Co esponding au ho : Uwem Ekwe e Inyang
Copy igh © 2025 Au ho (s) e ain he copy igh o his a icle. This a icle is published unde he e ms o he C ea i e Commons A ibu ion License 4.0.
The impo ance o boile eed wa e and i s ea men in a chemical plan
Uwem Ekwe e Inyang * and Chidiebe e O ji Olughu
Depa men o Chemical Enginee ing, Facul y o Enginee ing, Uni e si y o Uyo, Uyo, Akwa Ibom S a e, Nige ia.
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(01), 1624-1632
Publica ion his o y: Recei ed on 10 June 2025; e ised on 15 July 2025; accep ed on 17 July 2025
A icle DOI: h ps://doi.o g/10.30574/wja .2025.27.1.2705
Abs ac
Wa e has a highe hea capaci y han mos o he subs ances. This quali y makes i an ideal aw ma e ial o boile
ope a ions. Boile s a e pa o a closed sys em as compa ed o open sys ems in a gas u bine. This means ha he wa e
is eci cula ed h oughou he sys em and is ne e in con ac wi h he a mosphe e. The wa e is eused and needs o be
ea ed o con inue e icien ope a ions. Boile wa e mus be ea ed in o de o be p o icien in p oducing s eam. Boile
wa e is ea ed o p e en scaling, co osion, oaming, and p iming. Boile eedwa e is an essen ial pa o boile
ope a ions. The eed wa e is pu in o he s eam d um om a eed pump. In he s eam d um he eed wa e is hen
u ned in o s eam om he hea . A e he s eam is used, i is hen dumped o he main condense . F om he condense ,
i is hen pumped o he deae a ed eed ank. F om his ank i hen goes back o he s eam d um o comple e i s cycle.
The eedwa e is ne e open o he a mosphe e. This cycle is known as a closed sys em o Rankine cycle. Boile wa e
ea men is used o con ol alkalini y, p e en scaling, co ec pH, and o con ol conduc i i y. The boile wa e needs
o be alkaline and no acidic, so ha i does no uin he ubes. The e can be oo much conduc i i y in he eed wa e
when he e a e oo many dissol ed solids. These co ec ea men s can be con olled by e icien ope a o and use o
ea men chemicals. The main objec i es o ea and condi ion boile wa e is o exchange hea wi hou scaling, p o ec
agains scaling, and p oduce high quali y s eam.
Keywo ds: Boile ; Wa e ; Tu bine; S eam; Condense
1. In oduc ion
A boile is a class o essel used o ans o m wa e unde p essu e in o s eam by applica ion o hea . In he boile
u nace, he chemical ene gy in he uel is con e ed in o hea . The unc ion o he boile is o e icien ly ans e hea o
he con ained wa e . The olume o wa e inc eases up o 1600 imes as i boils, which is su icien o cause explosion
(Shok e, 2023).
Boile eed-wa e is an essen ial pa o boile ope a ions. The eed wa e is pu in o he s eam d um om a eed pump.
In he s eam d um he eed wa e is hen u ned in o s eam om he hea . A e he s eam is used, i is hen dumped o
he main condense . F om he condense , i is hen pumped o he deae a ed eed ank. F om his ank i hen goes back
o he s eam d um o comple e i s cycle. The eed-wa e is ne e open o he a mosphe e. This cycle is known as a closed
sys em o Rankine cycle (Mischissin, 2012).
Du ing he ea ly de elopmen o boile s, wa e ea men was no so much o an issue, as empe a u es and p essu es
we e so low ha high amoun s o scale and us would no o m o such a signi ican ex en , especially i he boile was
“blown down”. I was gene al p ac ice o ins all zinc pla es and/o alkaline chemicals o educe co osion wi hin he
boile . Many es s had been pe o med o de e mine he cause (and possible p o ec ion) om co osion in boile s using
dis illed wa e , a ious chemicals, and sac i icial me als. Sil e ni a e can be added o eed-wa e samples o de ec
con amina ion by seawa e . Use o lime o alkalini y con ol was men ioned as ea ly as 1900, and was used by he
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F ench and B i ish Na ies un il abou 1935 (Shok e, 2023). In mode n boile s, ea men o eed-wa e is c i ical, as
p oblems esul om using un ea ed wa e in ex eme p essu e and empe a u e en i onmen s. This includes lowe
e iciency in e ms o hea ans e , o e hea ing, damage, and cos ly cleaning.
