TRI SEC APH

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December 1, 2010

Power 101: Improving the Performance of

Boiler Auxiliaries, Part IBy Nenad Sarunac

Editor's note: In this second installment of our Power 101 series (the first installment was Flue

Gas Heat Recovery in Power Plants, published in three parts Part I , Part II , and Part III !, wee"amine boiler au"iliary components that may be secondary to the desi#n of the boiler itself but

which are absolutely essential to its operation$ %e be#in this multi&part series with an

introduction to the air preheater ('PH! performance calculations$ In Part II, well e"amine performance de#radation caused by corrosion and foulin# as a result of coal combustion flue

#as constituents plus the effects of ammonia and sodium bisulfite in)ection for *+ miti#ation$ In

Part III, well loo- at options for improvin# 'PH performance$ Future articles will center onimprovin# the performance of other boiler au"iliaries$

The Ljungstrom (or Rothemuhle) ar !reheater ("#$) trans%ers sensble heat n the %lue gaslea&ng the boler to the combuston ar, usng regenerat&e heat trans%er sur%aces n a rotatng

(Ljungstrom) "#$ or statonary (Rothemuhle) heat trans%er matr' ncreasng the tem!erature o%

the ncomng combuston ar ncreases boler e%%cency and reduces the !lant heat rate (*gure1) The ncrease n boler e%%cency s sgn%cant+ a 2* change n %lue gas tem!erature lea&ng

the "#$ results n an a!!ro'mately 1- (relat&e) change n net unt heat rate, .th a

corres!ondng reducton n /2 emssons

1. The e%%ect o% "#$ gas outlet tem!erature on net unt heat rate Source+ nergy Research

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Flue-Gas-Heat-Recovery-in-Power-Plants-Part-I_255.html

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Improving-the-Performance-of-Boiler-Auxiliaries-Part-II_300.html

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Flue-Gas-Heat-Recovery-in-Power-Plants-Part-III_278.html

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Improving-the-Performance-of-Boiler-Auxiliaries-Part-II_300.html

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Flue-Gas-Heat-Recovery-in-Power-Plants-Part-III_278.html

http://www.coalpowermag.com/ops_and_maintenance/Power-101-Flue-Gas-Heat-Recovery-in-Power-Plants-Part-I_255.html



/enter, Lehgh n&ersty (R/)

The %lue gas tem!erature lea&ng the econom3er (and enterng the "#$) s ty!cally reduced

%rom 400* to 500* to 26* to 70* at the "#$ outlet /ombuston ar s heated %rom about 50*

to 00* to 60*, de!endng on the coal heat and mosture content n theory, only the !rmary ar(the ar used to dry the coal n the !ul&er3ers and con&ey the !ul&er3ed coal to the burners)

could be heated *uel can be combusted .thout !reheatng secondary and tertary ar $o.e&er,

there s consderable ad&antage to the %urnace heat trans%er !rocess by heatng all o% thecombuston ar+ t ncreases the rate o% burnng and hel!s ncrease %urnace %lame tem!eratures

The Ljungstrom "#$ o!erates by contnuously re&ol&ng the heat trans%er matr' through the gas

(absorbng heat energy) and ar streams (releasng heat energy) .th a rotatonal s!eed n the 1r!m to 7 r!m range The Rothemuhle (or statonary !late) "#$ uses a statonary heat trans%er

matr' .th a rotatng ar8%lue gas hood (*gure 2)



2. The Rothemuhle regenerat&e "#$ Source+ R/

"#$s can be desgned as b9sector or tr9sector ty!es n a b9sector "#$, total combuston ar(secondary and !rmary ar) %lo.s through the ar sector o% the "#$ (*gure 7a) n a tr9sectordesgn, the !rmary ar %lo.s through a se!arate !rmary ar sector, .hle the secondary ar %lo.s

through the secondary ar sector (*gure 7b) " tr9sector desgn s used %or bolers %rng hgh9

mosture or lo.9ran: %uels .here hotter !rmary ar s needed %or e&a!oraton o% coal mosture n

mlls

3. B9sector (le%t) and tr9sector (rght) "#$ con%guratons Source+ R/



Due to a d%%erence n statc !ressure bet.een the %lue gas and combuston ar streams,

combuston ar can lea: nto the %lue gas stream The "#$ lea:age (;"#$,L) s ty!cally n the 5-

to 12- (by .eght) range %or Ljungstrom "#$s *or the Rothemuhle "#$, ar lea:ages n the2- to 70- range are not uncommon

Lea:age !aths %or a tr9sector "#$ are more com!le', com!ared to a b9sector "#$ n a tr9sector "#$, !rmary ar (#") lea:s nto the %lue gas and secondary ar (S") streams, .hle S"

lea:s nto the %lue gas stream Lea:age occurs both on the cold end (/) and hot end ($) sdes

o% the "#$ Due to large d%%erence n !ressure bet.een the #" and S" streams, as .ell as the #"and %lue gas streams, lea:age n a tr9sector "#$ s hgher than n a b9sector "#$ t<s also

m!ortant to note that %or a tr9sector "#$, the "#$ lea:age, as de%ned by =uaton 1 (all o% the

!er%ormance calculaton e=uatons re%erenced are ncluded n an "!!end' at the end o% ths

artcle), does not nclude the #" to S" lea:age and there%ore s not an accurate measure o% totalar lea:age *urthermore, the #" to S" lea:age cannot be measured ether by the o'ygen rse or

tracer gas techn=ues but has to be calculated usng n%ormaton on !ressure d%%erence bet.een

the #" and S" streams and assumed clearances

"r lea:age %or a tr9sector "#$ can be determned by a com!uter model, such as that !resented

n *gure > *or ths 6009?@ !o.er !lant %rng btumnous coal, lea:ages are calculated byusng n%ormaton on statc !ressure d%%erences bet.een the #", S", and %lue gas streams,

assumng t.o9thrds o% the lea:age occurs at the hot end o% the "#$ The ar to %lue gas lea:age

s 12- (by .eght) "s dscussed earler, ths lea:age does not nclude the #" to S" lea:age *orthe g&en statc !ressure dstrbuton around the "#$, a calculated &alue o% the #" to S" lea:age

s -

. The ngneerng Research /enter at Lehgh n&ersty has .rtten a com!uter model to

calculate ar and gas lea:age %or a tr9sector "#$ Source+ R/



"r lea:age also a%%ects the %lo. rate o% #", S", and %lue gas through the "#$ heat trans%er

matr' and, thus, a%%ects the "#$ ca!acty rate rato (/R , :no.n n the ndustry as the A rato)Ths !arameter has a sgn%cant e%%ect on "#$ !er%ormance The / lea:age a%%ects the

tem!erature o% the %lue gas lea&ng the "#$ The %lue gas tem!erature, do.nstream o% the "#$,

a%ter adabatc m'ng bet.een the %lue gas and ar lea:age streams (26* n ths e'am!le), slo.er com!ared to the %lue gas tem!erature measured at the "#$ outlet (70>* n ths e'am!le)

