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Co-pyrolysis of torrefied biomass and coal: Effect of pressure on synergistic reactions
No full textInternational audienceThe co-utilization of torrefied biomass and coal in thermochemical conversion technologies is an attractive process for the transition to green energy and chemicals. The main advantage of this process is the production of high quality oil products (closer resembling crude-oil) via synergistic interaction of primary products from the two feedstocks. These synergistic reactions often involve secondary reactions, which are promoted at high pressures. This paper reports quantitative results on the extent of synergistic reactions and the role of pressure on these reactions during co-pyrolysis of torrefied biomass and coal. Torrefied biomass was produced at 280 • C in a pilot rotary kiln and subsequently both pyrolysis and co-pyrolysis of torrefied biomass and coal was investigated in a fixed bed reactor (heating rate 7 • C/min) at temperatures of 400-600 • C and pressures of 1, 15 and 30 bar. The results show that the prior removal of hemicellulose during torrefaction maximized the potential of hydrogen transfer from cellulose/lignin-derived products to depolymerized coal fragments. Furthermore, the dehydration and condensation reactions of depolymerized fragments were suppressed during co-pyrolysis in favour of synergistic reactions between the fragments. These reactions occurred predominantly in the molten/ liquid phase and their rates could be indirectly controlled by pressure (through changing the evaporation rate), resulting in substantial changes in product distribution. In the presence of coal and its released vapours, the methoxyphenols (guaiacols) and furanics yields were significantly enhanced (positive deviation >54% and >40%, respectively, compared to additive predictions), whereas the phenol yields were inhibited (negative deviation >20%); suggesting the inhibition of demethoxylation reactions in the presence of coal depolymerized fragments. To date no studies have reported the molten phase synergistic reaction pathways occurring during copyrolysis of torrefied biomass and coal. Based on the findings in this paper, reaction pathways were proposed for these molten phase synergistic reactions
Effect of size, concentration, and nature of fillers on crystallinity, thermal, and mechanical properties of polyetheretherketone composites
No full textInternational audiencePolyetheretherketone (PEEK) composites exhibit high stiffness, chemical stability, and heat resistance and they are therefore employed in applications under severe operating environments. This work aims to provide insight into the effect of the size, concentration, and type of fillers on the thermal and mechanical properties of PEEK. A total of 32 composites are used to highlight the influence of nature (lamellae, such as boron nitride and graphite and silicon carbide and alumina), size (nano and micrometric), and content (2.5, 5, 7.5, and 10 vol%) of fillers. The melting temperature and lamellar thickness did not change regardless of the nature of the filler. The thermomechanical analysis demonstrates that lamellar fillers form a percolating network and contribute significantly to the enhancement of the storage modulus. The increase in the storage modulus is proportional to the filler content, and it is more pronounced for micro composites. As expected, the percolating network is formed at lower concentrations for lamellar fillers than for spherical ones. The highest conductivity is achieved with graphite at 0.823 W m−1 K−1, which is twice that of PEEK for 10 vol%. Moreover, the use of micrometric fillers results in thermal conductivity enhancement attributed to the higher amount of efficient hot zones for heat transfer
Effect of heat treatments on microstructural and mechanical characteristics of dissimilar friction stir welded 2198/2024 aluminum alloys
No full textInternational audienceThe 3rd generation of aluminum–lithium (Al–Li) alloys provides a desirable combination of high mechanical properties and low density compared to their traditional counterparts, exempt of lithium. Therefore, providing a reliable joint between new and conventional aluminum alloys is crucial for making hybrid structures. The present study focuses on improving the mechanical properties of dissimilar AA2198/AA2024 joints using different heat treatments before and after welding. Tensile tests paired with digital image correlation (DIC) techniques and micro-hardness maps were performed to document the macro-scale and local mechanical behavior of the joints. As-welded joints demonstrated a similar yield strength, 30% lower than that of the base metals in T3 and T8 metallurgical states. As-welded joints failed at the AA2198 side in the heat affected zone (HAZ), parallel to the thermo-mechanically affected zone (TMAZ), region experiencing intense strain concentration and minimal hardness values. Post welding-heat treatments (PWHT) was found to successfully strengthen HAZ on the AA2198 side, without abnormal grain growth in the nugget and impairing the hardness properties on AA2024 side. This improvement in local mechanical properties on the AA2198 side was related to the re-precipitation of dissolved T1 (Al2CuLi) and θ (Al2Cu) during welding as characterized by differential scanning calorimetry (DSC) and microscopy analyses. However, PWHT joint variants demonstrated a reduction in total elongation and ultimate tensile strength due to intense strain localization on the AA2024 retreating side compared to a much more homogeneous strain distribution in the as-welded joints
Solubility and Dissolution Kinetics Enhancement of a Hydrophobic Drug Using Dry Milling Mechanochemical Approach
