,873 381,93 5,590 468,91 4,222 574,01 2,398

306,51 6,791 395,16 5,384 489,14 3,893 - -

Fraction: 553.623 K

286,42 7,418 378,54 6,017 472,14 4,640 539,18 3,612

292,15 7,328 396,04 5,759 498,09 4,251 552,38 3,400

319,47 6,905 428,16 5,288 518,33 3,940 568,19 3,138

351,62 6,417 449,39 4,976 - - - -

Table 2

Coefficients of polynomial (1) for fractions of Mangyshlak oil

Fraction, K Л A1 Л A3 A4

IBP...335 14,130 -3,17471 -0,1117044 0,11271 -0,016311

335...358 13,50899 -2,799332 -0,09387484 0,088412 -0,012145

358...378 11,85931 -2,390906 -0,05709409 0,066587 -0,0090818

IBP...453 13,86255 -2,759420 -0,02043892 0,0618707 -0,0086532

453...513 12,29015 -2,007506 -0,05203901 0,043915 -0,0050604

453...463 12,47002 -2,115565 -0,02037927 0,039308 -0,0048448

463...473 12,23759 -1,948442 -0,06248407 0,044404 -0,0049632

473...483 11,96786 -1,752123 -0,1001859 0,0473515 -0,0048522

483...493 12,00088 -1,80538 -0,06873992 0,0414904 -0,0044415

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493...503 12,13129 -1,904066 -0,03340284 0,035366 -0,0040344

503...513 11,97810 -1,674636 -0,09831159 0,043439 -0,0042819

513...553 12,72956 -2,233720 0,06315853 0,020954 -0,0032737

553...623 12,40805 -1,800719 -0,04681912 0,03362 -0,0035441

The experimental a2 values for the investigated fractions of Mangyshlak oil were approximated by the polynomial:

=Z Л

Y 100 J

(1)

T - T

PC_

T - 293,15

V pc ' y

by Eq. (2), relative to the experimental ones, was 0,4 %.

Experimental data on surface tension for the investigated fractions were approximated in the form of the equation:

( T T ^^

The obtained approximation coefficients for each fraction are shown in table 2.

Experimental data on the capillary constant of the Samotlor oil fractions are described by the equation

о = o„

T - T

pc

T - 293,15

pc ' /

(3)

(2)

where a2293 is the capillary constant at 293,15 K; Tpc is the pseudocritical temperature, the value of which was calculated by the method of Riazi [4]; n is the individual exponent for each fraction.

The maximum magnitude of the root-mean-square error (RMSE) of a2 values calculated

where ct293 is the surface tension at 293 K; ^ is the exponent individually defined for each fraction of Samotlor oil. For the fractions of Mangyshlak oil a universal indicator ^ = 1,19 was determined, at which the maximum deviation of the calculated values from the experimental ones did not exceed 1,26 %.

To calculate ct293, a two-parameter correlation was proposed [5]:

= 16,83(p^)M77 M0

(4)

n=0

where p2^ is the relative density, M is the molecular mass. The RMSE in calculations using formula (4) was 1,65 %.

Table 3 shows the physicochemical properties (refractive index nf3 and boiling point Tb) and the values of constants a22g3, a2g3, Tpc, n and ^ in equations (2) and (3) for the fractions of Samotlor oil. For these fractions, the values of the specific excess entropy (Ss) and the surface layer energy (Us) were also calculated:

S. =-

do.

dT'

TT T do

Us = a - T—. s dT

Table 4 shows the smoothed values of a2, c, S and U .

Analysis of the experimental data on a2 and c showed that there were certain two-parameter dependences between the values of a\g3 and a2g3 of the investigated fractions of Samotlor oil and their different physicochemical characteristics:

c293 = a Q-x$(bX1 + cX2 + dXl X2) X"X{.

(7)

(5)

(6)

The coefficients of equation (7) and the RMSEs (S„ ) for the calculated a2g3 values vs the experimental ones are given in table 5.

