Hydrothermal aging modeling for SCR catalysts · and a SCR using IFP-Exhaust library coupled with a Simulink control platform ... Simon Dosda – Hydrothermal aging modeling for SCR

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Renewable energies | Eco-friendly production | Innovative transport | Eco-efficient processes | Sustainable resources

Hydrothermal aging modeling for SCR catalysts

Simon Dosda 2015 CLEERS WORKSHOP

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Simon Dosda – Hydrothermal aging modeling for SCR catalysts – 2015 CLEERS WORKSHOP

Interest of SCR modeling for control purpose

Urea-SCR is one of the most common technology used by car and truck manufacturers to meet the latest NOX emission standards

requires to optimize urea injection in order to limit ammonia slip while keeping a good NOX reduction efficiency

2

In this context, system simulation has significant advantages to set up optimal injection strategy:

Physical modeling: modeling level is adapted for control laws design in order to obtain accurate and consistent results in every real life case

Fast calculation time: about 10 times faster than the real time for a complex exhaust line coupled with a high frequency control

Adblue injector

NOX sensor

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Importance of aging on SCR performances

During engine lifetime, performance degradation of the SCR catalyst is observed due to harsh exhaust conditions

frequent filter regeneration subjects the SCR catalyst to high temperatures

hydrothermal aging will strongly decrease DeNOx and NH3 storage properties of the catalyst

Modeling hydrothermal aging impact on the catalyst allows to adapt urea injection strategy and avoid excessive amount of ammonia slip

only way to adapt injection strategy over the complete vehicle lifetime

3

Is there a way to model efficiently hydrothermal aging impact on a SCR catalyst ?

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Approach: from fresh to aged SCR model

1 - Fresh SCR model set up and validation:

a - SCR model is calibrated on specific Synthetic Gas Bench tests

b - SCR model is integrated in a complete exhaust line simulator and validated on chassis dynamometer on test cycles

2 - Aging model set up from SGB tests for various aging conditions

3 - Aging model validation on dyno on test cycles using an aged SCR

4

1 - Fresh SCR model

2 - Hydrothermal aging model SGB data

3 - Aged SCR model validation

dyno cycle data

a - Calibration SGB data

b - Validation dyno cycle data

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5

1 - Fresh SCR model



dyno cycle data



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Fresh SCR model presentation – Reactor scale

LMS Imagine.Lab Amesim model of SGB SCR using IFP-Exhaust library

reactions considered: NH3 adsorption/desorption, DeNOx reactions

(standard, fast & NO2 SCR) and NH3 oxidation

isolated sample: no thermal exchanges considered

SCR sample geometry: length = 3 inches, diameter = 2 inches, 350 cpsi

Synthetic Gas Bench - SCR

6

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SCR modeling set up for NH3 storage on SGB test

From NH3 TPD observation, two adsorption sites can be considered

NH3 adsorption reaction for each adsorption site:

NH3 + 𝐒𝐢 ↔ NH3−𝐒𝐢

𝒓𝒂𝒅 = 𝒌𝒂𝒅 × 𝑵𝑯𝟑 × (𝟏 − 𝜽𝑵𝑯𝟑) - 𝒌𝒅𝒆 × 𝒆−

𝑬𝒅𝒆 ×(𝟏−𝒂𝒍𝒑𝒉𝒂×𝜽𝑵𝑯𝟑)

𝑹×𝑻𝒔 × 𝜽𝑵𝑯𝟑

7

0

50

100

150

200

250

300

100 200 300 400 500 600ou

tlet

NH

3 m

ola

r co

nce

ntr

atio

n [

pp

m]

inlet temperature [°C]

SGB test - NH3 TPD - Tinlet 175°C

bench

site 1

site 2

site 1 + 2

Site 1

Site 2

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0 500 1000 1500 2000 2500 30000

50

100

150

200

250

300

350

SGB test - NH3 TPD - Tinlet 375 °C

Time [s]

NH

3 m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 30000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

0 500 1000 1500 2000 2500 30000

50

100

150

200

250

300

350


Time [s]

NH

3 m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 30000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

0 500 1000 1500 2000 2500 3000 35000

50

100

150

200

250

300

350


Time [s]

NH

3 m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 3000 35000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

