- S T A N D A R D D A T A B O O K - P A R T I I I ( P A G E i OF

D a U M STZING J F C ~ ~ C ~ ~ , Is-! .I ---- *

TAELE OF CONTEXTS

P t c 5

ex,Pmr3 R , i \ l ,N@, k . z z I Sunma ry 1

Descr ip t ion and S e l e c t i o n o f Process Drums R ZX. 1 1

.- -~ -. - I 2

Liquid Surpe Crux D ~ s i ~ n 2 .

Liquid-Liquid S e t t l e r Cesign €

L1apor-Liquid S e p a r a t s r Design - c V e r t i c a l S e p a r a t o r 1 G

Vaoor and Two I m i s c i b l e Liquids ? 2 vzpor and One Liquid Phzse Inc lud ing Knock-Out Drums

.. '1 L

- -- I _ Hcr izonta l Seoara t o r - c

I -

Vzpor and Tho I m i s c i b l e Liquids 15 S c g a r z t o r wi th a Eeavy Liquid Pot 1 7 Vzpor and One tiqu.id Ph<ss Inc lud ing Knock-Out Drums 212

Prccecs S t ~ z n Drums 27

.tux: 1 i a r y E c u i ~ ~ e n t and Drum I n t e r n a i s 2: Ui re-?*.es h Ent ra i nzen t Se7ara:or 2 ; Fes? and gu t le : koz:les --

L Z

Drains and Vents - - 2 L Draw G f f 5 c z z i e S i z i n g - Vortex Breakers 32 tieads T:

k s i g n Cri i ~ r i 2 f o r S c c i f i c Process An?! i c z t i o n s - - - - . - - - Liguic ?-?SF 5 b r z ~ l i c e - - . -

4-

czt;-g- L / 3 2 a t i c f c r P r o c ~ s s Crgns .. . 7. - - 7 * , - .---*.'=: us ,:,I :,-c.-. , I C ? : ~ C C ~ - + - - - *

TEZ?? 1 : isj ' i Caztcir:f and Surf2ce Area of Cyl indr ica ; Orucs 2nd S:ar;dard 3rLim i;iedds LC

Tc> le 2 : Se5~en:al Arezs f c r Chord !dicth/Diane;er Ra t fcs Uc t o 3.5 - F - - d d

Ficjure I : P z r t i a l Capac i ty f o r 5 - 5 0 X i q u i d Depths i n C y l i n d r i c z i S h e l l s ( p r f: o f 1 enor: ) - - - -

d"

Figure 2: P a r t i a l Capeci ty f o r 5-50: Liquid D e ~ t h s i n Hmis;heric.i Hezds cz - - FSpsre 3: P a r t i a l Caijzci t:; f c r 5-50",tiql;id Eeo;hs i n 2:; E l l i p t i c i i &ids

I 6 2

Ficure 4: P a r t i a l Cz?ac i ty f o r 5-50': Liquid Depths i n Dish?? Seads (KRuckie Radius = 0.06 D) 6:

.

Fi5uI-E 5: P a r t i a l C t ~ a c f t y f o r 5-5GXL;quid Gepths i n Standzrd Dished Hezds 62

Fictrre 6: P r e l i n i n z r y Diamzter o f fiori:or;tal Vapor-Liquid Se ;a ra tc r 63

F i s u r e 7: S u b n e q e n c e Char t f o r D r z w O f f Nozzle S i z i n g 6 3;

-

I CCNFISE1<TIhL COCLjKEI;T - N c t t o be Re;r~ducitd

---. - S J A N O A R r B - + & ~ ~ * - - P A R T I I I PAGE 1 OF 63 "u LUMMUS C" DRUM SIZING January, 1972

The purpose of t h i s chapter i s t o provide the design methods and c r i t e r i a t o be generzlly applied f o r s i z i n a th ree bas ic types of process drums: l i q u i d surge drums, l iquid- l iquid s e t t l e r s , and vapor-1 iquid sepa ra to r s , inc luding process steam drums. . -- --- -

The methods offered i n t h e chapter represent a good design p rac t i ce f o r s i z ing the mzjority of d r b ~ s foi.ind iti process desigr: work. Hawever, nzi m e rnetbcd or c r i t s r i c ? rhou:.? t e csn::'&-d tc be appl icable t o a l l cases . Design cases such as t h e ones l i s t e d below may require c e r t a i n depar- t u r e from the s tandard methods given i n the chapter.

