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

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 degrees C. The values of effective diffusivity (Deff over bar ) 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 Deff over bar and activation energy are in good agreement with the corresponding values obtained previously from Fe-Al2O3 and FeO-Al2O3 systems.