O reator anaeróbio de leito fixo tem demonstrado viabilidade para produzir hidrogênio a partir de águas residuárias. No entanto, a liberação do biogás não tem sido contínua devido à diminuição constante da carga orgânica volumétrica específica (COVe) causada pelo acúmulo de biomassa no leito ao longo do tempo. A redução da COVe junto com o envelhecimento da biomassa tem sugerido o estabelecimento de microorganismos consumidores dos constituintes do biogás (H2/CO2) responsáveis por cessar a produção de hidrogênio. Neste trabalho, cinco estratégias foram propostas visando a produção de hidrogênio por longo prazo operacional e com estabilidade, mediante a fixação da COVe, as quais incluíram a alteração da estruturação do leito, inverter o escoamento, realizar descartes periódicos de biomassa e variar a carga orgânica volumétrica aplicada (COV) por meio da variação do tempo de detenção hidráulica (TDH) e da concentração do substrato. Os resultados demonstraram que a manutenção da COVe em um valor adequado permite a produção contínua de hidrogênio. A ordenação do leito, utilizando polietileno de baixa densidade e espuma, e o escoamento descendente favoreceram a diminuição do acúmulo de biomassa e junto com os descartes de biomassa foi possível manter a COVe em um valor estável próximo de 5 g sacarose g-1 SSV d-1. A produção volumétrica de hidrogênio (PVH) foi contínua com valor médio de 0,6 L H2 L-1 d-1 e rendimento (YH2) próximo a 0,5 mol H2 mol-1 sc. Por outro lado, o escoamento ascendente e os descartes de biomassa em reator de leito empacotado e ordenado atingiram uma PVH média de 2,2 ± 0,2 e 3,13 ± 0,07 L H2 L-1 d-1 quando a COVe foi mantida em 2,6 e 4,4 g sacarose g-1 SSV d-1, respectivamente. Por último a variação da COV permitiu manter a COVe entre 3,8 e 6,2 g sacarose g-1 SSV d-1, atingindo um YH2 médio de 2 mol H2 mol-1 sc e um incremento da PHV de 2,4 a 8,9 L H2 L-1 d-1 durante 60 dias consecutivos. Ainda que com resultados satisfatórios referentes à manutenção por longo período operacional e estabilidade na produção de hidrogênio, a supersaturação deste gás no meio líquido, devido a limitações de transferência de massa, foi a principal causa de perdas de hidrogênio neste tipo de reator. / Fixed-bed, anaerobic reactor has been shown to be feasible for hydrogen production from wastewater. However, biogas release has not been continuous due to the continuous specific organic load (SOL) decrease, which in turn is caused by biomass accumulation in the bed, through the time. SOL reduction and biomass ageing have indicated the establishment of the microorganisms that consumes the biogas constituents (H2/CO2) as the main cause for ceasing hydrogen production. In this work, five strategies were proposed aiming at obtaining longterm, stable hydrogen production by using SOL maintenance, modifications of the bed structure, flow inversion, periodic biomass discards and diverse organic load rates (OLR), as a function of the hydraulic retention time (HRT) and of the substrate concentration. Results demonstrated that by maintaining the SOL at proper values, continuous hydrogen production can be accomplished. On one hand, structuring the bed by using low-density polyethylene and foam, together with a down-flow and biomass discards were shown to diminish biomass accumulation, which led to keep a stable SOL value close to 5 g sucrose g-1 VSS d-1. Volumetric hydrogen production (VHP) was continuous with an average value of 0.6 L H2 L-1 d-1 and a yield (YH2) close to 0.5 mol H2 mol-1 sc. On the other hand, up-flow with biomass discharges, when implemented structured-bed and packed-bed reactors reached average VHP values of 2.2 ± 0.2 and 3.13 ± 0.07 L H2 L-1 d-1 as SOL was maintained between 2.6 and 4.4 g sucrose g-1 VSS d-1, respectively. Eventually, SOL was kept between 3.8 e 6.2 g sucrose g-1 VSS d-1 by varying the OLR, thus reaching an average YH2 value of 2 mol H2 mol-1 sc and a VHP increase from 2.4 to 8.9 L H2 L-1 d-1, along sixty consecutive days. As a consequence of mass-transfer limitations, oversaturation of hydrogen at the liquid medium was found as the main factor that causes hydrogen losses concerning fixed-bed reactors, even though the proposed strategies did indeed demonstrate long-term and stable hydrogen production.

