Made available in DSpace on 2014-12-17T15:01:30Z (GMT). No. of bitstreams: 1 FranciscoESJ_DISSERT.pdf: 2170552 bytes, checksum: 7eb8333582d6093d8dba28f6fb660743 (MD5) Previous issue date: 2012-08-06 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In this research, the drying process of acerola waste was investigated by using a spouted bed drier. The process was conducted using high density polyethylene inert particles with the objective of producing an ascorbic acid-rich final product. The fruit waste was ground and used to prepare different water-maltodextrin suspensions. Initially, fluidynamical experiments were conducted in order to evaluate the feeding effect on the spouted bed drier fluidynamics behavior. The experimental planning 23 + 3 was used to investigate the effect of the following variables: solids concentration, drying air temperature, intermittence time, production efficiency, solids retention and product losses by elutriation of fine particles on drier walls. The effect of selected independent variables on the drier stability was also evaluated based on a parameter defined as the ratio between the feed suspension volume and the total inert particles volume. Finally, the powder quality was verified in experiments with fixed feed flow and varying air drying temperature, drying air velocity and intermittence time. It was observed that the suspension interferes in the spouted bed drier fluidynamics behavior, and higher air flow is necessary to stabilize the drier. The suspension also promotes the expansion of the spouted bed diameter, decreases the solid circulation and favors the air distribution at the flush area. All variables interfere in the spouted bed performance, and the solids concentration has a major effect on the material retention and losses. The intermittence time also has great effect on the stability and material retention. When it comes to production efficiency, the main effect observed was the drying air temperature. First order models were well adjusted to retention and losses data. The acerola powder presented ascorbic acid levels around 600 to 700 mg/100g. Similar moisture and ascorbic acid levels were obtained for powders obtained by spouted bed and spray drier. However, the powder production efficiency of the spray drier was lower when compared to spouted bed drier. When it comes to energetic analysis, the spray drier process was superior. The results obtained for spouted bed drier are promising and highly dependent on the operational parameters chosen, but in general, it is inferred that this drying process is adequate for paste and suspension drying / No presente trabalho estudou-se a secagem do res?duo industrial da acerola em secador de leito de jorro com part?culas inertes de polietileno de alta densidade, visando a obten??o de um produto seco com elevado valor agregado, principalmente no que concerne ao teor de ?cido asc?rbico. O res?duo foi triturado, preparando-se uma suspens?o com adi??o de ?gua e de maltodextrina em diferentes propor??es. Realizou-se inicialmente uma s?rie de experimentos fluidodin?micos para avaliar o efeito da alimenta??o da suspens?o sobre o comportamento fluidodin?mico do leito de jorro. Realizaram-se experimentos de secagem com base em um planejamento experimental 23 com 3 r?plicas no ponto central, onde foram avaliados os efeitos das vari?veis, teor de s?lidos, temperatura do ar de secagem e tempo de intermit?ncia sobre a umidade, efici?ncia de produ??o, reten??o de material no leito e perdas do produto em p? por elutria??o de finos e aderido ?s paredes do equipamento. Analisaram-se tamb?m os efeitos das vari?veis independentes sobre a estabilidade do secador representada a partir de um par?metro definido pela raz?o entre o volume de suspens?o alimentado ao leito e o volume total das part?culas inertes. Finalmente, com o objetivo de se verificar o desempenho do processo no que se refere ? qualidade do p?, realizaram-se na concentra??o de s?lidos mais favor?vel a obten??o do p?, experimentos de secagem fixando-se a vaz?o de alimenta??o e variando-se a temperatura e velocidade do ar de secagem e o tempo de intermit?ncia. De acordo com os resultados obtidos, a suspens?o interfere de forma importante no comportamento fluidodin?mico do leito, necessitando de maior vaz?o de ar para manter as condi??es de jorro. A suspens?o promove expans?o no di?metro do jorro, diminui a taxa de circula??o de s?lidos al?m de favorecer a distribui??o do ar na regi?o do jorro. Com respeito aos experimentos realizados conforme o planejamento experimental, todas as vari?veis interferiram no desempenho do secador, destacando-se o importante efeito do teor de s?lidos sobre a reten??o de material no leito e perdas, bem como o efeito da intermit?ncia sobre a estabilidade e reten??o de material no leito. Na efici?ncia de produ??o o efeito principal foi atribu?do ? temperatura do ar de secagem. Foram obtidos modelos de primeira ordem que se ajustaram bem aos dados de reten??o e perdas. Em rela??o aos experimentos finais, foram obtidos p?s com teor de ?cido asc?rbico na faixa de 600 a 700 mg/100g. Os resultados desses experimentos foram comparados com os resultados obtidos na secagem da mesma suspens?o, em spray dryer. A secagem no spray dryer forneceu um produto com teores de umidade e de ?cido asc?rbico compat?veis com o produzido no jorro, todavia na condi??o de opera??o testada a efici?ncia de produ??o de p? no spray foi inferior a do jorro. A compara??o dos dois processos mediante an?lise dos recursos energ?ticos favorece a opera??o de secagem no spray dryer. Todavia, os resultados obtidos no secador de leito de jorro s?o promissores, demonstrando que dependendo do ajuste das condi??es operacionais este secador se ad?qua bem a secagem de pastas e suspens?es

