Uma das principais preocupações em relação à crescente ocorrência de cianobactérias em sistemas aquáticos está relacionada à capacidade de algumas espécies em produzir e liberar toxinas, entre elas as microcistinas, que podem afetar a saúde humana. O processo convencional de tratamento de água é muitas vezes insuficiente para remover a toxina dissolvida na água. Entre as tecnologias que podem ser utilizadas para removê-la, estão os filtros de carvão ativado granular (CAG). Essa pesquisa se dedicou ao aprofundamento do conhecimento sobre o desempenho de colunas de CAG quando operadas para remover microcistina de águas de abastecimento. A água de estudo foi composta por água de poço artesiano contaminada por extrato de microcistina (MC), produzindo soluções com concentrações iniciais de MC-LR que variaram entre 14 µg/L e 92 µg/L. Em ensaios de adsorção em colunas de leito fixo, sob regime contínuo, foram avaliados três tipos de CAG, de origens diferentes, sendo um vegetal (CAG-Ccoco) e dois minerais (CAG-Hulha e CAG-Linhito). A partir das curvas de ruptura dos ensaios, foram avaliadas as remoções de microcistina e a capacidade de adsorção desse poluente pelos carvões ativados. Ao ajustar modelos matemáticos (Bohart-Adams, Thomas e Yoon-Nelson) às curvas de ruptura, foi possível obter informações sobre a capacidade de adsorção dos carvões. Os resultados mostraram que o CAG-Linhito possui melhor capacidade de adsorção (164 µg/g), seguido pelo CAG-Ccoco (79 µg/g) e, por último, GAG-Hulha (62 µg/g). A maior capacidade de adsorção de microcistina do CAG-Linhito foi atribuída ao maior volume de mesoporos (0,53 cm³/g) presente em sua estrutura (CAG-Ccoco = 0,05 cm³/g e CAG-Hulha = 0,06 cm³/g). A adsorção de microcistina por colunas de CAG se mostrou eficiente para remoção do poluente do meio líquido, em especial com a utilização do CAG-Linhito. / One of the main concerns about the increasing occurrence of cyanobacteria in aquatic systems is related to the ability of some species to produce and release toxins, including microcystins, which may affect human health. The conventional water treatment process is often insufficient to remove the toxin dissolved in the water. Among the technologies that can be used to remove microcystins are granular activated carbon (GAC) filters. This research focused on knowledge enhancement about the performance of GAC columns when operated to remove microcystin from supply water. The study water was composed of artesian well water contaminated by microcystin (MC) extract, producing solutions with initial concentrations of MC-LR that varied between 14 µg / L and 92 µg / L. In adsorption tests on fixed bed columns, under continuos regime, three types of GAC were evaluated, from different sources, being one vegetal (GAC-Ccoco) and two minerals (GAC-Hulha and GAC-Linhito). From the breakthrough curves, the microcystin removals and the adsorption capacity of this pollutant by activated carbons were evaluated. By adjusting mathematical models (Bohart-Adams, Thomas and Yoon-Nelson) to the breakthrough curves, it was possible to obtain information about the adsorption capacity of the GAC. The results showed that GAC-Linhito had better adsorption capacity (164 µg/g), followed by GAC-Ccoco (79 µg/g) and, finally, GAC-Hulha (62 µg/g). The highest adsorption capacity of GAC-Linhito was attributed to the higher volume of mesopores (0.53 cm³/g) present in its structure (GAC-Ccoco = 0.05 cm³/g GAC-Coal = 0.06 cm³/g). The adsorption of microcystin by GAC columns proved to be efficient for removal of the pollutant from the liquid medium, especially with the use of GAC-Linhito.

