Interaction of Pure Alumina Refractory with FeO–SiO₂ and FeO–SiO₂–CaO Slags Relevant to the Novel Flash Ironmaking Technology

Abstract

Interaction of alumina (Al2O3) refractory with FeO–SiO2 and FeO–SiO2–CaO slags relevant to the flash ironmaking technology (FIT) is investigated in this work. It is shown that for slags relevant to FIT, the interaction process can be described by a kinetic model based on counter diffusion of only Fe2+ and Al3+ cations through hercynite (FeAl2O4) formed as a result of the interaction. The diffusion of Si4+ and Ca2+ ions through FeAl2O4 can be neglected, and the only effect these cations have is that they affect the activity of iron oxide (FeO) at the slag–FeAl2O4 boundary. Analyses of reacted samples using X‐ray diffraction (XRD), scanning electron microscopy–energy dispersive X‐ray spectroscopy (SEM–EDX), and electron probe microanalyzer (EPMA) show that the proposed model appropriately describes the growth of FeAl2O4 with the parabolic rate law being obeyed for both FeO–SiO2 and FeO–SiO2–CaO slags in the temperature range of 1200–1400 °C. The values of effective diffusivity ( D eff 3extrue¯ ) are calculated independently from experiments with FeO–SiO2 and FeO–SiO2–CaO slags agreed with each other, with the activation energy values in the two cases being 246 and 253 kJ mol−1, respectively. These values of D eff 3extrue¯ and activation energy are in good agreement with the corresponding values obtained previously from Fe–Al2O3 and FeO–Al2O3 systems.

Effect of Erosion Behavior of FeO-CaO-SiO2-MgO-Al2O3 Blast Furnace Primary Slag on Al2O3 Substrate

“…The results demonstrate that Ca and Si diffuse to the interface layer and Al2O3 substrate dissolves into the slag during wetting. Sarkar et al [29] discussed the interaction of Al2O3 refractories with FeO-SiO2 and FeO-SiO2-CaO slag, and found that the effective diffusion coefficients of Fe 2+ and Al 3+ were reduced significantly due to the formation of high-melting-point compounds, such as hercynite (FeAl2O4), mullite (3Al2O3•2SiO2), and anorthite (CaAl2Si2O8), in the interface layer, indicating that the high-melting-point compounds may further inhibit the diffusion of Al 3+ ion into the slag. According to our experimental results, the Ca2Al2SiO7 and CaMg2Al16O27 phases can hinder the diffusion of Al 3+ .…”