【作者】 王洪昌；

【导师】 吴彦； 李锻；

【作者基本信息】 大连理工大学 ， 环境工程， 2010， 博士

【摘要】 高压放电等离子体处理气态有机污染物(VOCs)是一种新型的VOCs末端治理技术,因其具有效率高、无选择性、使用范围广等特点呈现出良好的应用前景。本论文以丙酮／苯／四氯乙烯／间二甲苯的混合气体为目标污染物,采用双极性窄脉冲高压电源与介质阻挡放电结合进行降解处理,探讨了混合VOCs降解时各组分间的相互影响规律,并对电源参数和反应器结构进行了优化。此外,论文还对DBD等离子体-催化体系降解混合VOCs的协同效应进行了研究。主要研究成果及结论如下：1.研究比较了DBD分别与工频交流电源和双极性窄脉冲电源结合时电压、电流波形,功率注入特性和VOCs的降解特性,发现脉冲DBD兼有脉冲放电的陡前沿、窄脉宽的特点,可产生瞬间大功率放电和高能电子,能更有效的去除VOCs。在注入功率均为15.0 W的条件下,处理气体流量为2.5 L/min,浓度均为200 ppm的丙酮／苯／四氯乙烯／间二甲苯混合气体时,交流DBD下四种污染物的降解率分别为10%／27%／45%／96%,而采用脉冲DBD则可提高至23%／52%／57%／99%。2.对脉冲DBD体系中电源和反应器的匹配进行了优化研究,考察了峰值电压、放电频率和脉冲成形电容等参数对能量注入和VOCs降解效率的影响。结果表明：增大脉冲峰值电压和频率可以提高能量的注入,促进对污染物的降解；脉冲成形电容与DBD反应器存在最佳匹配关系,对于线筒式DBD反应器,脉冲成形电容与反应器静态电容的最佳匹配关系为10～20倍。3.从功率有效注入和等离子体分布方面对DBD反应器结构进行了优化,考察了电极形式、放电间隙、介质尺寸和放电长度等参数对VOCs降解效果的影响。结果表明：与不锈钢螺纹电极相比,不锈钢棒电极下等离子体分布更加均匀,对VOCs的降解效率也更高；增大反应器的放电间隙,会引起反应器内功率密度变小和高能活性粒子的分布不均匀,使得对VOCs的降解效率下降；相同的放电间隙下,适当放大反应器的介质尺寸和放电长度有利于对VOCs的降解。4.通过考察四种混合VOCs的降解特性和尾气成分的分析,探讨了混合VOCs降解时各组分间的相互影响规律。结果表明：混合VOCs同时降解时,组分之间有相互的影响作用,分子结构不稳定,电离能较小的污染物会优先降解,降解产生的小分子中间产物会对其它组分的降解产生抑制作用。5.对脉冲DBD等离子体降解VOCs时CO2和CO选择性的变化特征进行了研究,发现尾气中的CO2和CO是由不同的降解途径生成的,增加放电电压并不能促进CO向CO2的转化。6.研究了DBD等离子体-催化体系下混合VOCs的降解特性和CO2选择性的变化规律,并探讨了相关作用机理。结果表明：DBD等离子体与催化结合不仅可以提高VOCs的降解率,还可以提高CO2选择性,抑制CO的生成；混合VOCs中各组分的催化降解性能与其在催化剂上的吸附能力大小有关,吸附能力越强,催化降解效果越明显。更多还原

【Abstract】 As a novel technology for the removal of gaseous VOCs, the nonthermal plasma process has such advantages as high removal efficiency, nonselective, wide using range and so on, and exhibits promising application perspective. In this paper, the mixture of acetone, benzene, m-xylene and perchloroethylene (PCE) was chosen as the object and a bipolar pulse DBD system was set up by combining the bipolar pulse high voltage and DBD to remove the mixed VOCs in air. The feasibility and mechanism of mixed VOCs decomposition by nonthermal plasma were studied. The optimization of power supply parameters and reactor structure was investigated. Furthermore, this paper also set up a nonthermal plasma-catalysis system for mixed VOCs decomposition and investigated the synergistic effect and mechanism of this system. The main results are summarized as follows:1. The voltage waveforms, current waveforms and characteristics of input power for industry frequency alternate current DBD as well as bipolar pulse DBD had been investigated. The results showed that comparing with industry frequency alternate current DBD, the bipolar pulse DBD exhibited the advantages of short pulsed corona discharge that sharp pulse edge and narrow pulse width which led to more quantities of high-energy particles generate and better for VOCs decomposition. Under the conditions of 15 W average power,2.5 L/min flow rate and 200 ppm concentraten, the decomposition rates of acetone, benzene, PCE and m-xylene in their mixture were 23%,52%,57% and 99% for the bipolar pulse DBD, comparing with industry frequency alternate current DBD were only 10%,27%,45% and 96%。2. For the bipolar pulse DBD system, the optimization of matching the power supply and reactor was investigated by studying the effects of pulse peak voltage, pulse repetitive rate and capacitance of the pulse capacitor. Experiment results indicated that increasing the pulse peak voltage and pulse repetitive rate could improve the energy injection and promote the decomposition of VOCs. For the wire-tube DBD reactor, the appropriate match rate between the pulse capacitor and the static capacitance of reactor was 10～20 times.3. The DBD reactor configuraten was optimized at the aspect of the effective power input and spatial distribution of energy. Effects of electrode material, discharge gap, size of barrier and discharge length on the VOCs decomposition had been studied. The results showed that comparing with the stainless steel bolt, the stainless steel rod as the electrode had more uniform plasma distribution and high decomposition rates of VOCs. The reactor energy density and decomposition rates of VOCs decreased with the increased of discharge gap. At the same discharge gap, appropriate enlarging the reactor size and discharge length was helpful to the remove of VOCs.4. The interactions among the components were investigated by studied the decomposition characteristics of four kinds of mixed VOCs and analyzed the exhaust components. The results showed that there were some interactions among the components when the mixed VOCs were removed simultaneously. The component that had smaller ionization energy was priority to be decomposed to micromolecule intermediate products which will reduced the degradation efficiency of other components.5. The CO2 and CO selectivity of VOCs degradation in DBD had been studied. The results indicated that the CO2 and CO were generated by different degradation pathway that increasing the pulse peak voltage could not promote the conversion of CO to CO2.6. The degradation characteristics and mechanisms of mixed VOCs and CO2 selectivity in nonthermal plasma-catalyst system had been studied. The results suggested that DBD nonthermal plasma combining with catalysis could both enhance the decomposition rates of VOCs and CO2 selectivity. For the mixed VOCs decomposition, the catalytic capability of metal catalyst was related to the adsorption capacity of each VOC component. Adsorption capacity of VOC component in catalyst surface was stronger, the more obvious effect of catalytic degradation.更多还原