ESP Seminar Raipur DT 1.2.11
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Transcript of ESP Seminar Raipur DT 1.2.11
PRESENTATION
ON
ELECTROSTATIC PRECIPITATOR
PRESENTED BY:-Sh. RAMESH BABU VSh.
B.CHAKRABORTYSh. S. NASKARMs. NIBEDITA PADHY
OUTLINE OF PRESENTATION
BASIC PRINCIPLE ,CONSTRUCTION DETAILS & OPERATING SYSTEM OF ESP
ESP PERFORMANCE & FACTORS AFFECTING THE PERFORMANCE
ESP PERFORMANCE IMPROVEMENT PLAN
NEW MEASURES/TECHNOLOGY BEING TAKEN TO REDUCE ESP EMISSION
NEED OF ESP
MECHANICAL & ELECTRICAL PROBLEMS
NEED OF ESPNEED OF ESP
ASH CONTENT IN INDIAN COAL IS HIGH (30~45)%.
20% OF ASH COLLECTED IN (BAH), REMAINING 80% IS
CARRIED ALONG WITH THE FLUE GAS.
CREATES AIR POLLUTION RESULTING IN HEALTH HAZARDS.
DUST COLLECTION IS NECESSARY THROUGH ESP IN THE
BOILER.
ESP EFFICIENCY IS OF THE ORDER OF 99.9%.
WEAR OF ID FAN BLADES ARE REDUCED DUE TO DUST
RESULTING IN REDUCED MAINTENANCE WORK IN ID FANS
BOILER CIRCUIT WITH PRECIPITATOR
ADVANTAGESADVANTAGES
• COLLECTS ALL TYPES OF DUST.
• LARGE VOLUME HANDLING CAPACITY .
• OPERATES OVER A WIDE RANGE OF INLET
CONDITIONS .
• LOW PRESSURE DROP (RARELY CROSSES 10–15mm of WC)
• LESS MAINTENANCE
ELECTROSTATIC PRECIPITATOR WORKING
PRINCIPLE
THE PRECIPITATION PROCESS INVOLVES 4 MAIN FUNCTIONS
CORONA GENERATION PARTICLE CHARGING PARTICLE COLLECTION REMOVAL OF PARTICLES
ESP - CORONA GENERATION
DUE TO THE IONISATION OF GAS MOLECULES, + VE IONS, -VE IONS AND FREE ELECTRONS ARE GENERATED.
CORONA DISCHARGE IN SPIRAL ELECTRODE
ESP - PARTICLE CHARGING
THE -VE CHARGES OF IONS AND FREE ELECTRONS TRAVEL TOWARDS +VE ELECTRODE AND THE +VE CHARGES OF IONS TRAVEL 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,
A
G
COLLECTING ELECTRODE EMITTING ELECTRODE
70 KV DC
e - A +
G -
PRINCIPLE OF PRECIPITATION
e -e -
Ge -
G -G -
G -
G -
ESP - PARTICLE COLLECTION
ESP - REMOVAL OF PARTICLE
ESP PROCESS
COLLECTING ELECTRODE,GROUNDED
RAPPING MECHANISMDISCHARGE ELECTRODE WITH-ve HIGH TENSION (20-60KV)
4
DUST LAYER
1
1.ELECTRON EMISSION
2
2.DUST PARTICLE CHARGING
3
3.MIGRATION
4.DUST COLLECTION
5
5.RAPPING
-ve
-ve
GD SCREENS
COLLECTIVE AND DISCHARGE ELECTRODES
RAPPING MOTORS
SHAFT & SUPPORT INSULATORS
HOPPER & INSULATOR HEATERS.
RECTIFORMERS.
ESP CONSTRUCTION DETAILSESP CONSTRUCTION DETAILS
UNIFORM GAS DISTRIBUTION IS
IMPORTANT FOR PROPER
FUNCTIONING OF ESP.
GAS DISTRIBUTION SCREENS AND
DEFLECTION PLATES ARE
PROVIDED TO ENSURE THIS.
