State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences
University of Chinese Academy of Sciences
Binzhou Institute of Technology

废弃煤矿的低体积分数甲烷（1%−3%）通常被直接排放到大气中，但其较高的升温潜势带来了严重的环境问题。在流向变换反应器中直接热氧化甲烷是一种有吸引力的解决方案，但潜在的爆炸和不稳定燃烧等风险限制了其应用。阐明低含量甲烷在流向变换反应器中热氧化的动力学行为是开发工业级反应器的基础。为此，采用数值模拟的方法分析了低含量甲烷热氧化流向变换反应器的自热操作边界，深入研究了热空气导出量对流向变换反应器行为的影响。结果显示，甲烷体积分数超过0.2%即可实现自热操作；甲烷体积分数从0.5%提升至3.0%，最高床温仍维持在1200 °C左右。当甲烷体积分数超过0.5%，可以回收部分热量；相同甲烷含量条件下，最高床温随着热气抽出量的增加而增加；随着甲烷体积分数从0.5%提升到3.0%，允许导出的热空气从12.5%几乎线性地增加到32%。进一步研究发现，以30−50 s的时间间隔反向流动可以确保甲烷的完全转化和床温稳定。上述结果表明，甲烷体积分数在1%−3%时，采用热氧化处理可以实现余热回收；此外，通过调整换向时间和热空气导出量可以实现床层温度控制。

Lean methane from abandoned coal mines or drainage gas with methane concentration of 1%−3% is in general directly discharged into the atmosphere due to the lack of appropriate technology, which has caused serious environmental concerns due to its high global warming potential. While direct thermal oxidation of ultra-low methane in a flow reversal reactor offers an attractive solution, it poses challenges such as potential explosions and unstable combustion flames. Elucidating the dynamic behavior of thermal oxidation of ultra-low methane in a flow reversal reactor is the basis for practical application. To this end, autothermal operation boundary of a pilot-scale thermal flow reversal reactor was examined and the effects of hot gas withdrawal on the behavior of flow reversal reactor was deeply studied. It was found that autothermal operation can be achieved with a methane content of over 0.2% and heat can be recovered if methane content is over 0.5%. Withdrawal of hot air has a significant impact on the dynamic behavior of the reactor: maximum bed temperature at the pseudo-steady state without hot gas extraction keeps almost constant with methane concentration varying in 0.5%−3.0%; whereas for heat recovery by hot gas withdrawal, the maximum bed temperature increases with the increase of the amount of hot gas extracted, and the allowable hot gas exported from the reactor increases nearly linearly from 12.5% to 32% as the methane content increases from 0.5% to 3.0%. Furthermore, the appropriate switching time decreases with the increase of the amount of hot gas withdrawn; for most cases, reversing flow direction at a time interval of 30−50 s can ensure complete methane conversion and stable bed temperature. Thus, it may be concluded that lean methane (1%−3%) can be mitigated by thermal oxidation without worrying about the bed temperature runaway or explosion.

李志凯, 吴志伟, 秦张峰, 董梅, 樊卫斌, 王建国. 低浓度甲烷热氧化流向变换反应器的动态行为及余热回收研究[J]. 燃料化学学报（中英文）, 2024, 52(4): 595-606.

LI Zhikai, WU Zhiwei, QIN Zhangfeng, DONG Mei, FAN Weibin, WANG Jianguo. Dynamic behaviors and heat recovery with hot gas withdrawal of flow reversal reactor for thermal oxidation of lean methane[J]. Journal of Fuel Chemistry and Technology, 2024, 52(4): 595-606.