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Explain the use of soft water resin
Publisher:Xiangtaihao Chemical  Release Time:2020-01-04 14:18:34  Browse Times: Second
Principle of resin softening water Soft water resin uses the built-in resin tank of the water softener to replace the hardness ions in the water when the water passes. It is commonly referred to as the "ion exchange softening method" and its principle is as follows: Ion exchange water treatment refers to the use of ion exchangers to exchange the ions in the exchanger and the aqueous solution to produce reversible exchanges that conform to the quantity rules of such substances, resulting in water quality. Water treatments that improve without the structure of the exchanger changing substantially (chemically). In this water treatment method, only those cations that participate in the exchange reaction are called cation exchange water treatment; those that have only anions in the exchange reaction are called anion exchange water treatment; those that have both cations and anions in the exchange reaction are called cation and anion exchange Water treatment. Because the quality of raw water varies widely, and the quality of the effluent water is diverse, there are many types of ion exchange and a combination of water treatment methods. The use of these water treatment methods to soften, remove alkali and remove salt. When the ion involved in the exchange reaction is sodium ion Na +, this method is called sodium (Na) type ion exchange method, and this exchanger is called sodium (Na) type cation exchanger. Similarly, there is hydrogen (H ) Type ion exchange method and hydrogen (H) type cation exchanger. Principle of Resin Regeneration After soft water resin replaces a certain amount of calcium, magnesium and other hardness ions in water, the water can no longer be softened. At this time, a water softener is required to regenerate the resin, which is the reduction and regeneration method after resin calcium pollution. (1) When regenerating strong cation exchange resin with Na solution, a stepwise regeneration method should be adopted. Regeneration was started with a low-concentration Na solution, because the Ca2 + concentration desorbed from the resin was high at this time, but the Na concentration was low, and even a small amount of Ca2 + Na precipitates would be washed away by the solution. Then gradually increase the Na concentration. At this time, the Ca2 + concentration desorbed from the resin is low, and no Na precipitate is formed. (2) Because the weak cation exchange resin is regenerated with the regeneration waste liquid of the strong cation exchange resin. Therefore, at the same time as the acid is fed, the weak cation exchanger must be fed with diluted water (filtered water from JF9201), and the amount of water fed is preferably not more than the acid inlet of the exchanger. In addition, pay attention to observe the color of the regeneration waste liquid discharged from the weak cation exchanger, such as white turbidity, even if the acid concentration is adjusted. (3) After the acid feeding, the weak cation exchanger must be immediately replaced with water after JF9201 filtration, and the strong cation exchanger must be immediately replaced with purified water. (4) Calcium pollution is more likely to occur in winter due to the low temperature of the regeneration solution. Therefore, before regeneration, the weak cation exchanger must be scrubbed and backwashed, and the pipeline for the regeneration waste liquid between the weak cation exchanger and the strong cation exchanger must be backflushed to prevent it from happening. This process takes 2-3 hours in a domestic water softener and is commonly referred to as water softener backwash regeneration. Depending on the type of water softener, a certain amount of resin regeneration agent (Na) is required. Regeneration conditions Resin regeneration is an important part of ion exchange water treatment. There are many factors that affect the regeneration effect, such as the regeneration method, the type, purity, and amount of the regenerant, the concentration, flow rate, and temperature of the regeneration solution. To obtain a good regeneration effect, adjustment experiments must be performed to determine the optimal regeneration conditions. 1. Regeneration mode The softening resin regeneration mode is divided into three types: forward flow, convection flow and shunt flow according to the regeneration liquid flow direction and the water flow direction during operation. Downstream regeneration refers to the regeneration mode where the regeneration liquid flows in the same direction as the water flow during operation, and usually flows from top to bottom. Convection regeneration means that the direction of regeneration fluid is opposite to the direction of water flow during operation. Conventionally, the water treatment process in which the water flow flows downward during the operation and the regeneration liquid flows upward is called a countercurrent regeneration process. The water treatment process in which the water flows upward during operation and the bed floats; the water treatment process in which the regeneration liquid flows downward during regeneration is called a floating bed process. Convection regeneration can maximize the regeneration degree of the resin layer on the water outlet side, and the water quality is good. Shunt regeneration means that the regeneration liquid enters from the upper and lower ends of the exchanger at the same time and is discharged by the drainage device in the middle of the resin layer. During operation, water flows from the top to the bottom. The upper bed of this exchanger adopts the co-current regeneration process, and the lower bed adopts the convection regeneration process. 2. Variety and purity of regenerant Generally speaking, the regeneration effect of hydrochloric acid is better than sulfuric acid, and the regeneration cost of sulfuric acid is lower than that of hydrochloric acid. The purity of the regenerant is high, the content of impurities is small, and the degree of regeneration of the resin is high, especially the anion resin has a greater impact. 