Development of Current and Future Diesel After Treatment Systems

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Development of Current and Future Diesel After Treatment Systems

Pakorn Bovonsombat, Byung-Sun Kang, Paul Spurk, Harald Klein, Klaus Ostgathe

Degussa Metals Catalysts Cerdec AG Rodenbacher Chaussee 4, P.O.Box 1351

D-63403 Hanau-Wolfgang, Germany

Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

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Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

Total cycle emissions in NEDC-cycle in [g/km]

Legislation

CO HC + NO

x

HC NO

x

PM

EURO III 0.64 0.56 0.06 0.50 0.05

EURO IV 0.50 0.30 0.05 0.25 0.025

Total cycle emissions in [g/kWh]

Legislation

CO NMHC HC NO

x

PM

EURO III 2.10 0.66 5.00 0.10

ESC- Test

Cycle EURO IV 1.50 0.46 3.50 0.02

EURO III 5.45 0.78 5.00 0.16

ETC- Test

Cycle EURO IV 4.00 0.55 3.50 0.03

EURO III and EURO IV legislation for diesel passenger cars in NEDC - cycle.

EURO III and EURO IV legislation for heavy-duty trucks.

Diesel Legislation

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Thailand Diesel Legislation

CO HC+NOx

PM

Less than 6 passengers 1.0 0.70 (0.90) 0.08 (0.10) More than 6 passengers 1.0 - 1.5 0.7 - 1.2 (0.9 - 1.6) 0.17 - 0.8 (0.10 - 0.20) Less than 2,500 Kg GW

( ) = Values for Direct Injection

Legislation for Light Duty Diesel

Total Cycle Emissions in R-83 Cycle (g/km)

Vehicle Category

CO HC NOx PM

More than 9 passengers

4.0 1.1 7 0.15

GW greater than 3,500 Kg.

Total Cycle Emissions in R-49 Cycle (g/ kwh) Legislation for Heavy Duty Diesel (Euro II)

Vehicle Category

optimized combustion

EURO IV

engine measure NOx-reduction

engine measure particulate reduction

particulate aftertreatment

NOx-aftertreatment NOx [g/km]

optimized combustion + better fuel

PM [g/km]

0.05

0.025

EURO III

0.25 0.50

NO

_x

/PM trade-off-curve for passenger cars. Emission values refer to

.

NEDC- cycle. Similar principle is valid for heavy-duty trucks.

NOx-PM Trade-off

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Requirement of NOx Conversion Efficiency for EU-IV

0,125 0,225 0,325 0,425 0,525 0,625 0,725 0,825

500 1000 1500 2000 2500

inertia test weight [kg]

NOxemission [g/km]

-50 -30 -10 10 30 50 70 90

required NOxconversion [%]

NOx emission EU 4 legal limits required NOx conversion

passive DeNO

_x

urea SCR NO

_x

adsorber

Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

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Function of Diesel Oxidation Catalyst

Catalytic Converter

Engine-out : CO Unburned HC

PM NO

_x

CO

₂

H

₂

O

Reduced emission of PM and NO

_x^*

C

_m

H

_n

+ (m+0.25n) O

₂

= m CO

₂

+ 0.5n H

₂

O CO + 0.5 O

₂

= CO

₂

* Passive NO

_x

conversion rate: Max. 10 %

Performance

of Diesel Oxidation Catalyst

0 10 20 30 40 50 60 70 80 90 100

NOx CO HC PM

total cycle conversion [%]

70 g Pt/cuft, fresh

V

cat

= 2.5 l 2.0 L DI CR ITW = 1,587 kg 406 wt. ppm S

Diesel oxidation catalyst for passenger car – performance in NEDC – cycle.

10

89

82

41

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Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

Support

Pt NOx

adsorber

NO + ½ O

2

NO

3

-

NO

2

Support

Pt NOx

adsorber N

2

NO

3

- NO

x

Red

NO

_x

- Adsorption NO

_x

- Reduction

Chemical model of NOx storage catalyst Source: N. Miyoshiet et al, SAE 950809 (1995)

Basic Concept of NO _x Adsorber

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N OC O , H C . P M . . .

