Modelos matemáticos oferecem grandes benefícios para a compreensão dos mecanismos envolvidos nos processos de tratamento de águas residuárias uma vez que fornecem interpretações e possibilitam previsões de desempenho, comparações de alternativas de tratamento, otimização de futuras plantas ou o aprimoramento das existentes, podendo subsidiar a elaboração de projetos em escala real. Em virtude disto, nesta pesquisa visou-se o desenvolvimento de um modelo bioquímico-matemático para descrever o processo de degradação da glicose em um reator anaeróbio de leito fixo com fluxo ascendente, com a resultante produção biológica de hidrogênio por meio do processo de fermentação. O desenvolvimento do modelo foi baseado em estudos sobre a cinética bioquímica e as características hidrodinâmicas do sistema. Os parâmetros de ajuste do modelo aos dados experimentais foram as constantes de velocidade das reações bioquímicas envolvidas na produção de hidrogênio. A calibração foi realizada manualmente buscando minimizar o desvio global. Para a determinação dos parâmetros foi utilizada a técnica de geração de números aleatórios com distribuição de freqüência uniforme e em seguida, o método de inversão de matrizes. O modelo matemático se revelou bastante adequado para a previsão do perfil de concentrações ao longo do reator, e possibilitou a representação das rotas de utilização da matéria orgânica. A reação de oxidação do ácido propiônico pelas bactérias acidogênicas produtoras de hidrogênio constitui a principal via de produção de \'H IND.2\' no sistema. / Mathematical models bring benefits to the understanding of mechanisms involved on wastewater treatment processes because they provide interpretations and make possible performance predictions, evaluation of design alternatives, optimization of future plants or the improvement to existing systems. Therefore, in this work a mathematical model to describe the glucose degradation process, with hydrogen production through the fermentation, in an upflow anaerobic packed-bed reactor is developed. The model equations were based on studies of biochemical kinetics and hydrodynamics features of the system. The parameters considered were the rates of the biochemical reactions involved in the hydrogen production. The calibration was made through the minimization of the global deviation. The parameters determination was obtained with the use of a technique of generation of aleatory numbers, and after that, the method of matrices inversion for the solution of the system of linear equations. The mathematical model developed showed to be adequate for the concentrations prediction along the reactor, and it made possible the representation of the routes of organic material utilization. The oxidation reaction of propionic acid is the main hydrogen production route in the reactor.

A presente pesquisa avaliou diferentes razões de recirculação do meio líquido com a finalidade de identificar a melhor condição de mistura para uma produção elevada e contínua de hidrogênio em um reator anaeróbio de leito fixo com fluxo ascendente alimentado com um meio contendo sacarose como fonte de carbono e uréia como fonte de nitrogênio. Foi utilizado polietileno de baixa densidade como meio suporte para imobilização da biomassa. O experimento foi iniciado com ensaios hidrodinâmicos (pulso, utilizando dextran blue como traçador) que determinaram as seguintes razões de recirculação em relação à vazão de alimentação utilizadas: R = 0,25, 0,5, 1,0 e 2,0. O experimento foi realizado em duas etapas, nas quais foram operados dois reatores idênticos