Removal of sulfur dioxide from flue gas

An improvement is provided in the regeneration system of aqueous regenerative processes for the removal of SO2 from SO2-containing gas streams which have a scrubbing system containing (1) a scrubbing zone through which a recirculating stream of sodium or potassium thiosulfate solution continuously passes as a vehicle for the SO2 absorbent, sodium or potassium carbonate, under conditions favorable to the formation of sulfite by the reaction of carbonate and SO2 and (2) a thiosulfate generation zone in which the sulfite is converted by reaction with a sulfide to thiosulfate. The improvement comprises converting, in a regeneration system, the net make of thiosulfate to a mixture of sulfide and carbonate by first converting the thiosulfate to sulfate, then reducing the sulfate to sulfide; and thereafter partially carbonating the sulfide to form a mixture of sulfide and carbonate for return to the scrubbing system.