Made available in DSpace on 2014-10-09T12:40:50Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:54Z (GMT). No. of bitstreams: 1 02949.pdf: 9168361 bytes, checksum: 474a2e1dcf103e26b6863b7d40ff33a1 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2015-05-14T13:21:09Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2168020 bytes, checksum: 4c76c2dedc4c3011463de068ef339d86 (MD5) Previous issue date: 2011-08-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Due to its territorial location and the sort of oily plant adapted to its clamate, Maranhão has a vast agricultural potential for producing vegetable oil and their bioderivates. Among them is the babassu palm (Orbignya pharlerata, Mart.), a vegetal rich in oil that is composed by 95% of triglycerides and traces of tocopherols. Such tocopherols act as antioxidative agents that prevent the degradation of unsaturated fatty acids of vegetal oils. Therefore, several methods have being proposed for quantifying these natural antioxidants in both oil and bioderivate products; however, they often require long time of analysis and a pretreatment of the sample. Thus, this paper aims to propose an alternative method for quantifing a-tocopherol in babassu oil, as well as, evaluating its degradation during the oil refining (industrial and laboratorial scales) by mean of high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR). Hence, no previous sample treatments were performed, being the sample only diluted in 2-propanol (HPLC) or chloroform (FTIR) solvents. The use of the spectroscopy technique was rather limited, once it was incapable of distinguish between the tocopherols and/or tocotrienols (β, γ and δ) presented in the media. Conversely, the developed chromatographic method provided an efficient separation of such compounds, yielding in a significant sensibility and good linearity, precision and accuracy of the results. / O Maranhão apresenta um grande potencial agrícola para produção de óleos vegetais já que várias espécies oleaginosas são adaptadas ao seu clima e geografia. Dentre estas se encontra a palmeira de babaçu (Orbignya pharlerata, Mart.), de onde é extraído um óleo rico em triglicerídeos (95%) e tocoferois. Em óleos vegetais, os tocoferóis atuam como agentes antioxidantes, inibindo a oxidação dos ácidos graxos insaturados. Neste sentido, diversas metodologias para quantificação deste antioxidante têm sido propostas, entretanto, tais procedimentos geralmente demandam elevados tempos de análises e pré-tratamento da amostra. Neste contexto, o presente trabalho propõe um método alternativo para quantificação de a-tocoferol em amostras de óleo de babaçu. Também foi avaliado o grau de degradação desta espécie durante o processo de refino do óleo de babaçu, em escalas (industrial e laboratorial) por cromatografia líquida de alta eficiência (CLAE) e espectroscopia de infravermelho com transformada de Fourier (FTIR). Para tanto, as amostras não foram submetidas a qualquer tratamento prévio, sendo apenas diluídas em 2-propanol (CLAE) e clorofórmio (FTIR). Os dados espectroscópicos indicaram uma baixa resolução do método uma vez que não foi possível distinguir entre os vários tipos de tocoferois e/ou tocotrienois (β, γ e δ) existentes nas amostras. Por outro lado, o método cromatográfico desenvolvido apresentou uma excelente separação e resolução do composto em estudo, além de uma boa linearidade, precisão e exatidão, sendo este validado.

