Method for removing iron in the manufacture of phosphoric acid
AssigneeJacobs Engineering Group Inc.
InventorsStephen W. Hilakos, Frank S. Hicks
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Abstract
In the manufacture of phosphoric acid from ore, the typical ore comprises minerals containing phosphorus and calcium along with varied amounts of other elements. Certain ores have substantial iron content which needs to be removed in order to produce quality phosphoric acid product. An improved method and associated chemical processing plant are disclosed for removing this iron. The method involves both reducing and adding oxalic acid to wet process phosphoric acid produced using an otherwise conventional manufacturing process. Iron oxalate precipitate is created which can then conveniently be separated therefrom.
Claims18
A method for manufacturing phosphoric acid from ore comprising phosphorus, calcium, and iron, the method comprising the following steps:
- a) preparing an aqueous mixture comprising the ore;
- b) adding sulfuric acid to the aqueous mixture thereby digesting the phosphorus, calcium, and iron and producing a solution comprising phosphoric acid and dissolved iron, and a precipitate comprising calcium sulfate;
- c) separating the precipitated calcium sulfate from the phosphoric acid and dissolved iron solution;
- d) reducing at least a portion of the phosphoric acid and dissolved iron solution wherein the reducing lowers the EMF of the solution relative to the standard hydrogen electrode to less than about 450 mV;
- e) adding oxalic acid to the portion of the phosphoric acid and dissolved iron solution;
- whereby iron oxalate precipitate and phosphoric acid solution is produced by the combination of steps d) and e);
- and
- f) separating the precipitated iron oxalate from the phosphoric acid solution.
Dependencies are inferred from the claim text.