Liquefaction of gases is physical conversion of a gas into a liquid state (condensation). The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders.
Uses
Liquefaction processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require pressurization as well. Liquefaction is used for analyzing the fundamental properties of gas molecules (intermolecular forces), or for the storage of gases, for example: LPG, and in refrigeration and air conditioning. There the gas is liquefied in the condenser, where the heat of vaporization is released, and evaporated in the evaporator, where the heat of vaporization is absorbed. Ammonia was the first such refrigerant, and is still in widespread use in industrial refrigeration, but it has largely been replaced by compounds derived from petroleum and halogens in residential and commercial applications.
Liquid oxygen is provided to hospitals for conversion to gas for patients with breathing problems, and liquid nitrogen is used in the medical field for cryosurgery, by inseminators to freeze semen, and by field and lab scientists to preserve samples. Liquefied chlorine is transported for eventual solution in water, after which it is used for water purification, sanitation of industrial waste, sewage and swimming pools, bleaching of pulp and textiles and manufacture of carbon tetrachloride, glycol and numerous other organic compounds as well as phosgene gas.
Liquefaction of helium (4He) with the precooled Hampson–Linde cycle led to a Nobel Prize for Heike Kamerlingh Onnes in 1913. At ambient pressure the boiling point of liquefied helium is 4.22 K (−268.93 °C). Below 2.17 K liquid 4He becomes a superfluid (Nobel Prize 1978, Pyotr Kapitsa) and shows characteristic properties such as heat conduction through second sound, zero viscosity and the fountain effect among others.
The liquefaction of air is used to obtain nitrogen, oxygen, and argon and other atmospheric noble gases by separating the air components by fractional distillation in a cryogenic air separation unit.
History
Further information: Timeline of low-temperature technology
Liquid air
Main article: Liquid air
Linde's process
Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid.
Claude's process
Air can also be liquefied by Claude's process in which the gas is allowed to expand isentropically twice in two chambers. While expanding, the gas has to do work as it is led through an expansion turbine. The gas is not yet liquid, since that would destroy the turbine. Commercial air liquefication plants bypass this problem by expanding the air at supercritical pressures.[1] Final liquefaction takes place by isenthalpic expansion in a thermal expansion valve.
See also
Air Liquide
Air Products & Chemicals
Air separation
The BOC Group
Chemical engineer
Compressibility factor
Fischer–Tropsch process
Gas separation
Gas to liquids
Hampson–Linde cycle
Industrial gases
The Linde Group
Liquefaction
Liquefaction point
Louis Paul Cailletet
Messer Group
Praxair
Siemens cycle
Turboexpander
References
Greenwood, Harold Cecil (1919). Industrial Gases. D. Van Nostrand. p. 87.
External links
Liquefaction of Gases
History of Liquefying Hydrogen - NASA
vte
Transport of hydrocarbon fuels
Oil
Oil tanker Oil terminal Tank car Tank truck List of oil pipelines
LNG and LPG
LNG carrier
Regasification Liquefaction Gas separation Natural gas storage Black powder in gas pipelines List of natural gas pipelines List of LNG terminals
Coal/Misc.
Industrial railway Intermodal freight transport Syngas
Hellenica World - Scientific Library
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