A numerical study of optimizing the well spacing and heating power for in situ thermal remediation of organic-contaminated soil

Abstract

The thermal conductive heating (TCH) technology has been widely applied to remediate fields contaminated by organic compounds in recent years, because of its broad applicability, high treatment effectiveness, and less sensitivity to geological heterogeneity of treated sites. However, the high cost of thermal energy of TCH technology creates a need for optimal operation including the selection of number of heating wells and the power of each heating well. In order to investigate the relationship between site characteristics and operating conditions to realize uniform underground heating and to lower energy consumption during the process of TCH, numerical simulations were performed using COMSOL Multiphysics based on a coupled water-vapor-heat transport model without considering the organic pollutants. The numerical results were first validated by comparing with the experimental data obtained with a single heating tube from field tests. The effects of well spacing, water content, soil type as well as the heating power were discussed, and two measures for temperature uniformity and the degree of overheating were proposed. The results showed that low-power uniform heating can improve the uniformity of temperature field and reduce the degrees of overheating. For the sites with various water contents, different well spacings should be adopted to improve the efficiency of TCH. For a clay field, it is more suitable to use low-power heating strategy, whereas for other soil types, the well spacing can be increased appropriately with respect to the heating power. These results can serve as guidelines for heating well arrangement towards energy-efficient TCH applications.