development and validation of multi site kinetic models ...€¦ · 10/2/2018 11 standard scr rates...

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CHINTAN DESAI* B PRASHANT BALIGA KRISHNA NATTI BRUCE VERNHAM Development and Validation of Multi Site Kinetic Models for SCR and ASC and Application for SCR Calibration * Presenter Isuzu Technical Center of America, Inc.

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Page 1: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

CHINTAN DESAI*

B PRASHANT BALIGA

KRISHNA NATTI

BRUCE VERNHAM

Development and Validation of Multi Site Kinetic Models for SCR and ASC and Application for SCR Calibration

* Presenter Isuzu Technical Center of America, Inc.

Page 2: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 2

Aftertreatment Simulation

Data Collection (Synthetic Gas Bench)

Model Validation (Dyno and SGB)

Model Application

Maps Generation by Models, SCR FF Cal

GT vs DCU Model Prediction, NH3 Storage

NOx Conversion, %

Cumulative NOx, g

NH3 Storage, g

EXP

MODEL

Page 3: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 3

Introduction, Objective and Purpose

Cu-CHA small pore SCR catalysts utilized worldwide due to increased range of temperature for high DeNOx, along with good hydrothermal stability

Due to the relatively simple structure of SSZ-13, it has been investigated intensively by researchers (DeNOx DOE Team, Schneider Group at U-Notre Dame, Gounder group at Purdue etc.)

Structure of SSZ-13 [3]

[1] Stewart et al. (2013) Global Kinetic SCR model with Two Ammonia Storage Sites. CLEERS 2013

[2] Olsson, L., Wijayanti, K., Leistner, K., Kumar, A., Joshi, S. Y., Kamasamudram, K., ... & Yezerets, A. (2015).

A multi-site kinetic model for NH 3-SCR over Cu/SSZ-13. Applied Catalysis B: Environmental, 174, 212-224.

[3] Gounder et al. (2016) New insights into the mechanisms and Active Site requirements of Low Temperature

NOx SCR with Ammonia on Cu-SSZ-13 zeolites. CLEERS 2016

Objective

Develop a kinetic model for NH3-SCR over Cu-SSZ-13 in a temperature interval of 150-550Β°C for 2 space velocities and 2 thermal ageing conditions

Purpose

Model-based SCR Calibration, Urea Dosing Calibration and Control

Feasibility studies for hardware modifications

Page 4: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 4

SCR Model Development

Page 5: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

SCR Model Development Results

10/2/2018 5

NH3 Storage

Fast SCR

NO2 SCR

Standard SCR

NH3 Oxidation

Simply by changing the site densities while keeping the kinetic parameters

constant, predictions were made

Page 6: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 6

Model Setup Key Conservation Equations (Quasi-Steady) [7]

Gas Phase Continuity :

Gas-Phase Species Mass Balance and Coverage Tracking:

Washcoat Diffusion:

Note: See Appendix for nomenclature

[7] GT-Suite Exhaust Aftertreatment Application Manual v2017 Kinetic Model Setup in GT-Suite v2017

Boundary Conditions:

Page 7: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 7

Modeling Approach governed by TPD data

Temperature (Β°C) NH3 Concentration (ppm) Catalyst Ageing

and SV (1/h) Low T Site

Desorption Peak High T Site

Desorption Peak Low T Site Desorption

Peak at 150Β°C High T Site Desorption

Peak at 150Β°C Degreened 30k 330 440 230 105

Aged 30k 310 n/a 280 n/a

Low T Site S2 High T Site S1

Low T Site

Ageing led to migration of High T Site to Low T

NH3 Oxidation insignificant below 400Β°C, but interferes with High T site peak

Low T & High T Site named as placeholders

Nature of sites will be discussed post NH3 storage model construction

Desorption Peaks in NH3 TPD (Temperature Programmed Desorption)test

Degreening 650Β°C for 16 hours

Ageing 700Β°C for 100 hours

Page 8: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 8

NH3 Storage Model – Results at SV: 30k/h and T=150Β°C

The plots represent a NH3 TPD test

Site 1 density reduced by 90%

while Site 2 density increased by

40% upon ageing

Same kinetic constants used for degreened and aged SCR

𝑁𝐻3 + 𝑆1 𝑁𝐻3 βˆ’ 𝑆1

𝑁𝐻3 + 𝑆2 𝑁𝐻3 βˆ’ 𝑆2 S2 Low Temp Site

S1 High Temp Site

Page 9: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 9

NH3 Oxidation Model – Results with 0.2% O2 at SV: 30k/h

4𝑁𝐻3 βˆ’ 𝑆1 + 3𝑂2 β†’ 2𝑁2 + 6𝐻2𝑂 + 4𝑆1

4𝑁𝐻3 βˆ’ 𝑆1 + 5𝑂2 β†’ 4𝑁𝑂 + 6𝐻2𝑂 + 4𝑆1

4𝑁𝐻3 βˆ’ 𝑆2 + 5𝑂2 β†’ 4𝑁𝑂 + 6𝐻2𝑂 + 4𝑆2

Aging leads to reduced oxidation (as would be expected if catalyzed by ZCuOH sites)

