Regular Article

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

State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, PR China

^* e-mail: ghzhang0914@ustb.edu.cn

Received: 8 December 2018
Accepted: 6 January 2019

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 (L_B) between slag and silicon are investigated. The results show that L_B 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.