DE102015118352A1 - Electrolyzer for electrochemical water treatment - Google Patents

Abstract

The invention relates to a cell element for a bipolar electrolyzer for electrochemical water treatment, comprising an anode half-shell (2) with an anode (10), a cathode half-shell (1) with a cathode (9) and between the anode (10) and the cathode (9 The anode half-shell (2) and the cathode half-shell (1) each have an outer wall with a flange region (3) for connecting the anode half-shell (2) to the cathode half-shell (10), wherein the anode half shell (2) and the cathode half-shell (1) each have a plurality of inlet openings (7a, 7b) and a plurality of drainage openings (8a, 8b), wherein the total area of the inlet openings (7a, 7b) is smaller than the total area of the drainage openings (81, 8b), and the cathode half-shell (1) has a gas feed device (11), via which a gas in the cathode half-shell, in particular one between the ion exchange membrane (13) and the cathode (9) arranged cathode space (14) can be introduced. Furthermore, the invention relates to a bipolar electrolyzer with a plurality of cell elements connected in series.

Description

The invention relates to a cell element for a bipolar electrolyzer for electrochemical water treatment, comprising an anode half-shell with an anode, a cathode half-shell with a cathode and arranged between the anode and the cathode ion exchange membrane, the anode half-shell and the cathode half-shell each having an outer wall with a flange for connecting the anode half-shell with the cathode half-shell. Furthermore, the invention relates to a bipolar electrolyzer with a plurality of cell elements connected in series.

The formation of sulfuric acid waters with high levels of heavy metal salts can be observed more frequently in active and inactive mining areas, where natural weathering has led to an increase in water acidification for many years. In particular, for the emerging by flooding opencast mines and the groundwater occurring in these areas, this is an ever greater problem. Sulfate ions are neither chemically inert nor sanitary or hygienic harmless, so that a high heavy metal and Sulfateeintrag in the ground and surface waters considerable negative impact on aquatic ecology and the technical usability of the water as drinking or service water means. High loads of heavy metals and sulphates in the groundwaters, for example, are inadmissible for the drinking water use, at the same time sulphate-rich, sulphurous waters also have a strong corrosive effect on steel and concrete.

The remediation of surface waters contaminated with sulphate, such as opencast mines, is currently being carried out mainly by flooding with possibly conditioned extraneous water due to the large quantities of water. However, this method is, among other things, severely limited by the available water supply, the cost of the transfer and the base capacity to be buffered. Remediation of the residual hole waters by liming is in most cases uneconomical because of the high stoichiometric excess of basic substances.

There are also known microbiological processes in which sulphate-rich waters can be biochemically reduced by microbes in the absence of air. The resulting sulfides are reoxidized with atmospheric oxygen to sulfuric acid. This process, whose use for the remediation of sulfuric acid waters has been studied for some time with rather little success, can naturally be observed regularly in sewage systems and in stagnant waters. Every year, it causes billion-dollar damage to the infrastructure throughout Germany due to sulphide / sulfuric acid corrosion.

In addition, electrochemical processes are known, according to which the water treatment can be carried out without admixture of additives. For example, in the DE19624023 B9 a process for the treatment of acidic iron-containing opencast mining wastewater described, the treatment effect is not achieved in contrast to the usual neutralization by the addition of liquor to water with high pH, but by separation of protons due to their electrochemical deposition in the cathodic partial reaction of the electrolysis process.

The low-pH hydrogen ions at the cathode are reduced to hydrogen. This hydrogen thus formed is discharged with the treated water from the cell and released into the environment. The reduction of the hydrogen ions is associated with an increase in the pH. This in turn causes the hydrolysis and precipitation of the hydrolyzable cations (eg Fe, Al, Mn), which are discharged with the neutralized water as a suspension from the cells: 4H ⁺ + 4e ^- → 2H ₂ (1) 4H ₂ O + 4e ^- → 2H ₂ + 4OH ^- (2) Me ^{n +} + nOH ^- → Me (OH) _n Me = Fe, Al, Mn etc. (3)

In the same way, in principle, the simultaneously occurring electrochemical reduction of oxygen dissolved in the water neutralizes hydroxide ions. 2H ₂ O + O ₂ + 4e ^- → 4OH ^- (4)

The reaction ( 4 ) contributes only slightly to cathodic water treatment. Through the use of an ion exchange membrane between the anode and cathode compartments of the electrolysis cell, it is additionally achieved that, in order to increase the pH, and the associated hydrolysis and precipitation of aluminum and heavy metal ions, the salt content of the waters is also considerably reduced. In this case, a coupling of the cathodic water treatment process is provided with an anodic synthesis process. In the presence of sulfate ions, the following reactions can occur anodically: 2H ₂ O → 4H ⁺ + O ₂ + 4e ^- (5) 2SO ₄ ^2- → S ₂ O ₈ ^2- + 2e ^- (6)

In a reaction according to equation (5), the resulting protons are saturated by the sulfate ions migrating into the anode space, wherein first sulfuric acid is formed and concentrated. In the second case sulfate ions are oxidized to peroxodisulfate and enriched in the anode compartment. Subsequent processes make it possible to obtain these products. Similarly, the hydrogen formed in the cathode reaction can subsequently be utilized as a product.

