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1. WHAT ARE THE P R E C A U T I O N S TO BE TAKEN W H I L E
ENTERING INTO ELECTROSTATIC PRECIPITATOR?
Ans:1. All voltages shall be considered dangerous even though voltage
may not be high enough to produce severe shock (80V onwards).
2. All electrical circuits are to be treated as live and no work i.e.
maintenance repairs cleaning etc is to be carried out on any part o! the
apparatus unless "
# $uch parts are dead i.e. totally de"energi%ed.
# &solated and all steps taken to lock o!! !rom live conductors.
# '!!ectively earthed.
# eleased to work by issuing work permit by authori%ed person.
# on!irmation !or de"energisation is received.
*. Visitors + unauthori%ed persons should not be allowed to touch or
handle electrical apparatus or come in danger %one o! high voltage
e,uipment.
-. oose clothing metal (straps) watch rings chains etc. should be
avoided.
/. aste causes many accidents be sure o! what you are doing.
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. se grounding chains whenever entering the precipitator 3"
switch enclosure or bus ducts. 3he precipitator can hold a high static
charge up to 1/ kV a!ter it is de"energi%ed. 3he only sa!e ground is
one that can be seen.
4. 5ever open a hopper door unless the dust level is positively below
the door. 6o not trust the level alarm. heck !rom the upper access in
the precipitator. ot dust can !low like water and severely burn or kill a
person standing below the door. 7ear protective clothing.
8. e on !irm !ooting prior to entering the precipitator. lear all trip
ha%ards. se the back o! the hand to test !or high metal temperatures.
9. Avoid o%one inhalation. :%one is created any time the discharge
electrodes are energi%ed. 7ear an air"line mask when entering the
precipitator !lues or stack when o%one may be present. 6o not use
!ilters cartridge or canister respirators.
10. 5ever poke hoppers with an uninsulated metal bar. ;eep sa!ety and
danger signs in place. lean bright signs are obeyed more than
deteriorated signs.
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Principles of Electrostatic precipitator
Electrostatic precipitatio is a !et"o# o$ #%st collectio t"at %ses
electrostatic $orces& a# cosists o$ #isc"ar'e (ires a# collecti'
plates. A "i'" )olta'e is applie# to t"e #isc"ar'e (ires to $or! a
electrical $iel# *et(ee t"e (ires a# t"e collecti' plates& a# also
ioi+es t"e 'as aro%# t"e #isc"ar'e (ires to s%ppl, ios. W"e 'as
t"at cotais a aerosol -#%st& !ist $lo(s *et(ee t"e collecti'
plates a# t"e #isc"ar'e (ires& t"e aerosol particles i t"e 'as are
c"ar'e# *, t"e ios. T"e Co%lo!* $orce ca%se# *, t"e electric $iel#
ca%ses t"e c"ar'e# particles to *e collecte# o t"e collecti' plates&
a# t"e 'as is p%ri$ie#. T"is is t"e priciple o$ electrostatic
precipitatio& a# Electrostatic precipitator appl, t"is priciple o ai#%strial scale. T"e particles collecte# o t"e collecti' plates are
re!o)e# *, !et"o#s s%c" as -1 #islo#'i' *, rappi' t"e collecti'
plates& -/ scrapi' o$$ (it" a *r%s"& or -0 (as"i' o$$ (it" (ater&
a# re!o)i' $ro! a "opper.
ia'ra! o$ t"e priciple o$ electrostatic precipitatio
Dust collection efficiency and electrical resistivity of dust
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T"e #%st collectio e$$iciec, o$ Electrostatic precipitator is a$$ecte#
*, t"e electrical resisti)it, o$ t"e #%st collecte#.
I t"e or!al resisti)it, area& t"e #%st collectio e$$iciec, is "i'"& so
#%st collectio is sta*le. 2ost o$ t"e aerosols "a#le# *, Electrostaticprecipitator are i t"is electrical resisti)it, area.
Particles i t"e lo(3resisti)it, area lose t"eir c"ar'e as soo as t"e,
arri)e at t"e collecti' plate& so t"e, are re3etraie# i t"e #%st
collectio area& a# t"e #%st collectio e$$iciec, is 'reatl, re#%ce#.
-Re3etrai!et
T"e #%st collectio e$$iciec, i t"e "i'"3resisti)it, area re#%ces as
t"e electrical resisti)it, o$ t"e #%st icreases. Also& partial #isc"ar'e
occ%rs (it"i t"e #%st la,er collecte# o t"e collecti' plates& a# as a
res%lt $las"o)ers $re4%etl, occ%r& t"e applie# )olta'e is re#%ce#& a#
t"e #isc"ar'e c%rret is re#%ce#. I$ t"e electrical resisti)it, o$ t"e #%st
is $%rt"er icrease#& t"e #isc"ar'e c%rret icreases a*or!all,& a#
t"e applie# )olta'e is re#%ce# -*ac5 coroa p"eo!eo. T"e
!o)i'3electro#e t,pe electrostatic precipitator (e #e)elope# is
s%ita*le $or "i'"3per$or!ace collectio o$ "i'"3resisti)it, #%st.
T"ere$ore& a i!portat $actor ("e plai' Electrostatic precipitator
is t"e electrical resisti)it, o$ t"e #%st to *e collecte#.
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pa'e top
Dust collection efficiency and particle size distribution
T"e #%st collectio e$$iciec, o$ Electrostatic precipitator is a$$ecte#
*, t"e particle si+e o$ t"e aerosol -#%st& !ist to *e collecte#. T"e
t"eoretical !i'ratio )elocit, at ("ic" a particle #ia!eter o$ se)eral
6! !o)es to(ar#s t"e collecti' plate is al!ost #irectl, proportioal
to t"e particle #ia!eter. W"e #%st collectio is per$or!e# o aaerosol (it" #i$$eret si+e particles %si' a electrostatic precipitator&
t"e collectio e$$iciec, is "i'" $or t"e lar'e particles& a# lo( $or t"e
s!all particles.
To o*tai t"e sa!e #%st collectio e$$iciec, $or a aerosol (it" s!all
particle si+e& t"e electrostatic precipitator !%st *e lar'er -to icrease
t"e treati' ti!e it ta5es $or t"e process 'as to pass t"ro%'" t"a t"at
o$ lar'e3si+e particles. T"ere$ore& t"e particle si+e #istri*%tio o$ t"eaerosol to *e collecte# is a i!portat $actor ("e plai' a
electrostatic precipitator.
Relationship between electrostatic precipitator collection
efficiency and the particle size
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Dust collection efficiency and aerosol concentration
T"e #%st collectio e$$iciec, o$ a electrostatic precipitator is 'reatl,
a$$ecte# *, t"e cocetratio i t"e 'as o$ t"e aerosol -#%st& !ist to
*e collecte#. 7or t"e sa!e re4%ire# )al%e o$ aerosol cocetratio at
t"e o%tlet o$ t"e electrostatic precipitator& t"e "i'"er t"e aerosol
cocetratio at t"e ilet& t"e lo'er t"e treat!et ti!e o$ t"e 'as i
t"e electrostatic precipitator& a# t"e lar'er t"e #e)ice.
Also& i$ t"e ilet aerosol cocetratio is "i'" a# t"e cotet o$ $ie
particles s!aller t"a se)eral 6! is "i'"& i or#er to create a c"ar'e
clo%# o$ c"ar'e# $ie particles *et(ee t"e #isc"ar'e (ires a# t"e
collecti' plates& t"e coroa #isc"ar'e $ro! t"e #isc"ar'e (ires is
re#%ce#& also re#%ci' t"e #%st collectio e$$iciec, -space c"ar'i'
e$$ect.
T"e aerosol cocetratio at t"e electrostatic precipitator ilet a# t"ere4%ire# o%tlet cocetratio are i!portat $actors ("e plai' a
electrostatic precipitator.
