| 摘要 |
PURPOSE:To enable high-yield production of phosphoric acid of high concentration using low-cost apparatus through simplified decomposition process, by feeding a mixed acid in which sulfuric acid is adjusted to a specifically low concentration, and decomposing the phosphate rock with the mixed acid at a specific temperature in an excessive concentration of sulfuric acid. CONSTITUTION:Phosphate rock 1 is fed to the single tank for decomposition 3. Further, the circulating acid which is composed of most of washing filtrate from semi-hydrate filter 7 and a part of the product, phosphoric acid of high concentration, from seal tank 3 is mixed with sulfuric acid 2 in dilution mixer 18 to adjust the concentration of sulfuric acid to 60wt.% and the mixed acid is fed into the decomposition tank 3. The phosphate rock is decomposed at 70-85 deg.C in 0.5-1.5wt.% sulfuric acid excessive concentration. Thus, a slurry which is composed of phosphoric acid of high concentration and semi-hydrated plaster is obtained. The slurry is filtered with semi-hydrate filter 7, the phosphoric acid of high concentration is sent to the seal tank 11 and a part of it is used to prepare the circulating acid. In the meantime, semi-hydrate plaster is rinsed with rinsing solution 8, taken out of line 9, while the rinsing filtrate is sent through the seal tank 15 and used to prepare the circulating acid.
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