Device for removing hydrogen from two-phase flows in connecting pipelines of electrolyzers and electrolysis plants

Abstract

Pipeline element for the passive depletion of hydrogen crossover gases in an electrolysis plant, comprising a pipe section designed for integration into an oxygen line, characterized by:◯ flow engineering means for phase separation (12, 13) of the two-phase flow guided in the pipe section into a gas-enriched partial flow (15) and a liquid-dominated partial flow (16),◯ at least one catalytically coated support matrix (20) arranged in the region of the gas-enriched partial flow,◯ and a passive temperature stabilization unit (21) which is thermally coupled to the support matrix (20) and is designed to dissipate reaction heat to the outside.

Description

State of the art The invention relates to a piping element for integration into the oxygen line of an electrolysis plant, in particular a PEM electrolyzer. In PEM electrolysis, hydrogen can reach the oxygen side due to membrane defects or diffusion. This leads to a mixture of water, oxygen, and potentially hydrogen in the fluid flow on the oxygen side. The coexistence of hydrogen and oxygen forms an explosive mixture, which can lead to deflagrations or detonations if the lower explosive limit (LEL) is exceeded. The resulting pressure waves endanger the integrity of the entire system. Current protective measures have the following disadvantages: • Normative gaps: Existing regulations for pipe design do not provide models for detonation scenarios in pipes. • Certification problems: Classic flame arresters (e.g., sintered bodies) are not permitted for systems with a two-phase flow (water and oxygen bubbles) because no certification criteria exist for this. • Complexity of active systems: Known solutions use active ignition devices. However, these require auxiliary electrical power, sensor monitoring, and control system evaluation, which limits technical reliability and increases maintenance costs.• Integration effort: Recombination layers integrated into the membrane increase manufacturing complexity and can negatively impact efficiency. Task The invention is based on the problem that previous technical solutions for the described operating conditions (two-phase flow) are either not permissible or require a failure-prone active control. Against this background, the invention aims to provide a device for an electrolysis plant that safely removes both small and large quantities of hydrogen through passive and inherently effective protective measures. The primary focus is on explosion protection by preventing explosive mixtures, without relying on external auxiliary energy or moving parts. The device should also be easy to maintain and retrofit into existing systems. Description of the device The solution to the problem according to the invention is achieved by a pipeline element for the passive depletion of hydrogen crossover gases, which is designed for integration into an oxygen line of an electrolysis plant. The piping element essentially comprises: • a vertical section for calming the two-phase flow, • an integrated phase separation device (gas separator) designed to spatially separate the gas phase (oxygen / hydrogen) from the liquid phase (water), • at least one recombination unit having a passive autocatalytic recombiner (PAR) and located in the area of ​​the separated gas phase, • and a temperature stabilization unit thermally coupled to the recombination unit for passive heat dissipation. Detailed design of the device components In an advantageous embodiment, the pipe element is designed as a vertical pipe section in which a coalescing filter is arranged. This serves to combine finely dispersed gas bubbles in the water flow into larger agglomerates and thus increase the buoyancy towards the gas separator. The gas separator is preferably designed as a chamber arranged above the main flow or as a dome-like bulge in the piping element. This ensures that the combustible gas phase moves past the catalytically active surfaces of the recombination unit in a spatially concentrated manner. The recombination unit comprises a support body with a catalytic coating (e.g., platinum or palladium). To prevent thermal overload and ensure compliance with ignition temperature limits, the unit is connected to a passive cooling system. This is preferably designed as a thermosiphon (heat tube) that dissipates the heat of reaction to the environment or to a separate cooling circuit without the need for external pumps. To increase safety at high hydrogen concentrations, the piping element can also be equipped with a Venturi injector. This is dimensioned so that the fluid flow creates a negative pressure, which draws in already depleted gas or ambient air and mixes it with the fresh gas for dilution (passive recirculation). Advantages of the device The described device offers the following advantages over the state of the art: 1. Passive safety: Depletion occurs purely through physical-chemical processes without electrical sensors or actuators. 2. Certification capability: Since the device can be considered a classic piping component with defined internals (and not a flame arrestor in the conventional sense), it avoids the approval issues for two-phase flows. 3. Maintenance-free operation: By eliminating moving parts and utilizing the inherent process heat for circulation, the system is virtually maintenance-free. 4. Compactness: The element can be integrated directly into existing plant periphery as a standard component (e.g., as a flanged piece). Brief description of the drawings Fig. 1 - schematically shows an electrolysis system according to the invention in various possible installation variants (horizontal or vertical installation of the piping element). Fig. 2 - schematically shows a part of the electrolysis system from Fig. 1 for horizontal installation of the device according to the invention. Fig. 3 - shows a further alternative embodiment of Fig. 2. Fig. 4 - schematically shows a part of the electrolysis system from Fig. 1 for vertical installation of the device according to the invention. Fig. 5 - shows a further alternative embodiment of Fig. 4. Detailed description of the drawings The following is an explanation of the invention with reference to drawings, showing the structure and, if applicable, the mode of operation of the invention as illustrated in various embodiments. Fig. 1 shows a schematic representation of a preferred embodiment of an electrolysis plant according to the present invention, wherein the method according to the invention can be carried out in this arrangement. The illustrated example is a plant for the electrochemical splitting of water using a proton exchange membrane (PEM). The electrolysis plant shown, as well as the one generally described within the scope of the invention, is designed for use on a commercial-industrial scale.

