| 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. |
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