Дисертації з теми "Phase equilibria modelling"

Le métamorphisme est un phénomène majeur affectant la distribution des phases minérales au sein de la croûte continentale et participant à sa stabilisation. L’étude des processus métamorphiques est donc essentielle pour comprendre la formation et l’évolution de la Terre. Ces processus exercent un contrôle sur le potentiel de préservation des roches à sa surface et nous renseignent entre autres sur les conditions de pression–température régnant en profondeur. Ils contrôlent également la production et le stockage de fluides au sein de la croûte ce qui influence les cycles géochimiques au sein de la lithosphère, de l’hydrosphère et de l’atmosphère et a, de fait, des implications importantes sur le climat et l’apparition de la vie sur Terre. La principale source de variabilité au sein de ces systèmes correspond à des changements de composition chimique résultant eux-mêmes de transferts de matière. Les techniques modernes de modélisation quantitative des équilibres de phases permettent de calculer l’assemblage minéralogique stable au sein d’un système à l’équilibre pour lequel les paramètres pression, température et composition chimique sont connus. Ceci étant, les programmes informatiques actuels ne possèdent que de fonctionnalités limitées pour modéliser et appréhender les conséquences de changements de composition chimique du système au cours du métamorphisme. Un nouvel outil informatique (Rcrust) a été développé pour permettre de calculer l’assemblage minéralogique stable dans un système soumis à des variations de composition lors de son évolution dans l’espace multidimensionnel pression–température–composition chimique
The investigation of metamorphic processes in the Earth’s crust is integral to understanding the formation and evolution of the Earth. These processes control the preservation potential of the geochronological rock record and give us insight into, amongst others, the pressure and temperature conditions of the Earth’s interior. Further, they control fluid generation and consumption within the crust which influences global geochemical cycles within the lithosphere, hydrosphere and atmosphere. This has important implications on the global climate and the creation of conditions conducive to life. The dominant mechanism of change both within and between these systems are compositional changes invoked by processes of mass transfer. Modern quantitative phase equilibrium modelling allows the calculation of the stable phase assemblage of a rock system at equilibrium given its pressure, temperature and bulk chemical composition. However, current software programs have limited functionalities for the sophisticated handling of a changing bulk composition. A new software tool (Rcrust) has been developed that allows the modelling of points in pressure–temperature–bulk composition space in which bulk compositional changes can be passed between points as the system evolves

Formation of gas hydrates can lead to serious operational, economic and safety problems in the petroleum industry due to potential blockage of oil and gas equipment. Thermodynamic inhibitors are widely used to reduce the risks associated with gas hydrate formation. Thus, accurate knowledge of hydrate phase equilibrium in the presence of inhibitors is crucial to avoid gas hydrate formation problems and to design/optimize production, transportation and processing facilities. The work presented in this thesis is the result of a study on the phase equilibria of petroleum reservoir fluids containing aqueous salt(s) and/or hydrate inhibitor(s) solutions. The incipient equilibrium methane and natural gas hydrate conditions in presence of salt(s) and/or thermodynamic inhibitor(s) have been experimentally obtained, in addition to experimental freezing point depression data for aqueous solution of methanol, ethanol, monoethylene glycol and single or mixed salt(s) aqueous solutions, are conducted. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, has been employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. Predictions of the developed model have been validated against independent experimental data from the open literature and the data generated in this work. The predictions were found to agree well with the experimental data.

Understanding gas hydrate inhibitor distribution in hydrocarbon phases is essential for the economic design of process equipment. In order to build a clear image of the inhibitor’s distribution in various phases, three experimental investigations were devised; solubility in liquid and vapour phase as well as saturation pressure measurements. These data will contribute significantly to the understanding of the partitioning of these components as the data in the open literature are fairly limited. Aiming at filling the experimental gap found in the literature, the solubility of methane in pure methanol and ethanol as well as 70 and 50 wt% aqueous solutions at 238.15 – 298.15 K and 0.3 – 47 MPa were measured. The data from the ethanol/solution solubility measurements were used to optimise the methane-ethanol Binary Interaction Parameters (BIPs) of the CPA-SRK72 Equation of State (EoS). The model calculations showed an absolute average deviation of 5.3% over the full pure data range. To improve the CPA-SRK72 EoS predictions for aqueous solutions, new methane-ethanol BIPs were regressed showing significant improvement for both solubility and quaternary bubble point predictions. In order to determine the inhibitor loss to the vapour phase, the inhibitor content of methane was measured using Gas Chromatography (GC) between 0.7 – 62 MPa and 273.15 – 298.15 K. Additionally, a number of bubble point measurements were conducted for binary, ternary and quaternary systems containing methane, a liquid hydrocarbon phase (C7 – C12), methanol/ethanol and water. This was to investigate the effect of the inhibitor phase in the ternary, and the dominant excess water phase in the quaternary system, on the bubble point pressure as well as evaluating the CPA-SRK72 predictions. The saturation pressures were measured at 253.15 – 313.15 K. The solubility of CO2 in Mono-ethylene glycol (MEG), Di-ethylene glycol (DEG) and Tri-ethylene glycol (TEG) and their aqueous solutions (90, 60 and 40 wt%), at pressures and temperatures ranging from 0.2 – 43.4 MPa and 263 – 343 K, were measured. The solubility of CO2 in pure MEG, DEG and TEG were predicted using the CPA-SRK72 EoS, using a single binary interaction parameter, showing an absolute average deviation of 5.13%, 9.51% and 2.55% respectively. Correlations for the solubility of CO2 in MEG, DEG and TEG aqueous solutions, using aqueous solution regressed BIPs, showed an overall absolute average deviation of 17.5%, 18.2% and 25.16% respectively, a significant improvement from the non-aqueous solution BIP optimised predictions.