Este trabalho de investigação refere-se ao uso do reator anaeróbio híbrido para tratamento de esgoto sanitário, com configuração baseada no reator anaeróbio de manta de lodo (UASB) com inclusão de: meio suporte sobre as calhas de coleta de gás (denominado reator anaeróbio híbrido - UAHB) e, também, meio suporte na zona de reação (denominado reator anaeróbio híbrido modificado - UAHBmod). Para o desenvolvimento desta pesquisa, no Campus I da USP de São Carlos-SP foram construídos dois reatores experimentais de 18,8 m3 cada: um reator UASB, com função de controle, e um reator UAHB. Primeiramente os reatores foram operados por período de 200 dias, com tempo de detenção hidráulica (TDH) de 6 h. Após serem inoculados, com 80 dias de operação, os reatores atingiram o estado de equilíbrio dinâmico aparente, com geração de alcalinidade, baixa concentração de ácidos voláteis e eficiência de remoção média de DQO, de 84% e 85% e de DBO de 87% e 91%, respectivamente para o UASB e o UAHB. Após esse período, os reatores foram submetidos a aumento da velocidade ascensional (Vasc) (mediante recirculação do efluente) de 0,78 m.h-1; 1,17 m.h-1; 1,56 m.h-1 e de 1,96 m.h-1. O UAHB mostrou ser menos susceptível ao aumento da Vasc do que o UASB. Além da análise da operação dos reatores, foram realizados os ensaios hidrodinâmicos e avaliada a estrutura da comunidade microbiana, por microscopia ótica, epifluorescência e pela técnica do DGGE. Após esse período preliminar, os reatores UAHB e UAHBmod, operados com TDH de 6h e Vasc de 0,78 m.h-1, atingiram o estado de equilíbrio dinâmico aparente, com geração de alcalinidade, baixa concentração de ácidos voláteis e eficiência de remoção média da matéria orgânica, de 71% e 76% em DQO, e de 72% e 87% em DBO, respectivamente para o UAHB e UAHBmod. Após este período, o reator UAHBmod, submetido a Vasc de 1,56 m.h-1, promoveu remoção de 74% de DQO, e de 87% de DBO. / This research refers to the use of a hybrid anaerobic reactor (UAHB) for domestic wastewater treatment. The configuration of this reactor is based on a sludge bed anaerobic reactor (UASB); in the first instance, a media support above the gas collection apparatus (also known as hybrid anaerobic reactor) was provided and later, a media support on the reaction zone (also known as hybrid modified anaerobic reactor - UAHBmod) was provided. Two reactors, with a volume of 18.8 m3, each, were built for this research at Campus I, USP in São Carlos - SP-Brazil. One UASB reactor acted as a control, and the other as a UAHB reactor. In the preliminary essays, the reactors were operated with 6h of hydraulic detention time (HDT) for 200 days. After inoculation, the reactors attained the apparent dynamic equilibrium state after 80 days of operation, with alkalinity generation, low volatile acids concentration and mean organic matter removal of 84% and 85% in terms of COD, and 87% and 91% in terms of BOD, for UASB and UAHB reactors, respectively. After this period, the reactors were submitted to an increasing in up velocity (Vup) of 0.78 m.h-1; 1.17 m.h-1; 1.56 m.h-1 and 1.96 m.h-1. The UAHB reactor showed lesser susceptibility for Vup increase than the UASB reactor. Hydrodynamic tests were also done on the reactors, in addition to routine operational analysis. The structure of the microbial community was evaluated by optical and epifluorescence microscopy, and the DGGE technique. After this step, the UAHB and the UAHBmod reactors were operated out 6h of HDT and Vup of 0.78 m.h-1. The reactors attained the apparent dynamic equilibrium state with alkalinity generation, low volatile acids concentration and mean organic matter removal of 71% and 76% in terms of COD, and 72% and 87% in terms of BOD for the UASB and UAHBmod reactors, respectively. After this period, the UAHBmod reactor was subjected to a Vup of 1.56 m.h-1 and achieved removal efficiencies of 74% COD and 87% BOD.

