Deionization systems (Ion Exchange) are vessels containing synthetic resins with reactive sites. Depending upon the resin used, these sites exchange hydrogen ions for positive ions and hydroxide ions for negative ions. Systems are operated with anionic resin containing vessels and cationic resin containing vessels in series. At WPT, the designs of these system internals take into account the feedwater characteristics in order to maximize efficiencies in resin life and cleaning cycles while eliminating channeling. Our robust internal designs separate WPT from the rest of the field.

Water softeners exchange sodium ions for hardness (calcium and magnesium ions) by passing the influent through a bed of synthetic polymer beads that have an affinity for cations. The beads, or resin, retain a high concentration of sodium ions that have a relatively-low electrical potential. Zoom This allows calcium and magnesium ions with a greater potential or charge to easily replace them. When the inlet water flows through the cation-resin bed, the calcium and magnesium ions in the water attach to the resin beads, forcing the beads to release the sodium ions.

When hardness monitoring or total-water-softened monitoring detects substandard water quality, the resins must be regenerated. Regeneration is an ion-exchange process in which the calcium and magnesium ions on the resin beads are exchanged for sodium ions. Flushing the system with a brine solution that contains a high concentration of sodium ions achieves ion exchange.

Separate bed ion exchange systems typically reduce the ions in water resulting in a product water conductivity of near 1 megohm-cm (approximately 1 ppm as CaCO3). Cocurrent ion exchange systems operate with the water flowing from the top of the vessel through the resin bed to the bottom of the vessel. When regenerating, the regenerant flows in the same direction as the process water.

Like the cocurrent operation, the feed water flows from the top of the vessel through the resin bed to the bottom of the vessel. Unlike the cocurrent vessels, the regenerant in the countercurrent system flows from the bottom of the vessel up through the resin bed and exits the vessel through the top. These types of ion exchange systems require that the feedwater be low in suspended solids.

Mixed bed ion exchange systems contain both anion and cation resin sites and are typically used to polish product water to much hgiher water quality. Product water from a mixed bed system is approximately 18 megohm-cm (0.028 ppm).

Packed bed ion exchange systems involve vessels that are essentially filled completely with ion exchange resins. These systems have the benefit of low leakage and lower waste generation. They do require low suspended solids in the feed and are regenerated in a countercurrent flow. These systems are built with external backwash tanks to allow cleaning after sluicing from the packed bed vessel.

Condensate polishers remove the suspended and dissolved minerals from steam cycle condensate streams. These utilize mixed bed ion exchange resin with deeper layer than conventional mixed bed exchangers.

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