Method for operating an electrolysis plant, control device, and electrolysis plant

Abstract

The invention relates to a method for operating an electrolysis plant (400, 600). The electrolysis plant has an electrolysis unit (1) and an oxygen gas separator (2) for separating oxygen gas from electrolyte, and the electrolysis unit (1) is connected to a power connection (4) for an energy supply (E) for electrolysis in the electrolysis unit (1). The method comprises receiving a control signal for ending an interruption of the electrolysis of the electrolysis unit (1) while the electrolysis is interrupted. The invention also relates to a control device and an electrolysis plant.

Description

[0001] P2024, 1159 WO N / P2024-20 - 1 - 5 March 2026

[0002] Description

[0003] Method for operating an electrolysis plant, control device and electrolysis plant

[0004] The present disclosure relates to a method for operating an electrolysis plant, a control device, and an electrolysis plant with which the method can be carried out. The electrolysis plant is designed for water electrolysis, in particular alkaline pressure electrolysis (pressure alkaline electrolysis).

[0005] In water electrolysis, the electrolysis gases hydrogen and oxygen are obtained from an aqueous electrolyte through the electrochemical splitting of water in a cell stack of the electrolysis plant. The separation of the two electrolysis gases takes place within the cell stack using a membrane. Subsequently, the electrolyte (liquid phase) is separated from the respective electrolysis gas (gaseous phase) in gas separators. At least one oxygen and one hydrogen gas separator, connected to the cell stack, are provided for this purpose.

[0006] Electrolysis plants are typically designed for continuous operation, where electrolysis is not interrupted and fresh electrolysis gas flows continuously into the respective gas separator, thus minimizing the risk of a hydrogen-oxygen reaction. With the increase in renewable energy sources and growing demands on the stability of energy grids, more flexible operating modes for electrolysis plants are required, enabling rapid interruption and restart of the electrolysis process. However, in such standby mode, there is an increased risk that hydrogen and oxygen gas will mix to form an explosive mixture in the gas separator if less or no fresh electrolysis gas flows into the separator.

[0007] It is desirable to specify an electrolysis plant and a method for improving the gas quality in the oxygen gas separator, which in particular enables an efficient and safe standby of the electrolysis operation.

[0008] Embodiments of the disclosure relate to methods for an electrolysis plant comprising at least one electrolysis unit and at least one oxygen gas separator for separating oxygen gas and electrolyte. Furthermore, an energy source for supplying energy to the electrolysis in the electrolysis unit is connected to the at least one electrolysis unit via an energy supply device. The energy is generally provided as electrical energy in the form of direct current. The energy source can, for example, be a power supply network or one or more power generators. P2024.1159 WO N / P2024-20 - 2 - 5 March 2026

[0009] The electrolysis unit can be an electrolysis cell stack, also referred to simply as a cell stack. If the cell stack is divided into cell sub-stacks in which the electrolysis or energy supply can be controlled independently, in particular interrupted and continued, then an electrolysis unit can also be a cell sub-stack.

[0010] The standby procedure for the oxygen gas separator involves determining the hydrogen gas content C(H₂) of the gas phase within the oxygen gas separator. Additionally or alternatively, the oxygen gas content c(O₂) of the gas phase within the oxygen gas separator is determined. Additionally or alternatively, the ratio of these gas contents, e.g., c(H₂) / c(O₂) or c(O₂) / c(H₂), is also determined. For improved process control, the measurement of the hydrogen gas content c(H₂), the oxygen gas content c(O₂), and / or their ratio can be performed, for example, at defined intervals, particularly periodic ones, or essentially continuously.

[0011] The measurement of the hydrogen gas content c(H2), the oxygen gas content c(O2), and / or their ratio can be initiated in response to a signal to interrupt the electrolysis of the electrolysis unit for standby mode. That is, the acquisition of the value(s) starts as soon as the interruption signal is received. If the value(s) are already being measured before the signal is received, the measurement process continues after the interruption signal is received.

[0012] The interruption signal can be triggered, for example, by user input from an operator or user of the electrolysis plant via a user interface. Alternatively or additionally, the interruption signal can be generated and / or triggered by a control device based on state and / or time parameters of the electrolysis plant and / or the electrical power supplied to the electrolysis system. The interruption signal can be triggered, for example, when no more electrical power is available for electrolysis and / or no more electrolysis gas is being requested and the production rate is to be reduced to zero. For example, the interruption signal is sent and / or received by the control device disclosed herein. For example, the control device may have several control sections.One of the control sections is configured to send the signal to interrupt when a predefined condition is met, or when several predefined conditions are met. Another of the control sections is configured to receive the signal to interrupt and to perform or initiate further steps, in particular to reduce the hydrogen content in the oxygen gas separator. Once the electrolysis plant is ready for standby, electrolysis is restarted in response to receiving the signal. P2024.1159 WO N / P2024-20 - 3 - 5 March 2026.

[0013] The interruption is actually interrupted. Therefore, it is possible that a period of, for example, several seconds or more elapses between receiving the interruption signal and the actual interruption. It is also possible that, in response to receiving the interruption signal, no interruption of the electrolysis process actually occurs, for example, if the electrolysis system does not reach a standby-compatible state.

[0014] The hydrogen gas content c(H₂) denotes the proportion of hydrogen gas in the gas phase separated in the oxygen gas separator; the same applies to the oxygen gas content c(Ü₂). The hydrogen gas content c(H₂) and / or the oxygen gas content c(Ü₂) can be determined directly or indirectly in the separated gas phase in the oxygen gas separator, e.g., by in-line measurement. Alternatively or additionally, it is possible to extract a portion of the gas phase from the oxygen gas separator and determine the hydrogen gas content c(H₂) and / or the oxygen gas content c(Ü₂) within it, e.g., by online measurement.

[0015] The gas contents c(H2) and / or c(Ü2) can be determined as volume concentrations, mass or molar concentrations, or partial pressures and, if necessary, converted to another reference quantity, and the disclosed method can be carried out depending on these quantities. In multi-stage gas separators, the gas contents of the gas volumes of the respective separator stages of the gas separator can be determined, and the disclosed method can be carried out depending on the highest hydrogen gas contents c(H2) and / or the lowest oxygen gas contents c(Ü2) of the separator stages.

[0016] For standby mode, electrolysis in at least one electrolysis unit is interrupted depending on the measured hydrogen gas content c(H₂) and / or oxygen gas content c(Ü₂), if the hydrogen gas content c(H₂), the oxygen gas content c(Ü₂), and / or their ratio in the oxygen gas separator are outside the range for a hydrogen / oxygen oxyhydrogen reaction. Electrolysis is interrupted by disconnecting or switching off the power supply to at least one electrolysis unit. With the interruption of electrolysis, no more oxygen gas is produced in the electrolysis unit and introduced into the oxygen gas separator.

[0017] The interruption / shutdown of the power supply can occur abruptly or through a gradual or continuous reduction of the electrolysis current and / or electrolysis voltage for the electrolysis unit. Accordingly, a state prior to the interruption of electrolysis or the power supply refers, for example, to a state in which the electrolysis or the power supply of the electrolysis unit has not yet been fully completed. P2024.1159 WO N / P2024-20 - 4 - March 5, 2026

[0018] The term "interrupted" or "switched off" refers to a state after the electrolysis or power supply has been interrupted, which can also include the process of interrupting the electrolysis or power supply, for example, if this occurs through a gradual or continuous reduction. A "post-interruption" state, for example, describes a state after the electrolysis or power supply has been interrupted and is still interrupted, and no more oxygen is being produced in the electrolysis unit and introduced into the oxygen gas separator. For example, the electrolysis current during the interruption / switch-off of the power supply is zero. Alternatively, the electrolysis current during the interruption / switch-off may be greater than zero and less than the minimum current required to start or begin electrolysis.

[0019] If the electrolysis process or the power supply is interrupted, at least one electrolysis unit can also be shut off from the oxygen gas separator. An oxygen supply line is provided between the electrolysis unit and the oxygen gas separator to transfer oxygen from the electrolysis unit to the oxygen gas separator. This line connects the electrolysis unit to the oxygen gas separator, so that oxygen gas produced during electrolysis is transferred from the electrolysis unit to the oxygen gas separator. Electrolyte that was not consumed during electrolysis is also introduced into the oxygen gas separator via this supply line.

[0020] An oxygen inlet valve can be arranged on the oxygen supply line. This valve is designed to control, and in particular interrupt, the flow of oxygen and electrolyte from the electrolysis unit into the oxygen gas separator. Control can be achieved via the control device. The oxygen inlet valve can be controlled depending on the electrolysis current I. It can be closed when the electrolysis or the power supply to the electrolysis unit is interrupted, in order to isolate the electrolysis unit from the oxygen gas separator. For example, the oxygen inlet valve remains closed as long as the electrolysis or the power supply is interrupted and only reopens when the electrolysis unit restarts and the interruption of the electrolysis or the power supply ends.

[0021] In addition to the oxygen supply line, the oxygen gas separator has an electrolyte drain line through which the electrolyte can be transferred from the oxygen gas separator to the electrolysis unit or recirculated. An electrolyte treatment device may also be provided between the oxygen gas separator and the electrolysis unit. In one embodiment, the oxygen supply line and the electrolyte drain line can be connected via a bypass line to which a bypass valve is attached. The oxygen inlet valve is P2024.1159 WO N / P2024-20 - 5 - March 5, 2026

[0022] The electrolyte drain valve is then located between the bypass line and the oxygen gas separator. An electrolyte drain valve can be located on the electrolyte drain line between the bypass line and the oxygen gas separator. The electrolyte drain valve and the bypass valve can also be controlled by the control device. To isolate the electrolysis unit from the oxygen gas separator, the bypass valve can be closed when the electrolysis or the power supply to the electrolysis unit is interrupted.

[0023] Shutting off the oxygen supply lines prevents oxygen and electrolyte from entering the oxygen gas separator from the electrolysis unit during standby mode. This would prevent uncontrolled changes to the hydrogen content (g(H2)) and hinder the accurate measurement of hydrogen gas content (C(H2)) and / or oxygen gas content (c(O2)) for the standby process. Closing the bypass valve prevents gas from entering the oxygen gas separator via the bypass line and the electrolyte drain line. If no bypass valve is present, or for added safety, the electrolyte drain valve can also be closed in addition to the oxygen inlet valve when electrolysis or the power supply to the electrolysis unit is interrupted.

[0024] The electrolysis system can also include a hydrogen gas separator, which, analogous to the oxygen gas separator, has a hydrogen supply line and an electrolyte drain line. A hydrogen inlet valve can be arranged on the hydrogen supply line, designed to control, and in particular interrupt, the flow of hydrogen and electrolyte from the electrolysis unit. The hydrogen inlet valve can be controlled depending on the electrolysis current I. It can be closed when the electrolysis or the power supply to the electrolysis unit is interrupted, in order to isolate the electrolysis unit from the hydrogen gas separator and to prevent excessively high differential pressures between the anode and cathode compartments in the cells. The hydrogen inlet valve can remain closed as long as the electrolysis or the power supply to the electrolysis unit is interrupted and only be opened again when the electrolysis unit is restarted.If the hydrogen supply line and the electrolyte drain line of the hydrogen gas separator are also connected to each other via a bypass line and a bypass valve, and an electrolyte drain valve is provided on the electrolyte drain line, then this bypass valve and / or the electrolyte drain valve can also be closed when the electrolysis or power supply is interrupted.

[0025] For safe standby operation, in the disclosed method, the hydrogen content g(H2) in the oxygen gas separator can be adjusted before and / or after the interruption of electrolysis or the standby power supply, depending on the hydrogen gas content determined in each case. P2024.1159 WO N / P2024-20 - 6 - 5 March 2026

[0026] The concentration of hydrogen (C(H2)) and / or oxygen (c(O2)) is reduced. This lowers the risk of a hydrogen-oxygen reaction, and allows for faster and safer interruption and restart of the electrolysis process.

[0027] The hydrogen content g(H2) in the oxygen gas separator also includes the hydrogen dissolved in the electrolyte within the separator. Depending on the measure taken to reduce the hydrogen content, the hydrogen content g(H2) is lowered in the gas phase, in the electrolyte, or in both, thereby also reducing the hydrogen gas content c(H2). Under normal operating conditions, the gas phase of the oxygen gas separator contains only oxygen and hydrogen. Impurities from other gases are negligible, so the gas contents c(H2) and c(O2) can be converted into each other, e.g., c(H2) = 100 vol.% - c(O2). Therefore, it is sufficient to determine either the hydrogen gas content c(H2) or the oxygen gas content c(O2). However, for increased safety, both values ​​can be measured or determined, thus ensuring redundancy.

[0028] For example, the hydrogen content g(H2) in the oxygen gas separator is reduced such that the hydrogen gas content c(H2) in the oxygen gas separator and / or the oxygen gas content c(O2) in the oxygen gas separator are outside the range for a hydrogen / oxygen oxyhydrogen reaction. The respective hydrogen or oxygen gas content is specifically set below a lower explosive limit (LEL). If the ratios of the gas contents, e.g., c(H2) / c(O2) or c(O2) / c(H2), are determined, the hydrogen content g(H2) can be reduced and / or the oxygen content g(O2) increased such that the gas contents c(H2) and c(O2) are outside the range for a hydrogen / oxygen oxyhydrogen reaction, specifically below a lower explosive limit (LEL).

[0029] For example, before interrupting electrolysis or the standby power supply, the hydrogen content g(H2) in the oxygen gas separator is reduced if a first threshold value CI(H2) of the hydrogen gas content in the oxygen gas separator is exceeded, and / or a first threshold value of the oxygen gas content Ci(O2) in the oxygen gas separator is undershot, and / or a predetermined first time duration ti is reached. If the ratios of the gas contents are determined, the hydrogen content g(H2) is reduced before interrupting electrolysis or the power supply when a first threshold value for the ratio is reached, e.g., B. a first threshold n for the ratio c(H2) / c(O2) is exceeded and / or a first threshold 1 / n for the ratio c(O2) / c(H2) is not reached. P2024.1159 WO N / P2024-20 - 7 - 5 March 2026

[0030] The exceeding or falling below the threshold values ​​does not usually have to occur as a sharp threshold, but can also be a smooth, continuous transition, which can even be controlled or regulated, for example with a PID control method (PID: proportional, integrating, and differentiating). For the predetermined time duration h or the predetermined time interval until a first time point ti, a time period from a reference time tvo=0 is generally used, which is typically the time the signal to interrupt is received. The first time duration or the first time point ti can be chosen such that the reduction of the hydrogen content g(H2) occurs immediately after the signal to interrupt is received.However, it may also be possible to initiate the reduction of the hydrogen content g(H2) with a time delay in order to first query and check current state parameters of the electrolysis plant, in particular state parameters of at least one electrolysis unit, on which the implementation of the hydrogen content reduction g(H2) may depend. Time-based control can also be used, for example, as a backup control in case the determination of the hydrogen gas content c(H2) and / or the oxygen gas content c(Ü2) should fail.

[0031] Furthermore, it is stipulated that before the electrolysis or energy supply is interrupted, the hydrogen content g(H2) in the oxygen gas separator is reduced until a second threshold value C2(H2) of the hydrogen content in the oxygen gas separator is undershot, and / or a second threshold value O2(O2) of the oxygen gas content in the oxygen gas separator is exceeded, and / or a second time period has elapsed or a second time point t2 is reached. If a ratio of the gas contents is determined, the hydrogen content g(H2) is reduced before the electrolysis or energy supply is interrupted until a second threshold value for the ratio is reached, e.g., until a second threshold value r2 for the ratio C(H2) / C(O2) is undershot, and / or a second threshold value 1 / r2 for the ratio C(O2) / C(H2) is exceeded.The first and second thresholds behave such that, for example, the first threshold for hydrogen gas content CI(H2) is typically greater than the second threshold C2(H2) for hydrogen gas content, and / or the first threshold Ci(Ü2) for oxygen gas content is less than the second threshold O2(O2) for oxygen gas content. Similarly, the first threshold n for the ratio c(H2) / c(O2) can be greater than the second threshold r2 for the ratio c(H2) / c(O2), and vice versa for the reciprocal ratio c(O2) / c(H2).

