Effect of TiO₂ on oxidation kinetics of vanadium titanomagnetite pellets

This study investigated the non-isothermal oxidation kinetics of pellets prepared by mixing two kinds of vanadium-titanium magnetite (VTM) with different TiO 2 contents and the effect of TiO 2 content on pellet properties. Using thermogravimetric (TG) experiments, we studied the oxidation kinetics of VTM, and it was found that three stages controlled the oxidation process of VTM pellets. The temperature ranges for stage I and stage II were 400–600 °C and 600–840 °C; the limiting steps were the chemical and phase boundary reactions, respectively. The TiO 2 content of 3.63% to 7.64% increased the activation energy (E) of stage I and stage II by 25.95 kJ · mol −1 and 10.23 kJ · mol −1 , respectively, inhibited the oxidation of pellets. In stage III (840–1050 °C), the increase of TiO 2 led to the decrease of E by 14.13 kJ · mol −1 . The oxidation mechanism of VTM pellets was elucidated using an oxidation roasting experiment, XRD, and SEM-EDS. The results showed that increasing TiO 2 content led to higher porosity and lower compressive strength in roasted pellets. During oxidation, TiO 2 transformed into Fe-Ti solid solution (Fe 2 TiO 5 and Fe 9 TiO 15 ) at the hematite grain boundaries, which impeded hematite recrystallization by forming a barrier to grain growth and led to the formation of a more porous structure in the roasted pellets. Hematite recrystallization was suppressed, and Fe 2 O 3 decreased with the increase of TiO 2 . The findings of this study offer theoretical and technical support for utilizing VTM in pellets.