?ajor com!onents o% a &ertcal9sha%t b9sector Ljungstrom "#$ and lea:age !aths are !resented

n *gure n ths arrangement, the %lue gas %lo.s do.n.ard, .hle combuston ar s %lo.ng

u!.ard The rotor, !ac:ed .th heat trans%er sur%ace, s su!!orted through a lo.er bearng at the

/ o% the "#$ and guded through a gude9bearng assembly located at the to! or $ o% the"#$

!. Ths llustraton o% a b9sector Ljungstrom "#$ ncludes seals and lea:age !aths Source+ R/

The con&entonal rotor sealng system contans o% lea%9ty!e labyrnth seals bolted to the rotor

radal members at the $ and / The radal seals !ress aganst radal !lates, located at the $

and / "'al seals are !ostoned along the !er!hery o% the rotor *or the &ertcal9sha%tLjungstrom, .here the rotor s su!!orted %rom belo., most o% the lea:age occurs at the $ o% the

"#$ "s a rule o% thumb, a!!ro'mately t.o9thrds o% the ar lea:age occurs at the $ o% the

"#$ (*gure ) *or a hor3ontal9sha%t "#$, a!!ro'mately t.o9thrds o% ar lea:age occurs at



the /

The trans%er o% heat %rom the hotter %lue gas stream to the colder ar stream creates tem!eraturegradents, .hch cause thermal dstortons throughout the structural members The relat&e

dstorton o% the &arous com!onents a%%ects clearances bet.een the seals and sealng sur%aces

There%ore, control o% "#$ lea:age s not an easy tas:, es!ecally n case o% a Rothemuhle "#$

The heat trans%er sur%ace o% Ljungstrom9 or Rothemuhle9ty!e ar !reheaters uses a combnaton

o% %lat or %ormed steel sheets .th corrugated, notched, or undulated rbbng, %ormnglongtudnal (a'al) !assages .thn the "#$ (*gure 4) The heat trans%er sur%aces are desgned

%or hgh heat trans%er and lo. !ressure dro! "s an a!!ro'mate rule, 1 nch n heght o% standard

Ljungstrom heat trans%er sur%ace reco&ers as much heat as 2 %eet o% sur%ace n a tubular heater

.th e=u&alent resstance to %lo. The com!act arrangement o% metal sheets !ermts a largeamount o% heat trans%er sur%ace to be !laced n a relat&ely small rotor Normally, the heat

trans%er sur%ace s d&ded nto t.o or more a'al layers "d&antages resultng %rom layerng the

sur%ace nclude these+

• " %eld9remo&able / secton, usually 12 nches n length (or heght), that can be easly

re!laced n case o% corroson damage or se&ere !luggng

• D%%erent heat trans%er sur%aces can be used n d%%erent layers to sats%y ste9s!ec%c

re=urements n addton, d%%erent9gauge materals can be used n each layer, .th the

/ layer ty!cally manu%actured o% the hea&est gauge materal

• ach layer can be constructed o% a d%%erent materal to accommodate %oulng and

corroson condtons that &ary .th %lue gas tem!erature



". *lat, notched, corrugated, and undulated steel !lates are used to %orm "#$ heat trans%er

sur%aces (to!) The sha!e sho.n on the bottom le%t s ty!cally used n the cold end layer o% the

"#$ The bottom rght con%guraton s tradtonally used n the ntermedate and hot end layers

Source+ R/

Tradtonally, "#$ desgn used %our a'al layers+ cold end, cold ntermedate, hot ntermedate,

and hot end layer Later, the %our9layer desgn .as sm!l%ed to a three9layer desgn *or the"#$s o!eratng do.nstream o% a select&e noncatalytc reactor or select&e catalytc reactor %or

N' control, .here ammona sl! and %ormaton and de!oston o% ammonum bsul%ate .thn

the "#$ s a !roblem, a t.o9layer "#$ desgn s used The t.o9layer desgn uses a dee! /layer manu%actured o% lo.9alloy /orten steel or enameled carbon steel that .as de&elo!ed to

%acltate better cleanng The t.o9layer "#$ desgn s used by the electrc utlty ndustry .th

&aryng degrees o% success

#stimating AP$ Air %ea&age

"r !reheater lea:age not only a%%ects !er%ormance o% the "#$, but t also has a detrmental

e%%ect on unt !er%ormance "r lea:ng %rom the combuston ar to the %lue gas stream s not

!artc!atng n the combuston !rocess, and t re!resents an addtonal burden on the %orced dra%t(*D) and nduced dra%t (D) %ans "s ar lea:age ncreases, the *D %an needs to handle an

addtonal &olume o% ar to su!!ly combuston ar to the boler "ddtonally, the D %an !o.er

ncreases, because the %an has to handle lea:age ar n addton to the combuston !roducts (%lue

gas) "s a result, staton ser&ce !o.er ncreases, causng an undesrable ncrease n net unt heat



rate

The e%%ect o% "#$ ar lea:age on net unt heat rate and staton ser&ce !o.er s !resented n*gure 6 %or a b9sector "#$ and a >009?@ !o.er !lant %rng btumnous coal The nlet gude

&ane %lo. control .as assumed %or *D and D %ans n ths e'am!le

'. The e%%ect o% "#$ ar lea:age on net unt heat rate and staton ser&ce loads Source+ R/

/hanges n net unt heat rate and staton ser&ce !o.er can be de&elo!ed as %unctons o% the "#$ar lea:age The 4- "#$ lea:age s used as a re%erence !ont, because t re!resents the desgn

&alue used by "#$ manu%acturers "s "#$ lea:age ncreases, the net unt heat rate !enaltyncreases lnearly " 10 !ercentage !ont ncrease n "#$ lea:age (%or e'am!le, an ncrease %rom

4- to 14-) ncreases staton ser&ce !o.er by about 11- and ncreases the net unt heat rate by

a!!ro'mately 02- lmnatng "#$ lea:age by usng gas9to9gas heat e'changers or heat !!eheat e'changers .ll m!ro&e net unt heat rate by a!!ro'mately 01-

The heat rate !enalty due to the "#$ ar lea:age s hgher %or tr9sector "#$s, .here hgh9 !ressure #" %rom the !rmary ar sector lea:s nto the S" and %lue gas streams, resultng n

ncreased #" %an !o.er re=urements, n addton to ncreased *D and D %an !o.er "

com!arson o% the heat rate !enalty %or !o.er !lants em!loyng b9sector and tr9sector "#$s s !resented n *gure 5