[0032] The predetermined second time period between the first time h and the second time t2 can, for example, be empirically determined for the respective electrolysis plant, such that for the respective plant, after the second time period, the second limit C2(H2) for which the hydrogen gas content in the oxygen gas separator is undershot, the second threshold 02(02)P2024.1159 WO N / P2024-20 - 8 - 5 March 2026

[0033] The second time interval is triggered when the oxygen gas content in the oxygen gas separator exceeds a certain threshold and / or the second threshold for the ratio of the gas contents is reached, e.g., the second threshold n for the ratio c(H2) / c(O2) falls below a certain threshold and / or the second threshold 1 / n for the ratio c(O2) / c(H2) exceeds a certain threshold. The time interval can be predetermined for the respective electrolysis plant or determined depending on the measured hydrogen gas content c(H2) and / or the measured oxygen gas content c(Ü2) in the oxygen gas separator, for example, at time tvo and / or h. If the gas contents are measured at different times, e.g., tvo and ti, the second time interval can be determined, in particular, depending on a gradient of the gas contents c(H2) and / or c(Ü2) over a period between tvo and h. The determination of the second time period can be carried out by the control device, in which the recorded gas contents are also stored.

[0034] The electrolysis or energy supply is only interrupted for standby mode, for example, when the second threshold value C2(H2) for the hydrogen gas content in the oxygen gas separator falls below a certain level, the second threshold value O2(O2) for the oxygen gas content in the oxygen gas separator is exceeded, the second threshold value for the ratio of the gas contents is reached (e.g., the second threshold value for the ratio c(H2) / c(O2) falls below a certain level), and / or the second threshold value for the ratio c(O2) / c(H2) is exceeded, and / or the predetermined second time period has expired. The electrolysis, and thus gas production, is therefore only stopped, for example, when a specific gas quality or gas composition is reached in the oxygen gas separator. The second threshold values ​​for the hydrogen gas content and / or...or the oxygen gas content is below a lower explosive limit for a hydrogen / oxygen reaction. The same applies to the ratios of the gas contents.

[0035] The standby process can be carried out with electrolysis systems in which exactly one electrolysis unit is assigned to each oxygen gas separator, meaning that oxygen from the electrolysis in a single electrolysis unit is introduced into the oxygen gas separator. However, in some embodiments, the process can also be carried out with electrolysis systems in which several electrolysis units, e.g., cell stacks and / or cell substacks, are connected to one oxygen gas separator.

[0036] For example, two or more cell stacks of a module can be connected to an oxygen gas separator. In some configurations, at least one cell stack may contain cell sub-stacks, each connected to the oxygen gas separator. The electrolysis or energy supply in the cell sub-stacks can be controlled independently, in particular, interrupted and resumed. The cell sub-stacks can be used for this purpose. P2024.1159 WO N / P2024-20 - 9 - 5 March 2026

[0037] They must be thermally, hydraulically and electrically isolated from each other and, for example, electrically connected in parallel to each other.

[0038] In such an electrolysis system, the electrolysis process or the standby power supply is interrupted in all electrolysis units connected to the oxygen gas separator, preventing any further oxygen from entering the oxygen gas separator. This interruption occurs when the second threshold value C2(H2) for the hydrogen gas content in the oxygen gas separator falls below a certain level, when the second threshold value O2(O2) for the oxygen gas content in the oxygen gas separator is exceeded, when the second threshold value for the gas content ratio is reached (e.g., the second threshold value for the C(H2) / C(O2) ratio falls below a certain level), and / or when the second threshold value for the C(O2) / C(H2) ratio is exceeded, and / or when the predetermined second time period has expired.

[0039] The standby procedure is performed, for example, directly after normal operation of the electrolysis plant. Therefore, the standby procedure is not performed during the initial commissioning of the electrolysis plant or electrolysis unit, nor is it performed following an emergency shutdown of the electrolysis plant or electrolysis unit.

[0040] In normal operation, the electrolysis gases hydrogen and oxygen are produced in at least one electrolysis unit. The electrolysis unit is connected to the power supply device, which is configured to provide energy from a power source for the electrolysis process within the electrolysis unit. The electrolysis unit is also connected to the oxygen gas separator, so that during electrolysis, oxygen from the at least one electrolysis unit is introduced into the oxygen gas separator, usually continuously. The oxygen inlet valve to the oxygen gas separator is open.

[0041] Electrolysis takes place in the electrolysis unit at an operating temperature T un It is operated at an operating pressure punit. The pressure in the oxygen gas separator typically corresponds to the operating pressure p during normal operation. UIn electrolysis units consisting of cell stacks with cell sub-stacks, state parameters such as operating temperature, operating pressure, and electrolysis current refer to the respective cell sub-stack. The operating temperature of the electrolysis unit during normal operation with alkaline electrolysis is between 40 °C and 90 °C. The operating temperature T un "it" usually refers to an average temperature value in the cells of the electrolysis unit. However, in some embodiments, it can also refer to the maximum temperature in the electrolysis unit as the operating temperature T. un it can be used. The electrolysis unit also has an operating temperature T. un it and the operating pressure P2024.1159 WO N / P2024-20 - 10 - 5 March 2026

[0042] The operating temperature (Tunit) during electrolysis and during the interruption of electrolysis, as well as the operating pressure (Punit) during electrolysis and during the interruption of electrolysis, can differ from each other.

[0043] The operating pressure for atmospheric alkaline electrolysis can range from 0.02 bar to 0.1 bar gauge during normal operation, while for alkaline pressure electrolysis it typically ranges from 20 bar to 35 bar gauge. The operating pressure p un It usually refers to an average pressure value in the cells of the electrolysis unit. However, in some embodiments, it can also refer to the maximum pressure of the electrolysis unit as the operating pressure p. s tack will be used.

[0044] According to embodiments of the method, normal operation with multiple electrolysis units is carried out such that the electrolysis units are operated alternately when the electrolysis plant is operating at partial load. Partial load operation means that in at least one electrolysis unit connected to the oxygen gas separator, the electrolysis or power supply is interrupted, while at least a second electrolysis unit is in operation, i.e., the electrolysis or power supply of this second electrolysis unit is not interrupted. Reasons for such partial load operation can be, for example, low demand for hydrogen and / or oxygen from the user or low availability of electrical power for the electrolysis power supply, which does not necessitate or allow full load operation.Alternating operation ensures that the electrolysis units are in a state that allows for safe standby.

[0045] In alternating operation, electrolysis units take turns operating. This can occur, firstly, when an electrolysis unit or group of electrolysis units, whose electrolysis or energy supply is interrupted, reaches a certain state (alternating operation 1), and / or secondly, when the number of electrolysis units whose electrolysis or energy supply is interrupted or which are in operation changes (alternating operation 2).

[0046] The change can depend on a state of the electrolysis units, such as the operating pressure punit, the operating temperature Tunit, the hydrogen and / or oxygen gas contents on the anode and / or cathode side c. ano (H2), c ano (O2), Ck a to(H2), Ck ato(O2), a mechanical stress Ounit, the electrolysis current I and / or the electrolysis gas throughput of the electrolysis units. For the changeover, at least one of these state parameters can be recorded and compared with a threshold value for the changeover. Alternatively or additionally, it is possible P2024.1159 WO N / P2024-20 - 11 - 5 March 2026

[0047] the change depends on several of the state parameters, in particular on the operating pressure punit and the operating temperature T un to be carried out with the electrolysis units. Which state parameter is considered for the change can be defined system-specifically and / or user-specifically and depends on the equipment of the electrolysis system. For example, in systems with gas analysis for the electrolysis units, in addition to the operating pressure p un it and the operating temperature T unThe gas content in the electrolysis units must also be taken into account for a changeover.

[0048] The following describes first the alternating operation 1, which can be carried out when a first electrolysis unit, whose electrolysis or energy supply is interrupted, reaches a certain state.

[0049] If at least one electrolysis unit, whose electrolysis or energy supply is interrupted, reaches a certain state, this first electrolysis unit is restarted. "Starting up" means that the interruption of the electrolysis or energy supply is ended and the first electrolysis unit is supplied with energy for electrolysis, so that electrolysis continues, oxygen is produced in the electrolysis unit, and fed into the oxygen gas separator. Instead of interrupting the electrolysis or energy supply of at least one first electrolysis unit, the electrolysis or energy supply of at least one second electrolysis unit is then interrupted. The first and second electrolysis units thus alternate in electrolysis operation. However, the oxygen gas separator does not go into standby mode because oxygen continues to be fed into the oxygen gas separator from the first electrolysis unit.

[0050] The start-up of the first electrolysis unit can be triggered, for example, by the control device, which contains the currently recorded state parameters of the electrolysis units connected to the oxygen gas separator, such as operating pressure p. un it, operating temperature Tunit, anode and / or cathode-side gas contents, mechanical stress o, electrolysis current I and / or the electrolysis gas throughput produced by the electrolysis units.

[0051] A state in which the first electrolysis unit is started up can be reached, for example, when the operating pressure p unThe pressure in the first electrolysis unit reaches or falls below a specific pressure value pwi_on for the changeover and / or decreases at a specific rate when the operating temperature Tunit of the first electrolysis unit reaches or falls below a specific temperature value Twi_on for the changeover and / or decreases at a specific rate and / or when a mechanical stress of the electrolysis unit reaches a specific voltage Owi_onP2024.1159 WO N / P2024-20 - 12 - 5 March 2026

[0052] The changeover point is reached or falls below a certain threshold. Furthermore, the first electrolysis unit can be started when it reaches a specific state regarding the gas composition. Since the gas in the electrolysis unit consists essentially only of the electrolysis gases hydrogen and oxygen, the gas concentrations can be converted into one another, e.g., c an o(H2)=100 vol-% - c ano(O2). For the gas composition, it is sufficient to measure one of the gas contents, the hydrogen gas content or the oxygen gas content, e.g. c ano (H2) / c ano (O2)= c ano (H2) / [100 vol-% - c ano (H2)].

[0053] For example, a first electrolysis unit can be started up when the hydrogen gas content on the anode side reaches Ca no (H2) reaches or exceeds a certain hydrogen gas content Cwiano_on(H2) for the changeover and / or the oxygen gas content c on the anode side ano(O2) reaches or falls below a specific oxygen gas content Cwiano_on(O2) for the changeover. On the anode side, this means in an anode compartment of an electrolysis cell of the electrolysis unit, between an anode compartment and an oxygen supply line, and / or in the oxygen supply line between the electrolysis unit and the oxygen gas separator, in particular between the electrolysis unit and an oxygen inlet valve in the oxygen gas separator. Furthermore, a first electrolysis unit can be started up in which, on the cathode side, the hydrogen gas content Ckato(H2) has reached or fallen below a specific hydrogen gas content Cwikato_on(H2) for the changeover, and / or on the cathode side, the oxygen gas content Ck aa specific oxygen gas content Cwikato_on(O2) has been reached or exceeded. On the cathode side, this means in a cathode compartment of an electrolysis cell of the electrolysis unit, between a cathode compartment and a hydrogen supply line, and / or in the hydrogen supply line between the electrolysis unit and the hydrogen gas separator, in particular between the electrolysis unit and a hydrogen inlet valve to the hydrogen gas separator. Alternatively or additionally, the electrolysis or energy supply of a first electrolysis unit can be started when a time period twi has elapsed since the interruption of the electrolysis or energy supply to the electrolysis unit. The time period twi_on can, for example, be determined empirically such that the pressure pwi_on, the temperature Twi_on, the voltage Owi_on, and / or at least one of the gas contents c W iano_on(H2), c W iano_on(O2), c W ikato_on(H2), c Wikato_on(O2) is reached in the first electrolysis unit.

[0054] The first electrolysis unit is then started up, for example, in such a way that it produces at least the same throughput of oxygen gas and / or hydrogen gas as the second electrolysis unit produced before the electrolysis or energy supply of this second electrolysis unit is interrupted. Instead of the throughput of electrolysis gas, which can also be referred to as the production rate, the electrolysis current of the first electrolysis unit can also be set up, up to an electrolysis current lwi_on that, for example, at least corresponds to P2024.1159 WO N / P2024-20 - 13 - 5 March 2026

[0055] Electrolysis current I corresponds to the current with which the second electrolysis unit was operated before the interruption of its electrolysis or energy supply.

[0056] The first electrolysis unit can, for example, be started up with an initial electrolysis current l0 > 0 A, which is increased by an electrolysis current ramp until it at least corresponds to the electrolysis current of the second electrolysis unit before its electrolysis or power supply was interrupted. The current ramp, i.e., the increase in current over time, can, for example, be greater than a current ramp during the initial start-up of the electrolysis unit or when starting the electrolysis unit from a pressureless state (p0). un (it “ 1 atm). For alkaline pressure electrolysis, a ramp can be, for example, larger than 0.6% l ma x / s (percent per second) relative to the maximum electrolysis current l ma x. Preferably, the ramp gradient can also be greater than 2% or greater than 10% of the maximum electrolysis current l. maThe current ramp should be x per second, preferably even 15% of the maximum electrolysis current per second or more. For alkaline pressure electrolysis with a maximum electrolysis current ax of 10 kA, this could, for example, be an electrolysis current ramp in the range of 60 A / s to 1500 A / s or more, such as a ramp of >200 A / s, >500 A / s, >1000 A / s or >1500 A / s.

[0057] If a group of first electrolysis units is started up simultaneously, it can be started up in such a way that it produces at least the same total throughput of oxygen gas and / or hydrogen gas as a group of second electrolysis units before their electrolysis or energy supply is interrupted. The total throughput can be determined, for example, from the sum of the respective throughputs of the individual electrolysis units in the respective group.

[0058] Instead of starting up the first electrolysis unit, the electrolysis or power supply is interrupted in a second electrolysis unit for the switchover. The selection of which electrolysis unit's electrolysis or power supply is interrupted can be predetermined by the control device. This selection can depend, for example, on the current state of the electrolysis units connected to the oxygen gas separator and / or on a time parameter. Regarding the state parameters, the interruption of the electrolysis or power supply can depend, in particular, on the hydrogen gas and / or oxygen gas content on the anode and / or cathode side, and the operating temperature T. un it, the operating pressure p unit, a mechanical tension Ounit, the electrical power for electrolysis, in particular the electrolysis current I, and / or the electrolysis gas throughput of the electrolysis units. P2024.1159 WO N / P2024-20 - 14 - 5 March 2026

[0059] For example, the electrolysis or energy supply of an electrolysis unit can be interrupted if its condition is particularly favorable because, on the anode side, there is a low hydrogen gas concentration with a certain threshold value Cwiano_off(H2) or below, and / or a high oxygen gas concentration with a threshold value Cwiano_off(O2) or above, and / or on the cathode side, there is a low oxygen gas concentration with a threshold value Cwikato_off(O2) or below, and / or a high hydrogen gas concentration with a threshold value Cwikato_off(H2) or above, where the gas concentrations are in each case outside the explosive range of a hydrogen / oxygen reaction. The threshold values ​​of the gas concentrations are typically chosen such that Cwiano_off(H2)<Cwiano_on(H2), Cwiano_off(O2)> c W iano_on(O2) or Cwi kato off (O2) < CW1 kato on (O2) , Cwi kato off ( H ​​2) > Cwi kato on ( H 2) ■

[0060] For example, the electrolysis or energy supply of an electrolysis unit can be interrupted if it exhibits a maximum or minimum state parameter relative to all electrolysis units connected to the oxygen gas separator. This could be an electrolysis unit with the highest oxygen gas content |c on the anode side. an o(O2)|max and / or has the lowest hydrogen gas content on the anode side |c an o(H2)|min and / or the lowest oxygen gas content on the cathode side |Ck a to(O2)|min or on the cathode side the highest hydrogen gas content |Ck a to(H2)|max.

