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The “Integrated Coal Gasification Combined Cycle” (IGCC) represents an advanced approach for green field projects for power generation. This process requires separation of carbon dioxide from the shifted-synthesis gas mixture (fuel gas). Treated fuel gas consists of approximately 40% CO2 and rest H2. Gas hydrate based separation technology for hydrate forming gas mixtures is one of the novel approaches for gas separation. The present study illustrates the gas hydrate-based separation process for the recovery of CO2 and H2 from the fuel gas mixture and discusses relevant issues from macro and molecular level perspectives. Propane (C3H8) is used as an additive to reduce the operating pressure for hydrate formation and hence the compression costs. Based on gas uptake measurement during hydrate formation, a hybrid conceptual process for pre-combustion capture of CO2 is presented. The result shows that it is possible to separate CO2 from hydrogen and obtain a hydrate phase with 98% CO2 in two stages starting from a mixture of 39.2% CO2. Molecular level work has also been performed on CO2/H2 and CO2/H2/C3H8 systems to understand the mechanism by which propane reduces the operating pressure without compromising the separation efficiency.

Using the NEPTUNE-Canada cable-linked ocean-floor observatory we plan continuous, real-time monitoring of the gas hydrate-associated, “Bullseye” cold vent offshore Vancouver Island. Our group inferred the presence of a massive gas hydrate deposit there, based on the significant resistivity anomaly in our controlled-source electromagnetic (CSEM) dataset, as well as anomalously heightened shear moduli, from seafloor compliance data. This interpretation was confirmed by drilling by IODP expedition 311 (site U1328), which indicated a 40 m thick gas hydrate layer near the surface. Sporadic venting and variations in blanking in yearly single-channel seismic surveys suggest the system is evolving in time. We are preparing two stationary semi-permanent imaging experiments: a CSEM and a seafloor compliance installation. These are designed not only to assess the extent of the gas hydrate deposit, but also for long-term monitoring of the gas hydrate/free gas system. The principle of the CSEM experiment is to input a particular electromagnetic signal at a transmitter (TX) dipole on the seafloor, and to record the phase and amplitude of the response at several seafloor receiver (RX) dipoles, at various TX-RX separations. The data are sensitive to the underlying resistivity, which is increased when conductive pore water is displaced by electrically-insulating gas hydrate. The experiment is controlled onshore, and can be expanded to include a downhole TX. Repeated soundings at this site, over several years, will allow measurement of minute changes in resistivity as a function of depth, and by inference, changes in gas hydrate or underlying free gas distribution. Similarly, the displacement of pore fluids by solid gas hydrate will affect elastic parameters. Thus, seafloor compliance data, the transfer function between pressure and seafloor displacement time series, most sensitive to shear modulus as a function of depth, will be gathered continuously to monitor the evolution of the gas hydrate distribution.

In the late spring of 2008, the Chevron-led Gulf of Mexico Gas Hydrate Joint Industry Project (JIP) expects to conduct an exploratory drilling and logging campaign to better understand gas hydrate-bearing sands in the deepwater Gulf of Mexico. The JIP Site Selection team selected three areas to test alternative geological models and geophysical interpretations supporting the existence of potential high gas hydrate saturations in reservoir-quality sands. The three sites are near existing drill holes which provide geological and geophysical constraints in Alaminos Canyon (AC) lease block 818, Green Canyon (GC) 955, and Walker Ridge (WR) 313. At the AC818 site, gas hydrate is interpreted to occur within the Oligocene Frio volcaniclastic sand at the crest of a fold that is shallow enough to be in the hydrate stability zone. Drilling at GC955 will sample a faulted, buried Pleistocene channel-levee system in an area characterized by seafloor fluid expulsion features, structural closure associated with uplifted salt, and abundant seismic evidence for upward migration of fluids and gas into the sand-rich parts of the sedimentary section. Drilling at WR313 targets ponded sheet sands and associated channel/levee deposits within a minibasin, making this a non-structural play. The potential for gas hydrate occurrence at WR313 is supported by shingled phase reversals consistent with the transition from gas-charged sand to overlying gas-hydrate saturated sand. Drilling locations have been selected at each site to 1) test geological methods and models used to infer the occurrence of gas hydrate in sand reservoirs in different settings in the northern Gulf of Mexico; 2) calibrate geophysical models used to detect gas hydrate sands, map reservoir thicknesses, and estimate the degree of gas hydrate saturation; and 3) delineate potential locations for subsequent JIP drilling and coring operations that will collect samples for comprehensive physical property, geochemical and other analyses

