Patent ID: 7041268

Claim:
An integrated process for preparation of sulphate of potash (SOP) from bittern comprising: (i) subjecting bittern to fractional crystallization to obtain kainite mixed salt with high kainite content and MgCl 2 -rich end bittern, and subjecting the MgCl2 rich end bittern to desulphation, (ii) treating the kainite mixed salt with water and mother liquor obtained in step (xiii) below to leach out substantially all NaCl from the mixed salt and simultaneously convert kainite into schoenite; (iii) filtering the schoenite and separating the filtrate hereinafter referred to as SEL; (iv) desulphating the SEL with aqueous CaCl 2 to produce gypsum; (v) filtering the gypsum produced in step (iv) and mixing the filtrate with MgCl 2 -rich filtrate obtained in step (vii) below, (vi) evaporating the resultant solution of step (v), hereinafter referred to as desulphated SEL, and cooling to ambient temperature to crystallize crude carnallite, (vii) centrifuging the crude carnallite and recycling the MgCl 2 -rich filtrate to step (v); (viii) decomposing the crude carnallite from step (vi) with an effective amount of water to yield cride KCl and carnallite decomposed liquor; (ix) filtering the crude KCl, and washing with water to remove adhering MgCl 2 and subjecting to hot leaching for production of muriate of potash (MOP) and NaCl; (x) mixing the carnallite decomposed liquor from step (viii) and washing from step (ix) and treating with hydrated lime to form a slurry; (xi) filtering the slurry and washing the resultant filter cake to produce Mg(OH) 2 and CaCl 2 -containing filtrate for the desulphatation process of step (iv); (xii) treating the schoenite produced in step (iii) with MOP produced in step (ix) to produce SOP under ambient condition; (xiii) filtering the SOP and collecting separately the mother liquor hereinafter referred to as KEL; (xiv) recycling the KEL of step (xiii) in the process of step (ii).