urea scr and dpf system for deisel sport utility vehicle

DEER Conference - August 25, 2002

1

Urea SCR and DPF System for Diesel Sport Utility Vehicle

Meeting Tier II Bin 5

DOE and Ford Motor Company Advanced CIDI Emission Control System Development Program

(DE-FC26-01NT41103)

Robert HammerleDiesel Engine Emission Reduction Conference

August 25, 2002


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Phase I - Initial build/test phase (12 mos.)Establish baseline emission control systemDeliver engine dynamometer NOx and PM test resultsDemonstrate and deliver prototype vehicle NOx and PM test resultsDeliver urea delivery (infrastructure) prototype

Phase II - System/component optimization phase (18 mos.)Define final system hardware componentsDeliver NOx and PM performance dataDemonstrate emission control system (includes NOx and PM data)

Phase III - Durability/Demonstration phase (18 mos.)Definition of durability test procedureFinal NOx and PM emission levels Define fuel sulfur limits for emission control systemFinal report for the completed program

DOE Ultra-Clean Fuels ProgramOutline of Ford’s program to achieve Tier II emissionstandards for 2007 using low sulfur diesel fuel as an enabler for a high efficiency aftertreatment system.

Primary Contractor

Subcontractors

Catalyst Suppliers


3

FEV Program

Concept Design• CFD Modeling including urea injection

Engine Dynamometer• Baseline and rapid warm-up testing• Urea SCR/DPF optimization• Transient FTP/US06 testing

Vehicle durability• 120,000 miles or 5000 hours


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ExxonMobil ProgramIntellectual property discussion delayed program for 9 months; program was then accelerated to contain original objectives.

SCR urea catalyst development• Durable, high NOx conversion from 150° to

600°C with low N2O make.Urea infrastructure studies• Co-fueling• Low temperature urea solutionFuel development• Make and use fuel, which will be typical of

2007 production with 15 ppm sulfur cap.


5

AcknowledgementsContributions to this program

FordKaren Adams, Dick Baker, Will Belanger, Brendan Carberry, Dick Chase, Dave Kubinski, Paul Laing, Christine Lambert, Mike Levin, Chris Mazur, Cliff Montreuil, Rick Soltis, Paul Tennison,Devesh Upadhyay, John Vanderslice and Scott Williams

FEVPhilipp Adomeit, Eric Koehler, Dean Tomazic

Exxon MobilJoan Axelrod, Jeff Beck, Bill Blazowski, Owen FeeleyMarcus Moore, Mike Noorman and David Stern


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Initial Configuration Choicesfor Tier II Bin 5

DOC CDPFUrea SCR

CDPF Urea SCR

Selected configuration

Unacceptable configuration

Oxidize HC, CO, NO Reduce NOx Control PM

Oxidize HC, CO, NOControl PM

Reduce NOx

urea

urea


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Urea SCR Model Prediction of Tailpipe NOx for Configuration Alternatives

System A

E T SCR

Urea

SiC Filter

System A

E T SCR

Urea

PM Filter

System B

T

Urea

SiC FilterSCRE DOC

System B

TTT

Urea

PM FilterSCRE DOC

System B

TTT

Urea

SiC FilterSCRE DOC

System B

TTTT

Urea

PM FilterSCRE DOCTT

Urea

PM FilterSCRE DOC

Rapid warm-up = extra 50°C ramped in over first 30s of test and off at 200s.

010

20

30

40

50

60

7080

90100

0 200 400 600 800 1000 1200 1400

FTP Cycle Time (seconds)

Cu

mu

lati

ve

NO

x (

% o

f e

ng

ine

ou

t)

Engine out

System A Tailpipe

System B Tailpipe

System B Tailpipe with rapid warm-up

Target90%

Conv.

010

20

30

40

50

60

7080

90100

0 200 400 600 800 1000 1200 1400

FTP Cycle Time (seconds)

Cu

mu

lati

ve

NO

x (

% o

f e

ng

ine

ou

t)

Engine out

System A Tailpipe

System B Tailpipe


Target90%

Conv.

Engine out

System A Tailpipe

System B Tailpipe



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Using Fresh DOC/SCR/DPF System, Focus Achieved ULEV II / Bin 5

Ford Research Laboratory showed Focus results using fresh catalysts:

FTP conversion for NOx is ~90% and PM is ~98%.

US06 conversion for NOx+HC is ~92%.


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Light-Duty Truck Exhaust System

Temperature sensor

SCRcatalyst

SCRCat

UreaInjector

DPF

Feedback controlof urea injection

ECU

Engine

Control of light-off

OxidCat

NOx sensorand/or

NH3 sensorDelta P Sensor

NOx Sensor

Fuel injection

Control of filterregeneration


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Temperatures and Space VelocityEPA-75 Test

0

50

100

150

200

250

300

350

400

0 500 1000 1500 2000

Time (seconds)

Tem

per

atu

re (

°C)

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Sp

ace

Vel

oci

ty (

hr-1

)

Turbo Out DOC in SCR in SCR out Space Velocity


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Vehicle Testing

• With initial system 1, 35% NOx conversion and high NH3 slip.

• Suspected poor urea distribution caused low NOx conversion.

• Developed new system 2 for improved urea distribution

• System 2 has increased length of the SCR entrance cone and mixing plate.


