Peng Robinson BIPs Estimation Method In Hysys

[Said92441322]

Dear All,
Whenever I am selecting the Peng-Robinson fluid package in Hysys, I find estimated values of Binary Interaction Parameters (BIPs) that are used for the calculation. Anyone have an idea by what method those BIPs are estimated ? is it Group Contribution method? or another method? or they are determined experimentally?

 

[chengg29]

Yes they are obtained experimentally for the said compounds, pure components and mixtures with these experiments conducted in a certain range of temperatures and pressures. Thermodynamic packages like UNIFAC use the Group Contribution Method and in this method the functional groups present on the molecules that make up the liquid mixture is used to calculate activity coefficients. The interactions for each of the functional groups present on the molecules, as well as some binary interaction coefficients, form the basis for the estimation of the the activity of each of the solutions / mixtures. Hence The UNIFAC correlation attempts to address the problem of predicting interactions between molecules by describing molecular interactions based upon the functional groups attached to the molecule. This helps in reducing the enormous number of binary interactions that would be needed to be measured to predict the state of the system by using any one of the appropriate thermodynamic packages.

A more detailed discussion should be there in your HYSYS software documentation that would have been provided along with your copy of HYSYS. Of course a good thermodynamics textbook should also answer your query above viz. Chemical Engineering Thermodynamics, Van Ness & Smith

 

[MortenA]

I would recommend that you use the option set all BIP to 0 My experience is that this gets the least problems with finding the critical point and (especially) the boiling point side of the envelope