Introduction to Precipitators
A electrostatic precipitator is a lar'e& i#%strial e!issio3cotrol
%it. It is #esi'e# to trap a# re!o)e #%st particles $ro! t"e e8"a%st
'as strea! o$ a i#%strial process. Precipitators are %se# i t"esei#%stries9
Po(er:Electric
Ce!et
C"e!icals
2etals
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Paper
I !a, i#%strial plats& partic%late !atter create# i t"e i#%strial
process is carrie# as #%st i t"e "ot e8"a%st 'ases. T"ese #%st3la#e
'ases pass t"ro%'" a electrostatic precipitator t"at collects !ost o$t"e #%st. Cleae# 'as t"e passes o%t o$ t"e precipitator a# t"ro%'" a
stac5 to t"e at!osp"ere. Precipitators t,picall, collect ;;.;< or !ore
o$ t"e #%st $ro! t"e 'as strea!.
Precipitators $%ctio *, electro staticall, c"ar'i' t"e #%st particles
i t"e 'as strea!. T"e c"ar'e# particles are t"e attracte# to a#
#eposite# o plates or ot"er collectio #e)ices. W"e eo%'" #%st "as
acc%!%late#& t"e collectors are s"a5e to #islo#'e t"e #%st& ca%si' itto $all (it" t"e $orce o$ 'ra)it, to "oppers *elo(. T"e #%st is t"e
re!o)e# *, a co)e,or s,ste! $or #isposal or rec,cli'.
epe#i' %po #%st c"aracteristics a# t"e 'as )ol%!e to *e treate#&
t"ere are !a, #i$$eret si+es& t,pes a# #esi's o$ electrostatic
precipitators. =er, lar'e po(er plats !a, act%all, "a)e !%ltiple
precipitators $or eac" %it.
Basic Principles
Electrostatic precipitatio re!o)es particles $ro! t"e e8"a%st 'as
strea! o$ a i#%strial process. O$te t"e process i)ol)es
co!*%stio& *%t it ca *e a, i#%strial process t"at (o%l# ot"er(ise
e!it particles to t"e at!osp"ere. Si8 acti)ities t,picall, ta5e place9
Ioi+atio 3 C"ar'i' o$ particles
2i'ratio 3 Trasporti' t"e c"ar'e# particles to t"e collecti'
s%r$aces
Collectio 3 Precipitatio o$ t"e c"ar'e# particles oto t"ecollecti' s%r$aces
C"ar'e issipatio 3 Ne%trali+i' t"e c"ar'e# particles o t"e
collecti' s%r$aces
Particle islo#'i' 3 Re!o)i' t"e particles $ro! t"e collecti'
s%r$ace to t"e "opper
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Particle Re!o)al 3 Co)e,i' t"e particles $ro! t"e "opper to a
#isposal poit
T"e !a>or precipitator co!poets t"at acco!plis" t"ese acti)ities are
as $ollo(s9
isc"ar'e Electro#es Po(er Co!poets
Precipitator Cotrols
Rappi' S,ste!s
P%r'e Air S,ste!s
7l%e Gas Co#itioi'
Design & Performance Requirements
esi'i' a precipitator $or opti!%! per$or!ace re4%ires proper
si+i' o$ t"e precipitator i a##itio to opti!i+i' precipitator
e$$iciec,. W"ile so!e %sers rel, o t"e precipitator !a%$act%rer to
#eter!ie proper si+i' a# #esi' para!eters& ot"ers c"oose to eit"er
ta5e a !ore acti)e role i t"is process or "ire o%tsi#e e'ieeri'
$ir!s.
Precipitator per$or!ace #epe#s o its si+e a# collecti' e$$iciec,.
I!portat para!eters icl%#e t"e collecti' area a# t"e 'as )ol%!e to
*e treate#. Ot"er 5e, $actors i precipitator per$or!ace icl%#e t"e
electrical po(er ip%t a# #%st c"e!istr,.
Precipitator si+i'
T"e si+i' process is co!ple8 as eac" precipitator !a%$act%rer "as a
%i4%e !et"o# o$ si+i'& o$te i)ol)i' t"e %se o$ co!p%ter !o#els
a# al(a,s i)ol)i' a 'oo# #ose o$ >%#'!et. No co!p%ter !o#elo its o( ca assess all t"e )aria*les t"at a$$ect precipitator
per$or!ace.
Collecti' E$$iciec,
Base# o speci$ic 'as )ol%!e a# #%st loa#& calc%latios are %se# to
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pre#ict t"e re4%ire# si+e o$ a precipitator to ac"ie)e a #esire#
collecti' e$$iciec,.
Po(er Ip%t
Po(er ip%t is co!prise# o$ t"e )olta'e a# c%rret i a electrical
$iel#. Icreasi' t"e po(er ip%t i!pro)es precipitator collecti'e$$iciec, %#er or!al co#itios.
Process ariables Gas c"aracteristics a# particle properties #e$ie
"o( (ell a precipitator (ill (or5 i a 'i)e applicatio. T"e !ai
process )aria*les to cosi#er are9
Gas $lo( rate
T"e 'as $lo( rate i a po(er plat is #e$ie# *, coal 4%alit,& *oilerloa#& e8cess air rate a# *oiler #esi'. W"ere t"ere is o co!*%stio&
t"e 'as $lo( rate (ill "a)e process3speci$ic #eter!iats.
Particle si+e a# si+e #istri*%tio
T"e si+e #istri*%tio i a po(er plat is #e$ie# *, coal 4%alit,& t"e
coal !ill setti's a# *%rer #esi'. Particle si+e $or o3co!*%stio
processes (ill "a)e si!ilar #eter!iats.
Particle resisti)it,
T"e resisti)it, o$ $l, as" or ot"er particles is i$l%ece# *, t"e
c"e!ical co!positio a# t"e 'as te!perat%re.
Gas te!perat%re
7ollo(i' are #etails o$ t"ese process )aria*les9
1. Gas 7lo( Rate
A precipitator operates *est (it" a 'as )elocit, o$ 0. 3 . $t:sec. At
"i'"er )elocit,& particle re3etrai!et icreases rapi#l,. I$ )elocit, istoo lo(& per$or!ace !a, s%$$er $ro! poor 'as $lo( #istri*%tio or
$ro! particle #ropo%t i t"e #%ct(or5.
/. Particle Si+e
A precipitator collects particles !ost easil, ("e t"e particle si+e is
coarse. T"e 'eeratio o$ t"e c"ar'i' coroa i t"e ilet $iel# !a, *e
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s%ppresse# i$ t"e 'as strea! "as too !a, s!all particles -less t"a 1
6!.
=er, s!all particles -@./ 3 @.6! are t"e !ost #i$$ic%lt to collect
*eca%se t"e $%#a!etal $iel#3c"ar'i' !ec"ais! is o)er("el!e#
*, #i$$%sio c"ar'i' #%e to ra#o! collisios (it" $ree ios.0. Particle Resisti)it,
Resisti)it, is resistace to electrical co#%ctio. T"e "i'"er t"e
resisti)it,& t"e "ar#er it is $or a particle to tras$er its electrical c"ar'e.
Resisti)it, is i$l%ece# *, t"e c"e!ical co!positio o$ t"e 'as
strea!& particle te!perat%re a# 'as te!perat%re. Resisti)it, s"o%l# *e
5ept i t"e ra'e o$ 1@ 3 1@1@ o"!3c!.
Hi'" resisti)it, ca re#%ce precipitator per$or!ace. 7or e8a!ple& ico!*%stio processes& *%ri' re#%ce#3s%l$%r coal icreases
resisti)it, a# re#%ces t"e collecti' e$$iciec, o$ t"e precipitator.
So#i%! a# iro o8i#es i t"e $l, as" ca re#%ce resisti)it, a#
i!pro)e per$or!ace& especiall, at "i'"er operati' te!perat%res.
