Electrostatic Precipitator

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

ELECTROSTATIC PRECIPITATOR

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CONTENTS

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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.

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

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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

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

 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

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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

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

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 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

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COLLECTING FRAME

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.

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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.

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8400mm

56

50

Hopper

ARRANGEMENTS: ESP 1 PASS

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Emitting electrodes - RSB Wire Emitting electrodes - Spiral Wire

ESP 1

ST

P

A

SS

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COLLECTING & EMITTING PLATE ARRANGEMENT FOR 1ST _{TO 6}TH _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

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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

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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

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Collecting Plate

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Collecting System

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Emitting System Support:

• Emitting System Support:

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SUPPORT INSULATOR AT FOUR CORNERS

SUPPORT INSULATOR AT FOUR CORNERS

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• EMITTING FRAME FOR 1ST _{to 6}TH _FIELD:

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INNER WALK WAY

EMITTING FRAME VERTICAL BOX



EMITTING FRAME FOR 7

_{TO 9}

_FIELD:

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

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Emitting Frame

Spiral Electrode

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VERTICAL BOX HORIZONTAL _EMITTING

•

HV inlet:

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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

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

ELECTROSTATIC PRECIPITATOR

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

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

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 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.

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TECHNICAL SPECIFICATION: [General Information about ESP]

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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

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 o_C 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

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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}

DISCHARGE ELECTRODE SPECIFICATION

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S. No Description Data

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}

BUS SECTION SPECIFICATION

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S. No Description Data

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}

COLLECTING RAPPER SPECIFICATION

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S. No

Description

Data

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}

DISCHARGE RAPPER SPECIFICATION

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S. No Description Data

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}

TRANSFORMER RECTIFIER UNIT

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S. No Description Data

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}

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S. No Description Data

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}

POWER CONSUMPTION OF ESP PER SG

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S. No Description Data

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}

ERECTION SEQUENCE

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Check and set out the foundation

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Erection of Steel Structures

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CHANNEL WITH INNERROOF

GABLE WALL

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GABLE WALL

DISTRIBUTION SCREEN – O/L OUTLET HOOD

5600/6192 COLLECTING PLATES ERECTED

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10768/6192 COLLECTING PLATES ERECTED

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PASS’A’ PASS’B’

5961/12384 COLLECTING PLATES ERECTED

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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

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Install the pressure-bearing insulator

Assemble the inlet funnel

Assemble the outlet funnel

Install the inlet/outlet funnel Install the heat insulation can and

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system

Install the rapping system

Install the grounding device Install and check the electrical

equipment