* Separation of two l i q u i d phases of very c lose density. * Separation of two l i q u i d phases when one l i q u i d i s i n the form of very f i n e l y d isper-

sed d rop le t s . * Renoval of a small amount of f i n e 1;iquid -. mist from a vapor phase.

These and o t h e r specia l s i t u a t i o n s may be b e t t e r and more economically handled w i t h devices such as v e r t i c a l and hor izonta l b a f f l e s , coalescing pads, and specia l wire-mesh arrancenents. which may be i n s t a l l e d i n ordinary process drums t o achieve a more e f f i c i e n t separation. Tho s i z ing techniques required f o r designing these more complex drums can be developed a f t e r consider- ing the specia l c h a r a c t e r i s t i c s of each case.

I DESCRIPTION AND SELECTION OF PROCESS DRVYS I ! I There a r e t h r e e main types of process drums coimnonly used by Lumus f o r which s i z ing procedures

and d e s i ~ n reccmendat ions a r e given i n t h i s chapter. They a r e I Liquid Surge Drums-

* Liqtrid-Liquid Se t t l e r s . * Yapor-Liquid Separators.

The se rv ice L+at each type of drum gives i n prscess p l an t s and same typiczl pmcess azs l ica- t ions f o r each type a r e dercribed i n t h e fo l lowins subsections. I

Liquid su r se drums a r e used t o provide s t c r z g e o r surge cspacity f o r l i qu id s t r e w s w h i d a r e s u b s t a n t i a l l y f r e e of vapor. As running s t o r a ~ e f o r the feed t o o t h e r precessing un j t s , they provide a convenient way o f assur ing r e l a t i v e l y ccns tan t or ra te-controi led flow. Surse dmrs may be bujl t i n e i t h e r hor izonta l o r v e r t i c a l pos i t ions .

'There i s no ooera t ional a d v a n t z c ~ fcr ~ i t h a r D O S ~ - * - ~ i o n . The drum is posit ioned bzsed on the

avz i i ab le space acccrding t o p lzn t layout , the c o s t of supporting s t ruct r r res , e t c .

I S e t t l i n g tanks a re used t o s e p a r a t e tuo i m i s c i b i e l iqu ids of di-rferent dens i t i e s which a r e e s s e n t i a l l y vapor-free. I

1 Typical proc2ss app l i ca t ions requir ing l iqu id - l iqu id s e t t l e r s a re I

To achieve aood se3ara t ion i n a s e t t l e r , t h e hold-up time f o r a

* Caustic-wash hydroczrbon s::s:e?s. * K-+- a , r r - ~ a s h hydroczr5on sysEens.

Sol vent ex t rac t ion sys t eas .

CO,,:F--n : t ~ t . . l ! l k i -- KC:J.U.EICT - :to1 to be Reproauced

l i q u i d phase should be l a r g e r than the time required by the drop le t s f o f the o t h e r phase t o s e t t l e ou t from t h i s phase. Horizontal drums pmvi de higher hol d-up t ime / se t t l i ng i l time r a t i o than v e r t i c a l drums. There- fo re , s e t t l i n g tanks a r e normally hor i -

;/I\ Light Liquid

- In te r face

Heavy Liquid zontal a s shown i n the f igu re .

- 11 -L-------,

S T A N D A R D D A T A B 0 6 ~ " - P A R T i 1 1 - P ~ G E 2 b~ 67 r* LUMMUS DRUM SIZING January , 1972

I Vapor-Liouid S e o a r a t o r s I

The main f u n c t i o n o f t h i s t y p e o f drum is t o s e p a r a t e v a p o r - l i q u i d mix tures and d e l i v e r sub- / s t a n t i a l l y l i q u i d - f r e e vapors t o o t h e r p rocess u n i t s . The v a p o r - l i q u i d s e o a r a t o r s may be b u i l t i n e i t h e r v e r t i c a l o r h o r i z o n t a l p o s i t i o n a s shown below.

