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Ashcroft, Alexander T. "Methane conversion over oxide catalysts." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305983.
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Richards, D. G. "Synthesis gas conversion to oxygenates using rhodium catalysts." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381157.
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Tsui, Li-Hsin. "Supported metal catalysts for water-gas shift conversion." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13384.
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Includes bibliographical references.The interests in an alternative, sustainable power generation method has greatly increased in the past decade due to increases in greenhouse gases and its impact on global climate change. The use of fuel cells as a form of energy generation is extremely promising as it converts chemical potential energy directly to electrical energy, bypassing the Carnot cycle limitations. Various types of fuel cells have been developed, with the proton exchange membrane fuel cell (PEMFC) being most promising for mobile and small-scale stationary uses under transient conditions. The PEMFC uses hydrogen and oxygen to generate electrical energy. While oxygen can be obtained from air, hydrogen does not exist in its elemental form; hence a process train is required to refine fuels (such as fossil fuels and bio-fuels) into pure hydrogen. This has been successfully achieved by large-scale industrial plants. A typical fuel processing train consists of a steam reforming stage converting the fuel into syngas. This is followed by a water-gas shift (WGS) stage to convert carbon monoxide, which is a poison for the platinum catalysts within fuel cells, into carbon dioxide. If the CO concentration required is extremely low, a methanation or preferential oxidation stage can be used subsequent to the WGS stage. This study focuses on the water-gas shift stage of the fuel processing train. Industrial base metal WGS catalysts are not suitable for a miniaturized fuel processing train due to the catalysts being developed for continuous operations, as miniaturized fuel processing trains are expected to operate at transient conditions. A slow and controlled reduction process is also required prior to operation, as well as the pyrophoricity of industrial catalysts after reduction. These can pose safety issues with non-technical personnel in household applications (e.g. CHP). PGM-based catalysts have shown high activities for the water-gas shift reaction in literature, are not pyrophoric and do not require lengthy and sensitive reduction processes prior to operation. The objective of this study was to investigate and compare two base metal catalysts (high temperature (HT) shift Fe₃O₄/Cr₂O₃ and low temperature (LT) shift CuO/ZnO/Al₂O₃ catalyst) with a PGM based counterpart, as well as to investigate whether the catalysts are able to achieve a required 1 vol% CO via the water-gas shift reaction. For these investigations a synthetic feedstock was used, based on typical exit concentrations of a steam methane reformer.
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Anheden, Marie. "Analysis of gas turbine systems for sustainable energy conversion." Doctoral thesis, KTH, Chemical Engineering and Technology, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2914.
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Increased energy demands and fear of global warming due tothe emission of greenhouse gases call for development of newefficient power generation systems with low or no carbondioxide(CO2) emissions. In this thesis, two different gasturbine power generation systems, which are designed with theseissues in mind, are theoretically investigated and analyzed.Inthe first gas turbine system, the fuel is combusted using ametal oxide as an oxidant instead of oxygen in the air. Thisprocess is known as Chemical Looping Combustion (CLC). CLC isclaimed to decrease combustion exergy destruction and increasethe power generation efficiency. Another advantage is thepossibility to separate CO2without a costly and energy demanding gasseparation process. The system analysis presented includescomputer-based simulations of CLC gas turbine systems withdifferent metal oxides as oxygen carriers and different fuels.An exergy analysis comparing the exergy destruction of the gasturbine system with CLC and conventional combustion is alsopresented. The results show that it is theoretically possibleto increase the power generation efficiency of a simple gasturbine system by introducing CLC. A combined gas/steam turbinecycle system with CLC is, however, estimated to reach a similarefficiency as the conventional combined cycle system. If thebenefit of easy and energy-efficient CO2separation is accounted for, a CLC combined cyclesystem has a potential to be favorable compared to a combinedcycle system with CO2separation.
In the second investigation, a solid, CO2-neutral biomass fuel is used in a small-scaleexternally fired gas turbine system for cogeneration of powerand district heating. Both open and closed gas turbines withdifferent working fluids are simulated and analyzed regardingthermodynamic performance, equipment size, and economics. Theresults show that it is possible to reach high power generationefficiency and total (power-and-heat) efficiency with thesuggested system. The economic analysis reveals that the costof electricity from theEFGT plant is competitive with the moreconventional alternatives for biomass based cogeneration in thesame size range (<10 MWe).
Keywords:power generation, Chemical Looping Combustion,CO2separation, oxygen carrier, biomass fuel, closedcycle gas turbine, externally fired gas turbine
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Yan, Wei. "Gas phase conversion of sugars to valuable C3 chemicals." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5504.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 31, 2009) Includes bibliographical references.
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Zeng, Fan. "Catalytic processes for conversion of natural gas engine exhaust and 2,3-butanediol conversion to 1,3-butadiene." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32777.
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Doctor of PhilosophyDepartment of Chemical Engineering
Keith L. Hohn
Extensive research has gone into developing and modeling the three-way catalyst (TWC) to reduce the emissions of hydrocarbons, NOx and CO from gasoline-fueled engines level. However, much less has been done to model the use of the three-way catalyst to treat exhaust from natural gas-fueled engines. Our research address this gap in the literature by developing a detailed surface reaction mechanism for platinum based on elementary-step reactions. A reaction mechanism consisting of 24 species and 115 elementary reactions was constructed from literature values. All reaction parameters were used as found in the literature sources except for steps modified to improve the model fit to the experimental data. The TWC was simulated as a one-dimension, isothermal plug flow reactor (PFR) for the steady state condition and a continuous stirred-tank reactor (CSTR) for the dithering condition. This work describes a method to quantitatively simulate the natural gas engine TWC converter performance, providing a deep understanding of the surface chemistry in the converter. Due to the depletion of petroleum oil and recent volatility in price, synthesizing value-added chemicals from biomass-derived materials has attracted extensive attention. 1, 3-butadiene (BD), an important intermediate to produce rubber, is conventionally produced from petroleum. Recently, one potential route is to produce BD by dehydration of 2, 3-butanediol (BDO), which is produced at high yield from biomass. This reaction was studied over two commercial forms of alumina. Our results indicate acid/base properties greatly impact the BD selectivity. Trimethylamine can also modify the acid/base properties on alumina surface and affect the BD selectivity. Scandium oxide, acidic oxide or zirconia dual bed systems are also studied and our results show that acidic oxide used as the second bed catalyst can promote the formation of BD, while 2,5-dimethylphenol is found when the zirconia is used as the second bed catalyst which is due to the strong basic sites.
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Bengtsson, Simon. "Economic and environmental implications of a conversion to natural gas." Thesis, Högskolan i Halmstad, Energivetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-27274.
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Swartz, Matthew M. "Nitric oxide conversion in a spark ignited natural gas engine." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=4009.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains xi, 79 p. : ill. Includes abstract. Includes bibliographical references (p. 67-70).
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Suárez, París Rodrigo. "Catalytic conversion of biomass-derived synthesis gas to liquid fuels." Doctoral thesis, KTH, Kemisk teknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-182690.
