Method for operating an electrolyzer, and electrolyzer

Abstract

The invention relates to a method for operating an electrolyzer (1) comprising an anode chamber (3) and a cathode chamber (5), in which water (H2O) is supplied as a reactant and hydrogen (H2) and oxygen (O2) are generated as product gases. On the anode side, the oxygen product gas, which also contains hydrogen as a foreign gas, is generated in a product flow out of the anode chamber (3) and is introduced into a horizontal anode-side collecting line (7) having a surrounding wall (11) and is removed via the collecting line (7), wherein water (H2O) is sprayed onto an inner surface of the surrounding wall (11) of the collecting line (7) so that the surrounding wall (11) is wetted with water and the inner surface is inerted. The invention additionally relates to an electrolyzer (1), in particular for carrying out the method.

Description

[0001] Description

[0002] Method for operating an electrolyzer and electrolyzer

[0003] The invention relates to a method for operating an electrolyzer for producing hydrogen and oxygen as product gases. The invention further relates to such an electrolyzer.

[0004] Hydrogen is now produced using proton exchange membrane (PEM) electrolysis or alkaline electrolysis, for example. Electrolyzers use electrical energy to produce hydrogen and oxygen from the supplied water.

[0005] An electrolyzer typically comprises a plurality of electrolysis cells arranged adjacent to one another. Water is split into hydrogen and oxygen in the electrolysis cells by means of water electrolysis. In a PEM electrolyzer, distilled water is typically added as the reactant on the anode side and passed through a proton-permeable membrane (proton exchange membrane).

[0006] PEM) into hydrogen and oxygen. The water is oxidized to oxygen at the anode. The protons pass through the proton-permeable membrane. Hydrogen is produced on the cathode side. The water is usually pumped from the bottom into the anode and / or cathode compartments.

[0007] This electrolysis process takes place in the so-called electrolysis stack, composed of several electrolysis cells. Water is introduced as the reactant into the electrolysis stack, which is subjected to a direct voltage. After passing through the electrolysis cells, two fluid streams consisting of water and gas bubbles (oxygen O2 and hydrogen H2) emerge as product streams. The respective separation of the water and gas phases in the fluid streams takes place in gas separators. For this purpose, a gas separator is provided for phase separation of the hydrogen product stream and the oxygen product stream.

[0008] In practice, there are small amounts of hydrogen in the oxygen gas stream and small amounts of oxygen in the hydrogen gas stream. The quantity of each external gas depends on the electrolysis cell design and also varies under the influence of current density, catalyst composition, aging and, in the case of a PEM electrolyzer, the membrane material. It is inherent in the system that the gas stream of one product gas always contains very small amounts of the other product gas. As the process progresses, even small traces of oxygen are generally removed from the hydrogen in downstream gas cleaning steps, sometimes using very complex and cost-intensive cleaning steps, particularly when a particularly high product gas quality is required, as is the case when the hydrogen is used, for example, for fuel cells.

[0009] In terms of plant technology, for example, in an electrolysis plant, both product gas streams from the electrolyzer can be fed to a catalytically activated recombiner for gas purification, in which a catalyst allows the hydrogen to recombine with the oxygen to form water (DeOxo unit). For this purpose, the gas stream must first be heated to at least 80°C to ensure that the conversion rates of the recombiner are sufficiently high and thus the required gas purity is achieved. However, the process plant used for this purpose is expensive and, due to its energy requirements, reduces the system efficiency of the entire electrolysis plant.It is therefore important to pay attention to the purity and quality of the product gas streams initially created in the electrolyzer and those discharged from the electrolyzer, not only to ensure operational safety but also to keep the costs and effort for the subsequent cleaning steps in the electrolysis plant within acceptable limits. The purity and quality of the two product gas streams of the gases originally produced in the electrolyzer depends on many parameters and can change during the course of operation of an electrolysis plant. This is problematic and particularly safety-relevant when the concentration of oxygen in hydrogen increases, but also when the concentration of hydrogen in oxygen increases. If a certain concentration limit is exceeded, the oxygen gas produced, for example, can no longer be used for further purposes.This is particularly problematic within the product-side anodic channel structure, the so-called Cy-manifold channels, with a number of collecting channels for the respective product gas stream, the connected product stream line, and the respective gas separator (vessel) connected to it directly downstream of the electrolysis cells. If the proportion of hydrogen in the oxygen product gas continues to rise, a flammable or explosive mixture can even form. This would then create a potentially dangerous operating condition in the gas separator (vessel), for example, which must be avoided at all costs for safety reasons. This also applies accordingly to the hydrogen side.

