• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 48
  • 20
  • 15
  • 7
  • 3
  • 1
  • 1
  • Tagged with
  • 108
  • 108
  • 28
  • 25
  • 24
  • 21
  • 20
  • 17
  • 17
  • 16
  • 14
  • 14
  • 13
  • 13
  • 12
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Hydrogen Production By Anaerobic Fermentation Using Agricultural and Food Processing Wastes Utilizing a Two-Stage Digestion System

Thompson, Reese S 01 December 2008 (has links)
Hydrogen production by means of anaerobic fermentation was researched utilizing three different substrates. Synthetic wastewater, dairy manure, and cheese whey were combined together at different concentrations under batch anaerobic conditions to determine the optimal hydrogen producing potential and waste treatment of each. Cheese whey at a concentration of 55% was combined with dairy manure at a concentration of 45% to produce 1.53 liters of hydrogen per liter of substrate. These results are significant because the control, synthetic wastewater, which was a glucose-based substrate, produced less hydrogen, 1.34 liters per liter of substrate, than the mixture of cheese whey and dairy manure. These findings indicate that cheese whey and dairy manure, which are of little value, have potential to produce clean combusting hydrogen fuel. The effluent from the anaerobic hydrogen fermentations was then placed into a second continuous-fed reactor as part of a two-phase anaerobic digestion system. This system was designed to produce hydrogen and methane for a mixture of approximately 10% hydrogen. The two-stage process also further treated the synthetic wastewater, dairy manure, and cheese whey. The two-phase anaerobic methanogenic reactor was shown to produce more methane in the second phase (56 L IBR anaerobic digester), 1.36 mL per minute per liter substrate, as compared to the single-phase anaerobic reactor (56 L IBR), which produced 1.22 mL per minute per liter substrate. In general, this research has suggested that agricultural and food processing wastes provide the needed nutrients for hydrogen production and that a two-phase anaerobic digestion system is ideally set up to produce hydrogen-methane mixtures while treating wastes for discharge into the environment.
52

Effect of Alternative Fuels on SCR Chemistry / Inverkanav alternative bränslen på SCR-kemin

Faramarzi, Simin January 2012 (has links)
In the time line of world industrial age, the most important era begins in the late 18th century when the use of fossil fuels was growing intensively. This approach has continued and developed up to the 20th century. Besides, this trend has had side effects like polluting environment. Air pollution is one of the critical issues nowadays that stems from using hydrocarbon fuels. One type of the problematic compounds in polluting air is nitrogen oxides that can be produced in combustion process from engines and industrial plants. Different solutions have been suggested to remove air polluting compounds. One method for removing nitrogen oxides is using the mechanism of Selective Catalytic Reduction in silencer of engines. This method has become practical in trucks’ engines. Therefore, research on SCR chemistry is important for improving the usage of this method in removing nitrogen oxides. SCR has its own problems when used in trucks. One of the problems is formation of white clumps on pipe wall of silencers using SCR which can cause back pressure in the engines and costs a lot to remove them from engines.  This report evaluates the effect of alternative fuels on SCR chemistry .Different parameters affecting deposit formation are studied and evaluated. Ethanol is one of the controversial fuels used in engines and acetic acid is one its byproducts. Also, urea and its by products are important materials in SCR chemistry, too. Consequently, the first part of the report studies the influence of acetic acid and Ferrite steel, one of the usual steels in silencers of engines, on urea, biuret and cyanuric acid decomposition. The instruments used in the first part include TGA-DSC (Thermo Gravimetric Analysis-Differential Scanning Calorimetric) which is connected to FTIR (Fourier Transform Infrared Spectroscopy).In the second part of the report, the effect of diesel exhaust and ethanol exhaust on cyanuric acid evaporation rate is evaluated. Cyanuric acid is the main compound forming deposit in silencers. The instrument used in the second part is TGA. The third part consists surveying effect of Adblue, aqueous solution of urea, and additivised Adblue, surfactant added Adblue to improve its efficiency, in a patented rig that is scaled down of a silencer of truck. The most important result for the first part includes the effect of Ferrite steel treated with acetic acid that accelerated the decomposition of cyanuric acid. This result can be investigated more in order to be used in silencers to accelerate the decomposition rate of clumps formed. In the second part, it is found out that cyanuric acid evaporates faster under ethanol exhaust than diesel exhaust. The third part’s results shows that in the current assembly of pipes in the rig, Additivised Adblue loses its improved efficiency which is an interesting result for engine welding in order to avoid this type of connection in engines.
53

