ELECTRO STATIC PRECIPITATORS & ASH DISPOSAL SYSTEM

A Dissertation Report Submitted To The

RAMAPPA ENGINEERING COLLEGE(JNT UNIVERSITY)

In partial fulfilment for the award of degree of

Bachelor of TechnologyIn

Electrical and Electronics EngineeringSubmitted By

N.VISHALA (07871A0226)PEERA TIRUPATHI (07871A0230)THUMMALA MAHENDER (07871A0243)

SHIVA KRISHNA (08875A0205)

Under the guidance of

Sri.G.Ramesh Lecturer

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Ramappa Engineering College(JNTU University)

Hunter Road, Warangal-5060012009-2010

1

RAMAPPA ENGINEERING COLLEGEWARANGAL-506001

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Certificate

Certified that the project work entitled” ELECTRO STATIC PRECIPETATORS &ASH

DISPOSAL SYSTEM” IN K.T.P.S KOTHAGUNDAM. Is a bonafied work carried out

by MS N.VISHALA in partial fulfilment for the award of degree of Bachelor of

Technology in Electrical and Electronics Engineering of the Jawaharlal Nehru

Technological University, Hyderabad during the year 2009- 2010. It is certified that all

corrections/suggestions indicated for internal assessment have been incorporated in the

report deposited in the library. The project report has been approved as it satisfies the

academic requirements in respect of project work prescribed for the Bachelor of

Technology Degree.

S.No Name of the students Roll No

1 N.VISHALA 07871A02262 PERA.TIRUPATHI 07871A02303 THUMMALA MAHENDER YADAV 07871A02434 SHIVA KRISHNA 08875A0205

Internal Guide HOD of EEE

Sri.G.Ramesh K.Ram Mohan Reddy

Lecturer Assoc. Professor.

Dr. V.JANAKI

2

Principal

Andhra Pradesh Power Generation Corporation Limited

This is to certify that B.Tech Third Year students of Department of Electrical

&Electronics Engineering “RAMAPPA ENGINEERING COLLEGE (JNT

UNIVERSITY)”

HUNTER ROAD, WARANGAL (Dist) have done their mini project on “ELECTRO

STATIC PRECIPITATORS & ASH DISPOSAL SYSTEM” with a specific view on

K.T.P.S- ‘C’ Station at Electrical Maintenance Division ,K.T.P.S –‘C’ station, polancha

during the academic year 2009-2010 Period From 21-6-2010 To 5-7-2010

S.No Name of the students Roll No

1 N.VISHALA 07871A0226

2 PERA.TIRUPATHI 07871A0230

3 THUMMALA MAHENDER 07871A0243

4 SHIVA KRISHNA 08875A0205

External Guide

(Sri.T.Ramakrishna) (Sri.G.Ramesh)

M.tech D.EEE

Assistant Divisional Engineer Additional Assistant Engineer

Electrical Maintenance II Electrical Maintenance II

K.T.P.S.” C”- Station K.T.P.S.” C”- Station

Polancha Polancha

Khammam (Dist) - 507115 Khammam (Dist)- 507115

3

ACKNOWLEDGEMENT

We acknowledge with heart felt thanks and gratitude to the several gentle men who have

given their valuable time for completion of our project.

We acknowledge our sincere gratitude to Sri G.Ramesh. D.EEE (Additional Assistant

Engineer) for providing the opportunity to work in Electrical Maintenance Department

KTPS Paloncha and giving us a rich experience in completing the project.

We extend our sincere thanks to Our Project guide Sri.T.Rama Krishna (Assistant

Divisional Engineer)

We sincerely express our gratitude and respect to all those who guided, inspired and

helped in the completion of the project. We are grateful to them who are generous and

cooperative during our project.

S.No Name of the students Roll No

1 N.VISHALA 07871A0226

2 PERA.TIRUPATHI 07871A0230

3 THUMMALA MAHENDER YADAV 07871A0243

4 SHIVA KRISHNA 08875A0205

4

ABSTRACT

The protection of the environment is becoming one of the preoccupations in our

country, especially with rapid growth of industries. The major impact of

industrialization is pollution.

Air pollution has become one of the serious problems and must be tackled at its

source .Thermal power plants have been identified as one of the major sources of

atmospheric pollution .of these particulate matter has received greater attention

and electro static precipitators have been acknowledged as one of the effective

means of particulate control in the world.

The basic purpose of this project of this project is to present a discussion on the

electrostatic precipitators to control particulate matter and about the BAPCON for

electrostatic precipitators and ash disposal system in K.T.P.S –“C” station.

This project also provides a discussion on the procurement methods for

precipitators for high efficiency control of ash emission under today’s complex

conditions .This is anticipated because of increasing dependence on coal for

power generation and stringent environmental requirements mandated by air

pollution act.

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DECLARATION

We are here by declaring that the project work entitled” “ELECTRO

STATIC PRECIPITATORS & ASH & DISPOSAL SYSTEM” is carried out

by us independently at “K.T.P.S Limited, Kothagudam (Polancha)”. Under

the able guidance of Mr.Sri.S.Ramesh .D.EEE, K.T.P.S and Department

of Electrical &Electronics Engineering, Ramappa Engineering, Warangal.

In partial fulfilment of the requirement for the award of the

degree of Bachelor of Technology in Electrical &Electronics Engineering

by Jawaharlal Nehru Technological University, Hyderabad.

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CONTENTS:-

1. INTRODUCTION 1

2. PROFILE OF ORGANIZATION 3

3. ELECTROSTATIC PRECIPITATOR 6

3.1 Principle of ESP 7

3.2 Parts of ESP 8

3.3 Material of construction of inner parts of ESP 9

3.4 Technical data 17

3.5 Variable parameters influencing the collecting efficiency of ESP 28

4 BHEL’S ADVANCED PRECIPITATOR CONTROLLER 32

4.1 Introduction 32

4.2 Features of BAPCON 32

4.3 Operation 33

4.4 SPARK rate 34

4.5 INTERMITTENT CHARGING 34

4.6 Charge Ratio Optimization 35

4.7 BASE Charging 36

4.8 Functional Displays and Settings 36

4.9 Technical Data 38

7

4.10 Alarm codes 39

4.11 BAPCON General scheme

5. ASH HANDLING PLANT 40

5.1 FLY ASH SYSTEM 45

5.2 ASH DISPOSAL SYSTEM 48

5.3 ASH DISPOSAL SYSTEM 51

6. CONCLUSION 60

6.1 PROTECTIONS 63

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INTRODUCTION

The atmosphere at industrial locations where large size coal fired boilers are used

contains high volume of dust, which besides impairing functional efficiency of

mechanical and electrical equipment, posses a health hazard. The dust ensuing out from

exhaust of these plants can most effectively be prevented from entering atmosphere by

employing electrostatic precipitator technique.

Rapid growth of power industry and the need for increasing power generation efficiency

have brought in their wake severe and complex particulate problems. One of the major

impacts of industrialization is pollution. Thermal power stations have been identified as

major sources of atmospheric pollution. The significant pollutants in the effluents from

boiler are

Particular matter

Sulphur oxides

Nitrogen oxides

Of this particulate matter has received greater attention in view of the growing numbers of coal fired power stations. Many types of collectors have been developed, out of the different types available; ESP’s are effective means for particulate control in the world.

The coal available for generation in India is one of high ash, low-sulphur content –type

and most of the fly ash is in the highresistivity region for the normal operating conditions

of precipitator’s .Added to this, the silica content in the ash is unduly high.