[0010] Therefore, one possible measure is reliable and continuous monitoring of the gas quality of the product gases during operation of the electrolysis plant with an electrolyzer by measuring the concentration in the gas separator. This applies in particular to the oxygen side of the electrolyzer, i.e. monitoring the concentration of hydrogen as a foreign gas in the oxygen produced during electrolysis. Monitoring and appropriate operational management represent an important protective measure for detecting critical operating conditions and taking safety measures, including temporarily shutting down the electrolysis plant. However, there are systemic limits to cell-level and local sensitivity to a critical foreign gas concentration in the electrolyzer in order to detect a dangerous situation in good time and initiate measures.Ultimately, monitoring the concentration by measuring downstream in the gas separator only yields an average value after the liquid and gaseous phases have largely demixed, i.e. after separation. Therefore, large safety reserves have been maintained to date for a permissible limit concentration, which in some cases then leads to premature safety shutdowns of the entire electrolysis plant or the electrolyzer, even though operation would still be possible. Critical foreign gas concentrations close to the cell and the associated operating conditions of the electrolyzer with a high risk of explosion or fire cannot be detected locally at all by monitoring alone, or at least not in a timely or precise manner, so that countermeasures cannot be initiated quickly.This is particularly critical for operation when carrying out PEM pressure electrolysis, where, for example, in a differential pressure operation of a PEM pressure electrolyzer, an inadmissibly high H2 gas transfer from the hydrogen side to the oxygen side is locally initiated and intensified, for example as a result of age-related membrane cracks.

[0011] The invention is therefore based on the object of enabling an electrolyzer to operate with improved safety and plant efficiency, in particular in an electrolysis plant having a pressure electrolyzer.

[0012] The object is achieved according to the invention by a method for operating an electrolyzer comprising an anode chamber and a cathode chamber, in which water is supplied as a reactant and hydrogen and oxygen are generated as product gas, wherein on the anode side the oxygen product gas, which also contains hydrogen as an extraneous gas, is led out of the anode chamber in a product stream and is introduced into a horizontally arranged anode-side collecting line with a surrounding wall and is transported away via the collecting line, wherein water is sprayed onto an inner surface of the surrounding wall of the collecting line, so that wetting of the surrounding wall with water and inerting of the inner surface is effected.

[0013] The invention considerably improves the intrinsic safety of the electrolyzer by inerting critical surfaces in the anodic collecting channel with water through targeted wetting of the surface. The invention has recognized that, under certain operational conditions and with a limited fill level of the product flow in the collecting line, there is a risk that the non-wetted surfaces above the fill level of the surrounding wall will tend to run dry. As a result, an ignitable gas mixture can arise, particularly in the anodic collecting line, in the event of increased gas transfer of hydrogen from the cathode compartment via a membrane or a separator membrane of the electrolysis cell into the anode compartment.This gas mixture above the liquid phase can ignite very easily on the dry surface of the surrounding wall, especially if there is an inhomogeneity of the surface or if there are catalytically active particles that promote ignition and adhere locally to the surface.

[0014] For example, in widely used polymer electrolyte membrane water electrolyzers (PEMWE), the gases hydrogen (H2) and oxygen (O2) produced by electrolysis are normally separated from each other by the polymer electrolyte membrane. However, aging effects or exceptional stresses such as unscheduled or unforeseen high differential pressures can cause holes or cracks in the membrane, which, particularly during prolonged differential pressure operation, allow a higher gas transfer than under normal conditions. Transfer of hydrogen to the oxygen side of the membrane is the more critical case because O2 on the H2 side can react relatively well at the cathode, which typically contains platinum, and the hydrogen gas flow is a factor of two higher than the oxygen gas flow.A large amount of H2 transfer in an area of ​​low O2 flow in an O2 collection device comprising one or more anodic manifolds is particularly unfavorable. For example, there may be three parallel anodic manifolds, so-called manifold channels, connected by small cross connections. A large amount of hydrogen transfer in this area can very easily lead to a locally ignitable gas mixture, for example with an external gas concentration of more than 4% hydrogen in oxygen in the anodic manifold. Instantaneous ignition can, for example, be initiated or promoted by a platinum particle adhering to the inner surface as a catalyst. If the surrounding wall of the manifold is incompletely wetted in the upper area, this can trigger a fire or even an explosion, particularly if the material of the collection channel is flammable in almost pure oxygen.This can, for example, be the case even with otherwise flame-resistant glass-fiber reinforced thermoplastics (polyphenyl sulfide, PPS), which are flammable in an oxygen environment.