ANEMOMETER READINGS ARE
TAKEN ACROSS THE CROSS
SECTION OF THE ESP DURING
COMMISSIONING & GD TEST
GAS DISTRIBUTION SCREENGAS DISTRIBUTION SCREEN
GAS FLOW
COLLECTING ELECTRODE
COLLECTING ELECTRODE
EMMITTINGELECTRODE
Flue gas flow Flue gas flow
SCHEMATIC DIAGRAM
ELECTRONICCONTROLLER
HIGH VOLTAGE RECTIFIER TRANSFORMER
415 V , 1 ØSUPPLY
ELECTROSTATIC PRECIPITATOR
EC C E C
POWER CIRCUIT
S F C O/L L
TH
RFC
E
C
HVRC
TR
RECTIFIER
SH
STAGE II SUPPORT INSULATOR
ESP ROOF TOP MANHOLE
ASH LEVEL INDICATOR (ALI)
INTEGRATED OPERATING SYSTEM
MICROPROCESSOR BASED CONTROL & MONITORING TECHNOLOGY.
FEATURES:- OPERATES THE FIELDS IN CHARGE RATIO MODE.
MINIMUM POWER CONSUMPTION WITH CHARGE RATIO OPTIMISATION.
AUTOMATIC ESP START UP AND SHUTDOWN FROM UCB.
BAPCON
INTERMITTENT CHARGING TECHNIQUE.
AUTOMATIC SELECTION OF CHARGE RATIO BASED ON V-I
CURVES.
REMOTE CONTROL FACILITY.
ANNUNCIATION OF WARNING & TRIP ALARM.
BASE CHARGE SETTING AND MEASUREMENT.
RAPCON
CONTROL & SURVEILLANCE OF OPERATION OF RAPPING MOTORS.
STARTING ,REPEAT & RUN TIME CONTROL.
COMCON
ST#I (200)
ST#II(500)
1. GAS FLOW RATE (m3/sec) 358.4 1030
2. APH OUTLET TEMPERATURE 136 ºC 140 ºC
3. I/L DUST CONCENTRATION (GM/NM3) 60.7
82.56
4. O/L DUST CONCENTRATION (MG/NM3) 300 396
5. PRECIPITATOR TYPE 2FAA -7 X 3211190-2 FAA -
6x45- 4x48125 -2
6. NO. OF PRECIPITATORS PER BOILER 1 1
7. PERFORATED GD SCREENS 2(INLET) 2/1
(IL/OL)
8. NO. OF FIELDS IN EACH GAS PASS 7 12
9.EFFICIENCY 99.49 % 99.52%
10. PRESSURE DROP (IN mmWC) 15 18
11. VELOCITY OF GAS AT ELECTRODE(m/s) 0.869 1
12. TREATMENT TIME IN SECONDS 24.975 27
13. ASH RESISTIVITY 2.5*10 @13
2.5*10 @13
ESP SPECIFICATIONSESP SPECIFICATIONS
ST# 1 ST#2
NO. OF ROWS OF COLLECTING ELECTRODES PER FIELD 38
65
NO. OF COLLECTING PLATES PER FIELD 304
390
TOTAL NUMBER OF COLLECTING PLATES PER BOILER 8512
9360
NOMINAL HEIGHT OF COLLECTING PLATES IN METERS 9
12.5
NOMINAL LENGTH OF THE COLLECTING PLATE (MM 400 750
SPECIFIC COLLECTING AREA (M2/M3/S) 166.5
167
COLLECTOR SYSTEMCOLLECTOR SYSTEM
EMITTING SYSTEMEMITTING SYSTEM
ST#1 ST#2
• TYPE OF EMITTING ELECTRODES SPIRAL
WITH HOOK
• SIZE (DIAMETER IN mm) 2.7 2.7
• NO. OF ELECTRODES IN FRAME 32
36
FORMING ONE ROW
• NO. OF ELECTRODES IN EACH FIELD 1184 1728
• TOTAL NO. OF ELECTRODES PER BOILER 33152
82944
• PLATE TO WIRE SPACING (mm) 150 150
PARAMETER VARIATION EFFECT ON ESP PERFORMANCE
SL NO
ESP PARAMETER VARIATION ESP PERFORMANCE REMARKS
1 GAS FLOW RATE
2 GAS TEMPERATURE
3 ESP I/L CONCENTRATION
4 FLY ASH RESISTIVITY
5 SULPHER IN COAL
6 MOISTURE IN GAS
7 FLY ASH ALKALI CONTENT
8 FLY ASH UNBURNT
PARAMETER VARIATION EFFECT ON ESP PERFORMANCE
SL .NO.
