Liquid Gas

Liquid gas is produced through the liquefaction or conversion of a gaseous substance or element into a liquid state. Liquefaction is commonly accomplished through the pressurization or compression of a gas, although the process can occur through changing the temperature of a substance and leading to its condensation. Liquid gas is produced for purposes of storage, but gas is also liquefied as a stage in numerous processes such as refrigeration and air conditioning.

Numerous gases are liquefied for storage, including oxygen (LOX; particularly in life support systems), nitrogen (liquid nitrogen; for system cooling and cryogenic preservation), methane or natural gas (liquid natural gas/LNG; allows for the more efficient storage and transportation of natural gas as a commodity fuel), and hydrogen (rocket fuel/oil refining). Over 300 LNG carriers (ships) currently facilitate the flow of natural gas to overseas markets from production sites.

Liquid gases can be produced from numerous sources including geological formations (natural gas) or from the air or atmosphere through fractional distillation or air separation (nitrogen, oxygen). Turbomachinery like industrial compressors pressurizes gas while heat exchangers draw away excess heat resulting from the higher pressure. The pressurized gas is then purified through membranes and other filters. Gas is then separated from other byproducts through a distillation column and then fully liquefied through refrigeration. Liquid hydrogen is supplied through the liquefaction of hydrogen produced typically from petroleum refining processes. Nearly all liquid gas requires insulation and/or refrigeration during storage to prevent vaporization.