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US 4,364,912 AGranted
Post precipitation control of low-iron phosphoric acid, without perlite
AssigneeW. R. Grace & Co.
InventorRichard N. Hill
Life of this patent
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Abstract
The Hill process for control of post-precipitation in wet process phosphoric acid can be made to work on low-iron phosphate rock, without the need of added perlite or other aluminum silicate.
Claims6
The method of preparing a solids-containing wet process phosphoric acid having a P.sub.2 O.sub.5 concentration of 56-62 weight % wherein said solids remain substantially suspended, and are soft, free-flowing, and non-caking;
- said acid prepared in the absence of perlite and consisting essentially of the following steps:
- (a) preparing a crude dilute acid in a wet process reaction train, said acid having a P.sub.2 O.sub.5 content of 22-45 weight percent and having an Fe.sub.2 O.sub.3 /P.sub.2 O.sub.5t weight ratio not in excess of 0.03;
- (b) removing a suspended solids from the said acid in a clarification zone to provide a clarified acid having less than 2% by volume of suspended solids and a sludge-containing residue;
- (c) evaporating the clarified acid to a P.sub.2 O.sub.5 content of 46-52%;
- (d) charging the evaporated acid to a crystallizing-settling zone to permit settling sludge from the acid, and settling for at least 8 hours;
- (e) passing substantially sludge-free acid from the crystallizing-settling zone to an evaporating zone, and evaporating said acid to a P.sub.2 O.sub.5 content of 56-62%, said acid characterized in that ammoniation is possible without substantial foaming.
3 more elements
Dependencies are inferred from the claim text.