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What is a Condensate Polisher?

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  • Written By: Paul Scott
  • Edited By: R. Halprin
  • Last Modified Date: 23 September 2016
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    Conjecture Corporation
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A condensate polisher is an installation designed to remove impurities and trace minerals from power plant steam. The condensate is collected as a byproduct for reuse as boiler feed water and requires that all impurities be removed prior to reintroduction into the system. This is a precautionary measure to prevent boiler corrosion damage 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 which serve as ion and physical filters to produce clean, demineralized water. Once the beads' cleansing action is exhausted, they are either rinsed and regenerated or, in the case of nuclear plant installations, sent to radioactive waste treatment facilities.

Most electric power generation plants produce large quantities of steam as a process byproduct. In most cases, the steam is allowed to condense for reuse as feed water for the facilities' boilers. This is a sound financial and environmental practice, thereby making the plants more cost effective with reduced environmental footprints. The reuse of condensate is problematic, though, due to the large amounts of process-generated impurities suspended and dissolved in the steam. Condensate polisher installations purge the condensate of both dissolved silica oxide impurities and suspended iron oxide solids, and return usable, mineral free water to the boilers.

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Condensate polishers function on both a chemical and mechanical level by utilizing ion exchange and physical filtering 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 a process of ion exchange between the beads and the dissolved impurities. The polymer resins used to manufacture the beads may be either of anion or canion types which remove negatively or positively charged ions respectively. In many applications, mixed resin beds are used which remove both simultaneously.

Suspended solid impurities are eliminated by a process of mechanical filtering while passing through the bead beds. Generally these are iron oxide particulates or solids which are shed from the facility equipment during the power generation process. After a period of use, the beads become saturated with solids and their ion exchange capabilities become exhausted. The beads may then be removed from the condensate polisher enclosures and rinsed to remove all trapped solids. The chemical structure of the beads is also regenerated during the process restoring their ion exchange capabilities. Due to the highly regulated nature of the nuclear power generation industry, however, exhausted condensate polisher beads from fusion plants are generally transferred to radioactive waste disposal facilities.

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