Browsing by Subject "Carbon dioxide"
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Item A compositional reservoir simulation study to evaluate impacts of captured CO₂ composition, miscibility, and injection strategy on CO₂-EOR and sequestration in a carbonate oil reservoir(2023-08-11) Alsousy, Abdulhamid; Sepehrnoori, Kamy, 1951-; Delshad, MojdehAs the global energy demand rises, concerns regarding the increasing carbon levels deepen. Pushing the international community to pour their time and resources into exploring all avenues that bear potential to aid the decarbonization efforts. The decarbonization efforts attempt to either reduce carbon dioxide emissions or to capture carbon dioxide from the atmosphere. The oil and gas industry’s role falls into the first category. Where captured CO₂ is sequestered into geological stable formations as part of carbon capture, utilization, and storage (CCUS) or carbon capture and storage (CCS) projects. CCUS and CCS technologies hold the keys to decarbonization, possessing a large capacity capable of storing over 8000 GtCO₂, utilizing oil and gas reservoirs, saline aquifers, and coal beds to discard CO₂. In addition, the sequestration in geological structures is long-term, with minimal risk of reintroducing the stored gas back to the surface. This work investigates two scenarios, one in which the reservoir undergoes a tertiary production and another where the reservoir has reached the abandonment stage of its life cycle. The analyses are carried out by employing a historically matched numerical model of a real carbonate reservoir to explore CO₂ storage implications on the reservoir’s performance (EOR) and the efficiency of the injected gas storage in the subsurface. For a holistic evaluation, the numerical model accounts for relative permeability hysteresis, phase trapping, geochemistry, and thermodynamics. Various analyses are conducted to establish the recommended gas blend injected, the importance of miscibility, and the manner of injection (WAG or gas flood). The results showcased how miscible injection outperforms immiscible in CO₂-EOR and sequestration efficiency. Furthermore, gas flood is recommended over WAG, especially when recycling produced gases is possible to store larger volumes of carbon dioxide.Item Application of miscibility calculations to gas floods(2003-08) Yuan, Hua, 1974-; Johns, Russell T.Local displacement efficiency from gas injection is highly dependent on the minimum miscibility pressure (MMP) or minimum miscibility enrichment (MME). The values for these design parameters depend in turn on the displacement mechanisms, vaporizing, condensing, or a combination of the two known as a condensing/vaporizing (CV) drive. Analytical methods, which are inexpensive and quick to use, have been developed to estimate MMP’s for complex fluid characterizations. This thesis presents a simplified and robust method for MMP or MME calculation and quantification of the displacement mechanism. The calculations are also applied to develop new correlations for CO2 floods. The approach relies on finding key crossover tie lines for a dispersion-free displacement using method of characteristic theory (MOC). The new method, however, differs from published methods by significantly reducing the number of equations and unknown parameters, and by providing a fast and robust method that can avoid trivial and false solutions. We demonstrate the improvements by calculation of the MMP and MME for a variety of gas/oil systems and also give new analytical solutions for constant K-value systems that give insight into the nature of the false solutions. A method also based on MOC theory is presented to quantify the fraction of a multicomponent gas flood that is vaporizing or condensing as the pressure or gas enrichment is increased. We quantify the displacement mechanism for any number of oil or gas components by calculating the displacement path lengths along ruled surfaces bounded by these key tie lines. Several multicomponent fluid characterizations are considered. The results show that as the pressure or enrichment is increased condensation occurs at the expense of vaporization. We also show by numerical simulation that the sensitivity of the local displacement efficiency to dispersion depends on the condensing fraction of the displacement. The analytical method is also applied to the displacement of multicomponent oil by CO2. Example calculations were performed for a variety of reservoir fluids. New correlations are also generated for more accurate MMP prediction for CO2 floods. In addition, a new lumping scheme for psuedoization is proposed and applied for CO2 floods so that compositional reservoir simulation can be used in field scale where the effect of dispersion is significant.Item Assessing the effectiveness of the EU ETS through the oil and gas sector(2019-07-09) Reid, Mark William; King, Carey Wayne, 1974-Following the initiation of the European Union Emissions Trading Scheme (EU ETS) in 2005 the scheme has received significant criticism pertaining to a lack of transparency in its operational mechanics and an inability to present conclusive evidence that it has encouraged a reduction in monitored emissions. This study utilizes an adaptation of the event study methodology proposed by Ball and Brown (1968) and Fama et al. (1969) in order to assess the