47
Programme Objectin Seri : PROBES/45/1Ϡ REPORT ON DESIGN A ND OPER ATING PA R AMETERS OF ELECTROSTATIC PRECIPITATORS Central Pollution Control Board East Arjun Nagar Delhi-110032
Programme Objectin Series : PROBES/45/1992
REPORT ON DESIGN A ND OPER ATING PA R AMETERS
OF ELECTROSTATIC PRECIPITATORS
Central Pollution Control Board East Arjun Nagar Delhi-110032
Programme Objective Series : PROBES/45/1992
REPORT ON DESIGN A ND OPER ATING PA R AMETERS
OF ELECTROSTATIC PRECIPITATORS
Central Pollution Control Board East Arjun Nagar Delhi-110032
1 .0
2.0
3.0
4.0
5.0
6.0
-- _ _ _ --- -�
CONTENTS
f.'lTRODUCTIO�
E.S.P. COMMITTEE
AIR POLLUTION CONTROL ACT
FLY ASH AND FLUE GAS CHARACTERISTICS
4.1 INTRODUCTION
4.2 COAL
4.3 FLUE GAS
4.4 GAS FLOW QUAi\rrrrY
4.5 FLY ASH
DESIGN CRITERIA FOR ELECfROSTATIC PRECIPITATORS
5. 1 INTRODUCTION
5.2 DESIGN CRITERIA
5.3 COLLECTION SURFACE
5.4 GAS VELOCITY
5.5 ASPECT' RATIO
5.6 TREATMENT TIME
5.7 HIGH TENSION SECI10NALISATION
5.8 NUMBER OF SERIES FIELDS
5.9 MIGRATION VELOCITY
PRECIPITATOR EQUIPMENT
6.) ELECTRODES
6.2 RAPPERS
PAGE
1
1
2
2
2
3
4
4
8
8
8
8
1 3
1 3
1 4
1 4
1 5
1 5
16
16
16
PAGE
6.3 GAS FLOW DISTRIBUTION MEAr\S 17
6.4 GAS FLOW MODEL STUDIES 18
7.0 REVIEW OF PERFORMANCE OF INSTALLED ESP 18
7 .I INTRODUCfiON 18
7.2 PERFORMANCE OF ESPs !�STALLED EARLIER TO 1976 19
7.3 PERFORMANCE OF ESPs INSTALLED LATER THAN 1976 19
8.0 REASOf\S FOR POOR PERFOR.\1ANCE OF F.SP 25
�-· INTRODUCfiO� ., -_)
8.2 FL�DA�1ENTAL PROBLEMS 25
8.3 \1ECHANICAL PROBLEMS -,-_)
8.4 OPERA TlONAL PROBLE.\lS .,-_)
9.0 MEASL RES TO IMPROVE THE PERFORMANCE OF ESP IN OLD POWER Pl.A NTS ?..7
9.1 INTRODUCTION 27
9.2 r-ILLJ�G UP THE DUM:-.1Y FIELDS 27
9.3 REPLACEME'\T OF EXlSTING ESP BY NEW ESP 27
9.4 AUGMENTATION 017 COLLECTION SURFACE 27
9.5 IMPROVED ELECTRICAL E�ERGISATIO'l 28
9.6 FLUE GAS CO'\DITIO��G 28
10.0 �1EASL.RES TO L!\SCRE CO:--.:TI:\LATION OF I0;1TIAL GOOD
PERFORMANCE 29 '•
10.1 H\TRODLCTIO:--.: 29
10.2 .\LIGNMENT OF ELECfRODF SYSTEM 30
10.3 CLEA:\1:'\G OF ELECTRODES 30
10.4 GAS TEMPERATURE
10.5 SPARK RATE
10.6 RAPPING FREQUENCEY
10.7 OIL COMBUSTION
10.8 AIR CONOfTTONING OF CONTROL CABrNS
10.9 HOPPER EVACUATION
10 . 10 DUST CONCENTRATION IN FLUE GAS
ANNEXURES - I
. II
- III
- IV
PAGE
30
30
3 1
3 1
3 1
3 1
32
33
35
36
37
FOREWORD
The present repon on Design and Operating Parameters of Elecrrostatic Precipitators (ESP) was prepared by a committee constituted by the Central Board under tbe Chairmanship of Dr. Tata Rao. The repon also contains a review of performance of ESPs already installed in the country and discusses reasons for the poor performance
of some of them. The discussion is followed by suggested measures to improve and
maintain the initial good performance of ESPs. I believe the repon would be useful
for the Thermal Power Plants in the selection, operation and maintenance of ESPs.
I thank Dr. Tata Rao, Ex-Chairman of A.P. Electricity Board and Dr. B. Sengupta,
Member convener of E.S.P. committee and the other members of the Committee for the painstaking effons taken in preparing this repon.
Delhi 24. 10.91
N.S. TIWANA Chairman
1.0 INTRODUCTION
An electrostatic precipitator (ESP) is a panicle control device that uses electrical forces
to move the panicles out of the flowing gas stream and onto collector plates. Basically
an electical precipita.tor provides three essential functions:
** the suspended panicles are given an electrical charge
** the panicles are subjected to an electric field to remove them from the gas stream
to a suitable collecting electrode and
** means are provided for removing the panicle layers from the electrode surfaces to
an outside receptacle with as little loss as possible.
Jn practice. electric charging of the particles is accomplished by means of ions produced
in the high voltage d-e corona. The collecung field is also provided b) the high voltge
d-e corona Removal of the collected particle layers 1s accompli<ihed by rapping (by
impact, or by virbation of the electrodes).
2.0 E.S.P. COMMITTEE
Chaim1an. Central Pollution Control Board constituted a committee comprising experts
and representatives of suppliers/manufacturers of the electrostatic precipitators in the
country to evaluate the performance of ESPs and to suggest measures for improvement.
The list of members of the committee has been g1vcn in 1\nnexure-I.
The tem1s of reference of the committee were:
1) To review the design criteria adopted by the manufacturers vis-a-vis the emission
standards evolved by Central Board.
2) To review the performance of the installed ESPs.
3) To identify the probable reasons for poor performance.
4) To suggest measures to improve performance.
5) To suggest measures to ensure continuation of initial good performance.
6) Any other matter considered relevant and assigned by the Chairman, Central
Board.
3.0 AIR POLLUTIO" CO:\'TROL ACT
Th�.: Air (Prevention and ContrOl of Pollution} Act, 1981 sripulates that no person shall
without the previous consem of Swte Board for prevcmion and contrOl of pollution
operate any indusrrial plant for the purposes of any indu')try in an air pollution control area (clause 21 of the Act). Every per:.on to whom consent has been gramed by the State Pollution Control Board shall install the control equipment of such specification the Stat� Board may approve and aher/replce the existing control equipment, if any, in accordance with the direction of the State Board.
The Central Pollution Control Board has stipulated the following emission standards for thermal power station for pulverised coal boilers.
(Ref: Emission Regulation Part-1).
Boiler size Particulate matter, mg!Nm3
Old
Less than 200 MW 600
200 MW & above
New (After 1979)
350
150
Protected area
150
150
While the emission standards laid down can be adhered in respect of new thermal stations, the enure problem lies in complymg with the standards in case of already running stations where there are not adequate control equtpment installed or the existing conrrol equipment is inefficient. The designers as well as the power station authorities are confronted with the problem of rerrofitting new control equipment in the existing plant.
4.0 FLY -ASH AND FLUE GAS CHARACTERISTICS
4.1 INTROOUCfiON
Electrostatic precipitator performance depends fundamentally on the physical and chemical properties of the gas and particulates rreated. In a power plant. these properties are governed by the coal burned, the furnace design and the overall operation of the bOtler. The composition, temperature and pressure of the nue gas govern the basic corona ch.tracteristics of the precipitator. while panicle stze, partic1e concentration and electncal rcsisth,it) of the ash affect both the corona and the particle collecting propemes of the precipitator.
�.2 COAL
Precipitator design and performance are strongly dependant on the properties of the coal burned 1n the furnace. The major constituents of coal are moisture. volatile matter, fixed carbon and ash. Typical values for a range of Indian coals are listed in Table- I. All coals contain significant amounts of ash or residues of combustion consisting chiefly of inert oxides and silicates. These complicate furnace operation and give rise to the fine
2
particles known as fly ash. The amount of fly ash produced in a given case depends
on the ash content, the hearing value and other properties of the coal. The variability
and uncertamty of coal properties reflect in the fly ash generated and can make the problem of fly ash collection singularly difficult. In order to cope successfully with
particulate air pollution from coal fired power plant it is necessary to apply consistently
a high order of technology.
