Separation Technologies Frequently Asked Questions
Purification, Recovery, Waste Treatment
- Resin conditioning
- Service flow rate
- How to measure a resin volume in a plant?
- What is important to know at the regeneration step?
- What precautions should be taken during prolonged shut down?
When the resin is in the suitable ionic form, the only necessary conditioning after the loading step is a backwash with deionized water. Otherwise, the resin is converted into the appropriate ionic form according to the regeneration instructions given in the product data sheet.
The service flow rate is fixed based on the performance and the pressure drop limitations. It is common practice to refer the flow rate in terms of bed volume per hour. The volume of the resin is called a "bed volume" or "BV". A flow rate of 1 to 20 BV/h can be used in the loading step. Please consult our product data sheets for recommended operating conditions.
The volume of resins should be measured immediately after filling the column, in the ionic form as delivered, i.e. before regeneration or exhaustion. The volume measurement should be done after backwashing, settling and draining the bed to the resin surface. The method described here is valid for ion exchange vessels with freeboard.
When the resin is exhausted, the column of resin is regenerated with a particular aqueous solution of regenerant. Three parameters have to be considered during the regeneration step: the solution concentration, the volume required and the flow rate through the column.
The chemicals used for regeneration must contain low levels of impurities. Substances that cause precipitation during regeneration cannot be tolerated. Impurities that dissociate and produce ions competing with the regenerant ions, i.e. cations other than H+ in the acids and anions other than OH- in the alkalis, reduce regeneration efficiency and operating capacity, and increase ionic leakage. Oxidants (mainly Cl2) may deteriorate the resin.
Generally, a concentration of about 1.0N is used. Regeneration should be preceded by backwashing and followed by rinsing. First, a slow rinsing using deionized water at the same flow rate as the regenerant solution is employed to remove excess regenerant then a fast rinse, usually at the service flow rate or at about twice the rate applied for the slow rinse.
Please consult our product data sheet for recommended operating conditions for ion exchange resins and resins with special functional groups.