Estudo da eficiencia de separação em uma coluna de discos rotativos perfurados

Orientador: Elias Basile TambourgiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaResumo: Extratores líquido ¿ líquido com discos rotativos tem sido utilizados nos mais diversos setores industriais. Estes extratores, também podem ser utilizados como alternativa tecnológica para processos convencionais de separação líquido ¿ líquido, dos quais podemos citar a purificação o antibióticos e do ácido fosfórico. Produzido através do ataque da rocha fosfática com ácido clorídrico. Com objetivo de obtermos experimentos comparativos das condições de inundação do extrator utilizando sistema bifásico, com transferência de soluto entre as fases, e estabelecermos as condições de transferência de massa no extrator de discos rotativos perfurados foram realizados experimentos com variações na geometria e nas condições operacionais do extrato. As variações estudadas na geometria do extrator foram o número de discos rotativos e a área livre de escoamento, as variações operacionais foram a velocidade de rotação e a relação entre as vazões das fases contínua e dispersa. O sistema adotado foi água ¿ n ¿ butanol ¿ ácido acético. Foram realizadas comparações entre os resultados obtidos experimentalmente com os resultados obtidos por correlações propostas por diversos outros pesquisadores para a velocidade característica, verificações da região de escomento em função da velocidade de rotação e foi proposta uma correlação para a determinação da eficiência de separação no extrator utilizado. Observou-se que o escoamento no interior do extrator é do tipo toroidal, que boas eficiências de separação foram obtidas mesmo a baixas velocidades de rotação dos discos e a correlação obtida descreveu os experimentos com um erro médio de 5%Abstract: : Rotary disc extractors have been utilized in different industrial sectors. Nevertheless this extractor can be used as technological alternative for many others conventional process of liquid ¿ liquid separation. Purification of antibiotics and fosforic acid are important examples of this used. The fosforic acid can be produced by the attack of phosfatic rock with chloridric acid. In an attempt to realize comparative experiments of flooding conditions, using bifase system with solute transport between fases and establish mass transfer conditions. Experiments were carried out at different operations conditions and extractor geometries. The different geometries of the rotary disc extractor used were, free area for flow and number of rotary disc. The differents operational conditions used were, disc rotating velocity and rate of fase¿s flow, continue and dispersed fases. The system utilized was water ¿ n-butanol ¿ acetic acid. The used solute substance was acetic acid. Comparactions of experimental results with results by correlations construct by other workers for characteristic velocity and verifications of flow region, how rotary velocity function, were realized. Also, a separation efficient correlation was construct to describe the studied extractor. The flow in the P.R.D.C. extractor is toroidal pattern, good separation efficiency have been observed and the observed correlation described the experimental results with 5% differenceMestradoMestre em Engenharia Químic

New Approaches to Preparation of SnO2-Based Varistors — Chemical Synthesis, Dopants, and Microwave Sintering

Tin oxides have applications such as sensors, solar cells, transistors, and varistors, which are being studied to replace ZnO varistors due to similar electrical properties, simpler microstructure, no formation of secondary phases, and lower concentration of agent modifiers to promote the varistor characteristics and densification. Varistors are ceramic with a high concentration of structural and electronics defects. The type and the amount of defects are related with agent modifiers and processing steps employed. The study in materials processing aims to improve the ceramics properties. Chemical synthesis ensures the homogeneous distribution of dopants used to promote electrical and structural properties. Microwave sintering appears as processing to optimize time and sintering temperature. Varistor application is linked to its breakdown voltage, which should be larger than the operating voltage. In an operating range of 1 kV to 1 MV, the varistors are used in electricity transmission networks. In a range of 24–1000 V, the application occurs in electronics and appliances and in a range smaller than 24 V, as protective of automotive electronics and computers. This chapter aims to provide information on new processing steps for the production of SnO2 varistors and to show the possibility to get electrical properties with non-ohmic characteristic for technological applications

