Heat Content of Petroleum-Oil Fractions at Elevated Temperatures H. M. WEIR AND G. L. E~ATON,Atlantic ReJining Company, Philadelphia, Pa. T H E T O T A L HEAT of Jive oils, in both liquid of many passages through cracking units, and was and vapor phases, has been determined at lempera- probably entirely different in chemical constitution lures u p to 540" C. (1004" F.). Four of these f r o m cuts direct f r o m crude oil. The data f o r this oils were of illidcontinent source and had densities oil are compared to those for the other oils as a gage ranging f r o m 0.747 to 0.934 (20" lo 58'' A. P. I.). of the variation in total heat which m a y occur with The data obtained for these four oils have been a n oil of widely different conslitution. incorporated into two equations, one for oapors and The eSfect of pressure on the total heat of a the other f o r liquids, which are recommended f o r naphfha capor has been investigated f o r certain Midcontinent source oils. The fifth oil studied was pressures and temperatures. Certain determinaa highly refractory gas-oil stock, which had a history tions of critical temperatures are reported.
D
ATA relating to the heat content of petroleum fractions a t high temperatures, in both liquid and vapor phase, are among the tools most frequently used by the designer of petroleum equipment. Heretofore, these high-temperature data have rested upon extrapolation of the many investigations made in the range of temperature between 0" C. (32" F.) and perhaps 350" C. (662" F.), Since most of the modern equipment in which oil is distilled, and all of that in which it is cracked, operates far above the maximum temperature of previously published investigations, it seemed worth while to study experimentally the heat-content relationships in this highly interesting temperature range. The present paper gives the results of this work with selected characteristic fractions of petroleum vapors and liquids up to about 540" C. (1004" Fa). A critical survey of the literature on the subject has been made, and certain of these literature data combined with the low- and hightemperature findings of the present authors to form the basis of curves. These curves present what is believed to be the best existing published data on the heal, content of oils, as liquid or vapor, in the temperature range of 0-540" C. (32-1004" F.), and as a function of their density (0.966-0.74 specific gravity or 13-60 A. P. I. gravity). Previous workers have been content t o limit their determinations of heat content or specific heat of oil fractions to temperatures below that a t which decomposition (cracking) is commonly supposed to occur. It is well known, however, that cracking is proportional to the product of some function of time, and another function of temperature. Certain types of commercial distillation equipment are designed with this relationship in mind, the effort being to heat the oil to the required temperature quickly, and to cool it below the range of rapid decomposition before significant chemical changes can occur. This desired result is frequently obtained to an extent which makes i t difficult to show, by usual physical tests of quality, that any decomposition whatever has occurred. The experimental equipment with which these high-temperature heat-content data were secured was designed to provide a very rapid sequence of heating and cooling effects, and the decomposition of the oil under the most severe conditions was found t o be so small as to affect the results t o a negligible extent only. Details of the experimental equipment and the mode of operation will be given in the last section of this paper under Experimental Equipment and Method For the
present it need only be stated that the stream of oil was heated continuously by passage through a tube in an electricresistance heated furnace. Means to hold any desired pressure on the oil passing through the furnace were provided, together with a sampling connection so that a small portion of the hot-oil stream could be diverted to a vacuum-jacketed calorimeter. The major portion of the oil was wasted to a condenser cooler of conventional type. At the start of an experiment the calorimeter, a silvered vacuum bottle of the thermos type, was packed with granular ice below 0" C. This ice was completely melted in the approximate 4-minute duration of an experiment, during which time 100-350 grams of hot oil were introduced into the calorimeter. The heat content under any given condition was calculated from a knowledge of the initial temperature of the oil, the heat equivalent of the calorimeter and fittings, the weight and temperature of the ice a t the start and of both water and oil a t the conclusion of an experiment. Seven oils were used in the experimental work. Their character is indicated by the data in Table I.
TABLEI.
PHYSICilL CHAR.4CTERISTICS OF STOCKS INVESTIGATEDa A
NAPHTHM B
c
REFINED OIL
Gas OILS A B
LUBRICATINQ-OIL STOCK
SP. gr. at 60" F. 0.7483 0.7475 0.7459 0.8203 0,8504 0.9639 0.9334 A. P.I. gr. 57.6 57.8 58.2 41.0 34.9 15.3 20.1 AMOUNT O V E R A. 9. T . hl. DISTILLATION 10 M M . Hg TEMPERATURE8 PRES0CRE .METHOD % F. O F. F. ' F. ' F. O F. .108 105 359 514 396 292 Initial 140 155 1 122 116 363 524 416 348 172 129 372 534 428 372 3 137 179 5 148 139 438 388 378 540 10 192 170 157 387 549 454 413 20 211 200 186 399 564 472 445 30 226 227 211 410 574 484 473 40 239 251 235 419 582 488 503 50 252 272 259 428 593 500 531 60 268 293 281 439 604 514 565 70 288 313 303 451 618 832 603 80 317 331 319 464 636 564 654 90 361 359 353 482 668 620 95 430 388 375 494 690 ... ... 406 409 513 700 700 Dry 487 97 98.5 98 95 94 88 %Off 98 a All of these stocks, except gas oil B were cuts from Midoontinent-type crudes obtained in pipe-still distillatio; and under what the refiner calls "non-cracking" conditions. No dpubt these oils reprment mixtures which are not radically different from similar boiling mixtures of trui original components of the crude. On the other hand, gas oil B had,a &story of man paseages through craoking units under the most drastic conditions and %ears no resemblance in ohemioal oonstitution to its original 8ouroe.
211
...
...
