WO1995006513A1

WO1995006513A1 - Electrodialysis process and device

Info

Publication number: WO1995006513A1
Application number: PCT/DE1994/001008
Authority: WO
Inventors: Peter Finke
Original assignee: Finke, Gretel; Bachmann, Magdalena
Priority date: 1993-09-03
Filing date: 1994-09-01
Publication date: 1995-03-09
Also published as: AU7607794A

Abstract

The invention relates to an electrodialysis process, especially for seawater desalination, in which a liquid to be dialysed, especially seawater, is taken to an electrodialysis device (5) of an electrodialysis plant (1) and exposed therein to a d.c. voltage applied between an anode (27) and a cathode (28). In order to obtain a continuous process in which no hardening salts are deposited in the electrodialysis device (5), no metal coating forms on the cathode and the exchange diaphragms are not attacked by halogen gases, according to the invention a separate stream of liquid, especially a partial stream of the process, passes through the anode (27) and/or the cathode (28) and the electrodes are separated from the liquid by a diaphragm unit.

Description

Electro-dialysis method and electro-dialysis device

Description:

The invention relates to an electro-dialysis method, in particular for salt water desalination, in which a liquid to be dialyzed, in particular salt water, is fed to an electro-dialysis device of an electro-dialysis system and the liquid in the electro-dialysis device is exposed to a DC voltage applied between an anode and a cathode. Furthermore, the invention relates to an electro-dialysis device of an electro-dialysis system with an outer housing, an inlet for a liquid to be dialyzed, in particular salt water, and an outlet for the dialyzed liquid to be supplied with direct current electrodes, namely one preferably anode arranged in the region of the inlet and a cathode preferably arranged in the region of the outlet and a plurality of anion-cathionic selectors located between the inlet and the outlet

Exchange membranes, the electro-dialysis device preferably working according to the aforementioned electro-dialysis process. In addition, the invention relates to an electro-dialysis system with an electro-dialysis device of the aforementioned type. Finally, the invention also relates to an electrode, in particular for an electro-dialysis device of the aforementioned type, and a method for producing such an electrode.

Electro-dialysis is a separation process based on the principle of dialysis, in which the migration of the ions through (perm-selective) membranes is accelerated by applying an electrical direct voltage. By cascading several anion- and cathion-selective exchange membranes, deionization of the liquid to be dialyzed - generally water - can be achieved with simultaneous enrichment of the ions in the electrode cells (concentration chambers). Electro-dialysis is used, for example, for seawater desalination, also for drinking water extraction from brackish water if the salt content is below 1 g / l, for regulating the hardness of the water, in the food industry for whey desalination and in winemaking Prevention of tartar separation. In addition, electro-dialysis can be used to recover valuable substances from galvanic waste water.

REPLACEMENT LEAF Conventional electro-dialysis processes work with stacks of anodic and cathodic membranes, which are arranged alternately. The opposite-pole electrode plates are attached to the respective stack ends, and DC current is applied to them. The volume flow to be desalinated flows parallel to the electrical field between the electrode plates in parallel through the stack of membranes. This is done in such a way that a pair of membranes through which this volume flow flows alternates with a pair of membranes in which the salt ions that pass through this membrane due to the force of the electric field accumulate. After the volume flow has flowed through the stack of membranes, its salt content has decreased more or less depending on the operating parameters. The solution concentrate from the adjacent spaces between the membrane pairs is derived.

By sequencing several membrane stacks, a complete desalination of the salt solution introduced at the beginning is possible. The production goal of these systems is always primarily the production of drinkable or drinkable water.

A major disadvantage of the known method is that the cathode is fogged up with metal from the salt ion pairs to be separated. Another disadvantage arises from the precipitation of hardness salts in the electro-dialysis device. It is known that the water occurring in nature, be it surface water (lake, pond, dam, river water) or groundwater (spring water, well water) and the ordinary tap water is not "chemically pure". In addition to dissolved gases (e.g. O2, N2, CO2), the waters contain a number of salts and other compounds that have been removed from the soils and rocks or, in the case of surface waters, also partly come from wastewater inlets. The most important components are the salts of calcium and magnesium, especially the chlorides, sulfates and hydrogen carbonates, which are known as so-called hardness agents. After precipitation, these hardness salts can impair the electro-dialysis process. To remove the precipitated hardness salts, additional process steps are usually required to clean the entire system. This often results in discontinuous operation of the entire electro-dialysis system with long downtimes. Finally there is another

REPLACEMENT LEAF A disadvantage of the known electro-dialysis devices is that during the electro-dialysis halogen gases, in particular chlorine gas, can arise which can attack the exchange membranes.

