RU2715164C1 - Electrodialysis desalination method of electrolyte solution - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention can be used in electrochemical treatment of solutions. One performs successive desalination of electrolyte solution in desalination stages, each of which includes circulation circuit of diluate 2 and circulation circuit of concentrate 4, connected to at least one electrodialysis module. Controlled supply of electrolyte to flow circuit of diluate 1 is performed, which is in-series connected to circulation circuits of diluate 2 of desalination stage, starting from the first and to last through at least one electrodialysis module. Electrolyte is fed into the electrodialysis module of the first demineralisation step and its desalination is carried out; then, the obtained diluate is directed through the circulation circuits of the diluate and the flow circuit of the diluate into the electrodialysis modules of the subsequent demineralisation stages. Concentrate 21 is fed into concentrate flow circuit 3, which is in series connected to circulation circuits of concentrate 4 of desalination stages, starting from last to first through series-connected electrodialysis modules, and passes in opposite direction relative to direction of flow circuit of diluate. Electrical resistance of the concentrate is determined at the output of the first desalination stage, and electric resistance of the diluate is determined at the output of the last step and the supply of electrolyte and concentrate is corrected based on the obtained results.

EFFECT: disclosed invention ensures the desalination process uninterrupted operation, reduced power consumption during electrodialysis desalination of the solution, increased speed of the process, its reliability and efficiency, as well as increased degree of equipment use.

6 cl, 4 dwg

Description

The invention relates to the field of electrochemical processing of electrolyte solutions by electrodialysis and, in particular, to methods for their deionization.

A known method of desalination of an electrolyte solution (USSR Author's Certificate No. 575111, class B01D 13/02, 1977), comprising a circulating type electrodialysis unit consisting of a water supply pipe, an electrodialyzer, diluent tanks, brine and washing liquid for electrode chambers, pumps with drainage pumps impellers forming the circuits of the diluent, brine and washing of the electrode chambers, characterized in that in order to prevent the flow of brine into the diluent, the installation is equipped with a distribution tank mounted on the pipe a water supply line connected in the upper part to the washing liquid container for the electrode chambers, in the middle part to the diluent and brine capacity, and to the bottom to the drain.

Although the known method has several advantages, in particular, ease of implementation and reliability, however, the possibilities of electrodialysis desalination are not fully used due to the limitation of plant performance at the end of the process due to a decrease in efficiency due to a decrease in the conductivity of the dilute.

A known method of desalination of an electrolyte solution (RF Patent No. 2248848, class C02F 1/469, B01D 61/44, 2005), including feeding the solution into the space between the ion-selective membranes, applying a direct current electric field, carrying out the process to a final concentration, measuring operational parameters the process, including the values of current and voltage, determining from them the electrical resistance of the electrodialyzer, adjusting the electrical parameter, characterized in that the electrical parameter is adjusted electrically resistance of the solution, to which a part of a dialysate concentrate or recycled to the beginning of the process.

The disadvantage of this method is the use of a circulation circuit of demineralization (with a common circulation circuit), which does not allow to achieve high productivity of the process. The rate of demineralization decreases as the diluent conductivity decreases.

The technical problem to be solved by the claimed invention is directed to the development of a high-performance method of electrodialysis desalination of an electrolyte solution.

The technical result of the invention is to achieve the continuity of the process of desalination, optimization of the method of electrodialysis desalination of the electrolyte solution, reduction of energy consumption in the process of electrodialysis desalination of the solution, increasing the speed of the process, its reliability and productivity, reducing the cost of equipment, as well as increasing the degree of use of equipment.

The indicated technical result is achieved in the method of electrodialysis desalination of an electrolyte solution, according to which a sequential desalination of the solution is carried out in desalination steps (electrodialysis desalination plants), each of which includes a dilution circulation circuit and a concentrate circulation circuit connected to at least one electrodialysis module. The steps are connected by the flow path of the diluate and the flow path of the concentrate. The steps also contain mixing tanks of the diluent and the concentrate, connected with the circulation circuits of the diluent and the concentrate, respectively, taps located on the circulation circuits of the diluent and the concentrate. To achieve the result, a controlled supply of electrolyte to the flow path of the diluent is carried out, which is connected in series with the circuits of the diluate of the desalination steps, starting from the first to the last (Nth) through at least one electrodialysis module containing sections of the concentrate and diluate, after whereupon the electrolyte is fed into the electrodialysis module of the first stage of demineralization and the electrolyte is desalted, then the resulting diluent through the circulation circuits of the diluate and the flow path of the diluent they are fed into the electrodialysis modules of the subsequent stages of demineralization, in this case, a controlled supply of concentrate to the flow path of the concentrate is carried out, which is connected in series with the concentrate tanks and the circuits of the concentrate of the desalination steps, starting from the last to the first through the series-connected electrodialysis modules and passes in the opposite direction relative to the direction flow path of the diluate. In this case, at the exit from the first stage, the electrical resistance of the concentrate is determined, and at the exit from the last stage, the electrical resistance of the dilute is determined. Based on the results obtained, the flow of electrolyte and concentrate is adjusted.

