CROSS-FLOW FILTRATION WITH AND WITHOUT CAKE FORMATION

A neutrally buoyant model particulate suspension has been used to examine the effect of channel flow fluid mechanics on filtrate flux kinetics. The incorporation of periodically spaced central baffles is shown to improve filtration performance by a factor of about two. Direct observations of particle activity at the cake surface show that this improvement is caused by filter cake erosion due to eddy circulation around the baffles. A novel piece of apparatus has been developed to produce oscillatory flow within the channel. When these oscillations were superimposed upon a steady net flow in the presence of baffles, more than tenfold filtrate flux enhancement was found. Optical observations of the filtration process show that in this mode of operation, cake build up is completely inhibited. It was also observed that more efficient filtration occurs when gas was entrained into the channel, through the filter.