Montpellier, France
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Andre C.,French National Institute for Agricultural Research | Andre C.,Laboratoire Of Genie Des Procedes | Demeyre J.F.,Toulouse 1 University Capitole | Gatumel C.,Toulouse 1 University Capitole | And 2 more authors.
Powder Technology | Year: 2014

This study investigates the bulk agitation of free flowing or nearly cohesive granular materials in a pilot-scale planetary mixer equipped with a torque measurement system. Our major aim is to investigate the effect of the flow properties of several powders, as well as that of the set of experimental conditions (engine speeds NR and NG), on the power consumption of such a mixer. Thanks to a previous dimensional analysis of the system, this influence is studied through the variations of the power P with a characteristic speed uch, defined from engine speeds and geometrical considerations. Two relationships involving dimensionless numbers are derived to describe the agitation process: NpG=fFrG,NRNG and NpM=f(FrM). For free flowing powders, a linear relationship is observed when plotting P against uch, and the resulting process relationship linking dimensionless numbers is NpM=15FrM -1. In the more cohesive case, power values vary around an average value (P=54W) and the resulting process relationship is NpM=1.8072FrM -1.467. It is argued that the exponent in the representation of NpM against FrM may be a useful parameter for powder classification, and should be linked to powder rheometrical considerations. © 2014 Elsevier B.V.

Andre C.,French National Institute for Agricultural Research | Andre C.,Laboratoire Of Genie Des Procedes | Demeyre J.F.,Albi-Carmaux School of Engineering | Gatumel C.,Albi-Carmaux School of Engineering | And 2 more authors.
Chemical Engineering Journal | Year: 2012

Powder mixing is crucial to the processing stages in many industries. However, there is still a paucity of information about the effects of process parameters on mixing efficiency. This paper investigates the homogenization of free flowing granular materials with a planetary mixer, TRIAXE®, examining the effect of the ratio of impeller rotational speeds (NR/. NG) on the mixing process. First, a dimensional analysis carried out with mixing time and power consumption as target variables, established that both a Froude number and NR/. NG controlled the process for the given free flowing powder mixture and planetary mixer. A further theoretical approach also suggested that these two dimensionless ratios which control hydrodynamics can be reduced to a modified Froude number providing that the maximum linear velocity achieved (uch) by the planetary mixer is introduced, replacing the dual impeller rotational speeds (NR and NG).Mixing time and power experiments validated the above hypothesis. Homogeneity tests performed in a granular media showed that the length of path achieved by the impeller governs the obtained mixing level. Finally, this work reflected that (i) dimensional analysis was also well suited to model powder homogenization with a planetary mixer. (ii) A concise set of dimensionless numbers governing mixing phenomena can be deduced through the introduction of the maximum linear velocity as obtained in previous studies on gas/liquid and miscible liquids mixing processes. © 2012 Elsevier B.V.

Khellaf N.,Annaba University | Bouhelassa M.,University of Mentouri Constantine | Zoulalian A.,Laboratoire Of Genie Des Procedes
Separation Science and Technology (Philadelphia) | Year: 2014

Sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, was removed from its aqueous solution by foam fractionation in an emulsion venturi, a gas-liquid contactor functioning in self-aspiration. The performance of the reactor was evaluated by measuring the self-aspired gas flow and the mass transfer coefficient in the presence and the absence of SDBS. Data confirmed that both the gas flow self-aspired and the mass transfer coefficient increased with increasing the recirculated liquid flow. However, the presence of SDBS decreased the mass transfer capacity of the reactor influencing self-aspiration capacity in a positive manner. The percentage removal of SDBS in the emulsion venturi increased with increasing the recirculated liquid flow; at the highest liquid flow value used in this work (1.4 m3/h), 96% of SDBS was removed from the solution after 20 min of foam operating. The process was dependant on initial surfactant concentration. Neutral pH and temperature of 25°C were the optimal conditions for the foam separation of SDBS in the emulsion venturi. © 2014 Copyright Taylor and Francis Group, LLC.

