This month, Wärtsilä’s NOx Reducer has been selected as Fathom CTech’s Tech Of The Month.
The Wärtsilä NOx Reducer (NOR) is an emission after-treatment system developed for nitrogen oxides (NOx) emission reduction requirements and is based on Selective Catalytic Reduction (SCR) technology.
By means of catalyst elements and a reducing agent, NOR can reduce the level of NOx emissions by approximately 80-90%, using either a 40% or 32.5% aqueous urea solution. Ammonia slip is kept below 10 ppm for optimum performance, while energy and power consumption is low, requiring approximately 1kW per NOR unit and consuming approximately 15 litres/MWh, at full engine load.
One NOR reactor is installed per engine and exhaust gas pipe. The standard reactor is designed in a flexible way for the initial loading of two or three catalyst layers depending on the ship structure. It can be installed either vertically or horizontally on-board the ship. Different customer-specific solutions are possible, such as integrating the SCR reactor with a silencer, a combined SCR and compact silencer system, a heater for outside installation in cold climate, and an additional oxidation catalyst for CO removal. In addition, NOR is compatible with other exhaust gas treatment units, such as sulphur oxides (SOx) scrubber systems and no bypass is required (unless required by class society) as the NOR can be run dry.
NOR’s innovative nature also means that the urea injection used to reduce NOx during combustion can be started and stopped based on the Global Positioning System (GPS) signal from the ship system, which identifies when the ship is operating inside the NOx Emission Control Area (ECA).
NOR is applicable to all ship types and four-stroke diesel engines, operating on marine gas oil (MGO), marine diesel oil (MDO) and heavy fuel oil (HFO) as both a retrofit option and to a newbuild. The system should be operated between 300-450°C for best performance and lowest ammonia slip.
Various sizes of NOR are available for maximum flexibility. Ranging between 3.2 x 2.1 x 2.0m for a 5MW engine and 4.1 x 3.9 x 3.7m for a 20MW engine, NOR is able to fit many different ship space requirements.
Furthermore, the system can be optimised for Norwegian NOx Fund operation or other NOx emission limits, while Wärtsilä provides pre-certified engine and SCR packages to optimise customer costs.
