Formation of slag in Si and FeSi production from SiO2 materials, limestone, and iron oxide

In the current work, slag formation by dissolution of limestone and iron oxide in quartz/ cristobalite/ condensate were investigated. SiO2-CaO and SiO2-FeO binary slags achieve equilibrium from 1400 to 1700 °C with extra SiO2, and the composition does not seem to change with location. Formed slag does not seem to hinder further reaction. A larger interface area enhances dissolution. The minor elements accumulate on quartz grain boundaries before the slag formation. Quartz type or SiO2 phases does not seem to influence the slag formation. The condensate reacting with limestone forms SiO2-CaO slag with roughly 10% lower SiO2 than quartz or cristobalite. SiO2- FeO-CaO ternary slags formed in the current work were solid at 1300 to 1600 °C. SiO2-CaO and SiO2-FeO binary slags wet very good SiO2 materials. The coalescence happens before the softening of raw materials. The viscosity of the SiO2-CaO and SiO2-FeO binary slags is in the range of 0.2 -144 Poise.