p. 1


# OAR Box 1870 Prepped by Ollie Stewart



## Document

Number: 

# 2DII-A-3 3 Docket Number: 

# A-90-1 9

Printed 11/28/20087:05:04 AM Sheet 21 of 67P. 2



# AI R POLLUTIO N ENGINEERIN G MANUA L

SECON D EDITIO N Compile d an d Edits d

by Joh n A . Doniolio n
AI R POLLUTIO N CONTRO L DISTRIC T COUNT YO F LO S ANGELE S 

# A-90-1 9 ll-A-3 3

ENVIRONMENTA L PROTECTIO N AGENC Y Offic e o fAi ron d Wate rProgram s Offic e o fAi rQualit yPlanning an d Standard s Researc h Triangl e Park , N. C 2771 1

Ma y197 3Ga s Absorptio nEquipmen t 20 7 P. 3

16
. Horizonta l positio nof acondense r

dis

tribute s th e vapo r

bette r an dpermit s easie r remova l o

f th e condensat e (Kern , 1950)
. 17
. Inth e horizonta l condenser , i t i s neces sar y t o preven t

cooled-condensat e fro m formin g liqui dpool s an dimpedin g th e flo w o f vapor s (Kern , 1950)
. IS
. Selectio no

f whic hmateria l shoul dpas s throug htube s canno t

b e decide db y fixe drules , becaus e o f factor s a t

avari

anc e wit hon e another
. Whe ncorrosiv e condensat e i s encountered , condensatio n withi nth e tube s rathe r tha nth e shel l i s usuall y desirabl e (Nelson , 1959)
. APPLICATION S Condenser s hav e bee nuse dsuccessfull y (eithe r separatel y o r

wit hadditiona l contro l equipment ) o nth e followin g processe s o r equipment : REFINER Y AND PETROCHEMICA L Alkylatio nuni t

accumulato r

vent s Amin e strippe r

unit s Butadien e accumulato r vent s Coke r blowdow n Keton e accumulato r

vent s Lub e oi l rerefinin g Polyethylen e ga s preparatio naccumulato r vent s Residiu mstrippe r

uni t accumulato r

vent s Storag e equipmen t Styrene-processin g unit s Toluen e recover y accumulato r vent s Ude x extractio nuni t CHEMICA L Manufactur e an dstorag e of ammoni a Manufactur e o

f Coope r naphthenate s Chlorin e solutio npreparatio n Manufactur e o

f ethylen e dibromid e Manufactur e o

f detergen t Manufactur e o

f insecticid e Manufactur e o

f late x Manufactur e of

nitri caci d Manufactur e o

f phthali canhydrid e Resi n reactor s Soi l conditione r formulator s Solven t recover y Thinnin g tank s MISCELLANEOU S Aluminu mfluxin g Asphal t manufacturin g Bloo dmea l drier s Coa l tar-dippin g operation s Degreaser s Dr y cleanin g unit s Esterficatio nprocesse s Pecti npreparatio n Renderin g cooker s (anima l waste ) Vitami nformulatio n 

### GA S ABSORPTIO N EQUIPMEN T Ga s absorptio ni s th e mechanis mwhereb y on e o r mor e constituent s ar e remove dfro maga s strea mb y dissolvin g the mi naselectiv e liqui d solvent
. Thi s i s on e o f th e majo r

chemica l engineerin g uni t

operation s an di s treate dex tensivel y i nal l basi c chemica l engineerin g text
books
. Thes e text s dea l wit hga s absorptio na s ametho do

f recoverin g valuabl e product s fro m ga s streams , fo r

example , i npetroleu mproduc

tion , natura l gasolin e i s remove dfro mwellhea d ga s steam s b y absorptio ni naspecia l hydro

carbo noil
. Absorptio ni s als o practice di nin

dustria l chemica l manufacturin g a s a nimportan t operatio ni nth e productio no f achemica l com pound
. Fo r

example , i nth e manufactur e o f hydrochlori c acid , on e ste p i nth e proces s in

volve s th e absorptio no f hydroge nchlorid e ga s i nwater . Fro ma nai r

pollutio nstandpoint , absorptio ni s usefu l a s ametho dof reducin g o r

eliminatin g th e discharg e of

ai rcontaminant s t o th e atmo
sphere
. Eve ni nthi s application , absorptio n ca nyiel dprofit s t o th e user . Fo rexample , i t ca nb e employe dt o remov e hydroge n sulfid e fro mproces s ga s stream s i napetroleu m re - finer y t o mee t

ai rpollutio nregulations . Wit h furthe r processing , thi s hydroge nsulfid e ca n b e converte dt o elementa l sulfur , avaluabl e product
. Th e gaseou s ai r

contaminant s mos tcommonl y controlle db y absorptio n includ e sulfu rdioxide , hydroge nsulfide , hydroge n chloride , chlorine , ammonia , oxide s o f

nitrogen , an d ligh thydro carbons .

K*"<Wr*bSJJ_ lP. 4

20 8 CONTRO L EQUIPMEN T FO RGASE S AND VAPOR S In othe rexamples , suc h a s solven trecovery , desorptio n o rstrippin gma y b e practice d afte r absorptio n no tonl y t o recove ravaluabl e ab sorbe d constituen tbu tals o t o recove rvaluabl e solven tfo rreuse . Sometimes , afte rabsorp tion , solut e and solven tar e no tseparate d but ar e use d a s aproduc to rintermediat e com poun d i n chemica l manufacture . Treyba l (1955 ) list s som e importan taspect s tha tshoul d b e considere d i nselectin g absorp tio n solvents . 1 . Th e ga s solubilit y shoul d b e relativel y hig h s o a s t o enhanc e th e rat e o f absorptio n an d decreas e th e quantit y of solven trequired . • Solvent s simila rchemicall y t o th e solut e generall y provid e goo d solubility . 2 . Th e solvent s shoul d hav e relativel y lo w volatilitie s s o a s t o reduc e solven tlosses . 3 . I f possible , th e solvent s shoul d b e non corrosiv e s o a s t o reduc e constructio n cost s of th e equipment . 4 . Th e solvent s shoul d b e inexpensiv e an d readil y available . 5 . Th e solvent s shoul d hav e relativel y lo w viscositie s s o a s t o increas e absorptio n an d reduc e flooding . 6 . I f possible , th e solvent s shoul d b e nontoxic , nonflammable , chemicall y stable , an d hav e lo wfreezin gpoints .
GENERA L TYPE S O F ABSORBER S PACKE D TOWE R DESIG N A packe d towe ri s atowe rtha ti s fille d wit h on e o f th e man y availabl e packin g materials , a s show n i n Figur e 142 . Th e packin g i s de signe d s o a s t o expos e alarg e surfac e area . Whe n thi s packin g surfac e i s wette d b y th e solvent , i tpresent s alarg e are ao f liqui d fil m fo rcontactin gth e solut e gas .

