Oxygen Gasification of Coal Some Unsolved Processing Problems 1. L. NEWMAN, U. S. Bureau o f Mines, Washingfan 25, J.
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P. McGEE, U. S.
Bureau of Mines, Morganfown,
U SPITE of the generd rise in gas consumption during the last
decade the use of solid fuels as the raw material for the manufacture of gas both for public utility distribution and the production of chemicals has been rapidly decreasing in the United States. At the end of 1954 the total gas utilities in the United States had 27,527,700 customers, including 266,600 receiving liquefied petroleum gas through utility mains. Of these customers, only 1,769,100were served with manufactured gas, whereas 4,093,600 received mixed gas containing s u b s t m t d quantities of natural gas and 21,398,400 received natural gas. Thus, 93% of the American consumers of public utility gas were dependent on natural gap (I). Similarly, in the American synthetic ammonia industry, with a total basic capacity of a 5 6 standard tons of anhydrous ammonia per day, only 1210 tons of capacity depended on water gas derived from coke for the supply of hydrogen, 110 tons on refinery gas, and 436 tons on chlorine cells, but 6600 tons on natural gas. Hence, 80% of the plant capacity for the manufmture of ammonia depended on natural gas (.80). Although over 65% of the fuel consumed for the production of electricity by public utilities was provided by coal in 1954, natural d as was a very contributor with more than " imnortant . 25% of the total fuel consumed (8). The reserves of natural gas are kept under constant review by the Committee on Reserves of the American Gas Association and the American Petroleum Institute. The proved recoverable resemes of natural gas in the United States at the end of 1955 have been reported t o have reached a new high of 223.7 trillion cubic feet, while the net production also attained a new peak of 10.1 trillion cuhio feet. !Net production is the gross produetion from produeingreservoirs lessthat gasreturned to producing reservoirs in cycling and repressuring projects.) The current ratio of proved recoverable rewves to net production, therefore, exceeds 22: 1 (8). Production, however, has been increab ing more rapidly than proved reserves (in 1946 the ratio of proved recoverable reserves to net production was 33:l). The rising demand indicates that every major consuming region in the United Sbates will soon be served with natwal gas, thus forcing further acceleration in the rate of inereease of production, Additional reserves will undoubtedly be found but, if the demand continues to increase, more supplementary supplies of manufactured gas will be required. Most of these sup plies are currently derived from the gasification of oil, but the time is not too far off when cad must be used again for. manufarturing gas t o supplement or replace natural gas and ta supply synthesis gas for chemicals and fluid fuels. From the projected demands given in the Paley report (191, Hafstad's extrapolation in Figure 1 Show8 that both uranium and fluid fuels from coal will begin to take their place as sources of primary energy in 1965; by 1975 Figure 1. or thereabouts, the long atiaited squeeze on fluid I
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W.Vu. fuels will begin to make itself felt (11). At that time coal is almost certain t o be gasified t o a greater extent than ever before in the United States. Even before 1965 local conditions may again permit economic gasification of coal. I n New England, for example, because of the distance from the source of nrttural gas, the combined demend charge and commodity cost of the gas delivered to the distributing companies is such a8 to permit them t o match pipeline costs by high B.t.u. gas from the gasification of oil. Gas from coal is not yet competitive there, hut students of the situs, tion are convinced that costs of high B.t.u. gas from coal will he lowered a8 fast 8 8 the major processing problems are solved ( I S ) .
Character of Gas Required Three broad categories of gas will be required for supplementing or replacing natural gas: Supplement to or Replacement for Public Utility Gas Supply, The gas must he interchangeable with natural gas. Among the principal factors affecting interchangeability, calorific value, specific gravity, and m p o s i t i a n are of major importance. These and other problems are being studied, and the criteria me becomina well understood (10.82 1. Synth;sis Gas for production.of Chemicals and Liquid Fuels. The composition of such gas will depend on the end product and the method of production. Thus, for production of liquid fuels by the hydrogenation of coal the gas will consist almost entirely of hydrogen; for synthetic ammonia, of approximately 3 parts hydrogen and 1 part nitrogen; for liquid fuels by the FischerTrapscb process or for methanol, of mixtures of carbon monoxide and hydrogeninvaryingratios.
U. S. consumption of primary energy may look like this by year 2000 ( 7 7 )
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
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Figure 2.
A N D CHEMICALS
Pilot plant flowsheet for Bureau of Miner high-pressure pulverized-coal gasifier, Morgantown, W. Vo.
