摘要
由于脉冲电晕放电等离子体烟气脱硫脱氮工艺具有传统方法所不具有的优点，因而成为近年来中外学者研究的热门课题之一。但大功率高压脉冲电源和烟气脱硫的能量效率是制约此技术工业应用的两个主要原因，因此本文进行了直流电晕放电氨气、水蒸气活化的烟气脱硫实验和脉冲放电脱硫反应器电极结构的优化配置研究。实验研究了直流电晕放电过程中离子电流和OH自由基生成的影响因素和直流电晕放电氨气和水蒸气活化烟气脱硫效率的影响因素，得到了设计直流电晕放电氨气、水蒸气同时活化的烟气脱硫反应器所需的数据和参数；同时，研究了脉冲放电烟气脱硫反应器的电极结构对一次流光能量、峰值电压等的影响，得到一些有用的结论。本文主要的实验结论如下：
1．在离子电流测试实验中，离子电流随活化电压的升高而增大；测试装置风速约为0.5m／s时，气流中的离子数目衰减一半的距离约为9cm。
2．利用二氧化硫与OH自由基的氧化反应测试了直流电晕放电过程中生成的OH自由基的数量。在本实验条件下，二氧化硫浓度为2000ppm，空气湿度为4.7％(w％)，活化电极注入功率为1.9W～2.9W时，测得的OH自由基数量级为10~(15)／cm~3。
3．针直径、水蒸气和氨气影响活化电极的放电特性。针直径减小和活化电压升高增大电晕电流；水蒸气和氨气降低电晕电流。
4．活化电压、氨气和二氧化硫的摩尔比(R)、氨气从放电针的喷出速度、烟气停留时间、湿度等因素影响直流电晕放电氨气活化的烟气脱硫效果。本实验条件下，烟气脱硫效率随活化电压、R、湿度的增大和烟气停留时间的延长而升高；直流电晕放电氨气活化时，每根针的喷气速度为0.13m／s-0.16m／s比较合适。
5．活化电压、烟气停留时间、水蒸气流量、放电针的内径影响直流电晕放电水蒸气活化时的烟气脱硫效果。本实验条件下，活化电压升高、烟气停留时间延长提高烟气脱硫效率；针内径为1mm的活化电极的烟气脱硫效率高于针内径为3mm的活化电极的烟气脱硫效率；烟气脱硫效率随水蒸气流量增大而升高，水蒸气活化时，每根针的喷气速度应大于3.54m／s。
6．根据实验数据，设计了一台烟气处理量为20000Nm~3／h，二氧化硫初始浓度为2000ppm的直流电晕放电水蒸气和氨气同时活化的烟气脱硫反应器。
7．研究了脉冲电晕放电等离子体烟气脱硫反应器的电极结构配置和放电特性，线-线间距(b)和板-板间距(d)满足关系b／d=0.4-0.6时，注入反应器的一次流光脉冲能量比较大。
The desulphurization and denitrification process by pulsed discharge plasma technology has been the recent research focus because of its advantages over traditional treatment methods for flue gas. But there are two main bottlenecks, the large scale pulsed high-voltage power and the energy efficiency, restraining the technology for industrial application. So the desulphurization process utilizing activated ammonia and water vapor by DC corona discharge and appropriate electrode configuration of pulsed discharge reactor are investigated. The factors influencing the ions' current and the number of OH radicals produced by DC corona discharge are investigated, and those influencing the desulphurization efficiency in the process of ammonia and water vapor activation are also studied, some useful data and parameters for designing a deSO2 reactor with the process of activated ammonia and water vapor are gained. Experimental study on electrode configuration and discharge characteristics of a pulsed discharge reactor
is finished, and some useful information is gained.
The main experimental conclusions gained are summarized below:
1. In our experiments for measuring ions' current, ions' current produced by DC corona discharge increases with higher voltage; and ions' current in the air decreased half at the distance of 9cm to the activation electrode when the velocity of air is 0.5.
2. The number of OH radicals produced by DC corona discharge has been measured utilizing the oxidation reaction between hydroxyl radicals and sulfur dioxide. In our experiments, when power infused into activation electrodes between 1.9W and 2.9W, vapor content and initial concentration of sulfur dioxide being 4.7%(w%) and 2000ppm respectively, the number of hydroxyl radicals detected is about 1015/cm3.
3. The discharge characteristics of activation electrodes are influenced by diameter of needles, water vapor and ammonia. The corona current increases with thinner diameter and higher voltage, and ammonia and water vapor decreases the corona current.
4. When using ammonia-activating process, the desulphurization efficiency is influenced by these factors, such as activation voltage, mol ratio(R) between SO2 and N3, ejection velocity of ammonia from needles, residence time and humidity of the flue gas. The desulphurization efficiency before and after activation increases with higher voltage, humidity, R and longer residence time; in our experiments, the appropriate ejection velocity of ammonia from needles is between 0.13m/s and 0.16m/s.
5. When using water vapor activating process, the desulphurization efficiency is influenced by activation voltage, residence time of the flue gas, and flux of water vapor and diameter of discharge needles. The desulphurization efficiency increases with higher activation voltage and longer residence time; in our experiments, the deSO2 efficiency using discharge needles with inner diameter of 1mm is higher than that with inner diameter of 3mm; the deSO2 efficiency before activation increases with bigger flux of water vapor, when water vapor activated, the ejection velocity of vapor should exceed 3.54m/s.
6. According to our experimental conclusions gained in previous chapters, a deSO2 reactor with flux of 20000Nm3/h of flue gas and initial concentration of 2000ppm using the process of simultaneously activated ammonia and water vapor by DC corona discharge is designed.
7. The electrode configuration and discharge characteristics of a pulsed discharge deSO2 reactor are studied and some useful information is gained. In our experiments, When wire-to-wire spacing (b) and plate-to-plate spacing (d) satisfy the relation: b/d=0.4-0.6, primary streamer energy infused into the reactor was greater.
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