Glossary
Boilers
Boiler
Also known as industrial boiler, utility boiler, steam generator.
A boiler is a closed vessel in which fuel chemical energy is converted to steam by transferring heat into water flowing through tube banks. Industrial and utility boilers serve electricity generation, district heating, process steam, WtE, biomass and pulp-and-paper operations. All of them foul; the only variables are how much and with what.
Boiler families
| Type | Fuel | Notes |
|---|---|---|
| PC boiler | Pulverised coal | Dominant utility design |
| CFB boiler | Coal, biomass, RDF, lignite | Tolerates wider fuel range; lower NOx |
| BFB boiler | Biomass, sludge, low-grade fuels | Bubbling fluidised bed |
| Recovery boiler | Black liquor (kraft pulp mills) | Combines chemicals recovery with steam |
| Hog-fuel boiler | Wood waste, bark | Common at pulp mills as side boilers |
| Gas / oil boiler | Natural gas, fuel oil | Lower particulate, less fouling |
| HRSG | Gas-turbine exhaust | See heat-recovery steam generator |
Where sonic horns sit
Sonic horns installed across the convective pass — between economiser, superheaters, reheater and air heater — dislodge ash and soot continuously, supplementing or partially replacing steam sootblowers. The benefit shows up as heat rate recovery, deferred outages and longer intervals between water washes.
Related terms
Related terms
- Pulverised-coal boilerA pulverised-coal boiler grinds coal to fine powder and injects it through burners into a furnace. The dominant utility-scale boiler design worldwide.
- Circulating fluidised-bed boilerA CFB boiler burns fuel in a turbulent bed of sand, ash and limestone circulated by an upward-flowing gas stream. Tolerates coal, biomass, RDF and lignite; produces low NOx.
- Bubbling fluidised-bed boilerA BFB boiler suspends fuel in a slowly-bubbling bed of inert solids. Lower fluidisation velocity than CFB; suited to high-moisture biomass and sludges.
- Recovery boilerA recovery boiler burns kraft black liquor to generate steam, electrical power and recovered pulping chemicals. Iconic application for sonic horns on superheater cleaning.
- WaterwallWaterwalls are panels of vertical evaporator tubes welded into a gas-tight membrane that line the furnace. They absorb radiant heat and produce most of the boiler's steam.
- EconomiserAn economiser is the final tube bank in a boiler's convective pass that recovers heat from the flue gas by preheating feedwater. Ash bridging in the economiser is a routine cleaning challenge.
- SuperheaterA superheater is a tube bank that raises steam temperature beyond the saturation point using flue-gas heat. Sticky alkali ash and slag deposits are the dominant fouling concerns.
- Air heaterAn air heater (also air preheater, APH) recovers low-grade heat from flue gas to preheat combustion air. Cold-end fouling and corrosion are the dominant operational challenges.
- 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.