Esta dissertação visa estimar o potencial de energia elétrica do biogás, conhecido também como gás de aterro, gerado por resíduos sólidos urbanos (RSU) no Brasil. A estimativa foi aplicada para todos os 5.565 municípios do Brasil. O método utilizado para estimar a geração de biogás foi o IPCC 2000 (First Order Decay - FOD), pois leva em consideração inúmeros parâmetros, como a composição da matéria orgânica no aterro, teor de umidade do lixo, grau de compactação, temperatura no interior do aterro. Adicionalmente, este método é o mais difundido mundialmente e é o mesmo método utilizado para inventários de Gases de Efeito Estufa no Brasil, permitindo, dessa forma, comparações entre os estudos. No método, foram empregados os dados dos censos do IBGE 1970, 1980, 1991, 2000, 2010 de forma a representar fielmente o crescimento populacional e possibilita estimar a quantidade de resíduos sólidos gerados para todos os anos estudados. No estudo, foram analisados três cenários distintos representando diferentes tendências na gestão de resíduos no Brasil (cenários de referência, otimista e pessimista). O potencial elétrico do biogás no Brasil de acordo com o Cenário de referência para 2013 é de 983 MW, representando 1,6 % da potência elétrica instalada atual e para o ano de 2020, o potencial é de 1.602 MW. Concluindo o estudo, foram realizadas análises financeira e de sensibilidade em três diferentes projetos para avaliação da viabilidade de cada projeto. / This dissertation aims to estimate the potential for energy recovery from landfill gas through municipal solid waste (MSW) in Brazil. The survey was carried out in all 5,565 municipalities in Brazil. The used method to estimate the generation of landfill gas was the IPCC 2000 (First Order Decay - FOD) because it takes into account several parameters, such as: the type of organic matter, the waste moisture content, degree of compaction and temperature inside the landfill. Additionally, this method is the most widespread in the world and it is the same method used in greenhouse gases inventories in Brazil, thus allowing comparisons between these studies. In the method, data from national census of 1970, 1980, 1991, 2000, 2010 was used in order to accurately represent the population growth and allows estimating the amount of solid waste generated in every year. The study analyzed three different scenarios representing different trends in the solid waste management in Brazil (reference, optimistic and pessimistic scenarios). The electrical potential of landfill gas in Brazil (in the reference scenario) in 2013 is 983 MW, representing 1.6% of the current installed capacity and for 2020, the electrical potential is 1,602 MW. Concluding this study, a financial and sensitivity analysis as carried out on three different projects to evaluate the feasibility of each project.

An in-depth study has been carried out to investigate refractory degradation during continuous steel casting processes. Slag/refractory interactions have been investigated through a study of the wetting behaviour and gas generation phenomena at the slag/refractory interface at 1550oC using sessile drop experiments. The influence of carbon content and slag composition was investigated. Two different steel casting slags (slag1: MnO 50%, SiO2 25%, Al2O3 25%; and slag2: MnO 40%, SiO2 60%) have been studied along with yttria stabilized zirconia refractory substrates respectively containing 10%, 15% and 20% carbon. The gas generation has been measured using the Infrared gas analyser, and its influence has also been investigated by taking optical images at varying times. The total amount of gases emitted has shown the dependence on the compositions of refractory substrates and the existence of casting slags. Under the investigation of zirconia-carbon refractory, a new phenomenon that the gas generated can push the liquid slags away and minimise the contact of slags and refractory substrates has been proven.

