COMPARISON OF THE PENG-ROBINSON AND SOAVE-REDLICH-KWONG EQUATIONS OF STATE USING A NEW ZERO-PRESSURE-BASED MIXING RULE FOR THE PREDICTION OF HIGH-PRESSURE AND HIGH-TEMPERATURE PHASE-EQUILIBRIA

The Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of stat e are probably the most widely used cubic equations of state in the re finery and gas-processing industries for the prediction of vapor-liqui d equilibria for systems containing nonpolar components. The new mixin g rules which have recently been developed that combine liquid activit y models with the equations of state, however, have extended the appli cation of such equations to highly nonideal systems. A new zero-pressu re-based mixing rule is presented here that reproduces, with extremely high accuracy, the excess Gibbs free energy as well as the liquid act ivity coefficients of any activity model without requiring any additio nal binary interaction parameters. We examine the performance of the P eng-Robinson and Soave-Redlich-Kwong equations of state using the NRTL liquid activity model with binary parameters determined at low temper atures in this new mixing rule, MHV1, and Wong-Sandler for the predict ion of high-pressure and high-temperature phase equilibria.