P.P.E UNIT II
Transcript of P.P.E UNIT II
-
8/13/2019 P.P.E UNIT II
1/44
PROPERTIES OF COAL :
1)Swelling index
2) Grindability
3) Weatherability
4) Sulpher content
5) Heating value
6) !h !o"tening te#perature$
1$ Swelling Index%Swelling index i! a &ualitative evaluation #ethod' u!ed
to deter#ine the extent o" ca(ing o" a coal$ "ree burning coal ha! a high
value o" !welling index' which indicate! that it !lightly expand! in volu#e
during co#bu!tion$hi! !welling index i! o" 1* i#portance "or pulveri!edcoal$
2$Grindability :+t i! one the i#portant propertie! in !electing the coal$hi!
property i! #ea!ure by !tandard grindability index$he grindability index i!
inver!ely proportional to the power re&uired to grind the coal to a !peci"ied
particle !i,e "or burning$
3$Weatherability :+t i! a #ea!ure o" how well coal can be !tored "or long
ti#e with out cru#bling to piece!$Generally #odern power plant! !tore! coal!upply o" -* day! in large'$ rape,oidal pile$.ver !ince cru#bling o" coal
due to cli#atic condition #ay re!ult in !#all particle! o" coal which can be
carried away by wind or rain$
4$Sulphur Cntent :Sulphur in coal i! co#bu!tible and generate! heat by
it! oxidation "or#ing S/2 i! very e!!ential during co#bu!tion$+t i! a #a0or
!ource o" air pollution$+t! re#oval i! very e!!ential$
5$!eating "alue :hi! property i! o" "unda#ental i#portance$+t i! the heattran!"erred when the product! o" co#plete co#bu!tion o" !a#ple o" coal are
cooled to the initial te#perature o" air and "uel$+t i! generally deter#ined by
o#b calori#eter$
-
8/13/2019 P.P.E UNIT II
2/44
6$ A#h S$tening Te%perature :he a!h !o"tening te#perature i! the
te#perature at which the a!h !o"ten! and beco#e! pla!tic$hi! te#perature
i! !lightly le!! than #elting te#perature o" a!h$hi! $S$$ i! an i#portant
"actor in de!igning a !tea# generator$
or a "urnace that would di!charge a!h in !olid "or#' a high $S$$ i!
re&uired otherwi!e clic(ne!! would be "or#ed$+t i! di""icult to re#ove the!e
clic(ne!! re!ulting ine""icient co#bu!tion$
&EC!A'ICAL FIRI'G (STO)ERS*
echanical !to(er! are co##only u!ed to "eed !olid "uel! into the "urnace in
#ediu# and large !i,e power plant!$
he variou! advantage! o" !to(er "iring are a! "ollow! %
i) arge &uantitie! o" "uel can be "ed into the "urnace$ hu! greater
co#bu!tion capacity i! achieved$
ii) oorer grade! o" "uel can be burnt ea!ily$
iii) Sto(er !ave labour o" handling a!h and are !el"7cleaning$
iv) y u!ing !to(er! better "urnace condition! can be #aintained by "eeding
coal at a uni"or# rate$
v) Sto(er! !ave coal and increa!e the e""iciency o" coal "iring$ he #aindi!advantage! o" !to(er! are their #ore co!t! o" operation and repairing
re!ulting "ro# high "urnace te#perature!$
Prin+iple# $ St,er#- he wor(ing o" variou! type! o" !to(er! i! ba!ed on
the "ollowing two principle!%
.- O"er$eed Prin+iple- ccording to thi! principle ig$) the pri#ary air
enter! the grate "ro# the botto#$
he air while #oving through the grate opening! get! heated up andair while #oving through the grate opening! get! heated up and the grate i!
cooled$
-
8/13/2019 P.P.E UNIT II
3/44
Fig- Sto(er!
he hot air that #ove! through a layer o" a!h and pic(! up additional
energy$ he air then pa!!e! through a layer o" incande!cent co(e where
oxygen react! with co(e to "or#78*2 and water vapour! acco#panying the
air react with incande!cent co(e to "or# 8/2' 8/ and "ree H2$ he ga!e!
leaving the !ur"ace o" "uel bed contain volatile #atter o" raw "uel and ga!e!
li(e 8/2' 8/' H2' 92 and H2/$ hen additional air (nown a! !econdary air i!
!upplied to burn the co#bu!tible ga!e!$ he co#bu!tion ga!e! entering the
boiler con!i!t o" 92' 8/2' /2 and H2/ and al!o 8/ i" the co#bu!tion i! not
co#plete$
/- 0nder$eed Prin+iple- ig$!how! under"eed principle$ +n under"eed
principle air entering through the hole! in the grate co#e! in contact with
the raw coal green coal)$
Fig- :nder"eed rinciple$
hen it pa!!e! through the incande!cent co(e where reaction! !i#ilar to
over"eed !y!te# ta(e place$ he ga!e! produced then pa!!e! through a
-
8/13/2019 P.P.E UNIT II
4/44
layer o" a!h$ he !econdary air i! !upplied to burn the co#bu!tible ga!e!$
:nder"eed principle i! !uitable "or burning the !e#i7bitu#inou! and
bitu#inou! coal!$
Type# $ St,er#- he variou! type! o" !to(er! are a! "ollow!%
Fig- ;ariou! ype! o" Sto(er!$
8harging o" "uel into the "urnace i! #echani,ed by #ean! o" !to(er! o"
variou! type!$ hey are in!talled above the "ire door! underneath the
bun(er! which !upply the "uel$ he bun(er! receive the "uel "ro# a
conveyor$
i) Chain Grate St,er- 8hain grate !to(er and traveling grate !to(er di""er
only in grate con!truction$ chain grate !to(er ig$) con!i!t! o" an endle!!
