enation of C elaves wi SOL WELLER, MICHAEL G. PELIPETZ, 31. KUHN, SAM FRIEDMAN,
AND
E. L. CLIRK
Central Experiment Station, Bureau of Mines, Pittsburgh, Pu.
in obtaining a commercial coke oven gas, a synthetic rnixture \\itis prepared which had the following analysis (mass-spectrometric) :
T h e use of coke oven gas to produce liquid fuels from coal has been investigated in small scale, batch autoclave experiments. Coal may be hydrogenated satisfactorilj with coke oven gas, but the results are not so good as those with pure hydrogen a t the same hydrogen partial pressure. Ethylene in the coke oven gas is reduced to ethane; carbon monoxide is not hydrogenated to methane, but part of i t undergoes the water-gas shift. A t hydrogen partial pressures below 1000 pounds per square inch, increase in temperature from 450' to 465" C. severely decreases liquefaction and increases gasification.
Constituent
APPARATUS, PROCEDURE, AVD MATERIALS
been published ( 1 ) . A 1.2-liter rotating autoclave, equipped with a removable glass liner, was employed. In all cases 50 grams of powdered coal, 0.5 gram of powdered tin, and 0.275 gram of ammonium chloride were used; the tin-ammonium chloride combination is one of the most effective coal hydrogenation catalysts known. When a vehicle was employed, 70 grams of a heavy oil product from coal hydrogenation was added. After sealing, the bomb was flushed and filled with either hydrogen or coke oven gas to the desired pressure, heated t o 450" or 46.5" C. over a period of about 1.3 hours, held at temperature for 1 hour, and then cooled. After cooling, the gases were discharged and analyzed, and the residue in the bomb was analyzed for benzene-insolubles and for asphalt (material soluble in benzene but insoluble in n-hexane). The per ccnt liquefaction v, as defined as coal charge
___-
Volunie % (Air-Free Basii,
RESULTS ANI) DISCUSSION
A detailed description of the hydrogenation equipmcnt has
x
Constituent
The experimental conditions, per cent liquefaction, and asphalt produced per unit of liquefaction are summarized i i j Table I. Runs 639, 481, 734, and 735 mere carried out in thv absence of vehicle. I t is apparent from the results that coal may be satisfactorily hydrogenated with coke oven gas. Within t h i range of pressures studied, however, t o obtain liquefactions with coke oven gas equivalent to that with hydrogen a t a given prcssure, the partial pressure of hydrogen in the coke oven gas must be somewhat greater than the given hydrogen pressure. Th(cause of this apparent inhibitory effect of the gases other t,hnl) hydrogen in coke oven gas is not known; in view of the sensitivity of the per cent liquefaction t o pressure in the range s t u d i d . the effect may disappear at high pressures. Because any commercial use of coke oven gas with currerit co:il hydrogenation techniques would involve the use of coaI-oi1 past(+ rather than dry coal, the remaining experiments were carried 0111 in the presence of a heavy oil vehicle. The experiment's in ti,(presence of vehicle are not directly comparable with those in i i absence. I n the first place, the solubility of the gases in t k l r , vehicle means that the calculated pressures are fict,itious whc'r~ vehicle is prescnt. I n t8he second place, the vehicle itself coiltained benzene-insoluble materials (12.9%) and asphalt (36.57,) which are themselves hydrogenated; in a control experimc:it (450' C., 1 hour, 940 pounds per square inch initial pressure ui' hydrogen) the benzene-insolubles were reduced to 4.870 and thc. asphalt to 14.0%* The data for liyuefactioii and asplitill, p o . duction in the experiments n j t h vehicle are not corrected for t h e benzene-insolubles and asphalt contributed by the vehicle; this accounts for the fact that some of the values for "asphalt p r y unit, liquefact'ion's in Table I arc greater than 1. From the results of the last eight experiment,s listed in Tdjlt~i, the following conclusions ma)- be tlrawn about hgdrogenai i o n when heavy oil is presenl,:
HE cost of hydrogen is one of the major itemsdeterminingthe economic feasibility of coal hydrogenation to produce liquid fuels. It is reported to have amounted to more than half of the total cost of producing gasoline from coal at the Leuna works in Germany ( 2 ) . In connection with a search for a cheaper source of hydrogen, some batch autoclave experiments have been carried out at the Bureau of Mines in which coke-oven gas has been substituted for hydrogen as a hydrogenating gas; this paper presents the results of these experiments. The use of coke oven gas for hydrogenating coal extracts has been suggested by Pott and Rroche (3),but no experiments have been previously reported.
