Patent ID: 7014832

Claim:
An integrated process for the simultaneous recovery of industrial grade potassium chloride and low sodium edible salt with overall KCl yield of 90–95%, which comprises (i) desulphatation of bittern with a solution of calcium chloride; (ii) subjecting the desulphated bittern to evaporation until density of 32 to 32.5° Be′ (sp.gr. 1.283–1.288) is achieved; (iii) mixing the desulphated bittern obtained in step (ii) with a concentrated solution of MgCl 2 to obtain high purity carnallite and a residual bittern; (iv) decomposing the carnallite with water to obtain ca. 60% of overall KCl and a first carnallite decomposed liquor; (v) crystallizing from the residual bittern residual NaCl and KCl in the form of crude carnallite and thereby obtaining a MgCl 2 -rich end bittern; (vi) decomposing the crude carnallite obtained in step (v) with water to produce KCl-enriched low sodium salt in 30–35% overall yield with respect to KCl in the original 32 to 32.5° Be′ (sp.gr. 1.283–1.288) bittern, as well as a second carnallite decomposed liquor; (vii) collecting the first and second carnallite decomposed liquors obtained in steps (iv) and (vi) above and treating the resulting mixture with upgraded lime to generate low boron magnesium hydroxide and filtrate containing CaCl 2 and KCl; (viii) recycling the filtrate obtained in step (vii) above to step (i) above for desulphatation of bittern while simultaneously recovering KCl lost in carnallite decomposed liquors; (ix) recycling the MgCl 2 -rich end bittern of step (v) for sustained production of high purity carnallite in step (iii) and also for production of CaCl 2 .