chain which "or#! a !upport "or the "uel bed$
Fig- 8hain Grate Sto(er$
he chain travel! over two !proc(et wheel!' one at the "ront and one at the
rear o" "urnace$ he traveling chain receive! coal at it! "ront end through a
Under
-
8/13/2019 P.P.E UNIT II
5/44
hopper and carrie! it into the "urnace$ he a!h i! tipped "ro# the rear end o"
chain$ he !peed o" grate chain) can be ad0u!ted to !uit the "iring condition$
he air re&uired "or co#bu!tion enter! through the air inlet! !ituated
below the grate$ Sto(er! are u!ed "or burning non7co(ing "ree burning high
volatile high a!h coal!$ lthough initial co!t o" thi! !to(er i! high but
operation and #aintenance co!t i! low$
he traveling grate !to(er al!o u!e! an endle!! chain but di""er! in that
it carrie! !#all grate bar! which actually !upport the "uel "ed$ +t i! u!ed to
burn lignite' very !#all !i,e! o" anthracite! co(e bree,e etc$
he !to(er! are !uitable "or low rating! becau!e the "uel #u!t be burnt
be"ore it reache! the rear o" the "urnace$ With "orced draught' rate o"
co#bu!tion i! nearly 3* to 5* lb o" coal per !&uare "oot o" grate area per
hour' "or bitu#inou! 2* to 35 pound! per !&uare "oot per hour "or
anthracite$
ii) Spreader St,er- !preader !to(er i! !hown in ig$ +n thi! !to(er the
coal "ro# the hopper i! "ed on to a "eeder which #ea!ure! the coal in
accordance to the re&uire#ent!$ eeder i! a rotating dru# "itted with blade!$
eeder! can be reciprocating ra#!' endle!! belt!' !piral wor#! etc$
Fig- Spreader Sto(er$
ro# the "eeder the coal drop! on to !preader di!tributor which !pread
the coal over the "urnace$ he !preader !y!te# !hould di!tribute the coal
evenly over the entire grate area$ he !preader !peed depend! on the !i,e
o" coal$
-
8/13/2019 P.P.E UNIT II
6/44
Ad"antage#
he variou! advantage! o" !preader !to(er are a! "ollow! %
1$ +t! operation co!t i! low$
2$ wide variety o" coal can be burnt ea!ily by thi! !to(er$
3$ thin "uel bed on the grate i! help"ul in #eeting the "luctuating load!$
4$ !h under the "ire i! cooled by the inco#ing air and thi! #ini#i,e!
clin(ering$
5$ he "uel burn! rapidly and there i! little co(ing with co(ing "uel!$
1i#ad"antage#
1$ he !preader doe! not wor( !ati!"actorily with varying !i,e o" coal$
2$ +n thi! !to(er the coal burn! in !u!pen!ion and due to thi! "ly a!h i!
di!charged with "lue ga!e! which re&uire! an e""icient du!t collecting
e&uip#ent$
iii) &ulti2retrt St,er- #ulti7retort !to(er i! !hown in ig$ he coal
"alling "ro# the hopper i! pu!hed "orward during the inward !tro(e o" !to(er
ra#$ he di!tributing ra#! pu!her!) then !lowly #ove the entire coal bed
down the length o" !to(er$ he length o" !tro(e o" pu!her! can be varied a!
de!ired$ he !lope o" !tro(e help! in #oving the "uel bed and thi! "uel bed#ove#ent (eep! it !lightly agitated to brea( up clin(er "or#ation$ he
pri#ary air enter! the "uel bed "ro# #ain wind box !ituated below the
!to(er$ artly burnt coal #ove! on to the exten!ion grate$ thinner "uel bed
on the exten!ion grate re&uire! lower air pre!!ure under it$ he air entering
"ro# the #ain wind box into the exten!ion grate wind box i! regulated by an
air da#per$
-
8/13/2019 P.P.E UNIT II
7/44
Fig- ulti7retort Sto(er$
! !u""icient a#ount o" coal alway! re#ain! on the grate' thi! !to(er
can be u!ed under large boiler! upto 5**'*** lb per hr capacity) to obtain
high rate! o" co#bu!tion$
-
8/13/2019 P.P.E UNIT II
8/44
Ad"antage#
i) he !y!te# i! !i#ple and cheaper than the central !y!te#$
ii) here i! direct control o" co#bu!tion "ro# the pulveri!ing #ill$
iii) 8oal tran!portation !y!te# i! !i#ple$
3in r Central Sy#te%- +t i! !hown in ig$ 8ru!hed coal "ro# the raw coal
bun(er i! "ed by gravity to a dryer where hot air i! pa!!ed through the coal
to dry it$ he dryer #ay u!e wa!te "lue ga!e!' preheated air or bleeder
!tea# a! drying agent$ he dry coal i! then tran!"erred to the pulveri!ing
#ill$ he pulveri!ed coal obtained i! tran!"erred to the pulveri!ed coal
bun(er bin)$ he tran!porting air i! !eparated "ro# the coal in the cyclone
!eparator$ he pri#ary air i! #ixed with the coal at the "eeder and the
#ixture i! !upplied to the burner
Fig-in or 8entral Sy!te#$
Ad"antage#
l$ he pulveri!ing #ill grind! the coal at a !teady rate irre!pective o" boiler
"eed$
2$ here i! alway! !o#e coal in re!erve$ hu! any occa!ional brea(down in
the coal !upply will not e""ect the coal "eed to the burner$
3$ or a given boiler capacity pulveri!ing #ill o" !#all capacity will be
re&uired a! co#pared to unit !y!te#$
1i#ad"antage#
1$ he initial co!t o" the !y!te# i! high$
-
8/13/2019 P.P.E UNIT II
9/44
2$ 8oal tran!portation !y!te# i! &uite co#plicated$
3$ he !y!te# re&uire! #ore !pace$
o a large extent the per"or#ance o" pulveri!ed "uel !y!te# depend!
upon the #ill per"or#ance$
he pulveri!ed #ill !hould !ati!"y the "ollowing re&uire#ent!%
1$ +t !hould deliver the rated tonnage o" coal
2$ ulveri!ed coal produced by it !hould be o" !ati!"actory "inene!! over a wide
range o" capacitie!$
3$ +t !hould be &uiet in operation$
4$ +t! power con!u#ption !hould be low$
5$ aintenance co!t o" the #ill !hould be low$
ig$!how! the e&uip#ent! "or unit and central !y!te# o" pulveri!ed coal
handling plant$
Fig- .&uip#ent! "or 8entral and :nit Sy!te#$
-
8/13/2019 P.P.E UNIT II
10/44
P0L4ERISE1 COAL 30R'ERS
urner! are u!ed to burn the pulveri!ed coal$ he #ain di""erence between
the variou! burner! lie! in the rapidity o" air7coal #ixing i.e., turbulence$ or
bitu#inou! coal! the turbulent type o" burner i! u!ed wherea! "or low
volatile coal! the burner! with long "la#e !hould be u!ed$ pulveri!ed coal
burner !hould !ati!"y the "ollowing re&uire#ent!%
i) +t !hould #ix the coal and pri#ary air thoroughly and !hould bring thi!
