276 Fermentation and Biochemical engineering handbook DEADEND FILTRATION CROSS-FLOW FILTRATION FEED CAKE 单o MEMBRANE FILTRATE PERMEATE Figure 2. Cross-flow versus dead end filtration On the other hand, in dead end filtration the retention is achieved by particle or gel layer buildup on the membrane and in the pores of the medium such as when a depth type filter is used. This condition is analogous to that encountered in packed-bed geometries In dead end filtration, the applied pressure drives the entire feed through the membrane filter producing a filtrate which is typically particle- free while the separated particles form a filter cake. The feed and filtrate travel concurrently along the length ofthe filter generating oneproduct stream forevery feed. In CFF, one feed generates two product streams, retentate and permeate. Per pass recovery in through-flow mode is almost 100%(sinc only the solids are removed) whereas in the cross- flow mode the per pass recovery typically does not exceed 20% and is often in the l to 5%range Recirculation of retentate is thus necessary to increase the total recovery at the expense of higher energy costs276 Fermentation and Biochemical Engineering Handbook DEADEND FlLTnATlON CROSS-FLOW FILTRATION FlLl r J I IT nhTE Figure 2. Cross-flow versus dead end filtration. On the other hand, in dead end filtration the retention is achieved by particle or gel layer buildup on the membrane and in the pores of the medium such as when a depth type filter is used. This condition is analogous to that encountered in packed-bed geometries. In dead end filtration, the applied pressure drives the entire feed through the membrane filter producing a filtrate which is typically particle￾free while the separated particles form a filter cake. The feed and filtrate travel concurrently along the length ofthe filter generating one product stream for every feed. In CFF, one feed generates two product streams, retentate and permeate. Per pass recovery in through-flow mode is almost 100% (since only the solids are removed) whereas in the cross-flow mode the per pass recovery typically does not exceed 20% and is often in the 1 to 5% range. Recirculation of retentate is thus necessary to increase the total recovery at the expense of higher energy costs. PERMEAT E