Continuous rotary vacuum filtration can be analysed by considering each revolution of the

drum as a stationary batch filtration. Per revolution, each cm² of filter cloth is used to form

cake only for the period of time it spends submerged in the liquid reservoir. A rotary drum vacuum filter with drum diameter 1.5 m and filter width 1.2 m is used to filter starch from an aqueous slurry. The pressure drop is kept constant at 4.5 psi; the filter operates with 30% of the filter cloth submerged. Resistance due to the filter medium is negligible. Laboratory tests with a 5-cm² filter have shown that 500 ml of slurry can be filtered in 23.5 min at a pressure drop of 12 psi; the starch cake was also found to be compressible with s=0.57. Use the following steps to determine the drum speed required to produce 20 m³ of filtered liquid per hour. Evaluate from the laboratory test data.