Method for sealing an electrolytic cell (II)

Abstract

The invention relates to a method for sealing and electrically insulating electrolytic cells, in which the two half-cells of the device are sealed along their perimeter by means of an outer frame made of plastic.

Description

Method for sealing an electrolytic cell (II) FIELD OF THE INVENTION

[0001] The invention is in the field of electrolysis technology and relates to a method for sealing and electrically insulating electrolysis cells and corresponding electrolysis cells. TECHNOLOGICAL BACKGROUND

[0002] A greenhouse gas-free economy within the next 30 years – this is Europe's stated goal to halt climate change. Renewable energies are intended to replace fossil fuels such as oil, coal, and gas. Hydrogen will play a key role in the sustainable transformation of the energy supply.

[0003] For clean mobility, the efficient supply of electricity and heat, as a storage medium to balance fluctuating renewable energies, as a basis for alternative fuels or as a process gas in industry - hydrogen is a very versatile energy carrier, can be used across sectors, offers great synergy potential and has an energy density three times higher than that of gasoline in terms of mass.

[0004] Sustainably and economically produced hydrogen is therefore a key component in massively reducing emissions, especially of the harmful greenhouse gas CO2, in the energy, transport, and industry sectors, and thus combating climate change. The development of a cross-sectoral and, if possible, global hydrogen economy also opens up enormous opportunities for new technologies and business models, as hydrogen's potential applications are diverse. Hydrogen-powered gas turbines are currently being researched for industrial use. It can be used in fuel cells for cars and buses. Hydrogen can not only be used for emission-free driving but, unlike electric vehicles, can also cover long distances and refuel vehicles quickly.

[0005] From an environmental perspective, the production of hydrogen through water electrolysis is of particular interest; in this context, it is therefore also referred to as "green hydrogen." The process is carried out in coupled electrolysis cells, so-called electrolyzers, similar to those used in chlor-alkali electrolysis. RELEVANT STATE OF THE ART

[0006] An electrolysis cell is already known from US Pat. No. 5,599,430 B (DOW), comprising a housing containing at least one pair of electrodes, namely a cathode and an anode, a current collector, and a membrane. Furthermore, an electrically conductive, hydraulically permeable elastic mattress is included, which is arranged substantially coplanar with the current collector and touches it on one side, and also coplanar with an electrode and touches it on the other side.

[0007] EP 1451389 B1 (UHDENORA) describes a current collector for electrochemical cells, consisting of a "sandwich" of compressible and elastic layers of metal wires, which imparts a predetermined mechanical load over a wide compression range.

[0008] The subject matter of EP 1766104 B1 (UHDENORA) relates to a conventional electrolysis cell with a sealing system consisting of individual elements, each containing two electrodes separated from each other by membranes, wherein the proportion of the inactive membrane area is minimized by a flange, so that the ratio between the area of ​​the flange of a half-shell and the active membrane area can be set to less than 0.045.

[0009] According to EP 1882758 A1 (TOAGOSEI), the elastic pressure in an electrolytic cell is transmitted by means of coils or woven nickel mats or resistant nickel alloys. In the case of the coils, the number of turns increases gradually from top to bottom, and in the case of the mats, the number of superimposed layers increases gradually, so that a pressure profile is finally established which is at least similar to the hydrostatic pressure on the anode side, which increases in the same direction.

[0010] EP 2356266 B1 (UHDENORA) describes an electrolysis cell equipped with a separator. It has a flat, flexible cathode held in contact with the separator by an elastic, conductive element pressed by a current distributor. The cell also contains an anode consisting of a stamped sheet or grid supporting the separator. The cell can be used in a modular arrangement to form an electrolyzer whose end cells are connected only to the electrical power supply.Electrical continuity between adjacent cells is ensured by conductive contact strips attached to the outer anodic walls of the shells that define each cell. The rigidity of the cathode current distributor and the anodic structure, and the elasticity of the conductive element, combine to maintain uniform cathode-to-separator contact with a homogeneous pressure distribution, while ensuring appropriate mechanical loading of the contact strips. The use of the elastic element thus avoids spacing between the electrodes.

[0011] EP 2746429 A1 (UHDENORA) proposes an electrolysis cell comprising an anode chamber with an anode and a cathode gas chamber with a gas diffusion cell. method, both electrodes being separated from each other by an ion exchange membrane, and a metallic elastic element which is clamped under compression between the rear wall of the cathode gas space and the gas diffusion cathode, said elastic element being clamped into the cathode gas space in such a way that the distance between the element and the rear wall increases in the direction of gravity.

