Academic literature on the topic 'Fluidized Bed Processing'

Orientador: Marco Aurélio Cremasco<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química<br>Made available in DSpace on 2018-08-18T08:24:24Z (GMT). No. of bitstreams: 1 Castilho_GuilhermeJosede_D.pdf: 4727634 bytes, checksum: 262e7551887344a4d33739e6ac52ca97 (MD5) Previous issue date: 2011<br>Resumo: Stringer (1989) sugeriu que um leito fluidizado gás-sólido pode ser um sistema caótico no qual seu comportamento irregular, entretanto determinístico, é causado por suas propriedades não-lineares. Desde então, surgiu uma nova forma de analisar flutuações de sinais em sistemas fluidizados: a análise não linear de séries temporais, comumente referida como análise de caos. A análise de caos é uma técnica muito utilizada no processamento de sinais em sistemas fluidizados, porém pouco difundida a nível nacional. Este tipo de análise baseia-se na reconstrução de atratores imersos em um espaço de fase e no estudo das propriedades deste atrator. Nesta Tese de Doutorado, avalia-se o comportamento fluidodinâmico em leito fluidizado circulante (LFC) operando sob condição de transporte pneumático diluído utilizando a análise de caos e também outras análises no domínio do tempo, como a distribuição de frequência e desvio médio absoluto. Os sinais avaliados foram obtidos por uma sonda de fibras ópticas, gerando séries temporais de flutuação de sinais elétricos que representam concentração de sólidos. A análise de caos demonstrou que os sistemas estudados apresentam comportamento caótico, por apresentar entropia de Kolmogorov positiva para todas as situações. A vantagem deste tipo de análise em comparação com as ferramentas usuais no domínio do tempo e no domínio da frequência (espectro de Fourier) é que a mesma considera o comportamento não-linear que existe neste tipo de reator multifásico. A partir de seus resultados, pôde-se descrever detalhadamente a fluidodinâmica do LFC, permitindo relacionar os parâmetros encontrados com fenômenos físicos como formação e repartição de clusters, turbulência do gás, interações partícula-partícula e partícula-parede e má alimentação. Tal análise permitiu, inclusive, a identificação de três regimes distintos: diluído, resultante de um escoamento mais complexo devido à turbulência da fase gasosa; concentrado, onde a presença de clusters diminui o caminho médio das partículas e por conseqüência reduz o grau de complexidade do sistema; e um terceiro regime ainda não publicado em trabalhos anteriores, referente às condições extremamente diluídas, onde o aumento do fluxo de sólidos provocou o aumento da complexidade. Neste regime, a fase gasosa predomina e o escoamento é mais previsível quando há presença de poucas partículas. Pretende-se, com esta Tese de Doutorado, incentivar a utilização deste método para, pelo menos, servir como complementação da técnica usualmente utilizada na análise de sinais nesta área de pesquisa, que são os espectros de potência de Fourier<br>Abstract: Stringer (1989) was the first to suggest that a gas-solid fluidized bed may be a chaotic system, in which the irregular, yet deterministic, behavior is caused by its nonlinear properties. Since then, another way to analyze signals fluctuations in fluidized systems came to light: the nonlinear time series analysis commonly referred to as chaos analysis. It is a technique widely used in the signal analysis in fluidized systems, but not very common at national level. This type of analysis is based on the reconstruction of attractors embedded in a phase space and the study of the properties of this attractor. This Ph.D. Thesis evaluates the fluid dynamic behavior of circulating fluidized bed (CFB) operating under conditions of dilute pneumatic conveying using chaos analysis of chaos and also further analysis in the time domain. The signals obtained were measured by an optical fiber probe which generated time series of fluctuating electrical signals representing solids concentration. The chaos analysis showed that the systems studied exhibit chaotic behavior, by having positive Kolmogorov entropy for all situations. The advantage of this type of analysis compared with the usual tools in the time domain and frequency domain (Fourier spectrum) is that it considers the nonlinear behavior that exists in this type of multiphase reactor. From their results, it was possible to describe in detail the fluid dynamics of the CFB, allowing correlating the parameters found with physical phenomena such as cluster formation and breakdown, the gas