Impeller-agitated aerobic reactor: The influence of tiny bubbles on gas hold-up and mass transfer in highly viscous liquids

Khare, A.S.; Niranjan, Keshavan

doi:10.1016/0009-2509(94)00474-6

Cited by 22 publications

(24 citation statements)

References 12 publications

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“…This last behavior is identical with that obtained with Rushton turbines 19 and can be attributed to the nearly bimodal bubble-size distribution: 5,34,35 while the smallest bubbles are easily entrained in the circulating liquid, the bigger ones reside in the tank for a shorter time. 13 The model is not adequate, therefore, to describe these systems; no attempt was made to interpret these conditions with a more reliable one.…”

Section: Influence Of Working Conditions and System Properties Onsupporting

confidence: 82%

“…The extent of this overall change is higher with higher viscosity (up to the maximum value investigated of 120 mPa‚s). This is likely related to the variable structure of the holdup with operating parameters and viscosity 5,34 and its complex relationship with the overall circulation, coalescence rate, and liquid entraining capability for the gas. Because of this complexity, no simple mathematical link between these parameters was found.…”

Section: Influence Of the Working Conditions Andmentioning

confidence: 99%

“…This behavior is similar to that already noticed with Newtonian 35 and pseudoplastic liquids. 36 Increasing the viscosity is apparently responsible for the change in bubble size and bubble-size distribution, 34 which in turn affects holdup.…”

Section: Influence Of the Working Conditions Andmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of the Fluid Dynamic Behavior of the Liquid and Gas Phases in Reactors Stirred with Multiple Hydrofoil Impellers.

Pinelli¹,

Magelli²

2000

Ind. Eng. Chem. Res.

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Liquid-and gas-phase macromixing behavior was studied in gas-liquid high-aspect-ratio reactors stirred with multiple hydrofoil impellers pumping downward. Water, a sodium sulfate solution, and poly(vinylpyrrolidone) solutions of viscosity up to 110 mPa‚s were used as the liquid. For characterizing the liquid phase, mixing time experiments were conducted at various operating conditions, while detecting the response curves at several positions inside the tank. Comparison of the experimental curves with the theoretical ones provided by simple fluid dynamic models showed that the axial dispersion model is quite acceptable. The influence of impeller speed, gas flow rate, and viscosity on the model parameter was studied, and dimensionless relationships are given. The gas behavior was studied by means of the RTD and modeled with the axial dispersion model, which proved good for water and acceptable with coalescence-inhibiting electrolyte solutions. The model parameter dependence on the operating conditions was studied.Comparison between hydrofoil impellers and radial Rushton turbines is also attempted.

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Section: Influence Of Working Conditions and System Properties Onsupporting

confidence: 82%

Section: Influence Of the Working Conditions Andmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of the Fluid Dynamic Behavior of the Liquid and Gas Phases in Reactors Stirred with Multiple Hydrofoil Impellers.

Pinelli¹,

Magelli²

2000

Ind. Eng. Chem. Res.

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“…16 Some workers14, 16 have considered that the irregularity in the effect of µ on ϕ gD may be brought about mainly by differences in bubble characteristics, depending on the range of µ. Other observations reported17–19 include the fact that in viscous liquids, while many tiny bubbles (diameter of the order of 0.1–3 mm) tend to accumulate during aeration and circulate with the liquid, large bubbles of the order of 10 mm or greater are also liable to form in the bulk liquid. This suggests that the gas hold‐up structure in the system with aerated viscous liquids may be bimodal.…”

Section: Resultsmentioning

confidence: 99%

Flow and mass transfer in aerated viscous Newtonian liquids in an unbaffled agitated vessel having alternating forward–reverse rotating impellers

Yoshida

Yamagiwa

Ito

et al. 2001

J of Chemical Tech & Biotech

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Flow and mass transfer characteristics in aerated viscous Newtonian liquids were studied for an unbaf¯ed aerated agitated vessel with alternating rotating impellers (AAVAI), ie with multiple forward±reverse rotating impellers having four delta blades. The effects of operating conditions such as gas sparging rate, agitation rate and the number of impeller stages, and the liquid physical properties (viscosity) on the gas hold-up, f gD , and volumetric oxygen transfer coef®cient, k L a D were evaluated experimentally. The dependences of f gD and k L a D on the speci®c total power input and super®cial gas velocity differed, depending on the ranges of liquid viscosity. Empirical relationships are presented for each viscosity range to predict f gD and k L a D as a function of the speci®c total power input, super®cial gas velocity and viscosity of liquid. Based on a comparative investigation of the volumetric coef®cient in terms of the speci®c total power input between the AAVAI and conventional aerated agitated vessels (CAAVs) having unidirectionally rotating impellers, the usefulness of AAVAI as a gas±liquid agitator treating viscous Newtonian liquids is also discussed.

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“…In addition, in such fluids, the gas hold-up structure is known to be very different from the one observed in water and other low-viscosity liquids: many tiny bubbles appear to accumulate during aeration and circulate with the liquid while large bubbles are also observed (bimodal bubble population). These tiny bubbles can actively contribute to mass transfer, depending whether they are in equilibrium with the level of dissolved solute in the liquid phase (high residence times) or not [26].…”

Section: Chemical Methodsmentioning

confidence: 99%

A consistent dimensional analysis of gas–liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties

Hassan

Loubière

Legrand

et al. 2012

Chemical Engineering Journal

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Delaplace. A consistent dimensional analysis of gas-liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties. Chemical Engineering Journal, Elsevier, 2012Elsevier, , vol. 184, pp.42-56. <10.1016Elsevier, /j.cej.2011 a b s t r a c tThis paper deals with gas-liquid mass transfer in an aerated stirred tank containing Newtonian or shearthinning fluids. The aim is to demonstrate that, for a given mixing system, an unique dimensionless correlation gathering all the mass transfer rates (150 k l a measurements) can be obtained if and only if the variability of the rheological material parameters is correctly considered when implementing the theory of similarity. More particularly, it is clearly illustrated that a too gross simplification in the relevant list of the parameters characterizing the dependence of apparent viscosity with shear rates leads to pitfalls when building the -space set. This is then a striking example showing that a robust predictive correlation can be established when the non-constancy of fluid physical properties ceases to be neglected.

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Impeller-agitated aerobic reactor: The influence of tiny bubbles on gas hold-up and mass transfer in highly viscous liquids

Cited by 22 publications

References 12 publications

Analysis of the Fluid Dynamic Behavior of the Liquid and Gas Phases in Reactors Stirred with Multiple Hydrofoil Impellers.

Analysis of the Fluid Dynamic Behavior of the Liquid and Gas Phases in Reactors Stirred with Multiple Hydrofoil Impellers.

Flow and mass transfer in aerated viscous Newtonian liquids in an unbaffled agitated vessel having alternating forward–reverse rotating impellers

A consistent dimensional analysis of gas–liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties

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