| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing gypsum having the specific surface area of <=2,000 cm3/g to enable its industrial separation to be easy when calcium is precipitated/separated as gypsum in producing phosphoric acid by the wet decomposition of mineral phosphate with acid. SOLUTION: When performing the wet decomposition of mineral phosphate with acid and precipitating calcium as gypsum to be separated, this method is to add the salt and/or hydroxide of aluminum or to add it/them together with fluoride. The concentration of gypsum is adjusted to <=20 wt.% or gypsum having the specific surface area of <=2,000 cm3/g is added as seed gypsum. Since the method for producing wet-process phosphoric acid enables by-product gypsum to have the specific surface area of <=2,000 cm3/g necessary to make its industrial separation easy, the method is useful as the method for producing wet-process phosphoric acid.
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