A flue gas desulfurization process wherein the liquid bottoms product from the scrubber tower is subject to forced oxidation in a reaction/oxidation tank. Afterwards, this oxidized bottoms product is delivered to hydroclone means for separation into an overflow stream containing an aqueous slurry of mostly fines, fly ash, and unused reagent and an underflow stream containing predominately a gypsum slurry. The overflow stream is initially recycled back to the tank with another stream being subsequently returned or recycled back to the scrubber tower while the underflow stream is dewatered for the removal of the gypsum therein.