Glossary
HRSG and gas path
Duct burner
Also known as HRSG duct burner, supplementary firing.
A duct burner is an auxiliary natural-gas or distillate-oil burner installed in the inlet duct of an HRSG to add heat to the gas-turbine exhaust before it enters the first tube bank. Duct burners are used for:
- Steam-flow boosting beyond the gas-turbine-only HRSG capacity
- Cogeneration peak shaping where process steam demand exceeds nominal HRSG output
- Cold-start steam-temperature ramp control
Effect on fouling
Duct-burner firing raises the temperature and changes the gas composition entering the finned-tube banks. On natural-gas-only HRSGs, this adds little fouling; on duct burners firing oil or in any unit firing back-up fuel, particulate loading rises substantially and convective-pass fouling accelerates.
Cleaning implications
HRSGs that operate with regular duct-burner firing on liquid fuels usually need more aggressive sonic-horn coverage on the HRSG harps than gas-only HRSGs do.
Related terms
Related terms
- Heat Recovery Steam GeneratorAn HRSG recovers heat from a gas turbine's exhaust to generate steam, the second cycle of a combined-cycle plant. Finned-tube ash deposition and ABS fouling are the main cleaning concerns.
- Combined-cycle gas turbineA CCGT plant combines a gas turbine with a steam turbine driven by an HRSG recovering exhaust heat. Plant efficiency reaches 55–62% LHV; HRSG cleanliness is critical.
- Finned tube and harp tubeFinned tubes carry helically-wound fins to multiply gas-side surface area in HRSGs. Harp tubes are the vertical bundle configuration. Fin geometry is particularly fouling-sensitive.