Reliquefaction Technology for LNG Carrier

Abstract

Unlike all cargo ships, liquefied natural gas (LNG) carriers have continued to use steam turbine propulsion plant despite more efficient diesel engine being available. This is because the gas that naturally evaporates from the cargo (called boil-off) is used as fuel for the steam turbines, and until recently there was no other use for it. The ability to reliquefy the gas given off by the cargo now makes it possible to increase the amount of LNG delivered to the discharge port, which is more profitable than using it as ship' s bunker.
Reliquefying LNG and returning it to the cargo tanks means that gas never enter the engine room, adding to the general safety margin. Total separation between cargo and engine room means that the propulsion system and type of fuel used can be chosen freely.