[0035] The electrolysis plant comprises an electrolysis unit 1, which, in the illustrated embodiment, includes, by way of example, two electrolysis cells or cell stacks. A proton exchange membrane (PEM) is arranged in each of these electrolysis cells, by which the respective electrolysis cell is divided into an oxygen-carrying region and a hydrogen-carrying region.The oxygen-side areas and the hydrogen-side areas assigned to the individual electrolysis cells can be considered together as the oxygen side and hydrogen side of the electrolysis unit, respectively. The electrolysis system further comprises a vessel 3, which is designed for gas separation and serves in particular as an oxygen separator or as a separator for an oxygen-water mixture. The vessel is connected to the electrolysis unit or to the individual electrolysis cells via at least one fluid connection 9. A fluid flow can be conveyed from the vessel to the electrolysis unit via this fluid connection, for example, using a pump 4. Additionally, the electrolysis unit is coupled to the vessel via further fluid lines, such as pipes. This connection allows fluid to be returned from the electrolysis unit, in particular from the oxygen side or the respective oxygen sides of the electrolysis cells, to the vessel, and the same pump can be used for this purpose as well.

[0037] Furthermore, the electrolysis system comprises a further gas separator 8, which is designed as a hydrogen separator or as a separator for separating a hydrogen-water mixture. A passive check valve (e.g., flow diodes) 7 is preferably arranged in the fluid line leading to hydrogen separation. This check valve is expediently positioned in close proximity to the electrolysis unit in order to largely prevent an undesired backflow of the fluid in the event of a sudden failure of the ion-conducting separating layer of the electrolysis unit. Although only one electrolysis unit is shown in the illustrated embodiment, the invention is not limited to this. Rather, depending on the design and the desired performance of the electrolysis system, several electrolysis units can also be provided. In such a case, the several electrolysis units can, for example, be connected together to a container for gas or oxygen separation and / or to a common hydrogen separator. During operation of the electrolysis plant, a water-containing fluid stream is pumped from the tank to the electrolysis unit. Within the electrolysis unit, the electrochemical splitting of the water into oxygen and hydrogen occurs under the application of an electrical voltage. The hydrogen produced is electrochemically transported across the proton exchange membrane to the hydrogen side and from there, possibly together with water vapor and a liquid water phase, is fed as a fluid stream to the hydrogen separator. In the hydrogen separator, the hydrogen is separated from the water and can then be discharged as a product stream, for example, used for further purposes or stored. The separated water can undergo suitable treatment and then be returned to the main water circuit of the electrolysis plant. The oxygen, along with the majority of the water, remains on the oxygen side of the electrolysis unit, although—as previously explained—small amounts of hydrogen may also be present on this side. The resulting fluid stream thus comprises both a liquid and a gaseous phase and contains, in particular, water, oxygen, and hydrogen. This fluid stream is then fed into a pipe element 2a / 2b, in which a catalytically coated support structure is arranged. The phase-separated fluid stream flows through the pipe element and is then fed as a vapor-dispersed fluid stream to a gas separator 3. The water separated in the gas separator can be recirculated for electrochemical water splitting. Any remaining residual heat can be removed from the fluid stream in a controlled manner by means of heat extraction 5. As previously explained, the gas, particularly the oxygen and any remaining hydrogen, is separated from the liquid phase within the container. The separated gas can then be discharged as a gas stream and, for example, used for other purposes or stored. For instance, the gas stream can be fed via an additional branch to a processing unit where any hydrogen present is removed and the gas is dried, or it can be fed to a compressor. Since water is converted into oxygen and hydrogen within the electrolysis unit and the resulting gases are discharged from the system, the amount of water available in the system decreases. To ensure continuous system operation, fresh water can therefore be supplied from outside the electrolysis plant as an additional feed stream, including the necessary treatment stage 6.Within the pipe element 2a / 2b, a recombination reaction is triggered on a catalytically active surface when the reactants oxygen and hydrogen are present simultaneously in a reactive mixture ratio. As a result of this reaction, the fluid flow exiting the pipe element contains only a hydrogen