PROCESS FOR PRODUCTION OF COMMERCIAL QUALITY POTASSIUM NITRATE FROM POLYHALITE

摘要

Patent No. 597791 Disclosed is a continuous method for producing KNO3 from polyhalite, said method comprising steps of: washing polyhalite; heating said washed polyhalite; contacting said washed and heated polyhalite with sufficient water to produce decomposition products comprising K2Ca(SO4)2, gypsum, and a solution comprising K+, Mg 2+, and SO4 2- ions; separating at least one solid product from said solution; contacting at least a portion of said at least one solid product separated from said solution with a quantity of HNO3 at least sufficient to produce a slurry; contacting said slurry with an alkaline Ca compound to precipitate sulfate as gypsum; filtering said contacted slurry to obtain a filtrate; washing gypsum obtained in the preceding steps; concentrating the filtrate obtained in said step of filtering the product of said step of contacting said slurry with an alkaline Ca compound; separating at least part of the CaSO4 contained in said filtrate from the liquid; separating KNO3 from the solution recovered in the previous step; adding an alkaline Ca compound to the solution recovered after said step of separating KNO3 from the solution recovered after said step of separating at least part of the CaSO4 contained in the filtrate; and separating at least part of the Mg(OH)2 produced in said step of adding an alkaline Ca compound to the solution recovered after said step of separating KNO3 from said solution; wherein said method produces KNO3 from raw polyhalite.