Nature of MgO and Al₂O₃ Dissolution in Metallurgical Slags

The nature of MgO and Al₂O₃ dissolution in metallurgical slags may affect production cost, efficiency, and product quality. However, the rate-limiting dissolution mechanism, chemical reaction or boundary layer diffusion, is not well understood. In the present report, the dissolution mechanism of MgO and Al₂O₃ in metallurgical slag was evaluated based on available literature data. The mass balance between the dissolving particle and the flux equation through the boundary layer was applied to predict the dissolution curve. The influence of fluid flow was taken into account to calculate the mass transfer rate at the oxide/slag interface. It was found that the rate-limiting step of MgO and Al₂O₃ dissolution is the same: mass transfer through the boundary layer. Depending on the slag composition and experimental temperature, the effective diffusion coefficient for MgO and Al₂O₃ dissolution falls in the range of 10⁻¹² to 10⁻⁹ m²/s.