Gas holdup in three-phase immobilized cell bioreactors
A number of studies in the published literature deal with gas holdup in three-phase reactors. However, very few address the cases in which the solid density approaches that of the liquid phases and where low gas velocities are involved. These conditions are commonly encountered in immobilized-cell bubble columns and in fluidized-bed bioreactors. This paper reports the effect of gas and liquid velocity upon gas holdup and bed expansion in fluidized-bed bioreactors. For liquid-fluidization of low-density alginate beads in the absence of gas, the terminal sedimentation velocity (v/sub T/), of the particles is a constant and expansion of the bed follows Richardson and Zaki's correlation. In the presence of gas, however, the apparent terminal sedimentation velocity value is affected by the velocity of the gas and liquid phases. For gas velocities above a minimum value, the calculated value of v/sub T/ depends upon liquid velocity only and a constant bed expansion was observed for a range of gas and liquid flow rates. For the gas-liquid interactions, a modified drift-flux model was found to be valid. For superficial gas velocities between 5 and 17 cm/min, the modified drift-flux velocity was observed to be a function of gas velocity suggesting the prevalence of a coalescence regime. 21 refs., 4 figs., 1 tab.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5782529
- Report Number(s):
- CONF-890509-3; ON: DE89016334
- Resource Relation:
- Journal Volume: 24-25; Journal Issue: 1; Conference: 11. symposium on biotechnology for fuels and chemicals, Colorado Springs, CO, USA, 8-12 May 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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