INDUSTRIAL AND ENGINEERING CHEMISTRY
212
O l W l 0
100
I
I
100
I
1
500
1
I
I
I
I
I
400 500 600 TEMPCRATVRE *r
1
1
700
I
I
BOO
1
1
900
'
Vol. 24, No. 2
1
/OOO
TEMPE8ATVR6 'F
FIGURE1. DATAON 58" A. P. I. NAPHTHA
FIGURE 2. DATAON 41' A. P. I. REFINED OIL
(Including comparison d t h literature)
(Including oompariaon with literature)
-
2 Fa&& and Whitman fir 5.- Eurwu d Stando& for
FIGURE 4. DATAON 2O.I" A. P. I. LUBRICATING OIL (Including cornparison with literature) rl7ENPESATUUT)E *F
FIGURE 3. DATAON 34.9' A. P. I. GAS OIL (Including comparison with literature)
TEMPERATURE
.f
0
GASOIL FIGURE5. DATAON 15" A. P. I. REFRACTORY
per square inch, by observation of the magnitude of the Joule-Thomson effect, i. e., the temperature change on adiabatic expansion of the gases. LIQUIDS. The heat content of the liquid state us. temperature, for the several stocks, was determined a t various pressures, dictated by the physical properties of the particular oil. For any given experimental temperature, the pressure maintained was greater than the vapor pressure of a pure paraffin hydrocarbon having a boiling point equal to the initial point of the particular material being studied, as determined by the A. S. T. &I. distillation. The vapor pressure-temperature relation was determined according to the method suggested by Cox (4). It was felt that this procedure would assure conditions under which no vaporization would occur a t the point where the temperature was read, and before release of oil to the calorimeter.
(Including comparison with literature)
CORRELATION OF DATA
DETERMINATION OF TOTAL HEATS VAPORPHASE. The heat of these materials in the vapor phase was determined a t substantially atmospheric pressure. The effect of pressure on the heat content of one of the naphthas, C, in the vapor phase, was also determined at several pressures, including a maximum of 2000 pounds
Some two hundred and thirty satisfactory determinations were made in the course of the work. The essential data appear in Table I1 and the results are shown graphically in Figures 1 to 5. The solid curves on each of these figures are the weighted or "best" lines through the data points.
I N D U S T R I A L .4ND E N G I N E E R I N G C H E M I S T R Y
February, 1932
TABLE11. NAPHTHA
DATAOBTAINED
EXPERIMENTAL
(58.0'
A. P, I . ) ~
HEAT CONTENT CorrnarTsn _. .._..- HEAT FOR DEVIACONTENT COOLINQ,TION
-
INITIALFINAL TEMP.
' F.
PRER8URE
Lb./ BQ
in.
ICE MIX WEIQHT W E I G H T A B O V E A B O V E F R O M TEMP. TEMP. OF ICE O F OIL 32' F. 32' F. CURVE B. 1. u./ E'. 1. u./ F. F: Grams Grams lh. lb. % fl.1 89.3 705 51.4 363.7 19.4 +1.2 668 94.9 65.5 328.4 ... 18.7 -1.2 646 153.1 2 6 . 0 1 1 2 . 5 390.1 ... -1.0 601 393.9 173.0 16.0 115.0 590 393.3 181.4 -0.6 22.0 123.0 -2.9 567 3.5 57.0 208.9 71.1
949 903 896 835 817 804
htm. Atm. Atm. Atm. Atm. Atm.
801 727 713 698
Atm. Atm. Atm. Atm.
23.5 16.0 7.5 10.4
117.0 78.0 53.6 42.8
177.6 397.8 328.0 264.3
8fi.5 159.6 117.5 82.0
572 532 518 622
606 6fi9 615 603 600
Atm. Atm. Atm. A tm. Atm.
10.2 19.0 23.0 10.0 17.6
57.2 98.0 59.5 86.7 49.6
370.0 392.4 407.2 276.0 280.9
133.9 192.7 167.0 144.7 108.6
517 492 451 448 450
596 530 503 500 487
Atm. Atm. Atni. Atm.
6.8 20.0 22.3 17.4 21.0
43.5 78.0 70.5 59.5 47.5
336.1 403.0 266.1 199.6 380.3
128.3 216.6 139.9 99.1 174.4
445 398 365 384 372
438 414 393 289 284
Atm. Atm. Atm. 340 325
26.0 19 0 31.0 14.7 21.2
67.5 81.0 92.0 82.0 84.0
417.8 341.6 384.6 168.5 222.2
238.2 232.1 285.3 2131.3 374.7
344 327 314 157 153
145 142
-1.8 -2.5 +0.7 +0.7
280 252 247 242 202
350 325 330 310 325
11.3 17.2 9.7 26.4 15.8
40.3 66.2 55.8 47.1 44.2
193.2 161.3 198.2 209.7 193.6
24.1 9 288.6 376.4 300.8 388.6
137 128 111 122 91
126 120 104 115 89
-8.7 0 -11.5 +0.9 -1.1
A!.m.
... ... ...
... ... ...
... ... ... ... ... ... ...
.
.
I
...
... ... ... ..,
...
-1.6 t0.8 0 $2.8 +2.1 $0.8 -0.3 $0.7 +l.6 +1.1 -0.5 +0.5 +0.7 -0.5 -0.6
192 200 520 450 415
325 400 500 500 500
27.0 14 9 23.0 31.0 20.0
48.2 56.6 122.0 82.0 94.0
197.2 146.2 343.0 363.3 371.2
415.7 344.7 318.2 309.0 383.1
67 92 316 267 244
86 90 29 1 242 220
+1.8 +1.0
300 353 288 362 347
500 500 5n0 650 675
23.0 27.0 26.0 24.5 14.4
59.0 45.0 91.4 66.5
397.6 241.2 355.4 189.2 214.9
373.3 253.0 402.2 230.9 226.7
204 191 154 213 205
183 171 142 192 185
-3.7 -7 6 -0.7 +0.3 $1.9
352 400 489 $78 667
800 1000 1225 1300 1500
9.4 19.0 16.1 23.9 20.0
60.0 57.0 84.0 52.2 123.0
188.0 256.1 173.0 295.0 411.9
188.6 189.0 137.4 174.2 273.4
203 254 304 302 426
183 230 278 276 413
640 637 633 607 580
1500 1575 1500 1500 1500
17.0 19.5 17.0 26.0 31.0
98.0 133.0 46.5 75.0
394.4 343.9 392.0 314.6 411.0
230.6 259.9 167.1 160.2 227.2
421 406 402 391 369
406 39 1 385 371 347
558 505 494 490 442
1500 1500 1500 1500 1500
29.0 26.0 22.0 16.0 12.0
39.0. 101.5 69.0 77.0 71.0
374.9 247.0 320.7 275.4 257.4
166.1 199.9 213.0 200.4 201.4
349 320 300 302 275
325 294 274 276 250
395 370 309 602 578
1500 1.500 1500 2000 2050
25.0 31.0 6.0 1.0 28.4
75.0 67.0 142.0 36.0 77.9
357.3 406.4 56.3 272.9 206.9
326.7 359.9 187.7 118.3 116.1
236 224 170 389 385
212 202 156 368 363
-0.9 +2.5 -0.3
565 5fi1 555 555
1800 2000 2090 2075
113.5 12.0 9.0 24.4
38.0 61.0 38.0 106.8
190.9 213.9 183.7 208.2
79.7 116.9 82.3 166.8
371 36 1 366 339
348 338 342 315
...
