Investigation on the urea deposit formation and thermal decomposition characteristics in the SCR aftertreatment system of a diesel engine  

作　　者：Menghan Li Yao Zhang Jiancheng Yang Xiaori Liu Zhenguo Li Qiang Zhang 

机构地区：[1]Tianjin Key Laboratory of Clean Energy and Pollution Control,School of Energy and Environmental Engineering,Hebei University of Technology,Tianjin 300401,China [2]School of Civil and Transportation Engineering,Hebei University of Technology,Tianjin 300401,China [3]National Engineering Laboratory for Mobile Source Emission Control Technology,China Automotive Technology&Research Center Co.,Ltd.,Tianjin 300300,China [4]State Key Laboratory of Engines,Tianjin University,Tianjin 300072,China [5]School of Energy and Power Engineering,Shandong University,Jinan,Shandong 250061,China

出　　处：《Journal of Environmental Sciences》2021年第5期157-171,共15页环境科学学报（英文版）

基　　金：supported by the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2018A10);the Science Fund for Young Scholars of Natural Science Fund in Hebei Province(No.E2019202198);the Science and Technology Research Project of Colleges and Universities in Hebei Province(No.QN2019056);the State Key Laboratory of Engines,Tianjin University(No.K2020-15)。

摘　　要：Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle(WHTC) urea deposits are urea, cyanuric acid(CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cu β and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cu β, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.

关 键 词：Urea deposit Decomposition characteristics Selective catalytic reduction Catalyst THERMOLYSIS 

分 类 号：X701[环境科学与工程—环境工程]