Production of purified strong wet-process phosphoric acid

Details Production of purified strong wet-process phosphoric acid Production of purified strong wet-process phosphoric acid

1983-01-17

1984-03-06

Heller, Gregory A.

Chemistry of inorganic compounds

Phosphorus or compound thereof

Oxygen containing

423319, 423320, 423472, C01B 2516

Patent

active

044353723

ABSTRACT:
The concentration of impurities in wet-process phosphoric acid limits the usefulness of the acid for the production of fertilizers, feedgrade phosphate and detergents. The aluminum, magnesium, and fluoride impurities are removed with the calcium sulfate hemihydrate filter cake by hydrolyzing and recycling the off-gas scrubber solutions in the presence of a ferric iron catalyst. The aluminum and magnesium are reduced to less than 0.1 percent in the acid product by the precipitation of (Ca,Mg)Al.sub.2 F.sub.8 .multidot.2H.sub.2 O, which is acid insoluble and suitable for storage with the byproduct calcium sulfate. Ferric iron also serves as a catalyst for the simultaneous precipitation of (Na,K).sub.2 SiF.sub.6. Subsequent additions of potassium as, for example, in the teachings of Gilbert (U.S. Pat. No. 3,338,675), can then be applied to obtain a purified phosphoric acid product suitable for most commercial applications.

REFERENCES:
patent: 3338675 (1967-08-01), Gilbert
patent: 3379501 (1968-04-01), Treitler et al.
patent: 3819810 (1974-06-01), Goldstein
patent: 4299804 (1981-11-01), Partis et al.
Lehr et al., "Precipitated Impurities in Wet-Process Phosphoric Acid," Agricultural and Food Chemistry, vol. 14, 1966, pp. 27-32.
Farr et al., "System CaO-P.sub.2 O.sub.5 -HF-H.sub.2 O: Equilibrium at 25.degree. and 50.degree.", Journal of Physical Chemistry, 66,318 (1962).
Progress Report of the Research Branch, Division of Chemical Development, TVA, Jan. 1982.
Frazier et al., "Chemical Behavior of Fluorine in Production of Wet-Process Phosphoric Acid," Environmental Science & Technology, 1977, pp.1007-1014.

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