Thesis (MScEng)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: During the production of pure Ti02 for the pigment industry, ilmenite, containing 35 - 60 % Ti02, is reduced to high titania slag, containing 85 - 95 % Ti02 and pig iron. These ilmenite smelters are operated in very tight operating windows. Over reducing the slag may lead to the formation of TiC and reducing much of the Ti02 to Th03. According to Namakwa Sands furnace operators, this does not only affect the grade of the product, but it can cause slag foaming and furnace eruptions. In under reducing conditions, the liquid slag is fluxed by the FeO and may corrode the furnace lining and consequently lead to run-outs. The reducing conditions in the furnace are not only controlled by carbon addition, but also by temperature. Standard practise in industrial ilmenite smelters is to operate the furnace with a slag freeze lining to protect the refractory lining from chemical and physical attack by the slag. It is therefore clear that it is of great importance to be able to predict the slag liquidus temperature at different compositions. This can help the operator to avoid dangerous operating conditions. Over the past few decades, a number of solution models have been developed to describe non-ideal solutions. With the rapid increase in computer power, these models became more valuable and practical to use in advanced control and decisionsupport. In this study, some of the better-known models are discussed and evaluated for the Ti02 - Th03 - FeO system, based on a critical review of properties and measurements published in literature. Two of these models, the "modified quasi-chemical" model and the "cell" model were chosen to be applied to the high-titania slag system. Both these models are based on statistical thermodynamics with some differences in the initial assumptions. In this study, the model parameters for the cell model were regressed from experimental data. The high-titania slag produced, consists mainly of titanium in different oxidation states and FeO, placing its composition inside the Ti02 - Th03 - FeO ternary system. Reliable experimental data for this system are very limited. All three binary systems contained in the Ti02 - ThO) - FeO system were considered, namely FeO - Ti02, Ti02 - ThO) and FeO - ThO). Only liquidus data for these three binaries were used to regress the model parameters. Accuracy of the models was determined by calculating the root mean square (RMS) error between the experimental data point and the value calculated using the model and the newly determined model parameters. These errors corresponded weil with the reported experimental error of the datasets for both the models and all the binary systems. Due to the fact that this study focussed on the liquidus surface of the system, the results were also plotted in the form of binary phase diagrams and ternary liquidus isotherms. The cell model uses only binary interaction parameters to describe the ternary system. These parameters are not expanded to higher order polynomials, which makes this model more robust, but also less accurate than other models such as the modified quasi-chemical model.
AFRIKAANSE OPSOMMING: Tydens die produksie van suiwer Ti02 vir die pigmentbedryf, word ilmeniet, wat 35 tot 60 % Ti02 bevat, gereduseer tot 'n hoë titaan slak, met 'n Ti02 inhoud van 85 tot 95 % Ti02, en potyster. Hierdie ilmeniet smeltoonde word binne baie nou bedryfskondisies beheer. Oor-redusering van die slak kan lei tot the formasie van TiC en die redusering van Ti02 tot Th03. Dit affekteer nie net die produk se kwaliteit nie, maar kan volgens Namakwa Sands oond operateurs ook slak skuiming en ontploffings tot gevolg hê. Gedurende onder-reduserende omstandighede in die oond, word die vloeibaarheid van die slak verhoog deur die hoër FeO inhoud in die slak. Dit maak die slak meer korrosief en kan lei tot faling van die vuurvaste stene. Die mate van redusering in die oond word nie net bepaal deur die toevoeging van koolstof nie, maar ook deur die temperatuur van die slak. Dit is 'n standaard praktyk van die industrie om die oond te bedryf met 'n gevriesde slak laag om sodoende die vuurvaste stene te beskerm teen chemiese en fisiese aanval van die slak. Dit is dus duidelik dat dit baie belangrik is om die slak se smeltpunt by verskillende samestellings te kan voorspel. Dit kan die operateur help om die oond binne veilige bedryfskondisies te hou. 'n Hele aantaloplossingsmodelle is oor die afgelope paar dekades ontwikkel vir die beskrywing van nie-ideale oplossings. Hierdie modelle het oor die afgelope paar jaar baie toegeneem in praktiese waarde as gevolg van die snelle toename in rekenaarkapasiteit en -spoed. Dit het veral groot waarde in gevorderde beheerstelsels en besluitneming steun. Sommige van die meer bekende modelle word in hierdie studie bespreek en ge-evalueer vir die Ti02 - Th03 - FeO stelsel, gebaseer op 'n kritiese evaluasie van eienskappe en eksperimentele data gepubliseer in die literatuur. Twee van hierdie modelle, die "gemodifiseerde kwasi-chemiese" model en die "sel" model, is gebruik om die hoë titaan slak stelsel te beskryf. Beide hierdie modelle is gebaseer op statistiese termodinamika en het klein verskille m.b.t. die aanvanklike aannames. Die model veranderlikes vir die sel model is in hierdie studie afgelei vanaf die eksperimentele data. Die hoë titaan slak wat tydens hierdie proses geproduseer word, bestaan hoofsaaklik uit FeO en titaan in sy verskillende oksidasie toestande. Dit plaas die samestelling van die slak reg binne die Ti02 - Th03 - FeO temêre stelsel. Betroubare eksperimentele data vir hierdie stelsel is baie beperk. In hierdie studie word daar gekyk al drie binêre stelsels binne die Ti02 - Th03 - FeO temêre stelsel, naamlik: FeO - Ti02, Ti02 - Th03 en FeO - Th03. Slegs die smeltpunt temperatuur data vir hierdie twee binêre is gebruik in die afskatting van die model veranderlikes. Die akkuraatheid van die modelle is bepaal deur die wortel van die gemiddelde kwadraat van die fout tussen die eksperimentele waardes en die berekende waardes te bepaal. Albei die modelle het 'n relatiewe klein fout in vergelyking met die geraporteerde eksprimentele fout gehad vir al die binêre stelsels. Hierdie studie het gefokus op die smeltpunt temperatuur van die slak en die resultate is daarom ook in die vorm van binêre fasediagramme en isoterme projeksies op die temêre fasediagramme gestip. Die "sel" model gebruik slegs binêre interaksie parameters om die temêre stelsel te beskryf Hierdie parameters word vir die "sel" model nie uitgebrei tot hoër order polinome en dit maak die "sel" model meer robuust, maar minder akkuraat as ander modelle soos byvoorbeeld die "kwasi-chemiese" model.

Hydrothermal processes play a major role in transporting mass and energy in Earth’s crust. These processes rely on hydrothermal fluid, which is dissolving, transporting and precipitating minerals and distribute heat. The composition of the hydrothermal fluid is specific for various geological settings, but in most cases it can be approximated by H₂O-NaCl-CO₂ fluid composition. The flow of hydrothermal fluid is controlled by differences in temperature, pressure and/or density of the fluid and hydraulic conductivity of the rock. In my work, I was focused on modeling of the hydrothermal fluid properties and experimental characterization of fluid that formed emerald deposit in North Carolina, USA. The dissertation based on the result of three separate projects. The first project has been dedicated to characterization of the H₂O-NaCl hydrothermal fluid ability to transport mass and energy. This ability of the fluid is defined by a change in fluid density and enthalpy in response to changing pressure or temperature. In this project we quantified the derivatives of mass, enthalpy and SiO₂ solubility in wide range of pressure, temperature and composition (PTx) of H₂O-NaCl fluid. Our study indicated that the PT region in which fluid is most efficiently can transport mass and energy, located in the critical region near liquid-vapor phase boundary and the sensitivity to changing pressure-temperature conditions decrease with increasing salinity. In second project we developed the revised H₂O-NaCl viscosity model. Revised model to calculate the viscosity of H₂O-NaCl reproduces experimental data with ±10% precision in PTx range where experimental data available and follows expected trends outside of the range. This model is valid over the temperature range from the H₂O solidus (~0 °C) to ~1,000 °C, from ~0.1 MPa to ≤500 MPa, and for salinities from 0-100 wt.% NaCl. The third project has been focused on the characterization of formation conditions of the emerald at North American Emerald Mine, Hiddenite, North Carolina, USA. The emerald formation conditions defined as 120-220 MPa, 450-625 °C using stable isotope, Raman spectrometry, and fluid inclusion analysis. Hydrothermal fluid had a composition of CO2-H2O±CH4, which indicates mildly reducing environment of emerald growth.
Ph. D.

In this thesis, a new approach to parameterization of the intermolecular potential models of ionic species in electrolyte solutions for the SAFT-VRE Mie theory is presented. Additionally, a predictive approach to the description of the fluid-fluid interface of non-electrolytic, non-associating mixtures is presented. These approaches are intended to support an integrated workflow for the study of the fluid systems relevant for carbon capture and sequestration. The parameterization methodology developed for the intermolecular potential models of ionic species in the SAFT-VRE Mie theory reduces the parameters to be estimated from solution data to a single interaction-energy per solvent-ion pair. This is achieved through the use of literature values for the ion-size parameter, and theoretical estimates for the ion-ion interaction energy. Additionally, the Born diameters of the ion models are taken to be those of Rashin and Honig, and not estimated from data. This approach is applied to the monovalent halides as well as select divalent ions. The resulting models reproduce the solvation energy in H2O to within 5 % error at standard conditions for the monovalent halides. Furthermore, the electrolyte models are demonstrated to provide a fair description of aqueous electrolytes when considering the limited parameterization. The predictive description of the fluid-fluid interface, is achieved by an approach in which the Square Gradient Theory (SGT) and the SAFT-VR Mie EOS are combined. The SGT influence parameter is mapped to the SAFT-VR Mie intermolecular model parameters through the relationship with the direct correlation function. The resulting model is parametrized by matching simulation data for the interfacial tension of λr-6 Mie monomeric fluids. A final evaluation of the model is carried out against non-associating systems of up to 4 species, for which predictive capabilities are demonstrated.

