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O c - c ritic a l su rface ten sio n o f pack ing m ate ria l [d ynes/cm ]

a = su r fa c e ten s io n [d y n e s /cm ] o r [k g /hr2]

S u b s c r i p t s

1 , 2 = b o t t o m a n d t o p o f c o l u m n , r e s p e c t i v e l y

G , L = g as a n d l i q u i d p h as e , r e s p e c t iv e l y

L it e r a t u r e c i t e d

1 F e l l i n g e r , L .: S c . D . t h e s i s , M.L.T.,

Cam bridge 1941)

2 ) F u j i t a ,

S .

an d S. S a k um a : C h e m . E n g . ( J a p a n ) , 1 8 , 6 4 (1 9 5 4 )

3 ) F u j i t a , S . a n d T . H a y a k a w a : ib id . , 2 0 , 1 1 3 ( 1 9 5 6 )

4 )

Fu r na s ,

C . C . a n d

M.

L .

T a y l o r :

T r a n s .

Am. In s t. C hem .

Eng r s . ,

3 6 ,

1 3 5 ( 1 9 4 0 )

5 ) H ik i t a , H ., T . K a t a o k a a n d K . N ak a n i s h i : K a g a k u K o g a k u ,

24 , 2 ( 1 9 60 )

6 ) H ik i t a , H . , M . S u g a ta a n d K . K a m o : ib id . , 1 8 , 4 5 4 ( 1 9 5 4 )

7

H i k i t a ,

H .:

i b i d . ,

2 4 , 9 ( 1 9 6 0 )

8 ) H o u s t o n , R . W . a n d C . A . W al k e r : I n d . E n g . C h e m . , 4 2 , 1 1 0 5

( 1 9 5 0 )

9 ) K at a y a m a, S . , T . K o y a n a g i a n d F . Y o s h i d a : K ag a k u K o g a k u ,

2 2 , 7 6 4 ( 1 9 5 8 )

1 0 ) L y n c h , E .J . a n d C . R . W i l k e : i b i d . , 1 , 9 ( 1 9 5 5

l l ) N o r m a n , W . S . a n d F . Y . Y . S a m m a k : T r a n s . I n s t . C h e m .

Eng r s . , 4 1, 1 0 9 (1 9 6 3 )

1 2 ) O n d a , K . , E . S a d a a n d Y . M ur a s e : A . I . C h . E . J o u r n a l , 5 ,

2 3 5 ( 1 9 5 9 )

1 3 ) O n d a , K . a n d E . S a d a : K a g a k u K o g a k u , 2 3 ,2 2 0 ( 1 9 5 9 )

1 4 ) O n d a , K . , T . O k a m o to a n d H . H o n d a : i b i d . , 2 4 , 4 9 0 (1 9 6 0 )

1 5 ) O n d a , K . , E . S a d a a n d M . S a i t o : i b i d . , 2 5 , 8 2 0 1 9 6 1 )

1 6 ) O n d a , K . , E . S a d a , C . K i d o a n d A . T a n a k a : ib i d . , 2 7 , 1 4 0

( 1 9 6 3 )

1 7 ) O n d a , K . , E . S a d a , C . K i d o a n d S . K a w a ta k e : i b i d . , 3 0 , 2 2 6

( 1 9 6 6 )

1 8 ) O n d a , K . , H . T a k e u c h i a n d Y . K o y a m a : i b i d . , 3 1 , 1 2 6 1 9 6 7 )

1 9 ) S a w i s t o w s k i , H . a n d W . S m i t h : I n d . E n g . C h e m . , 5 1 , 9 1 5

( 1 9 5 9 )

2 0 ) Sherwood, T. K. a n d

F.A.L. Ho l loway :

T r a n s . Am. Inst.

C h e m . E n g r s . , 3 6 , 2 1 ( 1 9 4 0 )

2 1 ) S h e r w o o d , T .K . a n d F .A . L . H o l l o w a y : i b id . , 3 6 , 3 9 ( 1 9 4 0 )

2 2 ) Shulman, H .L., C .F . U l l r i c h ,

A.Z . P rou lx

an d

J.O . Z im -

m e r m a n : A . I . C h . E . J o u r n a l , 1 , 2 5 3 ( 1 9 5 5 )

2 3 ) S u r o s k y ,

A.E. a n d B .F .

Dodge: Ind .

En g . C he m ., 4 2,1 11 2

1 9 50 )

2 4 )

Uey am a, K.,

H .

H i k i t a , S .

N i s h i g a m i

an d S . F un ah as hi:

K a g a k u K o g a k u , 1 8 , 6 8 ( 1 9 5 4 )

2 5 ) U c h i d a , S .,

e t

a l . :

i b i d . ,

ll ,

5 3 1 9 4 7 )

2 6 ) V an K r e v e le n , D . W . a n d P . J . H of t i j z e r : C h e m . E n g . P r o g r s . ,

4 4 ,

5 2 9 (1 9 4 8 )

2 7 ) V i v i a n , J . E . an d C . J . K i n g :

A.

