The present study is in two parts, the first part describes an investigation that was undertaken to determine the feasibility and hydrodynamic behaviour of a cold model circulating fluidized bed system proposed for the continuous combustion-gasification of biomass. The design is based on the principle that the char produced in the gasifier is circulated with the bed material and combusted in a separate reactor to generate the heat required for the gasification process. While high solid circulation rates are required to maintain the heat balance, product and flue gas mixing between the two units must be minimised or eliminated. The design of the circulating bed simply consists of two fluid bed units connected two together via a riser and a downcomer fitted with a non-mechanical valve. Various aspects such as solid circulation rate, gas mixing, solids mixing, and pressure component around the circulating loop were studied. Results show that the solid circulation and gas mixing are strongly influenced by the riser gas velocity, total solids inventory, and position of the riser from the riser gas jet. Solid circulation fluxes of up to 1 l5kg/m 2s were attained and easily controlled. The flue gas crossflow was less than 4% over the range studied. By analysing the experimental data, a series of mathematical correlations were obtained which successfully predict the exponential relationship that exists between the solid circulation rate, gas mixing and the operating parameters. The potential of this system for its purpose is highlighted. The second part of the study focuses on the design and development of a heated fluidized bed reactor with an on-line gas and solids sampling technique to study the steam gasification of biomass (almond shells). Experiments were conducted at temperatures of up to 800°C to investigate the gasification rates of biomass char under different operating conditions. Understanding the gasification and combustion rates of biomass char is an important step towards the proper designing of biomass gasifiers. In the heated fluid bed, the extent of the gasification of biomass increased with increasing temperature as indicated by an increase in the quantity of gaseous products. A hydrogen content of up to 43% by volume was obtained. The sampling technique adopted allows the collection of the bed sample at gasification conditions which can be used to predict the composition of the bed. The gasification rate of biomass (almond shell) char was found to be affected by the gasification temperature. In order to evaluate the char gasification rate constants, the shrinking core model with reaction controlling step (SCM) was applied to the char gasification data. The rate constant values obtained from the SCM were 5.14E-5, 7.67E- 5, and 1.26E-4 s' for temperatures of 712, 753, and 806 °C respectively. The activation energy was evaluated as 89 kJ/mol. These values were in close agreement with those published in the literature. SEM pictures of the surface of the chars shows that at high temperatures, the char formed is very porous and hence very reactive. With regards to practical gasifiers, the results obtained have been used to evaluate an --mum volume for a typical biomass gasifier operating at 850 °C. The aim of the present work were satisfactorily achieved.

A mathematical model for entrained flow coal gasification was developed with the objective of predicting the influence of coal properties and gasification conditions on the performance of entrained flow gasifiers operating at pressures up to 21 atmospheres (2.1MPa). The model represents gasifiers as plug flow reactors and therefore neglects any mixing or turbulence effects. Coal properties were predicted through use of correlations from a variety of literature sources and others that were developed from experimental data in the literature. A sensitivity analysis of the model indicated that errors in the calculated values of coal volatile yield, carbon dioxide gasification reactivity and steam gasification may significantly affect the model predictions. Similarly errors in the input values for gasifier wall temperatures and gasifier diameter, when affected by slagging, can cause model prediction errors. Model predictions were compared with experimental gasification results for a range of atmospheric and high pressure gasifiers, the majority of the results being obtained by CSIRO at atmospheric pressure for a range of coals. Predictions were accurate for the majority of atmospheric pressure results over a large range of gas feed mixtures. Due to the limited range of experimental data available for high pressure gasification the capability of the model is somewhat uncertain, although the model provided accurate predictions for the majority of the available results. The model was also used to predict the trends in particle reactions with gasification and the influence of pressure, gasifier diameter and feed coal on gasifier performance. Further research on coal volatile yields, gasification reactivities and gas properties at high temperatures and pressures was recommended to improve the accuracy of model inputs. Additional predictions and model accuracy improvements could be made by extending the model to include fluid dynamics and slag layer modelling. / PhD Doctorate

