8.5 - Introduction to Gas-solid Fluidized Bed Reactors

8/20/2019 8.5 - Introduction to Gas-solid Fluidized Bed Reactors

1/69

Introduction to

Gas-solid Fluidized Bed Reactors

CHEMICAL REACTION ENGINEERING LABORATORY

Proessor M! H! Al-"a##an


2/69

Outline$Contents

Introduction.

Fluidization Flow Regimes. Overall Gas (Voidage) and solids Hold-up.

Radial and Aial !olids Hold-"p #ro$iles.

Radial and Aial voidage distri%ution.

Gas and !olid &iing.

!cale-"p.

Reactor &odeling.



3/69

INTRO"%CTION



4/69

Fluidized Bed Reactor Co&'onents


T#e &aterial luidized is a solid (catal)st*!

T#e luidizin+ &ediu& is eit#er

a +as or a li,uid!

Gas distriutor

Inlet to c)clone


5/69

Advantages 'isadvantages

It as te a%ilit toprocess large volumeso$ $luid.

*cellent gas-solidcontacting.

Heat and mass trans$errates %etween gas andparticles are ig wencompared wit otermodes o$ contacting.

+o ot spot even wit

igl eotermalreaction.

*ase o$ solids andling.


,road residence time

distri%ution o$ te gas due

to dispersion and %pass

in te $orm o$ %u%%les.

,road residence time

distri%ution o$ solids due

to intense solids miing.

*rosion o$ internals.

Attrition o$ catalst

particles.

'i$$icult !cale-up due tocomple drodnamics.


6/69

Industrial Applications o$ Fluidized ,ed Reactor

Acrlonitrile % te !oio #rocess.

Fiscer-ropsc !ntesis.

#talic andride sntesis.

&etanol to gasoline and ole$in processes.

rac/ing o$ Hdrocar%ons (Fluid ataltic rac/ing0 etc).

oal com%ustion.

oal gasi$ication

ement clin/er production.

itanium dioide production.

alcination o$ A1(OH)2.

Granulation dring o$ east.

Heat ecange

A%sorption

+uclear energ ("ranium processing0 nuclear $uel $a%rication0

reprocessing o$ $uel and waste disposal).


3ang 4552


7/69

Fluidization Flow Regimes



8/69

Geldart.s Classic Classiication o Po/ders

Grou' A (Aeratale* 0- (e!+!1A&&o2idation o 'ro')lene* s&all&ean 'article size and$or lo/ 'article

densit) (345!6 +$c&7*1 +as ulesa''ear at &ini&u& ulin+ 8elocit)(%&*!

Grou' B (9and-Li:e* 0- (e!+!19tarc#*'article size 6;


9/69

Flow Regimes in Fluidized ,eds


6. Ruud van Ommen0 4552


10/69

&inimum Fluidization Velocit

mf

( ) ( )

+

Φ

−

Φ=− 75.1

1150

3

2

f mf p s

mf

mf p s

mf f

f pu D D

u g

ρ

µ ε

ε

ρ ρ ρ

is e7uation can %e used to calculate te minimum $luidization velocit

" i$ te void $raction em$ at incipient $luidization is /nown.

*perimentall0 te most common metod o$ measurement re7uires tat pressure drop

across te %ed %e recorded as te super$icial velocit is increased stepwise troug "m$

and %eond0 "m$ is ten ta/en at te intersection o$ te straigt lines corresponding to

te $ied %ed and $luidized %ed portions o$ te grap o%tained wen is plotted

against " on log-log coordinates.bed P ∆

>unii and Le8ens'iel (5??5*


11/69

,u%%ling Fluidization

is tpe o$ $luidization as%een called 8aggregative$luidization90 and undertese conditions0 te %edappears to %e divided intotwo pases0 te %u%%lepase and te emulsionpase.

e %u%%les appear to%e ver similar to gas%u%%les $ormed in ali7uid and te %eave ina similar manner. e

%u%%les coalesce aste rise troug te%ed.