- - - _ - . - _ _ - - - - -. *- - - - . .- - -- -- --

I VERTICAL

HORIZONTAL

Ti/([) L i g h t L iqu id

I n t e r f a c e - -

Heavy Liqu id

Y e r t j c a l v e ~ o r - l i ~ z i ' d s e z a r a t z r s a r e p r e f e r r e d f o r h a n d l i n g m'xt2res w i t h h i s ; va~3r/:i<:iC nzss flow r a t i o zna u s u a i l y on iy one l i q u i d phase. In c e r t a i n c z s e s , :he v z o o r - l i q u i d s e z ~ r < = S c n may t z k e p l a c e s imul taneous ly wi th t h e s e t t l i n g s e p a r a t i o n o f two l i q u i d phases. i n :he c z s e s where on ly a small amount of heavy phase i s p r e s e n t , v e r t i c a l drums may s t i l l be used.

Typical a p p l i c a t i o n s o f v e r t f c a l vzoor-l i o u i d s e o a r a t o r s a r e

* R e f l u r e c e i v e r s . * Flash drums.

P m c e s s compressor knock-out drums. . Fuel gas knock-out d r m s . Continuous blowdown drums.

Horizontal vaoor-? i o u i d s e o a r a t o r s a r e p r e f e r r e d t o handle t h e f o i lowi ng c a s e s :

Kixtures wi th low v a p o r / l i q u i d iilzss f low r a t i o and o n l y one l i q u i d phzse. Mixtures c o n t a i n i n g vapor and two i n m i s c i b l e l i q u i d phases.

An a t t a c h e d p o t may be used i n c e r t a i n c a s e s t o c a t c h t h e heavy phase o u t s i d e o f thedr;lm.thuS p e r m i t t i n g b e t t e r c o n t r o l o f t h e o p e r a t i o n and p o s s i b l y r e d u c i n g t h e d r ~ m s i z e .

Typical a @ p l i c a t i o n s o f h o r i z o n t a l v a o o r - l i c u i d s e o z r a t o r s a r e

Overhead condensate r e c e i v e r s on c rude o i l d i s t i l l z t i o n u n i t s . Water d i sengaging drums.

* Reflux r e c e i v e r s . * Steam Drums. * I n t e m i t t e n t blowdwn drums.

C) &,TOGID SURGE DRUM D E S I G ~

Des i on P r i nci ol e s

( 1 ) Surge t i n e to be s e l e c t e d from i n f o r n a t i c n on Pace 35, o r a s p e r s p e c i f i c prscess consicer::~ons issned by Process Design Mznzger o r L ~ a d I ~ D C ~ S S Engineer .

- - --- - * . - -- + :-- ,- . ' -- - ?-. LIQUI D'*WRG€ DRUM DESIGi i

HORIZONTAL SURGE DRUM Notes

DRUM SIZING

L i q u i d Feed Nozz le 1-

Vent - I

I - I 1

- -High L i q u i d Level - - --

Low L i q u i d Level- - - -

3 I I

L i q u i d 1- I O u t l e t Nozzle I

I I Tangent T a n g e n t

L i n e L i n e -LA

The h i g h and low l i q u i d l e v e l s i n d i c a t e t h e e f f e c t i v e measuring range of the-gauge ' rJlXs~s'?eV@l. . - - F..;r zczz?25 i n s t a ! 'e.5 cfi

t h e s h e l l , t h e min imm - dimensiori f rom the t a n g e n t

. l i n e t o t h e c e n t e r l i n e o f t h e n o z z l e i s

( 6 + d ) i n .

where d = n o z z l e d ia rne te r i n i n c h e s .

i h and hb = 9 i n . o r s e t by s t z n d a r d p r a c t i c e % -or .c C J Z U ~ C g l a s s E e l - i n s t a l l s t i o n .

I I Ve n r_ - I 1 I I

Too T a n g e n t L i n e

I

I - - - High Level L i q u i d -- - - L i q u i d Nozz 1 e Feed

t ! 1

i c D-

-- -Low L i q u i d - Level

hV and hb = 6 i n . or s e t & s t a n d a r d p r a c t i c e s

I Eot tcm T a n g e n t L i n e for gauge g l a s s l e v e l i n s t a i l a ~ o n .

I I ! L i a u i d I O u t l e t Nczz le I I

( 2 ) roe volurpe, corresponding t o above, ~ h o u l d be equivalent t o 8 0 - 9 E ~ f - the t o t a l drum volume, %te r accounting f o r useful head volume.

