Electrolyzer

Abstract

The present invention relates to a cell stack type electrolytic cell comprising first and second end plates having a plurality of cells axially stapled between the cell stack, a manifold for electrolyte flow from an electrolyte inlet of one of the end plates comprising a plurality of redirecting sections for redirecting the primarily axial electrolyte flow into a primarily radial plane of electrolyte flow, and a bypass at one of the redirecting sections for directing the electrolyte flow around another of the redirecting sections that is axially closer to the electrolyte inlet than the one of the redirecting sections.

Description

[Technical field]

[0001] The present invention relates to the field of electrolytic cells, and in particular to a cell stack type electrolytic cell comprising first and second end plates having a cell stack with a number of cells axially stapled therebetween, and a manifold for electrolyte flow from an electrolyte inlet of one of the end plates, the manifold comprising a number of redirectors for redirecting a predominantly axial electrolyte flow into an electrolyte flow in a predominantly radial plane. [Background technology]

[0002] Such electrolytic layers of the cell stack type are well known in the art and are disclosed, for example, in EP 0 212 240 B1 or DE 10 2014 010 813 A1.

[0003] During operation of such an electrolytic cell, when the cell frames are stapled together to form a cell stack, an electrolyte, for example a KOH solution, flows through the manifold or manifolds formed by the holes and openings in the cell frames, thereby passing through the interior active areas of the cells.

[0004] However, it has been found that such conventional electrolytic cells can suffer from poor performance due to the generation of unwanted electrical currents.

[0005] The underlying objective of the present invention is therefore to provide an electrolytic cell which has a good combination of reasonably stable operating conditions and yet sufficiently simple construction and flexibility of use. Summary of the Invention

[0006] To this end, the invention provides an electrolytic cell as initially introduced, which is essentially characterized by a bypass (21) for directing the electrolyte flow to one of the diverters, bypassing another of the diverters which is closer to the electrolyte inlet in the axial direction (X) than said one of the diverters.

[0007] With such a configuration, it has been identified that non-uniformity in pressure loss in electrolyte supply across the cell is responsible for the risk of inefficient cooling of the process, especially near the side opposite to the electrolyte inlet and outlet, and therefore at least partially responsible for the negative impact on the performance efficiency of conventional electrolysers. The bypass makes the pressure drop characteristics across the cell more balanced or homogenous, allowing better performance with a given number of cells or allowing an increase in the number of cells without degradation, relative to conventional electrolysers with fewer cells. Furthermore, with regard to electrical coupling, in an apparatus / plant with more than two electrolysers, there is still the possibility to connect two electrolysers in series with one rectifier. With the bypass, the flow does not have (radial) communication to the bypassed turn, but is forced to skip said turn at the respective axial position.

[0008] As will be explained later in the detailed description of the drawings, for the sake of simplicity, the division of the cell into half-cells is omitted, and the following description therefore applies separately to the electrolyte flow through the anode half-cell on one side and the cathode half-cell on the other side, respectively.

[0009] That is, if the cell structure itself comprises a bipolar plate and a membrane or diaphragm, and there is a separate channel on the inlet side, one for each of two groups of half cells, the present invention provides a cell stack type electrolyzer comprising first and second end plates having a cell stack with a number of cells stapled axially therebetween, and a manifold for electrolyte flow from an electrolyte inlet of one of said end plates, the cell comprising a bipolar plate, a membrane / diaphragm, and having an active area on the inside, the cell being further subdivided into half cells to have an anode side half cell and a cathode side half cell, the manifold being mainly for axial electrolyte flow. the electrolyte inlet port of the anode half-cell and the cathode half-cell are arranged in a radial direction such that the electrolyte inlet port of the anode half-cell is directed toward the electrolyte inlet port of the anode half-cell.

[0010] In these configurations, the multiple turn sections include multiple first or anode side turn sections and multiple second or cathode side turn sections, such that for the anode side insert flow, the flow has no (radial) communication to the respective bypassed anode side turn sections, but is forced to skip said turn sections at the respective axial positions, and vice versa for the cathode side.

[0011] In the case of using a common channel for all types of half-cells, the redirections are understood as being respectively assigned to one cell, the redirections being of course each comprising an anode branch and a cathode branch, as shown in the following figure 1, and the bypass is such that both the anode branch and the cathode branch of the redirection part assigned to one cell are skipped by the flow in the common channel, which differs in particular from the configuration known, for example, from US 4,950,370 A, where, as can be seen from said document, from the flow in one axial channel, a radial redirection takes place in succession, and only the cells are skipped which are provided with a flow from another channel.