404 398 396 288
2000 zoo0 2000
11.0 11.0 15.0 15.0
61.0 88.0 47.0 67.0
191.3 275.4 133.7 165.7
153.1 282.1 93.4 219.5
253 245 253
229 221 229 154
+4.1 +2.3 +6.7 +7.7
a
20,o
60.0
tiR.0
166
...
-4.1 -3.3
-0.9 +6.0
-1.1 +1.1
...
.. .. ..
... ... ...
... ...
-3.9 -2.1 +1.2
,..
...
... ... ...
Average deviation of vapor from curve = 0% Average deviation of liquid from curve = - 0 . 3 % First 23 runs, vapor phaRe; other runs, liquid phase.
INITIAL FINAL ICE hIIX TEMP. T E M P . TEMP. F. Lb./sq. in. F. F. PRESSDRE
DEVIACONTENT TION Grams
R E F I N E D O I L (c1.a'
957 950 920 896 855
Atm. Atm. Atm. Atm. Atm
30 23 22 22 21
51 61 111 68 64
I N HE4T-CONTENT DETER\II.VATIOVS
HEAT INITIAL FINAL CONCEAT ICE MIX WEIGHT WEIGHT A I ~ O Y E TEMF SUNE TEMP. TEMP. OF ICE OF OIL 3 2 ' F . Lb./s?. in. F. F. Grams Grams B.t. u./lb. O F. R E F I N E D OIL (concluded) 830 21 79 426.0 Atm. 150.6 595 Atm. 10 106 414.3 190.9 740 543 720 24 144 388.0 22S.O Atm. 529 640 22 80.8 362.6 Atm. 168.1 466 Atm. 635 29.5 375.4 128.8 40.8 45fi
PRES-
625 5fiO 560 .555 555
Atm. Atm. Atm. Atm. Atm.
22 20 20 22 22
540 841 830 7fi8 763
Atm. 300 300 300 300
7.59 668 6.56 c37 6.17 627
300 300 300 300 300 300
523 497 442 938 897 870
300 300 300 1025 925 900
A. P.
350.5 3fi7.9 376.1 403.9 421.9
WEIGHT A B O V E FROM OF OIL 82OF. CURVE Grams B . i'. u./lb. % I.) b
87.7 101.7 146.4 126.2 149.0
675 671 651 624 614
-1.5 -1.3 -0.8 -2.2 +1.3
DE~IATION FROM
CURVE
% ' +1.2 +3.8 $3.9 +2.2 +0.3
69 99 97 35 86
385.2 381.3 387.4 381.5 410.5
170.5 230.8 228.1 146.3 224.7
446 405 411 390 409
0 -0.2 $1.2 -1.0 +1,5
25.5 21 24 17 26
104 116 94 63
378.1 418.2 416.2 406.5 412.6
239.6 194.8 173.0 158.6 159.5
395 563 551 496 474
$0.2 +2.0 $1.7 +2.0 -1.5
23 25 15 20 16 27
142 130 64 80.7 62.7 38
60
383.6 365.8 431.7 411.8 388.9 411.0
-1.5 -0.2 +4.8 -0.3 -4.2 +5.4
423.7 413.6 414.0 388.5 397.3 422.4
-3.5 -0.4 +2.2 -2.8 -1.3 S2.6
Average deviation of vapor from curve = + 0 . 5 % Average deviation of liquid from curve = +0.3% b First sixteen runs, vapor phaae; other runn, liquid phase. 134 115 72 66 82
A . P. I., 331.5 362.2 357.6 379.0 403.1
171.4 168 1 142.9 141.0 178.7
586
46 70.5 59 108.5 68
428.5 323.9 382.8 438.5 387.1
151.2 147.0 165.5 252.3 176.1
499 467 453 457
-0.7 0 -3.4 -0.1 -0.5
38.5
424.3 294.9 248.4 378.3 405 2
225.1 197.0 253 1 301.1 395.6
314 316 319 307 294
-3.1 -1.9 -0.9 +3.0 +6.l
19 9 6 6 5
95.5 96 85.8 57.8 36.2s
265.5 312.7 227.5 253.7 265.2
265.4 327.5 257.7 247.5 334.5
257 251 224 208 116
12.0 -0.4 +5.9 +3.2 -0.4
10 15.5 14.5 7 24
34.6e 91.7 56 76.5 79
252.6 379.6 378.5 331.3 385.4
310 0 127.7 108.0 117.7 139.0
111 685 646
0 +2.0 -1.5
86 72 59 90.5 110
408.2 356.1 400.3 358.9 398.2
160.1 161.0 188.2 244.3 142.0
566 4Fjl 391 355 692
+1.4 -1.7 -0.4 -0.8 +1.2
32 21 26 21 30
73 86 69 85 123
369.6 398.1 431.6 343.9 377.7
122.4 131.6 136.0 140.4 169.2
593 663 615 612 596
+1.4
28 24 29 15 16 16
55 70.5 101 93 98.5 156
393.8 453.2 431.13 406.5 388.5 425.9
117.2 168.0 195.3 102.0 203.3 314.7
589 580 523 497 466 453
-2.6 -3.3 -1.3 -0.4 -0.4 -0.4
0 . ~ 0niL ( a 4 . P
840C 830C 760~ 7,50: 720
Atm. Atm. Atm. Atm. Atm.
2 9 10 12 12
720: 667 662C 655C
Atm. Atm. Atm. Atm. Atm.
