| 摘要 |
PURPOSE:To continuously and stably produce an alpha-type gypsum hemihydrate having high purity, by converting a slurry of gypsum dihydrate to alpha-type gypsum hemihydrate by hydrothermal treatment under pressure, cooling the resultant slurry of alpha-type gypsum hemihydrate in pressurized state, separating the solid from the liquid under normal or reduced pressure and drying the product. CONSTITUTION:A slurry of gypsum dihydrate 1 and a crystallization medium 2 are mixed in a mixing tank 3, transferred to a reaction tank 6 through a heat-exchanger 5 with a pressure pump 4 and converted to alpha-type gypsum hemihydrate by hydrothermal treatment under pressure at >100 deg.C. The slurry of alpha-type gypsum hemihydrate extracted from the reaction tank 6 is transferred to the heat-exchanger 5 keeping the pressurized state and cooled to <=100 deg.C. The cooled slurry of alpha-type gypsum hemihydrate is transferred through a normal-pressure tank 7 to a filter 8 and separated into solid and liquid under normal or reduced pressure. The recovered cake of alpha-type gypsum hemihydrate is dried with a drier 9 at <=80 deg.C under normal or reduced pressure to obtain high-purity alpha-type gypsum hemihydrate.
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