Gypsum transformation in hemihydrate-dihydrate wet process phosphoric acid production
In order to further optimize the hemihydrate-dihydrate WPA production process,improve the yield of phosphorus,the main influencing factors of SO3 and P2O5 concentration in the process of hemihydrate gypsum crystal transformation to prepare dihydrate gypsum are studied experimentally.The experimental results show that hemihydrate gypsum can quickly transform into dihydrate gypsum at a liquid phase SO3 concentration of 3%-6%and P2O5 concentration of 3%-6%.The transformation time is 20-30 minutes,and the actual production control time is 120-150 minutes.During the transformation process,the soluble P2O5,insoluble P2O5,and total P2O5 in hemihydrate gypsum are significantly reduced,improving the yield of P2O5 to 97.5%.During the crystal transformation process,Fe2O3 remains in the gypsum,Al2O3,MgO and F enter the phosphoric acid,which may bring impurity enrichment and affect the stable operation of the plant.
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