Made available in DSpace on 2014-10-09T12:42:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:59Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017. / Coal fly ash waste produced from the coal combustion process is becoming an ever increasing concern. It is produced in such abundance due to not only South Africa, but the whole of the world relying mainly on coal combustion for the main source of energy production. With the growing rate of the human population this energy production is ever increasing. The current methods of disposal of this fly ash is not sustainable, it is being dumped in ash dumps, and poses a risk to the surrounding environment and human population. Therefore, processes need to be developed to take this waste and turn it into useful materials. This would not only solve the problem of its disposal but also create useful products that can be applied to further protect the environment. It was discovered that one of the useful materials that can be synthesised from fly ash are zeolites. These nano-porous structures have a wide variety of uses. Therefore, many studies have been conducted around optimising the synthesis of various zeolites from coal fly ash. More recently these studies have focused on the scale-up conditions needed to synthesise these zeolites on the large industrial scale, regarding the sheer volume of fly ash produced annually. The most robust and widely used technique for zeolite synthesis involves a pre-synthesis fusion of the fly ash with sodium hydroxide at a temperature of 550 0C. This would not be feasible to scale-up to industrial scale because of the energy intensity. Therefore, alternative pre-synthesis techniques have been proposed. One of those techniques involves using a sonochemical treatment as a pre-synthesis. It can be argued that this technique may not be able to be easily scaled. To solve this problem, another alternative technique was investigated within this study. It involves the use of a jet loop pilot plant mixing system, which can be scaled-up very readily to industrial scale.

Cinzas de carvão mineral são resíduos gerados em grandes quantidades nas usinas termelétricas. Este é um dos resíduos de maior geração no Brasil, aproximadamente 1,7 milhões de toneladas por ano. A disposição muitas vezes irregular deste resíduo pode causar problemas de ordem ambiental, como contaminação de águas subterrâneas, do solo e desequilíbrio de sistemas ecológicos. Uma possibilidade de uso para estas cinzas é a síntese de zeólitas, que são minerais aluminossilicatos microporosos com propriedades interessantes para uso na indústria. Neste trabalho, estudou-se a síntese de zeólitas a partir de cinzas volantes visando à sua aplicação em dessulfuração de gases. A síntese foi realizada pelo método hidrotérmico, utilizando solução alcalina de KOH e relação solução/sólido de 2 mL g-1. As variáveis estudadas foram temperatura (100 e 150 °C), concentração da solução alcalina (3 e 5 mol L-1) e tempo de reação (8, 24, 48 e 72 h). Os produtos obtidos e as cinzas precursoras foram caracterizados quanto à composição química (FRX), mineralógica (DRX), morfológica (MEV), área específica (BET) e capacidade de troca catiônica (CTC). A partir da determinação das estruturas cristalinas (DRX) foi possível identificar a formação das zeólitas merlinoíta e perlialita em algumas das condições investigadas. O maior valor de área específica BET foi de 102,42 m2 g-1, nas condições de síntese de 150 °C, 5 mol L-1 e 72 h, representando um aumento de 30 vezes em relação à área das cinzas. Os valores de capacidade de troca catiônica ficaram entre 0,71 e 2,02 meq NH4+ g-1 para as diferentes condições estudadas. Com as amostras que apresentaram os melhores resultados nas caracterizações foram realizados testes de dessulfuração e seu desempenho foi comparado com as cinzas precursoras, carvão ativado e zeólita comercial. Foram construídas curvas de ruptura e isotermas de adsorção para esses sistemas. As zeólitas sintetizadas a partir das cinzas apresentaram maiores valores de adsorção máxima. A zeólita que apresentou melhor resultado de adsorção foi a sintetizada nas condições de 150 °C, 5 mol L-1 e 72 h de tempo de reação, sendo esta também a que apresentou maior valor de área específica. Sendo assim, a síntese de zeólitas a partir de cinzas de carvão, geradas no próprio processo de combustão em usinas térmicas, mostra-se como uma potencial aplicação no sentido de que estas podem ser utilizadas na própria usina para adsorção do SO2 gerado durante a combustão. / Coal ash is a waste generated in large quantities in the power plants. This is one of the wastes generated in larger