Experimental Study And Equipment Design For Microwave Treatment Of Organic Contaminated Soil

Soil pollution in some areas of China is serious,and many of the original industrial sites have been gradually developed into residential land or commercial Iand.Theenvironment of some abandoned land is prominent.The overall restoration of contaminated sites in China started late,and soil remediation technology and engineering practice experience also have shortcomings.At present,it mainly relies on the introduction and reference of foreign advanced technology,but foreign advanced technology cannot fully adapt to the current situation of contaminated soil in China.Microwave remediation has the characteristics of high thermal efficiency and environmental friendliness,and has attracted the attention of more and more scholars at home and abroad.In this thesis,the influencing factors of thermal effect in microwave processing was studied by numerical simulation and experimental methods.The electric field and temperature distribution in different input power,different frequency and different waveguide positions are simulated.The simulation results show that when the medium is placed in the reaction chamber,the electric field strength decreases by 28%,and the microwave power,microwave frequency and waveguide position will affect the temperature distribution of the electric field intensity in the microwave cavity.The experimental results are consistent with the simulation results,which proves that the model established by numerical simulation has credibility.Firstly,the parameters of microwave and ultrasonic methods were optimized by single factor and response surface method for the soil contaminated by xylene,and the optimal process parameters of the two methods were optimized.The optimum technological parameters were obtained as follows:when the microwave power is 530 W,the irradiation time is 3.4 min,and the water content is 32.88%,the predicted result is 79.745%,and the average experimental removal rate is 81.25%.The relative error between the two is 1.89%.When the ultrasonic power is 400 W,the ultrasonic time is 11 min,and the water content is 30%,the predicted result is 83.52%,and the average experimental removal rate is 82.97%.The relative error between the two is 0.66%.The results show that the quadratic regression equation established by response surface method has good fitness and can be used to accurately predict the remediation effect under given process parameters.The microwave-ultrasonic interaction method was used to remediation the contaminated soil of xylene,petroleum and crude oil,and the remediation effect was compared.It was found that the microwave-ultrasonic coupling method has a good remediation effect of gasoline and crude oil.It has a very obvious lifting effect,and the removal rate of the two increases from 33.96%and 12.5%of the microwave alone to 72.9%and 29.27%,and the removal rate increases by more than 100%.The mechanism of pollutants change before and after gasoline and crude oil contaminated soil was analyzed by infrared spectroscopy.Adding fly ash and activated carbon as sensitizer during the microwave process,and comparing its effect on the remediation,the experimental results show that the removal rate of xylene can reach 98.42%when the amount of fly ash is 15%.When the concentration of xylene in the soil is less than 315 mg/kg,the soil after the restoration can meet the Class A standard in the“Evaluation Standard for Soil Environmental Quality of Exhibition Sites".In the microwave remediation of gasoline and crude oil contaminated soil,the effect of fly ash on the remediation effect is also significant.On this basis,the contaminated soil microwave remediation equipment was designed based on numerical simulation and experimental results.The equipment can be used to verify the effect of microwave on soil remediation under different process parameters.It is highly integrated and can be used for industrial application testing.The three waveguide inputs are optimized for optimal input by three-dimensional modeling and numerical simulation.The optimal structural dimensions are 50 mm in length,15 mm in width and 6 mm in height.This thesis uses microwave-ultrasonic coupling to carry out experiments,which provides a broader research direction for improving the remediation effect of microwave remediation.The addition of fly ash in the microwave remediation process significantly improves the remediation effect of organic contaminated soil,and is conducive to promoting the resource utilization of fly ash.The designed continuous organic contaminated soil microwave processing equipment provides a theoretical basis for the industrial application of microwave remediation and equipment.