The circulation circuit of the stage diluate includes: desalination cavities of one or two electrodialysis modules connected to the diluate circulation pump and the diluent mixing tank. The stage concentrate circulation loop includes: concentration cavities of one or two electrodialysis modules connected to the dilution circulation pump and dilution mixing tank.

In the method, two to N desalination steps can be used.

Each stage may contain several series-connected electrodialysis modules.

Electrodialysis modules are filter-press type equipment and consist of two repeatedly repeating sections: a concentration section (for collecting concentrate) and a desalination section (for collecting diluate) with a cathode and anode placed on different sides of them. The concentration and desalination sections consist of a set of gaskets, cationite and anionite membranes.

An electric field of direct current and voltage is superimposed on the electrodialysis modules.

The flow circuit of the diluent consists of an electrolyte feed pump and a pipeline connecting in series the demineralization stages from the first to the Nth through the dilution mix tanks.

The flow path of the concentrate consists of a concentrate tank, a concentrate feed pump and a pipeline connecting the demineralization stages from N-th to the first through the concentrate mixing tanks.

The circulation circuit of the near-electrode solution (PER) consists of a PER tank, a PER supply pump, and a PER supply pipe.

As operational parameters of the process measure:

1. Values of current and voltage at the EDM power source. The measured values of current and voltage calculate the electrical resistance of the electrodialysis module as the ratio of voltage to current;

2. The electrical conductivity of the diluent at the output of the Nth stage;

3. The electrical conductivity of the concentrate at the outlet of the first stage.

The electric parameter of the conductivity of the concentrate is adjusted to achieve stability of the conductivity levels in the sections by regulating the supply of the concentrate to the flow path of the concentrate.

Correct the electrical parameter of the conductivity of the diluent by adjusting the supply of electrolyte to the flow path of the diluate to achieve the required conductivity of the diluate at the output of the Nth stage.

In addition, the pH of the electrolyte is adjusted by supplying a sodium hydroxide solution to the electrolyte. Thus, the acidity of the electrolyte is regulated and the required pH is achieved for a number of applications.

The supply of electrolyte and concentrate to the steps in opposite directions (concentrate to the flow path connecting the desalination stages from the last to the first, and the dilution to the flow path connecting the steps from the first to the last) promotes the electrodialysis of the electrolyte with the maximum possible current density in the electrodialysis module, with the maximum degree of use of current sources during the entire process of desalination of the solution. This is due to the fact that the conductivity of the electrolyte during desalination in the electrodialysis modules decreases from the first stage to the Nth, as a result of which the electric power of the current source decreases in the electrodialysis modules from the first stage to the nth. As a result, the performance of the desalination process drops significantly. The ability to supply the flow path concentrate in the opposite direction with respect to the diluent feed allows to increase the rate of demineralization of the electrolyte, which significantly reduces the energy consumption for the process and provides an increase in the productivity of the method.

In addition, the sequential introduction of the concentrate into the electrodialysis modules of each of the desalination steps in the reverse order, from the last step to the first, in principle, since the electrolyte conductivity in the last steps is significantly lower. Thus, the sequential introduction of concentrate into electrodialysis modules with an electrolyte with lower conductivity allows maintaining the stability of the electrolyte conductivity and, as a result, maintaining the power of the current source at all stages at approximately the same level, which significantly accelerates the desalination process, reduces the energy consumption for the process, and provides an increase method performance.

This method allows the use in the design of unified steps (blocks), by changing the number of steps you can increase / decrease the productivity of the method. The possibility of overlapping taps in the circulation circuits of the desalination stages allows each stage to be individually repaired without stopping production, which ensures uninterrupted desalination process.

