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Mixing time in a down-flow jet loop bioreactor

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Mixing time was determined in a down-flow jet loop bioreactor with Newtonian and non-Newtonian fluids. It was observed that the mixing time decreased with an increase in linear liquid velocity, superficial gas velocity, draft tube to column diameter ratio, nozzle diameter and shear thinning of media. The optimum draft tube to column diameter ratio was found to be about 0.44. Correlations were presented for prediction of mixing time.

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A m2 :

cross sectional area of the column

C kmol/m3 :

local tracer concentration

A D m2 :

flow area,A D =π/4 (D Z 2 -D TO 2 )

D m:

column diameter

D E m:

draft tube diameter

D TO m:

outside diameter of the air tube

D TFL m:

equivalent flow diameter,D TFL =(D Z 2 -D TO 2 )0.5

D z m:

nozzle diameter

g m/s2 :

gravitational acceleration

h %:


H m:

height of the column

H B m:

distance between the lower edge of the draft tube and the impact plate

H T m:

distance between the upper edge of the draft tube and the liquid nozzle

K :

consistency index in power-law model

L E m:

length of the draft tube

n :

flow index in the power-law model

Re j :

jet Reynolds number,Re j =(D TFL×w1×ρL)/μ eff

t M s:

mixing time

t sg m/s:

superficial gas velocity based onA

W l m/s:

linear liquid velocity based onD D

τ N/m2 :

shear stress

γ s:

shear rate

ρ kg/m3 :

density of liquid

σ N/m:

surface tension of the liquid

μ :

viscosity of liquid


concentration at infinite time maximum value of tracer concentration










  1. 1.

    Wachsmann, U.;Räbiger, N.;Vogelpohl, A.: The compact reactor — a newly developed loop reactor with a high mass transfer performance. Ger. Chem. Eng. 7(1984) 39–44

  2. 2.

    Velan, M.;Ramanujam, T.K.; Hydrodynamics in a down-flow jet loop reactor. The Can. J. of Chem. Eng. 69(1991) 1257–1261

  3. 3.

    Velan, M.;Ramanujam, T.K.: Gas-liquid mass transfer in a down-flow jet loop reactor. Chem. Eng. Sci. 47(1992) 2871–2876

  4. 4.

    Blenke, H.: Loop reactors. In: T.K. Ghose, A. Fiechter and N. Blakebrough (Eds.): Advance in Biochemical Engineering. Vol 13, pp. 121–214, Berlin: Springer 1979

  5. 5.

    Tatterson, G.B.: The effect of draft tubes on circulation and mixing times. Chem. Eng. Commun. 19(1982) 141–147

  6. 6.

    Bello, A.D.;Robinson, C.W.;Moo-Young, M.: Liquid circulation and mixing characteristics of airlift contactors. The Can. J. of Chem. Eng. 62(1984) 573–577

  7. 7.

    Sukan, S.S.;Varder-Sukan, F.: Mixing performance of air lift fermenters against working volume and draft tube dimensions. Bioprocess Eng. 2(1987) 33–38

  8. 8.

    Kawase, Y.;Moo-Young, M.: Mixing and mass transfer in concentric-tube airlift fermenters: Newtonian and non-Newtonian media. J. Chem. Tech. Biotechnol. 36(1986) 527–538

  9. 9.

    Rousseau, I.;Bu'Lock, J.D.: Mixing characteristics of a simple airlift, Biotech. Letters 2(1980) 475–480

  10. 10.

    Weiland, P.: Influence of draft tube diameters on the operation behaviour of airlift reactors. Ger. Chem. Eng. 7(1984) 374–385

  11. 11.

    Kawase, Y.;Moo-Young, M.: Liquid circulation time in concentric-tube airlift columns with non-Newtonian fermentation broths. J. Chem. Tech. Biotechnol. 46(1989) 267–274

  12. 12.

    Popovic, M.K.;Robinson, C.W.: Mixing characteristics of external loop airlifts. Chem. Eng. Sci. 48(1993) 1405–1413

  13. 13.

    Marquart, R.: Circulation of high viscosity Newtonian and non-Newtonian liquids in jet loop reactors. Int. Chem. Eng. 21(1981) 399–407

  14. 14.

    Weiland, P.;Onken, U.: Fluid dynamics and mass transfer in an airlift fermenter with external loop. Ger. Chem. Eng. 4(1981) 174–181

  15. 15.

    Warnecke, H.J.: On the mixing behaviour of gas-liquid jet loop reactors. Proc. Int. Conf. on Bioreactor Fluid Dynamics, Cambridge, England: 15–17 April (1986), pp. 126–138

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Correspondence to T. K. Ramanujam.

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Velan, M., Ramanujam, T.K. Mixing time in a down-flow jet loop bioreactor. Bioprocess Engineering 12, 81–86 (1995).

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