EP0026591 A1 or DE 3614005 A1 describe in principle suitable electrolysis devices for this aforementioned method DE19624023 B9 , although these were not tested on an industrial scale, but only show laboratory results.

In the WO 2007144055 A1 For the first time, a device for electrochemical water treatment was described, which is also suitable for technical use. The described apparatus for the electrochemical purification of acidic waters consisting of a cathode, an anode and an ion exchange membrane, wherein the membrane is arranged between the cathode and anode and is held at least circumferentially in the edge region, wherein on the upper and lower edge region of the electrolysis device a plurality of Zu - And processes are arranged, which are connected to the cathode or the anode space, so that forms a plug flow in the cathode and the anode space, which has a laminar profile in the ideal case.

Cell elements according to the principle of this device have already been tested on an industrial scale with 2.1 m ^{2 of} active electrolysis area. An electrolyzer consisting of five bipolar cell elements according to the principle of WO 2007144055 A1 was operated for about two years and the cathodic sulfate removal of sulfuric acid mining open pit waters investigated. Despite fluctuating sulfate inlet concentration of the sulfuric acid water in the range of 800 to 1000 mg / l, a separation of over 20% could be achieved with peaks of up to 25% sulfate. Depending on the setting of the anodic synthesis process, specific energy consumptions of on average less than 0.5 kWh / m ³ sodium peroxodisulfate, 0.7 kWh / m ³ sodium sulfate and 1.0 kWh / m ³ sulfuric acid were achieved. The cathodically generated basic buffer capacity of the treated water was about 1.2 mmol / l.

The disadvantage of this process was the precipitation of the cations present in sulfuric acid, especially iron and aluminum, which are precipitated as hydroxides or carbonates in the cathode compartment due to the increase in pH and contrary to expectation despite the high volume flow of about 1.2 m ³ / h are not discharged as a suspension, but remain as precipitated sludge in the electrolysis cell. The arranged between the rear wall and the membrane in the cathode, inert filling material is thereby clogged and further water flow obstructed. Regular opening and cleaning of the cell is required as simple backwashing is not sufficient to remove the precipitated sludge, thereby reducing electrolyzer availability.

In order to increase the sulfate cleaning performance, are in DE 10 2004 026 447 B4 various technical possibilities are disclosed that are beyond the in WO 2007144055 A1 revealed principle go out. Here, a three-compartment cell is described, which consists of two cathodes and an anode, which is separated by two membranes from the cathodes. In contrast to the known state of the art, the following properties can be determined:
The device has feeds for oxygen and / or air and / or carbon dioxide in the cathode space in order to be able to distribute the gases finely. As a result, it is first achieved that cathodic hydroxide ions are generated by the additionally offered oxygen, which enhance the neutralization of the sulfuric acid water. The introduced carbon dioxide buffer capacity is also introduced by reaction to Hydrogenkarbonationen in the reprocessed, sulfuric acid, so that the product water is stabilized in the neutral pH range and thus less sensitive to the pH introduced salt loads.

The anodic current density of the device is higher by a factor of 5 than the cathodic current density, since the carrier material of the anodic electrode is coated with only a maximum of 20%, preferably even with a maximum of 5%, with electrochemically active substances. The coating should optimally not be evenly distributed, but in the lower third of the anode arithmetically by 2-20% above the occupancy average, in the upper third by 2-20% below the occupancy average and in the middle third of the anodic electrode the arithmetical average occupancy density correspond to the coating.

Several embodiments are cited, in which the improved sulfate deposition is to be demonstrated by applying the mentioned properties. In a laboratory cells of size 0.05 m ² , a sulfate depletion of about 20% is achieved at an anodic current density of 50 A / cm ² and cathodic current density of 10 A / cm ² , the specific energy consumption of 0.82 kWh / m ³ Sulfate and 1,170 kWh / m ³ sulfuric acid. In another experiment, with a 0.013 m ² cell at least a degree of sulfate removal of about 28% could be achieved Anodenkreislauf sodium peroxodisulfate was produced at an energy consumption of 0.7 kWh / m ³ . The newly introduced basic buffer capacity of the cathodically treated water was 0.7 and 0.8 mmol / l in both cases.

