Orientador: Marcio Luiz de Souza-Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-25T12:20:22Z (GMT). No. of bitstreams: 1 BernalBernal_AndresFelipe_M.pdf: 2197321 bytes, checksum: 83a11d583679d2326d584615585e97d2 (MD5) Previous issue date: 2014 / Resumo: Novos desenvolvimentos da estratégia no conceito Fuel- Slurry Integrated Gasifier / Gas Turbine (FSIG / GT) para geração de potência termoelétrica aplicada ao caso de Bagaço de Cana de Açúcar (Sugar Cane Bagasse - SCB) são apresentados. O processo FSIG / GT permite a alimentação de combustível para uma unidade de potência baseada na gaseificação utilizando bombas de lama disponíveis no mercado, evitando, assim, os típicos sistemas de silos sequenciais, também conhecidos como sistemas de alimentação em cascata. Adicionalmente, dispensa a necessidade de oxigênio puro, algumas vezes misturado com hidrocarbonetos, para promover a ignição das partículas na suspensão injetada. A suspensão de combustível é preparada com uma alta concentração de sólido na lama e bombeada para um secador, do qual as partículas sólidas são injetadas ao gaseificador. Como ambos os equipamentos operam sob pressões semelhantes, válvulas rotativas simples e parafusos de Arquimedes podem efetuar da alimentação nesta segunda etapa. O gás é submetido a uma operação de limpeza de partículas bem como a uma redução da concentração de compostos alcalinos dentro dos limites aceitáveis para injeções em turbinas a gás convencionais. A atual fase do desenvolvimento para tal processo inclui o fluxo mássico de gás injetado e o diâmetro como variáveis de otimização do secador e gaseificador de leito fluidizado. Estas melhorias permitem uma eficiência global de geração de potência que traspassa o alcançado por outras estratégias, tais como os ciclos Rankine baseados em turbinas convencionais de alta pressão de vapor, processos BIG / GT, ou ciclos combinados usando caldeiras de câmara pressurizada / Abstract: Further developments of the strategy of the Fuel-Slurry Integrated Gasifier/Gas Turbine (FSIG/GT) concept for thermoelectric power generation applied to the case of Sugar Cane Bagasse (SCB) are presented. The FSIG/GT process allows fuel feeding to a power unit based on gasification using commercially available slurry pumps, thus avoiding the usual sequential lock-hoppers, also known as cascade feeding systems. It also dispenses with the need of pure oxygen, sometimes combined with hydrocarbons, to promote ignition of particles in the injected slurry. The fuel slurry is prepared to high dry-solid content and pumped into a dryer, from which the solid particles are fed into the gasifier. Since both equipment operate under similar pressures, simple rotary valves and Archimedes¿ screws might carry the secondary feeding. The gas is cleaned to bring the particle content and size as well alkaline concentration within the acceptable limits for injections into standard gas turbines. The present phase of development for such process includes the fluidized bed dryer and gasifier mass flow inlet gas and diameter as variables for optimizations. That allowed improvements on the overall power generation efficiency that surpasses the achieved by other strategies such as conventional Rankine based high-pressure steam turbines, BIG/GT process, or combined cycles using pressurized-chamber boilers / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Gasification is a flexible technology which is applied in industry for electricity generation, hydrogen production, steam raising and liquid fuels production. Furthermore, it can utilize one or more feedstocks such as coal, biomass, municipal waste and petroleum coke. This versatility, in addition to being adaptable to various emissions control technologies (including carbon capture) renders it an attractive option for years to come. One of the most common gasifier types is the entrained-flow slagging gasifier. The behaviour of inorganic fuel components in these gasifiers is still ill-understood even though it can be the determining factor in their design and operation. A literature review of inorganic matter transformation sub-models for entrained-flow slagging gasifiers is provided. Slag viscosity was identified as a critical property in the sub-models. Slag viscosity models are only applicable to a limited range of slag compositions and conditions, and their performance is not easily assessed. An artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. Furthermore, a toolbox was developed to assist slag viscosity model users in the selection of the best model for given slag compositions and conditions, and to help users determine how well the best model will perform. The slag viscosities of coal, petroleum coke and coal/petroleum coke blends were measured in the temperature range of 1175-1650ºC. Interaction of vanadium-rich slags with various materials was investigated. The results from the first two parts of a three-part research program which involves fuel characterization, testing in a 1 MWth gasifier, and computational fluid dynamics (CFD) modeling for entrained-flow slagging gasification are presented. The end goal is to develop a CFD model which includes inorganic matter transformations. Fuel properties were determined with prioritization based on their application; screening of potential fuels, ensuring proper gasifier operation, gasifier design and/or CFD modeling. Using CanmetENERGY’s 1 MWth gasifier, five gasification tests were completed with the characterized coals. Solid samples from the refractory liners, in-situ gas sampling probe sheaths and impingers, the slag tap, the slag pot, quench discharge water and scrubber water were collected and characterized.

