Preparation of lightweight magnesium carbonate process from dolomite

Light magnesium carbonate is white amorphous powder, easily soluble in acid, slightly soluble in water, density 2.16g/cm3, thermal stability is poor, 300°C start to decompose, 800 ~ 900°C is rapidly decomposed into magnesium oxide. Light magnesium carbonate is a senior inorganic filler, reinforcing agent and good flame retardant for rubber and plastic industry, filler for high-grade ink, pigment, toothpaste and cosmetics, raw material for high-grade ceramics, glass and fireproof coating.

The production process and production principle are as follows.

The dolomite is given into the vertical kiln and calcined at 900~1000°C to produce dolomite ash.

The dolomite ash is digested into dolomite ash milk by adding water.

Carbonize the appropriate concentration of ash milk with CO2 gas, at this time, CaCO3 precipitates out due to its small solubility in water, and when the partial pressure of CO2 is kept at 2~3 atmospheres, 80~90% Mg(OH)2 can be dissolved by reacting with CO2 to form Mg(HCO3)2, and generate saturated magnesium bicarbonate solution, at this time, filter, Mg++ remains in the solution, CaCO3 remains in the filter cake in the filter cake, can realize the separation of Ca++ and Mg++.

After the separation of calcium and magnesium ions, the filtrate is the supersaturated solution of Mg(HCO3)2, called heavy magnesium water, at this time, the magnesium oxide content in each liter of solution is only 20 ~ 30g. Therefore, the magnesium enrichment. Because of the poor thermal stability of Mg(HCO3)2, the solution can be heated to make the heavy magnesium water decompose.

Generate alkaline magnesium carbonate precipitate. Then the precipitate will be filtered, dried, broken up and depolymerized that is the finished product. At this time, the filtrate contains a part of Mg++ need to be recovered, this filtrate can be recycled to disintegrate dolomite ash, can be recycled Mg++.

The main factors affecting the quality of light magnesium carbonate product are: the quality of dolomite, calcination process and equipment, digestion process and impurity removal rate, carbonization process, Mg++ enrichment and separation process with Ca++ and drying and dehydration process, etc. The requirements of light magnesium carbonate production on raw material quality are: CaO>54%, MgO>18.0%, SiO2<1.0%, Al2O3+ Fe2O3<1.0%.