Air Pollution and Control: Electrostatic Precipitator

 Electrostatic Precipitator:

     An electrostatic precipitator (ESP) is defined as a filtration device that is used to remove fine particles like smoke and fine dust from the flowing gas. It is the most commonly used device for air pollution control. They are used in industries like steel plants, and thermal energy plants.

Principle of Electrostatic Precipitator

    An electrostatic precipitator (ESP) removes particles from a gas stream by using electrical energy to charge particles either positively or negatively.

Construction of Electrostatic precipitator

    An ESP is comprised of a series of parallel, vertical metallic plates (collecting electrodes) forming lanes through which the flue gas passes. Centered between the collecting electrodes are discharge electrodes which provide the particle charging and electric field.




Working of Electrostatic precipitator

       Electrostatic precipitator is a physical process by which particles are removed from gaseous stream. The stream of gas is passed between a pair of electrodes, across which high potential difference is maintained.

   Due to high potential difference a powerful ionising field is formed. Under the action of electric field gas moves rapidly towards the collecting electrode and transfer their charge to the particles causes them to drift towards and deposit on the collecting electrode

    The particle deposited on the electrode loses their charge and then are removed mechanically by rapping or vibration to a hopper below the electrical zones and are collected for the disposal.  When the particles are liquid droplets the collected droplets coalesce on the collecting electrode and dip off the bottom of that electrode into a collecting sump.

Advantages of electrostatic precipitator:

  • The durability of the ESP is high.
  • It can be used for the collection of both dry and wet impurities.
  • It has low operating costs.
  • The collection efficiency of the device is high even for small particles.
  • It can handle large gas volumes and heavy dust loads at low pressures.

Disadvantages of electrostatic precipitator:

  • Can’t be used for gaseous emissions.
  • Space requirement is more.
  • Capital investment is high.
  • Not adaptable to change in operating conditions.

Electrostatic Precipitator Applications

  • Two-stage plate ESPs are used in the engine rooms of shipboard as the gearbox produces explosive oil mist. The collected oil is reused in a gear lubricating system.
  • Dry ESPs are used in thermal plants to clean the air in ventilation and air conditioning systems.
  • They find applications in the medical field for the removal of bacteria and fungus.
  • They are used in zirconium sand for detaching the rutile in plants.
  • They are used in metallurgical industries to clean the blast.


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