En raison de l'exigence de protection de l'environnement, les briques d'argile cuites sont face à une nouvelle tendance de développement. Briques d'argile cuites ne sont pas seulement satisfaits de la mécanique force mais aussi augmentation de l'utilisation de l'énergie. La conductivité thermique est un paramètre très important mesurer l'utilisation de l'énergie. Sur le principe de garantir essentiellement propriétés mécaniques, la réduction de la conductivité thermique a été l'un des développements importants objectifs dans l'industrie du bâtiment.Basé sur l'analyse de la microstructure, les pores microscopiques ont un effet sur la macroscopie constantes élastiques et conductivité thermique. Micropores parallèles résultant de la production les méthodes provoquent l'isotropie transversale des briques d'argile cuites. Cependant, ce n'est pas clair que l'influence des micropores sur les propriétés macroscopiques. Bien que certains modèles étudié l'effet de la porosité sur les propriétés mécaniques des briques d'argile cuite, ces modèles sont empiriques et ont ignoré de nombreuses informations microscopiques. Un des buts de la thèse est d'analyser l'influence de la forme, l'orientation et la distribution spatiale de microscopique facteurs sur les propriétés mécaniques et la conductivité thermique afin de fournir une référence optimiser la micro-structure des briques d'argile cuites. / Due to the environmental protection requirement, fired clay bricks are facing new development tendency. Fired clay bricks are not only satisfied with mechanical strength but also rising energy utilization. Thermal conductivity is a very important parameter to measure the energy utilization. On the premise of guaranteeing the basically mechanical properties, reducing thermal conductivity has been one of important development goals in building industry.Based on the analysis of micro-structure, microscopic pores have an effect on macroscopic elastic constants and thermal conductivity. Parallel micropores resulting from producing methods cause the transverse isotropy of fired clay bricks. However, it is not clear that the influence of micropores on the macroscopic properties. Though some models studied the effect of porosity on mechanical properties of fired clay bricks, these models are empirical and ignored many microscopic information. One of the goals of the thesis is to analyze the influence of shape, orientation and spatial distribution of microscopic factors on mechanical properties and thermal conductivity in order to provide a reference to optimize the micro-structure of fired clay bricks.

In a country like Brazil, which has a high incidence of solar radiation, the use of solar energy is an alternative that has been researched and used with many advantages. This paper presents the design, construction and evaluation of the efficiency of a flat solar collector for pre-heating the air, executed with low cost materials, to be used in drying systems. The prototype of the solar collector with gravel bed was built to be made a survey of data from temperature and relative humidity, using a recording apparatus (data loggers), and carried out the calculations for determining the useful heat provided by the collector. Since in the state of Rio Grande do Sul there are approximately 85,560 farms growing tobacco, accounting to around 91,420 curing barns, for which the widest energy source is firewood, as a case study was proposed to use this solar collector to be used as a supplementary source of heat to the existing curing barns. A case study was conducted on the curing process, verifying the wood consumption needed for each phase of the process in order to determine its energy demands. It was observed that the application of a 3sqm surface collector represented a reduction of around 5.2% in firewood consumption, which demonstrated the economic viability of the system with a time of payback of 3.4 years. / Em um país como o Brasil, que possui alta incidência de radiação solar, o uso de energia solar é uma alternativa que vem sendo pesquisada e utilizada com muitas vantagens. O presente trabalho apresenta o projeto, a construção e a avaliação da eficiência de um coletor solar plano para pré-aquecimento do ar, executado com materiais de baixo custo, a ser utilizado em sistemas de secagem. O protótipo do coletor solar com leito de britas foi construido para que fossem feitos os levantamentos dos dados de temperatura e umidade relativa do ar, utilizando-se aparelhos registradores (data loggers), e efetuaram-se os cálculos para a determinação do calor útil fornecido pelo coletor. Sendo que no Rio Grande do Sul existem aproximadamente 85.560 propriedades produtoras de tabaco, que totalizam cerca de 91.420 estufas de cura, nas quais a fonte de energia mais utilizada é a lenha, como estudo de caso foi proposta a utilização deste coletor solar como sistema suplementar como aquecimento do ar no processo de cura do tabaco em estufas a lenha existentes. Um processo de cura foi acompanhado para verificação do consumo de lenha necessário para cada fase deste, para que fosse possível determinar a sua demanda energética. Observou-se que a utilização do coletor com 3m2 de área proporcionou a redução de 5,2% no consumo de lenha, o que demonstrou a viabilidade econômica da utilização do sistema com tempo de retorno do investimento de 3,4 anos.

