The composition and size distribution of cutting waste were characterized. The Si-rich powders were obtained from the cutting waste using a physical sedimentation process, and then further purified by removing impurity using acid leaching. The effects of process parameters such as acid leaching time, temperature and the ratio of solid to liquid on the purification efficiency were investigated, and the parameters were optimized. Afterwards, the high-purity Si ingot was obtained by melting the Si-rich powders in vacuum furnace. Finally, the high purity Si with 99.96%Si, 1.1×10^-6 boron （B）, and 4.0×10^-6 phosphorus （P） were obtained. The results indicate that it is feasible to extract high-purity Si, and further produce SoG-Si from the cutting slurry waste.
The rapid development of photovoltaic （PV） industries has led to a shortage of silicon feedstock. However, more than 40% silicon goes into slurry wastes due to the kerf loss in the wafer slicing process. To effectively recycle polycrystalline silicon from the kerf loss slurry, an innovative double-layer organic solvent sedimentation process was presented in the paper. The sedimentation velocities of Si and SiC particles in some organic solvents were investigated. Considering the polarity, viscosity, and density of solvents, the chloroepoxy propane and carbon tetrachloride were selected to separate Si and SiC particles. It is found that Si and SiC particles in the slurry waste can be successfully separated by the double-layer organic solvent sedimentation method, which can greatly reduce the sedimentation time and improve the purity of obtained Si-rich and SiC-rich powders. The obtained Si-rich powders consist of 95.04% Si, and the cast Si ingot has 99.06% Si.
Peng-fei XingJing GuoYan-xin ZhuangFeng LiGan-feng Tu
The removal of phosphorus in metallurgical grade silicon （MG-Si） by water vapor carried with high purity argon was examined. The effect of the nozzle types, refining time, refining temperature, refining gas temperature and refining gas flow rate on the phosphorus removed was investigated by the self-designed gas blowing device. The optimal refining conditions are nozzle type of holes at bottom and side, refining time of 3 h, refining temperature of 1793 K, refining gas temperature of 373 K, refining gas flow rate of 2 L/min. Under these optimal conditions, the phosphorus content in MG-Si is reduced from 94×10^-6 initially to 11×10-6 （mass fraction）, which indicates that gas blowing refining is very effective to remove phosphorus in MG-Si.
