Introduction to Liquefied Natural Gas

What is LNG???

The demand for energy is projected to double in the next 30 years and global consumers are increasingly turning to liquified natural gas, commonly called LNG, to meet this growing energy demand.? Despite the increase in LNG production, many people are still unfamiliar with the steps involved in producing LNG. What exactly is natural gas, and why has LNG been dubbed the energy of the future??

Let’s learn about Natural Gas.?

Natural gas is a hydrocarbon gas mixture made primarily of methane. Underground natural gas reservoirs exist worldwide and can be found in the United States, Russia, Iran, Qatar, Canada and Australia.?

Natural gas produces 70% less carbon emissions than other commonly used fossil fuel sources, such as coal or oil. If spillage occurs, natural gas does not react or mix with the environment like other fuel sources. Natural gas will evaporate and dissipate without leaving a residue.?

What is the Natural Gas to LNG Process??

The transition from Natural Gas to consumer-ready LNG is made through a 6-step process:??

1. Extraction?
2. Processing?
3. Liquefaction?
4. Transportation?
5. Regasification??
6. Distribution?

1. Extraction?

Over millions of years, pressure and high temperature causes deposits of organic matter to break down. These deposits are made up of plants, animals and microorganisms. In time, these deposits decompose and become natural gas reservoirs.?

Natural gas reservoirs are found in two types of wells:?

• In oil wells, where the natural gas may be dissolved in oil or in a layer above the oil.?
• In gas wells, where there is little to no crude oil, and the raw natural gas is harvested by itself.?

The most sought-after natural gas well is one that is economical to extract, easily accessible, and preferably in a pocket where the gas is trapped in permeable matter beneath impermeable rock, that prevents the gas from escaping. These rock formations are called sedimentary basins and trap huge reservoirs of natural gas. There are several ways to extract natural gas from both onshore and offshore reservoirs.

2. Processing?

Natural gas undergoes a treatment process prior to being liquefied for transportation. This treatment purifies the natural gas and removes contaminants, including carbon dioxide, water, and mercury.?

The processing phase, often referred to as pre-treatment, begins once the natural gas?has been extracted from the reservoir and fed to the processing facility. As part of the process, heavy hydrocarbons and impurities are removed from the raw gas, leaving mostly pure methane as the remaining natural gas. The processing or pre-treatment stage removes contaminants that may freeze or cause blockages during liquefaction. Propane and butane are also extracted during this process and can be reinjected into the LNG or reused in the liquefaction process.??

In some cases, extraction, processing, and liquefaction can all happen in one place. Some producers have started implementing floating LNG processing facilities, which position tankers above offshore gas fields.??

3. Liquefaction?

To make natural gas easier to transport, it must undergo a liquefaction process. During this process, natural gas is cooled to -160°C (-260°F). In this state, the gas liquefies into a cryogenic liquid, which is a gas kept in a liquid state at very low temperatures. During the liquefaction process, the natural gas is reduced in volume by 600 times.?

There are several methods and technologies available to liquefy natural gas. Propane Mixed Refrigerant Liquefaction (C3MR) and the ConocoPhillips Optimized Cascade Process are two common liquefaction methods.??

In its liquid state, LNG is a clear, odor-free substance with a low flammable window, making it safer to transport.?

Once the natural gas has been liquefied, an LNG transport carrier positions itself alongside the liquefaction plant storage and loading facility to transfer what is now liquefied natural gas into onboard storage tanks, ready for transport.?

4. Transportation?

Once sold, the LNG can be transported to the utility or country that has a need for it. There are several ways to transport LNG to the regasification plants, including by LNG train, by truck using specialized containers, or by LNG ship, which are commonly called tankers.?

Most LNG is transported by tankers using specialized cryogenic tanks that handle the low temperatures necessary for the natural gas to remain liquefied. The insulated containers onboard tankers limit the amount of LNG boil-off gas (BOG), which is an LNG vapor that can occur due to warming during the storage and transport process. In some cases, BOG is used to fuel the tankers transporting the LNG. When this is not the case, onboard liquefaction units are used to re-liquefy the BOG and return it to the insulated onboard storage containers.??

Once the LNG arrives at its destination, it must be regasified at the receiving terminal.??

5. Regasification?

Once the LNG has arrived at its destination, it is ready to be transformed back into a gaseous state through a process called regasification. This process involves warming the LNG in a heat exchanger at the receiving terminal, called a regasification plant. After LNG regasification, and prior to distribution, the regasified natural gas is metered and dosed with an odorizing agent, giving it its distinctive rotten eggs smell. Once this step is done, the natural gas is ready for use by consumers.??

6. Distribution?

Once the natural gas has been distributed to consumers, it can be used for a wide range of purposes. It is commonly used for energy purposes in both industrial and domestic settings, including cooking and heating homes, running machinery in factories, and even power generation.??

The increasing demand for cleaner burning and more efficient energy sources positions LNG as an important transition fuel and industry leader toward a greener future.