Flame Studies on Conventional, Alternative, and Surrogate Jet Fuels, and Their Reference Hydrocarbons

Hui, Xin 08 March 2013 (has links)
No description available.
54

Characterization of Biodiesel Blends Effects on Aftertreatment Systems and Aftertreatment-based Blend Level Estimation

Ibrahim, Umar 08 June 2016 (has links)
No description available.
55

The effect of compression ratio on emissions from an alcohol-fueled engine

Cambridge, Shevonn Nathaniel 12 September 2009 (has links)
The motivation for this work stems from the enacting of stricter emissions requirements for the mid 1990's by the California Air Resources Board. It is foreseen that these requirements will favor the use of alcohol fuels in quantities comparable to the present usage of gasoline and diesel in order to reduce emissions of carbon monoxides (CO) and nitrogen oxides (NOx). The use of alcohol fuels at this level will substantially increase the amount of aldehyde emissions. This poses a problem in that aldehydes are odorants, components of photochemical smog, and volatile aldehydes are eye and respiratory tract irritants; therefore, it is only a matter of time before they too are strictly regulated. This thesis focuses on a systematic analysis of aldehyde emissions from alcohol fuels with respect to compression ratio. Compression ratio has been selected as the primary variable for this study, because alcohol-fueled vehicles are usually modified to have higher compression ratios than their gasoline-fueled counterparts in order to take advantage of alcohols' higher octane rating. The investigation is being conducted using a single-cylinder variable-compression ratio Waukesha-CFR engine. The aldehyde emissions are measured for various fuel alcohol percentages at different compression ratios and MBT timing. The effects on conventional vehicle emissions (Le. NOx, CO, unburned hydrocarbons) are also being measured so that tradeoffs between conventional emissions and aldehyde emissions can be determined. The goal of this research was to locate any trends between alcohol fuels and compression ratios which will allow for an optimization of these parameters to minimize aldehyde emissions. It was desired that this be achieved without sacrificing engine performance or increasing other regulated emissions. The variance of compression ratio was found to affect the pollutant formation process via its effects on temperature. The increasing expansion ratio, which accompanies increasing compression ratio, resulted in lower post .. expansion burned-gas temperatures. Temperature's influence on the rate of reactions was found to be the driving force in the formation of most of the pollutants. The experiment showed a definitive reduction in CO emissions with the use of alcohol fuels. The results also indicated an inherent tradeoff between NOx and formaldehyde emissions. / Master of Science
56

Utilização de borracha triturada de pneu como substituto do coque em um forno elétrico a arco. / Using wasted rubber tyres as a substitute of injection coke in an electric arc furnace.

Ambrosio, Douglas Ferreira 09 November 2018 (has links)
O objetivo do presente trabalho é avaliar o uso de borracha triturada de pneu como carburante substituto do coque após a fusão e durante o refino primário oxidante em um forno elétrico a arco na produção de aço 1020. Para o teste foram produzidas 40 toneladas de borracha de pneu triturado em condições granulométricas semelhantes ao coque e abastecido nos silos que alimentam injetoras que adicionaram este material durante o refino primário oxidante. No sistema existem 3 silos e 3 injetoras que são capazes de operar com vazões independentes. O silo n° 1 e o silo n° 3 foram abastecidos com borracha triturada, enquanto que o silo n° 2 foi abastecido com o coque. Testou-se durante 152 corridas situações com injeção de borracha em 4 níveis como substituto do coque: 0% de borracha (somente coque), 33% de borracha, 66% de borracha e 100% de borracha. As vazões e quantidades totais injetadas de carburante foram mantidas em relação ao processo usual. Para evitar interferências manteve-se a receita de carga fria metálica para abastecer o forno bem como os programas elétricos e químicos. Em todas as corridas testadas foram coletadas amostras do aço e da escória no momento antes do vazamento. As amostras foram analisadas através de um espectrômetro de RX. Os resultados obtidos mostraram que é possível a substituição total do coque pela borracha de pneu triturada sem incorrer prejuízos ao processo. Não se observou incorporação de Enxofre no aço, preocupação esta que existia pelo fato da borracha triturada conter teores mais elevados deste elemento em comparação com o coque. / The purpose of this research is to evaluate the use of grinded wasted rubber tires as a carbon source to substitute the coke during the refine in an Electric Arc Furnace to produce steel - grade 1020. For the tests, it was produced 40 tons of grinded rubber in similar size grains of the coke and the material was filled up inside the tanks that feeds the carbon injectors and added the carbon source during the primary oxidant refine. The system is composed by 3 tanks and 3 injectors that can be operate independent. The tank number 1 and number 3 were filled up with grinded rubber, and the tank number 2 was filled up with coke. It was tested during 152 heats 4 different levels of rubber injection to substitute coke: 0% of rubber, 33% of rubber, 66% of rubber and 100% rubber. The flow and injected quantities were kept in the same levels of the normal process. The metallic raw material and electrical and chemical profile were kept the same to avoid interferences. Samples of the steel and the slag were taken before the tap. The samples were analyzed in the RX Spectrometer. The results showed that is it possible to substitute completely the coke with rubber without causing any issues to process. The sulfur content in the rubber did not contaminated the steel, although the rubber contains higher sulfur compared to the coke.
57