I. Ch.

E. Journa l , 1 0 , 2 2 1

( 1 9 6 4 )

2 8 ) Y o s h i d a , F. an d

T.

Koyanagi :

Ind .

En g . C hem ., 5 0 , 3 6 5

( 1 9 5 8 )

2 9 ) Y o s h id a , F . a n d T . K o y a n a g i : i b id . , 4 6 , 1 7 5 6 (1 9 5 4 )

3 0 ) Y o s h id a , F . a n d T . K o y a n a g i : A . I . C h . E . J o u r n a l , 8 , 3 0 9

( 1 9 6 2 )

3 1 ) We i sm a n , J. an d C.F. B o n i l l a : I n d . Eng . C h em . ,

4 2 , 1 0 9 9

( 1 9 5 0 )

3 2 ) W e n , C . Y . , H . D . S i m o n s a n d M . L e v a : W e s t V i r g . U n i v .

B u l l . E n g . E x p t . S t a . , 2 6 1 9 5 3 )

GAS ABSO RPTIO N W ITH CH EMICAL REACTIO N IN PACKED

COLUMNS

KAKUS ABUR O O NDA, EIZ O S ADA AN D H IR OS HI TAKEUC H I**

D e p t . o f C h e m . E n g . , U n i v e r s i ty o f N ag o y a , N ag o y a

I n t r o d u c t i o n

T h e o r e t i c a l a n a l y s e s f o r gas

a b s o r p t i o n

w i t h c h e m ic a l

r e a c t i o n

have b e en m a d e by many investigators3>4>6 18 :

owever i t i s d i f f i c u l t t o

a p p l y t h e s e t h e o r i e s t o t h e

proces se s i n a packed c o l umn , b e c a u s e t h e i n d iv id u a l

m a s s t r a n s f e r c o e f f i c i e n t s a n d t h e i n t e r f a c i a l a r e a c a n n o t

b e e s t i m a t e d s t r i c t l y

a t p re se nt .

The assum ption tha t the w etted su rface in p ack ing s is

i d e n t i c a l w i th

th e

g a s - l i q u i d i n t e r f a c e i s

n o t

o n l y c o n -

v e n i e n t f o r e s t i m a t i o n o f t h e a r e a b u t a l s o r e a s o n a b l e f o r

mass

transfer b e tw e e n

g a s a n d

l i q u i d

p h a s e s .

I n o u r

previous p a p e r s 1 1 > 1 2 \ t h e c o r r e l a t i o n s f o r aw ,

ko

and kL

were d e r i v e d a s f o l l o w s :

ajat = 1 - exp{- 1.45UWU5aW

( V a t / p L 2 g ) ~ Q ^ ( L 2 / p L aa t y - 2 }

k o R T / a t D o

= 5 . 2 3 G W f f ) 7 f i G / P O D G ) m a t D p ) 2 -

k L { p L / [ J t L g y n

= 0 . 0 0 5 l ( L / a w ^ L y / ( f i L / P L D L ) - 1 / 2 ( a tD p y - i ( 3 )

I n t h i s p a p e r , t h e a p p l i c a b i l i t y o f t h e f i l m t h e o r y 1 8 ) o f g a s

ab so rp tio n w ith s eco nd o rd er reac tio n to the ab so rp tio n o f

* Received

o n

J u l y 1 0 , 1 9 6 7

* * D e p t . o f I n d . C h e m ., S u z u k a C o l l e g e o f T e c h n o l o g y , S u z u k a

6 2

CO 2in to aqueous so lu tions o f NaO Hin a p acked co lum n

is c o n f i rmed

b y u s i n g

t h e s e c o r r e l a t i o n s . F u r t h e r m o r e ,

the assum ptio n o f a-aw is ascerta ined by com paring w ith

t h e d a t a f o r t h e g a s a b s o r p t i o n w i t h p s e u d o f i s t - o r d e r r e -

a c t i o n .

I

E x p e r im e n t a l W o r k

1

1 Apparatus a nd p ro ce du re

T h e p a c k e d c o l u m n c o n s i s t e d o f a 1 2 . 0 - c m I . D . j a c k e t e d

a c r y l - r e s i n t u b e p a c k e d t o t h e h e i g h t s o f 0 . 2 m o r 0 . 3 m

w i t h 1 5 m m c e r am i c R a s c h i g r i n g

a nd

1 / 2 - an d 1 -in .

c e r am i c spheres .

The

l i q u i d d i s t r i b u t o r

w a s

made of

a c r y l - r e s i n a n d h a d s i x t y o n e 3 . 5 m m I . D . g l a s s n i p p l e s

a r ranged in

a

l l .6mm t r i a n g u l a r p i t c h .

T h e a q u e o u s s o l u t i o n s o f 0 . 0 5 , 0 . 1 , 0 . 2 5 , 0 . 5 a n d 1 . 0 i V -

N a O H w e r e i r r i g a t e d o v e r t h e p a c k in g s a f t e r h ea t i n g i n

th e the rm o sta t tank w hich was c o n t r o l l e d

a t 3 0 l C .

