L’objectif de ce travail est d’étudier les phénomènes de condensation d’aérosols d’espèces inorganiques dans un procédé de gazéification de la biomasse. En effet, au cours du procédé de gazéification, la biomasse lignocellulosique se transforme entre 900 et 1500°C en un gaz de synthèse. Certaines espèces inorganiques contenues dans les cendres, sont en partie volatilisées, en particulier sous forme de chlorures (KCl, NaCl), et se condensent ensuite lors du refroidissement de ce gaz. Les composés peuvent alors provoquer corrosion, bouchage et polluer les catalyseurs utilisés lors des synthèses ultérieures. La compréhension et la modélisation de la condensation de ces espèces peut aider à leur maitrise, et pour limiter les difficultés rencontrées. Un dispositif expérimental analytique existant au laboratoire nous a permis de réaliser des essais de condensation de KCl et NaCl gazeux, dans des conditions expérimentales proches de celles rencontrées en gazéification dans un réacteur à flux entraîné, en particulier pour deux vitesses de refroidissement (1000K/s et 300K/s). L’influence des différents paramètres (présence ou pas de particules préexistantes dans l’installation comme les suies et représentées par des particules de C, concentration en sel, mélange…) sur les phénomènes qui régissent la condensation de la vapeur a été réalisée pour les deux vitesses de refroidissement. D’une manière globale, les résultats expérimentaux ont mis en évidence qu’en l’absence de particules de C, la condensation des espèces inorganiques provoque la formation de très nombreuses nouvelles particules, de très petite taille, par nucléation homogène. En présence de particules de C, cette vapeur a tendance à se condenser sur les particules préexistantes, ce qui permet de réduire les dépôts aux parois d’environ 10% en masse. Le comportement du mélange est un intermédiaire entre celui des deux espèces inorganiques élémentaires. A 300K/s un effet d’agglomération de particules lié à un temps de séjour plus long a été mis en évidence pour tous les essais. Le logiciel SOPHAEROS, développé par l’IRSN pour le calcul du transport et condensation des contaminants pour des applications nucléaires, a été adapté aux conditions expérimentales de cette étude, et été validé pour le KCl et le NaCl par comparaison calcul-expérience. Il a également permis d’expliquer les différences de comportement, d’une part, liées aux variations locales des pressions de vapeur saturante et pression partielle de sel et d’autre part, entre les deux vitesses de refroidissement. En conclusion de ce travail et afin de réduire les dépôts à la paroi, quelques pistes de solutions industrielles sont proposées / The purpose of this work is to analyze the condensation phenomena of inorganic species aerosols in a biomass gasification process. Indeed, during gasification, lignocellulosic biomass is transformed, in between 900 and 1500°C, into a Syngas. Some inorganic species initially present in the ash, are partly volatilized in chlorides (KCl, NaCl), and condense when the syngas cools down. These compounds may then, induce corrosion, blockages and deactivation of the catalysts used in further synthesis. The understanding and modeling of these species condensation may help to their management, and also to the imitation of the encountered difficulties. An experimental and analytical set-up, existing n the lab, allowed us to perform condensation tests from gaseous KCl and NaCl, under experimental condition close to the industrial gasification ones for an entrained flow reactor, especially for two cooling rates (1000 and 300K/s). The influence of the different parameters (presence or not of preexisting particles like soot and simulated by carbon particles, inorganic salts concentration, salts mixture…) on the vapor condensation phenomena, was performed for both cooling rates. Globally, the experimental results showed that, without carbon particles, the inorganic species condensation induce the formation of very small new particles by homogeneous nucleation. With carbon particles, this vapor tends to condense on the preexisting particles, which allows to reduce the wall deposits by about 10wt %. The mixture behavior is found to be in between the individual salt ones. A particle agglomeration effect is also evidenced at 300K/S, linked the increase of the residence time in the cooling part of the set-up. The SOPHAEROS software, developed by IRSN for the fission product transport and condensation in a nuclear power plant, was adapted to the experimental conditions of this work. The validation of this tool was obtained, comparing calculation and experimental results. It was then used to determine the main condensation and deposits phenomena varying the inorganic salt nature, their concentration, the presence of carbon particles and the cooling rate. It was showed that, the three main involved phenomena, occurring in the quench part of a gasification reactor, without carbon particles, are the direct wall condensation of the vapor, the homogeneous nucleation (favored at high cooling rate, 1000K/s), and gravitational settling deposits. When carbon particles are included, heterogeneous nucleation is predominant upon homogeneous one. The modelling could allow us to explain the behavior differences related to the local variation of salts partial pressure and saturation vapor pressure, as well as the influence of both cooling rates on the condensation results. Finally, some industrial possible solutions to decrease the wall deposits are proposed as a conclusion of the work

