Device for isolating vessel containing liquefied natural gas comprises layers of sealing membrane and insulation kept in inert atmosphere comprising mostly argon

摘要

An external shell (4) carries mechanical loads applied by two layers of porous isolation (5, 6), separated by a gas-tight secondary membrane (3) and supporting a gas-tight primary membrane (2) in direct contact with the cargo (1). A circuit with valves (14-17), a compressor (8), filters (9-11) and a reservoir (13) keeps the isolation space in an inert atmosphere containing mostly argon. Preferred Device: The inert gas is mostly argon and some percent nitrogen and is stored in liquid form at low pressure in the reservoir using cold vapors form the LNG cargo passing through the circuit (7), to ensure that at least part of the cooling energy required for the liquefaction and maintenance of cold lasts for the storage period. Separating the inert gas from one of its contaminants is carried out in an adsorption filter, which may operate at a cryogenic temperature cooled at least in part by cold vapors from the LNG passing through the circuit (7). The filtration systems are regenerated using nitrogen. Alternatively, the inert gas is separated from its contaminants using distillation, using cold vapors from the LNG passing through the circuit to ensure at least partial liquefaction of the mixture. The storage reservoir for the inert gas is placed inside the vessel containing the LNG. The inert gas in the reservoir, once cooled and liquefied, is re-injected under pressure via the circuit (18) and expanded directly into the isolation spaces through valves (16, 17)