Hydrodynamique et transfert gaz-liquide dans un réacteur verlifix rempli de différents garnissages

This study concerns several Verlifix three phase reactors formed by the association of a jet venturi upper on a column filled with different solid packings. The gas and liquid flows are downstream cocurrent. Four packings are studied: glass Raschig rings, Coming's monolithic ceramics, microporous alumina pellets and glass beads. For these packings and gas and liquid flow rates fixed, we measure the hydrodynamic characteristics (flow regime, liquid dynamic retention, pressure drop) of the fixed bed and gas-liquid mass transfer conductance of the whole reactor, then we specify the influence of the operative conditions and the type of packing.     

Etude numérique et paramétrique de la combustion de particules d'aluminium

Several numerical models have been investigated to study the reactivity of aluminium particles coming from the combustion of solid propellants in spatial launchers. The Law model has been rapidly selected as it yields a continuous model from an aluminium drop to an oxide drop. The model also gives the residue size at the end of the combustion process. This could explain the scaling observed in the rocket engines. In order to study the coupling between the flow and the combustion, the combusion of aluminium drops has been widely analyzed with 0D computation. The main mechanisms of the combustion process have been identified.     

Etude des propriétés des films préparés par evaporation des solutions d'un polymére dans différents solvants

Films of a plasticized random terpolymer were prepared by evaporation of solutions in several solvents. The glass transition temperatures of the films were determined and were found to follow the Fox's equation. Their tensile modulus, measured just below the glass transition temperature, was found to depend on the residual solvent content of the films.     

Etude de l'oxydation du pentachlorophénol dans différentes géométries de réacteurs à ultrasons de haute fréquence

The determination of the key geometric parameters used for high-frequency sonoreactor modeling has been studied. The methodology allowing the characterization of the different reactors built in our laboratory has been defined. The methods are: calorimetry, determination of the residence time distributions, the observation of the chemiluminescence of luminol and the degradations of a prototype molecule: pentachlorophenol. After characterization of the studied reactors, it seems that volumetric power, with equivalent emitting system, is the major parameter of the reactor's performance.     

Etude calorimétrique de la rétention de l'eau par les résines novolaques

Moisture retention in various substituted novolake resins has been investigated by differential scanning calorimetric analysis. Water molecules leave the polymer network in a two step drying process. The first one occurs at T > T_g, the second at T < T_g and requires an external energy supply. The energy recorded in the second drying step indicates the presence of a dipolar link.     

Etude cinétique de la déshydrtation du sulfate de cuivre par thermogravimétrie et thermogradientimétrie

A new type of thermobalance has been built, Sample temperatures have been determined by a new technique called “thermogradientimetry”. A special crucible assembly allows control of the atmosphere surrounding the sample. Kinetic results for the three successive stages in the dehydration of copper sulphate indicate that the reactions involved are of zero order. The apparent activation energy for each stage of the dehydration has been avaluated under isobaric conditions for different water vapor pressures.     

Etude de la viscosité dynamique complexe de quelques mélanges de polybutène-1 et de polypropène

Studies have been made on the dynamic oscillation and static properties in the molten state of blends from polybutene-1 and polypropene. Measurements were made with a balance-rheometer system Dr. Kepes and a capillary viscosimeter. Three experimental parameters, η₀, τ₀ and h have been determined. Steady shear and oscillatory shear viscosity data have been compared. A plot of intrinsic viscosity vs. composition of blends shows a minimum. Variation of η₀ and τ₀ with temperature follow the Arrhenius law but h does not depend on temperature.     

Contribution à l'étude de la dégradation photochimique du caoutchouc chloré par la lumière ultraviolette solaire. I. Etude physicochimique de i'évolution de la masse moléculaire

The esters were prepared by the acryloylation or methacryloylation of 1-formylamino-2,2,2-trichloroethanol and 1-(N-formylmethylamino)-2,2,2-trichloroethanol and characterized by the boiling point, melting point, and the IR spectra, The temperature of spontaneous thermal decomposition, the density, limiting oxygen number for continuous combustion and the glass transition temperature of the homopolymers of the titled compounds were also determined.     

