Method for continuously producing thiosulfate ions

Abstract

A process is provided for the removal of hydrogen sulfide out of a gas stream by contacting the hydrogen sulfide contaminated gas with a solution of chelated metal catalyst, such as iron EDTA, in a scrubbing vessel so as to result in a cleaned gas and a scrubbing solution containing elemental sulfur and a reduced chelated metal catalyst. A portion of the hydrogen sulfide contaminated feed gas is branched off from the rest of the hydrogen sulfide contaminated feed gas, at a location upstream of the scrubbing vessel, and injected into a bisulfide generating vessel where it is contacted with an aqueous caustic solution, such as an aqueous solution of potassium hydroxide, wherein the hydrogen sulfide reacts with the caustic solution to result in a cleaned gas and a solution containing bisulfide ions. The solution containing bisulfide ions and the scrubbing solution containing elemental sulfur and reduced chelated metal catalyst are both injected into an oxidation vessel where they are contacted with an oxygen containing gas which oxidizes the reduced chelated metal catalyst back into its reactive oxidation state and also oxidizes the bisulfide ions into thiosulfate ions. The regenerated scrubbing solution containing reactive chelated metal catalyst and thiosulfate ions are recycled back to the scrubbing vessel for further contact with the hydrogen sulfide containing gas. The thiosulfate ions protect the chelated metal catalyst from degradation.