Lecture Notes Chptr 4 Multiphase Reactor (1)

8/17/2019 Lecture Notes Chptr 4 Multiphase Reactor (1)

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MULTIPHASEREACTORS

CHAPTER 4

CPE624 FACULTY OF CHEMICAL ENGINEERING 1


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CPE624 FACULTY OF CHEMICAL ENGINEERING 2


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Types of Multiphase Reactors

Types of multp!"se #e"$to#%G"s & L'u( #e"$to#s

L'u(&L'u( #e"$to#s

G"s&)ol( #e"$to#s

L'u(&)ol( #e"$to#s

T!#ee P!"ses #e"$to#s

*!y multp!"se #e"$to#s+To #e"$t ,"ses- l'u(s ".( sol(s /t! e"$! ot!e# 0 Most sol(s p#o$esses

#e'u#e #e"$t., /t! ,"ses o# l'u(s ".( p#o(u$ts m"y "lso e ,"ses o#

l'u(s0

To use multple p!"ses to "tt". $o.e#so.s !,!e# t!". "tt"."le f#om

e'ul#um $o.st#".ts . " s.,le p!"se p#o$ess ".( to mp#oe m3.,

/t!. . t!e #e"$to# y "llo/., ,#"ty to $"use flo/s of p!"ses #el"te

to e"$! ot!e#0


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Types of Multiphase Reactions

• Gas-liquid without catalyst

• Gas-liquid with soluble catalyst

• Gas-liquid with solid catalyst• Gas-liquid-liquid with soluble

or solid catalyst

• Gas-liquid-liquid with soluble

or solid catalyst t/o l'u( p!"ses5

Straightforward

Complex

Reaction Type egree of ifficulty


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Key Multiphase Reactors


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Reactors…

6

C M l i h


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Common MultiphaseReactors…


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Middleton!"##$


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%ubble column reactor


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Features that distinguish multiphasereactors rom single phase reactors !

M"ss t#".sfe# steps et/ee. p!"ses /!$! "$$omp".y t!e

#e"$to. steps- f#e'ue.tly $o.t#ol t!e oe#"ll #e"$to. #"te0

M"ss e.e#,y "l".$e must e /#tte. ".( sole( fo# e"$!

spe$es . e"$! p!"se0

G#"ty s mpo#t".t . $o.t#oll., p"tte#.s l,!te# p!"se /ll

#se- (e.se# p!"se to f"ll5

M3., /t!. p!"ses ".( et/ee. p!"ses !"s (om.".t effe$t0

)olultes ".( p!"se (st#uto.s of spe$es et/ee. p!"ses

#e'u#e $"#eful "ppl$"to. p#.$ples0

17


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Reactor C!em$"l spe$es $". t#".sfe# et/ee. p!"ses ".( #ep#ese.ts

t!e $oupl., et/ee. t!e m"ss "l".$e e'u"to.s0

Resemles " mem#".e #e"$to# . /!$! pe#me"le "#e" A89

sep"#"tes t!e p!"ses0

Cl$:e# ;uesto.s% 5 *!"t (o α- β ".( γ #ep#ese.t+

5 *!"t (o A

αβ

".( Aβγ

#ep#ese.t+


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Before we take a look at massbalance equations for multiphasereactors, I suggest you refresh

yourself on mass balance equationsfor single-phase reactors. This willgive you better understanding on

the mass balance equation formultiphase reactors. Refer to

chmidt book!

i" Batch reactor #pg. $%-$&"ii" '(TR #pg. )*-)+"iii"TR #pg. %-%&"


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M"ss "l".$e fo# 8 p!"se f t!e flu( s unmixed 0e0% . PFR5%

Fo# mixed flu( 0e0% . C)TR5 "t t#".se.t%

Fo# mixed flu( 0e0% . C)TR5 "t ste"(y st"te%

Res(e.$e tme . 8 ".( 9 p!"se%

I. PFR%

β

β β

α

α α

ν τ

ν τ

V V == <

α

α

α

α α

ν

τ

u

LV ==

&&'ll equations (alid for no density change system reactor

)))

)))

)))

#cont$%

&


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phases M"ss t#".sfe# to o# f#om " m3e( p!"se

M"ss t#".sfe# fo# 8 p!"se . $o.t"$t /t! 9 p!"se . C)TR

T!e m"ss t#".sfe# $". e #e,"#(e( "s #ee#sle su#f"$e #e"$to.%β α j j A A ⇔

5== α β α

αβ

α

αβ

j j m C C k V

Ar V

Ar V

Ar −===

Mass transfer rate of

species * from phase + to ,


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Cont… At ste"(y st"te

M"ss t#".sfe# to o# f#om ". u.m3e(

p!"se0M"ss "l".$e "t ste"(y st"te . PFTR%

O# fo# #e"$t".t A . 8 p!"se%

CPE624 FACULTY OF CHEMICAL ENGINEERING 1>

57 α β α

αβ

α α α α τ τ A Am A A C C k V

Ar C C −+=−

5?

