WO1998017587A1

WO1998017587A1 - Method and device for the electrophysical treatment of water

Info

Publication number: WO1998017587A1
Application number: PCT/AT1997/000222
Authority: WO
Inventors: Klaus Leiter; Gerhard Walder; Klaus Neidhardt
Original assignee: Maitron Chemiefreie Wasserbehandlung Gmbh
Priority date: 1996-10-17
Filing date: 1997-10-17
Publication date: 1998-04-30
Also published as: EP0951448A1

Abstract

The invention concerns a method and device for removing carbonates from drinking water or water for domestic use, wherein the water is poured into a container in which are disposed a cathode and an anode to which an electrical direct voltage is applied, carbonate being precipitated and water from which carbonates have been removed then being discharged from the container as drinking water or water for domestic use. The invention is characterized in that the container houses a diaphragm which separates a chamber containing the cathode from a chamber containing the anode, the water from which carbonates are to be removed being poured into the cathode chamber and removed therefrom. A voltage of more than 1.22 volts is applied between the cathode and the anode such that water molecules are decomposed electrolytically at the cathode to form OH- ions, there being formed in the cathode chamber a basic medium in which carbonate, in particular in the form of calcium carbonate (chalk) and/or magnesium carbonate, is precipitated.

Description

Method and device for electrophysical water treatment

The invention relates to a method and a device for electrolytic water treatment. More specifically, the invention relates to a method for decarbonizing industrial and drinking water, in which the water is filled into a container in which a cathode and an anode are arranged. to which an electrical voltage is applied, carbonate precipitating, whereupon decarbonized water is taken from the container as process or drinking water. Furthermore, the invention relates to a device for performing this method

Before further describing the method and the setup, some basic terms of water treatment are given

Decarbonization in water treatment refers to the reduction of carbonate hardness. The carbonate hardness corresponds to the proportion of alkaline earth ions, in particular Ca ²⁺ and Mg ²⁺ ions, which are present in the water as hydrogen carbonates and can therefore be precipitated as carbonates (for example, lime)

Basically, two process principles for decarbonization are known

■ Decarbonization with cation exchange resins in the H ⁺ form

Decarbonization due to the precipitation of carbonates, especially lime

During the decarbonization with cation exchange resins in the I form, alkaline earth ions are bound to the resin in exchange for H ⁺ ions, the released H ⁺ ions react with the HC0 ₃ ions present in the water to form water and C0 ₂ , the C0 ₂ can be blown out of the water

In order to understand the decarbonization caused by the precipitation of carbonates, the lime precipitation is particularly described here

The basics of lime precipitation follow from the knowledge of the lime-carbonic acid equilibrium, the formation of stone nuclei and the lime growth Water can hold a certain amount of calcium and carbonate ions in solution at a given temperature. The solution equilibrium, the saturation, is defined via the solubility product [CA ²⁺ ] _e . [C0 ₃ ² -] _e = K _SO ι (the square brackets stand for the concentration of the respective ions, the index e for the equilibrium concentration); K _so is a constant at a given temperature (and ion activity). If the product of the ion concentration [CA ²⁺ ]. [C0 ₃ ² -] in a water is smaller than K _sol . then it is undersaturated or descaling water; if the product is [CA ²⁺ ]. [C0 ₃ ² -] larger than K _S0 |, then it is a lime-separating or supersaturated water.

It is common to determine the saturation state of a water with a logarithmic size, the so-called saturation index Sl. to describe:

If the water is undersaturated, the saturation index is less than 0; in the case of saturation Sl = 0 and in the case of oversaturation Sl> 0.

Basically, a supersaturated solution strives to separate the excess. However, this deposition is generally not spontaneous. Water has a relatively high tolerance regarding quay separation: In the supersaturation range between SI = 0 and Sl = 1, the water is metastable; Lime precipitation only takes place if suitable surfaces or germs are present (area of heterogeneous nucleation).

A method for decarbonizing metastable water is therefore to add suitable crystallization centers (lime or marble powder, certain aluminum silicates, etc.) to the water - seeding technique.

The so-called homogeneous nucleation is only likely if the supersaturation SI> 1 is high - crystal nuclei can form spontaneously in the solution and the excess lime can precipitate on these nuclei. In order to trigger homogeneous nucleation at a given temperature, either the calcium ion concentration and / or the carbonate ion concentration must be greatly increased.

