| 摘要 |
Monocalcium phosphate, phosphoric acid and/or potassium phosphate containing fertilizers are produced in a process involving acidulation of phosphate rock with phosphoric acid in the presence of added silicon dioxide and potassium ion whereby fluorides contained in the rock are converted to K2SiF6 and monocalcium phosphate dissolved in phosphoric acid is formed during acidulation. In an important feature, the K2SiF6 is separated and hydrolyzed to regenerate the K2O from K2SiF6 recycled KH2PO4/H3PO4 solution for further reaction with fluoride from fresh phosphate rock feed. A portion of the MCP/H3PO4 solution and/or crystallized monocalcium phosphate can then be reacted with potassium sulphate, potassium bisulphate, or mixtures thereof to form KH2PO4, or KH2PO4/H3PO4, solutions, and gypsum. In a closely related embodiment, the remaining MCP/H3PO4 solution is reacted with sulphuric acid to produce phosphoric acid product and/or the recycle phosphoric acid required in the phosphate rock acidulation step. |