A i r f r om

a b l owe r

a n d ca rb o n

d i o x i d e

f r om a c y lin de r

w e r e f e d t o t h e b o t t o m o f t h e p a c k e d c o l u m n a f t e r t h e

g as

mix t u r e

wasw e l l m ix e d

a n d

saturated w i t h w a t e r

vapo r. The CO 2con ten t in the a ir w as con tro lled by a

r e d u c i n g v a l v e a t t h e C O 2 c y l i n d e r . T h e p a r t i a l p r e s s u r e

o f t h e s o l u t e g a s , p , w a s m a i n t a i n e d c o n s t a n t i n e a c h r u n

J O UR N AL O F C H EM IC AL EN GIN EER IN G O F JAP AN

7/25/2019 Gas absorption with chemical reaction in packed.pdf

2/5

in th e range o f 0 .0 3~ 0 . 0 7a im .

The gas and l i q u i d samp le s f o r

a n a l y s i s

were taken at

th e

i n l e t

an d o u t l e t

o f

th e co lumn . CO2

i n

a g as ph as e

w a s a n a l y z e d b y a m o d i f i e d O rs a t a p p a r a t u s w h i c h h a d a

l O O c c g a s b u r e t t e w it h O .l c c . s c a l e s . T h e e r r o r o f a n a l y -

s i s

f o r

l O O c c

o f

s a m p l i n g ga s was about 0 . 0 5 . L i q u i d

samples

were analyzed f o r t h e concentrations o f t o t a l

a l k a l i a n d h y d r o x i d e b y t h e W i n k l e r m e t h o d .

1 2

E xp erim ental results

The o ve ra l l c a p a c i t y coefficients, Kg HCO3 5)

H CO 3 + O H > C O 3 + H 2O (6)

Reaction

5 ) m ay be c o n s i d e r e d

t o b e

r a te c o n t r o ll i n g

because

Reaction

6 ) i s

a p r o t o n

t r a n s f e r r e a c t i o n a n d

about

1 0 3

t i m e s

a s

r a p i d

a s R e a ct i o n

5 ) .

T h u s ,

t h e a b -

s o r p t i o n o f CO2 i n

a N a O H

s o l u t i o n

i s

r e g a r d e d as gas

a b s o r p t i o n

accompanied b y

a r e l a t i v e l y

s low s ec on d- or de r

reaction.

The rate of absorp tion with chem ical reaction can be

e x p r e s s e d b y E q . 7 ) .

NA = pkL {CA i - C ao) = kL \CA i - C ao) (7 )

whe r e / 3

is

th e s o - c a l l e d r e a c t i o n

f a c t o r an d

C a o b ec om e s

ze ro f o r a n i r r e v e r s i b l e r e a c t i o n . The reaction factor

d e p e n d s o n t h e k i n e t i c s o f t h e r e a c t i o n a n d o n t h e p a r a m e -

t e r s y , r a n d . q . H a t t a 6 ) , D a n ck w e r t s 4 ) , v a n K r e v e l e n

V O L . 1 N O . 1 1 9 6 8

T a b l e

E n d

e f fe c t o f

th e p a c k e d c o l u m n

N o rm a l i t y ( J V )

0 . 9 1 0 . 5 1 0 .2 7 0 .1 4 0 .0 7

E qu iv a l e n t p a c k in g

h e i g h t w ) 0 . 0 7 3

0 . 0 6 2

0 . 0 5 9 0 .0 5 8 0 .0 5 5

F ig. I KgOdata for CO2 absorp tion into aqueous NaOH

s o l u t i o n s a t 3O C

a n d H of t i j z e r 1 8 ) a n d B r i a n 2 3 ) p r e s e n te d r e l a t i o n s b e tw ee n

a n d 7 * ,

r

an d

q

f o r

second order or

p s eu do f ir st -o rd er

i r r e v e r s i b l e

r e a c t i o n s b a s e d

on

t h e

p a r t i c u l a r

m odels of

t h e f l u i d dynamics o f t h e p r o c e s s .

T h e r a t e c o n s t a n t s f o r R e a c t i o n ( 5 ) h a v e b e e n r e p o rt e d

b y m a n y i n v e s t i g a t o r s . I n o u r l a b o r a t o r y , M i w a9 ) f o u n d

k r o = 7 2 0 0 1 / m o l - s e c

a t 3 0 C where

k r o is

k r a t i n fi n i t e

d i l u t i o n u s i n g t h e l i q u i d j e t . F o r t h e s o l u t i o n o f a g i v e n

concentration,

t h e

f o ll o w i n g r e l a t i o n

i s

f o u n d a t 3 0 C

logfc = 3.875 +?/. 8)

where th e v a l u e o f f a c t o r , q, i s 0 .1 3 3 9 > 1 0 ) .