Table I
Typical Properties of Indian Coals
Coal mines Moisture Volatile Fixed Ash Sulphur High heat value
Singareni coals { Upper Kusumunda Lower Kusumunda
Turra
Singmuli coal fields upper
lower
Jharia coal fields
�eyveli lignite
4.3 FLUE GAS
{
%
9
10
10
10-12
08-10
16
10
10
16
10
13
42.52
maner % carbon%
23.92 29.08
24.63 33.37
21.46 36.54
20-25 21-31
20-25 24-25
21.6 32.4
18.9 26.1
19.8 25.2
14.4 23
21.25 34.16
16.9 27.5
22-27 17-22
'*· % Kcal/Kg
38 0.36 3800
32 0.35 4300
32 0.38 4300
32-49 0.27-0.36 3130-4275
40-48 0.24-0.28 3530-4020
30 0.27 4050
45 0.45 3425
45 0.23 3450
46 6 0.34 2700
34.16 0.5 4000 27.5 0.41 3200
03-12 0.46-0.81 2500-3200
Combustion gases from coal fired boilers consist chtefly of carbon dioxide, water vapour, nitrogen, oxygen and minor constirutents such as sulphur oxtdes, nitrogen
oxides and arogon. The amount of water vapour is determined by the hydrogen and
moisture content of the coal and the humidity of the combustion air. Oxygen is present
as the result of the excess air used for combustion and air tn-leakage through the
furnace, ducts and air preheater. The sulphur trioxide (S03) produced in the combustion
process is imponant in electrostatic precipitator because of its effect in reducing the
resistivity of the fly ash. Dew point of the flue gas is substantially elevated by the
3
•.
pressure of Soy The elevated dew point can have a profound effect on precipitator operation owing to the great reduction in fly ash resistivity induced by the adsorption of Lhe sulphur trioxide on the fly ash particles.
4.4 GAS FLOW QUANTITY
Gas flow rate is a fundamental factor in the design and performance of electrostatic precipitator. The quantity of combustion gas produced in the boiler depends on the composition and amount of coal burned, the excess air used for combustion and the air in-leakage through the furnace, flues and air-preheaters. The volume flow rate through the precipitator is also a function of gas temperature and pressure.
Dtscrepancies between gas flows measured by pHot rube methods and those calculated by heat balance or material balance methods frequently cause problems in practice because precipitator performance data banks are as a rule based on pitot tube measurements, whereas gas flow specifications for new precipitators commonly are calculated using the balance methods. Therefore, new precipitator designs may be based on gas flow figures which are too low by 10% or more unless adequate allowances are made for the differences. The actual deficiency may also be compounded by inadequate allowances for air in-leakage and the amount of excess air used for combustion. Actual operating gas flows may then exceed design as much as 15 to 20% thereby causing greatly increa"ied stack emissions.
4.5 FLY ASH
The amount of fly ash emiued from a furnace depends mainly on the amount and the composition of the coal burned, on furnace design and on furnace operation.
4.5.1 Chemical Composition
The chemical composition of fly ash varies widely and depends on the coal burned, the mining and the processing methods used and the degree of cleaning of the coal before burning. Major constituents of the fly ash are silica, alumina and iron oxides. Typical \alues of the constituents of Indian fly ash are given in Table-H.
4.5.2 Pa rticle Shape and Size
The particle shnpe is heterogenous and varies with the coal burned and the conditions of combustion.
Panicle size distribution is an important factor in the design and operation of precipitators. High efficiency removal of micron and sub-micron particles is of greatest importance in meeting today':, requiremems for essentially clean stacks. Particle size distributions of fly ash from representative power plants are shown in Table-III.
4
�.5.3 Resisthity
Corona current from the high tension electrode must pass through collected dust layers on the plates to reach grounded plate surfaces. Passage of the corona current builds up a voltage across the dust layer in accordance wuh Ohm's law. Theory and experience indicate that when the dust resistivity exceeds a critical value of about 1010 ohm/em corona currents are limited by electric breakdown of the collected dust layers.
This in tum limits operating voltage and reduces precipitator efficiency. The loss in performance increases quite rapidly for resistivities greater than 10'0 ohm/cu.m and resistivity is, therefore, a major factor in precipitator technology.
Fly ash resistivity depends primarily on the chemical composition of the ash, the flue gas temperature and the water vapour and S03 in the flue gas. At air preheater outlet gas temperatures ( 135 Deg. to 160 Deg.C.), surface conducuon over the fly ash particles 1s the prevaihng mode and the conductivity depends mainly on the amounts of S03 and ,..,atcr "apour adsorbed on the particles. The resisuvuy 1s very sensuive to the presence of SO, and water vapour. Although most of the sulphur 111 the coal is oxidized to S02, about I ''t IS convened to so). In general, the amount of sol' produced increases with the coal sulphur content. but furnace operation and other factors also exen an influence, so that no one-to-one relation exists between coal sulphur and resistivity. Experience over many years has shown that fly ash from low sulphur coals usually has high resistivity and 1s difficult to precipitate whereas fly ash from high sulphur coals has low re�1s11vity and is relatively easy to collect. I Iowcvcr, the relationship is statistical
because of the presence of other variables. The sulphur content of the coals is classified in accord with the following scheme.
Low sulphur coal s < 1%
Medium sulphur coal 1%<S<2.5%
l ligh sulphur coal s > 2.5%
The relation between coal sulphur and fly ash conductivity is tempered by several factors. hrst. the amounr of S01 generated depend on furnace conditions as well as on the sulphur coment of the coal. Second, the amount of SO, adsorbed on the fly ash is greatly affected by the gas temperature and the surface cond111on� of the particles. There IS evidence that S03 adSOrption is greater for finer particles bi!Cause Of their greater specific -.urfacc. The variation of dust resistivity with temperature for varying sulphur content 1s shown in Figure-!.
Field invesugations show that flue gas temperature 1s the most imponant variable in addilion to �ulphur content of the coal in detemltntng the conductivity of the ash. Pigure-2 lllustr.Hes the temperature variation of tl} ash res1stivit}.
5
Table II
Typical Chemical Analysis of Fly Ash from Indian Coal
Chern teal Stngarcni Kusurnunda Smgrauli Jharia Neyveli consutucnt<; coals Upper Lower Turra Purcwa lignite
uppcr/lo" cr
Si02 59.3 59.77 59 60.15 62.45 56.7 60.9 64.6 57.5 58.2 57.22 65.2
Alp3 21.1 22.R9 22.15 27.�4 27.41 27.5 24.8 24.8 26.8 25.48 26.9 13.27
Fep1 7.526 8.23 8.4 5.6 4.96 6.4 7.7 5.1 10.16 10. L2 10.3 3.6
T102 1.53 1.88 1.9 1.9 1.5 1.52 1.28 1.51
Pp$ 0.53 0.55 1.1 0.5 0.5 0.83 0.8 0.84
CaO 6.51 3.16 7.06 1.43 1.42 1.8 0.9 0.9 1.76 I 74 1.85 11.2
MgO 3.034 1.72 2.05 0.91 1.03 1.0 1.0 0.8 0.61 0.59 0.62 5.0
so, 0.36 0.1 0.3 0.2 0.3 0.6 0.58 0.6 1.37
1'-iap 1.99 0.15 0.4 0.2 0.2 0.16 0.3 0.16 0.32
Kp 2.5 1.5 1.2 - 0.04
MnO 0.06 0.05
6
Table III
Particle size distribution of Fly-Ash from Typical
Power Plants, Measured by Bahco Classifier
RANGE OF PARTICLE PLANT-WISE DISTRIBUT ION
SIZE (MICRONS)
2 3 4
< 3.4 14.7 17.3 27.5 26.2
3.4 5.2 17.0 13.1 31.8 11.9
5.2 8.5 9.6 8.0 14.7 8.6
8.5 14.5 11.7 16.7 16.5 9.6
14.5 26.5 13.8 8.4 4.6 5.4
26.5 44.0 10.5 7.2 2.7 5.7
44.0 55.0 5.7 3.1 0.8 3.1
55.0 65.0 12.0 2.0 0.6 2.7
65.0 400.0 5.0 24.2 0.8 26.2
7
The presence of sodium in the ash in amounts greater than about 1.5 to 2.0% as Na20 is sufficient to reduce resistivity of fly ash from low sulphur coal to below
1010 ohm/em. This effect is illustrated in Figure-3.
