Les réactions de catalyse hétérogène impliquant un gaz et un liquide sont mises en oeuvre dans des réacteurs à lit fixes. Ces réacteurs peuvent être assimilés à un milieu poreux. La nature complexe de ce milieu rend la compréhension des interactions entre phases difficile, et nécessite une étude exhaustive à l’échelle globale et locale afin d’identifier les paramètres clés de l’hydrodynamique, des transferts de chaleur et de matière. Nous avons donc développé une cellule miniaturisée bidimensionnelle transparente, qui permet l’observation directe des écoulements avec une très bonne résolution spatiale et temporelle. En faisant varier le débit total et le rapport des débits gaz/liquide, nous avons mis en évidence l’apparition des régimes ruisselant et pulsé, observés par ailleurs dans des systèmes tridimensionnels. Grâce à une méthode d’analyse d’image, nous sommes capables de quantifier et cartographier la saturation liquide locale apparente et la morphologie des phases. L’analyse des variances a permis d’étudier les transitions de régimes pour différentes propriétés de la phase liquide. Cette approche a permis de comparer avec la littérature, mais aussi de s’intéresser aux mécanismes de génération et propagation des instabilités lors des transitions. Il a été mis en évidence que l’apparition des instabilités responsables de la déstabilisation du régime ruisselant intervient pour un nombre deWeber liquide fixé, indiquant que le régime pulsé apparait suite à la déstabilisation des interfaces gaz /liquides par les forces inertielles. Enfin, une étude préliminaire des transferts thermiques dans la cellule a été réalisée. La cellule est utilisée pour réaliser la réaction exothermique d’hydrogénation de l’alpha-methylstyrène. Un modèle simple de transferts thermique a été utilisé pour caractériser l’augmentation de température dans la cellule. Bien que cette approche ne permette pas des mesures quantitatives, elle ouvre à la perspective de suivi de transferts thermiques par caméra infra-rouge. / Heterogeneously catalyzed reactions involving a gas and a liquid phase are frequently achieved in fixed bed reactors. These reactors can be described as a porous medium. The complex nature of this medium makes the understanding of the interplay between phases difficult, and requires a thorough study at the global andlocal scale to identify the key parameters of hydrodynamics, mass and heat transfers. Therefore, we have developed a miniaturized two-dimensional system that is transparent to allow the direct observation of the flow with very high spatial and temporal resolution. While varying the total flow rate and the gas/liquid flow rate ratio, we observe the appearance of the trickle and the pulse flow regime, which can be observed in threedimensional beds. Thanks to some image analysis techniques, we are able to quantify and to map the local apparent liquid saturation and the morphology of the phases. Variances analysis allowed the study of the transition for different liquid properties. This approach allowed the comparison with the existing state of art, but also the study of the onset and propagation mechanisms of the instabilities during the transition. We report that the onset of instabilities responsible for the destabilization of the trickle flow regime occurs at a fixed Weber number. This indicates that the pulsed regime is due to the destabilization of the gas/liquid interface by inertial forces. Finally, a preliminary study of thermal transfers in the device was realized. The device was used to perform the exothermic hydrogenation of alpha-methylstyrene. A simple model is used to characterize the temperature increase in the device. Although this approach does not allow quantitative measurements, it opens up the perspective of monitoring thermal transfers with an infra-red camera.

No description available.

