I
I
I
CHEMICAL ENGINEERING REVIEWS
I
UNIT PROCESSES REVIEW
I IS T H I S ninth annual review on the p>-rolysisof coal and oil shale discussion is restricted to only the more significant papers which have appeared during the past year. Other articles of interest are tabulated after the text material under the appropriate subheadings. T h e period under review is from December 1954 through April 1956, except for previous inadvrrtrnt omissions. Coal Pyrolysis General. An excellent over-all coniprehensive survey of the present and future status of coal technology was published by Rose (47.4). T h e author points out that coal carbonization accounts for approximately one fourth of all coal consumed in the U. s., and that roughly one third of the total crude tar is converted to chemicals. T h e article discusses the seven principal processes for conversion of coal to chemicals. Other nonfuel uses examined include-carbon for reduction, processes dependent upon physical properties of coal itself, and residual products from combustion. Subject
Fuel research in India during 1954, including carbonization Coke industry in U.S.S.R., its hiitory and present development
Literaturc Cited
aliphatic CH and phenolic OH groups as the most marked phenomena, in the carbonization range of 400' to 550' C. A pyrolysis mechanism was proposed, in lvhich carbon-carbon bonds between the aromatic systems replaced aliphatic groups. A subbituminous coal has been subjected to low temperature carbonization in the presence of nitric oxide ( 7 A ) . LVhen the nitric oxide was present a t the start of incipient pyrolysis even low concentrations were found to retard significantly the thermal decomposition. Higher nitric oxide concentrations increased the yield of loiv-boiling tar constituents, by inhibiting secondary polymerization. If nitric oxide was introduced above the decomposition temperature of the coal it had little effect. Kasatochkin (28A) examined a wide variety of carbonized substances, including coal, a n d concluded that the structural concept of a parallel block arrangement is not sound. H e reaffirms the theory of planar nuclei of a cyclically polymerized carbon structure, with the planes cross-linked through linearly polymerized side chains. Literature Cited
Su biect ( 75ll)
( 79A)
iMechanisms, Kinetics, Thermochemistry. A Japanese paper (47A) reports a theoretical study of various isothermal carbonization reactions during coking of coal. T h e carbonaceous nucleus was assumed to develop at the rxpense of peripheral structures. It is concluded that velocity of decomposition and not mass transfer of decomposition products is the rate-controlling step. Aronov ( 3 A ) , in a detailed study of thermal transformations during coking, concluded that i n the range of 400' to ,325' C. the carbon and hydrogen i n side chains are more reactive in the vaporphase products. Maximum splitting off of carbon occurred a t 400' to 450' C., and of oxygen a t 700' C. T h e presence of less cyclic carbon in gas coals is stated to be responsible for their greater reactivity to oxygen. I n a related study (77A) infrared spectra indicated loss of
Negligible effect of pressure on pyrolysis of solid fuels Effect of chloroformsoluble primary pyrolysis fraction on coal plasticity Solution zone between two different carbons fused during coking .4mechanical model of coal undergoing carbonization for rheological studies
( 74A )
(43A1 (9A)
(ZOA)
.4 differential equation of heat distribution through spherical coal particles during thermal decomposition heat
(29A)
flow
equations for temperature conditions in a coke oven
(38'4)
Raw Material Properties. Ulrich (52.4) examined various methods oC evaluating coking properties of coals. H e concluded that the ratio of volatile matter content to specific coal surface provided a useful index of sirelling. Correlations were made with the usual d r u m test, Koppers swelling pressure test, dilatometer test, and swelling index. T h e plasticity, swelling, and agglutinizing properties of coal \rere studicd again in a recent paper (57A). Special apparatus was constructed for plasticity and agglutinization and the results correlated lvith present practice. Subject Application of Burst-
lein grain-index to improve coking quality Mechanical aspects of coal pyrolysis, relationshiD of coal and coke properties Inner stresses in coke as a function of agglomeration and coal fineness
Literature Cited
(7A)
( 8 A1
(@A 1
High and Low Temperature Carbonization. A semi-industrial test of a continuous coking process has been conducted (5.4). Thc coal, in layers of 2 to 4 inches in thickncss, was contacted with very small amounts of air. Coking time was reduced from the usual 16 to
CHARLES H. PRIEN Denver Research Institute, University of Denver, Denver 10, Colo. CHARLES H. PRIEN, who prepares our annual reviews on coal and shale pyrolysis, i s head o f chemistry and chemical engineering division, Denver Research Institute, and professor of chemical engineering at the University of Denver. In addition to these activities, he hos published articles on the teaching o f unit processes and has conducted research on shale and synthetic fuels. Prien i s a graduate of Purdue University, receiving his Ph.D. there in 1948. He i s a registered engineer of the state of Colorado and holds memberships in the ACS, AIChE, ASEE, Sigma Xi, and Phi Lambda Upsilon.