Este trabalho apresenta o desenvolvimento de uma metodologia experimental visando à produção de extrato seco padronizado de Bauhinia forficata Link. Um planejamento experimental de três fatores e três níveis tipo Box-Behnken e análise multi-resposta foram empregados na otimização do processo de extração. Dois processos distintos de secagem foram investigados: o processo leito de jorro e a secagem por nebulização (ou spray-drying). O objetivo foi avaliar a viabilidade e desempenho de ambos secadores para a produção de extrato seco. As variáveis estudadas foram a razão percentual entre a vazão mássica da solução extrativa alimentada ao sistema pela capacidade de evaporação, (Ws/Wmáx), a temperatura de entrada do gás de secagem, (Tge), a posição do sistema de atomização no leito de jorro (top spray e bottom spray) e a vazão do gás de secagem utilizada no spray-dryer, (Wg). O desempenho operacional dos secadores foi avaliado principalmente através da produtividade, da eficiência térmica do processo, da taxa de evaporação volumétrica, da razão entre a massa de ar usada/massa de água evaporada e da taxa de recuperação do produto. O produto seco foi caracterizado quanto a distribuição granulométrica, morfologia das partículas, teor de umidade residual, taxa de degradação dos flavonóides (marcadores químicos) e características farmacotécnicas. Os resultados reportados mostram que o leito de jorro apresentou significativa superioridade em todos os parâmetros estudados em relação ao processo spray-dryer, para as configurações e condições operacionais investigadas. Isso permite concluir que o secador de leito de jorro é uma alternativa tecnologicamente viável para a produção de extratos secos de plantas medicinais brasileiras apresentando maior eficiência e produtividade, fornecendo um produto de alta qualidade e valor comercial. / This work presents the development of an experimental methodology aiming to the production of standardized dried extracts of Bauhinia forficata Link. An experimental planning of three factors and three levels type Box-Behnken and multi-response analysis were used in the optimization of the extraction process. Two different drying processes were studied: the spouted bed and the spraydrying processes. The objective was the evaluation of the viability and of the performance of both dryers for the production of dry extract. The investigated parameters were the percentile ratio between the mass feed flow rate of extractive solution to the system by the evaporation capacity of the dryer, (Ws/Wmáx), the inlet temperature of the drying gas, (Tge), the position of the atomization system in the spouted bed (top spray and bottom spray) and the mass flow rate of the drying gas used in the spray-dryer, (Wg). The operational performance of the dryers was evaluated mainly by the productivity, thermal efficiency of the process, rate of volumetric evaporation, ratio between the mass of air used by the mass of evaporated water and by the product recovery rate. The dried product was characterized by the particle size distribution, particles morphology, moisture content, flavonoid degradation rate (chemical marker), and by evaluation of pharmacotechnical properties. The results reported show that the spouted bed process presented a significant superiority in all parameters evaluated relative to the spray-drying process, for the configurations and operational conditions investigated. These results lead to the conclusion that the spouted bed process is an alternative technologically viable for the production of dry extracts of medicinal Brazilian plants, presenting high thermal efficiency and productivity, yielding a product of high quality and commercial value.

Orientadores: Rosiane Lopes da Cunha, Florencia Cecilia Menegalli / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-05T17:14:21Z (GMT). No. of bitstreams: 1 Christ_Divair_D.pdf: 2473666 bytes, checksum: ca400b2519c40ad806addec20990ae8c (MD5) Previous issue date: 2006 / Resumo: O objetivo deste estudo foi avaliar o processo de secagem da clara de ovo utilizando um secador de leito de jorro fluidizado bidimensional com esferas de vidro como inertes. Um planejamento fatorial completo 24 foi realizado, com 3 pontos centrais e oito axiais, utilizando-se as seguintes variáveis independentes: temperatura (55-95 °C) e vazão total do ar de secagem (97,1-138,3 m³/h), razão entre vazão de ar de jorro e ânulo (0,6-1,4) e vazão de alimentação de pasta (2,0-10,0 g/min). Como respostas foram avaliadas a distribuição de umidade no leito durante a secagem, teor de umidade do produto, massa de matéria seca retida pelas esferas inertes, eficiência de recuperação do pó, cor do produto em pó e depois de dissolvido em água, propriedades térmicas, teor de proteína, solubilidade em meio aquoso e propriedades reológicas a baixas e altas deformações de géis térmicos de clara de ovo. O uso de planejamento fatorial completo e superfícies de resposta foram fundamentais para avaliar o efeito simultâneo das condições de secagem em leito de jorro fluidizado sobre o processo e o produto obtido. Esta metodologia diminuiu significativamente o número de experimentos e se mostrou eficiente para conhecer a relação de causa e efeito das condições de processo sobre as respostas. Todas as condições de processo estudadas influenciaram nas características do produto obtido, porém a temperatura e a vazão de ar foram as mais importantes na definição da qualidade da clara de ovo seca em leito de jorro fluidizado. Para avaliar a relação entre as várias respostas obtidas e as variáveis de processo, bem como determinar as condições ótimas de operação do secador foi aplicada a técnica estatística da desejabilidade. Concluiu-se que os níveis ótimos de operação do secador seriam: temperatura de 73,7 °C, vazão de ar de 110,8 m³/h, razão vazão de jorro/vazão de ânulo de 1,1 (58,04 m³/h e 52,76 m³/h de vazão de jorro e ânulo, respectivamente) e vazão de pasta de 9,2 g/min. Nestas condições, 60% do total desejado para todas as respostas seria atendido, sendo que a eficiência de recuperação de matéria seca pelo ciclone seria de 74,4% e o grau de desnaturação das proteínas seria baixo (conalbumina: 42,1% e ovalbumina: 25,5%), o que resultaria em elevado grau de solubilidade (em torno de 98%). Neste caso, a temperatura de início de desenvolvimento da estrutura do gel seria estimada em 62 ºC, porém a força da rede seria dada pela desnaturação da ovalbumina (temperatura de desnaturação próxima a 80 oC) e por isto, as características reológicas de géis térmicos de clara de ovo foram estudadas. Os géis térmicos (80 ºC/30 min) de clara de ovo seca em leito de jorro fluidizado