Gas–Liquid and Gas-liquid-solid Reactions

8/18/2019 Gas–Liquid and Gas-liquid-solid Reactions

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Gas – Liquidand

Gas- Liquid –Solid Reactions

A. Gas –Liquid Systems


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Proper Approach to Gas-LiquidProper Approach to Gas-LiquidReactionsReactions

References• Mass Transfer theories• Gas-liquid reaction regimes• Multiphase reactors and selection criterion• Film model: Governing equations, problemcomplexities• xamples and !llustrative Results

• "olution #lgorithm $computational concepts%


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Transport E ects in Gas-LiquidTransport E ects in Gas-Liquid

ReactionsReactions

Two- lm theory &' ('G' (hitman, )hem' * Met' ng', + & . $& +/%' +' (' 0' 1e2is * (' G' (hitman, !nd' ng' )hem', &3, +&4$& + %'

Penetration theory 5' 6' 7anc82erts, Trans' Farada9 "oc', 3 / $& 4 %' 5' 6' 7anc82erts, Trans' Farada9 "oc', . / $& 4&%' 5' 6' 7anc82erts, Gas-1iquid Reactions, McGra2-;ill,


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Two- lm Theory AssumptionsTwo- lm Theory Assumptions

!" A sta nant layer e#ists in $oth the as andthe liquid phases"

%" The sta nant layers or lms ha&e ne li i$lecapacitance and hence a local steady-statee#ists"

'" (oncentration radients in the lm are one-dimensional"

)" Local equili$rium e#ists $etween the the asand liquid phases as the as-liquid interface

*" Local concentration radients $eyond thelms are a$sent due to tur$ulence"


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Two-Film Theory ConceptTwo-Film Theory Concept W.G. Whitman, Chem. & Met. Eng., 29 14 !192"#.W.G. Whitman, Chem. & Met. Eng., 29 14 !192"#.

Bulk LiquidBulk Gas

p A p Ai

CAi

•

•

CAb

x = 0

xx + x

L

Liquid FilmGas Film

x = Lx = G

p Ai = H A CAi


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Two-Film TheoryTwo-Film Theory- $ingle %eaction in the i'(i) Film -- $ingle %eaction in the i'(i) Film -

A (g) + b B (liq) P (liq)

RA kg-moles A

m 3liquid - s = - k mn C A

m C Bn

Closed form solutions only possible for linear kinetics or when linear appro imations are introduced

! " # are non$olatile


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Film Theory Mo)el *or a $ingle +on olatileFilm Theory Mo)el *or a $ingle +on olatileGa - i'(i) %eactionGa - i'(i) %eaction

2*

2

2

2

( ) ( ) ( )

0

0 0

A L

B L

A g bB l P l

d A D r at x A A at x A A

dx

d B dB D br at x at x B Bdx dx

δ

δ

+ →

= = = = =

= = = = =

% &iffusion - reaction equations for a sin'le reaction in the liquid film

are(

% )n dimensionless form* the equations become dependent on twodimensionless parameters* the +atta number +a and q , (

( )1/ 2

1* **

21

m nmn

m n D L B A mn L

R A

For r k A B

t B D Ha D k A B q

t m bA D

−

=

= =+>=


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% &iffusion - reaction equations for a

sin'le reaction in the liquid film are(

A A A A R xC Dt C +∂∂

=∂∂

2

2

B B

B B R

xC D

t C +∂∂=∂∂ 2

2

Penetration Theory +odelPenetration Theory +odel


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Compari on etween TheorieCompari on etween Theorie

• Film theory :– kL∝ D, δ - film thickness

• /enetration theory :

– kL∝ D1/2Higbie model t * - life of surface li uid

element

Danck!erts model s - a"erage rate of surface

rene!al

'

* A

L R D

k C C δ

=−>

'

* *2 A

L

R Dk

C C t π =−

>

'

* A

L

Rk Ds

C C =−

>

=

=

=


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Ga - i'(i) %eaction %egimeGa - i'(i) %eaction %egime

Very l!"

#apid pseud!$s% !r m%& !rder

' s%a %a e!us Fas% (m )

Ge eral (m ) !r ' %ermedia%e l!" *i usi! al

' s%a %a e!us , ur a-e


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%eaction-0i**( ion %egime 0e*ine)%eaction-0i**( ion %egime 0e*ine)y Characteri tic Timey Characteri tic Time

% Slow reaction re'ime %* //% # kL=k L0

– Slow reaction-diffusion re'ime ( %* //% # //% .