turbulence, particle-particle and particle-wall interactions and feed maldistribution. This analysis has led to the identification of three distinct regimes: diluted, resulted from a more complex flow due to turbulence of the gas phase; concentrated, where the presence of clusters decreases the average path length of particles and consequently reduces the complexity of the system; and a third regime not yet published in previous works, regarding the extremely dilute conditions, where the increased flow of solids caused the increase in complexity. In this condition, the gas phase and the predominant flow is more predictable when there is presence of a few particles. With this Ph.D. Thesis, it is intended to encourage the use of this method for at least as a complement to the technique usually used in signal analysis in this research area, that is, the Fourier power spectra<br>Doutorado<br>Engenharia de Processos<br>Doutor em Engenharia Química

Orientadores: Araí Augusta Bernárdez Pécora, Emerson dos Reis<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-20T09:39:28Z (GMT). No. of bitstreams: 1 RuedaOrdonez_YesidJavier_M.pdf: 20999298 bytes, checksum: 60bf64ff246a3515b0455a01ccb8e817 (MD5) Previous issue date: 2012<br>Resumo: Este trabalho apresenta o estudo de um equipamento para determinação das características dinâmicas de sistemas de medida de flutuações de pressão para aplicação em sistemas fluidizados. O equipamento foi projetado para gerar ondas de expansão ou rarefação dentro de um tubo no qual estão instalados dois sistemas de medição de pressão: um transdutor de referência ou padrão e outro composto por um sistema de medição que está sendo calibrado. Para a sua validação como sendo adequado para realizar calibrações, o equipamento foi sujeito a diferentes condições variando em dois níveis os seguintes parâmetros: (i) pressão interna do equipamento (15 e 30 kPa); (ii) espaçamento entre os transdutores (12 e 24 mm); (iii) material do diafragma (papel alumínio e papel celofane); e (iv) instrumento de rompimento manual do diafragma (estilete e agulha). Para cada condição testada foi avaliado o comportamento da onda gerada e de sua variação, quando foram consideradas duas faixas de limite de desvio da Função de Resposta em Frequência (FRF) de ±2% e ±10%, representada como a razão do módulo dos sinais no espaço da frequência registrados pelos transdutores de pressão. Nesta etapa, os resultados mostraram que para uma faixa de desvio da FRF de ±2%, o sistema é adequado para calibrações para a faixa de frequências de até 56 Hz, mas que tal faixa será maior se a faixa de desvio permitida for maior. Para uma faixa de desvio da FRF de ±10% o tubo de rarefação é apto para avaliar os sinais dinâmicos registrados por transdutores de pressão bem como verificar as características de um sistema de medida de pressão composto por tomada de pressão, mangueiras e transdutor eletrônico na faixa de frequência de 0 a 100 Hz. A melhor condição operacional encontrada foi a que utilizou papel celofane como material do diafragma, lâmina de aço para o rompimento do mesmo e pressão interna do sistema igual a 30 kPa. Numa segunda etapa, foram realizados: (v) testes para averiguação das tomadas de pressão e do comprimento de mangueiras sobre o desempenho do sistema de medida de pressão; e (vi) calibração dinâmica de um sistema de medida de pressão com sensor capacitivo SMAR LD-301. Nesta etapa os resultados mostraram que a mangueira de 0,1 m de comprimento afeta o sinal apenas para componentes de frequência acima de 18 Hz para faixa de desvio de ± 2% da FRF, caindo para 4 Hz (mangueira de 2m) e 3 Hz (mangueira de 4m), e que o SMAR LD-301, em dois modelos diferentes, é adequado para medir flutuações de pressão de até 14 Hz com faixa de desvio da FRF de ± 2% com tempo de resposta dos medidores, determinado através de análise dos sinais no tempo, de cerca de 0,15 s<br>Abstract: This work presents a study of a device to determine the dynamic characteristics of pressure fluctuations measurement systems to be used in fluidized beds. The device was developed to generate expansion or rarefaction waves into a tube where two pressure sensors were installed: a reference or standard one and another one being calibrated. In order to validate this device, it was subject to different conditions, at two levels the following parameters: (i) internal pressure in the device (15 and 30 kPa); (ii) distance between the sensors (12 and 24 mm); (iii) diaphragm material (aluminum foil and cellophane); (iv) manual bursting instrument of the diaphragm (paper knife and needle). The behavior of the generated wave and its variation were evaluated for each tested condition. Two limit deviation ranges were considered regarding the frequency response function (FRF), ±2% and ±10%, represented by the ratio of the signals amplitude in the frequency domain measured by the pressure transducers. At this stage, the results showed that for a deviation range of ±2% FRF, the system is appropriate for calibrations in the frequency range of 0 to 56 Hz. This frequency range increases with the deviation range increment. For a deviation range of ±10% FRF the rarefaction tube is a suitable device for the dynamic calibration of pressure transducers, as well as for the verification of the characteristics of pressure fluctuations measurement systems composed by pressure tap, hose and pressure transducer in a frequency range of 0 to 100 Hz. The best operational condition was found with cellophane as diaphragm material, paper knife as diaphragm bursting instrument and internal pressure in the tube of 30 kPa. In a second stage, the following tests were conducted: (v) experiments for evaluation of the pressure taps and length of the hoses on the performance of the pressure fluctuations measurement system, and (vi) dynamic calibration of a pressure measurement system with a capacitive pressure sensor SMAR LD301 - D2. At this stage the results showed that the hose with 0,1 m length only affects the signal for frequency components above 18 Hz, in a deviation range of ± 2% FRF, decreasing to 4 Hz (hose with 2m) and 3 Hz (hose with 4m) and the SMAR LD301 - D2, in two different models, is appropriate for the pressure fluctuations measurements up to 14 Hz in a deviation range of ± 2% FRF, presenting response time, determined through signal analysis in time domain, around 0,15 s<br>Mestrado<br>Termica e Fluidos<br>Mestre em Engenharia Mecânica

Orientador: Antonio Carlos Luz Lisboa<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica<br>Made available in DSpace on 2018-08-06T19:43:19Z (GMT). No. of bitstreams: 1 Porto_PauloSergiodaSilva_D.pdf: 16531970 bytes, checksum: 29f4837be6b441e6118e76a89e91a0ab (MD5) Previous issue date: 2005<br>Resumo: Xisto pirobetuminoso é uma rocha sedimentar que contém querogênio, um material orgânico que se encontra disseminado em sua estrutura mineral. O querogênio é extraído por aquecimento a altas temperaturas, em reatores conhecidos como retortas, 1iberando óleo e gás. Este óleo quando refinado produz destilados com as mesmas características encontradas nos de petróleo, sendo considerado uma fonte de energia alternativa. A existência de umidade no xisto na entrada do reator gera uma zona de secagem influenciando na redução da temperatura dos gases e diminuição da eficiência da retorta. O objetivo deste trabalho é investigar a perda de umidade durante a secagem de partículas de xisto, visando conhecer os mecanismos envolvidos. Para obter o perfil de umidade ao longo do tempo foram utilizadas partículas classificadas em três diferentes lotes quanto ao diâmetro médio de partícula (dp): partículas individuais do Lote A (dp = 80 mm e dp = 60 mm); partículas do Lote B que subdivide-se em quatro sublotes (~ = 5,3 mm, dp = 3 mm, dp = 1,5 mm e dp = 0,85 mm) e partículas do Lote C (dp < 0,074 mm). Os experimentos de secagem foram realizados em diversos secadores: partículas do Lote A secas em estufa com circulação de ar a 60°C e 90°C; partículas do Lote B secas em bandeja termogravimétrica a 40°C, 60 °c, 80°C e 100°C e em leito de jorro e leito fluidizado a 50°C e 70°C; partículas do Lote C secas em um analisador termogravimétrico, cujas temperaturas iniciais de 20°C variaram ao longo do tempo até atingir valores máximos de 40 °C, 70°C e 100°C. Exceto os experimentos realizados no ana1isador termogravimétrico, em todos os demais a temperatura foi mantida constante. Utilizou-se o modelo matemático de difusão de Fick, considerando geometrias uni e tri-dimensionais. Na solução destes modelos foram desenvolvidos programas em linguagem Fortran para descrever a variação de umidade das partículas de xisto ao longo do tempo e da posição, levando-se em conta a geometria da partícula e a temperatura do ar de secagem (constante ou variável). Os resultados preditos pelos modelos foram comparados com os experimentais apresentando boa concordância. Estes modelos podem contribuir na estimativa de parâmetros desconhecidos do processo. Quanto ao leito em jorro e leito fiuidizado, verificou-se que são técnicas adeqüadas para a secagem de xisto<br>Abstract: Oil