This work investigates the interactions of carbonaceous materials (metallurgical coke, natural graphite and HDPE/coke blends) with three EAF slags [FeO: 24% to 32%]. Experiments were conducted using the sessile drop technique (1500??C-1600??C) with off-gases (CO, CO2) measured using an IR analyzer; the wetting behaviour was determined from contact angle measurements. Estimation of slag foaming behaviour was determined from the droplet volume changes calculated using specialized software. At 1550??C, all slags were non-wetting with coke due to increased surface tension due to sulphur. At 1550??C, slag 1 was initially non-wetting on natural graphite due to gas entrapment in the slag droplet; the wetting improved after that. Other slags showed comparatively better wetting. At 1600??C, all slags were non-wetting with coke. Slags showed a shift from non-wetting to wetting behaviour with natural graphite. Slag/coke reactions produced high off-gases levels causing extensive FeO reduction; gas entrapment in the slag was poor (small volume droplets). Slag/natural graphite interactions revealed both slow gas generation rates and FeO reduction, and excellent gas entrapment (higher droplet volumes) with minor changes in slag properties due to low ash levels. The iron oxide reduction rates were determined to be 1.54x10-5 and 4.2x10-6 mol.cm-2/sec (Slag 1, 1550??C) for metallurgical coke and natural graphite respectively. Slag interactions with coke/HDPE blends showed increasing off-gas levels with increasing HDPE levels. Blend#3 produced the highest off-gas levels, extensive FeO reduction and displayed significantly higher slag foaming and better wetting compared to coke. Our line on trends compared well for slag/carbon interactions and resulted in deceased specific energy consumption and carbon usage and increased productivity. These findings have enhanced the possibility of utilizing polymeric wastes in blends with coke in EAF steelmaking for slag/carbon interactions.

An in-depth study has been carried out to investigate refractory degradation during continuous steel casting processes. Slag/refractory interactions have been investigated through a study of the wetting behaviour and gas generation phenomena at the slag/refractory interface at 1550oC using sessile drop experiments. The influence of carbon content and slag composition was investigated. Two different steel casting slags (slag1: MnO 50%, SiO2 25%, Al2O3 25%; and slag2: MnO 40%, SiO2 60%) have been studied along with yttria stabilized zirconia refractory substrates respectively containing 10%, 15% and 20% carbon. The gas generation has been measured using the Infrared gas analyser, and its influence has also been investigated by taking optical images at varying times. The total amount of gases emitted has shown the dependence on the compositions of refractory substrates and the existence of casting slags. Under the investigation of zirconia-carbon refractory, a new phenomenon that the gas generated can push the liquid slags away and minimise the contact of slags and refractory substrates has been proven.

This work investigates the interactions of carbonaceous materials (metallurgical coke, natural graphite and HDPE/coke blends) with three EAF slags [FeO: 24% to 32%]. Experiments were conducted using the sessile drop technique (1500??C-1600??C) with off-gases (CO, CO2) measured using an IR analyzer; the wetting behaviour was determined from contact angle measurements. Estimation of slag foaming behaviour was determined from the droplet volume changes calculated using specialized software. At 1550??C, all slags were non-wetting with coke due to increased surface tension due to sulphur. At 1550??C, slag 1 was initially non-wetting on natural graphite due to gas entrapment in the slag droplet; the wetting improved after that. Other slags showed comparatively better wetting. At 1600??C, all slags were non-wetting with coke. Slags showed a shift from non-wetting to wetting behaviour with natural graphite. Slag/coke reactions produced high off-gases levels causing extensive FeO reduction; gas entrapment in the slag was poor (small volume droplets). Slag/natural graphite interactions revealed both slow gas generation rates and FeO reduction, and excellent gas entrapment (higher droplet volumes) with minor changes in slag properties due to low ash levels. The iron oxide reduction rates were determined to be 1.54x10-5 and 4.2x10-6 mol.cm-2/sec (Slag 1, 1550??C) for metallurgical coke and natural graphite respectively. Slag interactions with coke/HDPE blends showed increasing off-gas levels with increasing HDPE levels. Blend#3 produced the highest off-gas levels, extensive FeO reduction and displayed significantly higher slag foaming and better wetting compared to coke. Our line on trends compared well for slag/carbon interactions and resulted in deceased specific energy consumption and carbon usage and increased productivity. These findings have enhanced the possibility of utilizing polymeric wastes in blends with coke in EAF steelmaking for slag/carbon interactions.

