Isothermal Reduction Behavior and Microstructural Evolution of Iron Ore Sinter Under Simulated Radial Blast Furnace Gas Atmospheres With Hydrogen Injection

This study investigates the isothermal reduction behavior of commercial iron ore sinter (B2 = 1.94) under radial blast furnace gas atmospheres derived from an industrial reference campaign. Twelve conditions were examined in a TGA at 700, 900, and 1100 °C, covering center and wall radial positions for a base case and a hydrogen‐injection scenario (20 kg H 2 /tHM). Reduction degree, phase transformations, microstructure, porosity, and BET specific surface area were characterized. At 700 °C, reduction remained partial (23%–45%), dominated by wüstite. Above 900 °C, near‐complete reduction to metallic iron was achieved, with kinetics accelerated at 1100 °C. Hydrogen injection enhanced reduction rates at 900 and 1100 °C under both radial positions due to the higher diffusivity and reducing potential of H 2 , whereas at 700 °C, it slightly lowered the final reduction degree primarily due to a lower thermodynamic reduction potential from elevated H 2 O, with the formation of a dense iron layer acting as a possible contributor to diffusion resistance. Wall atmospheres consistently exhibited a slower reduction rate and lower final reduction degrees than center atmospheres. Reduction progressed from the sinter sample periphery inward, generating a porous metallic iron network at high temperatures. Upon complete reduction, the sinter samples exhibited an increased porosity up to 65%–69%, while the BET surface area decreased from 0.6 m 2 /g (700 °C) to 0.1 m 2 /g (1100 °C) due to pore coarsening and sintering. The results indicate that hydrogen injection can improve sinter reducibility under sufficiently high‐temperature BF‐derived gas atmospheres, while low‐temperature, high‐H 2 O conditions require careful control of local gas potential and heat balance.