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PERFORMANCE O F AN AGITATOR ABSORBER INREMOVING .COz FROM A GAS
A Sta t i s t i c a l Inves t iga tion by Albert S. Moore a nd S idney 'Ka te l lU. S; Bur eau of Mines , Bran ch of Coal Gasi f ica t ion
Morgantown, West Virg in ia
ABSTRACT
The e ff ec t s o f p r oc es s p r e s su re , ca rbon d ioxide con ten t of t hefeed gas , so lu t ion th roughput , and l i qu id - to -gas r a t i o on the pe r fo rmanceof an ag i t a to r ab so rb e r a t levels of 200-300 p. s . i. g . , 10-20 m o l - p e r c e n t ,60-90 g al . / h r. , a n d 16.5-55 gal . /h r. so lu t ion per 1000 s td . cu. f t . g a s / h r . ,r e sp ec t iv e ly, have been de t e rmin ed . The abso rben t u sed was 40 weight-pe rce n t d i e thano lamine in wa te r ; t he gas u sed was in e r t gas w ith ca rbondioxide added.
T he d a t a a n d r e s u l t s f r o m t h r e e s e t s of s e q u e n t i a l f a c t o r i a le x p e ri m e n ts a r e p r e s e n t e d .of the four fac t ors a t thr ee lev els of opera t ion .
T h e e x p e r i m e n t s w e r e d e s i gn e d t o t e s t e a c h
h
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Not fo r Pub l i ca t ionP r e s e n t e d B e f o r e t h e D i v i s i o n of G a s a n d F u e l C h e m i s t r y
A m e r i c a n C h e m i c a l S o c ie t y
New York Ci ty Meet ing, Sept . 8-13, 1957
" P e r f o r m a n c e of a n A g i t a t o r A b s o r b e r i n R e m o v i n g C 02 F r o m a G a s "A S t a t i s t i c a l I n v e s t i g a t io n
A l b e r t S . Moore and Sidney Kate11U. S. Bu rea u of Mines , Bran ch of Coa l Gas i f i ca t ion
Morgantown. West Virgi nia
D u ri ng t he l a s t f if t ee n y e a r s , p r o c e s s e s f o r r e m o v i n g c a r b o nd iox ide and hydrogen su l f ide f r om indu s t r i a l ga se s by sc rubb ing with va r iou sa m i n e s h a v e b e c o m e g e n e r a l l y a c c e p t e d .employed convent ional g a s - l i qu id con tac to r s , packed columns and bubb le -c a p t o w e r s .
To d a te , t h e s e p r o c e s s e s h av e
I t has b e e n shown ha t the abso rp t iv e capa c i t i e s of the am in esi n c r e a s e m a r k e d l y wi th i n c r e a s e d c o n c e n tr a t i o n , b u t b e c a u s e of t h e o p e r a t i n gd i f f ic u l t i e s en c o u n t e r e d w h e n c o n ve n ti o na l s c r u b b e r s a r e u s e d t o p r o c e s sl iqu ids of even mod era t e v i sco s i ty, t he l imi t ing concen t ra t ion has been abou t15 pe rce n t amine in wa te r.c o m m e r c i a l i z a t i o n , m e t h o d s of gas - l iqu id contac ting ab le to to l e r a t e m or ev i scous s c rubb ing med ia mus t be developed .
T h u s , f o r t h e s e p r o c e s s e s t o r e a l i z e f u l l
This pape r d esc r ib es s tud ie s of the abso rp t ion of ca r bon d iox ide
F ig ure 1 shows a v e r t i c a l c r o s s s e c t i o n of t h e a b s o r b e r.i n 40 w e i g h t - p e rc e n t d i e t h a n o la m i n e i n w a te r u t i l iz i n g a n a g i t a t o r - t y p econ tac to r.a c t i o n w i th i n t he a b s o r b e r i s as fo llows : The l ea n so lu t ion is f ed in to the
Th e
vesse l t h rough a s p a rg e r r i n g . T h e l i q u i d is r a i s e d i n t he l i f t tube by thec e n t r if u g a l a c ti o n of t h e t u r b i n e a n d p r o p e l l e d f r o m t h e a b s o r b e r i m p e l l e rin t h e f o r m of a f i n e s p r a y. T h i s s p r a y of l i q u i d d r o p l e t s m o v e s a t a highs p e e d r e l a t i v e t o th e g a s s t r e a m , w hi ch p a s s e s t h r o u gh th e s p r a y c u r t a i n i nupward f low th rough the ab so rb e r. Inasmuch as t h i s is a r e l a t i v e l y n o v e lgas - l iqu id co n tac t o r, i t i s t o be expec ted tha t i t s mode of ac t ion would bed i s t inc t ive .