A α β

α α ν j j mi ij

j C C k r

dz

dC u −+=∑

5?

A α β

α α

A Am A C C k r

dz

dC u −−−=


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Summary of Multiphase ReactorEquations..

I. m3e( p!"se%

I. u.m3e( p!"se%

57α β

α

αβ α α α α τ τ A Am A A C C k

V

Ar C C −+=−

5?

A α β

α

α A Am A C C k r dz

dC u −−−=

Can be (e or can be .(e/

So! when is (e and when

is .(e)

Can be (e or can be .(e/

So! when is (e and when

is .(e)

0f species ' is a reactant! r will ha(e

a (e (alue/ Refer to page 11-1#

Schmidt to understand why/


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Flow conurations

Fou# flo/ $o.f,u#"to.s of t/o&p!"ses #e"$to#s%

CPE624 FACULTY OF CHEMICAL ENGINEERING 1@


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phase

O.ly . o.e p!"se+ *!"ts t!e use of ".ot!e# p!"ses t!e.++

E,0 I. $"t"lyt$ #e"$to# B #e"$to. o$$u#s o.ly "t t!e ou.("#y

/t! " sol( p!"se0

I. mo., e( $"t"lyt$ #e"$to# o# . " slu##y o# flu(e( e(

$"t"lyt$ #e"$to#- $"t"lyst p!"se s $o.t.uously "((e( ".(

#emoe( f#om t!e #e"$to# ".( . multp!"se #e"$to# t!e

#e"$to. o$$u#s o. t!e $"t"lyst su#f"$e0

f i l f


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!nterfacial surface area I.te#f"$"l "#e" et/ee. p!"ses- A89 $". $!".,e (epe.(.,

o.%Co.e#so.

Geomet#y

Flo/ $o.(to.s

)t##., /t! ". mpelle# o# t!e flo/ p"tte#. $"use( y ,#"ty

/ll "lso $o.t#ol t!e .te#f"$"l "#e"0)ut"le (es,. ".( posto.., of mpelle# o# p#opelle# $". p#o(e e#y

eff$e.t #e":ups of l'u(s .to (#ops ".( ules- ∴ .$#e"s., t!e.te#f"$"l "#e"0

)u#f"$e te.so. $". e e#y mpo#t".t . (ete#m.., (#op".( ule ses ".( s!"pes0 T!e p#ese.$e of su#f"$e "$te

",e.ts t!"t "lte# t!e .te#f"$"l te.so. et/ee. p!"ses $".

!"e e.o#mous .flue.$es . multp!"se #e"$to#s0


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Suitable design and

positioning of impeller or

propeller can pro(ide (ery

efficient brea2ups of liquids

into drops and bubbles!

increasing the interfacialarea/

flow pattern caused by

gra(ity also controls the

interfacial area


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0mpeller esigns3


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"hases A. e'ul#um (st#uto. of spe$es A et/ee. p!"ses 8 ".( 9 f t!e

p!"ses "#e . $o.t"$t fo# lo., tme%

M"ss t#".sfe# et/ee. p!"ses "t e'ul#um5%

Ho/ee# t!s (#., fo#$e fo# m"ss t#".sfe# of " spe$es (s"ppe"#s /!e.

t!e p"#t"l p#essu#e of t!e spe$es . t!e ,"s s . e'ul#um /t! t!e$o.$e.t#"to. of t!e l'u( p!"se0 T!e e'ul#um s $o.e.e.tly e3p#esse(

"s He.#ys L"/% At " $o.st".t tempe#"tu#e- t!e "mou.t of " ,e. ,"s t!"t

(ssoles . " ,e. type ".( olume of l'u( s (#e$tly p#opo#to."l to t!e

p"#t"l p#essu#e of t!"t ,"s . e'ul#um /t! t!"t l'u(0

α

β

αβ β α

Aeq

Aeqeq j j

C

C K A A =⇔ <

5#= α αβ β Aeq Am C K C k −=

j j j xH=P j jT j xH=Pyor

a/2/a/ partition coefficient or

distribution coefficient

Concentration gradient in the (icinity

of the interface is the dri(ing force of

the mass transfer


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#as$liqui% multiphase reactors.

