A preliminary technical and economic investigation of sea water demineralization by ion-exchange for calcium and bicarbonate ions and their subsequent removal by thermal decomposition (1)
✍ Scribed by John P. Ranck
- Publisher
- Elsevier Science
- Year
- 1969
- Tongue
- English
- Weight
- 805 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0011-9164
No coin nor oath required. For personal study only.
✦ Synopsis
Considerations
in the choice of a thermolytic salt to be exchanged for the ions in sea water are discussed. The literature relating to the decomposition and regeneration of calcium bicarbonate solutions is reviewed. Capital and operating costs for a plant producing one million gallons of demineralized water per day are calculated by the procedure suggested by the U.S. Office of Saline Water. Net cost is estimated to be $1.89 per thousand gallons, but could drop as low as $0.41 per thousand gallons if the process is credited with the value of by-products. INTRODUCTIOK fan-exchange processes have been suggested as a means of demineralization of sea water. Direct exchange of hydrogen ions and hydroxide ions for the cations and anions. respectively, in sea water has been prohibitivety expensive because of the high cost of regenerant chemicals. Gilliland (2) has suggested the exchange of ions of a "thermolytic" salt, such as ammonium carbonate, which is reversibly dissociable through pressure-temperature variations into two non-liquid components, at least one of which is gaseous. These components could be recovered and used for regeneration of the ion-exchange resin. A thermolytic salt which will dissociate into two gases will necessarily yield an acid anhydride and a basic anhydride. To be acceptable for this type of exchange process, a gaseous anhydride must have a limited solubility in water so as to be easily recoverable, must lack toxicity, should be safe and relatively easy to handle, should be available in the required quantiti~ at reasonable cost, and its ion must exchange suitably for sodium ion or chloride ion on an available resin. Among the common gaseous acidic anhydrides, fluorine and hydrogen fluoride are sufficiently corrosive to be ruled out from first considerations, chlorine and hydrogen chloride both provide chloride ion, the principal anion which is to Desalination, 6 (1969) 7185