The systems chosen for these vessels are Wärtsilä Hybrid Scrubbers, which enable the use of either closed or open loop technology to remove SOx from the exhaust. When operating in open loop mode, exhaust gases enter the system and are sprayed with seawater. The sulphur oxides in the exhaust react with the water to form sulphuric acid. Chemicals are not required since the natural alkalinity of seawater neutralizes the acid. When operating in closed loop mode, the natural alkalinity of seawater is boosted by an alkali. The hybrid approach enables operation in closed loop mode when required, for instance whilst in port and during manoeuvring using NaOH as a buffer. When at sea, the switch can be made to open loop using only seawater.
The ‘Balticborg’ and ‘Bothniaborg’ are both powered by Wärtsilä 46 main engines. The vessels have 1A super Ice Class classification and are designed to operate in temperatures of up to minus 25°C. The ability to operate in these extreme conditions was also included in the specifications for the scrubber systems.
Royal Wagenborg operates some 180 vessels, of which 70 are fully owned by the company.