Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-19T11:09:50Z No. of bitstreams: 1 SÍLVIO ALVES MOREIRA - TESE (PPGEP) 2013.pdf: 2013926 bytes, checksum: 3885f27bb2f69434b23233a4b6146158 (MD5) / Made available in DSpace on 2018-07-19T11:09:51Z (GMT). No. of bitstreams: 1 SÍLVIO ALVES MOREIRA - TESE (PPGEP) 2013.pdf: 2013926 bytes, checksum: 3885f27bb2f69434b23233a4b6146158 (MD5) Previous issue date: 2013-02-02 / Capes / No planeta em que vivemos, hoje com mais de sete bilhões de habitantes, é necessário rever conceitos para melhorar o mecanismo de produção e conservação de alimentos e evitar altos custos com tratamento de efluentes gerados por desperdício de matéria. Um exemplo significativo é o caso dos abatedouros de animais, especialmente bovinos, que lançam o sangue nos corpos de água causando poluição ambiental. Para minimizar estes impactos, foi desenvolvido um sistema automatizado de secagem por atomização para produção de proteína animal com o aproveitamento do sangue bovino. O sistema de secagem automático, construído com materiais de baixo custo e fácil aquisição, em módulos com possibilidade de alterações na configuração, apresenta capacidade de evaporação de 2,6 kg.h-1 de água e facilidade na operação. Os ensaios preliminares forneceram informações para atuação nas principais causas da baixa eficiência no processo de secagem por atomização. Com as ações adotadas foram obtidos resultados satisfatórios para a proposta do projeto. As principais características do sangue em pó obtido foram: boa fluidez; granulometria adequada à reconstituição e condições para armazenamento sem a petrificação do produto com a conservação da coloração. O sangue em pó com umidade em base úmida de 4,7% apresenta uma eficiência de produção de 67% e um rendimento de coleta de pó de 77%. A principal variável controlada foi a temperatura de saída, pela manipulação da vazão da suspensão, que têm influência direta na umidade do pó obtido. / Nowadays, with more than seven billion inhabitants living in the planet it is necessary to revise concepts to improve efficiency in the mechanisms of food production within the food chain and avoid high costs of wastewater treatment and high concentrations of organic matter. A significant example is the case of animals’ slaughterhouses, especially the bovine, that shed the blood into water bodies causing environmental pollution. To minimize these effects, an automated spray drying system was developed for animal protein production making use of the bovine blood. The automatic drying system, built with materials of cost low and acquisition easy in modules with a possibility of changes in layout, points out water evaporation capacity of 2.6 kg.h-1 and operation ease. Preliminary runs provided information to operate the main causes of low efficiency in the process of spray drying process. With the adopted actions satisfactory results were obtained for the project proposes. The main results were a blood powder with a particle size suitable for reconstitution, good fluidity and storage conditions for the product preserving its color without petrifying it. The blood powder with moisture content on a wet basis of 4.7% has a production efficiency of 67% and a powder collection efficiency of 77%. The main controlled variable was the output temperature through the suspension flow rate manipulation, which has a direct influence on the moisture content of the obtained powder.

Le séchage est une opération incontournable pour la valorisation énergétique des boues résiduaires. La flexibilité pour ajuster la teneur en matière sèche finale de la boue est un critère important pour le choix d'une technologie. Cet objectif est difficile à atteindre pour les sécheurs à palettes. La modélisation du processus est alors essentielle. Malheureusement, le comportement rhéologique des boues est complexe et la mécanique des fluides numérique est hors de portée. La notion de Distribution des Temps de Séjour est employée ici pour caractériser l'écoulement. Un protocole fiable et reproductible a été établi et mis en œuvre sur un pilote de laboratoire. Des injections Dirac d'oxyde de titane et de sels métalliques, avec la spectrométrie de fluorescence X comme méthode de détection, ont été employées pour caractériser les DTS du solide anhydre et de la boue humide. Pré-Mélanger la boue pâteuse, pour disperser le traceur par exemple, modifie la structure du matériau. Ceci a été mis en évidence par des mesures de distribution en taille des particules et par des caractérisations rhéologiques. Cependant, des expériences de séchage en batch ont montré que ce pré-Mélange n'a aucune influence sur la cinétique et sur la phase plastique. Nous avons montré que le solide anhydre et le solide humide s'écoulent de la même manière. Une seconde méthode, basée sur une détection par conductimétrie, a alors été développée. Plus facile à mettre en œuvre et moins onéreuse, cette méthode s'avère tout aussi fiable que la première. L'influence de la durée de stockage de la boue, avant séchage, a été évaluée. Le temps de séjour de la boue dans le sécheur double quand la durée de stockage passe de 24h à 48h. Finalement, un modèle d'écoulement, basé sur la théorie de chaînes de Markov, a été développé. L'écoulement du solide anhydre est décrit par une chaîne de n cellules parfaitement mélangées, n correspondant au nombre de palettes. Les probabilités de transition entre les cellules sont régies par deux paramètres : le ratio de recyclage interne, R, et la masse de solides retenus, MS. R est déterminé par la relation de Van der Laan et MS est identifié par ajustement du modèle aux données expérimentales. Le modèle décrit de manière satisfaisante les DTS. La masse de solides retenus identifiée est toujours plus faible que la quantité mesurée expérimentalement. Une partie de la boue, collée aux parois du sécheur et au rotor, agit comme un volume mort. / Drying is an unavoidable operation prior to sludge valorization in incineration, pyrolysis or gasification. The flexibility to adapt the solid content of the dried sludge to the demand is a major requirement of any drying system. This objective is difficult to reach for paddle dryers. Modeling the process is thus essential. Unfortunately, sludge rheological behavior is complex and computational fluid dynamics is out of reach for the time being. The concept of Residence Time Distribution (RTD) is used here to investigate sludge flow pattern in a paddle dryer. A reliable and reproducible protocol was established and implemented on a lab-Scale continuous dryer. Pulse injections of titanium oxide and of salt metals, with X-Ray fluorescence spectroscopy as detection method, were used to characterize the RTD of anhydrous solid and wet sludge, respectively. Premixing the pasty sludge, for tracer powder dispersion for instance, changes the structure of the material. This was highlighted through the measurements of particle size distributions and characterization of rheological properties. However, drying experiments performed in batch emphasized that premixing does not have any influence on the kinetic and the sticky phase. The RTD curves of the anhydrous solid are superimposed on those of the moist sludge. Consequently, a simpler protocol, based on pulse injection of chloride sodium and offline conductivity measurements, was established. Easier to implement in industry and cheaper, this method proves to be as reliable as the first one. The influence of storage duration prior to drying was assessed. The mean residence time doubles when the storage duration changes from 24h to 48h. Finally, a model based on the theory of Markov chains has been developed to represent the RTD. The flow of anhydrous solids is described by a chain of n perfectly mixed cells, n corresponding to the number of paddles. The transition probabilities between the cells are governed by two parameters: the ratio of internal recirculation, R, and the solids hold-Up, MS. R is determined from the Van der Laan's relation and MS is identified by fitting the model to the experimental RTD. The model describes the flow pattern with a good accuracy. The computed hold-Up is lower than the experimental one. Part of the sludge is stuck to the walls of the dryer, acting as dead volumes in the process.