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Abstract(s)
Para produzir refratários é necessário o acesso a diversas matérias-primas naturais como argilas, areias de zircão, bauxites, caulinos, dolomites, grafite, entre outros. A disponibilidade destas matérias-primas concentram-se maioritariamente em países emergentes, com riscos de instabilidade política e socioeconómica. Desta forma, é esperado que países desenvolvidos promovam a aposta em tecnologias capazes de aumentar a eficiência das matérias-primas, reutilizar e reciclar os seus produtos, nomeadamente os refratários.
Neste trabalho foram caracterizados os resíduos provenientes do desmantelamento do revestimento refratário de um forno elétrico de indução usado na fundição de aço. Após a moagem do resíduo e divisão granulométrica aplicou-se uma metodologia de separação magnética com o objetivo de minimizar o número de impurezas. Posteriormente, com uma matriz de alta-alumina e agregados de resíduo, desenharam-se granulometricamente duas misturas (auto-escoante e vibrada), que após adição de dois teores de água (0,160 g/m2 e 0,175 g/m2) obteve-se corpos de prova (100 mm x 25 mm x 25 mm) que se sinterizaram às temperaturas de 1350 e 1500°C.
As propriedades físicas das misturas foram avaliadas através de ensaios de índice de fluidez, retração linear, porosidade, absorção de água e densidade. Determinou-se o módulo de rutura e o módulo de elasticidade dinâmico através de flexão em três pontos e velocidade de propagação ultrassónica, respetivamente. Foram também realizadas, análises mineralógicas (DRX) às diferentes amostras, de modo a avaliar quais as fases presentes às diferentes temperaturas de sinterização. As superfícies de fratura foram observadas através de microscopia ótica. A microestrutura das superfícies polidas foi analisada em SEM, procedendo-se à sua análise química elementar (EDX), de modo a observar a forma do grão, a interface matriz-agregado e eventuais impurezas. Por fim, compara-se o comportamento da melhor mistura com resíduo refratário, com uma mistura similar com refratário virgem (coral A).
Por último, é discutida a viabilidade da reutilização do resíduo refratário proveniente do desmantelamento do revestimento de fornos elétricos de fundição de aço, como agregado num novo produto refratário.
In order to produce refractory materials, several raw materials are needed such as clay, zircon sands, kaolin, dolomites, graphite, bauxite and magnesite, among other types. The availability of these raw materials is more evident in emerging countries that are close to politic and social-economic instabilities. For this reason, is to be expected that more countries promotes the use of technologies with capacities to improve the efficiency of the referred raw materials and to re-use and recycle its derived products, namely, refractories. In this work, the waste from the dismantlement of the refractory lining of a steel melting electric induction oven was characterized. The waste was grinded and a granulometric division was applied. Subsequently, a magnetic separation methodology was applied to minimize the quantity of impurities. After, two granulometric mixes (q=0.21 for self-flowing and q=0.26 for pumping) were designed using an high-alumina matrix and waste aggregates. Two volume quantities of water (0.160 g/m2 e 0.175 g/m2) were added to the mixes and, as result, test specimens (100 mm x 25 mm x 25 mm) were obtained after being synthetized under temperatures of 1350 ºC and 1500 ºC. Physical properties of the mixes were assessed based on flowability index, linear shrinkage, porosity, water absorption and density tests. The modulus of rupture and the dynamic young modulus were determined by three points bending and ultrasonic velocity pulse propagation tests. Also, mineralogical analysis was performed the different samples in order to determine which phases were present in the distinct synthesis temperatures. Fracture surfaces were observed through optical microscopy. The polished surfaces microstructures were analyzed in SEM followed by its chemical elemental assessment in order to evaluate the grain shape, the matrix-aggregate interface and eventually impurities. The best mixture composed by the refractory waste are compared with similar mixtures of raw refractory material (coral A). Finally, is presented a discussion about the viability of the reutilization the waste obtained from the dismantlement of the refractory coating of steel melting electric oven as agglomerate in a new refractory product.
In order to produce refractory materials, several raw materials are needed such as clay, zircon sands, kaolin, dolomites, graphite, bauxite and magnesite, among other types. The availability of these raw materials is more evident in emerging countries that are close to politic and social-economic instabilities. For this reason, is to be expected that more countries promotes the use of technologies with capacities to improve the efficiency of the referred raw materials and to re-use and recycle its derived products, namely, refractories. In this work, the waste from the dismantlement of the refractory lining of a steel melting electric induction oven was characterized. The waste was grinded and a granulometric division was applied. Subsequently, a magnetic separation methodology was applied to minimize the quantity of impurities. After, two granulometric mixes (q=0.21 for self-flowing and q=0.26 for pumping) were designed using an high-alumina matrix and waste aggregates. Two volume quantities of water (0.160 g/m2 e 0.175 g/m2) were added to the mixes and, as result, test specimens (100 mm x 25 mm x 25 mm) were obtained after being synthetized under temperatures of 1350 ºC and 1500 ºC. Physical properties of the mixes were assessed based on flowability index, linear shrinkage, porosity, water absorption and density tests. The modulus of rupture and the dynamic young modulus were determined by three points bending and ultrasonic velocity pulse propagation tests. Also, mineralogical analysis was performed the different samples in order to determine which phases were present in the distinct synthesis temperatures. Fracture surfaces were observed through optical microscopy. The polished surfaces microstructures were analyzed in SEM followed by its chemical elemental assessment in order to evaluate the grain shape, the matrix-aggregate interface and eventually impurities. The best mixture composed by the refractory waste are compared with similar mixtures of raw refractory material (coral A). Finally, is presented a discussion about the viability of the reutilization the waste obtained from the dismantlement of the refractory coating of steel melting electric oven as agglomerate in a new refractory product.
Description
Keywords
Matérias-Primas Reciclagem Refratários Resíduo Industrial