Die ternären Systeme Ti/P/Te, Ce/P/Te und Si/P/Te wurden in der vorliegenden Dissertation hinsichtlich der Existenz neuer Verbindungen untersucht. Diese Verbindungen wurden insbesondere in Bezug auf ihre thermochemischen Eigenschaften charakterisiert. Durch Kombination von experimentellen Untersuchungen und thermodynamischen Modellierungen der ablaufenden Festkörper-Gasphasen-Gleichgewichte konnten die Synthesen der neuen Verbindungen optimiert werden. Abschließend erfolgte zudem die physikalische und kristallographische Charakterisierung der gefundenen Phosphidtelluride.

Die ternären Systeme Ti/P/Te, Ce/P/Te und Si/P/Te wurden in der vorliegenden Dissertation hinsichtlich der Existenz neuer Verbindungen untersucht. Diese Verbindungen wurden insbesondere in Bezug auf ihre thermochemischen Eigenschaften charakterisiert. Durch Kombination von experimentellen Untersuchungen und thermodynamischen Modellierungen der ablaufenden Festkörper-Gasphasen-Gleichgewichte konnten die Synthesen der neuen Verbindungen optimiert werden. Abschließend erfolgte zudem die physikalische und kristallographische Charakterisierung der gefundenen Phosphidtelluride.

Cette étude couvre la conception d'un nouvel appareil qui permet la mesure fiable de pressions de vapeur d'équilibres à plusieurs phases à partir de petits volumes (un maximum de 18 cm3). Les mesures d'équilibres de phase concernant la présente étude incluent : des équilibres "liquide-vapeur" (ELV), "liquide-liquide" (ELL) et " liquide-liquide-vapeur" (ELLV). La température de fonctionnement de l'appareil s'étend de 253 à 473 K pour une pression de fonctionnement qui s'étend du vide absolu à 1600 kPa. Le prélèvement des phases est réalisé grâce au Rapid On line Sampling Injector (ROLSI™). Une technique originale est ajoutée en complément du ROLSI™ pour éviter des chutes de pressions lors du prélèvement. Cette technique utilise une tige métallique afin de compenser les changements de volume lors des prélèvements. Des mesures de tensions de vapeur et d'équilibres de phase ont été entreprises pour caractériser le fonctionnement de l'appareil conçu et développé. Ensuite de nouvelles mesures de tensions de vapeur et d'ELV ont été mesurées sur des systèmes intéressant les compagnies pétrochimiques. Les données expérimentales de pression de vapeur obtenues ont été régressées en utilisant les équations étendues d'Antoine et de Wagner. Les données expérimentales d'ELV mesurées ont été régressées avec des modèles thermodynamiques au moyen des méthodes directes et combinées. Pour la méthode directe les équations d'état de Soave-Redlich-Kwong et de Peng-Robinson ont été employées avec la fonction (α) de Mathias et Copeman (1983) dépendante de la température. Pour la méthode combinée, l'équation du viriel (deuxième coefficient du viriel de la corrélation de Tsonopoulos (1974)) a été employée associée à un modèle de solution (coefficient d'activité) pour la phase liquide: TK-Wilson, NRTL et UNIQUAC modifié. Des tests de cohérence thermodynamique ont été exécutés pour toutes les données expérimentales de VLE mesurées. Presque tous les systèmes mesurés ont déclarés thermodynamiquement cohérents (test de point de Van Ness et autres (1973) et test direct de Van Ness (1995)
This study covers the design of a new apparatus that enables reliable vapour pressure and equilibria measurements for multiple liquid and vapour phases of small volumes (a maximum of 18 cm3). These phase equilibria measurements include: vapour-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE) and vapour-liquid-liquid (VLLE). The operating temperature of the apparatus ranges from 253 to 473 K and the operating pressure ranges from absolute vacuum to 1600 kPa. The sampling of the phases is accomplished using a single Rapid-OnLine-Sampler-Injector (ROLSITM). A novel technique is used to achieve sampling for each phase. The technique made use of a metallic rod in an arrangement to compensate for volume changes during sampling. As part of this study, vapour pressure and phase equilibrium data were measured to test the operation of the newly developed apparatus. New experimental vapour pressure and VLE data were also measured for systems of interest to petrochemical companies. The experimental vapour pressure data obtained were regressed using the extended Antoine and Wagner equations. The experimental VLE data measured were regressed with thermodynamic models using the direct and combined methods. For the direct method the Soave-Redlich-Kwong and Peng-Robinson equations of state were used with the temperature dependent function (α) of Mathias and Copeman (1983). For the combined method, the virial equation of state with the second virial coefficient correlation of Tsonopoulos (1974) was used together with one of the following liquid-phase activity coefficient model: TK-Wilson, NRTL and modified UNIQUAC. Thermodynamic consistency testing was also performed for all the VLE experimental data measured where almost all the systems measured showed good thermodynamic consistency for the point test of Van Ness et al. (1973) and direct test of Van Ness (1995)

Lors de l'extraction de l'uranium par lixiviation acide, AREVA fait face à des phénomènes transitoires de précipitation de phases mal cristallisées entrainant un colmatage des installations. Les analyses de ces précipités ont mis en évidence la formation d'un solide jaune minoritaire et d'un blanc majoritaire composé de sulfate de calcium et d'hydroxysulfate d'aluminium. Afin de comprendre les phénomènes menant à la précipitation et pour prévoir, éviter ou limiter leur apparition, les travaux de thèse ont consisté en l'étude expérimentale des équilibres solides-liquide du système complexe Al–Fe–K–P–S–H2O (± Ca et Mg) en milieu acide à 25°C, avec pour objectif l'identification des solides susceptibles d'apparaître en conditions industrielles. Les résultats permettront ainsi de compléter les bases de données thermodynamiques utilisées pour modéliser le comportement global du milieu lors des opérations. Après la mise au point de techniques analytiques appropriées, le travail s'est porté sur la délimitation des équilibres liquide-solides du système relatif au précipité blanc et particulièrement sur l'analyse des ternaires impliquant les hydroxysulfates d'aluminium. Le colmatage se produisant durant la phase d'acidification, l'évolution de la précipitation de ces hydroxysulfates en fonction du pH a été étudiée, afin de caractériser les solides formés en présence de cations minoritaires (Na+, K+, Mg2+, Ca2+) et de définir leurs constantes de solubilités à partir d'un modèle de calcul des coefficients d'activités des ions en solution. Des tests dynamiques sur colonne à partir de minerai naturel ont également été effectués et comparés aux résultats statiques
During the uranium extraction by acid leaching, AREVA observed the precipitation of not well crystallized solid phases, leading to the clogging of various equipment. The analyses of these precipitates highlighted the formation of a minor yellow precipitate and a major white precipitate containing calcium sulphate and aluminium hydroxisulphate. To understand the phenomena leading to the precipitation and to predict, prevent or at least limit their formation, this thesis work consisted of the solid-liquid equilibria experimental study of the Al–Fe–K–P–S–H2O (± Ca and Mg) system in an acidic environment at 25°C, with the identification of solid phases which may appear in natural ore as the major goal. The results could complete the thermodynamic database used to model global behaviour of the environment during acid mining. Based on the observed precipitates, two quaternary systems were defined, such as the H2O-Al3+, Ca2+ // O2-, SO42- system. After the development of appropriate analytical techniques, the work focused on the delimitation of the liquid-solid equilibria of the system based on the white precipitate and particularly on the analysis of the ternaries involving aluminium hydroxisulphates. As clogging occurs during acidification, the hydroxisulphate precipitation depending on the pH was studied in the presence of minority cations (Na+, K+, Mg2+, Ca2+), in order to characterise the solid phases which were formed, and to define their solubility constants. For the solubility constant determination, a calculation model of the ion activity coefficients in solution was used. A dynamic survey on a column containing natural ore was done and compared to static results