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This problem can be more easily understood by considering a 2000MW coal fired

thermal power plant. Requirement of coal for generation of 2000MW would be 20000

tones per day. Without any control mechanism, ash emission would be 6400 tones, for

coals with 40% fly ash and 20% collection as bottom ash. With 99.5% designed

electrostatic precipitators, the emission will be limited to less than 32 tones (less than 150

milligrams/Nm3).

With more stringent emission standards and norms stated as averages over a month, R&D

work on air pollution control equipment must be concentrated on improving precipitation

efficiency and utilization of the equipment. In view of rising cost of power production

power saving must also emphasize.

The technology and equipment used to meet current demands on environmental

protection related to use of fossil fuels and production of pulp, cement, chemical

substances etc, are

Electrostatic precipitators and fabric filters –for particulate matter

Scrubber systems- for oxides

Catalytic systems and primary combustion modifications –for oxides

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PROFILES OF THE ORGANISATION KOTHAGUDAM THERMAL

POWER POWER STATION

Kothagudam thermal power station, K.T.P.S. occupies a place of pride in the thermal

power station to set up in Andhra Pradesh State Electricity Board.

OBJECTIVES:

One of the important objectives of K.T.P.S. is to generate maximum thermal power

effectively and economically .It is also fulfilling the role of social responsibility objective

by employment to the people of the background and tribal areas. It has cores of rupees

controlling pollution by installing electrostatic precipitators.

LOCATIONS:

The actual site of the station is near Palavancha village, which is about

12 K.m .From the colliery town Kothagundam .The site of power station is Only about

3K.M the main road Bhadrachalam road. The project

Authorities to connect the main road with the power station have constructed feeder road.

RAIL HEAD:

K.T.P.S. is located about 12 K.M. from the near rail head at Bhadrachalam road Railway

Station, which is the terminus for the broad gauge branch line tacking off from Dornakal

on the South Central Railway.

EXTEND OF LAND:

In site of the power station and its apartment structures as well as the administration buildings and residential colonies are located.

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ASH POND:

The site of the power station has a low lying area to the north of it, where ash

pond is formed. The crusted ash dust is hydraulically disposed off in to the ash

pond.

WATER RESOURCES:

Water is one of the basic raw materials in the production of power in a thermal

power station .It is essential that the supply of water should be available at all

times with complete reliability . The total water requirements for the statins 1,

50,000 tones per day .The water supply for the power station is drawn from the

reservoir built across Kinnerasani River at a distance of 10 K.M from the power

station is through open concrete lined channel and the flow is by gravity. The

carrying of channel is 110 cases (4 cubic meters second).The Kinnerasani is one

of the principal tributes at the mighty rivers Godavari flowing on its right side in

Warangal and Khammam districts at AP.

OIL SUPPLIES:

This was constructed in two stages .This first two 60MW sets, in the first stage

were commissioned on 4-8-1996 respectively. The third and fourth units of

60MW each under stage two were commissioned on 27-05-1967 and 3-07-1967.

Three units were supplied and erected by M?S. I.H.I and M/S. HITACHI

LIMITED, JAPAN. The outdoor switch gear consisting of 33kv, 132kv and 12Kv

were supplied and erected by M/S. Brown BROVERY LIMITED,

SWITZERLAND. M/S. EW-BANK and partners London consulting engineers

finalized the plant layout specifications.

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World Bank financed the project. The total cost of the project has worked out to

Rs.40 Crores, includes Kinnerasani project works and railway siding. The

performance of the units has been good. At present the units are generating

55MWs each.

Initially when the units were commissioned only mechanical dust collectors were

provided for the collection of fly ash, there by the dust omission through

chimneys was high .Recently as a pollution control measures and to improve the

performance of the units. Electrostatic precipitators were erected and

commissioned for the collection of fly ash.

K.T.P.S.’c’ (UNIT VII &VIII):

Under stage 4 installed capacity of 2*110MW units are located at the adjacent B-

section. The two units were commissioned on 21-05-1977 & 10-02-1978

respectively. The expenditure on the project was RS.77.77 cores .These are the

second generation units of M/S .B.H.E.L.

The boilers are designed in collaboration with combustion engineering U.S.A.

who is one of the leading manufactures in the world.

After running for 5-years, it becomes necessary to replace air preheated and carry

out modifications to super heater. It is proposed to replace the instrumentation

with improved design instruments, work is in progress.

13

ELECTROSTATIC PRECIPITATORS

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Principle of ESP:

In the electrostatic precipitator the particles are removed from the gas stream by

utilizing electrical force .A charged particle in the electrical field experiences a force

proportional to the size of the charge and to the strength.

The precipitation process therefore requires.

A method of charging the particles electrically.

A means of establishing an electrical field and

A method of removing the collected particles.

An industrial ESP includes a large number of discharge electrodes. Pirated

wires and rows of collecting electrodes plates forming passage through which the gas

flows with velocity.

High voltage is applied to the discharge electrodes resulting in the high electric field

near the wire and an associated corona producing gas ions .The ions collide with and held

by ,the dust particles and this in turn become electrically charged the particles moved

towards the grounded collecting electrode plates from which the accumulated dust is

dislodged by rapping the dust falls to the bottom of the precipitator casing from which it

is removed by different methods.

15

Parts of the Precipitators:

The various parts of the precipitators are divided to two groups. Mechanical system

comprising of casing, hoppers, gas distribution system, collecting and emitting system,

rapping mechanisms, stair ways and galleries.

Electrical system comprising of transformer-rectifier units, electronic controllers

auxiliary control panels, safety interlocks and field devices.

16

Fig. Electrostatic precipitator

1).MECHANICAL SYSTEM:

A) Precipitator casing:

The precipitator casing is an all welded construction, consisting of prefabricated wall and the roof panels. The casing is provided with inspection doors for entry into the chamber. The doors are of heavy construction with machined surfaces to ensure a gas tight seal.

The roof carries the precipitator internals, insulator housing, transformers etc.The casing rests on supports, which allow for free thermal expansion of the casing during

17

Opertion.Galleries and stairways are provided on the sides of the casing for easy access to rapping moters, inspection doors, transformers.

b) Hoppers:

The hoppers are adequately sized to hold the ash, Baffle plates are provided in each

hopper to avoid gas sneak age. An inspection door is provided on each hopper.

Thermostatically controlled heating elements are arranged at the bottom portion to the

hopper to ensure free flow of ash. The precipitator casing is an all welded construction,

consisting of prefabricated

c) Gas distribution systems:

The performance of the precipitator depends on even distribution of gas over the entire

cross section of the field. Guide vanes, splitters and screens and screens are provided in

the inlet funnel to direct the flue gas evenly over the entire cross section of the ESP.

d) Collecting Electrode System:

The collecting plates are made of 1.5mm cold rolled milled steel plate and shaped in one

piece by roll forming .The collecting electrode has unique profile designed to give

rigidity and to contain the dust in a quiescent zone free from re-entrainment .The 400mm

collecting plates are provided with hooks to their top edge for suspension .The hooks

engage the slots of the supporting angles 750mm collecting plates in a row are held in

position by a shock bar at the bottom. The shock bars are spaced by guides.

e) Emitting Electrode System:

The most essential part of the precipitator is emitting electrode system.4 insulators

support this. The frames for holding the emitting electrodes are located centrally between

collecting electrode curtains. The entire discharge frames are welded to form rigid bars

18

Fig: ESP block Diagram

19

.

f) Rapping Systems:

Rapping systems are provided for collecting and emitting electrodes. Geared motors drive

these rappers. The rapping system employs tumbling hammers, which are mounted on the

horizontal shaft. As the shaft rotates slowly the hammers tumble on the shaft will clean

the entire field. The rapper programmer decides the rapping frequency. The tumbling

hammers disposition and the periodicity of rapping are selected in such a way that less

than 2% of the collecting area is rapped at any instant. This avoids re-entrainment of dust

and puffling at the stack. The rapping shaft from the gear motor drive by a shaft insulator.

