煤炭地下气化污染物富集和迁移规律——以王村矿煤矿为例

Law of pollutant enrichment and migration in underground coal gasification--taking Wangcun Coal Mine as an example

为了解煤炭地下气过程中污染物的富集和迁移规律,作为评估地下气化方法对生态环境造成影响的依据之一,对王村煤矿贫瘦煤地下气化进行了模型试验,搭建了气化模型试验台,模拟实际地下气化过程。对于污染物析出规律的研究,利用重铬酸盐法、纳氏试剂分光光度法、直接分光光度法测定了不同氧气浓度下COD、氨氮、挥发酚的浓度,结果表明,当氧气体积分数大于60%时,污染物析出随着氧气体积分数的增加而明显降低,在80%富氧浓度时,气化区特征污染物挥发酚质量浓度为105 mg/L、氨氮质量浓度为2.09×10^(3)mg/L、COD质量浓度为1.11×10^(4)mg/L;对于污染物迁移规律的研究,首先利用RTR-1000高温高压综合岩石测试系统测定了不同温度下水在底板岩层的渗透系数,结果表明,常温状态下水在底板岩层渗透系数为4.4169×10^(-8)cm/s,100℃条件下渗透系数为5.0238×10^(-7)cm/s;常温至500℃条件下气体在底板岩层渗透系数在1.373×10^(-9)~1.059×10^(-8)cm/s。之后将之前得到的实验数据及地质、煤质参数作为边界条件和参数,利用Visual Modflow 4.1对污染物迁移进行了模拟,模拟计算年限为50 a,结果表明污染物迁移主要发生在气化结束10 a内,污染物迁移最大面积为3515.73 m^(2),水平面横向最大迁移距离为10.3 m,纵向扩散距离为5.4 m,垂直方向上污染物向底板的最大渗透深度为1.37 m。

In order to understand the aggregation and migration of pollutants in the process of underground coal gasification,as one of the bases for assessing the impact of underground gasification methods on the ecological environment,a model test was carried out on the un⁃derground gasification of meager lean coal in Wangcun Coal Mine,and a gasification model test bench was built to simulate the actual un⁃derground gasification process.In order to study the precipitation of pollutants,the contents of COD,ammonia nitrogen and volatile phe⁃nols under different oxygen concentrations were determined by dichromate method,Nessler reagent spectrophotometry and direct spectro⁃photometry,The results show that when the oxygen concentration is higher than 60%,the emission of pollutants decreases with the in⁃crease of oxygen concentration.When the oxygen concentration is 80%,the concentration of volatile phenols,ammonia nitrogen and COD are 105 mg/L,2.09×10^(3)mg/L and 1.11×10^(4)mg/L respectively;In order to study the migration law of pollutants,the permeability co⁃efficient of water in the bottom slate layer under different temperatures was determined by the RTR-1000 high temperature and high pres⁃sure comprehensive rock test system.The results show that the permeability coefficient of water in floor rock is 4.4169×10^(-8)cm/s at room temperature,5.0238×10^(-7)cm/s at 100℃;the permeability coefficient of gas in floor rock is between 1.373×10^(-9)and 1.059×10^(-8)cm/s at room temperature and 500℃;After that,the experimental data and geological and coal quality parameters obtained before are taken as boundary conditions and parameters and use Visual Modflow 4.1 to simulate the pollutant migration which the simulation calculation period is 50 years.The results show that the pollutant migration mainly occurs within 10 years after gasification.The maximum area of pollutant migration is 3515.73 m^(2),the horizontal maximum migration distance is 10.3 m,the vertical diffusion distance is 5.4 m,and the vertical maximum penetration depth of pollutant to the floor is 1.37 m.