210d61b7-c21b-4e7f-a43f-14157b8e4c12-150508133022-lva1-app6891

7/24/2019 210d61b7-c21b-4e7f-a43f-14157b8e4c12-150508133022-lva1-app6891

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CHAPTER ONE

1 INTRODUCTION

The word lime refers only to manufactured forms of lime/quicklime (CaO) and hydrated

lime (Ca(OH)2 , though it is sometimes erroneously used to refer to a wide range of

calcareous materials including fine ground limestone and dolomite.

ime is a !ersatile material and has a wide !ariety of uses. "t is used as an alkaline

reagent in the chemical industry, a flu# in the iron and steel manufacturing industry, a

$inder in the %harmaceutical industry, and for making mortar in the $uilding and

construction industry. There are also numerous minor a%%lications in di!erse fields of

science. The shear im%ortance of lime can $e deduced from the fact that the &nited

'tates eological sur!ey year$ook estimates the total world %roduction of quicklime

and hydrated lime, including dead$urned dolomite for 2**+ at 2* million metric

tonnes (-iller, 2**).

The demand for lime in so many di!erse industries, some of which are situated here in

hana, makes the esta$lishment of a lime %roducing %lant a %otentially %rofita$le

!enture. resently there is only one %lant for the %roduction of lime. "t is owned $y

Carmeuse imestone roducts imited with a %roduction rate of **,*** t of lime %er

year. Howe!er with the market0s low saturation there is still an o%%ortunity for a lime%roduction com%any here. Thus this %lant design for the %roduction of lime is rele!ant

to the hanaian market at this time.

-ain o$1ecti!e


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The main o$1ecti!e of this %ro1ect is to design a %lant for the %roduction of +*,*** t of

lime (CaO) %er year.

.2 '%ecific o$1ecti!es

The s%ecific o$1ecti!es of this %ro1ect are as follows

i. to conduct literature re!iew,

ii. to select and descri$e a %rocess for %roducing lime,

iii. to calculate material and energy $alances of the %rocess,

i!. to s%ecify all equi%ments,

!. to design selected %rocess equi%ment,

!i. to select a location for the %lant,

!ii. to select rele!ant safety and %ollution controls for the %lant,

!iii. to select the rele!ant instrumentation and %rocess control scheme and

i#. to conduct an economic analysis of the %lant.

2


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CHAPTER TWO

2 LITERATURE REVIEW

2. History of lime %roduction and use

ime (CaO) is one of the oldest materials known to humans. "t was %ro$a$ly disco!ered

in %rehistoric times when limestone, which was used in the construction of fire%laces

and hearths, $roke down into lime and car$on dio#ide. Hydration $y rainwater %roduced

a sim%le ty%e of %utty that %rehistoric humans %ut to use %rinci%ally as a $inding agent.

3!idence from eastern Turkey re!eals that lime mortar was used in terra44o floors at an

archaeological site dated from 5,*** 2,*** 6C. 7irm e!idence e#ists for the early use

of lime from 8,*** 6C in the 9ear 3ast, as well as in the 6alkans where lime mortar

was used in the construction of a floor. The ancient 3gy%tians used lime for %laster in

the construction of the %yramids, while the Chinese added lime to mortar for the reat

:all of China. 5,*** years ago in Ti$et, lime ser!ed to sta$ili4e soil. Other ancient

ci!ili4ations that used lime for !arious a%%lications include the reeks, ;omans, "ncas,

-ayans and -ughal "ndians (raymont.com, 2**5* 6C. The formula

for lime cement was lost in time $ut redisco!ered in


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organic or inorganic su$stances. =$original %eo%le as well as ancient ;oman %hysicians

used lime in different medical treatments.

&% to the 2*th

century, lime kiln design was relati!ely sim%le. The easiest method of

%roduction was to dig a shallow %it, fill it with firewood and limestone, and set it a$la4e.

'ince ancient times, kilns were either a $eehi!e o!en design or a sim%le !ertical shaft

kiln. imestone was quarried from a local de%osit, and stones of * cm in diameter were

%laced in the shaft with alternating layers of firewood. The fuel and limestone $urned

for se!eral days. :hen the fire sto%%ed and the kiln cooled to an a%%ro%riate

tem%erature, the lime was remo!ed out of the shaft from the draft tunnel at the $ottom

of the kiln. The %roduct was then shi%%ed in $askets or $arrels to the site. (Aogal et al.,

2**8)

2.2 imestoneimestone is a fine grained calcareous rock of sedimentary nature made u% of the

mineral calcite and aragonite which ha!e the same com%osition, calcium car$onate

(CaCO@) $ut slightly different crystal structures (Aesler, ++>). "t is formed either $y

$iogenic %reci%itation from water (usually seawater) or $y mechanical trans%ort and

de%osition. ure calcite is clear and whiteB howe!er with a !ariety of im%urities the

limestone may assume different colours. imestone is easily weathered and eroded.

imestone can undergo metamor%hosis to mar$le and if it contains other materials such

as clay or sand, the calcite will react with them. imestone is mined with the use of

e#%losi!es to $reak u% large underground or surface de%osits. (3ncyclo%aedia

6ritannica, 2**+)

"n nature, the limestone $ed is found to occur in !arying %urity. enerally a %art of the

calcium molecules $eing re%laced $y magnesium tends towards magnesium limestone

or dolomitic limestone. imestone with more than * of mineral dolomite is termed

>


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dolomite limestone and that with 5*, magnesium limestone. The rock which

contains more than +5 of CaCO@is known as highcalcium limestone and if clastic

(com%osed of fragments of other rocks) silicate im%urities dominate, the rock is marl

(-ineral4one.com, 2**


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Ta$le 2.2 Ty%ical chemical com%osition of limestone

Cheical co!stitue!t Aou!t" #

ime, CaO @ D >2'ilica, 'iO2 5 D =lumina, =l2O@ @ D 5

-agnesium o#ide, -gO *.5 D @7eO G 7e2O@ D .5=lkalis D .5oss on ignition, O" @* D @2('ource -inerals4one.com, 2**.8* .@5 8.55 2.>* *.55

Doloitic liesto!e >5.55 5.25 . @. Doloite @*.5


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('ource Aesse, +5)

The results of the analyses of chemical com%osition of limestone %ros%ected e#tensi!ely

are %resented in Ta$le 2.> for com%arison.

Ta$le 2.> Chemical analyses (a!erage) of 6ui%e limestones %ros%ected

Area CaO" # '(O" # )iO2" # Al2O*" # +e2O*" # LOI" #

= >2.8+ .>* >.2* @.8 2.2 @5.6 >.8 2.2 @.58 @.> 2.*5 @>.8C >2.5* .> >.** @.>* .5 @5.5>

('ource eological 'ur!ey Ee%artment ;ussian Team, ++*)

Ta$le 2.5 Chemical analyses for measuredI resource

Area CaO"# '(O"# )iO2"# Al2O*"# +e2O*"# LOI"#

= >2.> .** @.>2 @.@+ 2. @>.+6 >2.* .>8 @. @.@8 2.* @5.>>C >.52 .28 >.5> >.2* 2.@8 @>.

('ource =ddo and 6irla, ++5)

Nauli limestone deposit

The 9auli limestone de%osit stretches from Aegan, a coastal !illage, which is to the

southsoutheast and runs in the westnorthwest direction through 9auli and 3du to the

Tano ;i!er at the hana"!ory Coast $order. Aesse (+5) states that a$out >** million

tonnes of %ro!en reser!es ha!e $een estimated at de%ths of 2> 2* m from recent $ore

hole tests, out of which a$out 2@ million tonnes could $e e#%loited $y o%encast mining.

The 9auli limestone has $een determined to $e suita$le for the manufacture of ortland

cement and lime %roduction. The summary of chemical analysis done on 9auli

limestone is gi!en in Ta$le 2.8.

Ta$le 2.8 'ummary of chemical analysis of 9auli limestone


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Area )iO2" # Al2O*" # +e2O*" # '(O" # CaO" # )" # LOI" #

3ast (3) @.+< 2.+ .5< *.8 >.< *.8 @+.8@:est (:) @.2> .+> .2+ .22 >.5 *.8> @+.@ .*> >.8 *.8@ @+.8+('ource Aesse, +5)

2$2$2 Calci!atio! reactio! o% liesto!e

The chemical %rocess of %roducing lime (CaO) from limestone (CaCO@) is termed

calcination. "t in!ol!es heating of the limestone to a tem%erature of +****JC at

which it dissociates into CaO and car$on dio#ide (CO2).

CaCO@(s) CaO(s)G CO2(g)

ilchrist (++) relates the i$$s free energy (KJ) of the %rocess to tem%erature as

KJ L 2


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t L time, min

The total heat for calcining is the sum of the sensi$le heat to achie!e the calcination

tem%erature of +****JC and the latent heat of calcination. The %ractical heat

requirement is usually a$out > ?/t, with >* of this amount $eing sensi$le heat and

the rest $eing latent heat (=ustin, +5).

2$* Lie

There are three distinct ty%es of quicklime that may $e %roduced. The different ty%es of

quicklime are defined $y their magnesium o#ide (-gO) content. Highcalcium

quicklime contains less than 5 -gO and is the most common ty%e of lime %roduced.

-agnesium quicklime contains 5 @5 -gO and dolomitic quicklime (also referred to

as dolime) contains @5 >5 -gO. 3ach has its uses and a%%lications, howe!er only

highcalcium limestone and dolomitic limestone are discussed here as these two

%roducts dominate the lime market (raymont.com, 2**


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analysis may show a certain amount of lime and yet only a fraction of that is truly

a!aila$le to react with water.