12/69

Hi+# solid #old-u's (t)'icall) =-7=

) 8olu&e*!

Li&ited a2ial &i2in+ o +as!

9uitale or e2ot#er&ic and astreactions!

Good +as-solid contact and #ence1

a8ors reactant con8ersion!

#i+# +as lo/-rates o'eration and +ood

or isot#er&al o'eration! Fa8orale ed to surace #eat transer!


ur%ulent Fluidization

Turulent re+i&e #as t#e ollo/in+ eatures0-

Canada et al! 5?@


13/69

!ome commercial processes in tur%ulent

$luidization


Process Particle classification Typical gas velocity(m/s)

FCC regenerators Group A 0.5-.5

Acrylonitrile Group A !0.5

"aleic an#y$ri$e Group A !0.5

P#t#alic an#y$ri$e Group A !0.5

%t#ylene $ic#lori$e Group A !0.5

&oasting of 'inc sulfi$e Group A !.5

Bi et al! ;;;


14/69

Fast Fluidized ,ed

e $ast $luidization occurs as a result o$

continuing increasing in operating velocit%eond tat re7uired at tur%ulent

$luidization0 a critical velocit0 commonl

called te transport velocit ("tr)0 will %e

reaced were a signi$icant particle

entrainment occurs.

e F, as signi$icant industrial

applications %ecause o$ its e$$icienc0

operational $lei%ilit0 and overall

pro$ita%ilit (,erruti et al.0 :;;


15/69

Transition et/een Fluidization Re+i&es!

Grace (:;=>a) summarized te e$$ects o$ particles properties and operating conditionson $luidization %eavior and prepared a $low regime diagram. e $low regime diagramwas $urter modi$ied % ?unii and 1evenspiel (:;;@).

For given particles and operating velocit0 te gas-solid contact pattern can %edetermined using tis diagram. 1i/ewise0 $or a given $low regime0 tis diagram couldprovide availa%le com%inations o$ particle properties and gas velocit.

Yan+ ;;7


16/69

Fluidization diagram

av

s

GsU U

ρ ε −= 9olid #old-u'

Yerus#al&i and Can:urt1 5?@;


17/69

&etods $or Regime ransition Identi$ication

!everal measurement metods ave %een utilized to

determine te transition $rom %u%%ling or slugging totur%ulent $luidization wic can %e classi$ied into treegroups-

Visual O%servation0. #ressure 'rop-versus Velocit diagram.

local and overall %ed epansion.

,ased on signals $rom pressure transducers0 capacitance

pro%es0 optical $i%er pro%es0 B-ra $acilities.


,i et al. 4555


18/69

Generalized e$$ect o$ operating and design parameters on

$low regime transition

Para&eter Eect on lo/ re+i&e transition

#ressure In general0 pressure accelerates te $low regime transition0 tere% decreasetransition velocit (1anneau 0 :;>50 ai et al. :;=;0 3ates :;;>).

emperature ransition velocit increases as te temperature is increased0 (#eeler et al.0:;;;0 ai et al.0 :;=; and Fo/a et al.0 :;;>).

!tatic ,ed Heigt

e transition velocit was almost independent o$ te static %ed eigt0 wicvaried $rom 5.C to :.5 m (Grace and !un :;;5). !imilar results were reported% ai (:;=;) and !atiDa and Fan (:;=


19/69

Eect o colu&n dia&eter

"c decreases wit increasing column diameter $or small columns

(less tan 4 m)0 %ecoming insensitive to column diameter $or 't E5.4 m.

!imilar trends were o%served % ao and 3ang (:;;:) in columnswit internals.


Cai (5??*


20/69

ai et al.0 :;=;0 *$$ect o$ operating temperature and pressure onte transition $rom %u%%ling to tur%ulent $luidizationJ0 AIH*

!mposium series0 =.

