Removal of cake by mass forces

Removal of Cake by Mass Forces. This method of limiting cake growth employs mass or electrophoretic forces on particles, acting tangentially to or away from the filter medium. Only mass forces are considered here because the electrophoretic effects have been discussed previously. 

At the start of a test the cylinder is completely filled by the solid/liquid mixture which can exhibit the characteristics of a slurry, where both filtration and consolidation processes take place, or by a networked semi-solid where consolidation commences from the start of the test. In general the mixture will be concentrated and/or composed of fine particulates that do not settle appreciably under gravity. The piston is introduced to the open end of the cylinder and the constant applied force causes pressure to be generated within the cylinder. Liquid is expelled through the filter medium and collected in either a measuring cylinder or, in more sophisticated units, a vessel mounted on a load cell or electronic balance. The volume or mass of liquid is measured at various time intervals from the start of expression. The thickness of suspension (or cake towards the end of the test) in the cylinder can be calculated from a knowledge of the volume of liquid removed from the cylinder, or from measurements of the piston displacement from the beginning of the test should an appropriate transducer be fitted. 

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