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International audience; This paper presents a theoretical description of a particle motion in a rotary dryer equipped with straight lifters distributed on its periphery. In this configuration, the transport of granular materials occurs with cyclic cascades that can be decomposed into three phases: lifting, discharging, and falling into the air stream. In order to describe each of these phases, we have focused on the motion of a single particle in a rotating drum. In this condition, the analytical solution of the motion equation of each phase is found. With these solutions, the position and the velocity of the particle at any time are thus expressed as a function of physical parameters of the particle, physical parameters of the drum, and physical parameters of air in the drum, called operating parameters in practice. With these equations, we are able to calculate the behaviour of the particle as a function of the operating parameters. The transposition to the industrial context is made with an application. We show how these equations particularly permit the estimation of the Mean Residence Time (MRT) of material during the drying process as a function of operating parameters. Such estimations have been validated by comparison with experimental data of MRT found in the literature. The work presented in this paper gives some useful mathematical relations for whose who are interested in drum design optimization (lifter length, drum radius, drum length, etc.). More specifically, they can be used to help with the choice of operational parameters values that would achieve a given value of MRT for particular product.

International audience; For several decades, it has been known that ozone emissions are harmful to humans, plants, and animals. Heterogeneous catalytic decomposition is an efficient process for removing ozone from air. This study examines the effect of the zeolite's framework and pore width on efficiency for decomposing gaseous ozone. Four highly hydrophobic zeolites are used: a large cavity zeolite (Faujasite/H‐FAU), a medium pore zeolite with parallel channel (Mordenite/H‐MOR), and two medium pore zeolites with interconnected channels (H‐ZSM‐5/H‐MFI and Na‐ZSM‐5/Na‐MFI). Experiments were conducted in fixed‐bed flow reactors loaded with zeolite at ambient conditions (20 °C and 101 kPa). Zeolite surfaces were analyzed during the experiments in order to understand the influence of physical and chemical surface properties on the ozone decomposition mechanism. A higher amount of ozone is eliminated using H‐MOR, compared with the zeolite samples H‐FAU, H‐MFI, and Na‐MFI. Pore width and micropore framework size distribution (channel and cages) appear to be key factors. A narrow channel or cage, slightly larger than the ozone molecule size, seems to promote ozone interactions with Lewis acid sites. Fourier transform infrared spectroscopy shows that Lewis acid sites (LAS), located on the walls of zeolite pores, decompose ozone. This leads to the formation of atomic oxygen species that could react with another ozone molecule to form dioxygen. Hence, LAS are regenerated, ready to decompose another ozone molecule once more.

International audience; The aim of this paper is to present the development of a simulation tool in order to assess the inherently safe characteristics of a heat‐exchanger reactor(HEX) operating reaction systems. The modelling of steady and transient states of a HEX reactor is performed following a hybrid dynamic approach. The global dynamic behaviour of this reactor can be represented by several continuous models, which are bounded by state or time events. Each continuous model is defined as a system of partial differential‐algebraic equations. The numerical scheme is based on the method of lines. Special attention is paid to the model initialization and a simulation strategy of the start‐up phase is presented. The validation of the model is made by numerous examples, such as the simulation of an exothermic reaction.

