Recycling Of Silicon And Silicon Carbide From Kerf Loss Slurry

For over10years the photovoltaic (PV) industry has sustained an average annual growth rate of over30%, with even higher growth rates in future years. The growth rate is around35%in2010, and will remain above20%by2015. Over90%of current dominant materials used in PV cells are silicon wafers. In the manufacturing of silicon wafer, only45%-50%o f the silicon feedstock ends up in a wafer, the remaining50%-55%lost in the wafer saw process and has not been effectivelty recovered so far. We should consider to recycle the lose slurry waste while increasing the production of the silicon. This paper mainly focuses on recycle of silicon and silicon carbide from the silicon slurry waste with different methods.HF acid etching sedimentation process was designed to recycle of silicon from cutting slurry waste in poly-silicon slicing process. The effects of HF acid concentration and HF processing time on the recovery rate and yield of silicon kerf loss slurry waste were systematically investigated. Also the effects of dispersion time of ultrasonic agitation prior to the HF acid etching sedimentation process were also studied. In considering the acceptable levels of both recovery rate and yield, a product with Si recovery rate of82wt%and the yield62%is obtained under the operating conditions by setting HF acid concentration at2%, HF processing time at24h and the agitation time at60min.In addition, a novel method to separate silicon and silicon carbide from kerf loss slurry by Al-Si alloying process has been reported in this paper. The kerf loss slurry was washed and dried, and then aluminum was added on the top of these dry powders with silicon and silicon carbide. The Al-Si alloying process was performed in argon atmosphere using a vacuum carbon tube furnace at1773K. In this way, an Al-Si ingot was obtained, on the surface of which a lot of hexagonal crystals were observed. The Al-Si ingot was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF) and electron probe micro-analyzer (EPMA). The XRD results indicated that the Al4C3phase was obtained on the top of the cast. The SEM, XRD and EPMA results revealed that the Al-Si alloy without silicon carbide phase formed in the ingot, which indicated that silicon and silicon carbide can be separated from slurry waste by this alloying process. It is indicated that through this method we can recycle the Si powder from slurry waste. Also it is noted that the powder we recovered from the slurry waste can be reused in the production of the silicon solar.