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Hydrogen enriched syngas production via gasification of biofuels pellets/powders blended from olive mill solid wastes and pine sawdust under different water steam/nitrogen atmospheres
No full textInternational audienceIn this paper we focused on the gasification of biomass charcoal using a macro TG under the CO2 gasifier agent mixed with nitrogen at different mass molar fractions; 40%, 70% and 100% respectively. Moreover, the gasification tests were conducted at different isothermal temperatures; 750°C, 800°C, and 900°C respectively. For this purpose, two densified residues were selected; the exhausted olive mill solid wastes (EOMSW) and the pine sawdust (PS). Then, four different samples were prepared from these residues when investigating the impregnated and the non-impregnated samples using the olive mill waste water (OMWW) as by-product for the impregnation process. A comparison between obtained results during this current study and those obtained during our latest study when using steam as gasifier agent was carried out. We observe that the mass loss profiles meet the usual lingo-cellulosic gasification behaviours. Moreover, the increase of the isothermal temperatures or of the CO2 percentage affects positively the conversion, the gasification rate and the char reactivity. It is worth noting that the CO2 agent acts differently by comparison to the steam. Indeed, the gasification process using steam is found to be faster and more reactive
Effect of interfacial crystalline growth on autohesion of PEEK
No full textInternational audienceThis work aims to clarify the role of the crystalline growth on the autohesion strength of amorphous PEEK below its melting temperature. The self-bonding strength versus temperature, pressure and time has been measured by lap shear test on 250-micron thick amorphous PEEK assembled at various conditions. The effect of the crystalline growth on the adhesion strength has been established at 155°C, 200°C and 250°C. Autohesion is temperature dependent, whereas pressure at less than 1 MPa and time up to 3 h, have less impact on the adhesion strength. Nevertheless, the evolution of the crystalline morphology with time results in increasing the interfacial strength: a gain of 40% is noticed between 1 and 3 h at 250 °C to reach 0.9 MPa. The degree of crystallinity is higher at the interface than elsewhere in the material, the interface acting as nucleating agent. The evolution of the crystalline morphology at the interface with time shows the refinement of the primary lattice when the temperature is higher than or equal to the previous crystallization temperature, corresponding to the highest temperature seen by the polymeric material. The crystalline growth has an ambivalent effect on the autohesion of PEEK: it reduces the mobility of the macromolecular chains and thus their interdiffusion through the interface and at the same time, it is observed that the improvement of its crystal lattice reinforces the interfacial strength
AnT²COK, an analytical model for cyclic oxidation kinetics of hot-work tool steels in transient thermal cycling conditions
No full textInternational audienceIn hot forming processes, steel tools are subjected to rapid temperature transients and cyclic oxidation. AnT²COK, a new analytical model based on diffusion-controlled oxide growth in cyclic conditions, is proposed to predict the parabolic oxidation kinetics in spallation-free conditions. Compared to cyclic oxidation models of the literature (COREST, COSP, DICOSM, etc.), it is applicable for any shape of thermal cycle, fully transient or with dwell time. The model is applied to thermal fatigue tests on X38CrMoV5 steel, for Tmax between 500 and 685 °C. Its validity is demonstrated above 550 °C, using frequency factor and activation energy calculated from isothermal tests
Biocomposite films based on poly(lactic acid) and chitosan nanoparticles: elaboration, microstructural and thermal characterization
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Simulation d'une unité de production d'hydrogène par des procédés de reformage
No full textNational audienceThis work aims to study the reforming of biogaz into syngas, in view of the production of green hydrogen.La dégradation biologique est une méthode peu chère et efficace pour la gestion des ordures ménagères et d’autres types de déchets organiques non dangereux [1] [2]. En France, environ 30% d’ordures ménagères sont mis en enfouissement. Le produit principal de cette dégradation biologique est le biogaz. Le biogaz peut être purifié et enrichie en qualité du gaz naturel pour l’injection dans le réseau de gaz de ville. Cela est déjà industrialisé[3] [4]. Le biogaz peut également être valorisé en produits à valeur ajoutée comme hydrogène pour la mobilité. Dans un tel procédé, le biogaz qui contient