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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Absorção de gás carbônico para beneficiamento de biogás utilizando carbonatos em coluna recheada. / Carbon dioxide absorption for biogas upgrade using carbonates in packed column.

Shibata, Fernando Shiniti 07 March 2017 (has links)
O objetivo desse trabalho foi o estudo da utilização do carbonato de potássio para a absorção de CO2, tendo como principal foco o uso dessa tecnologia para o beneficiamento de biogás em instalações de pequeno e médio porte. O estudo foi dividido em três partes. Na primeira, realizou-se um projeto fatorial, baseado em resultados obtidos por meio de simulação via ASPEN Plus, com o intuito de quantificar a influência da vazão de líquido, da vazão de gás, da concentração da solução e da temperatura do líquido na quantidade de gás carbônico absorvida. Na segunda, foram realizados ensaios de absorção de CO2 em coluna recheada com anéis de Raschig de vidro, utilizando soluções de carbonato de potássio, com objetivo de comparar os resultados obtidos pelo projeto fatorial e estudar o seu potencial para o processo de beneficiamento de biogás. Na terceira, quatro substâncias foram separadamente utilizadas em mistura com solução de carbonato de potássio, de maneira a verificar seu poder como promotores da reação de gás carbônico com carbonato de potássio. Os resultados do projeto fatorial apresentaram a temperatura, vazão e concentração de líquido como as variáveis independentes de maior influência positiva na absorção de CO2, enquanto que a vazão de gás teve influência negativa de baixa intensidade. A quantidade de gás carbônico absorvida em solução sem promotores e em pressão ambiente foi baixa, como relata a literatura. A utilização de promotores possibilitou um aumento substancial da absorção, principalmente com o uso da piperazina. / The objective of this work is to study the use of potassium carbonate for CO2 absorption, aiming to use this technology for biogas upgrade for small and medium scale plants. The study was divided in three parts. In the first one, a factorial design was done, based in results obtained by simulation via ASPEN Plus, to verify the influence of four process variables, namely: liquid volumetric flow rate, gas volumetric flow rate, solution concentration and liquid temperature. Secondly, CO2 absorption experiments were run in columns packed with glass Raschig rings, using potassium carbonate, in order to compare the results obtained by the factorial design and to study the solution\'s potential for biogas upgrade. Lastly, four substances were separately mixed into potassium carbonate solutions, aiming to verify their potential as CO2 absorption promoters. The results of the factorial design presented the liquid temperature, the liquid volumetric flow rate and the solution concentration as the most positively influential independent variables in carbon dioxide absorption, while the gas volumetric flow rate had a negative influence with low intensity. The amount of CO2 absorbed in solution without promoters and in ambient pressure was low, fact that is mentioned by other researchers. The use of promoters allowed a substantial increase in efficiency of CO2 absorption, mainly with the use of piperazine.
2

Avaliação do efeito dos parametros operacionais e geometricos sore a eficiencia de uma coluna de destilação Higee / Estimation oh the from geometric and operation parameter above a Higee distillation column efficiency