[0061] Alternatively or additionally to the hydrogen gas content and / or oxygen gas content, the operating temperature T can also be used to interrupt the electrolysis or energy supply. un it, the operating pressure p un it, the mechanical tension o unThe electrical power for electrolysis and / or the electrolysis gas throughput of the electrolysis unit are taken into account. It can be provided that the electrolysis or energy supply for an electrolysis unit is interrupted if it has at least a predetermined operating pressure pwi_off, a predetermined operating temperature Twi_off, and / or a specific mechanical stress Owi_off, and / or if it is operated with at least a specific electrolysis current lwi_off, and / or if it has at least a specific electrolysis gas throughput. The electrolysis current can, for example, be the maximum electrolysis current l max for electrolysis, i.e., an electrolysis current for full-load operation of the electrolysis unit. This usually corresponds to a maximum electrolysis gas flow rate, in particular a maximum hydrogen gas flow rate, so that instead of the maximum electrolysis current, a maximum electrolysis gas flow rate can also be used. The threshold values ​​for pressure, temperature, and / or mechanical stress can be chosen such that: pwi_ O ff> Pwi_on, Twi_ O ff> Twi_on, Owi_off > Owi_on.P2024.1159 WO N / P2024-20 - 15 - 5 March 2026

[0062] The operating pressure pwi_ofr for alkaline electrolysis can be, for example, at least 80%, at least 90%, or at least 95% of the maximum operating pressure Pmax of the electrolysis unit. The operating temperature Twi_off can be, for example, at least 66% or at least 80% of the maximum operating temperature T. max of the electrolysis unit. The mechanical stress can be measured, for example, as the stress in the longitudinal direction of the electrolysis unit, i.e., in the longitudinal direction of a cell stack and / or cell sub-stack, which is proportional to the operating temperature T. un it and / or the operating pressure p un it is.

[0063] In one example configuration, the electrolysis or energy supply is interrupted for each electrolysis unit whose operating pressure p un it, operating temperature Tunit, mechanical stress o unThe maximum hydrogen gas throughput, oxygen gas throughput, and / or electrolysis current I refer to all electrolysis units of the oxygen gas separator or the electrolysis plant. In any case, however, the electrolysis or energy supply will only be interrupted if the gas concentrations on the anode and cathode sides are within a safe range, in particular outside the explosion limit for a hydrogen / oxygen reaction.

[0064] In one exemplary embodiment of the process, the electrolysis or the energy supply to an electrolysis unit is only interrupted if the respective state parameter is reached for at least a certain period of time. The electrolysis or energy supply is therefore only interrupted if a predetermined hydrogen gas concentration c is reached in the electrolysis unit. W iano_off(H2) and / or c W ikato_off(H2), oxygen gas content c W iano_off(O2) and / or c Wikato_off(O2), operating pressure pwi_off, operating temperature Twi_off, mechanical stress Owi_off, electrical power for electrolysis or electrolysis current lwi_otf and / or electrolysis gas throughput, in particular a maximum oxygen and / or hydrogen throughput and / or a maximum electrolysis current l ma x, has already been reached for a predetermined period. This ensures that the respective electrolysis unit is in a stable state before it is switched off for the changeover. Due to its state, such an electrolysis unit can remain in an interrupted electrolysis state for a particularly long time. Therefore, if standby mode follows the alternating operation, the standby can be carried out safely for at least a certain period before one of the electrolysis units reaches a critical state and the standby is terminated. The described alternating operation thus enables a safe standby mode.

[0065] If none of the operating electrolysis units are in a favorable condition, the condition of one electrolysis unit can be improved to interrupt the electrolysis or energy supply in that unit. For this purpose, the electrolysis current can be adjusted, for example, as described in P2024.1159 WO N / P2024-20 - 16 - 5 March 2026.

[0066] The electrolysis current Iwiini > 1 in an electrolysis unit can be increased, in particular to the maximum electrolysis current lwiini = lmax. The electrolysis unit can then be operated with the increased electrolysis current Iwiini until the operating pressure p un with the electrolysis unit has increased to a pressure of at least pwi_off, the operating temperature T unthe temperature of the electrolysis unit has increased to at least Twi_off, the mechanical stress Ounit has increased to at least Owi_off, the anode-side oxygen gas content Cano (O2) has increased to at least Cwiano_off(O2), the anode-side hydrogen gas content c ano The electrolysis or energy supply to the electrolysis unit can be interrupted if the hydrogen gas content (CH2) has decreased to Cwiano_off(H2) or below, the hydrogen gas content on the cathode side Ckato(H2) has increased to at least Cwiano_off(H2), and / or the oxygen gas content on the cathode side Ckato(O2) has decreased to Ci(ano_off)(O2) or below.

[0067] Alternatively, the electrolysis unit can also be operated with the increased electrolysis current Iwiini for a specific duration twiim. The duration twiim can depend on the electrolysis current Iwiini and at least one measured state parameter, p. un it, Tunit, oun it, c ano (O2), c ano (H2), Ckato(O2), Ckato(H2), be determined such that during the time period twiim the operating pressure punit of the electrolysis unit increases to a pressure of at least pwi_ott, the operating temperature Tunit of the electrolysis unit increases to a temperature of at least Twi_otf, the mechanical stress o un If the voltage rises to at least Owi_otf, the anode-side oxygen gas content c ano (O2) increased to at least Cwiano_oft(O2), the anode-side hydrogen gas content c ano The electrolysis process can be interrupted if the hydrogen gas content (CH2) falls to or below Cwiano_oft(H2), the hydrogen gas content on the cathode side Ckato(H2) rises to at least Cwikato_oft(H2), and / or the oxygen gas content on the cathode side Ckato(O2) falls to or below Cwikato_off(O2).

[0068] For a particularly reliable standby mode, the electrolysis current I of an electrolysis unit can be increased each time before electrolysis or the power supply to the electrolysis unit is interrupted, regardless of the unit's state. The electrolysis unit's state can also be improved to a state where the operating pressure p un it, the operating temperature Tunit, the tension o un it and / or the gas contents are significantly improved beyond the threshold values ​​for the changeover, in particular to a maximum or minimum value, e.g. the maximum operating pressure p ma x, the maximum operating temperature Tmax, a maximum stress o ma x, a maximum anode-side oxygen gas content c ano _m a x(O2) and / or maximum cathode-side hydrogen gas content Ck a to_max(H2) and / or minimum anode-side hydrogen gas content c ano_min(H2) and / or minimum cathode-side oxygen gas content Ck a t o _min(O2) can be improved. However, this takes time, so for a quick change, the thresholds for switching to less P2024.1159 WO N / P2024-20 - 17 - 5 March 2026

[0069] They can be set very strictly, e.g., pwi_off <p ma x, T W i_off <T ma x. o W i_off <o ma x, Cwiano _off(O2) <C ano_max(O2), Cwi kato_off(H2) < *Ckato_max(H2), Cwiano_o ff(H2)>Cano_min(H2) and / or Cwi käto off (O2) < Ck a to_min(O2) .

[0070] To maintain the operating temperature T un it, the operating pressure p un it and the tension o un To improve or increase it, in addition to or as an alternative to increasing the electrolysis current I, the cooling of the electrolysis unit can also be reduced or switched off.

[0071] In another embodiment, a change in the electrolysis units can occur when the number of electrolysis units whose electrolysis or energy supply is interrupted, or which are in electrolysis operation, changes. Such a switching operation is described below. A change in the number of electrolysis units whose electrolysis or energy supply is interrupted, or which are in electrolysis operation, can be triggered, for example, if the amount of electrolysis gas to be produced changes and / or the electrical power available for electrolysis changes.

[0072] In a first step, it is checked whether a setpoint for a number x of electrolysis units to be operated—i.e., whose electrolysis or energy supply should not be interrupted—is zero. The setpoint can be determined in the control device, for example, depending on the electrical power available for electrolysis and / or a required production rate for the electrolysis gases hydrogen and / or oxygen. The electrical power and / or production rate can be stored in the control device or specified by a user via user input. Instead of a setpoint x for the number of electrolysis units to be operated, a setpoint y can also be defined for the number of electrolysis units whose electrolysis or energy supply should be interrupted.From the difference between a total number S of electrolysis units connected to the oxygen gas separator and the setpoint y, the setpoint x can be determined, x=Sn.

[0073] If the setpoint x is zero (x=0), no electrolysis units are required in electrolysis mode. The standby procedure is then started, for example, by means of the interrupt signal.

[0074] If the setpoint x is not zero, the next step involves comparing the setpoint x with an actual value n of the number of electrolysis units connected to the oxygen gas separator and currently operating in electrolysis mode, meaning their electrolysis or energy supply is not currently interrupted. If the difference between the setpoint and actual value (xn) > 0, or x > n, then P2024.1159 WO N / P2024-20 - 18 - March 5, 2026

[0075] Electrolysis units whose electrolysis or energy supply is currently interrupted must be started up in order to reach the target value x. If the difference between the target value and the actual value (xn) < 0, or x <n, so muss die Elektrolyse bzw. Energieversorgung von Elektrolyseeinheiten unterbrochen werden, die aktuell in Betrieb sind, um den Sollwert x zu erreichen.

[0076] In the first case, when x > n, a number (xn) of electrolysis units connected to the oxygen gas separator, whose electrolysis or power supply is interrupted, are activated. The selection of which electrolysis units are activated can depend on a current state parameter of the electrolysis units connected to the oxygen gas separator and / or on a time parameter. It can be determined, for example, in the control device where the state parameters are available.

[0077] For example, electrolysis units can be started up whose operating pressure p un it, operating temperature Tunit and / or tension o un it lies below a pressure pw2_on, a temperature Tw2_on, or a stress Ow2_on for a change, whose anode-side hydrogen gas content c ano (H2) and / or cathode-side oxygen gas content Ckato(O2) is above a hydrogen gas content Cw2kato_on(H2) or oxygen gas content Cw2ano_on(O2) for a changeover, and / or their anode-side oxygen gas content c anThe electrolysis unit must meet at least one of the following criteria: o(O2), and / or the cathode-side hydrogen gas content Ckato(H2) is below the oxygen gas content Cw2ano_on(O2) or hydrogen gas content Cw2kato_on(H2). If fewer than (xn) electrolysis units meet at least one of these criteria, electrolysis units whose state parameters do not meet the aforementioned criteria can also be started up. These are electrolysis units that are in a more favorable state. They are started up secondarily. Electrolysis units that are in an unfavorable state are started up first so that they can be brought back into a favorable state by continuing electrolysis, which then allows for a safe standby mode.

[0078] Alternatively, those (xn) electrolysis units can be used whose operating pressure Punit, operating temperature T un IT and / or tension o unit is particularly low, especially the lowest of the n electrolysis units, and / or their anode-side hydrogen gas content c ano (H2) and / or cathode-side oxygen gas content Ckato(O2) is particularly high, especially the highest of the n electrolysis units, and / or anode-side oxygen gas content Cano(O2), and / or cathode-side hydrogen gas content Ckato(H2) is particularly low, especially the lowest of the n electrolysis units. These are electrolysis units that are in an unfavorable condition. P2024.1159 WO N / P2024-20 - 19 - 5 March 2026

[0079] Alternatively or additionally to at least one of the state parameters, the time elapsed since the interruption of electrolysis or the interruption of the power supply to the electrolysis units can also be used when selecting which electrolysis units to start up. For example, electrolysis units can be started up whose operating time has exceeded a certain time tw2_on, meaning their electrolysis or power supply has already been interrupted for at least a time tw2_on. tw2_on can be chosen such that a specific state of the electrolysis unit has been reached since the interruption of electrolysis or the power supply, e.g., pw2_on, Tw2_on, Ow2_on, Cw2ano_on(O2) and / or Cw2kato_on(H2) has been reached or fallen below, and / or Cw2ano_on(H2) and / or Cw2kato_on(O2) has been reached or exceeded.

[0080] In one configuration of the alternating operation, for example (xn) electrolysis units can be started up whose duration since the interruption of electrolysis or energy supply is the maximum in relation to the durations of all n electrolysis units, whose electrolysis or energy supply has therefore already been interrupted for the longest time.

[0081] By performing the changeover solely based on the difference (nx) or (xn) between the n requested electrolysis units and the x electrolysis units currently operating, the changeover can be carried out very quickly. Alternatively, the changeover can also be performed by identifying, from the total number S of electrolysis units connected to the oxygen gas separator, n electrolysis units that are in an unfavorable state, and then selecting those electrolysis units whose electrolysis is interrupted.

[0082] The electrolysis current I, to which the electrolysis units are started, can be determined or specified by the control device. If several electrolysis units are started, they can each be started at the same or different electrolysis currents I. For example, the electrolysis units can be started with an initial electrolysis current l0 > 0 A, which is increased by an electrolysis current ramp until the electrolysis current I for electrolysis is reached. The current ramp can, for example, be a steep electrolysis current ramp. For alkaline pressure electrolysis, this could be a ramp with a gradient > 0.6% l. ma x / s (percent per second) relative to the maximum electrolysis current l ma x. Preferably, the ramp gradient can also be >2% l ma x / s or >10% l ma x / s of the maximum electrolysis current l max per second, preferably even >15% of the maximum electrolysis current per second. For alkaline pressure electrolysis with a maximum electrolysis current l ma x of 10 kA, this could, for example, be an electrolysis current ramp in a range of 60 A / s to 1500 A / s or more, for example a ramp of >200 A / s, >500 A / s, >1000 A / s or >1500 A / s. P2024.1159 WO N / P2024-20 - 20 - 5 March 2026

[0083] In the second case, when n > x, the electrolysis or energy supply is interrupted for a number (nx) of electrolysis units connected to the oxygen gas separator. The selection of which electrolysis unit is activated can also depend on a current state parameter of the electrolysis units connected to the oxygen gas separator and / or on a time parameter. It can be determined, for example, in the control device where the state parameters are available.

[0084] For example, the electrolysis or energy supply of at least one electrolysis unit can be interrupted, whose operating pressure p un it, operating temperature T un it, mechanical tension o un at least a pressure pw2_off, a temperature Tw2_off and / or a mechanical stress Ow2_off for a changeover must be present, whose anode-side hydrogen gas content cano (H2) and / or cathode-side oxygen gas content Ckato(O2) at a hydrogen gas content Cw2kato_off(H2) or at an oxygen gas content Cw2ano_off(O2) or below, and / or their anode-side oxygen gas content c an The electrolysis unit selection can be based on the electrolysis current I or an electrolysis gas flow rate (hydrogen and / or oxygen flow rate), and, for example, the electrolysis or energy supply of electrolysis units with at least one electrolysis current Iw2_off, in particular with the maximum electrolysis current l, is interrupted. Alternatively or additionally, the electrolysis current I or an electrolysis gas flow rate (hydrogen and / or oxygen flow rate) can also be considered when selecting the electrolysis units, and, for example, the electrolysis or energy supply of electrolysis units with at least one electrolysis current Iw2_off, in particular with the maximum electrolysis current l, can be interrupted. max are operated or produce a specific electrolysis gas throughput, in particular a maximum throughput. These are electrolysis units that are in a favorable state for interrupting the electrolysis or energy supply. For example, the electrolysis or energy device is interrupted in electrolysis units that meet at least two, for example at least three, of these criteria, in particular an operating pressure p. un i pw2_ O ff and an operating temperature Tunit — Tw2_oft as well as the maximum electrolysis current l ma x.

[0085] In one example embodiment, the electrolysis or energy supply for at least one electrolysis unit is interrupted, whose operating pressure p un it, operating temperature Tunit, mechanical stress o un it, hydrogen gas throughput, oxygen gas throughput, electrolysis current I, anode-side oxygen gas content c ano(H2) and / or cathode-side hydrogen gas content Ckato(H2) maximum is based on all electrolysis units of the oxygen gas separator and / or their anode-side hydrogen gas content c ano (H2) and / or cathode-side oxygen gas content Ck a to(O2) minimal refers to all electrolysis units connected to the oxygen gas separator. In any case, however, electrolysis or energy supply is only interrupted if the anode- and cathode-side gas contents in a P2024.1159 WO N / P2024-20 - 21 - 5 March 2026

[0086] is in a safe area, especially outside the explosion limit for a hydrogen / oxygen oxyhydrogen reaction.