VOL. 48, NO. 9, PART II
SEPTEMBER 1956
1653
UNIT PROCESSES REVIEW 20 hours to 12 to 20 minutes. 'The resulting coke was not of blast-furnace quality, but was suitable for many chemical and metallurgical purposes because of its high reactivity. T h e continuous low temperature fluidized carbonization pilot plant erected by United Engineers and Constructors at the Philadelphia Electric Co. was described recently by Minet ( 3 9 A ) .Capacity is rated a t 2 tons per day. Economic data for full-scale design, based on an investment of $500 per daily ton throughput, was presented. T h e Parry entrained low temperature carbonization of lignite and noncoking coals produced tar ( 4 4 ) yields as high as 135% of assay. Yields were shown to be proportional to the heat in the volatile matter in the coal. Simultaneous devolatilization and crumbling of high volatile coal to produce a smokeless fuel has been patented (45A). T h e heart of the process is a short, tubular vortex chamber in which air a t 400' F. entrains the coal particles, following which air a t 800' to 1200' F. is introduced. Devolatilization occurs in less than 20 seconds to thin, fragile granules. A review of current U. S. activity in low temperature carbonization has appeared ( 7 3 A ) . Included are descriptions of the Pitt-Consol fluidized process, to be erected in connection with Olin Mathieson's new Ohio Valley Aluminum plant; the entrained lignite process of Texas Power 6L Light and Alcoa at Rockdale, Tex. ; the fluidization research of Southern Research Institute for .4labama Power Co.; and the onevessel fluidization process under development a t Stanford Research Institute. Aromatics, electrode binder, roofing pitches, phenols, and creosote oils are among the by-products which, it is believed, will be economically marketable. 'The future of low temperature carbonization, if conducted in connection with power development, appears bright in the United States. The U. S. Bureau of Mines coinpared expansion results from sole w e n s and slot-type ovens ( 2 2 4 ) . Inert substances added to coal strongly modified expansion properties of the charge. Some 5%, of anthracite fines decreased expansioii pressures 30 to 50%. Subject Continuous 300 lb./day pilot plant for frac-
tional carbonization of Wyoming noncoking coal Use of a tumbling bed for low temperature carbonization Two-step carbonization of noncoking coal to blast furnace coke
1 654
Behavior of brown coal briquettes durinq stationary low temperature carbonization Extraction of bituminous substancc prior to low temperature pyrolysis yields stable coarse-grained cokr Effect of pressure of briquetting of peat or lignite on low-T carbonization yields
(5321 ,
(,?7'4
f 3-3'1
core and the sides of a coal charge during coking (30A). Some 1.5 to 3.5% of total gaseous products (containing 5 to 8% of all tar) was found to leave directly through the core. Further studies of this type are needed. Literature
1
)
O v e n Operation. Preliminary studies indicated that measurement of internal gas pressure may be just as reliable an indication of coal expansion as the usual wall-pressure measurements in experimental ovens (23'4). The method can be applied directly to commercial ovens. The relationship between coking time and width of oven becomes a quadratic one: according to a Russian paper (33d), \\.hen the thickness of the Jvalls is added to that of the charge. Increases in coking capacity as a function of flue temperatures and coke oven width were correlated. A laboratory study was made of thc relationship betivecii gas florj- f r o m thc
Subject
Electrical resistance of charge as a measure of coke readiness Preheating of coal prior to carbonization by gas-recirculation process
(-16A) (3JA) ( 50A 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
Figure 1.
(-12.4 )
(43'4
Coke and By-products. 'Two x-ray studies of coke structure are of interest. Bresler (70.4) showed that the latticed blocks of coke are not three dimensional but rather arranged in parallrl. -4 similar conclusion also was obtained by Kasatochkin (28~1). No significant change in crystallite dimensions of a Japanese coke were found (37.4) after a 3-hour exposure to steam at 750' C. Inouye (26-4) investigated the internal structure of a piece of blast-furnace coke alcng its length as a function of i t s distance f i u n the oven wall. T h r
Literature Cited
(5oA 1
Cited
Full scale shale retort at Denver, Colo.
