Acetic anhydride hydrolysis in water is considered a standard reaction for investigating activation energy parameters using cosolvents. Hydrolysis in water/acetonitrile cosolvent is monitored by measuring pH vs. time at temperatures from 15.0 to 40.0 °C and mole fraction of water from 1 to 0.750. This work utilizes a temperature controlled water bath and a Vernier glass-body pH probe with Vernier Logger Pro 3.10.1 software for automated data collection. Data analysis is used to determine observed kinetic rate constants under the assumption that hydrolysis is a pseudo-first-order reaction. Eyring plots were used to compare activation energy parameters under iso-mole fraction conditions. The hydrolysis reaction of acetic anhydride was enthalpically stabilized and entropically destabilized at mole fractions of acetonitrile greater than 0.17 and the reverse occurred at mole fractions less than 0.17. Activation enthalpy and entropy result in the reaction being less favorable to form products as mole fraction of acetonitrile increased.

The power generation industry is facing new challenging issues regarding accelerating growth of electricity demand, fuel cost and environmental pollution. These challenges accompanied by concerns of energy resources becoming scarce necessitate searching for sustainable and economically competitive solutions to supply the future electricity demand. To this end, supercritical carbon dioxide (S-CO2) Brayton cycles present great promise particularly in high temperature concentrated solar power (CSP) and waste heat recovery (WHR) applications. With this regard, this dissertation is intended to perform thorough thermodynamic analyses and optimization of S-CO2 Brayton cycles for both of these applications. A modeling tool has been developed, which enables one to predict and analyze the thermodynamic performance of the S-CO2 Brayton cycles in various configurations employing recuperation, recompression, intercooling and reheating. The modeling tool is fully flexible in terms of encompassing the entire feasible design domain and rectifying possible infeasible solutions. Moreover, it is computationally efficient in order to handle time consuming optimization problems. A robust optimization tool has also been developed by employing the principles of genetic algorithm. The developed genetic algorithm code is capable of optimizing non-linear systems with several decision variables simultaneously, and without being trapped in local optimum points. Two optimization schemes, i.e. single-objective and multi-objective, are considered in optimizing the S-CO2 cycles for high temperature solar tower applications. In order to reduce the size and cost of solar block, the global maximum efficiency of the power block should be realized. Therefore, the single-objective optimization scheme is considered to find the optimum design points that correspond to the global maximum efficiency of S-CO2 cycles. Four configurations of S-CO2 Brayton cycles are investigated, and the optimum design point for each configuration is determined. Ultimately, the effects of recompression, reheating, and intercooling on the thermodynamic performance of the recuperated S-CO2 Brayton cycle are analyzed. The results reveal that the main limiting factors in the optimization process are maximum cycle temperature, minimum heat rejection temperature, and pinch point temperature difference. The maximum cycle pressure is also a limiting factor in all studied cases except the simple recuperated cycle. The optimized cycle efficiency varies from 55.77% to 62.02% with consideration of reasonable component performances as we add recompression, reheat and intercooling to the simple recuperated cycle (RC). Although addition of reheating and intercooling to the recuperated recompression cycle (RRC) increases the cycle efficiency by about 3.45 percent points, the simplicity of RC and RRC configurations makes them more promising options at this early development stage of S-CO2 cycles, and are used for further studies in this dissertation. The results of efficiency maximization show that achieving the highest efficiency does not necessarily coincide with the highest cycle specific power. In addition to the efficiency, the specific power is also an important parameter when it comes to investment and decision making since it directly affects the power generation capacity, the size of components and the cost of power blocks. Consequently, the multi-objective optimization scheme is devised to simultaneously maximize both the cycle efficiency and specific power in the simple recuperated and recuperated recompression configurations. The optimization results are presented in the form of two optimum trade-off curves, also known as Pareto fronts, which enable decision makers to choose their desired compromise between the objectives, and to avoid naive solution points obtained from a single-objective optimization approach. Moreover, the comparison of the Pareto optimal fronts associated with the studied configurations reveals the optimum operational region of the recompression configuration where it presents superior performance over the simple recuperated cycle. Considering the extensive potential of waste heat recovery from energy intensive industries and stand-alone gas turbines, this dissertation also investigates the optimum design point of S-CO2 Brayton cycles for a wide range of waste heat source temperatures (500 K to 1100 K). Once again, the simple recuperated and recuperated recompression configurations are selected for this application. The utilization of heat in WHR applications is fundamentally different from that in closed loop heat source applications. The temperature pinching issues are recognized in the waste recovery heat exchangers, which brings about a trade-off between the cycle efficiency and amount of recovered heat. Therefore, maximization of net power output for a given waste heat source is of paramount practical interest rather than the maximization of cycle efficiency. The results demonstrate that by changing the heat source temperature from one application to another, the variation of optimum pressure ratio is insignificant. However, the optimum CO2 to waste gas mass flow ratio and turbine inlet temperature should properly be adjusted. The RRC configuration provides minor increase in power output as compared to RC configuration. Although cycle efficiencies as high as 34.8% and 39.7% can be achieved in RC and RRC configurations respectively, the overall conversion efficiency is less than 26% in RRC and 24.5% in RC.

