Os agregados eletrofundidos são largamente utilizados para a produção de refratários tendo em vista a melhoria geral de propriedades propiciada pelo emprego dos mesmos. Neste trabalho projetaram-se agregados eletrofundidos adequados para aplicação em refratários para a zona de queima de fornos de cimento. Para o projeto dos mesmos foi realizada inicialmente uma avaliação a alta temperatura das reações que ocorrem entre as fases refratárias e as fases presentes no clínquer de cimento Portland, visando identificar os sistemas refratários mais promissores. Em seguida foram realizadas eletrofusões de matérias primas pertencentes a estes sistemas, visando a obtenção de diferentes composições de agregados, cujas características foram avaliadas. A última etapa do desenvolvimento envolveu a escolha de alguns agregados para a formulação de refratários para a zona de queima de fornos de cimento; medindo e comparando as propriedades dos tijolos obtidos com um tijolo refratário padrão de magnésia-espinélio. Agregados pertencentes ao sistema MgO – TiO2 – CaO, mais especificamente ao triângulo de compatibilidade formado pelas fases MgO – Mg2TiO4 – CaTiO3, mostraram características adequadas para o desenvolvimento de refratários para a zona de queima de fornos de cimento. / Electrofused aggregates are largely used in refractory production due to the better performance reached when they are employed. In this work electrofused aggregates were designed for application in refractories for the burning zone of cement kilns. Initially reaction evaluation was conducted aiming the identification of the most prone refractory systems when single refractory phases react with Portland cement phases at high temperatures. In the next step, raw materials of the best refractory systems were electrofused to generate different aggregate compositions. The electrofused aggregates properties were evaluated and the classified ones were used to produce refractory bricks for the burning zone of cement kilns. General characteristics of these bricks were measured and compared with a standard magnesia-spinel refractory. Aggregates of the system MgO – TiO2 – CaO, more specifically aggregates belonged to the compatibility triangle MgO – Mg2TiO4 – CaTiO3, showed suitable characteristics for development of refractories for the burning zone cement kilns.

Os agregados eletrofundidos são largamente utilizados para a produção de refratários tendo em vista a melhoria geral de propriedades propiciada pelo emprego dos mesmos. Neste trabalho projetaram-se agregados eletrofundidos adequados para aplicação em refratários para a zona de queima de fornos de cimento. Para o projeto dos mesmos foi realizada inicialmente uma avaliação a alta temperatura das reações que ocorrem entre as fases refratárias e as fases presentes no clínquer de cimento Portland, visando identificar os sistemas refratários mais promissores. Em seguida foram realizadas eletrofusões de matérias primas pertencentes a estes sistemas, visando a obtenção de diferentes composições de agregados, cujas características foram avaliadas. A última etapa do desenvolvimento envolveu a escolha de alguns agregados para a formulação de refratários para a zona de queima de fornos de cimento; medindo e comparando as propriedades dos tijolos obtidos com um tijolo refratário padrão de magnésia-espinélio. Agregados pertencentes ao sistema MgO – TiO2 – CaO, mais especificamente ao triângulo de compatibilidade formado pelas fases MgO – Mg2TiO4 – CaTiO3, mostraram características adequadas para o desenvolvimento de refratários para a zona de queima de fornos de cimento. / Electrofused aggregates are largely used in refractory production due to the better performance reached when they are employed. In this work electrofused aggregates were designed for application in refractories for the burning zone of cement kilns. Initially reaction evaluation was conducted aiming the identification of the most prone refractory systems when single refractory phases react with Portland cement phases at high temperatures. In the next step, raw materials of the best refractory systems were electrofused to generate different aggregate compositions. The electrofused aggregates properties were evaluated and the classified ones were used to produce refractory bricks for the burning zone of cement kilns. General characteristics of these bricks were measured and compared with a standard magnesia-spinel refractory. Aggregates of the system MgO – TiO2 – CaO, more specifically aggregates belonged to the compatibility triangle MgO – Mg2TiO4 – CaTiO3, showed suitable characteristics for development of refractories for the burning zone cement kilns.

<p> The stress relieving mechanisms in two different batches of thermal-shock resistant calcia-PSZ have been investigated. The nature of the stress relief in the two materials appears to result from the transformation of the pure ZrO₂ component of the microstructure at temperatures below, within, and above the normal transformation temperature range. In the batch #1 material, which contains a larger volume fraction of monoclinic phase, the cubic matrix material behaves in a "brittle" fashion resulting in the production of a high density of microcracks in the body. The density of these cracks is such that the level of energy that can be stored in the body is limited and thermal shock resistance results. The batch #2 material contains considerably less monoclinic material and the evidence suggests that the cubic matrix within it can act in a ductile fashion. This ductility together with the twinning of the monoclinic component of the microstructure possibly relieves the stresses developed in the material on thermal shock. </p> <p> In the batch #2 material, large platelets were observed to develop following thermal cycling from temperatures above those of the normal transformation. It has been demonstrated that stress plays a major role in the development of these features. In view of the possible ductility of the cubic matrix in this material it is suggested that the thermal cycling "works" the material, texturing the pure zirconia component in it, so leading to the development of the observed platelets. </p> / Thesis / Master of Engineering (ME)

The present thesis gives a summary of results obtained through theoretical and experimental studies of systems with relevance to copper smelting and converting. Many chemical elements are involved in the copper production pro­cesses and a detailed experimental study would be very time- consuming and expensive. A complicating fact is also the corrosivity of the liquid phases towards container material. A powerful alternative is equilibrium calculations, in which models for the liquid phases as well as reliable basic thermodynamic data are needed. In the present thesis, a generalized structure based model for liquid silicates was developed and used in assessments of the sys­tems PbO-SiO2, Fe-O-SiO2, CuO0.5-SÌO2 and Cu-Fe-O-SiO2. In the model, the non-ideal silicate melt is treated as an ideal solu­tion but containing a few complexes. The PbO-Si02 melt could be described by introducing the complexes Pb3Si207, Pb4Si4010 and Pb13Si12O37 in addition to the components PbO and Pb2Si04. The species considered in the Fe-O-SiO2 melt were FeO, FeO1.5, Fe2Si04, Fe3Si207, Fe3Si6O15 and in the CUO0.5-SiO2 melt CuO0.5 ana CU4SiO4. Trie calculated phase diagrams, the activities of me­tal oxides and the oxygen partial pressures were all in good agreement with the published data. Two of the papers in this thesis concern the determination of Gibbs free energies for Cu2S(s,l) and Ca2Fe2O5(s) through emf measurements utilizing a solid electrolyte. Activities and termi­nal solubilities in the solid solution [Fet,Ca]0 were also deter­mined. The results obtained from the quantitative equilibrium calcula­tions for conventional copper smelting and converting were used to outline the overall reactions taking place and the outcome of changes in process parameters. Comparison with observed values, however, showed that the copper and magnetite contents in slag were calculated too low. These discrepancies could be completely explained by using a non-equilibrium approach in which the con­verter was assumed to consist of several segments with concentra­tion gradients between the segments. / digitalisering@umu.se