Education About Gas

How does Liquefied Natural Gas work?

 By Peter Ward
About gas

Liquefied Natural Gas has been touted as a major energy source for the future, particularly as we try and bridge the gap between fossil fuels and renewable energy. But what does the term even mean? And how is it shipped and stored around the world?…

Liquefied Natural Gas (LNG) is basically a natural gas that has been cooled to the point where it’s in a liquid state. The temperature of the gas is brought down to -260 degrees Fahrenheit, making it around 600 times smaller than its volume as a gas. That means you can export it in larger quantities for a cheaper price.

In the plants

Natural gas is converted to liquid in LNG plants. These plants consist of one or more LNG trains, or units capable of gas liquefaction. Currently, the largest LNG train in use is in Qatar, which has huge gas reserves and is the world’s largest LNG exporter. In fact, the tiny country, which has a population of just over 300,000 citizens, exported 77.2 million metric tons of LNG in 2016, accounting for 29.9 percent of the total amount of the gas exported in the whole world.
In the plants, the gas is first cleared of water, hydrogen sulfide, carbon dioxide and anything that will freeze when exposed to such cold temperatures. Then the massive temperature drop liquefies the methane in the natural gas. When the process is complete, the liquid is clear, colorless and odorless. The resulting LNG consists mainly of methane and usually contains ethane as well. The process was developed in the 19th century, and provides massive advantages to the natural gas industry.

LNG Plant in Japan (Herman Darnel Ibrahim, Panoramio)

Transport

The main reason for liquefying natural gas is to make it easier to transport. Gas is usually transported by pipeline, but that can be expensive and impractical over long distances, and doesn’t work if the gas is in a remote or hard to reach area.
By liquefying the gas, producers are able to export it easier to markets that are far away. When in its liquid, compact form, natural gas can be shipped in special tankers to terminals at the countries importing the gas. These ships are double-hulled, and specifically designed to handle the low temperature of the cargo. They are also insulated to limit the amount of LNG that evaporates of boils off. The ships are up to 1,000 feet long and require a minimum water depth of 40 feet when they’re fully loaded, according to data from Stanley LNG Carriers.
There are 439 LNG vessels in the global shipping fleet as of January 2017, according to an International Gas Union report. In 2016, 31 newly built ships were delivered from shipyards, a 7 percent increase on the previous year.

LNG carrier Adamawa in Santa Cruz de Tenerife (Carlos Teixidor Canedas, Wikimedia)

Back to gas

Once the LNG reaches its destination, it’s either stored or turned back into gas. To store LNG, you need special storage facilities. These tanks are built either above or below ground and keep the liquid at a low temperature to avoid evaporation. However, to keep the tanks safe and at a constant temperature, pressure must be released from them every now and then. Boil-off gas is allowed to escape the tanks, and is collected and used as a fuel source at the facility, or in the tankers that have transported it.
When the gas is ready to transport to the end user, it has to go through the regasification process. This involves passing LNG through a series of vaporizers that reheat the fuel to above the -260 degree Fahrenheit mark it reached to convert it to liquid. The fuel is then delivered to the final user via traditional methods, such as pipelines.

http://broadleaf.com.au/work/risks-and-treatments-for-an-lng-regasification-facility/
LNG regasification process schematic (broadleaf.com.au)

These regasification terminals play a crucial role in making LNG exports more accessible to countries. As of January 2017 there was 776.8 million tons per year of global regasification capacity, an increase from the previous year mainly due to more capacity in already established markets such as China, Japan and Turkey, according to the International Gas Union. Another 11 projects are under construction in China and India, the two countries that had the strongest growth in LNG demand in 2016, the IGU report said. The country that imported the most LNG last year was Japan, followed by South Korea.
LNG imports and exports are a crucial part of the world’s energy makeup, and provide an efficient and cost-effective way to transport natural gas large distances. As the world looks to move away from emission-heavy fuels, the process of liquefying natural gas could be even more important in the future.

READ MORE: The magic of LNG by Nicholas Newman

about the author
Peter Ward
Business and technology reporter based in New York. MA in Business Journalism at Columbia University Journalism School 2013. Five years experience reporting in the U.S., the U.K., and the Middle East.