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Com o intuito de elucidar os efeitos das propriedades físicas e morfológicas na efetividade da sacarificação enzimática das fibras de bagaço de cana-de-açúcar, este trabalho propõe o uso de diferentes métodos de processamento físico-químicos e -mecânicos para a modificação da estrutura da parede celular. Os tratamentos físico-mecânicos, através de fenômenos de fibrilação e delaminação, promovem a abertura estrutural das fibras e aumentam a acessibilidade às enzimas hidrolíticas, porém sem modificar a composição química do material. Para uma compreensão abrangente da ação dos métodos físico-mecânicos propostos nas características estruturais, as fibras de bagaço foram previamente tratadas por métodos físico-químicos - hidrotérmico e organossolve - de modo a obter cinco materiais de diferentes composições químicas. O estudo dos tratamentos físico-mecânicos foi realizado empregando-se equipamentos de diferentes configurações, cujos modos de ação e consequente impacto nas fibras diferem entre si, sendo estes dois tipos de refino - refinador de discos Bauer e moinho Jokro, e um tipo de moagem - moinho criogênico. A variável do refino em moinho Jokro foi o tempo de tratamento, enquanto as variáveis do processamento em refinador de discos foi o tempo de refino e a distância entre os discos. Já as condições da moagem criogênica foram definidas de modo a obter amostras homogêneas do ponto de vista macroscópico. As modificações provocadas na estrutura das fibras foram determinadas a partir das análises das áreas superficiais externa (dimensões das fibras) e interna (porosidade da parede celular), além da organização cristalina das fibrilas celulósicas. Primeiramente, estudou-se de modo detalhado os efeitos dos métodos mecânicos nas propriedades estruturais das amostras de bagaço, interpretando-se como os efeitos primários do refino evoluem de acordo com a severidade e o tipo tratamento empregado a partir das caracterizações dos efeitos secundários. Posteriormente, confrontaram-se os resultados obtidos nas análises físicas e morfológicas com o rendimento de açúcares obtido na hidrólise enzimática. Os resultados permitiram constatar que, enquanto o moinho Jokro promoveu um grande aumento no rendimento de glicose obtido por culminar, simultaneamente, no aumento da estrutura capilar pela intensa fibrilação interna, e da área superficial externa tanto pela formação de elementos finos quanto pela redução das dimensões das fibras por corte, o refinador de discos Bauer levou a uma melhoria menos pronunciada na hidrolisabilidade por resultar no aumento da porosidade, porém sem expressivos corte e fibrilação externa das fibras. Diferentemente, a moagem criogênica promoveu apenas a drástica e heterogênea redução das dimensões das fibras, enquanto não permitiu mudanças significativas na hidrolisabilidade das amostras. Por fim, os valores dos parâmetros estruturais determinados foram analisados pelo método estatístico de componentes principais (PCA) visando quantificar por qual fator cada uma destas características influencia na extensão da hidrólise da celulose do bagaço. A PCA permitiu visualizar que os fatores relacionados à superfície interna da parede celular, como a área de poros acessíveis e a dimensão lateral do cristalito de celulose, são os principais aspectos que regem o rendimento de sacarificação da biomassa lignocelulósica. Os resultados deste estudo permitiram assim a proposta de um modelo de predição do comportamento de hidrólise das amostras de bagaço. / In order to elucidate the effects of the physical and morphological properties on the effectiveness of enzymatic saccharification of sugarcane bagasse fibers, this work proposes different methods of physico-chemical and -mechanical processing to modify the cell wall structure. Through fibrillation and delamination phenomena, physico-mechanical treatments promote the structural opening of the fibers and increase the accessibility to hydrolytic enzymes, but without modifications on the chemical composition of the processed material. For a thorough comprehension about the action of the proposed physico-mechanical methods on the structural characteristics, the bagasse fibers were previously treated by physico-chemical methods - hydrothermal and organosolv - to obtain five materials with different chemical composition. The study of the physico-mechanical treatments was performed by equipment with different configuration, which operating modes and consequent impact on the fibers differ from each other. The equipment were two types of refiner - Bauer discs refiner and Jokro mill - and one type of mill - cryogenic mill. The refining variable considered for the Jokro mill was the refining time, while the processing variables for the disc refiner were the refining time and the discs gap. Concerning the cryogenic mill, the operation conditions were defined to achieve macroscopic homogeneous samples. Modifications on the fibers structure were assessed by analysis of the external and internal surfaces (fibers dimension and the cell wall porosity, respectively), as well as the crystalline organization of the cellulosic fibrils. Firstly, it was performed a thorough study concerning the effects of the mechanical methods in the structural properties of the bagasse samples. In this study, it was interpreted how the primary effects of refining evolve according to severity and type of treatment from the characterization of the secondary effects. Then, the results acquired in the physical and morphological analysis were confronted with the glucose yield obtained in the enzymatic hydrolysis. The results showed that the Jokro mill promoted a great increase in the glucose yield by culminating, simultaneously, in the increase of the capillary structure by the intense internal fibrillation, and of the external surface area both by the formation of fines as by the reduction of the dimensions of fibers by cutting. In turns, the Bauer discs refiner leaded to a lower improvement of the bagasse pulps hydrolysability, which was a consequence of the increased porosity, but without expressive cut and external fibrillation of the fibers. In a different way, the cryogenic milling promoted just a drastic and heterogeneous reduction of the fibers dimensions, without any significant change in the hydrolysability of the samples. Finally, the determined values of the structural parameters were analyzed by the statistical method of the principal component analysis (PCA), aiming to quantify by which factor each one of these characteristics influences in the extent of hydrolysis of bagasse cellulose. The PCA showed that the factors related to the internal surface of the cell wall, such as the accessible pore area and the lateral dimension of the cellulose crystallite, are the main aspects that govern the saccharification yield of the lignocellulosic biomass. The results of this study allowed the proposal of an empiric prediction model of the hydrolysis behavior of the bagasse samples.

