Technology of Aftertreatment for Simultaneous Reduction of NOx and Particulate Emissions Using High Frequency Barrier Discharge Plasma and Low Temperature Oxidation Catalyst

点击翻译按钮获取中文摘要

This study developed an aftertreatment system for reduction of NOx and particulate (PM) emissions from a diesel engine. Dielectric barrier discharge plasma and catalyst technologies are adapted to the system. The system is composed of a high-frequency barrier discharge reactor and PM oxidation part. In the barrier discharge reactor, the electrode has barrier discharge and produces plasma under low electric power condition. The air is activated by plasma and produces ozone, oxygen radical and nitrogen radical, resulting that NO is transformed to NO_2. In the PM oxidation part, particulates are oxidized under low temperature condition of less than 300℃ by using produced NO_2 and oxidation catalyst. Some experimental results are the follows. Consumed electric power and ozone formation in the reactor are strongly affected by barrier discharge electrode configuration and barrier material. The ozone formation controls the formation rate of NO_2. NO_2 formation rate is different with energy density of the reactor and is also affected by gas temperature, humidity and hydrocarbons. When introduced gas contains hydrocarbons, in particular C_2H_4 that is main decomposed hydrocarbons of diesel fuel, high NO_2 formation rate is obtained under low discharge power. Hydrocarbons restrain deterioration of NO_2 formation rate due to increase of gas temperature and humidity. Concerning particulate oxidation, plasma gas which has NO_2 and activated radicals can oxidize particulate under low temperature of 260℃ which is 100℃ lower than the case that particulate is oxidized by pure oxygen. Oxidation catalyst strongly promotes particulate oxidation. α-alumina and χ-alumina are effective as particulate catcher and catalyst holder.