To estimate

t h e d i f f u s i v i t y o f th e s o l u t e

i n * th e e le c t r o -

l y t e s o l u t i o n , D L , t h e m o d i f i e d S t o k e s - E i n s t e i n ' s e q u a t i o n

was used,

DlVl71 = const. 9)

M iw a 9 ) f o u n d t h a t n w a s 0 . 9 t o f i t t h e e q u a t i o n ( 9 ) t o

t h e experimental d a t a f o r t h e sys t ems o f v arious s olute

gas and one-valency electroly te solution containing sodium

ion.

He n c e

t h i s r e l a t i o n wa s used f o r

N a O H s olu t ion .

The d i f f u s i v i t i e s r a t i o , r=Don /D.ca* , i n potass ium or

sodium hydrox ide solution were 1.67 at 20C according

t o N i j s i n g e t a l . 1 0 ) a n d t h i s v a l u e w a s u s e d b y a s s u m in g

t h a t r

was

independent o f temperature

i n t h e

range of

20~30C.

S a t u r a t e d concentration

o f CO2 i n an e l e c t r o l y t e s o l u -

t i o n was e s t i m a t e d

b y

t h e van K revelen s m ethod19 ).

A l t h o u g h a p a r t o f N aO Hw o u l d c h a n g e i n t o N a 2 C O 3 i n

t h e p a c k e d c o l u m n , o n l y t h e i n i t i a l c o n c e n t r a t i o n o f N a O H

ha s been taken i n t o

a ccoun t a s

t h e s a l t i n g e f f e c t on th is

s a t u r a t e d

concentration, Caz , unde r

t h e a ss um p tion th at

t h e s a l t i n g e f f e c t s o f t h e s e two

s o l u t i o n s

t h a t i s N a O H

and N a2CO3 solutions) are the sam e.

The liquid side m ass transfer coefficient was calculated

b y E q. ( 3 ) .

E s t i m a t e d v a l u e s o f k r , D L a n d H c a l c u l a t e d b y t h e

above m entioned m ethods and liquid p rop erties used in

63

7/25/2019 Gas absorption with chemical reaction in packed.pdf

3/5

t h i s w o r k a r e t a b u l a t e d i n T a b l e 2 .

T h e th e o r e t i c a l r e a c t i o n f a c to r , / 3 , f o r e a c h e x p e r im e n t a l

c o n d i t i o n w a s c a l c u l a te d b y E q . ( 1 0 ) o f v a n K re v e le n 1 8 ) .

P ta nh rV l-E ^ -D /r?] UW

I n t h e c a l c u l a t i o n o f y - ^ J k r C j iD L / k L , t h e c o n c e n t r a t i o n

of N aOHwa s ca lcu la ted a s th e a r ithm etic m ea n va lue of

i n l e t a n d o u t l e t l i q u id c o n c e n t r a t io n s , C b . T he m a x im u m

conversion

o f

h y d r o x i d e t o

ca rbona te

amou n t ed

to 38

f o r

0 . 9 1 A b

s o l u t i o n

a nd

6 4

f o r

0 .07N.

T h i s

ra n ge of

th e con cen tra tion corresp on ds to th e regem es of th e p seudo

F i g

2

T h e o r e t i c a l

a n d o b s e r v e d v a l u e s o f f t f o r C O 2

a b s o r p t i o n i n to a q ue o u s N a O Hs o lu ti o n s

first-order rea ct ion a s wel l a s th e slow secon d-order rea c-

t ion .

T h e o b s e r v e d v a l u e s o f / 3 i n t h e p a c k e d c o l u m n f o r g a s

a b s o r p t i o n

w i t h a

ch em ica l rea ct ion

ca n b e d ete rm in ed

f r o m E q . ( l l ) a s s u m in g th e r e s i s t a n c e s in e a c h p h a s e a r e

a d d i t iv e ,

1/Ka a - 1/koa + l /H fikLa (l l )

a n d e v a l u a t i n g e a c h c a p a c i t y c o e f f i c i e n t , T z g c l a n d k , L a , f o r

p h y s i c a l a b s o r p t i o n

from

t h e product o f k a g i v e n b y E q .

( 2 ) o r k L b y E q . ( 3 ) a n d a m b y E q . ( l ) . T h e e v a lu a te d

v a l u e o f k a a a m o un te d to a b o u t 1 0 o f th e to t a l r e s i s t a n c e

f o r 1 .O N s o lu t i o n , b u t i n th e d i l u t e s o lu t i o n i t w a s l e s s

th an a few per cen t .

Th e

values o f / 3 O b S o b t a i n e d b y Eq . ll a r e c o m p ar e d

w i t h / 3 t h e o c a l c u l a t e d b y E q . 1 0 i n F i g . 2 . T h e o b s e r v e d

a n d

t h e o r e t i c a l values

o f Z

a r e

in

agreemen t

w i t h i n a n

er ror

o f 3 0 .

3 . R e l a t i o n s h i p b e t w e e n W e t t e d a n d I n t e r f a c i a l A r e a s

I n t h i s s t u d y , i t w a s a s s u m e d t h a t a w i s i d e n t i c a l t o a .

owever t h e

v a l i d i t y

o f

t h i s

assumption

n eeds fur th er

discussion.