As can be seen from table 5, the smallest RMSEs are given by calculations using the boiling point (Tb) and relative density (p^), as well as the two-parameter dependence are given by calculations using molecular mass (M) and relative density (p^).

s s'

Table 3

Physicochemical properties and the constants in equations (2) and (3) for Samotlor oil fractions

Fraction, K Tb, K n 293 "d P273, kg/m3 M a293'106, m2 a293 1 03, N/m Tpc- K n Ц

393...403 298,15 1,4125 745,5 108,8 6,262 22,92 579,1 0,9279 1,229

403...413 408,15 1,4295 764,8 112,6 6,314 23,68 596,2 0,9344 1,235

423...433 428,15 1,4370 780,4 131,4 6,388 24,44 623,0 0,8973 1,197

433...443 438,15 1,4385 782,1 136,5 6,414 24,59 631,3 0,9222 1,222

443...453 448,15 1,4435 791,0 138,1 6,499 25,20 639,8 0,9131 1,213

453...463 458,15 1,4450 793,7 141,6 6,530 25,41 646,7 0,9232 1,233

463...473 468,15 1,4540 811,2 151,9 6,766 26,90 663,5 0,9408 1,240

473...483 478,15 1,4525 809,0 148,8 6,740 26,73 663,6 0,9297 1,229

493...503 498,15 1,4635 828,1 172,0 7,070 23,70 693,2 0,9285 1,228

513...523 518,15 1,4675 834,9 190,6 7,207 29,49 713,7 0,9513 1,251

523...533 528,15 1,4700 838,2 196,0 7,231 29,91 721,7 0,9406 1,241

533...543 538,15 1,4725 842,3 201,0 7,374 30,44 729,7 0,9564 1,256

Table 4

Smoothed values of the capillary constant, surface tension, specific excess entropy and surface layer energy for Samotlor oil fractions

T, K a2103, m2 a-103, N/m S/103, N/(mK) Us-103, N/m T, K a2103, m2 a-103, N/m Ss 103, N/(mK) Us-103, N/m

Fraction, K: 293.303

233,15 7,481 23,96 0,1029 52,97 373,15 4,623 15,31 0,09139 49,41

253,15 7,079 26,92 0,1015 52,63 393,15 4,205 13,50 0,08927 48,60

273,15 6,675 24,90 0,1001 52,24 413,15 3,784 11,74 0,08697 47,67

293,15 6,269 22,92 0,09854 51,81 433,15 3,359 10,02 0,08445 46,60

313,15 5,861 20,96 0,09692 51,31 453,15 2,920 8,362 0,03164 45,35

333,15 5,451 19,04 0,09519 50,75 473,15 2,495 6,760 0,07846 43,86

353,15 5,038 17,15 0,09336 50,12 - - - - -

Fraction, K: 403.413

233,15 7,475 29,59 0,1006 53,07 373,15 4,741 16,21 0,08979 49,72

253,15 7,089 27,59 0,09935 52,74 393,15 4,343 14,43 0,08783 48,96

273,15 6,702 25,62 0,09796 52,33 413,15 3,942 12,70 0,08571 48,11

293,15 6,314 23,67 0,09650 51,95 433,15 3,538 11,01 0,08341 47,14

т, к а2-103, т2 а-103, Мт ^■103, Щт-К) Ц/103, Мт Т, К а2103, т2 а-103, Мт ^ 103, Щт-К) Ц.-103, Мт