content below the lower explosive limit. However, the heat of reaction released during recombination can cause the support structure to heat up considerably, reaching a temperature level above the ignition temperature of the respective gas mixture. To prevent such an undesirable temperature increase, a passively operating cooling device is provided according to the invention, which surrounds the pipe element at least partially.This cooling device is designed to reliably dissipate the heat generated by the reaction at both low and high hydrogen concentrations. The device shown operates without an external energy input; that is, it is passive. In the following explanation of the figures, identical reference symbols are used for components and features that are identical or at least functionally comparable in the different illustrations. Detailed descriptions of the design and / or function of individual features are generally only provided upon their first appearance. Unless individual features are explained in detail again later, their design and / or operating principle correspond to those of the previously described similar or functionally equivalent features. Figure 2 shows a simplified schematic cross-sectional view of a section of the electrolysis plant from Figure 1, specifically the fluid connection 9 from before to after the pipe element 2b. This pipe element has openings at the front / bottom and rear / top for unimpeded inflow and outflow. The pipe element, made of metallic pipe fittings in symmetrical or asymmetrical shapes, can be installed as a removable element, e.g., by means of flanges 10, 26, or as a permanent element, e.g., welded in all around, in the connecting pipeline between the electrolysis unit 1 and the oxygen gas separator 3 during installation or as a retrofit kit. Fluid flow 9, coming from the oxygen side of the electrolysis unit, enters the pipe element 2b, and fluid flow 25 exits at the end, leading to the gas separator. As already mentioned, the pipe element should be positioned as close as possible to the electrolysis unit. Positioning the pipe element above the electrolysis unit (in the direction of gravity) is particularly advantageous to ensure that the electrolysis unit remains submerged in water. Both the fluid inlet 11 and the fluid outlet 22 are designed such that a gradual pipe expansion occurs in the inflow area and a gradual pipe narrowing occurs in the outflow area. This results in significantly lower friction and separation losses than with abrupt changes in the cross-sectional area of ​​the fluid flow. A cylindrical section is provided between these two areas. After leaving the electrolysis unit, a binary mixture of liquid water and gaseous oxygen is present on the oxygen side. The gaseous oxygen is in the form of fine bubbles, so that, in terms of flow morphology, it can be described as a two-phase bubble flow. In Fig. 2, the aim is to achieve the greatest possible phase separation in the inflow region through fluid-mechanical separation operations / effects, since a conventional catalyst in a two-phase flow would be wetted by a thin layer of water through which hydrogen can only diffuse slowly. Therefore, the catalytic capacity of the support matrix surface should not be limited by wetting by liquid. Phase separation located upstream of the actual pipe element is therefore advantageous. This includes components that utilize effective physical differences between the gas phase and liquid phase in two-phase flows, such as momentum difference or density difference. Obstacles 12 (e.g., wire mesh) force the smaller bubbles coming from the electrolysis unit to collide and merge (coalescence). Larger bubbles have higher buoyancy and greater kinetic energy, thus ensuring stoichiometric reactivity in the piping element (premixing). Furthermore, larger bubbles can more effectively break through any liquid film that may be present on the catalyst. In turbulent pipe flow, gas bubbles tend to accumulate in the center of the pipe (core-peak distribution). Therefore, in the illustrated embodiment, a swirl body 13 is preferably arranged centrally. The liquid flow thus acquires a velocity component towards the pipe wall. A liquid layer forms at the pipe wall, while the lighter gas bubbles flow in the center of the pipe, as bubbles migrate to where the pressure is lowest. Simultaneously, this gas bubble concentration also causes the existing reactants, oxygen and hydrogen, to mix into a gas mixture. Due to the induced swirl (rotation), the denser water is flung outwards and from there carried to the liquid-side reaction zone 18. A centrally arranged channel 14a is preferably used for the targeted separation of the gas-dominated fluid flow in the middle of the two-phase flow. To separate any remaining liquid droplets, a demister 14b is arranged within channel 14a for dehumidification. Immediately downstream is a flow restrictor 27, which, due to the density differences, allows the gas phase to flow largely