CFD在气升式MBR中的模型建立及计算研究

Model Establishment and Computing Research of CFD in Airlift MBR

摘要: 膜生物反应器(Membrane Bioreactor, MBR)是一种将生物降解与膜的高效分离技术相结合的污水处理与回收技术，在实际的生产过程中，膜污染会造成膜的透过性与分离性不可逆的变化。本文用CFD构建了气升式MBR曝气过程中液体流动的计算模型，经检验该模型计算结果收敛，然后用此模型研究了气升式MBR的挡板对膜组件内液体以及膜表面剪切力的影响。通过FLUENT软件计算出无挡板MBR和气升式MBR两种不同膜组件构型的液体流线图以及剪切力云图，对比发现气升式MBR的挡板具有加速液体循环和提高膜表面平均剪切力的作用，气升式MBR的挡板使得膜组件中的液体围绕着挡板循环流动，循环流动的液体不仅提高了膜组件内液体的流速，而且能够在膜组件的两侧形成大半径的涡旋区，使膜表面各个区域的平均剪切力都有了显著提升。这使得气升式MBR在减缓膜污染和提高曝气效率方面都有着无挡板MBR所不具备的优势。

Abstract: Membrane Bioreactor (MBR) is a waste-water treatment and recovery technology that combines biodegradation with efficient membrane separation technology. In actual production process, membrane fouling will cause membrane permeability and separable irreversible changes. In this paper, the calculation model of liquid flow in airlift MBR aeration process is constructed by Com-putational Fluid Dynamics. After testing, the model results in convergence. Then this model was used to study the effect of the baffle of airlifted MBR on the liquid and membrane shear force in the membrane module. The flow diagram and the shear force cloud diagram of the two different membrane module configurations of the standard MBR and the airlift MBR were calculated by FLUENT software. It was found that the baffle of airlift MBR has accelerated liquid circulation and improved average shear of the membrane surface. The baffle of the airlift MBR causes the liquid in the membrane module to circulate around the membrane module, and the circulating liquid not only increases the flow rate of the liquid in the membrane module, but also forms a large radius vortex zone on both sides of the membrane module. The average shear force in each area of the membrane surface is significantly improved. This makes the airlift MBR have advantages that are not available in the standard MBR in mitigating membrane fouling and improving aeration effi-ciency. This study will be significant in space plasma diagnostic.