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US 4,301,131 AGranted
Oxidation of phosphoric acid plus K compound addition
AssigneeW. R. Grace & Co.
InventorMoises G. Sanchez
Life of this patent
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Abstract
This invention is directed to an improvement in the Hill phosphoric acid process, whereby the Hill process can be used with high-iron phosphate rock. The improvement involves oxidation of divalent iron in an early stage of the Hill process, followed by addition of a soluble potassium compound to the acid in the crystallizer.
Claims11
In the process of preparing wet process phosphoric acid with low post-precipitation characteristics, said process comprising the steps:
- (a) providing a clarified phosphoric acid feed containing about 22-46% phosphoric acid as P.sub.2 O.sub.5 ;
- 1.3-1.5% Fe as Fe.sub.2 O.sub.3 ;
- at least 15% of the Fe being present as divalent Fe;
- (b) adding aluminum silicate to the clarified acid in an aluminum silicate addition zone;
- (c) concentrating the acid to a P.sub.2 O.sub.5 content of about 45-52%;
- (d) passing the concentrated acid to a crystallizing zone to provide a product stream and a stream containing most of the crystals produced in the crystallizing zone;
- (e) further concentrating the product stream to a P.sub.2 O.sub.5 content of about 57-63%;
- the improvement comprising adding an oxidant to the clarified acid provided in Step (a), to oxidize most of the divalent Fe to trivalent Fe;
- and adding a potassium compound to the crystallizing zone in an amount effective to precipitate (Fe,Al).sub.3 KH.sub.14 (PO.sub.4).sub.8.4H.sub.2 O.
6 more elements
Dependencies are inferred from the claim text.