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

考虑到减少人为CO2排放，无化石燃料炼铁工艺在钢铁工业中不可或缺。氢基直接还原（HDR）是绿色炼铁路线的主要竞争者，而不会直接释放CO2排放。HYDRI项目旨在解开材料微/纳米结构与HDR动力学之间的相关性，以揭示获得的缺陷在HDR过程中的重要作用。因此，我提出了一个多尺度和时间分辨的歌剧表征方法来解决这个根本问题，在一个整体的方式。HYDRI的目标有三个：（1）将各个相的演变与整体HDR动力学相关联，从微观角度理解限速机制;（2）研究相间边界在HDR机制和动力学中的作用;（3）研究微/纳米孔隙率在质量传输中HDR动力学中的作用。因此，这些关键的微观特征如何在还原过程中改变并影响还原动力学将是我们社区所能接触到的。此外，所获得的微观结构信息将被转移到由MPIE内部合作者开发的铁矿石还原的多组分相场模型中，以验证模型参数。实验校准的模型允许的反应机理的理论理解和在各种条件下的还原动力学的预测。这种对微/纳米结构对还原动力学的影响的全面理解可以为改进球团矿的微观结构设计和优化热机械处理以加速还原动力学铺平道路。

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.