free of liquid components towards reaction zone 17. It is known that gas bubbles separate from such two-phase flows at flow velocities below 0.3 to 0.5 m / s. The separated liquid droplets flow towards the liquid-side reaction zone 18 due to gravity. The inlet area is designed such that the gas-phase-dominated fluid flow 15 is directed directly to the catalytically active surface of the support matrix, while the liquid-dominated fluid flow 16 is guided around it (vertically) or underneath it (horizontally). In the upper part of Fig. 2, catalytically coated support matrices 20 are arranged, over which the gas mixture flows. To prevent any electrochemical corrosion processes, this support matrix 20 with the catalytically active surface (e.g., palladium or platinum) is provided with suitable spacers 19 at the point where it meets the inner wall of the pipe (usually made of metal). These spacers should preferably be made of high-temperature-resistant and non-conductive plastics, e.g., polyetheretherketone (PEEK). Alternatively, the inner wall of the pipe element can also be provided with an internal coating 28 in this area. In aqueous atmospheres, the effectiveness of catalytically active surfaces is limited. This is explained in more detail in a technical article from the Canadian Nuclear Laboratories (CNL): Gardner, L., Vega, A., Tremblay, RP, Suppiah, S. and Ryland, D.: “HUMIDITY TOLERANT HYDROGEN-OXYGEN RECOMBINATION CATALYSTS FOR HYDROGEN SAFETY APPLICATIONS”. The surface of the support matrix 20 is preferably topographically designed such that nano- and microstructured areas are present on which the catalytic layer rests. A hydrophobic to superhydrophobic surface can prevent or reduce wetting by any remaining liquid droplets (lotus effect) in order to achieve the largest possible catalytically effective surface area. Thus, a water-tolerant embodiment of the catalysts used can be achieved. This can be accomplished, for example, by processes such as etching, laser ablation, or by applying nanoparticles. The support matrix comprises various material and geometric configurations onto which a catalytically active catalyst coating is applied. The base body of the support matrix can consist of a wide variety of materials, such as ceramics (e.g., silicates), as known from the fields of refractory construction or automotive engineering. In Fig. 2, the support matrix 20 includes various exemplary designs of packing materials. Numerous embodiments are known from the field of chemical process engineering (spheres, Raschig rings, Pall rings, layered packings). The gas mixture, or the reactants oxygen and hydrogen, flow over the surfaces due to the delivery pressure of the fluid flow from the electrolysis unit. Depending on the effectiveness of the support matrix, the hydrogen is either depleted or removed. To control the catalytic reaction, the support matrix can be only partially coated. The uncoated area then serves to absorb some of the heat of reaction. To prevent contact corrosion between the Pd-coated carrier matrix and the inner wall of the pipe element (e.g., made of austenitic stainless steel such as 1.4571), these are spaced apart from each other by a suitably designed holding device made of non-conductive material. Alternatively, an internal coating 28 of the pipe element can also be present. In Fig. 2, the spatially separated, liquid-dominated water side 18 is located below the gas-side reaction area 17. A holding device 19 separates the two areas. This holding device is not liquid-tight, so that any liquid flowing from 17 may reach this area due to gravity. Since recombination is strongly exothermic, there is a need for temperature stabilization at a level that ensures that the temperature increase in the piping element does not reach the ignition temperature applicable to the gas mixture present, does not cause the amount of liquid in the piping element to boil, and does not negatively affect the operational strength of the surrounding pipe material. The liquid flowing in 18 can partially absorb the heat of reaction generated in 17 due to thermal radiation and conduction. However, it should remain below its boiling point. To ensure this, a temperature stabilization unit 21 is arranged surrounding the pipe element. This passive thermal coupling allows the heat of reaction to be dissipated. In Fig. 2, this is illustrated by a simple cooling ring. The cooling system for temperature stabilization within the reaction zone is therefore a functional feature for maintaining the reaction kinetics. To detect a recombination reaction inside and also indicate it externally, reversible temperature-measuring paints or other temperature indicators can be applied to the cooling system. According to the invention, this device for temperature stabilization of the recombination reaction is to be designed as a passive system. Suitable systems include simple air cooling on the outside of the housing of the pipe element (e.g., in the form of cooling fins / cooling rings) or systems with an inherent phase change of a coolant 29, such as heat pipes (capillary action of the coolant) or thermosiphons (gravitational effect of the coolant in a vertical installation situation). Water vapor is produced after the reactants recombine. If this vapor were to reach the gas separator in large bubbles, it could lead to uncontrolled condensation and thus pressure surges. By breaking up the vapor phase into microbubbles in the outflow area using special internal components, the contact area between the vapor and the liquid is maximized (dispersion), enabling gentle and rapid condensation directly in the pipe. This protects the mechanical integrity of the entire system. According to the invention, the outflow area within the pipe element is designed with internal components 23 that effect such mechanical dispersion. Possible embodiments are shown in Figures 2, 3, 4 to 5. Suitable designs include porous injectors (sintered metal and ceramic injectors), static mixers, perforated plates, screen trays, or Venturi injectors. Depending on the flow conditions (volume flow rate) present in the system, a design with low pressure loss is preferable. Preferably, a design with porous injectors and liquid-supplying channels 24 should be chosen. Fig. 3 shows a simplified sectional view of a pipe element for passive catalytic recombination according to an alternative embodiment. In contrast to the embodiment of Fig. 2, in the embodiment of Fig. 3 only a coalescing unit 12 is arranged in the flow area. The actual phase separation is achieved here by a gradual pipe expansion (diffuser) and the associated reduction in flow velocity. Preferably in conjunction with a flow restrictor 27, the phase-separating density and momentum difference can thus be used to obtain a gas-dominated 15 and a liquid-dominated 16 fluid flow. Unlike in Fig. 2, the support matrix 20 in this embodiment consists of a honeycomb-shaped arrangement of plates. This design results in lower flow resistance during flow, as no turbulence-inducing effects can occur. Form-fitting caps 19 connected to the honeycomb shape ensure an equidistant distance to the inner wall of the pipe element. This is visible in view A. A centrally arranged support, as shown in Fig. 2, is not required in this embodiment. The passive temperature stabilization unit 21 is also shown in a modified form in Fig. 3. As is known from aerospace applications, heat pipes can dissipate large amounts of (reaction) heat (latent heat from phase changes) due to their specifically high heat flux density. They operate passively (no mechanical parts and no power requirement) and are virtually maintenance-free. The design utilizes capillaries located inside the heat pipe, allowing the working medium to flow back against gravity (wick effect), thus ensuring continuous operation. In Fig. 3, such a heat pipe is shown completely enclosing the piping element 2. To disperse the generated steam into the outgoing fluid stream, a more voluminous porous injector unit is shown in Fig. 3. The increased number of fine channels results in an even finer distribution of the steam bubbles and thus faster condensation. Fig. 4 shows a simplified sectional view of a pipe element for passive catalytic recombination according to an alternative embodiment. In contrast to the previous embodiments in Fig. 2 and Fig. 3, the embodiment in Fig. 4 shows a vertically arranged pipe element 2b. This vertical arrangement results in changed design requirements for the technical implementation of the problem according to the invention. The inflow area, similar to Fig. 2, features coalescing and phase-separating internals. In this embodiment, the feed channel 14b and the recombination area 17 are designed as Venturi nozzles to receive the gas-dominated partial flow. These nozzles are centrally fixed by holding devices 19. This, as is known, creates an acceleration effect. This, in turn, leads to improved mixing of the reactants on the flow side before they pass over the catalytically active support matrix 20, shown here as parallel and equidistantly arranged plates. The aim of this improved mixing is to generate a stoichiometrically optimal mixture in order to achieve the highest possible hydrogen removal rate. In this embodiment, a temperature stabilization unit 21 is missing. This is intended to show that, depending on the design scenario, the amount of water already present may be able to dissipate the resulting heats of reaction due to its specific high heat capacity. At the end of the Venturi nozzle, Fig. 4 again shows a porous injector unit, but this time without fine internal channels, as no liquid flows through it. This porous layer serves to generate the finest possible vapor bubbles before they enter the surrounding fluid flow. In this embodiment, static mixers are shown in the downstream section to disperse the vapor bubbles into the fluid flow. Since the overall pipe element should have the shortest possible installation