GA S OU T

LIQUI D OlSTRISurO R

LIQUI O RE-0ISTR18UTO R

M C I IN O SUPPOR

T a uI N naui o OUT 

### Figur e 142 . Schemati c diagra m o f a packe dtowe r (Treybal , 195 5 P . 134) .

•W l 

# L .

Ga s absorptio n equipmen ti s designe d t o provid e thoroug h contac tbetwee n th e ga aan d liqui d sol ven ti n orde rt o permi tinterphas e diffusio n o f th e materials . Th e rat e of mas s transfe rbe twee n th e tw o phase s i s largel y dependen tupo n th e surfac e exposed . Othe rfactor s governin g th e absorptio n rate , suc h aasolubilit y o f th e ga s i n th e particula rsolven tan d degre e o f chemica l reaction , ar e characteristi co f th e constituent s involve d an d ar e mor e o rles s in dependen tof

th e equipmen tused . Thi s contac t betwee n ga s an d liqui d ca nb e accomplishe d b y dispersin g ga s i n liqui d o rvic e versa . Absorber s tha tdispers e liqui d includ e packe d towers , spra y tower s o rspra y chambers , an d ventur i absorbers . Equipmen ttha tuse s ga s dispersio n include s tra y tower s an d vessel s • wit h spargin gequipment . Usuall y th e flo wthroug h apacke d colum ni s counte rcurrent , wit h th e liqui d introduce d a t th e to p t o trickl e dow n throug h th e packin g whil e ga s i s introduce d a tth e botto m t o pas s upwar d throug h th e packing . Thi s result s i n highes tpossibl e efficiency , since , a s th e solut e concentratio n i n th e ga astrea m de crease s a s i triae athroug h th e tower , ther e i s constantl y freshe rsolven tavailabl e fo rcon tact . Thi s give s maximu m averag e drivin g forc e fo rth e diffusio n proces athroughou tth e entir e column . I n concur-ren tflow , wher e th e ga astrea m an d solven tente ra tth e to p o f th e column , ther e i s initiall y aver y hig h rat e of absorptio ntha t constantl y decrease s until , wit h a n infinitel y tal l tower , th e ga aan d liqui d woul d leav e i nP. 5 i_____M_H- l Ga s Absorptio n Equipmen t equilibrium . Concurren tflo wi s no tofte n use d excep ti n th e cas e o f aver y tal l colum n buil ti n tw o sections , both locate d o nth e ground , th e secon d sectio nusin gconcurren t flo wmerel y a s a

n econom y measur e t o ob viat e th e nee d fo rconstructin gth e larg e ga s pip e fro m th e to p of

th e firs tsectio nt o th e botto m of

th e second . Moreover , fo ra n operatio n requirin g a n exceptionall y hig h solven tflo wrate , concurren tilo wmigh tb e use d t o preven tfloodin g tha tcoul d occu ri n countercurren tflow . Packin g Material s Th e packin g shoul d provid e alarg e surfac e are aand , fo rgoo d flui d flo wcharacteristics , shoul d b e shape d t o giv e larg e voi d spac e whe n packed . Itshoul d likewis e b e stron g enoug h t o handl e an d instal l withou texces siv e breakage , b e chemicall y inert , an d b e in - :pensive . Rockan d grave l hav e bee n use d bu thav e disadvantage s o

f bein g to o heavy , havin g smal l surfac e areas , givin g poo rflui d flo w and , a ttimes , no tbein gchemicall y inert . Cok e lump s ar e als o use d sometime s an d her e th e weigh tdisadvantag e i s no tpresent . Owin g t o it s porosity , cok e ha s alarg e surfac e are ape runi tvolume . Th e expose d surfac e i s not , however , a s larg e a s migh t b e expecte d sinc e th e pore s ar e s o smal l tha tthe y becom e fille d o rfilme d ove rb y th e solvent , whic h considerabl y reduce s th e effectiv e surface . Generally , packin g i npractic e consist s o f variou s manufacture d shapes . Raschi g ring s ar e th e mos tcommo ntype , consistin g o f hollo wcylinder s havin g a nexterna l di amete requa l t o th e length . Othe rshape s includ e Ber l saddles , Intalo xsaddles , Lessin g rings , cross-partitio n rings , spiral-typ e rings , an d drip-poin tgri d tiles . Figur e 14 3 show s severa l commo n shapes . Physica l characteristic s o f thes e variou s type s o

f packing s hav e bee nde termine d experimentall y an d compile d i n table s b y Lev a(1953) . Packin g ma y b e dumpe d int o th e colum nran domly , o rregularl y shape d packin gma y b e manuall y stacke d i na norderl y fashion . Ran doml y dumpe d packin gha s ahighe rspecifi c surfac e contac tare aan d ahigher , ga s pressur e dro p acros s th e bed . Th e stacke d packing s hav e a n advantag e of

lowe rpressur e dro p an d highe r possibl e liqui d throughout , bu tth e installatio n cos ti s obviousl y higher . Tabl e 5 7 an d Figur e 14 4 lis ttypica l packin g cost s an d packed-towe r installe d price s fo r1959 . fkll RIN G

Figur e 143 . Commo ntowe r packin g material s (Teller , 1960 . p . 122) . Tabl e 57 . COST S O F REPRESENTATIV E TOWE RPACKING S (Teller , 1960 )

Packin g Raschi g rings , cerami c Raschi g ringa . carbo n Ber l saddles , cerami c Intalo xsaddles , cerami c Intalo xsaddles , carbo n Tellerettes , polyethylen e Lo wdensit y Hig h densit y Pal l rings , ccram u (BASF ) Pal l rings , polypropylen e Pal l rings , sfainles s stee l Cos t ofpackin g l/2-in . 11 . 7 0 16.9 0 24.3 0 - J . 5 5

-

- •

- 41.0 0 IA6 . 5 0 1-in .

6.5 0 9.6 0 9.9 0 9.4 0 IB.6 0 16.0 0 .3.0 0 5.0 0 .6.0 0 96.0 0 $/(t 3 (l959basis ) l-l/.-in . 5.0 5 3.0 0 7 . 5 0 7 . 1 5 19.4 0

-

-

- 20.7 5 3).0 0 2-in .

4.3 5 6.6 0 7 . 7 0 7 . J O

-

-

- •- 13 . 5 0 69.0 0
Liqui d Distributio n Sinc e th e effectivenes s of apacke d towe rde pend s o n th e availabilit y o f alarge , exposed , liqui d film , the n obviously , i f poo rliqui d dis tributio n prevent s aportio n o f th e packin gfro m bein g irrigated , tha tportio n o f th e towe ri s ineffective . Poo rdistributio n ca n b e du e t o imprope rintroductio n o f th e liqui d a tth e to p o f th e towe ran d t o channelin gwithi n th e tower .P. 6

21 0 ' CONTRO LEQUIPMEN T FO RGASE S AN D VAPOR S

1 0 00 0

S : JO S

_100 

# ]

_ _ . 

