Dissertationen zum Thema „Solid alternative fuels“

The growing municipal solid waste generation rates have necessitated more efficient, optimized waste collection facilities. The majority of the US collection fleet is composed of diesel-fueled vehicles which contribute significant atmospheric emissions including greenhouse gases. In order to reduce emissions to the atmosphere, more collection agencies are investigating alternative fuel technologies such as natural gas, biofuels (bio-gas and bio-diesel), and hybrid electric technology. This research is an in-depth environmental analysis of potential alternative fuel technologies for waste collection vehicles. This study will evaluate the use of alternative fuels by waste collection vehicles. Life-cycle emissions, cost, fuel and energy consumption were evaluated for a wide range of fossil and bio-fuel technologies. Moreover, the energy consumption and the tail-pipe emissions of diesel-fueled waste collection vehicles were estimated using MOVES 2010a software. Emission factors were calculated for a typical waste collection driving cycle as well as constant speed. Finally, the selection of fuel type by the waste collection industry requires consideration of environmental, security, financial, operational, and safety issues. In this study, a qualitative comparison between alternative fuels was performed; a multifactorial assessment of these factors was conducted taking into account the opinion of the waste collection industry of the importance of each factor. Liquid-petroleum fuels have higher life-cycle emissions compared to natural gas; however landfill natural gas has the lowest life-cycle emissions compared to all other fuel categories. Compressed natural gas waste collection vehicles have the lowest fuel cost per collection vehicle mile travel compared to other fuel categories. Moreover, the actual driving cycle of waste collection vehicles consists of repetitive stops and starts during waste collection; this generates more emissions than constant speed driving. Finally, the multifactorial assessment indicates that natural gas and landfill gas have better environmental, economical, and energy security performance than current liquid-petroleum fuels.
ID: 030646260; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.Env.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 72-77).
M.S.Env.E.
Masters
Civil, Environmental and Construction Engineering
Engineering and Computer Science
Environmental Engineering

Incineration is an attractive solution to the problems of disposing of municipal solid wastes and supplying energy. Because up to 25 percent of the waste in refuse-derived-fuel systems is ash, the physical and chemical characteristics of ash become more and more important for its potential impacts and methods suitable for their disposal. Trace elements concentration in ash is of great interest because of its relationship to regulatory criteria under the Resource Conservation and Recovery Act (RCRA) regarding toxicity and hazards. The applications of a microwave oven sample dissolution method has been tested on a variety of standard reference materials, with reproducible and accurate results. Fourteen trace elements, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, V, and Zn, from the dissolved ash samples were determined by inductively coupled plasma atomic emission spectrometry.

This diploma thesis deals with the operational and economic assessment of the installation of new TG3 turbines in the Přerov Heating Plant. The beginning of this thesis deals with a brief theoretical introduction of this investment and describes the classical economic evaluation methods and the Monte Carlo method. Subsequently, the investment project was analyzed and inputs for the economic model were created. The economic model was then evaluated using classical methods and Monte Carlo methods, the results are then compared with each other. Based on the results of the economic evaluation, the most efficient variant of the Přerov Heating Plant technology was chosen.

This thesis explores the development of efficient engineered composite alternative anodes and the use of ethanol as a fuel for Solid Oxide Fuel Cells. SOFCs can in theory operate with fuels other than hydrogen. However, this requires the design of efficient alternative anode material that do not catalyze carbon formation and that are tolerant to redox cycles. An innovative concept has been developed that relies on the impregnation of perovskites into porous YSZ structures to form the anode functional layer. Catalysts are added to provide sufficient catalytic activity. Cells with anodes containing LSCM and Ce/Pd have displayed excellent performance. At 800°C, and with a 65 μm thick electrolyte, the power outputs were above 1W/cm² in humidified hydrogen and 0.7 W/cm² in humidified methane. These electrodes have shown the ability to reduce CO₂ electrochemically with an efficiency that is similar to that which can be achieved for H₂O electrolysis and the anodes could operate on pure CO₂. The importance of incorporating an efficient catalyst was demonstrated. The use of 0.5 wt% of Pd is sufficient to dramatically improve the performance in such electrodes. The microstructure of impregnated LSCM-YSZ composites plays an important role in the high performance obtained. A layer of LSCM nanoparticles covering the YSZ is formed upon reduction, offering a great surface area for electrochemical reactions. The fabrication method presented in this thesis is a powerful tool for designing microstructures in situ. Among the various fuels under consideration for SOFCs, ethanol offers outstanding advantages. Half cell measurements have been performed to characterize the performance of different types of anodes when operated on ethanol/steam mixtures. Steady performance was achieved on LSCM-CGO anodes. Carbon deposits from gas phase reactions have been evidenced and were found to be responsible for the performance enhancement when the cell is operated in diluted ethanol as compared to hydrogen. At high steam content, polarization resistances of LSCM-CGO-YSZ anodes in ethanol/ steam mixtures were shown to be below 0.3 Ω.cm² at 950°C.

