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International audience; The vaporization of drops of highly vaporizable liquids falling inside a cryogenic environment is far from being a trivial matter as it assumes harnessing specialized thermodynamics and physical equations. In this paper, a multi-component falling droplet evaporation model was developed for simulating the spray cooling process. The falling speed of the sprayed droplets was calculated with the momentum equations considering three forces (gravity, buoyancy and drag) applied to a droplet. To evaluate the mass and heat transfer between the sprayed droplet and the surrounding gas phase, a gaseous boundary film of sufficient thinness was assumed to envelope the droplet, while the Peng-Robinson equation of state was used for estimating the phase equilibrium properties on the droplet’s surface. Based on the relevant conservation equations of mass and energy, the key properties (such as temperature, pressure and composition) of the liquid and gas phases in the tank during the spray process could be simulated. To conclude, the simulation algorithm is proposed.

Three dimensional models that account for chemistry are useful tools to predict the chemical composition of (exo)planet and brown dwarf atmospheres and interpret observations of future telescopes. Recent Juno observations of the NH3 tropospheric distribution in Jupiter also indicate that 3D chemical modelling may be necessary to constrain the deep composition of the giant planets of the Solar System. However, due to the high computational cost of chemistry calculations, 3D chemical modelling has so far been limited. A solution to include chemical kinetics in a 3D model is to use a reduced chemical scheme. In this view, we have developed a reduced scheme containing 30 species and 181 reversible reactions, from the full chemical scheme of Venot et al. 2012. This scheme reproduces accurately the vertical profiles of the observable species (H2O, CH4, CO, CO2, NH3, and HCN) and has a large range of validity. It can be used to study all kind of warm atmospheres, except hot C-rich ones, which contains a high amount of C2H2. It can be used in 1D models, for fast computations, but also in 3D models for hot giant (exo)planet and brown dwarf atmospheres., 13 pages, 11 figures, accepted for publication in A&A

International audience; Membrane processes have been initially seldom considered within a post-combustion carbon dioxide capture framework. More traditional processes, particularly gas-liquid absorption in chemical solvents, are often considered as the most appropriate solution for the first generation of technologies. In this paper, a critical state of the art of gas separation membranes for CO2 capture is proposed. In a first step, the key performances (selectivity, permeability) of different membrane materials such as polymers, inorganic membranes, hybrid matrices and liquid membranes, including recently reported results, are reviewed. In a second step, the process design characteristics of a single stage membrane unit are studied. Purity and energy constraints are analysed as a function of operating conditions and membrane materials performances. The interest of multistage and hybrid systems, two domains which have not sufficiently investigated up to now, are finally discussed. The importance of technico-economical analyses is highlighted in order to better estimate the optimal role of membranes for CCS applications.

International audience; Theoretical and experimental investigations on the reactive absorption of CO 2 in aqueous solutions of PZ using a wetted wall column are presented. A rigorous two dimensional absorption model, accounting for kinetics, hydrodynamics and thermodynamics, has been developed for a wetted wall column. Major innovative features of the model, compared to previous work, are the account on the variation of the gas-side CO 2 concentration over the reactor height as well as the computation of the gas-liquid equilibrium by a thermodynamically consistent approach. A laboratory-scale wetted wall column was conceived and constructed and the gas-side mass-transfer coefficient was estimated. CO 2 absorption experiments were carried out on unloaded and loaded aqueous solutions of PZ over the range of 298-331 K, and for total PZ concentrations varying from 0.2 to 1 M. The reactor model permitted to predict the absorption fluxes in loaded as well as in unloaded solutions with an excellent accuracy, i.e. 3.2% AAD. In loaded solutions, the gas-side CO 2 concentration gradient, as well as the dicarbamate formation reaction has to be taken into account.

