Process for continuous modification of dihydrate gypsum and modified dihydrate gypsum obtained by th

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Provided is a process for continuous modification of dihydrate gypsum which comprises the hemihydrate formation step of firing a raw material dihydrate gypsum into hemihydrate gypsum and the re-crystallization step of subjecting the hemihydrate gypsum to hydration and recrystallization in an aqueous slurry to form a modified dihydrate gypsum having a crystal form different from that of the raw material dihydrate gypsum. In the recrystallization step, the aqueous slurry is kept at a constant temperature in a re-crystallization/reaction tank under such stirring as to make the aqueous slurry uniform, and the feed of hemihydrate gypsum into the re- crystallization/reaction tank and the withdrawal of recrystallized modified dihydrate gypsum from the recrystallization/reaction tank are conducted continuously or intermittently, while being so controlled as to make the feed rate of hemihydrate gypsum substantially equal to the withdrawal rate of re-crystallized modified gypsum. According to the process, a high-purity modified dihydrate gypsum consisting of large crystals, which cannot be generally obtained, can be produced by converting raw material dihydrate gypsum transiently into hemihydrate gypsum by means of firing and then re-crystallizing the hemihydrate gypsum. 3735777_ l (GHMatters) P86113.AU. 12/ 1