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SEAWATER DESALINATION AS A BENEFICIAL FACTOR OF CO2 SEQUESTRATION.Max, M.D., Sheps, K., Tatro, S.R., Brazel, L., Osegovic, J.P. 07 1900 (has links)
It is becoming increasingly recognized that the flood of anthropogenic CO2 into the atmosphere
should be reduced in order to mitigate the Earth’s atmospheric greenhouse and slow climate
change. If immediate action is required, then a number of greenhouse gas reduction strategies
may need to be implemented even before complete study of their impacts can be fully
understood. Energy production through combustion produces large amounts of CO2 in a
relatively small number of locations at which CO2 capture and compression to a liquid,
transportable form can be achieved. Physical disposal offers the best option for sequestering this
waste CO2. Because of the costs of transportation, geological sequestration will be most
applicable for one set of power plants, deep ocean sequestration may be most applicable for some
others. In both cases, the sequestration processes can provide some economic benefits. Ocean
CO2 disposal can produce desalinated, treated water as a byproduct.
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HYDRATE STUDIES OF NORTHERN CASCADIA MARGIN OFF VANCOUVER ISLAND: A REFERENCE SOURCERiedel, Michael, Hyndman, Roy D., Spence, George D. 07 1900 (has links)
This article provides a comprehensive reference list to the extensive studies of marine natural gas hydrate surveys and studies on the northern Cascadian margin of Western Canada. The references are divided into each of the major study methods, surveys, analyses and conclusions. A number of MSc and PhD theses are included. We first refer to the articles that address the local tectonics and sedimentary accretionary prism in which the hydrate forms, then those that describe the numerous geophysical and geological surveys and studies, and finally the articles that address the most important conclusions that have resulted from this work on the distribution , concentrations, and amounts of hydrates, and on the processes of hydrate formation and dissociation.
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HYDRATE NUCLEATION MEASUREMENTS USING HIGH PRESSURE DIFFERENTIAL SCANNING CALORIMETRYHester, Keith C., Davies, Simon R., Lachance, Jason W., Sloan, E. Dendy, Koh, Carolyn A. 07 1900 (has links)
Understanding when hydrates will nucleate has notable importance in the area of flow assurance. Attempts to model hydrate formation in subsea pipelines currently requires an arbitrary assignment of a nucleation subcooling. Previous studies showed that sII hydrate containing a model water-soluble former, tetrahydrofuran, would nucleate over a narrow temperature range of a few degrees with constant cooling. It is desirable to know if gas phase hydrate formers, which are typically more hydrophobic and hence have a very low solubility in water, also exhibit this nucleation behavior.
In this study, differential scanning calorimetry has been applied to determine the hydrate nucleation point for gas phase hydrate formers. Constant cooling ramps and isothermal approaches were combined to explore the probability of hydrate nucleation. In the temperature ramping experiments, methane and xenon were used at various pressures and cooling rates. In both systems, hydrate nucleation occurred over a narrow temperature range (2-3°C). Using methane at lower pressures, ice nucleated before hydrate; whereas at higher pressures, hydrate formed first. A subcooling driving force of around 30°C was necessary for hydrate nucleation from both guest molecules. The cooling rates (0.5-3°C/min) did not show any statistically significant effect on the nucleation temperature for a given pressure.
The isothermal method was used for a methane system with pure water and a water-in-West African crude emulsion. Two isotherms (-5 and -10°C) were used to determine nucleation time. In both systems, the time required for nucleation decreased with increased subcooling.
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CAN HYDRATE DISSOLUTION EXPERIMENTS PREDICT THE FATE OF A NATURAL HYDRATE SYSTEM?Hester, Keith C., Peltzer, E.T., Dunk, R.M., Walz, P.M., Brewer, P.G. 07 1900 (has links)
Here, we present a dissolution study of exposed hydrate from outcrops at Barkley Canyon. Previously, a field experiment on synthetic methane hydrate samples showed that mass transfer controlled dissolution in under-saturated seawater. However, seafloor hydrate outcrops have been shown to have significant longevity compared to expected dissolution rates based upon convective boundary layer diffusion calculations. To help resolve this apparent disconnect between the dissolution rates of synthetic and natural hydrate, an in situ dissolution experiment was performed on two distinct natural hydrate fabrics.