Submeteu-se um Reator Anaeróbio Horizontal de Leito Fixo (RAHLF) de bancada, ao aumento progressivo da concentração de matéria orgânica afluente, e a cargas de choque orgânicas, com o objetivo de verificar-se seu desempenho e estabilidade operacional. O RAHLF foi construído com um tubo de boro-silicato de 100 cm de comprimento, 5,0 cm de diâmetro e 1995 ml de volume total e preenchido com lodo anaeróbio imobilizado em matrizes de espuma de poliuretano. O reator foi alimentado, inicialmente, com substrato composto principalmente de carboidratos em concentrações, expressas como Demanda Química de Oxigênio (DQO) de, aproximadamente, 200, 1000 e 2000 mg/l. Posteriormente, os carboidratos foram substituídos por metanol e ácidos voláteis, em concentrações totais, aproximadas, de 2000, 3000, 4000 e 5000 mg DQO/l. Atingido o estado estacionário para cada condição operacional, foram aplicadas cargas de choque, aumentando-se em três vezes o valor da DQO afluente, durante período equivalente ao tempo de detenção hidráulica (sete horas). O sistema apresentou problemas operacionais durante os experimentos com carboidratos, quando submetido a 2000 mg DQO/l, correspondente à taxa volumétrica de carregamento orgânico de 8,77 KgDQO/m3.d. Não foi verificado qualquer problema operacional durante os experimentos com substrato contendo metanol e ácidos voláteis, e o reator apresentou eficiência de remoção de DQO superior a 90%. Para o experimento com DQO afluente igual a 2000 mg/l, os parâmetros cinéticos foram estimados a partir de modelo cinético de 1ª ordem, obtendo-se valor de k1 igual a 0,049 h-1, nos demais experimentos ajustou-se modelo cinético de 2ª ordem com valor médio de k2 equivalente a 2,0 x 10-4 l/mg.h Foram aplicadas cargas de choque orgânicas equivalentes a, aproximadamente, 17; 27; 40 e 47 kgDQO/m3.d. Os efeitos das sobrecargas orgânicas no reator foram transientes em todos os casos, tendo o reator voltado à condição inicial em, no máximo, 15 horas após o início das sobrecargas. / A Horizontal flow Anaerobic lmmobilized Sludge Reactor (HAIS) was subjected to progressively increasing concentrations of organic effluent material and to organic shock loads with the purpose of investigating its operational performance and stability. The HAIS, consisting of a 100 cm long, 5 cm diameter borosilicate tube with a total volume capacity of 1995 mL, was filled with anaerobic sludge immobilized in foam and polyurethane matrixes. The reactor was initially fed with a substrate composed mainly of carbohydrates in concentrations, expressed as Chemical Oxygen Demand (COD), of approximately 200, 1000 and 2000 mg/L. These carbohydrates were later replaced by methanol and volatile acids in total concentrations of 2000, 3000, 4000 and 5000 mg COD/L. Shock loads were applied after each operational condition became stationary, with the effluent COD tripled for a period equivalent to the hydraulic detention time (seven hours). The system presented operational problems during the experiments with carbohydrates when subjected to 2000 mg DQO/l, which corresponded to a volumetric organic load index of 8,77 Kg COD/m3.d. No operational problems were detected during the experiments with substrates containing methanol and volatile acids, and the reactor presented a COD removal efficiency of over 90%. The kinetic parameters for the COD effluent with 2000 mg/L were estimated based on a first arder kinetic model, which resulted in a k1 value of 0,049 h-1, while a kinetic model of the second order was used for the remaining experiments, with a mean value of k2 equivalent to 2,0 x 10-4 L/mg.h. Organic shock loads of approximately 17; 27; 40 and 47 kg COD/m3.d were applied. The effects of the organic overloads on the reactor were transient in every case, with the reactor returning to its initial condition at the most 15 hours after the beginning of the overloads.

