Water Solubility in Supercritical Methane, Nitrogen, and Carbon Dioxide: Measurement and Modeling from 422 to 483 K and Pressures from 3.6 to 134 MPa

A series of experiments to measure the water solubility in supercritical nitrogen and carbon dioxide have been conducted at experimental conditions up to 483 K and 134 MPa. The accuracy of the experimental procedure is verified by comparing the water content data of methane in the literature and our experimental data for the methane-water system. In addition, a fugacity-fugacity approach including the cubic-plus-association equation of state (CPA EoS) and a fugacity-activity approach based on the Peng-Robinson EoS and the Henry's law model are incorporated to predict the water content data of methane, nitrogen, and carbon dioxide. A comparison between our experimental data, literature data, and the results of the fugacity activity approach shows the reliability of the PR-Henry's law model for the phase behavior studies of the nitrogen-water system over a wide range of pressure and temperature conditions. However, the CPA equation is not capable of reproducing the high pressure vapor and liquid phase compositions of the water-nitrogen system. The concept of cross-association satisfactorily improves the performance of the CPA equation of state in predicting the water content data of supercritical methane. On the basis of the literature and new measured data in this study, it has been found that the CPA equation better represents the phase behavior of the water-carbon dioxide system if carbon dioxide is considered as a self- and cross-associating molecule.