External Water Treatment
{"Image DocumentName": "External Water Treatment", "Image ImageDescription": "Assessment of a Boiler. External Water Treatment. a) Ion-exchange process (softener plant) Water passes through bed of natural zeolite of synthetic resin to remove hardness. Base exchange: calcium (Ca) and magnesium (Mg) replaced with sodium (Na) ions. Does not reduce TDS, blow down quantity and alkalinity. b) Demineralization. Complete removal of salts. Cations in raw water replaced with hydrogen ions. Thermal Equipment/ Boilers. In the ion-exchange process, the hardness is removed when the water passes through a bed of natural zeolite or synthetic resin and without the formation of any precipitate. The simplest way to remove hardness through ion exchanges is \u2018base exchange\u2019 in which calcium and magnesium ions are exchanged for sodium ions. Since the base exchanger only replaces the calcium and magnesium with sodium, it does not reduce the TDS content, and blow down quantity. It also does not reduce the alkalinity. Demineralization is the complete removal of all salts. This is achieved by using a cation resin that exchanges the cations in the raw water with hydrogen ions, producing hydrochloric, sulphuric and carbonic acid. Carbonic acid is removed in degassing tower in which air is blown through the acid water. Following this, the water passes through an anion resin which exchanges anions with the mineral acid and forms water. Regeneration of cations and anions is necessary at intervals using, typically, mineral acid and caustic soda respectively. The complete removal of silica can be achieved by correct choice of anion resin. Ion exchange processes can be used for almost total demineralization if required, as is the case in large electric power plant boilers. \u00a9 UNEP 2006.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}