Made available in DSpace on 2016-12-08T17:19:39Z (GMT). No. of bitstreams: 1 Dissertacao Adilson - capa - p 20.pdf: 346950 bytes, checksum: a3100709576cd968b71593cb9c01e214 (MD5) Previous issue date: 2011-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aims to evaluate the effect of incorporation of particles of fired clay brick waste (CBW) in the physical and mechanical properties and their relation to the microstructure of concrete with Portland cement. The mixtures were obtained using the technique of fractional factorial design 33-1 for the design and analysis of experiments. For each factor, three levels were selected: CBW content (10, 20 and 30 wt. % of cement), water-to-cement ratio of 0.37, 0.45 and 0.55, and aggregate-to-cement ratio of 2.36, 3.64 and 4.70. The waste was characterized to evaluate their potential as a pozzolana. Fresh properties (consistency) and hardened (compressive strength at various ages, voids index, water absorption and density) were measured. Characterizations of microstructure and thermal using SEM / EDS and DTA / TG were performed to correlate the effect of waste content on the microstructure and properties of the hardened concrete. The waste presents properties adequate to be used as a pozzolan material. Consistency index decreases with the incorporation of the CBW, but is still possible to obtain concrete with adequate workability. For properties in the hardened concrete, the results show that the compressive strength increases with the increase of CBW content as an addition for concretes of Portland cement. Microstructural characterization reveals that the waste contributes to develop a more homogeneous microstructure with fewer pores and cracks when compared to concretes without waste. There is evidences that metakaolin contained in the waste contributes with the hydration reactions, consuming calcium hydroxide and producing more calcium silicate gel and hydrated phases, which keeps the aggregates more cohesive in the concrete microstructure. These microstructural characteristics improve the mechanical properties and durability of concrete. / Este trabalho tem como objetivo avaliar o efeito da incorporação de rejeitos particulados de tijolos (RPT) nas propriedades físicas e mecânicas e sua relação com a microestrutura de concretos de cimento Portland. Os traços foram formulados utilizando a técnica de planejamento fatorial fracionado 33-1 para o projeto e análise de experimentos. Para cada fator, três níveis foram selecionados: teor de RTP incorporado (10, 20 e 30 % em relação ao cimento), relações água-cimento de 0,37, 0,45 e 0,55, e relações agregado-cimento de 2,36, 3,64 e 4,70. O rejeito foi caracterizado para avaliar seu potencial quanto à pozolanicidade. Propriedades no estado fresco (consistência) e endurecido (resistênca à compressão em várias idades, índice de vazios, absorção de água e densidade) foram medidas. Caracterizações de microestrutura e térmica usando MEV/EDS e ADT/TG foram realizadas para correlacionar o efeito do teor de rejeito na microestrutura e propriedades no concreto endurecido. O rejeito apresenta características que possibilitam seu uso como material pozolânico. Para o índice de consistência observa-se que o mesmo diminue com a incorporação do RPT, porém ainda é possíviel obter concretos com adequada trabalhabilidade. Para as propriedades no concreto endurecido, os resultados mostram que a resistência à compressão aumenta com o aumento da porcentagem de RPT em adição ao concreto de cimento Portland. A caracterização microestrutural revela que o rejeito contribui para desenvolver uma microestrutura mais homogênea, com menos trincas e poros, quando comparadas às misturas sem o rejeito. Há indícios de que a metacaulinita contida no rejeito participa das reações de hidratação, consumindo hidróxido de cálcio e produzindo mais silicato de cálcio gel e fases hidratadas, as quais contribuem para manter os agregados mais coesos no corpo cerâmico. Estas características microestruturais melhoram as propriedades mecânicas e durabilidade dos concretos.

