Turboexpander

A turboexpander, also referred to as a turbo-expander or an expansion turbine, is a centrifugal or axial-flow turbine, through which a high-pressure gas is expanded to produce work that is often used to drive a compressor or generator. A turboexpander, also referred to as a turbo-expander or an expansion turbine, is a centrifugal or axial-flow turbine, through which a high-pressure gas is expanded to produce work that is often used to drive a compressor or generator. Because work is extracted from the expanding high-pressure gas, the expansion is approximated by an isentropic process (i.e., a constant-entropy process), and the low-pressure exhaust gas from the turbine is at a very low temperature, −150 °C or less, depending upon the operating pressure and gas properties. Partial liquefaction of the expanded gas is not uncommon. Turboexpanders are 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 (such as oxygen, nitrogen, helium, argon and krypton) and other low-temperature processes. Turboexpanders currently in operation range in size from about 750 W to about 7.5 MW (1 hp to about 10,000 hp).