shale is a sedimentary rock which contains kerogen, an organic matter scattered througout a mineral matrix. Kerogen is extracted by pyrolysis at high temperatures in reactors known as retorts producing oil and gas. The oil, when refined, produces distillates with the same characteristics as petroleum. Oil shale is considered an alternative energy source to petroleum. At the top of a moving bed retort oil shale moisture vaporization consumes energy, thereby reducing the retort efficiency. Oil shale drying has been investigated to optimize pyrolysis. The objective of this work was to investigate the moisture loss during oil shale particles drying to know the mechanisms involved. In order to obtain the moisture profile with time particles classified in three different categories<br>Doutorado<br>Engenharia de Processos<br>Doutor em Engenharia Química

Orientador: Arai Augusta Bernardez Pecora<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-14T08:26:21Z (GMT). No. of bitstreams: 1 CardenasFonseca_OscarLeonardo_M.pdf: 6620140 bytes, checksum: f3ecfb89fd126bbfe5400a37d419416d (MD5) Previous issue date: 2009<br>Resumo: Este trabalho apresenta o estudo experimental das flutuações de pressão de um leito fluidizado circulante operando com areia, um sólido tipo B de Geldart, como material particulado. As medidas formam realizadas em diferentes regimes de contato gás-partícula variando desde leito fixo até leito fluidizado rápido através da variação da velocidade superficial do gás. Os sinais de pressão foram medidos em três pontos considerados críticos no leito fluidizado, no plenum, na coluna principal à 1,05 m acima da placa distribuidora e na válvula de recirculação à 0,22 m da base da válvula. Os experimentos foram feitos para duas alturas de leito estático (0,17 e 0,25m) em um leito de 2,5 m de altura e 0,1 m de diâmetro interno, possuindo secções de vidro e acrílico intercaladas e unidas por flanges de aço carbono, o que permitiu acompanhar visualmente o processo. As flutuações de pressão foram analisadas no domínio da freqüência aplicando a Transformada Rápida de Fourier (FFT) o que permitiu diferenciar o comportamento dos regimes de fluidização do leito de partículas.<br>Abstract: This work shows the experimental study of pressure fluctuations in the riser of a circulating fluidized bed operated with sand, a Geldart B solid like powder. Tests were performed for different regimes of operation from fixed bed to fast fluidized bed for two static height of the material inside the bed (0.17 and 0.25 m). The pressure signals were measured in three critical points in the fluidized bed: plenum, riser and L-valve. The fluidized bed presented 2.5m height and 0.1m internal diameter, made by glass and acrylic sections inserted between carbon-steel flanges in order to allow visual observations. The pressure fluctuations were analyzed on the frequency domain using the fast Fourier transform (FFT) allowing the characterization of different gas-solid contact regimes.<br>Mestrado<br>Termica e Fluidos<br>Mestre em Engenharia Mecânica

Atmospheric freeze drying (AFD) is the lyophilization of a product at atmospheric pressure conditions and temperatures ranging generally between -15 and -5 ◦C (avoiding, thereby, ice melting). The quality of the obtained dried products is quite similar to the quality of products dried by vacuum freeze drying (VFD), but without the need of generating vacuum, maintaining temperatures around -50 ◦C in the condenser, or defrosting it. There are several ways to carry out AFD, such as the use of a fluidized bed or a tunnel conveyor. Nevertheless, AFD involves considerably longer drying times than VFD, and the process must be modified in some way in order to shorten them without loss of product quality at the same time. Moreover, since this process is usually carried out with air at very low temperatures, it can saturate rapidly. This situation leads to a reduction of the gradient of water concentration between air and product surface, and consequently, a diminution of the mass transfer rate. The use of an adsorbent material compatible with the food product (i.e., not toxic for human consumption) in a fluidized bed, could constitute an alternative for using other extra energy supplies (such as IR application, or heat pump). At the same time, the use of the adsorbent medium presents two additional advantages: the first, as the heat of adsorption of water vapour is of the same order of magnitude than sublimation heat of ice, no additional energy supply is necessary; second, it acts as