Boilers
Furnace (boiler)
Also known as boiler furnace, combustion chamber.
The furnace is the radiant combustion chamber of an industrial boiler — the space where the burner flame develops, fuel combusts, and the bulk of the heat release happens. Furnace temperatures vary by fuel and design: 1,300–1,700 °C in PC boilers, 850–900 °C in CFB, 900–1,100 °C in WtE grate boilers.
Heat transfer
Furnace heat is absorbed almost entirely by radiation onto the waterwall tubes forming the furnace enclosure. The flue gas leaves the furnace through a defined nose or screen and enters the convective pass where conductive heat transfer dominates.
Fouling at the furnace–convective interface
The transition from the radiant furnace to the convective pass — sometimes called the furnace outlet or nose — is where slag is most likely to accumulate. Hot ash particles approaching this interface lose energy fast enough to bond onto cooler tube surfaces. Sonic horns are generally not effective inside the furnace itself (molten slag is too well-bonded for acoustic energy to dislodge) but are effective immediately downstream where deposits are still partly dry. Furnace cleaning is dominated by steam sootblowers and water cannons.
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.
- 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.
- 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.
- Water cannonA water cannon projects a high-pressure water jet onto boiler waterwalls to crack slag deposits by thermal shock. The standard cleaning tool for furnace slag, with care for tube fatigue.