Hydrogen as a clean energy carrier has drawn great attention. Production of H2 from sustainable bio-oil is considered an alternative for conventional fossil fuel based energy system, since the overall process of bio-oil converting to H2 ideally is carbon-neutral and hence environmental friendly. This study focuses on developing an adequate catalyst for bio-oil steam reforming to produce H2. Ruthenium and/ or nickel based catalysts supported on alumina, ceria-alumina or ceria-silica were synthesized by sol-gel method or incipient wetness impregnation and characterized using BET Surface area analysis, Powder X-Ray diffraction (XRD), Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). Steam reforming of selected model compounds, n-propanol, glycerol and acetic acid, was investigated in a fixed bed tubular flow reactor over the prepared catalysts at 450 or 500 °C. The effects of support nature, preparation method, catalyst composition and reaction temperature on the steam reforming activity and stability of catalysts were studied. Catalysts showing better performance in terms of reactant conversion and H2 yield were selected for investigating the steam reforming of an acetic acid/glycerol aqueous mixture, consisting of acetic acid and glycerol with a weight ratio of 3/7 similar to a bio-oil generated from fast pyrolysis of cellulose. The steam-to-carbon ratio (S/C) and the flow rate of feed were constant at 4 and 0.1 ml/min, respectively. The effluent gas was monitored by GC/TCD and the evolution of carbon conversion and product gas distribution as a function of time was studied. Among all catalysts investigated, the one with nominal composition A10C10N1Rnc showed the best performance in steam reforming at 500 °C as indicated by higher and more stable H2 yields achieved regardless the reactant used. In order to investigate the sorption-enhanced steam reforming, three CaO-based CO2 absorbents were synthesized: two derived from calcium acetate with or without MgO support, noted as CAM and CA, respectively, and the other MgO-supported one derived from calcium d-gluconate, denoted as CGM. Results from the 15-carbonation/regeneration-cycle test suggested that the MgO-containing absorbent CAM has the highest CaO molar conversion and stable CO2 absorption capacity. Though significantly higher CO2 absorption capacity was shown from absorbent CA in the first one cycle, CA absorbent soon lost most of the CO2 absorption capacity due to severe sintering. In addition, the CO2 absorption capacity of absorbent CGM might be underestimated due to insufficient carbonation time. The A10C10N1Rnc catalyst and the CAM absorbent were applied in the steam reforming of acetic acid/glycerol mixture at 500°C. However, no significant improvement can be observed in the presence of absorbent CAM

The overall objective of the work described in this Dissertation was to develop and verify a general reaction and diffusion model for non-catalytic reactions between gases and porous solids, particularly those relevant to the clean use of fossil fuels. Here, the internal pore structure of the solid was characterised by observing the kinetics in a regime limited only by intrinsic chemical reaction. It was hypothesised that a simple arbitrary function, f(X), determined from experimental measurements of rate vs. conversion in a kinetically-controlled regime, could be used in place of formal, mathematical pore models, to describe the evolution of pore structure during a reaction influenced by intraparticle mass transfer. The approach was used to study (i) the gasification of chars by CO2, where the only product was gaseous, (ii) the calcination of CaCO3 cycled between calcined and carbonated states, where the products were a gas and a solid, and (iii) the sulphation of virgin and sintered CaO by SO2, the only product being solid. Studies of calcination showed that, at least for limestones subjected to a history of cycling between the calcined and carbonated states, a correctly-determined f(X) could be applied to different sizes of particles at temperatures different to that at which f(X) was determined. Somewhat surprisingly, it was found that the f(X) determined from one, cycled, limestone was successful in predicting the conversion of other cycled limestones of different geological origin. It was concluded that the process of cycling between the calcined and carbonated states at the same process condition had significantly reduced the differences apparent in the pore structures of the different limestones when first calcined from the virgin materials. The experimentally-observed effects of pressure, concentration of CO2 and temperature described in the literature were explained successfully by the mathematical model. Finally, the study of sulphation explained satisfactorily (i) the reason for there being a maximum in the ultimate conversion of CaO to CaSO4 at a specific temperature, and (ii) the processes controlling the overall uptake of SO2 by sintered CaO, such as might be produced from a calcium-looping cycle for capturing CO2 from flue gases. For both the virgin and the cycled calcines, the ultimate conversion to CaSO4 seemed to be limited by the pore volume below 300 nm diameter. Two mechanisms were identified to explain why CaO cannot be fully sulphated to CaSO4. In summary, this work has demonstrated the applicability of the general reaction and diffusion model to gasification, calcination and sulphation reactions, and verified the f(X) approach for describing pore evolution during reaction.

