A racionalização dos recursos hídricos tem sido uma das metas das indústrias em vários setores. Tais metas exigem inovações tecnológicas tanto para novos processos produtivos quanto para novas técnicas de tratamento e reutilização de água na cadeia de produção. Os custos elevados de água industrial no Brasil, particularmente nas regiões metropolitanas, têm estimulado as indústrias nacionais a avaliar as possibilidades de reúso. O objetivo deste trabalho é a aplicação do tratamento de águas de processo contendo polipropileno utilizando radiação ultravioleta e peróxido de hidrogênio, isto é, o sistema UV/H2O2, visando adequá-las para reúso no próprio processo, reduzindo a necessidade de captação de água pré-tratada e de descarte de efluente. A primeira parte do estudo consistiu na realização de experimentos em um sistema fotoquímico de batelada, empregando quatro diferentes correntes efluentes de processo, para a avaliação da viabilidade técnico-econômica do tratamento fotoquímico, bem como para a obtenção de dados referentes à cinética das reações fotoquímicas. Com base nas informações obtidas, na segunda parte do estudo foram realizados experimentos em um sistema fotoquímico contínuo, a fim de obter dados para o aumento de escala para aplicação industrial do processo de tratamento contínuo. Os resultados experimentais indicaram a viabilidade técnica de aplicação do sistema UV/H2O2 utilizando fonte de luz artificial para todas as correntes de processo estudadas, tendo sido alcançados níveis de remoção de matéria orgânica acima de 90%. No entanto, sob o ponto de vista econômico, apenas as correntes com baixo teor de carbono orgânico total dissolvido (COT), entre 6 e 12 mgC L-1, mostraram-se adequadas ao reúso, após o tratamento. / Rationalization of water use has been one of the goals in many industrial activities, and, in particular, in the petrochemical industry. Such goals demand technological innovations in the productive processes and in techniques for treatment and reuse of water in the production chain. The high costs of industrial water, particularly in some metropolitan regions, have stimulated the industries to evaluate the possibilities of water reuse. The objective of this work is to evaluate the feasibility of the UV/H2O2 photochemical process applied to the treatment of process waste water containing polypropylene, aiming at the reuse of the waste water in the as process water in the industrial complex, thus reducing the need for tap water supply and waste water generation rate. The first part of this study consisted of laboratory-scale experiments in a batch photochemical reactor with four different waste water streams to perform the technical and economical feasibility of the photochemical treatment, as well to obtain data on the degradation rate. Based on the results of the first part, the second part of this study consisted of experiments in a continuous photochemical reactor, aimed at obtaining experimental data for reactor scale-up. Experimental results indicate that the UV/H2O2 photodegradation process is able to remove more than 90% of the organic compounds contained in the waste water. However, only waste waters containing relatively low contaminant levels (between 6 and 12 mgC L-1) can be treated at economically favourable costs.

