EP1409769A2

EP1409769A2 - Electrolysis device

Info

Publication number: EP1409769A2
Application number: EP02716647A
Authority: EP
Inventors: Karl Lohrberg; Dirk Lohrberg
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-02-22
Filing date: 2002-01-03
Publication date: 2004-04-21
Also published as: WO2002068721A3; DE10108452A1; CA2435571A1; DE10108452C2; US20040074764A1; WO2002068721A2

Abstract

The invention relates to an electrolysis device, comprising at least one horizontal electrolytic cell with a housing (6) and an anode (8) that has a membrane or a diaphragm (18), and a cathode (9) that has a gas diffusion electrode (17). The device further comprises supply (21) and discharge (23) means for gas (3) which lead to or away from the gas chamber (22) of the cathode (9), and supply (16; 19) and discharge (16; 20) means for electrolytes (1) which lead to or away from the first electrolytic chamber (4) and to or away from the second electrolytic chamber (5). The anode (8) and the membrane or the diaphragm (18) have at least one respective opening for the supply (19) of electrolytes (1) to the second electrolytic chamber (5), and at least one further opening for the discharge (20) of electrolytes from the second electrolytic chamber.

Description

electrolyzer

The invention relates to an electrolysis device with at least one horizontally lying electrolysis cell, which has a housing and the anode of which is equipped with a membrane or a diaphragm and the cathode of which is equipped with a gas diffusion electrode, and with means for supplying and removing gas into or from the gas space of the cathode and means for supplying and removing electrolytes into and out of a first electrolyte chamber and into and out of a second electrolyte chamber, the electrolyte chambers being separated from one another by means of the membrane or the diaphragm ,

Such an electrolysis device is known for example from EP-A-182 144. The electrolyte is introduced and removed via openings which are arranged at the edge between the electrodes. Because of this, the cross-sectional area of the openings is limited by the dimensions and the distance between the electrodes. Since the distance between the electrodes is only a few millimeters, the cross-sectional area available for the feeding and removal of the electrodes is relatively small. Such electrolysis devices are therefore only suitable for electrolytically connected electrolytic cells, since these are penetrated by small amounts of electrolyte. In the case of an electrolytic series connection of the cells, as is known, for example, from EP-B-0 865 516, the amount of electrolyte to be enforced increases in accordance with the number of cells and, as a result of high electrolyte speeds, pressure losses at the openings which cannot be tolerated can occur. This applies in particular if an electrode is covered with a porous gas diffusion electrode. According to the pressure losses at the openings, a hydraulic pressure acts on the gas diffusion electrode, which can lead to the electrode being flooded if the gas pressure on the other side of the electrode is not sufficiently high. Gas diffusion electrodes are generally considered to be hydrophobic because they contain a considerable amount of Teflon to bind the carbon. In this way, they can be partially loaded with water columns over 500 mm without water penetrating into the pores. However, practice has shown that this is not the case in an electrolysis device, since under current flow and the presence of ions, the surface is wetted even at pressures below 40 mm water column. As the hydraulic pressure increases with the length of a pipeline through which it flows, the pressure acting on the gas diffusion electrode increases with an increasing number of cells in an electrolytic series connection. This leads to the highest pressure in the first and the lowest pressure in the last cell. In this case, flooding of the gas diffusion electrode can only be prevented if a specific gas pressure is maintained in each individual cell.

