Aspen Physical Property System - Physical Property Models

Ionic components
2 Thermodynamic Property Models 169
(114)
(115)
The contribution from ionic components can be written as follows:
(116)
(117)
(118)
(119)
(120)
(121)
where Hi ref and Gi ref are the enthalpy and Gibbs free energy of ionic
component i at the system conditions with a specified reference state
(symmetric or unsymmetric).
The property calculations for solvents and Henry components are the same
when the reference state is changed. Only for ionic components do the
property methods need to be specified with a reference state. The methods
with the unsymmetric reference state are available already in Aspen Plus and
Aspen Properties. New methods are needed only for the symmetric reference
state. Overall, the calculated total enthalpy or Gibbs free energy for the same
electrolyte solution should be the same, regardless of the reference state
specified.
Enthalpy and Gibbs free energy of ionic components with the symmetric
reference state can be written as follows:
(122)
(123)
where and are enthalpy and Gibbs free energy of ionic component
i with the unsymmetric reference state, respectively, and available already in