mostraram alta deformabilidade e características elásticas similares aos géis obtidos a partir de clara de ovo liofilizada. Assim, a partir da análise dos resultados obtidos foi possível otimizar a secagem da clara de ovo em leito de jorro fluidizado alcançando-se boa eficiência de processo e preservando suas propriedades funcionais / Abstract: The objective of this study was to evaluate an egg white drying process using a two-dimensional spouted fluidized bed dryer with glass spheres as the inert particles. A complete 24 factorial design was used, with 3 central and 8 axial points, using the following independent variables: temperature (55-95ºC), total drying air flow rate (97.1-138.3 m3/h), ratio between spout and annulus air flow rates (0.6-1.4)and paste feed flow rate (2.0-10.0 g/min). As responses, the moisture distribution in the bed during drying, product moisture content, mass of dry matter adhered to inert particles, powder recovery efficiency, product colour as powder and after dissolving in water, thermal properties, protein content, solubility in aqueous medium and rheological properties at high and low deformation of heat-induced egg white gels. The use of a complete factorial design and response surfaces was fundamental to evaluate the simultaneous effect of the drying conditions in a spouted fluidized bed on the process and obtained product. This methodology significantly reduced the number of experiments and showed to be efficient to understand the cause and effect relationship of process conditions on responses. All the process conditions studied influenced the characteristics of the product obtained, but temperature and air flow rate were the most important variables in defining the quality of the egg white dried in a spouted fluidized bed. The statistical technique of desirability was used to evaluate the relationship between the various responses obtained and the process variables, and to determine the optimum dryer operating conditions. It was concluded that the optimum operational levels for the dryer were: temperature of 73.7ºC, air flow rate of 110.8 m3/h, ratio of spout/annulus flow rate of 1.1 (58.04 m3/h and 52.76 m3/h of spout and annulus flow rate, respectively) and paste flow rate of 9.2 g/min. Under these conditions, 60% of the desired total for all the responses would be attained, the recovery efficiency of the dry material by the cyclone would be 74.4% and the degree of protein denaturation would be low (conalbumin: 42.1% and ovalbumin: 25.5%), resulting in very good solubility (about 98%). In this case, the temperature at the start of the gel structure development would be estimated at 62ºC, although the gel strength would be given by the ovalbumin denaturation (denaturation temperature near 80ºC) and for this reason, the rheological characteristics of the thermal egg white gels were investigated. The thermal gels (80ºC/30 min) of egg white dried in a spouted fluidized bed, obtained in this study, showed high deformability and elastic characteristics, similar to the gels obtained from freeze-dried egg white (literature data). Thus, from the analysis of the obtained results it was possible to optimize the drying of egg white in a spouted fluidized bed, obtaining good process efficiency yet preserving the functional properties / Doutorado / Doutor em Engenharia de Alimentos

Neste trabalho investigou-se o potencial tecnológico e econômico do processo de secagem em leito de jorro para a produção de extratos secos padronizados de plantas medicinais brasileiras utilizando como modelo experimental a Bauhinia forficata Link. O objetivo foi demonstrar que essa é uma tecnologia potencial para o processamento de plantas medicinais, mercado mundial que gira em torno de 22 bilhões de dólares anuais. Os extratos vegetais apresentam composição química complexa (ácidos graxos, açúcares, fibras, proteínas e resinas) o que torna a etapa de desidratação destes materiais uma tarefa desafiadora, principalmente quando a secagem ocorre sobre a superfície de corpos inertes como no secador de leito de jorro. Torna-se imprescindível, portanto, a utilização de adjuvantes de secagem como as maltodextrinas, amidos, dióxido de silício coloidal entre outros. Dentre os problemas operacionais frequentemente observados pode-se citar o acúmulo de produto sobre a superfície do material inerte tornando-o mais pesado e acarretando em instabilidades fluidodinâmicas e redução da produtividade do equipamento. Um aumento nas taxas de degradação térmica dos princípios ativos também é observado devido à elevação do tempo de exposição do material a elevadas temperaturas. A influência dos adjuvantes de secagem em diferentes proporções (20 a 80 %) sobre as propriedades físicas dos extratos foi avaliada através de ensaios de tensão superficial, ângulo de contato, desprendimento do filme de extrato da superfície inerte, densidade e comportamento reológico. Ensaios de secagem com diversos adjuvantes apontaram o dióxido de silício coloidal como o responsável pelos melhores resultados, sendo o material de escolha para os ensaios seguintes. Os ensaios de secagem realizados em duas configurações de leito de jorro (convencional e com instalação de tubo draft) foram delineados através de um planejamento composto central onde as variáveis estudadas foram a % de adjuvante (% Adj), a vazão do ar de secagem (Q/Qjm), e a vazão de suspensão alimentada ao sistema (Ws/Wg), sendo a temperatura de secagem (Tge), fixada em 150 C. Os resultados da análise estatística e as tendências observadas dos efeitos das variáveis independentes estudadas (% Adj, Q/Qjm e Ws/Wg) sobre as variáveis respostas, recuperação do produto (Rec), acúmulo de material no leito (Ac), perda por dessecação (Xp), degradação dos flavonóides (DTF), e diâmetro médio das partículas (Dp), mostram que as variáveis % Adj e Q/Qjm apresentaram significância estatística sobre o processo de secagem, para as condições operacionais estudadas. Análises físicas e químicas como Xp, DTF, Dp, perfil cromatográfico, difração de raios X e comportamento térmico, e o monitoramento do desempenho do equipamento de secagem (Rec e Ac) foram realizadas. Ensaios de atividade antioxidante e hipoglicemiante foram realizados