#ixture be"ore it enter! the "urnace in contact with additional air (nown a!
!econdary air to create !u""icient turbulence$
ii) +t !hould deliver and air to the "urnace in right proportion! and !hould
#aintain !table ignition
o" coal air #ixture and control "la#e !hape and travel in the "urnace$ he
"la#e !hape i! controlled by the !econdary air vane! and other control
ad0u!t#ent! incorporated into the burner$ Secondary air i" !upplied in too
#uch &uantity #ay cool the #ixture and prevent it! heating to ignition
te#perature$
iii) 8oal air #ixture !hould #ove away "ro# the burner at a rate e&ual to"la#e "ront travel in order to avoid "la!h bac( into the burner$
-
8/13/2019 P.P.E UNIT II
11/44
Fig- ulveri!ed 8oal urner Sy!te#$
he variou! type! o" burner! are a! "ollow! %
.- Lng Fla%e 3urner (02Fla%e 3urner*- +n thi! burner air and coal
#ixture travel! a con!iderable di!tance thu! providing !u""icient ti#e "or
co#plete co#bu!tion =ig$a)>$
/- Shrt Fla%e 3urner (Turbulent 3urner*- +t i! !hown in ig$b)$ he
burner i! "itted in the "urnace will and the "la#e enter! the "urnace
hori,ontally$
5- Tangential 3urner- tangential burner i! !hown in ig$ 4$2-c)$ +n thi!
!y!te# one burner i! "itted attach corner o" the "urnace$ he inclination o"
the burner i! !o #ade that the "la#e produced are tangential to an
i#aginary circle at the centre$
6- Cy+lne 3urner- +t i! !hown in ig$d)$ hi! burner u!e! cru!hed coal
intend o" pulveri,ed coal$
Fig- ;ariou! ype! o" urner!
-
8/13/2019 P.P.E UNIT II
12/44
Fig- ulveri!ed 8oal7"ired oiler$
+t! advantage! are a! "ollow! %
i) +t !ave! the co!t o" pulveri!ation becau!e o" a cru!her need! le!! power
than a pulveri!er$
ii) roble# o" "ly a!h i! reduced$ !h produced i! in the #olten "or# and
due to inclination o" "urnace it "low! to an appropriate di!po!al !y!te#$
ig$ !how! a pulveri!ed coal7"ired boiler$
-
8/13/2019 P.P.E UNIT II
13/44
C7CLO'E F0R'ACES
8yclone7"urnace "iring' developed in the 1-4*!' repre!ent! the #o!t
!igni"icant !tep in coal "iring !ince the introduction o" pulveri,ed7coal "iring in
the 1-2*!$ +t i! now widely u!ed to burn poorer grade! o" coal that contain a
high a!h content with a #ini#u# o" 6 percent to a! high a! 25 percent' and
a high volatile #atter' #ore than 15 percent' to obtain the nece!!ary high
rate! o" co#bu!tion$ wide range o" #oi!ture i! allowable with pre7drying$
/ne li#itation i! that a!h !hould not contain a high !ul"ur content or a high
e2/3? 8a/ @ g/) ratio$ Such a coal ha! a tendency to "or# high a!h7
"u!ion te#perature #aterial! !uch a! iron and iron !ul"ide in the !lag' which
negate! the #ain advantage o" cyclone "iring$
he #ain advantage i! the re#oval o" #uch o" the a!h' about 6*
percent' ao #olten !lag that i! collected on the cyclone wall! by centri"ugal
action and drained o"" the botto# to a !lag7di!integrating tan( below$ hu!
only 4* percent a!h leave' with the "lue ga!e!' co#pared with about A*
percent "or pulveri,ed7coal "iring$ thi! #aterially reduce! ero!ion and "ouling
o" !tea#7generator !ur"ace! a! well a! the !i,e o" du!t7re#oval precipitator!
or bag hou!e! at !tea#7generator exit$ /ther advantage! are that onlycru!hed coal i! u!ed and no pulveri,ation e&uip#ent i! needed and that the
boiler !i,e i! reduced$8yclone7"urnace "iring u!e! a range o" coal !i,e!
averaging -5 percent pa!!ing a 47#e!h !creen$
he di!advantage! are higher "orced7dra"t "an pre!!ure! and there"ore
higher power re&uire#ent!'the inability to u!e the coal! #entioned above'
and the "or#ation o" relatively #ore oxide! o" nitrogen'9/2 which are air
pollutant!' in the co#bu!tion proce!!$he cyclone i! e!!entially a water7cooled hori,ontal cylinder ig$) located out!ide the #ain boiler "urnace' in
which the cru!hed coal i! "ed and "ired with very high rate! o" heat relea!e$
8o#bu!tion o" the coal i! co#pleted be"ore the re!ulting hot ga!e! enter the
boiler "urnace$ he cru!hed coal i! "ed into the cyclone burner at le"t along
-
8/13/2019 P.P.E UNIT II
14/44
with pri#ary air' which i! about 2* percent o" co#bu!tion or !econdary air$
he pri#ary air enter! the burner tangentially' thu! i#parting a centri"ugal
#otion to the coal$ he !econdary air i! al!o ad#itted tangentially at the top
o" the cyclone at high !peed' i#parting "urther centri"ugal #otion$ !#all
&uantity o" air' called tertiary air' i! ad#itted at the center$he whirling
#otion o" air and coal re!ult! in large heat7relea!e7rate volu#etric den!itie!'
between 45*'*** and A**'*** tuBh$"t) about 4C** to A3** (WB#3)' and
high co#bu!tion te#perature!' #ore than 3***D 165*D8)$ he!e high
te#perature! #elt the a!h into a li&uid !lag that cover! the !ur"ace o" the
cyclone and eventually drain! through the !lag7tap opening to a !lag tan( at
the botto# o" the boiler "urnace' where it i! !olidi"ied and bro(en "or
re#oval$ he !lag layer that "or#! on the wall! o" the cyclone provide!