# H = i i



### <+y

- _ _ 

# "Y ^ j j =

_ - 

# fcffjjj

i M i r

i

X

—-+ - r

3 4 5 1 0 2 0 3 0 4 0 S O 10 0 OIABETE Rinche s Figur e 144 . Packed-towe rcosts , 1959 , wit h Raschi g ring s a s packin g (Te l ler , 1960 . p . 123) . A t leas t fiv e point s of

introductio nof

liqui dpe r squar e foo t

o f towe r cross-sectio nmus t

general

l y b e provide dt o ensur e complet e wetting
. Th e liqui drat e mus t

b e sufficien t

t o we t th e packin g bu t no t t o floodth e tower . Treyba l (1955 ) state s tha t asuperficia l liqui dvelocit y of a t leas t 80 0 pound s of

liqui dpe rhou r

pe rsquar e foo t

o f towe r cross-sectio ni s desirable . Solid-con e spra y nozzle s mak e excellen tdis

tributor s bu tma y plu g i f soli d particle s ar e presen ti n th e solvent . I n randoml y packe d towers , th e liqui d tend s t o channe l towar d th e walls , becaus e of

th e usuall y lowe rpackin g densit y nea rth e walls . Intal l tower s thi s channelin g i s controlle d b y liqui d redistribu tor s a tinterval s o

f 1 0 t o 1 5 feet . Moreover , thi s effec ti s minimize d i f th e packin gpiece s ar e les s tha none-eight h th e diamete ro f th e tower . Towe rCapacity Th e term s use d t o indicat e capacit y of a packe d colum n o rtowe rar e loa d poin tan d floo d point . Fo ragive n packin g an d liqui d rate , i f ga s pressur e dro p i s plotte dagains t ga s velocit y onalogarithmi c scale , ther e ar e tw o distinc t

breakpoint s wher e th e slop e of th e curv e increases
. A t lo w ga s veloci

tie s th e curv e i s almos t paralle l t o tha t

ob

taine dwit hdr y packing , bu tabov e th e break

points , th e pressur e dro p increase s mor e rapidl y wit h increase d ga s velocity . Th e low e ro f thes e tw o break s i s th e loa d poin tan d th e highe ron e th e floo d point . A s ga s velocit y increase s abov e th e loa d point , th e liqui d holdu p i n th e be d increase s until , a tth e secon d breakpoint , th e floo d point , mos tof

th e voi d spac e i n th e towe r i s fille d wit h liqui d an d ther e i s liqui d entrainmen ti n th e ga s stream . O f course , a tthi s poin tther e i s a n excessiv e pressur e drop . Column s shoul d seldo m b e operate d abov e th e loa d point , bu tsinc e th e loa d poin t i s sometime s mor e difficul tt o establis h tha n th e floo d point , i ti s commo n practic e t o de

- sig nfo r 4 0 t o 7 0 percen to f

th e floo d point . I n general , floodin g velocitie s ar e considerabl y highe rfo rstacke d packin gtha n fo rdumpe d packing . Th e plo tof Lob o (Figur e 145 ) ca n

• v«•. . .•-•/•__

•P. 7
Ga s Absorptio nEquipmen t 1 1

1. 0

0 1 I %

, Ol l a

~ 0 0 1

.Oo M .oO . .00 2
0 001 0 . 01 o m . t>». t 1 . 0 I • *v .

0 1 V T 1 0 I I . 1 i 7 .10. 0 Figur e 145 . Correlatio n fo rfloodin g rat e i n randoml ypacke d tower s (Lobo , 1945 , p . 693) .

b e use dt o determin e flo w rate s tha t wil l caus e flooding
. Thi s curv e i s base do nmeasurement s wit hsevera l liquid s an dgase s o navariet y of packings
. Fo r man y year s packe dtower s wer e designe d o n th e sam e basi s a s plat e o rtra y towers . Th e numbe ro

f theoretica l plate s o rtray s re quire d fo ragive n degre e of separatio nwa s calculate d an d thi s quantit y multiplie db y a figur e calle dheigh t

equivalen tt o atheoretica l plat e (HETP) . Thi s HET Pwa s a nexperi mentall y determine d figur e varyin gwidel y wit h packing , flo wrate s of eac h flui d used , an d concentratio n of

solut e fo ran y specifi csystem . Experimenta l evaluatio no f thes e variable s mad e us e o

f thi s syste m to o cumbersom e an d i ti s no wrarel y used . Desig nprocedure s no w emplo y th e concep to f th e transfe runit . Th e majo rdesig n item s t o b e calculate d ar e th e colum n diameter , numbe rof transfe runits , th e heigh to

T atransfe runit , an d th e syste m pressur e drop . Thes e wil l b e discusse d in dividually . Towe rDiomsto r A s mentione dpreviously , ga s velocit y i s limite d b y floodin g condition s i nth e tower ; B y us e of th e desig nga s volume , desig nsolven t flo w rate , an dtyp e of

packing , th e towe r

diamete r

ca nb e compute d b y usin gLobo' s correlatio n i nFigur e 145 . Packin g factor s ar e obtaine d fro m Figur e 146 . Th e procedur e i s a s follows : 1 . Calculat e th e facto r 

# ( P \ 0 ' 5

wher e L ' = liqui d flo wrate , lb/h r V = ga s flo wrate , lb/h r p

_= ga s density , lb/ft 3
p . = liqui d density , lb/f tP. 8

212 . CONTRO L EQUIPMEN T FO RGASE S AND VAPOR S

1 0 00 0

I 00 0

10 0

PAC

) S»0 l 

## 0%

•-.<

IN G FACTO R f LES . a i ] = 

# _V^ S

••. >

• *

O R 1 in . IN T 9 0 

# 7 ^

A10X i » -

0 5 1 0 I S 2 0 2 5

NOMINA L PACKIN G SIZ E "lctie s 3 0 3 5 Figur e 148 . Packin g factor s fo rRaschi g ring s an d saddle s (lobo , 1945 . p . 693) . 2 . Usin g th e calculate d valu e i n(1) , obtai n fro m Figur e 14 5 th e valu e of 

