CARB Aftertreatment Review 06 06 07 Final Editied … · • Logistics/handling challenges: ......

CARB aftertreatment reviewJuly 11, 2007

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GETransportation

Aftertreatment Impact to locomotives & locomotive operations

California Air Resources BoardSacramento, CA

June 6th, 2007


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Discussion topicsWhere we are & where are we goingWhere we are & where are we going

Tier 4 PM Tier 4 PM

Tier 4 NOxTier 4 NOx

Space & other constraintsSpace & other constraints

Operational impact Operational impact

Development requirementsDevelopment requirements

Summary Summary


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Discussion topicsWhere we are & where are we goingWhere we are & where are we going

Tier 4 PM Tier 4 PM Tier 4 PM

Tier 4 NOxTier 4 NOxTier 4 NOx

Space & other constraintsSpace & other constraintsSpace & other constraints

Operational impact Operational impact Operational impact

Development requirements Development requirements Development requirements

Summary Summary Summary


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Where we have come from

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

EPA Line-haul PM (g/hp-hr)

EPA

Lin

e-ha

ul N

Ox

(g/h

p-hr

)

Unregulated

Tier 0 (1973-2001)

Tier 1 (2002-2004)

Tier 2 (2005+)

-25%

-22%

-26%

-55%


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Tier 3 - ‘12

-50%Tier Technology3 - On-engine technologies

- Ultra low sulfur diesel

Where we are going

1.0

0.1 0.2

Tier 2

EPA Line-haul PM (g/hp-hr)

EPA

Lin

e-ha

ul N

Ox

(g/h

p-hr

)

2.0

3.0

4.0

5.0

6.0 Tier 4 – ‘15

-70%

4 - All Tier 3 technology- Diesel particulate filter

(DPF)- Ultra low sulfur diesel

Tier 4 – ‘17

-76%

4 - All Tier 4 PM technology- NOx aftertreatment(Urea SCR)

- Ultra low sulfur diesel


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Discussion topicsWhere we are & where are we goingWhere we are & where are we goingWhere we are & where are we going

Tier 4 PM Tier 4 PM




Development requirementsDevelopment requirementsDevelopment requirements



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Diesel Particulate Filter • Captures all forms of particulate

matter

• 90+% PM reductions are achievable

• Captured material must be periodically burned off (regenerated)

– Avoid high back pressure– SFC penalty

• Technology path defined

• Significant engineering challenge

• Logistics/handling challenges:– Size/weight/handling equipment– May require crane for change out

0

20

40

60

80

100

Organics (SOF)

Sulfates

Soot (DPM)

Fuel

Lube

Metals& Ash

DPF

Rep

rese

ntat

ive

% o

f Tot

al


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PM Aftertreatment ConcernsConsumables:• 1 to 2 % SFC increase . . . 35 – 70 tons/year of CO2

– added backpressure– regeneration energy

Maintenance:• Ash cleaning every 180 days a must to match service intervals

– Similar to power cylinder replacement (will require crane)– UX exchange process– Waste handling & disposal

Durability:• Anticipate replacement of DPF at end of useful life (engine overhaul)

Logistics:• DPF maintenance, handling & exchange process• Waste disposal


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Discussion topics

Where we are & where are we goingWhere we are & where are we goingWhere we are & where are we going

Tier 4 PMTier 4 PMTier 4 PM

Tier 4 NOxTier 4 NOx






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Tier 4 NOx: Areas of Concern

• No account for carbon, ammonia slip, fuel consumption and practical/safety implications

• Catalyst deterioration poorly known for zeolite,real exhaust, and loco environment

• References to truck “successes” are unproven in durability and degradation

• Marine/Loco proposals are not consistent


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Assessment Process

1. System Concept 3. Monte Carlo Analysis2. Analytical Model

Technical Basis:• Tier 2 engine-out NOx at 5.5g/hp-hr into SCR system• Urea SCR only using a zeolite catalyst• Locomotive exhaust temperature and duty cycle

PerformanceFr

eque

ncy


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Urea-SCR: Nominal System Configuration

Three-Catalyst System:

DOCNONO2

NONO2

SCR

urea

NH3Slip

NH3

N2 N2

16.5 cu. ft47,000 hr-1

4.9 cu. Ft.(JM design)