impact of the EU ETS on emissions in the European oil and gas sector as a sample reflective of the scheme on the whole. In doing so, this study compares the annual emissions of carbon dioxide, nitrous oxide and methane for dual listed, single listing and cross listed oil and gas companies on the New York Stock Exchange and the London Stock Exchange and how these emissions change over the period 2000-2017; from prior to the EU ETS until the period of most recent data availability. Analysis conducted on the data gathered infers that, while the EU ETS may have exerted some influence on operators’ behavior, the scheme has generally been ineffective in achieving its goal of lowering emissions and encouraging economic growth. This study also explores the limitations of the EU ETS and potential drivers of emissions changes for operators within the scheme. Through such discussion the intention is to better understand the tradeoff between the advantages of cap-and-trade, a quantity mechanism, and emissions taxation, a pricing mechanism. These mechanisms comprise the majority of the presently adopted emissions policies globally, including the EU ETS, and China’s and Canada’s emissions trading schemes. Therefore, in better understanding the implications and effects of these mechanisms, the intention is to contribute to the future adoption and implementation of global emissions policies.Item Buildup with Bremsstrahlung in the Martian atmosphere(2020-05-07) Gulabrao, Praneel Pratap; Clarno, Kevin T.Photon buildup is a function of energy, medium, and geometry and therefore must be specifically calculated for the case of interest. The Martian atmosphere, comprised mostly of carbon dioxide, is becoming more relevant to radiation researchers and therefore warrants the study of this gas mixture’s buildup properties for ionizing photon flux resulting from the secondary effects of Galactic Cosmic Rays (GCR) and solar flares. Specifically, this work uses MCNP6 code to develop Energy Absorption Buildup Factors (EABFs) in finite slab models for energies ranging from 40 keV to 15 MeV with Martian regolith as the backscattering medium. The Martian carbon dioxide cycle is accounted for by determining maximum and minimum mean densities as a function of orbital position. An isotropic point source model for the atmosphere is also developed using the Geometric Progression fitting function. Buildup is bounded to approximately a factor of 23 at 100 keV for normally incident photons at the top of the atmosphere (TOA). For conservatism, the design problem neglects coherent scattering but assumes Bremsstrahlung effects and uses Klein-Nishina free-electron cross sections for Compton scattering.Item Carbon dioxide absorption into piperazine promoted potassium carbonate using structured packing(2007-12) Chen, Eric; Rochelle, Gary T.A large-scale pilot plant (0.43 m ID) was extensively modified and converted into an absorber/stripper system to demonstrate CO₂ capture technology using aqueous piperazine promoted potassium carbonate for coalfired power plants. Four pilot plant campaigns were completed. Three campaigns were conducted using 5 m K⁺/2.5 m PZ and 6.4 m K⁺/1.6 m PZ. Flexipac 1Y and Flexipac AQ Style 20 structured packing were used in the absorber. The stripper was tested with 14 sieve trays, IMTP #40 random packing, and Flexipac AQ Style 20 packing. Monoethanolamine (7 m) was tested in the third campaign to establish a base case. An approximate rate analysis showed that 5 m K⁺/2.5 m PZ is two times faster than 7 m MEA and three times faster than 6.4 m K⁺/1.6 m PZ. The location of the temperature bulge moves from the top of the column to bottom as the liquid to gas flow rate ratio is increased. Foaming occurred in the absorber in the first two campaigns and occurred in the stripper in the fourth campaign. Data from the pilot plant was used to develop a K⁺/PZ absorber model in Aspen Plus® RateSep[trademark]. The Hilliard (2005) Aspen Plus® VLE model and the kinetics developed by Cullinane (2005) were incorporated in the model. Data-Fit was simultaneously used to reconcile pilot plant data and perform a regression of the interfacial area and heat loss parameters for the RateSep[trademark] absorber model. The lean loading for the pilot plant data was shifted down by 10% to account for a discrepancy with the Cullinane vapor-liquid equilibrium data. The Data-Fit results showed that the average interfacial area for Flexipac 1Y was 80% of the value measure by the air-water column. The average interfacial area for Flexipac AQ Style 20 for 5 m K⁺/2.5 m PZ was 56% of the air-water measurement. The CO₂ heat of absorption may not have been adequately predicted by the RateSep[trademark] absorber model because the regressed values of heat loss were consistent with forced convection.Item Carbon dioxide absorption, desorption, and diffusion in aqueous piperazine and monoethanolamine(2009-12) Dugas, Ross Edward; Rochelle, Gary T.This work includes wetted wall column experiments that measure the CO₂ equilibrium partial pressure and liquid film mass transfer coefficient (kg') in 7, 9, 11, and 13 m MEA and 2, 5, 8, and 12 m PZ solutions. A 7 m MEA/2 m PZ blend was also examined. Absorption and desorption experiments were performed at 40, 60, 80, and 100°C over a range of CO₂ loading. Diaphragm diffusion cell experiments were performed with CO₂ loaded