(. The e%%ect on !lant heat rate caused by "#$ ar lea:age %or b9sector and tr9sector "#$s

Source+ R/

Besdes a%%ectng staton ser&ce !o.er and net unt heat rate, "#$ ar lea:age has a negat&e

e%%ect on !er%ormance o% the ar !olluton e=u!ment by reducng treatment (resdence) tme due

to a hgher %lo. rate o% %lue gas "lso, ar lea:ageCncludng the "#$ and boler n9lea:ageC

has a negat&e e%%ect on the !ost9combuston /2 ca!ture system and ts e%%cency The s3e (andcost) o% the !ost9combuston /2 ca!ture system s drectly !ro!ortonal to the %lo. rate o% the

%lue gas that needs to be treated n addton, e%%cency o% the !ost9combuston /2 ca!turesystem s a%%ected by the concentraton o% /2 n the %lue gas, .hch decreases as ar lea:age

ncreases

The e%%ects o% "#$ ar lea:age on the %lue gas %lo. rate and /2 concentraton n the %lue gas are

!resented n *gures and 10 %or a b9sector "#$ nstalled on a ty!cal >009?@ !o.er !lant

%rng btumnous coal The %lo. rate o% %lue gas lea&ng the "#$ ncreases lnearly as the "#$

ar lea:age ncreases *or hgh le&els o% "#$ lea:age, ty!cal o% Rothemuhle "#$s, the ncreasen %lue gas %lo. rate s sgn%cant n ths stuaton, the concentraton o% /2 n the %lue gas

decreases .th ar lea:age *or hgh le&els o% "#$ lea:age, the decrease n the /2 concentraton s sgn%cant



). The e%%ect on %lue gas %lo. caused by changes n "#$ ar lea:age Source+ R/

10. /2 concentraton n the boler %lue gas decreases as "#$ ar lea:age ncreases Source+ R/

n the case o% an o'y9combuston retro%t, any ar lea:age .ll ha&e a se&ere negat&e e%%ect on



!lant e%%cency, retro%t cost, and /2 !urty and .ll ha&e to be elmnated Ths .ll re=ure

3ero9lea:age heat e'changers .hen %rng n the o'y9%uel mode

Air Preheater *eals

The "#$ lea:age usually dr%ts (slo.ly ncreases) .th tme, unless a catastro!hc seal %alureoccurs (*gure 11) ?ost ne. "#$s, a%ter ntal commssonng or .hen set u! correctly a%ter an

outage, can ache&e lea:age le&els that are close to desgn &alues $o.e&er, a%ter a !erod o%

o!eraton (t.o or more years), the lea:age .ll ncrease, ty!cally %rom 4- to 12- on thesecondary "#$s, and to bet.een 12- and 2- (or hgher) on !rmary ar !reheaters Smlar

ncreases n ar lea:age are e'!ected %or tr9sector "#$s

11. The "#$ ar lea:age .ll dr%t u! =uc:ly a%ter nstallaton Source+ ?odern3aton o%Rotatng ?atr' Regenerat&e "r #reheaters, $o.den #o.er Ltd, !resented at #o.erEen

14

n addton to hgher *D and D !o.er re=urements and hgher net unt heat rate, the

deteroraton n lea:age !er%ormance can ha&e other serous conse=uences These changesnclude reduced do.nstream tem!eratures (because o% the dluton e%%ect), causng a !otental %or

ncreased acd de!oston and corroson o% the do.nstream duct.or: and ncrease n the *ED

booster %an !o.er n se&ere cases, deratng the unt mght be re=ured due to %an lmtatons

A+usta-le *ector Plate. ?anually adjustable sector !lates are used to mnm3e "#$ lea:age,

as "#$ seals .ear o&er tme "n m!ro&ed &erson o% ths conce!t n&ol&es actuator9adjusted

radal and a'al sealng !lates (*gure 12) Sldng arrangement o% the to! and bottom radalsector !late !rmary seals allo.s mo&ement o% the sealng sur%aces These seals are !rone to .ear

and eroson by %ly ash n the %lue gas stream "lthough ntally these seals sho.ed good sealngcharacterstcs, a%ter years o% o!eraton, seal .ear contrbuted to ar lea:age around the sector !lates "s a drect conse=uence o% the lea:age, de!oston o% %ly ash behnd the sector !lates

caused reduced sector !late tra&el that caused the !lates to jam n !oston Smlar !roblems

occur on the a'al seal !lates The best .ay to sol&e the !roblem s com!lete remo&al o% theadjustment to the sealng sur%aces Durng the "#$ retro%t, the sector and a'al sealng !lates are

set to accommodate all clearance ga!s %or all o!eratonal dutes and are .elded n !oston,

elmnatng the need %or %uture adjustment or mantenance



12. "djustable seal !late desgn Source+ R/

a+ial an+ Axial *eals. Radal seals are used to mnm3e the drect ar to gas lea:age that

occurs at the center secton or sealng sur%aces n the "#$ The seals are attached to each

da!hragm (stay, s!ltter, or radal d&son !late) o% the rotor to mantan close contact .th thesealng sur%ace (that se!arates the ar and gas streams) and to a'al seal holdng bars Sngle9lea%

sealng str!s, %tted to the radal d&son !lates and a'al seal holdng bars, !ro&de a shar! edge

that allo.s %ne adjustment %or !ro!er seal settng

arly e'!erences sho.ed that t.o9lea% ty!e seals sho.ed better ntal sealng characterstcs

.th adjustable mechansms (adjustable sector !late), but because o% ths adjustment they .ere !rone to .ear Laboratory tests %ound that once .orn, t.o9lea% seals .ere no longer any better

than an e=u&alent sngle9lea% seal @th the mod%catons to %'ng adjustable sealng sur%aces,

the sngle9lea% seal .as %ound to be more e%%ect&e

There are many desgns o% sngle9lea% seals *or e'am!le, radal seals o%%ered by #aragon

"rheater Technologes are desgned to act l:e a s!rng and mantan a !ost&e contact bet.een

the seal and the sealng sur%ace (*gure 17) The s!rng %orce !re&ents the seal %rom o!enng dueto hgh d%%erental !ressure across the hot and cold ends o% the "#$ The bello.s archtecture

enables the seal to sel%9adjust o&er tme as .ear occurs on the sealng edge, or durng "#$

turndo.n The seal re!laces the ? seals and attaches to each da!hragm, utl3ng the e'stngholdng hard.are and the e'stng bolt holes on the da!hragms The seals are nstalled and

adjusted to mantan the a!!ro!rate %orce and clearance bet.een the seal and sealng sur%ace



