Enhanced fluidized bed hydrogen reduction of ilmenite through granulation modification with Fe₂O₃

To develop efficient direct reduction technology for ilmenite, this study innovatively proposed the use of Fe₂O₃ granulation modification to enhance its fluidized bed hydrogen reduction. Systematic fluidized bed hydrogen reduction experiments were conducted to investigate the mechanism of modification on the reduction behavior of ilmenite. The results demonstrated that Fe₂O₃ granulation modification exhibited a dual enhancement effect, as it can effectively inhibited defluidization at high temperatures and significantly increasing the reduction rate. The modified ilmenite particles could be stably fluidized in hydrogen at 940 ℃ for over 60 minutes, and the metallization degree of reduction product is increased from 12% to 97%. Mechanistic studies indicated that, at the level of physical effects, the granulation modification destroyed the dense iron shell newly formed on the surface of raw ilmenite particles. Simultaneously, the introduced non-sticky component materials acted as physical barriers, effectively reducing particle surface stickiness and thereby preventing the occurrence of defluidization. At the level of chemical effects, the granulation modification, through raw material refinement, completely eliminated the "chemical barrier effect" formed by the Fe_xMg_1-xO·TiO₂ solid solution. Kinetic studies revealed that the reduction process of the granulation-modified samples followed the 2D nucleation and grain growth model. The added Fe₂O₃ is converted into fine iron grains in the initial reduction stage. These grains acted as nucleation sites, greatly promoting the precipitation of iron from FeO·TiO₂ and significantly accelerating the nucleation rate. Calculation of the apparent activation energy for the reduction reaction showed that the activation energy for the Fe₂O₃-modified samples （80.47 kJ/mol） is lower than that of the unmodified samples （94.80 kJ/mol）, confirming its catalytic promoting effect on the reduction. Evaluation of the applicability to ilmenite from different sources verified the universal applicability of the Fe₂O₃ granulation modification method for enhancing reduction. This study provided a new approach to solving the challenges of defluidization and reduction stagnation in the fluidized bed hydrogen reduction of ilmenite and laid a theoretical foundation for the efficient utilization of ilmenite.