This thesis project investigates the granular flow of wood pellets inside a pilot-scale rotary kiln and its impact on the pyrolysis process. The study focuses on two key factors that must be determined to evaluate their effects on pyrolysis: the mass flow rate delivered by the feeding system at different motor frequencies and the mean residence time (MRT) of the wood pellets. The research is divided into two parts: the first characterizes granular flow without heat application, while the second examines the system behavior under high-temperature pyrolysis conditions. For the first part, the mass flow rate was assessed by measuring the emptying time of the feeding silo at different screw velocities. In contrast, the MRT was determinedwith two scenarios: (1) batches of different masses of wood pellets and (2) continuousfeed until a stable solid bed was formed that allowed tracer particle tracking. In the second part of the study, the drum’s rotational speed and fed mass flow rate were varied. Results indicated a direct proportionality between the mass flow rate delivered by the feeding systems and the screw motor frequency. Additionally, the MRT was found to follow an inverse relation with the drum’s rotational speed if the process was done in batches. In contrast, the MRT was 20 minutes at a feeding rate of 51 kg h-1 and a drum’s rotational speed of 0.36 rad s -1 with a continuous feeding process. Finally, the study concludes that the wood pellet feed rate and drum rotational speed significantly influence the pyrolysis process in the rotary kiln. The system remained stable for wood pellets inside the rotary drum, starting with a feeding rate of 8 kg h-1 and scaling up until a maximum of 21 kg h-1. This behavior is evidenced by the direct proportionality between the evolution of flue gas and pyrolysis gas temperatures over time and the necessity to adjust air supply to maintain system stability.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006. / The natural immune system is an exceptional pattern recognition system based on memory and learning that is capable of detecting both known and unknown pathogens. Artificial immune systems (AIS) employ some of the functionalities of the natural immune system in detecting change in dynamic process systems. The emerging field of artificial immune systems has enormous potential in the application of fault detection systems in process engineering. This thesis aims to firstly familiarise the reader with the various current methods in the field of fault detection and identification. Secondly, the notion of artificial immune systems is to be introduced and explained. Finally, this thesis aims to investigate the performance of AIS on data gathered from simulated case studies both with and without noise. Three different methods of generating detectors are used to monitor various different processes for anomalous events. These are: (1) Random Generation of detectors, (2) Convex Hulls, (3) The Hypercube Vertex Approach. It is found that random generation provides a reasonable rate of detection, while convex hulls fail to achieve the required objectives. The hypercube vertex method achieved the highest detection rate and lowest false alarm rate in all case studies. The hypercube vertex method originates from this project and is the recommended method for use with all real valued systems, with a small number of variables at least. It is found that, in some cases AIS are capable of perfect classification, where 100% of anomalous events are identified and no false alarms are generated. Noise has, expectedly so, some effect on the detection capability on all case studies. The computational cost of the various methods is compared, which concluded that the hypercube vertex method had a higher cost than other methods researched. This increased computational cost is however not exceeding reasonable confines therefore the hypercube vertex method nonetheless remains the chosen method. The thesis concludes with considering AIS’s performance in the comparative criteria for diagnostic methods. It is found that AIS compare well to current methods and that some of their limitations are indeed solved and their abilities surpassed in certain cases. Recommendations are made to future study in the field of AIS. Further the use of the Hypercube Vertex method is highly recommended in real valued scenarios such as Process Engineering.

