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CARB aftertreatment reviewJuly 11, 2007
1
GETransportation
Aftertreatment Impact to locomotives & locomotive operations
California Air Resources BoardSacramento, CA
June 6th, 2007
CARB aftertreatment reviewJuly 11, 2007
2
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
CARB aftertreatment reviewJuly 11, 2007
3
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
CARB aftertreatment reviewJuly 11, 2007
4
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%
CARB aftertreatment reviewJuly 11, 2007
5
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
CARB aftertreatment reviewJuly 11, 2007
6
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
Tier 4 NOxTier 4 NOxTier 4 NOx
Space & other constraintsSpace & other constraintsSpace & other constraints
Operational impact Operational impact Operational impact
Development requirementsDevelopment requirementsDevelopment requirements
Summary Summary Summary
CARB aftertreatment reviewJuly 11, 2007
7
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
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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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
Space & other constraintsSpace & other constraintsSpace & other constraints
Operational impact Operational impact Operational impact
Development requirementsDevelopment requirementsDevelopment requirements
Summary Summary Summary
CARB aftertreatment reviewJuly 11, 2007
10
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
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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Deterioration - DOC
DOC will require replacement in <6 months
Effect on SCR Performance:
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
15
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
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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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)
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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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 PM Tier 4 PM Tier 4 PM
Tier 4 NOxTier 4 NOxTier 4 NOx
Space & other constraintsSpace & other constraints
Operational impact Operational impact Operational impact
Development requirementsDevelopment requirementsDevelopment requirements
Summary Summary Summary
CARB aftertreatment reviewJuly 11, 2007
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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”
CARB aftertreatment reviewJuly 11, 2007
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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 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
Development requirementsDevelopment requirementsDevelopment requirements
Summary Summary Summary
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
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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 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
Summary Summary Summary
CARB aftertreatment reviewJuly 11, 2007
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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
CARB aftertreatment reviewJuly 11, 2007
25
Discussion topics
Where we are & where are we goingWhere 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 requirementsDevelopment requirementsDevelopment requirements
Summary Summary