Les carburants BtL (Biomass to Liquid) font partie des carburants alternatifs au pétrole dits de seconde génération car synthétisés à partir de biomasse solide (contenant de la lignocellulose). Le procédé de fabrication de tels carburants par voie thermochimique repose sur deux étapes successives : la gazéification de la biomasse suivie par un procédé de Fisher-Tropsch. Certains éléments contenus dans la biomasse comme les sels alcalins peuvent se retrouver après l’étape de gazéification et être à l’origine d’attaques sous forme de sels fondus et ainsi endommager les infrastructures. Le travail réalisé dans ce manuscrit consiste à simuler la corrosion de parois d’échangeur thermique en présence de sulfate et chlorure de sodium sous atmosphère de gazéification (CO/H2/CO2) très faiblement oxydante (~ 10−18 bar). Afin de comparer les résultats à ceux issus de la bibliographie, les essais ont également été conduits sous atmosphère fortement oxydante (Ar/O2). Les essais réalisés sur alliage chrominoformeur, HR-120 (38Ni-34Fe-25Cr) à une température de 900°C en présence de sulfate de sodium en milieu faiblement oxydant ont mise en évidence une corrosion de type catastrophique localisée et réversible de l’alliage. Le comportement de l’alliage aluminoformeur, 214 (76Ni-16Cr-4Al) apparaît plus protecteur dans des conditions similaires. En présence de chlorure de sodium, les deux alliages se comportent d’une manière totalement identique : corrosion catastrophique en milieu fortement oxydant et impact du sel négligeable sous atmosphère faiblement oxydante. Un chapitre remède prometteur a été développé en fin de manuscrit. / BTL (biomass to liquid) is an innovative process to synthesize second generation bio-gasoline from wood and farm residues. This process includes a gasification step in order to generate the synthetic gas (syngas) which is subsequently transformed into gas oil by the Fisher Tropsch process. Alkaline salts (mainly potassium and sodium sulphates and chlorides) are present in the biomass and can induce detrimental high temperature corrosion of the refractory alloys where they can condensate as a liquid phase. In this work, we simulate high temperature corrosion of heat exchanger tubes in presence of sulphate and sodium chloride under gasification environment (CO/H2/CO2), consider as weakly oxidizing (~ 10−18 bar). To compare the results with those from the literature, tests were also conducted under highly oxidizing atmosphere (Ar/O2). Results with the chromia-forming alloy HR-120 (38Ni-34Fe-25Cr) at 900°C with sodium sulfate under low oxygen partial pressure shows reversible localized catastrophic oxidation. The behavior of the alumina-forming alloy 214 (76Ni-16Cr-4Al) appears more protective under similar conditions. In presence of sodium chloride, the behavior of the two alloys is identical. Indeed, with oxidizing atmosphere corrosion became totally catastrophic while the impact of sodium chloride was insignificant under gasification atmosphere.

Submitted by Jordan Amaro Gutierrez (lococl7@hotmail.com) on 2018-04-18T13:40:29Z No. of bitstreams: 1 Dissertação de mestrado_Jordan Amaro Gutierrez.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-04-18T14:14:12Z (GMT) No. of bitstreams: 1 amarogutierrez_j_me_guara.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) / Made available in DSpace on 2018-04-18T14:14:12Z (GMT). No. of bitstreams: 1 amarogutierrez_j_me_guara.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) Previous issue date: 2018-02-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho tem como objetivo desenvolver um modelo de equilíbrio químico modificado para determinar a composição do syngas (gás de síntese), obtida a partir da gaseificação da biomassa em gaseificadores de leito fluidizado. Para este estudo, foi aplicado um processo de otimização para determinar os fatores de correção (que modificam as constantes de equilíbrio químico), a eficiência de conversão de carbono e a entalpia da reação. Os agentes de gaseificação considerados foram ar, vapor, ar-vapor e ar-vapor-oxigênio. No método de otimização foram utilizados os multiplicadores de Kuhn–Tucker para obter pequenos erros RMS. Foram selecionadas 76 composições experimentais de syngas. Entre estas composições, 60 foram utilizadas para obter correlações para o fator de correção, a eficiência de conversão do carbono e a entalpia da reação. Em seguida, um modelo de equilíbrio químico modificado foi elaborado selecionando estas correlações. O modelo de equilíbrio químico modificado foi validado mostrando uma boa precisão para a determinação da composição do syngas, obtendo-se erros RMS entre 0,94 e 4,84. / This work aims to develop a modified chemical equilibrium model to accurately determine the syngas (synthesis gas) composition, as obtained from fluidized bed gasifiers. In order to do so, an optimization process was applied to determine the correction factors (which modify the chemical equilibrium constants), the carbon conversion efficiency and the enthalpy of the reaction. The gasification agents considered were air, steam, air–steam, and air–steam–oxygen. The optimization method were used the Kuhn–Tucker multipliers in order to obtain small RMS errors. A total of 76 experimental compositions of syngas were selected. Among these data, 60 were used to obtain correlations for the correction factor, the carbon conversion efficiency and the enthalpy of the reaction. Then, a modified chemical equilibrium model was developed by selecting these correlations. The modified chemical equilibrium model was validated showing very good accuracy for the determination of the syngas composition, the RMS error were found to be in the between 0.94 and 4.84.