Este trabalho apresenta as avaliações de desempenho, das demandas operacionais e dos fatores intervenientes no aumento da escala da unidade piloto do Reator anaeróbio Horizontal de Leito Fixo (RAHLF) no tratamento de esgoto sanitário após passagem por peneira com malha de 1 mm, durante dois anos de operação. O reator dispunha de volume total de 237,5 1, construídos com tubos comerciais de PVC de 14,5 cm de diâmetro (D), dispostos em cinco módulos horizontais em série de 2,88 m, perfazendo um comprimento total de (L) de 14,4 m e relação de total de L/D de 100. O suporte de imobilização de biomassa, espuma de poliuretano em matrizes cúbicas de 1 cm de aresta, mostrou-se adequado ao desenvolvimento do biofilme. Em partida, sem inoculação prévia, ocorreu a sua consolidação a partir de 70 dias, com predominância de morfologia semelhante a Methanosaeta sp. em relação a da Methanosarcina. Em torno de 90 dias com afluente de 350 mg/l de DQO, observe-se a melhor qualidade do efluente, com valor de 100 mg/l de DQO. Em longa operação ocorreu queda de rendimento e menor reprodutibilidade das previsões do projeto, atribuída aos constantes entupimentos e ineficácia das operações de limpeza, com o comprometimento de volume reacional verificados por estudos de hidrodinâmica. Da investigação das origens dos equipamentos observou-se tratar mais de um efeito local e qualitativamente relacionado à biomassa retida que propriamente quantitativo e extensivo ao longo de todo reator, com produção continuada de polímeros extracelulares, promovendo um efeito sinérgico com os predominantes organismos filamentosos e com os sólidos particulados retidos no leito. Diante das potencialidades desta configuração de reator apontam-se alternativas de mitigação dos entupimentos e o direcionamento dos estudos necessários para novo aumento de escala para o tratamento de esgoto sanitário. / This work evaluated the performance, the operational demands and the intervenient factors in the scale-up of the horizontal flow anaerobic immobilized biomass (HAIB) reactor pilot unit, treating domestic sewage previously screened. The operation was monitored for two years. The five- module (2.88 m length each) reactor volume was 237.5 liters and it was built with commercial PVC pipes of 14.5 cm of diameter (D), resulting in a total length (L) of 14.4 m and in a total ratio L/D of approximately 100. The immobilization support, cubic matrices of polyurethane foam (1 cm edge), showed to be suitable for the anaerobic biofilm development. During the start-up, without previous inoculation, the biofilm seemed to be consolidated after 70 days, and Methanosaeta sp. morphology predominated, in detriment of Methanosarcina. With an affluent of 350 mg COD/L, the best reactor performance was observed in about 90 days of operation (100 mg COD/L in the effluent). However, with the continuous operation, its performance decreased and the project predictions did not seem to fit anymore. These facts were probably due to the frequent cloggings ant the inefficiency of the backwashing procedures, leading to a decreasing of the operational volume. The origin of the clogging seemed to be related to the extracellular polymer production, linked to a synergic effect with the filamentous organisms and the particulate solids in the bed. Despite these operational problems, there were found alternatives to mitigate the clogging, and studies about a new scale-up methodology, in order to treat domestic sewage, were strongly recommended.

O projeto consistiu na concepção e avaliação do desempenho de um sistema anaeróbio-aeróbio para tratamento de esgoto sanitário. O leito do reator foi dividido em quatro compartimentos de igual volume. Foi usada espuma de poliuretano para imobilização da biomassa e, para facilitar a partida do reator, esse material suporte foi previamente inoculado. O projeto teve três fases distintas: na primeira etapa, foi observada a importância da concentração de biomassa anaeróbia no desempenho de reator anaeróbio a princípio operado com metade do leito reacional com espuma e, a seguir, com o leito todo preenchido com espuma. Na segunda etapa, foram testados diferentes tempos de detenção hidráulica no reator que operou apenas em condições anaeróbias. Na última etapa foi operado o reator combinado anaeróbio-aeróbio. Ficou constatada a importância da concentração de microrganismos no desempenho do reator anaeróbio, pois com o aumento da quantidade de espuma, o reator atingiu resultados melhores e maior estabilidade operacional. Foi comprovada a influência do tempo de detenção hidráulica (TDH) no desempenho do reator. Tempos de detenção muito altos acarretam problemas de transferência de massa líquido-sólido, e baixos TDH dificultam adequada ação dos microrganismos. O melhor resultado para o reator em operação exclusivamente anaeróbia foi para o TDH de 10 horas, no qual se conseguiu reduzir a DQO de amostra bruta de 389 +/- 70 mg/L para 137 +/- 16 mg/L, em média. Para o reator operado anaeróbio-aeróbio a DQO de amostra bruta decresceu de 259 +/- 69 mg/L para 93 +/- 31 mg/L, em média. A comparação de todos os resultados obtidos, evidenciou a importância do pós-tratamento aeróbio na remoção de parcela de matéria orgânica não removida em tratamento unicamente