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T h e w o r k d e s c r i b e d h e r e w a s u n d e r t a k e n t o d e t e r m i n e t h e c h a r -ac te r i s t i c s of t he ag i t a t o r-a bso rbe r with r e sp ec t t o: (1) P r o c e s s p r e s s u r e ,( 2 ) car bo n dioxide content of the fee d ga s , ( 3 ) a b s o r b e n t s o lu t io n r a t e , a n d(4 ) l i q u i d - t o - g a s r a t i o .
DESCRIPTION O F GAS-PURIFICATION PIL OT PLA NT
F i g u r e 2 i s a flow d i ag ra m of the p i lo t p lan t .a b s o r b e r w a s i n s t a l l e d t o o p e r a t e w it h e x i st i n g s o l u t i o n - r e g e n e r a t i o nf a c i l i t i e s .
F o r t h i s s t u d y t he"
T h e A b s o r b e r
T he a b s o r b e i is shown in f igure 1. T h e e s s e n t i a l i n t e r n a l p a r t sa r e t h e a n n u l a r r i n g a n d l i f t t ub e a n d t h e t u r b i n e a n d i m p e l l e r. T h e t u r b i n ei m p a r t s a centr i fuga l ac t io n to the ab sorbe nt solut ion, which is d i r e c t e d b ythe annu la r r ing and l i f t t ube on to the imp e l l e r, whe re the s p ra y is f o r m e d .The l a t t i c ed f ac es o f t he i mp e l l e r a r e beveled to abou t 3 8 O off horizontal S O
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FLOW DlbGRbH OF ( G I s -PURlFlGbTlON PILOT PLbNT)
awm
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that the pr inc ipal por t ion of the sp ra y i s d i re cte d towa rd the wal ls of the
connected to the sha f t t h rough sheave pu l leys i s u se d to d r ive the tu rb in e .A cons tan t tu rb ine speed of 750 r . p , m . was us ed fo r these t e s t s .
, ' a b s o r b e r v e s s e l r a t h e r t h a n t he t o p. A 1-hp. mo tor (1.750 r . p . m .)
The React ivator'
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J
The reac t iv ato r tower i s a 17-foot length of 10- inch, schedu le40 pipe, which is packed to a depth of 15 feet wi th 314- inch Raschig r ingsand d i rec t-connec ted to the r eb o i l e r by IO-inch d ia me te r f l anges .bo i l e r is 10-feet i n length and 16 inch es in d i a m e t e r.p r es su re connect ion, connect ions fo r adding makeup condensa te and fo r
&ra ining the so lu t ion , and a the rmocoup le connec tion ins t a l l ed n ea r the endof the tube bundle . Ste am for reac t ivat ion is control led by a p r e s s u r e c o n-t ro l l e r and i s me as ure d by we igh ing the condensa te . The en t i r e un it i slagged with 2 inches of ma gn esi a insula t ion and 1/4 inch of t l Ins ulco te t l .
T he r e -It i s f i t t ed wi th a
1 Auxil iarv Eouioment
\
,
The so lu t ion hea t excha nger, so lu t ion coo le r, and ac id -gasc o o l e r a r e a ll s i m i l a r .s e c t io n s c o n n ec t ed i n s e r i e s .contain four, schedule 40, 3/4- i nch , G-f in pipes about 10 fee t long. The f i np ipes in the ac id -gas coo le r a r e abcu t 5 f ee t long .a r e i n s t a l l e d s o t h a t a l l i n l e t a nd o ut l et t e m p e r a t u r e s c a n be r e c o r d e d .
Each cons i s t s o f two Griscom -Russe l l tw in G- f inThe hea t exchanger and so lu t ion coo le r each
Thermocouple connect ions
A 1-114 by 4- inch t r ip lex , s ingle-act in g power pump ci rc ula testhe solution.a i r-ope ra ted bypass va lve .
