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HF wastewater is generally treated by adding CaCl2 and produced a large amount of calcium fluoride sludge for further disposal. The purity of calcium fluoride sludge is low and has limited recycle value. In this study, fluidized bed crystallization technology is studied to produce high-purity calcium fluoride crystals for recycle. Both the addition of fluorite and silica sand as carriers are studied. The optimum operating conditions are the fluoride area loading of 1-3 kg F/m2 h and the molar ratio of calcium and fluoride of 0.9-1.1. The results showed that the crystal growth rate is faster for the fluorite carrier. Purity of calcium fluoride higher than 97.5％ can be achieved by using fluorite carrier with suitable operation period and final crystal growth size. The high-purity calcium fluoride crystals can be recycled as raw material for anhydrous hydrofluoric acid production.

Author：邱聖壹,李茂松,張王冠
★Article source：9th IWA-ASPIRE Conference ＆ Exhibhtion 2023