13. Sngle9lea% adjustable radal seal Source+ #aragon "rheater Technologes

Tradtonal "#$ desgns ha&e ether 129sector rotors .th 70F sector !lates or 2>9sector rotors.th 1F sector !lates, .hch means that only one radal sealng str! s !assng under the sector

!late at a tme Damage, corroson, and eroson o% these seals dramatcally ncreases the lea:age

Theory sho.s that lea:age s drectly !ro!ortonal to the s=uare root o% the dr&ng !ressure

d%%erental, so t %ollo.s that % the number o% seals under the sector !late s doubled, e%%ect&elyhal&ng the !ressure d%%erental actng on each sealng sur%ace, the radal lea:age .ll be

decreased by a!!ro'mately 70- The double9sealed "#$ rotor desgn s !resented n *gure 1>



1. Double9sealed "#$ rotor desgn com!ared to the older sngle9sealed rotor desgn Source+

R/

/ircumferential an+ Bpass *eals. /rcum%erental seals !re&ent ar and gas %rom by!assng

the heatng sur%ace through the s!ace bet.een the rotor and the housng shell These seals are

retaned by mountng angles bolted to the crcum%erence o% the rotor /rcum%erental seals .earaganst the sealng rngs, .hch are .elded to the "#$ housng

By!ass seals d%%er %rom crcum%erental seals by reducng the =uantty o% ar %lo.ng o&er theouter rm o% the rotor, as the tas: o% reducng a'al lea:age s handled by the a'al sealng

system By!ass seals are mounted on the housng and seal aganst the rotor9mounted T9bar

/rcum%erental and by!ass seals are nstalled at the hot and cold ends o% an "#$ (*gure 1)By!ass reduces "#$ !er%ormance because the ar and %lue gas by!assng the "#$ rotor are not

!artc!atng n heat e'change "s a result, the tem!erature o% combuston ar lea&ng the "#$ s

lo.er, .hle the tem!erature o% the %lue gas s hgher, com!ared to the 3ero9by!ass case



1!. /rcum%erental and by!ass seals on an "#$ Source+ R/

The crcum%erental and by!ass seals o%%ered by #aragon "rheater Technologes are com!osed

o% t.o nterloc:ng members (*gure 14) The tabs and slots nterloc:, !ro&dng seal tabs %rom

beng torn lose n the e&ent that the "#$ rotor comes n contact .th the seal or a %oregn object,such as a cln:er lodged bet.een the rotor and the seal (*gure 16) The nec: (narro.) sectons

o% the seal do not o&erla!, !ro&dng greater %le'blty %or each o% the tabs @th standard

crcum%erental and by!ass seal desgns, t s &ery common %or seal tabs to be torn a.ay, thus

e'!osng large ga!s that !ro&de lea:age !aths around the "#$ rotor

1". nterloc:ng desgn o% crcum%erental and by!ass seals Source+ #aragon "rheaterTechnologes



1'. nterloc:ng !rocess o% sealng members Source+ #aragon "rheater Technologes

The use o% ad&anced and sel%9adjustng seals can reduce "#$ lea:age by a %actor o% t.o,

resultng n %an !o.er reducton, net !o.er out!ut ncrease, and reducton n o!eratng costs$o.e&er, e&en .th ad&anced seal desgns, "#$ lea:age should be chec:ed on an annual bass

Seals need to be adjusted or re!laced to :ee! "#$ ar lea:age and ar and %lue gas by!ass lo.

The o'ygen rse method s commonly used %or determnng ar lea:age The tracer gas techn=ues

are accurate, but &ery e'!ens&e

t should be noted that nternal by!ass o% combuston ar and %lue gas can also occur as aconse=uence o% e'cess&e clearances bet.een nd&dual "#$ bas:ets Ths stuaton mght occur

a%ter an "#$ bas:et re!lacement % ne. bas:ets are slghtly unders3ed (*gure 15) " care%ul

ns!ecton o% "#$ bas:et s3e s &ery m!ortant =ually m!ortant s detaled ns!ecton o% the

re9bas:eted "#$ to ensure there are no ga!s or clearances bet.een the bas:ets

1(. The locaton o% nternal by!ass through clearances bet.een "#$ bas:ets s sho.n by the

arro.s Source+ R/



The %%ect o% Boler Lea:age on "#$ #er%ormance "s the ar n9lea:age n a boler con&ect&e !ass ncreases, the &alue o% e'cess 2 measured n the econom3er gas e't duct ncreases Ths

ncrease s sensed by the combuston control system and nter!reted as an ncrease n ar%lo.

rate To mantan the 2 set!ont, the combuston control system reduces the %lo. rate o%combuston ar " lo.er %lo. rate o% combuston ar results n a lo.er %urnace e'cess ar (e'cess

2) le&el, ncreased / emssons, ncreased le&els o% unburned %uel n %ly ash, hgher %urnace

e't gas tem!erature, ncreased slaggng and %oulng rates, and hgher net unt heat rate

To llustrate the e%%ect o% boler con&enton !ass lea:age on "#$ and unt !er%ormance,

calculatons .ere !er%ormed %or a btumnous coal9%rng >009?@ unt con%gured .th a b9

sector "#$ The e'cess 2 set!ont o% 7- .as mantaned at the econom3er gas e't Theresults are !resented n *gures 1 to 22

1). The e%%ect o% boler con&ecton !ass lea:age on e'cess o'ygen le&els n the %lue gas Source+R/



20. Boler con&ecton !ass lea:age .ll change the ar and %lue gas %lo. rates Source+ R/

21. "#$ ca!acty rate rato as a %uncton o% boler con&ecton !ass lea:age Source+ R/



22. The change n %lue gas tem!erature at the "#$ outlet and net unt heat rate as a %uncton o%

boler con&ecton !ass lea:age Source+ R/

The %urnace e'cess 2 le&el decreases lnearly .th boler con&enton !ass lea:age, as the e'cess

2 set!ont s mantaned at the econom3er gas outlet "s the boler con&ecton !ass lea:age

doubles %rom the re%erence &alue o% -, the %urnace e'cess 2 decreases %rom 26- to 1-(*gure 1) /orres!ondng changes n combuston ar and %lue gas %lo. rate are !resented n

*gure 20 "n ncrease n boler con&ecton !ass lea:age %rom the re%erence &alue o% - to 10-

results n about a >>- decrease n ar%lo. The %lue gas %lo. rate ncreases slghtly because o%the hgher unt heat rate

These changes n ar and %lue gas %lo. rates result n a change n the "#$ ca!acty rate rato, /R ,