Esta dissertação visa estimar o potencial de energia elétrica do biogás, conhecido também como gás de aterro, gerado por resíduos sólidos urbanos (RSU) no Brasil. A estimativa foi aplicada para todos os 5.565 municípios do Brasil. O método utilizado para estimar a geração de biogás foi o IPCC 2000 (First Order Decay - FOD), pois leva em consideração inúmeros parâmetros, como a composição da matéria orgânica no aterro, teor de umidade do lixo, grau de compactação, temperatura no interior do aterro. Adicionalmente, este método é o mais difundido mundialmente e é o mesmo método utilizado para inventários de Gases de Efeito Estufa no Brasil, permitindo, dessa forma, comparações entre os estudos. No método, foram empregados os dados dos censos do IBGE 1970, 1980, 1991, 2000, 2010 de forma a representar fielmente o crescimento populacional e possibilita estimar a quantidade de resíduos sólidos gerados para todos os anos estudados. No estudo, foram analisados três cenários distintos representando diferentes tendências na gestão de resíduos no Brasil (cenários de referência, otimista e pessimista). O potencial elétrico do biogás no Brasil de acordo com o Cenário de referência para 2013 é de 983 MW, representando 1,6 % da potência elétrica instalada atual e para o ano de 2020, o potencial é de 1.602 MW. Concluindo o estudo, foram realizadas análises financeira e de sensibilidade em três diferentes projetos para avaliação da viabilidade de cada projeto. / This dissertation aims to estimate the potential for energy recovery from landfill gas through municipal solid waste (MSW) in Brazil. The survey was carried out in all 5,565 municipalities in Brazil. The used method to estimate the generation of landfill gas was the IPCC 2000 (First Order Decay - FOD) because it takes into account several parameters, such as: the type of organic matter, the waste moisture content, degree of compaction and temperature inside the landfill. Additionally, this method is the most widespread in the world and it is the same method used in greenhouse gases inventories in Brazil, thus allowing comparisons between these studies. In the method, data from national census of 1970, 1980, 1991, 2000, 2010 was used in order to accurately represent the population growth and allows estimating the amount of solid waste generated in every year. The study analyzed three different scenarios representing different trends in the solid waste management in Brazil (reference, optimistic and pessimistic scenarios). The electrical potential of landfill gas in Brazil (in the reference scenario) in 2013 is 983 MW, representing 1.6% of the current installed capacity and for 2020, the electrical potential is 1,602 MW. Concluding this study, a financial and sensitivity analysis as carried out on three different projects to evaluate the feasibility of each project.

<div>Many two-phase flow systems might undergo flow instabilities even if the system is adiabatic but operates near the saturation conditions, especially in vertical flow conditions. Such instabilities are caused by <i>flashing</i> of the fluid in flow. Flashing is a sudden phase change in the fluid caused when local saturation enthalpy falls below the fluid enthalpy and the excess energy is used as latent heat for gas generation.</div><div> In the current analysis, a mathematical model is presented for analysis of such instability analytically. The conservation equations have been obtained by statistical averaging in time and space. Then, the concerned system is divided into various regions based on flow conditions, and these averaged equations are used to describe the flow. For flashing-based instability, two parameters are derived from constitutive relationships for the fluid. These two parameters are <i>Flashing Boundary</i> and <i>Gas Generation due to Flashing</i>. These parameters provide for the closure of the mathematical model. Some simple models for flashing have been developed and discussed.</div><div> The mathematical model is then solved analytically for <i>Uniform Heat</i> and <i>Flat Model</i> for the heater and flashing region respectively. The solution is in terms of the characteristic equation which is used to predict the onset of instability caused by flashing. The results are then plotted on the Subcooling-Phase Change number plane. It is observed that inlet and outlet restrictions in the flow does <b>not</b> affect the onset of flashing induced instability as the flow rate is coupled with the pressure drop of the system. This is important as these restrictions play a major role in other two-phase flow instabilities such as <i>Density Wave Oscillations</i></div><div> Finally, the stability boundary in the stability plane is compared to experimental data present for flashing. The comparison was made with data of S. Shi, A. Dixit, and F. Inada. The stability boundary satisfactorily agrees with the experimental data thus corroborating the present mathematical model and analysis.</div>