During the last few decades, concerns about water shortages and pollution have increased. Consequently, environmental legislations and regulations for wastewater discharge have been issued. The objective of this work was to contribute in developing an efficient dsorbent for removing heavy metal ions from wastewater. The thesis focused on evaluating amine-modified SBA-15 as copper and other heavy metal ions adsorbent, by determining a variety of adsorptive properties with the aim of gaining a deep understanding of its behavior and to outline its advantages and limitations. The influence of synthesis conditions on the mesostructural stability of the resultant materials after different water treatments was systematically investigated. N2 adsorption results indicated that the material prepared via co-condensation and aged at 100 ºC was not stable and lost its ordered mesoporous structure after contacting water even at room temperature. Aging at 130 ºC and addition of inorganic salts resulted in materials that maintained their mesporous structure under different water treatments. The material synthesized in the presence of KCl was used as adsorbent for the rest of the thesis work. It was shown that the structural collapse observed in amine-modified SBA-15 prepared by conventional method when contacted with aqueous solutions is associated with the drying process, and not the treatment itself. This structural collapse was avoided by replacing water with more volatile liquids such as acetone, before drying. Amino-functionalized SBA-15 was tested for the removal of copper ions from aqueous solutions under different temperatures, pH, initial concentrations and agitation speeds. The obtained results indicated that the amino-functionalized SBA-15 was very efficient and equilibrium was achieved in less than 30 min at room temperature. The adsorption capacity increased dramatically with increasing temperature, initial copper concentration and pH. Under suitable conditions, the material exhibited high adsorption capacity even at very low copper concentration. To further investigate the effect of dsorption parameters, a 24 factorial design experiments were used to screen the factors affecting the copper removal efficiency. All the parameters main effects were significant within a 95 % confidence level. Surface composite design was used to develop a reliable model representing the adsorption process. The statistical tests used proved the adequacy of the second order model. Optimization of the factors levels was carried out and the recommended optimum conditions are: copper concentration of 20 mg/L, adsorbent/solution ratio of 1.57 g/L, pH of 6.5, and T = 294 K with 95% copper removal. The effect of regeneration conditions was investigated after three adsorption–desorption cycles, under different batchwise regeneration conditions. Using a composite surface design methodology, the effect of the regeneration conditions on the performance of the adsorbent was investigated. It was found that all the studied parameters have a statistically significant influence on the working dsorption capacity. With respect to structural properties and amine content, none of the factors was found to be significant. Regeneration using EDTA was found to be more efficient than acid treatment. Amino-functionalized SBA-15 was studied as potential absorbent for Cd2 +, Co2 +, Cu2 +, Zn2 +, Pb2 +, Ni2 +, Al3+ and Cr3 +. The adsorption capacity and selectivity of the material were investigated in single and multi-metal solutions. Using very dilute solutions, i.e., 10 ppm, more than 95% of cations were removed, except for Co2+ and Cr3 +, indicatingthe high sensitivity of the current adsorbent. The adsorption capacities in multi-metal solutions were lower than in single-metal ones because of competition between metallic elements for the amine groups. The adsorbent was not affected in the presence of sodium, potassium, and calcium, indicating that the ionic strength does not affect the adsorption properties. Application of this material to remove copper in tap water, river water, and electroplating wastewater was shown to be successful. Dynamic experiments were carried out on the adsorption of copper ions in a laboratory packed-bed of amine-modified SBA-15. Breakthrough curves were analyzed at different flowrates and after two adsorption-desorption cycles. Furthermore, a model based on mass balance was developed and tested for predicting the breakthrough curves under different experimental conditions used. The results suggested that the developed model was in good agreement with the experimental data. Bed regeneration was performed by circulating 0.2 M EDTA solution through the column for 30 min. Résumé Durant les quelques dernières décennies, les préoccupations concernant les pénuries d'eau et la pollution en général ont augmenté. Par conséquent, des législations et des réglementations environnementales pour les rejets d'eaux usées ont été introduites. L'objectif de ce travail était de