Comparison of the Reducibilities of Hydrogen and Carbon Monoxide for Iron Oxides

Abstract—Thermodynamic analysis of the reduction of iron oxides in gas mixtures with H₂ and CO shows that the ratio of the reducibilities of these gases (γ) can decrease or increase with temperature or can be temperature-independent under different conditions. This contradicts the commonly accepted assertion that the reducibilities of H₂ and CO at 1093 K are equal and that the reducibility of H₂ increases with temperature when considering the intersection of the reduction curves and superimposing the equilibrium phase diagrams iron oxides–CO–CO₂ and iron oxides–H₂–H₂O. In this case, the parameters of a specific reduction technology, the composition of the formed water gas, and the possibility of soot carbon formation are ignored. In particular, when Fe₃O₄ is reduced to FeO in the presence of carbon in the temperature range 850–917 K and FeO is reduced to Fe in the range 850–955 K, the ratio of the reducibilities of H₂ and CO changes from zero to 5.76 depending on the temperature, the nature of the initial system, and its composition. It is shown that, for any technological organization, the reduction of Fe₃O₄ to FeO is characterized by γ = 1.71 in the presence of carbon at 917 K and the reduction of FeO to Fe at 955 K is characterized by γ = 2.30.