GB442764A - Process for the production of anhydrous magnesium carbonate (magnesite) - Google Patents

Abstract

In the production of magnesium compounds by treating dolomite or limestone with magnesium chloride liquor, the resultant intermediate solid phase is converted into anhydrous neutral magnesium carbonate by causing it to react with the required amount or a moderate excess of carbon dioxide at temperatures above 150 DEG C. in the absence of ammonium salts. In one method of applying the process, calcined dolomite or limestone is converted by magnesium chloride liquor into magnesium hydroxide and calcium chloride liquor and the resulting suspension treated in an autoclave, at say 180 DEG C., with carbon dioxide, preferably that obtained by calcining the initial material. In a second preferred method, crude dolomite or limestone is suspended in an amount of magnesium chloride liquor at least sufficient for the reaction, and is converted directly into anhydrous neutral magnesium carbonate at temperatures of 280--330 DEG C. with introduction of at least sufficient carbon dioxide to cover any loss; in this case the reaction temperature may be lowered by using an excess of magnesium chloride liquor, and by using 2 mols. of MgCl2 per mol. of CaCO3 the reaction occurs at 200 DEG C. with limestone and at 230 DEG C. with dolomite. When insufficient carbon dioxide is employed, a mixture of neutral magnesium carbonate with magnesium hydroxide is obtained.