Patent ID: 7588627

Claim:
A process for the removal of H 2 S and mercaptans from a gaseous hydrocarbon stream comprising these compounds, which process comprises the steps of: (a) removing H 2 S from the gaseous hydrocarbon stream by contacting the gaseous hydrocarbon stream in a H 2 S -removal zone with a first aqueous alkaline washing liquid buffered at a pH between 4.5 and 10, at a temperature between 5 and 70° C. and a pressure between 1 and 100 bar, to obtain a H 2 S -depleted gas stream and a sulphide-comprising aqueous stream; (b) removing mercaptans from the H 2 S -depleted gas stream obtained in step (a) by contacting the H 2 S -depleted gas stream in a mercaptan-removal zone with a second aqueous alkaline washing liquid buffered at a pH between 5.5 and 10, at a temperature between 5 and 70° C. and a pressure between 1 and 100 bar, wherein the pH of the aqueous alkaline washing liquid in the mercaptan-removal zone is higher than the pH of the aqueous washing liquid in the H 2 S -removal zone, to obtain a mercaptan-depleted gas stream and an thiolate-comprising aqueous stream, said mercaptan-depleted gas stream having a level of H 2 S below 10 ppmv and a level of mercaptans below 6 ppmv; (c) contacting the combined aqueous streams comprising sulphide and thiolates obtained in step (a) and step (b) 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; (d) separating at least part of the sulphur slurry obtained in step (c) from the regenerated aqueous alkaline washing liquid; and (e) recycling the regenerated aqueous alkaline washing liquid from the oxidation reactor to the H 2 S -removal zone in step (a) and to the mercaptan-removal zone in step (b).