Study On Cleaning-Thermal Desorption Remediation Of Oil Contaminated Soil

High concentration oil contaminated soil has become one of the important environmental problems in oil fields.Common technologies include thermal desorption,chemical washing and biodegradation.After thermal desorption remediation of organic contaminated soil,the pollutants are completely desorbed,but the energy consumption is high and the requirements for materials are strict.The two single technologies of cleaning and thermal desorption are coupled,and the oil contaminated soil is preliminarily treated through washing to reduce the workload of thermal desorption,and adjust the optimal material parameters of small particle size soil to thermal desorption,so as to reduce the energy consumption of thermal desorption from two aspects.In this thesis,the contaminated soil of a large domestic oil field was selected as the experimental soil sample.Through the determination experiment of occurrence characteristics of the contaminated soil and the soil washing-thermal desorption coupling remediation experiment.Firstly,the physical and chemical properties of the contaminated soil,the distribution of oil and its components were analyzed.Secondly,the influence of washing agent formula and washing parameters on petroleum desorption effect of soil particle size were studied.Finally,the influence of thermal desorption parameters on petroleum desorption efficiency of raw contaminated soil and clay component after washing were investigated.After obtaining the process parameters through laboratory research,industrial field tests were carried out accordingly.The main conclusions are as follows:（1）The soil is unevenly distributed under each particle size and belong to sandy soil.The total petroleum content was 9.07%.The adsorption proportion of petroleum hydrocarbons in fine-grained soil is relatively high.The adsorption of petroleum by coarse diameter sand is mainly surface adhesion,while the petroleum by small clay also has internal infiltration,which is difficult to desorb,different repair technologies should be adopted for sandy components and clay components.（2）The elution effect of surfactant and inorganic electrolyte is better.Under the conditions of heating temperature 70℃,cleaning time 60 min,solid-liquid ratio 1:6,secondary reinjection and reuse ratio 30%,the removal of petroleum is most favorable.Under the optimal parameters,the total removal rate of oil in soil was 89.56%.The removal rate of coarse diameter sand is higher,reaching 97.21%,96.95%and 92.51%,respectively,the removal rate of small clay is lower,reaching 79.83%.After washing,the oil content of coarse diameter soil fractions is 0.45%and meets the target of remediation,while the oil content of fine diameter soil fractions is higher than 2.0%,which requires further treatment.（3）Under the conditions of heating time 210 min,heating temperature 450℃,initial moisture content 15%and heating rate 10℃·min^-1,the desorption effect is the best.The desorption efficiency of clay component after washing is higher than raw contaminated soil.Under the optimal parameters,the desorption rates of the two kinds of soil are 99.21%and98.53%respectively,and the oil content of small-grained soil after remediation is 0.02%,which meets the coupling remediation goal.（4）Under the optimal parameters,about 60%of the soil could be precipitated and separated after cleaning and repair,and the content of petroleum hydrocarbon was 1.23%.The remaining 40%of fine-grained soil was exported in slurry state,and was subjected to thermal desorption after pressure filtration,dehydration and drying.The content of petroleum hydrocarbon was 0.48%.Compared with the simple thermal desorption process,the energy consumption per ton of soil remediation in the former is 13.12%lower than that in the latter.