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Climate change is one of the biggest global threats of the 21st century. Fossil fuels constitute by far the most important energy source for transportation and the different governments are starting to take action to promote the use of cleaner fuels. Biomass-derived fuels are a promising alternative for diversifying fuel sources, reducing fossil fuel dependency and abating greenhouse gas emissions. The research interest has quickly shifted from first-generation biofuels, obtained from food commodities, to second-generation biofuels, produced from non-food resources. The subject of this PhD thesis is the production of second-generation biofuels via thermochemical conversion: biomass is first gasified to synthesis gas, a mixture of mainly H2 and CO; synthesis gas can then be catalytically converted to different fuels. This work summarizes six publications, which are focused on the synthesis gas conversion step. Two processes are principally examined in this summary. The first part of the PhD thesis is devoted to the synthesis of ethanol and higher alcohols, which can be used as fuel or fuel additives. The microemulsion technique is applied in the synthesis of molybdenum-based catalysts, achieving a yield enhancement. Methanol cofeeding is also studied as a way of boosting the production of longer alcohols, but a negative effect is obtained: the main outcome of methanol addition is an increase in methane production. The second part of the PhD thesis addresses wax hydroconversion, an essential upgrading step in the production of middle-distillate fuels via Fischer-Tropsch. Bifunctional catalysts consisting of noble metals supported on silica-alumina are considered. The deactivation of a platinum-based catalyst is investigated, sintering and coking being the main causes of decay. A comparison of platinum and palladium as catalyst metal function is also carried out, obtaining a fairly different catalytic performance of the materials in terms of conversion and selectivity, very likely due to dissimilar hydrogenation power of the metals. Finally, a kinetic model based on the Langmuir-Hinshelwood-Hougen-Watson formalism is proposed to describe the hydroconversion reactions, attaining a good fitting of the experimental data.Klimatförändringarna är ett av de största globala hoten under det tjugoförsta århundradet. Fossila bränslen utgör den helt dominerande energikällan för transporter och många länder börjar stödja användning av renare bränslen. Bränslen baserade på biomassa är ett lovande alternativ för att diversifiera råvarorna, reducera beroendet av fossila råvaror och undvika växthusgaser. Forskningsintresset har snabbt skiftat från första generationens biobränslen som erhölls från mat-råvaror till andra generationens biobränslen producerade från icke ätbara-råvaror. Ämnet för denna doktorsavhandling är produktion av andra generationens biobränslen via termokemisk omvandling. Biomassa förgasas först till syntesgas, en blandning av i huvudsak vätgas och kolmoxid; syntesgasen kan sedan katalytiskt omvandlas till olika bränslen. Detta arbete sammanfattar sex publikationer som fokuserar på steget för syntesgasomvandling. Två processer är i huvudsak undersökta i denna sammanfattning. Den första delen av doktorsavhandlingen ägnas åt syntes av etanol och högre alkoholer som kan användas som bränsle eller bränsletillsatser. Mikroemulsionstekniken har använts vid framställningen av molybden-baserade katalysatorer, vilket gav en höjning av utbytet. Tillsatsen av metanol har också studerats som ett sätt att försöka få en högre koncentration av högre alkoholer, men en negativ effekt erhölls: huvudeffekten av metanoltillsatsen är en ökad metanproduktion. Den andra delen av doktorsavhandlingen handlar om vätebehandling av vaxer som ett viktigt upparbetningssteg vid framställning av mellandestillat från Fischer-Tropsch processen. Bifunktionella katalysatorer som består av ädelmetaller deponerade på silica-alumina valdes. Deaktiveringen av en platinabaserad katalysator undersöktes. Sintring och koksning var huvudorsakerna till deaktiveringen. En jämförelse mellan platina och palladium som funktionella metaller genomfördes också med resultatet att det var en ganska stor skillnad mellan materialens katalytiska egenskaper vilket gav olika omsättning och selektivitet, mycket sannolikt beroende på olika reaktionsmönster hos metallerna vid vätebehandling. Slutligen föreslås en kinetisk modell baserad på en Langmuir-Hinshelwood-Hougen-Watson modell för att beskriva reaktionerna vid vätebehandling. Denna modell ger en god anpassning till experimentella data.
El cambio climático es una de las mayores amenazas del siglo XXI. Los combustibles fósiles constituyen actualmente la fuente de energía más importante para el transporte, por lo que los diferentes gobiernos están empezando a tomar medidas para promover el uso de combustibles más limpios. Los combustibles derivados de biomasa son una alternativa prometedora para diversificar las fuentes de energía, reducir la dependencia de los combustibles fósiles y disminuir las emisiones de efecto invernadero. Los esfuerzos de los investigadores se han dirigido en los últimos años a los biocombustibles de segunda generación, producidos a partir de recursos no alimenticios. El tema de esta tesis de doctorado es la producción de biocombustibles de segunda generación mediante conversión termoquímica: en primer lugar, la biomasa se gasifica y convierte en gas de síntesis, una mezcla formada mayoritariamente por hidrógeno y monóxido de carbono; a continuación, el gas de síntesis puede transformarse en diversos biocombustibles. Este trabajo resume seis publicaciones, centradas en la etapa de conversión del gas de síntesis. Dos procesos se estudian con mayor detalle. En la primera parte de la tesis se investiga la producción de etanol y alcoholes largos, que pueden ser usados como combustible o como aditivos para combustible. La técnica de microemulsión se aplica en la síntesis de catalizadores basados en molibdeno, consiguiendo un incremento del rendimiento. Además, se introduce metanol en el sistema de reacción para intentar aumentar la producción de alcoholes más largos, pero los efectos obtenidos son negativos: la principal consecuencia es el incremento de la producción de metano. La segunda parte de la tesis estudia la hidroconversión de cera, una etapa esencial en la producción de destilados medios mediante Fischer-Tropsch. Los catalizadores estudiados son bifuncionales y consisten en metales nobles soportados en sílice-alúmina. La desactivación de un catalizador de platino se investiga, siendo la sinterización y la coquización las principales causas del problema. El uso de platino y paladio como componente metálico se compara, obteniendo resultados catalíticos bastante diferentes, tanto en conversión como en selectividad, probablemente debido a su diferente capacidad de hidrogenación. Finalmente, se propone un modelo cinético, basado en el formalismo de Langmuir-Hinshelwood-Hougen-Watson, que consigue un ajuste satisfactorio de los datos experimentales.
QC 20160308
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Du, Toit Ernest. "The direct conversion of synthesis gas to chemicals / Ernest du Toit." Thesis, Potchefstroom University for Christian Higher Education, 2002. http://hdl.handle.net/10394/9624.
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The catalytic conversion of synthesis gas, obtainable from the processing of coal, biomass or
natural gas, to a complex hydrocarbon product stream can be achieved via the Fischer-Tropsch
process. The Fischer-Tropsch synthesis process has evolved from being mainly a fuel producing
process in the early 1950's to that of a solvent and speciality wax production process towards the
end of the 1970's. From the early 1980's there has been a clear shift towards the production of
commodity chemicals in addition to fuel.
Advances in reactor technology, volatile crude oil markets and a world trend towards "clean"
fuels may cause a shift towards coal and natural gas as the feedstock of choice for the chemical
industry. Fischer-Tropsch plants are capital intensive ventures due to the complexity of the
process. Viable returns on such projects can only be realised by adding value to the products
obtained from such processes. The chemical industry places a high premium on certain
chemicals such as olefins and higher alcohols. More selective production of such chemicals can
contribute to increased 'profitability and thus more economically viable processes. The C8+
alcohol and C6+ olefin product range can be labelled as valuable chemicals. A major limitation
in the traditional Fischer-Tropsch process is the low selectivity towards these valuable chemicals.
The product distribution observed for a Fischer-Tropsch catalyst system conforms to the SchulzFlory
polymerisation mechanism, which is inherently non-selective.
This investigation deals with an iron-based catalyst that can best be described as a chemically
selective Fischer-Tropsch catalyst. The product spectrum achieved with this so-called "ChemFT"
catalyst can be seen as a breakthrough in terms of producing chemicals directly from syngas.
The investigation covers the following aspects:
a review of the development of the ChemFT catalyst used in this investigation,
the characterisation of the ChemFT catalyst,
an experimental verification of the catalyst product spectrum with respect to alcohols and
olefins, on both laboratory and pilot plant scale,
the development of rate equations for'Fischer-Tropsch and Water-Gas-Shift activity. Experimental performance results of the ChemFT catalyst show high selectivity towards the
desired alcohol product compared to traditional low temperature iron catalysts (8- 14 C atom%
vs. 2 - 4 C atom %). Similar olefin selectivity is obtainable with lower long chain paraffin
selectivity (little or no wax formation). It is concluded that the ChemFT catalyst differs from
conventional Fischer-Tropsch iron catalysts as far as selectivity and typical process conditions
are concerned. Published reaction rate equations were evaluated for applicability to such a
scenario. Known Fischer-Tropsch reaction rate equations described the catalyst kinetics fairly
well. The theoretical base thereof was further improved by modifYing the equations to include
the effect of catalyst vacant sites. Published Water-Gas-Shift rate equations did not adequately
describe the catalyst. It was shown that the accuracy of the Water-Gas-Shift equation could be
improved by modifYing it to account for C02 adsorption. Reaction rate equations for both the
Fischer-Tropsch and Water-Gas-Shift reaction rates that are valid in the typical operating
conditions are proposed.Thesis (PhD (Chemical Engineering))--Potchefstroom University for Christian Higher Education, 2003
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Maduna, Kubefu Albert. "Water-gas shift conversion in microchannel reactors using noble metal catalysts." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9119.
