控制排放中NO2体积分数提高SCR效率的研究

Research of Improving SCR Efficiency by Adjusting NO2 in Exhaust

为适应排放法规要求,根据选择性催化还原(selective catalytic reduction,SCR)的反应机理,通过在特定工况下调节SCR上游NOx排放中NO2的体积分数,抑制慢反应,保证SCR内部的快反应顺利进行,提高SCR的反应速率。利用氧化催化器(diesel oxidation catalyst,DOC)的氧化作用及比例、积分、微分(proportion,integral,differential,PID)闭环控制,通过调节DOC的旁通电磁阀使SCR上游NO2体积分数达到设定值,实现提高SCR整体效率的目的。试验验证表明,该方法在特定工况下能够有效提高SCR的转换效率。

In order to satisfy the gradually strict emission regulation, it is an effective method to improve the SCR (selective catalytic reduction) efficiency by adjusting the NO2 ratio in NOx emission under certain operation conditions, since it could promote the fast reaction as well as inhibit the slow reaction, according to the mechanism of chemical reaction in SCR. The closed loop control based on PID and oxidation control of DOC (diesel oxidation catalyst) were used. During the experiments, a bypass-valve next to the DOC control the NO2 ratio upstream of SCR to a certain value, which help to improve the efficiency of SCR in certain conditions.