Air Pollution Control Devices and their Functioning

At present, many cities are suffering from high levels of air pollution. The need of the hour is to make efforts to deal with it.  Major Air Pollution Control Devices are


Air Pollution Control Devices


Filters

Filters are used in electric power plants to separate particulate matter from gases. The device has a series of cloth bags through which the smoke passes. This helps in trapping the particulate matter in the bags.

Gravitational Settling Chamber

  • A gravitational settling chamber is a rectangular chamber in which several horizontal trays are fixed.
  • When the polluted gas stream enters the chamber, its velocity is kept low so that the particulates get sufficient time to settle because of gravity.
  • The high-density pollutants settle at the bottom of the chamber and are then removed.

Scrubber

  • A wet scrubber is a device which is used for trapping the emissions of water-soluble gases such as sulphur dioxide, nitrogen oxide and ammonia.
  • In a wet scrubber, spray nozzles are fitted through which water is sprayed into the device in a way that it goes downwards.
  • As polluted gases rise upwards, their particulate matter collides with water drops. Because of the gravitational force, the water drops containing particulate matter settle at the bottom and the pollutants are segregated.

Electrostatic Precipitator

  • This device is used for removing fly ash after combustion of coal or other materials.
  • After combustion of coal and other materials, polluted gas or smoke enters the electrostatic precipitator.
  • The device is electronically charged. The polluted air and impurities become negatively charged as they gain electrons on their surface.
  • Negatively charged dust particles are then drawn towards the positively charged electrode plates and are deposited there.
  • Impurities are then dislodged by mechanical rappers and get collected at the bottom of the unit in a hopper.
  • An electrostatic precipitator is a very efficient device which removes more than 99% of impurities.

Cyclone Separator

  • It is a device which is used for removing impurities and particulate matter. It works in the following ways:
  • Dust-laden air is made to enter the metallic cylinder at a high speed. It has a conical shape.
  • As the speed of the air is high, a vortex or a whirlwind mass of the air is created.
  • As a result the particulate matter falls to the bottom and the gas moves upwards.
  • The particulate matter then slides down the walls of the cylinders and gets discharged from the outlet.

Also, Read How to control Pollution?