The Manufacturing Method of α-Calcium Sulfate Hemihydrate from FGD Gypsum by Heating under Reduced Pressure

摘要

PURPOSE: Provided is a method for producing alpha-gypsum hemihydrate (alpha-CaSO41/2H2O) from desulfo-gypsum(CaSO42H2O) by decompression and heating. The resultant alpha-gypsum hemihydrate, having much improved physical properties compared with alpha-gypsum hemihydrate from phospho-gypsum, is produced at a lower temperature in a short time. CONSTITUTION: The alpha-gypsum hemihydrate(alpha-CaSO41/2H2O) is obtained by decompressing calcium sulfate dihydrate, desulfo-gypsum(CaSO42H2O), at -650 to -750torr and heating at 80-120deg.C for 1.5-2.5hrs, wherein the used desulfo-gypsum is a byproduct generated from the fuel gas desulphurization process. The desulpho-gypsum used as a starting material comprises 95wt.% of CaSO42H2O, 1.5wt.% of CaCO3, 0.5wt.% of CaCO31/2H2O, 1.6wt.% of SiO2, 0.8wt.% of Al2O3+Fe2O3, and 0.6wt.% of soluble salts.