Now the results of the three-chamber cell after DE 10 2004 026 447 B4 with the two-cell cell after WO 2007144055 A1 In comparison, it is immediately apparent that the measures referred to as improvement do not increase the cathodic sulfate depletion, reduce the specific energy consumption for the anodic production of sulfuric acid, sodium sulfate or sodium peroxodisulfate, nor do they introduce any more buffering capacity into the cathodically treated water.

Further disadvantages arise from the cell principle itself. An increase in scale requires the interconnection of many individual cells in order to have as few conversions as possible and short lossy current paths. A three-chamber cell can only be interconnected in parallel - ie monopolar - by electrically connecting all the cathodes and all the anodes to one another. As a result, the voltage of all cells is the same, but the current according to Kirchhoff's or Ohm's law is variable, since it is determined by the individual resistance of a cell. However, since this ohmic resistance is determined by slight differences in each cell, especially in the electrochemical properties of the anodic coating or the membrane and by the different precipitation processes occurring in each cell, many cells can not be controlled hydraulically independently of one another. Each cell must be individually adjusted to achieve the same neutral effluent pH or not exceed a maximum pH, which may also lead to further precipitation processes. A monopolar electrolyzer thus requires a high control and cabling effort, which impairs its economic operation.

A three-chamber cell with two membranes must be taken out of service even in the event of faults in a membrane. Despite the same performance of a two-chamber cell, the risk of default is twice as high, which is a serious disadvantage from a technical point of view. Commercially available membranes can only be operated for a maximum of 3-4 years and can receive defects in advance due to mechanical stress, which impair the cleaning performance and can even contaminate the cathodically conducted water by means of sulfate compounds.

The application of the unevenly distributed anodic coating is also a considerable problem under industrial-scale aspects. Compared to the homogeneous uniform distribution of the coating, the labor and production costs during production are markedly increased, so that a possible advantage of a smaller coating fraction of the electrode is a maximum of 20%. and thus a potential precious metal savings is nullified. The inhomogeneous coating also leads to an inhomogeneous current density distribution, which has an adverse effect on the cell voltage and thus the energy requirement of the process in the form of increased resistances.

Against this background, it is an object of the invention to increase the availability of the electrolyzer and to increase the water treatment performance.

The object is achieved by a cell element for a bipolar electrolyzer for electrochemical water treatment, comprising an anode half-shell with an anode, a cathode half-shell with a cathode and an arranged between the anode and the cathode ion exchange membrane, wherein the anode half-shell and the cathode half-shell each having an outer wall with a flange portion for connecting the anode half-shell to the cathode half-shell, the anode half-shell and the cathode half-shell each having a plurality of inlet openings and a plurality of drain openings, wherein the total area of the inlet openings is smaller than the total area of the drain openings, and wherein the cathode half-shell has a gas feed device via which Gas in the cathode half-shell, in particular a arranged between the ion exchange membrane and the cathode cathode space is introduced.

Surprisingly, it has been found that when using an electrolyzer according to the invention a sulfate cleaning can be achieved, which is well above the results, which with three-chamber cells on a laboratory scale after DE 10 2004 026 447 B4 or with two-chamber cells after WO 2007144055 A1 can be achieved. By structurally optimized flow control of the water to be treated between the cathode and membrane, injection of air or CO ₂ through the gas feed device into the cathode space and targeted adjustment of the throughput sulfate depletion of about 40% could be achieved, which thus by 25-50% over the hitherto known sulfate removal services such as DE 10 2004 026 447 or WO 2007144055A1 known, lie.

The area of the inlet openings and outlet openings are chosen such that the discharge of suspended heavy metal salts is considerably greater than previously known from the prior art. Therefore, downtime can be avoided and the Increase plant availability. In the case of an increased accumulation of precipitated heavy metals in the cell element, the construction allows a simple backwashing from the drainage openings to the inlet openings by means of a corresponding connection via a flow reversal. In addition, rinsing nozzles can optionally be attached to the vertical sides of the cathode in order to allow a rinsing possibility transverse to the main flow direction.

Thus, the cell element of the invention increases the availability of the electrolyzer and increases the water treatment performance.

According to an advantageous embodiment, the total area of the inlet openings is at least 30%, preferably at least 50%, smaller than the total area of the drainage openings. As a result, the discharge of suspended heavy metal salts can be increased.

Advantageously, the gas feed device has at least one tubular gas distributor which extends over the entire width of the cathode half-shell. The gas feed device is preferably arranged horizontally. Particularly preferably, the gas feed device is arranged in a range of 300 to 400 mm and / or from 600 to 800 mm above an inlet channel having the inlet openings. Via the gas feed device, a gas, for example air or CO ₂ , can be finely distributed into the water to be purified located in the cathode compartment.

