Non-isothermal Hydrogen Reduction and Kinetic Behavior of Iron Ore Pellets Under Simulated Shaft Furnace Conditions

Abstract Utilizing hydrogen for iron ore reduction presents a promising route to significantly mitigate or even eliminate CO 2 emissions associated with traditional iron production, yet its behavior under realistic shaft furnace conditions remains complex. A shaft furnace operates as a dynamic packed bed reactor where temperature and gas composition vary significantly both axially and radially, which causes strong variations in the local chemical potential due to the evolving H 2 /H 2 O ratio. In this study, the reduction behavior of a single iron ore pellet was experimentally examined under non-isothermal and time-dependent gas compositions corresponding to three radial positions as near-wall, intermediate, and axis, derived from CFD simulations of shaft furnace. Thermogravimetric (TGA), X-ray diffraction (XRD), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS) analyses were employed to characterize the reduction, phase evolution and morphology of the reduced samples. The results revealed after approximately 105 minutes, complete reduction (100 pct) near the wall, partial reduction (90 pct) in the intermediate region, and limited reduction (12 pct) in the axis due to high water vapor content and lower temperature. The influence of gas flow rate on reduction kinetics was also investigated. Kinetic modeling using the Coats–Redfern method indicated that, under high H 2 O concentrations, solid-state diffusion predominated as the controlling mechanism across most reduction stages.