Soot-free diesel exhaust gases from generator sets are becoming more and more desirable on superyachts. This rise has not necessarily been driven by regulations, but by owner request. Owners want to avoid particulates on deck, greasy deposits while swimming and the smell of diesel fuel, not the mention the never-ending cleaning of waterlines to remove black tide marks, which damages the paint and reduces the overall lifespan of the coatings.

The need for reduced nitrogen oxide emissions (NOx) in exhaust gases, however, has been driven by Tier III of the IMO NOx regulations, which aims to reduce NOx by approximately 70 per cent compared with the current Tier II standards. The regulations apply in designated Emission Control Areas (ECAs) for yachts above 500gt with keels laid after 1 January, 2016. The coastal waters of North America and the Caribbean, for example, are now ECAs and more ECAs are expected to be established in the near future.

This legislation, in addition to yacht owners’ wishes to protect the environment, has led to the installation of Selective Catalytic Reduction (SCR) systems that reduce the harmful NOx in exhaust gases. These systems use diesel exhaust fluid to react with NOx and convert pollutants into natural elements such as nitrogen, water and minuscule amounts of carbon dioxide.

In addition to other main exhaust players, Xeamos has announced its ability to design and supply such Tier III and Class-approved solutions to reduce soot output and NOx emissions. Its solutions include electrical zero-soot systems, fuel burner zero soot systems, zero NOx systems and dual exhaust after treatment systems for propulsion and generator engines. It also specialises in custom engineered combinations of SCRs, diesel particulate filters (DPFs) and silencers.

Its electrically regenerated zero soot systems are available for diesel engines of 4,4 to 13 litre swept volume. The electrical heater can be applied for both regeneration and load bank functions. An automatic safety bypass valve is provided as a standard feature to ensure maximum availability of the generator in case of unforeseen issues.

The fuel burner regenerated zero soot systems are available for diesel engines of six litre swept volume and above. With these systems, Xeamos guarantees reliable regeneration at any engine load, even with sulphur containing fuels. An optional harbour mode maintains a minimum exhaust gas temperature to ensure optimum hydrocarbon reduction at low generator loads.

The zero NOx system – a Tier III compliant SCR system – is available in both in-line and compact versions to fit into narrow engine rooms. The NOx is reduced by SCR with the addition of a urea injection in the exhaust gases.

Finally, the dual exhaust after treatment system offers combinations of zero soot and zero NOx systems in one reactor/silence unit or as two separate reactor units. The system is equipped with an electrical heater or a fuel burner to regenerate the diesel particle filters.

While the technology is clearly beneficial to the on-board experience, and to the environment, it is important for designers to know how feasible it is to incorporate these additional bits of kit, which take up valuable space in the engine room, on superyachts.

“Due to the flexibility of the different Xeamos products, integration is not that difficult,” reassures Paul Loftus, sales manager at Versilia Supply Services Spain, Xeamos’ Spanish agent. “A custom solution will fit into almost every narrow engine room layout during a refit or new build. Since the new IMO requirement for SCRs, Xeamos engineers can combine solutions to replace existing silencers and achieve the desired result.”

By 2021, all yachts under 500gt but over 24m LOA will be required to meet Tier III regulations as well, so the superyacht industry will not be able to ignore the technology. It is essential that the industry starts paying attention to the solutions available on the market now in order to be prepared for the future.

Images: electrical zero soot system (1) and dual exhaust after treatment system on generator set (2)

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