,i et al.0 (4555)0 A state-o$-art review o$ gas-solid tur%ulent

$luidizationJ0 emical engineering science0


21/69

ODERALL GA9 (DOI"AGE*

AN" 9OLI" HOL"%P



22/69

Overall gas oldupIt is an important drodnamic parameter wic is de$ined as te $ractiono$ reactor dnamic volume occupied % te gas. pical relationsip

%etween overall gas (voidage) oldup and super$icial gas velocit in were

is sown in $ollowing scematic

A8idan and Yerus#al&i1 5?@;


23/69


*$$ect o$ operating and design parameters on gas oldup or %ed

densitInertial %ed

eigtIt is independent on initial %ed eigt (Hilal et al.0 4554).

#article size e dimensionless densit (ρρm$ ) decreases as te particle

size is reduced. e %ed epansion is larger $or a wide tan

a narrow distri%ution o$ particles. (Grace and !un0 :;;:).#articledensit

ρρm$ decreases as te particle densit decreases.

olumndiameter

e %ed epansion increases wit increasing %ed diameter.

emperature e voidage increases wit increasing temperature.

Hil l t l 4554


24/69

*$$ect o$ column diameter

e %ed epansion

increases wit increasing%ed diameter (Vol/ et al.:;>40 Bavier et al.0 :;@=).

e %ed epansiondecreases wit increasing%eds0 a condition eattri%uted to tedevelopment o$ %u%%lecanneling in te larger%eds ('e-Groot :;>@).

e %ed densit is greatest$or te smaller diameter %edat te same ecess velocit(Hilal et al.0 4554).

Hilal et al. 4554

&atsen :;;>


25/69

*$$ect o$ pressure

Higer operating pressures reduced te %ed epansion (H Hmf )

(&iller et al.0 :;=:) .

e increase o$ %ed epansion wit pressure (i%a et al.0 :;=>0 and

itester et al.0 :;=C) .

e psical properties o$ te $luidizing gas0 densit and viscosit didnot ave an signi$icant e$$ect on %ed epansion ('enloe0 :;=4)0

and ?nowlton0:;@@).

,ed epansion increased signi$icantl wit pressure %ut tis

in$luence0 ver strong at low pressures0 seemed to reac a maimumat approimatel =55/#a and decreased terea$ter up to :455/#a

(1lop et al.0 :;;


26/69

!ome !elected Re$erences

Avida and 3erusalmi (:;=4)0 ,ed epansion in ig velocit

$luidizationJ0 #owder tecnolog0 240 442-424.

&eller et al.0 (:;=C)0 e e$$ect o$ particle densit on te old-up in

a $ast $luid %edJ0 AIH* !mposium series0 +o.42C0 =50


27/69

Radial and A2ial 9olids Hold-%' Proiles



28/69

Radial #ro$ile

Altoug0 overall gas oldupas %een traditionall used$or caracterization o$drodnamics o$ $luidized%ed columns0 it is a singlelumped parameter. Hence0$or detailed caracterization0one need to loo/ at te wasolid is distri%uted across tereactor.

e local solid oldup wasgreater near te wallcompared to tat near tecenterline and tat te radialparticle velocit was nearlpara%olic (Van oonen0 :;>4K&a%rou/ et al. 455


29/69

Aial #ro$ile

&a%rou/ et al. 455<

e aial solid old-up o%tained % $i%er optical needle pro%e and AR#

sows a 7uasi linear pro$ile (&a%rou/ et al. 455


30/69

Measure&ent tec#ni,ues o Radial and A2ial 9olids Hold-%' Proile

&a%rou/ et al. 455<AR#



31/69


,i et al.0 (4555)0 A state-o$-art review o$ gas-solid tur%ulent$luidizationJ0 emical engineering science0


