固态SCR技术降低柴油机尾气NO_(x)的排放

Reduction of NO_(x)emissions from diesel engines by solid SCR technology

为解决尿素SCR技术在低排气温度时NO_(x)转化效率低、整车实际运行过程中易产生尿素结晶的问题,在发动机台架和实际道路开展了实验,研究固态SCR对NO_(x)污染物的排放影响。结果表明:携带相同质量还原剂时,固态SCR系统的体积仅为尿素SCR系统的1/3;当排气温度为160℃时,固态SCR系统对NO_(x)转化效率可达到40%;相同氨氮比下,WHSC循环对NO_(x)转化效率提升了3.3%,WHTC循环对NO_(x)转化效率提升了4.5%;将固态SCR起喷温度降低到160℃后,NO_(x)转化效率提升明显,较200℃起喷温度的固态SCR系统、尿素SCR系统分别提升9.7%和15.5%。基于功基窗口法对固态SCR与尿素SCR的NO_(x)比排放进行了分析,功基窗口数在(0,20]时,匹配尿素SCR系统的柴油车NO_(x)污染物排放量,分别是160℃起喷温度和200℃起喷温度固态SCR系统的2.38和1.73倍。

The urea-SCR technology is prone to low NO_(x)conversion efficiency and urea crystallization in the low exhaust temperature actual operation process of the vehicle.To address this,engine test bench studies are conducted to investigate the effectiveness of solid SCR technology on NO_(x)emission reduction.Results show that the volume of the solid SCR system is only 1/3 of the urea-SCR when carrying the same amount of reductant.The NO_(x)conversion efficiency of the solid SCR system reaches 40%when the exhaust temperature is 160℃.Based on the same ammonia nitrogen ratio setting,the NO_(x)conversion efficiency improves by 3.3%and 4.5%by applying the WHSC and WHTC cycles respectively.The NO_(x)conversion efficiency improves significantly when the starting temperature of the solid SCR is reduced to 160℃,which is 9.7%and 15.5%higher than that of the solid SCR system and urea-SCR systems at 200℃,respectively.The emission of NO_(x)pollutants from diesel vehicles with the urea-SCR system is significantly higher,which is 2.38 and 1.73 times that of solid SCR system with injection temperature at 160℃and 200℃according to the work based windows analysis((0,20]).