Optimization of a Dry Low NOx Micromix Combustor for an Industrial Gas Turbine Using Hydrogen-Rich Syngas Fuel

Keinz, Jan 11 September 2018 (has links) (PDF)
Environmentally friendly and efficiently produced energy from sustainable and renewable resources is of great importance. Carbon dioxide (CO2) and nitric oxides (NOx) are the main emissions of air-breathing gas turbines in power plants. Gas turbines of the power generation industry are normally fueled with liquid fuels, natural gas or syngas in changing qualities. Syngas can be produced by gasification processes in IGCC power plants and consist of varying percentages of the main fractions hydrogen (H2) and carbon monoxide (CO). CO2 emissions can be reduced by a decrease of the CO-share and an increase of the hydrogen-share in the syngas fuel, and by using pre-combustion carbon capture and sequestration (CCS) technology. For low NOx, current gas turbine combustion chamber technologies require diluents, a rather low H2 content and modifications of the combustor hardware. A feasible solution for low NOx hydrogen and syngas combustion in gas turbines is the Micromix principle developed at Aachen University of Applied Sciences. The goal of this doctoral thesis is the research on a Micromix combustor with increased power densities fueled with hydrogen-rich syngas with about 90% by volume hydrogen, and going up to 100% hydrogen in the fuel. Test burner experiments are used to characterize the combustion and emission properties of a multitude of key drivers. Based on this optimization with a variety of scaled model test burners, a prototype dual-fuel hydrogen/syngas Micromix combustor is designed and integrated into the annular combustion chamber of an industrial gas turbine. In the gas turbine, the performance characteristics of the prototype-combustor are investigated under real operational conditions with hydrogen-rich syngas and pure hydrogen. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
58

Digestão anaeróbia de polímero orgânico a base de fécula de mandioca / Anaerobic digestion of organic polymer based on manioc starch

Cremonez, Paulo André 09 February 2015 (has links)
Made available in DSpace on 2017-07-10T15:14:33Z (GMT). No. of bitstreams: 1 DissertacaoPauloCremonez.pdf: 2171148 bytes, checksum: 995ec964a2e225fff5ce8c4199d9738e (MD5) Previous issue date: 2015-02-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The increase in the generation and accumulation of solid residues mainly compounds for packaging, led to a search for development technologies of plastics and biodegradable films eligible for treatment by conventional processes used for organic materials. Currently, various plastics, expanded polystyrene and biodegradable films are produced from the most diverse forms. The present work aims to evaluate primarily anaerobic degradation of biodegradable polymers based on manioc starch. The dissertation is divided into two chapters, the first aims at assessing the anaerobic digestion of organic polymer based on manioc starch diluted in residual water of pigs in various concentrations. Meanwhile, the second chapter aims to compare the cassava-based biodegradable polymer with other material widely studied as an additive in the biodigestion process, the glycerol. The anaerobic biodigestion process proves to be effective in the degradation and stabilization of polymeric materials based on cassava and guarantee high rates of production of biogas, rich in methane that can be used for multiple purposes, ensuring energy savings in production processes. The polymer can still be considered interesting additive on digestion processes of other agro-industrial waste aimed at quickly increased production of biogas and showing superior results to other widely used additives as glycerol. Nevertheless, for easy and quick production material degradability of volatile acids, the addition of high concentrations of polymer is not indicated by the possibility of acidification of the reactors. / O aumento na geração e acúmulo de resíduos sólidos compostos principalmente por embalagens, acarretou uma busca por tecnologias de desenvolvimento de plásticos e filmes biodegradáveis passíveis de tratamento a partir de processos convencionais utilizados para materiais orgânicos. Atualmente, diversos plásticos, poliestireno expandido e filmes biodegradáveis, são produzidos das mais diversas formas, sendo que o presente trabalho visa avaliar principalmente a degradação anaeróbia de polímeros biodegradáveis à base de fécula de mandioca. A dissertação é dividida em dois capítulos sendo que o primeiro visa avaliar a digestão anaeróbia de polímero orgânico à base de fécula de mandioca diluído em água residual de suínos em diversas concentrações. Enquanto isso, o segundo capitulo tem por finalidade comparar o polímero biodegradável à base de mandioca com outro material largamente estudado como aditivo no processo de biodigestão, o glicerol. As utilizações de processos de biodigestão anaeróbia mostram-se eficientes na degradação e estabilização de materiais poliméricos a base de mandioca e garantem elevadas taxas de produção de biogás rico em metano, podendo ser utilizado com diversas finalidades energéticas, garantindo economia em processos produtivos. O polímero ainda pode ser considerado interessante aditivo em processos de digestão de outros resíduos agroindustriais visando-se rápido aumento da produção de biogás e apresentando resultados superiores a outros aditivos largamente empregados como o glicerol. Apesar disso, pela fácil degradabilidade do material e rápida produção de ácidos voláteis, a adição de altas concentrações de polímero não é indicada pela possibilidade de acidificação dos reatores
59