Consequently, e!en the %urest high calcium limes ha!e less than +5 in a!aila$le lime,

usually a small %ercentage less than total o#ide content. The o!erall %urity of lime

de%ends on the le!el of im%urity of the limestone and its mode of manufacture. ;esults

from a ty%ical chemical analysis of quicklime are %resented in Ta$le 2.* k?/kg of CaO and 8 k?/kg of dolomitic lime. This strong e#othermic

reaction will $oil water easily and under certain hydration conditions, tem%eratures of

2+* @5oC ha!e $een reached causing dehydration of freshly slaked lime. Fuicklime

can $e so reacti!e that it e#%lodes on contact with water. "m%urities and uncalcined

limestone core affect hydration $y decreasing the amount of total lime. The finer

*


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fraction of runofkiln tends to ha!e a higher content of these im%urities. 7uels such as

coal also contri$ute to total amount of im%urity. "f dolomite is %resent in the stone feed,

it also can inhi$it hydration, resulting in a slower reaction nearly three orders of

magnitude slower than that of %ure CaO. (Aogal et al, 2**8)

Fuicklime has a high affinity for water, this causes quicklime to air slake, which may

reduce its reacti!ity significantly. =fter %artial hydration it also has a high affinity for

CO2and tends then to com$ine with low le!els of CO2in the air to form CaCO@.

On slaking into a slurry, or milkoflime, the saturated solution ioni4es immediately into

Ca2G, -g2Gand OHions, creating one of the strongest $ases. 3!en a trace of lime will

yield a %H of .2 and u% to nearly %H @ at saturated solution and low tem%erature.

Eolomitic quicklime has 8 greater neutrali4ing %ower than CaO $ecause of its -gO

content. Trace elements, such as lead, arsenic, moly$denum, and chromium, which are

considered to#ic, can make the quicklime unsuita$le for certain a%%lications such as

water treatment if such im%urities are o$ser!ed (Aogal et al, 2**8).

Physical properties

"m%ortant %hysical %ro%erties of lime are listed in Ta$le 2.. ime is ty%ically white

with !arying intensities of $rightness, although de%ending on the %resence of %articular

im%urities, it may ha!e a light cream, $uff, or grey cast. ime has either no odour or a

slightly earthly odour. =lthough its te#ture is earthy, a%%earing amor%hous, lime isactually microcrystalline, ha!ing a rock salt cu$ic crystal structure.

orosity of commercial quicklime is de%endent in %art on the original %orosity of the

original limestone and on the decom%osition %rocess in the kiln. The se!erity of

calcinations (tem%erature and time) affects $oth the %orosity and chemical reacti!ity of

lime. :hen lime is soft$urned (slightly sintered and calcined at relati!ely low

tem%eratures of +** 2**JC), !ery little or no shrinkage occurs, and a %orous, softer,


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!ery reacti!e lime is %roduced. ightly $urned lime can ha!e %orosities u% to 55 $y

!olume.

:hen lime is hard $urned (sintered at relati!ely high tem%eratures of @** 8**JC and

o!er $urned) a denser, %hysically stronger, and less reacti!e lime is the result. "n either

case, the lime will readily hydrate in water, although ra%idity of hydration is much

greater with soft $urned lime than hard $urned lime. =ssociated with the reaction of

quicklime with water is a corres%onding increase of 2.5 times its original !olume.

Ta$le 2. hysical %ro%erties of ty%ical commercial lime %roducts

0uiclies

Property Hi(h Calciu Doloiticrimary constituents CaO CaO and -gO'%ecific gra!ity @.2 @.> @.2 @.>6ulk density (%e$$le lime), kg/m@ * D +5* * D +8*'%ecific heat at @oC, k?/kgJC *.> *.+>Hy,rates

Property Hi(h calciu Doloitic

rimary com%onents CaO Ca(OH)2-gO'%ecific gra!ity 2.@2.> 2.** D 58* >** D 58*

'%ecific heat at @o

C, k?/kgJC *.82 *.82

('ource Aogal et al, 2**8)

2$*$2 Uses o% lie

ime is one of those usually unseen %roducts that ha!e a %rofound effect on our daily

li!es. "t is used in many im%ortant sectors such as construction and materials,

en!ironmental, agricultura and industrial a%%lications.

Construction and materials uses

"n the construction and materials industry lime currently %lays an im%ortant %art in the

drying, im%ro!ement and sta$ilisation of soils to %ro!ide a %latform for hea!y

construction. "t is used as a com%onent of mortars, e#terior rendering and interior

2


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%lasters. "t is also used as an antistri%%ing agent in the %roduction of as%halt and tarmac

for road construction and as a $inder in the %roductions of $ricks, aerated concrete

$locks, fire resistant $oards and lime concrete.

Environmental and agricultural uses

:ithin the en!ironmental and agricultural fields, lime is used in effluent treatment to

ad1ust the %H of harmful acidic effluents and in sewage works to treat sewage that

contains sus%ended solids, dissol!ed organic matter, nutrients (%hos%hate and ammonia)

and hea!y metals. "t is also used in soil sta$ilisation so as to increase the suita$ility for

agricultural use and ad1ust %H for im%ro!ed cro% yield. ime is also used in %roducing

chicken feed su%%lements and in fish farming to raise and control the %H of acidic

%onds. "n fruit farming, it is used to forestall %remature ri%ening. "t can also $e used to

manufacture inorganic salts such as Ca(O>)2 used in other %roducts and in the

manufacture of sugar from sugar $eet (6ritishlime.org, 2**)

Industrial and other uses

"ndustrially, lime is also used in the manufacture of steel for remo!ing im%urities and in

the manufacture of %lastics to remo!e unwanted water. "n the %roduction of aluminium,

it is used as a continuous casting lu$ricant in the leather industry for dehairing of hides

tanning. "t is also used as an oil additi!e that acts as a detergent and im%ro!es the life of

engines (6ritishlime.org, 2**).

2$*$* Worl, lie pro,uctio!

"n 2**, 2+8 million metric tonnes of lime were %roduced and an estimate of 2*

million tonnes %roduced in 2**+ on worldwide $asis (-iller, 2**). The largest

%roducer of lime %roducts is China, followed $y the &nited 'tates. The steel industry is

@


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the largest user of lime in the industriali4ed nations (-iller, 2**). Howe!er, the gold

mining industry is the ma1or lime consumer in hana. =s of 2**8, annual consum%tion

was at 8*,*** metric tonnes %er year (hanamining.org, 2**8).

2$*$ Paca(i!( a!, Tra!sportatio!

ime can $e lum%, %e$$le, or %elleti4ed. These large %article si4e limes are rarely

handled in $ags. Howe!er, in the &.'. when %ackaged in $ags, these $ags are made of

multiwall %a%er with %olyethylene liners to %rotect the lime from moisture and

ca%acities of 22.< or @8.> kg, and $ulk $ags u% to . t. The finer si4es of quicklime

(fine, granular, and %ul!eri4ed) are shi%%ed in $ulk or in $ags as well (-iller, 2**@).

ime can also $e %ackaged in $arrels or sheet iron drums, usually in a$out * or 2* kg

amounts %er $arrel or drum (=ustin, +5).

ime can con!eniently $e trans%orted $y land or $y sea. 'hi%%ing $ulk lime is done

using %neumatic tank carriers that can %ro!ide $oth an enclosed container and a safe

handling system such that the o%erator can a!oid direct contact with the %roduct. arger

amounts can $e mo!ed $y $arge on inland waterways.

ime is considered a %erisha$le %roduct $ecause of its affinity for water, and $ecause it

may slake $y a$sor$ing moisture from am$ient humidity (air slaking). "t is therefore

recommended that quicklime should not $e stored in $ags for more than @ months. To

%rotect quicklime from moisture, storage containers and trans%ort media must $e water

tight (-iller, 2**@).

>


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2$*$3 Pro,uct prici!(

ime is considered a commodity mineral that has low to moderate unit !alue and high

%lace !alue. The cost of lime de%ends on many factors such as the cost of raw material,

cost of %roduction (including fuel cost), la$our, trans%ortation, demand and su%%ly,

com%etition from su$stitute goods, %ackaging and go!ernment %olicies. The a!erage

%rices of !arious ty%es of lime are com%osed in Ta$le 2.+.

Ta$le 2.+ ime %rices

2445 2446

Ty%e M/ tonne M/ tonne

'old and used

Fuicklime >.8* +.+*

Hydrate *2.>* *


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('ource -iller 2**)

=!erage !alue %er tonne, on freeon$oard%lant $asis, including cost of containers.

2

"ncludes dead$urned dolomite.

CHAPTER THREE

* PROCE)) )ELECTION AND DE)CRIPTION

@. ime kilns

The most im%ortant as%ect of a lime %roduction %lant is the kiln. This is $ecause the kiln

requires the highest energy in%ut and its feed si4e determines the si4ing of other

equi%ment in the %lant. There are three main categories of lime kilns. They are shaft

kilns, rotary kilns and %arallel flow regenerati!e kilns. Howe!er, newer kilns ha!e $een

de!elo%ed and are also $riefly included herein.

*$1$1 )ha%t il!s

The acce%ta$le feed si4e ranges from a minimum of 2* mm to a to% si4e of ** k?/kg. 'haft kilns can ha!e out%ut

within a range of 25 2** t/day. 'haft kilns are suita$le for o%eration on gaseous, liquid

and %ul!eri4ed solid fuels, while the o%tions for others are more restricted. "n a shaft

kiln, the limestone mo!es counter flow to the hot gases in the shaft. This gi!es shaft

kilns the lowest fuel consum%tion of any ty%e of kiln. Howe!er, $ecause of the weight

of the $ed of material in the shaft, there are limits on the si4e and strength of the ty%e of

8


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limestone that can $e calcined. The main $enefits of shaft kiln include higher efficiency,

less $reaking of lime due to handling, control systems for entire facility, ca%a$le of

installation anywhere in world and its a$ility to efficiently calcine feed of large %article.

Ta$le @. shows the different ty%es of shaft kilns, fuels used and feed si4es.

Ta$le @. 'haft kiln characteristics

7il! type +uels use, Output ra!(e" t8,ay +ee, si9e ra!(e"

Eou$leinclined kiln as, iquid, 'olid * 8* 2* D 2**

-ulticham$er kiln as, iquid, 'olid >* 225 2* D 5*

=nnular shaft kiln as, iquid, 'olid * 8** * D 25*

-i#edfeed shaft kiln 'olid 8* 2** 2* D 2**

Central $urner as, 'olid >* * >* D 5*

3#ternal cham$ers as, iquid >* 2* * D @5*

6eam $urner as, iquid, 'olid 5* ** 2* D


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$e controlled, rotary kilns can %roduce a wider range of reacti!ities and lower CaCO@

le!els than shaft kilns. ;elati!ely soft feed, such as shell de%osits, and limestone that

decre%itates (crackles when heated), are unsuita$le as feed to shaft kilns $ut may %ro!e

to $e acce%ta$le for rotary kilns. ;otary kilns can $e fired with a wide range of fuels.