7 5 4 3 4
580d 578d 578d 545d 515.1
Atm. Atm. Atm. Atm. Atm
7 1 4
480d 480d 420d 405.1 265d
Atm. Atm. Atm. Atm. Atm
255d 95OC 930C 878C 840C
A tm 60 55
800C 750d 668d 625; 965
65 65 65 65 275
18 21 25 9 28
890d 97% 918d 9l2d 912d
275 300 300 300 300
9l2d 850d 830.1 7954 7606 7456
300 300 300 300 300 300
660C
c
60 60
Vapor phase.
HEAT
mEIGHT O F ICE
213
6
7
.
65 129 89 114
-4tm. Atm. Atm. Atm. Atm. 300 300
5'4 536 500
4fi2
fil? 580
-0.3 0 -0.9 +2.5 -0.5
-0.6
-1.2
-0 3 +0.7 +1.2 -1.5
Averape deviation of vapor from curve = -0.1yo Average deviation of liquid from curve = + O . l % d Liquid phase. e Refers t o grams of ice u nmelted. L E B R I C A T I N Q STOCK (20.1'
595 548 506 452 403 722 663
589
31.5 22.0 17.0 26.0
24.0 23.0 22.0
60 74 85 86 69 143 98
441.4 365.6 377.9 405.4 399.4 391.0 406.8
A . P. I . ) f
252.1 282.0 351.6 434.2 421.1 304.0 263.3
318 273 240 217 105 400 373
11.0 -2.8 -1.6 -0.2 +4.0 -2.3 +2.5
Average deviation from curve = + O . l % / Liquid phase.
INDUSTRIAL AND ENGINEERING CHEMISTRY
214
Vol. 24, Yo. 2
DATAOBTAINEDIN HEATCONTENT DETERMINATIONS (Concluded) TABLE11. EXPERIMENTAL HEAT DEVIAISITIAL FIKAL CONTENT T I O N ICE MIX WEIGHTWEIGHTABOVE FROM TEMP. S ~ R E TEMP. TEMP. OF ICE O F O I L 32OF. CURVE a F. Grams Grams B . t , u . / l b . 70 ' F . Lb./sq. in. O F . PRES-
REFRACTORY GAS OIL (16.3'
A. P . I . ) O
1003 1002 950 906 856
Atm. Atm. Atm. Atm. Atm.
22 25 26 16 22
49 52 53 66 60
411.4 386.5 429.5 375.7 380.2
112.2 107.8 121.6 125.6 127.2
613 607 604 582 548
-1.9 -2.9 f1.7 +2.4 $1.5
844 738 900 854 800 757
Atm. Atm. 1500 1500 1500 1500
16 20 20 16 13 14
73 63 45 52 68 57
335.8 302.3 381.3 364.7 395.1 369.2
130.4 123.2 123.2 133.7 177.0 166.6
528 471 508 481 447 410
-0.9 +0.9
702 650 588 502 410 403
1500 1500 1500 1500 1500 1500
15 20 16 22 14 18
60 64 53 87 34.5 45
368.7 327.4 322.9 364.2 315.1 364.9
184.1 183.1 199.3 346.7 278.2 334.7
379 345 291 244 174 178
...
40:: -0.d
4-1.7 +2.4 -1.2 +2.1 -5.4 -1.1
Average deviation of vapor from ourve = +O.l% Average deviation of liquid from ourve = -0.2% D First seven runs, vapor phase; other runs, liquid phase.
S t M M A R Y OF DATA O N EFFECT, ETC.
(conchkded)
TEMP. CALORIMECHANGE CALORIME- TER FROM TEMP.IN VALVE TER OUTLET BLOCK PRESSUREPRESSURE, BLOCK J TEMP. TEMP. J TO AT VALVE CALORIMEThermo- Thermo- THERMOTHERMOCALORIMEJ TER S oouple K oouple Y COUPLE T COUPLE .Y TER S BLOCK Lb./sq. in. Lb./sq. t n . F. a F. F. F. F. 1450 626 -110 0 744 7381' 634 1050 639 -101 0 749 745 648 1450 -127 547 541 0 674 6681 546 -117 1050 0 670 661i 553 485 -133 1450 0 623 617i 490
1050 1450 1050 2000 2000
0 0 0 0 0
2000 400 1450 1050 200 400 i Unreliable couple Y .
0 0 0 0 0
623 573 574 548 522
497 947 937 947 551 0 549 value due t o small
614i 569 567i 547 514i
488 425 428 390 354
485 422 425 387 351
-135 -148 -146 -158 -168
320 -174 494 323 908 - 27 950 920 867 852 - 70 946 945 891 879 - 56 514 531; 507 -37 423 -123 545 426 amount of naphtha flowing past thermo-
SUMMARY OF DAT.4 (STEAM)
BTEAMh
1000 982 920 835 715
Atm. Atm. Atm. Atm. Atm.
24.0 18.0 28.0 25.5 23.5
123.0 56.2 70.0 80.0 86.5
701 635 610 600 550
Atm. Atm. Atm. Atm. Atm.
7.0 20.0 18.0 5.0 24.0
76.5 72.0 75.0 87.0 62.0
257.1 410.0 396.6 247.9 426.2
41.3 59.4 59.5 44.0 59.6
+0.7 +3.0 +3.0 -0.2 +1.5
515 507 401 365 320
Atm. Atm. Atm. Atm. Atm.
