On Local Cake Properties in Liquid Filtration

Prof. Hans Theliander, Chalmers University of Technology, Sweden

The traditional way of studying filtration properties has been to determine the average specific filtration resistance (e.g. the Ruth equation) and average porosity (or average solidosity). If the solid material forms filter cakes that is only slightly compressible and blinding of the filter medium can be neglected, the average measures are often sufficient and can often be used to scale up laboratory/pilot plant data to industrial scale.

However, if the solid material forms compressible filter cakes it is a great advantage to use local filtration data when scaling up laboratory data to industrial scale. Local data is also necessary in the study of the mechanisms of filtration of material forming compressible filter cakes and is also very useful in troubles shouting (e.g. blinding of filter media).

There has been two pathways for the determination of local filtration properties: direct measurements of local pressure and local solidosity (porosity), and by using the so-called “compression permeability cell” (CP-Cell). Both methods gives data that may be considered as “local”, but the CP-Cell methodology has some drawbacks: e.g. it is doubtful if the packing of the particles will be the same as in a filter cake during the build up of the cake and that it is difficult to eliminate errors related to the boundary between the filter cake and the cell wall. The direct method has of course also some drawbacks: e.g. that the equipment becomes more complicated, that the pressure probes must be placed correct and that the accuracy of the solidosity measurements depends both on the equipment used and the material in the filter cake.

The intention with this talk is to shred some light on how local filtration properties can be measured with the direct methods and what to think about in order to make the measurements as accurate as possible. Furthermore, to give examples on how and why local filtration properties may be used in scale up as well as in trouble shouting.

Session: K4 - Keynote Lecture IV
Day: 12 October 2016
Time: 09:00 - 10:15 h