O t"e ot"er "a#& lo( resisti)it, ca also *e a pro*le!. 7or e8a!ple
-i co!*%stio processes& %*%re# car*o re#%ces precipitator
per$or!ace *eca%se it is so co#%cti)e a# loses its electrical c"ar'e
so 4%ic5l, t"at it is easil, re3etraie# $ro! t"e collecti' plate.
. Gas Te!perat%re
T"e e$$ect o$ 'as te!perat%re o precipitator collecti' e$$iciec,&
'i)e its i$l%ece o particle resisti)it,& ca *e si'i$icat.
. Iteractios to Cosi#er
Particle si+e #istri*%tio a# particle resisti)it, a$$ect t"e co"esi)eess
o$ t"e la,er o$ precipitate# !aterial o t"e collecti' plates a# t"e
a*ilit, o$ t"e rappi' s,ste! to #islo#'e t"is la,er $or trasport itot"e precipitator "opper (it"o%t e8cessi)e re3etrai!et.
!bout Discharge Electrodes -Bac5 to top
isc"ar'e electro#es e!it c"ar'i' c%rret a# pro)i#e )olta'e t"at
'eerates a electrical $iel# *et(ee t"e #isc"ar'e electro#es a# t"e
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collecti' plates. T"e electrical $iel# $orces #%st particles i t"e 'as
strea! to !i'rate to(ar# t"e collecti' plates. T"e particles t"e
precipitate oto t"e collecti' plates. Co!!o t,pes o$ #isc"ar'e
electro#es icl%#e9
Strai'"t ro%# (ires T(iste# (ire pairs
Bar*e# #isc"ar'e (ires
Ri'i# !asts
Ri'i# $ra!es
Ri'i# spi5e# pipes
Spiral (ires
isc"ar'e electro#es are t,picall, s%pporte# $ro! t"e %pper #isc"ar'e
$ra!e a# are "el# i ali'!et *et(ee t"e %pper a# lo(er
#isc"ar'e $ra!es. T"e %pper #isc"ar'e $ra!e is i t%r s%pporte# $ro!
t"e roo$ o$ t"e precipitator casi'. Hi'"3)olta'e is%lators are
icorporate# ito t"e s%pport s,ste!. I (ei'"te# (ire s,ste!s& t"e
#isc"ar'e electro#es are "el# ta%t *, (ei'"ts at t"e lo(er e# o$ t"e
(ires.
!bout "ollecting Plates -Bac5 to top
Collecti' plates are #esi'e# to recei)e a# retai t"e precipitate#
particles %til t"e, are itetioall, re!o)e# ito t"e "opper.
Collecti' plates are also part o$ t"e electrical po(er circ%it o$ t"e
precipitator. T"ese collecti' plate $%ctios are icorporate# ito t"e
precipitator #esi'. Plate *a$$les s"iel# t"e precipitate# particles $ro!
t"e 'as $lo( ("ile s!oot" s%r$aces pro)i#e $or "i'" operati' )olta'e.
Collecti' plates are s%spe#e# $ro! t"e precipitator casi' a# $or!t"e 'as passa'es (it"i t"e precipitator. W"ile t"e #esi' o$ t"e
collecti' plates )aries *, !a%$act%rer& t"ere are t(o co!!o
#esi's9
Plates s%pporte# $ro! a)il *ea!s at eit"er e#
T"e a)il *ea! is also t"e poit o$ i!pact $or t"e collecti' rapper
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Plates s%pporte# (it" "oo5s #irectl, $ro! t"e precipitator casi'
T(o or !ore collecti' plates are coecte# at or ear t"e ceter *,
rapper *ea!s& ("ic" t"e ser)e as i!pact poits $or t"e rappi'
s,ste!
Top& ceter& or *otto! spacer *ars !a, *e %se# to !aitai collecti'
plate ali'!et a# s%stai electrical clearaces to t"e #isc"ar'e
s,ste!.
!bout Power #upplies and "ontrols -Bac5 to top
T"e po(er s%ppl, s,ste! is #esi'e# to pro)i#e )olta'e to t"e
electrical $iel# -or *%s sectio at t"e "i'"est possi*le le)el. T"e
)olta'e !%st *e cotrolle# to a)oi# ca%si's%staie# arci' or spar5i' *et(ee t"e electro#es
a# t"e collecti' plates.
Clic5 "ere to )ie( aprecipitator po(er
s,ste!ai!ate# sc"e!atic s"o(i' represetati)e
co!poets.
Electricall,& a precipitator is #i)i#e# ito a 'ri#&
(it" electrical $iel#s i series -i t"e #irectio o$ t"e
'as $lo( a# oe or !ore *%s sectios i parallel
-cross3(ise to t"e 'as $lo(. W"e electrical $iel#s are i series& t"e
po(er s%ppl, $or eac" $iel# ca *e a#>%ste# to opti!i+e operatio o$
t"at $iel#. Li5e(ise& "a)i' !ore t"a oe electrical *%s sectio i
parallel allo(s a#>%st!ets to co!pesate $or t"eir #i$$ereces& so t"at
po(er ip%t ca *e opti!i+e#. T"e po(er s%ppl, s,ste! "as $o%r
*asic co!poets9
A%to!atic )olta'e cotrol
Step3%p tras$or!er
Hi'"3)olta'e recti$ier
Sesi' #e)ice
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1. =olta'e cotrol
A%to!atic )olta'e cotrol )aries t"e po(er to t"e tras$or!er3recti$ier
i respose to si'als recei)e# $ro! sesors i t"e precipitator a# t"e
tras$or!er3recti$ier itsel$. It !oitors t"e electrical co#itios isi#e
t"e precipitator& protects t"e iteral co!poets $ro! arc3o)er#a!a'es& a# protects t"e tras$or!er3recti$ier a# ot"er co!poets
i t"e pri!ar, circ%it.
T"e i#eal a%to!atic )olta'e cotrol (o%l# pro#%ce t"e !a8i!%!
collecti' e$$iciec, *, "ol#i' t"e operati' )olta'e o$ t"e
precipitator at a le)el >%st *elo( t"e spar53o)er )olta'e. Ho(e)er& t"is
le)el caot *e ac"ie)e# 'i)e t"at co#itios c"a'e $ro! !o!et to
!o!et. Istea#& t"e a%to!atic )olta'e cotrol icreases o%tp%t $ro!t"e tras$or!er3recti$ier %til a spar5 occ%rs. T"e t"e cotrol resets to
a lo(er po(er le)el& a# t"e po(er icreases a'ai %til t"e e8t spar5
occ%rs.
!utomatic oltage "ontrollers-$or Electrostatic Precipitators
A electroic #e)ice %se# to cotrol t"e applicatio o$ .C. po(er
ito a $iel# o$ a electrostatic precipitator. -PIC O7 2=C 7ACE
PANEL AN PIC O7 INTER7ACE BOAR
$heory
Optimize power applicationD T"e pri!ar, p%rpose o$ a )olta'e
cotroller is to #eli)er as !%c" %se$%l electrical po(er to t"e
correspo#i' electrostatic precipitator $iel#-s as possi*le. T"is is ot
a eas, >o* electrical c"aracteristics i t"e $iel#-s are costatl,
c"a'i'& ("ic" is (", a )olta'e cotroller is re4%ire#. Spark reactionD W"e t"e )olta'e applie# to t"e electrostatic
precipitator $iel# is too "i'" $or t"e co#itios at t"e ti!e& a spar5 o)er
-or coroa #isc"ar'e (ill occ%r. etri!etall, "i'" a!o%ts o$
c%rret ca occ%r #%ri' a spar5 o)er i$ ot properl, cotrolle#& ("ic"
co%l# #a!a'e t"e $iel#s. A )olta'e cotroller (ill !oitor t"e pri!ar,
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a# seco#ar, )olta'e a# c%rret o$ t"e circ%it& a# #etect a spar5
o)er co#itio. Oce #etecte#& t"e po(er applie# to t"e $iel# (ill *e
i!!e#iatel, c%t o$$ or re#%ce#& ("ic" (ill stop t"e spar5. A$ter a
s"ort a!o%t o$ ti!e t"e po(er (ill *e ra!pe# *ac5 %p& a# t"e
process (ill start o)er.Protect system components by adhering to component limitationsD
T"e Tras$or!er Recti$ier set -TR set ca *e #a!a'e# *, e8cessi)e
a!o%ts o$ c%rret or )olta'e $lo(i' t"ro%'" it. Eac" TR set "as
)olta'e a# c%rret li!its esta*lis"e# *, t"e !a%$act%rer& ("ic" are
la*ele# o a attac"e# a!eplate -PIC O7 A NA2EPLATE. T"ese
a!eplate li!it )al%es -t,picall, pri!ar, a# seco#ar, c%rret& a#
)olta'e are pro'ra!!e# ito t"e )olta'e cotroller. T"ro%'"!eteri' circ%its& t"e )olta'e cotroller (ill !oitor t"ese )al%es& a#
es%re t"ese li!its are ot e8cee#e#.
