低膜面流速下曝气对管式膜水力特性及膜污染影响

采用曝气强化管式膜超滤高岭土混合液，考察了低膜面流速下曝气对强化膜分离过程影响，探讨了曝气对膜面水力特征及膜污染过程影响，并对过滤介质影响及膜污染阻力构成进行了研究。结果表明，在低膜面流速下，通过向管式膜引入曝气使膜表面形成气液两相流，可实现膜通量稳定保持在15L/(m²·h)以上。不仅如此，曝气的引入使膜表面雷诺数由1800~2500增至3300~4500，显著增强了膜表面湍流程度，并且实现了低膜面流速下使膜污染指数控制在较低水平，节省了运行能耗。此外，曝气的引入主要减轻了膜表面滤饼污染，使膜过滤总阻力减小且对高岭土截留效率影响不大，但强烈的膜面传质使高岭土粒径有减小趋势，并且膜表面形成污染阻力以不可逆污染层为主，不利于膜污染长周期控制。

Influence of aeration on hydrodynamic characteristic and membrane fouling in a low cross-flow velocity microfiltration

The effect of aeration on the process of membrane separation at a low superficial liquid velocity was researched in an air sparging tubular membrane system for filtering a Kaolin suspension. The influences of aeration on the hydraulic characteristics in membrane module and the membrane fouling process were discussed, and the impacts of aeration on the filter medium and the composition of membrane filtration resistance were also studied. The results showed that a gas-liquid two-phase flow was formed on the membrane surface by injecting air, and the membrane flux could be stably maintained above 15L/(m²·h) at a low membrane superficial liquid velocity. Moreover, the Reynolds number increased from 1800—2500 to 3300—4500, indicating that the turbulence on the membrane surface was significantly enhanced by aeration. Besides, the membrane fouling number was controlled at a low level under a low membrane superficial liquid velocity, which saved operating energy consumption. In addition, the membrane cake layer could be reduced by air injecting, leading to a reduction in the total membrane resistance, but which had little effect on the retention rates of Kaolin suspension. However, the Kaolin particle size became smaller as a result of the strong gas-liquid mass transfer, and the membrane surface formed a filtration resistance dominated by an irreversible pollution layer, which was not conducive to the long-term control of membrane fouling.