Le contrôle thermique des réactions dans les réacteurs à lits fixes nécessite la maîtrise du transfert thermique en proche paroi. Afin d’optimiser leur conception et en particulier de maintenir un chemin réactionnel le plus proche possible de l’isothermicité, un modèle de transfert thermique pertinent dans un tel milieu est indispensable. Deux premières thèses au Laboratoire d'Energétique et de Mécanique Théorique et Appliquée ont permis de mettre au point un modèle dispersif utilisable à cœur de réacteur. La présente thèse met en évidence un effet de paroi non négligeable causé par la variation de porosité du lit à l’approche de la paroi. Ce travail propose un raccordement du cœur, où le modèle thermique précédent est légitime, à la paroi, par une couche homogénéisée. Cette approche est validée par une caractérisation expérimentale des paramètres du modèle sur un dispositif de laboratoire en utilisant une méthode d’inversion originale reposant sur une approche Bayesienne. Une validation de cette caractérisation dans une géométrie plus proche d’un réacteur industriel est également effectuée / Thermal control for chemical reactions conducted in fixed-bed reactors requires a fine knowledge about heat transfer in the near-wall region of the bed. In order to optimize the process design, to minimize the mass of catalyst that is needed, one must attempt to maintain the operational path of the reactor the closest of the isotherm functioning. A pertinent and reliable heat transfer model is then required. Two thesis were realized in the Laboratoire d'Energétique et de Mécanique Théorique et Appliquée in order to construct a corresponding dispersive model. This model can be used at the core of the reactor, where the porous medium can be homogenized. This thesis shows a wall effect that cannot be neglected. This wall effect is directly caused by the important variation of the porosity distribution near the wall of the bed. This work proposes a junction between a core layer, where the previous model is still valid, and the wall through an homogenized near-wall layer. This approach is validated by the mean of an experimental characterization of the model parameters, using an original inversion technique based on a Bayesian approach. A validation of this characterization in another geometry is also done. This geometry is closer to an industrial reactor

En raison de la raréfaction des ressources de pétrole et des variations des prix avec le contexte géopolitique, la réaction de catalyse de Fischer-Tropsch qui permet la production d’hydrocarbures à partir du mélange syngas des gaz CO et H2 en présence d’un catalyseur à base de fer ou de cobalt, présente aujourd’hui un regain d’intérêt tant de la part des industriels que des académiques. Bien que découverte en 1923 par les allemands Franz Fischer et Hans Tropsch, les mécanismes qui entrent en jeu lors de cette réaction et les paramètres importants des propriétés des catalyseurs demeurent encore incertains. Dans ce contexte, les travaux présentés dans cette thèse visent à étudier l’impact de paramètres tels que la structure cristallographique et la forme de nano-objets de cobalt, phase active du catalyseur pour cette réaction. Ceci passe par la synthèse de catalyseurs modèles à base de nano-objets de cobalt et l’étude de leurs propriétés catalytiques. Dans un premier temps, la préparation d’un catalyseur à base de cobalt présentant une structure cristallographique hcp et une morphologie anisotrope a été réalisée, via une voie de synthèse par décomposition d’un précurseur organométallique de cobalt, conduisant à la formation de nano-objets de cobalt anisotropes. Puis, des tests catalytiques ont été réalisés en réacteur slurry, en collaboration avec un partenaire industriel, l’IFP-EN. Cela a permis la réalisation de tests Fischer-Tropsch en conditions proches des conditions industrielles réelles. Ces études ont permis de mettre en évidence la très grande stabilité de ces catalyseurs en comparaison à des catalyseurs de référence.Enfin, différents catalyseurs à base de cobalt, supportés sur des supports originaux de type macrostructurés permettant une meilleure gestion des échanges thermiques de la réaction, ont été préparés et leurs propriétés catalytiques étudiées sur un réacteur de type lit-fixe, mis en œuvre durant cette thèse. / Due to the decreasing the oil resources, and because of the the fluctuations of the price as a result of the geopolitical context, the Fischer-Tropsch synthesis, that enables the production of hydrocarbons form the syngas mixture (CO and H2) in the presence of a catalyst based on cobalt or iron, has recently gained a renewed interest from industrial as well as form the academic communities. Although this reaction was discovered in 1923 by the Germans Franz Fischer and Hans Tropsch, the mechanisms that come into play during this reaction and the crucial properties of the catalyst properties remain uncertain. In this context, the work presented in this thesis, aims to investigate the impact of parameters such as the crystallographic structure and the shape of the cobalt nano-objects, which is the active phase of the catalyst for this reaction. For this purpose, model cobalt nano-objects were synthetized and their catalytic properties were studied. As a first step, a cobalt based catalyst exhibiting an hcp crystallographic structure and an anisotropic shape was prepared via a synthetic route involving the decomposition of an organometallic precursor of cobalt and leading to the formation of anisotropic cobalt nano-objects. Catalytic tests were then conducted in a slurry reactor, in collaboration with an industrial partner, IFP-EN. This collaboration allowed performing catalytic studies under conditions that are very close to the actual industrial conditions. These studies revealed an increased stability of these catalysts compared to reference catalysts that deactivate with time. Finally, several cobalt-based catalysts, supported on innovative supports, such as macrostuctured supports, allowing a better control of the exothermicity, were prepared and their catalytic properties studied on a fixed-bed reactor that was set up during the course of this thesis work.