MEA and PZ solutions to characterize diffusion behavior. All experimental results have been compared to available literature data and match well. MEA and PZ spreadsheet models were created to explain observed rate behavior using the wetted wall column rate data and available literature data. The resulting liquid film mass transfer coefficient expressions use termolecular (base catalysis) kinetics and activity-based rate expressions. The kg' expressions accurately represent rate behavior over the very wide range of experimental conditions. The models fully explain rate effects with changes in amine concentration, temperature, and CO₂ loading. These models allow for rate behavior to be predicted at any set of conditions as long as the parameters in the kg' expressions can be accurately estimated. An Aspen Plus® RateSep™ model for MEA was created to model CO₂ flux in the wetted wall column. The model accurately calculated CO₂ flux over the wide range of experimental conditions but included a systematic error with MEA concentration. The systematic error resulted from an inability to represent the activity coefficient of MEA properly. Due to this limitation, the RateSep™ model will be most accurate when finetuned to one specific amine concentration. This Aspen Plus® RateSep™ model allows for scale up to industrial conditions to examine absorber or stripper performance.Item Carbon dioxide and ozone in high school classrooms(2017-05) Lesnick, Leigh Alexandra; Corsi, Richard L.; Novoselac, AtilaHigh school classrooms are important places of learning and working for millions of students and teachers. Because small discomforts can cause losses in student productivity and achievement, ensuring a healthy working environment is vital. As the primary method of supplying outdoor air to classrooms, mechanical ventilation systems are an important component of the indoor space and have the power to affect concentrations of indoor pollutants. The objective of this research was to investigate mechanical ventilation systems and the concentrations of two specific indoor pollutants, carbon dioxide and ozone, in high school classrooms. As part of this study, a two-year field researching campaign was conducted in seven high schools. Carbon dioxide concentrations were measured in the supply airstream and the general room area of classrooms. Through use of steady-state and dynamic mass balance analyses, classroom ventilation rates were estimated. Ozone concentrations were monitored on school rooftops and in classrooms to investigate the influence of mechanical system operation on ozone concentrations indoors. Mechanical ventilation systems were found to be an important consideration when studying the indoor environment, with system operation affecting indoor carbon dioxide and ozone concentrations. When compared to the outdoor air recommendations provided by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) in Standard 62.1, it was found that many classrooms did not receive sufficient fresh air. Classrooms located in portable structures were found to receive large amounts of outdoor air through infiltration and natural ventilation when compared to classrooms in permanent structures. A relationship between average carbon dioxide concentrations and indoor-to-outdoor ozone concentrations was observed, indicating the influence of outdoor air on the concentrations of both pollutants indoorsItem Carbon dioxide and water emulsion stability and rheology with nonionic hydrocarbon surfactants or particles(2009-05) Adkins, Stephanie Sue; Johnston, Keith P., 1955-For the first time the interfacial properties of nonionic hydrocarbon surfactants at both the air-water and CO₂-water interfaces are investigated in terms of surfactant structure to determine the changes in surfactant efficiency (negative of the logarithm of the surfactant concentration to create a surface pressure of 20 mN/m). At the air-water interface, linear surfactant tails are more efficient due to the higher packing ability of the straight chains in the dense surfactant monolayer. However, at the CO₂-water interface, surfactant adsorption is small and tails can be solvated. Thus, branching which increases both tail solvation and tail hydrophobicity also enlarges the hard disk area of the surfactant to ultimately increase the efficiency of the surfactant at the CO₂-water interface. CO₂-in-water concentrated emulsions (foams) are studied over short and long times to evaluate the foam stability as a function of both surfactant structure and foam conditions using in-situ optical microscopy. The surface pressure measured at the CO₂- water interface is correlated with the short time stability of coalescing foams with very small cell sizes (under 0.4 [mu]m in diameter). Long time stability of bubbles to coalescence is shown under a variety of conditions. The rheology of these bulk CO₂-in-water foams under high-pressure conditions are also evaluated through measurements of the pressure drop over a capillary tube. Viscosities in excess of 200 cP are measured, an increase of over 1000 time that of pure CO₂ (0.09 cP at 24 °C and 2000 psia). The viscosity of the C/W foams are found to correlate with bubble size, continuous phase viscosity, shear rate, and interfacial tension. Hydrophobic silica particles adsorbed at the interface are also used to stabilize water-in-CO₂ emulsions as an alternative to surfactant stabilizers. The difficulties of tail solvation associated with many hydrocarbon surfactants in CO₂ can be removed by using particles instead of surfactant. A porous cross-linked shell is formed about the hydrophilic (colloidal and fumed) silica to render the particles CO₂-philic and the crosslinking removes ligand tails from the particle surface.Item Carbon dioxide enhanced oil recovery potential and sequestration capacity in the Gulf Coast : a CO₂ sink analysis near Texas City(2005-12) Nunez-Lopez, Vanessa, 1972-; Van Rensburg, Willem C. J.The Permian Basin in West Texas has seen a long history of CO₂ enhanced oil recovery (EOR). Over 65 sandstone, limestone, and dolomite reservoirs have been subject to miscible CO₂ floodings in the last 30 years. However, the experience gained has not been extended to the much more porous and permeable clastic depositional systems of the Gulf of Mexico. Proximity to possible anthropogenic CO₂ sources, enabling reduced costs and infrastructure, and the petrophysical character of these sandstones are just two of the many attributes that showcase the Gulf Coast formations as an attractive option for this type of tertiary recovery. Results of this assessment indicate that mature Gulf Coast clastic oil reservoirs are a new large potential target for CO₂ enhanced oil recovery when experience in the Permian Basin is retooled for this setting.Item Carbon dioxide plasticization and conditioning of thin glassy polymer films monitored by gas permeability and optical methods(2012-05) Horn, Norman Randall; Paul, Donald R.; Freeman, Benny; Biewlawski, Chris; Ellison, Christopher J.; Sanchez, IsaacThis research project investigated physical aging and carbon dioxide plasticization behavior of glassy polymer films. Recent studies have shown that thin glassy polymer films undergo physical aging more rapidly than thick films. This suggests that thickness may also play a role in the plasticization and conditioning responses of thin glassy films in the presence of highly-sorbing penetrants such as CO₂. The effect of film thickness on CO₂ permeation and sorption was studied extensively through carefully defined and controlled methods that provide a basis for future study of plasticization behavior. Thin films are found to be more sensitive than thick films to CO₂ exposure, undergoing more extensive and rapid plasticization at any pressure. The response of glassy polymers films to CO₂ is not only dependent on thickness, but also on aging time, CO₂ pressure, exposure time, and prior history. Thin films experiencing constant CO₂ exposure for longer periods of time exhibit an initial large increase in CO₂ permeability, which eventually reaches a maximum, followed by a significant decrease in permeability for the duration of the experiment. Thick films, in contrast, do not seem to exhibit this trend for the range of conditions explored. For a series of different polymers, the extent of plasticization response tracks with CO₂ solubility. There is little data available for gas sorption in thin glassy polymer films. In this work, a novel method involving spectroscopic ellipsometry is used to obtain simultaneously the film thickness and CO₂ sorption capacity for thin glassy polymer films. This allows a more comprehensive look at CO₂ permeability, sorption, and diffusivity as a function of both CO₂ pressure and exposure time. Like the gas permeation data, these experiments suggest that thin film sorption behavior is substantially different than that of thick film counterparts. Dynamic ellipsometry experiments show that refractive index minima, fractional free volume maxima, and CO₂ diffusivity maxima correlate well with observed CO₂ permeability maxima observed for thin Matrimid® films. These experiments demonstrate that plasticization and physical aging are competing processes. Aging, however, dominates over long time scales. Over time, CO₂ diffusivity is most affected by these competing effects, and the evolution of CO₂ diffusivity is shown to be the main contributing factor to changes in CO₂ permeability at constant pressure.Item Carbon dioxide removal from natural gas by membranes in the presence of heavy hydrocarbons and by aqueous diglycolamine®/morpholine(2004) Al-Juaied, Mohammed Awad; Rochelle, Gary T.; Koros, William J.Intrinsically defect-free asymmetric hollow fiber polyimide membrane modules were studied in the presence and absence of saturated and aromatic components. Results suggest that an essentially defect-free, non-nodular morphology offers advantages in stability under demanding operating conditions. Earlier work showed serious losses in performance of membranes comprised of similar materials, when the selective layer had a pronounced fused nodular nature as opposed to the intrinsically defect-free skin layers reported on here. Under some conditions for the ternary system, the permselectivity of the membrane is scarcely affected, while under other conditions, permselectivity is negatively affected by as much as 25%. In most cases, for the ternary feeds, significant depression in fluxes was observed due to competition between the CO2, CH4 and heavier hydrocarbons but the effect was even more pronounced for the toluene. In addition to steady state tests in the presence and absence of n-heptane and toluene, modules were conditioned for