ESP PARAMETER VARIATION
ESP PERFORMANCE
REMARK
9 FLY ASH PARTICLE SIZE
10 GAS VELOCITY
11 ASPECT RATIO
12 TREATMENT TIME
13 GAS SNEAKAGE
14 GAS DISTRIBUTION POOR
15 REENTRAINMENT
PARAMETERS THAT CAN BE CONTROLLED DURING RUNNING
EXTERNAL FACTORS AFFECTING ESP PERFORMANCE
BOILER OVERLOAD.
IMPROPER ASH EVACUATION FROM ESP HOPPERS.
INADEQUATE MAINTENANCE/MAINTENANCE PRACTICES.
UNHEALTHINESS OF TRANSFORMER RECTIFIER UNIT.
ELECTRIC HEATERS NOT FUNCTIONING.
SUDDEN STOPPAGE OF MILLS.
MECHANICAL PROBLEMS
POOR ELECTRODE ALIGNMENT DISTORTED/SKEWED COLLECTING PLATE VIBRATING DISCHARGING ELECTRODE DAMAGED DISTRIBUTION SCREEN SHOCK BAR BENT EXCESSIVE ASH DEPOSIT ON EMITTING/COLL ELECTRODE EROSION OF GRIP COUPLING RAPPING SHAFT DAMAGE FALLING/HANGING HOPPER DEFLECTION PLATES
COLLECTING ELECTRODE DAMAGED PORTION ST-II
CRM SHAFT DAMAGED PORTION
SHOCK BAR DAMAGED
ELECTRICAL PROBLEMS
UNSTABLE ELECTRICAL CONTROLS
RAPPING MOTORS/HEATERS NOT IN SERVICE
HEAVY ARCING/SPARKING
TRANSFORMER TRIPPING
INSULATOR CRACK
DAMAGED SHAFT & SUPPORT INSULATOR
PIN BROKEN
SUPPORT INSULATOR CRACK
BACK CORONABACK CORONA
++
++
--
-
-
-
-
-
+
+
+
+
+
ASH
LAYER
INTERMITTENT CHARGING INTERMITTENT CHARGING WITH BASE CHARGING
ESP PERFORMANCE AND
IMPROVEMENT PLAN
OBJECTIVES
ESP PERFORMANCE MONITORING
ESP PERFORMANCE OPTIMISATION
ENSURE MAXIMUM FIELD AVAILABILITY
PREPARATION OF DAILY EXCEPTION REPORT & WEEKLY REVIEW
POG RECOMMENDATIONS
DURING UNIT OPERATION DURING OIL FIRING DURING OVERHAULING
ROUTINE CHECKS
MONITORING OF ESP PARAMETERS.
HEALTHINESS OF HOPPER HEATERS .
HEALTHINESS OF ASH LEVEL INDICATOR.
HEALTHINESS OF RAPPING MOTORS.
MONITORING OF ASH FLOW IN HOPPERS.
AIR INGRESS IN ESP AREAS (FLUE GAS DUCT,
APH HOPPER, ESP HOPPER AREA & ESP ITSELF)
CLEANLINESS OF ESP ROOF AND EQUIPMENTS.
DURING OIL FIRING
ONLY TWO PASS IN SERVICE THAT TOO WITHOUT CHARGE RAPPING FREQUENCY MORE
HOPPER CHOKING MONITORING HEATERS IN SERVICE
WORKS CARRIED OUT DURING UNIT O/H
MECHANICAL:
WATER WASHING
INTERNAL REPAIR
REPLACEMENT / REPAIR OF EQUIPMENTS.