Abstract In the first part of the thesis, novel glass-ceramic compositions based on Al2O3 and BaTiO3 and bismuth-zinc borosilicate (BBSZ) glass, sintered at ultra-low temperatures, were researched. With adequate glass concentration, dense microstructures and useful dielectric properties were achieved. The composite of BaTiO3 with 70 wt % BBSZ sintered at 450 °C exhibited the highest relative permittivity, εr, of 132 and 207 at 100 kHz and 100 MHz, respectively. Thus, the dielectric properties of the composites were dominated by the characteristics of glass, BaTiO3, and Bi24Si2O40 phase, especially the contribution of Bi24Si2O40 for the samples with 70-90 wt % glass. Actually, the existence of the secondary phase Bi24Si2O40 may not hinder but enhance the dielectric properties. The Al2O3-BBSZ composition samples showed a similar situation, not only for densification but also for their microstructures and phases (Al2O3, BBSZ, Bi24Si2O40), explaining the achieved dielectric properties. The second part of the thesis mainly discusses the composite of BaTiO3 with 50 wt % BBSZ with different thermal treatments. After sintering at 720 °C, dense microstructures and the existence of Bi4BaTi4O15, BaTiO3, Bi24Si2O40 phases were observed. The results also showed that the size of glass powder particles did not influence the dielectric properties (εr = 263-267, tan δ = 0.013 at 100 kHz) of sintered samples, but the addition of LiF degraded the dielectric properties due to the features and amount of Bi4BaTi4O15. These results demonstrate the feasibility of the BBSZ based composites for higher sintering temperature technologies as well. At the end, a novel binder system, which enables low sintering temperatures close to 300 °C, was developed. A dielectric multilayer module containing BaTiO3-BBSZ and Al2O3-BBSZ composites with silver electrodes was co-fired at 450 °C without observable cracks and diffusions. These results indicate that these glass-ceramic composites provide a new horizon to fabricate environmentally friendly ULTCC materials, as well as multilayers for multimaterial 3D electronics packages and high frequency devices. / Tiivistelmä Väitöstyön ensimmäisessä osassa tutkittiin ja kehitettiin uudentyyppisiä, ultramatalissa sintrauslämpötiloissa (ULTCC) valmistettuja lasi-keraami komposiitteja käyttäen vismuttisinkkiborosilikaatti -pohjaista lasia (BBSZ). Täyteaineina olivat alumiinioksidi (Al2O3) ja bariumtitanaatti (BaTiO3). Materiaaleille saatiin riittävän suuren lasipitoisuuden avulla tiheät mikrorakenteet ja sovelluskelpoiset dielektriset ominaisuudet. BaTiO3:n komposiitti, joka sisälsi 70 p-% BBSZ lasia, saavutti 450 °C lämpötilassa sintrattuna korkeimman suhteellisen permittiivisyyden: εr=132 (@100 kHz) ja εr=207 (@100 MHz). Komposiittien dielektrisiä ominaisuuksia määrittivät tällöin lasi-, BaTiO3- ja Bi24Si2O40- faasien ominaisuudet ja erityisesti Bi24Si2O40 -faasi näytteissä, joissa on 70-90 p-% lasia. Sekundäärinen faasi Bi24Si2O40 ei välttämättä heikentänyt, vaan jopa paransi dielektrisiä ominaisuuksia. Vastaavilla Al2O3-BBSZ –komposiiteilla saavutettiin samanlaisia tuloksia tihentymisen, mikrorakenteiden ja faasien (Al2O3, BBSZ, Bi24Si2O40) suhteen. Lisäksi tässä tapauksessa saavutetut dielektriset ominaisuudet voidaan selittää näiden kolmen faasin yhdistelmän olemassaololla. Väitöstyön toinen osa käsitteli pääasiassa eritavoin lämpökäsiteltyjä BaTiO3:n komposiitteja, joissa on 50 p-% BBSZ-lasia. Näillä saavutettiin tiheä mikrorakenne sintrattaessa 720 °C lämpötilassa ja havaitiin Bi4BaTi4O15-, Bi24Si2O40-faasien muodostuminen BaTiO3 lähtöfaasin rinnalle. Tulokset osoittivat myös, että lasijauheen partikkelikoko ei vaikuttanut sintrattujen näytteiden dielektrisiin ominaisuuksiin (εr = 263-267, tan δ = 0.013 (@100 kHz)). LiF -lisäys sen sijaan heikensi dielektrisiä ominaisuuksia ja vähensi Bi4BaTi4O15 faasin muodostumista. Tämä aiheutui Bi4BaTi4O15-faasin ominaisuuksista ja oli riippuvainen kyseisen faasin määrästä. Nämä tulokset osoittivat BBSZ -pohjaisten komposiittien käytettävyyden myös korkeampien sintrauslämpötilojen teknologioihin. Viimeisenä kehitettiin uudentyyppinen sideainesysteemi, joka mahdollistaa ultramatalien keraamien yhteissintraamisen jopa noin 300 °C lämpötilassa. Hyödyntäen kehitettyä sideainesysteemiä monikerrosrakenne, jossa käytettiin dielektrisiä BaTiO3-BBSZ- ja Al2O3-BBSZ-komposiitteja ja hopeaelektrodeja, yhteissintrattiin 450 °C lämpötilassa. Valmistetuissa rakenteissa ei havaittu murtumia eikä diffuusioita. Tulokset osoittavat, että kehitetyt lasi-keraami komposiitit mahdollistavat ympäristöystävällisten ULTCC -materiaalien valmistuksen. Lisäksi osoitettiin kehitettyjen materiaalien soveltuvuus monikerroksisten rakenteiden käyttöön monimateriaali-3D-elektroniikan pakkauksissa ja suurtaajuuskomponteissa.