principalement CH4 et CO2 est d’abord reformé en syngas (mélange riche en CO et H2) à haute température (cf. 700°C). Le syngas est ensuite injecté dans un réacteur « Water-Gas-Shift » (WGS) pour convertir le CO et H2O en CO2 et H2. H2 pure est obtenu par la séparation PSA (Pressure Swing Adsorption). Le CO2 issu du procédé PSA peut être valorisé pour la production de NaHCO3 pour le traitement de fumée d’incinérateur. L’étape clé de cette chaine de production est le reformage qui est très énergivore. En général, cette étape est faite à l’échelle industrielle par le vaporeformage en utilisant un rapport molaire de H2O/CH4 de 3 à 4. L’étape WGS ne nécessite que la température de 250-350°C et donc une perte importante d’énergie peut avoir lieu lors du refroidissement du gaz en sortie du réacteur de reformage, malgré l’utilisation d’échangeur thermique. La recherche actuelle porte sur des procédés de reformage utilisant peu de vapeur d’eau comme RSB (Reformage à Sec du Biogaz) et Tri-RB (Tri-Reformage du Biogaz). Dans cette optique, la simulation par ASPEN Plus – développé par ASPEN TECHNOLOGY – est un outil efficace pour étudier l’effet des conditions opératoires sur le bilan énergétique de ces différents procédés de reformage.Le travail comprend deux parties. La première concerne la simulation d’un procédé de reformage simplifié en utilisant un seul réacteur Gibbs afin d’obtenir des paramètres optimaux. Ensuite, les conditions obtenues dans la 1èr étape sont injectées dans la simulation du procédé global de production d’hydrogène afin de comparer le bilan énergétique de ces différentes configurations. Dans cette deuxième étape, l’objectif est de déterminer les conditions pour maximiser la productivité d’hydrogène, minimiser la consommation d’énergie du procédé global de production et minimiser la sélectivité en coke.En fixant la température à 909°C et la pression totale à 16 bars pour le reformage, les résultats ont montré que le procédé de Tri-RB est le plus compétitif pour la production d’hydrogène. Comme exemples de résultats, la Figure 1 montre l’influence du rapport molaire de vapeur d’eau/méthane (S/C) et d’oxygène/méthane (O/C) sur la conversion du méthane et la sélectivité en coke. Il est nécessaire de travailler au rapport S/C = 0,72 et de O/C = 0,1 pour atteindre 75% de conversion en CH4 et 0% de sélectivité en coke pour l’étape de reformage. La Figure 2 montre le schéma du procédé de production global intégrant le tri-reformage
Metal-Phosphate catalysts properties for biofuel production
No full textInternational audienceBiogas reforming allows obtaining synthetic gas (syngas) under adequate conditions of temperature and pressure. A solid catalyst must generally be used to have exploitable reaction kinetic. At the industrial scale, steam methane reforming has largely been deployed to reform natural gas. However, this process is strongly energy-consuming since it works with a high steam-to-carbon ratio (S/C close to 3.5/1) to keep the catalyst stable over long reaction time. The objective of this work is to develop an efficient catalyst for the reforming of methane at low S/C ratio (i.e. close to the stoichiometry).Calcium hydroxyapatite (Ca10(PO4)6(OH)2) – or HAP – has recently been investigated as catalyst support for the dry reforming of methane (DRM) reaction. Very promising results have been obtained [1]. By controlling the molar ratio of Ca to P, the acido-basicity of this support can be adjusted which is a crucial factor for CO2 adsorption and dissociation. This support is also well known by its high thermal stability as well as its good ionic exchange capacity for divalent metals such as nickel and cobalt. In this work, DRM reaction over HAP-based catalysts has been studied. HAP support was synthesized from calcium carbonate (CaCO3) or calcium nitrate (Ca(NO3)2) as calcium sources and ammonium dihydrogen phosphate (NH4H2PO4) as phosphate source. Different monometallic or bimetallic catalysts containing Ni and/or Co were prepared and evaluated in DRM reaction. Different physico-chemical characterizations such as metal-support interaction, acid-base nature, surface area, support porosity etc. were also carried out to link the catalytic performance with the properties of the prepared catalysts
Modeling of the polymerization and crystallization kinetic coupling of polyamide 6 synthesized from ε-caprolactam
