- Electrostatic Precipitator Definition: An electrostatic precipitator is a device that removes pollution-causing particles from a gas using an electrostatic charge.
- Types of Electrostatic Precipitators: There are two main types: dry and wet electrostatic precipitators.
- Dry Electrostatic Precipitator: Collects dry particles by charging them and trapping them on oppositely charged electrodes.
- Wet Electrostatic Precipitator: Collects wet particles by charging them and using continuously sprayed liquid collectors to form sludge.
- Applications: Used in thermal power plants and industrial settings to clean air and reduce pollution.
The two main types of electrostatic precipitator used on electrical power and other electricity plant gas streams are dry and wet. Coal power plants still use them widely, though coal is not the only fuel mix and a baghouse is another common particulate control. An Electrostatic precipitator charges particles in a flowing gas and collects them on plates. Many thermal power plant flue-gas trains include one because emission limits demand low dust, not because every jurisdiction names the ESP itself as the only legal device.
Particles in the air are charged by ionization and then made to flow between charged electrodes. The particles and electrodes have opposite charges, so the pollutant particles are attracted to the electrode plates, where they are collected. Dry units rap the plates so dust falls into a hopper. Wet units wash the collectors. Clean gas leaves the precipitator in both cases.
There are different types of electrostatic precipitators. The two below are the usual split by how the collector is cleaned:
Dry Electrostatic Precipitator
This type collects pollutants like ash or cement in a dry state. It collects dust particles from the air stream by first ionizing them to make them electrically charged. These charged particles then flow through oppositely charged electrodes, where they are collected. The dust is gathered by rapping the electrodes and collected in a hopper for extraction. Dry electrostatic precipitators are used in thermal power plants to remove fly ash from flue gases and in some ventilation systems to clean the air.
Wet Electrostatic Precipitator
Wet electrostatic precipitators remove wet particles like resin, oil, paint, tar and acid in industrial applications where there is a high risk of explosion and for particles with high resistivity or corrosiveness. In wet ESPs, particles are charged by passing through a corona, similar to dry ESPs. The main difference is in the collectors, which are continuously sprayed with liquid, usually water, forming sludge. This sludge is collected and treated separately. Wet ESPs are used for sticky, corrosive or high-resistivity particles that dry ESPs struggle to hold. The continuous or intermittent liquid washing prevents particle re-entrainment due to rapping, which can occur in dry ESPs.