REPLACEMENT & ALIGNMENT OF RAPPING SHAFTS.
INSPECTION FOR POSITION OF RAPPING HAMMER SEQUENCE .
INSPECTION OF SPRING BACK ON EMITTING ELECTRODES AND
REPLACEMENT AS PER REQUIREMENT .
ALIGNMENT OF THE ELECTRODES AND RECTIFICATION OF HITTING
POINT.
REPLACEMENT / REPAIR OF THE COLLECTING ELECTRODES AND G.D
SCREENS .
INSPECTION OF ESP CASING AND HOPPERS FOR WEAR AND PATCHING
AT
ERODED PORTION .
SERVICING OF THE RAPPING GEAR BOXES AND ALIGNMENT .
REPLACEMENT OF BROKEN SUPPORT AND SHAFT INSULATOR.
DISMANTLING OF THE FLUSHING APPARATUS AND REPAIR.
REPLACEMENT OF EXPANSION BELLOWS.
REPAIR / REPLACEMENT AND CLEARING OF NOZZLES, HOLDERS, TIPS
AS
PER REQUIREMENT .
SERVICING OF HP/LP V/VS.
WORKS CARRIED OUT DURING UNIT O/H (cont.)
ELECTRICAL:-
CLEANING/CHECKING OF SHAFT/SUPPORT INSULATOR AND HOPPER
HEATERS.
CLEANING OF HVR,EC PANELS,MOTOR & HEATER MODULES.
REPAIR OF CRM,ERM & GDRM AND REPLACEMENT OF OIL SEALS.
REPLACEMENT OF SILICA GEL IN HVR.
CHECKING /REPAIRING OF DISCONNECTING SWITCH .
ATTENDING HVR OIL LEAKAGE.
CLEANING / REPLACEMENT OF ALI PROBES AND CARDS.
MEGGERING & RESISTANCE MEASUREMENT OF ALL INSULATOR &
HOPPER
HEATERS.
RELUGGING OF ALL BURNT CABLES.
TRIAL RUN OF ALL MOTORS AND HEATERS.
AIR LOAD TEST .
WORKS CARRIED OUT DURING UNIT O/H
NEW MEASURES/TECHNOLOGIES BEING TAKEN TO REDUCE EMISSION
FLUE GAS CONDITIONING
AMMONIA DOSING SYSTEM HAS BEEN INSTALLED IN BOTH 200 MW & 500MW UNITS BEFORE ESP INLET
PERFORMANCE TEST IS CARRIED OUT BY M/S SGS (India) Pvt. Ltd- Environment services-
Kolkata ON 08.01.2008-22.01.2008.
THERE IS A HIGH COST OF INSTALLATION AND RECURRING RUNNING COST
Effect of NH3 on SPM emission in 200 MW unit
0.020.040.060.080.0
100.0120.0140.0160.0
NH3 05Kg/hr NH3 10Kg/hr NH3 15Kg/hr NH3 25Kg/hr NH3 35Kg/hr
Rate of NH3 injection
Em
issi
on
co
nce
ntr
atio
n
Emission (mg/NM3)
•The emission was less than 50 mg/Nm3 at ammonia dosage rate of 10 Kg/hr. ( I.D.Fan-A O/L- 49.80 & I.D.Fan-B O/L – 23)•The emissions were less than 100 mg/Nm3 even after 5 hours of stopping of dosing.
THE EMISSION WAS LESS THAN 100mg/Nm3 at AMMONIA
DOSAGE RATE OF 20Kg/hr .
