Patent ID: 7811535

Claim:
An improved process for the preparation of MgO, the said process comprising the steps of: i) desulphating brine or bittern with calcium chloride, ii) evaporating the clarified brine/bittern after separation of gypsum to separate out the common salt and carnallite (KCl.MGCl 2 .6H 2 O), iii) recovering MGCl 2 rich and other salt free end bittern from step (ii), iv) further evaporating end bittern of step (iii) to obtain crystalline MGCl 2 .6H 2 O), v) seeding MGCl 2 .6H 2 O, obtained in step (iv) either as such or after recrystallization, in solid or solution form, with Mg(OH) 2 and treating it with ammonia (NH 3 ), vi) filtering the resultant slurry obtained in step (v) to obtain the crude Mg(OH) 2 and NH 4 Cl/residual NH 4 OH filtrate, vii) drying the above crude Mg(OH) 2 , followed by calcination to convert Mg(OH) 2 into MgO, and converting adhering MGCl 2 into MgO and HCl gas, and NH 4 C 1 into sublimed vapor, viii) absorbing the hot sublimed vapor of NH 4 Cl generated in step (vii) from the calciner into the NH 4 C 1 /residual NH 4 OH filtrate of step (vi) to further enrich the filtrate in NH 4 Cl and also for heating up the filtrate, ix) treating the above said hot filtrate with lime to obtain CaCl 2 solution and ammonia vapor, x) using the ammonia vapor obtained in step (ix) in a process step (v) to complete the loop while using the by-product CaCl 2 solution in step (i).