Heat Recovery Steam Generator (HRSG)
A Heat Recovery Steam Generator is a heat exchanger that captures hot exhaust gas — typically from a gas turbine — and uses it to produce steam. It is the link between the gas turbine and the steam turbine in a combined-cycle power plant and a core component of many cogeneration systems.
An HRSG passes a turbine's hot exhaust over banks of finned tubes carrying water, generating steam without burning additional fuel. The steam can then drive a steam turbine to produce extra electricity or supply process heat, recovering energy that would otherwise be lost up the stack.
HRSGs are arranged in sections — economiser, evaporator and superheater — and may produce steam at several pressure levels to extract as much energy as possible. Surfaces such as the economiser and superheater govern how efficiently the exhaust heat is captured.
In combined-cycle and combined-heat-and-power plants the HRSG is what lifts overall efficiency well above that of a simple gas turbine, making it central to fuel saving and lower carbon intensity per unit of output.
Related terms
Waste Heat Recovery · CHP / Cogeneration · Economiser · Superheat