New two-stroke SCR from MAN Diesel & Turbo

Malcolm Latarche
Malcolm Latarche

27 April 2017


A two-stroke version of an established four-stroke high-pressure compact SCR has been demonstrated at a joint event in Japan held by MAN diesel and Turbo and Mitsui Engineering & Shipbuilding. The MAN SCR-HP is available for two-stroke engines of all bore sizes and reduces – through internal catalytic reaction – NOx exhaust emissions to IMO Tier III limits. With specially developed honeycombs and honeycomb materials, as well as an integrated mixing unit, the overall size of the reactor has been drastically reduced compared to typical market designs and its medium-speed counterpart. MAN Diesel & Turbo expects to deliver the first system from the beginning of 2018. Bjarne Foldager, Vice President MAN Diesel & Turbo and Head of Sales & Promotion Two-Stroke Business, said: “The development of our new SCR offers additional choices to shipowners who can now choose from all NOx reduction technologies and select the optimal solution for their MAN Diesel & Turbo two-stroke engines. The reactor design has been driven by the desire to reduce the SCR system’s overall size, while still maintaining the effectivity of a much larger design. Reaching this target was only possible by focussing on key cornerstones of the design – the honeycombs as well as the reactor concept. The system comes in six frame sizes, covering engines up to 25 MW with one reactor for the entire exhaust stream. Larger engines will require two reactors, which can be arranged in a multi-setup similar to turbochargers. The SCR-HP system consists of the reactor – including mixing unit, urea injection lance, honeycombs and soot blowers – along with a module-based supply system, as well as the reactor’s control unit that communicates with the engine-control system. It is available for Scheme A and Scheme B classification approval. Scheme A approval includes a certification of the complete system on the engine test bed, SCR and original piping. Approval via Scheme B reduces complexity for all involved parties. The engine is tested in IMO Tier II mode on a test bed. MAN Diesel & Turbo then models the SCR system and calculates the Tier III mode. On the parent engine, this mode is certified on board during engine commissioning. This Scheme B approval is confirmed by several classification societies and reduces the test demands required of the engine licensee. The process is well established in MAN’s medium-speed sector, and over 100 systems are already in the order book awaiting Scheme B certification.