Through thermodynamic smelting experiments, nonisothermal and isothermal kinetics experiments, the effects of CO₂–containing gas injection on the smelting of chromia–bearing vanadiferous titanomagnetite ore were investigated. The experiments at 900 °C, 1000 °C, 1100 °C, 1200 °C, and 1300 °C, and CO₂ concentration of 0, 10 vol.%, 20 vol.%, and 30 vol.% were studied. The samples after the kinetics experiments were analyzed through thermodynamic calculations and characterized by XRD, XRF, XPS, and SEM. The results of thermodynamic experiments show that the injection of CO₂–containing gas significantly improves the softening–melting–dripping behavior during the smelting process. As the concentration of injected CO₂ increased from 0 vol.% to 30 vol.%, the range of softening temperature [T₄₀–T₄] decreased from 109 °C to 97 °C, and the range of droplet temperature [T_d–T_s] decreased rapidly from 196 °C to 162 °C. Moreover, when CO₂ concentration was 20 vol.%, the minimum apparent activation energy of nonisothermal kinetics reached 75.58 kJ·mol⁻¹. Combining the lowest permeability index and the fastest nonisothermal reduction rate, the optimal CO₂ concentration in the fuel gas was considered to be 20 vol.%. The isothermal parameters were fitted according to 1 − (1 − α)^1/3 − t (CG₃ model), and the apparent activation energy was 121.93 kJ·mol⁻¹ (less than 150 kJ·mol⁻¹), which means that the restrictive step of the polymetallic reaction is mainly determined by diffusion. Finally, thermodynamic calculations and characterizations show that CO₂–containing gas injection helps titanium stabilize in a higher valence state, which is conducive to improve the high–temperature characteristics of titanium–containing slag.

The effects of high-basicity pellet on smelting chromium-bearing vanadia-titania magnetite are investigated via thermodynamic smelting and non-isothermal kinetics experiments. The thermodynamic results indicated that the high-basicity pellet significantly affects and ameliorates the softening-melting-dripping behaviors during the smelting process. As the high-basicity pellet ratio increased from 0 wt.% to 52 wt.%, the range of softening temperature [T₄₀–T₄] decreased from 121 °C to 84 °C and the melting-dripping temperature [T_d–T_s] decreased from 224 °C to 169 °C. Moreover, the apparent activation energy of non-isothermal kinetics also decreased from 99.91 kJ·mol⁻¹ to 66.74 kJ·mol⁻¹. Additionally, the reaction mechanism of high-basicity pellet on smelting chromium-bearing vanadia-titania magnetite was investigated via thermodynamic calculations of Gibbs free energy and characterizations of the titanium slag. Therefore, combined with the lowest permeability index, the fastest non-isothermal reduction rate, the highest recovery of valuable elements and the minimum content of titanium carbonitride, the preferable high-basicity pellet ratio was considered to be 11~23 wt.%.