PYROLYSIS OF COAL AND SHALE same author has also studied (25+4)blastfurnace coke prepared from various blends of Japanese slacks. I n both cases degree of agglomeration was found to control the physical properties obtained. It is predicted that by-product coal chemicals such as tars; tar acids: phenols, and cresylic acid, may require intensivr market rcsearch t o avoid future overproduction ( 7 2 4 . ..in oversupply is likely to develop, i t is felt, if lignittcarbonization, shale treatment. coal hydrogenation and sirnilar new processes reach large-scale proportions. Only naphthalene promises to continue in short siijiply for some tirnc to come. Literatiire
Cited
Sxbjccf
Symposium on coke in Great Britain, .4pplication of coke anisotropes t o blends Removal of naphtlia-
(27A) (2.1
lene from coke-oven gas with activated
carbon Removal of ammonia, HzS,HC?;frorn cokeoven gas with \vai.te pickle liquor
m.1
( 7b.l
8
Removal of benzene and naphthalene from coke-oven gas by refrigeration Use of oil injection in coke oven to increase olefin and benzene yields
(77.4)
(78A)
Analysis and Testing. Flickinger states (27'4) that the Bureau of hlines.imerican Gas .4ssociation assay carbonization method correlates sufficiently accurately with plant practice to indicate tvhere plant operation is faulty. Raw gas loss, excessive coking temperature, and poor recovery are detectable by comparison of plant and assay data. Differential tliermal analysis curves of coking coals \vere shown to correlate with Gieslcr plastometer data and the German Rank Classifications ( 2 J A ) . They are felt to be adequate preliminary indicators of coking abilitv. Literature Citd
Subject
Improved plastometer for studving agslutinating behavior of coking coals
(1'4)
Courtesy The O i l Shale Corp.
Figure 2.
Pre-pilot plant Aspeco oil shale retort, Denver Research Institute
Determination of sulfur in coal and coke by Sheffield high temperature method Improvements in simultaneous determination of sulfur and chlorine in coke by Beet and Belcher method Critical discussion of various methods of coke analysis by microscopy
(4Okl I
(6.4 )
(33.4
1
Oil Shale Pyrolysis General. Activity in oil shale has continued in the U. S. during the past year, both with respect to acquisition of properties, and in the development of new technology. General Petroleum Co. purchased 25,000 acres of land with oil reserves in excess of 4 billion barrels, in northwestern Colorado. T h e Oil Shale Corp. of Los Angeles acquired option to purchase 1,300 acres in the same area. Eaton Shale Co. made public its sale of several years ago of 15,000 acres (reseriTes of 2 billion barrels) to Standard Oil of California. This now shows Standard of California to be the largest private o\vncr of oil shale properties (62,000 acres, reserves 10.5 billion barrels) in the E. S. Prien and Savage (29B) reviewed in detail the current status of oil shale technology in the U. S. Included in this article are a tabulation and map of all private companies with oil shale properties, mining and crushing practice, the water situation, nature of oil shale, current retorting and refining methods, research and development problems, production of shale pctrochemicals, and a brief' review of shale economics. In a recent article Cameron (7B) claims that total Bureau of Mines cxpenditures for oil shale research and development have totaled $20,000,000 since 1944. An investment cost of $6:000 per daily barrel of shale oil is required for industrial development. 'The author also describes recent acrivity in Brazil, Spain, and the Union of South Africa. The Union Oil Co. of California is proceeding with erection of its $5,000,000 pilot plant in western Colorado. h demonstration retort 40 feet high, with a feeding piston of feet in diameter has been constructed in Denver by the Stearns-Roger hlanufacturing Co. (Figure 1). Capacity of the retort, using ',/?-inch shale feed, is 300 tons per day. T h e current status of Union's operations was summarized by Pownall (28B) and by Berg (5B). The Denver Research Institute has recently entered into contract with the Oil Shale Corp., Los Angeles, to construct and operate in Denver a 24-tonper-day oil shale pilot plant using the Swedish Aspeco process. This novel
VOL. 48, NO. 9, PART II
SEPTEMBER 1956
1655
UNIT PROCESSES REVIEW process (Figure 2) employs a rotating kiln in which countercurrent contact of crushed shale occurs with hot steel or ceramic balls (70B). Processing research a t the Bureau of Mines demonstration plant at Rifle has been discontinued, but mining research is still in process. T h e current annual report of the Bureau’s activity in oil shale, a t Rifle and a t Laramie, has not been published a t this time. T h e American Gilsonite Co. has announced a $10,000,000 plant to produce coke and gasoline from U t a h gilsonite (ZB).The plant will produce 50% green coke, 35% gasoline, and 15y0 gas (1400 B.t.u./cubic foot). Also of interest is the pilot plant of Can-Amera Oil Sands Development to process Athabascan tar sands (9B). Both processes are potential competitors of oil shale in producing synthetic fuels. Mechanism, Kinetics, Thermochemistry. Little new information on the fundamental nature of oil shale has appeared during the period under review. Dunning (25B) extracted the porphyrins in Colorado oil shale with polar solvents and reported 0.35% in a methanol-chloroform extract. Most of the porphyrin was chelated with iron, although a small amount of nickel chelate was also found. Similar results were also found in a concurrent unpublished study recently completed by the Denver Research Institute. Although received somewhat late for review, a study on the combustion rate of the carbon on spent shale is included because it is the only data available on this subject in the literature. I t was found (77B) a t 700’ to 800’ C. that diffusional resistance of oxygen through the porous “ash” layer is the ratecontrolling step. Subject
Literature Cited
Bitumen from shale of the Godorsk region, composition, oxidation products.