Made available in DSpace on 2014-06-11T19:30:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-05Bitstream added on 2014-06-13T19:18:32Z : No. of bitstreams: 1 magalhaes_lc_me_guara.pdf: 2627349 bytes, checksum: 8fadf3c86720e6a184e9fb846efb6c45 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta dissertação analisou a viabilidade técnica de gaseificação de lama de alto de alto forno da ArcelorMittal Tubarão para produção de gás visando uma utilização interna. A gaseificação foi conduzida através de simulação em modelo de equilíbrio químico TCW - Termochemical Information and Equlibrium Calculation. Foram simuladas 3 misturas para gaseificação: a) 100% carvão metalúrgico de alto volátil (base das misturas), b) de lama de alto forno com 85% de carvão metalúrgico alto volátil e c) de lama de alto forno com 75% de carvão metalúrgico alto volátil. Os dois parâmetros principais que definiram a viabilidade técnica de gaseificação de lama de alto forno foram poder calorífico inferior - PCI e faixas de trabalho temperaturas no reator. O PCI do gás foi calculado a partir das frações molares de H2 e CO contidas no gás obtidos nas misturas simuladas / This dissertation analyzed the technical viability of blast furnace slurry gasification with the objective of using the obtained gas at ArcelorMittal Tubarão. The process was simulated using an equilibrium program, the TCW - Termochemical Information and Equilibrium Calculation. Three mixtures were considered for gasification: a) 100% high volatile metallurgical coal (the base of the mixtures), b) 15% slurry and 85% coal, and c) 25% slurry and 25% coal. The two main parameters that defined the technical viability of the blast furnace slurry were the mixture Low Heat Value (LHV) and the temperature ranges for work in the gasification reactor. The LHV was calculated from the molar fractions of H2 and CO in the gas obtained in the simulation

[pt] A partir das equações fundamentais da teoria clássica das misturas, é proposto um modelo simplificado, em regime pseudo-estacionário e isotérmico, da gaseificação do carvão sofrendo gaseificação com vapor dágua é analisada por meio de balanços diferenciais de conservação de massa de cada espécie química. O modelo leva em conta as reações do vapor dágua com o carbono e o monóxido de carbono. Estas duas reações aparecem no modelo como condições de contorno lineares, que englobam fenômenos intraparticulares, os quais são agrupados à superfície. As condições ambientais são consideradas constantes. Também são incluídas equações diferenciais que permitem calcular a taxa de consumo de vapor dágua e calor, a taxa de gaseificação e a taxa de geração de monóxido de carbono, dióxido de carbono e hidrogênio. Por meio de simulação digital foi possível estudarem-se os efeitos, sobre o processo, da granulometria, temperatura e fração volumétrica de vapor dágua no meio ambiente. As equações cinéticas utilizadas neste trabalho são aquelas do carvão de charqueadas, Rio Grande do Sul, Brasil. / [en] A simplified model for steady, isothermal diffusion in the layer surrounding a spherical carbon particle undergoing steam gasification process is considered by way of the classical theory of reacting fluid mixtures. The model accounts for the steam – carbon reaction and the steam – carbon monoxide reaction. These two reactions appear in the model as linear boundary conditions that comprise the intraparticle effects, which are lumped at the surface. The ambient conditions are assumed to be constant. Differential equations for the calculation of steam and heat rate consumption, carbon monoxide, carbon dioxide and hydrogen rate generation and rate of gasification are also included. By means of digital simulation it was possible to study the effects of particle radius, temperature and steam concentration on the process. The kinect equations used in this paper are those of coal from Charqueadas, State of Rio Grande do Sul, Brasil.

