Este estudo tem como objetivo estudar o fósforo total e as especiações de fósforo nos sedimentos superficiais associados aos processos biogeoquímicos em dois sistemas estuarinos, na plataforma continental sudeste e na região polar antártica. Amostras de água de fundo foram coletadas em dois períodos sazonais (verão-inverno) nos estuários sob diferentes graus de impacto ambiental antrópico. A metodologia de extração das frações de (SEDEX) aplicada para obter as especiações químicas de fósforo foi testada com padrões certificados antes das análises. Os resultados foram reprodutivos e a eficiência da extração foi aceitável. As concentrações das espécies químicas de fósforo sedimentar nos dois estuários mostraram diferenças entre os setores seguindo as características granulométricas, influência da maré, condições redox das águas de fundo bem como, as ações antrópicas reveladas pelos dados quantitativos e qualitativos. Uma influência sazonal mínima foi observada. No caso da plataforma sudeste, altos valores de matéria orgânica foram observados em núcleos ao longo da plataforma, junto às estações externas das radiais de Santos e Ilha Grande mostrando uma diferenciação acompanhada pelas frações de fósforo orgânico e carbono orgânico. Nas demais radiais, altos valores de CaCO3 foram observados nas estações mais externas. Na Baía do Almirantado as frações predominantes foram P mineral, P detrítico, P-ligado à apatita autigênica, sendo que a forma orgânica foi baixa e associada a baixos valores de carbono orgânico. A quantificação e distribuição das espécies de fósforo nos sedimentos constituem importante ferramenta para compreender o ciclo biogeoquímico do fósforo e dos demais nutrientes nos ecossistemas marinhos. / This work aims to study the total and chemical species of phosphorus in the surface sediments associated to the biogeochemical processes in two estuarine systems, the southeastern continental shelf and Antarctic polar region. Bottom water samples were collected in two seasonal periods (summer-winter) in the estuaries under different degrees of environmental anthorpic impacts. The fraction extraction methodology (SEDEX) applied to obtain the chemical phosphorus species was tested in relation to the certified standards before analyses. The results were reproductive and the extraction efficiency was acceptable. The chemical species concentrations of sedimentary phosphorus in the two estuarine systems showed differences between sectors following the granulometric characteristics, tide influence, redox conditions of the bottom waters as well as anthropic actions revealed by quantitative and qualitative data. A minimum seasonal influence was observed. In the case of eastern continental shelf, high values of organic matter were found in nuclei distribution along the platform in the external stations of Santos and Ilha Grande radials showing a differentiation accompanied by organic phosphorus and C org., fractions. In the other radials high CaCO3 values were observed in the external stations. In the Admiralty Bay the predominant fractions were detrital apatite and authigenic/biogenic apatite, being that organic form was low, linked to low values of organic carbon. The quantification and distribution of P species in the sediments constitute important tools to understand the P and the other nutrient biogeochemical cycles in the sea ecosystems

