Portail HAL IMT Mines Albi
Not a member yet
5440 research outputs found
Sort by
Combustion performance of solid refuse fuel-derived biochars for energy production
No full textInternational audienceA drastic reduction in greenhouse gas emissions in the short term is required. In this context, high carbon industrial processes, typically using fossil fuels, should move towards the use of alternative renewable fuels. Biochar obtained from biomass through thermochemical processes, such as pyrolysis can play a role, as it has thermal and processing properties closer to those of coal, which makes it a suitable biosourced alternative to fossil fuels at industrial scale [1]. This work aims at studying biochar combustion, to be used for energy application in various industries. To do this, biochar from Solid Refuse Fuel (SRF) was produced by carbonization, followed by a devolatilization step (650 to 850°C). Biochar samples were characterized in terms of structural properties (BET, microscopy), chemical composition (CHNS, ICP-OES, FTIR), and thermal behavior (TGA-DTG, calorimetric bomb). The results obtained showed that an increase in the devolatilization temperature resulted in a higher C/H ratio. Under an inert atmosphere, the thermal behavior of carbonized SRF was shown to be similar to that of hard coal. TGA-DTG combustion experiments were carried out at different heating rates (5, 10, and 20 °C.min -1 ), revealing fixed carbon oxidation. Combustion performance was evaluated through the combustion performance index (S), the maximum reactivity (Rmax), and the ignition index (D) [2]. Thus, the ignition temperature rose from 267 °C to 320 °C for carbonized SRF after devolatilization at 750 °C. The fate and quality of emissions versus the composition of the initial feedstocks will be discussed
Prédiction de l'arrivée des appels dans un centre relais pour sourds et malentendants
No full textNational audienceDans un centre d'appels, la prévision du nombre d'appels entrants est un véritable défi à cause de son caractère incertain et de son impact sur le nombre d'agents à affecter. Cette prévision peut être réalisée, avec un certain degré d'erreur, grâce à des lois statistiques, ou à l'aide de réseaux de neurones. La principale difficulté est de déterminer le modèle de prédiction le mieux adapté au problème et les valeurs optimales de ses hyperparamètres. Cet article résume les modèles testés et les résultats obtenus pour atteindre la meilleure précision possible dans la prévision du nombre d'appels entrants quotidiens d'un centre relais pour sourds et malentendants.Dans un centre d'appels, la prévision du nombre d'appels entrants est un véritable défi à cause de son caractère incertain et de son impact sur le nombre d'agents à affecter. Cette prévision peut être réalisée, avec un certain degré d'erreur, grâce à des lois statistiques, ou à l'aide de réseaux de neurones. La principale difficulté est de déterminer le modèle de prédiction le mieux adapté au problème et les valeurs optimales de ses hyperparamètres. Cet article résume les modèles testés et les résultats obtenus pour atteindre la meilleure précision possible dans la prévision du nombre d'appels entrants quotidiens d'un centre relais pour sourds et malentendants
Conception de réacteurs ultrasonores optimisés pour l’intensification de procédés : modélisation et caractérisation
No full textInternational audienc
Élaboration de biomatériaux phosphocalciques macroporeux à partir d'émulsions de Pickering concentrées
No full textApatitic calcium phosphate (or apatites) based ceramics are widely used as bone substitutes due to their biocompatibility and bioactivity. Nowadays, phosphate calcium bioceramics available on the market are usually obtained at high temperature sintering (> 1000°C). However, their bioresorbability, surface reactivity and association with biomolecules are limited, due to their low specific surface area and poor chemical reactivity. Moreover, as pores size (>200 µm) and morphology of biomaterials are directly related to bone formation, interconnected macroporosity is also essential to improve bone growth in these bioceramics.The aim of this work is to optimize biologic and/or therapeutic efficacity using a recently patented method to develop low temperature biomimetic ceramics with controlled porosity using Pickering emulsions for filling bone defects. Pickering emulsions were stabilized by hydroxyapatite (HAp), particles have been synthetized and thoroughly characterized. Careful consideration has been given to their behavior in solution. Different formulations were varied in the solid emulsion, then they were studied and characterized to choose the best properties for porous bioceramics. Afterwards, its aqueous phase was mineralized by adding some calcium phosphate gel to obtain ceramic biomaterials. Various key parameters of the biomaterials were the evaluated such as their physicochemical composition, their pores size, or their interconnection. Solid emulsions used as template for porous calcium phosphate bioceramics enables to control their composition and porosity, for medical application.Les biocéramiques phosphocalciques (CaP) sont largement utilisées depuis de nombreuses années en raison de leur biocompatibilité et de leur bioactivité. Actuellement, les céramiques CaP implantables disponibles sur le marché sont obtenues par frittage à haute température (> 1000°C) conduisant à des matériaux ne présentant qu'une faible réactivité de surface et un caractère peu ou pas résorbable, limitant notamment leur capacité à adsorber des biomolécules comme des principes actifs. Par ailleurs, la taille des pores des biocéramiques en CaP (>200 microns) et leur morphologie (interconnexion) sont directement liées à la repousse osseuse. L'objectif