A sodium-based flue gas desulfurization process, employing reductive burning and a Claus recovery system, has the advantage of producing elemental sulfur as a byproduct. This study optimized the process conditions for two steps in the proposed reaction scheme : (1) removing approximately one-sixth of the sulfur in the spent scrubbing liquor by a combination of acidification and evaporation and (2) precipitation of 50% of the remaining Na2SO3(s) by the addition of NaHCO3/Na2CO3 slurry. Several combinations of process conditions can be used to produce favorable results, but the optimum from a technical perspective is to add concentrated H2SO4 to the spent liquor to 1.5% v/v, concentrate the mixture to 70% by weight, and then treat it with a > 70% solids slurry of NaHCO3/Na2CO3. The optimum from an economic perspective is dependent on the relative costs of H2SO4 and the steam needed to concentrate the spent liquor.