METHOD OF PROCESSING GYPSUM Russian patent published in 2015 - IPC C01F11/18 C01B17/69 C01C1/24 C01C1/02 C01F11/46 

FIELD: chemistry.

SUBSTANCE: invention can be used in inorganic chemistry. A method of processing gypsum includes treating a gypsum suspension with ammonium carbonate solution to obtain chalk and ammonium sulphate. The ammonium sulphate is thermally decomposed to ammonium bisulphate and ammonia. The ammonia is returned for preparation of the ammonium carbonate solution. A solution of ammonium bisulphate and an auxiliary sulphate, which forms a bisulphate with ammonium sulphate, is prepared, followed by precipitation and separation of the bisulphate. The obtained diluted sulphuric acid solution is purified by precipitating impurities. The impurities are separated and the purified diluted sulphuric acid solution is evaporated to obtain commercial-grade sulphuric acid. The bisulphate is decomposed into ammonium sulphate, which is returned for decomposition into ammonium bisulphate and ammonia, and into the auxiliary sulphate, which is returned for preparation of ammonium bisulphate solution and the auxiliary sulphate, which forms a bisulphate with ammonium sulphate. Said auxiliary sulphate is a sulphate which forms a Tutton salt or alum with ammonium sulphate.

EFFECT: invention enables to recycle gypsum without using ammonia a sulphuric acid by-product.

14 cl, 5 ex