RU2516167C2 - Method of external regeneration of mixed ionite layer - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in power engineering, nuclear industry, microelectronics, pharmaceutics and other fields of industry, where highly desalted water is required. To realise the method mixture of monodisperse ionites are reloaded from working filter of mixed action into cationite-regenerating filter, pure cationite and anionite are separated from mixture, anionite is loaded out into anionite-regenerating filter and regenerated, cationite is regenerated in cationite-regenerating filter and reloaded into anionite-regenerating filter. Separation of pure cationite and anionite from mixture of ionites is carried out by method of hydraulic separation. As cationites used are particles of monodisperse cationites with size 0.5-0.7 mm, and as anionite particles of monodisperse anionites with size 0.4-0.6 mm. Intermediate layer, containing 70-90% of cationite in H⁺ - form and 10-30% of anionite in $$S{O}_4^{-2}$$

- form, is created in cationite-regenerating filter by processing cationite and calculated amount of waste anionite by passing through them sulfuric acid solution. Intermediate layer constitutes from 1 to 10% of the total volume of loaded ionites and is not loaded out from cationite-regenerating filter when cationite and anionite are.

EFFECT: method makes it possible to reduce the number of reloadings of ionites with preservation of quantity of purified water, as well as completely eliminate possibility of contaminating ionites that have been regenerated by other forms of ionites.

3 cl, 10 dwg, 1 ex

Description

The invention relates to a technology for water purification, in particular to methods for desalting water using the ion exchange method. The proposed method can be used in energy, nuclear industry, microelectronics, pharmaceuticals and other industries where desalted water is used as process water or as a coolant and water with a high degree of desalination is required.

Currently, in the energy sector, nuclear industry and microelectronics, desalted water is required with an ultrahigh purity, determined by its electrical resistance, at the level of 10-18 MΩ / cm, which is approaching the maximum possible value. This raises the question of developing new and effective methods for its desalination.

The most promising technologies for ensuring the reliability and cost-effectiveness of deep water desalination are various technologies using ion exchange resins (ion exchangers), which differ in the characteristics of the used ion exchangers and filtration equipment, as well as the features of the filtration process (A. Kopylov, V.M. Lavygin) ., Ochkov V.F. Water treatment in the energy sector. - M .: MEI Publishing House, 2003. p.104-166).

It is known (Bogatyrev V.L. Ionites in a mixed layer, L .: Chemistry, 1968) that to achieve the greatest depth of water purification it is advisable to use a mixed layer of ion exchangers consisting of anion exchange resin in the OH ^- form and cation exchange resin in the H ⁺ form. Filters that use a mixed layer of ion exchangers are called mixed action filters (FSD). In them, water sequentially repeatedly contacts the grains of cation exchange resin in the H ⁺ form and anion exchange resin in the OH ^- form, which ensures the most complete removal of dissolved salts. After saturation, the ion exchangers must be regenerated, and the mixed layer before regeneration should be separated into cation exchange resin and anion exchange resin, which are then treated separately (cation exchange resin - acid, and anion exchange resin - alkali). The regenerated layers of ion exchangers are then washed, mixed with each other and again used for water treatment. The degree of regeneration of each ion exchanger and the purity of their separation are among the most significant factors for achieving the maximum depth of desalination of water.

Currently, to prevent the possibility of acid and alkali getting into the circuit with particularly pure water at the power plants of thermal power plants and nuclear power plants, the so-called remote regeneration of ion exchangers in special devices located in a separate room (Half a century of condensate polishing, http://www.graver.com/downloads/condensate.pdf) To carry out remote regeneration, it is necessary to perform the following operations: completely reload the spent resins from the working FSD in the regeneration unit; loosen the resin to remove solid impurities that have accumulated during condensate treatment; as completely as possible to separate the mixture of resins into pure cation exchanger and anion exchanger; overload one or both ion exchangers into the appropriate apparatus with minimal contamination with another ion exchange resin; separate regeneration of cation exchanger and anion exchanger with appropriate chemical solutions; thoroughly wash cation exchange resin and anion exchange resin with demineralized water; mix cation exchange resin and anion exchange resin and wash the resulting mixture; overload the resin mixture into the working FSD, thoroughly mix the cation exchange resin and anion exchange resin and finally wash the resulting mixture.

Since the quality of the water obtained ultimately depends on the effectiveness of each of these operations, a large number of options have been developed for the organization of hardware-technological schemes for remote regeneration.

