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Abstract

A process for removing sulfur dioxide and nitrogen oxides from a hot gaseous stream, in a scrubbing unit, by use of an aqueous medium containing calcium and magnesium scrubbing components to remove sulfur dioxide and a ferrous chelate to remove the nitrogen oxide, a portion of the ferrous chelate being oxidized to ferric chelate during the process. The ferric chelate is regenerated to ferrous chelate by contacting the hot gaseous stream, prior to entry into the scrubbing unit, with a prescrubbing aqueous medium containing magnesium scrubbing components for sulfur dioxide, forming bisulfite ions in the aqueous medium. The heated prescrubbing aqueous medium, containing bisulfite ions and ferric chelate, is separated from the gaseous stream and contacted with an iron source, at the elevated temperature to convert the iron source to ferrous ions which dissolve in the aqueous medium and reduce the ferric chelate therein to ferrous chelate for use in the scrubbing unit to remove nitrogen oxide from the hot gaseous stream.

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First Claim