A Comparative Study on the Reduction Mechanism of Fe2O3 Under Different Heating Methods

The mechanisms for magnetizing roasting of Fe 2 O 3 into Fe 3 O 4 under microwave heating and electrical heating have been studied through thermogravimetric analyses, x-ray diffraction (XRD) measurements, and reaction kinetic calculations. In the reduction process, activated carbon was used as a reducing agent and argon as the protective gas. The results of heating tests indicated that the temperature heating speed during microwave heating is 50 times faster than that of electrical heating. The maximum conversion ratio of Fe 2 O 3 by microwave heating is 24.5% higher than that by electrical heating. XRD results showed that the required temperature for Fe 2 O 3 to completely convert into Fe 3 O 4 by microwave heating is 200°C lower than that by electrical heating. Reaction kinetics parameters calculation results showed that the controlling step of microwave magnetizing is a phase boundary reaction of the contracted ball at 250–450°C with an apparent activation energy of 45 kJ/mol, whereas the controlling step of electrical magnetizing is a chemical reaction of stochastic coring at 450–650°C with an apparent activation energy of 225 kJ/mol.