An LNG terminal has multiple functions: reception of the LNG tankers, unloading of the LNG (liquefied natural gas) cargos, tanking, regasification, metering, odorization. End goal: the supplying of the transmission system with natural gas on behalf of its customers.
An LNG terminal carries out four main functions:
Reception and unloading of the ships
On arrival at the terminal, the LNG tanker is moored at the unloading dock. Articulated pipes (“arms”) are connected to the tanker’s isothermal tanks and unload the ship of its cargo. The LNG then goes through pipes designed to withstand very low temperatures (- 160°C), which transport it to the tanks.
Tanking of the LNG
The LNG is then stored in cryogenic tanks (designed for very low temperatures) that are able to withstand a temperature of -160°C in order to keep it in a liquid state. The outer shell of the tanks is made of reinforced prestressed concrete (as is the case at Fos-Cavaou) or of steel. Their insulation makes it possible to limit boil-off. The low-volume boil-off that nevertheless occurs (low heat leak into the equipment) is collected by compressors and reincorporated into the LNG.
The capacity of the tanks was sized to ensure the continuity of supply of the transmission system between two deliveries of liquefied natural gas.
The liquefied natural gas is removed from the tank, pressurized (between 70 and 100 bars), then regasified using heat exchangers that use sea water to reheat the gas.
Emission into the transmission system
Having returned to a gaseous state, the gas undergoes different types of processing (metering, analysis, odorization) before being injected into the natural gas transmission system.
In the case of Fos-Cavaou, the natural gas is sent out into the transmission network at around 90 bars via one gas pipelines to the Saint Martin de Crau interconnection station, situated 24 km from the terminal.