Tier 3 compliant two-stroke engine unveiled

24 Mar 2011
The first Tier-III-compliant, two-stroke engine – an MAN B&W 6S46MC-C8 type – pictured at Hitachi’s Ariake works.

The first Tier-III-compliant, two-stroke engine – an MAN B&W 6S46MC-C8 type – pictured at Hitachi’s Ariake works.

MAN Diesel & Turbo has reported that a 6S46MC-C8 engine with integrated SCR has been successfully tested in Japan to the forthcoming IMO Tier 3 emission standards.

The engine, rated at nearly 7,000kW, was built in autumn 2010 by licensee Hitachi Zosen Corporation at its Ariake works in southern Japan. The engine will be fitted to a general cargo carrier, to be built at the Nakai shipyard and scheduled for delivery during 2011. The ship was ordered by Japanese customer, BOT Lease, and will be operated by Nissho Shipping Company.

The engine was first started in January 2011, when a MAN team commissioned the control system and optimised the integration of the selective catalytic reduction (SCR) system to remove NOx from the exhaust gas.

The SCR system is designed for:

  • more than 80% NOx reduction based on the load cycle;
  • more than 70% NOx reduction on each load point in the load cycle;
  • easy switching between on/off modes for optimal emission performance on high seas and coastal waters.

Following subsequent tests MAN Diesel & Turbo was able to confirm that the engine meets the emission requirements stipulated by the IMO Tier 3 legislation, due to come into force in 2016.

MAN says that both SCR and exhaust gas recirculation (EGR) techniques can enable large diesel engines to meet Tier 3. For this application, the company opted for the high pressure, urea-based SCR configuration.

To achieve the desired, higher exhaust-gas temperature and to remove the maximum NOx removal, MAN says that the SCR system has been placed before the turbocharger. The correct exhaust gas temperature is ensured through various patented engine control system technologies.

Søren Jensen – vice president research & development, marine low-speed MAN Diesel & Turbo – said: “We haven’t just provided an engine and added an SCR system to it. On the contrary, we have delivered a bespoke system. As engine designer, builder and catalyst designer, MAN Diesel & Turbo and Hitachi Zosen comprise a group of specialists that have delivered an optimised propulsion/emissions package of engine, engine-control system and SCR system.”

Jensen concluded: “In the future, MAN Diesel & Turbo wants not only to develop engines but also to design engines with complete, emission-reduction systems. To that end, we envisage collaborating with many other partners in times to come in the same successful fashion as we have seen in Japan.”

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