LNG stands for Liquefied Natural Gas, i.e. natural gas in its liquid form, which is achieved by cooling the gas to -160oC.

Natural gas is a clean fuel and is, hence, in demand the world over.

When converted back to its gaseous state, it is utilised for domestic and industrial uses. Domestic uses include cooking and heating, while industrial uses include fuelling factories and power generation. In many countries, it is used as an alternative fuel.

Like the air around us, natural gas in its normal state occupies a lot of space. But it must be sent in large quantities to be economically viable. It can be sent to customers in its natural form via pipelines, but laying pipes to customers who may be thousands of kilometres away is neither practical nor economic. In its liquid form, it reduces in volume by 600 times, making it possible to load huge quantities of gas on to tankers to be shipped to customers around the globe.

Liquefaction is achieved by the following process:-

When natural gas is produced from the fields, it is usually made up of methane, hydrocarbons, carbon dioxide, sulphur, water, oxygen and nitrogen. It is transported to a specialised plant where it is cooled below its boiling point. When it reaches approximately minus 161 degrees Celsius (around -259 Fahrenheit), it becomes liquid At this point it is primarily composed of methane with small amounts of hydrocarbons.

LNG is transported to what is known as a receiving terminal; to import LNG, a country must have one or more LNG receiving terminals. In these terminals, LNG undergoes a re-gasification process, where it is warmed up in heat exchangers to return back to its gaseous form.

LNG is colourless and odourless and is neither corrosive nor toxic. The liquid weighs around 45% of the weight of water and would float in the event of a spill. If heat is transferred from water to spilled LNG, the LNG will resume its gaseous form very quickly, releasing significant energy which may cause an explosion. However LNG itself is not explosive unless its vapour is confined to an enclosed space.

While natural gas contains propane, ethane, nitrogen, oxygen, water, carbon dioxide, sulphur compounds and methane, LNG can be almost 100% methane, although in most cases it is produced with small amounts of hydrocarbons.

In addition to the Sultanate of Oman, the largest producing countries include Qatar, Algeria, Brunei, Indonesia, Malaysia, Australia, Libya, Trinidad and Nigeria. Russia is also fast becoming a large producer.

The largest importing countries include South Korea, Japan, Europe and the United States of America.

LNG is transported in ships that are equipped with double-hulled tanks. These are specifically designed tanks with insulation between the hulls to keep the LNG cool and reduce evaporation. There are two types of ships; the first has cylindrical tanks which have larger storage capacities and can maintain low storage pressure. The second type carries vacuum-jacketed horizontal or vertical tanks. Either type can be as long as 1000 feet and require more than 40 feet depth when loaded.

To remain in liquid form, LNG must be kept below minus 117 Fahrenheit. In addition to the insulation, LNG boil-off vapour is released out of the tanks to maintain constant degrees of pressure and temperature inside. This process is known as auto-refrigeration. The boil-of vapour is often collected and used as a fuel supplement in the tanker or the facility where it is stored. LNG is stored in insulated tanks built above or below ground at receiving terminals. The process of storing it in such tanks is similar to that used when transporting it in double-hulled tankers.