CELL FRAME ASSEMBLY FOR AN ELECTROLYZER, ELECTROLYZER AND METHOD OF MANUFACTURING THEREOF

Abstract

 The invention relates to a cell frame assembly for an electrolzyer of the cell-stack type, comprising a plurality of stacked individual inner cell frame parts and at least temporarily during manufacturing and/or mounting an integral outer reinforcing shell or an axial holding arrangement extending over a subset of at least two stacked inner cell frame parts.

Description

[0001] The invention is related to a cell frame assembly for an electrolyzer, electrolyzer and method of manufacturing thereof.

[0002] Such cell frame assemblies, respectively cell frames forming a cell frame assembly for an electrolyzer are known f.i. from DE 10 2014 010 813 A1. A frame structure of the cell frame has close to its outer border an embedded reinforcement ring to provide availability of such electrolysis cells also for electrolysis being performed under high pressure.

[0003] During manufacturing of such reinforced cell frame, the reinforcing ring may be set into a mold for forming the cell frame and is, thereby, embedded therein. Then, the cells may be completed by adding the various membrane, bipolar pellets, sealings, and other parts to create, cell by cell, the cell stack being eventually sandwiched between end-plates of the electrolyzer to form the electrolyzer.

[0004] It is an object of the invention to improve the manufacturing of such electrolyzers of the staple-type.

[0005] This object is achieved by a cell frame assembly for an electrolzyer of the cell-stack type, comprising a plurality of stacked individual inner cell frame parts and at least temporarily during manufacturing and/or mounting an integral outer reinforcing shell or an axial holding arrangement extending over a subset of at least two stacked inner cell frame parts.

[0006] In one possible embodiment, a plurality (subset of at least two) (inner) cell frame parts are provided with an integral outer reinforcing shell, even a larger number of at least 3 or 4, at least 6, at least 8, or even more. For instance, said outer shell can be provided in form of a wrapping.

[0007] In one sub-embodiment regarding this embodiment, after applying said outer shell, the construction of the plurality of inner cell frame parts and outer shell is divided again to the level of single inner cell frame parts, f.i. by cutting. Such cutting could be mechanical cutting, f.i. sawing or other techniques as laser cutting can be provided. Thereby, it is sufficient to cut only the outer shell, since the inner cell frame parts are axially not connected anyway. Thereby, manufacturing of reinforced cell frames becomes easier in the overall performance irrespective of the apparent double work to first combine and later separate the inner cell frame parts.

[0008] For such embodiment, the mounting of the re-separated cell frames to form electrolyzer cells and forming the electrolyzer cell stack by such electrolyzer cells can be as usual in a one-by-one mounting process.

[0009] However, in a further preferred embodiment, the mounting of the electrolyzer cells between the end-plates of the electrolyzer is not one-by-one, but by modules containing already a subset of at least two pre-mounted cells. Such pre-mounting can be effected at a different location than the mounting location of the electrolyzer, advantageously shifting mounting time from the final mounting process to preparatory mounting processes which can be organized in advance and which allow also to have already mounted modules on hold. This enables also to increase the safety level for the final mounting process, involving a lower number of parts to be handled, in particular in consideration of the several sealings to be applied with high accuracy in the final mounting process according to the actually practiced mounting process in the art.

[0010] It is to be understood that such pre-mounting can be effected for (inner) cell frame parts prepared in accordance with the above, that is from single reinforced cell parts irrespective of the kind of reinforcement (inner, as with an inner reinforcement ring in accordance with DE 10 2014 010 813, or outer reinforcing shell, in particular by a wrapping-reinforcement explained above).

[0011] To this end, an axial holding arrangement can be provided to hold a subset of electrolysis cells axially together in the pre-mounting process. The holding mechanism of the holding arrangement may comprise axial bars extending through manifolds in the cell frames later used for electrolyte transport. It is understood that such axial holding arrangement is for temporary mounting only and is removed prior to final mounting. Outer clamping brackets can be used, also.

