公开(公告)号：US3505013A

公开(公告)日：1970-04-07

申请号：US3505013D

申请日：1966-09-20

申请人： NIPPON KOKAN KK ,  TOYO ENGINEERING CORP

发明人： ARAKI KAZUO ,  IIJIMA YASUO ,  SANO KOICHI ,  SHINDO KAZUO ,  SAITO YOO ,  KAWAGUCHI IWAKICHI ,  HOSODA MINORU ,  MURAKAMI KEIICHI

IPC分类号： C01B25/22 ,  C01B25/18

CPC分类号： C01B25/22

公开(公告)号：US3627485A

公开(公告)日：1971-12-14

申请号：US3627485D

申请日：1968-11-05

申请人： NIPPON KOKAN KK

发明人： HORI SHOICHIRO ,  MURAKAMI KEIICHI ,  TANAKA HIROBUMI

IPC分类号： C01F11/46 ,  C01B25/22

CPC分类号： C01F11/46 ,  C01F11/468

摘要： PHOSPHORIC ACID-FREE AND STRONTIUM-FREE CALCIUM SULFATE DIHYDRATE IS OBTAINED FROM PHOSPHATE ROCK BY DECOMPOSING PHOSPHATE ROCK WITH SULFURIC AND/OR PHOSPHORIC ACID OF SUCH TEMPERATURE AND CONCENTRATION THAT A SLURRY OF CALCIUM SULFATE DIHYDRATE WILL BE OBTAINED. THE TEMPERATURE OF THE SLURRY IS THEN RAISED TO THE CONVERSION TEMPERATURE OF THE CALCIUM SULFATE DIHYDRATE INTO CALCIUM SULFATE SEMIHYDRATE SO THAT THE CALCIUM SULFATE DIHYDRATE WILL BE CONVERTED INTO CALCIUM SULFATE SEMIHYDRATE. THEREAFTER, THE TEMPERATURE IS REDUCED TO BELOW THE CONVERSION TEMPERATURE OF THE CALCIUM SULFATE SEMIHYDRATE INTO CALCIUM SULFATE DIHYDRATE WHEREBY THE CALCIUM SULFATE SEMIHYDRATE WILL BE CONVERTED INTO CALCIUM SULFATE DIHYDRATE OF HIGH PURITY WHICH MAY THEN BE RECOVERED IN CONVENTIONAL MANNER, FOR INSTANCE BY FILTRATION. PREFERABLY DURING THE CONVERSION OF THE SEMIHYDRATE INTO THE DIHYDRATE, SEED CRYSTALS CONSISTING OF TWIN CRYSTALS OF CALCIUM SULFATE DIHYDRATE ARE INTRODUCED.