Os modelos moleculares são construídos com base na caracterização da composição do petróleo, que consiste em conhecer informações moleculares detalhadas com o objetivo de identificar os compostos presentes. Este trabalho tem como objetivo construir um banco de dados para a classificação de componentes constituintes de asfaltenos em grupos moleculares. A classificação é feita através da semelhança entre suas massas moleculares em grupos de séries homólogas. Tal classificação é feita por meio da utilização dos dados provenientes da análise de espectrometria de massa e de um algoritmo de busca em linguagem VBA (Visual Basic for Applications), com o objetivo de identificar uma molécula específica em um conjunto de moléculas conhecidas (banco de dados). O método proposto nesse trabalho é baseado na classificação dos compostos através de suas massas moleculares, isto é, os compostos presentes em uma mistura são separados em classes por uma diferença de massa tão pequena quanto se queira. Pode-se, assim, observar a que grupo de moléculas um composto de petróleo pertence por meio de sua massa molecular. Como o banco de dados foi gerado por compostos cuja composição é conhecida, sabe-se que composição um dado composto terá entre as possíveis composições. Para gerar moléculas baseado no conhecimento da composição de petróleo, usam-se as fórmulas gerais dos compostos orgânicos que são formados por séries homólogas. Séries homólogas são séries de compostos orgânicos com propriedades químicas similares cujos componentes diferem entre si por uma massa molecular relativa constante (CH2). Tais séries são geradas e seus pesos moleculares são calculados e armazenados juntamente com suas fórmulas moleculares, em ordem crescente de massa, podendo assim, gerar os grupos moleculares com o auxílio de uma rotina computacional em linguagem VBA. / Molecular models are built based on the characterization of the composition of oil, which consists of detailed molecular information to know in order to identify the compounds present. This work aims to build a database for classifying constituent components of asphaltenes in molecular groups. The classification is done by the similarity of their molecular weights with the use of groups of homologous series. This classification is made by using data from the analysis of mass spectrometry and a search algorithm in language VBA (Visual Basic for Applications) with the aim of identifying a molecule in a specific set of molecules known (database data). The method proposed in that work is based on the classification of the compounds through their molecular weights, i.e., the compounds in a mixture are separated into classes by a mass difference as small as one likes. One can therefore see that the group of molecules from petroleum belongs through its molecular weight. Because the database is generated from compounds whose composition is known, it is known that a given compound composition will have all the possible compositions. To generate molecules based on knowledge of the oil composition, it is used the general formulas of organic compounds which are formed by homologous series. Homologous series are series of organic compounds with similar chemical properties whose components differ by a constant relative molecular mass (CH2). Such series are generated and their molecular weights are calculated and stored together with their molecular formulas, in ascending order of mass, being able to generate the molecular groups with the help of a computing routine in VBA language.

As origens dos elementos residuais (trace element) nas ligas à base de Ni provém basicamente de duas fontes: (1) minérios e (2) sucatas. O controle da concentração destes elementos residuais é muito importante, pois afetam as propriedades mecânicas dessas ligas. Alguns estudos mostram que os elementos Pb e Bi têm um sério impacto negativo nos resultados dos ensaios de fluência das ligas a base de Ni. A presença dessas impurezas causa o aumento da quantidade de cavidades nos contornos de grão que resultam em fracasso prematuro na vida útil desse material. Dessa forma, este trabalho tem como objetivo estudar a cinética da remoção de elementos residuais, tais como Pb e Bi da liga VAT32 através da aplicação de vácuo durante a elaboração da liga. Os resultados obtidos demonstraram que a taxa de remoção dos residuais Pb e Bi no refino a vácuo atingiram percentuais de 99,6% e 96,1% respectivamente. Fatores como volume do cadinho, elevação de temperatura, níveis de vácuo abaixo de 10-4 mbar, limpeza do sistema que compreende câmara e cadinho (residuais de corridas anteriores), contribuem significativamente para as taxas acima descritas. Por outro lado, quanto maior o volume de liga fundida, diminuição de temperatura, vácuo deficiente ou contaminação do sistema, a taxa de remoção de Pb e Bi são prejudicadas. / The origins of trace elements in Ni-based alloys come basically from two sources: (1) minerals and (2) scrap. Control of the concentration of trace elements is very important because they affect the mechanical properties of these alloys. Some studies show that the elements Pb and Bi have a serious negative impact on the results of creep tests of Ni based alloys. The presences of these impurities cause the increase of the number of cavities at grain boundaries that result in premature failure of this material. Thus, this work aims to study the kinetics of removal of trace elements such as Pb and Bi in alloy VAT32 by applying vacuum during the preparation of the alloy. The results showed that the rate of removal of residual Pb and Bi in the vacuum refining reached 99.6% and 96.1% respectively. Parameters such as the crucible volume, high temperature, vacuum levels below 10-4 mbar, cleaning of the system which comprises chamber and crucible (residual from previous races), contribute significantly to the rates described above. Moreover, the higher the volume of molten alloy, low temperature, vacuum system contamination and low vacuum pressure decrease, refining degree of Pb and Bi.

