Glossary
Boilers
Tubular air preheater
Also known as tubular APH, TAPH.
A tubular air preheater (TAPH) is a fixed shell-and-tube air heater in which flue gas flows inside vertical tubes and combustion air flows around the outside in cross-flow or counter-flow. The construction is mechanically simpler than the rotating Ljungström design but offers less surface area per unit volume.
Where TAPHs are used
- Smaller industrial boilers
- Recovery boilers at pulp mills
- WtE and biomass duty where rotating-basket Ljungströms are vulnerable to sticky-ash agglomerates
- Some retrofit installations where the existing Ljungström has reached end of life
Fouling
Tubular APH tubes plug from the inside if flue gas carries sticky ash or ammonium bisulphate. Cleaning options:
- Steam sootblowing
- Sonic horns mounted at the tube-bundle gas inlet
- Off-line high-pressure water washing
- Manual rodding during major outages
Related terms
Related terms
- 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.
- Ljungström air preheaterA Ljungström air preheater uses a rotating matrix of heat-exchange baskets that cycle between the flue-gas and combustion-air sides. The dominant utility APH design worldwide.
- 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.