【作者】 赵磊；

【导师】 骆仲泱； 施正伦； 高翔；

【作者基本信息】 浙江大学 ， 工程热物理， 2013， 博士

【摘要】 目前,燃煤电厂中所排放的细微颗粒物PM25成为了我国各大城市主要的大气污染物。由于细微颗粒物的存在导致了可见度的下降,尤其是我国华北地区大城市受影响最为严重,并且危害到了我国居民的生活质量和身体健康。因此,对于细微颗粒物的治理已经迫在眉睫。传统的烟气除尘技术,例如静电除尘和袋式除尘技术对于细微颗粒物PM25的脱除效率有限,不能有效控制其的排放。本文采用脉冲电晕放电的方式使细微颗粒物在电场中由扩散荷电和电场荷电的作用实现非对称异极性荷电,然后在库仑力的作用下进行凝并与脱除。与此同时,在脉冲电晕放电区域,由于大量强氧化性自由基的生成,可以氧化燃煤电厂烟气中的气态污染物,例如氮氧化物等。本文在细微颗粒物荷电的理论研究方面,建立了颗粒物进入到脉冲电晕放电电场当中的数学模型,对细微颗粒物在电场中的电场荷电和扩散荷电机理进行了研究,并且进行了建模计算。同时研究了不同能量注入下、不同电场当中,各个粒径段颗粒物的荷电特性。本文在实验方面建立了脉冲电晕放电结合直流放电细微颗粒物PM25脱除系统。在细微颗粒物的实验研究方面,针对细微颗粒物的脱除,首先研究了在不同电场作用下,PM25在全粒径段的荷电情况,得出的结论与前面理论计算结论基本吻合。然后研究了在不同含氧量、不同相对湿度下细微颗粒物的荷电情况和脱除效果。实验证明,在粒径大于0.2μm的粒径范围时,随着粒径的增大,颗粒物的脱除效率增大；在粒径小于0.1μm时,随着粒径的增大,细微颗粒物的脱除效率逐渐减小。也就是说0.1-0.2μm粒径范围内细微颗粒物的脱除效率最低。但是对于整个粒径段的PM25来说,在脉冲电晕放电的作用下的脱除效率有着极其显著的提高。针对氮氧化物转化的实验研究方面,首先研究了脉冲电晕放电反应器几何尺寸的变化对于氮氧化物转化的影响。然后在不同的含氧量和相对湿度下对氮氧化物的转化过程和转化效率进行了研究,最后讨论了脉冲电晕放电条件下氮氧化物转化所需要的能耗。针对上述结论,进行了脉冲电晕放电结合直流放电烟气多种污染物协同脱除的实验。在模拟烟气中同时加入细微颗粒物和氮氧化物来进行脱除。结论是细微颗粒物的存在对氮氧化物的转化造成很大影响,但是氮氧化物的存在对细微颗粒物的脱除影响甚微。最后对协同脱除系统进行了能耗分析。在小试实验结果的基础上,设计了脉冲电晕放电结合直流放电多种污染物协同脱除的中试实验平台。该实验平台由直流预收尘区域、脉冲电晕放电区域和直流收尘区域组成。最后对其进行能耗分析,讨论了脉冲电晕放电结合直流放电多种污染物协同脱除系统的工业应用前景。更多还原

【Abstract】 The particulate matter from flue gas of the power plant, especially PM2.5has already become a major type of air pollutions in China recently, which has not only affected the visibility of the surrounding atmosphere, but also seriously harm to human health. Therefore, PM2.5has aroused severe discussion in China. A much stricter air pollution control standard has been issued by Chinese government in2012which included the specific emission standard of PM2.5for the first time. Traditional technologies for particular matter control such as electrostatic precipitator or fabric filtration has lower efficiency of PM2.5. Pulsed corona discharge has been considered to be an efficient technology for the abatement of pollutants which are generated in flue gas. It has been utilized in industrial applications particularly when the plasma reactor is used as wire-plate configuration. The particles can be charged to either polarity depend on the differences of their diameter. Then the charged particles will be agglomerated by the Coulomb force between them. After the agglomeration, small particles such as PM2.5will grow larger and easier to be removed by ESP. There are large numbers of high energy electrons generated by pulsed corona discharge. In the processes of collisions between high energy electrons with background gas molecules, many different kinds of oxygenated radicals (e.g., O and OH radicals) and other active species (e.g., H2O2, O3, and HO2) are generated. All these active species can oxidize pollutions such as NO and SO2to NO2and SO3molecules which are soluble in alkaline solution.In this dissertation, the removal of PM2.5and NOx using pulsed corona discharge has been investigated both theoretically and experimentally. In the theoretical study, particle charging in different electric fields is investigated. Both field charging and diffusion charging are calculated. In the mean time, the charging characteristic of small particles in different electric fields and energy consumption are investigated.In the experimental study, a simultaneous removal system based on pulsed corona discharge for small particles and NOx has been established. First of all, particle charging characteristic by both pulsed and DC power supply has been investigated. The result is a perfectly match compare with the theoretical calculation. Then, the charging and removal efficiency of PM2.5has been studied in different oxygen concentration and relative humidity of flue gas. Experimental results show that when the particle diameter is larger than0.2μm, particle removal efficiency increases along with the increase of diameter. When the diameter is smaller than0.1μm, the result is just opposite, particle removal efficiency decrease along with the increase of diameter. In the diameter region of0.1-0.2μm, particle removal efficiency is the lowest. The total PM2.5removal efficiency has a very significant improvement using pulsed corona discharge than DC power supply. With the decrease of oxygen concentration and increase of the relative humidity, PM2.5removal efficiency increases.In the NO conversion experiment study, an optimized geometry structure of laboratory scale plasma discharge reactor has been investigated. The conclusion we obtain can be a theoretical basis for further industrial application. Three different experimental methods are performed to study the geometry structure of the plasma reactor. They are electrical experiment, optical experiment and NO conversion experiment. Then, NO removal efficiency under different oxygen concentration and relative humidity has been studied. Energy consumption of the NO conversion process is calculated.Simultaneous removal of PM2.5and NO from flue gas by pulsed corona discharge has been investigated. The result shows that the existence of PM2.5has a huge impact on the NO conversion efficiency. NO conversion efficiency drops nearly20%with the existence of PM2.5in the flue gas. However, the existence of NO has little effect on PM25removal efficiency.Based on the results of the laboratory scale experiment, an ESP with pulsed corona discharge system has been designed to control PM2.S and NO from flue gas. The system consists of DC pre-removal area, pulsed corona discharge area and ESP. Finally the energy consumption of the system has been calculated. A discussion has been made about the future industrial application about pulsed corona discharge.更多还原