simultaneamente, testando-se duas razões de recirculação diferentes. A DQO da água residuária foi de 2000 mg/L. O tempo de detenção hidráulica teórico foi de 2 horas e a temperatura foi mantida em 25 graus Celsius. A remoção de sacarose apresentou valores médios de 67%, 79%, 71% e 70% para R = 0,25, 0,5, 1,0 e 2,0, respectivamente. Os valores médios de rendimento de hidrogênio foram 1,14 mol \'H IND.2\'/mol sac, 1,43 mol \'H IND.2\'/mol sac, 1,34 mol \'H IND.2\'/mol sac e 0,86 mol \'H IND.2\'/.mol sac e de produção volumétrica de hidrogênio foram 74,34 mL \'H IND.2\'/(h.L), 124,78 mL \'H IND.2\'/(h.L), 96,57 mL \'H IND.2\'/(h.L) e 73,49 mL \'H IND.2\'/(h.L) para as vazões de recirculação de 0,25, 0,5, 1,0 e 2,0, respectivamente. O biogás produzido foi composto de \'H IND.2\', e \'CO IND.2\', com valores percentuais médios para \'H IND.2\', de 50%, 56%, 56% e 46% para R = 0,25, 0,5, 1,0 e 2,0, respectivamente. Não houve presença de metano em nenhuma fase de operação. Os principais produtos intermediários produzidos durante a produção de \'H IND.2\', foram ácido acético, ácido butírico e etanol, de forma similar para todas as fases de recirculação. Analisando todos os parâmetros de operação, foi possível notar que a melhor vazão de recirculação obtida foi de R = 0,5. Ajustando os dados obtidos a uma função polinomial, porém, chegou-se a um ponto de ótimo em R = 0,6. Durante os experimentos observou-se uma queda na produção do biogás, provavelmente por atuação de microrganismos consumidores deste. / The present research evaluated different recirculation rates of the liquid medium for the purpose of identify the best mixture condition for a high and continuous hydrogen production in an anaerobic upflow fixed-bed reactor fed with a medium containing sucrose as carbon source and urea as nitrogen source. Low density polyethylene was used as medium for biomass immobilization. The experiment began with hydrodynamic tests (pulse, using dextran blue as tracer) which led to the following recirculation rates related with the feed flow rate used in this work: R = 0,25, 0,5, 1,0 and 2,0. The experiment was conducted in two stages, where two identical reactors were operated simultaneously, by testing two different recirculation rates. COD from wastewater was 2000 mg/L. The theoretical hydraulic retention time was 2 hours and the temperature was maintained at 25 Celsius degrees. The average values of sucrose consumption were 67%, 79%, 71% and 70% for R = 0,25, 0,5, 1,0 and 2,0, respectively. The average values of hydrogen yield were 1,14 mol \'H IND.2\'/mol sac, 1,43 mol \'H IND.2\'/mol sac, 1,34 mol \'H IND.2\'/mol sac and 0,86 mol \'H IND.2\'/mol sac and of hydrogen production rate were 74.34 mL \'H IND.2\'/(h.L), 124.78 mL \'H IND.2\'/(h.L), 96.57 mL \'H IND.2\'/(h.L) and 73.49 mL \'H IND.2\'/(h.L) for recirculation rates of 0.25, 0.5, 1.0 and 2.0, respectively. The biogas produced was composed by \'H IND.2\', and \'CO IND.2\', with average values for \'H IND.2\', of 50%, 56%, 56% and 46% for R = 0,25, 0,5, 1,0 and 2,0, respectively. Methane was not detected. The main intermediate products produced during the hydrogen production were acetic acid, butyric acid and ethanol, similar in all stages of recirculation. Analyzing all operating parameters, it was identified that the better recirculation rate obtained during the experiments was R = 0.5. Adjusting all data obtained with a polynomial function, it was found an optimal recirculation rate of R = 0.6. During the experiments there was a drop in biogas production, probably by the activity of microrganisms consumers of this biogas.