150 200 250 300 350 400 450 500 5500

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Inlet temperature [°C]

NH

3 q

ua

nti

ty [

g]

SGB test - NH3 TPD

Bench - adsorbed

Bench - desorbed

Model - adsorbed

Model - desorbed

SCR model calibration for NH3 storage on SGB test

NH3 storage calibration is done on NH3 TPD tests with various inlet temperature

8

Good results consistency for the overall test

data

0 500 1000 1500 2000 2500 30000

50

100

150

200

250

300

350


Time [s]

NH

3 m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 30000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

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SCR model calibration for DeNOx reaction on SGB test

Standard SCR reaction calibration:

4 NH3-Si + 4 NO + O2 4 N2 + 6 H2O + 4 Si

𝒓𝒔𝒕𝒅 = 𝒌𝒔𝒕𝒅 × 𝒆−

𝑬𝒔𝒕𝒅𝑹×𝑻𝒔 × 𝑵𝑶 × 𝜽𝑵𝑯𝟑

Calibration is done on DeNOx SGB test with an upstream NO2/NOx ratio of 0 %

0 1000 2000 3000 4000 5000 60000

50

100

150

200

250

300

350

SGB test - DeNOx - Tinlet 175 °C / NO2/NO

X 0 %

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

]

0 1000 2000 3000 4000 5000 60000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

0 500 1000 1500 2000 2500 3000 3500 4000 45000

50

100

150

200

250

300

350


X 0 %

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 3000 3500 4000 45000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

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Fast SCR reaction calibration:

2 NH3-Si + NO + NO2 2 N2 + 3 H2O + 2 Si

𝒓𝒇𝒂𝒔𝒕 = 𝒌𝒇𝒂𝒔𝒕 × 𝒆−

𝑬𝒇𝒂𝒔𝒕

𝑹×𝑻𝒔 × 𝑵𝑶 × 𝑵𝑶𝟐 ×

𝜽𝑵𝑯𝟑

calibration is done on DeNOx SGB test with an upstream NO2/NOX ratio of 50 %

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

50

100

150

200

250

300

350


X 50 %

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

0 200 400 600 800 1000 1200 1400 16000

50

100

150

200

250

300

350


X 100 %

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

]

0 200 400 600 800 1000 1200 1400 16000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

10

NO2 SCR reaction calibration:

4 NH3-Si + 3 NO2 5,5 N2 + 6 H2O + 4 Si

𝒓𝑵𝑶𝟐 = 𝒌𝑵𝑶𝟐 × 𝒆−

𝑬𝑵𝑶𝟐𝑹×𝑻𝒔 × 𝑵𝑶𝟐 × 𝜽𝑵𝑯𝟑

calibration is done on DeNOx SGB test with an upstream NO2/NOX ratio of 100 %

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150 200 250 300 350 400 450 500 5500

10

20

30

40

50

60

70

80

90

100


NO

x c

um

ula

tiv

e e

ffic

ien

cy [

%]

DeNOx efficiency - inlet NO2/NO

X ratio 100 %

Bench

Model

150 200 250 300 350 400 450 500 550 6000

10

20

30

40

50

60

70

80

90

100


NO

x c

um

ula

tiv

e e

ffic

ien

cy [

%]


X ratio 0 %

Bench

Model

150 200 250 300 350 400 450 500 5500

10

20

30

40

50

60

70

80

90

100


NO

x c

um

ula

tiv

e e

ffic

ien

cy [

%]


X ratio 50 %

Bench

Model


Ammonia oxidation reaction calibration:

4 NH3-Si + 3 O2 2 N2 + 6 H2O + 4 Si

𝒓𝑵𝑯𝟑𝒐𝒙 = 𝒌𝑵𝑯𝟑𝒐𝒙 × 𝒆−

𝑬𝑵𝑯𝟑𝒐𝒙𝑹×𝑻𝒔 × 𝑶𝟐 × 𝜽𝑵𝑯𝟑

calibration is done on DeNOx SGB test with an high upstream temperature

Standard SCR Fast SCR NO2 SCR

This calibration allows to obtain consistent results on the overall test data

0 500 1000 1500 2000 2500 30000

50

100

150

200

250

300

350


X 0 %

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

]

