electrostatic precipitator

Thursday, June 21, 2012

Thursday, June 21, 2012 2 x 600 MW Mahan Thermal Power Project

ELECTROSTATIC PRECIPITATOR

CONTENTS

INTRODUCTION

PRECIPITATOR COMPONENTS

ARRANGEMENTS

BASIC PRINCIPLE

TECHNICAL SPECIFICATION

ERECTION SEQUENCE

INTRODUCTION We are Setting up 2x600 MW Coal Based Thermal Power Plant at Mahan Bandhaura Site.

Electrostatic Precipitator is playing a vital role in most of the industries, such as

1) Thermal Power Plant

2) Cement Plant

3) Chemicals industries

4) Steel Plant

5) Paper Industries & etc

An electrostatic precipitator is a large, industrial emission-control unit. It is designed to trap and remove dust particles from the exhaust gas stream of an industrial process.

In large power plants may actually have multiple no. of fields for each unit. In our plant, there are 9 no. of fields per unit.



MAJOR COMPONENTS OF ESP: 1) Rectifier Transformer

2) Discharge Electrodes

3) Collecting Electrodes

4) Gas Distribution Systems

5) Rapping system

6) Hopper.

About Rectifier Transformer:-

The power supply system is designed to provide high voltage to the field to increase the collection efficiency at the highest possible level

The power supply system has four basic components:

1) Step-up transformer

2) High-voltage rectifier

3) Sensing device

4) Automatic voltage control



DESCRIPTION ABOUT THE POWER SUPPLY SYSTEM

The voltage must be controlled to avoid causing sustained arcing or sparking between the electrodes and the collecting plates

Automatic voltage control varies the power to the transformer-rectifier in response to signals received from sensors in the precipitator and the transformer-rectifier itself.

AVR monitors protects the internal components from arc-over damages, and protects the transformer-rectifier and other components in the primary circuit.

Automatic voltage control would produce the maximum collecting efficiency by holding the operating voltage of the precipitator at a level just below the spark-over voltage.



Spark reaction

When the voltage applied to the field is too high, then spark over will occur.

A voltage controller will monitor the primary and secondary voltage and current of the circuit, and detect a spark over condition.

Once detected, the power applied to the field will be immediately cut off or reduced, which will stop the spark.

After a short amount of time the power will be ramped back up, and the process will start over.



Tripping

When a condition occurs that the voltage controller cannot control, often times the voltage controller will trip.

A trip means the voltage controller (by way of the contactor) will shut off the individual precipitator power circuit.

A short inside the electrostatic precipitator field caused by a fallen discharge electrode (wire), or a shorted out Silicone Controlled Rectifier are examples of

conditions that a voltage controller cannot control.





（高低压控制柜电路图1）Circuit Diagram of control cabinet 1.dwg

About Discharge Electrodes:-

Discharge electrodes emit charging current and provide voltage that generates an electrical field between the discharge electrodes and the collecting plates.

The particles then precipitate onto the collecting plates. Common types of discharge electrodes include:

1) Straight round wires 5) Rigid frames

2) Rigid spiked pipes 6) Spiral wires

3) Twisted wire pairs 7) Barbed discharge wires

4) Rigid masts



Rigid Electrode Spiral Electrode



About Collecting Electrodes:-

Collecting plates are designed to receive and retain the precipitated particles until they are intentionally removed into the hopper. Collecting plates are also part of the electrical power circuit of the precipitator.



About Gas distribution system:

Gas velocity distribution can be most effectively influenced by the use of gas distribution devices. Ideally, uniformity is desired in:

1. Gas velocity

2. Gas temperature

3. Dust loading

Gas distribution devices consist of turning vanes in the inlet ductwork and perforated gas distribution plates and in the outlet fields of the precipitator, flat distribution plate is used.



INLET GD SCREEN OUTLET GD SCREEN



Rapping System:

To improve collection efficiency and ensure proper functional use of the precipitator, a rapping system is applied to the collection and emitting electrodes to dislodge the collected dust layer.

1) Collecting Rapping System:

Collecting plate rapping must remove the bulk of the precipitated dust. The collecting plates are supported directly with hooks from the precipitator casing.

The impact of the rapping system is directed into the Shock bar located at the leading and/or trailing edge of the collecting plates.

The first electrical field generally collects about 60-80% of the inlet dust load. So the first field plates should be rapped often for the every cycle.



