Elengy
An LNG terminal is a facility at which liquefied natural gas is “regasified” (turned back into a gaseous state) after shipment by sea from the area of production.
LNG terminals have four main functions:
On arriving at the terminal, the LNG tanker (200-300 metres in length) is moored at the unloading dock, where articulated pipes (“arms”) are connected to transfer the LNG to the storage tanks. The LNG flows into pipes specially designed to withstand the embrittling effect of extremely low temperatures (below -160°C). This process is completed in under 12 hours.
Boil-off gas is returned to the ship to maintain pressure in the cargo tanks.
The LNG is stored in double-walled insulated tanks to limit boil-off. These tanks are able to withstand the temperatures of below -160°C needed to keep the gas condensed in a liquid state. The outer walls are made of pre-stressed reinforced concrete or steel.
Despite the high-quality insulation, a small amount of heat still penetrates the LNG tanks, causing minor evaporation. The resulting boil-off gas is captured and fed back into the LNG using compressor and recondensing systems. This recycling process prevents any natural gas escaping the terminal under normal operating conditions.
The LNG is subsequently extracted from the tanks, pressurised and regasified using heat exchangers.
The tanks are equipped with submerged pumps that transfer the LNG towards other high-pressure pumps. The compressed LNG (at around 80 times atmospheric pressure) is then turned back into a gaseous state in vaporizers.
Elengy terminals feature a range of technology, including:
Once returned to its gaseous state, the natural gas is treated in a number of ways, including metering and odorising, before it is fed into the transmission network.
How is LNG vaporised/regasified?
The LNG is simply warmed using the heat from sea water. This is done in a heat exchanger (with no contact between the gas and the sea water), producing only a slight drop in the temperature of the sea water, which reaches 6°C at the end of the discharge pipe, quickly becoming imperceptible once diluted.
Does natural gas have an odour?
Natural gas is odourless.Although non-toxic, it is inflammable and is therefore odorised to ensure even the slightest leak can be identified. This is done by injecting tetrahydrothiophene (THT)—an odorant detectable in very small doses—at the terminal before the natural gas is distributed.
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