The easiest way to increase the carbonate ion concentration is to raise the pH: To do this, you have to know that the total carbonate dissolved in water is present in 3 different species that are in equilibrium with each other: C0 ₂ , HC0 ₃ ^" and C0 ₃ ^{2 '} The concentration ratios of the species to one another are determined by the pH value. At pH values below 6.3 the main proportion (<50%) of the total carbonate is in the form of C0 ₂ ; from a pH value of 10.3 the main proportion is (> 50% ) in the form of C0 ₃ ^" ions; the middle pH range is determined by HC0 ₃ ^" ions. As a rule of thumb for increasing the C0 ₃ ^2" concentration: If the pH value is increased by one unit in the range <ph <10, the C0 _{3 increases} ^{2 '} concentration by one unit, the C0 ₃ ^2' concentration increases by an order of magnitude; the saturation index increases accordingly by 1

Common drinking and process water have pH values between 6 5 and 8.5. In terms of process engineering, raising the pH to values between 9 5 and 10.3 is favorable for triggering homogeneous crystal nucleation.

On a large industrial scale, decarbonization is achieved by raising the pH value for drinking and industrial water by adding lime milk (Ca (OH) ₂ ) and / or sodium hydroxide solution (NaOH) and / or soda (Na ₂ C0 ₃ ) to the water.

The disadvantage of these processes is that large amounts of chemical additives have to be added to the water. The addition of lime milk brings additional Ca ²⁺ ions into the water, which are not always completely precipitated in the subsequent quay failure process. The limit values for sodium ions limit the use of sodium hydroxide and soda in drinking water.

A further problem is the pH value of the water, which is too high after the lime precipitation (the pH value is only slightly reduced due to the carbon dioxide released in the event of lime precipitation). Consequently, further measures have to be taken, such as Add acid or C0 ₂ to reduce the pH value to between 7 and 8 5 after the lime precipitation

Electrochemistry offers alternative methods for producing the alkali (OH ^' ions) required for raising the pH. Such a method is known, for example, from EP 0 548 242, where the OH ions on a cathode are obtained directly from the water Dissolved oxygen formed In this process, however, it is important to carry out the electrode reactions below the water decomposition voltage of 1 23 volts, since otherwise H ⁺ ions are formed on the anode, which would lower the pH again. This results in the success of the process in the water existing oxygen and its electrochemical conversion at the cathode are limited

In this invention, the necessary OH ions are now formed by electrolytic decomposition of water on the cathode. A diaphragm prevents the OH ions from recombining with H ⁺ ions formed on the anode. Preferred methods and devices are also used specified how the H ⁺ ions formed can be used to lower the pH of the decarbonized water. This enables a decarbonization process to be carried out which works without chemical additives and has a high decarbonization efficiency

Further advantages and details of the invention are explained in more detail with reference to the following description of the figures

Figure 1 shows a schematic representation of an electrolytic cell. Figure 2 shows a schematic representation of a first exemplary embodiment of a device according to the invention for performing the method according to the invention

Figure 3 shows schematically the alternative structure of a diaphragm Figure 4 shows schematically a further alternative structure of the diaphragm with a water withdrawal along the diaphragm

Figure 4a shows schematically a structure of the diaphragm with a water withdrawal across the diaphragm

FIG. 5 shows an exemplary embodiment suitable for continuous operation FIG. 6 shows details of a further exemplary embodiment in a schematic representation

Since the other explanations constantly refer to terms of electrolysis, some basic terms of electrolysis are repeated first

An electrolytic cell (see FIG. 1) is understood to mean a system in which two electrodes AK are conductively connected via an electrolyte (here water). By applying an external voltage source 1 to the electrodes, electrochemical reactions at the electrodes are made possible or a Current flow through the electrolyte causes

If an electrical voltage of at least 1 23 volts is applied to electrodes A and K (theoretical minimum value for water decomposition), the following reactions occur between the electrodes and the water

Cathode 2 H ₂ 0 + 2 e → H ₂ + 2 OH (i) resp

2 H ⁺ +2 e → H ₂ anode 2 H ₂ 0 - 4e → 0 ₂ + 4 H ⁺ (u) resp

4 OH - 4e → 2 H ₂ 0 + 02

D h is generated at the cathode in addition to hydrogen OH or H ^{+ is} reduced to H ₂ , at the anode in addition to oxygen H + is generated or OH is oxidized to 0 ₂

