SIPAT POWER PLANT ESP PRESENTATION

1. A Presentation by
SACHIN RAWAT

2. ELECTROSTATIC PRECIPITATOR WORKING PRINCIPLE
The precipitation process involves 4 main functions
 Corona generation
 Particle charging
 Particle collection
 Removal of particles

3. CORONA DISCHARGE IN SPIRAL ELECTRODE

4. ESP - PARTICLE
COLLECTION

5. ESP - REMOVAL OF
PARTICLE

6. ESP PROCESS STEPS
Discharge electrode with
Negative high tension (20-70kV)
1
1.Electron emission
2
2.Dust particle charging
Collecting
electrode,
grounded
3
4
Dust layer
3.Migration
4.dust collection 5
Rapping mechanism
5.Rapping

7.  ESP Works on five steps in the process of
Precipitation
Ionization of gasses

Charging of dust particles
Migration of particle towards Collecting Electrode
Deposition of charged particles on the Collecting Surface
Dislodging of particles from collecting surface

8.  Ionization of Gasses : CORONA Effect
1. CORONA is an electric discharge phenomenon.
2. Under the influence of high strength electric field free electrons are accelerated to terminal
velocity.
3. The rapidly moving electrons collide with the orbital electron of gas molecule and release it
from the orbit.
4. This process continues till the energy of free electrons reduces to the level that it can not
dislodge the orbital electron of gas molecule.
5. These free electrons are captured by the Dust particle and assumes -VE charge.
6. Under the influence of electric field ,these -Ve charged gas molecules move where it gives up
its charge and stick there due to intermolecular cohesive/adhesive forces.
7. More the intensity of electric field, more fast and more the no. of free electrons, accordingly
more ionisation &more efficiency of ESP.

9. Collector System:
No of Rows of Collecting electrode/field: 61
No of collecting electrode /field: 366
Total No of Collecting Plate/boiler: 14640
Collecting Plate Dimension (HXL): 13mX750mm
Emitting system:
Type & Size: Spiral with Hooks, 2.7 mm dia
No of Electrode/frame forming one row: 54
No of Electrode/field: 3240
Total No of Electrode/boiler: 129600
Plate/wire spacing: 150 mm (300 mm Pitch)

10. Ash level indicator (ALI)
 TOTAL QUANTITY: 256 Per UNIT
ALI(low) = 128nos and ALI(high) = 128nos.
ALI(low) = 3mts from hopper base.
ALI(high) = 10mts from hopper base.
 WORKING PRINCIPLE: RADIO FREQUENCY PRINCIPLE.
 COMPOENTS OF ALI:
1. ELECTRONIC UNIT (PCB – I & PCB – II CARD)
2. LEVEL SENSING PROBE

11. • FACTORS AFFECTING ESP PERFORMANCE
Resistivity of dust particles
Flue gas velocity
Particle size & field strength
Rapping frequency
Sparks rate
Hopper evacuation

12. Spark rate
 RECOMMENDED :5-10 SPM
 Field strength is adjusted in such a way that limited sparks takes place.
With some sparks/min. , we are able to create more strong field . The
outage due to spark is offset by achieving more strong electric field
with limited spark. However, if spark is too high then frequent collapse
of field will reduce the efficiency and increase the erosion of emitting
electrode.

13. Rapping is also a complex phenomenon in ESP .
If rapping frequency is too high then it will not allow the dust
to deposit on collecting electrode and hence the collection /removal
of dust will be difficult.
Similarly, if rapping frequency is too low then very thick layer of ash
will deposit on C.E. which will cause considerable voltage drop or can
cause back corona if resistivity is very high .
Frequency of Rap:
For Collector varying from 15 rap per hour at the entry field To
1 rap per hour at exit field
For Emitting Rod Approximately one drop hammer for two rows
of electrode
Frequency of Rap:

14. Flue Gas Velocity
There are two forces acting on the dust particles having
perpendicular to each other as shown in above diagram.
The first one is due to flow of gas and the second one is due to
electric force on the ionized dust particle perpendicular to the
motion of gas.
The path followed by the dust particle will be resultant of two
forces as shown above.
The efficiency of ESP decreases with increase in velocity &
decrease in voltage.
ELECTRIC FORCE
FORCE
DUE
TO
VEL.

15. Gas velocity
 velocity is decided by the gas flow and collection efficiency required
 Higher the gas velocity, higher the carryover of dust particles without
collection - Re-entertainment
 Very poor velocity alters the flow distribution and effects settling of
dust particles
 optimum velocity depends upon the application will improve the
performance.

16. Resistivity of dust particles
Resistivity of dust particles play major role in ESP performance
A too high resistive dust does not readily charge & give up its negative
charge to collective electrode whereas low resistive dust particle readily
gives up its negative charge and assumes positive charge.
Inlet flue gas temp , Sulpher content & moisture content play major role in
controlling resistivity of flue gas.
Low resistivity - 104-107 ohm-cm
Normal resistivity- 108-1010 ohm-cm
High resistivity - more than 1010 ohm-cm

17. Motor for Rapping collecting electrode:
Qty: 20 per ESP pass
Rating : geared motor 0.33 hp , 2.5 rpm, 3 phase 415 volt 50hz,ac
Location : On the side panel of the casing
Rapper size: 4.9 kg

18. Operational Problem and troubleshooting
Whenever ESP fails to achieve the desired efficiency it is imperative to
find out possible reason and taking corrective action
The Probable Reason may be associated with
Boiler overload
Excessive air leakage through ducting
Temperature of exhaust gases is very high
Inadequate maintenance
Changes in gas flow due to dust accumulation
Misalignment and wrapping of electrode
Dust deposit on electrode not being dislodged properly
Problem Includes
Wire Snapping, Ash build up in hopper, Rain water leakage, Ash disposal
system failure.

19. Trouble shooting and technique
For overcoming high resistivity maintain electrode cleanliness through
effective rapping.
The problem of wire snapping can be overcomed by aligning the emitting
electrode midway between Collector plate ie; distance between emitting
rod and collector plate 125 to 150 in 300 mm pitch
Before cleaning of ESP dust thickness to be inspected to find out any
possible Rapping system failure and realignment and rapping frequency to
be adjusted accordingly
Due care must be taken to find out any possible Ash Build up through Ash
Level Indicator

20. Gas Distribution System:
Inlet: Perforated plate (02 Nos ) at the inlet of the ESP
Outlet: Thin sheet forming U shape with 600 mm Pitch