Hydrogen is currently considered by many as the “fuel of the future”. It is particularly favoured as a replacement for fossil fuels due to its clean-burning properties; the waste product of combustion being water. While hydrogen is relatively easy to produce, there is currently a lack of practical storage methods for molecular H2, and this is greatly hindering the use of hydrogen as a fuel. Gases are normally stored in vessels under only moderate pressures and in liquid form where possible, which yields the highest energy density. However, to store reasonable quantities of hydrogen in similar volume containers, cryogenic temperatures or extreme pressure are required. Many potential hydrogen storage technologies are currently under investigation, including adsorption on metal hydrides, nanotubes and glass microspheres, and the chemical breakdown of compounds containing hydrogen to release H2. Recent studies have sparked interest in hydrates as a potential hydrogen storage material. The molecular storage of hydrogen in clathrate hydrates could offer significant benefits with regard to ease of formation/regeneration, cost and safety, as compared to other storage materials currently under investigation. Here, we present new experimental hydrate stability data for sII forming hydrogen–water (up to pressures of 180 MPa) and hydrogen–water–tetrahydrofuran systems, the structure-H forming hydrogen–water–methyclycohexane system, and semi-clathrate forming hydrogen–water–tetra-n-butyl ammonium bromide/tetra–n-butyl ammonium fluoride systems.

Ultraviolet-visible spectra are presented for a polycrystalline sample of chlorine clathrate hydrate and two single crystal samples of bromine clathrate hydrate. The data shows that the UV-visible spectroscopy is a sensitive probe for studying the interactions between the halogen guest molecule and the host water lattice. The spectrum for chlorine hydrate shows a surprisingly strong temperature dependence. The spectra reported for bromine clathrate hydrate single crystals reinforce our previous conclusion that there is a stable cubic type II structure as well as the tetragonal structure. There is also a metastable cubic type I structure. The new results are discussed in the context of previous results, resonance Raman spectroscopy, and how the molecules fit into the host cages.

The Batumi Seep Area, offshore Georgia, Black Sea, has been intensively cored (gravity cores and TV-guided multi-cores) to investigate the methane turnover in the surface sediments. The seep area is characterized by vigorous methane gas bubble emanations. Geochemical analyses show a microbial origin of the methane and a shallow fluid source. Anaerobic methane oxidation rapidly consumes the SO4 2- within the top 5-20 cm, but significant upward fluid advection is not indicated by the porewater profiles. Hence, the Batumi Seep Area must be dominated by methane gas seepage in order to explain the required CH4 flux from below. 1-D transport-reaction modelling constrains the methane flux needed to support the observed SO4 2- flux as well as the rate of near-surface hydrate formation. The model results correlate well with the hydro-acoustic backscatter intensities recorded and mapped bubble release sites using the sonar of a ROV.

