Mixed-action filters purify water through a layer of granular material, which is a mixture of anion exchange resin and cation exchange resin. These materials perform their functions sequentially and at the outlet they allow to obtain water freed from decay products.
Mixed-action filters have the function of removing hydrated salts from the treated water. Such plants have their own filter, a valve system for reinstalling flows, and schemes for preparing, dosing, and storing regeneration solutions. Filters of mixed action (FSD) can be regenerable and non-regenerable. The first type has a fundamentally different design and external regeneration. The second refers to bulk filters and does not have a control unit.
How do FSDs work?
FSD carry out pressure filtration of water through a layer of granular material. This is the mixture of anion exchange resin and cation exchange resin. The grain size of the cation exchanger should be larger so that during the operation of loosening and a subsequent decrease in the pressure of water, the cation exchanger precipitates and the layer of anion exchange resin is located on top. A feature of mixed-action filters is the use of both resins in the same housing. As a result, such a load can work as an infinite number of cationite and anionite microinstallations that perform their functions in series.
The design of the FSD includes distribution devices for supplying water and regeneration solutions, a drainage system and an intermediate collector. Compressed air is supplied to the bottom of the unit, which facilitates the mixing of ion exchangers after regeneration. During the recovery process, the acid solution enters through the lower drainage device and is discharged through the intermediate manifold. To prevent it from entering the anion exchange resin, desalted water is passed through it from top to bottom, which is also discharged through an intermediate distribution system.
