| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing gypsum by adding water to gypsum dihydrate produced by a drain-free type dry gypsum production method, aging the mixture with stirring, separating water from the aged product and subsequently drying the aged product, capable of modifying the gypsum and removing impurities soluble in water. SOLUTION: This method for producing gypsum comprises kneading sulfuric acid with a raw material containing calcium carbonate as a main component, adding water to the kneaded product in a state that the reaction of the calcium carbonate with the sulfuric acid proceeds until the half way of the reaction, further continuing the mixture reaction to produce gypsum dihydrate (particle size is <= about 10μm), adding water to the obtained gypsum dihydrate, aging the mixture in an aging tank 15 for about 2-3 hr with stirring, thus allowing the gypsum dihydrate to grow into long and slender crystals having particle diameters of about 100-200μm, separating water from the aged gypsum dihydrate in a water-separating device 16, and finally drying the obtained gypsum dihydrate down to a water content of <= about 10%. Thereby, the obtained crystalline gypsum dihydrate can easily be slurried and handled, and has good flowability.
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