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Includes bibliographical references.Fuel cell technology will play a crucial role in future sustainable energy generation. Different types of fuel cells had been developed, of which Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are the fuel cells of choice for small scale stationary and mobile applications that operate under transient conditions.The feed for PEMFCs is hydrogen. For small scale stationary and mobile applications, the hydrogen, typically, has to be produced on-site from other energy sources, such as fossil fuels or fuel from renewable sources. At present, the most favourable approach appears to be production train that startsith a steam reformer stage, which converts most of the primary fuel to syngas. In the subsequent water-¬‐gas-¬‐shift stage,most of the carbon monoxide in the syngas is converted to additional hydrogen and carbon dioxide. In a last stage, the small amount of carbon monoxide that remains in the stream is reduced to acceptable levels for use in the fuel cell. In large scale industrial hydrogen production, the above concept (steam reforming –water gas-shift-hydrogen purification) is the state of the art, with the units operating under steady conditions for years years once started. In contrast, the said small scale units will typically operate under transient conditions and in on/off mode. This requires catalysts that are stable with respect to occasional contact with air and condensation of the steam co-fed with the primary fuel and which do not require any activation or other conditioning prior to restart. Only noble metal based catalysts meet these requirements at present.This study was aimed at the water-gas-shirhift (WGS) stage within this train. The basis of the study was the comparison of three commercial supported noble metal WGS catalysts and a state-¬‐of-¬‐the-¬‐art industrial iron/chromium high temperature WGS catalyst. All the catalysts were applied washcoated into stainless steel microchannel reactor, either coated in - house or by the catalyst manufacturer, as well as defining an operational window for the noble metal catalysts.
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Nisar, Jawad. "Atomic Scale Design of Clean Energy Materials : Efficient Solar Energy Conversion and Gas Sensing." Doctoral thesis, Uppsala universitet, Materialteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179372.
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The focus of this doctoral thesis is the atomic level design of photocatalysts and gas sensing materials. The band gap narrowing in the metal oxides for the visible-light driven photocatalyst as well as the interaction of water and gas molecules on the reactive surfaces of metal oxides and the electronic structure of kaolinite has been studied by the state-of-art calculations. Present thesis is organized into three sections. The first section discusses the possibility of converting UV active photocatalysts (such as Sr2Nb2O7, NaTaO3, SrTiO3, BiTaO4 and BiNbO4) into a visible active photocatalysts by their band gap engineering. Foreign elements doping in wide band gap semiconductors is an important strategy to reduce their band gap. Therefore, we have investigated the importance of mono- and co-anionic/cationic doping on UV active photocatalysts. The semiconductor's band edge position is calculated with respect to the water oxidation/reduction potential for various doping. Moreover, the tuning of valence and conduction band edge position is discussed on the basis of dopant's p/d orbital energy. In the second section of thesis the energetic, electronic and optical properties of TiO2, NiO and β-Si3N4 have been discussed to describe the adsorption mechanism of gas molecules at the surfaces. The dissociation of water into H+ or OH- occurs on the O-vacancy site of the (001)-surface of rutile TiO2 nanowire, which is due to the charge transfer from Ti atom to water molecule. The dissociation of water into OH- and imino (NH) groups is also observed on the β-Si3N4 (0001)-surface due to the dangling bonds of the lower coordinated N and Si surface atoms. Fixation of the SO2 molecules on the anatase TiO2 surfaces with O-deficiency have been investigated by Density Functional Theory (DFT) simulation and Fourier Transform Infrared (FTIR) spectroscopy. DFT calculations have been employed to explore the gas-sensing mechanism of NiO (100)-surface on the basis of energetic and electronic properties. In the final section the focus is to describe the optical band gap of pristine kaolinite using the hybrid functional method and GW approach. Different possible intrinsic defects in the kaolinite (001) basal surface have been studied and their effect on the electronic structure has been explained. The detailed electronic structure of natural kaolinite has been determined by the combined efforts of first principles calculations and Near Edge X-ray Absorption Fine Structure (NEXAFS).
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Kent, Ryan Alexander. "Conversion of Landfill Gas to Liquid Hydrocarbon Fuels: Design and Feasibility Study." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6102.
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This paper will discuss the conversion of gas produced from biomass into liquid fuel through the combination of naturally occurring processes, which occur in landfills and anaerobic digesters, and a gas-to-liquids (GTL) facility. Landfills and anaerobic digesters produce gases (LFG) that can be converted into syngas via a Tri-reforming process and then synthesized into man-made hydrocarbon mixtures using Fischer-Tropsch synthesis. Further processing allows for the separation into liquid hydrocarbon fuels such as diesel and gasoline, as well as other middle distillate fuels. Conversion of landfill gas into liquid fuels increases their energy density, ease of storage, and open market potential as a common “drop in” fuel. These steps not only allow for profitable avenues for landfill operators but potential methods to decrease greenhouse gas emissions. The objective of this paper is to present a preliminary design of an innovative facility which processes contaminated biogases and produces a valuable product. An economic analysis is performed to show feasibility for a facility under base case scenario. A sensitivity analysis is performed to show the effect of different cost scenarios on the breakeven price of fuel produced. Market scenarios are also presented in order to further analyze situations where certain product portions cannot be sold or facility downtime is increased. This facility is then compared to traditional mitigation options, such as flaring and electricity generation, to assess the effect each option has on cost, energy efficiency, and emissions reduction.
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Udell, Thomas Gregory. "Reducing emissions of older vehicles through fuel system conversion to natural gas." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19896.
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Li, Yuanda. "Electrochemical conversion of a fluorinated greenhouse gas using a lithium battery configuration." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111724.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-60).
The demand for technological advancement of greenhouse gas conversion and mitigation strategies is ever increasing. In this thesis, a non-aqueous electrochemical platform with metal lithium (Li) as the anode and carbon as the cathode has been developed to convert the most potent greenhouse gas, sulfur hexafluoride (SF 6), into benign solids Li2S and LiF under room temperature conditions at an electrode - electrolyte interface. Galvanostatic discharge demonstrated that the reaction between Li and SF 6 is capable of delivering modest cell voltages up to - 2.4 V vs. Li/Lie and capacities up to ~3800 mAh/gc. The electrochemical reaction between Li and SF6 in two different battery solvents has been characterized with a suite of solid and liquid phase analyses, which showed the reaction to be an 8 - electron transfer process with high Coulombic efficiency. Rotating disk electrode studies were also employed to demonstrate that the overpotential of this system is intrinsically governed by kinetics. This work demonstrates a non-aqueous system capable of both reducing a fluorinated gas, SF6 under room temperature conditions at an electrode surface, and acting as a primary battery based on halogen ligand chemistry.
by Yuanda Li.
S.M.
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Acocella, Angela J. (Angela Josephine). "System model of small-scale gas-to-methanol conversion by engine reformers." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98548.
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Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, Engineering Systems Division, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 88-93).
As global energy demands grow and environmental concerns over resource extraction methods intensify, high impact solutions are becoming increasingly essential. Venting and flaring of associated natural gas represents significant environmental and financial losses yet it continues in the North Dakota Bakken oil play. The valuable gas resource is wasted due to unfavorable economics and limited pipeline capacity. Similarly in India, underdeveloped gas transport infrastructure and restrictive regulatory frameworks prevent distribution and marketing of natural gas from the northeast regions, leaving it stranded in marginal fields. This thesis establishes a techno-economic model, utilizing Aspen Plus chemical processing software, and a discounted cash flow model to estimate economic feasibility of implementing MIT engine reformer-based gas-to-liquids (GTL) systems in the US or India. The system reforms natural gas via partial oxidation into synthesis gas (syngas) in the cylinders of an internal combustion engine, and can significantly reduce capital costs over conventional GTL reforming processes. The engine is operated in fuel rich conditions to generate the syngas, which is synthesized into methanol and dimethyl ether (DME). Once produced on-site, these liquids are more easily transported than gases. This study assesses the regulatory structures surrounding the upstream methane resource and downstream end product marketability for three scenarios: use of DME to replace existing local (1) diesel and (2) liquefied petroleum gas (LPG), or (3) sale of methanol as a commodity chemical on domestic or global markets. The analysis shows the system is economical in both locations. In the US, the minimum economically efficient production capacity with a 1-2 year payback period is 400,000- 860,000 standard cubic feet per day (scfpd) of natural gas for the range of end use scenarios considered. Differences in costs and product market characteristics in India result in a minimum efficient capacity of 330,000-810,000 scfpd of natural gas for the three scenarios.
by Angela J. Acocella.
