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The increasing concern for emissions and pollutants from power generation plants has increased the desire for and the study of biomass fuels. Biomass combustion produces less carbon monoxide as well as other greenhouse gases. Black liquor is a byproduct from the Kraft process in making paper. Black liquor can be gasified and used as a fuel in recovery boilers and fluidized bed steam reformers. Recovery boilers have a low efficiency and are used today because of their reliability. Steam reformers have a much higher efficiency but they are a relatively new science and are not as reliable. One of the reasons why steam reformers are not reliable is due to the agglomeration of the particles in the fluidized bed. The particles will stick together, agglomerate, at temperatures much lower than their melting temperature. The strength of these bonds and the temperature at which the bed agglomerates were studied as well as the effect of particle size on the heat transfer coefficient from the heaters to the bed material by means of experimentation and analysis. As the carbon content decreases, the agglomeration temperature also decreases. For 0.3% carbon content coated particles, the agglomeration temperature is approximately 490 ºC. The temperature at which the inter-particle bond strength increases dramatically also decreases. By comparing the inter-particle force with the collision force between particles, it was observed that when the velocity of the particles decreases below 1/500th of the free stream velocity, the particles will agglomerate.

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The use of shallow fluidized beds for heat exchange has been suggested because they give high bed-to-surface heat transfer rate and require very low bed pressure. However, in comparison with research on deep fluidized beds, only relatively few studies have been devoted to heat transfer in shallow beds, and results from the available literature are often inconsistent. This study represents an integrated research on the hydrodynamics and bed-to-surface heat transfer in shallow beds. The results from this study provide the quantitative basis for the design and efficient operation of shallow fluidized-bed heat-recovery systems. Based upon their physical appearance, shallow fluidized beds have been categorized into nine different types. A "phase diagram" (plot of superficial gas velocity versus static bed height) can be used to delineate the ranges of fluidization variables within which each type of shallow beds will be seen. Pressure-drop data in gas flowing upward through a shallow bed reflect pressure recovery in jets formed immediately above a gas distributor at the bottom of the bed. Pressure-recovery data provide an effective means of distinguishing a shallow bed from a deep one, and suggest that the power consumption across a fluidized bed can be reduced dramatically by dividing a single deep bed into many multi-staged shallow beds. A computerized light probe has been developed for measurements of particle volume-fraction distribution and its statical fluctuation (standard deviation). These data have been shown to quantitatively define: (1) different types of shallow beds; (2) relative magnitude of solid mixing; (3) bed surface and bed height; and (4) jet penetration depth. Based upon observations of the hydrodynamic behavior of shallow fluidized beds, three regions can be identified for heat-transfer applications: a jet-affected region at the bottom, a free-board region at the top, and, sandwiched between theses, a homogeneous region. Only heat-transfer data in the homogeneous region are sufficiently well-behaved to be subjected to quantitative correlation in terms of fluidization variables. For relatively coarse particles (Geldart's Group B particles) the vigor of solid mixing can be the most important factor in affecting the heat-transfer performance. Bed voidage and static electricity effects are found to be important for smaller and/or lighter particles (i.e., Geldart's Group A particles). / Ph. D.

Hydrodynamics and heat transfer characteristics found in fluidization were studied in a small scale laboratory fluidized bed. Experiments were designed to capture field data on multiple slit jet gas distributor systems for the validation of computational models. Localized data was quantified through the use of several novel non-intrusive experimental measurement techniques. The analyses provide a unique study that connects full field-of-view multiphase flow dynamics with transient heat transfer distributions. The gas-solid hydrodynamics were captured through three non-invasive measurement techniques, viz. Particle Image Velocimetry (PIV), Digital Image Analysis (DIA), and pressure drop spectral analysis. The effects of inlet gas flowrate, Geldart B and D classified particle types, and the number inlet gas slit jets were investigated. Frequency analysis of a differential pressure signal resulted in the classification of four difference flow regimes. The coupling of PIV with DIA captured particle velocity, solid circulation rates, average cycle times, dead zone sizes, jet merging effects, gas void fraction distributions, and maximum expanded bed heights. The heat transfer in fluidized and spouted beds containing a heated inlet gas source was studied through transient heat transfer measurements and analyses. Innovative experimental procedures were introduced to quantify bed-to-wall and gas-to-particle heat transfer characteristics. Two techniques were developed to overcome the spatial, time varying, and instrumental intrusive limitations often found in multiphase flow heat transfer studies. Infrared thermography was utilized along with derived discrete differential equations, and an inverse heat conduction analysis to solve for transient localized heat flux profiles and heat transfer coefficient distributions. As a result new data containing increased spatial resolution is presented on gas, wall, and particle temporal maps. Computations based from the thermal gradients quantified bed-to-wall heat flux profiles, gas-to-particle heat transfer coefficients, and localized rates of energy stored. / Master of Science

