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Method Of Using Mixed Bed Anion And Cation Exchange Resin And Filling Steps

Jul 21, 2020

New resin pretreatment:


  Due to various reasons such as transportation and storage, it is easy to dehydrate the new resin. It can be found by the naked eye and feel. In this case, in order to prevent the resin from contacting with water and other regenerated liquids and cause bursting and fragmentation, causing unnecessary waste, such resins must be soaked in 8% salt water for about 16 hours (frequently stirred during soaking). Fully swell the resin and use it after rinsing with water until it has no salty taste. Without the above phenomenon, the resin does not need to be pretreated.


   Resin filling:


The resin filling height of the domestic mixed bed equipment is 5(6)00mm for cation resin and 10(2)00mm for anion resin. When it is not re-ecological (that is, when the cation resin is sodium type and the anion resin is chlorine type), the cation resin filling height cannot be high Pass the middle discharge, but it should not be lower than the middle discharge 5cm. The filling ratio of yin and yang resin is 2:1 (or 1.5:1). The 001×7MB cation exchange resin is on the bottom, and the 201×7MB anion exchange resin is on the top.


   Resin flushing:


   After the resin is loaded into the exchanger, backwash the resin layer with clean water until the water is clear, odorless, and free of finely divided resin.


   Use a 4-5% HCl solution of about 2 times the volume of the resin to pass through the resin layer at a flow rate of 2m/h. After all in, soak for 4-8 hours, drain the acid solution, and rinse with clean water until the effluent is neutral, and the rinse flow rate is 10-20m/h.


   Use about 2 times the resin volume of 2-5% NaOH solution, pass and soak in the HCl solution as above. Drain the lye, rinse with clean water until the effluent is neutral, and the flushing flow rate is the same as above. If the acid and alkali solution can be repeated 2-3 times, the effect will be better.


   Yin and Yang resin mix:


After flushing, open the lower inlet and upper discharge valves, start the middle water pump (backwash to loosen the resin layer), and close the middle water pump and the inlet valve when the water in the column is discharged to 100-150mm above the resin layer; 2. Open a small amount of emptying valve, open and control the air intake of the intake valve (intake pressure is 0.1-0.15Mpa), observe the rhythmic boiling and mixing of the resin in the upper and lower sight glasses, so that the color of the upper and lower resins is consistent. The intake time is generally 10-15 minutes; 3. After the mixing is over, close the intake valve and the exhaust valve, and then quickly open the upper intake valve, the middle water pump, and the lower exhaust valve (to make the resin settle quickly to prevent the resin from regenerating during the settling process. Layered). At the same time, prevent the resin from coming out of the water, otherwise there will be bubbles between the resins, which will affect the effluent quality of the mixed bed (if the mixing effect is not good, the mixing operation can be repeated).


  Precautions:


   After running for more than one year, the actual filling height of the resin must be checked. If the resin layer is not high enough, the resin needs to be filled accordingly.


   There are two main indicators of mixed bed effluent, one is conductivity <0.2us/cm, and the other is silicon content Csio2<0.02mg/L, which is qualified.


   If the amount of water produced in the mixed bed cycle decreases significantly, the effluent index is unstable, and the regeneration acid and alkali consumption and water consumption remain high, it is necessary to regenerate or test whether the resin is contaminated and the resin strength.


  Demineralized water mixed bed regeneration requirements description:


  1. Chemical cleaning of reverse osmosis membrane with citric acid solution cycle cleaning


  2. Thorough stratification of the mixed bed, standard regeneration, qualified cleaning, uniform mixing = qualified effluent conductivity. 3. If it is iron poisoning, the resin will turn red, most of the reason is because the resin is in use because of the iron in the equipment and the iron in the treatment liquid. The resin pollution is generally high-priced iron, and about 5% of HCI can be used for the treatment cycle. It can be soaked for 5-8 hours to turn high-priced iron into low-priced iron. After processing, the resin is cleaned with water.


   The mixed bed needs to be regenerated when the outlet water resistivity ≤ 1MΩ. The operating procedure for the regeneration of anion and cation resin in this mixed bed adopts the "two-step regeneration method"-that is, the anion (upper part) is first regenerated by alkali; then the cationic resin (lower) is regenerated by hydrochloric acid.


   One, yin and yang resin layering


Backwashing: Open the lower inlet valve, upper discharge valve, start the intermediate water pump, rinse with RO effluent at a large flow rate (about 3000L/h) for 20 minutes, and rinse with a small flow rate (about 600L/h) for about 15 minutes to loosen the resin layer. .


  The quality of resin delamination is also related to the degree of resin failure. The greater the degree of resin failure, the easier the delamination.