adsorbent medium for generated water vapour, allowing air recirculation, which means an additional reduction of operative costs. In particular, non-food wheat bran is an interesting material to be applied as adsorbent in this process; this adsorbent is not only compatible with foodstuff, but also, since it is a by-product of the cereal processing industry, it is cheap and can be easily discarded (and reused, for example, in compost) without recovering it by means of a thermal treatment. Nonetheless, as it is the hard outer layer of cereals consisting of combined aleurone and pericarp, its particles exhibit a very irregular plane shape, with rests of grain brush and, in some cases, broken pericarp. These characteristics confer to the particle a rough surface and, as undesired consequence, the possibility of mechanical interaction during fluidization. However, when two different materials are fluidized in a fluidized bed, the mixture may undergo segregation, causing a poor contact between the adsorbent and the food particles. Thus, instead of using a traditional fluidized bed, a spout-fluid bed (an apparatus similar to the spouted bed, with lateral air injectors beside the main jet) may be utilized, and thereby enhancing mixing. On the other hand, CFD simulation would offer a great potential for simulating the AFD process, its optimization from the fluid dynamic point of view, and the design of new equipment. Various investigators have been working on the application of CFD models for simulating AFD in fluidized bed. However, in general, they simulated a single piece of foodstuff, but not the complete system with air, food material, and adsorbent (when it is applied). The general objectives of the PhD work are to determine the hydrodynamic conditions under which AFD in adsorbent fluidized bed is feasible, and to obtain a first approach to a CFD model of the process. Particularly, the study of the hydrodynamics of the process (non-food wheat bran fluidization behaviour, and mixing of binary mixtures) in a fluidized bed as well as in a spout-fluid bed is aimed from the experimental point of view, while the evaluation of the possibility of simulation by means of a CFD code of the AFD process by immersion in adsorbent medium in a fluidized bed is intended in the theoretical field. Unlike sand or other materials in which regular bubbles are formed, non-food wheat bran exhibits canalization or preferential air paths formation, and bed does not expand after overcoming minimum fluidization velocity. In addition, bran particle diameter is represented by a population distribution whose majority is Geldart B. Therefore, considering other bran particles physical characteristics such as rough surface and rest of grain brushes, it can be said that this "pseudo-cohesive" behaviour is caused principally by mechanical interactions rather than electrostatic forces as occurs in cohesive powders. In general terms, it can be observed a cyclical behaviour of channels generation and collapse. The number of channels and their shape depend on air superficial velocity as well as the bed position where they are formed. Anyway, in general they follow the Channel Generation and Collapse Cycle where two main stages are represented: I, generation, and II, collapse. Experiments emulating different stages of the AFD process with adsorbent application (using fresh food, partially lyophilized material, and completely lyophilized foodstuff) were done employing different food particles (peas, carrot discs, and potato slabs). Experiments were carried out in a 35 cm squared base fluidized bed and in a 20x10 rectangle base fluid-spout bed. The effects on segregation of air superficial velocity, product volumetric fraction, and particle shape were evaluated. For evaluating the segregation, segregation indexes form literature were evaluated, but some difficulties were found using them, besides it is not possible to obtain information about the segregation profiles with them. Thus, a novel way for characterizing segregation was proposed (the Three Thirds Segregation Indexes Set, TTSIS), consisting of three numbers that evaluate the distribution profile of a material of interest (food product, for the current case) and a fourth one that gives an idea of the segregation level. TTSIS was found the best tool for quantifying the segregation phenomenon, as it allows not only to measure the segregation level, but also classify the segregation pattern. As it was expected from the theory, it was evidenced that, even for a binary mixture composed