1.1. Cha ac e is ics o boile eed-wa e
Wa e has a highe hea capaci y han mos o he subs ances. This quali y makes i an ideal aw ma e ial o boile
ope a ions. Boile s a e pa o a closed sys em as compa ed o open sys ems in a gas u bine. The closed sys em ha is
used is he Rankine cycle. This means ha he wa e is eci cula ed h oughou he sys em and is ne e in con ac wi h
he a mosphe e. The wa e is eused and needs o be ea ed o con inue e icien ope a ions. Boile wa e mus be
ea ed in o de o be p o icien in p oducing s eam. Boile wa e is ea ed o p e en scaling, co osion, oaming, and
p iming. Chemicals a e pu in o boile wa e h ough he chemical eed ank o keep he wa e wi hin chemical ange.
These chemicals a e mos ly oxygen sca enge s and phospha es (Sendelbach, 2018). The boile wa e also has equen
blowdowns in o de o keep he chlo ide con en down. The boile ope a ions also include bo om blows in o de o ge
id o solids. Scale is p ecipi a ed impu i ies ou o he wa e and hen o ms on hea ans e su aces. This is a p oblem
because scale does no ans e hea e y well and causes he ubes o ail by ge ing oo ho . Co osion is caused by
oxygen in he wa e . The oxygen causes he me al o oxidize which lowe s he mel ing poin o he me al. Foaming and
p iming a e used when he boile wa e does no ha e he co ec amoun o chemicals and he e a e suspended solids
in he wa e which ca y o e in he d y pipe (Shok e, 2023). The d y pipe is whe e he s eam and wa e mix u es a e
sepa a ed.
1.2. Boile eedwa e ea men
Boile wa e ea men is used o con ol alkalini y, p e en scaling, co ec pH, and o con ol conduc i i y. The boile
wa e needs o be alkaline and no acidic, so ha i does no uin he ubes. The e can be oo much conduc i i y in he
eed wa e when he e a e oo many dissol ed solids. These co ec ea men s can be con olled by e icien ope a o
and use o ea men chemicals. The main objec i es o ea and condi ion boile wa e is o exchange hea wi hou
scaling, p o ec agains scaling, and p oduce high quali y s eam. The ea men o boile wa e can be pu in o wo pa s.
These a e in e nal ea men and ex e nal ea men . (Sendelbach, 2016) The in e nal ea men is o boile eed wa e
and ex e nal ea men is o make-up eed wa e and he condensa e pa o he sys em. In e nal ea men p o ec s
agains eed wa e ha dness by p e en ing p ecipi a ing o scale on he boile ubes. This ea men also p o ec s agains
concen a ions o dissol ed and suspended solids in he eed wa e wi hou p iming o oaming. These ea men
chemicals also help wi h he alkalini y o he eed wa e making i mo e o a base o help p o ec agains boile co osion.
The co ec alkalini y is p o ec ed by adding phospha es. These phospha es p ecipi a e he solids o he bo om o he
boile d um. A he bo om o he boile d um he e is a bo om blow o emo e hese solids. These chemicals also
include an i-scaling agen s, oxygen sca enge s, and an i- oaming agen s. Sludge can also be ea ed by wo app oaches.
These a e by coagula ion and dispe sion. When he e is a high amoun o sludge con en i is be e o coagula e he
sludge o o m la ge pa icles in o de o jus use he bo om blow o emo e hem om he eed wa e . When he e is
a low amoun o sludge con en i is be e o use dispe san s because i dispe ses he sludge h oughou he eed wa e
so sludge does no o m (Bane, 2006).
1.3. Deae a ion o eed wa e
Oxygen and ca bon dioxide a e emo ed om he eed wa e by deae a ion. Deae a ion can be accomplished by using
deae a o hea e s, acuum deae a o s, mechanical pumps, and s eam-je ejec o s. In deae a ing hea e s, s eam sp ays
incoming eed wa e and ca ies away he dissol ed gases. The deae a o s also s o e ho eed wa e which is eady o
be used in he boile . This means o mechanical deae a ion is used wi h chemical oxygen sca enging agen s o inc ease
e iciency (Sendelbach, 2016). Deae a ing hea e s can be classi ied in wo g oups: sp ay ypes and ay ypes. Wi h ay
ype hea e s he incoming wa e is sp ayed in o s eam a mosphe e o each sa u a ion empe a u e. When he
sa u a ion empe a u e is eached mos o he oxygen and non-condensable gases a e eleased. The e a e seals ha
p e en he econ amina ion o he wa e in he sp ay sec ion. The wa e hen alls o he s o age ank below. The non-
condensables and oxygen a e hen en ed o he a mosphe e. The componen s o he ay ype deae a ing hea e a e a
shell, sp ay nozzles, a di ec con ac en condense , ay s acks, and p o ec i e in e chambe walls. The sp ay ype
deae a o is simila o he ay ype deae a o . The wa e is sp ayed in o a s eam a mosphe e and mos o he oxygen
and non-condensables a e eleased o he s eam. The wa e hen alls o he s eam sc ubbe whe e he sligh p essu e
loss causes he wa e o lash a li le bi which also aids he emo al o oxygen and non-condensables. The wa e hen
o e lows o he s o age ank. The gases a e hen en ed o he a mosphe e. Wi h acuum deae a ion a acuum is
applied o he sys em and wa e is hen b ough o i s sa u a ion empe a u e. The wa e is sp ayed in o he ank like
he sp ay and ay deae a o s. The oxygen and non-condensables a e en ed o he a mosphe e. (Sendelbach, 2016).
