Reduction of chengde vanadium titanium magnetite concentrate by microwave enhanced Ar–H2 atmosphere

Abstract

In this study, a new method of microwave-enhanced hydrogen reduction was developed to carry out isothermal reduction experiments. The effects and mechanisms of different hydrogen volume fractions on the direct reduction behavior of a vanadium titanium magnetite concentrate (VTM) were investigated. The experimental results and theoretical analysis proved that combining the advantages of microwaves and hydrogen to reduce the VTM is feasible. The thermodynamics of the non-microwave field indicated that the hydrogen reduction of iron titanium oxides was more difficult than that of iron oxides and required a higher reaction temperature. Under microwave heating conditions, with an increase in hydrogen volume fraction, the metallization rate and reduction degree increased, the microscopic morphology developed into a porous sponge-like structure, the size of the internal pores increased, and the migration of metallic iron to the edges of the particles became obvious. When the hydrogen volume fractions exceeded 60%, the products did not contain TiO2, and the final products consisted of metallic iron containing a small amount of dissolved Ti. The reduction reaction was controlled by gas phase diffusion, and the average apparent activation energy was calculated to be 84.05 kJ/mol using a new kinetic model. Moreover, increased hydrogen volume fraction weakened the gas phase diffusion and was converted into internal diffusion.