| 1. |
- Dahlin, Sandra, et al.
(författare)
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Chemical aging of Cu-SSZ-13 SCR catalysts for heavy-duty vehicles –Influence of sulfur dioxide
- 2018
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Ingår i: Catalysis Today. - Amsterdam : Elsevier. - 0920-5861 .- 1873-4308. ; 320, s. 72-83
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Tidskriftsartikel (refereegranskat)abstract
- Selective catalytic reduction of nitrogen oxides is an efficient technique for emission abatement in heavy-dutyvehicles. Cu-SSZ-13 SCR catalysts are more active than vanadium-based catalysts at low temperatures, but aremore sensitive to deactivation by sulfur. Consequently, there is a need to study poisoning by sulfur for thiscatalyst material. This experimental investigation focuses on the effect of sulfur on the low-temperature per-formance of Cu-SSZ-13 SCR catalysts. The effect of sulfur exposure temperature, and the influence of the NO 2 /NO x ratio, are considered and two different regeneration temperatures are compared. In addition, catalystsamples from an engine-aged catalyst are evaluated. The SO 2 exposure temperature is shown to have an im-portant impact on the deactivation of the Cu-SSZ-13 catalyst. The lowest sulfur exposure temperature (220 °C)results in the most severe deactivation, while the highest temperature during sulfur exposure (400 °C) results inthe lowest degree of deactivation. This was found to be related to the amount of sulfur on the catalyst.Additionally, SO 2 exposure was shown to decrease the N 2 O selectivity. The engine-aged catalyst has a decreasedperformance in terms of both decreased activity and increased N 2 O selectivity. For this catalyst, impurities fromfuel and engine-oil can play a role in the deactivation. Different deactivation mechanisms are seen for the lab-and engine-aged catalysts.
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| 2. |
- Lundberg, Björn, 1982, et al.
(författare)
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DOC modeling combining kinetics and mass transfer using inert washcoat layers
- 2016
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 191, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to develop a kinetic and transport model for diesel oxidation catalysts (DOC) with a satisfactory compromise between accuracy and computational demands for robust simulation of transient full-scale operation. Specifically the model accounts for surface concentrations of key species needed to capture transient features for typical lean exhaust conditions. In addition, the model accounts for transport limitations and distinguish them from reaction kinetics as well as apparent NO oxidation inhibition effects due to reactions. To achieve this, lab scale experiments were performed with DOCs with different platinum loadings and three different washcoat configurations of which two had an inert top layer. Both kinetic parameters for a detailed kinetic model and effective diffusivities were optimized for the experimental data using a single channel catalyst model. The experiments showed a clear effect of increased transport resistance for propene and CO and also that NO2 plays an important role as an oxidizing agent for preferentially CO at low temperature (
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| 3. |
- Lundberg, Björn, 1982, et al.
(författare)
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Model-based experimental screening for DOC parameter estimation
- 2015
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Ingår i: Computers and Chemical Engineering. - : Elsevier BV. - 0098-1354. ; 74, s. 144-157
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Tidskriftsartikel (refereegranskat)abstract
- In the current study a parameter estimation method based on data screening by sensitivity analysis is presented. The method applied Multivariate Data Analysis (MVDA) on a large transient data set to select different subsets on which parameters estimation was performed. The subset was continuously updated as the parameter values developed using Principal Component Analysis (PCA) and D-optimal onion design. The measurement data was taken from a Diesel Oxidation Catalyst (DOC) connected to a full scale engine rig and both kinetic and mass transport parameters were estimated. The methodology was compared to a conventional parameter estimation method and it was concluded that the proposed method achieved a 32% lower residual sum of squares but also that it displayed less tendencies to converge to a local minima. The computational time was however significantly longer for the evaluated method.
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| 4. |
- Tayamon, Soma, et al.