The flow of the s olut ion to the ab so rb er is con t ro l l ed by an
The ga s i s s t o r e d , b e f o r e c o m p r e s s i o n , i n a we t -t y pe gas ho lde rhaving a capacity of 1,000 cubic feet . T h e 2 - st a g e g a s c o m p r e s s o r c a n
\ del iver 7 ,200 s tan dard cubic feet pe r hour a t 350 p. s . i . g.
Solut ion and Gas Flow
The flow of solution an d gas i n the pilot plant is typ ica l of mos tgas -pur i f i ca t ion sys tems .m o l - p e r c e n t , is t a k en f r o m th e g a s h o l d e r, c o m p r e s s e d t o a bo u t 350 p. s . i. g. ,and fed to the abso rbe r.
I n e r t g a s , v a r yi n g in C 0 2 co n te n t f r o m 7 o 10
The c a r b m dioxide ne ce ss ar y to br ing the carbon diolEide contentof the unpuri f ied ga s to the lev el of predet erm ined exp er im enta l condit ionsis added to the suct ion l ine of the c om pr es so r.
The lean die thanolamine solut ion en te rs thro ugh the top of thea b s o r b e r. I t i s d is t r i b u te d b y a spa rge r r ing d i re c t ly above the l iqu id l eve land jus t below the top of the l i f t tube and leaves the absorber through a s ideconnection 6 i nches f r o m the bo t tom.is mainta ined to a depth of 12 inches ( indi cate d by the b roke n l ine i n f igure 1) .
The l eve l o f so lu tion in the abs orb e r
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,
\ .
The die thanolamine i s for ced up in to the l i f t tube by the turbine; baff les i nt he l i f t t ube e l imina t e any swi r l i ng ac t ion .a b s o r b e r i m p e l l e r , a de f lec to r des igned to g ive ma x im um sp r ay com me n-su r a t e w i th t he d imens ions of t he abso rbe r ves se l . Th ree d is t i nc t s p r ayp a t t e r n s a r e f o r m e d - - ( l ) th e i n i ti a l s p r a y f r o m t h e a b s o r b e r i m p e l l e r , c on -s i s t i ng of sm a l l d rop le t s mov ing a t ve ry h igh ve loc i t i e s , ( 2 ) i m p a c t s p r a yfo rm ed when the in i t i a l sp ra y r ebounds f ro m the wa l l s o f t he ve s se l , and( 3 ) c on ju nc ti ve s p r a y f o r m e d w he n t h e i n i t i a l s p r a y a n d i m p a c t s p r a y c o ll id e .
The r i s in g so lu t ion con tact s t he
T h e f e ed g a s e n t e r s at the ba se of the abso rbe r to the r ig ht ofthe l if t tube.s p r a y p a t t e r n , a n d l e a v e s t h e to p of t h e a b s o r b e r i n t o a n e n t r a i n m e n t s e p a r a -t o r as p u r i f i e d g a s . I t i s th e n r e t u r n e d to the gasho lde r fo r f eed -gas makeup .
I t bubbles through the d ie thanolamine , pa ss es through the
The fouled ami ne solu t ion leaving the bot to m of the abs orb er i shea t ed by hea t exchange with l ean am ine so lu t ion and r ege ne ra t ed in t her e a c t i v a t o r w ith i n d i r e c t h e a t f r o m l o w - p r e s s u r e s t e a m .t h e t o p of t he r e a c t i v a t o r a n d p a s s e s t h ro u gh a c o o l e r w h e r e e n t ra i n e d s t e a mi s condensed and re tur ned to the column.the holder f or fee d-ga s makeup.
The ac id gas l e a v e s
T h e a c i d gas is t h en r e t u r n e d t o
The r eac t iv a t ed d i e thano lamine l eaves t he r eac t iv a to r, flowst h rough the hea t exchange r w here it g ives up a por t ion of it s hea t t o t he fouledso lu tion l eav ing the ab so rbe r, and is pumped through a wate r- co o led so lu t ionc o o l e r b a c k t o t h e a b s o r b e r.