The analysis of empirical sorption equilibrium datasets is still vital to gain insights into material–property relationships as computational methods remain in development, especially for complex materials such as flexible MOFs. Therefore, the Dubinin-based universal adsorption theory (D-UAT) was revisited and evaluated as a simple visualization, analysis, and prediction tool for sorption equilibrium data. Within the theory, gas properties are normalized into corresponding states using the critical temperatures of the respective sorptives. The study shows theoretically and experimentally that the D-UAT is able to condense differences of sorption data visualized in reduced Dubinin plots to just three governing parameters: (a) the accessible pore volume, (b) the reduced enthalpy of sorption, and (c) the framework’s reduced free energy differences (in case of flexible behavior). This makes the theory a fast visualization and analysis tool, the use as a prediction tool depends on rough assumptions, and thus is not recommended.

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid solid oxide fuel cell (SOFC) – gas turbine (GT) – steam turbine (ST) systems ranging in size from 1.5 MWe to 10 MWe. The fuel cell model used in this thesis is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The SOFC/GT subsystem is based on previous work done by Francesco Calise during his doctoral research (Calise, 2005). In that work, a HRSG is not used. Instead, the gas turbine exhaust is used by a number of heat exchangers to preheat the air and fuel entering the fuel cell and to provide energy for district heating. The current work considers instead the possible benefits of using the exhaust gases in an HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this M.S. thesis work: a single-pressure, a dual-pressure, a triple-pressure, and a triple-pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost. / Master of Science

Surface force measurements previously conducted with thiolated gold surfaces showed a decrease in excess film entropy (£GSf), suggesting that hydrophobic force originates from changes in the structure of the medium (water) confined between hydrophobic surfaces. As a follow-up to the previous study, surface force measurements have been conducted using an atomic force microscope (AFM) with hydrophobic silica surfaces at temperatures in the range of 10 to 40¢XC. The silica sphere and silica plate were treated by both chemisorption of octadecyltrichlorosilane (OTS) and physical adsorption of octadecyltrimethylammonium chloride (C18TACl). A thermodynamic analysis of the results show similar results for both of the samples, that both ""Sf and excess film enthalpy ("Hf) become more negative with decreasing thickness of the water layer between the hydrophobic surfaces and decreasing temperature. |"Hf | > |T"Sf| represents a necessary condition for the excess free energy change ("Gf ) to be negative and the hydrophobic interaction to be attractive. Thus, the results obtained with both the silylated and C18TACl-adosrbed silica surfaces in the present work and the thiolated gold suefaces reported before show hydrophobic forces originate from structural changes in the medium. Thermodynamic analysis of SFA force measurements obtained at various temperatures revealed that "Sf were much more negative in the shorter hydrophobic force ranges than in the longer ranges, indicating a more significant degree of structuring in the water film when the two hydrophobic surfaces are closer together. It is believed that the water molecules in the thin liquid films (TLFs) of water form clusters as a means to reduce their free energy when they cannot form H-bonds to neighboring hydrophobic surfaces. Dissolved gas molecules should enhance the stability of structured cluster due to the van der Waals force between the entrapped gas molecules and the surrounding water molecules1, which may enhance the strength of the hydrophobic force. Weaker long-range attractive forces detected in degassed water than in air-equilibrated water was found in the present work by means of AFM force measurements, supporting the effect of dissolved gas on the structuring of water. At last, temperature effects on hydrophobic interactions measured in ethanol and the thermodynamic analysis revealed similar results as those found in water, indicating that the hydrophobic force originates from H-bond propagated structuring in the mediums. / Ph. D.