anaeróbio. / The project consisted in the design and performance evaluation of an anaerobic-aerobic system for wastewater treatment. Polyurethane foam was used for biomass immobilization and, to smooth the reactor start-up, this supporting material was previously inoculated. The project was divided in three distinct phases. In the first one, the importance of the anaerobic biomass concentration was observed in the performance of the anaerobic reactor in a way to operate the reactor primarily with half of the reaction bed filled with foam and subsequently operate it with the bed completely filled with foam. In the second phase, different times of hydraulic retention were tested with the reactor operating exclusively in anerobic conditions. In the third and last phase, an anaerobic-aerobic combined reactor was operated. It was possible to confirm the importance of microorganism concentration in the performance of the anaerobic reactor, since the increase in the amount of foam allowed the reactor to reach better results and greater operational stability. The influence of the hydraulic retention time in the reactor performance was also proved. Very high retention times cause problems in the liquid-solid mass transference, while low retention times do not allow an adequate action of microorganisms. The best result for the reactor with an exclusive anaerobic operation was the 10 hour retention time, when it was possible to reduce the COD of a 389 +/- 70 mg/L gross sample to a 137 +/- 16 mg/L in average. On the other hand, for the anaerobic-aerobic operating reactor, the COD of a gross sample dropped from 259 +/- 69 mg/ L to 93 +/- 31 mg/L in average. Finally, comparing all the obtained results, it was possible to verify the importance of the anaerobic post treatment in the removal of a part of the organic matter not removed in an exclusively anaerobic treatment.

A atividade industrial diversificada tem sido responsável pelo lançamento, no ambiente, de resíduos que contém materiais tóxicos e/ou de difícil degradação. Benzeno, tolueno, etilbenzeno e xilenos (BTEX) são compostos importantes, por estarem presentes em águas superficiais e subterrâneas, geralmente a partir de contaminações por derivadas de petróleo. Enquanto a degradação aeróbia de BTEX já está amplamente entendida e descrita, a aplicação de processos anaeróbios de tratamento, indicados na década de 80 ainda requer mais estudos. Reatores anaeróbios horizontais de leito fixo de bancada preenchidos com cubos de espuma de poliuretano, contendo lodo anaeróbio proveniente de diversas fontes trataram a água residuária sintética a base de proteínas, carboidratos, lipídios, contendo solução etanólica de BTEX e solução de BTEX em detergente comercial; e solução etanólica de BTEX como únicas fontes de carbono. A influência da adição de nitrato e sulfato como aceptores de elétrons na degradação anaeróbia também é discutida. Os reatores foram capazes de remover BTEX nas concentrações testadas de até 15,0 mg/L de cada composto, com tempos de detenção hidráulica de 11,4 horas e 13,5 horas. Os reatores forneceram condições excelentes para o desenvolvimento de biofilme complexo capaz de degradar BTEX, contendo organismos degradadores de BTEX, acetogênicos, acetoclásticos e hidrogenotróficos. Arqueas metanogênicas representaram menos de 0,5% do total de organismos anaeróbios na biomassa dos reatores. O modelo cinético de primeira ordem com residual foi o que melhor representou os dados experimentais e as velocidades de degradações de BTEX, estimadas neste trabalho, foram cerca de 10 a 94 vezes maiores que as encontradas na literatura, em ensaios realizados em microcosmos. / The diversified industrial activity has been responsible for discharge in the environment of toxic and/or difficult degradation compounds. Benzene, toluene, ethylbenzene and xylenes (BTEX) are important compounds present in surface and ground waters, usually from petroleum products contamination. While BTEX aerobic degradation is extensively understood and described, anaerobic treatment application, started in the eighties, associated to fundamental studies need to be improved. Bench-scale horizontal-flow anaerobic immobilized biomass reactors filled with polyurethane foam matrices, containing immobilized anaerobic biomass from various sources, treated synthetic substrate containing protein, carbohydrates, lipids, BTEX solution in ethanol and BTEX solution in commercial detergent, as well as BTEX solution in ethanol as the sole carbon source. The influence of the addition of nitrate and sulfate as electron acceptors on anaerobic degradation is also discussed. The reactors were able to remove up to 15.0 mg/L of each BTEX compound, with hydraulic detention time of 11.4 hours and 13.5 hours. The reactors provided excellent conditions for developing a complex biofilm with BTEX-degraders, acetogenic, acetoclastic and hydrogenotrophic microorganisms. Methanogenic archaea were found to represent less than 0.5% of the total anaerobic organisms in the biomass inside the reactors. Residual first order kinetic model fitted well the experimental data and the BTEX degradation rates, estimated in this work, were about 10- to 94-fold higher than those found in the literature, in microcosms studies.

