Álvaro Niedersberg Correia Lima

Heat Transfer in Steelmaking Ladle

The heat transfer in a steelmaking ladle was studied. The evaluation of heat transfer of the steel was performed by measuring steel temperature in points including all refining steel process. In the ladle, the temperatures in the refractories and the shell were also measured. To evaluate the thermal profile between the hot and cold faces of the ladle in the slag line position, an experiment which shows the importance of thermal contact resistance was carried out. Higher heat losses in the tapping and the vacuum were verified. The temperature measurements of the ladle indicate distinct thermal profiles in each stage of steel refining. Moreover, as each stage of the process depends on the previous one, the complexity of the ladle thermal control is incremental. So a complete model of heat losses in the ladle is complex.

Nanomaterials for Applications in Refractory Materiais

Refractories based on nanostructured materials are emergent technological products in several applications in the steel and cement industries. To better understand the nanostructured materials in refractories applications this chapter shows a general perspective of the use of these materials in industrial refractories. Refractories research and development based on conventional technical concepts and techniques seem to have been conducted exhaustively. If refinement of refractory technology is to be expected, the introduction of new technologies is indispensable. Nanostructured materials improve several properties of refractory materials like mechanical resistance, thermal conductive, carbon oxidation protection.

Preparação e caracterização de espinélio MgAl2O4 nanoestruturado através de síntese por combustão em solução

This study aimed to investigate the synthesis and characterization of nanostructured MgAl2O4 spinel by different routes of combustion in solution. The MgAl2O4 spinel was synthesized using aluminum nitrate and magnesium nitrate as the sources of metal cations and sucrose as fuel in continuous combustion system (SCCS), and sequencing batch (CS), followed by heat treatment. The obtained powders were characterized by thermogravimetric analysis, gas adsorption for surface area analysis, laser diffraction for particle size measurement, X-ray diffraction, transmission electron microscopy for crystallographic analysis, and scanning electron microscopy (SEM) for powder morphology analysis. Both routes provided high purity powders and nanosized crystallites in the form of micrometric aggregates, whose properties varied depending on the oxide/fuel ratio. The SEM analyzes confirmed the aggregation of powder particles, as particles with irregular and porous morphology. The SCCS route resulted in a powder with similar properties to the CS route with the advantage of being a continuous process with high potential for industrial scale production.

Avaliação de revestimentos para proteção contra a descarbonetação de tijolos refratários MgO-C durante o aquecimento de panelas de aciaria

This work aims to evaluate the utilization of different coatings to prevent the decarburization of refractory bricks MgO-C used in ladles. This oxidation causes the loss of thickness of the bricks and the reduction of its useful live. The three types of coatings A, B e C were prepared in laboratory and then were applied on MgO-C bricks. The samples were tested at temperatures of 850oC, 950oC and 1050oC. It was verified that the three tested coatings only minimize the decarburization, since they vitrify and become effective at temperatures higher to the beginning of the oxidation temperature. Moreover, it was noticed that the thickness of the decarburized layer is directly proportional to the firing temperature. The coating that presented better results was C, which showed better characteristics of flowing and viscosity. Besides that, it vitrified at lower temperature comparing to coatings A and the B.