Thèses : « CO2 fluid »

1

Kus, Bartosz. « Oil-free turbocompressors for CO2 as working fluid ». Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23781.

Texte intégral

Résumé :

Compressing equipment can be found in almost every area of our industrialized society. Compressors drive our fridges, air conditioning systems and enable turbine engines to propel the aircrafts we use when going for holidays or a business trip. Without compressors an operation of virtually any conventional power plant providing electricity to our houses would not be possible. The compressor technology can therefore be regarded as a mature area of engineering with a vast theoretical and operational experience. It may happen however that a traditional approach to certain new problems will not suffice, and alternative ways must be searched for. Such open-mindedness was required when the idea of introducing an oil-free compressor for a CO2 commercial refrigeration system was born. Initially, hermetic radial turbomachinery was identified as a potential candidate for this task. However, it turned out that rather special properties of carbon dioxide, compared to other common refrigerants, will result in challenges uncommon in turbomachinery found in other applications. While the initial technology choice still seemed feasible, high density of the CO2 at relevant operating conditions and significant rotational speeds required for a relatively small machine were indicating excessive levels of windage losses generated by the spinning rotor of the compressor. It was decided to build a 1D tool for prediction of efficiencies for a wide range of machines based on a radial turbocompressor principle, but designed for CO2 applications with different operating pressures and capacities. The predictions of the tool were compared against numerical and experimental data. Good match was found. The 1D study revealed that high compression efficiencies, exceeding 70 %, are possible for the oil-free radial compressor concept in a relatively wide range of capacities provided that the inlet pressure is low, around 1 MPa, and that the pressure ratio is moderate, below 3. Potential for good efficiency is expected to deteriorate rapidly with increasing operational pressures due to windage losses. There is no obvious strategy for improvement of overall compressor efficiency when smaller capacities and close to supercritical pressures are in the focus. The major fraction of undesirable rotational losses is generated by the electrical motor. It can be reduced either by installing longer more slender motor or by reduction of rotational speeds. Efficiency improvement reached with application of a longer motor is shown to be of limited impact and is expected to be challenging from the rotordynamics point of view. Alternatively, multi-stage multi-shaft machine can be designed, but economic viability of such a strategy remains questionable. Reduction of the compressor speed is not straightforward either, especially at low volumetric flows when low speeds would be detrimental to the impeller and diffuser efficiency. A non-standard approach introducing partially admitted radial machine was therefore proposed. A numerical analysis of a partially admitted compressor stage with a 16 cm impeller rotating at 13000 rpm is carried out. Transient 2D simulations indicate more than 80% efficiency of the wheel at the total pressure ratio of around 1.4. To estimate the final stage efficiency, 3D effects such as the end-wall losses, the radial leakage, and the diffuser performance must be taken into account. A transient 3D analysis of the complete stage of the novel compressor has not been completed due to its time consuming nature. 3D simulations performed for various diffuser configurations indicate however that around 75% overall stage efficiencies might be possible. It would require further optimization of both blade and diffuser shapes. Comparison of non-stage losses, for both centrifugal and partial admission concepts, allow presuming that the novel machine could be superior in terms of the overall performance provided that comparable systems are characterized by close to supercritical mean operating pressures and capacities typical for commercial scale applications. To verify the initial insights of the present work, further research, including laboratory testing, is needed.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Gharbi, Oussama. « Fluid-rock interactions in carbonates : applications to CO2 storage ». Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24928.

Texte intégral

Résumé :

It is well established that more than half of the world's hydrocarbon reserves are contained in carbonate reservoirs. In a global context, which is characterized by an increasing demand in energy, population growth and overall economic development, it is very important to unlock potential carbonate resources while mitigating the effects of climate change. Moreover, significant volumes of carbon dioxide - the major greenhouse gas contributor to global warming - can be stored in carbonate subsurface formations such as carbonate depleted reservoirs and deep saline aquifers. Therefore, better understanding of carbonate porous media has a wide range of major industrial and environmental applications. However, because of complex pore structures, including the presence of micro-porosity, heterogeneities at different scales, combined with high chemical reactivity, it remains very challenging to describe flow and transport in carbonates. In this thesis, we focus on carbonate porous media and aim to better describe flow, transport and reaction in them. The main application of this work is related to carbon storage in deep saline carbonate aquifers. More particularly, we address fluid-rock interactions e.g. wettability alterations and reactive transport, that occur in carbonate formations. First, we investigate the impact of wettability alteration on multi-phase flow properties. We use pore-network modelling to analyze the impact of wettability alteration by modelling water-flood relative permeability for six different carbonate samples with different connectivity. Pore-scale multi-phase flow physics is described in detail and the efficiency of water-flooding in mixed-wet carbonates is related to the wettability and pore connectivity. We study six carbonate samples. Four quarry samples - Indiana, Portland, Guiting and Mount Gambier - and two subsurface samples obtained from a deep saline Middle Eastern aquifer. The pore space is imaged in three dimensions using X-ray micro-tomography at a resolution of a few microns. The images are segmented into pore and void and a topologically representative network of pores and throats is extracted from these images. We then simulate quasi-static displacement in the networks. We represent mixed-wet behaviour by varying the oil-wet fraction of the pore space. The relative permeability is strongly dependent on both the wettability and the average coordination number of the network. We show that traditional measures of wettability based on the point where the relative permeability curves cross are not reliable. Good agreement is found between our calculations and measurements of relative permeability on carbonates in the literature. The work helps establish a library of benchmark samples for multi-phase flow and transport computations. The implications of the results for field-scale displacement mechanisms are discussed, and the efficiency of waterflooding as an oil recovery process in carbonate reservoirs is assessed depending on the wettability and pore space connectivity. Secondly, we investigate at the laboratory column scale (50 cm), fluid-rock interactions that occur through the injection of an acidic solution into carbonate porous media. Laboratory columns are packed with crushed and sieved porous Guiting carbonate grains. Therefore a homogenous porous medium at the Darcy scale is created and the effect of micro-heterogeneities on transport and reactive transport properties is highlighted. We first conduct a series of passive tracer experiments. Salinity is used as a non-reactive tracer as brine is injected at a constant flow rate into columns pre-saturated with equilibrated deionised water. Solute breakthrough curves are experimentally obtained by measuring the conductivity of collected effluent samples. Subsequently, by solving the advection-dispersion equations using PHREEQC geochemical software, we compare the experimental measurements with numerical predictions of breakthrough curves. A good match is obtained for a dual porosity model and a dispersion coefficient is estimated. We then investigate reactive transport by injecting at constant flow rate acidic brine (hydrochloric acid diluted in saline brine with an overall pH of 3) into columns pre-saturated with equilibrated brine. We measure the effluent concentrations using ICP-AES (inductively coupled plasma atomic emission spectroscopy) Moreover; scanning electron microscopy (SEM) is used to determine single grain-scale changes. We assess the impact of flow rate on the resident time distribution of solutes and reaction profiles along the columns. We discuss challenges encountered regarding the reproducibility of the results and we highlight the implications of such phenomenological studies on carbon storage in carbonates. Finally, we experimentally examine fluid-rock interactions that are induced by the injection of supercritical CO2 (sc-CO2) in carbonate formations at the pore scale. I designed and built a novel experimental apparatus that allows the injection of brine enriched with sc-CO2 at typical CO2 storage conditions. In our experiments the temperature is 500C and the injecting pressure is 9MPa. A novel methodology that combines pore-scale imaging, core flooding and pore-scale modelling is applied in the context of CO2-carbonate-brine interactions. We experimentally use a high pressure and temperature mixing vessel to generate brines enriched with sc-CO2.The mixture is then injected using high precision piston pumps at a constant flow rate (Q=0.1 ml/min) into carbonate micro samples (5 mm diameter and 20 mm length) saturated with pre-equilibrated high salinity brine. We measure the permeability changes in real time during the injection of reactive fluids, In addition, dry high-resolution micro-computed tomography scans are obtained prior to and after the experiments and the pore structure, connectivity and computed flow fields are compared using image analysis and pore-scale modelling techniques. We perform direct simulations of transport properties and velocity fields on the three-dimensional scans and we extract representative pore-throat networks to compute average coordination number and assess changes in pore and throat size distributions. Moreover, we assess the impact of reaction rate on reactive transport. We alter the reaction rate and hence the Damköhler number by under saturating the sc-CO2/brine mixture with crushed and sieved carbonate grains. Two regimes of dissolution are experimentally observed: dominant wormholing and a more uniform dissolution regime. High resolution 3D scans of the dissolution patterns confirm these observations. Permeability increases over several order of magnitude with wormholing whereas for the uniform dissolution, the increase in permeability is less pronounced. Overall, fewer pore and throats are present after dissolution while the average coordination number does not change significantly. Flow becomes concentrated in the wormhole regions after reactions although a very wide range of velocities is still observed. We then compare the observed results for single phase flow (wormholing induced by the injection of single phase brine saturated with sc-CO2) to two-phase flow reactive flow experiments (co injection of sc-CO2 and brine). Results show that wormholing is also seen in the two-phase experiments. Directions for future research in the area of fluid-rock interactions are then discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

3

REMIGI, SAMANTHA. « On the application of Raman micro-spectroscopy to the characterization of Earth's CO2 fluids ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/325898.

Texte intégral

Résumé :

Questa tesi indaga l'applicabilità della micro-spettroscopia Raman per migliorare la caratterizzazione dei fluidi a CO2 terrestri, intrappolati come inclusioni fluide (FI) nelle peridotiti. Nello spettro Raman della CO2, la distanza delle due vibrazioni fondamentali è densità (d) dipendente, inoltre sono visibili le vibrazioni 13CO2 e 12CO2. Ciò permette alla micro-spettroscopia Raman di avere il potenziale per caratterizzare in situ FI a CO2, consentendo di comprendere meglio i meccanismi di trasporto del C all'interno della Terra. La proporzionalità tra le aree 13CO2 e 12CO2 con la loro concentrazione molare permette di calcolare il δ13CCO2 tramite micro-spettroscopia Raman. I rapporti delle aree richiedono precisione sulla 4° decimale per dare valori di δ13CCO2 rappresentativi dei serbatoi naturali terrestri. Gli spettri Raman sono influenzati da inevitabili effetti casuali che riducono la precisione dell'area. 42 FI a CO2 pura di alta d, provenienti dalla regione del Lago Tana e da El Hierro, sono state analizzate. Per ogni FI sono state acquisite due serie di spettri con tempi di acquisizione diversi. Di 84 serie di analisi, 23 avevano rapporti di area 13CO2/12CO2 diversi tra loro di più di un ordine di grandezza. Questi sono stati rimossi dal dataset. Il 95% dei restanti 61 set aveva riproducibilità dei rapporti di area <≈4‰, consentendo di calcolare valori di δ13CCO2 con precisione <±≈2‰. Solo poche analisi erano caratterizzate da una minore precisione. I valori di δ13CCO2 calcolati per FI nelle peridotiti dalla regione del Lago Tana hanno mostrato un’origine di mantello per la CO2, mentre quelli nelle peridotiti di El Hierro dai valori tipici di mantello. L'accuratezza delle misure è stata verificata tramite spettrometria di massa. Questa ha dimostrato che i valori di δ13CCO2 calcolati erano accurati, e consentivano di modellare la variazione isotopica a scala minerale. L’applicabilità della micro-spettroscopia Raman come densimetro per i fluidi a CO2 è stata precedentemente studiata. Molte equazioni di densimetro calcolano d differenti per gli stessi Δ, con distribuzione grafica bimodale, la cui origine non è stata ben compresa. L'origine di questa distribuzione è stata studiata nel presente lavoro calcolando la d di 40 FI a CO2 pura, provenienti da El Hierro, mediante microtermometria. I Δ sono stati misurati acquisendo spettri Raman con una procedura simile a quella adottata per altri densimetri, con risoluzione spettrale per px ≈1,50 cm-1/px. La distribuzione dei dati Δ-d è stata fittata al meglio con un'equazione polinomiale di III°, permettendo di calcolare le d della CO2 con un errore di ±0.015 g/cm3. L’equazione plottava con quelle ottenute mediante una risoluzione spettrale per px simile. Gli intervalli di confidenza al 95% della distribuzione Δ-d per tutte le equazioni sono stati calcolati mediante un algoritmo statistico. I CI hanno permesso di valutare l'accuratezza dei valori Δ-d e di definire un punto di cut-off al di sotto del quale la potenza di stima della d era bassa. Per tutti i densimetri, il punto di cut-off corrispondeva al punto in cui le distanze relative dei CI erano <7.5% (coincidenti con CO2 gassosa a P-T ambiente). Il confronto tra CI al 95% delle equazioni a bassa ed alta risoluzione spettrale per px ha mostrato che densimetri con risoluzione calcolano d statisticamente equivalente con una confidenza del 95%. Al contrario, densimetri con risoluzione diversa calcolano d non confrontabili. I risultati ottenuti hanno consentito di proporre un metodo preliminare per calcolare in situ i δ13CCO2 con una precisione ≈±2% per il 95% delle analisi. Inoltre, questi hanno migliorato la conoscenza della distribuzione Δ-d dei densimetri Raman, indicando che d di CO2 calcolate per mezzo di equazioni con risoluzione spettrale simile sono statisticamente equivalenti al 95% di confidenza per FI aventi d vicino e al di sopra del punto critico di CO2.
This thesis investigates the applicability of Raman micro-spectroscopy for CO2 density (d) and δ13CCO2 values calculations to improve characterisation of CO2 Earth’s fluid trapped as fluid inclusions (FI) in peridotites. Based on the properties of CO2 Raman spectrum, where the distance of two main vibrations is d-dependent and 13CO2 and 12CO2 vibrations are present, Raman micro-spectroscopy has the potential to become a complementary technique for in situ characterisation of CO2 FI, allowing to better understand the C transport mechanisms within Earth. The calculation of CCO2 isotopic composition by mean of Raman micro-spectroscopy is possible due to the proportionality between 13CO2 and 12CO2 areas with their molar concentration. Calculation of area ratios requires precision at 4th decimal place to obtain δ13CCO2 values representative of Earth’s natural reservoirs. Raman spectra are affected by unavoidable random effects that reduce area measurements’ precision. 42 high-d CO2-pure FI from Lake Tana region and El Hierro have been analysed. For each inclusion, two sets of spectra have been acquired by mean of different acquisition times. Among the 84 set of measurements, 23 were characterised by 13CO2/12CO2 area ratios differing more than one order of magnitude one another. These have been removed from dataset. 95% of remaining 61 sets were characterised by area ratios reproducibility <≈4‰, allowing to calculate FI δ13CCO2 values with precision <±≈2‰. Only few analyses were characterised by lower precision. Calculated δ13CCO2 values for FI trapped in peridotites from Lake Tana region showed CO2 mantle origin, while for those in peridotites from El Hierro differed from mantle isotopic signature. Accuracy of measurement has been checked by bulk measurements, proving that calculated δ13CCO2 values were accurate, and allowing to model δ13CCO2 variations at single mineral scale. The adoption of Raman micro-spectroscopy for calculating CO2 fluid d has been previously investigated. Many densimeter equations calculate different d for the same Δ values, with a bimodal graphic distribution, whose origin was not well understood. The origin of this distribution has been investigated in present work by calculating the d of 40 CO2-pure FI trapped in mantle xenoliths from El Hierro by mean of microthermometry. CO2 FI Δ values have been measured by acquiring Raman spectra applying analytical parameters common to those adopted for other densimeter equations, with spectral per px resolution ≈1.50 cm-1/px. A 3rd order polynomial equation best fitted obtained Δ-d data distribution. Equation calculates CO2 d with an error of ±0.015 g/cm3, and plots with those obtained by mean of a similar spectral per px resolution. The 95% confidence interval (CI) of Δ-d distribution for all the equations has been calculated by a bootstrapping statistical algorithm. CIs allowed to assess the accuracy of measured Δ-d values and define a cut-off point below which the CO2 d estimation power is low. For all the densimeters, cut-off point has been set where the relative distances of computed CIs were <7.5%, which corresponded for all the equations to gas-like CO2 at ambient conditions. The comparison of 95% CIs calculated for high and low spectral resolution per px equations showed that densimeters with similar spectral per px resolution calculate statistically equivalent CO2 d at 95% confidence. In contrast, densimeters with different resolution calculate incomparable CO2 d.Obtained results allowed to preliminarily propose an analytical procedure to calculate in situ δ13CCO2 with a precision of ≈±2% for 95% of the analyses. Moreover, these improved the knowledge about Δ-d distribution of Raman densimeters, indicating that CO2 d calculated by mean of equations having similar spectral resolution are statistically equivalent at 95% confidence for CO2 FI having d values near and above the CO2 critical point.

