PROCESS FOR PRODUCING CALCIUM CARBONATE Russian patent published in 1995 - IPC

FIELD: chemical industry. SUBSTANCE: essence of this process resides in treating calcium nitrate with ammonia and carbon dioxide and/or ammonium carbonate, separating end product precipitate by filtration, washing it with water and drying, treating washed-off precipitate with either sodium hydroxide or carbonate prior to drying, maintaining consumption of reagent within limits of 1.5 to 3.0 mol per 1 mol of water-soluble ammoniacal nitrogen admixed with calcium carbonate, using sodium hydroxide preferably in the form of 10 - 20 % aqueous solution and sodium carbonate preferably in the form of 15 - 20 % aqueous solution. End product is suitable for use in manufacture of glass, linoleum and other products and recovery of calcium in process of comprehensive nitrate treatment of apatite concentrate to produce compound fertilizers. EFFECT: treating desired product before drying with disclosed reagent allows reducing content of ammoniacal nitrogen to about 0.01 - 0.02 %. 4 cl, 3 tbl