five days with ternary mixture of CO2, CH4 and one or the other of these heavy hydrocarbons. Following this conditioning process, the modules were studied with a simple binary 10% CO2 /90 % CH4 mixture. These conditioning studies provide insight into the fundamental effects induced in the membrane due to the long term exposure to the complex mixtures. Following exposure to the ternaries containing n-heptane, negligible CO2 permeance increase was seen, while significantly increased permeances were seen under some conditions following toluene exposure even at low pressures of the ternary toluene/CO2/CH4 vii conditioning gas mixture. Although a more protracted process occurs in the case of heptane/CO2/CH4 at 35 0C and 500 ppm, a serious loss in selectivity occurs in the actual ternary tests after exposure for five days. The problem caused by 300 ppm toluene at 35 0C is more immediately apparent, but the ultimate selectivity loss is similar. In addition to the selectivity, in the presence of toluene the permeability is also depressed significantly, presumably due to a greater capability to toluene to compete for added free volume elements introduced in the conditioning process. The permeation enhancement due to toluene exposure is lost slowly when the module downstream is put under vacuum and the gas no longer in contact with the module for up to three weeks. The conditioning treatment has negligible effect at 55 0C, suggesting that that the sorption affinity of toluene decreases with increasing temperature. It is seen from the sorption experiments that penetrant induced conditioning of toluene allows a significant increase in diffusivity than in solubility coefficients, thus allowing for higher permeability and lower selectivity. Solubility, rate of absorption and NMR data were obtained for carbon dioxide in aqueous morpholine (MOR), diglycolamine® (DGA) and aqueous mixtures of MOR and DGA®. Solubility and rate data were acquired in a wetted wall contactor. 23.5 wt%, 65 wt% DGA and 11 wt% MOR/53 wt% DGA concentrations were studied at 298K to 333K. MOR forms an unstable carbamate upon reaction with CO2 compared to DGA which forms a very stable carbamate. Morpholine at 11 wt% of the total amine increases the CO2 equilibrium partial pressure by a factor of 5 to 7 at high loading. The working capacity of 11 wt% MOR/53 wt% DGA was found to be 10% smaller compared to 65 wt% DGA under the conditions studied. The heat of reaction of 11 wt% MOR/53 wt% DGA® was found to be comparable to the 65 wt% DGA. MOR was found also to be more volatile than DGA. The second order rate constant of DGA was found to increase linearly with loading by a factor of 5 over a loading range from 0 to 0.4. Experiments with 65 w% DGA, glycolic acid and potassium formate suggest that viii rate constant increases with loading in the same way as in 65 wt% DGA. The second order rate constant for MOR (k 25C 2=22000 L/mol s) is four times greater than DGA (k 25C 2=6600 L/mol s). The MOR reaction with CO2 was found to follow the zwitterion mechanism; DGA shows zwitterion mechanism in 25 wt% DGA and second order kinetics in 65 wt% DGA. Predictions made with a rigorous eddy diffusivity theory suggests that 11 wt% MOR/53 wt% DGA outperforms 65 wt% DGA of the same concentration by 50 % in terms of CO2 absorption rate. The CO2 enhancement decreases as CO2 loading increases.Item Carbon dioxide solubility and mass transfer in aqueous amines for carbon capture(2015-08) Li, Ph. D., Le; Rochelle, Gary T.; Freeman, Benny D; Sanchez, Isaac C; Svendsen, Hallvard F; Dugas, Ross EAmine scrubbing is the state of the art technology for CO2 capture, and solvent selection can significantly reduce the capital and energy cost of the process. This work presents rigorous CO2 mass transfer and solubility data at expected process conditions for more than 20 aqueous amines and amino acid salts. Amino acid salts are generally not competitive with aqueous amines as solvents for CO2 capture, particularly from coal fired power plants. The capacity of amino acid salts is intrinsically low (0.2 – 0.35 mol/mol alkalinity). Piperazine (PZ) blends have good overall performance. 3.5 m PZ/3.5 m 2-amino-2-hydroxymethyl-propane-1,3-diol (Tris) shows good absorption rates, good capacity, and low solvent viscosity. 6 m PZ/2 m hexamethylenediamine (HMDA) has moderate absorption rates, capacity, and a high viscosity. High solvent viscosity has been shown to reduce CO2 absorption rate and increase sensible heat cost. A simplified speciation model (SSM) was developed in MATLAB to represent CO2 VLE in a mono-amine solvent using only four adjustable parameters. The model can also predict liquid phase speciation. Primary and secondary amines were shown to have different CO2 VLE dependence on amine pKa. At pKa higher than 8, secondary amines have lower carbamate stability than primary amines. A correlation was developed to predict the SSM parameters based on the amine type and amine pKa. The third order overall reaction kinetic expression better explains the mass transfer data at process conditions than the more widely applied second order overall expression. A new Bronsted correlation was developed to represent the third order concentration based kinetic constant at 40 °C for primary and secondary amines: 〖log〗_10 (〖k_(c-3)〗^* )=-11.728+1.113∙p〖K_a〗_amine. This work shows the absorption