Lang, Jean Pierre 04 June 2005 (has links)
Orientadores: Teresa Massako Kakuta Ravagnani, João Alexandre Ferreira da Rocha Pereira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-05T04:47:12Z (GMT). No. of bitstreams: 1 Lang_JeanPierre_M.pdf: 1967050 bytes, checksum: 0383f4c0388e6e7aa19f19c4c4688052 (MD5) Previous issue date: 2005 / Resumo: As colunas de recheio são equipamentos intensamente aplicados em operações de separação tais como destilação, absorção de dessorção. No entanto, a sua capacidade à transferência de massa em contracorrente é limitada devido à sua inundação. Uma nova tecnologia HIGEE ('high g¿ ¿ alta gravidade é proposta para superar esta limitação. Uma cluna HIGEE utiliza um recheio rotativo que induz acelerações centrífugas acima de 1000 vezes a aceleração da gravidade terrestre. O aumento da força motriz permite o aumento da capacidade e da eficiência da coluna. De acordo com vários autores, o tamanho do equipamento fica consideravelmente reduzido, apresentando vantagens econômicas e operacionais. A principal proposta deste trabalho é avaliar a forma como a coluna com recheio rotatico se comporta quando o raio externo do rotos é aumentado de 8 (Nascimento, 1999 e 2003) para 13cm.Os experimentos foram conduzidos em condições de refluxo total, sendo utilizando dois sistemas destilantes: n-hexano/n-heptano e etanol/água. A velocidade do rotor foi variada de 500 a 2300 rpm, criando acelerações contrifugas de 26 a256 vezes a aceleração da gravidade. O efeito da vazão de vapor, velocidade de rotação e do sistema destilante sobre o coeficiente de transferência de massa, 'K IND. y¿¿a IND. e¿ depende do fluxo de vapor, mas fracamente da velocidade do rotor...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Packed colummns are equipment intensively applied in separations such as distillation, absorption and stripping , absorption and strippig. However, its for counter-current mass transfer is limited due to its flooding. A new HIGEE (high g ¿ high gravity) technology is proposal to overlap this limitation. A HIGEE column uses a rotating machine that promotes centrifugal accelerations above 1000 times the terrestrial gravity acceleration. The increase of the driving force allows the increase of column¿s capacity and efficiency. In accordance with some authors, the equipment size considerably reduced presenting economic and operational advantages. The main proposal of this work is to evaluate how the mass transfer behavior of the HIGEE column changes when the external rotor radius is increased from 8 (Nascimento 1999 and 2003) to 13 cm. The experiments had been conduced in total reflux conditions using two distilling system n-hexane/n-heptane and ethanol/ water. The rotor's speed was vaied from 500 to 2300 rpm , provided centrifugal accelerations from 26 to 556 times higher than terrestrial gravity acceleration. The effect of the vapor outflow, rotation speed and distilling system on mass transfer coefficient 'K IND. y¿¿a IND. e¿ and transfer unit area, 'AUT IND. G¿had been analyzed for each rotor size...Note: The complete abstract is available with the full electronic digital thesis or dissertations / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química
3

Absorção de gás carbônico para beneficiamento de biogás utilizando carbonatos em coluna recheada. / Carbon dioxide absorption for biogas upgrade using carbonates in packed column.

Fernando Shiniti Shibata 07 March 2017 (has links)
O objetivo desse trabalho foi o estudo da utilização do carbonato de potássio para a absorção de CO2, tendo como principal foco o uso dessa tecnologia para o beneficiamento de biogás em instalações de pequeno e médio porte. O estudo foi dividido em três partes. Na primeira, realizou-se um projeto fatorial, baseado em resultados obtidos por meio de simulação via ASPEN Plus, com o intuito de quantificar a influência da vazão de líquido, da vazão de gás, da concentração da solução e da temperatura do líquido na quantidade de gás carbônico absorvida. Na segunda, foram realizados ensaios de absorção de CO2 em coluna recheada com anéis de Raschig de vidro, utilizando soluções de carbonato de potássio, com objetivo de comparar os resultados obtidos pelo projeto fatorial e estudar o seu potencial para o processo de beneficiamento de biogás. Na terceira, quatro substâncias foram separadamente utilizadas em mistura com solução de carbonato de potássio, de maneira a verificar seu poder como promotores da reação de gás carbônico com carbonato de potássio. Os resultados do projeto fatorial apresentaram a temperatura, vazão e concentração de líquido como as variáveis independentes de maior influência positiva na absorção de CO2, enquanto que a vazão de gás teve influência negativa de baixa intensidade. A quantidade de gás carbônico absorvida em solução sem promotores e em pressão ambiente foi baixa, como relata a literatura. A utilização de promotores possibilitou um aumento substancial da absorção, principalmente com o uso da piperazina. / The objective of this work is to study the use of potassium carbonate for CO2 absorption, aiming to use this technology for biogas upgrade for small and medium scale plants. The study was divided in three parts. In the first one, a factorial design was done, based in results obtained by simulation via ASPEN Plus, to verify the influence of four process variables, namely: liquid volumetric flow rate, gas volumetric flow rate, solution concentration and liquid temperature. Secondly, CO2 absorption experiments were run in columns packed with glass Raschig rings, using potassium carbonate, in order to compare the results obtained by the factorial design and to study the solution\'s potential for biogas upgrade. Lastly, four substances were separately mixed into potassium carbonate solutions, aiming to verify their potential as CO2 absorption promoters. The results of the factorial design presented the liquid temperature, the liquid volumetric flow rate and the solution concentration as the most positively influential independent variables in carbon dioxide absorption, while the gas volumetric flow rate had a negative influence with low intensity. The amount of CO2 absorbed in solution without promoters and in ambient pressure was low, fact that is mentioned by other researchers. The use of promoters allowed a substantial increase in efficiency of CO2 absorption, mainly with the use of piperazine.
4