The use in the method of the nth number of desalination steps and the presence in each of the desalination steps of the installation of the diluent circulation loop, the concentrate circulation loop connected to at least one electrodialysis module, the diluent and concentrate mixing tanks associated with the dilute and concentrate circulation loops, respectively , taps located on the circuits of the diluent and concentrate, allows the process of desalination to run smoothly. This is achieved due to the possibility of shutting off valves located on the circulation circuits of the diluent and concentrate, connected to the electrodialysis modules of one of the stages in the event of a stage failure and directing the electrolyte to desalinate along the flow path of the diluent to the next stage. As a result, it is possible to maintain uninterrupted operation of the installation and the performance of the desalination process. In addition, the ability to add additional steps to the installation to replace failed ones also ensures that performance is maintained at a given level.

The use of the block design of the electrodialysis desalination plant contributes to:

1) reducing the length of pipelines in the circulation circuits, reducing the height of the product — reducing the hydraulic resistance in the pipeline, thereby increasing the flow rate of the product through the electrodialysis module, which favorably affects the performance of electrodialysis;

2) to reduce costs in the flow path, which are equal to the productivity of the installation, which contributes to the use of pipelines of smaller cross-section, which ensures cost savings;

3) each unit operates in its own mode and does not change its electrical power during operation, thereby there is no need to install maximum power sources in all units - increasing the degree of equipment utilization.

In addition, in the present method, the flow of concentrate is adjusted to maintain the conductivity of the concentrate at the outlet of the concentrate circuit to achieve comparable conductivity of the diluent and concentrate in the circulation circuits. This helps to increase the reliability of the electrodialysis module (and the desalination process as a whole) by significantly reducing the likelihood of a short circuit, as well as increasing the life of the electrodialysis modules of the desalination steps by increasing the life of anionite and cationite furniture.

The ability to control the flow rate of the electrolyte into the flow path of the diluate provides the desired degree of desalination of the electrolyte at the outlet of the flow path of the dilute.

The possibility of sequential inclusion of electrodialysis modules in the circulation circuits allows to reduce the number of pumping equipment, and, thus, to further simplify the method and reduce its complexity.

In addition, the concentrate circuit of the desalination stage of the electrodialysis unit (electrodialysis desalination unit) can be connected to the stage for the separation of hydrochloric acid and sodium hydroxide from the concentrate, in particular with at least one electrodialysis module, which allows acid solutions to be separated from the concentrate (salt solution) and alkali, which can be used in the process of CIP-washing of the installation for cleaning membranes from contamination.

The stage of separation of acid (e.g. hydrochloric acid) and alkali (e.g. sodium hydroxide) from the concentrate (acid and alkali separation system) may contain one or more electrodialysis modules, the amount of which is determined by the required plant capacity and the required acid and alkali concentration.

A significant number of electrodialysis demineralization processes are characterized by the fact that the main component of the concentrate is sodium chloride (NaCl). The use in the method of electrodialysis desalination of an electrolyte solution of electrodialysis separation of acid and alkali solutions allows to obtain in the process of desalination a solution of hydrochloric acid and caustic soda, which are used in the SIW-washing equipment. Thus, as a result of the implementation of this method, it is possible to further increase the environmental friendliness of the process due to a significant reduction in the amount of wastewater, as well as a significant reduction in the cost of production due to the saving of reagents in the SIP-washing process.

The invention is illustrated by figures. The figure 1 shows a functional diagram of the technological process of electrodialysis desalination of an electrolyte solution. The figure 2 shows a diagram of an electrodialysis module. The figure 3 shows a functional diagram of the technological process of electrodialysis desalination of an electrolyte solution with a step of separation of acid (hydrochloric acid) and alkali (sodium hydroxide) from the concentrate. The figure 4 shows a diagram of an electrodialysis module that provides the allocation of solutions of acid and alkali.

In the figures, positions 1-53 indicate:

1 - pipeline flow circuit of the diluate,

2 - circuit circulation diluate,

3 - flow path of the concentrate,

4 - circuit circulation of the concentrate,

5 - pipeline for supplying PER to the electrodialysis modules,

6 - circuit circulation PER,

7 - pump for supplying electrolyte to the mixing tank of the diluent,

8 - dilution circulation pump,

9 - concentrate feed pump,

10 - pump circulation of the concentrate,

11 - pump feed PER,

12 - crane

13 - bipolar membrane

14 - cation exchange membrane

15 - anion exchange membrane,

16 - the first stage of desalination (demineralization),

17 - the second stage of demineralization,

18 - N-stage (last stage) of demineralization,

19 is a first electrodialysis module,

20 is a second electrodialysis module,

21 - tank with concentrate,

22 - tank mixing diluent,

23 - tank mixing concentrate,

24 - tank PER,

25 - electrode cathode,

26 - electrode anode,

27 - camera diluate,

28 - chamber concentrate,

29 - diluent collector,

30 - concentrate collector,

31 - crane

32 - crane

33 - crane

34 - a diluate pump of an acid and alkali extraction step,

35 is an acid solution pump,

36 is an alkali solution pump,

37 - circulation tank for alkali solution,

38 - electrodialysis module for the allocation of acid and alkali,

39 - circulation tank for demineralized water (diluate),

40 - circulation tank for an acid solution,

41 - storage tank alkali,

42 - storage tank acid

43 - overflow (pipeline) into the alkali storage tank,

44 - circuit alkali solution,

45 is an outline of an acid solution,

46 is a circuit of the diluate of the stage of acid and alkali,

47 - overflow (pipeline) in an acid storage tank,

48 - drainage of demineralized water (dilute),

49 - stage allocation of acid and alkali,

50 - a chamber of a dilute of an electrodialysis module of an acid and alkali extraction step,

51 is a chamber of an alkali solution of an electrodialysis module of an acid and alkali extraction step,

52 is a chamber of an acid solution of an electrodialysis module of an acid and alkali extraction step,

53 - supply of near-electrode solution (PER).

The electrolyte is fed into the pipeline of the flow circuit of the diluate 1 and then to the mixing tank of the diluate 22 of the first desalination (demineralization) 16 via the electrolyte supply pump 7. The circulation circuit of the diluate 22 is connected to the circulation circuit of the diluate 2 through the electrodialysis modules 19, 20 connected in series. diluate 2, the electrolyte is supplied by pump 8. In each of the electrodialysis modules, which are filter-press type equipment and consisting of two repeatedly repeating chambers (sections): concentrator chambers ata 28 (concentration sections) for collecting the concentrate and a diluate chamber 27 (desalination sections) for collecting the diluate, a cathode 25 and anode 26 are connected to which a direct current source is connected, as well as cation exchange 14, anion exchange 15 membranes, bipolar membranes 13. Thus, the cathode 25 and the anode 26 are located in the near-electrode regions, the migration of ions to which is limited by bipolar membranes 13 and which are washed by a special near-electrode solution - sodium hydroxide solution. The use of bipolar membranes 13 prevents the entry of cations and anions from the working medium into the electrode space. Thus, the constancy of the composition of the near-electrode solution is ensured, which ensures a constant value of the electrical conductivity of the near-electrode solution and increases the productivity of the installation, increases the service life of the electrodes. From the mixing tank of the diluate 22, the electrolyte is supplied to the electrodialysis modules 19, 20. Before turning on the direct current, all sections of the electrodialyzer are uniformly filled with cations and anions of the electrolyte. When the current is turned on, the cations migrate through the cation exchange membranes 14 to the cathode 25, however, their further electromigration to the cathode is limited by the bipolar membrane 13, which is impermeable to them. Accordingly, the anions migrate to the anode 26 through the anion exchange membrane 15, but further electromigration to the anode prevents bipolar membrane 13, which is slightly permeable to anions. The result is a symmetrical process in which cations and anions from even chambers (sections), called chambers (sections) of diluate 27, migrate to odd chambers, where they accumulate, and chambers (sections) are called concentrate chambers (concentration sections) 28. The resulting diluate from the diluate sections of the electrodialysis modules enters the diluent collector 29, the diluent mixing tank 22 and then through the dilute flow path to the diluate mixing tank 22 of the second demineralization stage 17 for similar demineralization right up to the exit of the diluate (finished product) and further to the subsequent stages of N.

The concentrate from the chamber of the concentrate enters the collector of the concentrate 30.