32/69

Gas and 9olid Mi2in+



33/69

(a* A2ial 9olid Mi2in+


1ee and ?im :;;5

'u et al. 4554


34/69

(* Radial 9olid Mi2in+

'u et al. 4554



35/69

(a* A2ial Gas Mi2in+


Fo/a et al. :;;>

Gas Mi2in+

!elected gas miing studies


36/69

nvestigators "o$el Tracer

inection

$p (*m) +(m) , (m/s) ,c (m/s) +'g (m/s)

Lee and Kim (1989b)(Air-CO2)

Diff!i"n #r"$e!! %i&'aia and radiadi!#er!i"n $"effi$ien&!

*&ead+ !&a&e 3,2 0.1 0.80.881.001.081.20

0.85 0.220.2350.2300.250.215

Li and ein!&ein (1989)(Air-/e)

One dimen!i"nadi!#er!i"n

*&ead+ !&a&e 59 0.152 0.10.51.3

0.3 0.10.550.,0

Li and (1991)(Air-/2)

1D #!ed"-'"m"gene"!diff!i"n

"n-idea #!e 58 0.09 1.01.01.0

0. 0.50.510.5,

"ka e& a. (199)(Air-Ar)


!e 75 0.1 0.170.51,0.,1

0.,910.7920.8920.9771.0511.12

0.7 0.0800.1020.11

0.1950.1300.1,70.0970.0,00.075

"ka e& a. (199,)(Air-Ar)

%"-#'a!e m"de "f4anDeem&er (1980)

!e (e!! &'an0.5 !)

75 0.1 0.210.0.50.,

0.70.80.9

0.55 0.090.1,0.190.175

0.10.130.1

'ang e& a. (199,)(Air-O2)

!ed"-'"m"gene"!m"de %i&' aia andradia di!#er!i"n

*&ead+ !&a&e 77., 0.19 0.3920.5880.781.078

0.5 0.370.510.,190.783

ei e& a. (1993)(Air-fe ga!)


*&ead+ !&a&e 58 5.7, 1.2,1.1

0.1 3.053.

ar!i&" e& a. (2002)('eim and #'"!#'"r)

2-D Di!#er!i"n m"de 6n!&ead+ !&a&e ,0 0.203 0.21-1.5 0.5 "&&ed in ig.

!elected gas miing studies


37/69

(%) Radial Gas &iing

For tur%ulent $luidized %eds0 almost all gas miing studies ave %eenconcentrated on te aial miing0 ver limited in$ormation is availa%le regarding

te radial gas miing ('u et al. 4554).

Lee and >i& 5?? "u et al! ;;

9olids lo/ 'attern and &i2in+


38/69

Radioactive particle trac/ing tecni7ue $or solids miing investigations

&ostou$i and aou/i0455:

:


39/69

Radioactive particle trac/ing

selected results

&ostou$i and aou/i0455:

!olids di$$usivities &ostou$i and aou/i 455:


40/69

!olids di$$usivities &ostou$i and aou/i0 455:


41/69

Velocit $ield0 velocit gradient

and aial solid di$$usivit

&ostou$i and aou/i0

455:


42/69


1ee and ?im (:;=;)0 Gas miing in slugging and tur%ulent $luidized

%edsJ0 em. *ng. omm.0 =>0 ;:-:::.

Fo/a et al.0 (:;;>)0 Gas pase drodnamics o$ a gas-solid

tur%ulent $luidized %ed reactorJ0 emical engineering science0+o.


43/69

Fluidized ,ed !cale-up


9cale u' criteria


44/69

Glic/sman et al0 :;;20 :;;=

Horio et al.0 :;=>

van den ,lee/ and !couten0 :;;>

9cale-u' criteria

!anderson and Rodes0

455<


!anderson and Rodes0 455


45/69

#roperties o$ te !ilica !and ,ed &aterials "sed in te !imilarit *periments

Dertical distance ro& to' surace o distriutor 'late to eac# 'ressure

ta''in+ 'oint!

e tapping point eigts correspond to te same dimensionless pro%e eigt

(hHs) at eac scale.