TrippingD W"e a co#itio occ%rs t"at t"e )olta'e cotroller
caot cotrol& o$te ti!es t"e )olta'e cotroller (ill trip. A trip
!eas t"e )olta'e cotroller -*, (a, o$ t"e cotactor (ill s"%t o$$ t"e
i#i)i#%al precipitator po(er circ%it. A s"ort isi#e t"e electrostatic
precipitator $iel# ca%se# *, a $alle #isc"ar'e electro#e -(ire& or a
s"orte# o%t Silicoe Cotrolle# Recti$ier are e8a!ples o$ co#itios
t"at a )olta'e cotroller caot cotrol. -PIC O7 CLOSE3UP O7
TRIP LIGHT ON 2=C 7ACE PANEL
%peration
To !a8i!i+e electrostatic precipitator e$$iciec, a )olta'e cotroller
%s%all, atte!pts to icrease t"e electrical po(er #eli)ere# to t"e $iel#.
Ho(e)er i so!e co#itios a )olta'e cotroller !%st >%st !aitaipo(er at a costat le)el. Icrease# electrical po(er ito t"e
electrostatic precipitator #irectl, correlates (it" *etter precipitator
per$or!ace& *%t t"ere is a li!it. I$ too !%c" )olta'es is applie# $or a
'i)e co#itio -as !etioe# i t"e spar5 reactio sectio& a spar5
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o)er (ill occ%r. %ri' a spar5 o)er precipitator per$or!ace i t"at
$iel# (ill #rop to +ero& re#eri' t"at $iel# te!poraril, ie$$ecti)e.
To o)erco!e t"e crippli' e$$ect t"at spar5 o)er "as to icreasi' t"e
electrical po(er i t"e precipitator $iel#& spar5 respose al'orit"!s
"a)e *ee #e)elope# t"at (ill iterr%pt po(er %po #etectio o$ aspar5& t"e ra!p po(er *ac5 %p to a "i'" le)el. T"ese respose
al'orit"!s ca 'reatl, i$l%ece o)erall precipitator per$or!ace.
1. Tras$or!er3Recti$iers
T"e tras$or!er3recti$ier rati' s"o%l# *e !atc"e# to t"e loa#
i!pose# *, t"e electrical $iel# or *%s sectio. T"e po(er s%ppl, (ill
per$or! *est ("e t"e tras$or!er3recti$iers operate at F@ 3 ;@< o$
t"e rate# capacit,& (it"o%t e8cessi)e spar5i'. T"is re#%ces t"e!a8i!%! coti%o%s3loa# )olta'e a# coroa po(er ip%ts. Practical
operati' )olta'es $or tras$or!er3recti$iers #epe# o9
o Collecti' plate spaci'
o Gas a# #%st co#itios
o Collecti' plate a# #isc"ar'e electro#e 'eo!etr,
At seco#ar, c%rret le)els o)er 1@@ !A& iteral i!pe#ace o$ a
tras$or!er3recti$ier is lo(& ("ic" !a5es sta*le a%to!atic )olta'e
cotrol !ore #i$$ic%lt to ac"ie)e. T"e #esi' o$ t"e tras$or!er3
recti$ier s"o%l# call $or t"e "i'"est possi*le i!pe#ace t"at is
co!!es%rate (it" t"e applicatio a# per$or!ace re4%ire!ets.
O$te& t"is li!its t"e si+e o$ t"e electrical $iel# or *%s sectio.
It is 'eeral practice to a## a##itioal i!pe#ace i t"e $or! o$ a
c%rret3li!iti' reactor i t"e pri!ar, circ%it. T"is reactor (ill li!it
t"e pri!ar, c%rret #%ri' arci' a# also i!pro)e t"e (a)e s"ape o$
t"e )olta'e:c%rret $e# ito t"e tras$or!er3recti$ier./. Coroa c%rret #esit,
Coroa c%rret #esit, s"o%l# *e i t"e ra'e o$ 1@ 3 1@@ !A:1@@@ $t/
o$ plate area. -Calc%late t"is %si' seco#ar, c%rret #i)i#e# *,
collecti' area o$ t"e electrical $iel# or *%s sectio. T"e act%al le)el
#epe#s %po9
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o Locatio o$ electrical $iel# or *%s sectio to *e eer'i+e#
o Collecti' plate area
o Gas a# #%st co#itios
o Collecti' electro#e a# #isc"ar'e (ire 'eo!etr,
!bout as Distribution #ystems -Bac5 to top
Oe electrical $iel# or *%s sectio o$ a electrostatic precipitator is *,
itsel$ a i#epe#et precipitator. Its operatio is 'o)ere# *, t"e ilet
'as a# #%st co#itios& as (ell as t"e collecti' plate a# #isc"ar'e
electro#e 'eo!etries.
Wit"i t"is electrical $iel# or *%s sectio& oe 'as passa'e is also a
i#epe#et precipitator 3 'o)ere# *, t"e sa!e $actors. -Note t"at t"e'as passa'e s"ares t"e )olta'e le)el (it" t"e a#>acet 'as passa'es o$
t"e sa!e electrical $iel# or *%s sectio& *%t ot t"e coroa c%rret
le)el& ("ic" ca *e #i$$eret i eac" 'as passa'e.
T"is poits to t"e i!portace o$ creati' si!ilar 'as a# #%st
co#itios 1 at t"e ilet o$ eac" electrical $iel# or *%s sectio& a# /
$%rt"er at t"e ilet o$ eac" 'as passa'e o$ t"e electrical $iel# or *%s
sectio. I#eall,& %i$or!it, is #esire# i9
Gas )elocit,
Gas te!perat%re
%st loa#i'
Gas )elocit, #istri*%tio ca *e !ost e$$ecti)el, i$l%ece# *, t"e %se
o$ 'as #istri*%tio #e)ices.
T"e 4%alit, o$ 'as )elocit, #istri*%tio ca *e !eas%re# i a scale#3
#o( !o#el o$ t"e precipitator a# its #%ct(or5& a# also i t"e
precipitator itsel$. T,pical criteria are *ase# o ICAC -Istit%te o$Clea Air Co!paies reco!!e#atios %si' a)era'e 'as )elocities
or o a calc%late# R2S statistical represetatio o$ t"e 'as )elocit,
patter.
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I 'eeral& 'as #istri*%tio #e)ices cosist o$ t%ri' )aes i t"e ilet
#%ct(or5& a# per$orate# 'as #istri*%tio plates i t"e ilet a#:or
o%tlet $iel#s o$ t"e precipitator.
!bout Rapping #ystems -Bac5 to top
Rappers are ti!e3cotrolle# s,ste!s pro)i#e# $or re!o)i' #%st $ro!t"e collecti' plates a# t"e #isc"ar'e electro#es as (ell as $or 'as
#istri*%tio #e)ices -optioal a# $or "opper (alls -optioal.
