Cruise ship tests exhaust scrubbing to meet new standards

As marine operators consider installing exhaust gas scrubbers to meet clean-air regulations, one pilot project is already up and running.

Holland America’s cruise ship Zaandam began testing an exhaust gas cleaning system in 2010. The Hamworthy Krystallon scrubber uses seawater to cleanse sulfur compounds out of engine exhaust aboard the 781-foot vessel.

Zaandam sails from California to Mexico, Hawaii and Alaska. The cruise line is preparing for the day when emission control zones will limit the allowable levels of pollutants.

Sigurd Jenssen, Hamworthy Krystallon’s managing director, said Zaandam’s scrubber stack removes 98 percent of the sulfur.

“The Zaandam (project) is to prove the scalability of the design and to provide operational data in a variety of operating conditions,� Jenssen said. “The Zaandam sees everything from brackish waters on the Canadian coast down to Mexico where you have a much higher temperature and higher salinity in the seawater.�

At least seven large ships worldwide are testing exhaust gas cleaning systems. So-called “open� systems use seawater to separate SOx out and wash the pollutants into the ocean, while “dry� systems employ granules of hydrated lime to absorb sulfur dioxide and soot. “Closed-loop� systems use fresh water and caustic soda to neutralize acids.

Beginning in 2015, ships sailing through International Maritime Organization (IMO)-designated emission control areas must emit no more than 0.1 percent sulfur content in exhaust.

Donald Gregory, director of the Exhaust Gas Cleaning Systems Association, said ship operators need to begin shopping for solutions now.

By 2020, a global limit of 0.5 percent sulfur content is scheduled to be enforced everywhere.

Supplies of low-sulfur fuel could be limited when the 2015 rules cause demand to spike, said David St. Amand, president of Navigistics Consulting, a Boxborough, Mass.-based firm which provides analysis on ship pollution and fuel usage. An exhaust gas cleaning system would allow a ship to avoid buying the more expensive fuel.

“If you’re not running a scrubber, you’re almost definitely going to have to switch to distillates, and there’s a real premium for that,� St. Amand said. “It’s not clear that there’s enough refining capacity to make enough distillate to run the marine fleet.�

Low-sulfur fuel currently costs about $50 per ton more than legacy fuels, but Gregory said that differential could soar to $500. He said exhaust gas cleaning systems cost $1 million to $4 million per ship.

“After that cost, you will reap the benefits of being able to use flexible fuels,� Gregory said. “So it’s worth it to sort of get off your hands and begin talking to the industry.�

Engineering challenges still need to be solved, including the large size of the stack and how to dispose of the scrubbed matter safely. Wärtsilä Corp. sought to avoid washing pollutants out with seawater.

“We prefer to use a closed system that uses fresh water,â€� said John Hatley, vice president at Wärtsilä North America Inc. “The residuals are stored aboard in a slops tank, and then they are disposed of ashore.â€�

Michael Pilson, professor of oceanography at the University of Rhode Island, said washing scrubbed compounds into the sea is relatively safe.

“The amounts involved are such that it is reasonable to neglect the effect on the ocean, which has a considerable buffering capacity, and has a lot of sulfate in it anyway,� Pilson said.

On top of the disposal issues, IMO restrictions on nitrogen compounds come into force in 2016. Exhaust scrubbers will need to be compatible with the selective catalytic reducers in Tier 4 engines.

“So there’s a whole bunch of Catch-22s going on,� St. Amand said. “And is this setting up another stream for ‘magic pipes’?�

By Professional Mariner Staff