para os melhores extratos apresentando resultados promissores. De posse do conhecimento tecnológico do processo, realizou-se um levantamento de sua viabilidade econômica. Foram estimados os gastos necessários para a montagem de uma unidade (pequena escala) produtora de extratos secos e os custos médios envolvidos na obtenção do produto final. Os resultados deste trabalho indicam a viabilidade técnica e econômica do processo em leito de jorro para a obtenção de extratos secos de plantas medicinais, despontando como um processo alternativo frente ao spray dryer comumente usado nas indústrias de processamento fitoterápico. / The aim of this work was to investigate the technological and economical feasibility of the spouted bed drying process for production of the standardized dried extracts of Brazilian medicinal plants using the Bauhinia forficata Link as an experimental model. The objective was to demonstrate the potential of this technology for the processing of medicinal plants, a world market of 22 billions of dollars a year. Vegetable extracts have a complex chemical composition (fatty acids, sugars, fibers, proteins and resins), making the dehydration of these materials a challenging task, mainly for drying on the surface of inert bodies, like the spouted bed drying. Thus, the use of drying aids like maltodextrins, starch, colloidal silicon dioxide is mandatory. Among the operating problems frequently observed, there is the product accumulation on the surface of the inert material increasing its weight, causing hydrodynamic instabilities and reduction of the equipment productivity. A high increase in the thermal degradation of the active substances is also observed. This behavior is attributed to the increase in the exposure time of the material at high temperatures. The effects of the different proportions of drying aids (20 to 80 %) on the physical properties of the extracts were evaluated through determination of the surface tension, contact angle, detachment of the extract film from the surface of the inert material, density and rheological behavior. Drying tests carried out with several drying aids showed a better performance with the colloidal silicon dioxide, being the selected material for the further tests. Drying runs were carried out in two spouted bed configurations (conventional and with draft tube), according to a central composite design. The variables studied were the % of the drying adjuvant, the drying gas flow rate, parameterized by the ratio Q/Qjm, and the flow rate of the extract fed to the system (Ws/Wg). The statistical analysis results and the effects presented by independent variables (% Adj, Q/Qjm and Ws/Wg), on the responses product recovery (Rec), product accumulation in the bed (Ac), loss on drying (Xp), flavonoid degradation (DTF), and mean powder diameter (Dp), showed a significant effect of the parameters % Adj and Q/Qjm, for the operating conditions investigated. Physical and chemical analysis of the dried product, such as loss on drying, degradation of the active substances, particle size distribution, chromatographic profiles, X-ray diffraction, thermal behavior, and the monitoring of the equipment performance (Rec and Ac) were performed. Evaluation of the antioxidant and hypoglycemic activity were carried out for the extracts obtained at optimized conditions, presenting promising results. After the technological investigation, an evaluation of the economical viability of the process was carried out. The installation costs of a small scale unity for production of dried extracts, and the average costs involved for the obtaining of the final product were estimated. The results of this work indicated the technical and economical feasibility of the spouted bed drying for the production of dried extracts of medicinal plants, emerging as an alternative to the spray drying, commonly used in the phytotherapic processing industries.

Le séchage est une opération unitaire pratiquée depuis des millénaires pour laquelle les connaissances scientifiques sont encore très incomplètes. Il est cependant de plus en plus nécessaire de « bien » sécher afin d’atteindre une combinaison optimale du temps de séchage, de l’énergie consommée et surtout de la qualité du produit final. Ceci est d’autant plus vrai dans le cadre du séchage alimentaire où de nombreux produits sont très sensibles à la température et à la déshydratation. C’est le cas de la levure de boulanger dont la capacité à dégager du CO2, pour faire gonfler la pâte à pain par exemple, diminue très souvent lorsque le séchage est réalisé dans des mauvaises conditions opératoires. L’utilisation de séchoirs particuliers tels que les lits à jet coniques devrait permettre d’améliorer le séchage en terme d’efficacité et de qualité finale. L’objectif principal de cette thèse est de contribuer à mieux comprendre et modéliser le séchage de levures en lit à jet conique en utilisant une approche multi-échelles. <p>Le séchage d’un grain de levure isolé est caractérisé à l’aide d’un nouveau dispositif thermogravimétrique dans lequel il est possible de mesurer l’évolution des dimensions du grain ainsi que sa température de surface. Les résultats obtenus sont alors utilisé pour construire et valider un nouveau modèle du séchage d’un grain de levure basé sur l’existence de trois types d’eau et permettant de prédire l’évolution du contenu en eau et de la température du grain. L’analyse combinée du modèle et des résultats expérimentaux permet de mettre en avant que le rétrécissement des grains de levures au cours du séchage n’a pas d’impact significatif sur la vitesse de séchage et qu’il est essentiel de modéliser correctement la température du grain.