In order to enable a technically less complex and therefore economically higher operation of the cells with only one gas pressure, a cascade flow must be generated, ie the electrolyte runs from the outlet pipe of one cell into the inlet pipe of the next cell. At the point of a hold-up, which corresponds to a height-adjustable overflow according to EP-B-0 865 516, the hydraulic pressure drops, so that the same pressure is present in each cell. In the case of cells with vertically standing electrodes, this can be done in a simple manner by the length of the hydraulic pressures Inlet and outlet pipes can be realized. In contrast, this is not possible for cells with horizontally lying electrodes, such as those according to EP-A-0 182 114 or EP-B-0 856 516. The tolerance range of the permissible hydraulic pressure is determined here by the overall height of the cell. This is usually a few centimeters to save material and space. One way of generating only correspondingly low hydraulic pressures is therefore to constructively enlarge the inlet and outlet openings. This can be achieved in that the inlet and outlet openings are not arranged between the electrodes, but next to the electrodes, as in EP-A-0 168 600, EP-A-0 330 849 and EP-B-0 865 516 proposed. The cross-sectional area of the openings is then no longer limited by the spacing of the electrodes from one another, but can be adapted to the increased amounts of electrolyte in an electrolytic series connection via the appropriate design of the frame geometry. A disadvantage of such an arrangement of the openings, however, is the additional production of a sealing frame, which connects the membrane or the diaphragm to the frame in a gas-tight and liquid-tight manner, so that mixing of the quantities in the individual chambers is prevented. Such a frame also, because it lies between the electrodes, means that the distance between the electrodes is increased by the frame thickness. This increases the voltage drop in the electrolyte and thus the energy consumption.

An increase in the distance can be prevented by bending the membrane or the diaphragm or, as suggested in US Pat. No. 4,436,608, even the gas diffusion electrode on the sides. However, this entails the risk that too great a shear force acts at the corners of the frame and that the membrane or the diaphragm is no longer sealed due to damage. The invention is therefore based on the object of proposing an electrolysis device of the type mentioned at the outset in which the aforementioned problems of the prior art have been eliminated, and in particular an electrolysis device of this type which can be constructed simply and can be operated economically.

This object is inventively z. B. solved in that the anode and membrane or the diaphragm each have at least one opening for supplying electrolytes in the second electrolyte chamber and at least one further opening for discharging electrolytes from the second electrolyte chamber.

It is particularly advantageous here if the membrane or the diaphragm in the area of the electrolyte supply opening and the electrolyte discharge opening is clamped in a gas-tight and liquid-tight manner by means of a sealing frame, the thickness of which does not exceed the thickness of the anode, as well as on the sealing frame and the anode. Such an arrangement has the advantage that the distance between the electrodes is not influenced by the clamping and the shear forces acting on the membrane or the diaphragm are minimized.

Most electrolysis cells today are constructed from metal, since the appropriate alloys ensure long-term resistance of the cells to chemical and mechanical loads at very high temperatures. Disadvantages of metal structures, however, are the mostly high costs for the material and the production, which usually include complex welding work. This is particularly true for cells that use different materials for the anode and cathode, such as. B. a chlor-alkali membrane cell, in which the anode consists of a ruthenium oxide-coated titanium-palladium alloy and the Nickel cathode. Such cells are basically made up of an anode and a cathode tub with the respective electrodes. In the case of an electrical series connection, the individual tubs are welded to one another, for example, by means of explosively plated, bipolar strips. The welding of the cells over such strips is ideally carried out with a laser, in which the welding area or the temperature zone can be spatially arranged in such a way that mixing of the different alloys and thus corrosion is prevented. The manufacture of an electrolytic cell is easier if the anode and cathode are made of the same material as, for example, a cell for producing hydrogen peroxide in an alkaline solution using a gas diffusion cathode. In this case, nickel can be used as the material. In order to obtain a bipolar cell, the electrodes are simply electrically connected to one another via bridges made of nickel or the cell walls themselves. It is important in this cell that when using a diaphragm on the anode there is a gas-tight partition between the anode and cathode, as in EP-B-0 865 516, so that the gas pressure, which should prevent the gas diffusion electrode from flooding through the catholyte, does not also acts on the anolyte. In contrast to a membrane, a diaphragm is permeable to liquid, so that a pressure acting on the anolyte also acts on the catholyte. Without a partition, a pressure difference would therefore be present at the gas diffusion electrode and lead to flooding. The introduction of such a partition wall, however, requires a high level of manufacturing expenditure, since the requirement for a seal against gas does not permit spot welding. The partition must therefore be welded to the webs and the cell walls using continuous welds. However, this usually leads to a delay because the material should be as thin as possible for economic reasons and the welding heat is not dissipated. As with chlor-alkali membrane electrolysis, laser welding is also an option here, since the temperature zone can be determined very precisely in terms of space. Through a However, complex welding, long preparation times and high quality requirements make laser welding very cost-intensive.