An advantageous embodiment provides that the anode at a distance of at least 0.5 mm and a maximum of 20 mm, preferably at least 8 mm and a maximum of 12 mm, is disposed away from the ion exchange membrane, wherein the distance reaches via the introduction of a non-conductive material is used, wherein as a non-conductive material, a fabric, mesh, threads, cloths, fleece or webs are used.

It is advantageous if the cathode is arranged at a distance of at least 0.5 mm and a maximum of 20 mm, more preferably at least 8 mm and a maximum of 12 mm from the ion exchange membrane, wherein the distance is achieved via the introduction of a non-conductive material , Where used as a non-conductive material fabrics, mesh, threads, cloths, fleece or webs.

According to a preferred embodiment, the anode is connected to a rear wall of the anode half shell cohesively or adhesively. The anode may be formed as a metallic fabric, as expanded metal or as a perforated plate. The anode may have a surface corresponding to 30% to 70%, preferably 40% to 60%, of the surface of the ion exchange membrane.

It is preferred if the anode consists of titanium and the entire surface of the anode is coated with an electrochemically active substance.

In this context, it has proven to be advantageous if a mixture of iridium and tantalum or a mixture of platinum and iridium is used as the electrochemically active substance.

Advantageously, the occupation density of the anode with the electrochemically active substance is at least 5 g / m ² . Particularly advantageous is a coverage of at least 10 g / m ² . Preferably, the coverage of the anode with the electrochemically active substance is uniform, so that the current density distribution over the entire surface of the anode during normal operation is uniform. A preferred embodiment provides that the anode has an opening degree of 40-50% and a uniform coating of about 10 g / m ² , so that the sulfate transport to the anode side is significantly increased. As a result, a higher throughput-specific product yield of sulfate species such as sulfuric acid or ammonium sulfate and the unified current density distribution a lower voltage and thus a lower specific energy consumption can be achieved.

Preferably, the cathode and the anode are formed such that the anodic current density is higher than the cathodic current density by a factor between 1.4 and 3.3, more preferably by a factor between 1.7 and 2.5.

An advantageous embodiment provides that the cathode is formed as a flat, metallic plate. The cathode preferably consists of a chemically stable material against acidic media, in particular nickel or stainless steel.

An embodiment in which a rear wall of the cathode half-shell is identical to the cathode is advantageous, so that a structurally simpler construction of the cathode half-shell results.

The anode half-shell preferably has a stabilization device for stabilizing the rear wall of the anode half-shell and / or the cathode half-shell has a stabilization device for stabilizing the rear wall of the cathode half-shell. The stabilization device is particularly preferably provided outside the cathode space or outside the anode space arranged between the ion exchange membrane and the anode. This makes it possible, so that both the cathode compartment and the anode compartment can be made largely obstacle-free. The distances between the anode or the cathode and the membrane can be adjusted by introducing a nonconducting material, wherein as a material preferably woven, mesh, threads, cloths, fleece or spun be used, in contrast to the known in the prior art packing only have a low flow resistance. Preference is given to an embodiment in which the cathode is stabilized by a plurality of, in particular nine, triangular webs which are connected to the rear side of the cathode materially or adhesively bonded or adhesively and from two at an angle of preferably 40 ° to 60 ° to each other inclined and welded sheets exist. Likewise, the anode can be stabilized via a plurality of, in particular nine, triangular webs which are connected to the rear side of the anode in a materially or adhesively bonded or adhesively bonded manner and consist of two sheets each inclined and welded at an angle of preferably 40 ° to 60 °.

According to a preferred embodiment, the anode half-shell and the cathode half-shell each have at the bottom a, in particular rectangular, inlet channel, via which feed solutions can be fed, wherein the inlet channel has the inlet openings. It is preferred if the anode half-shell and the cathode half-shell each have at the top a, in particular rectangular, drainage channel, via which the product solutions can be discharged, the drainage channel having the drainage openings.

According to a structural design, a centrally arranged inlet nozzle is welded to the inlet channel centrally above a longitudinal side of the inlet channel. A further constructional embodiment provides that in each case a drain pipe is welded to the bottom of a down-side of the drain channel to the drain channel.

It has proved to be advantageous if the cathodic inlet channel at the bottom and the cathodic outlet channel are connected at the top to the cathode in a cohesive or adhesive manner. Furthermore, it is advantageous if the anodic inlet channel at the bottom and the anodic outlet channel at the top are materially or adhesively connected to the anode rear wall.

