A process for obtaining phosphoric acid and calcium sulphate dihydrate from apatite

Abstract

The disclosure relates to a continuous process for obtaining phosphoric acid and calcium sulphate dihydrate from apatite, and sulphuric acid using hydrochloric acid as an intermediate attacking agent, comprising the steps: Leaching (101) apatite (11) with an aqueous solution of hydrochloric acid (12,13) to solubilize phosphorus compounds contained in the apatite, thereby obtaining a solution (15) containing phosphate (H3PO4) and calcium chloride (CaCI2); extracting (103) said solution (15) with organic solvent (16), yielding an organic extract (17) loaded with phosphate ions, and an aqueous raffinate (21) containing calcium chloride and residual impurities; re-extracting the phosphate ions from the organic extract (17) with water (18), thus yielding an aqueous extract (19) of phosphoric acid, and an unloaded organic phase substantially free of phosphoric acid, reacting (107) the raffinate (21) containing calcium chloride with sulphuric acid (26) to cause precipitation of calcium ions in the raffinate as calcium sulphate dihydrate and to recover chloride ions in the raffinate in the form of hydrochloric acid (12), filtering off (108) precipitated calcium sulphate dihydrate (27) from the previous step (107) and washing it with water, dividing (113) the remaining hydrochloric acid (12) aqueous solution into a primary stream (12a) and a secondary stream (12b); and recycling (112) the primary stream (12a) of the aqueous solution of hydrochloric acid (12) to the step (101) of the leaching apatite, and at least partially removing the secondary stream (12b) from the process.