a comparison of simulated distillation to true boiling point

Q

A COMPARISON OF SIMULATED DISTILLAT O N TO TRUE B O I L I N G POINT DISTILLATION OF H-COAL DISTILLATES

Melvin D. Kiser A s h l a n d P e t r o l e u m Company R e s e a r c h a n d Development D e p a r t m e n t P . 0 . Box 391 A s h l a n d , Kentucky 41101 D o n a l d P. Malone Ashland S v n t h e t i c F u e l s . I n c . P: 0 . Box 391 ’ Ashland, Kentucky 41101

INTRODUCTION A v e r y i m p o r t a n t c h a r a c t e r i s t i c o f l i q u i d h y d r o c a r b o n s d e r i v e d from e i t h e r petroleum o r s y n t h e t i c f u e l feedstocks i s t h e b o i l i n g p o i n t distribution. I n many p l a n t o p e r a t i o n s , a l l y i e l d c a l c u l a t i o n s , m a t e r i a l b a l a n c e s , p h y s i c a l p r o p e r t y c o r r e l a t i o n s , and computer p r o c e s s simulat i o n s a r e b a s e d upon t h e t r u e b o i l i n g p o i n t (TBP) d i s t i l l a t i o n c u r v e o f t h e streams i n q u e s t i o n . U n t i l t h e advent of simulated d i s t i l l a t i o n , t h e r e were two b a s i c m e t h o d s f o r d e t e r m i n i n g t h e TBP d i s t i l l a t i o n f o r a sample: (1) t o a c t u a l l y p e r f o r m a TBP d i s t i l l a t i o n , w h i c h i s a t i m e cor s u m i n g p r o c e d u r e ( u s u a l l y a minimum o f e i g h t h o u r s ) , o r ( 2 ) t o p e r f o r m s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n ( d e s i g n a t e d b y t h e American S o c i e t y for T e s t i n g a n d M a t e r i a l s as Method D-861 f o r a t m o s p h e r i c d i s t i l l a t i o n s , a n d Method D-11602 f o r vacuum d i s t i l l a t i o n s ) , a n d c o n v e r t i n g t h e d a t a t o TBP by m a t h e m a t i c a l c o r r e l a t i o n s . With t h e i n t r o d u c t i o n o f s i m u l a t e d d i s t i l l a t i o n b y gas c h r o m a t o g r a p h y ( d e s i g n a t e d ASTM D,28873), a method, w h i c h o f f e r s a r e l a t i v e l y s h o r t a n a l y s i s time o f a p p r o x i m a t e l y o n e h o u r , became a v a i l a b l e t o t h e a n a l y s t , The v a l i d i t y o f t h e u s e o f s i m u l a t e d d i s t i l l a t i o n f o r H-Coal0 l i q u i d s h a s b e e n q u e s t i o n e d d u e t o t h e p r e s e n c e o f o x y g e n a t e d compounds a n d l a r g e c o n c e n t r a t i o n s o f a r o m a t i c c o m p o n e n t s . The o b j e c t i o n t o t h e u s e o f s i m u l a t e d d i s t i l l a t i o n f o r t h e a n a l y s i s o f h i g h l y a r o m a t i c o i l s , s u c h a s t h o s e d e r i v e d from c o a l l i q u e f a c t i o n p r o c e s s e s , i s t h a t t h e i n d i c a t e d b o i l i n g p o i n t s o f p u r e m u l t i p l e r i n g comp o n e n t s as d e t e r m i n e d by s i m u l a t e d d i s t i l l a t i o n w i l l d i f f e r s u b s t a n t i a l l y ( 2 0 t o 100°F) from t h e p u r e component b o i l i n g p o i n t s . ASTM D-2887 suggests t h a t t h i s i s due a t least i n p a r t t o d i f f e r e n t behavior o f t h e vapor-pressure-temperature r e l a t i o n s h i p f o r a r o m a t i c compounds a s compared t o other hydrocarbon t y p e s . One n o t e s , h o w e v e r , t h a t a l l o f t h e c o m p o n e n t s m e n t i o n e d by t h e ASTM m e t h o d d o n o t c o n t a i n a n y m u l t i p l e r i n g a r o m a t i c compounds t h a t h a v e a l k y l s u b s t i t u e n t g r o u p s . The p u r p o s e of t h i s p a p e r i s t o e x a m i n e a c o m p a r i s o n o f s i m u l a t e d d i s t i l l a t i o n t o TBP d e r i v e d from b o t h a c t u a l TBP d i s t i l l a t i o n s a n d s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n s c o n v e r t e d t o TBP f o r v a r i o u s H-Coal0 d i s t i l l a t e s .

