By default, SuperPro Designer uses Raoult’s law as the default option for calculating the physical state of material with the rigorous toolbox. Such calculations require pure component data only. Specifically, they require the estimation of a pure component’s vapor pressure at a given temperature based on Antoine’s coefficients. In situations where components and conditions are such that Raoult’s law no longer produces satisfactory results, users have the option to employ more sophisticated VLE models, see (Vapor-Liquid Equilibrium Modeling). These VLE models attempt to capture the non-ideal behavior of the vapor and liquid phase with increased accuracy by employing binary interaction coefficients. These coefficients participate in the following equations of state (see Equations Of State (EOS) for details):
● Virial
● Peng Robinson
● Soave-Redlich-Kwong
and the following activity coefficients models (see Activity Coefficient Models):
● Wilson
● NRTL (gij, gji)
● NRTL (aij)
The ‘Designer’ databank includes binary interaction coefficients for over 60 binary mixtures and users can add their own data in the ‘SuperPro (User)’ portion of the databank. For more information on binary coefficient databanks, see Binary Coefficients Databank.
When engaging non-ideal models to predict the vapor-liquid split of several components, it is critical to make sure that the model chosen produces sufficiently accurate values for each binary component combination on its own. If the binary behavior is not captured accurately, then there’s little hope that the predictions for the entire mixture will be accurate. SuperPro Designer allows you to view binary x-y diagrams generated based on your choice of model (see Vapor-Liquid Equilibrium Modeling) and the values of bij (binary coefficients) provided through The Rigorous PS Calculation Toolbox Dialog.
For information on the interface used to choose VLE options such as fugacity models, and specify the binary coefficients for each method, see The Rigorous PS Calculation Toolbox Dialog.