Treatment of fuel cell feed H2 for the removal of CO is important owing to the poisoning of the catalysts, thereby affecting the performance of the fuel cell. Strong and preferential adsorption of CO over the catalyst takes place resulting in a reduction of the power output of the cell. Therefore, it is important to treat the fuel cell feed H2 to reduce its CO content below the tolerable limit. Development of efficient catalysts for the treatment of synthesis gas for the removal of CO and and H2 enrichment of the gas to make it suitable for fuel cells is one of the two goals of this thesis. One of the various possible strategies for the removal of CO from the synthesis gas can be the use of the water-gas shift reaction. We have developed noble metal substituted ionic catalysts for catalyzing the water-gas shift reaction and have studied in detail the kinetics of the reactions by proposing the relevant reaction mechanisms. Solution combustion, a novel technique for synthesizing nanocrystalline materials, was used for the synthesis of all the catalysts. All the compounds synthesized were solid solutions of the noble metal ion and transition or rare earth metal oxide support. Three different supports were used, viz., CeO2, ZrO2 and TiO2. Substitution of Zr and Ti in CeO2 up to 15 at% was also carried out to obtain the compounds with enhanced oxygen storage capacity. All the compounds were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In some cases, where it was required, the use of FT-Raman spectroscopy was made for structural analysis. The compounds were nanocrystalline with metals substituted in ionic form in the support. The water-gas shift reaction was carried out over the synthesized catalysts with a reactant gas mixture that simulated the actual refinery gas composition. The variation of CO concentration with temperature was traced. The changes in the oxidation state of the metal showed the involvement of the various redox pairs over the reducible oxide like substituted CeO2 and TiO2. The mechanism of the reaction over ZrO2-based compounds was found to take place utilizing the surface hydroxyl groups. Rate expressions for the reactions over all the catalysts following different mechanisms were derived from the proposed elementary processes. Nonlinear regression was used for the estimation of various parameters describing the rate of reaction. Having established the high activity of Pt-ion substituted TiO 2 for the reactions, steam reforming of wood gas obtained from the gasification of Casuarina wood chips was carried out. The enrichment of the gas stream, which initially consisted of nearly 10% H 2 was carried out by steam reforming and H2-rich stream was obtained with H2 as high as 40% by volume in the treated gas. The second motive behind this thesis was to test the activity of the noble-metal substituted ionic catalysts for the treatment of the exhaust gas coming out of a fuel cell. In the fuel cell utilizing H2, the exhaust gases contain certain amount of unreacted H2, which can not be recovered or utilized economically. However, the gases are combustible and H 2 has to be removed in order to make the gas clean. We have shown high activity of the combustion-synthesized ionic compounds for catalytic combustion of H2. All the compounds showed high activity for H2 combustion and complete removal of H2 was possible. The rates were found to increase with an decrease in H2:O2 ratio and complete conversion of H2 was possible within 100 oC with air. A mathematical model was developed for the kinetics of catalytic H2 combustion based on the elementary processes that were proposed using the spectroscopic evidences. CO tolerant capacity of the catalysts was also tested. It was found that the temperature requirement for most of the catalysts increased with the introduction of CO. However, it was still possible to obtain complete conversions within 200 oC. To summarize, fuel cell processing systems utilizing H 2 remained central to the study. Treatment of the gases, both before and after reaction from the fuel cell was carried out over noble metal-substituted ionic catalyst, synthesized by solution combustion technique. Mechanisms of the reactions were proposed on the basis of spectroscopic evidences and the kinetic rate parameters were estimated using non-linear regression.

