Fundamental Research Of The Treatment Of Volatile Organic Compounds With Gliding Arc Discharge Plasma

Organic waste gas is particularly burdensome for both the natural environment and human health. It is widely emitted from the processes containing the uses of paint, dope, and lube, etc. The main components of this type of gaseous pollutants are so-called the volatile organic compounds (VOCs). Currently, the applications of conventional technologies for VOCs removal process can't simultaneously meet the economic and technical requirements owing to their own disadvantages, so the development of innovative VOCs removal technology is essentially necessary. In this dissertation the gliding arc discharge non-thermal plasma (NTP) is applied into the region of environmental protection: a theoretical system which can be used for the guidance of industrial application is built based on both the theoretical analysis and experimental researches; the device structure is developed to fit for the practical application; and the technical and economic assessments are performed based on the results of a demo project. Furthermore, the explorative work on the methane reforming with carbon dioxide is also carried out.Chapter one is the background review, mainly including the definitions of VOCs, the sources of VOCs, the harm of VOCs, the conventional VOCs removal technologies, the concept of NTP, the various styles of NTP sources, and the application of NTP in the gaseous emission control areas, etc. The gliding arc discharge plasma has been paid particular attentions, mainly focusing on the operation phenomenon, the features of plasma region, the state-of-art of current application, as well as the comparison of which with other NTP sources. In this chapter, the framework and the structure of this dissertation are also introduced.Chapter two is on the researches on the physical characteristics of gliding arc discharge plasma. An experimental scale AC gliding arc discharge reactor is used for the discharge parameters detection, the arc movement analysis, and the gas field and velocity field simulation calculation. Then the non-thermal property of gliding arc evolution is analyzed with the comparison between experimental results and thermodynamic equilibrium calculation data, and also based on the plasma region spectral analysis results.Chapter three is on the preliminary researches about the VOCs decomposition with gliding arc discharge. Firstly, the VOCs decomposition performances of gliding arc discharge are investigated, with the targets as single compound VOCs, dilute VOCs mixtures, and concentrated VOCs mixtures, respectively. Then the influences of discharge parameters, i.e. supply voltage, VOCs initial concentration, background gas component, and the background oxygen concentration, etc. on the VOCs decomposition performance are investigated, with hexane (n-C₆H₁₄) is chosen as the typical VOCs. Based on the above, the mechanism of gliding arc discharge assisted VOCs decomposition is preliminarily discussed and analyzed. Finally, the gliding arc discharge reactor structure is analyzed based on the researches of the influences of electrodes gap and throat height on the VOCs decomposition efficiency and specific energy consumption, etc.Chapter four is on the mechanism of VOCs decomposition in gliding arc discharge plasma atmosphere. The investigation on the influences of background relative humidity and oxygen concentration on VOCs decomposition is chosen as the entry point. Firstly, the influences of background relative humidity and oxygen concentration on the gliding arc discharge characteristics are investigated, and then the researches on the effects of background relative humidity and oxygen concentration on three different types of VOCs, i.e. tetrachloromethane (CCl₄), n-butane (n-C₄H₁₀) and toluene (C₇H₈), are carried out. Based on above experimental results, the dominant decomposition channels and species under gliding arc non-thermal plasma conditions for different VOCs structures are discussed.Chapter five is on the nitrogen dioxide formation in the gliding arc discharge assisted VOCs decomposition processes. NO₂ formation in dry air gliding arc discharge is mechanistically discussed based on the thermodynamic equilibrium calculation and plasma region spectra analysis. Then the influences of VOCs chemical structure, supply voltage, background humidity, and reactor geometry on NO₂ formation are experimentally investigated. The pathways of NO₂ formation inhibition are discussed based on the above.Chapter six is on the gliding arc discharge device development and the design for industrial application. The scale-up analysis on traditional gliding arc facility is studied based on the laboratory experiments and numerical simulation. An innovative developed gliding arc discharge reactor based on a modified gas feed system is proposed. The performances of developed gliding arc discharge reactor in the decomposition of VOCs with relative high gas flow rate, including the decomposition efficiency, the specific energy consumption, and the decomposition by-products, are investigated, with tetrachloromethane (CCl₄), n-butane (n-C₄H₁₀) and toluene (C₇H₈) are chosen as the typical VOCs. The economic and technical assessments are performed with the comparison with multi-electrode gliding arc discharge device, and the design of multi-electrode developed gliding arc discharge device is proposed. At the end, the economic analysis on the activated carbon-gliding arc technology for the treatment of industrial VOCs emission control is also carried out.Chapter seven is on the gliding arc gas discharge assisted dry methane reforming (DMR). The influences of feed gas proportion on the reagents conversion and main by-product distribution are investigated in different supply voltage conditions. Based on the present investigation, the performance of the plasma assisted DMR process of gliding arc discharge facility is assessed by the comparison between experimental result and theoretical thermodynamic equilibrium calculation data. Finally, the economic assessment on the gliding arc assisted DMR process is carried out via the comparison with traditional DMR process and other plasma assisted DMR processes, based on which the potential of the application of gliding arc discharge in the assistance of DMR process is also analyzed.Chapter eight mainly includes the conclusions and the innovative point of this dissertation, and the prospect of future work.