114

EXPERIMENTAL \

,

The t r u e b o i l i n g p o i n t d i s t i l l a t i o n d a t a p r e s e n t e d was o b t a i n e d u s i n g a Tod& d i s t i l l a t i o n c o l u m n , h a v i n g f i f t e e n ( 1 5 ) t h e o r e t i c a l p l a t e s a n d a f i v e t o o n e r e f l u x r a t i o . The o v e r h e a d m a t e r i a l was meas u r e d on t h e b a s i s o f t r u e w e i g h t p e r c e n t , i . e . , t h e w e i g h t o f o v e r h e a d m a t e r i a l was compared t o t h e w e i g h t of m a t e r i a l o r i g i n a l l y c h a r g e d t o t h e d i s t i l l a t i o n . The d i s t i l l a t i o n was c a r r i e d o u t u n d e r a t m o s p h e r i c c o n d i t i o n s a s much a s p o s s i b l e , w i t h vacuum b e i n g a p p l i e d a s n e c e s s a r y t o p r e v e n t t h e r m a l d e c o m p o s i t i o n ( c r a c k i n g ) . The s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n s w e r e p e r f o r m e d as p e r t h e i r r e s p e c t i v e ASTM m e t h o d . The methods u s e d t o c o n v e r t t h e s i n a l e t h e o r e t i c a l D l a t e d i s t i l l a t i o n d a t a t o TBP d a t a a r e t h o s e o u t l i n e d - i n t h e American' P e t r o l e u m I n s t i t u t e T e c h n i c a l Data Book. The method u s e d t o c o n v e r t ASTM D-86 d a t a t o TBP I n t h e c a s e of ASTM D-1160 d i s t i l l a t i o n s , d a t a was A m p r o c e d u r e 3 A 1 . 1 4 . t h e p r o c e d u r e was more c o m p l e x , r e s u l t i n g from t h e a d d i t i o n a l v a r i a b l e o f vacuum. Any d i s t i l l a t i o n d a t a n o t c a r r i e d o u t a t 1 0 mm Hg was f i r s t c o n v e r t e d t o d i s t i l l a t i o n d a t a a t 1 0 mm Hg u s i n g A P I p r o c e d u r e 5A1.85. The ASTM D-1160 d i s t i l l a t i o n d a t a a t 1 0 mm Hg w a s t h e n c o n v e r t e d t o TBP d a t a a t 1 0 mm Hg u s i n g A P I p r o c e d u r e 3A1.Z6. The r e s u l t i n g TBP d a t a at 1 0 mm Hg was c o n v e r t e d t o TBP d a t a a t 760 mm H g u s i n g A P I p r o c e d u r e 5A1.137. A l l s i m u l a e d d i s t i l l a t i o n d a t a p r e s e n t e d was o b t a i n e d u s i n g a H e w l e t t Packarddb 5 7 3 1 g a s c h r o m a t o g r a p h e q u i p p e d w i t h d u a l flame i o n ization detectors. The columns u s e d w e r e 1 0 % UCW-982 on Chromasorb PAW ( 2 0 i n c h e s i n l e n g t h , 1/8 i n c h e s i n d i a m e t e r ) , w i t h t h e t e m p e r a t u r e of t h e column o v e n programmed from - 5 O O C t o 35OoC a t a r a t e o f 8 O c p e r minute, during t h e a n a l y s i s . Calibration f o r the simulated d i s t i l Call a t i o n w a s b a s e d upon n o r m a l p a r a f f i n h y d r o c a r b o n s (nC2 t o n 4 4 ) . c u l a t i o n s were p e r f o r m e d a s p e r ASTM D-2887 u s i n g a Mod Comp& c o m p u t e r . S i n c e t h e response of a flame i o n i z a t i o n d e t e c t o r i s p r o p o r t i o n a l t o t h e number o f c a r b o n a t o m s p r e s e n t , i t i s a s s u m e d s i m u l a t e d d i s t i l l a t i o n d a t a o b t a i n e d u s i n g t h i s t y p e of d e t e c t o r c l o s e l y a p p r o x i m a t e s w e i g h t p e r c e n t d a t a . A d d i t i o p a l d e v i a t i o n s may o c c u r w i t h t h e p r e s e n c e o f h e t e r o a t o m compounds, h o w e v e r , i t i s f e l t t h a t t h e r e s u l t i n g d a t a w i l l b e c l o s e r t o w e i g h t p e r c e n t d a t a t h a n a n y o t h e r method o f r e p o r t i n g . With t h i s i n mind, a l l TBP d a t a were e x p r e s s e d i n w e i g h t p e r c e n t . Meas u r e m e n t s from t h e d i r e c t TBP d i s t i l l a t i o n were t a k e n i n w e i g h t p e r c e n t , a n d t h e volume p e r c e n t s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n d a t a was c o n v e r t e d t o w e i g h t p e r c e n t d a t a u s i n g a l e a s t s q u a r e d r e g r e s s i o n dev e l o p e d by Hydroc r b o n R e s e a r c h , I n c . w h i c h r e l a t e s d e n s ' t y t o b o i l i n g p o i n t s f o r H-Coal6 l i q u i d s d e r i v e d f r o m I l l i n o i s # 6 c o a l $ .

