Electrostatic precipitators
Discharge electrode
Also known as emitting electrode, corona electrode, discharge wire, rigid discharge electrode.
The discharge electrode (also called the emitting electrode) is the high-voltage element inside an electrostatic precipitator that generates the corona discharge. It is energised at 40–80 kV DC negative relative to the grounded collecting electrodes.
Geometry
Two families dominate:
- Wire electrodes — fine spiral or barbed wires, typically weighted at the bottom and suspended from a top frame. Lightweight; easy to retrofit; prone to fatigue and breakage under rapping impacts.
- Rigid discharge electrodes (RDE) — pipe or mast sections with formed spikes or points. Used in modern American-style and rigid-frame ESPs. More robust against rapper breakage but heavier.
Fouling on discharge electrodes
Just like the collecting plates, discharge electrodes accumulate dust. A thick coating on a wire or RDE reduces the local field gradient, suppresses corona, and lowers collection efficiency. The cleaning challenge is geometrically harder than for plates — discharge electrodes are point or line sources surrounded by gas. Sonic horns addressing the whole field volume help dislodge dust from discharge electrodes as well as from plates.
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.
- Collecting electrodeThe collecting electrode is the grounded plate or tube on which charged particulate accumulates inside an ESP. Dust must be released to hoppers without re-entraining into the gas stream.
- Corona dischargeCorona discharge is the electrical breakdown around an ESP's discharge electrode that ionises gas molecules and charges dust particles for collection.
- Back-coronaBack-corona is reverse ionisation through a high-resistivity dust layer on ESP collecting plates. It collapses collection efficiency and is mitigated by keeping plates clean.
- 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.