Research On Pretreatment Process Of PCBs Contaminated Soil And On-line Monitoring Of Pollutant Emission Performances

Polychlorinated biphenyls(PCBs) are synthetic organic chemical products, which were used as insulating oil in power capacitors、 pressure medium in hydraulic systems and so on. Since PCBs have been produced, a lot of PCBs entered environment due to leakage and emission in consumption process. Because of its high toxicity、 persistence and refractory, PCBs have become the important monitoring objective. Soils are very easy to absorb PCBs, so that the content of PCBs in the soils near sealed power equipment exceeded seriously. The problems of PCBs contaminated soils need to be solved urgently.Nowadays the main disposal methods of PCBs contaminated soils are bioremediation、 chemical remediation physical remediation and combined remediation. Treatment objects are high concentration、 middle concentration and low concentration of PCBs contaminated soils. Thermal desorption is considered as most effective remediation method, but in China it is still lack that research on thermal desorption of high concentration of PCBs contaminated soils. So rely on863project and based on the technique demand of thermal desorption, this dissertation do researches on PCBs contaminated soil during thermal desorption pretreatment process for the purpose of high efficient and low energy consumption.Reviews PCBs characteristics、 pollution status、 detection-analysis technique and disposal methods., and then test the physical and chemical properties of the high concentration of PCBs contaminated soils. Based on an experimental-scale paddle dryer, researches on drying characteristics of soils show that the internal diffusion of the moisture in the soil was the main factor to influence drying rate. Based on atmospheric permeability model, calculate heat transfer process in paddle dryer and analyze the effect of some parameters on the desiccation area.HRGC/HRMS is used to do research on PCBs distribution characteristics in gas phase and solid phase during low temperature drying process. Measurements of PCBs species and contents in gas phase and solid phase、 analysis of high-TEF PCBs and calculations of various PCBs emission show that monochloro-、 dichloro-、 trichloro-biphenyl and total PCBs have the performance that the higher drying temperature is,the less increase amplitude spaces are. However, tetrachloro-、 pentachloro-、 hexachloro-、 heptachloro-biphenyls. indicative PCBs and TEQ have opposite performance. In addition, evaluate the safety in low temperature drying process.Developments of TOFMS on-line monitoring are introducted. Polychlorinated benzene、 polychlorinated phenol and polychlorinated biphenyls are monitored in certain concentration. A good correlation between the signal intensity and real concentration has been found. Evaluation on detection ability of VUV-TOFMS has been achieved. The functional groups of chlorine and hydroxy may decrease ionization efficiency.TOFMS is used to do research on PCBs emission performances during thermal desorption pretreatment process in inert atmosphere. Compare PCBs emission responses in different drying temperaturen initial mass of heated substance and rate of flow. The studies on emission rate、 anaphase stability and tendency of emission response show that drying temperature and rate of flow may influence the time of reaching max emission rate, but initial mass of heated substance mainly affect the emission stability. Meanwhile, achieve the correlation between2-4chloro-biphenyl off-line data and the signal intensity...