- Electrostatic Precipitator Definition: An electrostatic precipitator is a device that removes dust particles from flue gases using a high-intensity electric field.
- Discharge Electrodes: These electrodes create an electric field to ionize dust particles, making them easier to collect.
- Collecting Electrodes: These attract and collect the ionized dust particles from the air stream.
- Transformer Rectifier Unit: This unit steps up and rectifies voltage to power the discharge electrodes.
- Hopper: A container that collects the dust particles dislodged by rapper coils from the collecting electrodes.
The main components of Electrostatic precipitators in thermal power plants and other power plants are discharge electrodes, collecting plates, a transformer-rectifier, rappers, hoppers and insulators. They use a high-intensity electric field to ionize dust in the flue-gas stream. Opposite plates collect the charged dust. Rapping or washing then drops it into the hopper.
The components in an electrostatic precipitator in the diagram match that list and show how electrostatic precipitator work on flue gas.
A basic diagram of an electrostatic precipitator shows an AC supply fed to a control cabinet. The voltage is increased using a high-voltage step-up transformer and then rectified by diodes. The DC voltage is then fed to the discharge electrodes, which ionize the flue gases. The ionized particles are attracted to the oppositely charged collector electrodes. Periodically, the collector electrodes are rapped to release the dust particles into the hopper.
The same components in an electrostatic precipitator appear in this list. Plant AC voltage follows the site; 440 V 50 Hz three-phase is one common rating, not every grid:
- Electrodes
- 440v 50hz 3 phase supply
- High voltage transformer
- Rectifier
- Hooper
- Insulators
A more detailed layout of the same parts is shown here
The sections below cover those parts in more detail:
Electrodes
Discharge Electrodes: Some designs use tubes with small-diameter wires, often steel rather than copper, hung vertically to produce corona discharge. Rigid mast and weighted-wire emitters are also common. Their main function is to generate a high-intensity electric field and ionize particles in the flue gas.
Collecting electrodes are made of sheet metal. They attract the particulate matter.
Rapper Coils
Rapper coils deliver a shearing force of high strength to dislodge the particles from the collecting electrodes. They hit the collecting electrodes at set time intervals so the dust falls into the hopper. Magnetic, pneumatic and tumbling rappers are also used.
Transformer Rectifier Unit
Transformer Rectifier Unit: High-voltage DC is needed to charge the discharge electrodes and produce the corona effect. First, the voltage is stepped up using a high voltage transformer, then the AC supply is converted into DC, which is then fed to the discharge electrodes.
Hopper
A hopper is a large pyramidal steel container that collects the particulate matter. Dust on the collecting electrodes falls into the hopper when rappers dislodge it. Rotary valves or screw conveyors then empty the hopper on a timed cycle, not only when it is packed full. Vibrators on the outer walls help the dust flow.
