Maximum Freeboard for Ion Exchange Backwash
Maximum Freeboard for Ion Exchange Backwash
(OP)
Does anyone know what the maximum recommended freeboard height to accomplish backwash of a single bed ion exchanger. I have observed industry standards for minimum freeboard at approx. 75% based on 50% bed expansion, but I have not seen guidelines for maximum freeboard and the impact.





RE: Maximum Freeboard for Ion Exchange Backwash
1. Is is cation resin or anion resin or mixed bed resin.
2. What is the water temperature.
3. What is the backwash flow rate.
4. What is the resin beads particule size.
Cation resins are heavier than anion resins. Bed lifting is different for different water temps and flow rates.
Most of the Tech Data Bulletins have graphs and curves that show how much the bed will expand.
Gary Schreiber, CWS VI
The Purolite Co.
RE: Maximum Freeboard for Ion Exchange Backwash
As you mentioned, most resin suppliers specify minimum freeboard (i.e. 50-75%) based on 30-50% bed expansion as you describe, but is there a limit to how much freeboard. One document rule of thumb states that you need 3 volumes (bed + freeboard) needed to achieve a 95% flush out of the solids from a completely stirred tank reactor (CSTR). Does this apply to IX
RE: Maximum Freeboard for Ion Exchange Backwash
Gary Schreiber, CWS VI
The Purolite Co.
RE: Maximum Freeboard for Ion Exchange Backwash