[0087] In one exemplary embodiment of the process, the electrolysis or the energy supply of an electrolysis unit is only interrupted if the respective state parameter is reached for at least a certain period of time. The electrolysis or energy supply is therefore only interrupted if at least a predetermined hydrogen gas content Cw2ano_off(H2) and / or Cw2kato_off(H2), oxygen gas content Ci, is present in the electrolysis unit. ano _off(O2) and / or Cw2kato_off(O2), operating pressure pw2_ O ff, operating temperature Tw2_ O ff, mechanical stress Ow2_off, electrolysis current Iw2_off and / or electrolysis gas throughput, in particular a maximum oxygen and / or hydrogen throughput and / or a maximum electrolysis current l max, has already been reached for a predetermined period. This ensures that the respective electrolysis unit is in a stable state, and that a subsequent standby mode can be carried out safely for at least a certain period of time.

[0088] If fewer than (nx) electrolysis units meet at least one or all of these criteria for a favorable state, the state of an electrolysis unit can be improved before the electrolysis or energy supply for that electrolysis unit is interrupted. For this purpose, the electrolysis unit can be operated, as previously described for switch 1, for a specific period with the increased electrolysis current Iw2ini, in particular with the maximum electrolysis current l. ma x, be operated until the state has improved and / or a time duration tw2ini has been reached that is necessary to improve the state, in particular such that p U nit^pw2_off, T unit^Tw2_off, Ounit— Ow2_off, Cano (O2)— Cw2ano_off(O2), C an o(H2)^Cw2ano_off(H2), Ckato(H2)SCw2kato_off(H2) and / or Ckato(O2) -C\A / 2kato_off(O2) .

[0089] Similar to switching 1, in a version of switching 2, an increase in the electrolysis current I of an electrolysis unit can be carried out each time before the electrolysis or energy supply of the electrolysis unit is interrupted, regardless of the state of the electrolysis unit.

[0090] The state of the electrolysis unit can also be improved to a state where the state is significantly improved beyond the threshold values ​​for the change, in particular to a maximum or minimum value, e.g. p U nit=Pmax,Tunit=T m ax, a maximum tension O U nit=O max, Cano(O2) — Cano_max (O2), Ckato(H2) — Ckato _max(H2), C a no(H2) — C ano_min(H2) Und / OdeT Ckato(O2)=Ckato_min(O2) improved. The maximum and minimum gas contents are the gas contents that can be achieved with the electrolysis unit at the respective electrolysis current Iw2ini. However, such a procedure takes time, so for a faster P2024.1159 WO N / P2024-20 - 22 - 5 March 2026

[0091] The thresholds for switching may be set less strictly, e.g.

[0092]

[0093] In addition to or as an alternative to increasing the electrolysis current I, cooling of the electrolysis unit can also be reduced or switched off to lower the operating temperature T. un it, the operating pressure punit and the tension o un to increase it.

[0094] Alternating operation 1 and / or alternating operation 2 can be performed simultaneously. If both alternating operation 1 and 2 are configured, the threshold values ​​for alternating operation 1 are disregarded during alternating operation 2. For example, the threshold values ​​for starting up in alternating operation 1 can be set more stringent than the threshold values ​​for starting up in alternating operation 2. This generally allows alternating operation 2 to be performed more quickly. Furthermore, the threshold values ​​for starting up can be set more stringent than the critical threshold values ​​for starting up from standby.

[0095] Alternating operation ensures that the electrolysis units are maintained in good condition during normal operation before standby mode is triggered, allowing for safe subsequent standby operation for a specific period. Alternatively or additionally, the risk of an oxyhydrogen reaction during standby can be further reduced by lowering the hydrogen content g(H2) in the oxygen gas separator when standby mode is initiated. This reduction can be achieved by one or more of the measures described below. These measures are also applicable to electrolysis systems with only a single electrolysis unit, where alternating operation of multiple electrolysis units is not possible.

[0096] According to embodiments, a degassed electrolyte is used for electrolysis before the electrolysis or standby power supply is interrupted. This electrolyte can be supplied to the at least one electrolysis unit whose electrolysis or standby power supply is interrupted, as well as to other electrolysis units that may be connected to the oxygen gas separator. For example, a degassed electrolyte is used for electrolysis in all electrolysis units connected to the oxygen gas separator. Thus, less hydrogen gas escapes from the electrolyte during standby, i.e., after the electrolysis or power supply is interrupted, and also when starting up from standby, and the hydrogen gas content c(H2) in the oxygen gas separator is reduced. The degassed electrolyte can, for example, have a content of P2024.1159 WO N / P2024-20 - 23 - 5 March 2026

[0097] of dissolved hydrogen H2 of at most 5 x 10 -7 wt.%, for example of at most 1 x 10' 7 wt.%, for example of at most 1 x 10' 8 exhibit wt.%.

[0098] The degassed electrolyte can be supplied to the respective electrolysis unit in addition to or instead of the electrolyte recirculated from the oxygen gas separator, for example, from a separate storage tank. Alternatively, it is also possible to use the electrolyte recirculated during electrolysis and to reduce the concentration of dissolved gases in this electrolyte in a separate degassing unit. "Separate" in this context means that the degassing takes place outside the electrolysis unit and the oxygen gas separator, thus reducing the operating pressure (p) in the electrolysis unit. unIt is not affected in the oxygen gas separator, thus maintaining the production of electrolysis gas. In some configurations, the electrolyte processing device can be designed as a degassing unit or have one.

[0099] After the electrolysis or power supply is interrupted, i.e., when the electrolysis or power supply is interrupted for standby, the electrolysis unit can also be heated with degassed electrolyte.

[0100] According to embodiments, the hydrogen content g(H2) in the oxygen gas separator is reduced by lowering the operating temperature T before interrupting the electrolysis or the standby power supply. un with which at least one electrolysis unit is lowered and / or the operating pressure p unThe temperature of at least one electrolysis unit is reduced. If several electrolysis units are connected to the oxygen gas separator, the operating temperatures (Tunit) and / or the operating pressures (p) are, for example, lowered. un The hydrogen content of all electrolysis units operating in electrolysis mode is reduced. This allows hydrogen gas dissolved in the electrolyte to escape in a controlled manner before the electrolysis or energy supply is interrupted and is extracted from the oxygen gas separator along with the oxygen gas, thus reducing the hydrogen content g(H2) in the oxygen gas separator.

[0101] In contrast to the previously described method, the electrolyte is degassed only in the electrolysis unit and the gas separator, and is not supplied to the electrolysis unit already degassed. The operating temperature of the Tunit is typically set to a temperature of no less than 70% of the maximum operating temperature T.ma x reduced and / or the operating pressure p un It is reduced to a pressure of not less than 73% of the maximum operating pressure Pmax. P2024.1159 WO N / P2024-20 - 24 - 5 March 2026

[0102] Below the maximum operating temperature T ma The temperature x can be understood as the maximum temperature of the electrolysis cells in the cell stack at which electrolysis in the electrolysis unit can be operated continuously, or at least for 1 to 10 years, without damage or failure of the electrolysis cells. In alkaline pressure electrolysis with aqueous alkaline solutions, such as potassium hydroxide (KOH), as the electrolyte, this temperature typically lies in the range between 60 °C and 90 °C.

[0103] The operating pressure p s Tack is the pressure in the anode and cathode compartments of the electrolysis cells. The maximum operating pressure p max is the maximum pressure in the electrolysis cells of the electrolysis unit at which electrolysis can be operated continuously, or at least for 1 to 10 years, without damage or failure of the electrolysis cells. It is usually dependent on the design of the electrolysis unit and can be between 85% and 95% of the design pressure. In atmospheric alkaline electrolysis, the maximum operating pressure p can be ma x, for example, lies in a range of 0.05 bar to 0.1 bar overpressure, while in alkaline pressure electrolysis it lies in a range between 25 bar and 35 bar overpressure.

[0104] Alternatively or in addition to lowering the operating pressure p unDepending on the operating temperature and / or the Tunit system, an electrolyte with an increased concentration CL of dissolved alkali salt, e.g., potassium hydroxide (KOH), can be used for electrolysis before the electrolysis or power supply is interrupted for standby mode, and / or the concentration of the dissolved alkali salt in the electrolyte can be increased to the concentration CL before the electrolysis or power supply is interrupted. For alkaline electrolysis, an increased concentration CL could, for example, be a KOH concentration in the range of 25 wt% to 30 wt%, or in the range of 27 wt% to 30 wt%, or 30 wt%.

[0105] The electrolyte concentration can be increased by replacing the electrolyte recirculated from the oxygen gas separator with an electrolyte of higher concentration (Cl), which may also be degassed. Alternatively, the electrolyte concentration can be increased by adding a more concentrated electrolyte (with a concentration greater than Cl) to the electrolyte recirculated from the gas separator, by adding less or no distilled / deionized water, and / or by adding alkali salts.

[0106] In a further embodiment of the process, the recirculated electrolyte is already an electrolyte with an increased concentration of CL. Thus, the electrolysis is already operated with an electrolyte of concentration CL before or at the beginning of the standby process, particularly during normal operation. For example, the electrolysis plant can already be operated with the increased concentration of CL as described in P2024.1159 WO N / P2024-20 - 25 - 5 March 2026.

[0107] The electrolyte concentration CL has been activated. A complex control system for increasing the concentration is therefore unnecessary, and the standby procedure can be carried out more simply and quickly.

[0108] Alternatively or additionally, the hydrogen content g(H2) in the oxygen gas separator is reduced before the electrolysis or power supply is interrupted for standby mode by lowering the electrolyte volume in the oxygen gas separator before the interruption of electrolysis or the power supply. Such a reduction in the electrolyte level in the oxygen gas separator is carried out, for example, when no inert gas is introduced into the oxygen gas separator. The electrolyte volume can be reduced, in particular, to a level lower than the electrolyte volume at the time the interruption signal is received. For example, it is reduced to a level lower than during normal operation. With the reduced electrolyte volume, the amount of dissolved hydrogen that can escape from the electrolyte is reduced, thereby lowering the hydrogen gas content c(H2) in the oxygen gas separator.

[0109] Under normal operating conditions, the electrolyte volume or level in the gas separators (oxygen and / or hydrogen gas separator) is typically set to ensure reliable transfer such that the liquid volume of electrolyte in the gas separators or their separation chambers is larger than the gas volume of the gas phase. The liquid levels in the gas separators can be equal. In the disclosed process, the electrolyte volume is reduced so that the liquid volume of electrolyte is smaller than the gas volume of oxygen in the oxygen gas separator. In particular, the electrolyte volume in the oxygen gas separator can also be smaller than the electrolyte volume in a hydrogen gas separator to which the electrolysis unit is connected.

[0110] In hydraulically coupled oxygen and hydrogen gas separators, at least one electrolyte-filled shuttle line should be provided between the gas separators to lower the fill level in the oxygen gas separator. This shuttle line connects the gas separators via the electrolyte in the shuttle line, based on the principle of communicating vessels. The shuttle line can be connected as low as possible in the separation chamber of each gas separator, for example, at the lowest point. This allows for very large fill level differences between the oxygen and hydrogen gas separators. This makes it possible to generate a large gas volume in the oxygen gas separator without unnecessarily increasing the size of the separation chamber, and also prevents the two electrolysis gases from mixing due to insufficient fill levels. P2024.1159 WO N / P2024-20 - 26 - 5 March 2026

[0111] The fill levels can be adjusted by controlling the flow rates of the electrolysis gases supplied to and removed from the gas separators. For example, to lower the fill level in the oxygen gas separator, the outflow rate q can be adjusted. ou The amount of oxygen gas from the oxygen gas separator can be reduced. The outflow rate can be controlled via the gas outlet valve on the oxygen gas separator. Alternatively or additionally, more hydrogen gas can be drawn from the hydrogen gas separator. The outflow rate can be controlled via a gas outlet valve on the hydrogen gas separator.

[0112] In electrolysis plants where the oxygen gas separator and the hydrogen gas separator are not hydraulically coupled, the fill levels can be adjusted by controlling the amount of electrolyte withdrawn from or supplied to a separate container. For example, to lower the fill level in the oxygen gas separator, electrolyte can be withdrawn and transferred to the separate electrolyte storage tank, resulting in a larger gas volume than electrolyte volume in the oxygen gas separator.

[0113] Alternatively or additionally, before interrupting the electrolysis or power supply for standby, the hydrogen content g(H2) in the oxygen gas separator is reduced by operating the electrolysis unit with an increased electrolysis current I, in particular with a maximum electrolysis current l. max, i.e., at full load. This means that the electrolysis current I, insofar as it is not yet the maximum electrolysis current l ma x corresponds to being increased to a value higher than the electrolysis current at the time the signal to interrupt is received, in particular to the maximum electrolysis current l ma x. By operating with an increased electrolysis current, more oxygen gas is produced in the electrolysis unit and introduced into the oxygen gas separator, thereby reducing the hydrogen content g(H2), and in particular the hydrogen gas content C(H2). If several electrolysis units are connected to the oxygen gas separator, all electrolysis units whose electrolysis or energy supply is not interrupted can operate at maximum electrolysis current l. ma x can be operated.

[0114] The maximum electrolysis current l max is the maximum current at which electrolysis in the electrolysis unit can be operated continuously, or at least for one to ten years, without damage to or failure of the electrolysis cells. It depends on the electrode surface area and is limited by the maximum heat that the electrolysis system can dissipate; typical current densities for alkaline pressure electrolysis range from 0.2 to 1.2 A / cm². 2 .P2024.1159 WO N / P2024-20 - 27 - 5 March 2026

[0115] In a further embodiment, the hydrogen content g(H2) in the oxygen gas separator is reduced before the electrolysis or standby power supply is interrupted by introducing inert gas into the oxygen gas separator before the electrolysis or power supply is interrupted. The gas separator can be purged with the inert gas, meaning that the inert gas can be introduced into the gas separator and a gas mixture of inert gas, hydrogen, and oxygen can be extracted from the gas separator, thus reducing the hydrogen content g(H2) in the oxygen gas separator.

[0116] An inert gas is, for example, a gas that does not form an explosive mixture with oxygen gas, such as nitrogen and / or compressed air. Introducing inert gas into the oxygen gas separator, just like the measures described previously, can reduce the hydrogen content g(H₂), and in particular the hydrogen gas content c(H₂), in the oxygen gas separator before interrupting electrolysis or power supply for standby. Introducing inert gas can be carried out as a single measure or in conjunction with one or more of the previously described measures for reducing the hydrogen content. In some configurations, inert gas can also be introduced during an interruption of electrolysis or power supply, especially if this is achieved by gradually or continuously reducing the electrolysis current and / or voltage in the electrolysis unit.

[0117] For example, the inert gas is supplied at a pressure pfm of at least 80%, for example at least 90%, for example at least 95% of the maximum operating pressure p. ma x, is introduced into the oxygen gas separator. The inert gas can be supplied as a pressurized gas for this purpose. It can be introduced into the oxygen gas separator, for example, using a stepwise or a continuous flow process.

[0118] In the stepwise process, the inert gas content in the oxygen gas separator is increased stepwise. Preferably, in a first step, with the gas outlet valve on the oxygen gas separator closed and the oxygen inlet valve between the oxygen gas separator and the electrolysis unit closed, the inert gas is introduced into the oxygen gas separator via an open inert gas inlet valve. In a second step, with the gas outlet valve open, a gas mixture is discharged from the oxygen gas separator. The inert gas is typically introduced into the oxygen gas separator in such a way that it mixes with the gas volume in the oxygen gas separator to form a gas mixture. In the second step, this gas mixture is discharged from the oxygen gas separator through the gas outlet valve. For example, the first and second steps are repeated. An electrolyte drain valve for the P2024.1159 WO N / P2024-20 - 28 - 5 March 2026

[0119] In both steps, the electrolyte is usually returned from the oxygen gas separator to an electrolyte preparation device or to the electrolysis unit in a closed loop.

[0120] In an oxygen gas separator that is hydraulically coupled, for example via a shuttle line, to a second gas separator, such as a hydrogen gas separator, the first step can be carried out, for instance, until the liquid level of the electrolyte in the oxygen gas separator has dropped to a specific level. The gas pressure in the oxygen gas separator can, for example, be kept constant during this process. In self-contained oxygen gas separators, i.e., oxygen gas separators that are not hydraulically coupled to hydrogen gas separators, the first step can be carried out, for example, until a specific gas pressure is reached in the oxygen gas separator.

