Question

Draw a neat labelled diagram of Electrostatic precipitator and explain how it is useful to control gaseous particulate emissions?

Answer 1

Principle:
The collection of particles by electrostatic precipitation involves the ionization of the stream
passing though the ESP, the charging, migration, and collection of particles on oppositely
charged surfaces, and the removal of particles from the collection surfaces.
Description and Working:

• ESP is made of a rectangular or cylindrical casing. All casings provide an inlet and outlet connection for the gases, hoppers to collect the precipitated particulate and the necessary discharge electrodes and collecting surfaces.
• There is a weatherproof, gas tight enclosure over the precipitator that houses the high voltage insulators.
• ESP use electrostatic charges to separate particles from a polluted gas stream.
•  High voltage, direct current electrodes are used to establish a strong electric field.
• This field (known as a corona) delivers a (usually) negative charge to particles as they pass through the device. This charge forces the particles onto the walls of collection surfaces.
• The collection surfaces (or collection electrodes) are then rapped, vibrated, or washed with water to dislodge the particles, which fall into a hopper to be disposed.

Applications:
ESPs are applicable in cement factories, pulp and paper mills, steel plants, chemical
industries, petroleum industries, electric power industries etc. ESPs are used mainly to
remove particulate matter from gas streams but can also be used to collect and recover
valuable materials from the gas stream.