| The high voltage pulsed discharge in water is a newly developed advanced oxidation technology, and it's also the combination of pusled power system, water environment treatment and free radical chemical oxidation. Because of the advantage of simplicity, high efficiency and no secondary pollution, this technology can deal with so many kinds of toxic and harmful organic substance without condition restriction and is potential for a propagation industry application.Some key factors of the technology were investigated in the dissertation, such as design and fabrication of power source/plasma reactor, pulsed discharge characteristic in water, active species formation, methylene blue(MB) oxidation, system parameters optimum, etc. The main research content and results presented in the dissertation are as follows:a) The newly designed high voltage nano-second generator is mainly consists of a variable DC power source for high voltage supply, two graded capacitors for energy storage and the mutiple-electrode rotating spark gap used as switch. The work principle of the main circuit is analyzed, and the dynamic running process is modeled and analytically solved. The results can be used for the design of PPS circuit and the choice of components. By means of calculated distortion characteristic of electrical field, which can ensure enough action time, reduction ablation and prolonging the life of the switch, a simulation model was set up for MER-SGS and the results demonstrate that the power output charactristic, including rise time(<100ns), pulse width(<1μs), repetition rate(20-600Hz) and average power(25W-2kW), etc, all of which reach the standard of experimental application.b) Gathering the advantage of needle-plate reactor and wire-plate reactor, the author designs a new style sawtooth wire-plate plasma reactor for water treatment enlargement. The reactor is mainly composed of four-quadrant electrodes which are made of stainless steel and the calculated capacity of this reactor reaches42L. It also can be series parallel connection for further scale up. This model of reactor is good for gas-liquid mass transfer enhancing and attaches more importance to air-liquid mixing discharge treatment result.c) The author makes research on pulsed discharge characteristic in pure water, incluing pulsed waveform characteristic and pulse energy utilization. The single pulse implantation energy is increasing constantly as the enhancing of AC input, the value of pulsed energy-storage capacity and solution conductivity. However, the development trend of implantation energy efficiency is so different for each parameter. The amplitude and shape of the output waveform are affected by the processing parameter of the designed system as well.d) The pollutant degradation is in accordance with the magnitude of the hydroxyl radical formation by analyzing the active species formation. H2O2and O3can be more powerful when they are translated into hydroxyl radical and the concentration of H2O2is much more than O3in the discharge process. Arranged by magnitude, the H2O2rates at different bubbling are as follows:no bubbling>oxygen>air>nitrogen, and the O3rates at different bubbling are as follows:oxygen>air>nitrogen>no bubbling. Bubbling gas changes the constitution of the discharge region and makes the affection of the conductivity decreased.e) Effect of the main parameters, such as AC input, discharge frequency, concentration, volume, air bubbling, pH value are studied on methylene blue waste degradation. Research of using pulsed discharge plasma, to oxidize high concentration methylene blue in the liquid phase, has obtained a remarkable progress. The experiment results show that the degradation efficiency and energy density increase with AC input and pulse frequency increment. However, MB degradation rate of increase is less than the rate of increase of energy, which can indicate that energy efficiency of low-voltage is larger and consumption of free radical is consistent with the characteristic of the secondary. Meanwhile, air bubbling, conductivity and mass transfer efficiency play important role in oxidation process as well. We also can be ensured that the system energy consumption will substantially drop when the reaction volume is larger after the matching optimized between power source and reactor has been realized.
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