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Made available in DSpace on 2014-10-09T12:23:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:13Z (GMT). No. of bitstreams: 1 00792.pdf: 2829266 bytes, checksum: 4d674b11215a8b74c9241b56eaec06e1 (MD5) / Tese (Livre - Docencia) / IEA/T / Faculdade de Ciencias Farmaceuticas, Universidade de Sao Paulo - CF/USP

No description available.

No description available.

Mathematical modeling helps researchers to understand the transport and kinetic phenomena within fuel cells and their effects on fuel cell performance that may not be evident from experimental work. In this thesis, a 2-D steady-state cathode model of a proton-exchange-membrane fuel cell (PEMFC) is developed. The kinetics of the cathode half-reaction were investigated, specifically the reaction order with respect to oxygen concentration. It is unknown whether this reaction order is one or one half. First- and half-order reaction models were simulated and their influence on the predicted fuel cell performance was examined. At low overpotentials near 0.3 V, the half-order model predicted smaller current densities (approximately half that of the first-order model). At higher overpotentials above 0.5 V, the predicted current density of the half-order model is slightly higher than that of the first-order model. The effect of oxygen concentration at the channel/porous transport layer boundary was also simulated and it was shown the predicted current density of the first-order model experienced a larger decrease (~10-15% difference at low overpotentials) than the half-order model. Several other phenomena in the cathode model were also examined. The kinetic parameters (exchange current density and cathode transfer coefficient) were adjusted to assume a single Tafel slope, rather than a double Tafel slope, resulting in a significant improvement in the predicted fuel cell performance. Anisotropic electronic conductivities and mass diffusivities were added to cathode model so that the anisotropic structure of the porous transport layer was taken into account. As expected, the simulations showed improved performance at low current densities due to a higher electronic conductivity in the in-plane direction and decreased performance at high current densities due to smaller diffusivities. Additionally, the concentration overpotential was accounted for in the model; however it had little influence on the simulation results. / Thesis (Master, Chemical Engineering) -- Queen's University, 2008-09-19 12:14:29.079

Air injection is an enhanced oil recovery (EOR) process in which compressed air is injected into a high temperature, light-oil reservoir. The oxygen in injected air is intended to react with a fraction of reservoir oil at elevated temperature resulting in in-situ generation of flue gases and steam, which, in turn, mobilize and drive the oil ahead towards the producing wells. To understand and determine the feasibility of the air injection process application to a given reservoir, it is necessary to understand the oxidation behaviour of the crude oil. The aim of this study is to screen two Australian light-oil reservoirs; Kenmore Oilfield, Eromanga Basin, and another Australian onshore oil and gas field “B”* for air injection EOR process, and to understand the oxidation reaction kinetics during air injection. It is carried out by the thermogravimetric and differential scanning calorimetric (TGA/DSC) studies to investigate the oxidation mechanism during an air injection process. There has not been any TGA/DSC evaluation conducted to date with regard to air injection for Australian light-oil reservoirs. A series of thermal tests was performed to investigate the oxidation behaviour of two selected reservoirs in both air and oxygen environments. The first step undertaken in this study is thermogravimetric and calorimetric characterization of crude oils to (i) identify the temperature range over which the oil reacts with oxygen, (ii) examine the oxidation behaviour within the temperature identified, and (iii) evaluate the mass loss characteristics during the oxidation. This study also examines the effect of pressure on oxidation at different temperature ranges and the effect of core material (rock cutting) on oxidation reactions. Finally, kinetic data are calculated from thermal tests results by literature described method. Kenmore and Field B both are high temperature and light-oil reservoirs. Hydrocarbon distribution indicates that Kenmore oil contains 84 mole% of lower carbon number n-C₅ - n-C₁ ₃ compounds. Reservoir B oil also contains a substantial amount (i.e., 95 mole %) of lower carbon number n-C₄ - C₁ ₉ compounds. These lighter components may contribute favourably towards efficient oxidation. However, a high content of lighter ends in the oil may also result in a lower fuel load. Generally, low molecular weight oil gives fastest mass loss from heavy crude oil. Thermal tests on Kenmore oil showed two distinct exothermic reactivity regions in temperatures of 200-340°C and 360-450°C, with a 85-95% mass loss when the temperature reached 450°C. Reservoir B oil showed a wider exotherm range between approximately 180°C-260°C with 90-95% mass loss by temperature 350°C. In the high temperature range, the combustion reactions of Reservoir B oil are weaker than Kenmore oil. This is due to insufficient fuel available for oxidations in high temperature region. Reservoir B oil has more chance to auto ignite; but it has less sustainability to the ignition process. Based on the sustainability study of the ignition process, between the two reservoirs, Kenmore is the better candidate for air injection. Based on the thermal tests, it is concluded that for light-oil oxidation, vaporization is the dominant physical phenomenon. At low temperature range, the addition of the core material enhanced the exothermic reactions of the oil. The elevated pressure accelerated the bond scission reactions. The largest amount and highest rate of energy generation occurred at the low temperature range. Activation energies (E) are calculated from thermal test results and the value of ‘E’ in oil-with-core combined tests is smaller than the oil-only test. This indicates that the rock material has a positive impact on the combustion process. Moreover, the compositional analysis result addresses the composition of oils, which can help understand the oxidation behaviour of light-oils. * For confidentiality reasons, the field name is coded as Field B at the request of the operating company. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1381084 / Thesis (M.Eng.Sc.) -- University of Adelaide, Australian School of Petroleum, 2010

