A kinetic comparison between microwave heating and conventional heating of FeS-CaO mixture during hydrogen-reduction

Kinetics of iron production via hydrogen-reduction of FeS-CaO mixture during both microwave heating and conventional heating was investigated at 750, 570, and 460 °C to clarify the effect of heating method on dominant rate-controlling mechanism. Results of conventional heating revealed that the rate controlling step during treatment in the first 500 s at 750 °C, 800 s at 570 °C, and 1000 s at 460 °C is interfacial chemical reaction; then it is changed to gas diffusion in micro pores of reduced Fe owing to the formation of Fe shell on the surface of FeS particles. In microwave treatment, the interfacial chemical reaction is rapidly progressed and gas diffusion is the dominant rate-controlling mechanism with an activation energy of 22.3 kJ.mol⁻¹. This study demonstrated that the microwave irradiation enhances the rate of chemical reaction during iron production from FeS-CaO mixture.