Ion exchange resins are high molecular weight insoluble compounds that can show a reaction when interacting with the ions of a solution. They have a three-dimensional gel or macroporous structure. They are also called ionites.
Varieties
These resins are cation exchange (divided into strong acid and weak acid), anion exchange (strong base, weak base, intermediate and mixed base) and bipolar. Strongly acidic compounds are cation exchangers that can exchange cations regardless of A, but weakly acidic compounds can function at a value of at least seven. Strongly basic anion exchangers have the property of exchanging anions in solutions at any pH. This, in turn, is lacking in weakly basic anion exchangers. In this situation, the pH should be 1-6. In other words, resins can exchange ions in water, absorb some, and in return give away those that were previously stored. And since it is H 2 O that is a multicomponent structure, you need to correctly prepare it, choose a chemical reaction.
Properties
Ion exchange resins are polyelectrolytes. They don't dissolve. A multiply charged ion is immobile because it has a large molecular weight. It forms the basis of the ion exchanger, is associated with small mobile elements that have the opposite sign, and, in turn, can exchange them in solution.
Production
If a polymer that does not have the properties of an ion exchanger is treated chemically, then changes will occur - the regeneration of the ion exchange resin. This is quite an important process. With the help of polymer-analogous transformations, as well as polycondensation and polymerization, ion exchangers are obtained. There is salt and mixed-salt forms. The first implies sodium and chloride, and the second - sodium-hydrogen, hydroxyl-chloride species. Under such conditions, ion exchangers are produced. Moreover, in the process they are converted into a working form, namely hydrogen, hydroxyl, etc. Such materials are used in various fields of activity, for example, in medicine and pharmaceuticals, in the food industry, at nuclear power plants for condensate treatment. An ion exchange resin for a mixed bed filter can also be used.
Application
An ion exchange resin is used for In addition, the compound can also desalt the liquid. In this regard, ion-exchange resins are often used in thermal power engineering. In hydrometallurgy they are used for non-ferrous and rare metals, in the chemical industry they are purified and various elements are separated. Ionites can also purify wastewater bodies, and for organic synthesis they are a whole catalyst. Thus, ion exchange resins can be used in various industries.
Industrial cleaning
Scale can appear on heat transfer surfaces, and if it reaches only 1 mm, then fuel consumption will increase by 10%. It's still a big loss. Moreover, the equipment wears out faster. To prevent this, you need to properly organize water treatment. For this, an ion exchange resin filter is used. It is by cleaning the liquid that you can get rid of scale. There are different methods, but with increasing temperature, their options become less.
H2O processing
There are several ways to purify water. You can use magnetic and you can retouch it with complexones, complexonates, IOMS-1. But a more popular option is filtration using ion exchange. This will cause the composition of the water elements to change. When this method is used, the H 2 O is almost completely desalinated and the contamination disappears. It should be noted that such purification is quite difficult to achieve in other ways. Water treatment using ion exchange resins is very popular not only in Russia, but also in other countries. Such cleaning has many advantages and is much more effective than other methods. Those elements that are removed will never remain sediment at the bottom, and reagents do not need to be dosed constantly. It is very easy to make this procedure - the design of the filters is of the same type. If desired, you can use automation. After cleaning, the properties will be preserved at any temperature fluctuations.
Purolite A520E ion exchange resin. Description
To absorb nitrate ions in water, a macroporous resin was created. It is used to purify H 2 O in various environments. Purolite A520E ion-exchange resin appeared especially for this purpose. It helps to get rid of nitrates even with a large amount of sulfates. This means that, in comparison with other ion exchangers, this resin is the most effective and has the best characteristics.
Working capacity
Purolite A520E has a high selectivity. This helps, regardless of the amount of sulfates, to remove nitrates efficiently. Other ion exchange resins cannot boast of such functions. This is due to the fact that with the content of sulfates in H 2 O, the exchange of elements decreases. But due to the selectivity of the Purolite A520E, this reduction does not really matter. Although the compound has a low, compared with others, complete exchange, the liquid in large quantities is cleaned quite well. At the same time, if there are few sulfates, then various anion exchangers, both gel and macroporous, will be able to cope with water treatment and the elimination of nitrates.
Preparatory operations
In order for Purolite A520E resin to perform at 100%, it must be properly prepared to perform the function of cleaning and preparing H 2 O for the food industry. It should be noted that before starting work, the used compound is treated with a 6% NaCl solution. In this case, twice the volume is used compared to the amount of the resin itself. After that, the connection is washed with food water (the amount of H 2 O should be 4 times more). Only after such processing can it be taken for cleaning.