[0012] That is, the bypass according to the invention results from the flow flowing in the same axial channel, i.e. the bypassed turn and the turn into which the flow skipping the bypass turn is directed start from the same axial flow path. This does not mean that the invention excludes solutions in which some of the cells are fed through one axial channel and other cells are fed through another axial channel. However, the bypass and skip according to the invention should be understood with reference to one and the same channel.

[0013] The invention thus provides an electrolytic cell comprising first and second end plates having a cell stack with a plurality of cells stapled axially therebetween, and a manifold for electrolyte flow from an electrolyte inlet of one of said end plates, the manifold comprising a plurality of redirecting sections for redirecting the electrolyte flow in a predominantly axial channel of said manifold into an electrolyte flow in a predominantly radial plane, characterized by a bypass for directing the electrolyte flow to one of said redirecting sections directly connected to said predominantly axial channel by bypassing another of said redirecting sections directly connected to said predominantly axial channel and axially closer to the electrolyte inlet than said one of said redirecting sections. The term "predominantly axial" is to be understood in the usual way that the directional component in the direction of extension of the channel in the axial direction is the predominant directional component, i.e. the axial component is greater than the directional component in the radial plane.

[0014] This reference / attribution of one turnaround and another (bypassed / skipped) turnaround to the same channel also applies when there is a separate channel, one for each group of anode side half-cells and cathode side half-cells.

[0015] In a preferred embodiment, all turning points are directly connected to one channel, preferably an axial channel having the same radial and azimuthal position (if this is the channel for all types of half-cells), with all turning points respectively belonging to the anode side being directly connected to one and the same such channel for the anode side electrolyte flow supply, while all turning points respectively belonging to the cathode side being directly connected to one and the same such channel for the cathode side half-cell electrolyte flow supply.

[0016] In a preferred embodiment, the length of the flow path from the electrolyte inlet to the other redirection section is greater than the length of the flow path from the electrolyte inlet to the one of the redirection sections. Even if there is no unidirectional flow, simple channel / passage structures can be used.

[0017] In a further preferred embodiment, more than the first plurality of turning sections are bypassed, preferably more than 20%, in particular more than 33%, which leads to a further increase in pressure loss axially further away from the cathode end plate. On the other hand, it is preferred that more than 20%, in particular more than 25%, of the third plurality of turning sections are not bypassed. This shifts the pressure loss problem to the other end by a limited amount, but the cooling problem is less severe due to the temperature gradient established in the electrolyte flow during operation. The invention is therefore particularly concerned with partial bypassing, i.e. there is no direct flow access to all cells in one and the same flow flow direction, in the order of the order of the arrangement of the cells.

[0018] Preferably, more than 20%, in particular more than 33%, of the flow upstream to the second plurality of turns is via said bypass. The second plurality may coincide with the third plurality. In a fairly simple arrangement, the second plurality preferably comprises less than 67% of the total cells, in particular less than 60% thereof.

[0019] In a further preferred embodiment, the manifold includes one or more branches that direct electrolyte flow in both axial directions, allowing the use of different axial electrolyte flow passages.

[0020] In a further preferred embodiment, the branch has an essentially radial and / or azimuthal electrolyte flow before the branch, i.e. the bypass is shifted radially and / or circumferentially (azimuthally) with respect to a projection plane perpendicular to the axial direction of the cell stack, in particular with respect to the channel extending axially through the cell and in which the turning section is located. In a preferred embodiment, the axial bypass channel and the channel adjacent to the turning section are displaced azimuthally with respect to each other. This allows for a more compact frame structure.

[0021] In a further preferred embodiment, the length of the flow path from the electrolyte inlet to the axially furthest turn is shorter than the length of the flow path from the electrolyte inlet to the axially nearest turn, which creates an asymmetric distribution of flow path lengths but further improves the pressure drop situation to some extent.

[0022] In a further preferred embodiment, it is provided that the electrolytic layer has axial channels that extend through more than 20%, in particular more than 33%, more preferably more than 50%, in particular through all the cells of the cell frame, said channels connecting a number of redirections. It is also envisaged to have more such channels, each connecting a part of a number of redirections.

[0023] In a further preferred embodiment, the axial position of at least one branch is closer to another end plate than the end plate with the electrolyte inlet, in particular at least 4%, preferably at least 8%, in particular at least 12%, which provides a reasonable distribution of the flow channel lengths.

