Kinetics of magnetite oxidation under non-isothermal conditions
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Oxidation of magnetite concentrates, which occurs during the pellet induration process, must be deeply understood to enable the appropriate design of induration machines. In the present paper, the kinetics of the magnetite oxidation reaction was studied. Primary samples were obtained from the Gol-e-Gohar iron ore deposit. Magnetic separation and flotation decreased the sulfur content in the samples to be approximately 0.1wt%. Thermogravimetric analysis was used to measure mass changes during the oxidation of magnetite and, consequently, the conversion values. The aim of this study was to use isoconversional methods to calculate the kinetic parameters. The Coats–Redfern method was also used to obtain the activation energy. Thermogravimetric analyses were run at three different heating rates. The Coats–Redfern results were too ambiguous for a meaningful interpretation. In the case of the isoconversional method, however, the mean activation energy and pre-exponential factor of the oxidation reaction were obtained as 67.55 kJ and 15.32 × 108 min−1, respectively. Such a large activation energy implies that temperature strongly affects the reaction rate. The oxidation reaction exhibits a true multi-step nature that is predominantly controlled by chemical reaction and diffusion mechanisms.
Keywordsmagnetite kinetics oxidation thermogravimetric analysis
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- K. Meyer, Pelletizing of Iron Ores, Vol. 1, Springer-Verlog, Berlin, 1980.Google Scholar
- S.P.E. Forsmo, S.E. Forsmo, P.O. Samskog, and B.M.T. Björkman, Mechanisms in oxidation and sintering of magnetite iron ore green pellets, Powder Technol., 183(2008, No. 2, 247.Google Scholar
- E.R. Monazam, R.W. Breault, and R. Siriwardane, Kinetics of magnetite (Fe3O4) oxidation to hematite (Fe2O3) in air for chemical looping combustion, Ind. Eng. Chem. Res., 53(2014, No. 34, 13320.Google Scholar
- S. Vyazovkin, K. Chrissafis, M.L.D. Lorenzo, N. Koga, M. Pijolat, B. Roduitf, N. Sbirrazzuoli, and J.J. Suñol, ICTAC Kinetics Committee recommendations for collecting experimental thermal analysis data for kinetic computations, Thermochim. Acta, 590(2014, 1.Google Scholar
- S.P.E. Forsmo, Influence of Green Pellet Properties on Pelletizing of Magnetite Iron Ore [Dissertation], Lulea University of Technology, Lulea, 2007, p. 37.Google Scholar
- T. Kujirai and T. Akahira, Effect of temperature on the deterioration of fibrous insulating materials, Sci. Pap. Inst. Phys. Chem. Res., 2(1925, 223.Google Scholar
- J.H. Flynn and L.A. Wall, A quick, direct method for the determination of activation energy from thermogravimetric data, J. Polym. Sci. Part C, 4(1966, No. 5, 323.Google Scholar
- ASTM, E1641: Standard Test Method for Decomposition Kinetics by Thermogravimetry, ASTM International, West Conshohocken, PA, 2004.Google Scholar
- R. Ebrahimi-Kahrizsangi and M.H. Abbasi, Evaluation of reliability of Coats–Redfern method for kinetic analysis of non-isothermal TGA, Trans. Nonferrous Met. Soc. China, 18(2008, No. 1, 217.Google Scholar
- J.E. House, Principles of Chemical Kinetics, 2nd Ed., Vol. 1, Academic Press, Burlington, 2007.Google Scholar