Khiari K.,Laboratoire Of Genie Des Procedes | Khiari K.,Polytechnic School of Algiers | Mahiout M.,Laboratoire Of Genie Des Procedes | Mahiout M.,Polytechnic School of Algiers | And 4 more authors.
6th International Conference on Thermal Engineering Theory and Applications | Year: 2012

Solid-liquid equilibria (SLE) data are essential for the design of purification processes for area chemicals and for the development of separation processes. In order to relate the nature of a given system to its thermodynamic properties, it is necessary to define the structure and the molecular interactions. Experimental data available in the literature concern essentially systems composed either by small molecules or by one heavy and one small component. New systems measured experimentally can enhance the SLE database for heavy organic mixtures. Thus, SLE of three binary organic mixtures formed by a polycyclic aromatic hydrocarbon (acenaphtene or phenanthrene or fluoranthene) in solution with 1- octadecanol were measured using differential scanning calorimetry (DSC). This technique is one of the most effective methods for mapping liquid-solid phase diagrams for binary systems. Activity coefficients of each polyaromatic compound in solution with the alcohol were determined and the thermodynamic behaviour of these compounds in mixtures was studied. The strongly non-ideal behaviour shown by alcohol and polycyclic aromatic hydrocarbon mixtures can be attributed to hydrogen bonding of the alcohol molecule. The mixtures properties are calculated from pure compounds properties and results obtained allow us to analyze the influence of components structure on mixtures thermodynamic properties. In all systems studied, the components are non-miscible in the solid phase and exhibit a simple eutectic diagram. The experimental data were well correlated by either NRTL, Wilson equations, UNIQUAC and UNIFAC models. The comparison between experimental and predicted solubilities for the three models tested was quite reasonable with a good average, particularly in the case of using UNIQUAC model. The deviations between experimental and predicted results increased according to the number of polyaromatic cycles.

Ait Mouheb N.,Ecole des Mines de Nantes | Ait Mouheb N.,Laboratoire Of Genie Des Procedes | Malsch D.,Institute For Photonische Technologien | Montillet A.,Laboratoire Of Genie Des Procedes | And 2 more authors.
Chemical Engineering Science | Year: 2012

Mass transfer within the T-shaped and cross-shaped micromixers has been studied using CFD and confocal laser scanning microscopy methods. The concentration profiles, based on flow regimes, were used to compare the T- and cross-geometries. The cross-shaped micromixer tends to intensify the mixing and this is occurring for lower flow rates in comparison to the T shape. The improvement made by the cross geometry is attributed to the stronger vortex stretching and high shear rate, which reduces the liquid transfer length. The presence of a single outlet in the T-shaped micromixer induces a smaller degree of freedom for the fluid. A higher pressure drop is calculated in T-shaped micromixer than in cross-shaped micromixer. © 2011 Elsevier Ltd.

Venault A.,Montpellier University | Vachoud L.,Laboratoire Of Genie Des Procedes | Bouyer D.,Montpellier University | Pochat-Bohatier C.,Montpellier University | Faur C.,Montpellier University
Journal of Applied Polymer Science | Year: 2011

Composite chitosan/activated carbon hydrogels were prepared with the vapor-induced phase separation process. A rheometric study was performed with a factorial fractional design to determine the formulation and process parameters significantly influencing the mechanical properties of the gels. The results revealed that three factors played a key role in the storage modulus of the gels. According to the model, these factors could be classified with respect to their relative influence on the storage modulus in the following descending order: chitosan concentration > gel time of exposure to ammonia vapors > temperature of the reactor. Increasing these parameters led to an increase in the physical crosslinking density within the matrices and resulted in a reinforcement of the mechanical properties of the hydrogels. Two interactions were also shown to be significant and promoted the formation of supplementary junction zones within the matrix: the first one corresponded to the interaction between the chitosan concentration and the exposure time to ammonia vapors, and the second one concerned the interaction between the chitosan concentration and the temperature of the reactor. A second-order model was obtained from statistical analysis. Because of the determination coefficient (89.4%) and the P value related to the lack of adjustment of the model (0.043), which was associated with a 95% confidence level, this model could be considered to be of good quality. Three gels were used to validate the model, and good accuracy was obtained. The maximum elastic modulus was obtained with the highest chitosan concentration [4% (w/v)], the highest temperature in the gelation chamber (50°C), and the longest time of exposure to ammonia vapors (24 h). © 2010 Wiley Periodicals, Inc.