No meio científico são bastante utilizados os modelos matemáticos para avaliar as características hidrodinâmicas de reatores, porém a literatura é pobre em informações relativas à aplicação do equacionamento matemático em regime não-permanente. Neste trabalho foi aplicado um modelo matemático simulando a hidrodinâmica de reatores tubulares com dispersão para avaliar o efeito da variação de vazão afluente sobre os parâmetros hidrodinâmicos. As simulações foram efetuadas considerando vazão e volume constantes, vazão e volume variáveis e vazão variável e volume constante. Foi investigada a influência de dois tipos de ensaios estímulo-resposta, pulso e degrau, para aplicação de modelos matemáticos e determinação das curvas de distribuição do tempo de residência (DTR) experimentais. Teoricamente ambos devem fornecer os mesmos resultados embora o ensaio em pulso costume apresentar maior sensibilidade experimental. Conforme esperado, ambos os ensaios apresentaram os mesmos resultados finais. Também foram avaliados os traçadores empregados nos dois tipos de ensaios estímulo-resposta, pulso e degrau. Foram empregados três traçadores diferentes - verde de bromocresol, azul de bromofenol e eosina Y que proporcionaram curvas com diferentes características. Como ferramenta auxiliar da modelação foram estudas a determinação das curvas DTR experimentais com auxílio de duas técnicas distintas. Para calibrar o modelo matemático proposto foram utilizados dados de reatores em escala de bancada com diferentes configurações submetidas a variações de vazões afluentes. Os dados de um reator UASB em escala piloto - submetido a variações cíclicas de vazão afluente de 40 e 60% - foram empregados para calibrar e verificar o modelo matemático proposto. Os resultados encontrados com o modelo matemático proposto nesta pesquisa demonstraram que a variação de vazão afluente não deve ser negligenciada. O modelo utilizado representou adequadamente o reator UASB. Seus resultados, quando comparados aos modelos matemáticos que não consideram a variação de vazão, mostraram que para flutuações de vazão elevadas, vazões com valores até 60% maiores do que a vazão média, os valores dos coeficientes de difusão diferem significativamente em função das hipóteses empregadas no desenvolvimento do modelo matemático. / Mathematical models for hydrodynamic characteristics evaluation of reactors are commonly used however there is a lack of information in the literature concerning the application of mathematical modeling for non-steady state flow. In this thesis, it is presented a non-steady mathematical model to simulate the hydrodynamic behavior of pipe flow reactors with diffusion in order to evaluate the effect of the variation of the influent flowrate in the hydrodynamic parameters. The simulations were performed considering constant flowrate and volume, variable flowrate and volume and, variable flowrate and constant volume. It was investigated the influence of two types of stimulus-response assays, pulse and step function, on the application of mathematical models and the determination of the experimental retention time distribution curves. Theoretically, both tests should provide the same results although the pulse stimulus assay usually presents higher experimental sensitivity. As it was expected, both tests presented the same final results. The tested tracers were also evaluated in relation to the pulse and step stimulus-response tests. Three tracers were tested (bromocresol green, bromophenol blue and eosin Y) and it was shown that they provided different curves. It was studied the construction of the experimental retention time distribution curves using two procedures as an auxiliary tool for modeling. The proposed mathematical model was calibrated with data of bench scale reactors submitted to different cyclical variations of flowrates. Moreover, data of UASB reactor in pilot scale - submitted to 40 and 60% of cyclical variations of flowrates were utilized to calibrate and verify the obtained mathematical model. The results found with the mathematical model proposed in this research showed that the variations in influent flow rate can not be neglected. The model adequately represented a pilot scale UASB reactor. The results showed that the diffusion coefficients differ significantly for high flowrate fluctuations, when compared to other mathematical models that do not incorporate variable flowrate, depending upon the hypothesis used to derive the model.

Water flow and geochemical processes within the unsaturated zone (UZ) in two distinct types of karst environment were investigated using natural tracers (chemistry, stable isotopes 13 C, 18 O, 2 H, and 3 H, 14 C, 87 Sr/86 Sr). The extent of horizontal flow component and the response of drip water chemistry to recharge events were examined in the Moravian Karst (Czech Republic), while the character of water flow and its chemistry were studied in salt diapirs in southeastern part of the Zagros mountains (Iran). Under the conditions of well-developed epikarst, the horizontal flow component, defined as Hmax/T (Hmax = horizontal migration component, T - thickness of VZ) typically reaches values of 0.1 - 0.6 (Moravian and Slovenian Karst). However, in areas where epikarst was stripped off by glacial or human activity, the proportion of horizontal flow component is far greater (Hmax/T 1.6 - 24). This parameter is vital for the design of water source protection zones above caves. Nitrate mean residence time in 120 m thick VZ of the Moravian karst exceeded 16 years. The VZ above the Ochoz Cave (Moravian Karst) represents a semi-open to open system with respect to soil CO2. Under a high drip rate (high flow), the event water only made 5% of the total. During the year, water degassing and so called prior...

