Electrostatic Precipitators (ESPs) by BCE
BCE electrostatic precipitators (ESP) are air pollution control devices which remove particulates from the air by using a high-voltage electric current to impart a negative electrical charge to the dust, which is then attracted to, and deposited on, positively charged plates in the unit. Â BCE has engineered and installed electrostatic precipitators for a variety of installations and performs maintenance on existing ESPs.
The plates of ESP are cleaned by periodic or continuous rapping. Dust falls into the hopper(s) and is removed by a pneumatic conveying system. Â ESP’s are primarily used to remove fly ash in coal-fired power plants, but can be used to remove dust from any application, and have also found use in the cement, chemical and paper industries. Â Depending on the application, precipitators are designed for efficiencies between 90% and 99.9%. Increasing the power input generally increases the efficiency. Â Particles over 1 micron can be collected with high efficiency, particularly when dust resistivity is low. Â Efficiency drops off rapidly for extreme submicron particles due to Brownian motion, or random collisions of particulates with air molecules.
Dust resistivity is a major factor in collection efficiency. Â The higher the resistivity, the more difficult it is for a particle to transfer its electrical charge. When a switch to low sulfur coal was made, it was discovered that many ESP’s no longer met emissions standards to the high resistivity of low sulfur coal. Â This resulted in larger units to achieve the required efficiency. Â To reduce resistivity, conditioning agents have been added to flue gases. Â Sulfur trioxide has been used successfully with basic dusts such as fly ash and ammonia works well with acidic dusts.
Where a high efficiency can be achieved, an ESP is an attractive alternative to a fabric dust collector. Some advantages are:
- Operating temperatures up to 800°F
- No compressed air required
- Infrequent maintenance (no bags to replace)
- Lower pressure drop, therefore less power required to convey air
BCE will be happy to analyze your application with you to see whether an electrostatic precipitator in lieu of a baghouse may be advantageous.