MARCH 10, 2015 — Three 55 m trawlers ordered by Iceland's HB Grandi will be fitted with MAN Diesel & Turbo's SCR (Selective Catalytic Reduction) system.
Designed by Nautic ehf and being built in Turkey by Celiktrans Shipbuilding Co. Ltd. (see earlier story), each vessel will be powered by an MAN six-cylinder L27/38 engine, accompanied by a four-bladed, 3.8-m, ducted MAN Alpha VBS 860 propeller.
HB Grandi says the SCR system will enable the trawlers' IMO Tier II-compliant engines to meet strict IMO Tier III NOx emission requirements.
Vilhjalmur Vilhjalmsson, CEO of HB Grandi said: "When we decided to renew our fresh-fish fleet, we immediately focused on the task of curtailing the ships' power requirements, both in terms of the propulsion plant as well as electricity production, so as to make the exhaust gas as clean as possible."
Mr. Vilhjalmsson said that HB Grandi pursues a green company profile and that its focus on clean and responsible fishing ultimately led to MAN technology being chosen for the trawlers
In addition to the cleaner exhaust gases and NOx reduction that the MAN package offers, a further advantage of choosing MAN was the relatively straightforward integration of engine, propeller, propulsion controls and SCR system that equipment from the same manufacturer entails.
MAN Diesel & Turbo says that special attention was given to selecting the optimal position for the SCR system aboard the trawler. This challenge was met and solved in great part through good cooperation with Icelandic specialist designer and ship consultant Nautic at an early stage of the project.
Propulsion package characteristics
The new HB Grandi wetfish trawlers benefit from several features to optimize operation. These include employing a floating-frequency concept that increases their flexibility and economical part-load pattern with an up to 17% lower engine/propeller speed and a commensurately lower fuel consumption.
MAN Diesel & Turbo's new, advanced Alphatronic 3000 generation propulsion-control system will be installed aboard the trawlers with features that include tailored "dual-propeller load curves: for optimizing towing/trawling and free-sailing conditions.
Selective Catalytic Reduction
MAN Diesel & Turbo says that SCR is the most tested and approved system for achieving NOx reduction rates up of to 90%. SCR involves the injection of ammonia or urea, into the diesel engine's exhaust stream. The urea decomposes into ammonia and carbon dioxide, with the ammonia subsequently reacting with NOx and oxygen in the presence of a catalyst, transforming into the ecologically-benign constituents of water and nitrogen.
To optimize the SCR process at part load, the engine is specified with a turbocharger bypass as part of the exhaust gas temperature system that ensures sufficiently high temperatures.MAN Diesel & Turbo's SCR system is available in fourteen different sizes to fully cover its entire portfolio of medium-speed engines and has been devised as a modular kit of components for reasons of simplicity and to minimise costs.
A special feature of the system is its communication with the engine control system that optimizes the temperature for the SCR system at individual load-points. A further special feature is its continuous NOx-emission control that saves urea and avoids ammonia slip.
MAN Diesel & Turbo also offers customised SCR systems on demand.
The main components of the MAN Diesel & Turbo SCR system are:
- an SCR reactor
- catalyst elements
- a soot-blowing system
- a dosing unit
- a mixing device
- a urea-injection lance
- a control unit
- a compressed-air reservoir module