3, the amount of regenerant The amount of regenerant is an important factor affecting regeneration. The concept is the amount of regenerant used per unit volume of resin, the unit is kg / m3 (resin) or g / L (resin). Another commonly used indicator is the specific consumption of regenerant, which refers to the ratio of the amount of regenerant input to the working exchange capacity of the obtained resin. There is also a notation of regenerant consumption, which is the estimated pure regenerant dose required to obtain a unit working exchange capacity, in g / mol. Softening resin theoretically, 1 mol regenerant should restore the exchange resin to 1 mol exchange capacity, but in practice, the regeneration reaction can only proceed to the equilibrium state of ion exchange chemical reaction at most. Regenerating the resin with only a theoretical amount of regenerant cannot Fully restored its capacity, so the amount must exceed the theoretical amount. Increasing the amount of regenerant can increase the degree of regeneration of the resin, but after the specific consumption of the regenerant increases to a certain extent, the increase in the degree of regeneration is not obvious. The amount of regenerant is related to the properties of the ion exchange resin. Generally, the amount of regenerant required for strong resin is higher than that for weak resin. Different regeneration methods have different amounts of regenerants. Generally, the amount of regenerants used in downstream regeneration is higher than that in countercurrent regeneration. When the softening resin regeneration method adopts a downstream flow, since the regeneration liquid first contacts the resin that completely fails at the upper part, this part of the resin is well regenerated. When the regeneration solution flows down again and comes into contact with the resin at the bottom of the exchanger, a large amount of replaced ions have accumulated in the regeneration solution, which seriously affects the regeneration degree of the exchange resin, so that this part of the resin is not fully regenerated, and the effluent quality . If you want to increase the degree of regeneration of this part of the resin, you need to increase the amount of regenerant. When the softening resin regeneration method adopts counter current, the resin at the bottom of the exchanger is always in contact with the fresh regeneration agent, so it can reach a high degree of regeneration. During operation, the water finally contacts the resin with a high degree of regeneration to ensure the quality of the water . When countercurrent regeneration is used, the resin on the upper part of the exchanger is poor in regeneration. Although it is in contact with the water first, the ion content can still be exchanged because the ion content exchanged from the resin in the water is small. Play. Therefore, this regeneration method is superior and widely used. 4. Concentration of softening resin regeneration solution The concentration of regeneration solution is related to the regeneration mode. Generally, the regeneration solution concentration in downstream regeneration should be higher than that in countercurrent regeneration. Generally, HCl is preferably 3% to 5%, and NaOH is preferably 2% to 4%. 5. Soften the temperature and flow rate of the resin regeneration solution. Increasing the temperature of the regeneration solution can increase the degree of resin regeneration, but the regeneration temperature cannot exceed the maximum allowable temperature of the resin. Generally, strong acidic cation resin does not require heating when it is regenerated with hydrochloric acid. The temperature of the regeneration solution of the strongly basic type I anion resin is 35-50 ° C. The suitable regeneration temperature of strong alkaline type II anion resin is 35 ± 3 ℃. The flow rate of the regeneration liquid affects the contact time between the regeneration liquid and the resin, and generally 4 to 8 m / h is appropriate. The flow rate of the regeneration liquid in the countercurrent regeneration should ensure that the resin does not mess up. When the temperature of the regeneration liquid is very low, it is not appropriate to increase the flow rate. How often do soft water resins change? Resin for water softening equipment is usually replaced every 3-5 years. If you use a good soft water salt, you can extend the life of the resin. There are certain skills to replace the softened water resin. If you meet the skills, you can extend the life of the resin and increase its life, otherwise it will damage its performance, and naturally there will be its replacement skills and methods. 1. There is a certain skill and order when removing softened water resin. You must follow the order. First remove the water inlet and outlet pipes, the sewage pipe, the salt suction pipe, and then remove the control valve head! 2. Withdrawing the central tube, this step is an important process, but if the diameter of the tank is greater than 500mm, it is not necessary to remove the central tube, because the central tube will not be polluted. 3. Use the siphon principle to extract the resin. This is a very scientific method and worthy of promotion. 4. Then install the central tube (if removed) and plug it with plastic cloth above the central tube. This is to prevent the resin from pouring into the central tube and causing blockage. 5. Pour the resin and install the control valve head to fix the resin. 6. Adjust the control valve to the back-flushing position (downstream regeneration) and keep the water speed constant. This method will exhaust the resin tank gas. 7. See if there is any water leakage. If everything is properly placed, then the resin will be replaced!

Keyword: Resin   unsaturated resin   soft resin  

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