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There are still some different understandings about deoxidization process from TiO 2 to Ti by FFC Cambridge process. Herein, an investigation was carried out on the phase transformations and deoxidation kinetics of the electrochemical reduction of TiO 2 to Ti in molten CaCl 2. The reaction goes through four different stages involving several phase transformations. The first stage is the deoxidation of TiO 2 with the formation of CaO and CaTiO 3. At this stage, Cl 2 is forcibly released from the anode because of the consumption of Ca 2+ on the cathode, balanced with Cl ¹ at the anode. The second stage is the deoxidation of CaTiO 3 and titanium suboxides. These two stages take 45% of the entire deoxidation time from TiO 2 to Ti [O]. The third stage is the deoxidation of titanium suboxides. This stage takes about 55% of the total time. The final stage is further deoxidation of TiO solid solution by electrochemical reduction or by calcium thermal reduction. There are no obvious kinetic barriers in the formation of CaTiO 3 , but the rate of deoxidation of titanium suboxides and CaTiO 3 is relatively slow. Therefore, the limiting step from TiO 2 to Ti by the FFC process in molten CaCl 2 is deoxidation of titanium oxides and the interphase of CaTiO 3 .

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Basicity of titanium bearing blast furnace (BF) slag is critical for its crystallization behavior. Thermodynamics calculation indicates that rutile is the main phase after crystallization (or at room temperature). It precipitates during the cooling when the basicity of the slag is lower than 0.7. With increasing basicity, perovskite appears and becomes the main phase instead which contains titanium. Crystallization temperature of perovskite is higher than that of rutile and the other phases. Namely, perovskite crystallizes firstly from the molten slag during decreasing temperature. XRD analysis shows that CaTi21O38 is the main phase with a basicity of 0.6. CaMg0.39Al0.87Ti0.48Si1.26O6, CaTiSiO5 and CaMgSi2O6 are the main crystallization phases with a basicity of 0.8. The difference between experimental and thermodynamics calculation is due to the complicate crystallization behavior of the multiple slag under super cooling rate. When the slag basicity increases to 1.1, the main precipitatied phase is perovskite, which agrees well with theory calculation. In addition, the crystal structure of the synthesized titanium bearing slag is basically similar regardless of the basicity.