Mechanism, onset and intensity of surface aeration in geometrically‐similar, sparged, agitated vessels

Veljković, Vlada B.; Bicok, K. M.; Simonović, Dušan

doi:10.1002/cjce.5450690414

Cited by 12 publications

(12 citation statements)

References 9 publications

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“…It was found that the creation of a vortex, which is advantageous for drawing down the floating solids, is not easy under aerated conditions (Bakker and Frijlink, 1989). Veljkovic et al (1991) …”

Section: Comparison With Literaturementioning

confidence: 97%

Stirring as foam disruption (SAFD) technique in fermentation processes

Hoeks

Wees-Tangerman²,

Luyben³

et al. 1997

Can J Chem Eng

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Foam reduction through stimng was studied in 20 L bioreactors with artificial media and with an actual biotransformation process. For a given stirrer configuration and within a certain range of the broth mass, the foam height was correlated with the broth mass, i.e. the distance between upper stirrer and dispersion surface, and with the superficial gas velocity. Increasing the stirrer speed often resulted in reducing the foam height. A mechanistic model was developed for the Stirring As Foam Disruption (SAFD) technique, relating the foam height to the horizontal liquid velocity near the dispersion surface. The model illustrates the general applicability of the SAFD technique and points to foam entrainment as the major mechanism for the foam disruption.On a etudie la reduction du moussage par I'agitation dans des bioreacteurs de 20 1 avec des milieux artificiels et avec un procede de biotransformation reel. Pour une configuration d'agitateur donnee et dans une certaine gamme de masse de bouillon de culture, la hauteur de mousse a ete correlee a la masse de bouillon, soit la distance entre I'agitateur superieur et la surface de dispersion, ainsi qu'a la vitesse de gaz superficielle. Augmenter la vitesse de l'agitateur conduit souvent a la reduction de la hauteur de mousse. Un modele mecanistique a ete mis au point pour la technique de desintkgration de mousse par agitation (SAFD); ce modele relie la hauteur de mousse a la vitesse liquide horizontale pres de la surface de dispersion. Le modele illustre I'applicabilite generale de la technique SAFD et suggere que I'entrainement de la mousse est le mecanisme essentiel de la desintegration de la mousse.

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Section: Comparison With Literaturementioning

confidence: 97%

Stirring as foam disruption (SAFD) technique in fermentation processes

Hoeks

Wees-Tangerman²,

Luyben³

et al. 1997

Can J Chem Eng

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“…The mass transfer coefficients of the multiple impeller system reported by Matsumura et al (1982b) appears to be superior as compared to the other designs. Wu (1995) has shown that submergence is an important parameter, and mass transfer coefficient decreases rapidly with an increase in the submergence. 5.…”

Section: Discussionmentioning

confidence: 98%

“…Whereas, the PdP, ratio for the bottom impeller was correlated with the aeration number. Wu (1995) has shown that, for a disc turbine located very close to the free liquid surface, the power number could be correlated with the Froude number. He has also shown that there was no effect of tank diameter on the power consumption.…”

Section: Power Consumptionmentioning

confidence: 97%

“…Keeping these results in mind, it becomes clear that, for achieving high rates of gas entrainment, and in turn, other performance characteristics, it is advisable to keep the impeller close to the top liquid surface (about 100-200 nini below the liquid surface), irrespective of the scale of operation. Wu (1995) has shown, qualitatively, the flow pattern produced by a disc turbine when located close to the top liquid surface. From these flow patterns it can be seen that the gas hold-up is quite high near the impeller, but the gas dispersion is poor in a major portion below the impeller.…”

Section: Selection Of the Geometry For Desired Design Objectivesmentioning

confidence: 97%

“…The effect of the lower impeller speed was not explicitly investigated, and this could result in a negative value of the exponent. Albal et al (1983) Wu (1995) has investigated the use of a disc turbine located near the free liquid surface. The mass transfer coefficients were calculated by absorption of oxygen in sodium sulfite solution.…”

Section: Fractional Gas Hold-up and Interfacial Areamentioning

confidence: 99%

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Design of stirred vessels with gas entrained from free liquid surface

Patwardhan

Joshi

1998

Can J Chem Eng

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In this review, the literature on surface aerators is critically analysed. In a number of studies, the critical speed for the onset of surface aeration has been correlated with the geometry of the system and the operating conditions. The studies on the rate of surface aeration, gas hold-up, mass transfer coefficients are inadequate for the design and scale-up. A comparison of the available designs, in terms of gas hold-up, and mass transfer coefficient is presented. A mathematical model has been proposed for surface aeration. Guidelines

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Oxygen transfer in intensive microbial culture

Fyferling

Uribelarrea

Goma

et al. 2008

Bioprocess Biosyst Eng

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Oxygen transfer performances in intensive microbial cultures are compared with those occurring in coalescing and non-coalescing mineral media. E. coli fed-batch cultures are carried out in a 22 L bioreactor. Biomass concentrations of 80 g(DW) L(-1) are reached, with oxygen consumption rates of up to 0.6 mol L(-1) h(-1). To achieve these high transfer performances, dissipated power e reaches 35 kW m(-3). The hold-up in the culture broth and in the corresponding supernatant matches the non-coalescing mineral medium. Oxygen transfer coefficients, K (L) a in mineral media, and K (T) in the culture broth, are compared. K (T), calculated online from a gas balance method, excesses 1 s(-1). Yet, for given values of e, K (T) is 4-8 times lower than K (L) a determined in the non-coalescing mineral medium. The cell activity modifies the chemical medium properties and reduces the oxygen transfer conductance, as in a non-coalescing ionic medium containing surfactant.

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Mechanism, onset and intensity of surface aeration in geometrically‐similar, sparged, agitated vessels

Cited by 12 publications

References 9 publications

Stirring as foam disruption (SAFD) technique in fermentation processes

Stirring as foam disruption (SAFD) technique in fermentation processes

Design of stirred vessels with gas entrained from free liquid surface

Oxygen transfer in intensive microbial culture

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