WO2025119649A1

WO2025119649A1 - Sealing of an electrolysis stack

Info

Publication number: WO2025119649A1
Application number: PCT/EP2024/082969
Authority: WO
Inventors: Michael Kress; Dennis Widuch
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2023-12-07
Filing date: 2024-11-20
Publication date: 2025-06-12
Anticipated expiration: 2026-06-07
Also published as: EP4567155A1

Abstract

Electrolysis stack comprising multiple electrolysis cells that each comprise an anode space having an anode, a cathode space having a cathode, and a diaphragm, wherein the electrolysis stack also has a conduit which passes at least through the diaphragms and which has a respective anode-side connection to the anode spaces and/or a respective cathode-side connection to the cathode spaces, wherein the conduit is composed of multiple segments, wherein the segments are each formed circumferentially around an interior space of the conduit, wherein the segments are each formed by a first portion and a second portion, wherein one of the diaphragms and an adjoining elastic element formed circumferentially around the interior space of the conduit are held in each case between the first portion and the second portion.

Description

SEALING OF AN ELECTROLYSIS STACK

The invention relates to an electrolysis stack having multiple electrolysis cells. The invention further relates to use of such an electrolysis stack.

Electrolysis of water, for example, is performed on an industrial scale, usually with what are called electrolysis stacks. These are a multitude of electrolysis cells in series. Conduits are often provided for the feeding of the electrolyte and for the draining of the electrolysis products, and these are conducted through the diaphragms of the electrolysis cell. In the case of known solutions of this kind, however, the sealing of these conduits is difficult. This is true in particular with regard to the thermal expansion to which the electrolysis stacks are often subject in operation. Thermal expansion is often a problem because plastic and steel, for example, have different expansion by several orders of magnitude.

Reliable sealing is important because it may otherwise be the case that the electrolysis products mix with one another. If, for example, there is mixing between hydrogen and oxygen as the electrolysis products of a water electrolysis, an explosive mixture may arise.

An electrolysis stack may have several hundred or even more than one thousand seals. If one fails, it may be difficult to find and exchange. For that specific reason, reliable sealing is of major importance.

Solutions disclosed in the prior art are in particular those in which asbestos diaphragms are used. The thickness of the diaphragms may, for example, be 3 mm. The use of asbestos makes these diaphragms highly compressible. As a result, it is easily possible to achieve a seal by pushing conduit pieces onto the diaphragms. Nowadays, however, the use of asbestos is no longer desirable or not even permissible. No comparable construction is directly possible with alternatively available materials for the diaphragms.

It is an object of the present invention to create a simple and reliable means with respect to the prior art of sealing conduits in an electrolysis stack. In particular, asbestos is to be dispensed with.

These objects are achieved by the electrolysis stack and the use thereof according to the independent claims. Further advantageous embodiments are specified in the dependent claims. The features illustrated in the claims and in the description are combinable with one another in any technologically meaningful manner.

The invention presents an electrolysis stack. The electrolysis stack comprises multiple electrolysis cells that are held adjacent to one another in a row along an axis, wherein the electrolysis cells each comprise an anode space having an anode, a cathode space having a cathode, and a diaphragm disposed between the anode space and the cathode space, wherein the electrolysis stack also has a conduit which passes at least through the diaphragms and which has a respective anode-side connection to the anode spaces and/or a respective cathode-side connection to the cathode spaces, wherein the conduit is composed of multiple segments, wherein the segments are each formed circumferentially around an interior space of the conduit, wherein the segments are each formed by a first portion and a second portion, wherein one of the diaphragms and an adjoining elastic element formed around the interior space of the conduit are held in each case between the first portion and the second portion.

The electrolysis stack described is preferably set up for water electrolysis. Hydrogen and oxygen can be obtained as electrolysis products by the water electrolysis. The electrolyte may be pure water or a water-containing mixture. In particular, it is preferable that the electrolysis stack is set up for alkaline electrolysis. But the advantages described herein can be achieved irrespective of which electrolyte is used and which electrolysis products are obtained. The electrolysis stack is preferably set up for high- pressure electrolysis. This is understood herein to mean electrolysis with an operating pressure of at least 10 bar. Specifically in that context, the advantages described hereinafter in relation to sealing are of relevance.

