IMO Tier III and 0.1% SOx are not far away

30 Nov 2011
One way of meeting the Tier III limits is the installation of exhaust gas after-treatment – this scrubber system, developed by Ecospec and endorsed by Wärtsilä, is said to effectively reduce NOx and CO2 as well as SOx emissions

One way of meeting the Tier III limits is the installation of exhaust gas after-treatment – this scrubber system, developed by Ecospec and endorsed by Wärtsilä, is said to effectively reduce NOx and CO2 as well as SOx emissions

IMO Tier III regulations on nitrogen oxides are the next challenge for engine manufacturers, writes Henrik Segercrantz, summarising the current situation with forthcoming exhaust emission limits.

These regulations require considerable further reductions of the permissible NOx emissions. The first step, Tier II, is already in force, as from 2011. Tier III will become applicable for ships with keel laying after January 1st 2016, but only inside the specifically designated ECAs (emission control areas, i.e. North American coasts, the North Sea and the Baltic Sea areas), whereas, outside of these ECAs, the Tier II regulation continue to apply. An order boom is expected before this date.

Tier III poses significant challenges to engine developers, who will need to cut NOx to between 3.4g/kWh and 2.0g/kWh. The engines have to be optimised for both requirements, and engine manufacturers need to provide technologies that allow switching between Tier II and Tier III operating modes with the engines in operation. Moreover, the Tier III requirements are not limited to compliance with respect to the cycle-weighted NOx emissions, but also include an additional ‘not-to-exceed’ clause stipulating that the NOx values at the individual points of the test cycle must not be more than 50% higher than the weighted average.

Engine manufacturers have looked at addressing Tier III by applying exhaust gas re-circulation and SCR (selective catalytic reactor), with the help of other engine technologies, such as two-stage turbocharging for medium speed engines. A third main solution actively proposed by the engine manufacturers is to consider LNG as fuel, providing a NOx reduction of some 85%.

In the US, for EPA Tier 2 and 3 for US flagged ships with Category 3 engines, exceeding 30litres/cyl displacement, the limits on NOx and fuel sulphur content including implementation dates are consistent with those adopted by IMO. The coastal areas of USA and Canada have been designated as an ECA. This means that NOx limits similar to IMO Tier II (2012) and Tier III (2016) and a fuel sulphur limit of 1,000ppm will be introduced (2015). A flue gas desulphurisation scrubber is an alternative to low sulphur fuel. In addition to the IMO requirements EPA is introducing the following amendments: limits on hydrocarbon, HC (2g/kWh) and carbon monoxide, CO (5g/kWh), particulate matter (PM) measurement is required at certification (no limit, but reporting to EPA is required) and testing of every new Tier 2 and Tier 3 engine for NOx during the vessel's sea trial is required.

Gas engines are treated in the same way as liquid fuel engines, just with the gas as test fuel. A separate EPA certificate is required as the EIAPP certificate is not sufficient for the EPA (Environmental Protection Agency). Gas turbines are included in the regulations. In addition there are separate EPA regulations for Category 1 and 2 engines, below 30 litre/cyl. Further EPA Tier 3 restrictions, on NOx plus total HC and PM, are to enter into force in 2013 or 2014 depending on engine power, and EPA Tier 4 between 2014 and 2017 (the information on EPA has been interpreted from material kindly provided by Wärtsilä).

Concurrently with the tightening NOx emission limitations, the sulphur oxide SOx and PM emissions are being further cut, with extremely tight levels to be introduced in the designated ECAs, and with an introduction of a global 0.5% limit to be decided on based on the outcome of a review to be completed by 2018. The review is to assess the availability on the market of marine fuel oil, which fulfils the set SOx requirement without engine modifications. The supply, demand, and development trends will lay a base for this review. Based on the outcome, the global limit of 0.5% will be implemented either in 2020 or 2025. The current global sulphur cap outside ECA areas is still 4.5%, to be reduced to 3.5% from 1 January 2012.

From 1 July 2010 in the European ECAs (and in the North American ECA which willapply from 1 August 2012) SOx emissions were cut to 1% and are to be limited to the extremely low value of 0.1% in these ECAs on 1 January 2015, although voices are raised, particularly in the Baltic area, to postpone this, so the continuing availability of lower sulphur fuel can be assured. In California, within 24 naut miles from the coast, this limit is to apply from year 2012. On 15 July 2011, IMO officially designated waters around Puerto Rico and the US Virgin Islands as an area in which stringent international emission standards will apply to ships. For this area, the effective date of the first-phase fuel sulphur standard (1%) is 2014, and the second phase begins in 2015 (0.1%). Stringent NOx engine standards begin in 2016.

As an alternative to switching to cleaner distillate marine fuels, shipowners have the alternative to install an exhaust gas cleaner, or scrubber, allowing heavy fuel oil to be used as fuel. Ships in European Union ports have had to run their engines on 0.1% sulphur fuels since year 2010.

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