Patent ID: 6893620

Claim:
A method of treating a feed gas stream comprising hydrogen sulphide, comprising the steps of: (a) in at least one first furnace oxidising to sulphur dioxide a part of the hydrogen sulphide content of at least one feed gas stream comprising hydrogen sulphide and reacting thus formed sulphur dioxide with residual hydrogen sulphide to form sulphur vapour and water vapour; (b) withdrawing from the first furnace a partially reacted gas stream including sulphur vapour, water vapour, residual hydrogen sulphide and residual sulphur dioxide; (c) extracting in a first sulphur condenser, sulphur vapour from the partially reacted gas stream so as to form a sulphur vapour depleted gas stream; (d) catalytically reacting hydrogen sulphide in the sulphur vapour depleted gas stream with sulphur dioxide in the sulphur vapour depleted gas stream to form further sulphur vapour and extracting the further sulphur vapour in a second sulphur condenser so as to form a further sulphur vapour depleted gas stream; (e) catalytically reducing with hydrogen to hydrogen sulphide the sulphur dioxide and any sulphur vapour content of the further sulphur vapour depleted gas stream so as to form a reduced gas stream comprising hydrogen sulphide; (f) extracting water vapour by condensation from the reduced gas stream so as to form a water vapour depleted gas stream; and (g) feeding the water vapour depleted gas stream to at least one Claus plant for recovering sulphur from hydrogen sulphide comprising at least one further furnace for the oxidation of hydrogen sulphide to sulphur dioxide and reaction of resulting sulphur dioxide with residual hydrogen sulphide, a first further sulphur condenser, and a plurality of further stages of catalytic reaction to form sulphur vapour, there being a second further sulphur condenser downstream of each stage of said catalytic reaction, and thereby extracting yet further sulphur vapour, wherein: a gas containing at least 40% by volume of oxygen molecules is employed as oxidant in step (a), and in step (g) the catalytic reaction is a Claus reaction between hydrogen sulphide and sulphur dioxide, or a selective oxidation of hydrogen sulphide to sulphur, or both.