Research On Refining And Purifying Industrial Silicon With Flux And Slag And Recovering Silicon From Silicon Slag

It is difficult for a single refining method to deeply remove impurities in industrial silicon,and a large amount of industrial waste silicon slag can not be effectively processed.In this paper,flux-directional solidification,flux-slag-leaching combined refining methods are used to study the industrial silicon deep impurity removal,and electromagnetic stirring combined with slag refining technology is used to separate and purify metallic silicon from industrial silicon slag to determine the optimal process conditions.Studies have shown that adding 1 wt.%flux Mn to silicon can enrich the scattered Al,Ti,Fe and P impurities in silicon in the flux phase.And then directional solidification of the flux phase in the induction furnace,most of the impurities enriched in the flux migrate to the top of the sample.Through the flux-slag-leaching combined refining experiment research,Ca O-Si O₂-Ca Cl₂,Ca O-Si O₂-Al₂O₃,Ca O-Si O₂-Al F₆Na₃,and Ca O-Si O₂-Mn O₂ ternary slag series were used to refine the Al-Si?Sn-Si?Mn-Sii alloy.Then the refined sample was leached in two stages,all showed good results in removing impurities.Using Ca O-Si O₂-Ca Cl₂,Ca O-Si O₂-Mn O₂to refine 50 wt.%Mn-Si alloy.The removal efficiency of Fe can reach 99.7%,the removal efficiency of Ti can reach 95.5%,the removal efficiency of Ni can reach 96%,and the removal efficiency of B can reach86.4.%,P removal rate reached 85.3%.The study also found that boron in silicon can be oxidized into Ca₃B₂O₆ by Ca O-Si O₂ slag agent or form Ca B₂Si₂O₈ into the slag.During leaching,the soluble boron oxide exposed to the acidic solution dissolves into the liquid phase again,and a small amount of insoluble boron remains in the silicon.At the temperature of 1550°C,the silicon can be effectively separated from silicon slag after stirred for 2 hours by argon in a well resistance electric furnace.The silicon slag raw material which mixed with ternary slag agent of Ca O-Si O₂-Ca Cl₂ was smelted for 60 minutes in induction furnace at the power of 15 Kw.The results show that the silicon recovery rate reached 96%,and the impurities in silicon could be effectively removed.The content of Al was reduced from 9308.64 ppmw to 174.92ppmw,the removal efficiency reached 98.1%,the titanium content decreased from807.48 ppmw to 143.11,the removal efficiency reached 82.2%,the removal efficiency of boron and phosphorus reached 66.6%and 36.0%?...