(18B)
Raw Materials a n d Properties. A detailed analysis of Urn Barek oil shale has been reported (76B). Included are elemental analyses, mineral content, results of extraction with organic solvents, retort products, and physical properties.
Subject
Isothermal decomposition of Baltic oil shale at 300” t o 440” C.
Literature Cited
(7B)
Retorting Processes, Thermal Extraction. One of the most interesting processes for separating the organic matter in oil shale was patented recently by Esso Research Rr Engineering (26B). Sonic or ultrasonic compressional waves were created in a mixture of finely ground (1 micron) shale suspended in a solvent, thus inducing cavitation. Using waves of 700 to 1500 kilocycles, a n electrical power input of 600 watts, and carbon tetrachloride as solvent it was found that solubility of organic matter increased from 5% to 49.8%. The small shale particle size required, of coursc, argues against commercial extraction by this method. California Research Corp. has patented (37B) a vertical shale retort in which the vapors are trithdrawn a t a n intermediate point above the retorting zone, just a t their deir point. Clinkering, internal refluxing, and fog formation are thereby reduced. .4fter removal of condensate the noncondensables are returned to the retort and continue upward into the preheat section. Socony-Mobil, in a recent patent (75B), proposed a vertical retort in which a static pool of condensed shale oil is maintained above the retorting zone by introduction of a high velocity gas stream just below this point. Product shale oil is withdrawn from the pool, after condensation on cold, incoming shale, while the cold shale flows downward through the pool to the retorting section below. Subject
Process for retorting oil shale in situ, similar to Frasch sulfur process Fluidized oil shale retort, at pressures up to 10 atmospheres Summation of development and operation of the Bureau of Mines gas combustion retort Engineering data on processing of Manchurian oil shale, recent improvements
Litrrature Cited
( 4 B1 (22B)
(24~)
(20Bj
Thermal extraction of Estonian shale with tar fraction, charac(7J5) teristics of gasoline Shale Oil and By-products. iMurphy and coivorkers (8B)have conducted a long overdue bench-scale evaluation of the sequence of shale oil refining operations proposed in the 1951 economic study of the National Petroleum Council. The ratio of gasoline to Diesel fuel produced was found to be 2.8 instead of 1.95, as calculated in the Council report. LVhile gasoline yields were higher, the over-all quality of the gasoline was poorer. The Bureau of Mines has investigated the hydrofining of thermally cracked shale oil naphtha (77B) a t 950’ to 1000’ F. and 400 to 800 pounds per square inch. Higher pressure was found most satis€actory for removal of sulfur and gumforming compounds. Better gasoline yields were obtained by hydrofining heavy naphtha and blending, instead of using whole naphtha. Thorne (34B) has presented an excellent summary of the chemicals potentially obtainable from oil shale. H e concluded that in the U. S. conventional low temperature retorting will not provide gases of any interest in chemical manufacturing. Subsequent refining of the heavy crude will yield low-boiling phenols and pyridine homologs, neutral nitrogen compounds, olefins, and aromatics. Higher retorting temperatures (1500’ F.), on the other hand, result in larger quantities of olefins, aromatics, oxygen, sulfur, and nitrogen compounds. A complete breakdown of yields by the two processes was given by the author. Literature Subject Influence of catalyst
pore diameter on catalytic cracking of shale oil Comparison of Brazilian and Colorado shale oil Characteristics of oils from Azerbaidzhan (Russian) oil shales Composition of the phenols in Russian shale tar Paraffin and naphthene in hydrocarbons cracked Baltic shale tar kerosine
Cited
(27Bj ( 13B)
(79B) (3 0 ~
(35Bj
I
“The production of metallurgical coke and coal chemicals b y the pyrolysis of bituminous coal at high temperatures will continue to grow with the steel industry, Meanwhile, research continues on pyrolysis at lower temperatures. An industrial coal-processing plant to produce boiler-fuel char and liquids to be refined into chemicals, has been announced. The char will be burned for power for an aluminum reduction plant and other consumers. New research techniques now in use for the study o f coal structure and coal pyrolysis products, are expected to lead to improved yields and new commercial products.” R. A. Glenn Bituminous Coal Research, Inc.
