喷射反应器内气液两相流体动力学特征

Hydrodynamic characteristics of gas-liquid two phase flow in jet reactors

喷射反应器是一种重要的化工过程强化设备,可有效强化传质与传热过程、加快反应速率、提高反应产率,近年来在多个领域得到应用。本文对两种典型喷射反应器的结构及其工作原理进行了描述,系统地分析了各操作参数和结构参数对气体吸入量和气泡直径的影响规律,指出研究气体吸入和气泡破碎两种机制的必要性。对采用计算流体力学方法模拟喷射反应器内气液两相流进行了分析,指出Mixture模型适合研究气体吸入量,无法准确描述气泡运动和破碎这两个重要过程,提出采用计算流体力学与群体平衡模型结合的方法进行模拟,关键在于建立适合喷射反应器的气泡破碎频率模型。另外,结合工业应用的实际情况,强调了加入催化剂颗粒相的多相流分析对于指导工业应用的重要意义。

Jet reactors are important equipment for process intensification and they have been applied in many industries in recent years.They can significantly enhance the mass and heat transfer,speed up the reaction rate and promote reaction yield.In this work,two structural styles of jet reactors and the hydrodynamic characteristics of gas-liquid two phase flow in these reactors were reviewed.Firstly,configurations and working principles of these two kinds of jet reactors were described.Secondly,influences of operating and structural parameters on the gas induction rate and bubble diameter were analyzed,respectively.It was pointed out that more studies should be conducted on the mechanisms of gas entrainment and bubble breakage.Finally,reviews on the modeling of gas-liquid flow using the computational fluid dynamics in the jet reactors were presented.It was noteworthy that although Mixture multiphase model can reproduce gas entrainment rate accurately,it cannot be employed to predict the processes of bubble motion and breakage,which were very important for the hydrodynamic characteristics.It was recommended that these two processes can be well described by combining Euler-Euler model with Population Balance Model.When the Population Balance Model was employed,an appropriate bubble breakage frequency model should be set up at first.Additionally,catalyst particle phase should also be taken into account since it existed in various multiphase catalytic reactions in industrial application,which can influence flow patterns.Gas-liquid-solid three phase flow simulation can produce more realistic results and it would play an important role in guiding the industrial applications of the jet reactors.