POLYHALITE IMI PROCESS FOR KNO3 PRODUCTION

摘要

Patent No. 597787 Disclosed is a process for producing solid KNO3 of at least 98.5% purity from polyhalite, 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 the solution obtained after said step of precipitating at least part of the Mg2+ remaining in said solution; precipitating at least part of the NaCl derived from said polyhalite, if any, from the solution obtained after the previous step; separating said precipitated NaCl, if any, from the reaction stream; separating as solid KNO3 at least part of the K+ and NO3- contained in the solution remaining after the step of precipitating at least part of the NaCl derived from said polyhalite; and recycling into the reaction vessel at least part of the solution remaining after said step of separating solid KNO3.