铁氧化物富氢还原动力学研究

发布时间：2018-01-02 05:00

本文关键词：铁氧化物富氢还原动力学研究　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：随着全球对CO：温室气体排放的限制越来越严格,冶金工作者们重新开始重视氢还原方面的研究。然而要实现氢还原在冶金中的实际应用,需要进一步全面了解氢还原的反应特征和控制方法。目前为止,虽然铁氧化物氢还原已有许多研究,但对某些特殊行为,如反应速率随温度的升高异常下降仍没有确切解释。此外,高温下产物易粘结、富氢还原低温易析碳、还原气体利用率低、廉价氢气的大规模制备等问题仍然存在,需要人们去解决。本文从氢还原动力学及产物结构变化的角度,对上述部分问题加以研究,分析不同还原条件对其的影响。使用热重分析法对Fe_2O_3粉体、Fe304粉体、FeO粉体和薄片状FeO在等温和非等温条件下的静态还原过程进行了研究,考察了温度、还原气体成分、分压、恒温时间等因素对还原动力学和反应机理的影响。结合扫描电镜和XRD检测,对不同还原条件下速率、还原分数变化及产物烧结现象进行了分析,主要结论如下。Fe_2O_3粉体和Fe304粉体在还原过程中均有反常温度效应出现,反应速率随温度升高而减小,速率异常变化与FeO→Fe阶段的还原有关。Fe_2O_3粉体873K以上还原过程中Fe3O4→FeO与FeO→Fe是同步进行的。纯氢中出现少量CO可使速率发生较大下降。温度低于1173K的保温过程不影响还原前后的反应速率和产物烧结,烧结只发生在还原过程中。FeO粉体在933-1073K还原过程中现了反常的温度效应,产物烧结和致密化现象是主要原因。H_2-Ar等温还原研究表明,在973 K-1023 K,氢气含量的增加使得最终还原度降低。产物结构分析显示,氢气含量增加使得新生铁相粘结加剧,阻碍反应气扩散。H_2-CO等温还原研究表明,873K和973K还原中存在明显的析碳反应。873K,30%H_2+70%CO条件下最易发生析碳反应,高温还原可有效避免其发生。
[Abstract]:With the global CO: to limit greenhouse gas emissions more and more strict, the metallurgy workers begin to attach importance to the hydrogen reduction of the hydrogen reduction. However in order to realize the practical application in metallurgy, the need for further comprehensive understanding of reaction characteristics and control methods of hydrogen reduction. So far, although there have been many studies on reduction of iron oxide, but for some special behavior, such as the reaction rate increases with the increase of temperature anomaly decline still did not explain exactly. In addition, the product is easily under high temperature bonding, hydrogen rich reducing carbon reduction gas at low temperature, low utilization rate, large cheap hydrogen gas production still exists, need to be solved. In this paper, angle reduction kinetics and product the structure changes from hydrogen, to study on the part of the problem, analysis of the influence of different conditions on the reduction. Using the thermogravimetric analysis of Fe_2O_3 powder, Fe304 powder, FeO powder and Slice FeO in static conditions under isothermal and non isothermal reduction process was studied, the effects of temperature, reducing gas composition, pressure, temperature and other factors on the impact of time reduction kinetics and reaction mechanism. Combined with scanning electron microscopy and XRD assay of different reduction conditions rate, reducing fraction and product sintering phenomenon has carried on the analysis, the main conclusions are as follows.Fe_2O_3 powder and Fe304 powder were in the reduction process of abnormal temperature effect, the reaction rate decreases with the increase of the temperature, the above reduction of.Fe_2O_3 powder 873K and FeO, Fe abnormal rate of change stage of the reduction process of Fe3O4, FeO and FeO, Fe is synchronized with the pure. In a small amount of CO can make the hydrogen rate greatly decreased. The temperature is lower than the thermal process of 1173K does not affect the reaction rate and product reduction before and after sintering, the sintering occurs only in the reduction process of.FeO powder in 9 In the process of the 33-1073K reduction effect of temperature anomalous, product sintering and densification phenomenon is the main reason of.H_2-Ar isothermal reduction studies show that in 973 K-1023 K, increasing the hydrogen content of the final reduction degree decreased. The analysis shows that the product structure, increase the content of hydrogen bond makes the new iron phase intensifies, hinder the reaction gas diffusion.H_2-CO isothermal reduction research show that 873K and 973K have obvious reduction of carbon precipitation reaction of.873K, the most prone to carbon deposition reaction under 30%H_2+70%CO conditions, high temperature reduction can be effectively avoided.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF511

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