<p>L’écoulement de solides dans le lit à jet conique est caractérisé expérimentalement au moyen de la technique de poursuite de particule radioactive (RPT). Un post-traitement des données brutes (évolution temporelle de la position du traceur) est développé pour déduire un certain nombre de paramètres liés à l’écoulement du solide :forme des régions du lit à jet (jet, anneau et fontaine), distributions de l’écoulement des solides entre les régions, distribution de temps de séjour des solides dans le lit, vitesses et débits moyens des solides, et taux de gaz dans le jet et l’anneau. Les résultats expérimentaux ont notamment permis de montrer que la forme du jet ne dépend quasiment pas de la vitesse d’injection de l’air; de même, le rapport du débit volumique de solides d’une région du lit à l’autre avec la vitesse moyenne du solide dans l’anneau donne une valeur constante pour une hauteur de lit stagnant donnée. Des corrélations empiriques sont également développées pour prédire les vitesses et débits moyens de solides ainsi que les temps de séjour moyens des solides dans les différentes régions du lit.<p>L’écoulement du gaz dans le lit à jet conique est caractérisé expérimentalement par la mesure des distributions de temps de séjour (RTD) du gaz dans le lit par l’injection et la détection d’un gaz radioactif dans le lit à jet en opération. L’existence d’un écoulement non négligeable du gaz dans l’anneau du lit est mise en évidence. Les vitesses moyennes du gaz dans le jet et l’anneau ainsi que la portion du débit total qui passe dans le jet sont déduites des courbes de RTD. Il est identifié que le gaz circule au moins deux fois plus vite dans le jet que dans l’anneau, ce qui mène à des échanges de matières entre un solide et le gaz plus intenses dans le jet que dans l’anneau.<p>Des expériences de séchage de levure sont réalisées dans un lit à jet conique afin de caractériser l’effet des conditions opératoires sur le séchage. Un nouveau modèle multi-échelles décrivant le séchage de levure en lit à jet est présenté; celui-ci est basé sur les résultats des caractérisations expérimentales et des modélisations du séchage d’un grain de levure isolé et de l’écoulement solide-gaz dans le lit à jet conique. Le modèle phénoménologique ne possède qu’un seul paramètre et permet de très bien reproduire les résultats des expériences de séchage de levure en lit à jet conique. Il tient notamment compte du fait que dans un lit à jet, la saturation de l’air en vapeur d’eau au passage du lit peut être un phénomène limitant pour la vitesse de séchage, surtout en début de séchage.<p>La caractérisation de l’évolution au cours du séchage de la capacité de la levure à dégager du CO2 dans une pâte à pain a également été réalisée pour un grain de levure isolé et pour le séchage en lit à jet conique. Des conclusions similaires sont présentées dans les deux cas. En effet, la dégradation de la levure est liée à l’enlèvement de l’eau intracellulaire (type D, fin du séchage en-dessous de contenu en eau d’environ 0,5 (d.b.)) et c’est avant tout la vitesse avec laquelle cette eau est enlevée qui contrôle la qualité finale du produit. L’enlèvement de l’eau intercellulaire (type E, début du séchage) n’a pas d’influence significative sur la dégradation de la levure. Dans tous les cas, la dégradation est amplifiée lorsque la température du solide dépasse 40°C.<p>/<p>Drying is a unit operation that is practiced since thousands of years and which for scientific knowledge is still very incomplete. However it is more and more necessary to dry « well » in order to reach an optimal combination between drying duration, consumed energy and also final product quality. This is even truer in the case of food drying involving a lot of products that are very sensitive to temperature and dehydration. Baker’s yeast often encounters a drastic decrease of its gassing power, which makes for instance inflate bread dough, when drying is operated in wrong conditions. Using special driers such as conical spouted beds should allow improving drying in terms of efficiency and final quality. The main objective of this thesis is to contribute to better understand and model Baker’s yeast drying in a conical spouted bed by using a multiscale approach.<p>Drying of a single Baker’s yeast pellet is characterised by using a new thermogravimetric set up where the evolution of the pellet dimensions and surface temperature can be measured during drying. The obtained results are then used to develop and validate a new model of the drying of a Baker’s yeast pellet. The model is based on the existence of three types of water in yeast and it allows predicting the evolution of the pellet’s moisture content and temperature during drying. The combined analysis of the model and the experimental results permits to put forward that pellet’s shrinkage during drying have no significant influence on the drying rate and that it is really essential to correctly model the pellet’s temperature.<p>Solid flow in the conical spouted bed is experimentally characterised by using a radioactive particle tracking technique (RPT). A post-treatment of rough data (time-evolution of the tracer position) is developed in order to predict a series of parameters linked to the solid flow: shape of the bed regions (spout, annulus and fountain), distributions of solid flow in the bed regions, residence time distribution of the solids in the bed, mean solids velocities and flowrates, and voidage in the spout and annulus. Experimental results allowed to show that the shape of the spout is nearly not influenced by inlet air velocity; also, the ratio of volumetric solid flowrate between the different regions of the bed and of the mean solids velocity in the annulus has a constant value for a given static bed height. Empirical correlations are also developed in order to predict the mean solids’ velocities and flowrates, and the mean residence time of the solids in each region of the bed.<p>Gas flow in the conical spouted bed is experimentally characterised by measuring gas residence time distributions (RTD) in the bed through the injection and detection of a radioactive gas tracer into the operated spouted bed. The existence of non-negligible gas flow in the annulus of the bed is highlighted. Mean gas velocities in the spout and annulus, and the part of the total gas flow going to the spout are deducted from the RTD curves. It is identified that gas moves at least twice faster in the spout than in the annulus, which leads to mass exchanges between solid and gas that are more intense in the spout than in the annulus.