Styles APA, Harvard, Vancouver, ISO, etc.

4

Kilpatrick, Andrew David. « Fluid-mineral-CO2 interactions during geological storage of carbon dioxide ». Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8889/.

Texte intégral

Résumé :

In order utilise geological carbon dioxide storage (GCS) at an industrial scale predictions of reservoir scale behaviour, both chemical and physical must be made. In order to ground-truth the geochemical data underlying such predictions, laboratory experiments at temperatures and CO2 pressures relevant to GCS are essential. Mineral dissolution rate, CO2 solubility and pH data has been collected from batch experiments carried out on quartz, K-feldspar, albite, calcite, dolomite and Sherwood Sandstone materials. These experiments were designed to assess the influence of a variety of factors on dissolution rates: changes in grain size from 125μm - 180μm to 500μm - 600μm; changes in fluid composition from deionised water to 1.36M NaCl solution; changes in CO2 pressure from 4 bar to 31 bar; changes in temperature from 22°C to 70°C. Experiments carried out on the Sherwood Sandstone material also included work on consolidated rock, rather than the powder used in other experiments. Calculated dissolution rates for silicates were found to agree well with values calculated from literature-sourced dissolution equations and the USGS-produced general rate equation (USGS 2004) was found to be suitable for predicting these rates. Calculated dissolution rates for the carbonate minerals was found to be strongly retarded due to transport effects, with literature-sourced equations significantly over-predicting dissolution rates. Dissolution of the sandstone material was found to be dominated by K-feldspar and dolomite dissolution, rates of which compare favourably with those obtained from the single mineral experiments. A significant increase in porosity was observed in the core flow-through experiment, associated with dolomite dissolution. Several experiments were carried out using a Hele-Shaw cell in order to visualise the formation and migration of density plumes which form as CO2 dissolved into unsaturated fluids. Introduction of NaCl and decreases in permeability were found to significantly retard migration of CO2 saturated fluid, while minor heterogeneities in the cells served to focus and accelerate plume movement. Modelling work suggests that predictive models currently underestimate the rapidity of formation and migration of these plumes.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Kleine, Barbara. « How do fluids move through rocks ? : High fluxes of CO2 in the Earth's crust ». Licentiate thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-84007.

Texte intégral

Résumé :

Metamorphic hydrous, CO2-bearing fluids play a critical role in the global carbon cycle. However, how big this influence is on the global carbon cycle and therefore on global climatic processes, is unknown. The actual amount of CO2 which is released into the atmosphere due to metamorphic processes is still debated. For this purpose, fluid-driven reactions in metamorphic rocks must be studied by tracking fluid-rock interactions along pathways of ancient fluids. In the study presented in this thesis, we study fluid-rock interaction in the southeastern part of the Greek island Syros in the Cycladic Archipelago (Aegean). On Syros fluid-rock interaction is recorded by the preservation of blueschist facies assemblages at greenschist facies conditions along a normal shear zone. Blueschist preservation is caused by a combination of metasomatic addition of SiO2 and Na2O and elevated XCO2 which is maintained by high fluxes of a CO2-bearing, hydrous fluid along the shear zone. This research aims to provide a better understanding of the role of mountain building in the carbon cycle. Flux estimates for climate-forcing fluid components (e.g. carbon) require that their concentration in the fluid, fluid volumes and velocities are known. This will be the focus of future work. Further, whole rock chemistry and the availability of specific minerals will be studied to achieve knowledge about which kind of parameters influence and enhance the propagation of fluids through rocks.

Styles APA, Harvard, Vancouver, ISO, etc.

6

Lindon, Michael Allen. « CO2 Dissociation using the Versatile Atmospheric Dielectric Barrier Discharge Experiment (VADER) ». Thesis, West Virginia University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3618122.

Texte intégral

Résumé :

As of 2013, the Carbon Dioxide Information Analysis Center (CDIAC) estimates that the world emits approximately 36 trillion metric tons of Carbon Dioxide (CO₂) into the atmosphere every year. These large emissions have been correlated to global warming trends that have many consequences across the globe, including glacial retraction, ocean acidification and increased severity of weather events. With green technologies still in the infancy stage, it can be expected that CO₂ emissions will stay this way for along time to come. Approximately 41% of the emissions are due to electricity production, which pump out condensed forms of CO₂. This danger to our world is why research towards new and innovative ways of controlling CO₂ emissions from these large sources is necessary.

As of now, research is focused on two primary methods of CO₂ reduction from condensed CO₂ emission sources (like fossil fuel power plants): Carbon Capture and Sequestration (CCS) and Carbon Capture and Utilization (CCU). CCS is the process of collecting CO₂ using absorbers or chemicals, extracting the gas from those absorbers and finally pumping the gas into reservoirs. CCU on the other hand, is the process of reacting CO₂ to form value added chemicals, which can then be recycled or stored chemically.

A Dielectric Barrier discharge (DBD) is a pulsed, low temperature, non-thermal, atmospheric pressure plasma which creates high energy electrons suitable for dissociating CO₂ into its components (CO and O) as one step in the CCU process. Here I discuss the viability of using a DBD for CO₂ dissociation on an industrial scale as well as the fundamental physics and chemistry of a DBD for CO₂ dissociation. This work involved modeling the DBD discharge and chemistry, which showed that there are specific chemical pathways and plasma parameters that can be adjusted to improve the CO₂ reaction efficiencies and rates. Experimental studies using the Versatile Atmospheric dielectric barrier Discharge ExpeRiment (VADER) demonstrated how different factors, like voltage, frequency and the addition of a photocatalyst, change the efficiency of CO₂ dissociation in VADER and the plasma chemistry involved.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Beier, Katja [Verfasser]. « CO2-Sequestration on Laboratory Scale : Geochemical Interactions Between Injected CO2, Saline Fluid Phases, and Potential Reservoir Materials / Katja Beier ». Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1023040786/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

8

Yang, Chen. « Thermodynamic Cycles using Carbon Dioxide as Working Fluid : CO2 transcritical power cycle study ». Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50261.

Texte intégral

Résumé :

The interest in utilizing the energy in low‐grade heat sources and waste heat is increasing. There is an abundance of such heat sources, but their utilization today is insufficient, mainly due to the limitations of the conventional power cycles in such applications, such as low efficiency, bulky size or moisture at the expansion outlet (e.g. problems for turbine blades). Carbon dioxide (CO2) has been widely investigated for use as a working fluid in refrigeration cycles, because it has no ozonedepleting potential (ODP) and low global warming potential (GWP). It is also inexpensive, non‐explosive, non‐flammable and abundant in nature. At the same time, CO2 has advantages in use as a working fluid in low‐grade heat resource recovery and energy conversion from waste heat, mainly because it can create a better matching to the heat source temperature profile in the supercritical region to reduce the irreversibility during the heating process. Nevertheless, the research in such applications is very limited. This study investigates the potential of using carbon dioxide as a working fluid in power cycles for low‐grade heat source/waste heat recovery. At the beginning of this study, basic CO2 power cycles, namely carbon dioxide transcritical power cycle, carbon dioxide Brayton cycle and carbon dioxide cooling and power combined cycle were simulated and studied to see their potential in different applications (e.g. low‐grade heat source applications, automobile applications and heat and power cogeneration applications). For the applications in automobile industries, low pressure drop on the engine’s exhaust gas side is crucial to not reducing the engine’s performance. Therefore, a heat exchanger with low‐pressure drop on the secondary side (i.e. the gas side) was also designed, simulated and tested with water and engine exhaust gases at the early stage of the study (Appendix 2). The study subsequently focused mainly on carbon dioxide transcritical power cycle, which has a wide range of applications. The performance of the carbon dioxide transcritical power cycle has been simulated and compared with the other most commonly employed power cycles in lowgrade heat source utilizations, i.e. the Organic Rankin Cycle (ORC). Furthermore, the annual performance of the carbon dioxide transcritical power cycle in utilizing the low‐grade heat source (i.e. solar) has also been simulated and analyzed with dynamic simulation in this work. Last but not least, the matching of the temperature profiles in the heat exchangers for CO2 and its influence on the cycle performance have also been discussed. Second law thermodynamic analyses of the carbon dioxide transcritical power systems have been completed. The simulation models have been mainly developed in the software known as Engineering Equation Solver (EES)1 for both cycle analyses and computer‐aided heat exchanger designs. The model has also been connected to TRNSYS for dynamic system annual performance simulations. In addition, Refprop 7.02 is used for calculating the working fluid properties, and the CFD tool (COMSOL) 3 has been employed to investigate the particular phenomena influencing the heat exchanger performance.
QC 20111205

Styles APA, Harvard, Vancouver, ISO, etc.

9

Elnan, Åsmund. « Development of new heat pump cloth drum dryer with CO2 as working fluid ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18342.

Texte intégral

Résumé :

Since early the early 20th century the electrical tumble dryer became an appliance to dry clothes. During many years of improvements different configurations to solve issues on decreased drying time and more energy efficient solutions has been performed. Several different configurations have been developed; air vented dryers, condensing dryers and the most recent heat pump dryers. The heat pumps in drying technology became the next solution based on improved drying time and decreased energy consumption. With today’s focus on energy consumption, with energy demanding appliance such as the clothes dryer; new technology that satisfy the customers need must be available. By introducing the heat pump to the drying technology, a suitable refrigerant must be chosen. The choice should be based on several factors; the performance of the heat pump and the refrigerants GWP and ODP values, its toxicity and safety for the consumer. This report is based on a heat pump dryer made for an R134a system. R134a has a global warming potential (GWP) 1300 times the value of R744 (carbon dioxide). This report will present the feasibility of replacing the R134a system with a system designed for carbon dioxide as refrigerant. Carbon dioxide or R744 is a natural refrigerant, and it is in contrast to other commonly used refrigerants operating in the transcritical region. This implies that the heat rejection is performed with gliding temperature exchange, not by condensation as for the R134a. This is due to the low critical temperature of carbon dioxide; a critical pressure of 73.8 Bara and a critical temperature of 31.1˚C. Despite the required high pressures, the heat exchange properties of carbon dioxide in the critical region are very good, and new technology can take advantage of this. By SINTEF developed simulation tool HX SIM Basic 2007, based on results from the R134a cycle, heat exchangers have been designed to reach the optimal solution. The capacity of the heat changers and the compressor will be the same as the R134a system. The system is built with a manual throttling valve in parallel to a capillary tube, during the experiments the system will be tested to find the most optimal set point. Evaporating pressures from 40 to 50 Bara and gas cooler pressures from critical pressures to 120 Bara have been applied in the experiments. The main purpose of the experiments is to find a system design that will fulfil both energy saving requirements and have a simple enough construction for it to be a market product. Based on the experiments on this first prototype and the results obtained; a conclusion is that the dryer with CO2 as refrigerant is using marginally more energy than the R134a system. However this is a first prototype and its potential should be investigated further.

Styles APA, Harvard, Vancouver, ISO, etc.

10

Wigley, Max Merlin. « Fluid-mineral reactions in an exhumed CO2-charged aquifer, Green River, Utah, USA ». Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608145.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

11

VITALI, MATTEO. « Thermodynamic and fluid-dynamic challenges associated with the transport of CO2 via pipelines ». Doctoral thesis, Università Politecnica delle Marche, 2022. http://hdl.handle.net/11566/299669.

Texte intégral

Résumé :

The emissions related to the human activities that led to greenhouse effect can be related, but not limited to, the carbon dioxide emissions. Carbon Capture Utilization and Storage (CCUS) is claimed as a solid climate mitigation strategy in particular for the most challenging missions. The development of an international CO2 transportation network is considered a necessary cross-cutting topic in the Carbon Capture and Storage sector. Indeed, the development of large-scale CCUS projects will require the management and transport of CO2 in the presence of impurities and with lower costs. The accuracy of modelling CO2 in the presence of other components needs to be further assessed and lots of thermodynamic aspects of CO2 management are still object of debate and research. In this work the thermodynamic and fluid-dynamic challenges associated with the transport of CO2 via pipelines have been investigated. A complete and critical review of the main thermodynamics aspects involved during the transport of CO2 at high-pressure has been presented. The aspects related to risk and safety of CO2 pipelines have been deeply analysed with specific focus on the modelling of accidental releases with computational fluid dynamic and simplified models. Furthermore, an assessment of the most suitable equations of state for the accurate modelling of CO2 in presence of impurities is also proposed with quantitative and qualitative conclusions. Moreover, the transient transport phenomena involved for the transport of dense-phase CO2 have been analysed experimentally and numerically. Horizontal depressurization behaviour have been modelled with numerical thermofluid-dynamic simulations and validated against experimental data obtained from high-resolution measurements on a state-of-the-art large scale laboratory. This work includes also some experimental activity performed for the study of vertical flows in CO2 pipes for injection and the development of a data extraction and processing tool. Finally, the simulation of running shear fracture and its implication in CO2 have been also discussed and a tool for the simulation of decompression in CO2-rich mixtures has been developed and validated.
Le emissioni legate alle attività umane che hanno portato all'effetto serra sono attribuibili alle emissioni di anidride carbonica. La cattura, utilizzo e stoccaggio dell’anidride carbonica (CCUS) è considerata una solida strategia di mitigazione del clima, in particolare per le missioni più impegnative. Lo sviluppo di una rete di trasporto internazionale di CO2 è considerato un tema trasversale necessario nel settore della cattura e dello stoccaggio del carbonio. Infatti, lo sviluppo di progetti CCUS su larga scala richiederà la gestione e il trasporto di CO2 in presenza di impurità e con costi inferiori. L'accuratezza della modellazione della CO2 in presenza di altri componenti deve essere ulteriormente valutata e molti aspetti termodinamici della gestione della CO2 sono ancora oggetto di dibattito e ricerca. In questo lavoro sono state studiate le sfide termodinamiche e fluidodinamiche associate al trasporto di CO2 tramite condotte. È stata presentata una rassegna completa e critica dei principali aspetti termodinamici coinvolti nel trasporto di CO2 ad alta pressione. Gli aspetti relativi al rischio e alla sicurezza delle condotte di CO2 sono stati approfonditi con focus specifico sulla modellazione dei rilasci accidentali con modelli fluidodinamici computazionali e semplificati. Viene inoltre proposta, con conclusioni quantitative e qualitative, una valutazione delle equazioni di stato più idonee per la modellizzazione accurata della CO2 in presenza di impurità. Sono stati altresì analizzati sperimentalmente e numericamente i fenomeni di trasporto transitorio coinvolti nel trasporto di CO2 in fase densa. Il comportamento della depressurizzazione orizzontale è stato modellato con simulazioni termofluidodinamiche numeriche e convalidato rispetto a dati sperimentali ottenuti da misurazioni ad alta risoluzione su un laboratorio all'avanguardia su larga scala. Questo lavoro comprende anche alcune attività sperimentali svolte per lo studio dei flussi verticali nei tubi di CO2 per l'iniezione e lo sviluppo di uno strumento di estrazione ed elaborazione dati. Infine, è stata discussa anche la simulazione della frattura duttile e la sua implicazione nella CO2 ed è stato sviluppato e validato uno strumento per la simulazione della decompressione in miscele ricche di CO2.

Styles APA, Harvard, Vancouver, ISO, etc.

12

López, de Ramos Aura Luisa. « Capillary enhanced diffusion of CO2 in porous media / ». Access abstract and link to full text, 1993. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9400131.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

13

Kampman, Niko. « Fluid-rock interactions in a carbon storage site analogue, Green River, Utah ». Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/244506.