IndusMal Fuel. Oil and natural gas will eventually become premium fuels for the generation of electricity. As the supply of t h w diminishes, coal and nuclear fuel will he used where fluid fuels would have been the normal murce of primary energy. Generally, however, the coal will he burned directly. In a limited number of instances the coal will he carbonized to recover the tar and chemicals, and the char will be uaed for generating steam. Complete gasification is not likely to he used as an intermediate step in large Eale steam generation. For other industrial applications the kind of gas produced will depend largely on the use. In general, produeer gas will resume ita former position when shortagesof oil and gas will become felt. Gas produced by underground gasification, having heating valuee equal to or M o w those of blast furnace gas, will find limited application only where the combination of geological conditions and utilization requirements will be favorable.
Available Methods of Manufacture
Proceases for gasifying coal with oxygen and stem may be confined to the production of high B.t.u. gas for public utility d b tribution or the synthesis of oil or chemicals. The major steps involved in any case include: ( a ) gasification, ( b ) purification, (e) carbon monoxide conversion when the initial concentration is high, and (d) synthesis to methane, oil, or chemic&. Processes that have attained a considerable degree of development are available for effecting steps b to d. These are subject to conventional chemical engineering treatment. Nevertheleas, there in much need for additional research and development work on these phases to improve the processes, equipment, ENhhiug or separation medium, and catdysta and to integrate them with the oxygen-g&cation proteases. Cyclic Water-Gas Generators. With coke or nondecrepitating anthracite of suitable size, @cation can be carried out in the conventional water-gas machine. Such fuel is expensive; this, for all practical purposes, eliminatesthe cyclic water-gas machine from consideration. July 19%
FUELS
To permit the w e of cheaper fuels the Bureau of Mines and other groups have studied the applicability of gasification with oxygen by processes that already had reached commercial stages of development. Fluidized-Bed Generctors. Fluidized pmeeesea were given full consideration, as they have appeal because of the marked succem of the fluid catalytic processes employed in petroleum refining operations. For petroleum operations the catalyst rehins its physical and chemical characteristics for long periods; in gasification, however, the Euidized coal is progressively consumed and is m u reduced to a size below the minimum required for retention in the bed and carried out of the gasification zone into oooler zones where the reaction rates are, for aU practical purposes, negligible. Conversion of carbon is, therefore, lower than for coal that is finely pulverieed and g a d i d in entrainment. &Ecation of Ruidised beds is semitive to the caktrg characteristics of the coal, while gasification in entrainment is v i r t d y independent of this particular property of the coal. Atmospheric-Pressure, Pulverized-Coal-Fired Generators. Accordingly, gasification of finely pulverized coal in entrainment by means of oxygen and steam was selected a8 the most promising method for producing synthetic liquid fuels, ammonia, and methanol. Gasification of pulverized coal at atmospheric pressure has recently attained commercial development. The K o p p dust gasification process has been used in Finland with Silesian bituminous coal (M), and a gasilier furnished by the Bahcock & Wilcox Co. has been installed in Du Pont's synthetic ammonia plant at Belle, W. Va., to gasify high volatile bituminous coal(9). High Pressure, Pulverized-Coal-Fired Generators. 'Khatever the use and composition of synthesis gas, it will generally be treated in high pressure reactors. When the gas is generated a t atmospheric pressure it must therefore he wmpreamd. Compression costs can be reduced materially if the gasis produced at h& pressure, as only oxygen thus needs to be w m p r d to the pressure of the generator. When the synthesis gas is generated at 30 atmospheres, ap-
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proximately 70% of the power required for compression is saved. In operations where the gas w generated at 30 atmospheres and subsequently must be compressed to 1000 atmospheres at le& half the energy required for compression is saved (16). Possible further saving in equipment cost may %me from increased throughput at elevated p r k , although this may be offset by aided costs of coal feeding, slag removal, uwte-heat recovery, ete.