In order to avoid these manufacturing and material costs by means of two metal tubs, such as are provided, for example, according to EP-A-0 182 114, it is proposed in a further development of the inventive concept that the housing of the electrolytic cell is formed by two plastic plates, between which are Use of frame-like seals, the electrolyte chambers and the gas space are limited.

In the case of a plurality of electrolysis cells arranged one above the other, the middle plastic plate (s) forms the base of the upper electrolysis cell and the cover of the electrolysis cell located below.

The electrolyte supply and discharge channels of the second electrolyte chamber can be introduced, in particular milled, into these plastic plates in a simple manner. The same applies to electrolyte supply and discharge channels of the first electrolyte chamber.

For example, PP, PVC and post-chlorinated PVC are suitable as plastics. These plastics are resistant to many chemicals, even at temperatures up to approx. 80 ° C. The plastic plates can be covered with seals in such a way that the required electrolyte and gas spaces are created between the electrodes and the plastic plate without great effort. This eliminates the need for a material-intensive version with two trays or the welding in of a partition.

In the case of electrolyses other than peroxide electrolysis, the plastic plates can preferably consist of different materials, since the anolyte and catholyte consist of different compounds. Since the anlolyte and catholyte are introduced via the same plastic plate, this can expediently consist of two different plastics.

In the case of a plurality of electrolysis cells, the respective electrolyte discharge channels of the upper electrolysis cell can be in flow communication with the respective electrolyte feed channels of the electrolysis cell located underneath via external connecting pipelines.

When using plastic plates as the housing, it is not possible to supply the electrodes with power via the housing wall, since this is then non-conductive. A conventional electrical connection via webs, which are located in the electrolyte area, should also be avoided, since these would have to be additionally sealed against the plastic plate. For this purpose, passages would also have to be milled into the plastic plate, which would reduce the rigidity of the plate.

According to the invention, it is therefore proposed that the anode and the cathode extend beyond the seals which delimit the electrolyte chambers and the gas space and are provided with their electrical connections or connections from the anode to the cathode outside the chambers.

The electrical connections and connections can also still be in the plastic plate, for which edge recesses or openings can be provided; but they can also be arranged outside. A

In this case, the rigidity of the plastic plate is not reduced.

The material of the electrical connections and connections can be chosen freely since they no longer bear the chemical-thermal load on the electrolyte are exposed. It is therefore also possible to use highly conductive copper, for example, which is normally not used at this point due to its poor chemical-thermal resistance. This leads to a cost-effective reduction in the number and dimensions of the electrical connections and connections, including corresponding busbars to which the electrical connections are connected.

A particularly simple assembly is ensured if the connections and / or connections are pressed with clamping elements with anode and cathode. Expensive welding is then unnecessary.

The gas requirement also plays a major role in the use of gas diffusion electrolysis. This must be a multiple of the stoichiometric requirement for the reaction taking place in gas diffusion electrolysis, so that there are no losses in efficiency. In most cases, oxygen is converted into a gas diffusion cathode with the hydrogen generated at the cathode to generate energy. For economic reasons, air is usually used instead of oxygen. As air is known to contain only 21% oxygen, correspondingly large amounts have to be introduced into the electrolytic cell. This requires inlet and outlet pipes with a correspondingly large cross section, as a result of which the thickness of the cell frame must disadvantageously be increased. A reduction in the cross-section while increasing the number of pipes is usually precluded for economic reasons.