.hch decreases as boler con&ecton !ass lea:age s ncreased (*gure 21) The ca!acty raterato has a large e%%ect on thermal !er%ormance (e%%ect&eness, G) o% an "#$ and re!resents the

rato o% ca!acty rates (!roduct o% s!ec%c heat and mass %lo. rate) o% ar to %lue gas streams "

lo.er /R &alue, there%ore, corres!onds to a lo.er %lo. rate o% ar through the "#$ and hghertem!erature o% %lue gas lea&ng the "#$ $gher %lue gas e't tem!erature, n turn, results n

hgher unt heat rate

/hanges n %lue gas tem!erature at the "#$ e't and net unt heat rate are !resented n *gure 22as %unctons o% the boler con&ecton !ass lea:age Both ncrease lnearly .th the ncrease n ar

lea:age The net unt heat rate ncreases by 0> !ercentage !ont as the boler con&ecton !asslea:age ncreases %rom - to 10- *or best unt !er%ormance, t s m!ortant to mantan boler

tghtness and :ee! con&ecton !ass lea:age at a mnmum

t s recommended that annual chec:s o% boler tghtness be !er%ormed The con&ecton !asslea:age s determned by measurng e'cess 2 le&el at the %urnace and econom3er e't !lanes "



tra&erse s needed at both locatons to account %or s!atal strat%catons " .ater9cooled hgh9

&elocty thermocou!le ($HT) !robe s used %or e'cess 2 measurement at the %urnace e't !lane

The alternat&e ncludes tem!erature ma!!ng by a !ermanently nstalled mult9grd acoustc ortunable laser measurement system n%ortunately, &ery %e. !lants are e=u!!ed .th such

systems, so manual $HT tra&erses are needed

AP$ /orrosion an+ ouling

!eraton o% a regenerat&e "#$ re!resents a com!romse bet.een !er%ormance andmantenance "s the tem!erature o% the %lue gas lea&ng the "#$ decreases, unt !er%ormance

m!ro&es (*gure 1) Lo.er %lue gas tem!erature, ho.e&er, results n the lo.er tem!erature o%

heat trans%er sur%aces and, as a result, the cold end o% the "#$ ty!cally o!erates belo. the acdde. !ont "s tem!erature decreases belo. the acd de. !ont, sul%urc acd condenses n the

%lue gas stream, %ormng mst, or on metal sur%aces, %ormng a l=ud, hydrosco!c, and stc:y

layer The .ater &a!or and %ly ash %rom the %lue gas are attracted to ths ntal layer, %ormngdlute (&ery corros&e) sul%urc acd and ash de!osts on the heat trans%er sur%ace

De!endng on the coal<s mneral content, these de!osts can be remo&ed easly (as s the case %or

btumnous coals) n the other hand, .estern coals and lgntes ha&e a hgh al:alne content,causng calcum and magnesum o'des %rom the %ly ash to sul%ate on the "#$ %urnace, %ormng

hard9to9remo&e de!osts ther "#$ %oulng mechansms nclude de!oston o% the ammonum

bsul%ate, njected addt&es, ntrc acd, and ammonum ntrate The latter could be aconse=uence o% ammne9enhanced %uel9lean gas reburn The e%%ect o% %oulng o% / !assages n

t.o "#$s s !resented n *gure 27

23. 'am!les o% %ouled "#$ cold end !assages Source+ R/

n case the de!osts cannot be remo&ed by the "#$ sootblo.ers, "#$ .ater .ashes are needed

to restore the "#$ !ressure dro! (*gure 2>) Scheduled and unscheduled outages %or "#$ .ater .ashng reduce unt a&alablty

The %ull9load o!eratng data %or a 409?@ unt (*gure 2>) sho. that as a conse=uence o% / !luggng, the secondary "#$ gas9sde !ressure dro! doubled+ t ncreased %rom about 6 nches to

1> nch .g n less than one year



2. Haratons o% the gas9sde !ressure dro! %or the !rmary and secondary "#$s are llustrated

%or a 409?@ coal9%red !lant The !rmary "#$s are not .ater9.ashed because they o!erate.th hgher e't %lue gas tem!erature com!ared to the secondary "#$s .ng to the hgher e't

tem!erature, the lght de!oston on the !rmary "#$ has caused a gas9sde !ressure dro!

ncrease o% 2 nches to 7 nches .g o&er a %&e9year !erod Source+ R/

% se&ere !luggng occurs, the unt mght become %an9lmted, causng a unt load derate untl the"#$ s .ashed and the "#$ !ressure dro! s restored n case o% hgh9al:al coals that !roduce

hard9to9remo&e de!osts, the "#$ !ressure dro! mght not be %ully restored by the .ater .ash

and, a%ter a %e. years o% o!eraton, "#$ bas:ets need to be re!laced

*gure 2 sho.s &araton n the "#$ gas9sde !ressure dro! as a %uncton o% cumulat&e

generaton (?@h) /umulat&e generaton s a better !arameter to use than ela!sed tme,

because the unt load !ro%le &ares .th tme The results sho. that due to hgh gas9sde "#$ !ressure dro! (n e'cess o% 12 nches .g) the heat trans%er bas:ets had to be re!laced @th ne.

bas:ets, the !ressure dro! .as cut n hal% $o.e&er, as hard9to9remo&e de!osts contnued to

de&elo!, the !ressure dro! ncreased, re=urng a .ater .ash "lthough the "#$ !ressure dro!.as reduced, t .as not restored #redctably, a%ter se&eral "#$ .ater9.ash cycles, the "#$

!ressure dro! .ll ncrease to a !ont .here bas:et re!lacement .ll be necessary "ggress&e

.ater .ashng mght cause eroson and .ar!ng o% / bas:ets, .hch reduces bas:et l%e,ncreases "#$ !ressure dro!, and mght cause !ressure oscllatons n the boler



2!. @ater .ashng the "#$ can restore !ressure dro! lost by contamnates The blue lne

re!resents the "#$ !ressure dro! be%ore a .ater .ashI the red lne s "#$ !ressure dro! a%ter a

.ater .ash Source+ R/

/orroson o% "#$ heat trans%er sur%aces results n reduced heat trans%er and reduced bas:et l%e

/orroson o% the / bas:ets s !resented n *gure 24 The loss o% heat trans%er sur%ace reduces !er%ormance o% the "#$ because o% the hgher tem!erature o% %lue gas at the "#$ e't Sam!le

calculatons %or the "#$ su%%erng %rom se&ere corroson o% / bas:ets are !resented n *gure