Numerical modeling and prediction techniques are used to determine pressure drop, minimum fluidization velocity and segregation for bubbling fluidized beds. The computational fluid dynamics (CFD) code Multiphase Flow with Interphase eXchange (MFIX) is used to study a two-stage reactor geometry with a binary mixture. MFIX is demonstrated to accurately predict pressure drop versus inlet gas velocity for binary mixtures. A new method is developed to predict the pressure drop versus inlet gas velocity and minimum fluidization velocity for multi-component fluidized beds. The mass accounting in the stationary system (MASS) method accounts for the changing bed composition during the fluidization process by using a novel definition for the mass fractions of the bed not yet fluidized. Published experimental data for pressure drop from single-, binary- and ternary-component fluidized bed systems are compared to MFIX simulations and the MASS method, with good agreement between all three approaches. Minimum fluidization velocities predicted using correlations in the literature were compared with the experimental data, MFIX, and the MASS method. The predicted minimum fluidization velocity from the MASS method provided very good results with an average relative error of ±4%. The MASS method is shown to accurately predict when complex multi-component systems of granular material will fluidize. The MASS method and MFIX are also used to explore the occurrence and extent of segregation in multi-component systems. The MASS method and MFIX are both shown to accurately predict the occurrence and extent of segregation in multi-component systems. / Master of Science

A vibrated bed is a mobile layer of solid particles contained in a vessel that is vertically vibrated. When a flow of gas is maintained through it , the bed is called an aerated vibrated bed and a vibrated gas-fluidized bed if the gas stream is greater than the minimum fluidization velocity of the particles. Mass transfer rates from solid particles coated with naphthalene to a nitrogen stream, the fluidizing gas, are determined using a gas chromatographic technique. Two kinds of coated beads of different densities are used: Master Beads and low-density glass beads. The investigation is done using a cylindrical vessel with bed depths of 24 mm, 12.7 mm, and 1 mm (ultra-shallow bed). A range of solid particles from 125 to 841 microns of geometric mean size is employed. Using a vibrational frequency of 25 Hz, the particle bed is vibrated at different intensities up to four times the gravitational acceleration. Vibrations increase the mass transfer rate to some extent depending on the bed depth. The mass transfer process is more important in shallow beds, where strong solid mixing occurs, than in deeper beds, where bulk-circulation patterns affect the naphthalene sublimation. Higher mass transfer rates are obtained with larger as well as heavier particles. / Master of Science

[pt] No presente trabalho apresenta-se um estudo fluido dinâmico e cinético da ustulação de um concentrado de sulfeto de zinco a 950 Graus Celsius. Os resultados foram coletados na literatura para experimentos realizados em um reator de leito fluidizado industrial com enriquecimento do ar com oxigênio. A caracterização teórica e experimental foi realizada com as variáveis operacionais de reatores industriais. Foram levantados diagramas fluido dinâmicos teóricos (Geldart, Schytill e Grace) para a prática industrial em condições específicas. Foi observado que mudanças na temperatura, diâmetro médio da partícula, velocidade superficial do gás e tamanho do reator afetam as fronteiras dos diagramas. Os programas para caracterizar o comportamento do leito do reator foram escritos no Mathcad. Um estudo cinético foi realizado para avaliar as influências dos parâmetros temperatura, pressão parcial de O2, tamanho da partícula, massa específica da partícula e do gás fluidizante e viscosidade do gás sobre a conversão de ZnS a ZnO. Os resultados mostraram que o enriquecimento do ar com oxigênio é uma alternativa recomendável para o aumento da eficiência da conversão de concentrados de ZnS em reatores de leito fluidizado. / [en] This work presents a fluid dynamics and kinetics study of the roasting of zinc sulphide concentrates at 950 Celsius Degrees. The data were collected in the literature for experiments carried out in an industrial fluidised bed reactor with an excess of oxygen. The theoretical and experimental characterisation was conducted with the operating variables of the industrial reactor. Theoretical fluid dynamic diagrams (Geldart, Schytill and Grace) were drawn for the industrial practice at certain conditions. It was observed that, with changing temperature, mean particle diameter, gas superficial velocity and reactor size, the boundaries of the diagrams were affected. Mathcad programs to characterise the bed behaviour are presented. The kinetics was studied to evaluate the influences of the following parameters: temperature, O2 partial pressure, particle size, gas and particle densities, and gas viscosity on the conversion of ZnS to ZnO. The results effectively demonstrate that, for the oxygen enrichment employed, the conversions increased in approximately 15 percent. Therefore, the oxygen enrichment is an advisable alternative to increase the efficiency of ZnS concentrates roasting in fluidised bed reactors.