# n?)(>n

g c P G P L wher e G ' = ga s flo wrate , lb/sec-f tof towe r cross-sectio n

—= packin gfacto rfro m Figur e 146 . p = liqui d density , lb/f t L ji ' = liqui d viscosity , centipoise s g = gravitationa l constant , 32. 2 ft/se c. Solv e fo rG' , th e superficia l mas s ga s ve locit y a tfloo d poin tfro m th e facto rdeter mine d i n (2) . Calculat e S , th e towe rcross-sectio n are a i n ft ^ fo rfractio n of

floodin g velocit y selec ted , f , b y th e equatio n

p

_= ga s density , lb/ft ' G S = (G«)(f)(3.600 ) (92 )



# ramm 

# mP. 9 Ga s Absorptio n Equipmen t 21 3 Calculat e th e tower' s insid e diameter , Dc , b y th e equatio n

D c 

# • w 0. 5 (93 ) Towe rdiamete rshoul d b e calculate d fo r condition s atboth to p an d botto m o f th e tower . Th e towe ri s designe d t o th e large r diameter . Numb. ro fTronsf. rUnit s (NTU ) A transfe runi ti s ameasur e o f th e difficult y o

f th e mas s transfe roperatio nan d i s afunctio n o f th e solubilit y an d concentration s of th e solut e ga s i n th e ga s an d liqui d streams . I ti s ex presse d a s NQ Q o rNQL , dependin gupo nwhethe r th e ga s fil m o rliqui d fil m resistanc e control s th e absorptio n rate . Th e ga s fil m resistanc e usuall y control s whe nsolubilit y o f solut e i n sol ven ti s hig h an d conversely , th e liqui d fil m con trol s whe n th e solubilit y i s low . In ai rpollutio n contro l wor kwhere , i ngeneral , arelativel y smal l concentratio nof solut e i s t o b e remove d fro m a nairstream , asolven ti n whic h th e solut e ga s i s highl y solubl e i s usuall y selecte d i n orde rt o obtai n th e highes tpossibl e economi cseparation . Thus , fo rth e majorit y o f case s encountered , th e ga s fil m resistanc e wil l b e controlling . On e of th e mos twidel y use d method s of determin in g th e numbe ro

f transfe runit s i s tha tpropose d b y Bake r(1935) , whic h i s base d upo na noperatin g diagra m consistin go f a n equilibriu m curv e an d a n operatin g line . Fo ragive ngas-liqui d system , if th e temperatur e i s constan tan d th e ga s partia l pressur e i s varied , th e ga s concentratio ni nth e liqui d change s t o a nequilibriu m concentratio n a teac h partia l pressure . I f th e syste m consist s of asolubl e ga s t o b e removed , a ninsolubl e carrie rgas , an d asolvent , then , a s th e amoun t o f solubl e ga s i n th e syste m increases , th e equilibriu m concentratio n of th e solubl e ga s i n th e liqui d .increase s bu tno tproportionally . Thes e equilibriu m condition s ca nexis tfo ra n infinit e numbe ro

f concentratio nstate s and , whe n plotte d o n X- Y coordinates , becom e th e equilib riu m curve . Th e operatin glin e represent s th e concentration s o

f solut e i nth e ga s strea m an d i n th e liqui d phas e a tvariou s point s i nth e tower . Whe n plotte d a s mole s solut e pe rmol e solven t versu s mole s solut e pe rmol e ga s o nX- Y co ordinates , th e jesul ti s astraigh tline . Thus , whe n th e compositio n o f th e inle tga s an d th e desire d o rrequire d degre e o f absorptio nar e known , th e point s on th e operatin glin e fo reac h en d o f th e colum n ca n b e calculated . Th e oper atin glin e i s th e straigh tlin e connectin g th e tw o points . Fo rabsorptio n t o occur , th e oper atin glin e mus tli e abov e th e equilibriu m curv e o n th e diagram . Th e relativ e positio n o f th e operatin g lin e an d equilibriu m curv e indicate s ho wfa rth e towe rcondition s ar e fro m equilib rium . Th e mor e widel y separate d th e lines , th e furthe rth e towe rcondition s ar e fro m equi libriu m an d th e greate ri s th e drivin g forc e fo rth e absorptio n operation . Figur e 147 illustrate s th e graphica l metho d o f determinin g th e numbe ro f transfe runit s fo racounte rcurren tpacke d towe rwit h th e ga s fil m controllin g th e absorptio n rate . Th e equilibriu m curv e (lin e AB ) fo rth e particula r gas-liqui d syste m i s plotte d fro m experimenta l data , which , fo rmos tcommo n systems , ha s bee n determined . Muc h o f thes e dat aca nb e locate d i n th e Internationa l Critica l Table s an d i n Perr y (1950) . Th e operatin g lin e i s astraigh tlin e draw n betwee n point s D an d C . D i s th e poin trepresentin gth e concentra tion s of solut e i n th e ga s strea m an d i n th e liqui d strea m a tth e ga s inle tan d liqui d out le t(botto m o

f th e tower) . Poin tC correspond s t o thes e concentration s a tth e to p o f th e column . Lin e E F i s draw n s o tha tal l point s o n th e lin e ar e locate d midwa y o n avertica l lin e betwee n th e operatin g lin e an d equilibriu m curve . Startin g a tpoin tC on th e operatin glin e (con dition s a tth e to p o

f th e column) , dra wahori zonta l lin e C

H s o tha tC

G = GH . The n dra wa vertica l lin e H

J bac kt o th e operatin gline .

J , 

# X' 1 

# y / X*0> t r* B

X= SOLUT E moles/SOI VEN Tmol e Figur e 147 . Graphica l determinatio n o f th e numbe ro ftransfe runits .

r

### -**S*mmP.1 0

21 4 CONTRO LEQUIPMEN T FO RGASE S AND VAPOR S Th e ste p CH J represent s on e ga s transfe r unit
. Thi s stepwis e procedur e i s continue dt o th e en do f th e operatin g lin e (condition s a t th e botto mof

th e column)
. Tw o ga s transfe r unit s (NOG ) ar eshow ni nFigur e 147
. I f th e liqui dfil mresistanc e i s th e controllin g facto r i nth e transfe r

o f solut e t o solvent , dra w th e lin e E Fs o tha t

al l point s onth e lin e ar e locate dmidwa y o nth e horizonta l axi s betwee n th e operatin g lin e an dequilibriu mcurve . Then , startin g a t

poin t D o nth e operatin g line , dra w avertica l lin e DK

s o tha t D L= LK
. Th e ste p i s complete db y drawin g alin e K J bac k t o th e operatin g line
. Thi s procedur e i s the ncon tinue dt o poin t

C o nth e operatin g line
. Figur e 14 7 doe s no t

accuratel y indicat e th e numbe r o f liqui dtransfe r

unit s sinc e th e lin e E Fwa s draw nfo r

th e cas e wher e th e ga s fil mresis

tanc e controls
. Heigh t o

fa Transfe rUni t Generalize dcorrelation s ar e availabl e fo r computin g th e heigh t

o f atransfe r

uni t an d ar e expresse da s H Qan dHj

_fo r height s o

f ga s an dliqui dtransfe r

unit s respectively
. Thes e us e experimentall y derive dfactor s base do nth e typ e of packin g an dth e ga s an dliqui dflo w rate s a s show ni nequation s 9 4 an d95
. wher e H , © G " .0. 5 0D P C G