International audience; This paper focuses on a new concept of Heat Transfer Fluid (HTF) for Concentrating Solar Plants (CSP) applications through fluidized bed. CSP plants with very high concentration (such as solar tower plant technology) offer good efficiencies because of high operating temperatures. CSP efficiency could be greatly increased through more efficient HTF. Molten salts, mineral oils, water and air have some of the following drawbacks: limited range of operating temperatures, corrosiveness, high pressure, low energy storage capacity and toxicity.To replace classical HTF, Dense Particle Suspension (DPS) fluidized with air (approximately 40% of solid) is proposed. DPS has a volume heat capacity similar to those of liquid HTF, does not need pressurization, is safe, inert and is only limited by the maximal working temperature of the receiver material (1100 K), thus opening new opportunities for high efficiency thermodynamic cycles. This work is the hydrodynamic study of a gassolid dense suspension upward flow at ambient temperature, in a vertical 2‐tube bundle of small diameter tubes, which have their bottom immersed in a slightly pressurized fluidized bed (pressure approximately equal to the ratio of the solid weight in a tube over its cross section area). This type of flow is yet implemented in the field of hyper‐dense phase vertical conveying of powders and it is currently under development for solar receivers using dense suspensions of particles as heat transfer and storage medium. This application was patented by Flamant and Hemati in 2010 (France 1058565 (2010) CNRS/INP Toulouse, G. Flamant, H. Hemati; PCT Extension, No. WO 2012/052661 A2), and its development is funded by the European Commission. In this technological breakthrough, the concentrated solar energy is collected, carried and stored directly by the fine particles flowing upward, with a suspension void fraction close to that of a dense fluidized bed. Contrary to circulating fluidized bed “risers”, it offers a good contact area between the wall and the particles. The important hydrodynamic and thermal coupling required a step‐by‐step approach. Ambient flows had to be understood and controlled first. Thus a 2‐pass “cold” mock‐up, each pass composed of two vertical parallel tubes, was built. Pressure drop, solid weight and helium volume fraction measurements demonstrated the ability to handle a regular solid upward flow (imperative here), with solid flow rates from 20 to 130 kg/h, with void fractions from 0.57 to 0.63 and with an even distribution of the solid flow rate between the tubes. Moreover, the governing parameters of this flow were established as: the solid feeding flow rate, the fluidization velocity, the solid holdup, the freeboard pressure and the aeration velocity. The secondary air injection, also called “aeration”, is the most important parameter for the stability and the even distribution of the total solid flow rate in the tubes. The 1D modelling of the suspension flow in the tubes was also performed in the flow direction. The flow structure was described using the bubble‐emulsion model formalism, and by adding the solid entrainment by the bubble wake. Predictions of the model are compared with the experimental measurements of driving pressure and axial pressure profile along the tubes.

International audience; The aim of the present work was to investigate the influence of the ionic composition on the demineralization of a saccharide solution containing glucose. Experiments were carried out in order to evaluate the influence of the ionic composition on the solvent and solutes fluxes (glucose and electrolytes) through the membrane under different conditions (ionic compositions: NaCl, Na2SO4 and CaCl2; with or without current). From diffusion experiments (without current), it was shown that the glucose diffusion flux decreases for increasing ion hydration. These results are in agreement with those obtained in a previous work showing that the transfer modification reflects changes in the membrane properties associated with the hydration of its counter‐ion which is likely linked to swelling mechanisms at a microscopic scale. From the experiments carried out in normal ED conditions (with current) an additional convective contribution was pointed out. This kind of result is rather scarce in the literature. The glucose flux was then the sum of two contributions: diffusion and convection, due to the electro‐osmotic flux which is proportional to the electrical current. The contribution of the glucose convection flux on the overall glucose transfer was ranged between 70 and 90 % according to the electrolyte nature (NaCl, Na2SO4 and CaCl2) and the electric current (150 or 300 A m−2). The variation of the convective flux has been further correlated to the hydration of the ions. Indeed increasing convection fluxes were obtained for decreasing anion (or cation) hydration. It was shown that the saccharide transfer increases in presence of salts and that this increase was correlated to the saccharide dehydration in presence of electrolyte. Finally, the solvent, ions and glucose fluxes were used to calculate the glucose loss factor versus the demineralization factor to evaluate the influence of the electrolyte nature on the demineralization process performances. It was observed that, for a fixed demineralization factor, the glucose loss factor (comprised between 4 and 5 % for a demineralization factor of 90 %) increased with the ion hydration due to the higher contribution of the glucose convection flux.

