The term packed-bed is used if the resin bed is compacted against the upper nozzles during either the running sequence or the regeneration sequence. Counter current regenerated packed-bed technology such as Amberpack, Reversed Amberpack, Upcore etc. - can offer several advantages compared to conventional co-flow regenerated ion exchangers.
The packed-bed system is simple in design and costs less than comparable conventional systems. The construction is compact and inert resins can be used when found necessary. Counter current regeneration is always utilized in packed-bed technology and the conventional “fast rinse to sewer” can normally be compensated by a recycling rinse. These attributes mean greater efficiency with less chemicals and less waste.
The feed water first meets the most exhausted resin, then flows towards the best regenerated or almost virgin resin. In an optimum situation the effluent side resin only sees the fresh regeneration chemical and the already treated DI water. In compact beds there is no mixing of different resin layers. The regeneration chemical can be introduced from the top or alternatively from the bottom, but always opposite to the water flow. As a product very low conductivity water can be obtained; the conductivity is normally less than 1.0 µS/cm after the separate beds, and without the polisher. A value of less than 10 ppb can usually be obtained for silica. To attain the most stringent product quality, an appropriate and constant recycling DI water flow must be maintained. The other method is to use polishers in series with the basic train.
Depending on the nature and the structure of the system, the backwash can be made simultaneously with the regeneration phase in the pressure vessel, step-by-step or layer-by-layer in the resin wash tank or on a batch basis in the resin wash tank. With increasing head loss a pressure strike can be given or alternatively some part of the resin can be moved into the resin wash tank.