La compréhension des phénomènes d’adsorption de gaz en présence d’eau dans des milieux confinés est une problématique importante tant d’un point de vue fondamental que du point de vue des applications industrielles Les travaux menés dans cette thèse ont principalement porté sur le développement d’un nouveau couplage NLDFT/SAFT-VR (Non-Local Density Functional Theory/ Statistical Associating Fluid Theory for potentials of Variable Range) pour modéliser les propriétés interfaciales et l’adsorption de méthane, d’eau et de leur mélange en milieu confiné. Les résultats théoriques obtenus sur ces fluides ont été comparés avec succès à des calculs de simulation moléculaire. Par ailleurs, des isothermes d’adsorption expérimentales de méthane et d’eau sur des charbons actifs ont été mesurées par la technique gravimétrique sur une balance à suspension magnétique. Afin de pouvoir comparer les isothermes expérimentales et théoriques, il est nécessaire de connaître la distribution en taille de pore des solides poreux. C’est pourquoi un nouveau modèle thermodynamique de caractérisation des milieux microporeux a été développé. Les comparaisons des isothermes d’adsorption de méthane ont montré un excellent accord entre résultats théoriques et expérimentaux. / Understanding the gas/water adsorption phenomena in confined media is an important issue from a fundamental point of view and for industrial applications. The main aim of this thesis was to develop a new NLDFT/SAFT-VR coupling (Non-Local Density Functional Theory/ Statistical Associating Fluid Theory for potentials of Variable Range) to model the interfacial properties and the adsorption of methane, water and their binary mixture in porous media. A successful comparison was found between theoretical results from this model and molecular simulation calculations. Moreover, experimental adsorption isotherms of methane and water were measured on activated carbons by gravimetric method on a magnetic suspension balance. In order to compare experimental and modeled adsorption isotherms, it is necessary to get the pore size distribution of the porous solids. To do this, a new thermodynamic model for the characterization of microporous media was developed. The comparison between adsorption isotherms of methane has shown an excellent agreement between theoretical results and experimental measurements.

Berlin, Techn. Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Berlin, Techn. Univ., Diss., 2002. / Computerdatei im Fernzugriff.

<p>The group for non-destructive testing at Uppsala University has recently implemented the phase shift migration method, which is a method to focus images acquired unfocused using ultrasound. However, their work has been limited to 2D data, while for many applications the gathered data is 3D. This project has extended the old implementation to 3D data. The new implementation has been done in two different ways, giving one algorithm that works fast but needs much RAM, and one algorithm that takes long time but works on smaller computers, not demanding as much memory. The fast algorithm works faster than the time it takes to acquire the raw data, which makes real-time use realistic. To test the performance of the two algorithms with respect to image improvement, both against each other and against the previous 2D implementation, a number of experiments were carried out, which showed that, apart from processing time, the two new algorithms were equal in performance. The experiments also showed that the obtained resolution in both x- and y-directions matched the theoretical discussion.</p>

El progrés i les millores assolides en el camp industrial han empès els investigadors a buscar eines més refinades per tal de modelar aquests processos amb un major grau de precisió. Les propietats termofísiques són necessàries i el seu coneixement ha de ser molt precís, ja que una predicció poc acurada pot afectar el disseny d'una operació unitària, amb una consegüent pèrdua de rendiment i diners. Actualment, els models teòrics han progressat com a eines modernes que poden proveir a l'usuari d'una quantitat ingent d'informació sobre un fluid de manera ràpida, neta i barata. En qualsevol cas, manca encara un llarg camí per trobar una eina poderosa capaç de calcular el comportament termodinàmic de qualsevol compost en qualsevol condició. Aquest treball utilitza una robusta equació d'estat anomenada soft-SAFT. El nom original prové de la Teoria Estadística de Fluids Associants (SAFT), que és una equació basada en principis de mecànica estadística. Posseeix una molt forta base molecular, proposant un model "físic" per a descriure el compost. Soft-SAFT és una variant de la SAFT original que utilitza un terme de referència basat en una interacció de tipus Lennard-Jones entre les molècules. Malgrat que l'equació prèvia ja havia estat provada de manera exitosa en un conjunt molt variat de treballs, encara fallava en una regió molt important del diagrama de fases: la regió crítica. En aquesta regió, les propietats sofreixen fortes fluctuacions i canvien dràsticament degut a les llargues correlacions que es produeixen entre les molècules. La versió original de la soft-SAFT no pot tenir en compte aquestes fluctuacions de llarg abast perquè està basada en una teoria de camp mig. Tanmateix, aquesta fallida de la teoria ha estat superada introduint un tractament específic de "crossover", que considera les fluctuacions inherents. El procediment està basat en la teoria del grup de renormalització de Wilson (1971) i va ser desenvolupada per White (1992). S'escriu com un joc de relacions recursives on les correlacions entre les molècules són considerades al llarg de vàries iteracions. L'objectiu d'aquest treball de tesi s'ha dedicat a la millora d'una equació d'estat