Modification of the Gas Outlet Structure on the Spouted Bed With Inner Draft-tube
Transcript of Modification of the Gas Outlet Structure on the Spouted Bed With Inner Draft-tube
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M O D IFIC A T IO N O F TH E G A S O U T L ET ST R U C T U R E O N T H E
SPO U TED BE D W ITH IN N ER D R A FT TU B E
Hiro tsugu HATTORI Atsu ro K OBAY ASHI Iw ao AIBA and Tetsuya K ODA
D e p a r tm e n t o f C h e m ic a l E n g in e e ri n g S h in s h u U n iv e r s i t y V e d a 3 8 6
K e y W o rd s: C h em ic al R e ac to r S po ute d B e d M o dif ic at io n D ra ft T u b e G a s O u t le t
T h e s id e - o u t le t s p o u te d b ed w i th i n n e r d r a f t - tu b e
h a s m a n y a d v an t a g e o u s c h a r a c t e r i s t i c s . O n e o f t h e m
t h a t a l l o f th e g a s p e r c o l a te s t h r o u g h th e a n nu la r
d e n se b ed a n d su c h a f lo w p a tte rn o f g a s g iv e s h ig h
e f f i c i e n c y o f g a s s o l i d c o n ta c t . T h e s i d e o u t l e t s p o u t e d
b e d w i t h i n n e r
d r a f t - t u b e
p r o v i d e s h i g h g a s c o n -
v e r s i o n s
in th e
f i r s t - o r d e r
s o lid - c a ta ly ze d re a c tio n .4
A n o th e r is th e p o s s ib il ity o f th e u s e o f re la tiv e ly f in e
s o l i d p a r t i c l e s . 1 } H o w e v e r t h e s i d e o u t l e t s p o u t e d b e d
w i th in n e r d r a f t - tu b e a ls o h a s s o m e d i s a d v a n t a g e o u s
c h a r a c te r is t ic s . T h e m o s t s e r io u s o n e l ie s in th e s t r u c -
t u r e o f th e g a s o u t l e t . F in e s c r e e n s a r e u s u a l ly p u t o n
th e g as o u tl e t o p en in g s o f th e s id e - o ut l e t s p ou te d b e d s
p re v io u s ly p ro p o s e d .2 ~ 4 S u c h a s tr u c tu r e o f th e g a s
o u t l e t c a u s e s p l u g g i n g o f s o l i d p a r t i c l e s w hen fin e
p a r t i c l e s o r f r i a b l e p a r t i c l e s a r e s p o u t e d . T h i s i s a n
im p o r t a n t p r o b le m a n d s h o u ld b e s o lv e d in o rd e r to
a p p ly th e s id e - o u t le t s p o u te d b ed w ith in n e r d r a f t -
t u b e
to
i n d u s t r i a l o p e ra ti o n s
W ep ro p o s e d in th e p r e v io u s p a p e r a d i f f e r e n t g a s
o u t l e t s t r u c t u r e to
a v o i d
t h e p lu gg in g o f
s o l i d p a r
t ic le s .^ A s ta tio n a ry so lid b ed w a s a tta c h ed o u ts id e
th e g a s o u t l e t o p e n i n g s . I n
t h i s
s t r u c t u r e
t h e r e
i s n o
screen
o n
t h e g a s o u t l e t
o p e n i n g s
an d th erefo re
p lu g gin g d oe s n o t o c c u r . H o w e v e r t h e a t ta c h m en t o f
a s t a t i o n a r y s o l i d b e d is n o t n e c e s s a r i l y a d e s i r a b le
m eth o d . T h e r e a s o n i s a s f o l lo w s . T h e m os t im po r t a n t
c ha r a c t e r i s t i c
o f
th e
s p o u t e d
b e d i s
t h a t
a l l t h e
p artic le s alw ay s m o ve with in th e ap para tu s an d th e
at tachment
o f
th e s t a t i o n a r y s o l i d b e d r em o v e s th is
c h a r a c te r i s t i c f r o m th e m od i f i e d s p o u te d b e d . F ro m
t h i s p o in t o f v i e w w e h a v e a g a in a t t e m p te d to m o d i f y
th e s t r u c t u r e
o f
th e
g a s
ou t l e t
a n d
have i n v e n t e d a
n e w o n e .
