Production of monobasic potassium phosphate with low chloride content from potassium chloride and phosphoric acid produced from the commercial wet process
AssigneePhosphate Engineering & Construction Co., Inc.
InventorsWilliam R. Erickson, Donald B. Stain, James D. Wilson
Life of this patent
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Abstract
Relatively pure monopotassium phosphate is produced from wet process phosphoric acid in a process wherein the phosphoric acid is mixed with potassium chloride and recycled components from downstream product and by-product recovery steps and heated to permit hydrogen and chloride to evolve from the melt as gases and wherein the melt is subsequently treated so as to remove impurities so that the monopotassium phosphate may be recovered as a relatively pure crystalline product with low chloride content.
Claims19
A process of producing monopotassium phosphate having a low chloride content from potassium chloride and wet process phosphoric acid comprising the steps of:
- a. Combining 52-54% phosphoric acid with potassium chloride in a reactor to form a mixture;
- b. Supplying heat to the mixture so as to drive off HCl and form a slurry including insoluble metallic impurity compounds, monopotassium phosphate, unreacted potassium chloride and unreacted phosphoric acid;
- c. Dissolving the slurry in a dissolution tank;
- d. Separating the insoluble metallic impurity compounds from the slurry and recovering a pregnant mother liquor containing monopotassium phosphates, unreacted potassium chlorides and unreacted phosphoric acid;
- e. Precipitating the monopotassium phosphate from the pregnant mother liquor to form a barren mother liquor and recovering the monopotassium phosphate.
A process of producing monopotassium phosphate having a low chloride content from potassium chloride and 52-54% wet process phosphoric acid comprising the steps of:
- a. Combining the phosphoric acid with potassium chloride in a reactor to form a mixture;
- b. Continuously mixing and supplying heat to the mixture within the reactor so as to drive off HCl and form a slurry including insoluble metal impurity compounds, monopotassium phosphate, potassium sulfate, unreacted potassium chloride and unreacted sulfuric acid;
- c. Dissolving the slurry in a dissolution tank wherein water is added to bring the solution to a point relatively near saturation relative to monopotassium phosphate;
- d. Separating the insoluble metallic impurity compounds from the solution and recovering the insoluble impurities and forming a pregnant mother liquor containing monopotassium phosphates, potassium sulfates, unreacted potassium chlorides and unreacted phosphoric acid;
- e. Introducing the pregnant mother liquor into a first cooler crystallizer and reducing the temperature of the mother liquor to a temperature which will precipitate monopotassium phosphate without precipitating the potassium sulfates in the mother liquor;
- f. Separating the monopotassium phosphate from the mother liquor;
- g. Subsequently introducing the mother liquor into a second cooler crystallizer and reducing the temperature of the mother liquor slurry to a temperature at which potassium sulfates are precipitated;
- h. Separating the potassium sulfates from the mother liquor to form a barren mother liquor;
- and
- i. Recycling at least a portion of the barren mother liquor to the dissolution tank.
A method of producing monopotassium phosphate having low chloride content from potassium chloride and commercial wet process phosphoric acid having impurity elements contained therein comprising the steps of mixing the wet phosphoric acid with the potassium chloride in a reaction vessel, heating the mixture so as to form a slurry and elevating the temperatures to approximately 265.degree. C. to drive off HCl gases and form insoluble compounds from the elements contained in the wet process phosphoric acid, dissolving the slurry and separating out the insoluble compounds from the slurry to form by-products and a pregnant mother liquor, and subsequently treating the pregnant mother liquor in order to precipitate out and remove substantially pure monopotassium phosphate and thereby creating a barren mother liquor.
Dependencies are inferred from the claim text.