分散填料曝气塔多相流态分析与传氧性能表征

针对分散填料曝气塔中多相流的流态与传氧过程,实验了布气方式以及海绵和陶粒2种填料对于体系的气含率εg、流态以及气-液传质性能的影响。在表观气速U范围(0.01～0.18 m/s)内观察到81孔布气板(Φ1 mm)体系出现3个明显相区,孔数过少(25孔),或者孔间距较小(225孔)均没有明显过渡区,在湍流区(U>0.118 m/s)3种布气板的气含率没有明显差别。海绵填料体积分数εs<25%时体系的气含率没有明显变化,35%时气含率下降且过渡区提前出现。在非均相区,海绵填料明显提高了体系的传质系数KLa。陶粒填料降低了气含率,固含率对εg的影响差别不明显,同时降低了多相流体系的KLa,且随着固含率的增加KLa降低。对比多种操作条件,单位体积空气传氧能力KLa/εg无明显差别,但在81孔布气板的过渡区KLa/εg出现一个明显的极小区间,说明过渡区传氧效率较低。在特定的实验操作条件下,KLa/εg较为稳定,这为深入理解两种气泡群体的共存体系在传氧性能方面各自的权重,提供了重要的量化参考。

Flow regime analysis and oxygen transfer measurement of multiphase flow in bubbling packed column

To study the multiphase flow regime and oxygen transfer in bubbling packed column,the effect of gas distributor style,sponge and ceramisite bio-medias on gas holdup εg、flow regime and gas-liquid mass transfer capacity was investigated.In the range of superficial gas velocity U,three apparent regimes were observed in the case of 81 holes(Φ1 mm) while no obvious transition regime in the case of 25 holes(less hole number) and 225 holes(less hole spacing).In churn-turbulent regime(U>0.118 m/s),there were no significant discrepancies in gas holdup among these three distributors.There was no obvious change in gas holdup as the sponge volume fraction εs<25%,whereas the gas holdup reduced and transition regime emerged ahead at 35% volume fraction.In heterogeneous regime,the volumetric mass transfer coefficient KLa enhanced significantly in the presence of sponge.The gas holdup reduced in the presence of ceramisite and there was no obvious difference in εg as a function of volume fraction.In the ceramisite system,KLa reduced as a function of εs.Compared with several aeration conditions,there were no significant differences in the oxygenation capacity per unit volume air,KLa/εg,which showed a minimal interval in the transition regime with 81 holes distributor indicating a lower oxygen transfer efficiency.Under specific operation conditions,KLa/εg was almost constant,which was an important reference on deep understanding of the oxygenation capacity in the system where two kinds of bubble populations coexisted.