I n t h i s p a p e r t h e n e w s t r u c t u r e o f t h e g a s o u t l e t o f
t h e s p o u t e d b ed i s p r o p o s e d . T h i s s t r u c t u r e r e q u i r e s
t h e a t t a c h m e n t o f n e i t h e r s c r e e n n o r s t a t i o n a r y s o l i d
b e d o n th e g a s o u t l e t
o p e n i n g s .
A l l th e p ar tic le s
c ir c u l a te w i t h in t h e a p p a r a tu s .
R e c e i v e d F e b r u a r y
1 6
1 9 8 3 .
C o rr e sp on de nc e c on ce rn in g
t h i s
a r t i c l e sh o u ld b e
addressedtoHHattori
1 2
1 . A N ew S tr u c t u r e o f G a s O u t le t
T h e m o d if i e d s t r u c t u r e o f t h e g a s o u t le t i s s h o w n in
F ig . 1 . A s c a n b e s e e n th e r e i n t h e c o lu m n w a l l i s
s e p a r a t e d i n t o tw o p a r t s : t h e u p p e r c o lu m n a n d t h e
l o w e r o n e . T h e d ia m ete r o f th e lo w e r c o lu m n is la rg e r
t h a n th a t o f th e u p p e r c o lu m n a n d t h e r e i s a s l i g h t
o v e r l a p b e tw e en th e tw o c o lu m n s .
I f th e s o l id p a r t ic le s a r e p o u re d in to th is a p p a ra tu s
and a su ffic ient
a m o u n t o f g a s i s
f e d
s p o u t in g b e -
h a v i o r b e g i n s . T h e s p o u t i s f o r m e d i n t h e i n n e r d r a f t
t u b e a n d a n a n n u la r b ed i s f o r m ed in th e s u r r o u n d -
i n g s o f th e s p o u t . I n th i s s t r u c tu r e tw o s t a g e s o f th e
b e d
s u r f a c e
a p p e a r a t
th e t o p
o f
th e
a n n u l a r b e d a s
s h o w n in F ig . 1 . T h e u p p e r s u r f a c e is f o rm ed a ro u n d
t h e t o p o f t h e i n n e r d r a f t t u b e a n d t h e l o w e r s u r f a c e i s
f o rmed
a round th e
l o w e r
en d
o f
th e
u p p e r c o lu m n .
T h e g a s g o e s o u t f r o m th e l o w e r s u r f a c e o n w h i c h n o
s c r e e n is a t ta c h e d a s s h o w n in F ig . 1 .
T h e m ot io n o f s o l id p a r t i c le s i s a l s o s h o w n in F ig .
1 . T he y a r e c a r r ie d u p w ard in th e in n e r d ra f t- tu b e a n d
f a l l o n t o th e above ment ioned upper s u r f a c e . T h en
th e y m ov e s lo w ly d o w n w a r d in th e a n n u la r b ed . I t i s
o b s e r v e d t h a t t h e s o l i d p a r t i c l e s f l o w r a d i a l l y f r o m t h e
i n s id e o f th e u p p e r c o lu m n w a l l t o th e b ed s u r f a c e o f
t h e l o w e r c o l u m n p a s s i n g t h r o u g h t h e p a r t j u s t b e l o w
th e e n d o f th e u p p e r c o lu m n . A f te r r e a c h in g th e l o w e r
s u r f a c e t h e s e p a r t i c l e s m o v e d o w n w a r d
a l o n g t h e
lo w e r c o lu m n w a l l r e c e iv in g a f r i c t io n a l f o r c e c a u s e d
b y t h e p a r t i c l e s m o v i n g t h r o u g h t h e i n n e r p a r t o f t h e
b ed . T h e a m o u n t o f p a r t i c le s r e a c h in g th e lo w e r
su r f a c e i s a lw a y s th e s a m e a s th a t o f p a r t ic le s le a v in g
t h e s a m e s u r f a ce . T h e re fo re t h e l o w e r s u rf a ce o f th e
a n n u la r b ed is k ep t a t a c o n s ta n t le v e l .