F lli Fil R t &FFR'


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Fallin Film Reactor &FFR'… Co.s(e# " e#t$"l tue of le.,t! L ".(

("mete# D7 /t! l'u( "(mtte( "t t!e top

su$! t!"t t fo#ms " f"ll., flm t!"t $o"tst!e /"ll tue0

G"s /"s "((e( .to t!e top of t!e tue

$o&$u##e.t5 o# .to t!e ottom $ou.te#&

$u##e.t5 B /ette( /"ll $olum.0

Assume t!e l'u( f"lls /t! " $o.st".t"e#",e elo$ty ul5 ".( fo#ms " l'u( flm

of t!$:.ess R7 B R R #"(us . t!e tue

"t t!e su#f"$e of t!e l'u( flm50

If t!e l'u( flm t!$:.ess s $o.st".t- t!e

$#oss se$to. o$$upe( y t!e ,"s s$o.st".t ".( t!e elo$ty of t!e ,"s u,5 s

.(epe.(e.t of posto. f t!e (e.sty of

,"s s $o.st".t0

4


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T!e ,"s /ll o$$upy " $#oss se$to."l "#e"%

T!e l'u( /ll o$$upy " $#oss&se$to."l "#e"%

T!e olumes o$$upe( y t!e p!"ses "#e%

T!e #es(e.$e tme fo# e"$! p!"se s%

2i R π

5 227 i R R −π

LR V

LR R V

i g

i l

2

227 5

π

π

=

−=

g

i

g

g

g

g

l

i

l

l

l

l

LR V

u

L

LR R V

u

L

ν

π

ν

τ

ν

π

ν τ

2

227 5

===

−===

&cont.'…

4


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Co.s(e# t!e follo/., #e"$to.%

Lets "ssume t!e follo/.,%

Re"$to.s "#e ##ee#sleP#o(u$ts $". e"sly es$"pe f#om t!e p!"ses- so t!e spesf$

p#o(u$ts "#e .ot mpo#t".t to :.o/0

t!e #e"$to. o$$u#s o.ly . t!e l'u( p!"se .o #e"$to. .

,"s p!"se5%

T!e #"te of m"ss t#".sfe# pe# u.t "#e" s% A#e" of .te#f"$e%

M"ss "l".$e fo# t!e p!"ses%

l g l g DC B A +→+

7 < == g l Bl Al

l r C C k r

5 l Agl g

AmAmA C K C k r −=

LR i π 2

54

5R&4

2

54R

2 7

2

2

7

2

l A

gl g Am

i l B

l A

l l Al

l A

gl g Am

i g Ag

C K C k

R

R C C k

dz

dC u

C K C k R

dz

dC u

−+−=

−−=

π

π

π

π

#cont$%!

4


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Re"$to# olume s p#opo#to."l to R72 /!le t!e su#f"$e "#e"

fo# m"ss t#".sfe# s p#opo#to."l to R- t!e f"ll., flm $olum.

/ll e less eff$e.t fo# l"#,e# #e"$to# ses0

T!e m"ss t#".sfe# $oeff$e.t s usu"lly mu$! lo/e# . t!e

l'u( p!"se ".( t!e#efo#e C Al s " fu.$to. of R (st".$e

f#om t!e /"ll to .te#f"$e5

P ti & ti FFR


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Practice &uestions or FFR15 ):et$! ".( l"el " l'u(&,"s $ou.te#$u##e.t f"ll., flm #e"$to#

t!"t s m"(e f#om " e#t$"l $yl.(#$"l tue of le.,t! L ".(

("mete# Do

0

25 E3p#ess t!e olumet#$ flo/ #"te of e"$! p!"se . t!e f"ll., flm

#e"$to# s:et$!e( . ;uesto. 1 . te#ms of #e"$to#s le.,t!- L ".(

t!e #es(e.$e tme of e"$! p!"se0 Assume .o (e.sty $!".,e .

t!e #e"$to#0

5 F"ll., flm #e"$to#s "#e /(ely use( . .(ust#y p"#t$ul"#ly .

p#o$esses t!"t .ole !y(#o,e."to.- $!lo#."to.- et!o3yl"to.