According to a further proposal of the invention, therefore, a gas supply channel and a gas discharge channel penetrate the plastic plates delimiting the electrolytic cell (s) and possibly the anode and the cathode, sealing against the electrolyte chambers and in flow connection with the respective gas space from top to bottom. The cross section of the feed and Discharge openings can thus be determined regardless of the plate thickness. For this purpose, openings with the same dimensions are present in the individual plastic plates and possibly the electrodes, which are aligned with one another so that the gas, for example the air, is distributed in an energetically favorable manner with the smallest possible pressure loss in the cell stack. The openings are designed so that the required cross-section is available, but there is still enough material for the current flow. The air flow from top to bottom allows electrolyte, which penetrates the gas diffusion electrode, for example, through small leaks, to be removed. Another advantage of the possibility of converting large amounts of gas is the increased absorption of the evaporation heat generated at the gas diffusion electrode, so that an internal cooling is created which replaces an external one and saves the costs for a heat exchanger.

According to the invention can thus be simple and economical

Set up electrolysis equipment for use in gas diffusion electrolysis. There is no need for complex welds. The individual parts can be put together directly at the place of use, which eliminates the costs for an intermediate assembly and reduces the transport costs. By combining different electrode and plastic materials, cells can be assembled in a cost-saving modular way for different electrolysis processes.

Further objectives, features, advantages and possible uses of the invention result from the following description of exemplary embodiments with reference to the drawing. All of the described and / or illustrated features, alone or in any combination, form the subject matter of the invention, regardless of their combination in individual claims or their relationship. Show it:

1 is a schematic representation of an electrolysis device constructed from four electrolysis cells according to the invention,

2, on the other hand, enlarged, the detail of a pair of electrodes in the region of an electrolyte feed opening or

Electrolyte discharge opening, and

3 is a top view of a sealing frame as shown in FIG. 2

Application.

The electrolysis device shown in FIG. 1 has four horizontally stacked electrolysis cells, with a housing 6 formed by plastic plates 6 ', 6 ", the uppermost plastic plate 6' a cover and the bottom plastic plate 6" a bottom of the top or bottom Form electrolysis cell, while the middle plastic plates 6 "simultaneously form the bottom of the electrolysis cell above and the lid of the electrolysis cell underneath.

Each electrolytic cell has an anode 8 with a membrane or a diaphragm 18 and a cathode 9 with a gas diffusion electrode 17, with corresponding seals 11, 12, 13 a first electrolyte chamber 4 as the anode space, a second electrolyte chamber 5 as the cathode space and on the outside of the cathode 9 a gas space 22 are formed.

Electrolyte 1 becomes the uppermost via an electrolyte supply channel 19 '

Plastic plate 6 'an opening 19 in the anode 8 and the associated

Membrane or the associated diaphragm 18 and thus the second electrolyte chamber 5 supplied. The removal of the electrolyte 1 from the second Electrolyte chamber 5 takes place via an electrolyte discharge opening 20 into an electrolyte discharge channel 20 ', which, like the electrolyte feed channel 19' in the uppermost plastic plate 6 'from the second electrolyte chamber 5, initially runs vertically and then milled horizontally in the plastic plate 6'. Corresponding channels and openings are also provided in the other plastic plates, anodes and membranes or diaphragms. Just as the electrolyte 1 is supplied to the outer edge of the uppermost plastic plate 6 'via a lateral feed pipe 26, the electrolyte 1 flows laterally outward from the electrolyte discharge channel 20' into a connecting pipeline 10 adjoining there to the second plastic plate 6 ", which is the uppermost one The electrolysis cell is delimited as the bottom and there into an electrolyte feed channel, which corresponds to the feed channel 19 'of the uppermost plastic plate 6', etc., until the electrolyte is discharged from the side of the penultimate plastic plate 6 "via an outlet pipe 25.

