Patent ID: 8021442

Claim:
A process for preparing industrial grade solar salt from brines in the field having >99% absolute purity and Ca 2+ to Mg 2+ ratio in the range of 3:1 to 1:1 after heap washing, the said process comprising the steps of: (a) subjecting the brine to solar evaporation to crystallize carbonate salt and gypsum and to obtain a concentrated brine; (b) feeding the concentrated brine as obtained in step (a) into pre-crystallizer and dosing alum into the concentrated brine fed into the pre-crystallizer to form suspended particles; (c) settling of the suspended particles formed in step (b) under gravity with concomitant clarification of concentrated brine in the pre-crystallizer to obtain clarified brine; (d) feeding the said clarified brine into a crystallizer by gradient flow through brine channels; (e) treating the clarified brine fed into the crystallizer in step (d) with an acid to lower the pH in the range of 5.5-6.9; (f) continuing solar evaporation of treated clarified brine of step (e) in the crystallizer to crystallize salt; (g) draining bittern from the crystallizer; and (h) harvesting and heap washing of the salt crystallized in step (f) followed by drying in the sun.