Loading and preparing cation exchange filters for operation - setting up and maintaining a chemical water desalination plant. Possible malfunctions in the operation of the cation exchanger installation and their elimination

Average resource work of backfill for water softening is about 5 years, after which it is necessary to carry out replacement of cation exchanger has lost its performance characteristics.

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 preparation.

Required quality of water entering the sodium cationization system

Total 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 oC

Color - no more than 30 degrees

Petroleum products - no

Sulfides and hydrogen sulfide - no

Stages of replacing cation resin in sodium cationization systems

Before starting work, it is necessary to organize a water supply to bypass the softener via a bypass line. Shut off the water inlet and outlet to the softener.

To operate safely in manual mode, set the filter control unit to regeneration mode to relieve pressure. Then put it into working mode. Then turn off the power to the water softening system and get down to the main work.

1. Disconnect the control unit, disconnected from the power supply, from the hydraulic piping and disconnect the salt line of the reagent tank.

2. Before replacing the cation exchanger carefully unscrew the control valve.

3. Without damaging the filter housing, remove any remaining water and spent cation exchange resin.

4. Rinse thoroughly and, if possible, disinfect the internal cavity of the housing.

5. Install the housing on a permanent workplace.

6. Screw the control valve all the way and set it to convenient location for subsequent use.

7. After choosing the optimal position, carefully unscrew the valve from the cylinder.

8. Vo inner part housing insert the central distribution system with slotted cap. Using a rotating motion, install the slotted cap into the seat at the bottom of the cylinder.

9. The upper hole 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 filling. The only condition when backfilling is that the plug should not fall into the central tube, this can damage the control system.

10. Fill the balloon with a small amount of water, approximately ¼ of the volume. This amount will be a buffer for the ion exchange resin being poured.

11. Insert a funnel into the neck of the cylinder, which will provide convenience when filling in the cation exchange resin.

12. Pour the required amount of gravel through the funnel. After backfilling with gravel, you must not remove the central distribution manifold from the cylinder, since trying to put it back in place can damage the lower slot cap.

13. Load the required amount of cation exchange resin into the filter.

14. Carefully remove the funnel through which the new filter material was added.

15. Remove the plug or device used to close the hole in the top of the central distribution tube.

16. Remove any remaining dust and filter material from the body neck and threads.

17. Place the control valve with the upper slotted cap onto the central distribution pipe.

18. Screw the control unit clockwise into the filter housing.

19. Connect the control unit to the central water supply network and supply power to it.

20. Connect the reagent salt line to the control unit.

21. After completing all the work, it is necessary to supply water to the installation and release the remaining air from the filter housing.

22. Check settings automatic control and carry out primary regeneration to wash the cation exchanger.

Low performance of the cation exchange filter depends mainly on two reasons:

• insufficient height of the sulfonated carbon layer 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 drainage pipes supplying water. To eliminate this phenomenon, it is necessary to unload the filter, dismantle the drainage device and remake it, increasing the number of branches and, accordingly, the number of nipples and caps. If the caps are missing, you need to mill them large quantity cracks on the side branches. If this does not help and does not give a noticeable effect, then it is necessary to replace all the pipes, increasing their diameter.

Reduced exchange working capacity of cation exchanger depends on several reasons:

• low quality table salt used for regeneration. The salt used for regeneration must be analyzed. To do this, prepare a 10% solution of it and determine in the usual way overall hardness. It should not exceed 40 mEq/L;
• damage to the drainage device in the filter, for example, when the caps are torn off, due to corrosion damage to the nipples, etc. In this case, it is necessary to unload the filter, inspect and repair the drainage device;
• inaccurate adherence to the regeneration regime (low intensity of loosening of the cation resin, increased rate of passage of the salt solution, non-compliance with 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 into full compliance with the filter maintenance instructions.

Intensive loss of cation exchanger during loosening accompanied by cloudy water. First of all, it is necessary to check the loosening mode, preventing the release of sulfonated coal into the wash water. This phenomenon can also occur when the quality of sulfonated coal is insufficient. If the storage rules for sulfonated coal are not followed, it becomes damaged and crumbles, changing its granulometric composition. The best way to store sulfur charcoal is in water. In addition, the increased air content in the water and its accumulation in the filter also contributes to the oxidation of carbon.

Flat depletion curve of the cation exchanger and its large “tail” exchange capacity.

This phenomenon is observed if the rate of water filtration in various places The cross section of the filter 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 resin layer to a depth of up to 1m. At the nearest major renovation Particular attention should be paid to the hydrodynamics of the lower drainage device.