RESULTS AND DISCUSSION

In o r d e r t o make a c o m p a r i s o n of s i m u l a t e d d i s t i l l a t i o n d a t a t o t r u e b o i l i n g p o i n t d i s t i l l a t i o n d a t a , a d e f i n i t i o n of TBP d a t a i s i n o r d e r . The i d e o l o g i c a l c o n c e p t of a TBP c u r v e r e s u l t s from a p l o t d e r i v e d from a c o m p l e t e c o m p o s i t i o n a l a n a l y s i s o f t h e s a m p l e a n d t h e p u r e component b o i l i n g p o i n t s o f t h e i n d i v i d u a l c o m p o n e n t s . F o r a s i m p l e m i x t u r e , t h i s p l o t would b e a s e r i e s o f p l a t e a u s , r e s u l t i n g i n a p l o t t h a t i n c r e a s e s i n a s t e p - l i k e manner a s t h e t e m p e r a t u r e i n As t h e number o f c o m p o n e n t s i n t h e m i x t u r e i n c r e a s e s , t h e creases. s t e p - l i k e n a t u r e o f t h e p l o t d e c r e a s e s , u n t i l w i t h a n i n f i n i t e number 115

o f c o m p o n e n t s , t h e p l o t becomes a smooth c u r v e . F o r v e r y complex mixt u r e s , t h e complete compositional a n a l y s i s r e q u i r e d f o r p l o t t i n g t h i s t y p e o f TBP c u r v e i s p r a c t i c a l l y i m p o s s i b l e f o r r o u t i n e s a m p l e s . The a l t e r n a t i v e t o t h i s t y p e o f TBP c u r v e i s o n e d e t e r m i n e d e m p i r i c a l l y by p l o t t i n g t h e o v e r h e a d t e m p e r a t u r e v e r s u s w e i g h t o r volume p e r c e n t of m a t e r i a l c o n d e n s e d i n a b a t c h d i s t i l l a t i o n i n w h i c h t h e number o f t h e o r e t i c a l p l a t e s and r e f l u x r a t i o i s set such t h a t an i n c r e a s e of e i t h e r w i l l p r o d u c e no s i g n i f i c a n t d e v i a t i o n s o f t h e d a t a . T h i s emp i r i c a l l y d e t e r m i n e d TBP c u r v e may d e v i a t e s u b s t a n t i a l l y f r o m t h e i d e o l o g i c a l t y p e o f TBP c u r v e d u e t o t h e f o r m a t i o n o f minimum o r maximum a z e o t r o p e s . I n a d d i t i o n t o azeotrope formation, t h e s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n t e c h n i q u e s u f f e r s from i n a d e q u a t e separation. S i n c e i t i s p r a c t i c a l l y i m p o s s i b l e t o compare s i m u l a t e d d i s t i l l a t i o n d a t a t o i d e a l TBP d a t a , d u e t o t h e e x t r e m e l y complex m i x t u r e s f o u n d i n t h e s e l i q u i d s , t h e o n l y a l t e r n a t i v e i s t o compare s i m u l a t e d d i s t i l l a t i o n d a t a w i t h t h e e m p i r i c a l l y d e t e r m i n e d TBP d i s t i l l a t i o n c u r v e . F i g u r e 1 c o m p a r e s t h e d i s t i l l a t i o n c u r v e s o b t a i n e d by d i r e c t w e i g h t p e r c e n t TBP d i s t i l l a t i o n a n d s i m u l a t e d d i s t i l l a t i o n f o r a f u l l r a n g e H-CoalR s y n c r u d e . Due t o l i m i t a t i o n s i n h e r e n t i n t h e s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n a r i s i n g f r o m t h e minimum o r maximum overhead t e m p e r a t u r e a l l o w e d , comparisons o f t h e b o i l i n g p o i n t d i s t r i b u t i o n o f f r a c t i o n s e r e made. F i g u r e s 2 3, a n d 4 compare b i l i n g p o i n t c u r v e s f o r H-CoaZ6 n a p h t h a (IBP t o 400*F & a c t i o n ) , H-Coal8 midd l e d i s t i l l a t e (400-650°F f r a c t i o n ) , a n d H-Coal h e a v y d i s t i l l a t e (6500F plus fraction). I n o r d e r t o compare s i m u l a t e d d i s t i l l a t i o n d a t a w i t h d e i g h t p e r c e n t TBP d a t a , t h e minimum, maximum a n d a v e r a g