Dissolution behavior of silica in molten CaO–SiO₂–Fe₂O₃–MgO–MnO slag

Abstract

The modification of basic oxygen furnace (BOF) slag by adding silica can improve the properties of BOF slag for applications in the cement industry. The rapid dissolution of silica is essential to hot slag modification. In this work, the dissolution behavior of silica in the molten CaO–SiO2–Fe2O3–MgO–MnO system as synthetic BOF slag was investigated by using the traditional rotating cylinder technique. Effects of rotation speed, temperature, immersion time, and slag basicity on the silica dissolution were studied. Scanning electron microscopy equipped with energy dispersive spectrometer (SEM‐EDS) and FactSage simulations were employed to reveal the dissolution mechanism. It was found that the dissolution of the silica rod was affected by both the thermodynamic driving force and the slag viscosity. The silica dissolution rate in molten CaO–SiO2–Fe2O3–MgO–MnO slag increased with increasing the rotation speed and temperature, but first increased and then decreased when decreasing the slag basicity from 2.5 to 1.5. A linear correlation between the logarithm of the dissolution rate and the logarithm of cylinder periphery velocity with a slope of 0.44 was observed, indicating the mass transfer within the boundary layer as the dissolution rate determining step. A direct dissolution way was found during the dissolution of silica in molten CaO–SiO2–Fe2O3–MgO–MnO slag.

Insight into Interaction Behavior of CeAlO3 Substrate and CaO‐Al2O3‐Based Slag

“…Due to the diffusion coefficient of Ce 3þ being higher than that of [AlO 4 ] 5À , a concentration boundary layer of Ce 3þ is formed at the interface along the direction from CeAlO 3 to the bulk slag. CeAlO 3ðsolidÞ þð4xÀ3ÞO 2À ¼ Ce 3þ þxAlO 4 5À þð1 À xÞ Al 3þ (5) where x represents the fraction of [AlO 4 ] 5À ions, Al 3þ represents Al in five or six coordination.…”

“…The dissolution of inclusions in the slag includes direct and indirect dissolution, which depended on the slag composition. Lin et al [ 5 ] investigated the effect of slag basicity on SiO 2 dissolution in the CaO‐SiO 2 ‐Fe 2 O 3 ‐MgO‐MnO system. The dissolution rate of silica first increased and then decreased when the slag basicity decreased from 2.5 to 1.5.…”