[0012] In a further envisaged embodiment, the axial holding arrangement is provided by an outer shell as f.i. in form of a wrapping. To this end, not only the cell frames as referenced above in another embodiment are combined for common wrapping, but a subset of at least two cells comprising already the remaining components such as membrane, sealings, bipolar plates are wrapped together. Such wrapping can be either a temporary wrapping removed and used only for mounting purposes as the above-described axial holding arrangement in general. Otherwise, the wrapping remains and serves as integral outer reinforcing shell.

[0013] For the latter, it is preferred that openings are made in the outer shell/the wrapping in order to allow passage of at least partly circumferential portions of the bipolar plates. This enables on the one hand side cell voltage measurements during operation of the electrolyzer.

[0014] In a preferred embodiment, the area of the bipolar plate accessible by passing through the openings in the shell is at least 6000 mm², preferably at least 15,000 mm², in particular at least 24,000 mm². This favors the possibility to bridge a defect cell by contacting the sandwiching bipolar plates. It may (also in interrupted manner) extend all around 360°. Said passing-through can be in the form of pins, spaced apart from each other. Also envisaged are configurations in which, between groups of cells provided with a common outer shell, an electrode plate (bipolar plate) extends radially over the dimensions of said outer shell such as to allow large area contact for bridging of a hole group.

[0015] It is preferred that the integral outer reinforcing shell provides for reinforcement against radial forces. Therefore, fixing between the outer shell and the inner cell frame against axial displacement is preferred for some embodiments, while not mandatory for other embodiments. The above-described embodiments can be applied alone and/or in combination. For instance, a first number of stacked cells can have the same outer shell, and two or more of such sub-assemblies with respective common outer shell can be axially held within an axially holding arrangement. In other embodiments, mounting can be done without pre-mounted stacks held by axial holding arrangements, but a single outer reinforcement shell for an individual inner cell frame part can be result of a separation process of a previously common integral outer reinforcing shell applied in a common working (application) step to a subset/plurality of individual inner cell frame parts.

[0016] The invention can be applied for any kind of electrolyzer of the cell-stack type. Particularly preferred are electrolyzers for alkali electrolysis. In a preferred application of a method of operating the electrolyzer, electrolysis of water to produce hydrogen (and oxygen) is preferred.

[0017] In a preferred embodiment, the overall number of cells is at least 20, preferably at least 40, in particular at least 60. However, the invention has advantages in particular also for even larger electrolyzers having at least 80, preferably at least 100, in particular at least 120 cells inbetween the end-plates of the electrolyzer.

[0018] In a further preferred embodiment, it can be provided that the outer shell or holding arrangement extends over at least or exactly 3 or 4, preferably at least or exactly 5, even 6 or more of the inner cell frame parts. This provides handable modules regarding in particular their overall weight.

[0019] In a further preferred embodiment, said plurality comprises all cells of a complete stack, and an outer reinforcement formed by one or more of said outer shells comprises not more than 60, preferably not more than 50, in particular not more than 40 integral outer shells.

[0020] Thereby, a mounting process can be simplified with still reasonable control of the weight of the single modules/subsets.

[0021] In a further preferred embodiment, the outer shell or axial/holding arrangement is detachably mounted to the inner cell frame parts. This allows better dismounting after end of temporary mounting state and/or for maintenance purposes.

[0022] In a further preferred embodiment, the shell is in form of a wrapping. For instance, a sheet material comprising or made of carbon fiber, glass fiber, and/or other materials as resin materials, f.i. PPS, PPE, PSU material can be wound over in particular cylindrically formed staples. A bonding agent, f.i. a resin can be applied between the first winding and the outer surface of the inner cell frame parts and/or between the surfaces of subsequent windings of the wrapping. In this regard it is preferred that the wrapping may comprise at least 2, preferably at least 4, in particular at least 6 full terms. This further increases resistance against radial forces arising due to the pressure in the process.

