基于气液两相DBD的火电厂NO_x废气处理的研究
发布时间：2018-11-08 17:55
【摘要】：氮氧化物(NOx)是主要的大气污染物之一,它不仅危害人和动物的健康,而且破坏生态环境。因为火电厂是NOx的主要排放源,所以控制火电厂的NOx排放成为电力行业亟须解决的问题。与传统NOx处理技术相比,低温等离子体技术具有占地面积小、投资少、没有二次污染等诸多优点。目前对于等离子体废气处理领域大多采用的是板板电极,而本文研究的是常温常压环境下气液两相介质阻挡放电反应器产生的等离子体对NOx的去除效果。因为羟基自由基(OH)在NOx去除过程中起着重要的作用,所以本文采用发射光谱法对低温等离子体中活性基团的类型及分布特征进行了诊断分析,着重分析了液相成分、峰值电压、电源频率以及相对空气湿度等对OH自由基的影响。主要结论有:OH自由基的光谱强度随着NaOH溶液浓度、峰值电压以及电源频率的增加而增加;OH自由基的光谱强度随着空气相对湿度的增加先增加后减小。相同实验条件下,气液两相介质阻挡放电的OH自由基光谱强度均高于传统板板电极介质阻挡放电,这将有利于NOx的去除。其次,本文研究了峰值电压、气体停留时间、NOx起始浓度、气体流量、NaOH溶液浓度、烟气相对湿度等条件对气液两相介质阻挡放电的NOx去除率和NO2生成量的影响,并对比分析了在相同实验条件下气液两相介质阻挡放电和板板电极的NOx去除率。研究发现:NOx的去除率与峰值电压呈正比,在峰值电压为21kV时达到最大值;NOx的去除率随着气体停留时间的增长而提高,气体停留大于30s时达到最大值;NOx去除率随着NOx起始浓度、气体流量的增加而减小;NOx去除率随着NaOH浓度的增加而增加,在NaOH浓度为1.5mol/L是达到最大值;NOx去除率随着烟气相对湿度的增加呈现先增加而后大幅减小的趋势,在相对湿度为50%时NOx去除率达到最大;液相为NaOH溶液的气液两相介质阻挡放电的NO2生成量远远小于传统板板电极。相同实验条件下,气液两相介质阻挡放电对NOx的去除率明显大于板板电极介质阻挡放电。本文的研究成果为气液两相介质阻挡放电在火电厂的脱硝应用提供一定的理论依据和应用价值。
[Abstract]:Nitrogen oxide (NOx) is one of the major atmospheric pollutants, which not only harms human and animal health, but also destroys the ecological environment. Because thermal power plant is the main emission source of NOx, controlling NOx emission of thermal power plant becomes an urgent problem to be solved in power industry. Compared with traditional NOx technology, low temperature plasma technology has many advantages, such as small area, less investment, no secondary pollution and so on. At present, plate electrode is used in plasma waste gas treatment, and the removal efficiency of NOx by plasma produced by gas-liquid two-phase dielectric barrier discharge reactor under normal temperature and atmospheric pressure is studied in this paper. Because hydroxyl radical (OH) plays an important role in the removal of NOx, the type and distribution of active groups in low temperature plasma were diagnosed and analyzed by means of emission spectrometry, and the composition of liquid phase was emphatically analyzed. The effect of peak voltage, power frequency and relative air humidity on OH free radical. The main conclusions are as follows: the spectral intensity of OH radical increases with the increase of the concentration of NaOH solution, the peak voltage and the frequency of power supply, and the spectral intensity of OH radical increases first and then decreases with the increase of air relative humidity. Under the same experimental conditions, the OH free radical spectral intensity of gas-liquid dielectric barrier discharge is higher than that of conventional plate electrode, which will be beneficial to the removal of NOx. Secondly, the effects of peak voltage, residence time of gas, initial concentration of NOx, flow rate of gas, concentration of NaOH solution and relative humidity of flue gas on NOx removal rate and NO2 production of gas-liquid two-phase dielectric barrier discharge are studied. The NOx removal rates of gas-liquid two-phase dielectric barrier discharge and plate electrode were compared and analyzed under the same experimental conditions. It is found that the removal rate of NOx is proportional to the peak voltage and reaches the maximum when the peak voltage is 21kV, and the removal rate of NOx increases with the increase of gas residence time, and reaches the maximum when the gas stays more than 30 s. The removal rate of NOx decreased with the initial concentration of NOx and the increase of gas flow rate, and the removal rate of NOx increased with the increase of NaOH concentration, and reached the maximum when the concentration of NaOH was 1.5mol/L. With the increase of relative humidity of flue gas, the removal rate of NOx increased first and then decreased significantly, and the removal rate of NOx reached the maximum when the relative humidity was 50. The NO2 production of gas-liquid two-phase dielectric barrier discharge in NaOH solution is much smaller than that of conventional plate electrode. Under the same experimental conditions, the removal rate of NOx by gas-liquid two-phase dielectric barrier discharge is obviously higher than that of plate electrode dielectric barrier discharge. The research results in this paper provide certain theoretical basis and application value for the application of gas-liquid two phase dielectric barrier discharge in denitrification of thermal power plant.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621;X773
