Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group iiia metal or beryllium
Patent
1975-08-29
1977-04-05
Carter, Herbert T.
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group iiia metal or beryllium
423131, 423158, 423183, 423184, 423317, 423321R, 423127, C01F 706, C01B 2518, C01F 714
Patent
active
040162389
ABSTRACT:
A process for the obtention of alumina and phosphate values by the alkaline decomposition of silica-containing aluminum phosphate ores comprises reducing the ore to a particle size of from about 6 to 13 mm; calcining the ore at a temperature of from 500.degree. to 750.degree. C in order to remove water of crystallization and combined water; grinding the calcined ore to a particle size of from 20 to 60 mesh (U. S. Sieve); treating the calcined and ground ore with an aqueous solution having a concentration of from 20 to 30% by weight caustic alkali at an initial temperature of from 65.degree. to 75.degree. C; quickly filtering the hot suspension thus obtained to remove the solid silica and heavy metal oxides; adding a 50% caustic alkali solution to the filtrate in an amount sufficient to obtain a total concentration of from 10 to 15% by weight of free caustic alkali; cooling the alkaline liquor accompanied by an elutriation action in an elutriator to a temperature of from 5.degree. to 10.degree. C in order to remove the crystallized tribasic alkali phosphate in the form of hydrated crystals which are recovered from the bottom of the elutriator; recovering the supernatant liquor from the top of the elutriator; heating said liquor to a temperature of 75.degree.-85.degree. C to obtain an alkali aluminate solution; and converting said alkali aluminate solution into hydrated alumina [Al(OH).sub.3 ] and then into alumina (Al.sub.2 O.sub.3) by known means. The alkaline liquors obtained therefrom are recycled to the alkaline decomposition step after concentration thereof.
The process can be rendered cyclic by converting the tribasic alkali phosphate into phosphoric acid by dissolving the phosphate in water, treating with CaO to form tricalcium phosphate and regenerate the caustic alkali, which is concentrated and recycled to the alkaline decomposition step, recovering the tricalcium phosphate, and reacting the same with sulfuric acid to obtain gypsum and phosphoric acid. The gypsum is reacted with carbon to produce lime and SO.sub.2 by known means for use in the process and the SO.sub.2 released is converted into sulfuric acid to use in the process.
REFERENCES:
patent: 1845876 (1932-02-01), Huber
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