Overall, the known electro-dialysis process, like all other processes which are used for the desalination of salt solutions or sea water, be it thermal or physico-chemical processes, is unsatisfactory from an economic point of view.

The invention now goes a new way. In a first embodiment of the electro-dialysis method mentioned at the outset, it is now provided according to the invention that a separate liquid flow, in particular a partial flow of the process, flows through the anode and / or the cathode. The flow through the electrodes can be from the front or from the rear. It goes without saying that the flow through the electrodes presupposes that the anode and / or cathode allow flow through at all, that is to say they are porous. Due to the possibility of flow through the electrodes, metals from the liquid to be dialyzed or dialyzed can no longer deposit on the cathode, since these are washed away as well as halogens formed atomically on the anode surface. As a result, the halogens washed away can no longer attack the exchange membranes of the electro-dialysis device.

In another embodiment of the electro-dialysis process according to the invention, the anode and / or cathode are separated from the liquid from the liquid to be dialyzed or dialyzed by a membrane unit which also has anion- or cathode-selective properties. By separating the electrodes from the liquid to be dialyzed or dialyzed, direct contact with the electrodes is initially ruled out. A significant advantage of this separation is that bases or acids formed in the area of the electrodes can be used for process control. For example, the H ⁺ ions located in the area of the anode can not only be used to rinse the electro-dialysis device, but also the brine that forms in the concentration chambers, so that a low pH value results. With a pH value of 3 or less, it is ensured that hardness salts do not precipitate out, but remain in solution. The OH ^_ ions located in the area of the cathode are removed from the area of the cathode

REPLACEMENT LEAF deducted. This creates an anion deficit in the area of the cathode, which has the consequence that the liquid as a whole becomes acidic, which in turn prevents precipitation of the hardness salts. The OH "ions discharged from the cathode are preferably fed to a settling or separating container adjoining the electro-dialysis device, in which the highly concentrated salt solution is removed from the electro-dialysis device. By feeding the OH ^_ ions the pH value in the separating tank increases, which leads to the precipitation of the hardness salts in the separating tank Finally, both the H + and the OH'-ions can be used to adjust the pH value of the end product, ie the drinking or drinkable water In addition, the partial stream used to rinse the anode, which is preferably fresh water, can be returned to the end product, which is enriched when the anode is passed through with the oxygen formed there (in the nascendi stage) and with chlorine gas As a result, the end product, ie the fresh water, tastes fresh due to the oxygen supplied to it, while the m It-guided chlorine gas is used to disinfect the drinking water.

Further features, advantages and possible uses of the present invention result from the further claims, the following description of exemplary embodiments with reference to the drawing and the drawing itself. All of the described and / or illustrated features, alone or in any combination, form the subject of the present invention , irrespective of how they are summarized in the claims or their relationship.

It shows:

Figure 1 is a schematic representation of an inventive

Dialysis machine,

Figure 2 is a schematic cross-sectional view of an electro-dialysis device according to the invention and

Figure 3 is a schematic representation of another

Embodiment of an electro-dialysis system according to the invention.

REPLACEMENT LEAF In Figure 1, an electro-dialysis system 1 is shown schematically. In the embodiment shown, the electro-dialysis system 1 has a filter 2, through which the liquid to be dialyzed, in particular a saline solution, namely sea water, is removed. The filter 2 is preferably made of porous plastic. The filter 2 is connected to a feed pump 4 via a line 3. An electro-dialysis device 5 is connected to the feed pump 4. The electro-dialysis device 5 can also be referred to as a desalination unit. The feed pump 4 and the electro-dialysis device 5 are connected to one another via a line 6, via which the salt solution is fed. Electro-dialysis is carried out in the electro-dialysis device 5. As the end product, drinking water or drinkable water is removed from the electro-dialysis device 5, which is shown by the arrow 7.

