Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Bubble column

Scale Effects on the Hydrodynamics of Bubble Column

Farah S. Jameel; Mohammad F. Abid

Engineering and Technology Journal, 2009, Volume 27, Issue 10, Pages 2142-2164

The main object of this study is to investigate the influence of the column
geometric and operating variables ( i.e., column diameter, superficial gas velocity
and liquid viscosity) on the hydrodynamic parameter ( i.e. , gas holdup, bubble
dynamics and liquid phase axial dispersion coefficient ). The experimental data
obtained showed that the gas holdup increases linearly with superficial gas
velocity at both homogeneous and heterogeneous regimes but the rate of
increasing is slower at the heterogeneous one. The bubble rise velocity was found
to decrease with increasing superficial gas velocity until a transition point was
reached and after that the relationship was linearly increasing. It was observed
that with an increase in liquid phase viscosity and increase in column diameters, a
decrease in gas holdup and an increase in bubble size were obtained. It was
observed that increasing axial position led to an increase in bubble diameter and a
decrease in bubble rise velocity. Axial dispersion coefficient which is measured
by tracer response technique was found to increase with gas superficial velocity,
increases with column diameter, increases with axial position and decreases with
liquid viscosity. This work also presents a theoretical analysis that is used to
calculate the axial dispersion coefficient. The measured axial dispersion
coefficient was generally consistent with the predictions of the well established
correlations from the literature. The validity of the model was settled by
comparing its predication with the objective function of the well-Known empirical
correlation formulated by ( Hikita and Kikukawa , 1974) .The comparison shows
that the present model is statistically significant at a 95% confidence level by
using goodness – of – fit test .
Also a statstical analysis was performed to get a general correlation for the gas
holdup (εg) as a function of the parameters studied:
= 0.15325 Fr 0.29617 Ga 0.09223 Bo -0.0424 g e
Where the correlation coafficient ( R ) was equal to ( 0.957) and the absolute
error (3.5%).

Modeling ofMixing in The Liquid Phase For Bubble Column

Ali H. Jawad

Engineering and Technology Journal, 2009, Volume 27, Issue 10, Pages 1992-2007

Hydrodynamic characteristics (mixing in the liquid phase) in a bubble column with a non-Newtonian liquid phase (aqueous solutions of carboxymethylcellulose, or CMC, at different concentrations) were measured and correlated. Experiments in a 0.2-m diameter, 2.4-m-high bubble column were carried out to determine degree of mixing
in the liquid phase at various gas and liquid flow rates. The axial dispersion model was used in the two operating modes, batch and continuous, and the tanks-in-series model was used just in the case of continuous mode. The axial dispersion model with closed-closed boundary conditions fit experimental data quite well and thus was used
to estimate the axial dispersion coefficient. This parameter was higher in batch mode than in continuous mode, and its trend was to increase as superficial gas velocity increased.