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. The 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 loss technique. Porosity measurements, reflected light microscope and X-ray diffraction analysis were used to elucidate the reduction kinetics. NiO was found to have a significant effect on the reduction of iron oxide. The rate of reduction at both the initial and final stages increased with the increases of dopant content at all reduction temperatures and this was attributed to the formation of mickel ferrite (NiFe2O4) phase and the consequent increase in the total porosity of compacts. Nix, Fey solid solution (ferronickel alloy) was produced during reduction at all tempetatures studied. The values of apparent activation energy calculated from the experimental results, the structure of partially reduced compacts and the application of gas-solid reaction model were used to elucidate the reduction mechanism.