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Gazéification de biomasse en lit fluidisé : étude phénoménologique de l’agglomération liée à la fusion des cendres

Abstract : Improving the knowledge on the driving phenomena of agglomeration during fluidized-bed conversion of biomass (700-1000°C) is essential to predict its occurrence at industrial scale. Agglomeration is due to liquid phase formation (molten salts and/or molten silicates) coming from the melting of inorganic species contained inside the biomass (ash). Their presence leads to bed materials defluidization, reducing the process efficiency and even going up to a “blockage” of the reactor. The phenomenology of agglomeration is investigated with three experimental approaches, using simulant and real materials, at three different scales, and with a temperature ranging from ambient one to 1000°C. The analysis of the mechanisms underlying the bed agglomeration indicates that the liquid formation is the single limiting parameter for agglomerates formation. This phenomenon leads to an increase of the apparent diameter of the bed particles and at the same time to a decrease of their density. These modifications can be seen as a shift among the Geldart’s classification, from the B to the D-class. Concerning the hydrodynamic aspect, the bed defluidization is due to the agglomerates segregation at the bottom of the reactor. This phenomenon contributes to degrade the homogenous fluidization gas distribution across the reactor. The total bed defluidization occurs for a very low liquid fraction in the bed (few % vol. of bed materials). Based on these results, a simplified model has been proposed in order to predict the operating time before defluidization of the reactor, taking into account the biomass composition and simplified operating conditions.
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https://tel.archives-ouvertes.fr/tel-01407243
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Submitted on : Thursday, December 1, 2016 - 7:59:44 PM
Last modification on : Tuesday, October 19, 2021 - 10:58:03 AM
Long-term archiving on: : Tuesday, March 21, 2017 - 5:56:57 AM

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  • HAL Id : tel-01407243, version 1

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Michael Balland. Gazéification de biomasse en lit fluidisé : étude phénoménologique de l’agglomération liée à la fusion des cendres. Alimentation et Nutrition. Université d'Orléans, 2016. Français. ⟨NNT : 2016ORLE2020⟩. ⟨tel-01407243⟩

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