Phase Equilibria from Equations of State - ACS Symposium Series

10 Phase Equilibria from Equations of State T. E. DAUBERT

Downloaded by UNIV OF AUCKLAND on May 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0060.ch010

Pennsylvania State University, University Park, PA 16802

As I am last to make opening remarks I have decided to take a slightly different approach to the problem. The previous six speakers have alluded to the meaning and application of various equations--their advantages, disadvantages and accuracy. As co-director of the API Technical Data Book project my major interest is in ascertaining what equation is the most generally interpolatable and extrapolatable with reasonable accuracy over a wide range rather than what is the most accurate equation within a limited range of applicability. My major premise is: No equation of state is necessarily better than the data used to validate it. In order to be generally valid any equation must be tested over a wide range of molecular type and weight of components, a wide range of compositions, and the entire temperature and pressure span. We've evaluated many of the equations available and conclude that a decision as to the universally "best" possible equation cannot be made with current data. In addition, I personally would suggest that until more data are available further refinements of existing base equations may be empty exercises. Thus, what I would like to do is show some examples of the data that are available and then point out where the largest gaps exist and what must be done aboutit.My discussion will be limited to hydrocarbon systems and systems of hydrocarbons and the industrially important gases--H, N2, HS, CO, and CO. It will become apparent that the easy data already have been taken and the difficult data are yet to be determined. 2

2

2

Discussion Table 1 shows the data which have been gathered for our work from a comprehensive survey of the literature. All binary data were rigorously tested for thermodynamic consistency using the method of Van Ness and co-workers (jL, 2) using the general coexistence equation reduced to constant temperature or constant pressure according to the data source. It is readily apparent that less than 224

In Phase Equilibria and Fluid Properties in the Chemical Industry; Storvick, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Phase Equilibria and Fluid Properties in the Chemical Industry; Storvick, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. Nonhydrocarbon

Nonhydrocarbon Hydrogen Nitrogen Hydrogen + Hydrogen

Nonhydrocarbon Hydrogen Hydrogen S u l f i d e Carbon Dioxide Carbon Monoxide Nitrogen

Quaternary Hydrocarbon Hydrocarbon - Water Petroleum F r a c t i o n s

Ternary Hydrocarbon -

Binary Hydrocarbon -

Binary Hydrocarbon Ternary Hydrocarbon Quaternary Hydrocarbon F i v e and S i x Component Hydrocarbon

Type System

Sulfide

Types and Amounts of VLE Data A v a i l a b l e

Table 1

209 97 54

750 350 700 240 450

2836 670 134 60

430 240 323 156 184

1850

P o i n t s of Data Available "Consistent"



226

P H A S E EQUILIBRIA A N D F L U I D PROPERTIES I N C H E M I C A L

INDUSTRY

t w o - t h i r d s of the b i n a r y data were c o n s i s t e n t . Thus, only the c o n s i s t e n t p o i n t s were used f o r data e v a l u a t i o n . The method was extended t o t e r n a r y systems. However, s i n c e necessary parameters f o r t e s t i n g o f t e n were not a v a i l a b l e f o r many data s e t s , a l l a v a i l a b l e data which were not o b v i o u s l y i n e r r o r were used f o r testing. From t h i s t a b l e i t i s apparent that data on t e r n a r y hydrocarbon-non-hydrcarbon systems are i n short supply as are data on a l l four and h i g h e r component systems. However, the former need i s the most c r i t i c a l f o r t e s t i n g purposes as e s t i m a t i n g equations which are a c c u r a t e f o r t e r n a r i e s , i n g e n e r a l , are accurate f o r higher multicomponent systems. The t a b l e a l s o shows no e n t r i e s f o r hydrocarbon-water o r petroleum f r a c t i o n systems. Such systems w i l l be d i s c u s s e d l a t e r . Table 2 breaks down the c o n s i s t e n t b i n a r y hydrocarbon data by Table 2 C o n s i s t e n t B i n a r y Hydrocarbon VLE Data

System Types A

Number o f Points

Carbon Number Range

B

B

A

r s

Paraffin - Paraffin

727

c

Paraffin - Olefin

160

c -c

Olefin - Olefin

c

2

?

