Prediction of Solid Polycyclic Aromatic Hydrocarbons Solubility in Water with the NRTL-PR Model

International audienceThe accurate prediction of high pressure phase equilibria is crucial for the development and the design of chemical engineering processes. Among them the modeling of complex systems, such as petroleum fluids with water, has become more and more important with the exploitation of reservoirs in extreme conditions. The aim of this work is to explore the capability of the NRTL-PR model to predict the solubility of solid polycyclic aromatic hydrocarbons in water. For this purpose, we first validate our methodology for fluid phase equilibria predictions of aromatic hydrocarbons and gas (CO2, C2H6) mixtures. Finally, we consider the prediction of the solid solubility of PAH in water, by fitting group parameters either only on SLE data or on both LLE and SLE data of aromatic hydrocarbon-water binary systems

Un algorithme faible nombre de Mach pour la simulation des écoulements de fluides supercritiques par des méthodes spectrales

Les simulations des écoulements de fluides supercritiques ont toujours été menées avec des méthodes de volumes finis. Les algorithmes itératifs qui doivent alors être utilisés pour résoudre les équations, fortement couplées en raison des comportements critiques, entraînent des temps de calcul très longs. Nous proposons un algorithme, associé à une méthode spectrale, pour découpler les équations d’énergie et d’état des équations de Navier-Stokes permettant ainsi de réduire les temps de calcul

Numerical study of adsorption for fluids mixture near critical point in a micro-cavity

International audienceThe main goal of this paper is the study of adsorption and mass transfer in a binary mixture near the solvent’s critical point. The physical model consists of a dilute mixture (naphthalene-supercritical CO2) enclosed in a rectangular cavity of height of order 1 mm with a hot and adsorbent plate at the bottom wall. To benefit from the supercritical fluid specific properties and optimize thermodynamics conditions allowing a better adsorption with a good mass transfer, effects of the critical point proximity and heating are the object of several numerical simulations in the present work. The mathematical model used is based on the solution of the Navier-Stokes equations, coupled with energy and mass diffusion equations with the Peng-Robinson equation of state. In order to reduce computational costs, these equations are solved in the low Mach approximation. The velocity field, perturbation of the mass fraction as well as the temporal evolution of the average Sherwood number are presented for different heatings. The confinement effect is also analysed. The results show that in the mixture critical point neighborhood and for a very high heated wall, the homogeneous adsorption of the solute is obtained. Among other key results, we cite that, under the same optimized conditions, the mass transfer on the adsorbent plate is better.L'objectif principal de cet article est l'étude d'une réaction d'adsorption et des transferts de masse associés dans un mélange binaire près du point critique du solvant. Le modèle physique consiste en un mélange dilué (naphtalène-CO2 supercritique) contenu dans une cavité rectangulaire d'une hauteur de l'ordre de 1 mm et présentant sur sa paroi inférieure une plaque chauffée et adsorbante. Pour tirer parti des propriétés spécifiques du fluide supercritique et optimiser les conditions thermodynamiques permettant une meilleure adsorption avec un bon transfert de masse, les effets de la proximité du point critique et du chauffage font l'objet de plusieurs simulations numériques dans le présent travail. Le modèle mathématique utilisé est basé sur la résolution des équations de Navier-Stokes, couplées aux équations d'énergie et de diffusion des espèces ainsi qu'à l'équation d'état de Peng-Robinson. Afin de réduire les coûts de calcul, ces équations sont résolues dans le cadre de l'approximation à faible nombre de Mach. Le champ de vitesse, la perturbation de la fraction massique ainsi que l'évolution temporelle du nombre moyen de Sherwood sont présentés pour différents chauffages. L'effet de confinement est également analysé. Les résultats montrent que, dans le voisinage du point critique du mélange et pour un fort chauffage de la paroi, on obtient l'adsorption homogène du soluté.Parmi les autres résultats clés, citons que, dans les mêmes conditions optimisées, le transfert de masse sur la plaque adsorbante est meilleur

Contribution of pervaporation in eco design of processes

International audienceThe pervaporation, a membrane separation process, can be an excellent alternative to distillation. Though it is a relatively young technology, the attention of industries towards it increases every year mainly due to its low energy consumption and high separation performance. The aim of our work was to emphasize the new horizons of solvent dehydration technology and mark the contribution of pervaporation in process eco design. We have experimentally and theoretically studied the pervaporation applied to a dehydration of an aqueous mixture of three glycol ethers which are widely used in different chemical industries all over the world. The interest was mainly pointed towards the separation efficiency and energy consumption. The results were compared to those of distillation for the same mixture. The modeling of both processes was also performed in order to optimize operating conditions and increase the efficiency

