VibraFilter

surface filtration in oscillatory shear

• Process flow diagram of equipment
  

• Example distributions
  

• Equipment arrangement for washing of fines out/Diafiltration

When operating at high shear a deposit, or secondary membrane, can be completely eliminated. Thus, it is possible to pass the finer particles in a distribution through a membrane whilst retaining the coarser ones. If fresh liquid is added to the system the fine particles can be washed out in a type of Diafiltration process. Hence, it is possible to remove the fines from a suspension of particles.

The economics of a diafiltration process are improved if the solvent forming the permeate can be recycled to wash more particles from the system. In this case, a second VibraFilter with a finer membrane is used to recover the solvent which is then recycled back to the diafiltration stage to wash more fines out.

• Example diafiltration size distributions

In this example the removal of material below 4 microns was required in a very high value product. The vessel size for the diafiltration was 0.5 litres and solvent was recycled according to the above schematic diagram.

The initial distribution shows a large number of particles less than 4 microns - the distribution is almost linear on the concentration scale. After one litre had passed through the VibraFilter, using a 5 micron slotted membrane, the distribution is developing a prominent mode between 5 and 6 microns. After three litres have passed only a small residual amount of sub-4 microns material is left.