5.0 DESIGN CRITERIA FOR ELECTROSTATIC PRECIPITATORS
5.1 INTRODUCTION
A fundamental task in precipitation technology is the design of optimum precipitation systems for given application. Precipitator design has changed in character during the past several years from a rather routine and casual function to a more serious enterprise
involving high performance and high financial stakes. This change has been forced by
the implementation of stringent air pollution control standards which requires substan
tially invisible stack emissions for new units. ll is, therefore, prudent that the design
criteria of electrostatic precipitators to meet a colJection efficiency of 99.5% and above
only are discussed.
5.2 DESIGN CRITERIA
The basic design criteria for electrostatic precipitators is the determination of the prin
cipal parameters for precipitator sizing, electrode arrangement and electrical energisa
tion needed to provide specified levels of performance. Auxiliary factors such as rap
pers, gas flow control methods, dust removal system and performance monitoring must
also be considered.
5.3 COLLECTION SURFACE
The collection surface required for a given gas Dow and efficiency is usually computed
from the modified Deutsch-Andersson equation.
E = ( 1 - e ·(wlc.SCA)O.S) X 1 ()()
Where, E = Collection efficiency, per cent.
wk = Migration velocity. m/sec.
SCA = Specific Collection Area
= Total projected collecting electrode surface area (A,m2).
Gas flow rate (Y,m3/sec)
e = Naperian logrithmic base
The relation between SCA and efficiency for a range of values of WK is shown in
Figure 4.
8
-- - .
X 0 I I f
� 0.75% SULPHUR I
X IN COAL :X:: 0 11
� 10
-
> I I /' "\..� \ - 1.75% t; { ....... &2 10 w 10 .x; E-� I I I y-- '� l \ \ i 2.?5% :J 0
130 150 170 210 250 FLUE GAS TEMPERATURE 0c
FIGURE -1: VARIATION OF DUST RESISTIVITI' WITH TEMPERATURE FOR VARYING SULPHUR CONTENT
� 0
I
� :X:: 0
� -> ........ t;; ........ ll2 1&1 g:; t;; � Q
6.6 96 101 2 I WATER \
� D RY AIR I BYVOLUME •
/'"-* 11 I / 13.5 96 "', \ 10 "i/ WATER � �,,
� �� 10 I 10
9 10 1 > 95°C 1 2�0°C 1 1 s/o °C
TEMPERATURE - 0c FIGURE- 2. VARIATION OF DUST RESISTIVITY WITH TEMPERATURE
FOR VARYING MOISTURE CONTENT
:E 0
I
:E :I: 0
� >-1-> t=�en w a:: :I: en < >-....1 LL
1014 --------------------------------------------------------------------------
1 Q13
1012
1011
1010
109 0.1 0.2 0.3 0.5 0. 7 1 3 5 7
SODIUM CONTENT AS Na20, PERCENT FIG. 3 VARIATION OF RESISTIVITY WITH SODIUM CONTENT FOR FLY
ASH FROM POWER PLANTS BURNING COALS
10
... z w 0 a: w
99.9
99.5
Q.� 99.3 > () z w u 99.2 LL: LL. w z 0 t; 99.1 w ..J ..J 0 () <
99.0 100
wk = 0.30 m/sec.
wk = 0.20 m/sec.
wk = 0.15 m/sec.
125 150 175 200 SPECIFIC COLLECTION AREA, m2Jm3Jsec
FIG. 4 SCA V5 m FOR VARYING WK
225 250
The specific collection area is expressed in m2/m3/sec. Pracucal values of SCA usually mnge between abour 140 and 250 m2/rn3/sec.
Considering the high resistivity of the fly ash encountered in our coals. the need for capturing submicron particles at higher efficiencies and to avoid defficient equipment, minimum specific collection area shown in Table 4 must be specified by the purchaser correspondmg to the collection efficiencies indtcated for the worst possible coal burnt
in Indian power plants.
Table 4
Minimum Specific Collection Area vs Efficiency
Collection efficiency (Per cent)
99.5
99.7
99.9 ----
SA GAS VELOCITY
Specific Collccuon Area
(m2/m1/sec )
140 - 150
170 - 180
235 - 250
The average gas velocity is calculated from the gas flow and the cross section of the precipitator. The cross-section is taken as the open area for gas flow between the collecting plates, disregarding the plate baffles. The importance of the gas velocity is its relation to rapping and re-entrainrnent losses. Above some critical velocity, these
losses tend to increase repidly because of the aerodynamic forces on the particle. The critical velocity depends on the quality of gas flow, plate configuration, precipitator size
and other factors, but for most fly ash precipitators does not exceed 1 . 1 m/sec. This setsa design limn on gas velocity of not more than OJ� m/sec. for high efficiency fly ash
precipitators.
5.5 ASPECT RATIO
Thts pammeter ts defined as the ratio of the total acuve length of the fields to the heightof the field. h 1s imponant in precipitator design because of Its effect on rapping loss. Collected dust released from the plates is carried forward b} the flow of the gas. If the tmal field length ts too shon compared to the height. �orne of the falling dust will be carried out of the precipitator before it reaches the hopper: thereby substantially increasmg the dust loss. For efficiencies of 99.5% or higher, the aspect rauo should be as per
th�: followmg Table 5.
13
Collection efficiency, %
99.5 - 99.6
99.7 - 99.9
5.6 TREATMENT TIME
TAISL� 5
Aspect ratio (minimum)
1.4 - 1.6
1.8 - 2.4
This parameter 1s defined as time taken by the flue gas to pass through the length of the collecting electrode zone. For efficiencies of 99.5% and higher, the minimum treatment time should be at least as shown in the Table-6 below:
Collection efficiency, %
TABLE 6
Treatment time, (Sec.)
-------------------------------------------------- ----------------
99.5
99.7
99.9
5.7 HIGH TENSION SECTIONALISATION
20
24
33
Theory and practical experience confmn the fact that precipitator performance improves with degree of high tension sectionalisation. There are several fundamental reasons for th1s improvement. Small sections have less electrode area for sparks to occur. Electrode
alignment and spacing are inherently more accurate for smaller sections. The amount of sparking caused by dust build-up on the plates and by rapping is less for smaller sections. Smaller rectifier sets needed are inherently more stable under sparking conditions and the sparks which occur are less intense and damaging to perfonnance. Outages of one or two electrical sections has a much smaller effect on efficiency where a relatively large number of high tension section are used.
Prudent design criteria for modem high efficiency fly ash precipitators requires that the outage of two or three corona sections should not reduce collection efficiency below the guarantee level. Beyond this requirement, the optimum degree of high tension sectionahsation 1s a balance between the increase in efficiency obtained with more
section and the increased cost of providing the additional sections. This balance is h1ghly dependent on ash propenies, gas temperature and efficiency required. For efficiencies of 99.5% and higher, the number of high tension sections per 1 000m3/mt of gas flow rate small be as per the Table 7.
14
Table 7
Number of High Tension Sections ,.s Efficiency
Collection efficiency
%
99.5
99.7
99.9
65
5.8 NUMBER OF SERIES FIELDS
No. of high-tension
section per 1000 m3/mt
of gas flow rate
0.73 - 0.78
0.89- 0.94
1.22 - 1.30
The number of fields in series needed for a precipitator installation depends mainly on
the efficienc) reqUlred and on the redundancy necessary to ensue performance with
secuon outages. For high collection efficiencies and h1gh ash concenrrations the ash
loadmg in the gas stream changes greatly between the inlet and outlet of the precipi
tator. At the precipitator inlet the corona current denslly is significantly reduced because
of space charge suppression in the gas srrearn and the heav) collection of ash on the
plates.
At the precipitator outlet the amount of ash is very small so that both these effects are
negligible and the corona current density approximates that of the clean gas. Good
design practice based on field experience calls for at least 5 or 6 separately energised
series of high tension sections for efficiencies of 99.5% and above.
