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The Role of MgO Powder in Preventing Defluidization during Fluidized Bed Reduction of Fine Iron Ores with Different Iron Valences
Author(s) -
Du Zhan,
Zhu Qingshan,
Yang Yafeng,
Fan Chuanlin,
Pan Feng,
Sun Haoyan,
Xie Zhaohui
Publication year - 2016
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.201600122
Subject(s) - materials science , iron powder , metallurgy , fluidized bed , diffusion , direct reduced iron , microanalysis , valence (chemistry) , electron probe microanalysis , chemistry , electron microprobe , physics , organic chemistry , thermodynamics
The role of MgO powder in preventing defluidization during the fluidized bed reduction of fine iron ores with different iron valences is investigated. The inhibiting effect of MgO powder on different types of fine iron ores is the same at 973 K, whereas it is sequenced as FeO > Fe 3 O 4 > Fe 2 O 3 at 1073 and 1173 K. Specific diffusion couples are employed to clarify the valence‐dependent inhibiting mechanism. Electron probe microanalysis, X‐ray diffraction results, and the estimation of diffusion activation energy indicate that the inhibiting effect of MgO powder on defluidization is mainly caused by the physical barrier effect for all iron oxides below 1073 K, while the defluidization prevention of Fe 3 O 4 and FeO at 1173 K is mainly attributed to the formation of Fe 2 MgO 4 and MgO · FeO compounds on the surface, respectively. As a result, the required MgO content to prevent defluidization is sequenced as m(Fe 2 O 3 ) > m(Fe 3 O 4 ) > m(FeO) at 1173 K. Consequently, the MgO addition at the FeO stage will be more effective in preventing defluidization than the addition at Fe 2 O 3 and Fe 3 O 4 stages during multi‐stage fluidized bed reduction of fine iron ores.