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The eed-wa e mus be specially ea ed o a oid p oblems in he boile and downs eam sys ems. Un ea ed boile
eed wa e can cause co osion and ouling.
2. Boile co osion
Co osi e compounds, especially O2 and CO2 mus be emo ed, usually by use o a deae a o . Residual amoun s can be
emo ed chemically, by use o oxygen sca enge s. Addi ionally, eed wa e is ypically alkalized o a pH o 9.0 o highe ,
o educe oxida ion and o suppo he o ma ion o a s able laye o magne i e on he wa e -side su ace o he boile ,
p o ec ing he ma e ial unde nea h om u he co osion. This is usually done by dosing alkaline agen s in o he eed
wa e , such as sodium hyd oxide (caus ic soda) o ammonia. Co osion in boile s is due o he p esence o dissol ed
oxygen, dissol ed ca bon dioxide, o dissol ed sal s (Shun’an e al., 2008).
2.1. Fouling
Fouling is he deposi ion o ma e ial on he hea ans e su ace which educes he ilm hea ans e coe icien . The
impac o ouling on he hea exchange is mani es ed as he educ ion o he mal and hyd aulic pe o mance, in which
he la e has a mino e ec . (Rehman e al 2022).
Mo eo e , Fouling e e s o he undesi able accumula ion o ma e ial on su aces, o en in indus ial equipmen like
hea exchange s o pipes. This buildup can educe e iciency, inc ease cos s, and e en lead o equipmen ailu e. Fouling
can be caused by a ious subs ances, including scale, algae, deb is, dissol ed me als, and biological ma e .
Deposi s educe he hea ans e in he boile , educe he low a e and e en ually block boile ubes. Any non- ola ile
sal s and mine als ha will emain when he eed-wa e is e apo a ed mus be emo ed, because hey will become
concen a ed in he liquid phase and equi e excessi e "blow-down" (d aining) o p e en he o ma ion o solid
p ecipi a es. E en wo se a e mine als ha o m scale (Shun’an e al., 2008). The e o e, he make-up wa e added o
eplace any losses o eed-wa e mus be demine alized/deionized wa e , unless a pu ge al e is used o emo e
dissol ed mine als.
The e a e di e en ypes o ouling, namely: pa icula e ouling, Chemical eac ion ouling, Co osion ouling, Bio ouling,
c ys alliza ion ouling and p ecipi a ion ouling (Rehman e al 2022).
2.2. Locomo i e boile s
A locomo i e boile is a specialized ype o boile designed o gene a e high-p essu e s eam, p ima ily o powe ing
s eam locomo i es. I 's a i e- ube boile wi h a ho izon al cylind ical shell con aining ubes h ough which ho gases
om he i ebox pass, hea ing he su ounding wa e and p oducing s eam (Wikipedia, 2025).
S eam locomo i es usually do no ha e condense s so he eed-wa e is no ecycled and wa e consump ion is high.
The use o deionized wa e would be p ohibi i ely expensi e so o he ypes o wa e ea men a e used. Chemicals
employed ypically include sodium ca bona e, sodium bisul i e, annin, phospha e and an an i- oaming agen
(Sendelbach, 2016).
2.2.1. Why ea boile wa e ?
Boile wa e ea men is essen ial o ensu ing he sa e, e icien , and long-las ing ope a ion o boile sys ems by
p e en ing issues like scale, co osion, and ca yo e . T ea ing boile wa e helps main ain op imal pe o mance,
p e en s cos ly down ime, and ex ends he equipmen 's li espan (Wikipedia, 2025). Comple e pu e wa e is no
achie able, impu i ies in boile wa e include dissol ed solids, dissol ed gases and suspended ma e .
