Wärtsilä has commercialised and improved reliquefaction technology since it was originally patented by Kværner and licensed by Hamworthy in the late 1990s.
Our boil-off gas (BOG) reliquefaction plants have been installed on numerous vessels, including the entire Q-Flex fleet of 216.000 m3 LNG carriers. The 31 Wärtsilä LNG BOG reliquefaction plants delivered to the Q-Flex fleet are installed on ships driven by slow speed diesel propulsion engines. We have also delivered the same type of systems to a number of LNG carriers with dual-fuel diesel electric (DFDE) propulsion.
Wärtsilä has a number of new contracts where our reliquefaction systems are combined with different propulsion systems. This means that we are supplying complete and integrated systems that include BOG reliquefaction and fuel gas supply systems as compressor solutions, and LNG pump solutions required for feeding engines with low and/or high pressure gas.
The installation of a BOG reliquefaction system on dual-fuel LNG carriers, allows ship operators the added flexibility to switch between fuels so as to take advantage of price differentials between LNG and heavy fuel oil. State-of-the-art propulsion systems are efficient and not all the boil-off gas can be utilized in the engine. Furthermore, slow speed sailing and ship holding operations often result in an excess of boil-off gas. Instead of burning this gas in a gas combustion unit, it can be reliquefied and returned to the cargo tanks.
The liquefaction of BOG on LNG carriers results in increased cargo deliveries and allows owners and operators to choose the optimal propulsion system and operating profile. The advantages are extremely attractive; a flexible fuel system, optimized operating costs, and increased delivered cargo capacity.