In order to obtain acid (H ^* ions) or lye (OH ions), one must prevent the OH and H ⁺ ions generated separately on the respective electrodes from migrating to the opposite electrode or recombining to H ₂ 0 in the water volume

This can be done using the following transport processes

■ Hike due to the existing electric field

■ Migration due to differences in concentration (diffusion) ■ Hike due to convection or prevailing currents

Since the concentration of H ⁺ and OH is initially very small (compared to the concentration of the other ions dissolved in the water), the contribution to the concentration compensation is negligible due to the existing electric field and due to the diffusion. Convective transport is not negligible

To prevent or reduce convective transport, in the simplest case a convection bar is sufficient - a diaphragm 2 Two spaces are created by inserting the diaphragm between the anode and cathode - a cathode space 4 and an anode space 3

On the other hand, the diaphragm must prevent the convective transport of the ions but must be such that a current flow between the anode and cathode in the electrolyte is possible when the voltage is applied. If an OH ion is generated on the cathode, for reasons of charge neutrality, either from the Anode space can be used to transport a cation as a counter ion into the cathode space through the diaphragm or an anion from the cathode space into the anode space. By generating an H ⁺ ion, the charge balance in the anode space can be achieved D h but also that for an effective lye - or acid production other cations than H ⁺ or other anions other than OH must be present in the electrolyte (conductive salt)

The molantate of the conductive salt ultimately determines the achievable alkali or acid concentration. As long as the concentration of the OH - and H ⁺ ions are low in relation to the ions of the conductive salt, the ions of the conductive salt dominate the current transport via the diaphragm. The concentrations of OH ions and H ⁺ ions in the order of magnitude of the ion concentrations of the conductive salt, they begin to dominate the current transport through the diaphragm. The concentration of OH in the cathode space or H ⁺ ions in the anode space can no longer be increased if this limit is reached, since recombination processes cancel the educational processes If the natural water nutrients are to be used as the conductive salt in drinking water applications, their maximum concentrations limit the maximum alkali or acid concentration that can be produced with electrolysis. Drinking water typically has ionic contents less than 10 ² mol / I, so that with the same large volumes of anode , in the anode compartment, at best, achieve a Kathodenrau and H ⁺ -Konzentratιon corresponding to a pH-value of 2, in the cathode compartment an OH ^~ tion concentration corresponding to a pH value of 12

2 shows the diagram of an electrolytic cell for the decarbonization of water according to the invention, anode A, cathode K and diaphragm 2 having a cylindrical shape and being located in a closed container 5

Only materials whose reaction products are harmless to health in terms of type and concentration in water in the drinking water area may be used as anodes. Graphite, noble metal, titanium or magnetite anodes coated with noble metal or metal oxides are suitable. Expanded metal or fabric is particularly suitable as cathode material Made of stainless steel Expanded metal or fabric is particularly well suited because the OH ions formed on the cathode can be freely distributed in the cathode compartment by convection (and stirring by means of a stirrer 6)

The diaphragm 2 can be made of clay, ceramic or plastic, but also membranes, in particular ion-selective membranes, can be used. For special water treatment modes (suppression of chlorine gas formation, lowering the pH value), multi-layer diaphragms are suitable, for example a diaphragm consisting of a bed of fine-grain cation exchange resin between membranes

In discontinuous operation, no water can be removed from the container 5 during the electrolysis and sedimentation of the lime (calcium carbonate). If it is also desired to have a continuous water supply with decarbonized water, it is advisable to set up a double system For low-chlorine waters ([Cl ^" ] <5 mg / 1) you can proceed as follows

The raw water to be decarbonized is let in via the inlet 7 and the container 5 is filled up. The valve 8 in the inlet 7 is closed and the direct voltage over 1 23 volts (for example 24 V) is applied to the electrodes A, K. At the anode A, the water is broken down into H ⁺ and 0 ₂ , at the cathode K OH ^" and H _{2 are} formed. The OH ^'formed should be distributed as evenly as possible in the cathode space, a stirrer 6 built into the container 5 supports the homogenization Oxygen formed in the anode compartment 3 must be removed via an automatic venting valve 9. The hydrogen formed in the cathode compartment 4 must also be removed via an automatic venting vent 9a

