Dolomite deposits are abundant in my country, mainly distributed in Haicheng, Liaoning; Leyu, Qinghai; Yongdeng, Gansu; Daye, Hubei; and Nanjing, Jiangsu. It is primarily used in ceramic blanks and glazes, alkaline refractory materials, and the glass industry. It is also used as a raw material for dolomite-based cement, a building material, and a commonly used flux in the metallurgical industry.
A method of preparing calcium and magnesium carbonate by direct carbonization of ammonium leachate from calcined low and medium grade phosphate ore, comprising the following steps:
(1) Calcining medium-low grade phosphate ore to obtain pyrolysis products with CO2 gas, the following reactions mainly occur in this process:
CaCO3·MgCO3 = CaO+MgO+2CO2;
(2) the pyrolysis products obtained and ammonium nitrate solution (or ammonium chloride solution) mixed leaching, to get containing calcium and magnesium salts of calcined low-grade phosphorite ammonium salt leach solution and NH3 gas, the process mainly occurs in the following reaction:
CaO+MgO+2H2O=Ca(OH)2+Mg(OH)2;
Ca(OH)2+2NH4NO3 = Ca(NO3)2+2NH3+2H2O;
Mg(OH)2+2NH4NO3 = Mg(NO3)2+2NH3+2H2O;
(3) the obtained calcined low-grade phosphorite ammonium salt leaching solution with the CO2 gas obtained in step (1) and the NH3 gas obtained in step (2) are passed into the calcined low-grade phosphorite ammonium salt leaching solution, so that the calcined low-grade phosphorite ammonium salt leaching solution is carbonized to precipitate calcium and magnesium, and calcium and magnesium carbonates are obtained, and the main reactions occurring in this process are as follows:
Ca(NO3)2+Mg(NO3)2+4NH3+ 2CO2+2H2O = CaCO3+MgCO3+4NH4NO3.