Le fonctionnement des batteries lithium-ion, qu’il soit normal ou dans des conditions abusives, est accompagné d’une génération de gaz en particulier lors des premiers cycles. Celle-ci est intrinsèque au dispositif et est soumise à de nombreux paramètres tels que les matériaux d’électrodes utilisés, l’électrolyte ou encore les conditions opératoires. Cette génération de gaz est délétère : elle conduit à l’augmentation de la pression interne des batteries et pose donc des problèmes de sécurité. Cette étude vise à quantifier les volumes de gaz générés et à comprendre les mécanismes liés à la surpression dans les batteries. A cet effet, le format de batterie « pouch cell » a été adopté tout au long de ce travail de thèse. L’électrolyte choisi est le mélange EC:PC:3DMC + 1 mol.L-1 LiPF6. La première partie de ce travail est dédiée à la mise au point d’un protocole expérimental basé sur (i) l’analyse des matériaux d’électrodes (NMC, LFP, Gr, et LTO), (ii) la solubilité de gaz (O2, H2) comparées à (CO2, CH4) par PVT, et (iii) la quantification des volumes de gaz générés durant le cyclage en pouch cell, corrélée aux performances électrochimiques. Une analyse préalable en demi-piles et en dispositifs complets Gr//NMC et LTO//LFP a également été réalisée afin d’anticiper les performances attendues en pouch cells. Une analyse critique des données (de la littérature et de nos mesures) a permis de définir une procédure optimisée pour obtenir des résultats reproductibles et comparables lors des mesures de volume en pouch cells. La seconde partie de cette thèse consiste en la quantification du volume de gaz produit au cours du cyclage des pouch cells Gr//NMC, Gr//LFP, LTO//LFP et LTO//NMC. Ainsi, les tensions de fin de charge, l’effet du sel et de la température ont été discutés pour dégager les paramètres déterminants dans la génération de gaz en particulier lors de la formation de la SEI. Enfin, une analyse de la composition du gaz récupéré a été effectué par GC-MS et FTIR. A partir de résultats obtenus, des mécanismes ont été proposés et discutés. / The functioning of lithium-ion batteries, may it be under normal use or under abusive conditions, is accompanied by gas generation, especially during the first cycles. This extent of gas generation is dependent on the choice of electrode materials, the electrolyte, and the operating conditions. This gas generation is detrimental: the build-up of pressure leads to the over-pressure in the battery, raising serious concerns. This study is aimed at understanding the fundamental mechanisms governing these reactions. To do so, the « pouch cell » configuration was adopted throughout this thesis. The electrolyte we worked on is the mixture EC:PC:3DMC + 1 mol.L-1 LiPF6. The first chapter of this work is dedicated to development of an experimental protocol based on (i) the analysis of the electrodes materials (NMC, LFP, Gr and LTO), (ii) the gas solubilities (O2, H2) compared to (CO2, CH4) by PVT method, and (iii) the quantification of the volume of generated gases during the cycling of pouch cells which was correlated to the electrochemical performances. A preliminary analysis of half-cells and full cells Gr//NMC and LTO//LFP were also conducted to foresee the performances of the pouch cells. A critical analysis of data taken from the literature and from our own experiments enabled the optimization of a proper procedure to get reproducible and comparable results. The second part of this thesis consists in the quantification of the volume of gases generated during the cycling of Gr//NMC, Gr//LFP, LTO//LFP and LTO//NMC pouch cells. In that respect, the voltages of the end of charge and the effect of salt and of temperature were discussed to figure out the essential parameters in the gas generation and in particular during the formation of SEI. Lastly, a compositional analysis of gases was performed using GC-MS and FTIR. Based on those results, a mechanism is proposed and discussed herein.

The Mildred Lake Settling Basin (MLSB) is the largest disposal site for mature fine tailings (MFT) at the Syncrude Canada Ltd oil sands plant. Since 1996, MFT densification in the MLSB has significantly accelerated due to microbial activity. Methane-producing microorganisms, known as methanogens, have become very active. A field and laboratory research program has been performed to study the mechanisms leading to the rapid densification. This research program consisted of historical monitoring data analyses, field investigations, small-scale column tests, and gas MFT densification tests. The field investigations have shown that the rapid densification of the MFT has occurred in the southern part of the pond ranging from 8 m to 15 m below the water surface. A connection existed between the rapid densification zone and the zone with intense microbial activity at the pond. The small-scale column tests demonstrated that, with increases of biogas generation, water drainage from the MFT was enhanced. Gas MFT densification tests showed that, stress histories and total pressure affected MFT densification property during microbial activity. Under high total pressure (6-7 m below pond surface) gas bubbles had difficulty to release. For MFT without pre-consolidation or under a preloading, during rapid gas generation, water was rapidly drained out. For over-consolidated MFT, water flowed back into MFT quickly during intense biogas generation. The concept of operative stress, the difference between the total stress and pore water pressure for the soil with large gas bubbles, was introduced to analyze the densification behavior of gassy MFT. Under high total pressure and under a preloading (1 kPa), excess pore pressure increased and operative stress decreased during rapid gas generation while water drainage from the MFT was accelerated. Total pressure and stress history also affected the structure and permeability of the MFT during microbial activity. Under low total pressure (1 m below pond surface) and without pre-consolidation, the MFT permeability increased after intense microbial activity. / Geotechnical Engineering