In this paper, the concept of a multiscale modeling approach is highlighted with which physical phenomena at different scales can be studied. The work reports a multiscale approach to describe the dynamics of a chain of bubbles rising in non-Newtonian fluids. By means of the Particle Image Velocimetry (PIV) and the Lattice Boltzmann (LB) simulation, a deep understanding of the complex flow pattern around a single bubble is gained at microscale. The interactions and coalescences between bubbles rising in non-Newtonian fluids are experimentally investigated by the PIV measurements, birefringence and rheological characterization for both an isolated bubble and a chain of bubbles formed from a submerged orifice. Two aspects are identified as central to interactions and coalescence: the stress creation by the passage of bubbles and their relaxation due to the fluid’s memory. This competition between the creation and relaxation of stresses displays non-linear complex dynamics. Along with the detailed knowledge around a single bubble, these fundamental mechanisms governing bubbles’ collective behavior in a train of bubbles at mesoscale lead to a cognitive modeling based on behavioral rules. By simulating bubbles as adaptive agents with the surround fluid via residual stresses, model predictions for consecutive coalescence between a great number of bubbles compare very satisfactorily with the experimental investigation at macroscale. Obviously this new approach captures important quantitative and qualitative features of the collective behaviors of bubbles at macroscale level which are predicted by the mesoscopic cognitive modeling approach of the interactions rules which are deduced from the understanding of the microscopic mechanism of the flow around a single bubble.

International audience; Membrane contactors have been proposed for decades as a way to achieve intensified mass transfer processes. Post-combustion CO 2 capture by absorption into a chemical solvent is one of the currently most intensively investigated topics in this area. Numerous studies have already been reported, unfortunately almost systematically on small, laboratory scale, modules. Given the level of flue gas flow rates which have to be treated for carbon capture applications, a consistent scale-up methodology is obviously needed for a rigorous engineering design. In this study, the possibilities and limitations of scale-up strategies for membrane contactors have been explored and will be discussed. Experiments (CO 2 absorption from a gas mixture in a 30%wt MEA aqueous solution) have been performed both on mini-modules and at pilot-scale (10 m 2 membrane contactor module) based on PTFE hollow fibers. The results have been modeled utilizing a resistance in series approach. The only adjustable parameter is in fitting the simulations to experimental data is the membrane mass transfercoefficient (km), which logically plays a key role. The difficulties and uncertainties associated with scaleup computations from lab scale to pilot-scale modules, with a particular emphasis on the km value, are presented and critically discussed.; Captage postcombustion du CO 2 par des contacteurs membranaires de fibres creuses : de l'échelle laboratoire à l'échelle pilote industriel — Depuis des décennies, les contacteurs membranaires sont proposés pour intensifier les procédés de transfert de matière. Le captage post-combustion du CO 2 par absorption dans un solvant chimique est actuellement l'un des sujets le plus intensivement examiné. Un grand nombre d'études ont déjà été reportées dans la littérature, malheureusement, elles ne concernent pratiquement que des expériences menées à l'échelle laboratoire sur de petits modules. Étant donné les débits de fumées qui doivent être traités dans une application industrielle du captage du CO 2 , une étude consistante à plus grande échelle est nécessaire à l'obtention d'un design rigoureux du procédé. Dans cette étude, les possibilités et les limites de l'échelle laboratoire et de l'échelle pilote industrielle ont été évaluées et seront discutées. Les expériences (absorption du CO 2 d'un mélange gazeux par une solution aqueuse de MEA à 30 %mass.) ont été menées à la fois sur un mini-module à l'échelle laboratoire et sur un module de taille industrielle (10 m 2), tous deux constitués de fibres PTFE. L'approche des résistances en série a ensuite été utilisée pour simuler les résultats. Un seul paramètre ajustable est utilisé : le coefficient de transfert de matière dans la membrane (k m) qui joue logiquement un rôle clé. Les difficultés et les incertitudes des calculs liées au changement d'échelle, plus particulièrement sur la valeur de k m , sont présentées et discutées.

