DOWEX Ion Exchange Resins WATER CONDITIONING MANUAL

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Ion Exchange Resin Operational Information Figure 24. Approximation of useful life of in-use cation exchange resins. (based on water retention capacity) Figure 25. Approximation of useful life of in-use anion exchange resins. (based on remaining salt splitting capacity) DOWEX Ion Exchange Resins 56 Water Conditioning Manual
Ion Exchange Cleaning Procedures 10 ION EXCHANGE CLEANING PROCEDURES 10.1.1 Removal of Iron and Manganese from Cation Resins Iron has a complex chemistry and may be present as inorganic precipitates (oxides/hydroxides), as cationic species, or as organometallic complexes. In water-treatment applications, iron is generally converted to the less-soluble Fe (III) form within the resin bed. Manganese also may be present as inorganic precipitates. Three possible cleaning procedures are described: Air brushing: This is used in condensate polishing and other water-treatment applications such as makeup demineralization to remove insoluble, particulate iron (crud). 1. Exhaust the resin. 2. Air-brush the bed and then backwash for 30 min. 3. Regenerate the resin as normal. If the particulates are large, backwashing may not be effective in removing them. In this case, the solids can be driven down to the bottom of the bed and removed through the screen/drain using the following procedure: 1. Air-brush the bed for 30 s at a rate of approximately four volumes air per min per volume resin and then drain the bed for 30 s, adding more water at the top. 2. Repeat step 1 about 10–20 times. 3. Regenerate the resin as normal. If soluble iron is also present, air-brushing should be followed by acid treatment. HCl treatment: This is used to remove crud and soluble contaminants. If possible, the acid injection in step 2 and the displacement step 4 should be made upflow into the resin bed to move the bed and increase contacting. If only downflow injection is possible, a normal backwash should be made first to loosen the bed prior to the treatment. 1. Exhaust the resin and backwash. 2. Pass two bed volumes of 10% HCl solution with a contact time of 30 min. 3. Leave to soak for 2–4 h. 4. Displace with two to three bed volumes of water. 5. Rinse out with three to five bed volumes of deionized water fast rinse (downflow). Note: HCl is very corrosive and can cause severe burns on contact. Avoid inhalation of the fumes and provide adequate ventilation when handling the acid. Refer to the manufacturer’s safety information. The acid can also cause problems with materials of construction, so ensure that the acid is compatible with the plant equipment before use. Reference Document: Tech Facts 177-01852 Reducing agent treatment: This treatment uses a reducing agent (sodium dithionite, Na2S2O4) to convert Fe(III) to the more soluble Fe(II). It is used in water softening and other applications, where acid can damage the materials of construction. If possible, steps 2, 4, and 6 should be made upflow into the resin bed to increase contact. If only downflow injection is possible, a normal backwash should be made first to loosen the bed prior to the treatment. Do not use air-brushing to agitate the resin bed because this will impair the reducing agent performance. 1. Exhaust the resin and backwash. 2. Pass one bed volume of 5% Na2S2O4 solution with a contact time of 30 min. 3. Leave to soak for 2 h. 4. Pass one bed volume of 5% Na2S2O4 solution with a contact time of 30 min. 5. Leave to soak for up to 24 h if possible. 6. Displace with two to three bed volumes of water. 7. Rinse out with three to five bed volumes of deionized water fast rinse. 8. Double regenerate the resin (same NaCl concentration, double time). DOWEX Ion Exchange Resins 57 Water Conditioning Manual
Page 1 and 2:
Dow Liquid Separations DOWEX Ion Ex
Page 3 and 4:
TABLE OF CONTENTS 1 Introduction to
Page 5 and 6: TABLE OF TABLES Table 1. Terms comm
Page 7 and 8: Introduction to Ion Exchange 1 INTR
Page 9 and 10: Terms, Acronyms, And Abbreviations
Page 19 and 20: Sodium Cycle Ion Exchange Process (
Page 27 and 28: Brackish Water Softening Using H2SO
Page 29 and 30: Brackish Water Softening Resin oper
Page 31 and 32: Dealkalization: Salt Splitting Proc
Page 33 and 34: Dealkalization: Weak Acid Cation Re
Page 35 and 36: Dealkalization: Weak Acid Cation Re
Page 37 and 38: Demineralization (Deionization) Pro
Page 39 and 40: Demineralization (Deionization) Pro
Page 41 and 42: The UPCORE Counter-Current Regenera
Page 47 and 48: Ion Exchange Resin Operational Info
Page 55: Ion Exchange Resin Operational Info
Page 59 and 60: Ion Exchange Cleaning Procedures Re
Page 61 and 62: Ion Exchange Cleaning Procedures 10
Page 63 and 64: Ion Exchange Cleaning Procedures Ta
Page 65 and 66: Designing an Ion Exchange system fr
Page 67 and 68: Designing an Ion Exchange system As
Page 69 and 70: Designing an Ion Exchange system 11
Page 71 and 72: Useful Graphs, Tables, and Other In
Page 91 and 92: Index 14 INDEX A Abbreviations · 9
Page 93: Dow Liquid Separations Offices. For
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