In-situ observation of the kinetic dissolution of Al₂O₃ particles in CaO-Al₂O₃-SiO₂ slags using laser confocal scanning microscopy

The dissolution kinetics of Al₂O₃ in CaO-Al₂O₃-SiO₂ slags was studied using high-temperature confocal scanning laser microscope at 1773 to 1873 K. The results show that the controlling step during the Al₂O₃ dissolution was diffusion in the molten slag. It was found that dissolution curves of Al₂O₃ particles was hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al₂O₃ of slag. A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al₂O₃ in slag. Diffusion coefficients of Al₂O₃ in slag were calculated as 2.8 ×10^-10 to 4.1 ×10^-10 m²/s. The dissolution rate of Al₂O₃ increased with higher temperature, CaO/Al₂O₃, and particle size. A new model was shown to be v_Al2O3 = 0.16 × R₀^1.58 × x^3.52 × (T-T_mp)^1.11 to predict the dissolution rate and the total dissolution time of Al₂O₃ inclusions with various sizes.