This work aims at modelling and evaluating a new type of photocatalytic reactors, named fixed-bed photocatalytic membrane reactor (FPMR). Such reactors are based on the deposition of a thin layer of photocatalysts on a permeable substrate by filtration. This layer serves as a photocatalytic membrane, named fixed-bed photocatalytic mem-brane (FPM), which is perpendicularly passed by the reactant solution and illuminated by a suitable light source. One advantage of FPMs is their renewability. The model, which was developed for this reactor, relates the overall reaction rate in the FPM with the intrinsic reaction kinetic at the catalyst surface and accounts for light intensity, structural and optical layer properties as well as the mass transfer in the pores. The concept of FPMR was realised by using a flat sheet membrane cell. It facilitated principal investigations into the reactor performance and the validity of the model. For this purpose, the photocatalytic degradation of organic compounds, such as meth-ylene blue and diclofenac sodium, was conducted at varying conditions. Pyrogenic ti-tania was used as a photocatalyst. The experimental data support the developed mod-el. They also indicate a significant impact of the flow conditions on the overall photo-catalytic activity, even though the Reynolds number in the FPM was very small; the to-tal mass transfer rate in the FPM amounted to more than 1.0 s−1. The experiments also showed a sufficient structural strength of the FPM and photocatalytic stability. In addi-tion, the renewal and regeneration of FPMs was successfully demonstrated. Furthermore, another FPMR was designed by means of submerged ceramic mem-branes. This reactor was mainly used to assess the effectiveness and efficiency of FPMRs at the example of the photocatalytic degradation of oxalic acid. The correspond-ing reactor was run closed loop and in continuous mode. The effectiveness of the reac-tor was evaluated based on common descriptors, such as apparent quantum yield, photocatalytic space-time yield and light energy consumption. The results showed that the FPMR based on submerged ceramic membrane had a higher efficiency than other reported photocatalytic reactors. The comparison of the different modes of operation revealed that the closed loop FPMR is most efficient with regard to light energy con-sumption. Finally, this work discusses the up-scaling of FPMRs for industrial applications and proposes a solution, which can e.g. be employed for wastewater treatment or CO2 conversion.:Abstract iii Kurzfassung v Acknowledgment vii Contents ix Nomenclature xiii 1 Introduction 1 1.1 Motivation 1 1.2 Aim and objectives of the work 3 1.3 Thesis outline 3 2 Heterogeneous photocatalytic reactors 5 2.1 Introduction to photocatalysis 5 2.2 Processes in heterogeneous photocatalysis 6 2.2.1 Optical phenomena 7 2.2.2 Mass transfer 8 2.2.3 Adsorption and desorption 9 2.2.4 Photocatalytic reactions 10 2.2.5 Factors affecting heterogeneous photocatalysis 12 2.3 Photocatalytic reactor systems towards water treatment 16 2.3.1 Introduction to photocatalytic reactors 16 2.3.2 Development of photocatalytic reactor designs 17 2.3.3 Quantitative criteria for evaluating photocatalytic reactor designs 21 2.4 Cake layer formation in membrane microfiltration 22 2.4.1 Suspension preparation 22 2.4.2 Cake layer formation 23 2.5 Fluid flow through a fixed bed of particles 25 2.5.1 Pressure drop through a fixed-bed 25 2.5.2 Liquid-solid mass transfer correlation in fixed-bed 25 3 Concept and mathematical modelling of FPMRs 29 3.1 Concept of fixed-bed photocatalytic membrane reactors 29 3.2 Modelling of fixed-bed photocatalytic membrane reactors 31 3.3 Model sensitivity analysis 37 3.4 Chapter summary 39 4 FPMR realised with flat sheet polymeric membrane 41 4.1 Introduction 41 4.2 Materials and set-up 41 4.2.1 Materials 41 4.2.2 Experimental set-up 43 4.3 Experiments and methods 