METHOD OF PRODUCTION OF CALCIUM CARBONATE Russian patent published in 2000 - IPC

FIELD: processing phosphate ores; conversion of calcium nitrate at obtaining calcium carbonate. SUBSTANCE: method consists in decomposition of natural phosphates with nitric acid, separation of calcium nitrate through crystallization, dissolving it in water, two-stage treatment of calcium nitrate solution with ammonium carbonate at intermediate filtration, separation of sediments of different degree of purity. Calcium nitrate solution is fed to first stage in two phases: first 21 to 50% of calcium nitrate solution is treated with 89- 142-% ammonium carbonate solution of stoichiometrically required amount for sediment of introduced calcium; at second stage, remaining calcium nitrate solution is introduced into suspension to pH of 6 to 7.9 and is subjected to filtration; calcium nitrate solution is also treated with ammonium carbonate at second stage. EFFECT: improved quality of calcium carbonate. 1 tbl