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Degradation of DeNOx Performance of a Urea-SCR System in In-Use Heavy-Duty Vehicles Complying with the New Long-Term Regulation in Japan and Estimation of its Mechanism
Technical Paper
2016-01-0958
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Degradation of the deNOx performance has been found in in-use heavy-duty vehicles with a urea-SCR system in Japan. The causes of the degradation were studied, and two major reasons are suggested here: HC poisoning and deactivation of pre-oxidation catalysts. Hydrocarbons that accumulated on the catalysts inhibited the catalysis. Although they were easily removed by a simple heat treatment, the treatment could only partially recover the original catalytic performance for the deNOx reaction. The unrecovered catalytic activity was found to result from the decrease in conversion of NO to NO2 on the pre-oxidation catalyst. The pre-oxidation catalyst was thus studied in detail by various techniques to reveal the causes of the degradation: Exhaust emission tests for in-use vehicles, effect of heat treatment on the urea-SCR systems, structural changes and chemical changes in active components during the deactivation were systematically investigated. Laboratory experiments to reproduce the degradation using simulant exhaust gases and catalyst samples were also conducted. Aluminum sulfate was indicated to be a major cause of the deactivation. It was produced mainly at approximately 300°C through oxidation of SO2 to SO3, reaction of SO3 with water, and finally reaction of Al2O3 with H2SO4 to generate Al2(SO4)3. The effects of aluminum sulfate on the activity of oxidation catalysts remained unknown.
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Authors
- Kenichiroh Koshika - National Traffic Safety and Environment Laboratory
- Nobuya Iwami - Tokyo Roki, Co. , Ltd.
- Takayuki Ichikawa - Tokyo Roki, Co. , Ltd.
- Hisakazu Suzuki - National Traffic Safety and Environment Laboratory
- Toshiro Yamamoto - National Traffic Safety and Environment Laboratory
- Yuichi Goto - National Traffic Safety and Environment Laboratory
- Masakazu Iwamoto - Chuo University
Topic
Citation
Koshika, K., Iwami, N., Ichikawa, T., Suzuki, H. et al., "Degradation of DeNOx Performance of a Urea-SCR System in In-Use Heavy-Duty Vehicles Complying with the New Long-Term Regulation in Japan and Estimation of its Mechanism," SAE Technical Paper 2016-01-0958, 2016, https://doi.org/10.4271/2016-01-0958.Also In
References
- Interim committee report of after-treatment devices for emission gases 2013 http://www.mlit.go.jp/common/000990922.pdf https://www.env.go.jp/press/16434.html
- Final committee report of after-treatment devices for emission gases 2014 Ministry of Land, Infrastructure, Transport and Tourism homepage http://www.mlit.go.jp/common/001046134.pdf https://www.env.go.jp/press/press.php?serial=17963
- Koshika , K. , Iwami , N. , Ichikawa , T. , Suzuki , H. Yamamoto , T. Goto , Y. and Iwamoto , M. Estimating the In-use Degradation Mechanism of a Pre-oxidation Catalyst for Heavy-duty Urea-SCR Vehicles Complying with the New Long-term Target-based Regulation in Japan 2015 JSAE Annual Congress (Spring) Proceedings 2015-5407
- Ishii , H. and Suzuki , H. Emission Characteristics of Urea SCR HD Vehicles The 12th International Symposium on Technology for Next Generation Vehicle & Machine proceedings 81 89
- Tennison , P. , Lambert , C. , and Levin , M. NOx Control Development with Urea SCR on a Diesel Passenger Car SAE Technical Paper 2004-01-1291 2004 10.4271/2004-01-1291
- Cavataio , G. , Girard , J. , Patterson , J. , Montreuil , C. et al. Laboratory Testing of Urea-SCR Formulations to Meet Tier 2 Bin 5 Emissions SAE Technical Paper 2007-01-1575 2007 10.4271/2007-01-1575
- Suzuki , H. , Yamamoto , T. and Yamaguchi , K. Emission Characteristic Trends of In-use Urea SCR HD Vehicles JSAE Transaction 2014 45 1 43 48