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A dehydration of fructose in the water/methyl isobuthyl ketone (MIBK) biphasic system can yield 5hydroxymethylfurfural (HMF) to be successfully extracted into the organic MIBK phase. The HMF production and yield in MIBK phase was discussed by using a simplified model taking into consideration of the slug flow. The extraction resistance of HMF across the interface between water and MIBK depended on the line velocity and the flow rate ratio. It was likely that the velocity field generated in the slug flow contributed to an increase in the mass transfer of HMF.

The effects of liquid velocity, nozzle diameter, gas chamber volume and gas flow rate on volumes, shapes and growth curves of bubbles formed at a nozzle submerged in a cocurrently upward flowing liquid in a bubble column were experimentally investigated. The bubble volume decreases with increasing liquid flow velocity. The effect of liquid flow velocity on the volume of bubble increases with an increase in the gas flow rate. To simulate bubble formation at a nozzle submerged in cocurrently upward flowing liquid, a revised non-spherical bubble formation model was proposed. Bubble volumes, bubble growth curves and shapes experimentally obtained in this study, as well as in previous experimental studies, are well predicted by the present model.On a etudie experimentalement les effets de la vitesse du liquide, du diametre de I'orifice, du volume de la chambre a gaz et du debit de gaz sur les volumes, les formes et les courbes de croissance des bulles formees au niveau d'un orifice immerge dans un liquide s'ecoulant a co-courant dans le sens ascendant dans une colonne a bulles. Le volume des bulles decroit avec I'augmentation de la vitesse de I'ecoulement liquide. L'effet de la vitesse de I'ecoulement liquide sur le volume des bulles s'accroit avec une augmentation du debit de gaz. Afin de simuler la formation des bulles au niveau d'un orifice immerge dans un liquide s'ecoulant a co-courant dans le sens ascendant, on propose un modele de formation de bulles non spheriques revise. Les volumes, les formes et les courbes de croissance des bulles obtenus experimentalement dans cette etude, ainsi que dans des etudes experimentales anterieures, sont convenablement predites par le present modele.Keywords: bubble, bubble column, bubble formation, bubble formation model, liquid flow. n many chemical units, such as bubble columns, gas I absorbers and gas-liquid reactors, high-efficient contact of a dispersed gas phase with a liquid continuous phase is very important. To desing well gas-liquid contacting equipment and to operate it under the most suitable conditions, interfacial areas of gas bubbles rising in a column must be estimated. When coalescence and breakage of rising bubbles is negligible, for example the operation with low gas hold-up at low gas flow rate in a bubble column, the bubble size is determined at detachment from a gas distributor. To predict the bubble volume at a gas distributor, many empirical correlation equations and some theoretical models have been proposed, which are reviewed by Tsuge (1986).Almost all studies on bubble formation were done in quiescent liquids. In practical chemical industries, however, continuous operation is more frequently used than batch and semi-batch operations, where not only gases but also liquids are continuously fed into a column. Therefore, it is essential to clarify the bubble formation mechanism in flowing liquids, and to estimate the bubble size.The effect of liquid flow on bubble formation depends on the relation between the direction of the liquid stream and the direct...

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