Doprinos odsumporavanju otpadnih gasova citratnim postupkom / A contribution to desulphurization of waste gases by citrate solution

Cvejanov Jelena 15 March 2002 (has links)
<p><strong>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</strong></p><p>Sumporni oksidi najče&scaron;će prisutni polutanti u atmosferi direktno utiču na zdravlje Ijudi i stvaranje kiselih ki&scaron;a ugrožavajući ekosistem. Razvijen je veliki proj postupaka odsumporavanja otpadnih gasova, dok je u naj&scaron;iroj upotrebi mokri neregenerativni postupak apsorpcije koji koristi jeftine hemikalije, kreč ili krečnjak. Zbog toga se posebna pažnja posvečuje i ispitivanju regenerativnih postupaka kod kojih se apsorpciono sredstvo delimično ili u potpunosti regeneri&scaron;e, a pri čemu su gubici apsorpcionog fluida zanemarljivi. Postupak sa limunskom kiselinom upravo ispunjava poslednji zahtev. Ostale prednosti ovog postupka su fleksibilnost, bez prisustva koplikovanih procesnih postupaka, mali oksidacioni gubici sumpor dioksida i netoksičnost reagensa.<br />Pri projektovanju kolone za odsumporavanje otpadnih gasova neophodno je poznavanje ravnotežnih podatka para-tečnost, hidrodinamičkih parametara (pad pritiska i količina zadržane tečnosti) i prenosa mase kao jednog od direktnih pokazatelja brzine apsorpcije ili ukupne brzine reakcije.<br />Izveden je matematički model ravnoteže za predvidjanje ravnotežnog parcijalnog pritiska sumpor dioksida iznad vodenog rastvora natrijum citrata za ceo opseg pH vrednosti pufera i temperature na osnovu eksperimentalnih vrednosti. Zaustavnom metodom je odredjena količina zadržane tečnosti u koloni. Analizirane su jednačine date u literaturi za predvidjanje pada pritiska i zapreminskih koeficijenata prenosa mase i odabrane one koje se mogu primeniti na odabrani sistem sumpor dioksid/citratni pufer.<br />Na osnovu eksperimentalnih podataka para-tečnost, hidrodinamičkih parametara i odabranih jednačina za prenos mase, izvr&scaron;en je proračun visine apsorpcione kolone sa Raschigovim prstenovima za izdvajanje sumpor dioksida iz otpadnog gasa i pokazano je da pad pritiska za eksperimentalno primenjene protoke gasa i tečnosti odgovara literaturno predloženom opsegu.</p> / <p><strong>Abstract was processed by technology for Optical character recognition (OCR).</strong></p><p>Control of sulfur dioxide emission has a relatively long history, especially in major industrial countries due to its common occurence and harmful effects. A number of dry and wet process comprising regenerable and throw-away process were investigated, but the wet throw-away process become the most widely accepted. The use of the flue gas desulphurization process with sodium citrate solution is recommended, as it is found that sodium citrate meets the specific needs of reversible sulphur dioxide absorption to buffer range as well as its capacity, chemical and physical stability.<br />Packed columns are widely used in the chemical industry for gas/liquid mass and heat transfer operations and they have found special use in small fractionating towers. Their use has also been found to be advantageous where corrosion control is essential. Fundamental steps necessary for design of absorption column for sulfur dioxide removal are:<br />- determination of vapor-liguid eguiiibrium data for the citrate buffer,<br />- determination of hydrodynamic parameters, i.e. holdup and pressure drop,<br />- determination gas-liquid mass transfer coefficients.<br />On the basis of the experimentally determined vapour pressures data, a model of the gas- equilibria was formulated. Holdups were measured for air/sodium citrate solution using the draining method. Also, literature-proposed eguations for determination of pressure drop, volumetric liquid-phase and gas-phase mass transfer coefficient in packed column were presented and chosen those that could be applied to flue gas/citrate puffer system. Therefore, on the base of obtained results the preposition for the design of packed column is presented.</p>
5

