13. ETH-Conference on Combustion Generated Nanoparticles , Zürich, 22.-24.06.2009

Combined SCR – A novel approach for NOx and PM aftertreatment M. Müller1, S. Schraml , P. Broll, H. Bülte, DEUTZ AG, Ottostr. 1, 51149 Cologne, Germany H. Harndorf, University of Rostock, Albert-Einstein-Str. 2 , 18059 Rostock, Germany

To meet the requirements of future emission legislation engine manufacturers will have to

offer a complete system consisting of an advanced diesel engine and an aftertreatment

unit. Future exhaust aftertreatment systems will most probably contain a selective catalytic

reduction catalyst (SCR) as well as a diesel particulate filter (DPF) to cope with stringent

NOx and PM emission limits. For off-road applications, DEUTZ has the ambition to couple

all active aftertreatment components directly to the engine in order to minimize the number

of variants and thus to lower application efforts. In compliance with the EU Stage 4 and US

Tier 4 emission limits, DEUTZ investigates a novel approach with the target to realize a

compact and cost optimised emission control system.

The exhaust aftertreatment concept, which is named "Combined SCR", essentially

consists of a burner-vaporiser unit, a V2O5 -coated SCR-catalyst and a coated diesel

particulate filter (cDPF). The employment of the burner-vaporiser unit on the one hand

enables to exceed an exhaust gas temperature which upstream of the SCR-catalyst is

greater than 300°C within the entire engine operation map. On the other hand, the

vaporization enthalpy for additionally injected diesel fuel is provided. The diesel vapour is

homogeneously mixed with engine exhaust gas, which allows excellent transport of

chemically bound energy within the exhaust system and thus lowers engineering efforts for

different applications.

A specific element of the concept is that the SCR-catalyst also serves as an oxidation

catalyst for the diesel vapour during thermal DPF regeneration. The described compact

system configuration allows not only to reduce nitrogen oxides (NOx) but also to generate

heat by at least partial oxidation of hydrocarbons. The target temperature of approximately

600°C upstream the DPF is reached in three steps. The first temperature increase of the

exhaust gas will be achieved by the burner, which has a constant thermal power. This heat

release ensures light-off temperature for the subsequent catalytic process and fuel

vaporization. In the second stage around 30-60% of the chemically bound energy is

released from partial oxidation of the hydrocarbons on the SCR catalyst.

1 corresponding author, Email: mueller.ma@deutz.com

13. ETH-Conference on Combustion Generated Nanoparticles , Zürich, 22.-24.06.2009

This in particular is a special feature of the hydrocarbons from the DEUTZ burner-

vaporizer unit. The remaining chemical energy, in a great portion bound to carbon

monoxide, is preferably released downstream the SCR on the cDPF. By extended test

bench investigations it has been shown that there is no degradation neither on SCR nor on

heat-up performance observed. In the figure below, a typical setup is shown for integrating

the combined SCR system to a complete Tier4 exhaust aftertreatment system.

Figure 1: Experimental test setup

As the burner/vaporizer unit ensures sufficiently high exhaust temperatures for all given

operation conditions, one of the main benefits of this system configuration is the

applicability for a broad variety of applications with no restrictions and without the need for

an additional heat mode calibration. Further, the SCR catalyst in front of the DPF allows

high NOx conversion rates even for cold cycles and the application of vanadium-based

technologies which – in contrast to zeolite SCR systems – gained a high maturity level and

offers high NOx conversion rates at moderate costs. Especially cold cycle SCR

performance is one of the key aspects for forthcoming emission legislations as the NOx

certification values have to be met for very challenging certification cycles. As a

consequence, the lack of the passive regeneration feature against the well known SCRT

configuration, which will be broadly used for Euro 6 on-road applications, can at least be

partly compensated by an advanced engine calibration. Further features and experimental

results of the combined SCR approach will be presented in more detail within this

presentation.

