Phase envelope and Vapor-Liquid Equilibrium Analysis
View: Process Flow Diagram
View: Simulation Results
This example shows the calculation of the phase envelope of a hydrocarbon stream in order to identify single and two phases regions.
The hydrocarbon stream is characterized with 11 components from C1 to C6 and an heavier fraction.
This heavy fraction is characterized as an hypothetical petroleum component with the following properties:
Normal boiling point 188.40 °C.
Api gravity 45.454
Molecular weight 149.7
The composition of the stream FEED, defined at -30°C and at a pressure of 133.3 bar, is summarized in the next table
|
No |
Component |
Molar flow rate, kmol/h |
|
1 |
NITROGEN |
16.24 |
|
2 |
CARBON DIOXIDE |
61.82 |
|
3 |
METHANE |
5575.0391 |
|
4 |
ETHANE |
307.3599 |
|
5 |
PROPANE |
89.01 |
|
6 |
ISOBUTANE |
18.66 |
|
7 |
BUTANE |
18.91 |
|
8 |
ISOPENTANE |
6.01 |
|
9 |
PENTANE |
5.36 |
|
10 |
HEXANE |
10.13 |
|
11 |
HEAVY |
9.54 |
At the conditions defined (-30°C and 133.3 bar) the stream is all vapor
In this case the Process Flow Diagram of this simulation is extremely simple. The same stream is used as feed stream of flash V1 and phase envelope PHAS01.
For the given stream the phase envelope (Bubble-point and dew-point lines) are calculated. In curves at constant molar vapor-fractions for values of 0.1, 0.2, 0.5, 0.7 and 0.9 are also calculated. All these curves may be viewed in a single graph.
A comparison of the phase envelope generated with the Peng-Robinson equation of state is shown on this figure. (SRK-PR phase envelope comparison).
As may be seen on the global printout, the phase envelope is generated with the dedicated unit operation and using the ‘VLE ANALYSIS’ feature through the definition of specific dew-point and bubble point curves.
<XPSIM> ...generated by XpsimWin v.1.06 ...
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RUN ID=PHASEN04 CUSTOMER=SP-GAS PROJECT=VLE-TEST
DESC EQUILIBRIUM CALCULATION TEST - SSI/2
DIMENSION MET
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Petroleum Data
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HYPO ID=H501 NAME=HEAVY NBP=188.40 API=45.454 MW=149.7 TCRIT=374.771 +
PCRIT=25.310 OMEGA=0.471
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System Data
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CHEMCOMP N2 / CO2 / C1 / C2 / C3 / IC4 / NC4 / IC5 / NC5 / NC6 / H501
THERMSET UID=M1
METHODS K=SRK H=LK
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Flowsheet Data
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STREAM=FEED TEMP=-30 PRES=133.3
COMP 16.24 / 61.82 / 5575.0391 / 307.3599 / 89.01 / 18.66 / 18.91 / +
6.01 / 5.36 / 10.13 / 9.54
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FLASH IN FEED OUT PROD1(V) PROD2(L) UID=V1
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PHASENV IN FEED UID=PHAS01
CALC PMIN=20 PMAX=200 TEST(DEWT)=100 VF=0.1,0.2,0.5,0.7,0.9 DPMAX=5.
PRINT PLOT
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VLE Analysis
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VLECURVE STR=FEED PROP XPRT KPRT PLOT
CALC BUBT TEMP=-60. PRES=20.,80. POINTS=8
CALC DEWP TEMP=-60.,20. PRES=70. POINTS=9
CALC DEWT TEMP=70. PRES=10.,150. POINTS=15
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END