Feeding Coal at High Pressure The problem of feeding coal under pressure is difficult. The feeder shown in Figuro 2, developed by the Bureau of Mines, receives coal from a transfer hopper which is filledwith pulverized coal at atmospheric pressure and then pressurized. A t suitahle iut,ervals hatches of cod are transferred under pressure to the continuous feeder. Tho coal in this feeder is kept in a state of suspension by recycled inert gas and continuously fed to the coal inlet nozzle of the generator. While this type of pneumatic feeder is adequate for pilot plant operations, i t would obviously be quite cumhersome commercially. Regular control of the feed rate is prevented by internal disturbanoes, and frequent refilling is necessary. Also, an excessive amount of coal dust is entrained in the fluidizing gas musing rapid wear of the recycle compressor. Work is nnderu-ay on a two-zone feeder in which lower fluidizing gas velocities have resulted in reduced coal entrainment and in increased capacity. At the Institute of Gas Technology feeding is done hy entraining coarse particles of coal io a stream of compressed gas or steam and expanding this fluid through an ori6ce or nozzle. The resulting suspension of coal in the jet is introduced into a vortex chamber forming the upper zone of the gasifier, where, with the addition of oxygeu and superheated process steam, additional particle degradation and partial gasification tske place. Further gasification occurs in the lower zone of the g d e r ($4). This system of feeding has been succesdul in pilot plant opere tious, hut the problem of scaling it to commercial operation remains to be solved. An entirely different approach to the method of feeding has been developed hy the Texaco Development Corp. Pulverized mal is mixed with water in a thickener to form a slurry. This slurry is pumped through heating coils from which, as a result of vaporization, it emerges as a mixture of steam and coal. This mixture is passed through a cyclone where the surplus steam is removed. Tbe remainder is fed to the generator through a suitable nozzle (7). This type of system for feeding coal into a pressurized reactor is especially attractive. Tests have shown that slurries of a p
I
roximately 50% water and 50% coal by weight can be pumped p to pressures of 30 atmospheres. However, mnah remsjna t o be !wued about the behavior of the slurry in the coil when there is a iange of phase from the liquid to vapor. Apparently at high ressures the change is smooth, and no slugging occurs. The eating coil is subject to erosion, and its useful life is yet to be etermined. Instead of coils several parallel Rets of straight tubes with xcially designed return bends prohebly will he used c o m e r ally. Erosion should he less in the tubes (where there will be D change in direction of flow) and greater in the return bends. %eese, however, can he plaeed outside the furnttce where repairs m he quickly made after isolation of the set of straight tubes in hich the damaged return bend is located. Thus erosion failures ill not cause a complete shutdown of the generator, and the loss i cspacity from the failure of one set of tubes may be compensated by temporarily overloading the remaining sets of t u b e . As no cyclone is capable of removing the last traces of solids from the carrier fluid the surplus steam skimmed off before i t reaches the generator is contaminated with more or leas coal, depending on the e5ciency of the cyclone. This poses the d u d problem of recovering the energy in the form of clean steam a d recovering the coal. The solution may be found in feeding the contaminated surplus steam into a steam accumulatox opersting on the principle of Ruth’s ~ c n m u h t a r(28) and provided with a sump for collecting the coal. Figure 3 s h m the relation of the sccumulator to the slurry feeding system. Periodic blowoffs of the accumulrrtor sump will permit tbe return of the coal to the slurry tank, simultaneously providing additional agitation. The success of the system will depend largely on adequate means of separating the coal from the water, and some experimental work in this connection should be carried out to provide essential design information, The hot blowoff into the slurry tank may lead to new problems in pumping. Slurry pumps for high pressure delivery are well developed for hydraulic fracturing in oil fields. They may not, however, function properly on slurries of hot water and coal In that case, apparatus similar to the acid egg may have to he resorted to. The flow of the reactants is downward in the pilot plants d e veloped by the Bureau of Mines, the Texaco Development Grp., and the Institute of Gas Technology, The problem of removing ash or slag is treated in essentially the Same m n e r in the Texaco and the bureau gmifiers. The latter is shown in Figure 4. The gas is cooled by a spray of water just below the reaction zone. Tbe hot slag disintegrates and drops to the bottom in granular form. It is removed intermittently through what is essentially a boiler blowoff valve. This valve requires more development work to e n m e that the granulated slag will never interfere with its closing, but the problem is not a very serious one. However, fluctuating pressure during the blowoff is serious, and an intermediate lock hopper may ultimately he reqnired.
Process Variables The optimum economic tbroughpnt represents a compromise between the fullest use of reactants and minimum investment in equipment. To determine this throughput the process variables must he studied-among them the volume needed for a given throughput of coal. The problem of mainbinkg refractories can be elimiuated by depending instead on the deposit of slag on water-cooled walls until an equilibrium thickness is attained. Slag thiekuess is a complex function of several variables and much of the gasifier development to date has followed cuband-try procedures in this connection; it will continue so until empirical relations have bem derived. Moreover, additional fundamental d a b we nwded on the flow characteristics of slags from American coals under conditions that exist in the gaifiers.
