Empirical reduction diagrams for reduction of iron ores with H2 and CO gas mixtures considering non-stoichiometries of oxide phases

For the investigation and modelling of direct reduction processes of iron ore fines detailed knowledge of stability areas of Fe, Fe3-delta O4, Fe1-yO and further of kinetic and structural parameters as functions of temperature and gas composition is necessary. Kinetic and structural parameters are supplied by detailed experimental work. For planning experimental test programmes, information about stability areas of iron and iron oxides is essential. As the calculation of equilibrium plots of quartary gas mixtures containing H-2, H2O, CO and CO2 is rather complex, a simplified empirical method for the determination of stability areas of iron and iron oxides is useful. To make experimental data acquisition easier, a detailed description on the calculation of empirical reduction diagrams including the non-stoichiometries of magnetite and wustite is given in this work. Stability fields of iron, wustite and magnetite are given as functions of temperature and gas composition of H-2, H2O, CO and CO2. The influence of non-stoichiometries concerning the achievable degree of reduction was developed for wustite and magnetite. In the case of wustite a significant effect was found.