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Graphitization of cellulose and lignin using non-conventionnal catalysts: towards graphene-like materials
No full textInternational audienceHighlights• Impregnation of cellulose and lignin with calcium, phosphorous or hydroxyapatite significantly improved their graphitization degree at 1800°C. • Combination of standard and advanced techniques to understand the graphitization.• Higher graphitization rate was obtained with impregnation of raw biomass compared to impregnation of pre-treated biochars. • Higher graphitization rate was obtained for lignin samples than for cellulose samples at the same catalyst concentration. PurposeGraphene is a bidimensional material with one atomic layer as thickness. Graphene sheets are highly organized in graphitic structure or randomly oriented into turbostratic structure [1], leading to the formation of carbon nanotubes, carbon fibers, carbon black. Depending on the characteristics such as the length and the orientation of the graphene sheets, various properties could be developed: electrical conductivity, mechanical or thermal resistance. Therefore, graphene is considered as a highperformance material, promising for a wide range of applications such as batteries, energy storage, electronics, and biology. To reach these high performances, materials are produced from petroleumbased industries (exfoliation or chemical vapor deposition), leading to a high negative environmental impact. The approach developed in this study promotes the utilization of biomass and biowastes as green graphene precursors where little research has been published so far [2-4]. Biochars obtained from pyrolysis under the desired operating conditions will lead to graphitic structures providing then a sustainable approach for graphene synthesis.Biomass is known to be a "non-graphitizable carbon" source. The use of well selected catalysts allowed to modify the carbon structure and favor highly organized graphene-like structures from biochars. Therefore, the aim of this study is to investigate the influence of non-conventional catalysts on the graphitization of lignin and cellulose biochars. Materials and methodsBiochars from microcrystalline cellulose and pure lignin, two of the main constituents of biomass, were produced by pyrolysis under nitrogen at 1800°C at 2°C•min-1. Both biomasses were also impregnated with either calcium, phosphorous or hydroxyapatite. The impregnations were conducted by immersion in 200 ml of deionized water containing the catalyst for 6 hours before drying. Calcium nitrate, phosphoric acid and a hydroxyapatite gel were used as catalyst sources. The same impregnation protocol was carried out on biochars previously obtained from the pyrolysis of raw biomass at 800°C.</div
Experimental and modelling study of volatile species released in biomass torrefaction based on extracted cellulose, hemicelluloses and lignin
No full textInternational audienceTorrefaction is a mild thermal treatment (200-300 °C, depleted-oxygen atmosphere) suitable for dry biomass. The main products are a torrefied solid, with properties closer to those of coal, and gaseous species, including permanent gases, volatile species and water. The study of volatile species released in torrefaction can contribute to explain biomass degradation mechanisms, as well as to identify the optimal operating conditions to enhance high-added value volatile species production. Furthermore, certain volatile species can be recovered as a source of high-added-value products.Up to now, condensable species recovery is limited due to the complexity of predicting the composition and separating the gaseous mixture. The heterogeneity of volatile species release in torrefaction is the main challenge to propose an accurate predictive model. Moreover, the suitability of using commercial compounds as biomass macromolecular component models was questioned. The objective of this work is determining production profiles in function of temperature for the main volatile species released in biomass torrefaction. Production profiles will be linked to biomass degradation mechanisms in the literature and thus constitute the basis for a predictive model of volatile species release dependant on the main operating conditions, biomass type and composition
Utilisation de catalyseurs biosourcés à base de nickel et de fer pour la conversion des oxides d'azote
No full textNational audienceLes oxydes d’azote (NOx) contribuent à 6% des émissions de gaz à effet de serre et N2O est 300 fois plus toxique que le CO2. La décomposition directe catalysée des NOx est une solution pour contribuer à sa réduction. Elle a lieu de 25 à 1000°C à pression atmosphérique et peut être catalysée par des éléments métalliques dont le fer (Fe) et le nickel (Ni). Typiquement, des catalyseurs commerciaux sont utilisés pour cette application. Une approche originale est proposée dans ces travaux, basée sur l’utilisation de biochars produits par pyrolyse de la biomasse issue de la phytoremédiation naturellement riche en métaux.L’objectif est de produire, caractériser et mettre en œuvre ces biochars pour catalyser la conversion de NOx. De plus, les conditions de préparation et d’utilisation de ces catalyseurs biosourcés seront optimisées via la simulation thermodynamique de la rétention et spéciation des métaux dans le biochar, ainsi que leur impact sur la décomposition des NOx
Vers un prototype de mise à jour des plannings long-terme dans le secteur du service à domicile
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Caractérisation de l'extrudabilité de matériaux à base d'hydrogel pour l'impression 3D de médicaments thermosensibles