Texte intégral

Résumé :

Reactions between CO2-charged brines and reservoir minerals might either enhance the long-term storage of CO2 in geological reservoirs or facilitate leakage by corroding cap rocks and fault seals. Modelling the progress of such reactions is frustrated by uncertainties in the absolute mineral surface reaction rates and the significance of other rate limiting steps in natural systems. This study uses the chemical evolution of groundwater from the Jurassic Navajo Sandstone, part of a leaking natural accumulation of CO2 at Green River, Utah, in the Colorado Plateau, USA, to place constraints on the rates and potential controlling mechanisms of the mineral-fluid reactions,under elevated CO2 pressures, in a natural system. The progress of individual reactions, inferred from changes in groundwater chemistry is modelled using mass balance techniques. The mineral reactions are close to stoichiometric with plagioclase and K-feldspar dissolution largely balanced by precipitation of clay minerals and carbonate. Mineral modes, in conjunction with published surface area measurements and flow rates estimated from hydraulic head measurements, are then used to quantify the kinetics of feldspar dissolution. Maximum estimated dissolution rates for plagioclase and K-feldspar are 2x10-14 and 4x10-16 mol·m-2·s-1, respectively. Fluid ion-activity products are close to equilibrium (e.g. DGr for plagioclase between -2 and -10 kJ/mol) and lie in the region in which mineral surface reaction rates show a strong dependence on DGr. Local variation in DGr is attributed to the injection and disassociation of CO2 which initially depresses silicate mineral saturation in the fluid, promoting feldspar dissolution. With progressive flow through the aquifer, feldspar hydrolysis reactions consume H+ and liberate solutes to solution which increase mineral saturation in the fluid and rates slow as a consequence. The measured plagioclase dissolution rates at low DGr would be compatible with far-from-quilibrium rates of ~1x10-13 mol·m-2·s-1 as observed in some experimental studies. This suggests that the discrepancy between field and laboratory reaction rates may in part be explained by the differences in the thermodynamic state of natural and experimental fluids, with field-scale reactions occurring close to equilibrium whereas most laboratory experiments are run far-from-equilibrium. Surface carbonate deposits and cementation within the footwall of the local fault systems record multiple injections of CO2 into the Navajo Aquifer and leakage of CO2 from the site over ca. 400,000 years. The d18O, d13C and 87Sr/86Sr of these deposits record rapid rates of CO2 leakage (up to ~1000 tonnes/a) following injection of CO2, but rates differ by an order of magnitude between each fault, due to differences in the fault architecture. Elevated pCO2 enhances rates of feldspar dissolution in the host aquifer and carbonate precipitation in fracture conduits. Silicate mineral dissolution rates decline and carbonate precipitation rates increase as pH and the CO2 charge dissipate. The Sr/Ca of calcite cements record average precipitation rates of ~2x10-6 mol/m2/s, comparable to laboratory derived calcite precipitation rates in fluids with elevated Mn/Ca and Fe/Ca, at cc of ~1 to 3. This suggests that far-from-equilibrium carbonate precipitation, which blocks fracture conduits and causes the leaking system to self-seal, driven by CO2 degassing in the shallow subsurface, can be accurately modeled with laboratory derived rates. Sandstones altered in CO2 leakage conduits exhibit extensive dissolution of hematite grain coatings and are chemically bleached as a result. Measurements of Eh-pH conditions in the modern fluid, and modeling of paleo-Eh-pH conditions using calcite Fe and Mn concentrations, suggests that the CO2-charged groundwaters are reducing, due to their low dissolved O2 content and that pH suppression due to high pCO2 is capable of dissolving and transporting large concentrations of metals. Exhumed paleo-CO2 reservoirs along the crest of the Green River anticline have been identified using volatile hosting fluid inclusions. Paleo-CO2-charged fluids mobilized hydrocarbons and CH4 from deeper formations, enhancing the reductive dissolution of hematite, which produced spectacular km-scale bleached patterns in these sediment.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Doyle, John Andrew. « Experimental study of the effect of H2O-CO2-NaCl fluid immiscibility on the reaction calcite + quartz + rutile = sphene + CO2 at 2 KBAR ». Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/53208.

Texte intégral

Résumé :

The minimum T-XCO₂ location of the reaction boundary calcite + quartz + rutile = sphene + CO₂ has been experimentally determined in H₂0-CO₂-NaCl fluids at 2 kbar. Extent and direction of reaction were monitored by the CO₂ weight change method using natural materials. All bulk compositions contain 23 wt. % NaCI, relative to NaCl-H₂0. Synthetic fluid inclusions trapped at the T-XCO₂ conditions of several points along the curve suggest unmixing of the fluid phase, as evidenced by coexisting CO₂ vapor-rich and aqueous, halite-bearing inclusions. Results from 450-520 °C are listed below.
Master of Science

Styles APA, Harvard, Vancouver, ISO, etc.

15

Li, Xingxun. « Experimental studies on pore wetting and displacement of fluid by CO2 in porous media ». Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10486.

Texte intégral

Résumé :

The study of multiphase flow in porous media is highly relevant to many problems of great scientific importance, such as CO2 storage and enhanced oil recovery. Even though significant progress has been made in these areas, many challenges still remain. For instance, the leakage of stored CO2 may occur due to the capillary trapping failure of cap rock. Approximately 70% of oil cannot be easily recovered from underground, because the oil is held in tight porous rocks. Although CO2 storage and enhanced oil recovery are engineering processes at a geological scale, they are predominantly controlled by the transport and displacement of CO2 and reservoir fluids in aquifers and reservoirs, which are further controlled by wetting and fluid properties at pore scale. This work focuses on experimental investigations of pore-scale wetting and displacement of fluids and CO2 in porous core samples. Pore wetting, which has been measured based on contact angle, is a principal control on multiphase flow through porous media. However, contact angle measurement on other than flat surfaces still remains a challenge. In order to indicate the wetting in a small pore, a new pore contact angle measurement technique is developed in this study to directly measure the contact angles of fluids and CO2 in micron-sized pores. The equilibrium and dynamic contact angles of various liquids are directly measured in single glass capillaries, by studying the effects of surface tension, viscosity and chemical structure. The pore contact angles are compared with the contact angles on a planar substrate. The pore contact angle of a confined liquid in a glass capillary differs from the contact angle measured on a flat glass surface in an open space. Surface tension is not the only dominant factor affecting contact angle. The static contact angle in a glass pore also varies with liquid chemical structure. Viscosity and surface tension can significantly affect the dynamic pore contact angle. A new empirical correlation is developed based on our experimental data to describe dynamic pore wetting. The CO2-fluid contact angle in porous media is an important factor affecting the feasibility of long-term permanent CO2 storage. It determines CO2 flow and distribution in reservoirs or aquifers, and thus ultimately finally the storage capacity. CO2-fluid contact angles were measured in small water-wet pores and oil-wet pores, investigating the effect of CO2 phase (gas/liquid/supercritical). The CO2 phase significantly affects the CO2-fluid contact angle in an oil-wet pore. Supercritical CO2-fluid contact angles are larger than gas CO2-fluid contact angles, but are smaller than liquid CO2-fluid contact angles. However, this significant CO2 phase effect on contact angle was not observed in a water-wet pore. Another key issue considered in this study is two-phase flow displacement in porous media. This strongly relates to the important macroscopic parameters for multiphase flow transport in porous media, such as capillary pressure and relative permeability. Here CO2-water displacements are studied by conducting CO2 flooding experiments in a sandstone core sample, considering the effects of CO2 phase, pressure and CO2 injection rate. The capillary pressure-saturation curve, water production behaviour and relative permeability are investigated for gas CO2-water, liquid CO2-water and supercritical CO2-water displacements in porous media. The pressure-dependant drainage capillary pressures are obtained as a result of CO2-water interfacial tension. Various water production behaviours are obtained for gas CO2-water and liquid CO2-water displacements, mainly due to the effect of CO2 dissolution. The significant irregular capillary pressure-saturation curves and water production behaviors can be observed for the supercritical CO2-water displacements. The water and CO2 relative permeabilities for CO2-water displacements in a porous media are then predicted.

Styles APA, Harvard, Vancouver, ISO, etc.

16

Lamy-Chappuis, Benoit. « Mineral-fluid interactions and their implications for the sequestration of CO2 in saline aquifers ». Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/8687/.

Texte intégral

Résumé :

It is known that acidification of reservoirs pore fluids during CO2 subsurface injection leads to fluid-rock interactions. Understanding the effect that these interactions could have on transport and mechanical properties of rocks is particularly relevant for calcite-bearing reservoirs in which rapid pores network evolution could compromise or reinforce the injection operation. In this work, specific experiments were conducted to study the impact of fluid rock interactions on petrophysical properties. The experiments involved the injection into rock cores of CO2-saturated brines to investigate rapid calcite dissolution effects and CO2 plus calcite saturated water to study calcite re-precipitation. Complementary fluid flow modelling at the pore scale was carried out to simulate changes in permeability brought by calcite dissolution. Calcite dissolution directly impacted the permeability and the rock strength in a way that would have been underestimated in classical reservoir simulations. The permeability increase ranged between 50 and 80% while widely used porosity-permeability relationships would predict 10 to 20%, pore scale modelling predictions were found to be more reliable. The change in the rock strength was even more spectacular with a decrease of the shear and bulk moduli of 20% when empirical equations would give a negligible change. Combined experiments and simulations were also used to test the long term CO2 stabilization process known as capillary trapping. The study concluded that CO2 dissolution in brine could give rise to CO2 accumulation in regions of the reservoirs containing larger pores. This could significantly modify CO2 mobility and goes against common belief of capillary trapping stability. This dissertation demonstrate CO2 injection can lead to critical modifications in rock petrophysical properties as well as CO2 trapping processes and that laboratory experiments and pore scale modelling can provide valuable insight into these changes.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Liao, Meng. « Modeling of fluid flows and heat transfer with interface effects, from molecular interaction to porous media ». Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1054/document.

Texte intégral

Résumé :

Les objectifs de la thèse sont d'étudier le transport de fluide et le transfert de chaleur dans les pores micro et nanométriques. Les expériences et les simulations ont révélé des preuves de l'augmentation du flux provoquée par la vitesse de glissement à la paroi solide. D'autre part, la résistance thermique finie à l'interface fluide-solide est responsable de la différence de température des deux phases. Ces deux phénomènes d'interface peuvent avoir un impact considérable sur la perméabilité et la diffusivité thermique des milieux poreux constitués de micro et nanopores. La contribution se concentre sur l'étude des trois problèmes suivants. Premièrement, nous examinons les effets de glissement des liquides confinés dans un canal de graphème en utilisant le formalisme de Green Kubo et la méthode de la dynamique moléculaire. On montre que lorsque la surface solide est soumise à une contrainte mécanique uniaxiale, la friction présente une anisotropie due à la modification de l'énergie potentielle et de la dynamique des molécules composant le fluide. Les formes moléculaires jouent également un rôle important sur les écarts de frottement entre les deux directions principales. Deuxièmement, nous étudions le régime des gaz raréfiés. Dans ce cas, la vitesse de glissement et le saut de température sont régis par les collisions entre les atomes de gaz et la paroi solide. Ces effets peuvent être déterminés à l’aide d’un modèle statistique qui peut être construit à partir des vitesses incidente et réfléchie des molécules de gaz. A cette fin, différentes méthodes basées sur des techniques d'apprentissage statistique ont été proposées. Enfin, la méthode des éléments finis est utilisée pour calculer la perméabilité et la diffusivité thermique des milieux poreux sous l'influence des effets d'interface
The objectives of the thesis are to study the fluid transport and heat transfer in micro and nano-scale pores. Both experiments and simulations revealed evidence of an enhancement of flow-rate, originated from slip velocity at the solid boundary. On the other hand, the finite thermal resistance at the fluid-solid interface is responsible for the temperature difference between the two phases. These two interface phenomena can have a considerable impact on the permeability and thermal diffusivity of porous media constituted of micro and nano-pores. This contribution focuses on studying the following three issues. First, we examine the slip effects of liquids confined in graphene channel using Green Kubo formalism and Molecular Dynamics method. It is shown that when the solid surface is subject to mechanical uniaxial strain, the friction exhibits anisotropy due to the modification of the potential energy and the dynamics of the fluid molecules. The molecular shapes also play an important factor on the friction discrepancies between two principal directions. The quantification of both effects is addressed. Second, we investigate the rarefied gas regime. In this case, the velocity slip and temperature jump are governed by the collisions between the gas and the solid boundary. Those effects can be determined via the study of scattering kernel and its construction from MD simulation data. To this end, different methods based on statistical learning techniques have been proposed including the nonparametric (NP) kernel and Gaussian mixture (GM) kernel. Finally, the finite element method is used to compute the permeability and the thermal diffusivity of porous media under the influence of the interface effects

Styles APA, Harvard, Vancouver, ISO, etc.

18

Frery, Emanuelle. « Circulation épisodique de fluides réactifs le long de failles de l'échelle de travertins à celle de bassins, sur l'exemple du plateau du Colorado (USA) ». Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00864036.

Texte intégral

Résumé :

Cette thèse s'attache à caractériser l'évolution dans le temps et l'espace des circulations de fluides le long des failles. Une approche multidisciplinaire et multi-échelle a été mise en place sur un exemple naturel dans la région du plateau du Colorado (Utah): du terrain à la modélisation et de la proche-surface au bassin. L'étude des minéralisations en proche surface et leur lien avec le transfert le long des failles a été effectuée sur des travertins récents. L'analyse isotopique et la datation U/Th des veines de travertins révèle des cycles de circulation de fluides enrichis en CO2 et de précipitation épisodiques de carbonates de calcium (travertin) correspondant à des cycles saisonniers ou climatiques (annuels et centennals) ainsi qu'à des cycles qui s'apparentent à des cycles sismiques de l'ordre du millier d'années. Ces données permettent de calibrer le volume de CO2 qui a fuit par la faille. Des zones de paléo-circulation, témoins de l'activité des failles sur le long-terme, sont observées sous forme de blanchiment chimique ("bleaching") des grès à l'affleurement, et ont été étudiées à l'échelle du bassin. Deux épisodes principaux de circulation de fluides le long des failles ont été distingués : une première circulation durant l'enfouissement maximum puis une seconde circulation le long des réservoirs et des failles, qui est reliée à des phénomènes tectoniques régionaux, compemporains de la remontée du Plateau du Colorado. La dernière circulation s'est découpée en plusieurs pulses avec des circulations de fluides de différente nature (tels que des saumures, des fluides riches en hydrocarbures ou en CO2) au cours du temps et le long des failles.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Jahan, Farjana. « Pore-scale, Computational Fluid Dynamics-based Simulation of Supercritical CO2-brine Flow through Porous Media ». Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75686.

Texte intégral

Résumé :

Carbon Capture and Storage (CCS) is one of the effective methods to manage CO2 emissions to mitigate global warming and associated environmental changes. This thesis provide insight into this aspects emphasising on investigating the two-phase (brine and scCO2) flow behaviour, and advanced understanding on residual saturation, relative permeability, and capillary trapping capacity under various drainage and imbibition conditions using pore-scale numerical simulations based upon computational fluid dynamics (CFD).

Styles APA, Harvard, Vancouver, ISO, etc.

20

Leal, Patricia Franco. « Obtenção de extratos vegetais com propriedades funcionais via tecnologia supercritica : uso de CO2 e CO2 + H2O ». [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254898.

Texte intégral

Résumé :

Orientador: Maria Angela de Almeida Meireles
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-04T02:50:47Z (GMT). No. of bitstreams: 1 Leal_PatriciaFranco_M.pdf: 2204024 bytes, checksum: 0b4a27a2c6db03ca4023ca90d6a49f65 (MD5) Previous issue date: 2005
Mestrado
Engenharia de Alimentos
Mestre em Engenharia de Alimentos

Styles APA, Harvard, Vancouver, ISO, etc.

21

Yuh, Sung H. « Time-lapse seismic monitoring of subsurface fluid flow ». [College Station, Tex. : Texas A&M University, 2004. http://hdl.handle.net/1969.1/430.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

22

Thomas, Carelle. « Influence of chemical reactions on CO2 convective dissolution : an experimental study ». Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/253102.

