Tortuous-path electrodialysis spacer

Fig. 9 Schematic diagram of a) a tortuous-path electrodialysis spacer gasket, and b) a sheet-flow clectrodialysis spacer gasket...

The membranes in electrodialysis stacks are kept apart by spacers which define the flow channels for the process feed. There are two basic types(3), (a) tortuous path, causing the solution to flow in long narrow channels making several 180° bends between entrance and exit, and typically operating with a channel length-to-width ratio of 100 1 with a cross-flow velocity of 0.3-1.0 m/s (b) sheet flow, with a straight path from entrance to exit ports and a cross-flow velocity of 0.05-0.15 m/s. In both cases the spacer screens are... 

Figure 8.5 Diagram of a tortuous-path spacer for an electrodialysis stack.

In normal electrodialysis the spacers are made of nonconductive material. However, ion-conducting spacers are used to receive extremely desalinated water. Depending on design, the fluid between the membranes can move through channels, which form either a tortuous path or a set of parallel paths. 

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