contribuer au développement d'un adsorbant efficace pour éliminer les ions de métaux lourds des eaux usées. Cette thèse porte sur l'évaluation de SBA-15 modifiée avec des amines comme adsorbant pour le cuivre et d'autres ions de métaux lourds par la détermination d'une multitude de propriétés d'adsorption dans le but d'acquérir une profonde compréhension de son comportement et d’identifier ses avantages et ses limites. L'influence des conditions de synthèse sur la stabilité des matériaux mésoporeux obtenus après différents traitements a été étudié de façon systématique. Les résultats d'adsorption de N2 ont indiqué que le matériel préparé par co-condensation et vieilli à 100 °C n'était pas stable et a perdu sa structure mésoporeuse ordonnée après avoir été en contact avec l'eau même à température ambiante. Le vieillissement à 130 °C, avec ajout de sels inorganiques, a abouti à des matériaux qui ont maintenu leur structure mésoporeuse sous différents traitements en présence d'eau. Le matériau synthétisé en présence de KCl a été utilisé comme adsorbant pour le reste du travail de cette thèse. Il a été démontré que l'effondrement de la structure observé dans la SBA-15 modifiée aux amines, préparée par la méthode conventionnelle en contact avec des solutions aqueuses est associé avec le processus de séchage, et non le traitement lui-même. Cet effondrement de structure a été évité en remplaçant l'eau avec des liquides plus volatils tels que l'acétone, avant le séchage. La SBA-15 amino-fonctionnalisée a été testée pour l'élimination des ions de cuivre des solutions aqueuses à différentes températures, pH, concentrations initiales et vitesses d'agitation. Les résultats obtenus ont indiqué que la SBA-15 amino-fonctionnalisée était très efficace et l'équilibre a été atteint en moins de 30 min à température ambiante. La capacité d'adsorption a considérablement augmenté avec la température, la concentration initiale de cuivre et le pH. Sous des conditions appropriées, le matériau a manifesté une grande capacité d'adsorption, même à des concentrations très faibles en cuivre. Afin d’étudier l'effet des paramètres d'adsorption, un plan factoriel de 24 expériences a été utilisé pour dépister les facteurs affectant l'efficacité d'élimination du cuivre. Tous les effets principaux des paramètres étaient importants à 95% de niveau de confiance. La méthodologie de la surface composite a été utilisée pour développer un modèle fiable qui représente le processus d'adsorption. Les tests statistiques utilisés ont prouvé la pertinence du modèle de second ordre. L’optimisation des niveaux des facteurs a été effectuée et les conditions optimales recommandées sont: la concentration en cuivre de 20 mg/L, le rapport adsorbant/solution de 1.57 g/L, pH de 6.5 et T = 294 K pour l'élimination de 95% de cuivre. L'effet des conditions de régénération a été étudié après trois cycles d'adsorption-désorption, sous différentes conditions de régénération. En utilisant la méthodologie de la surface composite, l'effet des conditions de régénération sur la performance de l'adsorbant a été étudié. Il a été constaté que tous les paramètres étudiés ont une influence statistiquement significative sur la capacité de travail d'adsorption. En ce qui concerne les propriétés structurelles et la teneur en amine, aucun des facteurs n’a été jugé significatif. La régénération à l'aide d'EDTA a été jugée plus efficace que le traitement acide. La SBA-15 amino-fonctionnalisée a été étudiée comme absorbant potentiel de Cd2+, Co2+, Cu2+, Zn2+, Pb2+, Ni2+, Al3+ and Cr3+. La capacité d'adsorption et la sélectivité du matériau ont été étudiées dans des solutions mono- et multi-métalliques. En utilisant des solutions très diluées, soit 10 ppm, plus de 95% de cations ont été enlevés, sauf pour le Co2+ et Cr3+, indiquant la forte sensibilité de l'adsorbant. Les capacités d'adsorption dans les solutions multi-métalliques étaient inférieures à celles des solutions mono-métalliques en raison de la concurrence entre les éléments métalliques pour les groupes amine. L'adsorbant n'a pas été affecté par la présence de sodium, de potassium et de calcium, ce qui indique que la force ionique n'affecte pas les propriétés d'adsorption. L’usage avec succès de ce matériau pour éliminer le cuivre dans l'eau de robinet, l’eau de rivière et les eaux usées de galvanoplastie a été démontré. Des expériences dynamiques ont été réalisées sur l'adsorption des ions de cuivre par la SBA-15 amine-modifiée sur une colonne à lit fixe de laboratoire. Les courbes de perçage ont été analysées à des débits différents et après deux cycles d'adsorption-désorption. De plus, un modèle basé sur le bilan de matière a été développé et testé pour prédire les courbes de perçage sous les différentes conditions expérimentales utilisées. Les résultats suggèrent que le modèle développé est en bon accord avec les données expérimentales. La régénération du lit a été réalisée en faisant circuler une solution EDTA à 0.2 M à travers la colonne pendant 30 min.

