Low-temperature hydrogen reduction of Carajás hematite: Synergistic effects of kinetics and pore evolution

The interplay between reaction kinetics and pore structure evolution during the low-temperature hydrogen reduction of Carajás hematite was systematically examined, offering insights into optimizing low-carbon metallurgical processes. The high reduction efficiency of Carajás hematite was primarily attributed to its well-developed pore network, which was further regulated by pore evolution dynamics. Kinetic modeling revealed that the reduction process followed the A2 reaction model, G(α) = [−ln (1−α)]^1/2, with an apparent activation energy of 52.84 kJ/mol. X-ray diffraction (XRD) analysis confirmed that hematite predominantly transformed into magnetite during reduction. Microstructural characterization, including scanning electron microscopy (SEM-EDS) and specific surface area analysis (BET), demonstrated that the raw Carajás hematite possesses a well-developed pore network, which serves as the foundation for its exceptional low-temperature reduction performance. During reduction, the progressive expansion of pores and cracks facilitated gas diffusion, collectively accelerating the reaction. This process was accompanied by the synchronous evolution of pore structure and phase transformation, as evidenced by the strong correlation between specific surface area, pore volume, and conversion rate. These findings underscore the pivotal role of the raw mineral's structural characteristics in governing its reduction behavior. Furthermore, controlling pore evolution is crucial for optimizing low-carbon metallurgical techniques and enhancing domestic iron ore utilization, providing a scientific basis for sustainable resource management.