amb base molecular anomenada soft-SAFT afegint el tractament específic de "crossover" mencionat abans. La meta general implica el desenvolupament d'una poderosa eina predictiva aplicable a tot tipus de condicions per càlculs termodinàmics. Un tractament específic per calcular les fluctuacions inherents presents a la regió crítica s'ha implementat dins de la equació. La nova equació, anomenada "crossover soft-SAFT" és utilitzada per estudiar tres famílies diferents d'hidrocarburs: els alcans, els alcanols i els perfluoroalcans, així com les seves mescles entre ells i amb altres compostos, com el diòxid de carboni o l'àcid clorhídric. Els paràmetres moleculars s'optimitzen emprant dades de densitat de líquid i pressió de vapor experimental pels primers vuit membres de cada família. Es proposa una correlació per a cada paràmetre respecte el pes molecular, i els paràmetres s'extrapolen per predir el comportament termodinàmic d'altres membres més pesats de la mateixa família, amb un grau de precisió similar a l'obtingut pels membres més lleugers. Les capacitats calorífiques, la compressibilitat isotèrmica o isentròpica i la velocitat del so han estat també calculats per totes aquestes famílies de compostos, obtenint novament un molt bon acord amb les dades experimentals en la majoria de casos. Els resultats obtinguts per a aquestes propietats resulta molt esperançador ja que aquests càlculs s'han realitzat d'una manera purament predictiva. S'han pogut reproduir les diferents singularitats observades experimentalment en la regió veïna al punt crític, mentre que el càlcul dels exponents crítics universals també ha revelat un acord amb les mesures experimentals. Aquest treball pretén ser un pas endavant en la millora de les eines de modelat molecular per aplicacions enginyerils. Malgrat que la natura sigui sempre sorprenent i difícil de reproduir, l'esforç dedicat a aquesta tasca és prou encoratjador per continuar buscant noves fórmules que ens donin la possibilitat d'acostar-nos una mica més al món real. / The progress and the improvements made in the industrial field have pushed the researchers to look for refined tools to model these processes with a higher degree of accuracy. Thermophysical properties are needed and have to be known in a precise way, because an inaccurate prediction may affect the design of a unit property, with a result of a loss in yield and money. Nowadays, the theoretical models have progressed as modern tools that can provide a huge amount of information of a fluid in a rapid, clean and cheap manner. In any case, there is still a long way to find a powerful tool able to calculate the thermodynamic behavior of any compound at any condition. This work uses a robust equation of state called soft-SAFT. The original name comes from the Statistical Associating Fluid Theory (SAFT), which is an equation based on statistical mechanics principles. It has a very strong molecular basis, proposing a "physical" model to describe the compound. Soft-SAFT is a variant of the original SAFT that uses a reference term based on a Lennard-Jones type interaction among the molecules. Although the previous equation had already been successfully tested in many different works, it still failed in a very important region of the phase diagram: the critical region. In that region, the properties suffer strong fluctuations and change drastically due to the long-correlations established among the molecules. The original soft-SAFT version of the equation can not take into account these long-range fluctuations because it is based in a mean-field theory. However, this lack of the theory can be now overcome introducing a specific crossover treatment that considers these inherent fluctuations. The procedure is based in the renormalization group treatment of Wilson (1971) and it was developed by White (1992). It is written as a set of recursive relations where the correlations among the molecules are considered in several iterations. The objective of this thesis work was to improve the molecular-based equation of state named soft-SAFT adding the specific crossover treatment before mentioned. The general aim was to develop a powerful predictive tool applicable under different conditions for thermodynamic calculations. The extended equation, called crossover soft-SAFT is employed to study three different families of hydrocarbons: the n-alkanes, the 1-alkanols and the n-perfluoroalkanes, and their mixtures among them and with other compounds such as carbon dioxide or hydrogen chloride. The molecular parameters are optimized using liquid density and vapor pressure data for the first eight members of each family. A correlation with molecular weight is then proposed, and the parameters are extrapolated to predict the phase behavior of heavier members of the same family, with the same degree of accuracy as that one obtained for the lighter members of the series. Heat capacities, isothermal and isentropic compressibility and the speed of sound have been calculated for these families obtaining very good agreement with experimental data in most of the cases. Results for these properties are very encouraging since calculations were performed in a pure predictive manner. The different singularities experimentally observed in the vicinity of the critical point have been reproduced and the universal critical exponents have also been found in agreement with the experimental measurements. This work intends to be a step forward in the improvement of the molecular modeling tools for engineering applications. Although nature is always surprising and difficult to reproduce, the effort devoted to this task is encouraging enough to continue looking for new formulas that give us the possibility of getting closer to the real world.

