Modification of Sako-Wu-Prausnitz equation of state for fluid phase equilibria in polyethylene-ethylene systems at high pressures

• Main Authors: F. Gharagheizi, M. Mehrpooya, A. Vatani
• Format: Article
• Language: English
• Published: Brazilian Society of Chemical Engineering 2006-09-01
• Series: Brazilian Journal of Chemical Engineering
• Subjects: Polyethylene-ethylene systems; Phase behavior
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322006000300012

In order to model phase equilibria at all pressures, it is necessary to have an equation of state. We have chosen the Sako-Wu-Prausnitz cubic equation of state, which had shown some promising results. However, in order to satisfy our demands, we had to modify it slightly and fit new pure component parameters. New pure component parameters have been determined for ethylene and the n-alkane series, using vapor pressure data, saturated liquid volume and one-phase PVT-data. For higher n-alkanes, where vapor pressure data are poor or not available, determination of the pure component parameters was made in part by extrapolation and in part by fitting to one-phase PVT-data. Using one-fluid van der Waals mixing rules, with one adjustable interaction parameter, good correlation of binary hydrocarbon system was obtained, except for the critical region. The extension of the equation of state to polyethylene systems is covered in this work. Using the determined parameters, flash and cloud point calculations were performed, and treating the polymer as polydisperse. The results fit data well.