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Gas Infrastructure Sustainability FAQ Glossary
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FAQ  
 
   
A. Natural Gas
B. Liquefied Natural Gas
C. Gas transportation and gas storage
 
Photo courtesy of Elengy
 
B. Liquefied Natural Gas
1. What is LNG?
2. How is LNG created from natural gas? How is it re-gasified? Is this conversion safe?
3. Where does LNG come from?
4. What are the advantages of LNG?
5. What is the difference between LNG and LPG?
6. What happens at an LNG receiving terminal?
7. How will the LNG be stored?
8. Is there a risk of explosion at an LNG terminal?
9. What is the environmental impact of LNG?
   
1. What is LNG?
 

Liquefied Natural Gas – or LNG – is a clear, odourless liquid produced by cooling natural gas to minus 162°C. In this liquid state, the volume of LNG is about 600 times less than that of natural gas. It can therefore be stored and transported very efficiently. If gas needs to be carried over long distances, LNG is a particularly good alternative to gas transport by pipeline.

2. How is LNG created from natural gas? How is it re-gasified? Is this conversion safe?
 

The conversion of natural gas into liquid is called liquefaction and is achieved through refrigeration. Liquefaction reduces the volume of natural gas by approximately 600 times, making it more economical to transport in specially designed ships. LNG is converted back to gas by warming the liquid above -160° Celsius. Both the liquefaction and regasification processes are performed using advanced technologies with proven safety records.

3. Where does LNG come from?
 

Most LNG comes from areas where large volumes of natural gas have been discovered such as North Africa, the Middle East and the West Indies. Countries that produce LNG include Trinidad, Nigeria, Algeria, Egypt, Oman, Qatar, Indonesia, Malaysia and Australia.

4. What are the advantages of LNG?
 

LNG takes up a much smaller fraction of space than natural gas. Since the volume of LNG is 600 times smaller than natural gas, it is more efficiently transported over long distances by sea. This takes place in specially designed ships. The real advantage is that LNG allows countries to import and export natural gas from and to other countries around the world.

5. What is the difference between LNG and LPG?
 

Liquefied petroleum gas (LPG) and LNG are often confused with each other. LPG consists chiefly of propane (C3H8) and butane (C4H10), and is used mainly in domestic and commercial applications (such as fuel for cars). LPG is liquefied by holding it under high pressure. LNG, by contrast, is a liquid at atmospheric pressure but at a very low temperature (approx. – 162°C). LPG's specific gravity is also totally different from LNG's: components are lighter than air and the gas does not disperse if it escapes. LNG (natural gas), by contrast, is heavier than air and disperses and rarefies very quickly into a mixture that is no longer flammable. The storage of LPG at pressure, unlike the storage of LNG at low temperature, requires the use of very different equipment (other material properties, thicknesses, insulation) and standards.

6. What happens at an LNG receiving terminal?
 

LNG arrives at the terminal by ship, is stored in tanks, warmed (or regasified) and then delivered to the gas transport network. At this point, its use is identical to that of conventional natural gas.

7. How will the LNG be stored?
 

The LNG will be stored in specially designed full containment tanks. A full containment tank consists of a metal inner tank and a concrete outer tank. Thermal insulation between the steel inner tank and the concrete outer tank will limit the evaporation of LNG to about 0.07% of the tank’s content per day.

8. Is there a risk of explosion at an LNG terminal?
 

An explosion of natural gas can only occur if the following three factors occur simultaneously:

  • a gas leak in an enclosed space
  • a mix of air and gas of between 5% and 15%
  • a spark or flame.

Every care is taken in at LNG terminals to prevent these three things occurring at the same time.

9. What is the environmental impact of LNG?
 

From the moment the LNG is regasified, the environmental impact is identical to that of natural gas (e.g. fewer CO2 emissions on combustion in comparison with coal). The energy needed for the regasification process can be produced by using some of the gas itself. If there is direct environmental exposure, for example through leakage, LNG causes less damage than an oil spill since it will immediately regasify.