The electrolysis stack comprises multiple electrolysis cells. In each of the electrolysis cells, the electrolysis may be conducted independently of the other electrolysis cells. In order to be able to obtain the electrolysis products on a large scale, several of the electrolysis cells are provided. The electrolysis cells are held adjacent to one another in a row along an axis. The electrolysis cells are preferably pressed against one another. This can be achieved, for example, via tie rods. These are rods which are arranged parallel to the electrolysis cells and by means of which a force is exerted on the electrolysis cells.

The electrolysis cells each comprise an anode space having an anode, a cathode space having a cathode, and a diaphragm disposed between the anode space and the cathode space. The anodes may be disposed within the respective anode space or at the edge of the respective anode space. The cathodes may be disposed within the respective cathode space or at the edge of the respective cathode space. The anodes and the cathodes may each be composed of one piece of metal or of multiple parts. For example, the cathodes may each be formed by a plate and an adjoining support weave made of wire. The plate may be very thin and very soft. The support weave may keep the plate in shape. In general, however, it is immaterial in respect of the concept described here how the anode spaces, anodes, cathode spaces and cathodes are configured. In particular, it is also possible to use any configuration of anode spaces, anodes, cathode spaces and cathodes that is known from the prior art.

The anode spaces and/or the cathode spaces are preferably each designed to withstand a pressure of at least 10 bar. The diaphragms are preferably asbestos-free.

The electrolysis stack also has a conduit which passes at least through the diaphragms and which has a respective anode-side connection to the anode spaces and/or a respective cathode-side connection to the cathode spaces. The conduit may also pass through further elements, especially the anodes and the cathodes, in addition to the diaphragms. If bipolar plates are used, the conduit may also pass through the bipolar plates. If the anodes and/or the cathodes are each composed of multiple parts, the conduit may in each case pass through one or more of these parts. It may be advisable for practical reasons that the conduit also passes through further elements in addition to the diaphragms. In respect of the concept described here, it is sufficient, however, that the conduit passes through the diaphragms.

If the conduit has the anode-side connections but not the cathode-side connections, the electrolysis stack is preferably set up to feed an anolyte to the anode spaces via the conduit or to drain anode-side electrolysis products from the anode spaces. The conduit in the first case may be referred to as an anode-side feed, and in the second case as an anode-side drain.

If the conduit has the cathode-side connections but not the anode-side connections, the electrolysis stack is preferably set up to feed a catholyte to the cathode spaces via the conduit or to drain cathode-side electrolysis products from the cathode spaces. The conduit in the first case may be referred to as a cathode-side feed, and in the second case as a cathode-side drain.

If the conduit has the anode-side connections and the cathode-side connections, the electrolysis stack is preferably set up to feed an electrolyte to the anode spaces and the cathode spaces via the conduit. The conduit in that case may be referred to as a feed.

The advantages described herein may be achieved for all the above-described feeds and drains. It is therefore sufficient that the electrolysis stack has a conduit formed as described in order to achieve the benefits of the invention. It is immaterial here whether this conduit is a feed or a drain. It is also immaterial whether this conduit is connected solely to the anode spaces, solely to the cathode spaces, or to the anode spaces and to the cathode spaces at the same time. It is preferable, however, that the electrolysis stack has multiple conduits formed as described. This is the case especially in the embodiments that follow.

In a first embodiment, the electrolysis stack has an anode-side feed, an anode-side drain, a cathode-side feed and a cathode-side drain. The anode-side feed has a respective anode-side connection to the anode spaces. The anode-side drain has a respective anode-side connection to the anode spaces. The cathode-side feed has a respective cathode-side connection to the cathode spaces. The cathode-side drain has a respective cathode-side connection to the cathode spaces. The electrolysis stack is set up to feed an anolyte to the anode spaces via the anode-side feed, to drain anode-side electrolysis products from the anode spaces via the anode-side drain, to feed a catholyte to the cathode spaces via the cathode-side feed, and to drain cathode-side electrolysis products from the cathode spaces via the cathode-side drain.