<p>This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated.</p><p>The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm^-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored.</p><p>Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding.</p> / QC20100608

Cerâmicas de alto conteúdo cristalino, como a zircônia policristalina tetragonal estabilizada por ítrio (Y-TZP), apresentam ótimas propriedades mecânicas quando comparadas às cerâmicas convencionais, sendo cada vez mais empregadas como materiais restauradores indiretos. Entretanto, seu sucesso também depende da formação de uma união confiável com os agentes de cimentação. Porém, o aumento do conteúdo cristalino modificou as características de adesão entre cerâmica e cimento resinoso, não existindo um protocolo de cimentação bem estabelecido na literatura. Portanto, este estudo teve como objetivo avaliar o efeito na resistência ao cisalhamento de diferentes tratamentos de superfície sobre a zircônia, utilizando dois cimentos resinosos, assim como avaliar as possíveis diferenças no modo das fraturas. Cento e vinte amostras retangulares de zircônia foram incluídas em resina acrílica e divididas em 12 grupos (n=10), de acordo com os tratamentos de superfície e os cimentos (Panavia F e Rely X U100). Para cada cimento, os grupos experimentais foram formados da seguinte maneira: RU e Pa - controle (sem nenhum tratamento de superfície); ApRU e ApPa (aplicação do Alloy Primer); MzRU e MzPa (aplicação do Metal/Zircônia Primer); JatRU e JatPa (jateamento com partículas de óxido de alumínio de 50µm); JatApRU e JatApPa (jateamento e aplicação de Alloy Primer); JatMzRU e JatMzPa (jateamento e aplicação do Metal/Zircônia Primer). Os corpos de prova foram armazenados em água destilada à temperatura de 37°C por 24 horas, antes do teste de cisalhamento em uma máquina de ensaio universal (EMIC). Os valores foram submetidos primeiro a ANOVA a um critério (resistência ao cisalhamento) e teste de Tukey (p 0,05), independente do tratamento e do sistema de cimentação. Em seguida, ANOVA a dois critérios (tratamento de superfície e sistema de cimentação) e o teste de Tukey foram aplicados para observar com maior precisão a interação entre cimento e tratamento de superfície. Os resultados apresentados foram: RU - 11,71a, ApRU - 21,49b,e, MzRU - 30,38c,d, JatRU - 34,40c, JatApRU - 30,66c,d, JatMzRU - 38,06c, Pa - 11,35a, ApPa - 11,98a, MzPa - 11,46a, JatPa - 33,50c, JatApPa - 23,14b,d,e, JatMzPa - 18,66a,e. Por meio dos resultados obtidos foi possível concluir que a resistência ao cisalhamento pode ser melhorada ao utilizar o jateamento com partículas de óxido de alumínio e, para o RelyX U100, somente a aplicação do Metal/Zircônia Primer resultou em valores de adesão comparavéis ao tratamento mecânico. O cimento RelyX U100 apresentou maior resistência de união quando comparado ao Panavia F. / High crystalline content ceramics, such as yttria stabilized tetragonal zirconia polycrystal (Y-TZP), show great mechanical properties when compared to conventional ceramics, being increasingly used as indirect restorative materials. However, its success also depends on the reliable bond formation with luting agents. Though, the high crystalline content modified the adhesiveness between ceramic and resin cement although there isnt any cementing protocol established in literature. Therefore, the purpose of this study was to evaluate the effect of the shear bond strength after different surface treatments on the zirconia, using two resin cements and to evaluate possible differences in fracture modes. One hundred and twenty rectangular samples of zirconia were embedded in acrylic resin and divided into 12 groups (n=10) according to the surface treatments and the cements (Panavia F and RelyX U100). For each cement, the experimental groups were formed as follow: RU and Pa - control (no surface treatment); ApRU and ApPa (application of Alloy Primer); MzRU e MzPa (application of Metal/Zirconia Primer); JatRU and JatPa (air abrasion with 50µm Al2O3 particles); JatApRU and JatApPa (air abrasion and application of Alloy Primer); JatMzRU and JatMzPa (air abrasion and application of Metal/Zirconia Primer). The specimens were stored in distilled water at 37°C for 24 hours prior to the shear bond strength test in a universal testing machine (EMIC). The data were first analyzed by one-way ANOVA (shear bond strength) and Tukey test (p<0.05), regardless of the treatment and the luting system. Then two-way ANOVA (surface treatment and luting system) and the Tukey test were applied in order to observe more accurately the interaction between cement and surface treatments.The results presented were: RU 11.71a, ApRU 21.49b,e, MzRU 30.38c,d, JatRU 34.40c, JatApRU 30.66c,d, JatMzRU 38.06c, Pa 11.35a, ApPa 11.98a, MzPa 11.46a, JatPa 33.50c, JatApPa 23.14b,d,e, JatMzPa 18.66a,e. Based on the results obtained, it was possible to conclude that the shear bond strength can be improved when air abrasion was used with aluminum-oxide particles and for the RelyX U100, only the application of Metal / Zirconia Primer resulted in adhesion values comparable to mechanical treatment. The RelyX U100 cement showed higher bond strength when compared to Panavia F.

