Comportement et stratégies de gestion des espèces inorganiques dans une installation de gazéification de la biomasse

Abstract : The purpose of this work is to analyze the condensation phenomena of inorganic species aerosols in a biomass gasification process. Indeed, during gasification, lignocellulosic biomass is transformed, in between 900 and 1500°C, into a Syngas. Some inorganic species initially present in the ash, are partly volatilized in chlorides (KCl, NaCl), and condense when the syngas cools down. These compounds may then, induce corrosion, blockages and deactivation of the catalysts used in further synthesis. The understanding and modeling of these species condensation may help to their management, and also to the imitation of the encountered difficulties. An experimental and analytical set-up, existing n the lab, allowed us to perform condensation tests from gaseous KCl and NaCl, under experimental condition close to the industrial gasification ones for an entrained flow reactor, especially for two cooling rates (1000 and 300K/s). The influence of the different parameters (presence or not of preexisting particles like soot and simulated by carbon particles, inorganic salts concentration, salts mixture…) on the vapor condensation phenomena, was performed for both cooling rates. Globally, the experimental results showed that, without carbon particles, the inorganic species condensation induce the formation of very small new particles by homogeneous nucleation. With carbon particles, this vapor tends to condense on the preexisting particles, which allows to reduce the wall deposits by about 10wt %. The mixture behavior is found to be in between the individual salt ones. A particle agglomeration effect is also evidenced at 300K/S, linked the increase of the residence time in the cooling part of the set-up. The SOPHAEROS software, developed by IRSN for the fission product transport and condensation in a nuclear power plant, was adapted to the experimental conditions of this work. The validation of this tool was obtained, comparing calculation and experimental results. It was then used to determine the main condensation and deposits phenomena varying the inorganic salt nature, their concentration, the presence of carbon particles and the cooling rate. It was showed that, the three main involved phenomena, occurring in the quench part of a gasification reactor, without carbon particles, are the direct wall condensation of the vapor, the homogeneous nucleation (favored at high cooling rate, 1000K/s), and gravitational settling deposits. When carbon particles are included, heterogeneous nucleation is predominant upon homogeneous one. The modelling could allow us to explain the behavior differences related to the local variation of salts partial pressure and saturation vapor pressure, as well as the influence of both cooling rates on the condensation results. Finally, some industrial possible solutions to decrease the wall deposits are proposed as a conclusion of the work
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Lucia Jimenez. Comportement et stratégies de gestion des espèces inorganiques dans une installation de gazéification de la biomasse. Autre. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0025⟩. ⟨tel-01751477⟩

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