Abstract: A process for producing dry flue gas gypsum substantially free of hemihydrate and anhydrous calcium sulfate comprises drying wet flue gas gypsum, typically having a free water content of about 4-12% by weight, in direct contact with a partial stream withdrawn from a primary stream of a dry dedusted flue gas. Flue gas gypsum produced in a wet desulfuration stage is fed to contact the partial stream and is separated from this partial stream and removed as dried flue gas gypsum. Remaining superfine flue gas gypsum is then fed to the intake side, or to the delivery side of a booster blower arranged upstream of the flue gas desulfuration device along with the partial flue gas stream discharged from the drying stage, and the superfine particulate flue gas gypsum is conducted from the booster blower into the flue gas desulfurizing device to serve as seed crystals for additional production of gypsum therein.