[0015] Compared to conventional safety concepts for countering the risk of fire or explosion in an electrolyzer, the invention is superior and intrinsically safe, particularly since it ensures effective inerting close to the cell in the anodic and, if necessary, also in the cathodic manifold by continuously spraying water onto the inner surface, thus preventing dry running. (In both the anodic manifold and the cathodic manifold, this inerting can be applied by targeted water injection onto the inner surface of the surrounding wall. The water for inerting can be branched off and taken from the fresh water supply of the water make-up in an electrolysis plant. It is then brought under injection pressure and sprayed specifically into the manifold of the electrolyzer.To provide nozzle pressure, existing make-up pumps for the electrolysis plant's process water can advantageously be used. Until now, for example, in commercial polymer electrolyte membrane water electrolyzers, the H2 in O2 concentration had to be measured continuously in order to detect the formation of an ignitable gas mixture and prevent it through suitable measures. However, detection is not sufficiently local and close to the cell, but only in downstream flow elements such as the electrolysis plant's gas separator. However, if the measurement is of product gas from the oxygen-soap gas separator, the possibility of detecting a locally ignitable gas mixture in the anodic collecting line is very limited and of only limited significance.To date, the probability of the formation of an ignitable gas mixture from the transfer of H2 to the O2 side has been minimized by setting and monitoring the differential pressure between the anode and cathode compartments at a low level and by regularly checking for internal leaks. However, this does not completely eliminate the described fire and explosion hazard. Intrinsic safety is not guaranteed.

[0016] The process of the invention, however, ensures continuous wetting of the inner surface of the oxygen-soap collecting line with liquid water. This virtually eliminates the risk of the material forming the collecting line catching fire. The cell sections of the anodic and cathodic collecting lines are preferably integral components of a respective cell frame of an electrolytic cell and are formed from the same material as a single-piece element to form a cell frame.

[0017] In a particularly advantageous embodiment of the method, water is sprayed vertically onto the surrounding wall from a large number of injection nozzles, so that the surrounding wall is sprayed and the inner surface is evenly wetted. The injection nozzles are arranged and aligned in such a way that in the collecting duct at least the inner surface in the half-space above a minimum operationally intended fill level is wetted as continuously and completely as possible during the water injection. For this purpose, a fan-shaped nozzle arrangement introduced into the upper half-space of the collecting duct can be advantageously used. Similar to a lawn sprinkler, water is continuously sprayed upwards through these openings under pressure, thus moistening the upper inner surface of the collecting line and, if applicable,The outside of the spray device built into the collecting line is also continuously wetted with water. The used spray water then mixes with the liquid product stream. This product stream contains water and the respective product gas, e.g. oxygen on the anode side, and forms a water-gas mixture under a fluid pressure at a fill level in the collecting line. This product stream is led out of the horizontal collecting line and out of the electrolyzer and fed to a gas separator as part of an electrolysis plant.

[0018] In a further preferred embodiment of the method, the product flow is guided in the horizontal collecting line up to a filling level in a liquid phase, so that a liquid space and a gas space adjacent to the liquid space are formed in the collecting line, the inner surface of the surrounding wall delimiting the gas space being wetted with water above the liquid space.

[0019] The nozzle arrangement for water injection and wetting can be selected with regard to the installation height in the collecting line so that, under operating conditions with the lowest volume ratio of oxygen in the gas phase and oxygen-to-soapy process water in the horizontal collecting line, the openings are above the fill level, i.e., the water level. If necessary, a corresponding process control can also be applied in the cathodic collecting line in order to achieve intrinsically safe fire and explosion protection there as well and to avoid dangerous situations resulting from an excessively high oxygen concentration in the hydrogen product gas in the cathode compartment by inerting the surfaces.

[0020] In a preferred embodiment of the method, water is continuously sprayed onto the inner surface of the surrounding wall delimiting the gas space.

[0021] This makes it possible to ensure complete wetting of the inner surface both during regular electrolysis operation at full or partial load of the electrolyzer and—at least temporarily—during shutdown or standstill operation of the electrolyzer. Thus, inerting is possible in every operating phase.

[0022] In a further preferred embodiment of the method, water is taken from the reactant water of the electrolyzer, in particular the make-up water, and fed under pressure to an injection device.

[0023] It is advisable to divert the water used to inertize the inner surface of the collecting line from the existing process water and extract it. In an electrolysis system with a pressure electrolyzer, for example, the system pressure provided by make-up pumps can be advantageously utilized to impose the required injection pressure on the water above the respective system pressure within the collecting line. The overpressure of the water injected into the collecting line is set to approximately 1-5 bar, in particular 3 bar above the system pressure.

[0024] In a particularly preferred embodiment of the method, the water H2O is fed under pressure to a distribution structure and distributed among several collecting lines. The distribution structure acts as a media distributor for the water to be injected into a collecting line. An injection device is connected to the outlet of the distribution structure and opens into a respective collecting line or projects horizontally. The injection device can be lance-shaped and is equipped with a plurality of injection nozzles. A feed line with a feed pump is connected to the inlet of the distribution structure.

[0025] In a particularly preferred embodiment of the process, pressure electrolysis is carried out, wherein a working pressure of up to 35 bar, in particular between 30 and 35 bar, is set in the anode compartment and in the cathode compartment.