16.0 -1.0 -1.0 30.0 32.0
65.0 110.0 109.0 61.0 85.0
444.3 247.1 218.0 403.1 380.4
68.5 52.1 47.8 59.1 66.1
-0.9 +l.2 +1.2 +1.3 +1.9
67.8 48.9 50.7 61.8 68.1
1573 1517 1516 1447 1401
$3.4 +0.3 +2.2 $0.2 $1.0
TEMP. CALORIMECHANGE TER FROM CALORIME.~ TEMP.I N VALVE TER OUTLET VALTE AT EBLOCK J TEMP. TEMP BLOCK J TO CALCD. VALVECALORIM Thermo- Thermo- THERMOTHERMO-CALORIMETEMP. BLOCK TER oouple K oouple YCOUPLET COUPLE X TER S CHANGE J S Lb./ LbJ a F. F. O F. a F. a F. a F. sq. zn. sq. tn. 738 -2 -14.6 750 754 748 90 2 -15.1 785 -4 90 2 800 803 796 883 -5 -12.6 905 895 90 2 900 1002 1002 995 90 2 980 -7 -10.6 PRES- PRESSURE
SURE IN
~
It will be noted that no determinations of total heat were made in the region of low temperatures. Accordingly, the statement that the solid curves are "best" lines through the h Vapor phase. data needs amplication. S U M M A R Y OF DATA Oh' EFFECT O F PRESSURE ON T O T h L H E h T (68' A . P . I . It should first be observed that the dotted curves on each NAPHTHA) figure correspond to the relationship of heat content of liquid TEMP. CALORIMECHANGE vs. temperature, calculated from specific-heat data of Fortsch FROM CALORIME- TER TEMP.I N VALVE TER OUTLET BLOCK and TThitman ( 5 ) ,and a Bureau of Standards publication ( 2 ) . J TEMP. TEMP. J TO PRESSUREPRESSURE, BLOCK AT VALVECALORIMETherrno- Thermo- THERMO-THERMOCALORIME- Furthermore, the dotted line showing the heat content of BLOCK J TER S oouple K couple Y COUPLE T COUPLE X TER S vapor us. temperature corresponds to calculation of this L b . ./ s o-. in. L b . ./ s a-. in. F. F. F. F. F. factor according t o the same Bureau of Standards publi653 654 3.5 0 650 642 + 4 747 750 0 0 745 736 + 2 cation. 847 854 0 0 848 836 +- 26 Although the Fortsch and Whitman equation was ap931 951 947 4.5 0 949 654 640 629 - 10 100 0 650 plied far above that justified by their experiments (where specific heat of the liquid was measured only to 554" F.), 753 739 725 -11 100 0 750 -13 851 837 . 821 100 0 850 inspection shows that it represents most of the liquid data 927 908 -18 948 100 0 945 -21 730 . 718 753 200 0 751 fairly well. Coincidence of the present authors' best lines 856 830 816 -23 200 0 853 with that of Fortsch and Whitman in the lower tempera915 -22 957 933 200 0 955 ture ranges is obtained by the simple extrapolation of these 809 795 -44 0 853 853 400 best lines t o 0" F., assuming that the relationship is para913 895 -36 0 949 953 400 0 946 949 887 871 -59 800 bolic. In the zone of higher temperature, where data were - 57 750 5 944 936; 887 874 obtained in this work, the solid-line extensions were de841 780 768 -64 750 0 844 termined by continuing the best parabolic curves through 795 - 40 845 806 400 0 846 7376 668 660 77 750 0 745 the data. That is, the best straight lines through data points - 42 707 697 0 749 741i 400 plotted on the coordinates, H/t-32 and t (" F.), were deter560 -101 567 0 668 665 750 mined by the method of averages. 565 -103 668 570 750 0 673 628 622 - 46 0 674 670 400 The curves so obtained can be incorporated into a single 638 - 29 680 645 200 0 674 relationship, Equation 1,which is recommended for calculating - 29 646 639 675 200 0 675 589 582 - 83 0 672 671 600 the liquid heat content of Midcontinent-source oils: Average deviation =
+ 1.3%
400 600 750 400 600
0 0 0 0 0
622 621 621 570 575
622 621 621 579 579
561 509 497 470 433
554 504 493 467 428
-61 -112 -124 -100 -142
750 600 600 1450 1050
0
575 752 846 844 846
577 740; 839; 840 83Bi
435 685 790 751 768
431 676 779 743 757
-140 - 67 - 56 -93 -78
0 0 0 0
'
+
H = (15d - 26) - (0.465d- 0.811)t 0.000290t' (1) where H = total heat cont2nt above 32' F., B. t. u. per lb. of oil 1 = temperature, F. d = sp. gr. of material as liquid at 60' F.
The solid or best vapor heat- content lines were calculated, using Bahlke and Kay's equation (1) for the specific
February, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
800
the Fork was done. The results obtained in its case are presented both as a rough gage of the possibility of applying the Midcontinent data to other types of oil, and as a picture of the behavior of refractory cracking stocks.
40' SO'
700 FON Line
3
- - -Mid- Continenf
Source
215
O//s
y 600 3 9 500
EFFECTOF PRESSURE ON HEATCONTENT OF
VAPORS
Aside from the interest which attaches to the determination of the Joule-Thomson effect from a theoretical standpoint-namely, for calculation 2 of co-aggregation and co-volume constants in gas 5 h 300 equations, it is of immediate practical applicagl tion] since immense quantities of petroleum are , h daily vaporized under considerable pressure. It T j 200 is unfortunate that time did not permit investi3 gation of the Joule-Thomson effect on all vapor 4 for which calorimetric data were obtained. The 100 E e x p e r i m e n t a l work, which was confined to naphtha, was practically complete when it was learned that Bahlke and Kay were to present re'0 /OO 200 300 400 SO0 600 700 BOO 400 /POP TEMPERATURE 'F sults on the same type of i n v e s t i g a t i o n of a naphtha vapor before the meeting of the AYERIFOR MIDCONTINENT CUTS IN FIGURE 6. 'rOTAL HEATUS. TEMPERATURE LIQUIDAND VAPORPHASES CAN CHEMICAL SOCIETYin September] 1931. Through the courtesy of these workers the present heat of petroleum vapors. When integrated this equation authors have been able t o inspect certain of their curves, showing their data which apparently agree well with present findbecomes: ings, considering the generic nature of the term "naphtha." H =K (0.415 - 0.104d)t (0.000310 - 0.000078d)t2 (2) At this writing the details of the work of Bahlke and Kay are where R = constant of integration (i. e., heat content of vapor unknown to the writers, so that further reference cannot at 0" F.) be made.