(ID FAN –A O/L:- 62.25 & ID FAN-C O/L :- 74.81)
Effect of NH3 on SPM Emission of 500MW
117.3
68.562.8 59.0 55.7
77.5
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
NH3 12 Kg/Hr NH3 20 Kg/Hr NH3 30 Kg/Hr NH3 40 Kg/Hr NH3 50 Kg/Hr NH3 30 Kg/Hr2FO
Rate of NH3 injection
Co
nce
ntr
atio
nEmission ( mg/NM3)
GD TESTS IN UNITS
GAS DISTRIBUTION TESTS ARE BEING CONDUCTED IN ALL THE UNITS ON A REGULAR BASIS TO IMPROVE ESP EFFICIENCY
UP-GRADATION OF ESP
• TO MEET REVISED EMISSION REQUIREMENT
• TO AVOID UNFORESEEN OUTAGES
• TO OPTIMIZE INSPECTION AND MAINTENANCE
SCHEDULE
• UP-RATING / CHANGE IN PLANT CAPACITY
• CHANGE IN FUEL OR RAW MATERIAL
CHARACTERISTICS
• CHANGE IN OPERATING CONDITION OF BOILER
• CORROSION OR EROSION OF MECHANICAL
COMPONENTS
• DETERIORATION IN PERFORMANCE DUE TO AGING
UPGRADING ESP
OPTION 1 OPTION 2
ADDITION OF ESP FIELD IN EACH PASS IN PARALLEL OR IN SERIES AS PER SPACE AVAILABILITY.
OPTION 3 :
OPENING SCREEN
HIGHLY RELIABLE DISPLAYS IN %LOCAL & REMOTE OPERATIONCR MODEWARNING & TRIP ALARMS
BHEL’s Advanced Precipitator CONtroller (BAPCON)
67
VARIOUS DISPLAYS IN BAPCON
- Precipitator current 5 U.V. LimitE Precipitator voltage 6 C.R.H Sparks per minute 7 Pulse current
limitO Im limit 8 Repeat time 1 Is limit 9 Address2 S control Peak & valley
voltage3 Time control P Base charge4 Stabilization time L Base charge
current
70
ALARMS IN BAPCON
o TRIP ALARMS:
o E1 - Safety chain broken.
o E2 - Eprom faulty.
o E3 - Power supply failure.
o E4 - Over voltage
o E5 - Ash level very high (for 10 min.)
o E6 - T/R temp very high / TH. Ovld.
o E7 - Bucholtz bottom float.
o WARNING ALARMS:
o T/R temp high.
o Bucholtz top float.
o Ash level high.
o Under voltage.
PARAMETERS IN RAPCON CONTROLLED BY IOS - P.C.
RAPPING FACTOR. PROGRAM SET NO. AUTO ON/OFF. MANUAL ON/OFF. SET REAL TIME. SET RAPPING TIME. GET RAPPING TIME. RESET ALARM.
RAPCON DISPLAY
IF ALIGNMENT IS NOT PROPER, LEAD TO UNEVEN CORONA GENERATION.
CORONA DISCHARGE WILL BE CONCENTRATED IN THE AREAS WHERE THE
ELECTRODES ARE CLOSER.
THIS UNEVEN CORONA LEADS TO UNEVEN PARTICLE CHARGING AND LOSS OF
EFFICIENCY.
THE SPARK-OVER VOLTAGE DEPENDS ON THE MAXIMUM CLEARANCE BETWEEN
THE ELECTRODES IN A FIELD.
IN CASE THIS CLEARANCE IS LESS, EVEN AT ONE PLACE IN THE ENTIRE FIELD,
THEN THE ENTIRE SECTION VOLTAGE COMES DOWN AND THE EFFICIENCY
REDUCES.
ELECTRODE ALIGNMENT
THE T/R CONTROL PANELS SHOULD BE ADJUSTED TO FEED THE MAXIMUM USABLE POWER TO THE RESPECTIVE FIELDS.
THE POWER REQUIREMENT VARIES CONTINUOUSLY WITH THE CHANGE IN PROCESS PARAMETERS WHICH IS TAKEN CARE BY AUTOMATIC CONTROLS.
POWER INPUT TO ESP FIELDS
DURING RAPPING, THE FALLING OF DUST PARTICLE TAKE A TRAJECTORY FORM.
LOWER THE ASPECT RATIO, THE TRAJECTORY DUST TRAVEL ALONG WITH GAS
FLOW WITHOUT FALLING IN TO HOPPERS – LEADS TO RE-ENTRAINMENT LOSS.