The space around the shaft insulator is continuously heated to avoid condensation.

g)Insulator Housing:

The support insulators, supporting the emitting electrodes housed in insulator housings.

The HVDC connection is taken through a bushing insulator mounted on the insulator

housing wall.

In order to avoid the condensation on the support insulators, each insulator is provided

with one electrical heating element. Heating elements of one pass are controlled by one

thermostat.

20

Fig: Mecanical overview of ESP

2) ELECTRICAL SYSTEM:

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a) High Voltage Transformer Rectifier (H.V.R) with electronic controller(E.C)

The transformer rectifier supplies the power for particulate charging and collection. The

basic function of the E.C is to feed precipitator with maximum power input under

constant current regulation.So,thereby any flash over between collecting and emitting

electrodes, the E.C will sense the flash over and quickly react by bringing the input

voltage ton zero and blocking it for a specific period. After the ionized gases are cleared

and the dielectric strength restored, the control will quickly bring back the power to the

present value and raise it to the original non-sparking level. Thus the E.C ensures

adequate power input to the precipitator while reckoning the electrical disturbances

within the precipitator. Regulated ac power from E.C is fed to the primary of the

transformer, which is stepped up and rectified to give a full wave power output. The

transformer rectifier is mounted on the roof of the precipitator while the E.C is located in

an air-conditioned control room.

b) Auxiliary control panel (A.C.P)

The A.C.P controls the power supply to the EP auxiliary i.e. rapping motors and

heating element dampers etc.The complete A.C.P. is of modular type with individual

modules for each feeder. Each module houses the power and control circuits with meters,

push buttons, switches and indicating lamps.

Following are the modules for the outgoing feeders

Hopper heaters for each field

Support insulator heaters

Shaft insulator heaters

collecting electrode rapping motor for each field

Emitting electrode rapping for each field

22

The program control circuit for the sequence and timing of operation for rapping motors

is included in the A.C.P.

For continuous operation of the rapping motors, the programmer can be bypassed

through a switch. Thermal overload relay is provided for overload protection to the

rapping motors. Local push buttons are available for tripping the motors to meet the

exigencies and for maintenance purposes.

Ammeters with selector switches to indicate line currents of motors and heating element

feeders are provided. Indicating lamps are provided “main supply on”, “overload trip”,

“local push button activated”, “space meter on”, and “control supply on”.

Potential free contacts are provided for remote indication for rapping motor trip due to

overload.

c) Safety Interlock:

A safety interlock system is incorporated to prevent accidental contact with live parts of

the precipitator and enable energisation only when the ESP is boxed up. The interlock

system covers all the inspection doors of casing, insulator housing and disconnecting

switches.

Warning: familiarity with this system may femon the operating personnel bypass the

interlock. As this would defend the very purpose of the interlocking system, such a

temptation should be resisted and the sequence of operation at every stage should be

systematically followed.

d) Disconnecting switch:

Each field is provided with one disconnecting switch for isolation of emitting system

from the associated transformer .In the on position the emitting system is connected to

the transformer and in the OFF position it is grounded.

23

Fig: BLOCK DIAGRAM OF ELECTROSTATIC PRECIPITATOR

24

O&M MANUAL INPUT (CONTROL)

TECHNICAL DATA

I. DESIGN CONDITIONS

a) Gas flow rate : 1 95 m3/sec

b) Temperature : 1500C

c) Inlet dust concentration : 85 gm/Nm3

d) Outlet dust concentration (at new ESP outlet) : 115mg/Nm3

e) FSP efficiency : 99.865

2. TYPE OF PRECIPITATOR (NEW ESP):2XFAA-2X45-11290-2

(Installed in series with existing ESP)

NUMBER OF PRECIPITATORS OFFERED PER UNIT : 2

NUMBER OF GAS PATHS PER ESP : 1

NUMBER OF FIELDS IN SERIES IN EACH GAS PATH : 2

PRESSURE DROP ACROSS THE PRECIPITATOR : 20MM

OF WATER COLUM

VELOCITY OF GAS INSIDE ESP : 0.96M/Sec

TREATMENT TIME : 9.30 Sec

25

3. COLLECTING ELECTRODES

a) No. of collecting electrodes per field : 29

b) No. of collecting electrodes : 174

c) No. of collecting electrodes arranged in each row per field : 6

d) Total No. of collecting plates per boiler : 696

e) Nominal height of collecting plate : 9 mts

f) Nominal length of collecting plate : 750 mm

g) Specific collecting area : 46.52 m2/m2/sec.

26

Fig: WET-ESP

27

4. EMITTING ELECTRODES

a) Type : spiral with hooks

b) Size 2.7 mm di

c) No. of electrodes in the frame forming one row : 36

d) No. of electrodes in each field : 1008

e) No. of electrodes per boiler : 4032

f) Total length of electrodes per field : 5655 mts.

g) Plate/ wire spacing : 200 mm

5. RAPPERS FOR COLLECTING ELECTRODES

a) No. and type of rappers : one drop hammer per row

Collecting electrode having

a collecting surface of 8 1

m2.

b) Rapper size : 4.9 kgs

c) Frequency of rapping : varying from 2 raps per

Hour at the inlet of I rap per

Hour at the exit field. The

Frequency o1 rapping at

Intermediate fields can h

28

Adjusted between 2 & I per

Hour according to

Requirement.

d) Drive : geared electronic motor

C) Location : at the bottom of collecting

Electrodes.

6. RAPPERS FOR EMITTING ELECTRODES

a) No. and type of rappers : approx. 1 drop hammers for

2 rows of electrodes.

b) Rapper size : 3 kgs

c) Frequency of rapping : 10 raps per hour

d) Drive : geared electronic motor

e) Location : on middle frames of

Emitting system frame work.

7. HOPPERS

a) Type : pyramidal

b) No. of hoppers : 4

c) Heating : electrical heating provided

At the bottom of hoppers.

29

d) Baffling arrangement : 2 sets of deflector plates

For each hopper across the

Gas flow direction

Underneath h the collecting

Plates 10 prevent gas

Sneak age.

30

Fig: Fundamental fig of ESP

31

8. GAS DISTRIBUTION SYSTEM

1) INLET:

a) Type and quality : perforated plate 2 sets

b) Location : inlet of precipitator

2) OUTLET:

a) Type and quantity : thin sheets formed to a

Shape out U located with 600

Mm pitch-I set.

b) Location : outlet of the precipitator

9. ELECTRICAL ITEMS

1) I-IV RECTIFIER (BY BHEL BHOPAL)

a) Rating : 80 kV DC (peak), 600 mA

DC (mean)

b) Quantity/ESP : 2

c) Type : silicon diode, full wave

Bridge connection

d) Location : mounted on the top of ESP

2) ELECTRONIC CONTROLLER:

a) Type of control : thyristors.