H = heigh t

o f aga s transfe r

unit , t t G= superficia l ga s rate , lb/hr-f t L= superficia l liqui drate , lb/hr-f t
o = apackin g constan t fro mTabl e 5 9 | 3 = apackin g constan t fro mTabl e 5 3 7 = apackin g constan t fro mTabl e 5 3 H

_= ga s viscosity , lb/hr-f t p

_= ga s density , .lb/f t G D

_= ga s diffusivity , f t /hr
. G

"""(*%• ) (94 )

Th e grou p | -—^

—| i s know na s th e Schmid t numbe r a s show ni nTabl e 59
.
Tabl e 58
. CONSTANT S FO RUS EINDETERMININ GGA S FILM' S HEIGH T O FTRANSFE RUNIT S (Treybal , 1955 , p . 239 ) Packin g Raschi g ring s 3/ 8 in
. 1 in
. 1-1/ 2 in
. 2 in . Ber l saddle s 1/ 2 in
. 1 in
. 1-1/ 2 in
. 3-in
. partitio nring s Spira l ring s (stacke d staggered ) 3-in
. singl e spira l 3-in . tripl e spira l Drip-poin t

grid s No
. 614 6 No
. 629 5 a 2
. 3 2 7.0 0 6.4 1 17.3 0 2.5 8 3.8 2 32.4 0 0.8 1 1.9 7 5.0 5 65 0
2.3 8 15.6 0 3.9 1 4.5 6 (

3 0.4 5 0.3 9 0.3 2 0.3 8 0.3 8 0.4 1 0.3 0 0.3 0 0.3 6 0.3 2 0.5 8
0.3 5 0.3 8 0.3 7 0
. 1 7 . 0.4 7 0.5 8 0.5 1 0.6 6 0.4 0 0.4 5 0.7 4 0.2 4 0.4 0 0.4 5 1.0 6
0.2 9 0.6 0 0.3 9 0.2 7 Rang e o f G ' 20 0 t o 50 0 20 0 t o 80 0 20 0 t o 60 0 20 0 t o 70 0 20 0 t o 70 0 20 0 t o 80 0 20 0 t o 70 0 20 0 t o 70 0 20 0 t o 80 0 20 0 t o 1,00 0 15 0 t o 90 0
130 t o 70 0 20 0 t o 1,00 0 130 t o 1,00 0 10 0 t o 1,00 0 L '

50 0 t o 1,50 0 40 0 t o 500 50 0 t o 4 , 50 0 50 0 t o 1,50 0 1,50 0 t o 4,50 0 50 0 t o 4 , 50 0 50 0 t o 1,50 0 1,50 0 t o 4,50 0 40 0 t o 4 , 50 0 40 0 t o 4 , 50 0 3,00 0 t o 10,00 0
3 , 00 0 t o 10 , 00 0 50 0 t o 3 , 00 0 3,00 0 t o 6,50 0 2,00 0 t o 11,50 0

mr>-P.1 1 Ga s Absorptio nEquipmen t 2 1 :

. 1 I.• Tabl e 5 9 DIFFUSIO NCOEFFICIENT S O F

GASE S AN D VAPOR S I NAI RA T 25° C AN D

1 AT M (Perry , 1950 ) Substanc e •/Ammoni a] Carbo ndioxid e I Hydroge n ; Oxyge n Wate r • Carbo ndisulfide ! ^Ethy l ethe r

! Methano l
• Ethy l alcoho l Propy l alcoho l v Buty l alcoho l Amy l alcoho l vHexy l alcoho l Formi c aci d J Aceti c aci d Propioni c aci d i-Butyri c aci d Valeri c aci d i-Caproi c aci d Diethy l amin e Buty l amin e Anilin e Chlor o benzen e Chlor o toluen e Propy l bromid e Propy l iodid e v Benzen e Toluen e Xylen e / Ethy l benzen e Propy l benzen e Dipheny l n-Octan e Mesitylen e D , c m/se c 0 . 23 6 0 . 16 4 0 . 41 0 0 . 20 6 0 . 25 6 0 . 10 7 0 . 09 3 0 . 15 9 0 . 11 9 0 . 10 0 0 . 09 0 0 . 07 0 0 . 05 9 0 . 15 9 0 . 13 3 0 . 09 9 0 . 03 1 0 . 06 7 0.06 0 0 . 10 5 0 . 10 1 0 . 07 2 0 . 07 3 0.06 5 0 . 10 5 0.09 6 0.08 8 0.08 4 0.07 1 0 . 07 7 0.05 9 0.06 8 0.06 0 0.06 7 

## HCL

H P wher e H
. 

## 0X77

0
. \X°\ H
. 

### fPD 0 0 0 0 0 1 1 0 1 1 1 2 2 0 1 1 1 2 2 1
. 1 2
. 2
. 2
. 1
. 1
. 1
. 1
. 2
. 2
. 2
. 2
. 2
. 2
. . 6 6

. 9 4 .ZZ 7 5 6 0 4 5 6 6 9 7 3 0 5 5 7 2 2 1 6 0 9 7 1 6 5 6 9 1 3 1 5 8 4 7 5 3 1 4 1 2 3 3 4 7 6 1 7 6 8 4 1 8 0 1 6 2 2 8 5 8 3 1 

# (*) " (X) p. SI

i. is 5
P , 7 ? (95 )



### 0 n = heigh t

o f aliqui d transfe runit , f t 2
= superficia l liqui d rate , lb/hr-f t

= liqui dviscosity , lb/hr-f t

= apackin g constant , Tabl e 6 0

= apackin g constant , Tabl e 6 0

= liqui ddensity , lb/f t Tabl e 60
. CONSTANT S FO RUS EIN DETERMININ GLIQUI D FILM' S HEIGH T O F TRANSFE RUNIT S (Treybal , 1955 , p . 237 ) Packin g Raschi g ring s 3/ 3 in
. 1/2 in
. 1 in
. 1-1/ 2 in
. 2 in . Ber l saddle s 1/ 2 in
. 1 in
. 1-1/ 2 in
. 3-in
. partitio nring s Spira l ring s (stacked ! staggered ) j 0 . 0013210 . 4 6 0 . 0035 7 I 0 . 3 5 0.010 0 ^0.2 2 0.011 1 ;0.2 2 0.012 5 0.2 2 0.00666^0.2 3 0.0053SJ0.2 3 0.0062 5 10.2 3 0.062 5 J0.0 9 Rang e of L

