Remanufacturing of silicon powder waste cut by a diamond-wire saw through high temperature non-transfer arc assisted vacuum smelting

Non-transfer arc assisted vacuum smelting technology is presented for the first time to recycle harmful silicon powder waste derived from diamond-wire cutting. The final yield and filling rate of silicon could reach 93.9% and 73%, respectively. The oxidation characteristics of silicon powder waste, formation mechanism of a hollow silicon block and removal efficiency of impurities were analyzed in detail to offer profound insights into a non transfer arc granulation method. The critical conditions for continuous and efficient preparation of a solid silicon block were further confirmed through orthogonal experiments with 7.5 kW welder output power, 3 mm vertical scanning height, and 5 mm/s scanning speed. The yield of the silicon block was more than 96%. Meanwhile, the granulating process demonstrated a favorable effect on removing most impurities, such as C, Al, and Na, without introducing any other impurities. The residual impurities could be further removed by vacuum directional smelting. Given the extremely low equipment cost and huge room for improvement, this work is crucial for large-scale recovery of silicon powder waste.