The highly concentrated saline solution produced in the electro-dialysis in the electro-dialysis device 5 is fed via line 8 to a separating or settling tank 9. A base is also added to the separating container 9, namely until the pH has risen to such an extent that the hardening salts in solution in the highly concentrated salt solution are precipitated out of the solution. This pH is around 6.7. OH ^_ ions are added as base, which are added to the separating container 9 via the line 10 from the electro-dialysis device 5. It should be pointed out that not all connections or lines between the separating container 9 and the electro-dialysis device 5 are shown. For example, two lines originating from the upper area of the separating container 9 are provided, but not shown, which enter the electro-dialysis device 5 from above. Also not shown are two connecting lines from the line leading the fresh water according to the arrow 7 back to the electro-dialysis device 5 and a further line which runs from the electro-dialysis device 5 to the fresh water line according to arrow 7. The individual lines (not shown) and their meaning are discussed in more detail below.

The hardness salts precipitated in the separating container 9 collect on the preferably conical container bottom 11 of the separating container 9 and are there via a cellular wheel lock 12, which is only indicated schematically, via a conveying means 13, for example a revolving conveyor belt or

REPLACEMENT LEAF Screw conveyor, an electrolysis tank 14 supplied. As usual, the electrolysis basin has an anode 15 and a cathode 16 for electrolysis. Manganese, calcium and / or magnesium, for example, can now be obtained electrolytically from the hardness salts.

The highly concentrated salt solution remaining in the separating container 9 and which no longer contains any hardness salts is pumped, for example, via an overflow 17 via a line 18 into a storage container 19. A pump, not shown, is used for this. From the storage container, which is not absolutely necessary, the highly concentrated salt solution is distributed via line 20 and branch lines 21 into salt basins 22. The salt pans 22 are a conventional salt pan per se. In the salt pans 22, the salt is "generated" by natural evaporation, that is, due to heat radiation from the sun. This salt is free of hardness salts and essentially consists of sodium halides.

FIG. 2 shows the electro-dialysis device 5 according to the invention. The electro-dialysis device 5 has a housing 23, which preferably consists of a non-conductive material. Furthermore, the electro-dialysis device 5 is provided with an inlet 24 for the saline solution to be dialyzed and an outlet 25 for the dialyzed saline solution, ie the fresh water. Inlet 24 and outlet 25 each have connecting pieces 26 on the one hand for the line 6 shown in FIG. 1 to the inlet 24 and on the other hand to the fresh water line according to arrow 7 (at the outlet 25). In the electro-dialysis device 5 there is an anode 27 in the area of the inlet 24 and a cathode 28 in the area of the outlet 25. The anode 27 and cathode 28 are each designed as plate-shaped electrode bodies and essentially take the free cross section within the housing 23 of the electro-dialysis device 5. The front side 29 of the anode 27 is directed towards the front side 30 of the cathode 28.

The anode 27 and the cathode 28 are each porous. The two electrodes preferably consist of metal spheres or spherical metal bodies made of titanium and can be coated as required with another metal which is selected from the chemical voltage series for the respective process conditions. The diameter of the spherical metal body is

REPLACEMENT LEAF preferably different within an electrode and is between 0.2 to 2.0 mm. In order to offer the advantage yet to be explained and in order not to hinder a flow through the electrodes too much, the diameter of the spherical metal bodies is in particular between 0.5 and 1.3 mm.

Basically, the electrodes can be made of sintered metal, so they are thermally "welded together". However, the spherical metal bodies are preferably pressed together between two non-conductive plates and then subjected to direct current transversely to the pressing direction. The current density of the direct current is chosen so high that the individual spherical metal bodies are welded to one another at a point. The different diameters of the individual spherical metal bodies result in an optimal swirling of a liquid stream which is passed or flushed through the porous electrodes.

Of course, the anode 27 itself, like the cathode 28, is provided with a power supply 31. A plurality of alternatingly arranged anionic exchange membranes 32 and cathionic exchange membranes 33 are located between the anode 27 and the cathode 28

Exchange membranes 32, 33 alternately form diluate chambers 34 and concentration chambers 35, in which the concentrated saline solution collects. The anode 27 is separated from the incoming or incoming salt solution by a membrane unit 36. The membrane unit 36 is thus set back in the housing 23 with respect to the inlet 24. An anode prechamber 37 is located between the membrane unit 36 and the first cathionic exchange membrane 33. The anode prechamber 37 is therefore delimited by the membrane unit 36 on the anode side. The membrane unit 36 is a double membrane, which likewise consists of an anionic exchange membrane 32 and a cathionic exchange membrane 33. In the area of the membrane unit 36 there are preferably on opposite sides of the housing 23 of the electro-dialysis device 5 an inlet 38 and an outlet 39 to the space between the membrane unit 36. Between the membrane unit 36 and the anode 27 there is an anode chamber 40, while on the other side of the anode 27 between the back 41 of the anode 27 and the housing end wall, not shown

REPLACEMENT LEAF Anode rear chamber 42 is formed. The anode chamber 40 has an inlet 43, while the anode rear chamber 42 has an outlet 44. Between the anode 27 and the membrane unit 36 are porous cylinders 45, which preferably consist of glued plastic granules. A part of the surface of the anode 27 is covered by the cylinders 45. In the illustrated embodiment, the inlet 43 and the outlet 44 are arranged on opposite sides of the housing 23.

