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 1766.    ---------------.  [KING, J. G.]  Complete Gasification of Coal – Thermal Considerations.  Gas World, vol. 122, 1945, pp. 220-226; Gas Jour., vol. 245, 1945, pp. 342, 344; Am. Gas Jour., vol. 163, No. 3, 1945, pp. 16-20, 60; Chem. Abs., vol. 39, 1945, p. 2191.

       Discusses outstanding processes, with special reference to those conditions that affect thermal efficiency.  The over-all thermal efficiency of a process is defined as the % that the thermal value of the products bear to the sum of the thermal values of the raw materials used and of the heat and power consumed.  It is apparent that complete conversion of coal to gas in a water-gas plant, which has had some application in the United States, must be thermally more efficient than the separate production of coal gas and water gas.  It may be calculated that the advantage is about 12%.  The Fuel Research Station, by adopting a special cycle, has gasified bituminous and sub-bituminous coals in a water-gas generator at a thermal efficiency of 64%.  Data are given for several processes.  The Tully, Humphreys-Glasgow (thermal efficiency 57% including the fuel for steam raising), Travers-Clark, and Broadhead (62% excluding power and steam) processes exemplify the type of combination carbonization and water-gas plant.  The German processes for complete gasification have received more intensive development for 3 reasons:  To utilize brown coal, to produce CO:H₂ mixtures for synthesis gas, and to make use of industrial O₂.  They fall into 3 classes:  (a) Those that involve heating by the circulation of hot gases, for example, Pintsch-Hillebrand, Koppers, and Wintershall-Schmalfeld, which gasify brown coal at an over-all thermal efficiency of 50%; (b) those that involve an externally heated reaction chamber, for example, Heller, Ahrens (78.2% efficiency), Strache, and Didier-Bublag (68.7% efficiency), have had industrial success as a flexible means of making synthesis gas at a CO:H₂ ratio of 2); (c) those that involve the use of O₂, for example, Winkler (77% excluding O₂ production), Lurgi-Drawe (62.2%, this process has probably reached the peak of efficiency under present operating conditions), Thyssen-Galoczy (80% including O₂ production).  The special advance of this last group has been brought about by the use of O₂ made available from synthetic NH₃ plants.  If O₂ were made specially for the purpose, the cost would be much higher.  The development of a fairly cheap O₂ plant for application in the gas industry is one of the pressing problems.