IDENTIFICAÇÃO E CARACTERIZAÇÃO DE PONTOS DE CAPTAÇÃO DE ÁGUA SUPERFICIAIS EM ÁREAS RURAIS DO MUNICÍPIO DE VIDEIRA-SC

Entre os usos prioritários para a água está a dessedentação humana e animal. Na área rural o método para obtenção de água é através de nascentes ou poços artesianos. Foi feito um estudo em 2015 no município de Videira/SC para avaliar a qualidade microbiológica e físico-química da água de 13 nascentes em propriedades da área rural, das quais a água era utilizada para consumo humano. Para tal foi utilizado o Índice de Qualidade da Água – IQA, que permite a classificação da água em ótima qualidade (100 pontos) a péssima (0 pontos). As análises foram realizadas por meio de amostras coletadas de junho a novembro de 2015, onde se avaliaram nascentes com sistema caxambu e poços escavados. Das amostras, 12 obtiveram qualidade boa e uma ficou com ótima qualidade. As variações entre as amostras estudadas foram grandes, o que provavelmente se deu devido a disposição geográfica dos pontos, do tipo de fonte utilizada (poço escavado ou caxambu), e das características ambientais encontradas. Os parâmetros que mais influenciaram o IQA foram: pH, coliformes fecais, fósforo, sólidos totais e oxigênio dissolvido. Pelos resultados analisados percebe-se que poderia haver uma melhor qualidade destas águas, principalmente nos padrões microbiológicos. A utilização de técnicas inadequadas no manejo das nascentes e atividades antrópicas ao entorno são fatores proponderantes na qualidade destas águas. Promover a preservação de mata ciliar e o isolamento das áreas de nascentes, bem como evitar o escoamento superficial são as soluções apresentadas para recuperação destas fontes de água. Palavras-chave: Nascentes. Sistema caxambu. Índice de qualidade da água

Value flow structure and analysis to support Lean initiatives in surgical centers

Lean in hospitals can provide expressive results and benefits for several stakeholders. In these settings, Lean introduction in surgical centers could support improvements, such as staff and patient’s satisfaction increase and reduction of non-value adding time, such as late starts and waiting times for surgeries. To achieve this, Value Stream Mapping (VSM) can be seen as a robust Lean tool, which could support process mapping and identification of wastes and their sources and enable means to prioritize improvements in healthcare process flows. In this paper, a VSM structure for surgical centers is presented in three phases, aiming to identify existing processes and wastes, and suggest improvements based on Lean practices. To support the proposed tool, a literature review of similar approaches was conducted and a case study in a Brazilian hospital was developed, in order to map the surgical center’s processes and exemplify the proposed VSM. This case study also provided practical examples about the VSM introduction and analyzed aspects such as a value aggregation index for the process and the comparison of the proposed tool and other papers in the literature. Based on the proposed approach, it is expected that practical and theoretical studies could use a VSM approach to plan and execute improvement projects in surgical centers and hospitals

A review of soil NO transformation: associated processes and possible physiological significance on organisms

NO emissions from soils and ecosystems are of outstanding importance for atmospheric chemistry. Here we review the current knowledge on processes involved in the formation and consumption of NO in soils, the importance of NO for the physiological functioning of different organisms, and for inter- and intra-species signaling and competition, e.g. in the rooting zone between microbes and plants. We also show that prokaryotes and eukaryotes are able to produce NO by multiple pathways and that unspecific enzymo-oxidative mechanisms of NO production are likely to occur in soils. Nitric oxide production in soils is not only linked to NO production by nitrifying and denitrifying microorganisms, but also linked to extracellular enzymes from a wide range of microorganisms. Further investigations are needed to clarify molecular mechanisms of NO production and consumption, its controlling factors, and the significance of NO as a regulator for microbial, animal and plant processes. Such process understanding is required to elucidate the importance of soils as sources (and sinks) for atmospheric NO

Effect of atmosphere and dopants on sintering of SnO2

Tin oxide is an n type semiconductor material with a high covalent behavior. Mass transport in this oxide depends on the surface state promoted by atmosphere or by the solid solution of aliovalent oxide doping. The sintering and grain growth of this type of oxide powder is then controlled by atmosphere and by extrinsic oxygen vacancy formation. For pure SnO2 powder the surface state depends only on the interaction of atmosphere molecules with the SnO2 surface. Inert atmosphere like argon or helium promotes oxygen vacancy formation at the surface due to reduction of SnO2 to SnO at the surface and liberation of oxygen molecules forming oxygen vacancies. As a consequence surface diffusion is enhanced leading to grain coarsening but no densification. Oxygen atmosphere inhibits SnO2 reduction by decreasing the surface oxygen vacancy concentration. Addition of dopants with lower valence at the sintering temperature creates extrinsic charged oxygen vacancies that promote mass transport at the grain boundary leading to densification and grain growth of this polycrystalline oxide

Sintering of tin oxide using zinc oxide as a densification aid

The physicochemical electronic characteristics of SnO2 render it useful in many technical applications, including ceramic varistors, stable electrodes used in electric glass-melting furnaces and electrometallurgy of aluminum, transparent windows and chemical sensors. The use of ZnO as a sintering aid was explored in this study to obtain SnO2 as a dense ceramic. Compacts were obtained by mechanical mixing of oxides, isostatic pressing at 210 MPa and sintering in situ inside a dilatometer at heating rates of 10degreesC/min. The grain size and microstructure were investigated by scanning and transmission electron microscopy (SEM/TEM). The phases and chemical composition were analyzed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that ZnO acts as a densification aid for SnO2, improving its grain growth with additions of up to 2 mol%. ZnO forms a solid solution with SnO2 UP to 1 mol%, above which SnZnO3 precipitates in the grain boundary, potentially inhibiting shrinkage and grain growth. (C) 2004 Kluwer Academic Publisher