鼓泡塔内气含率分布与流场的CFD模拟

CFD simulation of gas holdup and gas-liquid flow in bubble columns

采用CFD商业软件对单层分布器、双层分布器和带导流筒3种结构鼓泡塔内气液分散性能进行数值模拟。研究结果表明,随着通气量的增加,鼓泡塔内气含率增高,但其分布的均匀性变差。鼓泡塔内存在过渡流域和充分发展流域,在过渡流域,塔内水平截面平均气含率随轴向高度而增加,在充分发展流域,塔内水平截面平均气含率不随轴向高度变化,2种流域的分界线位置和鼓泡塔的结构有关,而几乎不受通气量大小的影响。在相同通气量下,双层分布器和带导流筒鼓泡塔内平均气含率比单层分布器鼓泡塔低,但双层分布器相对单层分布器鼓泡塔可改善在耗氧反应体系中氧气分布的均匀性,采用带导流筒鼓泡塔可改善液体在塔内循环,使气-液反应在塔内更加均匀。

The gas dispersion and flow velocities in bubble columns with single-stage gas distributor,double-stage gas distributor and with flow draft,respectively,are numerically simulated by using computational fluid dynamics （CFD） in this paper.The simulation results show that,with the increase of the gas inlet flow rates,the global gas holdup increase in the bubble column while the uniformity of the gas holdup distribution decrease.Flow pattern in bubble column can be divided into transient flow regime and fully developed flow regime.The average holdup in horizontal plane increases with the axial height in transient flow regime while almost keeps unchanged in fully developed flow regime.The dividing line position of the two flow regime affects by the structure of the bubble column while almost not by the gas inlet rate.Under the same operating conditions,the global gas holdup of double-stage gas distributor bubble column or the flow draft bubble column lower than that of single-stage gas distributor bubble column.The double-stage gas distributor bubble column can improve the uniformity of oxygen distribution for oxidation reaction system compared with the single-stage gas distributor bubble column.The flow draft can improve the liquid circulation in the bubble column.