Liquid Equilibrium Properties Research Articles

Extension of the Wong-Sandler mixing rule to the three-parameter Patel-Teja equation of state: Application up to the near-critical region

The Wong-Sandler mixing rule was extended to the Patel-Teja three-parameter cubic equation of state by introducing suitable corresponding parameters. The new model, PT–WS model, has been extensively tested on various classes of binary/ternary mixtures, special attention was paid to the effects on the representation of mixture phase behavior in the near-critical region. The test results indicate that the new model is capable of improving both the vapor–liquid equilibrium and volumetric properties significantly, especially for highly asymmetric systems. The proposed method of implementing the Wong-Sandler mixing rule can be applied to other multi-parameter cubic equations of state.

Gas Solubility Of Methane And Ethane In Cold Lake Bitumen At In Situ Conditions

Abstract The vapour-liquid equilibrium properties of methane-Cold Lake bitumen and ethane-Cold Lake bitumen mixtures were measured using a modified Ruska rocking cell apparatus. Data measured at three isotherms for these two pseudo-binary systems were used to develop a predicting method by means of equations of state. Two equations of state, the modified Soave-Redlich-Kwong and the Peng-Robinson, were chosen in this study. With an appropriate choice of bitumen characterization parameters and binary interaction coefficients, both of the equations of state can adequately represent the vapour liquid equilibrium properties of the two systems studied. Binary interaction coefficients of the modified Soove-Redlich-Kwong equation of state for the two systems were determined and correlated with temperature. Introduction Methane and ethane are commonly found in native Cold Lake oil sands bitumen, and are considered as possible additives for steam-based in situ bitumen recovery methods. Thus, the phase behaviour of methane-Cold Lake bitumen and ethane-Cold Lake bitumen mixtures under in situ conditions is important for reservoir engineers to determine the recovery of bitumen from Cold Lake deposits, as well as for process engineers to develop an adequate numerical simulation model Experimental data for these two pseudo-binary systems are not reported in the literature, and therefore one of the major objectives of this study was to measure their vapour-liquid equilibrium (VLE) properties. Experimental measurements are time-consuming and costly for these bitumen-containing systems. For the purpose of data reduction it is desirable to find methods which can predict their VLE properties with high accuracy. In this investigation, two cubic equations of state were selected to represent phase equilibrium properties. These are the modified Soave-Redlich-Kwong (MSRK) equation of state(1,3) and the Peng-Robinson (PR) equation of state (4,5). A commercially available "EQUI- PHASE" software package developed by DB Robinson and Associates was applied in vapour-liquid equilibrium calculations for the PR equation of state. Calculations were also performed with the PR equation of state using bitumen characterization parameters developed by Fu et al.(10) and binary interaction coefficients determined in this paper. The VLE properties measured in our laboratory are compared to the values calculated for the two gas-bitumen systems using both equations of state. Experimental Aspects Apparatus A schematic diagram of the experimental apparatus, which was verified for VLE measurements in a previous study(7), is shown in Figure 1. It consists of a charging and discharging unit, a constant temperature bath with a rocking equilibrium cell, and a sampling and analysis unit. The heart of the apparatus is the equilibrium cell which is located in a constant temperature bath container as shown in Figure 2. During measurements, the rocking cell is driven by a motor while a stirrer circulates the oil in the bath and keeps it homogeneous. Using this design, temperature was tested up to 423.2 K with an accuracy of ± 0.01 K, and pressure was tested up to 13.8 MPa with an accuracy of ± 1.0 kPa.

Phase equilibrium calculations of highly polar systems

It is well known that highly polar and hydrogen bonding mixtures pose a serious challenge to equations of state. In the present report it is shown that excellent correlations and predictions of complex systems can be achieved when the van der Waals mixing rules are properly associated with an equation of state. In this report the proper form of the van der Waals mixing rules is used with the Peng—Robinson equation of state to predict the vapor—liquid equilibrium properties of water—ketone, water—alcohol, alcohol—ketone, and other complex mixtures, which exhibit either positive or negative azeotropy, with an accuracy which was not achievable by the original form of Peng—Robinson equation of state of mixtures.

Second virial coefficients and the simulation of equilibrium properties of liquid nitrogen using model potentials

Computer simulations of liquid equilibrium properties and calculations of the gas second virial coefficient have been made using two of the available representations of the nitrogen intermolecular potential of Berns and van der Avoird. One representation (BV) employs a spherical harmonic expansion and the other (BVAA) employs an atom-atom representation of the same potential energy input data. A variant potential (BV(+)) in which the isotropic dispersion coefficients C 8 and C 10 are increased by 10 per cent and 15 per cent, relative to those in the BV potential, has also been studied. The virial coefficients for BV(+), but not for BV and BVAA, do not differ from experiment by more than the estimated experimental errors and there are significant differences between the BV(+), BV, and BVAA values. The liquid simulation results for the thermodynamic properties and radial distribution functions are compared with each other and with literature values obtained from simulations using effective potentials which ...

A further evaluation of the clausius equation of state in thermodynamic property calculations

A new modified procedure is proposed for the evaluation of the parameters of the Clausius equation in which the parameter Ω c is considered to be constant. The other two pure-component parameters Ω a and Ω b are considered to be temperature dependent and are evaluated from vapor pressures and saturated liquid volumes. The values obtained are used for calculating PVT data, heats of mixing H E, volumes of mixing V E and vapor—liquid equilibrium (VLE) properties. The representation of PVT data for liquid n-heptane by the proposed modification is not satisfactory. When the calculated H E and V E values are compared with those obtained by the previous modification in which all three parameters are considered to be temperature dependent, the results obtained in V E are comparable but the proposed method yields better H E values. However, the VLE values calculated by the proposed method do not provide significant improvement over the modified Redlich—Kwong equation. The systems studied include ethane—carbon dioxide, propane—carbon dioxide, hydrogen sulfide—n-butane, nitrogen—argon, nitrogen—oxygen, argon—oxygen, propane—ethane—carbon dioxide and nitrogen—argon—oxygen. The findings of this investigation may provide useful information for future development of new equations of state.