Heat transfer in the calcining 4one is largely $y radiation. The infrared emissi!ity

increases in the sequence gas, oil and solid fuel. ;otary kiln characteristics are shown in

Ta$le @.2

Ta$le @.2 ;otary kiln Characteristics

ong as, iquid, 'olid 8*5** Eust8*reheater as, iquid, 'olid 5*5** *8*

('ource =gnie4ka, 2**5)

*$1$* Parallel/%lo: re(e!erati;e il!

This kiln ty%e is characteri4ed $y two !ertical shafts connected to each other $y a cross

o!er channel. This allows for %arallel flow heating, i.e. the %arallel flow of the feedstock

and com$ustion gases in one shaft and the regenerati!e %reheating of the feedstock $y

the mi#ture of com$ustion gases and cooling air in the second shaft. The %arallel flow

%rinci%le is ideal for %roducing highly reacti!e quicklime and $urnt dolomite. The

o%eration of the kiln consists of two equal stages, of 5 min duration at full out%ut.

"n the first stage fuel is in1ected through the lances in shaft and $urns in the

com$ustion air $lown down that shaft. The heat released is %artly a$sor$ed the

calcination of limestone in shaft . =ir is then $lown into the $ase of each shaft to cool

the lime. The cooling air in shaft , together with the com$ustion gases and CO2 from

calcination, %ass through the interconnecting crossduct into shaft 2 at a$out *5*JC. "n

shaft 2, the gases from shaft mi# with the cooling air $lown into the $ase of shaft 2

and %ass u%wards. This then heats the stone in the %reheating 4one of that shaft. =fter


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5 min, the second stage commences. The fuel and air flows to shaft are sto%%ed,

and re!ersal0 occurs. =fter charging limestone to shaft , fuel and air are in1ected to

shaft 2 and the e#haust gases are !ented from the to% of shaft .

7igure @. arallel flow regenerati!e kiln

The standard kiln can $e designed to acce%t feedstones in the range of 25 2** mm. "t

can $e fired with gas, oil or solid fuel. Heat consum%tion in this ty%e of kiln is

a%%ro#imately @8** k?/kg (=gnie4ka, 2**5). These kilns are used at %roduction rates of

$etween ** 5* t/day. The kilns are designed to o%erate with a high le!el of e#cess

air (none of the cooling air is required for com$ustion), thus the le!el of CO 2 in the

e#haust gases is low at 2* $y !olume (dry).

"n conclusion, the annular shaft kiln is the $est since the kiln acce%ts a feedstone with a

to% si4e in the range @*25* mm and a $ottom si4e as low as * mm. =lso, it has a

+


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greater out%ut range of * 8** t/day. "t also has a relati!ely cool $urning 4one as

com%ared to other kilns which %re!ents o!er $urning.

Other ty%es of kilns are shown in Ta$le @.@.

Ta$le @.@ Characteristics of other ty%es of kilns

7il! type +uels use, Output ra!(e" t8,ay +ee, si9e ra!(e"

Tra!elling grate as, iquid, 'olid * @* 5 >5

To% sha%ed as, iquid, 'olid @* ** 5 >*7luidised $ed as, iquid @* 5* P27lash calciner as, iquid @** D 5** * 2;otating hearth as, iquid, 'olid ** D @** * >*

('ource =gnie4ka, 2**5)

The s%ecific energy usage of the different ty%es of kilns is shown in ta$le @.>

Ta$le @.> '%ecific energy usage of different ty%es of kilns

Ailn ty%eE!er(y usa(e -14

5* 2.+-gO 22* .5

'iO2 ,*>* 8.=l2O@ 5* 2.7e2O@ 2@8 *.Total 2,>>5 **

Tem%erature**C

Hy,rate, lie

Copo!e!

t

'ass" (8h 'ass" #

Ca(OH)2 2>, 2.>'iO2 8@ @.*=l2O@ 52+ 5.>

7e2O@ 2@8 *.Total 2,>>5 **

=ir classifier

Hy,rate, lie -o;er%lo: .

Copo!e!

t

'ass" (8h #

Ca(OH)2 2>, ++. *.*8'iO2 < *.*,8 **

Waste -u!,er%lo:.

Copo!e!

t

'ass" (8h #

-gO @@2 +.2CaCO@ 8


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>.2 3nergy $alance

@@


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@>

+lue (as to Recuperator

Com%onent

3nthal%y, k?/h

CO2 >*8*5@ @5.@'O2 25>2* .*

92 58*@82 5*.>*O2 @5< *.*>CaO 28+2@ 2.@2CaCO@ 22@5 *.-gO 5>88 *.*5'iO2 2*22 *.=l2O@ 8 *.*57e2O@ 2 *.*8

Total 822 *.*8

Total >225> 8


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@8

Water

Com%onent 3nthal%y, k?/hH2O 2,@>2,*>2Tem%erature85C

Lie %ro il!

Com%onent 3nthal%y, k? /hCaO -gO

CaCO@ 'iO2 =l2O@ 7e2O@ Total

Hydrator

)tea

Com%onent 3nthal%y, k?/hH2O 2,2* .*CaCO@ >@*+2 .'iO2 [email protected] 2.*7e2O@ 5+ *.5

Total2>*


37/204


38/204

Hopper

7unction 7or tem%orary storage of limestone, limeand hydrated lime.

Ca%acity 28* m@

Height @ m

9um$er required >-aterial of construction Car$on steel

Haer ill

7unction To grind limestone and limeCa%acity @* t/h, 8 t/h;eduction ratio >**7eed si4e 5* mm

9um$er required 2

ower consum%tion @*5.< k:-aterial of construction Cast iron steel

?ucet ele;ator

7unction To trans%ort limestone (5* D 25 mm) to kilnCa%acity 228 kg/hHeight @ m6ucket si4e 5* R 2* cm

9um$er required ower consum%tion . k:

-aterial of construction -ild steel

?elt co!;eyor

7unction To con!ey limestone and limeCa%acity


39/204

9um$er required 2ower consum%tion @+.2< k:-aterial of construction 'tainless steel

P!euatic co!;eyor 2

7unction To trans%ort hydrated lime from hydrator to the air classifier and from air classifier to ho%%er for $agging

Ca%acity 2 t/hength >5 mi%e diameter 22 mm

9um$er required 2ower consum%tion 5.+ k:-aterial of construction 'tainless steel

?lo:er 17unction To $low air to recu%erator Ca%acity @ m@/minTy%e centrifugal $lower O%erating %ressure atm

9um$er required ower consum%tion @> :-aterial of construction Car$on steel

?ur!er7unction To $urn fuel for calcinationCa%acity @@2 kg/h

9um$er required >ower deli!ery >* k:-aterial of construction 'tainless steel

+a!

7unction To $low air to cool lime at the $ottom ofkiln

Ca%acity t/hTy%e a#ial flow fan

@+


40/204

:idth .5+ m9um$er required ower consum%tion >> :-aterial of construction Car$on steel

Recuperator7unction -edium for e#change of heat $etween flue gas and air for

com$ustionCa%acity 8 t/h, + t/hTy%e Cellular =rea > m2

9um$er required -aterial of construction 'tainless steel

Heat echa!(er

7unction -edium for e#change of heat $etween steam and water forhydration

Ca%acity 22 t/h, > t/h9um$er required Ty%e shell and tu$e=rea +@ m2

-aterial of construction Car$on steel

?oiler

7unction To su%%ly steam for heating fuel storage tank Ca%acity 2** kg/hO%erating %ressure * $ar

9um$er required -aterial of construction Car$on steel

+ee,er" Rotary ta@le7unction To feed and discharge limestone and limeres%ecti!ely from the kiln

Ca%acity 2< t/h, 8 t/h9um$er required ower consum%tion . k:-aterial of construction Car$on steel

Pipes speci%icatio!

Pipeli!e 1

ocation from fuel storage tank to kiln.

=ssuming tur$ulent flow,Dopt=3.9 q

0.36

0.13

>*


41/204


42/204

m L mass flow of waterL@+5 kg/hL@.


43/204

Locatio! Type -*8hr. -#. -rp. Po:er

-W.

Co!structio!

7romstorage tankto kiln

Centrifugal%um%

7uel oil 2.2 .2> 'tainless

'teel

CHAPTER )IB

DE)I&N O+ A +UEL )TORA&E TAN7

8. ro$lem statementTo design a 2*** m@storage tank to store fuel oil at >*NC, %rior to the su%%ly of fuel for

the o%eration of the shaft kiln during the calcination %rocess.

8.2 "ntroductionThe calcination %rocess in the kiln needs a high amount of energy to achie!e com%lete

calcination of the limestone. This can $e o$tained from the fuel oil which has a heating

!alue of >>,@@.@ k?/kg (engineeringtool$o#.com, 2**). Thus a storage tank, as a

means to store the fuel, and safety consideration is rele!ant, %rior to the %lant o%eration.

'torage tanks are widely used in many industries. They are used to store a myriad of

liquid %roducts, $eing organic or nonorganic. The geometry of the tank, ty%e of roofing

and sha%e of the tank de%end on the %ro%erties of the material stored and en!ironmental

factors (ong and arner, 2**>).

;isks and en!ironmental ha4ards are associated with fuel oil storage tanks. ;e%orted

cases of e#%losion and fire from fuel storage tanks ha!e $een at an increase (Auan,

>@


44/204


45/204

$*$2 +loati!( roo% stora(e ta!

iquids stored at near atmos%heric %ressure are su$1ect to $reathing losses. =s the tank

cools during the night air is drawn in, then !a%ori4ation occurs to saturation, and the

!a%or mi#ture is e#%elled as the tank warms u% during the day. olatile liquids such as

gasoline consequently suffer a material loss and also a change in com%osition $ecause

of the selecti!e loss of lighter constituents. "n order to minimi4e such effects, floating

roof tanks are used. = floating roof is a deck which floats on the surface of the stored

liquid with a diameter of a$out @** mm less than that of the tank. The annular s%ace

$etween the float and the shell may $e sealed $y one of se!eral a!aila$le methods

(:alas, ++*).There are two ty%es of floating roof tanks, namely, e#ternal floating roof

tanks and internal floating roof tanks (erry, 2**).

