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Desempenho de meios filtrantes na remoção de partículas nanométricas de aerossóis
(Universidade Federal de São Carlos, 2009-03-12) Feitosa, Natália dos Reis; Coury, José Renato; https://lattes.cnpq.br/8001225323703772
The interest of studies on the development of techniques for removal of particles in the nanosized scale was promoted by concern about air quality and human health, in addition to restrictions on the control of ultrafine particles, wich are more intransigent by environmental laws. Additionally, the increasing application of nanoparticles in various areas of science and technology has stimulated the development of studies on the subject. Amongst the several equipments capable to operate with efficiency on the particle removal, the fibrous filters are distinguished. Such filters are, in principle, capable to act in sub-micrometer scale, but there is little information about its performance in the nano-sized scale. In this work the performance of a polyester filter, of a HEPA cellulose filter, of a quartz microfiber filter and also of cylindrical filtering membrane, provided by Pam-Membranas Seletivas Ltda, were evaluated. The experimental system was able to simulate a contamination of nanometric particles in a stream of ultrapure air, with the aim of investigating the efficiency of filter media in the removal of nanoparticles. The test aerosol was constituted by NaCl polydisperse nanoparticles, ranging from 6.15 to 245.1 nm. The performance of the filter was evaluated through the analysis of the efficiency of removal of nanoparticles, for the counting of particles before and after to cross the filtering media, using the electric mobility technique. This procedure was performed using the TSI Scannig Mobility Particle Sizer (SMPS), model 3936, which provides the particles concentration, in size range. The results, in general, have showed that the filter media loses efficiency with the increasing filtration velocity and increasing particle size, in the ranged studied, indicating the typical behavior of difusional mechanism. The filtering membranes have showed better performance in the removal of particles unlike the others filters analysed there was no tendency to increase the penetration of particles with increasing the velocity of filtration or particle diameter.
Fluidodinâmica de leitos fluidizados e vibrofluidizados operando com partículas planas
(Universidade Federal de São Carlos, 2009-03-12) Lima, Renata de Aquino Brito; Ferreira, Maria do Carmo; https://lattes.cnpq.br/7070885875161111; https://lattes.cnpq.br/5050641829811424
The use of fluidized beds as a unit operation for drying of particulate materials is common in industrial processes. However, most works published in the literature, focus the drying of uniform particles, in a narrow range of size distribution. The appealing characteristics of fluidization for drying led some authors to suggest its use for drying of particles of low sphericity (_ < 0.5), which are out of the range of usually fluidized particles. Aiming to contribute for the assessment of fluid dynamic behavior of this class of particles, in the present work was investigated the fluidization of flat particles, with _ varying from 0.063 up to 0.574, bulk density (b) from 0.038 to 0.923 g.cm-3 and ratios Ap/Vp (superficial area to volume) between 12 and 226 cm-1. The essays were carried out in a fluidized bed with a height of 0.30 m, and cross section of 0.20 m x 0.11 m, which could be also operated as a vibro-fluidized bed. The tests aimed to investigate the effects of size, shape and specific mass of particles in fluidization and fluid-dynamic behavior of such particles. Vibro-fluidization was tested as an alternative to improve fluidization patterns. Fluid dynamic characteristic curves of P as a function of air velocity were also obtained for the fixed beds in order to evaluate the resistive parameters of these beds as a way to quantify their resistance to the air flow. Tests were conducted using 14 different particulate materials, 9 of them being natural particles (leafs, seeds and cereals) and 5 being manufactured particles. The use of manufactured particles allowed to minimize size distribution and shape variations that are inherent to the natural products, avoiding interfering effects that might complicate an initial analysis. The fluid dynamic behavior was investigated through experimental curves of _P versus U and visual observation of the beds. The results showed that only the particles with sphericity around 0.5 and low ratios Ap/Vp presented homogeneous fluidization patterns, similar to the observed in fluidization of conventional particles. In fluidization of particles with _ 0.228 were observed poor fluidization patterns and highly non-homogeneous beds. The values of bulk porosity of static beds were higher than 80% for the beds constituted by leaves, and stayed between 30 and 70% for the remaining particles. The values of _b and _mf tended to decrease as the values of Ar increased, while Pmf tended to increase and Umf showed no clear dependence of Ar. The use of vibration did not reduce significantly the values of Umf and did not improve much the quality of fluidization as well, excepting for the particles of higher sphericity (around 0.5). But for some conditions obtained as fluidizing rigid particles, with large superficial areas, the vibration did provoke the alignment of particles into the beds, leading to a packing in which the contact area between particle and fluid is optimized, which might be interesting as drying applications are concerned.
