The heat recovery steam generator is an equipment that is used to recover heat that is produced by hot gas. The heat that is produced is often used in co-generation or to power a steam turbine.
Heat recovery steam generators are used in a variety of ways around the world. One of the most typical ways in which it is used is to capture and convert exhaust heat from gas turbines into steam to power steam turbines in combined cycle power plants. This sort of combination is thought to be able to produce electricity in a more efficient manner than either the steam turbine or the gas turbine can do on their own. It is also used in combined cycle power stations that use diesel engines to generate heat. Heat recovery steam generators are also used in co-generation power plants. These plants are generally thought to be more efficient than combined cycle plants. The inefficiency associated with the combined cycle plants is due largely to the level of energy loss from steam turbines.
There are some heat recovery steam generators which come with supplemental duct firing. The extra burners actually provides additional energy for the heat recovery steam generator, which generates more steam and therefore increases the steam turbines overall output. Duct firing is usually used for peak operations because it generally costs less to produce electricity. Some heat recovery steam generators even have regulator valves which are used to control inlet into the heat recovery generator. This makes it possible for the gas turbine to keep operating even when there is no demand for steam or if the heat recovery generator is being taken offline.
Emission control is also included in some heat recovery systems. They either have a system for selective catalytic reduction, which is used in the reduction of nitrogen oxide or some sort of catalyst for the removal of carbon monoxide, or both.