Effects of a Combined Diesel Particle Filter-DeNOx System (DPN) on Reactive Nitrogen Compounds Emissions: A Parameter Study

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• 作者：Norbert V. Heeb ; Regula Haag ; Cornelia Seiler ; Peter Schmid ; Markus Zennegg ; Adrian Wichser ; Andrea Ulrich ; Peter Honegger ; Kerstin Zeyer ; Lukas Emmenegger ; Yan Zimmerli ; Jan Czerwinski ; Markus Kasper ; Andreas Mayer
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：December 18, 2012
• 年：2012
• 卷：46
• 期：24
• 页码：13317-13325
• 全文大小：448K
• 年卷期：v.46,no.24(December 18, 2012)
• ISSN：1520-5851

文摘

The impact of a combined diesel particle filter-deNO_x system (DPN) on emissions of reactive nitrogen compounds (RNCs) was studied varying the urea feed factor (伪), temperature, and residence time, which are key parameters of the deNO_x process. The DPN consisted of a platinum-coated cordierite filter and a vanadia-based deNO_x catalyst supporting selective catalytic reduction (SCR) chemistry. Ammonia (NH₃) is produced in situ from thermolysis of urea and hydrolysis of isocyanic acid (HNCO). HNCO and NH₃ are both toxic and highly reactive intermediates. The deNO_x system was only part-time active in the ISO8178/4 C1cycle. Urea injection was stopped and restarted twice. Mean NO and NO₂ conversion efficiencies were 80%, 95%, 97% and 43%, 87%, 99%, respectively, for 伪 = 0.8, 1.0, and 1.2. HNCO emissions increased from 0.028 g/h engine-out to 0.18, 0.25, and 0.26 g/h at 伪 = 0.8, 1.0, and 1.2, whereas NH₃ emissions increased from <0.045 to 0.12, 1.82, and 12.8 g/h with maxima at highest temperatures and shortest residence times. Most HNCO is released at intermediate residence times (0.2鈥?.3 s) and temperatures (300鈥?00 掳C). Total RNC efficiencies are highest at 伪 = 1.0, when comparable amounts of reduced and oxidized compounds are released. The DPN represents the most advanced system studied so far under the VERT protocol achieving high conversion efficiencies for particles, NO, NO₂, CO, and hydrocarbons. However, we observed a trade-off between deNO_x efficiency and secondary emissions. Therefore, it is important to adopt such DPN technology to specific application conditions to take advantage of reduced NO_x and particle emissions while avoiding NH₃ and HNCO slip.