info topping 12

8/10/2019 Info Topping 12

1/6

EQUIP ~IENT

E X P E R I E N C E I N D E S I G N A N D S T A R T U P O F D I S T I L L A T I O N T O W E R S I N P R I M A R Y

C R U D E O I L P R O C E S S I N G U N I T

Yu. N. Lebedev, V. A. Sheinman,

G. V. Mamontov, V. V. Ukhin,

V. G. D'yakov, and I. A. Zil'ber berg

U D C 6 6 . 0 4 8 . 0 3 7

I n 1 98 2 , i n t he c i t y o f M a t h u r a ( I n di a ) , a r e f i n e r y w i t h a c a p a c i t y o f 7 m i l l i o n m e t r i c

t o n s of c r u d e p e r y e a r w a s p u t i n t o o p e r a t i o n ; t h i s r e f i n e r y w a s d e s i g n e d a n d c o n s t r u c t e d

w i t h t h e c o o p e r a t i o n o f S o v i e t s p e c i a l i z e d o r g a n i z a t i o n s . T h e r e f i n e r y i n c l u d e s t h e f o l -

l o w i n g u n i t s : A V T [ a t m o s p h e r i c - v a c u u m t u b e s t i l l u ni t ] f o r p r i m a r y c r u d e o i l p r o c e s s i n g ,

c a p a c i t y 7 m i l l i o n t o n s / y r; c a t a l y t i c c r a c k i n g , i m i l l i o n t o n s /y r ; v i s b r e a k i n g , i m i l l i o n

tons/yr; aspha lt 0.5 mil lion tons/yr; and other units.

A c c o r d i n g t o t h e d e s i g n , t h e A V T u n i t s h o u l d p r o c e s s a l :l m i x t u r e o f l i g ht A r a b i a n

a n d N o r t h R u m a i l a c r u d e s , p r o d u c i n g h i g h - q u a l i t y m o t o r f u e l c o m p o n e n t s a n d f e e d s t o c k s f o r

t h e c a t c r a c k i n g , v i s b r e a k i n g , a n d a s p h a l t u n i ts . G o o d s e p a r a t i o n s h o u l d b e o b t a i n e d w i t h i n

the range of 60% to 105% of the design cap acity. Actually, during the startup period, the

u n i t o p e r a t e d u n d e r m o r e d i f f i c u l t c o n d i t i o n s . E v e r y o n e o r tw o d a y s, t h e c r u d e o i l c o m -

p o s i t i o n w a s s w i t c h e d f r o m l i g h t A l g e r i a n w i t h a p o t e n t i a l c o n t e n t o f 73 % ( by w e i g h t )

f r a c t i o n s d i t i l i i n g b e l o w 3 8 0 ~ t o h e a v y A r a b i a n w i t h 4 2 % o f t h e s e f r a c t i o n s . T h e c o n t e n t

o f 3 8 0 - 5 3 0 ~ f r a c t i o n i n t h e a t m o s p h e r i c r e s i d c o r r e s p o n d i n g l y c h a n g e s f r o m 3 8 % to 7 1 % b y

w e i g h t . S i m u l t a n e o u s l y , t h e c h a r g i n g r a t e c h a n g e d f r o m 5 0 0 % t o 1 i 0 % o f t h e n o m i n a l . U n d e r

s u c h c o n d i t i on s , t h e q u a l i t y o f th e v a p o r a n d l i q u i d i n c e r t a i n s e c t i o n s o f t h e d i s t i l l a t i o n

t o w e r s d e v i a t e d m o r e t h a n t h r e e f o l d f r o m t h e d e s i g n i n d e x e s . N o n e t h e l e s s , t h e t o w e r s o p e r a t e d

s t a b l y, g i v i n g e n d - p r o d u c t s w i t h t h e r e q u i r e d q u a l i t y . T h i s w a s a c h i e v e d b e c a u s e o f h i g h -

q u a l i t y c a l c u l a t i o n , d e s i g n , f a b r i c a t i o n , a n d e r e c t i o n o f t he t o w e r e q u i p m e n t, a s w e l l a s a

c o r r e c t s e l e c t i o n o f t h e f l o w p l a n a n d c o n t r o l o f p r o c e s s c o n d i t i o n s .