Gas such as Oxygen or air are supplied from above into a gas supply channel 21 which passes through all the plastic plates 6 ', 6 "of the housing 6 from top to bottom and which is sealed gas and liquid-tight against the electrolyte chambers 4, 5, but in each case in flow connection with the corresponding one The gas supply channel 21 opens into the lowermost gas space at the bottom, and on the opposite side of the electrolysis cell stack a vertical gas discharge channel 23 extends from the uppermost gas space 22 into a lower outlet opening in the lowermost plastic plate 6 '.

In the middle of the plastic plates 6 ', 6 "are each a Elektrolysezufuhr- or -abfuhröffnung 16 of the first electrolytic chamber 4 (anode space) and the associated Elektrolytzufuhr- ^• and -abfuhrkanäle 16' are indicated. The respective channels 16 'may also in the plastic plates 6 ', 6 "can be milled in, like the channels 19', 20 'and those aligned with one another Gas passage openings in the edge region of the respective plastic plates 6 ', 6 ", which form the vertical gas channels 21, 23.

From FIG. 1 it can also be seen that the electrodes 8, 9 extend laterally beyond the seals delimiting the electrolyte chambers 4, 5 and the gas space 22 and in this way are also penetrated by the vertical gas channels 21, 23.

In the outermost edge region, the plastic plates 6 ′, 6 ″ are provided with edge recesses 24 which are aligned with one another. Electrical connections 7 for the anode 8 (top) and the cathode 9 (bottom) are provided on both sides at the top and bottom with current strips 2 , and in the middle plastic plates 6 "electrical connections 7 'between cathode 9 and anode 8 of successive electrolysis cells. The busbars 2 and the connections 7 and connections 7 'can be made of a material that conducts electricity well, such as copper. The connections 7 and the connections 7 'can furthermore be pressed with anode 8 and cathode 9 via clamping elements (not shown), so that welding is unnecessary.

FIG. 2 illustrates how sealing takes place in the area of an electrolyte supply opening 19 or an electrolyte discharge opening 20. While the gas diffusion electrode covering 17 runs continuously on the cathode 9 into the edge area of the cathode 9, where it is covered by a sealing element 12, the membrane or the diaphragm 18 is angled upward in the area of the openings 19, 20 and is supported on one Sealing frame 15 guided, which has no greater thickness than the anode 8. The sealing frame 15 is housed in a larger recess 27 of the anode 8 and delimits the openings 19, 20 inside. Above the angled area of the membrane or diaphragm 18 is a Sealing element 14 over the anode 8 and up over the sealing frame 15. In the vicinity of the openings 19, 20, the membrane or the diaphragm 18 is clamped in a gas-tight and liquid-tight manner with the edge facing the openings 19, 20 between the sealing frame 15 and the sealing element 14.

It can be seen from FIG. 3 that the sealing frame 15, which is shown in vertical section II in FIG. 2, has a narrow shape, the short sides of which are designed as arches, and thus surrounds the openings 19, 20.

LIST OF REFERENCE NUMBERS

1 electroyt

2 busbars, e.g. made of copper 3 gas, e.g. 0 ₂ or air

4 first electrolyte chamber (anode compartment)

5 second electrolyte chamber (cathode compartment)

6 housing

6 ', 6 "plastic plates 7, 7' electrical connections or connections

8 anode, patterned area covered with membrane or diaphragm

9 Cathode, patterned area covered with gas diffusion electrode

10 connecting pipeline 11, 12, sealing elements 13, 14 sealing elements

15 sealing frame

16 electrolyte supply and discharge opening of the first electrolyte chamber (anode space)

16 'Electrolyte supply and discharge channel of the first electrolyte chamber (anode space)

17 gas diffusion electrode

18 membrane or diaphragm

19 Electrolyte feed opening of the second electrolyte chamber (cathode compartment) 19 'Electrolyte feed channel of the second electrolyte chamber