48 4.3.1 Formation of fixed-bed photocatalytic membrane 48 4.3.2 Reactor performance 50 4.3.3 Parameters study and model verification 53 4.3.4 Catalyst layer characterisation 56 4.3.5 Measurement and evaluation of photocatalytic activity of FPM 59 4.4 Results and model verification 60 4.4.1 Reactor performance 60 4.4.2 Influence parameters 71 4.4.3 Model verification 79 5 FPMR realised with submerged ceramic membrane 92 5.1 Introduction 92 5.2 Materials and reactor set-up 93 5.2.1 Reactor set-up 93 5.2.2 Chemicals 97 5.3 Experiments and methods 97 5.3.1 Formation of fixed-bed photocatalytic membranes 97 5.3.2 Photocatalytic performance 97 5.3.3 Parameter study 98 5.3.4 Reactor model for calculating reaction rate constant of FPM 99 5.3.5 Comparison of different reactor schemes 102 5.4 Results and discussions 105 5.4.1 Reactor performance 105 5.4.2 Consistency of CPMR and LPMR data 107 5.4.3 Influence of catalyst loading 108 5.4.4 Influence of permeate flux and light intensity 109 5.4.5 Reactor efficiency 111 5.4.6 Comparison of different reactor schemes 113 5.5 Proposed up-scaled FPMR systems 113 5.6 Concluding remarks 116 6 Conclusion and outlook 118 6.1 Summary of thesis contributions 118 6.2 Discussion and outlook 120 References 122 List of Figures 134 List of Tables 138 Appendix A Calibration 139 A.1 Distribution of light intensity on the surface of catalyst layer 139 A.2 Concentration and absorbance of diclofenac 141 A.3 TOC concentration and electrical conductivity of oxalic acid 141 A.4 Concentration and absorbance of methylene blue 142 Appendix B Mathematical modelling 143 B.1 Influence of axial dispersion on the reaction rate 143 B.2 Special case 146 Appendix C Comparison the photocatalytic activity of TiO2 and ZnO 147 Appendix D Mathematical validation of model for LPMR and CPMR 148 D.1 Model for LPMR (cf. Eq. (5 12)):148 D.2 Model for CPMR (cf. Eq. (5 17)) 149 Appendix E Particle size distribution 151

Die Arbeit zeigt wichtige Nutzungswege von fester Biomasse in Form von Holzhackschnitzel (HHS). Einleitend wird das Potenzial und der derzeitige Stand dargestellt. Es werden die physikalischen und chemischen Eigenschaften mit dem Schwerpunkt Wassergehalt in bezug auf die energetische Nutzung der HHS behandelt. Kerne der Nutzungswege bilden dabei die Vergasung im Gleichstromvergaser und die Co-Verbrennung in der Zirkulierenden Wirbelschicht. Mit Hilfe eines Versuchsvergasers werden die Auswirkungen von HHS-Eigenschaften auf den Betrieb untersucht. Der Modellvergaser IGEL bietet durch seine Konstruktion die Möglichkeit, innere Vorgänge zu beleuchten und Messungen in verschiedenen Vergaserebenen durchzuführen. Die Auswirkungen von verschiedenen Brennstoffchargen mit unterschiedlichem Wassergehalt führten zu Änderungen in der Gaszusammensetzung. Eigene Untersuchungen ermittelten einen Grenzwassergehalt, mit dem der Vergaser noch betrieben werden kann. Die Experimente an der Pilotanlage mit zirkulierender atmosphärischer Wirbelschicht befass-ten sich mit der wichtigen Frage, ob und welches NOx-Minderungspotenzial beim Einsatz von Biomasse vorliegt. Die mathematische Modellierung verdeutlicht die Nutzbarkeit von Simulationsprogrammen bei der Untersuchung von Einflüssen der Co-Verbrennung auf die NOx-Bildung. Hier wurden die Gesichtspunkte der Luftzahl, der Luftstufung, des Wassergehaltes, das Mischungsverhältnis und die Brennstoffstufung betrachtet. Eine Wirtschaftlichkeitsbetrachtung führt zu dem Ergebnis, dass Anlagen zur reinen Stromerzeugung mit Biomasse nur nahe der gesetzlichen Höchstleistung von 20 MWel zur Einspeisevergütung von wirtschaftlich betrieben werden können. Die ökologisch und ökonomisch günstigste Variante stellt die Co-Verbrennung in vorhandenen Anlagen dar. Die Kalkulationen zu den in Deutschland benötigten 20-MWel-Anlagen verdeutlichen, dass bei den gegenwärtig geplanten Heizkraftwerken das Potenzial an HHS schnell aufgebraucht ist.