2.2.2. Majo p oblems associa ed wi h boile eed wa e
Majo p oblems associa ed wi h boile eed wa e include co osion, scale o ma ion, oaming, ca yo e , and sludge
accumula ion. These issues a ise om impu i ies in he wa e and can lead o dec eased e iciency, equipmen damage,
and cos ly epai s. Thus, scaling/deposi ion, co osion – oxygen a ack, caus ic co osion, boile wa e ca yo e ,
was ed uel due o scale may be app oxima ely 2-5%. Howe e , wa e ube boile s expe ience hea lux a es as high as
250,000B u/h ./ 2
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2.2.3. Common impu i ies in aw wa e
Common impu i ies in aw wa e include physical con aminan s like suspended solids (e.g., sil , clay, and us ), chemical
con aminan s like dissol ed mine als (e.g., calcium, magnesium, i on), and biological con aminan s such as bac e ia,
i uses, and pa asi es. These impu i ies can o igina e om a ious sou ces, including soil e osion, indus ial and
ag icul u al uno , and na u al mine al deposi s (Wikipedia, 2025). Examples o he impu i ies a e:
• Dissol ed solids – These a e subs ances ha will dissol e in wa e , ca bona e and sulpha es o calcium and
magnesium, which a e scale o ming when hea e . The e a e o he dissol ed solids which a e non-scale
o ming.
• Suspended solids – These a e subs ances ha exis in wa e as suspended pa icles. They a e usually mine als
o o ganic in o igin. These a e no a p oblem as hey can be il e ed.
• Dissol ed gases – Oxygen and ca bon dioxide can be eadily dissol ed in wa e . These gases a e agg essi e
ins iga o s o co osion.
• Scum o ming subs ances – These a e mine al impu i ies ha oam and scum, e.g. soda in o m o ca bona e,
chlo ide and sulpha e.
2.3. Ha dness
Wa e ha dness e e s o he concen a ion o dissol ed mine als, p ima ily calcium and magnesium, in wa e . I 's a
measu e o how much soap is needed o c ea e a la he and how e ec i ely soaps and de e gen s clean. Ha d wa e can
also cause mine al buildup in pipes and appliances (Wikipedia, 2025). Ha d wa e con ains scale o ming impu i ies
while so wa e con ains li le o none.
2.3.1. The e a e wo ypes o ha dness
Alkaline ha ness (also known as empo a y ha dness) Calcium and Magnesium ca bona es a e esponsible o his ype
o ha dness. These sal s dissol e in wa e o o m an alkaline solu ion. When hea is applied, hey decompose o elease
ca bon dioxide and so scale o sludge. Thei ha ness is emo able by boiling while non-alkaline ha ness and
ca bona es (also known as pe manen ha dness) calcium and Magnesium bu in he o m o sulpha e and chlo ides.
These p ecipi a e ou o solu ion due o hei educed solubili y as empe a u e ises and o m ha d scales which a e
di icul o emo e. The p esence o silica can also lead o ha d scale, which can eac wi h calcium and magnesium scales
o o m silica es, which can se e ely inhibi hea ans e and cause o e hea ing (Wikipedia, 2024).
To al ha dness in wa e e e s o he o al concen a ion o dissol ed di alen me al ca ions, p ima ily calcium and
magnesium, exp essed as equi alen calcium ca bona e (CaCO3). I essen ially indica es he "ha dness" o mine al
con en o he wa e . To al ha dness is he sum o concen a ions o calcium and Magnesium ions p esen when hese
a e exp essed as CaCO3
2.4. pH
A nume ical alue ep esen ing a po en ial hyd ogen con en o wa e –which is a measu e o he acidic o alkaline
na u e o he wa e . Alkalini y is a measu e o he capaci y o wa e o neu alize acids. Alkalini y o wa e is due
p ima ily o he p esence o Bica bona e, ca bona e and hyd oxide ions. Sal s o weak acids such as Bo a es may also
con ibu e. Ca bona e alkalini y is a measu e o he ca bona e and bica bona e ions in a solu ion (Wikipedia, 2024).
2.5. Oxygen co osion p e en ion in s eam gene a ion sys em
Oxygen co osion in s eam gene a ion sys ems is p ima ily mi iga ed h ough a combina ion o mechanical and
chemical me hods. Mechanical me hods in ol e deae a ion o emo e dissol ed oxygen, while chemical me hods u ilize
oxygen sca enge s and co osion inhibi o s o u he educe oxygen le els and p o ec me al su aces (Wikipedia,
2024).