Η λεπτομερής ιζηματολογική ανάλυση των αποθέσεων της τομής Μακρυλιά, έδειξε την ύπαρξη τουλάχιστον 5 κύκλων ιζηματογένεσης με αυξανόμενο προς τα πάνω κοκκομετρικό μέγεθος που αναπτύχτηκαν σε ένα περιβάλλον υφαλοκρηπίδας. Η κύρια λιθολογία είναι αμμούχος πηλός και τα ιζήματα μεταφέρθηκαν ως ομογενές αιώρημα. Το ποσοστό του ανθρακικού ασβεστίου είναι χαμηλό και τείνει αυξανόμενο προς τα πιο αδρομερή κλάσματα. Το ποσοστό του οργανικού υλικού έδειξε την παρουσία αρκετών δειγμάτων με αυξημένο οργανικό υλικό προτείνοντας την ύπαρξη εν δυνάμει μητρικών πετρωμάτων για την γένεση υδρογονανθράκων. Η σχέση μεταξύ του ανθρακικού ασβεστίου και οργανικού υλικού είναι κύρια αρνητική προτείνοντας ανοξικές συνθήκες. Η βιοστρωματογραφική ανάλυση έδειξε Πλειοκαινική ηλικία των ιζημάτων που αποτέθηκαν σε εναλλασσόμενες οξικές – ανοξικές συνθήκες. Από τα παραπάνω αποτελέσματα και περνώντας υπόψη τα υπάρχοντα αποτελέσματα των ιζημάτων που περιβάλλουν την περιοχή μελέτης φαίνεται πως οι μελετηθείσες αποθέσεις συγκεντρώθηκαν σε μια ρηχή με ήσυχα νερά ενδο-ορεινή λεκάνη στα περιθώρια της κύριας λεκάνης της Ιεράπετρας. / Detailed sedimentological analysis, in Makrylia cross-section deposits, showed at least five coarsening-upward cycles developed in a shelf environment. The main lithology is sandy silt and sediments transported as homogenous suspension in a low energy environment that deposited in a shallow water basin. Calcium carbonate (CaCO3) is low and tends to increase to the coarse-grained clasts. Organic carbon (TOC) ratio showed the presence of many high content samples in TOC suggesting potential hydrocarbon source rocks. There is mostly a negative relation between CaCO3 and TOC introducing generally anoxic conditions. Biostratigraphy analysis showed a Pliocene age for the studied deposits in alternating conditions with oxic- anoxic events. According to the above results and taking into account previous results from the surrounding sediments it seems that studied deposits accumulated in a shallow, low energy, intra-mountain basin at the margins of the main Ierapetra basin.

Le réchauffement climatique est lié aux augmentations des concentrations de gaz à effet de serre dans l'atmosphère terrestre et en particulier aux émissions anthropiques de CO2. La séquestration géologique a la capacité et la longévité potentielles pour diminuer de façon significative les émissions anthropiques de CO2. Cette séquestration à grande profondeur induit des risques de fuite des réservoirs géologiques. Parmi les scénarios de fuite envisagés, celui d'une fuite diffuse est le plus inquiétant puisque sans surveillance, cette fuite pourrait perdurer et entrainer des séquelles sur l'environnement ainsi que des risques pour les populations. Des outils et protocoles de surveillance doivent donc être mis au point pour la surveillance en proche surface. Ce travail de thèse s'inscrit dans le cadre de cette problématique. Il a pour objectif la caractérisation, la quantification et la modélisation du transport et des interactions du CO2 dans une zone non saturée carbonatée. Ce travail a suivi une approche expérimentale sur un site pilote naturel à Saint-Emilion (Gironde, France), avec la réalisation de fuites diffuses en ZNS carbonatée. Cette étude aborde plusieurs thématiques: la description et l'instrumentation du site pilote naturel ; la caractérisation physico-chimique de l'hétérogénéité du réservoir carbonaté ; l'étude du fonctionnement naturel de la ZNS carbonatée et en particulier la mise en place d'une ligne de base des concentrations en CO2 ; la caractérisation de l'extension des panaches de gaz suite à des expériences de fuite diffuse dans la ZNS carbonatée et l'étude par simulation numérique des interactions gaz-eau-roche lors d'une fuite diffuse de CO2 dans une ZNS carbonatée. Les résultats de ces travaux montrent l'importance de la caractérisation de l'hétérogénéité du réservoir carbonaté ainsi que des techniques d'échantillonnage et d'analyse des différentes phases en présence. L'établissement de la ligne de base a une importance particulière pour permettre de distinguer les variations naturelles de celles induites par une fuite diffuse de CO2 dans la ZNS carbonatée. Les modes de transport du CO2 vont évoluer en fonction des paramètres physico-chimiques. Ce transport se fait par advection et/ou par diffusion. L'utilisation de gaz inertes au niveau du site de séquestration géologique est très importante puisque la détection de ces traceurs permettrait de prédire les arrivées de panaches de CO2 en proche surface. Par ailleurs, les interactions chimiques doivent être prises en compte dans les modèles de transport afin de pouvoir définir les facteurs de retard et l'impact d'une fuite diffuse de CO2 sur une ZNS carbonatée.

