曝气方式对陶瓷膜分离过程的影响

Effects of aeration modes on ceramic membrane separation process

在膜分离中引入曝气可有效减轻浓差极化和膜污染,提高膜过程分离效率。文中采用实验对比验证和气液二相流理论计算的方法,研究了曝气方式对膜分离过程的影响。实验结果表明:采用导流板仅在膜通道曝气过程的曝气量为250 L/h时,可维持平均压力增长率为40 Pa/m in,能有效控制膜污染;继续增大曝气量,曝气方式对膜污染控制效果的影响变小;曝气方式对膜面悬浮液质量浓度影响显著,直接曝气使膜面悬浮颗粒质量浓度不断增大,膜面易形成膜污染。气液二相流理论计算表明,对膜通道曝气的膜面气液流速和剪切力是全膜曝气膜过程的2—13倍,并且其气液上升流和下降流分别控制膜通道表面和膜外壁膜污染。

Aeration process is effective in the control of concentration polarization and membrane fouling and improving separation efficiency.The experimental investigations and theoretical analysis were combined to study the effects of aeration modes on membrane separation processes.The experimental results show that when the rate of the aeration to the membrane channels is 250 L/h,the average transmembrane pressure（TMP） growth rate can be kept at 40 Pa/min;the effects of aeration modes on membrane fouling become small by continuously increasing the aeration rate.The solid suspension（SS） around the membrane surface is significantly affected by aeration modes,and direct aerating makes the SS mass concentration on membrane surface increase continually,thus causing membrane fouling easily.The hydrodynamics of the gas-liquid two-phase flow was calculated and the results show that in the mode aerating to the membrane channels,the gas-liquid velocity in the riser and wall shear stress is 2-13 times as high as aerating to all the membrane surface.Both the gas-liquid flow in the riser and downcomer can effectively reduce the membrane fouling.