Glossary
Boilers
Superheater
Also known as superheaters, primary superheater, secondary superheater, finishing superheater.
A superheater is a tube bank in a boiler's convective pass that raises the steam temperature beyond its saturation point using residual heat from the flue gas. Most utility boilers have at least two superheater stages: a primary superheater (cooler gas) and a secondary or finishing superheater (closest to the furnace, hottest gas).
Fouling
- Slagging on the finishing superheater — semi-molten ash from the furnace deposits on the hottest tubes
- Bonded ash on the primary superheater — drier deposits that sinter under sustained temperature
- Sodium / potassium-rich deposits on biomass, WtE and recovery boilers — sticky, low-melting, aggressive
Cleaning
Steam sootblowers and sonic horns work together:
- Sootblowers attack hard slag on the finishing superheater
- Sonic horns (60–125 Hz) keep dry ash from consolidating on the primary superheater and convective superheater
- Infrasonic cleaners below 30 Hz are used on deep recovery-boiler superheater cavities
The combination extends the interval between major water-washes and reduces steam-attemperation requirements that mask deteriorating heat transfer.
Related terms
Related terms
- BoilerA boiler is a vessel that converts fuel chemical energy into steam by heating water. Coal-fired, biomass, oil, gas and recovery boilers all foul; sonic horns clean heat-transfer surfaces.
- Convective pass and backpassThe convective pass is the downstream section of a boiler where heat transfer is by conduction across tube banks: superheater, reheater, economiser. The primary zone for sonic-horn cleaning.
- ReheaterA reheater is a tube bank in the boiler's convective pass that re-superheats steam returning from the HP turbine before it enters the IP turbine.
- SlaggingSlagging is the deposition of molten or semi-molten ash on radiant and high-temperature surfaces in the boiler furnace. Hard, bonded; usually requires water cannons or explosive deslagging.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.
- Sonic sootblowerA sonic sootblower is a sonic horn used specifically on boiler heat-transfer surfaces. It uses low-frequency sound instead of high-pressure steam, eliminating tube erosion and steam consumption.