Ocean Freight Carriers Seek Best Emission Reduction Technologies as Container Line Tests EGR System

WORLDWIDE – The recent 66th session of the International Maritime Organization’s Marine Environment Protection Committee (MEPC) at IMO Headquarters in London did more than decide changes to be made to the Polar Code as reported here previously. In a decision affecting ocean freight operators the MEPC adopted amendments to the MARPOL Convention to set a date for the implementation of ‘Tier III’ standards within emission control areas (ECAs) and to make the IMO Member State Audit Scheme mandatory. Now news reaches us of technology undergoing tests by Maersk Line, the world’s largest container shipping group to achieve such levels whilst still using ‘regular’ fuel oil.

Tier III air pollution regulations require the reduction of NOx emissions by 80% from existing Tier I limits during operation in ECAs such as North American coastal waters and the US Caribbean Sea and will apply to marine diesel engines of over 130 kW output power and installed from 1 January 2016 onwards (except for the engines of certain recreational vessels). Whilst many see the widespread installation of Liquefied Natural Gas (LNG) powered units as a cure all, for many the development costs and other factors may make the technology impractical.

A solution to the problem of reducing noxious emissions is currently being tested aboard the two A.P. Moller-Maersk vessels the Alexander Maersk and the Maersk Cardiff and involves the use of Exhaust Gas Recirculation (EGR) technology developed by MAN Diesel & Turbo with the support of the Marine Division at Alfa Laval. EGR, which involves the recirculation of exhaust gas, is one of two technologies being developed to meet Tier III NOx limits without resorting to liquefied natural gas. Unlike Selective Catalytic Reduction (SCR), which is an after-treatment technology that removes NOx with the help of a catalyst, EGR is integrated into the engine and prevents the formation of NOx during combustion.

The 1,092 TEU Alexander Maersk, whose MAN B&W 7S50MC engine was retrofitted with an EGR prototype in 2010, has spent more than 2200 hours operating at 50% NOx reduction over today’s basis emission level. Lessons learned in this installation have gone into the 4,500 TEU newbuild Maersk Cardiff, whose EGR-equipped engine is fully compliant with Tier III and is now also well past the 1000-hour operating mark. These seagoing installations, which involve water cleaning with Alfa Laval’s PureNOx, also show how fuel can be saved in Tier II operation.

The ability to save fuel in addition to complying with Tier III NOx limits likely to be of great interest to ship operators as they plan for 2016. A fuel-optimised Tier II operating mode, which facilitates an approximate 4 g/kWh reduction in fuel consumption at partial load, was introduced by MAN Diesel & Turbo with the two-stroke MAN B&W 6S80ME-C9 engine in 2012.1 This is the engine now installed aboard the Maersk Cardiff, where it is operated entirely by the crew and has logged nearly 350 hours in this mode.

The test for vessel operators will be to comply with the new raft of regulation while minimising the cost, those who fail to do so will, out of necessity, have to pass extra costs onto customers. Although utilisation of an SCR system will involve lower investment costs (€30 – 100 per kW of installed power as against €40 – 60 for EGR) MAN argues the amount of consumables and maintenance puts its operating costs at 7-10% of the fuel costs. EGR on the other hand, with no catalyst to maintain and the ability to operate in fuel-optimised Tier II mode, has an operating cost of just 4-6% of the fuel costs in Tier III mode.

The engine builders also argue that, with the variable engine loads demanded of an ocean vessel, the critical minimum exhaust gas temperature for urea injection, as well as a maximum temperature beyond which the system becomes inefficient at reducing NOx, make an SCR system unreliable, whereas they say EGR, by contrast, is effective instantly and requires no warming up of the exhaust gas. Nor is it sensitive to engine load fluctuations. Chief Engineer Larsen of the Alexander Maersk confirms MAN’s boasts, saying:

“There has been no effect whatsoever when changing engine load. The EGR system has run without any problem and the emission reduction performance has not been affected.”

What EGR does depend on is the effective cleaning of the wash water in the wet scrubber, which operates in a closed loop. Since marine engines employ a variety of fuels, various combustion products with qualities harmful to the engine are formed. These products are effectively removed by Alfa Laval’s PureNOx, a complete water treatment system based on high-speed centrifugal separation. Using centrifugal separation to clean the wash water ensures the highest possible efficiency and stability whilst taking up little space and costing comparatively little. Alfa Laval’s Kristina Effler, Business Manager, Water Treatment Exhaust Gas Emissions spoke of the outfitting of the Maersk ships and the results of the trials, saying:

“Alfa Laval is proud to be part of these pioneering EGR installations, where our PureNOx has the vital role of cleaning the wash water in the wet scrubber. No other vessel has EGR installed and operating reliably at Tier III. Moreover, it has been possible to demonstrate substantial fuel savings at Tier II. EGR is the only NOx abatement technology that offers fuel savings in addition to Tier III compliance. As such, it is the only technology that will offset the initial investment over time [and] the savings are more than theoretical, because they can be seen first-hand aboard the Maersk Cardiff.

“An EGR system is compact, because nearly everything, including the water cleaning, is integrated into the engine itself. Compare this to an SCR system, where significant engine room space is needed for the reactor and other components. Likewise, EGR is fully automated and has no filling elements to clean or replace, so it requires very little from the crew.

“PureNOx keeps soot and other compounds from the exhaust gas from accumulating in the scrubber, it safeguards efficiency, reduces maintenance and prolongs the service life of engine components by protecting them against corrosion. In addition, PureNOx enables the discharge of excess water in accordance with IMO criteria, it’s difficult for other technologies to compete in efficiency at such a low operating cost, Alfa Laval has developed a separator that is tailor-made for cleaning scrubber wash water, which is a tricky and difficult task – especially for anyone lacking our core separation expertise.

Between these two vessels PureNOx has shown its capabilities in nearly 3,500 hours of successful EGR operation [and] we are actively pursuing new possibilities, such as the potential of combining the EGR water cleaning system with that of a wet SOx scrubber. What we’ve seen aboard the Alexander Maersk and Maersk Cardiff is exciting, and we on the PureNOx team expect further exciting developments as 2016 approaches.”

This last comment refers to the additional PureNOx systems which have been delivered to Chevron Corporation for EGR on two lighter newbuilds powered by MAN B&W 6G70ME-C9.2 engines. A further delivery has also been scheduled to Mitsui Engineering & Shipbuilding.

Photo: MAN revealing the World’s First Tier-III-Compliant, Two-Stroke Engine.