C

2~ 10

C

C

2- 6

C

A 6" 7

C

29

C

P a r a f f i n - Naphthene

133

c

r 8

C

P a r a f f i n - Aromatic

450

c

r s

VS

O l e f i n - Aromatic

128

V 8

V 8

Naphthene - Aromatic

160

V 8

C

6" 8

C

C

7

C

7- 10

Naphthene - Naphthene

3

Aromatic - Aromatic

60

Total

1850

3 c

c

C

C

6

V 9 C

C

C

C

C

molecular type systems and carbon number range. Of systems of r e a l i n t e r e s t , date i s very sparse f o r naphthene-naphthene and aromaticaromatic systems. Data are n o n e x i s t e n t above C^Q f o r any of the system types.


10.

Phase Equilibria

DAUBERT

227

from Equations of State

Table 3 shows the d i s t r i b u t i o n of pressure ranges of the data Table 3 Pressure Range of B i n a r y Hydrocarbon Pressure Range (psia) P < 14.7 Downloaded by UNIV OF AUCKLAND on May 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0060.ch010

14.7

24

Olefin (C ) 3

Naphthene (C >

8

Aromatic (C^)

9

3

323 Carbon Monoxide

Paraffins

V

105 51

Aromatic (C^)

156 Nitrogen

P a r a f f i n s (CAromatic (C^)

C

10>

168 16 184


10.

Phase Equilibria

DAUBERT

229

from Equations of State

Table 5 3, 4, 5, and 6 Component Systems

Type System

No. of Systems

No. of Data Points

12 1 2

435 13 67

Hydrocarbon Ternary Hydrocarbon Paraffin (Ci - C ) P a r a f f i n - O l e f i n (Ci - C3 P a r a f f i n - Naphthene - O l e f i n (C5 - C7) M i s c e l l a n e o u s Systems w i t h P a r a f f i n s , O l e f i n s , Acetylenes


1 0

152 668

Quaternary Hydrocarbon P a r a f f i n ( C - Cy) P a r a f f i n - O l e f i n - D i o l e f i n - Acetylene ±

(c ) 3

P a r a f f i n - O l e f i n - D i o l e f i n - Acetylene (C ) 5

F i v e and S i x 5 Paraffin 6 Paraffin 6 Paraffin

4

15

1

53

1

Carbon Atom Hydrocarbon (C-^ - C^Q) (C^ - C ) - O l e f i n (C4)

66 134

28 17 15

1 0

60

Nonhydrocarbon Ternary Nonhydrocarbon Hydrogen - Methane - Ethane Hydrogen - Methane - Propane Hydrogen - Methane - Ethylene N i t r o g e n - Methane - Ethane N i t r o g e n - Methane - Hexane Hydrogen - Hydrogen S u l f i d e - C^ aromatic or p a r a f f i n o r naphthene Quaternary Nonhydrocarbon Hydrocarbon N i t r o g e n - Methane Ethane Hydrogen - Benzene - Cyclohexane - Hexane Hydrogen - Hydrogen S u l f i d e - Methane Isopropylcyclohexane

82 30 97 44 53 54

1 1

360

7 36

1 52


230

P H A S E EQUILIBRIA

2. 3.


4. 5. 6.

A N D F L U I D PROPERTIES

IN C H E M I C A L

INDUSTRY

Aromatic and naphthenic b i n a r y and t e r n a r y hydrocarbon systems. Nonhydrocarbon-naphthenic and aromatic b i n a r y and t e r n a r y systems, e s p e c i a l l y hydrogen-aromatic-naphthenic systems. Water-hydrocarbon b i n a r y and t e r n a r y systems of a l l types. Water-hydrocarbon-nonhydrocarbon t e r n a r y systems. Petroleum f r a c t i o n and petroleum fraction-nonhydrocarbon systems.

Progress i n o b t a i n i n g new data i s e s s e n t i a l i f the users of equations of s t a t e ever hope to adopt a r e l i a b l e , dependable, and accurate p r e d i c t o r .

References Cited 1. Van Ness, H. C., "Classical Thermodynamics of Non-Electrolyte Solutions," Pergamon Press, Oxford (1964). 2. Van Ness, H. C., Byer, S. M., Gibbs, R. E. AIChE Journal, (1973) 2, 238. Acknowled gment The R e f i n i n g Department of the American Petroleum I n s t i t u t e i s g r a t e f u l l y acknowledged f o r f i n a n c i a l support of t h i s work.


Phase Equilibria from Equations of State - ACS Symposium Series

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