N. Miki et al., ADVANCED FLUORITE REGENERATION TECHNOLOGY TO RECOVER SPENT FLUORIDE CHEMICALS DRAINED FROM SEMICONDUCTOR MANUFACTURING PROCESS, IEICE transactions on electronics, E79C(3), 1996, pp. 363-374
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.