NH3 storage data at 0.2% O2, along with oxidation data at 10% O2, allows for determination of O2 reaction order

Calibrated value ~ 0.5

Further ageing beyond 750Β°C will increase oxidation due to cluster formation

2𝑁𝐻3 βˆ’ 𝑆2 + 2𝑂2 β†’ 𝑁2𝑂 + 3𝐻2𝑂 + 2𝑆2

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10/2/2018 10

Standard SCR Model – Results at SV: 30k/h

4𝑁𝐻3 βˆ’ 𝑆1 + 4𝑁𝑂 + 𝑂2 β†’ 4𝑁2 + 6𝐻2𝑂 + 4𝑆1

4𝑁𝐻3 βˆ’ 𝑆2 + 4𝑁𝑂 + 𝑂2 β†’ 4𝑁2 + 6𝐻2𝑂 + 4𝑆2

4 global reactions used

Identical rate order w.r.t. O2 as the NH3 oxidation reaction

In general, reactions proceed on both sites, with different activation energies

2𝑁𝐻3 βˆ’ 𝑆1 + 2𝑁𝑂 + 𝑂2 β†’ 𝑁2 + 𝑁2𝑂 + 6𝐻2𝑂 + 4𝑆1

2𝑁𝐻3 βˆ’ 𝑆2 + 2𝑁𝑂 + 𝑂2 β†’ 𝑁2 + 𝑁2𝑂 + 6𝐻2𝑂 + 4𝑆2

Page 11: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 11

Standard SCR Rates at SV: 60k/h

4𝑁𝐻3 βˆ’ 𝑆1 + 4𝑁𝑂 + 𝑂2 β†’ 4𝑁2 + 6𝐻2𝑂 + 4𝑆1

4𝑁𝐻3 βˆ’ 𝑆2 + 4𝑁𝑂 + 𝑂2 β†’ 4𝑁2 + 6𝐻2𝑂 + 4𝑆2

S1 was the most active site for standard SCR above 250 Β°C, in line with its ability to store NH3 at high temperatures

Hydrothermal ageing led to a reduction of the SCR rate on the S1 site, along with a concomitant increase on the S2 site

This site-specific behavior of the global model follows the expected trends based on the deduced site definitions in the β€œNH3 Adsorption/Desorption Reaction” section

2𝑁𝐻3 βˆ’ 𝑆1 + 2𝑁𝑂 + 𝑂2 β†’ 𝑁2 + 𝑁2𝑂 + 6𝐻2𝑂 + 4𝑆1

2𝑁𝐻3 βˆ’ 𝑆2 + 2𝑁𝑂 + 𝑂2 β†’ 𝑁2 + 𝑁2𝑂 + 6𝐻2𝑂 + 4𝑆2

S2

High Temp Site

Low Temp Site

S1

Site 1 density reduced by 90%

while Site 2 density increased by

40% upon ageing

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10/2/2018 12

Fast SCR Model – Results at SV: 30k/h

2 global reactions used

In general, reactions proceed on both sites, with different activation energies

Low temperature N2O from nitrate formation and decomposition (discussed in later slides)

High temperature N2O from direct NH3 oxidation (shown earlier)

2𝑁𝐻3 βˆ’ 𝑆1 + 𝑁𝑂 + 𝑁𝑂2 β†’ 2𝑁2 + 3𝐻2𝑂 + 2𝑆1

2𝑁𝐻3 βˆ’ 𝑆2 + 𝑁𝑂 + 𝑁𝑂2 β†’ 2𝑁2 + 3𝐻2𝑂 + 2𝑆2

Page 13: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 13

NO2 SCR Model – Results at SV: 30k/h

8𝑁𝐻3 βˆ’ 𝑆1 + 6𝑁𝑂2 β†’ 7𝑁2 + 12𝐻2𝑂 + 8𝑆1

8𝑁𝐻3 βˆ’ 𝑆2 + 6𝑁𝑂2 β†’ 7𝑁2 + 12𝐻2𝑂 + 8𝑆2

Nitrate formation and decomposition accounted for explicitly in reaction model

Addition of enhanced SCR reaction on S2

In general, reactions proceed on both sites with different activation energies

N2O slip model captures overall trend, but needs improvement

2𝑁𝐻3 βˆ’ 𝑆1 + 2𝑁𝑂2 β†’ 𝑁2 + 𝐴𝑁 βˆ’ 𝑆1 + 𝐻2𝑂 + 𝑆1

2𝑁𝐻3 βˆ’ 𝑆2 + 2𝑁𝑂2 β†’ 𝑁2 + 𝐴𝑁 βˆ’ 𝑆2 + 𝐻2𝑂 + 𝑆2

𝐴𝑁 βˆ’ 𝑆1 β†’ 𝑁2𝑂 + 2𝐻2𝑂 + 𝑆1

𝐴𝑁 βˆ’ 𝑆2 β†’ 𝑁2𝑂 + 2𝐻2𝑂 + 𝑆2

𝐴𝑁 βˆ’ 𝑆2 + 𝑁𝑂 β†’ 𝑁𝑂2 + 𝑁2 + 2𝐻2𝑂 + 𝑆2

Page 14: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 14

Nitrate formation inhibits low temperature SCR reaction

Low Temperature NH4NO3 Inhibition of Fast SCR

Page 15: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 15

SCR Model Validation on Engine (Steady State & Transient)

