Recovery and purification of metallic silicon from waste silicon slag in electromagnetic induction furnace by slag refining method

The recovery of silicon from the waste industrial silicon slag is urgent for the cleaner production of silicon industry. The feasibility and optimization of recovering and purifying the metallic silicon from silicon slag are investigated by a united technology of combining electromagnetic separation and slag treatment. The physicochemical purification mechanism of silicon from slag was put forward. A calcium silicate slag reagent containing chlorine was added to the raw materials, which displays greatly role on separation and purification of metallic silicon. The optimized experimental conditions of melting time 60 min and heating power 15 kW were obtained. The recovery rate of silicon from waste silicon slag reaches about 96% and the removal rate of Al and Fe reaches 98.1% and 81.5%, respectively. The industrial tests on a scale of several thousand kilograms treatment capacity for silicon slag display that most impurities can be removed into slag phase and the output rate of silicon reaches over 81%.The united electromagnetic separation and slag treatment technology is expected to be used on a large scale in production. (C) 2019 Elsevier Ltd. All rights reserved.