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Process scale-up studies are, generally, non-linear. This basically means that it is not possible to take a chemical process in the laboratory and bring it to a pilot or production plant by simply increasing the quantities of chemicals and the equipment size proportionally. There are many physico-chemical processes involved (such as reaction kinetics, fluid mechanics and thermodynamics), plus over the years a myriad of different equipment (stirrers, baffles, jackets...) have been developed with different geometrical and performance characteristics. Therefore, scale-up studies involve engineering issues, economic considerations, and risks assessment to reduce them to acceptable levels for the successful commercial scale implementation. Mixing and heat transfer assessments are often required when scaling a process, troubleshooting poor performance or transferring from one plant to another. This is because the rates of these physico-chemical processes are a function of the details of the equipment set-up and operating conditions, so they can vary widely from one vessel to another. Due to this series of drawbacks and the large number of parameters involved, there is the increasing interest to make use of scientific approaches in the early stages of process development, both modelling and simulation tools along with experimentation to try to predict the behaviour of chemical processes on a larger scale and, consequently, reduce costs and efforts from the beginning. This project was aimed at implementing a method to characterize production equipment and calculate its heat transfer coefficient experimentally from a thermal test. Both the created database, which contains information of about 70 reactors, and the heat transfer coefficient values are then used in different case studies with the objective of predicting the behaviour of the chemical processes examined at different scales: laboratory, pilot and production. The scale-up parameters calculation is detailed for each project with emphasis on the results and conclusions regarding the mixing and heat transfer performances.

Die Vorteile des Systems „Horn“ gegenüber dem Gangbahn-Flügelrad System liegen in der faserschonenden und lageparallelen Flechtfadenverlegung sowie in der gesteigerten Flechtgeschwindigkeit. Die Herausforderung um das Potential des Systems „Horn“ zur Herstellung von Preforms durch Überflechten zu erschließen, bestand in der Integration eines dritten Fadensystems in eine antriebstechnisch umsetzbare Verlegetechnik zur Fertigung einer triaxialen Flechtstruktur. Für die Synthese dieser Antriebstechnik zur kinematisch optimalen Verlegung der Flechtfäden wurde eine prozessorientierte Synthesemethodik, auf Basis einer Technologiesynthese, erarbeitet. / Advantages of the system “Horn” versus the horn gear motion system lie in a gentle and parallel processing of the braiding materials as well as in an increased speed of braiding. The challenge in extrapolating the potential of the system “Horn” for the production of preforms by over-braiding was to integrate a third yarn system into a laying technique that is technically feasible for processing a triaxial braided structure. For the synthesis of this drive technology and to guarantee an optimal kinematic transfer of threads, a process-oriented synthesizing method, based on a technology synthesis, was elaborated.

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The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.

The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.

The objective of this study is to model and analyze a three dimensional single riveted lap joint (with and without a crack). By using finite element method, stress and fracture analyses are carried out under both the residual stress field and external tensile loading. Using a two step simulation, riveting process and subsequent tensile loading of the lap joint are simulated to determine the residual and overall stress state. Residual stress state due to riveting is obtained by interference and clamping misfit method. By employing different interference and clamping misfit values, the effects of riveting process parameters on stress state are examined. Two cracks namely the semi elliptical surface crack at faying surfaces of plates and the quarter elliptical corner crack at rivet hole are the most widely observed crack types in riveted joints. Fracture analysis of cracked riveted joints is carried out by introducing these two crack types to the outer plate at a plane perpendicular to the loading. The mixed mode stress intensity factors (SIFs) and energy release rates (G) around the crack front are obtained by using displacement correlation technique (DCT). Effects riveting process parameters (interference and clamping ratios) and geometrical parameters (crack shape and size) on fracture parameters are studied. The stress intensity factor solutions presented herein could be useful for correlating fatigue crack growth rates, fracture toughness computation, and multiple site damage (MSD) analysis in aircraft bodies.

Single-crystalline nanostructures often exhibit gradients of surface (and/or interface) curvature that emerge from fabrication and growth processes or from thermal fluctuations. Thus, the system-inherent capillary force can initiate morphological transformations during further processing steps or during operation at elevated temperature. Therefore and because of the ongoing miniaturization of functional structures which causes a general rise in surface-to-volume ratios, solid-state capillary phenomena will become increasingly important: On the one hand diffusion-mediated capillary processes can be of practical use in view of non-conventional nanostructure fabrication methods based on self-organization mechanisms, on the other hand they can destroy the integrity of nanostructures which can go along with the failure of functionality. Additionally, capillarity-induced shape transformations are effected and can thereby be controlled by applied fields and forces (guided or driven evolution). With these prospects and challenges at hand, formation and shape transformation of single-crystalline nanostructures due to the system-inherent capillary force in combination with external fields or forces are investigated in the frame of this dissertation by means of atomistic computer simulations. For the exploration (search, description, and prediction) of reaction pathways of nanostructure shape transformations, kinetic Monte Carlo (KMC) simulations are the method of choice. Since the employed KMC code is founded on a cellular automaton principle, the spatio-temporal development of lattice-based N-particle systems (N up to several million) can be followed for time spans of several orders of magnitude, while considering local phenomena due to atomic-scale effects like diffusion, nucleation, dissociation, or ballistic displacements. In this work, the main emphasis is put on nanostructures which have a cylindrical geometry, for example, nanowires (NWs), nanorods, nanotubes etc.

