Scrubbing up well

by | 23rd August 2019 | News

Home News Scrubbing up well

The Naval Architect: September 2019Scrubbing up

With mere months left before the introduction of IMO’s sulphur cap, refit yards are tackling a burgeoning number of scrubber installations. Meanwhile, many shipowners are left with little alternative but to wait and hope that their low-sulphur contingencies don’t come unstuck. Perhaps unsurprisingly, some scrubber manufacturers believe their optimism is misguided.


“There are 35-40,000 ships [suitable for scrubber installation] where the owners haven’t made their decision,” says Ken McClelland, technical director of Pacific Green Technologies (PGT), noting that the biggest surge of orders took place in the fall of 2018, when the more entrepreneurial shipowners took action.


“Every indication is there’s going to be a real spread of fuels in 2020. A scrubber is capital outlay but – depending on the size of ship and type of scrubber – you can pay that back in 9-14 months. The other scenario is that every time you bunker you pay higher priced fuel,” he adds.


Whether that’s how the post-2020 bunkers market eventually plays out is a matter for debate. However, as Devon Smith, Pacific Green Marine’s business development support manager, notes: “Scrubber-equipped vessels are currently attracting the premium charter rates and that’s expected to continue. If you have a vessel that’s scrubbed and one that’s unscrubbed, the scrubbed vessel’s going to command a bigger dollar figure per day.”


PGT’s marine scrubber business is currently almost entirely retrofit orders, but it’s expecting a shift towards newbuilding orders as the market progresses post-2020. The Vancouver-headquartered company, which also builds land-based scrubbers, has enjoyed significant growth since 2017, when it signed a joint venture agreement with equipment manufacturer Power China.


McClelland says: “Power China is one of the biggest engineering, procurement and construction companies in China. Its engineering resources and knowledge of the Chinese market has allowed us to expand our whole scope and support it with experienced engineers. Being state-owned, it has a bit of a family relationship with other state-owned companies, so it’s been very positive for us in terms of getting space in shipyards to do retrofits.”


Patented system
PGT’s marine scrubber, Envi-Marine, is based around a patented interface between the polluted combustion stream and the reagent solution that predominantly uses the natural alkalinity of seawater to remove the contaminants. “One of the major differences is that this is high, positive contact, not random. Our Turbohead process puts the flue gas into a very turbulent froth area, and because there are two heads it essentially takes out virtually all the sulphur,” says McClelland.


The process doesn’t use any media, meaning that less water needs to be run through the system, which creates back pressure. “It tends to make the scrubbers physically larger, or you have to reduce the media down to the point where operation is close to the threshold. So we operate only with our patented heads and get scrubbing results that are well within the 0.1% [as required in Emission Control Areas], while for the 0.5% [the 2020 global sulphur limit] we will tune the operating program to bring the reaction up and reduce the amount of energy.”


Every PGT scrubber installation is a bespoke job, beginning with a thorough analysis of the ship’s engines, volumes of gas that will need to be scrubbed and collaborating with the owner to develop a solution. Unlike some manufacturers, the tanks are rectangular, which usually makes it easier to fit them within confined spaces and allows for a more flexible footprint.


“We can put the scrubbers in two locations, either directly behind the funnel – which works well on tankers and bulk carriers where there is a winch deck directly after the funnel – or on the side of the ship, about three decks up,” explains McClelland. “If the funnel is laid out with either boilers or auxiliary engines across the aft of the funnel it’s a lot of work to get the largest duct through them. It’s sometimes easier if it’s right at the front of the funnel to go left and right to a side-mounted scrubber.”


PGT offers its system as either a simple, open loop model or as a hybrid system. Surprisingly perhaps, given the recent concerns regarding bans on scrubber washwater discharge, open loop models remain the overwhelming preference of their customers.


But Smith says they offer a third option: open hybrid ready. “It’s open loop but the engineering is done for the hybrid system. PGT’s official policy is to recommend open hybrid ready, in case environmental regulations change. It also gives some flexibility if the vessel is taken under a charterer who wants a hybrid or closed system.”

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