Molecular Dynamics Investigation on Coke Ash Behavior in the High-Temperature Zones of a Blast Furnace: Influence of Alkalis

With specific focus on local structural order, bonding networks, transport properties, and viscosity of the molten ash oxides, we report molecular dynamics simulations on the influence of alkalis (Na2O and K2O) on coke behavior within a blast furnace. Atomistic simulations were carried out on the Al2O3–SiO2–CaO–K2O–Na2O system at 2223 K for a range and relative proportions of Na2O and K2O. Alkalis were seen to have a strong effect on the oxygen bonding networks; the relative proportions of bridging and nonbridging oxygen showed a sharp increase, while significant reductions were observed for tricluster oxygens. Total diffusion coefficients and viscosity showed a highly nonlinear dependence on the relative proportions of two alkalis with large changes observed in the simultaneous presence of alkalis as compared to their individual presence. Our studies have shown that the combined influence of alkalis on the viscosity of molten ash, and associated coke degradation within a blast furnace, is likely to be much smaller than previously perceived and could even be negligible for some alkali concentrations.