Caracterización reométrica de polvos de uso industrial y de la respuesta de un reómetro de diseño propio.

Los polvos son materiales con un comportamiento mecánico complejo. Muchas veces son vistos como un conjunto de partículas, pero en realidad son una mezcla de sólidos en forma de partículas, líquidos (agua) en su estructura o en la superficie de partículas, y gases (aire entre partículas). Con ello su comportamiento y sus características son difíciles de prever y de analizar. Pero es importante de entender y ser capaces de medir todas las propiedades que caracterizan el comportamiento de un polvo (compresibilidad, fluidez, hidrofobicidad, permeabilidad, cargas electrostáticas…). Por lo tanto, los polvos pueden comportarse como una entidad sólida, deformándose de manera plástica, por ejemplo, fluir como un líquido al ser aireado o ser comprimido como un gas. En este proyecto se ha utilizado el nuevo instrumento GranuDrum y el clásico reómetro FT4 para medir distintos parámetros de diversos materiales (índice de cohesión, ángulo de reposo, BFE, SI, FRI…) con el objetivo de estudiar la fluidez (flowability) de estos materiales, además de analizar las diferentes informaciones proporcionadas por los parámetros medidos y encontrar las similitudes entre ambos resultados obtenidos con ambos instrumentos. Finalmente, se ha realizado una pequeña parte de simulación para conocer el funcionamiento del Software LIGGGHTS basado en el método DEM y los usos que se le puede dar en el campo de los polvos. <br /

Etude de l'empoussièrement des poudres par un test de fluidisation

National audienceThe aim of this study is to use a fluidized bed as a dustiness test based on entrainment and elutriation phenomena for a reconstructed model system. Once the operating conditions were identified, a simple phenomenological model was established, able to predict the amount of dust initially present in a mixture. In order to do that, a parametric study was conducted with bimodal powder mixtures. Thus, large particles simulate the powder and the fine dust. The experimental study was carried out with Geldart A and C particles, in a fluidized bed. Furthermore, the influence of some intrinsic and extrinsic parameters of the bulk on the dust emission was studied. Subsequently, different models present in the literature were tested in order to predict the dustiness. This comparison allowed choosing the model of Santana et al. (1999) which showed a better match with the results of this study.L'objectif de ce travail est d'utiliser un lit fluidisé comme test d'empoussièrement en se basant sur les phénomènes d'entraînement et d'élutriation pour un système modèle reconstitué. Suite à l'identification des conditions opératoires, un modèle phénoménologique simple capable de prédire la quantité de poussière initialement présente dans un mélange, a été établit. Une étude paramétrique a été réalisée avec des mélanges de poudres et de poussières de tailles différentes ; ainsi, les grosses particules simuleront la poudre et les fines les poussières. Par ailleurs, nous avons étudié l'influence de certains paramètres intrinsèques du mélange sur l'empoussièrement et testé différents modèles rencontrés dans la littérature permettant de prédire l'empoussièrement. Cette comparaison a permis de choisir le modèle de Santana et al. (1999) qui a montré une meilleure adéquation avec les résultats de cette étude

The Effects of the Toxicity of (Fe (so4).7H2o) on the isolated Mitochondria from the brain of rat

Introduction: Iron, through the reaction of Fenton, generates free radicals such as active oxygen radicals and activates the oxidative stress pathway. The oxidative stress due to the increased iron level in the brain regions plays &nbsp;an important role in creation of neurodegenerative diseases. Methods and Results:In this study, the mitochondria of the brain tissue of Wild Wistar Rat isolated from various centrifuge rounds and with the concentrations of Fe (so4).7H2o were incubated at 30 and 60 minutes. To determine IC50 Fe (so4).7H2o, the mitochondrial survival ratio was measured by MTT test. Mitochondrial suspension with the concentration of 0.5 mg protein/ml at various concentrations of Fe (so4).7H2o was placed in a shaker incubator at 37° C for 30 and 60 minutes. Then the activity of mitochondrial complex 2 and the formation ratio of reactive oxygen species was investigated. The results showed that IC50 ratio for Fe (so4).7H2o was 20 and 5 μg/ml at 30 and 60 minutes, respectively, and mitochondria incubation isolated from the brain tissue of the rat with Fe (so4).7H2o can disrupt be the electron transfer chain and significantly increases the formation of reactive oxygen species compared to the control group (P &lt;0.001). Conclusions:The findings of this study indicate that Fe (so4).7H2o disrupts electron transfer chain in the mitochondria and causes increasing ROS production. This excessive increase of ROS can activate the oxidative stress pathway and ultimately activate the cell toxicity pathways

