editing Extended Antoine parameters within Chemsep

[Stephan]

I use Chemsep as an external property package within Coco.
Within Chemsep I have specified Prausnitz (K-value), Hayden O'Connel(EOS), NRTL(Activity Coefficient) and Excess Enthalpy to get reasonable enthalpy-values for methanol and water
between 1-20 bar.

However, the calculated pure component steam pressures (dependent on temperature) do not match to empirical data (p as a function of T).
Therefore I fit the Extended Antoine parameters to empirical data and want to adjust the Extended Antoine parameters within Chemsep.
However, I'm unable to do that. Whenever I change one of the parameters, it switchs back to the original value after pressing enter.

Can those Extended Antoine parameters be changed at all within Chemsep when using Prausnitz?

[jasper]

(Quoting Prof. Taylor)

This answer does not really address the question but is intended to provide some background on the model because it is an easy one to misuse.

The Prausnitz model is a bit of a tricky one since it does not fall into the truly conventional cannon of EOS or gamma-phi models but is a bit of hybrid of both. The model comes from this book
Computer Calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria Prausnitz, J. M.; Anderson, T. F.; Grens, E. A.; Eckert, C. A.; Hsieh, R.; O'Connell, J. P.)

published in the early 1980s. I do not know if it is still available, perhaps from used book dealers.

The Prausnitz model was designed to be used with UNIQUAC, the q-prime version and the Hayden O'Connell (or chemical theory equations of state otherwise the parameters are not consistent. Within the framework of the model the vapor pressure is really an extrapolated pure species fugacity (a vapor pressure for subcritical species and related to Henry's law for supercritical species). The parameters for this combination of models that come with ChemSep are from the book noted above. They should not be changed without considerable attention to detail.

That said, it should be possible to use other sub-models within the framework of the Prausnitz model - as this user has attempted. But in that case all the model parameters would need to be refit. Not just the vapor pressure but the activity coefficients as well. (I would leave the HOC parameters alone - I don't think we allow refitting of those anyway. That does not address the users question however.)

[hkooijman]

Please download and install a new ChemSep LITE. This weekend an update was made available that should help to fix the problem of not storing information.
-Harry

[Stephan]