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Separation and purification of silicon from cutting kerf-loss slurry waste by electromagnetic and slag treatment technology
- Li, Xin, Wu, Jijun, Xu, Min, Ma, Wenhui
- Journal of cleaner production 2019 v.211 pp. 695-703
- cutting, melting, mixing, raw materials, silica, silicon, slags, slurries, solidification, wastes
- The recovery of silicon from cutting kerf-loss slurry waste for the polycrystalline silicon production has been becoming a meaningful and urgent issue. In this paper, a united method of combining electromagnetic separation and slag treatment technology was used to separate and purify silicon from silicon kerf. The low melting compound of Na3AlF6 is added to the synthetic binary CaO-SiO2 slag, which can improve the separation effect of silicon from slag phase. The mechanism of physical separation and chemical purification of silicon from cutting kerf-loss slurry waste was investigated. The experimental results show that the electromagnetic stirring has an obvious effect for silicon separation in spite of no slag addition. The addition of CaO-SiO2 or CaO-SiO2-Na3AlF6 slag can further improve the separation rate of silicon. The purity of separated silicon is about 99.47% after the synthetic CaO-SiO2-Na3AlF6 slag treatment and reaches 99.98% followed by a vacuum directional solidification treatment. The recovered silicon from cutting kerf-loss slurry waste by this method can meet the purity requirement to the raw materials for silicon ingot casting.