Process for the preparation of magnesia (MgO) from crude Mg (OH)2

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.MgCl2.6H2O);
• c. recovering MgCl2 rich and other salt free end bittern from step (b);
• d. evaporating the end bittern of step (c) to obtain crystalline MgCl2.6H2O;
• e. mixing MgCl2.6H2O 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. optionally filtering the resultant paste/slurry to obtain crude Mg(OH)2 and calcium chloride, or alternatively using crude Mg(OH)2 paste as such without filtration;
• g. drying the crude Mg(OH)2 paste, followed by calcining the crude Mg(OH)2 to convert Mg(OH)2 into MgO, and converting adhering MgCl2 into MgO and HCl gas;
• h. optionally 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. optionally 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 CaCl2 solution filtrate obtained in steps (f) or (i), for desulphatation of brine or bittern in step (a) if lime is used in step (e).