Mixing in bubble column

Zahradnik, J. and M. Fialova, The effect of bubbling regime on gas and liquid phase mixing in bubble column reactors. Chemical Engineering Science, 1996. 51(10) p. 2491-2500. 

In some respects, airlift reactors (airlifts) can be regarded as modifications ofthe bubble column. Airlift reactors have separate channels for upward and downward fluid flows, whereas the bubble column has no such separate channels. Thus, fluid mixing in bubble columns is more random than in airlift reactors. There are two major types of airlift reactors, namely, the internal loop (IL) and the external loop (EL). 

In contrast with this - and in analogy to the corresponding findings in the mixing vessel - the mixing (back-mixing) in bubble columns cannot be described by the intensively formulated quantity v. For this scale-up task, the Froude number is competent here. 

Ulbrecht, J. J. Baykara, Z. Sema "Liquid Phase Mixing in Bubble Columns with Dilute Polymer Solutions," paper presented at ACS Las Vegas Meeting, August 1980. 

A useful description of mixing in bubble columns is provided by the dispersion model. The global mixing effects are generally characterized by the dispersion coefficients El and Eq of the two phases which are defined in analogy to Fick s law for diffusive transport. Dispersion in bubble columns has been the subject of many investigations which have recently been reviewed by Shah et al. (45). Particularly, plenty of data are available for liquid-phase dispersion. 

Two main types of models are in common use for describing axial mixing in bubble columns. The most commonly used model is the Dispersion Model. Here, a diffusion-like process is superimposed on piston or plug flow. The stirred tanks-in-series model has also been used to describe flow of liquids in bubble columns. Levenspiel (1 ) presents a number of models incorporating various combinations of mixed tanks to model stagnant regions and backflow. 

Correlations and Theories for Axial Mixing in Bubble Columns... 

Ranade, V.V. (1993a), Turbulent flow and mixing in bubble columns, Proc. European Symposium on Computer Aided Process Engineering - 3, Eds Moser, F., Schnitzer and Bart, H. J., pp. 27-31. 

Buwa VV, Ranade VV (2003) Mixing in Bubble Column Reactors Role of Unsteady Flow Structures. Canadian J Chem Eng 81(3-4) 402-411. 

Liquid mixing in bubble columns is a result of global convective re-circulation of the liquid phase and turbulent diffusion due to eddies generated by the rising bubbles. By structuring the gas and the liquid flow, HyperCat reduces the axial dispersion for both phases leading to a large reduction in axial dispersion coefficients (Dax)- The real benefit of this reduced dispersion is that it is not a function of the colunm diameter (Dc) as is the case with conventional bubble colunm reactors. 

Hikita, H., andKikukawa, H. (1974), Liquid-phase mixing in bubble columns Effect of liquid properties, Chemical Engineering Journal and the Biochemical Engineering Journal, 8(3) 191-197. 

Le6n-Becerril, E., Cockx, A., and Lind, A. (2002), Effect of bubble deformation on stability and mixing in bubble columns, Chemical Engineering Science, 57(16) 3283-3297. 

Lorenz, O., Schumpe, A., Ekambara, K., and Joshi, J.B. (2005), Liquid phase axial mixing in bubble columns operated at high pressures, Chemical Engineering Science, 60(13) 3573. 

Garcia-Calvo E, Leton P. (1994) Prediction of fluid dynamics and liquid mixing in bubble columns. Chem. Eng. Sci., 49 3643-3649. 

Recently, Garcla-Calvo and Letdn [24] proposed a model for liquid mixing in bubble columns on the basis of an energy balance and suggested ... 

Degaleesan S Turbulence and liquid mixing in bubble columns (Doctoral dissertation), St. Louis, MO, 1997, Washington University. 

Chen, B. H. Holdup and Axial Mixing in Bubble Columns Containing Screen Cylinder. Ind. Eng. Chem. Process Des. 

Literature about axial mixing in bubble columns is quite extensive, i.e. (1), (2), (3). Unfortunately most of the publications refer to column diameters of less than 200 mm. Only a few studies have been done on bubble columns of large diameter. Argo and Cova (4) as well as Towell and Ackermann (5) have studied empty bubble columns up to a diameter of 1 m. No literature is known about packed columns of this size. The largest diameter packed columns studied by Carleton et al. (6) and by Hoogendoorn et al. (7) had a diameter of less than 0.5 m. 

Figure 4. Axial mixing in bubble columns—effect of diameter...

Figure 5. Axial mixing in bubble columns —effect of gas flow rate...

Ulbrecht, J. J. and Baykara, Z. S. (1981) Significance of the Central Plume Velocity for the Correlation of Liquid Phase Mixing in Bubble Columns , Chem. Eng. Comm. 10, 165-168. 

J., Fletcher, D., and Barton, G. (2015) Mixing in bubble column reactors experimental study and CFD modeling. Chem. Eng. /, 264, 291-301. 

Buwa VV, Ranade W (2002) Dynamics of gas-hquid flow in a rectangular bubble column experimental and single/multigroup CFD simulations. Chem Eng Sci 57(22-23) 4715-4736 Buwa W, Ranade W (2003) Mixing in bubble column reactors role of unsteady flow structures. Canadian J Chem Eng 81(3-4) 402- ll... 

Bai W, Deen NG, KuipersJAM Numerical investigation of gas holdup and phase mixing in bubble column reactors, Ind Eng Chem Res 51 1949—1961, 2012. 

Hikita H, Kikukawa H Liquid-phase mixing in bubble columns effect of liquid properties, Chem 9 171-174, 1974. 

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