If the yin and yang resin cannot be stratified due to mutual adhesion and clumping: slowly open a small amount of clean compressed air, and then adjust the emptying valve to make the compressed air enter and discharge from the mixed bed from the bottom to the top. Observe the loosening of the resin from the upper and lower sight glasses to facilitate stratification According to the situation, the operation time and frequency can be extended, and then the layering of the anion and yang resin can be treated according to the above-mentioned backwash method.


  The layering of yin and yang resin is one of the very critical and important steps in the regeneration operation.


   2. Remove the water in the column)


   Drainage and static settlement: close the middle water pump and inlet valve, open the middle and lower discharge valves, drain the water in the resin column (to prevent the regenerated liquid from being diluted), and let it stand for 5 minutes after the water is exhausted.


   3. Precautions for preparing acid and alkali solution


   Be careful when preparing acid and alkali solutions, wear goggles, rubber gloves and masks, and keep indoor ventilation; if it splashes on the skin, rinse with plenty of water or seek medical attention.


  Four, anion resin into alkali


1. Prepare the lye with pH=14 with purified water; 2. Adjust the outlet valve on the lye barrel, open the alkaline valve (upward), start the lye pump, open the drain valve to remove the air, and wait After the lye enters, when the anion resin layer is completely immersed, close the drain valve, open the middle drain valve and control the opening degree of the middle drain, the flow rate of the lye is 300-500l/h (the alkali is about 45 minutes); 3. The lye After entering, rinse the dilution lye tank and the alkali inlet pipeline with RO water in time for 20 minutes, then close the lye pump and the alkali inlet valve; 4. Open the upper inlet valve, start the intermediate water pump, and rinse with RO water to the middle The drain valve discharges until pH=10. Then open the lower drain valve and close the middle drain valve until water comes out


   Five, positive resin into acid


1. Prepare the acid solution with pH =1 with purified water; 2. Adjust the outlet valve on the acid tank, open the acid valve (downward), start the acid pump, open the drain valve to remove the air, and wait After the acid enters (flow rate is about


250-300l/h) When the cation resin layer is completely immersed (observed by the middle row looking through the sight glass), close the drain valve and open the middle drain valve at the same time and control its opening degree; 3. When the pH of the middle drain liquid is =1, it can be increased appropriately The acid flow rate is better so that the cation resin does not flicker (it takes about 40 minutes to enter the acid); 4. After the acid solution is finished, rinse the diluted lye tank and the acid inlet pipeline with RO water for 20 minutes, and close the acid solution Pump and acid inlet valve; 5. Open the upper inlet valve and lower inlet valve again, start the middle water pump and rinse with RO water. When the pH value of the outlet valve in the test is 7-8, close the upper inlet and lower inlet valves, and the middle row handles The water is drained.


   6. Yin and Yang resin mix


1. After the resin is cleaned qualified, open the lower inlet and upper discharge valves, start the intermediate water pump (backwash to loosen the resin layer), and close the intermediate water pump and the inlet valve when the water in the column is discharged to 100-150mm above the resin layer ; 2. Open a small amount of exhaust valve, open and control the intake of the intake valve (inlet pressure is


  0.1-0.15Mpa), observe the rhythmic boiling and mixing of the resin in the upper and lower sight glasses, so that the color of the upper and lower resins is uniformly mixed. The intake time is generally 10-15 minutes; 3. After the mixing is over, close the intake valve and the exhaust valve, and then quickly open the upper intake valve, the middle water pump, and the lower exhaust valve (to make the resin settle quickly to prevent the resin from regenerating during the settling process. Layered). At the same time, prevent the resin from coming out of the water, otherwise there will be bubbles between the resins, which will affect the effluent quality of the mixed bed (if the mixing effect is not good, the mixing operation can be repeated).


   Seven, mixed bed flushing


  After mixing, use RO effluent for positive washing. Normal washing flow rate is 2000L/h, washing for about 30 minutes, with the end point that the discharged water meets the purified water quality index.


   8. Possible problems and countermeasures during regeneration


1. After the resin is mixed, if there are bubbles between the resins, drain the water in the column through the lower drain valve, open the exhaust valve, and then backwash from the column at a very low flow rate (to make the resin layer immobile) The lower part is filled with water. When the liquid surface is flooded with all resin, stop the water intake immediately to prevent the resin from floating and stratifying. Then change to the normal washing method and rinse again.


  2. The factors that affect the degree of resin regeneration mainly include the amount, concentration, purity, regeneration time, flow rate of the regeneration agent, temperature during regeneration, etc., which should be paid attention to in actual operation. The allowable working pressure of the mixed bed is ≤0.2MPa.

Source:https://www.up-resin.com/

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