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1333. HALL, C. C., AND TAYLOR, A. H. Chemical Engineering Aspects of the Fischer-Tropsch Process. Trans. Inst. Chem. Eng. (London), Advance Copy, Jan. 7, 1947, 15 pp.; Ind. Chemist, 1947, pp. 231-239; Chem. Abs., vol. 41, 1947, p. 1827.
Summary of chemical engineering data on the Fischer-Tropsch process as collected in Germany by Allied investigators. Synthesis gas was produced from coke in standard water-gas generators, the ratio of H2:CO being boosted from approximately 1.25:1 to the desired 2:1 with additional H2 from coke-oven gas or by bringing a portion of the water gas into contact with a promoted Fe oxide shift catalyst. H2S was removed from the gas by the ordinary Fe oxide process. Organic S compounds were removed by a novel hot-purification process in which the gas at 300° passed through towers containing granules of 70% Luxmasse and 30% Na2CO3. The O2 (0.2%) in the inlet gas combined with the decomposition products of the organic S to deposit Na2SO4 on the granules. A drawing of the arrangement of equipment is shown. Synthesis was carried out at either atmospheric pressure or medium pressure (10 atm.). Separate systems were used for the 2 processes, and figures and tables are presented to give details of design, operation, efficiency, and costs of plants operating each process. Synthesis catalyst was granular (1-3 mm. in diameter), containing in parts, by weight: Co 100, ThO2 5, MgO 8, kieselguhr 200. The reaction was exothermic (80 B.t.u. per cu. ft. CO and H2 converted) and was carried out at a temperature of 170°-220°, depending on catalyst age. Approximately 80% of the reaction heat was recovered as steam generated in the cooling-water tubes running through the reaction zone. 2 reaction stages were used in the atmospheric-pressure process and 3 in the medium-pressure process. Catalyst in the 1st stage became coated with wax in 1-4 wk. and was solvent extracted with the 16.5°-320° cut of product to remove the wax. Primary products condensed and recovered included: (1) Liquefied C3-C4 gas, separated from other products by adsorption in active C and containing not more than 2% CO2; (2) gasoline, b. 30°-165°, sp. gr. 0.75, f.p. –40°, flash point 30°, cetane number 76, (4) gas gas oil, b. 230°-320°, used as raw material for detergent manufacture; (5) soft wax, b. 320°-460°, raw material for fatty acid synthesis; (6) hard wax, b. over 400°, m. 80°-90°, formed in the medium-pressure process only; and (7) catalyst wax, m. 80°-90°, recovered by solvent extraction of the catalyst. The chief obstruction to cost reductions in the German processes is the low space-time yield (maximum 0.2 ton primary product per cu. ft. reaction space per month, which is due to the necessity of having a large cooling surface for removing the heat of reaction. Alternate methods of cooling, which were in experimental stages, included gas recirculation or oil circulation, both through the catalyst space, with the heat being removed from the coolant outside the reaction zone. Mention is made of the recently developed American practice in which the use of the fluid catalyst technique has permitted a substantial increase in space-time yield.