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

Les procédés actuellement utilisés à bord de la Station Spatiale Internationale permettent un traitement physico-chimique des déchets avec un recyclage partiel des éléments en minimisant le réapprovisionnement en eau et oxygène. Voyager plus loin et sur de plus longues durées n’est possible que si un système de support de vie, permettant d’assurer une autonomie plus importante, est mis en place. Le projet MELiSSA est un système de support de vie biorégénératif ayant pour objectifs de recycler les déchets produits par l’homme, de régénérer l’oxygène et l’eau et d’assurer une production de nourriture. L’utilisation de microorganismes pour assurer ces différentes fonctions, n’est réalisable qu’en ayant la meilleure connaissance possible et surtout la maîtrise des processus et des souches impliqués. L’objectif de cette thèse est de développer un modèle prédictif pour le compartiment nitrificateur de la boucle MELiSSA. Dans un premier temps, les souches Nitrosomonas europaea ATCC® 19718 et Nitrobacter winogradskyi ATCC® 25391 ont été étudiées et ont permis de définir un modèle cinétique de ces deux bactéries en culture immergée. Dans un second temps, ce modèle a été combiné à un modèle N-bacs en série pour composer un modèle de nitrification dans une colonne à lit fixe à biomasse fixée : le modèle NitriSim. Ce modèle a été testé sur une expérience de long-terme menée dans une colonne à lit fixe dont le support est composé de billes Biostyr®. Le dernier chapitre de ce manuscrit décrit l’utilisation d’une souche dégradant l’urée, Cupriavidus pinatubonensis, dans le réacteur à lit fixe. Les différents résultats ont permis de définir un modèle de nitrification dans un réacteur à lit fixe et de présenter des perspectives possibles pour le traitement de l’urine au niveau du compartiment nitrifiant de MELiSSA. / Physico-chemical processes are used on the International Space Station for partial recycling of wastes in order to minimize the resupplies of oxygen and water. Further and longer explorations can only be possible if a life support system is applied to enhance autonomy to the station. MELiSSA is a biological life support system project aiming for waste recycling, water and air regeneration and production of simple food. The only way to assure these functions is the use of microorganisms which is requiring a high knowledge and a perfect control of processes implicated. The thesis objectives consist in developing a predictive model for the MELiSSA nitrifying compartment. First, a kinetic study of Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25391 in submerged bioreactors allowed defining a kinetic model of nitrification. Secondly, this model was combined to an N-tanks in series one to compose a nitrification model in fixed-bed biorectors : NitriSim. It was applied on a long-term experiment in a fixed-bed bioreactors where the bed was composed of Biostyr® beads. The last part of this work was about the use of a urea-degradating bacteria, Cupriavidus pinatubonensis, in the fixed-bed bioreactor. All of these results leaded to the development of a nitrification in fixed-bed reactors model and opened up interesting prospects for the urine degradation in the nitrifying compartment of MELiSSA.