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In addition to the savings in compression cost and smaller equipment, elimination of refractories and their erosion in generators operating under pressure is another advantage high pressure gasifiers are expected to have over those operating at atmospheric pressure. Enough experience has been gained in gasifying pulverized coal a t atmospheric and elevated pressures in pilot plants to justify the conclusions that, as far as the reactions are concerned for any particular coal, the relative amounts of oxygen, steam, and coal are far more important than the sequence of their admission to the generator. X o significant differences in gas analysis or extent of carbon conversion can be attributed to differences in operating pressures when the relative quantities of oxygen, steam, and coal and the heat losses remain unchanged. Recovery of waste heat in atmospheric pressure gasifiers is well advanced, but the problem has barely been tackled in high pressure gasification of pulverized coal. Steam generators employing combustion gas a t very high pressures have a very high heat transfer coefficient (roughly proportional to do.75, cl being the density of the gas). Furthermore the thickness of the boundary layer decreases because of the high velocity of the gas across the trthes, which is possible because a relatively large pressure differential can be tolerated in high pressure gasifier operation ( 1 7 ) . Deposition of slag on the tubes must be prevented to realize these advantages. I n any specific generator when pulverized coal is gasified, whether a t atmospheric or high pressure, the extent of carbon conversion depends principally on the rank of the coal and the oxygen-to-carbon ratios. Figures 5, 6, and 7 give typical results for the percentages of carbon gasified and the corresponding carbon and oxygen consumptions, respectively, at constant steamcarbon ratio and constant rate of throughput in the Bureau of hlines low pressure gasifier a t Morgantown, W. Va. The spread between the curves may be narrowed to an undetermined extent by altering some of the factors, and indeed the design of the generator, to suit the requirements of each particular coal. However, the relative positions of the curves are not expected to change. The unconverted carbon need not be a total loss. The portion that is recoverable by dry removal (cyclones or electrostatic precipitators) may be recycled to the generator if not required for steam generation. Where this residue is coarser than the original feed the best method of recycling is reintroduction with the coarsely crushed fresh coal entering the pulverizers. This method ensures thorough mixing of the recycled residue with the
REACTANT NOZZLE
,-PILOT DURNER
GAS SAMPLE
MAKE -GAS OUTLET
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Figure 4. Bureau of Mines high pressure pulverized-coal gasifier, Morgantown, W. Vu.
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Figure 6.
Carbon consumption and oxygencarbon ratio
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Figure 7. Oxygen consumption and oxygen-carbon ratio
Anthracite, l a k e DeSmet, and Sewickley coals gasified in atmospheric gasifier a t constant steam-carbon ratio of 0.70 Ib./lb. and a t constant carbon input of 430 Ib./hr.
July 1956
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fresh coal. Direct introduction, however, niay result in savings of giinding costs. After allowance is made for the greater heat losses inherent in pilot plant operations, oxygen consumption in pulverized-fuel gasifiers, even in those in which low rank fuel is converted, still is a t least 507, greater than in fixed-bed gasifiers. The extent of carbon conversion in fixed-bed generators is much greater and virtually independent of the rank of the coal. To attain the same extent of carbon conversion in pulverized-coal generators it n-ould be necessary to recycle all of the residue.