EXPERIMENTAL PROCEDURE
The ag i t a to r gas - l iqu id con tac to r is a nov el piec e of equipm ent.T o evaluate i t i n t e rm s of m ore convent iona l gas - c l ean ing appa ra tus , packedcolumns and bubble -cap tow ers , opt imu m opera t in g condi tions for the agi ta tora b s o r b e r p r o c e s s m u s t f i r s t be f ou nd .
E igh t obvious f ac to r s w i l l a ff ec t pe r fo rma nce of t he abso rb e r :(1) P r o c e s s p r e s s u r e , ( 2 ) carb on dioxide content of the fee d gas , ( 3 ) a b s o r b e n t -solu t ion throughput, (4) l iquid- to-gas ra t io , (5) conc entra t ion of the absorb entsolut ion , (6) f eed -gas t h roughpu t, ( 7 ) t he speed of t he t u rb ine , and (8 ) ca rb ondioxide content of the lean abs orbe nt so lu tion . Al though the opera t ional lev elsof a l l of h e se f a c t o r s a r e e a s i l y c o n t r o l l e d w i th in r e l a t i v e l y n a r r o w l i m i t s ,t h e r e i s no r ea so n to suppose tha t t he e ff i c i ency of t he p roc es s is an add i ti vefunction of any tw o of them. Cons equent ly, th e com ple te explora tion of thecaus a l r e l a t i ons among these f ac t o r s would r eq u i r e t ha t t he e ffec t of e a c hfacto r be o bser ved under a l l combinat ions of va lue s of the o ther fac to rs .a procedure wou ld r equ i r e a r e l a t i ve ly l a r ge number of t e s t s .
Such
To o v e r c o m e t h i s d i f fi c u lt y, a s e r i e s of s e q u e n t i a l f a c t o r i a l e x p e r -im en t s , each concerned with a group of r e l evan t f ac to r s , was in i t i at ed .a proc edur e a l l ows fo r m ax im um f l ex ib i l i t y i n p l ann ing and has t he i n he ren tadvan tage tha t , a s each f ac to r i a l is deve loped , t he f ac to r s i nvo lved may bed i r ec t ed toward op t imum condi t ions r e l eva n t t o a l l o t h e r f a c t o r s .
Such
Pr oc es s p r e s s u re : ca rbo n d iox ide conten t of t he f eed gas , abs o r-ben t so lu t ion th roughpu t, and l i qu id - to -gas r a t i o w ere chosen as the independent -v a r i a h l e s f o r t h e i n i t i al e x p e r i m e n t ; t h e l e v e l s c h o s e n f o r t h e s e f a c t o r s w e r e
2 0 0 - 3 0 0 p . s . . g . , 10-20 mo l -pe r cen t , 60-90 g .p . h., and 16.4 -55 r e spec t ive ly .
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Liqu id - to-gas r a t i o i n t h i s i n s t ance i s def ined as gal lons of so lu t ion pe r
ce s s i s t he t o t a l ca rb on d ioxide a bso rbed , s inc e all o the r va r i ab l e s fo rt h e s e e x p e r i m e n t s w e r e p r e d e t e r m i n e d .
I, 1 , 0 0 0 s t d . cu . f t . of feed gas per hour. The dependent var ia ble in t h e p r o -',
\
1, A s dic ta ted by subsequent opera t ion , a s e c o nd f a c t o r i a l w a sdes igned a t new ope ra t iona l l eve l s fo r t he fou r f ac t o r s . The pu rpo se of thesecond se t of exper ime nts w a s t o i nves t iga te fu r the r t he i n t e r ac t ions amongthe va r ious f ac to r s r evea l ed in the i n i t i a l s e t of t e s t s . T h e b l o c k d e s i g n f o re a c h f a c t o r i a l i s pre sen ted in Appendix 1.
DATA A N D RESULTS
Ta b l e 1 pres en t s t yp i ca l ope ra t ing cond it i dns p reva l en t t h rough-out the 30 t e s t s pe r fo rmed fo r t h i s s tudy ; t ab l e 2 p re s en t s t h e cumula t ived a t a f r o m t h e se t e s t s .
I
Table 1. - Typ ica l ope ra t ing r ange fo r all r u n sGas t e m p e r a t u r e , OF.