T h e o p e r a t i n g e f f i c i e n c y o f d i s t i l l a t i o n t o w e r s d e p e n d s o n t h e y i e l d a n d q u a l i t y o f t h e

d e s i r e d p r o d u c t s a n d a l so o n t h e t e c h n o e c o n o m i c i n d e x e s o f t h e o p e r a t i o n o f t h e A V T u n i t a s

a whole. Therefore, it is impor tant to consi der the features of opera tion of each tray up

and down the tower, in order to ensure the best condi tions of separation . In Figs. 1-3 we

s h o w d i a g r a m s o f t h e p r i n c i p a l d i s t i l l a t i o n t o w e r s i n t h e A V T u n i t . A l l t o w e r s a r e f a b r i c a t e d

w i t h s e c t i o n s d i f f e r i n g i n d i a m e t e r a n d w i t h d i f f e r e n t c o n t i n u i t i e s ( 1 - 4 ) o f t h e t r a ys . I n

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

l i q u i d h o l d u p f o r s t a b l e o p e r a t i o n . I n th e a t m o s p h e r i c a n d v a c u u m t o w e r s , i n t h e z o n e s a b o v e

the feed inlet, where the reflux densit y is low, sin gle-pas s trays have been used; in the

a t m o s p h e r i c t o w e r, t w o c o c u r r e n t - f l o w v a l v e t r a ys , a n d i n t h e v a c u u m t o w e r, s i x s i e v e t ra y s

w i t h s p e c i a l l y d e s i g n e d d e m i s t e r el e m e n t s , s o - c a l l e d d o u b l e - p a s s t r a y s . E a c h s i e v e t r a y h a s

a v e r t i c a l p a r t i t i o n a l o n g a d i a m e t e r . T h e l i q u i d f i r s t m o v e s a l o n g o n e si d e o f t h e t r a y,

t h e n t u rn s a n d m o v e s a l o n g t h e o t h e r s i d e i n t h e r e v e r s e d i r e c t i o n t o w a r d t h e o v e r f l o w . A s

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

i n o r d e r t o r e d u c e l i q u i d w e e p i n g , t h e d e c k s o f t h e d o u b l e - p a s s t r a y s a r e i n s t a l l e d w i t h

a s l o p e of a p p r o x i m a t e l y 5 ~ i n th e d i r e c t i o n o f l i q u i d o v e r f lo w . I n w o r k i n g o u t t he d e s i g n

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

t r a y s w i t h d i f f e r e n t f l o w s e q u e nc e , t o t h e f i t t i n g s f o r r e f l u x a n d f e e d i n t r o d u c t i o n a n d f o r

side strea m takeoff, etc.

T h e o v e r f l o w o f l i q u i d w h e n t h e r e i s a c h a n g e i n c o n t i n u i t y o f t h e t r ay s i n t h e a t m o s -

phe ric tower, from No. 12 to 13, 26 to 27, 36 to 37, and 46 to 47, in the sta bil ize r from

No. 16 to 17, and in the vacu um to wer from No. 6 to 7 and from 9 to i0, is accomp lishe d by

t h e u s e o f d o w n c o m e r p i p e s . I n t h e v a c u u m a n d a t m o s p h e r i c t o w e r s, a b o v e t h e f e e d i nl e t ,

b l i n d t r a y s a r e i n s t a l l e d i n t h e t o w er f o r t a k e o f f ~of a b l a c k p r od u c t , s o a s t o p r e v e n t

A l l - U n i o n S c i e n t i f i c - R e s e a r c h a n d D e s i g n I n s t i t u t e o f P e t r o l e u m M a c h i n e r y C o n s t r u c t i o n

( V N l l n e f t e m a s h ). A l l - U n i o n - S c i e n t i f i c - R e s e a r c h a n d D e s i g n I n s t i t u t e o f t h e P e t r o l e u m R e f i n -

i n g a n d P e t r o c h e m i c a l I n d u s t r y ( V N I P l n e f t ' ). T r a n s l a t e d f r o m K h i m i y a i T e k h n o l o g i y a T o p l i v

i Mase l, No. 3, pp. 17-20, Mar ch, 1985.