Non-thermal plasma generated in a dielectric barrier packed-bed reactor has been used for the remediation of chlorinated volatile organic compounds. Chlorinated VOCs are important air pollutant gases which affect both the environment and human health. This thesis uses non-thermal plasma generated in single and multiple packed-bed plasma reactors for the decomposition of dichloromethane (CH2Cl2, DCM) and methyl chloride (CH3Cl). The overall aim of this thesis is to optimize the removal efficiency of DCM and CH3Cl in air plasma by investigating the influence of key process parameters. This thesis starts by investigating the influence of process parameters such as oxygen concentration, initial VOC concentration, energy density, and plasma residence time and background gas on the removal efficiency of both DCM and CH3Cl. Results of these investigations showed maximum removal efficiency with the addition of 2 to 4 % oxygen to nitrogen plasma. Oxygen concentrations in excess of 4 % decreased the decomposition of chlorinated VOCs as a result of ozone and NOx formation. This was improved by adding an alkene, propylene (C3H6), to the gas stream. With propylene additives, the maximum remediation of DCM was achieved in air plasma. It is thought that adding propylene resulted in the generation of more active radicals that play an important role in the decomposition process of DCM as well as a further oxidation of NO to NO2. Results in the single bed also showed that increasing the residence time increased the removal efficiency of chlorinated VOCs in plasma. This was optimized by designing a multiple packed-bed reactor consisting of three packed-bed cells in series, giving a total residence time of 4.2 seconds in the plasma region of the reactor. This reactor was used for both the removal of DCM, and a mixture of DCM and C3H6 in a nitrogen-oxygen gas mixture. A maximum removal efficiency of about 85 % for DCM was achieved in air plasma with the use of three plasma cells and the addition of C3H6 to the gas stream. Nitrogen oxides are air pollutants which are formed as by-products during the decomposition of chlorinated VOCs in plasmas containing nitrogen and oxygen. Results illustrate that the addition of a mixture of DCM and C3H6 resulted in the formation of the lowest concentration of nitric oxide, whilst the total nitrogen oxides concentrations did not increase. A summary of the findings of this work is presented in chapter eight as well as further work. To conclude, the maximum removal efficiency of dichloromethane was achieved in air plasma with the addition of 1000 ppm of propylene and the use of three packed-bed plasma cells in series. The lowest concentration of nitric oxide was formed in this situation.

The aim of this thesis was to create a model of thermal conversion of solid fuel. This is achieved by means of standard modelling tools included in software ANSYS Fluent in combination with user-defined functions (UDF). In first part of thesis basic approaches to CFD modelling of solid fuel combustion are presented. Building of a mathematical model and corresponding algorithms follows. Individual parts of a created model and its parts are tested on simple physical cases and then on case of experimental reactor for analysing biomass combustion.

Tato diplomová práce se zabývá tématem výměny tepla v zásobníku tepla typu ”packed bed”. Cílem je popsat přenos tepla v zásobníku tepla obsahující kamínky malých průměrů, skrz který proudí horký vzduch. Toto je modelováno v prostředí MATLAB. Na začátku je krátký úvod do problematiky zahrnující ukládání tepla a jeho možné využití. Dále je uveden krátký přehled o základech přenosu tepla, typech přenosu tepla a termofyzikální vlastnosti systému vzduch-kámen. Ve třetí kapitole je představen zásobník tepla typu ”packed bed” a rozličné modely a dané podmínky jsou vysvětleny. Další kapitola se zabývá s numerickými metodami, převážně s metodou konečných diferencí použitou v této práci. Pátá kapitola se zaměřuje na obecnou optimalizaci daného problému přenosu tepla. Populačně založený metaheuristický optimalizační algoritmus zvaný Genetický algoritmus je popsán. Sestavení modelu je ukázáno v šesté kapitole, stejně jako prezentace výsledků získaných z programu MATLAB. V poslední kapitole je pak diskutován závěr a doporučení.