(3) See discussion on Page 36 f o r suggested L / D ranges.

( 4 ) See drawing cm Page 3 f o r addit ional design - recomndar iens . i - -

P A G E 4 OF 63

January, 1972 E* LUMMUS

Examole. A horizontal drum is t o be designed f o r holding l i q u i d e thylene a t -110°F and 90 ps ia . . Ethylene flows in to the drum a t a r a t e of 35,000 'Ib/hr. having a densi ty of 33.2 1 b / f t 3 a t the above flow condit ions. The drum i s feeding a r e a c t o r , and i t receives the l i q u i d ethylene from off -s i t e storage.

S T A N D A R D D A T A B O O K - P A R T I11

DRUM SIZING

(1) Se lec t a surge time, TS = 12 minutes.

Since P > 50 ps ig , a standard s i z e i s not ava i l ab le .

Se lec t an L/D of 3 .

(2 ) Surge volume required: (17.57)(12.0) = 210.8 f t 3

: .. j 1 j

CONFIDENTIAL D0CUYE:iT - Not t o be Reproduced

Yo1 m e t r i c flow ra te : u1 =

Q1 = q 35*000 = 1 7 . 5 7 f t 3 / m i n T60)(33.2)

v

S T A N D A R D D A T A . 8 0 0 K - P A R T 111 EE LUMMUS

- P A G E 5 O F 62

DRUM SIZING January, 1972

1 ( 4 ) According t o recornended values f o r horizontal drums. I hv = 9 inches

A - - . - L . - . - hb = 9 inches

(5) Since the mechanical design pressure wi l l be above 100 psig f o r a drum with an opera t ins pres- s u r e of 90 p s i a , s e l e c t 2:l e l l i p t i c a l heads f o r a 5 ft diameter drum. I

(6) Consider the addi t ional volume contributed by t h e two heads i n order t o obta in a more ecsncmi- cat s i z e .

X Depth a t 9 inches: (9)(100)/60 = 15% (Low l i q u i d l e v e l )

% Depth a t 51 inches: (51)(100)/60 = 85Z (High l i q u i d l e v e l )

Fjom Figure 3: - - --

- - (a) Caoacity of 2 e l l i p t i c a l herds a t 85: depth with 5 f t diameter: 231 ga l s . /

/ -

( O ) CapacSty of 2 e l l i p t f c z l h e 2 6 a r 15% dept? w f t h 5 ft diaaeter: 15 g a l s .

Then surqe vo'ime i n the tdo hezds:

vo 1 ume 1 e f ime,m :

(a) Capacity o f a 5 ft d iame te r s h e i l a t 85% d e ~ t h : 135.L-gaj/ft per ft of s h e l l

(b) Capacity of a 5 f t diameter s h e l l a t 15% d e ~ t h : 13.8 g a I / f i per ft of she l l --- -

Surge vo lum per foo t of s h e l l :

Lenqth o f s h e l l :

Say: 11 - 5 f t (saved 2 f t i n s h e l l length by accounting f o r volume of heeCs.) - (7) Final dimension;: u = 3 Fr --.

L a 11.5 ft L/D = 2.3 (Low, but acceptzble)

'!\

hv = 9 inches /. hb = 9 inches h i = d i s t acce between low and high l i q u i d leveis = 42 in . Two 5 f t d i a r e t e r e i l i p r f c a l hezds ---- - -- --

1 In -the-seprration by s e t t l i n g of two l i q u i d phasis of markedly d i f f e r e n t d e n s i t i e s , The dmp- l e t s o f t h e heavy pnzse have a tendency t o fa11 down and ou t o f t h e l i g h t phase under t h e in- fluence of gravi ty These heavy-li?~lid dmnlets a r c ~ ! e r z t e un t?? :kc f r ' c t j ~ c s ! d r a g force

1 balances t h e g rav r t a t i cna l forces. A t t h i s point , the heavy d r o p l e t s continue t o phase ou t o f the, l i g h t l i q u i d a t constant ve loci ty . This i s the terminal o r f r e e - s e t t l i n g veloci ty . An analoaous mechanism appl ies t a m e separa t ion of the l i g h t - l i q u i d d rop le t s t h a t may be present i n the bulk of the heavy phase, except t h a t i n t h i s case the d rop le t motion is upward, and t h e f r i c t i o n a l drag force created by t h i s m t i o n is opposed by the buoyancy fo rces ins t ead of gravi ty .

