Regulation of CH 4 ‐Related Reactions on Reduction, Carburization, and Production State in a Hydrogen‐Based Shaft Furnace: Insights From Computational Fluid Dynamics Simulation and Operating Diagram Analysis

This work develops a computational fluid dynamics model for the hydrogen‐based shaft furnace coupling flow, heat transfer, mass transfer, and key chemical reactions. The simulation reveals a low‐reactivity central region with slow gas renewal and divides the furnace into eight distinct zones. As the CH 4 volume fraction increases from 8.5% to 24.5%, carburization and reforming are promoted, bringing the furnace closer to the ideal thermodynamic state (the deviation of the current shaft furnace state from the ideal state, w value, decreases by 12.3%). However, the DRI metallization degree drops from 0.983 to 0.930 due to the strongly endothermic CH 4 reactions lowering furnace temperature. Increasing H 2 O from 1.5% to 7.5% enhances in‐situ CH 4 reforming, exacerbating heat consumption: at 12 m height, burden temperature decreases by 114K, metallization degree falls from 0.985 to 0.921, and carbon content drops from 0.030 to 0.016. CH 4 and H 2 O approach the ideal state through different mechanisms—CH 4 promotes both reforming and carburization, while H 2 O primarily drives reforming—but both reduce metallization, necessitating compensation via higher gas temperature or flow rate. These findings elucidate the competition for limited heat between strongly endothermic CH 4 reactions and weakly endothermic to exothermic iron oxide reduction, guiding hydrogen‐based shaft furnace optimization.