Collecting Rapping System



COLLECTING FRAME

COLLECTING PLATE

SHOCK BAR

Field No. Stage Efficiency % Rapping frequency, Raps/hr

1 80% 6/Hr

2 15% 4/Hr

3 3% 2/Hr

4 1.2% 1/Hr

5 0.55% 1/2Hr

6 0.11% 1/4Hr

7 0.032% 1/8Hr

8 0.007% 1/day

9 0.001% 1/2day


1) All the above data are estimated value, especial the rapping mechanism. It should be adjusted iterative according to actual working condition.

2) Each rapping time is 1.5 mins


Rapping cycle for the each field as follows:-

2) Emitting Rapping System

In general, discharge electrodes should be kept as free as possible of accumulated particulate. The rapping system for the discharge electrodes should be operated on a continuous schedule with repeat times in the 2 - 4 minute range, depending on the size and inlet particulate loading of the precipitator.



3) Rapping System for Distribution Screen

The gas distribution plates should also be kept free of excessive particulate buildup and may require rapping on a continuous base with a cycle time in the 10-20 minute range, depending on the inlet particulate loading of the precipitator and the nature of the particulate. Gas distribution plates in the outlet of the precipitator may be rapped less often (every 30 - 60 minutes).



4) Bottom Hopper

Precipitator hoppers are designed to completely discharge dust load on demand. Typically, precipitator hoppers are rectangular in cross-section with sides of at least 60-degree slope. These hoppers are insulated from the neck above the discharge flange with the insulation covering the entire hopper area. In addition, baffles are provided in the hopper to avoid the seepage.



8400mm

56

50

mm

Hopper



ARRANGEMENTS: ESP 1 PASS



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Emitting electrodes - RSB Wire Emitting electrodes - Spiral Wire

ES

P 1

ST P

AS

S

12.7m/s 12.4m/s

../ESP DETAILS.xlsx



COLLECTING & EMITTING PLATE ARRANGEMENT FOR 1ST TO 6TH FIELD.

Emitting plate – 4 layers

Collecting plate

EACH HEIGHT OF THE COLLECTING PLATE 15 M

EACH HEIGHT OF THE RSB WIRE 3.581 M

DETAILS OF COLLECTING ELECTRODE

NO. OF COLLECTING ELECTRODE IN HALF FIELD (8*43) 344 No's

NO. OF COLLECTING ELECTRODE IN ONE FIELD 688 No's

NO. OF COLLECTING ELECTRODE IN SINGLE PASS (688*9) 6192 No's

NO. OF COLLECTING ELECTRODE IN TWO PASS (6192*2) 12384 No's

400mm

200mm 200mm

ESP.dwg



COLLECTING & EMITTING PLATE ARRANGEMENT FOR 1ST TO 6TH FIELD.

DETAILS OF EMITTING ELECTRODES (RSB WIRE)

NO. OF RSB WIRE BETWEEN TWO COLLECTING ELECTRODE No's 4

NO. OF RSB WIRE IN HALF FIELD No's 1344

NO. OF RSB WIRE IN ONE FIELD No's 2688

NO. OF RSB WIRE IN SINGLE PASS FROM 1st TO 6th FIELD(2688*6) No's 16128

NO. OF RSB WIRE IN TWO PASS FROM 1st TO 6th FIELD(16128*2) No's 32256

ESP.dwg



COLLECTING & EMITTING PLATE ARRANGEMENT FOR 7TH TO 9TH FIELD

DETAILS OF EMITTING ELECTRODES (SPIRAL WIRE)

NO. OF SPIRAL BETWEEN TWO COLLECTING ELECTRODE No's 8

NO. OF SPIRAL WIRE IN HALF FIELD No's 2688

NO. OF SPIRAL WIRE IN ONE FIELD (2688*2) No's 5376

NO. OF SPIRAL WIRE IN SINGLE PASS FROM 7th TO 9th FIELD(5376*3) No's 16128

NO. OF SPIRAL WIRE IN TWO PASS FROM 7th TO 9th FIELD No's 32256

Emitting plate – 4 layers

Collecting plate

• COLLECTING PLATE SUPPORTED ARRANGEMENT



Collecting Plate

Emitting Plate

Guide Bar



COLLECTING FRAME

Collecting System



COLLECTING FRAME

COLLECTING PLATE

SHOCK BAR AVIL PLATE

RAPPER

SHAFT

Emitting System Support:



• Emitting System Support:



SUPPORT INSULATOR

HANGER BOLT

VERTICAL BOX

HORIZONTAL EMITTING FRAME

BEAM

BEAM

CHANNEL WITH INNER ROOF

TEMPORARY HANGER BOLT



SUPPORT INSULATOR AT FOUR CORNERS

SUPPORT INSULATOR AT FOUR CORNERS



VERTICAL BOX

HORIZONTAL EMITTING FRAME

EMITTING ELECTRODE (RSB

VERTICAL VIEW OF EMITTING SYSTEM SUPPORTTED

• EMITTING FRAME FOR 1ST to 6TH FIELD:



Emitting Frame

RSB Electrode

Emitting Frame

Collecting Electrode

TOP VIEW OF EMITTING FRAME



INNER WALK WAY

EMITTING FRAME

VERTICAL BOX

EMITTING FRAME FOR 7TH TO 9TH FIELD:



Emitting Frame

Spiral Electrode

Collecting Electrode



VERTICAL BOX HORIZONTAL

EMITTING FRAME

• HV inlet:



BASIC PRINCIPLES:-

Electrostatic precipitation removes particles from the exhaust gas stream by Six activities typically and they are

1) Ionization

2) Migration/Drift Velocity

3) Precipitation.

4) Charge Dissipation

5) Particle Dislodging

6) Particle Removal





Collecting electrode, grounded

Discharge electrode with Negative high tension volatge (72 KV)

4

Dust layer 1

1.Electron emission

2

2.Dust particle charging/ corona formation

5

5.Rapping

3

3.Migration

4. Precipitation

Working Principle:

The high voltage supply (72 KV) is applied to the Field, the discharge electrode emits the negatively charged ions.

Particles suspended in a gas enter the precipitator and pass through ionized zones around the high voltage discharge electrodes, the particles are get ionized with negative and positive charged ions. This is called as Corona Formation





The negatively charged gas field around each electrode charges the particles causing them to migrate to the electrodes of opposite polarity, i.e. the collecting electrodes.

The charged particles gather on the grounded collecting plates. Rappers dislodge the gathered particulate, which falls into the collection hoppers for removal.



ESP TERMINOLOGY

Terminology.doc

TECHNICAL SPECIFICATION: [General Information about ESP]



S. No Description Data

1 Manufacturer SUNYARD

2 Type and No. 2SY504-9

3 Overall dimensions (L X W X H) 73.93×53.15×33.7（m）

4 Number of ESP / Steam generator 2/1

5 Number of gas stream / ESP 2/1

6 Number of electrical fields in series in gas path / stream 9/1

7 Total active treatment length per stream (in m) 36

8 Treatment time (In sec) 40.9

9 Corona power per ESP stream (watts per 1000 m3 per min) 49

10 No. of hours ESP can run at specified gas flow and dust loading without emptying any hopper (hrs) 2

11 Total power input to the ESP per steam Generator 4400 KW

FLUE GAS:


S. NO DESCRIPTION UOM DESIGN COAL WORST COAL

FLUE GAS

1 Flue gas amount at inlet of E.S.P m3/hr 1604198 1696002

2 Flue gas temperature at inlet of E.S.P

oC 136 135

3 Excess air coefficient at inlet of E.S.P

1.34 1.333

4 Dust concentration of flue gas at inlet of E.S.P

g / Nm3 63.573 74.931

5 Dust concentration at the ESP outlet mg / Nm3 50mg/Nm3 50mg/Nm3


COLLECTING ELECTRODE SPECIFICATION




1 Type 480C

2 Material SPCC

3 Electrode thickness (mm) 1.5

4 Clear distance between collecting electrode plates(mm ) 400

5 Active length per electrode (in m) 0.48

6 Cross sectional area of each passage (in m2) 504×2

7 Active height per electrode(in m ) 15

8 Specific collection plate area (m2/m3/sec) 204.1

9 Total number of electrodes per SG 2×6192

10 Aspect ratio length / height 2.24

11 Average gas velocity in the electrical field(m/s ) 0.88

DISCHARGE ELECTRODE SPECIFICATION




1 Type I to VI field RSB,ⅤI to IX

field spiral wire.

