Full steam ahead

European shipping company DFDS has found an effective tool to meet coming international regulations for exhaust gas emissions at sea. The solution is an Alfa Laval Aalborg scrubber system – PureSOx.

DATE 2023-11-28 AUTHOR David Wiles

The families enjoying the late summer sun on their pleasure craft around the small rocky islands of the Gothenburg archipelago probably did not notice that the funnel on the DFDS ferry steaming past was more than twice as big as that on the other large ships in the harbour. But many would certainly have observed the unusual amount of white smoke billowing from the Ficaria Seaways’ funnel.

“People think it’s pollution,” says Søren Pedersen, Ficaria Seaways’ chief engineer, as he stands on the ship’s deck, looking up at the immense blue-and-white funnel. “They don’t realize that the smoke is steam, and that it means that this vessel actually pollutes much less than most others.” The reason for both the funnel’s size and for the steam coming out of it is an environmental technology that removes virtually all of the sulphur oxide (SOx) and most of the

Alfa Laval’s PureSOX, the exhaust gas scrubber fitted to the Ficaria Seaways, is the largest of its kind in operation on the world’s oceans today. The technology was first developed in a partnership between Alfa Laval and former Aalborg
Industries (later acquired by Alfa Laval) and diesel engine manufacturer MAN. Based on Alfa Laval’s separators and Aalborg’s existing scrubbers used in inert gas systems onboard tanker vessels, the technology was reconfigured to clean diesel exhaust gases and tried out on a 1-MW land-based engine in Denmark. Following successful tests the technology was scaled up and installed on the Ficaria Seaways in 2009. The vessel is propelled by a 21-MW MAN B&W two-stroke main engine that emits 200,000 kilograms of exhaust gas per hour. The fuel burned by the Ficaria Seaways is heavy fuel oil with a sulphur content of 2.2 percent, and the exhaust gas is washed in the scrubber so that the SOX content is brought down to the 0.1 percent level demanded by IMO regulations that come into force in 2015.

Alfa Laval’s PureSOX is a hybrid scrubber, meaning it is a combined seawater/freshwater system. “It can be simply described as a big shower cabinet placed in the funnel of the ship,” explains Olav Knudsen, head of R&D Exhaust Gas Cleaning at Alfa Laval. “Using water, either seawater or fresh water mixed with caustic soda, scrubbers wash the exhaust gas from the main engine of the ship.”

The first stage of the scrubbing process utilizes the heat in an exhaust gas economizer. In stage two, the exhaust gas is cooled by injection of water, and the majority of the soot particles in the exhaust gas are removed. In stage three, the exhaust gas is further cleaned of the remaining sulphur dioxide. To prevent visible condensation and corrosion, the small droplets are then removed from the exhaust gas before being discharged through the funnel of the ship.

“When we are operating in seawater mode, we can clean more than 98 percent of sulphur out of the exhaust gases,” says Knudsen. “When we are operating on fresh water we can clean more than 99 percent, as well as trap up to 80 percent of particulate matter.

“We expect big market demand because it is a very good business case to put a scrubber onboard a vessel, especially after 2015 in emission control areas where there will be a very big price gap between low-sulphur fuel and normal fuel.”

particulate matter – basically soot – from the Ficaria Seaways’ exhaust gases. Fitted with this exhaust gas cleaning system from Alfa Laval, the vessel will be able to continue operating on heavy fuel oil instead of the more expensive low-sulphur fuel in order to meet regulations from the International Maritime Organization that come into force in emission control areas in 2015 and worldwide in 2020.

“I think it’s a very good idea,” says Pedersen when asked for his opinion of the scrubber. “With this system we can carry on running with high-sulphur fuel oil. If we don’t have a system like this, then we have to start using low-sulphur fuel In 2015, and that will be very expensive. There is money to be saved here. They are talking about low-sulphur oil being up to twice as expensive as high-sulphur oil, so this system could pay for itself in a few years.” Alfa Laval’s PureSOx was installed on the Ficaria Seaways while she lay in dry dock in 2009. The system is 10 metres high – hence the need for the vessel’s funnel to be more than twice the size of that on its sister ship. The scrubber is basically a giant shower where the rising exhaust gases are sprayed with water – hence the steam coming from the funnel.

Within 12 nautical miles of shore the system is in freshwater mode, which means it is a closed system where the water used for cleaning the gas is circulated. When in freshwater mode, an Alfa Laval high-speed separator is used to clean the water. “Otherwise we would have to change water every eight or nine hours,” says Pedersen. “We don’t have enough fresh water onboard to change it so often.” The residue cleaned out of the water is collected for safe disposal

Once outside territorial waters, it is an open system where seawater is pumped onboard and used to clean the exhaust gases, before being released overboard. Seawater already has a high sulphate content, and experts say that even if all the sulphate from all the world’s oil reserves were put into the sea, it would be hard to measure the change to sulphate levels.

The shipping industry faces a number of challenges to meet new and pending environmental legislation, but tackling sulphur oxide emissions will be the most testing, says Gert Jakobsen, vice president DFDS Group Communications. “The new regulation forcing us to go down to 0.1 percent sulphur in the bunker oil is our biggest challenge,” he says. “In the regulation there is a paragraph that states that you have to go down to 0.1 percent sulphur or find equivalent methods. New technologies will be a very important part of the solution, and this scrubber will definitely be the most important one. We certainly wouldn’t be able to install it on all our ships by 2015, and not all ships can be fitted with one. But it will be a very good tool to solve part of the problem. We are very grateful that the scrubber has proven its efficiency in operation.”

Jakobsen says the solution has exceeded expectations. “It has had a very good effect not only on sulphur but also on particulate matter.”

But why did DFDS invest in such a solution a full six years before the SOx regulations come into effect? Jakobsen says it was partly to assess the options so that it could prepare for 2015, but also as part of the company’s wide-ranging efforts to reduce its environmental impact. Like many other shipowners and operators, DFDS welcomes moves to improve the environmental performance of the shipping sector. The company has set itself the target of reducing its CO2 emissions by 10 percent over five years and has invested in new efficient propellers and a planning system to select the most energy-efficient route for its vessels in an effort to reach that target.

But the company also believes the regulations are being brought in too swiftly. “In general we support the efforts to reduce the impact of our industry on the environment,” says Jakobsen. “But we believe the sulphur regulation comes too early and too fiercely. It could lead to more traffic being forced from the sea and onto the roads on routes that are parallel to shipping routes. We believe that will have the wrong environmental effect.” Looking out over the idyllic scene of the archipelago dotted with white sails, chief engineer Pedersen says it feels good to know that his ship is a trailblazer for a new technology that has proved to significantly reduce harmful SOx emissions and particulate matter. “We have to do something about these emissions into the air,” he says. “It is absolutely necessary. In general the legislation is a good thing, although in this case they go too far, too fast. But we have to do something, and legislation and technology are effective ways to do it, if they are done right.”