The group for non-destructive testing at Uppsala University has recently implemented the phase shift migration method, which is a method to focus images acquired unfocused using ultrasound. However, their work has been limited to 2D data, while for many applications the gathered data is 3D. This project has extended the old implementation to 3D data. The new implementation has been done in two different ways, giving one algorithm that works fast but needs much RAM, and one algorithm that takes long time but works on smaller computers, not demanding as much memory. The fast algorithm works faster than the time it takes to acquire the raw data, which makes real-time use realistic. To test the performance of the two algorithms with respect to image improvement, both against each other and against the previous 2D implementation, a number of experiments were carried out, which showed that, apart from processing time, the two new algorithms were equal in performance. The experiments also showed that the obtained resolution in both x- and y-directions matched the theoretical discussion.

Os grandes campos de petróleo offshore recentemente descobertos na camada pré-sal, localizada no sudeste do Brasil, representam um avanço significativo da participação brasileira nas reservas mundiais de hidrocarbonetos, que ainda são a principal matriz energética mundial. Nesse cenário, torna-se importante o desenvolvimento da produção desses campos. Um dos principais desafios tecnológicos da exploração desses campos é o processamento do gás natural associado, que possui altos teores de dióxido de carbono CO2. Esse contaminante deve ser separado para possibilitar a injeção no reservatório e/ou o escoamento desse gás através de dutos submarinos, dadas as restrições na legislação ambiental. Nas plantas de processamento instaladas no convés de grandes embarcações, são previstas instalações para a separação do CO2 e a remoção de umidade do gás a fim de evitar a formação de hidratos e a corrosão acentuada das linhas de escoamento, pois tanto a injeção quanto a exportação do gás são realizadas em condições de pressão e temperaturas extremas. Nesse contexto, o conhecimento acurado das condições em que se forma uma fase aquosa líquida é importante para garantir a viabilidade técnica e de segurança dessas operações. Considerando a relevância do assunto e as limitações da literatura para os cenários enfrentados no pré-sal brasileiro, esse trabalho tem o objetivo de fazer um estudo abrangente do equilíbrio de fases em sistemas contendo hidrocarbonetos em fase gasosa com altos teores de CO2 e traços de água, visando à obtenção de modelo para cálculo do ponto de orvalho da água. O uso de modelos rigorosos baseado na teoria dos fluidos associativos (PC-SAFT) mostrou-se adequado para o cálculo das condições de saturação em amplas faixas de pressão e temperatura. Com base em dados experimentais publicados foi possível fazer um ajuste preciso dos parâmetros de interação binária da equação de estado PC-SAFT. Como resultado, obteve-se um modelo capaz de descrever o comportamento de fases em misturas de hidrocarbonetos com composição próxima das encontradas no pré-sal brasileiro. / The giant offshore petroleum fields recently discovered in the pre-salt layer on the southeast of Brazil represent a significant increment in the Brazilian share of the global hydrocarbon reserves, which is still the most important energetic matrix. In this scenario, the development of production for these petroleum fields becomes important. One of the main technological challenges posed by these fields is the processing of the associated gas, which contains high amounts of carbon dioxide (CO2). Due to environmental laws, this contaminant must be separated to allow the injection back into the reservoir and/or the gas flow through subsea pipelines. The gas processing plants installed on large vessels comprise facilities that remove CO2 and moisture from natural gas, to prevent hydrate formation and severe corrosion throughout the pipelines, as both gas injection and gas exportation are performed in extreme pressure and temperature conditions. Thus, the accurate knowledge of conditions in which aqueous liquid phases are formed is important to ensure the technical viability and operational safety of these operations. Considering the relevance of this subject and the limitations of published works for the Brazilian pre-salt scenario, this work presents a comprehensive study on the phase equilibrium in systems with hydrocarbons in gas phase with high content of CO2 and traces of water, aiming at developing a model to calculate the dew point of water. The use of a rigorous method based on the associating fluid theory (PCSAFT) has shown to be appropriate to calculate the saturation condition for a large range of pressure and temperature. Based on the experimental data published, the fitting of the binary interaction parameter from the PC-SAFT equation of state was carried out. The resulting model was able to describe the phase behavior of hydrocarbon mixture with composition similar to those found in the Brazilian pre-salt.