Dans l'objectif de la transition vers de nouvelles sources énergétiques, l'hydrogène apparaît comme une source d'énergie idéale. L'hydrogène est doté d'excellentes propriétés physico-chimiques lui conférant la qualité de combustible d'avenir : il est une énergie propre, renouvelable avec un pouvoir calorifique trois fois supérieur à celui de l'essence. Mais les difficultés liées au stockage et le transport de l'hydrogène restent des obstacles majeurs au développement d'une économie de l'hydrogène comme vecteurs énergétiques. C'est dans ce contexte que l'hydrates d'hydrogène à été entrepris au cours de mon projet de recherche doctorale. C'est étude concerne la synthèse et la caractérisation des hydrates et des semi-hydrates, à l'aide d'analyse calorimétrique différentielle sous haute pression (40 MPa) et un réacteur isobarique pour les mesure volumétrique. Dans le premier temps, une famille particulière des semi-hydrates qui se forment à partir d'eau et de gaz en présence de sels d'ammoniums (TBAOH) ou de phosphoniums quaternaires (TBPBH4) a été étudiée. Nous présentons dans cette partie une étude du comportements des systèmes TBAOH-H2-H2O, TBPBH4-H2-H2O et N2-TBPBH4-H2O, leurs diagrammes de phase isobare (T,x) et une étude volumétrique sur la quantité de gaz stocké. Dans le deuxième temps, le concept de Tuning a été développé dans un mélange de H2-C3H8 à fin d'étudier son impact sur le stabilité de l'hydrate d'hydrogène. En suite, la séparation de l'hydrogène dans un mélange équimolaire de CO2-H2 a été étudié avec l'analyses de la compostions initiales et finales du mélange du gaz. Mots clé: Hydrates de H2, hydrates semi-clathrates, équilibre de phase, analyse calorimétrique différentielles, mesure volumétrique.

Gegenstand der vorliegenden Arbeit war es, die Grundlagen für ein mögliches technisches Verfahren zur Aromatennitrierung mit Salzhydratschmelzen (M(NO3)3 · n H2O, M = Fe, Cr, Bi, In, Al; n = 4 - 9) zu untersuchen. Es sollte geklärt werden, ob Toluol quantitativ zu Dinitrotoluol bzw. Benzol zu Nitrobenzol umgesetzt werden kann. In Screening-Versuchen wurden geeignete, nitrierend wirkende Salzhydrate ermittelt, sowie Wege untersucht, die Reaktivität der eingesetzten Salzhydratschmelzen durch Variation von Wasser- bzw. Säuregehalt, Durchmischung, verschiedenen Schmelzenzusätzen bzw. Reaktionstemperatur zu steigern. Das entstehende Verhältnis der Isomeren der Mono- und Dinitrierung wurde hinsichtlich einer möglichen Beeinflussung untersucht. Das Spektrum an Nebenprodukten wurde bestimmt, sowie Möglichkeiten aufgezeigt, diese zu vermeiden. Dabei konnte gezeigt werden, dass im Gegensatz zum etablierten Mischsäureverfahren beim Einsatz von Salzhydratschmelzen keine kresolischen Nebenprodukte gebildet werden. Weiterhin wurden Möglichkeiten zur Präparation wasserarmer Salzhydratschmelzen durch thermische Entwässerung bzw. Reaktion mit flüssigem N2O4 untersucht, die Löslichkeit der isomeren Zwischen- und Endprodukte in der Salzhydratschmelze bestimmt sowie das thermische Verhalten von Dinitrotoluol in Gegenwart der Salze betrachtet.

