国际海事组织：氮氧排放标准TierII IMO:Nitrogen oxide emission norms

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.