-форму и при последующей эксплуатации будет происходить проскок сульфат-ионов в обессоленную воду.One of the main difficulties in the effective implementation of remote regeneration is currently organizing the overload of one or both ion exchangers for its regeneration into the appropriate apparatus with minimal contamination with another ion exchange resin. Since in case some part of the cation exchanger appears in the anion exchange resin, during its regeneration with an alkali solution, this cation exchanger will be converted to the Na ⁺ form and during subsequent operation, sodium ions will slip into desalted water. Similarly, if some part of the anion exchanger appears in the cation exchanger, then upon its regeneration with an acid solution, this anion exchanger will be converted to $$S{O}_{\mathrm{four}}^{-2}$$

-form and during subsequent operation, a breakthrough of sulfate ions will occur in demineralized water.

Currently, the problem of the separability of resins is mainly solved by the use of monodispersed ion exchangers with a selected particle size, which allows them to be completely separated hydraulically, feeding water at a certain speed under the layer of ion exchangers. However, this aggravates the problem of overloading one or both ion exchangers for their regeneration into an appropriate apparatus with minimal contamination with other ion exchangers (Kalpakchiev Z.P. Development of a new method for the separation of ion exchangers in the FSD and optimization of the operation of BOW 1000 VVER units http: //www.gidropress .podolsk.ru / files / proceedings / seminar7 / documents / f06.pdf). This problem is caused, in particular, by the presence in ion exchangers of the so-called angle of repose and the imperfection of discharge systems.

To obtain pure ion exchangers, as a rule, various design solutions are proposed. In particular, there is a known method for remote regeneration of a mixed layer of Kononesep ion exchangers (US Patent 5391301, 1999), in which, after working out the ion exchange mixture in the working FSD, it is transferred to the anion exchange filter regenerator (FRA), where the ion exchange mixture is separated into pure cation exchange resin and anion exchange resin . Then pure cation exchange resin is discharged into a cation exchange filter regenerator (PRK), where it is regenerated with acid and washed with demineralized water. At the same time, the anion exchange resin is alkaline regenerated and washed with demineralized water. To ensure greater completeness of unloading of cation exchange resin from the FRA, the filter is made with a conical bottom, ending with a discharge pipe.

The disadvantage of this method is the presence of mutual contamination of ion exchangers (although to a lesser extent compared to traditional technologies), the need to use special non-standard devices and the difficulty of controlling the moment of completion of the discharge of cation exchanger.

Closest to the claimed technical solution is a method for remote regeneration of a mixed layer of ion exchangers, in which, to eliminate contamination of the ion exchangers, it is proposed that after working out the mixture of ion exchangers in the working FSD, it be reloaded into PRK, where the mixture of ion exchangers is separated. Then the upper layer of pure anion exchange resin is discharged into the FRA, where it is regenerated with alkali and washed with demineralized water. After that, the lower layer of anion exchange resin and the upper layer of cation exchange resin are discharged from the PRK into an additional tank. In PRK, only pure cation exchange resin remains, which is regenerated with acid and then washed with demineralized water (WBG - RSR Plus Resin separation and regeneration see http://www.wbg-kulmbach.de/downloads/WBG-RSR-Plus_e_web.pdf).

The disadvantage of this method is the great hardware complexity, in particular the introduction of an additional capacity for storing the mixture and a multi-stage process due to the need for multiple overloading and processing of a mixture of ion exchangers placed in an additional container.

The problem solved by the authors was the creation of a simpler and more technologically advanced method of regeneration of a mixed layer of ion exchangers, which, in particular, made it possible to reduce the number of overloads while maintaining the quality of the treated water.

-форме существенно отличается по плотности как от частично регенерированных в ФСД катионита в H⁺-Na⁺-форме и от анионита в $$O{H}^{-}-C{l}^{-}-S{O}_4^{-2}$$

-форме, так и от катионита в H⁺-форме. При гидравлическом разделении монодисперсных ионитов с размером частиц катионита размером 0,5-0,7 мм и анионита 0,4-0,6 мм этот слой располагается между частично насыщенными в ФСД катионитом и анионитом.The basis for the solution of this problem was the fact established by the authors that anion exchange resin $$S{O}_{\mathrm{four}}^{-2}$$

-form significantly differs in density from both the cation exchanger partially regenerated in FSD in the H ⁺ -Na ⁺ form and from the anion exchanger in $$O{H}^{-}-C{l}^{-}-S{O}_{\mathrm{four}}^{-2}$$

form, and from cation exchange resin in the H ⁺ form. In the hydraulic separation of monodisperse ion exchangers with a particle size of 0.5–0.7 mm cation exchange resin and 0.4–0.6 mm anion exchange resin, this layer is located between the cation exchange resin and anion exchange resin partially saturated in FSD.

-форме, который разграничивает слои катионита и анионита и при выгрузке катионита из ФРК не выгружается.The proposed technical solution consists in the fact that in the filter regenerator of the PRK cation exchanger an intermediate layer is created containing 70-90% of cation exchanger in the H ⁺ form and 10-30% of anion exchanger in $$S{O}_{\mathrm{four}}^{-2}$$

-form, which delimits the layers of cation exchange resin and anion exchange resin and is not unloaded when unloading cation exchange resin from PRK.