– Slow reaction kinetic re'ime ( %* //% . //% #

% ast reaction re'ime ( %* %# kL=1 A k L0 k L0

– )nstantaneous reaction re'ime( kL

= 1A

kL

0


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Gas Abs!rp%i! A--!mpa ied by #ea-%i! i %&e Liquid

Assume 3 - nd order rate

Ha%%a 4umber 3

1i 4umber3

1 &a -eme % Fa-%!r3

H k k K g L L

111 +=

2$


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1ig&% (A 6 H) regimes -a be dis%i guis&ed3

A7 ' s%a %a e!us rea-%i! !--urs i %&e liquid ilm

B7 ' s%a %a e!us rea-%i! !--urs a% gas8liquid i %er a-e

% Hig& gas8liquid i %er a-ial area desired% 4! 8is!%&ermal e e-%s likely

29


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C7 #apid se-! d !rder rea-%i! i %&e ilm7 4! u rea-%ed A pe e%ra%es i %!bulk liquid

*7 Pseud! irs% !rder rea-%i! i ilm: same Ha umber ra ge as C7

Abs!rp%i! ra%e pr!p!r%i! al %! gas8liquid area7 4! 8is!%&ermal e e-%s s%illp!ssible7

2;


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.aximum %empera%ure di ere -e a-r!ss ilm de el!ps a% -!mple%e mass%ra s er limi%a%i! s

>empera%ure di ere -e !r liquid ilm "i%& rea-%i!

>rial a d err!r required7 4! is!%&ermali%y se ere !r as% rea-%i! s7

e7g7 C&l!ri a%i! ! %!lue e

2?


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- $(mmary -- $(mmary -imiting %eaction-0i**( ion %egimeimiting %eaction-0i**( ion %egime

"lo2 reaction 8inetic regime• Rate proportional to liquid holdup and reaction rate and in?uenced b9

the overall concentration driving force• Rate independent of 8 la @and overall concentration driving force

"lo2 reaction-diAusion regime• Rate proportional to 8 la @and overall concentration driving force• Rate independent of liquid holdup and often of reaction rate

Fast reaction regime• Rate proportional to a @,square root of reaction rate and driving force to

the po2er $nB&%C+ $nth order reaction%• Rate independent of 8 l and liquid holdup

!nstantaneous reaction regime• Rate proportional to 8 1 and a @• Rate independent of liquid holdup, reaction rate and is a 2ee8 function

of the solubilit9 of the gas reactant


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Gas- liquid – solid systems


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9;

G Li id S lid C l / d R i A0'12!0l13#0l1


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Gas Limi%i g #ea-%a % (C!mple%ely e%%ed Ca%alys%)

( )( )

( ) ( )( )

( )( )

( )( )

( )

( ) pv B p s Bl

A

g

H

g Bvo A

sl p

a

g B

s B pv

Av

k ak a K

H A A

k R

sreact mmol

A Aa

A H

Aa

sreact mmol

sreact mmol Ak

scat mmol Ak

A

η ε

ε η

ε η

−++=−=

−

−

−

Ω=

1111

1

:.RATE(APPARENT)OVERALL

k :solid-Liquid-

:liquid-!"s-

lu#$%$"& o% ou i $%

.RATETRAN+PORT

lu#$%$"& o% ou i $%

.1 :,ATAL +TNRATE

olu#$&" "l s u i $%

.:RATENET ,

0

s

11

0

0

0

5$

Gas – Liquid Solid Cataly/ed Reaction A0'12!0l13#0l1

*epe de e ! Appare % #a%e C! s%a % ( k ) !


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*epe de -e ! Appare % #a%e C! s%a % ( k app ) !>ra sp!r% ( k ls , p ) a d i e%i- Parame%ers ( k v )

( ) ( ) ( )

( )

( )( )

( ) ( ) sreact mmol a B Bk

sreact mmol Bk

scat mmol Bk

l P l B g A

p sl ls

B s pv

v

.:lu#$)%$"& o% ou i( $%

%" $T%" s o%

.1:lu#$)%$"& o% ou i( $%

&" "l siR" $

.:olu#$)&" "l s u i( $%

%" $i $ i&&" "l s$ $d&o# l$ $lo ,"s$-l$)( o ol" i%$"& "li#i i 3Liquid

:R$"& io

0

0

0

−

−

=+

ε η

( )( )

( ) Bv p pls

L Lapp Bv p

k ak

B Bk Bk

sreact mmol

ε η

ε η

−+

=−−

111

1

.%"'$(" "%$ ')O $%"ll

1

Liquid limiting reactant (nonvolatile) 4 Case of completely wetted catalyst


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Clearly is determined by transport limitations and byreactor type and flow re'ime.