40 0 to 1 5 40 0 to 1 5 40 0 to I f 40 0 to 1 5 40 0 to 1 : 00 0

00 0 00 0 00 0 00 0 40 0 to 1 40 0 to I 40 0 to 1 5
. 00 0 i. 00 0
-. 00 0 3 , 00 0 t o 14
. 00 0
3-in
. singl e spira l 3-in . tripl e spira l Drip-poin tgrid s No . 614 6 No
. 629 5 0 0 0 0 00909| 0 0 1 1 6 ' 0 

### 1 015 4 l o 0072 5 l o 23 |

23 ! 3 2 3 3 3 1 1 2 1 40 0 t o 1 * 00 0 t o 1 4 50 0 t o 3 0 50 0 t o 12. 00 0

00 0 00 0 00 0

Th e grou p 

# (ft) - s th e Schmid t numbe r
a s show ni nTabl e 61
. Eac ho f thes e empirica l equation s neglect s th e effec t o f th e othe r

film' s resistance
. Actually , however , eve ni nth e cas e o f absorbin g highl y solubl e ammoni ai n water , experimenta l result s hav e show ntha t th e liqui dfil mresistanc e i s significant
. Th e heigh t o f a noveral l ga s transfe r unit , H_._ , i s determine db y th e followin g equation , whic h take s int o accoun t

th e liqui dfil mresistance
.

H 

## o c = H 

## o * (m l * m / (96 )

wher e 

# 0 ° slop e o f

th e equilibriu mcurv e ga s rate , lb-moles/h r liqui d rate , lb-moles/hr .

D = liqui d diffusivity , ft/hr . Thes e equation s ar e widel y accepte d fo rdesig n purposes . Anothe rgrou p o f equation s liste d b y Lev a(1953 ) includ e overal l ga s an d liqui d transfe rcoefficients , K g aan d K^a . Stil l mor e recently , Cornel l e tal. , (1960 ) publishe d corre - lation s base d o namas s o f experimenta l dat are porte d u p t o 1957 .

*
. »7.!»_ AP.1 2

21 6 CONTRO LEQUIPMEN T FO RGASE S AN D VAPOR S
Tabl e 61
. DIFFUSIO NCOEFFICIENT S I N LIQUID S A T 20° C (Perry , 1950 )
Solut e 

## o 2 

## co 2 N 2 0 NH 3 CI 2 Br 2 H 2 N 2 HC l H 2 S H 2 S 0 4 HNO 3 Acetylen e Aceti c aci d Methano l Ethano l Propano l Butano l Ally l alcoho l Pheno l Glycero l Pyrogallo l Hydroquinon e Ure a Resorcino l Urethan e Lactos e D x 10 5 (cm 2 /sec ) x 10 3 1
. 3 0 1
. 7 7 1
. 5 1 1.7 6 1.2 2 1.2 0 5
. 1 3 1.6 4 2.6 4 1
. 4 1 1
. 7 3 2.6 0 1
. 5 6 0.8 8 1.2 8 1.0 0 0.8 7 0.7 7 0
. 9 3 0.8 4 0.7 2 0
. 7 0 0
. 7 7 1.0 6 0
. 8 0 0.9 2 0.4 3 ___ .

p D 55 3 55 9 66 5 57 0 32 4 34 0 19 6 61 3 38 1 71 2 53 0 39 0 64 5 1 , 1 4 0 73 5 1,00 5 1 , 15 0 1 , 31 0 1,08 0 1,20 0 1,40 0 1 , 44 0 1 , 30 0 94 6 1,26 0 1,09 0 2,34 0 Maltos e Glucos e Mannito l Raffinos e Sucros e Sodiu mchlorid e Sodiu mhydroxid e 

### co 2 b Phenol " Chloroform 0 Phenol c Chloroform 0 Aceti c acid c Ethylen e dichloride 0 0.4 3 0.6 0 0
. 5 8 0.3 7 0
. 4 5 1.3 5 1.5 1 3.4 0 0.8 0 1.2 3 1
. 5 4 2
. 1 1 1.9 2 2.4 5 2 , 34 0

1,73 0 2,72 0 2,23 0 74 5 66 5 44 5 1,90 0 1,23 0 47 9 35 0 38 4 30 1
a Solven t

i s wate rexclep twher e indicated . ^Solven ti s ethanol . ' , c Solven ti s benzene . 1 M 0 r H P i Pressur e Drop Throug h Poc

k 

### -.11 in g 

### JL.



### 5"/77 '
Treyba l (1955 ) state s tha tpressur e dro p dat ao f variou s investigator s varie s widel y eve n fo r th e sam e packin g an d flo wrates . Thes e discrep - ancie s wer e probabl y du e t o difference s i n pack in g density . Moreover , no tenoug h wor kha s bee n don e o n liquid s o f hig h viscosit y fo rprope r evaluation , thoug h i ti s recognize d that , a tequa l mas s flo w rates , high-viscosit y liquid s caus e greate r ga s pressur e dro p tha nthos e o f lo w vis

cosit y do
. Leva' s empirica l relatio napplie s belo w th e Loa d point
. Thi s i s a s tollows : 

# • 1

____ _ Z m . (10- 3 )(10 n L ' / P L , 9L

1 P . (97 )

wher e P Z

m pressur e drop , lb/f t

packe dheigh t

of tower , f

t pressur e dro p constan t fro mTabl e 6 2
n= pressur e dro p constan t fro mTabl e 6 2 L ' = superficia l mas s liqui dvelocity , lb / hr-ft 2 G 1 = superficia l mas s ga s velocity , lb/hr

- ft 2 p = liqui ddensity , lb/f t p

_= ga s density , lb/f t .
Illustrativ e Proble m Th e followin g exampl e illustrate s th e precedin g principle s o f

packe dtowe r

design
. Knowin g th e amoun t o f solut e i nth e ga s stream , th e tota l flo w rat e o f th e ga s stream , th e mos t suitabl e solvent , a nacceptabl e packing , an dth e desire ddegre e o f absorption , calculat e th e towe r dimensions
. Given : Desig napacke dtowe r t o remov e 95 % o f

th e am - moni afro magaseou s mixtur e o f 13 % b y volum e o f ammoni aan d90 % b y volum e o f air
. Th e ga s mixtur e consist s o f 8 0 lb-moles/h r

a t 6 8 " Fan d 1 atm . Wate r

containin g n o ammoni ai s t o b e use da s solven t

an dth e packin g wil l b e 1-inc h Raschi g rings
. Th e towe r wil l b e designe dt o operat e a t