The technical result achieved in this case is that this change in technology allows sequentially unloading from the PRK a pure anion exchange resin that is regenerated by alkali in the FRA, and cation exchange resin in the H ⁺ -Na ⁺ form and an intermediate layer containing 70-90% cation exchange resin and 10- Regenerate 30% of anion exchange resin with sulfuric acid. The regenerated cation exchange resin in the H ⁺ form is discharged from the PRK to the PRF, and the intermediate layer remains in the PRK until the next regeneration.

The specific ratio of the ingredients of the intermediate (“buffer”) layer and its height are determined experimentally for the specific set of ion exchangers used and the type of cation exchanger discharge device. As a rule, the size of the created additional layer is from 1 to 10% of the total volume of loaded ion exchangers. Optimally, the height of this layer should exceed by 50-100 mm the distance from the drainage device to its highest part.

This “buffer” layer can be added to the PRK in the form of a previously prepared mixture or created directly in the PRK, choosing the appropriate treatment regime for the ion exchange mixture during acid regeneration of the cation exchange resin, preserving it in the PRK when unloading pure cation exchange resin and anion exchange resin and using it in subsequent regenerations.

The general technological scheme of the installation is shown in Fig.1-10.

Figure 1 shows the state of the system in water purification mode, figure 2 is a diagram of the overload of the spent mixture of ion exchangers; figure 3 is a diagram of the separation of ion exchangers; figure 4 - diagram of the unloading of anion exchange resin in the FRA; figure 5 - diagram of the regeneration: figure 6 is a diagram of the overload of the regenerated cation exchange resin; Fig.7 is the state of the system after the end of the overload; on Fig is a diagram of the mixing of ion exchangers; figure 9 - scheme of washing a mixture of ion exchangers; figure 10 is a diagram of the overload of ion exchangers in the FSD.

The following notation is used in the drawings:

1 - mixed-action filter - FSD;

2 - Filter-regenerator of cation exchange resin - PRK;

3 - Anion-exchange filter regenerator - FRA;

4 - spent mixture of ion exchangers;

5 - intermediate "buffer" layer;

6 - anion exchange resin;

7 - cation exchange resin;

8 - a mixture of ion exchangers in H ⁺ and OH ^- forms.

-форме.The method is implemented as follows. During operation (figure 1) in the working FSD 1 there is a mixture of 8 cation exchange resin in the H ⁺ form and anion exchange resin in the OH ^- form, during filtration through which water is deeply desalted. In the filter regenerator of cation exchanger 2 there is a “buffer” layer 5 of cation exchanger in the H ⁺ form and anion exchanger in $$S{O}_{\mathrm{four}}^{-2}$$

form.

After the end of the working cycle, the spent mixed ionite charge 4 is unloaded from the FSD 1 into the filter regenerator of the PRK 2 cation exchanger containing the “buffer” layer 5 (Fig. 2). After overload, the separation of ion exchangers into a layer of cation exchanger 7, anion exchanger 6 and the "buffer" layer 5 (figure 3). Then the layer of pure anion exchange resin is reloaded into the filter regenerator of the anion exchange resin FRA 3 (Fig. 4). After overload, the anion exchange resin is regenerated with an alkali solution, followed by washing in the FRA. In parallel, the cation exchanger layer 7 and the “buffer” layer 5 are treated with an acid solution, followed by washing in PRK (Fig. 5). To increase the efficiency of regeneration, regenerating solutions of acid and alkali are introduced directly above the layers of cation exchange resin and anion exchange resin (figure 5).

After regeneration, a layer of pure cation exchanger 7 is reloaded from the bottom of the PRK into the FRA 3 (Fig.6). In the FRA, a mixture of the cation exchange resin in the H ⁺ form and the anion exchange resin in the OH ^- form 8 (Fig. 8) is mixed and washed (Fig. 9). The resulting mixture of ion exchangers 8 is overloaded in FSD 1 (figure 10), where they are mixed with compressed air and finally washed.

The height of the buffer layer of the mixture of ion exchangers 5 remaining in the PRC is monitored during unloading, as a rule, using a conductivity sensor, or vibration or ultrasound.

In PRK 2 there remains a buffer layer 5 containing a mixture of cation exchange resin in the H-form and anion exchange resin in the sulfate form. If the buffer layer 5 is not previously introduced into the PRK 2, then during the first cycle of operation, when removing the pure anion exchange resin from the PRK 2, the PRK 2 leaves a certain amount of anion exchange resin sufficient to form a buffer layer after treatment of the cation exchange resin and the remaining anion exchange resin with sulfuric acid.