Applying mathematical models to dynamic contrast enhanced MRI (DCE MRI) data to perform quantitative tracer kinetic analysis enables the estimation of tissue characteristics such as vascular permeability and the fractional volume of plasma in a tissue. However, it is unclear to what extent modeling assumptions, particularly regarding water exchange between tissue compartments, impacts parameter estimates derived from clinical DCE MRI data. In this work, a new model is developed which includes water exchange effects, termed the water exchange modified two compartment exchange model (WX-2CXM). Two boundaries of this model (the fast and no exchange limits) were used to analyse a clinical DCE MRI bladder cancer dataset. Comparisons with DCE CT, which is not affected by water exchange, suggested that water exchange may have affected estimates of vp, the fractional volume of plasma. Further investigation and simulations led to the development of a DCE MRI protocol which was sensitised to water exchange, in order to further evaluate the water exchange effects found in the bladder cancer dataset. This protocol was tested by imaging the parotid glands in eight healthy volunteers, and confirmed evidence of water exchange effects on vp, as well as flow Fp and the fractional volume of extravascular extracellular space ve. This protocol also enabled preliminary estimates of the water residence times in parotid tissue, however, these estimates had a large variability and require further validation. The work presented in this thesis suggests that, although water exchange effects do not have a large effect on clinical data, the effect is measurable, and may lead to the ability to estimate of tissue water residence times. Results do not support a change in the current practise of neglecting water exchange effects in clinical DCEMRI acquisitions.

Le formaldéhyde, un des produits de base de la chimie, est synthétisé industriellement par un procédé multi-étapes, dans lequel l’efficacité énergétique est limitée. Ainsi, une synthèse par oxydation directe du méthane en phase gazeuse, qui pourrait être plus avantageuse, a été étudiée expérimentalement et par une modélisation cinétique, dans le cadre de ce travail. Pour favoriser la production du formaldéhyde, produit intermédiaire de l’oxydation du méthane, des temps de passage faibles (< 100 ms) ont été envisagés. Un microréacteur annulaire (espace annulaire de 0,5 mm) en quartz a été utilisé, dans lequel la réaction a été étudiée en faisant varier les paramètres opératoires suivants : température (600-1000°C), temps de passage (20-80 ms), rapport XO2/XCH4 (0,5-15) et teneur en NO2 ajoutée (0-0,6%). Sans NO2, les sélectivités en HCHO diminuent avec la conversion et le rendement maximal sans recyclage est de 2.4% (950°C, 60 ms et XO2/XCH4 = 8). L’ajout de NO2 permet de diminuer la température requise de 300°C, et d’augmenter le meilleur rendement en HCHO à 9% (700°C, 30 ms et XO2/XCH4 = 7 et 0,5% de NO2). À faible avancement, la réaction sans NO2 peut être modélisée avec le mécanisme Gri-Mech 3.0 sans aucun ajustement. Pour la réaction avec NO2, après quelques corrections et modifications fondées sur une étude bibliographique, le mécanisme de Zalc et al. (2006) permet de rendre correctement compte des résultats expérimentaux. L’analyse de flux a montré que l’inter-conversion entre NO2 et NO joue un rôle important dans le milieu réactionnel. Elle permet de former continuellement les radicaux réactifs OH•, et de convertir les radicaux CH3• et CH3O2• en radicaux CH3O• / Formaldehyde is one of the world’s top organic intermediate chemicals. It is currently produced by a complex three-step process but a one-step process might require less energy. In this work, the direct gas phase partial oxidation of methane to formaldehyde has been studied through experiments and kinetic modeling. As formaldehyde is an intermediate in the sequential oxidation of methane, short residence times (<100 ms) have been considered in order to optimize its production. Thus, a quartz annular flow microreactor (annular space 0.5 mm wide), was chosen. The undertaken experiments consist of a systematic investigation of the effects of temperature (600-1000°C), residence time (20-80 ms), input composition XO2/XCH4 (0.5-15) and initial NO2 concentration (0-0.6%). Without NO2, the HCHO selectivity decreases with the increasing methane conversion. For a single pass operation, the best HCHO yield is 