TiO2 and Reducing Gas: Intricate Relationships to Direct Reduction of Iron Oxide Pellets

Abstract In response to the imperative for sustainable iron production with reduced CO 2 emissions, this study delves into the intricate role of TiO 2 in the direct reduction of iron oxide pellets. The TiO 2 -dependent reducibility of iron oxide pellets utilizing H 2 and CO gas across varied temperatures and gas compositions is thoroughly investigated. Our findings unveil the nuanced nature of the TiO 2 effect, underscored by its concentration-dependent behavior, revealing an optimal range between 1 and 1.5 pct TiO 2 , where a neutral or positive impact on reduction kinetics and diffusion coefficient is observed. Notably, the synergistic interplay of CO and H 2 at 1000 °C emerges as particularly efficacious, suggesting complementary effects on the reduction process. The introduction of H 2 into the reducing atmosphere regulated by CO not only extends the transition range but also markedly expedites the rate of reduction. Furthermore, our study highlights the temperature sensitivity of the TiO 2 effect, with higher TiO 2 content correlating with prolonged reduction time in a 100 pct H 2 atmosphere at 900 °C. In a 100 pct H 2 atmosphere, the non-contributory role of TiO 2 stems from the water-gas shift reaction. Conversely, introducing H 2 into a CO-controlled reducing atmosphere with TiO 2 enhances the transition range and expedites the reduction rate. Additionally, our findings underscore the role of total iron content, revealing a direct correlation with the reduction process.