3 replies to this topic

[twell]

I am attempting to create a TPxy diagram for water-acethaldehyde at 400 K (PR package) but I get convergence errors in HYSYS 7.2, could you help to identify the reason ?

[MrShorty]

If I had to guess, I would guess that you are asking it to calculate the VLE at a point outside the 2 phase envelope or near a boundary of the phase envelope. I can't tell if that is the case or not based solely on the temperature.

[PaoloPemi]

at 400 K we are far from critical conditions but this is a binary difficult to model, if you generate a phase envelope with Peng Robinson and vdW mixing rules you'll get poor results, better to use complex mixing rules, models as CPA etc.
I am not familiar with the thermodynamics in your simulator, to give you some data I attach a TPXY for Water Acetaldehyde at 400 K generated with Prode Properties and Peng-Robinson-Uniquac with Wong Sandler mixing rules, you can download a copy from Prode.com and compare the results.
I hope this helps to understand the origin of the problems.

Attached Files

•  TPXY_400K.jpg   128.63KB   13 downloads

[Chellani]

Two quick questions - why are you using PR and what are you trying for PXY curve in which you are getting convergence error.
Use any activity coefficient PP e.g. NRTL and use Equilibrium Plots extension unit op. Somebody has already posted this extension in earlier forms, search for it or get it from official support team.