rate of CO2 at process conditions do not always increase with amine pKa. As the reaction rate constant increases with amine pKa, the free amine available for CO2 absorption decreases. As the result, for primary and secondary mono-amines, the optimum amine pKa for the best mass transfer performance is around 8.7 (at 40 °C).Item Carbonic anhydrase function and evolution in the respiratory gas exchange system of marine fishes(2021-08-15) Dichiera, Angelina Maria; Esbaugh, Andrew; Thomas, Peter; Brandl, Simon J; Brauner, Colin JMany marine fishes have adaptive respiratory strategies to enable sufficient oxygen (O₂) uptake, as well as the excretion of metabolically-produced carbon dioxide (CO₂). A central figure in the intertwined systems of CO₂ excretion and tissue O₂ delivery is the metalloenzyme carbonic anhydrase (CA). In my dissertation I expand, and in some cases challenge, the classical role of CA in CO₂ excretion and its emerging role in tissue O₂ extraction in both the red blood cell (RBC) and tissue membranes. I investigated the role of RBC CA in a diverse group of fishes, and demonstrated basal fishes with a membrane-bound CA isoform in their gills (branchial CA-IV) possess a low-activity RBC CA. Using site-directed mutagenesis, I restored increased function to a basal fish RBC CA to demonstrate that a single amino acid is critical for CA function. Furthermore, phylogenetic analysis suggested high-activity RBC CA may have coevolved with enhanced hemoglobin (Hb) pH sensitivity in teleosts. I explored this relationship and demonstrated RBC CA activity dictated Hb-O₂ offloading rate in almost a 1:1 manner in red drum (Sciaenops ocellatus). RBC CA is best known for its role in CO₂ excretion so this study is the first to demonstrate RBC CA may be rate-limiting for O₂ offloading as well. An additional CA isoform has recently been implicated in tissue O₂ extraction: membrane-bound CA-IV found in the red muscle, heart, and eye. With the plethora of CA-IV isoforms that function in other physiological systems (e.g. acid-base and ion regulation), I sought to define which isoforms should be studied for respiration, using publicly available membrane-bound CA sequences for a comprehensive phylogeny, and paired with tissue distribution analyses. I demonstrated functional divergence in CA-IV isoforms in which some species possess multiple CA-IV isoforms for disparate physiological functions. This highlighted CA-IVa as the primary isoform to target for future respiratory gas exchange studies. Finally, I challenged fish with low O₂ exposure (hypoxia) to understand the role CA-IV may play under environmental stress, and in contribution to whole-animal performance. While fish did not recruit CA-IV under hypoxia acclimation as predicted, they maintained CA-IV protein synthesis to theoretically sustain tissue O₂ extraction. Furthermore, hypoxia acclimation improved swim performance under control conditions; however, anaerobic rather than aerobic processes seem to be driving this performance. Overall, my work presents critical information regarding the emerging roles of CA in tissue O₂ extraction in marine fishes, providing mechanistic and evolutionary insight on the enzyme’s function in respiratory gas exchange.Item Effects of sulfur dioxide entrainer on the solubility of benzoic acid in supercritical carbon dioxide(1984) Lahiere, Richard Joseph, 1959-; Johnston, Keith P., 1955-Item Emulsions and microemulsions of water and carbon dioxide: novel surfactants and stabilization mechanisms(2005) Ryoo, Won Sun; Johnston, Keith P., 1955-During the last two decades colloid and interface science in the field of supercritical fluid technology has brought enormous potentials in the utilization of supercritical carbon dioxide as an environmentally benign solvent. Liquid or supercritical CO2 exhibits solvent properties that are tunable with pressure, and is essentially nontoxic and nonflammable. Emulsions and microemulsions of water and CO2, whether in the form of water-in-CO2 (w/c) or CO2-in-water (c/w), offer new possibilities for separations on the basis of polarity, and as media for reactions between polar and nonpolar molecules. For the first time, formation of thermodynamically stable c/w microemulsions was characterized by dynamic light scattering (DLS) technique. High-pressure carbon dioxide swells potassium carboxylate perfluoropolyether (PFPE-K) cylindrical micelles in water, elongating the micelles significantly from 20 up to 80 nm. As the micelles swell to form microemulsions, the solubility of pyrene increases by a factor of ca. 10. It was demonstrated w/c microemulsions may be formed with nonionic hydrocarbon surfactant. Methylated branched tail of the surfactant enhances formation of stable w/c microemulsions as it raises surfactant solubility in CO2, shifts the curvature towards bending about water, and weakens interdroplet interactions by reducing overlap between surfactant tails. As a novel medium for reactions, w/c microemulsions with low water content are utilized for the synthesis of TiO2 nanoparticles via the controlled hydrolysis of titanium tetraisopropoxide. The size of particles could be controlled by adjusting the water-to-surfactant ratio (wo). Based on DLS measurements, the size of TiO2 particles was comparable to that of the microemulsion droplets indicating steric stabilization was sufficient