<p>Baker’s yeast drying experiments are done in a conical spouted bed in order to characterise the effects of operating conditions on drying. A new multiscale model, describing Baker’s yeast drying in conical spouted bed, is presented; it is based on experimental results and on the models of a single pellet drying and of gas-solid flows in the conical spouted bed. This phenomenological model has only one unknown parameter and permits reproducing the experimental results of Baker’s yeast drying in conical spouted bed. It takes into account the fact that, in a spouted bed, vapour saturation of the air during its residence time in the bed can be a limiting phenomena for the drying rate, especially in the beginning of the drying.<p>The characterisation of the evolution of the Baker’s yeast gassing power in a bread dough during the drying has also been done in the case of a single pellet drying and in the case of spouted bed drying. Similar conclusions are presented for both cases. Indeed, yeast degradation is linked to intracellular water removal (type D, end of the drying below a moisture content of around 0,5 (d.b.)) and it is mostly the rate of this water removal that controls the final quality of the product. Intercellular water removal (type E, beginning of the drying) has no significant influence on yeast degradation. In all the cases, degradation is amplified when solid temperature is higher than 40°C.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Orientadores: Osvaldir Pereira Taranto, Flavio Vasconcelos da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-07T20:04:54Z (GMT). No. of bitstreams: 1 Pavanelli_PaulaEdilene_M.pdf: 1842381 bytes, checksum: ae8746d54834e8c938141f3e78903477 (MD5) Previous issue date: 2006 / Resumo: Este trabalho apresenta o controle e monitoramento em tempo real do regime de jorro estável através do método de identificação dos regimes de contato gás-sólido por medidas de pressão no leito de jorro. O trabalho foi realizado em duas etapas: 1) identificação em tempo real dos regimes fluidodinâmicos no processo em leito de jorro baseada na análise espectral das flutuações de queda de pressão do leito e 2) controle do processo em regime estável por malha PI. O sistema constitui-se de um leito construído em acrílico com dimensões de 0,70m de altura de coluna e 0,143m de diâmetro interno, operando com três diferentes partículas, esferas de vidro (dp = 2,59mm e Pp = 2,487 g/cm3), poliestireno (dp = 2,19mm e Pp = 1,196 g/cm3) e ABS (dp = 3,08mm e Pp = 1,029 g/cm3). Determinou-se a faixa da freqüência dominante 7,2-7,9 Hz, característico do regime de jorro estável, através do algoritmo da Transformada Rápida de Fourier (FFT) para cada partícula. Todas as medidas de pressão do leito durante o processo foram coletadas pelo sistema de aquisição através da placa PCI 6024E (National Instruments) utilizando o software LabView 7.1TM. Com o intuito de controlar o regime de jorro estável no processo em leito de jorro foram definidas como variáveis controlada e manipulada a freqüência dominante do espectro de potência (Hz) e o sinal de comando para o inversor de freqüência (V), respectivamente. A freqüência dominante foi determinada pela análise espectral das flutuações de queda de pressão no leito. O sinal de comando para inversor de freqüência atuava na variável de processo vazão de ar. Aplicaram-se perturbações degrau em malha aberta na variável manipulada para determinar os parâmetros do controlador e implementou-se a malha de controle no processo. Nos experimentos em malha fechada foram aplicadas perturbações na carga como adição de partículas e alteração na posição de abertura da válvula de ar de entrada no leito afim de testar o desempenho do controlador. Os resultados obtidos mostraram que o controlador PI manteve o sistema operando em regime estável mesmo quando aplicadas perturbações na carga, atingindo assim o objetivo do trabalho proposto / Abstract: This work describes the control and on line monitoring of the spouted bed steady regime using the gas-solid contact regimes identification method by pressure measurements. The work presents two main features: 1) the on line identification of fluid dynamic regimes in the spouted bed process based in the spectral analysis of the pressure fluctuations and 2) the process control using PI controllers. Experiments were performed in an acrylic cylindrical column 0.70m high and with 0.143m of internal diameter. The bed was made of three different particles: glass spheres (dp = 2.59mm and Pp = 2.4873 g/cm3), polystyrene (dp = 2.19mm and Pp = 1.1962 g/cm3) and ABS (dp = 3.08mm and p = 1.0286 g/cm3). The dominant frequency band was determined: 7.2-7.9 Hz for steady regime, through the algorithm of the Fast Fourier Transform (FFT), for each particle. All the measurements of pressure during the process were collected by a data acquisition system and using software LabView 7.0TM. The procedure to control the steady regime in the spouted bed process was: define the dominant frequency as the controlled variable and the signal of command for frequency inverter as the manipulated variable. The dominant frequency was determined by the spectral analysis of pressure fluctuations in the spouted bed. The command signal for frequency inverter affected the air flow variable. Step disturbances were applied in open loop in the manipulated variable to determine the parameters of the controller and control system was implemented in the process. Step disturbances like addition of particles in the spouted bed and change the position of opening of the air valve were applied in closed-loop to test the performance of the controller. The results show that PI controller was able to maintain the system operating in steady regime when disturbances were applied in the feed stream, which was the goal of this research / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Orientadores: Marcos José Salvador, Carlos Amilcar Parada / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-22T07:08:14Z (GMT). No. of bitstreams: 1 Teixeira_AlyneGrasiela_M.pdf: 2262328 bytes, checksum: 66c66f7a3fa3f4137fae0f3a0d3fe076 (MD5) Previous issue date: 2013 / Resumo: Este estudo teve por objetivo a preparação de extratos padronizados (fluidos e secos em leito de jorro) das folhas de Maytenus ilicifolia (Celastraceae), a elaboração de formulações tópicas (creme, gel e gel-creme) contendo