La thèse intitulée «Contributions aux systèmes de stockage d’énergie en utilisant des systèmes à partir de sources d’énergie alternatives» propose une étude des technologies de stockage d'énergie en sachant qu'elles sont considérées comme l'une des options qui peuvent faciliter une forte pénétration de sources renouvelables. Dans ce contexte, le travail présenté vise à comprendre les défis liés au stockage de l'énergie et à développer un modèle général d'étude utilisant l'air comprimé comme moyen de stockage d'énergie.La thèse est structurée dans dix chapitres dont les quatre premiers sont consacrés à la présentation potentielle des sources d'énergie renouvelables, à l'évolution du secteur de l'énergie au cours des dernières décennies et aux technologies de stockage d'énergie, notamment sous forme d'air comprimé. Les six autres chapitres concernent les calculs thermodynamiques théoriques dans la mesure où il s'agit d'étudier les performances d'un système de stockage d'énergie hybride et de présenter un modèle mathématique contenant les étapes prises en compte dans la conversion de l'énergie renouvelable en énergie mécanique, stockées dans une forme d'air comprimé et plus tard reconvertis en électricité. De plus, ces chapitres présentent des données expérimentales obtenues sur une installation de laboratoire qui ont contribué à la validation des résultats théoriques obtenus suite à une simulation Matlab, et enfin une étude de cas pour une application à petite échelle, 30 kWh d'énergie stockée, où vise à trouver une configuration optimale. De l'ensemble du système en termes de pression de travail de l'air, analysé sous deux points de vue, technique et économique. La thèse se termine par un chapitre de conclusions générales et nous constatons qu'il reste encore quelques défis à surmonter pour que le stockage de l'énergie sous forme d'air comprimé soit une solution possible d'une perspective économique. / The thesis entitled «Contributions to energy storage using hybrid systems from alternative energy sources» proposes a study of the energy storage technologies knowing the fact that these are considered one of the options that can facilitate a high penetration of renewable sources. In this context, the presented work aims to understand challenges in terms of energy storage and to develop a general studying model using compressed air as an energy storage medium.The thesis is structured in ten chapters from which the first four are dedicated to the presentation of the renewable energy sources potential, to the energy sector evolution in the last decades and to the energy storage technologies, especially in the form of compressed air. The other six chapters are dealing with the theoretical thermodynamic calculations as far as that goes in investigating the performances of a hybrid energy storage system and presenting a mathematical model containing the steps taken into account in the renewable energy conversion into mechanical energy, stored in a form of compressed air and later reconverted into electricity. In addition these chapters present experimental data obtained on a laboratory installation which helped in validating the theoretical results obtained following a Matlab simulation, and finally a case study for a small scale application, 30 kWh of energy stored, where is aiming to find an optimal configuration of the whole system in terms of air working pressure, being analyzed from two points of view, technical and economic. The thesis ends with a chapter of general conclusions and indicates that there are still challenges that must be overcome in order to make the energy storage in a form of compressed air a feasible solution from an economic perspective.

A rolling piston engine, operating according to a novel thermodynamic cycle is designed. Thermodynamic and structural analysis of this novel engine is carried out and thermodynamic and structural variables of the engine were calculated. The losses in the engine, friction and leakage were calculated and their effects on the engine were demonstrated.

Development of innovative thermodynamic cycles is important for the efficient utilization of low-temperature heat sources such as solar, geothermal, and waste heat sources. Binary mixtures exhibit variable boiling temperatures during the boiling process, which leads to a good thermal match between the heating fluid and working fluid for efficient heat source utilization. This study presents a theoretical and an experimental analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as the working fluid and produces power and refrigeration, while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low to mid-temperature sources such as geothermal and solar energy. A thermodynamic analysis of power and cooling cogeneration was presented. The performance of the cycle for a range of boiler pressures, ammonia concentrations, and isentropic turbine efficiencies were studied to find out the sensitivities of net work, amount of cooling and effective efficiencies. The thermodynamic analysis covered a broad range of boiler temperatures, from 85 °C to 350 °C. The first law efficiencies of 25-31% are achievable with the boiler temperatures of 250-350 °C. The cycle can operate at an effective exergy efficiency of 60-68% with the boiler temperature range of 200-350 °C. An experimental study was conducted to verify the predicted trends and to test the performance of a scroll type expander. The experimental results of vapor production were verified by the expected trends to some degree, due to heat transfer losses in the separator vessel. The scroll expander isentropic efficiency was between 30-50%, the expander performed better when the vapor was superheated. The small scale of the experimental cycle affected the testing conditions and cycle outputs. This cycle can be designed and scaled from a kilowatt to megawatt systems. Utilization of low temperature sources and heat recovery is definitely an active step in improving the overall energy conversion efficiency and decreasing the capital cost of energy per unit.