60 % o f th e floo dpoint , an disotherma l condition s a t

68° Fwil l b e assumed
. Th e wate r wil l no t b e recirculated
. Problem : Determin e wate r

flo w rate , towe r

diameter , packe dheight , an dtowe r pressur e drop
.P.1 3 Ga s Absorptio n Equipmen t 21 7 Tabl e 62 . PRESSUR E DRO PCONSTANT S FO RTOWE R

PACKIN G (Treybal , 1955 ) Packin g Raschi g ring s

Ber l saddle s

Intalo x saddle s Drip-poin t

gri d tile s Nomina l

. size , in
. 1/ 2 3/ 4 1 1-1/ 2 2 1/ 2 3/ 4 1 1-1/ 2 1 1-1/ 2 No
. 614 6 Continuou s flu e Cros s flu e No
. 629 5 Continuou s flu e Cros s flu e m

13 9 32
. 9 0 32
. 1 0 12.0 3 11
. 1 3 60
. 4 0 24
. 1 0 16
. 0 1 3.0 1 12
. 4 4 5.6 6 1
. 04 5

1
. 21 8 1.08 8

1
. 43 5 n 0.0072 0 0.0045 0 0.0043 4 0.0039 8 0.0029 5 0
. 0034 0 0
. 0029 5 0.0029 5 0.0022 5 0.0027 7 0.0022 5 0.0021 4
0.0022 7 0
. 0022 4

0.0016 7 Rang e o f L' , lb/hr-ft 2 30 0 t o 8 , 60 0 1,30 0 t o 10,80 0 36 0 t o 27,00 0 72 0 t o 13,00 0 72 0 t o 21,00 0 30 0 t o 14,10 0 36 0 t o 14,40 0 72 0 t o 78,80 0 72 0 t o 21,60 0 2 , 52 0 t o 14 , 40 0 2,52 0 t o 14, 40 0 3,00 0 t o 17,00 0
30 0 t o 17,50 0 85 0 t o 12,50 0
90 0 t o 12 , 50 0 Rang e

o f P/Z , lb /ft 2 -f t 0 t o 2
. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 2. 6 0 t o 0. 5
0 t o 0
. 5 0 t o 0
. 5

0 t o 0
. 5
Solution : 1 . Calculat e th e wate rrate : :
a . Equilibriu m dat afo rth e syste m ammonia - wate rar e a s follows : X 0.020 6 0.031 0 0.040 7 0.050 2 0.073 5 0.096 2 Y 0.015 3 0.024 0 0.032 9 0.041 8 0.066 0 0.092 0 Plo tth e equilibriu m curv e a s show n i n Fig - ur e 148 : Th e curv e i s straigh tapproximatel y t o th e poin tP , wit h aslop e o f abou t0 . 75 . Abov e poin tP , th e slop e i s variabl e an d highe r tha n 0.75 . Us e 0.7 5 a s th e slope , m , o f th e equilibriu m curve . b . Whe n th e temperatur e ris e o f th e solven t i s negligible , appl y th e relatio n

G (m ) m L m = 0.7 0
wher e
m = slop e o f

equilibriu m curv e = 0 . 7 5 ga s rat e = 8 0 lb-moles/h r liqui d rate , lb-moles/h r 

## ^il i = 85 

## . 81b 

## . moles/hr 

## .

2 . Fro m th e give nga s flo wrate , th e calculate d liqui d rate , an d th e degre e o f absorptio n de - sire d (95 % o f

ammonia) , tabulat e ga s an d liqui d flo wrate s a tbot h end s o f th e tower : Density , lb-moles/h rlb/h rlb/ft 3 Inle tga s (bottom ) 8 0 Outle tga s (top ) 72. 4 Inle twate r(top ) 85 . 8 Outle tliquo r(bottom ) 93. 4 2,22 1 0.072 0 2,09 2 0.075 0 1,54 2 62 . 4 1,67 1 62. 4
3 . Calculat e th e towe rdiameter :
a . Us e condition s a tto p o f tower : 0 . 5 = 0.025 6P.1 4

21 3 CONTRO LEQUIPMEN T FO RGASE S AND VAPOR S

0 . 0 9

0 0 5 0.0 4

0 <

^
J / 

# Vs ff

### 4

A ^ A 

### r—/\ / & S<y 

## w - » )

/ /

0 0 0 1 0 0 2 0 11 3 0 04 0 0 5 0 0 6 00 7 0 0 9 0 0 9 0 1 0 X -- n o le s NH , mol e H 2 0 •6 8 ° F Figur e 148
. Equilibriu m curv e fo rammonia wate rsystem
. (2 ) Fro mFigur e 145 , th e relationshi p 

# •'\7) (0(^(H 2 

### ) 0 . 2 (g c )(P G «P L ) = 0
. 1 9
(3 ) Fro mFigur e 146 , th e packin g factor!—r ) = 16 0



# (t f (4 ) Fro mth e relationshi p i n(2) , calculat e th e superficia l mas s ga s velocit y ( G ) a tflooding : (2 ) Fro m Figur e 145 , th e relationshi p



# M (G^W/- 2 (gc)(p Q )(p L ) (3 ) Fro mFigur e 146 , th e 0 . 1 9 packin g factor/- ^ \= lfc o (4 ) O ' = (0.19)(32.2M0.0720 M 62.4 ) = . ^ ^ ^

(160)(1 ) * (5 ) G J = 0.415(0.60 ) = 0.24 9 Ib/sec-ft ' £I (6 ) S = 2,22 1 lb/h r

(0.24 9 lb/sec-f t

)(3 , 60 0 sec/hr ) 2.4 3 ft '

c . Selec ttowe rwit h unifor m cross-sectio no f 2.4 8 ft 2 d . Towe rdiameter : 

# o c . (<^H_.f 5 1.7 8 f to r21
. 4 in
. 4 . Determin e th e numbe rof transfe runits : a . Calculat e mol e fraction s o f solut e i nga s liqui d stream s a tbot h end s of th e tower .