S.M. in Technology and Policy
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Mei, D. "Plasma-catalytic conversion of greenhouse gas into value-added fules and chemicals." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3001675/.
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Park, Talus. "Dual fuel conversion of a direct injection diesel engine." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=460.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains x, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 61-62).
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Abdollahi, Farhang. "Gas Separation by Adsorption in Order to Increase CO2 Conversion to CO via Reverse Water Gas Shift (RWGS) Reaction." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23993.
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In this research project, adsorption is considered in conjunction with the reverse water gas shift reaction in order to convert CO2 to CO for synthetic fuel production. If the CO2 for this process can be captured from high emitting industries it can be a very good alternative for reduced fossil fuel consumption and GHG emission mitigation. CO as an active gas could be used in Fischer-Tropsch process to produce conventional fuels. Literature review and process simulation were carried out in order to determine the best operating conditions for reverse water gas shift (RWGS) reaction. Increasing CO2 conversion to CO requires CO2/CO separation downstream of the reactor and recycling unreacted CO2 and H2 back into the reactor. Adsorption as a viable and cost effective process for gas separation was chosen for the CO2/CO separation. This was started by a series of adsorbent screening experiments to select the best adsorbent for the application. Screening study was performed by comparing pure gas isotherms for CO2 and CO at different temperatures and pressures. Then experimental isotherm data were modeled by the Temperature-Dependent Toth isotherm model which provided satisfactory fits for these isotherms. Henry law’s constant, isosteric heat of adsorption and binary mixture prediction were determined as well as selectivity for each adsorbent. Finally, the expected working capacity was calculated in order to find the best candidate in terms of adsorption and desorption. Zeolite NaY was selected as the best candidate for CO2/CO separation in adsorption process for this project. In the last step breakthrough experiments were performed to evaluate operating condition and adsorption capacity for real multi component mixture of CO2, CO, H2 in both cases of saturated with water and dry gas basis. In multi components experiments zeolite NaY has shown very good performance to separate CO2/CO at low adsorption pressure and ambient temperature. Also desorption experiment was carried out in order to evaluate the working capacity of the adsorbent for using in industrial scale and eventually temperature swing adsorption (TSA) process worked very well for the regeneration step. Integrated adsorption system downstream of RWGS reactor can enhance the conversion of CO2 to CO in this process significantly resulting to provide synthetic gas for synthetic fuel production as well as GHG emission mitigation.
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Kennaugh, Richard Juan. "Stability of a plasma in a noble gas magnetohydrodynamic power generator." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335847.
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Kossel, Elke, Christian Deusner, Nikolaus Bigalke, and Matthias Haeckel. "Magnetic Resonance Imaging of gas hydrate formation and conversion at sub-seafloor conditions." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184430.
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The production of natural gas from sub-seafloor gas hydrates is one possible strategy to meet the world’s growing demand for energy. On the other hand, climate warming scenarios call for the substitution of fossil energy resources by sustainable energy concepts. Burning natural gas from gas hydrates could be emission neutral if it was combined with a safe storage of the emitted CO2.
Laboratory experiments, that address corresponding strategies, need to be performed under high pressures and low temperatures to meet the thermodynamic conditions of the sub-seafloor environment. In this paper, we present a high-pressure flow-through sample cell that is suitable for nuclear magnetic resonance (NMR) experiments at realistic marine environmental conditions, i.e. pressures up to 15 MPa and temperatures from 5 to 20°C, and we demonstrate its suitability in applied gas hydrate research.
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Umoh, Reuben Mfon. "Direct synthesis gas conversion to alcohols and hydrocarbons using a catalytic membrane reactor." Thesis, Robert Gordon University, 2009. http://hdl.handle.net/10059/2117.
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In this work, inorganic membranes with highly dispersed metallic catalysts on macroporous titania-washcoated alumina supports were produced, characterized and tested in a catalytic membrane reactor. The reactor, operated as a contactor in the forced pore-flow-through mode, was used for the conversion of synthesis gas (H2 + CO) into mixed alcohols and hydrocarbons via the Fischer-Tropsch synthesis. Carbon monoxide conversions of 78% and 90% at near atmospheric pressure (300kPa) and 493K were recorded over cobalt and bimetallic Co-Mn membranes respectively. The membranes also allowed for the conversion of carbon dioxide, thus eliminating the need for a CO2 separation interphase between synthesis gas production and Fischer-Tropsch synthesis. Catalytic tests conducted with the membrane reactor with different operating conditions (of temperature, pressure and feed flow rate) on cobalt-based membranes gave very high selectivity to specific products, mostly higher alcohols (C2 – C8) and paraffins within the gasoline range, thereby making superfluous any further upgrading of products to fuel grade other than simple dehydration. Manganese-promoted cobalt membranes were found not only to give better Fischer-Tropsch activity, but also to promote isomerization of paraffins, which is good for boosting the octane number of the products, with the presence of higher alcohols improving the energy density. The membrane reactor concept also enhanced the ability of cobalt to catalyze synthesis gas conversions, giving an activation energy Ea of 59.5 kJ/mol.K compared with 86.9 – 170 kJ/mol.K recorded in other reactors. Efficient heat transfer was observed because of the open channel morphology of the porous membranes. A simplified mechanism for both alcohol and hydrocarbon production based on hydroxycarbene formation was proposed to explain both the stoichiometric reactions formulated and the observed product distribution pattern.
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Liu, S. "Plasma gas cleaning processes for the conversion of model tar from biomass gasification." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3021510/.
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Kossel, Elke, Christian Deusner, Nikolaus Bigalke, and Matthias Haeckel. "Magnetic Resonance Imaging of gas hydrate formation and conversion at sub-seafloor conditions." Diffusion fundamentals 18 (2013) 15, S. 1-4, 2013. https://ul.qucosa.de/id/qucosa%3A13724.
Full textAbstract:
The production of natural gas from sub-seafloor gas hydrates is one possible strategy to meet the world’s growing demand for energy. On the other hand, climate warming scenarios call for the substitution of fossil energy resources by sustainable energy concepts. Burning natural gas from gas hydrates could be emission neutral if it was combined with a safe storage of the emitted CO2.
Laboratory experiments, that address corresponding strategies, need to be performed under high pressures and low temperatures to meet the thermodynamic conditions of the sub-seafloor environment. In this paper, we present a high-pressure flow-through sample cell that is suitable for nuclear magnetic resonance (NMR) experiments at realistic marine environmental conditions, i.e. pressures up to 15 MPa and temperatures from 5 to 20°C, and we demonstrate its suitability in applied gas hydrate research.
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Myo, Min Win. "Thermochemical conversion characteristics of gas and tar generation from waste biomass and plastics." Kyoto University, 2020. http://hdl.handle.net/2433/253264.
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Brungs, A. J. A. "Transition metal carbides as catalysts for methane reforming." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365881.
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Rose, Lauren. "Carbon Dioxide Gas Separation from Syngas to Increase Conversion of Reverse Water Gas Shift Reaction via Polymeric and Mixed Matrix Membranes." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37897.
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Membranes are a promising, effective and energy efficient separation strategy for effluent gases in the Reverse Water Gas Shift (RWGS) reaction to increase the overall conversion of CO2 to CO. This process involves a separation and recycling process to reuse the unreacted CO2 from the RWGS reactor. The carbon monoxide produced from this reaction, alongside hydrogen (composing syngas), can be used in the Fischer-Tropsch process to create synthetic fuel, turning stationary CO2 emissions into a useable resource. A literature review was performed to select suitable polymers with high CO2 permeability and selectivities of CO2 over CO and H2. PDMS (polydimethylsiloxane) was selected and commercial and in-house PDMS membranes were tested. The highest CO2 permeability observed was 5,883 Barrers, including a CO2/H2 selectivity of 21 and a CO2/CO selectivity of 9, with ternary gas feeds. HY zeolite, silica gel and activated carbon were selected from previous research for their CO2 separation capabilities, to be investigated in PDMS mixed matrix membranes in 4 wt % loadings. Activated carbon in PDMS proved to be the best performing mixed matrix membrane with a CO2 permeability of 2,447 Barrers and comparable selectivities for CO2/H2 and CO2/CO of 14 and 9, respectively. It was believed that swelling, compaction and the homogeneity of the selective layer were responsible for trends in permeability with respect to driving force. The HY and silica gel mixed matrix PDMS membranes were believed to experience constraints in performance due to particle and polymer interfaces within the membrane matrix.