in!ulation again!t too #uch heat lo!! through the wall! and contribute! to
the e""iciency o" cyclone "iring$ he high te#perature! al!o explain the large
production o" 9/' in the ga!eou! co#bu!tion product!$ he!e ga!e! leave
the cyclone through the throat at right and enter the #ain boiler "urnace$
hu! co#bu!tion ta(e! place in the relatively !#all cyclone' and the #ain
boiler "urnace ha! the !ole "unction o" heat tran!"er "ro# the ga!e! to thewater7tube wall!$ 8yclone "urnace! are al!o !uitable "or "uel7oil and ga!eou!7
"uel "iring$
-
8/13/2019 P.P.E UNIT II
15/44
+nitial ignition i! done by !#all retractable oil or ga! burner! in the
!econdary air port!$ i(e pulveri,ed7coal !y!te#!' cyclone "iring !y!te#! can
be o" the bin' or !torage$ or direct7"iring type!' though the bin type i! #ore
widely u!ed' e!pecially "or #o!t bitu#inou! coal!' than in the ca!e o"
pulveri,ed coal$ he cyclone !y!te# u!e! one7wall' or oppo!ed7wall' "iring'
the latter being pre"erred "or large !tea# generator! he !i,e and nu#ber o"
cyclone! per boiler depend upon the boiler !i,e and the de!ired load
re!pon!e becau!e the u!ual load range "or good per"or#ance o" any one
cyclone i! "ro# 5* to 1** percent o" it! rated capacity$ 8yclone! vary in !i,e
"ro# 6 to 1* "v in dia#eter with heat input! between 16* to 425 #illion
tuBh about 4C'*** to 125'/aE (W)' re!pectively $
he cyclone co#ponent re&uiring the #o!t #aintenance i! the burner'
which i! !ub0ected to ero!ion by the high velocity o" the coal$ .ro!ion i!
#ini#i,ed by the u!? o" tung!ten carbide and other ero!ion7re!i!tant
#aterial! "or the burner liner!' which are u!ually replaced once a year or !o$
S&O)E A'1 10ST RE&O4AL
+n coal "ed "urnace! the product! o" co#bu!tion contain particle! o" !olid
#atter "loating in !u!pen!ion$ hi! #ay be !#o(e or du!t$ he production o"!#o(e indicate! that co#bu!tion condition! are "aulty and a#ount o" !#o(e
produced can be reduced by i#proving the "urnace de!ign$
+n !preader !to(er! and pulveri!ed coal "ired "urnace! the coal i! burnt
in !u!pen!ion and due to thi! du!t in the "or# o" "ly a!h i! produced$ he
!i,e o" du!t particle! i! de!ignated in #icron! 1 F *$**1 ##)$
-
8/13/2019 P.P.E UNIT II
16/44
-
8/13/2019 P.P.E UNIT II
17/44
direction o" "low =ig$b)> o" "lue ga!e! cau!e! the heavier particle! o" !ettle
out$ So#eti#e ba""le! are provided a! !hown in ig$c) to !eparate the
heavier particle!$
echanical du!t collector! #ay be wet type or dry type$ Wet type du!t
collector! called !crubber! #a(e u!e o" water !pray! to wa!h the du!t "ro#
"lue ga!e!$
Fig- echanical
-
8/13/2019 P.P.E UNIT II
18/44
he principal characteri!tic! o" an a!h collector i! the degree o"
collection$
-
8/13/2019 P.P.E UNIT II
19/44
range "ro# very "ine to very coar!e !i,e depending on the !ource$ article!
colour varie! "ro# light tan to grey to blac($ an colour indicate! pre!ence o"
ion oxide while dar( !hade! indicate pre!ence o" unburnt carbon$ ly a!h
particle! !i,e varie! between 1 #icron l F) to 3** F$ ly a!h concentration
in "lue ga!e! depend! upon #ainly the "ollowing "actor! %
i) 8oal co#po!ition$
ii) oiler de!ign and capacity$
ercentage o" a!h in coal directly contribute! to "ly a!h e#i!!ion while boiler
de!ign and operation deter#ine the percentage retained in the "urnace a!
botto# a!h and "ly a!h carried away by "lue ga!$ ly a!h concentration
widely varie! around 2*7-* gB##3 depending on coal and boiler de!ign$ ly
a!h particle !i,e di!tribution depend! pri#arily on the type o" boiler !uch a!
pulveri,ed coal "ired boiler typically produce! coar!er particle! then cyclone
type boiler!$ .lectro!tatic precipitator .S) i! &uite co##only u!ed "or
re#oval o" "ly a!h "ro# "lue ga!e!$
-
8/13/2019 P.P.E UNIT II
20/44
COOLI'G TOWERS
8ooling ower! re#ove heat "ro# the water di!charged "ro# the conden!er
!o that the water can be di!charged to the river or recirculated and reu!ed$
cooling tower extract! heat "ro# water by evaporation$ +n an
evaporative cooling tower' a !#all portion o" the water being cooled i!
allowed to evaporate into a #oving air !trea# to provide !igni"icant cooling
to the re!t o" that water !trea#$
8ooling ower! are co##only u!ed to provide lower than a#bient
water te#perature! and are #ore co!t e""ective and energy e""icient than
#o!t other alternative!$ he !#alle!t cooling tower! are !tructured "or only
a "ew litre! o" water per #inute while the large!t cooling tower! #ay handle
upward! o" thou!and! o" litre! per #inute$ he pipe! are obviou!ly #uch
larger to acco##odate thi! #uch water in the larger tower! and can range
up to 12 inche! in dia#eter$
WOR)I'G OF COOLI'G TOWERS: When water i! reu!ed in the proce!!' it
i! pu#ped to the top o" the cooling tower and will then "low down through
pla!tic or wood !hell!' #uch li(e a honeyco#b "ound in a beeJ! ne!t$ he
water will e#it heat a! it i! downward "lowing which #ixe! with the above
air "low' which in turn cool! the water$ art o" thi! water will al!o evaporate'
cau!ing it to lo!e even #ore heat$
T7PES OF COOLI'G TOWERS:
/ne way to di!tingui!h between cooling tower! i! how the air and water
interact'
pen +ling twer# r +l#ed +ling twer#-
/pen cooling tower!' al!o called direct cooling tower!' allow the water
to co#e into contact with out!ide air$ +" cooled water i! returned "ro# the
cooling tower to be u!ed again' !o#e water #u!t be added to replace the
water that ha! been lo!t$ ollutant! are able to enter into the water u!ed in
-
8/13/2019 P.P.E UNIT II
21/44
the!e proce!!e! and #u!t be "iltered out$ nother #ethod o" co#bating the
exce!! #ineral! and pollutant! i! !o#e #ean! o" a di!!olved !olid control'
!uch a! a blow down$ With thi!' a !#all percentage o" the "low i! drained o""
to aid in the re#oval o" the!e conta#inant!$ hi! i! "airly e""ective' but not
a! e""icient a! "iltration$
8lo!ed loop or clo!ed circuit) cooling tower !y!te#!' al!o called
indirect cooling tower !y!te#!' do not allow the water to co#e into contact
with any out!ide !ub!tance' there"ore (eeping the water #ore pure due to
the lac( o" "oreign particle! introduced$
nother cla!!i"ication o" cooling tower! i! #ade between $ield
a##e%bled twer#and $a+try a##e%bled twer#$ ield a!!e#bled
tower! are !hipped in piece! and a!!e#bled on !ite by a highly &uali"ied and
certi"ied in!tallation tea#$ actory a!!e#bled tower! typically only re&uire
the "an #otor to be #ounted$
'atural 1ra$t Twer#
9atural dra"t tower! are typically about 12* # high' depending on the
di""erential pre!!ure between the cold out!ide air and the hot hu#id air on
the in!ide o" the tower a! the driving "orce$ 9o "an! are u!ed$
Whether the natural or #echanical dra"t tower! are u!ed depend! on
cli#atic and operating re&uire#ent condition!$
he green "low path! !how how the war# water leave! the plant
proper' i! pu#ped to the natural dra"t cooling tower and i! di!tributed$ he
cooled water' including #a(eup "ro# the la(e to account "or evaporation
lo!!e! to the at#o!phere' i! returned to the conden!er$
&e+hani+al 1ra$t
echanical dra"t tower! u!e! "an! one or #ore) to #ove large &uantitie! o"
air through the tower$ hey are two di""erent cla!!e! %
a) orced dra"t cooling tower!