)mpro$in' only impro$es if we are not already transport

4ur task in catalytic reactor selection* scale-up and desi'n is toeither ma imi/e $olumetric producti$ity* selecti$ity or product

concentration or an ob5ecti$e function of all of the abo$e. 6he keyto our success is the catalyst. or each reactor type consideredwe can plot feasible operatin' points on a plot of $olumetricproducti$ity $ersus catalyst concentration.

vm

aS vm

#"5vm

#"5 x x #"5 x#"5vm

aS

io&o &$ %"&" "l s

"& i is $&i i&

0 =

=

reactor mcat kg

x

cat kg P kg

S a

2?


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ey M(ltipha e %eactorey M(ltipha e %eactor


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( le Col(mn in )i**erent mo)e( le Col(mn in )i**erent mo)e


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ey M(ltipha e %eactor /arameterey M(ltipha e %eactor /arameter

Tram$ou,e P" et al" .(hemical Reactors / 0rom1esi n to 2peration3 Technip pu$lications 4%55)6


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2@


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58$0908$00

$08$00$08;090008$0 9

$;08?00

90


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9$


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.ul%ip&ase #ea-%!r >ypes !r C&emi-alpe-ial%y a d Pe%r!leum Pr!-esses

95


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3. Basic Design Equations forMultiphase Reactors

5'#' Ramachandran, 5' 1' Mills and M' 5'7udu8ovic

rama>2ustl'edu D dudu>2ustl'edu

(hemical Reaction En ineerin

Multiphase Reaction Engineering:Multiphase Reaction Engineering:

mailto:[email protected]:[email protected]


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>ypes ! .ul%ip&ase #ea-%i! s

Gas8liquid "i%&!u% -a%alys%

Gas8liquid "i%& s!luble -a%alys%

Gas8liquid "i%& s!lid -a%alys% Gas8liquid8liquid "i%& s!luble

or s!lid -a%alys%

Gas8liquid8liquid "i%& s!luble

or s!lid -a%alys% 0two liquid phases1

%raig&% !r"ard

C!mplex

#ea-%i! >ype *egree ! *i i-ul%y


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Hierar-&y ! .ul%ip&ase #ea-%!r .!dels

1mpiri-al

'deal Fl!" Pa%%er s

P&e !me !l!gi-al

V!lume8A eragedC! ser a%i! La"s

P!i %8"ise C! ser a%i!La"s

%raig&% !r"ard

'mpleme %a%i! ' sig&%

Very li%%le

Very *i i-ul%!r 'mp!ssible

ig i i-a %

.!del >ype


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!asic Reactor 6ypes for Systems 7ith SolidCatalyst 0 three or four phase systems1

%Systems with mo$in' catalysts- stirred tank slurry systems- slurry bubble columns- loop slurry reactors- three phase fluidi/ed beds 0ebulated beds1

%Systems with sta'nant catalysts-packed beds with two phase flow( down flow*up flow* counter-current flow- monoliths and structured packin'

- rotatin' packed beds

P& ! A %i l # %! P !


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P&e !me a A e-%i g lurry #ea-%!r Per !rma -e

Fl!" dy ami-s ! %&e mul%i8p&ase dispersi!8 Fluid &!ldups , &!ldup dis%ribu%i!8 Fluid a d par%i-le spe-i i- i %er a-ial areas8 Bubble siDe , -a%alys% siDe dis%ribu%i! s

Fluid ma-r!8mixi g8 P*FEs ! #>*s !r %&e ari!us p&ases

Fluid mi-r!8mixi g8 Bubble -!ales-e -e , breakage8 Ca%alys% par%i-le aggl!mera%i! , a%%ri%i!

Hea% %ra s er p&e !me a8 Liquid e ap!ra%i! , -! de sa%i!8 Fluid8%!8"all luid8%!8i %er al -!ils e%-7

1 ergy dissipa%i!8 P!"er i pu% r!m ari!us s!ur-es

(e.g 7 s%irrers luid8 luid i %era-%i! s )

#ea-%!r .!del

P&e !me a A e-%i g Fixed8Bed #ea-%!r Per !rma -e


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Fluid dy ami-s ! %&e mul%i8p&ase l!"s

8 Fl!" regimes , pressure dr!p8 Fluid &!ldups , &!ldup dis%ribu%i!8 Fluid8 luid , luid8par%i-le spe-i i- i %er a-ial areas8 Fluid dis%ribu%i!

Fluid ma-r!8mixi g8 P*FEs ! #>*s !r %&e ari!us p&ases

Hea% %ra s er p&e !me a8 Liquid e ap!ra%i! , -! de sa%i!

8 Fluid8%!8"all luid8%!8i %er al -!ils e%-7

1 ergy dissipa%i!8 Pressure dr!p

(e.g 7 s%irrers luid8 luid i %era-%i! s )

#ea-%!r .!del

P&e !me a A e-%i g Fixed8Bed #ea-%!r Per !rma -e

8l t f th R t 9 d l


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8lements of the Reactor 9odel

.i-r! !r L!-al A alysis .a-r! !r Gl!bal A alysis

Gas 8 liquid mass %ra s er

Liquid 8 s!lid mass %ra s er

' %erpar%i-le a d i %er8p&ase mass %ra s er

' %rapar%i-le a d i %ra8p&ase di usi!