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Farina, Jordan Thomas. "Conversion of a Gas Turbine Engine to Operate on Lean-Premixed Hydrogen-Air: Design and Characterization." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31067.
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The continued use of fossil fuels along with a rise in energy demand has led to increasing levels of carbon emissions over the past years. The purpose of this research was to design a lean premixed hydrogen fuel system that could be readily retrofit into an existing gas turbine engine to provide a clean renewable energy solution to this growing problem. There were major hurdles that had to be overcome to develop a hydrogen fuel system that would be practical, stable, and would fit into the existing space.
High flame temperatures coupled with high flame speeds are major concerns when switching from jet fuel or natural gas to hydrogen. High temperatures lead to formations of pollutants such as oxides of nitrogen (NOx) and can potentially cause damage to critical engine components. High flame speeds can lead to dangerous flashbacks in the fuel premixers. Past researches have developed various hydrogen premixers to combat these problems. This research designed and developed new hydrogen premixers using information gathered from these designs and utilized new ideas to address their shortcomings.
A gas turbine engine was modified using 14 premixers and a matching combustor liner to provide lean operation with the existing turbomachinery. The engine was successfully operated using hydrogen while maintaining normal internal temperatures and practically eliminating the NOx emissions when compared to normal Jet-A operation. Even though full power operation was never achieved due to flashbacks in two premixers, this research demonstrated the feasibility of using lean-premixed hydrogen in gas turbine engines.
Master of Science
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Baumhakl, Christoph [Verfasser], and Jürgen [Akademischer Betreuer] Karl. "Substitute Natural Gas Production with direct Conversion of Higher Hydrocarbons / Christoph Baumhakl. Gutachter: Jürgen Karl." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1075832462/34.
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Fraser, Ian. "The feasibility of high synthesis gas conversion over ruthenium promoted iron-based Fischer Tropsch catalyst." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2588.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.One of the very promising synthetic fuel production strategies is the Fischer-Tropsch process, founded on the Fischer-Tropsch Synthesis, which owes its discovery to the namesake researchers Franz Fischer and Hans Tropsch. The Fischer-Tropsch Synthesis (FTS) converts via complex polymerisation reaction a mixture of CO and H2 over transition metal catalysts to a complex mixture of hydrocarbons and oxygen containing compounds with water as major by-product. The mixture of CO and H2 (termed syngas) may be obtained by partial oxidation of carbon containing base feedstocks such as coal, biomass or natural gas via gasification or reforming. The Fischer-Tropsch (FT) process thus presents the opportunity to convert carbon containing feedstocks to liquid fuels, chemicals or hydrocarbon waxes, which makes, for instance, the monetisation of stranded gas or associated gas a possibility. The FT-process is typically carried out in two modes of operation: low temperature Fischer-Tropsch (LTFT) and high temperature Fischer-Tropsch (HTFT). LTFT is normally operated at temperatures of 200 – 250 °C and pressures of 10 – 45 bar to target production of high molecular weight hydrocarbons, while HTFT is operated at 300 – 350 °C and 25 bar to target gasoline production. The catalytically active metals currently used commercially are iron and cobalt, since product selectivity over nickel is almost exclusively to methane and ruthenium is highly expensive in addition to requiring very high pressures to perform optimally. Fe is much cheaper, but tends to deactivate more rapidly than Co due to oxidation in the presence of high H2O partial pressures. One of the major drawbacks to using Fe as FT catalyst is the requirement of lower per pass conversion which necessitates tail gas recycle to extend catalyst life and attain acceptable overall conversions. A more active or similarly active but more stable Fe-catalyst would thus be advantageous. For this reason promotion of a self-prepared typical LTFT Fe-catalyst with Ru was investigated. A precipitated K-promoted Fe-catalyst was prepared by combination of co-precipitation and incipient wetness impregnation and a ruthenium containing catalyst prepared from this by impregnation with Ru3(CO)12. The catalysts, which had a target composition of 100 Fe/30 Al2O3/5 K and 100 Fe/30 Al2O3/5 K/3 Ru, were characterised using XRD, SEMEDX, ICP-OES, TPR and BET N2-physisorption, before testing at LTFT conditions of 250 °C and 20 bar in a continuously stirred slurry phase reactor.
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Armstrong, Lindsay-Marie. "CFD modelling of the gas-solid flow dynamics and thermal conversion processes in fluidised beds." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/192155/.
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Shehata, Nader. "Design of optical characteristics of ceria nanoparticles for applications including gas sensing and up-conversion." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49574.
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This thesis investigates the impact of doping on the optical and structural characteristics of cerium oxide (ceria) nanoparticles synthesized using chemical precipitation. The dopants selected are samarium and neodymium, which have positive association energy with oxygen vacancies in the ceria host, and negative association lanthanides, holmium and erbium, as well as two metal dopants, aluminum and iron. Characteristics measured are absorption and fluorescence spectra and the diameter and lattice parameter of ceria. Analysis of the characteristics indicates qualitatively that the dopant controls the O-vacancy concentration and the ratio of the two cerium ionization states: Ce+3 and Ce+4. A novel conclusion is proposed that the negative association lanthanide dopants can act as O-vacancies scavengers in ceria while the O-vacancy concentration increases in ceria doped with positive association lanthanide elements. Doped ceria nanoparticles are evaluated in two applications: dissolved oxygen (DO) sensing and up-conversion. In the first application, ceria doped with either Sm or Nd and ceria doped with aluminum have a strong correlation between the fluorescence quenching with the DO concentration in the aqueous solution in which the ceria nanoparticles are suspended. Stern-Volmer constants (KSV) of doped ceria are found to strongly depend upon the O-vacancy concentration and are larger than some of the fluorescent molecular probes currently used to measure DO. The KSV measured between 25-50oC is found to be significantly less temperature dependent as compared to the constants of commercially-available DO molecular probes. In the second application, up-conversion, ceria nanoparticles doped with erbium and an additional lanthanide, either Sm or Nd, are exposed to IR radiation at 780 nm. Visible emission is only observed after the nanoparticles are calcinated at high temperature, greatly diminishing the concentration of O-vacancies. It is concluded that O-vacancies do not play a dominant role in up-conversion, unlike that drawn for down-conversion, where the fluorescence intensity is strongly correlated with the O-vacancy concentration. Correlations between annealing temperatures, dopant, and dopant concentrations with the power dependence of up-conversion on the pump and the origin of the intensities of the visible emission are presented. These studies show the promise of doped ceria nanoparticles.Ph. D.
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Hunderup, James W. "An experimental investigation of the conversion of NO to NO2 in a simulated gas turbine environment." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063102/.
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Dvořáčková, Kateřina. "Konverze plynojemu, Ostrava - DOV." Master's thesis, Vysoké učení technické v Brně. Fakulta architektury, 2009. http://www.nusl.cz/ntk/nusl-215628.
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The subject of my diploma project is reconversion of a gasholder placed in Ostrava Vitkovice. The gasholder is noted as national culture heritage and is strongly contaminated. The concept is following the functional structure of the objects around and counts with their new use. The gasholder is placed in the middle of the area and lays on the crossing of conjuction of the main dominant s of the area. These cojuctions create streets which meet in the middle of the gasholder and create the square. The gasholder has now two faces, the old one faces the area is monofunctional and the other, new one faced to the inside is polyfunctional. The square is covered by the existing roof construction and creates safe place full of nice views and visual conjunctions of the main dominants.
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Shian, Samuel. "Shape preserving conversion reaction of siliceous structures using metal halides: properties, kinetics, and potential applications." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/37252.
