I am using Aspen to estimate the physical properties for a certain components. So my question is, which good method that has a function group for NH3+?
You have to create the thermodynamic package for any electrolytic components using Aspen Properties, which has a larger library of thermodynamic models that includes the 'electrolytic NRTL' models and so forth. Aspen properties will take care of simulating the ions for you at different pH. You can then import this thermo package in Aspen Plus / Hysys along with the constituting components.
As I think, what you need to do is to understand how to use Aspen Properties very well. Aspen Properties can be used to handle that problem. Success...
Thank you both for the advice but I faced another problem. I am trying to regress experimental data using the ELEC-NRTL equation. The NRTL equation has 6 elements (A, B, C, D, F). SO when I include these 6 elements in the parameters for regression, I won’t get result and the reason being is that element 3 and 4 are always symmetric and the rest are un-symmetric. Do you have any clues?