References of "Crine, Michel"
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See detailHYDRODYNAMICS IN A DISPOSABLE RECTANGULAR PARALLELEPIPED STIRRED BIOREACTOR WITH ELLIPTIC PENDULUM MOTION PADDLE
Collignon, Marie-Laure ULg; Droissart, Laurent; Delafosse, Angélique ULg et al

in Biochemical Engineering Journal (2015), 93

Stainless steel bioreactors increasingly fall behind to their disposable counterparts in pharma research as they do not require cleaning or sterilization. This led company ATMI LifeSciences to develop the ... [more ▼]

Stainless steel bioreactors increasingly fall behind to their disposable counterparts in pharma research as they do not require cleaning or sterilization. This led company ATMI LifeSciences to develop the “Nucleo™”. Original in design, this disposable bioreactor comprises a rectangular parallelepiped plastic bag stirred by a paddle revolving in elliptic pendulum motion. Studies covering this bioreactor showed good homogeneity of culture medium as well as good productivity for animal cell cultures. To further explain these good performances, the flow inside the “Nucleo™” had to be resolved. This paper focuses on the mean flow description, computed from stereo-PIV measurements performed in 20 verticals covering the whole volume of a 50 dm3 Nucleo™ bioreactor. As the flow is already turbulent in the chosen agitation conditions, its dimensionless mean velocity field does not vary with the paddle rotational speed. Mean flow pattern exhibits an axial symmetry – same flow is observed in opposite quarters of the tank – and can be described as a three-dimensional helix coiled on itself to form a distorted horizontal torus which covers the whole tank volume. Mean velocity value is on average doubled in the cone swept by the paddle, and its two horizontal components are twice higher than its vertical ones. However, mean velocity remains significant everywhere and, in particular, no stagnant area is observed in tank corners. Our results thus confirm previous studies observations. [less ▲]

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See detailInfluence of viscosity on Liquid Flow Inside Structured Packings
Bradttmöller, Christian; Janzen, Anna; Crine, Michel ULg et al

in Industrial & Engineering Chemistry Research (2015), 54

In this study, X-ray computer tomography and light-induced fluorescence were applied to investigate the morphology of liquid flow inside structured packings. Fluid dynamic parameters such as liquid holdup ... [more ▼]

In this study, X-ray computer tomography and light-induced fluorescence were applied to investigate the morphology of liquid flow inside structured packings. Fluid dynamic parameters such as liquid holdup and wetted surface were determined to study the effect of the variation of viscosity and liquid load. Flow patterns inside the packing were identified and categorized. Liquid film thickness and its distribution were analyzed on single sheets. For both methods, the measured holdup values are in good agreement, despite differences in the techniques of measurement. For the flow patterns and their relative contribution, as well as mean liquid film thickness, a strong dependency on the varied parameters was found. Furthermore, the density function of film thickness distribution changed characteristically with liquid load and viscosity. The complementary use of tomography and optical assessment allowed an improved insight into flow phenomena and the observed interdependency of physical, geometric, and operational parameters. [less ▲]

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See detailInvestigation of the links between mass transfer conditions, dissolved hydrogen concentration and biohydrogen production by the pure strain Clostridium butyricum CWBI1009
Beckers, L.; Masset, J.; Hamilton, C. et al

in Biochemical Engineering Journal (2015), 98

Fermentative hydrogen production has often been described as inhibited by its own gas production. In this work, hydrogen production by Clostridium butyricum was investigated in batch Biochemical Hydrogen ... [more ▼]

Fermentative hydrogen production has often been described as inhibited by its own gas production. In this work, hydrogen production by Clostridium butyricum was investigated in batch Biochemical Hydrogen Potential (BHP) tests and in a 2.5L anaerobic sequenced batch reactor (AnSBR) under different operating conditions regarding liquid-to-gas mass transfer. Through the addition of both stirring up to 400rpm and nitrogen sparging, the yields were enhanced from 1.6 to 3.1molH2molglucose -1 and the maximum hydrogen production rates from 140 to 278mLh-1. These original results were achieved with a pure Clostridium strain. They showed that hydrogen production was improved by a higher liquid-to-gas hydrogen transfer resulting in a lower dissolved hydrogen concentration in the culture medium and therefore in a lower bacterial inhibition. In addition, biohydrogen partitioning between the gas and the liquid phase did not conform to Henry's Law due to critical supersaturation phenomena up to seven-fold higher than the equilibrium conditions. Therefore, dissolved hydrogen concentration should be systematically measured instead of the headspace hydrogen partial pressure. A model was proposed to correlate H2 production yield and rate by the pure C. butyricum strain CWBI1009 with mass transfer coefficient KLa. [less ▲]