Os grandes campos de petróleo offshore recentemente descobertos na camada pré-sal, localizada no sudeste do Brasil, representam um avanço significativo da participação brasileira nas reservas mundiais de hidrocarbonetos, que ainda são a principal matriz energética mundial. Nesse cenário, torna-se importante o desenvolvimento da produção desses campos. Um dos principais desafios tecnológicos da exploração desses campos é o processamento do gás natural associado, que possui altos teores de dióxido de carbono CO2. Esse contaminante deve ser separado para possibilitar a injeção no reservatório e/ou o escoamento desse gás através de dutos submarinos, dadas as restrições na legislação ambiental. Nas plantas de processamento instaladas no convés de grandes embarcações, são previstas instalações para a separação do CO2 e a remoção de umidade do gás a fim de evitar a formação de hidratos e a corrosão acentuada das linhas de escoamento, pois tanto a injeção quanto a exportação do gás são realizadas em condições de pressão e temperaturas extremas. Nesse contexto, o conhecimento acurado das condições em que se forma uma fase aquosa líquida é importante para garantir a viabilidade técnica e de segurança dessas operações. Considerando a relevância do assunto e as limitações da literatura para os cenários enfrentados no pré-sal brasileiro, esse trabalho tem o objetivo de fazer um estudo abrangente do equilíbrio de fases em sistemas contendo hidrocarbonetos em fase gasosa com altos teores de CO2 e traços de água, visando à obtenção de modelo para cálculo do ponto de orvalho da água. O uso de modelos rigorosos baseado na teoria dos fluidos associativos (PC-SAFT) mostrou-se adequado para o cálculo das condições de saturação em amplas faixas de pressão e temperatura. Com base em dados experimentais publicados foi possível fazer um ajuste preciso dos parâmetros de interação binária da equação de estado PC-SAFT. Como resultado, obteve-se um modelo capaz de descrever o comportamento de fases em misturas de hidrocarbonetos com composição próxima das encontradas no pré-sal brasileiro. / The giant offshore petroleum fields recently discovered in the pre-salt layer on the southeast of Brazil represent a significant increment in the Brazilian share of the global hydrocarbon reserves, which is still the most important energetic matrix. In this scenario, the development of production for these petroleum fields becomes important. One of the main technological challenges posed by these fields is the processing of the associated gas, which contains high amounts of carbon dioxide (CO2). Due to environmental laws, this contaminant must be separated to allow the injection back into the reservoir and/or the gas flow through subsea pipelines. The gas processing plants installed on large vessels comprise facilities that remove CO2 and moisture from natural gas, to prevent hydrate formation and severe corrosion throughout the pipelines, as both gas injection and gas exportation are performed in extreme pressure and temperature conditions. Thus, the accurate knowledge of conditions in which aqueous liquid phases are formed is important to ensure the technical viability and operational safety of these operations. Considering the relevance of this subject and the limitations of published works for the Brazilian pre-salt scenario, this work presents a comprehensive study on the phase equilibrium in systems with hydrocarbons in gas phase with high content of CO2 and traces of water, aiming at developing a model to calculate the dew point of water. The use of a rigorous method based on the associating fluid theory (PCSAFT) has shown to be appropriate to calculate the saturation condition for a large range of pressure and temperature. Based on the experimental data published, the fitting of the binary interaction parameter from the PC-SAFT equation of state was carried out. The resulting model was able to describe the phase behavior of hydrocarbon mixture with composition similar to those found in the Brazilian pre-salt.