External floating roof tanks

=n e#ternal floating roof tank consists of an o%ento%%ed cylindrical steel shell

equi%%ed with a roof that floats on the surface of the stored liquid. The floating roof

consists of a deck, fittings, and rim seal system. 7loating decks that are currently in use

are constructed of welded steel %late and are of two general ty%es singledeck (%ontoon

ty%e) and dou$ledeck. :ith all ty%es of e#ternal floating roof tanks, the roof rises and

falls with the liquid le!el in the tank. The o!erall diameter of the roof is normally >**

mm smaller than the inside diameter of the tank, which has a$out 2** mm ga% on each

side $etween the roof and the inside tank wall. The %ur%ose of the floating roof and rim

seal system is to reduce e!a%orati!e loss of the stored liquid. The seal system slides

against the tank wall as the roof is raised and lowered. The e#ternal floating roof design

is such that e!a%orati!e losses from the stored liquid are limited to losses from the rim

seal system and deck fittings (standing storage loss) and any e#%osed liquid on the tank

walls (withdrawal loss). (kolmet4.com, 2**)

Internal floating roof tanks

>5


46/204

=n internal floating roof tank has $oth a %ermanent fi#ed roof and a floating roof inside.

The deck in internal floating roof tanks rises and falls with the liquid le!el and either

floats directly on the liquid surface (contact deck) or rests on %ontoons se!eral inches

a$o!e the liquid surface (noncontact deck). Contact decks can $e aluminum sandwich

%anels that are $olted together with a honeycom$ aluminum core floating in contact

with the liquidB or %an steel decks floating in contact with the liquid with or without

%ontoonsB or a resincoated fi$erglass reinforced %olyester with $uoyant %anels floating

in contact with the liquid. The ma1ority of internal contact floating decks currently in

ser!ice is aluminum sandwich %anelty%e or %an steelty%e. The fi$erglass reinforced

%olyester decks are less common. The %anels of %an steel decks are usually welded

together. 9oncontact decks are the most common ty%e currently in use. Ty%ical

noncontact decks are constructed of an aluminum deck and an aluminum grid

framework su%%orted a$o!e the liquid surface $y tu$ular aluminum %ontoons or some

other $uoyant structure. The noncontact decks usually ha!e $olted deck seams.

(e%a.go!, 2**8)

The internal floating roof %hysically occu%ies a finite !olume of s%ace that reduces the

ma#imum liquid storage ca%acity of the tank. :hen the tank is com%letely full, the

floating roof touches or nearly touches the fi#ed roof. Consequently, the effecti!e height

of the tank decreases, thus limiting the storage ca%acity. The reduction in the effecti!eheight !aries from a$out 5 8* cm, de%ending on the ty%e and design of the floating

roof em%loyed. (kolmet4.com, 2**)

=ll ty%es of internal floating roofs, like e#ternal floating roofs, commonly incor%orate

rim seals that slide against the tank wall as the roof mo!es u% and down. Circulation

!ents and an o%en !ent at the to% of the fi#ed roof are generally %ro!ided to minimi4e

>8


47/204

the accumulation of hydrocar$on !a%ors in concentrations a%%roaching the flamma$le

range. 7lame arresters are an o%tion that can $e used to %rotect the !essel from fire or

e#%losion. :hen these are used, circulation !ents are not %ro!ided. Tank !enting occurs

through a %ressure!acuum !ent and flame arrestor. (kolmet4.com, 2**)

8.> 3qui%ment selection= !ertically cylindrical fi#ed roof tank with a cone sha%ed roof is chosen for the

following reasons 7irstly the liquid to $e stored (industrial fuel oil) is non!olatile,

since it has a flash %oint of 8.5NC (engineeringtool$o#.com, 2**). 'econdly,

economically the fi#ed roof tank is the least e#%ensi!e to construct and to undertake

maintenance, and it also has a high le!el of safety. =n a$o!eground ser!ice is required,

and !ertical fi#ed roof tanks are constructed for a$o!eground ser!ices. =s a rule of

thum$, !ertical tanks mounted on concrete foundation are used for liquid storage tanks

of ca%acity $eyond @ m@. (:alas, ++*)

8.5 Chemical engineering designVoluetric %lo: rate

Q=m

:here F L !olumetric flow rate of fuel oil

= density of fuel oil L +** kg/m@(engineering tool$o#.com, 2**)

m L mass flow rate of fuel oil L ++ kg/h

Q=1989

900=2.21 m3/h

Ta! capacity

6asis @@ days of storage for o%eration.V=2.2124 33=1750.32m3

:here L !olume of fuel oil to $e stored, m@

=s a rule of thum$, free$oard (ullage) of * is used. This accounts for the o!erfill

%rotection ca%acity (:alas, ++*).

7ree$oard !olume 0.1 1750.32=175.03 m3

VT=V+V!

:here VT L design ca%acity of tank, m@

L !olume of fuel oil to $e stored L


48/204

V! L free$oard !olume L


49/204

E L diameter of tank L 5.@ m

HT' L =ctual tank height L 2 m

VT'=(15.3)2 12

4 =2206.25 m3

Desi(! pressure

Eesign %ressure L Hydrostatic %ressure G =tmos%heric %ressure. ('innott, 2**@)

Hydrostatic %ressure gH

:here L density of the fuel oil L +** kg/m@(engineeringtool$o#.com, 2**)

g L acceleration due to gra!ity L +. m/s2

H L liquid head, m

H=4 V

D i2

:here L !olume of fuel oil L


50/204

2*N h

5.@

7igure 8. = diagrammatic re%resentation of tank conical roof.

:here L length of the conical roof slo%e, mh L height of the conical roof, m

h=7.65tan 20(=2.78 m

&= 7.65

cos20 (=8.14 m

olume of tank conical roof is gi!en $y

Vr=1

3

r2

h

:here Vr L !olume of tank conical roof, m@

rL radius of the tank conical roof L


51/204

vi L inlet flow !elocity L m/s (assumed)

Qi L inlet line flow rate L *.*@ m@/s

A i=0.038

1 =0.038 m2

d i=4Ai:here d i L inlet diameter,

A iL area of the inlet L *.*@ m

2

di= 4 0.038 =0.220m=220 mm=ssuming an outlet flow !elocity of half the inlet flow !elocity, (O"'E, 2**5)

Ao=Qovo

:hereA o L area of the outlet, m2

vo L outlet flow !elocity L *.5 m/s (assumed)

Qo L inlet line flow rate L 2.2 m@/h L 8.> R *>m@/s

Ao=

6.14 104

0.5 =1.228 103

m2

Outlet diameter (do),

do= 4A o =41.038 103

=0.0395 m 40 mm

Ta! i!ter!al %itti!(s

5


52/204

"nternal heating coil will $e used in heating the content of the tank. 6affles and an

agitator will $e used to enhance e!enly distri$ution of the heat.

?a%%le ,esi(!

&sually four $affles are used (eanko%lis, ++@).

2

tw

DB =

(eanko%lis, ++@)

:herewB

L width of $affle, m

tD

L tank diameter L 5.@ m

*+=15.3

12 =1.3 m

a% $etween $affles and tank wall is usually *. D *.5 * + (eanko%lis, ++@)

a% $etween $affles and tank wall L *. R .@ L *.@ m L @* mm

A(itator ,esi(!

The !iscosity of the fuel oil is +.+ R *@a.s (engineeringtool$o#.com, 2**). ro%eller

agitators are used for liquids of low !iscosity (less than @ a.s). (eanko%lis, ++@).

'ideentering agitators are used for $lending low !iscosity liquids in large tanks, where

it is im%ractical to use con!entional agitators su%%orted from the to% of the tank

('innott, 2**@). Thus a three$lade %ro%eller agitator will $e used.

Da=0.2Dt for tank height to diameter ratio less than one (9agata, +


53/204

The %ower required is o$tained from the correlation gra%h of %ower num$er against

;eynolds num$er for a gi!en ty%e of agitator (9agata, +


54/204

:herecpD

L coil %i%e diameter, m

vD

L !essel diameter L 5.@ m

=15.3

30 =0.51m=510 mm

7or a steel %i%e diameter of 5* mm, the %i%e thickness L >5 mm (erry, 2**)

The coil %itch is usually around twice the coil %i%e diameter ('innott, 2**@)

Coil %itch L 2 R *.5 L .*2 m

N"m!#r o $oi) spira)s=Ta,k )iq"id h#ight$oi) pit$h

=9.51.02

=9.3

Total length of coil %i%e,

"nside tank diameter for the coils L tank diameter - 2($affletank ga% G $affle width)

15.32 (0.15+1.5 )=12m

Coil %i%e total length N$s D $i

:here N$s L num$er of coil s%irals L +.@

D$i L inside tank diameter for the coils L 2 m

Coil %i%e total length 9.3 12=350.6m

Ta! heati!(

'team at 2**NC and * $ar will $e used for the heating.

Fuantity of heat required,

q=m%p(T2T1 )

:here

q

L the quantity of heat required to heat the fuel, ?