A hydrate mound at Barkley Canyon was observed to contain a “yellow” hydrate fabric overlying a “white” hydrate fabric. The yellow hydrate fabric was associated with a light condensate phase and was hard to core. The white hydrate fabric was more porous and relatively easier to core. Cores from both fabrics were inserted to a mesh chamber within a few meters of the hydrate mound. Time-lapse photography monitored the dissolution of the hydrate cores over a two day period. The diameter shrinkage rate for the yellow hydrate was 45.5 nm/s corresponding to a retreat rate of 0.7 m/yr for an exposed surface. The white hydrate dissolved faster at 67.7 nm/s yielding a retreat rate of 1.1 m/yr. It is possible these hydrate mounds were exposed due to the fishing trawler incident in 2001. If these dissolution experiments give a correct simulation, then the exposed faces should have retreated ~ 3.5 m and 5.5 m, respectively, from 2001 to this expedition in August 2006. While the appearance of the hydrate mounds appeared quite similar to photographs taken in 2002, these dissolution experiments show natural hydrate dissolves rapidly in ambient seawater. The natural hydrate dissolution rate is on the same order as the synthetic dissolution experiment strongly implying another control for the dissolution rates of natural hydrate outcrops. Several factors could contribute to the apparent longevity of these exposed mounds from upward flux of methane-rich fluid to protective bacterial coatings.
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NMR studies on CH4 + CO2 binary gas hydrates dissociation behaviorRovetto, Laura J., Dec, Steven F., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
The dissociation behavior of the CH4+CO2 binary gas hydrate has been investigated using
Nuclear Magnetic Resonance (NMR) spectroscopy. This technique allows us to distinguish
the hydrate structure present, as well as to quantify phase concentrations. Single-pulse
excitation was used in combination with magic-angle spinning (MAS). Time-resolved in situ
decomposition experiments were carried out at different compositions in sealed, pressurized
samples. The decomposition profiles of the CH4+CO2 binary gas hydrate system obtained at
various compositions suggest that the decomposition rate is a strong function of the fractional
cage occupancy and temperature. An unexpected CH4 hydrate reformation was observed
during our decomposition experiments when the temperature reached the ice melting point. A
decrease on the CO2 content in the hydrate phase was found during the decomposition
experiment, as the pressure and temperature of the system increases.
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RHEOLOGICAL INVESTIGATION OF HYDRATE SLURRIESRensing, Patrick J., Liberatore, Matthew W., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
The oil and gas industry is often plagued by the formation of clathrate hydrates in oil pipelines.
While the industry originally had a heuristic of avoidance of clathrate hydrates they are moving to
a heuristic of risk management. To successfully implement a risk management heuristic, time
dependent phenomena of clathrate hydrate formation and flowline plugging must be known. The
study of time dependent phenomena of formation and agglomeration are investigated using a TA
Instruments AR-G2 rheometer with a pressure cell capable of operating at up to 13.8 MPa.
Pressurized rheological experiments examine clathrate hydrates formed in situ. Both shear and
oscillatory experiments have been conducted on the samples, giving flow and viscoelastic
parameters. Shear experiments show sharp increases in viscosity upon clathrate hydrate
formation indicating rapid aggregation. Transient oscillation experiments show a sharp increase
in the elastic and loss moduli followed by a decrease in the loss moduli. Thus, both in situ
clathrate hydrate formation and annealing are quantified. In addition these oscillatory
measurements provided a novel technique for non-destructive investigation of clathrate hydrate
aggregation over time.