[0026] It is also possible to set a predetermined differential pressure between the anode chamber and the cathode chamber, allowing differential pressure operation if required. This process is particularly advantageous for operating pressure electrolyzers under high system pressure. Especially at high system pressures, inerting the inner surface of the containment wall in the collecting line is particularly advantageous in order to reliably counteract the increased risk of fire or explosion.

[0027] A further aspect of the invention relates to an electrolyzer which is particularly suitable for carrying out the process according to the invention.

[0028] For this purpose, according to the invention, an electrolyzer is proposed which comprises a plurality of electrolysis cells with an anode chamber and a cathode chamber, in which an anodic collecting line is connected to the anode chamber and a cathodic collecting line is connected to the cathode chamber, and in which an injection device having a plurality of injection nozzles is inserted within the anodic collecting line. In this way, the inner peripheral wall of the anodic collecting line can be wetted with water on the upper side and rendered inert.

[0029] Preferably, in the electrolyzer, the injection device comprises a nozzle tube made of an electrically non-conductive material with a number of nozzle openings arranged along the tube axis, the normals of which are directed into the upper half-space of the collecting line.

[0030] During operation, when the collecting channel is partially filled up to a fill level, the inner surface in the half-space above the liquid level can be evenly wetted with water. The installation height of the injection device is selected so that under operating conditions with the lowest volume ratio of gaseous oxygen and anode-side process water, the nozzle openings are above the fill level, i.e. the water level. It is possible to insert and fasten an injection device in the cathode-side collecting line in a corresponding manner. The injection device can be designed and inserted so that it can be manipulated so that it can be raised and lowered vertically, e.g. using an electromechanical adjustment device, in order to adjust to a position just above the fill level.

[0031] Further preferably, in the electrolyzer, the nozzle tube is aligned horizontally within a collecting line along the stacked electrolysis cells and is fixed by a number of brackets.

[0032] The brackets serve to position and secure the nozzle tube within the manifold along a horizontal axis. It is advantageous for the nozzle tube bracket to be structurally integrated into the end plate of an electrolysis segment. An electrolysis segment comprises a plurality of axially stacked electrolysis cells, for example, 50 cells, which are defined by two segment end plates and joined together in a pressure- and fluid-tight manner.

[0033] In a particularly advantageous embodiment of the electrolyzer, it has a plurality of anodic collecting lines which are fluidically connected in parallel with regard to the anodic product flow, wherein a respective injection device is incorporated in a collecting line.

[0034] In this way, even large volume flows of anodic or cathodic product from a large number of electrolysis cells can be collected and discharged through the parallel-connected collecting lines. The collecting lines are arranged vertically above the electrolysis cells and are connected in parallel for fluidic purposes. Accordingly, a respective injection device, for example, comprising a nozzle tube, is incorporated at least in the anodic collecting lines.

[0035] The electrolyser is preferably provided with a feed line which is connected to an injection device and via which the injection device can be pressurised with water.

[0036] The water for operating the injection device can be taken from the reactant water circuit via a supply connection, e.g., by means of a branch line. The feed line can advantageously be implemented by connecting it to a supply line for the make-up water, in particular a supply line for demineralized water in a PEM electrolysis process. A withdrawal pump provides the required pressure and volume flow to convey the water via the feed line into the injection device for inerting, whereby a "pump-nozzle arrangement" is implemented. If necessary, a control valve can be provided to adjust the nozzle pressure.

[0037] In a particularly preferred embodiment of the electrolyzer, a media distributor is provided which has an inlet and a plurality of outlets, wherein the feed line is connected to the inlet and an injection device is connected to an outlet.

[0038] To distribute the extracted make-up water to the plurality of collecting lines, a corresponding multiple distributor structure is provided on the outlet side. This can either be formed in an additional plate, similar to an end plate of a segment of the electrolyzer, or be installed by modifying the existing segment end plate. In the latter case, the distributor structure is formed as an integral component of a segment end plate. This means that only one tap into the process water with a withdrawal line is required in order to supply all injection devices in the collecting lines with pressurized water via the distributor structure.

[0039] In a preferred embodiment of the electrolyzer , the feed line has an insulating section made of an electrically insulating material so that a potential separation is effected between the feed line and the injection device ( 19 ) .

[0040] It is expedient to provide an insulating section in the feed line in order to separate the potential of the segment end plate from the ground potential of the process engineering of an electrolysis plant comprising the electrolyzer. This can be achieved by an appropriate electrically insulating pipe or line section in the feed line. Appropriate insulating sections, e.g. made of glass fiber reinforced polyetheretherketone (PEEK for short) are particularly expedient here. This is a high temperature resistant thermoplastic and belongs to the group of materials known as polyaryletherketones. Its melting point is approximately 335°C. PEEK can be advantageously used here alongside PPS to provide an insulating section in the feed line. In a particularly preferred embodiment of the electrolyzer, an injection device having a number of injection nozzles is incorporated within a cathodic manifold.