".( sulfo."to.0 Its m". $!"#"$te#st$s "#e t!e moto. of l'u(

flm oe# " /ette( su#f"$e u.(e# t!e effe$t of ,#"ty0 Assum.,

t!e#e s .o ,"s p!"se #e"$to. . " f"ll., flm #e"$to#- (e#em"ss "l".$e e'u"to. fo# t!e ,"s ".( l'u( p!"ses fo# "

#e"$to. st"te( "s%

A, l → C, Dl - # l :lC A

lCl

45 A.s/e# "ll 'uesto.s " to ,5 . E3"mple 12&1 p",e 47 )$!m(t02J

P ti & ti FFR # t %


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(' )uestion ( Final "aper *ec +,-C/E0+(

Practice &uestions or FFR #cont$%

rac ce ues ons or


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rac ce ues ons or#cont$%0' )uestion + b' Final "aper *ec +,-1

C"E0+

'nswer3 film thic2ness 5 6/$ cm

Falling Film Catal'tic (all


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Falling Film Catal'tic (allReactor


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&BCR' I. f"ll., flm #e"$to# - su#f"$e "#e" .$#e"ses "s t!e pe#mete# of ,"s&l'u(

.te#f"$e .$#e"ses0 ?olume .$#e"ses "s t!e $#oss se$to."l "#e"

.$#e"ses0 He.$e- FFR /ll e less eff$e.t fo# l"#,e# #e"$to# ses0

To (es,. eff$e.t f"ll., flm #e"$to# - sm"ll tues . p"#"llel "#e .ee(e( to

.$#e"se t!e .te#f"$"l "#e"- /!$! s (ff$ult ".( .ot p#"$t$"l0

Ho/ee#- !,!e# .te#f"$"l "#e" $". e "$$ompls!e( /t! #s., ules o#

f"ll., (#ops0 T!s $". e (o.e y us., ule $olum. #e"$to# CR5 o#

sp#"y to/e# 0

K No#m"lly use( fo# #e"$to. /!e#e t!e

,"s&l' #3. s slo/ $omp"#e( to t!e m"ss

t#".sfe# #"te0K *(ely use( . o3("to.- !y(#o,e."to.

".( "l:yl"to.0K G"s ules .t#o(u$e( "t t!e ottom

.o#m"lly us., sp"#,e# 50K T!e ules #se0 *!y+K T!e ,"s sep"#"te( f#om t!e l'u( . t!e

!e"( sp"$e ".( pu#e l'u( s /t!(#"/.

"t t!e ottom0

%CR3


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F,u#e elo/ s!o/s t!e $o.$e.t#"to. p#ofle fo# #e"$t".t A

/!$! must m,#"te f#om " ule . CR5 o# " (#op . sp#"y

to/e#5 .to t!e $o.t.uous p!"se to #e"$t0

ule $olum.s #ely o. .oles sp"#,e#s5- m3., pl"tes ".(

mpelle#s /t!. t!e #e"$to# to $o.t#ol t!e ule se0


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ule p!"se olume o$$upy., " f#"$to. ,%

?olume of e"$! ule%

Assume t!"t "ll p"#t$les !"e t!e s"me se

V V g g ε =

4bR π

544

22

As Abm

b

b C C R k dt

dR

R −−= π ρ π ∴

Practice &uestions or "CR


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Practice &uestions or "CR15 A.s/e# "ll 'uesto.s " to (5 . E3"mple 12&2 p",e 46 )$!m(t0

25 ;uesto. $5 F."l P"pe# CPE624 u.e 2714

>'nswer3 7 5 "89/: m8

Practice &uestions or "CR #cont %


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Practice &uestions or "CR #cont$%5 ;uesto. 2 $5 Test 2 u.e 271> CHE62>

'nswer3 (l 5 "/:; x "6-


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45 ;uesto. 5 F."l P"pe# u.e 271 CPE624

Practice &uestions or "CR#cont$%

'nswer3 7 5 :;11; dm8


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References

)$!m(t- L0D0 277>50 The Engineering of Chemicl Rections-

2.( e(to.- Ne/ Yo#:% O3fo#( U.e#sty P#ess0

P.0 H"sym R"!m"t- F UTM )!"! Al"m0

P.0 )!"#meel" M"t"l- F UTM )!"! Al"m0

P.0 )t *"!("! Pu"s"- F UTM )!"! Al"m0

Lecture Notes Chptr 4 Multiphase Reactor (1)

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