Modified Peng-Robinson equation of state for prediction of PVT and critical properties

By considering the "alpha" and "b" parameters in the Peng-Robinson (PR) equation of state (EOS) as temperature-dependent, pressure volume temperature properties of liquids can be estimated more accurately. Also a new method is proposed for accurate estimation of critical compressibility factors of different compounds. The proposed modified PR-EOS has been compared with the original PR-EOS and Soave-EOS for estimation of liquid and vapor densities, vapor-pressure, critical compressibility, the vapor-liquid equilibrium ratios (K-i,s) and heats of vaporization for a variety of different compounds. Results show significant improvement for the prediction of these properties, especially critical density and liquid densities of heavy compounds.