Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 594-611. / Sc.D.

Os resíduos sólidos urbanos (RSU) no Brasil são na grande maioria direcionados para aterros e lixões a céu aberto, onde ocupam grandes áreas, geram transtornos relacionados ao trafego aéreo, emitem gases responsáveis pelo efeito estufa sem o devido reaproveitamento energético. Como alternativa para a minimização do passivo ambiental causado pelos RSUs e potencial reaproveitamento energético propõe-se um estudo comparativo de processos de gaseificação desses resíduos em diferentes meios gaseificantes. A modelagem e simulação dos processos foram feitas aplicando-se o método de minimização da energia livre de Gibbs não estequiométrica. Considerou-se a quantidade de resíduo sólido urbano destinado da sub-região de Campo Limpo - São Paulo - e a sua composição representativa expressa pelo método ultimate-analysis. O processo de gaseificação foi implementado em simulador de processo e o estudo se concentrou nas etapas do processo de gaseificação, investigando-se a ação dos seguintes meios gaseificantes: ar, vapor e mistura ar e vapor. Os principais resultados analisados foram a composição do produto da gaseificação e o potencial energético do produto. / The major destiny of Municipal Solid Waste (MSW) in Brazil is landfill. These sites occupy large areas; most of them are open, being simply disposal areas. This situation causes several problems ranging from greenhouse gases to air traffic jeopardizing. The use of MSW in energy generation addresses these problems, once it is one of most promising solutions to MSW treatment. This work is the study of gasification from the energy potential. It was carried out through minimization of Gibbs energy in a process simulator. The MSW considered was the one from area of Campo Limpo in São Paulo city. Its composition was expressed by ultimate analysis. The use of different gasification agents included air, steam and their mixtures was analyzed. The results were HHV and composition of generated gases.