Befo re ag i t a to r 75-85A f t e r agi ta tor 140-155
\
0
So lu tion t em pera t u re , F .
Bef ore agi ta tor 100-110
After agi ta tor 140-160
R e b o i l e r p r e s s u r e , p . s . i . g .
R e b o i le r t e m p e r a t u r e , OF. 265-275
Agi ta tor motor
6.5-8 .
A m m e t e r , a m p s 1 . 2- 1 .4Vol tme te r, vo l t s 470 ( cons t an t )
S t e a m p r e s s u r e , p. s . i. g. 22-30
Stea m consumpt ion , l b . / g a l .amine 0.6-0.8
Tu r b i n e s p e e d , r . p. m. 750 ( cons t an t )
A s t a t i s t i c a l ana lys i s of the da t a f ro m expe r ime n t "A" i s madeand an analys is of the cum ulat ive data f ro m expe r ime nts "A" and IlBl' isp r e s e n t e d .
An em pi r i c a l equa t ion r e l a t i ng the i ndependen t va r i ab l e s t o th eThe effec t of the sa m ee r f o r m a n c e of t he ag i t a to r abso rbe r is developed.
va r i ab l e s on the pe r fo rman ce of the agi ta tor i s p r e s e n t e d g r a p h i c a l ly i nc h a r t 1.
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T h e f ol lo w in g n o m e n c l a t u r e i s u s e d i n t h e s e p r e s e n t a t i o n s :
Y = t o t a l C 0 2 a b s o r b e d , c u b i c f e e t p e r h o u rL c L / C = l i qu id - to -gas r a t i o , ga l lons pe r hour so lu t ion
I, 000 s td . cu. f t . ga s / h r.S = so lu t ion th roughpu t , ga l lons / h r .C = CO2 con ten t of f eed ga s , mo l -pe rcen tP = p r o c e s s p r e s s u r e , p . s. i . g .d / 1 6 = su m of t he s qu a r e s of t he dependent va r i ab l e
accoun ted fo r b y a g i v e n f a c t o r , d i vi d ed b ythe number of t e s t s i nvo lved .
n = numb er of t es ts , cont ingent to a g iven ca l cu l a t ion .
EVALUATION OF DATA
Tab le 3 pres en t s an ana lys i s fo r s ign i f i cance of t he 16 runs of
Th i s ana lys i s was ma de us ing the m e thod of Ya te s .
T h e e r r o r m e a n s q u a r e w a s d e t e r m i n e d u si ng d at a f r o m t he
e x p e r i m e n t "A" i n wh ich the f a c to r s i nvo lved w er e t e s t ed a t t he h igh andlow l eve l s .
r u n s a t w h ic h th e f a c t o r s w e r e t e s t e d at t he med i an l eve l s . The ca l cu l a t ionw a s m a d e u s i n g t h i s r e l a t i o n s h i p :
E . M . S . = f , Y Z - (LY)'n = 3 3 . 2
n- 1
The s t an da rd dev ia tion by de f in i t ion i s t h e s q u a r e ro o t o f th e
e r r o r m e a n s q u a re .of CO2 a b s o r b e d .
In t h i s i n s t ance the s t and a rd dev ia t ion w a s 2 6 c u . f t . / h r .
The in t e r a c t ions be tween the ca rb on d iox ide con ten t and so lu t ionthrough put , a nd between the carb on dioxide content and l iquid- to-gas ra t i or e v e a l e d i n t he a n a ly s is of the data f r o m e x p e r i m e n t "A", w e r e eva lua t edf u r t h e r b y s o l vi n g t he n o r m a l e q u a t io n s u s in g m a t r i c e s s e t u p f r o m hecumula t ive da t a of e x p e r i m e n t s "A" and I tB1' .the coefficients of table 4 w e r e d e t e r m i n e d a n d a n e m p i r i c a l e q u at i onre l a t i ng the s ign i f i can t f ac to r s t o t he dependent va r i ab l e w a s s e t u p.