Dans le cadre du procédé de séparation cryogénique des gaz de l'air (T< 100 K), impuretés telles que le CO2 et le N2O peuvent se solidifier au niveau de l'échangeur de chaleur placé entre les deux colonnes de distillation cryogénique.La formation du solide doit être évitée pour deux principales raisons:- au niveau opérationnel, le solide constitue une résistance supplémentaire aux transferts de chaleur et de matière, et augmente les chutes de pression dans les colonnes de distillation;- au niveau sécurité, la présence d'une phase solide peut également favoriser l'accumulation d'hydrocarbures légers qui forment avec l'oxygène liquide des mélanges potentiellement inflammables.Les conditions de formation thermodynamique de la phase solide doivent être parfaitement maitrisées dans le cadre de la distillation cryogénique. C'est pourquoi, il est indispensable de disposer d'une équation d'état adaptée qui permette de représenter les diagrammes de phases impliquant une phase solide dans les conditions opératoire du procédé.L'objectif principal de la thèse est de développer un modèle thermodynamique pour représenter les équilibres de phases solide – fluides. Ce travail nécessite de mettre au point des algorithmes de résolution des équilibres bi et triphasiques et de déterminer le meilleur jeu de paramètres du modèle en s'appuyant sur la disponibilité des données expérimentales dans les conditions cryogéniques.Le modèle permet d'améliorer la connaissance des équilibres et constitue un outil indispensable pour maîtriser les risques associés à la présence de phases solides pour le procédé de distillation cryogénique
In the framework of the cryogenic air separation, impurities such as CO2 and N2O may solidify at the reboiler-condenser placed between the two distillation columns.The formed solid could provide an additional strength to the heat and material transfers, and increase the pressure drops in the distillation columns.Furthermore, the presence of a solid phase can promote the accumulation of light hydrocarbons which may form flammable mixtures with liquid oxygen.Therefore, the presence of solid phases must be controlled see avoided within the cryogenic air distillation process.The main issue of this thesis is to develop a suitable model for representing solid phases and their equilibrium with the liquid and vapor phases at the operating conditions of the process, and to obtain full phase diagrams which would improve the knowledge of phase equilibria and the control of the risks associated to the presence of solid phases

Essential oils are featured commodities in the global market due their many applications in food and chemical industries, in different medicine areas, and as antibacterial, antifungal, and antioxidant agent. One of the phenomena accountable for the loss of essential oils quality may be associated with the degradation of terpene hydrocarbons by oxidation when exposed to air, light or heat, causing disagreeable odors. The procedure of terpenes content reducing, known as deterpenation, can be performed by diverse techniques, among which the liquid-liquid extraction can be highlighted since this process can be operated without the use of heating and pressure changes, causing low impact on the essential oil sensory qualities and low energy consumption. This research was focused on the fractionation process of citrus essential oils, by liquid-liquid extraction, using ethanol/water mixtures as solvents. Experimental liquid-liquid equilibrium data of model and real citrus systems were obtained. The aroma profile of the crude citrus essential oils (orange - Citrus sinensis and lime - Citrus aurantifolia) and the phases from the liquid-liquid equilibrium was also evaluated. Moreover, the crude citrus essential oils were fractionated in a continuous operation equipment (perforated rotating disc contactor, PRDC). It was verified that the water has an important influence over the fractionation performance, but not over the aroma profile of the phases. The experimental data from the model systems (citrus essential oil model mixture + ethanol + water) were used to adjust parameters of empirical and thermodynamic models, which provided satisfactory results on the calculation of physical property values and compositions of the phases from the real systems (crude citrus essential oil + ethanol + water). The fractionation of citrus essential oils by liquid-liquid extraction technology was technically feasible and can be accomplished into continuous apparatus such as PRDC column. The solvents employed provided extract phases enriched in oxygenated compounds.
Óleos essenciais são importantes produtos comercializados mundialmente devido às suas diversas aplicações em indústrias alimentícias e químicas, em diferentes áreas da medicina, e como agentes antibacteriano, antifúngico e antioxidante. Um dos fenômenos responsáveis pela sua perda de qualidade pode estar associado à degradação dos hidrocarbonetos terpênicos por oxidação, quando estes são expostos ao ar, luz ou calor, ocasionando odor desagradável. O procedimento para redução do teor de terpenos no óleo essencial, conhecido como desterpenação, pode ser realizado por diferentes técnicas, entre as quais a extração líquido-líquido se destaca uma vez que pode ser conduzida sem o emprego de calor e mudanças na pressão, o que atenua o impacto nas qualidades sensoriais e demanda menor gasto energético. Este estudo se concentrou no processo de fracionamento de óleos essenciais cítricos, pela técnica de extração líquido-líquido, empregando misturas de etanol e água como solventes. Foram obtidos dados de equilíbrio líquido-líquido de sistemas cítricos modelo e reais. O perfil de aroma dos óleos essenciais brutos (laranja - Citrus sinensis e lima ácida Citrus latifolia) e das fases provenientes do equilíbrio líquido-líquido também foram avaliados. Além disso, os óleos essenciais brutos foram submetidos ao processo de fracionamento em equipamento de operação contínua (coluna de discos rotativos perfurados, PRDC). Verificou-se que a água possui uma importante influência sobre o desempenho do processo de fracionamento, mas não afetou o aroma das fases. Os dados experimentais dos sistemas modelo (mistura modelo de óleo essencial cítrico + etanol + água) foram utilizados para o ajuste de parâmetros de modelos empíricos e termodinâmicos, os quais apresentaram bons resultados no cálculo de valores de propriedades físicas e da composição das fases oriundas dos sistemas reais (óleo essencial cítrico bruto + etanol + água). O fracionamento de óleos essenciais cítricos pela tecnologia de extração líquido-líquido mostrou-se tecnicamente viável e pode ser conduzido em equipamentos contínuos como a coluna de extração PRDC. Os solventes empregados permitiram a obtenção de fases extrato enriquecidas com compostos oxigenados.