[0121] In the second step, the gas pressure in the oxygen gas separator is not reduced below, for example, 80%, 90%, or 95% of the maximum operating pressure (pmax). This keeps the oxygen gas separator at a high pressure level close to the operating pressure, allowing the electrolysis unit to quickly restart from standby to normal operation and oxygen to be introduced into the gas separator. In the case of an oxygen gas separator that is hydraulically coupled to a second gas separator, the gas pressure in the oxygen gas separator is kept constant in the second step.

[0122] In the stepwise process, the introduction of the inert gas between the first and second steps can be stopped or at least reduced, so that in the second step no inert gas or less inert gas than in the first step is introduced into the oxygen gas separator. In the first and / or second step, the inert gas can be introduced into the oxygen gas separator at a continuous flow rate or, for better mixing, at a variable flow rate, e.g., pulsed. The flow rate q f In particular, it can be varied periodically or aperiodically in such a way that changing turbulences, e.g. in a turbulent flow, are forced and thus an improved mixing of the gases in the oxygen gas separator takes place.

[0123] Instead of gradually increasing the inert gas content by alternately opening and closing the gas drain valve, it is also possible to increase the inert gas content c(lnert) continuously. For example, the oxygen gas separator can be filled with inert gas. P2024.1159 WO N / P2024-20 - 29 - 5 March 2026

[0124] In the flow-through process, the inert gas is continuously introduced into the oxygen gas separator, while a gas outlet valve continuously discharges the gas mixture of oxygen and nitrogen, and possibly hydrogen, from the oxygen gas separator into a discharge line. The gas pressure in the oxygen gas separator remains constant or close to the operating pressure. For example, it does not fall below 80% of the maximum operating pressure p. ma x is reduced. For example, it is reduced at >90%, for example at >95% of the maximum operating pressure p. max held. In alkaline electrolysis with KOH solution as the electrolyte, the maximum operating pressure p ma The pressure is typically in the range of 25 bar to 35 bar overpressure, for example, in the range of 29 bar to 33 bar overpressure, or in the range of 30 bar to 32.5 bar overpressure. Due to the high pressure level in the oxygen gas separator during inert gas injection or purging, a rapid start-up from standby is possible, and the electrolyte levels in the gas separators (hydrogen and oxygen) remain balanced, provided the gas separators are hydraulically coupled.

[0125] In the flow-through method, the continuous introduction of inert gas into the oxygen gas separator can, for example, be carried out with a constant inflow rate qnii > 0. However, it is also possible to change the inflow rate q fto vary the timing, especially to pulse for better mixing, e.g. to vary periodically or aperiodically between upper and lower thresholds, so that, for example, changing turbulences occur in the gas volume or the gas phase of the oxygen gas separator.

[0126] For both step and flow processes, it may be necessary to raise the electrolyte level in the oxygen gas separator to reduce the gas volume and thus limit the purging time and the inert gas usage, i.e., the inert gas inflow rate qmi and / or the duration of the inert gas injection. Any outgassing of dissolved hydrogen from the electrolyte is not critical because it is diluted with the inert gas and discharged from the gas separator. The electrolyte level can, for example, be raised so that there is a larger electrolyte volume than gas volume in the oxygen gas separator.

[0127] Raising the fill level can be carried out before introducing the inert gas. In hydraulically coupled gas separators, this can be achieved, for example, by increasing the gas outflow rate q. ouThe increase in fill level can be achieved either by removing gas from the oxygen gas separator or by reducing the gas outflow rate from the hydrogen gas separator. In the flow-through process, the increase in fill level can also be carried out during the introduction of the inert gas, for example by increasing the gas outflow rate q. ou t from the oxygen gas separator compared to the inert gas flow rate qmi. In self-contained gas separators, the fill level in the oxygen P2024.1159 WO N / P2024-20 - 30 - March 5, 2026

[0128] The gas separator can be raised by adding electrolyte or water from outside into the oxygen gas separator.

[0129] Once the inert gas injection process is complete, the electrolyte level in the oxygen gas separator can be lowered again. This can be achieved, in particular, by increasing the amount of inert gas injected into the oxygen gas separator, for example, by increasing the inflow rate q. f in increased and / or the gas outflow rate q ouThe electrolyte level in the hydrogen gas separator can be lowered. Alternatively or additionally, in hydraulically coupled gas separators, the electrolyte level can also be raised, e.g., by introducing the inert gas into the oxygen gas separator at a pressure higher than the gas pressure in the hydrogen gas separator. In the stepwise process, this can be done particularly in the last step, where the inert gas is introduced into the oxygen gas separator.

[0130] For standby operation, one or more of the previously described measures to reduce the hydrogen content g(H2) in the oxygen gas separator can be carried out before the electrolysis or power supply is interrupted.

[0131] If several measures are implemented to reduce the hydrogen content, at least two measures can be carried out partially or completely simultaneously, or sequentially. For this purpose, each of the measures to be implemented, Mj (i=1,2,3...), is assigned its own first and second threshold values.

[0132] Each measure Mj (i=1, 2, 3, ... ) can be assigned first threshold values ​​CMM(H2) for the hydrogen gas content in the oxygen gas separator, CMI_I(O2) for the oxygen gas content in the oxygen gas separator, or rMi_i for the ratio of hydrogen gas content to oxygen gas content in the oxygen gas separator and / or 1 / rMi_i for the reciprocal ratio of the gas contents, as well as second threshold values ​​CMI_2(H2) for the hydrogen gas content in the oxygen gas separator, CMi_2(Ü2) for the oxygen gas content in the oxygen gas separator, or TMI_2 for the ratio of hydrogen gas content to oxygen gas content in the oxygen gas separator and / or 1 / rMi_2 for the reciprocal ratio of these gas contents. The respective measure Mj is executed as long as the hydrogen gas content c(H2) and / or c(O2) is below the threshold value.or the oxygen gas content c(Ü2) in the oxygen gas separator is a value between the respective first and second threshold values, that is, if the detected hydrogen gas content c(H2) is between CMM(H2) and CMI_2(H2), the detected oxygen gas content c(Ü2) is between CMM(O2) and CMi_2(O2), and / or a ratio of these gas contents is between the first and second threshold values ​​for the respective ratio, e.g., c(H2) / c(O2) between TM and rMi_2 and / or C(O2) / C(H2) between I MM and 1 / rMi_2. Additionally or instead of these threshold values, for P2024.1159 WO N / P2024-20 - 31 - 5 March 2026.

[0133] A measure Mj(i=1,2,3,...) can also be directed to a first time point 1M and / or a second time point tMi_2, between which the respective measure Mj is carried out.

[0134] The time duration or interval between the first and second time parameters is determined such that the second threshold values ​​CML2(H2) and CMi_2(O2) are reached with the respective action Mj. The determination of the time duration between tMi_i and tMi_2 can depend on the other actions Mj (ji) that are carried out simultaneously with the respective action Mj. The reference time tvo=O for the times tMi_i and tMi_2 before the interruption of the power supply is typically the reception or generation of the signal to interrupt. The initial times tMi_i can be determined in such a way that a defined sequence of actions Mj is specified.

[0135] In the case of a measure Mj that is carried out at least temporarily simultaneously with one or more other measures Mj (j=1,2,3... , ji), the measure Mj has first or second threshold values ​​for the hydrogen gas content CMM(H2), CM 2(H2) and / or the oxygen gas content CMM(O2), CMi_2(O2) that correspond to or lie between the first or second threshold values ​​of the further measure or measures Mj:

[0136] CM L 2(H2) S CMM(H2) < c M j_i(H2) and / or c M j_2(H2) c M i_2(H2) <c M j_i(H2) or

[0137] CMj_i(O2) - CMi_i(O2) - CMj_2(O2) and / or CMj_i(O2)scMi_2(O2)scMj_2(O2)

[0138] and, if time parameters are given, the measure Mj has a first or second time point tMi_i, tMi_20 or a time interval between the first and second time point 1MM, tMi_2, which coincides with a first or second time point tMj_i, tMj_2 or the time interval between these time points tMj_i, tw^ of the further measure or measures Mj:

[0139] tMj_i - tMi_i - tMj_2or tMj_i -t Mi_2 - tMj_2or

[0140] t[\ / li_1 - tMj_1 and th / li_2 - tMj_2.

[0141] For measures that are carried out sequentially, the first and second thresholds CMM(H2), CMi_2(H2) and CMM(02), CMi_2(O2) of a measure Mj are each outside the first and second thresholds CMJ_I(H2), CMj_2(H2) and CMj_i(O2), CMj_2(O2) of the subsequent measure or measures Mj (j=1, 2, 3..., ji), and, if time parameters are given, the time points IMM, tMi_2 or the time interval between the time points do not overlap with the time points tMj_i, tMj_2 or the time interval between these time points of the subsequent measure or the subsequent measure Mj:

[0142] c M i_2(H2) > c M j_i (H2) or c M i_i (H2) < c M j_2(H2) or

[0143] c M i_i(O2) > c M j_2(O2) or c M j_2(O2) < c M j_i(O2) and / or

[0144] t[\ / li_1 > tMj_2 or tMi_2 < tMj_1.P2024.1159 WO N / P2024-20 - 32 - March 5, 2026

[0145] In one embodiment of the process, at least two measures Mj for reducing the hydrogen content in the oxygen gas separator can be carried out simultaneously. They therefore have the same first threshold values ​​CMM(H2) and second threshold values ​​CMI_2(H2) for the hydrogen gas content C(H2) in the oxygen gas separator. If the process is carried out depending on the oxygen gas content c(Ü2) and / or a time parameter, the measures Mj also have the same first threshold values ​​CMM(02) and second threshold values ​​CMi_2(Ü2) for the oxygen gas content c(Ü2) in the oxygen gas separator, or the same first and second time parameters 1MM, th / ii_2. By carrying out measures simultaneously, the hydrogen content g(H2) and, in particular, the hydrogen gas content c(H2) in the oxygen gas separator can be reduced very quickly, and the standby process can be carried out in a time-efficient manner.Furthermore, the redundancy of the measures improves the security of the standby procedure.

[0146] Measures that can be implemented simultaneously include, in particular, those that do not reduce the hydrogen production rate and / or do not involve the introduction of inert gas into the oxygen gas separator. For example, at least two of the following measures, which do not reduce the hydrogen production rate, can be implemented simultaneously, perhaps as the only measures:

[0147] Use of degassed electrolyte

[0148] Increasing the electrolysis current I, in particular to the maximum electrolysis current l ma x Use of an electrolyte with increased concentration of CL and / or increasing the electrolyte concentration to CL

[0149] Level reduction in the oxygen gas separator.

[0150] In one exemplary embodiment, the measures to be implemented, Mj, are carried out simultaneously. They therefore have the same threshold values ​​CMLI(H2)=CI(H2), CMi_2(O2)=C2(O2), ratios for the threshold values ​​rMi_i=H, rMi_2=r2, and time parameters tMM=ti, tMi_2=t2. Due to the simultaneity of the measures and the limited set of threshold and time parameters, the standby procedure can be carried out particularly quickly and with minimal effort for control and monitoring. The time interval between h and t2 can, for example, be chosen such that the first and / or second threshold values, C2(H2), O2(O2), r2, 1 / r2, are exceeded or fallen below within this time interval. h can, for example, be chosen such that the measures to reduce the hydrogen content are initiated immediately after receiving the signal to interrupt (ti=tvo).However, it is also possible to start the measures with a time delay (ti>tvo) in order to first record, for example, current state parameters of the electrolysis plant, in particular state parameters of the at least one electrolysis unit, on which the implementation of the measures may depend. P2024.1159 WO N / P2024-20 - 33 - 5 March 2026.

[0151] In a further embodiment of the standby procedure, at least two measures can be carried out sequentially. Measure M is responsible for this. m , which is feasible first, sets a second threshold CMm_2(H2) (m=1 ,2,3...) for the hydrogen gas content c(H2) in the oxygen gas separator, which is smaller than the first threshold CMn_i(H2) for the hydrogen gas content C(H2) in the oxygen gas separator of measure M n (n=1, 2, 3... , nm), which after this measure M mis feasible or is being carried out. If the standby procedure is carried out depending on the oxygen gas content c(Ü2) and / or a time parameter, then measure M indicates m a second threshold value CMm_2(O2) for the oxygen gas content c(Ü2) in the oxygen gas separator which is smaller than the first threshold value CMn_i(O2) for the oxygen gas content c(Ü2) of measure M n or a second time parameter twm_i that is smaller than the first time parameter tw n _i of measure M n This allows, for example, a sequence of measures M m and M n be predetermined.

[0152] As soon as inert gas is introduced into the oxygen gas separator as a measure Mj to reduce the hydrogen content, the subsequent measures Mj (ji) for reducing the hydrogen content before and / or after the interruption of electrolysis or energy supply are carried out, for example, only depending on the measured hydrogen gas content C(H2) or depending on the respective threshold values ​​for the hydrogen gas content CMJLI(H2), CMJ_2(H2). If the measures Mj are based on the time parameter tMj_2, they are determined such that the respective second threshold value of the hydrogen gas content CMj_2(H2) of the measure Mj is undercut.

[0153] By introducing inert gas into the oxygen gas separator, a gas mixture of oxygen, nitrogen, and hydrogen is present in the oxygen gas separator in both stepwise and continuous flow processes. This reduces not only the hydrogen gas content but also the oxygen gas content in the oxygen gas separator. Therefore, the oxygen gas content c(Ü2) can no longer be determined solely from the hydrogen gas content c(H2). It can, for example, be determined as a function of the inert gas flow rate q. f in and gas outflow rate q ou t can be determined or measured from the oxygen gas separator as well as the gas volume in the oxygen gas separator or the electrolyte level and total volume of the oxygen gas separator.

[0154] If the inert gas injection process continues until a second time parameter tMi_2 for the inert gas injection is reached, the second time parameter tMi_2 can, for example, depend on the total volume, gas volume and / or electrolyte volume or electrolyte level in the oxygen gas separator, the inflow rate q f inert gas into the oxygen gas separator and the outflow rate q ou t of gas mixture from the oxygen gas separator, such as P2024.1159 WO N / P2024-20 - 34 - 5 March 2026

[0155] It must be determined that the second threshold value CMI_2(H2) for the hydrogen gas content and / or the second threshold value CMi_2(Ü2) for the oxygen gas content is undershot within the second time period and / or a defined gas content of inert gas C2(lnert) is reached or exceeded. C2(lnert) is chosen such that, upon reaching C2(lnert), the gas mixture in the oxygen gas separator is outside the range for a hydrogen / oxygen oxyhydrogen reaction, in particular below a lower explosive limit (LEL).

[0156] The standby procedure can be carried out depending on the gas concentration(s) c(H2), c(Ü2) and / or their ratio, as well as depending on the first and second time parameters. In some embodiments, the standby procedure can also be carried out either solely depending on the gas concentration(s) c(H2), c(Ü2) and / or their ratio, regardless of the time parameters, or solely depending on the time parameters, regardless of the gas concentration(s) c(H2), c(Ü2) and / or their ratio.

[0157] If the procedure is carried out independently of the time parameters, depending on the gas concentration(s) C(H2), C(Ü2) and / or their ratio, then at least one measure Mi (i=1, 2, 3...) for reducing the hydrogen content in the oxygen gas separator is implemented when the respective measured gas concentrations c(H2), c(Ü2) and / or their ratio lie between the first threshold value CMM(H2), CMM(O2) and / or TMU or 1 / TMU, and the second threshold value CMi_2(H2), CMi_2(Ü2) and / or rMi_2 or 1 / rMi_2 of measure Mj. The electrolysis or energy supply is interrupted when the hydrogen gas concentration c(H2) in the oxygen gas separator falls below the minimum of the second threshold values ​​|CMi_2(H2)|min (i=1, 2, 3...).The process is interrupted if the minimum threshold value of all measures to be implemented falls below Mj and / or if – provided no inert gas has been or is being introduced into the oxygen gas separator – the oxygen gas content c(Ü2) in the oxygen gas separator exceeds the maximum of the second threshold values ​​|CMi_2(O2)|max (i=1, 2, 3...) of all measures to be implemented, Mj. The same applies to the gas ratios, provided no inert gas is introduced into the oxygen gas separator. For example, if the ratio c(H2) / c(O2) is considered, the electrolysis or energy supply is interrupted if the minimum threshold value |rMi_2|min (i=1, 2, 3...) of all measures to be implemented, Mj, for this ratio is undershot. For the reciprocal ratio, the electrolysis or energy supply is interrupted if the maximum threshold value for the reciprocal ratio is exceeded.

