Condensate polishers remove impurities from power plant steam to produce clean, demineralized water for reuse as boiler feedwater. They use ion exchange and physical filtration processes to remove dissolved silica and suspended iron oxide solids. The beads can be regenerated or sent to radioactive waste treatment plants.
A condensate polisher is an installation designed to remove impurities and trace minerals from the steam of a power plant. Condensate is collected as a by-product for reuse as boiler feedwater and requires all impurities to be removed before re-introduction into the system. This is a precautionary measure to prevent corrosion damage to the boiler and increased maintenance requirements. The Condensate Polisher removes impurities such as silica and iron oxides by passing the condensate through beds of specially formulated polymer resin beads that act as physical and ionic filters to produce clean, demineralised water. Once the cleaning action of the pearls has finished, they are rinsed and regenerated or, in the case of nuclear plants, sent to radioactive waste treatment plants.
Most power generation plants produce large amounts of steam as a by-product of the process. In most cases, the steam can condense to be reused as feedwater for plant boilers. This is sound financial and environmental practice, making plants more cost-effective with a reduced environmental impact. However, the reuse of the condensate is problematic due to the large quantities of process-generated impurities suspended and dissolved in the steam. Condensate polishers remove dissolved silica impurities and suspended iron oxide solids from the condensate and return usable, mineral-free water back to the boilers.
Condensate polishers work on both a chemical and mechanical level using ion exchange and physical filtration processes. Both functions are achieved by passing the condensate through beds of specially formulated cross-linked polystyrene polymer beads. During its passage through the bead bed, dissolved impurities such as silica oxides are removed from the condensate by an ion exchange process between the beads and the dissolved impurities. The polymer resins used to manufacture the beads can be of the anion or canonical type which remove negatively or positively charged ions, respectively. In many applications mixed resin beds are used which remove both at the same time.
Suspended solid impurities are removed by a mechanical filtration process as they pass through the bead beds. These are typically iron oxide particles or solids that are released from plant equipment during the power generation process. After a period of use, the beads become saturated with solids and their ion exchange capabilities are depleted. The beads can then be removed from the condensate polisher cases and rinsed to remove any trapped solids. The chemical structure of the pearls is also regenerated during the process, restoring their ion exchange capabilities. Due to the highly regulated nature of the nuclear power generation industry, however, spent condensate polish beads from smelting plants are typically transferred to radioactive waste disposal facilities.
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