Les récents succès de l'immunothérapie pour le traitement du cancer ont mis en évidence l'importance des interactions entre les cellules tumorales et les cellules immunitaires. Cependant, ces interactions reposent sur des mécanismes extrêmement complexes, ce qui rend difficile la conception de traitements efficaces visant à renforcer la réponse immunitaire. Par conséquent, les modèles mathématiques décrivant la croissance tumorale sont nécessaires pour reproduire et prédire fidèlement la dynamique spatio-temporelle de ces interactions. Le but de cette thèse est de proposer un modèle mathématique de croissance tumorale, décrivant l'interaction de la tumeur avec les cellules immunitaires. Pour ce faire, nous avons commencé par introduire un modèle mathématique destiné à décrire au moyen d'un système d'équations aux dérivées partielles les premières étapes des interactions entre les cellules immunitaires effectrices et les cellules tumorales. Le modèle est structuré en taille et en espace, et il prend en compte la migration des cellules effectrices cytotoxiques spécifiques de l'antigène tumoral vers le micro-environnement tumoral via un mécanisme chimiotactique. Nous avons étudié sur des bases numériques le rôle des paramètres clés du modèle tels que la division et les taux de croissance des cellules tumorales, ainsi que les taux de conversion et de mortalité des cellules immunitaires. Nos principales conclusions sont doubles. Premièrement, le modèle présente un contrôle possible de la croissance tumorale par la réponse immunitaire; néanmoins, le contrôle n'est pas complet en ce sens que les états d'équilibre asymptotiques conservent des tumeurs résiduelles et des cellules immunitaires activées. Deuxièmement, les hétérogénéités spatiales de la source des cellules immunitaires peuvent réduire considérablement l'efficacité de la dynamique de contrôle, faisant apparaître des schémas de rémission-récurrence. Par suite, nous avons développé des méthodes numériques pour prédire les paramètres des états d'équilibre sans exécuter des simulations du problème d'évolution. En utilisant des méthodes d'analyse de sensibilité globale, nous avons étudié le rôle des paramètres du modèle et identifié un impact prédominant du système immunitaire sur le taux de division des cellules tumorales. Nous avons montré que les meilleures stratégies thérapeutiques consistaient à augmenter la force de l'action létale des cellules immunitaires sur les cellules tumorales et le taux de conversion des cellules immunitaires naïves en cellules effectrices. Nous avons ensuite validé cette méthode à l'aide d'analyses rétrospectives expérimentales et cliniques. Ces résultats peuvent être utilisés dans le traitement du cancer pour concevoir des combinaisons thérapeutiques optimisées. Enfin, nous avons introduit un modèle mathématique destiné à décrire la double nature de la réponse immunitaire, avec l'activation de mécanismes à la fois anti-tumoraux et pro-tumoraux. La compétition entre ces effets antagonistes conduit soit à des phases d'équilibre, soit à des phases d'échappement. Ce modèle est utilisé pour étudier l'efficacité des stratégies d'immunothérapie comparant l'effet des monothérapies à l'effet la combinaison de thérapies. Les résultats ont indiqué que la combinaison de stratégies d'immunothérapie est plus efficace pour contrôler la croissance tumorale mais le succès du traitement est fortement conditionné par une combinaison appropriée entre la dose du traitement et le temps d'administration du traitement
The recent successes of immunotherapy for the treatment of cancer has highlighted the importance of the interactions between tumor cells and immune cells. However, these interactions are based on extremely complex mechanisms, making it difficult to design an effective treatment aimed at strengthening the immune response. Therefore, the mathematical models of tumor growth are needed to faithfully reproduce and predict the spatio-temporal dynamics of tumor growth. The aim of this thesis is to propose a mathematical model for tumor growth, describing the interaction of the tumor with the immune cells. We started by introducing a mathematical model intended to describe by means of a system of partial differential equations the earliest stages of the interactions between effector immune cells and tumor cells. The model is structured in size and space, and it takes into account the migration of the tumor antigen-specific cytotoxic effector cells towards the tumor micro-environment by a chemotactic mechanism. We investigated on numerical grounds the role of the key parameters of the model such as the division and growth rates of the tumor cells, and the conversion and death rates of the immune cells. Our main findings were two-fold. Firstly, the model exhibits a possible control of the tumor growth by the immune response; nevertheless, the control is not complete in the sense that the asymptotic equilibrium states keep residual tumors and activated immune cells. Secondly, space heterogeneities of the source of immune cells can significantly reduce the efficiency of the control dynamics, making patterns of remission-recurrence appear. Next, we developed numerical methods to predict the parameters of the equilibrium states without running simulations of the evolution problem. By using global sensitivity analysis methods, we investigated the role of the parameters of the model and identified a predominant impact of the immune system over division rate of tumor cells. We showed that the best therapeutic strategies were to increase the strength of the lethal action of immune cells on tumor cells and the conversion rate of naive immune cells into effector cells. We then validated this method using retrospective experimental and clinical analyses. These findings can be used in cancer treatments to design optimized therapy combinations. Finally, we introduced a mathematical model intended to describe the dual nature of the immune response, with the activation of both anti-tumor and pro-tumor mechanisms. The competition between these antagonistic effects leads to either equilibrium or escape phases. This model is used to investigate the efficacy of immotherapy strategies comparing the effect of monotherapies to the effect of combination of therapies. The findings indicated that combination of immunotherapy strategies are more efficient in controling tumor growth but the success of the treatment is strongly conditionned by the administrated dose and the time of the treatment administration

This thesis investigated the poorly constrained composition and evolution of the lower continental crust in Queensland through geochemistry, geochronology, and petrological modelling. The analysis of deep crustal rocks brought to the surface by explosive volcanism shows that the lower crust in Queensland is nearly devoid of many geologically significant trace elements. The modelling demonstrates that this lower crust formed through solid-melt interactions at the base of the crust. The combined data show that this depleted, hybridised crust could be more common than previously recognised and that hybridisation is likely a major driver of continent formation.