[0158] As an alternative to the minimum or maximum threshold, a threshold for interrupting the electrolysis or energy supply can be defined, at which point the electrolysis or energy supply is interrupted, for example P2024.1159 WO N / P2024-20 - 35 - 5 March 2026

[0159] a threshold value for the hydrogen gas content c O ff(H2) and / or 1 / r O ff for the ratio of hydrogen gas to oxygen gas in the oxygen gas separator, below which the electrolysis or energy supply is interrupted, and / or a threshold value for the oxygen gas content c O ff(O2) and / or 1 / r OThe ratio of oxygen gas to hydrogen gas in the oxygen gas separator is the limiting factor; exceeding this limit interrupts the electrolysis or energy supply. If inert gas is introduced into the oxygen gas separator, the electrolysis or energy supply can be interrupted when a threshold value for the inert gas content, Coff(lnert), is reached or exceeded. In some embodiments, this threshold can correspond, for example, to the second threshold value, C2(lnert), for introducing inert gas to reduce the hydrogen content.

[0160] Such a standby procedure, dependent on the gas concentration(s) C(H2), C(Ü2) and / or their ratio, allows the standby procedure to be carried out particularly efficiently, because no time parameters need to be determined and met. Furthermore, real-time determination or monitoring of the gas concentrations enables reliable process control.

[0161] If, in the standby procedure, the first and second time parameters IMM and tMi_2 are used instead of the threshold values ​​for the gas content(s) or their ratio, the respective action Mj is carried out in the time interval between and including tMi_i and tMi_2. The electrolysis or energy supply is interrupted when the maximum of the second time parameter |tMi_2|max (i — 1, 2, 3...) of all measures to be carried out Mj is reached, i.e., at the latest time for carrying out all measures Mj. This can be stipulated, for example, if the determination or recording of the gas contents is not possible or is faulty. The first time parameters tMi_i can define the sequence of the measures, while the duration of the measures is defined by the second time parameters tMi_2.

[0162] In an exemplary embodiment, the at least one measure Mj for reducing the hydrogen content g(H2) in the oxygen gas separator and the interruption of the electrolysis or energy supply is only carried out depending on the first and second time parameters tMi_i, tr ii_2 if the determination of the gas content(s) c(H2), c(Ü2) is disrupted, e.g., if no current recorded values ​​for the gas content(s) or their ratios are available in the control device, and is otherwise carried out depending on the gas content(s) c(H2), c(Ü2) and / or their ratio, i.e., independently of the first and second time parameters t M i_1, t M i_2.P2024.1159 WO N / P2024-20 - 36 - March 5, 2026

[0163] In a further embodiment of the procedure, the standby procedure can be implemented depending on the gas concentrations and / or one of their ratios and depending on time parameters. The respective measure Mj is then carried out in the time interval between and including tMi_i and tMi_2 as soon as the hydrogen gas concentration c(H2) in the oxygen gas separator exceeds the first threshold value CMM(H2) and / or, if no inert gas is introduced into the oxygen gas separator, the oxygen gas concentration c(Ü2) in the oxygen gas separator falls below the first threshold value CMM(O2). The measure is terminated when the second tMi_2 time parameter or point is reached and the hydrogen gas concentration c(H2) falls below the second threshold value CMi_2(H2) and / or the oxygen gas concentration c(Ü2) exceeds the first threshold value CMI_2(O2). Alternatively or additionally to the gas concentrations, a ratio of the gas concentrations or...The first and second threshold values ​​of the ratio can be set. Using the time parameters and threshold values ​​of the gas contents and / or their ratio, not only can a sequence of measures be determined, but also a prioritization of the measures can be achieved.

[0164] For example, several measures can have the same or at least overlapping time intervals between, including, the first and second time parameters 1MM, tMi_2, and the same or at least overlapping ranges between the first and second threshold values ​​of the gas concentrations c(H2), c(Ü2), and / or a ratio of the gas concentrations, so that these measures can be carried out simultaneously, at least temporarily. This allows for redundancy of the measures, which improves the reliability, functionality, and operational safety of the electrolysis plant in standby mode and also when starting up from standby. Furthermore, by carrying out several measures simultaneously, at least temporarily, the hydrogen concentration in the oxygen gas holder is reduced more quickly.

[0165] Alternatively or additionally, it can be stipulated that several measures for reducing the hydrogen content have the same or at least overlapping time intervals between the respective first and second time parameters, and that the ranges of the first to second threshold values ​​of the gas contents c(H2), c(Ü2), and / or a ratio of the gas contents do not overlap for these measures. If the gas quality deteriorates, i.e., if the hydrogen gas content c(H2) in the oxygen gas separator increases, the measure with the lowest first threshold value CMM(H2) for the hydrogen gas content is then implemented first. Further measures with higher first threshold values ​​are only implemented if the hydrogen content c(H2) continues to rise and reaches the higher threshold values. If the hydrogen gas content does not increase further, the further measures are not implemented. Measures with lower first threshold values ​​CMM(H2) are thus P2024.1159 WO N / P2024-20 - 37 - 5 March 2026.

[0166] For example, measures with higher initial thresholds are implemented, while those with higher initial thresholds serve as backup measures. Such prioritization of measures allows the process to be tailored particularly efficiently to the specific electrolysis plant.

[0167] Regarding the oxygen gas content, provided no inert gas is introduced into the oxygen gas separator, measures with the highest first threshold values ​​CMM(O2) for the oxygen gas content are implemented first. Further measures with lower threshold values ​​are only implemented once the oxygen gas content continues to decrease and the respective first threshold value for the oxygen gas content of the subsequent measure in the oxygen gas separator is reached. The same applies to the gas content ratios. If the hydrogen gas content c(H2) / c(O2) ratio is considered, measures with the lowest first threshold values ​​for this ratio are implemented first when the hydrogen gas content in the oxygen gas separator decreases. Conversely, for the ratio c(O2) / c(H2), measures with the highest first threshold values ​​for this ratio are implemented first.Monitoring the ratios of the gas contents allows changes in the gas composition to be detected more quickly if the oxygen gas content c(Ü2) and the hydrogen gas content C(H2) are determined or recorded separately and the ratio is calculated.

[0168] The electrolysis or energy supply can be interrupted when the maximum of the second time parameter |tMi_2|max (i=1, 2, 3...) is reached and the minimum of the second threshold values ​​|CMi_2(H2)|min (i=1, 2, 3...) for the hydrogen gas content is undershot, and / or the maximum of the second threshold values ​​|CMi_2(O2)|max (i=1, 2, 3...) for the oxygen gas content is exceeded. The respective action Mj is then carried out despite falling below the second threshold value CML2(H2) and / or exceeding the second threshold value CMI_2(O2) until the respective second time parameter tMi_2 is reached. This ensures a high level of process reliability. Alternatively, the electrolysis or energy supply can also be interrupted to accelerate the process even before reaching the maximum time parameter |tMi_2|max (i=1, 2, 3...).) occur when the hydrogen gas content c(H2) in the oxygen gas separator is the minimum of the second threshold values ​​|CMi_2(H2)|min (i=1 ,2,3...) or the defined threshold value c. O ff(H2) for the interruption falls below and / or, insofar as no inert gas is introduced into the oxygen gas separator, the oxygen gas content c(Ü2) in the oxygen gas separator falls below the maximum of the second threshold values ​​|CMi_2(O2)|max (i=1 ,2,3...) or the defined threshold value c O ff(O2) for the interruption exceeds. Alternatively or in addition to the gas contents, a ratio of the gas contents can also be used, as described above. P2024.1159 WO N / P2024-20 - 38 - 5 March 2026

[0169] In an exemplary further development of the procedure, the measure(s) for reducing the hydrogen content in the oxygen gas separator are carried out depending on the gas contents and / or one of their ratios and depending on time parameters. The respective measure Mj is carried out in the time interval between tMi_i and tMi_2 if the respective determined or measured gas contents c(H2), c(Ü2) and / or their ratio between the first threshold value CMM(H2), CMM(O2) and / or TM or I MM, and the second threshold value CMi_2(H2), CMI_2(O2) and / or rMi_2 or 1 / rMi_2 of the respective measure Mj is / are If the second threshold value CMi_2(H2) or rMi_2 is undershot and / or if the second threshold value of CMi_2(Ü2) or 1 / rMi_2 is exceeded, the respective measure Mj is terminated and the time parameters whose time has not yet been reached at time t=tvnew of the termination of measure Mj are recalculated.The process then continues with the newly calculated time parameters tMi_i(tv new) and tMi_2(tvnew). These new time parameters correspond to the difference between the respective previous time parameter and tvn. ew :

[0170] t|Vli_l(tvnew) — t[\ / li_1 tvnew And t|vii_2(tvnew) — t[\ / li_2 tvnew fÜT all t

[0171]

[0172] Time points that have already been reached, or whose duration has already elapsed since the reference time tvo=0, remain the same: t M i_i(vnew) = t M i_i and t M i_2(tvnew) = t M i_2 for all t M i_i, tr ii_2 < tvnew, i=1,2,3,...

[0173] As an alternative to recalculating the first and second time parameters, the reference time tvo can also be adjusted: tvonew=tvo-tvnew for all IMM , twi_2 >= tvnew, i=1 ,2,3, ...

[0174] By adjusting the time parameters, the process, similar to control based solely on gas content thresholds or their ratios, can be executed particularly quickly because the second time parameter is no longer waited for once the respective second threshold or ratio is exceeded or fallen below. Unlike control based exclusively on gas content or its ratios, the first time parameters allow for a predefined sequence of actions, and the control can be implemented using the first and second time parameters if necessary, for example, if gas content measurement is disrupted and no current values ​​are available. Furthermore, the second time parameters can be used to detect malfunctions in the measures for reducing the hydrogen content.Thus, if the respective second threshold value CMI_2 for the gas content(s) and / or a ratio of the gas contents is not exceeded or fallen below by the second time point th / ii_2, an error message and / or error routine can be triggered.

[0175] The fault routine may, for example, include the implementation of another measure Mj to reduce the hydrogen content in the oxygen gas separator, e.g., P2024.1159 WO N / P2024-20 - 39 - 5 March 2026

[0176] by introducing inert gas into the oxygen gas separator, or by aborting the standby and releasing the gas from the gas separator.

[0177] The previously described measures Mj for reducing the hydrogen content in the oxygen gas separator can be carried out before the electrolysis or power supply is interrupted. In embodiments of the process, they can also be carried out during the power supply interruption, with the exception of the measure of increasing the electrolysis current I, particularly if the interruption of the electrolysis or power supply of the respective electrolysis unit is achieved by a gradual or continuous reduction of the electrolysis current I and / or the electrolysis voltage. Furthermore, in embodiments of the process, it is possible for one or more of the measures to be carried out multiple times, e.g., repeated or at a later time with different first and / or second threshold values ​​for the gas content(s) and / or their ratio.

[0178] For this purpose, at least one measure Mj can have multiple sets (k=1, 2, 3, ... ) of first and second thresholds CMik_i(H2), CMik_2(H2), CMik_i(O2), CMik_2(O2), rMik_i, rMik_2, 1 / rMik_i, 1 / rMik_2 and / or time parameters tMik_i and tMik_2. The sequence and duration of the implementation of measures Mj can be determined via these thresholds and / or time parameters.

[0179] If the measure Mj is carried out depending on time parameters and depending on threshold values ​​for the gas content(s) and / or for a ratio of the gas contents, then the parameters of a set, i.e., the parameters with the same index k, are assigned to each other. The measure Mj is then carried out, for example, in the time interval from tMik_i to tMik_2 if the respective first threshold value CMik_i(H2), CMik_i(O2), rMik_i, 1 / rMik_2 is below or exceeded.

[0180] The selection, sequence, and prioritization of the measures Mj to be carried out in the process can be plant-specific and / or user-specific. The measures Mj to be carried out are, in principle, chosen so that they can be performed with the electrolysis plant. This means that the process only includes those measures Mj for which the electrolysis plant is designed. In one embodiment of the process, for example, the process may only include those measures Mj for which no separate electrolyte degassing devices and / or no inert gas supply device are provided.

[0181] Regarding the order of the measures to be carried out, Mj, for example, it may be planned to first carry out those measures that are suitable for reducing the hydrogen content g(H2) in the oxygen gas separator particularly quickly, dhP2024.1159 WO N / P2024-20 - 40 - 5 March 2026

[0182] faster than other measures to be implemented, and / or particularly energy- and / or cost-efficient. Further measures can be implemented subsequently. These may have larger initial time parameters and / or smaller initial threshold values ​​for the hydrogen gas content c(H2) and / or the hydrogen content to oxygen content ratio and / or larger initial threshold values ​​for the oxygen gas content c(Ü2) and / or the oxygen content to hydrogen gas content ratio.

[0183] Measures that can reduce the hydrogen content particularly quickly include increasing the electrolysis current I, lowering the fill level in the oxygen gas separator, or lowering the operating pressure p. unThis includes, but also the introduction of inert gas into the oxygen gas separator. The continuous use of an electrolyte with an increased concentration of Cl can be implemented as soon as the electrolysis plant is commissioned, thus also saving time. If one or more of these measures are carried out first, the transition to standby mode can be significantly faster. The process can also, in particular, consist exclusively of only one or more of these measures.

[0184] Alternatively or additionally, the selection and / or prioritization of measures can also be based on the availability of energy, auxiliary materials and / or raw materials for carrying out the respective measure, e.g. depending on the availability of degassed electrolyte or cooling or cooling water for lowering the temperature T. unwith the electrolysis unit. In one embodiment of the process, for example, measures can be carried out first or exclusively in which no degassed electrolyte is used, no inert gas is introduced into the oxygen gas separator, and no temperature reduction of the operating temperature T is performed. un It occurs and / or no increase in the electrolysis current I occurs. Measures that do not require auxiliary substances include, for example, lowering the fill level or lowering the operating pressure p. un or the increase of the electrolysis current I. One measure that can be carried out with low energy expenditure is lowering the fill level in the oxygen gas separator.

[0185] In one exemplary embodiment of the process, the first threshold value CMM(H2) of the hydrogen gas content for inert gas injection before the interruption of electrolysis or energy supply can be greater than the first threshold value CMJ_I(H2) of the hydrogen gas content in the oxygen gas separator of at least one measure, for example, of all measures, Mj (ji), to be carried out before the interruption of electrolysis or energy supply to reduce the hydrogen content g(H2). Alternatively or additionally, the injection of the inert gas can also be started depending on a first threshold value CMLI(O2) of the oxygen gas content in the oxygen gas separator that is lower than a first threshold value CMJ_I(O2) of the oxygen gas content of at least one measure. P2024.1159 WO N / P2024-20 - 41 - 5 March 2026

[0186] For example, all measures, Mj (ji), that are carried out to reduce the hydrogen gas content before the interruption of electrolysis or the energy supply are prioritized. This ensures that, prioritizing measures Mj (ji) for reducing the hydrogen content that do not require inert gas, in the event of an energy supply interruption, is implemented. Inert gas injection serves only as an emergency measure if the hydrogen gas content c(H2) cannot be reduced below the second threshold(s) CMJ_2(H2) and / or can be increased above the second threshold(s) CMJ_2(O2), particularly within a specific time period, for example, until the second time parameter twj_2 is reached. Thus, the consumption of inert gas can be reduced or even eliminated entirely.

[0187] Alternatively or additionally, the selection and / or prioritization of measures can be such that the production rate of electrolysis gases, i.e., the hydrogen gas throughput, does not decrease due to the measures taken to reduce the hydrogen content before the interruption of the energy supply. For example, the hydrogen content in the oxygen gas separator can be reduced before the interruption of electrolysis or the energy supply by increasing the electrolyte concentration, by reducing the electrolyte volume or level in the oxygen gas separator, and / or by increasing the electrolysis current I before the interruption of electrolysis or the energy supply, particularly to a maximum electrolysis current l. ma x, before the electrolysis or power supply is then interrupted for standby.