Air injection is an enhanced oil recovery (EOR) process in which compressed air is injected into a high temperature, light-oil reservoir. The oxygen in injected air is intended to react with a fraction of reservoir oil at elevated temperature resulting in in-situ generation of flue gases and steam, which, in turn, mobilize and drive the oil ahead towards the producing wells. To understand and determine the feasibility of the air injection process application to a given reservoir, it is necessary to understand the oxidation behaviour of the crude oil. The aim of this study is to screen two Australian light-oil reservoirs; Kenmore Oilfield, Eromanga Basin, and another Australian onshore oil and gas field “B”* for air injection EOR process, and to understand the oxidation reaction kinetics during air injection. It is carried out by the thermogravimetric and differential scanning calorimetric (TGA/DSC) studies to investigate the oxidation mechanism during an air injection process. There has not been any TGA/DSC evaluation conducted to date with regard to air injection for Australian light-oil reservoirs. A series of thermal tests was performed to investigate the oxidation behaviour of two selected reservoirs in both air and oxygen environments. The first step undertaken in this study is thermogravimetric and calorimetric characterization of crude oils to (i) identify the temperature range over which the oil reacts with oxygen, (ii) examine the oxidation behaviour within the temperature identified, and (iii) evaluate the mass loss characteristics during the oxidation. This study also examines the effect of pressure on oxidation at different temperature ranges and the effect of core material (rock cutting) on oxidation reactions. Finally, kinetic data are calculated from thermal tests results by literature described method. Kenmore and Field B both are high temperature and light-oil reservoirs. Hydrocarbon distribution indicates that Kenmore oil contains 84 mole% of lower carbon number n-C₅ - n-C₁ ₃ compounds. Reservoir B oil also contains a substantial amount (i.e., 95 mole %) of lower carbon number n-C₄ - C₁ ₉ compounds. These lighter components may contribute favourably towards efficient oxidation. However, a high content of lighter ends in the oil may also result in a lower fuel load. Generally, low molecular weight oil gives fastest mass loss from heavy crude oil. Thermal tests on Kenmore oil showed two distinct exothermic reactivity regions in temperatures of 200-340°C and 360-450°C, with a 85-95% mass loss when the temperature reached 450°C. Reservoir B oil showed a wider exotherm range between approximately 180°C-260°C with 90-95% mass loss by temperature 350°C. In the high temperature range, the combustion reactions of Reservoir B oil are weaker than Kenmore oil. This is due to insufficient fuel available for oxidations in high temperature region. Reservoir B oil has more chance to auto ignite; but it has less sustainability to the ignition process. Based on the sustainability study of the ignition process, between the two reservoirs, Kenmore is the better candidate for air injection. Based on the thermal tests, it is concluded that for light-oil oxidation, vaporization is the dominant physical phenomenon. At low temperature range, the addition of the core material enhanced the exothermic reactions of the oil. The elevated pressure accelerated the bond scission reactions. The largest amount and highest rate of energy generation occurred at the low temperature range. Activation energies (E) are calculated from thermal test results and the value of ‘E’ in oil-with-core combined tests is smaller than the oil-only test. This indicates that the rock material has a positive impact on the combustion process. Moreover, the compositional analysis result addresses the composition of oils, which can help understand the oxidation behaviour of light-oils. * For confidentiality reasons, the field name is coded as Field B at the request of the operating company. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1381084 / Thesis (M.Eng.Sc.) -- University of Adelaide, Australian School of Petroleum, 2010

Dimethyldioxirane oxidises nitrogen-containing substrates. The sites of oxidation are generally the sp3 nitrogen atoms in the molecules although other reactive groups can be oxidised if present. An indication of the reactivity of different dioxiranes was obtained qualitatively from the polarographic peak reduction potentials and quantitatively by reaction with the model substrate 4-nitro-N,N-dimethylaniline. The polarographic peak potentials were shown to be of a similar order to those of typical acyclic peroxides. The rank order in terms of reactivity was shown to be methyl(trifluoromethyl)dioxirane > dimethyldioxirane > ethylmethyldioxirane. The rate of the reaction was not influenced by pH or ionic strength but was accelerated greatly by the presence of water. An explanation for this observation was proposed through consideration of dielectric constant and hydrogen bonding effects.

No description available.

Geopolymers, a class of largely X-ray amorphous aluminosilicate binder materials, have been studied extensively over the past several decades, but largely from an empirical standpoint. The primary aim of this investigation has been to apply a more science-based approach to the study of geopolymers, including introducing a variety of mathematical modelling techniques to the field. The nanostructure of geopolymers is analysed via an extensive literature review, and conclusions regarding the presence and role of crystallinity within the geopolymer structure are drawn. Si/Al ordering within the tetrahedral aluminosilicate gel framework is described by a statistical thermodynamic model, which provides an accurate representation of the distribution of Si and Al sites within the framework as well as physically reasonable values for the energy penalty associated with ordering violation. Framework and extraframework structure within the geopolymer binder are also described by the pair distribution function (PDF) technique, whereby synchrotron X-ray scattering data are converted via a Fourier transform-based method into real-space structural data on an Ångstrom length scale. Real-space Rietveld analysis of geopolymers crystallised at high temperature is used to back-calculate and analyse the original geopolymer structure, and the primary change in very short-range structure from the as-synthesised geopolymer to the high-temperature crystalline product is observed to be a shift in the location of the extraframework charge-balancing cation.