32

b) Quantity /ESP : 2

c) Location : In the control room t the Ground

Level

3) ESPSG CONTROL PANEL:

a) Quantity per boiler : 1

b) Equipment controlled : Geared motor of rapping

Mechanisms of collecting and

emitting electrodes, heating elements

on hoppers, insulator housing and

shaft insulators.

c) Location : In the control room atground level.

4) RAPPING MOTORS:

RAPPING OF EMITTING ELECTRODES:

a) quantity/ESP : 2

b) Rating : Geared motor: 0.33 Hp, 2.5

Rpm, 3phase, 41 5V, 50Hz.

c) Location : At the ESP roof.

RAPPING OF COLLECTING ELECTRODES:

a) quantity/ESP : 2

b) Rating : Geared motor: 0.33 Hp, 2.5

33

Rpm, 3phase. 415V. 50Hz.

c) Location : on the side panels of the

Casing

RAPPING OF GAS DISTRIBUTION SYSTEM:

a) Quantity per boiler : not applicable

b) Rating : Geared motor: 0.33 Hp, 2.5

Rpm. 3phas. 15V, 50Hz, AC.

c) Location : On the housing.

HEATING ELEMENTS:

FOR HOPPER:

a) Quantity per ESP : 48

b) Rating : 0.5KW, 1phase. 415V,

50Hz, AC

c) Location : At the bottom of hoppers.

FOR SHAFT INSULATOR:

a) Quantity per ESP : 2

b) Rating : 1KW, 1phase, 415V, 50Hz,

AC.

c) Location : In the shaft insulator housing.

34

FOR SUPPORT INSULATORS:

a) Quantity per ESP : 8

b) Rating : I KW, 1 Phase, 415V, 50Hz.

c) Location : support insulator housing

GENERAL ARRANGEMENT DRG. NO: 0-00-1 1 1-2645.

Fig: CONVENTIONAL ELECTRO STATIC PRECIPITATORS

35

VARIABLE PARAMETERS INFLUENCING THE

COLLECTING EFFICIENCY OF ESP.

Gas Temperature: Low temperature increases the efficiency but the

Chances of corrosion due to condensation are severe. Increase in gas

Temperature decrease the dielectric strength and indirectly effects the

Possible power input to avoid flashover. If the temperature is mole than

220°C the porcelain bushings of the hi—tension are liable to get damaged a

Temperature f 1 500 C is ideal for optimum.

Gas composition:

Different gases have different mobile forces in an electric field. Water

vapor ions hove low value and increase the electric strength .SO2 and

ammonium posse’s similar property.

In the recovery boiler where the semi concentrated black liquor

undergoes evaporation 1i the secondary evaporator for increasing the

firing solids, water vapor is carried along with flue to SP .but there

alimentation in the water vapor depending up on the designed inlet in

solid black liquor to the secondary evaporator.

Dust bridges and resistivity:

During the process of transportation and removal dust the pathway

of electrical charges. Dust layers tend to accumulate in collecting plates

due to agglomeration there is resistance across and the result is flush over.

36

This phenomenon is known as ‘back corona”. Increasing the temperature of the gas as

already stated could reduce the dust resistively there is a limitation in the temperature.

GENERAL SPECIFICATIONS

1.0 INPUT:

1.1 Voltage : 41 5V, 50Hz, 1 phase.

1 .2 Variations : +/- 10% in voltage, +/- 5% m frequency.

2.0 OUTPUT:

2. 1 Wave form of output \voltage: full wave.

2.2 Load: Electrostatic precipitator

Fig: performance Data

37

3.0 General

3.1 Design form [actor: 1.4

3.2 Relative humidity: 100% temp 50°c.

3.3 HV Bushings as per attached to GA Drg.

3.4 Flange Dimensions & Details for HT Bus Duct; as per general arrangement

3.5 method of cooling

3.5.1 Control cubicle: Natural air cooling

3.5.2 Transformer rectifier set oil natural conversion cooling

3.6 Duty: Continuous operation (24hr a day)

3.7 Installation:

3.7. 1 Control cubicle: Indoor pressurized room or A/C’ room.

3.7.2 Trasformer Rectifier Set Outdoors.

38

4.0 MAJOR OPERATION:

HV DC Current maintained constant.

5.0 FEEDBACKS FOR OPERATION:

5.1 HV DC Voltage feed back for under voltage. Over voltage sensing and indication.

5.2 HV DC Current Feed Back for current Limit. Spark and Are Sensing and

measurement.

39

BHEL ADVANCED PRECIPITATOR CONTROLLER:

INTRODUCTION

It is designed specially for electrostatic precipitators, is one of the most sophisticated

power controllers available today.

The controller utilizes 8085(Intel) family of microprocessor components support

hardware. These components and support hardware have a proven reliability in control

instrumentation in industrial and utility application and environment.

Field programmability of operating perimeters an extremely high degree of

flexibility. The control automatically selects and optimizes precipitator electrical

operation based on field.

FEAIURES OF BAPCON:

Effective spark rate control

Detection of spark/are by di/dt or dv/dt

Automatic current control based on step & ramp control settings.

Intermittent charging technique.

Measurement of peak, mean and valley of secondary vo1ige.

Base charge setting and measurement

Automatic selection of charge ratio based on V-I characteristics of the ES P.

Annunciation of warning and trip alarms.

Facility of REMOTE control through +1- 10 mA balanced current loop.

40

The prime objective of BAPCON is to automatically provide optimum precipitator power

at all times. The objective is accomplished in the following ways.

Utilization of state of the art microprocessor technology. Components, hardware

and software.

Software developed specifically for precipitator operation based on I3HELs

experience in precipitators for two decades.

Ability to tailor the electrical operation based on the transformer- rectifier to

actual, real time precipitator operating conditions.

Fast response to sparks.

Separate control strategy [or operation under severe hack corona conditions.

BAPCON OPERATION:

The ESP is predominantly not a constant load to thyristor control panel. The

electrical field between the electrodes and there by the PSP current and voltages are

influenced by the gas composition, temperature and by the electrical properties of the

dust, on the contrary a voltage will give a low precipitator.

Bapcon controls the precipitator power by changing ignition angle of the thirstier. LSP

current voltage and zero crossing point of the primary voltage are used as I/p data. On

switching “on” the T/R set, the BAPCON slowly increases the filter current towards the

set current limit. The T/O action overrides start up time slightly at start. When a spark

occurs the set current is reduced to zero and thyristors are blocked for 20 mS after restart,

of the thyristors, the current quickly increases to a value, which is slightly lower than the

current at which the spark occurred. This current decrease is called STEP. After that, the

current will rise slowly as per the setting T control. The values of S-control and T-control

will decide the spark rate.

41

SPARK RATE:

The spark rate determined by the S-control and T-Control. Suppose T control is set at

20%which corresponds to 2 minutes, the tine required by the rectifier to reach the rated

current after a spark, from zero current will be two minutes. BAPCON will however

increase the current very fast upto control level; thereafter will follow T-control. Suppose

S-control is set 5%of the rated current, the time from S-control break point to next spark

will then be 5% of the T-control time(5% of 2 minutes),that is 6 sec.if we don’t account

for the thyristor block time(20 mS) then 6 sec is the statistical interval between sparks in

the ESP.

Thus, to summaries

Spark rate= 1000/S-control (%) x T-control (%)

As S-control and T-control are effected neither by the absolute value of the current nor at

the voltage at which spark occurs, the spark rate is constant

INTERMITTENT CHARGING:

To get an effective dust collection a high voltage is required to give an even and denser

ion formation at the emitting electrode. Abnormally high electric field strength in high

resistively dusts. Layers due to high current on collecting electrodes may cause spurious

discharge or hack corona to occur. This results in decreased voltage between the

electrodes despite a higher

Current i/p to avoid back corona formation in the collecting electrode a low average

current is required.

