Liquid hold-up measurement in Mellapak Plus 752Y packed bed using X-ray tomography

in VCIPT (Ed.) Proceedings of 6th World Congress On Industrial Process Tomography (WCIPT6), Beijing, China, 6-9 Septembre 2010 (2010)

Interfacial area measurement in a catalytic distillation packing using high energy x-ray CT

in Chemical Engineering Science (2010), 65(1), 511-516

In this paper, we report on the use of X-ray tomography to visualize and quantify the gas–liquid interfacial area in modular catalytic distillation packing elements. The calculation method is based on ... [more ▼]

In this paper, we report on the use of X-ray tomography to visualize and quantify the gas–liquid interfacial area in modular catalytic distillation packing elements. The calculation method is based on processing of tomographic images. It is validated by comparing specific surface area determined on dry packings (Mellapak™ 752Y and Katapak™ SP12) tomographic binary images (gas and solid) to values announced by manufacturers, based on geometrical considerations. These data agree fairly well. However, tomographic images show that the specific area is not distributed uniformly over the height of a packing element due to the presence of perforations in corrugated sheets and of wall wipers between the packing and the column wall. X-ray tomography is a unique technique to access to the spatial distribution of these geometrical details in a non-intrusive way. The method used to determine the specific surface area of dry packing is then applied to irrigated packing in order to determine the gas–liquid interfacial area. The axial distribution of the interfacial area is non-uniform and is correlated to the packing specific area. The maxima of the specific surface area correspond to the presence of wall wipers. The gas–liquid interfacial area averaged over the column length is determined. It increases logically with the liquid superficial velocity and slightly with the gas velocity. The effect of the gas velocity is however more pronounced when reaching loading point. [less ▲]

3D characterisation of the structure of activated carbon packed beds using X-ray microtomography

in 3rd International Workshop on Process Tomography (CD Rom) (2009, April)

Lattice Boltzmann 3D flow simulations on a metallic foam

in Journal of Computational & Applied Mathematics (2009)

Positively Cooperative Binding of Zinc Ions to Bacillus cereus 569/H/9 beta-Lactamase II Suggests that the Binuclear Enzyme Is the Only Relevant Form for Catalysis

in Journal of Molecular Biology (2009), 392(5), 1278-1291

Metallo-beta-lactamases catalyze the hydrolysis of most beta-lactam antibiotics and hence represent a major clinical concern. While enzymes belonging to subclass B1 have been shown to display maximum ... [more ▼]

Metallo-beta-lactamases catalyze the hydrolysis of most beta-lactam antibiotics and hence represent a major clinical concern. While enzymes belonging to subclass B1 have been shown to display maximum activity as dizinc species, the actual metal-to-protein stoichiometry and the affinity for zinc are not clear. We have further investigated the process of metal binding to the beta-lactamase H from Bacillus cereus 569/H/9 (known as BcII). Zinc binding was monitored using complementary biophysical techniques, including circular dichroism in the far-UV, enzymatic activity measurements, competition with a chromophoric chelator, mass spectrometry, and nuclear magnetic resonance. Most noticeably, mass spectrometry and nuclear magnetic resonance experiments, together with catalytic activity measurements, demonstrate that two zinc ions bind cooperatively to the enzyme active site (with K-1/K-2 >= 5) and, hence, that catalysis is associated with the dizinc enzyme species only. Furthermore, competitive experiments with the chromophoric chelator Mag-Fura-2 indicates K-2 < 80 nM. This contrasts with cadmium binding, which is clearly a noncooperative process with the mono form being the only species significantly populated in the presence of 1 molar equivalent of Cd(II). Interestingly, optical measurements reveal that although the apo and dizinc species exhibit undistinguishable tertiary structural organizations, the metal-depleted enzyme shows a significant decrease in its alpha-helical content, presumably associated with enhanced flexibility. (C) 2009 Elsevier Ltd. All rights reserved. [less ▲]

Simulations of Structures in Packed Columns and Validation by X-ray Tomography

in Industrial & Engineering Chemistry Research (2009), 48(1), 202-213

Packing simulations of generic, nonspherical pellets were performed and compared with experimental data sets obtained using X-ray Computerized tomography (CT). Two modified versions of what was previously ... [more ▼]

Packing simulations of generic, nonspherical pellets were performed and compared with experimental data sets obtained using X-ray Computerized tomography (CT). Two modified versions of what was previously a purely geometrical, digitally based packing algorithm were implemented. Both are aimed at incorporating the effects of particle interaction forces, one utilizing the distinct element method (DigiDEM) and the other an intermediate solution (collision-guided packing or DigiCGP). This article summarizes the models and the simulations performed using these two modified versions of DigiPac and, for model validation purposes, compares the predicted results with the corresponding X-ray tomographic scans of packed columns, in terms of bulk density, local packing density profiles, and pellet orientation distributions. For packed beds of relatively large and identical pellets, the simulation results indicate that particle-particle and particle-wall interactions cannot be ignored if realistic packing structures are to be obtained by simulation and even a simplistic treatment of these interactions can produce significantly more realistic packing structure than none at all. [less ▲]