Conversion of Carbon Dioxide and Hydrogen into Methane in Bench-scale Microcosms and Packed Column Reactors

Congiu, Brian Alexander January 2010 (has links)
No description available.
6

Packed Column Supercritical Fluid Chromatography : Applications in Environmental Chemistry

Riddell, Nicole January 2017 (has links)
Although gas and liquid chromatography have emerged as dominant separation techniques in environmental analytical chemistry, these methods do not allow for the concurrent analysis of chemically diverse groups of persistent organic pollutants (POPs). There are also a small number of compounds which are not easily amenable to either of these traditional separation techniques. The main objective of this thesis was to address these issues by demonstrating the applicability of packed column supercritical fluid chromatography (pSFC) coupled to mass spectrometry (MS) in various aspects of environmental chemistry. First, pSFC/MS analytical methods were developed for legacy POPs (PCDDs, PCDFs, and PCBs) as well as the emerging environmental contaminant Dechlorane Plus (DP), and issues relating to the ionization of target analytes when pSFC was coupled to MS were explored. Novel APPI and APCI reagents (fluorobenzene and triethylamine) were optimized and real samples (water and soil) were analyzed to demonstrate environmental applicability. The possibility of chiral and preparative scale pSFC separations was then demonstrated through the isolation and characterization of thermally labile hexabromocyclododecane (HBCDD) stereoisomers. The analytical pSFC separation of the α-, β-, and γ-HBCDD enantiomers as well as the δ and ε meso forms was shown to be superior to results obtained using a published LC method. Finally, technical mixtures of phosphorus flame retardants (RBDPP, BPA-BDPP, and DOPO; a group of related compounds which are challenging to analyze concurrently) were examined using multiple analytical techniques and pSFC was found to be the only method which facilitated the accurate determination of the components of all 3 mixtures. This thesis confirms the potential of pSFC/MS as a fast, green, and cost effective means of separating and analyzing environmental contaminants.
7

Modélisation par prise de moyenne volumique des phénomènes de transports en milieu poreux réactif : application au garnissage d’une colonne d’absorption gaz-liquide / Modeling of transport phenomena in reactive porous media using volume averaging method : Application to the packing of an absorption column

