Electrolysis cell

Abstract

The invention relates to an electrolysis cell, which includes a spacer (50) that is configured to support a separator, extends between a first and a second face (51, 52), and comprises: an inlet (7) and an outlet (8) configured to allow water to circulate within the electrolysis cell; a recess (9) which is intended to be occupied by the separator and is in fluid communication with the inlet and the outlet; a first primary groove (10) which is formed in a thickness of the spacer, opens onto the first face and extends around the recess, the inlet, and the outlet, to accommodate a first sealing member; a first secondary groove (60) which is formed in a thickness of the spacer, opens onto the first face and extends around the first primary groove to accommodate a first sealing device; and a through-hole (70) between the first and the second face, which through-hole is arranged between the first primary and secondary grooves.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: ELECTROLYSIS CELL

[0003] The present invention relates to the field of electrolysis and concerns a spacer for an electrolysis cell. The invention also relates to an electrolysis stack comprising such a spacer.

[0004] Water electrolysis involves dissociating water molecules into oxygen and hydrogen gas. The oxygen and hydrogen produced by water electrolysis can then be used as consumables in the chemical industry.

[0005] An electrolyzer consists of a series of electrolysis cells connected in series, with fluid distribution in parallel. The fluids flow tangentially to the plane of each electrolysis cell. The electric current flows perpendicular to the plane of the cells. Each water electrolysis cell is thus the site of the reaction that produces hydrogen and oxygen from water and electricity. The resulting stack of electrolysis cells is commonly called a stack. The stack is supplied with water and electricity by a set of auxiliary systems and equipment, called the Balance-of-Plant (BoP) of the electrolyzer. The electrolyzer is formed by the stack connected to its BoP.

[0006] Each water electrolysis cell is divided into two compartments, called the anodic structure and the cathodic structure. The separator, positioned between the anodic and cathodic structures, can be a cationic (proton-conducting) or anionic (hydroxyl-ion-conducting) polymer membrane. Other technologies utilize porous thermoplastic or ceramic separators.

[0007] In the case of liquid water electrolysis using PEM technology (proton-exchange membrane), the separator is a polymer membrane with a typical thickness between 50 and 250 micrometers. It is a solid electrolyte, with the ionic charge carriers remaining confined within. The electrocatalysts are deposited on each of the two faces of the membrane. The polymer membrane is thus coated with two catalytic layers with a typical thickness between a few micrometers and a few tens of micrometers. These two catalytic layers form the two electrodes of the cell. Such membrane-electrocatalyst assemblies are called CCMs (catalyst-coated membranes). An electrolyzer, for example of the proton exchange membrane type, includes two liquid water injection wells, or inlet wells, and two collection wells for biphasic mixtures, or outlet wells.Each compartment of each cell has an inlet, i.e., a water entry point supplied by the injection well, and an outlet, i.e., a reaction mixture outlet point (single-phase or two-phase depending on the technology) connected to the collection well. The anodic injection and collection wells are fluidically connected to the anodic circuit. The cathodic injection and collection wells are fluidly connected to the cathodic circuit. Liquid water circulates in each of these two circuits using a pump, following an internal vortex flow from the injection well to the collection well.Each circuit of the BOP includes different functional blocks, for example, a liquid-gas separator which allows the separation and collection of gases from the reaction, a heat exchanger which allows the heat produced in the cells during electrolysis to be extracted, a resin bed which allows the conductivity of the circulating water to be controlled, a pump which ensures the circulation of water in the circuit.

[0008] Figure 1 shows an exploded cross-sectional view of a prior art electrolysis cell 1, illustrating the stacking of components inside the cell. Electrolysis cell 1 is traversed by a direct electric current, which decomposes water into dioxygen and dihydrogen.

[0009] The electrolysis cell 1 comprises a separator 2 interposed between an anodic structure 30, or anode, generally made of titanium, and a cathodic structure 40, or cathode, generally made of titanium but which may contain carbon components. These structures are connected directly or indirectly to the positive and negative terminals of an external DC power source, not shown. For example, the separator 2 may be a membrane-electrocatalyst assembly if the electrolysis cell is a proton exchange membrane cell or an anion exchange membrane cell. In the case of an alkaline electrolysis cell, the separator is a diaphragm.

[0010] The anodic structure 30 comprises a bipolar plate 31 common to an adjacent upper cell, an anodic grid 32, and a porous anodic component 33 generally made of titanium particles or fibers sintered together under vacuum. The anodic structure 30 may also include fastening means 34 adapted to the shape of the electrolysis cell 1, which allow the bipolar plate 31, the anodic grid 32, and the porous anodic component 33 to be fixed. These three constituent elements of the anodic structure 30 optimize electrical conductivity and mechanical strength and contribute to good fluid distribution.The cathodic structure 40 also includes a second bipolar plate 41 common with an adjacent lower cell, a cathodic grid 42, and a porous cathodic component 43 of the same material as the porous anodic component 33, or alternatively made of carbon, all these components having the same properties as the elements integrated into the anodic structure 30. The electrolysis cell 1 further includes a spacer 5 supporting the separator 2 in its middle. The anodic structure 30 and the cathodic structure 40 fit into a recess 9 in the center of the spacer 5. The bipolar plates 31 and 41 cap the spacer 5 and hold the constituent elements of the anodic structure 30 and the cathodic structure 40 in place and in contact with each other. Thus, the porous anodic component 33 and the cathodic component 43 are in contact with the catalytic layers of the separator 2.The spacer 5 includes at least one inlet and one outlet to allow water to be introduced into and removed from the cell. The spacer 5 thus contributes to the circulation of water in each of the two compartments, supplying the reaction with water and ensuring the cooling of the electrolysis cell, whose components produce heat when the cell is operating, i.e., when a direct current flows through it. The electrolysis cell 1 can also rest on a support plate 6.

[0011] An electrolysis cell 1 includes several seals to ensure fluidic sealing between the inside of the stack and the outside. The spacer 5 extends between a first face 51, which will hereafter be referred to as the anodic face of the spacer, and a second face 52, which will hereafter be referred to as the cathodic face of the spacer.

[0012] To prevent leaks of water or reaction mixture (containing gas), the electrolysis cell includes sealing cords 35, 45, each extending along one face 51, 52 of the spacer 5 around the inlet, outlet, and recess 9. The sealing cords 35, 45 prevent water from leaking outside the electrolysis cell and thus ensure that the flow of water and gas passes through the cell. It should be noted that the cell also includes seals around the water inlets and outlets. Hereafter, we will refer to all these seals and cords, known from the prior art, as the primary barrier. However, despite the presence of the sealing cords, leaks may still occur, for example, due to gradual wear of the cords. Each stack typically consists of a stack of about one hundred electrolysis cells.Despite all the care taken during the design and assembly of the stacks, the frequency of leaks from an electrolysis stack in operation can be significant. Such a leak can lead to the release of water, hydrogen, oxygen, or a reaction mixture of water and gas.

[0013] A leak inevitably leads to incidents and can necessitate unplanned production shutdowns to secure the electrolyzer installation. In the case of a hydrogen-containing fluid leak, an explosive zone is created near the leak point, resulting in a safety risk for the electrolyzer operator.

[0014] Such external leaks are difficult to detect. Currently, their detection relies on periodic visual inspections by an operator. These inspections aim to detect any water seepage sometimes observed around the electrolysis cells or any hissing sound in the event of a significant gas leak. Alternatively, or in addition to periodic visual inspections, a containment tray can be installed beneath the electrolysis cells, in which a water level sensor is placed. This option only allows for the detection of significant water accumulation. To detect hydrogen leaks into the ambient air, the electrolyzer can be equipped with a combustible gas detector.

[0015] Existing solutions allow for external leak detection only after a leak has occurred. This delayed leak detection poses a safety risk on-site and generally results in the shutdown of the affected electrolyzer. Therefore, it is necessary both to improve the sealing of the electrolysis cells to prevent external leaks and to implement early leak detection to take the necessary safety measures and repair the electrolyzer.

[0016] The invention aims to overcome all or part of the problems mentioned above by providing an electrolysis cell incorporating a spacer with specific characteristics that limit the occurrence of external leaks in electrolysis cells incorporating such a spacer. More precisely, the invention makes it possible both to prevent external leaks and to automatically and early detect the failure of a sealing bead in an electrolyzer. The invention thus enhances safety during the operation of the electrolyzer.

[0017] To this end, the invention relates to a water electrolysis cell comprising an anodic structure, a cathodic structure and a separator interposed between the anodic structure and the cathodic structure, the water electrolysis cell being characterized in that it comprises:

[0018] a spacer configured to support the separator extending between a first face and a second face, and comprising:

[0019] o an inlet and an outlet configured to allow water circulation within the water electrolysis cell,

[0020] o a recess intended to house the separator and in fluidic communication with the inlet and outlet,

[0021] o a first primary groove cut into a thickness of the spacer opening on the first face and extending around the recess, the inlet, and the outlet, configured to house a first sealing element,

[0022] o a first secondary groove formed in a thickness of the spacer opening onto the first face and extending around the first primary groove to house a first sealing device; o a through-hole between the first face and the second face, disposed between the first primary groove and the first secondary groove, said spacer supporting the anodic structure, the cathodic structure and the separator, and in that the water electrolysis cell comprises:

[0023] a first sealing element housed in the first primary groove;

[0024] A first sealing device is housed in the first secondary groove. The spacer, comprising a first annular space, is located between the first sealing element and the first sealing device and is in fluidic connection with the through orifice. Thanks to these characteristics, in addition to the primary barrier formed by the first primary groove and its first sealing element, the spacer of the electrolysis cell of the invention includes a secondary barrier formed by the first secondary groove and its first sealing device. Between these two barriers, an annular space is created that can contain any leaking fluid following a failure of the primary barrier.

[0025] The through-hole, combined with the annular space, allows for the drainage of the leaking fluid. In addition to reinforcing the primary barrier, the secondary barrier creates a containment zone for the leaking fluid. This containment zone collects the leaking fluid and prevents its uncontrolled release outside the electrolysis stack. Specifically, the spacer of the invention keeps any hydrogen leakage contained, thus preventing the creation of an explosive zone near the electrolysis stack.

[0026] The through-hole allows the leakage fluid collected in the annular space between the primary and secondary barriers to drain away. In a stack of multiple electrolysis cells, the multiple through-holes form a drainage channel for the leakage fluid.

[0027] The secondary barrier, formed by the secondary sealing devices, and the through-holes ensure the drainage of any leaking fluids and, as will be described later, continuous monitoring of the electrolysis cells to detect any incipient leaks. It follows that the features of the spacer of the invention, combining the secondary barrier and through-holes, allow for the early detection of a leak and, in the case of a dihydrogen leak, prevent the formation of an explosive atmosphere in the environment of the electrolysis stack.

[0028] Thanks to this double barrier, the seal against potential leaks is reinforced. Furthermore, the annular space between the primary and secondary barriers allows for controlled containment of any leaking fluid and its evacuation through the through-holes.

[0029] According to an optional feature of the invention, on a segment locally perpendicular to the first secondary groove, the distance between the first secondary groove and the through-hole is less than the distance between the first primary groove and the through-hole. The through-hole is thus located as close as possible to the first secondary groove. In an electrolysis stack with its electrolysis cells stacked along a horizontal axis, this allows the through-hole to be located at the lowest point of the spacers. In this configuration, the drain channel is positioned at the lowest point of the electrolysis stack. The liquid portion of the leakage fluid, which accumulates in the lower part of the annular space, quickly reaches the drain channel.

[0030] In other words, the volume in the annular space that the leaking fluid must fill before reaching the through-orifice to exit the electrolysis cell is minimized. This results in early detection of a potential liquid leak.

[0031] According to an optional feature of the invention, the spacer comprises an inlet and outlet configured to allow water circulation within the water electrolysis cell, a second primary groove formed in a thickness of the spacer opening on the second face and extending around the inlet and outlet, configured to house a second sealing element. The spacer further comprises a second secondary groove formed in a thickness of the spacer opening on the second face and extending around the second primary groove to house a second sealing device. The same principle explained previously of collecting leakage fluid in an annular space between the sealing element and the sealing device also applies to the cathodic side of the electrolysis cell.In other words, a single electrolysis cell can include an annular space on the anodic side and an annular space on the cathodic side. Any leakage from an electrolysis cell is directed, depending on the location of failure of the primary barrier, towards one of the two annular spaces, connected by the through orifice, in order to be detected.

[0032] According to an optional feature of the invention, the second secondary groove is positioned such that, in axial projection in a cutting plane parallel to the first face, the second secondary groove coincides with the first secondary groove. In other words, the second secondary groove is superimposed on the first secondary groove. The sealing devices and elements on the anodic and cathodic sides are superimposed. This symmetry in their arrangement ensures proper positioning of the sealing devices and elements and guarantees secure retention of the sealing elements during the assembly and operation of the electrolysis stack.According to an optional feature of the invention, the through orifice being a first through orifice, the spacer further comprises a second through orifice between the first face and the second face, disposed between the first primary groove and the first secondary groove, the first through orifice and the second through orifice being disposed on either side of the recess.

[0033] In an electrolysis stack configuration with electrolysis cells stacked along a horizontal stacking axis, this ensures that there is a through-hole in the upper part of the spacer, intended for the evacuation of the gaseous part of the leakage fluid, and a through-hole in the lower part of the spacer, intended for the evacuation of the liquid part of the leakage fluid.

[0034] According to an optional feature of the invention, the water electrolysis cell comprises:

[0035] a second sealing element housed in the second primary groove; a second sealing device housed in the second secondary groove. The invention also relates to a water electrolysis stack comprising a plurality of electrolysis cells as previously defined, each electrolysis cell being delimited by two parallel and electrically conductive bipolar plates, the electrolysis cells being stacked one on top of the other along a stacking axis, each bipolar plate comprising, for each through orifice of the spacer it covers, a through opening opposite said through orifice of the spacer, the through orifices and openings of the electrolysis cells aligned with each other forming at least one fluid evacuation channel.

[0036] In an electrolysis cell stack, a spacer is positioned between two bipolar plates. Stacking electrolysis cells thus results in an alternating pattern of bipolar plates and spacers. The through-holes of the spacers and the through-holes of the bipolar plates are aligned. With the spacers and bipolar plates stacked against each other, the opposing through-holes and through-holes form a drainage channel. Since the through-hole of a spacer opens onto both faces of the spacer and is positioned between the primary and secondary barriers, the drainage channel is fluidically connected to the annular space, allowing it to drain any leakage fluid from the annular space.

[0037] According to an optional feature of the invention, each electrolysis cell comprises a first through-hole and a second through-hole arranged on either side of the recess. The electrolysis stack comprises two discharge channels, the first of these two discharge channels being formed by the first through-holes, and the second of these two discharge channels being formed by the second through-holes. The presence of the two discharge channels, one in the upper part and the other in the lower part of the electrolysis stack, allows for the discharge of the gaseous portion of the leakage fluid (in the upper part) and the liquid portion of the leakage fluid (in the lower part). As will be shown below, this distinction between discharge channels also allows for the monitoring of the stack.

[0038] According to an optional feature of the invention, the electrolysis stack includes a fluid detection system connected to one of the discharge channels, capable of detecting a leak in the electrolysis stack. The detection system may include a gas detection device (pressure sensor, mass spectrometer, by way of example), in which case the detection system is connected to the discharge channel at the top, where the gaseous portion of the leaking fluid is located. Alternatively or in addition, the detection system may include a water detection device, in which case this detector is connected to the discharge channel at the bottom of the electrolyzer stack, where the liquid portion of the leaking fluid accumulates.

[0039] Thanks to this invention, it is possible to detect an abnormal pressure increase in a drainage channel. The pressure sensor has the advantage of being non-selective with respect to leaks of water, oxygen, and hydrogen. The gas detector offers greater sensitivity than the pressure sensor, which relies on pressure variations. However, the gas detector can identify the specific leaking gas.

[0040] By creating annular spaces and drainage channels through the spacers and bipolar plates, and by using a fluid detection system, the invention enables continuous monitoring for leaks. According to an optional feature of the invention, the electrolysis stack includes an alarm system connected to the fluid detection system, capable of sending a signal when the detection system detects a leak in the electrolysis stack.

[0041] According to an optional feature of the invention, the electrolysis stack further comprises an inert gas source fluidically connected to at least one fluid discharge channel. Connecting the inert gas source to the discharge channel allows for the inerting of the electrolysis stack. The inert gas is injected into the discharge channel and circulates through the electrolysis cells to purge the gases present between the bipolar plates and the spacers. This allows for the inerting of the annular spaces, for example, after detecting a leak and making a repair to the electrolysis stack. The invention also covers a method for leak testing an electrolysis stack as described above, with the inlets and outlets each forming an inlet well and the outlets and discharges each forming a discharge well. The leak testing method comprises the following steps:

[0042] Connection of a tracer gas source to one of the admission wells of the electrolysis stack;

[0043] Tracer gas injection into the intake well;

[0044] Verification of the presence of tracer gas in an evacuation channel of the electrolysis stack by the detection system.

[0045] The leak testing process utilizes the creation of an annular space and drainage channels to verify the stack's leak-tightness, ideally after assembly and before delivery to the site. Tracer gas is injected into the electrolysis stack following the same path the water will eventually take. If a sealing component is defective or incorrectly assembled, the tracer gas will bypass the primary barrier at the faulty component. The tracer gas will then accumulate in the annular space before flowing into the drainage channel. The detection system can then identify the presence of tracer gas in the drainage channel, indicating a leak within the electrolysis stack.

[0046] The invention contributes to improving safety in the operation of an electrolysis stack. The combination of the secondary barrier with the primary barrier provides an additional layer of safety by reducing the risk of leaks. The operator of the electrolyzer stack is thus protected, as is the surrounding infrastructure, since any explosive situation is avoided.

[0047] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given by way of indication and not limitation with reference to the attached schematic drawings on the other hand, on which: [fig 1] represents an exploded cross-sectional view of an electrolysis cell of the prior art;

[0048] [fig 2] represents an exploded view of an electrolysis cell according to the invention;

[0049] [fig 3] schematically represents the two faces of the spacer of an electrolysis cell according to the invention;

[0050] [fig 4] schematically represents a portion of a cross-section of a stack of spacers according to the invention;

[0051] [fig 5] illustrates the annular space on the anodic face of the spacer of the invention; [fig 6] schematically represents an electrolysis stack according to the invention equipped with leak detection equipment;

[0052] [fig 7] represents the steps of a leak testing process for an electrolysis stack according to the invention.

[0053] The features, variations, and different embodiments of the invention, as described or as they will be presented in the detailed description that follows, can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variations of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0054] For the sake of clarity, the same elements are designated by the same references in the different figures.

[0055] Figure 1 represents an exploded cross-sectional view of a prior art electrolysis cell and was described in the introduction.

[0056] Figure 2 shows an exploded view of an electrolysis cell 1 according to the invention. The water electrolysis cell 1 comprises an anodic structure 30, a cathodic structure 40, and a separator 2 interposed between the anodic structure 30 and the cathodic structure 40. The separator 2 can be a polymer membrane, generally less than 250 micrometers thick. A catalyst layer is typically deposited on each of the two faces of the membrane. This is then referred to as a CCM (catalyst-coated membrane) assembly or a membrane-electrocatalyst assembly. The water electrolysis cell 1 includes a spacer 50 having a recess 9 in its center. The role of the spacer 50 is to support the anodic structure 30, the cathodic structure 40 as well as the separator 2 interposed between the anodic structure 30 and the cathodic structure 40. The anodic structure 30 and the cathodic structure 40 fit into the recess 9 in the center of the spacer 5.

[0057] As described in the introduction, the cathode structure 40 comprises, from the outside of the cell towards the spacer, a bipolar plate 41 common with an adjacent lower cell (lower being understood here as the cell contiguous to the cell represented and positioned in contact with the bipolar plate 41), a cathode grid 42 and a porous cathode component 43. Similarly, on the anodic side, the anodic structure 30 comprises, from the spacer towards the outside of the cell, a porous anodic component 33, an anodic grid 32, a bipolar plate 31 common with an adjacent upper cell (upper being understood here as the cell contiguous to the cell represented and positioned in contact with the bipolar plate 31).

[0058] The spacer 50 extends between a first face 51 and a second face 52. The spacer 50 includes an inlet 7 and an outlet 8 configured to allow water circulation within the electrolysis cell 1 of water on the cathodic side. Similarly, it includes an inlet 25 and an outlet 26 configured to allow water circulation within the electrolysis cell 1 of water on the anodic side.

[0059] The recess 9 is intended to be occupied by the separator 2 and is in fluidic communication with the inlet 7 and the outlet 8 on one side, and the inlet 25 and the outlet 26 on the other.

[0060] Figure 3 schematically represents the two faces 51, 52 of the spacer according to the invention. Face 51 is the face of the spacer 50 on the cathodic side of the electrolysis cell (on the right of the figure), face 52 is the face of the spacer 50 on the anodic side of the electrolysis cell (on the left of the figure).

[0061] The spacer 50 includes a first primary groove 10 formed in a thickness of the spacer 50 opening onto the first face 51. The first primary groove 10 extends around the recess 9, the inlet 7, and the outlet 8. It is configured to house a first sealing element 35 (visible in Figure 1). When the electrolysis cell is assembled, the first sealing element 35 is housed in the first primary groove 10. The first sealing element 35 is designed to ensure the cell is sealed and prevent any leakage of water or reaction mixture (water and gas) outside the cell. It constitutes a primary barrier to prevent fluid leakage. However, as explained in the introduction, the first sealing element may wear out during the life cycle of the electrolysis stack.It can no longer ensure a perfect seal of the electrolysis cell, and water and / or reaction mixture can escape from the electrolysis cell by flowing beyond the first primary groove 10 and generate a leak.

[0062] According to the invention, the spacer 50 comprises a first secondary groove 60 formed in a thickness of the spacer 50 opening onto the first face 51 and extending around the first primary groove 10 to house a first sealing device 65. It should be understood here that the first secondary groove 60 surrounds the first primary groove 10 while being at a distance from it, that is to say, without being in contact with the first primary groove 10. At any point of the first primary groove 60, a non-zero distance can be defined, perpendicular to the first primary groove 60 at that point, between the first secondary groove 60 and the first primary groove 10.

[0063] The spacer also includes a through hole 70 between the first face 51 and the second face 52, located between the first primary groove 10 and the first secondary groove 60. It is thus understood that the through hole 70 extends perpendicularly to the plane of the spacer and forms a channel between the face 51 and the face 52 of the spacer 50.

[0064] First, the description will focus on the details of the secondary groove and its advantages. The role of the through-hole will be detailed later.

[0065] The first secondary groove 60 extends along the face 51 all around the spacer, between the periphery of the spacer and the first primary groove 10. When the electrolysis cell is assembled, the first sealing device 65 is housed in the first secondary groove 60. The first sealing device 65 is designed to reinforce the cell's seal and prevent any leakage of water or reaction mixture (water and gas) that might have flowed beyond the first sealing element 35 housed in the first primary groove 10. It constitutes a secondary barrier to contain any fluid leakage not contained by the first barrier. Advantageously, the spacer 50 includes a second primary groove 20 formed in a thickness of the spacer 50 opening onto the second face 52 and extending around the recess 9, the inlet 25, and the outlet 26. This second primary groove 20 is configured to house a second sealing element 45.When the electrolysis cell is assembled, the second sealing element 45 is housed in the second primary groove 20. The second sealing element 45 is designed to ensure the cell is sealed and prevent any leakage of water or reaction mixture (water and gas) outside the cell. It also constitutes a primary barrier to prevent fluid leakage.

[0066] In the context of the invention, the spacer 50 includes in this configuration a second secondary groove 80 formed in a thickness of the spacer 50 opening onto the second face 52 and extending around the second primary groove 20 to house a second sealing device 85.

[0067] The second secondary groove 80 extends along the face 52 all around the spacer, between the periphery of the spacer and the second primary groove 20. When the electrolysis cell is assembled, the second sealing device 85 is housed in the second secondary groove 80. The second sealing device 85 is intended to reinforce the sealing of the cell and prevent any leakage of water or reaction mixture (water and gas) that may have flowed beyond the second sealing element 45 housed in the second primary groove 20. It also constitutes a secondary barrier to contain any fluid leakage not contained by the first barrier.

[0068] In an optional configuration of the invention, the second secondary groove 80 is positioned such that, in axial projection in a cutting plane parallel to the first face 51, the second secondary groove 80 coincides with the first secondary groove 60. In other words, the two secondary grooves 60 and 80 are superimposed one above the other. This arrangement is particularly visible in Figure 4.

[0069] As the electrolysis cells are stacked against each other, the overlapping of the grooves 60, 80, and therefore of the sealing devices 65, 85, allows a certain flexibility along the stacking axis Z and allows the bipolar plates to be pressed firmly against the spacers.

[0070] Figure 4 schematically represents a portion of a cross-section in the YZ plane of an electrolysis cell according to the invention. All the sealing elements 35, 45 and the sealing devices 65, 85 are lip seals. Such a seal comprises a flexible bearing edge 66 and ensures sealing by deformation of the bearing edge 66, also called the lip. This type of seal provides fluid and dust tightness. It is easy to position in its intended groove. Furthermore, the U-shaped design of the seal ensures good retention in its groove, without necessarily requiring the seal to be bonded to the groove. During the assembly of the electrolysis cell, the bipolar plate is pressed against the spacer fitted with its sealing gaskets. For each gasket, the lip 66 is compressed against the bipolar plate, which then comes into contact with the gasket.This configuration ensures the airtightness of the fluids inside the electrolysis cell. Furthermore, it guarantees that no external contaminants can enter the electrolysis cell.

[0071] However, it should be noted that the lip seal is given here as an example of a sealing device and component, and other types of sealing devices and components do not fall outside the scope of the invention. For example, these could also be O-rings.

[0072] The spacer can also traditionally include an additional groove 36 opposite the membrane 2 and in which a sealing gasket 37 is placed. This is the sealing gasket of the membrane 2.

[0073] As can be seen in Figure 4, the addition of the first secondary groove 60, in which the first sealing device 65 is located, forms an annular space 88 extending between the first sealing element 35 of the first primary groove 10 and the first sealing device 65 of the first secondary groove 60. Since the first secondary groove 60 (and therefore the first sealing device 65) extends all around the face 51 between the periphery of the spacer and the first primary groove 10 (and therefore the first sealing element 35), the annular space 88 forms a volume around the perimeter of the first primary groove 10. This annular space 88 constitutes a buffer volume to receive water or the reaction mixture from inside the electrolysis cell that may have breached the primary barrier following a failure of the first sealing element 35.The annular space 88 can thus be seen as a temporary retention basin for the leakage fluid. Being an annular space, it can receive the leakage fluid all around the primary barrier, regardless of the failure zone of the first sealing element 35.

[0074] At the top of Figure 4, a portion of the annular space 88 is shown when the annular space is filled with leakage fluid. It is understood from the preceding text that in the event of a failure of the first sealing element 35, leakage fluid escapes beyond the primary barrier into the annular space. This leakage fluid is blocked by the secondary barrier formed by the first sealing device 65. This leakage fluid can thus accumulate in the annular space 88.

[0075] The spacer 50 includes a through hole 70 between the first face 51 and the second face 52. The through hole 70 is located between the first primary groove 10 and the first secondary groove 60. On the face 51, it opens into the annular space 88.

[0076] According to an optional feature of the invention, the spacer 50 includes two through holes 71, 72 arranged on either side of the recess 9 (as can be seen in Figure 3).

[0077] In an electrolysis stack of the invention, each electrolysis cell is delimited by two parallel bipolar plates 31, 41. The electrolysis cells 1 are stacked one against the other along the stacking axis Z. According to the invention, each bipolar plate comprises, for each through-hole 71, 72 of the spacer 50 which it covers, a through-hole 91, 92 opposite said through-hole 71, 72 of the spacer 50. In other words, opposite the through-hole 71, the bipolar plates 31, 41 comprise a through-hole 91, and, if present, opposite the through-hole 72, the bipolar plates 31, 41 comprise a through-hole 92. It is thus understood from the above that the through-hole 91 and the through-hole 92 are arranged on either side of the recess 9.

[0078] Thus, the succession of through-holes 71 and through-openings 91 in the stack of electrolysis cells 1, with the through-holes and openings aligned with each other, forms a discharge channel 93 for the leakage fluid. Similarly, the succession of through-holes 72 and through-openings 92 in the stack of electrolysis cells 1, with the through-holes and openings aligned with each other, forms a discharge channel 94 for the leakage fluid. In fact, the discharge channel 93 and the discharge channel 94 are arranged on either side of the recesses 9 in the electrolysis cells.

[0079] Figure 5 illustrates the annular space 88 on the anodic face 52 of the spacer 50 of the invention. It can be seen that the annular space occupies the entire area between the second primary groove 20, equipped with its sealing element 45, and the second secondary groove 80, equipped with its sealing device 85.

[0080] Although the invention is not limited to this, the spacer 50 is rectangular in shape, and the recess 9 is also rectangular. The spacer 50 has two longitudinal edges 17 and two lateral edges 18.

[0081] In the illustrated example, the inlet 7 and outlet 8 are arranged symmetrically with respect to a central point O on the spacer 50. The same applies to the inlet 25 and outlet 26. This is, of course, an example of an embodiment. A person skilled in the art will understand that the invention applies similarly to other arrangements of the inlet and outlet, and the inlet and outlet.

[0082] The discharge channel 93 and the discharge channel 94 play a crucial role in the invention. The annular space 88 forms a collection zone for the leakage fluid when the primary sealing element 35 wears prematurely. The discharge channels 93 and 94 allow the leakage fluid to be evacuated. Since these channels are formed by alternating through-holes in the spacer and through-holes in the bipolar plates, for each of the electrolysis cells 1 of the electrolysis stack 100, each discharge channel 93 and 94 is thus fluidically connected to the annular space 88. During operation, if one of the electrolysis cells 1 leaks, the annular space 88 will gradually fill with the leakage fluid. The evacuation channels 93, 94 being fluidically connected to the annular space 88, the leakage fluid will then be evacuated through the evacuation channel(s) 93, 94.

[0083] The invention is therefore based on a spacer 50 comprising, on the one hand, a secondary barrier which complements the primary barrier to form an annular space 88 in the event of failure of the primary barrier, and on the other hand, at least one through opening 70 which, in the stack of electrolysis cells 1, forms an evacuation channel 93 connected to each annular space 88 of each of the electrolysis cells 1 and opening out to the outside of the electrolysis stack.At the level of each electrolysis cell 1, the combination of the annular space 88 and the through opening 70 allows both the collection and containment of the leakage fluid in an area perfectly delimited by the secondary barrier formed by the first sealing device 65 housed in the first secondary groove 60 and the drainage of this leakage fluid out of the electrolysis stack 100 by the evacuation channel 93 formed by the orifices 71 and through openings 91 of the spacers 50 and bipolar plates 31. In the electrolysis stack 100, the combination of the annular spaces 88 and the evacuation channels 93, 94 allows a leak to be identified and the leakage fluid to be collected in a controlled manner.

[0084] In one possible configuration of the invention, the electrolysis cells 1 are stacked one against the other along the stacking axis Z, and the stacking axis Z is perpendicular to the direction of gravity. In other words, the stacking axis Z is horizontal with respect to a reference plane defined as the plane on which the electrolysis stack 100 is arranged. It follows that each electrolysis cell extends perpendicularly to the reference plane. The XY plane in which each spacer 50 extends is therefore arranged vertically. Preferably, the longitudinal edges 17 are the lower and upper edges of the spacer, and the edges 18 are the lateral edges.

[0085] As shown in Figure 5, the spacer 50 includes two through holes 71 and 72. The through hole 71 is located in the annular space 88 between the first primary groove 10 and the first secondary groove 60, above the recess 9 of the spacer. The through hole 72 is located in the annular space 88 between the first primary groove 10 and the first secondary groove 60, below the recess 9 of the spacer. Relative to the recess 9, the through-hole 72 is thus positioned on the opposite side to the through-hole 71. In other words, the through-hole 71 and the through-hole 72 of the electrolysis cell are arranged on the same axis perpendicular to the longitudinal edges 17 of the spacer 50. On this same axis, the through-hole 71 is located at a first height from the lower longitudinal edge 17 of the spacer. The through-hole 72 is located at a second height from the lower longitudinal edge 17.And the first height of the through orifice 71 is greater than the second height of the through orifice 72.

[0086] The arrangement of the two through-holes 71 and 72 results in the event of a leak in the primary barrier, resulting in the collection of leakage fluid in the annular space 88. The gaseous portion of the leakage fluid (hydrogen or oxygen, depending on the leakage structure of the electrolysis cell) tends to rise and accumulates in the upper part of the annular space 88. The liquid portion of the leakage fluid (for example, water) accumulates, due to gravity, in the lower part of the annular space 88 up to a filling limit 89. This filling limit 89 is located at the second height of the through-hole 72. Once this liquid level is reached, the leakage fluid will have access to the discharge channel 94 and will be drained from the electrolysis stack 100.

[0087] According to an optional feature of the invention, on a segment locally perpendicular to the first secondary groove 60, the distance between the first secondary groove 60 and the through orifice 70 is less than the distance between the first primary groove 10 and the through orifice 70. This means that any through orifice is located closer to the first secondary groove 60 than to the first primary groove 10. Thus, the through orifice 72, and therefore the associated drain channel 94, is located as close as possible to the first secondary groove 60, i.e., at the lowest point of the electrolysis cell 1. In the event of a fluid leak, since the drain channel passes through the electrolysis stack 100 at the lowest point of the spacers 50, the filling limit 89 is reached quickly and the leak can be detected very early.

[0088] The invention has been described based on face 51 of the spacer and using the sealing elements 35 and sealing device 65 of the anodic structure of the electrolysis cell. The same principle applies to face 52, using the sealing elements 45 and sealing device 85 of the cathodic structure of the electrolysis cell.

[0089] Although the invention has been described using a rectangular spacer, the principle of the invention applies to all other shapes of spacers and electrolysis cells (circular, square, polygonal, etc.). Similarly, the invention applies to any other spacer design and any other type or shape of sealing device.

[0090] It is clear from the description of the invention that it is easy to implement and offers a low additional cost compared to prior art solutions. Furthermore, this principle is easily adaptable to any number of electrolysis cells since the components are integrated within the cell. It is simply necessary to provide an additional groove on each face of the spacer, to which a sealing device and at least one through-hole per spacer and bipolar plate are added.

[0091] Figure 6 schematically represents an electrolysis stack 100 according to the invention equipped with leak detection devices. A plurality of electrolysis cells 1 are stacked one against the other along the stacking axis Z. Each electrolysis cell 1, and therefore each spacer 50, is arranged perpendicular to the stacking axis Z. The spacers 50 each include the two through-holes 71, 72 described above. For each electrolysis cell 1, the bipolar plates 31, 41 include the through-holes 91, 92 respectively opposite the through-holes 71, 72.The discharge channel 93 is defined, by the successive alternation of a through orifice 71 and a through opening 91 of the bipolar plate, in the upper part of the electrolysis stack 100 and the discharge channel 94 is defined, by the successive alternation of a through orifice 72 and a through opening 92 of the bipolar plate, in the lower part of the electrolysis stack 100.

[0092] As shown in Figure 6, the electrolysis stack may further include a fluid detection system 200 connected to one of the discharge channels 93, 94 capable of detecting a leak in the electrolysis stack 100.

[0093] Furthermore, in one embodiment of the invention, the electrolysis stack 100 may include an alarm system 300 connected to the fluid detection system 200 configured to send a signal when the detection system 200 detects a leak in the electrolysis stack 100.

[0094] The fluid detection system 200 can be a pressure sensor 210 connected to the discharge channel 93, i.e., the discharge channel that extends through the annular spaces 88 of the electrolysis stack 100 where the leaking fluid, in gaseous or liquid form, will tend to accumulate. When a leak occurs, if it leads to an accumulation of gas in the discharge channel, the pressure in the discharge channel 93 increases. The pressure sensor 210 is able to determine this pressure increase. It is possible to define a pressure threshold beyond which action is required, for example, by an operator who must intervene or automatically by a programmable logic controller (PLC) managing the installation's safety.Beyond the previously defined pressure threshold, the 300 alarm system connected by wired or wireless connection to the 210 pressure sensor will send a signal, for example an audible or visual signal or a notification on a remote display device so that an operator can take the necessary measures to secure the stack.

[0095] Alternatively, or in addition to the pressure sensor 210, the detection system 200 can include a gas detector 220, for example, a mass spectrometer, also connected to the vent 93. Such a detector can detect and identify the gas molecules present. The advantage of a mass spectrometer is that, in addition to detecting a gas leak, it can determine which gas is leaking. Alternatively, an explosimeter can be used to verify whether an ATEX condition (i.e., an explosive atmosphere) is created based on the level of hydrogen present. Similar to the pressure sensor 210, the gas detector 220 is connected to the alarm system 300, which can then refine its warning signal according to the detected gas.

[0096] Alternatively, or in addition to the pressure sensor 210 and / or the gas detector 220, the detection system 200 may include a liquid detector 230, particularly for water, fluidically connected to the drain channel 94. Designed to detect a leak of liquid that accumulates in the lower part of the electrolysis stack 100 due to gravity, the liquid detector 230 is connected to the drain channel 94, which extends along the lower part of the stack 100. In the event of a fluid leak in an electrolysis cell, the liquid portion of the leaking fluid is collected in the lower part of its annular space 88. When the collected liquid reaches the fill line 89, it flows into the drain channel 94. The liquid detector 230 can then detect the liquid present in the channel.Similar to the pressure sensor 210 and the gas detector 220, the liquid detector 230 is connected to the alarm system 300 which can then send its alert signal indicating that a liquid leak has been detected.

[0097] The fluid-connecting conduit 94 and liquid detector 230 can be equipped with a drain valve 240, located downstream of liquid detector 230. In the direction of leakage fluid drainage, the drain channel 94 is connected to the liquid detector 230 and then to the drain valve 240. The drain valve allows the drain channel 94 to be emptied to prevent the leak fluid from stagnating after its presence has been detected.

[0098] The fluid-connecting conduit between the discharge channel 93 and the pressure sensor 210 and / or the gas detector 220 can be equipped with a vent valve 250 located downstream of the gas detector 220. This positioning allows the gas detector 200 to analyze the leak gas. The vent valve 250 allows the leak gas to be vented from the electrolysis stack 100. The vent valve 250 can be fluid-connected downstream to one or more storage tanks, in order to direct the detected leak gas to one or more of the storage tanks, depending on its nature. The electrolysis stack of the invention allows for immediate leak detection.

[0099] Because this detection is carried out early, any escalation and creation of a dangerous situation are prevented, and preventive actions can be implemented. For example, the leaking stack can be isolated while maintaining the operation of other electrolysis stacks in the installation.

[0100] The electrolysis stack 100 of the invention may also include an inert gas source 400 fluidically connected to one of the discharge channels, for example 94, of the leakage fluid. Thanks to this feature, inert gas, for example nitrogen, can be injected into said discharge channel 94. The inert gas then circulates through the electrolysis cells 1 to perform a complete sweep of the electrolysis cells 1 and flows from the discharge channel 94 to the annular spaces 88 between the bipolar plates 31, 41 and the spacers 50.

[0101] Figure 7 illustrates the steps of a leak testing procedure for an electrolysis stack 100 according to the invention. In the electrolysis stack 100, the inlets 7 and the inlets 25 each form an inlet well (anodic well: 410, cathodic well: 420). Similarly, the outlets 8 and the drains 26 each form a drain well 420, 410. The leak testing procedure is ideally carried out immediately after manufacturing, before delivery to the customer. As will become apparent from the description of the steps in this procedure, such a test ensures the correct assembly of the electrolysis stack and therefore its leak-tightness.

[0102] According to the invention, the leak testing method comprises the following steps. A source 500 of tracer gas (for example, hydrogenated nitrogen or helium) is connected (step 600) to one of the inlet wells of the electrolysis stack 100. Then, tracer gas from the source 500 is injected (step 610) into the well

[0103] The inlet is connected to the tracer gas source 500. The tracer gas circulates inside the stack. Finally, the presence (or absence) of tracer gas in an outlet channel 93, 94 of the electrolysis stack 100 is checked (step 620) by the detection system 200.

[0104] The tracer gas is injected into the stack through an inlet well. It enters the electrolysis cells via the inlets 7 and 25 of the electrolysis cells 1. In other words, the tracer gas follows the same path as the water injected into the operating electrolysis stack. If there is no leak, the tracer gas will flow entirely through the outlets 8 and 26 to exit the stack. If a leak occurs, for example, due to a defect in a primary sealing element 35 or 45, or an assembly failure, the tracer gas will escape into the annular space 88 associated with the defective cell. The tracer gas will then accumulate in the upper part of the annular space 88 and be discharged through the discharge channel 93. This channel being fluidically connected to the detection system 200, the tracer gas leak through the discharge channel 93 will be detected. This is a sign of a leak in the electrolysis stack.Countermeasures can then be initiated to correct the detected leak.

[0105] The leak testing method of the invention thus makes it possible to guarantee, even before the electrolysis stack is put into operation, that it is correctly assembled. Furthermore, by combining the connection of the gas detector 220 and the supply of tracer gas to a specific well (anodic or cathodic) via the valves 411, it is possible to determine the side from which the leak originates by monitoring the annular space 88.

[0106] Thanks to the integration of the spacer of the invention into the electrolysis cells, the occurrence of leaks external to the electrolysis cells is limited. The invention thus prevents external leaks. Furthermore, by connecting a fluid detection system to the stack, the invention enables early and automatic detection of a primary barrier defect in an electrolysis stack. Also, based on the features of the invention, it is possible to check the stack's leak-tightness before commissioning. The invention thus enhances safety during the operation of the electrolyzer.

[0107] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different embodiments of the invention can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

DEMANDS 1- Water electrolysis cell (1) comprising an anodic structure (30), a cathodic structure (40) and a separator (2) interposed between the anodic structure (30) and the cathodic structure (40), the water electrolysis cell (1) being characterized in that it comprises: a spacer (50) configured to support the separator (2), extending between a first face (51) and a second face (52), and comprising: o an inlet (7) and an outlet (8) configured to allow water circulation within the water electrolysis cell (1), o a recess (9) intended to be occupied by the separator (2) and in fluidic communication with the inlet (7) and the outlet (8), o a first primary groove (10) formed in a thickness of the spacer (50) opening onto the first face (51) and extending around the recess (9), the inlet (7), and the outlet (8), configured to house a first sealing element (35), o a first secondary groove (60) made in a thickness of the spacer (50) opening on the first face (51) and extending around the first primary groove (10) to house a first sealing device (65); o a through hole (70) between the first face (51) and the second face (52), disposed between the first primary groove (10) and the first secondary groove (60), said spacer (50) supporting the anodic structure (30), the cathodic structure (40) and the separator (2), and in that the water electrolysis cell (1) comprises: a first sealing element (35) housed in the first primary groove (10); a first sealing device (65) housed in the first secondary groove (60), the spacer comprising a first annular space (88) being disposed between the first sealing element (35) and the first sealing device (65) and in fluidic connection with the through orifice. 2- Electrolysis cell (1) according to claim 1, in which, on a segment locally perpendicular to the first secondary groove (60), the distance between the first secondary groove (60) and the through orifice (70) is less than the distance between the first primary groove (10) and the through orifice (70). 3- Electrolysis cell (1) according to claim 1 or 2, in which the spacer (50) comprises an inlet (25) and an outlet (26) configured to allow water to circulate within the electrolysis cell (1), a second primary groove (20) formed in a thickness of the spacer (50) opening on the second face (52) and extending around the recess (9), the inlet (25) and the outlet (26), configured to house a second sealing element (45), a second secondary groove (80) formed in a thickness of the spacer (50) opening on the second face (52) and extending around the second primary groove (20) to house a second sealing device (85). 4- Electrolysis cell (1) according to claim 3, in which the second secondary groove (80) is positioned so that, in axial projection in a cutting plane parallel to the first face (51), the second secondary groove (80) coincides with the first secondary groove (60). 5- Electrolysis cell (1) according to any one of claims 1 to 4, the through orifice (70) being a first through orifice (71), the spacer (50) further comprising a second through orifice (72) between the first face (51) and the second face (52), disposed between the first primary groove (10) and the first secondary groove (60), the first through orifice (71) and the second through orifice (72) being disposed on either side of the recess (9). 6- Electrolysis cell (1) according to claim 3 or 4, comprising: a second sealing element (45) housed in the second primary groove (20); a second sealing device (85) housed in the second secondary groove (80), the spacer comprising a second annular space (88) being disposed between the second sealing member (45) and the second sealing device (85) and in fluidic connection with the through orifice. 7- Water electrolysis stack (100) comprising a plurality of electrolysis cells (1) according to claim 6, each electrolysis cell being delimited by two parallel and electrically conductive bipolar plates (31, 41), the electrolysis cells (1) being stacked one on top of the other along a stacking axis (Z), each bipolar plate comprising, for each through orifice (71, 72) of the spacer it covers, a through opening (91, 92) opposite said through orifice (71, 72) of the spacer (50), the through orifices (71, 72) and the through openings (91, 92) of the electrolysis cells (1) aligned with each other and in fluidic connection with the plurality of annular spaces (88) forming at least one discharge channel (93, 94) of a leakage fluid originating from at least one of the plurality of electrolysis cells. 8- Electrolysis stack (100) according to the preceding claim, in which each electrolysis cell (1) comprises a first through orifice (71) and a second through orifice (72) arranged on either side of the recess (9), the electrolysis stack comprising two discharge channels (93, 94), a first (93) of the two discharge channels being formed by the first through orifices (71), a second (94) of the two discharge channels being formed by the second through orifices (72). 9- Electrolysis stack (100) according to claim 7 or 8, comprising a fluid detection system (200) connected to one of the discharge channels (93, 94) capable of detecting a leak in the electrolysis stack. 10- Electrolysis stack (100) according to claim 9, comprising an alarm system (300) connected to the fluid detection system (200) capable of sending a signal when the detection system (200) detects a leak in the electrolysis stack (100). 11- Electrolysis stack (100) according to any one of claims 7 to 10, further comprising an inert gas source (400) fluidically connected to at least one fluid discharge channel (93, 94). 12- Leak testing method for an electrolysis stack (100) according to any one of claims 9 to 11, the inlets (7) and the inlets (25) each forming an inlet well (410; 420) and the outlets (8) and the discharges (26) each forming a discharge well, the leak testing method comprising the following steps: Connection (600) of a source (500) of tracer gas to one of the admission wells of the electrolysis stack (100); Injection (610) of tracer gas into the intake well; Verification (620) of the presence of tracer gas in an exhaust channel (93, 94) of the electrolysis stack (100) by the detection system (200).

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