Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Patent
1975-12-24
1977-06-14
Carter, Herbert T.
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
423167, 423319, 423311, 423555, C01B 2522
Patent
active
040297438
ABSTRACT:
A process is described for producing high purity phosphoric acid from phosphate rock including low grade phosphate rock material such as Idaho phosphate ores having P.sub.2 O.sub.5 contents as low as 20 percent. Finely divided phosphate rock, sulfuric acid, phosphoric acid and water are charged to a mixing zone in proportions such that the pH of the resultant slurry is in the range 0.8 to 1.2 and the calcium ion content of the liquid phase of the slurry is in the range 3 to 4 percent by weight. Sulfuric acid is charged to the mixing zone in a quantity sufficient to convert the nonphosphate calcium compounds in the rock to calcium sulfate plus the quantity required to convert the contained calcium phosphate to monocalcium phosphate, phosphoric acidis charged to the mixing zone in quantities such that it is, on a molar basis, from about 1.2 to about 1.4 times the P.sub.2 O.sub.5 content of the phosphate rock and water is charged to the mixing zone in amount equal to from about 80 to about 90 percent by weight of the phosphate rock charged. The slurry formed in the mixing zone is removed and filtered to separate the calcium sulfate filter cake and a filtrate comprising monocalcium phosphate. In a second mixing zone, the filtrate is mixed with a quantity of sulfuric acid stoichio-metrically sufficient to convert the monocalcium phosphate contained in the filtrate to phosphoric acid and calcium sulfate. The slurry from the second mixing zone is passed into a settling zone. A portion of the contained phosphoric acid is removed as a product from the upper part of the settling zone and a slurry of calcium sulfate and phosphoric acid is returned to the first mixing zone. The returned slurry has a phosphoric acid content sufficient to supply the required quantity of phosphoric acid to the first mixing zone.
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Carter Herbert T.
Wheelock Eugene T.
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