Girard, Coralie 07 March 2013 (has links)
Le Laboratoire de Thermique, Energétique et Procédés de Pau travaille en parallèle depuis plusieurs années sur les deux thématiques suivantes, la modélisation des réacteurs multifonctionnels et la modélisation des transports en milieux poreux. Dans ce travail, un modèle général de transports en milieu poreux multiphasique multiconstituant réactif est développé puis appliqué au cas particulier de l’absorption réactive afin de décrire les phénomènes se produisant au sein du garnissage. La modélisation débute par une description classique de chacune des phases continues grâce aux équations de conservation de la masse, de la quantité de mouvement et de l’énergie. Les phases fluides sont multiconstituantes et le siège de réactions homogènes. Bien qu’à cette échelle les mécanismes soient parfaitement décrits, le passage à la simulation impose une étape d’homogénéisation par prise de moyenne. Ce changement d’échelle conduit à un système d’équations à l’échelle locale. Le modèle est appliqué à l’absorption du dioxyde de carbone dans une solution aqueuse d’hydroxyde de sodium au sein d’une colonne garnie. Les simulations bidimensionnelles instationnaires fournissent des informations locales sur le procédé. Les résultats obtenus montrent une bonne adéquation avec la connaissance classique des mécanismes d’absorption réactive. / The “Laboratoire de Thermique, Energétique et Procédés de Pau” works on the two following subjects, modeling of multifunctional reactor and modeling of transport in porous media. In this work, a general model of transport in multiphase multi component reactive porous media is developed and then applied to the specific case of reactive absorption in order to describe the phenomena which occur within the packing. Modeling begins with a classic description of each continuous phase through the equations of conservation of mass, momentum and energy. The fluid phases are multi component and reactive. Although mechanisms are perfectly described at this scale, the simulation imposes a homogenization by volume averaging. This change of scale leads to a set of equations at the local scale. The model is applied to the absorption of carbon dioxide in an aqueous solution of sodium hydroxide within a packed column. Unsteady two-dimensional simulations provide local information about the process. The results obtained show a good agreement with the classical knowledge of reactive absorption mechanisms.
8

Continuous Co-Separation by Liquid Absorption in Aqueous Cuprous Chloride (CuCl) and Magnesium Chloride (MgCl2) Solution

Foster, Paul J. 22 March 2007 (has links) (PDF)
The purpose of the research was to design, build, test, and recommend a process to economically separate CO from a gas mixture of CO, CO2, and O2. The general method considered in this research to accomplish the separation was liquid absorption in a packed column. Several experiments were performed to identify the best process solution to use in a prototype. The experiments, based on the COSORB process, consisted of CuCl mixed with a complexing agent (metal tri-chloride) and a solvent (metal tetra-chloride, toluene, ethanol, etc.). The best method consisted of an aqueous solution of CuCl and MgCl2, which has previously been used for CO absorption experiments reported in the literature. The absorption takes place at elevated pressure (30 psig) and ambient temperature, and the stripping occurs at approximately 75 ºC. Using the apparatus at approximate design conditions, the highest removal of CO was 88% with a product composition of 48%. The highest product composition achieved was 84%; in this case CO removal was 66%. Product composition was low because a significant amount of CO2 physically absorbed into solution (which also decreased the pH of the solution to about 4, according to calculation). The removal of CO should increase with a taller column and higher liquid flow through the column; however, this might decrease the product composition. Advantages of this process are that the raw materials used are relatively cheap, heating and cooling requirements are lower than similar processes, and operation is relatively simple.
9

Pore Size Characterization of Monolithic Capillary Columns Using Capillary Flow Porometry

