| 摘要 |
<p>Crude phosphate is leached with nitric acid to produce an acid slurry, which is thereafter neutralized with ammonia in two successive stages while simultaneously cooling it and adding acid, part of the crude phosphate phosphorus being replaced with phosphoric acid added to the slurry to be neutralized, and in such a manner that at maximum 40 % of the phosphoric acid is fed to the first neutralization stage and the rest is fed to the second neutralization stage, whereby the acidity of the slurry is adjusted to pH 2.5 - 4.5 during the first and to pH 5.0 - 6.0 during the second neutralization stage.</p> |