3 cu.ft.260,000 hr-1

Conversion %Ideal Conversion Conversion %

• 1.3g/bhp-hr requires 76% duty cycle NOx conversion at end of useful life

• Need ~85% peak conversion after degradation

NoxSensorFeedback

– DOC design provides optimum NO/NO2 ratio when new– Slip catalyst converts NH3 to N2 , with some NOx & NH3


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Deterioration - DOC

DOC will require replacement in <6 months

Effect on SCR Performance:


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“SCR catalysts that are engine aged with urea, deactivate in a more complicated manner than hydrothermal aging alone.” inlet outletSCR

Deterioration - SCR

Ref. SAE 07PFL-397 in press 2007


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Notch by notch dosing adjustment

Deterioration – Ammonia Slip Catalyst

At 1.3 g/hp-hr, ammonia slip will be above the odor threshold

Ref. BASF, SAE 2006-01-0640

• Deactivation of slip catalyst from 90% 80% ammonia conversion• Assume selectivity to nitrogen remains at 80% (zero degradation)• Inlet NOx for locomotive > trucks higher ammonia slip levels• Transient ammonia slip > 50 ppm possible due to large catalyst mass• Potential to form N2O due to NH3 slip catalyst degradation• Closed loop sensor needed – technology not available today


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Comparison of Loco and Trucks• Exhaust temperature in a locomotive is higher than in a

truck

• Trucks use V-based catalyst, not applicable to locomotives in US . . . Locomotives require Zeolite catalyst – not commercially available

• 120,000 miles on a truck is approximate 8 months of locomotive operation

• Ammonia slip concerns for locos– Continuous ammonia slip due to high dosing– Transient ammonia slip > 50 ppm possible due to large

catalyst mass


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SCR Limitations• Rate Limited (temperature)

• Mass Transfer Limited (catalyst size)

• NH3 Limited (dosing accuracy & maldistribution)

• Thermal Aging / Poisoning (loss of sites)


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• New catalyst entitlement –consensus

• Larger impact of system interactions and variation

• High risk technology breakthroughs needed to get to <2.0 gm/HP-hr

Summary Assessment of Tier 4 NOx

• Concern for ammonia slip• Full probabilistic analysis of variation

• Deterioration of catalysts • ASC reconversion of NOx

ASC conversion

Zeolite catalyst

SCR variation

NOx Sensor accuracy

NOx Sensor variation

ASC Selectivity

SCR degradation

DOC catalyst replace

Advances required


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Discussion topics




Space & other constraintsSpace & other constraints





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General Aftertreatment ConstraintsSensitive to Exhaust Temperature:• Low temperature and low power/idle operation

affects efficiency & soot loading• High temperature, high altitude, tunnel operation

affect durabilityPackaging/Weight:• Must mount above engine, limits device size and

plumbing for reductant mixing• High weight, will need significant structural

support• Impact to locomotive overall weight and balance

Mechanical Environment:• Large housing, response to operating

frequencies & thermal stress

• Shock loads due to hard couples, effect on substrate durability

SCR DPF

Plus, reductant handling system and storage

Plate “L”


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Discussion topics





Operational impact Operational impact




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Fuel impact . . . new builds

Tier 3 2015 2017

6+%*

1-2 %

2017

2017

* Includes fuel loss from the reduction in catalyst efficiency

Each point of fuel efficiency loss drives:• An additional 3,500 gallons of fuel burned/year• An additional 35 tons of CO2 exhausted/year• For every new locomotiveAssumes average locomotive fuel burn of 350k gallons/year


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Discussion topics






Development requirements Development requirements



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Tier 4 development timeline

Production launch

Rules promulgated

Concept development

Finalized concept

Detailed design

Lab test model Prototypes

Field demonstration

Based on successful Evolution launch . . .

Already feeling schedule pressure

Tier 4 PM

Tier 4 NOx

0 1 2 3 4 5 6 7 8 9 10 11

‘15‘14‘13‘12‘11‘10‘08 ‘09‘07

Production launch

Rules promulgated

Concept development

Finalized concept

Detailed design

Lab test model Prototypes

Field demonstration

0 1 2 3 4 5 6 7 8 9 10 11

‘15‘14‘13‘12‘11‘10‘08 ‘09‘07 ‘16 ‘17

R&D


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Discussion topics







Summary Summary

CARB Aftertreatment Review 06 06 07 Final Editied … · • Logistics/handling challenges: ......

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