A method for producing phosphoric acid of the dihydrate / Hemihydrate type

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 hemihydfate 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.