100
Volume yo (Air-Free Basiii
- benzene-insolubles - ___ coal charge
All quantities were calculated on a moisture- and ash-free bads. The initial (cold) pressures mwre obtained by calculation fioin the (bomb) gas volume and the weight of gas charged, as determined by weighing the bomb, before and after charging, on a bullion balance sensitive to 20 ing. Because of the solubilities of the gases in the heavy oil vehicle, the actual gas pressures when vehicle was used were less than the calculated pressures. Thc pressure attained a t reaction temperature was approximately double the initial pressure. For this reason, it was not possible, with the apparatus used, to employ initial pressures much greater than 2000 pounds per square inch. The coal used was Pittsburgh seam, high volatile A bituminous coal obtained from the bureau's experimental mine a t Bruceton, Pa. The coal as used contained 1.5% moisture and 7.2% ash. The heavy oil vehicle employed in most of the experiments contained 12.9% benzene-insolubles and 36.5% asphalt, the remaining 50.6% being soluble in n-hexane. Because of difficulty
The extent of hydrogenafion is very dependent on pressure C01, (initial) hydrogen partial pressures below 1000 pounds per square inch, in the presence of either coke oven gas or hydrogcii. Increase in temperature from 450 to 465' C. has a deletcrioux effect on the hydrogenation, in the presence of cit,hcr coke o w n gas or hydrogen. As in the case of the dry coal experiments. for (initial) hydrogen pressures below 1000 pounds per square inch, lirdrogen is a more effective hydrogenating agent than is coke oven gas with the s a m e hydrogen partial pressure.
It was of int,erest to detormine the behavior of each of the colieoven gas constituents during the hydrogenation. hlass-spectrometric analyses were obtained of tlheinitial and final gases ill these experiments. From the amalyses, weights of each constil uent, 972
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1949
TABLE11. MATERIAL BALANCE FOR GASES
TABLE I. HYDROGENATION OF B R U C ~ T O COAL N IN HYDROGEN AND IN COKEOVENGAS (1 hour a t temperature, 1.0% Sn Total ' Initial Pressure. Calcd ' Run Temp., Lb./Si. No. Vehicle C. Gas Inch C.0.G.a 2120 450 639 None Ha 1000 481 None 450 C.O.G. 1630 450 734 None 736 None Hz 830 450 C.O.G. 1650 H.0.b 450 657 C.O.G. 1610 658 H.O. 465 C.O.G. 1160 H.O. 450 659 C.O.G. 1120 H.O. 465 660 733 H.O. 450 Hz 870 H.O. 465 H.2 850 732 450 Ha 680 737 H.O. H.2 660 H.O. 465 736 a Coke oven gas. b Heavy oil.
+ 0.55% NH4C1) Initial Pressure of HI. Calcd., Lb./Sq. Inch 1170 1000 900 830 910 890 640 620 870 850 680 660
%
Liquefaction 86.3 86.1 75.2 86.0 73.5 51.7 62.3 25.8 85.4 75.1 79.2 54.8
Asphalt uer Unit Liquefaction 0.34 0.28 0.44 0.48 0.91 0.85 1.07 2.02 0.76 0.70 1.28 1.18
charged and bled were calculated; these weights, for runs 639 and 481, are listed in Table 11. The following items may be noted: The total weight of gas bled, as calculated from the volume and analysis of the gas, agrees well with that determined by direct wei hing of the bomb before and after bleeding. T%e decrease in carbon monoxide and increase in carbon dioxide in run 639 indicate that some of the carbon monoxide in coke oven gas undergoes the water-gas shift during the hydrogenation. The reaction CO 3Hz + CHI HzO does not occur appreciabl when coke oven gas is used. Etxylene in coke oven gas is hydrogenated to ethane.