5>


55/204

m L mass of fuel in tank, kg

%p L s%ecific heat of fuel L 2*+* ?/kg A (engineeringtool$o#.com, 2**)

T1L initial tem%erature of fuel L 2NC (assumed)

T2 L final tem%erature of fuel L >*NC

m=V

:here L density of fuel L +** kg/m@

V L !olume of fuel in the tank L


56/204


57/204

hD

k =%(D.2)

0.8

( %p 2k )0.33

( 22+)0.14

:here % L *.*2@ for non!iscous liquids.

h L heat transfer coefficient, :/m2A

D L equi!alent diameter, m

k L fluid thermal conducti!ity, :/m A

2 L $ulk fluid !iscosity, 9s/m2

2+ L fluid !iscosity at the wall, 9s/m2

w

!iscosity correction factor W ('innott, 2**@)

%p L fluid s%ecific heat ca%acity, ?/kg A

. L mass flu#, kg/m2s

7or the heat transfer coefficient of the steam at 2**NC,

E L *.5 m

k L *.*@>2 :/m A (eanko%lis, ++@)

2 L .< R * 59s/m2(eanko%lis, ++@)

%p L +@2 ?/kg A (eanko%lis, ++@)

.=mA

:here m L flow rate of steam L 2** kg/h L *.@@ kg/s (assumed) (tt$oilers.htm,

2*)

5


58/204

A

L crosssectional area of coil=

( )2.*

>

5.* 2

=

m2

.=0.33

0.2

=1.65 kg /m2 s

hi =

0.023 (0.51 1.651.7 105 )0.8

( 19321.7 105

0.0342 )0.33

0.0342

0.51 =8.43 W/m2'

7or the heat transfer coefficient of the fuel oil,

E L 5.@ m

k L *.5 :/m A (engineeringtool$o#.com, 2**)

2 L +.+ R *@ 9s/m2(engineeringtool$o#.com, 2**)

%p L 2*+* ?/kg A (engineeringtool$o#.com, 2**)

.=mA

:here m L mass flow rate of fuel oil L *.>< kg/s

A

L crosssectional area of tank=

( ),5.,@

>

@.5 2

=

m2

.= 0.47

183.85

=2.6 103 kg / m2 s

ho=

0.023( 15.3 2.6 103

9.9 103 )

0.8

( 2090 9.9 103

0.15 )0.33

0.15

15.3

3.49 103

W/m2'

1/

= 18.43

+ 45 10351.9 (

0.60.55 )+

13.49 10

3

5


59/204

/=286 W/m2'

As=942.6 1000

286 160 =20.6 m221 m2

Ta@le $1 )uary o% cheical e!(i!eeri!( ,esi(!

Paraeter Value

Ca%acity of fuel oil to $e stored, m@


60/204

with corrosion rates of *.@ *.5 mm/y with added thickness (corrosion allowance) to

ensure the achie!ement of desired ser!ice life (erry, 2**). '%ecial %aints such as

chlorinated ru$$er %aints and e%o#y$ased %aints are used to %rotect storage tanks from

atmos%heric corrosion ('innott, 2**@).

)hell ,esi(!

The use of courses with diminishing thickness will ha!e the effect that, at the 1oint

$etween two courses, the thicker lower course %ro!ides some stiffening to the to%

thinner course. This causes an increase in stress in the u%%er %art of the lower course

and a reduction in stress in the lower %art of the u%%er course. This reduction in stress in

the u%%er course is assumed to reach a ma#imum !alue at *.@ m a$o!e the 1oint. The

footI method is used to calculate the thickness required at design %oints *.@ m a$o!e the

$ottom of each shell course (ong and arner, 2**>). The minimum shell %late

thickness which must $e used is 8 mm for 5 D @8 m tank diameter. (=" 85*, 2**@)

)hell thic!ess

The required thickness of shell %lates for each course shall $e the greater of the !alue

com%uted as follows (=" 85*, 2**@)

Eesign shell thickness

td=4.9D (H0.3 ).

3d+ %A

Hydrostatic test shell thickness

tt=4.9D (H0.3 )

3 t

wheretd L design shell thickness, mm

tt L hydrostatic test shell thickness, mm

D L nominal tank diameter L 5.@ m

8*


61/204

H L height from $ottom of course under consideration to the to% of tank

shell, m

. L s%ecific gra!ity of the liquid to $e stored

L *.+ (engineeringtool$o#.com, 2**)

%A L corrosion allowance L @ mm ('innott, 2**@)

3d L allowa$le stress for the design condition

L 8* 9/mm2for car$on steel (ong and arner, 2**>)

3 t L allowa$le stress for the hydrostatic test condition

L )

+irst course -@otto course.

H L 2 m

td=4.9 15.3(120.3)0.9160 +3=7.9 mm8 mm

tt=4.9 15.3(120.3)

171 =5.1 mm

Therefore %late thickness of mm will $e used.

)eco!, course

H=122=10 m

td=4.9 15.3(100.3)0.9

160 +3=7.1mm7 mm

tt=4.9 15.3(100.3)

171 =4.3 mm

Therefore %late thickness of < mm will $e used.

8


62/204

Thir, course

H=102=8 m

td=4.9 15.3(80.3) 0.9

160

+3=6.2 mm6 mm

tt=4.9 15.3(80.3)

171 =3.4 mm

Therefore %late thickness of 8 mm will $e used.

+ourth course

H=82=6 m

td=4.9 15.3(60.3) 0.9

160 +3=5.4 mm

tt=4.9 15.3(60.3)

171 =2.5 mm

5.> mm is the greater of the two, $ut the minimum thickness required is 8mm. Therefore

%late thickness of 8 mm will $e used.

+i%th course

H=62=4 m

td=

4.9 15.3(40.3) 0.9

160 +3=4.6 mm

tt=4.9 15.3(40.3)

171 =1.6 mm


)ith course

H=42=2 m

82


63/204

td=4.9 15.3(20.3)0.9

160 +3=3.7 mm

tt=4.9 15.3(20.3)

171 =0.7 mm


Ta! @otto plate thic!ess

The tank $ottom is made u% of rectangular %lates. 7or larger tanks (o!er 2.5 m

diameter, according to 6' 285>), a ring of annular %lates is %ro!ided around the grou%

of rectangular %lates. The minimum thickness of the annular $ottom %lates, e#cluding

any corrosion allowance, shall $e mm when the $ottom course %late is + mm thick or

less. (6' 285>, ++)

t!=8+%A

wheret! L tank $ottom %late thickness, mm


t!=8+3=11mm

Roo% plate thic!ess

'elfsu%%orting cone roofs shall ha!e a minimum thickness of 5 mm and a ma#imum of

2.5 mm e#cluding any corrosion allowance. (=" 85*, 2**@)

tr$= D

4.8sin 4+%A

where tr$ L cone roof %late thickness, mm

D L tank diameter L 5.@ m


8@


64/204

4 L the angle of slo%e of the roof to the hori4ontal L 2*N

tr$= 15.3

4.8sin20+3=12.3 mm

Loa,i!( o! ta!

The main sources of load to consider are %ressure, dead weight of !essel and contents,

wind, seismic load and e#ternal loads im%osed $y %i%ing and attached equi%ment

('innott, 2**@).

Dea, :ei(ht loa,

This is the load due to the tank shell, fittings (manways, no44les) and e#ternal fittings

such as ladders, %latforms, %i%ing. 7or a steel !essel,

Wv =240%vDm(Hv+0.8Dm ) t ('innott, 2**@)

where Wv L total dead weight, 9

%v L a factor to account for the weight of fittings such as no44les, manways

and internal su%%orts L .5 for !essels with many internal fittings ('innott,

2**@)

Hv L height of the cylindrical shell L 2 m

Dm L mean diameter of !essel L (Di +t 10

3

) 5 m

Di L !essel internal diameter L 5.@ m

t L shell thickness L mm

Dm=(15.3+8 103 )=15.308m

Wv=240 1.15 15.308 (12+0.8 15.308 ) 8=819.52 kN

8>


65/204

Loa, ,ue to ta! co!te!t

W$=oVo g

:hereW$ L load due to content, 9

o L density of fuel oil L +** kg/m@(engineeringtool$o#.com, 2**)

Vo L !olume of fuel oil L


66/204

t L shell thickness L mm

Do L shell outer diameter L 5@** G (2 R ) L 5,@8 mm

allowa$le design stress L 8* 9/mm2

6$=2 104( 815316 )=10.45N/mm2

'ince *.>5 9/mm2P 8* 9/mm2, it im%lies $uckling will not occur.

Ta! support

=s a rule of thum$, !ertical tanks with ca%acity $eyond @ m@are su%%orted on concrete

foundations (:alas, ++*). The stress e#erted on the foundation is due to tank the dead

weight and content weight. The stress will $e tensile (%ositi!e) for %oints $elow the

%lane of the !essel su%%ort, and com%ressi!e (negati!e) for %oints a$o!e the su%%ort

('innott, 2**@).

)tress o! %ou!,atio!

6+ = W(Di +t)t

(3i,,ott 5 2003)

:here6+ L direct stress on foundation, 9/mm2

W L dead weight G content weight L +.52 G 5>5@.> L 8,2


67/204

6d= Wv

(Di+t) t(3i,,ott 5 2003)

:here 6d L dead weight stress, 9/mm2

Wv L total dead weight load L +.52 k9

Di L tank internal diameter L 5@** mm

t L tank shell thickness L mm

6d= 819520

(15300+8 ) 8=2.0

N

mm

2

Aial -lo!(itu,i!al. stress

6&=PiDi

4 t (3i,,ott 5 2003)

:here 6& a#ial stress, 9/mm2

Pi internal %ressure (%ressure due to liquid head) L *.*>*5 9/mm2

Di L tank internal diameter L 5@** mm

t L tank shell thickness L mm

6&=0.08405 15300

4 8 =40.2N/mm2

Hoop -circu%ere!tial. stress

6h=PiDi

2 t (3i,,ott 5 2003)

:here 6h hoo% stress, 9/mm2

6h=0.08405 15300

2 8 =80.4N/mm2

8


68/204

:ind stresses are disregarded $ecause of the high ratio of tank diameter to tank height

(;ay and ?ohnston, ++).

&%wind total stress 6&6d=40.22.0=38.27Pa

Eownwind total stress 6h6d=80.42.0=78.47Pa

;adial stress 0.5P i=0.5 0.08617=42.0 kPa

The downwind total stress is greater than the u%wind total stress, thus the resultant

stress will $e on the downwind side. The downwind total stress (*.> -a) is well

$elow the allowa$le design stress (8* -a), thus the tank can withstand the downwindstress.

Ta! appurte!a!ces

'a!holes

The cutting of an o%ening in the shell interferes with the structural action of the shell

and therefore a means of %ro!iding reinforcement to com%ensate for this weakness is

required. This reinforcement can $e %ro!ided $y one of the following ways a

reinforcing %late welded onto the shell %late at the o%ening sectionB an insert of a thicker

%late locally (in which the manhole is cut)B a thicker shell %late than that required for

that course of the shell. = manhole through the shell wall should $e at least 8** mm in

diameter (6' 285>, ++). "t is normally %ositioned 1ust a$o!e the $ottom of the tank.