Desfcn Principles --

r

E< LUMMUS

(1) The ob jec t ive of the s e t t l e r is t o achieve an e f f i c i e n t l i a u i d - l i q u i d sepa ra t ion , and not t o provide surge vo7ume. Once the l iquid- l iquid s e t t l e r has been designed, c e r t a i n mechanical arrangements silch as baff les can be i n s t a l l e d t o provide surge v o l m e wi th in the sane drum.

(2) For the p a r t i c l e s i z e s comonly found i n i n d u s t r i z l l i qu id - l iqu id s e t t l i n g opera t ions , t h e following equation based on the Stokes Law gives the f r e e - s e t t l ing ve loc i ty f o r the drople ts of one l iqu id out of the o the r continuous K q u i d phase.

!

6.- ' b l l t F R Earn

S T A N D A R D D A T A B O O K - P A R T 111

DRUM SIZING

= ' ks .hid , but n o t t o e x c ~ e d 1- u c

1 A, 2 4 r ? / k M '1 where ph = Densjty of heavy l iqu id phase, 1 b / f t 3

PAGE 6 OF63

January, 1972

I PI = Density of l i g h t l i qu id phase, 1 b / f t 3 / ' I

cc = Viscosity of continuous phase, cent ipoise

I f the rninimua p a r t i c l e s i z e f o r a given dispersed l iqu id phase is known, the following eqlra- L ~ , R is used:

where d i s t h e p a r t i c l e s i z e i n inches.

' I Since d is not generally avai lable , tbe foilowing titb'le can be used t o s e ' r c t a value f o r ks: I L i oht Phase Heavv Phzse

Assumed Hininun Drcpiet Size 45

Hydrocarbons Sp.gr. et 60PF < 0.85 Later o r Caustic 0.005 i n . = 123 z'crons 0.333 - Sp.gr. @ 60°F > 0.85 Water o r Caustic

Water Furfural MEK Water Sec-butyl alcohol Uater 0.0035 in . = EQ nicrons 0.163 Methyl: isoburyl ketone Water n Nonyl a1 coho1 Water \ O m'.w-s 3 c Lq:

\ - - - , - - - 2

(3 ) The s e t t l e r design should comply with the requirement tha f o r each continuous l i q u i d phase $ h e $ e & - a @ i s l a r g e r than the s e t t l i n g t i r n e , b needed by t h e d rop le t s o f t h e d i s - persed l i q u i d t o s e t t l e out. Therefore, according t o t h e accompanying f i g u r e ,

the r e t t l i n o veloc; r i ~ s 2 the l i c n t q n d he~vv--. T&c.% a re i n f ee t .

I

* A - - - -- - -- - --

LIQUID-LIQUID SETTLER D E S I G N

.-- - Lf ght Lfquid - - - - Ltquid Feed (see de ta i l below) Drawoff Nozzle

I

Interface --

I h, ( 1 f t minimum)

hh ( l f t minimum)

Heavy Liquid 1 Drawo f f Nozzle I

NOTES

1. For nozzles jnS:l!e? sn the s h e l l , the ti;^::,-

dimnsion frog the tzacent l i n e t o the cent57 i : r~ o f the nozzle t s

( 6 t d l fn.

where d = nozzle C:~-e'-er fn tnc$es.

! I

Tznaeni Tangent 2. The nozzles fo r <?;;%-

Ljne Line g lass :evels, t n c @, mlocrtec! a t 2' e ! e v z t ~ o n

L L

Detai1:Feed Pi;e Nozzle Arrz~gernents (Front v i e w ) F u g e glass level .ir.s-.Ila:ic.r..

Feed frcr, TCD Feed f m m Side

Feed t h r c u ~ h Head

- 7 I - Interface --- \, in G

( 5 ) See drawing on Page 7 f o r addit ional design recomnendations.

'. I L C L I . F . - --

L i m i t a t i o n s - . %% .-.. - -L

The p r inc ip le s described above should not be applied f o r designing s e t t l e r s t h a t handle

rI LUMMUS

Systems where one of t h e phases i s f i n e l y dispersed and amounts t o l e s s than 2: of tk t o t a l flow ra te . . I - Sys tem where the densi ty d i f ference amounts t o l e s s than 10% of t h e heavy l i q u i d den- s i t y .