Many processes used across, for example the cosmetics, pharmaceutical, food and chemical industries involve two-phase liquid–liquid interactions. The quality of liquid–liquid emulsification systems may be related to the droplet size distribution. The population balance equation (PBE) can be used as a modelling tool when accurate description of the dispersed phase is required. Still, the key challenge with the formulation of predictive population balance (PB) models is experimental determination of unknown breakage and coalescence functions. The complexity in the processes and phenomena governing the changes of dispersed systems makes the derivation of the corresponding models a significant challenge. The present study considers a PBE optimisation problem to allow parameter identification to experimental data. The experimental data are measured for a breakage dominated liquid–liquid emulsification system in a stirred tank. Parameter identifications to the breakage frequency models proposed by Coulaloglou and Tavlarides,[26] Alopaeus et al.[28] and Baldyga and Podgorska[27] are performed. The PBE is numerically solved using the high-order least-squares method. Moreover, the nonlinear parameter identification algorithm is based on the minimisation of the residual between the experimental data and the numerical solution in a least-squares sense. The problem has been implemented in the programming language MATLAB where the fmincon function has been used. Parameter estimation can sometimes be straight forward, for instance when the process and formulated model are relatively simple and sufficient data are available. These conditions are not always met, which may result in difficulties in determining accurate parameter values. A thorough statistical analysis is required in order to explore the actual accuracy of the estimated parameter values. The present study presents a relative comprehensive statistical study of the fit compared to what has been provided in previous PBE parameter estimation studies. Moreover, the optimisation algorithm and challenges associated with parameter estimation are discussed. The present study revealed, by systematically assessing the problem formulation and the fit, that a better understanding of the model and more successful parameter estimation can be achieved, or a limitation of the model is unveiled.

The breakage frequency and daughter size distribution functions by Coulaloglou and Tavlarides[1] are frequently adopted closures in population balance (PB) modelling. A survey of the extensions and modifications of the Coulaloglou and Tavlarides[1] breakage frequency function is provided. Furthermore, the daughter size distribution functions within the statistical category, herein the model proposed by Coulaloglou and Tavlarides[1], are outlined. Most of the breakage models available in literature commonly assume binary breakage only. Thus, the daughter size distribution function suggested by Diemer and Olson[2] is of interest as higher order breakage can be modelled. The breakage closures are evaluated solving the population balance equation (PBE) for a liquid–liquid emulsification system in a stirred tank. The results obtained from a least-squares solver are compared with the experimental data when available.

International audience; A detailed study of the effects of individual bubbles at high gas flow-rate has shown, that the dominant influence on skin friction over a solid sphere is the bubble volume in compared to bubble frequency. Nevertheless the bubble frequency is very important in case of low gas flow-rate. Referring to bubbles produced by a gas distributor, statistical and spectral analyses were performed to study the influence of bubbling on exposure time and magnitude of fluctuations. Referring to a calibrated bubble train, the existence of critical frequency is demonstrated. A bubble with larger volume and a mobile, oscillatory surface generates larger velocity gradient. In the case of gas distribution, histograms of the velocity gradient for a 2 mm glass sphere creating bubble coalescence reveal the maximum exceeds 48 000 s−1 in the front zone and 2000 s−1 in the rear zone (θ = 180°). For 5 mm plastic spheres creating bubble break-up, the maximum of the velocity gradient is only 8100 s−1 for the front part of the sphere and 2000 s−1 in the rear zone.

Improvement of mixing can lead to an enhancement of photobioreactors productivity, provided that the adverse effect of shear forces is kept below the fragility- threshold of cells. Implementation of a swirling decaying flow induced by a tangential inlet in an annular photobioreactor was investigated. The study focused on a compromise solution between the mixing and the resulting shear stress, and various hydrodynamical characteristics were measured for five types of tangential inlets and three Reynolds number values. Comparison with a pseudo-axial flow induced by a radial inlet indicates that swirling flows are suitable in the particular application of microalgal cultures. L'amelioration du melange peut permettre une meilleure productivite des photobioreacteurs, dans la mesure ou l'effet indesirable des contraintes de cisaillement est garde en-dessous du seuil de fragilite des cellules. On a etudie l'effet d'un ecoulement declinant tourbillonnaire induit par une entree tangentielle dans un photobioreacteur annulaire. L'accent a ete mis sur un compromis entre le melange et la contrainte de cisaillement qui en resulte, et diverses caracteristiques hydrodynamiques ont ete mesurees pour cinq types d'entrees tangentielles et trois valeurs du nombre de Reynolds. La comparaison avec un ecoulement pseudo-axial induit par une entree radiale indique que les ecoulements tourbillonnaires conviennent a l'application particuliere des cultures de microalgues.

