Lng transport vessel and method for storing and managing excess boil off gas thereon

Abstract

A liquefied natural gas (LNG) transport vessel for transporting liquefied natural gas (LNG) is disclosed which is capable of storing excess boil off gas BOG until needed for combustion in one or more combustion apparatus on the vessel. A method for managing the delivery of the BOG to the combustion apparatus is also described. The LNG vessel includes at least one insulated LNG storage tank which stores LNG. A first stage LNG receiver receives and stores BOG from the at least one LNG storage tank. A second stage or high pressure BOG storage tank receives compressed BOG from the receiver and stores the BOG as needed for combustion by one or more combustion apparatus of the vessel. A pressure regulator allows BOG gas to be delivered to the combustion apparatus if there is sufficient pressure in the high pressure storage tank to passively deliver the BOG at a predetermined delivery pressure. If the pressure in the high pressure BOG storage tank is insufficient to passively delivery the BOG to combustion apparatus, then a combustion apparatus compressor may be used to actively increase the pressure in BOG such that the BOG is delivered at the necessary delivery pressure. If there is still insufficient BOG in the high pressure BOG storage tank, then it may be necessary to supply supplemental auxiliary fuel to meet the needs of the combustion apparatus.