A heat recovery steam generator or HRSG is an energy recovery heat exchanger that recovers heat from a hot gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam turbine (combined cycle).
HRSGs
HRSGs consist of four major components: the economizer, evaporator, superheater and water preheater. The different components are put together to meet the operating requirements of the unit. See the attached illustration of a Modular HRSG General Arrangement.
Modular HRSGs can be categorized by a number of ways such as direction of exhaust gases flow or number of pressure levels. Based on the flow of exhaust gases, HRSGs are categorized into vertical and horizontal types. In horizontal type HRSGs, exhaust gas flows horizontally over vertical tubes whereas in vertical type HRSGs, exhaust gas flow vertically over horizontal tubes. Based on pressure levels, HRSGs can be categorized into single pressure and multi pressure. Single pressure HRSGs have only one steam drum and steam is generated at single pressure level whereas multi pressure HRSGs employ two (double pressure) or three (triple pressure) steam drums. As such triple pressure HRSGs consist of three sections: an LP (low pressure) section, a reheat/IP (intermediate pressure) section, and an HP (high pressure) section. Each section has a steam drum and an evaporator section where water is converted to steam. This steam then passes through superheaters to raise the temperature beyond the one at the saturation point.
Applications
Heat recovery can be used extensively in energy projects.
In the energy-rich Persian Gulf region, the steam from the HRSG is used for desalination plants.
Universities are ideal candidates for HRSG applications. They can use a gas turbine to produce high reliability electricity for campus use. The HRSG can recover the heat from the gas turbine to produce steam/hot water for district heating or cooling.
Large ocean vessels (e.g. Emma Maersk) make use of heat recovery
Manufacturers
Alstom
Ansaldo Caldaie S.p.a.
BHI Co.
Express Integrated Technologies (EIT)
Vogt Power/Babcock Power([4])
IHI Corporation
CMI Energy
Victory Energy
Nooter/Eriksen
NEM
Doosan Heavy Industries & Construction ([10])
BHEL
3DCAD (I) PVT LTD
Thermax Ltd
Innovative Steam Technologies
Larsen & Toubro Ltd
Hamon Deltak, Inc
Greshams Ltd
Rentech Boiler Inc.
AZARAB Industery Co.
DESCON Engineering Limited
Retubeco, Inc.
GREENS POWER EQUIPMENT INDIA PVT.LTD.
MAPNA Boiler