quantities in Brazil, approximately 1.7 million tons per year. The often irregular disposal of this waste can cause environmental problems, such as contamination of groundwater, soil and imbalance of ecological systems. One possibility for using ashes is the synthesis of zeolites, which are microporous aluminosilicate minerals with interesting properties for use in industry. In this work, the synthesis of zeolites from fly ash was studied, aiming its application for gas desulfurization. The synthesis was performed by the hydrothermal method using an alkaline solution of KOH and a solution/solid ratio of 2 mL g-1. The variables temperature (100 and 150 °C), alkaline solution concentration (3 and 5 mol L-1) and reaction time (8, 24, 48 and 72 hours) were studied. The products obtained and the precursory ashes were characterized by its chemical composition (FRX), mineralogical (XRD), morphological (SEM), specific surface area (BET) and cation exchange capacity (CEC). From the determination of the crystalline structures (XRD) it was possible to identify the formation of the merlinoite and perlialite zeolites for some of the investigated conditions. The highest BET surface area was 102.42 m2 g-1 under the synthesis conditions of 150 °C, 5 mol L-1 and 72 hours. This value represented an increase of 30 times in the surface area comparing to the ash. The cation exchange capacity values varied between 0.71 and 2.02 meq NH4+ g-1 for the different conditions studied. Desulfurization tests were carried out for the samples that showed the best characterization results and its performance was compared with the precursor ash, activated carbon and commercial zeolite. Rupture curves and adsorption isotherms were constructed for these systems. The zeolites synthesized from ash showed higher values of maximum adsorption. The zeolite that showed the best adsorption result was synthesized at the conditions of 150 °C, 5 mol L-1 and 72 hours of reaction time, which also had the highest surface area value. Thus, the synthesis of zeolites from coal ash, generated in the combustion process in thermal plants, is shown as a potential application in the sense that these can be used in the plant to adsorb SO2 generated during combustion.

O presente trabalho tem como objetivo o estudo e aproveitamento de cinzas leves da queima de carvão mineral em termoelétrica, como reforço para o Compósito de Matriz Metálica de cobre. Foram estudados diferentes percentuais de cinzas leves como reforço para o cobre, sendo misturados estes pós através de m , compactando os pós em diferentes pressões e sinterizando os corpos de prova obtidos pela compactação. A amostra sinterizada que apresentou a maior dureza entre todos os corpos de prova sinterizados, atingindo 89 HV, foi utilizada como base para a formulação e obtenção de novos corpos de prova, que foram estudados sob condições de moagem dos pós por moinho de bolas e moagem de alta energia. A fabricação do compósito seguiu os padrões industriais do processo de Metalurgia do Pó, como a mistura e moagem dos pós, compactação dos pós e sinterização em atmosfera controlada. Foi realizado o estudo das propriedades físicas e elétricas do compósito formado por cobre e cinzas leves, que comprovou o aumento da dureza para 122 HV, mantendo a condutividade do cobre puro. Este trabalho proporciona uma nova aplicação para as cinzas leves, utilizando estes resíduos de usinas termoelétricas como matéria prima para reforço mecânico na composição de peças à base de cobre, na indústria metalmecânica. / This paper aims to study and use fly ash from coal-fired thermal power plant, as reinforcement for copper Metal Matrix Composite. Different fly ash percentage were studied as reinforcement for copper. The powders were mixed by "Twin V Mixer'', were compacted at different pressures and the compacted samples were sintered. The sintered sample with the highest hardness among all samples reached 89 HV and was used as basis for the formulation and obtaining of new samples, which were studied under controlled conditions of ball milling and mechanical alloying. The manufacture of the composite was made using Powder Metallurgy processes like mixing and milling of powders, compacting of the powders and sintering at controlled atmosphere. A study on the physical and electrical properties of the composite formed by copper and fly ash was carried out proving the hardness increase to 122 HV and maintaining the conductivity of pure copper. This work provides a new application for fly ash using these power plants waste as raw material for mechanical reinforcement in the composition of copper parts in the metalworking industry.