The intermittent charging mode in the BAPCON, supplies the current in pulses which

provides a dense corona for a short time and at the same time gives a low average current

to avoid back corona. Some of the half cycles are skipped in the thyristors firing to

achieve this. The pulsed current max. Limit is allowed up to 200%of the normal mode

current in the ESP, hut the average current will he much lower. The longer between the-

pulses, the lower the average current.

42

To decide. The no. of half cycle periods the thyistor should he fired, the charge ratio

setting is to be adjusted. With intcrmi1ent charging, energy saving will he substantially

high apart from increase in collection

Efficiency of the ESP.

CHARGE RATIO OPTIMISTION:

With continuously varying conditions of the ESP, it will help very tedious for the

operator; to very frequently sot the optimum charge ratio in each tiled for the entire ESI.

The BAPCON does the job systematically and continuously. When optimizer mode is

selected, the VI characteristic of the: field studied by the BAPCON arid optimum charge

ratio is selected automatically. The process is repeats periodically at a present interval, to

accomplish this; the operator has to follow the following procedure while commissioning

the BAPCON.

Set a charge ratio close to the optimum value, by studying the trend of the

optimization of BAPCON in each field, starting, horn he field at the ESP inlet.

Set the stabilization time using pot No.4. This is the time allowed for stabilization

at each \‘value of the current set by the optimizer during VI characteristic study.

Set the repeat time using pot No.8. This is the time in1crva the optima take for

repeating the V1 characteristics measurement of the field to select optimum

charge ratio.

Select the optimizer mode ON.

The optimizer status is available in Two LEDS:

1 The LED inset in the OPTMR MODE push button glows permanently

when optimizer mode is selected.

2 The LED OPTIMUM REACHED has three statuses.

a. OFF-Optimizer not selected

43

b. BLINKING-Optimizer is measuring the VI- Characteristics of the

field.

c. ON-Optimum reached.

BASE CHARGING:

In the intermittent charging, the longer the time between each current pulse the lower IS

the average current as may be required for the high resistive ash. 1-lowever, the ESP

valley voltage also reduces pulling down the average voltage. To improve the valley

voltage! Average voltage small current pulses proportional to operating current pulses are

pumped during OFF periods of main current pulses. This maintains the average ESP

voltage always nears about the best possible voltage, thus the collection efficiency also is

further increased. This also protects the T/R set against possible core saturation during

higher charge ratios. To set base charge, pot P should he adjusted in such a way that the

base current pulse should not give any access average current.The

base charge current measured can be seen in the ‘ L ‘display.

Functional Displays and Settings:

PARAMETER DESCRIPTION POT.

METER

RANGE DEFAULT

SETTING

PRECIPITAOR

CURRENT

Measured current in % of

the l max_____ _____ _____

E-PRECIPITATOR

VOLTAGE

Measured voltage in % of

the kV max_____ _____ _____

H SPARKS/ MINNo. sparks/mm

measured_____ _____ _____

O-1M LIMIT Max. current in normal 0 0-104% 100%

44

mode

1- 1S LIMIT Operating current limit IS

LIMIT

0-1 M

LIMIT Set

_______

2 S-CONTROL Step control 2 0-25% 5%

3 T-CONTROL Time control 3 0-109%

10.9%mm

20% 2min

44. STABIL.TIME ((SEC. Stabilization time in sec 4 0-127 30sec

5 UV LIMIT Under voltage limit 5 0-104% 10%

6 CHARGE RATIO Intermittent charging ratio 6-CR 1 -159 1

7 PULSE Max. current when CR is 7 7 0-209% 200

CURRENT LIMIT Set more than 1:1 ratio

8. REPEAT TIME

(X 6 MIN)

Optimization repeats time 8 1-255 20

9. ADDRESS Address for control in remote

mode

9 0-99 0

P- BASE CHARGE SET Base charge current set P 0.49% 1%

L-BASE CHARGE

CURRENT

Base charge current

measured in % of one max

_____ ______ _____

PEAK VALLEY VOLTS Peak and valley voltage

measured (% of KV max)

_____ _____ _____

TECHNICAL DATA

45

DIMENSIONS:

Width : 280mm

Depth : 180mm

Height : 210mm

OUTOUT:

Width : 255mm

Height : 180mm

Eight : 6.5 Kg

Operation Temp : +5° C to +50° C

Storage temperature : +0° C to +70° C

Mains Requirement : 24V +/- 15°/u, Momcntarily-40%,50H z.

Panel protection : IP 54

INPUT SINGNALS:

ESP Voltage : 400 uA corresponds to 100% on the panel display

ESP Current : 1 V corresponds to 100% on panel

Display

OUTPUT SIGNALS:

46

THYRISTOR FIRING : 2 opto coupled NPN transistor output

Conduct for firing. If Max.30mA,

Voltage max, 40V

COMM UNICAION:

Standard : custom designed

Code : ASCH Hex.

TYPE : +/ 10mA balanced current loop.

Baud rate : 4800 hps

ALARAM CODES:

DISPLAY

CODE

FAULT DESCRIPTION

E1 SAFETY LANE BREAK

E2 BAPCON FIRMWARE FAULTY

E3 BAPCON INTERNAL POWER PROBLEM

E4 PRECIPATOR VOLTAGE VERY HIGH

E5 ASH LEVEL HIGH(FOR>10 Mm)

E6 PRIMARY CURRENT HIGH(Thermal overload)

E7 T/R BUCHHOLZ BOTTOM FLT. OPERATED

47

ASH HANDLING PLANT

ASH HANDLING PLANT

48

Ash handling plant at Kothagundam thermal Power stat Oil cui consists of specially

designed bottom ash and fly ash system for (two ) 110mw. BHEL steam generators for

each unit are identical and the following description applies to both the units

A detailed description other system is given in the following paragraph.

Fig: OVERVIEW OFASH HANDLING PLANT

1. GENERAL

49

The water impounded bottom ash hopper receives the bottom ash from the furnace, where

it is stored and periodically discharged to the clinker grinder and hydro-ejector for

transfer through the transport line in every eight hour working shift to the slurry sump,

which is common for both units. A maximum of 45 tones of bottom ash is collected in

every shift. The bottom ash system is capable disposing off this as with in one hour.

Dry. reflowing ash, collected in a total of 68 fly ash hoppers, is handled by two

independent fly ash systems the ash is removed pneumatically from the fly ash hoppers

in dry state and is curried torn a collecting tank where it mixes with water and the

resultant ash slurry falls by gravity into ash slurry sump. Normally both flash systems are

operated simultaneously inert connections has been provided between two systems. So

that in an emergency fly ash of one system can handled by the other system A removes

ash from the following 18 hoppers.

A) Second pass hoppers - 4hoppcrs

B) Electro static precipitator - 4 hoppers

C) Electro static precipitator row no2 -4 hoppers

D) New Electrostatic precipitators - 4 hoppers

E) Duct hoppers - 2 hoppers

System B removes ash from the following balance sixteen Hoppers

A) Second pass hoppers - 4 hoppers

B) Electro static precipitator - 4 hoppers

C) Electro static precipitators row no2 -4 hoppers

D) New Electrostatic precipitators - 4 hoppers

50

a maximum of about two hundred tomes of fly o\ash is collected in each shift. The fly

ash system is capable of disposing off this ash with in three hours.

