Blasenschwarmverhalten in hochviskosen Flüssigkeiten

Peschke, Günther; Lippert, Jürgen; Zakrzewski, W.; Schügerl, K.

doi:10.1002/cite.330521022

Cited by 5 publications

(5 citation statements)

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“…This last method is discussed thoroughly by Hewitt (1978) and Veteau and Charlot (1981). For columns operated batchwise, simple measurements of the level of the aerated liquid during operation and of the stagnant liquid at rest give the value of the gas hold-up (Akita and Yoshida, 1973;Peschke et al, 1980). The more traditional and still most frequently used methods are the bed expansion and the manometric techniques.…”

Section: Gas Hold-upmentioning

confidence: 99%

“…The more traditional and still most frequently used methods are the bed expansion and the manometric techniques. For columns operated batchwise, simple measurements of the level of the aerated liquid during operation and of the stagnant liquid at rest give the value of the gas hold-up (Akita and Yoshida, 1973;Peschke et al, 1980). This method becomes inaccurate when foam is formed at the surface of the liquid.…”

Section: Gas Hold-upmentioning

confidence: 99%

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Mixing characteristics and gas hold‐up of a bubble column

1986

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The hydrodynamic behavior of a bubble column has been studied for various Newtonian and non-Newtonian liquids (water, glycerol, carboxymethylcellulose and polyacrylamide solutions). The mixing time, the power consumption, the circulation time and the gas hold-up have been measured in a cylindrical column (diameter: 0.254 m, height: 0.9 m) for three air sparger plates with different numbers and distributions of I mm diameter orifices. It is shown that the mixing efficiency decreases as the viscosity or the shear-thinning and clastic properties of the liquid increase. The viscosity of the liquid has little influence on the gas hold-up which is, however, strongly affected by the sparger plate characteristics and increases as the liquid phase becomes more elastic. A model for predicting gas hold-up is proposed.Le comportement hydrodynamique d'une colonne a bulles utilisant diffcrents liquides newtoniens et non-newtoniens (eau, glycerol, solutions de carboxymCthylcellulose et de polyacrylarnide) a ete CtudiC. Le temps dc rndange, la puissance dissipte, le temps de circulation et le taux de vide ont Ct6 determinks dans une colonne cylindrique (diametre: 0.254 m, hauteur: 0.9 m). Trois differents types de distributeur d'air ont Cte utilises. Tous possedent des orifices de 1 mm de diametre, mais le nombre et la repartition des orifices different de I'un i I'autre. On constate que I'efficacite de I'action de melange decroit lorsque la viscositt du liquide augmente ou lorsque ses propriktds rhkofluidisantes et elastiques deviennent plus importantes. La viscositi du liquide a peu d'influence sur le taux de vide observe qui, par contre, varie beaucoup selon le type de plaque distributrice utilisk ct augmente avec le caractere Clastique du liquide. Un mod& pour la prediction du taux de vide est propose. ubble columns are more and more used in the chemical B industry for applications such as reactors, absorbers and extractors. They are flexible and present economic advantages over mechanically stirred columns: low investment and low operating costs. They are particularly attractive for applications in biotechnology where a strong mixing action has to be avoided. However, their use is not as widespread as could be expected (Schugerl et a]., 1977). It seems that the long industrial tradition of using mechanically stirred reactors is still strongly entrenched. Furthermore, well established design criteria are not yet available. Valuable efforts have been made in order to improve the knowledge of bubble column operation and design characteristics. Shah et al. (1982) have presented a thorough review of the recent work in this field.Most reactants in biochemical engineering show a non-Newtonian behavior, sometimes coupled with an elastic behavior. However, few studies have been conducted on bubble columns with non-Newtonian liquids. Chemical reactions, mass or heat transfer processes may be controlled by the hydrodynamics in a bubble column. Hence it is important to determine how the hydrodynamics is affected by the operating condit...

