Effect of Na₂O on the reduction of Fe₂O₃ compacts with CO/CO₂

Compacts of Fe₂O₃ and Fe₂O₃ doped with varying amounts of Na₂O were isothermally reduced at several temperatures, using CO/CO₂ mixed gas in a vertical resistance furnace. To determine the effect of Na₂O on the reduction of Fe₂O₃ compacts, the mass loss due to oxygen removal was continuously recorded, from which the reduction rate and rate constant were obtained. Na₂O was found to retard the reduction of Fe₂O₃ compacts. The apparent activation energy (E_a) of reaction and the mathematical relationship for pore gas diffusion suggested that the reduction behavior at the initial stages was controlled by a combination of pore gas diffusion and interfacial chemical reaction. At the intermediate and late stages of reduction, pore gas diffusion was the sole contributing factor. Morphological examination of the reduced compacts showed the formation of a liquid phase during the reduction process, which appeared to lower the rate of reaction.