HIGHER THE RATIO, PERFORMANCE WILL BE GOOD.
OPTIMUM ASPECT RATIO DEPENDS ON ALLOWABLE VELOCITY, REQUIRED
COLLECTION EFFICIENCY AND AVAILABLE SPACE.
ASPECT RATIO
Aspect ratio = Effective length of ESP Collecting electrode height
IT IS THE TIME AVAILABLE FOR CAPTURING THE DUST PARTICLE.
MORE TREATMENT TIME AT REASONABLE VELOCITY IMPROVES
THE COLLECTION EFFICIENCY.
PROBABILITY OF CAPTURING THE RE-ENTRAINED PARTICLES
IMPROVES WITH TIME.
TREATMENT TIME
Treatment time, sec = Effective length of ESP in m Flue gas velocity in m/s
EXCESSIVE SPARKING REDUCES THE OPERATING VOLTAGE, EFFECT EFFICIENCY,
THUS REDUCING LIFE OF THE ELECTRODES.
FIELD STRENGTH IS ADJUSTED IN SUCH A WAY THAT LIMITED
SPARKS TAKES PLACE.
WITH SOME SPARKS/MIN. , MORE STRONG FIELD IS OBTAINED.
IF SPARK IS TOO HIGH : FREQUENT COLLAPSE OF FIELD WILL REDUCE THE
EFFICIENCY AND INCREASE THE EROSION OF EMITTING ELECTRODE.
SPARK RATE SHOULD BE KEPT WITHIN THE DESIRABLE LIMIT BASED ON
ELECTRODE LIFE, OPERATING VOLTAGE, PARTICLE RE-ENTRAINMENT AND
EXPLOSIBILITY LIMIT OF THE PROCESS GAS. BY ADJUSTING THE T/R CONTROLS.
SPARK RATE
ESP GAS FLOW DISTRIBUTION PATTERN THROUGHOUT THE
CROSS SECTION OF THE ESP SHOULD BE UNIFORM.
IF IT IS NOT WITHIN THE SPECIFIED LIMITS, THE
EFFICIENCY WOULD BE AFFECTED.
GAS DISTRIBUTION INSIDE
IF RAPPING FREQUENCY IS TOO HIGH : NOT ALLOW THE DUST TO
DEPOSIT ON COLLECTING ELECTRODE,THUS RE ENTRAINMENT
OF THE COLLECTED DUST.
IF RAPPING FREQUENCY IS TOO LOW : 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 .
INADEQUATE RAPPING CAUSES EXCESSIVE SPARKING, REDUCES
THE POWER INPUT TO THE ESP AND REDUCES THE EFFICIENCY .
RAPPING SYSTEM
• GAS VOLUME
• PARTICLE SIZE DISTRIBUTION
• GAS TEMPERATURE
• GAS VELOCITY
• RESISTIVITY
EFFECT OF PROCESS PARAMETERS ON ESP PERFORMANCE
IN CASE OF HIGHER GAS VOLUME, WHICH MAY OCCUR
FROM A CHANGE IN FLUE IN THE BOILER, THE GAS
VELOCITY IN THE ESP EXCEEDS AND THE TREATMENT
TIME REDUCES.
THIS CAUSES PARTICLES TO ESCAPE THE ESP FIELDS
WITHOUT COLLECTION THEREBY REDUCING THE
EFFICIENCY.
LOW GAS VOLUME USUALLY DO NOT REDUCE THE
EFFICIENCY.
GAS VOLUME
DECIDED BY COAL QUALITY, THE COAL MILL SETTINGS AND
BURNER DESIGN A PRECIPITATOR COLLECTS PARTICLES MOST
EASILY WHEN THE PARTICLE SIZE IS COARSE.
THE GENERATION OF THE CHARGING CORONA IN THE INLET
FIELD MAY BE SUPPRESSED IF THE GAS STREAM HAS TOO
MANY SMALL PARTICLES (LESS THAN 1 ΜM).
