LNG stands for Liquefied Natural Gas. It is natural gas that has been cooled to a very low temperature (-162 degrees Celsius or -260 degrees Fahrenheit) to convert it into a liquid form. This process reduces the volume of the gas by about 600 times, making it easier and more economical to transport over long distances.
LNG is transported in specialized Cryogenic ships called LNG carriers. These carriers are double-hulled to ensure safety, with the inner hull containing the LNG and the outer hull acting as a protective layer. The LNG is stored in insulated tanks on board the ship and is kept at the required low temperature using onboard refrigeration systems.
Once the LNG reaches its destination, it can be regasified and injected into pipelines for distribution to consumers. The regasification process involves warming the LNG back to its gaseous state through heat exchange with seawater or other sources of heat.
What is LNG and how is it transported?
1. What is LNG?
Liquefied natural gas is mostly composed of methane (85-95%) but also contains a small percentage of ethane, propane, and butane (5-15%), as well as traces amounts of nitrogen. It is an odorless, non-toxic, non-corrosive liquid with low chances of inflammation.
Matter transitions from gaseous to liquid state under the right conditions of temperature and pressure: for example, at atmospheric pressure, liquid water enters its gaseous phase at 100 °C (212 °F). Under atmospheric pressure and ambient temperature, methane and all the other components of LNG are in a gaseous state.
Liquid methane enters its gaseous phase at -162 °C (-260 °F), which is about the lowest temperature that occurs on the moon(3). To obtain LNG, natural gas must be cooled to its liquid state, a process called liquefaction.
The volume of natural gas in its liquid state is 600 times smaller than in its gaseous state: the same amount of natural gas that would fill a beach ball can fit in a golf ball when liquefied. This property makes its containment and shipping a lot easier.
2. Transportation of LNG?
The transportation of liquefied natural gas (LNG) primarily occurs through two major methods:
- By pipelines
- By vessels (LNG Ships)
LNG pipelines are efficient for transporting natural gas between liquefaction facilities, storage facilities, tankers, and re-gasification facilities. However, they are costly to construct due to the need for significant insulation to maintain the low temperature of LNG.
On the other hand, LNG vessels, such as LNG tankers, are used for intercontinental shipping of LNG between export and import terminals. These vessels are equipped with specialized components, including LNG storage tanks, a double hull for added strength, and bow thrusters. (Ref. Different Parts Of A Ship explained in detail)
In addition to pipelines and vessels, limited quantities of LNG are now authorized for transportation by rail in the United States and Canada to meet increased demand and overcome pipeline capacity constraints. The transportation of LNG by rail involves the use of enhanced tank cars, advanced routing analysis, and specialized operations to ensure safety and regulatory compliance.
The liquefaction process?
A purification step is performed before the liquefaction: dust, pollutants, CO2, and water are removed to avoid corrosion and freezing in the pipes. Natural gas liquefaction is based on a refrigeration cycle, a four-step process that aims to progressively absorb heat from a gas using a liquid called a refrigerant. By repeating the cycle, natural gas is cooled continuously until reaching its temperature of liquefaction.
- First, the compressor increases the pressure of the refrigerant: it enters as a low-pressure, low-temperature gas and leaves as a high-pressure, high-temperature gas.
- Then, the condenser removes heat from the hot refrigerant vapor coming out of the compressor until it condenses into a liquid. The refrigerant is then a high-pressure, low-temperature liquid.
- The expander creates a drop in pressure after the refrigerant leaves the condenser. It becomes a low-pressure, low-temperature liquid.
- Finally, the refrigerant enters the evaporator: this is the step where the cooling is provided. A fan forces natural gas to flow through the evaporator and its heat is absorbed by the refrigerant that progressively turns back into gas. The refrigerant is then sent back to the compressor where the process restarts.
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Two main methods are used to cool natural gases: the cascade method has three refrigeration cycles that respectively use propane, ethylene, and methane as refrigerants. Each cycle brings natural gas to a lower temperature. The mixed refrigerants method (MR) is a single cycle that uses a blend of multiple light hydrocarbons as a refrigerant.
Cascade is more energy-efficient but requires more space, which limits its use to large-scale onshore plants (with a capacity superior to 1 million tons of LNG p.a.). MR is used onshore and offshore for small- and large-scale plants; the hydrocarbon mixture can be adjusted to optimally follow the cooling curve of natural gas.
LNG export terminals consume some of the gas delivered to the facility to operate the liquefaction equipment. The US Energy Information Administration estimates that about 15% to 18% of the natural gas delivered to LNG export facilities is used for liquefaction.
To meet the increasing demand for natural gas, research institutes and companies are trying to develop small-scale LNG plants to exploit the abundant smaller-sized gas resources, as well as more offshore plants.
However, offshore plants have different requirements than their onshore counterparts: the small footprint of the equipment, the ease of maintenance, and the sensitivity to motion are crucial because of the lack of deck space and the surrounding ocean environment.
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After Liquefaction process
After liquefaction, LNG is stored in tanks at a pressure slightly above atmospheric pressure. Those tanks often have an inner shell made of a special alloy of stainless steel, aluminum, or nickel, designed to resist low temperatures, and an outer concrete shell with reinforced slab and roof. Each tank is insulated to maintain LNG at the right temperature and is equipped with sophisticated protection systems that monitor the liquid level, pressure, temperature, and detect potential leakages.
Transportation is provided by special tanker ships with a double hull to limit the risks of leaks and spills in case of collisions. For overland delivery, trucks are the preferred solution, especially in the US; trains can also be used as carriers but are often avoided in populated areas, as an accident involving more than 100 tanks could potentially destroy a city.