Bottom ash or fly ash to be disposed off in slurry from si collected in the ash slurry sump.

Three ash disposal pumps, one operated and two stands by pump out the ash slurry to the

disposal area. Interconnecting valves in the three disposal lines permit the operation of

any of the lines with each of the pumps.

Normally fly ash and bottom ash systems of one unit are operated simultaneously. The

ash handling system of the second unit is operated after ash removal cycle of the first unit

is completed. Thus the ash handling system is operated for six hours only in an 8 hour

shift.

2. BOTTOM ASH SYSTEM:

The water filled ash hopper receives furnace ash from boiler, chilling it as it enters the

water to minimize clinking and storing it for periodic removal. The mixture of ash and

water is discharged through an inclined feed gate and clinker grinder, which reduces the

size of clinkers about 25mm size. Crushed clinkers and ash water mixtures falls into the

ejector feed sum and fed to hydro-ejector, which provides the jetting action by means of

pressured water to carry the mixture through discharge lines to ash slurry sump. Two

such sets of fed clinker grinder hydro ejector and discharge piping are provided One

operating and other act as stand by Twee flushing header assemblies with nozzles in the

bottom ash hopper agitate and remove sediment ash from the ash hopper. The clinker

grinder is equipped with an automatic reversing control. An overload should occur in the

grinder it stops automatically and reverses and a time delay relay keeps the grinder

running in the reverse direction for approx. 10 s .the grinder returns in the forward

direction after 20s. The same sequence is repeated if the overload.

51

FIG: BOTTOM ASH HANDLING PLANT

A pressure switch located in the bottom ash transport line will sense a high discharge

pressure, there by indicating a blockage or obstruction. When this occurs, clinker grinder

stops operating. When the pressure drops to a pre determined level, the grinder will again

commence operating this switch thus prevents the possibility of additional ash being

forced into discharge line if an obstruction or line blockage occurs.

Pressure switch located in the bubbled line to ash slurry sump sense the sump level and in

the event of sump level reaching a height limit, the bottom ash hopper gate is

automatically and the system operation recommences.

52

If water at desired pressure is not available at hydro ejector or for grinder sealing then the

ash hopper gate closes and the clinker grinder stops operating. When I he pressure of

Water at hydro ejector and for the grinder sealing becomes normal, and clinkers grinder

restarted the hopper gate reopens automatically.

3. FLY ASH SYSTEM:

Below each hopper one 8” X6” type ‘E’ air electric, self feeding, non overloading type

material handling valve is mounted, which is equipped with 2 adjustable spring

loadedairinlets. Each valve has a slain less steel slide gate to segregate the hopper from

the transport line. The slide gate is cylinder operated and a four way solenoid valve

controls its operation. Segregating valves are provided to isolate various headers

connected to the header have connected to the fly-ash system. This valve remains open

Fig: FLY ASH HANDLING PLANT

Fluidizing air supplied through porous ceramic pads located on the side of fly ash hopper

assist in the free flow, fly ash into the transport line.

The water operated by hydro ejector located at the ah water sump exhausts air from the

transport line running to the air electric operated material handling valves located at the

53

bottom of each of the fly ash hoppers. The resultant rise in vacuum of the system operates

high vacuum switch, The automatic sequential control of the system then energizes link

valve of the first ash hopper and the associated branch-segregating valve thus opening the

valves. The flow of air conveys the fly ash from this hopper to the wetting head where air

and fly ash is mixed with water and is discharged into the collector tank.Seperated air is

drawn from the collector tank through an air washer, in which fine gets of water spray

remove the entrained particles of dust from the air and clean air is then discharged in the

atmosphere through the hydro ejector.

FIG: SLURRY PUMP

The slurry from collector tank and air washer flows by gravity to the ash slurry sump.

As long as fly ash is available at the mouth at the ash hopper, it prevents excessive

entry of air in the fly ash system and these results in maintenance of high vacuum. On

evacuation of ash and with rush free into the system the vacuum drops. This energizes

54

another circuit in the automatic sequential control. After a pre set time delay the solenoid

valve controlling the fly ash valve is reenergized thus closing the value.

This results in the rise of vacuum, which will operate high vacuum switch to energize

solenoid valve of the following hopper in the sequence. The foregoing procedure is

repeated for each fly ash valve in turn after the valve closes the system automatically

shutdowns, the motor operated valve located in water supply line to hydro ejector and

Cylinder operated butterfly valves in water supply line to wetting head and air washer

remain open for a further preset time to purge the ash slurry line.

An air electric vacuum breaker provided in each transport line vents the system to

atmosphere in the event of in adequate pressure in water supply line to hydro ejector,

wetting head or air washer. from which it is not desired to remove material during any

particular operating cycle. Manual operation of individual dust valves is provided by

means of fly ash master switch located on the control panel. Individual bypass switches

allow bypassing of any valve

55

FIG: ASH COLLECTION HOPPERS

ASH DISPOSAL SYSTEM:

The slurry\ brined mixture of water and button fly ash is pumped from ash slurry sump to

the disposal area by means of hydro seal pumps through 12 cast iron pipes. This slurry

sump is a RCC tank with slopped bottom and lined with mild steel-ware plates under all

ash slurry discharge points. Two sets of’ flushing nozzle agitates the deposited materials

in the sump. Ash flow walls in suction line from ash slurry sump to each of the three ash

slurry pumps help pump isolation during the maintenance each of the ash slurry pumps is

connected to individual disposal pipe line up to the ash disposal area, which is approx.

1200 mts away. Interconnecting ash flow between three lines give operational flexibility

by permitting the use of any of the three discharge lines with individual pumps.

The pumps are belt driven and a special vary pitch sheaves on the motor allows variation

of speed of pump to account for normal ware and tear of pump and ash disposal line,

disposal piping has special “EZY” coupling joints to ensure is in periodic rotation of the

pipes for uniform ware. Water make up requirements of ash slurry sump are

automatically regulated by means of’ diaphragm operated butterfly valve which is

controlled by a pneumatic indicating controller. The controller senses the level in slurry

sump by means of’ bubblier tube arrangement dipped in slurry sump and sends a signal to

the valve positioned to operate the valve for sump make up. Sump high and low level

56

arms along with tripping of’ slurry pumps, when the level goes down below a preset level

arc provided.

PUMPS:

The following pumps are provided for both the units.

A. SEAL WATER PUMP-13.5m3 / hr AT I2OMWC TDH there are three seal water

pumps, one 1) Operating and two stands by, supply water to the following.

Sealing of high pressure water pumps.

Sealing of low pressure water pumps.

B.HIGH PRESSURE WATER SUMP-560m3/hr AT 1O5MWC TDH.

There are four HP water pumps with supply water to the HYDRO EJECTORS. Two

pumps are operated when bottom ash and fly ash of one unit is being disposed off. Thus

100% stand by pumps is available.

C. ASH SLURRY PUMP-575m3 /hr AT 20,8MWC TDH (150HP)

There are three ash slurry pumps, one operating and two stands by, which transfer the

slurry from the ash slurry sump to the disposal area. The pumps are V belt driven and the

speed of the pumps can be adjusted by vary pitch sheaves mounted on the motors.

15OHP, 110KW and 3-phase squirrel cage induction motor drive.

