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A State-Space Simplified SCR Catalyst Model for Real Time Applications
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 14, 2008 by SAE International in United States
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The use of Selective Catalytic Reduction (SCR) is becoming increasingly more popular as a way of reducing NOx emissions from heavy duty vehicles while maintaining competitive operating costs. In order to make efficient use of these systems, it's important to have a complete system approach when it comes to calibration of the engine and aftertreatment system. This paper presents a simplified model of a heavy duty SCR catalyst, primarily intended for use in combination with an engine-out emissions model to perform model based offline optimization of the complete system.
The traditional way of modelling catalysts using a dense discretization of the catalyst channels and non-linear differential equation solvers to solve the heat and mass balance equations, requires too much computational power in this application. The presented model is also useful in other applications such as model based control. The basic model structure is a series of continuously stirred tank reactors using discretized catalyst walls to describe the mass transport in the solid phase. The simplified model uses a state-space concept. At low temperatures the model uses an implicit method of calculating the coverage differential. At higher temperatures, the model is simplified to a first order system using an operating condition dependent characteristic time constant. These simple, yet robust methods allows for long step lengths in the process of solving the differential equations. This makes the model a useful improvement over current models.
CitationEricson, C., Westerberg, B., and Odenbrand, I., "A State-Space Simplified SCR Catalyst Model for Real Time Applications," SAE Technical Paper 2008-01-0616, 2008, https://doi.org/10.4271/2008-01-0616.
- Chi, J. Dacosta, H. “Modeling and Control of a Urea-SCR Aftertreatment System” SAE Technical papers 2005-01-0966 2005
- Ericson, C. Andersson, M. Egnell, R. Westerberg, B. “Modelling diesel engine combustion and NO x formation for model based control and simulation of engine and exhaust aftertreatment system” SAE Technical papers 2006-01-0687 2006
- Andersson, L. Gabrielsson, P Odenbrand, I “Reducing NO x in Diesel Exhausts by SCR Technique: Experiments and Simulations” A.I.Ch.E. J. 40 1994
- Andersson, L. “Mathematical Modelling in Catalytic Automotive Pollution Control” Doctoral Thesis Department of Chemical Reaction Engineering, Chalmers University of Technology 1995
- Ciardelli, C. Nova, I. Tronconi, E et. al. “SCR-DeNOx for diesel engine exhaust aftertreatment: unsteady-state kinetic study and monolithic reactor modelling” Chemical Engineering Science 59 2004
- Murzin, D. Salmi, T “Catalytic Kinetics” 408 285 288 Elsevier Amsterdam 2005
- Tronconi, E. Forzatti, P. “Adequacy of Lumped Parameter Models for SCR Reactors with Monolith Structure” AlChe Journal 38 1992