Preferably, the cathodic inlet channel, in particular below, inlet openings, which are arranged uniformly in series over the entire length of the inlet channel, wherein the distance between the inlet openings is preferably at least 20 mm and a maximum of 50 mm and the height of each inlet opening preferably at least 5 mm and a maximum 15 mm. The cathodic inlet channel can center have a drain connection for connecting a hose or pipe connection.

Preferably, the cathodic drainage channel, in particular above, drainage openings which are arranged uniformly in series over the entire length of the drainage channel and whose total area is preferably at least 30% and more preferably at least 50% greater than the total area of the inlet openings of the cathodic inlet channel. The cathodic drainage channel can centrally have a drain connection for connecting a hose or pipe connection.

It is preferred if the anodic inlet channel, in particular below, inlet openings, which are arranged uniformly in series over the entire length of the inlet channel, wherein the distance between the inlet openings is preferably at least 20 mm and a maximum of 50 mm and the height of each inlet opening preferably at least 5 mm and a maximum of 15 mm. The anodic inlet channel may have a central outlet connection for connecting a hose or pipe connection.

An advantageous embodiment provides that the anodic drainage channel, in particular at the top, has drainage openings which are arranged uniformly in series over the entire length of the drainage channel and whose total area is preferably at least 30% and particularly preferably at least 50% greater than the total area of the inlet openings of the anodic inlet channel. The anodic drainage channel can centrally have a drain connection for connecting a hose or pipe connection.

It is advantageous if the cathode half-shell has at least one, preferably two, flushing nozzles. It is particularly advantageous if the cathode half-shell has at least one flushing connection each at the left and the right-hand edge of the cathode. The flushing nozzles can be horizontally aligned and / or mounted on the front side.

In a bipolar electrolyzer with several cell elements connected in series, it contributes to the solution of the problem when the cell elements are designed as described above.

A bipolar electrolyzer, which consists of individual cell elements that are electrically connected in series - ie bipolar - is cheaper and easier to regulate than a monopolar electrolyser, for example, an electrolyzer constructed of three-chamber cells. When bipolar electrolyzer the current and thus the load is always the same, so that due to the same electrochemical production or implementation of a simple hydraulic control of the cathodically supplied Sulphurous water is possible. The cabling work and the enclosed space of a bipolar electrolyzer are also significantly lower and therefore more cost-effective.

The cell elements of the electrolyzer are designed so that they can be connected in bipolar, ie in series to a technical electrolyser, to allow the simplest possible power supply, which requires little effort in the form of wiring and personnel for installation while allowing the treatment of large amounts of water , Ideally, the inlet and outlet channels of the cathodes or anodes can be connected in such a way that centrally only one supply line is required, where the inflow and thus the amount of water to be treated can be regulated by means of suitable instruments. Due to the vertical arrangement of many elements in a steel frame, such an electrolyzer requires little space and reduces the space of the enclosure, which has been converted under economic aspects, in order to be able to professionally operate the installation under safety aspects.

The invention is based on a in 1 - 15 illustrated embodiment will be explained in more detail.

1 Interior view of the cathode half-shell of an electrolyzer according to the invention

2 External view of the rear wall of the cathode half-shell of an electrolyzer according to the invention

3 Schematic view of the arrangements of the back wall struts of the cathode half-shell of an electrolyzer according to the invention

4 Cross section of the cathode half-shell of an electrolyzer according to the invention

5 Schematic view of the inlet channel of the cathode half-shell of an electrolyzer according to the invention

6 Schematic view of the drainage channel of the cathode half-shell of an electrolyzer according to the invention

7 Schematic representation of the cross section of the cathodic device for gas supply and gas injection

8th Interior view of the anode half-shell of an electrolyzer according to the invention

9 External view of the rear wall of the anode half-shell of an electrolyzer according to the invention

10 Schematic view of the arrangements of the back wall struts of the anode half-shell of an electrolyzer according to the invention

11 Cross section of the anode half-shell of an electrolyzer according to the invention

12 Schematic view of the inlet channel of the anode half-shell of an electrolyzer according to the invention

13 Schematic view of the drainage channel of the anode half-shell of an electrolyzer according to the invention

14 Schematic representation of the arrangement of the anode and recesses of the drainage channel of an electrolyzer according to the invention for the discharge of the anolyte

15 Schematic representation of the arrangement of cathodic and anodic half-shell of an electrolyzer according to the invention in the assembled state

