| 摘要 |
<p>A process for producing low-fluorine calcium phosphate granules comprises a special roasting process in which the granules are heated to a temperature sufficient to expand the granules and evolve volatile fluorine compounds. The product resulting from the process according to the invention has a higher proportion of phosphorus than the granules from which it is produced, mixes well with conventional feeds, and exhibits good biological availability. The product is also useful as insulation. Processes are also disclosed for reducing the fluorine content of the phosphoric acid used to make the granules. The fluorine content of phosphoric acid can be reduced by precipitating fluorine salts from already-produced phsophoric acid in the presence of hydrochloric acid or by digesting phosphate rock with recycled phosphoric acid and hydrochloric acid to produce low-fluorine phosphoric acid directly. In either embodiment, reactive silica is used. Low-cost reactive silica can be made from vitreous crystalline silica by using the roasting process, eliminating the need for costly diatomaceous silica.</p> |
