Polyhalite IMI process for KNO₃production

摘要

A process for producing KNO3 from polyhalite to is disclosed. In a preferred embodiment, the process comprises steps of (a) contacting polyhalite with HNO3; (b) adding Ca(OH)2 to the solution, thereby precipitating as CaSO4 at least part of the sulfate present in said solution; (c) precipitating as Mg(OH)2 at least part of the Mg2+ remaining in said solution by further addition of Ca(OH)2 to the remaining solution; (d) concentrating the solution, thereby precipitating as a sulfate compound at least part of the sulfate remaining in solution; (e) separating at least part of the NaCl from the solution remaining; and (f) crystallizing as solid KNO3 at least part of the K+ and NO3-contained in the solution. The process enables direct conversion of polyhalite to KNO3 of purity exceeding 98.5% and that is essentially free of magnesium and sulfate impurities.

主权项

1. A process for producing solid KNO3 of at least 98.5% purity from polyhalite, said polyhalite containing NaCl as an impurity, wherein said process comprises:
contacting polyhalite with a substance comprising NO3−; adding at least one inorganic base to the solution obtained in the step of contacting polyhalite with a substance comprising NO3−, thereby precipitating as a solid at least part of the sulfate present in said solution; precipitating as Mg(OH)2 at least part of the Mg2+ remaining in said solution by adding at least one basic compound to the remaining solution; concentrating a solution obtained after said step of precipitating at least part of the Mg2+ remaining in said solution; precipitating at least part of said NaCl from the solution obtained after said concentrating; separating solid NaCl obtained in said step of precipitating at least part of said NaCl; separating as a quantity of solid KNO3 at least part of K+ and NO3− contained in the solution remaining after the step of precipitating at least part of said NaCl; and, recycling into the reaction vessel at least part of the solution remaining after said separating as a quantity of solid KNO3 at least part of said K+ and NO3−.