9
400
+
+
On choosing appropriate values of K , it was found that this equation coincided almost exactly with the best line through data of the present writers for the naphtha, refined oil, and gas oil in a temperature range far exceeding the experimental data obtained by Bahlke and Kay, whose maximum temperature was 662" F. (350" C.). The extrapolation of these vapor heat-content lines over a range of sereral hundred degrees back to the origin of abscissas (0' F,) could not be justified a t all were it not for the fact that the slopes of these lines are thus known for a range of nearly 1000" F., and the position fixed by the average of determinations in the upper several-hundreddegree range. As it stands, no great accuracy can be claimed for the total heat curves on vapors more than 100" F. or lower than the range of actual experimentation] but it is probable that the extrapolation is as good as any attempted calculation in which data on pure compounds are utilized together with the Clausius-Clapeyron relationship. Like the liquid data, it was found possible to incorporate the vapor heat content us. temperature relationship in a single recommended equation for Midcontinent oil vapors, involving the nomenclature already given.
H
= (215
- 87d)
+ (0.415 -(0.000310 0.104d)t + - 0.000078d)t2
(3)
In order to make the data on the heat content of the liquids and vapors convenient t o apply t o other Midcontinent oils, total heat curves mere calculated for intervals of even 5 or 10 A. P. I. degrees to form Figure 6 for data in the liquid and vapor phases. The so-called 15 A. P. I. dotted curve on Figure 6 was not calculated with the above equation but simply reproduces the data on the refractory gas oil, B. Gas oil R was chosen because of its extreme variance from the Slidcontinent-type oils upon which the bulk of
I
I
I
C H ~ N GON E ADIABATIC EXPANSION FIGURE 7. TEMPERATURE OF 58" A. P. I. NAPHTHA VAPOR
I n determining the effect of pressure on vapor heat content of naphtha, the present writers used a throttling calorimeter according to the method detailed in the next section of this paper. Figure 7 presents the data obtained (see also Table 11) on the temperature decrease occasioned by continuous adiabatic expansion of vapor from several known high temperatures and pressures to atmospheric pressure. Figure 8 was constructed by combining the data of Figure 7 with the known heat content of the same naphtha vapors (naphtha C), a t various temperatures and atmospheric pressure. The dotted curve a t the lower left of Figure 8 is intended to enclose the region in which a two-phase system can exist. The critical temperature is shown as 575' F., and the criti-
216
INDUSTRIAL AND ENGINEERING CHEMISTRY
cal pressure as 500 pounds per square inch gage. The choice of the critical conditions is supported by the fact, apparent from Figure 7, that the temperature decrease on expansion becomes more or less independent of initial pressure when the initial temperature is between 570-80' F., and the pressure is a t some value, not exactly determinable from the curves, but greater than 400 pounds and less than 600 pounds. Though there is admittedly an arbitrary element in the choice of the critical conditions, it is perhaps more important to appreciate that the shape of the phase boundary of Figure 8 is only a guess, which follows orthodox conceptions built around Amagat's and subsequent in-
zene indicate that the determinations are 4" to 5" F. high. It is therefore suggested that the critical temperature of naphtha C is 585' F. No doubt this value is more nearly correct than the estimate of 575" F. from the heat data, but the shape of the two-phase boundary on Figure 8 is not significantly altered by this fact. TABLEIv. DETERMIN.4TIONS O F CRITICAL TEMPERATURES METHOD OF OBSERVED CRITICALTEMPERATURES" FILLINQ TUBE NaDhtha C NaDhtha B Gas oil B Benzeneb Sealed while still containing air 590 592 556 590 595
.....
Sealed while evacuated, keeping part of tube containing 590 596 907-912 557 liquid in CO, snow 590 594 Air driven out bv evaooration of part of &be cbntents: 107 vaporized 606 605 ..... 20590 vaporized 610 608 ...,. ... a In all cases except gas oil B. each value of the oritical temperature represents Borne 10 tu 15 determinations with the same tube, lor which t h e critical temoerature never varied more than 2' F. I n the caee of ea8 oil B, the criti'cal temperature changed due to cracking. b Benzene sample was 9. P . melting point, 5 35O C. Critical temperature of pure benzeneis g i v e l i n International Critical Tables as 651.5' F.
4 ? L rp
9
EXPERIMENTAL EQUIPMENT AND METHOD A dual purpose colored the development of both equip-
t
t
Y
h.
a I
! 4
E R
TEMPERATURE 'E
FIGURE 8. EFFECTOF PRESSURE ON TOTAL HEATOF 58' A. P. I. NdPHTHA VAPOR
vestigators' work with carbon dioxide and the implications of the simple theory of the continuity of state. However, Callendar's work on steam (3) shows how a comparatively simple pure compound may present striking deviations from stereotyped phase diagrams. One can only hope that this work will stimulate study of the interesting but neglected field relating to the critical phenomena of complex mixtures. McKee and Parker ( 7 ) and Watson (9) have suggested methods for calculating the critical temperature of petroleum mixtures based on their observation of the disappearance of a meniscus in closed capillaries. Table I11 sets forth the results of calculation by the two methods applied to all oils studied in the work. It will be noted that the above-mentioned critical temperature of naphtha, 575" F., obtained in a different way, happens to be the exact mean of the two tabular values. TABLE111. CRITICAL TEMPERATURE CALCULATIONS MCKEEAND PARKER (7) O
Na htha (sample C) 58' A. P. I. ReEned oil 41' A. P:I. Gas gil (yakp!e A) 35" A. P. I . Lubnpating oil, 20' A. P . I. Gas oil (sample B), 15' A. P. I. a
Vol. 24, No. 2
F.
560 740 910 1110 810
9000
WATSON( 9 ) F. 590 760
950 1020
.. ..
Calculated using oonstant recommended lor aromatic compounda.