[0024] In a further preferred embodiment, the difference in axial flow path portions of the total flow path length to the outlet of the flow path through the cell axially furthest from the electrolyte inlet on the one hand and the flow path through the cell axially nearest to said inlet on the other hand, divided by their sum, is less than 20%, preferably less than 12%, in particular less than 8%. This allows for more uniform flow path lengths, in particular with respect to the longest flow path length from the inlet through the cell to the outlet.

[0025] In a further preferred embodiment, it can be provided that the difference in the axial flow section of the total flow path length to the outlet of the flow path through the cell axially farthest from the electrolyte inlet on the one hand and the flow path through the cell axially nearest to said inlet on the other hand, divided by their sum, is greater than 4%, preferably greater than 8%, in particular greater than 12%. In particular, the branching and collecting parts (corresponding to the reverse branching part on the outlet side) can be provided only in one cell frame.

[0026] In a further preferred embodiment, the electrolytic cell comprises at least 30 cells, preferably at least 50 cells, in particular at least 80 cells. It is also envisaged to have at least 100 cells, or even at least 120 cells, or even at least 140 cells.

[0027] The cell structure itself may preferably comprise bipolar plates and electrodes as well as membranes or diaphragms in a single frame for each cell, in this respect the structure described in Figure 1A of DE102014010813A1 is incorporated by reference, irrespective of the presence of additional stiffening rings.

[0028] The present invention further provides an apparatus or plant comprising at least one rectifier having poles connected to the end plates of the electrolytic cells, and two electrolytic cells are connected in series to one of said at least one rectifier, one or both of said two electrolytic cells being configured according to any of the previous aspects.

[0029] Furthermore, the present invention also provides a method of performing electrolysis, in particular the electrolysis of water, by using one or more electrolytic cells configured according to any of the aforementioned aspects.

[0030] Further features, details and advantages of the invention will become apparent from the following description, which refers to the accompanying drawings. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 shows a schematic of an electrolytic cell with an electrolyte manifold. [Diagram 2] FIG. 2 shows a schematic of an electrolytic cell with an alternative electrolyte manifold. [Diagram 3] FIG. 3 shows a schematic of an electrolytic cell equipped with yet another electrolyte manifold. [Figure 4] FIG. 4 shows a schematic of an electrolytic cell equipped with yet another electrolyte manifold. [Figure 5a]FIG. 5a shows a cross section of one embodiment of a cell frame in the bypass region. [Figure 5b] FIG. 5b shows a cross section of one embodiment of a cell frame in the bypass region. [Figure 6a] FIG. 6a shows a cross section just beyond the bypass region. [Figure 6b] FIG. 6b shows a cross section beyond the bypass region. [Figure 7a] FIG. 7a shows a cross section of a cell frame including connecting passages. [Figure 7b] FIG. 7b shows a cross section of the cell frame including the connecting passages. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] As can be seen in Fig. 1, the electrolytic cell 100 comprises a stack 10 of cells stapled in the axial direction X between end plates 30 (anode side) and 40 (cathode side, grounded). In the illustrated embodiment, although not recognizable from the axial cross-section, the cells with their cell frames are circular in projection perpendicular to the axial direction X (Figs. 5-7). For the sake of simplicity, the subdivision of the cells into half-cells is omitted. It is to be understood that for the concrete realization of a cell made of bipolar plates, the following description applies separately to the electrolyte flow through the anode-side half-cell on one side and the cathode-side half-cell on the other side.

[0033] The cell frames have axially extending through holes which, in a stacked arrangement, form an axially extending channel or passage 20 on the inlet side and another axially extending channel or passage 20 on the outlet side. Electrolyte flows essentially axially through the inlet channel 20. At a turn 25 the electrolyte flow is directed to the cell interior active area 27, where the electrolyte flow is essentially in a radial plane perpendicular to the axial direction X. At the outlet side, a (reverse) turn 26 directs the radial electrolyte flow back to an essentially axial electrolyte flow.

[0034] Such an arrangement of cell staples 10 according to the above partial description of FIG. 1 is well known and conventionally, the inlets 41 and outlets 42 of the end plate 40 are flush with the channel 20, so that the ranking of the cells in their axial distance from the cathode end plate 40 with the inlets 41 and outlets 42 corresponds to the ranking of the associated turnarounds with respect to their operation relative to the electrolyte flow path in the channel 20 from the inlet 41.

