Structure evolution in the reduction process of FeO powder by hydrogen

Transcription

1 Chinese Journal of Engineering Vol 37 No February huxiaojun@ ustb edu cn 773 ~ 1273 K 873 K 973 ~ 1073 K 973 K 1023 K 973 K 1023 K 1173 K 2 min TF55 Structure evolution in the reduction process of FeO powder by hydrogen YANG Xiao-bo HU Xiao-jun CHEN Zhi-yuan DANG Jie FANG Fei CHOU Kuo-Chih State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing Beijing China Corresponding author huxiaojun@ ustb edu cn ABSTRACT The isothermal hydrogen reduction kinetics of FeO powder at 773 ~ 1273 K was investigated by thermogravimetry Above 873 K there was a turning point in the kinetic curve which indicated that the reduction mechanism changed An unusual temperature effect that the reduction rate decreased with increasing temperature was observed from 973 K to 1073 K To discuss the effect of product structure on the reduction rate of iron oxide the morphology of samples reduced at different temperatures and for different reaction time was observed by scanning electron microscopy It was shown that holes on the sample surface increased gradually the dendritic characteristic appeared with increasing temperature and the sintered phenomenon was obvious at 973 K and 1023 K At a certain temperature holes on the sample surface increased and the sintered phenomenon appeared gradually with prolonging reaction time At 973 K and 1023 K the sample kept fairly the original shape but at 1173 K just reacted for 2 min a large number of dendritic products appeared and sintered gradually Combining the morphology and kinetic curves it can be summarized that interfacial chemical reaction is the rate-limiting step in the initial stage of hydrogen reduction But as the reaction proceeds the reduced iron sinters and the compact structure of the reduced product hinders the outward diffusion of produced gas The rate-limiting step changes to the outward diffusion of produced gas which leads to the decrease of the reduction rate of iron oxide by hydrogen KEY WORDS hydrogen reduction reduction kinetics temperature effect ferrous oxide CO D

2 CO 2 ULCOS COURSE50 H 2 CO Turkdogan Vinters 2 1 FeO X Fig 1 XRD pattern of the FeO powder 2012 POSCO Kim 19 FeO 1 FeO Fe 3 O 4 Fe 2 FeO Fig 2 Morphology of the FeO powder 190 ~ ~ 80 μm X 1 2 HCT K min - 1 H 2 40 ml min - 1 ± 0 5% 100 mg 773 ~ 1273 K ξ = W 0 - W 1 ΔW max W 0 W t ΔW max ΔW max = W 0 - W 3 FeO FeO Fig 3 Isothermal reduction curves of the FeO powder with pure hydrogen at different temperatures 3 FeO 973 ~ 1073 K 973 ~ 10 min 0 6 ~ 1173 K K 190 min 773 K 873 K

3 K 105 min 873 K 773 K 64 min 973 K 190 min 1023 K 93 min 1073 K 873 K 72 min 1173 K 35 min 973 K 1023 K K 1173 K 1173 K min 1173 K K Fig 4 4 a 773 K b 873 K c 973 K d 1023 K e 1073 K f 1173 K Morphologies of samples after reduction at different temperatures a 773 K b 873 K c 973 K d 1023 K e 1073 K f 1173 K Fig K a 2 min b 4 min c 6 min d 8 min e 190 min Morphologies of samples for different reaction time at 973 K a 2 min b 4 min c 6 min d 8 min e 190 min

4 min 2 min 4 ~ 8 min K 973 K Fig K a 2 min b 4 min c 6 min d 8 min e 93 min Morphologies of samples for different reaction time at 1023 K a 2 min b 4 min c 6 min d 8 min e 93 min Fig K a 2 min b 4 min c 6 min d 8 min e 35 min Morphologies of samples for different reaction time at 1173 K a 2 min b 4 min c 6 min d 8 min e 35 min

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