Conclusion
Due to the properties possessed by ion exchange resins, they can be used in the food industry not only for water purification, but also for processing food, various drinks and other things. Anion exchangers look like small balls. It is to them that calcium and magnesium ions stick, and they, in turn, give sodium ions into the water. During the washing process, the granules release these adhering elements. Be aware that pressure may drop in the ion exchange resin. This will affect its beneficial properties. Certain changes are influenced by external factors: temperature, column height and particle size, and their velocity. Therefore, during processing, an optimal state of the environment should be maintained. Anion exchangers are often used in water purification for an aquarium - they contribute to the formation of good conditions for the life of fish and plants. So, ion exchange resins are needed in various industries, even at home, as they can qualitatively purify water for its further use.
Poor performance of the cation exchanger depends mainly on two reasons:
- insufficient height of the layer of sulfonated coal in the filter. In this case, it is necessary to add sulfonated coal to the maximum, raise the upper drainage device as high as possible or increase the height of the filter by welding a cylindrical shell to the upper part;
- high hydraulic resistance of the pipes of the drainage device supplying water. To eliminate this phenomenon, it is necessary to unload the filter, dismantle the drainage device, remake it, increasing the number of branches and, accordingly, the number of nipples and caps. If there are no caps, it is necessary to mill more slots on the side branches. If this does not help and does not give a noticeable effect, then it is necessary to replace all pipes, increasing their diameter.
Reducing the exchange working capacity of the cation exchanger depends on several reasons:
- low quality salt used for regeneration. Salt used for regeneration must be analyzed. To do this, prepare a 10% solution of it and determine the general hardness in the usual way. It must not exceed 40 meq / l;
- damage to the drainage device in the filter, for example, when caps are torn off, when nipples are corroded, etc. In this case, it is necessary to unload the filter, inspect and repair the drainage device;
- inaccurate observance of the regeneration mode (low intensity of loosening of the cation exchanger, increased rate of passage of the salt solution, non-observance of the sequence when opening the taps, insufficient amount of salt loaded into the salt solvent). In these cases, it is necessary to bring the regeneration mode in full compliance with the filter maintenance instructions.
Intensive loss of cation exchanger during loosening accompanied by turbidity of the water. First of all, it is necessary to check the mode of loosening, avoiding the release of sulfonated coal into the washing water. This phenomenon can also occur when the quality of sulfo coal is insufficient. If the rules for storing sulfonated coal are not followed, it deteriorates, it crumbles, changing its granulometric composition. The best sulfonated coals are stored in water. In addition, the elevated air content in the water and its accumulation in the filter also contributes to the oxidation of coal.
Flat depletion curve of the cationite and its large "tail" exchange capacity.
This phenomenon is observed if the rate of water filtration in different places of the filter section is not the same, which occurs with different resistance to the passage of water at different points of the drainage device.
In this case, it is recommended to stop the filter, open the top hatch, remove the top contaminated layer, and shovel the cation exchanger layer to a depth of 1m. During the next overhaul, special attention should be paid to the hydrodynamics of the lower drainage device.
Increased salt washout period after regeneration.
The reason for this is usually increased dead space between the surface of the grout and the level of the caps. To eliminate this phenomenon, it is necessary to additionally fill, bringing it to the lower edges of the caps.
Ingress of cationite grains into softened water.
This indicates a malfunction in the drainage device as a result of the failure of the drainage caps. In this case, the filter is stopped, the drainage device is unloaded and repaired.
The loading of the cationite must be carried out through the upper hatch of the filter manually or with the help of a hydraulic loading device.
The cation exchanger is loaded into a filter filled with water by two thirds. When loading, the swelling coefficient of the cationite is taken into account and from here the height of the dry material loading is determined. After that, the cation exchanger is washed from the fines with a stream of water from the bottom up. Na-cation exchanger, in addition, is also washed from acidic water by a stream of water from top to bottom.
After loading the cation exchanger into the filter filled with water or NaCl solution, swelling of the ion exchanger during the day, it is washed from the bottom up, the layer of fines and dirt is removed from the surface and the layer height is brought to normal. Then the filter is closed, filled with water from below and regenerated with acid at a consumption of 100% H2SO4 from 17 to 25 kg per 1 m3 of cation exchanger. After the required amount of strong acid is supplied to the filter, its flow is stopped, and water continues to be supplied at the same rate, discarding the spent, usually neutral, regeneration solution supersaturated with gypsum. The amount of the discharged solution from the moment the acid supply is stopped must be equal to the volume of the cation exchanger loaded into the filter. After dumping this amount of solution and reducing its hardness to 10 - 15 mg-eq / l, they begin to fill the tank for recycling the spent regeneration acid solution or the tank for loosening. After filling them, if the wash water is still hard, continue washing, draining the wash water into the sewer.