I n t h e c a s e o f a p s e u d o f i r s t - o r d e r r e a c t i o n , i t i s p o s s ib l e

t o o b ta i n th e in t e r f a c i a l a r e a i n p ac k e d c o l u m n s w h e n th e

value o f

T

i s

g r e a t e r

t h a n 5 ,

because th e

value o f f l i s

n e a r ly e q u a l to T a n d f r o m th e d e f in i t i o n o f T , a i s d i r e c t ly

determined b y th e E q . (12 ).

kLa kLa

, >.

a=lkT=~7m5T

_ ( 1 2 )

whe r e Cb is a p p r o x i m a t e l y

cons tan t a n d

krCB r ep r es en t s

th e pseudo f i r s t - o r d e r r e a c ti o n r a t e c o n s t a n t.

Y o s h id a -M i u r a 2 1 ) r e p or te d th a t th e in t e r f a c ia l a r e a c a l -

c u l a t e d

b y

E q .

1 2 was-

i d e n t i c a l w i t h aw

o f H ik i t a s

e q u a t i o n

a n d t h i s is

shown

by a

d o t t e _ 4

l in e in F ig . 3 .

F ig . 3 I n t e r f a c i a l a r e a s f o r c h e m ic a l

a b s o r p t i o n

a n d

w e t t e d s u r f a c e a rea in

p ac ke d c o l u m ns

T a b l e 2 L i q u id p r o p e r t i e s o f N aO Hs o l u t i o n , d i f f u s i v i t i e s , H e n r y s l a w c o n s t a n t o f C O 2 in N aO Ha q u e o u s s o l u t i o n s a t 3 O C

OH '

K k g / m 3 ) M k g / m - h r )

( j( d y n e / c m ) D L x 1 0 6 ( m 2 / h r )

Hx102( -g ^^ )

k rx 1 0 ~ 7 f 1 ^ - r - )

\ m

atm

/ \kg-mole n r/

0 . 9 1 1 0 3 7 3 . 4 9

7 2 .5 6 .6 2 2 .2 6 3 .5 7

0 . 5 1 1 , 0 1 9 3 .2 3 7 1 .9 7 . 1 3 2 .5 4 3 .1 5

0 . 2 7

1 , 0 0 9 3 . 0 7 7 1 . 6

7 . 4 9

2 . 7 1 2 . 9 3

0 . 1 4 -1 ,0 0 4 2 .9 8 7 1 .4 7 .6 7 2 .8 4 2 .8 2

0..Q7 1 001 2.93 71.3 7.81 2.91 2.76

0

9 9 6

,

2 .8 8 7 1 .2 7 .9 2 2 .9 7 2 .5 9

6 4

JO URNAL O F CH E MICAL E NGIN E ERING O F JAPAN

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4/5

a w a s c a lc u la te d fro m K a a d a ta o f T e p e a n d D o d g e 1 7

a n d

L e v a 8

o n th e

a b s o r p t i o n o f C O 2 in

N a O H s o lu tio n

n e g l e c t i n g

th e

ga s

p hase

r e s i s t a n c e , a n d f r o m k La d ata

o f V a ss i l a to s2 0

o n th e a b s o r p t i o n

o f

C O 2

in t o a m m o n ia -

c a l s o l u t i o n using k r given b y Pinsent e t a l . . 1 3 A l l o f

t h es e d ata s e e m t o b e i n th e r e g io n o f th e p s e u d o f i r s t - o r d er

r e a c t i o n b e c a u s e o f t h e h i g h

concentration o f

a l k a l i a n d

th e lo w p a r t ia l p re s s u re o f C O 2 . T h e in te r f a c ia l a re a in

t h e p a c k e d c o l u m n s h as a l s o b e e n r e p o r t e d b y D a n c k w e rt s

e t a l . 5 a n d R ic h a r d e t a l . . 1 4 T h e s e d a ta a r e s h o w n i n

F i g . 3 w i t h a l i n e o f a w f r o m E q . l . T h e a g r e e m e n t

b e t w e e n awa n d a s h o w s t h a t th e g a s - l i q u i d

in t e r f a c e i s

uniformly

e f f e c t i v e an d

e s s e n t i a l l y

i d e n t i c a l w i th a w f o r

g as a b s o r p t i o n w i t h a p s e u d o

f i r s t - o r d e r

r e a c t i o n u n d e r

t h e s e c on d i t i o ns .

T h e in t e r f a c i a l a r e a f o r 1 - a n d l / 2 - in B e r l s a d d l e s w a s

c a l c u l a te d f r o m K G a d a ta f o r C O 2 -N aO H s y s t e m o f L e v a 8

a n d a re

s ow in

F i g . 4 .

K G a data

f o r 1 -

a n d l/2 -in :

s p h e r e s w e r e o b t a i n e d b y t h e a b s o r p t i o n o f C O 2 in t o 1 2 V -

aO s o l u t i o n

i n t h e s a m e

a p p a r a tu s

d e s c r i b e d

in th e

s e c t io n 1 -1 . T h e in t e r f a c ia l a r e a s f r o m th e s e d a ta a r e

sh o w n in F ig . 5 in w h ich th e ag reem en t b etw een a an d

a w i s a l s o f a i r ly g o o d .