La gazéification est un procédé de conversion thermochimique permettant de convertir un combustible solide en gaz de synthèse (syngaz), composé notamment de H2 et CO. L’utilisation de déchets non-dangereux sous forme de CSR doit, en plus de fournir une énergie avec de bons rendements, respecter les normes environnementales. Nos travaux évaluent les performances énergétiques et environnementales de la gazéification à l’air de CSR (bois, pneus, plastiques, boues de STEP) en réacteurs en lit fixe co-courant à l’échelle pilote et industrielle. Les méthodes d’analyse utilisées permettent un suivi de la composition du syngaz, ainsi que des polluants (soufrés, azotés, goudrons, métaux lourds) dans les effluents du procédé, par rapport à une ressource propre (bois brut). Les performances de gazéification du CSR Bois sont identiques au Bois. Cependant un ajout de 20%m de CSR Pneus, Plastique ou Boues de STEP à du CSR Bois conduit à une diminution de H2 et CO compensée par une augmentation d’hydrocarbures légers (CH4, C2), conduisant à un pouvoir calorifique similaire, compris entre 4,9 et 5,4 MJ/Nm3. Les performances de gazéification sont légèrement plus fiables avec les mélanges de CSR, entre 35 et 49% alors qu’elles atteignent 48 à 52% pour le Bois et le CSR Bois. Par rapport au Bois, seuls les composés azotés sont en plus grand nombre pour le CSR Bois. Pour les mélanges de CSR, les teneurs en goudrons, composés soufrés et azotés sont plus élevées. De plus, les teneurs en métaux lourds sont plus élevées dans les fines particules que dans les charbons, demandant probablement un traitement particulier. / Gasification is a thermochemical conversion process converting solid fuel into synthetic gas (syngas), containing H2 and CO. Sorting waste to produce SRF aims to allow a better energy recovery of waste, while satisfying environmental regulations. This study focuses on energetic and environmental performances of the air gasification of SRF (wood, tire, plastics, sewage sludge) using downdraft fixed bed reactors at pilot and industrial scale. Analytical procedures allow quantification of syngas composition as well as pollutant contents (sulfur, nitrogen, tars, heavy metals) in gasification outlet streams, considering raw wood as a reference. SRF Wood gasification performances are identical to Raw Wood. However adding 20%w of SRF Tire, Plastics or Sewage Sludge to SRF Wood leads to a decrease in H2 and CO contents, balanced by an increase in light hydrocarbons (CH4, C2), resulting in a similar syngas calorific value, ranging between 4.9 and 5.4 MJ/Nm3. Gasification performances are slightly lower with SRF mixes, ranging between 35 and 49%, while reaching 48 to 52% for Raw Wood and SRF Wood. Compared to Wood, only nitrogen containing pollutants are in higher concentrations with SRF Wood. In the case of SRF mixes, tars, sulfur and nitrogen containing pollutants are in higher concentrations. Moreover, heavy metals contents are higher in fine particles than in chars, resulting in a particular post-treatment.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / A biomassa lÃquida residual de processos agrÃcolas e agroindustriais em geral representa um recurso renovÃvel em quantidade expressiva sem uma destinaÃÃo econÃmica e ambientalmente sustentÃvel Como exemplo a soluÃÃo quanto aos estoques de glicerina resultante da transesterificaÃÃo de Ãleos vegetais para obtenÃÃo do biodiesel tem sido postergada pela carÃncia de alternativas de engenharia apropriadas ao aproveitamento adequado dessa biomassa Por essa razÃo foi iniciado o desenvolvimento de um reator de gaseificaÃÃo destinado à biomassa lÃquida pela via da oxidaÃÃo parcial onde à empregada uma tecnologia de combustÃo nÃo convencional a CombustÃo de FiltraÃÃo como base de projeto para a concepÃÃo do reator em que a biomassa de referÃncia utilizada foi o glicerol (C3H8O3) Este trabalho eminentemente experimental foi realizado com a construÃÃo de um protÃtipo de reator de gaseificaÃÃo em escala de laboratÃrio em que seu queimador à preenchido completamente por esferas cerÃmicas de alumina (Al2O3) formando assim uma matriz porosa inerte que fica parcialmente imersa no glicerol na sua extremidade inferior e que envolve um trocador de calor instalado na parte superior do reator O processo à investigado no sentido de identificar algumas caracterÃsticas fundamentais de projeto tais como: limite de operaÃÃo do reator em termos de misturas arcombustÃvel; presenÃa de fenÃmenos de instabilidade; velocidade de propagaÃÃo da onda de combustÃo; e influÃncia dos principais parÃmetros de operaÃÃo, razÃo de equivalÃncia taxa de consumo de combustÃvel e vazÃes de ar e Ãgua na reaÃÃo Embora toda a experimentaÃÃo tenha se restringido a ensaiar o gaseificador para produÃÃo de gÃs de sÃntese pelo mÃtodo da oxidaÃÃo parcial a investigaÃÃo teÃrica foi mais abrangente englobando a reforma autotÃrmica Os experimentos respaldados por instrumentos de monitoramento e anÃlise cromatogrÃfica foram apoiados por um estudo teÃrico a partir de um modelo analÃtico simplificado com base na reaÃÃo global de oxidaÃÃo parcial associada à reaÃÃo de deslocamento ÃguaâgÃs Resultados experimentais demonstraram a viabilidade do processo constatando estabilidade operacional em ampla faixa de razÃo de equivalÃncia e eficiÃncia de conversÃo (>20%) do glicerol em gÃs de sÃntese mantendo extraÃÃo de energia da reaÃÃo / The residual liquid biomass from agricultural and agroindustrial processes in general way represents a renewable resource in significant amount without an economically and environmentally sustainable destination For instance the solution concerning glycerin stocks remaining from the vegetable oil transesterification for obtaining biodiesel has been postponed due to the lack of engineering alternatives appropriate to the proper utilization of this biomass Therefore the development of a liquid biomass gasification reactor based on partial oxidation has been initiated where a non conventional combustion technology has been employed Filtration Combustion as a design basis for the reactor conception in which the reference biomass used was glycerol This work eminently experimental was carried out to build a gasification reactor prototype in laboratory scale in which its burner is completely filled by ceramic spheres of alumina (Al2O3) thus forming a inert porous matrix which is partially immersed in glycerol at its bottom end and which involves a heat exchanger installed at the top of the reactor The process is investigated to identify some key design features such as: reactor operation limit in terms of fuel-air mixtures; occurrence of instability phenomena; combustion wave propagation velocity; and influence of the main operation parameters equivalence ratio fuel consumption rate and air and water flow rates into the reaction Although all experimentation has been restricted to test the gasifier for the production of synthesis gas by partial oxidation method theoretical investigation was broader comprising the autothermal reforming The experiments supported by monitoring instruments and chromatographic analysis were supported by a theoretical study based on a simplified analytical model considering the global reaction of partial oxidation associated with water-gas shift reaction Experimental results have demonstrated the feasibility of the process providing operational stability over a wide range of equivalence ratio and conversion efficiency (>20%) of glycerol to syngas while maintaining energy extraction from reaction