The pH increase (OH ions in the cathode compartment 4) causes lime to precipitate; iron or manganese ions present in larger concentrations (more than 10 mg / l) are also precipitated in the form of the corresponding carbonates. The precipitated lime accumulates as lime sludge sloping floor 10 of the container The lime sludge must be removed regularly by draining (by opening the drain valve 11 in line 12 and flushing out the container) - otherwise anaerobic bacteria can multiply in the lime sludge, which for example can reduce sulfates in the water to H ₂ S - Even the smallest amounts of H ₂ S can be smelled

The duration of the electrolysis and the length of time necessary for the sedimentation of the lime depend on the water composition, the electrolysis current (determines the OH production) and the water volume in the cathode compartment and can be set once for the respective water Duration of the electrolysis and the electrolysis voltage depending on suitable process-determining parameters. For this purpose, for example, a control device 13 can be provided, which receives the electrolysis voltage via a voltmeter 14 and the electrolysis current via an ammeter 15 as input variables. Alternatively or additionally, a sensor 16 can be provided be, which detects the pH value, the turbidity and / or the conductivity in the cathode compartment 4 and feeds it to the control device 13 the line 17 an output signal are generated, which the voltage of the

Voltage source 1 changed or switched on and off

The water is removed from the container 5 by opening the inlet valve 8. If the inlet is close to the bottom of the container and the outlet on the cover, water is treated by stratification of the pipe water until layer% is removed to ensure that only treated, decarbonised water

If you want to lower the pH value of the water taken off via the removal line 18, it is advisable to add acidic water from the anode compartment 3 via a mixing valve 19. For the application, the lowest possible lime separation potential is important and corrosion - Problems with low pH values for the pipe or container material used in the subsequent installation are not to be expected, so water is recommended to be drawn directly from the anode compartment - in this case, a diaphragm that is either coarse-pored (low flow resistance) or has an open connection between the cathode and anode space at the bottom (opening or better a line with a check valve 21

Before starting a new electrolysis, it is advisable to flush the anode compartment via the anode compartment drain line 20

In the case of water containing chlorine [Cl]> 5 mg / l, it must be taken into account that chlorine forms at the anode A as a competitive reaction to water decomposition. Long-term electrolysis and higher chloride contents can lead to undesired chlorine gas concentrations in the anode compartment 3

The following options are available to avoid undesired chlorine gas concentrations

a) Repeated rinsing of the anode compartment 3 during the electrolytic treatment of the water (by opening the anode compartment drain line valve 20). The frequency and duration of the rinsing depend on chlorine content, electrolysis current and anode compartment volume

Repeated rinsing of the anode compartment 3 has the further advantage that the anions present in the water of the anode compartment, which have migrated as counterions from the cathode compartment 4 into the anode compartment, are also washed out

In this way, the concentration of interfering anions in the water (e.g. nitrates) can be significantly reduced

b) In addition, the use of a gas-impermeable, hydrophobic membrane as the diaphragm 2 in order to suppress the diffusion of chlorine gas into the cathode space 4

c) The use of a cation exchange membrane as the diaphragm 2, which prevents the migration of anions (and thus chlondions) from the cathode compartment 4 into the anode compartment 3. Only the chlorine ions that entered the anode compartment 3 during the filling of the reactor can then be oxidized to chlorine gas A single rinse of the anode compartment 3 at the end of the electrolysis is sufficient to remove the chlorine gas formed

d) By a combination of measures a) to c)

At the same time, the above measures for suppressing undesired chlorine gas concentrations prevent a sufficient concentration of H ⁺ ions being available in the anode compartment in order to reduce the pH of the decarbonized water by admixing it

This disadvantage can be countered by integrating a device in the arrangement which stores the H ⁺ ions generated during the electrolysis and which ensures that these are not lost again during a rinsing. For example, weakly acidic cation exchange resins or cation exchange nerves act as such a memory

In particular, it is recommended to integrate the resins or the fleece in the diaphragm In the simplest case, the diaphragm 2 is an approximately 1 to 3 cm thick fill of fine-grained weakly acidic cation exchange resins 22, for example realized by filling the resins in filter socks 23 Cation exchange fibers or the nonwoven must first be converted at least partially from the so-called H-form into a Ca-form (also Mg-form is suitable), ie be loaded with calcium ions. Only then does this resin nonwoven have the property of migrating to the other side Anode-formed H ⁺ ions effectively suppress in the cathode space The resin / fleece binds the H ⁺ ions in exchange for calcium ions (a resin fleece in the H ^* form cannot bind H ⁺ ions, consequently the H ⁺ - migrate ions unhindered by the resin bed) In this way, the migration of the H ⁺ ions is effectively prevented, on the other hand on the one hand, the ion exchange resin or fleece is partially regenerated by the electrolysis, ie loaded with H ⁺ ions (typically less than 5% of the theoretical capacity during a treatment phase). This H ⁺ supply of the resins can be used for lowering the pH value