length, SMV static mixers (structured packings with crossed corrugated sheet layers) are preferably used. Here, too, there are no moving parts. In contrast to the previous figures, in this embodiment the integration of the pipe element into the connecting pipe is shown as a fully welded, non-removable connection 10, 26. Fig. 5 shows a simplified sectional view of a pipe element for passive catalytic recombination according to a further alternative embodiment in vertical arrangement 2a. The inflow area, similar to Fig. 4, has coalescing and phase-separating internals. In this embodiment, the supply channel 14a and the recombination area 17 are designed as chambers to receive the gas-dominated partial flow, and these chambers are centrally fixed by holding devices 19. In contrast to Fig. 4, a hydrophobic membrane 14b is used here for the additional dehumidification of the gas-dominated fluid flow. Such membranes are known to have high gas permeability while retaining liquid water. Typically, these membranes are made of materials such as PTFE, which are themselves very durable, chemically resistant, and temperature-resistant. Since they do not absorb water, they do not clog. Because the water used here also contains no substances such as surfactants or organic liquids, blockage effects or foaming are not possible. The temperature resistance of the membrane materials can range from 250 to 300°C in continuous operation. In the illustrated configuration, cooling of the membrane is ensured by the water flow. The gas-dominated fluid stream then enters a chamber-like structural volume where a static pressure builds up. This static pressure is higher than the static pressure in the water-side fluid stream flowing around this chamber. Therefore, no water can penetrate this chamber. In this embodiment, the support matrix, with its catalytically active surface, is designed as a fine knitted fabric 17. Due to the pressure gradient, the gas mixture penetrates this layer and recombines within it. The resulting fine vapor bubbles thus enter the water-side fluid flow, which in turn flows out of the pipe element towards gas separator 3 via a static mixer already mentioned above. In this embodiment, the temperature stabilization unit 21 comprises a thermally coupled thermosiphon (shown here with cooling fins). Such heat dissipation systems are known, for example, from their use in solar systems or for stabilizing pipeline supports. Due to the vertical orientation of the thermosiphon, the working fluid rises after evaporation and can condense there through heat transfer to the surroundings. The condensate then flows back into the working fluid reservoir at the base of the thermosiphon as a film on the outside due to gravity. Common working fluids are water-glycol mixtures (if corrosion and antifreeze protection is required), pure water, or propylene glycol. The invention is not limited to the embodiments described above and illustrated in the drawings. Rather, numerous modifications are possible within the scope of the claims. Likewise, features described or illustrated in different embodiments can be combined with one another, provided there are no technical reasons to the contrary.

Claims

Pipeline element for the passive depletion of hydrogen crossover gases in an electrolysis plant, comprising a pipe section designed for integration into an oxygen line, characterized by: ◯ flow engineering means for phase separation (12, 13) of the two-phase flow guided in the pipe section into a gas-enriched partial flow (15) and a liquid-dominated partial flow (16), ◯ at least one catalytically coated support matrix (20) arranged in the region of the gas-enriched partial flow, ◯ and a passive temperature stabilization unit (21) which is thermally coupled to the support matrix (20) and is designed to dissipate reaction heat to the outside. Device according to claim 1, characterized in that the means for phase separation comprise a coalescence filter (12) for enlarging gas bubbles and / or a swirl body (13) for guiding the liquid phase close to the wall. Device according to one of the preceding claims, characterized in that the passive temperature stabilization unit (21) is designed as a heat pipe or thermosiphon. Device according to one of the preceding claims, characterized in that means for disperse mixing (23) of the gas and liquid phases are arranged downstream of the support matrix (20), preferably designed as porous injectors or static mixers. Device according to one of the preceding claims, characterized in that the support matrix (20) is spaced apart from the inner wall of the pipe element by spacer devices (19) made of electrically non-conductive, high-temperature-stable material. Device according to one of the preceding claims, characterized in that the pipe element is designed as a flangeable or weldable module for installation in the oxygen line between an electrolysis stack (1) and a gas separator (3).

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