1 3 0 0 0 0 9 - 3 0 9 2 / 8 5 / 0 3 0 4 - 0 13 0 5 0 9 . 5 0 9 1 9 85 P l e n u m P u b l i s h i n g C o r p o r a t i o n


2/6

F

p

Fig. I Fig. 2

F i g. i . D i a g r a m o f a t m o s p h e r i c t o w e r w i t h s t r i p p i n g s e c t i o n s i n A V T

unit: I) crude; II) steam; III,IV) second and first circul ating reflux,

respect ively; V) C~-C~ gas + naph tha cut; VI) live reflux; VII) keros ine

cut; VIII) light dies el fuel cut; IX) heavy diesel fuel cut; X) atmos-

pheric resid; XI) black product.

Fig. 2. Diag ram of stabi lize r tower: I) unst abil ized naphtha; II) CI-

C4 gas; III) live reflux; IV) vapo r-li quid mix tur e; V) heat carrier;

V I ) s t a b i l i z e d n a p h t h a .

wee ping of this produc t into the lower section. The black produc t (yield 1-2 on feed) is

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

f e e d v a p o r i z e d a t t h e t o w e r i nl e t . T h e fe e d e n t e r s t h e a t m o s p h e r i c a n d v a c u u m t o w e r s

t h r o u g h t r a n s f e r l i n e s w i t h r e s p e c t i v e d i a m e t e r s o f 9 00 a n d i0 0 0 m m . W i t h i n t h e to w e r, t h e

f e e d i n l e t i s c o n s t r u c t e d i n t he f o r m o f a g u i d e b o x i n w h i c h t h e v a p o r - l i q u i d m i x t u r e i s

r o t a t e d . U n d e r t h e i n f l u e n c e o f c e n t r i f u g a l f o r c e, t h e l i q u i d p h a s e s e g r e g a t e s o n t h e o u t e r

wall of the box, is collect ed :in a specially desig ned well an d overflo ws into the intake

well of the top tray in the stripping section of the tower; the vapor is with draw n and

u n i f o r m l y d i s t r i b u t e d a c r o s s t h e c o l u m n s e c t i o n t h r o u g h o p e n v a l v e s o n t he i n n e r w a l l o f

the guidebox. In the vacu um tower, above the feed inlet and in the upper section, knit

s c r e e n d e m i s t e r s a r e m o u n t e d , t h e d e m i s t e r a b o v e t h e f e e d i n le t b e i n g w a s h e d c o n t i n u o u s l y

w i t h a s m a l l q u a n t i t y o f v a c u u m g a s o i l . I n t h e s t a b i l i z e r , a h i g h l y r e c o m m e n d e d d e s i g n i s

u s e d f o r t h e l i q u i d i n l e t t o t h e t h e r m o s i p h o n o f t he r e bo i l e r . I t e n s u r e s s t a b l e o p e r a t i o n

of the reboi ler ev en when there are cons idera ble changes in the tower load.

T h e u s e o f r e l i a b l e p r o c e d u r e s f o r p r o c e s s a n d h y d r a u l i c c a l c u l a t i o n s h a v e m a d e i t p o s -

s i b l e t o s e l ec t t h e o p t i m a l p a r a m e t e r s f o r m a s s t r a n s f e r t r ay s , a n d t h i s h a s e n s u r e d e f f i c i e n

opera tion of the tower. In Table 1 and Fig, 4 we prese nt cer tain resul ts from a hydra ulic

c a l c u l a t i o n o f th e m a i n d i s t i l l a t i o n t o w e r s i n t h e A V T u n i t . E v e n t h o u g h t h e r e i s a c o n -

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

teristi cs of the trays are very clo se to each other, and they corres pond to the optimal

p a r a m e t e r s o f c o c u r r e n t - f l o w v a l v e t r a y s : f o r t h e v a c u u m t o w e r , t h e v a p o r l o a d fa c t o r

~ o = 1 3 - 1 6 k g ~ . m ~ f o r t h e a t m o s p h e r i c a n d s t a b i l i z e r t o w e rs , t h e l o a d i s 1 5 - 2 3

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

c y i s 6 0 - 7 0 . T h e s e h i g h l e v el s o f e f f i c i e n c y w e r e c o n f i r m e d i n a c t u a l o p e r a t i o n .