This Master´s thesis is about ways of packages of integration circuits and modules. Especially it´s about non-hermetic types of packages. One part of this paper are basic information about packaging and aspects in design of package. Next parts are design of test samples, which are package to epoxide powder material. Based on the results of the tests method, it will propose, where the technology will be used.

Cette étude est consacrée à la compréhension des phénomènes mis en jeu dans les écoulements fluidisés denses verticaux ascendant et descendant, ainsi que dans leur couplage avec un écoulement fluidisé dense horizontal dans une enceinte à pression contrôlée. Tout d'abord une étude hydrodynamique, réalisée dans une colonne de fluidisation classique sans circulation de solide, a permis de déterminer les différentes grandeurs caractéristiques de la suspension lors de sa fluidisation et de sa désaération, indispensables à la compréhension et à la modélisation des écoulements : Vitesses minimales de fluidisation et de bullage. Porosités au minimum de fluidisation et de bullage. Porosité de la phase dense. Vitesse de désaération et de sédimentation. Puis, l'influence des paramètres tant géométriques (diamètre de la colonne d'expédition, longueur de la partie horizontale, …) qu'opératoires (vitesses de fluidisation de la partie horizontale et d'aération de la colonne d'expédition, politique de dégazage, …) sur le comportement global de deux unités pilotes a mis en évidence les paramètres clés du procédé : Vitesse de fluidisation de la partie horizontale. Politique de dégazage. Aération de la colonne d'expédition. Les transferts de gaz entre les différentes zones du procédé ont également été mis en évidence grâce à l'utilisation d'un traceur gazeux. Enfin, une modélisation de type monodirectionnelle est entreprise dans le but de simuler le comportement des suspensions fluidisées denses en écoulement verticaux ascendant et descendant. Les résultats obtenus concordent de manière très satisfaisante avec les mesures expérimentales. Ils permettent de mettre en évidence les mécanismes de transport ascendant de solide. De plus, le logiciel de calcul ainsi créé permet d'optimiser les dimensions d'une conduite verticale accueillant une suspension fluidisée dense en écoulement descendant afin d'en garantir le bon fonctionnement. / This study is dedicated to the understanding of the phenomena involved in dense fluidized upward and downward flows, and their coupling with a dense fluidized horizontal flow in a pressure controlled chamber. First of all, a hydrodynamic study, conducted in a solid particles flow-free cylindrical fluidization column, is initiated to determine the fluidization and de-aeration characteristics parameters, required to the flows understanding and modeling: Minimum fluidization and minimum bubbling rates. Minimum fluidization and minimum bubbling voidages. Dense phase voidage. De-aeration and sedimentation rates. Then, the geometric (upward-flow zone diameter, horizontal chamber length, …) and operating (horizontal chamber fluidization rate, degassing policy, …) parameters influences on two pilot-scaled unities behavior highlights the process key parameters: Horizontal chamber fluidization rate. Degassing policy. Upward-flow additional aeration. The use of helium tracking also highlights the gas transfer phenomena between horizontal, vertical upward, and vertical downward flow zones. Finally, a monodirectional model is created in order to simulate dense gas/solid suspensions behavior in vertical upward and downward flows. The computed results are concordant with the experimental data and highlight the upward solid conveyance mechanisms. The computation software can also optimize the downward pipe dimensions with the aim of maintaining a good flow.