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This thesis describes the implementation of the conditional moment closure (CMC) combustion model in a numerical scheme and its application to the modelling of enclosure fires. Prediction of carbon monoxide (CO) in the upper smoke layer of enclosure fires is of primary interest because it is a common cause of death. The CO concentration cannot be easily predicted by empirical means, so a method is needed which models the chemistry of a quenched, turbulent fire plume and subsequent mixing within an enclosed space. CMC is a turbulent combustion model which has been researched for over a decade. It has provided predictions of major and minor species in jet diffusion flames. The extension to enclosure fires is a new application for which the flow is complex and temperatures are well below adiabatic conditions. Advances are made in the numerical implementation of CMC. The governing combustion equations are cast in a conserved, finite volume formulation for which boundary conditions are uniquely defined. Computational efficiency is improved through two criteria which allow the reduction in the size of the computational domain without any loss of accuracy. Modelling results are compared to experimental data for natural gas fires burning under a hood. Comparison is made in the recirculating, post-flame region of the flow where temperatures are low and reactions are quenched. Due to the spatial flux terms contained in the governing equations, CMC is able to model the situation where chemical species are produced in the high temperature fire-plume and then transported to non-reacting regions. Predictions of CO and other species are in reasonable agreement with the experimental data over a range of lean and rich hood-fire conditions. Sensitivity of results to chemistry, temperature and modelling closures is inves- tigated. Species predictions are shown to be quite different for the two detailed chemical mechanisms used. Temperature conditions within the hood effect the for- mation of species in the plume prior to quenching and subsequently species predic- tions in the post-flame region are also effected. Clipped Gaussian and ß-function probability density functions (PDFs) are used for the stochastic mixture fraction. Species predictions in the plume are sensitive to the form of the PDF but in the post-flame region, where the ß-function approaches a Gaussian form, predictions are relatively insensitive. Two models are used for the conditional scalar dissipation: a uniform model, where the conditional quantity is set equal to the unconditional scalar dissipation across all mixture fraction space; and a model which is consistent with the PDF transport equation. In the plume, predictions of minor species are sensitive to the modelling used, but in the recirculating, post-flame region species are not significantly effected.

Carbon Monoxide (CO) was discovered in the stratosphere of Neptune from the detection of the J=3-2 and J=2-1 rotational transitions in emission at 345.8 and 230.5 GHz respectively. It was conventionally thought that all of the atmospheric carbon should be in its reduced form of methane (CH₄). Two sources of stratospheric CO have been postulated: CO transported from the interior by convection due to Neptune's strong internal heat source (internal source); or, CO produced through photochemical reactions from an external supply of water (external source). <p>In this research project the J=3-2 transition of CO was observed to find the CO profile in Neptune's atmosphere and determine the mechanism producing CO. Three instruments were used at the James Clerk Maxwell Telescope (JCMT) to measure the CO line: the heterodyne receiver B3; the University of Lethbridge Fourier Transform Spectrometer (FTS); and, the Submillimeter Common User Bolometer Array (SCUBA). <p>The high resolution (1.25 MHz) of the heterodyne observations over a large frequency range (~20 GHz) produced a very powerful result because the narrow emission core from the stratosphere and the broad absorption feature arising in the lower atmosphere were measured simultaneously. The CO abundance profile was determined using a model of the J=3-2 CO transition in Neptune's atmosphere developed for this project. Calculations indicate a CO abundance of 1.9^+0.5_-0.3x10^-6 in the upper stratosphere and (0.8±0.2)x10^-6 in the lower stratosphere and troposphere. <p>The moderate resolution of the FTS data allowed the broad absorption feature to be measured. Uranus was originally chosen as the calibration source, but the discovery of CO in Uranus by Encrenaz et al. (2004), while this project was in progress, prompted both Neptune and Uranus to be examined for CO absorption. Two data sets (1993 and 2002) were analyzed and it was found that the 1993 spectra produced superior results, giving a CO mole ratio in the lower atmosphere between 0.8x10^-6 and 2x10^-5; this agrees, within the uncertainty limit, with the lower atmosphere heterodyne result. A tentative detection of CO in Uranus was also obtained from the 1993 data, with a CO abundance profile constrained to pressures greater than 0.5 bar with an abundance between 5x10^-7 and 1x10^-5. The 2002 data were found to be inferior to the 1993 data because of imperfect cancellation of thermal emission from the terrestrial atmosphere. <p> The 850ìm SCUBA filter profile is well matched to the width of the CO feature. Photometric observations of Neptune and Uranus were used to determine if the reduction in integrated flux due to CO absorption could be detected using SCUBA. A CO mole ratio in the range (1.2-1.7) x10^-6 was found for Neptune, calibrated against Uranus and assuming no CO in Uranus. Calibration of the Neptune and Uranus SCUBA data against Mars to produce an independent estimate of the CO abundance in both planets did not produce a useful result because of large calibration errors. <p>Comparison of the results from the three techniques determined that the heterodyne measurement was superior and the derived CO profile was used to determine the source of neptunian CO. It was concluded that the source of CO in Neptune is both internal and external. The lower atmosphere result indicates an interior dominated by water ice. The most likely mechanism for the upper atmosphere CO involves meteoritic ablation, photolysis of H₂O, and chemical reaction with by-products of methane photochemistry. The required H₂O influx for this mechanism is at least two orders of magnitude higher than previously observed, indicating either that the observed H₂O abundance is too small or that CO is produced by a different mechanism.

