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Understanding the torrefaction of woody and agricultural biomasses through their extracted macromolecular components. Part 2: Torrefaction model
No full textInternational audienceA new torrefaction model was proposed for predicting solid mass loss in torrefaction as a function of biomass main macromolecular composition and type, as well as on the operating conditions. To do this, solid degradation kinetics were modelled following a 2-successive reaction scheme for each macro-compound and the additive modelling approach through biomass macromolecular component behavior in torrefaction proposed by Nocquet et al. (2014). The use of extracted fractions from different woody and agricultural biomass species (ash-wood, beech, miscanthus, pine and wheat straw) instead of commercial compounds increased the accuracy of the prediction of solid kinetics in biomass torrefaction. The validation of the proposed model with 9 raw biomasses in torrefaction showed an accurate prediction for woods, while the prediction for agricultural biomasses was acceptable
Microstructural analysis of nitrogen-doped char by Raman spectroscopy: Raman shift analysis from first principles
No full textInternational audienceNitrogen-doped materials are known to possess unique functional properties, making these materials potentially useful for environmental applications, heterogeneous catalysis, and electronics. In this paper we constructed first principles-based models of various polyaromatic structures containing N functionalities to better understand the effect of these functional groups on char Raman spectra. The presence of N functional groups induces active vibrations in the regions between 1400 and 1550 cm−1 and 1605-1650 cm−1. We used these insights to inform the deconvolution of N-doped cellulose char produced between 350 and 700 °C using cellulose/melamine blends 2:1. A consistent increase in the intensity of the D and G bands is observed with temperature, which is related to an increase in size of the aromatic cluster. A consistent decrease in the A (the valley region) band is related to the loss of heteroatoms (mainly N and O) as the carbonization temperature increases from 350 to 700 °C. Although the modeling results reported in this manuscript are used to inform the deconvolution of N-doped char Raman spectra, they are also relevant to study other nanocarbon-based materials
Interpretation of Patients’ Location Data to Support the Application of Process Mining Notations
No full textInternational audienceThe application of indoor localization and process mining emerges as an intriguing tool for the researchers to address the structural issues related to the patient pathways inside healthcare organizations. However, there is a major gap in the literature. This is related to the lack of enough attention to the interpretation of location data. Therefore, as a contribution, this article presents the DIAG meta-model and relevant location data interpretation rules. This model-driven approach has been realized in the context of the R-IOSUITE application and it supports the further analyses by the process mining methods
Experimental evaluation of vitrified waste as solid fillers used in thermocline thermal energy storage with parametric analysis
No full textInternational audienceThis work presents the first use of Cofalit® (vitrified asbestos-containing waste) as a solid filler in pilot-scale thermocline thermal energy storage (TES). The thermocline size is 4 m³ connected to the MicroSol-R installation at the PROMES research facility in Odeillo, France. The study compares the thermal performance of the thermocline filled with Cofalit® to the reference case of alumina spheres for typical charge and discharge operations. It evaluates the actual thermal behavior of thermocline considering three leading performance indicators: process duration, thermocline thickness, and process efficiency. The investigation shows a 22% shorter charge duration in Cofalit® compared to alumina and 16% shorter discharge duration. Cofalit® exhibits about 16% lower thermocline thickness during both charge and discharge compared to alumina. The charge efficiency is slightly better in Cofalit® than alumina with an efficiency of 82% and 78%, respectively. Also, Cofalit® has a better discharge efficiency, 90% with respect to 84% for alumina. These results confim a good thermal performance of Cofalit® as filler material in thermocline TES. Considering the cost-saving and positive environmental impact of using Cofalit® as well as the good thermal performance of the thermocline filled with it, Cofalit® appears a very good filler material in TES. The obtained temperatures from radial positions indicate no significant variation during charge and discharge, and this confirms the one-dimensional thermal behavior of this setup. A parametric analysis is performed using a 1D continuous solid (C-S) model to investigate the influence of particle diameter, porosity, thermal conductivity, and volumetric heat capacity on the thermal performance of the thermocline. The analysis confirms the experimental findings, and it indicates that about a 10.9% longer process duration is associated with a 10% larger volumetric heat capacity and less affected with other parameters. Thermocline thickness is mainly affected by the diameter as well as the volumetric heat capacity of the solid filler; it grows 2.2% for each 10% diameter increase and around 3.23% for doubling the volumetric heat capacity. Charge efficiency demonstrates independency from evaluated properties. While discharge efficiency increases sharply at a tiny particle diameter before an optimum diameter value is reached, then it starts to decrease by 1.4% to each 10% bigger diameter
A Comparative Study of Hydroxyapatite‐ and Alumina‐Based Catalysts in Dry Reforming of Methane
No full textInternational audienceThe dry reforming of methane over hydroxyapatite‐ and alumina/magnesia (commercial Pural MG 30)‐supported nickel catalysts was investigated. The catalytic performance of the catalysts prepared with fresh supports highly depended on the basicity, the metal‐support interaction, and the metal particle size. Calcination of the supports at 1200 °C for 5 h made the catalysts less active because of specific surface area reduction and basicity destruction. However, this treatment allowed avoiding any further catalyst deactivation by thermal sintering and maintained excellent catalytic stability over 300 h of time‐on‐stream. These tests under simulated industrial conditions (high contact time and long time‐on‐stream) showed the competitiveness of the prepared catalysts in this important catalytic process
Alum sludge as an efficient sorbent for hydrogen sulfide removal: Experimental, mechanisms and modeling studies