Orientador: Caio Glauco Sánchez / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T10:47:21Z (GMT). No. of bitstreams: 1 Gonzalez_AnselmoDuenas_M.pdf: 1368739 bytes, checksum: 0338b09718228f3771fae35aff575d0b (MD5) Previous issue date: 2014 / Resumo: O presente trabalho apresenta o desenvolvimento de um processo de caraterização das cinzas das biomassas bagaço de cana-de-açúcar, eucalipto e capim elefante após sua queima quando utilizadas para geração de energia alternativa. É, então, analisada a influência de parâmetros físico-químicos na qualidade final das cinzas. O parâmetro químico avaliado foi a interpretação da composição elementar das cinzas estudadas por análises de Espectrometria de Fluorescência de Raios-X e Cromatografia de Íons e por Análise Química por, objetivando a caracterização e reutilização desses resíduos. As amostras de cinzas de biomassas estudadas neste trabalho, foram analisadas quanto à presença dos elementos Cloro (Cl-), Alumínio (em Al2O3), Cálcio (em CaO), Ferro (em Fe2O3), Fósforo (em P2O5), Magnésio (em MgO), Manganês (em MnO), Potássio (em K20), Sódio (em Na2O) e Silício (em SiO2), e foram caracterizadas conforme os percentuais em massa dos elementos presentes. Os resultados obtidos mostraram a possibilidade de reutilização adequada de cinzas das biomassas em função da alteração das propriedades químicas do solo, por ocorrência de elevação dos níveis de pH, Cálcio (Ca), Fósforo (P), redução dos teores de Alumínio (Al) trocável e melhoria substancial da capacidade de agregação das partículas e fertilização do solo. Também foram associadas as influências dos elementos presentes nas cinzas como alternativa viável na composição do cimento Portland, em especial, o Silício (em SiO2). As cinzas das biomassas possuem nutrientes que estão na forma solúvel e são libertados ao longo do tempo devido à sua decomposição contínua e também pela solubilidade dos compostos químicos, o que, consequentemente, torna os nutrientes menos suscetíveis à lixiviação / Abstract: This paper presents the development of a process of characterization of the ashes of biomass bagasse from sugar cane, eucalyptus and elephant grass after its burning when used for alternative energy generation. It then analyzed the influence of physicochemical parameters on the final quality of the ash. The chemical parameter evaluated was the interpretation of the elemental composition of the ash studied by analysis Fluorescence Spectrometry X-Ray and Ion Chromatography and Chemical Analysis, aiming at characterization and reuse of the waste. The ashes from biomass samples studied in this work were analyzed for the presence of chlorine (Cl-), aluminum (as Al2O3), calcium (as CaO), iron (as Fe2O3), phosphorus (as P2O5), Magnesium elements (as MgO), manganese (as MnO), Potassium (as K20) Sodium (as Na2O) and silicon (as SiO2), and were characterized as the weight percentage of the elements present. The results showed the possibility of proper reuse of ashes of biomass due to changes in chemical properties of the soil, by the occurrence of elevated levels of pH, calcium (Ca), phosphorus (P), reduced levels of aluminum (l) the significant improvement exchangeable capacity of aggregation of particles and soil fertilization. Were also associated with the influences of the elements present in the ash as a viable alternative in the composition of the Portland cement, in particular, silicon (as SiO2). The ash of the biomass have nutrients that are in soluble form and are released over time due to its continuous decomposition and also by the solubility of the chemical compounds, which consequently makes them less susceptible to leaching nutrients / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Orientadores: Maria Regina Wolf Maciel, Betânia Hoss Lunelli / Tese (doutorado) ¿ Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T13:48:19Z (GMT). No. of bitstreams: 1 Ardila_YuranyCamacho_D.pdf: 7705979 bytes, checksum: 19a2840a168991456944a44d857667ee (MD5) Previous issue date: 2015 / Resumo: A produção de biocombustíveis a partir da biomassa apresenta-se como uma alternativa para suprir as limitadas reservas de petróleo. A biomassa, atualmente, está sendo usada para diferentes processos termoquímicos, entre os quais a gaseificação é o de maior destaque. A gaseificação produz gás de síntese que é uma mistura, principalmente, de CO, H2 e CO2. Este gás serve para produzir energia, diferentes produtos químicos e biocombustíveis, como por exemplo, o bioetanol. A partir do gás de síntese, a produção de bioetanol pode ser realizada usando catalisadores químicos ou biocatalisadores, sendo este último processo conhecido como fermentação do gás de síntese. Para o processo integrado de gaseificação da biomassa e posterior fermentação para produção de bioetanol, as informações na literatura são escassas, o que dificulta avaliar a viabilidade desta nova tecnologia, em termos de condições operacionais. O uso de modelos matemáticos e sua simulação computacional podem auxiliar neste estudo. A literatura dispõe de vários estudos envolvendo simulações computacionais aplicadas à gaseificação de diferentes biomassas. Porém, poucos abordam a caracterização real do processo e as propriedades da biomassa utilizada, considerando apenas as propriedades para o carvão