Method of producing alkali metal phosphate
AssigneeKemira Oy
InventorsStig-Goran A. Weckman, Robert Perander, Sakari Riihmaki
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Abstract
The invention relates to a method for producing alkali metal phosphate, in particular monopotassium phosphate or its aqueous solution, by reacting fertilizer-grade phosphoric acid with alkali metal chloride at 350.degree. . . . 700.degree. C. to produce alkali metal metaphosphate, hydrolyzing thus obtained solid reaction product, removing the insoluble residue containing impurities from the hydrolysis solution in order to achieve a pure solution of alkali metal phosphate, and if further desired, crystallizing and separating the alkali metal phosphate from said aqueous solution.
Claims15
A method for producing an aqueous solution of an alkali metal phosphate or a water soluble alkali metal phosphate comprising the steps of:
- reacting a phosphoric acid component with an alkali metal chloride in a molar ratio of phosphorus to alkali metal in the range of 1:1 to 1.3:1 and at a temperature ranging from 350.degree. C. to 700.degree. C., the reaction time ranging from 15 to 120 minutes, to produce an alkali metal metaphosphate and hydrogen chloride, said phosphoric acid component comprising fertilizer-grade phosphoric acid;
- removing said hydrogen chloride liberated during said reacting step to produce a solid reaction product comprising said alkali metal metaphosphate;
- selectively hydrolyzing said solid reaction product at a temperature ranging from 60.degree. C. to 100.degree. C. to produce an aqueous hydrolyzing solution of said alkali metal phosphate and an insoluble residue containing impurities;
- and
- separating said insoluble residue from said hydrolyzing solution to produce a pure aqueous solution of said alkali metal phosphate;
- and optionally crystallizing and recovering said alkali metal phosphate from said pure aqueous solution.
Dependencies are inferred from the claim text.