Scaling in green liquor handling systems is a persistent problem in many kraft mills. Scaling is commonly believed to be the result of pirssonite (Na2Ca(CO3)2∙2H2O) deposition. In this work, scale characterization was performed by analyzing 12 scale samples obtained from 10 kraft mills. Only 4 samples were identified as pirssonite while the remaining consisted of CaCO3. The predominant presence of CaCO3 in the scale samples was found to be the result of selective dissolution of Na2CO3 from pirssonite scale, leaving CaCO3 behind. Experimental studies were also conducted to study pirssonite solubility under green liquor conditions. Results obtained from these studies were used to create and validate a database for pirssonite in the OLI Systems® software to predict its formation. This database was used to generate a family of pirssonite solubility curves that can be used by the kraft mills as operational guidelines to prevent pirssonite precipitation.

Scaling in green liquor handling systems is a persistent problem in many kraft mills. Scaling is commonly believed to be the result of pirssonite (Na2Ca(CO3)2∙2H2O) deposition. In this work, scale characterization was performed by analyzing 12 scale samples obtained from 10 kraft mills. Only 4 samples were identified as pirssonite while the remaining consisted of CaCO3. The predominant presence of CaCO3 in the scale samples was found to be the result of selective dissolution of Na2CO3 from pirssonite scale, leaving CaCO3 behind. Experimental studies were also conducted to study pirssonite solubility under green liquor conditions. Results obtained from these studies were used to create and validate a database for pirssonite in the OLI Systems® software to predict its formation. This database was used to generate a family of pirssonite solubility curves that can be used by the kraft mills as operational guidelines to prevent pirssonite precipitation.

Le centre de recherche ArcelorMittal de Montataire développent de nouvelles solutions acier innovantes associant métal et polymère. Pour les ailes de voiture, le composite retenu est un matériau multicouche composé d’une lame d’acier sur laquelle est déposé un film mince de polypropylène choc chargé avec des particules minérales par l’intermédiaire d’une fine couche de polypropylène fonctionnalisé par le greffage d’anhydride maléique. Afin de prévoir et de connaitre le comportement de la partie organique du matériau lors de sa mise en forme par emboutissage et à posteriori de prédire l’état de ses propriétés mécaniques lors de son utilisation, la détermination des lois de comportement mécanique vrai et intrinsèque sur le modèle de la loi G’sell et Jonas est nécessaire. Ces lois sont définies selon trois chemins de déformation : la traction uniaxiale, le cisaillement simple et la traction plane. Les micromécanismes de déformation de la microstructure semi-cristalline des différentes formulations des matériaux selon leur mode de sollicitation mécanique ont été étudiés. Les résultats obtenus Post Mortem et In Situ ont permis la description qualitative et quantitative des évolutions des principales modifications microstructurales. Ces dernières diffèrent avec l’ajout de charges minérales. Deux nouvelles méthodes, la Tomographie X et la spectroscopie Raman permettent la détermination de la déformation volumique dans le cas de matériau de géométrie fine (300 µm). Le retrait lors d’un cycle thermique est étudié. Les influences du chauffage, de la formulation et de la microstructure (orientation des chaînes macromoléculaires et endommagement volumique) sont décrites / The ArcelorMittal research centre of Montataire elaborates innovative steel / polymer products. In the case of automotive fenders, the composite is a multilayered material. A thin impact polypropylene film is laminated on steel using a thin layer of a functionalized polypropylene. Mineral particles are added to improve stiffness. In order to predict and understand the behaviour of the organic layer all along its production process and finally to be able to characterize the state of its mechanical properties in use, the determination of the true and intrinsic mechanical behaviour laws according to the G’sell and Jonas model is necessary. These laws are obtained for three different mechanical paths: uniaxial tensile, simple shear and plane tensile. The deformation micromechanisms of the impact polypropylene semi-crystalline microstructure which depend on the materials formulations and on the mechanical path used are studied. Post Mortem and In Situ results give qualitative and quantitative description of the main microstructural modifications. Two new methods, X Tomography and Raman spectroscopy allow the quantification of the volume deformation which is developed during tensile tests. They are mainly available for very thin samples. X radiography and VideoTraction™ are not suitable anymore for this kind of geometry. Finally, the thermo-mechanical phenomenon of shrinkage which occurs during thermal treatment above the material melting point is analysed. Influences of the heating conditions, of the material formulations and of the material microstructure are described. Special overviews are done on the macromolecular chains orientation and on the volume damage influences