Kinetics of steam gasification of both delayed and fluid cokes, byproducts from thermal cracking processes of Athabasca bitumen, have been studied in laboratory-size stirred and fixed bed reactors. The hydrogen sulphide in the product gas was captured in-situ using calcined dolomite and limestones as acceptors. Experiments were carried out at atmospheric pressure and at temperatures between 800°C and 930°C. The coke particle size ranged from 0.1 to 3.5 mm, and the steam partial pressure was varied from 15.15 to 60.6 kPa. The carbon and sulphur conversions were computed from the knowledge of gas compositions and flowrates and the gasification kinetics of both species established. The effects of sorbent type, particle size, calcination conditions, and Ca/S molar ratios on the extent of sulphur capture during gasification were examined in separate series of experiments. Scanning electron microscopy, surface area analysis, and mercury porosimetry were employed to relate physical structure changes in the solids to experimental kinetic data. The rate of gasification for the delayed coke was generally higher than that for the fluid coke, and both cokes were almost unreactive to steam gasification at temperatures below 800°C. Increased reaction temperatures or reduced particle sizes increased both carbon as well as sulphur conversion. The carbon conversion rates were found to go through maxima as the time of reaction and extent of conversion increased. As the reaction proceeded the surface area of the coke increased to a maximum of about five times its initial value and thenfell off sharply. The extent of carbon conversion alone dictated the specific surface area irrespective of temperature, particle size and steam partial pressure. Both calcined dolomite and calcined limestone were found to be effective in removing sulphur from the product gas. Sorbents possessing a larger specific area or smaller grain size had higher capacity to accept sulphur. At a Ca/S molar ratio of 2.0, the overall sulphur removal was approximately 90% for the first 3 hrs and the H₂S concentration in the produced gas was reduced to about 200 ppm from nearly 1250 ppm. The rate of sorbent conversion from CaO to CaS decreased monotonically with time. Three available kinetic models for gasification - the Random Capillary Model, the Random Pore Model and the Modified Volumetric Model, were tested with the experimental gasification data. Although reasonable fits were obtained for Xc-t results, the sharp drop in rate at high conversion could not be adequately modelled. Rate constants were established for the initial stage of reaction only. The Grain model and Continuous reaction models were tested with the experimental sulphidation results. The sulphidation process was controlled by chemical reaction at low sorbent conversion, and subsequently by diffusion through the product layer at higher conversions. The reaction rate constant and the effective diffusivity were accordingly established as functions of temperature. Values compared favourably with results of sulphidation kinetics done without simultaneous gasification reported in the literature. The results suggest that the gasification process and the sulphur capture process, which occur together in gasifiers with sorbent injection, can be treated independently. Indexing terms: Gasification, Carbon Conversion, Sulphur Conversion, Sulphur Removal, Calcine, Limestone, Dolomite, Hydrogen Sulphide, Sulphidation. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Three different Western Canadian coals were gasified with air and steam in a fluidized bed of 0.73 mm Ottawa sand and coal, at atmospheric pressure, and temperatures of 1023 - 1175 K to produce a low Btu gas. The coals tested were of two types: one non-caking and two caking coals. The results were compared with those previously obtained for the same three coals when gasified in essentially the same equipment, but operated as a spouted bed. The effects of temperature, coal feed rate, air to coal ratio, steam to coal ratio, coal quality, coal particle size, and bed depth on the gas composition, gas calorific value and the operating stability of the gasifier, were established by running gasification tests over a wide range of operating conditions. Typical calorific value of the gas obtained for all three coals was in the range of 2.0 - 2.6 MJ/m³, which is lower than reported for the spouted bed and commercially available fluidized bed gasifiers. Analysis of the results suggested that in the present low temperature gasifier, the combustion and pyrolysis reactions predominate over the gasification reactions. The ability to treat caking coals in fluidized bed and spouted bed reactors is discussed. It is concluded that the dispersion of coal in a bed of inert silica and ash, rather than hydrodynamic characteristics is the key-factor in their success in handling caking coals. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Unknown

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Gasification is a very efficient method of producing clean synthetic gas (syngas) which can be used as fuel for electric generation or chemical building block for petrochemical industries. This study performs detailed simulations of coal gasification process inside a generic two-stage entrained-flow gasifier to produce syngas carbon monoxide and hydrogen. The simulations are conducted using the commercial Computational Fluid Dynamics (CFD) solver FLUENT. The 3-D Navier-Stokes equations and seven species transport equations are solved with eddy-breakup combustion model. Simulations are conducted to investigate the effects of coal mixture (slurry or dry), oxidant (oxygen-blown or air-blown), wall cooling, coal distribution between the two stages, and the feedstock injection angles on the performance of the gasifier in producing CO and H2. The result indicates that coal-slurry feed is preferred over coal-powder feed to produce hydrogen. On the other hand, coal-powder feed is preferred over coal-slurry feed to produce carbon monoxide. The air-blown operation yields poor fuel conversion efficiency and lowest syngas heating value. The two-stage design gives the flexibility to adjust parameters to achieve desired performance. The horizontal injection design gives better performance compared to upward and downward injection designs.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 102 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 80-81).

With the limited reserves of fossil fuels and the environmental problems associated with their use, the world is moving towards cleaner, renewable, and sustainable sources of energy. Biomass is a promising feedstock towards attaining this goal because it is abundant, renewable, and can be considered as a carbon neutral source of energy. Syngas can be further processed to produce liquid fuels, hydrogen, high value chemicals, or it can be converted to heat and power using turbines. Most of the downstream processing of syngas occurs at high pressures, which requires cost intensive gas compression. It has been considered to be techno-economically advantageous to generate pressurized syngas by performing high-pressure gasification. Gasification utilizes high temperatures and an oxidizing gas to convert biomass to synthesis gas (syngas, a mixture of CO and H2). Most of the past studies on gasification used process conditions that did not simulate an industrial gasification operation. This work aims at understanding the chemical and physical transformations taking place during high-pressure biomass gasification at heating rates of practical significance. We have adopted an approach of breaking down the gasification process into two steps: 1) Pyrolysis or devolatalization (fast step), and 2) Char gasification (slow step). This approach allows us to understand pyrolysis and char gasification separately and also to study the effect of pyrolysis conditions on the char gasification kinetics. Alkali and alkaline earth metals in biomass are known to catalyze the gasification reaction. This potentially makes biomass feedstock a cheap source of catalyst during coal gasification. This work also explores catalytic interactions in biomass-coal blends during co-gasification of the mixed feeds. The results of this study can be divided into four parts: (a) pyrolysis of loblolly pine; (b) gasification of pine chars; (c) pyrolysis and gasification of switchgrass; (d) co-gasification of pine/switchgrass with lignite and bituminous coals.

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