For low-speed engines, our engineers have developed a system known as exhaust gas recirculation (EGR) that can reduce nitric oxide emissions in ships by up to 80 per cent. In 2010, a prototype is set to demonstrate its practical suitability on a ship owned by the major Danish shipping company A. P. Møller-Mærsk. Following successful testing in Copenhagen, our engineers have high expectations of this maiden voyage. EGR is currently also undergoing pilot testing for medium-speed engines.

By recirculating exhaust gas into the charge air, the oxygen content in the cylinder is reduced and the specific heat capacity increased. Both cause lower combustion temperatures and therefore fewer NOx emissions. The sulphur content of heavy fuel oil, however, can lead to soiling and the corrosion of components.
 
Our specialists are solving this problem with an exhaust gas scrubber, the first stage of the complex recirculation system. It cleans the exhaust gas to remove sulphur and particles. The unit is linked to a water purification plant, which neutralises the resulting sulphuric acid with caustic soda and collects the solid residues in tanks, so that they can be disposed of on land. After the scrubber follows a cooler, which reduces the exhaust gas temperature to no more than 100 degrees Celsius.

A “drip catcher” in the next stage removes the final traces of humidity from the exhaust gas. A fan then increases the pressure of the recirculated exhaust gas by 0.4 - 0.7 bar, before the gas is returned to the charge air. The exhaust gas recirculation function can be switched on or off depending on where the ship is being used and the environmental regulations that are applicable. Our engineers have designed the system in a way that it can be operated easily by on-board crews. In the event of a fault, it automatically takes itself out of service.