Process for producing HF from impure phosphoric acids

Details Process for producing HF from impure phosphoric acids Process for producing HF from impure phosphoric acids

1982-05-17

1985-03-19

Heller, Gregory A.

Chemistry of inorganic compounds

Halogen or compound thereof

Hydrogen halide

423319, 423320, 423321R, 423483, C01B 719, C01B 2516

Patent

active

045058849

ABSTRACT:
Substantially calcium-free fluoroaluminum phosphate precipitate (which also contains iron) can be produced by the aging of wet process phosphoric acid containing iron, fluorine and aluminum, preferably phosphoric acid analyzing in the range of about 15%-45 weight percent P.sub.2 O.sub.5, 2-4% Al.sub.2 O.sub.3 and 1-2% fluorine. One process involves digestion of phosphate ore matrix in recycled phosphoric acid, filtration to remove the insoluble residue, precipitation and filtration to remove gypsum, and aging of the product acid to precipitate the aluminum impurity as a fluoroaluminum phosphate compound. The fluoroaluminum phosphate can be decomposed (as by heating at about 195.degree. C.) to produce HF and aluminum phosphate.

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