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US 4,452,770 AGranted
Phosphoanhydrite process
AssigneeUnited States Gypsum Company
InventorsJay W. Palmer, John C. Gaynor
Life of this patent
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Abstract
A wet process for producing phosphoric acid and phosphoanhydrite by acidulation of phosphate rock with a phosphoric acid/sulfuric acid mixture containing a very high recycle content of small sized anhydrite seed crystals. A strong phosphoric acid is obtained having a concentration of at least about 35% P.sub.2 O.sub.5. Further, the phosphoanhydrite may be readily converted to an industrially usable gypsum product.
Claims11
A process for producing phosphoric acid and calcium sulfate from phosphate rock which comprises:
- continuously feeding finely divided phosphate rock, sulfuric acid, phosphoric acid, water and anhydrite seed to a mixing zone and mixing them to form a slurry;
- the quantities charged to the mixing zone being such as to provide a slurry comprising about 20-50 weight % total solids, about 62-73 weight % total phosphoric acid and sulfuric acid content with about 1-4 weight % sulfuric acid, and about 10:1-100:1 by weight of anhydrite seed to phosphate rock, and mixing at a temperature between about 60.degree. and 110.degree. C.;
- continuously withdrawing a leach slurry from said mixing zone and passing it to a first filtering separation zone to separate calcium sulfate slurry and phosphoric acid;
- recovering a strong phosphoric acid from the first separation zone;
- and
- recovering a slurry of calcium sulfate anhydrite in phosphoric acid from the first separation zone and returning it to the mixing zone.
3 more elements
Dependencies are inferred from the claim text.