REDUCTION OF CAO AND OR MGO-DOPED FE2O3, COMPACTS WITH CARBON-MONOXIDE 1173-1473 K/

Compacts of Fe2O3 doped with either (0.5-5.0%) CaO, 1.0% MgO and/or 1. 0% CaO fired at 1473 K for 20 hr, were isothermally reduced with CO ga s at 1173-1473 K. Thermogravimetric technique was used to follow up th e oxygen weight-loss as a function of time. Partially and completely r educed samples were subjected to chemical and carbon analyses while th eir internal structure was examined by optical microscope. Pore size a nalyser was used to characterize pore structure and pore size distribu tion. The different phases developed during reduction were also identi fied by X-ray diffraction technique. It was observed that the doping o f CaO revealed different effects on the reduction of pure Fe2O3 depend ing on CaO content, temperature and reduction extents. At tower temper atures (less than or equal to 1273 K), the doping of less than or equa l to 2.5% CaO promoted the reduction of Fe2O3 and a maximum effect was observed for compacts doped with 1.0% CaO. At greater than or equal t o 1373 K, the doping of CaO retarded the reduction of Fe2O3 at the lat ter stages due to the sintering and densification effects which increa sed with temperature. The influence of MgO on the reduction of Fe2O3 w as discussed in another publication. The doping of 1.0% CaO with 1.0% MgO in Fe2O3 compacts greatly promoted the reduction of Fe2O3 at <1273 K and this effect decreased with temperature. Heterogeneous gas-solid reaction formulations were examined and correlated with both of the a pparent activation energies and the internal structures of partially r educed compacts to elucidate the corresponding reduction mechanisms.