Selective Catalytic Reduction (SCR) systems for marine vessels

SCR technology is a cost efficient proven technology capable of meeting the regulatory requirements set for IMO Tier III for marine diesel engines.

SCR systems and Reagents (Reducing Agents)

SCR Maritime image

SCR technology in marine vessels requires a specific urea solution called AUS40 to function and reduce NOx emissions. AUS40 reagent is a high purity urea solution which meets a technical ISO standard for Urea Solution for Marine SCR applications. NOxCare from Yarwil can supply a quality reagent, produced to Yara’s quality standards, to anywhere in the world via Wilhelmsen’s distribution network.

Read more about the availability of NOxCare Marine’s AUS40 reducing agent.

How does the marine SCR system work with AUS40?

  • the SCR system is installed between the engine and the exhaust outlet
  • AUS40 is injected into the SCR system
  • the exhaust gases pass through the SCR catalyst
  • a chemical conversion takes place between the reagent and the NOx gases
  • the NOx is converted into harmless nitrogen and water and emitted to the atmosphere


Chemical reaction image

NOxCare 40 Marine is sprayed into the exhaust gas upstream the catalyst where it is converted to ammonia. The ammonia mixes with the exhaust gas and reacts with the NOx molecules on the catalyst surface and form harmless nitrogen gas (N2) and water (H2O)

Need a marine SCR system and AUS40 to reduce your NOx emissions?

Through our joint venture Yarwil, we offer our NOxCare Marine brand as a complete NOx control solution specifically to our marine clients. Comprising of both the marine SCR system and the SCR reducing agent (NOxCare 40), we are able to support our customers with helping them to reduce their NOx emissions. NOxCare Marine also offers a portfolio of services to help maintain your marine vessel’s SCR system and ensure optimal operation performance.

Read more on NOxCare 40, our NOx reduction reagent (AUS40) for SCR systems

Contact our NOx control expert today for Marine SCR systems, NOxCare 40 or additional NOx Reduction services.

How Selective Catalytic Reduction (SCR) works in a maritime vessel

NOx is reduced using a catalyst together with NOxCare 40 Marine, a high purity urea water solution

  • Exhaust gas passes through the catalyst where the NOx is converted into harmless nitrogen and water
  • Up to 99% reduction – ie approaching zero emissions of NOx
  • No increase in fuel consumption or CO2 emissions

NOxCare SCR Marine

  • Is installed between the engine and the funnel
  • Varies in size dependent on engine size and NOx reduction requirements
  • Can be tailored to match the layout of most engine rooms and casings
  • To accommodate space restrictions on retrofits existing silencers can be replaced by specially designed units
  • The vessel will require tanks for storage of NOxCare 40 Marine urea solution

NOxCare Marine is the only complete product offer which covers all your NOx reduction requirements worldwide through global availability of NOxCare SCR, NOxCare 40 urea solution and our global network of NOxCare Marine service engineers.

NOxCare Marine:

  • Offers a cost efficient and effective alternative
  • Training ensures optimal operation performance
  • On call experts will keep your system running smoothly
  • The result is lower operational cost

NOx Reduction benefits of the NOxCare SCR system

The Yarwil catalyst is a Full-Cat which is “Homogenous fully extruded”. This means that an active catalyst material is baked into the ceramic structure. The Full Cat is also protected by a specially designed canning solution.


  • Provides resistance against erosion of the active surface
  • Prevents degradation from vibrations and pulsations
  • Ensures a long life span
  • Results in excellent reduction efficiency with any type of fuel
Specially designed injector unit image

The NOxCare SCR system also benefits from a:

  • Pre-canned catalyst material which is easy to handle during installation and exchange
  • Dust blow system which provides efficient cleaning of the catalyst material, ensuring stable back pressure and extending the life time of the system
  • Specially designed injector unit which produces a fine mist of urea droplets with minimal air consumption
  • Bypass which is integrated in the catalyst housing. This reduces the risk of back pressure problems and extends the life time of the catalyst material

Further benefits of reducing NOx emissions using the NOxCare SCR system :

  • A type approved NOx analyser is provided per engine, with continuous monitoring to control the cleaning efficiency of the catalyst and provide data for emission reporting
  • An emission reporting module in accordance with IMO's NOx Technical Code (NTC 2008) can also be supplied
  • The sensor is small, robust and easy replaceable and can be installed directly on the stack together with the analyser, avoiding excessive use of excessive gas piping for sampling
  • Small units save installation space
  • Applicable to all vessel types
  • for both new builds and retrofits
  • Focus on robustness
  • Small control units and NOx analyzers save installation space
  • The user friendly system ensures easy operation and maintenance
  • Service packages tailored according to customer needs
  • To save space the silencer can be integrated as part of the catalyst housing