Durante la última década y paralelamente al incremento de la velocidad de computación, las técnicas de simulación molecular se han erigido como una importante herramienta para la predicción de propiedades físicas de sistemas de interés industrial. Estas propiedades resultan esenciales en las industrias química y petroquímica a la hora de diseñar, optimizar, simular o controlar procesos. El actual coste moderado de computadoras potentes hace que la simulación molecular se convierta en una excelente opción para proporcionar predicciones de dichas propiedades. En particular, la capacidad predictiva de estas técnicas resulta muy importante cuando en los sistemas de interés toman parte compuestos tóxicos o condiciones extremas de temperatura o presión debido a la dificultad que entraña la experimentación a dichas condiciones. La simulación molecular proporciona una alternativa a los modelos termofísicos utilizados habitualmente en la industria como es el caso de las ecuaciones de estado, modelos de coeficientes de actividad o teorías de estados correspondientes, que resultan inadecuados al intentar reproducir propiedades complejas de fluidos como es el caso de las de fluidos que presentan enlaces de hidrógeno, polímeros, etc. En particular, los métodos de Monte Carlo (MC) constituyen, junto a la dinámica molecular, una de las técnicas de simulación molecular más adecuadas para el cálculo de propiedades termofísicas. Aunque, por contra del caso de la dinámica molecular, los métodos de Monte Carlo no proporcionan información acerca del proceso molecular o las trayectorias moleculares, éstos se centran en el estudio de propiedades de equilibrio y constituyen una herramienta, en general, más eficiente para el cálculo del equilibrio de fases o la consideración de sistemas que presenten elevados tiempos de relajación debido a su bajos coeficientes de difusión y altas viscosidades. Los objetivos de esta tesis se centran en el desarrollo y la mejora tanto de algoritmos de simulación como de potenciales intermoleculares, factor considerado clave para el desarrollo de las técnicas de simulación de Monte Carlo. En particular, en cuanto a los algoritmos de simulación, la localización de puntos críticos de una manera precisa ha constituido un problema para los métodos habitualmente utilizados en el cálculo de equlibrio de fases, como es el método del colectivo de GIBBS. La aparición de fuertes fluctuaciones de densidad en la región crítica hace imposible obtener datos de simulación en dicha región, debido al hecho de que las simulaciones son llevadas a cabo en una caja de simulación de longitud finita que es superada por la longitud de correlación. Con el fin de proporcionar una ruta adecuada para la localización de puntos críticos tanto de componentes puros como mezclas binarias, la primera parte de esta tesis está dedicada al desarrollo y aplicación de métodos adecuados que permitan superar las dificultades encontradas en el caso de los métodos convencionales. Con este fin se combinan estudios de escalado del tamaño de sitema con técnicas de "Histogram Reweighting" (HR). La aplicación de estos métodos se ha mostrado recientemente como mucho mejor fundamentada y precisa para el cálculo de puntos críticos de sistemas sencillos como es el caso del fluido de LennardJones (LJ). En esta tesis, estas técnicas han sido combinadas con el objetivo de extender su aplicación a mezclas reales de interés industrial. Previamente a su aplicación a dichas mezclas reales, el fluido de LennardJones, capaz de reproducir el comportamiento de fluidos sencillos como es el caso de argón o metano, ha sido tomado como referencia en un paso preliminar. A partir de simulaciones realizadas en el colectivo gran canónico y recombinadas mediante la mencionada técnica de "Histogram Reweighting" se han obtenido los diagramas de fases tanto de fluidos puros como de mezclas binarias. A su vez se han localizado con una gran precisión los puntos críticos de dichos sistemas mediante las técnicas de escalado del tamaño de sistema. Con el fin de extender la aplicación de dichas técnicas a sistemas multicomponente, se han introducido modificaciones a los métodos de HR evitando la construcción de histogramas y el consecuente uso de recursos de memoria. Además, se ha introducido una metodología alternativa, conocida como el cálculo del cumulante de cuarto orden o parámetro de Binder, con el fin de hacer más directa la localización del punto crítico. En particular, se proponen dos posibilidades, en primer lugar la intersección del parámetro de Binder para dos tamaños de sistema diferentes, o la intersección del parámetro de Binder con el valor conocido de la correspondiente clase de universalidad combinado con estudios de escalado. Por otro lado, y en un segundo frente, la segunda parte de esta tesis está dedicada al desarrollo de potenciales intermoleculares capaces de describir las energías inter e intramoleculares de las moléculas involucradas en las simulaciones. En la última década se han desarrolldo diferentes modelos de potenciales para una gran variedad de compuestos. Uno de los más comunmente utilizados para representar hidrocarburos y otras moléculas flexibles es el de átomos unidos, donde cada grupo químico es representado por un potencial del tipo de LennardJones. El uso de este tipo de potencial resulta en una significativa disminución del tiempo de cálculo cuando se compara con modelos que consideran la presencia explícita de la totalidad de los átomos. En particular, el trabajo realizado en esta tesis se centra en el desarrollo de potenciales de átomos unidos anisotrópicos (AUA), que se caracterizan por la inclusión de un desplazamiento de los centros de LennardJones en dirección a los hidrógenos de cada grupo, de manera que esta distancia se convierte en un tercer parámetro ajustable junto a los dos del potencial de LennardJones.
En la segunda parte de esta tesis se han desarrollado potenciales del tipo AUA4 para diferentes familias de compuesto que resultan de interés industrial como son los tiofenos, alcanoles y éteres. En el caso de los tiofenos este interés es debido a las cada vez más exigentes restricciones medioambientales que obligan a eliminar los compuestos con presencia de azufre. De aquí la creciente de necesidad de propiedades termodinámicas para esta familia de compuestos para la cual solo existe una cantidad de datos termodinámicos experimentales limitada. Con el fin de hacer posible la obtención de dichos datos a través de la simulación molecular hemos extendido el potencial intermolecular AUA4 a esta familia de compuestos. En segundo lugar, el uso de los compuestos oxigenados en el campo de los biocombustibles ha despertado un importante interés en la industria petroquímica por estos compuestos. En particular, los alcoholes más utilizados en la elaboración de los biocombustibles son el metanol y el etanol. Como en el caso de los tiofenos, hemos extendido el potencial AUA4 a esta familia de compuestos mediante la parametrización del grupo hidroxil y la inclusión de un grupo de cargas electrostáticas optimizadas de manera que reproduzcan de la mejor manera posible el potencial electrostático creado por una molecula de referencia en el vacío. Finalmente, y de manera análoga al caso de los alcanoles, el último capítulo de esta tesis la atención se centra en el desarrollo de un potencial AUA4 capaz de reproducir cuantitativamente las propiedades de coexistencia de la familia de los éteres, compuestos que son ampliamente utilizados como solventes.
Parallel with the increase of computer speed, in the last decade, molecular simulation techniques have emerged as important tools to predict physical properties of systems of industrial interest. These properties are essential in the chemical and petrochemical industries in order to perform process design, optimization, simulation and process control. The actual moderate cost of powerful computers converts molecular simulation into an excellent tool to provide predictions of such properties. In particular, the predictive capability of molecular simulation techniques becomes very important when dealing with extreme conditions of temperature and pressure as well as when toxic compounds are involved in the systems to be studied due to the fact that experimentation at such extreme conditions is difficult and expensive.
Consequently, alternative processes must be considered in order to obtain the required properties. Chemical and petrochemical industries have made intensive use of thermophysical models including equations of state, activity coefficients models and corresponding state theories. These predictions present the advantage of providing good approximations with minimal computational needs. However, these models are often inadequate when only a limited amount of information is available to determine the necesary parameters, or when trying to reproduce complex fluid properties such as that of molecules which exhibit hydrogen bonding, polymers, etc. In addition, there is no way for dynamical properties to be estimated in a consistent manner.
In this thesis, the HR and FSS techniques are combined with the main goal of extending the application of these methodologies to the calculation of the vaporliquid equilibrium and critical point of real mixtures. Before applying the methodologies to the real mixtures of industrial interest, the LennardJones fluid has been taken as a reference model and as a preliminary step. In this case, the predictions are affected only by the omnipresent statistical errors, but not by the accuracy of the model chosen to reproduce the behavior of the real molecules or the interatomic potential used to calculate the configurational energy of the system.
The simulations have been performed in the grand canonical ensemble (GCMC)using the GIBBS code. Liquidvapor coexistences curves have been obtained from HR techniques for pure fluids and binary mixtures, while critical parameters were obtained from FSS in order to close the phase envelope of the phase diagrams. In order to extend the calculations to multicomponent systems modifications to the conventional HR techniques have been introduced in order to avoid the construction of histograms and the consequent need for large memory resources. In addition an alternative methodology known as the fourth order cumulant calculation, also known as the Binder parameter, has been implemented to make the location of the critical point more straightforward. In particular, we propose the use of the fourth order cumulant calculation considering two different possibilities: either the intersection of the Binder parameter for two different system sizes or the intersection of the Binder parameter with the known value for the system universality class combined with a FSS study. The development of transferable potential models able to describe the inter and intramolecular energies of the molecules involved in the simulations constitutes an important field in the improvement of Monte Carlo techniques. In the last decade, potential models, also referred to as force fields, have been developed for a wide range of compounds. One of the most common approaches for modeling hydrocarbons and other flexible molecules is the use of the unitedatoms model, where each chemical group is represented by one LennardJones center. This scheme results in a significant reduction of the computational time as compared to allatoms models since the number of pair interactions goes as the square of the number of sites. Improvements on the standard unitedatoms model, where typically a 612 LennardJones center of force is placed on top of the most significant atom, have been proposed. For instance, the AUA model consists of a displacement of the LennardJones centers of force towards the hydrogen atoms, converting the distance of displacement into a third adjustable parameter. In this thesis we have developed AUA 4 intermolecular potentials for three different families of compounds. The family of ethers is of great importance due to their applications as solvents. The other two families, thiophenes and alkanols, play an important roles in the oil and gas industry. Thiophene due to current and future environmental restrictions and alkanols due ever higher importance and presence of biofuels in this industry.