Using the methods of Davig,
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,
T2ble 3. - F a c t o r i a l a n a l y s i s - Ekpriment A
P C S L E - Fzc t o r & Signif icance-1 -1 -1 -1 A-11 296
-1 -1 -1 1 A- 4 96
-1 -1 1 -1 A-10 373
-1 -1 1 1 A-13 132
-1 1 -1 -1 A-3 350
-1 1 -1 1 A - l l I l@
-1 1 1 -1 A-19 496
-1 1 1 1 A- 7 303
1 -1 -1 -1 A-9 260
1 -1 -1 1 A-15 91
1 -1 1 -1 A-16 342
1 -1 1 1 A-2 155 -1 1 -1 -1 A-18 jcg
1 1 -1 I. 1:-6 201
1 1 1 -1 A - 1 51 5
1 1 1 1 A-17 294
~
0 0 0 o A-5 263
0 0 0 G A-8 270
o o o o A-12 271
3 0 0 0 A-20 275
.. .
Total
L/G
S
s L/G
C '
C L
cs
CSL
P
PL
1,211,100
136,900
41,820
2,601
51,984
812
. 5,625
462
2@
756
0.001
0.001
0.05
0.001
n i l
0 .01
n i l
n i l
n i l
PS 324
PSL 210
PC 56
PCL 225
PCS 2
PCSL 676
1,453,842
1,2ll 100
242 742
n i l
n i l
nil
n i l
n i l
n i l
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Table- 4. - E m p i r i c a l l y d e t e r m i n e d c o ef f i ci e n t sF a c t o r C o e f f i c i e n t
Cons t an tCSL /GS L/GCS
2 6 7 . 3t 5 7 . 0+57 .125-92.5-12.75+18.75
B y s u b s t it u t in g t h e s e r e a l f o r t h e c o d ed f a c to r s :
P = P-25050
C = C - 1 5 . 25
s = s - 7 5- I F 7
L = L / G . - 35.719. 3
and by a ffix ing the p rop e r coe ff i c i en t s and r educ ing , equa t io n (1) r e s u l t e d .
(1) Y = 7 8 . 3 - 7 . 3 5 C + l . l 8 S - 1 . 4 9 L - 0 . 0 4 4 S L f 0 . 2 5 C S
A n a n a l y s i s f o r v a r i a n c e w a s m a d e b y s o l v i n g t h e i n v e r t e d m a -
t r i x s e t up f r o m t h e c u m u l at i ve data of expe r imen t s A and B . aga in us ingt he m e t h o d s of D a v i s . T h i s r e v e a l e d t h a t t h e e m p i r i c a l e q ua t i o n w o ul daccount for 98.5 p e r c e n t of h e t o t a l s u m of squares of t he dependen t va r i ab l e .
A fu r th e r a na lys i s f o r s ign i f i cance was m ade us ing S tuden t ' s ' IT1't e s t a s p r e s e n t e d b y Vi l l a rs .c o n t a in s o n ly t h o se t e r m s s i g n if i c a nt at l e s s t h a n th e 5 p e r c e n t l e v e l.
B y th i s ca l cu l a t ion , t he emp i r i ca l equa tion
T h e c o m p a r i s o n of o b s e r v e d an d c a l c d a t e d v a l u e s f o r t h e r a t eof adso rp t ion of C 02 in t he ag i t a to r ab so rbe r, i nc luded in t ab l e 2 . was madeemploying equat ion (1).
C h a r t 1 pre sen t s g raph ic a l ly t he abso rb ing capac i ty of the ag i t a to ras a function of solu tion throughput a nd GO2 content of f e e d g a s w i th g a sr a t e s a n d l i q u id - t o -g a s r a t i o s a s p a r a m e t e r s .was evolved by sol v ing equat ion (1).
T h e d a t a f o r p l o tt in g c h a r t 1
-. DISCUSSION O F RESLILTS
The dependent var iable for t h e s e e x p e r i m e n t s w a s t a k e n a s t o t a lca rbon d iox ide abs o rbe d pe r hour.p r e s s u r e , ca rbo n dioxide content of the feed gas . so lu t io n throughput , andl iqu id - to -gas r a t i o on the pe r fo rmance of t he ag i t a to r a bs o r be r was de t e r -m i n e d o n t h a t b a s i s .
The effec t of the independent var iab les - -
. . . .... . . . . .... _. . ...-. - _ . .. _ _ . I -. - .. .