Etude des propriétés physiques et comportementales des peintures en poudre en relation avec le procédé d'application de l'industrie automobile

La législation européenne plus sévère en terme d'émission de composés organiques volatiles (COV), a motivé la plupart des constructeurs automobiles à remplacer les conventionnelles peintures solvantées par des peintures à faibles émissions comme les peintures en poudre, qui présentent d'importants avantages sur le plan environnemental et économique. Ce travail traite de l'incidence des caractéristiques physiques des apprêts poudre (granulométrie, masse volumique) sur leur comportement vis-à-vis des étapes clés du procédé d'application industriel (coulabilité, fluidisation, prise de charge électrostatique). Le développement de techniques de caractérisation spécifiques (rhéomètre à poudre, colonne de fluidisation/désaération) a mis en évidence le rôle déterminant de l'agent de fluidité sur la cohésivité des peintures en poudre et leurs performances lors des opérations de fluidisation ou de transport pneumatique du procédé. Ce travail est également un point de départ à une compréhension de l'abrasion des particules lors du transport pneumatique et des phénomènes de prise de charge électrostatique des particules au cours de l'application.As a consequence of recent restrictions in European legislation, concerning the volatile organic compound emissions (VOC), has motivated almost every car-makers to replace the conventional solvent-borne paints by new low emission paint systems, including powder coating systems, which present important advantages from ecological and economical points of view. This study is about the impact of the physical characteristics of powder paintings (particle size distribution, density) on their behavior in the important stages of the industrial application process (flowability, fluidization, electrostatic charging). The development of specific characterization techniques (powder rheometer, column of fluidization/de-aeration) highlights the determining effect of flow additive on the. cohesivity of powder paintings and their performances during the operations of fluidization or pneumatic conveying of this process. This work is also a beginning to an understandingof particles abrasion during the pneumatic conveying and phenomena of particles electrostatic charging during the application.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Formulation of a water-in-oil emulsion encapsulating polysaccharides to improve the efficiency of spraying of plant protection products

International audienceW/O emulsions were formulated with a vegetable oil and a water phase containing a polysaccharide and glycerol in order to reduce the loss of a phytosanitory product during its spraying on plants and therefore the amount used. Different kinds of polysaccharides were tested (CMC, guar and xanthan) and two kinds of surfactants were used (lecithin and PGPR). The stability of the emulsions was determined by different techniques bottle test, optical microscopy, laser granulometry and differential scanning calorimetry - whose principle is based on the correlation between the freezing temperature of the droplets and their radius. From the experiments performed by varying different parameters, a formulation of a suitable emulsion was developped 3% of CMC in the water phase, 50-70% V/V of water, 10-12% of PGPR. The release within a few minutes of the required amount of CMC in water checked by conductivity was obtained by adding another surfactant commercially named Cynthiorex

Etude des interactions formulation - rhéologie des suspensions concentrées en vue de leur séchage par pulvérisation

Le séchage par pulvérisation des suspensions est une opération énergétiquement coûteuse et requiert le développement de nouveaux procédés. Ce travail concerne le séchage par pulvérisation des suspensions concentrées de CaCO3. Deux procédés de séchage ont été étudiés : par pulvérisation classique et dans un lit fluidisé de particules inertes. L'utilisation adéquate de dispersant permet de préparer des suspensions pulvérisables et d'optimiser leur siccité. Le procédé classique conduit à l'obtention de grains sphériques de bonne coulabilité. Le séchage en lit fluidisé de billes de verre accroît fortement la surface de transfert de masse et de chaleur, et produit une poudre très fine, grâce aux chocs engendrés par le mouvement du lit fluidisé, permettant un broyage de l'enrobage. L'analyse du procédé est approfondie par l'étude à l'échelle locale : la cinétique de séchage, par la mise en place d'une veine de séchage, et le phénomène d'adhésion par la conception d'un test de cisaillement.Spray drying of suspensions often leads to high energy costs and requires the development of new processes. This work deals with spray drying of CaCO3 concentrated suspensions. Two processes of drying were studied : traditional spray drying and drying in a fluidized bed of inert particles. Through the adequate use of dispersant, it is possible to prepare pulverizable suspensions and to optimize their dryness. The traditional process gives spherical particles with a good flowability. Spray drying in a fluidized bed of inert glass beads strongly increases the surface for mass and heat transfer, and gives a very fine powder. Due to intensive interparticle shocks, induced by the fluidized bed movement, the crushing of the coating occurs. The process analysis is deepened by local scale studies: the drying kinetics, with the installation of a drying duct, and the adhesion phenomenon with the shear test setup.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Effect of Ca(OH)2 on the chemical precipitation of phosphates from solutions of a low concentration in fluidized bed reactor: hydrodynamic evaluation