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BaSIC, which stands for Bioclastic and Shape-preserving Inorganic Conversion, is shape-preserving chemical conversion process of biological (or man-made) silica structures for producing complex 3-D microscale structures. This dissertation reports the BaSIC reaction of halide gases (i.e., TiF4, ZrF4, and ZrCl4) with 3-D silica structures, (i.e., diatom frustules, silicified direct-write assembly scaffolds, and Stöber silica spheres) to produce titania and zirconia replicas of the original 3-D structures. The kinetics of reaction of silica with titanium tetrafluoride gas is analyzed by using a novel HTXRD reaction chamber, nitrogen adsorption, and transmission electron microscope (TEM). The crystal structure and the temperature-induced phase transformation (from the room temperature hexagonal R-3c structure to the higher temperature cubic Pm3m structure) of polycrystalline TiOF2 that was synthesized through metathetic reaction of silica with TiF4(g) is reported. Additionally, potential applications of the converted titania diatom frustules (i.e., as a fast micron-sized ethanol sensor, and as a pesticide hydrolyzing agent) are also demonstrated in this work.
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Reid, Patrick Earl Fitzgerald. "The integration of solid oxide fuel cell technology with industrial power generation systems." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18947.
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Halvarsson, Alfred. "Katalytisk omvandling av pyrolysgas i WoodRoll-processen för ökad processtillförlitlighet." Thesis, KTH, Skolan för kemivetenskap (CHE), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172412.
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This project was a cooperation between the division of Chemical Technology at KTH, Cortus Energy and Haldor Topsoe A/S. The goal was to build up a totally new setup for converting and deoxygenate pyrolysis bio-oil, in order to increase the performance of Cortus Energy’s WoodRoll process. Therefore an iron based catalyst from Haldor Topsoe was used. The building up of the new setup with all reactors and the control panel was a complicated and time-consuming work. This led to an only short time slot for performing experiments, which means that more work needs to be done to get more valuable results. The most important success of this project was to get all the knowledge about the system and to make everything (the whole experimental setup) running properly. However, the sampling system needs to be improved before making further experiments. The experiments which have been done show promising results and that the iron based catalyst was working well for converting the bio-oil. During the two hour long experiment there were not shown any indications of deactivation, when looking at the gas compositions, but the results from temperature programmed oxidation (TPO) show carbon deposition on the catalyst and the BET surface also shows a slight decrease in surface area.
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Hug, Stephan [Verfasser], and Bettina [Akademischer Betreuer] Lotsch. "Covalent triazine frameworks : structure, properties and applications in gas storage and energy conversion / Stephan Hug. Betreuer: Bettina Lotsch." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1075456975/34.
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Khan, Ashikur R. "Experimental studies of the homogeneous conversion of sulfur di-oxide to sulfur tri-oxide via natural gas reburning." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175798586.
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Parra, Amanda Silva [UNESP]. "Greenhouse gas balance in the conversion from extensive pasture to other agricultural systems in Andean region of Colombia." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126562.
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000842997_20200414.pdf: 86943 bytes, checksum: 7412fff38136c54a3f28ead5328f0880 (MD5)O desafio do setor agrícola é reduzir as emissões e aumentar a produção de alimentos, tendo em conta os aspectos ambientais. Na zona andina da Colômbia, há uma crescente necessidade de se desenvolver técnicas de mitigação de GEE (gases de efeito estufa) associados à produção de leite. Este trabalho considera as emissões de GEE e os potenciais sumidouros de carbono associados aos cenários de produção de leite na zona andina da Colômbia. Os cenários considerados foram: agricultura convencional de Pennisetum clandestinum em rotação com batatas (PRP), pastagens melhoradas de Lolium multiflorum (IP) e sistema silvipastoril de Pennisetum clandestinum em consórcio com Acacia decurrens e Trifolium repens (SPS). Com base nas metodologias do IPCC (2006) e considerando-se um ciclo de produção de 6 anos, o balanço anual das emissões compreende as fontes agrícolas e o consumo de gasolina relacionadas com as principais fases de produção agrícola, e o potencial de acúmulo de C no solo e a fixação de C na biomassa em todos os cenários estudados. Menores emissões de GEE foram estimados no cenário de PRP (3.864 kg CO2eq ha-1 ano-1), porém apresenta uma menor produtividade de leite. As maiores emissões de GEE foram observadas no cenário IP (7.711 kg CO2eq ha-1 ano-1), que apresentou uma maior produtividade de leite e um potencial considerável para o acúmulo de C no solo, que poderia ajudar na compensação das emissões. No cenário SPS, que tem uma produtividade de leite próximo de IP, apresentou o maior potencial para compensar as emissões de GEE (4.878 kg CO2eq ha-1 ano-1) devido ao acúmulo de C solo e a fixação de C na biomassa em árvores
The challenge of agricultural sector is to reduce emissions and increase food production, taking into account environmental aspects. In Andean zone of Colombia, there is a growing need to develop GHG (greenhouse gas) mitigation techniques associated to milk production. This work focuses on the GHG emissions and potential sinks associated to milk production scenarios in the Andean zone of Colombia. The scenarios considered were: conventional agriculture of Pennisetum clandestinum in rotation with potatoes (PRP), improved pastures of Lolium multiflorum (IP) and silvopastoral system of Pennisetum clandestinum in consortium with Acacia decurrens and Trifolium repens (SPS). Based on the IPCC (2006) methodologies, the annual emission balance for a 6-year production cycle included agricultural sources and gasoline consumption related to the main agricultural phases in field, and the potential for soil C accumulation and biomass C fixation in all studied scenarios. Lower GHG emissions were estimated in PRP scenario (3,864 kg CO2eq ha-1 yr-1), but this presents the lower milk productivity. The higher GHG emissions were observed in IP scenario (7,711 kg CO2eq ha-1 yr-1), which presented the highest milk productivity and a considerable potential for soil C accumulation, that could help into the offset of its emissions. But SPS scenario, which has a milk productivity close to IP, presented the highest potential to offset GHG emission (4,878 kg CO2eq ha-1 yr-1) due to soil C accumulation plus biomass C fixation in trees
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Hug, Stefan Jules [Verfasser], and Bettina [Akademischer Betreuer] Lotsch. "Covalent triazine frameworks : structure, properties and applications in gas storage and energy conversion / Stephan Hug. Betreuer: Bettina Lotsch." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1075456975/34.
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Parra, Amanda Silva. "Greenhouse gas balance in the conversion from extensive pasture to other agricultural systems in Andean region of Colombia /." Jaboticabal, 2015. http://hdl.handle.net/11449/126562.
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Orientador: Newton La Scala JuniorCoorientador: Eduardo Barretto de Figueiredo
Banca: Débora Marcondes Bastos Pereira Milori
Banca: Marcelo Valadares Galdos
Banca: Gener Tadeu Pereira
Banca: Glauco de Souza Rolim
Resumo: O desafio do setor agrícola é reduzir as emissões e aumentar a produção de alimentos, tendo em conta os aspectos ambientais. Na zona andina da Colômbia, há uma crescente necessidade de se desenvolver técnicas de mitigação de GEE (gases de efeito estufa) associados à produção de leite. Este trabalho considera as emissões de GEE e os potenciais sumidouros de carbono associados aos cenários de produção de leite na zona andina da Colômbia. Os cenários considerados foram: agricultura convencional de Pennisetum clandestinum em rotação com batatas (PRP), pastagens melhoradas de Lolium multiflorum (IP) e sistema silvipastoril de Pennisetum clandestinum em consórcio com Acacia decurrens e Trifolium repens (SPS). Com base nas metodologias do IPCC (2006) e considerando-se um ciclo de produção de 6 anos, o balanço anual das emissões compreende as fontes agrícolas e o consumo de gasolina relacionadas com as principais fases de produção agrícola, e o potencial de acúmulo de C no solo e a fixação de C na biomassa em todos os cenários estudados. Menores emissões de GEE foram estimados no cenário de PRP (3.864 kg CO2eq ha-1 ano-1), porém apresenta uma menor produtividade de leite. As maiores emissões de GEE foram observadas no cenário IP (7.711 kg CO2eq ha-1 ano-1), que apresentou uma maior produtividade de leite e um potencial considerável para o acúmulo de C no solo, que poderia ajudar na compensação das emissões. No cenário SPS, que tem uma produtividade de leite próximo de IP, apresentou o maior potencial para compensar as emissões de GEE (4.878 kg CO2eq ha-1 ano-1) devido ao acúmulo de C solo e a fixação de C na biomassa em árvores
Abstract: The challenge of agricultural sector is to reduce emissions and increase food production, taking into account environmental aspects. In Andean zone of Colombia, there is a growing need to develop GHG (greenhouse gas) mitigation techniques associated to milk production. This work focuses on the GHG emissions and potential sinks associated to milk production scenarios in the Andean zone of Colombia. The scenarios considered were: conventional agriculture of Pennisetum clandestinum in rotation with potatoes (PRP), improved pastures of Lolium multiflorum (IP) and silvopastoral system of Pennisetum clandestinum in consortium with Acacia decurrens and Trifolium repens (SPS). Based on the IPCC (2006) methodologies, the annual emission balance for a 6-year production cycle included agricultural sources and gasoline consumption related to the main agricultural phases in field, and the potential for soil C accumulation and biomass C fixation in all studied scenarios. Lower GHG emissions were estimated in PRP scenario (3,864 kg CO2eq ha-1 yr-1), but this presents the lower milk productivity. The higher GHG emissions were observed in IP scenario (7,711 kg CO2eq ha-1 yr-1), which presented the highest milk productivity and a considerable potential for soil C accumulation, that could help into the offset of its emissions. But SPS scenario, which has a milk productivity close to IP, presented the highest potential to offset GHG emission (4,878 kg CO2eq ha-1 yr-1) due to soil C accumulation plus biomass C fixation in trees
Arvores.
