5. System sizing

The sizing of an electrodialysis plant is based on pilot tests, carried out with a stack comprising several elementary units with characteristics representative of those used on an industrial scale. These tests are carried out in batch mode (recycling of fluids in the feed tanks) and at an imposed current density (constant current mode). Figure 13 shows a schematic diagram of a pilot plant. Temperature, potential difference across the stack and changes in fluid composition in the various feed tanks are monitored over time. This is determined by measuring conductivity, pH and volume. In the case of simple solutions, these global quantities are sufficient to carry out material balances, as conductivity is proportional to concentration. In the case of more complex fluids, additional analytical methods (e.g....