No full textInternational audienceThis paper firstly reported a systematic study of using alum sludge (waterworks residue) for H2S adsorption. Various trials were performed at ambient temperature in a fixed bed column to study the effects of H2S flow rate, sorbent bed depth on the alum sludge adsorption efficiency of H2S. The Breakthrough Curves were simulated by the Thomas model, Bed Depth Service Time model and Yoon-Nelson models. The mechanisms of H2S adsorption onto alum sludge was examined by different physiochemical characterizations of exhausted and raw alum sludge. Moreover, the mass transfer coefficients were determined from mathematical descriptions of breakthrough curves. The alum sludge adsorption capacity was determined to be 374.2 mg of H2S/g, slightly decreasing with the increasing flow rate and increasing with the increasing bed depth. All the three models successfully predict breakthrough curves which could be used for scaling-up purposes. The microporous structure, alkaline pH and the inherent metal species of the alum sludge promoted the formation of metal sulphate species. This study demonstrated that alum sludge could be used as cost-effective, largely available, and efficient sorbent for H2S removal
Syngas production from green waste using the combination of a rotary kiln with a tubular reactor
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Influence of solar heat sources on packed bed TES performances
No full textInternational audienceThe influence of solar constraints is investigated on the Eco-Stock®, a commercial packed bed developed by the company Eco-Tech Ceram (1.9 MWhth at 525°C). The first test takes into account the simulated solar power variation along the day. Power variation has a minor impact on the packed bed performance, with a 3% decrease on the yield at 0.8 of cutoff temperature. Numerical results match the experiment, proving the model to handle properly power variation. The second test takes into account intermittencies, due to potential clouds. The stand-by phases had a major impact, reducing the yield by 13% at 0.8 of cutoff temperature, due to heat losses and both axial and radial stratification
Traitement thermique de recyclage appliqué aux composites carbone/PEEK et aux mélanges de composites renforcés carbone. Solutions alternatives de valorisation des fibres recyclées
No full textCarbon Fiber Reinforced Composites (CFRC) are high technical materials applied in various fields from sports to aeronautics. During the last decade, the demand of CFRC has extended significantly resulting in increasing the volume of composite waste generated each year. Incited by European directives, thermal recycling treatments have been developed at industrial scale to recover carbon fibers, mostly from thermosetting composites. Nowadays CFRP in development used thermoresistant resins such as Poly Ether Ether Ketone (PEEK). Part of this work is to study the recycling feasibility of this type of CFRP alone and mixed with thermosetting and thermoplastics matrix based composites. Semi-industrial pilot was used in inert (pyrolysis) and reactive (steam-thermolysis, oxydation) atmosphere conditions. First results of mixture perform in nitrogen have revealed that inert atmosphere cannot allow the recovery of carbon fibers from thermoresistant resins. On the contrary trials on PEEK in oxydative atmospheres enable the extraction of fiber, but induce morphological and chemical modifications and tensile strength reduction. New approach on the recycled carbon fiber valorization have also been studied. These fibers have been coated by nanocellulose as sizing agent for their reuse in new composite formulations. Mechanical properties loss induce by recycling have been offset thank to this surface treatment. Recycled fibers was also incorporate in jute/PA6 composite to create a hybrid composite with balance properties in terms of strength, price and environmental impact.Les composites renforcés à fibres de carbone (CRFC) sont des matériaux de haute technicité appliqués à de nombreux domaines, du sport à l’aéronautique. Cette dernière décennie a vu leur demande croitre continuellement, générant en conséquence une augmentation du volume de déchets. Incités par les directives Européennes sur la gestion des déchets, des traitements thermiques de recyclage industriel ont été développés afin de récupérer les fibres de carbone issues des CFRC, principalement à matrice thermodurcissable. Actuellement, les CRFC en développement et/ou de dernières générations, utilisent des matrices thermostables telles que le Poly Ether Ether Cétone (PEEK). Une partie des travaux de thèse consiste à étudier la faisabilité de recyclage de ce composite thermostable, seul et en mélange avec d’autres types de composites à matrice thermodurcissable et thermoplastique. Un pilote semi-industriel a été employé sous atmosphères inerte (pyrolyse) et réactives (vapo-thermolyse et air). Les premiers résultats sur des mélanges ont montré que sous atmosphère inerte la récupération des fibres de carbone issues des matrices thermostables est quasi impossible. A l’inverse, les essais sur les composites PEEK en atmosphères oxydantes permettent l’extraction de la fibre mais induisent des modifications morphologiques et chimiques de la surface ainsi qu’une réduction de la résistance en traction. Les travaux de thèse se focalisent également sur des solutions alternatives de valorisation des fibres de carbone recyclées. Ces fibres ont été recouvertes de nanocellulose en tant qu’agent d’ensimage, en vue de leur réutilisation dans de nouvelles formulations. La perte de propriétés mécaniques induite par le recyclage a été partiellement compensée par ce traitement de surface. Des fibres recyclées ont également été incorporées dans un composite à renfort naturel de jute et matrice PA6 dans le but de créer un composite hybride offrant des propriétés équilibrées en termes de résistance, prix et impact écologique
Optimal sizing of an automated dispensing cabinet under adjacency constraints
No full textNational audienceIn this paper, we focus on the problem of determining the feasibility of medication assignment in an automated dispensing cabinet. Indeed, a cabinet is made up of several drawers. Each drawer is subdivided into compartments, each capable of receiving one medication type. There are medications which should not be placed in neighbouring compartments because of the risk of confusion, according to medication similarity (lookalike/sound-alike drugs) or the pharmacological incompatibility which may lead to errors in dispensing. Then, the problem consists in determining the boundary conditions necessary for the allocation of medications to the different compartments without similar/incompatible medications in close proximity to one another. First, we developed an algebraic model that calculates the upper limit (not to exceed) of appearances of a medication in all pairs of incompatible medications. Then we formulated an efficient mixed-integer linear program that checksthe existence of an acceptable solution to the assignment problem