关闭/废弃煤矿甲烷排放研究现状及减排对策

Research status and reduction strategies of methane emissions from closed/abandoned coal mines

全球正向低碳能源结构转型,加之煤矿资源枯竭、瓦斯灾害等问题,关闭/废弃煤矿数量快速增加。煤矿关闭退出后,采空区残存甲烷持续向地面逸散,成为温室气体重要排放源。针对关闭/废弃煤矿甲烷残存量、排放速率、减排措施等系列问题,通过大量文献调研、梳理,明确了国内外关闭/废弃煤矿数量及高瓦斯矿井分布,归纳总结了采空区残存甲烷来源及残存量的估算方法,并借鉴天然气成藏研究领域中甲烷地质渗漏理论与研究方法,分析了残存甲烷排放机制及监测手段,最后提出了残存甲烷减排对策及面临挑战。研究发现:我国山西、贵州、重庆、湖南、江西等地区存在大量关闭/废弃煤矿,且残余煤主要是具有强甲烷吸附力的无烟煤,导致矿井残存甲烷量大,成为重要甲烷排放源;关闭/废弃煤矿甲烷从残余煤中解吸释放至采空区,然后经由井口、采动裂隙等通道排放至大气;通过卫星遥感、通量室法、地球化学探针法、微气象技术等手段,可实现对煤矿甲烷排放的有效监测。基于甲烷排放预测模型预测,到2050年关闭/废弃煤矿排放甲烷在煤炭开采释放甲烷总量中占比可能超过20%,解决关闭/废弃矿井甲烷排放问题刻不容缓。为此,提出了抽采利用、原位爆燃发电、微生物降解甲烷、注水淹没、甲烷排放通道封堵等减排对策,综合考虑减排成本、甲烷排放持续时间、地下水污染等限制性因素,认为采用矿化修复方法封堵覆岩采动微裂隙,可低成本实现关闭/废弃煤矿甲烷减排目标。

With the global transition to a low-carbon energy structure,coupled with the depletion of coal mine resources,gas disasters,and other problems,the number of closed/abandoned coal mines is increasing rapidly.After the coal mine closes,the residual methane in the goaf escapes to the ground continuously,becoming an essential source of greenhouse gas emissions.In view of a series of issues such as methane residual stock,emission rate and emission reduction measures in closed/abandoned coal mines,the number of closed/abandoned coal mines and the distribution of high-gas mines athome and abroad were clarified through a large number of literature review,and the sources and estimation methods of methane residual stock were summarized.At the same time,the theory and research method of methane geological leak-age in the field of natural gas accumulation was used for reference,and the emission mechanism and monitoring means of residual methane were analyzed.Finally,the countermeasures and challenges of residual methane emission reduction were put forward.The study found that there are many closed/abandoned coal mines in Shanxi,Guizhou,Chongqing,Hunan,Ji-angxi,etc.,and the residual coal is mainly anthracite with strong methane adsorption capacity,resulting in a large amount of residual methane in the mine,which will become a critical methane emission source.Methane from closed/abandoned coal mines is desorbed and released to the goaf,and then discharged to the atmosphere through channels such as wellhead and mining-induced fractures.Methane monitoring in coal mines can be realized by means of satellite remote sensing,flux chamber method,geochemical probe method,micro-meteorological technology,etc.Based on the methane emission pre-diction model of closed/abandoned coal mines,the methane emissions from closed/abandoned coal mines may account for more than 20%of total methane emissions from coal mining operations by 2050,so it is urgent to solve the problem of methane emissions from closed/abandoned mines.Therefore,the countermeasures of emission reduction,such as extrac-tion and utilization,in-situ deflagration power generation,microbial degradation of methane,water flooding,and methane emission channel closure are put forward.Considering the limitations of cost,treatment time,groundwater contamination,and other limitation factors,it is concluded the mineralized remediation method can be used to seal large-scale mining-in-duced fractures in overlying rocks,which can achieve the methane emission reduction goal of closed/abandoned coal mines at a low cost.