When components are in a database it is easy to make calculations by using the properties from the database, but often it is necessary to use UNIFAC and other prediction methods to estimate properties. But what if the UNIFAC does not predict for a structure because of missing groups? How to deal with groups which are not in the UNIFAC table in Aspen Plus? This is the case with some of my compounds: furfuryl alcohol, methylfuran, etc.
Yeah.. actually I need a method for calculating liquid phase activity
@Yadollah Tavan sir, does NIST data base provide VLE data of all mixtures at specific pressures?
best way to estimate binary coefficients is by searching references. the last priority goes to UNIFAC model. there is a good article about estimating and challenges of predicting binary coefficients. it will clear the way for you. especially check table 4 & 5 for most reliable references.
ASPEN PLUS allows you to input a small amount of experimental data from which it can estimate the missing parameter. Also ASPEN allows you to read the equations that are used and discover how to do the estimation. The molecular structure can be entered into the properties section where ASPEN will attempt to match UNIFAC groups with data base properties. A warning is issued when it fails to match a group. You have the option to choose a substitute match for the missing group from the tables of groups, or change to a different estimation method, of which there are many to find a method that can match the groups.
Maybe you have seen the link
https://hal-mines-paristech.archives-ouvertes.fr/hal-01371510/document.
Hi, you can use the parameters fiited in this paper:
New modified UNIFAC parameters using critically evaluated phase equilibrium data.
Jeong Won Kang, Vladimir Diky, Michael Frenkel
i have the same problems, my compounds are: biphenyl, dibenzofuran, indole, naphtalene, ...
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