313,15 5,923 21,76 0,09496 51,50 453,15 3,130 9,368 0,08088 46,02

333,15 5,531 19,87 0,09334 50,57 473,15 2,719 7,778 0,07807 44,71

353,15 5,137 18,03 0,09162 50,38 - - - - -

Fractюn, К: 423.433

233,15 7,421 29,85 0,09168 51,23 373,15 4,978 17,52 0,08398 48,86

253,15 7,079 28,03 0,0974 51,00 393,15 4,619 15,86 0,08261 48,34

273,15 6,734 26,22 0,08975 50,74 413,15 4,257 14,22 0,08114 47,74

293,15 6,388 24,44 0,08871 50,44 433,15 3,891 12,61 0,07955 47,07

313,15 6,039 22,67 0,08762 50,11 453,15 3,521 11,04 0,07782 46,30

333,15 5,688 20,93 0,08643 49,74 473,15 3,147 9,503 0,07592 45,42

353,15 5,335 19,21 0,08527 49,33 - - - - -

Fractюn, К: 433.443

233,15 7,456 30,02 0,09216 51,51 373,15 5,000 17,68 0,08370 48,91

253,15 7,110 28,19 0,09111 51,25 393,15 4,462 16,02 0,08222 48,34

273,15 6,763 26,38 0,09001 50,97 413,15 4,281 14,39 0,08063 47,70

293,15 6,414 24,59 0,08887 50,64 433,15 3,918 12,79 0,07893 46,98

313,15 6,063 22,32 0,08768 50,23 453,15 3,551 11,23 0,07708 46,17

333,15 5,711 21,08 0,08642 49,87 473,15 3,182 9,716 0,07507 45,23

353,15 5,356 19,37 0,08510 49,42 - - - - -

Fractюn, К: 443.453

233,15 7,513 30,58 0,09122 51,85 373,15 5,114 18,33 0,08338 49,44

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253,15 7,180 28,76 0,09024 51,61 393,15 4,762 16,67 0,08201 48,92

273,15 6,840 26,97 0,08923 51,34 413,15 4,408 15,05 0,08054 48,33

293,15 6,498 25,20 0,08817 51,04 433,15 4,052 13,45 0,07897 47,66

313,15 6,155 23,44 0,08706 50,71 453,15 3,692 11,89 0,07728 46,91

333,15 5,810 21,71 0,08590 50,33 473,15 3,329 10,36 0,07544 46,06

353,15 5,463 20,01 0,08467 49,91 - - - - -

Fractюn, К: 453.463

233,15 7,547 30,77 0,09100 51,99 373,15 5,153 18,56 0,08299 49,53

253,15 7,209 23,96 0,09000 51,75 393,15 4,804 16,72 0,08160 49,00

273,15 6,870 27,17 0,08896 51,47 413,15 4,453 15,30 0,08012 48,40

293,15 6,530 25,40 0,08788 51,17 433,15 4,100 13,71 0,07854 47,73

313,15 6,188 23,66 0,08674 50,82 453,15 3,744 12,16 0,07683 46,98

333,15 5,845 21,93 0,08656 50,44 473,15 3,385 10,64 0,07499 46,12

353,15 5,500 20,23 0,08431 50,01 - - - - -

Fractюn, К: 463.473

243,15 7,622 31,48 0,09291 54,07 373,15 5,381 19,89 0,08499 51,61

253,15 7,280 29,63 0,09182 53,79 393,15 5,031 18,20 0,08355 51,05

273,15 7,109 28,71 0,09126 53,64 413,15 4,680 16,55 0,08202 50,43

293,15 6,765 26,90 0,09012 53,32 433,15 4,328 14,72 0,08039 49,75

313,15 6,421 25,11 0,08892 52,96 453,15 3,973 13,33 0,07865 48,98

333,15 6,076 23,34 0,08767 52,55 473,15 3,617 11,78 0,07678 48,11

353,15 5,729 21,60 0,08637 52,10 - - - - -

Fractюn, К: 473.483

253,15 7,410 30,29 0,09030 53,15 373,15 5,383 19,85 0,08345 50,99

273,15 7,076 28,50 0,08927 52,89 393,15 5,040 18,20 0,08211 50,45

293,15 6,740 26,72 0,08821 52,58 413,15 4,695 16,57 0,08069 49,90

313,15 6,403 24,97 0,08710 52,25 433,15 4,348 14,97 0,07917 49,26

333,15 6,064 23,24 0,08594 51,87 453,15 3,999 13,40 0,07756 48,55

353,15 5,724 21,53 0,08473 51,46 473,15 3,648 11,87 0,07582 47,74

Fractюn, К: 493.503

253,15 7,723 32,25 0,09005 55,05 373,15 5,746 21,81 0,08373 53,06

273,15 7,397 30,46 0,08910 54,80 393,15 5,412 20,15 0,08251 52,59

293,15 7,069 28,69 0,08811 54,52 413,15 5,076 18,51 0,08122 52,07

313,15 6,740 26,94 0,08708 54,21 433,15 4,739 16,90 0,07985 51,49

333,15 6,410 25,21 0,08601 53,87 453,15 4,399 15,32 0,07841 50,85

T, K a2103, m2 a-103, N/m Ss-103, N/(mK) ^■103, N/m T, K a2103, m2 a-103, N/m Ss 103, N/(mK) LV103, N/m