Thermodiffusion is one of the mechanisms in transport phenomena in which molecules are transported in a multicomponent mixture driven by temperature gradients. Thermodiffusion in associating mixtures presents a larger degree of complexity than non-associating mixtures, since the direction of flow in associating mixtures may change with variations in composition and temperature. In this study a new activation energy model is proposed for predicting the ratio of evaporation energy to activation energy. The new model has been implemented for prediction of thermodiffusion for acetone-water, ethanol-water and isopropanol-water mixtures. In particular, a sign change in the thermodiffusion factor for associating mixtures has been predicted, which is a major step forward in modeling of thermodiffusion for associating mixtures. In addition, a new model for the prediction of thermodiffusion coefficients for linear chain hydrocarbon binary mixtures is proposed using the theory of irreversible thermodynamics and a kinetics approach. The model predicts the net amount of heat transported based on an available volume for each molecule. This model has been found to be the most reliable and represents a significant improvement over the earlier models. Also a new approach to predicting the Soret coefficient in binary mixtures of linear chain and aromatic hydrocarbons using the thermodynamics of irreversible processes is presented. This approach is based on a free volume theory which explains the diffusivity in diffusion-limited systems. The proposed model combined with the Shukla and Firoozabadi model has been applied to predict the Soret coefficient for binary mixtures of toluene and n-hexane, and benzene and n-heptane. Comparisons of theoretical results with experimental data show a good agreement. The proposed model has also been applied to estimate thermodiffusion coefficients of binary mixtures of n-butane & carbon dioxide and n-dodecane & carbon dioxide at different temperature. The results have also been incorporated into CFD software FLUENT for 3-dimensional simulations of thermodiffusion and convection in porous media. The predictions show the thermodiffuison phenomenon is dominant at low permeabilities (0.0001 to 0.01), but as the permeability increases convection plays an important role in establishing a concentration distribution. Finally, the activation energy in Eyring’s viscosity theory is examined for associating mixtures. Several methods are used to estimate the activation energy of pure components and then extended to mixtures of linear hydrocarbon chains. The activation energy model based on alternative forms of Eyring’s viscosity theory is implemented to estimate the thermodiffusion coefficient for hydrocarbon binary mixtures. Comparisons of theoretical results with the available thermodiffusion coefficient data have shown a good performance of the activation energy model.

The phase behaviors and microstructures of various realistic and model mixtures of macro and micro molecules, such as polyolefin solutions and nanoparticle block copolymer composites, have been accurately predicted by the application of Statistical Associating Fluid Theory (SAFT) based approaches through various extensions that improve both the physical description of molecular interactions and efficiency of computations. The extensions are presented in a generic sense that is applicable to other studies. These rigorously derived theories have been demonstrated to capture material structure-property relationships and can be applied broadly to other fields including biology, medicine and energy industry. On the phenomenogical scale, the novel SAFT-Dimer equation of state has been extended to study the liquid-liquid phase boundary (cloud point) in polyolefin solutions. A simplified model of the polyolefin molecules has been followed and the effect of various parameters, such as temperature, molecular weight, solvent quality and comonomer content, on the phase behavior has been successfully captured by the theoretical model through comparison with experimental measurements. The presented approach requires less parameters than previous methods and is of critical value to the industrial productions of polymers, especially polyolefins with long branches. On the molecular scale, the interfacial SAFT (iSAFT) Density Functional Theory (DFT) has been extended to include a dispersion free energy functional that explicitly accounts for molecular correlations. The Order-Disorder Transition (ODT) between lamellar and disordered phase has then been investigated for pure block copolymer and copolymer nanocomposite systems. The extension has been shown to dramatically improve the ODT predictions of iSAFT as well as the self assembled microstructures in nanocomposites over previous DFT calculations, in comparison to coarse grained molecular simulations. The behavior of the equilibrium spacing of ordered structures is also examined against the variation of copolymer size and interactions. An efficient numerical scheme, Fast Fourier Transform (FFT), has been implemented and shown to drastically increase the computation efficiency. The theory has then been extended to study block copolymer morphologies with density variations in multiple dimensions. Comprehensive phase diagrams including lamellar, cylindrical and disordered phases have been obtained for copolymer nanocomposites for the first time using a single framework molecular theory. In addition, the nanoparticle induced morphological transition between cylindrical and lamellar phase has been studied using a pseudo arc-length continuation method. Transition evolution is tracked and metastable morphologies are examined and compared with existing experimental reports and theoretical calculations. With these extensions, iSAFT offers a powerful prediction tool that closely relates molecular structure to thermophysical properties and provides an efficient alternative to screen parameter space for specified material properties.