Actual determinations of the critical temperature by a closed-tube method, similar to that used by McKee and Parker ( 7 ) , yielded the results shown in Table IV. The apparatus was designed t o permit mixing of the contents of the tubes by inverting them repeatedly just before the critical phenomena were observed. Table I V shows the results obtained on two naphthas and the refractory gas oil R. The data reported for pure ben-
ment and method for obtaining the heat-content data presented above. Not only was it hoped to get reliable heatr content data at high temperatures, but every effort was made to keep the apparatus and manipulation simple enough to use "in the field" to obtain good heat data on flowing streams of unknown hydrocarbons in refinery apparatus. Xo further reference will be made to this application of the method since its feasibility will be obvious after the description is completed. Figure 9 diagrams the essential feature of the equipment used to heat the oil continuously, and Figure 10 shows a larger cross-sectional view of the special steel fitting a t the outlet of the heater adapted to injection of the hot hydrocarbon stream into the calorimeter shown as P . In Figure 9, the oil whose heat ca acity was to be measured was taken continuously from tank by plunger pump B, the capacity of which could be adjusted t o any one of several rates intermediate between 3 and 16 allons per hour. The furnace, C, consisted of a refractory bricklined chamber through which passed eighteen Glo-bar electrical-resistance heating elements 12 inches long by 5/8 inch in diameter, the whole capable of dissipating some 35 kw. These Glo-bars were arranged two in series across a directcurrent line, the voltage of which could be varied up t o 150 volts. Heating coil D, consisting of 30 feet of '/*-inch extra heavy pi e-size seamless steel tubing, was shaped to fit the furnace. Tiis furnace and accessories had been designed and built for use in unpublished experiments of a different character, but it served very nicely for this work with the following additions. At the outlet of the coil a steel 01098, E, was placed, one outlet of which led to a pressure.gage, F. A steel needle valve, G, through which some of the oil was vented t o a condenser, H , was provided for the opposite outlet. This valve was used only in the runs with vapors at atmospheric as a means to vent excess oil. The special fitting, J, s ~ ~ % ? ~ ~ Figure 10 was connected to the third outlet of the cross. The major portion of the oil passed at all times through this fitting, J, which was arranged SI? that the thermocouple, K , read the temperature at the point where the needle valve stem was seated. There was no.dead pocket in which oil could be trapped even momentarily on its way out t o condenser H through steel valve L. Just below the Beat of the needle valve in the special fitting, J, a 11/* inch length of l/8-inch pipe, N , threaded at the lower end was welded. This served as the outlet for 011 to the calorimeter. Before making a determination, a cool, dry, empty, vacuumjacketed bottle was first weighe?. The bottle was then filled with crushed ice (made from &stilled water) which had previously been cooled to some temperature well below 3%' F. (0' C.). After thorough shaking and mixing, a thermometer which could be read t o 0.5' F. was used to take the tempera-
1
February, 1932
I N D U S T R I A L A :Y D E N G I N E E R I N G C H E hI I S T R Y
ture at several points in the mass of crushed ice, and an average taken. The maximum difference in temperature between various points in the bottle was never greater than 2" F. Supercooling of the ice was necessary to prevent the presence of a thin film of water on the ice particles. The results of the fewoexperiments where an average temperature greater than 30 F. was recorded (see Table 11) should be given less weight than the other experiments. After the ice temperature was obtained, the t h e r m o m e t e r was withdrawn, and the bottle corked and carefully weighed. The 9 1 / 2 inch length of '/*-inch pipe and concentric jacket assembly, shown as M in Figure 10, whose weight and temperature were known, was then quickly attached to the pipe fitting a t the b a s e draw-off v a l v e , J. The bottle containing ice was carefully raised up a n d o v e r this pi e, and the needle valve openei'to allow oil to pass into the bottle at as ranid a rate as possible. Tempehures of the oil shown hy thermocouple K were recorded in rapid mccession during the period that oil was heing introduced into the bottle calorimeter. The pressure on the oil stream shown by gage F was held constant during the run. As soon as all the ice was melted, taking from 1 to 4 minutes, the needle valve was closed, the pipe assembly, M , quickly ,uncoupled a n d lowered into the bottle which was immediately corked and weighed. After thorough mixing, the cork was removed, and the temperature of the FIGURE 9. FURNACE AND AcCESSORIES FOR DETEI~MINA- water and oil mixture was taken TION OF TOTAL HEATOF OIL by a thermometer.
L
EXAMIXATIOX OF ESPERIMENTAL ACCURicy The following factors entering into the calculations, or bearing upon the accuracy of a determination, were examined quantitatively by more or less conventional methods. The average of the data accumulated for any factor is given directly after its listing: 1. Heat transfer from or to calorimeter during a run, less than 0.05 B. t. u. (12.6 cal.) in all cases. 2. Heat equiovalent of calorimeter, 0.0802 B. t. u. per O F . (36.4 cal. per C.). 3. Heat equivalent of pipe and coupling for introduting hot-oil stream; two pipes used-one 0.0298 B. 5 11. per F. (13.50cal. per "C.), the other 0.0571 B. t. u. per F. (25.9 cal. per C.). 4. Accuracy of pressure gages, thermometers, thermocouples, potentiometer, balance, etc., were all tested, but the integrity of these factors is most clearly shown by steam data, t o be mentioned.
