A modelagem computacional da gaseificação de uma biomassa (bagaço de cana-de-açúcar) para obtenção de uma mistura gasosa rica em hidrogênio foi efetuada com o auxílio do software Aspen Plus®. O modelo construído apresentou média de 74,4% de acurácia – valor considerado satisfatório diante da complexidade do sistema, quando comparado com o resultado de suas simulações com valores reais. Tendo sido o modelo validado e conhecida sua acurácia, foram efetuadas simulações para análise de sensibilidade do sistema de gaseificação, para duas condições distintas de fluxo de alimentação da biomassa, vapor d’água e ar nos equipamentos, no intuito de buscar condições operacionais otimizadas. Pelos resultados dessas análises, observa-se um máximo de 9% em volume de H2, obtido para produtos gasosos em base seca, inferindo-se faixas de condições operacionais recomendáveis para gaseificação do sistema.
Benevolência, Graça e Misericórdias são infinitas, Àquele sem o qual nada seria possível, Deus. Ao Prof. Delvonei Alves de Andrade, orientador desta tese, exemplo de pesquisador, professor e amigo, com o qual passei muitos momentos aprendendo, discutindo e crescendo profissionalmente. À minha querida esposa Sonia Maria, companheira ao longo de 35 anos de casamento, sempre paciente e compreensiva. Aos meus filhos Raphael e Danielle pelo amor e respeito dedicados à minha pessoa e aos meus ideais de vida. À minha nora Sheila pelo amor e respeito dedicado ao meu filho e respeito à minha pessoa. Ao meu futuro genro Stefan pelo seu exemplo de determinação e superação dos obstáculos da vida, pelo seu amor e respeito à minha filha, e pelo respeito à minha pessoa. Aos pesquisadores, amigos e companheiros de toda uma vida profissional, Dr.
Nowadays petroleum dependency in transportation is widely discussed all over the world. Atmospheric pollution and global warming are deleterious consequences of gasoline consumption. Ethanol is a natural substitute fuel that has been increasingly used. One of the most important raw materials used for ethanol production is the sugar cane. The exothermic fermentation reaction of the sugar cane juice in the ethanol production process requires a rigorous temperature control. This control is usually made by using cooling water from cooling towers. The heat released from cooling towers not only has an economical cost as well as it contributes to the global heating. Steam ejectors can substitute cooling towers thus improving the ethanol production plant efficiency and reducing world heating. Furthermore, steam ejectors are smaller, cheaper and are very simple equipment when compared with cooling towers. Furthermore, its use provides an improved thermal efficiency of the production plant resulting in the reduction of the global warming effects. In this work the use of steam ejector is proposed for the fermentation cooling of a typical Brazilian sugar and ethanol production plant. The steam which feeds the steam ejector is obtained from the plant utilities and the low temperature obtained from steam expansion within the ejector is used for sugar cane fermentation process cooling. The steam ejector discharge heat is recovered as it is used to sugar and ethanol production process heating. The sugar and ethanol production plant overall energy fluxes either using cooling towers as well as using steam ejectors are presented and the results are compared and discussed.
The experimental technique used for detection of subcooled boiling through analysis of the fluctuation contained in pressure transducer signals is presented. This work was partly conducted at the Institut für Kerntechnik und zertörungsfreie Prüfverfahren von Hannover (IKPH, Germany) in a thermal-hydraulic circuit with one electrically heated rod with annular geometry test section. Piezoresistive pressure sensors are used for onset of nucleate boiling (ONB) and onset of fully developed boiling (OFDB) detection using spectral analysis/ signal correlation techniques. Experimental results are interpreted by phenomenological analysis of these two points and compared with existing correlation. The results allow us to conclude that this technique is adequate for the detection and monitoring of the ONB and OFDB
A modelagem computacional da gaseificação de uma biomassa (bagaço de cana-de-açúcar) para obtenção de uma mistura gasosa rica em hidrogênio foi efetuada com o auxílio do software Aspen Plus®. O modelo construído apresentou média de 74,4% de acurácia – valor considerado satisfatório diante da complexidade do sistema, quando comparado com o resultado de suas simulações com valores reais. Tendo sido o modelo validado e conhecida sua acurácia, foram efetuadas simulações para análise de sensibilidade do sistema de gaseificação, para duas condições distintas de fluxo de alimentação da biomassa, vapor d’água e ar nos equipamentos, no intuito de buscar condições operacionais otimizadas. Pelos resultados dessas análises, observa-se um máximo de 9% em volume de H2, obtido para produtos gasosos em base seca, inferindo-se faixas de condições operacionais recomendáveis para gaseificação do sistema.
The fuel elements of a MTR (Material Testing Reactor) type nuclear reactor are mostly composed of aluminum-coated fuel plates containing the core of uranium silica (U 3 Si 2) dispersed in an aluminum matrix. These plates have a thickness of the order of millimeters and are much longer in relation to their thickness. They are arranged in parallel inside the fuel element assembly to form channel gaps between them of only a few millimeters wide through which the coolant flows. This configuration, combined with the need for a flow at high flow rates to ensure the cooling of the fuel element in operation, may create problems of mechanical failure of fuel plate due to the vibration induced by the flow in the channels. In the case of critical velocity, excessive permanent deflections of the plates can cause blockage of the flow channel in the reactor core and, lead to overheating in the plates. For this work an experimental loop capable of high volume flows and a test section that simulates a plate-like fuel element with three cooling channels was developed. The dimensions of the test section were based on the dimensions of the Fuel Element of the Brazilian Multipurpose Reactor (RMB), whose project is being coordinated by the National Commission of Nuclear Energy (CNEN). The experiments performed had the objective of reaching Miller's critical velocity condition. The critical velocity was reached with 14.5 m/s leading to the consequent plastic deformation of the flow channel plates.
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