Impact of the Binary Interaction Parameter Effect on the Phase Behavior Predictions

This paper deals with fitting of the binary interaction parameter for the Peng- Robinson equation of state using landmarks in the binary phase space such as K- and L-points. K- and L-points for the (Ethane + Ethanol) and (Methane + n-Hexane) systems were calculated using different values for the binary interaction parameter and It was observed that the location of K- and L-points varied significantly in P-T space with change in the binary interaction parameter. Additionally, for Ethane + Ethanol system a single value of the binary interaction parameter was not able to predict both K- and L-points well and a single value of binary interaction parameter without a pressure and/or temperature dependence was unable to predict the presence of both the K- and L-points simultaneously. The system exhibits Type-V phase behavior experimentally but The binary interaction parameter fitted using an L-point predicts Type-II phase behavior whereas the binary interaction parameter fitted using a K-point predicts Type-III phase behavior for the system. Not only did the binary interaction parameter fitted using a K- or an L-point fail to predict the correct type of phase behavior. But the results for methane + n-alkane system revealed that the binary interaction parameter fitted using the K- and/or L-point was successful in predicting the correct shape of the critical line and thus the correct type of phase behaviour.