2.4% (950°C, 60 ms, XO2/XCH4 = 8). The addition of NO2 decreases the reaction initiation temperature by 300°C and it remarkably enhances the HCHO yield. The highest HCHO yield attains 9% (700°C, 30 ms, XO2/XCH4 =7) in the presence of NO2 (0.5%). For the reaction without NO2, the mechanism Gri-Mech 3.0 fits well the experimental results. For the reaction with NO2, by using the mechanism of Zalc et al. (2006) with some modifications, we obtained a good agreement between the experimental data and the model. The production and consumption flux analysis shows that the inter-conversion between NO2 and NO plays an important role in the reaction, because it continuously produces the reactive radicals OH• and it converts the radicals CH3• and CH3O2• to radicals CH3O•

Ce travail porte sur l'étude de fours tournants équipés de releveurs. Ce sont des contacteurs gaz/solide largement répandus dans de nombreux secteurs industriels mettant en oeuvre des solides divisés. Cependant en raison d'une faible connaissance du fonctionnement de ces équipements notamment en matière d'écoulement ou de transfert thermique, leur utilisation repose encore beaucoup sur le savoir faire des opérateurs acquis avec le temps. Ainsi ce travail vise à fournir aux ingénieurs des outils de connaissance et d'extrapolation pour les accompagner dans les phases de dimensionnement, mais aussi d'optimisation de procédés existants, en particulier pour des fours tournants en chauffage indirect et équipés de releveurs. La première partie de cette étude porte sur l'influence des conditions opératoires sur l'hydrodynamique des solides divisés de forme et taille différentes. Pour ce faire, des procédures expérimentales pour la mesure de distribution des temps de séjours des particules solides ont été mises en oeuvres. Deux pilotes de four tournant ont été utilisés. Ces derniers ont un ratio longueur sur diamètre équivalent mais un ratio de taille de 2. L'hydrodynamique des fours a été caractérisée quantitativement à partir des résultats expérimentaux en terme de temps de séjour des solides, taux de remplissage du four ainsi que de la dispersion axiale des particules. Ces derniers ont été modélisés par analyse dimensionnelle dans un souci de généralité en prenant en compte la présence d'éléments internes (releveurs, grille) ou diaphragmes en sortie, mais aussi des paramètres opératoires tels que la vitesse de rotation du tube, son inclinaison ou le débit des particules solides. La seconde partie de cette étude s'intéresse aux processus de transfert thermique dans les fours tournants en chauffage indirect et équipés de releveurs. Cette étude repose sur la mesure des profils de température à la paroi, dans la phase gazeuse et le lit de particules solides. L'analyse de ces profils de température se focalise sur la détermination des coefficients de transfert de chaleur entre la paroi et le lit de solides d'une part, et entre la paroi et le gaz d'autre part. Une méthode d'analyse globale de système mince et un bilan global intégrant la puissance fournie pour la chauffe sont utilisés pour la détermination de ces coefficients de transfert. Les résultats obtenus permettent d'une part de mettre en évidence l'effet des releveurs ainsi que l'influence des paramètres opératoires sur ces coefficients de transfert de chaleur et d'autre part d'établir par analyse dimensionnelle des modèles pour ces derniers. Enfin, ce travail se termine par la mise en place d'un modèle dynamique simplifié de four tournant en chauffage indirect permettant la détermination des profils de température le long du four et pouvant être facilement adapté à divers procédés. / The present work addresses a fundamental study on flighted rotary kilns. They are gas-solid reactors, used in a variety of industries to process heterogeneous media. However, operating these kilns mainly relies on the know-how of operators due to insufficient fundamental understanding. The aim of this work is to provide engineers with relevant tools and models to assist in the design stage and the performance improvement of existing operating process units, in particular indirectly heated rotary kilns, inclined and equipped with lifters. In the first part, we studied the effects of operating parameters on the flow of materials of differing properties and shape. For this purpose, residence time distribution measurements were performed through experimental stimulus response tests. Two pilot-scale rotary kilns with similar