Doutor
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Aini, Fitri Khusyu. "Forest conversion to smallholder plantations : the impacts on soil greenhouse gas emissions and termite diversity in Jambi, Sumatra." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230506.
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Ongoing conversion of forests in Sumatra to agricultural lands might affect the biodiversity of soil fauna, such as termites, and emissions of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). To assess the impact of such forest conversions, this study was conducted in Jambi, Sumatra in an undisturbed forest (FR), a disturbed forest (DF), a one year old rubber plantation (RB1), a twenty year old rubber plantation (RB20) and an oil palm plantation (OP). The plantations belonged to smallholders and were not usually fertilized. The effect of fertilizer was assessed by applying N fertilizer and taking a series of intensive measurements. The N2O, CH4 and CO2 fluxes were measured using static chamber methods and termite species richness was assessed using a standard semi quantitative transect method. Forest conversion to smallholder plantations did not significantly affect the N2O, CH4 and CO2 fluxes, but the diversity and relative abundance of termites was decreased. this implies that the ecosystem services regulated by termites might decline. The application of N fertilizer at the conventional rate (141 kg N ha-1 y-1), with an emission factor of 3.1 % in the oil palm plantation, increased N2O emissions to twice as high as that in the undisturbed forest. The annual N2O and CH4 fluxes from termites amounted to 0.14, 0.21, 0.88, 2.47 and -0.56 kg ha-1 y-1 N2O-N and 0.85, 1.65, 3.80, 0.97 and 2.30 kg ha-1 y-1 CH4-C in the FR, DF, RB1, RB20 and OP, respectively. Further research is needed to understand the interannual variability of the N2O, CH4 and CO2 fluxes from soils and termites. Understanding the key drivers and underlying processes which regulate them would help to control the biodiversity loss and the change of N2O, CH4 and CO2 fluxes from soils and termites.
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Wilson, Sean M. W. "Adsorption Separation of CO2 from CO in Syngas: Improving the Conversion of the Reverse Water Gas Shift Reaction." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33169.
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In this research project, adsorption is considered for the separation of CO2 from CO for applications such as industrial syngas production and in particular to improve the conversion of the Reverse Water Gas Shift (RWGS) process. The use of adsorption technology for these applications requires an adsorbent that can effectively separate out CO2 from a gas mixture containing CO2, CO, and H2. However, adsorption of H2 is insignificant when compared to both CO2 and CO, with only CO2 and CO being the adsorbed species. The adsorption of CO2 and CO was investigated in this work for four major types of industrial adsorbents which include: activated aluminas, activated carbons, silica gels, and zeolites. Zeolites, with their ability to be fine tuned many parameters which may affect adsorption, were investigated in terms of the effect of the cations present, SiO2/Al2O3 ratios, and structure to determine how to optimize adsorption of CO2 while decreasing adsorption of CO. This will help to determine a promising adsorbent for this separation with focus on maximizing the selective adsorption of CO2 over CO.
To investigate this separation three scientific experimental methods were used; gravimetric adsorption isotherm analysis, volumetric adsorption isotherm analysis, and packed bed adsorption desorption breakthrough analysis. Gravimetric and volumetric methods allow for testing the adsorbent with the individual species of CO2 and CO. This investigation will let us determine the pure component adsorption capacity, heats of adsorption, regenerability, and basic selectivity. Packed bed adsorption breakthrough experimentation was then carried out on promising adsorbents for the CO2 separation from a mixture of CO2, CO, and H2. These experiments used a gas mixture that would be comparable to that produced from the RWGS reaction to determine the multicomponent gas mixture behaviour for adsorption. Temperature swing adsorption (TSA) with a purge gas stream of H2 was then used to regenerate the adsorbent.
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El-Hasan, Tareq Sadeq Fawzi. "Design of a permanent magnet axial flux high-speed generator." Thesis, University of Hertfordshire, 2002. http://hdl.handle.net/2299/14045.
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Electrical generating sets powered by gas turbines are required for many applications, in particular for emergency situations due to their critical attributes; high reliability, lightweight, small size, multi-fuel capabilities, low maintenance, low noise and low gas emissions. This research contends that a permanent magnet axial flux (PMAF) high-speed generator with a small gas turbine engine offers advantages over the radial flux permanent magnet generators. Higher power densities can be achieved with the axial flux configuration when compared to their counter parts of the radial flux machines of similar output power. The attributes of the PMAF machines were certainly appealing; lightweight, small size, high efficiency and ease of construction. In this research, a design approach for the PMAF high-speed generator which accounts for the mechanical and electrical aspects was provided. The machine's key components such as retainment ring was carefully designed and the materials utilised in their structures were appropriately selected to insure high mechanical integrity, ease of construction and low manufacturing cost. The generator's principle dimensions were determined from a theoretical model which was derived from the machine's main design parameters. This theoretical model was then correlated by some empirical coefficients determined through the manipulation of the experimentally validated finite element (FE) results. The analytical results have shown that with the appropriate design considerations, PMAF high-speed generators can be designed with high power densities in the range of 6-8 kW/kg and high efficiencies ideally in the range of 94 - 96 %. The mechanical integrity and the steady state electrical performance of the machine were analysed using three-dimensional (3D) FE models. More in this research, a parametric study was carried out on the most influential parameters of the machine to improve its electrical performance through minimise rotor and stator eddy current losses. In addition, the total harmonic distortion in the output waveform was minimised through the appropriate and careful design of the magnet shape and topology with the aid of 3D electromagnetic FE analysis. Furthermore, using FE it was possible to design, optimise and analyse the rotor back-iron disc through the selection of best material, shape and size for use in the PMAF high-speed generator. A prototype of the PMAF high-speed generator was constructed and tested preliminary at low speed for the purpose of the evaluation of the electrical performance of the machine. Experimental results have shown that the machine was capable to meet the design requirements. For the mechanical integrity of the machine, the rotors were safely tested on a cold run test rig at the speed of 47,000 rpm. This thesis describes also the trends and the technical details in the manufacturing, construction and experimental setup for the PMAF high-speed generator.
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Wei, Bo. "A novel solar-driven system for two-step conversion of CO2 with ceria-based catalysts." Doctoral thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-152899.
