New legislation governing SOx emissions of ships affects ship design and operation. If the vessel operates in areas where SOx emissions are controlled, compliance can be achieved by using low sulphur fuel, or by cleaning exhaust gases using SOx scrubbers, or by a combination of both.
Exhaust gas scrubbers offer shipowners an alternative to switching to more expensive marine gas oil as they prepare to meet tougher IMO regulations on sulphur oxide (SOx) Emissions. The fuel sulphur limit applicable in Emission Control Areas (ECA) will be reduced to 0.1% from January 2015. However, as yet, not everyone is convinced that the technology is all it’s cracked up to be.
Wärtsilä, beside Alfa Laval, is a well-known manufacturer of all kinds of marine related products. The company is aggressively contesting the SOx scrubber market. The company’s system uses fresh water, closed-loop configuration in which sulphur oxides in the exhaust are neutralized with caustic soda. A small amount of scrubbing water is extracted to remove contaminants in a treatment unit, thereby fulfilling the quality and monitoring requirements stipulated by the IMO.
In zero-discharge mode, the clean effluents are led to a holding tank for periodical discharge. Contaminants are always disposed of at reception facilities in port.
A recent contract calls for fresh water scrubbers to treat the exhaust gases of the main and auxiliary engines and oil-fired boilers of six (option two) Great Lakes bulk carriers ordered by Canada’s Algoma Central Corporation. The integrated systems – the first of their type from Wärtsilä – promise wqeight and space savings and are expected to remove more than 97% of Sox emissions.
The possibility to operate in zero-discharge mode will mean that no water is spilled into the lakes; system fresh water can also be tapped from the lakes, reducing or eliminating the need to produce water on board.

Wärtsilä's fresh water scrubber arrangement

Image: courtesy of Wärtsilä