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See detailCFD Comparison of hydrodynamics between BIOSTAT® Cultibag STR and standard Stirred Cell Culture Bioreactors
Calvo, Sébastien ULg; Delafosse, Angélique ULg; Crine, Michel ULg et al

Poster (2014, September 10)

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as ... [more ▼]

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as the BIOSTAT® Cultibag STR one, is limited. For example, technical constraints on weld seams limit angles to 30° and no baffle may be installed. The shape of standard re-usable vessels may thus not be exactly reproduced and the flow structure may thus significantly differs from the flow structure in standard bioreactors. [less ▲]

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See detailPreparation of polyaniline-modified local clay and study of its sorption capacity
Benhebal, Hadj; Chaid, Messaoud; Léonard, Angélique ULg et al

in Journal of Nanostructure in Chemistry (2014), 4(98), 6

Clay minerals are frequently used in adsorption processes with aqueous solution; it was found that the adsorption properties of clays change when the samples are modified. In this context, polyaniline ... [more ▼]

Clay minerals are frequently used in adsorption processes with aqueous solution; it was found that the adsorption properties of clays change when the samples are modified. In this context, polyaniline-modified clay nanocomposite (at 10 %) was prepared by in situ polymerization processes. The structural and morphological characteristics of the synthesized material are systematically examined by X-ray diffraction, scanning electron microscopy, thermo-gravimetry, differential scanning calorimetry and infrared spectroscopy techniques. The adsorption property of the modified clay was evaluated for the removal of a reactive dye (methylene blue) from aqueous solution at room temperature (25 C) via batch adsorption. [less ▲]

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See detailCFD-based Compartment model for description of mixing in bioreactors
Delafosse, Angélique ULg; Calvo, Sébastien ULg; Collignon, Marie-Laure ULg et al

in Chemical Engineering Science (2014), 106

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can ... [more ▼]

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can provide detailed modeling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of “Compartment” or “Network-of-zones” model which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow complexity. To overcome the limitations of these two methods, a solution is to combine compartment modeling and CFD simulations. The aim of this study is to propose a compartment model where the flow rates between two adjacent compartments are easily computed from the velocity fields obtained by CFD. The mixing evolution predicted by the CFD-based compartment model have been then compared with mixing experiment results. Unlike a CFD mixing simulation and a classical compartment model, the CFD-based compartment model proposed in this work reproduces with a good accuracy the spatial distribution of concentrations during the mixing process and this, without any adjustable parameters. [less ▲]

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See detailInfluence of liquid viscosity on separation efficiency of structured packings – modelling approach based on X-ray tomography investigations
Janzen, Anna; Steube, Julia; Crine, Michel ULg et al

in Proceedings (2014)

The objectives of this work are the investigation of liquid flow morphology inside a structured packing using X-ray tomography and the development of a modelling approach based on hydrodynamic analogy ... [more ▼]

The objectives of this work are the investigation of liquid flow morphology inside a structured packing using X-ray tomography and the development of a modelling approach based on hydrodynamic analogy between the real complex flow patterns and simplified fluid-dynamic elements. To study the influence of viscosity, water and mixtures of water and glycerine with varying glycerine fraction are used as working liquids. X-ray tomography is applied to determine the spatial distribution of liquid in the cross-section of a column filled with MellapakPlus 752.Y packing elements. The resulting images are used to evaluate liquid hold-up, gas-liquid interfacial area and to analyse liquid morphology. Liquid flow patterns (film flow, contact-point liquid, flooded regions) are identified, and the fraction of liquid within each flow pattern depending on flow rate and liquid viscosity is determined. The results of the liquid flow morphology analysis are used to develop a hydrodynamic analogy model. To implement the gas-liquid contact area and the flooded regions into this model, the packing is represented as a bundle of dry, filled and irrigated cylindrical channels, while the ratio between different type channels is determined from the analysis of tomographic images. This simplified hydrodynamic description allows a direct application of rigorous partial differential transport equations, and their solution yields local concentration fields which are used for the evaluation of the separation efficiency. The new modelling approach is validated by comparison with separation efficiency data obtained from experiments with CO2 desorption from saturated water-glycerine mixtures into air. The presented modelling approach is capable of predicting the influence of viscosity on separation efficiency of columns filled with structured packings. [less ▲]