26 The orgnal length o% the / layer s 12 nches "s heat trans%er sur%ace s lost due tocorroson, the length o% the / layer decreases " 0- loss o% heat trans%er sur%ace, there%ore,

corres!onds to the / layer length o% 4 nches *or ths "#R, ths loss o% sur%ace area !roduces aheat rate !enalty o% about 16 Btu8:@h

2". /orroson o% "#$ cold end bas:ets Source+ R/



2'. The e%%ect o% lost heat trans%er sur%ace due to corroson on "#$ !er%ormance *or ths "#$,the enterng gas .as at 400* and the enterng ar .as at 5* Source+ R/

AP$ hermal Performance

"ccordng to the G9NT theory o% heat e'changers, the thermal e%%ect&eness (G) o% a ty!cal

!o.er !lant Ljungstrom ar !reheater can be e'!ressed as a %uncton o% the NT and /R o% theheat e'changer The detals o% those calculatons are n the "!!end' n sum, % the !hyscal

constructon and materals o% a heat e'changer are :no.n, then ts !er%ormance can be

determned

Thermal e%%ect&eness, calculated by =uaton 5 (%ound n the "!!end') s !resented as a

%uncton o% number o% trans%er unts, NTo, %or /R &alues n the 040 to 0 range (*gure 25)

The thermal e%%ect&eness o% an "#$ ncreases as the s3e o% the "#$ ncreases (as NTo ncreases) and /R rato (the %lo. rate o% combuston ar relat&e to %lue gas) ncreases "ctual

"#$ !er%ormance (denoted as Test Data n *gure 25), determned %rom "#$ !er%ormance tests,

s com!ared to desgn !er%ormance (denoted as Desgn)



2(. " ty!cal "#$ !er%ormance dagram sho.ng desgn and test condtons Source+ R/

AP$ /orrection actors

Be%ore dra.ng any conclusons concernng actual and desgn "#$ !er%ormance, test results

ha&e to be corrected to o!eratng condtons s!ec%ed by the "#$ manu%acturer to account %ord%%erences n ar and %lue gas tem!eratures and ca!acty rate rato Because the manu%acturer

guarantees "#$ thermal !er%ormance (ty!cally %lue gas tem!erature at the "#$ outlet) at the

s!ec%c desgn condtons (nlet gas and ar tem!eratures, and %lo. rates o% %lue gas and arthrough the "#$), correctons are needed to correct test data to the desgn condtons "S?#T/ >7 code de%nes correctons %or correctng the test &alue o% Tgo,NL (%lue gas tem!erature

e'tng the ar !reheater, see the "!!end') %or de&atons n the %ollo.ng o!eratng !arameters

%rom ther desgn &alues+

• nlet ar rem!erature

• nlet gas tem!erature

• /a!acty rate rato

• *lue gas %lo. rate

The e=uatons determnng these %our ar !reheater !er%ormance correcton %actors and ther useare ncluded n the "!!end'

Air Preheater Performance /ase *tu+



" numercal e'am!le s !resented to llustrate actual &aratons n tem!eratures and ca!acty rate

rato and the magntude o% the correctons The actual "#$ o!eratng condtons are !resented n

*gures 2 to 72 The actual nlet ar tem!eratures .ere hgher com!ared .th the desgn &alue(*gure 2), .hle the actual %lue gas tem!eratures .ere lo.er (*gure 70) The actual ca!acty

rate rato, /R , calculated %rom =uaton 10, .as substantally lo.er com!ared .th the desgn

&alue (see *gure 71) The &alues o% %lue gas tem!erature at the "#$ outlet, corrected to nolea:age, Tgo,NL (calculated %rom =uaton 4), .ere substantally hgher com!ared to the desgn

&alue (*gure 72) " manu%acturer<s tolerance o% J5* s also sho.n

2). Test (measured) &alues o% ar tem!erature at the "#$ nlet Source+ R/

30. Test (measured) &alues o% %lue gas tem!erature at "#$ nlet Source+ R/



31. /alculated &alues o% the ca!acty rate rato Source+ R/

32. /alculated &alues o% %lue gas tem!erature at the "#$ outlet corrected to no lea:age Source+

R/

The &alues o% thermal e%%ect&eness %ound %rom =uaton 7 and dmensonless heat trans%er s3eo% the "#$ (NTo), calculated %rom =uaton 11, are !resented n *gure 25

/orrectons to Tgo,NL, calculated accordng to "S? #T/ >7, are !resented n *gure 77 Theresults sho. that the correcton due to /R de&aton consttuted the largest !art o% the total

correcton The corrected &alues o% Tgo,NL, !resented n *gure 7>, .ere much closer to the desgn



&alues, com!ared .th the uncorrected &alues The "#$ thermal !er%ormance ma! (*gure 7)

sho.s corrected &alues o% G algned along the /R K /R,Desgn lne The results sho. that n ths case

the ne. "#$ desgn dd not meet !er%ormance guarantees because G and NTo .ere belo. themanu%acturer<s guarantee, e&en .hen accountng %or the manu%acturer<s tolerance The nternal

ar and %lue gas by!ass .as the man reason %or reduced "#$ !er%ormance

33. "#$ correctons calculated accordng to "S? #T/ >7 Source+ R/

3. Test and corrected &alues o% %lue gas tem!erature at the "#$ outlet Source+ R/



3!. /om!lete !er%ormance dagram o% the "#$ Test data .as corrected accordng to "S?

#T/ >7 Source+ R/

AP$ o+eling: he / /o+e

@hen dealng .th the !re&enton or mtgaton o% "#$ %oulng and corroson, "#$ modelng snecessary to de&elo! e%%ect&e mtgaton strateges and e&aluate ther e%%ect on "#$ and unt

!er%ormance The ?etal Tem!erature /ode (?T/, %ormerly the R#$?T code) .as de&elo!ed

by the nergy Research /enter %or the lectrc #o.er Research nsttute

?T/ s a %nal9d%%erence code that !redcts thermal !er%ormance o% the "#$ (G and NTo) as

.ell as tem!eratures o% heat trans%er sur%aces and o% combuston ar and %lue gas .thn the "#$

heat trans%er matr' The code has been &er%ed aganst %eld data and can be used %or modelngo% Ljungstrom9 or Rothemuhle9ty!es o% "#$s The code allo.s determnaton o% the e%%ect o%

!lant o!eratng !arameters (tem!eratures and %lo. rates o% combuston ar and %lue gas trough

the "#$), "#$ o!eratng !arameters (ar lea:age and rotatonal s!eed), and "#$ desgn !arameters (length and number o% a'al layers and heat trans%er sur%ace ty!e) on thermal

