US 5,543,122 AGranted

Process for the removal of h.sub.2 S from non-condensible gas streams and from steam

AssigneeThe Dow Chemical Company

InventorsCharles A. Hammond, Shelby P. Oostwouder, Robert A. Lanning

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Abstract

A process for treating non-condensible gas streams containing H.sub.2 S, and for treating steam containing H.sub.2 S, is disclosed, the process being characterized by unique division of the noncondensible stream, or of a separated non-condensible H.sub.2 S-containing stream derived from the steam, with diverse oxidative treatment of the separated portions. The invention is particularly suited to treating the exhaust steam from a steam turbine which utilizes geothermal steam as the working fluid. In a preferred aspect, disposal of sulfur produced as normal byproduct of liquid oxidative steps may be reduced or avoided altogether by reaction of the sulfur with bisulfite and/or sulfite produced in the procedure to produce soluble thiosulfate.

Claims20

Dependent claims

A process for removing H.sub.2 S from a non-condensible gas stream containing H.sub.2 S and other non-condensible gases comprising dividing or partitioning said non-condensible gas stream into a first H.sub.2 S-containing stream containing the bulk of the H.sub.2 S in said gas stream and a second H.sub.2 S-containing gas stream containing a minor portion of the H.sub.2 S in the non-condensible gas stream;

oxidizing the H.sub.2 S in the first H.sub.2 S-containing stream in a thermal oxidation zone to produce a gaseous stream comprising SO.sub.2, and removing the SO.sub.2 from the gaseous stream by contacting said gaseous stream with an alkaline solution under conditions to produce a purified gas stream and a scrubbing zone solution containing bisulfite and/or sulfite ions;
while simultaneously contacting the second H.sub.2 S-containing gas stream with an aqueous solution of ferric chelate in an aqueous liquid oxidation zone under conditions to convert H.sub.2 S in said second H.sub.2 S-containing gas stream to sulfur in said solution, producing a purified residual gas stream, and removing sulfur from said aqueous liquid oxidation zone;
and combining scrubbing zone solution containing bisulfite and/or sulfite ions with sulfur from the aqueous liquid oxidation zone in a blending zone under conditions to react sulfur and sulfite and/or bisulfite ions to produce a solution containing thiosulfate ion and residual bisulfite and/or sulfite ions.

A process comprising condensing steam containing a minor amount of H.sub.2 S and other non-condensible gases in a condensation zone with an aqueous solution containing a ferric chelate under conditions to convert H.sub.2 S to sulfur, and ferric chelate to ferrous chelate, leaving a non-condensible gas stream containing the bulk of the H.sub.2 S in the steam;

dividing or partitioning said non-condensible gas stream into a first H.sub.2 S-containing stream containing the bulk of the H.sub.2 S in said gas stream and a second H.sub.2 S-containing stream containing a minor portion of the H.sub.2 S in the non-condensible gas stream;
oxidizing the H.sub.2 S in the first H.sub.2 S-containing stream in a thermal oxidation zone to produce a gaseous stream comprising SO.sub.2, and removing the SO.sub.2 from the gaseous stream by contacting said gaseous stream with an alkaline solution;
while simultaneously contacting the second H.sub.2 S-containing stream with an aqueous solution of ferric chelate in an aqueous liquid oxidation zone under conditions to convert H.sub.2 S in said second H.sub.2 S-containing stream to sulfur in said solution, producing a purified residual gas stream, and removing sulfur from said aqueous liquid oxidation zone.

A process comprising condensing steam containing a minor amount of H.sub.2 S and other non-condensible gases in a condensation zone, producing condensate and a non-condensible gas stream containing the bulk of the H.sub.2 S in the steam, and contacting the condensate with an aqueous solution containing a ferric chelate under conditions to convert H.sub.2 S to sulfur, and ferric chelate to ferrous chelate;

dividing or partitioning said non-condensible gas stream into a first H.sub.2 S-containing stream containing the bulk of the H.sub.2 S in said gas stream and a second H.sub.2 S-containing stream containing a minor portion of the H.sub.2 S in the non-condensible gas stream;
oxidizing the H.sub.2 S in the first H.sub.2 S-containing stream in a thermal oxidation zone to produce a gaseous stream comprising SO.sub.2, and removing the SO.sub.2 from the gaseous stream by contacting said gaseous stream with an alkaline solution;
while simultaneously contacting the second H.sub.2 S-containing stream with an aqueous solution of ferric chelate in an aqueous liquid oxidation zone under conditions to convert H.sub.2 S in said second H.sub.2 S-containing stream to sulfur in said solution, producing a purified residual gas stream, and removing sulfur from said aqueous liquid oxidation zone.

Dependencies are inferred from the claim text.