短程混凝-膜过滤工艺清洗过程中气液两相流对絮体形成的影响

Influence of gas-liquid flow on flocs formation in cleaning procedure of integrated coagulation-membrane filtration process

基于数值模拟的方法研究了不同填充密度和不同曝气强度下短程混凝-膜过滤工艺中膜清洗过程反应器内流场特性。结合絮凝动力学理论,引入微涡旋尺度参数来判定影响絮体形成的流场状态,以评估膜清洗过程中曝气强度对絮体形成及膜清洗效果的影响,并用实时图像技术对模拟结果进行验证。研究结果表明,反应器填充密度为7.38%,气水比为15:1时,反应器内平均有效能耗适中,且形成的微涡旋尺度也适中,不会对絮体产生明显的破坏作用,有利于形成较大尺寸的絮体;同时在膜组件附近产生较强的水流剪切速度,使膜面得到有效的清洗。结合实验分析,反应器填充密度为7.38%,气水比为15:1时,反应器内形成的絮体粒径较大且与数值模拟得到的微涡旋尺度相近,上清液UV254和TOC值最低,去除效果最好。

Based on numerical simulation, the flow field characteristics of integrated coagulation-membrane filtration process were investigated at different aeration intensities and module packing densities. According to the flocculation kinetics theory, the micro-vortex scale was introduced to analyze the flow field state. It was used to evaluate the effect of aeration intensity on flocs formation and membrane cleaning during the cleaning process. The simulation results were validated experimentally by the real-time imaging technology. When module packing density and air-water ratio were 7.38% and 15：1 respectively, mean effective energy consumption was moderate and vortex scale was sufficiently large. Moreover, under such conditions damage of flocs was not obvious, meaning that larger vortex was conducive to flocs formation. Meanwhile, a strong shear speed generated by the field near the membrane module was beneficial to membrane cleaning and hindered flocs breakage. Combining with experiment analysis, when module packing density and air-water ratio were 7.38% and 15：1 respectively, thesize of flocs particle formed in the experiment was the largest, close to the micro eddy scale obtained from numerical simulation. The values of Ug254 and TOC were minimum and flocculation effect was the best.