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Conversion of Biogas to Syngas via Catalytic Carbon Dioxide Reforming Reactions: An Overview of Thermodynamic Aspects, Catalytic Design, and Reaction Kinetics
No full textInternational audienceBiogas production has continuously increased worldwide during the last decades. Nowadays, heat, electricity, and biomethane production are the main utilization of biogas at large-scale industrial processes. The research and development on biogas valorization is currently related to synthesis gas production via reforming process, since syngas allows obtaining various chemicals and fuels of high-added value. However, biogas reforming is a complex process, which implies various reactions in parallel, and needs high temperature (>800 °C) to obtain high methane conversion. The development of a highly-performing catalyst, which must be active, selective, thermally stable, and resistant to solid carbon formation on its surface, is crucial. This chapter is devoted to an update of the thermodynamic aspect of biogas reforming under different conditions. This chapter also reviews recent significant works related to catalyst design as well as kinetic and mechanistic studies of biogas reforming processes
Characterization and modelling of cure-dependent properties and strains during composites manufacturing
No full textInternational audienceThe geometric stability of structural parts is a critical issue in the aeronautical industry. However, autoclave curing of primary structural composite parts may cause significant distortions and divergences between the mould nominal geometries and the final shapes of the parts. To be able to anticipate such distortions, a robust simulation tool is needed, which can be implemented only if the phenomena involved are properly understood and characterized. The thermo-kinetic behaviour of the M21EV/IMA prepreg is fully characterized in this paper. Thermal strains and chemical shrinkages are measured using Thermo-Mechanical Analysis during the cure and the experimental method developed allows the thermo-chemical strains to be obtained even during the early stages of the cure. An experimental setup is developed to measure the thermo-mechanical behaviour of the material during its cure. Thanks to these measurements, a new constitutive mechanical model, inspired from the CHILE model, is defined. These data are then used as inputs for an FEA simulation of the entire curing process. Finally, the model is validated using the cure degree, glass transition and temperature monitoring, and post-cure distortion measurements
Biomass Categories
No full textInternational audienceBiomass resources for the production of renewable energy, chemicals and polymeric materials are abundant. In this chapter, these resources will be categorized into woody biomass, agricultural residues and waste, municipal solid waste, sewage sludge and aquatic plants. The origins, use and typical composition (physical, chemical and biological) of the different biomass types will be presented
Handbook on Characterization of Biomass, Biowaste and Related By-products
No full textInternational audienceThis book provides authoritative information, techniques and data necessary for the appropriate understanding of biomass and biowaste (understood as contaminated biomass) composition and behaviour while processed in various conditions and technologies. Numerous techniques for characterizing biomass, biowaste and by-product streams exist in literature. However, there lacks a reference book where these techniques are gathered in a single book, although such information is in increasingly high demand. This handbook provides a wealth of characterization methods, protocols, standards, databases and references relevant to various biomass, biowaste materials and by-products. It specifically addresses sampling and preconditioning methods, extraction techniques of elements and molecules, as well as biochemical, mechanical and thermal characterization methods. Furthermore, advanced and innovative methods under development are highlighted. The characterization will allow the analysis, identification and quantification of molecules and species including biomass feedstocks and related conversion products. The characterization will also provide insight into physical, mechanical and thermal properties of biomass and biowaste as well as the resulting by-products
Classification using a three-dimensional sensor in a structured industrial environment
No full textInternational audienceUsage of a three-dimensional (3-D) sensor and point clouds provides various benefits over the usage of a traditional camera for industrial inspection. We focus on the development of a classification solution for industrial inspection purposes using point clouds as an input. The developed approach employs deep learning to classify point clouds, acquired via a 3-D sensor, the final goal being to verify the presence of certain industrial elements in the scene. We possess the computer-aided design model of the whole mechanical assembly and an in-house developed localization module provides initial pose estimation from which 3-D point clouds of the elements are inferred. The accuracy of this approach is proved to be acceptable for industrial usage. Robustness of the classification module in relation to the accuracy of the localization algorithm is also estimated
High Temperature Micromechanical Behavior of a Pt-Modified Nickel Aluminide Bond-Coating and of Its Interdiffusion Zone with the Superalloy Substrate
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In-situ Full Field Out of Plane Displacement and Strain Measurements at the Micro-Scale in Single Reinforcement Composites under Transverse Load
