To ensure the one-time success of the user during start-up and debugging, the new resin should undergo the following pre-treatment. Due to the presence of a certain amount of residual oligomers in the pores of the new resin during the manufacturing process, certain methods should be used for treatment to prevent potential impact on the effluent quality during initial operation and increase operational resistance.
1、 Bed bodies with backwashing space for forward and reverse flow regeneration (generally referring to fixed beds)
1. Pretreatment of cation resin:
1.1 After the cation resin is filled, backwash shall be carried out first to ensure 80% backwash expansion rate to remove impurities and fine resin particles until the backwash effluent is clear, colorless, tasteless and foam free.
1.2. Inject 3-4% HCl solution at a rate of 4 m/h. When the outlet concentration reaches 1.5-2%, stop the injection and soak for more than 8 hours. Then rinse with raw water until the pH of the effluent is 2-3 (the pH value depends on the content of strong acid anions at the inlet). The purpose of first passing the acid is: according to national standards, the factory type of 001 * 7 resin is RNa type. First passing the acid and then passing the alkali can cause the resin to undergo a secondary expansion and contraction process. The purpose of pre-treatment is to enable the new tree to spit out the remaining oligomers in its pore size through the volume expansion and contraction during transformation. However, starting with alkali and then acid, there is obviously only one transformational transformation, and its effect is worse than the former.
1.3. Introduce 2-3% NaOH solution at a flow rate of 3-4m/h. When the outlet concentration reaches 1.5-2%, stop introducing and soak for more than 8 hours. Then rinse with cation bed effluent or deionized water until the effluent pH is 7-8, and wait for regeneration.
2. Pre treatment of anion resin:
2.1. After filling the anion resin, first perform backwashing to ensure an 80% backwashing expansion rate to remove impurities and small resin particles until the backwashed water is clear.
2.2. Inject 2-3% NaOH solution at a flow rate of 4m/h. When the outlet concentration reaches 1.5-2%, stop the injection and soak for more than 8 hours. Then rinse with cation bed effluent or deionized water until the effluent pH is between 7-8. The purpose of first adding alkali is: according to national standards, the factory type of 201x7 resin is RCl type. Adding alkali first and then adding acid can cause the resin to undergo a secondary expansion and contraction process, and the purpose of pre-treatment is to enable the new tree to spit out the remaining oligomers in its pore size through the volume expansion and contraction during transformation. However, starting with acid and then alkali, there is obviously only one transformational transformation, and its effect is worse than the former.
2.3. Inject 2-3% HCl solution at a flow rate of 3-4m/h. When the outlet concentration reaches 1.5-2%, stop the injection and soak for more than 8 hours. Then rinse with cation bed effluent or deionized water until the effluent pH is around 7, and wait for regeneration.
2、 Bed bodies without backwashing space, such as double chamber floating beds, double chamber fixed beds, single chamber floating beds, full chamber beds, etc
Due to the lack of backwashing space for the above bed types, there is generally an external cleaning tank, which aims to: firstly, perform external cleaning to ensure sufficient backwashing space to remove suspended solids trapped by the resin; The second is that there is sufficient room for resin transformation and expansion during pre-treatment to prevent resin damage.
All resin pre-treatment requires temporary pipelines for acid (or alkali) to be connected to the bed or cleaning tank (except for mixed beds that do not require it), and the treatment method is completely the same as the above steps (weak acid resin is alkali first and then acid, pure water washing endpoint acid is about pH=7, alkali is about 8.5; weak alkali resin is acid first and then alkali, pure water washing endpoint acid is about pH=4.5, alkali is about 7; other parameters are completely the same).
3、 Filling and pre-treatment methods of anion and cation resins in mixed beds
The specific operation is as follows: Clean the bed and drain 1-2 meters of water (ensure that the water surface is above the resin layer):
1. The design height is filled with resin (the final height of the resin should be based on the ecological conditions).
2. After installing the cation resin first, backwash to make the resin surface flat, and then install the anion resin;
The previous two steps should prevent backwashing and resin layer disorder (for easy identification of the height of the anion and cation resins), and ensure that the water surface is higher than the resin surface. Then:
2.1. Inject a 3-3.5% HCl solution from the bottom and discharge it from the top. The disordered layer of the resin does not matter (at this time, the disordered layer does not matter), with a flow rate of 3-3.5m/h. When there is about 2% acid in the discharged liquid, stop passing the acid and soak it for more than 2 hours. Then clean it with deionized water until the water is neutral.
2.3. Inject 2-3% NaOH from the alkali inlet and discharge it at the bottom at a flow rate of 3-3.5m/h until about 2% alkali leaks out of the outlet. Stop the alkali flow and soak for more than 2 hours, then rinse with deionized water until neutral.
2.4. Conduct backwashing on the mixed bed, control the backwashing expansion rate of 80% -100%, until there is a clear layering surface of the anion and cation resins. Observe the suitability of the height of the anion and cation resins while still, and determine the height before proceeding with regeneration operation.