Comparison of various aeration devices for air sparging in crossflow membrane filtration

Gas sparging in tubular membranes has been proven to be a powerful tool for boundary layer and fouling control. Industrial application of this technique requires an appropriate air sparging device that allows adequate distribution of the gas phase to the entire cross-section of a multi-channel module. In this study, several aeration devices were designed and tested in conjunction with a standard industrial module. In terms of flexibility the aerators should function under various hydraulic conditions. Therefore, the performance of the devices was tested under different feed and air flow rates. The applicability of internals between the air sparger and the module to promote even air distribution, such as a static mixer or a Venturi channel, was also investigated. The air sparging devices were assessed with regard to the distribution of air over the module cross-section, the size and distance of the air bubbles. As well the robustness and simplicity of construction of the air sparging devices were considered. The results showed that complex aeration systems with multiple orifices injecting air homogeneously in the feed flow worked best. However, when the crossflow filtration unit is operated at a fixed crossflow velocity, simple tube air sparging devices may be more practical.