O objetivo deste trabalho é o estudo da cinza leve do carvão mineral da região de Criciúma (SC) para a sua utilização como fonte de matéria-prima na fabricação de placas cerâmicas para revestimento. Na cinza foram realizadas as seguintes análises: química, mineralógica, granulométrica, de área superficial específica e dilatométrica. Partindo destes resultados, foram definidas formulações do material em estudo com matérias-primas tradicionais. As formulações foram otimizadas com o desígnio de atender quesitos técnicos que viabilizassem o seu processamento e a obtenção de propriedades tecnológicas dos produtos cerâmicos após queima. Com teores de cinza variando entre 20 e 80% em peso, as formulações foram conformadas por prensagem uniaxial simples, secadas e queimadas a 11500C. Todas as formulações contendo até 60% em peso de cinza apresentaram atributos suficientes para o seu processamento e atingiram propriedades tecnológicas para serem aplicadas na fabricação de placas cerâmicas para revestimento, atendendo a norma NBR 13818 (ABNT, 1997) nos diversos grupos de absorção (prensado). Os resultados obtidos indicam que a cinza de carvão mineral incorporada à matériasprimas tradicionais para a obtenção de massas cerâmicas apresenta grande potencial em uma utilização como matéria-prima de placas cerâmicas para revestimento. / The objective of this work is the study of the fly ash of the mineral coa/ from the region of Criciúma (SC) for its use as raw material source in the manufacture of ceramic files. Fly ash was analyzed by the following tests: chemical, mineralogical, grain size distribution, specific superficial area and dilatometric. In according with these results were defined batches containing the f/y ash and traditional raw materiais. The batches had been optimized with the design to suit technical queries feasibly their processing and obtaining technological properties of the ceramic products after it burned. With fly ash quantity varying between 20 and 80% in weight, the batches had been conformed by uniaxial pressing, drying and they were burned at 1150°C. AI/ the batches containing up to 60% in weight of fly ash had presented enough attributes for their processing and they had reached technological properties for use in the manufacture of ceramic files, in according of standard N8R 13818 (A8NT, 1997) from groups of absorption (pressed) 8/b, 811a, 81/b and 8111. The results indicate that the incorporated fly ash added on the batches have great potential for use as raw material on cera mie files.

O presente trabalho foi desenvolvido como intuito de estabelecer uma metodologia de dosagem de concreto com uso de cinza volante, objetivo e racionalizado, visando à redução do consumo de cimento e a intensiva utilização de um resíduo poluente, contribuindo para o incremento na sustentabilidade da construção civil pela redução no consumo de clínquer e da liberação de dióxido de carbono para a atmosfera. Foi estabelecida como premissa basilar a hipótese de ser possível relacionar diretamente a trabalhabilidade de um concreto com seu volume de pasta, sendo este tanto menor quanto menor for o volume de vazios da estrutura granular representada pela composição de agregados. Foram empregados quatro agregados, duas areias naturais e duas britas. A mistura das areias foi definida pela menor massa unitária e os agregados graúdos, de maneira a ser obtido o menor volume de vazios. Com a composição de agregados otimizada é definido o volume ótimo de pasta no traço de melhor trabalhabilidade por verificar um dado índice de consistência com o menor teor de água sobre o total de materiais secos. Considerando a cinza volante parte integrante da pasta foram avaliados diferentes critérios para a definição das proporções a serem incorporadas à pasta, tendo como balizamento o volume ótimo de pasta. Foi desenvolvida uma metodologia de cálculo de traços não convencional uma vez que o parâmetro de entrada é a percentagem de substituição de cimento por cinza e não mais a relação água/cimento. Para fins de validação do método proposto foi desenvolvido um estudo baseado no estabelecimento de um paradigma representado por uma dosagem experimental de concreto, sem emprego de cinza volante, que permitiu o cálculo de traços de referência. Com os mesmos materiais e idêntico proporcionamento entre agregados foram desenvolvidas dosagens pelo método proposto que permitiram o cálculo de traços com base nas mesmas resistências à compressão e a comparação através do consumo de cimento calculado em cada situação. É o resultado da presente pesquisa, então, um método de dosagem, no qual a cinza volante é um insumo indispensável, baseado em conceitos diferentes daqueles adotados até então estabelecidos pelos critérios tradicionais da tecnologia do concreto. / This study was developed in order to create and a streamlined methodology of concrete mix proportioning using fly ash to reduce the cement content and an intensive use of a pollutant contributing to the increase of sustainability in construction through reducing consumption of clínquer and the release of carbono dioxide to the atmosphere. It was established as a basic premisse the possibility of connecting directly the workability of concrete with the volume of cement paste used determinate by the most dense aggregate-packing by the smaller volume of voids in the granular structure obtained in composition of many aggregates as necessary. It was used four commercial aggregates, two natural sands and two kind of crushed stone which were commonly found in a construction materials market around Porto Alegre. The sand were mixed according to the mixture that resulted in lower bulk density and coarse aggregate to be obtained the lower volume of voids as possible, being rightly measured. With the composition of aggregate optimized the optimum volume of cement paste that give the best workability with the lower water requirement will be definite. Considering fly ash as a part of the binder it was developed different criteria for define the amount of fly ash to be incorporate in binder having as foundation the volume admitted as responsible for the best workability mixture. To calculation the concrete mix proportions, was adopted an innovative methodology from the percentage replacement of cement by fly ash and no more by the water/cement ratio. The development of the proposed study was based on creating a paradigma represented by a mix-proportioning without fly ash which allowed the calculation of mix proportions of reference. With the same materials and same proportions between the aggregate, were calculated mix proportions to attend the same compressive strength to compare by the cement content of each situation. Thereby the rresults from this study a mix-proportioning method of concrete using fly ash as an imperative input, based in diferentes concepts of given for traditional concrete technology.