(författare)
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Model-based temperature control of a selective catalytic reduction system
- 2015
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Ingår i: IET Control Theory & Applications. - : Institution of Engineering and Technology (IET). - 1751-8644 .- 1751-8652. ; 9:2, s. 211-221
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Tidskriftsartikel (refereegranskat)abstract
- Selective catalytic reduction (SCR) systems are commonly used for exhaust gas aftertreatment in many applications. For optimal NOx reduction using the SCR technique a certain temperature must be reached. This study deals with modelling and control of the temperature inside the SCR system for optimal catalyst operation. A first principle-based model is described for the propagation of the temperature inside the catalyst. The model is described in linear parameter varying (LPV) state-space form and used for control of the temperature using a linear-quadratic-Gaussian (LQG) controller. Necessary conditions for obtaining an optimal controller without complete state information are defined. This leads to a discrete-time LQG controller for LPV systems. The results obtained for the controller are based on several assumptions to ensure the stability of the controller. The states of the proposed model are not measurable. For this purpose, a Kalman filter-based observer is designed for estimation of the states that are used for state feedback in the controller. The observer is designed for discrete-time LPV systems and necessary assumptions for the observer are derived in the work. The resulting model of the temperature gives a model fit of up to 77% for validation data and the controller requirements are met using the proposed controller applied in a simulator environment.
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| 5. |
- Lundberg, Björn, 1982, et al.
(författare)
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Parameter Estimation of a DOC from Engine Rig Experiments with a Discretized Catalyst Washcoat Model
- 2014
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 7:2, s. 1093-1112
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Tidskriftsartikel (refereegranskat)abstract
- Parameter tuning was performed against data from a full scale engine rig with a Diesel Oxidation Catalysts (DOC). Several different catalyst configurations were used with varying Pt loading, washcoat thickness and volume. To illustrate the interplay between kinetics and mass transport, engine operating points were chosen with a wide variation in variables (inlet conditions) and both transient and stationary operation was used. A catalyst model was developed where the catalyst washcoat was discretized as tanks in series both radially and axially. Three different model configurations were used for parameter tuning, evaluating three different approaches to modeling of internal transport resistance. It was concluded that for a catalyst model with internal transport resistance the best fit could be achieved if some parameters affecting the internal mass transport were tuned in addition to the kinetic parameters. However it was also shown that a model with negligible internal transport resistance still could obtain a good fit since kinetic parameters could compensate for transport limitations. This highlighted the inherent difficulties using kinetic models with high parameter correlation and also showed the importance of using a kinetic model with a structure that is capable of describing exclusively intrinsic kinetics.
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| 6. |
- Lundberg, Björn, 1982, et al.
(författare)
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New Methodology for Transient Engine Rig Experiments for Efficient Parameter Estimation
- 2013
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 6:4, s. 1995-2003
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Tidskriftsartikel (refereegranskat)abstract
- Introduction The diesel oxidation catalyst (DOC) is a well established technology to reduce CO and hydrocarbon (HC) emissions from diesel engines. Strengthened emission standards have made the importance of the DOC even greater in recent years since it plays an indispensible role in enhancing the performance of diesel particulate filters (DPF) and selective catalytic reduction (SCR) by utilization of NO oxidation to NO2. Therefore correct prediction of the DOC performance is very important for simulations of the entire aftertreatment system. When performing kinetic parameter estimation, laboratory scale experimental data is generally used. In laboratory scale it is possible to use essentially any combination of exhaust gas composition and temperature which makes it possible to estimate parameters over a wide range of conditions. However the applicability of these parameters in full scale models is often limited. Parameter estimation on full scale engine rig experiments on the other hand is limited by the exhaust compositions that are possible for the engine to produce. As a result, the fraction of CO is closely linked to the fraction of hydrocarbons and the fraction of NO is closely linked to the fraction of NO2. When switching between two engine operation points it generally takes several minutes before the properties of the emissions have stabilized. This does not only make the experiments time consuming, but it also complicates the transient modeling of the DOC since the changes in inlet properties are far from ideal step functions. In this study an experimental set-up is presented that makes it possible to change the inlet properties of the DOC without changing engine load point which results in much faster transients. The method also makes it possible to change the fraction of NO2 independently of the NO fraction. Method To achieve more controlled and faster changes in the inlet to the catalyst an extra DOC (DOC1) with the possibility for bypass flow and an SCR with urea injection are mounted before the catalyst. The fraction of exhaust gas flow through DOC1 allows variation in the conversion of HC and CO to CO2 and the conversion of NO to NO2. By injecting different amounts of urea the conversion of NO2 and NO to N2 is controlled. The SCR also makes it possible to obtain an inlet composition to the DOC that contains NO2 but is free of NO. Fast changes in inlet conditions are in other words possible and it is also possible to achieve compositions not achievable by only controlling the operation of the engine. Experiments have been performed at several engine conditions and using catalysts with different noble metal loading, lengths and washcoat thicknesses. To achieve high HC and CO concentrations the engine was tuned to run with late fuel injection. Significance A method to carry out engine rig experiments with a wider range of emission conditions makes it possible to more efficiently retune model parameters for a full-scale catalyst from literature data. This should result in faster model development which is of great importance in exhaust gas aftertreatment.
