Predicting natural gas dew points from 15 equations of state

This paper is a comparative study of 15 cubic equations of state (EoSs) for predicting natural gas dew points. Two-, three-, and four-parameter EoSs are used to predict the natural gas dew points. Natural gases contain a large amount of supercritical methane; therefore, the fugacity of methane, as a test of suitability of the EoSs, is predicted and compared to the recommended values in International Union of Pure and Applied Chemistry (IUPAC) tables. The vapor pressures of components that are normally present in natural gas mixtures, as another test of the suitability of the EoSs, are also predicted and compared with experimental data. The dew points of several natural gas mixtures then are predicted, using the EoSs, and compared to experimental values. Results reveal that the dew points of lean synthetic natural gases are predicted best by the Redlich - Kwong family of EoSs, whereas rich natural gases dew points are described significantly better by the Patel - Teja family of EoSs.