Statement of the Problem
Ion exchange processes are frequently used to remove unwanted ions from water. Typical ions removed include calcium and magnesium (hardness), dissolved iron and manganese, nitrate, or certain organics. The ion exchange media is typically a polymer which contains numerous locations for attachment of a benign ion which is exchanged for the unwanted ion in the water upon contact with the polymer. Eventually the exchangeable ions become depleted and the polymer must be regenerated with a fresh supply.
Control Strategy
Regeneration can be initiated based on time of day, time intervals or total flow through the exchange tank. In some applications, especially when there is a variable concentration of ions to be removed, time or flow based intervals may not be satisfactory. Under these conditions, either regeneration may not occur until after the tank has been exhausted or energy and resources may be wasted by regenerating too soon or too often.
An alternative is to base regeneration on a drop in ion removal efficiency, as measured by the detection of some minimum concentration of the removed ion in the exchange tank effluent.
Apparatus
ChemScan process analyzers can be used to detect ion exchange breakthrough in one or more exchange tank effluents. This information can be used to initiate backwash, initiate alarms and/or divert flow to alternate exchange tanks.
Ion Exchange Breakthrough, Copyright ASA Analytics
Ion exchange processes are frequently used to remove unwanted ions from water. Typical ions removed include calcium and magnesium (hardness), dissolved iron and manganese, nitrate, or certain organics. The ion exchange media is typically a polymer which contains numerous locations for attachment of a benign ion which is exchanged for the unwanted ion in the water upon contact with the polymer. Eventually the exchangeable ions become depleted and the polymer must be regenerated with a fresh supply.
Control Strategy
Regeneration can be initiated based on time of day, time intervals or total flow through the exchange tank. In some applications, especially when there is a variable concentration of ions to be removed, time or flow based intervals may not be satisfactory. Under these conditions, either regeneration may not occur until after the tank has been exhausted or energy and resources may be wasted by regenerating too soon or too often.
An alternative is to base regeneration on a drop in ion removal efficiency, as measured by the detection of some minimum concentration of the removed ion in the exchange tank effluent.
Apparatus
ChemScan process analyzers can be used to detect ion exchange breakthrough in one or more exchange tank effluents. This information can be used to initiate backwash, initiate alarms and/or divert flow to alternate exchange tanks.
Ion Exchange Breakthrough, Copyright ASA Analytics