Patent ID: 6113872
Filing Date: 2000-09-05
Classification: B01D,C01B,Y02P

Abstract:
A process for removing sulphur compounds H.sub.2 S, SO.sub.2, COS and/or CS.sub.2 contained in a residual sulphur-plant gas with the said compounds being recovered in the form of sulphur, which process comprises i) bringing the residual gas from the sulphur plant into contact with a catalyst for hydrolysis of COS and CS.sub.2 to H.sub.2 S, the catalyst being arranged in a hydrolysis unit, while operating at a temperature sufficient to produce a hydrolysed residual gas which contains H.sub.2 S and SO.sub.2 and is substantially free from COS and CS.sub.2, (ii) conveying the hydrolysed residual gas, after a step of cooling to a temperature below the dew point of sulphur, to a purification unit comprising a plurality of catalytic zones, each containing a Claus catalyst which promotes a Claus reaction and each operating in turn in a reaction phase, then in a regeneration phase and finally in a cooling phase so that, at any time during the process, there is at least one catalytic zone operating in the reaction phase and one catalytic zone operating in the regeneration or cooling phase, (iii) passing the hydrolysed residual gas through the purification unit comprising a catalytic zone in a reaction phase, while operating at a temperature below a dew point of sulphur, so that H.sub.2 S and SO.sub.2 present in the gas react with one another to form sulphur which deposits on the catalyst in the catalytic zone, so that a substantially purified residual gas is obtained at the outlet of the purification unit, (iv) circulating a hot non-oxidizing gas stream having a temperature between 200 C. and 500 C. through the catalytic zone containing a Claus catalyst in the regeneration phase loaded with sulphur, to regenerate the Claus catalyst and form an effluent gas loaded with vaporized sulphur, and (v) passing a gas stream at a temperature below 160 C. through the catalytic zone containing the catalyst which has just been regenerated, in order to cool the catalyst to a temperature required for promoting the reaction between H.sub.2 S and SO.sub.2 wherein the improvement comprises utilizing at least a portion of the hydrolyzed, residual gas leaving the hydrolysis unit as all of said hot non-oxidizing gas stream that regenerates the sulphur loaded Claus catalyst, and injecting all of the regenerating gas leaving the Claus catalytic zone into the hydrolyzed residual gas conveyed to the purification unit at a point downstream of the location where the portion of the hydrolyzed, residual gas is withdrawn from the gas leaving the hydrolysis unit and upstream of the cooling zone through which the hydrolysed residual gas is passed before it enters the purification unit, and utilizing at least a portion of the unhydrolyzed, residual gas as the gas which cools the catalyst to a temperature required for bringing it into contact with the hydrolyzed, residual gas, and injecting the cooling gas leaving the catalytic zone into the residual gas stream, at a point downstream of the location where the unhydrolyzed, residual gas is withdrawn and upstream of a heating zone for the unhydrolyzed, residual gas before this residual gas is introduced into the hydrolysis unit.