Fouling
Sintering (of deposits)
Also known as deposit sintering, ash sintering.
Sintering, when applied to fouling deposits, is the bonding-together of particles into harder consolidated layers under sustained temperature. A fresh deposit is friable and easy to remove; an aged deposit on a hot tube surface gradually fuses into a bonded film that resists all but the most aggressive cleaning.
Why early intervention matters
The asymmetry between fresh and sintered deposit cleanability is the underlying argument for continuous acoustic cleaning. A fresh dust layer responds to a single sonic-horn pulse; the same dust two days later may resist a full steam-sootblower cycle; two weeks later only water-washing during an outage removes it.
Temperature drives sintering rate
- Below 600 °C — sintering is slow; deposits remain friable for days
- 600–800 °C — sintering accelerates; friable phase lasts hours
- Above 800 °C — sintering is rapid; partly molten components bond on contact
This temperature-driven asymmetry is why recovery boilers, WtE boilers and high-AFR cement plants — all running at the higher end of these ranges — benefit most from continuous cleaning.
Related terms
Related terms
- Fouling (general)Fouling is the accumulation of unwanted deposits on process-equipment surfaces. The general umbrella term covering slagging, scaling, coking, sintering and many other specific mechanisms.
- 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.
- Low-melt sticky ashLow-melt sticky ash forms when alkali-rich ash particles soften at typical convective-pass temperatures and bond to tube surfaces. Defeats steam sootblowers; primary target for sonic horns.
- 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.