Made available in DSpace on 2016-06-02T19:56:54Z (GMT). No. of bitstreams: 1 5893.pdf: 957671 bytes, checksum: e4262a8881b2b32139eed237de0471ba (MD5) Previous issue date: 2014-03-24 / Financiadora de Estudos e Projetos / Most of the operations in an autonomous distillery for production of ethanol are carried on in a continuous fashion. The fermentation stage, however, may be projected to work either continously or semicontinuously. The steady-sate continuous operation (after the start-up) may be easily coupled to other unit operations of the process. On the other hand, in the semicountinuous operation, each fermentation vat operates in unsteady state, thus it is necessary to design a set of vats that enables the coupling between the fermentation and the process, which may be challenging. This study intended to implement mathematical models in EMSO process simulator of both industrial configurations of the fermentation process: a system of six parallel fed-batch bioreactors and a system of four continuous steady-state bioreactors in series. The process was modeled at macroscopic level based on the material balances for cells, substrate and product. Kinectic models accounting for product and substrate inhibition were used. Both configurations were added to a previously built model of a complete autonomous distillery in which the fermentation stage was represented by a stoichiometric conversion model. In the fed-batch process, due to the solution of mass and energy balances in the fermenters, it was possible to observe the temporal evolution of variables such as the concentrations of yeast, sugar and ethanol in their interiors, the volume of solution in each fermenter and the rate of heat removal needed in order to keep the fermenters temperatures constant. The simulated autonomous distillery processes 500 t/h of cane with varying levels of sucrose. For a content of 13% sucrose, 338.0 t/h of centrifugated wine were obtained in the continuous operation, containing 8.3% by weight of ethanol, which resulted in the production of 30.1 t/h of hydrate ethanol containing 93.5% ethyl alcohol in weight. In fed-batch operation, 417.5 t/h of centrifugated wine (6.3% ethanol by weight), which resulted in 27.9 t/h of hydrous ethanol (93.5% by mass). In both configurations, simulations were performed to evaluate the influence of the sucrose content in the process input (11 to 15% by weight of sucrose) over the process response. The results of these simulations were compared to those obtained for the model of stoichiometric conversion under the same conditions. Regarding the three evaluated configurations for the fermentation stage, it was observed that the model of stoichiometric conversion can be properly employed in the simulations, being mostly suitable for optimization studies of the autonomous distillery with semicontinuous operation due to its fast convergence. However, it is worth mentioning that the inhibitory effects are not reproduced in the fermentation step for this model, thus preliminary studies should be performed using the mathematical model implemented in continuous or discontinuous configuration. / Na produção de etanol a maioria das operações realizadas em uma destilaria autônoma e conduzida de forma continua. A etapa de fermentação, contudo, pode ser projetada para operar de forma continua ou semi-contínua. A operação continua em estado estacionário (após a partida do processo) pode ser facilmente acoplada as outras operações unitarias do processo. Por outro lado, na operação semi-contínua, cada dorna de fermentação opera em estado não estacionário, havendo a necessidade de se projetar um conjunto de dornas para que a etapa de fermentação seja acoplada ao processo, o que pode ser complicado. Este trabalho teve como objetivo implementar no simulador de processos EMSO modelos matemáticos das duas configurações industriais da etapa de fermentação: um sistema de fermentação composto por seis biorreatores em que cada dorna opera no modo batelada alimentada e um sistema composto por quatro biorreatores em serie operados em regime permanente. O processo foi modelado em nível macroscópico com base nas equações de balanço material para células, substrato e produto. Modelos cinéticos que levam em consideração inibição pelo substrato e pelo produto foram utilizados. As duas configurações foram adicionadas a um modelo de destilaria autônoma desenvolvido previamente no simulador EMSO, no qual a etapa de fermentação era representada por modelo baseado na conversão estequiométrica. No processo descontinuo, a solução dos balanços de massa e energia nos fermentadores tornaram possível observar a evolução temporal dos valores de variáveis como as concentrações de levedura, açúcar e etanol em seus interiores, o volume de solução nos fermentadores e a taxa de remoção de calor necessária para manter suas temperaturas constantes. A destilaria autônoma simulada processa 500 t/h de cana-de-açúcar com teores de sacarose variáveis. Para um teor de 13% de sacarose, foram obtidos 338,0 t/h de vinho delevedurado na operação continua com 8,3% em massa de etanol, que resultaram na produção de 30,1 t/h de etanol hidratado com 93,5% de álcool etílico em massa. Na operação descontinua foram obtidos 417,5 t/h de vinho delevedurado (6,3% de etanol em massa), que resultaram em 27,9 t/h de etanol hidratado (93,5% em massa). Nas duas configurações implementadas foram realizadas simulações para avaliar a influencia do teor de sacarose (11 a 15% em massa de sacarose) na entrada do processo na resposta do processo. Os resultados dessas simulações foram comparados vi com os obtidos para o modelo de conversão estequiométrica nas mesmas condições. Em relação as três configurações avaliadas na etapa de fermentação concluiu-se que o modelo de conversão estequiométrica pode ser empregado nas simulações, sendo principalmente indicado para estudos de otimização da destilaria autônoma com operação semi-contínua, pois tem convergência mais rápida. Contudo, vale lembrar que os efeitos de inibição não são reproduzidos na etapa de fermentação por este modelo, devendo estudos preliminares serem realizados empregando o modelo matemático implementado na configuração continua ou descontinua.