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 Technology In Electrical and Electronics Engineering Submitted By N.VISHALA (07871A0226) PEERA TIRUPATHI (07871A0230) THUMMALA MAHENDER (07871A0243) SHIVA KRISHNA (08875A0205) Under the guidance of Sri.G.Ramesh Lecturer 1
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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
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.
5
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
8
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
10
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
14
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:
21
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.
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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
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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
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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