M.Sc. / The increased demand for electricity in South Africa is expected to exceed supply between 2004 and 2007. Electricity supply options in the country would be further complicated by the fact that older power stations would reach the end of their design life beyond the year 2025. In light of this and considering the long lead times required for the commissioning of new plants, new power supply options need to be proactively investigated. The environmental impacts associated with coal-fired generation of electricity have resulted in increased global concern over the past decade. To reduce these impacts, new technologies have been identified to help provide electricity from fossil fuels. The alternatives considered are gas-fired generation technologies and the Integrated Gasification Combined Cycle (IGCC). This study attempts to document and understand the environmental aspects related to gas-fired and IGCC electricity generation and evaluate their advantages in comparison to conventional pulverised coal fired power generation. The options that could be utilised to make fossil fuel electricity generation more environmentally friendly, whilst remaining economically feasible, were also evaluated. Gas-fired electricity generation is extremely successful as electricity generation systems in the world due to inherently low levels of emissions, high efficiencies, fuel flexibility and reduced demand on finite resources. Associated benefits of a Combined Cycle Gas Turbine (CCGT) are lower operating costs due to the reduced water consumption, smaller equipment size and a reduction in the wastewater that has to be treated before being returned to the environment. A CCGT plant requires less cooling water and can be located on a smaller area than a conventional Pulverised Fuel (PF) power station of the same capacity. All these factors reduce the burden on the environment. A CCGT also employs processes that utilises the energy of the fuel more efficiently, with the current efficiencies approaching 60%. Instead of simply being discharged into the atmosphere, the gas turbines’ exhaust gas heat is used to produce additional output in combination with a Heat Recovery Steam Generator (HRSG) and a steam turbine. Furthermore, as finite resources become increasingly scarce and energy has to be used as wisely as possible, generating electricity economically and in an ecologically sound manner is of the utmost importance. The clean, reliable operation of gas-fired generation systems with significantly reduced noise levels and their compact design makes their operation feasible in heavily populated areas, where electricity is needed most. At the same time, energy can be consumed in whatever form needed, i.e. as electricity, heat or steam. The dependence of the South African economy on cheap coal ensures that it will remain a vital component of future electricity generation options in the country. This dominance of coal-fired generation in the country is responsible for South Africa’s title as the largest generator of carbon dioxide (CO2) emissions on the continent and the country could possibly be requested to reduce its CO2 emissions at the next international meeting of signatories to the Kyoto Protocol. Carbon dioxide emissions can be reduced by utilising gas-fired generation technologies. However, the uncertainty and costs associated with natural gas in South Africa hampers the implementation of this technology. There are currently a number of initiatives surrounding the development of natural gas in the country, viz. the Pande and Temane projects in Mozambique and the Kudu project in Namibia, and this is likely to positively influence the choice of fuel utilised for electricity generation in the future. The economic viability of these projects would be further enhanced through the obtaining of Clean Development Mechanism (CDM) credits for greenhouse gases (GHG) emissions reduction. Alternatively, more efficient methods of generating electricity from coal must be developed and implemented. IGCC is capable of achieving this because of the high efficiencies associated with the combined cycle component of the technology. These higher efficiencies result in reduced emissions to the atmosphere for an equivalent unit of electricity generated from a PF station. An IGCC system can be successful in South Africa in that it combines the benefits of utilising gas-fired electricity generation systems whilst utilising economically feasible fuel, i.e. coal. IGCC systems can economically meet strict air pollution emission standards, produce water effluent within environmental limits, produce an environmentally benign slag, with good potential as a saleable by-product, and recover a valuable sulphur commodity by-product. Life-cycle analyses performed on IGCC power plants have identified CO2 release and natural resource depletion as their most significant positive lifecycle impacts, which testifies to the IGCC’s low pollutant releases and benign by-products. Recent studies have also shown that these plants can be built to efficiently accommodate future CO2 capture technology that could further reduce environmental impacts. The outstanding environmental performance of IGCC makes it an excellent technology for the clean production of electricity. IGCC systems also provide flexibility in the production of a wide range of products including electricity, fuels, chemicals, hydrogen, and steam, while utilizing low-cost, widely available feedstocks. Coal-based gasification systems provide an energy production alternative that is more efficient and environmentally friendly than competing coalfuelled technologies. The obstacle to the large-scale implementation of this technology in the country is the high costs associated with the technology. CDM credits and by-products sales could possible enhance the viability of implementing these technologies in South Africa.