Hidrodinâmica e transferência de oxigênio em três biorreatores Airlift de circulação interna geometricamente semelhantes
(Universidade Federal de São Carlos, 2009-03-12) Cerri, Marcel Otávio; Badino Júnior, Alberto Colli; https://lattes.cnpq.br/7999741482353508
Internal-loop airlift reactors (ALR) are a special class of pneumatic reactors. The use of this type of reactor has been attractive for chemical and biological reactions because of their simple construction without moving parts and low energy costs when compared with stirred tank reactors. In the present work, a study related to hydrodynamic and oxygen transfer in three geometrically similar scales of internal tube airlift bioreactors (2, 5, and 10 L) was conducted. The aim was to obtain useful information for further studies related to the scale-up of such reactor configuration. The gas hold-up, circulation time, mixing time, volumetric oxygen transfer coefficient, average shear rate, and mean bubble diameter of the air bubbles were evaluated in order to achieve a better comprehension of the hydrodynamic and mass transfer in airlift bioreactors. Values of gas hold-up and oxygen transfer were obtained for the three scales of ALR utilizing eight Newtonian and five non-Newtonian fluids. The superficial gas velocity and liquid viscosity had opposite effects with same order of magnitude. General correlations based on the dimensional analysis were proposed to relate global gas hold-up (ε) and volumetric oxygen transfer coefficient (kLa) to the geometrical parameters of the system, physical properties of the Newtonian and Non-Newtonian fluids, and superficial gas velocity. The correlations presented excellent fittings to the experimental data obtained for the three scales of ALR. The influence of the reactor internal diameter on the volumetric oxygen transfer coefficient was considered positive showing that in largerscale reactors an appropriate oxygen transfer can be reached under smaller aeration conditions. New methodologies to estimate the mean bubble size (dB) and average shear rate ( m γ& ) in the three scales of ALR were proposed. The semi-theoretical method to estimate dB was based on Higbie´s penetration theory using experimental data of ε and kLa. The methodology for evaluating the m γ& in ALRs was developed for non-Newtonian systems. The volumetric oxygen transfer coefficient was chosen as the appropriate characteristic parameter. The results of dB and m γ& obtained by the proposed methods are in agreement with the experimental values found in the literature. The effect of shear rate on clavulanic acid (CA) production by Streptomyces clavuligerus was examined both in a stirred tank bioreactor (STR) of 4 L and in an ALR of 6 L working volume, respectively, based on experimental data of the literature. Results showed that CA production was positively affected by shear conditions. In addition, the ALR presented values of m γ& higher than those found in a STR operated under the same oxygen transfer conditions.
A representação literária da educação brasileira na transição do século XIX para o século XX : a perspectiva de José Lins do Rêgo
(Universidade Federal de São Carlos, 2009-03-12) Carlos, Erika Michela; Bittar, Marisa; https://lattes.cnpq.br/6727773492434012
This study is about the literary works by José Lins do Rêgo. Its objective is to apprehend the Brazilian society at the transition moment between the 19th and 20th centuries. As a consequence, it also reveals the author s view regarding education in Brasil, which the author had access to. The Literature was approached as an auxiliary source to the History of Education, with the intention of interpreting and explaining the multiple and complex expressions that resulted from the dialectic interactions and educational actions and Brazilian society. Therefore the literary works by José Lins do Rêgo are part of the primary sources, more specifically those that belong to the Sugar Cane Cycle - Ciclo da Canade- Açúcar: Menino de engenho, Doidinho, Banguê, O moleque Ricardo, Usina and Fogo morto. Due to the fact that theses literary works present particular potential for the study of the history of Brazilian education the choice is justified. Some extracts were selected, which portray the thematic Brazilian education in the transition between centuries. These extracts were analyzed considering as reference educational historiographical works. Such analysis was based on a Marxist view where the social environment and textual structure influence each other in constructing the works in a dialectic movement which understand art and society. It was possible to conclude through research that a negative view of education can be perceived: elitist education, reserved only for the sons of the elite, which excluded the poor boys and girls. The ladies from the elite were educated to guarantee social attributes, which prepared them to take on a social function, that is, to be wives and mothers. Therefore, José Lins do Rêgo presents a posthumous perspective of the Brazilian education within the context studied, which seems to be influenced by demands of changes in the school. This period is marked by other aspects, such as the emergence of the Manifest - Manifesto dos Pioneiros da Escola Nova.