Papers by Author: Eric Blond

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Authors: Jacques Poirier, Pascal Prigent, Marie Laure Bouchetou, Emmanuel de Bilbao, Eric Blond, Jean Michel Brossard
Abstract: 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:
Authors: Camille Gazeau, Eric Blond, Mickaël Reichmann, Pierre Marie Geffroy, Thierry Chartier, Nicolas Richet
Abstract: The transient stage is critical due to the stress induced by the chemical and thermal strain. In order to predict this strain, the oxygen activity field through the membrane needs to be known. Usually, the membrane is divided into three zones: the bulk where diffusion takes place and the two surfaces where exchanges between atmosphere and membrane take place. Oxygen bulk diffusion is well described by the Wagner theory. A consensus has not yet emerged regarding the surface exchange models proposed in the literature. Moreover, these models describe the permanent state, and cannot be extended to the transient stage. A new macroscopic surface exchange model which allows computing transient stage is proposed. This model assumed that the oxygen flux is governed by the association/dissociation of adsorbed oxygen and by the high energetic cost of oxygen reduction/oxidation. Then, the balance of transient specie only present on the surface is introduced to account for these two phenomena. The oxygen activity fields predicted by the proposed model are in agreement with the measures of chemical potential drop between the membrane and the atmosphere in permanent state. Transient stage measured during isothermal expansion test is partially reproduced.
Authors: Eric Blond, Tarek Merouki, Nicolas Schmitt, Emmanuel de Bilbao, Alain Gasser
Abstract: 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.
Authors: Eric Blond, N. Schmitt, Olivier Arnould, François Hild, J. Poirier, P. Blumenfeld
Authors: Emmanuel de Bilbao, Mathieu Dombrowski, Nicolas Traon, Thorsten Tonnesen, Jacques Poirier, Eric Blond
Abstract: 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.
Authors: Olivier Valentin, Eric Blond, Nicolas Richet
Abstract: This study deals with the modelling of the mechanical behaviour accounting for the expansion induced by the oxygen diffusion in MIECs membrane during semi-permeation transient stage. A dedicated model of chemical expansion and its numerical implementation is used to study the relationship between the mechanical stress and the oxygen flux. The impact of the ratio between oxygen bulk diffusion and surface exchange kinetics on mechanical stress in transient stage is discussed. At last, the need of a compromise between the oxygen flux performance and the mechanical reliability is underlined.
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