Regenerative heat exchangers are used in a wide range of industries and in the technical equipment of buildings. These heat exchangers play an important role in saving thermal energy and removing volatile organic compounds from flue gases. The theoretical part of the work deals with the division of regenerative exchangers into rotary and switching exchangers and the possibilities of their use. These types of heat exchangers are used in many applications, e.g. as a heat exchanger using waste heat to preheat the process gas (regeneration layer), or as catalysts to accelerate the reaction required to remove volatile organic compounds (catalytic layer), or as integrated equipment where both the regeneration layer and the catalytic layer. The aim of the diploma thesis is experimental support in the development of a computer program for the design of a specific integrated device. The program allows the calculation of the regeneration and catalytic bed, or both beds simultaneously, i.e. integrated equipment. The diploma thesis deals with the support of a mathematical model for the calculation of the regeneration bed. Pressure loss and heat transfer play an important role in the selection and subsequent calculation of a suitable bed. To calculate them, it is possible to find more available computational relationships that differ significantly in their accuracy. It is therefore necessary to select the most suitable ones for the computational model. The practical part of the work then deals with research, analysis, and assessment of the suitability of methods used to calculate pressure losses based on a comparison with the values measured on experimental equipment. Subsequently, the work deals with computational methods for determining the heat transfer coefficient of the packed bed. A significant part of the practical part deals with the modification of the experimental equipment for the verification of computational relations for the determination of heat transfer with measured data.

In the last decades, miniaturized flow chemistry has promised to bring the benefits of process intensification, continuous manufacturing and greener chemistry to the fine chemical industry. However, miniaturized catalytic processes where gas, liquid, and solids are involved have always been impeded by two main drawbacks: multiphase-flow maldistribution (i.e. gas channeling) and clogging of capillary reactors. In this thesis, first principle models have been used to capture the complexity of multiphase flow in micropacked-bed reactors, which can suffer from poor and unpredictable mass-transfer performance. When the particle size ranges 100 µm in diameter, capillary and viscous forces control the hydrodynamics. Under such conditions, the gas —and not the liquid— flows creating preferential channels that cause poor radial dispersion. Experimental observations from the literature were reproduced to validate a physical-based modeling approach, the Phase Field Method (PFM). This simulation strategy sheds light on the impact of the micropacked-bed geometry and wettability on the formation of preferential gas channels. Counterintuitively, to homogenize the two-phase flow hydrodynamics and reduce radial mass-transfer limitations, solvent wettability of the support needs to be restricted, showing best performance when the contact angle ranges 60° and capillary forces are still dominant. Visualization experiments showed that ultrasound irradiation can also be used to partially fluidized the bed and modify the hydrodynamics. Under sonication, residence time distributions (RTD) in micropacked-bed reactors revealed a two-order-of-magnitude reduction in dispersion, allowing for nearly plug-flow behavior at high gas and liquid flow rates. At a reduced scale, surfaces vibrating with a low amplitude were shown to fluidize, prevent and solve capillary tube blockage problems, which are commonly found in the fine chemical industry for continuous product synthesis. The modeling and simulation strategy used in this thesis, enables a fast prototyping methodology for the proper acoustic design of sonoreactors, whose scale-up was achieved by introducing slits in sonotrodes. In addition, a patent-pending helicoidal capillary sonoreactor has shown to transform longitudinal vibrating modes into radial and torsional modes, pioneering a new range of chemistry able to handle a high concentration of particles. The contributions of this thesis made in the fields of reaction engineering and process intensification have demonstrated how computational methods and experimental techniques in other areas of research can be used to foster innovation at a fast pace.