by a pseudo-cohesive powder and a solid whose particles are considerably greater than the powder ones, the air superficial velocity plays a very important role in mixing. Particularly, at high air flows (2.6 umf-adsorbent for the analysed cases) uniform distribution of the material of interest are reached when dried foodstuff is used. Nonetheless, product density plays a fundamental role, since disuniform segregation profiles were obtained when fresh or partially lyophilized food material was used. Uniform mixing profiles were reached in the fluid-spout bed with a good circulation of the food particles along the bed during the fluidization. These results shown to be independent of the product density. Thus, this kind of bed should be used if an uniform mixing between adsorbent and food product is desired. Segregation phenomenon in channelling fluidized beds and the mixing process in fluid-spout beds might be explained by means of two food particle transport mechanisms (passive and active) and two movement blocking effects (floor and roof effects) observed during experimentation (video analysis), and the Channel Generation and Collapse Cycle. Regarding to CFD simulations, relatively reasonable results were obtained from the hydrodynamic point of view only at high air superficial velocity. However, specific models for cohesive or pseudo-cohesive powders are required if an accurate simulation of this kind of solids or binary mixtures integrated by them is intended. In sum, from the experimental results, emerged that the fresh product completely segregates toward the bed bottom in fluidized bed when mixtures containing food material without drying were used. Thus, a good contact between the material to be dried and the adsorbent (desirable for utilizing the adsorption heat for ice sublimation) would be not possible for AFD with use of adsorbent in fluidized bed applications. In contrast, using a fluid-spout bed maintains a very good mixing even if fresh food particles are used. Thus, beside the already known applications of this kind of beds for catalytic processes, its utilization for AFD with adsorbent medium seems to be an interesting and novel option for this process. Nevertheless, CFD simulation might be performed only for non-cohesive powders since the simulation of pseudo-cohesive materials fluidization is currently limited because of the lack of hydrodynamic models for this kind of solids.

Orientador: Marco Aurélio Cremasco<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química<br>Made available in DSpace on 2018-08-23T18:40:20Z (GMT). No. of bitstreams: 1 Moura_HelderLimade_M.pdf: 13116282 bytes, checksum: b886f67e25c04de827b794c8f5a4c6ca (MD5) Previous issue date: 2013<br>Resumo: Sinais caóticos são sinais cujo comportamento é aperiódico e sensível às condições iniciais ou às pequenas perturbações. Sob este aspecto, diversos campos do conhecimento, tais como engenharia, biologia e economia, podem fazer uso da análise de séries temporais para descrever situações características a seus estudos. Contudo, encontram-se dificuldades para classificar sistemas dinâmicos caóticos a partir de métodos tradicionais como, por exemplo, o espectro de potência de Fourier. Para uma nova abordagem, a reconstrução de atratores, a partir do método de Takens, vem sendo apontada como alternativa de análise para diferenciar o caos determinístico de um comportamento estocástico. A partir do caos determinístico, várias propriedades conhecidas como invariantes caóticas podem ser determinadas, como a dimensão de correlação e a entropia de Kolmogorov. No entanto, estudos recentes têm mostrado que ruídos limitam o desempenho de várias técnicas empregadas na identificação e previsão de sistemas determinísticos e, portanto, influenciando no cálculo dos invariantes caóticos. A extensão da influência do ruído na análise de dados experimentais é difícil de entender devido à falta de conhecimento sobre o nível e a natureza do ruído. Este trabalho, além de construir uma ferramenta para o cálculo dos invariantes caóticos, propõe uma abordagem sistemática para a redução de ruído em séries temporais de sinais de concentração de partículas de FCC, obtidos experimentalmente por uma sonda de fibra óptica em uma seção de riser de um leito fluidizado circulante (LFC). Para a determinação e a redução do nível de ruído foi utilizado o algoritmo de máxima verossimilhança (Schouten et al., 1994a) e o método de Schreiber (1993), respectivamente. Para tanto, adiciona-se o ruído no mapa de Hénon para, a seguir, ser aplicado sobre