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微波氢等离子体反应特性研究

Reaction Characteristics of Microwave Hydrogen Plasma

  • 摘要: 氢气作为未来主要的清洁能源,将在未来绿色冶金领域发挥关键作用。本文以低温等离子体辅助氢气直接还原炼铁为背景,基于不同已有等离子体反应模型和LXcat数据库建立了二维微波氢气等离子体模型。对比文献实验结果验证了所建立等离子体反应模型和体系的正确与合理性,在此基础上研究得到了微波功率和气体压力变化对等离子体电子密度、以及在铁矿石还原中起主要作用的激发态氢气分子浓度等关键参数的影响特性。结果表明,介质压力一定而微波功率升高,则电子密度升高,但激发态氢气摩尔浓度存在一明显峰值变化过程;当微波功率一定而介质压力升高,则电子密度呈一定指数下降趋势,激发态氢气摩尔浓度保持单调递增状态,不过激发态氢气摩尔分数变化则存在一峰值。另外,分析讨论了微波功率相对过大或气体压力相对过小氢气分子激发态浓度及摩尔分数出现峰值变化的原因与特性。本研究在一定程度上揭示了微波等离子体随微波参数变化的机理特征,可为氢气还原氧化铁绿色冶金相关理论进一步研究和应用提供参考。

     

    Abstract: Hydrogen will be the main clean energy in the future, which will play a key role in the future’s green metallurgy. Taking low temperature plasma aided hydrogen direct reduction rection of iron ore as a background, a two-dimensional numerical model was established to study the reaction characteristics of microwave hydrogen plasma by combining reaction mechanisms from different literature and data from LXcat database. Compared with the experimental results in the literature, the rationality and reliability of the plasma model were verified. Based on that, the effects of the input power of the microwave and gas pressure of the plasma on the indicators such as electron density and concentration of excited hydrogen molecule (H2s) in the plasma were investigated, which obtained key parameters for the iron ore reduction. The results show that, at a constant pressure of plasma medium and an increasing input power of the microwave, the electron density increases, while there exists a peak value with the H2s concentration. When the pressure of the plasma medium increases, at a certain microwave power, the electron density decreases exponentially, and the H2s concentration keeps monotonically increasing, whereas its molar fraction shows a peak with the variation. Furthermore, the reasons and characteristics for having peak in variation of the concentration and the fraction of H2s, respectively, in the plasma reaction are discussed when the microwave power or the gas pressure reaches beyond a critical value. Such a study is expected to provide a theoretical reference for further research and application of hydrogen plasma iron oxide reduction in green iron making.

     

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