### ' • ( 0. 5 Q l a M. 19)(32 . 2)(0
. 0750)(62
. 4f t • ^
.. . ^ ^ (160)(1 ) 0. 2 (5 ) A t60 % of

flooding : G ' = (G)(0.60 ) = (0.424)(0.60 ) = 0 . 25 4 lb/sec-ft f (1 ) Botto m of tower : y = —= 0 . Il l mol e NH./mol e ai r

X = "£t\ ~ 0 . Q88 . mol e NH 3 /mol e wate r
(6 ) Towe rcros s section :

- 2,09 2 lb/h r (0.25 4 lb/sec-f t)(3 , 60 0 sec/hr ) = 2 . 2 9 f t (2 ) To p of

tower : 0. 4 

### * 2 •IT - 0.005 6 mol e NH./mol e ai r b . Us e condition s a tbotto m of tower :

= 0 . 025 6 X , = 0 (enterin gwate ri s N H free ) b . Plo tth e operatin glin e fro m th e dat ai n(a ) o n th e sam e grap h use d fo rth e equilibriu m curve .P.1 5

c . B y th e metho do f Bake r (describe dpreviously ) graphicall y determin e th e numbe r o f transfe r units : NT U= 6 5
. Calculat e th e heigh t of atransfe r

unit :
a . Ga s transfe r

unit : 0
. 5 • G p / >V
. ' H g Ga s Absorptio nEquipmen t 21 9

3 0 

## ___2_L/J_c_

\ L ^ ^G D G /
wher e G
. 2 ^ 211b/

. h r

- 39 6 lb/hr-ft 2 2
. 4 8 f t H = 0.0 1 J_J /622\ 0

- 2 2 (570)° , 5

. = 0.7 9 f t

c Overal l ga s transfe r uni t G H O G H G+ m 

# ft) 

# - . wher e
m= slop e o f

equilibriu mcurv e = 0.7 5 G ^ = ga s rat e = 3 0 lb-moles/h r L= liqui drat e = 85. 3 lb-moles/hr
. H
_1.9 2 + (0

- 7 5 >(30>(0-79 )
. 2 4 7 f t O G(35.3 )
L= 1 , 54 2 2.4 8 = 62 2 lb/hr-f t

a = 7
. 0 0 fro mTabl e 5 8 | 3 = 0
. 3 9 fro mTabl e 5 8 7 = 0
. 5 8 fro mTabl e 5 8 

# (jy...«
_

H , o mTabl e 59
.

(7.00)(896) 0,3 9 (0.66) 0 , 5

(622) 0 ' 5 8 = 1.9 2 f t

b
. Liqui dtransfe r unit : 

# " ^ -(tH*)* "

wher e

• = 0 . 0 1 fro m Tabl e 6 0
n= 0 . 2 2 fro m Tabl e 6 0 L = 62 2 lb/hr-ft 2

u _1 centipois e = 2.4 2 lb/hr-f t 6
. Calculat e th e packe dtowe r heigh t (Z) : Z - NT Ux H o c Z= 6 x 2.4 7 = 14. 8 f t

7
. Calculat e th e towe r pressur e dro p nL/fl , 

## *t = m 

## i' 1 0 

## " 8 

## ' 

# (-id)



# m-

= 57 0 Tro m Tabl e 6 1 A p = wher e Z A p = pressur e drop , lb/f t Z= packe dheigh t = 14. 8 f

t n i j = 32
. 1 0 fro mTabl e 6 2
n= 0
. 0043 4 fro m Tabl e 6 2 L = 62 2 lb/hr-ft 2 fi. = 62 . 4 lb/ft 3 G = 89 6 lb/hr-ft 2
P G= Av gga s densit y = 0 . 073 6 lb/ft 3 . 

## (32.ixio- 8 

## mo) ( 0


## - 00434)(622)/62


## - 4 (896) 2 (14.8 ) 0.073 6 A p = 57. 2 lb/ft 2 •fc* .P.1 6

220* CONTROLEQUIPMENT FO RGASE

S AN D VAPOR

S
57. 2 lb/f

t ( 1 in
. WC

)
. , . . ,„ „ A p = s
. L = 11. 0 in
. W

C 5.19 7 lb/f

t liquid
. The liqui denter s a t th e top o

f th e tower , flow s acros s eac hplat e anddown

war dfro mplat e t o plat e throug hdownspouts
. PLAT E O R TRA YTOWER S In. contras t

to packe dtowers , wher e ga s and solven t ar e in continuou s contac t throughou t

th e packe dbed , plat e tower s emplo y stepwis e con tac t b y mean s o

f anumbe r

o f tray s o r

plate s tha t ar e arrange ds o that th e ga s i s disperse d throughalaye r

o f liqui do

n eac hplate
. Eac h plat e i s mor e o r

les s aseparat e stage , an d th e numbe r

o f plate s require di s dependen t upo n th e difficulty o

f th e mas s transfe r

oper atio n andth e degre e o f separatio n desired
. Type s o f Plate s The bubbl e cap plat e o r tra y i s mos t

common , andmos t

genera l reference s dea l primaril y withi t whe n discussin g plat e towers . Othe r type s o f plate s includ e perforate dtrays , Turbogri dtrays , andFlexitrays
. A schemati c sectio n o f abubbl e cap tra y towe r i s shown i n Figur e 149
. Eac hplat e i s equippe d wit hopening s (vapo r

risers ) surmounte dwit h bubbl e caps . Typica l bubbl e cap s ar e illus

trate din Figur e 150
. The ga s rise s through th e towe r

andpasse s throug hth e opening s in th e plat e an dthroug hslot s in th e peripher y o f th e bubbl e caps , whic har e submerge di n 3 CA P SUPPORT S AT 120° F

VAPO RRISE R H010-00WN BA R •SLOT S 

# H o

-CAS T TRA T CAS T CA P

SHEE TMETA L CA P

SHEE TMETA L TRA T Figur e ISO . 1 1 lustratio n o f som e typica l bubbl e caps .

s« s ou r SHEL L — TfU Y 001NS P OU

T- TRA T SUPPOR T RINQ TR» Y STIFFIM R VAPOR RISER - FR0TH - 

## /? ; 

## ^£L#r uaui D IN

IUIU I CA P

__mTiRM0i m " •FEE D

^-LIQUI D OU

T The dept ho f liqui do

n th e plate , andliqui d flow pattern s acros s th e plat e ar e controlle d by variou s wei r

arrangements , whichwil l b e discusse di n greate r detail
. I n perforate dplate s o r siev e trays , th e ga s passe s upwar dthroug hapatter n o f hole s drille do r

punche din th e trays . Three

sixteenth-inch-diamete r hole s space d o

n a 3/4-inc htriangula r pitc har e commonl y used
. A disadvantag e o

f thi s typ e i s the tendency o f liqui dt o "weep " orlea kdow n throug

h th e hole s instea do

f throug hth e downspout s at low ga s velocities
. Moreover , th e tray s mus t b e installe dperfectl y level , o r chan

neling , wit

hresultan t

los s o f efficiency , wil l occur . O

n th e othe rhand , aperforate d tra y cost s only 6

0 to 70 percen ta s muc h as abubble ca

p plat e designe d forthe sam e throughput. Wit

h tower s o

f the sam e di ameter , perforate d tray s supposedl y have acapacity 1

0 to 4 0 percen tgreate rtha n tha t o f bubbl e cap plate towers . 

### Figur e 149 . Schemati c diagra m o f a bubble-ca ptray

tove r (Treybal , 1955 , p . 111) . Wit hTurbogri dtrays , license d b y Shell Develop

men t Company, th e vapo rpasse s u p throug

h the space s betwee n paralle l rod s o rbars , an d th e

•W R