VERY SMALL PARTICLES (0.2 - 0.4ΜM) ARE THE MOST
DIFFICULT TO COLLECT BECAUSE THE FUNDAMENTAL FIELD-
CHARGING MECHANISM IS OVERWHELMED BY DIFFUSION
CHARGING DUE TO RANDOM COLLISIONS WITH FREE IONS
PARTICLE SIZE DISTRIBUTION
IN CASE OF DEVIATION IN GAS TEMPERATURE FROM THE
DESIGNED VALUE, THE RESISTIVITY OF THE DUST PARTICLE
CHANGES AND IF IT EXCEEDS THE CRITICAL VALUE OF
RESISTIVITY THEN THE EFFICIENCY COMES DOWN.
IF GAS TEMPERATURE DROPS BELOW THE ACID DEW POINT
TEMPERATURE, THEN THERE IS A DANGER TO THE ESP
INTERNALS AS THEY MAY GET CORRODED
GAS TEMPERATURE
VARIATION OF ESP EMISSION W.R.T. GAS TEMPERATURE IS NOT
LINEAR.
FOR 20 DEG. C (15 %) INCREASE OF GAS TEMPERATURE,
EMISSION SHOOTS UP BY ABOUT 2 TIMES.
VELOCITY IS DECIDED BY THE GAS FLOW AND COLLECTION EFFICIENCY
REQUIRED.
THERE ARE TWO FORCES ACTING ON THE DUST PARTICLES HAVING
PERPENDICULAR
TO EACH OTHER AS SHOWN IN DIAGRAM.
HIGHER THE GAS VELOCITY, HIGHER THE
CARRYOVER OF DUST PARTICLES WITHOUT
COLLECTION –HENCE REENTERTAINMENT .
VERY POOR VELOCITY ALTERS THE FLOW
DISTRIBUTION AND EFFECTS SETTLING
OF DUST PARTICLES.
GAS VELOCITY
FO
RC
E D
UE
T
O V
EL
OC
ITY
.ELECTRIC FORCE
RESULT
ANT F
ORCE
GRAPH SHOWS THE EFFECT ON ESP EMISSION, DUE TO INCREASE OF GAS FLOW ONLY, WITHOUT CONSIDERING VARIATION IN GAS TEMP. & DUST LOAD.
VARIATION OF ESP EMISSION W.R.T. GAS FLOW IS NOT LINEAR. FOR 25 % INCREASE OF GAS FLOW, EMISSION SHOOTS UP BY
ABOUT 5 TIMES.
IT IS DEFINED AS THE ABILITY OF THE COLLECTED PARTICULATE MATTER TO ACCEPT OR RELEASE AN ELECTRIC CHARGE.
LOW RESISTIVITY : PARTICLES GIVE UP THEIR CHARGE TOO EASILY AND BECOME RE-ENTRAINED IN THE GAS
TOO HIGH RESISTIVE DUST DOES NOT READILY CHARGE& GIVE UP ITS NEGATIVE CHARGE TO COLLECTIVE ELECTRODE .
RESISTIVITY DEPENDS ON: - GAS TEMP., GAS MOISTURE,
SULPHUR CONTENT IN COAL,
ASH COMPOSITION (SiO2,
Na2O3 ,CaO etc)
CARBON CONTENT IN ASH
PARTICLE SIZE OF DUST.
LOW RESISTIVITY - 104-107 OHM-CM NORMAL RESISTIVITY - 108-1010 OHM-CM HIGH RESISTIVITY - MORE THAN 1010 OHM-CM
RESISTIVITY
RE
SIS
TIV
ITY
(oh
m-
cm
)
HOT-END ESP
ESP DESIGN CONSIDERATIONSHIGH INLET DUST REQUIRES LARGER ESP
EMISSION VS ESP EFFICIENCY FOR DIFFERENT DUST BURDEN
99.25
99.5
99.75
100
25 50 75 100 125 150
EMISSION REQUIREMENT- mg/Nm3
EFFIC
IEN
CY
REQ
UIR
EM
EN
T -
%
20g/Nm3
40 g/Nm3
60 g/Nm3
80 g/Nm3
100 g/Nm3