The area of the cathode 28 is configured similarly to the area of the anode 27. Between the last anionic exchange membrane 32 and the cathode 28 there is also a membrane unit 36 which has the configuration described above. Between the membrane unit 36 arranged in the area of the cathode 28 and the last anionic exchange membrane 32 there is a cathode pre-chamber 46. Between the front 30 of the cathode 28 and the membrane unit 36 there is a cathode chamber 47, while between the rear 48 of the cathode 28 and rear, not designated end wall of the housing 23 is a cathode rear chamber 49. The cathode rear chamber 49 has an inlet 50, while the cathode chamber 47 has an outlet 51.

Each pair of anionic and cathionic exchange membranes 32, 33, which form a concentration chamber 35, have a main flow channel 52, which is shown in each case with solid lines, and, preferably, a bypass flow channel 53. The arrangement of the main flow channels 52 of the individual pairs of Exchange membranes 32, 33 is such that the salt solution is passed through the electro-dialysis device 5 in an approximately meandering manner. In connection with the bypass flow channels 53, there is an approximately direct passage through the electro-dialysis device 5. However, the opening width of the bypass flow channels is adjustable.

The individual concentration chambers 35 are each connected to a rinsing line 54, while on the opposite side of the supply of the rinsing line a discharge line 55 is provided out of each concentration chamber 35, which opens into the line 8.

REPLACEMENT LEAF A pulsating delivery device, in particular a piston metering pump, which is not shown, is preferably inserted into the flushing line 54 as well as into the discharge line 55 or line 8.

The individual inlets and outlets are connected as follows:

The inlet 38 of the membrane unit 36 is connected to the separating container 9 on both the bottom and the cathode side, so that a highly concentrated salt solution freed from hardening salts can flow through both membrane units 36. The outlet 39 of the anode-side membrane unit is connected to the flushing line 54 via the piston metering pump (not shown). The outlet 51 is connected to the line 10 opening into the separating container 9. The flushing line 54 is connected to the outlet 26 for fresh water, while the inlet 43 of the anode chamber 40 and the inlet 50 of the cathode rear chamber 49 are connected to the outlet 25 of the fresh water line, which is indicated by arrow 7. It is not shown that in the rear cathode chamber 49 or the cathode chamber 47, a salt solution stream, preferably freed of hardness salts, originating from the separating container 9 can be added. The outlet 44 of the anode rear chamber 42 is in turn connected to the fresh water line indicated by arrow 7.

The method according to the invention now proceeds as follows:

The liquid or saline solution to be dialyzed enters the anode prechamber 37 via the inlet 24. The membrane unit 36 prevents direct contact of the incoming salt solution with the anode. The saline solution then runs through the main flow channels 52 in a meandering manner through the electro-dialysis device 5. A direct passage is made possible by the bypass flow channels 53 shown in dashed lines in connection (alternating) with the main flow channels 52. The intensity of this bypass flow can be controlled, which means that the salt concentration in the individual diluate chambers 34 can be adjusted in a certain way, which allows a reduction in the power requirement through more efficient process parameters. This results in better overall efficiency. When flowing through the electro-dialysis device 5, the salinity of the saline solution increases

REPLACEMENT LEAF steadily until finally fresh water is present in the anode antechamber 46, but at the latest at the outlet 25, which is then discharged.

Concentrated salt solution flows out of the separating container 9 through the double membrane of the two membrane units 36, the salt solution being freed of hardening salts. This saline solution enters via inlet 38 and outlet 39. In the illustrated embodiment, the liquid flow runs

Membrane units 36 in countercurrent to the liquid to be dialyzed. At the outlet 39 of the anode-side membrane unit 36 is connected - as already mentioned - the piston metering pump, not shown, which introduces the concentrated salt solution for flushing the concentration chambers 35 into the flushing line 54. It can be metered with a separate, not shown metering pump fresh water from the connection 26 or the line indicated by arrow 7. It should be pointed out that the metering of individual streams and the control of the overall process are automatic. For this purpose, measuring probes or the like are provided at various points in the electro-dialysis device 5 and in the settling tank 9, which record the individual operating parameters. The process is then controlled and regulated using a comparator between the target and actual values.

