UCG污染物苯酚在PRB中穿透行为及数值反演

Breakthrough behavior and numerical inversion of UCG organic pollutant phenol through PRB

煤炭地下气化(UCG)是集煤炭开发、转化为一体的煤炭清洁利用技术,但地下水污染风险已成为限制其推广应用的主要瓶颈之一。以有井式UCG为背景,以苯酚溶液为模拟UCG污染水,分别以砂、砂与有机膨润土和砂与活性炭混合材料构建模拟渗透反应墙(PRB)试验系统,利用有限元法和Python科学计算库NumPy及SciPy构建数值反演程序,研究苯酚在PRB中穿透现象。发现:①对充填砂和有机膨润土的PRB,随砂和有机膨润土质量比增加,扩散系数D和渗流速度q增大,弥散度λ和延迟因子R减小;对充填砂和活性炭的PRB,随砂和活性炭质量比增加,扩散系数D、渗流速度q和延迟因子R减小,弥散度λ增大。②混合材料质量比决定其孔隙率和吸附性能,对阻滞净化苯酚影响大。对砂和有机膨润土配制PRB墙体材料,质量比增大,PRB墙体孔隙率增大,苯酚初检时间缩短;对砂和活性炭配制PRB墙体材料,质量比增大,PRB墙体孔隙率减小,苯酚初检时间先增后减。③PRB对苯酚的吸附净化效果与机理:砂与有机膨润土构成墙体材料,其质量比存在阈值(本试验条件阈值2∶1),质量比小于该阈值时PRB对苯酚净化效果好,大于该阈值时净化效果急剧下降;砂与活性炭构成的墙体材料,其质量比小于2∶1时溶液渗流速度占主导作用,质量比大于2∶1时活性炭吸附性能占主导作用。

Underground coal gasification(UCG)is a coal utilization technique that combines coal extraction and conversion.However,the potential for groundwater pollution has emerged as a significant obstacle to its widespread acceptance and implementation.With the background of the UCG with shaft,phenol solution was used as the simulated UCG-contaminated water.Sand,a mixture of sand and organic bentonite,a mixture of sand and activated carbon were used respectively to construct the permeation reactive barrier(PRB).The finite element method and the Python scientific computing libraries,NumPy and SciPy were adopted to develop numerical inversion programs to study the breakthrough process of phenol in different PRB.The results show that:①When the PRB was filled with sand and organic bentonite,the diffusion coefficient D and seepage velocity q increased,while the dispersionλand retardation R decreased as the mass ratio of sand and organic bentonite increased.Conversely,when the PRB was filled with sand and activated carbon,the diffusion coefficient D,seepage velocity q,and retardation R decreased,while the dispersionλincreased with an increase in the mass ratio of sand and activated carbon.②The mass ratio of the mixed materials controls their porosity and adsorption capability,which significantly impacts the blockage and purification of phenol.When the PRB is constructed from sand and organic bentonite,increasing the mass ratio leads to an increase in porosity and a shorter initial detection time for phenol.On the other hand,when the PRB is constructed from sand and activated carbon,increasing the mass ratio results in a decrease in porosity,and the initial detection time for phenol increases at first and then decreases.③The adsorption and purification effect of a PRB on phenol and its mechanism can be explained as follows:in the case of a PRB material made up of sand and organic bentonite,there exists a threshold mass ratio(2∶1 in this experiment).When the mass ratio is below this threshold,the PRB effectively purifies phenol.However,when the mass ratio exceeds the threshold,the purification effect significantly decreases.On the other hand,in the case of a PRB material made up of sand and activated carbon,the dominant factor influencing the purification process is the seepage speed of the solution when the mass ratio of sand and activated carbon is below 2∶1.Conversely,when the mass ratio exceeds 2∶1,the adsorption performance of activated carbon becomes the dominant factor.