As a result of using the method, the possibility of cross contamination of ion exchangers is completely eliminated. Moreover, its use is quite simple and reliable, does not require additional equipment.

Using the method is illustrated by the following example.

Example. To purify the condensate of the CHPP, a BOU block desalting unit with three FSDs with a diameter of 2.6 m was used. Remote ionite regeneration was carried out in filter regenerators with a diameter of 2.0 m.

A mixture of cation exchanger DOW MONOS-PHERE 650C and anion exchanger DOW MONOSPHERE 550A was used as ion exchanger. The PRK cation exchanger filter regenerator was equipped with devices for distributed unloading of pure cation exchanger and anion exchanger, arranged so that after overloading and separating a portion of the ion exchanger mixture from the working FSD and its separation, the upper device is above the cation exchanger and anion exchanger boundary, and the lower one is at a minimum distance from the bottom PRK. During the separation of the ion exchangers, the anion exchange resin was first hydraulically discharged through the upper discharge device. Under these conditions, the anion exchange resin is completely pure, i.e. does not contain cation exchanger particles.

-форме и 80% катионита в Н-форме. Данный слой составлял 7% суммарного объема ионитов и постоянно остается в ФРК, выполняя разделяющую функцию при последующих регенерациях. Чистые отрегенерированные катионит и анионит перемешивали в ФРА и затем отмывали обессоленной водой и оставляли в ФРА до отработки загрузки в одном из рабочих ФСД. Взаимное загрязнение смеси составило менее 0,05%.All cation exchange resin remains in the column with the calculated amount of anion exchange resin in the sulfate form on top. Then, cation exchange resin is regenerated with a 4% sulfuric acid solution with a specific consumption of 2.5 g-eq / g-eq and anion exchange resin with a 4% sodium hydroxide solution also with a specific consumption of 2.5 g-eq / g-eq and their washing ion exchangers with demineralized water. In this case, all the anion exchange resin in the FRA passes into the OH form. In PRK, cation exchange resin transforms into the H-form, and the layer of anion exchange resin located on top transforms into the sulfate form. During subsequent unloading, only pure cation exchange resin is discharged from the PRK to the FRA through the lower discharge device. Unloading continues until the ion exchanger layer in the PRC drops to a predetermined level so that the anion exchanger particles cannot enter the transfer device. The height of the remaining layer was 200 mm above the false bottom switchgear. At the same time, a mixture of ion exchangers from 20% anion exchange resin - in $$S{O}_{\mathrm{four}}^{-2}$$

form and 80% cation exchanger in the H-form. This layer accounted for 7% of the total volume of ion exchangers and constantly remains in the PRK, performing a separating function during subsequent regenerations. Pure regenerated cation exchange resin and anion exchange resin were mixed in a PDA and then washed with demineralized water and left in a PDA until the charge was worked out in one of the working FSDs. Mutual contamination of the mixture was less than 0.05%.

Claims (3)

1. A method for remote regeneration of a mixed layer of monodispersed ion exchangers, which includes overloading a mixture of ion exchangers from a mixed-action filter into a cation exchange filter regenerator, isolating pure cation exchange resin and anion exchange resin from a mixture of ion exchangers, unloading anion exchange resin and regenerating it, regenerating cation exchange resin into filter-regenerator of cation exchange resin and its reloading into the filter regenerator of anion exchange resin, mixing the ion-exchange mixture and washing it, moving the resulting mixture of ion-exchange resin into the working filter and their secondary mixing, characterized in that the separation from the mixture of ion exchangers of pure cation exchange resin and anion exchange resin is carried out by the method of hydraulic separation, as cation exchange resin particles of cation exchange resin with a particle size of 0.5-0.7 mm are used, and as anion exchange resin particles of 0.4-0.6 mm in size, moreover, in the filter-regenerator of cation exchanger before unloading an intermediate layer is created containing 70-90% of cation exchanger in H ⁺ form and 10-30% of anion exchanger in

- the form that is created in the cation exchanger filter-regenerator by treating the cation exchanger and the calculated amount of spent anion exchange resin by passing a solution of sulfuric acid through it is from 1 to 10% of the total volume of charged ion exchangers and is not unloaded when the cation exchange resin and anion exchange resin are discharged. 2. The method according to claim 1, characterized in that the layer containing 70-90% of cation exchanger in H ⁺ form and 10-30% of anion exchanger in

- form, mixed and introduced into the filter regenerator of cation exchange resin before introducing into it a mixture of spent ion exchangers. 3. The method according to claim 1, characterized in that the layer containing 70-90% of cation exchanger in H ⁺ form and 10-30% anion exchanger in

- form, create in a filter-regenerator of cation exchange resin by processing cation exchange resin and the calculated amount of spent anion exchange resin, passing through them a solution of sulfuric acid.

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