0
. .. - _. ,. .
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Signif icant Effec ts
The f ac to r s of t hese e xpe r imen t s a r e t abu la t ed in th e fou r thcolu mn of table 3; he coe ff i c i en t s t ha t give these f ac t o r s quan t i t a t ivemean ing a r e t abu lat ed i n t ab l e 4. Examina t ion of t hese t ab l e s shows tha tthe pe r fo rmance of t he ag i t a to r abs o r be r w i l l apprec i a t e w i th h ighe rso lu tion throughpu t, h ighe r C 0 2 con ten t i n t he f eed g as and lower l i qu id -to -gas r a t i o s . The e ff ec t of these f a c t o r s a nd of t he i n t e r ac t ions amongtheni on the perfo rma nce of the agi ta tor a bso rbe r is given expl ic i t quan-t i t a t i ve mean ing in t he co r r e l a t i o n a ffo rded by equa t ion (1). Using thisequat ion the perform ance of the agi ta to r, in te rm s of cubic feet p e r h o urof ca rbon dioxide abs orbed , ca n be predic t ed t o an accu ra cy of p lus o rminus 13 cubic f ee t pe r hour w i th in t he r ang e of t hese t e s t s .
Opera ting r equ i r em en t s comm ensura t e w i th f eed gas comp os i -t io n m a y be o b s e r v e d d i r e c t l y b y r e f e r e n c e t o c h a r t 1.
Com par i son wi th Conven t iona l Sc ru bbe r s
Using the methods' of Cou lson and Ri cha rds on, the ov er -a l l m a s s -'
t r ans fe r coe ffi c i en t s fo r the a g i ta t o r a b s o r b e r w e r e c a l cu l a te d a t t h r e e s e t sof conditions, runs A-1, A-2. an d A-12.
U nt il s t r i c t c r i t e r i a f o r t h e c h oi c e of a g i t a t o r v o lu me a r e r e - -so lved , i t is not possible to make 'a gene ra l i zed comp ar i so n of t he pe r fo rma nceof the agi ta tor ab sor ber wi th convent ional scr ubb ers on the ba s i s of o v e r - a l lI
I
(,,\
''.
ma ss- t ra nsf er coeff ic ients . The pr inc ip le of opera t ion , and hence the f lowmechan ic s i n t he tw o s y s t e m s , a r e qui te d i fferent ; indeed, the flow mechanics
i n t he a g i ta t o r a r e e x t r e m e l y c o m pl e x. However, i t is poss ib l e t o comparethe pe r fo rmance of the two types of equipment fo r speci f ic oper a t ing condi t ionsand to desc r ibe the pe r fo rmance of t he ag i t a to r i n t e r m s of a phys i ca l t owerrequ i r ed to e ff ec t t he s am e deg ree of s c rubb ing at t hose ope ra t ing cond i t i ons .Th i s compar i son has been made and is presen ted in t ab le 5. I t shows the s ize
\
\ towers that would have to be employed i n place of the a g i ta t o r a b s o r b e r fo r the\ spec i f i ed runs .
Table 5. - Data fo r com par ing ag i t a to r ab so rbe r t o packed tower
Run 4:No. K Pack ingC r o s s To we r P a c k in gsec t ion , sq . f t . he igh t , f t .
A - 1 0.227 314 Ra schi g rin gs 0 . 5 5
A-12 .111 314 R a s c h i g r i n g s - 5 10A-2 .262 3 / 4 R a s c h i g r i n g s . 5 6
+KgA for agi ta tor ab sor ber = lb. -mol of CO2 absar bed( h r . ) ( at m .C O 2 p a r t i a l p r e s s u r e ) ( c u . f t . so lu t ion )
Cubic feet of solut ion is t aken a s t ha t vo lume of t he ab so rbe r ac -tu 'a ll y occup ied by so lu t ion , i r r e spec t ive .of the s p r ay . Fo r t hese ca l cu l a t ions ,tha t volume was co nsid ered to be a cy l inde r 18 i n c he s i n d i a m e t e r b y 12 n c h e sin height.height of 3. 5 f t .
\ .T h e a c t u a l a b s o r b e r has a cr os s sec t ion of 1 .42 sq . f t . and an ins ide
ii .