b) +nduced dra"t cooling tower!
-
8/13/2019 P.P.E UNIT II
22/44
he air "low in either cla!! #ay be cro!! "low or counter "low with re!pect to
the "alling water$ 8ro!! "low indicate! that the air"low i! hori,ontal in the
"illed portion o" the tower while counter "low #ean! the air "low i! in the
oppo!ite direction o" the "alling water$
he counter "low tower occupie! le!! "loor !pace than a cro!! "low
tower but i! taller "or a given capacity$ he principle advantage! o" the cro!!
"low tower are the low pre!!ure drop in relation to it! capacity and lower "an
power re&uire#ent leading to lower energy co!t!$
ll #echanical tower! #u!t be located !o that the di!charge air
di""u!e! "reely without recirculation through the tower' and !o that air
inta(e! are not re!tricted$ 8ooling tower! !hould be located a! near a!
po!!ible to the re"rigeration !y!te#! they !erve' but !hould never be located
below the# !o a! to allow the conden!er water to drain out o" the !y!te#
through the tower ba!in when the !y!te# i! !hut down$
Forced Draft
he "orced dra"t tower' ha! the "an' ba!in' and piping located within the
tower !tructure$ +n thi! #odel' the "an i! located at the ba!e$ here are no
louvered exterior wall!$ +n!tead' the !tructural !teel or wood "ra#ing i!covered with paneling #ade o" alu#inu#' galvani,ed !teel' or a!be!to!
ce#ent board!$
-
8/13/2019 P.P.E UNIT II
23/44
-
8/13/2019 P.P.E UNIT II
24/44
he induced dra"t tower !how in the "ollowing picture ha! one or #ore "an!'
located at the top o" the tower' that draw air upward! again!t the downward
"low o" water pa!!ing around the wooden dec(ing or pac(ing$ Since the
air"low i! counter to the water "low' the coole!t water at the botto# i! in
contact with the drie!t air while the war#e!t water at the top i! in contact
with the #oi!t air' re!ulting in increa!ed heat tran!"er e""iciency$
ig$+nduced dra"t
!ybrid 1ra$t
hey are e&uipped with #echanical dra"t "an! to aug#ent air"low$
8on!e&uently' they are al!o re"erred to a! "an7a!!i!ted natural dra"t tower!$
he intent o" their de!ign i! to #ini#i,e the power re&uired "or the air
#ove#ent' but to do !o with the lea!t po!!ible !tac( co!t i#pact$ roperly
de!igned "an! #ay need to be operated only during period! o" high a#bient
and pea( load!$
-
8/13/2019 P.P.E UNIT II
25/44
ig$ Hybrid dra"t
!AR1'ESS OF WATER
Hardne!! o" a water !a#ple i! a #ea!ure o" it! capacity to precipitate !oap'
i$e$ to prevent the lathering o" !oap$ Hardne!! i! cau!ed by #ultivalent#etallic cation! li(e 8a2@' and g2@ ion!$ t !uper!aturated condition!' the
hardne!! cation! will react with anion! in the water to "or# a !olid
precipitate$ he principal hardne!!7cau!ing cation! are the divalent calciu#'
#agne!iu#' !trontiu#' "errou! ion!' and #aganou! ion!$ he!e ion! react
with !oap which i! !odiu# !alt o" higher "atty acid! and "or# in!oluble !cu#!
precipitate!) o" calciu# or #agne!iu# !oap!$ typical divalent cation
reaction i! a! "ollow! %2 81C H35 8//9a @ 8a8l281CH358//)2 8a @ 2 9a8l
Sodiu# !tearate$
athering doe! not occur until all o" the hardne!! ion! are precipitated' at
which point the water ha! been K!o"tenedJ by the !oap$ he polyvalent ion!
-
8/13/2019 P.P.E UNIT II
26/44
occur in water o"ten in co#plex "or#! and not a! "ree ion!$ ! a re!ult' they
cannot precipitate !oap$ he #o!t i#portant anion! with which #ultivalent
#etallic cation! a!!ociated are bicarbonate carbonate)' !ulphate' chloride'
nitrate' and !ilicate$
Sur+e#
he #ultivalent #etallic ion! in water are derived largely "ro# contact with
the !oil and roc( "or#ation$ he ability to di!!olve i! gained in the !oil where
carbon dioxide i! relea!ed by bacterial action$ hi! carbon dioxide "or#!
carbonic acid to reduce the pH value$ :nder the low pH condition!' ba!ic
#aterial! are di!!olved in it$
Type# $ !ardne##
Hardne!! i! cla!!i"ied in two way! %
i) With re!pect to the #ultivalent #etallic ion' and
ii) With re!pect to the anion! a!!ociated with #ultivalent #etallic ion!$
!ardne## ba#ed n &etalli+ In
8alciu# and #agne!iu# are the #o!t abundant ion! in natural water which
contribute the greate!t portion o" the hardne!! occurring in natural water!$hu!' it i! a!!u#ed that the hardne!! due to the!e two #etallic ion! i!
con!idered a! total hardness$ 8alciu# hardne!! i! cau!ed by 8a2@ and i!
deter#ined a! the a#ount o" 8a2@ re&uired to !o"tening the li#e7!oda a!h$
Si#ilarly' #agne!iu# hardne!! i! due to g2@ ion! and i! deter#ined a! the
a#ount o" g2@ re&uired "or !o"tening li#e7!oda a!h$ +" #agne!iu# hardne!!
i! deter#ined' calciu# hardne!! i! obtained by !ubtracting #agne!iu#
hardne!! "ro# total hardne!!' a! "ollow! %otal hardne!! L #agne!iu# hardne!! calciu# hardne!!