A team at the University of Colorado at Boulder is working with the Bill & Melinda Gates Foundation to develop a novel technical solution for 2.5 billion people in the developing world with no access to basic sanitation. The university's Sol-Char toilet uses concentrated sunlight to convert human fecal sludge into biochar, which has potential as a value-added product. The feasibility of using feces-derived biochar as a solid fuel for heating and cooking is assessed, considering energy content and elemental analysis of biochars made under different reactor conditions, ease of briquetting, and durability of biochar briquettes. Fecal biochars made at 300°C were similar in energy content to wood biochars and bituminous coal, possessing a higher heating value of 25.6 MJ/kg, while fecal chars made at 750°C were significantly lower in energy content at 13.8 MJ/kg. Chars derived from simulant feces favored by other Bill & Melinda Gates Foundation sanitation research projects were found to differ significantly from fecal char in their energy content and briquetting characteristics. A frequently used correlation between elemental composition of chars and their higher heating values was adapted to be more applicable to feces-derived chars based on a review of fecal char literature and experimental results. Fecal chars made at low temperatures and briquetted with molasses and lime binders yielded briquettes of comparable strength and energy content to commercial charcoal briquettes, suggesting that briquettes made from human feces could be a significant contribution to the sanitation value chain.

The research presented in this thesis is a collection of many different, yet connected, parts that stemmed from the development of a new alternative material intended to be utilised as anode material in solid oxide fuel cells. The main part is the research conducted in the development and characterisation of the novel A-site deficient La₀.2₂Sr₀.₇₋ₓCaₓTiO₃. Calcium introduction resulted in reducing this perovskite unit cell volume which, at the beginning, enhanced its electrical conductivity in reducing conditions. However, the ideal cubic symmetry coud not be maintained, as in the starting material LA₀.₂Sr₀.₇TiO₃, as a result of the increased A-site ionic radius mismatch and two lower symmetries were observed at room temperature. These were the tetragonal I4/mcm for 0.1 ≤ x ≤ 0.35 and orthorhombic Pbnm for 0.4 ≤ x ≤ 0.7. Higher temperature NPD data showed that the orthorhombic samples transformed into higher symmetries with Pbnm → I4/mcm → Pm3-m phase transitions. Detailed crystallographic analysis is discussed; where the different unit cells showed changes to the tilts of the BO₆ octahedra, along with distortions to these octahedra. DC conductivity measurements showed a high electrical conductivity of 27.5 S/cm for a pre-reduced composition La₀.₂Sr₀.₂₅Ca₀.₄₅TiO₃ at 900°C and pO₂ = 10⁻¹⁹ atm. This material showed very encouraging features; which makes it a very promising anode material for SOFCs. A study was also done which explores the best renewable energy options for the United Arab Emirates given its local climate and other aspects. The reliance on seawater desalination is argued to by unsustainable for different reasons. Thus, water security should be a main element in the planning process for adopting renewable energy technologies. A system that combines different technologies; with a focus on fuel cells technology; is outlined which is thought of to be a very promising basis for a broader system that will secure power and water in a very environment friendly way. Different compositions of the system La₀.₂Sr₀.₇₋ₓCaₓTiO₃ were also studied using AC impedance spectroscopy in order to establish whether or not this system can show a ferroelectric behaviour. Results showed a variation in the dielectric constant of different samples with temperature; however, no Curie point was observed. Nonetheless, the results did show that the different compositions were very homogeneous when fully oxygenated and there were some indications of possible symmetry changes at sub-ambient temperatures. The final part of this thesis outlined the work done towards the development of a new analytical instrument. An existing TGA instrument was altered in order to provide a simultaneous thermogravimetric analysis and DC conductivity measurement for solid solutions at controlled temperature and oxygen partial pressure. Results were obtained for different samples of the system La₀.₂Sr₀.₇₋ₓCaₓTiO₃ which showed a great dependence of the electrical conductivity on the oxygen stoichiometry in these oxides. Also, a direct method is possible with this instrument to estimate the oxygen chemical diffusion coefficient using the electrical conductivity relaxation method. This new setup will be very useful for different electrochemical and thermal studies which can broaden the understanding of the different mechanisms that affect the performance of different solid state materials.

