Electrodialysis table salt production

Several other potential applications of electrodialysis in wastewater treatment systems which have been studied on a laboratory scale are reported in the literature. In most of these applications the average plant capacity, however, is considerably lower than that in brackish water desalination or table salt production. 

Electrodialysis. Electro dialytic membrane process technology is used extensively in Japan to produce granulated—evaporated salt. Filtered seawater is concentrated by membrane electro dialysis and evaporated in multiple-effect evaporators. Seawater can be concentrated to a product brine concentration of 200 g/L at a power consumption of 150 kWh/1 of NaCl (8). Improvements in membrane technology have reduced the power consumption and energy costs so that a high value-added product such as table salt can be produced economically by electro dialysis. However, industrial-grade salt produced in this manner caimot compete economically with the large quantities of low cost solar salt imported into Japan from Austraha and Mexico. 

Leading Examples Electrodialysis has its greatest use in removing salts from brackish water, where feed salinity is around 0.05-0.5 percent. For producing high-purity water, ED can economically reduce solute levels to extremely low levels as a hybrid process in combination with an ion-exchange bed. ED is not economical for the produc tion of potable water from seawater. Paradoxically, it is also used for the concentration of seawater from 3.5 to 20 percent salt. The concentration of monovalent ions and selective removal of divalent ions from seawater uses special membranes. This process is unique to Japan, where by law it is used to produce essentially all of its domestic table salt. ED is very widely used for deashing whey, where the desalted product is a useful food additive, especially for baby food. 

As discussed by Pletcher 24, electrodialysis is an electrically driven membrane separation process. The main use of electrodialysis is in the production of drinking water by the desalination of sea-water or brackish water. Another large-scale application is in the production of sodium chloride for table salt, the principal method in Japan, with production exceeding 106 tonne per annum. 

The second major application of electrodialysis is the production of table salt by concentration of seawater [8], This process is only practiced in Japan, which has no other domestic salt supply. The process is heavily subsidized by the... 

Electrodialysis was developed first for the desalination of saline solutions, particularly brackish water. The production of potable water is still currently the most important industrial application of electrodialysis. But other applications, such as the treatment of industrial effluents [45], the production of boiler feed water, demineralization of whey [46], de-acidification of fruit juices [47], etc. are gaining increasing importance with large-scale industrial installations. An application of electrodialysis which is limited regionally to Japan has gained considerable commercial importance. This is the production of table salt from sea water. Diffusion dialysis and the use of bipolar membranes have significantly expanded the application of electrodialysis in recent years [48]. 

The production of table salt from sea water by the use of electrodialysis to concentrate sodium chloride up to 2(X) g/L prior to evaporation is a technique developed and used nearly exclusively in Japan. More than 350,000 tons of table salt are annually produced by this technique requiring more than 5(X),000 square meters of installed ion-exchange membranes. Key to the success of this technology has been the low cost, high conductive membrane with... 

Electrodialysis 1. Desalination of brackish water 2. Production of table salt 3. Waste water treatment 4. Concentration of RO brines 5. Applications in the chemical, food, and drug industries... 

Electrodialysis has a number of other large-scale applications and these would include the manufacture of pure sodium chloride for table salt (in Japan, electrodialysis is the principal method, production exceeding 10 ton yr ), the demineralization of cows milk (for baby food), cheese whey and sugar solutions, the removal of excess acid from fruit juice and the isolation of organic acids from reaction streams. 

Seawater can also be concentrated by electrodialysis. An expenditure of about 150kWhrton of NaCl can bring the NaCl concentration up to 200gpl [20], This process has not found commercial application as an intermediate step in the production of large quantities of industrial salt. Where there is more value added on a smaller scale and not much competition from large producers, as in the production of table salt in Japan, it can operate successfully. 

Production of Table Salt and Drinking Water From sea water (30 0 g/L NaCl) and applying conventional electrodialysis technology, there can be obtained both a final diluate with... 

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