[0012] EP 2872675 B1 (UHDENORA) proposes an insulating frame for electrolysis cells. The frame has a geometric shape with corners. The frame is flat and has an anode and a cathode side, as well as an outer and an inner end face. The insulating frame has an edge region directly adjacent to the inner end face, which has recesses in the form of cutouts in the area of ​​the corners.

[0013] According to JP 2003 041388 A1 (ASFPONC), cell stabilization is achieved by a metallic zigzag profile installed in the cathode gas chamber. However, this electrolytic cell design presents a problem: Physics actually requires that the hydrostatic pressure in the anode chamber is not constant, but rather increases in the direction of gravity. Therefore, it would be desirable and entirely sufficient for the objective to be achieved for the pressure exerted by the elastic components to adapt to the hydrostatic pressure, i.e., increase in the direction of gravity.

[0014] From the aforementioned documents, it can be seen that a complex mechanical system is constructed in the sealing area, both externally and between the two half-shells. This system incorporates both a seal and an insulating body in the perimeter. This is compressed by an external force, creating a frictional connection. This fulfills the following functions: - Sealing between anode and cathode; - Sealing to the outside (pressure-stable); - Electrical insulation of the metallic parts of the anode and cathode in the perimeter; - Mechanical integrity of the entire cell; - Chemical resistance of the materials.

[0015] EP 2734658 B1 (NEW NEL HYDROGEN) describes a module for a filter press-type electrolyzer, comprising at least one closed frame defining at least one first opening. The module is made of a sealing and electrically insulating material, and this material at least partially covers the surface of the frame. Specifically, the sealing and insulation are created by an elastomer that is compressed under force. This force connection makes it possible to create a sealing effect. The force is introduced by the filter press and distributed between the seal and the internal components, if an elastic element is used inside. However, this results in the disadvantage of an uneven force distribution on the elastomer, which can lead to leaks.

[0016] DE 10 2021 103185 A1 (WEW), which forms the starting point of the present invention, discloses a material-to-material adhesive bond between the two half-shells. An electrically insulating adhesive, hot melt, or thermoplastic is placed between the two half-shells, creating a structure. The plastic compound can be introduced much more easily and quickly than with the other prior art methods mentioned, and, in particular, external force can be dispensed with. Specifically, a material bond is created between the insulating plastic as a sealing compound and the metallic half-cells. This results in a significantly more durable bond than a purely frictional bond.

[0017] DE 19926026 A1 (HELIOCENTRIS) is in the field of fuel cells and concerns a stiffening frame for a membrane electrode assembly consisting of a polymer electrolyte membrane and electrodes covering both sides. The frame consists of a hot-melt adhesive layer and a bending-resistant plate attached to it. TASK TO BE SOLVED

[0018] An electrolysis cell schematically consists of an anode and a cathode compartment (AR, KR), each containing the anode (A) and the cathode (K). The two electrodes are separated from each other by a diaphragm or separator membrane (S) and fixed in the corresponding housing sections ("half-cells") by means of an elastic or rigid spacer (X1, X2), as shown schematically in Figure 1. The figure also shows the seal (D), which separates the two electrode compartments at the perimeter and seals them off from the outside.

[0019] The anode and cathode compartments must be electrically insulated from each other to prevent short circuits. For optimal performance, it is also necessary that the electrodes rest flat—i.e., without gaps—on the separator membrane over their entire surface. This is achieved by one or more elastic spacers (X1, X2) within the cell. In addition, the electrolysis cell is placed under slight overpressure relative to the atmosphere, which means the seal must be both chemically and pressure-resistant.

[0020] Although seals made according to the method of DE 10 2021 103185 A1 have proven to be pressure-resistant, thermally and chemically resistant, it has been observed that their mechanical stability gradually decreases over longer periods of operation, which may mean that perfect sealing is no longer guaranteed.