5.9 MIGRATION VELOCITY (wk)
The most 1mponant variables which determine \\.k in t!nginecring pr.tctice are: resistiv
it) and panicle size distribution of the fly ash, gas "elocHy distnbution through the
precipitator, particle losses due to re-entrainment, rappmg and gas leakage, precipitator.
Gas velocity distribution and particle losses due to re-entrainment etc. are controlled
through proper design of the precipitator and associated nues. Precipitator electrical
conditions can be optimised b} maintaining accurate electrode ahgnmem. sufficient
high tensiOn secuonalisanon and lhe use of appropnate rectifier sets and automatic
control systems. In practice, the values of migration velocny arc determined by the
various precipitator manufacturers from bodies of experience accumulated over the
years.
15
6.0 PRECIPJT ATOR EQUIPMENT
6.1 ELECTRODES
Precipitators for fly ash collection are of the duct type because of the relatively large
gas flows treated, the high collection efficiencies necessary and the great amounts
of fly ash to be handled. Collecting electrode spacings range between 250 mm and
500 mm, wirh the wider spacings preferred for installations having very large collecting
plates. Wider spacings help maintain electrode spacings and alignment tolerances. Wide
spacings also reduce corona cu!Tent densities at the plate surfaces which is a significant
advantage when collecting higher resistiviry ashes.
Collecting elecrrodes probably have received even more attention than corona elec
trodes. fundamentally there are four basic technical requirements for effective collect
ing electrode design:
a) high sparkover vohage characteristics
b) aerodynamic shielding of collecting surfaces to prevent particle re-entrainment
c) good rapping characteristics
d) high mechanical strength coupled with light-weight construction.
1L seems evident that collecting electrodes should be rated in terms of these properties.
Solid sheet collecting plates with structural stiffeners are standard throughout the industry.
In some design these stiffeners have contours designed to improve gas flow and to
lower gas turbulence in the collecting space near the place surfaces. Aerodynamic
effectiveness of the baffles can be important in minimising re-enrrainment losses. Srruc
rural rigidity of the plates should be sufficient to maintain electrode spacing tolerances
of properly mounted plates within acceptable limits. Distorted and misaligned electrodes whether due to inadequate design or to improper installation lead to reduced
operating voltages and loss of efficiency.
6.2 RAPPERS
Removal of the accumulated deposits of fly ash from the electrodes is an essential
feature of efficient elecrrostatic precipitator. This is necessary not only to remove the
collected material from the precipitator but also to maintain optimum ele.crrical condi
tions in the precipitator zones. The deposits are dislodged by mechanicaJ impulse or
vibrations of the electrodes, a process generally known as rapping. A rapping system
must be highly reliable, adjustable as to inrensity and/or frequency and capable of
maintaining uniform rapping over long periods of rime without attention.
16
Substantial differences exist between the various rapping methods and philosophy adopted by different manufacturers. In the case of magnetic impulse rappers, a steel
plunger 1s raised by a current pulse in a coil and lhen allowed to drop back by gravity,
striking a rapper rod connected inside the precipitator to a number of plates. Both the
intensity and frequency are easily adjusted through the electrical control system for the rappers. Mechanical rappers consist of hammers mounted on a rotating shaft in such a way that the hammers drop by gravity and strike anvils attached to the collecting plates. Rapping tntensity is governed by the weight of the hammers and length of the hammer mounting arm. The frequency of rapping can be changed through electrical control system of the rappers.
Rapping intensity of the hammer rappers has been much greater than that of magnetic
impulse type1• The later type generally is designed with sufficiem power to provide
intense blows but in pracnce is operated at low intensities to m1mmise rapping losses of the collected fly ash. An argument sometimes putforth for heavy rapping is lhat the
plates are kept cleaner which could be an advantage when dealing with high resistivity ash. However, it is well known lhat it is impossible to keep the plates clean no matter how heavy rapptng blows are used and even thtn layers of htgh res1stivny ash can cause heavy sparking and back corona.
It is necessary to rap the corona electrodes also, to prevent build-up of excessive ash deposits which interfere with the corona. Particle deposus on wires frequently tend to
form 'doughnuts' These formations interfere with the corona dtscharge and thereby
reduce collectton effic1ency.
6.3 GAS FLOW DISTRIBUTION MEANS
Optimum performance of precipitators requires well balanced flow distribution through
the precipitator zones and a lower level of turbulence. However, tn practice the quality
of gas now in a precipitator depends only slightly on the precipitator itself, but strongly on the plant flue duct system and its connections to the precipitator. Because of space
limitations and equipment location constraints, the flue connections to the precipitator
in a typical power plant usually are contorted, asymmetrical and otherwise unfavourable
to good gas flow. For these reasons, special means and studies are nearly always
necessary lO achieve the level of gas flow quality needed for high efficiency perfor
mance. Poor gas flow can cause any or all of the following adverse effects viz.
l. (a) "Eicctroswuc Prcctpiwion of ny ash from Io� sulphur coal in power swtions" hy Mr. A.N. Lamb
& Mr. K.S. Watson, Electricity commission of New South Wales, Australta. Symposium on the
"Changmg Tcchnolog}' of clectroswtic Precipiwuon" Adclatde, \lovcmbcr 1974.
(b) " Role of Elcctro�lal.tc Precip itators in particulate control - A rctrospcct•vc and pro.,pcclivc view"
HafT) J White sympos1um on Elcctroswtic Prectpt!Altors for the control ol fine paruclcs, Pensacola
Dcach, Flonda, September 1974.
17
•.
a) lower collection rates of the particles from the gas stream
b) re-entrainment of collected panicles due to aerodynamic scouring of the collecting
plates
c) excessive rapping losses
d) gas sneakage past the collecting zones and
e) loss of dust from the hoppers.
Techniques available for controlling and correcting gas flow patterns include chiefly the
use of guidevanes to change gas flow direction, flue transitions to couple flues of
different sizes and shapes and various types of diffusion screens and device to reduce
turbulence. Guidevanes are used to prevent the flow separation which would otherwise
occur at turns and changes in flue cross sections. Diffusion screens are effective in
reducing turbulence and improving the uniformity of flow. Basically, a diffusion screen
comprises plate/plates with a periodic pattern of holes. The effect of the diffuser is to
breakup large scale turbulence into a large number of small scale turbulent zones. These
in turn decay rapidly and in a shon distance coleaps into a relatively low intensity
turbulent flow field. In some situations 2 or 3 diffusion plates may be used in series
to provide better flow distribution and lower turbulence than could be achieved with
only one diffuser.
6.4 GAS FLOW MODEL STUDIES
Many years of experience have shown that precipitator gas flow systems can seldom
be successfully designed by intuitive methods. The cramped space and asymmeo-ic
irregular shaped flues ntle out mathematical and fluid dynamic design methods. This
leaves scale model laboratory studies as the most reliable and practical approach to
precipitator gas flow systems. Model techniques are well documented and the close
correlation between model study results and field gas flow performance has been
demonstrated by experience with many insrallations. The models are usually con
structed of transparent plastics such as plexiglass for easy visualisation. Accuracy of
constntction is paramount and all significant parts of the flue system are included.
Geometric sirnilarity is maintained using typically a l: 1 0 scale.
Gas flow model studies are mandatory for modem high efficiency fly ash precipitatOrs
where the stakes are high and the cost of non-perfom1ance intolerable.
7.0 REVIEW OF PERFORMANCE OF INSTALLED E.S.P.
7.1 INTRODUCTION
The review of the perfom1ance of the installed electrostatic precipitators in various
thermal power stations must be considered under atleast two categories viz.
18
i) the perfonnance of the precipitators installed earlier to 1976 and
ii) the perfonnance of the precipitators installed later than 1976 and in particular after
the enactment of pollution control act.
7.2 PERFORMANCE OF THE PRECIPATORS £:\STALLED EARLIER TO 1976
Many of the ex1sting generating stations installed earlier to 1976 were initially designed
and erected with minimal dust collection equipment. The boiler units supplied have
either mechanical dust collectors having a collection efficiency of 80% or a combina
tion of mechanical and electrostatic precipitators having an efficiency of 95%. These
dust collecting plants were required only for the functional reqUirement of the boiler
viz. to reduce the erosion of the impellers of the induced draft fans and consequent
down time of the boiler. These dust collectors therefore, do not meet the requirement
of air pollution control regulations. Due to the many problems faced with inenial and
combination dust collectors like high power consumption. inadequate size, poor relia
bilit} of the system etc. many of these dust collectors have been retrofitted with
electrostatic pn!clpitators of adequate size.