Matériaux composites à base de bois rétifié, III. Etude de l'influence de la granulométrie des charges lignocellulosiques

Different composite materials, with retified or natural poplar and polyester resin were prepared by molding. The influence of the filler granulometry on certain physicochemical (density, humidity, hardness) or mechanical properties of the materials was studied. The density and the increase of mass in humid atmosphere were always found to be less when the wood was thermally treated. On the other hand, the hardness of the composites made from natural poplar was much higher. The mechanical properties were found to be weak when the wood was retified. When the wood was thermally treated, it was possible to optimise the three parameters, namely, density, water retention capacity and mechanical properties. The optimal granulometry of poplar was determined between 0.75 and 1.5 mm. The results obtained are discussed considering the physico-chemical properties of the different varieties of wood studied and the interactions which exist between the polar resin and the wood.     

Etude PAR spectroscopie de la deshydratation de dérivés de l'alcool polyvinylique: Mise en evidence d'une répartition séquentielle des substituants

The dehydration of sulfopropylic and alkyl derivatives of poly(vinyl alcohol), with varying degrees of substitution, was observed using ultraviolet and visible spectroscopy. The dehydration reactions were carried out in a KHSO₄/heptane system kept under nitrogen at 100°C. Spectroscopic results show that definite sequences of conjugated double bonds are formed. The distribution of the number and length of these conjugated sequences was determined and compared with the theoretical values obtained assuming statistical distribution of the substituents. From this work it is concluded that: (1) the grafting of propane-sultone onto poly(vinylalcohol) molecules does not follow a random, statistical pattern, rather the reaction is sequential, i.e., of a “zip” type. The product molecules contain blocks of sulfopropylic-substituted vinyl alcohol groups. (2) The grafting of alkyl groups onto the poly(vinyl alcohol) molecules also occurs in a sequential manner. Results obtained show that the polymer chains contain at least two unreacted hydroxyl functions between each substituent alkyl group; this is in agreement with x-ray studies of these derivates. Further evidence of an ordered distribution of the substituents along the polymer chain is given by the heterogeneity in the compositions of the substituted polymers. The difference in the observed structures of the two substituted polymers demonstrates the importance of the nature of the substituents in determining the reaction mechanism. It is concluded that the structural differences observed are due to differences in the solubility of the sulfopropylic and alkyl reactants in the original reaction medium, and the hydrophilic and hydrophobic character of the sulfopropylic and alkyl substituents in the polymer.     

Modélisation Mathématique de la Décantation de la Boue Rouge

A good performance of the solid‐liquid unit operation is required for the economical exploitation of the Bayer process. A computational fluid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of flocculated red mud particles, the feed flow rate and the radius of the feed well are critical parameters for the operation of the thickener.     

Applications de la spectrométrie de rayons x à l'analyse de matériaux macromoléculaires. II. Etude de polyéthylènes chlorés en surface

The chlorine concentrations in the range up to about 500 μg.cm^-2 of surface chlorinated polyethylene films were determined by X-ray fluorescence spectrometry. By using appropriate standards, it is shown that the investigated samples can be regarded as thin films only when the energy of the «equivalent» primary X-radiation is high enough. Results allow to estimate (in the range up to about 4 μm) the chlorinated film thicknesses versus duration of the halogenation processes.     

Etude des interactions eau-liaison imide II. Conductivité électrique de la poly-L-proline II selon ses états d'hydratation

The Characterization Of Water – Poly-L-Proline Ii Interactions As A Function Of Water Content Led Us To Study The Electrical Behaviour Of This Polyimidoacide During Hydration. The Static Conductivity Would Be Due To Electronic Charge Carriers Till The Water Content Rises To 8% (G Of Water Per 100G Of Dry Product) I.E., One Water Molecule For Two Carbonyl Groups. Then An Ionic Conduction Mechanism Appears, Which Becomes The Main One Above 18% Of Sorbed Water (I.E., One Water Molecule Per Carbonyl Group). A Conduction Mode Is Proposed For These Different Steps In Hydration.