User:Milton Beychok/Sandbox

An expansion turbine, also referred to as a turboexpander or turbo-expander, is a centrifugal or axial flow turbine through which a high pressure gas is expanded to produce work that is typically used to drive a gas compressor.

Because work is extracted from the expanding high pressure gas, the expansion is an isentropic process (i.e., a constant entropy process) and the low pressure exhaust gas from the turbine is at a very low temperature, often as low as 200 K (-100 °F) or less. Turbo-expanders are very widely used as sources of refrigeration in industrial processes such as the extraction of ethane and natural gas liquids (NGLs) from natural gas, the liquefaction of gases and other low-temperature processes.

In 1939, Pyotr Kapitza of Russia suggested the use of a centrifugal turbine for the isentropic expansion of gases to produce refrigeration. Since then, centrifugal expansion turbines have taken over almost 100 percent of the gas liquefaction and other low-temperature industrial requirements.

Example application

© Image: John D. Wilkinson et al, U.S. Patent 6915662
A schematic diagram of a demethanizer extracting hydrocarbon liquids from natural gas.