, _. ... . . . . . . . -
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i
G
3 2 0
0 1 0
O / O
O 1 O
O I O01 0
i
FACTORS T O B E INVESTIGATED
I t h a s b e e n s h o wn t h a t t h e p e r f o r m a n c e of a n a b s o r b e r of c e n -
T h e s p r a y p at t e r n i n t u r n is a l m o s t t o t a l ly a func tion of th et r i f u g a l d e s i g n is g r e a t l y a f f ec t ed b y t h e c h a r a c t e r i s t i c s of t h e s p r a y p a t t e r nit deve lops .t u rb i n e d e s i g n a n d s p e e d , t h e i m p e l l e r d e s i g n, a n d t h e v i s c o s i t y of t h e a b s o r -bent .d i e thano lamine an d on the he a t of abs o rp t io n deve loped .f a c t o r i a l w i ll b e e x p a nd e d t o i n c l u de t h e f a c t o r s (1) t u r b i n e s p e e d , ( 2 ) c o n-cen t ra t ion of abs o rb en t , and ( 3 ) hea t o f abso rp t ion .
The v i scos i ty o f t he abso rben t is depende nt on the concentra t ion of theConsequen t ly, t h i s
APPENDIX I
TH E BLOCK DESIGN FOR FACT ORIA L EXPER IME NTS A AND B
F a c t o r i a l E x p e r i m e nt A F a c t o r i a l E x p e r im e n t B
7
-1
-1
1
1
-1
-1
1
1
0
0-
i--1
1
-1
1
1
1
-1
1
0
0-
K1.
1
1
1
1
1
1
1
0
0-
S e tB-1
-1
-1
-1
1
1
1
1
0
-
0 ~ 0 ! 0 1 1 o i 0
LEVELSF a c t o r i a l A F a c t o r i a l B
In t e ra c t ion s Curved Effec t s-igh Me diu m Low High Low
A = r e s s u r e , p . s . i . g . 30 0 250 200 321 179B = 8 0 2 content of foul g as ,
mo l-p erc ent 20 15 10 22.4 8C = solut ion throughput gal . /hr . 90 75 60 96.2 53.8D = l i qu id - to -gas r a t io ,
gal . / lo00 s td . cu . f t . / h r . 55 35. 7 1 6 . 4 58.8 1 2 . 6The l e ve l des igna t ions : 1 , -1, 0, i,c, -y>, 1.2 and -1 .2 may be def ined
a s the value of the var iab le in quest ion minu s the m ea n value of that var ia bled iv ided by the in t e rv a l fo r t ha t va r i a b le .as t he va lue of t he va r i ab le des igna ted a s 1 minu s the va lue of t ha t va r i ab ledes ignated as 0.
T h e i n t e r v a l i n t u r n m a y b e d e fi ne d
1
E
3
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LITERATURE CITED
'\
1. Coulson, J. M. and R ic ha rd son , J. F . , P h y s i c a l P r i n c i p l e s o f C h e m i c a lP r o c e s s D e s ig n , M c C r aw - H i ll , N . Y., Vol ZI, (1956).
2. D a v i e s , 0. L. , Des ign and Ana lys i s of Indus t r i a l Expe r i me n t s ;H a f n e r P u b l i s h i n g C o . , N . Y., Appendix 11-A, pp 552-561, (1954).
3. Dixon, B. E . , S o m e A s p e c t s of t he Absorp t ive Mechan i sm inC e n t r i f u g a l A b s o r b e r s , Tr a n s . I n st n . C h e m . E n g r g . , Vol. 32.supp lem en t , pp S - 85 4- 95 , (1954).
4 . Vi l l a r s , D . S., S t a t i s t i c a l D e s ig n a n d A n a l y s i s of E ~ e r i m e n t s o rD e v e lo p m e nt R e s e a r c h , W m . C . Brown G o . , Dubuque, Iowa , pp 191and 378-379.
5 . Ya t e s , F., T h e D e s ig n a n d A n a ly s is of F a c t o r i a l E x p e r i m e n t s , I m p e r i a lB ur ea u of Soi l Sc ienc e , Ha rpe nde n, (1937), as found in Dav ie s , 0 . L . ,(Ref. 2 abov e) pp 263-286.