The present work focuses on the study of biomass gasification process for generating hydrogen rich synthetic gas with oxy-steam as reactants using experiments and modeling studies. Utilization of the syngas as a fuel in general applications like fuel cells, Fischer-Tropsch FT) process and production of various chemicals like DME, etc. are being considered to meet the demand for clean energy. This study comprises of experiments using an open top down draft reactor with oxygen and steam as reactants in the co-current configuration. Apart from the standard gasification performance evaluation; parametric study using equivalence ratio, steam-to-biomass ratio as major variables towards generation of syngas is addressed towards controlling H2/CO ratio. The gasification process is modeled as a packed bed reactor to predict the exit gas composition, propagation rate, bed temperature as a function of input reactants, temperature and mass flux with variation in thermo-physical properties of biomass. These results are compared with the present experiments as well as those in literature. Experiments are conducted using modified open top downdraft configuration reactor with lock hoppers and provision for oxy-steam injection, and the exit gas is connected to the cooling and cleaning system. The fully instrumented system is used to measure bed temperatures, steam and exit gas temperature, pressures at various locations, flow rates of fuel, reactants and product gas along with the gas composition. Preliminary investigations focused on using air as the reactant and towards establishing the packed bed performance by comparing with the experimental results from the literature and extended the study to O2-N2 mixtures. The study focuses on determining the propagation rate of the flame front in the packed bed reactor for various operating conditions. O2 is varied between 20-100% (vol.) in a mixture of O2-N2 to study the effect of O2 fraction on flame propagation rate and biomass conversion. With the increase in O2 fraction, the propagation rates are found to be very high and reaching over 10 mm/s, resulting in incomplete pyrolysis and poor biomass conversion. The flame propagation rate is found to vary with oxygen volume fraction as XO22.5, and stable operation is achieved with O2 fraction below 30%. Towards introducing H2O as a reactant for enhancing the hydrogen content in the syngas and also to reduce the propagation rates at higher ER, wet biomass is used. Stable operating conditions are achieved using wet biomass with moisture-to-biomass (H2O:Biomass) ratio between 0.6 to 1.1 (mass basis) and H2 yield up to 63 g/kg of dry biomass amounting to 33% volume fraction in the syngas. Identifying the limitation on the hydrogen yield and the criticality of achieving high quality gas; oxy-steam mixture is introduced as reactants with dry biomass as fuel. An electric boiler along with a superheater is used to generate superheated steam upto 700 K and pressure in the range of 0.4 MPa. Steam-to-biomass ratio (SBR) and ER is varied with towards generating hydrogen rich syngas with sustained continuous operation of oxy-steam gasification of dry biomass. The results are analysed with the variation of SBR for flame propagation rates, calorific value of product syngas, energy efficiency, H2 yield per kg of biomass and H2/CO ratio. Hydrogen yield of 104 g per kg of dry casuarina wood is achieved amounting to 50.5% volume fraction in dry syngas through oxy-steam gasification process compared to air gasification hydrogen yield of about 40 g per kg of fuel and 20% volume fraction. First and second law analysis for energy and exergy efficiency evaluation has been performed on the experimental results and compared with air gasification. Individual components of the energy input and output are analysed and discussed. H2 yield is found to increase with SBR with the reduction in energy density of syngas and also energy efficiency. Highest energy efficiency of 80.3% has been achieved at SBR of 0.75 (on molar basis) with H2 yield of 66 g/kg of biomass and LHV of 8.9 MJ/Nm3; whereas H2 yield of 104 g/kg of biomass is achieved at SBR of 2.7 with the lower efficiency of 65.6% and LHV of 7.4 MJ/Nm3. The energy density of the syngas achieved in the present study is roughly double compared to the LHV of typical product gas with air gasification. Elemental mass balance technique has been employed to identify carbon boundary at an SBR of 1.5. Controlling parameters for arriving at the desired H2/CO ratio in the product syngas have been identified. Optimum process parameters (ER and SBR) has been identified through experimental studies for sustained continuous oxy-steam gasification process, maximizing H2 yield, controlling the H2/CO ratio, high energy efficiency and high energy density in the product syngas. Increase in ER with SBR is required to compensate the reduction in O2 fraction in oxy-steam mixture and to maintain the desired bed temperature in the combustion zone. In the range of SBR of 0.75 to 2.7, ER requirement increases from 0.18 to 0.3. The sustained continuous operation is possible upto SBR of 1.5, till the carbon boundary is reached. Operating at high SBR is required for high H2 yield but sustained highest H2 yield is obtained as SBR of 1.5. H2/CO ratio in the syngas increases from 1.5 to 4 with the SBR and depending on the requirement of the downstream process (eg., FT synthesis), suitable SBR and ER combination is suggested. To obtain high energy density in syngas and high energy efficiency, operations at lower SBR is recommended. The modeling study is the extension of the work