de ce travail est d'optimiser l'efficacité biologique et/ou thérapeutique en s'appuyant sur une méthode récemment brevetée pour l'obtention de biocéramiques CaP à basse température à porosité contrôlée en combinant chimie douce et émulsions de Pickering pour des applications de comblements osseux. Les émulsions de Pickering ont été stabilisées par des particules d'hydroxyapatite (HAp) synthétisées et finement caractérisées, une attention particulière a été portée sur leur comportement en solution. Différentes formulations de l'émulsion solide ont été étudiées et caractérisées, afin de sélectionner les propriétés optimales pour l'obtention des biocéramiques poreuses ; sa phase aqueuse a ensuite été minéralisée par l'ajout d'un gel de phosphate de calcium et les monolithes poreux phosphocalciques obtenus ont été analysés : leur composition physico-chimique, la taille des pores ou leur interconnexion. L'utilisation des émulsions solides pour l'obtention de biocéramiques poreuses de phosphates de calcium permet le contrôle de la composition et de la porosité, en vue d'une application médicale
Improvement of nifedipine dissolution rate by particle size reduction and its impact on transdermal delivery
No full textInternational audienc
Preparation, characterisation and utilisation of biosourced nickel and iron-based catalysts for energy applications
No full textInternational audienceThe Paris Agreement, signed in 2015, engaged the 195 signatory nations to reduce greenhouse gas emissions. The valorisation of biomass and biowaste into hydrogen and biofuels may play a significant role in reaching this objective, due to the carbon neutrality and high availability of these bioresources. However, thermochemical conversion processes for bioresource conversion typically require high temperatures (between 500 to 1000°C) and the use of a catalyst. An example is synthetic fuels production through Fischer-Tropsch synthesis (FTS). This process, operating at 180 to 400°C and around 20 bar, requires noble or transition metal-based catalysts, including iron (Fe) and nickel (Ni) [1,2]. Commercial catalysts’ impact on the environment is non-negligible, due to metal extraction through energetic and solvent intensive processes, and also metal scarcity [3,4]. To overcome this burden, catalysts may be produced from bioresource inherent metal or metal-loaded bioresources. However, the complex and heterogeneous structure of bioresources needs to be carefully analysed and understood to lead to a performant catalytic material.The objective of this work is to prepare, characterize and utilize biosourced catalysts from bioresources loaded with heavy metals whose catalytic activity was identified for hydrogen or biofuels production
Renewable hydrogen from bioresources: evaluation of separation, purification and analytical techniques for monitoring and quantification
No full textInternational audienceThe increase of the share of renewables energies is essential to reach climate and energy goals defined by the United Nation's Sustainable Development Goals (SDGs) and the targets of the COP27 Glasgow Agreement. In this regard, renewable hydrogen (H2) due to its strong potential towards industry a transportation sector decarbonization is one of the key pillars to achieve a sustainable energy transition. Hydrogen is a carbon-free energy carrier, releasing only H2O as by-product and presenting a higher energetic content compared to other biofuels (HHV of 120 MJ/kg, while that of liquid biofuels is around 43 MJ/kg, 15 MJ/kg for lignocellulosic biomass and 30 MJ/kg for coal). Nowadays, hydrogen accounts for less than 1% of Europe’s energy consumption and is mainly produced through highly carbon-emitting pathways (‘grey’ hydrogen). However, the share of hydrogen in Europe’s energy mix is projected to grow to 13-14% by 2050, by favoring renewable production pathways leading to ‘green’ hydrogen, such as electrolysis and bioresources conversion [1].Different aspects of hydrogen-based energy system have been addressed, including production, endpoint application, storage, and safety. The quality of hydrogen to be considered is strongly dependent on the application. The small size, explosive nature, and relatively low reactivity of the hydrogen molecule made its detection, quantification and monitoring more challenging than that of other energetic gas molecules. This work proposes a review of analytical techniques for hydrogen monitoring and quantification as well as the purification via the removal of the main pollutants for targeted applications. This study intents to serve as a decision tool contributing to the development of renewable hydrogen (biohydrogen) production from bioresources, its storage and utilization at large-scale.In the literature, few studies are specifically devoted to the development of new analytical techniques for gaseous H2 detection, quantification, and modelling, as, in most of the cases, the standard techniques are used. In this review, these techniques are discussed in detail, as well as how they are implemented in hydrogen production processes from bioresources. The literature provides international standards that define the specifications for hydrogen detection apparatus, such as response time, precision, selectivity, stability, measuring range and poisoning (ISO 26142:2010, stationary applications). Hydrogen analytic techniques can be carried out off-line, after gas trapping or collection; or on-line using continuous and instantaneous detection methods or sensors [2]. Furthermore, these techniques can be classified in intrusive and non-intrusive methods whether the hydrogen flow is modified or not. The literature review showed that standard and well-stablished techniques such as micro-GC and mass