1 shows the interior view of a cathode half-shell 1 an electrolyzer according to the invention. The rectangular half-shell has a frame-like flange 3 over which the cathode half-shell 1 with the anode half shell 2 about a screw system that through screw holes 4 is connected. The sulfuric acid water is via an inlet pipe 16b in the inlet channel 5b fed in the bottom area of the cell, the water evenly distributed over the width through inlet openings 7b in the inlet channel 5b in the cathode compartment 14 enters and flows upwards. Over several gas supply devices 11 In the form of air or CO ₂ , gas is injected into the sulfuric acid water to be purified in order to accelerate the cathodic neutralization process. The installation height of the gas feed devices 11 depends on the pH value and the constituents of the sulfuric acid water and can therefore be varied depending on the process in order to achieve optimized sulfate depletion. In the schematic illustration, two heights are exemplified, wherein a first gas feed device 11 at a distance of 300-400 mm above the inlet channel 5b and a second gas feeding device 11 at a distance of 600-800 mm above the inlet channel 5b is arranged. During the upflow, the neutralization reaction takes place, the electrolysis current passing through the cathode 9 is supplied. The neutralized water leaves the cathode compartment 14 over drainage openings 8b to the drainage channel 6b from which the water flows through a drain neck 17b exit.

2 shows the cathode half shell 1 an electrolyzer according to the invention from the outside. Between the inlet channel located below 5b and the drainage channel located above 6b for the water is the back wall of the cathode compartment 14 , at the same time as a cathode 9 is working. The constructive stabilization of the cathode half shell 1 is performed by a stabilizer with nine evenly distributed over the cell width webs 12 whose schematic arrangement is in 3 is shown. The bridges 12 are triangular and with the cathode 9 welded completely or intermittently. The obliquely placed sheets of the webs 12 are inclined at an angle of 40 to 60 ° to the vertical.

The uniform distribution of the triangularly arranged webs 12 comes from 4 showing a cross section of the cathode half-shell 1 of the electrolyzer according to the invention shows.

In 5 is the rectangular inlet channel 5b the cathode half-shell 1 of a cell element according to the invention of an electrolyzer shown in cross section. To the inlet channel 5b is an oval-shaped inlet nozzle 16b welded on the center, which allows, for example, a hose connection, flexible pipe connections or the like, the supply of sulfuric acid water. The water enters via the inlet openings at the bottom 7b in the cathode compartment 14 passing through the ion exchange membrane 13 on the one hand and the cathode 9 on the other hand is defined. The cathode 9 is with the inlet channel 5b cohesive or adhesive liquid-tight connected.

6 shows analogously to the cross section of the rectangular discharge channel 6b the cathode half-shell 1 a cell element of an electrolyzer according to the invention. The neutralized water enters via the drainage openings in the upper channel 8b into the drainage channel 6b and is derived from there collected. The drainage channel 6b is with the cathode 9 cohesive or adhesive liquid-tight connected.

In 7 is a gas feed device 11 for supplying the cathode half-shell 1 shown schematically with gas in the form of air or CO ₂ in cross section. About a neck 19 the gas enters the tubular gas distributor 18 passed over the entire width of the cathode half-shell 1 is arranged. In the cell element according to the embodiment, a plurality of gas feeding devices 11 provided, via which the gas is injected finely distributed in the water.

8th shows the interior view of an anode half-shell 2 a cell element of an electrolyzer according to the invention. The rectangular anode half shell 2 has a frame-like flange 3 over which the anode half shell 2 with the cathode half shell 1 about a screw system that through screw holes 4 is conducted. The anolyte is via an inlet connection 16a in the inlet channel 5a supplied in the bottom region of the cell, wherein the solution evenly distributed over the width through inlet openings 7a in the inlet channel 5a in the anode compartment 15 enters and flows upwards. During the Aufströmens the sulphate-containing product is enriched due to the passage of the sulfate from the cathode compartment 14 with the electrolysis current across the anode 10 is dissipated. The anolyte leaves the anode compartment 15 over drainage openings 8a of the drainage channel 6a from which the anolyte via a drain neck 17a exit.

9 shows the anode half shell 2 a cell element according to the invention of the electrolyzer from the outside. Between the inlet channel located below 5a and the drainage channel located above 6a for the anolyte lies the back wall 21 of the anode compartment 15 that with the anode 10 is welded. The structural stabilization of the anode half shell 2 is performed by a stabilizer with nine evenly distributed over the cell width webs 12 whose schematic arrangement is in 10 is shown. The bridges 12 are designed triangular and with the anode back wall 21 welded. The obliquely placed sheets of the webs 12 are inclined at an angle of 40 to 60 ° to the vertical.

The uniform distribution of the triangularly arranged webs 12 comes from 11 showing a cross section of the anode half shell 2 of the electrolyzer according to the invention shows.

