Case studies - Pure component data
Introduction............................................................................................................................................... 1
Physical properties
of a pure component............................................................................................. 1
Defining the problem
interactively......................................................................................... 1
Producing a problem
setup file............................................................................................... 5
Obtaining properties
from Pure component Data option................................................... 5
Excel interface............................................................................................................................ 7
Although the primary purpose of Multiflash is to calculate the thermodynamic properties of mixtures there may be occasions when you simply want to know the properties of a pure component, particularly those from a particular data source. This is quite simple.
If you want the physical properties of a pure component, for example octane, over a range of temperatures you must either:
· Define the problem in Multiflash
· Load an existing problem setup file into Multiflash
· Edit an existing problem setup file and load it into Multiflash
· Write a new problem setup file and load it into Multiflash
If you want to know the stored values for the temperature independent properties or the correlation coefficients of a temperature dependent property you must choose Pure Component Data from the Tools option from the menu bar described earlier, see “Viewing and editing pure component data.” on page 92.
Defining the problem interactively
Having successfully loaded Multiflash, choose a suitable model for the problem. If you wish to obtain the properties from the data source correlations then you must use the ideal gas and ideal solution models. This is the Ideal Mixing model set. With this option all properties will be taken from the databank correlations except liquid Cp which is calculated from the vapour phase model and the enthalpy of vaporisation. (If any other model set is defined then only the pure component properties needed for that model set will be taken from the bank. Other properties will be calculated using the model set definitions which include models for the transport properties).
To specify the Ideal Mixing
model set:
Select Select from the menu, then
Select Model set, followed by
Selecting Ideal Mixing from the Activity Model selection. Choose the gas phase model as Perfect gas. The recommended and default model for transport properties is Mixing rules
You will see a message to say that the Ideal Mixing model set has been successfully defined.
Click on OK
For more information on models see “Models” on page 39.
Specify the pure component of interest in
this case octane
Click on the
Select Component button, 
or
Select Select then Select Component from the menu bar.
then specify the data source and component in the Select Components dialogue box
The data source is set by:
Clicking on the arrow to the right of the data source text box and
Clicking on the
data source of interest, in this case INFODATA, the
The component is specified by either:
Selecting the Name option button, typing the component name in the enter name box, then pressing the enter key or clicking on Add
Selecting the All components button, scrolling through the list of components which will appear in the dialogue box and either selecting octane, then clicking on Add or Double clicking on octane
or
Selecting the formula option button, typing C8H18 in the text box, clicking on Search, selecting octane in the “Components in databank” text box, then clicking on Add or double clicking on octane
Specifying the physical property
output level.
If you are interested in pure component data you will probably want to output all available physical property data except thermal property data relative to elements.
Select Select in the menu bar and then select Property output.
In the resulting dialogue box, the first two are the default options for output of thermodynamic data, click Heat capacity/Speed of Sound and the set of transport property data and finally click on OK.
Enter the composition for the stream.
In this case where we have a pure component the composition is not important provided it is a positive value.
In the main window, click on composition, then type 1.0 in the right-hand column of the table next to octane.
To obtain the properties of liquid octane on the saturation line you must carry out a bubble point flash calculation at a specified temperature.
Specify the temperature and the flash
calculation
Type the first temperature, say 250K, in the text box next to temperature in the input conditions section
Click on the
Bubble point at fixed temperature button
, or select Calculate from the menu bar, then select Bubble and Dew point flashes and finally select T, Bubble point flash.
The reported pressure is the saturated vapour pressure at 250K, the other properties are listed below the phase equilibrium output. As we are dealing with a pure component exactly the same results would be obtained if we had specified a dew point flash at the same temperature.
The next temperature should be entered in the text box in the Conditions section and the bubble point flash repeated at this temperature.
Producing a problem setup file
You can carry out the same calculation, or series of calculations using a problem setup file. We have provided an setup file for calculating the physical properties of pure octane over a temperature range from 250 to 500K at 50K intervals, OCTANEA.mfl. We hope that the commands used are self explanatory. (Simply edit this file if you wish to obtain pure component data for another compound or properties over a different range of temperatures). You can also overwrite the default choice of data source.
To write a problem setup file yourself, use the file shown as an example or save the problem you have specified interactively
Obtaining properties from Pure component Data option
Although the standard output from Multiflash does not contain any of the constant properties, or indeed the correlation coefficients for the temperature dependent properties, it is possible to obtain these.
Select the components you are interested in, for example octane, as described above. Select Tools from the menu bar, followed by selecting Pure Component data, the following dialogue box will then be activated.
As we are dealing with a single component this will be the only choice available so making sure it is highlighted. Select a property in the list of Select property, click on Edit to view or change the property. You can also print the properties in the results window by clicking Write to Output. This output can then can be saved or copied into other files.
show components
"OCTANE" data ;
1
OCTANE
MOLECULARWEIGHT 114.231
g/mol
TCRIT 569.32
K
PCRIT 2.49700E+06 Pa
VCRIT 2056.359 mol/m3
ACENTRICFACTOR .39690
TBOIL 398.82
K
HFORMATION -208446.9 J/mol
SSTANDARD 466.7252
J/mol/K
TMELT 216.37 K
HMELT 20740.