os extratos ativos, a caracterização química dos extratos por CLAE-DAD/ESI-MS e UPLC-MS e a avaliação in vitro da atividade antioxidante utilizando ensaios indiretos mediados pela transferência de elétrons, tais como redução do radical DPPH e Folin-Ciocalteu (FCR) e ensaios diretos baseados em mecanismos de transferência de hidrogênio, tais como ensaio beta-caroteno e ORACFL. O extrato fluido concentrado foi submetido ao processo de secagem por leito de jorro, utilizando como adjuvante de secagem o dióxido de silício coloidal (Tixosil 333®, Rhodia, São Paulo, Brasil) na proporção de 40, 60 e 80% em relação ao total de sólidos do extrato fluido e a capacidade antioxidante dos extratos foram analisados. Observou-se que tanto o extrato fluido concentrado, como os extratos secos apresentaram atividade antioxidante in vitro, porém os extratos secos mostraram atividade mais intensa, com destaque para o extrato seco com 40% de dióxido de silício coloidal (Mi40). A análise dos constituintes químicos presentes nos extratos ativos utilizando CLAE-DAD/ESI-MS e UPLC-MS sugeriu a presença de flavonols (aglicona e O-heterosídeos) e catequinas, sendo quantificados por UPLC-MS a (+)-catequina, (-)-epicatequina e rutina que apresentaram promissora atividade antioxidante nos ensaios DPPH e ORACFL. Os extratos (fluidos e secos em leito de jorro) mostraram considerável conteúdo de constituintes fenólicos (2,15 a 3,72 mg de GAE/kg), assim como atividade antioxidante elevada nos dois ensaios (IC50 entre 7,98 e 51,79 ?g/mL no DPPH e capacidade antioxidante entre 5828,3 e 15249,3 ?mol de TE/g de extrato no ORACFL). Os resultados demonstraram que, de maneira geral, a atividade antioxidante e os perfis cromatográficos dos extratos secos não foram consideravelmente afetados pela operação de secagem em leito de jorro, mas os melhores resultados quanto à atividade antioxidante e maior quantidade de (+)-catequina, (-)-epicatequina e rutina foram verificados no extrato seco Mi40 com menor percentagem de adjuvante de secagem. Visando avaliar o comportamento dos extratos ativos em formulação farmacêutica e com o propósito de avaliar a possibilidade de uma nova aplicação para o extrato hidroalcoólico das folhas de M. ilicifolia em uso tópico, os extratos com promissora atividade antioxidante foram incorporados em formulações tópicas (creme, gel e gel creme), estabelecendo-se um estudo comparativo da atividade antioxidante dos extratos (fluidos e secos em leito de jorro) e destes nas formulações elaboradas. Os melhores resultados observados em termos de atividade antioxidante foram para as formulações creme, gel e gel creme contendo como ativo o extrato seco Mi40 a 10% / Abstract: This study aimed to the preparation of standardized fluid and spouted bed-dried extracts from the leaves of Maytenus ilicifolia, preparation of topical formulations (cream, gel and gel-cream) containing the active extracts, chemical characterization of the extracts by HPLC-DAD/ESI-MS and UPLC-MS and in vitro evaluation of antioxidant activity assays using indirect mediated electron transfer, such as reduction of DPPH and Folin-Ciocalteu (FCR) and direct assays based on hydrogen transfer, such as beta-carotene assay and ORACFL. The concentrate fluid extract was subjected to spouted bed drying, using as drying adjuvant, the colloidal silicon dioxide (Tixosil 333®, Rhodia, Sao Paulo, Brazil) in a proportion of 40, 60 and 80% in relation to total solids of the fluid extract, and the antioxidant capacity of the extracts was analyzed. It was observed that both the concentrated fluid extract, such as spouted bed-dried extracts showed antioxidant activity in vitro, but the dried extracts showed the strongest activity, with emphasis on the dried extract with 40% colloidal silicon dioxide (Mi40). The analysis of chemical constituents present in the active extracts using HPLC-DAD/ESI-MS and UPLC-MS suggested the presence of the flavonols (aglycone and O-glycosides) and catechin. Using UPLC-MS analysis were quantify the (+)-catechin, (-)-epicatechin and rutin that showed antioxidant activity in the DPPH and ORACFL assays. The fluid and spouted bed-dried extracts showed significant content of phenolic constituents (2.15 to 3.72 mg of GAE kg) and high antioxidant activity in both methods (IC50 between 7.98 and 51.79 ?g/ mL in DPPH and antioxidant capacity between 5828 and 15249 micromol TE/g extract in ORACFL). The results showed that, in general, the antioxidant activity and the chromatographic profiles of the dried extracts were not significantly affected by the drying operation in spouted bed, but the best results for antioxidant activity and higher amount of (+)-catechin, (-)-epicatechin and rutin were observed in the dry Mi40 with lowest percentage of drying adjuvant. To evaluate the behavior of active extracts in pharmaceutical formulation, the extracts with antioxidant activity have been incorporated into topical formulations (cream, gel cream and gel), setting up a comparative study of the antioxidant activity of the fluid and spouted bed-dried extracts and these in developed formulations. The best results were observed in terms of antioxidant activity for formulations cream, gel and gel cream containing the dried extract Mi40 as active at 10% / Mestrado / Fármacos, Medicamentos e Insumos para Saúde / Mestra em Biociências e Tecnologia de Produtos Bioativos