' %rapar%i-le a d i %ra8p&ase &ea% %ra s er

Ca%alys% par%i-le "e%%i g

Fl!" pa%%er s !r %&e gas liquid a d s!lids

*y ami-s ! gas liquida d s!lids l!"s

.a-r! dis%ribu%i! s !%&e gas liquid a d

s!lids Hea% ex-&a ge

%&er %ypes ! %ra sp!r%

p&e !me a


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#ea-%!r *esig Variables

#ea-%!r Pr!-ess #ea-%i! Fl!" =

Per !rma -e Variables #a%es Pa%%er s

C! ersi! Fl!" ra%es i e%i-s .a-r!

ele-%i i%y ' le% C , > >ra sp!r% .i-r!

A-%i i%y Hea% ex-&a ge

Feed #ea-%!r i

> iC i

Pr!du-%!u%

> !u%C !u%

d l d d l l


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'dealiDed .ixi g .!dels !r .ul%i8p&ase ( >&ree P&ase) #ea-%!rs

.!del Gas8P&ase Liquid P&ase !lid8P&ase #ea-%!r >ype

$ Plug8 l!" Plug8 l!" Fixed >ri-kle8Bed

Fl!!ded8Bed

5 Ba-k mixed Ba-k mixed Ba-k mixed .e-&a i-ally agi%a%ed

2 Plug8Fl!" Ba-k mixed Ba-k mixed Bubble -!lum 1bulla%ed 8 bed Gas8Li % , L!!p

'deal Fl!" Pa%%er s i ul%ip&ase #ea %!rs


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deal Fl! Pa%%er s i .ul%ip&ase #ea-%!rs1xample3 .e-&a i-ally Agi%a%ed #ea-%!rs

t

XG(t)

0

δ (t)

t

XL(t)

0

δ (t)

t

EG(t)

0

δ (t- g )

τ g

t

EL(t)

- t / Leτ L

0

H

QL

QG

QL

QG

τ ε ε

L

r ! L

L

"

#= − −( )1τ ε ! r !

!

"

#=

V R = v G + V L + V C 1 = ε G + ε L + ε C

or

i t Ab l t 9 t f th


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irst Absolute 9oment of the6racer Response for 9ulti-phase Systems

For a single mobile phase in contact with p stagnant phases:

µ1 =V1 + K 1j V j

j = 2

p

∑Q 1

For p mobile phases in contact with p - 1 mobile phases:

µ1 =V1 + K 1j V j

j = 2

p

∑Q1 + K 1j Q j

j = 2

p

∑

K1j =C jC1

equil.is %&e par%i%i! -!e i-ie % ! %&e %ra-er

be%"ee p&ase $ a d I

R l ti ' th #& f th 6 ) l


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Relatin' the #& of the 6racer )mpulseResponse to Reactor #erformance

JF!r a y sys%em "&ere %&e -! aria -e ! s!I!ur %imes is Der!(i.e., "&e %&e %ra-er lea es a d re8e %ers %&e l!"i g s%ream a%%&e same spa%ial p!si%i! ) %&e P*F ! s!I!ur %imes i %&e rea-%i!e ir! me % -a be !b%ai ed r!m %&e exi%8age P*F !r a

! 8ads!rbi g %ra-er %&a% remai s -! i ed %! %&e l!"i g p&ase

ex%er al %! !%&er p&ases prese % i %&e sys%em7K

F!r a irs%8!rder pr!-ess3

∫ ∞

0

H-A

p

e = X - dt1t08: e tt10kc

∫ ∞

0

(-e = dt1t08 e tt1;


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)llustrations of )deal-9i in' 9odelsfor 9ultiphase Reactors

D

G L Plug8 l!" ! gas Ba-kmixed liquid , -a%alys%

Ba%-& -a%alys% Ca%alys% is ully "e%%ed

D

G L Plug8 l!" ! gas Plug8 l!" ! liquid

Fixed8bed ! -a%alys% Ca%alys% is ully "e%%ed

%irred %a k

Bubble C!lum>ri-kle 8 Bed

Fl!!ded 8 Bed

Li iti ' f ) t i i R ti R t


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Limitin' orms of )ntrinsic Reaction Rates

Reaction SchemeD A 4 6 &8 4l6 (4l6

G Li i%i # % % d Pl 8Fl!" ! Li id


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D

G L

Gas Limi%i g #ea-%a % a d Plug8Fl!" ! Liquid

$7 Gase!us rea-%a % is limi%i g

57 Firs%8!rder rea-%i! "r% diss!l ed gas

27 C! s%a % gas8p&ase -! -e %ra%i!

97 Plug8 l!" ! liquid

;7 's!%&ermal !pera%i!