!ardne## ba#ed n Anin#
hi! hardne!! i! cla!!i"ied a! carbonate hardness and non-carbonate
hardness' depending upon the anion with which it a!!ociate!$ When the
-
8/13/2019 P.P.E UNIT II
27/44
hardne!! ion! are a!!ociated with 8/32M and H8/3
M ion! in water' the
hardne!! i! called carbonate hardne!!' otherwi!e' it i! called non7carbonate
hardne!!$ he carbonate hardne!! i! che#ically e&uivalent to the carbonate
plu! bicarbonate al(alinity pre!ent in water$ hu!'
When al(alinity N total hardne!!
8arbonate hardne!! in #g L1) al(alinity in #g L1)$
When al(alinity O total hardne!!
8arbonate hardne!! in #g L1) total hardne!! in #g L1)
he carbonate hardne!! i! al!o (nown a! temporary hardness which can be
re#oved by boiling$
he non7carbonate hardne!!' (nown a! permanent hardness' can be
deter#ined a! %
9on7carbonate hardne!! total hardne!! L carbonate hardne!!
he per#anent hardne!! cannot be re#oved by boiling$ he non7carbonate
hardne!! cation! are a!!ociated with chloride' nitrate and !ulphate anion!$
P#eud !ardne##
he #etallic cation which i! not a hardne!!7cau!ing cation' but exhibit!
hardne!! when pre!ent in high concentration i! (nown a! pseudo-hardness$or exa#ple' !odiu# #etal ion which i! pre!ent in very high concentration in
!ea and brac(i!h water' exhibit! hardne!!$
Re%"al $ !ardne##
a) Re%"al $ Carbnate r Te%prary !ardne##
8arbonate hardne!! i! !en!itive to heat and precipitate readily at high
te#perature!$ hu!' it i! re#oved a! precipitate! a! %
he other #ethod! o" re#oval are a! "ollow! %
-
8/13/2019 P.P.E UNIT II
28/44
he carbonate hardne!! o" calciu# #ay be re#oved che#ically by u!ing
li#e 8a/)' cau!tic !oda 9a/H) and !oda a!h 9a28/3) a! depicted below$
8arbonate hardne!! o" #agne!iu# #ay be re#oved che#ically by u!ing
li#e "ollowed by cau!tic !oda a! "ollow! %
b) Re%"al $ 'n2+arbnate r Per%anent !ardne##
9on7carbonate calciu# hardne!! calciu# with non7carbonate anion!) can be
conveniently re#oved by u!ing !oda a!h 9a28/3)$ hu!'
8a8l2 @ 9a28/38a8/3 @ 2 9a8l
he non7carbonate #agne!iu# hardne!! #agne!iu# with non7carbonate
anion!) can be re#oved by u!ing cau!tic !oda or a co#bination o" li#e and
!od! a!h$ he repre!entative che#ical reaction! are %
Order of Removal
he order o" re#oval depend! on the !olubility o" the precipitate! li(e 8a8/ 3
and g/H)2$ Since g/H)2 i! #ore in!oluble than 8a8/3' the reactionproducing g/H)2 !hould ta(e precedence$
c) Split Treat%ent
Water with a high concentration o" #agne!iu# i! !o"tened by !plit
treat#ent$ +n thi! treat#ent' the raw water i! !plit into two !trea#!' the
-
8/13/2019 P.P.E UNIT II
29/44
-
8/13/2019 P.P.E UNIT II
30/44
Si#ilarly' the anion exchange resins are !tyrene divinyl ben,ene or a#ine
"or#aldehyde copoly#er!' which contain &uaternary a##oniu# group! a!
an integral part o" the re!in #atrix$ he M /H group! pre!ent in the!e re!in!
can enter into the exchange reaction with anion! in water$
3OILER CORROSIO' A'1 ITS PRE4E'TIO'
8orro!ion i! a proce!! in which the #etal ato#! leave their location on the
!ur"ace and !tabili,e in the "or# o" ion! in !olution$ 8orro!ion in an a&ueou!!y!te# occur! due to the interaction between the !ur"ace o" the #aterial!
and water body under condition! o" che#ical !tre!!' i$e$ acidic or al(aline$
Water i! a polar #olecule and the polari!ibility o" the water #olecule! on
contact with the iron !ur"ace lead! to the wea(ening o" the / L H bond$
=e H2/)5 /H>@i! the pri#ary corro!ion product which give! !econdary
hydroly!i! product' a! e /H)2$ he other !econdary product! are e/$/H'
e/' e3/4' e2/3 etc$ ll the!e !econdary product! are pH dependent$
3iler Crr#in
-
8/13/2019 P.P.E UNIT II
31/44
oiler corro!ion i! the deterioration o" the boiler #aterial by direct che#ical
or electroche#ical attac( o" it! a&ueou!) environ#ent$ +n high pre!!ure
boiler!' the "ailure o" boiler tube! #ade up o" carbon !teel i! due to internal
corro!ion and external Phot corro!ionQ$ he external corro!ion i!
