Abstract
The use of green hydrogen to reduce iron ore is a promising approach to drastically decrease CO2 emissions in the steel industry. To enable the rapid adoption of this technology, it is essential to start from the fundamentals, namely understanding the intrinsic kinetics of iron oxide reduction. In this work, a kinetic investigation was conducted in a PBRlike system using both pure and commercial iron oxide powders under a wide range of operating conditions. The thermal conductivity of the outlet gas was measured and innovatively correlated with the extent of solid reduction through a rigorous mathematical procedure. To simulate the reduction process and determine the kinetic parameters, a deterministic axial dispersion model was developed in conjunction with a dynamic multistep shrinking core model. The model incorporates the particle size distribution of the solid into the mass balance and includes a reactionfront control mechanism to ensure physical consistency during kinetic parameter estimation. The model successfully reproduced all experimental data, confirming that the controlling mechanisms were predominantly chemical, internal diffusion, or mixed, depending on the type of solid material used. Furthermore, the model not only demonstrates excellent predictive capabilities through the validation of kinetic parameters but also provides new insights into the key phenomena governing iron oxide reduction.