Emmanuel de Bilbao

Effect of Slag Impregnation on Macroscopic Deformation of Bauxite‐Based Material

This work aims at studying the volume change of bauxite corroded by a molten slag. Cylindrical samples were prepared by mixing ground bauxite with slag. Optical measurement at high temperature (1450 °C) of deformation with a high-resolution camera has been developed. Image processing allowed for determining the change in diameter of the sample. We showed that the deformation was induced by the precipitation of new expansive crystallised phases observed by SEM-EDS analyses. Adding pellets of the same slag upon the samples allowed to emphasize the effect of the slag amount on the size change. The change in diameter significantly increased in the impregnated area.

Multiphysics Modelling Applied to Refractory Behaviour in Severe Environments

It is a common practice to design refractory linings with the help of thermal computations, thermochemistry analyses and strong workman know-how. Their mechanical design is often limited to simple thermo-elastic computations. Sometimes computations are refined considering non-linear mechanical behaviour, even if corrosion often induces additional chemical strain and strong change in service of the mechanical behaviour of the refractory. The aim of this presentation is to briefly recast the irreversible thermodynamic framework in order to underline the implications of some basic thermodynamic concepts in term of refractory behaviour modelling. Then, the use of these concepts to develop fully 3D finite element simulations accounting simultaneously for thermal, mechanical and chemistry phenomena will be illustrated on the particular case of SiC-based refractory. Comparison between long duration oxidation test at high temperature and model prediction allows the validation of the proposed approach. Then, an extension to the industrial case of refractory lining in Waste to Energy plant will be illustrated. The interest of taking into account the thermo-chemo-mechanical coupling effects is shown.

Mechanisms of SiC Refractory High Temperature Corrosion by Molten Salts (Na,K,Ca,Cl,S) in Waste to Energy Facilities

Damage of SiC oxide bonded refractories in waste-to-energy facilities (WtE) has been characterized. Different phenomena were observed: wear by slag phases, volume expansion of tiles and fracture in different locations. These results are in agreement with laboratory experiments. The role of gas composition and tiles temperature profile on deposit composition, on condensation of gaseous alkali chloride and on formation of liquid phase inside the porosity of the refractories has been emphasized. Gaseous alkali species are involved, not only in the formation of liquid phases, but also as a precursor of cristoballite formation around the SiC grains as well as in the rich alumina-silica matrix. On the hot face of the refractories, oxo-reduction reactions produce the formation of wollastonite. Post-mortem analysis after several thousand hours of operation point to three main corrosion mechanisms:

Study of Reactive Impregnation and Phase Transformations during the Corrosion of High Alumina Refractories by Al2O3-CaO Slag

Corrosion of refractories results from reactive transport namely, transport of agents and chemical reactions of these agents with impregnated medium. On one hand, the transport involves either diffusion or impregnation depending on the state of the corrosive agents and the microstructure of the host media. On the other hand, chemical reactions may be very numerous and complex. This study focused on the reactive impregnation of Al2O3-CaO slag into porous high alumina refractory.Transport properties of the porous media have been assessed by performing wicking test. Chemical reactions between the solid high alumina skeleton and Al2O3-CaO slag involve successive dissolution/precipitation mechanisms forming aluminates of lime. Contrary to the thermodynamic properties of the binary system, the kinetics of these solid/liquid reactions is not well known. Corrosion tests associated with quenching method, XRD and high temperature XRD were performed for a better understanding of the kinetics.

Modelling of the Swelling of SiC-Based Refractory Lining Used in Waste-to-Energy Plants

This work provides a computational model of the chemo-mechanical behavior of based refractories used in waste to energy plant (WTE) linings. In this application, oxygen gas present in the atmosphere diffuses through the porosity and reacts with the refractory producing silica (SiO2). This new phase clogs gradually the pores and causes swelling of the refractory lining. The proposed thermo-chemo-mechanical model which simulates these phenomena is briefly summarized. The results obtained from the model implemented in a F.E code prove the ability of the model to reproduce qualitatively the swelling of post-mortem bricks taken from WTE linings.Copyright