Measurements with multi‐point microprobes: Effect of suspended solids on the hydrodynamics of bubble columns for application in chemical and biotechnological processes

Abstract

Many experimental studies reveal that suspended solids considerably alter the coalescence behaviour and hydrodynamic functions of two-phase flow. But no systematic efforts have yet been undertaken to separate the effects of different particle properties on local gas hold-up, bubble size and interfacial area gasiliquid. The aim of this paper is to present the local values of these parameters in three-phase fluidized beds of different solids, using miniaturized optical fibre and conductivity needle probes. It is shown that particle concentration, size and, in particular, density are decisive for the change in coalescence behaviour. Ranges of normal (e, > eL) and inverse fluidization (e, < eL) must be distinguished and the flow regime also exerts a strong influence on the interactions between the dispersed phases, the transition point itself being a function of particle properties. For certain combinations of solid parameters, even increased interfacial areas gaslliquid can be observed. This effect is evaluated for different column diameters, between 0.1 and 0.3 m.

Hydrodynamics of a Multi‐Stage Internal Loop Airlift Reactor

“…Furthermore, the mean bubble Sauter diameter increased with increasing gas velocity. This was similar to the results obtained by Okada et al [13] and Wolff et al [14] in the ELALR.…”

Mass Transfer and Diffusion of a Single Bubble Rising in Polymer Solutions

“…Thus the concentration of the dissolved gas can be quantified from the variation of the fluorescence intensity on the recorded images. The pioneering application of PLIF-I was carried out by Wolff et al 8 to measure the concentration gradient near the gas-liquid interface. Then the technique was implemented to visualize the mass transfer around bubbles 9,10 , in the planar gasliquid interface 11,12 , or in Tailor flow 13,14 .…”

“…Thus the concentration of the dissolved gas can be quantified from the variation of the fluorescence intensity on the recorded images. The pioneering application of PLIF-I was carried out by Wolff et al to measure the concentration gradient near the gas–liquid interface. Then the technique was implemented to visualize the mass transfer around bubbles, , in the planar gas–liquid interface, , or in Tailor flow. , Thanks to the discovery of pH-sensitive dye, CO 2 molecules can also act as quenchers and make it possible to visualize the mass transfer for a CO 2 bubble. − In the past 10 years, PLIF-I has proved to be capable of quantifying the mass transfer in the vicinity of a freely rising bubble or in the bubble wake.…”

Production Characteristics of Fullerenes by Means of theJ×BArc Discharge Method

“…Conductivity probes of various types have been constructed and used for measurements of turbulent mixing in the past [8][9][10][11][12]. It should be noted that conductivity probes of similar types have also been used extensively in the past for void-fraction measurements in twophase gas/liquid flows [13][14].…”