At import terminals, LNG is offloaded from the ships and stored before being turned back into gas to be transported through local pipelines. The regasification is done by heating LNG: a small amount can be burned, which produces the heat necessary to gasify the remaining liquid. Or, more frequently, LNG goes through a heat exchanger, a device that transfers heat from one medium to another; the heater used is ambient seawater or river water that is returned to its source afterwards.
3. LNG carriers/Ships
After liquefaction, LNG is stored in tanks at a pressure slightly above atmospheric pressure. Those tanks often have an inner shell made of a special alloy of stainless steel, aluminum, or nickel, designed to resist low temperatures, and an outer concrete shell with reinforced slab and roof. Each tank is insulated to maintain LNG at the right temperature and is equipped with sophisticated protection systems that monitor the liquid level, pressure, temperature, and detect potential leakages.
Transportation is provided by special tanker ships with a double hull to limit the risks of leaks and spills in case of collisions. For overland delivery, trucks are the preferred solution, especially in the US; trains can also be used as carriers but are often avoided in populated areas, as an accident involving more than 100 tanks could potentially destroy a city.
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At import terminals, LNG is offloaded from the ships and stored before being turned back into gas to be transported through local pipelines. The regasification is done by heating LNG: a small amount can be burned, which produces the heat necessary to gasify the remaining liquid. Or, more frequently, LNG goes through a heat exchanger, a device that transfers heat from one medium to another; the heater used is ambient seawater or river water that is returned to its source afterwards.
LNG ships (also called tankers, carriers, or vessels) are specifically equipped to transport LNG in bulk. Modern ships carry in average between 125,000 m3 and 175,000 m3 of LNG. They are divided into three main types.
- The Moss type carries spherical tanks that are self-supporting, meaning they are not a part of the ship hull and are not essential to its strength. Tanks sit half above the deck level, and half within the hull.
- In the Membrane type, LNG is maintained at low temperature by using thin inside tanks and covering them with a wrinkled stainless steel “membrane” (see: the inside of the tank). They are not self-supporting: the outer part of the tank is in contact with the hull that also helps to maintain insulation. The tank provides high visibility towards the front of the vessel because of the minimal protrusions on the deck.
- The self-supporting Prismatic shape IMO type B (SPB) carries an independent tank made of an aluminum alloy or stainless steel to provide heat insulation. It is broadly used because the tank can be built to match the hull shape, therefore increasing space efficiency; it also has no protruding structures on the deck. It is particularly adapted to serve in rough seas.
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LNG Global Exports & Imports
In 2021, Australia was the biggest producer of LNG with 87.6 million metric tons mainly exported to the Asian market. Qatar followed with 77.4 million metric tons, sent all over the world. Lastly, the US produced 71.6 million metric tons.
LNG exports account for 45% of the US natural gas export; almost half of this gas is sent to five main countries. The US is however expected to be the world’s largest LNG exporter in 2022, as a new export facility and an additional liquefaction unit will be completed at the end of the year.
In 2022, according to the U.S. Energy Information Administration (EIA), global trade in liquefied natural gas (LNG) set a record high in 2022, averaging 51.7 billion cubic feet per day (Bcf/d), a 5% increase compared with 2021.
The top two global LNG exporters in 2022 were Qatar and Australia, with exports averaging 10.5 Bcf/d and 10.4 Bcf/d, respectively. The United States became the world’s top LNG exporter for the first time in the first half of 2022, but its exports declined in the second half of the year due to the shutdown of the Freeport LNG export terminal.
Europe had the largest increase in LNG imports globally, increasing by 65% (6.5 Bcf/d) compared with 2021, replacing imports by pipeline from Russia.
In 2023, US overtook Qatar and Australia in LNG Exports in 2023
US topped the LNG exports in 2023. The resumption of production at the Freeport liquefied natural gas (LNG) terminal in Texas helped the US overtake Qatar and Australia.
United States was the biggest exporter of LNG in 2023, with record production levels in December positioning the country to become the largest exporter of LNG in the world in 2023. Full-year exports from the U.S. rose by 14.7% to 88.9 million metric tons, driven largely by the return to full production of the Freeport LNG plant and increased processing efficiency at other facilities.
This information is based on data from LSEG, and U.S. government data. While QatarEnergy has the largest LNG export capacity of any natural gas company in the world, the U.S. led in actual exports in 2023.
LNG Demand & Future
LNG demand is projected to grow moderately but steadily throughout the coming decades. According to McKinsey, LNG demand will grow by 0.5% annually from 2035 to 2050, requiring more than 200 million metric tons of new capacity.
Asia will continue driving global LNG demand growth, although China’s dominance may decrease after 2035, with South and Southeast Asia taking over as key demand drivers. By 2040, global LNG demand is expected to reach 625-685 million tons per year.
Key factors influencing LNG demand include the shift towards cleaner energy sources, such as coal-to-gas switching in China, and the increasing adoption of LNG for cooking and power generation in emerging markets like Southeast Asia.
Key points regarding LNG demand and future trends:
- Moderate growth in LNG demand, with an emphasis on Asia and Southeast Asia
- Decreasing influence of China as a primary driver of LNG demand post-2035
- Increased focus on environmental concerns, such as emission reduction and methane mitigation
- Continued reliance on LNG as a flexible and reliable energy source
- Expansion of LNG imports among new countries, such as Antigua, Australia, Cyprus, and Nicaragua.
- Emphasis on diversifying energy infrastructure and investments.
LNG and it’s Transportation Explained in this Youtube Video