Carbon Monoxide (CO) was discovered in the stratosphere of Neptune from the detection of the J=3-2 and J=2-1 rotational transitions in emission at 345.8 and 230.5 GHz respectively. It was conventionally thought that all of the atmospheric carbon should be in its reduced form of methane (CH₄). Two sources of stratospheric CO have been postulated: CO transported from the interior by convection due to Neptune's strong internal heat source (internal source); or, CO produced through photochemical reactions from an external supply of water (external source). <p>In this research project the J=3-2 transition of CO was observed to find the CO profile in Neptune's atmosphere and determine the mechanism producing CO. Three instruments were used at the James Clerk Maxwell Telescope (JCMT) to measure the CO line: the heterodyne receiver B3; the University of Lethbridge Fourier Transform Spectrometer (FTS); and, the Submillimeter Common User Bolometer Array (SCUBA). <p>The high resolution (1.25 MHz) of the heterodyne observations over a large frequency range (~20 GHz) produced a very powerful result because the narrow emission core from the stratosphere and the broad absorption feature arising in the lower atmosphere were measured simultaneously. The CO abundance profile was determined using a model of the J=3-2 CO transition in Neptune's atmosphere developed for this project. Calculations indicate a CO abundance of 1.9^+0.5_-0.3x10^-6 in the upper stratosphere and (0.8±0.2)x10^-6 in the lower stratosphere and troposphere. <p>The moderate resolution of the FTS data allowed the broad absorption feature to be measured. Uranus was originally chosen as the calibration source, but the discovery of CO in Uranus by Encrenaz et al. (2004), while this project was in progress, prompted both Neptune and Uranus to be examined for CO absorption. Two data sets (1993 and 2002) were analyzed and it was found that the 1993 spectra produced superior results, giving a CO mole ratio in the lower atmosphere between 0.8x10^-6 and 2x10^-5; this agrees, within the uncertainty limit, with the lower atmosphere heterodyne result. A tentative detection of CO in Uranus was also obtained from the 1993 data, with a CO abundance profile constrained to pressures greater than 0.5 bar with an abundance between 5x10^-7 and 1x10^-5. The 2002 data were found to be inferior to the 1993 data because of imperfect cancellation of thermal emission from the terrestrial atmosphere. <p> The 850ìm SCUBA filter profile is well matched to the width of the CO feature. Photometric observations of Neptune and Uranus were used to determine if the reduction in integrated flux due to CO absorption could be detected using SCUBA. A CO mole ratio in the range (1.2-1.7) x10^-6 was found for Neptune, calibrated against Uranus and assuming no CO in Uranus. Calibration of the Neptune and Uranus SCUBA data against Mars to produce an independent estimate of the CO abundance in both planets did not produce a useful result because of large calibration errors. <p>Comparison of the results from the three techniques determined that the heterodyne measurement was superior and the derived CO profile was used to determine the source of neptunian CO. It was concluded that the source of CO in Neptune is both internal and external. The lower atmosphere result indicates an interior dominated by water ice. The most likely mechanism for the upper atmosphere CO involves meteoritic ablation, photolysis of H₂O, and chemical reaction with by-products of methane photochemistry. The required H₂O influx for this mechanism is at least two orders of magnitude higher than previously observed, indicating either that the observed H₂O abundance is too small or that CO is produced by a different mechanism.

The room temperature photocatalytic oxidation of carbon monoxide in excess air was examined over silica/titania and 0.1%palladium/silica/titania catalysts under UV irradiation. The experiments were conducted in batch re-circulated reactor with the initial 1000 ppm carbon monoxide in air and 0.5 g catalyst charge and the conversion of carbon monoxide to carbon dioxide was followed by FT-IR spectro-photometer. The change in gas composition in dark and under 36 Watts of UV irradiation exposed to a catalyst area of 12.4 centimeter square indicated both adsorption of carbon monoxide and conversion of carbon monoxide to carbon dioxide over the catalyst samples. The effect of catalyst composition (silica/titania) ratio and the presence of palladium oxide were investigated. The catalyst samples were synthesized by sol-gel technique and all samples were hydrothermally treated before calcination in air. The catalyst samples were characterized by XRD and nitrogen adsorption techniques. XRD results indicated that titania is comprised of pure anatase phase and palladium oxide preferantially dispersed over titania. BET surface area of the samples were observed to increase with silica loading and the BJH results showed isotherms of Type V v with H2 hysteresis loops. The highest carbon monoxide adsorption rate constant was achieved with pure silica with the highest surface area. Photocatalytic activity measurements indicated that carbon monoxide in excess air can be successfully oxidized at room temperature over the titania photocatalyts. Higher physisorption was observed over higher silica containing samples and higher oxidation activity was observed with increasing titania/silica ratio. The optimum titania/silica ratio was determined by the titania content and surface area of catalyst. The activity tests were also indicated that the addition of palladium oxide phase synergistically increased the adsorption and oxidation activity of the catalysts.

