After-treatment NOx socks off emissions
Engine manufacturers have put a great deal of thought and money into reducing emissions in recent years. As regulations, particularly in the US and Europe, are becoming more stringent, the engineers have responded by tuning the engine design with everything from electronic injectors to redesigned combustion chambers.
Since further mandated reductions in emissions are anticipated, some operators are not waiting for the regulations to tighten but are going to the next level with the aid of independent suppliers.
One such vessel benefitting from this approach is the inland waterways cargo ship the MV Anda. Visscher Scheepsreparatie BV completed the 135m hull and a pair of Cummins QSK38-M engines supplied by De Groot Scheepstechniek BV provide main propulsion, producing a continuous duty rating of 895kW (1,200hp) at 1,800rpm.
The engines employ a modular common rail fuel system to provide constant high injection pressure regardless of engine speed or load conditions. In addition to reduced noise and vibration, idle stability and improved low end torque, this feature contributes to the engine meeting EU Stage IIIA, IMO and U.S. EPA Tier 2 requirements for reduced emissions.
The owner, J Verdonk, and the builders of the MV Anda have taken the emission reduction a step further by adding an after treatment system to the engine exhaust. Two sets of the multi-component after treatment system, one on each engine, were supplied and installed by Emitech BV.
Each system consists of a NOx Selective Catalytic Reduction Catalyst (SCR), a NOx control unit, ureum tank, two pieces of urea doseur, a NOx sensor and a NOx buster Bluejet G2 control. Each engine exhaust was also fitted with a DPF Diesel Particulate Filter with a burner and control unit.
In January 2010 tests were carried out to measure the emissions of the two engines with the after-treatment relative to earlier emissions without it. The results were spectacular. In tests carried out by TNO Industrie en Techniek under the protocols of ISO 8178, the after-treatment system showed that on both engines the NOx emissions are reduced on the weighted test points by almost 90% (port engine 87% and starboard engine 88%). This brings the NOx emissions on both engines to well below the norm of 2 g/kWh for new ships. These numbers result in the MV Anda being named the ‘cleanest vessel in the Netherlands’ and perhaps all of Europe.
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