The dissolution process of CaO·2Al₂O₃ (CA2) particles in CaO-SiO₂-Al₂O₃ steelmaking slags was in situ investigated at 1550 °C. To better understand the role of particle porosity in dissolution kinetics, the particles with two different porosity levels, i.e., 0.08 and 0.20 were used in this study. The porosity (φ) and surface area of CA2 particles were characterized through X-ray Computed Tomographic Imaging (XCT), and the surface area ratio (f(φ)) between the porous and full dense particles was expressed as f(φ)=0.9398e5.9498φ. The obtained results indicated that an increase in the porosity from 0.08 to 0.20 led to an increase in the average dissolution rate from 0.35 to 0.59 μm/s. Moreover, the motion of CA2 particles during the dissolution process was observed, suggesting its importance to include in the modeling approach. A novel mathematical model was developed to predict the dissolution time of inclusion particles by incorporating both the motion and porosity of particles. This model was validated against the existing literature data and aligned well with the current experimental findings. The model predictions demonstrated that the dissolution time of CA2 particles was decreased with an increase in the velocity and porosity of particles and concentration difference of dissolving species between particle–slag interface and molten slag (∆C), and a decrease in slag viscosity.

Dissolution kinetics of CaO·2Al₂O₃ (CA₂) particles in a synthetic CaO–Al₂O₃–SiO₂ steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope. Effects of temperature (i.e., 1500, 1550, and 1600 °C) and slag composition on the dissolution time of CA2 particles are investigated, along with the time dependency of the projection area of the particle during the dissolution process. It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity. Moreover, a higher ratio of CaO/Al₂O₃ (C/A) leads to an increased dissolution rate of CA₂ particle at 1600 °C. Thermodynamic calculations suggested the dissolution product, i.e., melilite, formed on the surface of the CA₂ particle during dissolution in slag with a C/A ratio of 3.8 at 1550 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA₂ particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA₂ particle. The formation of this layer during the dissolution process was identified as a hindrance, impeding the dissolution of CA₂ particle. A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided, especially using calcium treatment during the secondary refining process.