#etallurgical in nature' there"ore' we !hall di!cu!! about the internal
corro!ion$
Cau#e#
he internal boiler corro!ion i! cau!ed due to the "ollowing i#portant
rea!on! %
i)
-
8/13/2019 P.P.E UNIT II
32/44
(ii*3y &e+hani+al 1eaeratin : he deaeration i! done by a vacuu# pu#p
to re#ove all the "ree ga!e! /2) a! it provide! high te#perature' low
pre!!ure and large !ur"ace area
Dissolved CO/
-
8/13/2019 P.P.E UNIT II
33/44
Re%"al $ A+id#
y adding acid neutrali,ed al(ali to the boiler water$
Cau#ti+ E%brittle%ent
+t i! a type o" boiler corro!ion cau!ed by u!ing highly al(aline water in the
boiler$ +n high pre!!ure boiler!' when 9a28/3 hydroly!e! with water re!ulting
in !odiu# hydroxide and carbon dioxide' the 9a/H #a(e! the boiler water
cau!tic$
hi! 9a/H containing water "low! into the #inute hair crac(!' u!ually "ound
on the inner wall! o" the boiler by capillary action$
-
8/13/2019 P.P.E UNIT II
34/44
Pri%ing and Fa%ing
+n the !tea# "or#ation proce!!' !o#e drop! o" water carried along with
!tea# i! called pri#ing$ ri#ing i! cau!ed #ainly due to the "ollowing "actor!
i) rapid boiling o" water
ii) the pre!ence o" !u!pended !olid!
iii) high level o" water in boiler
iv) the growth o" algae
v) !udden change o" !tea# production rate
vi) i#proper boiler de!ign$
ri#ing can be #ini#i,ed by the "ollowing "actor! %
i) by "itting #echanical !tea# puri"ier$
ii) #ini#i,ing the a#ount o" di!!olved and !u!pended i#puritie!$
iii) avoiding rapid change in !tea#ing rate$
iv) #aintaining low water level!$
Fa%ing
oa#ing i! the "or#ation o" continuou! and per#anent "oa# or bubble! in
the boiler water which do not brea( ea!ily and are carried over !tea#
-
8/13/2019 P.P.E UNIT II
35/44
cau!ing pri#ing$ hu!' pri#ing and "oa#ing occur together which i!
ob0ectionable$
he #ain proble#! cau!ed by "oa#ing are %
i) +" the bubble! do not brea(' they #ay be carried along the !tea# to
!upper heater and turbine blade! where the water evaporate! and the
di!!olved !alt! get depo!ited$
ii) ctual water level in!ide the boiler cannot be 0udged properly$
iii) he!e decrea!e the li"e ti#e and e""iciency o" the #achinery$
oa#ing can be #ini#i,ed by the "ollowing way! %
i) dding anti7"oa#ing agent! li(e ca!ter oil' polya#ide! etc$
ii) e#oving oil content "ro# boiler7"eed water by adding alu# and !oda
a!h$ iii) y blow down operation$
WATER TREAT&E'T
Water treat#ent generally con!ider! the puri"ication o" raw water "or
drin(ing purpo!e!$ he drin(ing water !hould be colourle!!' odourle!!' "ree
"ro# !u!pended i#puritie!' ger#!' bacteria and other di!!olved i#puritie!
which are in0uriou! to health$ +t !hould be "ree "ro# ob0ectionable di!!olved
ga!e!' turbidity' #ineral!$ he pH value o" the drin(ing water !hould be
within the range o" 6$5 to A$ here"ore' to #a(e pure drin(ing water' !o#e
i#portant !tage! o" puri"ication o" raw water are %
a) retreat#ent
b) Sedi#entation
c) iltration
d)
-
8/13/2019 P.P.E UNIT II
36/44
he raw water i! !tored "or !o#e period be"ore the actual treat#ent !tart! in
order to i#prove the &uality o" water by natural !edi#entation o" !ilt and
inactivation o" certain pathogenic organi!#!$
ii) Prechlorination
he !torage water !ub0ected to prechlorination to re#ove algal cell! and
bacteria$ rechlorination i! !uitable to low !ilt load water and it reduce! the
colour and !li#e "or#ation$ o !o#e extent' it oxidi!e! the iron and
#angane!e which are precipitated out$
iii)eration
he raw water i! "ir!t !aturated with oxygen by bubbling co#pre!!ed air$
he "ree ga!e! li(e 8/2' H2S i" pre!ent' will be re#oved$ he proce!! o"
aeration help! in re#oving ta!te! and odour! cau!ed by algal !ecretion in
the "or# o" volatile oil!$ ew e2@ and n2@ will al!o be oxidi,ed and
precipitated out$
iv) Coagulation and !locculation
he aerated water which #ay contain !#all particle! in the colloidal range'
can be re#oved by pro#oting their agglo#eration by "locculation in the
pre!ence o" coagulant!$ he "ollowing are the #o!t co##only u!edcoagulant! a) alu#' b) !odiu# alu#inate' coppera! or "errou! !ulphate!$
coagulant i! a che#ical which react! with water to "or# a bul(y precipitate
called floc$ he agglo#erated particle! called floccules are latter !eparated
"ro# water by "iltration$ he reaction! are
he overall reaction i!
-
8/13/2019 P.P.E UNIT II
37/44
he "loccule! are !eparated by !edi#entation and "iltration$
b) Sedi%entatin
he water with "loccule! are allowed to !ettle down "or !o#e period in a
!edi#entation ba!in in which "loccule particle! !ettled down at the botto#
due to the "orce o" gravity$
he clear !upernatant water i! then pu#ped out$ he !etteling rate depend!
on the #a!! and den!ity o" the particle!$
c) Filtratin
he partly clari"ied water "ro# the !edi#entation ba!in i! then pa!!ed to the
!tand gravity "ilter! to re#ove the !#all "loc particle! and #icroorgani!#!
!till re#ained in water a"ter !edi#entation$
ll the !u!pended #atter are "iltered out in the !and bed$ he!e "ilter! are o"
two type! %
i) apid !and "ilter! iltering rate i! #ore and i! rapidly exhau!ted)' and
ii) Slow !and "ilter! ate i! !low but durable)$
Generally' !low !and "ilter! are u!ed in the ab!ence o" coagulation and
!edi#entation$
(d* 1i#in$e+tin
he "inal !and "iltrate i! very clean but #ay not be "ree "ro#
#icroorgani!#!$ here"ore' di!in"ection o" that "iltered water i! &uite
e!!ential which i! obtained by i) chlorination' and ii) o,oni!ation$(i* Chlorination
8hlorine i! a power"ul di!in"ectant a! it produce! H/8l' /8l' 8hlora#ine!$
-
8/13/2019 P.P.E UNIT II
38/44
he hypochlorou! acid i! an un!table co#pound and &uic(ly deco#po!e! by
relea!ing na!cent oxygen$ he pre!ence o" a##onia in water lead! to the
"or#ation o" chlora#ine! a! "ollow! %
he che#ical !pecie! H/8l' /8l are "ree chlorine re!idual! wherea!