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See detailVisible-light photo-activity of alkali metal doped ZnO
Benhebal, Hadj; Chaib, Messaoud; Malengreaux, Charline ULg et al

in Journal of the Taiwan Institute of Chemical Engineers (2014), 45(1), 249-253

In order to utilize visible light more efficiently in the field of photocatalysis, Li, Na and K-doped ZnO nanoparticles were prepared using a sol–gel method. The obtained samples were characterized by BET ... [more ▼]

In order to utilize visible light more efficiently in the field of photocatalysis, Li, Na and K-doped ZnO nanoparticles were prepared using a sol–gel method. The obtained samples were characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy and UV–vis analysis. The photocatalytic activity of the photocatalysts was evaluated for the degradation of p-nitrophenol (p-NP) under visible light irradiation. It has been observed that these photocatalysts could be a promising photocatalyst for degradation of organic molecules as compared to transition metal doped ZnO under visible light. Li-doped ZnO is the most active photocatalyst and shows high photocatalytic activity for the degradation of p-nitrophenol (p-NP). The enhanced photocatalytic activity of Li-doped ZnO is mainly due to the electron trapping by lithium metal ions, small particle size, large surface area, and high surface roughness of the photocatalysts. [less ▲]

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See detailModeling of Wastewater Sludge Drying with Determination of Diffusivity Moisture
Bennamoun, Lyes ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

in Journal of Residuals Science and Technology [=JRST] (2013), 10(4), 165

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See detailDévéloppement intégré de matériaux hybrides photosynthétiques par encapsulation de micro-algues en vue de la production de méthabolites à haute valeur ajoutée (projet FOTOBIOMAT)
Duprez, Marie-Eve; Hantson, Anne-Lise; Thomas, Diane et al

Poster (2013, November 15)

La production de métabolites à haute valeur ajoutée tels que les caroténoïdes peut se faire au travers de la culture de micro-algues de type Dunaliella sp. notamment. La croissance de la biomasse en ... [more ▼]

La production de métabolites à haute valeur ajoutée tels que les caroténoïdes peut se faire au travers de la culture de micro-algues de type Dunaliella sp. notamment. La croissance de la biomasse en cellules libres a pour inconvénient majeur la destruction de la souche micro-algale lors des différentes étapes d’extraction des composés d’intérêt. Le projet FOTOBIOMAT (subsidié par le programme Greenomat de la Région wallonne) a pour but de développer un nouveau type de photobioréacteur dans lequel sont mises en oeuvre les micro-algues encapsulées dans des billes constituées d’un matériau hybride (alginate-silice). Les billes sont maintenues en suspension dans un lit fluidisé (mélange assez doux ne compromettant pas l’intégrité des billes). Ce type de mélange permet de renouveler les billes à la paroi du photobioréacteur, au contact de la source lumineuse. Le processus de photosynthèse est ainsi utilisé afin de convertir du CO2 en composé à haute valeur ajoutée (-carotène par exemple). La viabilité des micro-algues encapsulées doit être très importante (minimum 6 mois). Idéalement, le -carotène produit devrait être récupéré par une voie non polluante et ce, quasi en continu. Le projet est réalisé conjointement par quatre institutions universitaires (Université de Namur, Université Catholique de Louvain, Université de Liège et Université de Mons). Nous présentons ici différents résultats relatifs aux transferts gazeux et de matière au sein des billes, des billes vers une solution liquide ou de la solution vers les billes. L’oxygène produit par les micro-algues ainsi que le dioxyde de carbone consommé, preuves d’une bonne activité photosynthétique, doivent pouvoir migrer entre la matrice solide et le milieu de culture. La consommation de certains nutriments, les nitrates par exemple, essentiels à la croissance et à la survie de la souche micro-algale choisie peut également être suivie au cours du temps. Pour ce faire, différents types de sondes ont été utilisés avec plus ou moins de succès (Tableau 1). Les métabolites à haute valeur ajoutée produits (ici, le -carotène) doivent pouvoir être extraits des micro-algues et du matériau afin d’être récupérés dans la phase liquide. Des mesures de diffusion de composés tels que la rhodamine B (colorant) et de -carotène d’une solution agitée aux billes a été étudiée (Figures 1 et 2). Enfin, afin d’étudier leur capacité d’extraction du -carotène en-dehors des billes, différents solvants, dont la plupart sont connus pour leur capacité efficacité d’extraction de caroténoïdes hors des micro-algues, ont été testés. Il s’est avéré que si quelques solvants permettaient effectivement d’extraire du -carotène en-dehors des billes, ils étaient « agressifs » vis-à-vis du matériau (Tableau 2) ou de la biomasse. En outre, à l’heure actuelle, si aucun solvant « vert » et biocompatible n’a pu encore se dégager, l’huile de tournesol est en cours de test, tout en étudiant également l’action de procédés plus physiques (sonication, variations légères de température, …). [less ▲]