dados experimentais. Para avaliar a eficácia do método proposto, investiga-se a precisão da previsão para as séries caóticas a partir das redes neuronais artificiais e o valor da dimensão de correlação e entropia de Kolmogorov. Os resultados para identificação do nível de ruído e a sua redução mostram que a técnica proposta neste trabalho é promissora, pois conhecendo o nível de ruído, a redução deste é feita com maior precisão, em consequência disto, os resultados finais mantêm as características caóticas da dinâmica original. Sendo assim, é possível obter uma maior confiabilidade no grau de liberdade e previsibilidade na aplicação em sistemas experimentais<br>Abstract: Chaotic signals are signals whose behavior is aperiodic and sensitive to initial conditions or to small perturbations. In this regard, various fields of knowledge such as engineering, biology and economics, can make use of time series analysis to describe typical situations to its studies. However, it is difficult to classify chaotic dynamic systems from traditional methods such as Fourier power spectrum. Towards a new approach, reconstruction of attractors from the Takens's method has been suggested as an alternative analysis to differentiate the deterministic chaos of a stochastic behavior. Several properties known as chaotic invariants can be determined from the deterministic chaos such as the correlation dimension and Kolmogorov entropy. However, recent studies have shown that noise limits the performance of various techniques used in the identification and prediction of deterministic systems and influences the calculation of chaotic invariants. The extent of the noise influence in the analysis of experimental data is difficult to understand due to the lack of knowledge about the level and nature of the noise. This work elaborates a tool for the calculation of chaotic invariants and proposes a systematic approach to noise reduction in time series of particle concentration signals. The particle concentration signals were obtained experimentally by an optic fiber probe in a riser section of a circulating fluidized bed (CFB). To evaluate and reduce the noise levels the maximum likelihood algorithm (Schouten et al., 1994a) and the method of Schreiber (1993), were used, respectively. Therefore, the noise is added to the Hénon map to be applied on experimental data. To evaluate the effectiveness of the proposed method the accuracy of prediction by the artificial neural networks, the value of correlation dimension and Kolmogorov entropy from the chaotic time series are investigate. The results for the identification and reduction of noise show that the proposed technique is promising. The reduction is performed with higher accuracy knowing the noise level. Consequently, the final results maintain the original characteristics of chaotic dynamics. Therefore, it is possible to obtain a greater reliability in the degree of freedom and predictability in the application in experimental systems<br>Mestrado<br>Engenharia de Processos<br>Mestre em Engenharia Química

In this study, new methods and processing equipments for sesame dehulling were investigated. First, water absorption of sesame seed was studied at 20, 30, and 40&deg<br>C. The data could be modeled using Peleg equation where it was found that the constant k1 was inversely related to temperature but the effect of temperature on k2 was negligible. In the second phase of the work a lab scale continuous screw conveyor as dehuller and two equipments, (1) fluidized bed dryer and (2) hull separator to function as agitator, dryer and separator, for hull separation were designed. Fluidized bed unit was unsuccessful as it caused rapid drying of seeds before hulls can be removed. Using designed dehuller and hull separator, seeds at 30.5, 50.4 and 70.7 % db moisture contents were processed at dehuller speeds of 420, 840, and 1150 rpm. It was found that the percentage of dehulled seeds was linearly dependent on moisture content, optimal speed of designed dehuller was 840 rpm, and results for the efficiency of dehulling the seeds were significantly the same at 420 and 1150 rpm. Repeated passes of seeds through dehuller not only increased the efficiency of dehulling but also the percentage of damaged seeds. A dehulling efficiency of about 92.5 % was attained after four passes. The possibility of soaking seeds in an enzyme solution before dehulling was also investigated. By this means, after soaking in 0.2 % (v/v) Peelzyme-I solution for 15 min, a dehulling efficiency of 95 % was achieved.

