METALLURGICAL RECYCLING OF SILICON KERF FROM WAFER SAWING SLURRY

摘要

Currently the solar grade silicon (SoG-Si) is dependent exclusively on the electronic grade silicon scrap generated in electronic industry. A rapid growth of photovoltaic (PV) industry causes a serious shortage in silicon feedstock, which cannot be fulfilled by the current structure of the silicon refining industry. At the same time about 70% of solar grade silicon is getting lost during ingot growing, wafer sawing, and solar cell manufacturing. Silicon recycling will play an important role in reducing the shortage of the silicon feedstock for PV industry. In the present paper, a potential approach on recycling of silicon wafer sawing slurry is explored. Various techniques were attempted including distillation, heavy liquid separation wet-chemical leaching and pyrometallurgical processing. After distillation, the polyethylene glycol can be separated and reused. By dissolving silicon from the kerf into a clean silicon metal or scrap, or into an alloying metal like Cu, SiC can also be separated and recovered. Depending on the impurity level, solar grade silicon can be finally produced from this waste stream in combination with any necessary refining treatment for the applications in the PV industry. It is expected that the present research can pave a way to develop a total recycling route for an optimum use of the resource during solar cell production, and further to minimize the environmental risk of the waste disposal.