Multiscale and Operando Studies on the Role of Micro- and Nanostructures in Hydrogen-based Direct Reduction of Iron Oxides (HYDRI)

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The fossil-free ironmaking processes are indispensable in the steel industry considering the mitigation of anthropogenic CO2 emissions. Hydrogen-based direct reduction (HDR) is a major contender for the green ironmaking route without a direct release of CO2 emissions. The HYDRI project aims at disentangling the correlation between material micro-/nanostructures and the HDR kinetics, to reveal the vital role of acquired defects in the HDR process. Herewith, I propose a multiscale and time-resolved operando characterization approach to tackle this fundamental question in a holistic manner. The HYDRI targets three objectives: (1) To correlate the evolution of individual phases and the overall HDR kinetics, understanding the rate-limiting mechanisms from a microscopic perspective; (2) To study the role of interphase boundaries in HDR mechanisms and kinetics; and (3) To investigate the role of micro/nano porosity in HDR kinetics in mass transport. Consequently, how these key microscopic features alter during the reduction and affect the reduction kinetics will be accessible to our community. Also, the obtained microstructural information will be transferred to the multi-component phase-field model of iron ore reduction developed by the internal collaborator at the MPIE to verify the model parameters. The experimentally calibrated model allows for the theoretical understanding of the reaction mechanisms and the prediction of the reduction kinetics in various conditions. Such a comprehensive understanding of the effect of micro-/nanostructures on the reduction kinetics can pave the way for the improved microstructure design of the ore pellets and the optimization of the thermo-mechanical treatment to accelerate the reduction kinetics.