In a Gas Processing Plant, the purpose of the Turbo expander is to efficiently perform two distinctly different, but complimentary, functions in a single machine. The primary function is to efficiently generate refrigeration in the process gas stream, which is performed by the Expansion Turbine end efficiently extracting the potential heat energy from the gas stream, causing it to cool dramatically. This extracted energy can then be converted to mechanical energy to rotate the Shaft to the Booster Compressor end of the Turbo expander, which partially recompresses the residue gas stream. The Turbo expander operates according to the thermodynamic and aerodynamic laws of physics. When designed properly, the Turbo expander can yield very high efficiencies at the "Design Point" and reasonable efficiencies at other, or "Off-Design", Points. Hence, requiring an state-of-the-art design, to take place in order to overcome various process and mechanical constraints.
All above indicated sizes can be combined with a booster compressor to form a turbo-expander / compressor package.