Moreover, with an increase in the number of steps passed by the diluate, its conductivity decreases. The power of the current source, which depends on the conductivity, also decreases, as a result of which the speed of the desalination process decreases, as well as the productivity. In each subsequent stage, the conductivity of the diluate is less than in the previous one. To increase and stabilize the conductivity of the electrolyte, the concentrate is simultaneously fed into the pipeline of the flow path of the concentrate 3 by pumping the concentrate 9 and then to the concentrate mixing tank 23 of the last stage N of demineralization 18. The concentrate 4 circulation loop is connected to the concentrate mixing tank 23 through electrodialysis modules 19 connected in series 20. The concentrate is fed into the electrodialysis module by the concentrate circulation pump 10. Next, the concentrate obtained from the product from the concentrate mixing tank 23 enters through the flow path of the concentrate to the concentrate mixing tank 23 of the previous demineralization stage N-1 in a similar manner up to the first demineralization stage 16 and the concentrate is drained into the concentrate tank 21. The electrode circuit (PER) 6 is circulated to supply the electrode electrode with a PER 11 feed pump from the PER 24 tank to the near-electrode chambers of the electrodialysis modules 19, 20.

If the electrodialysis modules of stage 2 fail, the valves 32, 12 are shut off during the repair, as a result of which the electrolyte is sent to the concentrate mixing tank and the electrodialysis modules of the next stage. Due to the possibility of simple connection to the installation of additional desalination steps (step extensions), it is possible to use additional steps for the repair of one of the stages, which ensures uninterrupted operation of the installation at high productivity.

Additional stages are connected by connecting the mixing tank of the stage diluate to the pipeline of the flow circuit of the diluate and the mixing tank of the concentrate - to the flow circuit of the concentrate 3, as well as the electrodialysis module to the pipeline for supplying the PER 5 to the electrodialysis modules.

The required degree of desalination at the outlet is achieved by regulating the performance of the pump for supplying the electrolyte 7 to the flow circuit of diluate 1.

To reduce the energy consumption of demineralization of the electrolyte, the serial concentrate circuit passes through the demineralization steps in the reverse order, from the last to the first, to equalize the conductivity levels in the concentration sections and diluate sections of the electrodialysis modules 19, 20. The stability of the conductivity levels in the sections is ensured by adjusting the degree of conductivity of the concentrate at the discharge from the first stage of demineralization 16.

The above example is a special case and does not exhaust all possible implementations of the invention.

The block structure of the process allows you to create a modular installation, which is an advantage in terms of the convenience of adding steps to change the performance of the process or turn off the steps from the process for maintenance and repair, by shutting off the taps 12, 31, 32, 33 in the circulation circuits.

When implementing the method of electrodialysis demineralization of an electrolyte solution with parallel extraction of acid and alkali from the resulting concentrate, the concentrate contour 3 is connected to the step for separating hydrochloric acid and sodium hydroxide from concentrate 49. The brine (concentrate) from the previous desalination step (Step 1) 16 enters through the concentrate 3 contour 3 into the circulating tank for demineralized water 39 and further along the circuit of the diluate of the acid and alkali separation system 46. The concentrate is supplied by the pump of the dilute of the acid separation system and alkali 34 into the diluate chamber 50 of the electrodialysis module 38 of the acid and alkali separation stage 49. The electrodialysis acid and alkali separation module 38 is a chamber bounded on the cathode side 25 by a cation exchange membrane 14 and on the anode side 26 by an anion exchange membrane 15. Thus, when applying an electric field, the cations migrate through the cation exchange membrane 14 to the cathode 25, and the anions through the anion exchange membrane 15 to the anode 26. The electrode chambers 6 are limited by bipolar membranes 13, which are washed by a special rielektrodnym solution 53 - sodium hydroxide solution, to prevent the ions in the sheath region. Cations and anions are concentrated in the chambers of the alkali solution 51 and the chambers of the acid solution 52. In addition, in the chambers of the electrodialysis module (EDM) from the circulation tanks for the acid solution 40 and for the alkali solution 37 along the contours of the alkali and acid solutions 44, 45 with the corresponding pumps 35, 36 alkali and acid are supplied. In the EDM chambers, alkali is supplied along the circuit of the alkali solution 44, and acid is fed through the circuit of the acid solution 45. The concentrate is introduced into the EDM chambers along the dilute of the acid and alkali separation system 46. As a result of the process, demineralized water is formed in the chamber 50, which is discharged along the demineralized circuit water 46 into the circulation tank for demineralized water 39 and is discharged through circuit 48 (thus, initially into the tank for demineralized water 39 is filled with concentrate, but as a result of the circulation process, demineralization cation, in the tank 39 the diluent enters, diluting the concentrate, and as a result, instead of the concentrate in the tank 39, a dilute is obtained, which is discharged through the circuit 48). The acid and alkali solutions obtained in the EDM chambers are discharged along the corresponding circuits 44, 45 into the circulation tanks for the alkali solution 37 and acid 40, and then the acid storage tanks 42 and alkali 41 are discharged through pipelines 47 and 43, respectively. The required installation performance is achieved by creating a set of N-cameras (up to 250-300), combined into a single circuit. If necessary (increase in productivity, concentration of acid and alkali) additional modules are installed. N-chambers of acid and N-chambers of alkali are also combined in the contours of solutions of acid and alkali.