Texte intégral

Résumé :

(EN) Carbon dioxide (CO2) sequestration in deep saline aquifers is one of the technologies considered to reduce the accumulation of this greenhouse gas in the atmosphere. The injection of CO2 into these deep geological formations and its dissolution in salt water lead to a buoyantly unstable stratification of denser CO2-enriched brine on top of less dense brine, which can give rise to buoyancy-driven convective fingering in the fluid. This convective dissolution of CO2 in brine is a favourable process for its sequestration as it accelerates the mixing of CO2 into the aqueous phase and therefore enhances the safety of the storage in the saline aquifer. The influence of chemical reactions between species and CO2 dissolved in the brine and hence of the physico-chemical characteristics of the geological reservoir on the development of this instability is still not completely understood. In this context, our goal is to determine experimentally whether chemical reactions in the aqueous phase can improve the efficiency of CO2 convective dissolution. To do so, we have developed an experimental device consisting of a vertical Hele-Shaw cell in which gaseous CO2 dissolves from above in aqueous solutions containing chemical reactants of various nature and concentration. The convective dynamics occurring within the transparent fluid are visualised with the help of a schlieren technique. First, we show that the presence of a color indicator in the aqueous solution can affect the fingering dynamics and that such indicators should therefore be used with caution in this kind of studies. We then study the stabilising effect of an increase in the salt concentration on CO2 convective dissolution in brine. In the reactive case, we show that the fingering instability develops faster in basic solutions of MOH (where M+ is an alkali metal cation) than in pure water and that convection is enhanced if the reactant concentration is increased. In addition, a change of the counter-ion M+ changes the density profile, not only through solutal effects, but also through differential diffusivity effects, which impacts the development of the convective instability. Finally, we explore the changes in the convective dynamics induced by precipitation reactions due to CO2 dissolution in aqueous solutions of Ca(OH)2 and CaCl2 in variable concentrations. Diverse precipitation and convective patterns develop in the aqueous solution depending on the nature and concentration of the reactant in the aqueous phase. Our results show that the convective dissolution of CO2 can be strengthened by chemical reactions and that this effect depends on the nature of the reactants and their concentrations. We conclude that chemical reactions can be favourable to the CO2 sequestration process and that a detailed analysis of the chemical composition of a potential storage site should be a prerequisite to assess its efficiency in dissolving CO2.
(FR) La séquestration du dioxyde de carbone (CO2) dans les aquifères salins profonds est l’une des technologies envisagées afin de réduire l’accumulation de ce gaz à effet de serre dans l’atmosphère. L'injection de CO2 dans ces formations géologiques profondes et sa dissolution dans l'eau salée génèrent une stratification de densité instable d’une saumure dense enrichie en CO2 au-dessus d’une saumure moins dense, pouvant donner naissance à une instabilité de digitation de densité dans la phase aqueuse. Cette dissolution convective du CO2 accélère le mélange de CO2 dans le réservoir et donc améliore la sécurité du stockage dans l’aquifère salin. L’influence des réactions chimiques entre les espèces et le CO2 dissous dans l’eau salée et donc des caractéristiques physico-chimiques du réservoir géologique sur le développement de cette instabilité est aujourd’hui encore peu connue. Dans ce cadre, notre objectif est de déterminer expérimentalement si une réaction chimique dans la phase aqueuse peut améliorer l’efficacité de la dissolution convective du CO2. Pour ce faire, nous avons mis au point un dispositif expérimental consistant en une cellule de Hele-Shaw verticale dans laquelle du CO2 gazeux se dissout par le haut dans des solutions aqueuses contenant des réactifs chimiques de nature et concentration variées. La dynamique convective est visualisée dans les solutions aqueuses transparentes à l’aide d’une technique schlieren. Tout d’abord, nous montrons que la présence d’un indicateur coloré dans la solution aqueuse peut affecter la dynamique de digitation et que ces indicateurs doivent être utilisés avec prudence dans ce genre d’études. Nous étudions ensuite l’effet stabilisateur d’une augmentation de la concentration en sel sur la dissolution convective de CO2 dans la saumure. Dans les cas réactifs, nous montrons que l’instabilité de digitation se développe plus vite dans des solutions basiques de MOH (où M+ est un cation de métal alcalin) que dans l’eau pure et que la convection est renforcée si la concentration du réactif est augmentée. De plus, un changement du contre-ion M+ de la base modifie le profil de densité, non seulement par le biais d’effets solutaux, mais aussi par des effets de diffusivité différentielle, ce qui modifie le développement de l’instabilité convective. Enfin, nous explorons les changements de dynamiques convectives induits par des réactions de précipitation dues à la dissolution de CO2 dans des solutions aqueuses de Ca(OH)2 et de CaCl2 de concentrations variables. Divers motifs de précipitation et de convection peuvent être obtenus selon la nature et la concentration du réactif dans la phase aqueuse. Nos résultats montrent que la dissolution convective de CO2 peut être renforcée par des réactions chimiques et que cet effet dépend de la nature des réactifs et de leur concentration. Nous concluons que les réactions chimiques peuvent favoriser le processus de séquestration du CO2 et qu’une analyse détaillée de la composition chimique d’un site potentiel de stockage devrait être un préalable à l’évaluation de son efficacité à stocker le CO2.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Styles APA, Harvard, Vancouver, ISO, etc.

23

Fall, Andras. « Application of fluid inclusions in geological thermometry ». Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/30265.

Texte intégral

Résumé :

Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition (PTX) of the environment of formation, hence understanding PTX properties of the fluid inclusions is required. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of geologic events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Synthetic fluid inclusions trapped in the one-fluid-phase field are formed at a known and relatively constant temperature. However, microthermometry of synthetic fluid inclusions often reveals Th variations of about ± 1- 4 degrees Centigrade, or one order of magnitude larger than the precision of the measurement for an individual inclusion. The same range in Th was observed in well-constrained natural FIAs where the inclusions are assumed to have been trapped at the same time. The observed small variations are the result of the effect of the fluid inclusion size on the bubble collapsing temperature. As inclusions are heated the vapor bubble is getting smaller until the pressure difference between the pressure of the vapor and the confining pressure reaches a critical value and the bubble collapses. It was observed that smaller inclusions reach critical bubble radius and critical pressure differences at lower temperatures than larger inclusions within the same FIA. Homogenization temperature (Th) variations depend on many factors that vary within different geological environments. In order to determine minimum and acceptable Th ranges fro FIAs formed in different environments we investigated several geologic environments including sedimentary, metamorphic, and magmatic hydrothermal environments. The observed minimum Th ranges range from 1-4 degrees Centigrade and acceptable Th range from 5-25 degrees Centigrade. The variations are mostly caused by the fluid inclusion size, natural temperature and pressure fluctuations during the formation of an FIA and reequilibration after trapping. Fluid inclusions containing H₂O-CO₂-NaCl are common in many geologic environments and knowing the salinity of these inclusions is important to interpret PVTX properties of the fluids. A technique that combines Raman spectroscopy and microthermometry of individual inclusions was developed to determine the salinity of these inclusions. In order to determine the salinity, the pressure and temperature within the inclusion must be known. The pressure within the inclusions is determined using the splitting in the Fermi diad of the Raman spectra of the CO₂ at the clathrate melting temperature. Applying the technique with to synthetic fluid inclusions with known salinity suggests that the technique is valid and useable to determine salinity of H₂O-CO₂-NaCl fluid inclusions with unknown salinity.
Ph. D.

Styles APA, Harvard, Vancouver, ISO, etc.

24

Kokh, Maria. « Rôle du CO2 dans les transferts des métaux d'intérêt économique par les fluides géologiques ». Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30006/document.

Texte intégral

Résumé :

Le CO2 est le deuxième après l'eau constituant des fluides de haute température (T) et haute pression (P) qui opèrent dans la lithosphère, transportent la matière et forment des dépôts économiques des métaux. Cependant, son effet sur la mobilisation et la précipitation des métaux reste quasiment inconnu faute de données directes et de modèles physico-chimiques. Dans ce travail de thèse, nous avons mis en œuvre des méthodes expérimentales et des analyses chimiques et spectroscopiques sur des fluides modèles riches en CO2, couplées à une modélisation thermodynamique, afin de quantifier, pour la première fois de manière systématique, la solubilité, le partage et la spéciation de divers métaux d'intérêt économique (Fe, Cu, Au, Mo, Pt, Sn, Zn) dans les systèmes eau-gaz-sels typiques des fluides hydrothermaux métallifères. Des mesures de solubilité des principaux minéraux de ces métaux (sulfures, oxydes et métaux natifs) et de leurs coefficients de partage ont été effectuées dans des fluides supercritiques H2O-CO2-S-KCl à 450°C et 500-700 bar et dans des systèmes liquide-vapeur H2O-CO2-S-KCl-NaCl à 350°C, 130-300 bar, à l'aide d'autoclaves à cellule flexible et de réacteurs à séparation de phase que nous avons mis au point. Les conditions d'acidité, de redox et de fugacité de soufre ont été contrôlées par des équilibres entre les minéraux sulfures et oxydes de fer et alkali-aluminosilicates ou entre le sulfate et le sulfure en solution. Les données ont été analysées dans le cadre d'un modèle thermodynamique couplé à une révision critique des données sur la spéciation des métaux en phase fluide. Ce modèle électrostatique ne requière pas de paramètres ajustables; il utilise la constante diélectrique du solvant H2O-CO2 et le paramètre de Born des espèces dominantes en phase aqueuse. Nos résultats montrent que la mobilité des métaux dans les fluides riches en CO2 est contrôlée par la nature et la charge de leurs complexes principaux. La présence du CO2 favorise la stabilité des complexes neutres (FeCl20, AuHS0, CuHS0, ZnCl20, KMoO40, Pt(HS)20) alors que celle des espèces chargées de ces métaux (FeCl42-, Au(HS)2-, CuCl2-, ZnCl42-, HMoO4-, PtCl3-) est considérablement affaiblie. Il en résulte un fractionnement important de certains métaux selon la composition du fluide et le contexte géologique. Notre modèle explique bien l'enrichissement en Fe et l'appauvrissement en Cu des gisements métamorphiques d'or (orogéniques) formés par des fluides riches en CO2. Le transport de l'or par ces fluides est favorisé à faible teneur en soufre (Au(HS)0 est dominante), alors que dans les fluides riches en soufre, typiques des gisements porphyres cuprifères où les complexes chargés sont dominants (Au(HS)2-, Au(HS)S3-), la présence du CO2 aura pour effet d'abaisser la solubilité de l'or. Cependant, même à fortes teneurs en CO2 (>50 wt%), la capacité des fluides à transporter l'or sous forme d'espèces neutres (~100s ppb) reste comparable à celle d'un fluide aqueux, ce qui explique les associations de minéralisations aurifères avec des fluides riches en CO2. L'effet du CO2 sur la mobilité de Mo, Zn et Si qui forment des espèces neutres, est faible dans la plupart des contextes géologiques, alors que celle de Sn pourrait être favorisée par des complexes carbonatés et celle de Pt par des complexes carbonyles (CO). Le rôle direct du CO2 sur le partage liquide-vapeur pour la plupart des métaux est relativement faible devant celui du soufre réduit (H2S) dont la présence favorise fortement l'enrichissement de la phase vapeur en Au, Pt, Mo et Cu. Ainsi le CO2 intervient dans ces processus de démixtion de manière indirecte, en élargissant le domaine T-P d'immiscibilité du fluide. Cette étude démontre que, contrairement aux modèles métallogéniques actuels, la présence du CO2 peut favoriser la mobilité de certains métaux et engendrer des fractionnements importants entre différents métaux lors de l'évolution des fluides dans la croûte terrestre
Carbon dioxide is the second component after water of geological fluids that operate at high temperature (T) and pressure (P) in the lithosphere, transport the metals and form economic deposits. However, its effect on the mobilization and precipitation of metals remains virtually unknown owing to a lack of direct data and physical-chemical models. In this thesis, we have developped experimental methods and chemical and spectroscopic analyzes of CO2-rich fluids, coupled with thermodynamic modeling, to systematically quantify, for the first time, the solubility, distribution and speciation of various metals of economic interest (Fe, Cu, Au, Mo, Pt, Sn, Zn) in gas-water-salt systems typical of metalliferous hydrothermal fluids. Measurements of the solubility of the major minerals of these metals (sulfides, oxides and native metals) and of metal partition coefficients were carried out in supercritical fluids H2O-CO2-S-KCl at 450°C and 500-700 bar and in two-phase vapor-liquid systems H2O-CO2-NaCl-KCl-S at 350°C, 130-300 bar, using flexible-cell and phase-separation reactors that we have set up. The conditions of acidity, redox potential and sulfur fugacity were controlled by equilibria among iron sulfide and oxide minerals and alkali-aluminosilicate minerals or between sulfate and sulfide in the fluid. The data obtained were analyzed in the framework of a thermodynamic model coupled with a critical review of the literature on the metal speciation in the fluid phase. The electrostatic model that we used does not require any adjustable parameters; it is based on the dielectric constant of the CO2-H2O solvent and the Born parameter of the dominant species in the aqueous phase. Our results show that the mobility of metals in CO2-rich fluids is controlled by the nature and electrical charge of their main aqueous complexes. The presence of CO2 favors the stability of the neutral complexes (FeCl20, AuHS0, CuHS0, ZnCl20, KMoO40, Pt(HS)20) whereas that of the charged species of these metals (FeCl42-, Au(HS)2-, CuCl2-, ZnCl42-, HMoO4-, PtCl3-) is largely weakened. This results is significant fractionations between some metals, depending on the composition of the fluid and the geological context. Our model accounts for the enrichment in Fe and depletion in Cu observed in metamorphic orogenic gold deposits formed by CO2-rich fluids. The transport of gold by these fluids is favored at low sulfur content (Au(HS)0 is dominant), whereas in S-rich fluids typical of porphyry copper deposits and high T orogenic gold deposits where the charged complexes are dominant (Au(HS)2-, Au(HS)S3-), the presence of CO2 leads to lowering the solubility of gold. However, even at high CO2 content (> 50 wt%), the ability of fluids to carry gold as neutral species (~100s ppb) remains comparable to that of an aqueous fluid, which explains the associations of gold mineralizations with fluids rich in CO2. The effect of CO2 on the mobility of Mo, Zn and Si, which form neutral species, is weak in most geological situations, whereas that of Sn could be promoted by carbonate complexes and that of Pt by carbonyl (CO) complexing. The direct role of CO2 in the vapor-liquid partitioning of most metals is relatively small compared to that of reduced sulfur (H2S) whose presence strongly favors the enrichment of the vapor by Au, Pt, Mo and Cu. Thus, the main impact of CO2 in these demixing processes is to expand the fluid T-P domain of immiscibility. This study demonstrates that, contrary to common belief, the presence of CO2 can promote the mobility of certain metals and cause significant fractionations between different metals during the evolution of fluids in the crust

Styles APA, Harvard, Vancouver, ISO, etc.

25

Strauss, William C. « Saturation and foaming of thermoplastic nanocomposites using supercritical CO2 ». Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4745/.

Texte intégral

Résumé :

Polystyrene (PS) nanocomposite foams were prepared using supercritical fluid (SCF) CO2 as a solvent and blowing agent. PS was first in-situ polymerized with a range of concentrations of montmorillonite layered silicate (MLS). The polymerized samples were then compression molded into 1 to 2mm thick laminates. The laminates were foamed in a batch supercritical CO2 process at various temperatures and pressures from 60°-85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron microscopy to determine effect of MLS on cellular morphology. Differential scanning calorimetry was used to determine the impact of nanocomposite microstructure on glass transition of the foamed polymer. X-ray diffraction spectra suggested that the PS/MLS composite had an intercalated structure at both the 1% and 3% mixtures, and that the intercalation may be enhanced by the foaming process.

Styles APA, Harvard, Vancouver, ISO, etc.

26

Baig, Muhammad. « Extraction de composant de biomasse lignocellulosique oléagineuse en milieu eau et CO2 subcritique et fonctionnalisation enzymatique ». Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20215/document.

Texte intégral

Résumé :

La thèse vise l'application du concept de bioraffinerie (extraction, fractionnement, séparation de composés à partir de biomasse avant transformation ultérieure), via le développement d'étapes de production destinées à être associées en un procédé continu. La complexité du solide nécessite une étape de prétraitement effectuée avec une technologie à faible impact environnemental et l'eau subcritique est déjà utilisée comme solvant d'extraction des produits naturels, en sus de leur hydrolyse. Ces travaux ont porté sur l'hydrolyse de polysaccharides (son de riz) et de triacylglycérols (TAG, huile de tournesol) choisis comme modèles. Les caractéristiques de l'eau subcritique (produit ionique, constante diélectrique) mise en œuvre en réacteurs à circulation construits dans ce but, ont permis l'hydrolyse quasi-totale de l'hémicellulose et des TAG. L'addition de CO2 et donc d'acide carbonique a eu un effet positif sur l'hydrolyse de l'hémicellulose. Les acides gras libres résultant de l'hydrolyse ont été estérifiés en ester éthyliques en présence d'une lipase en réacteur continu en milieu CO2 supercritique, avec un taux de synthèse de 95%. Les cinétiques des réactions ci-dessus d'hydrolyse et d'estérification ont été étudiées. La complexité des interactions entre les nombreux paramètres mis en jeu a conduit à appliquer des méthodes de plans d'expérience. Ces méthodes ont été validées avec succès avec les données expérimentales, montrant ainsi leur utilité dans le développement de procédés. La question importante de la solubilité des extractibles dans l'eau subcritique a été traitée et une méthode de prédiction mise au point et validée avec succès avec les données expérimentales. En conclusion, ce travail montre la possibilité d'appliquer le concept novateur de la Bioraffinerie Intégrée en réacteur continu avec des fluides sub- ou supercritique, contrairement à leur mise en œuvre actuelle en réacteur fermé, pour la production de composés commercialisables
This work addresses the integrated biorefining concept (extraction, fractionation, separation of compounds from biomass prior to further transformation) by developing discrete units with the ultimate objective of coupling them to enable a continuous flow configuration. Due to the complexity of solid, there is a need for a sustainable and environmentally friendly pre-treatment technology. Sub-critical water has been used as a solvent for extracting natural compounds in addition to hydrolysis. This work investigated the hydrolysis of carbohydrates (rice bran) and triacylglycerols (TAG; sunflower oil) chosen as models. The attribute of subcritical water (ion product and dielectric constant) in continuous flow reactors built for the purpose, allowed almost quantitative hydrolysis of hemicellulose and TAG. The effect of adding CO2 and therefore carbonic acid was positive on the hydrolysis of hemicellulose. Further, free fatty acids were transformed to ethyl esters using lipase within continuous flow super critical CO2 resulting in 95% yield. The hydrolysis and esterification reaction kinetics were studied. To address the complex interplay between multiple processing parameters response surface methodologies (RSM) were developed. Using the empirical data the models were successfully validated, therefore showing the utility of the RSM to assist process development. The important question of solubility of extractible in subcritical water was also addressed, through the development of a prediction method, validated with experimental data. In summary this work shows the possibility of applying the innovative Integrated Biorefining concept under continuous flow conditions -instead of the current application under batch conditions- for producing valuable compounds

Styles APA, Harvard, Vancouver, ISO, etc.

