Grandes líneas de la geografía de la Antártida - Por Romualdo Ardissone - Revista Geográfica Americana, XII (Buenos Aires, 1939), 237-256.

Fil: Serris de Canosa, Ana. Universidad Nacional de Cuyo. Facultad de Filosofía y Letra

Centros volcánicos del Domuyo y Payún Matru

Fil: Serris de Canosa, Ada S.. Universidad Nacional de Cuyo. Facultad de Filosofía y Letra

Modelling and Simulation of Acid Gas Condensation in an Industrial Chimney

International audienceCoal power stations as well as waste incinerators produce humid acid gases which may condense in industrial chimneys. These condensates can cause corrosion of chimney internal cladding which is made of stainless steel, nickel base alloys or non metallic materials. In the aim of polluting emission reduction and material optimal choice, it is necessary to determine and characterize all the phenomena which occur throughout the chimney and more especially condensation and dissolution of acid gases (in this particular case, sulfur dioxide SO2)

Modelling and simulation of condensation phenomena of acid gases in an industrial chimney

National audienceCoal power stations as well as waste incinerators produce humid acid gases which condensate in industrial chimneys. These condensates may cause corrosion of the internal cladding made of stainless steels, nickel base alloys or non metallic materials. In the aim of polluting emission reduction and material optimal choice, it is necessary to determine all the phenomena which occur throughout the chimney such as condensation and dissolution of acid gases (in this particular case, sulphur dioxide SO2). The production of energy from fossil fuels (coal, petroleum, natural gas, etc.) brings about the emission of gas containing sulphur compounds (SO2, SO3) as well as chlorine and fluorine compounds. To avoid this atmospheric pollution and its harmful effects (acid rains, impact on the health) due to hydrochloric, sulphuric and hydrofluoric acids produced in the presence of air, it is necessary to steam these flue gases. Nevertheless, a considerable quantity of residual acid gases remains in the gas discharge which also contains large amounts of water vapour. Thus, condensation may occur and by the way an acid attack of the internal cladding of the chimney. This results in high costs of maintenance and a reduction of their structural stability. The knowledge of the phenomena of heat and mass transfer during the condensation of these acid gases in chimney is essential for their conception and materials choice

Suivi en-ligne des procédés de cristallisation en solution en milieux pur et impur par émission acoustique

National audienceMany mechanical and physical processes are associated with the generation of acoustic waves produced by the rapid release of energy from localized sources within a material. Acquiring and processing these waves allows non-destructive control of phenomena such as the extension of cracks in a structure under stress, plastic deformation, phase transitions, etc. Few works were devoted in past to acoustic emission (AE) during crystallization processes. Moreover, most available studies are purely descriptive and do not provide results enabling to quantitatively monitor basic crystallization phenomena (i.e., nucleation, growth, agglomeration, etc.) New results dealing with the monitoring of batch solution crystallization operations are presented here. The acquired acoustic signals are interpreted thanks to the joint monitoring of the continuous phase (Measurement of the solute concentration thanks to ATR FTIR spectroscopy) and of the dispersed phase, thanks to the video in situ acquisition of images of crystals in suspension. It is shown that acoustic emission sensors "perceive" the development of the crystallization process and, in particular, that an early detection of the nucleation of crystals is allowed. Analysing the parameters of acoustic waves is shown to allow separate monitoring of basic crystallization phenomena which remain to be identified. As far as online monitoring of industrial crystallization processes is concerned, the measurements thus obtained open promising perspectives.De nombreux processus mécaniques et physiques s'accompagnent de la génération d'ondes acoustiques dues à une libération rapide et localisée d'énergie au sein des matériaux. L'acquisition et le traitement de ces ondes permet un contrôle non-destructif de nombreux phénomènes tels que la fissuration sous contrainte, la déformation élastique, le changement de phase, etc. Peu de travaux ont été consacrés par le passé à l'émission acoustique (EA) pendant les procédés de cristallisation et l'essentiel des travaux disponibles, purement descriptif, ne fournit pas de résultats susceptibles de permettre une évaluation quantitative indirecte des processus élémentaires de la cristallisation (i.e., nucléation, croissance, agglomération, etc.). On présente ici des résultats nouveaux obtenus pendant le suivi de cristallisations discontinues en solution. Les signaux acoustiques recueillis sont interprétés grâce à la mesure, en parallèle, de la phase continue (mesure de concentration par spectroscopie ATR FTIR) et de la phase dispersée, par acquisition d'images de la suspension à l'aide d'une sonde vidéo in situ. On montre que les capteurs d'émission acoustique "perçoivent" le déroulement de la cristallisation et, en particulier, qu'elle permet une détection extrêmement précoce de la nucléation des cristaux. Une analyse des composantes des signaux acoustiques montre également que l'EA permet de suivre séparément plusieurs processus élémentaires de la cristallisation qui restent à identifier clairement. Les mesures ainsi obtenues ouvrent des perspectives prometteuses quant au suivi en-ligne des opérations de cristallisation industrielle

