Iranian Journal of Chemical Engineering (IJChE)

Abstract This work deals with estimation of temperature dependent binary interaction parameters (k ij) for binary systems containing CO 2 using the Soave-Redlich-Kwong equation of state with a group contribution method. In this paper six groups, namely CH 3, CH 2, CH, CH 4 (methane), C2H 6 (ethane), and CO 2 (carbon dioxide) are defined and their relevant values of group interaction parameters are optimized. Using this method, it is possible to estimate the k ij of any mixture containing carbon dioxide and hydrocarbons at any temperature along the coexistence curve. The results obtained in
this study are, in most cases, accurate.

Abstract In this work, the ability of different mixing rules for the prediction of hydrate formation pressure are compared. For this purpose, by using Van der Waals–Plauteeuw model for solid hydrate phase and PR equation of state for calculation of fugasity of components in gas and liquid phases, the pressure of hydrate formation in different mixtures has been calculated by four different mixing rules: Van der Waals, Danesh, GNQ and Wong-Sandler, then by comparison of the calculated results with experimental data, the accuracy of the mixing rules were determined. Studied systems contain binary mixtures CH4, C2H 6, C3H 8, i-C4H 10, CO 2, and H 2S with water in hydrate forming conditions. The interaction parameters in each mixture have been optimized by using two phase equilibrium data W(V L ) and then the optimized parameters have been used for three phase equilibrium W(V L H ) calculations. Comparison of the calculated
pressure of hydrate forming with experimental pressure shows that for most mixtures in the studied temperature and pressure ranges, the GNQ mixing rule with an average percent of error 6% has more accuracy than the three other mixing rules: Van der Waals, Danesh and WS. According to the obtained results for methane equilibrium concentrations in liquid phase, it seems that Danesh mixing rule is more efficient for the prediction the mole concentrations of components. Since Danesh rule considers the polarity of the water molecule, it has greater precision in predicting the equilibrium fractions.

Abstract Lennard-Jones-Devonshire equation of state is an old but theoretical based EOS. The concept of the nearest neighboring molecules or coordination number is proposed to be a function of temperature and volume, whereas it is a constant in the original. The dilute gas and hard sphere limits of molecules are employed to determine this function. Improvement of this modification is demonstrated by property calculations for Lennard-Jones fluid. Results of the modified LJD equation of state offer senior accord with simulation data of Lennard-Jones fluid than those of the original version.    

Abstract In this work the volume expansion for the binary systems of ethanol and toluene, as industrial organic solvents, in the presence of nearcritical and supercritical carbon dioxide, CO2, at a temperature range of 293 to 333 K has been meticulously measured. The effect of the temperature and pressure of binary systems on volume expansion for organic solvents have also been investigated. It can be observed that by increasing the pressure of the system at a constant temperature, the volume of the liquid phase increases smoothly, while at higher pressures a sudden volume expansion can occur. The range of pressure that can lead to a sudden increase in the volume expansion of the liquid phase in each specified temperature can be reported as a proper condition in producing micro and nanoparticles. The experimental data for the volume expansion of organic solvents were modeled using the conventional cubic Peng Robinson equation of state. The Average Absolute Relative Deviation percent (AARD%) for the binary systems of ethanol + CO2 and toluene + CO2 were reported as 14.9% and 15.1%. As inferred, it is vital to develop a thermodynamic model with greater accuracy in order to correlate the volume expansion of the systems studied in this work at various conditions.

Abstract In this work, the recently proposed SAFT-based Equation of State (EOS), the GV- SSAFT EOS, was used to study the phase behavior of associating and non-associating pure polymer melts as well as polymer-solvent mixtures at various conditions. The regressed values of the parameters for the GV-SSAFT equation of state for a wide spectrum of pure homopolymer melts were obtained using the corresponding Pressure- Volume- Temperature (PVT) experimental data available in the literature. In case of the non-associating polymers the GV-SSAFT EOS has three adjustable parameters while the number of parameters is increased to five for associating polymers. The parameters were meticulously tuned for segment number, segment molar volume, and segment- segment interaction energy, and their values for the systems studied in this work were also reported. The results obtained from the GV-SSAFT EOS were unequivocally compared with those of the Simplified version of the SAFT (SSAFT) EOS for both associating and non-associating pure polymer melts as well as polymer-solvent mixtures. The results showed that the GV-SSAFT EOS can accurately correlate the experimental data for liquid density of pure polymer melts at wide temperature ranges. In case of polymer-solvent mixtures, inferior results obtained by employing the GV- SSAFT EOS to the VLE experimental data. The results also showed that while considering the specific site-site interactions for the associating polymers makes the SAFT-based equations of state more complicated, the final results cannot be much affected by such complexity. Therefore, this kind of molecular interaction could be neglected to a good approximation. It would be worth noting that in order to do a fair comparison between the results obtained from the GV-SSAFT EOS with those of the SSAFT EOS, the same sets of experimental data and the same optimization procedure were used for both equations of state to render their regressed parameters.

Abstract In this paper, a simplified formulation for a compositional reservoir simulator is presented. These type of simulators are used when interphase mass transfer depends on phase composition as well as pressure. The procedure for solving compositional model equations is completely described. The Peng Robinson equation of state is used for preparing a compositional thermodynamic program for equilibrium calculation, property estimation and pseudo component determination. Another purpose of this paper is to prepare an experimental apparatus for the displacement of oil by gas injection. In each test, oil recovery as a function of injected pore volume was measured. The application of the developed simulator to simulate the results of the oil recovery from slim tube experiments is also presented. Finally, the model was run for a 2-D reservoir. Acceptable trends were obtained from the model predictions.