A s s h o w n in F ig s . 3 , 4 a n d 5 , t h e a g r e e m e n t b e t w e e n

a a n d a w f o r R a s c h ig r in g s , B e r l s a d d l e s a n d s p h e r e s s u b -

s t a n t i a t e s t h e

u se o f E q . l f o r e s t im a t io n o f t h e in t e r -

f a c i a l area in pack ed colum ns.

F ig . A I n t e r f a c i a l a r e a s f o r g a s a b s o r p t io n w i th p s e u d o f i r s t -

o r d e r

r e a c t i o n

a n d

wetted

s u r f a c e

areas fo r e r l s a d d l e s

F i g 6 E f f e c t o f a l k a l i

c on ce nt r a t i o n o n

rate o f absorp tio n of C O 2

I n t h i s w o r k , t h e r e a c t i o n f a c to r , / 3 , f o r a s e c o n d o r d e r

r e a c t io n h as b e e n o b ta in e d f ro m th e e x pe r im e n ta l r e s u l t s b y

a s s u m i n g a = a w . T h u s , / 3 o t > s c a l c u l a t e d b y E q . l l c o i n c i d e s

w i t h

/ 3 t n e o

c a lc u la te d f ro m E q . 1 0 a s

s h o w n

in F ig . 2 .

T h i s a g re em e n t b e tw e e n / 3 t h e o a n d / 3 O b s w i t h in a r e as o n a b le

e rro r su bsta ntia te s th e a ssu m ptio n th at a =a wm ay b e a p-

p l i c a b l e f o r

th e

c h e m i c a l

a b s o r p t i o n

in p a c k e d c o l u m n s.

T he re a re o bv io usly so me d iffe re n ces b etw ee n a w a n d a

i n p a c k e d c o l u m n s, b e c a u s e t h e w e tt e d s u r f a c e m e as u r e d

is th e s o l i d - l i q u i d

i n t e r f a c e an d i t d o e s no t i n c l u d e t h e

a re a o n c o lu m n s w a ll. O n th e o th e r h a n d , th e c h a n g e

o f l i q u i d

p a t h

an d th e i so l a t e d d r o p l e t s

o n

th e pack ing

p i e c e s

m a k e aw larger. I t s e e m s , h o w e v e r ,

t h a t t h e s e

m a t t e r s c o m p e n s a t e e a c h other a n d h e n c e

E q . l a g r e e s

w e l l w ith th e in te r f a c ia l a re a .

i \ . E f f e c t o f A l k a l i C o n c e n t r a t i o n o n K G C t

T h e

rate o f

a b s o r p t i o n

o f C O 2

i n t o

a n a lk a l i so lu t io n

d e p e n d s

n o t

o n l y o n th e concentration

o f C O 2 a t t h e

in t e r f a c e , C a i , b u t a l s o o n th e c o n c e n t r a t i o n o n h y d ro x id e

i o n s

in

l i q u i d , C b .

F i g . 6 s h o w s t h e e f f e c t o f a l k a l i c o n c e n t r a t io n o n K aa

in th e

l i te r a t u r e 1 > 1 7 .

A s s h o w n

in

F i g .

6 ,

th e d a t a o f

T ep e- D o d g e1 7 ar e in th e r an g e

o f

h i g h concentration of

Na O Ha n d s h ow s th e m ax im ump o in t o f K gc i a t a b o u t

F ig . 5 I n t e r f a c i a l a r e a s f o r g a s a b s o rp t io n w i th p s e u d o

f i r s t - o r d e r

r e a c t i o n a n d

wetted

s u r f a c e a r e a s

f o r sp he re s

V

O L . 1

N O . 1

1 9 6 8

6 5

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5/5

1 . 8 A T . T h e r e l a t i o n i s s eemed t o b e o r i g i n a t e d i n t h e

changes o f t h e

d i f f u s i v i t y

an d

s o l u b i l i t y

o f s o l u t e

g a s i n

e l e c t r o l y t e s o l u t i o n . T h e h i g h e r C b i s , t h e m o r e v i s c o u s

t h e s o l u t i o n i s a n d h e n c e D l, b e c o m e s s m a l l e r .

As s umi n g

th e

r e a c t i o n t o b e

a pseudo

f i r s t - o r d e r , K a a

f o r a lk a l i s o lu t io n c a n b e c a l c u l a t e d b y E q . ( l l ) a n d ( 1 2 ) .

A s shown

in

F i g .

6 ,

KGa c a l c u l a t e d f o r C O 2 - a bs or p ti o n

i n t o

NaOH s o l u t i o n agrees so w e l l w i t h t h e o b s e r v e d

va lue o f T e pe -D o d ge , and sh o w s th e m axim um p o in t at

1 . 7 5 A T .