[0021] The object of the present invention was therefore to improve the method of DE 10 2021 103185 A1 and to combine its known advantages with an improved mechanical stability of the seal or the electrolysis cell, without This would make the solution more technically complex. Preferably, the alternative process should enable a simpler and more cost-effective manufacturing process. DESCRIPTION OF THE INVENTION

[0022] In a first embodiment, the invention relates to a method for sealing and electrically insulating electrolysis cells, comprising or consisting of the following steps: (a) Providing an electrolysis cell (Z) containing or consisting of: (a1) two metallic half-cells (AR) and (KR), which form the anode and cathode compartments Q1 and Q2, respectively, (a2) an anode (A) and a cathode (K) arranged therein, (a3) a separator membrane (M) and (a4) optionally spacers (E1, E2) which position the two electrodes in their respective electrode spaces, the two half-cells being separated across their perimeter (P) by a space (S) and the separator membrane (M), and (b) Arranging the separator membrane (M) between the electrodes so that it (bl) protrudes into the space (S) or (b2) is flush with the end of the space (S) or protrudes from the space (S), and (c) Enclosing the perimeter (P) with a plastic.

[0023] Surprisingly, it was found that the requirements profile described at the beginning can be fully met in this way.

[0024] Compared to the process described in DE 10 2021 103185 A1, the surrounding frame holds the cell in shape and stabilizes it. At the same time, the adhesive bond is optimally supported, as the excess pressure generated inside the cell during operation exerts pressure on the adhesive bond, improving the seal.

[0025] Compared to the previously mentioned state of the art, this solution features a very simple method of cell closure, allowing for a free form, e.g., by casting the outer frame. This allows for the adoption of cost-effective manufacturing processes from injection molding. A massive steel frame, which must be constructed in an insulated manner, is omitted. This leads to reduced assembly time and labor, as no screws are required, as well as a significant weight savings and resource conservation. Sealing the electrolysis cell

[0026] In the case of the prior art cited as the starting point for the invention, peeling stress on the adhesive surface is triggered by the internal pressure, which can be disadvantageous with regard to the longevity of the adhesive surface. By using a seal between the two cell rear walls, the chemical stress on the adhesive bond of the outer frame can be further reduced. A special embodiment of the method according to the invention therefore consists in arranging the separator membrane (M) between the two electrodes (E1, E2) such that it projects into the intermediate space (S), and filling the remaining intermediate space volume with a plastic.

[0027] It is further preferred that the perimeter (P) be enclosed and / or the intermediate space (S) be sealed by adhesive bonding, for example, by thermal direct joining, gluing, hot melt, or lamination. Potting with adhesives or resins is preferred. Plastics selected from the group consisting of adhesives, thermoplastics, and potting compounds are particularly suitable for enclosing the perimeter (P) and / or sealing the intermediate space (S). Electrically insulating thermoplastics, for example, from the group of polyamides (PA), are used for this purpose. Inlet and outlet connections

[0028] In a further preferred embodiment of the present invention, inlet and outlet connections are introduced into the joints between the two half-cells. In particular, connections that are known from the food industry, such as welded spouts made of injection-moldable plastic, are considered. Corresponding connections or spouts are the subject of EP 2644530 A1 (POPPELMANN), the teaching of which, as far as the nature of the spouts is concerned, is incorporated by reference. The connections or spouts have a neck (3) provided with a pouring channel (2) having a vertical longitudinal central axis (1), as well as two outer side surfaces connected to the neck and preferably provided with weld lines (4), which are intended for welding to the seal of the electrolysis cell and on whose associated side walls a plurality of stiffening webs are arranged on the inside.

[0029] Typically, these outlets or spouts have a base, also called a "boat," whose side walls have outer side surfaces that merge into one another at their ends. The side surfaces are connected, particularly welded, to and between the two film walls of a container. Typically, a collar-like area is formed integrally onto the boat or the side surfaces, which merges into a neck with a vertical longitudinal central axis. Such a neck is often provided with a thread on the outside to secure a filled film bag with a closure to prevent it from being emptied through the pouring channel. Alternatively, the neck can also merge, at least partially, directly into the boat. The side surfaces of the Shuttles can be flat, roughened, with or without ribs, and / or with weld lines. In addition, the neck can have guide bars that can be used for guidance in a filling or sealing system.

[0030] According to the teaching of EP 2644530 A1, the connections or spouts are usually connected to the seal by ultrasonic welding. In this invention, weld-in spouts are preferably incorporated directly into the joining process. electrolysis cell

[0031] Another subject of the invention relates to an electrolysis cell which has been sealed according to the method according to the invention. Specifically, an electrolysis cell comprising or consisting of (a1) two metallic half-cells (AR) and (KR), which form the anode and cathode compartments Q1 and Q2, respectively, (a2) an anode (A) and a cathode (K) arranged therein, (a3) a separator membrane (M) and (a4) optionally spacers (E1, E2) which position the two electrodes in their respective electrode spaces, wherein (i) the two half-cells are separated across their perimeter (P) by a space (S) and the separator membrane (M), (ii) the separator membrane (M) is arranged between the electrodes in such a way that it either projects into the intermediate space (S), is flush with the end of the intermediate space (S) or projects out of the intermediate space (S) and (iii) the perimeter (P) is enclosed by a plastic frame.

[0032] Preferably, the anode and cathode are arranged schematically in the cell as shown in Figure 1, namely in such a way that the two electrodes are positioned flat and free of gaps over their entire surface, with only the separator membrane making direct contact.

[0033] The half-cells are preferably made of stainless steel, nickel or titanium as well as corresponding alloys, which may also contain other foreign metals such as vanadium.

[0034] The spacers can be coils, rings, foams, mattresses, or rigid structures, as discussed in the initial assessment of the prior art. They can be static or elastic, although it is preferable to equip at least one electrode chamber with elastic spacers. To ensure ensure that the electrodes lie flat. The individual electrolysis cells can be combined into groups ("electrolyzers") and used, for example, in chlorine-alkali electrolysis; however, the preferred application is the production of hydrogen through water electrolysis. Short description of the drawings

[0035] Figure 1 shows a longitudinal section through an electrolysis cell (Z) with anode and cathode compartments (AR, KR) and the two electrodes (A, K) located therein, separated from each other by the separator membrane (M). Furthermore, two spacers (E) are present. This shows the case where the membrane protrudes slightly from the intermediate space (S). Therefore, there is no free space volume that needs to be filled. The adhesive bond, in which the parameter is surrounded by a plastic box, can therefore be implemented directly.

[0036] Figure 2 shows a section of an electrolysis cell (Z) in which the separator membrane (M) extends only into the perimeter (P). Here, the remaining space is filled with a plastic and sealed.

Claims

PATENT CLAIMS 1. A method for sealing and electrically insulating electrolytic cells, comprising or consisting of the following steps: (a) Providing an electrolysis cell (Z) containing or consisting of: (a1) two metallic half-cells (AR) and (KR), which form the anode and cathode compartments Q1 and Q2, respectively, (a2) an anode (A) and a cathode (K) arranged therein, (a3) a separator membrane (M) and (a4) optionally spacers (E1, E2) which position the two electrodes in their respective electrode spaces, the two half-cells being separated across their perimeter (P) by a space (S) and the separator membrane (M), (b) Arranging the separator membrane (M) between the electrodes so that it (bl ) protrudes into the space (S) or (b2) is flush with the end of the space (S) or protrudes from the space (S), and (c) Enclosing the perimeter (P) with a plastic.

2. Method according to claim 1, characterized in that the remaining volume of the intermediate space (S) is filled with a plastic.

3. Method according to claims 1 and / or 2, characterized in that the enclosing of the perimeter (P) space is carried out by adhesive material bonding.

4. Method according to at least one of claims 1 to 3, characterized in that the enclosing of the perimeter (P) and the sealing of the intermediate space (S) are carried out by adhesive bonding.

5. Method according to at least one of claims 1 to 4, characterized in that the enclosing of the perimeter (P) and / or the provision of the intermediate space (S) is carried out by thermal direct joining, gluing, casting or hot melt.

6. The method according to at least one of claims 1 to 5, characterized in that the enclosing of the perimeter (P) and / or the provision of the intermediate space (S) is carried out with a plastic which is selected from the group consisting of adhesives, thermoplastics, thermosets and casting compounds.

7. A process according to claim 6, characterized in that the plastics used are electrically insulating thermoplastics and / or adhesives.

8. The method according to claim 7, characterized in that electrically insulating thermoplastics selected from the group of polyamides (PA) are used 9. A method according to claim 7, characterized in that electrically insulating adhesives or casting compounds selected from the group of epoxy adhesives are used.

10. Electrolysis cell (Z) comprising or consisting of (a1) two metallic half-cells (AR) and (KR), which form the anode and cathode compartments Q1 and Q2, respectively, (a2) an anode (A) and a cathode (K) arranged therein, (a3) a separator membrane (M) and (a)4 optionally spacers (E1, E2) which position the two electrodes in their respective electrode spaces, wherein (i) the two half-cells are separated across their perimeter (P) by a space (S) and the separator membrane (M), (ii) the separator membrane (M) is arranged between the electrodes in such a way that it either projects into the intermediate space (S), is flush with the end of the intermediate space (S) or projects out of the intermediate space (S) and (iii) the perimeter (P) is enclosed by a plastic frame (R).

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