As necessidades de energia global são, na sua maioria, dependentes de combustíveis fósseis. Hidrogênio é uma energia limpa alternativa a esses combustíveis fósseis. Bactérias fototróficas produzem hidrogênio a partir de compostos orgânicos por meio de processo anaeróbio dependente de luz. Assim, este trabalho visou avaliar o efeito das concentrações iniciais de ácido acético e biomassa, e a influência da intensidade luminosa, na produção de hidrogênio por bactéria fototrófica púrpura não-sulfurosa. Foram utilizados reatores em batelada de 2000 mL, com volume útil de 1000 mL e headspace de 1000 mL preenchido com hélio. Nos reatores foi adicionado ácido acético e glutamato de sódio (0,8 mmol/L) como fontes de carbono e nitrogênio, respectivamente, e cultura de bactéria fototrófica púrpura não-sulfurosa previamente purificada. O aumento da concentração inicial de ácido acético de 10 mmol/L para 17 mmol/L não promoveu mudanças significativas tanto no crescimento celular, quanto, na produção de hidrogênio (8,3 mL \'H IND.2\'/g massa seca.h e 8,8 mL \'H IND.2\'/g massa seca.h, respectivamente), para intensidade luminosa de 9000 - 10.000 lux. Nessa mesma intensidade luminosa, o aumento da concentração de biomassa inicial de 0,02 g/L para 0,04 g/L favoreceu o aumento da produção de hidrogênio de 8,8 mL \'H IND.2\'/g massa seca.h para 10,6 mL \'H IND.2\'/g massa seca.h, respectivamente. A produção de hidrogênio diminuiu acentuadamente de 10,6 mL \'H IND.2\'/g massa seca.h para 1,0 mL \'H IND.2\'/g massa seca.h com a diminuição da intensidade luminosa de 9000 - 10.000 lux para 4000 - 5000 lux. Na ausência de luz não ocorreu crescimento e produção de hidrogênio. A cultura manteve-se predominantemente avermelhada e as análise microscópicas mostraram a predominância de bacilos curvos, gram-negativos, aglomerados em formações de roseta; características típicas de alguns gêneros de bactérias fototróficas púrpuras não-sulfurosas. Todos os ensaios foram realizados à temperatura de 30 \'+ OU -\' 1 grau Celsius. A análise da estrutura da comunidade microbiana foi realizada por reação de polimerização em cadeia (PCR) de fragmentos de gene RNAr 16S, seguida de eletroforese em gel de gradiente desnaturante (DGGE), e revelou que não houve variações relevantes na estrutura das populações microbianas em função das diferentes condições de cultivo. / The global energy requirements are mostly dependent on fossil fuels. Hydrogen is a clean energy alternative to these fuels. Phototrophic bacteria produce hydrogen from organic compounds by an anaerobic light-dependent electron transfer process. Therefore, this study aimed at to evaluate the effect of the initial concentrations of acetic acid and biomass, and the influence of the light intensity on hydrogen production by purple non-sulfur phototrophic bacteria. The experiments were performed in batch operation, in reactors of 2000 mL, with culture volume of 1000 mL and headspace of 1000 mL, filled with helium. Acetic acid and sodium glutamate (0.8 mmol/L) were used as sources of carbon and nitrogen, respectively, and culture of purple non-sulfur phototrophic bacteria previously purifided. The increase of the initial acetic acid concentration from 10 mmol/L to 17 mmol/L did not promote significant changes in the cell growth and in the hydrogen production (8.3 mL \'H IND.2\'/g dry weight.h and 8.8 mL \'H IND.2\'/g dry weight.h, respectively), under a light intensity of 9000 - 10,000 lux. In this same light intensity, the increase of the initial biomass concentration from 0.02 g/L to 0.04 g/L resulted in an increase in the hydrogen production from 8.8 mL \'H IND.2\'/g dry weight.h to 10.6 mL \'H IND.2\'/g dry weight.h, respectively. The hydrogen production suddenly decreased from 10.6 mL \'H IND.2\'/g dry weigh.h to 1.0 mL \'H IND.2\'/g dry weight.h with the reduction of the light intensity from 9000 - 10,000 lux to 4000 - 5000 lux. Hydrogen production was not observed in absence of light. The culture remained predominantly purple and the microscopic analysis showed the predominance of rod-shaped cells, gram-negative, accumulated in formation of rosettes; typical characteristics of some types of purple non-sulfur phototrophic bacteria. The analysis of the structure of the microbial community was carried out by reaction of polymerization in chain (PCR) of the RNAr 16S, followed of denaturing gradient gel electrophoresis (DGGE), and reveled that the structure of the microbial populations did not change significantly in function of the different conditions of culture.