High Pressure, Fixed-Bed Generators Conventional and slagging gas producers have been successfully adapted to oxygen-blown operation for supplying synthesis gas for the production of ammonia. These processes, however, require expensive coke or anthracite, although reduced consumption of fuel combined with savings in attendance, maintenance, and repairs, and init'ial cost of equipment amply offset the cost of the oxygen. Conventional producers, in which relatively thin beds of caking coal are gasified with the aid of levelers or agibators, might also be converted to operation with oxygen. The presence of hydrocarbons, undesirable for production of ammonia, may be avoided by washing FTith liquid nitrogen or catalytic conversion, both commonly used at present. The cost of synthesis gas which can be afforded for the manufacture of ammonia in select,ed locations is prohibitive for high B.t.u. gas or synthetic liquid fuels. Fixed-bed, oxygen-blown pressure gasifiers provide t,hree possible means for reducing the cost-cheaper fuel, reduced consumption' of oxygen, and lower cost of compression. Xhen coal is gasified in fixed beds under pressure, methane is synthesized in the bed, and, in addition, noncondensible distillation products are retained in the gas. Hence, a fourth saving is possible in high l3.t.u. gas production: four volumes of carbon monoxide and hydrogen are required to synthesize one volume of methane; therefore, for each volume of methane, or its equivalent in calorific value in higher hydrocarbons, the requirements are reduced by three volumes of carbon monoxide and hydrogen. When World War I1 began the Lurgi pressure gasification process was fully engineered and proved for selected sizes screened from the breakage of brown coal briquets. These are noncaliing. Since t'he war further developments, including the addition of an agitator to the generator, have permitted the use of aealily caking coals, and several large Lurgi installat'ions are under may (12,22). For the cheaper sizes of noncaking Pennsylvania anthracite and many of our western noncaliing coals, the Lurgi process offers an immediate solution, But, for pressure gasification of the strongly caking American coals the process is not directly applicable. Pretreatment of the coal to reduce its caking tendencies sufficiently for trouble-free us? may be one method of approach, provided the cost of pretreatment is loiv enough. This, in essence, is the major problem that must be solved for Lurgi operation. Another problem is to reduce t,he consumption of steam. The high steam consumption is not inherent in the process but is caused by the requirements of the ash-removal equipment. The Lurgi grat'e, unlike those provided with intermittent wat'er-gas machines, is not designed to break and remove hard clinker formations. Consequently high ratios of steam to oxygen are maintained to prevent fusion of the ash. Clinker-breaking grates would reduce the steam consumption to some extent, but they are expensive. As a result the alternative of high steam consumption has been accepted. Another possible alternative is to eliminate grates ent'irely and to operate slagging. This is easy enough a t atmospheric pressure but requires considerable experimentation before the 1116
problem can be adequately solved for high pressure operation Slagging operation, in addition to providing savings in steam consumption, Kill provide the added possibility of using high ash coals, which should result in further savings because of the eliinination of washing costs where freight and transportation costs are low. Cost of Oxygen
The cost of oxygen is a significant factor in the cost of production. 4 nex approach suggested by the Institute of Gas Technology is utilization of the pressure and temperature of t'he gas leaving the generator by expanding it through a gas turbine, as shown in Figure 8, to meet all the power requirements for oxygen production and oxygen and gas compression. This procedure eliminates the boiler plant, 13% of the coal requirements, and reduces the capital investment by substituting the gas t'urbine for heat exchanging equipment and electric motors or steam turbines in air-separation plants (18). This assumes that the problems relating to high temperature operation of directfired pulverized coal gas turbines will be solved. Other possibilities of lowering the cost of oxygen appear to be quite remote. Nevertheless, the problem of using chemicai met,hods of separating the oxygen from air more economicalllt'han by liquefact,ion and dist'illation is challenging. Xore challenging still is the possibility of complete elimination of oxygen, as by indirect gasification of coal by processes such as the reduction of iron oxide by producer gas and reaction of the elemental iron with steam and carbon dioxide or by direct gasification of steam and coal in a nuclear rcact'or. h discussion of processes in which the use of oxygen is eIiminated would go far beyond the scope of this paper.
Gas Treatment Processes
The cost of operat,ing many unit processes employed in treating t'he gas is significant, Therefore research and development work must be continued on the unit processes both individually and iri combination. As stated earlier, t'he means for purificat'ion, carbon monoxide conversion, and synthesis to methane, oil, or chemicals are snbject to conventional chemical engineering practice and have at'tained a considerable degree of development. Severtheless, the relations between the unit processes employed for the treatment of r a v gas are such as to have considerable influence on the basic operations of the generator. This point is illustrated by two examples: 1. The techniques of operating gas turbines may he applied for more efficient recovery of dry, unconverted carbon. Consequently additional provisions for recycling and entirely diff erent ratios of oxygen to steam to coal may become necessary. 2. A sulfur-resistant catalyst might be developed lor the conversion of cnrhon monoxide (6). I n that event sulfur would need to be removed only after conversion, and simultaneous removal of sulfur and carbon dioxide might be feasible. Furthermore, cooling of the gas could be eliminated, resulting in saving the unrcacted steam for the water gas shift reaction and reducing rhe steam consumption to that extent. Methods of removing dust, developed for operating pulverized-coal gas turbines, would solve the problem of preventing clogging of the catalyst.
Thermodynamics and Kinetics So far in this article, scant attention has been given t o thelniodynamic and kinetic considerations. The thermodynamics of the gasification system has been fairl3- well defined, and numerouz reports have been pieFented on methods of calculating gas compositions and temprrntures based on certain equilibria ( 14 ) and the practical application of these calculations for the propel choice of process variables (5).