Production of hydrogen from biomass steam gasification can be enhanced by using calcium oxide sorbents for CO2 capture in the gasifier. Calcium looping suffers from two main drawbacks: the need for high-purity oxygen in order to regenerate the sorbent under oxy-fuel combustion conditions and the loss of sorbent reactivity over several cycles due to sintering of pores upon calcination at high temperatures. One method of addressing the issue of oxygen supply for calcination in calcium looping is to combine the calcium looping and chemical looping processes, where the heat produced by the reduction of an oxygen-carrier by a fuel such as natural gas or gasification syngas, drives the calcination reaction. The technologies can be integrated by combining an oxygen carrier such as CuO with limestone within a composite pellet, or by cycling CuO and limestone within distinct particles. The goal of this project is thus to investigate the different sequences of solids circulation and the cyclic performance of composite limestone-CuO sorbents under varied operating conditions for this novel process configuration. Using a thermogravimetric analyzer (TGA), it was found that using composite CaO/CuO/alumina-containing cement pellets for gasification purposes required oxidation of Cu to be preceded by carbonation (Sequence 2) as opposed to the post-combustion case where the pellets are oxidized prior to carbonation (Sequence 1). Composite pellets were tested using Sequence 2 using varying carbonation conditions over multiple cycles. While the pellets exhibited relatively high carbonation conversion, the oxidation conversion underwent a decrease for all tested conditions, with the reduction in oxygen uptake particularly drastic when the pellets were pre-carbonated in the presence of steam. It appears that the production of a layer of CaCO3 fills up the pellets pores, obstructing the passage of O2 molecules to the more remote Cu sites. Limestone-based pellets and Cu-based pellets were subsequently tested in separate CaL and CLC loops respectively to assess their performance in a dual-loop process (Sequence 3). A maximum Cu content of 50% could be accommodated in a pellet with calcium aluminate cement as support with no loss in oxidation conversion and no observable agglomeration.

Orientador: Tânia Forster Carneiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-27T14:35:47Z (GMT). No. of bitstreams: 1 Lachos-Perez_Daniel_M.pdf: 2146698 bytes, checksum: bd9a09fc30626088c9dff682785f1200 (MD5) Previous issue date: 2015 / Resumo: Novas tecnologias de reaproveitamento de resíduos para a produção de novos produtos com gasto energético estão emergindo como uma forma eficiente e economicamente viável. Tecnologias utilizando água supercrítica podem representar uma alternativa ambientalmente correta, uma vez que promovem o desenvolvimento sustentável em relação aos métodos convencionais. Processos de hidrólise em água supercrítica dispensam solventes ácidos e processos de gaseificação em água supercrítica dispensam a secagem da amostra, ou seja, permitem o emprego de resíduos húmidos. Adicionalmente, processos de hidrólise e gaseificação utilizando fluidos supercríticos permitem um eficiente controle do processo através de pequenas variações nas condições de operação (pressão, temperatura, vazão, etc.). Trata-se de uma tecnologia em fase de desenvolvimento, existindo poucos relatos na literatura sobre sistemas de hidrólise e/ou gaseificação com água supercrítica e processos similares. A unidade piloto proposta neste trabalho permite o estudo dessa tecnologia e utilizando água supercrítica de forma a integrar em um mesmo equipamento dois processos: hidrólise seguida de gaseificação; proporcionando uma melhor relação custo-benefício associada a essas tecnologias. O sistema proposto tem aplicações no desenvolvimento de processos com água em condições sub e supercríticas de temperatura e pressão, buscando a obtenção de açúcares fermentáveis e/ou gases de interesse energético, tais como hidrogênio e metano. O objetivo principal deste trabalho foi projetar e construir um sistema em escala piloto capaz de realizar a conversão do bagaço da cana-de-açúcar em produtos de maior valor agregado, a partir de um reator de hidrólise operando em condições subcríticas de temperatura e pressão, seguido de um reator de gaseificação operando em condições supercríticas de temperatura e pressão, em regime semicontínuo. Testes preliminares foram realizados no reator de hidrólise com o objetivo de otimizar as condições de temperatura e pressão no primeiro reator previamente ao reator de gaseificação. Os resultados das cinéticas de hidrólise, com duração entre 15 e 25 minutos, indicaram altos valores de rendimento de açúcares redutores e redutores totais nas temperaturas de 200 e 250 ºC, independentemente dos valores de pressão estudados. Por outro lado à temperatura de hidrólise de 250 °C foi obtida maior rendimento de hidrólise, esse comportamento pode ser indicado devido a maior formação de açúcares observado neste experimento / Abstract: Waste recycling technologies to produce new products with energy recovery are emerging as efficient and economically viable alternative. Technologies using supercritical water can represent an environmentally friendly alternative, as they promote sustainable development compared to conventional methods. Hydrolysis processes in supercritical water do not require acid solvents and gasification processes in supercritical water dispense sample drying, or allow the use of wet waste. Additionally, hydrolysis and gasification processes using supercritical fluids allow an efficient control of the process by small variations in the operating conditions (pressure, temperature, flow rate, etc.). Since this is a technology under development, there are few reports in the literature on hydrolysis and / or gasification systems with supercritical water and similar processes. The pilot plant proposed in this work allows the study of supercritical water technology to integrating in one device two processes: the hydrolysis followed by gasification, providing a cost-benefit associated with these technologies. The proposed system has applications in process development with water in sub- and supercritical conditions of temperature and pressure to obtain fermentable sugars and / or gases such as hydrogen and methane. The main objective of this work was to design and to build a system at pilot plant scale capable of performing the conversion of sugar cane bagasse into higher added value products and energy, from a hydrolysis reactor operating in subcritical conditions of temperature and pressure followed by a gasification reactor operating in supercritical conditions of temperature and pressure, in a semi-batch system. Preliminary tests were carried out in the hydrolysis reactor in order to determine the optimal temperature and pressure conditions in the first reactor previous to gasification reactor. The results of the hydrolysis kinetics, lasting between 15-25 minutes showed high yield values of reducing sugars and total reducing sugars at the temperatures of 200 and 250 °C, independently of the pressure values studied. On the other hand, to the hydrolysis temperature of 250 ° C was obtained a yield higher hydrolysis, this behavior may be indicated due to larger formation of sugars observed in this experiment / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