Elosrouti R.,Université Ibn Tofail | Sallek B.,Université Ibn Tofail | Chaair H.,Laboratoire Of Genie Des Procedes | Digua K.,Laboratoire Of Genie Des Procedes | Oudadesse E.H.,Laboratoire des science des Materiaux
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2014

Le comportement sous atmosphère humide des mélanges initiaux de la calcite et du di-ammonium hydrogénophosphate à différents rapport atomique (Ca/P)initiala été étudié. Lanalyse par diffraction des rayons X (DRX) montre que les produits obtenus ont tous une structure apatitique. Il montre la présence à côté de celle de lapatite, des raies identifiables à la calcite pour des rapports atomiques initiaux supérieurs à 1.50. Par ailleurs, la spectroscopie dabsorption infrarouge (IR) révèle dans les différents cas, la présence autre que les bandes attribuables aux ions PO4 3-dans une apatite, des bandes à 875 cm-1caractéristique des groupements HPO4 2-dans une apatite déficiente en ion calcium. De même, le traitement thermique à 1000°C des poudres synthétisés a mis en évidence que les apatites formées sont non stœchiométriques. Les analyses chimiques montrent, par ailleurs, que lorsque le rapport atomique Ca/P du mélange initial est inférieur à 1.50, lapatite formée a un rapport atomique Ca/P égal à 1.58. Par contre, lorsque le rapport Ca/P initial est supérieur à 1.50, le produit formé est biphasique et a un rapport atomique Ca/P de 1.62. Ce rapport est dû essentiellement à la présence dun excès de CaCO3dans le mélange initial (DRX, IR). Mots clés Apatite; atmosphère humide; calcite; hydrothermal; synthèse Abstract The behavior, in a humid atmosphere, of the initial mixtures of calcite and diammonium hydrogenophosphate at different atomic ratio (Ca/P) was studied. The X-ray diffraction (XRD) analysis shows that all the products obtained have apatite structure. For initial atomic ratios greater than 1.50, the XRD analysis shows the presence of reflections different from those of apatite, which may be attributed to calcite. Analysis by infrared (IR) absorption spectroscopy allows to distinguish between the two cases: in addition to the presence of bands due to the PO4 3-ions in apatite further bands at 875 cm -1characteristic of HPO4 2-in apatite deficient with respect to calcium ions are observed. Similarly, the powders synthesized by heat treatment at 1000°C showed that nonstoichiometric apatites are formed. Chemical analyses show, that when the atomic ratio Ca/P of the initial mixture is less than 1.50, the apatite formed has an atomic Ca/P ratio of 1.58. When the initial Ca/P ratio is greater than 1.50, the product formed is biphasic and has an atomic ratio Ca/P of 1.62. This result is mainly due to the presence of an excess of CaCO3in the original mixture (XRD, IR). © 2014 Copyright Taylor and Francis Group, LLC.

Chroqui W.,Moulay Ismaï University | Akhiyat I.,Moulay Ismaï University | Belouafa S.,Moulay Ismaï University | Chaair H.,Moulay Ismaï University | And 3 more authors.
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2010

Oxygenated phosphocalcic apatite is an apatite with an excellent biocompatibility, osteoconduction, and having antiseptic properties able to limit the proliferation of the micro-organisms in the site implementation, without using an antibiotic. However, the synthesis of this apatite encounters several difficulties. On one hand, it depends on many factors such as pH of the reaction, atomic ratio Ca/P of the reagents, temperature of the reaction (T), duration of reaction (D), and concentration in ions calcium ([Ca2+]). On the other hand, the product to be developed must have a chemical composition allowing it a dissolution speed in compliance with the bone neoformation and having antiseptic properties. Aiming to control the synthesis of these apatites and to limit the number of experiments necessary to this study, we applied the methodology of the experimental designs. The mathematical models elaborated in this study allowed us to forecast the optimum conditions of the oxygenated phosphocalcic apatite synthesis. Copyright © Taylor & Francis Group, LLC.

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