Modification of vapor-liquid equilibrium prediction model for asymmetric alkane systems

In this paper, the EOS-GE vapor-liquid equilibrium prediction model was modified so as to be suitable for highly asymmetric alkane systems. The volume translated PR-EOS is adopted as the equation of state, and GE is calculated by the UNIFAC solution model. In the group contribution method, it is assumed that all groups in the solution are isotropic. To eliminate the shortage of this assumption, the combined activity coefficient of UNIFAC model was modified by the nonlinear sum of volume parameters. The original and the modified UNIFAC model were compared in term of prediction error. It is indicated that when the content of light components in the systems is low, the prediction accuracy of bubble point by two models is about the same. When the content of light components in the systems is high, the predicted bubble point of the original UNIFAC model is much lower than the measured value, and that of the modified UNIFAC model is consistent with the measured value. Based on the modification of EOS-GE vapor-liquid equilibrium prediction model, the prediction accuracy of vapor-liquid equilibrium of asymmetric alkane systems is improved, and the application range of EOS-GE model is extended.