Recovery and purification of metallurgical silicon from waste silicon slag by blowing refining

Abstract

In this paper, metallurgical silicon (MG-Si) from waste silicon slag (WSS) is recycled by blowing refining, which is feasibility and urgent for full utilization of resources and sustainable the photovoltaic industry development. In the process of blowing refining, CaF2 additive was added to WSS to reduce the viscosity and increase the collision of liquid silicon particles, which had a significantly more positive effect on the separation of MG-Si. On this basis, the optimization of recovering and purifying MG-Si from WSS was investigated and the optimized experimental conditions were 20 wt% CaF2, 45min refining time at 1550 °C and 5min blowing time. The recovery rate and the purity of MG-Si from WSS were 65.58% and 99.28% with the optimum conditions. Besides, the contents of Al and Ca decreased from 1395 ppm to 851 ppm–703 ppm and 646 ppm, respectively. The mechanism indicates that MG-Si in WSS with the addition of CaF2 can be effectively separated and recovered by blowing refining. Blowing refining is a novel, simple and effective method of separation and purification, which enriches the system for recovering MG-Si from WSS as a new contribution and is expected to be widely used in a business-friendly and environmentally friendly manner.