| 摘要 |
<p>Method for the preparation of phosphoric acid and calcium sulphate wherein calcium phosphate is attacked by a mixture of sulphuric acid and phosphoric acid comprising at least three successive crystallization steps: a first step (1) for the reaction between the phosphate (2) and the phosphoric and sulphuric acids (3 and 4) forming hemihydrate alpha of calcium sulphate, a second step (12) recrystallizing the hemihydrate alpha into dehydrate and a third step (18) transforming the latter into hemihydrate alpha, anhydrite II or a mixture of the two, the latter being then subjected to a separation process (22), the product phosphoric acid (10) being drawn off in the first step. </p> |