No full textInternational audienceOptimization of polyamide 6 (PA6) composite manufacturing by liquid processes requires a better prediction of kinetics during synthesis. This study proposes a new modeling approach that considers the interaction between PA6 polymerization and crystallization over a wide temperature range (403–473 K). Different polymerization and crystallization models taken from literature were used in this study. Few attempts to describe the coupling between phenomena have been reported, and all have raised physical limitations. A new coupling equation was adapted from Hillier coupling, first introduced to model secondary crystallization of semi-crystalline thermoplastics. This equation properly predicted kinetics at high temperature when the coupling is limited. However, it failed in predicting the particular crystallization kinetics in the early stages of polymerization at low temperature, as crystallization may require that polymerized chains reach a certain length or concentration in the reactive mixture. A factor was successfully introduced in order to correct the crystallization behavior. From this new model, a wide isothermal Time-Temperature-Transformation (TTT) diagram was produced, which assists in cure path design for composite manufacturing
Charpy test investigation of the influence of fabric weave and fibre nature on impact properties of PEEK-reinforced composites
No full textInternational audienceThe aim of the work is to use Charpy impact test for quick evaluations of different Polyether-ether-ketone (PEEK)-reinforced composites to be used for impact protection. In the first part, the influence of weave pattern was first analysed by comparing the impact behaviour of three PEEK composites reinforced with plies of unidirectional (UD) tapes, 5H satin fabrics and 2 × 2 twill fabrics made of high-strength carbon fibres. In the second part, the influence of fibre nature was investigated for the same weave pattern. The impact behaviour of five 2 × 2 twill fabrics made from inorganic fibre (carbon, glass and basalt) and organic fibre (aramid and poly(p-phenylene-2,6-benzobisoxazole) (PBO)) has been compared. Two main types of failure modes were identified: a brittle behaviour mode with high failure strength and a highly deformable behaviour mode in which energy absorption is more important. The balance between brittle behaviour and highly deformable behaviour results from competition between the yarn crimp, weave pattern and fibre properties of the composite. Slight yarn crimp and small ply thickness increase the stiffness of the composite and induce brittle behaviour characterized by fibre failure in tension and a steep peak on the loading curves. This behaviour is observed in UD and 5H satin carbon-reinforced composites or 2 × 2 twill glass and basalt fabric-reinforced composites. In contrast, aramid and PBO 2 × 2 twill fabric composites exhibit high shear strength. The highly deformable behaviour of the specimens during the Charpy impact led, in the case of organic fibres, to a non-breakage of the fibres and consequently to a high level of energy absorption. This behaviour is necessarily interesting in armour applications
Integrating Model-Driven Engineering as the Next Challenge for Artificial Intelligence – Application to Risk and Crisis Management
No full textInternational audienceArtificial Intelligence (AI) is currently on top of the hype regarding simultaneously research publications and industrial development. However, the current status of AI makes it quite far and different from the current understanding of Human intelligence. One suggestion that is made in this article is that Model-Driven approaches could be considered as an interesting avenue to complement classical visions of AI and to provide some missing features. Specifically, the use of Model-Driven Engineering tools (such as metamodel and model transformation) could benefit to the domain of AI by introducing a way to extend the apprehension of unknown situations. To support that proposal, an illustrative example is provided regarding the domain of risk and crisis management
An optimization of the local hall-petch relationship using slip trace analysis technique and scale transition rules: application in equiaxed ti-6al-4v titanium alloy
No full textInternational audienceThe aim of this work is to optimize the relative and the absolute Critical Resolved Shear Stress (CRSS) of slip mechanism in α-phase of Ti-6Al-4V titanium alloy. The influence of grain size is then modeled through a local Hall-Petch relationship. A slip trace analysis technique coupled with statistical reasoning were used to identify the CRSS ratios of basal a , prismatic a and pyramidal c + a slip systems. The multiscale transition rule of Berveiller-Zaoui was then used to determine the absolute CRSS in three different microstructures; Ti-6Al-4V with ultra fine grains (UFG), fine grains (FG) and standard grains (SD). Finally, the local Hall-Petch relationship was optimized. As expected, plastic deformation is mainly accommodated by prismatic and then basal slip systems. Due to their high CRSS, sliding in pyramidal systems is more difficult. Grain size shows a significant role on the activation of slip systems. By increasing the grain size, the CRSS of each slip system type decreases and thus sliding becomes easier in coarse grains