During the electrolysis, the anode compartment 3 is rinsed several times in order to prevent the formation of undesired chlorine gas concentrations. The water is withdrawn directly from the anode compartment 3, the water from the cathode compartment 4 being carried out through the resin bed 22 against H ⁺ ions on the resin abgetauscht, the thus becoming free-H ⁺ ions lower the pH value of the water

With the thickness of the rubble, the volume of the resin, the coordination of the water volume in the cathode compartment and the electrolysis capacity, the pH value of the water removed can be adjusted within a wide range

An improved construction of a diaphragm 2, which is suitable for use in chlorine-containing water and at the same time allows a pH reduction, looks as follows (FIG. 4) First of all, it is mentioned that similar to FIG. 3, where the container 5 and the lines are not shown, this container 5 is also not shown in FIG. 4. The naturally present cathode is also not shown

The resin bed 22 'is delimited on the left and right by membranes 23', the resin bed is thus separated from both the anode space 3 and the cathode space 4. The anode-side membrane 23 'is preferably a cation exchange membrane in order to suppress the migration of chlorine ions into the anode space H ⁺ -Ions that are formed in the anode compartment can pass through the anode-side membrane and are bound to the resin 22 ′ via ion exchange. The water is removed via a separate line 18, so that the water removed from the cathode compartment 4 runs through the resin bed. The bottom 24 is perforated Anode compartment can be spooled via its own line 20

4a shows a variation of the previously described diaphragm. With the height of the resin fill, the hydraulic resistance of the fill increases. Since the membrane must in principle be permeable to water, the flow resistance of the membrane may be lower than that of the fill with higher fillings A substantial part of the water flowing out of the cathode space in the direction of the water extraction line 18 then no longer reaches the resin bed via the perforation on the bottom 24, but through the membrane on the cathode side. This can cause the membrane to be laid and the resin bed to flow undefined come

In order to prevent this, it is advisable to conduct electricity across the resin bed. A water collection channel 18a is required between the resin bed and the anode-side membrane. The water collection channel ends in the extraction line 18 the pore size should be larger than 80 μm) As an alternative to the resin bed, a cation exchanger can also be used with this diaphragm structure The diaphragms described last are also suitable for use in low-chloride waters.

When continuously operating an electrolytic decarbonization system, the flow rate is limited by the maximum possible electrolysis current:

With an electrolysis current of 10 amperes, for example, approximately 0.4 mol of OH ^' ions can be generated at the cathode K per hour. If one takes into account that about 1 mmol / l OH ^{'has to be added to} the water for the decarbonization of a calcareous water. it then follows that you can process around 400 liters per hour with this electrolysis output.

It should also be noted that lime precipitation does not occur instantaneously, i.e. you have to plan a certain process time (typically 30 to 60 minutes).

In the simplest case, a decarbonization system is combined as described in FIG. 2 with a downstream filter 25, which accelerates the lime precipitation from the solution (through existing lime powder or special pellets) and filters the precipitated lime from the solution. The structure, operation and maintenance of such a filter can be found, for example, in DIN 19605.

The process duration of 30 to 60 minutes with a treatment rate of 400 liters per hour defines a volume of decarbonization system and filter of 200 to 400 liters.

In general, water is not continuously drawn from a household; if one can refer to the usual withdrawal quantities and withdrawal frequencies, much smaller systems can also be dimensioned (for a single-family house with 4 people approx. 50 liters); if necessary, the use of a filter 25 can be dispensed with.

A simultaneous lowering of the pH value is possible with chloride-free water by simply adding water from the anode compartment 3. With lower chloride Concentrations you have to consider whether the amount of chlorine gas generated per unit of time and added to the flowing water can exceed the legal limit values.

If you want to completely exclude chlorine gas pollution, you have to seal off the anode compartment 3 from the cathode compartment 4 with a membrane and specifically spool through it.