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Section: Gas Hold-upmentioning

confidence: 99%

Section: Gas Hold-upmentioning

confidence: 99%

Mixing characteristics and gas hold‐up of a bubble column

1986

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“…Greek symbols e phase holdup e G established ®nal value of the total gas holdup in the reactor e Gr established ®nal value of the mean total gas holdup in the riser e GLB established ®nal value of the large bubble hold-up e GSB established ®nal value of the small bubble hold-up e GSt small bubble hold-up at the aeration time t e Gt total gas hold-up at the aeration time t Dh difference of the liquid heights in the upper and lower piezometric tubes Dh m distance between the location points of the piezometric tubes g a mPas apparent suspension viscosity g L mPas liquid viscosity q kg.m A3 density Aeration of the highly viscous liquids is especially of important signi®cance in biotechnology. An accumulation of small bubbles was observed during the aeration time of the highly viscous liquids in the bubble column [1,3,5,6,8,12,13,14]. Buchholz et al [1] and Peschke et al [12] found a large number of small bubbles in the aerated carboxymethyl cellulose solutions.…”

Section: B Kawalec-pietrenko W Pietrenkomentioning

confidence: 96%

“…An accumulation of small bubbles was observed during the aeration time of the highly viscous liquids in the bubble column [1,3,5,6,8,12,13,14]. Buchholz et al [1] and Peschke et al [12] found a large number of small bubbles in the aerated carboxymethyl cellulose solutions. Schumpe and Deckwer [14] observed the two-stage disengagement of the bubbles after stopping the gas feeding in the bubble column.…”

Section: B Kawalec-pietrenko W Pietrenkomentioning

confidence: 96%

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

Kawalec-Pietrenko¹,

Pietrenko²

1999

Bioprocess Engineering

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The time-dependent gas hold-up is investigated during the aeration of the Saccharomyces cerevisiae suspension, the aqueous saccharose solutions and the glycerol solutions in the external loop airlift reactor. Due to the time-dependent bubble size distribution the fraction of the small bubble hold-up in the total gas hold-up decreases with an increase of the gas¯ow rate and with a decrease of the viscosity. The course of the accumulation process of the small bubbles is described by the ®rst-order kinetic equation. The small bubble accumulation rate is investigated in the airlift reactor and the bubble column. It is showed that the small bubbles form and disappear exclusively in the riser of the airlift reactor. It is found that the small bubble-liquid mass transfer coef®cient is several times larger than the overall oxygen transfer coef®cient. List of symbolsA d m 2 cross-section of the downcomer A r m 2 cross-section of the riser B, C parameters in the equation (10) D r m diameter of the riser D d m diameter of the downcomer D BC m diameter of the equivalent bubble column with the cross-section area equal to the sum of the riser and the downcomer cross-section areas H m height of the unaerated liquid (suspension) k s A1 accumulation rate constant of the small bubbles k d s A1 disengagement rate constant of the small bubbles k L a SB s A1

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“…Schumm [44] determined interfacial areas in an air-lift loop reactor which, due to the long residence time of the bubbles, were almost within the range of the free jet reactor; here an additional power input is not necessary.…”

Section: Sauter Mean Diametermentioning

confidence: 99%

Mass transfer area in different gas‐liquid reactors as a function of liquid properties

1987

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Using pilot-scale test plant, the interfacial area per unit volume was investigated in different gasliquid reactors, i.e. packed column, bubble column and free jet reactor. The interfacial area was studied as a function of liquid viscosity and of operating parameters. As a rule, identical test conditions were maintained in all the measurements, in order to obtain comparable results. The interfacial area-was determined by chemical means using the sulphite system (a solution of sodium sulphite in water as model liquid and air as gaseous medium). The viscosity of the solution can be increased by adding carboxymethyl cellulose without significantly affecting the reaction kinetics. The addition of a surfactant to the sulphite system allowed comparative measurements at reduced surface tension. Based on a large number of measurements, the correlations of the interfacial area are expressed as power laws. The inclusion of experiments with a jet tube reactor and a stimng vessel allows an extensive comparison of all reactors. All tests were carried out with the same material system and the same method was used to determine the interfacial area per unit volume. Therefore, a comparison with respect to mass transfer is possible.

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Blasenschwarmverhalten in hochviskosen Flüssigkeiten

Cited by 5 publications

References 0 publications

Mixing characteristics and gas hold‐up of a bubble column

Mixing characteristics and gas hold‐up of a bubble column

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

Mass transfer area in different gas‐liquid reactors as a function of liquid properties

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