Maximum stable drop size measurements indicate turbulence attenuation by aeration in a 3m3 aerated stirred tank

Daub, Adrian; Böhm, Melanie; Delueg, S.; Mühlmann, Martina; Schneider, Gerhard; Büchs, Jochen

doi:10.1016/j.bej.2014.02.006

Cited by 12 publications

(20 citation statements)

References 46 publications

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“…The experimental method based on the measurement of maximum stable drop sizes was successfully applied in a 3 m 3 pilot scale reactor with 1.2 m inner diameter to investigate the influence of aeration on the maximum local energy dissipation rate. The results were reported in Daub et al [ 24 ]. It was shown for impeller configurations B-1 and B-3 (for geometrical details see Table 2 ) that energy dissipation in the impeller region is much less intense for aerated operating conditions than for unaerated operating conditions when compared at equal volumetric power input.…”

Section: Introductionsupporting

confidence: 74%

“…It was already reported in Daub et al [24] for configurations B-1 and B-3 that if results are compared on the basis of aerated volumetric power input the aeration rate has no relevant influence on the maximum stable drop size in the investigated range. Hence, with aerated volumetric power input as the correlating parameter, the influence of aeration on energy dissipation is directly reflected.…”

Section: Resultsmentioning

confidence: 80%

“…The results were reported in Daub et al [24]. It was shown for impeller configurations B-1 and B-3 (for geometrical details see Table 2) that energy dissipation in the impeller region is much less intense for aerated operating conditions than for unaerated operating conditions when compared at equal volumetric power input.…”

Section: Introductionmentioning

confidence: 60%

“…Power numbers were estimated with Eq. 10, except for setup B-1 and B-3 for which Power numbers could be measured. a for 0.1 vvm aeration rate: 2.6 m 3 , see Daub et al [24]. …”

Section: Introductionmentioning

confidence: 99%

“…Most available data was measured in lab scale with low agitation intensity. A review on existing data for maximum local energy dissipation was presented in [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of hydromechanical stress in aerated stirred tanks up to 40 m3 scale by measurement of maximum stable drop size

et al. 2014

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BackgroundTurbulence intensity, or hydromechanical stress, is a parameter that influences a broad range of processes in the fields of chemical engineering and biotechnology. Fermentation processes are often characterized by high agitation and aeration intensity resulting in high gas void fractions of up to 20% in large scale reactors. Very little experimental data on hydromechanical stress for such operating conditions exists because of the problems associated with measuring hydromechanical stress under aeration and intense agitation.ResultsAn indirect method to quantify hydromechanical stress for aerated operating conditions by the measurement of maximum stable drop size in a break-up controlled dispersion was applied to characterize hydromechanical stress in reactor scales of 50 L, 3 m3 and 40 m3 volume with a broad range of operating conditions and impeller geometries (Rushton turbines). Results for impellers within each scale for the ratio of maximum to specific energy dissipation rate ϕ based on measured values of maximum stable drop size for aerated operating conditions are qualitatively in agreement with results from literature correlations for unaerated operating conditions. Comparison of data in the different scales shows that there is a scale effect that results in higher values for ϕ in larger reactors. This behavior is not covered by the classic theory of turbulent drop dispersion but is in good agreement with the theory of turbulence intermittency. The data for all impeller configurations and all aeration rates for the three scales can be correlated within ±20% when calculated values for ϕ based on the measured values for dmax are used to calculate the maximum local energy dissipation rate. A correlation of the data for all scales and all impeller configurations in the form ϕ = 2.3∙(ϕunaerated)0.34∙(DR)0.543 is suggested that successfully models the influence of scale and impeller geometry on ϕ for aerated operating conditions.ConclusionsThe results show that besides the impeller geometry, also aeration and scale strongly influence hydromechanical stress. Incorporating these effects is beneficial for a successful scale up or scale down of this parameter. This can be done by applying the suggested correlation or by measuring hydromechanical stress with the experimental method used in this study.

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Section: Introductionsupporting

confidence: 74%

Section: Resultsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 60%

“…Power numbers were estimated with Eq. 10, except for setup B-1 and B-3 for which Power numbers could be measured. a for 0.1 vvm aeration rate: 2.6 m 3 , see Daub et al [24]. …”

Section: Introductionmentioning

confidence: 99%

“…Most available data was measured in lab scale with low agitation intensity. A review on existing data for maximum local energy dissipation was presented in [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

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