No full textInternational audienceMicromechanics damage models applied to composites predict stresses and strains in the matrix and fibers as a function of the microstructure, constituting phases mechanical properties and load histories. Material parameters, like interface properties, are identified through inverse methods based on macroscopic stress-strain curves. Predictions are also benchmarked against macroscopic measurements. This situation does not capture local phenomena and hinders the robustness of the indentification/validation process. The purpose of this work is to provide full displacement and strain fields at the scale of a single fibre embedded into a matrix to allow the modelling community to either develop and identify micromechanics damage models or to benchmark their own predictions. Such data is critically lacking in the community. To that end, we have investigated three single fibers having radically different bonding strength with epoxy in addition to a bundle of about a hundred carbon fibers that were used as reinforcements of standard “dogbone” epoxy specimens. A laser scanning confocal microscope (LSCM) is used for micro digital image correlation (μDIC) during in-situ quasi-static tests of single-reinforcement dogbone specimens. For all specimens, damage initiated with fiber debonding at the free surface along the tensile direction. The crack then propagates around the interface while slightly growing along the fiber. The interfacial crack is shown to grow faster for couples with weak interfacial bonding. Strong fiber / matrix bonding is shown to stop Mode II transverse interfacial debonding which significantly delays specimen failure. Analysis of the LSCM micrographs with μDIC is used to provide measurements of displacements, strains, and measure depth during each test. The importance of out of plane displacements in interfacial debonding is highlighted. Out of plane displacement is shown to play a role in interfacial crack opening and growth and ought to be considered when studying or modeling damage in FRCs. μDIC is shown to be a promising technique to provide a better understanding of the damage mechanisms at the fiber or bundle scales and to determine interfacial toughness of a specific fibre / matrix couple in order to perform accurate damage modeling in FRCs. Displacement, strain, and confidence field results for each pixel from each experiment and at each time step are also provided in an extensive data package for detailed comparison with simulation results
Three viewpoints on null-collision Monte Carlo algorithms
No full textInternational audienceIn 2013, Galtier et al. [10] have theoretically revisited a numerical trick that had been used since thevery beginning of linear-transport Monte-Carlo simulation: introducing “null” scatterers into a hetero-geneous field to make it virtually homogeneous.The rigorous connection between null-collision algorithms and integral formulations of the radiativetransfer equation led to null-collision algorithms begin used in distinct contexts, from atmospheric orcombustion sciences to computer graphics, adressing questions that may strongly depart from the initialobjective of handling heterogeneous fields (handling large spectroscopic databases, non-linearly couplingradiation with other physics).We here briefly describe some of these researches and we classify them by proposing three alternativeviewpoints on the very same null-collision concept: an intuitive, physical point of view, called similitude;a viewpoint built on the probability theory, where the null-collision method is seen as rejection sampling;and a more formal writing where the nonlinear exponential function is expanded into an infinite sum oflinear terms.By formulating the null-collision concept under three distrinct formalisms, our intention is to increasethe reader’s flexibility in its use. As it is defended and illustrated in this paper, being able to explorenull-collision algorithms under their different forms has often led to a broadening of the space of solutionswhen facing difficult problems, including ones where the Monte Carlo method was consensually consideredinapplicable
Transformations physico-chimiques et comportement thermomécanique de mélanges argileux lors de la cuisson
No full textThis work was devoted to the understanding of physicochemical transformations and thermomechanical behavior of industrial clay-based mixtures during the firing cycle. A particular focus was made on the development of a viscous phase. For ceramics, the viscous phase plays an important role in the densification mechanism at high temperature and can lead to a decrease of the sintering temperature. Therefore, it is very important to understand its interaction with the clay matrix. To this end, a specific approach based on a combination of standard characterization techniques (dynamic scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal analysis (TGA-DTA), mass spectroscopy (TGA-MS), and thermomechanical analysis (TMA)) and advanced one (acoustic resonance, AR) was used. The overall thermal behavior of three industrial clay-based mixtures during firing was investigated using a combination of dynamic characterization techniques, in order to establish a relationship between these transformations and the development of the viscous phase. Thus, the formation of the viscous phase and the associated effects in terms of densification acceleration were particularly revealed by following the damping of AR signals and by dynamic high-temperature SEM observations. Further analysis using TEM at room temperature revealed that the glassy phase resulting from the solidification of the viscous phase is predominantly composed of silicon, aluminum, oxygen, and potassium with traces of iron. Moreover, the kinetic modeling approach based on the experimental results of TMA analysis has contributed to a better understanding of the kinetic and mechanisms in the sintering step. The results obtained are original as they highlight the contribution of the viscous phase in the mechanisms involved in sintering, compared to existing models. The influence of different fluxing oxides on the mechanisms associated with the presence of the viscous phase in an industrial clay-based mixture was also investigated. From this study, it will be possible to determine to which extent the temperature of the development of the viscous