La valorisation, comme granulats, des matériaux issus du recyclage du béton de démolition contribueà diminuer les surfaces dédiées au stockage des déchets et à limiter le recours systématique auxressources naturelles. L’emploi de fines recyclées à partir de béton de déconstruction s’inscrit danscette démarche et permet par ailleurs, quand la fine est utilisée en substitution partielle du cimentlors de la fabrication de nouveaux matériaux cimentaires, de réduire l’impact sur l’environnement deces matériaux.Cet usage conduit à mettre en présence dans la pâte à l’état frais du ciment anhydre et du cimenthydraté, ce qui pose la question de l’impact de cette situation sur le matériau. Pour y répondre enpartie, les travaux de recherche présentés dans cette thèse ont pour objectifs principaux d’étudier leprocessus d’hydratation d’une phase anhydre en présence d’autres phases hydratées, et d’analyserl’influence des conditions thermo-hydriques de conservation (HR et T°) sur les cinétiquesd’hydratation des matériaux cimentaires.Pour ce faire, une campagne expérimentale a été menée sur des mortiers et leurs pâtes de cimentéquivalentes fabriqués en remplaçant une partie de leur ciment Portland par une fine issue durecyclage d’une pâte de ciment durcie et bien hydratée. Un suivi au cours du temps des teneurs enPortlandite, de la porosité totale, de la résistance à la compression ainsi que de la résistance à lacarbonatation accélérée des matériaux a été réalisé. Les résultats obtenus montrent qu’il est possiblede fabriquer des mortiers en substituant le ciment par une fine obtenue uniquement par concassageet broyage d’une pâte de ciment durcie. Cependant, l’augmentation du taux de substitution massiquedu ciment par la fine recyclée s’accompagne d’une altération des propriétés et performances desmortiers. Les résultats du suivi d’hydratation couplés aux résultats d’analyse de la microstructure ontmontré que l’effet des conditions thermo-hydriques de conservation sur les cinétiques d’hydratationdes différentes pâtes de ciment dépend de leurs propriétés intrinsèques (microstructure). Celapourrait expliquer l’absence de consensus dans la littérature sur la valeur de l’humidité relativeambiante conduisant à l’arrêt de l’hydratation.En parallèle à l’étude expérimentale, une étude numérique de l’influence des conditions thermohydriquesde conservation sur l’hydratation des pâtes de ciment a été menée. Pour les besoins del’étude, une réadaptation du code de calcul utilisé, CEMHYD3D, a été nécessaire. Les résultatsobtenus montrent que, lors de l’hydratation, la Portlandite initialement présente dans le matériau(apportée par la fine recyclée) se dissout au contact de l’eau alors que la phase encore anhydre enproduit. Cette étude a également permis de conforter les résultats expérimentaux quant à l’influencede l’humidité relative ambiante sur l’hydratation. / The use, as aggregates, of recycled materials from demolished concrete contributes to limit landfill and the systematic use of natural resources. Using recycled fines from the deconstruction concrete is an extension of this approach. When used as a partial substitution for cement in cementitious materials, it may also be a solution to reduce the environmental impact of these materials.This specific use induces the presence of anhydrous cement particles and hydrated cement phases in the fresh material. This raises the question whether and how it can impact the hydration process. With the aim to answer, at least partially, to this question, the thesis presents a study of the hydration process of an anhydrous phase in the presence of other hydrated phases, and analyzes the influence of the conservation conditions (RH and T°) on the hydration kinetics of cementitious materials.An experimental campaign was conducted on mortars and their equivalent cement pastes designed by replacing a part of their Portland cement by a recycled cement paste fine. The monitoring of the Portlandite content, the total porosity, the compressive strength and the accelerated carbonation of the materials was achieved. The obtained results show that it is possible to design mortars by substituting their cement by a fine obtained only from crushing and grinding of a hardened cement paste. However, increasing the substitution ratio of the cement by the recycled fine was find to be accompanied by a deterioration of the mortars properties and performances. The results of the hydration monitoring coupled to investigations of the microstructure showed that the effect of conservation conditions on the hydration kinetics of the different cement pastes depends on their intrinsic properties (microstructure). This could explain the lack of consensus in the literature on the drying conditions under which hydration kinetics are strongly affected.In parallel to the experimental study, a numerical study of the influence of the conservation conditions on the hydration of cement pastes was conducted. Readjustments of the parameters of the used code (CEMHYD3D) were necessary. The obtained results show that, during hydration, the Portlandite originally present in the material (provided by the recycled fine) dissolves in contact with water, while the anhydrous phase produces new Portlandite. This study consolidated moreover the experimental results on the influence of the ambient relative humidity on hydration.