In 12 is the rectangular inlet channel 5a the anode half shell 2 of a cell element according to the invention of the electrolyzer shown in cross section. To the inlet channel 5a is an oval-shaped inlet nozzle 16a welded on the center, which allows for example via a hose connection, flexible pipe connection or the like, the supply of the anolyte. The solution enters via the inlet openings at the bottom 7a in the anode compartment 15 passing through the ion exchange membrane 13 on the one hand and the anode 10 on the other hand is defined. The anode 10 is with the anode back wall 21 and these with the inlet channel 5a welded.

13 shows analogously to the cross section of the rectangular discharge channel 6a the anode half shell 2 a cell element of the electrolyzer according to the invention. The enriched anolyte enters through the drainage channel 6a top drain holes 8a into the drainage channel 6a and is derived from there collected. The drainage channel 6a is with the anode back wall 21 welded.

The execution of the anode 10 a cell element of the electrolyzer according to the invention is shown schematically in FIG 14 shown. The anode 10 is designed as a perforated plate and has regular openings 20 whose total area is 50 to 60% of the total area of the anode 10 is. The electrochemically active surface of the anode 10 is thus 40-50% of its arithmetic area of length multiplied by width. The anode 10 is designed so that the drain holes 8a to the drainage channel 6a not from the anode 10 be covered to the total area of the surface of the drainage holes 8a to be able to use. Accordingly, the anode covers 10 not even the inlet openings 7a of the inlet channel 5a in the bottom area of the anode half shell 2 ,

• – Monopolare Verschaltung der Einzelelemente zu einem Elektrolyseur mit hohem Platzbedarf und Verkabelungsaufwand,
• – relativ hohes Anlagenausfallrisiko durch Membranwechsel,
• – ungleichmäßige Stromdichteverteilung,
• – hoher Personal- und Fertigungsaufwand zur Herstellung der anodischen Elektrodenbeschichtung,
• – aufwändige Maßstabsvergrößerung,
• – hoher Regelungsaufwand,
• – mangelnde Reinigungsmöglichkeit zur Entfernung kathodisch erzeugter Fällprodukte und
• – geringe Anlagenverfügbarkeit durch regelmäßiges Entfernen des Fällschlamms.

15 finally shows a schematic representation of the arrangement of cathodic and anodic half-shell 2 a cell element according to the invention of the electrolyzer in the assembled state. The inlet channels 5a . 5b and the drainage channels 6a . 6b the anode half shell 2 and the cathode half shell 1 are each oriented to each other. The cathode half shell 1 and the anode half shell 2 are over the flanges 3 screwed together. The anode half shell 2 and the cathode half-shell 1 each have several inlet openings 7a . 7b and several drainage holes 8a . 8b on, taking the total area of the inlet openings 7a . 7b smaller than the total area of the drainage holes 8a . 8b , The cathode half shell 1 further includes a gas feeding device 11 on which a gas enters the cathode half-shell 1 , in particular one between the ion exchange membrane 13 and the cathode 9 arranged cathode compartment 14 can be introduced. This increases the availability of the electrolyzer and increases the water treatment performance. In addition, the following disadvantages of the prior art are overcome by the cell element according to the invention:

• - Monopolar interconnection of the individual elements to an electrolyzer with a high space requirement and cabling costs,
• - relatively high plant failure risk due to membrane changes,
• Uneven current density distribution,
• High labor and manufacturing costs for producing the anodic electrode coating,
• - elaborate scale-up,
• - high regulation effort,
• - Lack of cleaning ability to remove cathodically generated precipitates and
• - low system availability through regular removal of the precipitated sludge.

LIST OF REFERENCE NUMBERS

1

 Cathode half-shell

2

 Anode half shell

3

 Frame-like flange area

4

 Screw bushings

5a

Anodic inlet channel

5b

 Cathodic inlet channel

6a

 Anodic drainage channel

6b

 Cathodic drainage channel

7a

 Openings anodic inlet channel

7b

 Openings cathodic inlet channel

8a

 Openings anodic drainage channel

8b

 Openings cathodic drainage channel

9

 cathode

10

 anode

11

 Device for gas supply

12

 web

13

 ion exchange membrane

14

 cathode space

15

 anode chamber

16a

 Inlet neck anodic inlet channel

16b

 Inlet neck cathodic inlet channel

17a

 Drain nozzle anodic drainage channel

17b

 Drain nozzle cathodic drainage channel

18

 gas distributor

19

 Gas supply nozzle

20

 Openings in the anode

21

 Anode backplane

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 19624023 B9 [0005, 0010]
• EP 0026591 A1 [0010]
• DE 3614005 A1 [0010]
• WO 2007144055 A1 [0011, 0012, 0014, 0017, 0023, 0023]
• DE 102004026447 B4 [0014, 0017, 0023]
• DE 102004026447 [0023]