mineral, o que acaba gerando divergência nos resultados. Além disso, a maioria fundamenta suas simulações em modelos simples com base na caracterização elementar-imediata, que acaba limitando o desenvolvimento de plantas virtuais, que são baseadas na análise composicional da biomassa quando focadas na produção de bioetanol como etapa final ou como integração do processo. Assim, este trabalho tem como objetivos estudar o processo completo de gaseificação e realizar um estudo preliminar da fermentação do gás de síntese, mediante simulações computacionais, para definir as melhores condições e variáveis que afetam o processo global quando o bagaço de cana-de-açúcar é utilizado como matéria-prima. As simulações foram desenvolvidas utilizando o simulador comercial Aspen Plus¿ e os resultados validados com dados experimentais da literatura e dados obtidos nos Laboratórios LDPS/LOPCA/BIOEN/FEQ/UNICAMP. Para a completa simulação do processo, várias etapas foram estudadas e divididas para melhor entendimento. Foram desenvolvidos modelos matemáticos para predizer propriedades necessárias para o desenvolvimento de processos termoquímicos. Simulações baseadas nas análises elementar-imediata e composicional da biomassa foram realizadas para definir a decomposição inicial da biomassa, demonstrando os diferentes rendimentos e produtos que são gerados e que são a base da etapa inicial da gaseificação. Simulações completas da gaseificação foram desenvolvidas para estudar a gaseificação em diferentes tipos de reatores. A influência das condições de operação na gaseificação como temperatura, razão de equivalência (ER), injeção de vapor e temperatura do pré-aquecedor do ar no desempenho do gaseificador foram avaliadas. Com as condições operacionais da gaseificação definidas foi proposta uma simulação para representar a fermentação do gás de síntese. A partir dos resultados obtidos foi constatado que a composição do gás de síntese é alterada pelo aumento do ER e pela injeção de vapor no processo, e diferentes concentrações de bioetanol são obtidas quando a pressão de entrada do gás de síntese é alterada / Abstract: The production of biofuels from biomass is presented as an alternative to save the limited oil reserves. Currently, biomass is being used for different thermochemical processes, including gasification which is the most prominent. Gasification produces synthesis gas which is a mixture mainly of CO, H2 and CO2. This gas is used to produce energy, several chemicals and biofuels, such as ethanol. The ethanol from synthesis gas may be produced using chemical catalysts or biocatalysts, this latter process is known as fermentation of syngas. The information in the literature is scarce for the integrated gasification of biomass and subsequent fermentation to produce ethanol, making it difficult to see the feasibility of this new technology, in terms of operating conditions. The use of mathematical models and their computer simulation can help this study. Typically, numerous studies involving computer simulations, applied to different biomass gasification, are found in the literature. However, few of them approach the real characterization of process and properties for used biomass, considering only the properties for coal, which ends up generating divergence in the results. Moreover, most of the simulations are grounded on simple models based on proximate-ultimate characteristics, which end up limiting the development of virtual plants, which are based on biomass compositional analysis when focused on the production of ethanol as the final step or as integration process. Thus, the aims of this work are to study the complete gasification process and to carry out a preliminary study of synthesis gas fermentation, through computer simulations, in order to define the best conditions and variables that affect this global process when sugarcane bagasse is used as raw material. The simulations were developed using Aspen Plus ¿ simulator and the results validated with experimental data from literature and data obtained in the laboratories LDPS / LOPCA / BIOEN / FEQ / UNICAMP. For the full simulation of the process, several steps were studied and divided for a better understanding. Mathematical models were developed to predict properties required for the development of thermochemical processes. Simulations based on biomass analysis as proximate-ultimate and compositional were done to define the initial decomposition of biomass, demonstrating the different yields and products that are generated and which are the basis of the initial stage of the gasification. Complete simulations of gasification were carried out to study different types of gasification reactors. The influence of operating conditions at gasification performance was investigated; variables such as temperature, equivalence ratio (ER), steam injection and preheater temperature were evaluated. With the set conditions of gasification was proposed a simulation to represent the fermentation of syngas. It was demonstrated that the synthesis gas composition is changed when increased the ER and steam injection; and different ethanol concentrations are obtained when the input pressure of the synthesis gas is changed / Doutorado / Desenvolvimento de Processos Químicos / Doutora em Engenharia Quimica