Electrostatic precipitators
Specific collection area
Also known as SCA, collecting area per gas flow.
Specific collection area (SCA) is the ratio of total collecting-electrode area to volumetric gas flow rate through an ESP. It is normally expressed in m²/(m³/s) or in ft²/1000 acfm in US practice. SCA is the single most informative sizing parameter for predicting collection efficiency.
Typical SCA ranges
| Application | Typical SCA (m²/(m³/s)) |
|---|---|
| Coal-fired utility boiler, high-sulphur fuel | 40–60 |
| Coal-fired utility boiler, low-sulphur fuel | 80–140 |
| Cement kiln ESP | 60–120 |
| WtE / biomass | 50–100 |
| Iron-ore sinter plant | 80–150 |
Higher SCA buys more efficiency for the same gas flow, but at higher capital cost.
Effective SCA and fouling
The nameplate SCA assumes clean, fully active plates. As dust builds up, the effective SCA falls because the electrical and aerodynamic performance of fouled plates is lower than that of clean plates. Keeping plates clean with sonic horns maintains the effective SCA closer to the design value, which is one of the underlying reasons acoustic cleaning extends collection efficiency over the operating cycle.
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.
- Collection efficiencyCollection efficiency is the fraction of inlet particulate captured by an ESP, baghouse or cyclone. Reported as a percentage; modern ESPs achieve 99.5%+, baghouses 99.9%+.