【作者】 张祥龙；

【导师】 王毅；

【作者基本信息】 北京交通大学 ， 电气工程， 2012， 博士

【摘要】 高压脉冲水中放电降解有机物是一种新型的水处理高级氧化技术,是脉冲功率技术与环境水处理、等离子体化学等多学科的交叉融合；集合高能电子辐射、紫外光辐射、自由基氧化等多种高级氧化技术于一体。不但对目前各种难降解有机污染物具有普遍的适用性,更因其简便、高效、无二次污染等特点具备了广阔的工业应用前景。本文从能量角度出发,采用气液两相放电等离子体和化学的方法,在分析高压脉冲水中放电特性及系统参数对亚甲基蓝模拟废液降解影响因素的基础上,搭建一套反应器扩大条件下的水处理实验平台,为高压脉冲水处理技术的进一步放大和工业化应用打下基础,提供有益参考。论文主要研究内容及创新性结论包括：1)设计研制了一种新型纳秒级高压脉冲电源。采用电容储能方式的双火花隙充放电回路隔离设计；通过对电路建模及解析求解,分析了电源主电路的最佳工作状态并由此确定电路各参数值。利用工程电磁场仿真软件对电源核心元件多电极旋转火花隙开关,其不同旋转角度下的关合开断电场强度进行仿真计算,结果表明：旋转火花隙充放电回路中强烈的电场畸变能够保证开关的可靠动作；同时达到减小电极烧蚀,延长工作寿命和降低放电分散性等目的。实测结果表明,所设计研制的纳秒级脉冲电源具有：单脉冲能量可调(0.25J-20J)、平均功率可调(25W-2kW)、高重复频率(20-600Hz)、陡峭上升沿(<100ns)、窄脉宽(<1μs)、可靠开断、耐烧蚀等优点,能够达到等离子体水处理应用要求。2)结合传统针-板反应器与线-板反应器特点,设计研制了大容量水处理用等离子体锯齿线-板放电反应器。该反应器总设计容量达到42L,采用四象限锯齿线电极,可以根据需要组成多单元串并联放电模式,在形成多个放电通道的同时更加注重气液混合放电的协同效果。3)研究了单一水介质条件下系统主要参数对脉冲放电特性的影响,包括波形特征和脉冲能量利用情况。实验表明：提高交流输入电压、增大脉冲储能电容及溶液电导率,减小放电间距等都能够使单脉冲注入能量得到不同程度的提升。但能量注入效率发展情况却各有不同：提高输入电压使得能量注入效率呈现先增后减趋势；增大脉冲储能电容只能让能量注入效率一直下降；增大溶液电导率及减小放电间距却可以保持能量注入效率不断提高。4)分析了高压脉冲水中放电过程中起主要降解作用的活性物质(如羟基自由基、臭氧、过氧化氢等)成因及各自降解转化机理。放电产生的过氧化氢和臭氧分别在25min和9min左右的反应时间出现溶解转化,过氧化氢的生成浓度远高于臭氧。过氧化氢和臭氧的产率都随放电间距和溶液电导率的减小而线性增大；曝气的加入削弱了电导率对放电特性的影响。不同曝气条件下,过氧化氢产生浓度次序为：无曝气>氧气>空气>氮气；臭氧产生浓度次序为：氧气>空气>氮气>无曝气,均与各自反应历程和能量利用情况有关。5)依托所设计研制的电源/反应器系统,从直接氧化角度和能量利用角度两方面出发,考察了系统主要参数对亚甲基蓝污染物降解效果的影响,以此为参考对各参数进行优化总结,达到整体电源/反应器系统的良好匹配。亚甲基蓝溶液的氧化效率和氧化速度都随交流输入电压、脉冲重复频率、脉冲储能电容的增大而有不同程度的提高,但这种提高通常以高能耗为代价。放电间距和溶液电导率的加大降低了亚甲基蓝氧化效率；入口质量浓度、空气曝气量及溶液pH的增大有助于亚甲基蓝氧化速度和系统能量利用效率的提升。不同反应溶液体积的实验结果表明：在反应器扩大化条件下,处理量越大,能耗越低,运行成本在系统优化整合后可以得到有效控制。更多还原

【Abstract】 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.更多还原