The use of electrode probes in determinations of filter cake formation and batch filter scale-up

A well controlled apparatus was used to obtain new data for constant pressure cake formation in a batch leaf filter which could be fitted with electrode type sensing probes. For aqueous suspensions of calcite and talc, the influence of the intrusive electrodes on cake formation was quantified with respect to filtration parameters. As the electrode length and diameter were altered such that the projected cross-sectional area occupied up to 2.6% of the filter area, the average specific cake resistance (as determined by classical filtration theory) was observed to increase by up to 49% and the average cake porosity decreased by up to 21%. When the electrodes were small relative to the dimensions of the filter cell, their influence on macroscopic cake properties was low. The additional information which electrical resistance measurements provide is discussed in relation to the results and observations by previous researchers and the benefits to filter test analysis and batch filter calculations are highlighted. For moderately compressible cake filtrations it is postulated that the incorrect assessment of cake porosity can typically account for an ~12% error in scale-up calculations for batch filters.