Die vorliegende Arbeit beschäftigt sich mit rohstofflichen und verfahrenstechnischen Einflussfaktoren bei der Biomassepyrolyse. Ausgehend von der Entwicklung einer kleintechnischen Festbettpyrolyseapparatur, erfolgten experimentelle Untersuchungen an 26 biogenen Einsatzstoffen unter verschiedenen Prozessbedingungen. Die Apparatur erlaubt eine vollständige Bilanzierung und Gewinnung aller Produkte, zudem können Einflüsse durch sekundäre Reaktionen in der Gasphase minimiert werden. Die Einsatzstoffe, welche u. a. auch Zellstoff, Xylan und Alkali-Lignin einschließen, wurden hinsichtlich brennstofftechnischer und physikalischer Eigenschaften sowie der Stoffgruppenzusammensetzung charakterisiert. Sie repräsentieren eine große Bandbreite möglicher Zusammensetzungen. Bei den Prozessparametern wurde die Pyrolysetemperatur im Bereich von 200 bis 750 °C, die Aufheizrate zwischen 5 und 100 K/min, die Feststoffverweilzeit von 0 bis 30 min sowie die Partikelgröße (0 bis 5 mm) variiert. Aus den Untersuchungen zum Einfluss der Prozessparameter für die verschiedenen Einsatzstoffe wurden unter Anwendung einer geeigneten Bilanzierungsmethodik geschlossene Masse- und Elementbilanzen für jeden Versuchspunkt aufgestellt. Unter den Prozessvariablen konnte die Temperatur erwartungsgemäß als wichtigste Einflussgröße identifiziert werden. Der zweistufige Zersetzungsverlauf der Biomassen ermöglicht die mathematische Beschreibung der temperaturabhängigen Ausbeuten mittels der zweistufigen Boltzmann-Funktion für den gesamten Temperaturbereich mit hohen Bestimmtheitsmaßen. Die rohstofflichen Einflussgrößen wurden unter Anwendung der Rangkorrelationsmethode nach Spearman und der Produkt-Moment-Korrelation nach Pearson mit den definierten Zielgrößen (Ausbeuten, Produktzusammensetzung, Kokseigenschaften, Heizwerte, Energieeinbindung) bei verschiedenen Pyrolysetemperaturen korreliert. Neben der Stoffgruppenzusammensetzung konnten bei den rohstofflichen Einflussfaktoren die Gehalte an Alkalien sowie der Gesamtgehalt an potentiell katalytisch aktiven Bestandteilen (Na, K, Mg, Ca, Fe) als Haupteinflussgrößen identifiziert werden. Korrelationen ergeben sich auch für brennstofftechnische Eigenschaften, wobei neben dem Flüchtigen- und dem Aschegehalt, das O/C-Verhältnis signifikant ist. Die gefundenen statistischen Zusammenhänge können weitestgehend mechanistisch begründet werden. Zur Quantifizierung der ermittelten Zusammenhänge für die Zielgrößen wurden multiple Regressionsmodelle erstellt und anhand von Bestimmtheitsmaß, Informationskriterium und mittleren Modellfehlern bewertet. Somit konnten 42 Regressionsgleichungen für die Produktausbeuten bei verschiedenen Pyrolysetemperaturen entwickelt werden, die auf den Gehalten verschiedener Stoffgruppen und dem Gesamtgehalt an katalytisch aktiven Elementen basieren. Weitere 56 Regressionsgleichungen stehen für die Berechnung von Teer/Öl-Elementarzusammensetzung, Kokszusammensetzung, Teer/Öl-Heizwert sowie Energieeinbindung im Koks bei verschiedenen Pyrolysetemperaturen zur Verfügung. Die Prognoseeignung der Gleichungen wurde anhand eines weiteren Datensatzes für Apfeltrester überprüft. Für die Koks-, die Gas- und die Kondensatausbeute sowie die genannten Produkteigenschaften ergab sich eine gute Vorhersagequalität, die jedoch stark von der verwendeten Gleichung abhängt. Die Validierung mit Literaturdaten konnte aufgrund fehlender Datensätze, die sowohl die notwendigen Rohstoffparameter als auch Produktausbeuten und -eigenschaften enthalten, nur anhand der Koksausbeute erfolgen. Für verschiedene Biomassen und biogene Reststoffe führte dies zu einer guten Anpassung. Die mathematische Beschreibung der Ausbeuten und bestimmter Produkteigenschaften über Regressionsgleichungen auf Grundlage von Rohstoffparametern stellt einen vielversprechenden Ansatz für die Vorhersage der maximalen Ausbeuten bei bestimmten Bedingungen dar. Dies ermöglicht eine Abschätzung zur Einsatzeignung von Biomassen bzw. biogenen Reststoffen für verschiedene Anwendungszwecke. Bisher existiert kein derartiges Modell zur Vorhersage der definierten Zielgrößen. Grundsätzlich wäre die Entwicklung einfacher Gleichungen mit wenigen, einfach bestimmbaren und standardisierten Parametern erstrebenswert. Die Ergebnisse haben jedoch gezeigt, dass Ein-Variablen-Modelle die Trends zwischen den Biomassen aufgrund der komplexen Zusammenhänge zwischen Pyrolyseverhalten und Rohstoffparametern häufig nicht richtig wiedergeben können. Für robuste Modelle sind somit mindestens zwei unabhängige Modellparameter mit idealerweise gegensätzlichem Einfluss notwendig. / The intention of this work was an intensive study of the influence of feedstock properties and process variables on biomass pyrolysis. Due to a lack in consistent data sets, including various feedstock parameters as well as product yields, compositions, and further properties, a laboratory fixed bed reactor was developed to overcome this