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SYNTHETIC FUELS A N D CHEMICALS
RAW SYNTHESIS GAS FROM
F E E D WATER PREHEATER
COS REMOVAL COURTESY INSTITUTE OF GAS TECHNOLOOY
Figure 8.
Production of natural-gas substitutes from coal by pressure gasification and methanation
Ais both homogeneous and hetereogeneous reactions occur simultaneously in the complex reacting system, the gasification reactions have been investigated extensively for a great number of years ( 3 , 4). No single study has been adequate t o clarify completely the kinetics involved. I n the aggregate the vast literature on the subject has contributed enormously t o our insight of the carbon-oxygen-steam reactions. Much, however, remains to be learned regarding the factors affecting the rate data that will serve as a basis for future design of equipment. There should, therefore, be no abatement of research on kinetics of the gasification reactions. Meanwhile design of equipment will continue to be a n artnot an exact science-and the intuitive approach, combined with judgment and imagination, will continue to be the most effective one t o solving the problems of gasifying coal. Literature Cited (1) rlinerican Gas Association, New York, N. Y., “1955 Gas Facts, A Statistical Record of the Gas Utility Industry,” 1954 data, Table 1. ( 2 ) American Gas Association and American Petroleum Institute, Committee on Natural Gas Reserves, Oil Gas J. 54, No. 46, 122-4 (March 19, 1956). (3) Batchelder, H. R., Busche, R. M., IND. ENG.CHEM.46, 2501-8 (1954). (4) Batchelder, H. R., Busche, R. M., Armstrong, W. P., Ibid., 45, 1856-78 (1953). (Extended bibliography.) (5) Batchelder, H. R., Sternberg, J. C., Zbid., 42,877-882 (1950). (6) Bridger, C. L., Gernes, D. C., Thompson, H. L., Chem. Eng. Progr. 44, No. 5, 363-82 (1948). (7) Eastman, D., “Gasification and Liquefaction of Coal,” pp. 739, ,4m. Inst. Mining and Met. Engrs., New York, 1953.
July 1956
(8) Federal Power Commission, Washington 25, D. C., Publ. 5-119, 1954. (9) Grossman, P. R., Curtis, R. W., Trans. Am. SOC.Mech. Engrs. 76, NO.4,689-95 (1954). (10) Grumer, J., Am. Gas Assoc. Proc. 1952,pp. 852-6. (11) Hafstad, L. R., presented before New York State Bankers Associatian, The Chase Manhattan Bank, New York, N. Y . , January 24, 1955. (12) Hardwick, J. M. D., Gas Times 81,No.836,492-4, Dec. 24,1954. (13) Henry, H. M., f f a s Age 115,36, 37, 40-49, 70, 72, 73 (Xarch 10, 1953). (14) Katz, S., Parent, J. D., Inst. of Gas Technology, Chicago, Ill., Bull. 2,January 1948. (15) McGee, J. P., Schmidt, L. D., Danko, J. A , , Pears, C. D., “Gasification and Liquefication of Coal,” p. 81, Am. Inst. Mining and Met. Engrs., New York, 1953. (16) Marks, L. S., hlechanical Engineers’ Handbook (L. 5. Marks, editor), 5th ed., p. 327, McGraw-Hill, Kew York, 1951. (17) Mercier, E., Fourth International Conference on Industrial Heating, Group 111, Sect. 33, Paper 228, Paris, 1952; Gas Turbine and Oscillating Compressors,” pp. 14, 15 and figures 15, 16, lZiercier Developments, New York, N. Y. (18) Pettyjohn, E. S., Coal Age 60, N o . 3, 54-7 (1955). (19) President’s Materials Policy Commission, vol. 11, Energy Fuels, pp. 127-30, U. S. Government Printing Office, Washington 25, D. C., 1952. (20) Reidel, J. C., Oil Gas J.,53, No. 18,83-98 (1954). (21) Searight, E. F., Boyd, J. R., Parker, R., Linden, H. R., Am. Gas Assoc. Proc. 1954,pp. 675-97. (22) Swaminathan, V. S., Petroleum Processing 10, Yo. 7, 985-8 (1955). (23) Totzek, F., Chem. Eng. Progr., 50, No. 4 , 182-7 (1954). (24) VonFredersdorff, C. G., Pyrcioch, E. J., Am. Gas Assoc. Proc. 1952,pp. 685-701. RECEIVED for review October 14, 1955.
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