L’hydrogène peut être utilisé (et est utilisé depuis peu) comme un vecteur d’énergie propre. Il permet la transition du monde énergétique actuel, basé sur les énergies fossiles, vers le monde énergétique futur basé sur les énergies renouvelables et l’hydrogène. Cette transition ne sera envisageable que lorsque les problématiques liées à la production en masse de l’hydrogène et à son stockage seront résolues.L’objectif de ce travail de thèse est de produire l’hydrogène à partir de matériaux à base de magnésium en utilisant deux méthodes : (i) l’hydrolyse et (ii) la méthode micro-ondes.Notre premier objectif était d’élaborer des matériaux pour lesquels le phénomène de passivation du magnésium serait limité et présenteraient ainsi des rendements de production d’hydrogène optimaux. Le broyage mécanique à haute énergie est utilisé pour élaborer les différents composites à base de magnésium ou de son hydrure (Mg – 10 % en masse Additifs) afin d’accentuer la corrosion de ces derniers. Nous avons essentiellement focalisé nos efforts sur l’effet des additifs (i.e. Métaux de transition, Carbone et Oxydes) sur la réaction d’hydrolyse. Les tests d’hydrolyse ont été effectués dans une solution contenant 35 g/L NaCl (i.e. eau de mer). Notre stratégie, pour la résolution des problèmes de cinétique d’absorption/désorption (très lentes même à haute température (i.e. 350°C)), est basée essentiellement sur l’application de l’énergie micro-ondes. Notre deuxième objectif est donc l’utilisation des micro-ondes pour déshydrurer plus rapidement l’hydrure de magnésium (MgH2 – C) grâce à une élévation de température très rapide par rapport au procédé conventionnel. On a traité l’effet des irradiations micro-ondes sur la cinétique de désorption de mélange MgH2 – C, la morphologie et les propriétés de la poudre après un traitement micro-ondes. D’autre part, nous avons présenté une perspective possible de l’application des micro-ondes : la production de fines poudres de titane à partir de son hydrure. / A drastic reduction of emissions requires a partial or a full phase-out of fossil fuels and switch to renewable based energy production. Hydrogen appears to be a potential candidate to replace hydrocarbon fuels for producing clean energy. In this context, production and storage of hydrogen is one of the key challenges in developing the hydrogen economy.The objective of this thesis is to produce hydrogen from Mg-based materials using (i) hydrolysis and (ii) microwaves methods.The first aim of this thesis is to elaborate Mg-based materials with good hydrolysis kinetics and high yield of hydrogen generation (i.e. reducing the formation of the passivation layer on magnesium). For this study, we focalize essentially on the effect of various additives (Transition metals, Carbon or Oxides) on the hydrolysis reaction of Mg-based materials. The mixtures were prepared by ball milling. Chloride solution (3.5 wt. % NaCl, i.e. sea water) was used as reaction medium to beneficiate of chloride ions effect. Our strategy, to solve the problems related to the low absorption/desorption kinetics (even at high temperature (i.e. 350°C) of Mg-based materials, is based on microwaves energy application. Our second goal for this thesis is to investigate the dehydriding reaction of magnesium hydride catalyzed by carbon (i.e.MgH2 – C) under microwave irradiations. We have studied the effects of microwaves on the kinetics of hydrogen desorption, the morphology and sorption properties of Mg powder after microwave treatment. On the other hand, we have presented another microwaves application which appears very promising: production of fine titanium powder from titanium hydride.

