Reduction and reconstruction of vanadium-containing steel slag at high temperature

Abstract

The effective recovery of metallic iron and vanadium from steel slag and ensuring the gelling properties of the residual slag after metal separation are crucial for their high-value-added utilisation. In this study, we established suitable process conditions for high-temperature reduction and reconstruction using the Si/Al ratio as an adjustment parameter and employing rice husk ash, SiO2, and Al2O3 as the adjustment materials. The influence of the reconstructed steel slag composition and structure on the iron reduction rate and vanadium migration was investigated. Additionally, we tested the compressive strength of the cement slurry at different times to compare the gelling performance of the tailings after iron reduction from the Vanadium-containing steel slag.The results showed that the high-temperature reduction method effectively reduced metallic iron and vanadium in the steel slag. The iron reduction rate reached as high as 98.53%, and inert components such as the CaO-FeO-MgO-MnO solid solution (RO) phase, C2F, and Fe3O4 in the original steel slag could be effectively reconstructed to form a glass-phase structure with certain gelling properties. Moreover, the content of the glass phase remained stable above 90%. For the same temperature, the liquid viscosity of the reconstructed steel slag increased, and after cooling, the glass-phase content decreased with decreasing Si/Al ratio. This resulted in an increase in the amount of crystalline-phase minerals such as Ca3Mg(SiO4)2, Ca2Al2SiO7, and C2S. The iron reduction rate generally exhibited a downward trend, and the change in the vanadium content was consistent with the iron reduction rate. Following the reduction and reconstruction of iron separation, the gelling properties of the vanadium-containing steel slag improved, with a 28-day strength that was 64.26% higher than that of the original steel slag.