四边形折流式膜生物流化床内填料浓度及液相流场特性研究

针对研究开发的四边形折流式膜生物流化床,构建了气、固、液三相流可视化平台,应用取样法和激光粒子图像测速(PIV)技术剖析了不同进水流量和曝气强度组合对流化床内的填料浓度及液相流场特性的影响.结果表明,折流板上部形成的曝气死区,提高了升流区的填料浓度;折流板和导流锥形成的进水角度使流场冲击反应器底部的填料,提高了在低曝气强度下流化床的填料浓度,在实际运行过程可降低曝气能耗;四边形折流式膜生物流化床的结构特点导致填料与膜组件相互碰撞的概率增大,强化了膜污染的控制.曝气强度和进水流量的变化改变了液相的轴向返混强度和剪切力,进而改变了填料浓度,使气、固、液三相冲刷膜组件的作用增大,最终影响膜面传质系数和浓差极化边界层厚度,降低了膜污染.通过流化床结构的改变提高填料浓度和改善流场特性,为高浓度有机废水好氧生物的处理提供了一个研究方向.

The characteristics of packing fraction and liquid phase flow field in a quadrilateral baffled membrane biological fluidized bed

A visualization platform of gas-liquid-solid three phase flow was constructed for a quadrilateral baffled membrane biological fluidized bed.The sampling method and laser particle image velocimetry (PIV) were used to analyze the effects of the flowrate and the aeration intensity on the packing fraction of the fluidized bed as well as on the liquid-phase flow field characteristics.The results show that the aeration dead zone above the baffle plate elevates the packing fraction of the riser; the influent inflow angle formed by the baffle plate and the guiding cone directs the flow to flush on the packing materials at the bottom of the reactor, and therefore increases the packing fraction of the fluidized bed under low aeration intensity and reduces the aeration energy consumption in real operation. The quadrilateral structure of this biological fluidized bed increases the probability of the collisions between the packing materials and membrane, and thus enhances the control on membrane fouling. Changes in the aeration intensity and the influent flow rate boost the liquid-phase axial back mixing and change the packing fraction. These enhance the membrane flush by gas-liquid-solid and the impact on the mass transfer coefficient at the membrane surface and the thickness of concentration polarization layer. Consequently, reduce the membrane fouling. The increase of packing fraction and the improvement of flow field was achieved by the alteration in the structure of fluidized bed. it opened a new research area for aerobic biological treatment of high concentration organic wastewater.