Orientador: Maria Regina Wolf Maciel / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T09:30:10Z (GMT). No. of bitstreams: 1 JaimesFigueroa_JaiverEfren_D.pdf: 4291833 bytes, checksum: dc5592f8288a01f2f792aac9bf02f01b (MD5) Previous issue date: 2015 / Resumo: Os processos termoquímicos permitem a conversão da biomassa em outros produtos de maior interesse e valor agregado. Dentre os processos termoquímicos destacam-se a pirólise e a gaseificação, sendo o alcatrão e gases, os principais produtos resultantes. Estes produtos possuem um grande potencial como intermediários químicos, combustíveis, lubrificantes e energia, tornando os processos termoquímicos muito atrativos. Este trabalho teve como objetivo avaliar experimentalmente dois processos termoquímicos: pirólise e gaseificação, usando bagaço de cana-de-açúcar como matéria-prima. Foram avaliados dois tipos de reatores: leito fixo e leito fluidizado. Inicialmente, foi realizada uma revisão bibliográfica para a obtenção das propriedades físico-químicas da matéria-prima, valores típicos sobre dimensionamento de reatores, cinéticas de reação e características dos produtos obtidos pela via termoquímica, com a finalidade de estudar o comportamento fluidodinâmico do sistema. Posteriormente, foi realizada uma simulação no software comercial ANSYS-FLUENT V12TM, obtendo-se pequenos desvios entre os valores preditos e os encontrados na literatura, o que gerou uma ferramenta computacional com potencial para avaliação dos processos termoquímicos utilizando material lignocelulósico. Após o estudo computacional, foram realizados dois estudos experimentais: um do processo de pirólise e outro de gaseificação. Os estudos experimentais foram realizados usando dois tipos de reatores com características diferentes, quando comparados aos reatores encontrados na literatura. A pirólise lenta a altas temperaturas do bagaço foi desenvolvida em reator de leito fixo em batelada, contendo uma mistura de bagaço e alumina/sílica (carga máxima de bagaço 4 g). Foram testadas várias temperaturas, superiores a 500 °C, e encontrado que um aumento nesta variável significou em um aumento da quantidade de gases e diminuição de carvão produzido. O alcatrão obtido foi independente da temperatura (20 % mássico). Utilizando o mesmo reator, foi realizada uma reação de gaseificação de bagaço de cana-de-açúcar a 900 °C e relação mássica vapor/bagaço igual a 2,0, obtendo-se maior rendimento de gases e menor de carvão. Além disso, o gás produzido continha porcentagem maior de hidrogênio quando comparado ao gás obtido por pirólise empregando a mesma temperatura. A gaseificação do bagaço foi realizada em um reator de leito fluidizado (elaborado e desenvolvido pelo grupo de pesquisa LOPCA/BIOEN/FEQ/UNICAMP para esta tese). Este reator foi instalado, testado e colocado em funcionamento com uma vazão de bagaço de até 3 kg/h. As reações foram feitas usando diferentes relações ER (razão mássica entre as relações (ar/bagaço) e (ar necessário para combustão completa/bagaço). Cada relação ER testada proporcionava uma temperatura de reação diferente, obtendo-se uma distribuição de produtos com características diferentes entre si. Os produtos da gaseificação foram caracterizados. Valores de ER mais elevados ofereceram maiores temperaturas de reação e, consequentemente, maiores rendimentos de gases e porcentagens de H2 e CO / Abstract: The thermochemical processes allow the biomass conversion in others products, producing simpler structures, which are more interesting. Two main thermochemical processes are the pyrolysis and gasification, which produce tar and gases. These products have an enormous potential as intermediate chemical compounds, fuels, lubricants and energy, making the thermochemical processes very relevant. In this work, both processes aforementioned were object of experimental study, using sugarcane bagasse as raw material. Two different reactors were analyzed: fixed bed and fluidized bed. A bibliographic research was made as a starting point, collecting enough information about the properties of the raw material, typical dimensions of the reactors, reaction kinetics and characteristics of the products. In order to study the fluid-dynamic behavior of the system some simulations were performed, using the ANSYS-FLUENT V12TM software. The simulation results presented small deviation compared to the experimental results