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Global warming is an unequivocal fact proved by the persistent rise of the average temperature of the earth. IPCC reported that scientists were more than 90 % certain that most of the global warming was caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. One alternative to combat the GHG is to explore technologies for utilizing CO2 already generated by current energy systems and develop methods to convert CO2 into useful combustible gases. Two-step conversion of CO2 with catalysts is one of the most promising methods. Ceria (CeO2) is chosen as the main catalyst for this conversion in the thesis. It releases O2 when it is reduced in a heating process, and then absorbs O2 from CO2 to produce CO when it is re-oxidized in a cooling process. To make the conversion economic, solar power is employed to drive the conversion system. In this thesis, a flexible system with fluidized bed reactors (FBRs) is introduced. The thermogravimetric analysis (TGA) was carried out to examine the performance of ceria during its reduction and oxidation. Subsequently, the exergy analysis was used to evaluate the system’s capability on exporting work. The theoretical fuel to chemical efficiency varied from 4.85 % to 43.2 % for CO2 conversions. To investigate the operation mechanism of the system, a mathematical model was built up for the dynamic simulation of the system. Variables such as temperatures and efficiencies were calculated and recorded for different cases. The optimum working condition was found out to be at 1300 ⁰C for the commercial type of ceria. Finally, an experimental system was set up. The hydrodynamics and heat transfer in the fluidized bed reactor were studied. A CFD model was built up and validated with the experimental trials around 120 ⁰C. The model was then used as a reliable tool for the optimization of the reactor. The entire work in the thesis follows the procedure of developing an engineering system. It forms a solid basis for further improvements of the system to recycle CO2.QC 20141006
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Remaci, Ahmed. "Étude et mise en place d’une méthodologie pour la conduite de systèmes distribués de type micro-réseaux : application à de nouvelles architectures de conversion et de stockage d’énergie du type Power-To-Gas." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0102.
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Nos travaux s’inscrivent dans le contexte global de la transition énergétique et de l’émergence des micro-réseaux, et de leur capacité, à terme, d’intégrer la production distribuée d’énergie tout en assurant la stabilité et la qualité du service. Parmi les technologies émergentes, les procédés Power-To-Gaz et en particulier le Power-to-Methane que nous étudions ici (production de CH4 à partir de l’électricité, en passant par H2 et CO2) ont l’avantage : d’absorber le surplus de production électrique, de récupérer et valoriser les émissions de CO2, et d’offrir des capacités de stockage importantes et de longue durée.Notre problématique porte sur la modélisation et la simulation d’un système PtM avec comme objectif d’assurer la continuité d’alimentation en CH4, ainsi que la sécurité du système en fonctionnement.Dans un premier temps nous effectuons le choix de technologies adaptées afin de déterminer la structure d’un système PtM avant de dimensionner ce système. Nous nous appuyons sur la modélisation REM (Représentation Energétique Macroscopique) pour intégrer les comportements physiques des équipements du système en régime stationnaire, mais également en régime transitoire, en prenant en compte des phases comme : le démarrage, le préchauffage…, et ainsi simuler le fonctionnement de ce système.Dans un second temps, nous développons une stratégie de gestion d’énergie multiniveaux afin de garantir le bon fonctionnement des équipements et du système dans sa globalité. Nous choisissons de la mettre en œuvre à travers la proposition d’un système multi-agents (SMA) et nous modélisons chacun des agents. Nous implémentons partiellement ce SMA et nous le simulons en connexion avec le modèle REM du système PtM pour montrer la faisabilité de notre approcheOur work is concerned with energy transition and the emergence of micro-grids and their ability to integrate distributed power generation while at the same time ensure stability and service quality. Among the emerging technologies, the Power to Gas process and in particular the Power to Methane process which we are addressing here (production of CH4 from electricity, via H2 and CO2), have the advantage of absorbing surplus of electricity production, recovering CO2 emissions, as well as offering significant and long-term storage capacity.Our concern was in relation to the modeling and simulation of a PtM system with the objective of ensuring the continuity of CH4 supply and ensuring the safety of the system in operation.First, we chose the appropriate technologies to determine the structure of a PtM system before sizing this system. We utilised the REM modeling (Energetic Macroscopic Representation) to integrate the physical behaviors of the equipment of the system in a steady state, and in a transient state, taking into account phases like starting, preheating…, and ultimately the simulation of the operation system.In the second phase, we developed a multilevel energy management strategy to ensure the proper working order of each piece of equipment and of the global system. We chose to implement it through a multi-agent system (MAS) and we modeled each one of the agents. We partially implemented the MAS and simulated it with the REM model of the PtM system to show the feasibility of our approach
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Hare, Bryan J. "Supported Perovskite-type Oxides: Establishing a Foundation for CO2 Conversion through Reverse Water-gas Shift Chemical Looping." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7628.
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Perovskite-type oxides show irrefutable potential for feasible thermochemical solar-driven CO2 conversion. These materials exhibit the exact characteristics required by the low temperature reverse water-gas shift chemical looping process. These properties include structural endurance and high oxygen redox capacity, which results in the formation of numerous oxygen vacancies, or active sites for CO2 conversion. A major drawback is the decrease in oxygen self-diffusion with increasing perovskite particle size. In this study, the La0.75Sr0.25FeO3 (LSF) perovskite oxide was combined with various supports including popular redox materials CeO2 and ZrO2 along with more abundant alternatives such as Al2O3, SiO2, and TiO2, in view of its potential application at industrial scale. Supporting LSF on SiO2 by 25% mass resulted in the largest increase of 150% in CO yields after reduction at 600 °C. This result was a repercussion of significantly reduced perovskite particle size confirmed by SEM/TEM imaging and Scherrer analyses of XRD patterns. Minor secondary phases were observed during the solid-state reactions at the interface of SiO2 and TiO2. Density functional theory-based calculations, coupled with experiments, revealed oxygen vacancy formation only on the perovskite phase at these low temperatures of 600 °C. The role of each metal oxide support towards suppressing or enhancing the CO2 conversion has been elucidated. Through utilization of SiO2, the reverse water-gas shift chemical looping process using perovskite-based composites was significantly improved.
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Wijewardane, Samantha. "Assessment of Methods to Manipulate Thermal Emission and Evaluate the Quality of Thermal Radiation for Direct Energy Conversion." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4420.
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ABSTRACT
Control of spectral thermal emission from surfaces may be desirable in some energy related applications, such as nano-scale antenna energy conversion and thermophotovoltaic conversion. There are a number of methods, from commercially available paints to advanced surface gratings that can be used to modify the thermal emission from a surface. To find out the proper emission controlling technique for a given energy conversion method all the surface emission controlling methods are comprehensively reviewed regarding the emission control capabilities and the range of possible applications. Radiation with high degree of coherence can be emitted using advanced surface emission controlling techniques. The entropy of the thermal radiation, and therefore the exergy, is a function of the degree of coherence. A methodology is presented to calculate the exergy of partially coherent wave fields so that the radiation fields can be evaluated based on exergy. This exergy method is extended to develop a rigorous evaluation criterion for thermal emission controlling methods used in frequency dependent energy conversion applications. To demonstrate these developed criteria using actual data, a surface plasmon emitter is designed and fabricated. Also, possible ways of improving the emitter performance and the research needed to be carryout to fabricate cost effective emitters are described.
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Davis, Stanley Casey. "Stress and microstructural evolution during shape-preserving silica magnesiothermic reduction." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/51760.
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Shape-preserving silica magnesiothermic reduction is a gas-solid reaction used to convert complex, 3-dimensional SiO₂ structures into replicas composed of a two-phase product of MgO and Si. The MgO/Si components of this reaction are found to form an interwoven aggregate product structure, which is suitably robust that the MgO phase can be selectively dissolved to yield porous Si. Here, the kinetics and mechanisms of growth of this robust product structure have been studied. The aggregate product structure was deduced to result because stacked layers of MgO/Si product phases with planar interfaces are geometrically unstable, owing to the growth kinetics of the products. The interwoven nature of the aggregate may be explained by the presence of an amorphous magnesium silicate phase ahead of the MgO/Si product during reaction. Complex composition gradients in the magnesium silicate can lead to tortuous and branching growth of MgO and Si phases as the magnesium silicate is consumed by reaction. In addition, a large residual stress (> 5 GPa) was measured in the MgO/Si product layer formed during reaction of planar quartz. Despite the presence of such a large stress, no distortion or cracking of reacted structures was found to occur after reaction in the temperature range 650-900 °C. XRD-based residual stress measurements and morphological observations of product films on reacted quartz substrates were used to evaluate possible mechanisms of stress relief in the structure. It was found that the migration of MgO to the external surface of the product layer could be correlated to the rate of stress relaxation that occurred in annealed product films. Finally, applications of silica magnesiothermic reduction and derivative processes were studied in the fields of chemical catalysis and optical chemical sensing.