基于CFD的超薄平板膜MBR流态模拟及优化分析

CFD based-flow pattern simulation and optimization analysis of ultra-thin flat membrane MBR

随着MBR的广泛应用,为控制膜污染导致高运行成本问题,优化新型平板膜MBR的曝气条件成为目前的一个研究热点。本研究通过使用CFD Fluent软件,结合多相流模型和湍流模型进行超薄平板膜MBR的高质量流态模拟,量化膜面剪切力,并从流场及膜污染角度分别对3种气水比(10∶1、15∶1和20∶1)工况下的MBR进行了优化分析,选择出超薄平板膜MBR的最优气水比。研究结果表明,膜片之间的流速分布均存在中间大、两侧小的不均匀性,且单个膜面剪切力分布与MBR流态特征密切相关,膜面颗粒沉积概率与剪切力均值呈负相关;对比了以0.1m·s^(-1)为临界流速的不同曝气下的流场形态分布特性,并综合考虑曝气能耗及膜面冲刷,确定3种气水比中的最优值为15∶1。

With the wide application of MBR, the problem of high operating cost caused by membrane fouling is becoming more and more prominent. Therefore, optimizing the aeration conditions of new flat membrane MBR has become a research hot spot. In this study, the CFD Fluent software was used to simulate the highquality flow pattern of the ultra-thin flat membrane MBR combined with the multi-phase flow model and the turbulence model. The membrane surface shear force was quantified, and the MBR operation at three gas-water ratios(10∶1, 15∶1 and 20∶1) was optimized and analyzed from the perspectives of flow field and membrane fouling, so as to select the optimal gas to water ratio of the ultra-thin flat membrane MBR. The results show that the flow velocity distribution between the membranes presented an uneven characteristic of large in the middle and small in both sides, and the shear force distribution on a single membrane surface was closely related to the flow pattern characteristics of MBR. The deposition probability of particles on the membrane surface was negatively correlated with the mean shear force. The flow field distribution characteristics under different aeration conditions with 0.1 m·s^(-1) critical flow rate were compared. Considering the aeration energy consumption and membrane surface erosion, the optimal gas-water ratio was determined as 15∶1 among above three ratios.