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[lindaar]

Hello,

in the progress of designing a hydrogenation process I am modeling a few things using Aspen Plus.

At the moment a flash is giving me headaches. Its basically a vapour-liquid flash of tert-butanol, Hydrogen and some Ammonia. I am working at pressures of 150bar, 150°C and struggeling with chosing a property method.
I already did some reading in guides on chosing property mehtods, but still am not sure which ones to use. When using EOS's, lots of tert-BuOH goes out with the vapour phase.
With activity coefficient prop. methods, the system behaves as I would expect - most of H2 as vapour, most of tert-BuOH as liquid - but it's recommended NOT to use activity coefficient methods at high pressures - so I am kind of confused.

- maybe i just got a wrong understanding of the system, and there is some good physical explanation why this much of tert-BuOH leaves my flash as a vapour...


I would appreciate any advice!

thanks so much

[MrShorty]

Ultimately when selecting a thermo model, you want the one that best mimics reality. I would suggest at this point that you find some VLE data in the literature for H2 systems and see which of your models seems best. I know there are data out there for H2 + hydrocarbon systems; I'm not sure how extensive the data for H2 + alcohol systems are.