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NOx Emission
Standards
NOx emission
limits are set for diesel engines depending on the engine maximum
operating speed (n, rpm), as shown in Table 1 and presented
graphically in Figure 1. Tier I and Tier II limits are global,
while the Tier III standards apply only in NOx Emission Control
Areas.
Table 1. MARPOL
Annex VI NOx Emission Limits Tier Date NOx Limit,
g/kWh
n < 130 130 ≤ n
< 2000 n ≥ 2000
Tier I 2000 17.0
45 · n-0.2 9.8
Tier II 2011 14.4
44 · n-0.23 7.7
Tier III 2016† 3.4
9 · n-0.2 1.96
† In NOx Emission
Control Areas (Tier II standards apply outside
ECAs).
Figure 1. MARPOL
Annex VI NOx Emission Limits
Tier II standards
are expected to be met by combustion process optimization. The
parameters examined by engine manufacturers include fuel injection
timing, pressure, and rate (rate shaping), fuel nozzle flow area,
exhaust valve timing, and cylinder compression volume.
Tier III standards
are expected to require dedicated NOx emission control technologies
such as various forms of water induction into the combustion
process (with fuel, scavenging air, or in-cylinder), exhaust gas
recirculation, or selective catalytic reduction.
Pre-2000 Engines.
Under the 2008 Annex VI amendments, Tier I standards become
applicable to existing engines installed on ships built between 1st
January 1990 to 31st December 1999, with a displacement ≥ 90 liters
per cylinder and rated output ≥ 5000 kW, subject to availability of
approved engine upgrade kit.
Testing. Engine
emissions are tested on various ISO 8178 cycles (E2, E3 cycles for
various types of propulsion engines, D2 for constant speed
auxiliary engines, C1 for variable speed and load auxiliary
engines).
Addition of
not-to-exceed (NTE) testing requirements to the Tier III standards
is being debated. NTE limits with a multiplier of 1.5 would be
applicable to NOx emissions at any individual load point in the
E2/E3 cycle.
Engines are tested
using distillate diesel fuels, even though residual fuels are
usually used in real life operation.
Further technical
details pertaining to NOx emissions, such as emission control
methods, are included in the mandatory “NOx Technical Code”, which
has been adopted under the cover of “Resolution 2”.
Sulfur Content of
Fuel
Annex VI
regulations include caps on sulfur content of fuel oil as a measure
to control SOx emissions and, indirectly, PM emissions (there are
no explicit PM emission limits). Special fuel quality provisions
exist for SOx Emission Control Areas (SOx ECA or SECA). The sulfur
limits and implementation dates are listed in Table 2 and
illustrated in Figure 2.
Table 2. MARPOL
Annex VI Fuel Sulfur Limits Date Sulfur Limit in Fuel (%
m/m)
SOx ECA
Global
2000 1.5%
4.5%
2010.07
1.0%
2012
3.5%
2015
0.1%
2020a
0.5%
a - alternative
date is 2025, to be decided by a review in
2018
Figure 2. MARPOL
Annex VI Fuel Sulfur Limits
Heavy fuel oil
(HFO) is allowed provided it meets the applicable sulfur limit
(i.e., there is no mandate to use distillate fuels).
Alternative
measures are also allowed (in the SOx ECAs and globally) to reduce
sulfur emissions, such as through the use of scrubbers. For
example, in lieu of using the 1.5% S fuel in SOx ECAs, ships can
fit an exhaust gas cleaning system or use any other technological
method to limit SOx emissions to ≤ 6 g/kWh (as SO2).
国际防止船舶污染公约附件。IMO Tier II 在2011.1.1或之后建造的船舶安装的发动机的氮氧化物排放限值将根据速度关联函数，比原来的IMO Tier I的水平减少大约20％。IMO Tier III是2016.1.1，限值比IMO Tier I减少80％。
IMO agrees to retain
NOx emissions effective date of January 1, 2016
London
(Platts)--4Apr2014/618 pm EDT/2218 GMT
The International
Maritime Organization's Marine Environment Protection Committee
agreed to retain the existing effective date of January 1, 2016,
for Tier III Nitrogen Oxide emission standards, according to the
draft report for MEPC's 66th session, which ended Friday.
MEPC held its 66th session this week to review NOx emissions within
Emission Control Areas and review the timing of sulfur emissions
outside ECAs.
In the previous session, MEPC agreed in principle to postpone the
international NOx emissions limits from 2016 to 2021.
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