chlora#ine! are co#bined re!idual! and re#ain in water body "or a longer
period which help to (ill the #icroorgani!#! even in a di!tribution !y!te#$
he bacterial action o" chlorine i! #ainly becau!e o" the toxic nature o" there!idual! and the oxidation o" bio#olecule! by the na!cent oxygen$ he
do!e! o" chlorine are decided depending upon the pH' 8/2' te#perature and
the ti#e o" contact with water$
i&uid chlorine i! #o!t e""ective and the apparatu! u!ed "or thi! purpo!e i!
called Chlorinator$
Ad"antage#
i) +t i! e""ective$ii) +t i! very #uch !table and doe! not deteriorate on (eeping$
iii) +t can be u!ed at low a! well a! high te#perature!$
iv) +t introduce! no !alt i#puritie! in the treated water$
v) +t i! a very power"ul di!in"ectant$
1i#ad"antage#
i) .xce!! o" chlorine produce! unplea!ant ta!te and odour$ +t al!o produce!
irritation on #u!cu! #e#brane$ +t !hould be u!ed within the range o" *$1 to*$2 pp#$
ii) +t i! le!! e""ective in al(aline condition!$
(ii* Ozonisation
/,one behave! in a !i#ilar #anner to chlorine by relea!ing na!cent oxygen$
-
8/13/2019 P.P.E UNIT II
39/44
-
8/13/2019 P.P.E UNIT II
40/44
-
8/13/2019 P.P.E UNIT II
41/44
i) +t re#ove! ionic' nonionic' colloidal and high #olecular weight
co#pound!$ ii) he li"e ti#e o" #e#brane i! &uite high$
iii) he #e#brane! can be replaced very ea!ily
Ele+trdialy#i#
+t i! another #e#brane technology which i! u!ed "or the concentration o"
ion!$ +n thi! #ethod the ion! are pulled out o" the brac(i!h water' under an
electric "ield$
Si%ple Ele+trdialy#i#
+t con!i!t! o" three cha#ber! and electrode! cathodic and anode) are u!ed
in the !ide cha#ber!$ he brac(i!h water i! "ed in all the cha#ber!$ ro#
the central co#part#ent' the ion! are pulled out "ro# !alt water by pa!!ing
direct current through the pla!tic #e#brane pair$ Since the cell #e#brane!
with "ixed charge negative or po!itive)' whereby the #e#brane! beco#e
i#per#eable to either cation! or anion!$ here"ore' in brac(i!h water 9a@
!tart! #oving toward! cathode while the 8lM ion! toward! the anode through
the #e#brane$ he rate o" pulling out o" the ion! "ro# the !alt water
depend! on the !alinity o" water$
Ele+trdialy#i# Cell u#ing In Sele+ti"e &e%brane#+on !elective #e#brane! are generally e#ployed "or e""icient !eparation$
hi! type o" electrodialy!i! cell con!i!t! o" !everal pair! o" pla!tic
#e#brane!$ or !ati!"actory electrodialy!i!' "luorocarbon #e#brane
#aterial! !uch a! P9a"ionQ are pre"erred$ n ion !elective #e#brane i!
per#eable to one (ind o" ion! only' i$e$ per#eable to either cation or anion$
cation !elective #e#brane! are poly!tyrene poly#er! with !ulphonic acid
group! M S/3M
)$ ecau!e o" the pre!ence o" "ixed negative charge on the#e#brane' it i! per#eable only to the cation!$ Si#ilarly' &uarternary
a##oniu# group 9H4@) i! u!ed a! anion !elective #e#brane$
Method
-
8/13/2019 P.P.E UNIT II
42/44
he cation and anion !elective #e#brane! are (ept alternatively !o that
#any cha#ber! can be #ade through which brac(i!h water pa!!e! $y the
pa!!age o" direct current to the electrode!' the cation !elective #e#brane
repel! negative charged ion!' but allow! the @ve ion! to enter' while the
rever!e i! true "or the anion !elective #e#brane$ here"ore' water in one
cha#ber o" the cell i! de!alinated water' while the !alt water concentration
increa!ed in the next cha#ber$ hu!' we get alternative !trea#! o" pure
water and concentrated brine !olution$ Hence' thi! #ethod enhance! the
e""icient !eparation$
he i#portant u!e! o" the electrodialy!i! are in treat#ent o" #etal
plating wa!te!' battery #anu"acturer' gla!! etching and de!alination o"
e""luent!$
p! 4AL0E A'1 WATER TREAT&E'T
The Cn+ept $ p!
Soren!on 1-*-) propo!ed to expre!! the hydrogen7ion activity in ter#! o"
negative logarith#! o" hydrogen7ion activity and de!ignated the!e value! a!
pH$
When the !olution i! very dilute'
Si#ilarly' the activity o" /HM ion! expre!!ed in ter#! o" p/H$
-
8/13/2019 P.P.E UNIT II
43/44
hu!' a! pH increa!e!' p/H #u!t decrea!e and vice7ver!a$ +n pure water'
which i! neutral ' i$e$
the pH o" water i! C$ Hence' the neutral !olution ha! a pH C$ ny !olution
having pH le!! than C will be acidic and a !olution having pH #ore than C
will be al(aline$ he pH !cale range! "ro# * to 14' with pH C at
25C/HH1*88MM@o8 repre!enting ab!olute neutrality$
he value o" "w change! with change in te#perature' hence' the pH o"neutrality change! with te#perature$ +t i! C$5 at *o8 and 6$5 at 6*o8$
pH doe! not #ea!ure total acidity or total al(alinity$ he
value! can never be reduced to ,ero' no #atter how al(aline or acidic'
re!pectively a !olution beco#e!$ he!e are only the co#parative value!
depending on the degree o" ioni,ation$ or exa#ple' 9B1* !olution! o"
!ulphuric acid and acetic acid which have !a#e neutrali,ing value? the pH o"
9B1* !ulphuric acid i! approxi#ately 1 becau!e o" it! high degree o"
ioni,ation' and the pH o" acetic acid i! about 3 becau!e o" it! low degree o"
ioni,ation$ pH i! an i#portant "actor which #u!t be con!idered in control o"
the water &uality$
-
8/13/2019 P.P.E UNIT II
44/44