Esse trabalho investigou a influência de diferentes dosagens de cálcio na produção biológica de hidrogênio a partir de água residuária sintética a base de sacarose em reatores anaeróbios de leito fixo estruturado e fluxo ascendente. Cilindros de polietileno de baixa densidade foram usados como material suporte para aderência da biomassa. Os reatores foram operados com tempo de detenção hidráulica (TDH) de 2 h e a 25ºC. Foram avaliadas diferentes concentrações de cálcio (Ca): 0,50; 1,06; 1,37; 1,87; 2,45 e 3,61 mg L-1 na alimentação. A remoção de sacarose apresentou valores médios acima de 54% para todas as concentrações. O biogás produzido foi composto de H2 e CO2, com porcentagens médias de H2 superiores a 60% para todas as concentrações avaliadas. Os principais produtos intermediários produzidos foram o ácido acético, o butírico e etanol. Os resultados demonstraram que há influência da suplementação de cálcio na produção de hidrogênio e a concentração de cálcio de 1,37 mg L-1 foi a que apresentou melhores resultados em relação a produção de hidrogênio, com rendimento de 1,4 mol de H2 mol-1 de sacarose, vazão molar de hidrogênio de 5,4 mmol h-1 e produção volumétrica de hidrogênio de 57 mL H2 h-1 L-1. Relacionaram-se as concentrações de cálcio com o rendimento médio de produção de hidrogênio e as curvas foram ajustadas a uma spline. Para a função ajustada chegou-se a um ponto de ótimo de rendimento de 1,5 mol H2 mol-1 sacarose obtido com concentração de cálcio de 1,54 mg L-1. / This paper investigated the influence of different dosages of calcium in the biological production of hydrogen from synthetic sucrose based wastewater in upflow anaerobic structured-bed reactor. Low density polyethylene cylinders were used as support material for biomass attachment. The reactors were operated with hydraulic retention time (HRT) of 2 h at 25° C. The wastewater was amended with different concentrations of calcium (Ca): 0.50; 1.06; 1.37; 1.87; 2.45 e 3.61 mg L-1. The removal of sucrose showed values above 54% for all concentrations. The biogas produced was composed of H2 and CO2 with H2 average percentages above 60% for all concentrations evaluated. The main intermediates produced were acetic acid, butyric acid and ethanol. The results showed that there is influence of calcium supplementation in the production of hydrogen and calcium concentration of 1.37 mg L-1 showed the best results regarding hydrogen production, with yield of 1.4 mol H2 mol-1 sucrose, hydrogen molar flow of 5.4 mmol H2 h-1 and volumetric production of hydrogen of 57 mL H2 h-1 L-1. Calcium concentrations were correlated with the average yield of hydrogen production and the curves were fitted to a spline. From this function, an optimum yield of 1.5 mol H2 mol-1 sucrose was reached with calcium concentration of 1.54 mg L-1.

Neste trabalho foram preparados catalisadores Co/Al2O3 e Co/SiO2 por impregnação com concentração metálica entre 4,0% e 20,0% e avaliados frente às reações de reforma a vapor e reforma oxidativa de etanol, com o objetivo de avaliar a estabilidade catalítica e o rendimento em hidrogênio. Os catalisadores foram caracterizados por espectrofotometria de absorção atômica, difração de raios-X, espectroscopia Raman, redução a temperatura programada, fisissorção de nitrogênio e análise elementar de carbono. A caracterização das amostras mostrou a formação da fase Co3O4 e interações de espécies de cobalto com o suporte. Evidenciou-se que apenas os sítios de Co0 são ativos para as reações de reforma a vapor e oxidativa de etanol. A produção de hidrogênio variou de 50-70% e a de CO de 0-10%. Alta concentração metálica sobre a superfície do suporte acarretou uma baixa produção de monóxido de carbono. As reações tiveram deposições de carbono nos catalisadores variando de 2,7 a 12,7 (mg. h-1), indicando que a desativação dos materiais é devido a deposição de coque. O uso de oxigênio diminuiu a produção de coque sobre os catalisadores Co/Al2O3 e Co/SiO2. / In this work Co/Al2O3 and Co/SiO2 catalysts were prepared by impregnation with metal load between 4,0% and 20,0% and were evaluated in the reactions of ethanol steam reforming and ethanol oxidative reforming to study the catalytic stability and the hydrogen yield. Atomic absorption, X-ray powder diffraction, Raman spectroscopy, temperature programmed reduction, nitrogen fisisorption and elemental analysis of carbon were applied to describe the physical and chemical characteristics of these catalysts. The characterization of the catalysts showed the Co3O4 phase and interactions of cobalt species with the support. It was evidenced that only Co0 sites are active for the steam reforming and oxidative reforming of ethanol. The production of hydrogen was about 50-70% and CO was 0- 10%. A high metallic load gave less carbon monoxide production. In the reactions, 2,7-12,7(mg.h-1) of carbon was deposited on all catalysts, indicating that the deactivation of the materials is due to coke deposition. The use of oxygen decreases the production of carbon on the catalysts Co/Al2O3 and Co/SiO2.