In a second embodiment, the electrolysis stack has a feed, an anode-side drain and a cathode-side drain. The feed has a respective anode-side connection to the anode spaces and a respective cathode-side connection to the cathode spaces. The anodeside drain has a respective anode-side connection to the anode spaces. The cathodeside drain has a respective cathode-side connection to the cathode spaces. The electrolysis stack is set up to feed an electrolyte to the anode spaces and the cathode spaces via the feed, to drain anode-side electrolysis products from the anode spaces via the anode-side drain, and to drain cathode-side electrolysis products from the cathode spaces via the cathode-side drain.

What was stated herein in respect of the conduit is respectively applicable correspondingly to the feeds and drains described for the first embodiment and for the second embodiment. Merely for the sake of simplicity, the text that follows will refer generally to “the conduit”.

The conduit is composed of several segments. The segments each constitute an axial section of the conduit, where adjacent segments may overlap axially. The configuration of the conduit with segments can facilitate the production and maintenance of the electrolysis stack. The segments may be fixedly bonded to one another. However, this is not a requirement. The segments may also be loosely attached to one another and held together by means of an external force. This external force may be the same force that also holds the electrolysis cells together.

The segments are each formed circumferentially around an interior space of the conduit. The segments may thus be regarded as conduit sections or as pipe pieces. The segments are each formed by a first portion and a second portion. The first portion and the second portion are preferably each formed circumferentially around the interior space of the conduit.

The division of the segments into the first portion and the second portion can facilitate the production of the segments. In addition, this division enables reliable holding of the diaphragms against the conduit. For this purpose, it is envisaged that one of the diaphragms and an adjoining elastic element formed circumferentially around the interior space of the conduit are held in each case between the first portion and the second portion. The diaphragm may be clamped between the two portions. The diaphragm may be held in a force-fitting manner between the two portions, especially by means of the elastic element. The elastic element is preferably compressible.

The elastic element may contribute to reliable holding of the diaphragm between the two portions. The elastic element may press the diaphragm against the second portion. The diaphragm preferably adjoins a face of the second portion. The face is preferably structured. This may contribute to holding of the diaphragm against the face with sealing. Even if the elastic element serves primarily to reliably hold the diaphragm, the elastic element may also contribute to sealing. This is supported by the structured configuration of the face of the second portion. The face preferably has sealing grooves. This is an example of the described structured configuration of the face.

The elastic element is preferably in annular form. The elastic element more preferably takes the form of an O-ring. The elastic element is preferably formed from a plastic. The use of the elastic element means that the diaphragms need not be elastic, as is the case for the asbestos diaphragms known from the prior art.

In the electrolysis stack described, the sealing is no longer achieved in that conduit pieces are pressed onto compressible diaphragms. Instead, it is sufficient that the segments of the conduit are held against one another. The diaphragms are held by the elastic element. The elastic element contributes to sealing of the conduit.

For achievement of the advantages described herein, it is immaterial how many segments are used to assemble the conduit. It is been found to be particularly advantageous that each of the electrolysis cells is assigned exactly one of the segments. The conduit in that case has exactly one segment per electrolysis cell. In that case, it is preferable that the diaphragm of the electrolysis cell assigned to the segment and an elastic element adjoining the diaphragm and formed circumferentially around the interior space of the conduit are held in each case between the first portion and the second portion. If the conduit has exactly one segment for each of the electrolysis cells, all the diaphragms may be held as described above. However, there is also nothing to oppose provision of more or fewer segments than electrolysis cells.

If bipolar plates are used, the division of the conduit into the segments may also be utilized to hold the bipolar plates. It is envisaged that bipolar plates are disposed between adjacent electrolysis cells, which are each held between two adjacent segments. The bipolar plates are preferably held, especially clamped, in each case between the first portion of one of the segments and the second portion of the next segment in axial direction. The fact that the bipolar plates are also held via the conduit can increase the stability of the electrolysis stack.

In a preferred embodiment of the electrolysis stack, the segments each have a projection that extends in axial direction and an opening, wherein the projections each engage in the opening of the next segment in axial direction.

In the case of two adjoining segments, the projection of one segment thus engages in the opening of the other segment. This allows the segments to be held together reliably. It is sufficient that the projection is inserted into the opening. No force-fitting connection between projection and opening is required. The segments may also be loosely attached to one another and held together by means of an external force. This external force may be the same force that also holds the electrolysis cells together.

