| 摘要 |
The process for producing calcium phosphate from phosphoric rocks with a low content of P2O5 and a high content of calcite consists in treating said rocks with a sufficient amount of nitric acid in order to transform insoluble calcium carbonate into soluble calcium nitrate, and insoluble calcium phosphates into soluble calcium phosphates such as phosphoric acid and mono calcium phosphate. The production process comprises a second step in which the reacted mass is filtered and the solution thus obtained is subsequently reacted with a lime slurry in order to transform soluble phosphates into insoluble di-calcium phosphates, having a side production of soluble calcium nitrate, said insoluble di-calcium phosphates are then separated by a filtrating and washing process. The calcium nitrate solution thus obtained is treated with 98% of sulphuric acid in order to transform the whole calcium nitrate into nitric acid and calcium sulphate crystals, which are separated from nitric acid by a filt rating and washing process. The nitric acid thus obtained is transferred to an area to be dried and marketed.
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