A theoretical and experimental study on cake filtration with sedimentation

Sedimentation occurs in almost all cake filtration. To study the role of se dimentation during filtration, filtration-permeations were carried out for suspensions of various concentrations. The average specific cake resistance s calculated by the traditional method using the filtration data and initia l concentration of suspension give different values according to the suspen sion concentrations. But the average specific cake resistances from the per meation period show almost the same values in spite of the various suspensi on concentrations. To exclude the influence of sedimentation, a complete se dimentation was performed before beginning filtration and then filtration-p ermeation of the sediment was performed. The average specific cake resistan ce from the filtration period calculated with the mass fraction of sediment and that from the permeation period coincide very well. These values also coincide well with the former average specific resistances during permeatio n within the experimental error limits. It can be concluded that the averag e specific cake resistances by permeation operation give almost the same va lues for various concentrations of suspension. A new definition of a cake a nd a new concept of the filter medium R-m, are proposed based on the analys is of experimental results.