Orientador: Jose Vicente Hallak d'Angelo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-09T15:39:11Z (GMT). No. of bitstreams: 1 Santos_PauloRenatodos_M.pdf: 964248 bytes, checksum: 21cab8449ad59d56ad3ec7f876ee846d (MD5) Previous issue date: 2007 / Resumo: O setor de papel e celulose gera a maior parte da energia consumida em seus processos pela queima de dois combustíveis: biomassa e licor negro, sendo este último o mais utilizado entre eles. O setor vem ao longo dos anos utilizando sistemas de cogeração, que geram energia elétrica para o processo a partir da queima desses combustíveis. Nos últimos anos o setor vem tendo um aumento crescente em sua produção e com isso vem sendo gerada uma grande quantidade de licor negro, formando gargalos na unidade de recuperação (evaporação e caldeira de recuperação). Problemas como corrosão, incrustação e perigo de explosões na planta vêm se tornando realidade nesses anos. Outro fator é o tempo de vida útil das caldeiras de recuperação que vem se esgotando em várias indústrias brasileiras. Diante desse contexto, sobre crescente consumo de energia elétrica, aumento de produção de papel e celulose e maior quantidade de resíduos gerados, a gaseificação de licor negro se torna uma proposta interessante como processo alternativo. Foi analisado um sistema de cogeração de energia a partir da gaseificação do licor negro, como forma de avaliar a viabilidade técnica de se utilizar esse processo em substituição ao processo tradicional utilizado para geração de vapor de processo e energia elétrica. Para isso foi realizada uma simulação do sistema de cogeração em um simulador comercial (HYSYS© 2.2 daHyprotech), avaliando a influência da composição dos gases obtidos no gaseificador sobre as perdas exergéticas no sistema de cogeração. São apresentados os modelos para o sistema de gaseificação através de balanços de massa, energia e exergia, verificando e quantificando as irreversibilidades do ciclo. Os resultados obtidos demonstraram que a composição dos gases gerados no gaseificador tem grande influência sobre o processo, principalmente com relação à presença de água, hidrogênio e monóxido de carbono. Isso pôde ser verificado pelas perdas exergéticas analisadas, sendo o combustor o detentor das maiores perdas do processo. A gaseificação de licor negro é uma tecnologia ainda incipiente e relativamente nova e sua plena utilização nos processos industriais ainda requer estudos mais detalhados. Porém ela vem se tornando cada vez mais atraente e estudos no sentido de avaliar melhor sua viabilidade pode ser importante para que, num futuro próximo, essa tecnologia seja definitivamente implementada / Abstract: The pulp and paper industries generate most part of energy for self consumption burning two different fuels: biomass and black liquor, which is more used than the first one. This industrial sector has been used cogeneration systems, to produce electric energy from the combustion of these fuels. In the last years an increase in the production of the industries has caused an increase in the amount of black liquor available for burning, generating a bottlenecking effect in the recovery unit (evaporators and recovery boiler). Operational problems due to corrosion, fouling and explosions risks have aroused because of this great production of black liquor. Another important factor parallel to this is the lifetime of recovery boilers which is near to its end in many brazilian pulp and paper industries. In this scenario of increasing in electric energy consumption and pulp and paper production, generating more industrial residues, the black liquor gasification process has become an interesting alternative to use the excess of black liquor produced in the industries to produce more energy or as a substitute for the traditional recovery boilers. In this work an energy cogeneration system from gasification of black liquor was studied in order to evaluate the technical viability of using this process to replace the traditional one used to produce process vapor and electric energy. To do this a simulation of the cogeneration system was performed in a commercial simulator (HYSYS© 2.2 from Hyprotech), analyzing the influence of the composition of the gas stream from the gasificator over the exergetic losses in the cogeneration system. Mass, energy and exergy balances are presented for the system studied, verifying the irreversibilities of the cycle. The results obtained have shown that the composition of the gases produced in the gasificator has a great influence over the exergy balance of the process, mainly related with the presence of water, hydrogen and carbon monoxide. This was verified buy an exergetic analysis, that has shown that the greatest losses occur in the combustion chamber of the gases. Black liquor gasification process is an incipient and relatively new technology and its full usage in industrial scale still requires more detailed researches. Despite of this, it is becoming more and more attractive and any study that contributes to evaluate its viability may be important to help in the consolidation of this technology / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

