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Saint-Nazaire, France

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.

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.

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.

Chroqui W.,Moulay Ismai University | Akhiyat I.,Moulay Ismai University | Belouafa S.,Moulay Ismai University | Chaair H.,Moulay Ismai 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.

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.

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