0 500 1000 1500 2000 2500 30000

100

200

300

400

500

600

700

Inle

t T

em

pe

ratu

re [

°C]

Bench - inlet

Bench - outlet

Model - outlet

Temperature

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1 - Fresh SCR model



dyno cycle data



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Exhaust line model presentation

LMS Amesim model of a complete exhaust line composed of a DOC, a DPF and a SCR using IFP-Exhaust library coupled with a Simulink control platform

Upgrade from SGB models:

convective and radiative heat transfer modeled

light adjustment of catalysts calibration

13

chassis dynamometer bench – DOC + DPF + SCR

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0 200 400 600 800 1000 12000

50

100

150

200

250

300

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

] NEDC cycle

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

Time [s]

NO

X c

um

ula

tiv

e m

as

s f

low

[m

g]

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

Fresh SCR cycle simulation results on NEDC cycle

NOX reduction is well represented by the model

Almost no NH3 slip on this cycle with a fresh SCR

14

0 200 400 600 800 1000 12000

10

20

30

40

50

60

70

Time [s]

NH

3 m

ola

r co

nc

en

trati

on

[p

pm

]

NEDC cycle

Bench - Inlet SCR / 100

Bench - Outlet SCR

Model - Outlet SCR

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1 - fresh SCR model



dyno cycle data



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Hydrothermal aging effects on SCR catalyst : Cu-Zeolite

Catalyst changes with aging:

at low aging, copper migrates from exchanged positions to form copper oxide aggregates in the zeolite porosity

during this phase, copper in exchanged positions protects the zeolite structure against dealumination

with increasing aging, copper is completely removed from exchanged positions and dealumination occurs.

16

Ref. « Hydrothermal aging effects on Cu-zeolite NH3-SCR catalyst » M. Valdez Lancinha Pereira, A. Nicolle, D. Berthout, IFPEN doi:10.1016/j.cattod.2015.03.027

http://dx.doi.org/10.1016/j.cattod.2015.03.027

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Hydrothermal aging effects on SCR catalyst : Cu-Zeolite

Aging model description:

loss of copper and aluminum ions contributes to a loss of catalytic sites: modeled by a coefficient on active surface and on NH3 capacities

𝑺𝒂𝒄𝒕𝒊𝒗𝒆𝒂𝒈𝒆𝒅 = 𝑪𝒐𝒆𝒇𝒇𝑪𝒖 × 𝑺𝒂𝒄𝒕𝒊𝒗𝒆 𝒇𝒓𝒆𝒔𝒉

𝛀𝑵𝑯𝟑𝒔𝒊𝒕𝒆𝟏𝒂𝒈𝒆𝒅 = 𝑪𝒐𝒆𝒇𝒇𝒔𝒊𝒕𝒆𝟏 × 𝛀𝑵𝑯𝟑𝒔𝒊𝒕𝒆𝟏 𝒇𝒓𝒆𝒔𝒉

𝛀𝑵𝑯𝟑𝒔𝒊𝒕𝒆𝟐𝒂𝒈𝒆𝒅 = 𝑪𝒐𝒆𝒇𝒇𝒔𝒊𝒕𝒆𝟐 × 𝛀𝑵𝑯𝟑𝒔𝒊𝒕𝒆𝟐𝒇𝒓𝒆𝒔𝒉

17

CuO aggregates promote NH3 oxidation: modeled by a coefficient on NH3 oxidation activation energy

𝒓𝑵𝑯𝟑𝒐𝒙 = 𝒌𝑵𝑯𝟑𝒐𝒙 × 𝒆−

𝑪𝒐𝒆𝒇𝒇𝑪𝒖𝑶

×𝑬𝑵𝑯𝟑𝒐𝒙𝑹×𝑻𝒔 × 𝑶𝟐 × 𝜽𝑵𝑯𝟑

no other changes in the calibration of the kinetic constants (kj, Eaj) determined on the fresh sample

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Aging impact set up for NH3 storage - Reactor scale

NH3 storage capacity reduction with aging is observed on SGB NH3 TPD tests

hydrothermal impact on NH3 capacity is higher on “low temperatures” NH3 storage sites

Desorption reaction rate reduction due to active surface reduction with hydrothermal aging temperature is well modeled

