ELECTROSTATIC PRECIPITATOR (ESP)

Prepared bys.yokesh

ELCTROSTATIC PRINCIPLE :-

An electrostatic precipitator (ESP) is an device that removes dust particles from a flowing gas (such as air) using the force of an induced electrostatic attraction (i.e, like charges repel; unlike charges attract)

Electrostatic precipitators are highly efficient filtration devices that allow the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.

COMPONENTS USED IN ELECTROSTATIC PRECIPITATOR

Electrodes

440V 50HZ 3φ AC supply

High voltage transformer

Rectifier

insulators

Hooper

20 – 80 KV dc

BASIC DIAGRAM OF AN ELECTROSTATIC PRECITATOR

440V, 50Hz

Control cabinet High voltagetransformer

Rectifier Dust gas

Clean gas

Hooper

Discharge electrode

Collectorelectrode

Control cabinet

Control cabinet is used to interconnect the 3φ ac supply and transformer through wires.

Transformer

Transformer is used to step up or step down the voltage asper the design of Electrostatic precipitator.

Rectifier

Rectifier is used to convert the given ac supply into dc supply.

Hooper

Hooper is used to store the dust particles and ash content coming out from the Electrostatic precipitator.

Electrodes : -

Based on DC current flow terminals elctrodes can be divided as below:-

Discharge electrode :-

Electrodes wire which carries negatively charged high voltage (between 20 to 80KV) act as discharge or emitting electrodes.

Collector electrode :-

Electrode wire which carries positively charged high voltage act as Collecting electrodes.

Collector electrodes

Discharge electrode

WORKING OF ELECTROSTATIC PRECIPITATOR

Several things happen very rapidly (in a matter of a millisecond) in the small areaaround the discharge electrode. Electric field is emerged due to dc terminalarrangement. The applied (-) voltage in discharge electrode is increased until it produces a corona discharge, which can be seen as a luminous blue glow aroundthe discharge Electrode.

Due to the formation of corona discharge, free electrons are emitted with high velocity from discharge electrode.

This fast moving free electrons strikes the gas molecule thus emission of free electron from gas molecules takes place.The positive ion molecule move towards discharge electrode by electrostatic attraction

As a result using gas molecule more free electrons are emitted near the discharge electrode.

Stage - 1

Stage - 2As the electrons leave the strong electrical field area around the discharge electrode, they start slowing down. This free electron again strikes the gas molecule but this time they are captured by gas molecule and became negatively charged ion.

As the gas molecule are negatively ionized they move towards the (+) electrode (i.e., collector electrode).

This negative gas ion fills the space of Dust particle and becoming negatively charged particle.

This particle are captured by collector electrode using electrostatic attraction.