>l A B

C C 1/ >>l L L A A B B

C DC D ν

Gas Reactant Limitin' and #lu' low of Liquid


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Gas Reactant Limitin and #lu low of Liquid

)onstant gas phaseconcentration valid for pure

gas at high ?o2 rate

) o

n c e n

t r a

t i o n o r #

x i a l ; e

i g h t

Relative distance from catal9st particle

( ) ( ) 0d$% A A Aad$' k A A Aak A# A#r sl p sr l

(

Bl d$ $ l l $ l l −−+−

+

$


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Concept of Reactor 8fficiency


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Concept of Reactor 8fficiency=

Rη Rate of r#n in the Entire Reactor with Transport E ects

+a#imum Possi$le Rate

)onversion of Reactant @


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) @$in terms of Reactor cienc9%


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Gas #ea-%a % Limi%i g a d Ba-kmixed Liquid

D

G L

$7 Gase!us rea-%a % is limi%i g

57 Firs%8!rder rea-%i! "r% diss!l ed gas

27 C! s%a % gas8p&ase -! -e %ra%i!

97 Liquid a d -a%alys% are ba-kmixed

;7 's!%&ermal !pera%i!

a k

Bubble C!lum

Key Assumptions


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Gas Reactant Limitin and 8ac;mi#ed


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LiquidA at the catalyst surfaceDA at the catalyst surfaceD

0or Reactant 8D0or Reactant 8D$


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LiquidSol&in the +odel Equations

Fl!" Pa%%er C! -ep%s


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Fl! Pa%%er C! ep%s!r Vari!us .ul%ip&ase ys%ems

A BA 8 i gle plug l!" p&ase l!" !gas !r liquid "i%& ex-&a ge be%"ee%&e m!bile p&ase a d s%ag a % p&ase7

Fixed beds, rickle-beds, packed

bubble columnsB 8 i gle p&ase l!" ! gas !r

liquid "i%& ex-&a ge be%"ee apar%ially ba-kmixed s%ag a % p&ase7

!emi-batch slurries, "luidi#ed-beds,ebullated beds

Fl!" Pa%%er C! -ep%s


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p!r Vari!us .ul%ip&ase ys%ems

C * 1C * 8 C! -urre % !r-!u %er-urre % %"!8p&asel!" (plug l!" !r dispersedl!") "i%& ex-&a ge

be%"ee %&e p&ases a ds%ag a % p&ase7

rickle-beds, packed orempty bubble columns

1 8 1x-&a ge be%"ee %"!l!"i g p&ases ! e !

"&i-& &as s%r! g i %er alre-ir-ula%i! 7$mpty bubble columns and"luidi#ed beds

Strate ies for +ultiphase Reactor


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Selection

• Strate y le&el JD (atalyst desi n strate y

gas-solid s9stems: catal9st particle siEe, shape, porousstructure, distribution of active materialgas-liquid s9stems: choice of gas-dispersed or liquid-disperseds9stems, ratio bet2een liquid-phase bul8 volume and liquid-phase diAusion la9er volume

• Strate y le&el JJD JnKection and dispersion strate ies$a% reactant and energ9 inHection: batch, continuous, pulsed,staged, ?o2 reversal$b% state of mixedness of concentrations and temperature:2ell-mixed or plug ?o2$c% separation of product or energ9 in situ$d% contacting ?o2 pattern: co-, counter-, cross-current

• Strate y le&el JJJD (hoice of hydrodynamic owre ime

e'g', pac8ed bed, bubbl9 ?o2, churn-turbulent regime, dense-phase or dilute-phase riser transport

Strate ies for +ultiphase Reactor


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Selection

R' 0rishna and "'T' "ie, ) ", , p' + $& %

Two-0ilm TheoryD +ass and eatTwo-0ilm TheoryD +ass and eat


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) J ( T ), j ( C g g

i 11

Gas 0ilm Liquid 8ul;

) J ( T ), j ( C g g i ) J ( T ), j ( C L L

i

) J ( T ), j ( C L L

i 11

Gas 8ul;

∑=

∆−= )R

* R

+ *

+

H Rdx

, d

12

2

)(κ

∑=

−= )R

*

+ * *-

+ -

- RdxC d

D1

2

2υ

Liquid 0ilm

(ell B th0 X

f

) j ( ,i N

1 X

f

) j ( ,i N

1 X f

) j ( ,i q0)(6 = .

