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Effects of CaO on Precipitation Morphology of Metallic Iron in Reduction of Iron Oxides Under CO Atmosphere

Effects of CaO on Precipitation Morphology of Metallic Iron in Reduction of Iron Oxides Under CO Atmosphere
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摘要 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 4% (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. 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 Fe2 O3-CAO by thermal decomposition at high temperature. In-situ observation was con-ducted using a stereo optical microscope and a hot-stage. And reduction kinetics of samples was studied by thermo gravimetrie (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 indi-cate that during the reduction of iron oxides with CO, metallic iron is mostly precipitated as whisker and the precipi- tation behavior mainly depends on reduction rate. Doping CaO can significantly increase the reduction rate and effec-tively change the precipitation morphology of metallic iron after the reduction. When CaO doping concentration is less than 4% (mass percent), CaO can promote whisker formation of reduced iron; as it reaches 6% (mass per- cent), CaO inhibits iron whiskers growth; as it is more than 8% (mass percent), no whiskers could be observed. Therefore, controlling the quantity of Ca^2+ 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.
作者 ZHAO Zhi-long TANG Hui-qing GUO Zhan-cheng ZHAO Zhi-long, TANG Hui-qing, GUO Zhan-cheng (1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China~ 2. Iron and Raw Material Handling Division, MCC Capital Engineering and Research Incorporation, Beijing 100176, China)
出处 《钢铁研究学报:英文版》 SCIE CAS CSCD 2013年第7期16-24,共9页 Journal of Iron and Steel Research
基金 Item Sponsored by National Natural Science Foundation of China (50834007) National Basic Research Program of China (2012CB720401)
关键词 铁氧化物 降水形态 金属铁 CAO CO 傅里叶变换红外光谱 Fe(NO3)3 还原动力学 stereo optical microscopes in-situ observations gaseous direct reductions iron whiskers sticking
作者简介 ZHAO Zhi-long(1984-), Male, Doctor; E-mail: zz1123222@126, com; Corresponding Author: TANG Hui-qing(1970-), Male, Associate Pro{essor; E-mail: hqtang@ustb, edu. cn
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