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The Ediacaran to Cambrian (600-500 Ma) intraplate Petermann Orogeny significantly affected the crustal architecture of Central Australia, resulting in the exhumation of the Musgrave Province from beneath the Centralian Superbasin. In the western Musgrave Province response to intensive deformation is variable, with pervasive mylonitic reworking and localised migmitisation in the western Mann Ranges, and discrete mylonitisation in the eastern Mann Ranges. The duration of this period of intraplate orogenesis is a currently debated topic. Ti-in-zircon thermometry coupled with SHRIMP U-Pb zircon geochronology indicate that peak temperatures of 733±23°C in the western Mann Ranges occurred at circa 540 Ma. Combined diffusion-cooling modelling, U-Pb rutile and titanite isotopic data and calculated phase equilibria of recrystallised metagranites from the Cockburn Shear Zone and kyanite-bearing mylonites from the Mt. Charles Thrust indicate exhumation driven cooling from peak P-T conditions of 12-14 kbars and 700-750°C to 6-7 kbars and 550-600°C at c. 500 Ma occurred at a rate of 3.75-5.6°C/ My. These results indicate a slow-cooling and long-lived thermal regime and additionally suggests that final exhumation of the Musgrave Province had not occurred by c. 500 Ma, much younger than previously estimated. These findings suggest that granulite-facies metamorphism in the Musgrave Province was regional and that other factors such as fluid, control the variations in style of structural reworking. This study lends support to the notion that the intraplate Petermann Orogeny was long-lived and does not advocate short-lived orogenesis or the theory that shear heating is the driving force for metamorphism.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2010

This thesis presents research on high-temperature metamorphic processes. A recent development in petrological modelling of granulite facies rocks is reintegration of melt generated and lost during metamorphism. The aim of melt reintegration is to create bulk compositions suitable for modelling prograde subsolidus evolution. Melt reintegration methodology was applied to a low-pressure granulite assemblage containing unambiguous textural evidence for subsolidus andalusite. Melt reintegration methodology resulted in a bulk composition that stabilised subsolidus and modally correct andalusite, providing validation of this petrological modelling technique. Melting and melt loss modifies rock chemistry and a long-standing paradigm is that melting depletes rocks in heat producing elements (HPEs). However, comprehensive K–U–Th datasets taken from a number of terranes show that in metapelites, melting and melt loss does not deplete U–Th concentrations, with overall terrane averages suggesting bulk heat production partitioning between melt and residuum is essentially 1:1. Modelling of HPE concentrations derived from terrane-scale elemental mapping in central Australia show that low-pressure (150–175 °C/kbar) granulite-facies metamorphism was driven by elevated crustal heat production. This energy source resulted in extremely long-lived (> 150 Ma) low-P–high-T metamorphism. High thermal gradient metamorphism driven by this energy source is characterised by contractional structures, kinematically late temperature maxima, and tight clockwise P–T loops. Petrochronology (the nexus between the isotopic age of a mineral and its compositional controls) is being increasingly used to interrogate the thermobarometric record contained in metamorphic rocks. Combined zircon and monazite REE-isotopic U–Pb compositions from interlayered metapelite and metabasic granulites show essentially identical peak metamorphic assemblages were achieved by substantially different P–T–t paths. The metabasic rock composition reached peak conditions at least 30 Ma before the metapelite. While speculative, the thermal delay recorded by the metapelite may reflect thermal buffering associated with partial melting and persistent structurally focussed melt streaming.
Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2019

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Anglesey in North Wales is considered to contain the oldest exposures of lawsonite-glaucophane blueschist in the world, marking the first appearance of lawsonite in the geological record, and heralding the emergence of truly modern subduction thermal regimes. The blueschists formed in the late Neoproterozoic during subduction beneath Avalonia. Interlayered within the blueschist unit are rare lenses of garnet-bearing metapelite that form part of a lithological association with more voluminous garnet-free metapelites. Detrital U-Pb zircon geochronology of the metapelites indicates that deposition of the protolith occurred ~630-590 Ma ago. The dominant detrital zircon ages correspond to the age of arc magmatism along the inferred margin of Avalonia, suggesting that the bulk of the detritus was derived from erosion of the arc. The presence of less abundant older zircons that range in age up to 2Ga, suggest that the arc was built on an ancient continental margin. This suggestion is supported by Nd isotopic compositions of the metapelites, which indicate derivation from an evolved source. The rare garnet metapelites contain the metamorphic assemblage garnet-muscovite-chlorite-albite-quartz-titanite-rutile-pyrite in which coronas of rutile surround titanite. Phase equilibria forward modelling of the metapelites indicates a prograde burial path that culminated with conditions around 400-450°C, at pressures of 10-12kbar. These conditions give an average thermal gradient of around 40°C/kbar, which is comparatively warm for lawsonite-bearing rocks. This suggests the Anglesey lawsonite-bearing blueschists record the onset of global subduction thermal regimes in the late Neoproterozoic that can stabilise lawsonite, rather than simply being a fortuitous preservation of widely developed refrigerated metamorphic rock systems.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2017

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The Warumpi Province has been interpreted to be exotic and accreted to the Northern Australian Craton (NAC) during the Liebig Orogeny at c.1640Ma. However, phase equilibria modelling of melt-deficient, Mg-Al rich granulite facies rocks at Hill 830, in the Mount Liebig area show contradictory evidence of a decompressional pressure-temperature path and a high metamorphic gradient of 90°Ckbar. This interpretation in conjunction with abundant c.1780- 1740Ma and c.1640Ma magmatism in the southern Aileron and Warumpi Provinces, indicate that the tectonic regime at c.1640Ma may instead be a south-migrating, extensional scenario, compared to the previously accepted collisonal regime; speculating that the Warumpi Province is not ‘exotic’ to the NAC.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2015

Hereby I present a PhD thesis by publications. The thesis includes five journal papers, of which two have already been published and three have been submitted for publication and are presently under review. The journals include high-impact-factor ones (Water Resources Research, Applied Mathematics Letters and Transport in Porous Media), and also Journal of Petroleum Science and Engineering, which is a major academic journal in petroleum industry. The thesis develops a new version of so-called splitting theory. The current 2006- version of the theory encompasses analytical modelling of thermodynamicallyequilibrium conservation law systems for two-phase multicomponent flow in porous media. The theory allows the derivation of numerous analytical solutions. The thesis generalizes the splitting method and applies it for flow systems with dissipation, nonequilibrium phase transitions and chemical reactions. It is shown how the general n×n system is split into an (n-1)×(n-1) auxiliary system and one scalar lifting equation. The auxiliary system contains thermodynamic parameters only, while the lifting equation contains transport properties and solves for phase saturation. First application of the splitting method is developed for low-salinity waterflooding. Two major effects are accounted for: the wettability alternation and the induction of fines migration, straining and attachment. One-dimensional (1D) problems of sequential injection of high-salinity water slug, low salinity water slug and high-salinity water chase drive corresponds to one of the most promising modern processes of Enhanced Oil Recovery, which currently is under intensive investigation in major world oil companies. Both auxiliary and lifting problems allow for exact solutions. The exact analytical solution consists of implicit formulae for profiles of phase saturations, salinity and fine particle concentrations. The exact solution allows for deriving explicit formulae in oil recovery. The solution permits the comparative study of the impact of both effects, which are the wettability alternation and the induction of fines migration, on incremental recovery. It was found out that both effects are significant for typical values of the physics constants. The exact solution allows for multi-variant study to optimize the injected water composition in a concrete oilfield. The second application of the splitting method corresponds to 1D displacement of oil by a low-salinity polymer slug followed by a low-salinity water slug and, finally, high salinity water chase drive. This problem corresponds to the Enhanced Oil Recovery Method that merges two traditional methods of polymer- and low-salinity water-floods. The exact analytical solutions are the result of the splitting system. The method was also generalized for the case of several low-salinity slugs and Non- Newtonian properties of the polymer solution. The exact solution yields explicit formulae for propagation of saturation and concentration shocks, dynamics of different flow zones and explicit formulae for incremental oil recovery. The analytical model developed allows optimizing polymer concentration and its slug size, salinity concentration and sizes of slugs for secondary and tertiary oil recovery. The third application of the new splitting method is oil displacement by suspensions and colloids of solid micro particles. The injection of one suspension or colloid with multiple particle capture mechanisms is assumed. The novelty of this work is considering numerous particle capture mechanisms and kinetic equations for the capture rates, which do not have a conservation law type. However, the system is susceptible for splitting by the introduction of Lagrangian co-ordinate and using it instead of time as an independent variable in the general system of Partial Differential Equations (PDEs). Introduction of the concentration potential linked with retention concentrations yields an exact solution for auxiliary problem. The exact formulae allow predicting the profiles and breakthrough histories for the suspended and retained concentrations and phase saturations. It also allows the calculation of penetration depth. The analytical models derived in the thesis are applicable also in numerous environmental and chemical engineering processes, including the disposal of industrial wastes in aquifers with propagation of contaminants and pollutants, industrial water treatment, injection of hot- or low-salinity water into aquifers and water injection into geothermal reservoirs.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, Australian School of Petroleum, 2016.

