Improving the quality of silicon metal by the method of x-ray radiometric separation of raw material and finished products

In this research, we investigate the process of X-ray radiometric separation of both raw materials (quartz, carbonaceous reducing agent) used for silicon smelting in ore-smelting furnaces and the resulting smelting products. The research objects were quartz from the Aktas field (Kazakhstan), coal from the Shubarkol field and silicon metal of various grades smelted at the Tau-Ken Temir LLP (Karaganda, Kazakhstan). X-ray diffraction analysis was performed using a Philips powder diffractometer. To determine the SiO₂ and Fe₂O₃ content, an ARL PERFORM’X X-ray fluorescence spectrometer was used. To remove impurities, a СРF1-150М single-strand radiometric separator was used. We found that the radiometric separation of original quartz samples with the Fe₂O₃ content of ~ 0.1–0.15% produces pure quartz with the Fe₂O₃ content of ≤ 0.05% and a yield of 65–70%. Provided that the Fe₂O₃ content in the original quartz sample does not exceed 0.5%, concentrates with the Fe₂O₃ content of 0.05% and a yield of 35–55% can be obtained. The yield of pure quartz with the Fe₂O₃ content of 0.01% does not exceed 15–20%. The use of radiometric separation is established to reduce the amount of phosphorus in the final product by 2–3 times. This method is effective for obtaining coal concentrates of varying ash content (2.0, 4.1 and 7.3%); the resulting concentrated product obtained with a yield of 25% contains 1.5% of ash. Separation of silicon metal (with the initial iron content of 1.2–1.5%) yields a product matching silicon grade 773 (product yield ~ 50%), 553 (~ 35%) or 441 (20%). It is concluded that radiometric separation allows the content of impurities in quartz, silicon metal and coal ash to be reduced, thus facilitating the production of higher-grade silicon.

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