CALCIUM CARBONATE PRODUCTION PROCESS (OPTIONS) Russian patent published in 2006 - IPC C02F11/18 

FIELD: production of inorganic compounds.

SUBSTANCE: process of invention can be used for conversion of calcium nitrate formed during polythermal crystallization of nitric acid extract of apatite or another phosphate raw material to produce calcium carbonate and ammonium nitrate. Process comprises treating calcium nitrate in continuous mode at stirring and temperature 50-80^°C with ammonium carbonate solution by way of simultaneously supplying into conversion reactor calcium nitrate and ammonium carbonate solutions using 0.05-0.50% excess of ammonium carbonate (taking into account free carbon dioxide); separating calcium carbonate by filtration; washing and drying. Mass portion of calcium nitrate in solution is controlled in the range 10-13% by adding ammonium nitrate solution to acidic melt of calcium nitrate tetrahydrate. Filter residue is washed with process condensate at solid-to-liquid ratio (1÷3):1 in one step or in two steps using second-step filtrate in first-step washing. Calcium carbonate production process according to invention is compatible with existing production, provides desired degree of washing ammonium compounds out of precipitate, and improves quality of calcium carbonate owing to reduced mass portion of water-soluble ammonium nitrogen in product to 0.005-0.03%.

EFFECT: enhanced process efficiency and improved quality of product.

2 cl, 2 tbl, 2 ex