Boron Removal from Metallurgical-Grade Silicon by Slag Refining and Gas Blowing Techniques: Experiments and Simulations

To enhance the removal of B from metallurgical-grade Si (MG-Si) by the CaO-SiO₂-CaCl₂ slag refining technique, Ar gas was injected during the refining process. The effects of the refining time, Ar gas flow rate, and the blowing-pipe immersion depth on the removal of B from MG-Si were studied. The results show that the injection of Ar gas can effectively stir and then mix the Si and slag phases, resulting in an increase in the Si/slag contact area and in an acceleration of the mass transfer rate of B. With the combined slag-refining and Ar gas-blowing approach, the reaction time for the removal of B was reduced to 5 min from 75 min required with the slag-refining approach. Correspondingly, the content of B was reduced from 23.91 to 10.42 ppmw, with a removal efficiency of 56.42%. The results were confirmed by the coupled large-eddy simulation model and the volume of fluid multiphase flow model.