After loading the cation exchanger into the filter, washing it from the bottom up, removing the layer of fines and dirt from the surface, the filter is filled with water from below and regenerated with acid at a flow rate of 100% H2SO4 from 17 to 25 kg per 1 m3 of the cation exchanger.
After loading the cation exchanger, it is washed with reverse current at a speed of 8 - 10 m / h to clear water.
Formula (2) has a certain practical meaning: having determined the coefficient K, one can easily calculate the volume of cation exchanger loading required to process the required amount of solution at a given time. Having a given amount of loaded cation exchanger, it is possible to determine the time of working out the ion exchange resin.
The settling tank and saturator were installed, and the expansion of the cationite part of the water treatment was carried out by the workshop by increasing the height of the filters by 1 m with the corresponding loading of the cationite and replacing glauconite with sulfonated coal.
Before loading in cationite filters, a mark is made (with chalk) along its height, to which the cationite must be loaded, or the weight or volume of the cationite required for loading is determined. Consideration should be given to the degree of its swelling a.
For a rational choice of the scheme and design of the H - cation exchange filter of the desalination plant in relation to the specific composition of water and regeneration conditions, it is necessary to determine: the height of the cation exchanger layer, which must be completely regenerated by acid, and the specific acid consumption, which ensures complete regeneration of the necessary part of the cation exchanger load.
In order to improve the reliability of the filters, the actual consumption of acid must be increased by 20 - 30% relative to the found one. Attention should be paid to the fact that the total height of the cation exchanger loading must be chosen in such a way that, at a given specific consumption for the regeneration of the protective layer, its excess would be absorbed in the subsequent cation exchanger layers along the course of the regenerate. For hydrochloric acid, the provision of the noted conditions does not present any difficulties, since already at its stoichiometric consumption for regeneration, the height of the completely regenerated cation exchanger layer significantly exceeds the height of the protective layer. For sulfuric acid, the provision of these conditions is somewhat difficult. However, as follows from § 5.7, subject to certain requirements, it is possible to ensure the required degree of regeneration of a given layer height and the corresponding working depth.
Indeed, in direct-flow ioning, due to the established distribution of ions in the column before regeneration, calcium and magnesium ions displaced during regeneration by the acid solution remove sodium ions from the cation exchanger, as a result of which, after regeneration, sodium ions are practically not contained in the cation exchanger. In the case of countercurrent regeneration, sodium ions are displaced only by monovalent hydrogen ions and pass through the entire layer of the cation exchanger. For these reasons, it seems to us that the countercurrent method of regeneration and ae has found wide application under ordinary conditions of H - cationization.
According to these standards, the addition to ion-exchange filters in the first year of operation is 20% for sulfocoal, 15% for KU-2 cation exchanger, in subsequent years 12% for sulfocoal, 7% for KU-2. According to Mosenergo, the number of filters for both sorbents is almost the same, since with a decrease in the volume of loading of the KU-2 cation exchanger compared to sulfo-coal (approximately 2 times), a large amount of water cushion is needed to loosen the first one.
Loading FSD consists of cation-ta KU-1G produced by the Nizhny Tagil plastics plant and anion exchange resin AV-17 produced by the Kemerovo plant Karbolit. One FSD with internal regeneration is loaded with KU-2 cation exchanger. The grain size of cation exchangers is 0 5 - 10 mm, anion exchanger 0 25 - 10 mm. The loading height of the cation exchanger in all FSDs is 600 mm;
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On desalination plants, H-cationite filters are loaded with cationite of various grades. The amount of dry cationite loaded into the filter should be calculated based on the required height of the filtering layer of the cationite in the swollen state.
In H-cation exchanger filters of the first stage, the layer of wet cation exchanger must have a height that allows the volume of the cation exchanger to increase by approximately 50% during loosening. In H-cationite filters of the II and III stages, it is advisable to have a layer of wet cationite with a height of 1.0-1.5 m under the same conditions.
After loading into the filter, the cation exchanger is kept in water for swelling for 10-12 hours. After swelling, the cation exchanger is washed from contamination by a stream of water from the bottom up. Sulfonated coal begins to be loosened at a water rise rate of 7-8 m/h and is brought up to 12-15 m/h as the washing water becomes clarified.
After washing the cation exchanger, the filter is opened, the top layer of fines is manually removed (its thickness depends on the quality of the cation exchanger), by adding or shipping the cation exchanger, the layer height is adjusted to the calculated one. After that, the height of the cationite layer in the swollen state is measured.