Oxygen in addi ion o being dissol ed in eed wa e may en e a s eam gene a o combined wi h co osion p oduc s
such as e ic oxide (Fe2O3), coppe oxide (CuO) e c. Oxidized I on o example is no emo ed by deae a ion and may
cause co osion in high hea ans e a eas o he s eam gene a ion.
4Fe2O3 + Fe → 3Fe3O4 …………Equa ion 1
I on is aken om he coil me al as Fe2O3 is educed o magne ic I on oxide (Fe3O4). Hyd azine can minimize his ype
o a ack by eac ing wi h and educing hese oxidized co osion p oduc s.
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N2H4 + 6Fe2O3 → 4Fe3O4 + N2 + 2H2O …………..Equa ion 2
Oxygen is hen di ec ly emo ed by he magne ic I on oxide o med as shown
4Fe3O4 + O2 → Fe2O3 …………. Equa ion 3
In p ac ice high ini ial dosage o hyd azine a e needed be o e a esidual is es ablished. This ends o con i m ha
Hyd azine is used up by i s eac ing wi h oxidized co osion p oduc s. The s a ing dosage o Hyd azine is usually
absen wice he amoun needed o eac wi h oxygen.
Ca bona e alkalini y in he s eam gene a o can hyd olyze unde he ac ion o hea and libe a e ca bon dioxide which
will be ca ied along wi h he s eam o o m a co osi e ca bonic acid p oduc wi h he condensa e in p ocess hea
exchange o condensa e piping. Ammonia has been success ully employed o neu aliza ion o ca bon dioxide and
ele a ion o pH. I is an icipa ed ha no mo e han 0.2 o 0.3 ppm o ammonia will be equi ed o main ain he desi ed
pH ange (Lyon e al., 2012).
2.6. Scale
A scale inhibi o is a chemical ea men used o p e en o educe he o ma ion o mine al scale deposi s on su aces
in con ac wi h wa e o o he luids, pa icula ly in indus ial and oil ield applica ions. These chemicals wo k by
in e e ing wi h he c ys al g ow h o scale- o ming mine als, p e en ing hem om adhe ing o su aces and causing
blockages o educed low (Wikipedia, 2024).
The p ima y cause o scale o ma ion is he ac ha he solubili y o he scale- o ming sal s dec eases wi h an inc ease
in empe a u e. The highe he ope a ing empe a u e (and p essu e) in a s eam gene a o he mo e insoluble he
inc us ing sal s become. The chie mechanism o scale o ma ion is due o he c ys alliza ion o scale o ming sal s om
he solu ion, locally supe sa u a ed.
C ys alliza ion o scale esul s di ec ly on he hea ing su ace e en when he solubili y o he scale o ming sal s has no
been exceeded in he s eam gene a o wa e . A boiling empe a u es, calcium and Magnesium bica bona es decompose
o hei espec i e ca bona es and ca bon dioxide being p oduced in he eac ion. The solubili y o mos calcium and
magnesium sal s dec ease wi h inc ease in empe a u e. These sal s a e collec i ely e med “Ha dness” Magnesium
sulpha e is he excep ion, bu i usually eac s in s eam gene a o wa e o o m less soluble Magnesium sal s. Calcium
sulpha e, a highe empe a u es dec ease in solubili y and ends o deposi ou in he ho e pa s o he s eam
gene a o whe e scale can cause he mos damage (Wikipedia, 2024).
In gene al, all ha dness sal s a e po en ial scale o me s, since hey deposi ou o solu ion as wa e is hea ed. The
solubili y o sodium inc eases as wa e is hea ed and does no no mally cause s eam gene a o deposi s. Should a highe
deposi o sodium be ound in a s eam gene a o deposi , i indica es an unusual condi ion such as whe e wa e is
e apo a ed o i ual d yness.
Scale may o m o he i ems such as silica o p oduc s om silica may deposi ou as calcium silica e and p o e o be
qui e oublesome in s eam gene a o ope a ion. Main enance o high alkalini y concen a ion in s eam gene a o wa e
is an aid in con ol o his p oblem; howe e , only limi ed silica concen a ions can be con olled. Soluble i on en e ing
a s eam gene a o wi h he eed wa e will be p ecipi a ed by a s eam gene a o wa e pH o 10 o mo e and
consequen ly his pH ange is gene ally main ained in a high-p essu e s eam gene a o .
