Liao Jianxiong, Hu Jie, Zhong Jing, Yan Fuwu, Chen Peng, Hu Youyao, Zhu Lei
Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan, 430070, People's Republic of China.
Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan University of Technology, Wuhan, 430070, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Sep;29(42):63815-63836. doi: 10.1007/s11356-022-20152-x. Epub 2022 Apr 25.
An integrated aftertreatment system consisting of diesel oxidation catalyst (DOC), catalytic diesel particulate filter (CDPF), and selective catalytic reduction (SCR) is an effective way of reducing both NOx and particulate matter (PM). In this paper, the effect of DOC + CDPF + SCR on NO and particle emissions is investigated during different operations to assess applicability of this aftertreatment for meeting more rigorous non-road emissions standard. Meanwhile non-negligible issue about regeneration emission is studied. The results show that the DOC + CDPF have no significant effect on NOx but increase the NO/NOx ratio which is correlated with load. SCR is the main NOx reduction device with average efficiency of 86.5% for steady-state operations. Meanwhile, NH slip is lower than 16 ppm. During cold and hot non-road transient cycles (NRTC cycles), average NOx efficiencies are 56.7% and 57.8%, respectively, along with NH slip below 10 ppm. DOC + CDPF + SCR maintain filtration efficiency over 97% and 99% for PM and particle number (PN) for either steady-state operation or NRTC cycle, but particle size distributions change. Compared with the original emissions, NOx, PM, and PN emission factors are all below non-road China-IV limit after equipping with DOC + CDPF + SCR. However, during regeneration the aftertreatment does not maintain a high filtration performance but becomes particle generator. The penetration of nuclear particles and decomposition of agglomerated particles lead to high CDPF-out PN of 1.5 × 10 #/cm-3.5 × 10 #/cm. During regeneration, accumulated NOx is negligible, but the PM is 121.6 and 44.5 times higher than cold and hot NRTC cycles, respectively. In summary, DOC + CDPF + SCR is excellent way to improve non-road emissions but low SCR efficiency at low-temperature and high accumulated PM during regeneration process should be further addressed.
由柴油氧化催化剂（DOC）、催化型柴油颗粒过滤器（CDPF）和选择性催化还原（SCR）组成的集成后处理系统是减少氮氧化物（NOx）和颗粒物（PM）的有效方式。本文研究了DOC+CDPF+SCR在不同运行工况下对NO和颗粒物排放的影响，以评估该后处理系统满足更严格非道路排放标准的适用性。同时，对不可忽视的再生排放问题进行了研究。结果表明，DOC+CDPF对NOx无显著影响，但会提高与负荷相关的NO/NOx比值。SCR是主要的NOx还原装置，稳态运行时平均效率为86.5%。同时，氨逃逸低于16 ppm。在冷、热非道路瞬态循环（NRTC循环）中，平均NOx效率分别为56.7%和57.8%，氨逃逸低于10 ppm。DOC+CDPF+SCR在稳态运行或NRTC循环中对PM和颗粒数量（PN）的过滤效率均保持在97%和99%以上，但颗粒尺寸分布会发生变化。与原始排放相比，配备DOC+CDPF+SCR后，NOx、PM和PN排放因子均低于中国非道路国四限值。然而，在再生过程中，后处理系统无法保持高过滤性能，反而成为颗粒物发生器。核颗粒的穿透和团聚颗粒的分解导致CDPF出口处PN高达1.5×10⁶/cm³至3.5×10⁶/cm³。在再生过程中，累积的NOx可忽略不计，但PM分别比冷、热NRTC循环高121.6倍和44.5倍。综上所述，DOC+CDPF+SCR是改善非道路排放的极佳方式，但低温下SCR效率较低以及再生过程中PM累积量较高的问题仍需进一步解决。
