A quasi-chemical nonrandom lattice fluid model: General derivation and application to pure fluids and mixtures

A quasi-chemical nonrandom lattice fluid model without temperature dependence of the close packed volumes of a mer, segment numbers and energy parameters of pure systems is presented. The explicit nonrandom lattice fluid (NLF) model with quasi-chemical approach was capable of describing properties for complex systems, but this model had strong the temperature dependence of energy parameters and segment numbers of pure systems. In this work, a quasi-chemical nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems is proposed. And the model was extended to mixtures by using consistent method for phase equilibrium calculation with fugacity coefficients derived from the present equation of state. We tested consistently the present model on 17 phase equilibrium data sets of vapor–liquid equilibria and compared with the NLF model and the SAFT model. The present model (three pure parameters for pure component and one binary interaction parameter) showed better results for most systems than the NLF model (six adjustable pure parameters and one binary interaction parameter) and the SAFT model (three pure parameters and one binary interaction parameter).