Effect of alkali metal on gas-solid reduction of iron oxide

Fe₂O₃ and Fe₂O₃ doped with Na₂O from 1.0 to 5.0 mass percent compacts were isothermally reduced at various temperatures from 1073 to 1273K with CO/CO₂ mixed gas in a vertical resistance furnace. To determine the effect of Na₂O on the reduction of Fe₂O₃ compacts, mass loss due to oxygen removal was continuously recorded from which the reduction rate and rate constant was obtained. The morphology change was also observed by SEM. The results show that Na₂O retards the reduction of Fe₂O₃ compacts. Morphological examination of reduced compacts and the binary phase diagram of FeO-Na₂O show liquid phase formation during the reduction, which decreases the rate of reduction. Porosity and volumetric expansion of reduced compacts were investigated, which shows that the volume and porosity of reduced Fe₂O₃-Na₂O compacts are both decreased with higher Na₂O content due to the existence of liquid phase.