[0041] In a corresponding manner, the cathodic manifold is also advantageously made inert, so that an increased oxygen concentration in the hydrogen gas of the cathode compartment is prevented and the risk of fire and explosion is avoided.

[0042] The electrolyzer according to the invention is preferably a system component within an electrolysis plant, which comprises further process engineering and electrical supply components as well as measuring and control devices.

[0043] The advantages and preferred embodiments cited with regard to the method can be applied analogously to the electrolyzer, and vice versa. Examples of embodiments of the invention are explained in more detail with reference to a drawing. These show, schematically and in a highly simplified manner:

[0044] FIG 1 an electrolyzer with a plurality of axially stacked electrolysis cells;

[0045] FIG 2 a sectional view of an electrolytic cell;

[0046] FIG 3 shows a longitudinal section through an anodic manifold with a built-in injection device;

[0047] FIG 4 an injection device with a plurality of injection nozzles;

[0048] FIG. 5 shows a simplified view of a segment end plate of an electrolyzer with a plurality of anodic collecting lines; FIG. 6 shows a view of a segment end plate of an electrolyzer in a modified embodiment with respect to the water distribution compared to FIG. 5.

[0049] The same reference symbols have the same meaning in the figures.

[0050] FIG 1 shows an electrolyzer 1 comprising four electrolysis modules 35, which are sometimes also referred to as electrolysis segments. Each electrolysis module 35 comprises a plurality of electrolysis cells 37, so that a group of four electrolysis modules A, B, C, D is connected in series. A plurality of electrolysis cells 37 stacked along the horizontal axis are each arranged as a group between two pressure plates 39 and connected together to form an electrolysis module 35. The pressure plates 39 press the electrolysis cells 37, which comprise, for example, a proton exchange membrane (PEM), together tightly and precisely in a pressure-tight and fluid-tight manner. The pressure plates 39, which are arranged at the axial ends of the electrolyzer 1, are electrically connected via an electrical connection 41. Three electrical switching devices 43 are arranged in parallel to the electrolysis modules B, C and D of the electrolyzer.The switching devices 43 are arranged electrically parallel to the electrolysis modules 35. In this example, each switching device 43 bridges an electrolysis module 35. Thus, each switching device 43 is electrically connected to the pressure plates 39 that define an electrolysis module 35.

[0051] In this example, the electrolysis, in particular the decomposition of water H2O into hydrogen H2 and oxygen O2, takes place in all electrolysis modules 35, since all switching devices 43 are open. The electrolysis is carried out with direct current. The switching devices 43 are therefore designed as direct current switching devices. A diode 45 is connected in series with the switching element in the forward direction. The polarity and a protective voltage for the stack are thus advantageously maintained. The electrolyzer 1 is operated at full load in this example. If the electrical power in the grid decreases, in particular due to little wind and little sun, at least one switching device 43 can be closed. In this way, the electrolysis modules B, C and D can be switched off or bypassed in a modular manner, as needed. In this example, the electrolysis module A is always operated when the electrolysis system 1 is in operation.If the other modules are now switched off depending on the available electrical power, the electrolysis module A can be operated at a constant power density. This advantageously means that no electrolysis modules 35 or electrolysis cells 37 are operated at partial load. It is particularly advantageous to bridge the electrolysis modules one after the other. In particular, module A can be bridged first for a set period of time. Then module B or module C can be bridged for a similar period of time. The modules are thus operated and loaded evenly. Bridging prevents the electrolysis cells 37 from aging quickly. It is also ensured that the product gas quality, in particular of the hydrogen, remains constant over a long period of time.

[0052] In addition to the electrical supply and connection of an electrolyzer 1 with electrolysis current, the hydraulic supply of reactant water and the discharge of the product streams obtained from the electrolysis process are important for safe operation. While the electrolysis cells 37 are electrically connected in series, the hydraulic conveyance of the reactant water to the individual electrolysis cells and the discharge of the product streams from the electrolysis cells 37 usually takes place in a parallel connection. Fully demineralized water H2O is fed as process water to the electrolyzer 1 on the inlet side via a reactant stream line 47. A product stream line 51 for hydrogen H2 and a separate product stream line 49 for oxygen O2 are connected to the electrolyzer 1 on the outlet side. The product stream comprises a phase mixture of water H2O and the respective product gas, which is hydrogen H2 or oxygen on the cathode side. Oxygen f 02ist on the anode side.The phase mixture is separated and further processed in components (not shown in detail) of an electrolysis plant comprising electrolyzer 1, so that gaseous hydrogen H2 and oxygen O2 are obtained as product gases. The hydraulic design of electrolyzer 1 allows for high operating pressures.