during the rapid hydrolysis. Finally, electrostatic repulsion between water droplets of w/c emulsion was explored as an alternative to the steric stabilization mechanism. Negative zeta-potentials as high as 70 mV are measured for emulsion droplets by microelectrophoresis. Unprecedented crystalline structure of the droplet array with a spacing of several droplet-diameters is identified by microscopy, and investigated in terms of a balance between long-range electrostatic repulsions acting through the low dielectric medium (εr = 1.5 for high pressure CO2) and the gravitational force which tends to decrease inter-droplet distances.Item Enhanced oil recovery by carbon dioxide and diethyl ether as mutual solvents(2017-12) Alzayer, Ahmed Jamal; Mohanty, Kishore Kumar; Sepehrnoori, Kamy, 1951-Increasing the oil recovery factor from existing fields is the key towards meeting future oil demand. The injection of solvents, an established EOR technique, has shown significant improvement in oil recovery over conventional water floods. However, the injection of pure solvent slugs can be quite costly for field operators. To mitigate this problem, recent literature has suggested the use of brines that are saturated with mutual solvents (dissolve in both oil and water) such as Carbon Dioxide (CO₂) and Dimethyl Ether (DME). This practice minimizes the amount of used solvent since it is governed by its limited solubility in water. The solubility of CO₂ and DME is much higher in oil than in water. Therefore, a mass transfer takes place once CO₂ or DME saturated brines come into contact with oil. As these solvents go into the oil phase, they promote oil swelling and reduce the oil viscosity, thereby making it movable and increasing the oil recovery as a result. Although there has been recent lab work performed with this EOR method, most of the work performed so far involved short cores, high injection rates and in some cases limited to sandstone cores. In this thesis, we investigated the effect of using brines that were saturated with CO₂ and Diethyl ether (DEE) on oil recovery. The results came out to be mixed and not completely in line with previous literature for CO₂ rich brine (Carbonated Water). Injecting carbonated water into sandstone cores did not improve the oil recovery. However, there was an improvement in oil recovery as a result of carbonated water injection in carbonate cores, which also displayed effluent line plugging. For the case of DEE-rich brine, there was a noticeable improvement in oil recovery but it took more pore volumes to have an effect in comparison to DME-rich brine literature results. The experimental work was further supplemented with numerical modeling. The simulator was not able to capture the effects of carbonated water observed in the experiment, due to the absence of rock–fluid interaction in the modeling mechanism. In contrast, the DEE rich brine case was successfully matched with the compositional simulator since it did not involve rock reactions and was strictly based on fluid–fluid interactionsItem Examining supercritical CO₂ dissolution kinetics during carbon sequestration through column experiments(2011-08) Kent, Molly Elizabeth; Bennett, Philip C. (Philip Charles), 1959-; Romanak, Katherine; Cardenas, Meinhard B.Carbon sequestration is a method of capturing and storing excess anthropogenic CO₂ in the subsurface. When CO₂ is injected, the temperature and pressure at depth turn it into a supercritical (SC) fluid, where density is that of a liquid, but viscosity and compressibility resemble a gas. Ultimately the SC CO₂ is trapped at depth either by low permeability sealing layers, by reactions with minerals, or by dissolving into fluids. The injected CO₂ is buoyant and initially exists as a non-aqueous hydrophobic layer floating on top of the subsurface brine, up against the upper sealing formation, but over time it will dissolve into the brine and potentially react with minerals. The details of that initial dissolution reaction, however, are only poorly understood, and I address three basic questions for this research: What is the fundamental kinetics of SC CO₂ dissolution into water? How fast does dissolved CO₂ diffuse away from the source point? And what geochemical conditions influence the dissolution rate? To answer these questions I employed a high pressure flow-through approach using a column packed with coarse quartz sand. The system was both pressure and temperature controlled to have either liquid or SC CO₂ present, and was typically run at 100 Bar, 0.5 to 2.5 mls/min, and 28-60°C. After establishing the hydraulic parameters for the column using two conservative tracers (Br, As), injections (5 and 20 [mu]l) were made either as aqueous solutions equilibrated to high pressure CO₂, or as pure liquid or SC CO₂ into 0.1 mmol NaOH. For all experiments the pH of the system was monitored, and [CO₂] over time was calculated from those data. For injections of brine with dissolved CO₂, transport was conservative and was nearly identical to the conservative tracers. The CO₂ quickly mixes in the column and does not react with the quartz. The liquid and SC CO₂ injections, however, do not act conservatively, and have a very long tailing breakthrough curve that extends to tens of pore volumes. I hypothesize that the SC CO₂ is becoming trapped as a droplet or many droplets in the pore