length-to-diameter ratios, but a dimension ratio of about two were used in this study. We focused on the effects of lifter shape and configurations. The effects of the rotational speed, the kiln slope, the mass flow rate and the exit dam height were also analyzed. The flow of solids was quantitatively characterized primarily by the experimental mean residence time, hold-up, and axial dispersion coefficient. Using a dimensional analysis, models were established to predict the mean residence time, the filling degree and the axial dispersion coefficient, providing basic information on the kiln design, solid particle properties and operating conditions. In the second part, we studied the heat transfer mechanisms occurring in the flighted rotary kiln by measuring temperature profiles at the wall, the freeboard gas and the bulk of solids. Analysis of the temperature profiles focused on two main issues: assessment of the heat transfer coefficient between wall and gas, and assessment of the heat transfer coefficient between wall and solid particles. The lumped system analysis and a heat balance using the power supplied for the heating were applied to determine the experimental heat transfer coefficients. The effects of operating conditions and lifting flights were analyzed. Both heat transfer coefficients were then correlated through dimensional considerations. Lastly a global dynamic model mainly based on the models developed in this study can be used to determine wall, gas and bulk solids axial temperature profiles in an indirectly heated flighted rotary kiln. This global model needs to be completed with specific models related to a reaction so as to be used as a framework for the simulation of specific industrial rotary kilns.

L’enrobage à sec par action mécanique permet de formuler des particules composites dont les fonctionnalités et les propriétés physiques, comme l’écoulement, sont améliorées et cela sans l’ajout de solvant ou de liant. Actuellement la plupart des procédés d’enrobage à sec sont conduits en mode discontinu. L’objectif de ce travail est donc de développer et d’étudier une opération d’enrobage à sec par un procédé continu innovant, une extrudeuse bi-vis corotative sans filière, constituant une rupture technologique dans son domaine. Dans le cadre de ce travail, des sphères de cellulose microcristalline, appelées particules hôtes sont enrobées avec soit des talcs de différentes granulométries soit du stéarate de magnésium, nommées particules invitées. Dans un premier temps, le comportement des particules hôtes est étudié dans le procédé. Les particules sorties du procédé sont analysées par microscopie électronique à balayage, par granulométrie laser et par voluménométrie. Pour la configuration de vis présentant que des éléments de transport, la vitesse de rotation des vis (25 à 200 rpm) et le débit d’alimentation (0,5 à 2 kg/h) choisis influencent le taux de remplissage dans le fourreau, et pour un taux supérieur à environ 14 % : la quantité de particules endommagées est négligeable. Un taux de remplissage faible favorise les frictions particules-particules ou particules-métal au niveau de l’entrefer. L’ajout de zones de mélanges dans la configuration des vis accentue ce phénomène de brisure par l’augmentation des contraintes de cisaillement. Par ailleurs, des masses retenues de la poudre dans le fourreau évoluent linéairement en fonction de la masse de poudre transportée en un tour de vis pour différentes configurations de vis. Ces relations laissent penser à l’existence d’un volume mort. Les mesures de distribution de temps de séjour mettent en évidence par l’application d’un modèle d’association de réacteurs idéaux, la présence d’écoulement piston et d’un volume mort. Dans un second temps, la faisabilité d’une opération d’enrobage à sec par le procédé étudié est analysée. Une couche d’enrobage continu de talc modifiant le comportement hydrophile des particules hôtes, est obtenue pour une vitesse de rotation de vis de 50 rpm et une configuration de vis cisaillante. Le type de particules invitées influence la morphologie de la couche d’enrobage : de type film avec le stéarate de magnésium et de type discret avec le talc micronisé. Néanmoins les propriétés de taille, d’écoulement, de compressibilité des particules composites sont semblables à celle des particules hôtes, seule la propriété de mouillabilité est modifiée. La présence de stéarate de magnésium diminue le temps de