Process for the reclamation of calcium sulfite produced by a calcium-based FGD system

A method of producing calcium sulfate with a flue gas scrubbing facility having a gas-liquid contactor that uses a calcium-based slurry to absorb sulfur dioxide from a flue gas containing acidic gases, wherein a byproduct containing calcium sulfite precipitate is produced that is accumulated in a reservoir, such as a pond, apart from the gas-liquid contactor. Such a facility is modified to produce calcium sulfate by installing an acidifier vessel and an oxidation receptacle in series between a source of the flue gas and the gas-liquid contactor. The flue gas containing the acidic gases is caused to flow through the acidifier vessel, into which the byproduct is delivered from the reservoir so that some of the acidic gases of the flue gas are absorbed by the byproduct and the pH of the byproduct is sufficiently lowered to allow the calcium sulfite precipitate to dissolve in the byproduct. The flue gas from the acidifier vessel is then delivered to the gas-liquid contactor where sulfur dioxide is absorbed by the calcium-based slurry, and the byproduct from the acidifier vessel is accumulated in the oxidation receptacle. Within the oxidation receptacle, the calcium sulfite dissolved by the byproduct is oxidized to produce calcium sulfate, which is then removed from the oxidation receptacle.