ADVANCED FLUORITE REGENERATION TECHNOLOGY TO RECOVER SPENT FLUORIDE CHEMICALS DRAINED FROM SEMICONDUCTOR MANUFACTURING PROCESS

A regeneration technology of fluorite (CaF2) from spent HF and Buffere d HF (BHF) has been investigated. The mechanism of ''direct conversion '' of granular calcite (CaCO3) into granular fluorite has revealed and several special phenomena are first found to be efficient. An advance d system has been developed. This system regenerates granular fluorite by conversion of granular calcite filled in a column. High purity and low water fluorite is recovered as a substitute for natural fluorspar (CaF2). The fluorine concentration in the processed effluent is minim ized to a level of 5 ppm. The separation of the HF processing line and BHF processing line equipped ammonia stripper is an important to syst em design because ammonia generated from BHF significantly retards the conversion efficiency from CaCO3 to CaF2. The new system reforming th e conventional slaked lime processing solves long-pending problem, res ulting in a very compact system with a very small amount of product.