The NO
x
emissions limits in the IMO standards are expressed as dependent on engine speed. These are
shown in figure 1.1 on next page.
Figure 13.1
IMO NO
x
emission limits
IMO Tier 1 NO
x
emission standard
The IMO Tier 1 NOx emission standard applies to ship built from year 2000 until end 2010.
The IMO Tier 1 NO
x
limit is defined as follows:
= 45 x rpm
-0.2
when 130 < rpm < 2000
NO
x
[g/kWh]
The NO
x
level is a weigthed awerage of NO
x
emissions at different loads, in accordance with the applicable
test cycle for the specific engine operating profile.
IMO Tier 2 NO
x
emission standard (new ships 2011)
The IMO Tier 2 NO
x
emission standard entered into force in 1.1.2011 and applies globally for new marine
diesel engines > 130 kW installed in ships which keel laying date is 1.1.2011 or later.
The IMO Tier 2 NO
x
limit is defined as follows:
= 44 x rpm
-0.23
when 130 < rpm < 2000
NO
x
[g/kWh]
The NO
x
level is a weighted average of NO
x
emissions at different loads, and the test cycle is based on the
engine operating profile according to ISO 8178 test cycles. IMO Tier 2 NO
x
emission levels corresponds
to about 20% reduction from the IMO Tier 1 NOx emission standard. This reduction is reached with engine
optimization.
IMO Tier 3 NO
x
emission standard (new ships 2016, in designated areas)
The IMO Tier 3 NO
x
emission standard will enter into force from 1 January 2016. The IMO Tier 3 NOx
standard applies only for new marine diesel engines > 130 kW installed in ships which keel laying date is
1.1.2016 or later when operating inside designated emission control areas (ECA).
The IMO Tier 3 NO
x
limit is defined as follows:
= 9 x rpm
-0.2
when 130 < rpm < 2000
NO
x
[g/kWh]
112
Product Guide Wärtsilä 34DF - 3/2012
Product Guide
13. Exhaust Emissions