<div>Adsorbent technology is widely used in many industrial applications including waste heat recovery, water purification, and atmospheric revitalization in confined habitations. Astronauts depend on adsorbent-based systems to remove metabolic carbon dioxide (CO₂) from the cabin atmosphere; as NASA prepares for the journey to Mars, engineers are redesigning the adsorbent-based system for reduced weight and optimal efficiency. These efforts hinge upon the development of accurate, predictive models, as simulations are increasingly relied upon to save cost and time over the traditional design-build-test approach. Engineers rely on simplified models to reduce computational cost and enable parametric optimizations. Amongst these simplified models is the axially dispersed plug-flow model for predicting the adsorbate concentration during flow through an adsorbent bed. This model is ubiquitously used in designing fixed-bed adsorption systems. The current work aims to improve the accuracy of the axially dispersed plug-flow model because of its wide-spread use. This dissertation identifies the critical model inputs that drive the overall uncertainty in important output quantities then systematically improves the measurement and prediction of these input parameters. Limitations of the axially dispersed plug-flow model are also discussed, and recommendations made for identifying failure of the plug-flow assumption.</div><div><br></div><div>An uncertainty and sensitivity analysis of an axially disperse plug-flow model is first presented. Upper and lower uncertainty bounds for each of the model inputs are found by comparing empirical correlations against experimental data from the literature. Model uncertainty is then investigated by independently varying each model input between its individual upper and lower uncertainty bounds then observing the relative change in predicted effluent concentration and temperature (<i>e.g.</i>, breakthrough time, bed capacity, and effluent temperature). This analysis showed that the LDF mass transfer coefficient is the largest source of uncertainty. Furthermore, the uncertainty analysis reveals that ignoring the effect of wall-channeling on apparent axial dispersion can cause significant error in the predicted breakthrough times of small-diameter beds.</div><div><br></div><div>In addition to LDF mass transfer coefficient and axial-dispersion, equilibrium isotherms are known to be strong lever arms and a potentially dominant source of model error. As such, detailed analysis of the equilibrium adsorption isotherms for zeolite 13X was conducted to improve the fidelity of CO₂ and H₂O on equilibrium isotherms compared to extant data. These two adsorbent/adsorbate pairs are of great interest as NASA plans to use zeolite 13X in the next generation atmospheric revitalization system. Equilibrium isotherms describe a sorbent’s maximum capacity at a given temperature and adsorbate (<i>e.g.</i>, CO₂ or H₂O) partial pressure. New isotherm data from NASA Ames Research Center and NASA Marshall Space Flight Center for CO₂ and H₂O adsorption on zeolite 13X are presented. These measurements were carefully collected to eliminate sources of bias in previous data from the literature, where incomplete activation resulted in a reduced capacity. Several models are fit to the new equilibrium isotherm data and recommendations of the best model fit are made. The best-fit isotherm models from this analysis are used in all subsequent modeling efforts discussed in this dissertation.</div><div><br></div><div>The last two chapters examine the limitations of the axially disperse plug-flow model for predicting breakthrough in confined geometries. When a bed of pellets is confined in a rigid container, packing heterogeneities near the wall lead to faster flow around the periphery of the bed (<i>i.e.</i>, wall channeling). Wall-channeling effects have long been considered negligible for beds which hold more than 20 pellets across; however, the present work shows that neglecting wall-channeling effects on dispersion can yield significant errors in model predictions. There is a fundamental gap in understanding the mechanisms which control wall-channeling driven dispersion. Furthermore, there is currently no way to predict wall channeling effects a priori or even to identify what systems will be impacted by it. This dissertation aims to fill this gap using both experimental measurements and simulations to identify mechanisms which cause the plug-flow assumption to fail.</div><div><br></div><div>First, experimental evidence of wall-channeling in beds, even at large bed-to-pellet diameter ratios (<i>d</i>_bed/<i>d</i>_p=48) is presented. These experiments are then used to validate a method for accurately extracting mass transfer coefficients from data affected by significant wall channeling. The relative magnitudes of wall-channeling effects are shown to be a function of the adsorption/adsorbate pair and geometric confinement (<i>i.e.</i>, bed size). Ultimately, the axially disperse plug-flow model fails to capture the physics of breakthrough when nonplug-flow conditions prevail in the bed.