The rapid increase in the demand on fresh water due the increase in the world population and scarcity of natural water puts more stress on the desalination industrial sector to install more desalination plants around the world. Among these desalination plants, multistage flash desalination process (MSF) is considered to be the most reliable technique of producing potable water from saline water. In recent years, however, the MSF process is confronting many problems to cut off the cost and increase its performance. Among these problems are the non-condensable gases (NCGs) and the accumulation of fouling which they work as heat insulation materials. As a result, the MSF pumps and the heat transfer equipment are overdesigned and consequently increase the capital cost and decrease the performance of the plants. Moreover, improved process control is a cost effective approach to energy conservation and increased process profitability. Thus, this study is motivated by the real absence of detailed kinetic fouling model and implementation of advance process control (APC). To accomplish the above tasks, commercial modelling tools can be utilized to model and simulate MSF process taking into account the NCGs and fouling effect, and optimum control strategy. In this research, gPROMS (general PROcess Modeling System) model builder has been used to develop the MSF process model. First, a dynamic mathematical model of MSF is developed based on the basic laws of mass balance, energy balance and heat transfer. Physical and thermodynamic properties of brine, distillate and water vapour are included to support the model. The model simulation results are validated against actual plant data published in the literature and good agreement with these data is obtained. Second, the design of venting system in MSF plant and the effect of NCGs on the overall heat transfer coefficient (OHTC) are studied. The release rate of NCGs is studied using Henry’s law and the locations of venting points are optimised. The results reveal that high concentration of NCGs heavily affects the OHTC. Furthermore, advance control strategy namely: generic model control (GMC) is designed and introduced to the MSF process to control and track the set points of the two most important variables in the MSF plant; namely the Top Brine Temperature (TBT) which is the output temperature of the brine heater and the Brine Level (BL) in the last stage. The results are compared to conventional Proportional Integral Derivative Controller (PID) and show that GMC controller provides better performance over conventional PID controller to handle a nonlinear system. In addition, a new control strategy called hybrid Fuzzy-GMC is developed and implemented to control the same aforementioned loops. Its results reveal that the new control outperforms the pure GMC in some areas. Finally, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms of calcium carbonate and magnesium hydroxide with more relaxation of the assumptions. Since the MSF plant stages work as a series of heat exchangers, there is a continuous change of temperature, heat flux and salinity of the seawater. The proposed model predicts the behaviour of fouling based on the physical and thermal conditions of every single stage of the plant.

