Patent ID: 8721999

Claim:
A process for the simultaneous production of sulphate of potash (SOP), ammonium sulphate, surface modified magnesium hydroxide and/or magnesium oxide being characterized in the co-generation of the said products using kainite mixed salt and ammonia as the only consumable raw materials, the said process comprising the following steps: a) converting in a first reaction zone, kainite mixed salt into schoenite by the process of aqueous leaching, wherein the aqueous leaching process comprises reacting kainite mixed salt with water and SOP end liquor of step (e) followed by separating the pure schoenite and schoenite end liquor (SEL); b) treating the clear schoenite end liquor obtained in step (a) with aqueous CaCl 2 to separate out sulphate in the form of gypsum followed by filtering the mass to recover gypsum and desulphated schoenite end liquor; c) subjecting the desulphated schoenite end liquor obtained in step (b) to evaporation to obtain solid carnallite and liquor rich in MgCl 2 ; d) decomposing the carnallite obtained in step (c) with water to recover KCl and carnallite decomposed liquor (CDL) containing MgCl 2 and residual KCl; e) treating the pure schoenite of step (a) with KCl obtained in step (d) to produce sulphate of potash (SOP) while recycling the SOP end liquor in the process of step (a); f) washing the gypsum recovered in step (b) to minimize adhering impurities; g) contacting in a second reaction zone gypsum obtained in step (f) with liquor ammonia or recycled ammonium sulphate mother liquor obtained in step (i) and carbon dioxide obtained in step (k) to produce ammonium sulphate solution and by-product CaCO 3 by the Merseberg reaction; h) filtering out the CaCO 3 , from the products of step (g) followed by neutralizing the filtrate with sulphuric acid to convert residual ammonia into ammonium sulphate; i) evaporating the neutralized filtrate obtained in step (h) to recover ammonium sulphate while recycling the ammonium sulphate mother liquor in step (g); j) washing the CaCO 3 obtained in step (h) with water to minimize unreacted gypsum and adhering soluble impurities followed by calcinations to obtain CO 2 and quicklime of high purity; k) bottling the CO 2 , and recycling in step (g); l) slaking the lime generated in step (j) with decarbonated water and treating with CDL generated in step (d) and/or MgCl 2 -rich liquor obtained in step (c) to produce dispersion of Mg(OH) 2 and aqueous CaCl 2 ; m) adding a surface modifying agent to facilitate filtration of Mg(OH) 2 , while simultaneously obtaining surface-modified Mg(OH) 2 , required for special compounding applications; n) separating the surface-modified Mg(OH) 2 , from the slurry obtained in step (m) and recovering CaCl 2 -containing filtrate followed by recycling it for the desulphatation process of step (b); o) calcining the Mg(OH) 2 , obtained in step (n) to recover MgO of high purity which simultaneously burns off the surface modifier.