Multiscale Modeling for Hydrogen‐Based Direct Reduction of Iron Ore with CFD–DEM: From Single Pellet to Packed Bed

A computational fluid dynamics–discrete element method (CFD–DEM) model was developed for simulating the direct reduction of iron ore under H 2 ‐based and mixed reducing atmospheres. The gas phase is resolved via CFD, while individual ore pellets are tracked using DEM, with interphase coupling through heat and mass transfer as well as source terms based on reaction rates. A three‐layered unreacted shrinking core model is embedded to capture the dynamic phase transformations and morphological evolution during reduction. The model is validated against experimental data at both single‐particle and fixed‐bed scales, demonstrating high accuracy in predicting reduction kinetics and phase evolution under H 2 , CO, and H 2 /CO conditions. Parametric studies under H 2 ‐based conditions further highlight the critical roles of gas flow rate, pressure, temperature, pellet size, and porosity in governing reduction performance. This article presents a versatile, scalable modeling framework for the design and optimization of H 2 ‐based ironmaking reactors, supporting the advancement of low‐carbon steel production technologies.