煤炭地下气化酚污染迁移数值模拟

基于我国西部某煤炭地下气化试验，以气化特征污染物之一--挥发酚为例，建立地下水流运动和污染物迁移数学模型，对气化炉闭炉后的污染物迁移规律进行了数值模拟。结果表明： 20 a 预测期内，挥发酚具有极弱的向煤层隔水顶板上覆咸水含水层的迁移倾向，水动力弥散是其迁移的主要方式；煤层内部挥发酚的迁移只发生在燃空区附近，在气化后20 a，污染晕为以燃空区为中心的椭圆形，长轴方向大约500 m，短轴方向大约300 m，煤层的低渗透性、水力坡度小和介质的吸附作用是阻碍挥发酚在煤层内扩展的主要原因；煤层与含水层之间的水头差、燃空区上下方隔水层的破坏程度和范围以及水动力弥散作用是含水层污染评价的关键因素。地下水污染风险须通过科学选址、气化过程控污、煤层燃空区污染处理等措施进行综合防治。

Numerical simulation of phenol migration for underground coal gasification

Taking the western UCG site in China as the example,the mathematic model of groundwater flow and phenol migration after gasification were established,and numerical simulation was conducted.The results indicate that no obvious phenol pollution is found in the neighboring upper aquifer during the prediction period of 20 years.Molecule diffusion is the main path of phenol migration toward the upper aquifer.Phenol migration in the coal seam occurs near the UCG cavity,and elliptic shape area with with long axis of 500 m and short axis of 300 m is found.Low permeability of coal seam,lower hydraulic gradient,and the absorption by the surrounding strata make big contributions to prevent phenol migration in the coal seam.In addition,the water head difference,the destroy extent of the confining strata,and molecule diffusion are the key factors for groundwater pollution evalution.Groundwater pollution should be prevented by the combination way of site selection,process pressure control,and cavity pollution disposal.