The extensive growth of nanotechnology has necessitated the development of economical and robust methods for large scale production of nanomaterials. It requires detailed quantitative understanding of lab-scale processes to enable effective scale-up and development of new contacting strategies for their controlled synthesis. In this thesis, attempts are made in both the directions using experimental and modelling approaches for synthesis of different nanoparticles. The two-phase Brust--Schiffrin protocol for the synthesis of gold nanoparticles was investigated first. The mechanism of transfer of reactants from aqueous to organic phase using phase transfer catalyst (PTC) was investigated using the measurement of interfacial tension, viscosity, SLS, SAXS, 1H NMR, DOSY-NMR, and Karl-Fischer titration. The study shows that the reactants are transferred to organic phase through the formation of hydrated complexes between reactants and PTC rather than through the solubilization of reactants in water core of inverse micelles of PTC, proposed recently in the literature. The particle synthesis reactions thus occur in the bulk organic phase. The extensive body of seemingly disparate experimental findings on Brust--Schiffrin protocol were put together next. The emerging picture ruled out both thermodynamic considerations and kinetics based arguments as exemplified by the classical LaMer's mechanism with sequential nucleation growth capping for size control in Brust--Schiffrin protocol. A new model for particle synthesis was developed. The model brought out continued nucleation--growth--capping based size control, an hitherto unknown mechanistic route for the synthesis of monodisperse particles, as the main mechanism. The model not only captured the reported features of the synthesis but also helped to improve the uniformity of the synthesized particles, validated experimentally. The two-step mechanism of Finke--Watzky---first order nucleation from precursor and autocatalytic growth of particles---proposed as an alternative to LaMer model to explain an induction period followed by a sigmoidal decrease in precursor concentration for the synthesis of iridium nanoparticles was investigated next. The mechanism is tested using an equivalent population balance model for its ability to explain the experimentally observed near constant breadth of the evolving size distribution as well. The predictions show that while it captures precursor conversion well, it fails to explain particle synthesis on account of its inability to suppress nucleation. A minimal four-step mechanism with additional steps for nucleation from reduced iridium atoms and their scavenging using particle surface is proposed. The new mechanism when combined with the first or second order nucleation, or classical nucleation with no scavenging of reduced atoms also fails to suppress nucleation. A burst like onset of nuclei formation with homogeneous nucleation and the scavenging of reduced atoms by particles are simultaneously required to explain all the reported features of the synthesis of iridium nanoparticles. A new reactor is proposed for continuous production of CaCO3 nanoparticles in gas-liquid reaction route. The key feature of the new reactor is the control of flow pattern to ensure efficient mixing of reactants. A liquidliquid reaction route for production of CaCO3 nanoparticles is also optimized to produce nanoparticles at high loading. Optimum supersaturation combined with efficient breakup of initial gel-like structure by mechanical agitation and charge control played a crucial role in producing nano sized CaCO3 particles.

No description available.

The rapid increase in the demand on fresh water due the increase in the world population and scarcity of natural water puts more stress on the desalination industrial sector to install more desalination plants around the world. Among these desalination plants, multistage flash desalination process (MSF) is considered to be the most reliable technique of producing potable water from saline water. In recent years, however, the MSF process is confronting many problems to cut off the cost and increase its performance. Among these problems are the non-condensable gases (NCGs) and the accumulation of fouling which they work as heat insulation materials. As a result, the MSF pumps and the heat transfer equipment are overdesigned and consequently increase the capital cost and decrease the performance of the plants. Moreover, improved process control is a cost effective approach to energy conservation and increased process profitability. Thus, this study is motivated by the real absence of detailed kinetic fouling model and implementation of advance process control (APC). To accomplish the above tasks, commercial modelling tools can be utilized to model and simulate MSF process taking into account the NCGs and fouling effect, and optimum control strategy. In this research, gPROMS (general PROcess Modeling System) model builder has been used to develop the MSF process model. First, a dynamic mathematical model of MSF is developed based on the basic laws of mass balance, energy balance and heat transfer. Physical and thermodynamic properties of brine, distillate and water vapour are included to support the model. The model simulation results are validated against actual plant data published in the literature and good agreement with these data is obtained. Second, the design of venting system in MSF plant and the effect of NCGs on the overall heat transfer coefficient (OHTC) are studied. The release rate of NCGs is studied using Henry’s law and the locations of venting points are optimised. The results reveal that high concentration of NCGs heavily affects the OHTC. Furthermore, advance control strategy namely: generic model control (GMC) is designed and introduced to the MSF process to control and track the set points of the two most important variables in the MSF plant; namely the Top Brine Temperature (TBT) which is the output temperature of the brine heater and the Brine Level (BL) in the last stage. The results are compared to conventional Proportional Integral Derivative Controller (PID) and show that GMC controller provides better performance over conventional PID controller to handle a nonlinear system. In addition, a new control strategy called hybrid Fuzzy-GMC is developed and implemented to control the same aforementioned loops. Its results reveal that the new control outperforms the pure GMC in some areas. Finally, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms of calcium carbonate and magnesium hydroxide with more relaxation of the assumptions. Since the MSF plant stages work as a series of heat exchangers, there is a continuous change of temperature, heat flux and salinity of the seawater. The proposed model predicts the behaviour of fouling based on the physical and thermal conditions of every single stage of the plant.