131


3/6

g

T A B L E i

D i a m e t e r m

T r a y t y p e

F i g .

3 .

D i a g r a m o f v a c -

u u m t o w e r : I ) a t m o s p h e -

r i c r e s i d ( > 3 8 0 ~ I I ,

V ) s e c o n d a n d f i r s t c i r -

c u l a t i n g r e f l u x , r e s p e c -

t i v e l y ; I I I) v a c u u m g a s -

o i l ; I V ) d i e s e l f u e l

c u t ; V l ) g a s a n d s t e a m ;

V I I ) d i e s e l f u e l c o m -

p o n e n t ; V I I I ) b l a c k p r o -

d u c t ; I X ) s t e a m ; X ) v a c -

u u m r e s i d .

Index

AtmospheriC[towerStabilizer[ VacuUmtower

f

5 5 ; 6 4 ; 5 5 2 ; 3 4 5 ; 7 ; 5

v a l v e c o - c u r r e n t f l o w c o c u r r e n t - v a l v e w i t h

k n i t

s c r e e n

d e m i s t e r

N u m b e r o f t r a y s

tota l 56 36 21

i n

c o n c e n t r a t i n g s e c t i o n 4 8 1 6 1 5

M a x i m u m v a p o r l o a d f a c t o r ~ 0 , . 2 2 ,7 5 /2 3 ,7 1 1 4 , 9 / 1 5 , 2 1 8 ,9 - /2 1 ,2

kg0.5/ sec .

m ~

Overf low load, m3 /( m, h) 53,2/54.4 54,0 /56.0 55,2/53,9

A v e r a g e e f f i c i e n c y ,

i n c o n ce n tr a [i n~ [ s e c t i o n 7 0 , 0 / 7 0 , 0 6 2 , 0 / 6 2 , 0 6 0 , 0 / 6 0 , 0

i n

s t ri p pi n g s e c u o n 5 0 , 0 /5 0 , 0 5 0 , 0 / 5 0 , 0 5 0 , 0 / 5 0 , 0

H y d r a u l i c r e s is t a n c e , k P a

i n

con cen t ra t i ng sec t i on 0 ,6 /0 ,532 0 ,55 4/0 ,55 8 0 ,36/0 ,5

i n s t r i pp ing sec t i on 0 ,545/0 ,53 0 ,4 79/0 ,465

0,45/0,42

N o t e . W h e r e t w o v a l u e s a r e s h o w n, t h e f i r s t i s t h e

d e s i g n v a l u e , t h e s e c o n d t h e a c t u a l v a l u e .

A n a n a l y s i s o f t h e r e s u l t s f r o m a f i x e d r u n h a s d e m o n s t r a t e d t h e r e l i a b i l i t y o f t he

p r o c e d u r e s u s e d i n t h e h y d r a u l i c c a l c u l a t i o n o f t h e c o c u r r e n t - f l o w v a l v e t r a y s. T h e e x -

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

a r e w i t h i n t h e r e g i o n o f e f f i c i e n t o p e r a t i o n o f t h e t r a y s ( s e e Fi g . 4 ) .

1 3 2


4/6

2~

=,-.

~ ~2

i , , I , I I I 1 I

Io 2o so ~o 5 6 zo 8o 9

L v , m ~ / ( m 9 h ) "

Fig. 4. Regio n of stable operation (I)

a n d e f f i c i e n t o p e r a t i o n ( I I- I V) o f c o c u r -

r e n t - f l o w v a l v e t r a y s ( ~o i s t h e v a p o r

load; L v is the liquid load): I) accord-

ing to techn ical manual; II,III,IV) wi th

respe ctive effici encie s of 50 , 70 , and

75 ; +, o, e) actua l loa ds on trays in

a t m o s p h e r i c , v a c u u m , a n d s t a b i l i z e r

towers, respectively.