Due to the piston metering pump, there is a pulsating rinsing process for the concentration chambers 35. As a result, various effects are achieved simultaneously. Hydrogen ions diffuse from the area of the anode 27, in particular from the anode chamber 40 and there essentially through the cylinders 45, into the concentrated salt solution in the membrane unit 36. These H + ions are then fed directly into the concentration chambers 35 via the piston metering pump, whereby can set a desired pH there depending on the volume flow and process conditions. Since the concentrated salt solution used for rinsing is freed of hardness salts and a lowering of the pH value by the H + ions is possible, there is no fear of hardness salts precipitating. The prevention of the settling of hardness salts is further supported by the pulsating current, so that it is also possible to keep the pH greater than 3. The piston metering pump provided in line 8 also causes a highly concentrated salt solution to be drawn off when the (hard salt-containing) is drawn off

REPLACEMENT LEAF Sedimentation of hardness salts reliably prevented even at pH values greater than 3.

In addition, the individual pairs of exchange membranes 32, 33 are inflated and contracted again by the pulsating volume flow. During the inflation, the gap in the diluate chambers 34 is reduced. The applied direct current is clocked synchronously with it. It reaches its maximum current in the bloating phase. Due to the narrowing of the gap in the diluate chambers 34, the path that the salt ions have to travel in the electrical field until they pass the corresponding exchange membrane 32, 33 is minimized, which is reflected in a particularly low energy requirement for the desalination work. In the phase of widening the gap in the diluate chambers 34, the salt solution can easily flow in at a low electrical current. This clocked operation takes into account both the requirement for a narrow gap for minimizing the electrical energy requirement and the requirement for a large gap for good flow.

A partial stream is branched off from the outlet 25 of the fresh water and fed to the anode chamber 40 via the inlet 43. This water passes through the porous anode 27 and takes with it all of the chlorine gas formed on its way through this electrode. This prevents the exchange membranes 32, 33 of the membrane unit 36 from being attacked by the chlorine gas formed on the anode surface. The oxygen also formed there (in the nascendi stage) is recombined to O2 by the swirling of the volume flow inside the electrode. The same applies to the chlorine gas. The fresh water enriched with the oxygen and the chlorine gas flows after passing the anode 27 through the anode rear chamber 42 and is admixed again via the outlet 44 of the fresh water line designated by arrow 7. The fresh water tastes fresh due to the oxygen dissolved in it. The chlorine gas carried is used for additional disinfection of the drinking water. The cylinders 45 arranged in the region of the anode chamber 40 ensure that the H + ions are not carried away by the fresh water flowing in via the inlet 43, but rather can enter the membrane unit 36 essentially unaffected. On the cathode side, the membrane unit 36 - as already mentioned - is supplied with concentrated salt solution from the separating containers 9 via the inlet 38 and

REPLACEMENT LEAF via the outlet 39 and the line 10 fed back to the separating tank. As a result, some of the OH "ions formed in the cathode chamber 47 enter the separating container 9 in order to raise the pH there until the hardening salts are precipitated. In order to avoid electrolytic metal deposition on the cathode 28, it is passed through the inlet 50 flushed through the cathode rear chamber 49 with pure or fresh water from the outlet 25. The OH "ions formed which are caused by the electric field to migrate to the membrane unit 36 on the cathode side are discharged from the volume flow in the same direction Inlet 50 supports. At the same time, however, the volumetric flow from the inlet 50 which is opposite the direction of migration of the metal ions from the salts reliably prevents electrolytic attachment of the metal ions to the surface of the cathode 28. The volume flow from the inlet 50 then leaves the cathode chamber 47 via the outlet 51 and, since it is also enriched with OH ^_ ions, is fed to the separating container 9.