The di e en ypes o scale o med, all possess a low deg ee o hea conduc i i y. The p esence o scale is he e o e
equi alen o sp eading a hin ilm o insula ion ac oss he pa h o hea a el om he ho gases o he s eam gene a o
wa e . This hea insula ing ma e ial will e a d hea ans e and cause a loss o s eam gene a o e iciency.
E en mo e impo an han he e ec o scale in causing hea loss, howe e is he e ec o scale causing he o e hea ing
o boile me al and subsequen ube ailu e (Wikipedia, 2024).
3. T ea men
To p e en scale o ma ion in s eam gene a o s, a mul i- ace ed app oach is c ucial, encompassing wa e ea men ,
chemical condi ioning, and p ope main enance p ac ices. This includes using wa e so ene s, chemical ea men s like
oxygen sca enge s and scale inhibi o s, and egula blowdown o emo e accumula ed solids (Wikipedia, 2024).
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T ea men o p e en s eam gene a o scale is needed in e e y scale. E en hough he eed wa e ha dness is less han
1ppm, ea men is usually equi ed. One ppm o eed wa e ha dness (o I on) slipping h ough a so ene adds up o
abou 200kg o po en ial scale a yea , in a s eam gene a o making 50,000lbs/h (20,000kg/h ) (Lyon e al., 2012).
T ea men in ol es
• Con olling ha dness p ecipi a ion – eac ion should occu in he coole a ea o he s eam gene a o d um a o
nea he eed wa e en ance. The ha dness should come ou o solu ion and be suspended in he wa e a he
han deposi ing ou di ec ly on s eam gene a o me al
• Condi ioning s eam gene a o wa e suspended solids o sludge.
• The sludge mus be p ope ly ea ed be o e passing o he ho s eam gene a o a ea o keep i om s icking o
he ubes.
• The excess sludge mus be emo ed by blowdown. This is done by in e mi en blowdown a he low poin in
he s eam elease a ea in he s eam gene a o d um.
3.1. S eam con amina ion
S eam con amina ion e e s o he p esence o unwan ed subs ances in s eam, comp omising i s pu i y and po en ially
impac ing i s in ended use in a ious applica ions like powe gene a ion, chemical p ocessing, and ood p oduc ion.
This con amina ion can in oduce solids, liquids, o gases in o he s eam, a ec ing i s quali y and leading o a ious
issues in he sys ems whe e i 's used (Wikipedia, 2024). S eam con amina ion may occu when s eam gene a o eac s
in any one o he ollowing ways: Foams, P imes o du ing ca yo e
3.2. Foaming
Foaming is he condi ion esul ing om he o ma ion o bubbles on he su ace o he s eam gene a o wa e . The oam
p oduced may en i ely ill he s eam space o i may be o ela i ely mino dep h. In ei he case, his oaming condi ion
causes app eciable en ainmen o wa e wi h he s eam. I should be poin ed ou ha demis ing pad and o he
mechanical equipmen a e used o p e en he elease o we s eam o he sys em. Rega dless o mechanical p o ision,
s eam gene a o wa e should be main ained as pu e as possible o con ain oaming (Sendelbach, 2016).
3.3. P iming
P iming is a mo e iolen and spasmodic ac ion esul ing in he h owing o slugs o s eam gene a o wa e o e wi h
he s eam. This condi ion can exis because o high wa e le el, b oken ba ling, a sudden d as ic inc ease in s eam load
and a sudden o se e e con amina ion o s eam gene a o wa e (Wikipedia, 2024).
Ve y o en a combina ion o se e al o hese condi ions con ibu es o p iming.
3.4. Ca yo e
Ca yo e is he e m applied o he con inuous en ainmen o ela i ely small quan i y o s eam gene a o wa e solids
wi h he s eam. The e m ca yo e is also used o co e he gene al condi ions mo e exac ly di ided in o oaming,
p iming and ca yo e .
When s eam gene a o wa e solids a e ca ied o e in he s eam (such as silica) deposi s will occu in non- e u n and
s op al es, supe hea e s, s eam piping and u bines. Such deposi s can p omo e ailu e o supe hea e ubes and loss
in u bine e iciency (Sendelbach, 2016).
