磁场对含CaO铁氧化物还原的影响

doi:10.11900/0412.1961.2018.00492

金属学报

2019, Vol. 55

Issue (3): 410-416 DOI: 10.11900/0412.1961.2018.00492

本期目录 | 过刊浏览

磁场对含CaO铁氧化物还原的影响

金永丽^1,²,于海²,张捷宇¹,赵增武³(

)

1. 上海大学材料科学与工程学院上海 200444
2. 内蒙古科技大学材料与冶金学院包头 014010
3. 内蒙古科技大学内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室包头 014010

Effects of Magnetic Field on Reduction of CaOContaining Iron Oxides

Yongli JIN^1,²,Hai YU²,Jieyu ZHANG¹,Zengwu ZHAO³(

)

1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
2. School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China
3. Inner Mongolia Key Laboratory for Utilization of Bayan Obo Multi-Metallic Resources, Inner Mongolia University of Science and Technology, Baotou 014010, China

引用本文:

金永丽,于海,张捷宇,赵增武. 磁场对含CaO铁氧化物还原的影响[J]. 金属学报, 2019, 55(3): 410-416.
Yongli JIN, Hai YU, Jieyu ZHANG, Zengwu ZHAO. Effects of Magnetic Field on Reduction of CaOContaining Iron Oxides[J]. Acta Metall Sin, 2019, 55(3): 410-416.

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摘要:

以分析纯Fe₂O₃和Fe₂O₃掺杂2.5%CaO (质量分数) 2种体系为研究对象，在1073 K、75%CO+25%CO₂ (体积分数)气氛中进行有磁和无磁条件下的等温还原实验，研究了磁场作用下CaO对铁氧化物还原的影响。结果表明：磁场加快了铁氧化物还原生成金属Fe的反应速率，反应过程中相组成未发生变化；磁场促进了Ca元素在Fe₂O₃+2.5%CaO体系内的扩散，还原样品呈疏松多孔状。通过热力学计算可知，磁场降低了Fe₂O₃还原和CaFe₅O₇相分解反应的Gibbs自由能，提高了反应平衡常数，使铁氧化物的还原和中间相CaFe₅O₇的分解反应更容易进行。

关键词 ：磁场, 直接还原, Fe₂O₃, CaO, 平衡常数

Abstract：

Iron ore direct reduction is an attractive alternative route for effective use of low-grade complex symbiotic iron ore resources as well as reducing CO₂ emissions from steel making. In this process, solid iron ore pellets are converted to so-called direct reduced iron with a reduction gas such as CO and H₂. However, the slow reduction rate of iron oxides at lower temperatures has restricted the productivity of direct reduced iron. We have been studying the use of a magnetic field to enhance the direct reduction process, and investigating the influences of the magnetic field on the reduction of iron oxides and morphology of direct reduced iron. Iron ores are rich in iron oxides and also contain other oxides. The presence of other oxides, for instance CaO, is likely to interact with iron oxides during reduction so as to enhance the reduction rate by varying the lattice structure of solid iron oxides and gas/solid mass transport. In the present work, the effects of magnetic field on the reduction of CaO-containing iron oxides were studied. Isothermal reduction of compact samples of pure Fe₂O₃ and 2.5%CaO (mass fraction) containing Fe₂O₃ was carried out at 1073 K under a reaction atmosphere 75%CO+25%CO₂ (volume fraction). A constant magnetic field (B=1.02 T) was applied during reduction to compare with the reaction under a normal condition without a magnetic field applied. The results showed that the magnetic field accelerates the reaction rate of Fe₂O₃ reduction to metallic Fe, and there are no phase compositions change during reduction in a constant magnetic field. The magnetic field promotes the diffusion of Ca in Fe₂O₃+2.5%CaO, and the reduced sample obtained in a magnetic field appears loose and porous. Thermodynamic calculation indicated that the Gibbs free energy of Fe₂O₃ reduction and CaFe₅O₇ phase decomposition is decreased with an interaction of magnetic field, resulting in an increase of the reaction equilibrium constant thus making the reduction of Fe₂O₃ and decomposition of intermediate phase CaFe₅O₇ occur more readily.

Key words： magnetic field direct reduction Fe₂O₃ CaO equilibrium constant

收稿日期: 2018-11-01

ZTFLH:

TF01

基金资助:国家自然科学基金项目(51464039);国家自然科学基金项目(51464040)

作者简介: 金永丽，女，1973年生，副教授

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https://www.ams.org.cn/CN/10.11900/0412.1961.2018.00492 或 https://www.ams.org.cn/CN/Y2019/V55/I3/410

图1 磁场还原炉示意图

图2 纯Fe2O3和Fe2O3+2.5%CaO体系等温还原度曲线图

图3 磁场条件和常规条件下不同还原时间Fe2O3+2.5%CaO体系样品的XRD谱

表1 图4中各点EDS分析结果

图4 磁场和常规条件下纯Fe2O3和Fe2O3+2.5%CaO体系在不同时间还原后样品的SEM像

图5 磁场条件下还原30 min后Fe2O3+2.5%CaO样品SEM像和面扫描

Process	Equation (2)		Equation (3)
	Equation (2)		Equation (3)
	Gibbs free energy J·mol^-1	K	Gibbs free energy J·mol^-1	K
	Gibbs free energy J·mol^-1		Gibbs free energy J·mol^-1

NC	$Δ G ?$ = -3.0720×10⁴	31.299	$Δ G ?$ = -3.4127×10⁵	9.4330×10³
CMF	ΔG^T= -3.1523×10⁴	34.243	ΔG^T= -8.4863×10⁵	1.3531×10⁴

表2 还原过程中反应Gibbs自由能和平衡常数

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