reported on the literature, which indicates that the simulated system is a powerful tool to validate thermochemical processes that involve lignocellulosic materials. Subsequently, two experimental studies were developed: one for pyrolysis and other for gasification. For each process mentioned before, we used two types of reactors that differ from the reactors found on the literature. Bagasse pyrolysis was made on a fixed bed batch reactor, using a mixture of bagasse and alumina-silica (the bagasse does not exceed 4 grams). Different temperatures above 500 ºC were used, showing that the quantity of obtained gases were proportional to the temperature, while the quantity of carbon was inversely proportional. On the other hand, the tar produced in the reaction does not depend on the temperature (20 % mass). The same reactor was used to do the gasification of sugarcane bagasse at 900 ºC and a steam/bagasse mass ratio of 2.0, obtaining a bigger production of gas and smaller production of carbon. Additionally, the obtained gas contains a bigger proportion of hydrogen than the gas produced with pyrolysis, using the same temperature. Finally, other gasification were performed, using a fluidized bed reactor acquired by the LOPCA/BIOEN/FEQ/UNICAMP research group, which produces a bagasse output up to 3 kg/h. All reactions were made using different ER relations (air/bagasse mass ratio). Each ER relation produced a different reaction temperature, obtaining a product distribution with different characteristics between them. The products obtained were characterized. The higher ER values offered bigger temperatures of reaction and consequently, higher yield of gas and percentages of H2 and CO proportions / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22428号 / 工博第4689号 / 新制||工||1732(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 酒井 伸一, 教授 田中 宏明, 准教授 平井 康宏 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The effects of elevated pressure and high heating rates on coal pyrolysis and gasification were investigated. A high-pressure flat-flame burner (HPFFB) was designed and built to conduct these studies. The HPFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ~10^5 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Pyrolysis experiments were conducted at particle heating rates of ~10^5 K/s and maximum gas temperatures of ~1700 K at pressures of 1 to 15 atm. A new coal swelling correlation was developed that predicts the effects of heating rate, pressure, and coal rank on the swelling ratio at heating rates above ~10^4 K/s. A coal swelling rank index system based on 13C-NMR chemical structural parameters was devised. The empirical swelling model requires user inputs of the coal ultimate and proximate analyses and the use of a transient particle energy balance to predict the maximum particle heating rate. The swelling model was used to explain differences in previously reported bituminous coal swelling ratios that were measured in facilities with different heating rates. Char gasification studies by CO2 were conducted on a subbituminous coal and 4 bituminous coals in the HPFFB. Pressures of 5, 10, and 15 atmospheres were used with gas compositions of 20, 40, and 90 mole % CO2. Gas conditions with peak temperatures of 1700 K to 2000 K were used, which resulted in char particle temperatures of 1000 K to 1800 K. Three gasification models were developed to fit and analyze the gasification data. A simple 1st-order model was used to show that the measured gasification rates were far below the film-diffusion limit. The other two models, designated CCK and CCKN, were based on three versions of the CBK models. CCKN used an nth-order kinetic mechanism and CCK used a semi-global Langmuir-Hinshelwood kinetic mechanism. The two CCK models fit the HPFFB gasification data better than the 1st-order model. The fits of the gasification data with CCK and CCKN were comparable to each other. The fit of the data in CCK suggests that Knudsen diffusion may have influenced the gasification rates in the HPFFB experiments. The gasification rate parameters in each of the three models were correlated with coal rank. 13C-NMR parameters were used to estimate a structural parameter of the coal char. Char-CO2 gasification rate coefficients correlated better with this NMR-based char structure index than it did with the carbon and oxygen content of the parent coal.

