| 摘要 |
PURPOSE:To obtain a refined sodium silicofluoride having high purity, with simple operation, by heating a mixture of crude sodium silicofluoride and water, separating insoluble component from the resultant slurry, and recrystallizing the objective salt by cooling the residual liquid. CONSTITUTION:Crude sodium silicofluoride containing gypsum and a phosphate and recovered from a wet process for production of phosphoric acid, is supplied to a dissolving tank 4 through the line 1, and at the same time, water is charged to the tank through the line 2. The mixture is stirred under heating at 40-100 deg.C. The obtained slurry is introduced into the separator 7, and the solid component is taken out from the line 6. The residual liquid is charged to the crystallization tank 9, and recrystallized by cooling at about 10-40 deg.C. The slurry containing precipitated sodium silicofluoride crystals is introduced into the separator, and the remaining liquid is discharged through the line 11. The crystal of sodium silicofluoride separated by the separator 12 is washed with water supplied from the line 14, and the residual liquid is recycled together with washing water to the dissolution tank 4 through the line 3. The washed refined sodium silicofluoride is taken out from the line 13.
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