There are 150 million tons of Municipal Solid Waste (MSW) annually produced in the United States, which is approximately equivalent to 150 million barrels of oil. MSW production is inexhaustible, and is increasing on an annual per capita basis of approximately three per cent. After controlling the moisture and adding a binder, the combustible portion of MSW was converted to pellets. The objects of this project were to 1) evaluate the binder, 2) prepare the pellets, and 3) evaluate the pellets with regard to density. The manufacture of pellets was conducted at the Naval Air Station, Jacksonville, Florida. The evaluation of the binders and the pellets was done at North Texas State University (NTSU). There were three procedures for measuring the density. The first, using water displacement, was from the American Society for Testing and Material (ASTM). The second, using wax coating, was also from ASTM. The third, using sharply-cut cylindrical pellets, was developed at NTSU.

The United States leads the world in per capita production of Municipal Solid Waste (MSW), generating approximately 200 million tons per year. By 2000 A.D. the US EPA predicts a 20% rise in these numbers. Currently the major strategies of MSW disposal are (i) landfill and (ii) incineration. The amount of landfill space in the US is on a rapid decline. There are -10,000 landfill sites in the country, of which only 65-70% are still in use. The Office of Technology Assessment (OTA) predicts an 80% landfill closure rate in the next 20 years. The development of a viable energy resource from MSW, in the form of densified Refuse Derived Fuel (dRDF), provides solutions to the problems of MSW generation and fossil fuel depletions. Every 2 tons of MSW yields approximately 1 ton of dRDF. Each ton of dRDF has an energy equivalent of more than two barrels of oil. At current production rates the US is "throwing away" over 200,000,000 barrels of oil a year. In order to be considered a truly viable product dRDF must be extensively studied; in terms of it's cost of production, it's combustion properties, and it's potential for environmental pollution. In 1987 a research team from the University of North Texas, in conjunction with the US DOE and Argonne National Laboratory (ANL), cofired over 550 tons of dRDF and bdRDF with a high sulfur Kentucky coal in a boiler at ANL. This work examines the emission rates of polychlorinated dioxins (PCDDs) and furans (PCDFs) during the combustion of the dRDF, bdRDF, and coal. Even at levels of 50% by Btu content of dRDF in the fuel feedstock, emission rates of PCDDs and PCDFs were below detection limits. The dRDF is shown to be an environmentally acceptable product, which could help resolve one of the major social and environmental problems facing this country today.