J/mol
SMELT J/mol/K
CPMELT 50.00791
J/mol/K
VMELT 50814.48 m3/mol
RUNIQUAC 5.8486
QUNIQUAC 4.9360
THLWATER K
VHLWATER m3/mol
DIPOLEMOMENT .00000
debye
PARACHOR 351.40
(dyn cm-1)1/4 cm3/mol
RADGYR 0.468040E-9 m
HOCASS .00000
GFORMATION 16000.
J/mol
TTRIPLE 216.38
K
PTRIPLE 2.1083
Pa
HCOMBUSTION -5.07415E+06 J/mol
V25 6120.925 mol/m3
SOLUPAR 15448. (J/m3)1/2
SOLIDSOLUPAR (J/m3)1/2
ZCRIT .2587676
REFRACTINDEX 1.39505
TFLASH 286.00
K
TAUTO 479.00
K
FLAMLOWER .80000
vol %
FLAMUPPER 6.5000 vol
%
SPGRAVITY .7066211
EXPANSIVITY 1/K
OMASCALE
OMBSCALE
CNUMBER
REFVISCOSITY Pas
LJEVISC
LJBVISC
EOSC
TYPE 1.
COMPREFNO
93.
MCRKS1
MCRKS2
MCRKS3
MCPR1
MCPR2
MCPR3
HYDOC
HYD1
HYD2
HYD3
ASSBETA
ASSEPSILON J/m
ASSGAMMA
ASSDELTA 1/K
ASSFF
ASSAC J
m3/(mol)2
ASSBC m3/mol
ASSKAPPA
SAFTKAPPA
SAFTEPSILON K
SAFTGAMMA
SAFTFF
SAFTEK 242.78
K
SAFTSIGMA 3.83730E-10 m
SAFTLAMBDA
SAFTM 3.8176
1/mol
VSHIFT1
VSHIFT2
VSPR1
VSPR2
CPIDEAL 1.0000 -32384.514 -3721.3925 4.0000
76.000 290.00 -1.3945 5.6330
-5.7709999 0.0000 0.0000 10000.
CPSOLID 5. -24. 1.94719999 -0.008536
1.34E-5 2.094E-8 20. 216.37
PSAT 3.0000 -7.9121099 1.38007
-3.8043499
-4.5013199 260.00 568.95001
HVAP 1.0000 54909.031 .37750 .00000
.00000 .00000 .00000 568.38098
LDENS 1.0000 2032.52 5407.5898 0.375
.00000 568.38098
LVISC 2.0000 -20.462999 1497.4 1.3789999
.00000 .00000 216.38 398.83
VVISC 1.0000 3.11910E-08 .92925 55.092
.00000 216.38 1000.0
LTHCOND 5.0000 .21560 -2.94830E-04 .00000
.00000 .00000 216.38 398.83
VTHCOND 1.0000 -8758.0 .84480 -2.71210E+10
.00000 339.00 1000.0
STENSION 1.0000 5.27890E-02 1.2323 .00000
.00000 .00000 216.38 568.70
CPLIQUID 5.0000 224.83 -.1866 9.5891E-04
.00000 .00000 216.38 460.00
SDENS 5.0000 8340.9 -3.1515 .00000
.00000 .00000 133.15 216.38
CPSOLID 5.0000 -24.000 1.9472
-8.53600E-03
1.34000E-05 2.09400E-08 20.000 216.37
VIRIALCOEFF 1.0000 2.73900E-04 -5.65219E-04 -3.63347E-04
-1.16166E-05 2.58796E-06 284.38 1500.0
CARNUMBER 000111-65-9
FORMULA C8H18
FAMILYCODE AA
UNIFAC CH3 2 CH2 6
The output includes the pure component constant properties and the coefficients for the temperature dependent property correlations. The definitions of the pure component correlations are given in the Models and Physical Properties manual and the Multiflash Programmers Guide.
Excel interface
The current version of Multiflash does not include options for tabular output or for producing graphical output for properties other than phase boundaries. If this is important to you then we would recommend our Excel interface. For example, the ideal.mfc file with the components set to octane was used in conjunction with this interface and Excel to produce the following output for octane.
Liquid properties on the saturation line
|
TEMP |
PRESSURE |
CP |
ENTHALPY |
DENSITY |
VISCOSITY |
THCOND |
SURTEN |
|
|
|
|
|
|
|
|
|
|
|
Pa |
J/mol/K |
J/mol |
mol/m3 |
Pas |
W/m/K |
N/m |
|
275 |
427.762 |
231.4236 |
-47031.7 |
6254.853 |
0.000694 |
0.134522 |
0.023412 |
|
300 |
2038.06 |
247.738 |
-41042.5 |
6116.615 |
0.000497 |
0.127151 |
0.020986 |
|
325 |
7232.427 |
264.3592 |
-34641.4 |
5970.103 |
0.000378 |
0.11978 |
0.018612 |
|
350 |
20571.97 |
281.3794 |
-27819.2 |
5813.892 |
0.000302 |
0.112409 |
0.016294 |
|
375 |
49413.7 |
298.9716 |
-20563.4 |
5646.112 |
0.000249 |
0.105039 |
0.014036 |
|
400 |
104100.9 |
317.4437 |
-12855.7 |
5464.231 |
0.000212 |
0.09767 |
0.011846 |
|
425 |
197831.5 |
337.3402 |
-4668.02 |
5264.678 |
0.000184 |
0.091347 |
0.009729 |