PHYSICAL PROPERTIES OF HYDROCARBON...

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PHYSICAL PROPERTIES OF HYDROCARBON FLUIDS Physical Constants for Pure Components Pitzer: w = - log Pr – 1 where Pr = P*/Pc; P*: vapor pressure at T = 0.7 Tc

Transcript of PHYSICAL PROPERTIES OF HYDROCARBON...

PHYSICAL PROPERTIES OF HYDROCARBON FLUIDS

Physical Constants for Pure Components

Pitzer: ω = - log Pr – 1

where Pr = P*/Pc; P*: vapor pressure at T = 0.7 Tc

Mixture Combination Rules:

Kay’s Rule: ∑ ∑== cii'ccii

'c TyTandPyP

Examples, NG at 2021 psia and 595 oR:

Comp yi Pc Pc’ Tc Tc’ MW MW’

N2 0.0046 492 2.26 227 1.04 28 0.13

CO2 0.0030 1073 3.44 548 1.64 44 0.13

H2S 0.1438 1306 188 673 97.0 34 4.89

C1 0.8414 673 568 343 288 16 13.5

C2 0.0059 708 4.17 550 3.24 30 0.18

C3 0.0008 617 0.49 666 0.53 44 0.04

i-C4 0.0003 529 0.16 735 0.22 58 0.02

n-C5 0.0002 490 negl 846 negl 72 negl

Σ 1.0000 767 psi 392 oR 18.89

P/Pc’ = Pr’ = 2021/767 = 2.64, T/Tc’ = Tr’= 595/392 =1.52

Use Fig. 5.1: Z = 0.80

Correction for CO 2 and H2S:

Metric: 35560 ε.TT 'c

"c −= ( ) 55601 3 .BBT

TPP

'c

"c

'c"

c ε−+=

English: 3ε−= 'c

"c TT ( ) 31 εBBT

TPP

'c

"c

'c"

c −+=

B is mole fraction H2S in the gas

Tc” = 392 – 21 = 371 oR

Pc” = (767)(371)/[218+(0.1438)(0.8562)(21)] = 720 psia

Pr” = 2.8 and Tr” = 1.6 à Z = 0.83

EMR Approach (please read ref.: Campbell)

LIQUID PHYSICAL PROPERTIES

Physical properties of liquid mixture are rather complex.

Especially oil mixture, which has many components involve.

Watson Characterization Factor

( )ρω .lRe

TAK

/B

31

=

A = 1.22 in Metric Unit; A = 1.0 in English Unit

TB = average molal boiling point, K or oR

Rel. ρ = relative density (specific gravity)

For exp, paraffin base crudes, the values range 11.9 – 12.2

How to measure TB ? à ASTM distillation, results

what is called a true boiling point (TBP) curve.

What is relative density (specific gravity) ?

ρ (g/cm3) = (Rel. ρ) (1.0); ρ (lb/ft3) = (Rel. ρ) (62.4)

Density of water at 15 oC (60oF) = 1.00095 g/cm3

API Gravity

API..

cm/g.lReo+

==5131

51413ρ

API Barrel

The word “barell” means “API barell” = 42 US gallons

= 5.615 ft3 = 159 liters

Rel. ρ vs Molecular weight

NOMOGRAPHS

Kw = 11.0-12.0

11

22 ρρ

CC

=

Effect of Methane and Ethane

Density of LNG (Liquefied Natural Gas)

∑∑

−=

Cxvx

Mx

mii

iiρ

Mι = mol.wt. of component i

xι = mol fraction of component i

vι= molar volume of i

xm = mol fraction of methane

C = correction factor for volume reduction

Assignment

Use NIST software to calculate Z for Natural Gas as examples’ conditions

(pseudocritical method & EMR method). Compare with these two methods

and PR-EOS method.

Use NIST software, and PR-EOS method to calculate density of LNG as an

example above. Discuss the results !