Inclusions Removal in Industrial Silicon by SiO2-CaO-Al2O3 Based Slag System

The existence of inclusions in industrial silicon seriously affects the conversion efficiency of organic silicon monomer synthesis, making it difficult to meet the requirements of polycrystalline silicon production for raw materials. In this work, the basic slag system SiO2-CaO-Al2O3 was used to remove inclusions in industrial silicon. The microstructure and chemical composition of metal inclusions formed by the main metal impurities in industrial silicon were considered, and the physical and chemical behavior and evolution process of inclusions in industrial silicon before and after refining were analyzed. The effect of the CaO/SiO2 ratio on the removal of inclusions was examined. It was found that when CaO/SiO2 = 0.38, the removal effect of metal inclusions in industrial silicon was the best; the removal rates of Fe, Al, Ca, and Ti reached 27.1%, 68.7%, 25.1% and 99.1%, respectively. This study provides an idea for industrial silicon refining technology and high-quality industrial silicon product development.