Technologies Salt and Marine Chemicals

Integrated process for the recovery of sulphate of potash and refractory grade magnesia from sea bittern

Inventor: P K Ghosh

IPR Status: US Patent No: 7,041,268

The present invention is directed to a novel integrated process for the recovery of sulphate of potash (SOP) from sulphate rich bittern. The process requires bittern and lime as raw materials. Kainite type mixed salt is obtained by fractional crystallization of the bittern, and is converted to schoenite which is subsequently reacted with muriate of potash (MOP) for its conversion to SOP. End liquor from kainite to schoenite conversion (SEL) is desulphated and supplemented with MgCl2using end bittern generated in the process of making carnallite. Decomposed carnallite liquor produced is reacted with hydrated lime for preparing CaCl2 solution and high purity Mg(OH)2 having low boron content. It is shown that the liquid streams containing potash are recycled in the process, and the recovery of potash in the form of SOP is quantitative.

Advantages of the invention:

(i) SOP is a dual fertilizer containing 50% K2O and 18% sulfur.
(ii) SOP is virtually free of chloride and hence ideal for saline soils and chloride sensitive crops.
(iii) SOP has lower salt index i.e low osmostic effect
Salt index of sodium nitrate = 100
Muriate of potash (MOP) = 116.3
Nitrate of potash (KNO3) = 73.6
Sulphate of potash (SOP) = 46.1


Technology licensed to:

Ms/ Archean Group of Chemical Industries , Chennai