3.4.1. Silica ca yo e
One o he mos common ypes o ca yo e s is silica ca yo e . The key o minimizing silica ca yo e is o main ain
silica con en o he s eam gene a o below 3.5ppm when a an ope a ing p essu e o 105.5kgcm-2 (1,500psig). The
dissol ed silica in he s eam p oduc ion unde no mal ope a ing condi ions would be no mo e han 0.02ppm. Wi h a
s eam silica con en o 0.02ppm o less as de e mined empi ically by u bine expe s and u ili ies ope a o s, app eciable
u bine deposi s would no occu . Thus, his con en is a p ac ical maximum limi
3.5. Coo dina ed phospha e ea men
Coo dina ed phospha e ea men in boile sys ems aims o con ol wa e chemis y o p e en co osion and scale
o ma ion. I in ol es main aining a speci ic a io o phospha e o hyd oxide (o alkalini y) in he boile wa e , ypically
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using a combina ion o di-sodium phospha e and i-sodium phospha e. This app oach helps o manage he pH and
p e en he o ma ion o ee caus ic, which can lead o co osion (Wikipedia, 2024).
In he phospha e ea men , a small quan i y o caus ic is added o he s eam gene a o o main ain i in an alkaline s a e,
bu a oiding he p esence o excessi e ee hyd oxide. A 5% solu ion o di/ i-sodium phospha e is injec ed
in e mi en ly o con inuously in o he s eam gene a o d um as equi ed o main ain a small phospha e esidual o 10-
20ppm.
The p ima y pu pose o phospha e addi ion o he wa e is o p ecipi a e he ha dness cons i uen s unde he p ope
pH condi ions o be ween 9.5 and 10. The coo dina ed phospha e ea men is no gene ally used in s eam gene a o s
ope a ing abo e 112.5kgcm-2
3.6. Coo dina ed phospha e cu e
A "coo dina ed phospha e cu e" ypically e e s o a con ol me hod used in powe gene a ion boile s o manage
phospha e le els and p e en co osion and scale o ma ion. I in ol es main aining a speci ic a io o sodium o
phospha e in he boile wa e , ypically using a mix u e o isodium phospha e (Na3PO4) and disodium phospha e
(Na2HPO4). This app oach helps main ain a desi ed pH le el and minimize he isk o caus ic a ack on boile
componen s (Wikipedia, 2024).
Howe e , coo dina ed phospha e con ol o con ol in he mode a ely high p essu e s eam gene a o s ope a ion
should be on o below he cu e o p e en ee caus ic in he s eam gene a o . I ope a ing abo e he cu e as aces o
impu i ies en e he cycle wi h he make-up wa e , he phospha e will be p ecipi a ed p oducing ee hyd oxide. The
ee hyd oxide can be con olled by adding di-sodium phospha e (Shun’an e al., 2008). Gene ally, ee hyd oxide should
be main ained wi hin 0 – 1ppm
4. Solid accumula ion
"Solid accumula ion" gene ally e e s o he buildup o collec ion o solid ma e ials o e ime. This could e e o a ious
hings, including was e accumula ion, sedimen accumula ion in a na u al en i onmen , o he accumula ion o solids in
indus ial p ocesses. The con ex o "solid accumula ion" is impo an o unde s and i s speci ic meaning (Wikipedia,
2024).
I suspended solids (sludge) and dissol ed solids a e allowed o accumula e because o low blowdown a e, he
possibili y o sludge deposi s and ca yo e in he s eam is enhanced. Du ing s a up pe iods, suspended I on migh be
high in ela ion o o al solids and blowdown migh be pa ly o en i ely based on I on concen a ion. High suspended
I on in s eam gene a o wa e can p oduce se ious deposi p oblems.
The impo ance o equen in e mi en high- a e blowdown du ing bo h he ini ial and subsequen s a ups should be
emphasized o ensu e as comple e a emo al o solids as possible in a minimum pe iod o ime. I he s eam gene a o
wa e is isibly di y a he blowdown a e hea ing is s a ed, he blowdown equency should be abou wice an hou
o a du a ion o one o wo minu es a each blowdown poin . When he wa e appea ance is abou no mal, samples
should be analyzed o o al dissol ed solids, I on and silica. The e will be equen pe iods o wo- o h ee-hou s
du a ion, such as du ing egene a ion o he demine alize uni , ha a sligh inc ease o solids will be p esen in he
s eam gene a o eed wa e . This sligh inc ease o solids may be compensa ed o by phospha e injec ion and sligh ly
inc eased blowdown.
5. Phospha e hideou
Phospha e hideou is a phenomenon in boile s whe e phospha e compounds, used o wa e ea men , p ecipi a e ou
o solu ion unde high hea and p essu e, only o edissol e when condi ions change, po en ially leading o co osion
and con ol issues (Wikipedia, 2024).