[0053] The electrolyzer 1 shown in FIG. 1 is designed, for example, as a pressure electrolyzer and is designed for a high operating pressure of up to 35 bar. The structure and function are explained in more detail below with reference to FIG. 2, which shows a sectional view of an electrolysis cell 37. A section through the cathode chamber 3 of an electrolysis cell 37 is illustrated as an example.

[0054] The electrolysis cell 37 has a one-piece housing 53. The housing 53 is divided into several chambers, some of which communicate with each other fluidically. Essential for providing the functions for operating a water electrolysis is the presence of a cathode chamber 5 on the cathode side of the electrolysis cell 37 and of an anode chamber 3 opposite the cathode chamber 5 on the cathode side of the electrolysis cell 37. In the view of FIG 2, the anode chamber 3 is indicated in the image plane as being behind the cathode chamber 5. The anode chamber 3 is separated from the cathode chamber 5 by a membrane 55. This can be a so-called polymer electrolyte membrane (PEM). Also required for the function is the provision of an anode in the anode chamber 3 and a cathode in the cathode chamber 5.These electrodes, not shown in detail, can be applied directly to opposite sides of the membrane 55 as an electrically conductive electrode layer with a porous structure for the required transport properties of the media involved. The electrical supply to the electrolysis cells 37 is provided by contacting the electrical connection 41 according to FIG. 1.

[0055] In order to enable the electrolysis process, a water supply from the underside of the electrolysis cell 37 is also required. For this purpose, a water inlet 57 is provided in the housing 53 on the underside of the anode compartment 3, which water inlet provides a connection to an anode supply channel 59 arranged on the underside. Correspondingly, opposite the membrane 55, also on the underside of the cathode compartment 5 in the housing 53, there is a water inlet 57. This forms the connection to the cathode supply channel 61 arranged on the underside. The anode supply channel 59 is separated from the adjacent cathode supply channel 61 by a water partition 63 of the housing 53. The anode supply channel 59 and the cathode supply channel 61 as well as the water partition 63 extend continuously from the anode side to the cathode side.Consequently, the anode supply channel 59 and the cathode supply channel 61 are open on both sides to enable the transport of water H2O, in particular the reception or supply of reactant water H2O via the reactant flow line 47 according to FIG. 1. This makes it possible to axially stack a plurality of identical electrolysis cells 37 and to connect them hydraulically in parallel and electrically in series with one another in the electrolyzer 1.

[0056] An oxygen outlet 65 is provided on the top side of the anode chamber 3 in the housing 53 for the removal and discharge of the product gases produced during the electrolysis process, as well as for the discharge of the process water H2O to be circulated. Opposite, the housing 53 has a corresponding hydrogen outlet 67 above the cathode chamber 5. Important for the design of the electrolysis cell 37 is the presence of an anode-side collecting line 7 in the housing 53 above the oxygen outlet 65, as well as the presence of a cathode-side collecting line 9 hydrogen chamber 25 in the housing 53 above the hydrogen outlet 67. During the electrolysis process, the anodic collecting line 7 is partially filled with the oxygen O2 produced and with water H2O in a phase mixture up to a fill level L. Analogously, in the cathodic collecting line 9 there is hydrogen H2 and water H20 in a phase mixture.In the present case, in the electrolysis cell 37, the anodic collecting line 7 is arranged adjacent to the cathodic collecting line 9. The cathodic collecting line 9 and the anodic collecting line 7 hydrogen chamber are separated from one another in a fluid-tight manner by a gas partition wall 69. Accordingly, in an electrolysis cell 37, the anodic collecting line 7 and the cathodic collecting line 9 as well as the gas partition wall 69 extend continuously from the anode side to the cathode side of the electrolysis cell 37. The anodic collecting line 7 and the cathodic collecting line 9 are open on both sides. This makes it possible to stack a large number of identical electrolysis cells 37 axially and to connect them hydraulically in parallel and electrically in series with one another in the electrolyzer 1.This construction results in a separation of the anode chamber 3 and the cathode chamber 5 as well as the adjacent and axially extending anodic collecting line 7 and the cathodic collecting line 9 when a plurality of electrolysis cells are stacked in an electrolyzer 1.

[0057] The anodic collecting line 7 and the cathodic collecting line 9 are each delimited by a surrounding wall 11, so that in an electrolyzer 1 a respective axial channel is formed, which is aligned horizontally and extends in a tubular manner. During operation of the electrolyzer 1, a liquid chamber 15 is formed in each of the collecting lines 5, 7, as well as a gas chamber 17 arranged above the liquid chamber 15. In order to reliably counteract the risk of fire and explosion, an injection device 19 is introduced at least into the anodic collecting line 7, which is positioned in the gas chamber 17 immediately above the usual operating level L. This injection device 19 is provided for the intimate wetting and inerting of the inner surface of the surrounding wall 11 by means of the injection device 19, during operation, specifically injecting water H2O onto the inner surface in the region of the gas space 17 of the surrounding wall 11.This reliably prevents, in particular, dry running of an inner surface of the surrounding wall 11 in the anodic collecting line 7, and thus eliminates the risk of ignition in the event of the formation of an ignitable mixture of oxygen O2 with critical foreign gas proportions of hydrogen H2. In this case, water H2O is sprayed into the gas space 17 under continuous application essentially or almost perpendicularly onto the inner surface of the surrounding wall 11, so that a uniform wetting of the inner surface is achieved. In a corresponding manner, an injection device 19 can be specially introduced into the cathodic collecting line 9 in order to counteract ignitable concentrations of oxygen O2 in the hydrogen H2 and a fire hazard.