Increased period of salt washing after regeneration.

This is usually caused by increased dead space between the grout surface and the coping level. To eliminate this phenomenon, it is necessary to additionally fill, bringing it to the lower edges of the caps.

Getting cation exchange resin grains into softened water.

This indicates a problem with drainage device as a result of failure of drainage caps. In this case, the filter is stopped, the drainage device is unloaded and repaired.

Cationite

Technical term. Filter medium in backfill automatic installations to remove hardness salts from water. Form - ion exchange resin, strong basic cation exchanger. Restores filtration properties when washed with salt solution (NaCl).

The most important area of ​​application of cation exchange resins (ion exchange resins) is water treatment. The filter, in which ion exchange resin is the main reagent, allows you to obtain demineralized water for steam power plants, technological processes and household needs. One of the processes where ion exchange resins are indispensable is the deionization of water. Anion exchangers are used for purification, extraction, concentration and separation of substances, for analytical purposes, and also as a catalyst in organic synthesis.

Ion exchange resins belong to the group of synthetic ion exchangers and play a leading role in its application. Ion exchangers are poorly soluble materials capable of ion exchange, i.e. to the absorption of “+” or “-” ions from electrolytes, and the release in return of other ions having a charge of the same sign.

Types of ion exchange resins - cation exchangers

Ion exchange resins - cation exchangers are divided into:

• strongly acidic ion exchange resins that exchange cations in solutions at any pH value
• weakly acidic ion exchange resins capable of exchanging cations in alkaline media at pH > 7.

Cationite:

• KU-2-8
• KU-2-8chs
• KU-23

CATION EXCHANGE RESINS (polyacids, cation exchangers), synthetic. network polymers capable of exchanging cations in water and water-org. solutions of electrolytes. In a polymer matrix (framework) K. s. fixed ionogenic groups that can dissociate into polyanions and mobile cations (counterions) compensating their charges, for example. (for one group) P-SO3HDП-SO3-+Н+, participating in ion exchange with decomp. other cations. The acidity of the resin is determined by the chemical. structure of ionogenic groups.

Regeneration of depleted cation exchanger can be carried out with a solution of calcium chloride or calcium hydroxide (lime water).

Regeneration of depleted cation exchange resin (sulfo-coal) during MH4-"cationization" is carried out with a solution of ammonium sulfate, which gives ammonium cation exchange resins to the depleted cation exchange resin (sulfo-coal), and itself receives calcium and magnesium cation exchange resins. The resulting solutions of calcium sulfate and magnesium sulfate are removed into the drainage.

Restoring the exchange capacity of the depleted cation exchanger is carried out using a 2% solution of sulfuric acid; in this case, the hydrogen of the acid passes into the cation exchanger, and the calcium and magnesium obtained from the feed water replace the hydrogen and form calcium and magnesium sulfate, which are removed into the drainage.

The nature of the distribution of absorbed Ca2+ (and Mg2+) in the layer of normally depleted cation exchange resin and hydrogen ions in the layer of normally regenerated (by the usual excess of acid) material during H-cationization is basically the same as during Na-cationization. The degree of regeneration of the H-cation exchanger also depends on the nature of the absorbed cation. Thus, sodium is more easily replaced by H+ ions than Ca2+. The lower the exchange capacity of the cation exchanger for a given cation, the easier the cation exchanger saturated with it is regenerated.

Regeneration of each filter is carried out with an appropriate reagent solution of a certain concentration. The regeneration mode of depleted cation exchanger is considered optimal if, with minimal consumption of the regenerating substance, deep softening of water is ensured with a sufficiently high working capacity of the cation exchanger. Typically, when regenerating a Na-cation exchange filter, a 6...8% solution of table salt is passed through it at a speed of 4...6 m/h. Restoration of the exchange capacity of the N-cation exchanger is carried out with sulfuric acid with a concentration of 1 ... 1.5% at a speed of at least 10 m/h in order to avoid “plastering” the cation exchanger. The specific consumption of sulfuric acid for regeneration depends on the total content of chloride and sulfate ions in the softened water and is 75...225 g/g-equiv for stage I filters and 70 g/g-eq for stage I filters. To save reagents, usually part of the regeneration solution (the last portions) is taken to the tank and used for subsequent regeneration. Reagent solutions are prepared using their own filtrate for each group of filters. The duration of the solution supply is 15...30 minutes.