International audience; The aim of the work was to improve the understanding of the role of ion hydration on the transfer during nanofiltration of saccharides. More precisely, it consisted in evaluating the physical relevance of the dehydration assumption to explain the increased transfer of saccharides in presence of electrolytes. Experiments were carried out using saccharides (xylose, glucose) and electrolytes containing ions of different hydration levels (NaCl, Na2SO4). The Filmtec NF membrane (previously referred to as NF45) was used. Unlike saccharide/NaCl solutions, Na2SO4 had a weak influence on the saccharide transfer. This means that the impact of the electrolyte on the transfer of saccharide was strongly affected by the ions retention. Indeed, SO42‐ ions were much more often retained than Cl‐. Thus, an enhanced saccharide transfer was expected as the electrolyte concentration in the permeate was high. The physical relevance of the assumed dehydration was evaluated. The decrease of the saccharide radius was determined from the mass transfer modelling. It was shown that the decrease was physically relevant with the dehydration phenomenon since this decrease corresponded to a fraction of the water molecule (2–3 %). Next, the increased transfer was compared with the variation of the apparent molar volume, characterizing the hydration state of solutes, to better understand the mechanisms involved. For a given electrolyte, the transfer increased continuously with saccharide dehydration. This result could confirm that the increase of the transfer could be attributed to the saccharide dehydration caused by the electrolyte.

International audience; Cette étude expérimentale décrit l'effet d'un agitateur sur l'hydrodynamique et le transfert de matière à l'intérieur d'un contacteur airlift à boucle interne. La contribution des deux éléments moteurs (gaz et agitateur) est identifiée. Suivant les conditions de fonctionnement, ou bien ces deux effets s'ajoutent et favorisent la circulation du liquide ou bien ces effets sont opposés, la vitesse du liquide est alors réduite. Par contre, en ce qui concerne le transfert gaz—liquide, l'utilisation de l'agitateur est bénéfique puisque, pour certaines conditions opératoires, le coefficient de transfert est multiplié par 4 par rapport à celui obtenu sans agitation. L'analyse des diverses contributions énergétiques dans l'appareil montre que la présence de l'agitateur est justifiée uniquement dans les cas où le débit de gaz doit rester faible.

International audience; A model is examined in order to predict the behaviour of a granular bed made with conductive particles subjected to an inductive electromagnetic field. The model shows how heat generated in the bed can be described by its electric impedance for the high‐frequency generator required for inductive heating. Once the relationship between electrical characteristics and power dissipation has been established, comparisons between experimental and theoretical results are presented and the validity of the model is discussed.

International audience; A process coupling absorption of a gaseous pollutant in an organic phase and biodegradation was considered to treat hydrophobic volatile organic compounds (VOC). The purpose of this work was to choose the best solvent for the absorption of some VOC (dimethylsulfide, dimethyldisulfide, and toluene) and to examine solvent biodegradability as well as VOC biodegradation by activated sludge. Some experiments were carried out on some selected solvents leading to select di-2-ethylhexyl-adipate (DEHA) and poly-di-methyl-siloxane (PDMS) for their high absorption capacity. Biodegradation experiments showed that toluene and DMDS can be removed in solvent on water emulsions, while DMS removal by biodegradation remains to confirm owing to its high volatility. However, experiments showed DEHA biodegradation, contrarily to PDMS which was therefore selected for subsequent experiments.

International audience; Nous présentons un modèle de transfert pour la distillation catalytique utilisant les équations de Maxwell-Stefan et incluant la diffusion effective dans le catalyseur poreux. L’écriture et la résolution de ce modèle ont été adaptées à son inclusion dans un simulateur commercial. Il est donc robuste et souple. Nous étudions l’infl uence des caractéristiques du catalyseur, de la confi guration de la colonne, de la non-idéalité du mélange et de la qualité de l’échange liquide/vapeur. La conclusion principale de ces essais est l’existence d’un optimum de fonctionnement notamment pour le taux de refl ux et l’emplacement du catalyseur.

International audience