[0035] In the embodiment of FIG. 1, the location of the inlet 41 in the radial plane is displaced relative to the location flush with the axial channel 20. Additionally, the cell frame of the cell closer to the cathode end plate 40 is provided with an additional through hole, which in the staple configuration forms a second channel or passage 21 that extends axially through the cells, parallel to the channel 20, approximately halfway through the cells of the cell staple 10 in the embodiment of FIG. 1. In the cell 12 that is approximately in the axial center of the cell staple 10, there is a connecting passage 23 that connects the second axial channel 21 to the (first) axial channel 20. This causes the electrolyte flow to enter the axial passage 20 rather at the axial center of the cell staple 10, despite being directed through the inlet 41 in the cathode end plate 40.

[0036] From here, the electrolyte flow is directed in an axial flow direction towards the anode end plate 30 on the one hand, and "counterflow" axially towards the cathode end plate 40 against said "forward" flow on the other hand. A further flow of electrolyte then passes again through the active area 27 of the cell through the turn 25 and thereafter is collected in the outlet axial channel 20 in this exemplary embodiment. The final electrolyte outflow is again displaced in a radial plane relative to the (first) passage 20 into a second axial passage 22 which in the illustrated embodiment is flush with the outlet 42 in the cathode end plate 40. In the embodiment shown in FIG. 1, the fluid connection between the outlet passages 20 and 22 is made via a portion 24 substantially diametrically opposite the connecting passage 23 in the cell frame of the cell 12. However, said connection can also be arranged in another axial position.

[0037] In the embodiment shown, there is only one connecting passage 23, 24 on the inlet side and one on the outlet side, respectively. However, in other embodiments not shown, there may be more of them. In such a case, the connecting parts can be throttled differently from each other so as to adjust the relative flow along all the flow paths through the different cells in terms of volume flow rate.

[0038] In the embodiment of Fig. 1, the displacement of the second axial passages 21, 22 relative to the axial passage 20 is shown as a radial displacement. This is one possible solution chosen for the sake of explanation and also for the sake of representation in the figures. However, it can also be configured, and is more preferred, as a circumferential displacement (azimuthal displacement) or a displacement including radial and azimuthal components.

[0039] 1, the connections between channels 21, 22 and 20 are approximately in the axial center of staple 10. However, in other embodiments having electrolytic cell 101 as shown in FIG. 2, an asymmetric arrangement can be used, with each of the connections being shifted away from the cathode side and toward the anode side.

[0040] In the embodiment shown in Figure 3 with electrolytic cell 102, there is a "double asymmetric arrangement" where the cathode side connection 23 is shifted with respect to the anode side while the outlet side connection 24 is shifted with respect to the cathode side (referenced to the axial centre of staple 10). In the embodiment of Figure 3, the flow path lengths of the cell axially closest to the cathode endplate 40 and the cell axially closest to the anode endplate 30 are essentially equal.

[0041] In the embodiment of Fig. 4 with electrolytic cell 103, the bypass is implemented in such a way that the division of the flow is already done outside the end plate: a part of the cells closer to the inlet side is fed via a first feed channel, while the other cells are fed bypassing the feed of said part. Also in the embodiment of Fig. 4, a modification in which the channels (shown radially displaced) are azimuthally displaced is possible and preferred.

[0042] Figure 5a shows a cross section of a cell frame 13' corresponding to the cell frame 13 of figure 1, but in a modified embodiment, the channel 21 is not radially displaced from the channel 20, but azimuthally displaced, like the channels 22, 20 for counterflow. References 41, 42 in figure 5a indicate the connection to the respective fluid inlet 41 and fluid outlet 42 of figure 1. Furthermore, as can be seen from the embodiment of figure 5a, on the inlet side there are channels 20 and 21 for each of the two groups of half-cells, in a symmetrical arrangement with respect to the outlet side, where separation is required. However, there is also the possibility of using only one channel 20 and 21 as a common channel for all types of half-cells. This is shown in figure 5b.

[0043] Figures 6a and 6b correspond to the different embodiment of Figures 5a and 5b, but for a cell frame 11' located in the place of the cell frame 11 of Figure 1. The black crosses of the channels 21, 22 indicate that there is no fluid passing through them. This is because the channels 21, 22 (see Figure 1) do not continue to the other end plate, but merge with the channel 20 at the connecting passage 23. As can be easily recognized from Figures 6a, 6b, through holes for the channels 21, 22 are not necessary and may not be present, but through holes can be present (even if they are not used), so that the cell frames 11' and 13' can be manufactured in the same way.