<p>Car exhaust catalysts were introduced in the early 1980’s, to limit the release of pollutants such as hydrocarbons, carbon monoxides and nitrogen oxides. These catalysts contain noble metals such as palladium (Pd), platinum (Pt) and rhodium (Rh) and are able to simultaneously abate all three of the above-mentioned pollutants, hence the name three-way catalyst (TWC). The exposure to high temperatures (800-1000 °C) during operation and the presence of additives in petrol such as lead, calcium, silicon, magnesium, manganese, chromium, sulphur and phosphorus will after a certain time start to lower the overall effectiveness of the catalyst. These effects are either of a mechanical or a chemical nature. High temperatures reduce the active area by causing the noble metals to agglomerate and sinter whereas the additives alter the activity by either fouling the pores of the support material (phosphorus) or by interacting with the metals (sulphur and lead).</p><p>The main objective of this work was to develop a method to redisperse the catalytically active sites, comprising Pd, Pt and Rh on the washcoat surface, in an effort to regain lost catalyst activity. For this purpose, a wide spectrum of different commercial car exhaust catalysts containing varying noble metal loadings, aged under various driving conditions and with mileages ranging from 30 to 100 000 km were evaluated.</p><p>The influence of a thermal treatment in a controlled gas atmosphere, such as oxygen or hydrogen and a redispersing agent, e.g. chlorine, on the activity of TWC was investigated by means of laboratory-scale activity measurements. Several complementary characterisation methods such as SEM/TEM, XRD, BET and TPR were used to verify the effects of the regeneration treatments on the catalyst morphology (Paper I). Partial regeneration of catalyst activity and noble metal dispersion was achieved after thermal treatment in an oxygen-chlorine rich atmosphere at temperatures below 500 °C.</p><p>Finally, an investigation of the effects of an oxy-chlorine thermal treatment for regeneration of a ‘full-scale’ commercial automotive three-way catalyst was performed. Catalyst activity and performance prior to and after the oxy-chlorine thermal treatment was measured on a test vehicle in accordance with the European driving cycle (EC2000). The catalyst surface was further characterised using XRD and EDX (Paper II). Improved catalyst activity for a high mileage catalyst could be observed, with emissions lowered by approximately 30 to 40 vol% over the EC2000 driving cycle</p>

This work presents the first known attempt to model the dairy business from a multiscale modelling perspective. The multiscale nature of the dairy industry is examined with emphasis on those key decision making and process scales involved in production. Decision making scales identified range from the investor level to the plant operator level, and encompass business, production, plant, and operational levels. The model considers scales from the production manager to the unit operation scale. The cheese making process is used to demonstrate scale identification in the context of the important phenomena and other natural levels of scrutiny of interest to decision makers. This work was a first step in the establishment of a multiscale system model capable of delivering information for process troubleshooting, scheduling, process and business optimization, and process control decision-making for the dairy industry. Here, only material transfer throughout a process, use of raw materials, and production of manufactured product is modelled. However, an implementation pathway for adding other models (such as the precipitation of milk protein which forms curd) to the system model is proposed. The software implementation of the dairy industry multiscale model presented here tests the validity of the proposed: • object model (object and collection classes) used to model unit operations and integrate them into a process, • mechanisms for modelling material and energy streams, • method to create simulations over variable time horizons. The model was implemented using object oriented programming (OOP) methods in conjunction with technologies such as Visual Basic .NET and CAPE-OPEN. An OOP object model is presented which successfully enabled the construction of a multiscale model of the cheese making process. Material content, unit operation, and raw milk supply models were integrated into the multiscale model. The model is capable of performing simulations over variable time horizons, from 1 second, to multiple years. Mechanisms for modelling material streams, connecting unit operations, and controlling unit operation behaviour were implemented. Simple unit operations such as pumps and storage silos along with more complex unit operations, such as a cheese vat batch, were modelled. Despite some simplifications to the model of the cheese making process, the simulations successfully reproduced the major features expected from the process and its constituent unit operations. Decision making information for process operators, plant managers, production managers, and the dairy business manager can be produced from the data generated. The multiscale model can be made more sophisticated by extending the functionality of existing objects, and incorporating other scale partial models. However, increasing the number of reported variables by even a small number can quickly increase the data processing and storage demands of the model. A unit operation’s operational state of existence at any point of time was proposed as a mechanism for integrating and recalculating lower scale partial models. This mechanism was successfully tested using a unit operation’s material content model and is presented here as a new concept in multiscale modelling. The proposed modelling structure can be extended to include any number of partial models and any number of scales.

