A heat recovery steam generator is plant which recovers heat from a gas stream to generate useable steam, with the most common application being from a gas turbine. The steam produced can be used for process purposes or for driving a steam turbine to produce electrical power, known as cogeneration and combined cycle respectively.
HRSGs can be supplied in a modular arrangement with evaporator, economiser and superheater elements, a packaged assembly with a water cooled furnace, or in a once through design, where the inlet feedwater flows in a continuous path without segmented sections for economizers, evaporators, and superheaters. HRSGs can be installed with supplementary burners known as duct burners, to increase the steam output.