GB640907A - An improved method of producing normally gaseous fuels from carbon-containing materials - Google Patents

Abstract

Hydrocarbon fuel gas is produced by passing a gas mixture containing carbon monoxide and hydrogen at conversion conditions conducive to the predominant formation of gaseous hydrocarbons, particularly methane, through a turbulent, dense, fluidized hydrogenation catalyst, said gas mixture being preheated to substantially the conversion temperature prior to its entry into the catalytic zone from which heat is withdrawn to maintain the desired temperature level, and normally gaseous hydrocarbons being recovered. The feed gas may be obtained by gasification of solid carbonaceous material such as coal, coke, shale and the like, especially the residue from a carbonization process operated according to the fluidized solids technique. Hydrogen may be added to increase the ratio to carbon monoxide to from 1.3 to 3 : 1. The heat of solids removed from the gasification zone may be used to preheat the said feed gas. This preferably enters the base of the converter, although part may be fed at a higher level, and products are withdrawn overhead, an enlarged separating space and mechanical or other separators for catalyst being provided. Suitable catalysts are iron group metals, and oxides or sulphides of Groups 5 and 6, alone or on carriers, especially nickel on kieselguhr. Particles are preferably of less than 150, e.g. 5-100 microns, with not more than 60 per cent of 0-20 microns. Superficial gas velocities of 0.1-2 ft./sec. and pressures up to 2000 p.s.i. are suitable. Temperature varies from 500-700 DEG F. Cooling medium may flow within the converter or fluidized catalyst may be withdrawn by standpipes, passed through a heat exchanger or directly contacted with cooling gas, and returned. At higher reaction temperatures, carbon must be burnt off from the catalyst as by passing it, suspended in air, to an oxidation chamber of similar construction to the converter, if desired reducing with hydrogen in a further chamber, and returning it to the converter. Two or more converters may be used in succession with intermediate removal of water or part of the product gas may be recycled after water removal. Carbon dioxide may also be removed from the product. The carbonization of coal, fluidized in air or other gas, at 700-1200 DEG F., removal of fluidized coke and gasification with oxidizing gas and steam in fluid state is described. The heat of the catalyst or of the conversion product is used to preheat the feed gas. This may be supplemented by a coal gas obtained in the carbonization process. In an example, finely ground coal is fluidized in coal gas and coked at 1100 DEG F. by injecting a stream of ash at 1800 DEG F. from a separate combustion chamber. The coke is in part suspended in steam and passed to a water gas chamber and in part suspended in air and fed to the said combustion chamber from which hot ash is recycled to the coking chamber and to the water gas chamber. Purified gases from the coking and water gas chambers are combined and used as feed for the catalytic converter.