The Dow Chemical Company

William R Behr

Larry H Kirby

Van A Kent

Gas feed streams containing sulfur dioxide such as flue gas streams are first contacted with an aqueous solution of inorganic sulfites and bisulfites having a pH range from about 2 to about 6.5 to remove a minor amount of sulfur dioxide. The same gas stream is then contact with a second aqueous solution of sulfites and bisulfites having a pH range from about 7.0 to about 12.5. Alkali metal hydroxide or ammonium hydroxide solution is added to the liquid inlet of the second contactor and the solution of the second contactor is pumped to the liquid inlet of the first contactor.

Process for selectively removing sulfur dioxide

Fluid streams containing hydrogen sulfide from a steam tubine or from a sour gas stream are contacted with an aqueous solution of a polyvalent metal chelate and a bisulfite whereby the hydrogen sulfide is converted to free sulfur and then to soluble sulfur compounds. The metal chelate is reduced to a lower oxidation state metal chelate and reduced metal chelate is subsequently oxidized with air back to the higher oxidation state and reused. The bisulfite is formed by combustion of a portion of the fluid stream and subsequent absorption of the sulfur dioxide formed thereby in a two-stage countercurrent scrubber operating at conditions favorable for high bisulfite and low sulfite formation and selective away from carbon dioxide absorption.

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Lake Jackson, TX, United States of America

William R Behr