(ong and arner, 2**>)

No99les

9o44les are required through the shell for inlet and outlet and through the roof for !ents.

=ccording to 6' 285>, for smaller no44les (diameter P 5* mm), no reinforcement is

necessary, the e#tra material is considered sufficient. arger holes must $e reinforced in

the same way as manholes (ong and arner, 2**>).

8


69/204

Pressure a!, ;acuu relie% ;al;e

This is used for tanks o%erating under an internal %ressure. The !ent o%ens only when

the set internal %ressure is e#ceeded (during filling). On the !acuum side, the !al!e

o%ens when the set internal !acuum is e#ceeded, as is the case during withdrawing

(ong and arner, 2**>).

)tair:ay

=ccording to =85*, tanks taller than 8m must $e furnished with a s%iral stairway.

(Xacine et al, 2**2). Handrailing is required on the inside stringer of a s%iral staircase

where the ga% $etween the stringer and the tank shell e#ceeds 2** mm according to

$oth 6' 285> and =" 85*. The ma#imum slo%e for a staircase is >5N according to 6'

285> (ong and arner, 2**>).

8+


70/204


71/204

Ta@le $2 )uary o% echa!ical e!(i!eeri!( ,esi(!

Paraeter Value

Eesign stress, -a 8*Eesign tem%erature, NC >*=#ial stress, -a >*.2

Hoo% stress, -a *.>;adial stress, ka >2'tress on foundation, -a >2.@Eead weight, k9 +.5:ind ressure, a


72/204

CHAPTER )EVEN

5 DE)I&N O+ AN ELECTRO)TATIC PRECIPITATOR

5 kg/h of flue gas at @** oC and atm from a shaft kiln in controlling

air %ollution.


73/204

the collector %lates is from electrodes maintained at high !oltage in the center of the

flow lane.

The %articles collected on the %lates are remo!ed from it without reentraining them into

the gas stream. This is usually accom%lished $y knocking them loose from the %lates,

allowing the collected layer of %articles to slide down into a ho%%er from which they are

e!acuated (arker, +


74/204

Plate ESP

late3's are %rimarily used to collect dry %articles. They can ha!e wire, rigidframe,

or occasionally, %late discharge electrodes. Eirty gas flows into a cham$er consisting of

a series of discharge electrodes that are equally s%aced along the center line $etween

ad1acent collection %lates. Charged %articles are collected on the %lates as dust, which is

%eriodically remo!ed $y ra%%ing or using water s%rays (e%a.go!, ++).

Single stage and to! stage ESP

'inglestage 3's use !ery high !oltage (5*


75/204

:et 3's run a liquid o!er the collection %lates to remo!e %articles or when dust is !ery

sticky, corrosi!e, or has !ery high resisti!ity. The water flow may $e a%%lied

continuously or intermittently to wash the collected %articles from the collection

electrodes into a sum%. They ty%ically result in higher ca%ture of su$micron %articulate

due to the $etter adhesion of the %articles to the collection surfaces0 cleaning liquid, and

!irtually no reentrainment.

Ery 3's use ra%%ers to remo!e the collected %articulate matter from the collection

%lates. The term dry is used $ecause %articles are charged and collected in a dry state

and are remo!ed $y ra%%ing as o%%osed to water washing which is used with wet 3's

(e%a.go!, ++).

5$*$2 EFuipe!t selectio!

7rom the classification of the electrostatic %reci%itators, the %late 3' with discharge

electrodes made u% of long wires weighted and hanging $etween the %lates or are

su%%orted there $y mastlike structures (rigid frames) will $e the $est o%tion. This is

$ecause it has an ad!antage for handling large !olumes of gas. The need for ra%%ing the

%lates to dislodge the collected material can also$e di!ided into sections, often three or

four in series with one another, which can $e ra%%ed inde%endent. =lso the %ower

su%%lies are often sectionali4ed in the same way to o$tain higher o%erating !oltages, and

further electrical sectionali4ation may $e used for increased relia$ility.

Chemical engineering designVoluetric %lo: rate o% %lue (as

The !olumetric flow rate of flue gas from the shaft kiln is gi!en $yB

Q=

:here

L mass flowrate L 5@,>5 kg/h (material $alance calculation)


76/204

Q L !olumetric flowrate, m@/h

L density of flue gas, kg/m@

The density of the flue gas can $e estimated $y the ideal gas law asB

=7P

8T

:here - L a!erage molecular weight of gas, kg/kmol

L %ressure of the gas L *@25 a

T L a$solute tem%erature of the gas L @**L 5 ?/kmolA

The a!erage molecular mass of the flue gas is

7=Na7a+N!7!+9+N171

Nt

:here 9#L num$er of moles of s%ecies Y, mol

-# L molecular masses of s%ecies Y, g/mol 9tL total num$er of moles of s%ecies, mol

*"t N= m

71

:here m L mass of s%ecie Y

Ta$le

9O2 >8

Hence for flue gas com%ositionB


77/204

N%:2=20082

44 =456,409.1mo)

N3:2=872

64=13,625 mo)

NN2=28397

28 =1,014,178.6mo)

N:2=1966

32 =61,437.5 mo)

NH2 :=2148

18 =119,333.3 mo)

NN:2=20

46=434.8 mo)

Therefore, the total num$er of moles

9tL >58,>*+. G @,825 G ,*>,@@>. L ,885,> mol

Then, the a!erage molecular weight is

7=53,485,001.4

1,665,418 =32.1 kg/kmo)

The density of the flue gas $ecomes

=32.1 101325

8314 573 =0.6831 kg /m3

Q= 53,4850.6831 =78,297.5 m3 /h

Q=78,297.5

3600 =21.75 m3/ s

Collectio! area

=ssum%tions


78/204

The assum%tions of which the equation for determining the total collection area for an

3' include %article si4es are $elow * Zm, %articles are uniformly distri$uted, no $ack

corona, ra%%ing reentrainment of %articles are neglected, no electrical resisti!ity of

%articles and no gas sneakage around the field (e%a.go!, ++).

The Eeutsch=nderson equation for an 3' is gi!en $y

=1#+A

Q (Coo%er and =lley, 2**2)

:here L fractional collection efficiency L *.++ (cedengineering.com, +++)

w L drift !elocity of %articles in an electrical field L *.*5 m/s

(cedengineering.com, +++)

= L total collection area of 3', m2

e L $ase of natural logarithm L 2.


79/204

N= A

Ap+Ns=

6677.5

36 +3=188.6;189

,=189

3 =63

This im%lies that there are 8@ %lates in each section in the direction of flow of gas.

The height of the 3' is gi!en $y

H3L .5 H (Coo%er and =lley, 2**2)

:here H3L height of 3'

H3L .5 R 8 L + m

The length of the %reci%itator is gi!en $y

L 9sG (9sD ) s (Coo%er and =lley, 2**2)

:here L length of %reci%itator, m

sL s%acing $etween electrical sections L .5 m (Coo%er and =lley, 2**2)

L (@ R @) G (@ D ).5 L 2 m

Collector plate spaci!(

Eue, in %art, to stringent %articulate matter control requirements, the %lateto%late

s%acing is 5 cm. This s%acing is required so as to accommodate the rigid frame

discharge electrode su%%orts $etween the collecting %lates (e%a.go!, ++).

Wire G plate separatio!

The wires in the 3' are well s%aced $etween the collecting %lates to im%ro!e its

%erformance, thus the se%aration of the wires and the collecting %lates is 5 cm

(e%a.go!, ++).

Coro!a po:er

The corona %ower which is the %ower that energi4es the discharge electrodes and thus

creates the strong electric field is related to the collection efficiency of the 3' as

=1#k P$

Q


80/204

:here cL corona %ower, :

k L a constant L *.55 (Coo%er and =lley, 2**2)

F L 2.>5 m@/s L


81/204

Car$on steel is the %referred material used to $uild the 3'. Car$on steel has e#cellent

ductility and it is !ery welda$le. Car$on steel also has !ery good tensile strength.

Car$on steel is used for com%onents of the 3' such as the ho%%er casing, collecting

electrode, shell and the structural su%%ort. "t is used to maintain o%timum gas flow

characteristics and mechanical rigidity for com%onent such as the collecting electrode.

Ees%ite its limited corrosion resistance, an additional thickness (corrosion allowance)

can assure the achie!ement of desired ser!ice life. They do resist atmos%heric corrosion

as well as attack $y natural or neutral water and neutral soil. Car$on steel is also !ery

chea% as com%ared to the other materials (erry, +++).

'i!iu shell thic!ess

The minimum shell thickness required to resist internal %ressure can $e determined from

#= Pi&

2 Pi

:here L length of %reci%itator L 2*** mm

f L design stress L 5 9/mm2for car$on steel at @**('innott, 2**5)

e L minimum shell thickness, mm

#=0.1114575 12000

2 (85 )0.1114575=7.9 mm

7or car$on and lowalloy steel, where se!ere corrosion is not e#%ected, a minimum

corrosion allowance of 2 mm is used ('innott, 2**5).

#=7.9+2=9.9 ; 10 mm

Lo!(itu,i!al stress

The longitudinal stress is gi!en $y the equation


82/204

6&=Pi&

4 t

:here 6& L longitudinal stress, 9/mm2

t L thickness of shell L * mm

6&=0.1114575 12000

4 (10) =33.44N/mm2

Ta!(e!tial stress

The tangential stress is gi!en $y the equation

6h=Pi&

2 t

:here6h L tangential stress, 9/mm2

6h=0.1114575 12000

2(10) =66.87N/mm2

Wei(ht o% ;essel

7or a steel !essel, the weight of the !essel is gi!en $y the equation

:!L 2>*C!Em(H! G *.Em) t

:here t L wall thickness L * mm

H! L height of !essel L + m

C!L a factor L .* ('innott, 2**5)

EmL mean diameter of !essel (L EiG t R *@), m

:!L weight of !essel, 9

Dm=12+10 103=12.01m

Wv =240 1.08 12.01( 9+0.8 12.01 )10=579 kN

Wei(ht o% E)P co!te!t

2


83/204

W$ m$g

:here mcL mass of flue gas L 5@,>5 kg

g L acceleration due to gra!ity L +. m/s2

W$=53,485 9.81=524,688N ; 525 kN

Dea, :ei(ht stress

The dead weight stress is gi!en $y

6+ = W

(&+ t) t

:here 6+ L dead weight stress of !essel, 9/mm2

: L total weight of !essel

W=Wv +W$

W=579+525=1,104kN

6+ = 1,104,000

(12000+10 ) 10=2.93N/mm2

Desi(! o% %lat e!,s

The minimum thickness of flat ends is gi!en $y

#=%p&Pi:here C%L design constant, de%endent on edge constraint L *.55 ('innott, 2**5)

#=0.55 12000

0.1114575

85

=238.9 ; 239mm

@


84/204

)upport ,esi(!