7.3 PERFORMANCE OF THE PRECIPITATORS INSTALLED LATER THAN 1976
For units installed in late seventies and onwards, the indigenous manufacturer M/s.
BHEL has supphed the 1mproved design of electrostatic precipitators. A bener under
standing of the "anous propenies of coal and fly ash parucles that profoundly influence
the selection and sizing of the precipitators, rev1ew of various design philosophies and
methods used earlier in the engineering design of precipitators for fly ash panicularly
in the light of increased unit ratings and environmental standards and the need to meet
increasingly higher efficiencies and much greater reliability have witnessed the intro
duction of precipitators with large specific collection area. The precipitators designed
and installed afler 1976 have been found to provide a satisfactory performance with
efficiencies between 99.5% and 99.9%.
Precipitator practice is best illustrated by means of data for a variety of power plants.
The example listed in Tables 8 to 11 co"er the main features and provide a broad cross
secuon of design pracuces. Some point:> of particular 1n1erest to be noted are the great
increases m gas now rate capacity and collecuon efficiencies over the years.
19
Table 8
Summary of Desigh data for Representative Fly-Ash Precipitators
Unit Rating : 500 MW
SL PA!{A�iETER SI�GRALU KORBA RA.'AAG UNDA.'.1 RIHA.'lD FARAKKA CHANDRAPUR
No.
01. Gas now rate, m3/scc. 980 1030 710 768 785 750
02. 1 cmpcraLurc of flue gao;, •c 140 140 ns 140 133 123
03. Inlet dusL concenLralion, 73.5 82.56 42 54.08 70.2 74.51
gm/Nm1
04. Efficiency, % 99.5 99.52 99.9 99.81 99.95 99.93
05. :-.:o. of casings 4 4 4 4 2 4
06. f'.o. of scncs lields 7 6 6 6 6 6
07. Manufacturer of ESP BH.EL BHEL BHEL LODGE.- MARTIN- BHEL
COTfRELL ELL!
U.K. C01TRELL,
ITALY
'•
20
Table 9
Summary of Design data for Representath·c Fly-Ash Precipitators
Unit Rating : 200/210 MW
SL. PARAMETER VIJAYAWADA MEJIA GANDHINAGAR RAICHUR KORBA CHANDRAPUR
No. 3&4 3&4 3 WEST 1&2 3&4
01. Gas now rate, m1/SJX 382 380 338 352 367 356
02. TemperaLurc of gas, •c 146 142 136 148 144 137
03. lnlcL dust concentration 90 56 58 73 57 39
gm/Nm,
04. Efficicncy,<J �
99.89 99.73 99.74 99.88 99.48 99.24
05. No. of casings 4 2 2 2 2 2
06. No. of series fields 6 6 7 6 6 5
07. ManufaclUrcr of ESP BHEL BHEL BHEL BHEL BHEL BHEL
21
Sl . PARAMETER RAMA· DADRI ROPAR KOTA METIUR ANPARA KOLA- KOLA No. GUN DAM 3&4 3&4 GHAT GHAT
5&6 1,2&3
0 I. Gas now rate. m3/sec. 341 332 370 347 361 361 356 306
02. Temperature of ga._, ·c 145 134 127 134 145 145 133 141
03. Inlet du�t concentration 62 62 62 39 42 43 51 51
gm/Km1
04. Efficiency.% 99.52 99.9 99.75 99.62 99.6-t 99.3 99.7 98.5
05. :\o. of casmgs 2 4 2 .., 2 2 2 2
06. �o. of scric� fields 4 6 7 6 6 '7 5 4
07. Manuracturcr of ESP Flakt, BHEL BHEL BHEL BHEL BHEL BHEL VOLTAS
Il.aly.
22
Table 10
Summary of Design data for Representative Fly-Ash Precipitators
Unit Rating : 100/110/120 MW
SL P ARA�1F1T:.R MUZAFFAR· SABAR· KORADI KALCO 8\SORE PARICIIA I'A'IiKI SIKKA OUR-'lio. PUR \1ATIIY GAPUR
PROJ.
Ecrs LTD
0 1 . Gas now rate. m '/sec. 202 197 242 217 275 207 230 220 182
02. Temperature or gas. •c 145 152 180 140 200 143 180 137 142
03. Inlet dust concentration 50 40 50 43 70 4 1 62 72 78
gm/Nml
04. Efficiency. % 99.50 99.74 99.7 99.4 99.R6 99.1 99 84 99.79 99
05. No. of casings 2 2 2 2 2 2
06 No or �eric.� field 7 6 4 6 6 6 4 6 5
07. Manufacturer of ESP BHEL BHEL BHEL BHEL BHEL BHEL BHEL BHEL VOL-
TAS
•
23
Table 1 1
Summary of Design data for Representative Fly-Ash Precipitators
Unit Rating : 60/62.5/67.5 MW
SL PARAMETER RAMAGU RAJG- INDRAP· ENN- CESC RENu- KOlliA· KOTiiA
NO. NOAM 'B' HAT RASTHA ORE SARAR GUDAM GUO AM
0 1 . Gas now rate, mlfs 132 132 150 150 143 145 106 106
02. Temperature of gas, °C 152 138 150 200 140 160 ISO 150
03. Inlet dust concemn. 9-1 66 66 70 68 85 108 108
gm/Nm'.
04. Effictency, % 99.63 99.8 99.81 99.86 99.8 99.8 99.63 99.61
05. No. or casings 2 2 2 2 2
06. No. or series fields 4 5 4 6 5 5 4 4
07. Manufacturer of ESP BHEL BHEL BliEL BHEL BHEL BHEL A PH MEL VOLT AS
24
8.0 REASONS FOR POOR PERFORMANCE OF ESPs
8.1 INTRODU<..IION
Many year� of experience have shown that problem of some magnirude are encountered in a s•gnificant percentage of fly ash precipitators These problems fall into three major categories: Fundamental, mechanical and operational. The underlying causes of poor performance are attributable to deficiencies m one or more of these
pnmary areas. Diagnosis and cure of problem proceeds most smoothly and expeditiously by sc1entific and systematic methods. A list of frequently encountered
problems 1s given in Table-12.
8.2 FUNDA \1ENTAL PROBLEMS
Fundamental difficulties include high resJsuvuy particles, panicle re-entrainment, poor gas flow, poor rapping, badly designed electrode equipment and i n some
cases undersize precipitators. Scientific procedures exist for determining and isolaung these difficulties.
8.3 MECHA "'-ICAL PROBLEMS
�echamcal troubles comprise principally poor alignment of clecmxles, vibrating
or swinging corona wires, bowed or distorted collecting plates, excessive dust
build up or deposits on the collecting and corona electrodes, air in leakage in
hoppers, gas ducts etc. and dust mountains or piles in connecting gas ducts. The
correction of these difficulties usually is fairly obvious, once they are located. Again,
systematic methods based on symptoms, measurements and observations are most
effective.
8.4 OPERATIONAL PROBLEMS
Difficulties attributable to operational factors cover such items as hoppers full or overflowing with collected dust poor electrical settings, failure to empty hoppers,
over loading precipitator equipment by excessive gas flow or dust
concentration and upsets in operation of boiler to which the precipitator is con
nected.
Table 12
Summary of Precipitator Problems and Difficulties
A. Fundamental problems
0 I . lligh resistivity particles
02. Rc-enrrainmenl of collected panicles
25
03. Poor gas flow
04. Inadequate rapping equipment
05. Badly designed electrode systems
06. insufficient or unstable rectifier equipment
07. Insufficient number of corona sections
08. Undersize precipitators
09. Gas velocity too high
10. Aspect ratio too small
B. Mechanical problems
0 1 . Poor electrode alignment
02. Vibrating or swinging corona wires
03. Distoned or skewed collecting plates
04. Excessive dust deposits on collecting electrode and corona electrodes
05. Air in leakage into hoppers, shells or gas ducts
06. Formation of dust mountains in precipitator inlet and outlet ducts.
07. Gas sneakage through hoppers and around precipitator zones.
C. Operational problems
01. Full or overflow hoppers
02. Shoned corona sections
03. Precipitator overloaded by excessive gas now
04. Predpitator overloaded by excessive dust concentration
05. Process upsets (poor cumbusrion, steam leaks etc)
06. Rectifier sets or controls poorly adjusted
07. Poor adju�tment of rapper intensity/frequency.
26
9.0 MEASURES TO IMPROVE THE PERFORMANCE OF ESP I N OLD POWER
PLANTS
9.1 INTRODt:CfiON
As demands on particulate erruss10ns become more and more stringent in order
to comply with the requirements of pollurion control act, many electricity boards and power generating corporations have to improve the efficiency of the existing
electrostatic precipitator. In electrostatic precipitator technology it is called
upgrading/retrofitting.
