An electrostatic precipitator (ESP) removes particulate matter from a flue-gas stream in two stages: a thin discharge electrode at high negative voltage ionises the surrounding gas (corona discharge), and free electrons attach to dust particles as they pass through, charging them. The charged particles then drift sideways across the gas flow toward grounded collection plates under the electric field, driven by:
Particle charge: q ≈ 3πε₀ d² E_c (saturation, field charging)
Drift velocity: w = q·E / (3πμd) (Stokes drag balance)
Collection (Deutsch-Anderson):
η = 1 − exp(−w·A / Q)
A = total plate area, Q = gas volumetric flow rate
Bigger particles pick up more charge (q ∝ d²) but also drag more (∝ d), so net drift velocity w still grows with size — larger dust is easier to collect, which is why very fine sub-micron particles are the hardest fraction to trap. Higher plate voltage raises the field E and the corona charge, directly raising w and efficiency. Faster gas velocity shortens the time available to migrate to the plates for a given plate length, which is captured here by the Q (flow rate) term in the exponent.
- Voltage — raises the electric field between the discharge wire and the plates, increasing both the charge particles pick up and the force pulling them sideways.
- Gas velocity — faster flow means less residence time between the plates, lowering the fraction that reaches a plate before exiting.
- Particle diameter — sets both charge (∝ d²) and drag (∝ d); the simulator recomputes drift velocity live from these two competing terms.
- Rap plates — in a real ESP the collected dust cake is periodically knocked loose by mechanical rapping and falls into a hopper; here it clears the visualised buildup and drops it as collected mass.
Real-world relevance: ESPs are the dominant particulate-control technology on coal power plants, cement kilns and industrial incinerators, routinely reaching 99%+ collection efficiency on PM at a fraction of the pressure drop of fabric filters.