Removal of boron from metallurgical grade silicon by CaO-SiO2 based slags

Abstract

Slag refining is one of the most effective methods to remove boron from metallurgical grade silicon (MG-Si). In this paper, the removal of boron from metallurgical grade silicon was proposed by adding CaF2, BaO or rare earth oxides (La2O3 and CeO2) to CaO-SiO2 based slags. The effects of the BaO content, the CaF2 content, the rare earth oxides content, the molar ratio of CaO to SiO2 and the mass ratio of slag to silicon on the partition coefficient of boron (LB) between slag and silicon are investigated. The results show that LB has a maximum value of 5.17 in 45% CaO-45% SiO2-10% BaO slags at 1550 °C after reacting for 6 h with a slag to silicon mass ratio of 2. Besides, it is found that the addition of La2O3 or CeO2 shows better de-boronization ability compared with the addition of BaO.