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 CO₂ emissions, this study delves into the intricate role of TiO₂ in the direct reduction of iron oxide pellets. The TiO₂-dependent reducibility of iron oxide pellets utilizing H₂ and CO gas across varied temperatures and gas compositions is thoroughly investigated. Our findings unveil the nuanced nature of the TiO₂ effect, underscored by its concentration-dependent behavior, revealing an optimal range between 1 and 1.5 pct TiO₂, where a neutral or positive impact on reduction kinetics and diffusion coefficient is observed. Notably, the synergistic interplay of CO and H₂ at 1000 °C emerges as particularly efficacious, suggesting complementary effects on the reduction process. The introduction of H₂ 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 TiO₂ effect, with higher TiO₂ content correlating with prolonged reduction time in a 100 pct H₂ atmosphere at 900 °C. In a 100 pct H₂ atmosphere, the non-contributory role of TiO₂ stems from the water-gas shift reaction. Conversely, introducing H₂ into a CO-controlled reducing atmosphere with TiO₂ 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.