46/69

Results or t#e a8era+e asolute de8iation

o di&ensionless 'ressure or correct and

&isscaled eds!

&aterials A and , in te :C>- and 255-mm%eds0 respectivel0 are correctl scaled.

&aterials AP and ,P in te :C>- and 255-mm

%eds0 respectivel0 are also correctl scaled0

%ut di$$erent $rom te AQ, pair.

Co&'arison o t#e di&ensionless a8era+e

c)cle re,uenc) or t#e 'ressure

luctuation data or all 'reli&inar)

e2'eri&ents!

9cale-u' criteria e8aluation in s&all scale luidized eds

!anderson and Rodes0 455<


9 l it i l ti i l l l idi d d


47/69

Ran+es o 9u'ericial and "i&ensionless

9u'ericial Gas Delocities and Particle

Re)nolds Nu&er or t#e H)drod)na&ic

9i&ilarit) E2'eri&entsP

Co&'arison o t#e nor&alized ense&le-

a8era+ed a&'litude s'ectra or t#e

di&ensionless 'ressure luctuations

ro& t#e 56-&& ed /it# &aterial A and

t#e 7;;-&& ed /it# &is&atc#ed ed

&aterial B at lo/ +as 8elocit)!


9cale-u' criteria e8aluation in lar+e scale luidized eds


!anderson and Rodes 455


48/69


asolute de8iation o 'ressure &easured

ro& 'ressure 'roes located at h $Hs=;!@@

and r $R=; in all i8e luidized eds or a

ran+e o di&ensionless +as 8elocities!

All %eds0 wit te eception o$ te >55-mm

%ed wit material '0 ave %een scaled using

te simpli$ied scaling criteria.


c)cle re,uenc) o 'ressure &easured

ro& 'ressure 'roes located at h $Hs=;!6

and r $R = ; in all i8e luidized eds or a

ran+e o di&ensionless +as 8elocities!

All %eds0 wit te eception o$ te >55-mm

%ed wit material '0 ave %een scaled using

te simpli$ied scaling criteria.



! d d R d 455


49/69

A+ree&ent &a' s#o/in+ ,ualitati8el) #o/ /ell t#e 'ressure luctuations

ro& t#e 8arious 'roe locations and su'ericial +as 8elocities ro& 5!=

to 7!=Umf &atc# or t#e scaled luidized eds!

,lac/ dots indicate te location o$ te pro%e tips in te actual measurementrunsK te results ave %een etended across te %ed widt assuming te

%eavior to %e aismmetric (ecellent agreement trends are

indistinguisa%leK good agreement trends are similar wit some scatterK poor

agreement trends are onl marginall %etter tan $or te misscaled scenario).



!anderson and Rodes 455


50/69

Co&'arison o t#e nor&alized 'roailit)

distriutions or t#e correctl) scaled eds

(7;; &&1 &aterial B 5=; &&1 &aterial "*

/it# t#e &is&atc#ed ed (;; &&1 &aterial

"* at lo/ +as 8elocit) or t#e 'roe located

at r $R=; and h $H M;!!

Co&'arison o t#e nor&alized 'roailit)

distriutions or t#e correctl) scaled eds

(56 &&1 &aterial A 7;; &&1 &aterial B

5=; &&1 &aterial "* at #i+# +as 8elocit)

or t#e 'roe located at r $R M; and

h $H M;!@@!



Additional e8aluation or scale u' criteria Glic:s&an et al 5??7


51/69

Additional e8aluation or scale-u' criteria1 Glic:s&an et al!1 5??7



52/69

!olid $raction pro$iles0 plastic particles!olid $raction pro$iles0 glass particles

1ow velocit

Hig velocit

9elected Reerences


53/69

:. !anderson0 6on0 and Rodes0 &artin0 ,u%%ling Fluidized ,ed !caling 1aws

*valuation at 1arge !cales0 AI* 6ournal0 455-4>;C.

