Dihydrate-hemihydrate process for producing phosphoric acid
AssigneePrayton Technologies
InventorsAntoine Hoxha, Dorina Fati
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Abstract
A method for producing phosphoric acid, comprising attack in an aqueous medium of phosphated rock with sulfuric acid, with formation of a first dihydrate slurry suspended in an aqueous phase having a free P2O5 content between 38 and 50% and a free SO3 content of less than 0.5%, conversion of this first slurry by heating with recrystallization of the solubilized calcium sulfate giving rise to a second hemihydrate slurry, and separation in the second slurry between a production phosphoric acid and a hemihydrate cake, characterized in that it comprises during the attack, addition of a fluorine source in the first slurry in a content from 1% to 5% by weight of F relatively to the P2O5 contained in the phosphated rock.
Claims10
A method for producing phosphoric acid, comprising
- attack in an aqueous medium of phosphated rock with sulfuric acid at a first temperature comprised between 70 and 90° C., with formation of a first slurry of calcium sulfate dihydrate crystals suspended in an acid aqueous phase, the acid aqueous phase of this slurry having a free P2O5 content comprised between 38 and 50% by weight and a free SO3 content from 0.05% to 0.4% by weight, an addition of a fluorine source in the first slurry in a content of 1% to 5% by weight of F relatively to the P2O5 contained in the phosphated rock taking place during the attack,
- conversion of this first slurry by heating to a temperature above 90° C., with solubilization of the calcium sulfate dihydrate crystals and recrystallization of the solubilized calcium sulfate giving rise to a second slurry formed with calcium sulfate hemihydrate crystals suspended in an aqueous phase based on phosphoric acid, and
- separation in said second slurry between a production phosphoric acid, having a P2O5 content from higher than 35% to 45% by weight and a free SO3 content of less than 2% and greater than 0.05% by weight, and a separation cake based on calcium sulfate hemihydrate.
Dependencies are inferred from the claim text.