Architecture of a Grid-Enabled Lattice-Boltzmann Middleware

Poster (2008, May)

Lattice-Boltzmann (LB) simulation methods constitute a family of computational fluid dynamics methods that can deal with complex multiphysics models and are easily parallelizable. They are based on ... [more ▼]

Lattice-Boltzmann (LB) simulation methods constitute a family of computational fluid dynamics methods that can deal with complex multiphysics models and are easily parallelizable. They are based on modified lattice-gas automata. The algorithm of LB simulations is quite simple. Space is discretized into a lattice. Each node of this lattice has a state. This state indicates the proportion of particules moving along fixed directions (these proportions are generally called “fields”). At each time step, the state of all lattice nodes is updated. Each node first receives fields coming from its neighbors and then “collides” them by applying a collision operator which generates the new state. Grid computing can be defined as “coordinated resource sharing and problem solving in dynamic, multi-institutional collaborations”. In practice, a Grid user (which can be a software component) submits a job composed of tasks to the Grid. The tasks are automatically run on available computational resources across organizational boundaries (i.e. clusters of multiple departments). LaBoGrid is an application combining the concepts of LB modelling and Grid computing. It is able to run LB simulations on an arbitrary number of computational resources from a Grid. It deals with operating system and hardware performance heterogeneity. The former because LaBoGrid is written in Java. The latter thanks to load-balancing. This is essential because all LaBoGrid tasks are inter- connected and depend on information from one another. A slow LaBoGrid task will slow down the overall process. LaBoGrid is based on asynchronous agents exchanging messages. The two main agents are the Controller agent (CA) and the distributed agent (DA). In a deployed LaBoGrid system, the CA exists in only one instance. It keeps track of the DAs and their topology. A task agent running some arbitrary code can be attached to the CA (CAT) and the DAs (DAT). In LaBoGrid, LB-specialized task agents are used (this system could be adapted to other problems). A configuration file parsed by the LB CAT gives the parameters of an LB simulation. The LB CAT configures automatically the LB DATs which handle the simulation code. Currently, LB simulations are done on 3D fluids with 19 fields per state. However, the code can be adapted very easily to other fluid dimensions and different state definitions, storage and computation precisions and collision types. [less ▲]

In situ observation of wall effects in activated carbon filters by X-ray microtomography

in Separation & Purification Technology (2008), 64(1), 127-130

X-ray microtomography is a powerful non-invasive visualisation technique which can be advantageously used to get a better understanding or dynamic adsorption processes. In the present work, this technique ... [more ▼]

X-ray microtomography is a powerful non-invasive visualisation technique which can be advantageously used to get a better understanding or dynamic adsorption processes. In the present work, this technique is shown to be able to detect wall effects during the dynamic adsorption of methyl iodide on activated carbon filters. The analysis of transversal cross-sections along the filter height clearly shows the existence of radial concentration profiles. These radial adsorption profiles are directly linked to velocity profiles due to a higher permeability at the wall. Obtaining Such in situ information constitutes a real progress in order to validate simulation models allowing predicting reliable breakthrough times. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

Intérêt de la microtomographie à rayons X pour la formulation de produits agroalimentaires

in SFGP (Ed.) Récents progrès en génie des procédés N° 96 2007 : actes du 11° Congrès de la Société Française de Génie des Procédés 9-10-11 Octobre 2007, Saint-Étienne, France (2007, October)

A Grid-enabled Lattice-Boltzmann-based modelling system

in Wyrzykowski, Roman; Dongarra, Jack; Karczewski, Konrad (Eds.) et al Parallel Processing and Applied Mathematics (2007, September)

Lattice-Boltzmann (LB) methods are a well-known technique in the context of computational fluid dynamics. By nature, they can eas- ily be parallelized but their adaptation to the Grid environment is not ... [more ▼]

Lattice-Boltzmann (LB) methods are a well-known technique in the context of computational fluid dynamics. By nature, they can eas- ily be parallelized but their adaptation to the Grid environment is not trivial due to hardware heterogeneity (CPU, memory. . . ) in a Grid. A load balancing method to dynamically handle the differences in terms of CPU number and power among the machines of a Grid is presented. The CPU power is dynamically estimated using a benchmark. An estimation method of execution time is also given. [less ▲]