多裂隙盖层下煤堆积床阴燃的实验和反演计算

Experimental and Inverse Computational Study on Smoldering in Packed Coal Beds Under Multi-Cracks Covering Layers

摘要

为了解地表裂隙对地下煤火（UCFs）中氧传输及温度分布的影响机制，设计了含多裂隙盖层的煤阴燃实验系统。通过控制裂隙间距与宽度，对多裂隙条件下煤堆积床的阴燃传播过程、温度场及烟气排放特性进行了实验研究，并结合氧反应-输运模型反演计算了煤层内部氧浓度分布。结果表明：裂隙宽度显著影响阴燃传播，在本实验条件下（褐煤样品，粒径小于 0.5 mm）维持阴燃自传播的临界裂隙宽度接近 6 mm；多裂隙条件下阴燃传播呈现非连续特征，局部高温区域与缺氧区域具有一致性，阴燃平均峰值温度较开放环境降低 21.1%；数值计算发现，横向扩散与热浮力协同作用使局部区域氧浓度衰减延迟 0.75 h，衰减幅度减少 49%，从而形成并维持高温热点.研究结果可为揭示多裂隙覆盖层下煤层阴燃特性提供一定参考.

Abstract

To investigate the influence of the surface cracks on oxygen transport and temperature distribution in underground coal fires（UCFs），an experimental system of coal smoldering with the multi-cracked covering layers was designed.The smoldering propagation，temperature field，and the emission of the packed coal bed were studied by controlling the crack spacing and width.The oxygen concentration distribution inside the coal seam was in-versely calculated by combining an oxygen reaction-transport model.The results showed that：（1）The critical frac-ture width for self-sustained smoldering propagation was found to be ≈6 mm in lignite samples（particle diameter < 0.5 mm），confirming fracture width as a dominant parameter.（2）Under multi-crack conditions，discontinuous smoldering propagation was observed，where localized high-temperature zones were found to coincide with oxy-gen-deficient regions，and the average peak temperature was reduced by 21.1% compared to that in an open envi-ronment.（3）Through numerical calculations，oxygen concentration decay in localized regions was delayed by 0.75 h and its magnitude was reduced by 49% due to the synergistic effect of transverse diffusion and thermally buoyant transport，thereby enabling the formation and maintenance of high-temperature hotspots.These findings provide insights into the smoldering characteristics of coal seams under multi-cracked covering layers.

关键词

地下煤火 / 多裂隙盖层 / 阴燃 / 温度场 / 氧浓度反演

Key words

underground coal fires / multi-cracked covering layers / smoldering / temperature field / oxygen concentration inversion

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基金资助

国家自然科学基金资助项目(52276130)