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Theses

Thermo-physical properties of insulating refractory materials

Abstract : The performance of insulating refractory materials is determined by the thermo-physical properties. The first part of this thesis is dedicated to the evaluation of the thermal conductivity, which is an input parameter in modelling studies of heat transfer through a steel ladle lining. Comparison of different methods for its determination leads to some variation in the experimental results. However, taking into account effects such as heat losses, humidity, anisotropy and heterogeneity, the discrepancy could be reduced to within 10% when the same heat flow direction through the material is considered. Thermal conductivity is significantly modulated by the microstructure. Given that refractories are multi-phase materials, model materials with similar microstructures were studied to identify the role of factors such as porosity, grain boundaries, grain size and presence of second phases. Then three real cases of industrial interest were examined. The ladle is a vessel made by different bricks. Therefore, joints play an important role. The interface thermal resistance was estimated to be in the range 10-4 to 10-3 m2·K·W-1 useful as a first approximation in computer modelling. In fact the lining is subjected to hydrostatic pressure when the ladle is filled with hot liquid steel implying the materials require sufficient compressive strength. For compression loads up to 0.4 MPa on the thermal expansion and up to 0.04 MPa on the thermal conductivity of insulating lining materials, no significant effect was observed. Finally, one of the main problems for steelmaking industry is represented by corrosion, which can require replacement of the materials in order to guarantee the same operation condition for all the campaign. The role of carbon contamination for the thermal conductivity of the insulating lining was evaluated.
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Submitted on : Friday, July 16, 2021 - 4:39:09 PM
Last modification on : Saturday, July 17, 2021 - 3:31:11 AM

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  • HAL Id : tel-03289147, version 1

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Diana Vitiello. Thermo-physical properties of insulating refractory materials. Materials. Université de Limoges, 2021. English. ⟨NNT : 2021LIMO0034⟩. ⟨tel-03289147⟩

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