Made available in DSpace on 2016-06-02T19:55:39Z (GMT). No. of bitstreams: 1 5956.pdf: 2655473 bytes, checksum: dfaa0329652cfa24fb1dd3934c5b664b (MD5) Previous issue date: 2014-03-28<br>Universidade Federal de Sao Carlos<br>The aim of this study was to evaluate the influence of hydraulic retention time (HRT), the origin of different inoculum (sludge from a UASB reactor for swine wastewater treatment and poultry slaughterhouse), and different carbon source (glucose, cassava processing wastewater and cheese whey) on the stability and efficiency of the anaerobic fluidized bed reactor (AFBR) for producing hydrogen. Twelve identical reactors were used, and in two reactors the mixture of glucose with cheese whey (R1S, R2S) was used as a substrate, six reactors were used with mix cassava processing wastewater and glucose (R1M, R2M, R3M and R4M). It was evaluated use of cheese whey (R3S, R4S, R5s and R6S) and cassava processing wastewater (R5M and R6M). The AFBRs were inoculated with sludge from a UASB reactor used in the treatment of swine wastewater (R1S, R3S, R1M, R3M, R5S, R6S, R5M and R6M) and sludge from a UASB reactor that treated poultry slaughterhouse wastewater (R2S, R4S, R2M, R4M), both heat treated. Variations of HRT (12-1 h) and substrate concentrations were performed (2-15 g .L -1), with temperature control at 30 ° C. The reactors that used cheese whey as substrate showed a greatest potential for hydrogen production, with yields (HY) of 3.2 mmolH2.g-1COD (R6S) and 2.6 mmolH2.g-1COD (R5S) were obtained by applying a HRT of 6 and 14 hours, with a concentration of 3 and 5 g.L-1, respectively. Both substrates showed potential for the production of ethanol with yields (EtOHY) of 4.2 mmolEtOH.g-1COD (R6M) and 3.5 mmolEtOH.g-1COD (R2S). In the comparison between the two inocula used, both showed a balance in terms of hydrogen production, but in terms of ethanol production, the sludge from poultry slaughterhouse showed highest potential. By cloning and sequencing of the 16S rRNA gene for bacteria domain reactor R4S (whey), there was a predominance of the genus Selenomonas (69 % of the sequences) and Clostridium (8 % of the sequences). For the reactor R3M (glucose and cassava) analyzes cloning and sequencing of bacterial consortium revealed similarities with Lactobaccilus. As for the archaeal domain, the sequencing of the 16S rRNA gene had highly similar to the genus Methanobacterium (98.5 % and 95 % of the sequences), for R4S and R3M, respectively reactors.<br>O objetivo deste estudo foi avaliar a influência do tempo de detenção hidráulica (TDH), da origem de diferentes inóculos (lodo de suínos e lodo de aves), e da fonte de carbono (glicose, manipueira e soro de queijo) sobre a estabilidade e eficiência do reator anaeróbio de leito fluidizado (RALF) na produção de hidrogênio e etanol. Foram utilizados doze reatores idênticos, sendo que em dois reatores foram utilizados mistura de glicose com soro de queijo (R1S, R2S), seis reatores foram utilizados a mistura de água do processamento da mandioca (manipueira) e glicose (R1M, R2M, R3M e R4M). Também foi avaliado o uso individual do soro de queijo (R3S, R4S, R5S e R6S) e da manipueira (R5M e R6M). Os RALFs foram inoculados com lodo proveniente do tratamento de águas residuárias de suinocultura (R1S, R3S, R1M, R3M, R5S, R6S, R5M e R6M) e de águas residuárias do abatedouro de aves (R2S, R4S, R2M, R4M), ambos tratados termicamente. Foram realizadas variações de TDH (14-1 h) e concentrações de substrato (2- 15 g. L-1), com controle de temperatura a 30°C. Os reatores que utilizaram soro de queijo como substrato apresentaram um maior potencial para a produção de hidrogênio, com rendimentos (HY) de 3,2 mmolH2.g-1DQO (R6S) e 2,6 mmolH2.g-1DQO (R5S), por meio da aplicação de um TDH de 6 e 14 horas, com uma concentração de 3 e 5 g.L-1, respectivamente. Ambos os substratos apresentaram potencial para a produção de etanol, com rendimentos (EtOHY) de 4,2 mmolEtOH.g-1DQO (R6M) e 3,5 mmolEtOH.g-1DQO (R2S). Na comparação entre os dois inóculos utilizados, ambos apresentaram um equilíbrio em termos de produção de hidrogênio, porém em termos de produção de etanol, o lodo proveniente do abatedouro de aves apresentou um maior potencial. Por meio da clonagem e sequenciamento do gene RNAr 16S para o domínio bactéria do reator R4S (soro de queijo), houve a predominância do gênero Selenomonas (69% das sequências) e do gênero Clostridium (8% das sequências). Para o reator R3M (glicose e manipueira) as análises de clonagem e sequenciamento do consórcio bacteriano revelaram semelhanças com Lactobaccilus. Já para o domínio archaea, o sequenciamento do gene RNAr 16S, teve altas similaridades com gênero Methanobacterium (98,5% e 95% das sequências), para os reatores R4S e R3M, respectivamente.