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Urea Distribution on SUV & Focus


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Sport Utility Vehicle TestingSystem 2 - Weighted EPA-75 Emissions

0.015

0.008 0.103(47%)

0.065(55%)

0.0430.053(76%)

0.019(96%)

0.006 (98%)0.026(94%)

0.045(82%)

0.005 (94%)

0.012 (93%)

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

THC NMHC CO/10 NOX

gram

s/m

ile Bag 3Bag 2Bag 1

Tier 2 - Bin 5 Standard, 120k

(Catalyst efficiency)

0.091 (89%)

0.169 (81%)

0.077 (84%)

0.066

.42


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SUV TestingAccumulated NOx (Bags 1-2)

0

5

10

15

20

25

0 200 400 600 800 1000 1200 1400

Time (s)

No

rmal

ized

Tai

lpip

e N

OX (

% o

f to

tal F

eed

gas

)

Vehicle TestModelModel with rapid warm-up

Tier II Bin 5Target


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Effect of NH3 Storage on NOx ConversionNOx Conversion with varying NH3 Storage Amounts and 0% NO2 Feedgas

0

10

20

30

40

50

60

70

80

90

100

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

Temperature (oC)

NO

x C

on

vers

ion

(%

)

Increasing NH3 Storage


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• Good prediction of adsorption/desorption levels and positions versus time

NH3 Adsorption/Desorption ModelDegreened Urea-SCR Catalyst - Base Metal Zeolite Formulation

350 ppm NH3 - 100oC

0

50

100

150

200

250

300

350

400

0 50 100 150 200 250 300

time (min)

NH

3 (p

pm

)

0

100

200

300

400

500

600

Tem

per

atu

re (

o C)

Release Storage TPD Release Model Fit T Ramp 5 C/min

NH3 Storage @ 100oC

NH3 Off

NH3 Release @ 100oC

Temperature Ramp 5oC/min

100-500oCTPD NH3 Release


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NOx Sensor Development

Status:• Start of production 4Q/2001• Range 500 or 2000 ppm +/- 10

ppm • Valid for A/F from 10 to 8 • Detects NO and NO2 with

similar sensitivity

Issues:• To limit thermal shock cracking,

response time remains about 0.7 sec.

• Cross sensitive to NH3 giving ~60% NO response

• Costly

Amperometric - O2 and NOx Pumping• Prototype NOx sensors from NGK Locke

• Other suppliers (NTK, Denso, Delphi, Bosch)Other sensor types:• Resistive (NASA/Makel)• SiCFET (NASA Glenn)• Electrochemical mixed-potential


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Ammonia Sensor Development

• Four technologies are being evaluated:1) Mixed potential (two suppliers)2) Zeolite (Dornier, Daimler-Chrysler, Temic)3) SiC-based FET (S-Sense, Linköping U.) 4) Metal oxide resistors (SUNY)

• Collaborative development of the four technologies 1) Vehicle testing of prototype sensors

− Initiated mixed potential sensor testing on vehicle

• Will select the most promising from these four technologies.


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Urea Infrastructure ChoicesA. Fill Aqueous Urea during Oil Change Service

1. Which vehicles can carry sufficient urea on-board?2. Which customers will use professional service stations?3. Which customers will carefully re-fill urea by themselves?4. What warnings will be positively perceived rather than negatively?5. Will incentives work (free urea, free oil changes, etc.)?6. Can this approach start infrastructure for key truck stops & fleets?

B. Fill Aqueous Urea during Fueling1. Which vehicles have limited package space for urea?2. Which customers are unlikely to follow directions for periodic

service? 3. Can urea be added during fueling with no extra actions? Co-fueling.

Note: Concept for co-fueling was presented at DEER 2001. 4. How could co-fueling be introduced to general public?

To be successful, a low-cost urea supply infrastructure must be developed that is convenient and does not impose a significant burden onto customers.


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0

2

4

6

8

10

12

14

16

18

20

0 5000 10000 15000 20000Miles driven

Ure

a st

ora

ge

volu

me,

gal

40 mpg; 1.5% of fuel 40 mpg; 2.5 % of fuel

20 mpg; 1.5 % of fuel 20 mpg; 2.5 % of fuel

On-Board Urea Storage Volume


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Urea InfrastructureAqueous urea co-fueling for light-duty vehicles

Aqueous urea delivery for light-duty vehicles

• requires no extra consumer actions• co-fueling with diesel into separate tanks may be possible

Formulation of aqueous urea

• Concentration– 32.5 wt% has lowest freeze point (12oF, -11°C)

• Freeze point additives must not be toxic or poison catalyst

• Heated system may be required for colder climates


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Co-Fueling Design RequirementsDesign Requirements

1. Deliver urea during diesel fueling 2. Independent on / off3. Prevent dispensing diesel without urea4. Avoid cross-contamination5. Easy to operate / no training needed6. Backward compatibility7. Minimize investment8. Avoid dry out, plugging9. Manage freezing

Current Design

a

aa?a?

aa

a?a?a?

“a“ = requirements met. “a?“ = issues remain.


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Status of NOx Control Development• Achieved 96% NOx conversion on FTP when

SCR catalyst is above 200°C.• Need warm-up within ~1 min. to meet target.• Need to optimize NH3 storage for best cold-

start NOx control, but must control urea injection to prevent NH3 slip.• control model for optimizing urea injection• durable NOx and NH3 sensors

• Need more durable NOx catalyst to use DOC for DPF regeneration.

• Urea supply infrastructure remains a major issue.

urea scr and dpf system for deisel sport utility vehicle

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