Preparation of Low-Boron Silicon from Diamond Wire Sawing Waste by Pressure-Less Sintering and CaO–SiO<sub>2</sub> Slag Treatment
Yaohao Zhang, Sheng Wang, Liuqing Huang, Sa Zhang, Guangyu Chen, Chentong Zhang, Huaxian Cai, Jinshui Meng, Xuetao Luo
Abstract
In order to recover silicon from diamond wire sawing waste, silicon extraction and boron removal are two key issues that need to be addressed. In this study, a combined process of pressure-less sintering and CaO–SiO2 slag treatment was proposed. Low -boron silicon was prepared and considered as raw materials in solar cell production. The results confirmed that pressure-less sintering was beneficial for the digestion of the silicon oxide layer, and the molar percentage of oxygen in silicon kerf was reduced from 14.83 to 7.24% after pressure-less sintering at 1400 °C for 2 h. The effect of slag composition on boron removal was investigated. It was found that an optimum boron removal efficiency of 86.91% was obtained when the optical basicity reached 0.68 and no CaF2 was added; the CaO–SiO2 mass ratio was 1.2, the holding time was 40 min, and the slag to silicon mass ratio was 1. Although the addition of CaF2 can decrease the viscosity, it affects the activity and the oxygen potential of slag.