Water Treatment

Optimize your industrial water softener with a brine elution study

By Paul Sharpe, Industry Consultant - Boiler and Cooling, Kurita America Inc

Most industrial boiler systems require soft feedwater and without this softening pre-treatment, boilers are at risk of developing hard insulating deposits that reduce heat transfer efficiency and increase energy use. Severe deposit formation can permanently damage boiler tubes or cause dangerous failures from overheating. This article describes how water softening ion exchange process can remove these deposits and prevent such damage to boiler tubes and failures due to overheating.


ater softening is an ion exchange technique used for removing calcium and magnesium ions that form hard water scale such as calcium and magnesium carbonate. The process involves exchanging source water calcium

and magnesium cations for sodium cations that have been adsorbed onto resin beads filled with exchange sites. As water flows through the softener system, sodium ions are released (exchanged) from the resin, and the hard water ions are collected on the exchange sites. This process can be used to prevent the build-up of hard insulating deposits in boilers and thereby prevent any damage to boiler tubes or overheating of boilers.

When a softener with new (or regenerated) resin is placed in service, sodium ions adsorbed on the exchange sites within the resin are immediately exchanged with calcium and magnesium cations. This produces soft water with very little residual hardness in the effluent water. The resin bed will continue to exchange its sodium ions with

calcium and magnesium to a point where the exchange sites are reduced, and hard water can be detected in the softener output.This is referred to as the saturation point and is the point at which regeneration is needed. Cation softener regeneration requires a concentrated solution of sodium chloride (salt water) to be rinsed through the resin bed; this is a physicochemical process that uses osmotic pressure and physical flow to remove the hard water ions from the resin. The regeneration process uses at least three distinct sequences:

1. Backwash

Resin is counterflow backwashed using a specified flow rate based on water temperature and manufacturer’s specifications noted in the service manual. Using the correct flow rate is important in preventing loss of resin; if too high, the resin could be washed over to drain. Backwash serves to remove broken resin beads, dirt and debris, and reclassifies the bed for proper water flow during service.

Elution curve

A good regeneration that uses a minimum of salt

Using more salt than necessary. Reduce the brine draw flow by installing a dole valve or decrease the slow rinse rate.

Insufficient brining, increase the brine draw time cycle. 56

Brine eductor draws too slowly, check valve for blockage or adjust/replace brine valve.

March/April 2021 • Issue 2

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