Cellulose flat-sheet filter

In Situ Filter Membranes In situ membranes are being fitted into incinerator flue-gas stacks in an attempt to reduce hydrocarbon emissions. Two types of commercially available gas separation membranes are being studied (1) flat cellulose acetate sheets and (2) hollow-tube fiber modules made of polyamides. 

An industrial application of dialysis is the recovery of caustic from hemi-cellulose solutions produced in making rayon by the viscose process. Flat-sheet membranes are placed parallel to each other in a filter-press arrangement (see Chap. 30, p. 1004) and water is passed countercurrent to the feed solution to produce a dialyzate with up to 6 percent NaOH. Recovery of salts or sugars from other natural products or other colloidal solutions could be achieved by dialysis, but ultrafiltration is more likely to be used because of the higher permeation rates that can be obtained. 

In a lenticnlar modnle, cellulose-based Alter media identical to those in flat-sheet Alters are mounted in sealed nnits, ready for use (Figure 11.13). Implementation is simpler and there is no risk of leaks at high pressnre (a common problem in tray filters). 

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