Ion-exchange membrane electrodialysis program and its application to multi-stage continuous saline water desalination

The first part of this article describes the program of a one-stage continuous electrodialysis process operating at a constant current mode. The full continuous electrodialysis program is developed and explained definitely by arranging equations systematically with the following supplementary steps. For preventing scale formation in concentrating cells, salt solutions supplied to the desalting cells are also fed to the concentrating cells. Influence of temperature to the performance of the electrodialyzer is taken into account. Pressure drop in the electrodialyzer is evaluated by incorporating the functions of hydrodynamic diameters of desalting and concentrating cells and slots. An electric current screening effect of a spacer is determined by the volume ratio of spacer rods in a desalting and concentrating cell. In the second part of this article, saline water is desalinated with the multi-stage electrodialysis program by operating the process at a constant concentration mode. Changing salt concentration of a feeding solution in each stage incrementally, the performances of the electrodialyzer such as; ion and solution flux across a membrane pair; cell voltage; current density; salt concentration in concentrating cells; energy consumption; water recovery; limiting current density; pressure drop in the cells and slots are computed in each stage. Energy consumption, water recovery, pressure drop and membrane area are computed in the total stages to produce drinking water. (C) 2012 Elsevier B.V. All rights reserved.