phase could be controlled, in order to reduce the firing temperature. The results revealed that the temperature at which the viscous phase appeared and the mechanical properties of the produce clay-based materials depend mainly on the nature of the additive and its physical properties. The study demonstrated that both an improvement in the densification kinetics and a decrease of the densification temperature can lower the firing temperature. Introducing a higher amount of B2O3 decrease the temperature of the viscous phase formation of 80°C. Otherwise, a higher amount of K2O and Fe2O3 improve the densification kinetics and thus leads to a reduction of 20°C in the firing temperature. This original approach allowed an outstanding description of complex mechanisms involved during the firing of clay-based mixtures, specifically during the sintering step, bringing new insights in regards to the state-of-the-art. In particular, this approach depicted the dynamics of the physicochemical transformations that were until now only an assumption. Also, this approach can be beneficial in the terracotta industry as it can be used to predict and tailor the final microstructure of clay-based materials and promote a decrease in their firing temperature.Ce travail est consacré à la compréhension des transformations physico-chimiques et du comportement thermomécanique de mélanges argileux industriels lors de la cuisson, notamment en lien avec le développement de phase visqueuse. En effet, la phase visqueuse joue un rôle important à haute température dans les produits de terre cuite, car elle est conjointement liée à la consolidation du matériau et peut conduire à une diminution de la température de début de frittage. Il est alors important de bien comprendre son interaction avec les autres constituants du mélange de fabrication. À cet effet, une démarche basée sur la combinaison de techniques expérimentales standard (analyses thermiques (ATG - ATD), spectrométrie de masse (ATG - MS), dilatométrie (ATM), diffraction des rayons X (DRX), microscopie à balayage dynamique (MEB), et microscopie électronique à transmission (MET)) et avancée (résonance acoustique en température) a été mise en œuvre. Le suivi du comportement global de trois mélanges argileux industriels lors de la cuisson a été réalisé grâce au couplage de techniques expérimentales in-situ, permettant ainsi d’établir une relation entre ces transformations et le développement de phase visqueuse. La formation de la phase visqueuse et les effets associés en termes d’accélération de la densification ont été mis en évidence avec le suivi de l’amortissement de signaux de résonance acoustique et d’observations à haute température au MEB. Des observations complémentaires à température ambiante au MET ont montré que la phase vitreuse résultant de la formation de phase visqueuse à haute température était composée d’oxygène, de silicium, d’aluminium et de potassium ainsi que des traces de fer. Par ailleurs, l’approche de modélisation basée sur les résultats expérimentaux de l’ATM a contribué à une meilleure compréhension de la cinétique et des mécanismes mis en œuvre au cours du frittage. Les résultats obtenus sont originaux car ils mettent en évidence la contribution de la phase visqueuse dans les mécanismes impliqués dans le frittage comparés aux modèles précédemment développés dans le cadre du projet de laboratoire commun RESPECTc sur des mélanges argileux. L’étude de l’impact de différents oxydes sur les mécanismes associés à la présence de phase visqueuse sur un mélange argileux industriel a aussi été réalisée. L’objectif applicatif à terme est de voir dans quelle mesure les températures d’apparition de la phase visqueuse pourront être contrôlées pour abaisser la température de cuisson des produits. Les résultats ont montré que la nature de l’additif et ses propriétés physiques ont une influence non négligeable sur la température d’apparition de la phase visqueuse et sur les propriétés mécaniques. L’étude a démontré qu’une amélioration de la cinétique de densification et une diminution de la température de début de densification peuvent toutes les deux conduire à un abaissement de la température de cuisson. L’ajout de B2O3 en grande quantité peut permettre un abaissement de la température de cuisson par une diminution importante, de l’ordre de 80°C, de la température d’apparition de la phase visqueuse. En revanche, la présence en grande quantité d’oxyde de potassium et de fer améliore la cinétique de densification et conduit à une réduction de 20°C de la température de cuisson. Cette approche originale a permis une compréhension fine des transformations physico-chimiques se produisant au cours de la cuisson de mélange argileux, spécifiquement lors du frittage en se basant sur des hypothèses qui donnent accès à la dynamique de ces transformations. De plus, elle peut être bénéfique pour l’industrie de la terre cuite dans la mesure où elle peut permettre, dans une certaine mesure, de prédire et orienter la microstructure finale et favoriser une diminution de la température de cuisson des produits de terre cuite
Polliniser les matins malins ou le plaisir d'enseigner ! Qu’est-ce qui fait le succès des partages autour de la pédagogie entre enseignants chercheurs ?
No full textInternational audienceWe would like to share a pedagogical experience: a debate, six time a year, between teachers to challenge their courses. The pleasure is central in this experience: pleasure to share, to explain, to debate, to give, to receive, etc. The question is: which conditions do we need to make this kind of exchange a success?Cet article retrace une belle expérience d’échange entre enseignants chercheurs autour de notre plaisir d’enseigner. Ce sont des rencontres ritualisées, entre quatre et six fois par an, où témoins et collègues débattent autour d’une pratique pédagogique. Le mot clé est le plaisir : échanger, partager, polliniser, s’enrichir, donner, recevoir... Un rituel bienveillant mais aussi exigeant. La question est posée sur les conditions pour faire vivre de telles instances