In addition, the possibility of regulating the acidity of the electrolyte by feeding a solution of sodium hydroxide allows you to achieve the desired pH for a number of applications, in particular, in the demineralization of whey.

Washing (washing) of ion-exchange membranes of electrodialysis modules, equipment and pipelines of the installation in the process of demineralization provides an additional increase in the speed of the process, its reliability and productivity due to the elimination of the formation of salt deposits in the equipment. The washing of the electrodialysis unit covers all, without exception, the constituent parts of the unit that were in direct contact with the treated solutions. In the present method, washing is carried out using a new electrochemical washing method, comprising the following steps:

1. The first water flushing of pipelines and plant equipment, ion-exchange membranes of electrodialysis modules,

2. Alkaline flushing of pipelines and plant equipment, ion-exchange membranes of electrodialysis modules (alkaline solution is used). In this case, the system is flushed with a simultaneous supply of voltage to the electrodialysis modules with periodic polarity reversal. Flushing is performed until the electrical resistance of the module is equalized in the forward and reverse directions),

3. The second washing with water of pipelines and plant equipment, ion-exchange membranes of electrodialysis modules (leaching of alkali residues from the system),

4. Acid washing of pipelines and plant equipment, ion-exchange membranes of electrodialysis modules (an aqueous solution of acid is prepared and the system is washed with voltage being applied to the electrodialysis modules with periodic polarity reversal, washing is performed until the set time is reached),

5. The third washing with water of pipelines and equipment of the installation, ion-exchange membranes of electrodialysis modules (leaching of acid from the technological system),

6. Electrochemical washing of pipelines and plant equipment, ion-exchange membranes of electrodialysis modules (a high degree of purification of the membranes of the electrodialysis module by conducting demineralization of water to achieve the set conductivity value).

Thus, the invention can be used for deep desalination of saline water, desalination of natural salt and brackish water, deionization of industrial wastewater, to produce natural and concentrated curd whey, demineralized by electrodialysis, designed to produce dairy, milk-containing, sour-milk products, ice cream and frozen desserts, use in the production of canned milk, children's and dietary products, bakery and confectioners products, in sausage production and can find application in other industries where similar methods are used.

Claims (10)

1. The method of electrodialysis desalination of an electrolyte solution, characterized in that sequential desalination of the solution is carried out in desalination steps, each of which includes a dilute circulation circuit and a concentrate circulation circuit connected to at least one electrodialysis module, taps located on the dilute and concentrate circulation circuits , for this, a regulated supply of electrolyte is made into the flow path of the diluate, which is connected in series with the circulation circuits of the diluate of the mortar desalination, starting from the first to the last through at least one electrodialysis module, after which the electrolyte is fed into the electrodialysis module of the first stage of demineralization and its desalination is carried out, further, the resulting dilute through the circulation circuits of the dilute and the flow circuit of the dilute is sent to the electrodialysis modules of the subsequent stages of demineralization, in this case, a controlled supply of concentrate to the flow path of the concentrate is carried out, which is connected in series with the circuits of the concentrate of desalination steps, starting from the last to the first through the series-connected electrodialysis modules, and passes in the opposite direction relative to the direction of the flow path of the diluent, in this case, at the outlet from the first stage of desalination, the electrical resistance of the concentrate is determined, and at the outlet from the last stage, the electrical resistance of the dilute is determined and adjust the supply of electrolyte and concentrate based on the results. 2. The method according to p. 1, characterized in that carry out the sequential inclusion of electrodialysis modules. 3. The method according to claim 1, characterized in that a bipolar membrane is installed in the electrodialysis module. 4. The method according to p. 1, characterized in that the near-electrode space of the cathode and anode, limited by bipolar membranes, serves near-electrode solution. 5. The method according to p. 1, characterized in that the concentrate circuit of the desalination stage can be connected to the stage of separation of hydrochloric acid and sodium hydroxide from the concentrate containing the electrodialysis module. 6. The method according to p. 1, characterized in that carry out electrochemical washing of ion-exchange membranes.

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