[pt] O pigmento de titânio, que representa a maior parte do consumo desse metal, em geral possui duas rotas de produção conhecidas como sulfatação e cloretação. Nos últimos anos o TiO2 é produzido majoritariamente por cloretação devido ao fato de possuir vantagens sobre o tradicional processo de sulfato, como custo e geração de resíduo. Esse processo utiliza concentrados de ilmenita e de rutilo (natural ou sintético) como as principais matérias prima. Porém, em virtude da baixa quantidade de reservas de rutilo e do custo relacionando a concentração ilmenita, buscar novas fontes da matéria prima se torna cada vez mais relevante. Neste contexto, o presente trabalho propôs avaliar rotas de recuperação do TiO2 contido em um rejeito da concentração de magnetita, uma das fases da produção do óxido de vanádio, através do processo de ustulação seguido lixiviação ácida. Segundo a caracterização feita por Difração de Raios-X, o rejeito é constituído de 22,2 porcento de espécies contendo dióxido de titânio e o restante com outros minerais complexos: Clinocloro llb-2 e Tremolita. Concomitantemente, a análise de Fluorescência de RaiosX demostrou que o titânio compõe 15,9 porcento em massa de uma amostra do rejeito como recebido. Para o estudo, foi feito a avaliação termodinâmica das prováveis reações entre as espécies do rejeito e os agentes químicos selecionados, assim como os efeitos das variáveis de processos, a saber, proporção mássica do reagente e temperatura. A ustulação foi feita em um forno tipo mufla, com auxilio de cadinhos contendo a amostra e um dos dois reagentes propostos (NaOH e Na2HPO4). Em seguida, em água destilada aquecida, a amostra será imersa, e logo depois filtrada e seca para posteriormente ser lixiviada com HCl 5 porcento aquecido, filtrada e seca. O produto final do trabalho obtido será caracterizado através métodos convencionais: MEV; EDS; DR-X e FRX. Por intermédio da analise termodinâmica constatou-se a viabilidade para obter um produto insolúvel rico em titânio e as impurezas fosse carregadas na etapa de lixiviação. Os resultados mostraram um aumento na perda de massa ao decorrer das etapas e que a quantidade de reagente é a variável que mais influencia, enquanto a variação da temperatura não altera drasticamente. Ao final, as amostras que reagiram com NaOH, na temperatura de 850 graus celsius por 120 min com uma proporção e 50 porcento a mais em massa de reagente da quantidade equivalente estequiométrica obtiveram um composto com 65 porcento de CaTiO2 e algumas impurezas de Fe e Si, obtendo um proporção de 39,2 porcento de Ti em relação a massa do produto final, representando 51,6 porcento em massa de recuperação do titânio. Para as amostras ustuladas com fosfato de sódio dibásico obtiveram produtos com maior quantidade de impurezas, sendo o melhor resultado também nas mesmas condições que hidróxido de sódio, recuperando um material com 20,3 porcento de titânio. / [en] Titanium pigment, which represents most of the consumption of this metal, generally has two production routes known as sulfation and chloride. Currently, TiO2 is produced mainly by chlorination due to the fact that it has advantages over the traditional sulfate process, such as cost and waste generation. This process uses concentrates of ilmenite and rutile (natural or synthetic) as the main raw materials. However, due to the low amount of rutile reserves and the cost related to Ilmenite concentration, seeking new sources of raw material becomes increasingly relevant. In this context, the present study proposed to evaluate routes of recovery of TiO2 contained in an waste of the concentration of magnetite, one of the phases of the production of vanadium oxide, through the process of roasting followed by acid leaching. According to the characterization made by X-Ray Diffraction, the waste consist of 22.2 percent of species containing titanium dioxide and the rest with other complex minerals: Clinochlor llb-2 and Tremolite. Concomitantly, the X-Ray Fluorescence analysis showed that titanium makes up 15.9 percent by mass of a sample of the tailings as received. For the study, a thermodynamic evaluation of the probable reactions between the species of waste and the selected chemical agents was carried out, as well as the effects of process variables, namely, reagent mass proportion and temperature. Roasting was carried out in a muffle furnace, with the aid of crucibles containing the sample and one of the two proposed reagents (NaOH and Na2HPO4). Then, in heated distilled water, the sample will be immersed, and soon afterwards filtered and dried to later be leached with heated 5 percent HCl, filtered and dried. The final product of the work obtained will be characterized by conventional methods: SEM; EDS; XRD and XRF. Through thermodynamic analysis, the viability to obtain an insoluble product rich in titanium was verified and the impurities were loaded in the leaching stage. The results showed an increase in mass loss during the steps and that the amount of reagent is the variable that most influences, while the temperature variation does not change drastically. At the end, the samples that reacted with NaOH, at 850 celsius degrees for 120 min with a proportion and 50 percent more by weight of the stoichiometric equivalent amount obtained a compound with 65 percent CaTiO3 and some Fe and Si impurities, obtaining a proportion of 39.2 percent of Ti in relation to the mass of the final product, representing 51.6 percent by mass of titanium recovery. For samples roasted with Sodium phosphate dibasic, they obtained products with a greater amount of impurities, the best result being also in the same conditions as Sodium hydroxide, recovering a material with 20.3 percent titanium.