Claims (18)

Cell element for a bipolar electrolyzer for electrochemical water treatment, comprising an anode half-shell ( 2 ) with an anode ( 10 ), a cathode half-shell ( 1 ) with a cathode ( 9 ) and one between the anode ( 10 ) and the cathode ( 9 ) arranged ion exchange membrane ( 13 ), wherein the anode half shell ( 2 ) and the cathode half-shell ( 1 ) each have an outer wall with a flange area ( 3 ) for connecting the anode half-shell ( 2 ) with the cathode half-shell ( 10 ), characterized in that the anode half-shell ( 2 ) and the cathode half-shell ( 1 ) each have a plurality of inlet openings ( 7a . 7b ) and several drain openings ( 8a . 8b ), wherein the total area of the inlet openings ( 7a . 7b ) is smaller than the total area of the drainage openings ( 8a . 8b ), and the cathode half-shell ( 1 ) a gas feed device ( 11 ), via which a gas in the cathode half-shell ( 1 ), in particular one between the ion exchange membrane ( 13 ) and the cathode ( 9 ) arranged cathode space ( 14 ) can be introduced. Cell element according to claim 1, characterized in that the total area of the inlet openings ( 7a . 7b ) is at least 30%, preferably at least 50%, smaller than the total area of the drainage openings ( 8a . 8b ). Cell element according to one of the preceding claims, characterized in that the gas feed device ( 11 ) a tubular gas distributor ( 18 ), which extends over the entire width of the cathode half-shell ( 1 ). Device according to one of the preceding claims, characterized in that the anode ( 10 ) with a back wall ( 21 ) of the anode half shell ( 2 ) is bonded cohesively or adhesively. Device according to one of the preceding claims, characterized in that the anode ( 10 ) consists of titanium and the entire surface of the anode ( 10 ) is coated with an electrochemically active substance. Apparatus according to claim 5, characterized in that the electrochemical substance is a mixture of iridium and tantalum or a mixture of platinum and iridium. Device according to one of the preceding claims, characterized in that the occupation density of the anode ( 10 ) with the electrochemically active substance is at least 5 g / m ² , preferably at least 10 g / m ² . Device according to one of the preceding claims, characterized in that the cathode ( 9 ) and the anode ( 10 ) are formed such that the anodic current density is higher than the cathodic current density by a factor between 1.4 and 3.3, more preferably by a factor between 1.7 and 2.5. Device according to one of the preceding claims, characterized in that the cathode ( 9 ) is formed as a flat, metallic plate. Device according to one of the preceding claims, characterized in that the cathode ( 9 ) consists of a chemically stable material against acidic media, in particular nickel or stainless steel. Device according to one of the preceding claims, characterized in that a rear wall of the cathode half-shell ( 1 ) with the cathode ( 9 ) is identical. Device according to one of the preceding claims, characterized in that the anode half-shell ( 2 ) a stabilization device for stabilizing the rear wall ( 21 ) of the anode half shell ( 2 ) and / or the cathode half-shell ( 1 ) a stabilizing device for stabilizing the rear wall of the cathode half-shell ( 1 ), wherein the stabilization device outside the cathode space ( 14 ) or outside between the ion exchange membrane ( 13 ) and the anode ( 10 ) arranged anode space ( 15 ) is provided. Device according to one of the preceding claims, characterized in that the anode half-shell ( 2 ) and the cathode half-shell ( 1 ) at the bottom one, in particular rectangular, inlet channel ( 5a . 5b ), via which feed solutions can be supplied, wherein the inlet channel ( 5a . 5b ) the inlet openings ( 7a . 7b ) having. Device according to one of the preceding claims, characterized in that the anode half-shell ( 2 ) and the cathode half-shell ( 1 ) each one above, in particular rectangular, drain channel ( 6a . 6b ) are discharged through the product solutions, wherein the drainage channel ( 6a . 6b ) the drainage openings ( 8a . 8b ) having. Device according to one of the preceding claims, characterized in that the cathodic inlet channel ( 5b ) below and the cathodic drain channel ( 6b ) above with the cathode ( 9 ) are bonded cohesively or adhesively. Device according to one of the preceding claims, characterized in that the anodic inlet channel ( 5a ) below and the anodic drainage channel ( 6b ) at the top with the anode back wall ( 21 ) are bonded cohesively or adhesively. Device according to one of the preceding claims, characterized in that the cathode half-shell has at least one, preferably two, flushing. A bipolar electrolyzer with a plurality of cell elements connected in series, characterized in that the cell elements are designed according to one of the preceding claims.

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