TABLE 2

A t m o s p he r ic S t a b i l iz e r ~ a c u u m t o w e rn d e x

[ t o w er I

C a p a c i t y , m e t r i c t o n s / h 8 45 ,4 /8 70 ,0

1 3 0 2 / 1 4 2 0 2 7 8 0 / 2 8 5 5

Pre ssur e , k P a 244,4 /181,0 977,5 /880,0 5 ,3 /6 ,65

T e m p e r a t u r e , " C

to w er t o p 1 2 0 /1 2 6 7 6 /7 0 8 0 /1 0 5

f ee d a t i n l e t 3 7 0 /3 6 7 1 5 2 /1 4 9 4 0 0 /3 9 8

l i v e r e f l u x 5 5 / 4 6 5 5 /6 5 - -

f i rs t c i r c u l a t i n g r e f l u x

a t t a k e o f f 1 9 8 / 2 1 2 - - 135/140

a t i n l e t 1 0 0/ 80 - - 7 0 / 5 0

s e c o n d c i r c u l a t i n g r e f l u x

a t t a k e o f f 2 7 9 /3 0 0

--

2 7 0 /2 9 0

a t i n l e t 1 5 0 /1 0 8 - - 1 0 0 / ! 1 5

to w er b o t to m 3 5 9 /3 6 0 ! 7 6 /1 6 7 3 6 0 /3 6 5

R e l a t l v e ~ e a t r e m o v a l b y

r e f l u x ,

l iv e 35 ,3 /35 ,2 100/100 - -

c i r c u l a t i n g

f i rs t 39 ,7 /30 ,2 - - ! 0 ,0 /21 ,9

s eco n d 2 5 , 0 /3 4 , 6

- - - - 9 0 0 / 7 8 I

S t e a m t n j~ u t t o b o t t o m o f ! , 3 8/ ! ,0 3

--

3,0 /3 ,15

t o w e r ,

~/o

Note. The first valu e shown is the design value, the

s e c o n d t h e a c t u a l v a l u e .

The AVT unit was started up in two stages. First, the atmosph eric part of the unit was

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

I n s t a r t i n g u p t he un i t a n d b r i n g i n g i t o n t o c o n d i ti o n s , t h e c h a r g i n g r a t e w a s 6 5 - 7 0 o f

t h e d e s i g n r at e ; t h e e q u i p m e n t o p e r a t e d r e l i a b l y a n d e f f i c i e n t l y. S o m e d i f f i c u l t i e s a r o s e

i n c o n t r o l l i n g t h e v a c u u m t o w e r t o p t e m p e r a t u re , w h i c h , a c c o r d i n g t o d e s i g n , s h o u l d b e 8 0 ~

b u t a c t u a l l y n e v e r d r o p p e d b e l o w 1 0 0 ~ e v e n t h o u g h t h e r e w a s no c a r r y o v e r o f l i g h t h y d r o c a r -

b o n s i n t o t he b a r o m e t r i c t a n k. S u c h c a r r y o v e r w a s a v o i d e d b e c a u s e o f t h e o p e r a t i o n o f t h e

t h r e e t o p t r a y s u n d e r l o a d s t h a t w e r e l o w e r t h a n t h e m a x i m u m a l l o w a b l e , a s i t u a t i o n c a u s e d

b y t h e o p e r a t i o n o f t he u n it o n a c r u d e w i t h a c o m p o s i t i o n d i f f e r e n t f r o m t h a t u s e d i n t h e

design.

T h e r e s u l t s o f a f i x e d r u n at m a x i m u m c a p a c i t y a n d w i t h a f e e d c o m p o s i t i o n c l o s e t o t h a t

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

e q u i p m e n t a n d p r a c t i c a l l y c o m p l e t e c o n f o r m a n c e o f th e q u a l i t y i n d e x e s o f t h e d e s i r e d p r o -

ducts to the design speci fica tions (Tables Z-4), In the atmo spher ic tower, sharp separation

was achieved. The gap betwe en the end point (95 ) of the napht ha cut and the initia l boiling

133


5/6

TABLE 3

Index

: ] S t a b i l i z e d ~ K e r o s i n ~ D i e s e l f u e l c u t s

J n a p h t h a I c u t 0 4 o - Ugh~l h - ~ - [ ~ y : ( ~ 2 o -

1 2 ~ o c ) . L ~ - c ) ~ s o c )

710/700 79 0/7 90 840/840 870/870

LPG

Den~ty, kg/m

560/570

Sulfur con-

~ent , wt, %

to ta t - - 0,02/0,017 0,25/0,2 1,2/ 1, 0 2 2,0/1,66

m e r c a p t a n - - - 0,1/0,027 0,055/0,011 - - - -

PeS

c o n t e n t ,

0,15 /0 ,145 . . . .

l e m p e r a t u r e , t . ;

f l as h p o i n t - - - - 38/40 95/87 145/148

so lid p o i n t . . . .