27

Chakravarthy, Deepak. « Application of X-ray CT for investigating fluid flow and conformance control during CO2 injection in highly heterogeneous media ». Texas A&M University, 2005. http://hdl.handle.net/1969.1/2370.

Texte intégral

Résumé :

Fractured reservoirs have always been considered poor candidates for enhanced oil recovery. This can be attributed to the complexities involved in understanding and predicting performance in these reservoirs. In a fractured system, the high permeability fracture forms the preferred pathway for the injected fluids, and a large amount of oil that is stored in the matrix is bypassed. Hence, a good understanding of multiphase fluid flow in fractures is required to reduce oil bypass and increase recovery from these reservoirs. This research investigates the effect of heterogeneity and injection rates on oil bypass and also the various techniques used for the improvement of sweep efficiency in heterogeneous systems. Several coreflood experiments were performed using homogeneous and heterogeneous cores and a 4th generation X-Ray CT scanner was used to visualize heterogeneity and fluid flow in the core. Porosity and saturation measurements were made during the course of the experiment. The experimental results indicate that injection rates play a very important role in affecting the recovery process, more so in the presence of fractures. At high injection rates, faster breakthrough of CO2 and higher oil bypass were observed than at low injection rates. But very low injection rates are not attractive from an economic point of view. Hence water viscosified with a polymer was injected directly into the fracture to divert CO2 flow into the matrix and delay breakthrough, similar to the WAG process. Although the breakthrough time reduced considerably, water ??leak off?? into the matrix was very high. To counter this problem, a cross-linked gel was used in the fracture for conformance control. The gel was found to overcome ??leak off?? problems and effectively divert CO2 flow into the matrix. This experimental research will serve to increase the understanding of fluid flow and conformance control methods in fractured reservoirs.

Styles APA, Harvard, Vancouver, ISO, etc.

28

Shukla, Ruchi. « An Experimental Study on a Density Driven Solar Water Heating System Using Supercritical CO2 as Working Fluid ». Thesis, North Dakota State University, 2013. https://hdl.handle.net/10365/26918.

Texte intégral

Résumé :

For supercritical carbon dioxide, a small change in temperature or pressure can result in large change in density, especially close to its critical point. At this pseudocritical region, density decreases rapidly with increase in temperature which aids the thermosyphon flow. Encouraged by this idea, an experimental investigation has been performed to investigate the feasibility and performance of thermosyphon solar water heating (SWH) system using R-744 (CO2) as the working fluid. Experimental results have shown that it is possible to induce the natural convective flow even during solar-adverse conditions. Although during winter this proposed density driven system was not possible to extract any useful heat gain, the system did show some promising results when operated during spring. The time-averaged collector and heat recovery efficiencies for summer were about 58% and 45%, respectively.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Azbej, Tristan. « The Role of Fluids in Geological Processes ». Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29074.

Texte intégral

Résumé :

The role and behavior of fluids in hydrothermal and magmatic environments have been studied. Experimental studies have been carried out to determine fluid properties, in natural environments and in both synthetic and natural fluid and melt inclusions. One of these studies dealt with the effect of composition on the critical P-T-X properties of aqueous salt solutions approximated by the H2O-NaCl-KCl-CaCl2 system. The results indicate a systematic variation in critical properties as a function of composition over the range of P-T-X studied. A technique for analyzing individual H2O-CO2 inclusions using Raman spectroscopy has also been developed. The resulting empirical equation relating Raman intensities and composition is valid for compositions â ¤50mol% CO2. The technique has been applied to H2O-CO2 inclusions from the Butte, MT Porphyry Cu-Mo deposit and the results agree with compositions estimated from microthermometric and petrographic observations. The aim of another study was to study water loss from melt inclusions during laboratory heating. Melt inclusions had lost insignificant amounts of water when held at experimental conditions (800Â°C, 1 kbar) for â ¤24 hours. However, significant water loss was observed for longer duration experiments. Ocelli, which are globular bodies of felsic minerals are interpreted as products of magmatic melt immiscibility. As such, the carbonate aggregates in Cretaceous lamprophyres from Hungary with similar petrographic characteristics have also generally been interpreted to be products of magmatic immiscibility. Petrographic and geochemic studies have shown three three distinct genetic groups for these aggregates, none of which were consistent with a magmatic origin.
Ph. D.

Styles APA, Harvard, Vancouver, ISO, etc.

30

Puttiwongrak, Avirut. « Geomechanical Studies on Fluid Flow Behaviour Influencing Rock Deformation Mechanisms of Mudstones and Sandstones ». 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180488.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

31

Santiago, Heber Peleg Cornelio. « Medida da solubilidade de óleo de café verde (Coffea arabica L.) em dióxido de carbono supercrítico e modelagem termodinâmica ». Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-05102015-101828/.

Texte intégral

Résumé :

O objetivo do presente estudo foi medir experimentalmente a solubilidade do óleo de café verde em dióxido de carbono supercrítico em condições preestabelecidas de pressão (P) e temperatura (T), e a partir dos dados experimentais estabelecer ajustes em modelos termodinâmicos que empregam a equação de estado (EDE) de Peng-Robinson com a regra de mistura clássica de van der Waals para predição do equilíbrio de fases. Foi obtido óleo a partir de grãos de café verde (Coffea arabica), cultivar (cv.) Catuaí Amarelo moído (dm de 0,8409 mm) usando CO2 supercrítico, nas condições de 40, 50, 60, 70, 80 °C e nas pressões de 300 e 350 bar. A solubilidade foi medida pelos métodos dinâmico e estático nas mesmas condições. Foi determinado o perfil de ácidos graxos por cromatografia gasosa acoplada à espectrometria de massas (CG/EM) e, a partir destes resultados, a composição em triacilgliceróis (TAGs) foi estimada. Foram determinadas as propriedades físico-químicas dos TAGs pelo método de contribuição de grupos. Nas condições de P e T estudadas, os maiores rendimentos do óleo de grãos de café verde, 7,58% e 7,60%, foram obtidos nas condições de 70 °C e 300 bar e 80 °C e 350 bar, respectivamente. Normalmente o rendimento do óleo aumentou com o aumento da temperatura, com exceção das condições de 80 °C e 300 bar e 70 °C e 350 bar. O aumento do rendimento com a temperatura reflete nos dados experimentais da solubilidade (0,0099 a 0,026 g/gCO2) que aumentou com a temperatura a 300 e 350 bar para o método estático e para o método dinâmico a 350 bar (0,0058 a 0,0065 g/gCO2). Um comportamento distinto ocorreu com a medida de solubilidade pelo método dinâmico a 300 bar. Neste caso a solubilidade diminuiu com o aumento da temperatura. Para a maioria das condições de P e T estudadas, o comportamento da solubilidade foi semelhante em função destas variáveis, o mesmo para os métodos estático e dinâmico, no entanto com ordens de grandezas distintas. As condições de extração não influenciaram na composição dos ácidos graxos no óleo nem na predição dos TAGs presentes. Os TAGs apresentaram variações entre número de carbonos (C50 a C58). As propriedades físico-químicas dos seis principais TAGs presentes no óleo de grãos de café verde (PSL, PLL, PLP, PLO, PLA e POP), temperatura do ponto de ebulição normal (Tb), temperatura crítica (Tc), pressão crítica (Pc) e fator acêntrico (ω) foram estimadas por métodos de contribuição de grupos. Estas variáveis são dados de entrada para a predição do equilíbrio de fases entre o óleo de grãos de café verde, representado pela mistura dos seis TAGs em maior concentração neste óleo, e o CO2 supercrítico. Os valores de Tb dos TAGs variaram de 821,52 a 844,50 K, os valores de Tc de 909,12 a 930,02 K, os valores de Pc de 5,0115 a 4,7221 bar e o ω de 1,5704 a 1,7452. Os dados de propriedades físicas e da solubilidade convertida em fração molar foram usados para predizer os parâmetros de interação binária da regra de mistura clássica de van der Waals entre cada TAG e o CO2 supercrítico, já que estes parâmetros também são dados de entrada para a modelagem termodinâmica que emprega a EDE de Peng-Robinson. No entanto, o programa não rodou, não sendo possível este cálculo, nem tão pouco a predição do equilíbrio de fases. Os dados experimentais da solubilidade do óleo de grãos de café verde em CO2 supercrítico determinados pelos métodos estático e dinâmico indicou que àqueles determinados pelo método estático são mais precisos e confiáveis.
The objective of this study was to experimentally measure the solubility of green coffee oil in supercritical carbon dioxide under predetermined pressure (P) and temperature (T) conditions and, from the experimental data, establish thermodynamic models that use the Peng-Robinson equation of state (EOS) and the classic mixing rule of van der Waals to predict phase equilibrium. The oil was obtained from ground green coffee beans (Coffea arabica L.) cultivar (cv.) Yellow Catuaí (dm of 0.8409 mm) using supercritical CO2 under temperatures of 40, 50, 60, 70 and 80 °C and pressures of 300 and 350 bar. The solubility was measured by dynamic and static methods under the same conditions. The fatty acid profile was determined by gas chromatography-mass spectrometry (GC/MS) and, from these results, the composition of triacylglycerols (TAGs) was estimated. Physicochemical properties of TAGs were determined by the group contribution method. In the studied conditions of P and T, higher yields of green coffee beans oil, 7.58% and 7.60%, were obtained at 70 °C and 300 bar and 80 °C and 350 bar, respectively. Normally, the oil yield increased with increasing temperatures, except for the conditions of 80 °C and 300 bar and 70 °C and 350 bar. The increase of yield with temperature reflects in the experimental solubility data (from 0.0099 to 0.026 g/g CO2), which, also increased with T at 300 and 350 bar for the static method and, for the dynamic method, at 350 bar (from 0.0058 to 0.0065 g/g CO2). A different behavior occurred with the solubility measured by dynamic method at 300 bar. In this case, the solubility decreased with increasing temperature. For most of the P and T conditions studied, the solubility behavior was similar in function of these variables, the same for static and dynamic methods, but with different magnitude orders. The extraction conditions did not affect the composition of fatty acids in the oil and nor the TAGs prediction. The TAGs showed variations between carbon numbers (from C50 to C58). The physicochemical properties of the six major TAGs present in green coffee bean oil (PSL, PLL, PLP, PLO, PLA and POP), boiling temperature (Tb), critical temperature (Tc), critical pressure (Pc) and acentric factor (ω) were estimated by group contribution methods. These are input variables for the prediction for the phase equilibrium between the green coffee oil, represented by the mixture of the six TAGs in higher concentration in this oil, and supercritical CO2. The Tb values of TAG ranged from 821.52 to 844.50 K, Tc values from 909.12 to 930.02 K, Pc values from 5.0115 to 4.7221 bar and ω from 1, 5704 to 1.7452. The data of physical properties and solubility converted to mole fraction were used to predict the binary interaction parameters of the classic mixing rule of van der Waals between each TAG and supercritical CO2, since these are also input parameters for the thermodynamic modeling that use Peng-Robinson EOS. However, the program did not run and this calculation was not possible, nor the prediction for the phase equilibrium. The experimental data on the solubility of the green coffee beans oil in supercritical CO2 determined by static and dynamic methods indicated that those determined by the static method are more accurate and reliable.

Styles APA, Harvard, Vancouver, ISO, etc.

32

Butzke, Alan de Siqueira 1986. « Pré-tratamento de bagaço de cana com CO2 supercrítico visando hidrólise enzimática = Sugarcane bagasse pretreatment with supercritical carbon dioxide aiming enzymatic hydrolysis ». [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266071.

Texte intégral

Résumé :

Orientadores: Maria Aparecida Silva, Mariana Altenhofen da Silva
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-26T02:47:52Z (GMT). No. of bitstreams: 1 Butzke_AlandeSiqueira_M.pdf: 3517066 bytes, checksum: 98ea507901df168f0fbaa1708f00b19a (MD5) Previous issue date: 2014
Resumo: A utilização de biomassa para a produção de etanol de segunda geração é de grande importância para o setor energético mundial, no entanto o uso do bagaço de cana excedente nas usinas sucro-alcooleiras depende de um pré-tratamento para criar condições necessárias para a hidrólise enzimática. O objetivo deste trabalho foi avaliar a composição estrutural das frações de bagaço e a influência da umidade, temperatura e pressão na conversão em açúcares antes e após o pré-tratamento com CO2 supercrítico. Os experimentos de caracterização e hidrólise enzimática das frações de bagaço foram desenhados por um planejamento experimental fatorial completo 23 com triplicata no ponto central. A remoção de hemicelulose no pré-tratamento aumentou consideravelmente o teor de celulose nas frações de fibra (retida na peneira 48 mesh da série Tyler) e de medula. Verificou-se para condição de 60ºC e 250 bar, um aumento máximo de aproximadamente 50 % (umidade de 0 % em base seca) e de 30 % (umidade de 100 % em base seca) no teor de celulose nas frações de fibra e medula, respectivamente. O melhor resultado da conversão em glicose da fração de fibra (7,7 g/L) foi para um teor de umidade igual a 0 % (base seca) em 24 horas de hidrólise enzimática, para a condição de 40ºC e 100 bar no pré-tratamento, com aumento de 16 % em relação à fração fibra sem pré-tratamento no mesmo tempo. O melhor resultado da conversão em glicose da fração de medula (8,2 g/L), foi para um teor de umidade igual a 100 % (base seca), para 60ºC e 100 bar, em 48 horas de hidrólise enzimática com um aumento de 16 % em relação à fração de medula sem pré-tratamento no mesmo tempo. Análises de difratometria de raios X mostraram alterações na cristalinidade da celulose para ambas as frações e a determinação da área superficial mostrou um aumento na quantidade de poros após o pré-tratamento. Verificou-se também a ausência do composto inibidor hidroximetilfurfural (HMF) nas frações de fibra e medula
Abstract: The use of biomass for second generation ethanol production is very important to the global energy sector, however, the use of sugarcane bagasse surplus in the sugar and alcohol plants depends on a pretreatment to create necessary conditions for enzymatic hydrolysis. The aim of this study was to evaluate the structural composition of bagasse fractions and moisture, temperature and pressure influence in sugars conversion before and after pretreatment with supercritical CO2. The physical characterization and enzymatic hydrolysis experiments of bagasse fractions were designed by a 23 full factorial design with three replications at the center point. The removal of hemicellulose by the pretreatment increased the cellulose content of fiber (retained in the sieve of 48 mesh Tyler series) and pith fractions. It was found that for 60°C and 250 bar, a increase of approximately 50 % (0 % moisture on a dry basis) and 30 % (moisture of 100 % on dry basis) in cellulose content for fiber and pith fractions, respectively. The best result of glucose conversion for fiber fraction (7,7 g/L) was for moisture content equal to 0 % (dry basis) after 24 hours of enzymatic hydrolysis, for 40°C and 100 bar, with an increase of 16 % compared to the fiber fraction without pretreatment for the same period. The best result of glucose conversion for pith fraction (8.2 g/L) was for moisture content of 100 % (dry basis) after 48 hours of enzymatic hydrolysis, for 60°C and 100 bar, with an increase of 16 % compared to the pith fraction without pretreatment at the same interval. X-ray diffraction analysis exhibited crystallinity changes of cellulose for both fractions and surface area revealed an increase in the pores number after pretreatment. It was also presented the absence of inhibitor compound hydroxymethylfurfural (HMF) for fiber and pith fractions
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

Styles APA, Harvard, Vancouver, ISO, etc.