= skirt su%%ort consists of a cylindrical or conical shell welded to the $ase of the !essel.

The skirt must $e sufficient to withstand the deadweight loads and $ending moments

im%osed on it $y the 3' ('innott, 2**5).

?e!,i!( stress i! the sirt

The $ending stress in the skirt is gi!en $y the equation

6!s= 47s

(Ds+ts ) tsD s

:here -sL ma#imum $ending moment, e!aluated at the $ase of the skirt, 9m

6!s L $ending stress in the skirt, 9/mm2

tsL skirt thickness L * mm

EsL inside diameter of the skirt L ** mm ('innott, 2**5)

*"t 7s=+ 1

2

2

:here w L load %er unit length due to wind %ressure, 9/m

# L height of 3' L + m

=lso w L wR

:here wL wind %ressure L 2* 9/m2('innott, 2**5)

Then, w L 2* R 2 L 5,@8* 9/m

Therefore, the ma#imum $ending moment

7s=15,360 9

2

2 =622,080Nm

Then,

>


85/204

6!s= 4 622080 10

3

(1800+10 )10 1800=24.31N/mm2

Dea, :ei(ht stress i! the sirt

The dead weight stress in the skirt is gi!en $y the equation

6+s= Wv

(D s+ts ) ts

:here 6+s L dead weight stress in the skirt, 9/mm2

6+s= 579000

(1800+10 )10=10.18N/mm2

Resulta!t stresses i! the sirt

Te!sile stress

[s(tensile) L [$s [ws ('innott, 2**5)

[s(tensile) L 2>.@ D *. L >.@ 9/mm2

Copressi;e stress

[s(com%ressi!e) L [$s + [ws ('innott, 2**5)

[s(com%ressi!e) L 2>.@ G *. L @>.>+ 9/mm2

&nder the worst com$ination of wind and deadweight loading, the following design

criteria are not e#ceeded.

6s (t#,si)# )ssin < s ('innott, 2**5)

6s ($ompr#ssiv# )0.125= ( tsD s )sin< s ('innott, 2**5)

:here fsL ma#imum allowa$le design stress L @5 9/mm2 for car$on steel at 2*oC

('innott, 2**5)

< s L $ase angle of a conical skirt L +*o

5


86/204

3 L Xoung0s modulus at 2+NC L 2**,*** 9/mm2 ('innott, 2**5)

6s (t#,si)# )135sin90

14.13135

6s ($ompr#ssiv# )0.125 200,000 ( 101800 ) sin 90

34.49138.9

'ince $oth criteria are satisfied, it im%lies the skirt su%%ort is not deemed to fail.

Ta$le .@Eead weight stress in the skirt, 9/mm2 *.Tensile stress in the skirt, 9/mm2 >.@Com%ressi!e stress in the skirt, 9/mm2 @>.>+-aterial of construction Car$on steel

8


87/204

CHAPTER EI&HT

6$4 DE)I&N O+ A LI'E H>DRATOR

. ro$lem statementThe aim of this work is to design a lime hydrator that would %ro!ide o%timum

conditions for %roducing 852* kg/h %er hour of Ca(OH)2 from


88/204

%roduct would follow after the reaction, $ut it is still necessary that the reactor is

modeled for higher con!ersion of the reactant.

.@ Hydration %rocessHydration %rocess is a dissolution %reci%itation reaction in which quick lime is fed to a

stirred reactor and gi!en enough time for the reaction to com%lete. "n the mi#er, water is

added to the quicklime (unhydrated lime) in calculated %ro%ortions.

The flow of the quicklime is metered $y a $elt feeder such that, 1ust the calculated

amount is fed for reaction. The addition of water is controlled $y metering, such that,

the reaction starts when the mi#ture is a$out to dro% into the seasoning cham$er and to

ensure moisture content and the tem%erature of the %roduct are constant. High discharge

tem%erature indicates deficiency of water and low tem%eratures indicate e#cess water.

The seasoning cham$er is where the actual reaction occurs, %roducing %owdered

hydrated lime. (-etso.com, 2**)

The moisture content of the %roduct is regulated $y tem%eraturecontrolled water su%%ly

to the reactor and retention time. The o%eration tem%erature of the reactor is ** oC

(internationallime.org, 2**), corres%onding to *.5 free moisture content of the

hydrate. =n attem%t to %roduce $one dry hydrate may result in o$taining a lot of

unreacted acti!e raw material (metso.com, 2**)

The hydrator consists of a mi#ing cham$er with a shaft and %addle arrangement in

which quicklime and water are $rought into contact. The shaft and %addle arrangement

is for turning the lime so as to s%eed u% the reaction.

The second cham$er, called seasoning cham$er is also equi%%ed with a shaft and

%addles. "t is in this cham$er that the actual reaction and drying u% of the hydrate occur.

The u%%er %art of the seasoning cham$er is a deduster for handling the steam and dust


89/204

Reactor vesselQuicklime inlet

Steam out

Hyrate prouct

!"itator sha#t

$ater inlet

coming out from the seasoning cham$er. The collected hydrate dust dro% $ack into the

seasoning cham$er and reenters the %rocess stream.

7igure . = sketch of lime hydration unit

.> Chemical 3ngineering EesignHy,ratio! rate

The%ro%erties of the hydrated lime are controlled $y %rocess %arameters. The need for

high %roduction efficiency requires good knowledge a$out the hydration mechanism.

Thus, a model of the kinetics of the reaction is key to the design of the hydrator.

The mechanism of the hydration reaction can $e descri$ed as a dissolution %reci%itation

mechanism, though it cannot $e descri$ed easily $y only one model such as the

shrinking core model, %rogressi!e con!ersion model and %orous reactant model for gas

solid reactions. "t is therefore %redicted that the hydration reaction occurs through a lot

of %rocessesB %hysical adsor%tion of the water, chemical reaction with water and inert

%ortions to water

The rate law equation for the hydration reaction is gi!en $y the relation

+


90/204

( )xinp

inAo

AA

d

Mv

x!"

rdt

d!

==

@

8

('hete et al, 2**>)

k L rate constant for the reaction 77.7 105 $m s

1

(6riss et al, 2**)

C=o L initial concentration of quicklime, kmol/m@

m L initial mass of quicklime L22


91/204

11

dp

d %A

dt

=rA=6 k(%* m17v)

6 (7.77 107 3600 )mh

[(54.41( 22783 157.4 14.24 ))kmo)m3 ]6 10

3m (11 )

1

3

rA=152.3577.951

3(11 )

5kmo) /m3 h

Ta$le . rate of reaction

Con!ersion(#) ;ate of reaction

(r=), kmol/([email protected])

/r=,

([email protected])/kmol*.* 52.@5 *.**88*.2* >* >@.88 *.**@.2+ *.**


92/204


93/204


94/204

V=3 D

3

4 =D=

3( 4 V3 )=3( 4 0.76 m3

3 )=1.47=1.47 m

Thus, &=3 1.47=4.4 m

)pace tie

The %erformance of a flow reactor is characteri4ed $y the s%acetime and s%ace

!elocity. '%ace time ( > ) is the time required to %rocess one reactor !olume of feed

measured at s%ecified conditions. "t is gi!en $y the relationB

>=%

AoVFAo

:here C=oL concentration of feed, kmol/[email protected]

7=o L molar flow rate of the feed, kmol/h

L !olume of the reactor, m@(e!ens%iel, +++).

%Ao= ,

v+at#r=

m

7 v+at#r=

22783

57.4 14.24

=27.87kmo)

m3

FAo= mass

mo)ar mass=

22783

57.4 =396.92

kmo)

ho"r

>=%AoV

FAo=

27.87 1.52

396.92 =0.11ho"r=6.6 mi,"t#s

)pace ;elocity

'%ace !elocity(s) is the num$er of reactor !olumes of feed which can $e %rocessed in

one minute at s%ecified conditions. "t is the in!erse of s%acetime. (e!ens%iel, +++)

s=1

>=

1

6.6=0.15 mi,1

I!let !o99le ,iaeter

Ta@le 6$2 De!sities o% %ee, copo!e!ts

+>


95/204

copo!e!t De!sity" (8* 'ass %ractio!

%ro aterial

@ala!ce

CaO @@** *.2@

-gO @5* *.*>CaCO@ 2


96/204


97/204


98/204

Eiameter of the im%ellerB this %arameter is greatly affected $y the nature of the $ottom

of the reactor. d imp#))#r =D

2 . Howe!er, the o%timum diameter of im%eller for !essels

with s%herical $ottom is gi!en $yBdopt=0.35D .

The length of the shaft,&shat=27D

Eistance $etween im%ellersLE/2 (9agata, +5.*

2.*.*

d

B%

ds

&

p

'N

=

:here N L the minimum im%eller s%eed to achie!e com%lete sus%ension, r%s

s L a dimensionless constant (]wietering, +5) %resented gra%hically as a

function of E/c and E/d.

