The Role of MgO Powder in Preventing Defluidization during Fluidized Bed Reduction of Fine Iron Ores with Different Iron Valences

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• 作者：Zhan Du ; Qingshan Zhu ; Yafeng Yang ; Chuanlin Fan ; Feng Pan ; Haoyan Sun and Zhaohui Xie
• 刊名：steel research international
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：87
• 期：12
• 页码：1742-1749
• 全文大小：1589K
• ISSN：1869-344X

文摘

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 > Fe₃O₄ > Fe₂O₃ 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 Fe₃O₄ and FeO at 1173 K is mainly attributed to the formation of Fe₂MgO₄ and MgO · FeO compounds on the surface, respectively. As a result, the required MgO content to prevent defluidization is sequenced as m(Fe₂O₃) > m(Fe₃O₄) > m(FeO) at 1173 K. Consequently, the MgO addition at the FeO stage will be more effective in preventing defluidization than the addition at Fe₂O₃ and Fe₃O₄ stages during multi-stage fluidized bed reduction of fine iron ores.