To lower the pH value, a diaphragm 2 from a chess acidic cation exchange resin bed can be used again (see FIG. 4), through which filtered water is passed during removal. If the volume of the cathode chamber 4 and the average flow or withdrawal quantity are matched to one another, then there is no need for filtration.

A diaphragm made of cation exchange resin, which is delimited on both sides by a cation exchange membrane, is particularly suitable for this mode of operation.

The following process principles can be combined in such a diaphragm (cf. FIG. 6), the anode space drain line 20 'being arranged coaxially as a tube in the tube 26. (The water flows out of the cathode chamber 4 through the resin 22 'and the pipe 26).

i) Lime precipitation and thus decarbonization in the cathode compartment 4

By raising the pH value (OH ^~~ ion generation at the cathode K) in the cathode compartment 4, homogeneous nucleation is induced and lime precipitates.

li) At the same time ion exchange. Regeneration of the resins and transport of Ca ²⁺ ions into the cathode compartment.

Continuous operation in the resin bed results in a balance between the following processes:

Binding of cations, in particular Ca ²⁺ ions, in exchange for H ⁺ ions to the resin 22 '. ■ Regeneration of the resin 22 'by H ⁺ ions formed in the anode compartment 3 with simultaneous release of Ca ²⁺ ions.

Migration of the Ca ²⁺ ions from the resin bed 22 ′ through the outer cation exchange membrane 23 ′ into the cathode space 4

In this way, the efficiency of the decarbonization can be increased, since some of the non-precipitated Ca ²⁺ ions are continuously returned to the cathode compartment. The efficiency and the pH that can be set can be determined by means of the height of the rubble and the thickness of the resin bed and by means of the electrolysis current Taxes

The described invention and device is also suitable for producing seed crystals using the seeding technique. Lime crystals smaller than 5 μm are particularly suitable for seeding technology, since the setting speed of these crystals is slow enough to carry these crystals from the point of origin to the entire installation system to be protected. Wherever the water is oversaturated, the growth of these crystals is particularly high in hot water generators Competitive process for quay separation on the wall

For the production of seed crystals, it is expedient to pass a partial stream of the water to be treated into an electrolytic decarbonization line according to the invention. Appropriate process control (high pH in the cathode compartment and a short average residence time of the water in the cathode compartment) makes it possible to obtain lime crystals of the desired type Generate great. The content of the cathode compartment is added directly to the water flow to be treated. The time of removal from the cathode compartment is controlled, for example, by a device for particle size measurement, in particular a turbidity sensor

The invention is of course not limited to the exemplary embodiments shown. For example, multiple arrangements and / or cathodes can also be present. It is also possible to design part of the container wall as an anode or cathode

Claims

claims

Process for decarbonizing industrial or drinking water, in which the water is filled into a container in which a cathode and an anode are arranged, to which an electrical direct voltage is applied, carbonate precipitating, whereupon de-arbonized water is used as domestic or drinking water is removed from the container, characterized in that a diaphragm is arranged in the container which separates a cathode space containing the cathode from an anode space containing the anode, the water to be decarbonized being filled into and removed from the cathode space, and between A voltage of over 1 22 volts is applied to the cathode and anode, so that water molecules on the cathode decompose electrolytically to form OH ions, a basic environment being created in the cathode space in which carbonate, in particular in the form of calcium carbonate (lime) and / or magnesium carbonate fails

A method according to claim 1, characterized in that the pH of the decarbonized water originating from the cathode compartment - preferably to a value below 9 - is lowered before it is fed to a removal line

A method according to claim 2, characterized in that the basic water removed from the cathode compartment acidic water from the

Anode space is mixed

A method according to claim 2, characterized in that the pH is reduced by lime precipitation by observing a predetermined sedimentation time, during which no water is drawn off

Method according to one of claims 2 to 4, characterized in that the decarbonized water originating from the cathode space is passed through a cation exchange material, the cation exchange material being preferably a weakly acidic cation exchange resin in the Ca

Form or Mg form is used

Method according to one of claims 1 to 5, characterized in that the water originating from the cathode compartment is passed through a filter which accelerates the lime precipitation and retains the precipitated lime, for example by means of lime powder or pellets

Method according to one of claims 1 to 6, characterized in that in order to avoid undesired chlorine gas concentrations, one or more of the following measures are taken a) pulsed or continuous rinsing of the anode space during the electrolysis b) use of a gas-impermeable membrane or a fleece as a diaphragm or part of the same , which have a gastight closure of the