There are various approaches available to upgrade the electrostatic precipi
tators. The technical and organisational capabilities required by major retrofit
projects are similar to or even more complicated than those required by new systems.
9.2 FILLING UP TilE DUMMY FIELDS
A number of earlier precipitator installations have been provided with an added
feature of a dummy field (empty section) at inlet/outlet end of the precipitator.
This was included in case it proved desirable to increase precipitator size at a later
date.
The empty secuons can be filled with electrodes to provide additional collection
surface needed. Annexure-II furnishes a list of projects where th1s philosophy has been
adopted.
9.3 REPLACEMENT OF EXISTING ESP BY NKW ESP
Many of the existing generating stations were located in urban areas necessitating
a compact plant general arrangement. When these stations were· initially designed and
erected, minimal dust collection equipment only were installed and no provisions
have been made for future installations. The dust collecting plants installed were
required only for the functional requirement of the boiler viz. to reduce the erosion
of the impellers of induced draft fans and consequent downtime of the boiler.
Consequent to the awareness on controlling particulate emission control, the existing
precipitators which were found inadequate to meet the emission regulations have
been replaced with adequately sized elecrrostauc precipitator. Annexure-ill
furnishes a list of projects taken up under this category.
9.4 AUGME"JTATION OF COLLECTION SVRFACE
This approach entails the installation of additional retrofit electrostatic precipitators
after thorough study of site conditions by prov1ding more collection area and
thereby reducing the emission. This approach has the unique advantage in that the new
27
•.
equ1pment can be erected without disturbing the operation of the boiler. The installation of additional precipitator independent of the existing boiler system is
advantageous from the point of vie"' of reduced downtime and consequent loss of revenue. Prior to the installation of the new additional precipitator a detailed
stud)' of the effect of the additional pressure drop in the ducong and the precipitator on the operation of the boiler unit will have to be essentially carried out to ascenain the suitability of the induced draft fan to meet the present requirement.
Many of the renovation of electrostatic precipitators carried out by reputed
manufacturers of electrostatic precipitators fall under this category of approach. A list of projects where such renovation through augmentation of collection area has been
taken up is furnished in Annexure-TV.
9.5 IMPROVED ELECTRICAL ENERGISATION
Being an electrical equipment, the electrostatic precipitaLOr will work only if the electrical equipment and particularly the rectifiers work. The technology incorporating
the sem1pulse and multi-pulse concepts yield 1mproved precipitation, increased rehabiluy and unparalleled convenience for the operation These advantages are often
ach1eved with substantially reduced power consumption.
9.5.1 Semipulse Energisation
By changing the mode of operation of transformer rectifier control. an appropriate number of half waves can be blocked between the firing of the rectifier thyristOrs. Thus the charging of the precipitator is made an an mtermment \\ay which means
that a pulsating corona with pulse width of some milli-seconds IS fom1ed in the ESP.
D1fferent charging modes can be switched on from a pmentiometer to suit the
andtvidual field. Semi-pulse energisation is today in operation in many power plants and a lot of experience has been achieved.
9.5.2 Multi-Pulse Energisation
Pulsed encrgisation of elecrrostatic precipitator is a way of improving the perform
ance of the precipitator especially when high resisti\it} dusts are present The equipm�;nt bemg used creates pulses of shon duration of approximately 1 00 mtcro
s�;conds High spark over \:Oltages compared to convcnuonal energisation can, thl!reforc, be usl!d. A reduction m power consumpuon when switchmg to pulsed
encrgisation can also be achieved. The serious drawbacks for the pulsed TR sets so
far have been high cost comparen to conventional eqUipment. If the precipitator can be made smaller. the total cost is attractive however.
9.6 FLUE GAS CONDITIONING
Control if particle resistivuy by moisture and chemical condl!loning of the earner gases is achtcved by adsorption of moisture and chemical substances. The
28
- -----
adsorpuon and hence the conductivity is a surface effects and ts greater at lower temperatures.
9.6.1 Moisture Conditioning
Conditioning by steam injection or \\Jter sprays is a standard method and can be more effective at temperatures below about ISO Deg. Cent. as would be expected because of the grl!ater adsorption of the water vapour on the panicles at these temperatures.
9.6.2 Chemical Conditioning
Chemtcal agl:nts such as S03, NH3 and t-\aCI have found considerable use as conditioning agents but have definite limitations owing to cost and apphcation factors. By far the most 1,\:idely used conditiomng agent i'\ SO, (or H2S04). However, the application ol SO, conditioning to large coal fired power plants burning low sulphur coals is beset wuh a number of problems. These are related to the handling of the large quantities of the chemicals required. maintenance problems. the unfamiliarity of power plant engineers with chemical techniques and under some conditions the posstble cmtssion of sol.
Ammonia conditioning was tried m one of the power plants but showed no observable effect of any kind.
10.0 MEASLRES TO E'St;RE CO�T�UATION OF 11\ITIAL GOOD PERFORM
ANCE
10.1 11\IRODU(.IION
The number of elcctro<;tatic precipitator mstallations have grown at an accelerated pace. While much has been discussed and ,., ritten on attaining collecting performance with the precipitator, a major '01d has occurred in the idennfication and transfer of infonmllion needed to keep reduce maintenance costs and to prevent deterioration of the collector perfom1ance through the failure of C<.tUtpment. This section is intended to highlight many of the repllitive problems that have plagued the users of precipitators. The existence of these problems could be related to the complexity of the process or to a le1ck of well defined operating techniques among other reasons.
The perfonnance of the precipitator is influenced by a number of factors, many of wh1ch an.: controllable. Bas1cally a precipitator may seem to be a rather static piece·of e4uipment. involving only a few moving pans. Howt!vcr. the mtemals are rather heavily loaded and operate in a dirty environment under relatively high and unfavourable temperature conditions.
29
10.2 ALIGNMENT OF ELECTRODE SYSTEM
Accurate alignment of corona and collecting electrode is of major importance for good performance. Off-center and misaligned elecrrodes may easily result in a loss of 10% or 15% in operating voltage of a precipitator. Electrode alignment should be one of the major checks to be made by operators during equipment outage and overhaul periods.
10.3 CLEANJNG OF ELECTRODES
The performance of an electrostatic precipitator depends on the amount of elecrrical power absorbed by the system. The highest collection efficiency is achieved when maximum possible elecrrical power for a given set of operating conditions is utilised in the precipitation process. During the operation of a precipitator, the applied vollage is reduced by the potential drop across the deposited dust layer on the collecting electrodes due to the current flowing through it. This results in reduction of the effective voltage which consequently reduces the collection efficiency. Too thick a dust layer on the collecting electrodes will also lead to unstable operating conditions. The dust deposited on the emitting wires results in non-uniform corona. Therefore, the efficiency decreases with increased or abnormal dust deposits on the collecting and emiuing electrodes. This necessitates that the rapping system of both collecting and emitting electrodes are kept in working conditions.
10.4 GAS TEMPERATURE
Operation of the precipitator at gas temperaturs below the acid dew point results in the following:
- Failure of emining electrodes due to stress corrosion cracking
- Corrosion of the internals
- Collection of wet dust on the electrodes leading to fonnation of 'hard-to-rap' layers and consequent reduction in the performance of ESP.
10.5 SPARK RATE
The operating voltage and current keep changing with operating conditions. This is taken care of by an automatic voltage controller in the electronic controller unit. Too high a flash-over rate will not only result in reduction of useful power and interruption of precipitation process but will also cause snapping of emitting electrodes due to elecrrical erosion. It is recommended that for the best performance the flash-over rate shall not exceed 5 sparks per minute.
