Simulation and measurement of gas holdup in bubble columns
Advancing the chemical engineering fundamentals
Multifase Flows - III (T2-5c)
Keywords: Gas holdup, bubble column, Simulation, Inclination, Gas inlet height, Gas sparger arrangement
Bubble columns are widely used as gas liquid reactors and bio-reactors, because of simple structure and high perforamance. Gas holdup is a very important parameter for design and scale up of bubble columns. Therefore, there have been many studies about gas holdup in bubble columns. It has been reported that gas holdup depends on many factors such as gas and liquid velocity, physical property of gas and liquid, type and arrangement of gas spargers, gas inlet height and inclination of bubble columns.
Recently CFD has remarkably developed because of development of effective personal computers and softwares. CFD is very useful for research, design and scale up of bubble columns. In this work, the effects of inclination of a bubble column, arrangement of gas spargers, gas density and viscosity, and gas inlet height on gas holdup were simulated by FLUENT software. The results were analyzed and discussed, and were compared with experimental results.
1）Effect of inclination of bubble column on gas holdup EG
EG decreased with increasing inclination angle, because bubbles rise along the upper wall of the bubble column. The results showed a good agreement with experimental results.
2) Effect of arrangement of gas sparger on EG
EG for the gas sparger in the center of the bottom of bubble column was much larger than that for the gas sparger near the wall, because the gas sparger near the wall caused mal- distribution of bubbles. The results showed a good agreement with experimental results.
3) Effect of density De and viscosity Vis of gas on EG
Though Hikita et al. has reported that EG is proportional to De and Vis of gas , the simulation results have shown that EG does not depend on De and Vis of gas for constant bubble diameter. If bubble diameters depend on De and Vis of gas, it is possible that EG by the simulation will change. Effect of De and Vis of gas on bubble diameters is experimentally under investigation.
4) Effect of gas inlet height H on EG
EG decreased with increasing height H of gas inlet, because the region under H became bubble-free. Liquid circulates in the bubble column, however, bubbles don’t fall into the region under the gas inlet. The results showed a good agreement with experimental results.
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 09:05 to 09:25, in session Multifase Flows - III (T2-5c).