</div><div><br></div><div>The final chapter of this dissertation develops a two-dimensional (2-D) adsorption model to examine the interplay of wall-channeling and adsorption kinetics and the adsorbent equilibrium capacity on breakthrough in confined geometries. The 2-D model incorporates the effect of radial variations in porosity on the velocity profile and is shown to accurately capture the effect of wall-channeling on adsorption behavior. The 2-D model is validated against experimental data, and then used to investigate whether capacity or adsorption kinetics cause certain adsorbates to exhibit more significant radial variations in concentration compared than others. This work explains channeling effects can vary for different adsorbate and/or adsorbent pairs—even under otherwise identical conditions—and highlights the importance of considering adsorption kinetics in addition to the traditional <i>d</i>_bed/<i>d</i>_p criteria.</div><div><br></div><div>This dissertation investigates key gaps in our understanding of fixed-bed adsorption. It will deliver insight into how these missing pieces impact the accuracy of predictive models and provide a means for reconciling these errors. The culmination of this work will be an accurate, predictive model that assists in the simulation-based design of the next-generation atmospheric revitalization system for humans’ journey to Mars.</div>

In den 80-iger Jahren war die DDR hinter den USA und Kanada der drittgrößte Uranproduzent mit einer Jahresproduktion von ca. 200.000 Tonnen. Die Gewinnung erfolgte durch konventio­nellen Bergbau, durch in- situ- oder offene Haufenlagerung. Die Urangewinnung auf dem Ter­ritorium der ehemaligen DDR wurde nach der Wiedervereinigung eingestellt und mit der Sa­nierung der Altstandorte begonnen. Nach Einstellung des Uranabbaus muss die Wasserhaltung solange betrieben werden, bis eine kontrollierte Flutung der Bergbauschächte erfolgen kann. Die dabei anfallen­den Grubenwässer werden je nach Schadstoffkonzentration direkt in den Vorfluter abgeleitet oder in geeigneten Aufbereitungsanlagen meist durch Flockung und Adsorption behandelt. Dieses praktisch oft angewandte Grubenwasserreinigungsverfahren bezüglich Uran und den auftretenden Begleitelementen Chrom und Arsen hat den entscheidenden Nachteil, dass die anfallenden schwermetallhaltigen Fällschlämme auf Deponien verbracht werden müssen. Durch Niederschlags­ereignisse oder ansteigendes Grundwasser besteht die Gefahr, dass die Deponien wieder ausgelaugt werden und somit eine erneute Mobilisierung von Schwermetallen in die Umwelt erfolgt. Die Sanierung kontaminierter Gebiete, insbesondere Sedimente, Sondermüll-deponien, Standorte ehemaliger Galvanikbetriebe, Betriebsflächen chemischer Industriestandorte, Rieselfelder oder Orte der Klärschlammaufbereitung erfordern neue Herangehensweisen an das gegenwärtig hochaktuelle Problem der Rehabilitation. Es wurde deshalb u.a. im Rahmen dieser Arbeit ein Konzept auf Grundlage der elektrochemischen Umset­zung im &amp;quot;verdünnten&amp;quot; elektrochemischen Festbettreaktor entwickelt, das es gestattet, die mo­bilen Schwermetallspezies im Boden bzw. Deponiekörper in immobile Schwermetallverbindungen um­zuwandeln. Damit kann die Nachsorge und Sicherung solcher Deponiekörper bezüglich einer Remobilisierung wesentlich kostengünstiger gestaltet werden. Ausgehend von diesem Konzept sollen Möglichkeiten, Einsatzbedingungen und -grenzen der Immobilisierung von Schwermetallen am Beispiel von Uran(VI), Chrom(VI), Arsen(III) und chlorierten Kohlenwasserstoffe aufgezeigt werden. Elektrochemische Verfahren zur Sanierung kontaminierter Böden, Schlämme und Sedimente befinden sich international in einer dynamischen Forschungs- und Entwicklungsphase. Sie sind einzeln und in Verfahrenskombinationen einsetzbar und werden, bei verantwortungsvoller Handhabung, in absehbarer Zeit auch als zertifizierte Verfahren in Deutschland in bestimmten Sanierungsvorhaben ihre Leistungsfähigkeit beweisen. Gegenwärtig befinden sie sich in Deutschland noch im Stadium der Forschung und Entwicklung, während international (z.B. USA, Niederlande) schon kommerzielle Anwendungen angeboten werden. Zur objektiven Beurteilung ihrer Leistungsfähigkeit und Einsatzgrenzen bedarf es spezieller Grundkenntnisse. Elektrochemische Remediationsverfahren können als ergänzende, in Einzelfällen auch als alternative Verfahren zur Sediment- und Bodensanierung angesehen werden. Sie haben dann eine Chance auf Einsatz, wenn vor Ort (in- situ) saniert werden soll. Von ihrem Prinzip her, sind sie preiswerter als Bodenaushub und Verbrennung. Das Sanierungsziel besteht in einer möglichst vollständigen Konzentrierung oder Umsetzung der Wasserschadstoffe an der Feststoffmatrix.

Made available in DSpace on 2017-07-10T18:07:58Z (GMT). No. of bitstreams: 1 Lucas Maycon Hoff Zeni.pdf: 1421377 bytes, checksum: 75c6a9407a955e26c7fd4db2939b1b79 (MD5) Previous issue date: 2012-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Configuration of fixed bed that operates with biphasic flow is used in industrial operations such as the Fischer-Tropsch, hydrogenation, and residual water treatments. Vital information for the project and operation of this type of bed is in its characteristics fluid-dynamic and among these characteristics the flow regime because these have a direct influence transferring heat and mass present in the bed. In the two-phase flow with ascendant flow through fixed bed, three distinct regimes can be identified: the bubble regime, for low gas flow; pulsating regime, for moderate liquid and gas flow; and spray regime; for low flow of liquid and high flow rates of gas. Although there are different techniques to determine flow regimes, the most used is the visual identification. Thus, this research aims to develop, by using artificial neural networks (ANNs) a way to determine, for