A new scrubber technology that does not use water to remove sulphur from exhaust gases has been installed without drydocking on La Méridionale ro-pax ferry Piana.
The 42,180-GT ferry, which sails between Marseille and Bastia on the island of Corsica, had one of two exhaust channels fitted with a dry scrubber system from supplier Andritz in April 2019. By eliminating water, the system reduces power consumption (by water pumps, for example) while avoiding regulatory uncertainty concerning wash water discharge.
The exhaust ducts on the Piana are routed through two casings in its starboard and port funnels. In the first installation phase, three scrubber chambers were connected to the starboard side funnel ducts, which handle part of the exhaust from the vessel’s seven Wärtsilä engines, with a total power output of 42.18 MW.
Andritz sales manager for southern Europe, Marco Dierico, explained that Piana was a good candidate for the first dry installation because its two side funnels meant that the retrofit could be performed with no loss of cargo space and no impact on the ship’s appearance from the side. The fixed sailing route will allow the companies to optimise the supply chain for the reagent, sodium bicarbonate. Truck loading is easier for ferries than for most other vessels and big ferries also offer greater stability, which can be a concern when installing heavy scrubber technologies on a higher deck of the ship.
The installation was completed in less than two weeks without drydocking, and the ship’s acceptance and performance tests will take place over June and July this year. Mr Dierico said that class approval had been smooth as there was no need for additional water outlets or sea chests, no wastewater discharge and no need for water monitoring.
The Andritz SeaSOx dry scrubber doses sodium bicarbonate powder to the exhaust gases and feeds them through bag filters enclosed in chambers that can be assembled in modular arrangements. Each chamber can handle exhaust equivalent to the emissions from a 5-MW four-stroke engine. Exhaust from multiple engines can be processed through one filter.
The technology also removes all other gaseous acid components and reduces fine particle emissions (to below PM1). Andritz plans to verify the efficiency of emission reductions through an independent third party.
The residues produced contain sodium sulphate, a non-hazardous substance which can be safely stored in silos on board. Residues will be discharged on land for disposal or recycling. An on-board recycling process by Solvay (which handles logistics chemical supply and residue disposal) will reduce waste by more than 90%.