Experimental Study On NOx Removal Based On SCR Combined With Plasma

Among the exhaust aftertreatment technologies for diesel vehicle's NOX emission control, selective catalytic reduction (SCR) is considered to be one of the most promising methods to meet the Euro V and above emission regulations. However, there are some disadvantages in current vehicle SCR systems which have been tested in Europe, such as poor NO removal efficiency at low temperature, and low efficiency of reducing agent supplying. Besides, the high sulfur content of domestic diesel must be taken into account, if SCR is adopted to reduce diesel engine NO emission in China.In order to solve the problems mentioned above, an experimental research on a novel SCR system of diesel engine was investigated in this study, which mainly consists of four sections as followed.(a) A DBD reactor was designed and its oxidation efficiency on NO was checked. The effects of different reaction conditions (reactor gas composition, discharge voltage, etc.) on the oxidation performance of DBD reactor were investigated. In addition, the energy consumption in the oxidation reaction was also analyzed. The results show that the presence of O and C H can significantly increase the oxidation efficiency of NO. And optimal ranges of O and C H concentration were found, during which the oxidation efficiency of NO, the quantity of byproducts and energy consumption could be improved overall.(b) An experimental bench of SCR system was set up and on which, a series of experiments aiming to study the DeNO performance of SCR system with different reaction conditions (gas composition, reaction temperature, etc.) were carried out. The results reveal that the DeNO efficiency of SCR system rises when more NH is added. However, the quantity of NH must be carefully controlled to prevent itsleakage. The results also show that at low temperature, the DeNO efficiency rises with the increase of NO2/NO ratio, and reaches it maximum value at NO2/NO=1. At the temperature of 350℃,NO2 has less influence on NOX conversion efficiency(c) The performance of the novel SCR system combined with DBD reaction was tested under different reaction conditions (discharge voltage, gas composition and temperature, etc.). The performance difference between SCR system and DBD-SCR was analyzed. The results indicate that with the addition of C H , the DeNO efficiency could be improved obviously. And it also can be found that the DeNO efficiency of DBD-SCR system is better than that of the SCR system by comparison.(d) A storage device of NH based on the strong NH adsorption ability of CaCl was designed, by which the NH adsorption / desorption performance on the CaCl /expanded graphite adsorbent was tested. It is found that the NH adsorption capibility of this adsorbent is 0.2kg/kg. Ammonia desorption stops after 20min under 200℃, and small part of NH3 remains in the adsorbent.