a given set of liquid-gas flow what out-flow regime the bed presents. To do so, firstly, the out-flow regime were identified by using water and air, respectively flux mass flowing varying from 2 to 16.5 kg.m-2.s-1 and from 0 to 0.6 kg.m-2.s-1, flowing up-words through a fixed bed packed with glass spheres measuring from 2.7 to 3.5 mm of diameter. The network proposed to identify the regimes contains Multiple Layers Perceptron architecture (PML) trained by the back propagation algorithm put together by applying the Multiple Back-Propagation (MBP) software, version 2.2.3 consistently with two input neurons, two intermediate layers, and four output neurons. The number of neurons of the intermediate layers was assorted to find out the best configuration. As activation of function, logistic, tangent, hyperbolic, and Gaussian were tested. Observed results showed that it is possible the identification of regimes through neural networks and among those tested the one that showed the best performance was the one that used the hyperbolic-tangent activation function; 10 neurons in the first hidden layer, and 12 neurons in the second hidden layer. / A configuração de leito fixo que opera com escoamento bifásico é muito utilizada em operações industriais, tais como síntese de Fischer-Tropsch, hidrogenação e tratamento de águas residuais. Uma informação vital para projeto e operação deste tipo de leito está nas características fluidodinâmicas, e dentre estas características podem ser citados os regimes de escoamento, pois estes influenciam diretamente nas transferências de calor e massa presentes no leito. No escoamento bifásico com fluxo ascendente através de leito fixo podem ser identificados três regimes distintos: regime bolha, para baixas vazões de gás; regime pulsante, para vazões moderadas de líquido e gás; e regime spray, para baixas vazões de líquidos e altas vazões de gás. Apesar de haver diferentes técnicas para a determinação dos regimes de escoamento, a mais empregada é a identificação visual. Sendo assim, esta pesquisa tem por objetivo desenvolver, por meio da utilização de redes neurais artificiais (RNA s), uma maneira de determinar, para um dado conjunto de vazões gás-líquido, qual regime de escoamento o leito apresenta. Para isto, os regimes de escoamento primeiramente foram identificados utilizando água e ar, respectivamente com fluxo mássico variando de 2 a 16,5 kg.m-2.s-1 e de 0 a 0,6 kg.m-2.s-1, escoando em fluxo ascendente por meio de um leito fixo recheado com esferas de vidro de diâmetro entre 2,7 e 3,5 mm. A rede proposta para a identificação dos regimes possui arquitetura perceptron de múltiplas camadas (MLP) treinada pelo algoritmo backpropagation e foi montada utilizando o programa freeware Multiple Back-Propagation (MBP) versão 2.2.3 sempre com dois neurônios de entrada, duas camadas intermediárias e quatro neurônios de saída. O número de neurônios das camadas intermediárias foi variado a fim de descobrir a melhor configuração. Como função de ativação, foram testadas as funções logística, tangente hiperbólica e gaussiana. Os resultados observados mostram que é possível a identificação dos regimes por meio de redes neurais e dentre as configurações testadas, a que apresentou melhor desempenho foi a rede que utilizou a função de ativação tangente hiperbólica, 10 neurônios na primeira camada oculta e 12 neurônios na segunda camada oculta.

Made available in DSpace on 2017-07-10T18:08:16Z (GMT). No. of bitstreams: 1 Thiago DArisbo.pdf: 2108504 bytes, checksum: 7b8aad29ec7d75a6fd370e54a95cd849 (MD5) Previous issue date: 2011-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ion exchange is a process that is used in the treatment of aqueous industrial effluents containing organic compounds and heavy metals. The fixed bed columns are longer applied by allowing the process to occur continuously (cycles of regeneration). The design and process optimization of the ion exchange column requires the use of mathematical models. Phenomenological models of these systems involve the solution of partial differential and algebraic equations. The equilibrium data for ion exchange processes are usually described by the Mass Action Law (MAL), which can be considered non-ideality of aqueous and solid phases. Artificial Neural Networks (ANN) are being used successfully for the study of equilibrium data because they are empirical models and don t demand a mathematical rigor. This work aimed to evaluate the applicability of the hybrid model to describe the dynamics of ion exchange in fixed beds of binary systems. This system consists of partial differential equations obtained from mass balance in fluid phases in the ion exchanger and ANN to describe the balance. LAM was adjusted to experimental data of ion exchange equilibrium and then were generated 4200 data sets for each binary pair studied, which served as training for RNA. We tested networks with different structures, with one and two input layers. The 3-3-2 structure was used in the simulations of the hybrid model because it was the best represented the systems during the training phase. The differential equations were solved by the lines method. A computer program in FORTRAN language was developed for solving the model equations. DASSL subroutine was used to solve the equations. The performance of the hybrid model was evaluated from the results obtained with the phenomenological model, in which case the equilibrium description was made with the use of MAL. It also was