abstract: Alkali-activated aluminosilicates, commonly known as "geopolymers", are being increasingly studied as a potential replacement for Portland cement. These binders use an alkaline activator, typically alkali silicates, alkali hydroxides or a combination of both along with a silica-and-alumina rich material, such as fly ash or slag, to form a final product with properties comparable to or better than those of ordinary Portland cement. The kinetics of alkali activation is highly dependent on the chemical composition of the binder material and the activator concentration. The influence of binder composition (slag, fly ash or both), different levels of alkalinity, expressed using the ratios of Na2O-to-binders (n) and activator SiO2-to-Na2O ratios (Ms), on the early age behavior in sodium silicate solution (waterglass) activated fly ash-slag blended systems is discussed in this thesis. Optimal binder composition and the n values are selected based on the setting times. Higher activator alkalinity (n value) is required when the amount of slag in the fly ash-slag blended mixtures is reduced. Isothermal calorimetry is performed to evaluate the early age hydration process and to understand the reaction kinetics of the alkali activated systems. The differences in the calorimetric signatures between waterglass activated slag and fly ash-slag blends facilitate an understanding of the impact of the binder composition on the reaction rates. Kinetic modeling is used to quantify the differences in reaction kinetics using the Exponential as well as the Knudsen method. The influence of temperature on the reaction kinetics of activated slag and fly ash-slag blends based on the hydration parameters are discussed. Very high compressive strengths can be obtained both at early ages as well as later ages (more than 70 MPa) with waterglass activated slag mortars. Compressive strength decreases with the increase in the fly ash content. A qualitative evidence of leaching is presented through the electrical conductivity changes in the saturating solution. The impact of leaching and the strength loss is found to be generally higher for the mixtures made using a higher activator Ms and a higher n value. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) is used to obtain information about the reaction products. / Dissertation/Thesis / M.S. Civil Engineering 2012

abstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed. / Dissertation/Thesis / M.S. Engineering 2013

abstract: Concrete is the most widely used infrastructure material worldwide. Production of portland cement, the main binding component in concrete, has been shown to require significant energy and account for approximately 5-7% of global carbon dioxide production. The expected continued increased use of concrete over the coming decades indicates this is an ideal time to implement sustainable binder technologies. The current work aims to explore enhanced sustainability concretes, primarily in the context of limestone and flow. Aspects such as hydration kinetics, hydration product formation and pore structure add to the understanding of the strength development and potential durability characteristics of these binder systems. Two main strategies for enhancing this sustainability are explored in this work: (i) the use of high volume limestone in combination with other alternative cementitious materials to decrease the portland cement quantity in concrete and (ii) the use of geopolymers as the binder phase in concrete. The first phase of the work investigates the use of fine limestone as cement replacement from the perspective of hydration, strength development, and pore structure. The nature of the potential synergistic benefit of limestone and alumina will be explored. The second phase will focus on the rheological characterization of these materials in the fresh state, as well as a more general investigation of the rheological characterization of suspensions. The results of this work indicate several key ideas. (i) There is a potential synergistic benefit for strength, hydration, and pore structure by using alumina and in portland limestone cements, (ii) the limestone in these systems is shown to react to some extent, and fine limestone is shown to accelerate hydration, (iii) rheological characteristics of cementitious suspensions are complex, and strongly dependent on several key parameters including: the solid loading, interparticle forces, surface area of the particles present, particle size distribution of the particles, and rheological nature of the media in which the particles are suspended, and (iv) stress plateau method is proposed for the determination of rheological properties of concentrated suspensions, as it more accurately predicts apparent yield stress and is shown to correlate well with other viscoelastic properties of the suspensions. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2014