+ *-q

mδ δ

yyTransferTransfer

eat0ilm


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-Transfer


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∑=

∆−=

)R

* * *r

+

L R H d/ , d

162

2

))((λ

8"("!

8"("%

( )01

600

)()(====

−∆−+−=−∑ /

+ -

-

)S

- - s

+

$

g

o0t g /

+

L d/

dC D H , ,

d/

d, λ

( )m

+ /

L

L

/

+

Lm

, ,

d/

d,

δ δ λ λ δ

δ −−−=− =

=

)(

Gas-Liquid lm

Transfer

8u$$le (olumn +i#in (ell +odel8u$$le (olumn +i#in (ell +odel


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8u$$le (olumn +i#in (ell +odel8u$$le (olumn i#in (ell odel

- )ells arranged in diAerent modes to simulate the averaged ?o2

patterns-

(ells in seriesDG and L mi#ed ow

(ells inseries-parallel

com$ination

E#chan e$etweenMpward anddownwardmo&in liquid

Liquid Gas Liquid Gas

(ell !

(ell 9

(ell K

(ells in seriesDG plu ow L mi#ed ow

Prototype cell

+i#in (ell +odel for as-liquid+i#in (ell +odel for as-liquid


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systemssystems9o&el features

•


70/100

9on-1imensionali,ed parameters

7aria$les

Reaction $ased

re+ -

+

- + - g re+ -

g

- g - C C cand C C c 66==

re+ - g

re+ -re+ - H C C 666 /=%

L%$

L&$ll3L

Au

k "V=α %$ %$ 6ii ,,=ω

re+ *

re+ L

m Lcell * R

C #

a" M

)( δ ε −=re+

a* *

R,

E =γ

re+ L p L L DC Le ρ λ =

%$ L

L

%$ 76% 7 T,

,89

ρ∆

−=%$ %$

2#

%$ 72

7 ,:

R 8"

δ=

-

g re+ -m- M D

k H B- 66

δ =

+ass transfer $ased

re+ L

re+ re+ *r

*,

C D H

λ β

)( 6∆−=

L

m g H B- λ

δ =

re+ L

re+ ---S -S ,

C D H

λ β 666

)( ∆−=

re+ - g re+

L

re+ +- H 0

0

6=γ

%$

iis =

g pm g

Lcell gl g

C m

" aS

6δ λ

=m L p L

Lcell gl L

C m

" aS

δ λ

6

=

eat transfer $ased

odel

m

/ δ ξ = g re+ g

g

## + =

re+

L

L

, , =θ

re+

g

g

, , =θ

+eat of reactionparameter

!ulk reaction number +atta number Arrheniusnumber +eat of reactionparameter

&amkohler number !iot number

!iot number +eat of solutionparameter

Liquid heattransfer number

Gas heattransfer number

Lewis number

&iffusi$itiesratio

8ffecti$e G


71/100

- 6as @hat R'7', van "2aaiH ('5'M', 0uipers, J'#'M', 6ersteeg,G'F', KMasstransfer 2ith complex chemical reaction in gas-liquid L, )hem' ng' "ci',

4 , &+&-&/3, $& %

- 6as @hat R'7', van "2aaiH ('5'M', 0uipers, J'#'M', 6ersteeg,G'F', KMasstransfer 2ith complex chemical reaction in gas-liquid L, )hem' ng' "ci',4 , &/.-& ., $& %

- #l- baidi @';' and "elim M';' $& +%, K Role of 1iquid Reactant 6olatilit9in Gas #bsorption 2ith an xothermic ReactionL, #!)h J', /N, /3/-/.4,$& +%

- @hattachar9a, #', Gholap, R'6', )haudhari, R'6', KGas absorption 2ithexothermic bimolecular $&,& order% reactionL, #!)h J', //$ %, &4 .-&4&/,$& N.%

- Pan ar;ar 7"G" Sharma +"+ ', K)onsecutive reactions: Role of Mass Transfer factorsL, + , 43&-43 , $& . %

- Pan ar;ar 7"G" Sharma +"+ ', K"imultaneous absorption and reactionof t2o gasesL, + , ++ .-+/ 3, $& . %

Reactions

Types of eat GenerationTypes of eat Generation


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Types of eat GenerationTypes of eat Generation

!" %eat of solution 4N s 6 which is enerated at the as-

liquid interface due to the physical process of asdissolution

% %eat of &apori'ation 4N &6 of &olatile reactants due toe&aporati&e coolin in o#idation reaction

'" %eat of reaction 4N r 6 which is enerated in the lmnear the as-liquid interface 4for fast reactions6 or inthe $ul; liquid 4for slow reactions6"O Mncontrolled heat eneration can lead toD