In this present work, the phosphate is precipitated chemically at 22°C using synthetic water at different Ca/P molar ratios ranging from 0.5 to 12. Various parameters have been optimized to a range of realistic conditions relative to chemical precipitation of phosphates (superficial velocity of fluid Uf = 0.58 cm/s, [PO4] = 10 mgP/L). A hydrodynamic evaluation of the chemical precipitation of phosphates in a fluidized bed reactor, contains sand particles as a substrate for the precipitate layer, from an ascending water stream using Ca(OH)2 was made. As a function of Ca/P, the occurrences domains of the different hydrodynamics parameters are given. The effect of the Ca(OH)2 on the porosity and the velocity of the fluidized bed it also presented. For the inlet Ca/P molar ratio, was lower than 4, the phosphate removal efficiency is 35~74%. While, for the suitable conditions of Ca/P&gt;4, the phosphate removal efficiency ranging from 75 to 92%. It is found that the [Ca] and [PO4] significantly affect the velocity of fluidization and the porosity of the fluidized bed. In this connection, the experimental data of several authors provide a useful starting point for our comparisons.Keywords: Chemical precipitation - Fluidized bed - Phosphate - Porosity - Molar rati

Atomization of molten materials for particle coating: Prediction of mean droplet size for two-Fluid nozzles

Coating is the process of covering solid particles' surfaces with a homogeneous layer of a coating agent comprising one or multiple components. For processes carried out in fluidized beds, coating is achieved by spraying the coating agent on the particles in suspension. The aim of the present work was to study the atomization of molten materials prior to their application to powder coating in fluidized beds. Several external mixing binary nozzles were used for the atomization of a stearic- palmitic acid mixture and different polyethylene glycol grades (1000, 1500, 2050, 4000, and 6000) at different temperatures (60°C, 70°C, 80°C, and 90°C). The droplet size distributions, from which experimental mean droplet sizes were calculated, were measured by the laser diffraction technique. Subsequently, mean droplet sizes were satisfactorily modeled using different correlations reported in the literature. For a given nozzle, it was found that some fitting parameters were constant for all the polyethylene glycol grades, whereas others showed a dependency with the material viscosity. This latter was the property with the highest variability over the experimental domain. The fitted models did not provide a good prediction of the experimental data corresponding to different nozzle configurations or molten materials; therefore, new fittings were performed. This fact highlights the difficulty in obtaining models at least applicable to the atomization of molten materials.Fil: Pacheco, Consuelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universite de Technologie de Compiegne; FranciaFil: Piña, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Saleh, Khashayar. Universite de Technologie de Compiegne; Franci

L'eau en poudre

Cette étude a pour objet l'élaboration de poudres sèches en apparence mais qui contiennent une quantité importante de matière active sous forme liquide. Ainsi, l'eau en poudre (à base de silice pyrogénique hydrophobe) peut incorporer jusqu'à 98% d'eau en masse. Les particules ont une taille moyenne d'environ 150 m et présentent une bonne coulabilité. La libération de l'eau s'effectue par évaporation ou par pression mécanique. La structure des particules a été étudiée par microscopie électronique après cryofracture ou sublimation de l'eau. Les particules individuelles se composent d'une gouttelette d'eau enrobée par une coquille de silice. Il existe deux modes de fabrication: les procédés à fort taux de cisaillement de type mixeur et les procédés de pulvérisation de type granulateur. La qualité du produit dépend de la contribution énergétique du procédé et de l'angle de contact liquide/particule (évalué par intrusion d'eau). Les perspectives d'applications sont nombreuses.Water-rich powders, also called "dry water", containing up to 98% (by weight) of water and still maintaining the same flow properties as a dry powder were prepared by a simple mixing process. Dry water particles are a very convenient carrier system that can be easily produced at industrial scale. Water can be released by evaporation or under mechanical stress. The structure of individual particles bas been studied by electronic microscopy after freeze fracture or water sublimation. Each particle consist in a micrometric water droplet (average diameter of 150 m) surrounded by a network build up by association of hydrophobic fumed silica particles. Two types of mixing processes were used: high shear processes and atomization processes such as granulators. The quality of the final product depends on the energetic contribution of the process and on the solid/liquid contact angle (evaluated by water intrusion). Potential applications are numerous in the food, pharmaceutical, and cosmetics industry.COMPIEGNE-BU (601592101) / SudocSudocFranceF