How Does LNG Work?

Because of its physical state, natural gas is inherently a domestic product. As a gas, the hydrocarbon must be transported by pipeline, which restricts the number of end users. Liquefied Natural Gas (LNG) was developed in 1964 as a solution to this problem.

With LNG, gas is liquefied and transported internationally via tankers and then regasified into its original state for distribution and sale. Additionally, the hydrocarbon takes up significantly less space as a liquid than a gas; LNG is approximately 1/600th the volume of the same amount of natural gas.

LNG Liquefaction PlantSource: Center for Liquefied Natural Gas

LNG has transformed the natural gas market, making previously unrecoverable natural gas finds an economic reality. In other words, stranded gas reservoirs, for which pipelines were too costly to construct, can now be produced, transformed into LNG and transported via tanker.

Liquefaction

When in the reservoir, natural gas is found in three states: non-associated, where there is no oil contact; gas cap, where it is overlying an oil reserve; and associated gas, which is dissolved in the oil. The composition of the natural gas defines how it will be processed for transport. Whether staying in its gaseous state or being transformed into a liquid, natural gas from the well must undergo separation processes to remove water, acid gases and heavy hydrocarbons from the recovered natural gas.

The next step in processing is determined by what type of transport the gas will undergo, and specifications are met according to the transportation system. For LNG, additional processing is required before the condensation of the gas to remove the threat of crystallization in the heat exchangers in the liquefaction plant. When chemical conversion is used to liquefy natural gas, the conversion process determines which preliminary process must be used. Additionally, fractionation between methane and heavier hydrocarbons is performed during liquefaction. This way, after regasification the fuel can be loaded directing into the distribution network of pipelines.

LNG Liquefaction PlantSource: Center for Liquefied Natural Gas

Natural gas is liquefied by lowering the temperature of the hydrocarbon to approximately -260 degrees Fahrenheit (-160 degrees Celsius). This temperature drop liquefies the methane present in the natural gas, making transportation at atmospheric pressure in the form of LNG possible. LNG is mainly constituted of methane and generally contains ethane, as well. Liquefied Petroleum Gas (LPG) may also be present in the LNG.

Transportation

LNG is then introduced into specially insulated tankers and transported around the world. LNG is kept in its liquid form via autorefrigeration. This is a process in which the fuel is kept at its boiling point. Through autorefrigeration any additions of heat are offset by the energy lost from the LNG vapor, vented out of the storage and used to power the tanker.

LNG Being Loaded Onto a TankerSource: Center for Liquefied Natural Gas

LNG Tanker at SeaSource: Center for Liquefied Natural Gas

LNG has little to no chance of igniting or exploding should a spill occur. When LNG is vaporized into its gaseous form, the fuel will only burn when mixed with air in concentrations of 5 and 15%. Additionally, LNG and the vapors associated with it do not explode in an open environment.

Regasification

LNG Regasification PlantSource: Center for Liquefied Natural Gas

Once it has reached its destination, the LNG is offloaded from the tanker and either stored or regasified. The LNG is dehydrated into a gaseous state again through a process that involves passing the LNG through a series of vaporizers that reheat the fuel above the -260 degree Fahrenheit (-160 degrees Celsius) temperature mark. The fuel is then sent via established transportation methods, such as pipelines, to the end users.

Applications

Although limited because of the number of liquefaction and regasification facilities located worldwide, LNG is gaining momentum. Major ongoing LNG projects include the multi-billion-dollar Gorgon LNG project in Australia, as well as the Olokola LNG project in Nigeria and the LionGas LNG project in the Netherlands.

According to the EIA, countries in Asia Pacific are the largest exporters of LNG, and the Middle East is also a leading LNG exporting region. Historically some of the largest importers of LNG, Japan and South Korea depend almost solely on internationally produced LNG for their natural gas needs. European countries also import a large percentage of the LNG produced globally. Emerging markets for the fuel are China and India, although those countries are currently pursuing major pipeline deals in an effort to increase their natural gas imports.

Currently, LNG represents only about 1% of the natural gas consumed in the United States. Right now, the country imports LNG from Trinidad and Tobago, Qatar, Algeria, Nigeria, Oman, Australia, Indonesia and the UAE.

According to the US Federal Energy Regulatory Commission (FERC), there are currently eight LNG processing facilities in operation in the country; seven are regasification plants, and one is a liquefaction facility. Presently, there are 40 additional LNG projects under consideration in the US. LNG imports are expected to increase to an average of 15.8% or 4.8 Tcf of the natural gas used in the US by 2025.