33

RIZZO, ANDREA LUCA. « The composition of noble gas and CO2 in the European subcontinental lithospheric mantle ». Doctoral thesis, Università degli studi di Ferrara, 2020. http://hdl.handle.net/11392/2487890.

Texte intégral

Résumé :

This PhD thesis reports an integrated study of petrography and geochemistry of the minerals with noble gases and CO2 (when available) in fluid inclusions (FI) from selected mantle xenoliths erupted in Europe during alkaline magmatism. The aim of the thesis is to show how the occurrence of partial melting, metasomatism, refertilization, magmatic degassing, volatile recycling, and mixing of volatiles modified the pristine composition of fluids stored in European SCLM and give clues on its geodynamic evolution. Mantle xenoliths from a few key regions where magmatism occurred in different temporal and geodynamic conditions were selected: Lower Silesia (Eger Rift) in SW Poland, Persani Mts. (Transylvania) in Romania, Eifel and Siebengebirge in Germany. The main outcomes of this thesis are: -The chemistry of FI in mantle xenoliths from the studied areas revealed is dominated by CO2, with N2 as second major species. Noble gas are in trace. Oliv are systematically gas-poor respect to Px from the same xenoliths. Among Oliv from European xenoliths, those from Lower Silesia display the highest CO2 concentrations suggesting carbonated-like metasomatism, as also inferred from trace elements in cpx. -Ne and Ar concentration and isotopic ratios indicate variable extents of contamination by atmosphere-derived fluids. This contamination is likely derived from the recycling into the mantle of atmospheric-derived material inherited by local/recent or fossil subduction. This is more evident in the xenoliths from Persani Mts., where a recent subduction occurred. -Oliv and Px display variable extents of partial melting and metasomatism/refertilization, as indicated by the mineral chemistry and He/Ar* in FI. The highest degrees of melting (25-30%) are found in samples from Lower Silesia and Siebengebirge, which are also among the oldest within the suite of samples (>6 Ma). Evidences of low degrees of melting and/or refertilization are found in Persani Mts. and West Eifel, which are Quaternary. This suggests that refertilization process is likely occurred in Quaternary, postponing mantle melting still recorded in Lower Silesia and Siebengebirge. -The 3He/4He corrected for air contamination (Rc/Ra) is within European SCLM range (6±1 Ra) that is lower than MORB (8±1 Ra). This indicates a widespread recycling of crustal material below Europe if compared to other continental rift (e.g., Antarctica, East African). However, the careful investigation of olivine, cpx, and opx in single localities allowed distinguishing variations of 3He/4He that are related to the local history of the mantle. In detail, Persani Mts. show the lowest 3He/4He values within the dataset that indicate highest degree of crustal recycling due to the recent subduction that plays an important role in contaminating the mantle. Instead, metasomatism involving asthenospheric MORB-like fluids well explains the highest 3He/4He values recognized in all the studied localities. -Ne-Ar-He isotopic systematics indicates that most of the data fall along a mixing between air and a MORB mantle. The presence of a plume (lower mantle) beneath the studies localities can be excluded. -I presented the first data of carbon isotope composition of CO2 (δ13C V-PDB) in the Lower Silesia mantle xenoliths, which suffered a metasomatism by carbonated-rich fluids. The δ13C values are about -3.9 ‰ and are within MORB range with <0.1% limestone contamination. -The comparison of 3He/4He signature measured in mantle xenoliths from the three target areas with that of CO2-dominated gas emissions located within or nearby shows that only gases emitted along Eger Rift are representative of the local mantle signature, suggesting an active magmatic activity below this area. Instead, gases emitted in East Eifel and nearby Persani Mts. are slightly to strongly contaminated by crustal fluids during their rising toward the surface or are released from a cooling and aging magma residing within the crust.
Questa tesi riporta lo studio integrato di petrografia e geochimica dei minerali con gas nobili e CO2 in inclusioni fluide (FI) di xenoliti di mantello eruttati in Europa durante il magmatismo alcalino. Lo scopo della tesi è mostrare come il verificarsi di fusione parziale, metasomatismo, rifertilizzazione, degassamento magmatico, riciclo e miscelazione di volatili nel mantello abbia modificato la composizione originaria del mantello litosferico sub-continentale Europeo e fornito indizi sulla sua evoluzione geodinamica. Sono stati selezionati campioni provenienti da alcune regioni in cui si è verificato il magmatismo in diverse condizioni temporali e geodinamiche: Bassa Silesia (Eger Rift) nella Polonia meridionale, Mt. Persani (Transilvania) in Romania, Eifel e Siebengebirge in Germania. I principali risultati di questa tesi sono: -La composizione chimica delle FI negli xenoliti delle aree studiate è dominata dalla CO2, con N2 come seconda specie principale. I gas nobili sono in traccia. Le Olivine (Ol) sono sistematicamente povere di gas rispetto ai pirosseni (Px) degli stessi xenoliti. Tra i campioni studiati, le Ol della Bassa Silesia mostrano le più alte concentrazioni di CO2 che suggeriscono un metasomatismo carbonatato, come dedotto anche dagli elementi in traccia nei Px. -La concentrazione ed i rapporti isotopici di Ne e Ar indicano variabili gradi di contaminazione da parte di fluidi atmosferici. Questa contaminazione è causata dal riciclo nel mantello di materiale derivato dall'atmosfera ereditato dalla subduzione locale, recente o fossile. Ciò è più evidente negli xenoliti di Mt. Persani, dove si è verificata una subduzione recente. -Oliv e Px mostrano variabili percentuali di fusione parziale e metasomatismo/rifertilizzazione, come indicato dalla chimica dei minerali e dall’He/Ar* nelle FI. I più alti gradi di fusione (25-30%) si trovano in Bassa Silesia e Siebengebirge, che sono anche tra i più antichi all'interno della suite di campioni (>6 Ma). Bassi gradi di fusione e/o rifertilizzazione sono ipotizzati nei Mt. Persani e nella parte occidentale dell’Eifel, che sono quaternari. Ciò suggerisce che il processo di rifertilizzazione è avvenuto nel Quaternario. -Le misure di 3He/4He corretto per la contaminazione dell'aria (Rc/Ra) rientrano nell'intervallo di valori noto per il mantello Europeo (6±1 Ra) e sono inferiori a quello MORB (8±1 Ra). Ciò indica un diffuso riciclo di materiale crostale al di sotto dell'Europa rispetto ad altre zone di rift continentale (ad es. Antartide, Africa orientale). Tuttavia, l'attenta indagine su Oliv e Px nelle singole località ha permesso di distinguere le variazioni di 3He/4He correlate alla storia locale del mantello. Nel dettaglio, i Mt. Persani mostrano 3He/4He più bassi, indicando il più alto grado di riciclo di materiale crostale nel mantello. Invece, il metasomatismo da fluidi astenosferici simili al MORB spiega i più elevati 3He/4He presenti in tutte le località studiate. -La sistematica di Ne-Ar-He indica un trend di mescolamento tra l'aria e un mantello MORB e l’assenza di un contributo del mantello inferiore (plume) al di sotto dell’Europa. -I primi dati sulla composizione isotopica del carbonio di CO2 (δ13C V-PDB) negli xenoliti del mantello carbonatato della Bassa Silesia indicano valori di circa -3.9 ‰, che rientrano nel range MORB con una contaminazione di carbonati <0.1%. -Il confronto tra gli 3He/4He misurati negli xenoliti di mantello delle tre aree e quelli dei gas emessi all'interno o nelle vicinanze mostra che solo i gas emessi lungo l’Eger Rift sono rappresentativi della firma del mantello locale, suggerendo un'attività magmatica ancora attiva sotto quest’area. Invece, i gas emessi nell'Eifel e nelle vicine dei Mt. Persani sono variabilmente contaminati da fluidi crostali acquisiti durante la loro risalita verso la superficie o sono rilasciati da un magma in raffreddamento e invecchiamento all'interno della crosta

Styles APA, Harvard, Vancouver, ISO, etc.

34

Chauvet, Margot. « Extrusion assistée par CO2 supercritique appliquée au moussage d’un biopolymère, le poly(acide lactique), seul ou en mélange à de l’amidon : étude expérimentale et modélisation ». Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2017. http://www.theses.fr/2017EMAC0008/document.

Texte intégral

Résumé :

Actuellement, les mousses de polymères thermoplastiques (ou plastiques expansés) sont utilisées dans de nombreuses applications de la vie courante. On peut les retrouver dans l’isolation, l’absorption de choc, l’emballage ou encore dans des applications spécifiques du secteur biomédical. Un des inconvénients majeurs est l’utilisation de matières synthétiques. Pour pallier cette problématique, l’utilisation de polymères biosourcés et biodégradables représente une alternative intéressante. L’objectif de ce travail est d’élaborer des mousses de PLA (poly-(acide lactique)), un polymère biosourcé, biodégradable et biocompatible. Pour réaliser ces matériaux poreux, la technique d’extrusion couplée à l’injection de CO2 supercritique est une solution performante. En effet, selon les conditions opératoires et la solubilité du CO2 dans le biopolymère utilisé, son injection dans le fourreau d’une extrudeuse va modifier les propriétés rhéologiques du polymère. Il va, de plus, jouer le rôle d’agent moussant lors de la dépressurisation que subit le polymère au cours de son passage dans la filière. L’avantage de cette technique par rapport aux techniques classiques est, qu’ici, l’agent physique moussant (le CO2) n’est pas toxique, est acceptable d’un point de vue environnemental et ne laisse aucun résidu dans le produit. Ce procédé a montré un grand potentiel pour la création de matériaux poreux avec différentes morphologies. Des mousses avec une porosité supérieure à 95 % ont pu être obtenues. À ces très hautes porosités, deux types de structure ont été observés en fonction de la température : une mousse fortement expansée radialement avec des cellules ouvertes de grande taille, ou une mousse fortement expansée longitudinalement présentant une faible teneur en cellules ouvertes de petite taille. Une étude paramétrique (T, P, % CO2), a été menée avec le PLA seul et en mélange à de l’amidon sous différentes formes. Ce dernier permet d’améliorer la biodégradabilité du PLA et de modifier son comportement durant le moussage. Afin de parvenir à une meilleure compréhension et donc une meilleure maîtrise du procédé, un modèle a été développé. Il s’appuie sur le couplage entre l’écoulement du mélange dans la filière avec les phénomènes de nucléation et croissance des bulles dans ce mélange. Il a été validé grâce à la comparaison avec les résultats expérimentaux préalablement obtenus
Nowadays, foams of thermoplastic polymers (or expanded plastics) are used in many applications of day life. They can be found in insulation, shock absorption, packaging or biomedical specific applications. One of the major drawbacks lies in the use of synthetic materials. To overcome this problem, the use of biobased and biodegradable polymers represents an interesting alternative.The aim of this work is to elaborate foams with the biopolymer poly(lactic acid), PLA. To manufacture such a porous material, the process of extrusion assisted by supercritical CO2 is an efficient solution. Indeed, depending on operating conditions and CO2 solubility in the biopolymer, its injection in the barrel of an extruder modifies the rheological behaviour of the polymer. It also plays the role of an expansion agent during the depressurization undergone by the polymer while flowing through the die. The main advantages in comparison with traditional methods, are that, here, the physical blowing agent (CO2) is not toxic, environmentally friendly while leaving no residue in the final product. This process shows great potential for the creation of porous materials with different morphologies. Foams with porosity as high as 95 % have been produced. For such a high porosity, two structures have been observed: foams with a large radial expansion with only open cells of large size, or foams with a large longitudinal expansion with low content of open cell having small size. A parametric study (T, P, CO2 %) was conducted with PLA both pure and mixed with starch in various forms. The latter makes it possible to improve the biodegradability of the PLA and to modify its behaviour during the foaming. Modelling of the process could allow a better understanding. A model based on the coupling between the polymer flow in the die with the nucleation and growth phenomena, has been developed. It has been validated by comparison with the experimental results previously obtained

Styles APA, Harvard, Vancouver, ISO, etc.

35

Karstens, Jens [Verfasser]. « Focused fluid conduits in the Southern Viking Graben and their implications for the Sleipner CO2 storage project / Jens Karstens ». Kiel : Universitätsbibliothek Kiel, 2015. http://d-nb.info/1072410192/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

36

Knoph, Oyvind Lomeland. « Development of an energy efficient and environmentally friendly drum dryer using a heat pump with CO2 as working fluid ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26351.

Texte intégral

Résumé :

The drum dryer is a common appliance for drying clothes in households today. It is constantly developed in order to reduce its environmental impact and energy consumption. An industrial partner has initiated a research project with the aim to substitute R134a with CO2 as refrigerant. R134a has a global warming potential (GWP) 1300 times the GWP of CO2, thus CO2 is a much more environmental friendly refrigerant. A drum dryer driven by a heat pump was previously modified to use CO2 as refrigerant. This system has now been further developed to include a two-stage compressor and a liquid separator at an intermediate pressure. The flash gas is separated on the intermediate pressure stage and injected into the compressor. Theoretically the result should be a higher mass flow on the high-pressure stage and reduced work required for 1st stage compression. Closing a blocking valve at the intermediate stage can disable the flash gas recycling process. This gives the opportunity to compare the results to the results from a regular cycle.The results from the experiments in this study are compared to results from similar experiments. Results are available from experiments by former students and initial tests by the industrial partner. The industrial partner also provided an ultimate goal of 0.26 kWh/kgtextiles, which is the state of the art consumption for R134a heat pumps. The two main performance measures are specific energy consumption based on weight of the textile load and specific energy consumption based on weight of the removed water. The best experiment in this study consumed 0.37 kWh/kgtextiles and 0.61 kWh/kgremoved water. These results were achieved by disabling the flash gas injection. The corresponding results using flash gas injection were 0.41 kWh/kgtextiles and 0.70 kWh/kgremoved water. In the current setup the flash gas injection has not contributed to reduced energy consumption. There has been a challenge to control the flash gas injection while keeping the superheat low out of the evaporator. Suitable modifications have been suggested to overcome this issue.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Nabati, Hamid. « Numerical Analysis of Heat Transfer and Fluid Flow in Heat Exchangers with Emphasis on Pin Fin Technology ». Doctoral thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-14409.

Texte intégral

Résumé :

One of the most important industrial processes is heat transfer, carried out by heat exchangers in single and multiphase flow applications. Despite the existence of well-developed theoretical models for different heat transfer mechanisms, the expanding need for industrial applications requiring the design and optimization of heat exchangers, has created a solid demand for experimental work and effort. This thesis concerns the use of numerical approaches to analyze and optimize heat transfer and fluid flow in power generation industry, with emphasis on pin fin technology. This research begins with a review on heat transfer characteristics in surfaces with pin fins. Different pin fins shapes with various flow boundaries were studied, and thermal and hydraulic performances were investigated. The impact of parameters such as inlet boundary conditions, pin fin shapes, and duct cross-section characteristics on both flow and heat transfer were examined. Two important applications in power generation industry were considered for this study: power transformer cooling, and condenser for CO2 capturing application in oxy-fuel power plants. Available experimental data and correlations in the literature have been used for models validation. For each case, a model based on current configuration was built and verified, and was then used for optimization and new design suggestions. All numerical modeling was performed using commercial CFD software. A basic condenser design was suggested and examined, supplemented by the use of pin fin technology to influence the condensation rate of water vapour from a CO2/H2O flue gas flow. Moreover an extensive review of numerical modeling approaches concerning this condensation issue was conducted and presented. The analysis results show that the drop-shaped pin fin configuration has heat transfer rates approximating those of the circular pin configuration, and the drop-shaped pressure losses are less than one third those of the circular. Results for the power transformer cooling system show those geometrical defects in the existing system are easily found using modeling. Also, it was found that the installation of pin fins in an internal cooling passage can have the same effect as doubling the radiator’s height, which means a more compact cooling system could be designed. Results show that a condensation model based on boundary layer theory gives a close value to experimental correlations. Considering a constant wall temperature, any increase in CO2 concentration results in lower heat transfer coefficients. This is a subsequence of increased diffusivity resistance between combustion gas and condensing boundary layer. Also it was shown that sensitivity of heat transfer rate to inlet temperatures and velocity values decreased when these parameters increased. The application of numerical methods concerning the condensation process for CO2 capturing required significant effort and running time as the complexity of multiphase flow was involved. Also data validation for the CO2/H2O condenser was challenging since this is quite a new application and less experimental data (and theoretical correlations) exist. However, it is shown that models based on numerical approaches are capable of predicting trends in the condensation process as well as the effect of the non-condensable CO2 presence in the flue gas. The resulting data, conclusions, applied methodology can be applied to the design and optimization of similar industrial heat exchangers, such as oil coolers which are currently working at low efficiency levels. It can also be used in the design of electronic components, cooling of turbine blades, or in other design applications requiring high heat flux dissipation. Finally, the finding on water vapour condensation from a binary mixture gas can be referenced for further research and development in this field.

