Heat Recovery Steam Generator

A heat recovery steam generator, or HRSG, is a heat exchanger that captures heat from a hot exhaust gas stream, most often the exhaust of a combustion gas turbine, and uses it to raise steam rather than letting that heat go to waste. Water is drawn through an economizer, an evaporator and a superheater in turn, each stage adding more heat until the water leaves as steam suited to driving a turbine or serving an industrial process. In a combined cycle power plant, the HRSG links the gas turbine to a following steam turbine, letting the plant draw a second round of electricity from heat that a gas turbine running alone would simply exhaust into the atmosphere, which is what gives combined cycle plants their higher overall efficiency. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/