[0058] FIG 3 shows a simplified representation in a longitudinal section of an electrolysis module 35 with an anodic collecting line 7 and with an injection device 19 built into the anodic collecting line 7. The horizontally aligned collecting line 7 is designed as a flow channel from the usually large number of electrolysis cells 37 stacked axially on top of one another, specifically in the cell frame vertically above the electrolysis cells 37. In this case, according to the number of electrolysis cells 37, a respective oxygen outlet 65 per electrolysis cell 37 opens into the anodic collecting line 7. The injection device 19 has a long nozzle tube 23 with a large number of injection nozzles 13, which are each introduced into the nozzle tube 23 along the horizontally aligned tube axis. At least one injection nozzle 13 is provided for each electrolysis cell 37, by means of which water H20 can be sprayed under pressure onto the inner surface of the surrounding wall 11.The nozzle tube 23 is positioned and fixed in the manifold 7 in the area of ​​the pressure plate 39 or module end plate by means of a respective holder 71. As a result, the axial area of ​​the electrolysis module 35 with the electrolysis cells 37 and with a respective oxygen outlet 65 opening into the manifold 7 is not impaired by the holder 71 and the spray function of the injection device 19 is fully guaranteed. In this case, it is structurally possible for the holder 71 to be incorporated into the pressure plate 39 as a functional element in one piece into the material of the pressure plate 39. Water H2O is supplied via a feed line 25 by means of a high-pressure pump in order to provide a high pressure for the injection of water H2O. An electrolyzer 1 designed as a pressure electrolyzer can thus be equipped in a special way.The feed line has an insulating section 33 or an insulating portion made of a non-conductive material, so that an electrical potential separation is effected with the process technology of an electrolysis plant having the electrolyzer 1 and its process-related electrical and hydraulic functional elements. The injection water H2O for inerting is branched off from the feed water of the electrolyzer 1, for example by a connection of the feed line 25 to a water supply device for demineralized water (not shown in detail in FIG. 3). The nozzle tube 23 is also made of or equipped with an electrically insulating material, for example PPS or PEEK.In an electrolyzer 1 with a corresponding plurality of axially interconnected electrolysis modules 35, the length of the nozzle tube 23 corresponds to the dimensions of the electrolyzer 1 and traverses and supplies the anodic manifolds 7 of all electrolysis modules 35. For the sake of simplicity, only one electrolysis module has been shown here.

[0059] Compared to FIG. 3, in FIG. 4 the injection device 19 is shown and illustrated separately as such with the nozzle tube 23, so to speak as a separate component disassembled from the electrolysis module 35 shown in FIG. 3. The injection device 19 is stabilized by a connecting plate 73 and can also be mounted or integrated onto the pressure plate 39. As an alternative to an additional connecting plate 71, the fastening of the injection device and the transport and distribution of the water H2O can also be fully integrated into a modified pressure plate 29.

[0060] It is also possible to apply the concept to electrolyzers 1 which have a plurality of anodic collecting lines 7a, 7b, 7c. FIG 5 shows a simplified view of a pressure plate 39 or module end plate of an electrolyzer 1 which has a plurality of anodic collecting lines 7a, 7b, 7c, in this case three. The three anodic collecting lines 7a, 7b, 7c are fluidically connected in parallel with regard to the anodic product flow, with a respective injection device 19 being introduced into a collecting line 7a, 7b, 7c. A distributor structure 21 with a media distributor 27 is provided for distributing the pressurised water H2O to the injection devices 19.The media distributor 27 has an inlet 29 and a plurality of outlets 31a, 31b, 31c, wherein the feed line 25 is connected to the inlet 29 and an injection device 19 of the associated anodic collecting line 7a, 7b, 7c is connected to an outlet 31a, 31b, 31c. The feed line 25 has an insulating section 33 made of an electrically insulating material, so that a potential separation is brought about between the feed line 25 and the injection device 19. In FIG. 5, the pressure plate 29 is partially integrated in the distributor structure 21 of the media distributor 27 and the distribution to a respective injection device 19 in a collecting line 7a, 7b, 7c takes place completely within the pressure plate 39 or end plate.