1 656
INDUSTRIAL AND ENGINEERING CHEMISTRY
PYROLYSIS OF COAL AND SHALE Neutral osyqen compounds in middle tar fraction from Baltic shales Composition of UmBarek (Israelian) shale oil Gilqonite as a source of easoline and other synthetic fuels
(27s) ( 32% (7 2 ~ )
Analysis and Testing. Smith (33B) has examined the relationship betIreen oil yield (by assay) and specific gravity colorado shale cores. i\-ithin an>’ geologically homogeneous area (gtograpl1ically/ proximate) estimatm t m e d on specific gravity can be within + 2 , j c , of assay values, s u c h correlations permit rapid estimation of reserves [rithout the necessity of time-consuming assays. For areas geographically widely separated in the deposits correlation between cores \\’as much poorer. L i f ~ ~ a ef u i Cited
Su b,i ect
Three modified Fisher assay retorts i:sed on Oklahoma shales Quantitntivr derrction and determin,ition of benzo [alpvrene in Colorado shale Spect:ophotoInetr ic analysis of a s h from oil shale
(3B)
(6B: ( 3R I
Acknowledgment The author appreciates the aid cf Pauline hlilner in preparing the manuscript, and of Isabell prien in collecting and cataloging ieftx-ence material.
BIBLIOGRAPHY Coal Pyrolysis (1.4) Abramski, C., Gluckauj 91, 714-27 (l955!. (2.4) -4lpet.n. B . Centre d’Etudes et Rec’lerches des Charbonnages de France, Document Interior KO. 623 ( J u l y 1355). (3.4) Aronov. S. G.. Nesterenko, L. L., S:ul 15, 6-8-87 (1955). (4-4) Barthaurr‘ G. L.: -4nui. Chem. 27, 969-’1 (1955). (5.4) Baum. K . , Con;husfion26, No. 5$61-5 (1 954 j. (6.4) Belcher, R., Spooner, C. E., Fuel 34, 164-8 (1955). (7.4) Berkolvitz, K.. Dammeyer, W., Ibid., 35, 19-30 (1955). (8‘4) Boyer. ’4. F., Centre d’Etudes et Recherches des Charbonnages de France, Document Interior No. 653 (Sept. 1955). (9-4) BoYer! A. F.. others, ComPt. rend. 239, 1791-2 (1954). (10A) Bresler, A . E., others, Doklady Akad. A‘aauk S.S.S.R. 87, 567-70 (1952). (lIA) J. K ’ $ J. (London) 1955, pp. 752-7. (12*4) Chem. En!. 34, 792-6 (1956). (13A) Ibid., pp. 1318-20. (14A) Chernychev, A. B., others, Izuest. Akad. .Yauk S,S,S.R., Otdel. T&h, Nauk 1953, pp. 1393-1400. (15A) Coke and Gas 17, 363-5 (1955). (16A) Dixon, T. E., Iron Age 175, No. 12, 91-3 (1955). (17A) Engel, Erich, Harpener Bergbau Akt.-Ges., Brit. Patent 727,028 (March 20, 1955). IVews
(18.4) Ewers, J.. Brennstaff-Chem. 36, 33-7 (1955). (19A) Far. MI.,Coke and Gas 17, 389-96 (1955). (20.4) Fitzgerald, D., .Vature 175, 515-16 (1955). (21A) Flickinger, C. H., Graham, 5. P.
