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1D Simulation Modeling of SCR Catalyst at Steady State Condition
Presented by
Hitesh Chaudhari & Mohak Samant
The Automotive Research Association of India, Pune
6th February 2017
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Design, Development & Testing . . . 2
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Design, Development & Testing . . .
SCR catalyst material and size selection for required performance
Establish 1D simulation methodology for kinetic parameter tuning
Ammonia storage modelling
Prediction of NOX conversion efficiency
Sensitivity study of parameters like,
• Exhaust temperature
• Space Velocity
• Species concentration such as NO/NO2 ratio
3
Objective
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Design, Development & Testing . . . 4
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Design, Development & Testing . . . 5
SCR Chemical Kinetics
R = reaction rate (mole/sec)
A = pre-exponent multiplier
T = temperature (wall)
b = temperature exponent
Ea = activation energy
R = Universal gas constant
{conc} = concentration expression
f(Gi) = general and inhibition function
g(θ) = coverage expression
θ = coverage
R = A*Tb*exp(-Ea/RT)*{conc}*f(Gi)*g(θ)
SCR Reaction rate expression (Modified Arrhenius form):
SCR Reaction Mechanism:
NH3 + θ θNH3 (Adsorption/ Desorption)
4θNH3 + 4NO + O2 4N2 + 6H2O + 4θ (Standard)
2θNH3 + NO + NO2 2N2 + 3H2O + 2θ (Faster)
4θNH3 + 3NO2 3.5N2 + 6H2O + 4θ (Slowest)
2θNH3 + 2NO2 N2 + N2O + 3H2O + 2θ (N2O Formation)
NO + 0.5O2 NO2 (Oxidation)
• Current study focusses on calibrating above mentioned reaction rate for relevant reactions pertaining to reactor data
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• NH3 step feed data used for NH3 storage modelling calibration
• TPR experimental data used for calibrating transient behaviour
NH3 Step Feed Experiment
Image source: Winkler, SAE 2003-01-0845
Temperature Programmed Reaction (TPR) Experiment
Typical Synthetic Gas Bench Reactor (SGB)
Image source: J. Nicolas, GT Publication,2007
Image source: “Study of Urea-Water solution injection spray in De-Nox SCR system”, ISSN-2249-555
Experimentation for Model Calibration
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Assumptions for 1D SCR Model Building
Standalone SCR Model Assumptions:
Molar fraction basis
Excludes DOC,DPF, Urea dozer
Adiabatic substrate
Intra-porous diffusion is excluded
Uniform Urea decomposition
Uniform mixing
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Design, Development & Testing . . . 8
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Design, Development & Testing . . . 9
Validation: Vanadium Based Catalyst
Reaction Pre Exponent multiplier
Activation energy, Ea(kcal/kmol)
NH3 Adsorption 0.604 0
NH3 Desorption 199000 23400
Standard NO reduction 839000 14200
Reference: L.Lietti, I. Nova, “Transient Kinetic Study of SCR De-NOX system”, Catalysis Today.1998
• Adsorption/desorption reactions calibrated with Temperature programmed desorption (TPD) data
• NH3 Step feed data at 220 deg C to calibrate NOX reduction reaction
• Feed is assumed free of NO2 hence Fast and Slow reactions not considered
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Design, Development & Testing . . . 10
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Reaction Activation energy, Ea(Kcal/Kmole)
Pre Exponent multiplier, K
NH3 adsorption 0 0.8
NH3 desorption 96000 3.63E6
Standard Reaction 11640 90000
Fast Reaction 27020 5E15
NO Oxidation 7420 51
NH3 Oxidation 42600 2.78E9
Validation: Iron Exchanged Zeolite Catalyst
Reference: D. Chatterjee, T. Burkhardt, “Numerical Simulation of Zeolite and V-Based SCR Catalytic converters” SAE 2007-01-1136
• Adsorption/desorption reactions calibrated with Temperature Programmed Desorption (TPD) data
• NOX reduction reactions are calibrated with transient TPR data
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Design, Development & Testing . . . 12
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Validation: Copper Exchanged Zeolite Catalyst Reaction Activation energy,
Ea(J/mole) Pre Exponent multiplier, K
NH3 adsorption 0 2.66
NH3 desorption 79866 80210
Standard Reaction 84900 1E12
Fast Reaction 85100 1.9E12
Slow Reaction 72300 1.1E7
NH3 Oxidation 162400 8.6E10
NO Oxidation 48000 10
Reference: K. Narayanaswamy, Yongsheng He, “Modelling of Copper Zeolite Selective Catalytic Reduction(SCR) catalysts at steady and transient conditions” SAE 2008-01-0615
• Adsorption/desorption reactions calibrated with TPD data
• Steady state experiments to validate NOX reduction reactions
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Design, Development & Testing . . . 14
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Design, Development & Testing . . . 15
NH3 Adsorption/Desorption Calibration
Simulated TPD experiment with single site modelling approach
Inputs for Ammonia storage modelling: • TPD Experiment data from SGB • Inlet gas feed mass flow rate • Inlet gas feed composition • Catalyst sample volume
Image source: “Study of Urea-Water solution injection spray in De-Nox SCR system”, ISSN-2249-555