e d e v i a t i o n s l e t w e e n t h e two t y p e s o f a n a l y s e s a n d r e p l i c a t e a n a l y s e s v i a t h e same n e t h o d were computed ( s e e T a b l e I ) . S i n c e a l l d i s t i l l a t i o n s , w i t h t h e ? x c e p t i o n o f t h e d i r e c t TBP d i s t i l l a t i o n w e r e p e r f o r m e d i n d u p l i c a t e or t r i p l i c a t e , t h e d e v i a t i o n s b e t w e e n t h e t y p e s o f a n a l y s e s w e r e b a s e d upon a v e r a g e v a l u e s f o r e a c h b o i l i n g p o i n t . One n o t e s t h a t i n a l l c a s e s , t h e d e v i a t i o n v a l u e s c a l c u l a t e d for r e p l i c a t e s i m u l a t e d d i s t i l l a t i o n d a t a a r e l o w e r t h a n t h e d e v i a t i o n v a l u e s c a l c u l a t e d f o r r e p l i c a t e TBP data. It i s a l s o n o t e d t h a t t h e maximum a n d a v e r a g e d e v i a t i o n s b e t w e e n t h e a v e r a g e s i m u l a t e d d i s t i l l a t i o n d a t a a n d t h e a v e r a g e TBP d a t a i s s m a l l e r t h a n t h e d e v i a t i o n f o r r e p l i c a t e TBP a n a l y s e s i n a l l c a s e s e x c e p t for t h e n a p h t h a f r a c t i o n . It i s f e l t t h a t t h e l a r g e r d e v i a t i o n o f t h e n a p h t h a f r a c t i o n b o i l i n g p o i n t c u r v e s i s due t o t h e i n a d e q u a t e separation inherent i n single theoretical plate d i s t i l l a t i o n s . It i s a l s o o b s e r v e d t h a t f o r t h e d i r e c t TBP d i s t i l l a t o n , t h e g r e a t e r d e v i a t i o n s o c c u r r e d when vacuum was a p p l i e d t o t h e s y s t e m . T h i s o b s e r v a t i o n i s c o n s i s t e n t w i t h t h e f a c t t h a t a small change i n a reduced p r e s s u r e b o i l i n g p o i n t w i l l m a g n i f y when c o n v e r t e d t o an a t o m o s p h e r i c pressure boiling point. A s a r e s u l t , from t h e e x a m i n a t i o n o f t h e d i s t i l l a t i o n d a t a i t becomes a p p a r e n t t h a t s i m u l a t e d d i s t i l l a t i o n d a t a compares f a v o r a b l y w i t h w e i g h t p e r c e n t d i s t i l l a t i o n d a t a , w h e t h e r d e r i v e d from d i r e c t TBP d i s t i l l a t i o n or s i n g l e t h e o r e t i c a l p l a t e d i s t i l l a t i o n d a t a a n d c o n v e r t e d t o TBP d a t a .

116

ACKNOWLEDGEMENT \

The a u t h o r s w i s h t o a c k n o w l e d g e t h e s u p p o r t g i v e n by A s h l a n d Pet r o l e u m Company, a n d A s h l a n d S y n t h e t i c F u e l s , I n c . d i v i s i o n s o f A s h l a n d O i l , Inc. i n p r e p a r a t i o n o f t h i s paper. The H-Coal' P r o c e s s w a s d e v e l o p e d by H y d r o c a r b o n Resear h , I n c o r The H-Coa16 P i l o t porated, a d i v i s i o n of Dynaelectron Corporation. P l a n t i s a j o i n t industry/government c o a l l i q u e f a c t i o n p r o j e c t funded b y t h e U n i t e d S t a t e s D e p a r t m e n t o f E n e r g y u n d e r C o n t r a c t No. DE-AC0576ET10143. P a r t i c i p a n t s a n d c o n t i b u t o r s s h a r i n g p r o j e c t c o s t s a n d m a n a g e r i a l g u i d a n c e t o t h e H-Coal6 P i l o t P l a n t a r e : A s h l a n d S y n t h e t i c F u e l s , I n c . , Commonwealth o f K e n t u c k y , Conoco C o a l Development Company, E l e c t r i c Power R e s e a r c h I n s t i t u t e , M o b i l O i l Company, S t a n d a r d O i l Comp a n y ( I n d i a n a ) , a n d R u h r k o h l e O i l a n d Gas GMBH. REFERENCES Annual Book ASTM St a n d a r d s , Part 2 3 , American S o c i e t y f o r T e s t i n g 1. ~ - of and M a t e r i a l s ,