spaces, and the long breakthrough tail is related either to the rate of dissolution into the aqueous phase, the diffusion of dissolved CO₂ away from the phase boundary, or the reaction with the NaOH, limited to the narrow contact zones in the pore throats. Because of the speed at which acid-base reactions occur (nanosecond kinetics), I infer that the rate limiting step is either surface dissolution or diffusion. From plots of ln[CO₂] v. time I obtained values for k, the specific rate of the dissolution reaction R=-k[CO₂]. No trend for k was seen with respect to changes in temperature, but k did show a trend with respect to changing flow rate. k increased from an average value of 3.05x10⁻³ at 0.5 ml/min to an average value of 3.38x10⁻³ at 1.6 ml/min, and then held constant at the higher flow rates, up to 2.5 ml/min. I interpret these data to show that at low flow rates, the reaction is diffusion limited; the fluid nearest the contact zone becomes saturated with dissolved CO₂. At higher flow rates, the fluid is moving fast enough that saturation cannot occur, and the kinetics of the dissolution reaction dominate. Simple geometric models indicate that the CO₂/water interface is shaped like a spherical cap, indicating that the snapped-off CO₂ is forming a meniscus in the pore throat, limiting the surface area across which dissolution can occur.Item Experimental Study of CO2 Foam Flow in Porous Media and Application of Fractional-Flow Method to Foam Flow(2001-08) Dong, Yang; Rossen, William R.Foam flow in porous media is a complicated process. Recent research using N2 identified two distinct regimes for foam flow: a high- quality regime and a low-quality regime. Pressure gradient is independent of gas flow rate in the high-quality regime and independent of liquid flow rate in the low-quality regime. The purpose of this research is to see whether the two regimes exist for C02 foam. Previous studies with C02 have found one regime or the other, but not both. An apparatus was constructed to conduct high-pressure C02 foam core flooding experiments. The experiments were performed at room temperature of 740F and at pressures above 1500 psig. Surfactant solution and super-critical C02 were co-injected into Berea sandstone cores at various flow rates. Superficial velocities of surfactant solution and C02 ranged from 0.18-1.84 ft/d and 0.48-3.79 ft/d, respectively. The surfactant used was Chaser CD1045 at 0.25 wt % and 0.8 wt % concentration in a synthetic brine of 3 wt % NaCl and 0.01 wt % CaC12. Steady-state pressure drop along the core was recorded. In these results pressure gradient increases with increasing gas flow rate at constant liquid flow rate and decreases with increasing liquid flow rate at constant gas flow rate. The data from the experiments at different surfactant concentrations have the same trend of pressure gradient change with flow rates, but do not show the characters of either flow regime as seen with N2 foam or in other studies with C02. Fractional-flow methods were used to analyze and compare several foam models in the literature. Useful insights about the mechanisms controlling behaviors in these models are obtained from this analysis.Item Exploring solvent properties of high pressure carbon dioxide via computer simulation(2003) Lee, Kenneth Michael; Sanchez, Isaac C.There has been significant interest in the use of liquid and supercritical carbon dioxide (CO2) as an environmentally responsible solvent. Although CO2 has properties that make it a suitable solvent, many organic solutes are only sparingly soluble in CO2. We use Monte Carlo and molecular dynamics computer simulations of CO2 to explore solvation. We characterize the structure of CO2 using cavity size distributions. These distributions are compared to water. The distributions show that lowering density increases average cavity size, but lowering temperature has minimal affect. Water and CO2 at their triple point have similar cavity sizes. We calculate the infinite dilution Henry’s Law solubility of 31 small organic molecules using the Expanded Ensemble method. The solubility is measured at 12 liquid, near-critical, and supercritical conditions. Results show that increasing the number of fluorine atoms or methyl group substitutions for hydrogen atoms on a methane molecule increases solubility, despite the larger molecular size. The solubility data correlate well to a functional form with mean field attractive terms and scaled particle theory repulsive terms. This correlation is based on the temperature and density of CO2 and the intrinsic properties of the solute molecule. The simulations provide a solubility ranking for the molecules, and allow for calculation of partition coefficients between CO2 and water. We explore changes in freely jointed Lennard-Jones polymer chain conformation with changes in CO2 density and temperature. We find that higher temperature or solvent density increases chain dimensions, although there is a limit to chain extension from increasing density. We find that increasing density depresses the temperature where the chain transforms from a coil to a globule. We also examine the effects of changing the model parameters of the polymer.Item Gaseous reactions produced by high frequency discharges : effects due to variations in frequency(1933) Swearingen, Judson S.; Schoch, Eugene P. (Eugene Paul), 1871