Hemihydrate type process for phosphoric acid manufacture using a

Details Hemihydrate type process for phosphoric acid manufacture using a Hemihydrate type process for phosphoric acid manufacture using a

1978-01-04

1980-09-02

Carter, Herbert T.

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Alkaline earth metal

423319, 423320, 423266, C01B 2522, C01F 1146

Patent

active

042206308

ABSTRACT:
When sulfate ions and a solution of monocalcium phosphate are reacted under conditions which result in the formation of a slurry comprising calcium sulfate hemihydrate and phosphoric acid of about 35% to about 55% P.sub.2 O.sub.5, filtration is improved when a sulfonic acid, a sulfonic acid salt, tall oil fatty acid or alkoxylated or esterified tall oil fatty acid and mixtures thereof is present in the slurry (preferably at 1-1000 ppm). Preferably a two vessel reaction system is used in which the reaction slurry undergoes intra- and inter- vessel circulation (preferably through a draft tube). The solution portion of the slurry in the first vessel (the "dissolver") is preferably maintained at a negative sulfate concentration (i.e. excess Ca.sup.+2) and the solution in the second vessel (the "crystallizer") is preferably maintained at a positive sulfate ion concentration, most preferably at a reduced pressure, (e.g. to provide evaporative cooling). Better filtration rates can thus be obtained due to the lower viscosity of the slurry and/or favorable shape, dominant size and size distribution of the hemihydrate crystals.

REFERENCES:
patent: 3418077 (1968-12-01), Robinson
patent: 3522003 (1970-07-01), Lopker
patent: 3522004 (1970-07-01), Lopker
patent: 3653827 (1972-04-01), Hey et al.
Shack, "Phosphoric Acid, vol. 1," pp. 383-386, Marcel Dekker, N.Y. 1968.
Sikdar et al., "AICHE Journal," vol. 23, May 1977, pp. 380-382.

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