Molecular Dynamics Simulation on the Effect of MgO/Al₂O₃ Ratio on Structure and Properties of Blast Furnace Slag Under Different Basicity Conditions

The SiO₂-Al₂O₃-CaO-MgO is the basic structural system of blast furnace slag and the composition directly affects the performance of the slag. Molecular dynamics simulations were carried out to analyze the local structure, structural unit, bond angle, transport properties, and enthalpy of the slag with the increase of MgO/Al₂O₃ mass ratio under different basicity conditions. It was found that the change of MgO/Al₂O₃ ratio does not affect the short-range order structure, but it will reduce the overall stability of the network structure. Through the analysis of the structural unit of the slag, it was found that the polymerization degree of the system decreases with the increase of MgO/Al₂O₃ ratio, indicating that the complex network structure of the system is partially depolymerized. Besides, the self-diffusion coefficients of each ion were concluded and the magnitudes were observed to be in the following order: Mg²⁺>Ca²⁺>Al³⁺>O^2->Si⁴⁺. The diffusivity of the slag increases with the increase of MgO/Al₂O₃ ratio and the corresponding viscosity decreases. And the enthalpy of the slag is increased with the increase of MgO/Al₂O₃ ratio or basicity, therefore the fuel consumption should also be properly adjusted during the operation of blast furnace to ensure the target temperature.