séjour des particules dans le procédé grâce à son caractère lubrifiant. / Dry particle coating with mechanical action allows the production of composite particles whose functionalities and physical properties, such as flowability, are improved thanks to the absence of solvent or binder. Currently, most of dry particle coating processes are carried out in a discontinous mode. The objective of this work is thus to develop and study a dry particle coating operation with a continuous innovative process, twin screw co-rotating extruder without die, constituting a technological rupture in this application field. For this, spherical particles of microcristalline cellulose, as host particles, are coated with either talc particles of two sizes or magnesium stearate particles (MgSt), as guest particles. Firstly, the host particles behaviour is studied in the process. The exiting particles are analyzed by scanning electronic microscopy, laser granulometry and tapping test. Regarding the transport configuration, the chosen screw speed (between 25 an 200 rpm) and the feed rate (between 0.5 and 2 kg/h) have an important influence on the filling level in the barrel. For a filling level superior to approximatly 14 %, the quantity of broken particles is not significant. A low filling level facilitates the particle-particle or particle-metal friction in the barrel gap. When more mixing zones are added to the screw configuration, the shear stresses increase and, therefore, the breakage particle phenomenon becomes more prominent. Futhermore, the retained powder mass increases linearly when the transported mass in one screw turn increases for all the screw configurations. These evolutions suggest the existence of a dead volume. The residence time distribution mesurements highlight, thanks to the application of flowing model, the presence of plug-flow and a dead volume. Secondly, the feasibility of using the process for dry particle coating is analyzed. A continuous coating layer of talc modifiying the hydrophilic behaviour of the host particles is obtained for a low screw rotation speed (50 rpm) and a screw configuration with one mixing zone. The type of guest particles influence the morphology of the coating layer: film layer with the MgSt particles and discontinous layer with the micronized talc. However, size, flow and compressibility of the coated particles are similar to the ones of the initial host particles, only the wettability properties are modified. The presence of MgSt decreases the particle mean residence time in the process thanks to its lubricant action.

Knowledge of the properties of single molecule diffusion is important for controlling dynamic self-assembly of molecular structures. A powerful experimental technique for determining diffusion coefficients is the recording of diffusion-induced signal fluctuations by a locally fixed point-like probe. Here, the signal becomes modified, whenever a molecule enters a certain detection area on the surface under the probe. The technique is minimal invasive and has a very good time resolution, enabling the investigation of highly mobile molecules. Theories are necessary for the analysis of the fluctuations and the extraction of diffusion properties. In this thesis, three methods are presented, which are based on the autocorrelation function, the distribution of peak widths and the distribution of interpeak intervals. Analytical expressions are derived for the distributions and the autocorrelation function in case of molecules, which can be described by circular or rectangular shapes. For rectangular shaped molecules, rotational diffusion can influence the recorded fluctuations. To allow for a simultaneous determination of rotational and translational diffusion coefficients the analytical treatment is extended. Furthermore, new methods are developed to determine the diffusion tensor for anisotropic stochastic molecular motion, using either one linearly extended probe or two individual probes. Coarse-graining the signal recorded by a point-like probe, which repeatedly moves on a line or a circle, is suggested for experimental implementation. All facets of the evaluation methods are verified against kinetic Monte Carlo simulations. Applications to experimental data, recorded by a locally fixed scanning tunneling microscope tip, are demonstrated for copperphthalocyanine and PTCDA molecules diffusing on Ag(100).

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