Process for removing so.sub.2 from effluent gases and for removing heat

Abstract

Improvement in processes for the selective removal of sulfur dioxide with respect to carbon dioxide from a gas mixture containing same wherein the gas mixture is contacted with an aqueous absorbent solution, such as an alkanolamine, an alkali metal or ammonium hydroxide, or sulfites thereof, to remove sulfur dioxide from the gas mixture and form a SO.sub.2 -rich aqueous absorbent solution which is moved to a stripping zone where sulfur dioxide is driven off to form a SO.sub.2 -depleted aqueous absorbent solution which is recycled and re-contacted with the gas mixture, the improvement comprising removing sulfur oxyanions of heat stable salts which accumulate in the aqueous absorbent solution by contacting it with an anion exchange resin having bisulfite anions displaceable by the heat stable sulfur oxyanions whereby the bisulfite anions of the resin are replaced by the heat stable divalent sulfur oxyanions which are thus taken out of the solution. The anion exchange resin preferably is a weak base anion exchange resin which can be regenerated by contacting it with aqueous ammonium hydroxide to replace the heat stable sulfur oxyanions on said resin with hydroxyl anions and thereafter contacting the resin with aqueous-sulfur dioxide to replace the hydroxyl anions with bisulfite anions.