F or

KO

s o l u t i o n s ,

Kgcl

values

c a l c u l a t e d b y

Eqs . ll )

a n d

1 2 ) i s

s h o w n

by a curve

5

i n F i g . 6 a n d

t h e m a x i m u m p o i n t i s f o u n d a t a b o u t 4 . 5 A T . T h i s d i f -

ference o f C b b etw een NaOHand KOHsolutio n co mes

from the fact that the variation of the viscosity of KOH

s o l u t i o n w it h C b i s s m a l l e r t h a n t h a t o f t h e v i s c o s i t y o f

N a O H s o l u t i o n s .

C o n c l u s i o n

T h e e xp erim e nts

o f t h e

a b s o r p t i o n o f c arb on d io xid e

in to aq ueous sod ium hy droxide so lutions w ere carried out

i n t h e c o l u m n p a c k e d w i t h 1 5 m m R a s c h i g r i n g s a n d 1 / 2 -

in

an d

1 - i n S p h e r e s .

Kaa

fo r

t h e c h e m i c a l a b s o r p t i o n i s p r o p o r t i o n a l t o t h e

1 / 3 ~ 1 / 2 p o w e r o f th e

l i q u i d

r a t e

in

th e range o f 1 . 0 ~

0 .05iV -NaOH. T hese values of Kgcl can be evaluated by

u s i n g

t h e

r e a c t i o n

f a c t o r

o f th e

f i l m

t h e o r y fo r g a s a b -

s o r p t i o n w it h s e c o n d - o r d e r r e a c t i o n d e r i v e d b y K r e v e l e n ,

w i t h E q . 1 ) f o r a w , E q . 2 ) f o r k G a n d E q . 3 ) f o r k L .

B y m e a n s o f t h e g a s a b s o rp ti o n w i t h p s e u d o f i r s t - o rd e r

r e a c t i o n s , it

h a s been s u b s t a n t i a t e d

t h a t th e wetted sur-

f a c e

a rea

o f E q. l) m ay b e a pp ro xim a te ly e q u a l t o t h e

i n te r f a c ia l a r e a .

T h e d ep en de nc ie s o f Ka a o n NaOHco nce ntratio n w as

c l a r i f i e d an d t h i s tendency c o i n c i d e d q u i t e w e l l w i t h t h e

e xperim en tal data .

Nomenclature

a = in te r facial a rea in packin g [m 2/m 3 ]

a t = to tal surface a re a o f p ack in g [m 2 /m 3 ]

< X w . = w e tte d surface a rea o f p ack ing [m 2/m 3 ]

C a i , C ^ i o - c o n c e n t r a t i o n o f c o m p o n e n t a b s o rb e d a t i n te rf a c e a n d

c B

D

G

G M i

g

H

K G

k G

6 6

in

th e

b u l k o f l i q u i d ,

r e s p e c t i v e l y [ k g - m o l e s / m 3 ]

concentration o f

th e

reactant

i n th e

b u l k o f l i q u i d

[k g -m o le s /m 3 ]

av erage concentration o f

th e

r e a c t a n t [ k g -m o le s/ m 3 ]

d i f f u s i v i t y [ m 2 / h r ]

s u p e r f i c i a l

m a s s v e l o c i t y o f g a s [ k g / m 2 - h r ]

s u p e r f i c i a l mola r v e l o c i t y o f i n e r t g a s

[kg moles/m2 hr]

g r a v i t a t i o n a l c o n s t a n t [ m / h r 2 ]

He n ry s law c o n s ta n t

[ k g - m o l e s / m 3

- a tm ]

overall coefficient [kg-m oles/m 2 - hr - atm ]

g a s- ph a se m a s s t ra n sf e r c o ef fic ie n t

[kg moles/m2 hr atm]

liq uid-ph ase m ass tran sfe r coe ffic ien t [m /h r]

l i q u i d - p h a s e c o ef f i c i e n t f o r c h e m ic a l a b s o r p t i o n

[ m / h r ]

k r

N A

P

= re actio n ra te c on sta nt fo r se co nd -o rd er re actio n

[mVkg mole hr]

= s u p e r f i c i a l m a s s v e l o c i t y o f l i q u i d [ k g / m 2 - h r ]

= ra te o f ab so rp t io n [k g -m o le /m 2 -h r ]

= to tal p re ssure [atm ]

= partial p ressure [atm ]

= p a r a m e t e r d e f i n e d b y { C b q / v C a i ) [ - ]

= g a s c o n s ta n t [m 3 -a tm /k g -m o le - K]

r a t i o

o f l i q u i d d i f f u s i v i t i e s , D o n / D e o . ,

a b s o lu te t e m p e ra tu re

m o l e r a t i o o f

s o l u t e in

g a s p h a s e

m o l e

f r a c t i o n

o f

s o l u t e

in

g a s p h a s e

h e i g h t o f p a c k i n g s

Gr ee k le tt er s

P = r e a c t i o n c o e f f i c i e n t d e f i n e d b y k i P /k z

7 = p a r a m e t e r d e f i n e d b y { \ l k r C s D L /k z )

P viscosity

P = de nsity

[- ]

[K]

[- 1

[- ]

[m l

[- 1

[- 1

[kg/m-hr ]

[k g / m 3 ]

a = surface ten sio n [dy ne s/cm ] o r [kg /h r2 ]

O c = c r i t i c a l s u r f a c e t e n s i o n o f p a c k i n g m a t e r i a l

[ dynes cm]

v = s to ic h io m e tr ic fa c to r [ -]

Sub sc r ip t s

1 , 2 = b o t t o m a n d t o p o f c o l u m n , r e s p e c t i v e l y

G , L = g a s a n d l i q u i d p h a s e , r e s p e c t i v e l y

L it e r a t u re c i t e d

1 ) B l u m , H . A ., L . F . S t u t z m a n a n d W .S . D o d d s . : I n d . E n g .