!" Mndesired production of $y-products%" Thermally-induced product decomposition'" Jncreased rate of catalyst deacti&ation)" Local hot spots and e#cess &apor eneration*" Reactor runaway and unsafe operation

O +odelin of simultaneous mass and heat transporte ects in the lm is necessary for accurate predictions

w+ass Transfer Rates in Gas Liquid+ass Transfer Rates in Gas Liquid


73/100

+ass Transfer Rates in Gas-Liquid+ass Transfer Rates in Gas-LiquidReactionsReactions

!" Physical transport and thermodynamicproperties of the reaction medium e#hi$it

&arious de rees of temperature dependence

%" >inetic parameters e#hi$it e#ponentialdependence on the local temperature

'" Jnsta$ilities at the as-liquid reactioninterface that are dri&en $y surface tension

e ects 4+aran oni e ect6 and density e ects

Typical $y tem with +ota le 3eat E**ectTypical $y tem with +ota le 3eat E**ect


74/100

Typical $y tem with +ota le 3eat E ectTypical $y tem with +ota le 3eat E ect

#hah $ %hattachar&ee, in'(ecent)d"ances +, 1 .

/ropertie an) nter*acial Temperat(re/ropertie an) nter*acial Temperat(re


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/ropertie an) nter acial Temperat(rep ) p (%i e *or $ome /ractical $y tem%i e *or $ome /ractical $y tem

#hah $ %hattachar&ee, in '(ecent )d"ances in the 0ngineering )nal sisof ulti3hase (eacting # stems,+ 4ile 0astern, 1 .

t % t *t % t *


76/100

a oratory %eactor *ora oratory %eactor *orGa - i'(i) %eaction ineticGa - i'(i) %eaction inetic

(ase !D Sin le non-isothermal reaction(ase !D Sin le non-isothermal reaction


77/100

G1 second order reaction

B Ak dx Ad

D A 222

=

A D

Bk Ha 02

22 δ =


78/100

! "# $ %

& ' '$ ( % % 4Bi! F!"*6 ' % 4Bi! F56

Temp'

)onc'

Reaction "cheme:# B v@ );a O & , q O ' 4, γ O ++,γ s O -.'4, γ vap O +,βsO ' &, βvap O - ' 4,@i;g O &


79/100

m g Hg B-

δ κ

=

Bi Hg ↑ → Temp ↓

A

b B m ref

D

C k Ha

22 δ

=

Ha ↑ → Rxn ↑ → Temp. ↑


80/100

Axial *ispersi! .!del ( i gle P&ase)


81/100

p ( g )@asis: 5lug ?o2 2ith

superimposed KdiAusionalL orKedd9L transport in the

direction of ?o2 R

d$ C

0 $

C D

t C

ax +∂−

∂∂=

∂∂

2

2

> E O $ C

D0C C 0 ax ∂∂

−=00> E O 1

0=∂∂ $ C

1et L $

2 =ax

ax D0L

Pe =0 L

3 =

R3 2d C

2C

Pet C

3 ax

+∂−∂∂=

∂∂

2

21

> η O 2

C

PeC C

ax ∂

∂−=

10 > η O & 0=

∂

∂

2

C

Axial *ispersi! .!del


82/100

R3

2d

C

2

C

Pet

C 3

ax

+∂−∂∂=

∂∂

2

21

> η O 2C

PeC C

ax ∂∂

−=1

0 > η O & 0=∂∂

2C

Axial *ispersi! .!del !r %&e Liquid "i%&C! s%a % Gas8P&ase C! e %ra%i! 8 $


83/100

C! s%a % Gas8P&ase C! -e %ra%i! 8 $+ass 8alance of A in the liquid phase

$


84/100

C! s%a % Gas8P&ase C! -e %ra%i! 8 5

Axial *ispersi! .!del !r %&e Liquid "i%&C! s%a % Gas8P&ase C! -e %ra%i! 8 2


85/100

C! s%a % Gas8P&ase C! -e %ra%i! 8 2

A*. .!del3 B!u dary C! di%i! s


86/100


87/100

Comments re'ardin' a ial dispersion model


88/100

Comments re ardin a ial dispersion model0A&91

% 6he model is $ery popular because it has only a sin'leparameter* a ial dispersion coefficient* & a * the $alue ofwhich allows one to represent R6&s between that of astirred tank and of a plu' flow. 6he reactor model is usually

written in dimensionless form where the #eclet number fora ial dispersion is defined as(

'i#$&o $&'ios'i&&;"%"&'$%i

'i#$dis $%sio"5i"ls'i&&;"%"&'$%i

/

//

2

===5 L

D L D L5 Pe axaxax

#e a => plu' flow

#e a =? complete back mi in'

A&9 comments continued-:


89/100

% @se of A&9 was populari/ed by the work of&anckwerts* Le$enspiel* !ischoff* 5. Smith andmany others in the : B?s throu'h : ?s.

