Abstract
Growth process of iron whiskers and mechanism of CaO influence on precipitation morphology of metallic iron at the gas-solid interfaces was studied. Analytical reagents of Fe(NO3)3 and Ca(NO3)2 aqueous solution were used to prepare sheet film sample of Fe2O3-CaO by thermal decomposition at high temperature. In-situ observation was conducted using a stereo optical microscope and a hot-stage. And reduction kinetics of samples was studied by thermo gravimetric (TG) method. Some samples after reduction were analyzed by using the scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and fourier transform infrared (FT-IR) spectrometer. Results indicate that during the reduction of iron oxides with CO, metallic iron is mostly precipitated as whisker and the precipitation behavior mainly depends on reduction rate. Doping CaO can significantly increase the reduction rate and effectively change the precipitation morphology of metallic iron after the reduction. When CaO doping concentration is less than i% (mass percent), CaO can promote whisker formation of reduced iron; as it reaches 6% (mass percent), CaO inhibits iron whiskers growth; as it is more than 8% (mass percent), no whiskers could be observed. Therefore, controlling the quantity of Ca2+ is effective to control the formation and growth of iron whiskers during gaseous reduction and thus eliminating ore grain sticking caused by intertexture of iron whiskers.
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References
Institute of Chemical Metallurgy of Chinese Academy of Sciences, Institute of Scientific and Technical Information of China. Gas ironmaking in Fluidized Bed [M]. Beijing: Scientific and Technology Literature Publishing House, 1977 (in Chinese).
Komatina M, Gudenau H W. The Sticking Problem During Direct Reduction of Fine Iron Ore in the Fluidized Bed [J]. Meta-lurgija, 2004, 10(4): 309 (in German).
FANG Jue. Sticking Problem in Fluidized Bed Iron Ore Reduction [J]. Iron and Steel, 1991, 26(5), 11 (in Chinese).
QI Yuan-hong, XU Hai-chuan. Separating Morphology of Iron and Sticking Behavior of Iron Ore in Reducing Fluidized Bed [J]. Journal of Iron and Steel Research, 1996, 8(5): 7 (in Chinese).
Iguchi Y, Uyeda Y, Goto K, et al. In Situ Observation of Nu-cleation and Growth of Iron Whiskers From Supersaturated Wüstite [J]. Oxidation of Metals, 1994, 42(1): 103.
Bleifuss R L. Calcium as a Cause of Catastrophic Swelling of Pellets During Reduction [J]. Trans Soc Min Eng AIME, 1970, 247(3): 225.
Burghardt O, Kortmann H, Grover B. Influence of Mineral Composition on the Quality of Iron Ore Pellets [J]. StahlEisen, 1970, 90(13): 661.
Degel R. Iron Ore Reduction in Fltrfdized-Bed With Hydrogen-Rich Gas: Sticking and Approaches [D]. Aachen: RWTH Aachen, 1996.
Hayashi S, Sayama S, Igushi Y. Relation Between Sulphur-pressare and Sticking of Fine Iron Ores in Fluidized Bed Reduction [J]. ISIJ International, 1992, 32(9): 962.
Abdel Halim K S, Bahgat M, El-Kelesh H A, et al. Metallic Iron Whisker Formation and Growth During Iron Oxide Reduction; Basicity Effect [J]. Ironmaking and Steelmaking, 2009, 36(8): 631.
Schiller M. Micro-Morphology of Iron Phase as Result of Reduction of Iron Oxides [D]. Aachen: RWTH Aachen, 1987.
Shigematsu N, Iwai H. Effect of CaO Added With SiO2 and/or Al2O3 on Reduction Rate of Dense Wüstite by Hydrogen [J]. ISU International, 1989, 29(6): 486.
Kashiwaya Y, Yamaguchi Y, Kinoshita H, et al. In Situ Observation of Reduction Behavior of Hematite With Solid Carbon and Crystallographic Orientation Between Hematite and Magnetite [J]. ISIJ International, 2007, 47(2): 226.
Gillot B, Benloucif R M, Rousset A. A Study of Infrared Absorption in the Oxidation of Zinc-Substituted Magnetites to Defect Phase γ and Hematite [J]. Journal of Solid State Chemistry, 1981, 39(3): 329.
Fukuyama H, Hossain K, Nagata K. Solid-State Reaction Kinetics of the System CaO-FeO [J]. Metallurgical and Materials Transactions, 2002, 33B(2): 257.
Shannon By R D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances [J]. Acta Cryst, 1976, 32A(5): 751.
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Foundation Item: Item Sponsored by National Natural Science Foundation of China (50834007); National Basic Research Program of China (2012CB720401)
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Zhao, Zl., Tang, Hq. & Guo, Zc. Effects of CaO on Precipitation Morphology of Metallic Iron in Reduction of Iron Oxides Under CO Atmosphere. J. Iron Steel Res. Int. 20, 16–24 (2013). https://doi.org/10.1016/S1006-706X(13)60120-X
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DOI: https://doi.org/10.1016/S1006-706X(13)60120-X