353,15 6,079 23,50 0,08490 53,48 473,15 4,058 13,76 0,07686 50,14

Fraction, K: 513.523

263,15 7,695 32,14 0,08928 55,64 373,15 5,896 22,64 0,08321 53,70

273,15 7,532 31,25 0,08878 55,50 393,15 5,566 20,99 0,08196 53,21

293,15 7,207 29,49 0,08775 55,2 413,15 5,235 19,36 0,08064 52,68

313,15 6,880 27,74 0,08668 54,89 433,15 4,903 17,77 0,07926 52,10

333,15 6,553 26,02 0,08557 54,53 453,15 4,570 16,19 0,07780 51,45

353,15 6,225 24,32 0,08442 54,13 473,15 4,236 14,65 0,07625 50,74

Fraction, K: 523.533

273,15 7,600 31,65 0,08754 55,56 393,15 5,670 21,51 0,08122 53,44

293,15 7,281 29,91 0,08658 55,29 413,15 5,345 19,89 0,08000 52,95

313,15 6,960 28,18 0,08559 54,99 433,15 5,018 18,31 0,07872 52,41

333,15 6,639 26,48 0,08456 54,66 453,15 4,691 16,74 0,07737 51,81

353,15 6,317 24,80 0,08350 54,29 473,15 4,361 15,21 0,07594 51,15

373,15 5,994 23,14 0,08238 53,88 - - - - -

Fraction, K: 533.543

273,15 7,696 32,20 0,08862 56,40 393,15 5,749 21,93 0,08195 54,17

293,15 7,374 30,43 0,08760 56,12 413,15 5,422 20,32 0,08067 53,65

313,15 7,050 28,69 0,08656 55,80 433,15 5,094 18,72 0,07933 53,09

333,15 6,726 26,97 0,08547 55,45 453,15 4,765 17,15 0,07793 52,46

353,15 6,401 25,27 0,08434 55,06 473,15 4,435 15,60 0,07644 51,77

373,15 6,076 23,60 0,08317 54,64 - - - - -

Table 5

Coefficients of equation (7) for calculating o293 and the correspondent root-mean-square deviations from the experimental results

X2 a b c d e f ^ , % ° 293

Tb 293 P277 56,8524 -0,849052 -0,0691389 0,0008953 24,1719 -11,5563 0,22

M 293 P277 11,6194 -1,44777 -0,120163 0,0014774 37,5973 -5,70514 0,13

Tb «if 265,939 -0,261762 -252,404 0,226661 -7,68965 411,307 0,77

M "if 312,311 -1,29402 -308,185 0,898216 1,9525 403,038 0,87

Earlier [1] a formula was obtained that describes the dimensionless dependence of a on temperature:

c* = — = 2,672[exp(-l,025x) - 0,371t], (8)

where a06 is surface tension at a reduced temperature x = T/Tpc = 0,6. The RMSE in calculations using this formula was 1,65 %. This formula is correct from the point of view of the theory of thermodynamic similarity, and can be recommended for a wide variety of fractions; however, it is necessary to clarify the method for calculating a0,6.

***

The proposed methods for calculating the surface tension based on the experimental data obtained in this article describe the surface tension in the investigated temperature range for fractions of two oil fields with a sufficient degree of accuracy. However, additional research is needed to determine a universal method for calculating the surface tension of all petroleum products.

References

1. NEMZER, B.V. Surface tension of paraffinic hydrocarbons and petroleum products [Poverkhnostnoye natyazheniye parafinovykh uglevodorodov i nefteproduktov]. Candidate thesis (engineering). Grozny, 1985.

