GASEOUS REDUCTION OF MGO-DOPED FE2O3 COMPACTS WITH CARBON-MONOXIDE AT1173-1473 K

Fired pure Fe2O3 and 0.5-5.0% MgO-doped Fe2O3 compacts, were isotherma lly reduced with CO at 1173-1473 K. The course of reduction was follow ed up by thermogravimetric technique. The structure of compacts were m icroscopically examined while the different phases were identified by X-ray diffraction analysis. Mercury pressure porosimeter was used to c haracterize the pore structures. The isothermal reduction curves obtai ned showed that MgO revealed different effects on the reduction behavi our of Fe2O3. At the initial stages up 25% extents, the doping of MgO showed no measurable influence on the reduction process. At the interm ediate stages (25-85% extents), the doping of 0.5% MgO retarded the re duction while the presence of 1.0% MgO promoted the reduction of Fe2O3 . The retardation and promotion effects were increased with the extent of reduction and decreased with rise in temperatures. At final stages of reduction, a slowing down in the rate due to the doping of MgO was observed which was attributed to the formation of hardly reducible ma gnesiowustite phase. The rate controlling step in the reduction proces s was determined from the values of apparent activation energy, gas-so lid mathematical formulations and the microstructure of partially redu ced compacts. It was found that the reduction was controlled by a comb ined effects of gaseous diffusion and interfacial chemical reaction at the initial stages. While at the latter stages, a solid-state diffusi on is contributed to interfacial chemical reaction as the rate control ling mechanism depending on MgO content in compacts.