Styles APA, Harvard, Vancouver, ISO, etc.

38

Tiraboschi, C. « COH FLUIDS AT UPPER-MANTLE CONDITIONS : AN EXPERIMENTAL STUDY ON VOLATILE SPECIATION AND MINERAL SOLUBILITY IN THE MS+COH SYSTEM ». Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/260613.

Texte intégral

Résumé :

COH fluids play a fundamental role in many geological processes, controlling the location of melting in subduction zones and promoting mass transfer from the subducting lithosphere to the overlying mantle wedge. The properties of COH fluids are strictly dependent on the composition of the fluid in subduction systems, i.e., the speciation of the volatile components of the fluid itself and the presence of solutes deriving from the dissolution of rock-forming minerals. In the scientific literature, the speciation of COH fluids has been generally determined through thermodynamic calculations using equations of state of simple H2O–non-polar gas systems (e.g., H2O–CO2–CH4), equations that do not consider the complexity related to dissolution processes, which are substantially unexplored in COH fluids and limited so far to aqueous fluids (Newton & Manning, 2002). The aim of this work is to experimentally investigate the speciation of COH volatile components of the fluid and the dissolution of mantle minerals in carbon-saturated COH fluids at buffered fO2 conditions. Our experimental approach relies on two different techniques: i) analysis by means of quadrupole mass spectrometer (QMS) of the COH fluid from pierced run capsules to retrieve speciation of volatile components and ii) analysis of frozen COH fluid with laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) to measure the amount of solutes. Experiments were conducted at P = 1–3 GPa and T = 700–1200 °C using a rocking piston-cylinder apparatus. Mantle minerals in equilibrium with COH fluids are represented by synthetic forsterite, enstatite and natural magnesite. fO2 conditions were controlled employing the double capsule technique and nickel–nickel oxide (NNO) buffer. We also performed a series of experimental runs in the COH-only system in single or double capsules, varying the packing material that surrounds the capsule and the oxygen buffer, to evaluate the differences in COH volatile speciation determined by the choice of the experimental setup. Quantitative analyses of COH volatile speciation were retrieved by piercing the capsule in a gas-tight vessel at T = 80 °C and convoying evolved gases to a QMS through a heated line to avoid the condensation of water. Our experimental results on COH volatile speciation highlighted the importance of the experimental verification of volatile speciation, which can diverge considerably compared to the thermodynamic model (Perplex; Connolly, 1990) depending on the experimental strategies adopted. In particular, when single capsules are employed, the packing material that surrounds the capsule exerts a major control on the COH volatile speciation. Double capsule experiments provided similar COH volatile speciation compared to thermodynamic modeling for what concerned the COH-only system. However, the addition of mantle minerals in the experimental charge at the same P–T–fH2 conditions determines a shift in the COH fluid composition toward more CO2-rich terms. At P = 1 GPa, data show an increase in CO2 of + 11 mol% at T = 800 °C and of + 26 mol% at T = 900 °C in the COH fluid in equilibrium with forsterite + enstatite compared to a pure COH fluid. To evaluate if this shift could be determined by interactions of the COH fluid with solid phases, we retrieved the solubility of mantle minerals in COH fluids through the cryogenic LA-ICP-MS technique described by Kessel et al. (2004). With this method the COH fluid is trapped into a diamond layer, the aqueous part of the COH fluid is frozen to avoid any precipitation of solutes and is analyzed through LA-ICP-MS. Experimental results on mantle minerals solubility in COH fluids suggest that the amount of dissolved material in COH fluids is similar compared to mantle mineral solubility in H2O-only fluid and ranges from the 2 wt.%, expressed as MgO + SiO2, at P = 1 GPa and T = 800 °C, to 12 wt.% at P = 2 GPa and T = 1100 °C for the forsterite + enstatite assemblage. The formation of dissolved species containing carbon, such as CO32- and Mg(HCO3)+ lead to an increase in the amount of carbon in the fluid, but not in CO2 species. In order to get the increase of CO2 that we observed in experiments analyzed through quadrupole mass spectrometry, we suggest a series of possible dissolution reactions involving Mg-solutes, which could lead to increase the amount of CO2 in the fluid. As a consequence, the quantity of CO2 infiltrating into the mantle-wedge could be remarkably high, compared to the COH fluid composition predicted by thermodynamic modeling.

Styles APA, Harvard, Vancouver, ISO, etc.

39

Vanagaitė, Margarita. « Agactache foeniculum L. eterinių aliejų ekstrakcija superkritiniu CO2 ir jų dujų chromatografinė – masių spektrometrinė analizė ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120620_124507-76688.

Texte intégral

Résumé :

Anyžinis lofantas (Agastache foeniculum (Pursh) Kuntze) – tai vaistinis, prieskoninis daugiametis augalas. Vienas iš notrelinių šeimos dekoratyvus, daugiametis žolinis augalas, kilęs iš Šiaurės Amerikos. Lietuvoje kol kas dar mažai paplitęs. Auginamas botanikos soduose ir darželiuose, vertinamas kaip labai kvapnus, medingas ir vaistinis augalas. Anyžinis lofantas dirvai mažai reiklus, turi gerai išvystytą šaknų sistemą, todėl nebijo sausros. Geriau auga derlingesnėje žemėje, nepiktžolėtose priesmėlio arba lengvo priemolio dirvose, atviroje, saulėtoje vietoje. Žydi nuo birželio vidurio iki spalio mėnesio. Žiedai – ryškiai violetiniai arba melsvi. Agastache foeniculum paruoštas VDU Kauno Botanikos sode, 2010 metais masinio žydėjimo metu. Sausoje žaliavoje yra 1,71-2,10 % eterinio aliejaus, kurio svarbiausios dalys yra D-limonenas ir estragolis. Nupjauta žolė džiovinama paskleista plonu sluoksniu gerai vėdinamoje arba 35°C temperatūros patalpoje. Išdžiovinta žolė atskiriama nuo stambesnių stiebų ir laikoma sudėta į medžiaginius maišus. Tinkamai išdžiovinta žolė yra 12 - 14 % drėgnumo. Džiovinimas – vienas svarbiausių etapų, kuris labiausiai įtakoja galutinę vaistinės žaliavos kokybę. Šiame darbe – buvo identifikuoti Agastache foeniculum eterinių aliejų komponentai: D- limonenas, estragolis, kariofilenas. Vaistinio anyžinio lofanto eterinių aliejų ekstraktai ruošti naudojant superkritinio skysčio CO2 ekstrakciją. Jų analizė atlikta dujų chromatografu– masių spektrometrijos... [toliau žr. visą tekstą]
Blue giant hyssop (Agastache foeniculum (Pursh Kuntze) is medicinal perennial plant. This ornamental plant is native to North America. In Lithuania is not yet widely spread. It is cultivated in botanical gardens and is valuable because is a fragrant, melliferous medicinal plant. Blue giant hyssop is not strict for soil and has a well developed system of the roots, so it is resistant to drought. This plant prefers a good soil and sunny places. It blooms from the middle of June to October. The flowers are violet or royal-blue. Agastache foeniculum raw material was prepared in Kaunas botanical garden of VMU during flowering season in 2010. In dry raw material is about 1.71 – 2.10  of essential oils, the basic components are D-limonene and estragol. The grass after cutting was spread in a thin layer in well ventilated room or in the room at 35 C temperature. The dried grass was separated from stems and stored in huckaback bags. The well dried grass has about of 12-14  moisture. The drying is one of the most important periods which influence the final quality of drug raw material. In this work the components of essential oils of Agastache foeniculum have been identified. The extracts of volatile oils of Agastache foeniculum were prepared by supercritical CO2 extraction. After the analysis the relative quantities of essential oils components as well as composition have been evaluated by gas chromatography-mass spectrometry detector. Investigations have showed that the... [to full text]

Styles APA, Harvard, Vancouver, ISO, etc.

40

Pimentel, Hélio Oliveira. « Utilização de extração com CO2 supercrítico e de lixiviação assistida por ultra-som para a regeneração de catalisadores automotivos ». Instituto de Química, 2007. http://repositorio.ufba.br/ri/handle/ri/20527.

Texte intégral

Résumé :

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-15T14:22:53Z No. of bitstreams: 1 Tese Hélio O. Pimentel.pdf: 2196448 bytes, checksum: b81d660c75daf2b43a78c84dc7e07cf7 (MD5)
Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-15T14:27:40Z (GMT) No. of bitstreams: 1 Tese Hélio O. Pimentel.pdf: 2196448 bytes, checksum: b81d660c75daf2b43a78c84dc7e07cf7 (MD5)
Made available in DSpace on 2016-09-15T14:27:40Z (GMT). No. of bitstreams: 1 Tese Hélio O. Pimentel.pdf: 2196448 bytes, checksum: b81d660c75daf2b43a78c84dc7e07cf7 (MD5)
FINEP / CNPq / RECAT
Esta tese é uma contribuição na perspectiva de melhoramento da tecnologia para o tratamento catalítico dos gases de emissão automotiva, reconhecidos como poluentes ambientais. Os catalisadores ou conversores automotivos (Three-Way Catalysts, TWC) são uma tecnologia bem estabelecida para o abatimento de gases poluentes emitidos pelos veículos, mas esses sistemas desativam sob condições severas às quais estão submetidas. As causas de desativação reconhecidas para o TWC são: a exposição às altas temperaturas durante a operação do motor, que causam danos ao washcoat e sinterização dos sítios ativos, bem como o depósito de fases inativas como fosfatos, sulfatos e compostos carbonáceos, além de outros venenos provenientes dos aditivos da gasolina e óleos lubrificantes. Muitos esforços têm sido destinados à regeneração da atividade catalítica, aumentando a durabilidade do TWC, por razões econômicas e ambientais. A remoção de fases inativas, venenos e a redispersão das espécies ativas sinterizadas são algumas das estratégias investigadas na literatura. Neste trabalho, amostras de conversores envelhecidos num táxi, na condição real de tráfego em Salvador-Bahia-Brasil, foram caracterizadas por MEV, FRX, DRX, TG, XPS, TPR e análises texturais, bem como por testes de avaliação catalítica na redução de NO com CO, empregada como reação modelo. Dois procedimentos de regeneração foram investigados: i) lixiviação assistida por ultra-som (LUS), utilizando solventes e soluções diluídas de ácidos; e ii) tratamento com fluido supercrítico de CO2 (FSC), usando metanol como agente modificador. Como a eficiência da extração com CO2 supercrítico depende de vários parâmetros, tais como temperatura, pressão e solventes modificadores, o estudo foi realizado usando um planejamento fatorial 2k (k = 3). Ambos os procedimentos mostraram-se promissores levando a recuperação da atividade catalítica. O ácido clorídrico diluído mostrou-se o meio mais adequado para a lixiviação assistida por ultra-som, removendo venenos e fases inativas, bem como causando redistribuição das fases ativas de metais nobres. O tratamento com FSC também é eficiente, mas as condições operacionais precisam ser bem controladas de modo a evitar danos estruturais ao washcoat. As modificações texturais observadas, redispersão das fases ativas, remoção de fases inativas e venenos, na condição de 100ºC, 1500 psi e 10% de metanol, favoreceram a recuperação da atividade catalítica.
This thesis is a contribution in perspective to technology improvement of catalytic treatment automotive gases, recognized as environmental pollutants. Automotive catalysts (Three-Way Catalysts, TWC) are well established technology for abatement of gaseous pollutants emitted from vehicles, however they deactivate under the tough conditions to which they are subjected. The TWC deactivation factors are recognized as the exposition at high temperatures during the motor operation, due to the temperature sintering effects on alumina washcoat and active sites, as inactive phase deposition like phosphates, sulfates, graphite and other carbonaceous, and other poisons resultant of the gasoline and lubricant oil addictives. A lot of effort has been applied in order to regenerate activity, thus improving TWC durability, both for economical and environmental reasons. The removal of inactive phases and poisons and re-dispersion of sintered active species are some regeneration strategies that have been investigated in the literature. In this work, samples of aged converters, in actual transit condition vehicle taxi fleet of Salvador-Bahia-Brazil, were characterized by SEM, XRF, XRD, TG, XPS, TPR and textural analysis, as well as, catalytic evaluation tests by the NO with CO reduction, as the reaction model. Two regenerated proceedings were investigated: i) ultrasound attended lixiviation (USL), with solvents and dilute acid solutions, and ii) CO2 supercritical fluid (SCF), with methanol as modifier agent. Once the efficiency of supercritical fluid extraction depends on various parameters, such as temperature, pressure and presence of modifier solvents, the study has been performed using a factorial design 2k (k = 3). Both proceedings showed promising to carry the catalytic activity regeneration. The dilute hydrochloric acid was the best adequate means to the ultrasound attended lixiviation, removing poisons and inactive phases and leading to the re-dispersion of active phases of noble metals. The SCF treatment is also efficient; however, the operational conditions need to be well controlled to avoid the washcoat structural damages. The observed textural modifiers, active phase re- dispersion, inactive phases and poisons removal, in the condition of 100ºC, 1500 psi and 10% methanol, aid the catalytic activity recovery.

Styles APA, Harvard, Vancouver, ISO, etc.

41

Hijazi, Nibal. « Développement de composites nanostructurés à base de biopolyesters et de nanoparticules de chitosane générées par des procédés assistés par CO2 supercritique ». Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2014. http://www.theses.fr/2014EMAC0016/document.

Texte intégral

Résumé :

Dans une logique d’éco-conception et de développement durable, de nombreux travaux ont pour objectif l’étude de polymères biosourcés. Parmi les recherches menées à ce jour, une piste d’étude consiste à les structurer aux échelles micro et nanoscopiques tout en valorisant certaines de leurs propriétés spécifiques, l’objectif étant la création de matériaux à propriétés fonctionnelles originales et performantes. Dans ce contexte, une attention particulière a été portée sur l’utilisation du dioxyde de carbone supercritique (CO2-sc). En effet, sa capacité à se solubiliser en grande quantité dans de nombreux polymères et donc d’en modifier les propriétés (viscosité, tension interfaciale, …) peut permettre une amélioration des matériaux composites fabriqués. Ce projet s’intéresse plus particulièrement à l’élaboration d’assemblages de biopolymères nanostructurés et revêt deux enjeux principaux : (1) la synthèse de nanoparticules de biopolymères (dans notre cas, du chitosane), (2) l’élaboration d’assemblages de biopolymères nanostructurés. La première étape a consisté à concevoir et développer de nouveaux procédés de génération de nanoparticules de chitosane par des procédés utilisant le CO2-sc soit comme antisolvant soit comme agent de dissolution et d'atomisation. Pour la deuxième étape, des films composites à base de poly (acide lactique) PLA et de poly (hydroxybutyrate-co-valérate) PHBV ont été préparés par la voie hot-melt par extrusion bi-vis. Des analyses thermiques, moléculaires et structurales, morphologiques et de granulométrie ont permis de caractériser les films biocomposites ainsi produits
In a logic of eco-design and sustainable development, many works aim to study the bio-sourced polymers. Among these studies, a promising concept consists in structuring materials at micro and nanoscales while enhancing some of their properties, the objective being the creation of original materials with improved functional properties and performance. In this context, particular attention has been paid to the use of supercritical carbon dioxide (sc-CO2). Its ability to dissolve into many polymers in large quantities and thus to change their properties (viscosity, interfacial tension, ...), can improve both the composite material and its manufacturing process. This project focuses on the development of nanostructured biopolymers and addresses two main issues: (1) the synthesis of biopolymer nanoparticles (in this case, chitosan), and (2) the development of nanostructured biopolymers. The first step consisted in designing and developing new processing methods to generate biopolymer nanoparticles, using sc-CO2 as antisolvent agent or as dissolving and atomizing agent. For the second step, poly (lactic acid) PLA and poly (hydroxybutyric-co-hydroxyvaleric acid) PHBV based composite films were prepared by a hot-melt process by twin-screw extrusion of the nanoparticles and the matrix. Thermal, molecular and structural analysis, as well as morphological and particle size distribution studies allowed a good characterization of the biocomposite films

Styles APA, Harvard, Vancouver, ISO, etc.

