Influences of interstage height and superficial gas velocity in multistage internal airlift loop reactor on performance of mixing and mass transfer

doi:10.11949/j.issn.0438-1157.20171647

Abstract

Abstract:

A simple multistage internal airlift loop reactor (MIALR), which has been widely employed in the chemical industry, was designed and investigated. The influences of interstage height and superficial gas velocity in the MIALR on the performance of the mixing and mass transfer were inspected. Three typical regimes, i.e., abnornal, transition and regular regimes, in the MIALR were observed and proposed in this work for the first time. There were two critical superficial gas velocities impacted by the interstage height in the MIALR for the flow regime transition, and two mathematical models were proposed here for the prediction of flow regimes. The results showed that a higher superficial gas velocity was desired for reaching a regular regime when the interstage height of the MIALR increased. In addition, the respective gas holdups in the riser and the downcomer would be promoted if there was an increment of the interstage height in the MIALR. The gas holdups in the riser and the downcomer at the third stage were the highest at the same conditions, and those at the first stage were the lowest among the three stages in the reactor. Moreover, the higher the interstage height, the higher the circulating liquid velocity in the downcomer was. The highest circulating velocity in the downcomer was measured at the first stage, and the lowest value was obtained at the third stage. Finally, a reduction of mixing time was gained when the interstage height increased, while an increase of volumetric mass transfer coefficient was obtained at the same conditions. Therefore, a guideline for the scientific design, scaling up and operating of this kind of industrial MIALRs was provided.

Key words: multistage internal loop airlift reactor, interstage height, gas holdup, circulating liquid velocity, mass transfer, two-phase flow

摘要：

针对应用广泛的简单多级环流反应器，研究了级间隙高度和表观气速对其混合和传质的影响规律。发现简单多级环流反应器的各级存在着非正常流动、过渡及正常流动三个典型流动状态，且流动状态的转变存在着受级间隙高度影响的两个临界表观气速，并提出了相应的预测模型。研究结果表明：级间隙高度越大，多级环流反应器内形成正常流型所需的表观气速越大；各级上升管和降液管的气含率会增高，且相同条件下第三级气含率最大，第二级次之，第一级气含率最小；各级的循环液速会增大，且第一级循环液速最大，第二级次之，第三级最小；混合时间会缩短，而传质系数会增大。本研究可为工业多级环流反应器的科学设计、放大和操作提供重要指导。

关键词: 多级环流反应器, 级间隙高度, 气含率, 循环液速, 传质, 两相流

CLC Number:

TQ021.1

TAO Jinliang, HUANG Jiangang, XIAO Hang, YANG Chao, HUANG Qingshan. Influences of interstage height and superficial gas velocity in multistage internal airlift loop reactor on performance of mixing and mass transfer[J]. CIESC Journal, 2018, 69(7): 2878-2889.

陶金亮, 黄建刚, 肖航, 杨超, 黄青山. 级间隙高度和表观气速对多级环流反应器混合和传质的影响[J]. 化工学报, 2018, 69(7): 2878-2889.

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