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

A well controlled apparatus was used to obtain new data for constant pressu re cake formation in a batch leaf filter which could be fitted with electro de type sensing probes. For aqueous suspensions of calcite and talc, the in fluence of the intrusive electrodes on cake formation was quantified with r espect 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 cl assical filtration theory) was observed to increase by up to 49% and the av erage cake porosity decreased by up to 21 %. When the electrodes were small relative to the dimensions of the filter cell, their influence on macrosco pic cake properties was low. The additional information which electrical re sistance measurements provide is discussed in relation to the results and o bservations by previous researchers and the benefits to filter test analysi s and batch filter calculations are highlighted. For moderately compressibl e cake filtrations it is postulated that the incorrect assessment of cake p orosity can typically account for an similar to 12 % error in scale-lip cal culations for batch filters. (C) 1999 Elsevier Science Ltd. All rights rese rved.