FIG. 3 shows a schematic illustration of a further installation according to the invention. It should be noted that the diluate chambers and the concentration chamber are sealed off from both the anode and the cathode by an additional membrane, so that the salt solution supplied does not come into direct contact with the electrodes made of sintered metal or metal balls, as previously described is coming. The input product, sea or salt water, is introduced into the anode prechamber 106 of the system at the nozzle 13. It flows past the membrane of the anode 105 made of sintered metal and passes through the overflow channel 116 into the first diluate or dilution chamber 106a. The desalination process takes place in the dilution chambers in that the anions and cathions diffuse through the membranes 117 and 118 forming the concentration chambers 107 into them by means of the applied electric field.

After passing through all the dilution chambers 106 a, the product stream passes through the last overflow channel 116 into the cathode pre-chamber 106 b, which is separated by a membrane from the cathode 105 a, which likewise consists of the metal mentioned. The OH 'ions formed here are now in the cathode rear chamber by the negative pressure generated by the pump 1 1 1

REPLACEMENT LEAF 108 sucked through the porous cathode 105 a. The negative pressure at the pressure measuring point 109 is determined and set by means of the control valve 110. In this way, an anion deficiency occurs in the concentration chambers 107, as a result of which a pH value <3 can be set in order to keep the hardness salts in solution. The concentrated brine or solution from the concentration chambers 107 flows via line 1 14 a into the separating tank, not shown. There is so much anion fed from line 1 12 via control valve 1 14 until the hardness salts have precipitated. This process is monitored by a pH value measuring point in the separating tank. In addition, the anode chamber has a feed line 19 in front of the anode 105 in order to control the liquid flow through the anode 105 in any desired direction. The same applies to the cathode 105 a, which has this supply line 120 in the cathode compartment. In addition, a gas extraction nozzle 121 is located behind and in front of the cathode in the cathode chamber, which is closed off by a membrane.

In the case of input solutions with a salt content of <1 g / l, concentrated salt solution is mixed in from the separation tank until an optimum concentration for the process is reached. The line 1 12, which leads the OH "ions, opens into the anode rear chamber 104 and is monitored there by the pressure measuring point 115. Depending on the position of the control valve 102 in the line 103 of the anode rear chamber 104 to the product outlet 101, a more or less portion of the OH ^" ion current is passed through the porous anode 105 into the anode prechamber 106 via the line 119 into the supply line 13. This can influence the formation of atomic chlorine gas on the anode surface and thus adjust the disinfectant amount of chlorine gas in the end product.

The porous anode 105 is up to the outlet opening for the line

103 drawn so that the OH ^_ ion-containing water stream must flow through the porous anode. This ensures that atomic oxygen and hydrogen ions are formed, which are required to adjust the pH of the starting product. The atomic oxygen makes the water fresh in taste. The input product flows past the surface of the anode 105 and comes out of the anode rear chamber when the countercurrent is switched off

104 in contact with it. Here hydrocarbons, which are emulsified as dirt (oil residues) in the water, become electrolytic by the oxygen formed there in the nascendi stage

REPLACEMENT LEAF oxidized ". Germs and viruses are also eliminated in this way.

In order to achieve complete oxidation of all organic constituents in the input product, the system can be operated in such a way that the input product is introduced into the anode rear chamber 104 and the control valve 102 remains closed. It is thereby achieved that the entire volume flow has to flow through the porous anode 105 and is thus intensively exposed to the atomic oxygen which is formed there. Via the line 1 19, the volume flow at the nozzle 1 13 is then introduced into the usual process. The OH'-ion-carrying product portion from the cathode rear chamber 108 is then mixed via line 1 12 with the input product in order to achieve a particularly intensive formation of atomic oxygen on the anode surface.

It should be pointed out that the objective features and method steps shown in the exemplary embodiment according to FIG. 3 - as far as technically possible - can also be implemented in the electro-dialysis device 5 shown in the embodiments in FIGS. 1 and 2.

REPLACEMENT LEAF Reference symbol list:

