Unsteady dissolution and diffusion process of CaO in high-aluminum, low-magnesium CaO-MgO-Al2O3-SiO2-FeO acidic slags based on molecular dynamics simulation

Abstract

The dissolution behavior of high-aluminum acidic slag by CaO was investigated using molecular dynamics simulations. At 1700 °C, the average solution-diffusion rates of Ca²⁺ and O^2– ions with target basicity of 0.90, 1.00, 1.10 and 1.20 were 0.96, 1.00, 1.01 and 1.03 times that of 0.80 during 1000 ps, respectively. From 25 °C to 1700 °C, the dissolution of Ca²⁺ ions in the slag were initiated at approximately 800 °C, followed by rapid dissolution around 1200 °C. The dissolution rates increased significantly as the transitions from solid-phase dissolution to liquid-phase dissolution. Furthermore, a mechanism for the unsteady dissolution of CaO was proposed, in which the dissolution process is divided into two stages: interfacial dissolution and mass transfer diffusion. At low temperatures and high CaO content, interfacial dissolution was identified as the rate-limiting step. Once a substantial amount of CaO had dissolved at the interface, mass transfer diffusion gradually became the dominant process.