Dissolution of Lime in High-Basicity CaO-SiO2-FetO-MgO Slag Under Dynamic Conditions

This study examines the dissolution behavior of solid lime in high-basicity CaO-SiO2-FetO-MgO slags at 1600 degrees C, using a stirring rod at a rotation speed of 110 rpm for 70 s after the lime being dropped in the molten slag. The investigation focuses on slag basicity ranging from 2.1 to 3.3, with constant MgO (7 wt%) and FeO (20 wt%). The results show that at a basicity of 2.1, layers of C2S and C3S + CaO-FeO are formed at the slag-lime interface. A dense C2S layer significantly impedes lime dissolution, resulting in the lowest dissolution rate, with chemical reaction assumed as rate-controlling mechanism. As the basicity increases to 2.4, the precipitation of MgO occurs, facilitating the formation of a discontinuous C3S layer interspersed with CaO-FeO, which promotes material flow and results in the highest dissolution rate. However, at higher basicity (2.7-3.3), a discontinuous C3S + CaO-FeO layer reappears, accompanied by excessive MgO precipitation at the interface, hindering dissolution. The increasing layer thickness and MgO concentration, combined with decreasing solubility of MgO at higher basicity, slow the dissolution process. Diffusion through a boundary layer is assumed as the rate-controlling mechanism.