Assessment of Energy Efficiency of In-situ Thermal Desorption: Creation and Application

With the development of industrialization, soil environmental safety has become a serious matter in China. In-situ thermal desorption technology (ISTD) is one of the technologies with high remediation efficiency in short-term period. However, the high energy consumption and high cost become the "bottleneck" for its wide application. Currently, there is no unified quantitative method for evaluating the energy efficiency of in-situ thermal desorption, both home and abroad. To address this issue, energy efficiency evaluation method based on pollutants and energy efficiency evaluation method based on polluted soil/water volume were developed on the bases of the principle of in-situ thermal desorption and energy consumption calculation model of in-situ thermal desorption, as well as the characteristics of organic pollution sites in China. The applicability of these methods was explored through an engineering project involving in-situ thermal desorption and coupled chemical oxidation technology in North China. Based on the energy consumption analysis of the technology receptors (including coupled chemical oxidation technology), it was found that the energy consumption of in-situ thermal desorption applied to soil and water heating accounted for 61.80% to 74.43% of the total energy consumption, while the energy consumption applied to pollutants only accounted for 2.11% to 17.57%. To account for the uncertainty in the energy consumption analysis of thermal desorption technology and the calculation of pollutant amount, it is believed that using the volume energy efficiency evaluation method is more meaningful for in-situ thermal desorption technology. The results of the pollutant soil-water volume energy efficiency evaluation indicate that the energy efficiency of the coupled zone is 7.91×10^-6 m³·kJ^-1, while that of the thermal desorption zone is 1.06×10^-6 m³·kJ^-1. After coupling chemical oxidation technology, the energy efficiency of in-situ thermal desorption technology is increased by about 6.5 times.