Gasification of biomass has become an area of key interest as it is a reasonably quick and direct way of converting material into a fuel source that works in many industrial systems. The purpose of the present work is to explore biomass gasification and in particular pyrolysis behavior of corn kernels, oat hulls, and paper sludge. For the materials, low temperature gasification behavior was studied. Here, tests were performed with pyrolysis temperatures from 400 - 800°C, at 1 atm and a rapid heating rate. A small concentration of O2 was added to the gasification agent (N2) to enhance CO yields, similar to modern industrial gasifiers. The evolution of CO, CO2, CH4, H2, and O2 were measured throughout the pyrolysis process. Results show a direct correlation between temperature and the composition of the gas byproduct for all biomasses. CO production increases with an increase in temperature while CO2 shows no temperature correlation. O2 depletion mimics the CO evolution and increases with an increase in temperature. CH4 production was observed, however the results were rarely repeatable due to the sensor's sensitivity to moisture and tar in the gas byproduct. No hydrogen was observed, as would be expected for the short experimental residence time (0.2 seconds).

In this work the differences between and characteristics of water and high solids, heated black liquor sprays from air-assist atomizers are examined. Sprays were imaged with a high speed camera and the images analyzed with computer code to produce droplet size data and macroscopic spray characteristics such as mass distribution. Fluid flow rates were measured to allow relevant dimensionless groups for the spray to be calculated. A 1000 degree C tubular furnace was placed around the spray to determine the effect of industrially relevant temperatures on the droplet formation process, relative to room-temperature conditions. It was found that high solids black liquor forms long, thin ligaments rather than droplets. In high-temperature surroundings the size of these ligaments increases, which from a comparison with theory in the literature was attributed to enhanced skin-formation driven by heat transfer. The data suggest that this skin formation may prevent secondary breakup. All sprays for both fluids produced droplet size mass distributions that were well described by the square-root normal distribution. The normalized width (s*) of these distributions was similar for all sprays and consistent with literature data for other nozzle designs (0.24 < s* < 0.38). The image analysis method assumed droplets were spheres with the same projected area. When this assumption was changed for black liquor sprays to a cylindrical droplet assumption, the shape and normalized width of the resulting mass distributions remained the same, but the representative diameter (calculated from surface area to volume ratios) decreased. Based on the agreement between the normalized distribution width in this work and that in the black liquor spraying literature it was concluded that the addition of atomizing air cannot be considered a means to narrow a droplet size distribution independent of droplet size. The results also indicate the importance of including the effects of skin formation and temperature- and time-dependent fluid properties in spray modeling. It is intended that these results contribute to increased understanding of the black liquor atomization process and lead to improved computational modeling of the same.