EFFECT OF NICKEL-OXIDE DOPING ON THE KINETICS AND MECHANISM OF IRON-OXIDE REDUCTION

Experiments were conducted on pure Fe2O3 fines (-250 mesh) which were mixed with 1, 2.5, 5 and 10% by weight of pure NiO of the same size. T he powder mixtures were pressed into compacts and fired at 1473 K for 20 h. The fired compacts were isothermally reduced at 1173-1473 K with hydrogen. The reduction course was followed up by means of weight los s technique. Porosity measurements, reflected light microscope and X-r ay diffraction analysis were used to elucidate the reduction kinetics. NiO was found to have a significant effect on the reduction of iron o xide. The rate of reduction at both the initial and final stages incre ased with the increase of dopant content at all reduction temperatures and this was attributed to the formation of nickel ferrite (NiFe2O4) phase and the consequent increase in the total porosity of compacts. N i-x,Fe-y solid solution (ferronickel alloy) was produced during reduct ion at all temperatures studied. The values of apparent activation ene rgy calculated from the experimental results, the structure of partial ly reduced compacts and the application of gas-solid reaction model we re used to elucidate the reduction mechanism.