• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • 1
  • 1
  • Tagged with
  • 11
  • 11
  • 6
  • 6
  • 6
  • 6
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Estudo do aproveitamento do rejeito da minera??o de esmeraldas na produ??o de refrat?rios conformados isolantes

Barros, Jo?o Alfredo de Almeida 16 May 2013 (has links)
Made available in DSpace on 2014-12-17T14:58:22Z (GMT). No. of bitstreams: 1 JoaoAAB_DISSERT.pdf: 2621016 bytes, checksum: 39aa654f0df748b1db86062c61ed8f35 (MD5) Previous issue date: 2013-05-16 / Emerald mining is an important area of the economy in Brazil, country which is in second place among the exporting nations of this gem. Due to the process of extraction, a great amount of reject is generated. Since there is no appropriate destination, the reject is abandoned around the mining industries, contributing to environment degradation. Nowadays, some of the most relevant things to an industry in general are: energy conservation, cost reduction, quality and productivity enhancement. The production of isolating, transformed refractory materials achieves the sustainability dimension when protection of the environment is incorporated to such process. This work investigates the use of emerald mining rejects in the ceramic body of refractory materials, aiming at obtaining a product whose characteristics are compatible with commercial products and, at the same time, allow the use of such rejects to solve the environmental issue caused by its disposal in nature. X-ray fluorescence analysis show that the emerald reject obtained after the flotation to extract molybdenum and mica has 70% of silica and alumina (SiO2+Al2O3) and 21% of a basic oxides and alkaline metals and earthy alkaline mixture (Na2O, K2O, CaO e MgO). Because of the significant amount of silica and alumina present in the reject, four refractory ceramic bodies were prepared. Samples with a rectangular shape and dimensions 100x50x10 mm were pressed in a steel mold at 27,5 MPa and sintered at 1200?C for 40 min. under environment atmosphere in a resistive oven. The sintered samples were characterized in relation to the chemical composition (FRX), mineralogical composition (DRX), microstructure (MEV) and physical and mechanical properties. The results indicate that the mixture with 45% of reject, 45% of alumina and 10% of kaolin presents a refractory quality of 1420?C, dimensional linear variation below 2.00%, apparent specific mass of 1,56 g/cm3 and porosity of 46,68%, which demonstrates the potential use of the reject as raw material for the industry of isolating transformed refractory materials / A minera??o de esmeraldas ? uma importante ?rea da atividade econ?mica do Brasil, pa?s que ocupa o segundo lugar entre as na??es exportadoras dessa gema. Em virtude do processo de extra??o, uma grande quantidade de rejeito ? gerada. Como n?o h? uma destina??o apropriada, o rejeito ? abandonado ao redor das mineradoras, contribuindo, assim, para a degrada??o do meio ambiente. Atualmente, alguns dos pontos de maior relev?ncia para a ind?stria em geral s?o: conserva??o de energia, redu??o de custos, melhoria de qualidade e produtividade. A produ??o de refrat?rios conformados isolantes ganha a dimens?o de sustentabilidade quando a prote??o ao meio ambiente ? incorporada a tal processo. Este trabalho investiga o uso de rejeitos da minera??o de esmeraldas na massa cer?mica de materiais refrat?rios, com intuito de obter um produto com caracter?sticas compat?veis aos produtos comerciais e, ao mesmo tempo, viabilizar a utiliza??o de tais rejeitos para solucionar o problema ambiental gerado por seu descarte na natureza. An?lises de fluoresc?ncia de raios x mostram que o rejeito de esmeraldas obtido ap?s a flota??o para retirada de molibd?nio e mica possui 70% de s?lica e alumina (SiO2+Al2O3) e 21% de uma mistura de ?xidos b?sicos de metais alcalinos e alcalinos terrosos (Na2O, K2O, CaO e MgO). Em fun??o dos significativos teores de s?lica e de alumina presentes no rejeito, quatro massas cer?micas refrat?rias foram preparadas. Corpos de prova com forma retangular e dimens?es 100x50x10 mm foram prensados em uma matriz de a?o a 27,5 MPa e sinterizados a 1200?C por 40 min. sob atmosfera ambiente em forno resistivo. Os corpos de prova sinterizados foram caracterizados com rela??o ? composi??o qu?mica (FRX), composi??o mineral?gica (DRX), microestrutura (MEV) e propriedades f?sicas e mec?nicas. Os resultados obtidos indicam que a mistura com 45% de rejeito, 45% de alumina e 10% de caulim apresenta uma refratariedade de 1420?C, varia??o linear dimensional inferior a 2,00%, densidade de massa aparente de 1,56 g/cm3 e porosidade total de 46,68%. Isto demonstra que o rejeito possui um potencial como mat?ria-prima para aplica??o na ind?stria de materiais refrat?rios conformados isolante

Page generated in 0.1073 seconds