International audience; The growing demand of bio-sourced products leads to an increasing interest for the development of new resources of raw materials. In order to generate a higher economic value in the oleoproteaginous sector, meals, co-products of oil extraction present qualities capable of being exploited in a wide range of sectors. These meals are mainly commercialized in feed application , but remain relatively weak used in the chemistry domain or even in food. To enlarge these applications, the pre-treatment of the raw material by grinding and air-classification offers technological outlooks for the conception of new extraction processes of interesting components. The present publication has the following goal: to examine the diversification of oleoproteaginous meal market, out of traditional usage in the chemistry domain; to characterize the meals chemical composition and their techno-functional properties; to evaluate the feasibility of valorizing these meals and their derivatives as substitutes or additives allowing the reduction of the level in petro-chemical product, for example, for the production of adhesive formulations for particle boards. To achieve this, different actions have been performed: evaluation of the potential and accessible market starting from metropolitan crops; analysis of the panoramaof intellectual property for the identified markets; chemical characterization of ground plant meals and their soluble and insoluble fractions; applicability of the different obtained fractions, in terms of foaming power, emulsifier and gelifier; first application tests starting from rapeseed and sunflower meals in the wood panel board domain. The obtained results have allowed: to draw up a map of the inventive activity bound to the valorization of proteins from rapeseed, sunflower and soy meals and pea flour in various applications, highlighting the dynamism and the growing interest for industrials and academics to use oleo-proteaginous plant proteins; to explore techno-functional properties brought by these plantmeals and their derivatives, in particular in the wood panel domain.; La demande mondiale en produits bio-sourcés en pleine expansion engendre un intérêt croissant pour la recherche de nouvelles ressources de matières premières. Pour générer une valeur économique accrue dans les filières oléo-protéagineuses, les tourteaux, co-produits de l'extraction de l'huile, présentent des qualités pouvant être exploitées dans des secteurs diversifiés. Ces tourteaux sont principalement commercialisés en alimentation animale, mais restent peu utilisés dans le secteur de la chimie ou encore de l'alimentation humaine. Afin d'en étendre les applications, le prétraitement de la matière par broyage et classification granulométrique offre des perspectives technologiques pour la conception de nouveaux procédés d'extraction de composés d'intérêt. Le présent article a pour objectif : d'examiner la pertinence d'une diversification du marché des tourteaux, hors usage traditionnel et dans le secteur de la chimie ; de caractériser la composition chimique des tourteaux ainsi que leurs propriétés techno-fonctionnelles ; d'évaluer la faisabilité de valoriser ces tourteaux ainsi que leurs différentes fractions comme substituts ou additifs permettant la réduction de la teneur en produits d'origine fossile, par exemple, dans la production de formulations adhésives pour les panneaux de particules. Pour ce faire, un certain nombre d'actions ont été menées : évaluation du marché potentiel et accessible à partir des cultures métropolitaines ; analyse du panorama de la propriété intellectuelle pour les marchés identifiés ; caractérisation chimique des tourteaux broyés et de ses fractions solubles et insolubles ; applicabilité des différentes fractions obtenues, en termes de pouvoir moussant, émulsifiant et gélifiant ; premiers tests d'application à partir de tourteaux de colza et de tournesol dans le domaine des panneaux de bois composite. Les résultats obtenus ont permis : de dresser une cartographie de l'activité inventive liée à la valorisation des protéines de tourteaux de soja, colza, tournesol et farine de pois dans des applications variées en mettant en avant le dynamisme et l'intérêt croissant d'industriels et d'universitaires pour l'utilisation des protéines d'origines oléo-protéagineuses ; d'explorer les propriétés techno-fonctionnelles apportées par ces tourteaux broyés et leurs dérivés, en particulier dans les domaines des panneaux de bois composite

International audience; This article draws a state of knowledge of the dissolution of uranium dioxide in nitric acid media. The chemistry of the reaction is first investigated, and two reactions appear as most suitable to describe the mechanism, leading to the formation of monoxide and dioxide nitrogen as reaction by-products, while the oxidation mechanism is shown to happen before solubilization. The solid aspect of the reaction is also investigated: manufacturing conditions have an impact on dissolution kinetics, and the non-uniform attack at the surface of the solid results in the appearing of pits and cracks. Last, the existence of an autocatalytic mechanism is questionned. The second part of this article presents a compilation of the impacts of several physico-chemical parameters on the dissolution rates. Even though these measurements have been undertaken under a broad variety of conditions, and that the rate determining step of the reaction is usually not specified, general trends are drawn from these results. Finally, it appears that several key points of knowledge still have to be clarified concerning the dissolution of uranium dioxide in nitric acid media, and that the macroscopic scale which has been used in most studies is probably not suitable.