Tem

pe

ratu

re [

°C]

325

375

425

475

525

575

625

675

725

Time [min]

0 10 20 30 40 50 60

Burner/

Vaporizer

HC-Dosing

SCR

AdBlue©

SCR-Mixer

ASC CDPF

11,25” x 9” x 4” 11,25” x 12”

FIDFID FTIRFTIR AMA (2-line)AMA (2-line)

Tupstream SCR Tdownstram SCR Tdownstram ASC Tdownstram DPF

SCRQ&SCRQ&

ASCQ&

CDPFQ&

ASCQ&ASCQ&

CDPFQ&CDPFQ&

Combined SCR – A novel approach for Nox and PM aftertreatment13. ETH-Conference on Combustion Generated Nanoparticles (22.-24.06.2009)

M.Müller, Dr. H.Bülte, Dr. S.Schraml, Dr. P.Broll, DEUTZ AG, Cologne Prof. Dr. H.Harndorf, University of Rostock

ETH Conference 2009 · 222.-24.06.2009

Content

Introduction………………………………………………………………………………...3System - concepts for off-road emission regulations..........................................….. 8A novel approach - Combined SCR……………………………………………………. 10Experimental setup………………………………………………………………………. 11Test results………………………………………………………………………………...12Summary and outlook…………………………………………………………………….19

Slide

ETH Conference 2009 · 322.-24.06.2009

Introduction

Construction Infrastructure

NutritionAgriculture

Daily demandCommercial

DEUTZ manufactures engines for different applications in a power range of 9 – 500 kW…

ETH Conference 2009 · 422.-24.06.2009

Totally different market requests for the different applications concerning:

TechnologyPerformanceLoad profilesMaintenance

Future exhaust aftertreatment systems will most probably comprise selective catalytic reduction (SCR) as well as wall-flow diesel particulate filters (DPF) to cope with stringent NOx and PM emission limits

DEUTZ will offer a complete system consisting of the diesel engine and the aftertreatment unit with the target to realize a compact and cost optimised system to meet the emission standards

Minimized application effortsMaximized customer value

Introduction

High number of variants of one engine

ETH Conference 2009 · 522.-24.06.2009

Introduction

DEUTZ strategy for forthcoming emission legislation

NOx (+ HC)[g/kWh]

Parti

culat

es [g

/kWh] 0,25

0,20

0,15

0,10

0,05

0,00

0 1 2 3 4 5

DPF98% Optim

ized I

njecti

on,

Comb

ustio

n an

d Tur

boch

argin

g

130 – 560 kW

Features Tier 4 interim (from year 2011)DEUTZ Common Rail (DCR®) 2000 bar Advanced nozzle designWaste gate turbochargerCharge air coolerExternally cooled EGRBurner for DPF regenerationDPF

Additional Features Tier 4 (from year 2014)SCRVGTDual-stage turbocharger w/ and w/o intercooling

TIER 3TIER 3

Tier 4 finalTier 4 final

Tier 4 interimTier 4 interimSCR0,025

0,4

ETH Conference 2009 · 622.-24.06.2009

Active components closed coupled to the engine Space consuming components (catalyst, muffler, acoustics, etc…) located in the machinery

Introduction

DEUTZ strategy for Tier 4 interim

DOC diesel oxidation catalystCDPF coated diesel particulate filter

DOC diesel oxidation catalystCDPF coated diesel particulate filter

Engine

ECU

DosingmoduleFuel

Temperatureupstream/downstream

Air

Pressureupstream/downstream

Burner/Vaporizer ExhaustDOC CDPF

Variants in customer applications

Muffler

ETH Conference 2009 · 722.-24.06.2009

TCD2013 L06 4V Tier4 interim

Heat mode for DPF-regeneration

Key facts of the burner / vaporizer unit:

Introduction

15 kW powerEngine independent preheating of catalystExhaust gas temperature ≥ 300 °C Provides vaporisation enthalpyAdditional HC doser includedHomogeneous dispersion of the vaporized diesel fuel on the catalyst surface

Key facts of the burner / vaporizer unit:

15 kW powerEngine independent preheating of catalystExhaust gas temperature ≥ 300 °C Provides vaporisation enthalpyAdditional HC doser includedHomogeneous dispersion of the vaporized diesel fuel on the catalyst surface

T upstr. DOC ≥ 300°C

T engine out

Heat up by

burner

T light-off DOC≈ 15 kWTe

mpe

ratu

re[°C

]

Time [s]

Heat release by DOC T thermal regeneration

DEUTZ strategy for Tier 4 interim

ETH Conference 2009 · 822.-24.06.2009

Pros and cons:+ Passive DPF-regeneration feasible + Application of the Tier4 interim muffler feasible- AdBlue© - dosing upstream DOC not possible (NH3 oxidation)- AdBlue© - doser cannot be closed coupled to the engine- High application efforts- High precious metal quantity