30
10.6 RAPPI'JG FREQliENCY
The frequency and sequence of rapping of collecting and emitting electrodes are
programmed by the synchronous programme/master controller.
The time intervals between the raps for the various fields can be optimally chosen to
permit build-up of sufficiently thick layer so that when rapped, the dust is dislodged
in the form of agglomerates.
Too high a rapping frequency will dislodge the dust layer before formation of agglo
merates, resulting m a re-enrrainment and puffs through the stack.
10.7 OIL COMBUSTION
The quality of oil used during start-up or stabilisation of coal firing can have an
important impact on precipitator operation. Unburnt oil if passed into ESP can coat the collecting and emitting electrodes.
This fouling of ch:ctrodes deteriorates the electncal conditions 1.e. reduces the pre
cipitator operating voltage due to high electrical resisuvity and consequently the
ESP performance deteriorates. The precipitator performance remains poor untill the oil vaponses and the layer gers rapped off, which usually takes a few weeks time.
Also the unbumt oil in the ESP poses the danger of fire hazard. Hence. 1m .. · current
settings (without any flashover) are recommended during oil firing.
10.8 AIR CONDITIONING OF CONTROL CABINS
The ESP control room houses sophisticated electronic controls apart from the related switch gear and control gear. The reliable operation of these controls directly reflects
on the precipitator performance. In order to ensure the controls in proper working
conditions, it is essential to maintain a dust free atmosphere with conrrolled
ambient conditions. Therefore. the air conditioners should be kept in proper working
condition.
10.9 HOPPER EVACUATION
Improper/incomplete hopper evacuation is a major cause for the prectpitator mal
function. If the hoppers are not emptied regularly, the dust will build up to the
high tension emitting system causing shons. Also the dust can push the internals
up causing misalignment of the electrodes. Though the hoppers have been designed
for a storage capacity of 8 hours under MCR condiuons. this provision shalJ be used only in the case of emergency. Normally the hoppers should not be tre<hed as
storage space for the collected dust.
3 1
10.10 DUST CONCENTRATION IN FLUE GASES
The dust concentration in the gases is much higher in the front part of the precipitator
than in the rear. The current distribution is influenced by the dust concentration. Where
it is high, the current is suppressed i.e. inlet fields will rake less current than the outlet
fields.
32
LIST OF MEMBERS OF ESP COMMITTEE
Dr. N. Tata Rao
Ex-Chairman
Andhra Pradesh State Elecoiciry Board
Vidyt Soudha
Hyderabad-500 049
Sri A. Raman
Director
Central Electricity Authority
Sewa Bhawan
R.K. Puram
New Delhi- 1 1 0 066
Sri R.K. Narayan
General Manager
National Thermal Power Corporation Ltd.
Sk1pper House
62 - 69 Nehru Place
New Delhi - 1 1 0 019.
Sri S.N. Krishna
Addl. General Manager
Boiler Auxiliaries Plant
Bharat Heavy Elecrricals Ltd.
Ranipet-632 406
Sn S. Balagurunathan
Engg & Devpt Manager
Air Quality Conrrol Systems
Engineering & Development Centre
Bharat Heavy Electricals Limited
Ranipet-632 406.
Sri M.S.K. Prasad
Chief Engineering Manager
Engineering Projects Division
Manakji Building
127 Mahatma Gandhi Road
Bombay - 400 023
33
ANNEXURE - I
. . . . Chairman
. . . . Member
. . . . Member
. . . . Member
. . . . Member
. . . . Member
Sri Anup Guha
General Manager
M/s. Andrew Yule & Co. Ltd.,
Air Pollution Control Unit
225-E, A. J. Chandra Bose Road Calcutta - 700 020
Sri S. Ghosh
Manager
ESP Depanment
M/s. F1akt (India) Ltd.,
Post Box 4 1 1
Calcuua - 700 02 1 .
Sri N. Bagchi Director (CP)
Ministry of Environment & Forests
'Paryavaran Bhawan'
C.G.O. Complex
Locii Road
New Delhi - 1 10 003
Dr. B. Sengupta
Senior Scientist
Central Pollution Control Board
Ministry of Environment & Forests East Arjun Nagar
Delhi- 1 1 0 032.
. . . . Member
. . . . Member
. . . . Member
. . . . Member Convener
34
ANNEXURE-ll
LIST OF THERMAL POWER STATIONS WHERE THE DUMMY FIELDS EXISTED IN THE PRECIPITATOR HAVE BEEN/ ARE BEING FILLED UP
SL. Plant Name/ Capacity
No. Unit No(s). (MW)
0 1 . Turicorin 1,2 2 x 210
02. Kolhagudam 7,8 2 x 1 10
03. Koradi 5 1 x 200
04. Bhusawal 2 1 x 2 10
05. Parli 3 1 x 210
06. Nashik 3,4,5 3 x 210
35
A!'iNEXURE-111
LIST OF THERMAL STATIONS VVHERE TilE ELECTROSTATIC PRECIPITATORS
OF INADEQUATE SIZE HAVE BEE1'i/ARE BEil\G REPLACED WITH ONES OF
ADEQUATE SIZE TO J\.1EET THE EMISSION REGULATIONS
SL. Plant �arne/ Capacity (MW)
No. Unit No(s)
0 1 . Koradi 1 ,2,3,4 4 x 120
02. Ennore 1 ,2 2 x 60
03. Ennore 3,4,5 3 X 1 10
04. Panki 3,4 2 x 1 10
OS. Faridabad I ,2 2 x 60
36
ANNEXURE-IV
LIST OF THERMAL STATIONS WHERE RENOVATION OF ELECTROSTATIC
PRECIPITATORS THROUGH AUGME:\TA TIO� OF COLLECTION AREA
HAVE BEEN/ ARE BEING TAKEN UP
SL. Plant ::-\arne/ Capacity (MW)
No. Unit �o(s)
OL Gandhinagar I ,2 2 x 120
02. Bada.rpur 1 .2.3 3 x 100
03. Gurunanak Dev 1 ,2,3.4 4 x 100
04. Al)larkamak 3.4 2 x 120
05. Indraprastha 2.3,4.5 4 x 60
06. Kothagudam 5.6 2 x l l0
07. Pathrathu 7,8 2 x 1 10
37
l.IST OF PUBLICATIONS CONTROL OF URBAN POLLUTION SLRJCS
l . Union Territory of Delhi (Detailed): CUPS 2 1978-79 2. Industrial Survc} Lmon Territo!) of Delhi: CUPS 3 1 978-79 3. Waste\\ater Collection. Treatment & Dtsposal m Class I
Ciue� CliPS 4 1 978-79 4. Status of Water Suppl) and Wastewater Collection. Treatment &
Disposal in class-11 TO\\ns m lndta: CCPS 6 1979-�0 5. Inventory & Assessment of Pollution Emission in and Around
Agra-Mathura Reg10n (Abridged): CUPS/7' 198 1 -82 6. Umon Territor} of Chandigarh:Prelimmar) Rcpon:CUPS 8 1981 -82 7. Union Territory of Pondichcrr): CUPS 9/1 9R3-f<� 8. Vehicular Air Pollutton m Delhi - A Preliminan study
1982-83:CLPS 1 0/1982-83 9. Asstmilation Capactt} of Point Pollution Load. The River
Yamuna, U.T of Delhi:CUPS1 12fl982-83 10. A Method to Determination of Minimal Stack Height: CUPS/ 1 3/ 1984-g5
PROGRAMME OBJECTIVE SERlE.�
1 . Episodal Pollution: A case study Union Territory of a Goa: PROBES
Rs. 80/Rs. 40/-
Rs. 100/-
Rs. 100/-
Rs. 50/Rs. 50 -Rs 50 -
Rs. 40/-
Rs. 40/-
511979-80 Rs. 1 5 -.., Proceedings of the Workshop on Biological Indicators and Indices
on Emironmental Pollution: PROBES 6 1982-83 R�. 65 -3. Ocean Outfall for Pondicherr} Paper Ltd. A Case Study Union
fcrritory of Pondtcherry: PROBES 7 1982-83 Rs. 30/-4 lmtial En'vironmental Evaluation - Otl Drilling and Group Gathcnng
Station�: PROBFS g 1981 -82 Rs 30/-5 Stmplc Guide CodL of Pracucc for Bcuer Hou e Keeping and
Pollution Control in Electroplating lndustl) ( Engitsh Hindi): PROBES 9 1981 -82 Rs. OS -
6 Water Pollution Control - An Ovcrvie\\ . PROBES/ I I 1 982-83. 7 Report on Caustic Soda untls: Hindustan Heavy Chemicals:
West Bengal. PROBES/ 12 / 1982-83 Rs. 20/-8 . Status of Environmental Pollution: Kcsoram Rayon. West Bengal
PROBES 13 1982-83 Rs. 25 -9. Pt!rformance Study of Wastcv.aLer Treatment Plant of Gancsh
Floor Mills. PROBES 1 5 1982-83 1 0. Environmental Status: Barapani Lake. Meghala}a. PROBES 1 7/1 983-84 I I . Assessment of Generation and Control of Water Pollution in
J . . K. Rayon Industry. Kanpur:PROBES/18/1 982-83 Rs. 1 5'-1 2. Pollutton Control m Man-Made Ftbrc Industry wtth special Reference
to Zmc. at Harihar ?oly-hbre. Karnataka. A Case Stud) : PROBLS 19 19 3-84 Rs. 1 5 -
1 3. Procced1r.gs of the National Workshop on \tarine Outfall::. (April 26-2 1984. Panaji. Goa): PROBES 20 1983-84 Rs. 50 -
1 4 Dust Pollution From Stone Crushers (Sohna Tourist Camp. Gurgaon Distl. Haryana: PROBES 2 1 1 983-84 Rs. 30,-
1 5. Performance Study of Vanaspati Wastewater Treatment Plant at M/s Shriram roods and Fertilizer� lndustr;.. PROBES 22 1983-8� Rs. 30/-
1 6 State of Progress of ProJect "Operation Pollution Control in Damodar Rt\erN As on March 3 1 .1 984: PROBES 23 1984-85.
