污染场地原位热传导强化气相抽提多场演化与污染物去除机理研究

As the quick development of industry and acceleration of urbanization in China, many volatile or semi-volatile contaminated sites are urgently required to be remediated. The in situ thermal enhanced soil vapor extraction is presently becoming a great potential pioneering remediation technology which adapts to the national conditions. However, the engineering practice of this technology goes ahead of theoretical research work. There’s a lack of systematic mechanism research on the evolution of multi-fields including moisture, temperature, airflow, and chemistry as well as the removal of contaminants. Aiming at the mechanism problems of multi-field evolution and contaminant removal, the project selects typical volatile and semi-volatile organic compounds and conducts laboratory physical model tests and numerical simulation analysis. The existence, transformation and migration mechanisms of organic compounds in the pore space of unsaturated soils, the evolution mechanism of multi-fields including moisture, temperature, airflow and contaminant concentration of the contaminated site with time are studied. In addition, the numerical simulation analysis of the multi-field evolution during soil vapor extraction and the remediation effect is specially made in consideration of the effect of thermal conduction enhancement. The research achievements are of great scientific value for supplement and perfection of present remediation theories.

随着我国工业化发展及城市化进程加速，许多挥发和半挥发性有机物污染场地亟待治理，原位热强化气相抽提技术正成为一种适应国情、具有巨大潜力的前沿修复技术。然而该技术工程实践超前于理论研究，对于修复过程中场地土体内水分、温度、气流、化学场演化以及污染物去除机理缺乏深入研究。本项目针对原位热传导强化气相抽提修复技术中的多场演化与污染物去除机制问题，选择典型挥发和半挥发性有机物，开展室内模型试验和数值模拟分析。研究原位热传导强化气相抽提修复过程中有机物在非饱土孔隙空间赋存、转化与迁移机理；水分、温度、气流和污染物浓度场等随时间演化机制；开展考虑热传导强化作用的气相抽提多场演化过程及场地修复效果数值模拟。研究成果对于丰富和完善污染场地修复理论具有重要的科学意义。

原位热强化气相抽提技术是一种适应国情、具有巨大潜力的前沿修复技术。但相关理论滞后于工程实践，常导致原位修复效果不佳和实测数据与理论计算不符。目前对热强化气相抽提修复场地中的水分场、温度场、化学场以及污染物的去除机理缺乏深入的研究。本项目主要从以下三个方面进行研究：1）控温气相抽提条件下土体孔隙中有机物赋存与去除特性研究；2）热传导强化气相抽提水分-温度-气流场演化与污染物去除规律研究；3）热传导强化气相抽提修复多场演化过程数值模拟研究。本项目开展了大量的室内模型试验和数值模拟分析，取得了如下的研究成果：.1）提出了NAPLs与水在污染土中的赋存规律；2）得出了不同含水率、温度和土性条件下水和甲苯的挥发规律，以及水和甲苯协同挥发机制；3）结合VGM模型和BCM模型，推算三相体系中空气、NAPL和水的kr-S-P关系；4）揭示了污染浓度、饱和度、干密度、矿物类型等对污染土导热系数的影响机制；同时分别提出了污染干土/饱和土的归一化导热系数预测模型；5）基于低场核磁的SVE修复过程，揭示了SVE修复过程中的优势流作用机制以及水和NAPLs的微观去除机制。6）基于一维土柱模型得出了多因素影响的热强化气相抽提去除效果，揭示了气相抽提过程中的多相传质过程的规律。7）通过热强化气相抽提的三维模型试验，分别研究了土壤传热特性、温度场和水分场演化以及污染物去除规律。8）通过理论分析和数值模拟，提出了描述SVE过程的理论模型，并通过该模型对SVE过程进行数字建模，研究了SVE过程中场地的NAPLs浓度、水分场变化规律。项目研究成果将丰富和发展工程地质学科污染场地修复理论，提高我国原位气相抽提修复和热修复的设计水平，为该技术在我国的土壤修复场地的推广应用，提供重要的理论依据和技术支撑。