| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a simple continuous treatment method for reforming a dihydrate gypsum, which prevents the occurrence of blackishness of gypsum products caused by impurities other than calcium sulfate contained in gypsums using, as a raw material, natural gypsums, by-product gypsums, waste gypsums and the like when gypsum products such as gypsum plasters are manufactured, and can provide a white reformed dihydrate gypsum having a high purity and a large crystal grain diameter. <P>SOLUTION: The method for reforming the dihydrate gypsum includes a baking step of baking a dihydrate gypsum as a starting raw material to make a gypsum hemihydrate, a recrystallization step of using a slurry containing as a solid content the gypsum hemihydrate obtained in the baking step, and hydrating and recrystallizing the slurry gypsum hemihydrate in the presence of a surfactant and/or a defoamer to thereby reforming the dihydrate gypsum to a dihydrate gypsum having an improved degree of whiteness as compared with the dihydrate gypsum as the starting raw material, and a sorting step of sorting the reformed dihydrate gypsum by elutriation from the slurry after the completion of the recrystallization step. <P>COPYRIGHT: (C)2013,JPO&INPIT |
