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External Loop Airlift Bubble Column (external + loop_airlift_bubble_column)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Effect of Suspended Liposomes on Hydrodynamic and Oxygen Transfer Properties in a Mini-Scale External Loop Airlift Bubble Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006
M. Yoshimoto
Abstract The circulating liquid velocity, gas holdup, bubble size distribution, and liquid phase oxygen transfer coefficient were measured in a mini-scale external loop airlift bubble column (MELBC) with the liquid volume suspending enzyme-free liposomes of varying diameters. These values were compared to those for liposome-free MELBC, normal bubble column (NBC), and a larger scale airlift column. The liposomes suspended in the MELBC are incorporated into the liquid film around the bubbles, leading to the development of a foam layer, where the incorporated liposomes exert negligible effect on the oxygen transfer in the film. [source]

Measurement and Correlation of Critical Gas and Liquid Velocities for Complete Circulation of Solid Particles in External Loop Airlift Bubble Columns

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003
Katsumi Nakao
Abstract The external loop airlift bubble column provides an easy way of good contacting among gas, liquid and solid phases due to a relatively high recirculating liquid velocity UL. The critical gas and liquid velocities for complete circulation of solid particles, UG,C and UL,C, were measured in two different scales of columns with air, tap water and aqueous CMC solutions, and ion exchange resin and glass beads (155,3834 µm) were employed. The UG,C was determined as the inflection point on the plot of the pressure drop due to the suspended solid particles in the downcomer as a function of the gas velocity UG. The critical liquid velocity UL,C corresponding to the UG,C was obtained from the measured relationship between UL and UG. As a result, a unified dimensionless empirical correlation of UL,C was obtained within an error of ±20% and a dimensionless empirical relationship between UL and UG was developed within an error of ±15%. La colonne à bulles de type airlift à boucle externe offre un moyen facile pour le contact entre les phases gazeuse, liquide et solide grâce à la vitesse de liquide en recirculation UL relativement élevée. Les vitesses de gaz et de liquide critiques pour la circulation complète des particules solides, UG,C et UL,C, ont été mesurées dans deux colonnes d'échelle différente avec de l'air, de l'eau du robinet et des solutions aqueuses de CMC, et des billes de verre et de résine échandeuse d'ions (155,3834 µm) ont été employées. La vitesse UG,C est déterminée comme étant le point d'inflexion sur la courbe de la perte de chgarge causée par les particules solides suspendues dans le déversoir en fonction de la vitesse de gaz UG. La vitesse de liquide critique UL.C correspondant à la vitesse UG.C est obtenue à partir de la relation mesurée entre UL et UG. Ainsi, on obtient une corrélation empirique adimensionnelle unifiée de UL.C avec une erreur de ± 20% et une relation empirique adimensionnelle entre UL et UG est établie avec une erreur de ±15%. [source]

Glucose Oxidation Catalyzed by Liposomal Glucose Oxidase in the Presence of Catalase-Containing Liposomes

BIOTECHNOLOGY PROGRESS, Issue 3 2006
Makoto Yoshimoto
A catalase-containing liposome (CAL) was prepared and characterized in terms of stability during storage and catalysis of the decomposition of hydrogen peroxide (H2O2) that was initially added or produced in the oxidation of glucose catalyzed by the glucose oxidase-containing liposomes (GOL). The reactors used were a test tube and an external loop airlift bubble column as the static liquid and circulating liquid flow systems, respectively. The free catalase (CA) at low concentrations was unstable during storage at 4 °C as a result of dissociation of the tetrameric CA subunits. On the other hand, the deactivation of the CA activity in the CAL was depressed because of the high CA concentration in the CAL liposome. The CAL effectively catalyzed the repeated decompositions at 25 °C with 10 mM H2O2 added initially, whereas the free CA was significantly deactivated during the repeated reactions. The high stability of the CAL was attributed to the moderately depressed reactivity, which was essentially derived from the diffusion limitation of the CAL membrane to H2O2 in the liquid bulk. In the GOL-catalyzed prolonged oxidation of 10 mM glucose at 40 °C in the static liquid in a test tube, both the free CA and CAL could continuously catalyze the decomposition of H2O2 produced. This was because the glucose oxidation rate was small due to the limited reactivity of the GOL to glucose with its low permeability through the GOL membrane. In the glucose oxidation catalyzed by the GOL with the free CA or the CAL in the airlift, much larger oxidation rates were observed compared to those in the test tube because the permeability of the GOL membrane to glucose was increased in the gas-liquid two phase flow in the airlift. The GOL/CAL system in the airlift operated in an acidic condition, which was preferable to the GO activity, gave the largest oxidation rate with negligible accumulation of the H2O2 produced. On the other hand, the GOL/free CA system gave an oxidation rate smaller than that of the GOL/CAL system even under the acidic condition due to an unfavorable interaction of the free CA molecules with the GOL membranes leading to the decreased reactivity of the GOL. [source]