1st concept: EAT-system consisting of DPF + SCR (SCRT© -configuration)Add-on system to Tier4 interim setup

System concepts for Tier 4 final

System - concepts for off-road emission regulations

CDPFDOC

Burner/vaporizer

DOC diesel oxidation catalystCDPF coated diesel particulate filterSCR selective catalytic reduction cat.ASC ammonia slip catalyst

DOC diesel oxidation catalystCDPF coated diesel particulate filterSCR selective catalytic reduction cat.ASC ammonia slip catalyst

SCR ASC

AdBlue©

ETH Conference 2009 · 922.-24.06.2009

2nd concept: SCR-system upstream DOC and DPF Scope: All active components (HC and AdBlue© dosing unit) coupled close at the engine

System - concepts for off-road emission regulations

Alternative options for Tier 4 final

SCR

AdBlue©

CDPFDOC

HC-Dozer

Does the HC-dosing damage the SCR coating during an active DPF regeneration?

SCR

AdBlue© + HC-Dosing

CDPFDOC

ETH Conference 2009 · 1022.-24.06.2009

All active components can be mounted at the engineHydrocarbons partially oxidised on the catalytic coating of the SCR – catalyst (V2O5) Heat release for the DPF – regeneration is partially generated by the SCR - coatingNOx – conversion up to 95 % (steady state) in dependency of the engine operating point100 % soot reduction by the DPF (wall-flow)The burner guarantees an exhaust gas temperature ≥ 300 °C within the whole engine mapProbably only one muffler required like TIER4 interim Cost benefit due to saving of precious metal

━ No NO2 formation for passive regeneration (CRT)

A novel approach - Combined SCR

Benefit of the Combined SCR system

SCR

AdBlue©

CDPF

Burner Closed coupled to engine

ASC

ETH Conference 2009 · 1122.-24.06.2009

Oxidation behaviour of the hydrocarbons (HC) on the vanadium-based SCR-coating?Main focus:

Does HC-dosing and oxidation damage the SCR - coating?Which exothermic is produced on the catalytic coating?How is the temperature distribution in the catalyst?Does the catalyst oxidise the dosed diesel fuel completely? HC/CO-slip?How does the system work at low temperatures ?

Experimental setup

FID Flame ionisation detectorFTIR Fourier transform infrared

FID Flame ionisation detectorFTIR Fourier transform infrared

Burner/Vaporizer

HC-Dosing

SCR

V2O5

AdBlue©

SCR-Mixer

11,25” x 9”

FIDFID FTIRFTIRTCD 2013 L06 4V (Euro4 / 235 kW)

ETH Conference 2009 · 1222.-24.06.2009

Test results

Alternating admission of diesel fuel and NH3 to the SCR - coating

Test cycle: Combination of a DPF-regeneration + ESC test cycle, duration: 62 min / cycle295 test cycles were accomplished

HC

-Dos

ing

[ml/m

in]

0

10

20

30

40

50

Time [s]0 500 1000 1500 2000 2500 3000 3500 4000

engi

ne s

peed

[1/m

in] /

torq

ue [N

m]

0

500

1000

1500

2000

2500

Engine speed Engine torque HC-dosing

DPF - regeneration AdBlue© - Dosing

ETH Conference 2009 · 1322.-24.06.2009

Test results

SCR performance after 295 test cycles 300°C / 40000 1/h 400°C / 40000 1/h

NH3 N2O

NO

x co

ncen

trat

ion

[ppm

]

0

200

400

600

800

1000 After aging 145 test cycles 295 test cycles

NO

x-co

nver

sion

rate

[%]

0

20

40

60

80

100

NO

x co

ncen

trat

ion

[ppm

]

0

200

400

600

800

1000

NO

x-co

nver

sion

rate

[%]

0

20

40

60

80

100

NH

3 / N

2O [p

pm]

0

10

20

30

40

50

Feed ratio [-]0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

NH3 N2O

NH

3 / N

2O [p

pm]

0

10

20

30

40

50

Feed ratio [-]0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

ETH Conference 2009 · 1422.-24.06.2009

Test results

HC-dosage for a target temperature of 630°C upstream DPF HC conversion [%]

100009000800070006000500040003000200010000

T up

str.

