Experimental Study On Removal Of NO_x From Simulative Diesel-Engine Exhaust Using Strong Ionization Discharge

Pollution of diesel-engine exhaust is getting worse with increase of the number of vehicles in our country. Because catalyst method usually used doesn't remove NOx well and can bring secondary pollution, many scholars begin to study plasma chemistry method. Considering the key problems of current research of reduction of diesel-engine exhaust NOx with plasma chemistry method, it is brought forward that strong ionization discharge method ionizing and decomposing O2 and H2O into high concentration active radicals on a molecular scale, then oxidizing NOx into HNO3, which is based on the key NSFC Project (No.: 60031001) and the key project of ministry of communications. (No.: 95-06-02-19)The paper is divided into three parts:1. The radiation of DBD plasma is studied at atmospheric pressure in its device with a transparent electrode and an observed side section. As a result, the applied voltage, applied frequency and the configuration of DBD can effect on its radicalization. Some methods, including the narrow discharge gap and thinner dielectric layer, high-frequency high-voltage power supply, were used in the micro-gap DBD at atmospheric pressure. These improvements are very helpful in increasing the electrical filed strength and power density in discharge gap of DBD. Thereby, it is a useful means for accomplishing strong ionization discharge at atmosphere pressure.2. Plasma source is designed by using the narrow discharge gap and thinner a-Al2O3 dielectric layer and high-frequency high-voltage power supply. Then resonance of DBD system is resolved. These improvements are very helpful in increasing the electrical filed strength and ionization region in discharge gap of DBD. As a result, strong ionization discharge is accomplished at atmosphere pressure.3. The results of strong ionization discharge remove NOx are shown as following: Influence of removal efficiency of NOx by several factors such as applied voltage, oxygen concentration, H2O concentration, primary concentration of NO, gas flow et al.is discussed. Through improving plasma source and gas mixing device, adding watering device, when gas flow is 10L/min, the primary concentration of NO is 800×10-6(v/v), removal efficiency of NOx is 82.7%, which is much higher than that of traditional plasma chemical method.