C L the im%eller clearance a$o!e the $ase of the !essel, m

_ L the kinematic !iscosity of the liquid, m2/s

d%L the diameter of the %article, m+


99/204

g L gra!itational constant, +. ms2

& L the density of the liquid, kg/m@

0 L difference in solid and liquid densities, kg/m@

E L the diameter of the reactor, m

d L the diameter of the im%eller, *.2 m

6 L the %ercentage ratio of mass of solid %hase to mass of liquid %hase.(Aee et

al, 2**2)

s L 8. atD

d

=2.9 andD

%

=4 (Aee et al, 2002)

iscosity of water at 85oC, ?=0.43555 103 kg

m@ s . (eanko%lis, +++)

Eensity of water at 85oC L +*.5@ kg/m@

=

, m2

/s (eanko%lis, +++)

s /*>>.>5@.+,*

***>@555.* 2


100/204

N=

s 0.1

dp0.2( g 0 &)

0.45

*0.13

d0.85

=

6.8 (4.44 107 )0.1

(0.006 )0.2( 9.81 2377.32980.53 )0.45

(163.23 )0.13

(0.476 )0.85

8.3 rps=497 rpm

7or %ro%er mi#ing and $etter distri$ution of water within the solid, it is good that the

solid is mi#ed to fluidi4e. The %ower required $y the mi#er to mi# and fluidi4e the

material is gi!en $y the relationB

( )

i

isp

water

%dP

M

8

@

@

2

=

(9agata, +5


101/204

i=+#ight o )iq"id+ +#ight o so)id

tota) vo)"m#o so)id)iq"id =

13958+227836.78+14.24

=1747.91kg

m3@

;earranging the equation a$o!e results in

( )2

@

@

8

=

i

isp

water

%dMP

( ) ( ) ( )"*

%dMP

i

isp

water 8.+.


102/204

Eiameter of im%eller, m *.52:idth of im%eller, cm .>5o

'%eed of the agitator, r%m >+8 ka

*@


104/204


105/204


106/204

)*

)h)h

)*

7igure .2 The reactor under wind loading

Nw DP ow /8.,,>*

2

8.,,

2

===

The ma#imum !alue of -#is o$tained at an end of the !essel where #L> m.

"NxMx 2.,,.+>*,.+>* >.> 22 ===

)tresses acti!( o! the reactor

The !essel is su$1ected to different stresses due to the different kinds of loading and

%ressures acting on it. Consider a section of the reactor, the diagram $elow shows the

stresses acting on it.

7igure .@ stresses acting on the !essel

[4 L longitudinal stress, -a

*8


107/204


108/204


109/204

,5.2*>.58.5 ==+= bw&, -a

( ) ( ) MPa,-,- +2.*+@.>+2.*5.*>5.* +@.>+2.* 222

=

++=

+++=

( ) ( ) MPa,-,- ,5.2,5.2+2.*5.*>5.* ,5.2+2.* 222

2 =

+=

++=

&sing the ma#imum %rinci%al stress theory to access the sta$ility of the reactor

The ma#imum %rinci%al stress theory states that, a mem$er will fail when one of the

%rinci%al stresses reaches the failure !alue in sim%le tension, [e. The failure %oint is the

yield %oint stress. ('innott, 2**5)

The !alue of [eL2


110/204


111/204


112/204

Circumferential stress acting on the !esselB the ma#imum circumferential stress occurs

at the horn of the saddle and is due to local $ending and direct stresses. The

circumferential stress can $e calculated from the formulaB

6%= Q4 t(!+10t)

3'3 Q2 t

2 (]ick, +5)

:here [C L circumferential stress, -a

6 L width of the saddle L *.@*> m for steel material (]ick, +5)

A@L*.*52 (]ick, +5)

t L thickness of !essel L *.**


113/204


114/204

CHAPTER NINE

< Desi(! o% a sha%t il!

+. ro$lem statement"t is required to design a shaft kiln for the %roduction of 2,5** kg/h of CaO. The CaO

is to e#it the kiln at *NC.

+.2 "ntroductionThere are !arious kilns em%loya$le for the %roduction of lime. They fall into three $road

grou%s which are shaft, rotary and %arallel flow regenerati!e kilns.

'haft kilns are !ertical cylindrical hollow structures through which limestone flows

down and is countercurrently, cocurrently or in some cases as in the annular shaft kiln

$oth countercurrently and cocurrently contacted with hot gases e!ol!ed from the

$urning of fuel. Ta$le +. shows different kilns and their characteristics.

Ta$le +. 'haft kiln characteristics

)ha%t 7il! type +uels use, Output ra!(e" t8,ay +ee, si9e ra!(e"

Eou$leinclined kiln as, iquid, 'olid * 8* 2* D 2**

-ulticham$er kiln as, iquid, 'olid >* 225 2* D 5*

=nnular shaft kiln as, iquid, 'olid * 8** * D 25*

-i#edfeed shaft kiln 'olid 8* 2** 2* D 2**

Central $urner as, 'olid >* * >* D 5*

3#ternal cham$ers as, iquid >* 2* * D @5*

6eam $urner as, iquid, 'olid 5* ** 2* D


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116/204


117/204

T&3/&!z=(T1T2)

ln(T1)

(T2)

=(1200900)

ln( 1200900) =1044.3

:here TL ma#imum limestone/lime tem%erature in $urning 4one L 2**NC

T2L minimum limestone/lime tem%erature in $urning 4one L +**NC

T'/$4L log mean limestone/lime tem%erature in $urning 4one

The tem%erature of the fluid film ne#t to the limestone/lime surface, T' is

T=T&3/&!z+T&7%.

2 =1079(.#a,kop)is5 2003)

Ta$le +.@ -ean C%!alues at film and $ulk tem%erature in the $urning 4one

)pecie

s Aou!t" (8h %P! " =8(7

%P & =8(7

CO2 8@>5*.8

@ .> .@

92 2@+8.*..2*.*5

5 2.+ 2.

O2 +85. *.*5 .*8 .*5

'O2 2


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119/204

turn set $y the mass flow rate determined in the mass $alance and the cross sectional

area of the kiln.

.!zE =

7F.A

=38903

1.52=2.1

kg

m2

s

:here .!zE

L flue gas flu# in $urning 4one

= L cross sectional area of kilnL .+ kg/s

Heat transfer coefficient h is found $y the following correlationB

h

%P.E(%P?k )

2

3 =2.876?

Dp .E +0.3023( ? D p.E)

0.35

(.#a,kop)is 5 2003)

:here CL s%ecific heat ca%acity of $ulk fluid L .+ k?/kgA

C'L s%ecific heat ca%acity of fluid at film tem%. L . k?/kgA

Z'L !iscosity of fluid at film tem%. L *.*5> c L 5.> R*5kg/ms

k'L thermal conducti!ity of fluid at film tem%. L .> R*5k:/mA

L !oid fraction L *.>*

EL log mean of si4e range (*.25*.*5) L *.* m

0.40 h

1.2 2.1 ( 1.17 5.4 105

8.4 105 )

2

3=2.876 5.4 10

5

0.08 2.1 +0.3023( 5.4 10

5

.08 2.1)0.35

h=0.15 kWm

2'

The rate of heat transfer required in the $urning 4one is the mass flow rate of limestone

in to the $urning 4one multi%lied $y the s%ecific heat of dissociation of limestone.

q!z=7&3 hd=28,126 1670=13,047.3 kW

:here 7&3 L mass flow rate of limestone into $urning 4oneL228 kg/hL


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hdL heat of dissociation of limestoneL8 m2/kg (=gnie4ka, 2**5)

-'L mass of limestone in the $urning 4one at any time, kg

T&7F. L log mean tem%erature of com$ustion %roduct in $urning 4one L

2.NC

T&7&3 L log mean tem%erature of limestone in $urning 4one L *>>.@NC

13047.3=0.15 0.014 7&3!z (1112.81044.3 )

7&3 !z=94480 kg

The !olume of the $urning 4one is the !olume that will contain the limestone and the

!oid fraction of the $ed of lime. L *.>*. The $urning 4one constituents are a

continuum from limestone to lime hence a more accurate re%resentation of the mass of

su$stance in the $urning 4one is the a!erage of the mass of limestone that can $e in the

$urning 4one and the mass of lime that amount of limestone would %roduce.

7&3 !z/&=94480+(0.56 94480 )

2 =73694 kg

'imilarly the density of this mi#ture !aries from limestone to lime so a good estimate of

the density of the mass in the 4one is

&3/&=&3+&

2 =2600+3300

2 =2950 kg /m3

2*


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V!z=V&3 /&+VV=V&3/& +0.40

0.60V&3/&=1.67 V&3

V&3 /&=7&3 !z /&

&3/&=

73684 kg

2950kg

m3

=25 m3

V!z=1.67 25 m3=41.8 m3

H!z=V&3A

= 57.6

1.52

=5.9 m

:here $4L !olume of the $urning 4one, m@

V&3/& L !olume of mass of limestone/lime in $urning 4one, m@

L !olume of the !oid s%aces, m@

S'/L density of limestone/ime mi#ture, kg/m@

H$4L height of $urning 4one, m

7&3 !z/&

L mass of limestone/lime mi#ture, kg

$eight of cooling %one

;ate of necessary heat transfer in cooling 4one to cool lime from 2**NC to *NC is

found $y

|q&|=7& 80

1200

%P& dT

:here%P& L s%ec. heat ca%acity of lime L *.>(TT0)

0.13

,(=gnie4ka, 2**5) (TL

tem%erature and ToL @


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123/204

= L cross sectional area of kiln, m2

h

%P.E(%P?k )

2

3 =2.876?

Dp .E +0.3023( ? D p.E)

0.35

(.#a,kop)is 5 2003)

:here CL s%ecific heat ca%acity of $ulk air L .*@ k?/kgA (eanko%lis, 2**@)

C'L s%ecific heat ca%acity of air at film tem%. L .*> k?/kgA (eanko%lis, 2**@)

Z'L !iscosity of air at film tem%erature L 2.*< R*5kg/ms (eanko%lis, 2**@)

k'L thermal conducti!ity of fluid at film tem%erature L >.8+ R*5k:/mA

(3ngineeringtool$o#.com)

L !oid fraction L *.>*

EL diameter of lime %articlesL log mean of si4e range (*.***.*>) L *.*85 m

"nserting the !alue of 0 for the $urning 4one gi!es

0.40 h

1.03 0.7 ( 1.04 2.074.69 ) 2

3=2.876 2.07 10

5

0.0650.7 +0.3023 ( 2.07 10

5

0.065 0.7 )0.35

h=0.066 kW

m2'

q$z=hG asG 7& (T&7%AT&7&)

:here hL heat transfer coefficientL *.*88 k:/m2A

as L s%ecific su

210d61b7-c21b-4e7f-a43f-14157b8e4c12-150508133022-lva1-app6891

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