Recovery of cutting fluids used in polycrystalline silicon ingot slicing

Abstract

A recovery process for effective separation of silicon, silicon carbide micro powders and polyethylene glycol from the wire sawing slurry is proposed. The separation between silicon and silicon carbide is based on their size difference and surface charging state. The aim of this work is the study of the solid phase and liquid phase separation of silicon carbide and Silicon. Some methods applied for this purpose are the centrifugation process, phase-transfer separation as well as liquid–liquid extraction followed by the regeneration of polyethylene glycol by the distillation process. It is verified experimentally that silicon and silicon carbide micro powder can be effectively separated by phase transfer separation, centrifugation, chemical cleaning, filtering and distillation. In this study, the liquid–liquid extraction was used to separate a particle from a powder mixture. The removal of liquid component from a solution via a solvent separated considerably larger silicon carbide particles. The optimal results showed that Si content can reach 82% in the Si-rich powder and 3.8% wt% in the silicon carbide-rich powder. By separating the mixed powder the content reached 31.2wt% of silicon, 63.3wt% of silicon carbide as the raw material, 5.3wt% of the iron fragment, and 0.2wt% of other impurities.