2 Material I to VI field SPCC,ⅤI to IX

field stainless steel.

3 Total number of electrodes / SG (RSB Wire) 2 X 16128

4 Total number of electrodes / SG (Spiral Wire) 2 X 16128

5 Electrode dimension height (m) 3.581

6 Effective length of electrode(m) 15

High Voltage Conductor

7 Manufacturer SUNYARD

8 Type taper

9 Size Φ150x400（mm）

BUS SECTION SPECIFICATION




1 Total numbers 36

2 Number of bus sections in parallel in gas path 4

3 Number of sections in parallel in gas path 2

4 HT Voltage [kV (peak)] 72

5 Total power on HT electrode(kW) 4400KW

6 Number of sections lost if one transformer is out of service 1/2

COLLECTING RAPPER SPECIFICATION




1 Type Side driven, flexible arm

rapper.

2 Total no. of rapper drive 2 x 18 no’s

3 Total number of rappers per SG 2 x 774 No’s

4 Maximum number of electrodes rapped by a rapper at any one time 8

5 Percentage of plates rapped at one time ( % ) 50

6 Rapping acceleration force minimum / plate(g ) 150

7 Average input rapping power to rapping system (kW ) 13.32

8 Rapper controller type electronic program

DISCHARGE RAPPER SPECIFICATION




1 Type Top driven, flexible arm

rapper.

2 Total no. of rapper drive 2 x 18 No’s

3 Total number of rappers 1476

4 Percentage of electrodes rapped at any time ( % ) 50

5 Rapping energy of each rapper ( kgs.) 50

6 Average input power to rapping system ( kW ) 13.32

7 Rapper controller type electronic program

TRANSFORMER RECTIFIER UNIT




1 Total numbers 36

Transformer

2 Type of transformer oil immersed

3 Class of insulation F

4 Temperature rise of oil over ambient ( 0C ) ±50

5 Class of bushing 35KV

6 Rating of each set

Input power kVA 206 kVA

7 Output power kW 120 kW

8 Output Voltage KV 72 KV

9 Output current mA 2000 mA




10 Volume of oil (Liters ) 900 Liters

Rectifier

11 Type Bridge type

12 Half-wave / full wave full wave

13 Guaranteed life ( hours ) 80000 hours

Rating-each Rectifier unit

14 Number offered 36 sets

15 Type of cabinet MNS

16 Voltage for controller AC 110V

17 Arc suppression 2500V

18 Protection IP42

19 Instrumentation provided as required Volt meters, ampere

meters,

POWER CONSUMPTION OF ESP PER SG




1 Input power (kVA ) 206 kVA

2 Output power from TR sets kW 120 Kw/TR

3 Output voltage KV 72 kV

4 Output current mA 2000 mA

5 Total connected load kW 118 kW

6 Maximum power requirement kW 154 kW

7 Corona power available Watts / m2 26 Watts / m2

8 Auxiliary power kW 0.25 kW

9 Rapping system kW 0.74 kW

10 Seal air fan kW 0.01 kW

11 Seal air heaters (during start up/ normal) kW 0.05 kW

12 Hopper heaters kW 4.5 kW

ERECTION SEQUENCE



Check and set out the foundation


Check and set out the foundation



Erection of Steel Structures




Erection of pedestal



Assemble the ash Hopper



Erect the ash hopper



Erection the Ash hopper



Erect the casing

CASING STRUCTURE CASING WALL LRB TRB LRB



CHANNEL WITH INNERROOF

GABLE WALL

GABLE WALL



GABLE WALL

DISTRIBUTION SCREEN – O/L OUTLET HOOD

70

5600/6192 COLLECTING PLATES ERECTED


PASS ’A’

71



PASS ’B’

72

PASS’A’ PASS’B’





Erect the stairs and approaches

Assemble the emitting frame

Lift the collecting and emitting frame

Lift the emitting hanging beam

Check the emitting and collecting system



Install the roof

Install the pressure-bearing insulator

Assemble the inlet funnel

Assemble the outlet funnel

Install the inlet/outlet funnel

Install the heat insulation can and insulation axis



Install the HV leading-in wire

Install the top penthouse and lifting system

Install the rapping system

Install the grounding device

Install and check the electrical equipment

Install the hopper wall vibrator, ash exhaust, level indicator and electric heater.

electrostatic precipitator

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