carried by Dasappa (1999) by incorporating wood pyrolysis model into the single particle and volatile combustion for the packed bed of particles. The packed bed reactor model comprises of array of single particles stacked in a vertical bed that deals with the detailed reaction rates along with the porous char spheres and thermo-physical phenomenon governed by the mass, species and energy conservation equations. Towards validating the pyrolysis and single particle conversion process, separate analysis and parametric study addressing the effects of thermo-physical parameters like particle size, density and thermal conductivity under varying conditions have been studied and compared with the available results from literature. It has been found that the devolatilisation time of particle (tc) follows closely the relationship with the particle diameter (d), thermal conductivity (k), density () and temperature (T) as: The complete combustion of a single particle flaming pyrolysis and char combustion has been studied and validated with the experimental results. For the reactor modeling, energy, mass and species conservation equations in the axial flow direction formulate the governing equations coupled to the detailed single particle analysis. Gas phase reactions involving combustion of volatiles and water gas shift reaction are solved in the packed bed. The model results are compared with the experimental results from wood gasification system with respect to the propagation rate, conversion times, exit gas composition and other bed parameters like conversion, peak bed temperatures, etc. The propagation rates compare well with experimental data over a range of oxygen concentration in the O2- N2 mixture, with a peak at 10 mm/s for 100 % O2. In the case of oxy-steam gasification of dry biomass, the results clearly suggest that the char conversion is an important component contributing to the bed movement and hence the overall effective propagation rate is an important parameter for co-current reactors. This is further analyzed using the carbon boundary points based on elemental balance technique. The model predictions for the exit gas composition from the oxy-steam gasification matches well with the experimental results over a wide range of equivalence ratio and steam to biomass ratio. The output gas composition and propagation rates are found to be a direct consequence of input mass flux and O2 fraction in oxy-steam mixture. The present study comprehensively addresses the oxy-steam gasification towards generating hydrogen rich syngas using experimental and model studies. The study also arrives at the parameters for design consideration towards operating an oxy-steam biomass gasification system. The following flow chart provides the overall aspects that are covered in the thesis chapter wise.

Ce travail porte sur le développement d’un système de stockage de chaleur en vue d’assurer le confort thermique de l’habitacle d’un véhicule électrique. Ce dispositif, appelé batterie thermique, se présente comme un réservoir composé d’un lit fixe de matériaux à changement de phase (MCP). Ce type de matériau a la propriété d’emmagasiner de fortes quantités de chaleur (latente) sous de faibles volumes, permettant d’envisager un système très compact. A l’échelle du matériau, une investigation sur la cinétique des transferts thermiques au sein de plusieurs MCPs a été évaluée. Une expression phénoménologique décrivant l’évolution temporelle de la température d’un MCP en phase de solidification a été proposée. Elle permet d’estimer la durée de solidification du matériau en fonction de ses caractéristiques géométriques et thermiques. A l’échelle du système, un prototype de batterie thermique a été réalisé et la dynamique des transferts en phase de stockage et déstockage a été étudiée. Les durées de stockage et déstockage suivent des lois de puissance avec le débit imposé ; les pertes de charges s’avèrent insignifiantes. En parallèle, un modèle numérique simulant le comportement dynamique et thermique d’un lit fixe de particules de MCP a été développé et validé sur les données expérimentales. Il pourra être utilisé pour le dimensionnement du futur prototype et servira également d’outil pour optimiser les performances de la batterie en ajustant les paramètres de contrôle / This study focuses on the development of a heat storage system used to ensure passenger compartment thermal comfort in an electric vehicle. This device, called a thermal battery, is a packed bed latent heat tank filled with phase change materials (PCM). This type of material has the property of storing large amounts of latent heat in small volumes, allowing a very compact system. At the material scale, an investigation on heat transfer dynamics within several PCM was studied. A phenomenological expression which depicts the temporal evolution of the PCM temperature for a solidification phase was suggested. This allows the estimation of the material solidification duration in terms of geometric and thermal characteristics. At the system scale, a thermal battery prototype was set up and the thermal transfer dynamics during the charging and discharging phases were studied. The charging and discharging durations are fitted by power laws in terms of the flow rate; the pressure drops are insignificant. Simultaneously, a numerical model which simulates the dynamic and thermal behavior of a PCM particle fixed bed was developed and validated with the experimental data. It can be used for future prototype sizing and will also serve as a tool to optimize the performance of the battery by setting the control parameters