[0023] In a further preferred embodiment, the integral outer shell may comprise reinforcement fibers, in particular carbon fibers and/or fibers in form of staple fibers.

[0024] Moreover, it is preferred that the fibers are comprised in an amount of at least 6, preferably at least 12, in particular at least 24 weight% of the integral outer shell. In particular, the fibers can be embedded in a resin material, f.i. those indicated above.

[0025] The invention also provides an electrolyzer of the cell-stack type, comprising a cell frame assembly according to any of the preceding aspects and/or manufactured according to any of the precedingly described aspects of manufacturing. Such electrolyzers combine the advantages of reasonable resistances in particular against radial pressure forces on the one hand side with facilitated manufacturing and/or mounting on the other hand side.

[0026] In particular with view to maintenance of the electrolyzer after some operation time, the invention provides also a method of operating the electrolzyer, wherein the cell frame assembly is kept in a working state with the integral outer reinforcing cell frame part being mounted to the individual inner cell frame parts in a first state in which the electrolyzer performs electrolysis of a liquid, in particular produces hydrogen from water, wherein for maintenance the integral outer shell is removed from the individual inner cell frame parts in preparation for a second maintenance state in which access to the cells is given, and the integral outer reinforcing cell frame part is reapplied after maintenance.

[0027] This method is applied in case that the outer reinforcing shell is not only temporarily applied in the manufacturing process of the cell frames, but also kept after mounting and in particular acting as axial holding arrangement. As an alternative to the removal of the shell, the shell can also be not removed but cut on a level of the individual inner cell frame parts such as to allow separation thereof.

[0028] Regarding in particular the mounting process, the invention also provides a method of manufacturing such electrolyzer, comprising stacking a plurality of cell frame parts, thereby providing a cell frame staple, and mounting an integral outer reinforcing shell extending over a subset of at least two stack inner cell frame parts of the cell frame staple. As already partly described above, such method provides better reliability of the final mounting process and allows in particular lower mounting times at the location of final mounting, which preferably can be the location where the electrolyzer is placed for later operation.

[0029] As already said before, said mounting may comprise to apply the outer shell in form of a wrapping. Apart from the advantages explained above, this also allows a setting of reinforcement level against radial forces by varying, in particular increasing the number of turns of the wrapping.

[0030] Moreover, the invention provides a method of manufacturing the electrolyzer, comprising the steps of forming, at a first location, a cell staple of a plurality of cells and applying thereto a temporary axial holding arrangement axially holding the staple together, transporting said staple held by the holding arrangement to a second location where the staple is inserted between end-plates of the electrolyzer and where the holding arrangement is removed.

[0031] Further, the invention provides a method for manufacturing cell frames to form a cell frame stack for an electrolyzer of the staple-type, comprising the steps of forming a number of cell frames corresponding to the number of cells of the electrolyzer, providing a subset of at least two of said cell frames with an outer reinforcement shell, in particular in form of a wrapping, separating the common outer shell such as to re-establish individual cell frames having each an individual outer reinforcement shell from the previous integral outer reinforcing shell, mounting the cell staple of the electrolyzer on the basis of said individual cell frames with individual outer shell, one-by-one or in form of pre-mounted modules comprising two or more cells.

[0032] The advantages of such method, in particular regarding the simplification of manufacturing, are already given above.

[0033] Further features, details and advantages of the invention are subsequently described with reference to the accompanying figures, where

Fig. 1 shows a cell 60 in a simplified explosive view,

Fig. 2 shows a (main) frame,

Fig. 3 shows a wrapping device for a cell (frame) ensemble,

Fig. 4 shows a reinforced cell frame ensemble,

Fig. 5 shows a cutting/separation mechanism,

Fig. 6 shows a separated ensemble,

Fig. 7 shows a cell ensemble,

Fig. 8 shows a reinforced cell ensemble, and

Fig. 9 shows a temporarily clamped cell ensemble.