' S T A N D A R D D A T A B O O K - P A R T 111

Systems where an excessive foaming tendency i s expected.

In these cases, o ther separation equipment nay have t o be considered.

PAGE 8 OF63

DRUM SIZING

Exam~le. A 50.000 lb /hr strean.containing 80% by weight of aromatics and t h e balance as water, is t o be delivered a t 100°F and atmospheric pressure t o a s e t t l i n g drum t o recover t h e a n - rnatics. Desion the drum as a horizontal s e t t l e r . A t flow condi t ions t h e physical p n ? e r - t i e s a r e

January, 1972

Aromatfc phase: p1 = 53.0 lb/:t3 Water: ph = 62.0 I b / f t 9 p1 = 0.550 cp ph = 0.682 cp

(4) See discussion on Page36 f o r suggested L/D ranges.

(1 Preliminary design data:

( 2 ) Volumetric l i q u i d ra tes :

01 = 40,DOO/ii50i(55.0)l = 12.58 f t 3 / n i n -\

Qh = 10,000/[(60)(62.0)] = 2.69 ft3/min

Both values s a t i s f y : .vse t t l jng < 10 inches/rr;in

~ r e 1 i n l n ; t r v may be estimated from the expression

D = 2.3 Ql V l + Qh Vh

, f t , where Q is i n f t3 /min and v i n inches/rzin.

a s sming L/D = 3. \ Then D = 3.30 ft- /

L = 3(D) = 3(3.30) = 9.90 f t

Rounding o f f , D = 3.5 ft L = 10.0 f t

L/D = 2.86. This i s O.K.

Proceed t o detennine the s e t t l i n g heiants of t h e l i o h t and heavy phases. Rake necessary a d j u s t rnents t o comply with t h e i l l u s t r a t i o n f o r l i qu id - l iqu id s e t t l e r des<gn on Pdge 7.

us- - - L E%ELUMMUS .'I S T A N D A R D D A T A e o o u - P A R T - 111

DRUM SIZ ING Decenber. 1975

3.5 = 0.62 f t

!

i

i u.. 3

' -' ,I

I I

1 ---

I

Then a c c o r d i w the recornended value, - &.A=. 6

hh = 1 f t [m;~imum he igh t )

and h i = D - hh = 3.5 - 1.0 = 2.5 ft = 30 inches 9-

(6) Check t h a t the s- do n o t exceed the residence times.

12 (hh) - 12 (1.0) = 2-73 minutes t h = - - Vh 4.39

Fmm Table 2 f o r # = = 0.286, Ah = 0,236 7r

and Ah = 0.236 ( ~ / 4 ) ( 3 . 5 ) ~ = 2.27 ft2

Then Eh = Ah = 2 2 . 2 7 ( l o ) = 8-44 minutes Qh 2.6%

Therefore eh > q,

Then A1 = A - Ah = 9.62 - 2.27 = 7.35 f t2

and 91 = A7 = '7.35 (10) = 5.24 minutes 9 1 12-58

Therefore > t.1

(7) F i n a l Dimensions: D = 3.5 ft L = 10.0 ft

VD = 2.86 h i = 30 inches h i = 2.5 ft hh = 12 inches

L i q u i d

I n t e r f a c e

hh = 1.0 ft

POR-LIOUID SEPARP.TCR DESi

V e r t i c a l and ho r i zon ta l drums are cornonly used tc seDarate v a p o r - l i q u i d mixtures. When o n l y one ' l iqu id phase i s involved, the f a c t o r s a f fec t ing the desion are the vapor v e l o c i t y and, if re- quired, the- l i q u i d surge time. Whenever two i nm isc ib le l i q u i d phases a re present, the desiori becomes more complex because the s e t t l i n g c h a r a c t e r i s t i c s of the two l i q u i d s be teken i n t o account. I n add i t i on , process considerat ions may detern ine t h a t an at tached p o t or t r a ~ o u t boot be used t o c o l l e c t the heavy l i q u i d phases.

The f o l l o w i n g sketch sumar izes the desfgn methods f o r v a ~ o r - l i q u i d sepa rzb rs :

CONF!DEBTiAL WCUt?ENT - Not to be Reproduced