A process for removing sulfur oxides, other acid gases, and particulate from a flue gas, said process comprising: treating the flue gas in a spray dryer utilizing a slurry formed from water and an alkaline reagent, wherein a portion of the acid gases is removed from the flue gas and a dry by-product is produced; filtering the flue gas to remove fly ash and at least a portion of said dry by-product and causing further reduction of the acid gases; wet scrubbing the flue gas exiting said spray dryer in a wet scrubber as a polishing step for removal of acid gases and particulate; adding a lime or limestone reagent to said wet scrubber, wherein said lime or limestone reagent reacts with at least a portion of the remaining acid gases present in said wet scrubber to produce a wet scrubber by-product; and at least one step selected from the group comprising: (i) discharging a purge stream from said wet scrubber to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and the purge stream, and producing gypsum from said wet scrubber by-product, (ii) discharging a part of said wet scrubber by-product to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and said wet scrubber by-product, and (iii) adding said dry by-product from the spray dryer to said wet scrubber. treating the flue gas in a spray dryer utilizing a slurry formed from water and an alkaline reagent, wherein a portion of the acid gases is removed from the flue gas and a dry by-product is produced; filtering the flue gas to remove fly ash and at least a portion of said dry by-product and causing further reduction of the acid gases; wet scrubbing the flue gas exiting said spray dryer in a wet scrubber as a polishing step for removal of acid gases and particulate; adding a lime or limestone reagent to said wet scrubber, wherein said lime or limestone reagent reacts with at least a portion of the remaining acid gases present in said wet scrubber to produce a wet scrubber by-product; and at least one step selected from the group comprising: (i) discharging a purge stream from said wet scrubber to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and the purge stream, and producing gypsum from said wet scrubber by-product, (ii) discharging a part of said wet scrubber by-product to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and said wet scrubber by-product, and (iii) adding said dry by-product from the spray dryer to said wet scrubber. (i) discharging a purge stream from said wet scrubber to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and the purge stream, and producing gypsum from said wet scrubber by-product, (ii) discharging a part of said wet scrubber by-product to said spray dryer, wherein said treating the flue gas in the spray dryer utilizes a slurry formed from water, alkaline reagent and said wet scrubber by-product, and (iii) adding said dry by-product from the spray dryer to said wet scrubber.