Vapor-Liquid Equilibrium

ACTIVITY++ provides a comprehensive set of activity coefficient models which can be used to model most processes found in the chemical industry:

Ideal Solution	Ideal solution liquid phase
Margules	Margules 3 suffix activity coefficients
Margules4	Margules 4 suffix activity coefficients
Monsanto van Laar	van Laar activity coefficients as defined by Null
Wilson	Wilson activity coefficients
Tsuboka-Katayama-Wilson	Wilson activity coefficients as modified by Tsuboka and Katayma for 3 phase systems
Refinery Soave-Redlich-Kwong	Implementation of Soave-Redlich-Kwong as specified by the American Petroleum Institute
Non-Random-Two-Liquids	NRTL activity coefficient equation
Universal Quasi-Chemical Activity Coefficients	UNIQUAC activity coefficient equation
UNIQUAC Functional Group Activity Coefficients	UNIFAC activity coefficients
Chao-Seader	Chao-Seader liquid fugacity model
Grayson-Streed	Grayson-Streed liquid fugacity model

The model parameters are a function of temperature for added flexibility when simultaneously modeling VLE and LLE.



To account for vapor phase non-idealities several different equations of state are available:

• Ideal Gas
• Redlich-Kwong
• Soave-Redlich-Kwong
• Peng-Robinson
• Virial

Important non-condensable industrial gases such as Nitrogen, Oxygen, Hydrogen and Carbon Dioxide are included and automatically handled using Henry's law modified for handling of multi-component mixtures.