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See detailProcédé de fabrication d'un matériau hybride photosynthétique obtenu par encapsulation de micro-algues en vue de sa mise en oeuvre dans un photobioréacteur à biomasse fixée
Lox, Frédéric ULg; Crine, Michel ULg; Toye, Dominique ULg et al

Poster (2013, November 15)

La méthode d’encapsulation a une grande influence sur la productivité et sur la viabilité des microalgues car elle conditionne leur environnement immédiat au sein du matériau hybride. Le contrôle de la ... [more ▼]

La méthode d’encapsulation a une grande influence sur la productivité et sur la viabilité des microalgues car elle conditionne leur environnement immédiat au sein du matériau hybride. Le contrôle de la porosité, de la composition chimique et la stabilité mécanique est fondamental. Cette étape de recherche consiste en la détermination des formulations chimiques idéales (densité cellulaire, compositions chimiques, porosité,…) et des conditions de synthèse (précurseurs chimiques, conditions d’encapsulation sol-gel) des matériaux hybrides photosynthétiques avec des microalgues sélectionnées; la géométrie (forme et dimensions) d’un matériau hybride donné (densité cellulaire, composition chimique, porosité) a une grande influence sur le transfert de matière (CO2, nutriments) et sur la transmission de la lumière jusqu’aux microalgues et donc sur l’activité métabolique et la viabilité de celles-ci. Le projet FOTOBIOMAT (subsidié par le programme Greenomat de la Région wallonne) est réalisé conjointement par quatre institutions universitaires Université de Namur (UNAMUR), Université Catholique de Louvain (UCL), Université de Liège (ULg) et Université de Mons UMONS)). La composition de départ du MHPS a été déterminée par UNAMUR. Nous aborderons ici les étapes de conception, construction et mise au point d’un dispositif de fabrication en continu de billes de matériau hybride photosynthétique contenant une microalgue du genre Dunaniella ainsi que l’adaptation du protocole de synthèse des billes en vue de permettre une production importante puis une production en continu qui ont été développées par le Laboratoire de Génie Chimique (LGC) de l’Université de Liège. Nous présenterons des études sur la caractérisation des MHPSs : -le transfert de lumière au sein du matériau et la diffusion de composés tels qu’un colorant (la rhodamine B), un pigment (le b-carotène) ou une protéine (l’hémoglobine) d’une solution agitée aux billes ont été réalisées ainsi que des tests d’extraction de b-carotène encapsulé directement dans les billes (UMONS) ; -la résistance, la distribution de la composition, la surface spécifique et la porosité de la couche La méthode d’encapsulation a une grande influence sur la productivité et sur la viabilité des microalgues car elle conditionne leur environnement immédiat au sein du matériau hybride. Le contrôle de la porosité, de la composition chimique et la stabilité mécanique est fondamental. Cette étape de recherche consiste en la détermination des formulations chimiques idéales (densité cellulaire, compositions chimiques, porosité,…) et des conditions de synthèse (précurseurs chimiques, conditions d’encapsulation sol-gel) des matériaux hybrides photosynthétiques avec des microalgues sélectionnées; la géométrie (forme et dimensions) d’un matériau hybride donné (densité cellulaire, composition chimique, porosité) a une grande influence sur le transfert de matière (CO2, nutriments) et sur la transmission de la lumière jusqu’aux microalgues et donc sur l’activité métabolique et la viabilité de celles-ci. Le projet FOTOBIOMAT (subsidié par le programme Greenomat de la Région wallonne) est réalisé conjointement par quatre institutions universitaires Université de Namur (UNAMUR), Université Catholique de Louvain (UCL), Université de Liège (ULg) et Université de Mons UMONS)). La composition de départ du MHPS a été déterminée par UNAMUR. Nous aborderons ici les étapes de conception, construction et mise au point d’un dispositif de fabrication en continu de billes de matériau hybride photosynthétique contenant une microalgue du genre Dunaniella ainsi que l’adaptation du protocole de synthèse des billes en vue de permettre une production importante puis une production en continu qui ont été développées par le Laboratoire de Génie Chimique (LGC) de l’Université de Liège. Nous présenterons des études sur la caractérisation des MHPSs : -le transfert de lumière au sein du matériau et la diffusion de composés tels qu’un colorant (la rhodamine B), un pigment (le b-carotène) ou une protéine (l’hémoglobine) d’une solution agitée aux billes ont été réalisées ainsi que des tests d’extraction de b-carotène encapsulé directement dans les billes (UMONS) ; -la résistance, la distribution de la composition, la surface spécifique et la porosité de la couche externe des MHPS (UNAMUR) ; -la répartition des dimensions et de la densité des billes obtenue en fonction du mode de production (ULg). [less ▲]