57

OPERATING PROCEDURE FOR FLY

ASH HANDLING SYSTEM

1. In the operating procedure, the procedure for operating only the pump/set of pumps or

blower is mentioned. However, in actual practice all pumps/blowers should operate in

potation so that the availability of stand by equipment is ensured and the wear and tear of

equipment is even.

2. The setting on all pressure switches and timers with similar tag number are same

1 Preliminary operating instruction

a) Before starting the operation the following must be supplied

a) Air: Air least at 5kg/cm2 to material handling valves, sag

Regulating valves, vacuum breakers, butter fly valves etc.

b) Water: To recirculation water sump make up.

c) Electricity: To fly ash MCC and fly ash control panels. Put” ON” the main

switch all MCB’s. Green lamps located above the push buttons are put” ON”.

58

2). The settings for all the switches and timers with similar tag numbers arc

identical.

I. preliminary operating instructions

Before starting the operation the following must be supplied

AIR: For all cylinders operated fly ash valves and spring loaded fluidizing air valves.

2. WATER: For sluice way nozzle valves.

3. ELECTRICITY: For fly ash control panel.

4. LUBRICATION: Refer to the “MAINTFNANCF”, “vendor brochures” and

“recommended lubrication” section of M manual.

A. Setting on pressure/vacuum switches and timers should be as follows.

1. “HWPS” (hydro water pressure switch). This pressure switch is located in the

water supply line to hydro vector. It has a setting range of 2 to l 7 atmg and is set

closed at 7.5 atmg rising pressure. The differential pressure is set at .5atmg. The

switch prevents the closing of the vacuum breaker until set operating pressure is

obtained and opens the vacuum breaker if the pressure falls during operating of

fly ash system.

2. “WIIWVPS” (Wetting I lead Water Pressure Switch). I his pressure switch is

located in water supplying to the wetting head. it has a setting range of 0.2-6 atrng

and is set to close at 4aimg rising pressure. The differential pressure is set at 0.2

atmg the switch prevents the closing of the vacuum breaker if the pressure falls

during the operation of fly ash system.

3. “AHVS” (Alarm Vacuum Switch) this vacuum switch is located in the purge unit

near vacuum breaker. It has a setting range of’ 0 -76 cms of Hg and is set to

closed at 5cm of Hg rising vacuum. The differential vacuum is set at 4cm of Hg.

59

The switch initiates an alarm “Fly Ash Vacuum High “in the event high vacuum

persists in the system for more than 2mins.

4. “HVS” (High Vacuum Switch) this vacuum switch is located in the purge unit

near vacuum breaker, it has a setting range of 0-76cm of H and is set to close at

30cm of Hg rising vacuum. The differential vacuum is set at 4cm of Hg .The

switch opens material handling valves when fly ash system is on auto mode of

operation.

5. “LVS” (Low Vacuum Switch) this switch is located in the purge unit near

vacuum breaker. it has been a setting range of 0-76cm of Hg and is set to close at

17cm of Hg falling vacuum . the switch closes material handling valves when fly

ash system is en “AUTO” mode of operating and also initiates an alarm “FLY

ASH VACUUM LOW “if vacuum persists at or falls below the set value for more

than 30sec.

6. “HPWHPS” (HP Water Header Pressure Switch) this pressure switch is located

in the common discharge header of HP water pumps.

It has a setting range of 2- 1 7 atmg and is set to open at 10 atmg. The deferential

pressure is set at 0.5 atrng. The switch initiates an alarm “HP

60

FIG WET ASH PLANT

WATER I IDR PR LO” If set header pressure doesn’t develop within a

predetermined time of starting of the pump.

vii. ‘SWDHPS’ (Seal Water Discharge Header Pressure Switch) .This

pressure switch is located in the common discharge header line seal water pumps. it has

setting range of 2-17 atmg and is set to open at 12.5 atmg the deferential pressure is set at

0.5 atmg. The switch initiates an alarm ‘Seal Water Discharge Hdr Pr Lo’ if set header

pressure doesn’t develop within a predetermined time of the starting of the sum.

61

viii. ‘SWSI-IPS’ (Seal Water Suction header pressure switch): This pressure located

in the common suction header line seal water pumps. It has a setting range 1-10

atmg and is set to at 7 atmg. This switch initiates au alarm “Seal Waller Suction

Fold Pr Lo”. This prevents the operation of sc& water pumps until set operating

pressure is obtained at trips and pumps when the pressure falls during its

operation.

ix. ‘LPWHPS’ (Low’ Pressure Water I leader Pressure Switch) this pressure switch

is located in the common suction header line o water pumps. it has a setting range

of 1 - 1 0 atmg and is set at 7.580 atmg. The deferential pressure is set at 0.5

atmg. This switch initiates an alarm “LP Water Hdr Pr Lo” if set header pressure

does not develop within a predetermined time of the starting of the pump.

x. ‘ABDHPS’ (Air Blower Discharge Header Pressure Switch) this pressure switch

is located in the discharge header line of the air blower. It has a setting range of 1-

10 atmg arid it is set to open at 6 atmg. The differential pressure is set at 0.5 atmg.

This switch initiates an alarm “Air Blower Discharge Pressure Lo”

if set header pressure doesn’t develop within a predetermined time of the starting

of the air blower.

xi. ‘BPSWPS’ (Bilge Pump Seal Pressure Switch) this pressure switch is located in

the lubricating water Supply line to Bilge pump. It has a setting range of 1-10

atmg and is set at 2.5atmg rising. The switch prevents the starting of the pump

until set seal water pressure is obtained and trips the pump when the pressure falls

during its operation.

xii. HPWPSWPS’ (HP Water Pump Seal Water pressure switch this pressure switch

is located in the lubricating water supply line to hp water pump. It has a setting

range of 2-17 atmg and it. is set at 11 atmg. The differential pressure is set at 0.5

atmg. This switch prevents the starting of the pump until set water pressure is

obtained and trips the pump when the pressure falls during its operation.

62

xiii. LPWPSWPS’ (LP Water Pump Seal Water Pressure Switch) this pressure switch

is located in the lubricating water supply line to LP water pump. It has a setting

range of 2-17 atmg and it is set at. 11 atmg. The differential pressure is set at 0.5

Atmg. This Switch prevents the starting of the pump until set water pressure is

obtained and trips the pump when the pressure falls during its operation.

xiv. ‘MECWPS’ (Mechanical Exhauster Cooling water pressure Switch) one pressure

switch is provided in the main header of water line supplying water to the

mechanical exhauster jacket. The switch prevents starting of mechanical

exhauster unless set pressure is available in the cooling water line. The exhauster

trips during running if pressure falls below the set value during operation, it has a

setting range of 1-10 atmg and is set at 7 atmg. The differential pressure is set at

0.5 atmg.

2. TIMERS:

i. “A VI IT” (Alarm High Vacuum Timer). This timer initiates an alarm ‘Fly Ash

Vae Hi’ in the vent of sustained high vacuum in the fly ash line. It has a setting

range of 18-80 second ON time delay and is set at 120 sec.

ii. “VLT’ (Vacuum Low Timer). This timer delays the closing of material handling

valve after fly ash hopper has been emptied. It has a setting range of 6-60 sec ON

time delay and is set at 20 Sec.

iii. “FAPT” (Fly Ash Purge Timer). This timer delays the closing of butterfly valves

in wetting head, air washer & hydro ejector water supply lines after fly ash system

has been stopped. It has a setting range of 30-300 sec OFF time delay and is set at

3 mm.

iv. “VI,AT” (Vacuum Low Alarm Timer) this tinier initiates an alarm Fly Ash Vae

Lo’ in the vent of sustained high vacuum in the fly ash line. It has a setting range

of 6-60 sec ON time delay and is set at 30 sec.

