Glossary
HRSG and gas path
Cyclone separator
Also known as cyclone, cyclones, gas cyclone.
A cyclone separator removes particulate from a gas stream by centrifugal force: gas enters tangentially at the top of a vertical cylinder, spirals downward, and exits axially at the top through an inner pipe (vortex finder); heavier particles are thrown outward to the wall, slide down the conical bottom, and discharge through the dipleg below.
Where cyclones are used
- CFB boiler primary separators — large-diameter, high-temperature
- Cement preheater cyclones — multi-stage gas-to-meal heat exchange
- Pre-cleaners ahead of baghouses and ESPs — knock out coarse dust to reduce downstream load
- Process gas separation in chemical and refining duty
Cyclone fouling
- Wall build-up — dust accretes on the wall and gradually narrows the gas path; flow re-organises and efficiency drops
- Dipleg pluggage — separated material backs up in the dipleg, eventually re-entraining
- Vortex finder fouling — alters internal swirl pattern
Cleaning
Sonic horns installed on the cyclone shell or dipleg keep wall deposits from consolidating. On cement preheater cyclones particularly, sonic horns are the standard preventive against the coatings that form under alternative-fuel firing.
Related terms
Related terms
- 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.
- Cyclone diplegThe cyclone dipleg is the vertical pipe at the bottom of a cyclone separator that carries separated solids back to a hopper or recirculation circuit. Pluggage is a chronic operational issue.
- 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.
- Preheater cycloneA preheater cyclone is one stage of a cement-plant preheater tower. Lower stages (stage 4-5) suffer the worst build-up and are the primary target for sonic-horn cleaning.
- 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.