GB978535A - Process for the purification of hot gases obtained by partial combustion and containing soot and carbonyl sulphide - Google Patents

Abstract

A process for purifying hot gases obtained by the partial combustion of carbonaceous combustible materials and containing soot and carbonyl sulphide comprises contacting the gas with enough water to saturate the gas and cool it to below its dew point, whereby the soot is largely removed in aqueous suspension, contacting the cleaned gas, in the absence of liquid water, with a carbonyl sulphide conversion catalyst (preferably between 120 DEG and 200 DEG C.) and treating the final gas with an agent for removing H2S and, if desired, carbonyl sulphide. The catalyst is one capable of catalyzing the hydrolysis of COS to H2S + CO2. Suitable catalysts, which may be in fixed or moving bed form or fluidized, may be alumina, bauxite, activated clays, aluminium phosphate, thoria, or MgCl2 and preferably contain at least one Group VI and/or Group VIII metal. Cobalt molybdate on alumina is mentioned. The H2S-removing agent may be conventional, e.g. an aqueous solution of an alkanolamine, potassium phosphate, caustic soda, or cyclotetramethylene sulphone with an alkanolamine with or without water. A mixture containing iron oxide may be used. The original gas is preferably indirectly cooled, e.g. to within the range 150 DEG to 500 DEG C., before the first washing stage, which may be carried out by spraying water into a downwardly-sloping tube as described in Specification 826,209. To prevent decline in catalytic activity, the washed gas should be rendered free of liquid water, e.g. by heating to 7 DEG to 10 DEG C. above its dew point, e.g. by steam jackets, or by lowering its pressure, and a second water spray washing preferably succeeds the conversion step to remove further soot. If the final H2S-removal step is intended also to remove further COS, aqueous solutions of dipropanolamine are preferred. Steam may be added to the gas after the first washing, as described in Specification 851,655. Two specific examples are described. Specifications 780,120 and 879,090 are referred to.