Study On Thermal Ventilation Technology For Rehabilitation Of Toluene Contaminated Soil

With the development of ecological civilization construction,the Chinese government has an increasing demand for environmental protection of soil.As a result,the technology soil remediation is high-profile.Thermal desorption-ventilation technology is one of the conventional remediation technologies which are used to renovate the organo-contaminated soil.The technology can separate and gasify the volatile organic compounds from polluted soil by heating organic contamination.As a result,the soil remediation can be achieved.This technique can improve restoration efficiency and reduce the impact on the soil environment.In this experiment,toluene was taken as the target pollutant,and cinnamon soil which is common in north China was taken as the research object.Then selected four factors which may affect the efficiency of thermal analysis-ventilation repair?soil content of toluene,ventilation?gas velocity?,air temperature,soil moisture content?.Under the condition of continuous ventilation for 240 minutes,the toluene removal experiment was carried out on a one-dimensional soil column in the laboratory.To conclude,there are four main achievements shown as following:Under the experimental conditions of toluene concentration 2.5-20 g·kg^-1,ventilation volume 10-40 L·min^-1,ventilation temperature 100-140?,moisture content 5-20 mg·kg^-1,the removal rate of toluene is more than 98%by using thermal desorption-ventilation technology.In addition,the residual concentration of toluene is less than 150 mg·kg^-1 and achieved the national standards of commercial land and municipal land.Normal temperature ventilation experiment is used to repair the soil polluted by toluene.The highest removal rate of toluene is 75.2%.The residual concentration of toluene is 640mg·kg^-1.Compared with this method,thermal desorption-ventilation technology has a better performance in the tests.Then,Four factors which may affect the removal efficiency were analyzed by orthogonal design and range analysis.The results showed that ventilation temperature was the most critical factor affecting the removal efficiency,followed by the concentration of toluene in the soil,while the effects of ventilation and soil moisture content on the removal efficiency were relatively low.Thirdly,In the orthogonal experiment,the optimal levels of various factors were selected:when the toluene content in the soil was 2.5 g·kg^-1,the aeration rate was 20L·min-1(about 1m·s^-1),the aeration temperature was 120?,and the soil moisture content was 5%,the highest restoration efficiency could be achieved.Finally,The results of experiment are regressed.By analyzing the fitted curves,the mathematical model is completed.