Acoustic on-line monitoring of solution crystallization process in pure and impure media

International audienceWe show that acoustic emission (AE) is a very attractive non intrusive technique for monitoring crystallization processes. AE has been successfully applied in many fields of material sciences and it was also used in the pharmaceutical industry for monitoring various chemical engineering processes including fluidized bed granulation, fluidized bed coating, powder compaction, etc. However, few studies deal with the use of AE to monitoring crystallization processes. The objective of this work is to evaluate the potential for using acoustic emission to monitor polythermal batch crystallization in the absence and presence of impurities. The basic concept behind AE monitoring of crystallization processes is that the phase transitions occurring during crystallization in solution induce physicochemical changes in the suspension. Such changes release energy and therefore generate acoustic elastic waves propagating in the liquid medium. Furthermore, as crystal particles are generated, the elastic properties of the dispersed phase also change. The latter changes affect the acoustic emission caused by the particle collision impacts and inter-particles and/or particles-wall frictions. The elasticity of crystals and their kinetic energy are also affected by many other properties such as size, shape, hardness, density, uniformity of composition which obviously depend on the presence of impurities during the process. We report preliminary batch solution cooling experiments obtained with the model system Ammonium Oxalate/water (AO) in the presence of Nickel Sulfate as impurity. The experiments are monitored using AE, ATR FTIR measurement of supersaturation and CSD analysis performed thanks to in situ image acquisition. Complex but promising information is obtained thanks to AE monitoring

Influence of temperature on the compaction of an organic powder and the mechanical strength of tablets.

International audienceThe purpose of this work consists in following the dependence of physical properties on the temperature during the compaction of an organic component. A special thermo-regulated die has been developed to realize uniaxial compression at different constant temperatures. This study has shown that a temperature change modifies the microstructures and the mechanical behaviour of the tablets. The measurement of the tablet porosity during the compression cycle allows us to conclude that temperature influences mainly the phenomena occurring during the isobaric stage of the compression cycle and not the ones during the pressure increase. On the other hand, during the pressure increase, the acoustical activity of the powder is reduced when temperature increases. The tensile strength of tablets realized at different temperatures was also studied and shows a maximum around 60°C that can be explained by the SEM analysis of the microstructure of the tablets

Controlled precipitation of an inorganic compound in solution using a polymeric matrix

National audiencePrecipitation of strontium molybdate was performed from aqueous solutions of sodium molybdate and strontium chloride in presence of hydroxypropylmethylcellulose. Three experiments were conducted: without cellulose, with dissolved cellulose and with a tablet containing cellulose and strontium chloride powder. The first one results in agglomerates of bipyramidal crystals, the second one in smaller monosized bipyramidal crystals and the last one in a mixture of bipyramidal, spherical, ellipsoidal particles and their agglomerates. Explanations based on the effect of solution viscosity are proposed

Fragmentation de grains de sable. Suivi par émission acoustique et bilans de population.

6 pagesDevenue très courante dans le domaine du contrôle non destructif, l'étude des ondes acoustiques est beaucoup moins utilisée pour suivre l'évolution de certains phénomènes. Pourtant elle peut se révéler utile, notamment pour caractériser les phénomènes intervenant lors de la compression des poudres. L'analyse de l'émission acoustique (E.A.) au cours de la compression de plusieurs poudres pharmaceutiques telles que l'aspirine, l'amidon, le saccharose et le kétoprofène a permis de mieux cerner les phénomènes qui se produisent pendant la formation du comprimé [1,2]. Les ondes acoustiques émises par la poudre dépendent des phénomènes se produisant pendant la compression, tels que le réarrangement granulaire, la fragmentation et la déformation plastique des grains. Serris [1,2] a également remarqué que l'intensité de l'émission acoustique est fonction de la poudre. L'émission d'ondes acoustiques peut alors être considérée comme une caractéristique intrinsèque d'une poudre

La réception d’Empédocle dans la poésie latine : Virgile (Buc. 6), Lucrèce, Gallus et les poètes élégiaques

Ce papier vise à montrer, à partir d’une série d’analyses de textes de Virgile, de Lucrèce et des poètes élégiaques, que la lecture faite par Gallus, non d’Empédocle directement, mais de la réception de ce dernier chez Lucrèce a joué un rôle fondamental dans la genèse de grands motifs élégiaques. À ceux du furor et de l’absence de remèdes à l’amour,on peut ajouter en effet le déploiement de deux des étymologies de Vénus exploitées par Lucrèce dans sa version de l’épisode homérique des amours de Mars et de Vénus perçu par les Anciens comme empédocléen : uincere et uincire. La première étymologie a donné lieu à la thématique de la victoire de l’amour et des combats de Vénus opposés aux guerres menées par les Romains, la seconde à celle de la première nuit d’amour, qui ‘lie’ les amants et initie le début de foedera souhaités pérennes mais soumis à d’incessantes fluctuations