Defluorination of phosphoric acid
AssigneeJ. R. Simplot Company
InventorKlaas J. Hutter
Life of this patent
Estimating the term…
Abstract
Fluorine in the form of fluoride is removed from phosphoric acid having an initial phosphate concentration of less than about 50 percent by determining the concentration of fluoride to be removed from the acid and the concentration of silicon in the acid. Silica is added to the acid in an amount sufficient that the molar ratio of fluoride to be removed from the acid to silicon in the acid is about 6. The acid is concentrated to a final phosphate concentration of greater than about 50 percent, whereupon fluoride is reacted to fluosilicic acid. By maintaining the indicated concentration ratio of fluoride to be removed and silicon, fouling of condenser and scrubber components with deposited silica is avoided.
Claims16
A method for producing defluorinated phosphoric acid, comprising the steps of:
- providing phosphoric acid;
- determining the concentration of fluoride to be removed from the acid and the concentration of silicon in the acid;
- adding silica to the acid in an amount sufficient that the molar ratio of fluoride to be removed from the acid to silicon in the acid is about 18/3;
- and
- removing fluorine from the phosphoric acid in a manner such that silicon tetrafluoride hydrolyzes and silica reacts with hydrogen fluoride.
A method for producing defluorinated phosphoric acid, comprising the steps of:
- providing phosphoric acid;
- determining the concentration of fluoride to be removed from the acid and the concentration of silicon in the acid;
- adding silica to the acid in an amount sufficient that the ratio of molar concentration of HF in the acid to molar concentration of SiF.sub.4 in the acid is about 2/1;
- and
- removing fluorine from the phosphoric acid in a manner such that silicon tetrafluoride hydrolyzes and silica reacts with hydrogen fluoride.
A method for producing defluorinated phosphoric acid, comprising the steps of:
- providing phosphoric acid having an initial phosphate concentration of less than about 50 percent and characterized by a fluorine reaction during concentration by heating according to a relation:
- 3 SiF.sub.4 (g)+6 HF(g)=3 H.sub.2 SiF.sub.6 ;
- determining the concentration of fluoride to be removed from the acid and the concentration of silicon in the acid;
- adding silica to the acid in an amount sufficient that the molar ratio of fluoride to be removed from the acid to silicon in the acid is about 18/3;
- and
- concentrating the acid by heating, to a final phosphate concentration of greater than about 50 percent.
Dependencies are inferred from the claim text.