Gas-based reduction and carbonization of titanium minerals in titanium-bearing blast furnace slag: A combined thermodynamic,experimental and DFT study

The utilization of titanium-bearing blast furnace slag (TBFS) has been widely concerned, which is mainly related to the recovery of titanium resources. In order to realize the efficient and clean recovery of titanium resource, the main titanium-bearing phases (CaTiO₃, MgTiO₃ and Mg₂TiO₄) in TBFS with high content of MgO were investigated in CH₄–H₂ system in this work. Thermodynamic calculation indicated that CaTiO₃, MgTiO₃ and MgTi₂O₄ could be ultimately reduced to TiC_xO_y at 1300 °C, 1200 °C and 1200 °C respectively. The reduction experiments were carried out in flowing CH₄–H₂, which considered the influences of time, temperature and addition, the results of which showed that the optimal reduction temperatures of CaTiO₃ and MgTiO₃ were 1400 °C and 1200 °C respectively. DFT calculation results also confirmed that MgTiO₃ had stronger CH₄ adsorption capacity than CaTiO₃ and Mg₂TiO₄. However, Mg₂TiO₄ could not be reduced completely even at 1450 °C, because excessive MgO in the reduced products prevented further reaction in kinetics. Both increasing temperature and adding iron oxides contributed to the reduction kinetics. The results suggested that the appropriate increase of the proportion of MgO in TBFS was beneficial to titanium extraction. This work provides a way to develop new process to extract titanium from TBFS, especially the slag with high MgO.