International audience; Ethanol (EtOH) is now produced from fermentation of carbohydrates. Guerbet reaction is a possible w ay to couple C-C bonds of aliphatic alcohols towards higher carbon skeleton molecules that are suitable for di sel, gasoline, aviation fuel and chemicals. When vaporized EtOH is contacted to solids at temperatures near 673.15 K, a lot of different products are obtained containing olefins, paraffins, longer alcohols, diolefins, ketones, aldehydes, ethers, etc. Some H 2 is produced and carbonaceous deposits are formed. In this work, the EtOH to butanol (But-OH) probe reaction was studied. Most of catalytic data available on C-C coupling of EtOH are on the gas phase at 1 bar, for that reason this condition was studied. However, in fermentation process, EtOH is produced in a solution of water (at ~6 wt.% EtOH) [1], this aqueous solution was also studied. It is expected that higher alcohols (like octanol) separate spontaneously from water by decantation, avoiding energy-intensive distillation (consider that fuel EtOH should be anhydrous).

39th Edition of the Joint European Days on Equilibrium between Phases (JEEP), Nancy, FRANCE, MAR 19-21, 2013; International audience; Progressive depletion of world oil resources, combined to increasing energy consumption as well as the negative environmental impact of fossil fuel use, led to a shift toward alternative renewable sources of energy. Biodiesel is among the most viable liquid transportation fuels for the foreseeable future, with the potential of contributing significantly to sustainable development in terms of socioeconomic and environmental concerns. Indeed, biodiesel is a mixture of alkyl esters obtained by transesterification (alcoholysis) of triglycerides from vegetable oils or animal fats with an alcohol (methanol or ethanol). The transesterification reaction is commonly carried out in the presence of a catalyst the main drawback of which is to be water sensitive, preventing the use of non-conventional feedstocks (such as waste cooking oils or algal biomass) [1]. Emerging non- catalytic alcoholysis methods based on supercritical fluids allow solving this problem. Nevertheless, their industrial scale application is limited because of the severe operating conditions required (high temperature, high pressure, and high alcohol to oil molar ratio) which can be successfully reduced by addition of a co-solvent, such as CO 2 [2 -4]. To optimize the supercritical process via simulation, the phase behaviour under high temperatures and pressures for systems containing CO 2 and components involved in biodiesel production must be firstly investigated...

This paper describes a technique which permits to drastically reduce comprehensive primary mechanisms which can be obtained by computer aided design in the case of the gas-phase oxidation of alkanes. This procedure has been tested by reducing a primary mechanism which had been automatically generated in the case of the normal-butane oxidation by the software EXGAS which is developed in Nancy. The reduced mechanism thus obtained permits to obtain results very close to those computed by using the complete mechanism in the case of the modelling of the normal-butane oxidation both at low temperature between 554 and 737K, in the negative temperature coefficient field, and at higher temperature at 937 K.

Our purpose is to release a chemical network, and the associated rate coefficients, developed for the temperature and pressure range relevant to hot Jupiters atmospheres. Using this network, we study the vertical atmospheric composition of the two hot Jupiters (HD209458b, HD189733b) with a model that includes photolyses and vertical mixing and we produce synthetic spectra. The chemical scheme is derived from applied combustion models that have been methodically validated over a range of temperatures and pressures typical of the atmospheric layers influencing the observations of hot Jupiters. We compare the predictions obtained from this scheme with equilibrium calculations, with different schemes available in the literature that contain N-bearing species and with previously published photochemical models. Compared to other chemical schemes that were not subjected to the same systematic validation, we find significant differences whenever non-equilibrium processes take place. The deviations from the equilibrium, and thus the sensitivity to the network, are more important for HD189733b, as we assume a cooler atmosphere than for HD209458b. We found that the abundances of NH3 and HCN can vary by two orders of magnitude depending on the network, demonstrating the importance of comprehensive experimental validation. A spectral feature of NH3 at 10.5$\mu$m is sensitive to these abundance variations and thus to the chemical scheme. Due to the influence of the kinetics, we recommend the use of a validated scheme to model the chemistry of exoplanet atmospheres. Our network is robust for temperatures within 300-2500K and pressures from 10mbar up to a few hundreds of bars, for species made of C,H,O,N. It is validated for species up to 2 carbon atoms and for the main nitrogen species., Comment: 20 pages, 10 figures. Accepted for publication in Astronomy & Astrophysics