flowmeters are the most frequently used. However, the main challenges remain the improvement of the response time, the reliability of hydrogen quantification in gaseous mixtures and the determination of the detection limit as well as sensitivity of the techniques. To this end, the use of standards for calibration of the matrix effects in gaseous mixtures will be crucial in increasing the accuracy. A special focus was put on the development of portative, fast-response analytic devices, due to their interest for assisting process monitoring and detecting leaks. Furthermore, the development of high-pressure refueling stations requires an accurate monitoring of the hydrogen dynamic filling process in a large range of temperature and pressure (up to 87.5 MPa), which represents a challenge for available flowmeters [3]. Different impurities and contaminants may be present in biohydrogen depending on the production process used and the feedstocks that may contain chemical elements that may cause catalyst poisoning, corrosion, and fouling in hydrogen applications. Impurities include particulate matter, benzene (C6H6), C1-2 linear hydrocarbons, nitrogen (N2), ammonia (NH3), hydrogen sulfide (H2S), hydrogen chloride (HCl), sulfur dioxide (SO2), hydrogen cyanide (HCN), oxygen (O2), carbonyl sulfide (COS), water (H2O) and tars [4]. Hydrogen impurities and pollutants are firstly separated by physico-chemical methods, such as absorption, scrubbing, electrostatic methods, catalytic and/or oxidative processes. Then, hydrogen purification undergoes Pressure Swing Adsorption (PSA) that upgrades hydrogen quality to fulfill specifications for various applications. The required level of separation and purification of the produced hydrogen-rich gas varies significantly depending on the endpoint technology, storage technology and environmental regulations [5]. [1]“A Hydrogen strategy for a climate-neutral Europe”, COM (2020) 301 final, European Commission, July 2020.[2]Nzihou A, editor: Handbook on Characterization of Biomass, Biowaste and Related By-products. Springer International Publishing; 2020.[3]Murugan, A., de Huu, M., Bacquart, T., van Wijk, J., Arrhenius, K., te Ronde, I., Hemfrey, D.: Measurement challenges for hydrogen vehicles, International Journal of Hydrogen Energy. 44, 19326–33 (2019).[4]Awe, O.W., Zhao, Y., Nzihou, A., Pham Minh, D., Lyczko, N.: A Review of Biogas Utilisation, Purification and Upgrading Technologies, Waste Biomass Valorization. 8, 267–83 (2017).[5]Aprea, J.L.: Quality specification and safety in hydrogen production, commercialization and utilization, International Journal of Hydrogen Energy. 39, 8604–8 (2014)
Optimisation de l’obtention de poudres de stévioside et rébaudioside A à partir de jus bruts ou purifiés extraits de feuille de stevia bio
No full textStevia Rebaudiana is a perennial herbaceous plant, part of the Asteraceae family and native to Paraguay. It has been cultivated in China and Southeast Asia for several decades and more recently in France, in the Occitanie region. More commonly known as “Stevia”, it is a new source of natural sweetener since it contains steviol glycosides with a sweet taste. These molecules have a sweetening power 100-300 times greater than sucrose and they are calorie-free. The major steviol glycosides in the plant are Stevioside (Stv) and Rebaudioside A (Reb A). The objective of this thesis is the development of unit operations with controlled properties of crystallization and drying in order to obtain purified powders, from juices extracted from organic stevia leaves. This project was carried out in collaboration with the start-up Oviatis, the Occitanie region and École des Mines d'Albi.La Stevia Rebaudiana est une plante herbacée vivace, faisant partie de la famille des Asteraceae et originaire du Paraguay. Elle est cultivée en Chine et en Asie du Sud-Est depuis plusieurs décennies et plus récemment en France, en région Occitanie. Plus communément appelé « Stévia », c'est une nouvelle source d'édulcorant naturel puisqu'elle contient des glycosides de stéviol ayant un goût sucré. Ces molécules possèdent un pouvoir sucrant 100-300 fois supérieur au saccharose et ne sont pas caloriques. Les glycosides de stéviol majoritaires dans la plante sont le Stévioside (Stv) et le Rébaudioside A (Reb A). L'objectif de la thèse est la mise au point des opérations unitaires de cristallisation et de séchage pour l'obtention de poudres purifiées à propriétés contrôlées, à partir de jus extraits de feuilles de stévia bio. Ce projet a été réalisé en collaboration avec la start-up Oviatis, la région Occitanie et l'Ecole des Mines d'Albi
Introduction to the DIRECT minitrack (Disaster Information, Technology, and Resilience) in the Digital Government track
No full textInternational audienceAfter a year 2021 placed under the sign of the global pandemic, it is not surprising to find nearly a third of the articles selected for the DIRECT minitrackaddressing the subject of COVID-19 (30%). Overall, almost half of the articles in this edition of the DIRECT minitrack deal with communication betweenand among citizens (46%), two articles deal with the notion of evacuation (15%), and almost a quarter deal directly with resilience (23%). Finally, there are a few original topics that are not often covered in the minitrack DIRECT, such as cybersecurity or traffic management. The global feeling is that the next editions should probably slowly slide from instantaneous and short terms events mainly articles (e.g., earthquake) to long terms and continuous crisis articles (e.g. global warming and refugees), The DIRECT minitrack of the eGov track of HICSS 55 presents thirteen great papers addressing these issues but also these perspectives. The following presents each of these articles