Methane Slip Emissions from Ships:
summary based on measurement data
Sergey Ushakov, Norwegian University of Science and Technology
Dag Stenersen, SINTEF Ocean
Per Magne Einang, SINTEF Ocean
2
Outline
• Introduction– Global shipping overview
– Regulations and future solutions for lower emissions
– LNG as marine fuel and available gas engine technologies
• Study on methane slip from ships– Overvier and limitations
– Results for LBSI and LPDF engines
• Summary and conclusions
Image source: www.iea.org International Energy Agency, photo: Getty Images
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Global shipping
Image source: Balcombe et al. How to decarbonize international shipping: Options for fuels, technologies and policies. Energy Conversion and Management
182 (2019) 72-88.
• Shipping is responsible for 80-90 % of
the world’s trade
• Most cost- and energy-efficient way of
commercial transport– 3.2 Mt of NOx emitted ( <5% of global)
– 2.3 Mt of SOx
– 1.1 Gt of CO2 (around 3% of global)
• Diversity of ship classes/sizes operating
with different operating profiles– Biggest vessels are the most efficient in terms
of gCO2/tonne-km, but are the biggest
pollutants
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Regulations and
emission reduction
• SOx emissions
– Tightening global sulfur cap: 0.5% S from 2020
– More Emission Control Areas (ECAs)
• NOx emissions
– Tightening regulations: Tier III for new-built
• CO2 emissions– Energy Efficiency Design Index (EEDI): design measures
– Ship Energy Efficiency Management Plan (SEEMP):
operational measures
– IMO’s 2050 50% GHG emission reduction target
• Market growth should be considered
• New (lower carbon/zero carbon) fuels have to be used
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Transition paths
Sources (upper left, * data): N. Olmer et al. Greenhouse gas emissions from global shipping, 2013-2015. ICCT, 2017
(lower left): Psaraftis and Kontovas, CO2 emission statistics for the world commercial fleet, WMU Journal of Maritime Affairs, 2009
Crude oil carriers
86%
HFO
HFO
HFO
Diesel
HFO
Biofuel /(bio) LNG / NH3 /H2
SCR
EGR + scrubber
IMO’s CO2 target for 2050 is 50 % reduction per tonne-km
≈3% of global
CO2 emissions*
HFO Fuel cell (H2)
HFO Battery
ICEs
non-ICEs
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Feasibility of available solutions
7
LNG as alternative marine fuel
(Right chart *) - numbers are based on seach algorithm through the final programmes using the keywords gas, methane, dual fuel, lean burn, etc.
*
Methane slip
8
Three main gas-fuelled engine
concepts• LNG is the only alternative fuel currently
available for deep-sea shipping
• Fuel flexibility is essential for bridging
technologies towards carbon-free shipping
• HPDF concept is fuel flexible and has no
methane slip-related issues
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Key characteristics of
gas engine concepts
• LBSI, medium speed– Rolls-Royce Bergen Engines (NO)
• LBSI, high speed– Mitsubishi (JP)
• LPDF, medium speed– Wärtsilä (FI)
• LPDF, low speed– Win-GD (CH)
• HPDF, medium speed– Wärtsilä (FI) – on-land application only
• HPDF, low speed– MAN Diesel and Turbo (DE)
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Frames of current measurement
study• Marine gas engines
– Medium speed, 4-stroke
– LBSI and LPDF
– Different gas technology generations
• Methane slip– Additional measurements of NOx and
other emissions
• Measurement data– Test-bed vs. on-board
– E2 and E3 cycles
• Different fuel composition– Methane number variation considered
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LBSI engines
• Same engine model– Test-bed: LBSI9 (E2), LBSI10 (E3)
– On-board: LBSI8
– LBSI1 – old gas engine technology (prior 2010)
• Expected emission trends– With load increase: better combustion due to
increasing fuel-air ratio
– NOx ↑, CO and CH4 ↓
– Tier III requirements are fullfilled
• Challenging low load conditions– Incomplete combustion due to very lean
conditions
– Additional effect from variation in fuel
composition, operational state, etc.
• Important to consider vessels’
operating profile (vessel type)– LBSI1 – passanger/car ferry
Overview
Same engine model, different ships
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LBSI engines (cont.)
LBSI9 LBSI8
• No evidence of methane slip in case of
test-bed measurements– CH4 emissions peak only at 10% load
– Laboratory infrastructure: better control of test
conditions and possibilities for tuning
• Possible LBSI8 engine «overtuning»
for low NOx
– Final engine tuning, based on on-board
measurements under real operation, can be
proposed
• Good stability of measurement results
for the most of the considered engines– Extensive planning and equipment preparation
– Shipowners are interested in results in order to
optimize engine/ship performance
– Need for field testing for better evaluation of
different gas technologies
Same engine model
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LPDF engines
• Test engines– Test-bed: LPDF2
– On-board: LPDF1 (E3), LPDF3 (E3)
– LPDF1 and LPDF2 – same engine model
• Challenging low load conditions – also
for presise measurements– Unstable combustion (keep in mind amount of
pilot fuel) and effect of actual load variation
– Below 25% load - large variation in results
• Expected emission trends (as for
LBSIs)– With load increase: better (and more stable)
combustion due to increasing fuel-air ratio
– NOx ↑, CO and CH4 ↓
– Tier III requirements are fullfilled (with the
exception of LPDF1)
Overview
Same engine model
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LPDF engines (cont.)
• Generally higher NOx emissions that
from LBSI engines– Effect of pilot fuel (important for maintaining the
stability of the combustion)
– Although, controlling the amount of pilot fuel
injection can be used to control methane slip
• Clear indication of low NOx tuning at
75% load– Highest weighting factor (0.5) according E2
and E3 test cycles – need for compliance
– Lower margin can be used – possibility for
optimization
• Variation in cylinder power rating has
only a minor effect on methane slip at
loads above 50%– Considerable effect at lower loads
– The opposite effect on NOx emissions
Same engine model
Same engine model
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LBSI and LPDF: summary
• Test engines– Modern LBSI and LPDF
– Older (prior 2012) LBSI
• Both LBSI and LPDF engines achieve Tier 3
compliance without aftertreatment– Tuning of engine for low NOx has to be used
• Higher NOx emissions from LPDF engines– Amount of pilot fuel has to be considered
• Higher methane slip from LPDF engines– Major part is believed to be a consequence of lean
operating conditions
– Fuel quality (methane number) is also essential
• Huge progress in gas technology during the
last 5 years– Methane slip has been reduced for both LBSI and
LPDF engines by around 50%
• Methane slip regulations in the future?
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Summary
• LNG as marine fuel is one of the most promising options («transition fuel» towards full decarbonization)
– Technology is available (only infrastructure is delayed)
– Fullfilling both NOx and sulfur regulations, lower CO2 emissions
– Methane slip is one of the problems to be solved (??? use of HPDF ???)
• Large difference in both NOx and methane slip emissions measured in lab and at sea
– Low loads (below 25%) are especially challanging
– Better control of test conditions in laboratory and possibilities for additional engine tuning
• Overtuning of the engine for lowest NOx results in excessive (and unnecessary) methane slip
– Minimize margins used
• Standard E2 and E3 test cycles is not a perfectsolution for covering all vessel types
– Operational pattern is vital to consider
Image source: www.klawlng.com, LNG vessel bunkering, accessed May 2019
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Thank you for your attention!
Any questions?
Image source: www.toonpool.com
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