Electrostatic precipitators
Wet electrostatic precipitator
Also known as WESP, wet electrostatic precipitator, wet ESPs.
A wet electrostatic precipitator (WESP) is an ESP in which the collecting surfaces are continuously washed with water rather than rapped dry. WESPs are specified where the particulate is sub-micron, sticky, hygroscopic or acidic — typically downstream of FGD scrubbers, on biomass and waste-to-energy plants, in coke-oven flue paths and on certain refinery and metals off-gas streams.
Tube-type vs plate-type WESPs
Most WESPs are tube-type, with vertical cylindrical collectors and a coaxial discharge electrode in each tube. Plate-type WESPs also exist for retrofit duty into existing dry-ESP shells. Water sluicing is either continuous, intermittent flushing, or condensate-driven.
Where sonic horns help
The wash-water film usually keeps the collecting surfaces clean, but solids accumulate in the sumps and dust-handling hoppers below the WESP. Sonic horns prevent sludge bridging and pluggage in these low-level hoppers and pipework, where conventional rapping is impractical and manual cleaning is hazardous.
Related terms
Related terms
- Electrostatic precipitatorAn ESP removes particulate from flue gas by charging dust and collecting it on plate electrodes. Sonic horns are widely used to dislodge ash from plates and to keep hoppers from bridging.
- Plate-type and tube-type ESPsPlate-type ESPs use vertical parallel collecting plates with discharge wires between rows. Tube-type ESPs use cylindrical collectors with a coaxial discharge electrode, common in WESPs.
- Corona dischargeCorona discharge is the electrical breakdown around an ESP's discharge electrode that ionises gas molecules and charges dust particles for collection.
- 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.