Oxidation Kinetics and Mechanism of Boron in Metallurgical-Grade Silicon Melt by CaO-SiO2 Slag Refining

Kinetic research on impurity removal from metallurgical-grade silicon is an important theoretical basis for silicon product upgrading and optimization. In this paper, the oxidation mechanism of boron removal from metallurgical-grade silicon by CaO-SiO2 slag at 1823 K was investigated by experimental measurements and ab initio molecular dynamics simulation calculation. By fitting the relationship between refining time and boron concentration in refined silicon, the apparent rate constant and the mass transfer coefficient of boron were obtained. The experimental results showed that there was no significant change in silicon loss rate with increasing refining time. Ab initio molecular dynamics simulation shows that there was an interaction between boron atom and three O atoms in the silicon melt, which results in the oxidation of boron in silicon to borate (BO33-). The particle trajectories in CaO-SiO2 molten slag were statistically analyzed by Materials Studio software, and it is calculated that the diffusion coefficient D-B of boron in CaO-SiO2 slag at 1823 K was found to be 1.29 x 10(-8) m(2).s(-1).