Phospha e hideou is no usually encoun e ed in he ope a ion 105-kgcm-2 s eam gene a o s, bu will p obably be
e iden o some deg ee. I is he e m used o exp ess he phenomenon o he pa ial disappea ance o phospha e in he
s eam gene a o wa e upon inc ease in load and i s eappea ance upon load educ ion
The e m is used whe e he hideou is g ea e han 5ppm change be ween high load and low load. High p essu e s eam
gene a o ope a ion, phospha e esidual le els a e main ained a a low-le el ange o a oid app eciable phospha e
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hideou . A p ecise blowdown schedule canno be a i ed a by wa e analysis alone. Inspec ion o sys em componen s
o deposi s and labo a o y analysis o sampled deposi s a e a pe iod o ope a ion, and any emedial measu es aken
a e equi ed be o e a emp ing inaliza ion o blowdown p ac ice (Shok e, 2023).
In e mi en blowdown is no e icien a main aining a consis en le el o solids in he s eam gene a o , so a con inuous
blowdown connec ion should be p o ided o minimize solid luc ua ion in he s eam gene a o wa e and o p o ide a
mo e accu a e con ol o he a e. This blowdown connec ion is usually loca ed on he s eam d um nea he discha ge
om he gene a ing ubes and away om he eed wa e inle . An in e nal collec o pipe is usually supplied o his
nozzle.
Un il he s eam gene a o wa e pu i y app oaches no mal, he s eam gene a o p essu e should be limi ed o
app oxima ely 35.2kgcm-2 wi h minimum s eam load. As s eam gene a o wa e pu i y app oaches no mal he blow
down equency can be educed acco dingly and p essu e can be g adually inc eased. Blowdown om u nace ubes
should be s opped
Analysis o s eam gene a o wa e samples should be made a he equen ly since ela i ely wide luc ua ions could
concei ably occu in he quali y o he wa e . Be o e ho gases a e s a ed o elemen s o s eam gene a o sys em no
ye in se ice, hey should be ho oughly blown down o be su e hey a e ee o any solid accumula ion. The blowdown
will also p ehea hose elemen s o ope a ion (Bane, 2013). Once hey a e in se ice as a gene al ule, no hea ecei ing
ube bundle should be blown down.
6. Conclusion
The expec ed s eam quali y o 50ppb is achie ed by using a high pu i y eed wa e , an e ec i e eed wa e ea men
p og am, and by good con ol o he s eam gene a o wa e composi ion in a well-designed sys em wi h p ope and
e icien ope a ion suppo ed by accu a e sample analyses. Co osi e compounds, especially O2 and CO2 mus be
emo ed, usually by use o a deae a o . Residual amoun s can be emo ed chemically, by use o oxygen sca enge s.
Addi ionally, eed wa e is ypically alkalized o a pH o 9.0 o highe , o educe oxida ion and o suppo he o ma ion
o a s able laye o magne i e on he wa e -side su ace o he boile , p o ec ing he ma e ial unde nea h om u he
co osion. This is usually done by dosing alkaline agen s in o he eed wa e , such as sodium hyd oxide (caus ic soda)
o ammonia. Co osion in boile s is due o he p esence o dissol ed oxygen, dissol ed ca bon dioxide, o dissol ed sal s.
I is also essen ial ha he s eam gene a o be p ope ly secu ed du ing sho e m ou o se ice pe iods which could
esul om equipmen mal unc ion o by s a up delays. Du ing hese pe iods, he s eam gene a o d um should be
immedia ely blanke ed wi h Ni ogen and a posi i e p essu e o Ni ogen main ained un il such ime ha he s eam
gene a o sys em is eadied o s eam p oduc ion. In addi ion, small esidual o O2 sca enge should be main ained.
Compliance wi h e hical s anda ds
Disclosu e o con lic o in e es
No con lic -o -in e es o be disclosed.
Re e ences
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in Mode n S eam T ac ion o Railways. Yo k, UK. A chi ed om he o iginal (PDF).
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[3] Cha ac e is ics o boile eed wa e . (n.d.). Re ie ed Ma ch 21, 2015, om
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[4] Lyon, F ank. Hinds, A.W. (2012) Ma ine and Na al Boile s. The Lo d Bal imo e P ess.
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[9] Sendelbach, M. (2016). Boile -wa e ea men : Why, wha and how. Chemical Enginee ing, 95(11), 127 - 132
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[11] Shun'an, C., Qing, Z., & Zhixin, Z. (2008). A s udy o he in luence o chlo ide ion concen a ion on he co osion
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[12] h ps://en.wikipedia.o g/wiki/Boile _ eedwa e . Accessed 15 h Feb ua y 2024
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