柴油机尿素SCR催化剂储氨特性与氨泄漏影响因素的试验研究

Experimental Study on Ammonia Storage Characteristics and Factors Affecting the Ammonia Slip of Diesel Engine Urea SCR

在一台满足国-Ⅳ排放标准的柴油机上对尿素选择性催化还原系统中的氨泄漏及储氨特性进行了试验研究。重点研究了空速、温度及储氨量对氨泄漏的影响。研究结果表明：20 000h-1空速下,从尿素起喷到该工况下最大转化效率所用时间随温度增加而减小;达到饱和储氨量的时间随温度升高呈减少趋势;各工况下饱和储氨量为1.23～8.56g,随温度升高呈下降趋势。250℃催化剂入口温度下,从尿素起喷到该工况下最大转化效率所用时间随空速增加而减少;达到饱和储氨量的时间随空速增加呈减少趋势;各工况下饱和储氨量为2.68～12.10g,随空速增加呈下降趋势。固定空速条件下,随氨氮比增加,NOx转化效率呈升高趋势,但在250℃以下升幅并不明显;不同氨氮比下的氨泄漏量随催化剂入口温度的升高均呈先升高后降低的趋势。固定催化剂入口温度条件下,不同氨氮比下的氨泄漏量随空速的增加而升高。

The study on the factors affecting the ammonia slip and ammonia storage characteristics of urea SCR system was conducted on a diesel engine bench. The research focused on the effects of the temperature, space velocity and the ammonia storage on the ammonia slip. The results show that at the space velocity of 20 000 h^-1 , the time from the injection start to the maximum NOx conversion efficiency and the time from zero to the saturated amount of storage ammonia tend to decrease with increased temperature. The saturated amounts of storage ammonia are 1.23 g-8.56 g under various engine modes which tend to decrease with increased temperature. At the catalyst inlet temperature of 250 ℃, the saturated amounts of storage ammonia are 2.68 g- 12.10 g under various engine modes. The time from the injection start to the maximum NO, conversion efficiency and the time from zero to the saturated amount of storage ammonia decrease with increased space velocity. At the fixed space velocity, the NOx conversion efficiency increases with increased NSR, but does not increase obviously at lower than 250 ℃. The amount of ammonia slip with various NSR shows a trend of rise first then fall. At the fixed inlet temperature, the amount of ammonia slip will increase with the increase of space velocity.