The EU is in concerned about the level of NOx emissions in key parts of Europe, and remains concerned that even if NOx Tier III requirements are being implemented in the Baltic and North Sea in 2021, these will be too slow to take effect, as they only apply to new builds. There is a change of implementation of local or regional regulations for NOx emissions on top of existing Marpol requirements.
Selective Catalytic Reduction is a simple, low-cost means of converting nitrous oxides in the exhaust with the help of a catalyst into diatomic nitrogen and water. Utilisation of marine SCR technology allows for achieving the IMO Tier III emissions limits.
Marine SCR Systems typically use a urea solution of 40%, and can remove up to 99% of NOx emissions. SCR technology and infrastructure is well developed and has been employed for many years in a range of applications, including the reduction of NOx from power plants and generators.
SCR technology is the industry standard for removing NOx emissions from diesel truck engines and has been used in marine applications for around 30 years.
Small quantities of urea solution are injected into the exhaust upstream of the catalytic converter. The hot exhaust vaporises the urea solution into ammonia and carbon dioxide. The ammonia mixing in the catalytic converter converts the N0x into harmless nitrogen and water.