% Since & a encompasses the effects of thecon$ecti$e flow pattern* eddy as well asmolecular diffusion* prediction of the A ial #ecletDumber with scale –up is e tremely difficult as atheoretical basis e ists only for laminar andturbulent sin'le phase flows in pipes.

% 9oreo$er use of A&9 as a model for the reactoris only ad$isable for systems of #eclet lar'erthan E 0preferably :?1.

A&9 comments continued


90/100

A&9 comments continued -

% +owe$er* A&9 leads to the boundary $alueproblem for calculation of reactor performancewith inlet boundary conditions which are neededto preser$e the mass balance but unrealistic for

actual systems. Since at lar'e #eclet numbersfor a ial dispersion the R6& is narrow* reactorperformance can be calculated more effecti$elyby a tanks in series model or se're'ated flowmodel.


91/100

i l C


92/100

inal Comments% 6o impro$e predictability of multiphase reactor

models and reduce the risk of scale-up* theyshould be increasin'ly de$eloped based onproper physical description of hydrodynamics in

these systems.% )mpro$ed reactor scale descriptions coupled withad$ances on molecular and sin'le eddy 0sin'leparticle1 scale will facilitate the implementation of

no$el en$ironmentally beni'n technolo'ies byreducin' the risk of such implementations.


93/100

#ea-%i! ys%em


94/100

y

9<

*isad a %ages ! emi8Ba%-& lurry #ea-%!r


95/100

g y

% Ba%-& a%ure 6 ariable pr!du-%

% L!" !lume%ri- pr!du-%i i%y (due %! l!" -a%alys% l!adi ga d limi%ed pressure)

% Pressure limi%a%i! (s&a % seal)

% Hig& p!"er -! sump%i!% P!!r sele-%i i%y (due %! &ig& liquid %! -a%alys% !lume

ra%i! a d u desirable &!m!ge e!us rea-%i! s)

% Ca%alys% il%ra%i! %ime -! sumi g

% Ca%alys% make8up required

% xyge mass %ra s er limi%a%i! s

9

P!%e %ial Ad a %ages ! Fixed Bed ys%em


96/100

g y

9?

lurry s Fixed Bed% i%& ! d i ! % l % %i l k d8b d


97/100

% i%& pr!per desig ! -a%alys% par%i-les a pa-ked8bedrea-%!r "i%& -!8-urre % d!" 8 l!" ! gas a d liquid b!%&i par%ial "e%%i g regime a d i i du-ed pulsi g regime-a ar surpass %&e !lume%ri- pr!du-%i i%y a dsele-%i i%y ! %&e slurry sys%em ye% require a !rder !mag i%ude less ! %&e a-%i e -a%alys% -!mp! e %7

% M desirable &!m!ge !us rea-%i! s are suppressed i%&e ixed bed rea-%!r due %! mu-& &ig&er -a%alys% %!liquid !lume ra%i!

% Fa%&er ad a %age is a--!mplis&ed i ixed beds by!pera%i! a% &ig&er pressure ( ! m! i g s&a %s %! seal)7

% Fixed bed !pera%i! requires l! g %erm -a%alys% s%abili%y!r ease ! i si%u rege era%i! 7

9@


98/100

#e ere -es


99/100

:. &uduko$ic* 9.#.* Larachi* .* 9ills* #.L.* K9ultiphaseReactors – Re$isited * Chem. 8n'. Science* EM:* : E-: E 0: 1.

. &uduko$ic* 9.#.* Larachi* .* 9ills* #.L.* K9ultiphaseCatalytic Reactors( A #erspecti$e on Current Nnowled'eand uture 6rends * Catalysis Re$iews* MM0::1* : F- MB

0 ?? 1.F. Le$enspiel* 4cta$e* Chemical Reaction 8n'ineerin'* F rd

8dition* 7iley* : .

M. 6rambou/e* #.* 8u/en* H.#.* KChemical Reactors – rom

&esi'n to 4peration * ) # #ublications* 8ditions 68C+D)#*#aris* rance 0 ?? 1.

9;

or any process chemistry in$ol$in' morethan one phase one should (


100/100

than one phase one should (

% Select the best reactor flow pattern based on thekinetic scheme and mass and heat transferrequirements of the system*

% Assess the ma'nitude of heat and mass transfereffects on the kinetic rate

% Assess whether desi'n requirements can be metbased on ideal flow assumptions% &e$elop scale-up and scale-down relations% ;uantify flow field chan'es with scale if needed

for proper assessment of reactor performance% Couple physically based flow and phasecontactin' model with kinetics

Documents

Gas–Liquid and Gas-liquid-solid Reactions