低温等离子体用于柴油机尾气脱硝的实验

Experimental of diesel engine denitration by non-thermal plasma

柴油机作为卡车、重型机械以及船舶的主动力装置仍被广泛采用,其尾气中氮氧化物的脱除技术也是目前的研究热点。本文搭建了模拟柴油机尾气的配气系统,采用介质阻挡放电产生低温等离子体(non-thermal plasma,NTP)的方法对模拟柴油机尾气进行了脱硝的实验研究。实验结果表明:针对本系统,电源效率和能量密度随着输入电压的增大而升高,当输入电压高于60V时,电源效率在90%以上;在O2/N2条件下,随着O2浓度以及能量密度的增加,NO生成量逐渐增加,NO2生成量先增加后降低最终趋于稳定;在NO/N2条件下,低温等离子体对NO的脱除率接近100%;在NO/O2/N2条件下,随着NO浓度的增加,临界O2浓度升高,O2体积分数为1%时脱硝效率在90%以上,O2体积分数高于14%时低温等离子体的脱硝率为负值,且随着能量密度的增加,生成的NOx浓度也更高,O2浓度对低温等离子体的脱硝性能起决定性作用;在低能量密度时,加入NH3会提高脱硝性能,高能量密度时NH3会略微降低NTP的脱硝性能,当加入H2O模拟真实柴油机尾气成分且喷氨时,获得的脱硝率最高为40.6%。

Diesel engines are still widely used as main power equipment for trucks, heavy machinery and ships. The technologies of nitrogen oxides removal from diesel exhaust are hot research topics. This paper sets up a gas supply system that simulates the diesel exhaust, and uses a dielectric barrier discharger(DBD) to generate non-thermal plasma(NTP) to investigate the removal of nitrogen oxides. The experimental results showed that the power efficiency and energy density increase with the input voltage for this system. The power efficiency is above 90% when the input voltage is higher than 60 V. In the O2/N2 system, NO generation increases with the O2 concentration and energy density, while NO2 increases first,then decreases and stabilizes. The removal rate of NO is close to 100% by NTP in NO/N2N system. For the NO/O2/N2 system, the critical O2 concentration increases with NO concentration. With the increase of energy density, the denitrification efficiency is above 90% at 1% O2 volume fraction and negative when O2 volume fraction is higher than 14%. The O2 concentration plays a decisive role in the denitration performance of the NTP. NH3 improves the denitration rate at low energy density while slightly reduces the denitration rate at high energy density. The denitration rate is 40.6% at simulating real diesel exhaust conditions when H2O and ammonia is added.