No description available.

In this study SBA-15 mesoporous silica template was synthesized and used as a sacrificial template in the preparation of ordered mesoporous carbon material. A chemical vapour deposition (CVD) technique using LPG or alternatively sucrose, pyrolyzed upon a mesoporous Si matrix were used to produce nanostructured ordered mesoporous carbon (OMC) with graphitic character after removing the Si template. The sucrose method was found to be a suitable route for preparing OMC. The OMC was used as a conductive three dimensional porous support for depositing catalytic nanophase Pt metal. Deposition of Pt nanoparticles on OMC was accomplished using a CVD method with Pt(acac)2 as a precursor. The synthesized nano-composite materials were characterized by several techniques such as, HRTEM, HRSEM, EDS, XRD, BET, TGA, FT-IR and CV.

The SuperCritical Water-cooled nuclear Reactor (SCWR) is one of six Generation-IV nuclear-reactor concepts currently being designed. It will operate at pressures of 25 MPa and temperatures up to 625°C. These operating conditions make a SuperCritical Water (SCW) Nuclear Power Plant (NPP) suitable to support thermochemical-based hydrogen production via co-generation. The Copper-Chlorine (Cu‒Cl) cycle is a prospective thermochemical cycle with a maximum temperature requirement of ~530°C and could be linked to an SCW NPP through a piping network. An intermediate Heat eXchanger (HX) is considered as a medium for heat transfer with operating fluids selected to be SCW and SuperHeated Steam (SHS). Thermalhydraulic calculations based on an iterative energy balance procedure are performed for counter-flow double-pipe design concept HXs integrated at several locations on an SCW NPP coolant loop. Using various test cases, design and operating parameters are recommended for detailed future research. In addition, predicted effects of heat transfer enhancement on HX parameters are evaluated considering theoretical improvements from helically-corrugated HX piping. The effects of operating fluid pressure drop are briefly discussed for applicability in future studies. / UOIT

The significance of hydrogen production is increasing as fossil fuels are being depleted and energy security is of increasing importance to the United States. Furthermore, its production offers the potential to alleviate concerns regarding global warming and air pollution. In this thesis we focused on examining the efficiency of hydrogen production from current biomass compared to that from fossil fuel coal. We explored the efficiencies of maximum hydrogen production from biomass and from coal under current technology, namely coal gasification and biomass pyrolysis, together with following-up technologies such as steam reforming (SR). Bio-oil, product from pyrolysis and precursor for steam reforming, is hard to define. We proposed a simulation tool to estimate the pyrolytic bio-oil composition from various biomasses. The results helped us understand the accuracy that is needed for bio-oil composition prediction in the case it is converted to hydrogen. Hydrogen production is energy intensive. Therefore, heat integration is necessary to raise the overall thermodynamic efficiencies for both coal gasification and biomass pyrolysis. The results showed that considering the ultimate energy source, sunlight, about 6-fold more sunlight would be required for the coal to hydrogen than that for biomass to hydrogen. The main difference is in the efficiency of conversion of the ancient biomass to coal and therefore, for modern mankind, this loss has already been incurred.