The exchange capacity of the NH4 cation exchanger, the speed of water and its consumption for technological operations when servicing filters can be assumed to be the same as for Na-cationization. To regenerate the depleted cation exchanger, a solution of ammonium chloride salt (NH4C1) or a solution of ammonium sulfate salt [(NH4)2SO4] is used. Basically, a 2-3% solution of ammonium sulfate is used for regeneration as it is more accessible and cheaper. A higher concentration is not allowed to avoid gypsuming of the cation exchanger grains. The regeneration solution of ammonium sulfate should be alkalized with soda, sodium hydroxide or ammonia until the phenolphthalein reaction is slightly alkaline, which is necessary to bind sulfuric acid residues.

During the Na-cationization process, there is no decrease in the total salt content of softened water. When softening water, the cation exchanger is depleted and to restore it must be regenerated, that is, a solution of table salt is passed through the layer of depleted cation exchanger. In this case, sodium cations displace previously absorbed calcium and magnesium cations from the cation exchanger, and the cation exchanger, enriched with exchangeable sodium cations, again gains the ability to soften water.

To restore the exchange capacity of the depleted sodium cation exchange material, it is treated with a 5-10% solution of sodium chloride. By this process, called regeneration, sodium cations displace calcium and magnesium cations from the depleted cation exchanger; the latter go into solution in the form of calcium chloride and magnesium chloride and are removed with the wash water into the drainage. Cation exchanger, enriched with exchangeable sodium cations, again gains the ability to soften hard water.

Counterions in the regeneration solution have a similar effect. When a NaCl solution is passed through a filter, the concentration of Ca2+ and Mg2^ cations displaced from the cation exchanger increases and it becomes depleted in Na+ ions. An increase in the concentration of counterions (Ca2+ and Mg2+) in the regeneration solution suppresses the dissociation of the depleted cation exchanger and weakens the ion exchange process, that is, it inhibits the regeneration of the ion exchanger. As a result, as the regeneration solution moves into the lower layers, a certain amount of Ca2+ and Mg2+ cations remains undisplaced, so the regeneration of the cation exchanger proceeds less completely. To eliminate this drawback, you can increase the salt consumption, which greatly impairs the economics of the process. It is much more rational to use countercurrent cationization, which eliminates the unfavorable location of ions in the layer, since softened water will come into contact with the most well-regenerated layers of cation exchanger before leaving the filter, which ensures deeper softening of the water. The countercurrent cationization method makes it possible to significantly reduce the consumption of reagents for the regeneration of the cation exchanger, approaching stoichiometric ratios.

The process of cation exchange in the filter occurs until the cation exchanger is depleted, i.e., it stops softening the water. To restore this ability, it is necessary to remove the cations retained by it from the cation exchanger, which is done by the so-called regeneration (restoration) of the cation exchanger. This is done by passing through a layer of depleted cation exchanger: a) during sodium cationization - a solution of table salt; b) during hydrogen cationization - sulfuric acid.

Ion exchange resin is used in filters of water treatment systems to soften water. During the softening process, sodium cation exchanger removes calcium and magnesium ions from water. It is the presence of these ions that makes water hard. The removed hardness ions are replaced by a corresponding amount of sodium ions. In the case of equivalent replacement of ions, the anionic composition (negatively charged ions) and pH (hydrogen index, acidity of the medium) of the water do not change.

When the filter-softener operates, the process of sorption (absorption) of hardness ions occurs and the efficiency of the filter material (exchange capacity of the resin) gradually decreases. As a result, the efficiency of the filter deteriorates. Hardness salt ions do not linger on the resin granules and enter the home water supply system. The hardness of tap water increases, as a result of which the quality of the water decreases, and a white coating forms on plumbing equipment and dishes.

To ensure that the quality of the output from the filtration system does not deteriorate drinking water, it is necessary to regularly carry out special actions called “regeneration of the ion exchange resin”. Regeneration will return the filter softener media to its ability to effectively reduce the hardness of well water.

Filter softener regeneration process

1. Suspended salts are removed from the filter by washing with water.
2. The ions bound to the ion exchange resin are removed by the regeneration solution (NaCl).
3. The filter is washed with water to remove the regeneration solution.

One of the advantages of filters based on ion exchange resins is that the regeneration of cation exchangers is carried out with a solution of ordinary table salt (sodium chloride, NaCl). That is, there is no negative impact on human health and the state of the environment. The salt must always be in the salt tank, from which it is supplied in portions to the container during regeneration.

Restoring the properties of the filter reagent allows you to reuse one backfill. However, the ability of the ion exchange resin to soften water gradually decreases, since regeneration does not return the ion exchange resin to 100% of its properties.

