Collection efficiency

Collection efficiency is the fraction of inlet particulate captured by an ESP, baghouse, cyclone or other particulate-control device. It is calculated as (inlet mass loading - outlet mass loading) / inlet mass loading and reported as a percentage.

Typical values

Device	Typical collection efficiency
Single cyclone separator	70-90%
Multi-cyclone	85-95%
Venturi scrubber	95-99%
Electrostatic precipitator (modern)	99.5-99.95%
Baghouse	99.9-99.99%
Wet ESP (WESP)	99.9% (especially fine PM)

How fouling erodes collection efficiency

Each device fouls in characteristic ways that degrade its collection efficiency:

ESP - back-corona, hopper bridging, re-entrainment
Baghouse - bag blinding, cake bridging, bag failures
Cyclone - wall build-up, dipleg pluggage

Sonic horns address the first three mechanisms in their respective applications.

How it is measured

Collection efficiency can be calculated from inlet and outlet particulate mass rates, from concentration and flow measurements, or from emission tests tied to a reference method. The same percentage can hide very different outlet emissions. Moving from 99.0 percent to 99.9 percent is a tenfold reduction in outlet mass, not a small rounding improvement.

Particle-size distribution matters. A collector may capture coarse particles easily while allowing fine particulate to pass. For ESPs, electrical resistivity and particle charging dominate. For baghouses, media condition, cake behaviour and leaks dominate. For cyclones, particle size, density and inlet velocity dominate.

Operational failure modes

Efficiency falls when gas bypasses the collection zone, dust is re-entrained, bags leak, ESP fields trip, hoppers overfill, flow maldistributes or cleaning systems become too aggressive. A plant may still show high theoretical efficiency while failing a stack limit if the inlet loading is high or if a small leak path bypasses the main collection mechanism.

Operators use stack particulate, opacity, pressure drop, fan power, hopper discharge, bag leak detection, ESP power input and maintenance inspections together. No single number explains the whole collection system.

Acoustic-cleaning context

Sonic horns protect collection efficiency by keeping collector internals clean and discharge paths open. In ESPs they reduce plate and electrode build-up and can lower re-entrainment peaks. In baghouses they support stable cake release and lower differential pressure. In cyclones and hoppers they reduce wall build-up and pluggage that would otherwise disturb flow or force bypass operation.

The useful project metric is not just a claimed efficiency percentage. It is a sustained reduction in outlet particulate, fewer opacity excursions, lower pressure drop, fewer manual cleanouts and stable operation at the same or higher inlet dust loading.

Field checks

Collection efficiency is only meaningful when the inlet loading, outlet loading, gas volume and test method are clear. A device can show high percentage efficiency while still emitting too much mass if the inlet dust load is very high. Conversely, a low outlet limit may require polishing performance that percentage efficiency hides. Operators therefore read efficiency alongside stack concentration, opacity, fan load, pressure drop and energy consumption.

The common failure modes are different by equipment type. A cyclone loses efficiency when velocity, inlet wear or re-entrainment changes the particle path. A baghouse loses efficiency through leaks, poor cake formation, blinding or failed bags. An ESP loses efficiency through high resistivity, poor energisation, rapping losses or gas maldistribution. Acoustic cleaning improves collection efficiency only indirectly, by preserving gas-path area, preventing deposits that upset flow, and reducing re-entrainment or pressure-drop excursions. It does not replace correct sizing, intact filter media, sound ESP electrical controls or compliant stack testing.