I N D U8TRIAL A N D ENGINEERING CHEMISTRY
32
Vol. 17, No. 1
Gas Formation in the Cracking Process’ By Gustav Egloff and Jacque C. Morrell UNIVERSAL OIL PRODUCTS c o . , CHICAGO, IJ.,I..
From other information which may be obtained aside from gas formation, it is to be observed that continued work with any one type of oil will give improved results with regard t o gasoline yield and charging oil throughput.
I
N THE cracking process considerable gas is invariably formed. This gas is an important economic item as a fuel as well as for other purposes. The production of alcohols and other chemical derivatives from it indicates its possibilities as a raw material for various products. I n present practice, however, the gas formed is piped to the furnace to be burned, thus effecting a considerable saving in fuel consumption.
Nature of Gas Formed
Table I1 shows the proximate composition of the gases formed as well as the specific gravity and calorific values. These analyses are of an order of precision used for good control work and were made as follows:
Amount Formed
The amount of gas formed per unit quantity of oil charged, or, from another view, per unit quantity of gasoline formed, depends on so many factors that for any one type of oil a series consisting of many experiments would be necessary. Not only is the quantity of gas formed a function of the type of charging stock and operating conditions, such as temperature and pressure and the extent to which conversion has taken place, but it may also be dependent upon local conditions in the heating coil and the reaction chamber. For a complete study, therefore, all the factors should be carefully regulated, changing only one variable for any set of experiments with particular reference to the study of gas formation. This has not been done in the present case, the data shown below being rather of a statistical nature based on actual commercial practice.
’ Carbon dioxide plus hydrogen sulfide was determined by absorption in sodium hydroxide solution. The percentage of carbon dioxide is usually less than 1.5, so that hydrogen sulfide may be taken as the difference. For special cases, arsenious acid, cadmium chloride, and iodine solutions may be used as absorbents for hydrogen sulfide; in the latter event the excess iodine is determined by titration with sodium thiosulfate. The unsaturated hydrocarbons were determined by absorption in an aqueous solution of bromine; oxygen by absorption in an alkaline solution of pyrogallol ; carbon monoxide by absorption in cuprous chloride; hydrogen by fractio’nal oxidation, using porous cuprous oxide. The straight-chain or saturated hydrocarbons (plus nitrogen) were assumed to make up the difference in volume. The specific gravities were determined by weighing in a Dumas bulb, comparing under the same conditions with air. The bulb was evacuated before filling. The calorific values were determined in a Sargent calorimeter.
TABLE I SamGravity ple CHARGING STOCK ’ BB. 1 Midcontinent gas oil 35.6 2 Midcontinent kercsene distillate 38.4 3 North Texas kerosene distillate 39.5 4 Midcontinent fuel oil 26.9 5 Midcontinent topped crude 28.9 6 Rangertoppedcrude 26.8 7 Healdton crude 29.6 8 Montana topped 38.4 crude 25.5 9 Kentucky fuel 10 Mexicandistillate 26.3 11 Mexican gas oil 21.0 12 Panuco residuum 9.7 (Mex.) 13 Panuco residuum 9.7 (Mex.) 14 Panuco residuum 9.7 (Mex.) 15 Panuco residuum 9.7 (Mex.) 12.6 Panuco crude 16 17 Panuco crude 12.6 13.4 18 Venezuela fuel I9 Venezuela fuel 13.4 20 Tarakan crude (Borneo) 18.2 21 Tarakan crude (Borneo) 18.2
Uncon- Cracked PER CENT OR RAWOIL densable distil- (IBP-EP) CUBICFEETGASPBR BEL late Navy Cracked Operating 18% Per cent gaso- Gas oil Resid- Raw distilGasopressure Bbls. cu. ft. oil cracked line Bottoms uum oil late line of system 1793 543 79.90 44.3 34.0 7.1 303 378 684 120
Liquid temperature 861
Hours continu-
ous crack-
ing 235
1053
280
90.86
52 6
34.3
0.0
266
272
506
135
849
198
578 2007
40 341
96.61 51.25
41 9 36.8
53.2 12.0
2.6 45.6
69 170
72 331
164 tl62
136 120
856 850
102 177
969 674 707
183 112 84
60.01 59.75 65.19
41.6 41.5 45.1
15.9 14.0 18.1
34.1 39.7 26.8
189 166 119
315 278 182
454 400 264
120 120 120
845 843
...
82 52 51
251 924 861 1070
13 171 125 253
83.95 59.7 60.19 54.95
48.2 43.9 39.6 41.7
8.4 12.0 19.6 9.7
14.5 34.5 35.3 38.5
52 185 145 236
62 310 241 430
108 421 366 566
135 120 120 120
820 865 816 871
43 72 82 89
1048
130
21.86
18.9
1.9
73.1
124
566
656
120
831
69
530
660
120
823
60
1012 682 648 716 1373 1051 974
‘
141
26.32
21.1
3.9
66.5
139
96
22.09
18.2
2.8
66.0
141
637
773
120
802
45
23.5 30.8 34.1 30.9 38.5
18.5 23.7 28.2 23.3 26.9
4.0 6.0 4.5 5.7 10.0
70.6 62.9 64.2 61.0 52.2
110 110 173 111 137
466 358 506 360 355
595 464 614 476 508
115 110 110 110 105
844 822 825 838 832
34 41 94 58 54
71 79 237 117 133
1199
376
60.62
32.4
25.6
28.8
314
518
969
130
857
110
1187
413
61.69
30.6
27.8
26.6
348
564
1137
125
867
117
All the runs indicated in Table I were made in a Dubbs cracking still with a charging capacity of 250 barrels per day. Despite the fact that from the data presented it is difficult t o draw any generalized conclusions with regard to gas formation it is believed that, covering such a wide range of charging materials as it does with commercial yields of gasoline for each type of charging material, the table will be useful. 1 Presented under the title “Gas Formation in the Cracking Process as a Function of the Conversion of Various Type Oils into Gasoline” before the Division of Petroleum Chemistry at the 67th Meeting of the American Chemical