The average service life of the ion exchange resin is 3 years, under certain operating conditions - up to 6 years. Completely used cation exchangers must be disposed of.

Loading the cation exchanger must be done through the top hatch of the filter manually or using a hydraulic loading device.  

The cation exchanger is loaded into a filter two-thirds filled with water. When loading, the swelling coefficient of the cation exchanger is taken into account and from here the loading height of the dry material is determined. After this, the cation exchanger is washed from the fines with a current of water from bottom to top. Na-cation exchanger, in addition, is washed away from acidic water by flowing water from top to bottom.  

After loading the cation exchanger into a filter filled with water or NaCl solution, swelling of the ion exchanger for 24 hours, it is washed from bottom to top, 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 feeding into the filter required quantity strong acid, its supply is stopped, and water continues to be supplied at the same speed, discarding the spent, usually neutral, regeneration solution, supersaturated with gypsum. The amount of solution discharged from the moment the acid supply is stopped must be equal to the volume of cation exchanger loaded into the filter. After dumping this amount of solution and reducing its hardness to 10 - 15 mEq/l, they begin to fill the tank for recycling the spent acid regeneration solution or the loosening tank. After filling them, if the cleaning water is still hard, continue washing by discharging the washing water into the sewer.  

After loading the cation exchanger into the filter, washing it from bottom to top, removing a layer of fines and dirt from the surface, the filter is 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 loading the cation exchanger, it is washed with reverse current at a speed of 8 - 10 m/h to light water.  

Formula (2) has a certain practical meaning: having determined the coefficient K, you can easily calculate the volume of cation exchanger loading required to process the required amount of solution in a given time. Having a given amount of loaded cation exchange resin, it is possible to determine the processing time of the ion exchange resin.  

The settling tank and saturator were installed, and the expansion of the cation exchange 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 cation exchange and replacing glauconite with sulfonated carbon.  

Before loading into cation exchanger filters, a mark is made (with chalk) along its height to which the cation exchanger should be loaded, or the weight or volume of the cation exchanger required for loading is determined. The degree of its swelling should be taken into account a.  

For a rational choice of the scheme and design of the H - cation exchange filter of a desalting plant in relation to the specific composition of water and regeneration conditions, it is necessary to determine: the height of the cation exchange resin layer, which must be completely regenerated with acid, and the specific acid consumption, ensuring complete regeneration of the required part of the cation exchange resin load.  

In order to increase the reliability of filter operation, the actual acid consumption must be increased by 20 - 30% relative to the found one. It should be noted that the total loading height of the cation exchanger must be selected in such a way that, for a given specific consumption for the regeneration of the protective layer, its excess would be absorbed in the subsequent layers of cation exchanger along the regenerate. For hydrochloric acid, ensuring the noted conditions does not present any difficulties, since even at stoichiometric consumption for regeneration, the height of the completely regenerated cation exchanger layer significantly exceeds the height of the protective layer. For sulfuric acid, ensuring these conditions is somewhat difficult. However, as follows from § 5.7, if certain requirements are met, it is possible to ensure the required degree of regeneration of a given layer height and the corresponding processing depth.  

Indeed, during direct-flow nonation, due to the established distribution of ions in the column before regeneration, calcium and magnesium ions displaced during regeneration by an acid solution remove sodium ions from the cation exchanger, as a result of which, after regeneration, the cation exchanger contains practically no sodium ions. In the case of countercurrent regeneration, sodium ions are replaced only by monovalent hydrogen ions and pass through the entire cation exchanger loading layer. For these reasons, it seems to us, the countercurrent method of regeneration and ae has found wide application under normal conditions of H - cationization.  

According to these standards, the addition to ion exchange filters in the first year of operation is 20% for sulfonated coal, 15% for cation exchange resin KU-2, in subsequent years 12% for sulfurized coal, 7% for KU-2. According to Mosenergo, the number of filters for both sorbents is almost the same, since when the loading volume of KU-2 cation exchanger is reduced compared to sulfo-coal (by about 2 times), a large volume of water cushion is required to loosen the former.  

The FSD loading consists of KU-1G cations produced by the Nizhny Tagil plastics plant and AV-17 anion exchanger produced by the Kemerovo Karbolit plant. One FSD with internal regeneration is loaded with KU-2 ion exchanger. The grain size of cation exchange resins is 0 5 - 1 0 mm, anion resin 0 25 - 1 0 mm. The loading height of the cation resin in all FSDs is 600 mm, the loading height of the anion resin in the FSD with internal regeneration is 800 - 900 mm, in the FSD with external regeneration it is 500 - 600 mm.