(Cathode space) 0 electrolyte discharge opening of the second electrolyte chamber (cathode space) 0 'electrolyte discharge channel of the second electrolyte chamber (cathode space) Gas supply channel

headspace

Gas discharge channel

edge cutouts

outlet pipe

feed pipe

recess

Claims

claims

1. Electrolysis device, with at least one horizontally lying electrolysis cell, which has a housing (6) and the anode (8) with a membrane or a diaphragm (18) and the cathode (9) with a gas diffusion electrode (17) are equipped with means for supplying (21) and removing (23) gas (3) into and from the gas space (22) of the cathode (9) and means for supplying (16; 19) and removing (16; 20) electrolytes (1 ) into or out of a first (n) electrolyte chamber (4) and into or out of a second (n) electrolyte chamber (5), characterized in that the anode (8) and the membrane or the diaphragm (18) each have at least one opening for supplying (19) electrolytes (1) into the second electrolyte chamber (5) and at least one further opening for discharging (20) electrolytes (1) from the second electrolyte chamber (5).

2. Electrolysis device according to claim 1, characterized in that the membrane or the diaphragm (18) in the region of an electrolyte supply opening (19) and an electrolyte discharge opening (20) by means of a sealing frame (15), the thickness of which is not the thickness of the anode (8) exceeds, and on the sealing frame (15) and the anode (8) adjacent seals (14) is clamped gas and liquid-tight.

3. Electrolysis device according to claim 1 or 2, characterized in that the housing (6) of the electrolyte cell of two plastic plates (6, 6 ', 6 ") is formed, between which the electrolyte chambers (11 to 13) using frame-like seals (11 to 13) 4, 5) and the gas space (22) are limited.

4. Electrolysis device according to claim 3, characterized in that the plastic plates (6 ', 6 ") consist of different material.

5. Electrolysis device according to claim 3 or 4, characterized in that a plastic plate (6 ") consists of two different materials.

6. Electrolysis device according to one of claims 1 to 5, characterized in that in the case of a plurality of electrolyte cells arranged one above the other, the middle (n) plastic plate (s) (6, 6 ") in each case forms the bottom of the upper electrolyte cell and the lid of the electrolyte cell located underneath ( form).

7. Electrolysis device according to one of claims 1 to 6, characterized in that in the plastic plates (6 ', 6 ") electrolyte supply (19 ^' ) and discharge channels (20 ^' ) of the second electrolyte chamber (5) are introduced, in particular milled.

8. Electrolysis device according to one of claims 1 to 7, characterized in that in the plastic plates (6 ', 6 ") electrolyte supply and discharge channels (16') of the first electrolyte chamber (4) are introduced, in particular milled.

9. Electrolysis device according to one of claims 1 to 8, characterized in that in the case of a plurality of electrolysis cells arranged one above the other, the respective electrolyte discharge channels (16 ', 20 ^' ) of the upper electrolysis cell with the respective electrolyte supply channels (16 ^' , 19 ^' ) of the electrolysis cell located below via external ones Connection pipes (10) are in flow connection.

10. Electrolysis device according to one of claims 1 to 9, characterized in that the anode (8) and the cathode (9) via the Eletrolytkammem (4, 5) and the gas space (22) outwardly bounding frame-like seals (11 to 14) and outside the chambers (4, 5; 22) with their electrical connections (7) or connections (7 ^' ) to each other are provided.

11. Electrolysis device according to one of the preceding claims, characterized in that the electrical connections (7) to upper and lower busbars (2), for. B. made of copper.

12. Electrolysis device according to one of the preceding claims, characterized in that the connections (7) and / or the connections (7 ^' ) are received in edge recesses (24) of the plastic plates (6', 6 ").

13. Electrolysis device according to one of claims 1 to 12, characterized in that the connections (7) and / or the connections (7 ^' ) are pressed via clamping elements with anode (8) and cathode (9).

14. Electrolysis device according to one of the preceding claims, characterized in that a gas supply channel (21) and a gas discharge channel (23) which delimit the electrolysis cell (s) plastic plates (6 ', 6 ^" ) and optionally the anode (8) and the cathode ( 9), sealing against the electrolyte chambers (4, 5) and in flow connection with the respective gas space (22) from top to bottom.