- Electrostatic Precipitator Definition: An electrostatic precipitator (ESP) is defined as a device that uses a high-intensity electric field to ionize dust particles in an air stream, which are then collected by oppositely charged collectors.
- High Efficiency: ESPs can remove up to 99% of dust particles, making them highly effective in cleaning air streams.
- Types of ESPs: There are dry ESPs for collecting dry pollutants and wet ESPs for removing wet particles.
- High Capital Costs: The initial cost of installing ESPs is high, which can be a barrier for small-scale industries.
- Limited to Particulate Pollutants: ESPs can only collect dry and wet particles, not gaseous pollutants, which limits their application.
Electrostatic precipitators in thermal power plants have a known set of advantages and disadvantages. An electrostatic precipitator uses a high-intensity electric field to ionize dust particles in the air, which are then collected by oppositely charged collectors (electrodes). These dust particles are periodically removed from the collector plates by rapping or by washing on wet units.
The usual advantages are high dust-collection efficiency, dry or wet particle collection and low pressure-drop running cost. The usual disadvantages are high capital cost, large footprint, limited later change of rating and no removal of true gases.
Note: ESP will mean electrostatic precipitator whenever it is used in the articles.
Advantages of Electrostatic Precipitator
• The High Efficiency of Removal of Particles/Pollutants
The efficiency of an electrostatic precipitator depends on a lot of factors like the resistivity of the particles, the corona power ratio etc. For removal of particles under normal circumstances, well-designed units often reach about 99% removal of dust particles. Collection stays high over a wide size range (∼0.05-5 μm), with a known dip for some mid-range sizes. 100% capture is not achieved.
• Collection of Dry as Well as Wet Pollutants
There are two types of electrostatic precipitators: wet and dry. Dry ESPs are used for collection of dry pollutants like ash or cement particles. Wet ESPs are used to remove wet particles like resin, oil, paint, tar, acid or other sticky or misty loads.
• Low Operating Costs
Fan energy is often lower than a baghouse because pressure drop is low. Corona power and rapping still cost money, so “low operating cost” is relative, not a free run.
Disadvantages of Electrostatic Precipitator
• High Capital Costs
Electrostatic precipitators have a high initial capital cost, which makes it prohibitive for small-scale industries. They are expensive to purchase and install.
• Requires Large Space
Besides being expensive, ESPs require a lot of space for installation. This further reduces their appeal for small-scale industries, which may not have the necessary space or funds.
• Not Flexible Once Installed
Electrostatic precipitators do not offer the flexibility of operation. Once installed, it is difficult to change the capacity of the ESP or move it to a different location. So proper planning needs to be done regarding the capacity, type and location for installing the ESP.
• They cannot be used to collect gaseous pollutants
An electrostatic precipitator can only collect dry and wet particles, not true gases. Acid mists can be collected as droplets in a wet unit, but sulphur dioxide and other gases pass through unless a separate absorber is used.
Those points decide whether an ESP belongs in a given thermal power plant flue-gas train. The initial cost is high, which can block small plants. Space and a fixed rating also have to be planned before install. ESPs collect dry and wet particles well when resistivity and corona power are in range. They do not replace a gas-absorption plant.