The projection is preferably formed circumferentially around the interior space of the conduit. The projection may thus be in annular form. The opening preferably takes the form of a counterpart to the projection of the next segment in axial direction. This is already implicit in the formulation that the projection engages in the opening. The opening is preferably formed circumferentially around the interior space of the conduit. The opening may thus take the form of an annular recess.

In a further preferred embodiment of the electrolysis stack, the projections each engage in the opening of the next segment in axial direction with sealing by an O-ring.

The conduit is formed by the mutually adjoining segments. For the conduit to have integrity, it may be sufficient to press the segments against one another. In the present embodiment, however, O-rings are additionally provided for sealing of the conduit. O- rings between the segments seal the interior space of the conduit with respect to an environment of the conduit - i.e. in particular with respect to the anode spaces and the cathode spaces. This sealing is not a barrier to the described attachment of the conduit to the anode spaces and/or the cathode spaces. The O-ring may be held in each case in a gap between opening and engaging projection. The O-ring is preferably in contact both with the projection and with an edge of the opening. The O-ring thus bridges and hence seals the gap. The O-ring is preferably arranged radially between the edge of the opening and the projection engaging in the opening.

In this embodiment, the O-ring may be provided for the purpose of sealing the conduit, while the elastic element is provided for the purpose of holding the diaphragms. These two functions may thus be separated from one another. Nevertheless, the elastic element may also contribute to sealing of the conduit.

In a further preferred embodiment of the electrolysis stack, the openings each have, on a radially inward side, a recess formed circumferentially around the interior space of the conduit, wherein the O-rings are each partly accommodated in one of the recesses.

The O-ring in this embodiment is arranged radially between the edge of the opening and the projection engaging in the opening. This may in principle be the case in that the O-ring is arranged radially within the projection or radially outside the projection. In the present embodiment, the O-ring is arranged radially within the projection. Correspondingly, a recess for the O-ring is provided on the radially inward side of the opening. The O-ring is accommodated partly but not completely therein. The O-ring thus projects radially outward beyond the recess. As a result, the O-ring is able to fulfil its function of sealing a gap between projection and opening. The recess allows the O-ring to be held in position. This facilitates the production and maintenance of the electrolysis stack.

In a further preferred embodiment of the electrolysis stack, the openings and the projections each have a screw thread, wherein the projections each engage in the opening of the next segment in axial direction with connection by means of the screw thread.

The screw connection allows the projections to be held reliably in the corresponding openings. This increases the stability of the conduit.

As an alternative to the present embodiment, the projections may also be held force- fittingly, form-fittingly or force- and form-fittingly in the corresponding opening in some other way. The projections may alternatively engage loosely in the openings and be held therein by an external force. This external force may be the same force that also holds the electrolysis cells together. In a further preferred embodiment of the electrolysis stack, the segments are each spaced apart from the next segment in axial direction by a gap formed outside the projection.

In this embodiment, it is sufficient that the adjacent segments are in contact with one another in that the projection engages in the corresponding opening. Furthermore, the gap is formed between the segments. The gap has the advantage of being able to compensate for the thermal expansion of the segments. This can even make it possible to dispense with the springs that are customarily used on the tie rods.

In a further preferred embodiment of the electrolysis stack, the first portions and/or the second portions of the segments are each formed from a polymer. The “and” case is preferred.

It has been found that the use of polymer makes the production of the portions particularly simple.

In a further preferred embodiment of the electrolysis stack, the diaphragms each have a thickness of less than 1 mm.

The diaphragms preferably each have a thickness in the range from 0.01 to 0.8 mm.

This embodiment contrasts in particular with the solutions with asbestos diaphragms that are known from the prior art, which have a thickness of 3 mm for example. Instead, in the present embodiment, diaphragms having a thickness of less than 1 mm should be used, for example having a thickness of 0.5 mm. The diaphragms are preferably not compressible. The diaphragms are preferably asbestos-free. Because of the low thickness, there is no possibility of achieving sealing as in the prior art solely via the elasticity of the diaphragms and via external pressure. However, the described configuration of the segments with the elastic element nevertheless achieves good sealing.

Apart from that, the described form of the seal has the advantage over sealing by contact pressure of conduit pieces onto the diaphragms that thermal expansion has a smaller influence on integrity.