High temperature gas cooled nuclear reactors often make use of Tristructural Isotropic (TRISO) coated fuel particles. In these particles, a layer of silicon carbide plays the key role of providing mechanical strength and acting as a diffusion barrier so preventing the release of fission products. TRISO particles are produced by a chemical vapor deposition (CVD) process in a spouted bed coater. Operating conditions of chemical vapor deposition processes are known to influence the properties of the deposited material. In the case of silicon carbide deposited by pyrolysis of methyltrichlorosilane (MTS) in a hydrogen atmosphere, process parameters that may influence the properties of the silicon carbide deposited include deposition temperature, MTS concentration and hydrogen flow rates. In this study the coating process was investigated using a laboratory scale spouted bed CVD coater. In all the test work conducted, carbon coated zirconia particles were used as a starting material. Only silicon carbide was deposited during these trials. Process parameters investigated were temperature, MTS concentration and hydrogen flow rate. The range investigated was 1250 °C to 1550 °C for temperature, 0.5 % to 2.5 % for MTS concentration and 10.0 l.minute-1 to 15.0 l.minute-1 for hydrogen flow. This covered the range that is typically used for small-scale production coaters. Two different gas inlet configurations, a conventional water cooled inlet and an inlet without any cooling, were used in the investigation. Properties of the coating process, such as the deposition rate and coating efficiency, as well as material properties were measured. Material properties investigated included: density, crush strength, micro-hardness, fracture toughness, nano-hardness, Young’s modulus, elemental composition, phase composition and microstructure. It was found that, of the variables investigated, temperature had the strongest effect while hydrogen flow rate had the least effect on material properties. There was considerable variability in all measured parameters; this introduced considerable uncertainty into the predicted effects of process conditions on material properties. / Thesis (PhD)--University of Pretoria, 2012. / Materials Science and Metallurgical Engineering / unrestricted

[EN] The aim of the present PhD Thesis is to define, develop and evaluate a methodology for an improved and more sustainable management of waste, in particular agricultural residues, turning them into a new source of energy and into added value products. Particular attention is paid to the use of rice straw as an energy vector and as a precursor of silica-based compounds. The recovery of energy was carried through the gasification of biomass within a Spouted Bed Reactor. An initial definition of the main physico-chemical and thermal properties of the feed was performed. The design and operational parameters of the reactor were set according to the characteristics of the biomass. Due to the particular configuration of the reactor, its fluid dynamic properties were analysed in detail in a lab scale unit. The conditions of stability of the reactor and the prevention of segregation phenomena were studied. A scaled-up unit was used for the evaluation of the reactions of gasification of the different residues. The behaviour of the system was modelled at both fluid dynamic and thermo-chemical levels with the aid of different commercial softwares. Finally, a material valorisation was performed. The extraction of silica from the ashes resulting from the thermo-chemical process was studied. Their application as adsorbent materials for the removal of nitrates in water was discussed. / [ES] El objetivo de la presente tesis doctoral es definir, desarrollar y evaluar una metodología eficiente de gestión de residuos, en particular agrícolas, para convertirlos en una nueva fuente de energía y en productos de valor añadido. Se estudia con especial atención el uso de la paja de arroz como vector energético y como precursor de productos basados en sílice. Las reacciones de recuperación energética se han llevado a cabo a través de la gasificación de la biomasa en reactores de tipo Spouted Bed. Para ello, se han definido las propiedades físico-químicas y de comportamiento térmico de los residuos estudiados. Los parámetros de diseño y operación del reactor han sido definidos de acuerdo a las características del material tratado. Debido a la particular configuración del reactor, las propiedades fluido- dinámicas del sistema se han analizado en detalle en una unidad a escala de laboratorio. En ella se han estudiado las condiciones de estabilidad del reactor y aquellas que previenen los procesos de segregación. Se ha utilizado una unidad escalada a dimensiones de planta piloto para llevar a cabo las pruebas de gasificacion de los residuos. El comportamiento del reactor se ha modelado tanto a nivel fluido dinámico como a nivel térmico mediante el uso de diversos códigos comerciales de simulación. Finalmente, se ha realizado una valorización material basada en la extracción de sílice de las cenizas resultantes del proceso de valorización térmica. Por último, se han realizado pruebas preliminares de la posible aplicación de dicha sílice en procesos de adsorción de nitratos presentes en agua. / [CA] L'objectiu de la present tesi doctoral és definir, desenvolupar i evaluar una metodologia eficient de gestió de residus, en particular agrícoles, per convertir-los en una nova font d'energia i en productes de valor afegit. S'estudia amb especial atenció l'ús de la palla d'arròs com a vector energètic i com a precursor de productes basats en sílice. Les reaccions de recuperació energètica s'han dut a terme a través de la gasificació de la biomassa en uns reactors de tipus Spouted Bed . Per això, s'han definit les propietats físico-químiques i de comportament tèrmic dels residus estudiats. Els paràmetres de disseny i operació del reactor han estat definits d'acord a les característiques del material tractat. A causa de la particular configuració del reactor, les propietats fluid - dinàmiques del sistema s'han analitzat amb detall en una unitat a escala de laboratori. S'hi han estudiat les condicions d'estabilitat del reactor i aquelles que prevenen els processos de segregació. S'ha utilitzat una unitat escalada a dimensions de planta pilot per dur a terme les proves de gasificació dels residus. El comportament del reactor s'ha modelat tant a nivell fluid dinàmic com a nivell tèrmic mitjançant l'ús de diversos codis comercials de simulació. Finalment, s'ha realitzat una valorització material basada en l'extracció de sílice de les cendres resultants del procés de valorització tèrmica. Per ùltim, s'han realitzat proves preliminars de la possible aplicació d'aquesta sílice en processos d'adsorció de nitrats presents en aigua. / Moliner Estopiñán, CE. (2016). Valorisation of Agricultural Residues [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68495 / TESIS / Premios Extraordinarios de tesis doctorales

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