[0034] Fig. 1 shows in an explosive view and without details the general structure of part of a cell stack assembly. A pressure frame 30 holds a membrane 20 against a main frame 10, which has holes 12 being part of a manifold to provide the electrolyzer with electrolyte and to discharge the electrolyte. A bipolar plate 40 is sandwiched between the cell frame 10 and subsequent cell frame 10. However, the invention is by no means restricted to the type of electrolyzer, although an electrolyzer for water electrolysis to produce hydrogen (and oxygen) is preferred. The electrolysis technique can be that of alkali electrolysis, PEM electrolysis, or other.

[0035] In Fig. 2, main frame 10 of Fig. 1 is shown separately. Again, structural details as protrusions, recesses, positioning pins, channels for proper coupling to membrane, pressure frame, sealings, and so on, are omitted, as they are well known to the person skilled in the art. The main frame 10 as shown in Fig. 2 could be manufactured by f.i. diecasting.

[0036] For some applications in particular in case of a high pressure in the system, additional reinforcing to the main frame is provided. In one preferred example, a plurality of such main frames 10 as shown in Fig. 2 are axially stapled to form an ensemble 100 of cell frame bodies axially adjacent one to another. In this state, each frame 10, the ensemble 100 is provided with an outer reinforcement 11.

[0037] This is shown in Fig. 3. The ensemble is rotatably held by holding arrangement 200. During rotation of the ensemble 100, a wrap of reinforcing material in form of a strap 310 is wound for a plurality of windings onto the circumferential outer surface of the ensemble 100. Inbetween two layers of the winding, a fixing liquid is applied to the last wound winding (and before winding the first winding), such that the continuously wound strap 310 rolled from a strap roll 300 is appropriately fixed. Thereby, the ensemble 100 of a plurality of cell frames 10 obtains each a reinforcement 11 (by its share of shell 110) together in one and the same manufacturing step.

[0038] The fixing agent may be applied by spraying via nozzle 400 or otherwise. The machining step shown in Fig. 3 may be carried out semi-automatically or even manually.

[0039] In Fig. 4, the ensemble 100 comprising the plurality of cell frames 10 is shown with common reinforcement shell 110.

[0040] In order to obtain single cell frames 10 with reinforcing 11, the common reinforcement shell 110 is cut by a suitable cutting arrangement 500 with cutter 501, as shown in Fig. 5. To this end, the ensemble 100 of the plurality of cell frames can be held again by holding arrangement 200. It is understood that the representation of Fig. 5 is a schematical representation, and various kinds of cutting techniques may be applied, such as the (shown) mechanical cutting, as well as other cutting techniques such as laser cutting. Important for this exemplified embodiment is the separation of the reinforcing shell 110 in single reinforcings 11, one for each cell frame 10. At the end of the cutting step (Fig. 6), one obtains a staple of cell frames 10 having each an outer reinforcement 11 comprising a plurality of windings of reinforcing strap fixed to each other by f.i. the resin applied during manufacturing of reinforcing shell 110 shown in Fig. 3. The single reinforced cell frames 10 can be separated from each other, thereby dismounting the ensemble to obtain reinforced cell frames 10, which can then be used to build up cells and a cell frame staple according to the structure shown in Fig. 1.

[0041] In another embodiment, formation of an ensemble of cells and formation of a common reinforcing shell for the ensemble can be created in a similar way as illustrated in Figs. 3 and 4. The difference with respect to this earlier exemplified embodiment is that the ensemble is not only formed by cell frames 10, but already by a plurality of stacked cells 60. In one possible example, there is no more need to cut the common reinforcing shell 110 into separated reinforcings 11 for each cell, that is the cutting step shown in Fig. 5 can be omitted. Of course, access to the electrodes, in the present embodiment bipolar plates 40, need to be created, which could be, in one example, by drilling holes into the common reinforcing shell 110, to be able to contact bipolar plates 40.

