| 摘要 |
PURPOSE: To improve the hydrating property of anα-hemihydrate gypsum, save the energy, simplify the production process and reduce the cost by washing and drying anα-hemihydrate gypsum obtained as a by-product of a wet-process for producing phosphoric acid by decomposing an igneous phosphate rock and adding an inorganic alkali to the washed and dried gypsum. CONSTITUTION:α-Hemihydrate gypsum obtained as a by-product of a wet- process for producing phosphoric acid by decomposing an igneous phosphate rock with sulfuric acid by a dihydrate-hemihydrate process is washed with 0.2-5.0kg (based on 1kg of the hemihydrate gypsum in dry base) of water, dried at 40-90 deg.C filtered to remove the water as far as possible, dried at 50-150 deg.C, pulverized and incorporated with 0.001-0.050kg (based on 1kg of the hemihydrate gypsum in dry base) of an inorganic alkali.
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