Effects of aeration modes on ceramic membrane separation process

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.