[0044] And the only cell frame that is manufactured separately (required) is the one that contains the connecting passage 23 (23') between the channels 20 and 21 on the inlet side and 22, 20 on the outlet side. Cross sections of these cell frames 12' are shown in Figure 7(a) (symmetrical arrangement) and in Figure 7(b) (one channel 20 on the inlet side only), where again the reference number 12' indicates that an embodiment is shown with an azimuthal displacement between the channel 22 and the bypass channels 21, 22, whereas in the diagrammatic representation for the cell 12 of Figure 1 there is a radial displacement (mainly for purposes of illustration, but also as an advantageous embodiment).

[0045] As can be seen from the above, the connection details can be varied based on the above characteristics. The presence of the bypass 21 achieves a more uniform pressure drop situation which is more favorable for the electrolyte flow, leading to improved performance of the electrolyzer.

[0046] The invention is not limited to the details given in the description of the drawings. Rather, the features of the above description and the following claims may be essential to the invention either alone or in any combination.

Claims

1. A cell stack type electrolytic cell (100, 101), first (30) and second (40) end plates having a cell stack with a plurality of cells (18, 13, 12, 11, 19) axially stapled therebetween; and a manifold for electrolyte flow from an electrolyte inlet (41) of one of said end plates, said manifold comprising a plurality of redirecting portions (25) for redirecting a primarily axial electrolyte flow into a primarily radial electrolyte flow; Equipped with an electrolytic cell characterized by a bypass (21) for directing the flow of electrolyte to one of the redirection sections (25k), bypassing another of the redirection sections (25j) that is closer to the electrolyte inlet in the axial direction (X) than the one of the redirection sections.

2. 2. The electrolytic cell of claim 1, wherein a flow path length from the electrolyte inlet to the other of the redirecting portions is greater than a flow path length from the electrolyte inlet to the one of the redirecting portions.

3. 2. An electrolysis device according to claim 1, wherein more than the first plurality of redirections are bypassed, preferably more than 20% thereof, in particular more than 33% thereof.

4. 2. An electrolytic cell according to claim 1, wherein the flow upstream to the second plurality of turns is preferably more than 20%, in particular more than 33%, via the bypass.

5. 2. The electrolytic cell of claim 1, wherein the manifold comprises one or more branches (23) for directing electrolyte flow in both axial directions.

6. 6. The electrolytic cell of claim 5, wherein the bifurcation has essentially radial and / or azimuthal electrolyte flow prior to bifurcation.

7. 2. The electrolytic cell of claim 1, wherein a length of a flow path from the electrolyte inlet to the redirection section axially furthest is less than a length of a flow path from the electrolyte inlet to the redirection section axially closest.

8. 2. The electrolytic cell according to claim 1, having axial channels extending through more than 20%, in particular more than 33%, more preferably more than 50%, in particular all the cells of the cell frame.

9. 6. The electrolytic cell according to claim 5, wherein the axial position of at least one branch is closer to another end plate than to the end plate having the electrolyte inlet, in particular by at least 4%, preferably by at least 8%, in particular by at least 12%.

10. 2. An electrolytic cell according to claim 1, wherein the difference in the axial flow path portions of the total flow path length to the outlet of the flow path through the cell axially furthest from the electrolyte inlet on the one hand and the flow path through the cell axially nearest to the inlet on the other hand, divided by their sum, is less than 20%, preferably less than 12%, in particular less than 8%.

11. 2. An electrolytic cell according to claim 1, wherein the difference in the axial flow path portions of the total flow path length to the outlet of the flow path through the cell axially furthest from the electrolyte inlet on the one hand and the flow path through the cell axially nearest to the inlet on the other hand, divided by their sum is greater than 4%, preferably greater than 8%, in particular greater than 12%.

12. Electrolytic cell according to claim 1, comprising at least 30, preferably at least 50, in particular at least 80 cells.

13. at least one rectifier having poles connected to the end plates of the electrolytic cell; 13. An apparatus in which two electrolytic cells are connected in series to one of said at least one rectifier, one or both of said two electrolytic cells being constructed according to any of claims 1 to 12.

14. 1. A method for performing electrolysis, in particular the electrolysis of water using a cell-stack type electrolytic cell, characterized in that a predominantly axial electrolyte flow is redirected into a predominantly radial planar electrolyte flow, at least a part of said predominantly axial electrolyte flow bypassing a redirection area of ​​said flow redirection towards at least another cell of said electrolytic cell, and electrolyte flow towards one of the redirection areas downstream of the bypassed redirection area.

15. 15. A method of carrying out the electrolysis according to claim 14 using one or more electrolytic cells according to any of claims 1 to 12.

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