Rappi' s,ste!s !a, *e act%ate# *, electrical or pe%!atic po(er& or
*, !ec"aical !eas. T%!*li' "a!!ers !a, also *e %se# to
#islo#'e as". Rappi' !et"o#s icl%#e9
Electric )i*rators
Electric soleoi# pisto #rop rappers Pe%!atic )i*rati' rappers
T%!*li' "a!!ers
Soic "ors -#o ot re4%ire tras!issio asse!*lies
1. isc"ar'e Electro#e Rappi'
I 'eeral& #isc"ar'e electro#es s"o%l# *e 5ept as $ree as possi*le o$
acc%!%late# partic%late. T"e rappi' s,ste! $or t"e #isc"ar'e
electro#es s"o%l# *e operate# o a coti%o%s sc"e#%le (it" repeat
ti!es i t"e / 3 !i%te ra'e& #epe#i' o t"e si+e a# ilet
partic%late loa#i' o$ t"e precipitator.
/. Collecti' Plate Rappi'
Collecti' plate rappi' !%st re!o)e t"e *%l5 o$ t"e precipitate# #%st.
T"e collecti' plates are s%pporte# $ro! a)il *ea!s or #irectl, (it"
"oo5s $ro! t"e precipitator casi'. Wit" a)il *ea! s%pport& t"e
i!pact o$ t"e rappi' s,ste! is #irecte# ito t"e *ea!s locate# at t"e
lea#i' a#:or traili' e#'e o$ t"e collecti' plates. 7or #irect casi's%pport& t"e i!pact is #irecte# ito t"e rapper *ea!s locate# at or ear
t"e ceter o$ t"e top o$ t"e collecti' plates.
T"e $irst electrical $iel# 'eerall, collects a*o%t @3@< o$ t"e ilet
#%st loa#. T"e $irst $iel# plates s"o%l# *e rappe# o$te eo%'" so t"at
t"eir precipitate# la,er o$ partic%late is a*o%t 0: 3 1:/ t"ic5. T"ere is
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o a#)ata'e i rappi' !ore o$te sice t"e precipitate# #%st "as ot
,et a''lo!erate# to a s"eet ("ic" re4%ires a !ii!%! la,er
t"ic5ess. S"eet $or!atio is essetial to !a5e t"e #%st #rop ito t"e
precipitator "opper (it"o%t re3etrai!et ito t"e 'as strea!.
Rappi' less $re4%etl, t,picall, res%lts i a #eterioratio o$ t"eelectrical po(er ip%t *, a##i' a a##itioal resistace ito t"e
po(er circ%it. Oce a opti!%! rappi' c,cle "as *ee $o%# $or t"e
$irst electrical $iel# -("ic" !a, )ar, across t"e $ace o$ a lar'e
precipitator& t"e opti!%! rappi' c,cles $or t"e #o(strea!
electrical $iel#s ca *e esta*lis"e#.
T"e collecti' plate rappi' s,ste! o$ t"e $irst $iel# "as a repeat ti!e
T e4%al to t"e ti!e it ta5es to *%il# a 0: 3 1:/la,er o t"e collecti'plates. T"e plates i t"e seco# $iel# s"o%l# "a)e a repeat ti!e o$
a*o%t T& a# t"e plates i t"e t"ir# $iel# s"o%l# "a)e a repeat ti!e o$
/T. I#eall,& t"ese repeat ti!es ,iel# a #eposite# la,er o$ 0:31:/ $or
t"e plates i all t"ree $iel#s. A#>%st!et !a, *e re4%ire# $or $actors
s%c" as #%st resisti)it,& #%st la,er co"esi)eess& 'as te!perat%re
e$$ects& electrical $iel# "ei'"t a# le't"& a# t"e collecti' area
ser)e# *, oe rapper.
0. Gas istri*%tio Plate a# Hopper Wall Rappi'
T"e 'as #istri*%tio plates s"o%l# also *e 5ept $ree o$ e8cessi)e
partic%late *%il#%p a# !a, re4%ire rappi' o a coti%o%s *ase (it"
a c,cle ti!e i t"e 1@3/@ !i%te ra'e& #epe#i' o t"e ilet
partic%late loa#i' o$ t"e precipitator a# t"e at%re o$ t"e partic%late.
Gas #istri*%tio plates i t"e o%tlet o$ t"e precipitator !a, *e rappe#
less o$te -e)er, 0@ 3 @ !i%tes.
. I!pro)i' Rappi' S,ste! Per$or!aceAll precipitator rappi' s,ste!s allo( a#>%st!et o$ rappi'
$re4%ec,& or!all, starti' (it" t"e "i'"est $re4%ec, -t"e least ti!e
*et(ee raps& pro'ressi' to t"e lo(est $re4%ec,. T"e ti!es t"at are
act%all, a)aila*le !a, *e li!ite#. Rappi' s,ste!s (it" pe%!atic or
electric act%ators allo( )ariatios o$ t"e rappi' itesit,. Pe%!atic
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or electric )i*rators allo( a#>%st!ets o$ t"e rappi' ti!e. State3o$3
t"e3art rapper cotrols allo( selectio o$ rappi' se4%eces& selectio
o$ i#i)i#%al rappers& a# pro)i#e ati3coici#ece sc"e!es ("ic"
allo( ol, oe rapper to operate at a 'i)e ti!e.
Rappi' s,ste!s ca *e opti!i+e# $or top precipitator per$or!ace
%si' precipitator po(er ip%t a# stac5 opacit, as criteria.
Opti!i+atio o$ t"e rappi' s,ste! starts (it" t"e #isc"ar'e electro#e
rappi' s,ste! operati' o its o( ti!e sc"e#%le& $or e8a!ple (it"
repeat ti!es o$ / 3 !i%tes. T"e rappi' s,ste! $or t"e 'as
#istri*%tio screes i t"e ilet a# o%tlet o$ t"e precipitator s"o%l#
t"e *e operate# (it" repeat ti!es o$ /30 !i%tes $or t"e ilet a# / 30 "o%rs $or t"e o%tlet screes.
T"e ol, rappi' s,ste! re4%iri' opti!i+atio is t"e collecti' plate
rappi' s,ste!. T"e opti!i+atio s"o%l# start (it" t"e Collecti'
Plate Rappi' Sc"e#%le #eter!ie# a*o)e. Ne8t& t"e rappi'
$re4%ec, o$ t"e ilet $iel# s"o%l# *e icrease# or #ecrease# %til t"e
electrical po(er ip%t o$ t"e ilet $iel# re!ais costat. Ne8t& t"e
rappi' $re4%ec, o$ t"e ot"er $iel#s s"o%l# *e a#>%ste# i se4%ece
%til t"eir electrical po(er ip%ts re!ai costat. I$ t"e stac5 opacit,
trace s"o(s rappi' spi5es& t"e rappi' itesit, s"o%l# *e re#%ce#
("ile o*ser)i' t"e electrical po(er ip%t o$ t"e precipitator.
T"e a#>%st!et o$ t"e rappi' s,ste! $or opti!%! precipitator
per$or!ace is a slo( process. It re4%ires a s%*statial a!o%t o$ ti!e
$or sta*ili+atio a$ter eac" a#>%st!et.
!bout 'oppers -Bac5 to top
Precipitator "oppers are #esi'e# to co!pletel, #isc"ar'e #%st loa# o#e!a#. T,picall,& precipitator "oppers are recta'%lar i cross3
sectio (it" si#es o$ at least @3#e'ree slope. T"ese "oppers are
is%late# $ro! t"e ec5 a*o)e t"e #isc"ar'e $la'e (it" t"e is%latio
co)eri' t"e etire "opper area. I a##itio& t"e lo(er 1:3 1:0 o$ t"e
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"opper (all !a, *e "eate#. isc"ar'e #ia!eters are 'eerall, 3
1/.