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SIMULATION OF HYDRATE AGGREGATE STRUCTURE VIA THE DISCRETE ELEMENT METHODRensing, Patrick J., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
As the oil industry moves from a heuristic of avoidance of hydrates to a heuristic of risk management time dependent phenomena of hydrate formation and plugging must be known. One of the key parameters to this process is the aggregation of hydrate particles, the fractal networks they form, and the effect these two parameters have on flow. Unfortunately the aggregation and fractal structure information is extremely difficult to acquire experimentally, for this reason a three-dimension discrete element method (3D-DEM) model has been implemented.
The 3D-DEM model calculates detailed solutions to Newton's equations of motion for individual particles. In addition these particles are coupled with the surrounding fluid through computational fluid dynamics (CFD). This coupled 3D-DEM can be used to investigate what the effects of shear, suspending viscosity, attractive forces, and other relevant variables have on the structure, stresses, and positions of the hydrate particles over time. In addition, the effect on viscosity has been calculated using CFD and compared back to basic hard sphere theory.
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HYDRATE PLUG FORMATION PREDICTION TOOL – AN INCREASING NEED FOR FLOW ASSURANCE IN THE OIL INDUSTRYKinnari, Keijo, Labes-Carrier, Catherine, Lunde, Knud, Hemmingsen, Pål V., Davies, Simon R., Boxall, John A., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
Hydrate plugging of hydrocarbon production conduits can cause large operational
problems resulting in considerable economical losses. Modeling capabilities to predict
hydrate plugging occurrences would help to improve facility design and operation in
order to reduce the extent of such events. It would also contribute to a more effective
and safer remediation process. This paper systematically describes different operational
scenarios where hydrate plugging might occur and how a hydrate plug formation
prediction tool would be beneficial.
The current understanding of the mechanisms for hydrate formation, agglomeration and
plugging of a pipeline are also presented. The results from this survey combined with the
identified industrial needs are then used as a basis for the assessment of the capabilities
of an existing hydrate plug formation model, called CSMHyK (The Colorado School of
Mines Hydrate Kinetic Model). This has recently been implemented in the transient
multiphase flow simulator OLGA as a separate module.
Finally, examples using the current model in several operational scenarios are shown to
illustrate some of its important capabilities. The results from these examples and the
operational scenarios analysis are then used to discuss the future development needs of
the CSMHyK model.
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STRUCTURE AND TUNING PATTERN IN THE IONIC DOUBLE CLATHRATE HYDRATESShin, Kyuchul, Cha, Jong-Ho, Choi, Sukjeong, Lee, Huen 07 1900 (has links)
A number of notable studies on pure ionic clathrate hydrates have utilized their unique ionic
characteristics for electric applications, including their use as an electrolyte for nickel-metal
hydride batteries. Although quaternary ammonium salt hydrates have recently been applied to gas
separation and storage areas with the expectation of the small co-guest occupancy in empty cages,
most of the researches have been oriented to macroscopic approaches based on hydrate phase
equilibria and many other process variables. On the other hand, spectroscopic analyses for
identifying the structure transition of ionic clathrate hydrates together with a comprehensive
consideration of their complex phase patterns have not yet been reported in spite of their
importance to the energy and environmental fields. Accordingly, in this study, we present the
report of an extraordinary structural transition accompanying the occurrence of more than two
coexisting clathrate hydrate phases and channel-induced tuning pattern in ionic double hydrate
systems. In particular, the tuning observation uniquely occurring in the ionic clathrate hydrates is
quite surprising, even though the tuning behavior is more commonly observed in the non-ionic
hydrate systems. The remarkable feature of this work is that the icy ionic hydrate materials can be
effectively used in energy devices. Moreover, the microscopic analyses of ionic clathrate hydrates
for identifying the physicochemical characteristics are expected to provide new insights into a
variety of inclusion chemistry fields.
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Prof Nyokong receives another Science awardMatiwana, Zamuxolo January 2011 (has links)
The Rhodes University professor of Medicinal Chemistry and Nanotechnology, Tebello Nyokong, says the Award for her Scientific Achievements by the International Conference on Frontiers of Polymers and Advanced Materiel (ICFPAM) is an honour, especially since it is awarded in memory of the centenary of the first Nobel Prize in Chemistry awarded to a woman: Marie Curie.
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