C h e m . , 4 4 , 2 9 6 9 ( 1 9 5 2 )

2 B r i a n , P.L.T.:

S c .

D . t h e s i s , M.I .T. ,

C am bridge (1956 )

3

B r i a n , P.L.T . ,

J . F .

Hurley

an d

E . H.

H a s s e l t i n e :

A. I. C h.

E . J o u r n a l , 7 , 2 2 6 ( 1 9 6 1 )

4 ) D a n c k w e r ts , P . V .: T r a n s . F a r a d a y S o c , 4 6 , 3 0 0 ( 1 9 5 0 )

5 ) D a n c k w e r t s , P . V ., A . M . K e n n e d y a n d D . R o b e r t s : C h e m .

Eng. S c i . ,

1 8 ,

6 3 ( 1 9 6 3 )

6 H a t t a , S. :

J.

Soc.

C h e m . I n d . ( J a p a n ) , 35 , 1 3 8 9 1 9 3 2 ) , 3 1 , 8 6 9

1 9 2 8 )

7 ) H i k i t a , H . a n d T . K a t a o k a : K a g a k u K o g a k u , 2 0 , 5 2 8 ( 1 9 5 6 )

8 L e v a , M .: A . I. C h . E.Journa l , 1 , 2 24 ( 1 95 5)

9 ) M iw a , Y .: S c . M . t h e s i s , N a g o y a U ni v e r s i ty , N a g o y a ( 1 9 6 4 )

1 0 ) N ij s i n g , R . A .T . O . , R . H . H en d r i k s z a n d H .K r a m e r : C h e m .

Eng.

Set.,

1 0 , 8 8 ( 1 9 5 9 )

l l ) O n d a , K ., H .T a k e u c h i a n d Y . K o y a m a : K a g a k u K o g a k u ,

3 1 , 1 2 6 1 9 6 7

2

O n d a , K. , H.

Takeuchi

an d Y . Okum o to : J.

C he m . E n g .

J apan ,

1 ,

6 1 9 6 8 )

1 3 ) P i n s e n t , B . R . W . , L . P e r s o n a n d F . J . W . R o u g h t o n : T r a n s .

F a r a d a y S o c . y 5 2 , 1 9 5 4 1 9 5 6 )

1 4 ) R ic h a r d s , G . M . , G . A . R a t c l i f f a n d P . V . D a n c k w e r t s : C h e m .

Eng. S c i . , 1 9 , 3 2 5 ( 1 9 6 4 )

1 5 ) S h e r w o o d , T . K . a n d R . L . P i g f o r d : A bs o r p t i o n a n d E x -

t r a c t i o n 2 n d . p . 3 3 6 , M cG ra w -H il l , N e w Y o r k ( 1 9 5 2 )

1 6 S h u l m a n , H . L . , C . F . U l l r i c h , A . Z . P r o u l x a n d J . O . Z i m m e r -

man:

A. I. C h .

E . Journal ,

1 , 2 5 3 ( 1 9 5 5 )

1 7 ) T e p e , J . B . a n d B . F . D o d g e : T r a n s . A m . I n s t . C h e m . E n g r s . y

3 9 , 2 5 5 ( 1 9 4 3 )

1 8 ) V a n K r e v e l e n , D . W . a n d P . J . H of t i j z e r : R e c . T r a v . C h i m . ,

6 7 , 5 6 3 , 5 8 7 ( 1 9 4 8 )

1 9 ) V a n K re v e l e n , D . W . a n d P . J . H o f t i j z e r : C h i m . I n d u s t r .

XXIeme

C o n g r . Int .

C h i m .

Industr.,

1 6 8 ( 1 9 4 8 )

2 0 ) V a s s i l a t o s , G.,

O.

T rass and

A.I. Johnson: C a n . J. C hem .

E n g . , 4 1 , 7 ( 1 9 6 3 )

2 1 ) Y o s h id a ,F . a n d Y . M i u r a : A . I . C h . E . J o u r n a l , 9 , 3 3 1 ( 1 9 6 3 )

2 2 ) W eisman , J. an d C.F .

B o n i l l a : Ind.

E n g . C h e m . ,

4 2 , 1 0 9 9

( 1 9 5 0 )

J O U R N A L O F C H E M I C A L

E N G I N E E R I N G - O F J A P A N