1 7 . Charactensttcs and Treatment of Waste\\ater From on Electric Bulb Manufactunng L'nit: PROBES 24 1983-84.
1 8. Control of Air Pollution from Coal Fired Reverberatory 1-urnal:c· PROBES/25/ 1984-85.
19. Brochure on Effiuenl Treatment Plant Built in Karnataka State. As in 1984: PROBES 26 1985.
20. Zonal Committee Repon on Assessment of Pollution Control Measures in Chlor-Alkali Industries (Mercuf) Cell): PROBES 27 1985.
2 1. National Inventory of Water Polluting Industries and Effiuent Treatment Plant Status: PROBES 28 1984-85.
22. An Assessment of Mercury Problem at Kothari lndustnes Ltd. Madras - A case study. PROBES 29 1985.
23. Episodal Pollution caused by a Barrier Across Eloor branch of Periyar River PROBES 14/ 1982-83.
24. Performance study of Wastewater Treatment Plant at Mother Datry PROBES/ 16/ 1982-83.
25. Performance study of Ton-Exchange Resin Treatment System for Mercury Removal From Wastewater at Gujarat Alkalies and Chemicals Limited, Baroda, GuJarat PRO BES/30/ 1985-86.
26. A Study on the Environmental Damage Due to Lethal Chemical Catastrophe in Bhopal PROBES 3 1 1985.
27. Report on Identification of Import component of Waste Treatment Technolog} and Know-how PROBES 32/1985-86.
28. Impact Study and Evaluation of Pollution Status of Oil Dnlling and Group Gathering Stations of Assam PROBES 33/1985.
29. Groundwater Quahty in the Union Territory of Delhi - Abridged Repon PROBES/34/ 1985-86
COMPREHENSIVE INDUSTRY DOCUMENT SERIES
1 . Comprehensive Industry Document Man-Made Fibre Industry: COINDS/ 1/1979-80
2. Minimal National Standards Man Made Fibre I ndustry: COIN DSt2/ 1979-80
3. Comprehensive Industry Document Oil Refineries: COINDS 3,1981-82 4. Minimal National Standards: COINDS/4 1981-82 5. Comprehensive Industry Document, Chlor-Alkali (Abridged) Industry:
COINDS/5/1979-80 6. Minimal National Standards Caustic Soda Industry: COINDS
6 1979-80 7. Comprehensive Industf) Document Khandsari Sugar Industry:
Rs. 100/-
Rs. 40/Rs. 100.'Rs. 40/-
Rs. 50 -
Rs. 40/-
CO E'•-i OS 7 1980-8 1 Rs. 40 -8. Minimal �attonal Standards Sugar Industl): COII\DS 9 1980-8 1 Rs. 50 -9. Comprehenst\'e Industry Document Fermcntauon (Moltcnes. Breven� and
Distilleries) Industr} Series: COINDS 10/198 1-82 Rs. 100/-10. Mmimal Nat10nal Document Fermentation (Moltenes, Breweries and
Distillenes) Industry Series: 1 1. Emission RegulatiOns (July 1984) Part I : COJNDS/17/1983-84
12. Minimum National Standards Pesticide Manufacturing and Formulating Industry COINDS!l5/ 1985-86
13. Emission RegulatiOns (July. 19H5) Part II: COINDS 18. 1984-85
Rs. 20 -Rs. 20t-
14 Minimal li,Jational Standards Straight Phosphatic fertiliser Industry COIND() '1 91 1984-85
\SSLSS:\-1£:\T & DE\ E.LOP:\IL''T Sf 0\' OF RIVI:I� BA ' I� SERlE...�
I . Un'c.r Territory of Daman. Dadra & '\.Jgar 1-fa ... eli (Abridged): A DSORBS I 1 ?78-79 Rs. 40 -
2. Basm Sub-Basm Inventor) of \Vater Pollution. The ganga Basin part One. The 'r umun .. Sub-Basin: ADSORBS 2 1978-79 R:-t. lOO -
3. Scheme for Zoning ana Cl<.ts�ification ot Indian Rhcrs Estuaries and Coastal Waters (Pt. One Sweet Water). ADSORBS 3 1978-79 Rs. 40 -
4. Comprehensive Pollution Survey and Studies of Ganga River Basin m West Bengal: ADSORBS14/1980-8 1 Rs. 200/-
5 Union Territory o.' Goa. Daman and Diu (Dist. Go<.t) Abridged: ADSORBS 5/1982-83 Rs. 50 -
6. Stream Water Quality in Major Rivers (Gujarat St •. tc} During Btennium 1979-80 Survey: ADSORBS/6/1 982-83 Rs. 50/-
7. Ganga Basin Report (Part If-Entire Ganga Bastn): ADSORBS/7 1982-83 Rs. 500 -8. Ionic Balance of ·water Quality at Uttarakhand Ganga Forming
Tributaric�: ADSORBS 9 1 982-83 Rs. 50 -9. Quality and Trend of River ) amuna 1979-�Q: ADSORBS 10 1 982-83 10. Basm Sub-Basin Inventory of Water Pollution: The Brahmaputra Basin
Part-1. The Dilli-Disanl! Sub Basm: ADSORBS I I 1983-8.., Rs. 25 -I I . Water Quality Monito.mg . . \n Indian Experience: ADSORBS 12 19R4- 5 R!). 20 -1 2. \Va c Po'lu 'on from Mass-Bathing - Case Studic.;; in Ganga
ADSORBS 8 1983-84 13. Atlas (River Ba�in)
ADSORBS/1 3/ 1984-85
COASTAL POLLl!TIO� CO:\TROI. SERIES
l . lJse Classification of Indtan Coast and ConOtcts Part I : Tamil Nadu Coast: COPOCS/ 1 ' 1982-83
2. Use Classification of India Coast and Conflicts Part I I . Kanya Kumari to Goa: COPOCS 2 1984-85
RESOURC� RECYCLING SERIES (RERES)
1 . Recycling of Sewage and Industrial Effiuent on Land - Monitoring and Survcillanc.� Report on Chandigarh Sewage Fam1 RER ES I /1985
LABORATORY <\NALYTICAL TECHN1QUES SERIES (I.ATS)
1 . Measurem�:nts of Mercuf) by Cold Vapour Atomic A b orption Technique LATS/ 1 / 1 985-86
2. Lindane Analysis by Gas Chromatograph Technique LA TS 2/1 985-86
Rs. 550 -
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