lengths, sized to engine output. An SCR twin- catalyst system is used for higher-powered engines, each catalyst aligned with a cylinder bank and matched to the engine power output. In most applications the SCR system replaces the silencer within an equivalent envelope and provides similar sound suppression. DEF, a product certified by the American
Petroleum Institute, consists of an aqueous solution of 32.5 per cent high purity urea and 67.5 per cent deionised water, and requires no special handling. Cummins Filtration supplies Air Shield DEF to the group’s on-highway distribution network for trucks powered by EPA 2010-compliant engines. Cummins and other DEF suppliers will offer a service for off- highway engine users when required for Tier 4 Final introduction. Valuable experience gained by Cummins in
extreme duty applications such as large mining excavators and frac rigs will benefit Tier 4 Final QSK engines with SCR systems. Before
pursuing SCR after-treatment
solutions, Cummins evaluated alternative Tier 4 Final emission reduction technologies such as exhaust gas recirculation and variable valve actuation. Both these approaches, however, were considered less effective for large high- horsepower engine platforms as they require major re-engineering of the base engine, generate additional heat rejection for the cooling system to manage, and compromise serviceability. The group’s own SCR after-treatment system offered a simpler and more robust solution in achieving NOx emissions reduction. No extra service requirements are imposed by the QSK Tier 4 Final engine compared with Tier 2 engines; and minimal external changes mean
that ease of servicing remains the same. All the key enabling Tier 4 Final technologies are designed, manufactured and integrated as a single system by Cummins. Over 350,000 SCR systems have been produced by Cummins Emission Solutions, one of the world’s largest suppliers of exhaust after-treatment solutions. Since validating emissions performance Cummins has focused on integration and field
test optimisation with equipment
manufacturers. Production of the first Cummins Tier 4 Final QSK engines with integrated SCR exhaust treatment will start in 2014, ahead of the effective date (1 January 2015) for engines rated above 560kW.
Full production of all current QSK and
K-series high-horsepower engines will be maintained for worldwide applications imposing less stringent emissions levels than Tier 4 Final.
SCR system guidelines from ClassNK
New guidelines from ClassNK for selective catalytic reduction (SCR) and reduction agent supply systems address IMO’s Marpol Annex VI NOx emission regulations. SCR is expected to be widely applied in meeting the 80 per cent cuts in NOx emissions from engines from 2016, and the Japanese classification society’s guidelines were developed to support shipbuilders and operators in implementing SCR installations. “We conducted a study of all relevant equipment, including reductant agent tank arrangements and piping specifications of SCR systems in order to determine which measures are necessary for their safe operation,” says Yukihito Fujinami, general manager, Class NK’s machinery rules development department. Standard design specifications based on
the IBC Code, IGC Code and Rules for Cargo Refrigerating Installations are summarised; and guidance provided on the specific requirements for systems using reduction agents that call for safe storage specifications, such as urea and ammonia. • ClassNK has awarded its first Statement of Fact for IMO Tier III NOx reductions to a marine diesel engine incorporating an SCR system. The document, issued last November,
SCR chamber
4NO+4NH3+O2 4N2+6H2O 6NO2+8NH3 7N2+12H2O
T/C control unit engine Basic SCR and reduction agent supply system
verified the emission measurement results for a main engine equipped with a pre-turbocharger SCR system developed by Hitachi Zosen. The six-cylinder Hitachi-MAN B&W S46-
EEDI explained by ABS
Newbuildings will have to meet mandatory energy efficiency design index (EEDI) baseline values from as
early as 1 January 2013,
advises ABS vice president and chief engineer Kirsi Tikka.
“The EEDI is a design target, a technical measure currently applicable to seven
www.mpropulsion.com
ship types, which is to improve the energy efficiency of new ships. The aim is to encourage innovation and technical development,” she explains. “It is a baseline or benchmark, the index providing a measurable method for propulsion that is intended to express carbon dioxide emissions in relation to the ship’s
work capacity, such as tonne-miles.” The new regulation, which will be included as Chapter 4 in Marpol Annex VI, mandates that all new ships of 400gt and above be certified with an International Energy Efficiency Certificate. The certificate attests that an attained EEDI does not exceed ›››
Marine Propulsion I February/March 2012 I 97
C7 low speed engine is now powering the 37,800 dwt general cargo ship Santa Vista which entered service with Nissho Shipping from the Naikai Zosen yard at end-October.
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