+
Gas
Constituent H2 CHI CzH4 ClHS CaHa CaHs C4Hs CiHio CsHio CsHie N2
co coz
Air Total Total (direct weighing) Total hydrocarbon gases
Weight of Constituent, Calculated from Gas Analysis Run 639 Run 481 Charged, Bled, Change, Charged, Bled, Change, g. g. 8. g. g. g. 6.2 4.0 -2.2 5.5 4.2 -1.3 27.5 28.6 $1.1 0 2.1 +2.1 -0.Y 0 -0.9 0 0 0 3.9 +4.8 0 8.7 1.6 +l.6 0.2 '0.2 0 0 0 0 1.9 3.7 +1.8 0 1.5 +1.5 0.3 0.7 $0.4 0 0.2 +0.2 0.7 1.3 +0.6 0 1.0 +l.O 0 0.3 +0.3 0 0.3 +0.3 +0.3 0 0 0.3 0.2 +0.2 5.0 5.0 0 0 0 0 9.5 8.0 -1.5 . 0 0 0 +1.9 0 0.2 2.1 0.3 $0.3 0.8 0.8 0 0 0 0 57.i 63.7 +6.6 5 3 11.4 $.5.9 (57.1) 64.2 +7.1 (5.5) 11.2 +5.7 35.4
43.8
+8 . 4
0
6.9
$6.9
sure from 1630 to 1140 pounds per square inch does not appreciably influence gaseous hydrocarbon formation, increase in temperature from 450' t o 465' C. ( a t 1140 pounds per square nch initial pressure) almost doubles the gasification. ACKNOWLEDGMENT
Thanks are due to R. A. Friedel and his group for providing tho mass-spectrometric analyses of gases.
+
Similar gas balances have been made for runs 657, 659, and 660. The results are in agreement with the conclusions listed above. I n addition, it appears that (1) the consumption of hydrogen is about the same in all the experiments (approximately 2 grams), and (2) although change in initial coke oven gas pres-
973
LITERATURE CITED
(1) Fisher, C. H., Sprunk, G. C.,Eisner, A., O'Donnell, H. J., Clarke, L., and Storch, 13. H., U. S. Bur. Mines, Tech. Paper 642 (1942). (2) Holroyd, R.,U. S. Bur. Mines, Information Circ. 7370 (1946). (3) Pott, A.,and Rroche, H., U. S. Patent 1,881,927 (Oct. 11, 1932), RECEIVED January 12, 1949. Presented before the Division of Industrial CHEMICAL and Engineering Chemistry at the 113th Meeting of the AMERICAN BOCIETY, Chicago, Ill. Published by permission of the Director, Bureau of Mines, U. S.Department of the Interior.
Mass Transfer in Liquid-Liquid Agitation Systems ARTHUR W. HIXSON AND MELVIN I. SMITH' Columbia University, New York 27, N . Y .
A procedure is developed which may be used to predict the quantitative performance of an agitator in a liquidliquid extraction system. An equation relating the weight of solute transferred from one liquid to a second immiscible liquid is derived; it is verified experimentally on the almost Ideal system water-iodine-carbon tetrachloride in a series of geometrically similar vessels. The numerical effect of speed of agitation upon rate of solute transfer is given.
T
HIS research is intended to extend the earlier work of Hixson and co-workers (1-4) into the realm of two-phase
liquid-liquid systems in which mass transfer occurs. The cube root law and its modifications, developed to describe the behavior "of solid-liquid systems in agitation vessels, are useful in the design -ofsuch agitators and as an index of the efficiency of such a vessel 1 Present
address, Socony-Vacuum Oil Qompany, Brooklyn, N . Y.
already in use. The purpose of this investigation is to derive a workable equation from theoretical considerations, to establish its validity experimentally, and to correlate the data obtained under various conditions in such a manner as to make feasible the design of an agitation vessel which will efficiently transfer a solute from one liquid to another. I n their work with solid-liquid systems, Hixson and eo-workers found the "dissolution constant" t o be a convenient index of the efficiency of agitation. This constant is a mass transfer coefficient in the true sense and is readily measurable. In this investigation of a liquid-liquid system, a hybrid coefficient is evolved which includes two mass transfer coefficients and the interfacial area of contact; none of these quantities lends itself to measurement. This new coefficient, easily determined, is a measure of transfer rate. I n the following derivation, the usual assumption of the existence of two films is made. I n addition, the interfacial area is