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| 7. |
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| 8. |
- Lundström, Andreas, 1980, et al.
(författare)
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Modelling of urea gas phase thermolysis and theoretical details on urea evaporation
- 2011
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 225:10, s. 1392-1398
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Tidskriftsartikel (refereegranskat)abstract
- A model study of droplet decomposition of a urea–water solution (UWS) for selective catalytic reduction applications (SCR) has been undertaken. A new vapour pressure equation for urea has been adopted to predict the rate of urea evaporation. The vapour pressure above liquid urea is obtained by extrapolating the vapour pressure above solid urea. Gas phase decomposition of urea into ammonia and isocyanic acid is further assumed to be fast, dictating the boundary conditions for the evaporation process. The rate of UWS evaporation is compared to recently published data and shows good agreement. A set of Antoine parameters was fitted to the derived vapour pressure to facilitate future simulations.
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| 9. |
- Westerlund, Clas, et al.
(författare)
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Model Predictive Control of a Combined EGR/SCR HD Diesel Engine
- 2010
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2010-01-1175, s. 1175-1175
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Tidskriftsartikel (refereegranskat)abstract
- Materials Noise, Vibration and Harshness Parts and Components Power and Propulsion Quality, Reliability and Durability Safety Tests and Testing Transportation Systems Vehicles and Performance Other Options Papers by Event SAE Home > Papers> By Event> SAE 2010 World Congress & Exhibition Model Predictive Control of a Combined EGR/SCR HD Diesel Engine Date Published: 2010-04-12Paper Number: 2010-01-1175 DOI: 10.4271/2010-01-1175 Author(s): Claes Westerlund - Scania CV AB Bjorn Westerberg - Scania CV AB Ingemar Odenbrand - Lund Univ. Rolf Egnell - Lund Univ. View All CollapseAbstract Achieving upcoming HD emissions legislation, Euro VI / EPA 10, is a challenge for all engine manufacturers. A likely solution to meet the NO x limit is to use a combination of EGR and SCR. Combining these two technologies poses new challenges and possibilities when it comes to optimization and calibration.
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| 10. |
- Westerberg, Björn, et al.
(författare)
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Transient modelling of a HC-SCR catalyst for diesel exhaust aftertreatment
- 2003
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Ingår i: Chemical Engineering Journal. - 1385-8947 .- 1873-3212. ; 92:1-3, s. 27-39
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of a catalyst for hydrocarbon-selective catalytic reduction (HC-SCR) exhaust aftertreatment has been examined by means of transient experiments on a heavy-duty diesel engine rig. The influences of temperature, NO2 concentration, and the transient injection of hydrocarbon on the conversion of NO,, CO, and hydrocarbon were studied in a systematic manner. Hydrocarbon conversion was high and NO, conversion was related to the amount of injected hydrocarbon at high temperatures. At lower temperatures hydrocarbon conversion was low and NOx conversion was not directly related to hydrocarbon injection rate. Increased exhaust NO2/NO ratio resulted in NOx conversion at lower temperatures and also in accumulation of NO., on the catalyst surface. The findings are in agreement with results from recent studies of the selective catalytic reduction of NO by propene. A catalyst model was designed in accordance to these studies and fitted to results from tailored and standard European transient cycles (ETC). The model shows reasonable agreement with experimental CO, NO, and NO2) data. Experimental hydrocarbon data are not as well reproduced, presumably due to the model approximation of hydrocarbons to one species. The full catalyst model used in the study is presented, including reaction kinetics and equations for mass and heat transfer. Mechanistic aspects are discussed and related to other studies. (C) 2002 Elsevier Science B.V. All rights reserved.
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