1 electro-dialysis system

2 filters

3 line

4 feed pump

5 Electro-dialysis facility

6 line

7 arrow

8 line

9 separation tanks

10 line

1 1 tank bottom

12 rotary valve

13 grants

14 electrolysis pools

15 anode

16 cathode

17 overflow

18 management

19 storage containers

20 line

21 branch line

22 salt pans

23 housing

24 inlet

25 outlet

26 connection

27 anode

28 cathode

29 front

30 front

31 power supply

32 anionic exchange membrane

33 cathionic exchange membrane

34 diluate chamber

35 concentration chamber

36 membrane unit

37 anode prechamber

38 inlet

39 outlet

40 anode chamber

REPLACEMENT LEAF back

Anode rear chamber

Inlet

Outlet

cylinder

Cathode antechamber

Cathode chamber

back

Cathode posterior chamber

Inlet

Outlet

Main flow channel

Bypass flow channel

Flush line

Exhaust line

Product outlet

Control valve

management

Anode rear chamber

Anode a cathode

Anode pre-chamber a Dilution chamber b Cathode pre-chamber

Concentration chamber

Cathode posterior chamber

Pressure measuring point

Control valve

pump

management

Connection a line

Pressure measuring point

Overflow channel

membrane

Supply

Gas sampling nozzle

REPLACEMENT LEAF

Claims

Claims:

1 . Electro-dialysis method, in particular for salt water desalination, in which a liquid to be dialyzed, in particular salt water, is fed to an electro-dialysis device of an electro-dialysis system and the liquid in the electro-dialysis device is between an anode and a Is exposed to the cathode applied DC voltage, characterized in that the anode (27) and / or the cathode (28) is flowed through by a separate liquid flow, in particular a partial flow of the process.

2. Electro-dialysis method according to claim 1, characterized in that the anode (27) and / or the cathode (28) with deionized water, in particular obtained in the electro-dialysis process, is flowed through.

3. Electro-dialysis method according to claim 1 or 2, characterized in that the anode (27) is flowed through from the front to the rear, that is from its front (29) to its rear (41) and that, preferably, by the Anode (27) passed liquid stream, which is obtained in the electro-dialysis process, added to dialysed liquid.

4. Electro-dialysis method according to one of the preceding claims, characterized in that the cathode (28) from behind to the front, that is from its back (48) to its front (30) is flowed through with deionized water, and that, preferably , the liquid stream flowing through the cathode (28) is fed to a separation container (9) in which the liquid concentrate of the electro-dialysis method, in particular concentrated saline solution, is collected.

5. Electro-dialysis method according to one of the preceding claims, characterized in that the liquid stream flowing through the cathode (28), in particular a hard salt-free liquid, in particular salt solution, can be added and that, preferably, this liquid is removed from the separating container 9.

6. Electro-dialysis method, in particular for salt water desalination, in which a liquid to be dialyzed,

REPLACEMENT LEAF in particular salt water, an electro-dialysis device of an electro-dialysis system is supplied and the liquid in the electro-dialysis device is exposed to a DC voltage applied between an anode and a cathode, in particular according to one of the preceding claims, characterized in that the anode (27) and / or the cathode (28) is separated from the liquid by a membrane unit (36) from the liquid to be dialyzed or dialyzed.

7. Electro-dialysis method according to one of the preceding claims, characterized in that the H + ions formed in the region of the anode (27) and / or the OH ^_ ions formed in the region of the cathode (28) for process control and / or to adjust the pH of the end product, especially fresh water.

8. Electro-dialysis method according to one of the preceding claims, characterized in that by the anode and / or cathode-side membrane unit (36), which has an anionic and a cathionic exchange membrane (32, 33), a concentrated, preferably hardness salts freed saline solution flows and that, preferably, the saline solution is removed from the separating tank.

9. Electro-dialysis method according to one of the preceding claims, characterized in that the salt solution guided through the anode-side membrane unit (36) is provided for rinsing the concentration chambers (35) located in the electro-dialysis device (5).

10. Electro-dialysis device according to one of the preceding claims, characterized in that the salt solution passed through the anode-side membrane unit (36) for rinsing is supplied to the concentration chambers (35) by means of a pulsating conveyor.

1 1. Electro-dialysis method according to one of the preceding claims, characterized in that the salt solution flowing through the cathode-side membrane unit (36) is fed to the separating container (9).

REPLACEMENT LEAF

12. Electro-dialysis method according to one of the preceding claims, characterized in that the concentrate withdrawn from the concentration chambers (35) is withdrawn via a pulsating conveyor, preferably a piston metering pump.

13. Electro-dialysis method according to one of the preceding claims, characterized in that the applied direct current is clocked synchronously with the pulsation of the conveying device such that it reaches its maximum current when the concentration chambers (35) are inflated.

14. Electro-dialysis method according to one of the preceding claims, characterized in that the anode (27) and / or the cathode (28) passing through liquid streams and / or through the membrane units (36) guided saline streams can be controlled depending on the process.