Orientador: Marisa Masumi Beppu / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-12T23:04:08Z (GMT). No. of bitstreams: 1 Tiba_RafaelMassao_M.pdf: 4156025 bytes, checksum: 6b7f2bf2c33d458475abf019c06c839f (MD5) Previous issue date: 2009 / Resumo: O objetivo do trabalho foi analisar a adequação de Gráficos de Controle (coloquialmente chamadas também de Cartas de Controle) para o controle da qualidade e do desempenho de processos químicos. Dentro deste tema, Cartas de Controle usualmente aplicadas na indústria foram testadas e analisadas para verificar o seu impacto e aplicabilidade com dados provenientes de processos transientes. Os resultados obtidos indicaram que a utilização inadvertida dessas ferramentas (inicialmente concebidas para a indústria mecânica) pode trazer impactos indesejáveis como ocorrência de alarmes falsos e atraso na detecção. Os dados provenientes de indústrias químicas, particularmente quando apresentam autocorrelação, devem ser analisados de maneira diferenciada. Voltado para essa necessidade, uma ferramenta inédita foi criada para o controle de qualidade quando há esse tipo de dados: a carta para coeficientes angulares, que utiliza as tendências lineares de pequenos trechos de dados para antecipar a detecção de causas especiais. Entre as vantagens dessa ferramenta estão facilidade de aplicação (a carta dispensa recursos computacionais específicos ou utilização de séries temporais), alto desempenho e robustez frente a ruídos nos dados. Os gráficos de controle apresentam a vantagem de dispensar o conhecimento prévio do processo, podendo tratá-lo como uma "caixa preta", abordagem muito conveniente para processos muito complexos, com grande número de etapas e variáveis, onde abordagem fenomenológica e fundamental através de modelos diferenciais matemáticos entre variáveis dependentes e independentes pode ser bastante laboriosa na prática do controle. Para verificar se um ajuste comum ao processo possa não ser suficiente para fazer o processo convergir novamente ao "set point" (e voltar à zona de controle), sugere-se o uso de uma ferramenta auxiliar, a Dinâmica de Sistemas. Ela seria usada na indicação da necessidade de intervenção especial em um processo. Com o seu método particular de criar modelos multivariados, a Dinâmica de Sistemas fornece uma maneira qualitativa e quantitativa de identificar as variáveis críticas para a qualidade do processo e para analisar seu comportamento dinâmico bem como as relações multivariadas existentes em uma planta química, consistindo em uma grande oportunidade para ser aplicada no nível operacional. Ela pode servir para mostrar se uma determinada intervenção especial faria o sistema se descontrolar ainda mais (fato comum de processos com excesso de controle, "over-controlled") ou se poderia servir para fazê-la convergir novamente a uma zona de controle / Abstract: The purpose of this study was to examine the suitability of using ordinary control charts such as Shewhart's and Averages chart to control the quality and performance of chemical processes. Within this theme, control charts commonly used in industry were tested and analyzed to determine its impact and applicability with data from transient processes. The obtained results indicate that the inadverted use of such tools (originally designed for mechanical engineering, which has discrete processes) can lead to undesirable effects such as the occurrence of false alarms and delay on special causes detection. Therefore, data originated at chemical industries, especially when autocorrelation is present, must be analyzed through special techniques. Towards this need, a new tool was created specially to this sort of data: The Slope Chart, which uses the linear trends of small subgroups of data to anticipate special causes detection. The main advantages of this tool are ease of application (this charts does not requires specific computer resources or time series modeling), higher performance and robustness against noise. Control Charts allow users to deal with the process as "Black Boxes", not requiring previous knowledge about the process for special cause detection. For a high complexity process, where there are a considerable number of steps and variables, this is an advantage provided that classic control would require phenomenological studies which might be laborious. Therefore, an auxiliary tool in the cases where an ordinary correction may not