This report travels through multiple disciplines to seek innovative and sustainable energy solutions for wastewater treatment plants. The first subject is a report about increased global temperatures and an over-exploitation of natural resources that threatens ecosystems worldwide. The situation is urgent where the current trend is a 2°C increase of global temperatures already in 2040. Furthermore, the energy-land nexus becomes increasingly apparent where the world is going from a dependence on easily accessible fossil resources to renewables limited by land allocation. A direction of the required transition is suggested where all actors of the society must contribute to quickly construct a new carbon-neutral resource and energy system. Wastewater treatment is as required today as it is in the future, but it may move towards a more emphasized role where resource management and energy recovery will be increasingly important. This report is a master’s thesis in energy engineering with an ambition to provide some clues, with a focus on energy, to how wastewater treatment plants can be successfully integrated within the future society. A background check is conducted in the cross section between science, society, politics and wastewater treatment. Above this, a layer of technological insights is applied, from where accessible energy pathways can be identified and evaluated. A not so distant step for wastewater treatment plants would be to absorb surplus renewable electricity and store it in chemical storage mediums, since biogas is already commonly produced and many times also refined to vehicle fuel. Such extra steps could be excellent ways of improving the integration of wastewater treatment plants into the society. New and innovative electric grid-connected energy storage technologies are required when large synchronous electric generators are being replaced by ‘smaller’ wind turbines and solar cells which are intermittent (variable) by nature. A transition of the society requires energy storages, balancing of electric grids, waste-resource utilization, energy efficiency measures etcetera… This interdisciplinary approach aims to identify relevant energy technologies for wastewater treatment plants that could represent decisive steps towards sustainability.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
This study aimed to investigate different types of materials for the production of compressed biofuel. The selected materials were: tree pruning waste, corrugated cardboard, cartons and sludge of water treatment obtained by flotation technique; these materials were chosen because of its abundance in the urban environment, the ease of finding them in urban areas and also the few studies related to them. The studywas divided into three chapters: in chapter I, was determinedthe physical, chemical and thermal characteristics of the residuesto give support for the subsequent chapters. In chapter II briquettes composed of mixtures of these residues were produced, using the urban pruning residues as the basis for the different blends, mainly because of its lignocellulosic composition; chemical and physical analysis were also made in the briquettes to analyze if the compactation process of the mixtures was effective and if the final product has favorable characteristics for energy use. In chapter III was described the production and evaluation of pellets composed by municipal solid waste, and similarly, we used the urban pruning residues as the main material for the blends with the other materials. After all analysis, it was observed that the urban pruning residues, the corrugated cardboard andthe aseptic cartons showed positivecharacteristics for use as biofuel, but the flotation sludge showed aninorganic character, presenting a low calorific value and high ash content. Nevertheless, the sludge was used for the production of briquettes and pellets in order to evaluate possible mixtures to minimize those problems. Even for the briquettes or for the pellets it was observed that the addition of sludge in the composition provided increases in the strength and density, but reduced the calorific value and increased the ash content. The incorporation of cardboard or carton caused an increase in density and strength and a small reduction in calorific value. It could be concluded that the municipal solid residues used in this researchhad characteristic to use them to produce compressed fuelsas asustainable alternative for energy production. Regards about the mixing ratios of the residues should be taken to optimize the overall process.
Este estudo teve por objetivo pesquisardiversos tipos deresíduos sólidos urbanos para a produção de combustíveis compactados. Foram selecionados resíduos de poda de árvores, papelão ondulado, embalagens cartonadas e lodo de tratamento de águas pela técnica de flotação. Optou-se por estes materiais devido a sua representatividade no ambiente urbano, pela facilidade em encontra-los e também por haver poucos estudos relacionados a eles. O trabalho foi dividido em três etapas, inicialmente, foram determinadas as características físicas, químicas e térmicas dos resíduos como forma de embasamento para os próximos capítulos. Na sequencia foram produzidos briquetes compostos por diferentes proporções destes resíduos, usando como base para as misturas os resíduos de podade árvores devido sua composição lignocelulósica; também foram feitas análises químicas e físicas nos briquetes para avaliar se o processo de compactação das misturas foi eficiente e se o produto final apresentou características energéticas favoráveis ao uso. Finalmente, avaliou-sea produção de pellets produzidos com os resíduos sólidos urbanos, e da mesma forma, utilizaram-se os resíduos de poda urbana como base para as misturas com os outros materiais. Após as análises observou- se que, os resíduos de poda urbana, papelão ondulado e embalagens cartonadas apresentaram características favoráveis para o uso como biocombustível, porém o lodo de flotação apresentou caráter inorgânico, com baixo poder calorífico e alto teor de cinzas. Apesar disso, o lodo foi utilizado para a produção dos briquetes e pellets com o intuito de avaliar possíveis misturas que minimizem estes problemas. Tanto para os briquetes quanto para os pellets, observou-se que a adição de lodo na composição destes materiais proporcionou incrementos na resistência e densidade, porém reduziu o poder calorífico a aumentou o teor de cinzas. A incorporação de papelão ou embalagens cartonadas ocasionou aumento na densidade e na resistência e uma pequena redução no poder calorífico. Conclui-se que os resíduos sólidos urbanos utilizados neste estudo apresentaram potencial para produção de combustíveis compactados, tornando-se uma alternativa sustentável para produção de energia, desde que otimizadas as proporções das misturas de materiais.

A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, modifying metal additives, tailoring the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been used to increase the burning rate by increasing the surface area; however, the manufacture of propellant grains and the observation of geometric effects with reactive components has been restricted by traditional manufacturing and viewing methods. In this work, a printable reactive filament was developed that is tailorable to a number of use cases spanning reactive fibers to photosensitive igniters. The filament employs aluminum fuel within a printable polyvinylidene fluoride matrix that can be tailored to a desired burning rate through stoichiometry or aluminum fuel configuration such as particle size and modified aluminum composites. The material is printable with fused filament fabrication, enabling access to more complex geometries such as spirals and branches that are inaccessible to traditionally cast reactive materials. However, additively manufacturing the reactive fluoropolymer and propellant together comes attendant with many challenges given the significantly different physical properties, particularly regarding adhesion. To circumvent the challenges posed by multiple printing techniques required for such dissimilar materials, the reactive fluoropolymer was included within a solid propellant carrier matrix as small fibers. The fibers were varied in aspect ratio (AR) and orientation, with aspect ratios greater than one exhibiting a self-alignment behavior in concordance with the prescribed extrusion direction. The effective burning rate of the propellant was improved nearly twofold with 10 wt.% reactive fibers with an AR of 7 and vertical orientation.

The reactive wires and fibers in propellant proved difficult to image in realistic sample designs, given that traditional visible imaging techniques restrict the location and dimensions of the reactive wire due to the necessity of an intrusive window next to the wire, a single-view dynamic X-ray imaging technique was employed to analyze the evolution of the internal burning profile of propellant cast with embedded additively manufacture reactive components. To image complex branching geometries and propellant with multiple reactive components stacked within the same line of sight, the dynamic X-ray imaging technique was expanded to two views. Topographic reconstructions of propellants with multiple reactive fibers showed the evolution of the burning surface enhanced by the geometric effects caused by the faster burning fibers. These dual-view reconstructions provide a method for accurate quantitative analysis of volumetric burning rates that can improve the accessibility and viability of novel propellant grain designs.