| Summary: | 博士 === 國立臺灣大學 === 化學工程學研究所 === 105 === The circulatory economy has been paid much attention for the sustainable society. However, two major wastes, kerf-loss silicon and used broken quartz crucibles, are produced from the PV industry. This waste not only causes the environmental burden, but also increases the cost for silicon wafers.
Two different kerf-loss slurries (SiC and diamond-wire slicing) were obtained from our company partners. Contineous sedimental, and acid washing and sedimental method were used for silicon recycle. The suitable processes for scaling up were proposed. The metal impurities, B and P were also measured and reported here.
Although Si could be enriched easily to 85 wt.% from the waste, it was extremely difficult to further increase the purity of over 99 wt.% due to tiny SiC particles and metallic debris. We proposed a novel rapid thermal process, which was about one hundred times faster than the previous high-temperature treatment, to agglomerate Si in a couple minutes from the pretreated solid powder. With proper conditions, SiC particles and metals could be easily segregated to the surface of Si agglomerates. The high purity Si could be obtained by surface etching, and the best recycle yield was over 70 wt.%. The factors, such as temperature, holding time, and the surface oxidation of Si, were further discussed.
Finally, we aim to develop feasible processes to recycle the kerf-loss silicon and use it for making high purity Si3N4 crucibles used for multi-crystalline silicon (mc-Si) ingot growth. More importantly, the crucible could be reused for a couple times. In principle, the crucible should be purer than the current quartz crucibles used in industry. Moreover, the impurities decrease after ingot growth.
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