A crucial parameter in the production of mechanical pulp through refining is energy consumption. Although low consistency (LC) refining has been shown to be more energy efficient than conventional high consistency refining, the degradation of mechanical properties of the end-product paper due to fiber cutting has limited the widespread adoption of LC refining. In conventional control strategies, the onset of fiber cutting is determined by post-refining measurement of pulp properties which does not enable rapid in-process adjustment of refiner operation in response to the onset of fiber cutting. In this dissertation, we exploit a piezoelectric force sensor to detect the onset of fiber cutting in real time. Detection of the onset of fiber cutting is potentially beneficial in low consistency refining as part of a control system to reduce fiber cutting and increase energy efficiency. The sensor has a probe which replaces a short length of a refiner bar, enabling measurement of normal and shear forces applied to pulp fibers by the refiner bars. The custom-designed sensors are installed in an AIKAWA pilot-scale 16-in. single-disc refiner at the Pulp and Paper Centre at the University of British Columbia. Trials were run using different pulp furnishes and refiner plate patterns at differing rotational speeds and a wide range of plate gaps. Pulp samples were collected at regular intervals and the pulp and paper properties were measured. We observe distinct transitions in the parameters that characterize the distributions of peak normal and shear forces which consistently correspond to the onset of fiber cutting. In addition, the analysis of the power spectrum of the sensor data shows that the magnitude of the dominant frequency can be used as an indicator of fiber cutting. The power of the time domain signal of the normal force is shown to be the most reliable and consistent indication of the onset of fiber cutting. This parameter consistently identifies the onset of fiber cutting, as determined by fiber length data, for all tested pulp furnishes and plate patterns. In addition, we investigate the effect of pulp furnish and plate pattern on bar forces in LC refining. For tested pulp furnishes and at all plate gaps, the plate with higher bar edge length (which has smaller bar width and groove width) results in lower mean peak normal and shear forces but higher mean coefficient of friction. Moreover, at the onset of fiber cutting, the mean peak normal force of softwood pulp is higher than that for hardwood pulp. Our results also show that the mean coefficient of friction at the onset of fiber cutting is a function of plate gap, pulp furnish, and plate pattern. / Graduate / 2019-01-09

Dissertation submitted in the compliance with the requirements for the Masters Degree in Technology: Electronic Engineering, Light Current at Technikon Natal, 2000. / The CANEGRO model is a mechanistic model that describes environmental, physiological and managerial features of the agricultural sugarcane production system. The model originated from many sources of crop, climatic and soil research work. This caused a fragmentation in the model's components. The objectives of this study was to give a detailed model overview after an investigation into the model's code, published and unpublished documentation and to propose a mechanistic approach in the modelling of tiller populations. / M

Please read the abstract in the front section of this document / Dissertation (M Eng (Metallurgical Engineering))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

Submitted in partial fulfilment of the academic requirements for the Degree of Master's Degree in Technology: Chemical Engineering, ML Sultan Technikon, 2001. / There are two process operations in the sugar factory that directly affect the recovery of sugar from evaporated syrup, namely crystallisation (boiling) and centrifugal operation. Successful automation of the vacuum pans (boiling) has been implemented using brix (total dissolved solids) control, but to date on-line measurement of continuous centrifugal performance has not been successfully accomplished in South Africa. The purpose of this investigation was to continue the preliminary work performed by Tongaat Hulett Sugar in developing a purity meter for the measurement of sugar purity (sucrose content) in a continuous centrifugal. This instrument would provide the centrifugal operator with a reliable tool to perform on-line measurement of sugar purity and would also facilitate the automation of the centrifugal / M