1 0 / - - 9

+ 1 0 / + 1 5

i n i t i a l c ry s . . .

5 0 / - - 5 2

- - - -

t a l l i z a t i o n

V a p or pre s su re 0 ,7/0 ,74 0 ,05/0 ,05 - - - - - -

( a t 65=C, MPa )

Visc o s i ty ( a t . _ _ - - 7 , 5/4 ,62 10/12 ,3

. 3 ~ . 8 ~ . c ,

m m 7 s e c )

D i s t i i l a t l o n , ' C

IBP

28/38 138/150 232/230 290/259

5 % 6 0 / 5 7 1 6 3 / 1 5 7 2 5 1 / - -

0 % 66 /62 167 /173 257 /244 317 /300

3 0 % 7 9 / 7 6 1 7 7 / - - 2 7 2 / - - 3 3 2 / - -

50% 94/96 195/200 280/281 344/347

7 0 %

1 1 1/ 11 3 2 1 5 / - - 2 8 9 / - -

3 5 4 / - -

9 0

% 130/132 240/232 304/316 372/355

9 5 % 1 3 8 / 1 4 6 .

250/242 312/326 .388/3 66

E P 1 5 0 / 1 5 2

2 5 8 / 2 6 0 3 2 0 / 3 4 1 3 9 3 / -

N o t e .

F i r s t v a l u e l i s t e d i s d e s i g n v a lu e , s e c o n d i s a c-

t u a l v a l u e .

TABLE 4

I n d e x

~ e n s i t v k ~ / m s

ota l ~ f il ff fr c on te n t , %

V i s c o s i t y , m i n d / s e e

a t 50 C

a t 9 8 , 9 ( :

C o n r a d s o n c a r b o n r e s i d u e ,

T w t .

e m p e r a m r e , C

s o l i d p o i n t

f l a s h p o i n t

P e n e t r a t i o n

M e t a l c o n t e n t ( = V + 1 0

N i ) , p p m

D i s t i l l a t i o n , C

I | P

90O/o

95

EP

Note.

[ D i e se l f u e l c o m p o n e n t V a c u u m s a s o i l

880/900 920/920

2 , 2 / 2 , 0 7 2,4/2,3

m / 1 1 3

0,06/0,026

96O1971

3 , 5 1 2 , 9

3 8 0 - - 4 1 0 / 5 8 0 - - 6 8 0

9 , 8 / [ 0 , 5

' ' 1 'V a c uu m res i' d

I (>

530 C)

1 0 1 0 / 1 0 2 0

4 , 6 / 4 , 0 6

38 51

7 ,8 /8 ,0 75071270

0 , 5 / 0 , 0 5

20113,5

21/21 10/24 36/39 39/50

--- /200 145/152 170/170

- -

. . . . . /2 3O --2 4 0

- - - - < ~ 2 , 5 / 0 , 8 5 - -

39--904/3 /270 300/284

- -

322/313 393/390

- -

452/470 342/332 422/425

- -

5 1 5 / 5 2 5

3 5 2 / 3 4 8 4 4 4 / 4 5 0

5 3 5 ( 5 5 % ) / ( 5 3 5 ( 5 4 % ) 3 6 5 ( 7 0 % ) / 3 6 6 ( 6 7 % ) 5 1 0 / 4 9 5

- - - - - - / 5 o o - -

..