15. Electro-dialysis device of an electro-dialysis system with an outer housing, an inlet for a liquid to be dialyzed, in particular salt water, and an outlet for the dialyzed liquid, to be supplied with direct current electrodes, namely one preferably in the area of the inlet arranged anode and a cathode preferably arranged in the area of the outlet and a plurality of anion- and cathion-selective exchange membranes located between the inlet and the outlet, characterized in that the anode (27) and / or the cathode (28) are porous.

16. Electro-dialysis device according to one of the preceding claims, characterized in that the anode (27) is assigned an inlet (43) for supply and an outlet (44) for discharging fresh water in such a way that the fresh water in particular the anode flows from front to back, that is, from its front side (29) towards its rear side (41) and that, preferably, the inlet (43) communicates with the outlet (25) of the fresh water of the electro-dialysis device (5) while , in particular, the outlet (44) associated with the anode communicates with the line carrying the electro-dialysis product, in particular fresh water.

REPLACEMENT LEAF

17. Electro-dialysis device according to one of the preceding claims, characterized in that the cathode (28) is assigned an inlet (50) for supply and an outlet (51) for discharging fresh water in such a way that the fresh water is connected to the cathode (28 ) flows from the back to the front, that is to say from the rear (48) towards the front (30) and that, preferably, the inlet (50) communicates with the outlet (25) of the fresh water of the electro-dialysis device (5) , while the outlet (51) associated with the cathode (28) communicates with the separating container (9).

18. Electro-dialysis device according to one of the preceding claims, characterized in that the cathode is assigned an inlet (38) which communicates with the separating container (9) for salt solution freed from hardening salts.

19. Electro-dialysis device of an electro-dialysis system with an outer housing, an inlet for a liquid to be dialyzed, in particular salt water, and an outlet for the dialyzed liquid, to be supplied with direct current electrodes, namely one in the area of the inlet Anode arranged and a cathode preferably arranged in the region of the outlet and a plurality of anion- and cathion-selective exchange membranes located between the inlet and the outlet, in particular according to one of the preceding claims, characterized in that the anode (27) and / or the cathode (28 ) is separated from the liquid to be dialyzed or dialyzed by a membrane unit (36).

20. Electro-dialysis device according to one of the preceding claims, characterized in that the membrane unit (36) has an anion- and cathion-selective exchange double membrane (32, 33).

21. Electro-dialysis device according to one of the preceding claims, characterized in that the membrane unit (36) is assigned an inlet (38) which communicates with the separating container (9).

22. Electro-dialysis device according to one of the preceding claims, characterized in that the anode side

REPLACEMENT LEAF Membrane unit (36) has an outlet (43) which is connected to the concentration chambers (35) via a flushing line (54).

23. Electro-dialysis device according to one of the preceding claims, characterized in that at least one porous cylinder, preferably made of glued plastic granules, is provided between the anode-side membrane unit (36) and the anode (27).

24. Electro-dialysis device according to one of the preceding claims, characterized by a pulsating conveyor for flushing the concentration chambers (35) and / or a pulsating conveyor for withdrawing the concentrate from the concentration chambers (35).

25. Electro-dialysis device according to one of the preceding claims, characterized in that the cathode-side membrane unit (36) is assigned an outlet (39) which communicates with the separating container (9).

26. Electro-dialysis system with an electro-dialysis device according to one of the preceding claims.

27. Electrode, in particular anode (27) and cathode (28) for an electro-dialysis device (5) of an electro-dialysis system (1), characterized in that the electrode is porous.

28. Electrode according to one of the preceding claims, characterized in that the electrode consists of porous metal.

29. Electrode according to one of the preceding claims, characterized in that the electrode consists of sintered metal.

30. Electrode according to one of the preceding claims, characterized in that the electrode preferably has spherical metal bodies which consist in particular of titanium and are coated with a metal adapted to the respective process conditions.

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31 Electrode according to one of the preceding claims, characterized in that metal bodies of different diameters are provided in the electrode.

32. Electrode according to one of the preceding claims, characterized in that the diameter of the metal body is between 0.2 and 2 mm, in particular 0.5 to 1, 3 mm.

33. A method for producing an electrode for an electro-dialysis device (5) of an electro-dialysis system (1) and preferably according to one of the preceding claims, characterized in that preferably spherical metal bodies, which consist in particular of titanium and with a are coated metal adapted to the respective process conditions, pressed together and subjected to an electric current of such a high current density that adjacent metal bodies connect to each other.

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