1. Is%latio
Is%latio pro)i#es protectio $or $acilit, persoel as (ell as (or5i'
to retai as !%c" "opper (all te!perat%re as possi*le. Hopper (allte!perat%re retetio #isco%ra'es co#esatio o t"e isi#e o$ t"e
"opper. Heaters are a##e# to es%re "ot !etal s%r$aces i!!e#iatel,
a*o)e t"e $l, as" #isc"ar'e.
/. 7acilitati' "opper #isc"ar'e
Hopper #isc"ar'e pro*le!s are ca%se# *, co!pactio o$ t"e $l, as" i
t"e "opper. Co!pactio c"aracteristics are a$$ecte# *, !oist%re
cotet& particle si+e a# s"ape& "ea# o$ !aterial& a# )i*ratio. T"e$lo( o$ $l, as" o%t o$ t"e "opper ca *e $acilitate# *, t"e %se o$
e8teral )i*rators. T"ese ca operate o t"e o%tsi#e (all o$ t"e "opper
or o a iteral "opper *a$$le.
0. Hopper $l%i#i+ers
Hopper $l%i#i+ers "a)e a !e!*rae t"at per!its air $lo( to t"e $l, as"
#irectl, a*o)e. T"is air $lo( $ills t"e )oi#s *et(ee t"e $l, as"
particles at a sli'"t press%re& c"a'es t"e repose a'le o$ t"e particles&
a# pro!otes 'ra)it, $lo(.
. As" "a#li' s,ste!
T"e $l, as" "a#li' s,ste! e)ac%ates t"e $l, as" $ro! t"e "oppers&
a# trasports t"e $l, as" to reprocessi' or to #isposal. T"e as"
"a#li' s,ste! s"o%l# *e #esi'e# a# operate# to re!o)e t"e
collecte# $l, as" $ro! t"e "oppers (it"o%t ca%si' re3etrai!et ito
t"e 'as $lo( t"ro%'" t"e precipitator. T"e #esi' o$ t"e as" "a#li'
s,ste! s"o%l# allo( $or $le8i*ilit, o$ sc"e#%li' t"e "opper#isc"ar'es accor#i' to t"e $l, as" *ei' collecte# i t"ese "oppers.
Eit"er t"e precipitator "opper or t"e $ee#er "opper is %se# $or
te!poraril, stori' !aterial prior to #isc"ar'e. T"ree t,pes o$
"a#li' s,ste!s are i %se9
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Ne'ati)e press%re or )ac%%! s,ste!
Coects to t"e "opper *, a si!ple #isc"ar'e )al)e
Positi)e press%re #il%te p"ase s,ste!
Uses a airloc53t,pe $ee#er t"e $ee#er is separate# $ro! t"e "opper *,
a ilet 'ate a# $ro! t"e co)e,i' lie *, a #isc"ar'e 'ate Positi)e press%re #ese p"ase s,ste!
Coects to t"e "opper (it" a airloc5 t,pe $ee#er.
!bout Ductwor( -Bac5 to top
%ct(or5 coects t"e precipitator (it" %pstrea! a# #o(strea!
e4%ip!et. T"e #esi' o$ t"e #%ct(or5 ta5es ito cosi#eratio t"e$ollo(i'9
Lo( resistace to 'as $lo(
Ac"ie)e# *, selecti' a s%ita*le cross3sectio $or t"e #%ct(or5 a# *,
istalli' 'as $lo( cotrol #e)ices& s%c" as t%ri' )al)es a# $lo(
strai'"teers
Gas )elocit, #istri*%tio
Gas $lo( cotrol #e)ices are %se# to !aitai 'oo# 'as )elocit,
#istri*%tio
2ii!al $allo%t o$ $l, as"
7allo%t ca *e !ii!i+e# *, %si' a s%ita*le trasport )elocit,
2ii!al strati$icatio o$ t"e $l, as"
A s%ita*le trasport )elocit, also re#%ces $l, as" strati$icatio i t"e
'as strea!
Lo( "eat loss
T"e 'oal is to re#%ce t"e "eat loss o$ t"e $l%e 'as to a le)el t"at (illpre)et aci# or !oist%re co#esatio i t"e #o(strea! e4%ip!et&
re4%iri' t"e %se o$ t"er!al is%latio protecte# *, e8teral si#i'.
Str%ct%ral ite'rit,
%ct(or5 str%ct%re s%pports its total loa#& icl%#i' (i# a# so(
loa#s. T"e #esi' also allo(s $or acc%!%late# $l, as"&
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e'ati)e:positi)e operati' press%re& a# 'as te!perat%re. E8pasio
>oits are %se# to acco!!o#ate t"er!al 'ro(t".
!bout as elocity Distribution -Bac5 to topE$$iciet precipitator per$or!ace #epe#s "ea)il, %po "a)i'
si!ilar 'as co#itios at t"e ilet o$ eac" electrical $iel# or *%s sectio
a# at t"e ilet o$ eac" 'as passa'e o$ t"e electrical $iel# or *%s
sectio. Ui$or!it, o$ 'as )elocit, is also #esira*le 3 'oo# 'as
)elocit, #istri*%tio t"ro%'" a precipitator !eets t"ese re4%ire!ets9
< o$ all !eas%re# 'as )elocities J 1.1 ti!es t"e a)era'e 'as
)elocit, ;;< o$ all !eas%re# 'as )elocities J 1.@ ti!es t"e a)era'e 'as
)elocit,
1. I!pro)i' Gas =elocit, istri*%tio
T"e 'as )elocit, #istri*%tio i a precipitator ca *e c%sto!i+e#
accor#i' to t"e #esi' o$ t"e precipitator a# t"e c"aracteristics o$
t"e #%st particles. Tra#itioall,& precipitators "a)e *ee #esi'e# (it"
%i$or! 'as )elocit, #istri*%tio t"ro%'" t"e electrical $iel#s& to a)oi#
"i'"3)elocit, areas t"at (o%l# ca%se re3etrai!et. W"ile t"is is still
a reco!!e#e# practice& t"ere is a a#)ata'e i so!e cases to
#e)elopi' a )elocit, pro$ile t"at *ri's !ore particles closer to t"e
"opper.
Bot" o$ t"ese sc"e!es "a)e applicatios i site3speci$ic co#itios.
Gas )elocit, #istri*%tio ca *e cotrolle# *, t"e $ollo(i'9
A##i':i!pro)i' 'as $lo( cotrol #e)ices i t"e ilet #%ct(or5
A##i':i!pro)i' $lo( cotrol #e)ices i t"e ilet o$ t"eprecipitator
A##i':i!pro)i' $lo( cotrol #e)ices i t"e o%tlet o$ t"e
precipitator
A##i' a rappi' s,ste! to t"e $lo( cotrol #e)ices -("ere
applica*le
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A##i':i!pro)i' ati3sea5 *a$$les at t"e perip"eries o$ t"e
electrical $iel#s
A##i':i!pro)i' "opper *a$$les
Eli!iati' air lea5a'es ito t"e precipitator
!bout Re)entrainment -Bac5 to top
Re#%ci' rappi' re3etrai!et to a accepta*le le)el 'eerall,
re4%ires a s%*statial i!pro)e!et o$ t"e 'as )elocit, #istri*%tio a#
t"e electrical po(er #esit, a# %i$or!it,& as (ell as a e8te#e#
opti!i+atio pro'ra! $or t"e collecti'3plate rappi' s,ste!.
