In a significant step, the Augsburg branch of PrimeServ, MAN Diesel’s after-sales group, has successfully retrofitted an SCR (Selective Catalytic Reduction) system aboard a Norwegian tanker.

This represents the first time that MAN Diesel PrimeServ alone has project-managed, sold and put such a system into commission on a marine, medium-speed engine. The project also marks an important step into the exhaust-gas after-treatment market as well as this particular retrofit segment.

Norwegian legislation
Governmental authorities, especially in Scandinavian countries, provide incentives to marine operators that implement emission-reduction technologies. One example of this is the Norwegian NOx fund that subsidises investment in NOx-reduction measures on vessels sailing in Norwegian waters.

Knutsen OAS Shipping, Norway approached MAN Diesel PrimeServ, Augsburg in the spring of 2009 to provide a technical solution for the reduction of NOx emissions aboard its product tanker, M/V “Liv Knutsen”. Negotiations concluded with Knutsen awarding MAN Diesel the contract for the supply and commissioning of an SCR catalyst to operate downstream of the MAN 6L48/60B main engine.

The project was managed by PrimeServ Augsburg’s Upgrade and Retrofit team in close cooperation with Knutsen and the shipyard where work was carried out.

SCR system main-components
An SCR system’s main components comprise a reactor containing ceramic catalyst elements, a urea system that covers storage, supply, dosing and injection, as well as a control system. Depending on the fuel’s sulphur content, the exhaust-gas temperature in the catalyst must be controlled. The temperature must remain above a critical temperature to prevent the formation of ammonia sulphate and resultant clogging of the catalyst surface.

In the case of the Liv Knutsen, MAN Diesel used its extensive know-how to implement an exhaust-gas temperature control using a charge-air blow-off flap. The operation map of the control system reflects the exhaust-gas temperature and sulphur content of the fuel currently in use. In this way, optimal SCR operation was achieved at all engine loads.

The NOx reduction process
NOx emissions can be reduced to nitrogen (N2) and water (H2O) in a dedicated, ceramic catalyst by adding ammonia (NH3) to exhaust gas. However, as ammonia is a hazardous substance, an aqueous urea solution (CO(NH2)2) is normally used that breaks down to NH3 and CO2 when introduced to the hot exhaust-gas before reaching the catalyst.

The future
Thomas Traupe, Head of Upgrade and Retrofit at MAN Diesel PrimeServ, Augsburg says: “The installation of the SCR system concluded successfully to the customer’s full satisfaction. With this project, PrimeServ Augsburg is reaping the rewards of its strategy of intensively promoting and anticipating environmental issues. Our Upgrade and Retrofit team is dedicated to upgrade issues and we are looking forward to fulfilling all upgrade expectations in 2010 and beyond.”

MAN Diesel’s Marine Medium Speed business unit in Augsburg also offers a full product line of SCR systems for all engine types in its sales program.

Source: MAN Diesel

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