Modelling of the liquid distribution in a trickle flow packed column based upon X-ray tomography images

in Chemical Engineering Communications (1999), 175

X-ray tomography is used to characterise the liquid distribution in a 0.6 meter diameter and 2 meter height column filled with gas-liquid absorption polypropylene packing elements (Cascade Mini-Ring 1A ... [more ▼]

X-ray tomography is used to characterise the liquid distribution in a 0.6 meter diameter and 2 meter height column filled with gas-liquid absorption polypropylene packing elements (Cascade Mini-Ring 1A, Glitsch Benelux). The liquid holdup distribution is determined for liquid flowrates ranging from 1000 l/h to 6000 l/h, that correspond to superficial velocities ranging from 10(-3) to 6 10(-3) m/s, in several cross sections situated at different heights in the packed column. A characteristic length, corresponding to the smallest scale beyond which the packing properties may be supposed statistically homogenous and isotropic, as determined by Means of the autocorrelation function method applied to the images of the solid distribution. Both local and global liquid holdup measurements are satisfactorily modelled by means of a partial wetting model based on a probabilistic approach. [less ▲]

Local measurements of void fraction and liquid holdup in packed columns using X-ray computed tomography

in Chemical Engineering & Processing (1998), 37(6), 511-520

A 'tailor made' computed X-ray tomographic scanner has been developed as a tool for the analysis of the distribution of gas, liquid and solid phases in packed columns. The very good spatial resolution of ... [more ▼]

A 'tailor made' computed X-ray tomographic scanner has been developed as a tool for the analysis of the distribution of gas, liquid and solid phases in packed columns. The very good spatial resolution of the scanner has first been assessed by the imaging of objects of known shape and size, called 'physical' phantoms. Images have then been realized on a 0.6 m diameter and 2 m height column packed with Cascade Mini-Ring 1A packing elements, which is a random polypropylene packing designed to be used in absorption columns. The solid phase distribution, leading to the void fraction distribution, has been analyzed on cross-section images of the dry packed column (without any liquid flowrate). The measured value of the bed void fraction is equal to the value provided by the manufacturer. The analysis of the axial profile of void fraction shows that the 'end effect' may be neglected, whereas the analysis of the radial profile evidences the existence of a non negligible 'wall effect'. Images have then been carried out on the packed column irrigated by a liquid flowrate ranging between 0 and 6000 1 h(-1) (0-6.10(-3) m s(-1)). Hold-up values have been measured in different cross-sections of the column and averaged in order to obtain the total hold-up value in the bed. The computed values are in very good agreement with those reported in the literature for similar packing. The dependence of the liquid hold-up on the liquid superficial velocity can be expressed in terms of a power law. The fitted value of the exponent, equal to 0.65, is in the range of exponent values found in correlations of the literature. (C) 1998 Elsevier Science S.A. All rights reserved. [less ▲]

X-ray tomography in random packings

Scientific conference (1997, September 30)

Modelling of the liquid distribution in a packed column based upon X-ray tomography images

Conference (1997)

Oxydation photochimique de lixiviats de décharge

in Tribune de l'Eau (La) (1997), 590-591

L'hydrodynamique dans les lits bactériens : le rôle du garnissage

Conference (1996)

Computer-assisted tomography for liquid imaging in trickle-flow columns

in Non-invasive Monitoring of Multiphase Flows (1996)

Modelling of multiphase flow in packed beds by computer-assisted x-ray tomography

in Measurement Science & Technology (1996), 7(3), 436-443

The high resolution which can be obtained by computer-assisted x-ray tomography is used to investigate Various scale heterogeneities of the flow texture characterizing multiphase flow in packed beds. The ... [more ▼]

The high resolution which can be obtained by computer-assisted x-ray tomography is used to investigate Various scale heterogeneities of the flow texture characterizing multiphase flow in packed beds. The direct counting of 'irrigated' pixels allows the determination of the number of individual liquid rivulets as well as their size. The evolution of the liquid flow texture versus the liquid velocity agrees quite well with the predictions of a percolation-based model. This agreement is further confirmed by the comparison of the experimental hold-up values averaged over the column cross-section with the theoretical model. [less ▲]

Saturation of Penicillin-Binding Protein 1 by Beta-Lactam Antibiotics in Growing Cells of Bacillus Licheniformis

in Molecular Microbiology (1995), 16(2), 365-72

With the help of a new highly sensitive method allowing the quantification of free penicillin-binding proteins (PBPs) and of an integrated mathematical model, the progressive saturation of PBP1 by various ... [more ▼]

With the help of a new highly sensitive method allowing the quantification of free penicillin-binding proteins (PBPs) and of an integrated mathematical model, the progressive saturation of PBP1 by various beta-lactam antibiotics in growing cells of Bacillus licheniformis was studied. Although the results confirmed PBP1 as a major lethal target for these compounds, they also underlined several weaknesses in our present understanding of this phenomenon. In growing cells, but not in resting cells, the penicillin target(s) appeared to be somewhat protected from the action of the inactivators. In vitro experiments indicated that amino acids, peptides and depsipeptides mimicking the peptide moiety of the nascent peptidoglycan significantly interfered with the acylation of PBP1 by the antibiotics. In addition, the level of PBP1 saturation at antibiotic concentrations corresponding to the minimum inhibitory concentrations was not constant, suggesting that additional, presently undiscovered, factors might be necessary to account for the experimental observations. [less ▲]

Computer assisted X-ray tomography : a tool for fluid distribution analysis in trickle-bed reactors

Conference (1995)