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Theses

Agglomération humide de poudres à réactivité de surface - Approche mécanistique de la morphogenèse de structures alimentaires agglomérées

Abstract : Wet agglomeration is a crucial step in the shaping technology of powders because of its strong impact on the final quality of the elaborated products. Despite its interest in the elaboration of many products (food, pharmaceutical, engineering,...) as well as different technological process (horizontal mixers, vertical, low or high shear rate, fluidized bed, ...), it remains insufficiently mastered due to the difficulty in establishing operating diagrams taking into account, in the same time, products and process contributions. This thesis focuses on the study of the agglomeration mechanisms related to the characteristics of the formulation and process parameters. The identification and representation of the way particles come together during the wetting / mixing operation is one of the central challenges of this work. From experiments with two different food powders (durum wheat semolina and milk powder), agglomeration is induced either by wet contacts in mixer at low shear rate or by collisions between sticky particles in a fluidized bed. Mechanisms of semolina wet agglomeration developed in a low shear mixer are described as a process of morphogenesis that correlates the agglomerates size to their texture via a fractal dimension. The influence of the liquid binder physicochemical properties on the agglomeration mechanisms is studied according to the values taken by the fractal parameters of the model. The detailed study of the distribution of size and textural properties of agglomerated structures make it possible to identify the rule that lead to their layout: the association is mainly possible between structures belonging to the same class concerning their hydro-textural and dimensional characteristics. Agglomeration regimes depending on the mode of water supply (low flow, high flow) are studied based on the notion of dimensionless spray flux. Concerning milk powder agglomeration in a fluidized bed, agglomeration mechanisms are studied by following the evolution of the size and water content of the samples taken during the operation of wetting / drying and thereafter studying the impact of some operational conditions and formulation on the properties of the final agglomerates and agglomeration regimes. A link between the processes (low shear mixer and fluidized bed) is discussed and opens onto a redefinition of granular flow regimes and the surface reactivity of particles.
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https://tel.archives-ouvertes.fr/tel-00796735
Contributor : Amal Barkouti <>
Submitted on : Monday, March 25, 2013 - 11:35:59 AM
Last modification on : Thursday, July 2, 2020 - 2:26:33 PM
Long-term archiving on: : Wednesday, June 26, 2013 - 4:01:42 AM

Identifiers

  • HAL Id : tel-00796735, version 2
  • PRODINRA : 330408

Citation

Amal Barkouti. Agglomération humide de poudres à réactivité de surface - Approche mécanistique de la morphogenèse de structures alimentaires agglomérées. Génie des procédés. Université Montpellier II - Sciences et Techniques du Languedoc, 2012. Français. ⟨tel-00796735v2⟩

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