the analysis of results from the comparison of experimental data. To evaluate the model we used data from the literature of ion exchange in Amberlite IR 120 resin on the systems Cu-Na and Zn-Na and in NaY zeolite on Fe-Na and Zn-Na. Both models were efficient to describe the dynamics of ion-exchange fixed bed columns, and the hybrid model had the advantage of the reduced computational time (82% reduction on average) as a result of not needing to solve a nonlinear equation. / A troca iônica é um processo muito utilizado no tratamento de efluentes industriais aquosos contendo compostos orgânicos e metais pesados. As colunas de leito fixo são mais aplicadas por permitir que o processo ocorra de maneira contínua (ciclos de regeneração). O projeto e a otimização de processos de troca iônica em coluna requer o uso de modelos matemáticos. Os modelos fenomenológicos destes sistemas envolvem a resolução de equações diferenciais parciais e algébricas. Os dados de equilíbrio de processos de troca iônica geralmente são descritos pela Lei da Ação das Massas (LAM), na qual podem ser consideradas as não idealidades das fases aquosa e sólida. As Redes Neurais Artificiais (RNA) estão sendo utilizadas com sucesso para o estudo destes dados de equilíbrio por serem modelos empíricos e não demandarem tal rigor matemático. Esta dissertação teve por objetivo avaliar a aplicabilidade do modelo híbrido para descrever a dinâmica do processo de troca iônica em leito fixo de sistemas binários. Este sistema é constituído de equações diferenciais parciais obtidas por meio de balanço de massa nas fases fluida e no trocador iônico e de RNA para descrever o equilíbrio. A LAM foi ajustada a dados experimentais de equilíbrio de troca iônica e, então, foram gerados conjuntos de 4200 dados para cada par binário estudado, os quais serviram como treinamento para a RNA. Foram testadas redes com diferentes estruturas, com uma e com duas camadas de entrada. A estrutura 3-3-2 foi utilizada nas simulações do modelo híbrido, pois foi a que melhor representou os sistemas na etapa de treinamento. As equações diferenciais foram resolvidas pelo método das linhas. Um programa computacional em linguagem FORTRAN foi desenvolvido para a resolução das equações do modelo. Foi utilizada a sub-rotina DASSL para resolver as equações. O desempenho do modelo híbrido foi avaliada a partir dos resultados obtidos com o modelo fenomenológico, sendo que neste caso a descrição do equilíbrio foi feita pelo uso da LAM. Também foi feita a análise dos resultados a partir da comparação dos dados experimentais. Para avaliar o modelo foram utilizados dados da literatura de troca iônica em resina Amberlite IR 120 dos sistemas Cu-Na e Zn-Na e na zeólita NaY dos sistemas Fe-Na e Zn-Na. Ambos os modelos foram eficientes para descrever a dinâmica de troca iônica de colunas de leito fixo, sendo que o modelo híbrido apresentou como vantagem o menor tempo computacional (82% de redução em média) em decorrência de não necessitar resolver a equação não-linear.

Les procédés de gazéification de bois à lits fixes étagés sont adaptés à la production d'électricité de petites puissances. Dans ces procédés, la pyrolyse est opérée dans un réacteur continu à lit fixe descendant. La particularité de ce type de réacteur est son fonctionnement autothermique. L'énergie nécessaire au chauffage, au séchage et à la pyrolyse est apportée par la combustion partielle du bois : on parle de “pyrolyse oxydante”. L'injection d'air par le haut du réacteur provoque la propagation d'une zone d'oxydation dans le milieu poreux à contre-courant des écoulements des solides et des gaz. Les travaux présentés dans ce manuscrit visent une meilleure description de cette étape du procédé. Le problème posé est de type multi-échelles. Ainsi, nous avons préalablement mené une étude à l'échelle de la particule isolée avant de s'intéresser au comportement global du lit fixe. A l'échelle de la particule, nous avons quantifié l'effet de l'oxygène et de la taille des particules sur la cinétique de la pyrolyse oxydante. Cette étude nous a guidés pour la mise en place d'un modèle cinétique de cette transformation. A l'échelle du lit fixe, la propagation de la zone d'oxydation a été caractérisée par des approches expérimentale et numérique, offrant ainsi une meilleure connaissance de cette étape du procédé étagé. / Wood Multi-staged gasification in a fixed bed reactor is suitable for small-scale electricity generation. In these processes, the pyrolysis is performed in a continuous downward fixed bed reactor. The main feature of this reactor is the autothermal operation. Energy for heating, drying and pyrolysis is supplied by partial combustion of wood, known as “oxidative pyrolysis”. The air introduced from the top of the reactor induces a combustion front that propagates countercurrent with the solids and gazes flows. The work presented in this document aimed to achieve a better description of this process. A multi-scale approach was considered. Therefore, we have firstly studied the behavior of an isolated particle before focusing on the overall fixed bed. At the particle scale, we have quantified the effect of oxygen and of particle size on the oxidative pyrolysis kinetics. This led us to the setup of a kinetic model for this transformation.At the fixed bed scale, the propagation of the combustion front was studied considering the experimental and numerical approaches, which provides a better understanding of this step of the wood staged gasifiers.