PREPARATION OF CALCIUM CARBONATE Russian patent published in 2015 - IPC C01F11/18 C09C1/02 C09C3/08 

FIELD: chemistry.

SUBSTANCE: invention may be used in the chemical industry. A method for the preparation of calcium carbonate from lime involves providing an aqueous solution having pH of at least 11.5 and comprising 10-35 % by weight of a dissolved polyhydroxy compound and 1-5 % by weight of dissolved calcium hydroxide, expressed as Ca(OH)₂. The polyhydroxy compound has formula HOCH₂(CHOH)_nCH₂OH, where n ranges from 1 to 6. The solution is treated to remove solids, including suspended solids. Dispersing carbon dioxide through the solution so as to form calcium carbonate with a consequential reduction in the pH of the reaction mixture is executed. During a time period beginning at the start with a sudden short rise in pH and ending with a subsequent fall in pH but before it reaches 9.5 the dispersion of carbon dioxide is terminated and an alkaline reagent is added to maintain pH for the product mixture of at least 9.5. Recovering precipitated calcium carbonate is carried out.

EFFECT: invention enables production of calcium carbonate of higher purity and a uniform particle size.

26 cl, 4 dwg, 4 ex