Wärtsilä Diesel Engines Mated with Scrubbers for New Lakers

By George Backwell at February 07, 2012 09:45
Filed Under: General

St. Lawrence  –  Great Lakes Seaway shipping line Algoma Central Marine is spending $300 million on new ships, including six that will be 45% more fuel efficient per cargo tonne/kilometre than existing vessels. These ‘Equinox-class’ lakers  provide Wärtsilä with a $12 million ground-breaking order for complete propulsion packages that come with fully integrated fresh water scrubber systems.  The lakers to be delivered by China’s Nantong Mingde Heavy Industrial Stock Company shipyard over the next couple of years are designed to lift 30,000 dwt of bulk cargo, wheat and ore, for carriage through the seaway to the American heartland in ‘Lakers’ hallmark slim 225 m long hulls.

Algoma Equinox-class Laker: Image credit – Algoma Central Corporation

Replacement of the St Lawrence Seaway Fleets

The big three fleet operators, Algoma Central, Canada Steamship Lines and Fednav, all with relatively elderly ships, have been spurred to invest in new building, aware of the huge positive impact of the waterway on the North American economy  (maintained in 2010 despite economic downturn) and more significantly by the Canadian Government’s decision to abolish the 25% duty on foreign ship construction. The new ships on order by the various operators are all  IMO Tier ll compliant, while Algoma looking further ahead chose to go for the Wärtsilä scrubber integrated installation option which saves space, weight, and time on a retrofit.

Wärtsilä RT-flex50 Engine with Integrated Scrubber

Exhaust gas scrubbing is a cost effective alternative to making a switch to more expensive low sulphur content MDO fuels in order to reduce SOx emissions. Wärtsilä says its water scrubber has a SOx removal efficiency exceeding 97%, making it possible to operate ships with 3.5% sulphur content fuel yet still comply with a 0.1% sulphur fuel limit. These economic benefits to shipowners can be substantial; in SOx Emission Control Areas (SECA) the cost savings will increase with time as the price of of low sulphur content fuel rises to an expected peak in 2015 when the sulphur limit in fuel is decreased to 0.1%.  How does the system work?

Briefly, exhaust gas from the uptakes passes through the closed loop, seawater cooled, fresh water/caustic soda mix scrubber unit spray, and a bleed-off from the loop is fed off to the water treatment plant. Clean effluents can be safely discharged overboard or held in a holding tank, while noxious waste (including particulate matter extracted) is piped from the water treatment plant to a sludge tank for periodic discharge to a special shore facility.

All propulsion system components for the Algoma Equinox-class lakers are to be supplied by Wärtsilä. The main engine is a slow-speed 5-cylinder RT-flex50 version D, rated 8725 kW at 124 rpm. A controllable pitch propellor will give a service speed of 12 kts and tunnel thrusters type CT200 are to be provided for added manoeuvrability. Three heavy oil-burning Auxpac 6-cylinder generating sets from the same manufacturer will supply electrical needs.

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