4. Glic/sman 1R0 Hre &0 olosun ?. !impli$ied scaling relationsips $or

$luidized %eds. Powder Technol. :;;2K@@:@@-:;;.

2. Horio &0 +ona/a A0 !awa 30 &uci I. A new similarit rule $or $luidized %ed

scale-up. AIChE J . :;=>K24:C>>-:C=4.

C. Glic/sman 1R. !caling relationsips $or $luidized %eds. Chem Eng Sci.

:;==KC2:C:;-:C4:.

.

=. Glic/sman 1R. Fluidized %ed scale-up. In 3ang -0 ed. Fluidization !olids

Handling and #rocessingIndustrial Applications. #ar/ Ridge0 +6 +oesK

:;;;.

9elected Reerences



54/69

Reactor &odeling


Re8ie/ o Fluidized ed reactor &odelin+(&aeca and Grace et al 455>)


55/69

#redicting te %eavior o$ a gas-solid $luidized-%ed reactor re7uires in$ormation on te stoiciometr0 termodnamics0eat and mass trans$er0 reaction rates and $low pattern o$ te di$$erent pases in te reactor (?unii0 1evenspiel0 :;;5).

&an reactor models ave %een proposed $or $luidized %ed reactors.

In addition to tose reviewed % 3ates (:;=2)0 race (:;=>) and Ho (4552)0 more recent ones include (ompson0 ,i etal. :;;;)0 (A%%a0 Grace et al. 4552) and (en0 3ang et al. 455C).

*ac o$ tese incorporate a di$$erent set o$ assumptions leading to a di$$erent set o$ matematical epression tosimulate te reactor.

&ost models are developed $or a speci$ic process0 or else so simpli$ied tat te cannot ade7uatel descri%e allimportant $eatures o$ reactors and processes o$ real practical interest. &oreover0 te availa%le models areoverwelmingl restricted to stead state operation.

ile progress as %een made in adding some o$ te compleities encountered in practice0 e.g. allowance $or gradualtransitions %etween $low regimes (ompson0 ,i et al.0 :;;;K A%%a0 Grace et al.0 4552)0 volume cange due to reaction(A%%a0 Grace et al.0 4554)0 mem%ranes to selectivel introduce or remove one species (en0 #rasad et al.0 4552)0 anduse o$ a sor%ent to selectivel capture one product component (#rasad0 *lnasaie0 455C).

"ntil 455< tere are no models general enoug to incorporate all o$ tese $eatures. Recent wor/ as %een done toandle and include all tese $eatures (&aeca and Grace et al. 455>)0 wile also $acilitating te analsis o$ dnamic%eavior.

(&aeca and Grace et al. 455>).

F%N"AMENTAL "IFFERENTIAL "YNAMIC MO"EL FOR


56/69

F%N"AMENTAL "IFFERENTIAL "YNAMIC MO"EL FOR

CATALYTIC 9Y9TEM9

e model is initiall developed in rectangular coordinates $or simplicit0 %ut can %etrans$ormed to an oter coordinate sstem (e.g. clindrical curvilinear) using elementarvector calculus teor o$ vector operators (&aeca and Grace et al. 455>).

is model includes most eisting $luid %ed reactor models as special cases0 allowingclear connections to %e esta%lised among te models and sowing te signi$icance and

implications o$ eac simpli$ing assumption. is will lead to a more sstematic approacto $luidized-%ed reactor modeling0 $acilitating wat as %een called te optimum degree o$sopisticationJ (Aris0 :;>:).