This diploma thesis deals with impurities in waste gases and syngas. Those gases usually have low heating value and contain impurities which are the main issue of those gas fuels. Waste gases and syngas can replace natural gas after right gas treatment. First part is theoretical. It starts with description of biomass and gasification technology. Then the waste gases are described – their origin and usual composition. Next part is dedicated to impurities and is followed by impurities treatment technologies. For removing of almost every type of impurity wet scrubber can be used which is described in detail in following part. There are other types of gas cleaning technologies, so they are described too but not in such detail as wet scrubber. In second part the wet scrubber is designed, and its function is tested by cleaning syngas from fluidized-bed gasifier called Biofluid. During gas cleaning in wet scrubber the influence of water temperature on efficiency of tar removal is examined.

Gasification is a process which produces gas of low heating value, however, generated gas contains several pollutants. This thesis is dealing with the issue of purity and cleaning of generated gas. Theoretic part of thesis consists of research, describing the very process of gasification itself, mapping of possible pollutants appearing during gasification and particular ways of purifying gas, looking in detail at wet scrubbing with several scrubbing liquids. Further, it looks into proposition of conditions for wet scrubbing and balance of scrubbing liquids. Next part deals with calculation of purifying line. Main goal of calculations, is to determine the length of the pipeline, transfering polluted gas from the gasifier to the filter for elimination of solid particles and wet scrubber. Key aspect of length calculation was the input and output temperature of the gas, determined by characteristics of the filter. Calculation for wet scrubber istelf is also included, to detremine if the output temperature of the scrubbing liquid after the passage of the gas needs to be modified by additional cooling or heating. For experimental purposes, syngas generated by gasification of biomass, is gathered from the atmospheric gasifier Biofluid 2. Experiment itself inquires into the purity of the gas before and after the passage through solid particles filter and through the wet scrubber. The purpose of this thesis is to determine the chemical composition of gas before and after wet scrubbing, the difference of composition of tar gathered from purified and nonpurified gas and using gathered data to evaluate the effectiveness of wet scrubbing.

The aim of the diploma thesis is to discuss the gasification of biodegradable waste. The theoretical part deals with gasification with focus on gasification phases, types of gasification reactors and pollutants contained in the generated gas, especially tar. Further, there is listed the characteristic of alternative biomass fuels, namely digestate and sludge waste. The practical part is devoted to gasification on a fluidized bed reactor with the aim to test the possibilities of gasification of these fuels, to determine their specifications and the influence of various gasification media. In the final part there are discussed the results of the collected gases and tar.

Mathematical models of gasification are suitable for predicting gas composition and its properties. The aim of the diploma thesis is to compile a mathematical model for biomass gasification. The first part deals with the description of gasification and the technologies used. Theoretical part consists of the search of modeling methods. Other theoretical part is devoted to the description of the model and equations presented in the thesis. Part of the assignment is a parametric study that shows changes in gas production and its properties when changing the parameters. Finally, the model is compared with the data obtained in the experiment on the fluid reactor biofluid 2.

This diploma thesis deals with the problem of so-called two-stage gasification, which have the potential of producing gas-fuel with a very low tar value, which has a parameter of its quality evaluation is very important. The thesis deals with processes that are taking part in pyrolysis and gasification, further attention is focused on finding parameters and optimal conditions of operation in order to suggest the basic design of gasification unit. The actual design of the unit consists of a simplified energy and mass balance model and the design of its own partial and significant components. The work is supplemented by an experiment and its evaluation.

The diploma thesis contains calculations of gasification of coal boiler. The first part of thesis contains stochiometric calculations, heat balance and calculations of combustion chamber. In the next part are calculations of heat exchange surfaces and at the end of this part are calculations of regenerative air heater and total boiler balance. Calculations are made by regard to investments costs, preservation of the steam parameters and keeps emissons limits.