三段进气环流反应器气泡参数与传质特性研究

Bubble Parameters and Mass Transfer in an Airlift Loop Reactor with Three Air-in Spargers

多级环流反应器通常在段间安装多孔分布板或其它内构件,增加了流体流动的阻力,导致环流液速降低。为此,今在多级环流反应器研究的基础上,设计了一种新型三段进气、多级环流反应器,利用新通入气体的抽提力和喷射力,缓解了段间的流动压降,并加速气泡的破碎;重点考察了进气量在各段中的分配比例对分段进气多级环流反应器流体力学的影响。应用多通道电导探针气泡特征参数测量仪和溶解氧分析仪分别测量气泡参数(气含率、气泡速度、气泡直径)及体积传质系数。实验结果表明:三段同时进气时,气泡直径明显减小,气液接触比表面积增加显著;体积传质系数远高于多级环流反应器,最大值约为多级环流反应器的2.3倍。根据修正双膜理论,计算得到了三段进气时体积传质系数的经验关联式,较好地反映出体积传质系数的变化规律。

There are some perforated plates or other internals in multi-stage airlift loop reactor （MSALR）, which can increase the flow resistance, and lead to reduce circulating liquid velocity. In order to solve these defects, a three sparger multi-stage airlift loop reactor （TS-MSALR） was proposed, in which because of the gas ejection force, the flow pressure drop is reduced, and the bubble breaking is enhanced. This study focuses on the gas inlet ratio among the three air-in spargers, which plays an important role for the hydrodynamics in the reactor. The gas-liquid two-phase flow hydrodynamic properties including gas holdup, bubble velocity, bubble diameter and mass transfer coefficient at various gas inlet ratios were measured by dual electrical resistivity probes and DO probe. The results show that the bubble diameter decreases obviously, the gas-liquid surface area increases significantly, and the volumetric mass transfer coefficients of TS-MSALR are much higher than that of MSALR. The maximum mass-transfer coefficient of the TS-MSALR is 2.3 times of that of the MSALR. Based on the modified double film theory, correlation of volumetric mass transfer coefficient of TS-MSALR was obtained.