1d simulation modeling of scr catalyst at steady state ... · pdf file1d simulation modeling...

Powertrain Engineering - Your Partner in Engine

Design, Development & Testing . . .

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


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



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



Objective










Summary

Overview




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



• 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



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



Objective










Summary

Overview



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



Objective










Summary

Overview



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



Objective










Summary

Overview



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



Objective










Summary

Overview



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



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



Objective










Summary

Overview



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



• 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




Significant Under-predictions at higher NO2 fraction in gas feed




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



Adsorption/Desorption reaction rate constants

NOX reduction reaction rate constants



Objective










Summary

Overview



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



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



Objective










Summary

Overview



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



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

27

Future work



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.

28

Acknowledgement

THANK YOU!!

1d simulation modeling of scr catalyst at steady state ... · pdf file1d simulation modeling...

Documents