No full textInternational audienceSemi-solid extrusion (SSE), one of the additive manufacturing techniques, is attracting particular attention due to its use for printing thermosensitive drugs. Among the materials used in SSE, hydrogels have received the most attention in pharmaceutical applications due to their ability to provide spatial and temporal control of the release of various therapeutic agents. 3D printing of these hydrogel-based materials requires a fundamental understanding of their non-Newtonian flow during extrusion. In this work, agar gels were subjected to extrusion tests at apparent shear rates corresponding to their printing speeds. The rheology of these gels was then studied using a laboratory setup consisting of a syringe piston pushed by varying weight and the data obtained was modelled using the Herschel–Bulkley equation to obtain the yield stress, the consistency and flow indices. The 4% (w/w) concentration of agar gel showed the best fit to the modelled data and had the optimal rheological properties. This concentration was thus used in printing cylindrical objects, and the effect of the infill density on the porosity of the objects as well as on the dissolution of a tracer was studied.L’extrusion semi-solide (SSE ; semi-solid extrusion ), une des techniques de la fabrication additive, attire particulièrement l’attention en raison de son utilisation pour l’impression de médicaments sensibles à la température. De plus, parmi tous les matériaux utilisés en SSE, les hydrogels ont reçu la plus grande attention dans les applications pharmaceutiques en raison de leur capacité à fournir un contrôle spatial et temporel de la libération de divers agents thérapeutiques. L’impression 3D de ces matériaux à base d’hydrogel nécessite une compréhension fondamentale de l’écoulement non-newtonien lors de l’extrusion. Dans ce travail, des gels d’agar ont été soumis à des tests d’extrusion sous des taux de cisaillement apparents qui correspondent aux vitesses d’impression. Un montage de laboratoire utilisant une seringue a été utilisé pour étudier la rhéologie d’agar. Les données obtenues ont ensuite été modélisées à l’aide de l’équation de Herschel–Bulkley pour obtenir la contrainte seuil ainsi que les indices de consistance et d’écoulement. La concentration de 4 % (w/w) en agar dans l’hydrogel a montré la meilleure corrélation et possédait les propriétés rhéologiques optimales et a donc été utilisée pour l’impression d’objets cylindriques. L’effet du taux de remplissage sur la porosité des objets et sur la dissolution d’un traceur a ensuite été étudié
Écoulement et comportement en compression de poudres avec des poinçons à rainures profondes
No full textThe production of compacts with complex geometries by means of powder die compaction can be a delicate task. The compression process, used in many industrial sectors, is based on the densification of a powder bed by the application of an external load to obtain compacts. In some situations, the presence of defects (for example, cracks) in the compacts can be observed following the compression process. These lead to the degradation of the mechanical properties of the compacts and therefore their properties of use, thus leading to the non-conformity of the sample. Defects in powder compacts can be mainly due to the homogeneity of the compact, the mechanical behaviour of the powder and the complexity of the geometric shape of the sample. The work of this thesis contributes to the analysis of the compaction of pharmaceutical powders on large compacts with complex geometry (presence of grooves). In particular, to further understand the impact of the geometry of the compression tools on the final state of the compacts, both experimental and numerical studies were carried out. In order to model the mechanical response of the powder in compression to an external load, the Drucker Prager Cap (DPC) model was employed. To overcome a scaling problem, a hybrid calibration method of the DPC model was introduced in this work to provide a more realistic prediction of the powder behaviour in compression. The numerical results obtained by finite element simulation were validated by means of tomographic analysis.La fabrication de pièces à géométries complexes, par compression de poudres, peut s’avérer délicate. Le procédé de compression, utilisé dans de nombreux secteurs industriels, consiste à densifier un lit de poudre par l’application d’une charge afin de produire des compacts. Dans certaines situations la présence de défauts (fissures par exemple) dans les compacts est observable suite à la compression. Ceux-ci mènent alors la dégradation des propriétés mécaniques des compacts et donc leurs propriétés d’usage, leur présence entraine alors la-non-conformité de l’échantillon. Les défauts sur des compacts de poudre peuvent trouver leur origine principalement dans l’homogénéité du compact, le comportement mécanique de la poudre ainsi que la complexité de la forme géométrique du compact. Les travaux de cette thèse apportent une contribution dans l’analyse de la compression de poudres pharmaceutiques sur des compacts de grande taille à géométrie complexe (présence de rainures). Plus particulièrement, pour aller plus loin dans la compréhension de l’impact de la géométrie des outillages de compression sur l’état final des compacts, une étude à la fois expérimentale et numérique a été mise en place. Afin de modéliser la réponse mécanique de la poudre en compression soumise à une charge externe, le modèle de Drucker Prager Cap (DPC) a été employé. De manière à pallier à un problème d’échelle une méthode hybride de calibration du modèle de DPC a été mise en place dans le cadre de ces travaux pour obtenir une prédiction du comportement de la poudre en compression plus réaliste. Les résultats numériques obtenus par simulation éléments finis ont été validés par le biais d’analyses tomographiques