In a further preferred embodiment of the electrolysis stack, the diaphragms are held merely in a force-fitting manner between the elastic element and the second portion of the respective segment.

The diaphragms are held between the portions of the respective segment by means of the elastic element. In particular, the elastic element contributes to holding the diaphragms in a force-fitting manner. A further aspect of the invention presented is use of an electrolysis stack formed as described for alkaline electrolysis.

The described advantages and features of the electrolysis stack are employable in and applicable to the use, and vice versa. The electrolysis stack described is preferably set up for alkaline electrolysis

The electrolysis is preferably a high-pressure electrolysis. The electrolysis is preferably operated at an operating pressure of at least 10 bar, for example at an operating pressure of 30 bar. Specifically in connection with such high pressures, the advantages described in relation to sealing are of particular relevance.

The invention is elucidated in detail hereinafter with reference to the figures. The figures show a particularly preferred working example, but the invention is not limited thereto. The figures and the size ratios shown therein are merely schematic. The figures show:

Fig. 1 : an electrolysis stack according to the invention,

Fig. 2: a detail view of the electrolysis stack from Fig. 1 ,

Fig. 3: a further detail view of the electrolysis stack from Fig. 1 ,

Fig. 4: a segment for a conduit as usable in the electrolysis stack from Figs 1 to

3.

Fig. 1 shows an electrolysis stack 1 having four electrolysis cells 2. The electrolysis stack 1 may be utilized for alkaline water electrolysis. The electrolysis cells 2 are held adjacent to one another in a row along an axis 3. The electrolysis cells 2 each comprise an anode space 4 having an anode 6, a cathode space 5 having a cathode 7, and a diaphragm 8 disposed between the anode space 4 and the cathode space 5. The diaphragms 8 each have a thickness of less than 1 mm. In the diagram of Fig. 1 , the thickness of the diaphragms 8 is the extent of the diaphragms 8 in right/left direction. The anodes 6 and the cathodes 7 are each arranged close to the diaphragm 8 in between. The electrolysis cells 2 are connected to one another by bipolar plates 24. At the left-hand and right-hand edges of the electrolysis stack 1 , an end plate 25 is provided rather than a bipolar plate 24. The anodes 6 and the cathodes 7 are each connected in an electrically conductive manner to one of the bipolar plates 24 or one of the end plates 25. This is indicated schematically by hatched connections.

The electrolysis stack 1 also has two conduits 9 that pass through each of the diaphragms 8, the anodes 6 and the cathodes 7. The conduit 9 shown at the top in Fig. 1 has a respective anode-side connection 10 to the anode spaces 4. An anolyte may be supplied to the anode spaces 4 via said conduit 9. Alternatively, a mixture of anodeside reaction products and unconsumed anolyte may be drained from the anode spaces 4 via said conduit 9. The conduit 9 shown at the bottom in Fig. 1 has a respective cathode-side connection 11 to the cathode spaces 5. A catholyte may be supplied to the cathode spaces 5 via said conduit 9. Alternatively, a mixture of cathode-side reaction products and unconsumed catholyte may be drained from the cathode spaces 5 via said conduit 9.

The conduits 9 are each composed of several segments 12. This is indicated schematically in Fig. 1 by dotted lines. This is shown more specifically in the figures that follow. Each of the electrolysis cells 2 is assigned one of the segments 12. The segments 12 are each formed circumferentially around an interior space 13 of the conduit 9.

Fig. 2 shows a detail of the electrolysis stack 1 from Fig. 1. One of the conduits 9 is apparent. The diagram in Fig. 2 is applicable to both the conduits 9 shown in Fig. 1.

Orifices are apparent over the circumference of the conduit 9, and these constitute the anode-side connections 10 or the cathode-side connections 11 . Three of the segments 12 are shown. These are shown in detail in the figures that follow.

Fig. 3 shows a detail from Fig. 2. Three of the segments 12 are also shown therein, albeit some of them incompletely. The segments 12 are each formed by a first portion 14 and a second portion 15 composed of a polymer. The diaphragm 8 of the electrolysis cell 2 assigned to the segment 12 and an elastic element 16 adjoining the diaphragm 8 and formed circumferentially around the interior space 13 of the conduit 9 are held in each case between the first portion 14 and the second portion 15. The diaphragms 8 are held merely in a force-fitting manner between the elastic element 16 and the second portion 15 of the segment 12 assigned to the respective electrolysis cell 1.