F ig u re 2 s h o w s th e p re s s u re d is t r ib u t io n a n d th e g a s
s t r e a m l i n e s in th e a n n u l a r b e d . T h e g a s s tr e am l in e s
a r e d r a w n in s u c h a w a y t h a t th e v o lu m e t r ic f lo w r a te
o f th e g a s p a s s in g th ro u g h e a c h s tre a m tu b e b etw e e n
tw o
a dj a ce nt s t r e am l in es is
o n e - t e n t h o f a l l t h e g a s
pe r c o l a t i n g t h r o u g h th e annulus .
N o u nd es i ra ble
c h a ra c te r i s t ic s c a n b e fo u n d in th e g a s f lo w p a tte rn .
T h e s e r e s u l t s w e r e o b ta in e d b y u s in g s p h e r i c a l g l a s s
p a r t i c l e s o f 1 .8 m ma v e r a g e d i a m e t e r a n d a i r a t r o o m
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
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F i g . 1 . M o d i f i e d s t r u c t u r e o f g a s o u t l e t .
F ig . 2 . P r e s s u r e d i s t r i b u t i o n a n d a i r s t r e a m l i n e s i n a n n u l a r
b e d .
t e m p e r a t u re . P h y s i c a l p ro p e r t i e s o f t h e s e p a r t i c l e s a r e
s h o w n i n T a b l e 1 .
T a b l e 1 . P h y s i c a l p r o p e r t i e s o f s o l i d p a r t i c l e s
G la s s b e a d s s p e c i f i c g r a v i t y = 2 . 5
rp verage diameter Terminal velocity
Tylermesh 7 r /
mm ms]
9 1 0 1 . 8 1 0 . 5
C o n c l u s i o n
A m od if ied s tru c tu re o f th e ga s ou tle t o f th e
s p o u te d b e d w i t h i n n e r d ra f t - t u b e w a s d e v e l o p e d a n d
t h e g a s s t r e a m l i n e s i n t h e b e d w e r e m e a s u r e d . T h e
new
s t r u c t u r e r e q u i r e s t h e a t t a c h m e n t
o f n e i t h e r
s c r e e n no r
s t a t i o n a r y
s o l i d b e d o n t h e g a s o u t l e t
o p e n i n g s . I t w as fo und t h a t t h e
p r o b l e m
o f t h e
p l u g g i n g o f s o l i d p a r t i c l e s c a n b e a v o i d e d w i t h o u t
p r e v e n t i n g c i r c u l a t i o n o f t h e p a r t i c l e s i n t h e v e s s e l .
A c k n o w l e d g m e n t
W e would lik e to exp re ss ou r th ank s to D r. T akash i S h ira i o f
Tokyo
S c i e n c e
U n i v e r s i t y f o r
h is h e l p f u l
s u g g e s t i o n s .
W e a r e
g r a t e f u l
t o D r.
T a i i c h i S h i b u y a and
D r. H i d e om i
M atsu d a o f
S h i n s h u
U n i v e r s i t y f o r h l p u l d i s c u s s i o n s and
f o r
r e a d i n g t h e
m a n u s c r i p t .
N o m e n c l a t u r e
D =g a s i n l e t
d i a m e t e r [ m ]
U t = ave ra g e g a s ve lo c ity a t g a s in le t [m /s ]
L it e ra t u re C it e d
1 H a t t o r i , H . a n d K . T a k e d a : J , C h e m . E n g . J a p a n , l l , 1 2 5
1 9 7 8 .
2 H at t o r i , H ., K . T a n a k a a n d K . T a k e d a : / . C h e m . E n g . J a p a n ,
1 4 , 4 6 2 1 9 8 1 .
3 T a k e d a , K . a n d H . H a t t o r i : K a g a k u K o g a k u R o n b u n s h u , 1 ,
1 4 9 1 9 7 5 .
4 T a k e d a , K . a n d H . H a t t o r i : K a g a k u K o g a k u R o n b u n s h u , 2 ,
5 0 7 1 9 7 6 .
V O L 1 7
N O .
1 1 9 8 4
10 3