Properties evaluation of electric smelting furnace slag: Viscosity and sulfide capacity under different FeO content

Abstract

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO2-6wt.%MgO-10 wt%Al2O3-FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process.