Thermodynamics and kinetics of carbothermal reduction of zinc ferrite by microwave heating
(1. Faculty of Metallurgy and Energy Engineering, Kunming University of Science and Technology,
Kunming 650093, China;
2. Key Laboratory of Unconventional Metallurgy, Ministry of Education,
Kunming University of Science and Technology, Kunming 650093, China;
3. Engineering Laboratory of Microwave Application and Equipment Technology, Kunming 650093, China;
4. Kunming Metallurgy Research Institute, Kunming 650093, China)
Kunming 650093, China;
2. Key Laboratory of Unconventional Metallurgy, Ministry of Education,
Kunming University of Science and Technology, Kunming 650093, China;
3. Engineering Laboratory of Microwave Application and Equipment Technology, Kunming 650093, China;
4. Kunming Metallurgy Research Institute, Kunming 650093, China)
Abstract: The kinetics of carbon reduction of ZnFe2O4 in the temperature range of 550-950 °C was investigated in a microwave tank-type reactor. The mechanism of formation of ZnO and Fe3O4/FeO by the decomposition of ZnFe2O4 was detailed using the equilibrium calculations and thermodynamics analysis by HSC chemistry software 6.0. In addition, the effects of decomposition temperature, the C/ZnFe2O4 ratio, the particle size and the microwave power were assessed on the kinetics of decomposition. Zn recovery as high as 97.93% could be achieved at a decomposition temperature of 750 °C with C/ZnFe2O4 ratio of 1:3, particle size of 61-74 μm and microwave power of 1200 W. The kinetics of decomposition was tested with different kinetic models and carbon gasification control mechanism was identified to be the appropriate mechanism. The activation energy for the carbon gasification reaction was estimated to be 38.21 kJ/mol.
Key words: zinc ferrite; activation energy; microwave; carbothermal reduction