Oxygen or oxygen-enriched air is employed to support combustion in furnaces
(16) and (26) of part of the hydrogen sulphide content of a first
feed gas stream. Sulphur vapour is extracted in condenser (32) from the
resulting gas mixture so as to form a sulphur vapour depleted gas stream. The sulphur
vapour depleted gas stream is passed into a catalytic reduction reactor (40)
in which all the residual sulphur dioxide is reduced to hydrogen sulphide. This
reduced gas mixture has water vapour extracted therefrom in a quench tower (52).
The resulting water vapour depleted gas stream flows to a Claus plant for treatment
typically together with a second feed gas steam comprising hydrogen sulphide. Employing
both furnaces (16) and (26) makes it possible to obtain effective
conversions to sulphur of the hydrogen sulphide in the feed gas without having
the recycle any of the water vapour depleted gas.
