MAN solution proves its worth

27 May 2014
MAN's ERG solutions features Alfa Laval's PureNOx system

MAN's ERG solutions features Alfa Laval's PureNOx system

MAN Diesel and Turbo’s Exhaust Gas Recirculation (EGR) solution, being developed with support from Alfa Laval, is proving successful onboard two AP Moller-Maersk vessels.

EGR, which involves the recirculation of exhaust gas, is one of two technologies being developed to meet Tier III NOx limits without resorting to LNG. Unlike Selective Catalytic Reduction (SCR), 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.

“AN EGR system is compact, because nearly everything – including the water cleaning – is integrated into the engine itself. Likewise, EGR is fully automated and has no filling elements to clean or replace, so it requires very little from the crew,” Kristina Effler, business manager, water treatment exhaust gas emissions at Alfa Laval.

The solution is currently installed onboard Alexander Maersk, a 1,092 teu vessel with a MAN B&W 7S50MC engine, which was retrofitted with an EGR prototype in 2010. Since installation, the vessel has spent more than 2,200 hours operating at 50% NOx reduction over today’s basis emission level.

As a result, the EGR has also been installed on the 4,500 teu Maersk Cardiff, making its engine fully compliant with Tier III and also well past the 1,000-hour operating mark.

“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,” Ms Effler explained.  

The company says while SCR entails a slightly lower investment, the amount of consumables and maintenance puts its operating costs at 7-10% of the fuel costs, yet EGR, with no catalyst to maintain and the ability to operate in fuel-optimised Tier II mode, has an operating costs of 4-6% of the fuel costs in Tier III mode.

An integral part of the solution is Alfa Laval’s PureNOx water treatment system. “It [PureNOx] safeguards efficiency, reduces maintenance and prolongs the service life of engine components by protecting them against corrosion. In addition, PureNOx enabled the discharge of excess water in accordance with IMO criteria,” added Ms Effler.

As the Alexander Maersk and Maersk Cardiff continue to sail, additional PureNOx systems 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 for Mitsui Engineering and Shipbuilding.

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