2. GRIGORYEV, B.A., B.V. NEMZER,

G.D. TATEVOSOV. Experimental study of the surface tension of n-pentane, n-hexane and n-heptane [Eksperimentalnoye issledovaniye poverkhnostnogo natyazheniya n-pentana, n-geksana i n-geptana]. Izvestiya Vyschikh Uchebnykh Zavedeniy. Neft i Gaz, 1985, no. 8, pp. 53-58, ISSN 0445-0108. (Russ.).

3. GRIGORYEV, B.A., A.A. GERASIMOV, I.S. ALEKSANDROV. Thermophysical properties of hydrocarbons among petroleum, gas condensates, natural and associated gases [Teplofizicheskiye svoystva uglevodorodov

nefti, gazovykh kondensatov, prirodnogo i soputstvuyushchikh gazov]: in 2 vls. Moscow: Moscow Power Engineering Institute, 2019. (Russ.).

4. RIAZI, M.R., T.E. DAUBERT. Characterization parameters for petroleum fractions. Industrial and Engineering Chemistry Research, 1987, vol. 26, no. 4, pp. 755-759, ISSN 0888-5885.

5. GRIGORYEV, B.A. (Ed.), G.F. BOGATOV, A.A. GERASIMOV. Thermophysical properties of oil, oil products, gas condensates and their fractions [Teplofi zicheskiye svoystva nefti, nefteproduktov, gazovykh kondensatov i ikh fraktsiy]. Moscow: National Research University "Moscow Power Engineering Institute", 1999. (Russ.).

Экспериментальные исследования поверхностного натяжения нефтепродуктов в широком диапазоне температур

Б.В. Немзер1*, В.А. Малофеев2, Б.А. Григорьев3

1 Иллинойсский университет в Урбана-Шампейн, США, IL 61820, Иллинойс, Шампейн, Ист Грегори драйв, д. 52

2 Грозненский государственный нефтяной технический университет им. акад. М.Д. Миллионщикова, Российская Федерация, 364024, г. Грозный, проспект Исаева, д. 100

3 ООО «Газпром ВНИИГАЗ», Российская Федерация, 142717, Московская обл., г.о. Ленинский, пос. Развилка, Проектируемый пр-д № 5537, зд. 15, стр. 1

* E-mail: bnemzer@futureceuticals.com

Тезисы. В статье представлены результаты экспериментальных исследований поверхностного натяжения (а) фракций мангышлакской (нефтяное месторождение Узень) и самотлорской нефти, проводившихся в лаборатории теплофизики Грозненского нефтяного института. Измерения выполнены дифференциальным методом капиллярного поднятия с использованием пяти откалиброванных стеклянных капиллярных трубок разного диаметра (разброс внутренних диаметров не превышал 0,04%-ного отклонения от средней величины). Температура измерительной ячейки выставлялась с точностью ±0,02 К и измерялась эталонным платиновым термометром сопротивления ПТС-10. Визуальное наблюдение уровня мениска в капиллярных трубках осуществлялось при помощи катетометра КМ-6. Погрешность измерений капиллярной константы в выбранном диапазоне температур не превышала 0,5 %. Суммарная погрешность индивидуального измерения а составила 0,5.0,8 % и 1,0.1,2 % в диапазонах температур 233.423 К и 423.573 К соответственно.

В статье приводятся экспериментальные значения капиллярной константы и поверхностного натяжения для исследованных фракций мангышлакской и самотлорской нефтей, а также усредненные значения этих величин. Полученные данные позволили вывести приближенную зависимость поверхностного натяжения исследованных нефтепродуктов от их физико-химических характеристик. Для фракций самотлорской нефти также рассчитаны значения удельной избыточной энтропии и энергии поверхностного слоя.

Генерализованная зависимость получена с использованием аппарата теории соответственных состояний, что позволило с высокой точностью рассчитать поверхностное натяжение для фракций мангышлакской нефти в выбранных диапазонах температур. Применительно к мангышлакской нефти показана также возможность использовать для расчета а уравнение ван дер Ваальса с постоянным показателем степени.

Ключевые слова: нефтепродукты, капиллярная постоянная, поверхностное натяжение, псевдокритическая температура, поверхностная энергия.

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