\

P h i l a d e l p h i a , P A , 1 9 7 8 , D-86

2.

i b i d , P a r t 2 3 , D-1160

3.

i b i d , P a r t 2 4 , D-2887

4.

American P e t r o l e u m I n s t i t u t e T e c h n i c a l Data Book - P e t r o l e u m Ref i n i n g , American P e t r o l e u m I n s t i t u t e , W a s h i n g t o n , D C , 1 9 7 7 , 3 A l . l

-

2.

i b i d , 5A1.8

1.

i b i d , 3Al.2

7.

i b i d , 5A1.13

8.

Data Book, F i r s t I s s u e , P r e p a r e d for US E n e r g y R e s e a r c h a n d H-Coal' Development A d m i n i s t r a t i o n , ( R e v i s e d C o n t r a c t No. EF-01-75-1544 Hydrocarbon R e s e a r c h , I n c . a n d H R I E n g i n e e r i n g , I n c . , 1976.

117

.

1

J,

...

do

io

c

.1.1.1. 04.1141.11..

40 80 w e l p h t Percent 0werhe.d

100

to the simulated d s t i l l a t i o n Naphtha. c u r v e o f an H-Coal'

.'. .

...

.I..I.,..

.I..,.*.. 01.,11,.11..

01.1111.11..

io

eo

60

..-.

. . . . .

.*I.

io

tbo

F I G U R E 2 - C o m p a r i s o n o f the TBP d i s t i l l a t i o n c u r v e (wt.%)

to t h e simulated d i s t i l l a t i o curve o f a full r a n g e H-Coal' Svncrude.

Wmlphl P e r c e n t O v e r h e a d

.

c * 9

20 4'0 (10 8b Weight P e r c e n t O v e r h e e d

F I G U R E 1 - C o m p a r i s o n of the TBP d i s t i l l a t i o n c u r v e (wt.%)

...

.9

. . . .-

0

:

tbo

F I G U R E 3- Comparison o f the TBP d i s t i l l a t i o n c u r v e (wt.%)

SO

4'0 (1.0 00 W e l p h l Percent O v e r h e a d

150

-

FIGURE 4 C o m p a r i s o n o f the TBP d i s t i l l a t i o n c u r v e (wt.X)

t o t h e simulated d s t i l l a t i o n Middle curve o f a n H-Coal' Distillate

to the simulated d s t i l l a t i o n c u r v e of an H-Coal' Heavy Distillate

118

V 0

0

0

. . . o.m .= T. . . .

LnoLn ddLn

+Id + I

+I

Lnorl

+1+1+1

0

c,

...

000

O O N

V

c

rlP-=T

N +=I

c

d

+1+1+1

+ I+

a

CL

0 v, H

LT

,

a a E

d

E

a O

w* 3J w a w z m a

E+

Z W

a

Ha

E+

a

Q

c, 0 aJ

[I)

V 0

V 0 otnm

V

V 0

. . . o. r .l o. . . .

mt-m ow4 +l+I+l

+1+1+1

O L ~ N

000

+l+I+l

0

... o m 4 0 mu3

+I+ I+I

o m

V

E V

aH J >a

I

l

l

'

'

I

0 V

u 0

. . . o. m. 3.

omm oao +1+1+1

OOLn

+1+1+1

0

C k

m

a 0

V

X

119

V 0 oor-

...

rlmz

+ H + I +I

a

c,

4

z w w[I)

c, rl rl

a

H

d

rl d

a m

E

z

c,

H

H

0

d

0

ln

J

c

C

d

w a

3

0

a

0

c,

d c, rl

2

t

d

3

0

1

u

I+I

a '3 a

C

m a

u

V 0

d

P

u

ln d

P

rl rl

d

u UY

d .

PO.

m

Om

W

a . rlc, m a 4 s m DE

a o

Hc,

EO,

$a 5o

h D

DO.

a

ao

h a J

E a 10

ac, c h M

a''

0,

ale

aaJ 5

d

d d

dc,

L

Ear L 3

c E

chn

a J a J c, c,o

aJ

aJc,

e o

;;

W c , P)

L