problem. The pyrolysis reactor was used for experiments with 26 biogenous feedstock under variable process conditions. The reactor is suitable to assure nearly closed mass balances and a complete product recovery. Furthermore, it allows the minimization of secondary reactions. The used feedstock, which include cellulose, xylan, and lignin amongst others, represent a broad range of possible compositions and were intensively characterized by determination of fuel and physical properties as well as biopolymer composition. The varied process parameters are: temperature between 200 and 700 °C, heating rate in the range of 5 to 100 K/min, solid residence time from 0 to 30 min, and particle size up to 5 mm. Closed mass and element balances were done for every set of parameters. As expected, amongst process variables the temperature was identified as the main factor influencing biomass pyrolysis. The temperature depending products yields could be fitted well by the double boltzmann approach due to the two-stage pyrolytic decomposition of biomass. Correlation of feedstock properties with different target parameters, including yields, product composition, heating values, remaining energy content in char, and char properties, was done by Spearman´s rank correlation and Pearson´s correlation for different temperatures. Biopolymer composition as well as alkaline content and total content of potential catalytic elements (Na, K, Ca, Mg, Fe) were identified as main factors influencing biomass pyrolysis product yields and compositions. Further correlations arise with fuel properties like volatile matter and ash content besides O/C atomic ratio. The obtained correlations can be mainly related to pyrolysis mechanisms. The received relationships were quantified by means of multiple regression models. Model evaluation was done by coefficient of determination, information criteria and mean squared errors. 42 regression models, based on different biopolymer contents and the total content of catalytic elements, were provided for the mathematical description of product yields for different process temperatures. Another 56 equations are suitable for the calculation of product properties like tar/oil and char composition, tar/oil heating value, and remaining energy content in the char at different temperatures. The predictability of the regression models was proved using another data set for apple pomace. The yields of char, gas, and condensate as well as the aforementioned product properties can be predicted very well, although, the predictability varies with the applied equation. Validation of the models by literature data was only possible for the char yield, because of the mentioned lack in suitable and complete data sets. Application of regression model to fixed bed char yields for different biomass and biogenous residues from literature resulted in a good predictability. Mathematical description of pyrolysis product yields and properties by means of regression models based on feedstock parameters is a promising approach to predict maximum yields at defined conditions and, therefore, to make an estimation of suitability of the biomass to different applications. Up to now such models do not exist. In general, the development of simple equations based on a few standardized parameters which are easy to determine is worthwhile. Hence, the results showed that the overall trend between different biomass feeds was often not predicted correctly using one-parameter models. This is due to the complex relationships between pyrolysis behavior and feedstock properties. Consequently, at least two parameter models, where the variables show the opposite trends, were most appropriate.

Automated start–up and shutdown procedures increase the profitability and safety of a process, but are difficult to implement due to the complex nature of the concepts that must be incorporated. Generic components used specifically for the implementation of automated startup and shutdown procedures were defined to streamline the implementation process. The generic components developed are based on Sequential Function Charts and were applied to the startup of a fixed–bed gasification unit, for which a dynamic simulation model was developed. The application showed that the automated startup can be defined by a few generic components and that the flexibility of the startup procedure is increased through the incorporation of a fault accommodation module. The use of a visual–based definition of sequential processes increases the understanding of the complex scheduling procedures as well as the efficiency of the development of these automated procedures. In addition, iterative learning was incorporated into the generic definition to optimise controller performance during the non–linear phases of operation. / Dissertation (MEng (Control Engineering))--University of Pretoria, 2006. / Chemical Engineering / MEng / Unrestricted