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See detailImpact of sludge storage duration on its dewatering and drying ability
Pambou, Yvon-Bert; Salmon, Thierry ULg; Fraikin, Laurent ULg et al

Poster (2013, October)

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See detailDéveloppement d'un dispositif de trajectographie optique nécessaire pour la caractérisation expérimentale par une approche Euler-Lagrange des écoulements dans des bioréacteurs à cuve agitée
Collignon, Marie-Laure ULg; Delafosse, Angélique ULg; Delvigne, Frank ULg et al

in Récents Progrès en Génie des Procédés (2013, October)

Les bioréacteurs à cuve agitée sont des dispositifs largement utilisés dans l’industrie pharmaceutique. Les performances globales des cultures menées dans ces bioréacteurs dépendent fortement de ... [more ▼]

Les bioréacteurs à cuve agitée sont des dispositifs largement utilisés dans l’industrie pharmaceutique. Les performances globales des cultures menées dans ces bioréacteurs dépendent fortement de l’environnement physico-chimique et hydrodynamique local rencontré par les microorganismes et ce au cours du temps. Pour parvenir à caractériser cet historique de conditions locales rencontrées, une approche Euler-Lagrange doit être adoptée. La difficulté dans ce type d’approche est d’être capable de mesurer de manière fiable la trajectoire suivie par le microorganisme au sein du bioréacteur. Pour ce faire, le Laboratoire de Génie Chimique de l’Université de Liège a conçu un dispositif de trajectographie optique. L’objectif de cet article est de présenter ce dispositif, les développements qui ont été nécessaire à sa mise en œuvre et les résultats obtenus. Le dispositif se compose de deux caméras observant selon deux axes de l’espace un bioréacteur rétro-éclairé par des panneaux leds. La trajectoire suivie par une particule noire en gel d’alginate de calcium de 491 µm de diamètre est construite à partir des images acquises par ces deux caméras préalablement modélisée par un modèle pinhole et traitées par une approche rationnée. La validité des trajectoires mesurées a été prouvée dans un bioréacteur de 20 L mélangé par une hélice TTP en comparant les champs de vitesse moyen et d’énergie cinétique turbulent extraits de la trajectoire avec ceux obtenus par la technique eulérienne Stéréo P.I.V. La convergence de ces deux champs avec le temps d’acquisition de la trajectoire a également été démontrée. [less ▲]

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See detailCaractérisation expérimentale et modélisation des conditions de mise en suspension homogène d’un solide dans une cuve agitée industrielle
Calvo, Sébastien ULg; Delafosse, Angélique ULg; Collignon, Marie-Laure ULg et al

in Récents Progrès en Génie des Procédés (Cd-ROM) (2013, September)

In this work, we study the conditions needed to reach homogeneous distribution of solid particles of aluminium salts in water inside a GRC bottom shape stirred tank of 70L equipped with Pfaudler RCI type ... [more ▼]

