Wärtsilä NOx Reducer (NOR)

The Wärtsilä NOx Reducer (NOR) is an emission after-treatment system based on the Selective Catalytic Reduction (SCR) technology for Nitrogen Oxide (NOx) reduction.

The NOR is optimized and validated for Wärtsilä medium speed engines in terms of reliability, flexibility, size and easy installation and maintenance onboard. It is available for both newbuild and retrofits and is compatible for operation on both distillate and heavy fuel oils. Furthermore, with the Wärtsilä NOx Reducer, the overall performance of the engine and exhaust gas cleaning system is optimized in  terms of emissions reduction, noise abatement and engine efficiency.  Wärtsilä provides IMO and EPA Tier III EIAPP certificates for a complete package of engine and SCR.

The Wärtsilä NOx Reducer

-          ensures you can operate with different fuels, globally

-          reduces emission based operation fees


    The NOR is compatible with the entire portfolio of Wärtsilä 4-stroke engines. The technology has been developed and tested with Wärtsilä engines to ensure safe and flexible operation, and features an integrated communication system.  The product also works very well in combination with the Wärtsilä compact silencer and any of Wärtsilä’s scrubbing systems. Together, this forms a complete package comprising efficient energy production, silencing, and a full emissions reduction system. In addition to marine newbuild installations, the Wärtsilä NOx Reducer is used for retrofit installations and land based power plant applications.
    Tier III NOx standards
    The IMO’s Tier III regulations typically require SCR systems to be used with diesel operated engines. A marine diesel engine installed on a ship constructed on or after 1 January 2016, and operating in the North American ECA and the United States Caribbean Sea ECA, must comply with the Tier III NOx standards. Also starting from 1 January 2021 countries bordering Baltic Sea, North Sea and English Channel will form a NOx Emission Control Area. Earlier these countries have formed a SOx ECA since 2015. You can read more about the IMO rules at  www.imo.org.
    Local regulations
    There are other strong drivers for compliance, such as the US EPA rules for diesel boats and ships (https://www3.epa.gov/otaq/marine.htm), the Norwegian NOx tax, several inland waterway rules, and local discounts in port and fairway fees.
    Technical diagram

    The main component of the NOR installation is the Reactor with a soot blowing unit and the catalyst elements, which are validated with Wärtsilä engines and with different fuel oil qualities.  Other modular essential parts of the NOR system are Power Distribution Unit, Urea pump unit, Urea dosing unit, which controls the SCR functionality and Urea Mixing and injection unit.

    NOR layout

    Product hologram

    Selective Catalytic Reduction, or SCR, is one of the few technologies capable of reducing Nitrogen Oxides down to the levels required by today’s most stringent regulations, and since year 1990 Wärtsilä has delivered hundreds of SCR systems. The Wärtsilä NOx Reducer (NOR) has been developed to enable vessels to comply with the IMO’s Tier III emission levels, while still maintaining a compact design optimised for marine applications. It is also available for land based installations and other NOx levels.


    • Arctia Offshore
      The turnkey project involved the fitting of combined Wärtsilä NOx Reducer (NOR) and Oxidation Catalysts (OXI) to the MSV Fennica and MSV Nordica.

      Arctia Offshore

    • Gitte Henning S349
      The propulsion equipment package include a Wärtsilä 9L32 main engine with new design, gear, controllable pitch propeller (CPP), HR Nozzle, Wärtsilä 8L26 auxiliary engine, as well as related equipment – including NOx reducers for both engines.

      Gitte Henning S349

     Related products

    Catalyst Team

    Jussi Uusipaavalniemi

    Jussi Uusipaavalniemi
    General Manager, Sales

    Jussi-Petteri Soikkeli
    Jussi Koljonen

    Jussi Koljonen
    Sales Manager

    © 2022 Wärtsilä