COST REDUCTION THROUGH CREATIVE CHEMICAL TECHNOLOGY

Technical Data Sheet

ION EXCHANGE RESIN CLEANING

General

Much has been written on the fouling of ion exchange resins.  However, for the purpose of discussion of cleaning procedures, it is only necessary to know the most common foulants of cation resins are iron, copper, manganese and aluminum while for anion resins, colloidal silica and organics pose the most problems.  Once it has been determined what the major cause of the fouling is and appropriate cleaning chemicals selected, the actual cleaning procedures are quite similar. 

Preparation for Cleaning

Prior to any cleaning operation, the resin must be converted back to its exchange form (sodium or hydrogen for cation resins and most commonly hydroxide for anion resins) in order to maximize the performance of the cleaning chemicals.  Therefore, the units should be regenerated immediately prior to cleaning.  Also, where the units are typically regenerated at lower regenerant dosages (i.e. 6-10 lbs. salt/ft.³ for sodium zeolite softeners) for economy, if possible the regenerant strength should be increased to the maximum recommended (i.e. 15 lbs. salt/ft.³) for this regeneration. 

Cleaning Procedure

Once the unit is regenerated and isolated from the system, it must be partially drained and the top handhole plate removed.  Then the predetermined amount of the cleaning chemical should be added and then water added to bring the level to just above the resin bed (1" is good).  Do not drain the unit until ready to start the cleaning as the resin must always remain in a moist condition or it can be ruined. 

An air lance should then be inserted into the resin bed to provide agitation and good mixing of the chemicals and resin for cleaning.  It is recommended that a pipe be securely tied or welded to the air lance pipe so that the lance cannot be inserted into the resin support bed which, if sufficiently disturbed, could result in major resin losses into the system.  During the cleaning operation, the air lance should be moved frequently to assure coverage of the entire resin bed. 

Typically, the cleaning operation will require from 4-8 hours.  When complete, remove the lance, fill the unit with water, replace the handhole cover and backwash thoroughly.  Then double regenerate the unit and return it to service.

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