Method of producing fluoride-free phosphoric acid
US4055626A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 15, 1976 |
| Grant date | Oct 25, 1977 |
| Priority date | — |
| Expiry date | Jun 15, 1996 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01B25/303
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
Substantially fluoride-free phosphoric acid is produced by the acidulation of phosphate rock with sulfuric acid wherein the acidulation reaction is conducted in the presence of added potassium as K.sub.2 O bearing compounds, e.g. KHSO.sub.4, K.sub.2 SO.sub.4, KH.sub.2 PO.sub.4 or KOH, and additional silica, to precipitate fluorides and silica as potassium silicofluoride and then removed on separation of the gypsum formed. Optionally, additional silica may be added to the phosphoric acid solution recovered after precipitation and removal of the gypsum, to precipitate additional fluoride as potassium silicofluoride to further purify the phosphoric acid. In a further embodiment sufficient potassium may be added along with additional silica in the acidulation step to produce potassium dihydrogen phosphate and phosphoric acid as additional products. The phosphoric acid and potassium dihydrogen phosphate are recovered substantially free from fluoride contamination and the reaction is carried out in the substantial absence of fluorine evolution into the atmosphere. Also disclosed is a process for conducting a conventional phosphoric acid facility to produce phosphoric acid and gypsum wher…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.