In this work, we study the conditions needed to reach homogeneous distribution of solid particles of aluminium salts in water inside a GRC bottom shape stirred tank of 70L equipped with Pfaudler RCI type impeller and three equispaced vertical baffles. The aim of the present study is to develop a CFD model describing the quality of particle distribution at the industrial scale. This model, validated with experimental data, is afterward used to developed scale-up and scale-down correlation to predict the minimum impeller speed needed to reach homogeneous solid distribution Nhs. The commercial CFD tool Fluent 14 is used to model the fluid flow and the solid particle distribution in the tank. The 3D geometry of the tank and the associated mesh are realized respectively by Ansys 14 DesignModeler and Meshing. The Sliding-Mesh approach is used to take into account the impeller motion. Assuming that only the continuous phase is present, the fluid flow dynamics may be simulated independently using the wellknown k-ε turbulence model. The behaviour of the liquid-solid mixture is then described implementing the Eulerian Mixture model. Liquid velocity fields simulated by CFD have been validated by comparison with PIV (Particle Image Velocimetry) measurements. Computed Nhs is well compared to experimental data obtained with a nephelometric probe. Results obtained at different scales allowed correlating Nhs and volumetric power consumption. [less ▲]

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See detailExperimental characterisation and modelling of homogeneous solid suspension in an industrial stirred tank
Calvo, Sébastien ULg; Delafosse, Angélique ULg; Collignon, Marie-Laure ULg et al

in Advances in Mechanical Engineering (2013), Volume 2013

In this work, we study the conditions needed to reach homogeneous distribution of aluminium salts particles in water inside a torispherical bottom shaped stirred tank of 70 L equipped with a Pfaudler RCI ... [more ▼]

In this work, we study the conditions needed to reach homogeneous distribution of aluminium salts particles in water inside a torispherical bottom shaped stirred tank of 70 L equipped with a Pfaudler RCI type impeller and three equispaced vertical baffles. The aim of the present study is to develop a CFD model describing the quality of particle distribution in industrial scale tanks. This model, validated with experimental data, is used afterwards to develop scale-up and scale-down correlations to predict the minimum impeller speed needed to reach homogeneous solid distribution Nhs.The commercial CFD software Fluent 14 is used to model the fluid flow and the solid particle distribution in the tank. Sliding Mesh approach is used to take the impeller motion into account. Assuming that the discrete solid phase has no influence on the continuous liquid phase behaviour, the fluid flow dynamics is simulated independently using the well-known k-ε turbulence model. The liquid-solid mixture behaviour is then described by implementing the Eulerian Mixture model. Computed liquid velocity fields are validated by comparison with PIV measurements. ComputedNhs were found to be in good agreement with experimental measurements. Results fromdifferent scales allowed correlating Nhs values to the volumetric power consumption. [less ▲]

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See detailApproche de la Complexité en Génie des Procédés
Crine, Michel ULg

Conference (2013, June 02)

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See detailConvective drying of wastewater sludge: Introduction of shrinkage effect in mathematical modeling
Bennamoun, Lyes ULg; Crine, Michel ULg; Léonard, Angélique ULg

in Drying Technology (2013), 31(6), 643-654

Drying of two kinds of wastewater sludge was studied. The first part was an experimental work done in a discontinuous cross-flow convective dryer using 1 kg of wet material extruded in 12-mm-diameter ... [more ▼]

Drying of two kinds of wastewater sludge was studied. The first part was an experimental work done in a discontinuous cross-flow convective dryer using 1 kg of wet material extruded in 12-mm-diameter cylinders. The results show the influence of drying air temperature for both sludges. The second part consisted of developing a drying model in order to identify the internal diffusion coefficient and the convective mass transfer coefficient from the experimental data. A comparison between fitted drying curves, well represented by Newton's model, and the analytical solutions of the equation of diffusion, applied to a finite cylinder, was made. Variations in the physical parameters, such as the mass, density, and volume of the dried product, were calculated. This allowed us to confirm that shrinkage, which is an important parameter during wastewater sludge drying, must be taken into account. The results showed that both the internal diffusion coefficient and convective mass transfer coefficient were affected by the air temperature and the origin of the sludge. The values of the diffusion coefficient changed from 42.35 × 10−9 m2 · s−1 at 160°C to 32.49 × 10−9 m2 · s−1 at 122°C for sludge A and from 33.40 × 10−9 m2 · s−1 at 140°C to 28.45 × 10−9 m2 · s−1 at 120°C for sludge B. The convective mass transfer coefficient changed from 4.52 × 10−7 m · s−1 at 158°C to 3.33 × 10−7 m · s−1 at 122°C for sludge A and from 3.44 × 10−7 m · s−1 at 140°C to 2.84 × 10−7 m2 · s−1 at 120°C for sludge B. The temperature dependency of the two coefficients was expressed using an Arrhenius-type equation and related parameters were deduced. Finally, the study showed that neglecting shrinkage phenomena resulted in an overestimation that can attain and exceed 30% for the two coefficients. [less ▲]

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