42

Richey, David J. « Fault Seal Analysis for CO2 Storage : Fault Zone Architecture, Fault Permeability, and Fluid Migration Pathways in Exposed Analogs in Southeastern Utah ». DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/6060.

Texte intégral

Résumé :

Geologic storage of anthropogenic carbon dioxide (CO2) by injection into underground porous sandstone reservoirs has been proposed as a method for the reduction of anthropogenic greenhouse gas emissions. Upwards migration and leakage of injected fluids along natural fault and fracture networks is a key risk factor for potential injection locations. We examine exposed natural analogs to evaluate the impacts of faulting and fracturing on reservoir and top-seal pairs and to evaluate evidence for paleomigration of fluids along the fault zone. We examine the Iron Wash fault, a 25-km long normal fault which cuts Jurassic sedimentary rocks and has throws that range from 20-120 m, to examine how a fault may affect seal integrity. Field mapping, kinematic analysis, petrographic analysis, characterization of the fault zone facies and fault architecture, analysis of altered and mineralized rocks in and around the fault zone, and modeling of fault seal capacity was conducted to provide an understanding of the Iron Wash fault zone. Field data and observations were combined with well log and borehole data to produce three types of models for the Iron Wash fault: 1) geometric model of the fault in the subsurface, 2) predictive models of fault zone behavior and fault seal analysis, and 3) predictive geomechanical models of the response of the fault zone to an imposed stress field and increasing the effective stress on the fault. We conclude that the Iron Wash fault zone has low sealing capacity and will likely not behave as a seal for fluids against the fault zone due primarily to modest throw on the fault and high frequency of fractures associated with the fault zone. Analysis of fluid alteration and mineralization around the fault zone indicates that the fault zone was conduit for paleo-fluids. We conclude that the fault is not likely to develop a sealing membrane and therefore will most likely fail as a seal to fluids moving through the reservoirs modeled here. Modeling results indicate that a reduction in the effective normal stress on fault surfaces may induce failure of faults resulting in earthquakes or increased hydraulic conductivity of fractures.

Styles APA, Harvard, Vancouver, ISO, etc.

43

Parada, Hernández Natalia Lorena 1982. « Study and evaluation of CO2 laser application in the epoxy resin production in microreactors ». [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266951.

Texte intégral

Résumé :

Orientador: Rubens Maciel Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-17T01:43:12Z (GMT). No. of bitstreams: 1 ParadaHernandez_NataliaLorena_M.pdf: 3447077 bytes, checksum: 71ef0ac11523fdfcfd56b1e719487b5f (MD5) Previous issue date: 2010
Resumo: O estudo das resinas epóxicas é de grande interesse científico e tecnológico devido à versatilidade apresentada por estes materiais. Esta versatilidade é o resultado das diferentes reações químicas envolvidas e das características físico-químicas dos diferentes endurecedores, catalisadores e reagentes que possibilitam diferentes processos e combinação de propriedades objetivando aplicações específicas. A resina epóxi obtida a partir de epicloridrina e bisfenol A, o diglicidil éter de bisfenol A, continua sendo um intermediário importante na tecnologia da resina epóxi. Os microreatores tem provado melhorar a distribuição da massa molar dos polímeros sintetizados dentro destes microaparelhos, isto como consequência das altas taxas de transferência de calor e massa e da mais rápida e melhor mistura apresentada nos microcanais graças à diminuição do tamanho. Levando isto em conta, foi estudada a síntese da resina epóxi em microreatores usando o laser na polimerização rápida da resina dentro destes pequenos reatores. Para o desenvolvimento do projeto foi estudada a síntese da resina em escala laboratorial e calculados os parâmetros cinéticos da reação de obtenção da resina epóxi líquida. O projeto de microreatores requer o conhecimento do comportamento da mistura dentro dos microcanais destes aparelhos, razão pela qual se fez uso da fluido dinâmica computacional, CFD, o qual permitiu a avaliação da mistura dos reagentes dentro das configurações testadas neste trabalho, uma configuração tipo T e tipo Y.
Abstract: Epoxy resin study is of a great scientific and technologic interest due to the versatility showed for these materials. This versatility is the result of different chemical reactions involved and the physical-chemical characteristics of the several hardeners, catalysts, and reagents that make possible uncountable process and properties combination objectify specific applications. Epoxy resin from epicholorohydrin and bisphenol-A continues being an important intermediary in the epoxy resin technology. Microreactors have shown to improve molecular weight distribution of the synthetized polymer within these microdevices; this can be explained by the high heat and mass transfer fluxes, and the faster and better mixture shown in the microchannel due to the size reduction. In this context, the epoxy resin synthesis was studied using a laser in the rapid polymerization of the resin within these small reactors. It was studied the resin synthesis in laboratorial scale and calculated the kinetic parameters of the liquid epoxy resin obtaining reaction. Since microreactor design requires knowing the mixture behavior in the microchannels, computational fluid dynamics (CFD) was used in order to evaluate the mixture grade of the reagents for the tested configuration in this work, the "T" and "Y" configuration types.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

Styles APA, Harvard, Vancouver, ISO, etc.

44

Bennour, Ziad. « Effect of Hydraulic Fracturing Fluid Viscosity on Stimulated Reservoir Volume for Shale Gas Recovery ». 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225563.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

45

Padilla, Antunez Suyapa. « EFFECT OF REDUCED SODIUM CHEESE ON THE GROWTH OF PATHOGENIC BACTERIA AND INACTIVATION OF LISTERIA INNOCUA USING SUPERCRITICAL FLUID EXTRACTION WITH CO2 ». DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1646.

Texte intégral

Résumé :

Listeria monocytogenes continues to challenge the dairy industry in causing post-process contamination of cheeses. To reduce risk of contamination, it is crucial to understand the growth and survival of pathogenic bacteria in cheese products and to develop post-process mitigation strategies. This study evaluated the fate of pathogens in reduced and regular sodium Mozzarella cheese, and the potential of Supercritical Fluid Extraction with CO2 (SFE) to reduce Listeria innocua on Mozzarella and Queso Fresco. The survival of L. monocytogenes, Salmonella, and E.coli O157:H7 (2-3 log CFU/g) in reduced sodium Mozzarella (1.62%), compared to regular sodium Mozzarella cheese (2.15%) at 4ºC and 12ºC for 90 and 30 days, respectively, was evaluated. Salmonella and E. coli O157:H7 populations decreased over incubation time at both temperatures and no difference (pListeria monocytogenes population also decreased during incubation time at 4°C regardless of the sodium concentration in Mozzarella cheese. However, there was a difference in the population of L. monocytogenes for regular and reduced sodium incubated 12°C, and its populations increased 1 log CFU/g in reduced sodium Mozzarella cheese. Additionally, this study determined the bactericidal effect of SFE on the population of L. innocua, a surrogate for L. monocytogenes, in Mozzarella and Queso Fresco cheese (6 log CFU/g) treated with SFE at two pressures and temperatures (120 bar at 40°C and 150 bar at 50°C) for 30 min. SFE treatment at 120 bar, 40°C for 30 min decreased L. innocua by approximately 3.0 and 3.5 log CFU/g in Mozzarella and Queso Fresco cheeses, respectively. SFE at 150 bar and 50°C reduced L. innocua by approximately 3.78 and 5.2 log CFU/g in Mozzarella and Queso Fresco cheeses, respectively. Since SFE had a minimal effect on the physico-chemical characteristics of the cheeses assayed, the results suggest SFE might be used to reduce L. monocytogenes in cheeses without negatively impacting product quality.

Styles APA, Harvard, Vancouver, ISO, etc.

46

John, Yakubu M. « Kinetic modelling simulation and optimal operation of fluid catalytic cracking of crude oil : Hydrodynamic investigation of riser gas phase compressibility factor, kinetic parameter estimation strategy and optimal yields of propylene, diesel and gasoline in fluid catalytic cracking unit ». Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17323.

Texte intégral

Résumé :

The Fluidized Catalytic Cracking (FCC) is known for its ability to convert refinery wastes into useful fuels such as gasoline, diesel and some lighter products such as ethylene and propylene, which are major building blocks for the polyethylene and polypropylene production. It is the most important unit of the refinery. However, changes in quality, nature of crude oil blends feedstock, environmental changes and the desire to obtain higher profitability, lead to many alternative operating conditions of the FCC riser. There are two major reactors in the FCC unit: the riser and the regenerator. The production objective of the riser is the maximisation of gasoline and diesel, but it can also be used to maximise products like propylene, butylene etc. For the regenerator, it is for regeneration of spent or deactivated catalyst. To realise these objectives, mathematical models of the riser, disengage-stripping section, cyclones and regenerator were adopted from the literature and modified, and then used on the gPROMS model builder platform to make a virtual form of the FCC unit. A new parameter estimation technique was developed in this research and used to estimate new kinetic parameters for a new six lumps kinetic model based on an industrial unit. Research outputs have resulted in the following major products’ yields: gasoline (plant; 47.31 wt% and simulation; 48.63 wt%) and diesel (plant; 18.57 wt% and simulation; 18.42 wt%) and this readily validates the new estimation methodology as well as the kinetic parameters estimated. The same methodology was used to estimate kinetic parameters for a new kinetic reaction scheme that considered propylene as a single lump. The yield of propylene was found to be 4.59 wt%, which is consistent with published data. For the first time, a Z-factor correlation analysis was used in the riser simulation to improve the hydrodynamics. It was found that different Z factor correlations predicted different riser operating pressures (90 – 279 kPa) and temperatures as well as the riser products. The Z factor correlation of Heidaryan et al. (2010a) was found to represent the condition of the riser, and depending on the catalyst-to-oil ratio, this ranges from 1.06 at the inlet of the riser to 0.92 at the exit. Optimisation was carried out to maximise gasoline, propylene in the riser and minimise CO2 in the regenerator. An increase of 4.51% gasoline, 8.93 wt.% increase in propylene as a single lump and 5.24 % reduction of carbon dioxide emission were achieved. Finally, varying the riser diameter was found to have very little effect on the yields of the riser products.

Styles APA, Harvard, Vancouver, ISO, etc.

47

Rubert, Yolaine. « Contribution à la connaissance des migrations de CO2 naturel dans le Bassin du Sud-Est de la France : enseignements pour le stockage géologique du CO2 dans les réservoirs sédimentaires ». Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00452660.

Texte intégral

Résumé :

Le stockage géologique du CO2 est un des enjeux scientifiques majeurs envisagés pour contrôler le réchauffement climatique lié aux gaz à effet de serre. Le stockage en domaine sédimentaire nécessite une connaissance des facteurs stabilisant/destabilisant les réservoirs, qui peut être apportée par l'étude d'analogues naturels. L'utilisation de méthodes pétrographiques, microthermométriques et géochimiques appliquées aux carottes du forage V.Mo.2 traversant le réservoir naturel de CO2 de Montmiral (France), permettent de suivre les migrations de CO2. Dans le socle Paléozoïque, les inclusions fluides carboniques témoignent de la démixtion sous forte couverture d'un fluide aquo-carbonique chaud, probablement à la fin du Crétacé ou au Paléogène, qui marquerait le remplissage du réservoir de Montmiral. L'étude des unités sédimentaires sus-jacentes montre que le CO2 est resté confiné dans les niveaux rhéto-sinémuriens sous les marnes du Domérien à l'Oxfordien Moyen. Ces marnes jouent le rôle de barrière étanche aux fluides au cours des principaux stades de circulations reconnus. Un premier stade lié à l'extension téthysienne affecte les séries sous-jacentes aux marnes. Un deuxième stade, rattaché à la compression pyrénéenne grâce à une étude de terrain, induit une karstification des séries sus-jacentes à l'écran marneux. A la base du forage, c'est à cette période que le réservoir fuit, mais cette fuite reste confinée sous l'écran marneux. La stabilité du réservoir de Montmiral est due à la présence de l'épais niveau marneux et à la structuration en blocs du bassin de Valence et de son socle limités par des failles jouant le rôle de barrière latérale.

Styles APA, Harvard, Vancouver, ISO, etc.

48

Paes, Mariana Schincariol. « Influência do pré-tratamento de tubérculos e rizomas de priprioca (Cyperus articulatus L.) na obtenção de óleo essencial por extração com CO2 supercrítico ». [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266845.

Texte intégral

Résumé :

Orientadores: Osvaldir Pereira Taranto, Theo Guenter Kieckbusch
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-18T13:08:50Z (GMT). No. of bitstreams: 1 Paes_MarianaSchincariol_M.pdf: 5069814 bytes, checksum: a63adbbd40bd6a5a6b57af8796d19087 (MD5) Previous issue date: 2011
Resumo: Óleo essencial é uma mistura de componentes voláteis produzido por vegetais e tem as funções de proteção contra predadores e de atrair agentes polinizadores. É utilizado pelas indústrias de alimentos, de cosméticos e também pela farmacêutica. O rendimento e a composição do óleo essencial variam de acordo com inúmeros fatores, dentre eles as condições de acondicionamento da matéria-prima e de extração empregados. O presente trabalho teve como objetivo estudar a influência do tratamento precedente à extração de óleo essencial de rizomas e de tubérculos moídos de Cyperus articulatus L., conhecido como priprioca, no rendimento e na composição do produto. Para isso foram empregados a secagem natural e os secadores do tipo leito fluidizado pulsado e estufa, operados em três diferentes níveis de temperatura (40, 50 e 60°C). O óleo essencial foi extraído com CO2 supercrítico de matéria-prima com três diferentes faixas de diâmetro (0,15-0,30; 0,42-0,575 e 0,70-0,85mm). Foi observado que não há diferenças estatísticas entre os rendimentos de óleos essenciais obtidos através do emprego de diferentes secadores operados sob a mesma condição de temperatura. Os resultados de rendimentos foram favorecidos quando usadas partículas com menores faixas de diâmetro em todas as condições de secagem empregadas. O uso de maiores temperaturas de secagem reduziu significativamente o rendimento somente quando utilizado o secador leito fluidizado pulsado. As análises cromatográficas dos óleos essenciais e também o uso de detector de massas permitiram identificar como principais componentes os sesquiterpenos mustakona e corimbolona. A presença dos monoterpenos foi favorecida quando utilizadas temperaturas amenas de secagem e, em algumas situações, o uso de partículas com maiores diâmetros também favoreceu a obtenção dos monoterpenos
Abstract: Essential oil is a mixture of volatile components produced by plants whose functions are protecting against predators and attracting pollinator agents. Essential oils are used by the food, cosmestic and farmaceutical industries. The yield and composition varies according to many factors, such as the raw-material storage conditions and the extraction process adopted. This work aimed to study the influence of the treatment of ground tubercles and rhizomes of Cyperus articulatus L., known as "priprioca", on the essential oil yield and composition. Therefore, the raw material was submitted to three different drying methods prior to the extraction process: a natural drying, a pulsed fluidized bed dryer and oven. The dryers were used in three different temperature levels (40, 50 and 60°C). The essential oil was extracted with supercritical CO2 from priprioca particulate in three different diameter ranges. The results demonstrated no difference between the essential oil yield obtained by different dryers at the same temperature condition. Whereas, the yield was improved by the usage of smaller particles in all drying conditions. Higher temperatures in the pulsed fluidized bed reduced significantly the essential oil yield. The sesquiterpenes mustakone and corymbolone were observed by gas chromatography analysis with mass detector as the two major components. The monoterpenes presence was improved when mild drying conditions were used and, in some cases, the usage of larger particulates also improved monoterpenes attainment
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

Styles APA, Harvard, Vancouver, ISO, etc.

49

Liao, Jianxing [Verfasser], et Michael Z. [Akademischer Betreuer] Hou. « Development of coupled THM models for reservoir stimulation and geo-energy production with supercritical CO2 as working fluid / Jianxing Liao ; Betreuer : Michael Z. Hou ». Clausthal-Zellerfeld : Technische Universität Clausthal, 2020. http://d-nb.info/1231239247/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

50

Lehto, Heather L. « Self-Potential Anomalies and CO2 Flux on Active Volcanoes : Insights from Time and Spatial Series at Masaya, Telica, and Cerro Negro, Nicaragua ». [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002108.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Thèses sur le sujet « CO2 fluid »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres