Bipolar plate, electrolytic cell, electrolytic cell stack and assembly method associated therewith

Abstract

The invention relates to a bipolar plate for an electrolytic cell, the plate comprising, on at least one of its main faces: a first region extending circumferentially; a second region extending circumferentially so as to border the first region on the outside; a third region extending circumferentially so as to border the second region on the outside, each region being arranged on a perimeter of an associated major face. The invention also relates to a corresponding cell, an electrolytic cell stack and a method of assembly.

Description

[0001] The present invention relates to a bipolar plate.

[0002] The present invention relates to an electrolytic cell comprising such a plate.

[0003] The present invention also relates to an electrolytic cell stack comprising such an electrolytic cell.

[0004] The present invention also relates to a method for assembling such an electrolytic cell stack. Background of the Invention

[0006] The general architecture of an electrolytic cell stack is generally composed of electrolytic cell blocks and seals. These electrolytic cells are stacked in series from an electrical point of view and in parallel from a fluid point of view.

[0007] The purpose of each electrolytic cell is to promote the electrolysis of an electrolyte solution (alkaline water, pure water, non-purified water, salts, aqueous chloride solutions, aqueous bromide solutions, aqueous hydrochloric acid solutions, etc.). For example, the function of an electrolytic cell stack is to promote the reaction that produces hydrogen (H2) and oxygen (O2) gases from the dissociation of water after injecting direct current into an alkaline solution (usually potassium hydroxide (KOH) or sodium hydroxide (NaOH)).

[0008] Each electrolytic cell (which is considered to be a conductive part mainly made of metal (but some of its parts can be non-metallic)) is usually composed of two bipolar plates, which flank two inserts (more commonly called flow field materials), and these two inserts in turn flank two electrodes, which are usually in the form of metal plates or grids or meshes. In the case of an alkaline electrolytic cell stack, the electrodes are usually made of nickel. The two electrodes (cathode and anode) are separated by a membrane (also called a diaphragm or a porous separator in the case of an alkaline electrolytic cell), which ensures electrical insulation between the two electrodes, gas separation, and ion conduction within the electrolytic cell.

[0009] The inserts have two functions: i) providing a low-resistivity metal path between each bipolar plate and the associated electrode, and ii) allowing proper circulation of the electrolyte solution to cool the electrolytic cell stack and transport the generated gases.

[0010] The name "bipolar plate" comes from the fact that since the electrolytic cells are all placed side by side, the potential of bipolar plate N:

[0011] - is higher than that of the downstream bipolar plate N+1, such that bipolar plate N will act as an anode in the electrolytic cell defined by bipolar plates N and N+1;

[0012] - is lower than that of the upstream bipolar plate N-1, such that bipolar plate N will act as a cathode in the electrolytic cell defined by bipolar plates N-1 and N.

[0013] In addition to the bipolar plates, other metal parts also include distribution plates (which enable the supply and distribution of electric power to the electrolytic cells) and base plates (which enable the definition of the components of the electrolytic cells and ensure that the cells are tightened together and sealed).

[0014] In fact, the electrolytic cell stack ends with two base plates, which are located directly in front of the first electrolytic cell of the stack and directly behind the last electrolytic cell of the stack, that is to say, one base plate is located upstream of the electrolytic cell block and the other base plate is placed downstream of the electrolytic cell block in order to physically define the two ends of the electrolytic cell block.

[0015] The electrolyte solution present in each electrolytic cell, together with the gases generated by electrolysis (such as hydrogen, oxygen, chlorine, and halogen gases, etc.), must not leak from the edges of the diaphragm outside the electrolytic cell under discussion, but must only circulate through dedicated pipes (each pipe dedicated to only the electrolyte or to the electrolyte mixed with one of the gases, taking into account that these two gases cannot be mixed together either).

[0016] Therefore, if a leak is observed, the electrolytic cell stack cannot operate continuously, and the leak comes from the electrolyte solution, from the gases generated by electrolysis, or from any other substance.

[0017] This means that in many cases, various problems that have a negative impact on the environment and on the safety of the operator occur with different severities, and these problems can be very serious and may lead to irreversible consequences.

[0018] Conventionally, in the electrolytic cells as described above, the components applied to avoid any leakage from the electrolyte solution, from one or more gases generated by electrolysis, and / or from any other substance are based on the use of multiple thin seals in the form of sheets or multiple O - rings, and these thin seals are usually elastomeric, such that the seals or O - rings are positioned between the anode and cathode or the membrane of the electrolytic cell, or directly between two adjacent bipolar plates. Thus, the diaphragm is clamped between these different sealing elements.

[0019] Although these seals have satisfactory sealing properties, they may be damaged due to creep phenomena, and the creep phenomena are more or less intense depending on the quality and composition of the materials used. Therefore, if such seals are used, the sealing of the electrolytic cell stack will ultimately usually deteriorate (and even more specifically, this is the case within each electrolytic cell). In addition, if one of the influencing factors (such as temperature) has an undesirable effect on the seals under discussion, this creep phenomenon occurs faster.

[0020] Object of the Invention

[0021] An object of the present invention is to propose a solution that enables the long - term satisfactory sealing of an electrolytic cell stack. Summary of the Invention

[0022] To this end, the present invention relates to a bipolar plate for an electrolytic cell, which plate comprises, on at least one of its main faces:

[0023] - a first region that extends circumferentially,

[0024] - a second region that extends circumferentially such that the second region is in contact with the first region on the outside, and the second region defines at least one narrowing of the thickness of the plate,

[0025] - a third region that extends circumferentially such that the third region is in contact with the second region on the outside, and the third region defines at least one narrowing of the thickness of the plate,

[0026] These different regions are arranged on the periphery of the associated main face.

[0027] Thus, the present invention ingeniously has different regions, each of which enables specific sealing to be ensured by different components (gas circulation pipes, membranes, another bipolar plate, etc.) outside the bipolar plate.

[0028] The inventors have particularly observed that such a bipolar plate has a surprising effect, that is, even when using a seal with a simple geometry (for example, by way of non - limiting example, a seal in the form of a ring), it is possible to very successfully compress the seal between this bipolar plate and another bipolar plate. When such a plate is arranged in an electrolytic cell stack, the sealing of the electrolytic cell stack is thus improved, even in the long term.

[0029] The present invention is particularly suitable for electrolytic cell stacks with large dimensions, where the bipolar plates may have an electrode area of up to several square meters per electrolytic cell.

[0030] Optionally, the narrowing is formed by at least one shoulder between two successive regions.

[0031] Optionally, the first region is textured.

[0032] Optionally, the textured first region also extends circumferentially on the other main face of the bipolar plate.

[0033] Optionally, the second region and / or the third region is non - textured.

[0034] Optionally, the bipolar plate has a circular outer periphery.

[0035] Optionally, the first region includes stripes.

[0036] Optionally, the second and third regions form at least two shoulders therebetween so as to form a narrowing of the thickness of the plate.

[0037] Optionally, at least three orifices are formed in the second region.

[0038] The invention also relates to an electrolytic cell comprising at least a first bipolar plate as described above, at least a second bipolar plate as described above, and a single seal disposed between the two bipolar plates.

[0039] Optionally, the seal is made of a monomeric material or a polymeric material.

[0040] Optionally, the seal is in the shape of a flat ring.

[0041] Optionally, the seal is made of a glass fiber reinforced material and / or a carbon fiber reinforced material.

[0042] The invention also relates to an electrolytic cell stack comprising a plurality of electrolytic cells as described above.

[0043] The invention also relates to a method for assembling an electrolytic cell stack as described above, the method comprising the steps of:

[0044] - assembling the electrolytic half-cell pairs individually,

[0045] - assembling the electrolytic half-cell pairs together, disposing a seal between each pair to form a block,

[0046] - applying successive heating and cooling phases to the block, and applying at least one tightening operation to the block between two different heating and cooling phases.

[0047] Optionally, the block is heated for tightening by injecting steam or hot water into the block.

[0048] Other features and advantages of the invention will become apparent by reading the following description of non-limiting specific embodiments of the invention. Description of the Drawings

[0049] Reference will be made to the drawings, in which:

[0050] Figure 1 Figure 1 is an exploded schematic view of an electrolytic cell according to a specific embodiment of the invention,

[0051] Figure 2 Figure 2 is Figure 1 a perspective view of the bipolar plate of the electrolytic cell shown,

[0052] ​​​​Figure 3a Figure 3a is Figure 2 a cross-sectional view of a part of the bipolar plate shown,

[0053] Figure 3b Figure 3b is Figure 2 a cross-sectional view of a part of the bipolar plate shown, also showing the membrane of the electrolytic cell,

[0054] Figure 3c Figure 3c is Figure 1 a cross-sectional view of a part of the electrolytic cell shown,

[0055] Figure 4 Figure 4 is a view of an electrolytic cell stack including the electrolytic cells shown as Figure 1 shown,

[0056] Figure 5 Figure 5 is a graph showing the average reduction in the thickness of the seal of one of the cells in the stack when assembling the electrolytic cell stack shown as Figure 4 shown. DETAILED DESCRIPTION

[0057] Referring to the respective figures, the electrolytic cell stack 1 extends longitudinally in the general direction A.

[0058] The electrolytic cell stack 1 includes an electrolytic cell block 2, which includes at least two electrolytic cells that are mounted side by side in the general direction A. Inside the block 2, the electrolytic cells are mounted in parallel from a fluid perspective and in series from an electrical perspective.

[0059] At both ends (in the general direction A) of the block 2, the electrolytic cell stack 1 includes two base plates 3 and 4.

[0060] These base plates 3 and 4 form supports between which the electrolytic cells are compressed, such that the electrolytic cell stack 1 is sealed and such that a high-quality electrical contact is formed inside the electrolytic cells.

[0061] In addition, the base plates 3 and 4 are capable of withstanding the forces generated by the pressure inside the block 2 and the forces outside the block 2 necessary to ensure the compression of the block 2.

[0062] The base plates 3 and 4 can act as electrical conductors and current distributors.

[0063] Preferably, the electrolytic cell stack 1 includes a first distribution plate 5 associated with the first base plate 3 and a second distribution plate 6 associated with the second base plate 4. In this case, the distribution plates 5 and 6 act as electrical conductors and current distributors.​​​​​​​​​​

[0064] The first distribution plate 5 (associated with the positive terminal) is arranged upstream of the block 2, and the second distribution plate 6 (associated with the negative terminal) is arranged downstream of the said block 2.

[0065] The concepts of "upstream" and "downstream" are defined in the direction in which the current circulates through the block 2.

[0066] The first of the two distribution plates 5 is connected to the positive terminal of the electrolytic cell stack 1. Accordingly, a part of the inner main surface (the main surface facing the block 2, in particular the distribution plate 5) of the first substrate 3 is covered with an electrically insulating material patch. The said part is arranged, for example, at the center of the said inner main surface.

[0067] The second of the two distribution plates 6 is connected to the negative terminal of the electrolytic cell stack 1. The second substrate 4 is at the same potential and also serves as a bridge for supplying the electrolyte solution and discharging the same solution carrying the gas formed during electrolysis in the block 2.

[0068] Therefore, holes are formed in the said second substrate 4. The holes generally have different cross-sections between the two main surfaces of the second substrate 4. For example, the outer main surface (the main surface facing the outside of the block 2) includes one or two holes (for example, cylindrical holes) for supplying the electrolyte solution and two holes for discharging the electrolyte reaction products in addition to the heated electrolyte solution. For the same purpose, three or four holes (for example, oblong holes) are formed in the inner main surface of the said second substrate 4 (on the side opposite to the outer main surface) so as to improve the distribution or collection of the fluid. For example, the holes in the outer main surface are provided with flanges adapted to connect the electrolyte solution inlet hose and the return hose.

[0069] Furthermore, here, the electrolytic cell stack 1 is supplied with direct current.

[0070] For example, the first distribution plate 5 has a potential of approximately 700 volts, while the second distribution plate 6 has a potential of 0 volts. The supply and discharge of the electrolyte solution are carried out through the second distribution plate 6 and the second substrate 4, and the second distribution plate 6 has a potential of 0 volts, which prevents any current leakage (the potential of the second distribution plate 6 is the ground potential).

[0071] Inside the electrolytic cell stack 1, the current passes through the electrolyte solution through the membrane 11, which will be described below. There are seals in the block 2 (which will be described below); the materials selected for these seals have a much higher resistance than the electrolyte solution.

[0072] The electrolytic cell stack 1 includes an end seal (not shown in the figure) disposed between the first distribution plate 5 and the first substrate 3. The first substrate 3 is grounded so that the potential difference at the end seal reaches the same value as the voltage applied between the positive and negative terminals of the electrolytic cell stack 1, for example, approximately 700 volts.

[0073] Therefore, the first substrate 3 is electrically insulated from the block 2.

[0074] For example, the electrolytic cell stack 1 includes a layer (not shown in the figure) made of an electrically insulating material, which is disposed between the first substrate 3 and the first distribution plate 5.

[0075] This layer is, for example, an inserted disk or a deposit formed on the first substrate 3 and / or the first distribution plate 5.

[0076] The electrolytic cell stack 1 includes means for fastening the individual electrolytic cells 10 together by means of a joint tightening.

[0077] For example, the fastening means includes a plurality of tie rods 7. Each tie rod 7 extends linearly in the electrolytic cell stack 1. Therefore, each tie rod 7 extends longitudinally in the electrolytic cell stack 1 parallel to the overall direction A. Each tie rod 7 is in the shape of a shaft.

[0078] Therefore, the tie rods 7 all extend parallel to each other.

[0079] The tie rods 7 are positioned on the periphery of the individual electrolytic cells. Preferably, the tie rods 7 are all distributed around the block 2, preferably at regular intervals.

[0080] The tie rods 7 extend through the substrates 3 and 4 of the electrolytic cell stack 1, through specific holes in the substrates 3 and 4, and thus each has two ends located outside the block 2.

[0081] Preferably, the tie rods 7 are partially covered with a sleeve made of an electrically insulating material. This makes it possible to avoid short circuits between the electrolytic cells in the case of contact or splashing. For example, the sleeve extends over the entire section of the tie rod 7 disposed between the two substrates 3 and 4.

[0082] Preferably, the ends of the tie rods 7 are threaded.

[0083] For example, the thread at the end is a rolled thread. The rolled thread has the advantage of making it easier to machine the tie rod 7, especially if the tie rod 7 is very long (for example, several meters long).

[0084] The fastening means further includes nuts 8 screwed onto the ends of the tie rods 7.

[0085] The nuts 8 make it possible to push the two substrates 3 and 4 together, and thus push the individual electrolytic cells together, which ensures a satisfactory seal of the electrolytic cell stack.

[0086] Preferably, the fastening means further comprises means for prestressing the two substrates 3 and 4 together and thus prestressing the individual electrolytic cells together. The prestressing means also makes it possible to absorb deformations and / or thickness variations of the components of the electrolytic cell stack 1 caused by thermal expansion or mechanical stress variations outside and inside the electrolytic cell stack 1, such as the pressure inside the electrolytic cell stack.

[0087] The prestressing means is received on the end of the tie rod 7 such that for a given end, these prestressing means are arranged between the nearest substrate (3 or 4) and the nut 8 arranged on the same end.

[0088] For example, the fastening means includes a spring washer 9, such as a Belleville washer. The spring washer 9 is received on the end of the tie rod 7.

[0089] Here, more specifically, when each tie rod 7 has passed through the nearest substrate (3 or 4), the spring washer 9 is positioned on the tie rod, on the outer part of the tie rod 7.

[0090] The above-described fastening means allows the electrolytic cell stack 1 to withstand in particular thermal expansion and / or mechanical stress variations outside and inside the electrolytic cell stack 1, such as the pressure inside the electrolytic cell stack.

[0091] In the present case, all the electrolytic cells of the electrolytic cell stack 1 are identical to each other, and thus the following description of one electrolytic cell 10 also applies to the description of the other electrolytic cells 10.

[0092] Such an electrolytic cell 10 includes a central membrane 11, which is flanked on both sides by two electrodes 12a and 12b (anode and cathode respectively), which two electrodes are in turn flanked by two inserts 16 (or flow field materials), which two inserts are in turn flanked by two bipolar plates 14. In addition, the electrolytic cell 10 also includes a seal 13 (the existence of which has been mentioned above), which is compressed between the two bipolar plates 14 of the electrolytic cell 10.

[0093] The membrane 11, the inserts 16, and the electrodes 12a and 12b are known in the prior art and will not be described in detail herein.

[0094] The two bipolar plates 14 of the electrolytic cell 10 are identical to each other, and the following description of one of the bipolar plates also applies to the other bipolar plate 14 of the same electrolytic cell 10. The bipolar plate 14 is made of a material capable of withstanding the corrosive environment prevailing inside the electrolytic cell 10.

[0095] The bipolar plate 14 is, for example, nickel-based and is made of nickel or nickel carbon steel, for example.

[0096] The bipolar plate 14 is further configured such that the bipolar plate has two main faces: a first main face that faces the interior of the electrolytic cell 10 under discussion; and a second main face that faces the exterior of the electrolytic cell 10 under discussion.

[0097] As will be seen hereinafter, the bipolar plate 14 (along a plane of symmetry passing through the center of the bipolar plate under discussion) is asymmetric. Thus, within the same electrolytic cell 10, the first face of the described bipolar plate 14 faces the second face of another bipolar plate 14 that is the same as the described bipolar plate. Within block 2, all bipolar plates 14 are oriented in the same way.

[0098] Hereinafter, axes X and Y are defined, and these axes, together with an axis Z (which is perpendicular to the plane XY), form a plane in which one of the main faces of the bipolar plate 14 extends.

[0099] When the bipolar plate 14 is in place in the electrolytic cell 10 (which in turn is in place in the electrolytic cell stack 1), the axis Z coincides here with the overall direction A.

[0100] The thickness of the bipolar plate 14 (along the axis Z) is less than its other dimensions.

[0101] The bipolar plate 14 is configured such that the bipolar plate has a transverse cross-section (in the plane XY) of any geometric shape (square, rectangular, disc-shaped, etc.). Here, the bipolar plate has a disc-shaped transverse cross-section.

[0102] The outer perimeter of the bipolar plate 14 is defined by a first region 21, a second region 22, and a third region 23.

[0103] Here, the first region 21 extends above the entire circumference of at least one of the main faces of the bipolar plate 14. Thus, the first region 21 is a ring that forms the outer perimeter of the main face.

[0104] The first region 21 enables improving the resistance of the bipolar plate 14 to the pressure prevailing inside the electrolytic cell stack 1 and enables improving the sealing of the electrolytic cell 10 relative to the exterior of the electrolytic cell stack 1. In particular, the first region 21 enables increasing the resistance of the bipolar plate 14, especially to a radial pressure load applied to the bipolar plate 14 (when the electrolytic cell 10 is arranged in the electrolytic cell stack 1). For example, the first region 21 is designed to comply with the standards applicable to pressure vessels and, for example, complies with the standard PED 2014 / 68 / EU.

[0105] The first region 21 is preferably textured. For example, the first region 21 includes grooves, stripes, irregularities, a rough appearance, etc. on at least one of the main surfaces of the bipolar plate 14 and preferably on both main surfaces of the bipolar plate 14.

[0106] Conversely, the circular edge of the bipolar plate 14 (that is, the surface connecting the two main surfaces of the bipolar plate 14) is smooth, i.e., textureless.

[0107] Furthermore, the second region 22 extends circumferentially such that the second region meets the first region 21 on the outside. The second region 22 is coaxial with the first region 21.

[0108] Here, the second region 22 extends above the entire circumference of at least one of the main surfaces of the bipolar plate 14. Thus, the second region 22 is a ring.

[0109] The second region 22 is smooth, i.e., textureless.

[0110] The second region 22 is located around the pipes for supplying the electrolyte and for discharging the electrolytic gaseous products.

[0111] The thickness of the second region 22 (the thickness considered along the axis Z) is less than the thickness of the first region 21. For example, the bipolar plate 14 is configured to have at least one shoulder between the first region 21 and the second region 22. Preferably, the bipolar plate 14 is configured to have two shoulders between the first region 21 and the second region 22. Here, the two shoulders are the same (as can be seen in Figure 3a and are formed on both main surfaces of the bipolar plate 14.

[0112] Thus, the bipolar plate 14 is symmetric in its first region 21 and second region 22 along the central symmetry plane parallel to the axes X and Y.

[0113] The narrowing between the first region 21 and the second region 22 enables different seals to be achieved between the two regions.

[0114] Furthermore, the third region 23 extends circumferentially such that the third region meets the second region 22 on the outside. The third region 23 is coaxial with the second region 22.

[0115] Here, the third region 23 extends above the entire circumference of the bipolar plate. The third region 23 is a ring.

[0116] The thickness of the third region 23 (the thickness considered along the axis Z) is less than the thickness of the second region 22. For example, the bipolar plate 14 is configured to have at least one shoulder between the second region 22 and the third region 23.

[0117] Preferably, the bipolar plate 14 is configured to have a single shoulder between the second region 22 and the third region 23. This shoulder is formed on the first major surface of the bipolar plate 14, that is, on the surface facing the interior of the electrolytic cell 10. This shoulder enables the accommodation of the membrane 11.

[0118] Preferably, the second region 22 and the third region 23 extend continuously on the second major surface of the bipolar plate 14.

[0119] Therefore, there is no shoulder between the second region 22 and the third region 23 on the second major surface.

[0120] Therefore, it should be understood that the second surface of the bipolar plate 14 does not have such a shoulder, and thus the second surface of another bipolar plate of the electrolytic cell under discussion does not have such a shoulder. Therefore, the membrane 11 is arranged between two bipolar plates such that the membrane is only accommodated in the shoulder of one of the two bipolar plates 14.

[0121] Therefore, when considering the aforementioned three regions, the bipolar plate 14 is asymmetric along a central symmetry plane parallel to the axes X and Y (as can be seen most clearly in Figure 3a , Figure 3b and Figure 3c ).

[0122] The third region 23 is completely smooth (i.e., texture - free), or partially smooth, or completely textured. Preferably, the third region 23 is textured on the first major surface of the bipolar plate 14. This makes it easier to hold the membrane 11 in place. For example, on the said first major surface, the third region 23 includes grooves, stripes, irregularities, a rough appearance, etc.

[0123] Preferably, the third region 23 is smooth on the second major surface of the bipolar plate 14.

[0124] Therefore, the thickness of the bipolar plate 14 (along the axis Z) gradually decreases with the shoulder at the junction between the first region 21 and the second region 22, and also at the junction between the second region 22 and the third region 23. Therefore, the bipolar plate 14 is thicker in its first region 21 than in its second region 22, and thicker in its second region 22 than in its third region 23.

[0125] The first region 21, the second region 22, and the third region 23 together form a crown 25. Therefore, the crown 25 forms the circumferential perimeter of the bipolar plate 14.

[0126] In addition, the central portion 24 of the bipolar plate 14 extends such that this central portion interfaces with the third region 23 on the outside. The central portion 24 is coaxial with the third region 23.

[0127] The central part 24 is solid. Thus, the central part 24 forms a circular platform.

[0128] The thickness of the central part 24 (the thickness considered along the axis Z) is less than the thickness of the third region 23.

[0129] For example, the bipolar plate 14 is configured to have at least one shoulder between the third region 23 and the central part 24. Preferably, the bipolar plate 14 is configured to have two shoulders between the third region 23 and the central part 24. Here, the two shoulders are identical and are formed on two main surfaces of the bipolar plate 14.

[0130] The central part 24 may optionally then have at least one shoulder such that its thickness (the thickness considered along the axis Z) narrows towards the center of the plate.

[0131] Thus, the central part 24 is the thinnest part of the bipolar plate 14 (the thickness considered along the axis Z).

[0132] The central part 24 can be smooth or textured.

[0133] The central part 24 acts as a current collector and transmits the current to the inserts 16, which are located on both sides of the central part.

[0134] In addition, the bipolar plate 14 includes orifices 15 that pass through the bipolar plate from one side to the other side. These orifices 15 are dedicated to supplying the electrolyte solution and discharging the electrolysis products.

[0135] For example, the bipolar plate 14 includes three to six orifices. These orifices are, for example, associated in pairs of two, and the two orifice pairs are evenly distributed on the circumference of the bipolar plate 14. Thus, the bipolar plate can include three pairs of two orifices.

[0136] For example, at least one of the orifices 15 is formed in the second region 22. In the present case, all the orifices 15 are formed in the second region 22.

[0137] The orifices can have a circular, oval or another shaped cross-section. For example, at least one of the orifices 15 has an oval cross-section.

[0138] In a manner known per se, one or more additional orifices extend from the orifices 15 towards the central part 24 in order to enable the supply of the electrolyte solution to the interior of the electrolysis cell and the discharge of the electrolysis products from the interior of the electrolysis cell. These additional orifices extend, for example, radially. In order to prevent the seal 13 from blocking the orifices, these orifices are preferably at least partially formed on the surface of the bipolar plate 14 and are laterally closed by one or more covers, which in turn contact the seal.

[0139] In fact, the function of the central part 24 is not to actually bear the high pressure against the crown 25. Therefore, the main function of the central part 24 is to act as a support for the components stacked within the electrolytic cell 10 (i.e., the insert 16, the electrodes 12a and 12b, and the membrane 11). Therefore, the forces on the two faces of the central part 24 are equal.

[0140] Therefore, the bipolar plate 14 has a specific geometry. The thicknesses of each of the aforementioned regions differ from each other by tenths of a millimeter to several millimeters. Under the influence of the thermal expansion of the bipolar plate 14, the thicknesses of the aforementioned regions also have variable values (due to thermal expansion, the variability of the thickness of each region also varies from region to region).

[0141] As already stated, within the electrolytic cell 10, the two bipolar plates 14 compress the seal 13 therebetween.

[0142] It should be noted that within the electrolytic cell stack 1, all the bipolar plates 14 are separated from each other in pairs by the seals 13 (since each bipolar plate 14 acts as the cathode of one electrolytic cell 10 and the anode of another adjacent electrolytic cell 10).

[0143] Advantageously, the two bipolar plates 14 compress a single seal 13 therebetween.

[0144] Advantageously, all the seals 13 of the electrolytic cells 10 are the same within the cell block 2. Therefore, the following description of one of the seals 13 also applies to the other seals 13 of the other electrolytic cells 10.

[0145] The main functions of the seal 13 are as follows: i) to seal each electrolytic cell 10 relative to the exterior of the electrolytic cell stack 1, ii) to seal the conduit for conveying one gas generated within the block 2 relative to the conduit for conveying another gas generated within the block 2, iii) to seal the chambers in which the electrolytic reactions for generating the two aforementioned gases occur so as to isolate these chambers from each other and also to seal these chambers relative to the just-mentioned conduits, iv) to act as an electrical insulation layer between two adjacent bipolar plates 14, and v) to define the thickness to which the electrolytic cell 10 is compressed in the Z direction.

[0146] Advantageously, a single seal 13 is compressed between two adjacent bipolar plates 14 within the same electrolytic cell 10.

[0147] Preferably, the seal 13 is shaped such that the seal has a square or rectangular cross-section (along the cross-sectional plane).

[0148] Therefore, the seal 13 is referred to as a "flat seal".

[0149] Preferably, the seal 13 is shaped such that the seal corresponds to the shape of the crown 25 of the associated bipolar plate 14.

[0150] In the present case, the seal 13 is generally in the shape of a ring and the associated bipolar plate 14 is disc-shaped.

[0151] It should be noted that the seal 13 is pierced with a plurality of holes.

[0152] This enables the supply and discharge of fluid to and from the block 2. For example, the holes formed in the seal 13 correspond to the holes formed in the region 22 of the bipolar plate 14.

[0153] The seal 13 is configured such that its diameter (the diameter of its transverse section) is as constant as possible over all its inner and outer circumferences and / or its thickness (along the axis Z) is as constant as possible over its entire extent (and from one seal 13 to another).

[0154] This enables the efficiency of the electrolytic cell 10 of the electrolytic cell stack 1 to be improved.

[0155] In particular, this enables the faces of the seal 13 to be as parallel to each other as possible and as parallel as possible to the main faces of the opposing bipolar plates 14.

[0156] This further improves the sealing of the assembly.

[0157] The tolerances on the dimensions of the seal 13 depend on the intended application of the seal (for example, the thickness tolerance is ± 0.1 mm).

[0158] As has been stated and as can be seen more clearly in Figure 3c the seal 13 is compressed between two adjacent bipolar plates 14, and more particularly between the two outer perimeters of the opposing main faces of said bipolar plates 14, and more particularly between the two opposing crowns 25 of said bipolar plates 14.

[0159] Due to the particular geometry of the bipolar plate 14 on its outer perimeter, in particular its crown 25, when the bipolar plate 14 compresses the seal 13, these bipolar plates in turn deform the seal such that these bipolar plates define and characterize the seal 13 as three separate parts.

[0160] However, the seal 13 is not compressed between the central parts 24 of the two bipolar plates 14.

[0161] The diameter of the seal 13 (along the transverse section) is such that the seal 13 extends from the lateral edge of the bipolar plate 14 to the junction between the third region 23 and the central part 24 (preferably extending beyond the third region 23).

[0162] Thus, each part of the seal 13 performs a separate sealing function and is characterized by a specific compression level, which varies from part to part. The physical and mechanical consequence is that the thickness of the seal 13 decreases variably depending on the part considered.

[0163] When the seal 13 is at rest, the seal thus has a conventional annular shape and a substantially uniform initial thickness.

[0164] When the seal 13 is compressed between two plates 14:

[0165] - Between the first regions 21 of the two bipolar plates 14, the seal 13 has a corresponding textured first part, as this first part follows the geometry of the first regions 21,

[0166] - Between the second regions 22 of the two bipolar plates 14, the seal 13 has a corresponding smooth second part, and then the seal 13 also has a greater thickness than its first part,

[0167] - Between the third regions 23 of the two bipolar plates 14 and the membrane 11, the seal 13 has a corresponding smooth and / or grooved third part.

[0168] In its first part, the seal 13 is directly compressed between the two first regions 21 (without intermediate components).

[0169] In its second part, the seal 13 is directly compressed between the two second regions 22 (without intermediate components).

[0170] However, in its third part, the seal 13 is not directly compressed between the two third regions 23. In fact, the membrane 11 is also present between these two third regions 23. Thus, the seal 13 is directly compressed on one of its faces by one of the third regions 23 and on its other face by the membrane 11, which in turn is directly compressed by the third region 23 of the opposite bipolar plate 14.

[0171] In its third part, the seal 13 then has a significantly smaller thickness than in its second part, and the membrane 11 fills the rest of the space between the two third regions 23. Thus, the membrane 11 is sealed.

[0172] Thus, the seal 13 is distributed over its three parts over its entire height (along the axis X), and thus over the three regions of the crown 25.

[0173] Thus, the parts of the electrolytic cell 10 located in the first regions 21 of the two bipolar plates 14 and the first part of the seal 13 make it possible to prevent the electrolyte solution or gas from leaving the electrolytic cell stack 1, that is to say, the electrolytic cell stack is dedicated to sealing the electrolytic cell 10 with respect to the external environment. For example, when using helium to measure the leakage rate, this ensures that the leakage rate is less than or equal to 10 -3 milligrams per meter per second (mg / (m*s)), and preferably the leakage rate is less than or equal to 10 -4 mg / (m*s).

[0174] The first part is characterized by the presence of a texture on the bipolar plate 14, where the seal 13 is deformed. In particular, by deforming, the seal 13 can fill the hollow part of the first part of the bipolar plate 14 and thus increase the sealing of the electrolytic cell 10. This is because these textures form an additional barrier for the gas and other substances present to find a path to leave the electrolytic cell stack 1. The presence of the texture is also used to promote the friction between the electrolytic cells 10 and thus promote the self-holding ability of a plurality of electrolytic cells 10 stacked to form the block 2. This advantage increases when the block is horizontal during operation.

[0175] For example, the compression of the seal 13 causes the seal 13 to reach a maximum thickness (along the axis Z) of 94%, and preferably 78%, and preferably 75% of its initial thickness (when the seal is at rest, lying flat on a flat surface without external stress) in the first part. The initial thickness is, for example, equal to or greater than 3.0 millimeters. Preferably, the initial thickness is not greater than 3.5 millimeters.

[0176] The second part of the electrolytic cell 10 located in the second regions 22 of the two bipolar plates 14 and the second part of the seal 13 makes it possible to prevent any exchange between the pipes for transporting hydrogen and oxygen in the electrolytic cell 10 or from the electrolytic cell 10 itself (starting from the third region 23 and the central part 24) to said pipes.

[0177] For example, the compression of the seal 13 causes the seal 13 to reach a thickness (along the axis Z) between 92% and 97% of its initial thickness (when the seal is at rest, lying flat on a flat surface without external stress) in the second part, and preferably to reach a thickness of 92% of its initial thickness. In any case, the seal 13 is compressed less in the second part and thus has a greater thickness than in the first part.

[0178] The widening of the seal 13 between the first region 21 and the second region 22 makes it possible to achieve different seals between the first region 21 and the second region 22. In particular, the seal between the first region 21 and the second region 22 has high quality.

[0179] The third location of the electrolytic cell 10 in the third regions 23 of the two bipolar plates 14 and in the third part of the seal 13 enables the membrane 11 to be received, as already stated.

[0180] Thus, this third location ensures the seal between the anode compartment and the cathode compartment of the electrolytic cell 10.

[0181] Thus, it should be noted that in this third location, both the membrane 11 and the seal 13 are then compressed between the two bipolar plates 14; thus, in this location of the electrolytic cell 10, the seal 13 is superimposed on the membrane 11.

[0182] This ensures a very good seal around the membrane 11 on its periphery and towards the fluid supply and discharge pipes.

[0183] Thus, the third part of the seal 13 defines a third compression zone that is intended to hold the membrane 11 and seal its periphery.

[0184] For example, the compression of the seal 13 causes the seal 13 to reach a thickness (along the axis Z) between 86% and 92% of its initial thickness (when the seal is at rest, lying flat on a flat surface without external stress) in the third location, and preferably to reach a thickness between 88% and 92% of its initial thickness, and preferably to reach a thickness of 90% of its initial thickness.

[0185] According to another aspect, the seal 13 is made of a monomeric material or a polymeric material and is, for example, made of a plastic material.

[0186] For example, the seal 13 is made of polytetrafluoroethylene or a material of the polytetrafluoroethylene type (commonly abbreviated as PTFE or better known by its trade name Teflon (registered trademark)).

[0187] Preferably, the material is made of or based on polytetrafluoroethylene or a material of the polytetrafluoroethylene type, and at least one filler is added to the polytetrafluoroethylene or a material of the polytetrafluoroethylene type. The filler is, for example, glass fiber.

[0188] The material is, for example, reinforced polytetrafluoroethylene. Reinforced polytetrafluoroethylene is, for example, glass fiber reinforced polytetrafluoroethylene, or reinforced polytetrafluoroethylene is carbon fiber reinforced polytetrafluoroethylene.

[0189] The properties of the seal 13 described are defined as follows:

[0190] - Long-term satisfactory behavior of the material and maintenance of satisfactory mechanical properties at the operating temperature of the electrolytic cell 10, which is significant (usually on the order of 90 degrees Celsius to 95 degrees Celsius);

[0191] - Long-term tolerance to the corrosive environment inside the electrolytic cell 10;

[0192] - Satisfactory sealing properties;

[0193] - Satisfactory electrical insulation properties (provided by a satisfactory resistance), even at the operating temperature and in contact with the electrolyte solution;

[0194] - Low creep, thus allowing the stack of electrolytic cells 10 to have a satisfactory lifespan;

[0195] - However, slight creep behavior in order to closely follow the geometric features of the area 21 where the seal 13 is located as closely as possible;

[0196] - Consistent thickness (along the axis Z).

[0197] According to one option, the end seal disposed between the first distribution plate 5 and the first substrate 3 is made of the same material as the seal 13 of the electrolytic cell 10 as described above. The end seal is, for example, the same as the seal 13. The end seal is optionally made of a monomeric material or a polymeric material and is, for example, made of a plastic material.

[0198] According to one option, the layer made of an electrically insulating material between the first substrate 3 and the first distribution plate 5 is made of the same material as the end seal disposed between the first distribution plate 5 and the first substrate 3. According to one option, the layer made of an electrically insulating material between the first substrate 3 and the first distribution plate 5 is made of the same material as the seal 13. The layer is optionally made of a monomeric material or a polymeric material and is, for example, made of a plastic material.

[0199] According to one option, the end seal disposed between the second distribution plate 6 and the second substrate 4 is made of the same material as the seal 13 of the electrolytic cell 10 as described above. The end seal is, for example, the same as the seal 13. The end seal is optionally made of a monomeric material or a polymeric material and is, for example, made of a plastic material.

[0200] According to one option, the patch disposed on the inner surface of the first distribution plate 5 is a layer of material directly attached to the first distribution plate 5 or is formed by powder coating (e.g., by Halar (registered trademark) coating).

[0201] Due to the specific compression of the seal 13 between the bipolar plates 14, the electrolytic cell 10 described in this way has very good sealing.

[0202] In addition, it should be noted that the electrolytic cell 10 is sealed by a single seal 13 and has three different sealing areas and compression areas.

[0203] Using a single seal 13 made of plastic (instead of elastomer in the prior art) also enables improving the sealing of the electrolyzer stack.

[0204] This is because the seal 13 better withstands the corrosive environment prevailing inside the electrolyzer stack 1, even over long periods.

[0205] Thus, the seal 13 is made of a hard material that can withstand the significant mechanical compression to which the electrolyzer stack is subjected.

[0206] A method for assembling the electrolyzer stack 1 will now be described.

[0207] According to the first step, sub-assemblies are constructed individually, each sub-assembly being formed by assembling two inserts 16 and two electrodes 12a, 12b on both sides of a bipolar plate 14. Strictly speaking, each sub-assembly forms two electrolytic half-cells placed side by side.

[0208] In the second step, the sub-assemblies are stacked in sequence (the sub-assemblies being separated from each other by a membrane 11 and a seal 13), thereby forming the electrolytic cells 10 connected in series electrically. The last electrolytic cell 10 at one end of the block 2 is covered by a second distribution plate 6 and then by a second substrate 4, and the last electrolytic cell 10 at the other end of the block 2 is covered by a first distribution plate 5 and then by a first substrate 3, thereby defining the electrolyzer stack 1.

[0209] During the third step, the newly assembled electrolyzer stack 1 is compressed by tie rods 7, nuts 8, and spring washers 9.

[0210] To this end, a pre-tightening of the electrolyzer stack 1 (and thus of the various layers of the electrolytic cells 10 together, as well as of the seal 13) is carried out.

[0211] This third step is preferably carried out at ambient temperature. For example, this third step is carried out at a temperature between 15 degrees Celsius and 25 degrees Celsius, and for example between 18 degrees Celsius and 22 degrees Celsius.

[0212] For example, the pre-tightening is obtained by acting on the nuts 8 of the tie rods 7. Preferably, several nuts 8 are tightened simultaneously. Preferably, all the nuts 8 are divided into groups, each group being tightened one after the other, and the nuts in the same group are tightened simultaneously. Preferably, these groups are tightened in a staggered or star sequence. For example, a group of nuts 8 can be tightened simultaneously, then move on to the next group, the next group of nuts being positioned as close as possible to the first group of nuts 8, and so on. Preferably, all the nuts 8 are tightened during this stage.

[0213] During the third stage, several nuts 8 thus act simultaneously, but not all the nuts 8 of the block are tightened simultaneously.

[0214] This enables ensuring that the thickness of the seal 13 is reduced relatively uniformly and consistently over the entire circumference of each seal.

[0215] Pre-tightening can be carried out, for example, using a hydraulic device (e.g., a hydraulic cylinder).

[0216] During this third step, the electrolyzer stack is preferably tightened such that the electrolyzer stack reaches the threshold characteristic of the desired initial compression ratio of at least one, and preferably all, of the seals 13.

[0217] For example, the threshold can be defined according to at least one of the following conditions:

[0218] - At the end of the first phase, at least one of the seals (and preferably all of the seals 13) must ensure contact between the two bipolar plates 14 and the membrane 11 within a given cell, and / or

[0219] - At the end of the first phase, the compression ratio of at least one of the seals (and preferably all of the seals 13) must be between 25% and 50% of the desired final compression ratio of at least one of the seals 13, and preferably all of the seals 13.

[0220] Thus, the threshold can be the target thickness of at least one of the seals, or of a plurality of seals, or the target thickness of the electrolyzer stack 1, or the target tightening torque of the electrolyzer stack. To estimate whether the tightening is approaching the threshold (e.g., during the first phase), the thickness of at least one of the seals, or the thickness of the electrolyzer stack, or the tightening torque applied to the electrolyzer stack is correspondingly measured.

[0221] In particular, this third step includes a series of tightening processes such that the electrolyzer stack is tightened in stages. Preferably, at the end of each stage, the distance from the threshold is estimated in order to control the tightening torque of the next stage.

[0222] During the fourth step, the electrolyzer stack 1 and thus the block 2 then undergo successive tightening cycles.

[0223] The tightening cycle includes the following phases.

[0224] First phase: Heating the electrolyzer stack 1.

[0225] This first stage is carried out, for example, by injecting a gas or a liquid (such as steam, for example water vapor, or a hot liquid, for example hot water) through some of the inlet and outlet orifices of the substrate 4 in order to heat the entire interior of the electrolyser stack 1, in particular the seals 13. Alternatively, the gas or liquid inside the electrolyser stack may be at ambient temperature. For example, a heating device may be temporarily introduced into the electrolyser stack 1 in order to heat the gas or liquid (for example, the heating device may include one or more resistors). Optionally, the heating device is temporarily introduced into the electrolyser stack 1 through the orifice 15 of the bipolar plate 14.

[0226] Second stage: Tightening of the electrolyser stack 1 (and thus of the various layers of the electrolytic cell 10 together, and of the seals 13).

[0227] For example, tightening is obtained by acting on the nuts 8 of the tie rods 7. Preferably, a plurality of nuts 8 are tightened simultaneously. Preferably, all the nuts 8 are divided into groups, each group being tightened one after the other and the nuts in the same group being tightened simultaneously. Preferably, these groups are tightened in a staggered or star sequence. For example, a group of nuts 8 can be tightened simultaneously and then moved on to the next group, the next group of nuts being positioned as close as possible to the first group of nuts 8, and so on. Preferably, all the nuts 8 are tightened during this stage.

[0228] During the second stage, a plurality of nuts 8 thus act simultaneously, but not all the nuts 8 of the block are tightened simultaneously.

[0229] This makes it possible to ensure that the thickness of the seals 13 is reduced relatively uniformly and consistently over the entire circumference of each seal.

[0230] Tightening can be carried out, for example, using a hydraulic device (such as, for example, a hydraulic cylinder).

[0231] It should be understood that, due to the previous stage, the tightening is carried out hot and not at ambient temperature as in the third step.

[0232] Third stage: Cooling of the electrolyser stack 1.

[0233] This cooling can be natural (by stopping the heating of the electrolyser stack 1 since the electrolyser stack is in contact with air at ambient temperature, which allows natural cooling of the electrolyser stack) and / or forced [for example, by the following steps: injecting a gas or a liquid (such as cold water) through some of the inlet and outlet orifices of the substrate 4 in order to cool the entire interior of the electrolyser stack 1, in particular the seals 13 / ventilation / etc.].

[0234] Fourth stage: Tightening of the electrolyser stack 1 and thus of the various layers of the electrolytic cell 10 and of the seals 13.

[0235] This tightening is carried out as in the second stage, but at ambient temperature as in the third pre-tightening step (where a given temperature range can also be applied).

[0236] During the fourth step, a series of tightening operations are thus carried out on the electrolyser stack 1 and thus on the block 2, these operations being carried out first hot and then at ambient temperature. Given that the hot tightening is carried out at a higher temperature than the ambient temperature tightening, it can also be said that a series of tightening operations are carried out on the electrolyser stack 1 and thus on the block 2, these operations being carried out first hot and then cold.

[0237] The second stage (especially during its first iteration, if stages 1 to 4 are repeated several times) allows a significant reduction in the individual thicknesses of the respective seals 13.

[0238] Stages 1 to 4 are repeated again, preferably until a threshold is reached which characterises at least one of the seals 13 and preferably the desired final compression ratio of all the seals 13.

[0239] For example, the threshold can be defined by considering the following:[[]]END]]

[0240] - the desired sealing performance of at least one of the seals 13 and preferably all the seals and preferably of the electrolyser stack 1 as a whole, and / or

[0241] - the desired geometric compression of the electrolyser stack 1 such that the electrical contacts are satisfactory for achieving a given output and / or a given electrical continuity, and / or

[0242] - the desired mechanical stability of the material forming one or more of the seals 13 such that creep phenomena do not unduly impair the sealing of the electrolyser stack 1.

[0243] Preferably, the aforementioned threshold is associated with at least one compression ratio of at least one of the seals 13 and preferably all the seals 13.

[0244] Preferably, the aforementioned threshold is associated at least with the compression ratio of at least one of the seals 13 (and preferably all the seals 13) of the part connected to the first region 21 of the opposing bipolar plate 14.

[0245] Even more specifically, the aforementioned threshold is associated with the compression ratios defined above, which are associated with at least one of the seals and preferably different parts of all the seals 13.

[0246] It should be noted that up to the first iteration, the thickness of the seals 13 is close to its target value. Subsequent iterations are thus more aimed at eliminating the plastic behaviour of the seals within their operating range.

[0247] Preferably, after each tightening stage (the second and fourth stages), at least one of the following parameters is measured: the thickness of at least one of the seals in the seal, the thickness of the electrolytic cell stack or block, the distance between substrates 3 and 4, and the tightening torque applied to the electrolytic cell stack. For example, after each tightening stage, the thickness of all the seals 13 is estimated by measuring the distance between substrates 3 and 4 or the tightening torque applied to the electrolytic cell stack 1.

[0248] Procedure 1 This enables the repetition of stages 1 to 4 to be controlled by estimating the progress towards a final threshold. For example, the final threshold is the target thickness value of the electrolytic cell stack 1. For example, after each tightening stage, the thickness of the electrolytic cell stack 1 is checked. Optionally, the thickness of the block 2 is measured by measuring the thickness between substrates 3 and 4 at different points on the circumference of the block 2; then the average value of the different values obtained is found in order to obtain the average thickness of the block 2; based on the number of cells and the thickness of the different elements of each cell, the average thickness of each of the seals 13 in the seal is derived. From this, the ratio Hn+1 / Hn is derived, where Hn is the thickness change to be achieved in order to reach the target thickness (here the final threshold) just after the tightening stage just carried out, and Hn+1 is the thickness change to be achieved in order to reach this target thickness during the next tightening stage. This ratio enables the progress of the fourth step to be monitored. Preferably, the fourth step is implemented such that this ratio remains within a given range throughout the fourth step. Preferably, when the second stage is first implemented, the aim is for the ratio Hn+1 / Hn to be less than 0.5 (meaning that the thickness change is reduced by more than 50%) and preferably less than 0.4 (meaning that the thickness change is reduced by more than 60%). For example, the aim is for the ratio Hn+1 / Hn to be between 0.5 and 0.25, and preferably between 0.4 and 0.25.

[0249] Procedure 2

[0250] This makes it possible to estimate the regions in the electrolyzer stack 1 where the thickness is abnormally greater than other regions of the stack. Then, during the next tightening phase, the tightening can be adapted by targeting the nuts through which the priority tightening must be carried out in order to correct the regions that are abnormally thick compared to other regions of the electrolyzer stack 1. Thus, the lack of parallelism between the bipolar plates 14 and / or the cells can be corrected during the respective tightening phases. This is essential for ultimately ensuring satisfactory electrical contact of each electrolytic cell 5 over the entire surface of the cell. This also makes it possible to maintain the electrolyzer stack 1, which is as straight as possible and as centered as possible on its axis Z. This also enables the substrates 3 and 4 to be correctly aligned and parallel to each other. For example, the inventors have observed that for an electrolyzer stack 5 meters long (length taken along the axis Z), any lack of parallelism between the substrates 3 and 4 is less than one millimeter.

[0251] Preferably, the first program and / or the second program are also implemented for the third pre-tightening step.

[0252] Preferably, steam (by steaming) is used to heat the seal 13. This makes it possible to carry a large amount of energy in a small amount of fluid corresponding to the size of the pipe. More specifically still, the thickness of the seal 13 is permanently reduced in order to achieve a predefined compression ratio. In addition, the plastic behavior (or creep) of the seal 13 decays during the thermal tightening cycle and the ambient temperature tightening cycle until it reaches the elastic behavior range. Thus, at the end of this fourth step, the seal 13 exhibits a linear deformation behavior. This behavior makes it possible (due to the counterbalancing force caused by the spring washer 9) to ensure the sealing of the various regions of the bipolar plate 14, particularly taking into account the expansion and pressure applied to the electrolyzer stack 1.

[0253] Thus, the plastic nature of the seal 13 is eliminated.

[0254] Thus, through the plastic deformation of the seal 13, the thickness of the seal 13 (along the axis Z) gradually but sharply decreases. Figure 5 This shows this decrease in the thickness of the seal 13 during the various steps and stages of the described assembly method. Thus, the curve shows the variation in the average thickness of the seal 13 (as described above or determined by another method) during the different steps and stages of the described assembly method, with the 100% value corresponding to the target thickness reduction.

[0255] For example, at least in some parts of the seal 13, the thickness of the seal 13 is reduced by at least 10%, or at least 15%, or at least 20%, or at least 25%.

[0256] This makes it possible to limit the creep of the seal 13 during the actual operation of the electrolyzer stack 1.

[0257] Thus, the seal 13 ensures a very good seal of the electrolyzer stack 1, even over time on a time scale of 10 or 20 years.

[0258] Some of the tightening is carried out ingeniously hot, which makes it possible to take advantage of the softer (less hard) nature of the material of the seal 13 at high temperature.

[0259] When the voltages at the terminals of each electrolytic cell 10 are different and the current is connected only to one or more points on the periphery of each of the distribution plates 5 and 6, such an assembly with thick distribution plates 5 and 6 and thin flat bipolar plates 14 allows for the homogeneity of the current in all the electrolytic cells 10 of the electrolyzer stack 1.

[0260] Furthermore, due to the specific shape of the bipolar plates 14 and the satisfactory tightening of each seal 13, these bipolar plates are parallel to each other within the block 2. This further improves the homogeneity of the current in all the electrolytic cells 10.

[0261] In particular, the above-described assembly method enables each seal 13 to:

[0262] - deform according to the geometry imposed by the bipolar plate clamping the seal,

[0263] - sink into the texture of the first region 21 in order to fill these first regions,

[0264] - deliberately age prematurely the material from which the seal is made,

[0265] - eliminate as much as possible the plastic behavior of the material from which the seal is made,

[0266] - introduce a certain range of elastic behavior into the material of the seal (centered on the operating point of the electrolyzer stack),

[0267] - reach a desired tightening value that achieves both the desired seal and the electrical contact between the various components, making it possible to achieve the envisaged energy performance.

[0268] At the end of the fourth step, the temperature and pressure prevailing inside the electrolyzer stack 1 may change, but the seal will advantageously always remain within the elastic range obtained. The nominal operating point of the electrolyzer stack is, for example, 85 degrees Celsius at 3 megapascals.

[0269] Of course, the present invention is not limited to the described embodiments, but covers any variant falling within the scope of the present invention as defined by the claims.

[0270] The described assembly method is advantageously applicable to all types of electrolyzer stacks 1, regardless of their thermal and mechanical properties, number or size, or the nature of the materials forming the electrolyzer stack 1.

[0271] One or more end seals may be different from seal 13.

[0272] The electrolyzer stack 1 may be assembled using a method different from the method described.

[0273] Although the electrolyzer stack is cooled here (naturally and / or forcedly) to ambient temperature, the electrolyzer stack may be cooled to a value greater than ambient temperature. For example, the electrolyzer stack may be cooled such that its temperature is less than 35 degrees Celsius and, for example, between 15 degrees Celsius and 35 degrees Celsius and, for example, between 20 degrees Celsius and 35 degrees Celsius. Thus, cold tightening may be carried out at different temperatures between two successive cold tightening operations (thus, provided that the electrolyzer stack is at a temperature lower than the hot tightening temperature and close to ambient temperature, preferably not dropping below 15 degrees Celsius, which may impede the plasticity of the seal material) and / or at a temperature different from the first tightening stage.

[0274] The electrolyzer stack may be used horizontally, vertically, or in any other position. The electrolyzer stack may be assembled horizontally, vertically, or in any other position. Preferably, the electrolyzer stack is assembled vertically and used horizontally.

Claims

1. A bipolar plate (14) for an electrolysis cell (10), the bipolar plate (14) comprising, on at least one of its main faces: - A first region (21) that extends circumferentially, - A second region (22) that extends circumferentially such that the second region is in contact with the first region (21) on the outside, the second region (22) and the first region (22) together defining at least one narrowing of the thickness of the plate, - A third region (23) that extends circumferentially such that the third region is in contact with the second region (22) on the outside, the third region (23) and the second region (22) together defining at least one narrowing of the thickness of the plate, The different regions (21, 22, and 23) are arranged on the perimeter of the associated main face.

2. The bipolar plate (14) according to claim 1, wherein, The first region (21) is textured.

3. The bipolar plate (14) according to claim 2, wherein, The textured first region also extends circumferentially on the other main face of the bipolar plate (14).

4. The bipolar plate (14) according to one of the preceding claims, wherein, The second region (22) and / or the third region (23) is / are non-textured.

5. The bipolar plate (14) according to one of the preceding claims, the bipolar plate having a circular outer perimeter.

6. The bipolar plate (14) according to one of claims 2 to 5, wherein, The first region (21) includes stripes.

7. The bipolar plate (14) according to one of the preceding claims, wherein, The second region (22) and the third region (23) form at least two shoulders between them to form the narrowing of the thickness of the plate.

8. The bipolar plate (14) according to one of the preceding claims, wherein, At least three orifices are formed in the second region (22).

9. An electrolysis cell (10) comprising at least one first bipolar plate (14) according to one of the preceding claims, at least one second bipolar plate (14) according to one of the preceding claims, and a single seal (13) arranged between the two bipolar plates (14).

10. The electrolytic cell (10) according to claim 9, wherein, The seal (13) is made of a monomeric material or a polymeric material.

11. The electrolytic cell (10) according to claim 9 or claim 10, wherein, The seal (13) is in the shape of a flat ring.

12. The electrolytic cell (10) according to one of claims 9 to 11, wherein, The seal (13) is made of a glass fiber reinforced material and / or a carbon fiber reinforced material.

13. An electrolysis cell stack (1) comprising a plurality of electrolysis cells (10) according to one of claims 9 to 12.

14. A method for assembling an electrolysis cell stack (1) according to claim 13, the method comprising the following steps: - Assembling electrolysis half-cell pairs (10) individually, - Assembling the electrolysis half-cell pairs (10) together, arranging a seal between each pair to form a block, - Applying successive heating and cooling phases to the block, and applying at least one tightening operation to the block between two different heating and cooling phases.

15. The method according to claim 14, wherein, Heating the block by injecting steam or hot water into the block to perform the tightening.

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