Investigation of plasma NOx treatment method for diesel exhaust gas at-exhaust gas temperature ranges

对柴油机排气在排气温度范围内的等离子体NOx处理进行了研究。柴油机在满负荷工作时，排气温度可达400℃左右。这种高温气体的等离子体处理与低温处理的效率不同，因为在高温下化学反应会变得活跃。以一台2.4kVA柴油发电机组的废气为处理对象，在实验室搭建了耐高温的专用实验系统。采用直接放电法和臭氧注入法考察了温度对NO脱除效率的影响，第一年考察了直接放电法脱除高达150℃的NO效率，发现在90~130℃温度范围内，直接放电法脱除NO的效率提高到30g/kWh左右。研究还发现，尽管人们怀疑臭氧在高温下会被破坏，但臭氧注入方法至少可以应用到180摄氏度。在废气中添加氢碳被认为是一种提高NO脱除效率的方法，但在高温到150℃时的效果与较低的气体温度相比没有显著差异。第二年，通过增加一些气体加热系统，对实验系统进行了改进，使其在更高的温度下进行等离子体处理。进行了高达220℃的实验，效率提高到30~35g/kWh。为了在更高的温度下进行实验，建立了一种新的紧凑型实验系统，使用了1/10的废气。实验结果表明，当气体温度为250℃时，脱氮率最高可达60g/kWh。

Investigation of plasma NOx treatment for diesel exhaust gas at exhaust gas temperature ranges was carried out. Temperature of exhaust gas from diesel engine attains to about 400 deg at full power. Plasma treatment for this high temperature gas will be different from that for lower temperature in its efficiency, because chemical reactions become active at elevated temperature. Exhaust gases from a 2.4kVA diesel engine generator was used as a target of processing, and special experimental system that endures the high temperature was build in laboratory. Direct discharge and ozone injection method were used to investigate the effect of temperature for NO removal efficiency.In the first year, the NO removal efficiency up to 150 degree was investigated, and it was found that the NO removal efficiency by direct discharge method increases to about 30g/ kWh at the temperature range from 90 degree to 130 degree. It was also found that ozone injection method can be applied to at least up to 180degree, in spite of the suspicion that ozone is destroyed at high temperature and will not work. Hydro-carbon addition to exhaust gas has been known as a method to improve the NO removal efficiency; however there was no significant difference in the effect at high temperature up to 150degree in comparison with lower gas temperature.In the second year, the experimental system was improved to perform the plasma treatment at much higher temperature by adding some gas heating system. Experiments up to 220 degree were carried out, and it was found that the efficiency increases to 30 to 35 g/ kWh. In order to do experiment at much higher temperature, a new compact experimental system, which uses 1/10 of exhaust gases, was built. The plasma treatment up to 250 degree was become possible, and the experimental results showed that the NO removal efficiency increased up to 60g/kWh at gas temperature of 250 degree.