Abstract: For the purpose of revealing the impacting mechanism of mechanical activation on the gas based reduction of iron oxides, the correlation between the gas based reduction thermodynamics and stored energy acquired through mechanical activation for iron oxides is discussed. The result shows that there is a characteristic threshold CO or H₂ pressure fraction for each iron oxide reduction. If only the minimum CO or H₂ pressure fraction for reduction higher than the threshold value, reduction temperature decreases with the increase of stored energy, otherwise, increases, which renders the mechanical activation for iron oxides is advantageous only to some gas based reductions, while disadvantageous to others, in terms of lowering the reaction temperature. However, the minimum CO pressure fraction of CO or H₂ for all reductions decreases with the increase of stored energy, which makes mechanical activation be advantageous to all the reductions in improving the gas utilization ratio.

Key words: Mechanically-activated iron oxide, Gas-based reduction, Stored energy, Thermodynamics, Reduction temperature, CO or H₂ pressure fraction