Effect of coal-based composite binders on isothermal oxidation kinetics of vanadium-titanium magnetite pellets

The isothermal oxidation kinetics of vanadium-titanium magnetite (VTM) pellets prepared with 3Co-binder (coal-based colloidal composite binder) and F-binder (pulverized Funa binder) are compared. The oxidation process was analyzed using the first-order irreversible reaction, following the shrinking unreacted nucleus model. The results demonstrate that VTM pellets prepared with 3Co-binder exhibit a faster oxidation rate than those with F-binder across the temperatures ranging from 1073 to 1473 K. In both cases, the oxidation process was controlled by an interfacial chemical reaction during the pre-oxidation stage and by internal diffusion during the mid-oxidation stage. The type of binder did not influence the primary oxidation control mechanism of the VTM pellets. However, the apparent rate constants in the pre-oxidation stage and the internal diffusion coefficients in the mid-oxidation stage were higher for pellets with 3Co-binder compared to those with F-binder. The apparent activation energies for the 3Co-binder pellets were similar to those of bentonite, indicating favorable kinetic conditions without negative impacts on the oxidation process. Nonetheless, it is important to note that pellets with F-binder required a longer oxidation time than those with 3Co-binder.