Glossary
HRSG and gas path
Cyclone dipleg
Also known as dipleg, cyclone discharge leg.
The cyclone dipleg is the vertical pipe at the bottom of a cyclone separator that carries separated solids out of the cyclone — either back into a recirculation loop (in CFB boilers and cement preheaters) or into a discharge hopper.
Pluggage problems
Dipleg pluggage is one of the most operationally disruptive failures in any cyclone system. Once the dipleg blocks:
- Separated solids back up into the cyclone cone
- Re-entrainment into the gas stream rises
- Collection efficiency collapses
- Process flow imbalance follows immediately
A single plugged dipleg can knock out an entire multi-cyclone tube or a major CFB combustor.
Cleaning
Sonic horns mounted at the dipleg keep separated material flowing. On large industrial cyclones, multiple horns are sometimes distributed along the dipleg length to address pluggage at any elevation.
Related terms
Related terms
- Cyclone separatorA cyclone separator removes particulate from a gas stream by centrifugal force. Wall build-up and re-entrainment from the dipleg are the dominant operational issues.
- Multi-cycloneA multi-cyclone is a parallel array of many small cyclones in a common housing, used as a pre-cleaner ahead of ESPs and baghouses on coal and biomass plants.
- Bridging (bulk-solids)Bridging (also arching) is the formation of a stable arch of bulk solids above the discharge outlet of a hopper or silo, stopping material flow. The universal failure mode of bulk-solids storage.
- 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.