[0061] In comparison, FIG 6 shows an alternative embodiment of the media distributor 27 in which the distribution of the water H2O to the three branch lines via the outlets 31a, 31b, 31c takes place completely outside the pressure plate 39. This can have advantages during maintenance. A respective supply line of the outlets 31a, 31b, 31c is then led into the pressure plate 39 and connects fluidically or hydraulically to the injection device 19 introduced into the respective collecting line 7a, 7b, 7c. Both embodiments of FIG 5 and FIG 6 have in common functionally that during operation water H2O is injected into the gas space 19 via the injection device 19 under high pressure, so that a continuous humidification and inerting of the inner surface is effected.The injection device 19 is arranged in the gas space 19 just above the liquid space 15 so that the half space above the liquid space 15 and thus the corresponding inner surface of the surrounding wall 11 can be wetted as completely as possible.

Claims

Patent claims 1. Method for operating an electrolyzer (1) comprising an anode chamber (3) and a cathode chamber (5), in which water (H2O) is supplied as a reactant and hydrogen (H2) and oxygen (O2) are produced as product gas, wherein on the anode side the oxygen product gas, which also contains hydrogen as an extraneous gas, is led out of the anode chamber (3) in a product stream and is introduced into a horizontally arranged anode-side collecting line (7) with a surrounding wall (11) and is transported away via the collecting line (7), wherein water (H2O) is sprayed onto an inner surface of the surrounding wall (11) of the collecting line (7) so that wetting of the surrounding wall (11) with water and inerting of the inner surface is effected.

2. Method according to claim 1, wherein water is sprayed perpendicularly onto the surrounding wall (11) from a plurality of injection nozzles (13) so as to cause spray wetting of the surrounding wall (11) and to effect uniform wetting of the inner surface.

3. Method according to claim 1 or 2, wherein in the horizontal collecting line (7) the product flow is guided in a liquid phase up to a filling level (L), so that in the collecting line (7) a liquid space (15) and a gas space (17) adjoining above the liquid space (15) are formed, wherein the inner surface of the surrounding wall (11) delimiting the gas space (15) is wetted with water above the liquid space (15).

4. Method according to one of the preceding claims, in which water (H20) is continuously sprayed onto the inner surface of the surrounding wall (11) delimiting the gas space (15).

5. Method according to one of the preceding claims, wherein water (H20) is taken from the reactant water of the electrolyzer (1), in particular the make-up water, and is supplied under pressure to an injection device (19).

6. Method according to claim 5, wherein the water (H20) is supplied under pressure to a distribution structure (21) and distributed to a plurality of collecting lines (7a, 7b, 7c).

7. Method according to one of the preceding claims, wherein a pressure electrolysis is carried out, wherein a working pressure of up to 35 bar, in particular between 25 and 35 bar, is set in the anode chamber (3) and in the cathode chamber (5).

8. Electrolyzer (1) comprising a plurality of electrolysis cells with an anode chamber (3) and with a cathode chamber (5), in which an anodic collecting line (7a, 7b, 7c) is connected to the anode chamber (3) and a cathodic collecting line (9) is connected to the cathode chamber (5), and in which an injection device (19) having a plurality of injection nozzles (13) is introduced within the anodic collecting line (7a, 7b, 7c).

9. Electrolyzer (1) according to claim 8, wherein the injection device (19) comprises a nozzle tube (23) made of an electrically non-conductive material with a number of nozzle openings arranged along the tube axis, the normals of which are directed into the upper half-space of the collecting line (7a, 7b, 7c).

10. Electrolyzer (1) according to claim 8 or 9, wherein the nozzle tube (23) is aligned horizontally within a collecting line (7a, 7b, 7c) along the stacked electrolysis cells and is fixed by a number of brackets.

11. Electrolyzer (1) according to one of claims 8, 9 or 10, which has a plurality of anodic collecting lines (7a, 7b, 7c) which are fluidically connected in parallel with regard to the anodic product flow, wherein a respective injection device (19) is installed in a collecting line (7a, 7b, 7c).

12. Electrolyzer (1) according to one of claims 8 to 11, in which a feed line (25) is provided which is connected to an injection device (19) and via which the injection device (19) can be pressurized with water (H2O).

13. Electrolyzer (1) according to claim 12, wherein a media distributor (27) is provided which has an inlet (29) and a plurality of outlets (31a, 31b, 31c), wherein the feed line (25) is connected to the inlet (29) and an injection device (19) is connected to an outlet (31a, 31b, 31c).

14. Electrolyzer (1) according to one of claims 12 or 13, wherein the feed line (25) has an insulating section (33) made of an electrically insulating material, so that a potential separation is effected between the feed line (25) and the injection device (19).

15. Electrolyzer (1) according to one of claims 8 to 14, wherein an injection device (19) having a number of injection nozzles (13) is introduced within a cathodic manifold (9).

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