[Context] While the existence of more than 1800 exoplanets have been confirmed, there is evidence of a wide variety of elemental chemical composition, that is to say different metallicities and C/N/O/H ratios. Atmospheres with a high C/O ratio (above 1) are expected to contain a high quantity of hydrocarbons, including heavy molecules (with more than two carbon atoms). To correctly study these C-rich atmospheres, a chemical scheme adapted to this composition is necessary., [Aims] We have implemented a chemical scheme that can describe the kinetics of species with up to six carbon atoms (C0-C6 scheme). This chemical scheme has been developed with combustion specialists and validated by experiments that were conducted on a wide range of temperatures (300−2500 K) and pressures (0.01−100 bar)., [Methods] To determine for which type of studies this enhanced chemical scheme is mandatory, we created a grid of 12 models to explore different thermal profiles and C/O ratios. For each of them, we compared the chemical composition determined with a C0-C2 chemical scheme (species with up to two carbon atoms) and with the C0-C6 scheme. We also computed synthetic spectra corresponding to these 12 models., [Results] We found no difference in the results obtained with the two schemes when photolyses were excluded from the model, regardless of the temperature of the atmosphere. In contrast, differences can appear in the upper atmosphere (P> ~ 1−10 mbar) when there is photochemistry. These differences are found for all the tested pressure-temperature profiles if the C/O ratio is above 1. When the C/O ratio of the atmosphere is solar, differences are only found at temperatures lower than 1000 K. The differences linked to the use of different chemical schemes have no strong influence on the synthetic spectra. However, with this study, we have confirmed C2H2 and HCN as possible tracers of warm C-rich atmospheres., [Conclusions] The use of this new chemical scheme (instead of the C0-C2) is mandatory for modelling atmospheres with a high C/O ratio and, in particular, for studying the photochemistry in detail. If the focus is on the synthetic spectra, a smaller scheme may be sufficient, because it will be faster in terms of computation time., O.V. acknowledges support from the KU Leuven IDO project IDO/10/2013 and from the FWO Postdoctoral Fellowship programme.

A general review [1, 2] is presented concerning joi ntly the crystallographic structures and the transition physicochemical data (Tfus, �fusH, �fusS, �ebH, �subH, Cp) in the pure normal alkanes, as well as the structural and thermodynamic behavior of their synthetic binary, t ernary and multinary model mixtures and of real petroleum waxes, particularly the solubility and mixture prop erties [3-6]. A major part of the structural and thermodyn amic data of the literature and our experimental results are listed from methane up to the alkane with carbon at om number equal to 390 [1, 2] as well as their variati ons versus the atom carbon number. The experimental results [3] and those of literatur e concerning the pure n-alkane dissolution enthalpies allow to determine the enthalpy of the formation of one o r several crystallized solid solutions of the mixture s [4] and to highlight the influence of the characteristic pa rameters of the paraffinic distribution (theoretical average chain length, n-alkanes number, monophasic or polyphasic state) on the excess properties in the solid state. This data bank permits to test the predictive capacities of t he UNIQUAC thermodynamic model. After modifying the expression of the interaction energy to take into a ccount the effect of the size difference between the n-alk anes of the mixtures and the internal disorder induced by t he nalkane length distribution, this model give very go od results for the prediction of the excess enthalpy o f complex multialkane samples [4].