Create the arrangement space opposite the cathode space or removal space c) Use a cation exchange membrane or a cation exchange tube as a diaphragm or part of the same

Method according to one of claims 1 to 7, characterized in that the lime crystals formed in the cathode compartment are at least partially washed out into the installation system adjoining the container

A method according to claim 8, characterized in that by controlling the pH during the electrolysis, electrolysis time and sedimentation time, lime lime nuclei are produced less than 5 μm

A method according to claim 8 or 9, characterized in that the time of removal from the cathode compartment in dependence on the particle size of the Kaikkπstalle formed or in dependence on the turbidity or others

Parameters - in particular the conductivity and / or the pH value - of the

Water is set in the cathode compartment Method according to one of claims 1 to 10, characterized by whirling up the sedimented crystal nuclei from the bottom of the container into the cathode compartment, for example by stirring, ultrasound sonication or circulation

Process according to claims 1-11, characterized in that the diaphragm acts as an efficient H ⁺ blocker during the electrolysis by partially loading it with H ⁺ ions, the diaphragm being used as a source of H ⁺ ions at pH during water withdrawal -Value reduction serves

Device for decarbonizing industrial or drinking water, in particular for carrying out a method according to one of claims 1 to 12, with a container in which a cathode and an anode are arranged, to which a direct voltage is applied, characterized in that in

A diaphragm is arranged which separates a cathode compartment containing the cathode from an anode compartment containing the anode, and that a device for applying a voltage of over 1.22 volts is provided between the cathode and the anode

Device according to claim 13, characterized in that the feed line merges directly into the cathode compartment, preferably in the lower region thereof

Device according to claim 13 or 14, characterized in that the extraction line is connected to the cathode compartment

Device according to claim 15, characterized in that the extraction line extends directly from the cathode compartment - preferably from its upper region

Device according to claim 15, characterized in that a cation exchanger is arranged between the extraction line and the cathode space, through which water flows out of the cathode space

18. Device according to claim 17, characterized in that the cation exchanger is arranged between the anode and cathode and a free removal space is formed between the cation exchanger and the anode, the removal space being preferably delimited from the arrangement space by a gas-tight membrane.

19 Device according to claim 17 or 18, characterized in that the cation exchanger is a weakly acidic cation exchange resin or cation exchange in the Ca form or Mg form.

20 Device according to one of claims 13 to 19, characterized in that the diaphragm is formed by a cation exchanger

21 Device according to one of claims 17 to 20, characterized in that the cation exchanger towards the anode space is at least partially covered by a cation exchange membrane, wherein preferably a water collection channel (18a) is arranged between the cation exchanger and the cation exchange membrane

22 Device according to one of claims 17 to 21, characterized in that the cation exchanger to the cathode space is covered by a cation exchange membrane.

23. Device according to one of claims 13 to 22, characterized by a device for lowering the pH of the water coming from the cathode compartment

24 Device according to claim 23, characterized in that the device for lowering the pH comprises a mixing device in which from the

Water originating in the anode compartment can be mixed with water originating in the cathode compartment

25. Device according to claim 23 and one of claims 19 to 22, characterized in that the device for lowering the pH comprises the cation exchanger through which water can be removed from the cathode compartment.

26. Device according to one of claims 13 to 25, characterized in that the diaphragm preferably cylindrical surrounds the anode space and the cathode space is arranged outside the diaphragm.

27 Device according to one of claims 13 to 26, characterized in that the anode compartment communicates with the cathode compartment via a check valve opening towards the anode compartment.

28. Device according to one of claims 13 to 27, characterized by a stirrer in the cathode compartment

29. Device according to one of claims 13 to 28, characterized by a filter in a line leading from the cathode compartment.

30 Device according to one of claims 13 to 29, characterized by a device for detecting the amount of water removed from the container or supplied to the container.

31 Device according to one of claims 13 to 30, characterized by a device for detecting the pH of the turbidity and / or the conductivity in the cathode compartment

32. Device according to one of claims 13 to 31, characterized by a device for detecting the electrolysis current flowing over the anode and cathode

33 Device according to one of claims 30 to 32, characterized by a device for regulating the voltage applied to the anode and cathode and / or the duration of the application of this voltage depending on the detected amount of water withdrawn or supplied, the detected pH value in the cathode compartment, the detected conductivity, the detected turbidity and / or the electrolysis current.