Oil Shale Pyrolysis
(1B) .4arna, A. Ya, Zhur. Priklad. Khim 28, 1138-42 (1955). (2B) Armstrong, T.2 011 Gas J. 54, 90-1 (1955). (3B) Bannerjet, x. s,, COlliSS, B. c‘. S. Bur. .Mines, Tech. Papers Fuel 34, S 7 1 4 8 3 (April 1955). No. 726, 51-5 (1949). (4B) Belser, C., K. S. Patent 725,939 (Dec. 6, 1955). (22.1) Gayle, J. B., Eddy, W. H.: C. S. Bur. .\fines, Refit. Imest. 5176 ( j B ) Berg, Clyde, Chem. Prog7. 5 2 , (1955). NO. 1, 225-65 (1956). (6B) Cahnmann, H. J., A n a l . Chem. 27, (23.-\j Gayle, J . B., others. .jm. c ; .dssoc., ~ ~ 1235-40 (1955). Proc. 36, 628-34 (1934). (24.1) Glass. H. D., Fuel 34, 253-68 il955j. (7B) Cameron, R. J . , Tb’orld Ppt,-oieum 27, NO. 2, 58-61 (1956). (25.4 I Inouye. K., Roppongi, .A,, Ibid..34, 471-9 (1955). (8B) Carpenter, E€. C., others, 128th (26.1j Inouye, K.: Tani. H., Ibid., 34, Meeting, ACS, hlinneapolis, 356-62 (1955). hfinn., September 1955. (27.4) Inst. Gas Engrs., Copyright Pub/. S o . (gB) Chem. 6 2 , No. 6, l30-2 (19j5). 476 (1955). (10B) Chem. Eng. Progr. 52, S o . 2, 52 (28.4) ~ ~ ~ ~V. ~I,, ~pctst, ~ L.pad, h k i ~ , (1956). .Tad S.S.S.R., Otdel. Tekh. .\7~ul; (11B) Cottingham, p. L., others, 128th 1953, pp. 1401-16. Meeting, ACS, Minneapolis, Minn., September 1955. (29.4) Kashurichev, A. p., ChUkhanov, Z . F., Doklady A k a d . .\-auk S.S.S.R., (12B) Cottingham, p. L.: others, I d . E%?. Chem. 47, 328-32 (1955). 101, 115-18 (1955). (30.4) Khudokormova. N. P.: S t d 15, (13B) Dinneen, G. U., others, 129th 295-301 (1955). Meeting, ACS, . Dallas, Tex. April 1956. (31.4) Krafft, K., Ger. Patent 828,398 (14B) D’yakova. 11. K . , Davtvan, N. A., (Jan. 17, 1952). (32.4) Kuczynski, \V., Xndrzejak, .I.: Izuest. Ailad. N a u k , S.S.S.R., Otdel. Roczniiii Chem. 28, 643--55 (1954) T e k h . .L’au/i 1954, S o . 9, pp. 124-44. (English summarv). (33.4) Kustov, B. I., Stal 1‘5, 391-6 ( 1 9 j j ) . (133) Elliott, K. h f . (to Socony Slobil Oil Co.), U. S. Patent 2,723,225 (34.4) Lesher, C. E. (to Lesher Br .4ssoc., Inc.). U. S. Patent2,723,226(Nov. ( S o v . 18: 1955). 8, 1955). (16B) Gil-.\v, E., others, Bull. Research Council 1sral.i 4, 136-43 (1954). (35.4) Mackowsky, hf. T . , Brennsi?f-C,hem. (17B) Hellinckx, L. J., Chem. Eng. Sci. 3, 36, 304-14 (1955). 201-8 (1954). (36-4) hlalherbe, Ll., Comfit. rend. congr. ind. gaz (Assoc. tech. ind. gaz (18B) Karavaev, s. hf., others, Trudy France) 70th Congr., Paris 1953, last. Goryuch. Izkopaemykh Akad. h’auk S.S.S.R. 2, 285-95 (1950). pp. 498-507. (19B) Kesamanb, G. D.2 DokladY (37.4) Xlatsuyama, E., J . Fuel Soc. J a p a n 34, 553-7 (1955). .Vauk Azerbaidzhan. S.S.R. 10, XO.1, 23-(; (13543. (38.4) Millard, D. J., J.Imt. Fuel 28, 345(20B) Kitawaki, K . , J.Fuel $06. Japan 34, 51 (1955). (39.4) Minet. R. G., preprint, Regional 292-301, 366-72 (1955) (English summary). Sleeting American Coke and Coal Chemicals Institute, Rye, (21B) Lanin, V. .\., others, TTud? Inst. Goryuch. Iskopaemykh, A k a d . . T a d , N. Y.! %lay 1955. S.S.S.R. 3, 95-108 (1954). 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