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Tuning the Standard SCR Reaction Kinetics to Model NO Conversion in a Diesel Engine Exhaust SCR Catalyst System Under Steady State Conditions in 1D and 3D Geometries Using Ammonia Gas as the Reductant
ISSN: 0148-7191, e-ISSN: 2688-3627
Published September 10, 2012 by SAE International in United States
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Removal of NOx from lean diesel exhaust can be achieved by the use of selective catalytic reduction technology. The supplied reductant is often ammonia, either as urea or as ammonia gas released from a storage medium. Experiments have been carried out on an engine test rig run to steady state conditions using NOx composed mainly of NO, with ammonia gas as the reductant. This was essentially a 1D study because a long 10 degree diffuser was used to provide uniform temperature and velocity profile to the SCR catalyst brick in the test exhaust system. Tuning of the standard reaction, the NO SCR reaction, in a kinetic scheme from the literature and adjustment of the ammonia adsorption kinetics achieved improved agreement between the measurements and CFD simulations. This was carried out for studies at exhaust gas temperatures between 200 and 300°C. The effect of diffuser geometry upstream of the SCR catalyst on NOx conversion was then investigated experimentally using a 180 degree sudden expansion as a 3D diffuser. These were also steady state studies with the exhaust NOx composed mostly of NO. The SCR brick was short, 45 mm in length, to provide a rigorous test of the kinetics. Observed NOx conversion profiles for ammonia supplied in quantities ranging from deficient to excess showed that the combined influence of temperature and velocity profiles upstream of the SCR was apparent in this 3D case. 2D axially symmetric CFD simulations have been carried out to model the 3D case and the predictions are discussed and compared with engine test data in this paper.
CitationBenjamin, S., Gall, M., and Roberts, C., "Tuning the Standard SCR Reaction Kinetics to Model NO Conversion in a Diesel Engine Exhaust SCR Catalyst System Under Steady State Conditions in 1D and 3D Geometries Using Ammonia Gas as the Reductant," SAE Technical Paper 2012-01-1636, 2012, https://doi.org/10.4271/2012-01-1636.
- Olsson, L., Sjovall, H., Blint, R. J.. A kinetic model for ammonia selective catalytic reduction over Cu-ZSM-5. Applied catalysis B: Environmental. Vol. 81 (2008) pp 203-217
- Chi, J. and DaCosta, H., “Modeling and Control of a Urea-SCR Aftertreatment System,” SAE Technical Paper 2005-01-0966, 2005, doi:10.4271/2005-01-0966.
- Chatterjee, D., Burkhardt, T., Weibel, M., Nova, I. et al., “Numerical Simulation of Zeolite- and V-Based SCR Catalytic Converters,” SAE Technical Paper 2007-01-1136, 2007, doi:10.4271/2007-01-1136.
- Kamasamudram, K., Currier, N. W., Chen, X., Yezerets, A.. Overview of the practically important behaviors of zeolite based urea-SCR catalysts, using compact experimental protocol. Catalysis Today. Vol. 151 (2010) pp 212-222
- Salasc, S., Skoglundh, M. and Fridell, E.. A comparison between Pt and Pd in NOx storage catalysts. Applied Catalysis B: Environmental. Vol. 36 (2002) 145-160
- Watling, T., Tutuianu, M., Desai, M., Dai, J. et al., “Development and Validation of a Cu-Zeolite SCR Catalyst Model,” SAE Technical Paper 2011-01-1299, 2011, doi:10.4271/2011-01-1299.
- Sturgess, M., Benjamin, S., and Roberts, C., “Spatial Conversion Profiles within an SCR in a Test Exhaust System with Injection of Ammonia Gas Modelled in CFD using the Porous Medium Approach,” SAE Technical Paper 2010-01-2089, 2010, doi:10.4271/2010-01-2089.
- Benjamin, S. F., Gall, M., Sturgess, M. P., Roberts, C. A.. Experiments on a light duty SCR test exhaust system using ammonia gas to provide data for validation of a CFD model. Proceedings of I Mech E Conference Internal Combustion Engines: Improving Performance, Fuel Economy and Emissions, London, November 2011
- Tronconi, E., Nova, I., Ciardelli, C., Chatterjee, D., Bandl-Konrad, B., Burkhardt, T.. Modelling of an SCR catalytic converter for Diesel exhaust after treatment: Dynamic effects at low temperature. Catalysis Today. Vol. 105 (2005) pp 529-536
- Fedeyko, J. M., Chen, B., Chen, H-Y. Mechanistic study of the low temperature activity of transition metal exchanged zeolite SCR catalysts. Catalysis Today. Vol. 151 (2010) pp 231-236
- Kamasamudram, K., Currier, N., Szailer, T., and Yezerets, A., “Why Cu- and Fe-Zeolite SCR Catalysts Behave Differently At Low Temperatures,” SAE Int. J. Fuels Lubr. 3(1):664-672, 2010, doi:10.4271/2010-01-1182.
- Benjamin, S. F., Roberts, C. A., Three-dimensional modelling of NOx and particulate traps using CFD: A porous medium approach. Applied Mathematical Modelling. Vol. 31 (2007) 2446-2460
- Benjamin, S. F., Roberts, C. A.. The porous medium approach applied to CFD modelling of SCR in an automotive exhaust with injection of urea droplets. Proceedings of IMechE Internal Combustion Engines: Performance, Fuel Economy and Emissions, London, December 2007
- Quadri, S. S., Benjamin, S. F., Roberts, C. A.. An experimental investigation of oblique entry pressure losses in automotive catalytic converters. Proc I Mech E Part C: J Mech Eng Sci. Vol. 223 (2009) 2561-2569
- Yakhot, V., Orszag, S. A., Thangam, S., Gatski, T. B., Speziale, C. G.. Development of turbulence models for shear flows by a double expansion technique. Physics of Fluids. Vol. A4(7) (1992) 1510-1520
- CD-adapco. Methodology Manual for Star-CD software, Version 4.14