尿素-SCR技术对NOx转化率和NH3排放的影响

摘要

在AVL发动机台架上就尿素-SCR技术对NOx转化率和NH3排放的影响进行了试验,催化剂为钒氧化物,尿素质量分数从0变化到50%.研究发现,排气温度、空速、尿素浓度、尿素喷射量对NOx转化率和NH3排放有着重要影响:排气温度升高,NOx转化率先升高后下降,400～450℃是转折点;提高排气空速,NOx转化率线性下降,NH3排放线性增加;增加尿素浓度或喷射量,NH3与NOx物质的量之比n(NH3):n(NOx)≤1时,NOx转化率迅速提高,NH3排放没有明显变化,但当n(NH3):n(NOx)＞1时,NH3排放迅速增加.%The influences of urea-SCR technology on NOx conversion rate and NH3 emission were studied by the experiment of AVL engine bench. The used catalyst was vanadium oxide. The urea mass concentration increased from 0 to 50％. The result shows that the temperature and space velocity of exhaust and the concentration and injection quantity of urea have important influences on NOx conversion rate and NH3 emission. When the exhaust temperature rises, the NOx conversion rate first increases and then decreases, and its turning point is 400-450 ℃. When the space velocity increases, the NOx conversion rate declines linearly and the NH3 emission increases linearly. When the urea concentration or quantity increases, the NOx conversion rate increases rapidly, the NH3 emission keeps almost unchanged when the ratio of NH3 and NOx is not beyond 1 and increases rapidly when the ratio is higher than 1.