Exhaust aftertreatment systems prepare the marine industry for tougher emission standards

Many diesel-powered boats in the North Sea and the Baltic Sea will be subject to new Tier III NOx regulations
From 2021 onward, the Tier III NOx regulations will apply to all vessels with diesel engines with more than 130 kW power that operate on or enter the North Sea and the Baltic Sea. This vast maritime region is a NOx Emission Control Area (NECA). Similar NECAs already exist in the US Caribbean and along most of North America’s mainland coastline.

Any vessel with this diesel engine type that operates on or passes through these areas must comply with the new Tier III NOx regulations. This puts new demands on boat engines and emissions control, both for big and small vessels; not least in terms of efficacy, cost-efficiency and practical design.

Repowering a passenger ferry with a new engine and exhaust aftertreatment system
There are already plenty of passenger ferries, shuttle ferries, charter boats, and other marine vessels equipped with Volvo Penta’s exhaust aftertreatment system (EATS). One of them is M/S Monsun, a midsize passenger ferry operating in the Stockholm archipelago, east of the Swedish capital.

M/S Monsun is operated by the local shipping company Krokholmens sjötrafik AB. She is the first ferry of her kind in the Stockholm archipelago with a Volvo Penta D13 MH 500 engine, complete with an exhaust aftertreatment system. The system’s significant emission reduction was an essential aspect during procurement, with the new engine running in accordance with the new NOx regulations. “The new engine has also lowered our fuel consumption, and reduced the noise levels for our passengers”, says Gustav Eriksson, captain of M/S Monsun.

After the engine was successfully installed in early 2020, M/S Monsun once again started welcoming new passengers in April.

A compact exhaust aftertreatment system design makes for an easy, quick and cost-efficient installation
Lack of engine room space can be a challenge when installing a new engine and exhaust aftertreatment system, especially on a smaller vessel. As such, the physical design should ideally be rather compact. Keeping things simple has many benefits; an abundance of components and connections makes the whole construction more exposed to mounting, installation and maintenance problems. Even more importantly, a quick and easy installation will require less time and thus reduce one’s installation costs.

M/S Monsun’s new exhaust aftertreatment system is a good example of this, according to Sigge Björkskog at Rindövarvet, the shipyard in Stockholm that made the engine installation. “Installing Volvo Penta’s EATS was smooth and simple. It’s a very compact unit, which results in a quicker installation for us, and lower labor costs for the customer. We placed the SCR unit in the engine room, and connected it to the exhaust pipe in the funnel. We were able to keep the existing engine muffler, which together with the SCR unit reduces the noise levels significantly.”

Efficient selective catalytic reduction units for the marine industry
Exhaust aftertreatment systems use a selective catalytic reduction (SCR) unit to reduce NOx emissions. An aqueous urea solution (AUS, also known as DEF – diesel exhaust fluid), is injected into the exhaust air stream containing NOx, where it evaporates into ammonia (NH3) due to a physical reaction triggered by the energy contained in hot exhaust gas. Once the exhaust gas and ammonia mixture comes into contact with the SCR catalyst surface, a reduction reaction occurs, breaking down the NOx (NO and NO₂) and NH3 into nitrogen gas (N₂) and water vapor (H₂O).

At Volvo Penta, we have used our experience of on-road SCR units to make SCR units for the marine industry. By focusing on fuel efficiency and convenient design, we ascertain that our exhaust aftertreatment systems reduce weight and save space. This is significant, as these systems generally tend to be large and heavy. As outlined above, this can be especially problematic in a cramped engine room; one that should also fit a urea tank and other components.

Additional advantages of our exhaust aftertreatment system

• It is a “plug and play” system.
  The exhaust aftertreatment system is easy to install and use, as it is fully integrated with the Volvo Penta engine.
• No engine muffler necessary.
  The selective catalytic reduction unit reduces noise significantly, and also acts as a spark arrester.
• The system can run temporarily without urea/DEF.
  Most competing systems cannot, thus requiring an exhaust bypass valve along with a catalytic converter and a system muffler.

You can read more about our work with Stage V and emission technology on the Volvo Penta website.