场地有机污染土壤原位热修复过程中热质传递机制研究

Study on heat and mass transfer mechanism during in-situ thermal remedi-ation of contaminated soil

中文关键词: 原位土壤修复  效果分析  热质传递  数值模拟

英文关键词: In situ soil remediation  energy saving and consumption reduction  Heat and mass transfer  numerical sim-ulation

中文摘要:

      针对现有原位热修复技术能耗较高且在修复过程中热质传递机制不明的问题，研究了现场试验过程中的土壤温度场变化、修复效果和能耗，采用数值模拟方法对温湿度场的变化进行了验证。结果表明：加热井呈正六边形排布时，修复区域的受热较为均匀，各测温点在修复35天后，温度均达到200 ℃以上，修复后场地满足第二类用地筛选值；试验过程中天然气用量总计685664 Nm3，每修复1 m3污染土壤约消耗62.8 Nm3天然气；加热井热量主要为修复场地侧壁供能，对于位置低于加热井的土壤作用较小，加热井轴向土壤体积含水率分布较为均匀，但加热井底部体积含水率较高，修复区域底部水分不利于修复场地温度的提升，数值模拟和试验数据的吻合度较高，平均相对误差MRE为20%．该研究结果可为场地有机污染土壤原位热修复技术应用提供技术支撑。

英文摘要:

      Aiming at the problems of high energy consumption and unclear heat and mass transfer mechanism during the remediation process of existing in-situ thermal remediation technologies, the energy-saving and emission re-duction effects during the experimental process were studied, and the changes in soil temperature and humidity fields were verified using numerical simulation methods. The results show that the on-site reburning system was used to reduce natural gas consumption by 20588 Nm3 and carbon dioxide emissions by 40.4 t. The operating time of the heating well determines whether the overall repair temperature could be significantly increased. A longer heating time could form a stable thermal repair environment and improve the thermal repair efficiency. The heat of the heating well mainly provided energy for the side wall of the repair site, and had little effect on the soil located lower than the heating well. During the thermal remediation process, the distribution of soil volumetric moisture content in the axial direction of the heating well was relatively uniform, but the volumetric moisture content at the bottom of the heating well was relatively high. The moisture content at the bottom of the remediation area had a side effect on improving the temperature of the remediation site. The coincidence between numerical simulation and experimental data is high, and the mean relative error MRE is 20%. The re-sults of this study can provide technical support for the design and operation of in situ thermal desorption re-mediation of organic contaminated soil.