A supplementary-fired HRSG is basically a convective unit with a design quite similar to an unfired HRSG. However the firing capability provides the ability to control the HRSG steam production—within the capability of the burner system— independent of the normal gas turbine operating mode. Fully-Fired HRSG. A few industrials have used the exhaust of the gas turbine as preheated combustion air for a fully-fired HRSG. A fully fired HRSG is defined as a unit having the same amount of oxygen in its stack gases as an ambient-air-fired power boiler. The HRSG is essentially a power boiler for which the gas turbine exhaust serves as the source of preheated air supply. Steam.