!er%ormance and metal and %lud tem!eratures The ?T/ code s an nds!ensable tool used to

sol&e !roblems assocated .th "#$ !er%ormance, %oulng, and corroson

The metal and %lud tem!eratures .thn the "#$ heat trans%er matr', !redcted by the ?T/

code %or s!ec%c "#$ geometry and o!eratng condtons, are !resented n *gures 74 and 76 "s

the "#$ metal matr' rotates through the %lue gas duct (or, n case o% the Rothemuhle9ty!e "#$,as the %lue gas hood s !assng o&er the %'ed heat trans%er matr'), the tem!erature o% the matr',

Tm, ncreases %rom the mnmum to ma'mum &alue (*gure 74) The mnmum &alue occurs as

the matr' enters the %lue gas stream, .hle the ma'mum &alue s ache&ed as the matr' lea&esthe %lue gas stream Durng the ar cycle, Tm decreases and reaches ts mnmum &alue as matr'



s lea&ng the ar stream The heatng and coolng cycle re!eats as matr' s tra&elng though the

gas and ar cycles The d%%erence bet.een the mnmum and ma'mum &alues, Tm, s called the

metal tem!erature s.ng

3". #er!heral &araton o% the "#$ matr' tem!erature %or a secondary "#$ at %ull load .th

ne. bas:ets at desgn o!eratng condtons Source+ R/

3'. "'al &araton o% "#$ matr' tem!erature .th ne. bas:ets as a %uncton o% dstance %rom

the cold end Source+ R/

" %amly o% the heatng and coolng cycles (*gure 74) corres!onds to d%%erent a'al locatons

%rom the "#$ / "t a'al locatons closer to the /, metal tem!eratures are lo.er The matr'



tem!erature s lo.est at the / o% the "#$ (0 %eet %rom / n *gure 74), n ths e'am!le n the

10* to 200* range The Tm &alue at the entrance o% the / layer (1 %t %rom / n *gure 74) are

hgher and, n ths e'am!le, range %rom 260* to 700* ?etal tem!eratures n the hot ntermedatelayer are e&en hgher

"'al &araton o% !redcted matr' and %lud tem!eratures (%lue gas and ar) s !resented n*gure 76 %or the "#$ consstng o% three a'al layers+ /, hot ntermedate, and $ The

mnmum and ma'mum tem!eratures are !resented The &alues o% Tm and T%lud are the hghest at

the hot end (%lue gas nlet) sde o% the "#$ The matr' and %lue gas tem!eratures decrease ndrecton o% the %lue gas %lo. and reach ther mnmum &alues at the / (ar nlet) sde o% the

"#$ ?etal tem!eratures at the $ are !rmarly controlled by the nlet tem!erature o% %lue gas,

.hle tem!erature o% the nlet ar has a !redomnant e%%ect on Tm n the / layer o% the "#$

"s a conse=uence o% the matr' or hood rotaton, the %lue gas tem!erature lea&ng the "#$

ncreases, .hle the tem!erature o% the combuston ar lea&ng the "#$ decreases n the drecton

o% the rotaton, causng tem!erature strat%catons n the outlet %lue gas and ar streams Ty!cal

gas and ar tem!erature strat%catons are !resented n *gure 75

3(. Tem!erature strat%caton at the "#$ e't Source+ R/

Large tem!erature strat%caton n the %lue gas stream lea&ng the "#$ can negat&ely a%%ect !er%ormance o% the electrostatc !rec!tator (S#) Ths occurs because resst&ty o% the %ly ash

s a%%ected by tem!erature Tem!erature strat%catons, measured n the e't ducts o% t.o "#$s

o!eratng n !arallel and rotatng n the cloc:.se drecton, are clearly sho.n n *gure 7 The%lue gas tem!erature s lo.er at the le%t sde and hgher at the rght sde o% both ducts "s a

conse=uence, the lo.9resst&ty 3ones are set u! at the le%t sde o% the S#, .hle the hgh9

resst&ty 3ones are near the rght .all o% the S# Ths strat%caton o% tem!erature and %ly ashresst&ty re=ures strat%ed njecton o% S7 to mantan a relat&ely un%orm %ly ash resst&ty



across the S# nlet duct

3). ?easured tem!erature strat%caton n %lue gas stream lea&ng the "#$ Source+ R/

n order %or heat trans%er to occur bet.een the %lue gas and metal matr', the tem!erature o% the

%lue gas s abo&e the metal tem!erature /on&ersely, %or the metal matr' to trans%er heat to

combuston ar, the metal tem!erature must be hgher than the ar tem!erature Ths tem!eratured%%erence, es!ecally bet.een the %lue gas and metal matr', ma:es t d%%cult to montor the

!otental %or acd de!oston n the / layers o% the "#$ Ths s because only the a&erage %lue

gas tem!erature lea&ng the "#$ s measured, and metal tem!eratures need to be n%erred %rom

measured &alues o% the %lue gas tem!erature

The ?T/ code s used e'tens&ely to de&elo! strateges %or e%%ect&e control o% acd de!oston

n the / layer o% the "#$ and ammonum bsul%ate de!oston nsde the $ layer o% the "#$

The results are used to e&aluate tradeo%%s bet.een de!oston !otental and heat rate !enaltesassocated .th hgher matr' and %lue gas tem!eratures

ore to /ome

n #art , .e<ll e'amne !er%ormance degradaton caused by corroson and %oulng that results%rom the combuston o% coal !lus the e%%ects o% ammona and sodum bsul%te njecton %or S 7

mtgaton n #art , .e<ll loo: at o!tons %or m!ro&ng "#$ !er%ormance

C Nenad Sarunac s !rnc!al research engneer and assocate drector at the nergy Research /enter, Lehghn&ersty The llnos /lean /oal nsttute %unded a !orton o% ths .or:

Appen+ix

"r !reheater ("#$) lea:age s, by con&enton, e'!ressed as+

4AP$,% 5 Air %ea&age6fg,AP$,in x 1007 8#9uation 1

.here+



?"r Lea:age K ?ass %lo. rate o% combuston ar lea:age nto the %lue gas

?%g,"#$,n K ?ass %lo. rate o% %lue gas u!stream o% the "#$

$eat #xchanger hermal Performance

"ccordng to the G9NT theory o% heat e'changers, the thermal e%%ect&eness (G) o% a ty!cal

!o.er !lant Ljungstrom ar !reheater can be e'!ressed as a %uncton o% the NT and /R o% theheat e'changer+

; 5 f<=>o, / ? 8#9uation 2

.here+

G, thermal e%%ect&eness s de%ned as+

; 5 8ao @ ai68gi @ ai 8#9uation 3

or+

; 5 8gi @ go,=%6/ 8gi @ ai 8#9uation

ME K Eas9sde e%%cency

CD 5 8gi @ go,=%68gi @ ai 5 ;/ 8#9uation !