A Validation of the Family Involvement Questionnaire-High School Version

The purpose of this study was to validate the Family Involvement Questionnaire (FIQ) for use in high school settings (9th-12th grade). After the FIQ was redesigned for use in the high school setting, 517 parents completed the questionnaire online. Internal consistency for the 40-item questionnaire was high (alpha = 0.93). A confirmatory factor analysis failed to substantiate the FIQ-HS to the elementary version from which it was adapted. However, an exploratory factor analysis yielded three factors consistent with the FIQ-E. Family demographics were compared to participants\u27 responses, and significant effects for students\u27 school and special education status were found

A direct spectral domain decomposition method for the computation of rotating flows in a T-shape geometry

International audienceThis paper presents a direct domain decomposition method, coupled with a Chebyshev collocation approximation, for solving the incompressible Navier-Stokes equations in the vorticity-streamfunction formulation. The method is based on the influence matrix technique used to treat the lack of vorticity boundary conditions on no-slip walls as well as to enforce the continuity conditions at the interfaces between adjacent subdomains. The multi-domain approach is proposed in order to extend the use of spectral approximations to non-rectangular geometries and singular solutions. It is applied to the computation of a four domain configuration, corresponding to a forced throughflow in a rotating channel-cavity system which is important in air cooling devices and cannot be modeled by single-domain spectral approximations

Un Algorithme Faible Nombre de Mach pour la Simulation des Ecoulements de Fluides Supercritiques par des Méthodes Spectrales.

The numerical simulations of supercritical fluids flows were always performed using finite volume methods. These methods were used in association with iterative schemes for coupling all the equations, leading to very time-consuming computational codes. In this paper, we propose a new algorithm for an uncoupled solution of energy and Navier-Stokes equations in the low Mach number approximation with a spectral method. Indeed, spectral methods are known to ensure the highest accuracy and to allow the use of very fast techniques, such as FFT and complete diagonalization of the operators, leading to very efficient computational codes. The algorithm proposed is evaluated on a problem of natural convection for which results obtained with a finite volume method are available in literatur

A 3D finite volume method for the prediction of a supercritical fluid buoyant flow in a differentially heated cavity

International audienceThis paper describes a three-dimensional finite volume method for the prediction of supercritical fluid buoyant flows in heated enclosures. The space and the time accuracies of the method are checked on an exact analytical solution, and the solver is validated for several benchmark tests for natural convection inside a differentially heated cavity both in the Boussinesq and in the low Mach number approximations. Then, the influence of the linearization of the van der Waals equation of state on the global convergence is discussed. Comparisons, based on the Rayleigh number, between the supercritical fluid and the perfect gas flows in a side heated cavity, show many similarities in the thermal equilibria and considerable differences in the transient behaviours

An empirical correlation for the relative permittivity of liquids in a wide temperature range: application to the modeling of electrolyte systems with a GE/EoS approach.

International audienceRelative permittivity, also known as static dielectric constant, is a key property of solvents in electrolyte solutions. It strongly influences the solubility of solutes and, therefore, it can be used as a predictive tool in chemical engineering processes. Relative permittivity also plays an essential role in the modeling of phase equilibria of electrolyte systems, since it is involved in the Debye-Hückel model and in the Mean Spherical Approximation, commonly used to represent long-range interactions between ions. In this paper, we propose a new temperature-dependent correlation for the relative permittivity of liquid water, methanol and ethanol, valid in a wide temperature range, including very high temperatures. Comparison with other literature equations evidenced that the main interest of the proposed correlation is to allow satisfactory predictions of the relative permittivity, not only in the range of validity of other literature models, but also in the high temperature domain, including supercritical temperatures for water. The new correlation is then used with the NRTL-PRA EoS to predict vapor pressure of water with several salts, including single electrolytes and two-salts mixtures; it must be noted that the modeling presented in this work is relevant for any GE/EoS model, since in this case (binary interactions between water and ions being equal to zero), the excess Gibbs energy reduces to the Long-Range term derived from the Pitzer-Debye-Hückel model. A temperature-dependent correction of the solvent relative permittivity is proposed to account for its dependence on ion mole fraction in this Long-Range term. Results thus obtained show that this correction leads to an accurate prediction both: for vapor pressures of aqueous electrolyte solutions in a very wide temperature domain and for the modeling of vapor-liquid equilibria of methanol-water and ethanol-water mixtures with several salts

Numerical study of non-isothermal adsorption of Naphthalene in supercritical CO2: behavior near critical point

International audienceIn this study, adsorption in a model binary mixture is investigated near the critical point in a side-heated cavity. The diverging behavior of the equilibrium constant and the Piston effect are taken into account and their influence on the adsorption process is pointed to. The modeling is based on numerical integration of the differential equations, considering the Navier-Stokes equations coupled with the energy and mass diffusion balances. By means of this model, the temperature, density and adsorbed concentration profiles are drawn at different times. Some fundamental concepts about the system’s response to the heating are illustrated. The results reveal that the adsorption process is influenced by the combined effect of several parameters, such as the gravity and the proximity to the critical point. In particular, the adsorbed amount exhibits a reversed dependency on the wall heating very close to the critical point, which confirms the complexity of such a process in binary systems near critical conditions