SCR

[°C

]

300

350

400

450

500

550

600

650

90

80

80

7058 627267

74777281

82 8280 80

8183 777979 78

96 73 76

100100 9999100

HC

- co

nver

sion

[%]

1009080706050403020100

T up

str.

SCR

[°C

]

300

350

400

450

500

550

600

650

Space velocity [1/h]10000 20000 30000 40000 50000 60000 70000

2851 32214464417851245942

443156906422 5323

5879 571444595219 394152545810 4952

3623 1675 2523

7231047 10618661411

CO

- co

ncen

trat

ion

[ppm

]

CO downstream SCR [ppm]

ETH Conference 2009 · 1522.-24.06.2009

Test results

Heat generation on the SCR coating / Target temperature upstream DPF of 630°C

T up

str.

SCR

[°C

]

300

350

400

450

500

550

600

650

405 437460443481486

505519486 522

510 523545550 551541537 542

564 578 585

611626 619624634

Tem

pera

ture

dow

nstr

. SC

R [°

C]

600575550525500475450425400

T downstream SCR [°C]

T up

str.

SCR

[°C

]

300

350

400

450

500

550

600

650

Space velocity [1/h]10000 20000 30000 40000 50000 60000 70000

100

25

50

75

125

12597 122139122

146148143147

91 12594 105

104102 977769 69

37 40 36

2820 121116

Hea

t gen

erat

ion

on S

CR

[°C

]

2001751501251007550250

Heat generation on SCR coating [°C]

ETH Conference 2009 · 1622.-24.06.2009

Test results

Axial temperature distribution during the DPF-regeneration at peak HC-dosage

Axial temperature distribution during DPF regeneration (test cycle)10 35 60 85 115 145 170 195 [mm]

0

HC - Dosing FTIR / FIDTe

mpe

ratu

r [°

C]

425

450

475

500

525

550

575

10 35 60 85 115 145 170 195 [mm]0

HC - Dosing

Reg

ener

atio

n tim

e [s

]

Tem

pera

ture

[°C

]

430

450

470

490

510

530

700

500

300

100

600

400

200

0

100

200

300

400

500

600

700

800

FTIR / FID

ETH Conference 2009 · 1722.-24.06.2009

Tem

pera

ture

[°C

]

325

375

425

475

525

575

625

675

725

Time [min]0 10 20 30 40 50 60

Test results

Heat-up performance of the Combined SCR system at max. space velocity of 60000 1/h

Burner/Vaporizer

HC-Dosing

SCR

AdBlue©

SCR-Mixer

ASC CDPF

11,25” x 9” x 4” 11,25” x 12”

FIDFID FTIRFTIR AMA (2-line)AMA (2-line)

SCRQ&

ASCQ&CDPFQ&

1. Heat release by the burner/vaporiser unit2. Heat release from partial oxidising of the hydrocarbons on the SCR coating3. Heat release of the remaining chemical energy on the ASC and CDPF

Tupstream SCR Tdownstram SCR Tdownstram ASC Tdownstram DPF

ETH Conference 2009 · 1822.-24.06.2009

Summary and outlook

HC-oxidation on the SCR coatingThe vanadium-based SCR - coating (V2O5) shows oxidising characteristic and serves as an oxidation catalyst for the diesel vapour during DPF regeneration

The precious metal loadings on the ammonia slip catalyst and the coated DPF can be reduced

The formation of CO is a favourable featureThe high quantities of CO almost completely oxidised on the ASC + CDPF.

The SCR-coating is thereby protected from excessive temperatures

SCR performanceNo substantial degradation for…

NOx - conversionNH3-SlipSecondary emission (N2O)

ETH Conference 2009 · 1922.-24.06.2009

Summary and outlook

Temperature distribution Axially homogeneous heat release rate (locally moderate thermal stress)An incomplete heat release can be excluded. The decrease of the temperature gradient at the end of the SCR - catalyst describes a sufficient dimensioning of the catalyst volume No axial „Shifting “of the reaction zone, stable over 295 test cycles ≈ 2500 engine operation hours

Heat mode for the DPF regeneration in three steps1. Heat release by the burner/vaporiser unit2. Heat release from partial oxidising of the hydrocarbons on the SCR coating3. Heat release of the remaining chemical energy on the ASC and CDPF

OutlookSystem development based on this concept System integration to muffler designComprehensive study of the global reactions