Once te more general model as %een developed and de%ugged0 we will %e in a positionto appl it to important and potentiall via%le industrial processes suc as partial oidationreactions and drogen production processes (&aeca and Grace et al. 455>).J


Generalization o Models


57/69

Generalization o Models

e set o$ generalizations $or te model is as $ollows

:) e dnamic e7uations ta/e into consideration in a rigorous manner te eat and masscapacities o$ te gases and solids in eac pseudo-pase (*lnasaie0 *lsisini0 :;;2).

4) e model e7uations can %e written in an coordinate sstem.

2) e development is $or a sstem o$ !C" components and !#" reactions0 depending on te$eedstoc/reactions.

C) e model is not restricted to a single $low regime. Its drodnamic parameters can %e

calculated as proposed % (A%%a0 Grace et al.0 4552) $or several adDacent $low regimes.

) e model deals wit anisotropic mass di$$usion and eat conduction.

@) e model ta/es into consideration tree-dimensional convective velocities (,ird0 !tewart et al.04554).

=) e convective velocities can %e calculated using an $unction (e.g. accounting $or canges in tenum%er o$ moles and gas volumetric $low (A%%a0 Grace et al.0 4554)). anges wit time0temperature0 pressure and cemical reaction are also covered.J



Generalization o Models (cont!*


58/69

;) e model accounts $or catalst cemisorption (*lnasaie0 *lsisini0 :;;2) andsolid capture o$ an species.

:5) Hdrodnamic parameters are o%tained $rom appropriate correlations and e7uationsrelevant to te di$$erent $low regimes (Grace0 A%%a et al.0 :;;;).

::) e model accounts $or deactivation o$ catalst (en0 3an et al.0 455C).

:4) e model considers te use o$ mem%ranes to remove certain products (i.e. to %rea/

te termodnamic %arrier) or to suppl certain reactants (i.e. to improve te sstemselectivit to a desired product). &em%rane deactivation $uctions can also %eincluded (Raic S Fole0 :;;) can %e used including0 were appropriate0 sensi%leand latent eats (in case o$ cange o$ pase).

:).

Pseudo '#ase a''roac#


59/69

Pseudo-'#ase a''roac#

ontrol volumes $or te conservation %alances include %ot gas and solid

pases0 witout ignoring te e$$ect o$ te solids on te sstem dnamics (Gascarried inside te solids and te eat and mass capacitances o$ te solids are

included in te mole and energ %alances).

erms are included $or an non-cataltic solid pase0 wic sor%scaptures ano$ te species in te reactor (i.e. $or car%on dioide capture to enance steam

re$orming and separate O4 $or su%se7uent se7uestration).

9olid sorent (se,*


Mole and Ener+) Funda&ental alances


60/69

Mole and Ener+) Funda&ental alances

&aeca and Grace et al. 455>).


Mole Balance


61/69

Mole Balance

e num%er o$ mole %alance e7uations is !C .! (P ) were !C is te num%er o$

cemical species and ! (P ) is te num%er o$ pseudo-pases. e generalized mole

%alance o$ eac compound in pase (p) is as $ollows-

e molar rate %alance over a di$$erential element $or pase ($) is given %


Ener+) Balance


62/69

+)

*nerg dissipation due to viscous e$$ects is neglected. e num%er o$ energ %alance

e7uations is ! (P ) were ! (P ) is te num%er o$ pseudo-pases. e generalized energ

%alance $or pase (p) is as $ollows-

e di$$erential energ %alance $or pase ($) is given %


Pressure Balance


63/69

Pressure Balance

A simpli$ied di$$erential pressure %alance in te z direction $or pase ($) is given %

e densit o$ pase ($) can %e calculated using te void $raction as


Boundar) and Initial Conditions


64/69

e di$$erential control volume o$ pseudo-pase ($) as no eternal ecange wit te surroundings.

e interaction o$ te pseudo-pase wit its surroundings sould tus %e included in te %oundar

conditions.

e %oundar conditions sould %e speci$ied according to te geometric arrangement o$ te sstem0

and ma var $rom case to case. e %oundar conditions (i.e. $or te simplest single-pase case) ma assume aial smmetr0 zero

