Marine diesel engines, prime movers for almost all merchant ships, may either burn more expensive, cleaner fuels to comply with increasingly severe exhaust gas emission controls, or else continue to burn cheaper fuels and rely on a scrubber unit to clean up exhaust gas emissions; broadly that is the choice for shipowners and operators. With that choice in mind an ingenious compact scrubber from Green Tech Marine is worth a mention.
The GTM R15 scrubber has recently been installed for pilot evaluation tests in Royal Caribbean International’s cruise ship Liberty of the Seas; cleverly retrofitted while the ship was in continuous service. Unusually, the compact design of the scrubber demanded no extra space to be taken up as the unit replaced the ship’s exhaust silencer.
Scrubber Placement: Image courtesy of Green Tech Marine
Green Tech Marine, with facilities in Sweden and Norway, claim that beyond the efficient removal of SOx and other particles, their scrubber, which requires virtually no external chemicals, offers a number of advantages over others because of its minimal footprint, low weight and energy efficiency.
Prior to its installation this scrubber was subjected to almost a year’s experimental testing ashore, and now, after a four-month installation period, successful results have come from the Liberty of the Seas pilot study. The system (often referred to as a ‘hybrid’) used seawater in full-scale operation with the ship’s engine running from 2 to 12.4 MW in both open loop and closed loop modes of operation .
Liberty of the Seas: Photo credit Wiki CCL Roger Wollstadt
The scrubber unit of course consumes energy itself, an amount defined as the percentage of the main engine power that it takes up. Green Tech say that the technology they use results in an energy consumption of less than 1.5%, which was calculated during land-based testing.
The GTM R15 scrubber comes with a smart control system (it has a touchscreen user interface) which constantly monitors intake water, exhaust gas discharge and overboard wash-water discharge with regard to SOx, NOx, CO2, pH, PAH and turbidity.
Coincidentally, Lloyds Register has just published an excellent freely available .PDF guide – ‘Understanding Exhaust Gas Treatment Systems’ – to give ship owners and operators an overview of the related technology and emerging environmental regulations in order to make sound business decissions.