Hereby I present a PhD thesis by publications. This thesis includes seven journal papers, of which six have already been published in peer-reviewed journals and one has been submitted for publication and is presently under review. This thesis shows that the commonly used single particle-single surface Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations do not always effectively predict particle detachment. Therefore, the mobilisation of clustered structures under particle-particle attraction is investigated. The critical detachment velocity of clusters is higher than for single colloids and provides better agreement with the laboratory results. The behaviour of particles and clusters was also investigated during drainage and imbibition in visualisation experiments. Particles remain on the air-water interfaces of residual liquid patches left behind the drainage front. Later, these particles join the imbibition front away from the substrate. In a previously dried channel, the vapour condensation ahead of the imbibition front detaches particles from the surface by a rising air-water interface. This thesis presents an extension of the traditional mathematical model for colloid transport by including equations for the particle re-attachment rate and the attached-concentration-dependency of permeability. The new model captures the effect of permeability increase due to colloid mobilisation and further re-attachment in stagnant zones of the porous space. This effect was observed during high-salinity water injection in cores with low kaolinite concentrations. This model is also extended to account for the presence of a residual phase. Compared with fines migration under single-phase flow, having a residual phase significantly reduces the permeability variation. Analytical solutions for over and undersaturated state of fines were also derived in this thesis. Oversaturation means that particles begin to detach as soon as the flow starts. In the undersaturated case, particle detachment occurs only with further increase in detaching torque or decrease in attaching torque. The derived models allow formulating the fingerprints for the flow of over and undersaturated fines in porous media. Novel analytical models for one-dimensional linear and axisymmetric suspension-colloidal transport accounting for fines detachment and capture were also derived. Laboratory experiments with low-salinity water injection were performed. The model coefficients obtained from laboratory data treatment were used for reliable laboratory-based prediction of well injectivity decline. The results show that fines migration during low-salinity water injection results in significant well injectivity impairment. The thesis also investigates low-salinity water slug injection followed by a high-salinity chase drive in a two layer-cake reservoir. The formation damage caused by fines mobilisation during low-salinity water injection diverts the injected water flux into low-permeability zones and enhances sweep efficiency. An optimal low-salinity slug size existed for all simulated cases. The optimal slug size is similar to the pore volume of the high-permeability layer. The analytical models derived in this thesis are applicable in numerous environmental and engineering processes, including the injection of low-salinity or hot water in a reservoir, ocean water invasion into aquifers, freshwater storage, and contamination of subterranean waters by viruses and bacteria. It also has many applications in hydrology and ecology, such as ground cleaning from non-aqueous phase liquids, remediation of contaminated soil and groundwater, and natural filtration of pathogenic microorganisms.
Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum and Energy Resources, 2020

The studied area extends from the Ochtiná Unit in Western Carpathians to the Veitsch Nappe Eastern Alps. The thesis represents a complex multidisciplinary work that combines the structural analysis, petrology and geochronology. The three main objectives of this thesis: reevaluation of the structure, deformation and metamorphic records, and original position of the Ochtiná Unit, understanding the distinct metasomatic processes recorded along the contact of two major units of the Central Western Carpathians - in the Gemer-Vepor Contact Zone - and their relation to distinct tectono-metamorphic events, testing the possible links between the Ochtiná Unit in the Gemer-Vepor Contact Zone of the Western Carpathians and the Veitsch Nappe in the Greywacke Zone of the Easten Alps, both well known for the Lower Carboniferous shale/schist sequence accompanied by the abundant presence of magnesite ore bodies. Keywords: Central Western Carpathians, Greywacke Zone, Ochtiná Unit, Veitsch Nappe, U-Pb zircon dating, Phase equilibrium modelling

Doutoramento em Matemática Aplicada à Economia e Gestão
The inevitability of taxes and regulations, that cause agents to go underground, forces the authorities to tolerate some underground economic activity and grants the underground economy natural features. The natural level of the underground economy is defined as the level of underground economic activity in the decentralized equilibrium, provided that the actual structural characteristics of the economy and social preferences are accounted for by imbedding them in the Walrasian system of general equilibrium equations. Its existence is proven using two variants of neoclassical general equilibrium models. The underground economy is found to influence the successfulness of fiscal consolidation programmes, depending on the position of the economy relative to critical fiscal thresholds associated with the natural level of the underground economy. Tax increases yield higher tax proceeds up to the threshold, and lower tax proceeds, passed the threshold, due to a stronger expansion of the natural level of the underground economy. Tax proceeds reach their maximum at the threshold. Tax based programmes are found ineffective in high tax developed economies, operating passed the threshold. In contrast, its successfulness in the developing world, where most economies operate below the threshold with low taxes, is not influenced by the underground economy.
Perante a inevitabilidade de impostos e regulamentação, que estão na origem da economia subterrânea, as autoridades vêem-se forçadas a tolerar actividades económicas subterrâneas. Isto confere um carácter natural à economia subterrânea. A existência de uma taxa natural de economia subterrânea é provado utilizando dois modelos neoclássicos de equilíbrio gereal. A taxa natural de economia subterrânea define-se como o nível de actividade económica subterrânea no equilíbrio descentralizado, dadas as propriedades estruturais da economia e das preferências sociais, que se incluem no sistema Walrasiano de equações de equilíbrio geral. Prova-se que a economia subterrânea influencia o resultado de programas de consolidação orçamental. Isto depende da localização da economia face a valores fiscais críticos associados à taxa natural de economia subterrânea. A seguir a um aumento de impostos, as receitas começam por crescer, atingindo o máximo no ponto crítico, para a seguir cair, devido a uma expansão da taxa natural de economia subterrânea. Programas assentes no aumento de impostos não são bem sucedidos em países desenvolvidos com cargas fiscais elevadas, que operam além do ponto crítico. Já os países em desenvolvimento, cuja maioria opera abaixo do ponto crítico com cargas fiscais baixas, a economia subterrânea não parece influenciar a eficácia dos programas. Palavras chave: Economia subterrânea, evasão de impostos, politica orçamental, consolidação orçamental, defice, divida, modelos de equilíbrio geral aplicados, modelos de crescimento economico de dois sectores, simulação.
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