enough is proposed. Furthermore, it has been proposed the use of System Dynamics as an auxiliary tool to indicate whether or not it is necessary to act at the process. With its particular method of creating multivariate models, the System Dynamics serves the purpose of quality control, providing both qualitative and quantitative ways to see critical variables to the process quality and to analyze its dynamic behavior and the existing multivariate relations in chemical industries, consisting of a significant opportunity to be used at operational level. It can be useful to simulate whether a potential action would bring more variability to the process (which is usual in overcontrolled processes) or would be useful to correct the process / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Orientador: Maria Teresa Moreira Rodrigues / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-15T23:04:02Z (GMT). No. of bitstreams: 1 EstombeloMontesco_RichardAndres_D.pdf: 4286461 bytes, checksum: eb67a872094b54e948fda33c92db4f3a (MD5) Previous issue date: 2010 / Resumo: A tendência nos últimos anos é de utilizar eficientemente a capacidade instalada de plantas de produção descontínua (flexível, multipropósito) de forma a analisar a viabilidade das demandas sem padrão dos diferentes produtos. O objetivo principal de produção é atender aos pedidos em um tempo relativamente curto, direcionado ao cliente e permitindo flexibilizar a planta. O objetivo deste trabalho é de propor uma análise de integração das etapas de planejamento e programação. Esta integração deve permitir medir corretamente as possibilidades reais de execução de planejamentos alternativos, e assim, propor um novo modelo a partir das variáveis comuns destes sistemas. Inicialmente analisou-se o método de propagação de restrições como um elo comum das duas etapas o qual, além de garantir que durante o processo de propagação de restrições não sejam eliminadas soluções factíveis, também permite recalcular as novas soluções integradas. Com esta integração consegue-se que as variáveis externas em determinadas etapas do processo de solução evitem re-processos computacionais, os quais em sistemas de grande porte podem significar gastos de tempo importante. As características do novo modelo são: utilização de janelas de processamento, planta descontínua, produção em batelada com restrições sobre os recursos compartilhados (equipamentos) e sobre armazenagem, com modo de operação na planta por atendimento de pedidos (direcionada ao cliente) / Abstract: The efficient use of installed capacity in discontinued production plants (flexible, multi-purpose) in such a way as to analyze the feasibility of standard-less demands of different products is a trend in recent years. The main objective of the production problem is to fulfill orders in a relatively short time, in a way that it is client-focused and enables keeping the plant flexible. The objective of this work was to introduce an analysis of the integration of the production planning and scheduling stages. This integration allows the correct measurement of the actual performance possibilities of alternative plans, introducing a new model based on the common variables of these systems. Initially, we analyzed the method of constraint propagation as a common bond of two stages, and besides, we guarantee the search space also allowed to recalculate the new integrated problems. With this integration, it was determined that the external variables at certain points in the solution process avoid re-computational processes in which large systems can mean spending important time. The characteristics of this new model are: usage of processing-windows; the use of discontinued plants; batch production with constraints on shared (equipment) and storage resources; and on-demand operation mode (client-focused) / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Cerâmicas de alto conteúdo cristalino, como a zircônia policristalina tetragonal estabilizada por ítrio (Y-TZP), apresentam ótimas propriedades mecânicas quando comparadas às cerâmicas convencionais, sendo cada vez mais empregadas como materiais restauradores indiretos. Entretanto, seu sucesso também depende da formação de uma união confiável com os agentes de cimentação. Porém, o aumento do conteúdo cristalino modificou as características de adesão entre cerâmica e cimento resinoso, não existindo um protocolo de cimentação