A new equation of state based on nonrandom two-fluid lattice theory for complex mixtures

A new simplified equation of state (EOS) was derived based on the nonrandom lattice fluid model with the introduction of the two-fluid theory. Admittedly the new EOS was originated from the density dependent combinatory and has features similar to the UNIQUAC model. However, it results in volumetric EOS instead of excess Gibbs energy model. The new EOS was tested for its capacity to represent the phase equilibrium behaviors of pure components and mixtures. The model was applied to density, equilibria of vapor-liquid and vapor-solid phases for nonpolar/nonpolar, nonpolar/polar, and polar/polar binary mixtures of simple and complex molecules. The simplified EOS was successfully applied to the activities of solvents in polymer solutions. With two parameters for pure components and one binary interaction energy parameters, results obtained to date demonstrate that the model is quantitatively applicable to a wide range of temperatures, pressures and densities.