--

550/550

--

F i r s t v a l u e l i s t e d i s d e s i g n v a l u e , s e c o n d i s a c t u a l v al u e .

point (5 ) of the kero sine cut was 5-20~ (according to the design, 5~ the overlap of the

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

0 - 5 ~ a n d t h at o f t h e i n i t i a l b o i l i n g p o i n t a n d t h e e n d p o i n t o f th e li g h t a n d h e a v y d i e s e l

f u e l c u t s w a s 5 - I 0 ~ T h e c o n t e n t o f f r a c t i o n s d i s t i l l i n g b e l o w 3 8 0 ~ i n t h e a t m o s p h e r i c

r e s i d w a s n o g r e a t e r t h a n 3 -5 b y w e i g h t ( t he d e s i g n s p e c i f i e d a m a x i m u m o f 6 .5 ) . T h e

v a c u u m g a s o i l w a s a l s o h i g h - q u a l i t y ; i n i t s p r i n c i p a l q u a l i t y i n d e x e s , i t c o n f o r m e d c o m p l e t e l y

t o t h e d e s i g n ; a n d in s o m e o f t h e q u a l i t y i n d e x e s ( c a r b o n r e s i d u e , c o l o r , m e t a l c o n t e n t ) ,

i t w a s c o n s i d e r a b l y b e t t e r t h a n t h e d e s i gn .

134


6/6

A n a n a l y s i s o f t h e q u a l i t y i n d e x e s f o r t h e p r o d u c t s f r o m t h e a t m o s p h e r i c t o w e r h a s i n-

d i c a t e d t h a t t h e r e i s a c e r t a i n r e s e r v e i n t he s h a r p n e s s o f s e p a r a t i o n o f t h e n a p h t h a a n d

k e r o s i n e c u t s . O b v i o u s l y , t h e n u m b e r o f t r a y s i n th e n a p h t h a s e c t i o n ( 1 2 ) a n d in t he s t r i p -

p i n g s e c t i o n ( i 0 ) c a n be r e d u c e d s o m e w h at .

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

w a s c h a n g i n g e v e r y o n e o r t w o d a y s, w i t h f r e q u e n t r e a d j u s t m e n t o f o p e r a t i n g c o n d i t i o n s , h a s

s h o w n t h a t i t i s a d v i s a b l e t o s e l e c t p u m p s w i t h a d e q u a t e r e s e r v e c a p a c i t y, p a r t i c u l a r l y f o r

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

t h e b o t t o m o f th e a t m o s p h e r i c t o w er . M o r e o v e r , i t i s v e r y i m p o r t a n t t o p r o v i d e r e l i a b l e

c o n t r o l o f t h e l i q u i d l e v e l i n t h e b o t t o m o f t h e t o we r a n d a n a d e q u a t e r e s e r v e o f t o w e r

v o l u m e b e l o w t h e b o t t o m t r a y , s o as t o a l l o w n o r m a l o p e r a t i o n w h e n t h e l iq u i d l e v e l b e c o m e s

u n d u l y h i g h d u r i n g t h e a d j u s t m e n t o f p r o c e s s c o n d i t i o n s i n t h e to w e r. I t i s a d v i s a b l e t o

i n s t a l l l i q u i d l e v e l i n d i c a t o r s i n t h e b l i n d t r a y s f r o m w h i c h t h e c i r c u l a t i n g r e f l u x i s w i t h -

drawn. These trays should be tightl y sealed.

T h e s t a r t u p a n d o p e r a t i o n o f t h e A V T a n d v i s b r e a k i n g u n i t s h a v e d e m o n s t r a t e d t h e h i g h

r e l i a b i l i t y a n d e f f i c i e n c y o f S o v i e t e q u i p m e n t a n d i t s c a p a b i l i t y f o r g i v i n g h i g h - q u a l i t y

p r o d u c t s o v e r a b r o a d r a n g e o f v a r i a t i o n o f c h a r g i n g r a t e .

I n t h e A V T u n i t , t h e d e s i g n i n c o r p o r a t e s t h e m o d e r n s c h e m e o f s i n g l e - s t a g e v a p o r i z a t i o n

of the crude (with one atmo spher ic tower) and a ration al sche me of heat exchange, giving

a h i g h d e g r e e o f h e at u t i l i z a t i o n ( ~ 5 0 ) a s a r e s u l t o f h e a t i n g t h e i n c o m i n g c r u d e t o 2 5 4 ~

by the was te heat of the streams leavin g the tower; he at is supplied to the bott om of the

s t a b i l i z e r i n a t h e r m o s i p h o n r e b o i l e r , u s i n g as a h e a t c a r r i e r t h e l o w e r c i r c u l a t i n g r e f l u x

a n d t h e h e a v y d i e s e l f u e l c u t f r o m t h e a t m o s p h e r i c t o w er .

135

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