| 摘要 |
A process is provided for the production of high-purity gypsum, which comprises reacting a calcium source with a mineral acid in a water phase to have the calcium source sufficiently dissolved as a calcium salt in the water phase, separating and removing undissolved residue from a resulting water phase, adding sulfuric acid to a water phase, which has been obtained by the removal of the undissolved residue, to crystallize gypsum, and separating the crystallized gypsum from the water phase. According to the process, plate-like or short prism-like crystals of dihydrate gypsum of high purity, high whiteness, large bulk density and small aspect ratio can be efficiently obtained even when a low-purity calcium source is used. Calcination of such crystals of dihydrate gypsum can also provide calcined gypsum of high purity, which is satisfactory in spray mixing water amount, setting time, and physical properties such as tensile strength. |
