METHOD FOR RECOVERING FLUORINE AND METHOD FOR PURIFYING CALCIUM FLUORIDE

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PROBLEM TO BE SOLVED : To provide a dry recovering method of fluorine, by which high-purity calcium fluoride can be obtained. SOLUTION : A reaction apparatus is constituted by packing in a reaction cylinder a fluorine-absorbing chemical consisting of the salt, hydroxide or oxide of an alkaline earth metal such as calcium or a mixture thereof. A gaseous mixture containing at least SiF4 gas and HF gas is circulated through the reaction apparatus so that the HF gas is reacted with the fluorine-absorbing chemical to recover fluorine as a fluoride of the alkaline earth metal. At that time, the concentration of the SiF4 gas in an outflow gas flowing out of the reaction cylinder is measured/monitored, the fact that the concentration of the SiF4 gas in the outflow gas reaches the predetermined concentration is detected, the supply of the gaseous mixture to the reaction cylinder is stopped, and the fluoried of the alkaline earth metal is withdrawn from the reaction cylinder to obtain the high-purity alkaline earth metal fluoride. COPYRIGHT : (C)2010, JPO&INPIT