Investigation of Reduction Mechanism and Kinetics of Vanadium Titanomagnetite Carbon Composite Hot Briquette at 1173-1373 K

The isothermal reduction of vanadium titanomagnetite carbon composite hot briquette, simulated Blast Furnace condition at the temperature range of 1173-1373 K, is investigated in an electric resistance furnace. The samples reduced at different temperature are characterized by X-ray diffraction (XRD). The phase transitions during reduction process can be described as follows: Fe3O4 -> FeO -> Fe; Fe(2.75)Ti(0.25)O4 -> Fe2.5Ti0.5O4 -> Fe2TiO4 -> FeTiO3 -> TiO2; FeTiO3 -> TiO2; Fe2VO4 -> V2O3; FeCr2O4 -> Cr2O3. Then, model fitting methods are used to evaluate the apparent activation energy during this process. The reduction process can be divided into three stages, and the apparent activation energies of the three stages are 40.26, 66.46, and 90.96 kJ mol(-1), respectively. The rate controlling step of the initial stage is gas diffusion and interfacial chemical reaction. However, as the reduction proceeding, the rate controlling steps of the intermediate and final stage are gradually transformed to interfacial chemical reaction.