18

0

10

20

30

40

50

60

70

80

90

100

active surface NH3 capacity site 1 NH3 capacity site 2co

rrec

tive

co

effi

cien

t [%

]

Parameters variation

5h 800°C 5h 900°C 5h 1000°C

250 300 350 400 450 500 550 6000

50

100

150

200

250

Temperature [°C]

NH

3 m

ola

r co

ncen

trati

on

at

SC

R o

utl

et

[pp

m]

SCR aging impact on NH3 slip - Tinlet 225 °C

Bench - 5h 800°C

Model - 5h 800°C

Bench - 5h 900°C

Model - 5h 900°C

Bench - 5h 1000°C

Model - 5h 1000°C

SGB NH3 TPD tests

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Aging impact set up for DeNOx reaction - Reactor scale

At low hydrothermal aging temperature, main aging impact is a loss of catalyst efficiency at high temperature due on NH3 oxidation

impact of CuO aggregates

DeNOx reactions rates reduction is well represented by the reduction of the active surface in the model

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0

20

40

60

80

100

120

active surface NH3 oxidation activation energy

corr

ect

ive

co

eff

icie

nt

[%]

Parameters variation

5h 800°C 5h 850°C 5h 900°C 5h 1000°C

100 150 200 250 300 350 400 450 500 5500

10

20

30

40

50

60

70

80

90

100

Temperature [°C]

SC

R D

eN

Ox e

ffic

ien

cy [

%]

SCR aging impact on DeNOx efficiency

Bench - 5h 800°C

Model - 5h 800°C

Bench - 5h 850°C

Model - 5h 850°C

Bench - 5h 900°C

Model - 5h 900°C

Bench - 5h 1000°C

Model - 5h 1000°C

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1 - fresh SCR model



dyno cycle data



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5h 1000°C aged SCR cycle simulation results - NOx

NEDC cycle is realized with an aged SCR

hydrothermal aging of 5h at 1 000°C

Coefficients from previous aging model are used:

Active surface: 2 %

NH3 capacity of site 1: 0,5 %

NH3 capacity of site 2: 1 %

NH3 oxidation activation energy: 85 %

Impact on DeNOx efficiency is well modeled

21

0 200 400 600 800 1000 12000

50

100

150

200

250

Time [s]

NO

X m

ola

r co

nc

en

trati

on

[p

pm

] NEDC cycle

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

0 200 400 600 800 1000 12000

500

1000

1500

2000

2500

3000

Time [s]

NO

X c

um

ula

tiv

e m

as

s f

low

[m

g]

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

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5h 1000°C aged SCR cycle simulation results - NH3

Impact on NH3 slip is well modeled : right timing and level of release

While NH3 slip for the fresh SCR was almost inexistent, more than half of NH3 injected quantity is released in the atmosphere for the aged SCR

Injection strategy can be optimized

22

0 200 400 600 800 1000 12000

500

1000

1500

Time [s]

NH

3 m

ola

r co

ncen

trati

on

[p

pm

]

NEDC cycle

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

0 200 400 600 800 1000 12000

100

200

300

400

500

600

700

Temps [s]

NH

3 c

um

ula

tive m

ass f

low

[m

g]

Bench - Inlet SCR

Bench - Outlet SCR

Model - Outlet SCR

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Summary

Simple hydrothermal aging model with reduced parameterization:

one coefficient for active surface reduction

two coefficients for NH3 storage capacities, close to active surface

coefficient

one coefficient for NH3 oxidation activation energy

Need only SGB data

Consistency in results on NOX and NH3

Efficient methodology to model SCR aging impact from a fresh SCR

calibration

This hydrothermal aging model will be integrated in IFP-Exhaust

library for the next LMS Amesim release

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Renewable energies | Eco-friendly production | Innovative transport | Eco-efficient processes | Sustainable resources

www.ifpenergiesnouvelles.com

For further questions, please contact: Simon Dosda [email protected] Engine and Vehicle Modeling Department IFP Energies nouvelles 1 et 4 avenue de Bois-Préau 92852 Rueil-Malmaison Cedex - France

mailto:[email protected]

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Hydrothermal aging modeling for SCR catalysts · and a SCR using IFP-Exhaust library coupled with a Simulink control platform ... Simon Dosda – Hydrothermal aging modeling for SCR