Patent ID: 7655205

Claim:
A process for the removal of sulfur from a first gas stream comprising SO 2 , HCN and H 2 S, which said process comprises the steps of: (a) removing SO 2 from the first gas stream by contacting the first gas stream in a hydrogenation zone with a hydrogenation catalyst in the presence of hydrogen to convert SO 2 to H 2 S and to obtain a second gas stream comprising H 2 S; (b) removing HCN from the second gas stream obtained in step (a) by contacting the second gas stream in a hydrolysis zone with a hydrolysis catalyst in the presence of water to convert HCN to ammonia and to obtain a third gas stream comprising NH 3 ; (c) removing NH 3 from the third gas stream by contacting the third gas stream in a NH 3 -removal zone with an aqueous acidic washing liquid to obtain an ammonium-comprising aqueous stream and a fourth gas stream; (d) removing H 2 S from the fourth gas stream by contacting the fourth gas stream in a H 2 S-removal zone with an aqueous alkaline washing liquid to obtain a H 2 S-depleted gas stream and a hydrogensulphide-comprising aqueous stream; (e) contacting the hydrogensulphide-comprising aqueous stream obtained in step (d) with sulphide-oxidizing bacteria in the presence of oxygen in an oxidation reactor to obtain a sulphur slurry and a regenerated aqueous alkaline washing liquid; (f) separating at least part of the sulphur slurry obtained in step (e) from the regenerated aqueous alkaline washing liquid and; (g) recycling the regenerated aqueous alkaline washing liquid obtained in step (e) as the aqueous alkaline washing liquid to the H 2 S-removal zone in step (d).