本文编号：2319246
[Abstract]:Nitrogen oxide (NOx) is one of the major atmospheric pollutants, which not only harms human and animal health, but also destroys the ecological environment. Because thermal power plant is the main emission source of NOx, controlling NOx emission of thermal power plant becomes an urgent problem to be solved in power industry. Compared with traditional NOx technology, low temperature plasma technology has many advantages, such as small area, less investment, no secondary pollution and so on. At present, plate electrode is used in plasma waste gas treatment, and the removal efficiency of NOx by plasma produced by gas-liquid two-phase dielectric barrier discharge reactor under normal temperature and atmospheric pressure is studied in this paper. Because hydroxyl radical (OH) plays an important role in the removal of NOx, the type and distribution of active groups in low temperature plasma were diagnosed and analyzed by means of emission spectrometry, and the composition of liquid phase was emphatically analyzed. The effect of peak voltage, power frequency and relative air humidity on OH free radical. The main conclusions are as follows: the spectral intensity of OH radical increases with the increase of the concentration of NaOH solution, the peak voltage and the frequency of power supply, and the spectral intensity of OH radical increases first and then decreases with the increase of air relative humidity. Under the same experimental conditions, the OH free radical spectral intensity of gas-liquid dielectric barrier discharge is higher than that of conventional plate electrode, which will be beneficial to the removal of NOx. Secondly, the effects of peak voltage, residence time of gas, initial concentration of NOx, flow rate of gas, concentration of NaOH solution and relative humidity of flue gas on NOx removal rate and NO2 production of gas-liquid two-phase dielectric barrier discharge are studied. The NOx removal rates of gas-liquid two-phase dielectric barrier discharge and plate electrode were compared and analyzed under the same experimental conditions. It is found that the removal rate of NOx is proportional to the peak voltage and reaches the maximum when the peak voltage is 21kV, and the removal rate of NOx increases with the increase of gas residence time, and reaches the maximum when the gas stays more than 30 s. The removal rate of NOx decreased with the initial concentration of NOx and the increase of gas flow rate, and the removal rate of NOx increased with the increase of NaOH concentration, and reached the maximum when the concentration of NaOH was 1.5mol/L. With the increase of relative humidity of flue gas, the removal rate of NOx increased first and then decreased significantly, and the removal rate of NOx reached the maximum when the relative humidity was 50. The NO2 production of gas-liquid two-phase dielectric barrier discharge in NaOH solution is much smaller than that of conventional plate electrode. Under the same experimental conditions, the removal rate of NOx by gas-liquid two-phase dielectric barrier discharge is obviously higher than that of plate electrode dielectric barrier discharge. The research results in this paper provide certain theoretical basis and application value for the application of gas-liquid two phase dielectric barrier discharge in denitrification of thermal power plant.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621;X773
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