63

v. “WHWAT’’ (Wetting Head Water Alarm Timer) This timer initiates an alarm

“Wetting Head Pr Lo” in the event Of 6-60 sec ON time delay and is set at 30 see.

vi. “SWDHAT” (Seal Water Discharge Heater Alarm Timer). This timer initiates an

alarm ‘‘Seal Water Discharge Hdr prlo” in the event of inadequate pressure in the

discharge header line of’ lubricating water pumps. It has a setting range of 6-60

sec ON time delay and is set at 30 sec.

vii. “SWSAT” (Seal Water Suction Discharge Alarm Timer). This timer initiates an

alarm “Seal Water Suction I Hdr Pr Lo” in the event of inadequate pressure in the

suction header line of seal water pumps. It has a setting range of 6-60 see ON

time delay and is set at 30 sec.

viii. “LPWHAT” (Low Pressure Water Header Alarm Timer). This timer initiates an

alarm “Low Pressure V1atc Header Pr Lo” in the event of inadequate pressure Li

the suction header line of seal water pumps. It has a setting range of 6—60 sec

ON time delay and is set at 30 sec.

ix. “HPWHAT” (High Pressure Water Header Timer).This timer initiates an alarm

“High Pressure Water Pr Lo” in the event of inadequate pressure in the suction

header line of seal water pumps it has a setting range of 6-60 sec on time delay

and is set at 30 sec.

x. “ABDAT” (Air Blower Discharge Alarm Timer). This timer initiates an alarm

“Air Blow Discharge Pr Lu” in the event of’ inadequate pressure in the Suction

header line of seal water pumps. It has a setting range of 6-60 sec ON time delay

and is set at 30 sec.

c. Unlock the lockable stop push buttons for mechanical exhauster HPW Pumps, LP,

Seal water pumps and air blower which are mounted near the respective

equipments (Local Push Button Station).

d. Open all isolating valves in water supply lines o wetting heads, air washers and

pump suctions.

64

e. Open the needle valves for pressure/vacuum switches.

f. Apply electrical power to control panel.

1. Put on all IVICB s in fly ash control panel

2. Green light located above stop push buttons for the following pumps is put on.

a. LP water pumps.

b. i1J water pumps

c. Seal water pumps

d. Ash slurry pumps.

e. Bilge pumps.

f. Mechanical exhausters.

OPERATING INSTRUCTIONS ………. FLY ASH SYSTEMS

65

Fig: Gass path

FLY ASH SYSTEM

Notify boiler operator of the intention to operate the fly ash System.

1. start two (2) seal water pumps,1LP water pump, 1HP water pump and lair blower from

control panels of units 7and 8 as usual.

2. Fly ash control panel

3. Select fly ash control switch-7A (FACS-7A) marked close auto-Open’

to ‘Auto’ position

Select the six by pass switches-7A (BP-7a) marked by” pass”collect’to ‘collect’ position

66

FIG: ASH VACCUM SYSTEM

67

CONCLUSION

After completion of our study on electric static precipitators and ash disposal system in

KTPS - C Station, the following are observed.

(1) ESP’s

1. The boilers of 7 and 8 units have each 2 parallel paths for flowing of fly ash and flow

gas. There are 6 numbers ESP’s in each path of the boiler. That is total 12 number

ESP’s for each unit. And each ESP field is having 2 fly ash hoppers. The high

voltage rectifier transformer controls the ESP and microprocessor based controller. If

any fault occurs in ESP i.e., either electrical or mechanical it should be attended

during the shutdown of the unit. Because there is no way to enter into the ESP

chamber while the unit is in service. If the fault is Continuous, then there is no ash

collection in the particular ESP the result will be overloaded on the impeller of the

concerned ID fan. if it is very high. Then the impeller may be failed. If the ENP’s are

in separate parallel chamber, then the fault clearance is easy even through the unit is

in service.

2. The coal supplied by the boilers of 7 and 8 units is having high ash content. So the

production of fly ash is more than the desired quantity for the same 120 MW

power output. Hence his existing fly ash hoppers are not sufficient to collect fly

ash delivered by the boilers. It is proposed to increase the hopper quantity in the

corning renovation.

Also, the present system was completed 20 years of service. Hence M/S BHEL is

proposed to renovate the system by adding some new technologies in there power

plant improvement techniques. They proposed 2 numbers extra ESP’s in each path

i.e.. 4 ESP’s for each unit and 8 extra fly ash hoppers for each unit in the coming

refurbishment program. Thereby we can improve emission levels of the units.The

present emission level for the seventh unit is 1 l 2 mg /m3 (Sample date 30-06-2010)

68

For 8’ unit 11 8 mg/m3

World standard value = 115 mg/rn3

Emission level means flow gas particles i.e., suspended particles/m at chimney.

The data collected from E & P (Efficiency and Planning) department.

Coal analysis of 7 & 8th units

1. Total Moisture : 6.675%

2. Ash Control : 48.8%

3. Volatile Matter : l6.83%

4. Fixed Carbon : 27.60%

5. Calorific Value : 3193 cal/gm

6. Useful Heat Value : 1456 cal/gm (G grade).

Ash analysis of 7 & 8th units

1. Unburned Coal in bottom ash = 47% (should he

2. Unburned Coal in fly ash = 0.92% (should he

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III. Ash disposal systems:

In the present system the fly ash which is collected through ESP is to be removed

by the vacuum streams and mixed with low pressure water in the collector tank

and then passed on to the ash slurry sump by gravity force. There are 2

vacuum streams called A & B for each unit. The fly ash can be removed from

the hoppers through A & B vacuum steams at a time i.e., 1 hopper in A stream

and another in B stream, The shut of vacuum maintained is nearly 450 mm

water column. From ash slurry sump, the slurry will be disposed through ash

slurry pumps to ash pond, which is 2.5km away from the plant. At present there

ore 2 ash Slurry pumps continuous in service to dispose the slurry to ash pond.

And during bottom ashing 4 pumps are in ser vice. This is due to increasing the

length and height of the ash pond.

In refurbishment works the rerouting of ash disposal line have completed up.

Because of this rerouting, 0.5 km distance will be reduced and I slurry pump is

sufficient to dispose this slurry without any hesitation. During bottom ashing time

2 pumps are sufficient to maintain the sump. Thereby we can save the auxiliary

consumption of nearly 150 HP (110 KW) motor for 24 hours

During refurbishment program, M/S BHEL has constructed a separate ash

disposal plant for 7 & units. The refurbishment of unit. Main aim is to increase

the life of units up to another 20 years. It is already 20 years completed for the

present system.

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6.0 PROTECTIONS:

6. 1 Input HRC Fuses

6.2 Thermal Overload Relay

6.3 Input line surge suppressing network

6.4 Snubber network for thyristors.

6.5 Linear Reactor for limiting short circuit current on primary side

6.6 Air Cored choke for limiting di/dt of HV rectifier diodes on

Secondary Side

6.7 Electronic output current limit

6.8 Protection against dangerous voltages from DC Current &

Voltage Iced back by over voltage protectors.

6.9 The winding of the transformer is electro statically shielded to

Protect against any sudden voltage surge during precipitator

Operation

6.1 0 Equipment is provided with gas alarm/trip & Oil temperature

Alarm/trip of protection

6. 11 Pressure release valve.

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