Patent ID: 6444185
Filing Date: 2002-09-03
Classification: B01D,C01B

Abstract:
A process for the removal of sulphur compounds H2S, SO2, COS and/or CS2 out of a residual gas from a sulphur plant comprising the steps of:(a) contacting the residual gas originating from the sulphur plant, wherein the H2S to SO2 molar ratio in the residual gas has a value equal to or higher than 2:1, with a catalyst for hydrolysis of the compounds COS and CS2 to H2S, in an oxidation and hydrolysis unit, wherein a gas flow containing free oxygen is injected into the oxidation and hydrolysis unit and an oxidation of H2S to SO2, and optionally to sulphur is performed in the unit, in addition to the hydrolysis of COS and CS2 to H2S, the operation being carried out at a temperature which is sufficient to produce a hydrolyzed residual gas containing H2S and SO2 and is substantially free from COS and CS2; (b) passing the hydrolyzed residual gas, after having brought the temperature of the gas to a value lower than 160Â° C. into a Claus catalytic purification unit in which said gas is brought into contact with a Claus catalyst to form sulphur by reaction between H2S and SO2, the contact being performed at a temperature which is below the dew point of the sulphur formed to deposit sulphur on the Claus catalyst and to discharge from the unit, a substantially purified residual gas containing H2S as the only sulphur compound, the H2S concentrations, expressed as volume percentages (H2S) and (SO2), in the hydrolyzed residual gas entering the purification unit being maintained at values such that the quantity (H2S)âˆ’2(SO2) ranges from 0.25% to 0.5% by varying the flow rate of the gas flow containing free oxygen introduced into the oxidation and hydrolysis unit; and (c) introducing the substantially purified residual gas and a gas stream containing free oxygen, at a temperature of between 85Â° C. and 100Â° C. into a catalytic oxidation unit containing a catalyst for selective oxidation of H2S to sulphur, the quantity of oxygen in the gas stream being in excess in relation to the stoichiometric quantity needed for oxidizing H2S to sulphur in the substantially purified residual gas, and maintaining the substantially purified residual gas and the gas stream containing free oxygen in this catalytic oxidation unit in contact with the oxidation catalyst at a temperature ranging from 90Â° C. to 120Â° C. to oxidize H2S into sulphur which deposits on the oxidation catalyst and to discharge from the oxidation zone a purified residual gas virtually free of sulphur compounds.