7actors A$$ecti' Re3etrai!etRe3etrai!et o$ collecte# particles is t"e !a>or cotri*%tor to
partic%late e!issios o$ t"e precipitator. I so!e cases& re3etrai!et
acco%ts $or @ 3 @< o$ t"e resi#%al. T"e !a>or ca%ses o$ re3
etrai!et are as $ollo(s9
Particles9 Lo( co"esi)eess
Lo( a#"esio to collecti' plates
Particle si+e
Lo( resisti)it,
=olta'e
Cotrols9Spar5 rate setti'
esi'9 Collecti' plate #esi'
isc"ar'e electro#e #esi'
Plate spaci'
Rappi'
S,ste!9
7re4%ec,
Itesit,%ratio -i$ applica*le
Electrical
7iel#9
Collecti' plate a# #isc"ar'e electro#e rappi'
Spar5i'
Saltatio
Erosio -locali+e# "i'" 'as )elocit,
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Sea5a'e
Hopper9 Hopper #esi'
Lea5a'e -"opper )al)e
Hopper 'as $lo(
!bout "orona Power -Bac5 to top
Precipitator coroa po(er is t"e %se$%l electrical po(er applie# to t"e
$l%e 'as strea! to precipitate particles. Eit"er precipitator collecti'
e$$iciec, or o%tlet resi#%al ca *e e8presse# as a $%ctio o$ coroa
po(er i Watts:1@@@ ac$! o$ $l%e 'as& or i Watts:1@@@ $t o$
collectio area.
T"e separatio o$ particles $ro! t"e 'as $lo( i a electrostaticprecipitator #epe#s o t"e applie# coroa po(er. Coroa po(er is t"e
pro#%ct o$ coroa c%rret a# )olta'e. C%rret is ee#e# to c"ar'e t"e
particles. =olta'e is ee#e# to s%pport a electrical $iel#& ("ic" i t%r
trasports t"e particles to t"e collecti' plates.
I t"e lo(er ra'e o$ collecti' e$$iciecies& relati)el, s!all icreases
i coroa po(er res%lt i s%*statial icreases i collecti' e$$iciec,.
O t"e ot"er "a#& i t"e %pper ra'es& e)e lar'e icreases i coroa
po(er (ill res%lt i ol, s!all e$$iciec, icreases.
E4%all,& i t"e lo(er ra'e o$ t"e coroa po(er le)els& a s!all
icrease i t"e coroa po(er res%lts i a s%*statial re#%ctio i t"e
'as strea! particle cotet. I t"e %pper ra'e o$ t"e coroa po(er
le)el& a lar'e icrease is re4%ire# to re#%ce t"e particle cotet.
Opti!i+i' Coroa Po(er
Opti!%! co#itios #epe# %po t"e locatio o$ t"e $iel# -ilet&
ceter a# o%tlet& $l, as" c"aracteristics -resisti)it, a# p",sicalco#itios -collecti' plates a# #isc"ar'e (ires. Coroa po(er
le)els ca *e opti!i+e# *, a#>%sti' or opti!i+i' t"e $ollo(i'9
Gas )elocit,9 Ui$or!it,
7l, As"9Particle si+e Resisti)it,
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=olta'e
Cotrols9
Spar5 rate setti'
C%rret )olta'e li!its
esi'9 Plate spaci'
Collecti' plate #isc"ar'e electro#e #esi'
Rappi'S,ste!9
7re4%ec, itesit,
S%pport
Is%lator9P%r'e air s,ste! operatio
!bout Performance Improvements -Bac5 to top
I!pro)e!et or opti!i+atio o$ precipitator operatio ca res%lt i
si'i$icat sa)i's. 2a, speci$ic sit%atios eco%ra'e a re)ie( o$precipitator operatio9
eterioratio o$ e8isti' e4%ip!et
Ti'"tei' o$ air poll%tio e!issio re'%latios
C"a'es i pro#%cts a#:or pro#%ctio rates
7re4%et $orce# o%ta'es
e3rati' o$ pro#%ctio
To lear !ore a*o%t per$or!ace i!pro)e!et pro'ra!s& re$er to t"e
appropriate sectio9
Gas =elocit, istri*%tio
Coroa Po(er
Re3etrai!et
Process I!pro)e!ets
7l%e Gas:7l, As" Co#itioi'
E4%ip!et I!pro)e!ets
Equipment Improvements -Bac5 to top
T"e o*>ecti)es o$ e4%ip!et i!pro)e!ets are to opti!i+e coroa
po(er& re#%ce re3etrai!et& a# opti!i+e 'as )elocit, #istri*%tio
isi#e t"e precipitator. So!e i!portat topics to cosi#er ("e
plai' e4%ip!et i!pro)e!ets icl%#e9
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1. Precipitator Si+e
W"e si+i' t"e precipitator& it is i!portat to pro)i#e a cross3sectio
t"at (ill !aitai a accepta*le 'as )elocit,. It is also i!portat to
pro)i#e $or eo%'" total #isc"ar'e (ire le't" a# collecti' plate
area& so t"at t"e #esire# speci$ic coroa c%rret a# electrical $iel# ca*e applie#.
/. Gas =elocit, istri*%tio
I!pro)i' 'as )elocit, #istri*%tio i t"e precipitator re#%ces particle
re3etrai!et a# *oosts precipitator e$$iciec,. T,picall,& a %i$or!
'as )elocit, is #esire#& *%t t"ere are site3speci$ic e8ceptios. Gas
)elocit, #istri*%tio ca *e !o#i$ie# *, %si' $lo( cotrol #e)ices
a# *a$$les. Re$er to t"e special sectio o 'as )elocit, #istri*%tio.0. Coroa Po(er
T"e separatio o$ #%st particles $ro! t"e 'as $lo( i a electrostatic
precipitator #epe#s o t"e applie# coroa po(er. Coroa po(er is t"e
pro#%ct o$ coroa c%rret a# )olta'e. C%rret is ee#e# to c"ar'e t"e
particles. =olta'e is ee#e# to s%pport a electrical $iel#& ("ic" i t%r
trasports t"e particles to t"e collecti' plates. 7or a##itioal
i$or!atio& re$er to Coroa Po(er.
. Sectioali+atio
T"e precipitator is #i)i#e# ito electrical sectios t"at are cross3(ise
a# parallel to t"e 'as $lo( to acco!!o#ate spatial #i$$ereces i 'as
a# #%st co#itios. Opti!i+atio o$ coroa po(er i)ol)es a#>%sti'
t"e coroa po(er -seco#ar, )olta'e a# c%rret i eac" electrical
sectio $or opti!%! co#itios.
. Particle Re3etrai!et
2ii!i+i' re3etrai!et o$ #%st particles is i!portat toi!pro)e!et o$ precipitator e$$iciec,. 2ost precipitator e4%ip!et
a$$ects t"e re3etrai!et le)el. 7or a #etaile# #isc%ssio& )isit t"e
special sectio o re3etrai!et.
. A##itioal E4%ip!et
Per$or!ace i!pro)e!et optios icl%#e t"e istallatio o$ a seco#
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precipitator i series (it" t"e e8isti' precipitator %si' $a*ric $ilters
#o(strea! o$ t"e precipitator a# a##i' a seco# particle collector
i parallel (it" t"e e8isti' collector. Ot"er possi*ilities icl%#e soic
or electrostatic particle a''lo!erators %pstrea! o$ t"e precipitator a
!ec"aical %pstrea! collector or a electrostaticall,3e"ace# or!ec"aical collector& or a $ilter #o(strea! o$ t"e precipitator.
F. Re)ie( t"e Geeral E4%ip!et Re4%ire!ets
Re)ie(i' t"e Ne%#or$er Ko(le#'e Base sectios o e4%ip!et
(ill pro)i#e a##itioal isi'"t ito per$or!ace i!pro)e!ets.
7or !ore i$or!atio& see t"ese relate# topics9
Gas =elocit, istri*%tioCoroa Po(er
Re3etrai!et
isc"ar'e Electro#es
Collecti' Plates
Po(er S%pplies
Gas istri*%tio
Rappi' S,ste!s
Hoppers a# %st Ha#li'
%ct(or5
"ombustion Process Improvements for Power Plants -Bac5 to
top
Co!*%stio process co#itios !ail, a$$ect t"e coroa po(er le)el.
