Green Steel: The Evolution of Porosity during Hydrogen-Based Direct Reduction of Iron Oxide

Hydrogen-based direct reduction (H-DR) of iron oxide has attracted immense attention as a promising alternative to producing green steel and mitigating CO2 emission in the steel industry. During H-DR, the volume mismatch between the educt and product phases results in the generation of a large number of pores. Thorough time-resolved 3D characterization of the porosity and the connectivity of the free volume is highly needed for understanding their effects on the reaction kinetics. Hereby, we propose to employ in-situ high-resolution X-ray computed tomography enhanced by phase contrast to fully disclose and quantify the evolution of local microstructures during H-DR of iron oxide, in particular, the size, morphology, distribution, and 3D connectivity of porosity. This information will be further correlated with the reaction kinetics, paving the way to speeding up the solid-gas reaction by the microstructural design of ore pellets as well as thermomechanical process optimization.