铁精粉单颗粒高温还原过程中的演化特征

孙爽; 沈中杰; 朱玉龙; 梁钦峰; 刘海峰

doi:10.14135/j.cnki.1006-3080.20201127006

铁精粉单颗粒高温还原过程中的演化特征

doi: 10.14135/j.cnki.1006-3080.20201127006

华东理工大学上海煤气化工程技术研究中心，上海 200237

基金项目: 国家自然科学基金青年基金项目（21908063）；中央高校基本科研业务费专项资金（222201814052）

详细信息

作者简介:
孙爽：孙　爽（1996—），男，硕士生，研究方向为高温气固反应

通讯作者:
沈中杰，zjshen@ecust.edu.cn

中图分类号: TF557
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出版历程
- 收稿日期: 2020-11-27
- 网络出版日期: 2021-01-07

Evolution Characteristics of Single Iron Concentrate Particle During the High-Temperature Reduction Process

Shanghai Engineering Research Center of Coal Gasification, East China University of Science and Technology, Shanghai 200237, China

摘要

摘要: 采用高温热台显微镜原位研究了铁精粉单颗粒在高温及CO气氛下还原过程的演化特征。通过原位实验记录了铁精粉单颗粒的高温还原过程，并利用拉曼光谱仪验证了还原反应产物（单质铁）。结果表明，颗粒表面出现单质铁的时间受温度影响显著，受气体流量影响小。其中，当温度从1 100 ℃升至1 300 ℃时，单质铁的生成时间缩短约75%；当温度从1 300 ℃升至1 400 ℃时，单质铁的生成时间基本不变。当温度为1 100~1 350 ℃时，铁精粉颗粒在还原过程中表面会产生瘤状物，且瘤状物尺寸随着温度升高而增大。引入瘤状物长宽和的平均值为特征尺度l，当还原温度由1 100 ℃升高至1 350 ℃时，l由6 μm增大至15 μm。当还原温度高于1 400 ℃时，铁精粉颗粒出现熔融态的产物分层现象：内层为还原铁，中层为熔融氧化亚铁被还原的树根状金属铁，外层为含有Al、Ca和Si等元素集聚的铁渣。
- 铁精粉 /
- 高温还原 /
- 颗粒演化 /
- 一氧化碳 /
- 显微结构
Abstract: The evolution characteristics of the reduction process of single-iron concentrate particles under high temperature and CO atmospheres were tested in-situ experiment with a high temperature stage microscope. The high-temperature reduction process of the single iron concentrate was recorded via in-situ experiment, and the reduced product (elemental iron) was verified by Raman spectrometer. The results showed that the initial formation time of elemental iron on the particle surface was mainly determined by temperature, and the influence from the gas flow rate was smaller. The initial formation time decreased by 75% when the reducing temperature increased from 1 100 ℃ to 1 300 ℃, but it hardly changed when the temperature increased from 1 300 ℃ to 1 400 ℃. Nodular structures were found on the surface of iron concentrate particles during the reduction process between 1 100 ℃ and 1 350 ℃, and their sizes increased with the rising reduction temperature. A characteristic number l, which was self-defined as the mean value of the length and width of the particles, increased from 6 μm at 1 100 ℃ to 15 μm at 1 350 ℃. When the reduction temperature was above 1 400 ℃, layered melting products were observed for the iron concentrate particle. The product on the core was reduced iron, the one on the second layer was the root-shaped metal iron with reduced molten ferrous oxide, and the other one on the outer layer was the iron slag containing Al, Ca, Si, and other elements.
- iron concentrate particle /
- high temperature reduction /
- particle evolution /
- CO /
- microstructure

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图 1 铁精粉的XRD图谱

Figure 1. XRD of iron concentrate particles

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图 2 高温热台显微镜的结构示意图

Figure 2. Structure diagram of HTSM

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图 3 1 300 ℃下铁精粉在CO（200 mL/min）气氛下还原10 min后与反应前的拉曼光谱对比图

Figure 3. Comparison of Raman after and before reduction at 1 300 ℃ and 200 mL/min CO for 10 min

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图 4 不同温度下CO（200 mL/min）还原铁精粉的过程

Figure 4. Process of reducing iron concentrate particle by CO (200 mL/min) at different temperatures

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图 5 铁精粉颗粒在不同的CO流量下生成单质铁的时间随温度的变化

Figure 5. Change of the time of elemental iron produced by iron concentrate particles with temperature under different CO flow rates

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图 6 1 400 ℃铁精粉颗粒还原反应后的SEM-EDS

Figure 6. SEM-EDS of iron concentrate particles after reduction reaction at 1 400 ℃

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图 7 1 400 ℃熔融部分面扫描结果

Figure 7. Results of melting part surface scanning at 1 400 ℃

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图 8 铁精粉颗粒在不同温度下的SEM

Figure 8. SEM of iron concentrate particles at different temperatures

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图 9 不同CO流量下瘤状物特征尺度随温度变化图

Figure 9. Characteristic scale of nodules varies with temperature under different CO flow rate

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图 10 低温（1 100 ~1 350 ℃）下铁精粉单颗粒还原生成铁单质的结构变化图

Figure 10. Structure change diagram of single-particle reduction of iron concentrate partical at low temperature (1 100 ~1 350 ℃) to produce iron

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图 11 高温（1 400 ℃以上）下铁精粉单颗粒还原生成铁单质的结构变化图

Figure 11. Structure change diagram of single-particle reduction of iron concentrate particle at high temperature (above 1 400 ℃) to produce iron

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表 1 铁精粉的化学组成

Table 1. Chemical composition of iron concentrate powder

w/%
TFe SiO₂ MgO CaO Al₂O₃

53.04 19.37 2.897 6.52 1.46

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表 2 各种铁氧化物的拉曼频率^[26-27]

Table 2. Raman frequency of different iron oxide^[26-27]

Sample Raman shift/cm⁻¹

α-Fe₂O₃ 227　246　293　411　497　612　1 320
Fe₃O₄ 302　513　534　663
γ-FeOOH 252　380　526　650　1 307

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