Fang, Yan 25 September 2009 (has links) (PDF)
A simple capillary flow porometer (CFP) was assembled for pore structure characterization of monolithic capillary liquid chromatography columns based on ASTM standard F316-86. Determination of differential pressures and flow rates through dry and wet samples provided the necessary information to determine the through-pore throat diameter, bubble point pore diameter, mean flow pore diameter, and pore distribution. Unlike measurements in bulk using traditional techniques to provide indirect information about the pore properties of monolithic columns, monoliths can be characterized in their original chromatographic forms with this system. The performance of the new CFP was first evaluated by characterizing the pore size distributions of capillary columns packed with 3, 5, and 7 µm spherical silica particles. The mean through-pore diameters of the three packed columns were measured to be 0.5, 1.0 and 1.4 µm, which are all smaller than the pore diameters calculated from a close-packed arrangement (i.e., 0.7, 1.1 and 1.6 µm), with distributions ranging from 0.1 - 0.7, 0.3 - 1.1 and 0.4 - 2.6 µm, respectively. This is reasonable, since visual inspection of SEM images of the particles showed relatively large fractions of smaller than specified particles in the samples. Typical silica monoliths were fabricated via phase separation by polymerization of tetramethoxysilane (TMOS) in the presence of poly(ethylene glycol) (PEG). The mean pore diameter and pore size distribution measured using the CFP system verified that a greater number of pores with small throat diameters were prepared in columns with higher PEG content in the prepolymer mixture. SEM images also showed that the pore diameters of monoliths fabricated in bulk were found to be smaller than those in monoliths synthesized by the same procedure, but confined in capillary tubes. The CFP system was also used to study the effects of column inner diameter and length on pore properties of polymeric monoliths. Typical monoliths based on butyl methacrylate (BMA) and poly(ethylene glycol) diacrylate (PEGDA) in capillary columns with different inner diameters (i.e., 50 to 250 µm) and lengths (i.e., 1.5 to 3.0 cm) were characterized. The mean pore diameters and the pore size distributions indicated that varying the inner diameter and/or the length of the column affected little the pore properties. The latter finding is especially important to substantiate the use of CFP for determination of monolithic pore structures in capillaries. The results indicate that the through-pores are highly interconnected and, therefore, pore structure determinations by CFP are independent of capillary length. A negatively charged polymer monolith based on BMA, ethylene glycol dimethacrylate (EDMA) and 2-acryloylamido-2-methylpropanesulfonic acid monomer (AMPS), was successfully prepared in silica sacrificial layer, planar (SLP) microchannels. Extraction of FITC (fluorescein 5-isothiocyanate) labeled phenylalanine and capillary electrochromatography (CEC) of FITC labeled glycine using this monolithic stationary phase were demonstrated.
10

