Patent ID: 7771682

Claim:
A process for the preparation of MgO, the process comprising the steps of: a. desulphating brine or bittern with CaCl2; b. evaporating the clarified brine/bittern after separation of gypsum to separate out the common salt and carnallite (KCl.MgCl 2 .6H 2 O); c. recovering MgCl 2 rich and other salt free end bittern from step (b); d. evaporating the end bittern of step (c) to obtain crystalline MgCl 2 .6H 2 O; e. mixing MgCl 2 .6H 2 O with seeds of Mg(OH) 2 , followed by treating with alkali or hydrated lime/lime slurry to obtain by precipitation reaction a crude Mg(OH)2 paste/slurry; f. filtering the resultant paste/slurry to obtain crude Mg(OH) 2 and calcium chloride, g. drying the crude unwashed and unpurified Mg(OH) 2 paste comprising calcium chloride, followed by calcining to convert Mg(OH) 2 into MgO, and converting adhering MgCl 2 into MgO and HCl gas; h. treating the calcined mass of MgO with water to crumble the lumps and thereby dissolving calcium chloride and other soluble salts in water to obtain a MgO slurry; i. filtering the MgO slurry, followed by washing the residue with water to make a wet cake substantially free from impurities; j. drying the resultant MgO and recalcining it to obtain a purified MgO; and k. using the CaCl 2 solution filtrate obtained in steps (f) or (i), for desulphatation of brine or bittern in step (a) if lime is used in step (e).