Page 16: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Full-Scale SCR Model Setup

10/2/2018 16

SCR Model setup in GT with appropriate initial and boundary conditions

Aged kinetics utilized for validation purpose (further Degreened data required for additional validation)

Provision to add ASC kinetics and validate tailpipe NOx

Key Assumptions:

1. Urea-NH3 Conversion = 100%

2. No significant difference between dyno part (hydrothermally aged at 650Β°C for 100 hours with minor engine ageing) and reactor part (hydrothermally aged at 700Β°C for 100 hours)

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Steady-State Validation Results

10/2/2018 17

Inlet Conditions Parameter Units Value

Temperature Β°C 353 NO2/NOx Ratio 0.41

Standard Space Velocity 1/h 14785

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Transient SCR Model – Simulation Sequence

10/2/2018 18

1. Pre-conditioning HDT

2. Overnight Soak

1 and 2 provide NH3 storage distribution on both sites for start of cold HDT

The absolute NH3 storage in g is scaled to match the SCRMod_mEstNH3Ld variable at t=0 for Cold HDT

3. Cold HDT

4. Intermediated Hot Soak

5. Hot HDT

Page 19: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Initial NH3 Coverage (g/L)

10/2/2018 19

Prior to cold HDT cycle, the

preconditioning cycle was

simulated to obtain the pre stored

NH3 and axial distribution

Most of the pre stored NH3 is near

the front of the catalyst

Page 20: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Cold HDT Results – Mid-Bed Temperature and SV

10/2/2018 20

H2O Storage Exotherm

H2O storage can be

modeled with a

reversible H2O

adsorption/desorption

reaction

Page 21: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Cold HDT Species Concentration

10/2/2018 21

There is NO storage at the

beginning of the cycle indicating low

temperature storage followed by a

large peak

NO storage model required to

predict this behavior (This can be added to the mechanism later)

Later peak locations and

magnitudes predicted reasonably

well

N2O trend also predicted well

Page 22: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Cold HDT Cumulative Mass & NH3 Storage

10/2/2018 22

Mass based NOx conversion

predicted within 3% for both cold

and hot HDT

N2O slip also predicted reasonably

well with minor underestimation

NH3 storage prediction indirectly

tells about the NH3 slip at around

720 s where there is a sharp rise in

the temperature

Page 23: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 23

ASC Model Development & Validation

Page 24: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

ASC Dual Layer S.V. 70K

10/2/2018 24

Degreened

Aged

The results shown are of dual layer

(PGM+SCR layers)

Intra-porous diffusion in the dual layer

ASC was accounted by the asymptotic

approach by GT

No significant increase in

computational time

The porosity/tortuosity ratios was

calibrated using the dual layer data

These are the NOx yields for NH3 O2

oxidation and NH3 NO O2 interaction

Significant improvement seen in the model

by using the parallel pore diffusion model

compared to constant effective diffusivity

as per the following equation

Page 25: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

ASC Validation on Engine

10/2/2018 25

NOx slip generated in

ASC

Cold and hot HDT cycle normalized

instantaneous NOx concentrations

from 600 to 1200 s

After 700 s unselective conversion of

NH3 to NOx predicted by the model

Development of ASC model is

important to predict the NOx

generation across it

Page 26: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

Model Applications

10/2/2018 26

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10/2/2018 27

SCR Calibration

MODEL

ENGINE

This data is normalized

This is the NOx conversion

map against temperature

and NH3 load

Remaining maps were also

generated by model

Good correlation observed

Manual calibration time

and effort would be

reduced

Page 28: Development and Validation of Multi Site Kinetic Models ...€¦ · 10/2/2018 11 Standard SCR Rates at SV: 60k/h 4 𝐻3βˆ’π‘†1+4 + 2β†’4 2+6𝐻2 +4𝑆1 4 𝐻3βˆ’π‘†2+4 + 2β†’4

10/2/2018 28

GT- DCU Co-Simulation

β€’ Simulink (Control Model) – Master, GT (Plant Model) as Slave

β€’ GT model gives current NH3 load to control model β€’ Control model gives urea dosing to GT model (plant

model)

GT (Plant) Model

Input from Control model (test data)

Urea Dosing Calculated by Control model using NH3 storage from GT (Plant) model

Current NH3 load to control Model

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10/2/2018 29

Urea Dosing

Control Model Improvement required

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10/2/2018 30

NH3 Storage

Figure shows reasonable correlation between test data and GT-DCU simulation

GT model could be used to generate maps simultaneously minimizing the dyno tests

NH3 Storage on different engine

Test 1 Test 2 Test 3

Plots shown here are for 2 different

engines and aftertreatment systems

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Thank You

10/2/2018 31