[0042] In a further exemplified embodiment, bipolar plates are formed with radially extending pins 41, which radially extend beyond the outer diameter of the cell frames 10. This is shown in Fig. 7, where an ensemble 160 of cells 60 is shown in axially stapled manner. In this embodiment, a plurality of circumferentially arranged and radially extending pins 41 are protruding radially outwards. It is understood that pins 41 can be and preferably are integral with bipolar plates 40. For instance, bipolar plates 40 can be manufactured with a larger diameter than that of cell frame 10, and material can be removed to leave pins 41. This could be, f.i. done by mechanical cutting, laser cutting, or any other cutting technique as water jet cutting or other. A lower number of pins 41 than shown can also be provided, f.i. when for the purpose of contacting for measuring the cell voltage. Also taps instead of or additionally to pins can be provided, for bridging purposes.

[0043] During the step of applying the common reinforcing shell 110, f.i. in the same way as shown in Fig. 3 having cell stack assembly 160 clamped between the clamping anchors 210 of holding arrangement 200 rotatable around the staple axis, pins 41 penetrate strap 310 during its winding around the ensemble 160. Therefore, as shown in Fig. 8, after formation of the common outer reinforcing shell 110 formed by a plurality of windings of reinforcing strap 310 and the fixing agent, the pins 41 still radially extend out of the reinforced ensemble 180, composed of 160, 110, and can be contacted for proper working, but give also the possibility to measure cell voltages, respectively to bridge a possibly defect cell.

[0044] When mounting a plurality of reinforced cell stacks 180 to form an electrolyzer having a large number of cells (f.i. 20 reinforced cells 180 of each five cells can create an electrolyzer with 100 cells), also the mounting procedure for mounting the electrolyzer requires a lower number of mounting steps, since the mounting of reinforced ensemble 180 is already done. While there is no significant time advantage in overall mounting time, there is some increased flexibility since part of the working time is timely and in particular also locally separable/separated from the final mounting procedure when the cells are clamped between (not shown) end plates of the electrolyzer.

[0045] In a further exemplified embodiment, this flexibility and different mounting approach can also be applied even in case that there is not the integral common reinforcing cell 110, due to the cutting step shown in Fig. 5. In this case, in an exemplary mounting process it can still be provided that a sub-stack 190 of cells 60 is pre-mounted and held together by clamping means 290, as shown for an example in Fig. 9, with four clamping brackets 290 axially holding the plurality, in the shown embodiment five cells 60 together. It is understood that the number of cells 60 held by clamping means 290 can be selected in particular also in dependency of the overall weight of one cell 60, such that for smaller electrolyzer with lower diameter, maybe more cells can be held together, while for larger diameter electrolyzer, the number may be appropriately selected and be lower. However, even when only two or three cells 60 are pre-mounted for a sub-stack 190, the mounting time for mounting the complete cell stack in the final mounting process can be significantly reduced.

[0046] It is further understood that such division of the mounting process in a first pre-mounting to create sub-stacks 190 axially held together, and to do final mounting by forming the cell stack between the end plates of the electrolyzer of a plurality of the preassembled sub-stacks 190 can be done irrespective of how the cells are manufactured, in particular how the cell frames 10 are manufactured and can, thus, be also implemented without the manufacturing steps shown in Figs. 3 or 5.

[0047] In a (not shown) modification of the mounting aspect shown in Fig. 9, one can provide that bipolar plates 40 radially extend beyond the cell frames 10, similar as shown in Fig. 8 not in form of the pins 41 but with larger surface areas or even completely. In order to obtain this, one may either work with separately reinforced cell frames 10 as that of Fig. 6, in case that an outer winding reinforcement 11 is desired. Otherwise, one could also (not shown) insert cutting means between strap roll 300 and the ensemble of cells held by holding arrangement 200 (Fig. 3) such as to create slits in strap 310 where portions of bipolar plate 40 are to extend out of common reinforcing shell 110. In such cases it is preferred that rotation of the ensemble and actuating of said cutting means for cutting said slits are synchronized.