Tg K ?easured nlet %lue gas tem!erature

Tgo K ?easured nlet %lue gas tem!erature

Ta K ?easured nlet ar tem!erature

Tao K ?easured outlet ar tem!eratureTgo,NL K *lue gas tem!erature at the "#$ outlet, corrected to the no9lea:age condton s

calculated accordng to the "S? #T/ >7 code %or ar !reheaters by assumng all lea:age

occurs at the "#$ cold end

go,=% 5 4% /pa6/pg 8go @ ai E go 8#9uation "

/ !a K ?ean s!ec%c heat o% ar

/ !g K ?ean s!ec%c heat o% %lue gas

NTo K Dmensonless heat trans%er s3e o% the "#$, de%ned as+

=>o 5 >A6/air 8#9uation '

K &erall heat trans%er coe%%cent

" K Total heat trans%er area

/R K /a!acty rate rato, also :no.n n the ndustry as the AR rato, de%ned as+

/ 5 /air6/gas 8#9uation (

/ar K /a!acty o% the ar stream %lo.ng through the "#$



/gas K /a!acty o% the gas stream %lo.ng through the "#$

The relatonsh! bet.een G, NTo, and /R %or a rotatng regenerat&e heat e'changer can bea!!ro'mated by the %ollo.ng e=uaton+

; 5 1@ exp8@=>o81@/ 61@/ exp8@=>o81@/ 8#9uation )

%ten, thermal !er%ormance o% the "#$ s not :no.n and has to be determned by !er%ormng

the "#$ !er%ormance test The !rocedure %or determnng G and NTo s as %ollo.s+

• se measured nlet and outlet &alues o% ar and %lue gas tem!erature Ta, Tao, Tg, and Tgo,

and "#$ ar lea:age (;L) to correct outlet %lue gas tem!erature to the no9lea:age

condton, usng =uaton 4

• /alculate ca!acty rate rato usng+

/ 5 8gi @ go,=%68ao @ ai 8#9uation 10

•

/alculate thermal e%%ect&eness, G, usng =uatons 7 or >• /alculate number o% trans%er unts NTo by n&ertng =uaton The resultng

e'!resson s+

=>o 5 ln81 @ ;/ 681 @ ;681 @ / 8#9uation 11

*gure 25 llustrates a com!arson o% the calculated &alues o% G and NTo to desgn or guaranteed

&alues

/orrection actors

Inlet Air emperature /orrection. "ccordng to the "S? #T/ >7 code, the &alue o% Tgo,NL corrected %or de&aton n the nlet ar tem!erature %rom ts desgn &alue s determned %rom+

go,=%,corr for ai 5 ai,+es8gi @ go E gi8go @ ai68gi @ ai 8#9uation 12

.here+

Tgo,NL,corr %or Ta K *lue gas tem!erature at the "#$ outlet corrected %or no lea:age and nlet ar

tem!erature de&atonTa,des K Desgn &alue o% ar tem!erature at the "#$ nlet

Inlet Das emperature /orrection. The &alue o% Tgo,NL corrected %or the de&aton n the nletgas tem!erature %rom the desgn &alue s, accordng to the "S? #T/ >7 code, determned

%rom+

go,=%,corr for gi 5 gi,+es8go @ ai E ai8gi @ go68gi @ ai 8#9uation 13

.here+

Tgo,NL,corr %or Tg K *lue gas tem!erature at the "#$ outlet corrected %or no lea:age and nlet gas



tem!erature de&aton

Tg,des K Desgn &alue o% nlet gas tem!erature

=uatons 12 and 17 .ere de&elo!ed by assumng a constant &alue o% the gas sde e%%cency

"lthough the gas sde e%%cency does not reman constant as the nlet ar or gas tem!eratures

change, =uatons 12 and 17 re!resent good a!!ro'matons %or small to moderate changes nnlet tem!eratures

The nlet ar and gas tem!erature correctons can, alternat&ely, be de&elo!ed by usng the G9NTtheory (=uatons 7 and >) and desgn &alue o% the "#$ e%%ect&eness and ca!acty rate rato The

resultng e'!ressons, de&elo!ed by the author o% ths artcle are+

go,=%,/orr. for ai 5 gi,+es @ /,+es ;+es 8gi,+es @ ai,act 8#9uation 1

go,=%,/orr. for gi 5 gi,act @ /,+es ;+es 8gi,act @ ai,+es 8#9uation 1!

=uatons 12 and 17 g&e &rtually dentcal results to the results that come %rom =uatons 1>and 1

/apacit ate /orrection. "ccordng to the "S? #T/ >7 code, the &alue o% Tgo,NL corrected

%or the de&aton n the ca!acty rate rato %rom the desgn &alue s determned %rom+

go,=% correcte+ for / 5 gi81@CD6x E ai CD 6x 8#9uation 1"

.here+

Tgo,NL corrected %or /R K *lue gas tem!erature at the "#$ outlet corrected %or no lea:age and ca!actyrate rato de&aton

*' K "S? correcton %actor %or de&aton o% /R

"s s!ec%ed by the "S? code, correcton %actor *' s determned %rom the a!!ro!rate desgn

correcton cur&e (usually su!!led by the manu%acturer), .hch can be &er%ed by %eld tests,

although such !rocedure s consdered m!ractcal t has to be noted that the *' cur&e andnumercal &alue o% *' correcton %actor are not nde!endent o% the "#$ s3e, and "#$9s!ec%c

cur&es are, there%ore, re=ured /orrecton %actor *' %or an "#$ s !resented n *gure "1 as a

%uncton o% the ca!acty rate rato



A1. /a!acty rate correcton accordng to "S? #T/ >7 Source+ "S?

The alternat&e a!!roach %or !er%ormng correcton %or /R .as de&elo!ed by the author o% thsartcle Ths a!!roach enables a !lant to de&elo! ts o.n correcton cur&es and, there%ore, not

de!end on the manu%acturer<s correctons The correcton to %lue gas tem!erature lea&ng the

"#$ (%or the no9lea:age condton) s calculated as a %uncton o% de&aton n ca!acty rate rato,/R , %rom desgn condtons The correctons .ere determned by usng the G9NT theory o%

heat e'changers, and the ?etal Tem!erature /ode (?T/) %or rotatng regenerat&e "#$s

The results, !resented n *gure "2, sho. that a sm!le G9NT theory correcton .or:s .ell n

cases .here /R &aratons do not sgn%cantly e'ceed J00 *or larger de&atons n /R %rom

ts desgn &alue, the ?T/ code results should be used %or better accuracy

TRI SEC APH

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