Industry awaits scrubbing solution
Te alternative means of meeting low sulphur emissions limits, gas scrubbing, appears technically feasible. So what is the industry waiting for? Neville Smith reports.
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April 2008 marked a watershed for the makers of shipboard exhaust gas cleaning systems.
But, while the attention was focused on what the adoption of revisions to IMO’s Marpol Annex VI would mean for price and availability of low sulphur and distillate fuel, scrubber-makers were quietly congratulating themselves on a lower-profile victory. With exhaust gas scrubbing given its
own guideline within the revised Annex VI, it became clear that the nascent industry had achieved a degree of respectability. It was, as Wärtsilä’s Torbjörn
Henriksson notes: “a day of remarkable decisions”, which made clear that “the return on investment in scrubbers will be very short”, given the potential economic advantages of burning heavy fuel oil and scrubbing the exhaust gas over using distillate. Krystallon’s Chris Leigh-Jones agrees the adoption of the amendments has proved to be “a tangible spur,” which has prompted increased enquiry.
Today, shipowners might examine
scrubber designs from Wärtsilä, Krystallon, MES, Clean Marine, Ecospec and Aalborg Industries. The first four have working products but all are still testing and fine-tuning to one degree or another. The concept, they say, is proven, but details remain to be resolved. For Wärtsilä, the main focus is on
providing sulphur reduction in sea areas of low alkalinity, using a closed-loop freshwater system with caustic soda as an additive. It claims the system will perform equally well in areas of high alkalinity but the advantage is clear in the low alkaline Baltic Sea region – site of the first IMO emission control area. Drawing on its experience of
land-based sulphur scrubbing, Wärtsilä is conducting tests onboard a tanker and says the resulting system will be available for newbuildings and as a retrofit. It is also developing an integrated
scrubber, using a single unit to clean the exhaust of all main and auxiliary engines including diesel-generators and oil-fired boilers. This has been developed to
satisfy low sulphur limits while sailing and future port regulations, with application targeted for ro-pax ships and tankers with high fuel consumption. Krystallon has the only scrubber
installation working in the cruise sector, onboard Holland America Lines’ Zaandam, sailing in deep-sea Pacific, Alaskan and Hawaiian waters, achieving ‘satisfactory’ SOx removal at less than full capacity. Independent tests run on a two stroke unit at Mitsui Engineering and Shipbuilding’s Tomano works have achieved 96-97% of sulphur dioxide reduction – the same range as Wärtsilä. For Michael Crye of the Cruise Line
Industry Association, scrubbing is “ very much under development and still being proven”. While the results for sulphur reduction are encouraging, he notes concerns over “compatibility with the selective catalytic reduction technology which may be needed to reach NOx reduction goals going forward”. Mr Leigh-Jones says the focus has
shifted from the scrubber itself, and onto achieving wash water cleaner than that demanded by IMO criteria. “Irrespective of what IMO says, you need to achieve what the local ports and harbours say. If you wouldn’t want it in your swimming pool then it can’t go into the harbour.” Krystallon is already “well within”
the IMO wash water criteria on ph, polycyclic aromatic hydrocarbons and turbidity but Mr Leigh-Jones says it needs to do a lot better if it is to have a future-proof technology. Working with cruise destination ports is essential since the US has been among the strongest advocates of the emissions control area concept. The fact that cruiseships spend most of their trading life within 200
The cruise industry awaits the full results of gas scrubber trials onboard the Holland America Line ship Zaandam.
The Naval Architect February 2009 41
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