METHOD OF PRODUCING CALCIUM SULPHATE Russian patent published in 2012 - IPC C01F11/46 

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. The method of producing calcium phosphate involves decomposition of limestone with sulphuric acid to obtain a pulp, separation of calcium sulphate precipitate via filtration and then washing the precipitate. Limestone is decomposed with 60-98% H₂SO₄ at temperature 80-100°C while maintaining content of solid substances therein at 25-40% and content of sulphuric acid in the liquid phase of the pulp at 25-50% with crystallisation of calcium sulphate anhydrite. Calcium sulphate is separated by filtration and washing until achieving residual content of sulphuric acid therein of 0.05-1.0%. Washing solutions are recycled to the limestone decomposition step in an amount required to maintain said content of solid substances in the pulp and sulphuric acid in the liquid phase of the pulp.

EFFECT: intensification of limestone decomposition and crystallisation of calcium sulphate and obtaining easily filtered calcium sulphate.

5 cl, 1 tbl, 5 ex