An investigation of the pressure-volume-temperature behavior of paraffinic systems in the presence of olefins, aromatics, and contaminants

Abstract

A group of equations has been developed for predicting the volumetric behavior of pure unsaturated hydrocarbon liquids, pure non-hydrocarbon liquids, paraffin-aromatic liquid mixtures, paraffin-olefin liquid mixtures, olefin-olefin liquid mixtures, paraffin-contaminants liquid mixtures, and pure non-hydrocarbon gases. In this study the term "liquid" indicates a state below that corresponding to the critical temperature and a pressure in excess of the bubble-point pressure. The constants for the equations of state presented for the above mentioned liquid mixtures were derived on the basis of the constants for pure components. The equations presented are similar in form to van der Waals' equation, but the constants "a" and "b" were found to be functions of temperature. The equations for pure fluids contain four constants characteristic of each material in addition to the gas constant "R". When compared with experimental values found in the literature, the average absolute deviation in the calculated molal volumes was found to be 0.35 percent for 762 measurements on pure liquids. The pure liquids studied were: propene, i-butene, benzene, cyclohexane, hydrogen sulfide, carbon dioxide and water. The equation derived for hydrocarbon liquid mixtures describes the volumetric behavior with an absolute average percent deviation of 0.96 for 2,044 measurements made on 20 mixtures involving propane-propene, propane-benzene, and propene-i-butene systems. The correlation proposed for predicting the molal volumes of hydrocarbon-non-hydrocarbon liquid mixtures yielded an absolute average percent deviation of 0.97 for 2,641 measurements on 30 mixtures involving propane-carbon dioxide, n-butane-carbon dioxide, n-pentane-hydrogen sulfide, and decane-hydrogen sulfide systems. An equation of state was also developed to describe the volumetric behavior of the gases nitrogen, oxygen, hydrogen, air, hydrogen sulfide, and carbon dioxide with an absolute average percent deviation of 0.45 over a total number of 1,205 data points.