Transportation By LNG Carrier and RegasificationPublished on 01.06.2015
5 min read
Once liquefied, natural gas is loaded onto specially designed ships called LNG carriers. After its trip, the is regasified at a dedicated terminal. In light of the growing importance of natural gas as an energy source, the LNG shipping sector is poised to play an increasing role in the global energy supply.
© ZAMORA PHILIPPE / TOTAL - The LNG carrier Arwa Spirit arrives in Japan with a cargo of liquefied natural gas at -162°C.
Natural gas is processed in a train before being loaded onto purpose-built vessels for shipping to a regasification terminal. There are currently about 380 LNG carriers crisscrossing the world’s oceans. These huge double-hulled, 200- to 350-meter-long ships can carry up to 260,000 cubic meters of LNG. The gas is maintained at -160°C for its journey of many thousands of kilometers.
There are two main types of LNG carrier presently in use:
- Carriers with insulated aluminum spherical tanks anchored to the ship's hull by a steel skirt.
- Membrane carriers, whose tanks are part of the double hull structure.
Despite the quality of the tank insulation system, however, a certain amount of the LNG warms up and returns to a gaseous state. The boil-off rate amounts to roughly 0.15% per day. The boiled-off gas is recovered and used to the ship’s engines.
Lastly, the carriers must be operated, maintained and manned according to the highest safety standards. Crew members closely monitor temperature and pressure, check for the presence of oxygen and apply stringent tank inspection procedures. LNG carriers are built according to the most stringent standards.
Arrival at the Regasification Terminal
When a carrier arrives at a receiving terminal, the LNG is offloaded and stored in large tanks at atmospheric pressure. It is subsequently pumped out of the tanks, then pressurized, heated and regasified using seawater or steam. Lastly, the gas is fed into the natural gas transmission network for delivery.
LNG has the same chemical composition as natural gas and consists primarily of methane. It is returned to a gaseous state at the regasification terminal. Because natural gas is odorless, utilities add tetrahydrothiophene (THT) to give it a smell so that leaks can be easily detected.
LNG Shipping, A Promising Sector
Natural gas, the third-ranked source in the world behind oil and , has averaged growth of 3% a year over the last several decades. Production is expected to increase by 50% by 2030, making it the second most widely used fossil in the world.
The LNG shipping sector is set to grow in line with demand for natural gas, due to its many advantages:
- It is cheaper to transport gas over long distances by ship than by pipeline, despite the LNG industry’s use of very expensive, high-quality materials.
- Gas pipelines can pose technical challenges (deepwater conditions) and raise geopolitical issues. Shipping bypasses these problems and connects producing countries and consumer countries more easily. Reserves located far from main consumer areas can be tapped.
- A shipment of LNG can be diverted en route, unlike gas that is transported by pipeline. This flexibility allows consumer countries to manage their supply more efficiently and enables producing nations to unlock the full value of their resources.
Thanks to these advantages, the LNG shipping sector is set to play a promising role in the global energy supply.