The difficulties inherent to determining high temperatures accurately, particularly if the material being investigated is a gaq, has been the subject of much discussion in the literature. Had it not been for the fortunate fact that the accuracy of the high-temperature measuring devices and of the extra calorimetric equipment could be checked by determining the total heat of steam and comparing it with the accepted data on this material. the task of proving the present method sound would have been much more difficult. As it was, data plotted as points in Figure 11 (see Table 11) were obtained for steam, using the same general method as for the oils and applying the same corrections. Marks
217
and Davis (6) give data corresponding to the solid line. The average deviation of present data from the line is +1.3 per cent, the maximum deviation being $3.4 per cent. This agreement mas considered satisfactory since one of the principal factors which necessarily influenced design and operation of this equipment was the possibility of cracking the oils. Adjuncts which might h a w increased the apparent accuracy of the determinations were not applied on account of this fact, and it was gratifying to obtain such checks on the heat content of steam for which data of very high order of accuracy exist. It is clear, however, that the determination of the heat content of steam does not involve one possible source of considerable error in measuring the heat content of a liquid by apparatus such as that diagrammatically illustrated in Figure 10. On releasing a liquid from high pressure, and temperature above the vaporization point, to atmospheric pressure by the opening of the needle valve, J , a large amount of vaporization could be expected to occur in the conduit, N . This vaporization would cause instantaneous cooling of the stream when released. The channel, N , in the steel block \rake, J , did indeed transfer a considerable amount of heat to the cooled stream in the run? with naphtha. It was thus necessary t o subtract a correction term from each determined value of the total heat in those runs with naphtha in the liquid phase. These corrected values are shown in Table 11. The magnitude of the correction term mas obtained by the following argument. It seemed wasonable to assume that Equation 1, found to hold for refined oil, gas oil, and lubricating oil, should also hold for the naphtha. As a matter of fact, uncorrected naphtha d a t a at 200" F., where little flash vaporization could occur, did a g r e e well w i t h the equation. The deviation appeared at higher temperatures. It was known that at 400" F., or above, the naphtha could exist only as a vapor a t atmospheric p r e s s u r e . Since the latent heat of vaporization w a s k n o w n approximately, the temperature differential between the valve block, J , a n d t h e naphtha, instantaneously a n d completely flashed t o vapor, could be calculated. The heat-transFIGURE 10. BOTTLECALORIMETER fer coefficient between AND VALVEASSEMBLY FOR OBTAINING TOTAL HEATS pipe and vapor, necessarv to account for the diffkrence between the uncorrected liquid-heat content and the (assumed) correct value determined from Equation 1, could then be calculated above 400" F. By applying Piroomov and Beiswenger's method (8) of calculating the percentage of Vaporization us. temperature relationship for a given petroleum fraction, the necessary data for calculating such heat-transfer coefficients down to 250" F. was at hand. On actually carrying out such calculations the results were as follows:
I N D U S T R I A L . 4 N D E N G I N E E R I N G C H E 11 1 S T R Y
218
CALCULATED HEAT-TRANBFER TO COEFFICIENT, METALSURFACE VAPORIZINQ NAPHTHA B. t . u./hour/m. ft./” F.
LIQUIDTEMPERATURE BEFORE RELEASEOF PRESSURE
* F.
100
500 450 400
Vol. 24, No. 2
sure and temperature readings were recorded for the various positions in the apparatus. These data have been summarized and appear on Figure 7, and in Table 11.
107 121 127
551) ...
121 122
300 250
The rough constancy of these values was deemed strong evidence that the magnitude of the correction term could be calculated by this method, and conversely that the deviation of the naphtha data from general Equation 1 was due to this fact of vaporization and abst.raction of heat by the naphtha passing through conduit N .
4
t -
u
FIGURE12. ADIABATIC THROTTLING CALORIMETER FOR DETERMINING EFFECT OF PRESSURE ON HEAT CONTENT OF NAPHTHA VAPOR
The accuracy of the method as a whole was studied by making runs with steam instead of naphtha vapor. These data also appear in Table 11. It is apparent upon study of these data that the calorimeter was very nearly adiabatic. This fact is brought out also in the data reported for naphtha where no pressure drop occurred from block J to calorimeter S. /
I
.?do
I
400
I
600
TEMPERATURE
FIGURE 11.
D.4TA
I 800
I
ACKNOWLEDGMENT
‘F
OBTAINED O N TOTAL
HEAT OF STEAM
While a theoretically more exact means of correcting the naphtha data might have been applied, the simple calculation indicated above was used to obtain the figures for naphtha liquid shown as column 8, Table 11. The order of the correction term is not more than 10 per cent for the naphtha data and is negligibly small for data on the other liquids. Thus the corrected values, for naphtha only, appear in Table 11. DETERMIKATION OF EFFECTOF PREBSURE ox HEAT CONTENT OF VAPORS The throttling calorimeter, used to determine the effect of pressure on the heat content of naphtha vapor, is indicated diagrammatically in Figure 12. The vapors from the heater of Figure 9 pass over thermocouples Y and K , through needle valve L, and out to the condenser. Valve L served to re ulate the pressure on the vapor in the valve block, J . Part of the oil flo+ng through yalve J was allowed to pass through the outlet, N , into the calonmeter, 8. The course of the vapor, after expansion into 8, was through a layer of steel wool, R-R, thence downward over thermorouple T , through ports V , up through annular jacket W , and out t o the condenser over thermocouple X . The pressure in the atmospheric chamber, S , was never more than a few inches of water above atmospheric pressure, as indicated by the pressure gage shown. The pressure before expansion was read from a gage not shown in Figure 12. Before taking readings, calorimeter conditions remained constant for many minutes, after which a number of pres-
The writers wish to acknowledge their indebtedness to
C. A. Porter and F. I. L. Lawrence of The Atlantic Refining Company for their assistance in carrying out the experimental work and for the many suggestions made in the course of this work. Acknowledgment is also due other members of the Process Division, who aided in obtaining analytical data, and whose criticism was very helpful. LITERATURE CITED (1) Baldke, JV. H , and Kay, W. B., IND.ENQ. CHEM.,21, 942-5 (1929). (2) Bureau of Standards, Publication 97, 26-37 (1929). (3) Callendar, H. L., Proc. Roy. SOC.(London),8120, 460-72 (1938). (4) Cox, E. R., IND.ENQ.CHEY.,15, 592-3 (1923). (5) Fortsch, A. R., and Whitman, W. G., Ibid., 18, 795-800 (1926).
(6) Marks, L. S., and Davis, H. N., “Steam Tables and Diagrams,” 1st ed., p. 24, Longmans, 1925. (7) IMcKee, R. H., and Parker, H. H., IND.ENO.CHEM.,20, 1169-72 (1928). ( 8 ) Piroomov, R. S., and Beiswenger, G. A., Am. Petroleum Inst., Proc. Ninth Annual Meeting, [11] 10, No. 2, 52-68 (1929). (9) Watson, K. M., IND.ENQ.CHIN., 23, 360-2 (1931). RECEIVED October 26, 1931.
CORRECTION. In the paper entitled “1931 Passes in Chemical Review” [IND. ENG.CHEM.,24,6 (1932)], the second item in the synthesis of Duprene should be monovinylacetylene instead of monovinylacetate. On page 9 of the same article, the name of the new honorary fraternity, founded a t the University of Illinois, should be Omega Chi Epsilon instead of Theta Chi Epsilon; it should be added that this is strictly a chemical engineering organization, as chemistry students are not admitted tomembeFship.