bem estabelecido na literatura. Portanto, este estudo teve como objetivo avaliar o efeito na resistência ao cisalhamento de diferentes tratamentos de superfície sobre a zircônia, utilizando dois cimentos resinosos, assim como avaliar as possíveis diferenças no modo das fraturas. Cento e vinte amostras retangulares de zircônia foram incluídas em resina acrílica e divididas em 12 grupos (n=10), de acordo com os tratamentos de superfície e os cimentos (Panavia F e Rely X U100). Para cada cimento, os grupos experimentais foram formados da seguinte maneira: RU e Pa - controle (sem nenhum tratamento de superfície); ApRU e ApPa (aplicação do Alloy Primer); MzRU e MzPa (aplicação do Metal/Zircônia Primer); JatRU e JatPa (jateamento com partículas de óxido de alumínio de 50µm); JatApRU e JatApPa (jateamento e aplicação de Alloy Primer); JatMzRU e JatMzPa (jateamento e aplicação do Metal/Zircônia Primer). Os corpos de prova foram armazenados em água destilada à temperatura de 37°C por 24 horas, antes do teste de cisalhamento em uma máquina de ensaio universal (EMIC). Os valores foram submetidos primeiro a ANOVA a um critério (resistência ao cisalhamento) e teste de Tukey (p 0,05), independente do tratamento e do sistema de cimentação. Em seguida, ANOVA a dois critérios (tratamento de superfície e sistema de cimentação) e o teste de Tukey foram aplicados para observar com maior precisão a interação entre cimento e tratamento de superfície. Os resultados apresentados foram: RU - 11,71a, ApRU - 21,49b,e, MzRU - 30,38c,d, JatRU - 34,40c, JatApRU - 30,66c,d, JatMzRU - 38,06c, Pa - 11,35a, ApPa - 11,98a, MzPa - 11,46a, JatPa - 33,50c, JatApPa - 23,14b,d,e, JatMzPa - 18,66a,e. Por meio dos resultados obtidos foi possível concluir que a resistência ao cisalhamento pode ser melhorada ao utilizar o jateamento com partículas de óxido de alumínio e, para o RelyX U100, somente a aplicação do Metal/Zircônia Primer resultou em valores de adesão comparavéis ao tratamento mecânico. O cimento RelyX U100 apresentou maior resistência de união quando comparado ao Panavia F. / High crystalline content ceramics, such as yttria stabilized tetragonal zirconia polycrystal (Y-TZP), show great mechanical properties when compared to conventional ceramics, being increasingly used as indirect restorative materials. However, its success also depends on the reliable bond formation with luting agents. Though, the high crystalline content modified the adhesiveness between ceramic and resin cement although there isnt any cementing protocol established in literature. Therefore, the purpose of this study was to evaluate the effect of the shear bond strength after different surface treatments on the zirconia, using two resin cements and to evaluate possible differences in fracture modes. One hundred and twenty rectangular samples of zirconia were embedded in acrylic resin and divided into 12 groups (n=10) according to the surface treatments and the cements (Panavia F and RelyX U100). For each cement, the experimental groups were formed as follow: RU and Pa - control (no surface treatment); ApRU and ApPa (application of Alloy Primer); MzRU e MzPa (application of Metal/Zirconia Primer); JatRU and JatPa (air abrasion with 50µm Al2O3 particles); JatApRU and JatApPa (air abrasion and application of Alloy Primer); JatMzRU and JatMzPa (air abrasion and application of Metal/Zirconia Primer). The specimens were stored in distilled water at 37°C for 24 hours prior to the shear bond strength test in a universal testing machine (EMIC). The data were first analyzed by one-way ANOVA (shear bond strength) and Tukey test (p<0.05), regardless of the treatment and the luting system. Then two-way ANOVA (surface treatment and luting system) and the Tukey test were applied in order to observe more accurately the interaction between cement and surface treatments.The results presented were: RU 11.71a, ApRU 21.49b,e, MzRU 30.38c,d, JatRU 34.40c, JatApRU 30.66c,d, JatMzRU 38.06c, Pa 11.35a, ApPa 11.98a, MzPa 11.46a, JatPa 33.50c, JatApPa 23.14b,d,e, JatMzPa 18.66a,e. Based on the results obtained, it was possible to conclude that the shear bond strength can be improved when air abrasion was used with aluminum-oxide particles and for the RelyX U100, only the application of Metal / Zirconia Primer resulted in adhesion values comparable to mechanical treatment. The RelyX U100 cement showed higher bond strength when compared to Panavia F.

