VibraFilter

surface filtration in oscillatory shear

• Particle size distribution of the challenge
  

• Flux behaviour - before and after vibration used
  

• Rejection of the solids - in the absence of secondary membrane
  

• size of challenge

The size distribution was measured on a Malvern Mastersizer and shows most material below 26 microns, with a median size of 8 microns. There was a large amount of fines, with 10% of the distribution below 1.5 microns.

• Filtration flux performance

Note the extremely low starting pressure differential across the filter membrane. For the first 900 seconds vibration wasn't used and a gentle fouling of the membrane can be seen. At 900 seconds the vibration was switched on and the flux remained constant at 640 l m^-2 h^-1 (constant rate filtration). On switching on the vibration the differential pressure dropped to a value close to the starting pressure and remained stable thereafter.

• Filtration rejection performance

After switching on the vibration samples were taken for size analysis of the permeate; i.e. to ensure that the membrane rejection was due to the membrane and not any secondary membrane effect. The rejection performance of this nominal 2.5 micron slotted membrane is illustrated here. If complete removal of measurable solids is required then a polishing filter can be used in conjunction with the VibraFilter. The pressure drop is so low that the VibraFilter can be on the suction side of a pump - the polishing filter on the discharge side.

Using a combination of The VibraFilter and a polishing filter provides a cost-effective method of filtering high concentrations of suspensions and providing guaranteed quality of the permeate. The polishing filter will last for a long time as it is protected by The VibraFilter.