An all-solid-state continuous-wave (cw) laser system for mid-infrared absorption measurements of the carbon monoxide (CO) molecule has been developed and demonstrated. The single-mode, tunable output of an external-cavity diode laser (ECDL) is difference-frequency mixed (DFM) with the output of a 550-mW diode-pumped cw Nd:YAG laser in a periodically-poled lithium niobate (PPLN) crystal to produce tunable cw radiation in the mid-infrared. The wavelength of the 860-nm ECDL can be coarse tuned between 860.78 to 872.82 nm allowing the sensor to be operated in the 4.4 – 4.8 µm region. Results from single-pass mid-IR direct absorption experiments for CO concentration measurements are discussed. CO measurements were performed in CO/CO2/N2 mixtures in a room temperature gas cell that allowed the evaluation of the sensor operation and data reduction procedures. Field testing was performed at two locations: in the exhaust of a well-stirred reactor (WSR) at Wright-Patterson Air Force Base and the exhaust of a gas turbine at Honeywell Engines and Systems. Field tests demonstrated the feasibility of the sensor for operation in harsh combustion environments but much improvement in the sensor design and operation was required. Experiments in near-adiabatic hydrogen/air CO2-doped flames were performed featuring two-line thermometry in the 4.8 µm spectral region. The sensor concentration measurement uncertainty was estimated at 2% for gas cell testing. CO concentration measurements agreed within 15% of conventional extractive sampling at WSR, and for the flame experiments the repeatability of the peak absorption gives a system uncertainty of 10%. The noise equivalent CO detection limit for these experiments was estimated at 2 ppm per meter, for combustion gas at 1000 K assuming a SNR ratio of 1.

The A-cluster of acetyl-CoA synthase (ACS) catalyzes the formation of acetyl- CoA from CO, coenzyme-A, and a methyl group donated by a corrinoid iron-sulfur protein. Recent crystal structures have exhibited three different metals, Zn, Cu, and Ni, in the proximal site, which bridges a square-planar nickel site and a [Fe4S4] cubane. Contradicting reports supported both the nickel and copper containing forms as representing active enzyme. The results presented here indicate that copper is not necessary or sufficient for catalysis and that copper addition to ACS is deleterious. Several proposed mechanisms exist for the synthesis of acetyl-CoA, the two most prominent are the ‘paramagnetic’ and ‘diamagnetic’ mechanisms. The ‘diamagnetic’ mechanism proposes a two electron activation that precedes methylation to produce an EPR silent Ni2+-CH3 species. This then reacts with CO and coenzyme-A to form acetyl- CoA and regenerate the starting species. The ‘paramagnetic’ mechanism assumes a one electron activation prior to the methylation of the paramagnetic Ni1+-CO state to form an unstable Ni3+-acetyl species. This is immediately reduced by an electron shuttle. Results are presented here that no shuttle or external redox mediator is necessary for catalysis. This supports the ‘diamagnetic’ mechanism, specifically that a two-electron reductive activation is necessary and that the Ni1+-CO species is not an intermediate. The two-electron reductive activation required by the ‘diamagnetic’ mechanism results in an unknown electronic state. Two proposals have been made to describe this form of the A-cluster. The first hypothesis from Brunold et al involves a one-electron reduction of the [Fe4S4]2+ cube and a one-electron reduction of the Nip 2+. This should result in a spin-coupled state that is S = integer. The Ni0 hypothesis requires both electrons to localize on the Nip 2+ forming a zero-valent proximal nickel. Mössbauer spectroscopy has been used to probe the oxidation state and spin state of the [Fe4S4] cube in the reduced active form. No integer spin system is found and this is interpreted as supporting the Ni0 hypothesis. Additionally, spectra are presented that indicate the heterogeneous nature of the A-cluster is not caused by the occupancy of the proximal site.

Thesis (M.Ch.E.)--University of Delaware, 2009. / Principal faculty advisor: Jochen A. Lauterbach, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--York University, 2000. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 370-416). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ59143

Thesis (MTech. degree in Mechanical Engineering)--Tshwane University of Technology, 2009. / South Africa produces 41.3 GWe per year of which 90% is coal-derived. During combustion of coal, sulfur contained in the fuel is converted to SO2. The gas poses a serious danger for the human and environmental health. The health hazards associated with SO2 include hair loss, throat inflammation, impaired vision and respiratory illnesses. Sulfur dioxide is also forms acid rain, which leads to acidification of soils, waterways and forests. The main objective of this investigation is to explore methods of increasing lime utilization using South Africa calcium/siliceous-based sorbents for the purposes of removal of SO2 in the Flue Gas Desulfurization (FGD) system. Consequently, this study presents experimental findings on the preparation, characterization and sulfation of locally available fly ash, calcium oxide (CaO) and bottom ash. CaO was obtained from calcination of limestone in a laboratory kiln at a temperature of 900 °C and CaO/fly ash sorbent prepared using an atmospheric hydration process.