O presente trabalho foi desenvolvido como intuito de estabelecer uma metodologia de dosagem de concreto com uso de cinza volante, objetivo e racionalizado, visando à redução do consumo de cimento e a intensiva utilização de um resíduo poluente, contribuindo para o incremento na sustentabilidade da construção civil pela redução no consumo de clínquer e da liberação de dióxido de carbono para a atmosfera. Foi estabelecida como premissa basilar a hipótese de ser possível relacionar diretamente a trabalhabilidade de um concreto com seu volume de pasta, sendo este tanto menor quanto menor for o volume de vazios da estrutura granular representada pela composição de agregados. Foram empregados quatro agregados, duas areias naturais e duas britas. A mistura das areias foi definida pela menor massa unitária e os agregados graúdos, de maneira a ser obtido o menor volume de vazios. Com a composição de agregados otimizada é definido o volume ótimo de pasta no traço de melhor trabalhabilidade por verificar um dado índice de consistência com o menor teor de água sobre o total de materiais secos. Considerando a cinza volante parte integrante da pasta foram avaliados diferentes critérios para a definição das proporções a serem incorporadas à pasta, tendo como balizamento o volume ótimo de pasta. Foi desenvolvida uma metodologia de cálculo de traços não convencional uma vez que o parâmetro de entrada é a percentagem de substituição de cimento por cinza e não mais a relação água/cimento. Para fins de validação do método proposto foi desenvolvido um estudo baseado no estabelecimento de um paradigma representado por uma dosagem experimental de concreto, sem emprego de cinza volante, que permitiu o cálculo de traços de referência. Com os mesmos materiais e idêntico proporcionamento entre agregados foram desenvolvidas dosagens pelo método proposto que permitiram o cálculo de traços com base nas mesmas resistências à compressão e a comparação através do consumo de cimento calculado em cada situação. É o resultado da presente pesquisa, então, um método de dosagem, no qual a cinza volante é um insumo indispensável, baseado em conceitos diferentes daqueles adotados até então estabelecidos pelos critérios tradicionais da tecnologia do concreto. / This study was developed in order to create and a streamlined methodology of concrete mix proportioning using fly ash to reduce the cement content and an intensive use of a pollutant contributing to the increase of sustainability in construction through reducing consumption of clínquer and the release of carbono dioxide to the atmosphere. It was established as a basic premisse the possibility of connecting directly the workability of concrete with the volume of cement paste used determinate by the most dense aggregate-packing by the smaller volume of voids in the granular structure obtained in composition of many aggregates as necessary. It was used four commercial aggregates, two natural sands and two kind of crushed stone which were commonly found in a construction materials market around Porto Alegre. The sand were mixed according to the mixture that resulted in lower bulk density and coarse aggregate to be obtained the lower volume of voids as possible, being rightly measured. With the composition of aggregate optimized the optimum volume of cement paste that give the best workability with the lower water requirement will be definite. Considering fly ash as a part of the binder it was developed different criteria for define the amount of fly ash to be incorporate in binder having as foundation the volume admitted as responsible for the best workability mixture. To calculation the concrete mix proportions, was adopted an innovative methodology from the percentage replacement of cement by fly ash and no more by the water/cement ratio. The development of the proposed study was based on creating a paradigma represented by a mix-proportioning without fly ash which allowed the calculation of mix proportions of reference. With the same materials and same proportions between the aggregate, were calculated mix proportions to attend the same compressive strength to compare by the cement content of each situation. Thereby the rresults from this study a mix-proportioning method of concrete using fly ash as an imperative input, based in diferentes concepts of given for traditional concrete technology.