ESP for air pollutant removal.

1. ELECTROSTATIC
PRECIPITATOR
Krishna

2. Electrostatic precipitator (ESP)- PRINCIPLE
• An electrostatic precipitator (ESP) is a device that
removes dust particles from a flowing gas (such as air)
using force of an induced electrostatic attraction (i.e. like
charges repel; unlike charges attract)
• Electrostatic precipitators are highly efficient filtration
devices that allow flow of gases through device, and can
easily remove fine particulate matter such as dust and
smoke from air stream.

3. ESP

4. How it works !!

5. Schematic Diagram

6. Components
• Control cabinet
– Control cabinet is used to interconnect the 3φ(phase) ac supply
and transformer through cables
• Transformer
– Transformer is used to step up or step down voltage as per
design of Electrostatic precipitator.
• Rectifier
– Rectifier is used to convert ac supply into dc supply.
• Hooper
– Hooper is used to store dust particles and ash content coming
out from the Electrostatic precipitator.

7. • Electrodes : - Based on DC current
flow terminals electrodes 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 plate /
wire which carries positively charged
high voltage act as Collecting
electrodes. Collector electrodes
Discharge electrode
Collector
electrode
Discharge
electrode

8. Working Principle
The precipitation process involves 4 main functions : -
• Corona generation
• Particle charging
• Particle collection
• Removal of particles

9. • Corona generation:
 Due to ionization of gas molecules
+ve ions, -ve ions and free electrons
are generated
• Particle charging:
 The –ve charges of ions and free
electrons move towards +ve electrodes
and the +ve charges of ions move
towards –ve electrodes.
 When –ve ions travel towards +ve
electrodes, the – ve charges get
attached to the dust particles and thus
the dust particles are electrically
charged Particle charging

10. Working of ESP
• Several things happen very rapidly (in a matter of a millisecond) in
the small area around the emitting electrode. Electric field is
emerged due to dc terminal arrangement. The applied (-) voltage in
emitting electrode is increased until it produces a corona discharge,
which can be seen as a luminous blue glow around the emitting
Electrode.
• Due to the formation of corona discharge, free electrons are emitted
with high velocity from discharge electrode.
• As a result using gas molecule more free electrons are emitted near
the discharge electrode
• This negative gas ion fills the space of Dust particle and becoming
negatively charged particle.
• This particle are captured by collector electrode using

11. Factors Affecting Working Of ESP
Velocity
• Velocity is decided by the gas flow and collection
efficiency required
• Higher the velocity, higher the carryover of particles
without collection
• Very poor velocity alters the flow distribution pattern and
affects the settling of dust particles
• Optimum velocity improves the performance of the ESP

12. Aspect ratio
• During rapping, the dust particles fall in a trajectory path
• Lower the aspect ratio, the trajectory dust travel along
with gas flow does not fall into hoppers- Leads to Re-
entrainment
• Higher the ratio, better the performance
• Optimum aspect ratio depends on allowable velocity,
required collection efficiency and available space

13. Treatment time
• Time available for capturing the dust particles
• More treatment time at reasonable velocity improves the
collection efficiency
• Probability of capturing the re-entrained particles
improves with time