The thesis, entitled 'Investigation of the conversion of fuels in the presence of solid oxygen carriers and the development of a plasma-assisted chemical looping system for H2 production', presents the work of Yaoyao Zheng in the Department of Engineering, University of Cambridge, for the degree of Doctor of Philosophy. The thesis focused on chemical looping conversion of fuels, which employ oxygen carriers to supply oxygen, followed by the regeneration of the reduced oxygen carriers in air. Combustion of a Polish coal-derived char was first carried out in a fluidised bed reactor in the presence of Fe2O3 or ZrO2-supported Fe2O3. CO2 was introduced to the fluidised bed, to allow the char to be gasified in situ, prior to the reaction with the oxygen carriers. The presence of Fe2O3 did not alter the gasification step, given that the gasification of the char was free of external mass transfer limitation. A numerical model was developed to describe the gasification behaviour, as well as predicting the effect of CO on gasification. The inhibition effect of CO on char gasification was found more significant than expected. Combustion of biomass (wood pellets), by Fe2O3 or mayenite-supported CuO was studied in a fluidised bed. This was to understand how efficient the wood pellets were combusted by the oxygen carriers, as well as the distribution of the products. A tar measurement system, based on a plasma reactor, was first developed. With the developed measuring system, it was found that both Fe2O3 and mayenite-supported CuO were efficient for combusting wood pellets. Particularly, the CLOU nature of CuO makes mayenite-supported CuO a promising candidate for direct combustion, without introducing any reactive gaseous oxidant. The final part of the dissertation was focused on developing a plasma-assisted chemical looping system for H2-rich gas production (PCLH) from CH4 at mild temperatures (~ 673 K). SrFeO3-, Fe2O3, and Ni-doped SrFeO3- and Fe2O3 were investigated as the packing material. Total combustion of CH4 was observed in SrFeO3-. The addition of Ni onto SrFeO3- significantly improved the selectivity towards H2; whilst it was only active in the fresh cycle. Fe2O3 was found to be inert for converting CH4; however, the addition of Ni to form NiO/Fe2O3 dramatically improved H2 production and the reactivity maintained high for three redox cycles. The energy cost of such PCLH was comparable to that of water electrolysis.

An increasing emphasis on mitigating global climate change (global warming) over the last few decades has created interest in a broad range of sustainable or alternative energy systems to replace fossil fuel combustion. Biomass, when harvested responsibly, is a renewable fuel with many uses in replacing fossil fuels. Cofiring biomass with coal in traditional large-scale coal power plants represents one of the lowest risk, least costly, near-term methods of CO2 mitigation. Simultaneously, it is one of the most efficient and inexpensive uses of biomass. Alternatively, biomass can be transformed into useful products through gasification to produce clean syngas for highly efficient gas turbines, or feedstock to produce light gases, fuels, chemicals or other products. A large portion of this investigation focused on the effect of cofiring biomass on the near burner region of a commercial coal flame. This research included first-of-their-kind field measurements of flame structure and particle properties in front of a full-scale burner fired with biomass and coal, including measurements of particle size and composition, gas velocity, composition, and temperature in the near-burner region of multiple cofired flames in a 350 MWe full-scale power plant in Studstrup, Denmark. A novel sampling and analysis technique was developed enabling the estimation of the fraction of biomass in the flow as a function of position and the burnout of biomass and coal particles separately. These data show that biomass particles do not follow gas stream lines to the same extent that coal particles do. This is consistent with the larger sizes, slower heating and reaction rates, and higher momentum of biomass particles. This research also includes first-of-their-kind single particle continuous measurements of particle mass, surface and internal temperature, size, shape, during biomass pyrolysis and gasification. The single particle measurements provided among the most highly resolved and repeatable biomass gasification results reported to date for wood, switchgrass and corn stover. All three samples showed greater gasification reactivity to H2O than to CO2. The experiments included results in both reactants individually and combined. One of the most important findings of this work was the experimental confirmation that as the char particles gasify, their ash fractions increase and reaction rates decrease on both an intrinsic and external surface area basis. The analyses in this work show that this decrease in burnout quantitatively corresponds to the change in the predicted fraction of the surface that is ash and does not reflect any change in organic reactivity. Reaction rate parameters suitable for relatively simple power-law models based on external surface area describe all the data reasonably well.

Biomass is an attractive renewable energy resource for electricity generation, which has the potential to protect air quality, reduce dependence on fossil fuel, and improve forest health. Biomass gasification is a technology that transfers solid or liquid biomass into gaseous energy carrier (syngas) to increase the efficiency of electricity generation. The objective of this thesis is to supply a detailed feasibility study and provide a state-of-the-art economical pathway on biomass gasification application. The work of this dissertation can be separated into two parts: commercial-scale biomass integrated gasification combined cycle (BIGCC) power plants comparison and other biomass gasification system design. The first part compares eight BIGCC systems with three groups of technology variations of gasification agent, syngas combustion method, and CO2 capture and storage. By comparing on performance, economic, and environmental indicators of these systems, it is found that BIGCC systems have higher exergy efficiency and lower emissions than biomass combustion electricity production system and electricity grid. However, its levelized cost of electricity is around 27% higher than the average electricity market price. To reduce the BIGCC system’s cost, in the second part of this thesis, the potential for waste material gasification has been discussed. This part discussed the tire gasification and the gasification technology application for avian influenza poultry management. Results showed that tire gasification has a lower cost than natural gas which has the potential to reduce the BIGCC system’s cost. Moreover, gasification is an effective and economical available approach for avian influenza poultry management.

