Liquefaction of Gases

The most important advantage of liquefying gases is that they can then be stored and transported in much more compact form than in the gaseous state. Two kinds of liquefied gases are widely used commercially for this reason, liquefied natural gas (LNG) and liquefied petroleum gas (LPG). LPG is a mixture of gases obtained from natural gas or petroleum that has been converted to the liquid state. The mixture is stored in strong containers that can withstand very high pressures. LPG is used as a fuel in motor homes, boats, and homes that do not have access to other forms of fuel.

Liquefied natural gas is similar to LPG, except that it has had almost everything except methane removed. LNG and LPG have many similar uses.

In principle, any gas can be liquefied, so their compactness and ease of transportation has made them popular for a number of other applications. For example, liquid oxygen and liquid hydrogen are used in rocket engines. Liquid oxygen and liquid acetylene can be used in welding operations. And a combination of liquid oxygen and liquid nitrogen can be used in aqualung devices.

Liquefaction of gases is also important in the field of research known as cryogenics. Liquid helium is widely used for the study of behavior of matter at temperatures close to absolute zero—0K (-459°F [-273°C]).