Applications of an Association Activity Coefficient Model, NRTL-PA, to Alcohol-Containing Mixtures

A new activity coefficient method for associating systems,
NRTL
Plus Association (NRTL-PA), is developed and evaluated for alcohol
+ hydrocarbon systems. The method combines Wertheim’s perturbation
theory using the PC-SAFT form of the association strength with Flory’s
theory and a residual contribution represented with NRTL. The model
is capable of accurate representation of simultaneous VLE, LLE, and
excess enthalpy with the same set of parameters. The association contribution
is fixed using literature values during regression to provide focus
on the capabilities of combining Wertheim statistical mechanics with
a residual activity model. The model is shown to be superior to the
traditional NRTL model and represents accurately the increase in excess
enthalpy as temperature increases. The NRTL-PA model is publicly available
as an Aspen Plus user model.