[0188] Alternatively or additionally, the selection and / or prioritization of measures can depend on at least one state parameter of the electrolysis plant. The selection and / or prioritization of measures can be made by the control device in which the state parameters are available. State parameters can include, for example, the concentration of dissolved hydrogen in the electrolyte, the electrolysis current, the operating pressure and / or the operating temperature of the at least one electrolysis unit, the concentration of the electrolyte, or the electrolyte level in the oxygen gas separator and / or hydrogen gas separator.

[0189] For example, it may be stipulated that the reduction of the hydrogen content in the oxygen gas separator by means of a degassed electrolyte only occurs if the electrolyte in the electrolysis plant, particularly in the oxygen gas separator and / or in the cell stack, is not already degassed. Furthermore, the reduction of the hydrogen content by means of a degassed electrolyte may be carried out depending on whether degassed electrolyte and / or electrolyte degassing are available and / or operational. The increase of the electrolysis current I, particularly to the maximum electrolysis current l ma x, only occurs if the electrolysis unit, P2024.1159 WO N / P2024-20 - 42 - 5 March 2026

[0190] whose electrolysis or energy supply is to be interrupted, not already with the maximum electrolysis current l ma x is operated. For lowering the operating pressure p un it and / or the operating temperature T unThe electrolysis unit and / or the electrolyte level in the oxygen gas separator may be designed so that these processes only take place if the respective state parameter is not already below a certain threshold value, e.g., if the operating pressure p is exceeded during pressure alkaline electrolysis. un it is not already below 73%, for example not below 80% of the maximum operating pressure p ma x is or the temperature T unit is not below 70%, for example below 75%, of the maximum operating temperature T ma x is located. Similarly, an increase in electrolyte concentration is only carried out if the concentration is not yet above a certain threshold value CL, e.g. above 30% in alkaline pressure electrolysis.

[0191] In some implementations of the procedure, the selection and / or prioritization of measures can be carried out by an operator or user of the electrolysis plant. For this purpose, user input can be made via a user interface of the electrolysis plant, where the user selects one or more measures Mi to be implemented from at least one list. The list can, for example, only contain those measures Mj that are feasible with the currently recorded state parameters of the electrolysis plant or the at least one electrolysis unit. Whether a measure is feasible can be determined, for example, by the control device based on state parameters as described above.

[0192] Alternatively or additionally, at least one list can be compiled according to further criteria. For example, it can only include measures Mj that can be implemented particularly quickly and / or that do not reduce the production rate of electrolysis gases and / or that do not introduce inert gas into the oxygen gas separator. In one embodiment, the measures on the list can also be arranged in a specific sequence so that the process can be carried out as quickly as possible and / or, for example, through redundancy of measures, be carried out particularly safely.

[0193] The previously described measures Mj concern the reduction of the hydrogen content before the interruption of electrolysis or the power supply. In an exemplary further development of the process, the hydrogen content g(H2), in particular the hydrogen gas content C(H2), in the oxygen gas separator is also reduced after the interruption of electrolysis or the power supply, when the electrolysis or power supply is interrupted for standby. For this purpose, for example, inert gas can be introduced into the oxygen gas separator. P2024.1159 WO N / P2024-20 - 43 - 5 March 2026

[0194] The introduction of the inert gas into the oxygen gas separator can be continuous or stepwise. In particular, it can be carried out in the same manner as the previously described introduction of the inert gas before interrupting the electrolysis or power supply, for example, using the described stepwise or flow-through method. In the case of pressurized alkaline electrolysis, the gas pressure in the oxygen gas separator is, for example, at least 80%, at least 90%, or at least 95% of the maximum operating pressure p. ma x of the electrolysis unit.

[0195] The reduction of the hydrogen content by introducing inert gas after interrupting electrolysis or the power supply is initiated when a third threshold value C3(H2) of the hydrogen gas content C(H2) in the oxygen gas separator is exceeded and / or a third threshold value O3(O2) of the oxygen gas content c(O2) in the oxygen gas separator is undershot. Alternatively or additionally, a third time period t3 can be used. For the third time period t3, the time elapsed since the interruption of electrolysis or the power supply at time tNo=O is generally used. Purely time-based control can be implemented as a precaution in case, for example, the measurement or determination of the gas contents C(H2) and C(O2) malfunctions.

[0196] In one exemplary embodiment of the process, the third threshold C3(H2) is greater than or equal to a second threshold CMi_2(H2), (i=1,2,3...) of at least one measure Mj for reducing the hydrogen gas content before interrupting the electrolysis or energy supply, in particular greater than or equal to the maximum of the thresholds |CMi_2(H2)|max. Additionally or alternatively, the first threshold of the oxygen gas content c(O2) is less than or equal to a second threshold CMi_2(O2), (i=1,2,3...) for the oxygen gas content c(O2) in the oxygen gas separator of at least one measure Mj before interrupting the electrolysis or energy supply, in particular less than or equal to the minimum of the thresholds |CMi_2(O2)|min. This means that at least one threshold value CMi_2(O2), CM 2(H2) before the interruption of electrolysis or energy supply is chosen more strictly than the threshold values ​​C3(H2) or c3(O2) after the interruption of electrolysis or energy supply.Energy supply such that the hydrogen gas content C(H2) after the interruption of electrolysis or energy supply is below the third threshold C3(H2) for the start of inert gas injection and / or, if no inert gas has been injected before the interruption of electrolysis or energy supply, the oxygen gas content c(O2) is above the third threshold 03(02) for the start of inert gas injection after the interruption of electrolysis or energy supply: c(H2, tNo=O) < C3(H2) and / or C(O2, t. N o=O) > c3(O2).P2024.1159 WO N / P2024-20 - 44 - March 5, 2026

[0197] The gas quality in the oxygen gas separator is thus improved before the interruption of electrolysis or energy supply by one or more measures Mj to reduce the hydrogen content to such an extent that in standby, after the interruption of electrolysis or energy supply, inert gas is only introduced if the gas quality deteriorates so much after the interruption of electrolysis or energy supply that the values ​​of the gas contents c(H2) are again above Ca(H2) or c(Ü2) are again below O3(O2).

[0198] It is therefore possible for standby mode to occur after an interruption of electrolysis or power supply even without the introduction of inert gas, for example, when CMi_2(H2) values ​​are 1 vol.% and CMi_2(H2) < Ca(H2) S 2 vol.%. Here, CMi_2(H2) and Cs(H2) denote process-dependent constants, of which CMi_2(H2) has a value less than or equal to 1 vol.% and Cs(H2) has a value less than or equal to 2 vol.%, with Cs(H2) being greater than CMi_2(H2). If the hydrogen gas content c(H2) remains below C3(H2), for example, because the interruption of electrolysis or power supply and thus the standby mode is only brief or hardly any hydrogen is released from the electrolyte in the oxygen gas separator, then no inert gas needs to be used with this approach.This means that when starting up from standby, inert gas does not first have to be blown out of the oxygen gas separator, but rather a high oxygen content is still present, allowing oxygen gas of high quality to be quickly drawn from the gas separator again.

[0199] The same applies to the oxygen gas content c(O2). Before interrupting the power supply, the oxygen gas content c(Ü2) can be increased to, for example, CMi_2(Ü2) = 99 vol.% or above by lowering the hydrogen content using one of the previously described measures. After interrupting the power supply, the introduction or purging of inert gas should only begin when the oxygen gas content falls below a third threshold value O3(O2), which is lower than CMi_2(Ü2), for example, O3(O2) = 98 vol.%. If the oxygen gas content c(Ü2) remains above O3(O2), for example, because the interruption of the electrolysis or power supply, and thus the standby phase, is only brief, or because hardly any hydrogen is released from the electrolyte in the oxygen gas separator, then no inert gas is used in the oxygen gas separator with this approach. This procedure therefore reduces inert gas consumption.

[0200] According to embodiments, the reduction of the hydrogen content g(H2) by introducing inert gas into the oxygen gas separator is started after the interruption of electrolysis or power supply when the third threshold of the hydrogen gas content for inert gas introduction or purging Cs(H2) is exceeded and / or the third threshold of the oxygen gas content for inert gas introduction or purging 03(02) is undershot, wherein P2024.1159 WO N / P2024-20 - 45 - 5 March 2026

[0201] The third threshold value Ca(H2) is smaller than the second threshold values ​​CMi_2(H2) for the hydrogen gas content, i.e., in particular, smaller than the minimum of the second threshold values ​​|CMi_2(H2)|min, and / or the third threshold value of the oxygen content O3(O2) is larger than the second threshold values ​​CMi_2(Ü2) for the oxygen gas content, in particular, larger than the maximum of the second threshold values ​​|CMi_2(O2)|max. This means that the threshold values ​​for inert gas injection Ca(H2) and O3(O2) are chosen to be stricter than or equal to the second threshold values ​​CMi_2(H2) and CMi_2(O2), respectively, so that after the interruption of electrolysis or the power supply, inert gas is introduced into the oxygen gas separator in any case to further reduce the hydrogen gas content, for example, to a fourth threshold value for inert gas purging (C H2).The introduction of the inert gas can be done stepwise, for example in the stepwise method, or continuously, for example in the flow-through method.

[0202] According to embodiments, after the interruption of electrolysis or energy supply, the hydrogen content g(H2) in the oxygen gas separator is reduced by introducing inert gas into the oxygen gas separator until a fourth threshold value of the hydrogen gas content for inert gas introduction (C4(H2)) in the oxygen gas separator and / or a fourth threshold value of the oxygen gas content (O4(O2)) in the oxygen gas separator is undershot, and / or a fourth time period t4 has elapsed. The threshold values ​​C4(H2) and / or O4(O2) are selected such that the gas contents c(H2) and c(O2) in the oxygen gas separator are outside the range for a hydrogen / oxygen oxyhydrogen reaction when one or both threshold values ​​are reached, in particular below a lower explosive limit (LEL).

[0203] The fourth time parameter t4 is determined empirically for the process, for example, whereby the time duration from t3 to t4 is chosen to be long enough so that at least one of the fourth threshold values ​​C4(H2) or O4(O2) is reached for the respective electrolysis plant. The time duration can depend in particular on the hydrogen gas content c(H2) and / or oxygen gas content c(Ü2) in the oxygen gas separator at the beginning of the inert gas introduction, the total volume, the gas volume and / or the electrolyte volume or level in the oxygen gas separator, the inflow rate qfiii of the inert gas into the oxygen gas separator, and the outflow rate q. ou The duration of the gas mixture from the oxygen gas separator may also depend on the measures taken to reduce the hydrogen content before the interruption of the power supply.

[0204] If the inert gas is introduced into the oxygen gas separator using the stepwise or continuous flow method, the respective method can be carried out until the fourth threshold value for the hydrogen gas content in the oxygen gas separator C4(H2) and / or the fourth threshold value 04(02) for the oxygen gas content in the oxygen gas separator is undershot. P2024.1159 WO N / P2024-20 - 46 - 5 March 2026

[0205] and / or the fourth time parameter t4 is reached. Instead of the fourth threshold values ​​for the hydrogen and / or oxygen gas content or the fourth time parameter, the introduction of inert gas can also be stopped when a defined inert gas content C4(lnert) is reached or exceeded. C4(lnert) is chosen such that, upon reaching C4(lnert), the gas mixture in the oxygen gas separator is outside the range for a hydrogen / oxygen oxyhydrogen reaction, in particular below a lower explosive limit (LEL).

[0206] In one iteration of the process, the inert gas injection can be carried out multiple times after the interruption of electrolysis or the power supply, i.e., repeated at a later time interval. For each iteration, a set of third and fourth threshold values ​​CB(H2), 013(O2), Ci4(H2), 04(O2) for the gas concentration(s) and / or third and fourth time parameters ti3 can be provided. The parameters of a set are each designated with the same index 1=1, 2, 3...

[0207] In another embodiment, the introduction of inert gas after an interruption of electrolysis or the power supply only occurs if inert gas is available for introduction into the oxygen gas separator and / or an inert gas supply device is available and functional. These parameters can be stored and checked, in particular, in the control device.

[0208] In a further exemplary embodiment of the process, the introduction of inert gas into the oxygen gas separator to reduce the hydrogen content in the oxygen gas separator before, during, and after the interruption of electrolysis or the power supply is not required. Instead, one or more of the previously described measures Mj for reducing the hydrogen content in the oxygen gas separator, which do not require the introduction of inert gas, are implemented. Thus, no inert gas needs to be stored. An inert gas supply device for introducing and removing the inert gas, as well as for providing the inert gas, can be omitted.

[0209] If the hydrogen gas content c(H2) cannot be reduced below the lowest of the second threshold values ​​|CMi_2(H2)|min by the measure(s) Mj, and / or the oxygen gas content c(Ü2) cannot be increased above the highest of the threshold values ​​|CMi_2(O2)|max, then the standby procedure cannot be continued as before. Depending on the measured hydrogen gas content C(H2) and / or the oxygen gas content c(Ü2) in the oxygen gas separator and / or their ratio, the at least one electrolysis unit can then remain in normal operation – the electrolysis or energy supply of the at least one electrolysis unit is therefore not interrupted. Alternatively, the at least one electrolysis unit or the entire P2024.1159 WO N / P2024-20 - 47 - 5 March 2026

[0210] The electrolysis plant can be shut down. Shutdown can be initiated by a shutdown command, which can be generated or received, for example, by the control device.

[0211] In the previously described embodiments of the process, it is possible to select the first and / or second threshold values ​​for the gas concentration(s) c(H₂), c(Ü₂), and / or their ratio in such a way that a measure to reduce the hydrogen concentration in the oxygen gas separator before interrupting the electrolysis or the energy supply does not only begin when the respective first threshold value is exceeded or fallen below, but rather begins as soon as a first threshold value is reached; and / or a measure to reduce the hydrogen concentration does not only end when the respective second threshold value is exceeded or fallen below, but rather ends as soon as a second threshold value is reached. The respective time parameters can be selected such that, instead of the reaching of the time parameter or duration, the trigger is the exceeding of a duration or time parameter.The interruption of electrolysis or energy supply can therefore also depend on reaching the second threshold and / or exceeding the second time parameter.

[0212] Similarly, for the inert gas injection after the interruption of electrolysis or the power supply, the third and / or fourth threshold values ​​for the gas concentration(s) c(H2), c(Ü2), and / or their ratio can be selected such that the inert gas injection does not begin only when the third threshold is exceeded or fallen below, but rather as soon as a third threshold is reached, and / or does not end only when the respective fourth threshold is exceeded or fallen below, but rather as soon as a fourth threshold is reached. The third and / or fourth time period can be selected such that the inert gas injection depends on exceeding the specified time period or point in time.

[0213] According to certain embodiments, temperature monitoring and / or voltage monitoring is performed during or after an interruption of the electrolysis or power supply. The temperature monitoring detects an operating temperature T. un with at least one electrolysis unit. If this temperature reaches or falls below a critical temperature TM, the electrolysis unit is cooled to an operating temperature T. un It is heated to a temperature greater than the critical temperature TM.

[0214] During stress monitoring, mechanical stress on the Ounit electrolysis unit is detected, and the electrolysis unit is shut down when a critical value is reached or falls below a certain threshold. P2024.1159 WO N / P2024-20 - 48 - 5 March 2026

[0215] Threshold value of the stress is heated until the detected stress o un The greater the critical tension is Okrit.

[0216] For example, a tension monitoring system can be provided on a tensioning device of the electrolysis unit. The mechanical tension o un It can be measured, for example, on tension rods or anchors of the tensioning device using stress sensors. A mechanical stress, or its component in the longitudinal direction of the tension rods, can be measured. The tension rods or anchors are typically guided through openings in end plates at opposite ends of a cell stack, so that they tension the end plates and the electrolysis cells of the cell stack against each other.