The segments 12 each have a projection 17 extending in axial direction (to the left in the example of Fig. 3) and an opening 18. The projections 17 each engage in the opening 18 of the next segment 12 in axial direction with sealing by an O-ring 19. For this purpose, the openings 18 each have, on a radially inward side 20, a recess 21 formed circumferentially around the interior space 13 of the conduit 9. The O-rings 19 are each partly accommodated in one of the recesses 21.

The openings 18 and the projections 17 each have a screw thread 22. The projections 17 each engage in the opening 18 of the next segment 12 in axial direction with connection by means of the screw thread 22. The segments 12 are each spaced apart from the next segment 12 in axial direction by a gap 23 formed outside the projection 17.

It is also apparent from Fig. 3 that the bipolar plates 24 are held between the segments 12. For this purpose, the bipolar plates 24 are clamped in each case between the first portion 14 of one of the segments 12 and the second portion 15 of the next segment 12 in axial direction.

Fig. 4 shows a segment 12 for a conduit 9 as usable in the electrolysis stack 1 from Figs 1 to 3. What are apparent in particular are the first portion 14, the second portion 15, the elastic element 16 and the O-ring 19.

List of reference numerals electrolysis stack electrolysis cell axis anode space cathode space anode cathode diaphragm conduit anode-side connection cathode-side connection segment interior space first portion second portion elastic element projection opening O-ring radially inward side recess screw thread gap bipolar plate end plate

Claims

1 . Electrolysis stack (1) comprising multiple electrolysis cells (2) that are held adjacent to one another in a row along an axis (3), wherein the electrolysis cells (2) each comprise an anode space (4) having an anode (6), a cathode space (5) having a cathode (7), and a diaphragm (8) disposed between the anode space (4) and the cathode space (5), wherein the electrolysis stack (1) also has a conduit (9) which passes at least through the diaphragms (8) and which has a respective anode-side connection (10) to the anode spaces (4) and/or a respective cathode-side connection (11) to the cathode spaces (5), wherein the conduit (9) is composed of multiple segments (12), wherein the segments (12) are each formed circumferentially around an interior space (13) of the conduit (9), wherein the segments (12) are each formed by a first portion (14) and a second portion (15), wherein one of the diaphragms (8) and an adjoining elastic element (16) formed circumferentially around the interior space (13) of the conduit (9) are held in each case between the first portion (14) and the second portion (15).

2. Electrolysis stack (1) according to Claim 1 , wherein the segments (12) each have a projection (17) that extends in axial direction and an opening (18), and wherein the projections (17) each engage in the opening (18) of the next segment (12) in axial direction.

3. Electrolysis stack (1) according to Claim 2, wherein the projections (17) each engage in the opening (18) of the next segment (12) in axial direction with sealing by an O-ring (19).

4. Electrolysis stack (1) according to Claim 3, wherein the openings (18) each have, on a radially inward side (20), a recess (21) formed circumferentially around the interior space (13) of the conduit (9), and wherein the O-rings (19) are each partly accommodated in one of the recesses (21).

5. Electrolysis stack (1) according to any of Claims 2 to 4, wherein the openings (18) and the projections (17) each have a screw thread (22), and wherein the projections (17) each engage in the opening (18) of the next segment (12) in axial direction with connection by means of the screw thread (22).

6. Electrolysis stack (1) according to any of Claims 2 to 5, wherein the segments (12) are each spaced apart from the next segment (12) in axial direction by a gap (23) formed outside the projection (17).

7. Electrolysis stack (1) according to any of the preceding claims, wherein the first portions (14) and/or the second portions (15) of the segments (12) are each formed from a polymer.

8. Electrolysis stack (1) according to any of the preceding claims, wherein the dia- phragms (8) each have a thickness of less than 1 mm.

9. Electrolysis stack (1) according to any of the preceding claims, wherein the diaphragms (8) are held merely in a force-fitting manner between the elastic element (16) and the second portion (15) of the respective segment (12).

10. Use of an electrolysis stack (1) according to any of the preceding claims for alka- line electrolysis.