Orientador: José Luz Silveira / Resumo: As maiores restrições ambientais impostas por autoridades de todo o mundo, no sentido de buscar a redução dos níveis de emissões de poluentes, bem como a crescente escassez de recursos minerais como o petróleo, impõe a alguns países a real necessidade de investir em novas tecnologias que melhor aproveitem os recursos disponíveis com menos agressão ao meio ambiente aliado a maior geração de receita. Nesse sentido a tecnologia IGCC – Integrated Gasification Combined Cycle é apresentada como uma possibilidade para atingir estes objetivos, inclusive para países como o Brasil que dispõe de grandes reservas petrolíferas e que tem a necessidade de aumentar a produção de insumos como hidrogênio, vapor e energia elétrica. Este trabalho apresenta uma breve revisão da bibliografia sobre o refino de petróleo, sobre a gaseificação dos resíduos provenientes do refino e sobre a tecnologia IGCC em seus aspectos gerais, abordando os principais componentes do sistema e como esta tecnologia pode ser utilizada em uma planta de refino. Na sequência, as aplicações da tecnologia IGCC são exemplificadas com três exemplos reais em funcionamento no mundo. A refinaria do vale do Paraíba é utilizada como estudo de caso para a implantação de uma planta IGCC, utilizando 100% do coque verde de petróleo produzido como matéria prima para a gaseificação, tendo como objetivo a produção exclusiva de energia elétrica para a geração de dividendos à refinaria. A análise termodinâmica da planta apresentou eficiênci... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The greater environmental restrictions imposed by authorities around the world, in the sense of seeking to reduce levels of pollutant emissions, as well as the growing scarcity of mineral resources such as oil, impose on some countries the real need to invest in new technologies that best utilize available resources with less aggression to the environment combined with greater revenue generation. In this sense the Integrated Gasification Combined Cycle (IGCC) technology is presented as a possibility to achieve these objectives, including for countries such as Brazil that has large oil reserves and that has the need to increase its production of inputs such as hydrogen, steam and electricity. This paper presents a brief review of the literature on oil refining, gasification of waste from refining and IGCC technology in its general aspects, addressing the main components of the system and how this technology can be used in a refining plant. Following, the applications of the IGCC technology are exemplified with three real examples in operation in the world. The Paraíba Valley Refinery is used as a case study for the implementation of an IGCC plant, using 100% of the Petcoke produced as a raw material for gasification, with the objective of producing exclusively electric energy for generation of dividends to the refinery. The thermodynamic analysis of the plant presented net efficiency in electricity production of 41,2% with a production capacity of 260 MW. The economic analysis... (Complete abstract click electronic access below) / Mestre

Mathematical models were developed to understand cavity growth mechanisms, heat and mass transfer in combination with chemical reaction, and the factors which affect gas production from an underground coal gasifier. A model for coal gasification in a one-dimensional spatial domain was developed and validated through comparison with experimental measurements of the pyrolysis of large coal particles and cylindrical coal blocks. The effects of changes in operating conditions and coal properties on cavity growth were quantified. It was found that the operating conditions which have the greatest impact on cavity growth are: temperature, water influx, pressure and gas composition, while the coal properties which have the greatest impact are: the thermo-mechanical behaviour of the coal, the coal composition and the thickness of the ash layer. Comparison of the model results with estimates from field scale trials, indicate that the model predicts growth rates with magnitudes comparable to those observed. Model results with respect to the effect of ash content, water influx and pressure are in agreement with trends observed in field trials. A computational fluid dynamics model for simulating the combined transport phenomena and chemical reaction in an underground coal gasification cavity has been developed. Simulations of a two-dimensional axi-symmetric cavity partially filled with an inert ash bed have shown that when the oxidant is injected from the bottom of the cavity, the fluid flow in the void space is dominated by a single buoyancy force due to temperature gradients established by the combustion of volatiles produced from the gasification of carbon at the cavity walls. Simulations in which the oxidant was injected from the top of the cavity reveal a weak fluid circulation due to the absence of strong buoyancy forces, leading to poor gasification performance. A channel model of gas production from underground coal gasification was developed, which incorporates a zero-dimensional cavity growth model and mass transfer due to natural convection. A model sensitivity study is presented and model simulations elucidate the effects of operating conditions and coal properties on gas production.

Includes an addendum. / Bibliography : leaves 217-233. / iii, 284 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1994