Method of producing calcium sulfate dihydrate
Abstract
Abstract 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.
Inventors
- 👤 Shoichiro Hori
- 👤 Keiichi Murakami
- 👤 Hirobumi Tanaka
Bibliographic Details
Claims Analysis
Total Claims: 0References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-13 | 1975-06-14 | 1975-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-13 | 1979-06-14 | 1979-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-13 | 1983-06-14 | 1983-12-14 | $7700.00 | Window Closed / Lapsed |