GB1431685A - Removing sulphur dioxide from gases containing the same - Google Patents

Abstract

1431685 Sulphur dioxide removal INSTITUT FRANCAIS DU PETROLE 10 Sept 1973 [15 Sept 1972] 42399/73 Heading C1A Sulphur dioxide is removed from a gas containing it by contacting the gas, (a), with an aqueous ammonia and/or ammonium sulphite solution, so as to absorb sulphur dioxide in the form of ammonium sulphite and/or bisulphite, then (b), heating at least a portion of the solution obtained in (a) so as to decompose the sulphite and/or bisulphite to a gas containing sulphur dioxide and ammonia, then, (c), heating the gas from step (b) with a gas capable of reducing sulphur dioxide to hydrogen sulphide, preferably at a temperature of 150-600‹ C., in the presence of a catalyst capable of catalysing the reaction between the reducing agent and sulphur dioxide, so as to produce a gas containing hydrogen sulphide, sulphur dioxide and ammonia, with a molar ratio of H 2 S/SO 2 of from 1À7 to 2À3, then contacting this gas, (d), with a second catalyst capable of catalysing the reaction between H 2 S and SO 2 , to form sulphur and a residual ammonia containing gas, (e) separating the sulphur and the residual gas, suitably (f) by contacting with an organic solvent to remove residual sulphur and sulphur compounds, and (g) using the residual gas, which contains ammonia, to constitute an aqueous ammonia and/or ammonium sulphite solution to be used in step (a). Where the treated gas contains also sulphur trioxide, after decomposition of the sulphites the ammonium sulphates are treated with a reducing agent, suitably in a bath of molten sodium sulphate, so as to convert them to SO 2 and NH 3 which are subsequently subjected to step (c) of the process. The first catalyst may be at least one metal (or oxide or sulphide thereof) selected from Groups VIa and VIII of the Periodic Table; a mixture of cobalt and molybdenum oxides on alumina is preferred. Alternatively, copper, silver, vanadium, manganese, rhenium or zinc (or their oxides or sulphides) may be used. The second catalyst may be alumina or bauxite, and the organic solvent may be polyethylene glycol. As reducing gas, a mixture of carbon monoxide and hydrogen is preferred.