This master's thesis deals with the design of stoker-fired boiler for combustion of biomass. The main points of work are stoichiometry calculation of combustion, determining the dew point of flue gas, calculation of losses, which ones serves for determination of boiler efficiency, dimension design and detail calculation of thermosetting surfaces. In the last chapter is numbered total balance and real thermal efficiency of boiler.

The strength of materials such as glass and ceramics can be influenced by the environment (stress corrosion). Under applied stress defects (cracks) can grow sub-critically below fracture toughness K_Ic. The aim of this work was to develop a three-dimensional finite-element model to analyze the subcritical crack growth behavior of ceramic-based particulate composites. The maximum tangential stress criterion (MTS) was used to predict the direction of the crack propagation in the framework of linear elastic fracture mechanics. The modeled material was a Low Temperature Co-fired Ceramics (LTCC), containing alumina particles embedded in a glass matrix. The main aim of this work was to develop a 3D model describing the crack growth. Conclusions from this work can contribute to a better understanding of subcritical crack propagation in particle composites.

Subcritical crack growth in composite materials plays quite an important role in determination of the service life and leads to the defects growth below the fracture toughness. The thesis presents search of the several scientific works dealing with the determination of the crack growth direction in composite materials. The aim of this diploma thesis was to create 2D and 3D finite element models to analyse crack growth in Low Temperature Co-fired Ceramics (LTCC). These models were compared based on the time calculation of the crack propagation under the subcritical growth conditions.

This master‘s thesis deals with denitrification of brown coal-fired boiler of electric power plant. First chapters describe technical characteristics of the boiler and possible measurements which would lead to lowering NOx emissions. In order for boiler to meet emission standards valid from 1.1.2016 flue gas treatment by selective catalytic reduction is proposed. Main part of the thesis is thermal calculation of the boiler with modifications necessary in order to apply SCR. The aim of calculation is to determine flue gas exit temperature and temperature at catalyst area in order to assess the suitability of proposed modifications.

This thesis solves a design of a grate boiler burning wood chips or brown coal with a heat output of 160 MW. Stoichiometry flue gas is calculated according to the specified composition of each fuel. The dimensions of the individual heating surfaces are primarily calculated for burning wood chips and subsequently checked for the combustion of brown coal. Design of the boiler is completed by checking the overall heat output. Boiler design is accompanied by drawing documentation.