Rolls-Royce has launched an integrated selective catalytic reduction system for mtu Series 2000 marine engines, completing its exhaust after-treatment offer across its main marine propulsion ranges.
Rolls-Royce is certifying the new system with UK exhaust after-treatment specialist Eminox. It is intended to allow offshore supply vessels, ferries, crew boats, and patrol vessels fitted with Series 2000 engines to operate within maritime areas governed by IMO Tier III nitrogen oxide limits.
The system has a stated design life of up to 16,000 operating hours, depending on vessel load profile, and does not require compressed air for urea dosing. Rolls-Royce has also designed the package for integration across different vessel arrangements, where machinery-space volume, exhaust routing, access, and supporting equipment can determine whether emissions treatment is straightforward or difficult to install.
Selective catalytic reduction introduces an aqueous urea solution into the exhaust stream so that nitrogen oxides can be converted across a catalyst principally into nitrogen and water. Rolls-Royce says the Series 2000 package reduces NOx emissions by 75% compared with IMO Tier II limits.
The regulatory requirement is especially relevant in the North Sea and Baltic Sea emission control areas. Qualifying vessels operating there have to meet substantially tighter Tier III limits, making after-treatment part of the propulsion-system specification rather than an optional environmental accessory.
That distinction becomes more important on working vessels with variable duty cycles. Offshore vessels, ferries, and patrol craft can move repeatedly between low-load operation, manoeuvring, transit, station-keeping, and periods of much higher power demand. Exhaust temperature and gas flow consequently change throughout an operating cycle.
SCR performance has to remain controlled across those conditions. Catalyst temperature must stay within an effective range, dosing has to follow engine operation accurately, and the installation must avoid unacceptable exhaust back pressure. The catalyst, dosing equipment, controls, exhaust routing, and propulsion system therefore have to function as one engineered package.
Rolls-Royce introduced variable-speed Series 2000 generator sets in August, including an SCR option as part of a wider hybrid and electric propulsion offer. The latest announcement provides the dedicated after-treatment specifications that were not central to that earlier generator-set launch.
The absence of a compressed-air requirement is significant in smaller machinery spaces. Removing an auxiliary air supply can eliminate compressors, receivers, pipework, electrical demand, and maintenance points that would otherwise have to be incorporated into the vessel. It also gives ship designers more freedom when the exhaust system has to be packaged around existing machinery.
The 16,000-hour design life provides an additional reference for operators planning maintenance, although actual service depends on load profile. Catalyst condition is also influenced by operating temperature, contamination, engine condition, urea quality, and the number of hours accumulated at different loads.
Access is consequently part of lifecycle cost. A catalyst with a long theoretical life still becomes expensive if modules, sensors, injectors, or pumps cannot be inspected and changed without dismantling surrounding machinery. New-build vessels can allow for that requirement during layout design; retrofits have to work with the space already available.
The new package also illustrates the interaction between fuel efficiency and emissions treatment. Variable-speed and hybrid propulsion can reduce fuel use by operating engines closer to efficient load points or allowing engines to stop when battery power is sufficient, but lower and changing exhaust temperatures can complicate catalytic conversion if the after-treatment system is not calibrated for the complete duty cycle.
Certification with Eminox remains an important step before that integration can be treated as a finished compliance route. Marine emissions performance depends on an approved engine and after-treatment configuration meeting defined test and documentation requirements rather than the performance of individual components considered separately.
For shipyards, a standard Series 2000 package can reduce engineering compared with developing a bespoke SCR installation around each engine. Vessel-specific work will remain around exhaust uptakes, urea storage, structural supports, fire protection, electrical supplies, controls, and maintenance access.
Operators will also need to account for consumables and onboard storage. Urea demand varies with engine load and emissions output, so tank capacity and replenishment intervals have to be matched to voyage length, operating profile, and the practical availability of suitable reagent at the vessel’s ports of call.
Rolls-Royce now has a defined Tier III after-treatment route across Series 2000 as well as its more powerful Series 4000 range. The engineering measure will be how consistently the integrated package combines NOx conversion, engine performance, installation space, and maintenance across the variable operating profiles for which these vessels are built.