$lu at te walls and 'anc/werts criteria wen te di$$usion in te $ore and a$t sections is negligi%le

('anc/werts0 :;


65/69

CA9E 9T%"Y0 APPLICATION OF MO"EL TO AN

OYCHLORINATION FL%I"IE"-BE" REACTOR

Here0 as an eample o$ application o$ te compreensive model0 itsimulates an industrial scale $luidized %ed reactor wic is carried out wit

special empasis on te oclorination process as a means o$ producing

etlene dicloride (*') $rom etlene (*3). ile tis represents a

simpli$ied special case o$ te $ull model0 it demonstrates man o$ te

$eatures o$ te model0 wile also $acilitating veri$ication o$ te numerical

code (written in &atla% @)0 since tis case as alread %een solvedpreviousl (A%%a et al.0 4554) using g-#RO&!.

e etlene oclorination process involves comple reactions wit

non-linear temperature dependence (A%%a0 Grace et al.0 4554). 'espite

te great industrial impact o$ oclorination reactions0 $ew studies are

availa%le in te literature (arru%%a0 !pencer0 :;@5) and detailed studies(e.g. (*llis0 A%%a et al.0 4555) are proprietar.J

(&aeca and Grace et al. 455>)




66/69


OYCHLORINATION FL%I"IE"-BE" REACTOR (ContJd*

Reactor 'ara&eters

e reaction networ/ was simpli$ied as suggested % (A%%a0

Grace et al.0 4554). e assume tat te main product is *'.

,products include a $ew percent o$ car%on oides (O) and less

tan one percent clorinated drocar%ons (I) tat eclude

*'.


Results(&aeca and Grace et al. 455>).


67/69

redi$&ed !&ead+-!&a&e m"ar f"%! in &'e 'ig'-

and "%-den!i&+ #!ed"-#'a!e! 4! 'eig'& in &'e rea$&"r.

redi$&ed !&ead+-!&a&e /C m"ar f"%! in &'e 'ig'-

and "%-den!i&+ #!ed"-#'a!e! 4! 'eig'&.

redi$&ed !&ead+-!&a&e "+gen m"ar f"%! in &'e

'ig'- and "%-den!i&+ #!ed"-#'a!e! 4! 'eig'&.redi$&ed !&ead+-!&a&e DC m"ar f"%! in &'e

'ig'- and "%-den!i&+ #!ed"-#'a!e! 4! 'eig'&.

&aeca and Grace et al. 455>).

Results (ContJd*

(&aeca and Grace et al 455>)


68/69

redi$&ed !&ead+-!&a&e /2O m"ar f"%! in &'e

'ig'- and "%-den!i&+ #!ed"-#'a!e! 4!

'eig'&.

redi$&ed !&ead+-!&a&e CO m"ar f"%! in &'e

'ig'- and "%-den!i&+ #!ed"-#'a!e! 4! 'eig'&.

redi$&ed !&ead+-!&a&e im#ri&+ m"ar

f"%! in &'e 'ig'- and "%-den!i&+

#!ed"-#'a!e! 4! 'eig'&.

re!!re 4! rea$&"r 'eig'&. redi$&ed aia #r"fie "f !&ead+-!&a&e

"4era $"n4er!i"n.


Re&ar:s


69/69

T e generalized dnamic model provides a new approac $or simulating

comple $luidizedQ%ed cataltic sstems.

T e model is a%le to descri%e $luidized %ed reactor sstems reling on $ewer

assumptions tan oter models in te literature. en di$$erent com%inations

o$ assumptions are incorporated in te model0 it simpli$ies to a num%er o$ $luid

%ed reactor models previousl presented in te literature.

Re&ar:s(&aeca and Grace et al. 455>).

Documents

8.5 - Introduction to Gas-solid Fluidized Bed Reactors