C l e a n e x h a u s t

I l e a n p h a s e ; s t o r a g e o f n i t r o g e n o x i d e s

I I r i c h p h a s e ; r e g e n e r a t i o n o f t h e a d s o r b e r T i m e

1

λ

Operation principle of diesel NO

_x

–storage catalyst.

Operation Concept of NO _x Adsorber

0 10 20 30 40 50 60 70 80 90 100

100 150 200 250 300 350 400 450 500

NO

_x

conversion [%]

Temperature in front of catalyst [°C]

Conversion Efficiency of NO _x Adsorber

Model Gas composition:

• Simulation of typical diesel exhaust gas composition

• Adjustment lean / rich sumulation:

60 s lean / 10 s rich setting; SV = 30,000

NOx conversion as function of temperature in front of diesel Nox-storage catalyst

Model gas test

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Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

1.Diffusion 2,3. Inertia effects Fibre

exhaust

Surface filter Fibre filter

Particulate Filter System

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896

89

376

213 0 200 400 600 800 1000 1200

Vehicle A (0.112 g/km) Vehicle B (0.047 g/km) Number of regenerations

Distance between regenerations [km]

PM raw emissions measured in NEDC-cycle

Calculation of required filter regeneration cycles during 80,000 km in NEDC- cycle. Particulates loading in the filter: 10 g.

Number of Regenerations vs. PM Raw Emission

Examples of filter regeneration methods.

Type of Filter Regeration

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Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

Basic System of SCR

S O V

urea (NH

₂

)

₂

CO

exhaust

SCR catalyst (S)

4NH

₃

+ 4NO + O

₂

4N

₂

+ 6H

₂

O 2NH

3

+ NO + NO

2

2N

2

+ 3H

2

O 8NH

3

+ 6NO

2

7N

2

+ 12H

2

O

Guard catalyst (O) 4NH

3

+ 3O

₂

2N

₂

+ 6H

₂

O Pre-catalyst (V)

2NO + O

₂

2NO

₂

„4HC + 3O

2

2CO

2

+ 2H

2

O“

2CO + O

2

2CO

2

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0 200 400 600 800 1000

0 200 400 600 800 1000 1200

time [s]

NOx concentration [vppm]

0 20 40 60 80 100

NH3 / N2O concentration [vppm]

NOx raw

NOx after SCR system NH3 after SCR system N2O after SCR system

ECE 22 %

EUDC 83 %

total 63 %

ECE 22 %

EUDC 83 %

total 63 %

Engine Test Result of Urea-SCR (MVEG A)

aging status NO

x

conversion [%]

0 20 40 60 80 100

fresh 50 hrs 100 hrs 150 hrs 200 hrs conditioned ECE part EUDC part total

Durability of Urea-SCR

(MVEG A)

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Content:

1. Overview 1-1. Legislation

1-2. PM & NO _x trade-off

1-3. Requirement of NO _x conversion efficiency for EU-IV

2. Diesel Oxidation Catalyst 3. NO _x adsorber

4. Diesel Particulate Filter 5. Urea-SCR

6. Summary

Summary:

1. From 2000 onwards, diesel emission legislation based on modified EU-I & -II has been enforced in China, India and Thailand .

2. Diesel oxidation catalyst as the basic technology for diesel aftertreatment, combined with engine calibration can fulfill EU-III limits.

3. For EU-IV, diesel oxidation catalyst with NO _x aftertreatment and/ or with particulate filter, combined with improved engine technology could be required.

4. System developments of reducing NO _x over 50 %, e.g., NO _x adsober and Urea-SCR, are ongoing.

5. Particulate filter can trap PM with efficiency over 90 %.

To develop filter regeneration method is a main challenge.

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Development of Current and Future Diesel After Treatment Systems