A model and optimization of alternative fuel vehicle fleet composition with triple bottom line concerns

Zullo, Johnathon 06 July 2012 (has links)
Alternative fuel types and technologies are increasingly being advocated for transportation needs to ameliorate concerns around energy security, climate change, and fuel cost. Each fuel type has unique advantages and disadvantages for cost structure and emissions. Meanwhile, corporate fleet customers are often making more sustainable choices of vehicle type due to public perception and other influencing factors. The sustainability of these vehicles can be viewed from a triple bottom line perspective of financial, environmental, and societal implications. However, there is currently a lack of organized knowledge that would allow a decision-maker to elect the appropriate vehicle type beyond lifecycle cost and carbon emissions. The simplification of the impact of fuel type choice disregards issues that are emerging in prominence around water consumption and public health. Water consumption is of particular importance to investigate as fuel types that have reduced carbon emissions are often more water intensive. This thesis develops a tool that examines these issues through modeling to provide a more holistic lifecycle view of a prospective fleet's impact. The choice of vehicle type then can be optimized by utility theory preference elicitation of the different customer desires. Various scenarios of corporate preference and fleet specifications are explored to provide case studies that exemplify the complexity of the decision process. Each potential scenario has its own characteristics that cannot be optimally fulfilled by an overarching fuel type but rather should be thoroughly examined individually to understand the true consequences.
60

Routing and Scheduling of Electric and Alternative-Fuel Vehicles

January 2014 (has links)
abstract: Vehicles powered by electricity and alternative-fuels are becoming a more popular form of transportation since they have less of an environmental impact than standard gasoline vehicles. Unfortunately, their success is currently inhibited by the sparseness of locations where the vehicles can refuel as well as the fact that many of the vehicles have a range that is less than those powered by gasoline. These factors together create a "range anxiety" in drivers, which causes the drivers to worry about the utility of alternative-fuel and electric vehicles and makes them less likely to purchase these vehicles. For the new vehicle technologies to thrive it is critical that range anxiety is minimized and performance is increased as much as possible through proper routing and scheduling. In the case of long distance trips taken by individual vehicles, the routes must be chosen such that the vehicles take the shortest routes while not running out of fuel on the trip. When many vehicles are to be routed during the day, if the refueling stations have limited capacity then care must be taken to avoid having too many vehicles arrive at the stations at any time. If the vehicles that will need to be routed in the future are unknown then this problem is stochastic. For fleets of vehicles serving scheduled operations, switching to alternative-fuels requires ensuring the schedules do not cause the vehicles to run out of fuel. This is especially problematic since the locations where the vehicles may refuel are limited due to the technology being new. This dissertation covers three related optimization problems: routing a single electric or alternative-fuel vehicle on a long distance trip, routing many electric vehicles in a network where the stations have limited capacity and the arrivals into the system are stochastic, and scheduling fleets of electric or alternative-fuel vehicles with limited locations to refuel. Different algorithms are proposed to solve each of the three problems, of which some are exact and some are heuristic. The algorithms are tested on both random data and data relating to the State of Arizona. / Dissertation/Thesis / Ph.D. Industrial Engineering 2014

Page generated in 0.1027 seconds