Etude de l'écoulement ruisselant dans les lits fixes par tomographie à rayons X

Toye, Dominique 17 January 1997 (has links)
Lobjet du présent travail est létude expérimentale et théorique de lhydrodynamique des écoulements dans des colonnes à garnissage et, plus particulièrement, lanalyse par tomographie à rayons X de la distribution spatiale des phases liquide et solide dans des lits fixes parcourus par un écoulement de liquide. La distribution des phases est observée à différents niveaux, depuis léchelle locale jusquà léchelle de la colonne dans son ensemble. Lintroduction permet tout dabord de rappeler les principales applications industrielles des colonnes à garnissage, ainsi que les caractéristiques particulières associées à chacune dentre elles. Lhydrodynamique des écoulements dans ce type dappareils résulte de phénomènes extrêmement complexes, intervenant à une échelle très petite. Cet état de choses a poussé les chercheurs à développer des modèles de plus en plus détaillés, dont la validation requiert une connaissance de plus en plus fine de la répartition des phases au sein des lits fixes. Lobtention de mesures à une échelle très locale savère donc indispensable. Après un bref rappel des différentes techniques de mesure plus ou moins locales qui ont été appliquées, dans le passé, à létude des écoulements dans des colonnes à garnissage, lensemble des techniques tomographiques, ainsi que leurs principaux champs dapplication sont présentés. Parmi ces applications, la tomographie à rayons X semble particulièrement bien adaptée, car elle permet daccéder à une cartographie complète de la distribution spatiale des différentes phases présentes dans une colonne à garnissage de relativement grandes dimensions. Le chapitre I présente en détail les bases de la technique expérimentale utilisée. La tomographie consiste à reconstruire limage dune section droite dun objet à partir de données de transmission, obtenues en illuminant cet objet sous un grand nombre dangles différents. Lalgorithme permettant de reconstruire les images à partir des données de projection est lalgorithme de rétro-projection filtrée, adapté à la géométrie du dispositif de radiographie (faisceau plan angulaire et détecteurs colinéaires équidistants). Cet algorithme, qui est le plus utilisé en pratique, a dû être modifié pour tenir compte dimperfections géométriques existant au niveau du dispositif de mesure. Le chapitre II décrit linstallation expérimentale, qui comprend le tomographe à rayons X, la colonne à garnissage et leurs éléments périphériques respectifs. Le tomographe consiste en un dispositif de radiographie (source de rayons X et détecteur linéaire) fixé sur un manipulateur. Le pilotage de linstallation, ainsi que lacquisition des données expérimentales sont réalisés grâce à un pupitre de commande et à un P.C. Le dispositif de tomographie permet de réaliser des images de sections droites dune colonne à garnissage, irriguée grâce à un dispositif dalimentation et dévacuation des fluides. Après une description relativement détaillée de tous ces éléments, le mode opératoire suivi pour la réalisation des différentes mesures expérimentales est présenté. Dans les chapitres III à V sont regroupés les différents résultats expérimentaux, ainsi que les discussions et commentaires sy rapportant. Le chapitre III présente les différents essais réalisés en vue de valider le dispositif de tomographie. Dans ce but, des objets de forme et de taille connues ont été radiographiés. La confrontation des images reconstruites et des objets originaux permet deffectuer cette validation, mais également dapprécier la résolution de la technique tomographique de mesure. Le chapitre IV expose les résultats obtenus sur base des images de sections droites de la colonne sèche. Dans un premier temps, les différentes opérations effectuées sur les images, après leur reconstruction, sont décrites. Ces opérations ont pour but de donner une signification physique réelle aux valeurs des pixels composant les images, mais également daméliorer la représentation graphique de ces dernières. Une des premières grandeurs calculées sur les sections reconstruites est la fraction de vide de lempilage. Les valeurs de porosité ainsi calculées sont comparées à dautres valeurs obtenues expérimentalement, ainsi quaux valeurs annoncées par les fabricants dempilages. Une dimension caractéristique, propre à chacun des types dempilage, est ensuite calculée grâce à lapplication de différentes méthodes comme lanalyse de lentropie de configuration, lanalyse de la distribution de la fraction de solide ou encore lanalyse de la fonction dautocorrélation. La dimension caractéristique ainsi déterminée permet daccéder à la taille des cellules élémentaires susceptibles de représenter la morphologie de la phase solide dans le cadre dune modélisation des phénomènes hydrodynamiques intervenant au sein du lit fixe. Après une brève conclusion récapitulative, la dernière partie du chapitre IV est consacrée à la visualisation des différentes échelles caractéristiques présentes dans les images analysées. Le chapitre V décrit les résultats obtenus sur base des images de sections droites de la colonne irriguée. Dans un premier temps, les images obtenues sur des sections irriguées font lobjet dune analyse purement qualitative. Cette analyse permet dobserver linfluence exercée par le distributeur de liquide sur la distribution du liquide au sein de sections droites situées à différentes hauteurs au sein de la colonne, pour différentes valeurs du débit de liquide. Elle permet également dobserver la corrélation existant entre les distributions des phases liquide et solide au sein de la colonne. Ensuite, les valeurs globales de la rétention de liquide calculées sur base des valeurs des pixels composant les images reconstruites sont confrontées à des valeurs de rétention obtenues par dautres méthodes, expérimentales ou théoriques, afin de valider les résultats obtenus par tomographie. Dans ce but, des comparaisons sont effectuées avec des résultats expérimentaux présentés dans la littérature, avec des valeurs de rétentions mesurées par essais de traceur, ainsi quavec des valeurs calculées grâce à des corrélations proposées dans la littérature et plus particulièrement grâce à la corrélation issue dun modèle découlement en canaux. Un modèle hydrodynamique basé sur une approche probabiliste est ensuite utilisé pour modéliser lhydrodynamique au sein de la colonne à garnissage. Cette approche permet non seulement de rendre compte de lévolution des valeurs globales de la rétention de liquide, mais également de modéliser la distribution des valeurs locales de la vitesse du liquide dans les différentes sections de la colonne à garnissage. Pour terminer, la conclusion résume lensemble des résultats issus de la présente étude, avant de lancer quelques pistes pour des travaux de recherche à venir.

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