煤田火区自燃气体滞留机制及早期探测技术研究

Coal fire is a kind of natural disaster which caused by coal spontaneous combustion and other external factors in coalfield outcrop and shallow region, with great harm and wide influence scope. In China, coalfield fire areas are all concentrated in the northwest area and the northwest region will be the largest coal production base in the future. Identification and monitoring of coalfield fire area, coal fire treatment and comprehensive utilization, and fire area ecological restoration are the main tasks and imperative requirements for the government and coal enterprises in the future. The content of the project include: (1) study the dominant channels, vertical leakage and soil retention of spontaneous combustion gas products in coal field fire area; (2) analyze the soil microchange caused by spontaneous combustion product, the spatial and temporal distribution characters and differences of spontaneous combustion gas products in soil; (3) develop the soil-atmospheric spontaneous combustion product flux monitoring technology in spontaneous combustion area based on geochemical detection and unmanned detection; (4) study the mass transfer law in soil-atmospheric boundary of coalfield fire area; (5) develop the detecting early spontaneous combustion standard of coal fires and its practice application. The fruits will provide theoretical and technical support for the early detection of coalfield fire area and the prediction of the development trend of the existing coal field fire area. It is significant to raise early detection and control level of coal fire, reduce the difficulty and engineering quantity of extinguishing coal fire, and save the cost and time of extinguishing fire.

煤火是煤田露头和浅部区域因煤层自燃和其他外部因素引发产生的一种自然灾害，危害大，影响范围广。我国煤田火区全部集中在西北地区，西北地区将是我国未来主要的煤炭生产基地。煤田火区的识别和监测、煤火治理与综合利用以及火区生态恢复仍将是今后政府和煤炭企业的主要任务和迫切需求。项目以煤田火区为研究对象，研究煤田火区自燃气体产物迁移的优势通道、垂向渗漏和土壤滞留规律，自燃产物引起的土壤微变化规律，自燃气体产物在土壤中时空分布特征和差异性；研究基于地球化学探测与无人探测相结合的自燃火区土壤-大气自燃产物通量监测技术，煤田火区气体的土壤-大气边界传质规律及煤火早期自燃探测指标，并进行现场实践应用。研究成果对于较为准确地探测早期煤田火区及预测现存煤田火区发展趋势提供强有力的理论和技术支撑，对提高煤田火区早发现和早治理水平、降低煤田火区灭火难度和工程量、节约灭火成本和灭火时间有重要意义。

项目研究了煤田火区自燃气体产物在上覆介质中的迁移和滞留规律，以及火区自燃初期状态判别标准和早期综合探测技术。基于煤田火区实地调研，分析了我国西北地区原始煤田火区的燃烧状态以及地下煤火自燃产物引起地表土壤、植被的特性，获取了原始煤田火区浅层地表及火区填埋区浅层地表自燃气体浓度分布及其与土壤理化性质变化的相关性，揭示了地下煤火自燃气体产物滞留对土壤介质理化性质的影响特征，确定了煤田火区早期探测的关键性指标。研发了一种含裂缝、断层以及土壤的煤火综合模拟实验台和气体采集分析系统，实现了对煤田火区典型自燃气体运移规律的实验分析，获取了不同地质条件下浅层地表中自燃气体的扩散规律，确定了影响浅层地表自燃气体分布的主要地质因素。构建了大气环境影响煤田火区模拟实验平台，获取了大气环境参数对煤田火区浅层地表自燃气体迁移规律的影响特征。基于浓度梯度法，研发了一种多区域同步监测煤田火区燃烧早期自燃气体通量的设备与系统，实现了地表环境因素、土壤物理因素、裂隙口物理特征、CO2与CO浓度的同步在线耦合探测。并在实际火区不同区域通过同步监测的方式，获取了示范煤火区域的自燃气体的土壤-大气界面传质机制以及垂向分布特征。分析了煤田火区自燃气体碳源-碳汇特征和排放途径，构建了煤田火区自燃气体排放通量模型。基于对煤田火区早期阶段土壤、大气、环境特征的调查结果，构建了由浅层土壤、大气空间、地表环境三部分组成的煤田火区土壤-大气-环境早期自燃状态判别指标体系，提出了适用于煤田火区早期探测稳定性的临界深度，并进行了实践应用。项目研究成果对于提高煤田火区早发现、早治理水平，以及丰富评估煤田火区环境效应理论具有重要的理论意义和实践价值。