CONTINUOUS METHOD FOR MODIFYING DIHYDRATE GYPSUM

• Main Authors: YOKOYAMA ITARU, KAWAMURA YASUO, KATSUMOTO HIROSHI
• Format: Patent
• Language: English; Japanese
• Published: 25.05.2017
• Subjects: CHEMISTRY; COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM,CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THERARE-EARTH METALS; INORGANIC CHEMISTRY; METALLURGY

PROBLEM TO BE SOLVED: To provide a method for modifying raw material dihydrate gypsum into high-purity modified dihydrate gypsum composed of large crystals by calcining the raw material once to convert the same to hemihydrate gypsum, followed by recrystallization.SOLUTION: Provided is a continuous method for modifying dihydrate gypsum, comprising: a hemihydration step of wet-calcining raw material dihydrate gypsum to convert the same to hemihydrate gypsum; and a recrystallization step of hydrating and recrystallizing the hemihydrate gypsum in an aqueous slurry to convert the same to 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 maintained at a constant temeperature in a recrystallization reaction tank under such stirring as to make the aqueous slurry uniform, and feeding of the hemihydrate gypsum and withdrawal of the recrystallized modified dihydrate gypsum are conducted continuously or intermittently, while a feeding amount of the hemihydrate gypsum into a recrystallization reaction tank and a withdrawal amount of the recrystallized modified dihydrate gypsum withdrawn from the recrystallization reaction tank are controlled so that both become 20% or less of a total amount of gypsum present in the recrystallization reaction tank.SELECTED DRAWING: Figure 1 【課題】出発原料とする二水石膏を、一旦焼成して半水石膏とした後に再結晶化することで、一般的には得ることができない大きい結晶からなる高純度の改質二水石膏にする方法の提供。【解決手段】原料とする二水石膏を湿式焼成して半水石膏にする半水化工程と、該半水石膏を水性スラリー中で水和・再結晶化させて、原料とする二水石膏とは別の結晶形態の改質二水石膏とする再結晶化工程とを有し、該再結晶化工程において、再結晶化反応槽中で、水性スラリーを均一になるように撹拌しつつ一定の温度に保持し、かつ、再結晶化反応槽への半水石膏の供給量、及び、再結晶化反応槽から再結晶化した改質二水石膏を抜き出す抜き出し量とがいずれも再結晶化反応槽内の全石膏量の２０％以下になるよう制御し、連続して又は間歇して半水石膏の供給及び再結晶化した改質二水石膏の抜き出しを行う二水石膏の連続式改質方法である。【選択図】図１