Orientadores: Flávio Vasconcelos da Silva, Pedro Leite de Santana / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-23T16:15:48Z (GMT). No. of bitstreams: 1 Jesus_JosiasMaximode_D.pdf: 3058451 bytes, checksum: e1bd549f7ad9180f71742e7b191881cb (MD5) Previous issue date: 2013 / Resumo: Os reatores de leito fixo constituem importantes sistemas da engenharia química, com muitas aplicações em diversos processos industriais, notadamente no campo das indústrias de refino do petróleo e petroquímica. Do ponto de vista da analise de processos químicos, se mostra relevante o estabelecimento de modelos matemáticos representativos que possam ser aplicados ao projeto, a otimização e ao controle desses sistemas. Neste trabalho, apresenta-se a modelagem matemática fenomenológica de um reator de leito fixo para a síntese de anidrido ftalico por oxidação de o - xileno, considerando-se as resistências difusionais mássicas e térmicas externas associadas ao processo de reação catalítica, o qual e realizado com catalisadores não porosos a base de óxidos de vanádio e titânio. O modelo matemático foi implementado como um modulo computacional para simulação do processo nos estados estacionário e dinâmico, a partir do qual se fez um estudo de sensibilidade paramétrica que mostrou à forte influencia da temperatura e da concentração de o - xileno na corrente de alimentação, bem como da temperatura do fluido térmico, no comportamento global do reator. Essas constatações permitiram a proposição de estruturas de controle com o objetivo de regular a concentração do produto na saída do reator e manter uma condição térmica operacional segura. Para o controle do reator foram consideradas duas estruturas: (i) um esquema de controle direto da concentração utilizando um controlador convencional PI e um controlador por lógica fuzzy (Fuzzy-PI) e (ii) um esquema de controle cascata concentração-temperatura utilizando também controladores convencionais PI e Fuzzy-PI nas duas malhas (primaria e secundaria) que compõem a estrutura cascata. Cada controlador teve seu desempenho analisado mediante perturbações do tipo degrau impostas nas condições de alimentação dos reagentes (composição e temperatura). Os resultados evidenciaram um bom desempenho das estruturas de controle cascata, que se mostraram eficientes para controlar a concentração do produto na saída do reator e garantir ao mesmo tempo um regime térmico seguro. Na presença de ruído, os controladores Fuzzy-PI apresentaram um desempenho superior ao dos controladores PI convencionais / Abstract: Fixed bed reactors are important systems in chemical engineering with several applications in many industrial processes, mainly in petroleum refining and petrochemical industries. A comprehensive view on these systems through mathematical modeling is crucial for design, optimization and control issues. This work presents a phenomenological mathematical model for a fixed bed reactor applied to the phthalic anhydride synthesis from o-xylene oxidation using supported non-porous V2O5-TiO2 catalyst. All resistances due to mass and heat flows from the fluid phase to the catalytic particle surface are considered in the mathematical formulation. The mathematical model consisted of a Matlab based computational code for the process simulation both in dynamic and steady-state conditions, providing a parametric sensitivity study that showed the intensive influence of the feed conditions in terms of temperature and o-xylene concentration, as well as the effect of thermal fluid temperature on the global reactor behavior. These observations provided control structures to regulate product concentration leaving the reactor and to avoid the formation of excessive hot spots along the catalytic bed, what is a necessary condition to maintain a safe thermal system operation. It were proposed two structures to control the reactor: (i) a straightforward scheme to control the concentration of phthalic anhydride in the reactor outlet using conventional PI and fuzzy PI controllers, and (ii) another scheme based on a cascade control temperature-concentration also using conventional and fuzzy PI controllers in two (primary and secondary) loops. The behavior of each controller was analyzed by imposing stepwise perturbations in inner o-xylene concentration and in the temperature of the feed. The results showed a good performance of cascade-type controllers, providing the proper regulation of the controlled variable and a safe thermal regime for the system operation. On the other hands, fuzzy logic controllers exhibited better performance for the reactor regulation when measurement noise was taken in account / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química