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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
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