| 摘要 |
PROBLEM TO BE SOLVED: To provide a process for producing a high-purity modified dihydrate gypsum consisting of large crystals, which cannot be generally obtained, by once firing dihydrate gypsum as a starting raw material into hemihydrate gypsum and then recrystallizing the hemihydrate gypsum.SOLUTION: The process for continuous modification of dihydrate gypsum comprises the hemihydrate formation step of firing a raw material dihydrate gypsum into hemihydrate gypsum and the recrystallization 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 recrystallization reaction tank under such stirring as to make the aqueous slurry uniform, and the feed of hemihydrate gypsum into the recrystallization 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 recrystallized modified dihydrate gypsum. |