[0048] Accordingly, as one can take from the above description, the several aspects can synergize to reduce the overall workload and/or possibility to manufacture and assemble an electrolyzer of the staple type. Moreover, it is to be understood that the single detail features shown in the above detailed description of the invention are not restricted for the subject invention. Rather, the features of the above description as well as those of the subsequent claims can be, alone-standing or in combination, essential for the invention.

Claims

1. Cell frame assembly (100; 180, 190) for an electrolzyer of the cell-stack type, comprising a plurality of stacked individual inner cell frame parts (10) and at least temporarily during manufacturing and/or mounting an integral outer reinforcing shell (110) or an axial holding arrangement (290) extending over a subset of at least two stacked inner cell frame parts (10).

2. Cell frame assembly according to claim 1, wherein the outer shell or holding arrangement extends over at least 3, preferably at least 4, in particular at least 5 of the inner cell frame parts.

3. Cell frame assembly according to claims 1 or 2, wherein said plurality comprises all cells of a complete stack, and an outer reinforcement formed by one or more of said outer shells comprises not more than 60, preferably not more than 50, in particular not more than 40 integral outer shells (110).

4. Cell frame assembly according to any of the preceding claims, wherein the outer shell or axial/holding arrangement is detachably mounted to the inner cell frame parts.

5. Cell frame assembly according to any of the preceding claims, wherein the shell is in form of a wrapping.

6. Cell frame assembly according to any of the preceding claims, wherein the wrapping comprises at least 2, preferably at least 4, in particular at least 6 full turns.

7. Cell frame assembly according to any of the preceding claims, wherein the integral outer shell comprises reinforcement fibers, in particular carbon fibers and/or fibers in form of staple fibers.

8. Cell frame assembly according to claim 7, wherein the fibers are comprised in an amount of at least 6, preferably at least 12, in particular at least 24 weight% of the integral outer shell.

9. Cell frame assembly according to any of claims 7 or 8, wherein the fibers are embedded in a matrix, the matrix comprising a resin material, f.i. one or more of PPS, PPE, PSU.

10. Electrolyzer of the cell-stack type, comprising a cell frame assembly (180, 190) according to any of the preceding claims.

11. Method of operating the electrolyzer of claim 10, wherein the cell frame assembly is kept in a working state with the integral outer reinforcing cell frame part being mounted to the individual inner cell frame parts in a first state in which the electrolyzer performs electrolysis of a liquid, in particular produces hydrogen from water, wherein for maintenance the integral outer shell is removed from the individual inner cell frame parts in preparation for a second maintenance state in which access to the cells is given, and the integral outer reinforcing cell frame part is reapplied after maintenance.

12. Method of manufacturing the electrolyzer of claim 10, comprising
stacking a plurality of cell frame parts (10), thereby providing a cell frame staple, and mounting an integral outer reinforcing shell (110) extending over a subset of at least two stack inner cell frame parts of the cell frame staple.

13. Method according to claim 12, said mounting being in form of a wrapping.

14. Method of manufacturing the electrolyzer of claim 10, comprising the steps of forming, at a first location, a cell staple (190) of a plurality of cells and applying thereto a temporary axial holding arrangement (290) axially holding the staple together, transporting said staple held by the holding arrangement to a second location where the staple is inserted between end-plates of the electrolyzer and where the holding arrangement is removed.

15. Method of manufacturing cell frames to form a cell frame stack for an electrolyzer of the staple-type, comprising the steps of forming a number of cell frames corresponding to the number of cells of the electrolyzer, providing a subset of at least two of said cell frames with an outer reinforcement shell, in particular in form of a wrapping, separating the common outer shell such as to re-establish individual cell frames having each an individual outer reinforcement shell from the previous integral outer reinforcing shell, mounting the cell staple of the electrolyzer on the basis of said individual cell frames with individual outer shell, one-by-one or in form of pre-mounted modules comprising two or more cells.

Drawing