Preparation of a fresh cation exchanger for work is carried out by its regeneration with an excess amount of an acid solution. When washing, the hardness and acidity of the washing waters are determined. In those cases. when washing is delayed, and the hardness of the washing water does not decrease for a long time, it is advisable to perform additional regeneration.
During primary regenerations, the passage of the regeneration solution of 1.5-2.0% sulfuric acid is carried out slowly, over a period of 1.5-2.0 hours, which increases the duration of contact of the regeneration solution with the cation exchanger and contributes to its better working out. Approximate consumption of 100% sulfuric acid is up to 30 kg per 1 m 3 of the cation exchanger; the rate of filtration of the regeneration solution determines the time of its contact with the cation exchanger; usually it is 9-10 m/h and is finally set during commissioning. The washing water is filtered at a rate of - 10 m/h.
Washing of the cation exchanger in the filters of the 1st stage is carried out with clarified water.
Acid regeneration solution for regeneration of H-cationite filters of I, II and III stages is prepared only on H-cationic water.
The washing of the cation exchanger ends when the hardness of the washing water is ~ 50 µg-eq/kg and the acidity exceeds the content of the sum of SO‚-+Cl″ ions in the source water no more than 500 µg-eq/kg.
The primary regeneration of H-cationite filters of the II stage is carried out with the same acid consumption, concentrations of the regenerating solution and its flow rate as the H-cation exchanger filters of the I stage. Washing of the H-cationite filter of the II stage is carried out with partially desalted and decarbonized water. H-cationite filters of the II stage are washed to the acidity of the filtrate of 0.15 meq/kg.
The duration of preliminary preparation of the filter for operation depends on the quality of the cation exchanger and can vary from several hours to a day.
Within I-2 days after putting the filter into operation after regeneration, the water may be slightly opalescent (cloudy); Approximately 2 days after the filter is turned on, all cationic water should come out completely transparent.
The average service life of backfill for water softening is about 5 years, after which it is required to replacement of the cation exchanger lost its performance.
For the longest service life of the cation exchanger, it is necessary to correctly program the control unit during the first start-up and ensure preliminary water treatment.
Required quality of water entering the sodium cation system
General hardness - up to 20 mg.eq./l
Total salt content - up to 1000 mg/l
Total iron - no more than 0.3 mg / l
Water temperature - 5-35 °C
Color - no more than 30 degrees
Oil products - no
Sulfides and hydrogen sulfide - no
Stages of replacement of the cation exchanger in sodium cationization systems
Before starting work, it is necessary to organize the water supply bypassing the softener through the bypass line. Shut off the water inlet and outlet to the softener.
For safe manual operation, put the filter control unit into regeneration mode to relieve pressure. Then switch to working mode. Then de-energize the water softening system and take up the main work.
1. Disconnected from the power supply, disconnect the control unit from the hydraulic piping and disconnect the brine line of the reagent tank.
2. Before replacement of the cation exchanger carefully unscrew the control valve.
3. Without damaging the filter housing, free it from the remnants of water and spent cation exchanger.
4. Rinse well and, if possible, disinfect the internal cavity of the housing.
5. Install the body on a permanent workplace.
6. Screw the control valve all the way down and set it in a convenient place for subsequent operation.
7. After choosing the optimal position, carefully unscrew the valve from the cylinder.
8. Insert the central distribution system with slotted cap into the inside of the housing. Rotate the slotted cap into the socket on the bottom of the cylinder.
9. The upper opening of the central distribution pipe must be closed with a plug or other device that will prevent ion exchange resin from entering the distribution system during backfilling. The only condition when backfilling the plug should not fall into the central tube, this can disable the control system.
10. Fill the balloon with a small amount of water, approximately ¼ volume. This amount will buffer the ion exchange resin being loaded.
11. Insert a funnel into the neck of the cylinder, which will provide convenience when filling the cation exchanger.
12. Pour the required amount of gravel through the funnel. After backfilling with gravel, the central distribution manifold must not be pulled out of the cylinder, as if you try to put it in place, you can damage the lower slotted cap.
13. Load the filter with the required amount of cation exchanger.
14. Carefully remove the funnel through which the new filter material was added.
15. Remove the plug or tool used to cover the hole in the top of the center distribution tube.
16. Remove any remaining dust and filter material from the housing neck and threads.
17. Push the control valve with the top slotted cap onto the central distribution pipe.
18. Screw the control box clockwise into the filter housing.
19. Connect the control unit to the central water supply and supply power to it.
20. Connect the reagent brine line to the control box.
21. After completion of all work, it is necessary to supply water to the installation and release the remaining air from the filter housing.
22. Check the automatic control settings and carry out the primary regeneration to wash the cation exchanger.
