焦化类污染场地堆式燃气热脱附工程示范与效果评估

近年来，有机污染土壤堆式燃气热脱附技术因具有二次污染可控、污染物去除率高以及修复成本低等优势得到快速发展，然而目前国内外关于该技术的工程示范与效果评估仍有待研究. 针对我国北方某退役焦化厂污染土壤，开展了2 000 m3的堆式燃气热脱附工程试验，系统分析热脱附过程中土壤的温湿度变化规律、修复效果以及能源消耗等情况，并提出堆式燃气热脱附技术的应用条件和优化方法. 结果表明:当加热运行至35 d时，堆体测温点平均温度达175 ℃，抽检的12组土壤样品中污染物浓度均远低于GB 36600—2018《土壤环境质量 建设用地土壤污染风险管控标准(试行)》中第一类用地筛选值，修复达标率为100%；运行至39 d时，收集水量共计310.4 m3，土壤体积含水率从25.8%降至10.3%左右；同时，该试验采用的烟气余热再利用技术将排烟温度降至300 ℃以下，使修复能耗降低约11.5%，即每修复1 m3污染土壤消耗约49.5 Nm3天然气和16 kW?h电量；此外，采用COMSOL软件模拟堆体的温度和湿度结果与试验结果的平均相对误差分别小于7.36%和7.49%，具有较好的吻合性. 研究显示，热脱附修复过程中堆体的底层平均温度处于较低水平，需提高底层加热管温度，或铺设岩棉板进行隔热保温措施，以提高堆体底层土壤的修复效率，研究结果可为有机污染土壤堆式燃气热脱附技术应用提供技术支撑. 

Demonstration and Effect Evaluation of Ex-situ Thermal Pile Desorption in Coking Contaminated Soil

In recent years, ex-situ thermal pile desorption has been used widely to remove organic pollutants from polluted soil in engineering practices due to its advantages of controllable secondary pollution, high pollutant removal rate and low operational costs. However, the mechanisms controlling the pollutant removal still need to be systematically examined. In this study, an engineering-scale ex-situ thermal pile desorption experiment of 2000 m3 was carried out to remove pollutants in contaminated soil in a decommissioned coking plant in North China. The effects of operational variables, such as temperature and soil moisture, on the remediation and energy consumption were systematically analyzed, and suggestions for improving the performance of ex-situ thermal pile desorption were put forward. The results showed that when the pile temperature reached 175 ℃ (on day 35), the concentrations of pollutants in 12 groups of soil samples were all below the Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land (GB 36600-2018), indicating that the remediation goal was achieved. The amount of water collected during the thermal desorption was 310.4 m3, and the bulk water content of the soil decreased from 25.8% to about 10.3% (on day 39). Meanwhile, the waste heat of flue gas was reused, which reduced the energy consumption of ex-situ thermal pile by 11.5%, and reduced the net energy consumption per cubic meter of polluted soil remediation to 49.5 Nm3 of natural gas and 16 kW?h of electricity. In addition, the temperature and humidity of the thermal pile were mathematically simulated, and the average relative errors between the measured and the simulated results were less than 7.36% (temperature) and 7.49% (water content), respectively, which had a good agreement. The simulation results also showed that the average temperature of the bottom layer of the thermal pile was relatively low during the operation. Therefore, it is recommended to increase the temperature of the bottom heating pipe or install insulation measures (such as stone-wool board) to improve the remediation efficiency. The results of this study can provide technical support for the design and operation of ex-situ thermal pile desorption remediation of organic contaminated soil.