Ammonia-based flue gas desulfurization system and method

Abstract

Wet flue gas desulfurization systems and methods for contacting a flue gas with a scrubbing liquid to produce ammonium thiosulfate. The scrubbing liquid absorbs sulfur dioxide and optionally additional acidic gases from the flue gas to produce a scrubbed flue gas, the scrubbing liquid with the absorbed sulfur dioxide therein is collected, and ammonia and elemental sulfur are introduced into the collected scrubbing liquid to react the ammonia, the absorbed sulfur dioxide, and the elemental sulfur in the collected scrubbing liquid to produce ammonium thiosulfate.

1 . A wet flue gas desulfurization system comprising:
 an absorber through which a flue gas flows;   a contact region in the absorber having means for contacting the flue gas with a scrubbing liquid so that the scrubbing liquid absorbs sulfur dioxide and optionally additional acidic gases from the flue gas to produce a scrubbed flue gas;   a reaction tank located so that the scrubbing liquid is received in the reaction tank after the scrubbing liquid has absorbed the sulfur dioxide from the flue gas;   a source of elemental sulfur; and   a device for introducing the elemental sulfur from the source into the scrubbing liquid within the reaction tank;   wherein the scrubbing liquid contains ammonia and ammonium thiosulfate is produced as a byproduct of a reaction of the ammonia, the sulfur dioxide, and the elemental sulfur in the scrubbing liquid.   
     
     
         2 . The wet flue gas desulfurization system of  claim 1 , further comprising an injector that injects the ammonia into the scrubbing liquid. 
     
     
         3 . The wet flue gas desulfurization system of  claim 1 , wherein the device for introducing the elemental sulfur is an injector. 
     
     
         4 . The wet flue gas desulfurization system of claim, wherein the absorber is a converted absorber of a pre-existing calcium-based flue gas desulfurization system. 
     
     
         5 . The wet flue gas desulfurization system of  claim 1 , wherein the absorber is a converted absorber of a pre-existing ammonia-based flue gas desulfurization system. 
     
     
         6 . A wet flue gas desulfurization method comprising:
 contacting a flue gas with a scrubbing liquid so that the scrubbing liquid absorbs sulfur dioxide and optionally additional acidic gases from the flue gas to produce a scrubbed flue gas;   collecting the scrubbing liquid with the absorbed sulfur dioxide and introducing ammonia and elemental sulfur into the collected scrubbing liquid to react the ammonia, the absorbed sulfur dioxide, and the elemental sulfur in the collected scrubbing liquid to produce ammonium thiosulfate.   
     
     
         7 . The wet flue gas desulfurization method of  claim 6 , the method further comprising controlling operating parameters including temperature, pH, and sulfur concentration in the collected scrubbing liquid to form the ammonium thiosulfate without forming a secondary byproduct. 
     
     
         8 . The wet flue gas desulfurization method of  claim 7 , wherein the method is performed with a wet flue gas desulfurization system. 
     
     
         9 . The wet flue gas desulfurization method of  claim 8 , the method further comprising constructing the wet flue gas desulfurization system by converting a pre-existing calcium-based flue gas desulfurization system. 
     
     
         10 . The wet flue gas desulfurization method of  claim 8 , the method further comprises constructing the wet flue gas desulfurization system by converting a pre-existing ammonia-based flue gas desulfurization system.