T"e pri!ar, cotri*%tors to co!*%stio process co#itios a# t"eir
e$$ects icl%#e9Coal
7l%e 'as $lo( rate
7l%e 'as !oist%re cotet
7l, as" resisti)it,
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7l, as" ilet loa#i'
7l, as" particle si+e
Coal !ills
7l, as" particle si+e
U*%re# car*o -LOI7%race
Base loa#:s(i' loa# operatio
7l%e 'as $lo( rate
B%rers
7l%e 'as te!perat%re
7l, as" resisti)it,
U*%re# car*o -LOIAir pre3"eaters
Rotatio
Gas $lo( patter
Gas te!perat%re patter
SO0 #istri*%tio patter
"oal
Bit%!io%s coals $ro! Easter !ies& s%*3*it%!io%s a# li'ite
coals $ro! Wester !ies& a# li'ites $ro! Te8as !ies are
s%*statiall, #i$$eret $ro! eac" ot"er i t"e co!*%stio process. Coal
*le#i' is o( %se# $or operatioal a# $iacial *ee$its. T"is
res%lts i a (i#e ra'e o$ *oiler a# precipitator operati' co#itios.
Precipitati' $l, as" $ro! #i$$ic%lt coals ca *e i!pro)e# (it"
co#itioi' s,ste!s. Ho(e)er& t"e $%race a# its associate#e4%ip!et ca still ca%se pro*le!s i t"e precipitator& partic%larl,
coal !ills& *%rers& a# air pre3"eaters.
"oal *ills
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T"e setti' o$ t"e coal !ills a# classi$iers #e$ies t"e coal particle
si+e ("ic" i t%r i!pacts t"e $l, as" particle si+e. Lar'er coal
particles are !ore #i$$ic%lt to co!*%st& *%t lar'er $l, as" particles are
easier to collect i t"e precipitator.
+urnace
Base3loa# operatio o$ t"e *oiler is %s%all, *etter $or precipitator
operatio t"a s(i'3loa# operatio #%e to !ore sta*le operati'
co#itios. Boiler operatio at lo( loa#s !a, *e as pro*le!atic $or
t"e precipitator as operati' t"e *oiler at its !a8i!%! loa# le)el& #%eto $allo%t o$ $l, as" i t"e #%ct(or5& lo( 'as te!perat%res& a#
#eterioratio o$ t"e 4%alit, o$ t"e 'as )elocit, #istri*%tio.
I$ lo( loa# operatio caot *e a)oi#e#& t"e istallatio o$ a##itioal
'as $lo( cotrol #e)ices i t"e ilet a# o%tlet o$ t"e precipitator !a,
pro)e *ee$icial.
"oal Burner
T"e operatio o$ coal *%rers& to'et"er (it" t"e setti' o$ t"e coal
!ills a# t"eir classi$iers& a$$ects t"e perceta'e o$ %*%re# car*o
-LOI or UBC i t"e $l, as". T"e %se o$ Lo3NO8 *%rers icreases t"is
perceta'e& a# ca%ses re3etrai!et a# icrease# spar5i' i t"e
precipitator. 7%rt"er& t"e UBC te#s to a*sor* SO0& ("ic" i t%r
icreases t"e $l, as" resisti)it,. O)er3$ire air opti!i+atio or coal3
re*%r s,ste!s !a, re#%ce UBC i t"e $l, as".
!ir Pre)heater
Re'eerati)e air pre3"eaters ca%se te!perat%re a# SO0strati$icatio
i t"e #o(strea! 'as $lo(. T"is pro*le! is !ore se)ere i closel,
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co%ple# s,ste!s& ("ere t"e precipitator is locate# close to t"e air pre3
"eater. epe#i' %po site3speci$ic co#itios& $lo( !i8i' #e)ices
!a, *e istalle# i t"e #%ct(or5 to t"e precipitator& or $l%e 'as
co#itioi' s,ste!s !a, *e %se# to e4%ali+e t"e 'as $lo(
c"aracteristics.
+ly !sh and +lue as "onditioning -Bac5 to top
7l%e 'as a# $l, as" c"aracteristics at t"e ilet #e$ie precipitator
operatio. T"e co!*iatio o$ $l%e 'as aal,sis& $l%e 'as te!perat%re
a# $l, as" c"e!istr, pro)i#es t"e *ase $or $l, as" resisti)it,.
T,picall,& $l, as" resisti)it, i)ol)es *ot" s%r$ace a# )ol%!eresisti)it,. As 'as te!perat%re icreases& s%r$ace co#%cti)it,
#ecreases a# )ol%!e resisti)it, icreases.
I lo(er 'as te!perat%re ra'es& s%r$ace co#%cti)it, pre#o!iates.
T"e c%rret passi' t"ro%'" t"e precipitate# $l, as" la,er is co#%cte#
i a $il! o$ (ea5 s%l$%ric aci# o t"e s%r$ace o$ t"e particles.
7or!atio o$ t"e aci# $il! -$ro! SO0a# H/O is i$l%ece# *, t"e
s%r$ace c"e!istr, o$ t"e $l, as" particles.
I "i'"er 'as te!perat%re ra'es& )ol%!e co#%cti)it, pre#o!iates.
C%rret co#%ctio t"ro%'" t"e *o#ies -)ol%!e o$ t"e precipitate# $l,
as" particles is 'o)ere# *, t"e total c"e!istr, o$ t"e particles.
7l, as" resisti)it, ca *e !o#i$ie# -'eerall, (it" t"e itet to re#%ce
it *, i>ecti' oe or !ore o$ t"e $ollo(i' %pstrea! o$ t"e
precipitator9
S%l$%r trio8i#e -SO0
A!!oia -NH0 Water
#ulfur $rio,ide and !mmonia "onditioning #ystems
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I !ost cases& a s%l$%r trio8i#e co#itioi' s,ste! is s%$$iciet to
re#%ce $l, as" resisti)it, to a accepta*le le)el. T"e so%rce o$ s%l$%r
trio8i#e ca *e li4%i# s%l$%r #io8i#e& !olte ele!etal s%l$%r& or
'ra%late# s%l$%r. It is also possi*le to co)ert ati)e $l%e 'as SO/to
SO0.I so!e istaces& a!!oia aloe "as *ee pro)e a s%ita*le
co#itioi' a'et. It $or!s a a!!oia3*ase# partic%late to icrease
t"e space c"ar'e. T"e so%rce o$ a!!oia !a, *e li4%i# a",#ro%s or
a4%eo%s a!!oia& or soli# %rea.
7iall,& s%l$%r trio8i#e a# a!!oia !a, *e %se# i co!*iatio.
T"is sol%tio "as *ee s%ccess$%l *eca%se it ca lo(er $l, as"
resisti)it, a# also $or! a!!oia *is%l$ate. T"e latter icreases t"ea#"esio o$ particles& a# t"%s re#%ces re3etrai!et losses.
-ater In.ection
T"e i>ectio o$ (ater %pstrea! o$ t"e precipitator lo(ers t"e 'as
te!perat%re a# a##s !oist%re to t"e $l%e 'as. Bot" are *ee$icial i
col#3si#e precipitator applicatios. Ho(e)er& care !%st *e ta5e t"at
all o$ t"e (ater is e)aporate# a# t"at t"e (alls i t"e #%ct(or5 or 'as
#istri*%tio #e)ices #o ot 'et (et.
G E N E R A L S A 7 E T M P R E C A U T I O N S
Ans:Accidents do not
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2. &mmediately report to person in"charge any dangerous condition or practice
you have observed.
*. e!ore working on motors or other rotating machines make sure that it
cannot be set in motion without your permission by removing !uses +
installing danger board on controlling switch.
-. 3horoughly discharge all cables to earth be!ore starting the work.
/. >lace rubber mats in !ront o! switchboards.
. 6o not close any switch unless you are !amiliar with the circuit which it
controls and know the reasons !or it being open.
4. 6o not work on live circuits. ?ake sure that all sa!ety precautions have been
taken.
8. 6o not close or open switch hesitantly. " do it ,uickly and positively.
;. o ot t"ro( (ater o li)e electrical apparat%s i case o$ $ire. Use proper e8ti'%is"er.