Temperature Programmed Desorption Experiment (TPD)
Simulated TPD experiment with two site modelling approach
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NH3 Adsorption/Desorption Calibration- Two Site Approach
Reference: K. Narayanaswamy, Yongsheng He, “Modelling of Copper Zeolite Selective Catalytic Reduction(SCR) catalysts at steady and transient conditions” SAE 2008-01-0615
• Model is calibrated with TPD at 150 degC • Calibrated rate constants are verified with remaining experiments • Two site modelling approach offers more proximity to experimental data
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Design, Development & Testing . . . 17
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Steady State NOX Reduction Calibration
Typical steady state experiments used for calibration*
Inputs Required: • Steady state experiment data from SGB • Calibrated reaction rate constants from TPD
experiment • Inlet gas feed mass flow rate • Inlet gas feed composition • Catalyst sample volume
*Ref.: K. Narayanaswamy, Yongsheng He, “Modelling of Copper Zeolite Selective Catalytic Reduction(SCR) catalysts at steady and transient conditions” SAE 2008-01-0615
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• Log space optimisation is faster and precise optimisation technique
• Genetic Algorithm with parameter sweep offers robust solution
Surface reaction template with two site approach
Minimised error function with Genetic Algorithm
Calibrated log spaces for reaction rate constants
Total Error function
Steady State NOX Reduction Calibration
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Significant Under-predictions at higher NO2 fraction in gas feed
Steady State NOX Reduction Calibration
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1D Numerical Model Calibration Methodology
Calibrated 1D SCR model
Temperature, Mass flow rate, Composition, Catalyst properties
Simulate Ammonia step feed experiment
Simulate transient gas bench experiments for further maturity of
the model
SCR standalone model building
Fine tune Model predictions using optimiser tool
Opt for 2 site modelling approach for better prediction quality
Simulate Steady state gas bench experiments for NOX reduction
Fine tune Model predictions using robust optimiser tool
Synthetic gas bench experiment data
Synthetic gas bench experiment data
Synthetic gas bench experiment data
Adsorption/Desorption reaction rate constants
NOX reduction reaction rate constants
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Design, Development & Testing . . . 22
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Model Prediction for Synthetic Test Bench Data
Test Conditions: • Catalyst = Fe-Zeolite • ANR = 1 • NOX = 500PPM • O2 = 5% • CO2 = 5% • H2O = 5%
Case-1: Space velocity = 86000, NO2/NOX = 0 Case-2: Space velocity = 86000, NO2/NOX = 0.3 Case-3: Space velocity = 40000, NO2/NOX = 0.3
NO2 in the feed gas improves SCR performance at lower temperatures which is attributed to Fast conversion reaction
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Model Prediction for Synthetic Test Bench Data
Test Conditions: • GHSV = 86K • Alpha = 1 • NOX = 500PPM • NO2/NOX = 0.0 • O2 = 5% • CO2 = 5% • H2O = 5%
Cu-Zeolite catalysts are suitable for low temperature application whereas Fe-Zeolite catalysts are preferred at higher temperatures
Powertrain Engineering - Your Partner in Engine
Design, Development & Testing . . . 25
Objective
SCR Chemical Kinetics
SCR Model Validation at Steady State Condition
• Vanadium Catalyst
• Fe-Zeolite Catalyst
• Cu-Zeolite Catalyst
1D Simulation Methodology for Cu-Zeolite Catalyst
• Ammonia Storage modelling
• NOX reduction reactions modelling
Model Predictions for Supplier Data
Summary
Overview
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Summary
SCR 1D simulation model calibration methodology is developed
Accurate Experimental data is a prerequisite for precise model calibration
Synthetic gas bench experiment is more flexible approach for model calibration
Robust optimisation algorithm is necessary for numerical model calibration
Two site modelling approach improves model prediction quality
Transient response can be calibrated by running transient engine test cycles on SGB
Developed calibration methodology provides good initialization without requiring extensive
catalyst data
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Design, Development & Testing . . .
Transient response calibration
Porous diffusion modelling across the substrate
Urea dosing system
Integrated exhaust after-treatment system modelling
Engine plus after-treatment modelling
Integrated 1D+3D system modelling
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Future work
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We would like to thank Mr. N. V. Marathe (HoD PTE), Mr. N. H. Walke, Dr. S. Juttu and our
colleagues for supporting us through this study. We specially thank Mr. Ryan Dudgeon
from Gamma Technologies and Mr. Mangesh Dusane from ESI for their continual support
and fruitful suggestions.
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Acknowledgement
THANK YOU!!
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