[0217] For both temperature and voltage monitoring, the electrolysis unit can be heated by passing electrolyte at a temperature TL through it. The temperature T of the introduced electrolyte is higher than the critical temperature Tcrit. The electrolyte can be heated directly to temperature TL, e.g., by means of pipe tracing or a flow heater, or indirectly via hot water or another hot medium that is in thermal exchange with the electrolyte via a heat exchanger.

[0218] If the electrolysis unit is a cell part stack of a cell stack, then, for example, all cell part stacks of the cell stack will be heated.

[0219] A drop in temperature within the electrolysis unit would lead to a decrease in pressure and the release of hydrogen from the electrolyte. After the electrolysis process or power supply is interrupted, the released hydrogen gas would no longer be carried out of the electrolysis unit along with oxygen, thus increasing the risk of an oxyhydrogen reaction both within the electrolysis unit and during start-up in the oxygen gas separator.

[0220] This outgassing due to a temperature drop is prevented or reduced by temperature and / or voltage monitoring and heating. Temperature and / or voltage monitoring thus enables safe standby mode and also safe start-up from standby. Furthermore, the electrolysis unit remains at a high temperature level close to the operating temperature, so that the electrolysis unit can be restarted quickly. P2024.1159 WO N / P2024-20 - 49 - March 5, 2026

[0221] To determine the critical temperature TM, above which heating begins or is not reached, it is recommended to set it to at least 65%, for example at least 70%, for example at least 75% of the maximum operating temperature T. max of the electrolysis unit. For alkaline electrolysis, especially alkaline pressure electrolysis, the critical temperature Tcrit can be, for example, above 60 °C, above 78 °C, or above 80 °C. The temperature to which the electrolysis unit is heated can be, for example, 85% to 98% of the maximum operating temperature Tmax. ma The amount is x.

[0222] The mechanical stress of the electrolysis unit depends on the temperature T. un in the electrolysis unit. The critical mechanical stress Okrit can be chosen such that it corresponds to a mechanical stress at the critical temperature Tcrit, Okrit(Tcrit) - The electrolyte can be introduced for heating, for example, until the mechanical stress o un with the electrolysis unit of a voltage of the electrolysis unit at an operating temperature T unit corresponds to an operating temperature T above 60 °C, for example above 78 °C, for example above 80 °C. un it between 85% and 98% of the maximum operating temperature T ma x

[0223] According to embodiments, a pressure p is un in at least one electrolysis unit after interruption of the electrolysis or the power supply, while the electrolysis or power supply is interrupted, at least 73%, for example at least 80%, for example at least 90% of a maximum operating pressure p ma x. These pressure ranges are maintained by heating the electrolysis unit, i.e., T un it is increased, or the electrolysis unit is restarted, i.e., electrolysis is resumed as soon as the pressure in the electrolysis unit drops faster than a critical rate and / or reaches or falls below a critical value Pcrit.

[0224] Heating can be carried out in the same way as temperature monitoring. The electrolysis unit can therefore be heated not only when a critical temperature Tcrit is reached or fallen below, but also when a critical pressure p is reached or fallen below. un It can be triggered. For heating, for example, an electrolyte whose temperature TL is higher than the critical temperature Tcrit can be passed through the electrolysis unit. With heating, not only does the temperature T increase. un it in the electrolysis unit, but also the pressure p un it in the electrolysis unit.

[0225] If a temperature increase is not possible, the electrolysis unit can be restarted by ending the interruption of the electrolysis process or the power supply to the electrolysis unit and then resuming the electrolysis. The electrolysis unit can be used in particular with P2024.1159 WO N / P2024-20 - 50 - 5 March 2026

[0226] The disclosed method allows the machine to be started after receiving a command to start. The command to start can, for example, be received or generated in the control device as soon as the pressure p is reached. un it decreases faster than a critical rate in the electrolysis unit and / or reaches a critical value p kr it falls below.

[0227] This design ensures that the pressure in the electrolysis unit does not drop too drastically after an interruption of electrolysis or the power supply, thus preventing hydrogen gas from escaping the electrolyte. Furthermore, the electrolysis unit can return from standby to normal operation as quickly as possible.

[0228] The critical pressure drop rate is generally determined using the average pressure in the electrolysis unit. In one embodiment, for electrolysis systems with separate electrolyte circuits, in addition to the pressure in the electrolysis unit, the differential pressure between the anode and cathode compartments in the electrolysis cells of the electrolysis unit can also be determined. If a critical pressure difference is exceeded, the standby mode is terminated and electrolysis is resumed.

[0229] According to embodiments, a gas volume V is used in the oxygen gas separator for the detection or determination of the hydrogen gas content C(H2) and / or the oxygen gas content c(O2) of the gas phase. me ss (sample volume) with a sampling frequency f me ss taken from the oxygen gas separator and in the gas volume V taken from it mess the hydrogen gas content C(H2) and / or the oxygen gas content c(O2) of the gas phase of the oxygen gas separator is determined, wherein the sampling frequency f me ss and / or the gas volume me The hydrogen content after the interruption of electrolysis or the energy supply is lower than before the interruption, especially if no inert gas is introduced into the oxygen gas separator to reduce the hydrogen content after the interruption. This is due to a reduction in the gas volume V. me By reducing the sampling frequency (ss) and / or the sampling frequency (fmess), a pressure drop in the oxygen gas separator is also reduced. This lowers the risk of hydrogen outgassing and thus also the risk of an oxyhydrogen reaction in the oxygen gas separator.

[0230] The gas volume V me ss and / or the sampling frequency f meThe volume can be reduced, for example, so that a maximum of 0.7 vol% of the gas phase is extracted from the oxygen gas separator per hour, for example, only a maximum of 0.5 vol% of the gas phase, for example, a maximum of 0.2 vol% of the gas phase. When reducing the gas volume, it is possible to determine both the hydrogen gas content c(H₂) and the oxygen gas content c(O₂) in the extracted gas volume Vmess and to use the procedure if no inert gas is introduced into the oxygen gas separator. P2024.1159 WO N / P2024-20 - 51 - 5 March 2026

[0231] The process is initiated depending on a ratio of these gas contents, e.g., c(H2) / c(O2) or C(O2) / C(H2), since larger changes occur in these ratios, which are easier to identify.

[0232] The measures and procedures described above are carried out, for example, before or during an interruption of the electrolysis or power supply, when the oxygen gas separator is in standby mode. However, the standby procedure can also be designed to ensure a safe restart from standby, i.e., when the interruption of the electrolysis or power supply is ended, one or more electrolysis units are started up, and oxygen is once again fed into the oxygen gas separator.

[0233] When the electrolysis unit is started up, the interruption of the electrolysis or energy supply for at least one electrolysis unit is ended, and this electrolysis unit is supplied with energy for electrolysis. The start-up occurs, for example, in response to a received control signal to end the interruption. The control signal to end the interruption of the electrolysis unit is received, in particular, while the electrolysis is interrupted for standby.

[0234] The control signal, hereinafter also referred to as a command, can be generated and / or received, for example, in the control device. The control signal can be generated within the electrolysis unit and sent and received internally, for example, when predefined thresholds are exceeded or fallen below. The control signal can also be received from outside the electrolysis unit, for example, from the control device or an external controller. Starting up one or more electrolysis units can occur for various reasons:

[0235] Firstly, at least one electrolysis unit can be started up if it reaches a critical state. Secondly, starting up at least one electrolysis unit may be necessary if the oxygen gas separator reaches a critical state. A start-up can also be triggered if the operation of a larger number of electrolysis units is required. This could be the case, for example, if the available electrical power for electrolysis increases or a higher hydrogen gas throughput is required, thus necessitating an increase in the electrolysis gas production rate. P2024.1159 WO N / P2024-20 - 52 - 5 March 2026

[0236] As previously described, restarting an electrolysis unit due to a critical condition of the electrolysis unit can occur, for example, when the pressure p unit decreases faster than a critical rate in the electrolysis unit and / or reaches a critical value p kr it reaches or falls below. In alkaline pressure electrolysis, this critical pressure p kr it 73%, for example 80%, for example 90% of the maximum operating pressure p ma The amount is x.

[0237] Critical conditions in an electrolysis unit can also include a gas composition with an increased risk of hydrogen explosion in the electrolysis unit, or a cooling of the temperature T. un it at or below the critical temperature T kr it, for example, if no temperature monitoring with heating is provided, or if this is faulty and no heating takes place, and / or if a critical stress level is not reached o k A critical gas composition can occur, for example, if the hydrogen gas content on the anode side is c ano(H2) in an electrolysis unit reaches or exceeds a certain value Ckrit_ano(H2), if the anode-side oxygen gas content Cano(O2) in an electrolysis unit reaches or falls below a certain value Ckrit_ano(O2), if the cathode-side hydrogen gas content Ckato(H2) in an electrolysis unit reaches or falls below a certain value Ckrit_kato(H2) and / or if the cathode-side oxygen gas content Ckato(O2) in an electrolysis unit reaches or exceeds a certain value Ckrit_kato(O2).

[0238] For the standby procedure, at least one of these state parameters p is used. un it, Tunit, Okrit, Cano(H2), c anoThe values ​​of (O2), Ckato(H2), and / or Ckato(O2) are detected and compared with the critical threshold of the state parameter to determine whether a critical state exists. This comparison can be performed by the control device, which, if a critical state is detected, then generates a command to start the respective electrolysis unit that is in a critical state. If several of the electrolysis unit state parameters, e.g., the pressure p, are affected, the system will automatically start the electrolysis unit. un If the temperature and the temperature Tunit are monitored for a critical state, a critical state already exists if one of these state parameters reaches or exceeds or falls below its critical threshold, e.g. Punit^Pcrit or T un it t— Tkrit ■

[0239] The critical thresholds of the state parameters can, for example, be chosen to maximize the duration of the electrolysis or standby power supply interruption. In one exemplary implementation of the method, the critical state parameters can be determined depending on the design and / or other state parameters of the respective electrolysis unit, such as the maintenance status, age, number of operating hours, and / or the number of electrolysis or power supply interruptions of the respective electrolysis unit. P2024.1159 WO N / P2024-20 - 53 - 5 March 2026

[0240] If, before the electrolysis or standby power supply is interrupted, several electrolysis units are operating alternately, then in one embodiment of the method at least one threshold value for starting the electrolysis units in alternating operation can be chosen more strictly than a critical threshold value for starting the electrolysis units from standby:

[0241]

[0242] This ensures that the electrolysis units are kept in such a favorable condition during alternating operation that standby mode does not have to be terminated immediately due to a critical condition, but can be safely maintained for a certain period of time. During alternating operation, an electrolysis unit can, for example, be started up as soon as it reaches a pressure pwi_o. n of 80% of the maximum operating pressure p ma x is reached, while a critical pressure p is maintained in standby mode. krIt may still be permissible to operate at 73% of the maximum operating pressure. The electrolysis or energy supply of the electrolysis unit can therefore remain safely interrupted for standby until its pressure p un it from 80% to 73% of the maximum operating pressure p ma x has fallen before the standby mode is terminated due to the critical pressure condition and the electrolysis unit is started.

[0243] In an alternative implementation of the procedure, the threshold values ​​for alternating operation are as strict or less strict than the critical state parameters for starting an electrolysis unit from standby:

[0244]

[0245] This can be particularly useful if measures are taken before and / or after interrupting electrolysis or the standby power supply to improve the condition of the electrolysis units. One such measure could be heating the electrolysis unit when the critical pressure pcrit, critical temperature Tcrit, and / or critical stress Ocrit are reached or fall below the critical values. Standby mode then continues as long as the heating process raises the pressure, temperature, and / or stress above the critical values ​​pcrit. kr it, TM and / or Okrit is reached. Standby will only end when the critical condition can no longer be resolved by heating. TheP2024.1159 WO N / P2024-20 - 54 - March 5, 2026

[0246] The electrolysis unit is only started up, for example, when the critical pressure p is reached. krThe critical temperature Tcrit and / or critical stress Okrit is reached or fallen below for a specific time period tcrit. The time period tcrit can be defined such that, within the time period tcrit, after the respective critical value pcrit, Tcrit, and / or Okrit has been reached by heating the electrolysis unit, a pressure, temperature, and / or stress exceeding the respective critical threshold pcrit, Tcrit, Okrit is achieved.

[0247] Standby mode can be terminated when an electrolysis unit reaches a critical state and is started up. Starting up an electrolysis unit may also be necessary if the oxygen gas separator reaches a critical state. This start-up can be triggered by a start-up command. Such a command can be generated, for example, when a critical threshold value Ccrit(H2) of the hydrogen gas content in the oxygen gas separator is exceeded, or when the ratio of hydrogen gas content to oxygen gas content c(H2) / c(O2) in the oxygen gas separator exceeds a critical ratio Tcrit. If inert gas is introduced into the oxygen gas separator after an interruption of the electrolysis or power supply, the start-up command can also be generated and / or received if the fourth threshold value C(H2) is not undershot by the fourth time interval t4.Alternatively, if no inert gas has been or is being introduced into the oxygen gas separator, i.e., only oxygen and hydrogen gas are present in the gas phase of the oxygen gas separator, a critical threshold value Ccrit(02) of the oxygen gas content in the oxygen gas separator may fall below a critical threshold value Ccrit(02) or the ratio of oxygen gas content to hydrogen gas content c(O2) / c(H2) in the oxygen gas separator may fall below a critical ratio 1 / rknt.

[0248] Alternatively or additionally, it can be stipulated that a threshold value for another state parameter of the oxygen gas separator and / or a time parameter is reached, exceeded, or fallen below. For example, a lower limit of the temperature and / or pressure in the oxygen gas separator and / or in the hydrogen gas separator can be reached, thereby triggering a start-up.

[0249] A start-up from standby can also be triggered if a larger number of electrolysis units are required for electrolysis operation. This might be the case, for example, if the available electrical power for electrolysis increases or a higher throughput of electrolysis gas (hydrogen and / or oxygen) is required, thus necessitating an increased production rate. The hydrogen and / or oxygen throughput can be requested, for example, via user input on a user interface. P2024.1159 WO N / P2024-20 - 55 - March 5, 2026

[0250] or determined by the control device, whereby the amount of gas can be determined, for example, depending on the consumption of the respective electrolysis gas.

[0251] If several electrolysis units are connected to the oxygen gas separator, only the number of electrolysis units necessary to provide a specific amount of hydrogen and / or oxygen, e.g., as requested by the user, and / or to utilize a specific available electrical power for electrolysis, will be activated.

[0252] The start-up process can also be initiated by a start-up command. This command can be generated and / or received, for example, by the control device. The selection of which electrolysis units are started can depend on a time parameter, gas content, and / or state parameter of the electrolysis units. This selection can be made by the control device or be predefined.

[0253] For example, at least one electrolysis unit can be started up in which a certain hydrogen gas concentration has been reached or exceeded and / or a certain oxygen gas concentration has been reached or fallen below. Similar to alternating operation, electrolysis units with an unfavorable condition, such as a high hydrogen gas concentration on the anode side, can be started up first. ano (H2) and / or a low oxygen gas content c ano (O2) is present and / or a high oxygen gas content Ck on the cathode side a to(O2) and / or low hydrogen gas content Ck a to(H2) is present.

[0254] For example, electrolysis units of an oxygen gas separator can be selected based on their maximum or minimum state parameter relative to all electrolysis units of the oxygen gas separator and / or the electrolysis plant. These can be, in particular, electrolysis units with the lowest oxygen gas content |c on the anode side. ano (O2)|min exhibit or have the highest hydrogen gas content | c a no(H2)|max and / or the highest oxygen gas content on the cathode side |Ck a t o (O2)|max or the lowest, in particular minimum, hydrogen gas content |Ckato(H2)|min. However, only electrolysis units whose gas composition is within a safe range on both the anode and cathode sides may be used, in particular below the lower explosive limit for a hydrogen-oxygen oxyhydrogen reaction (LEL).

[0255] The same applies to the hydrogen and oxygen gas content of an electrolysis unit if the electrolysis unit is connected to only a single oxygen gas separator. An electrolysis unit is only started up if the gas composition on the anode side meets the requirements of P2024.1159 WO N / P2024-20 - 56 - March 5, 2026.

[0256] and is located on the cathode side outside an explosion range for a hydrogen / oxygen oxyhydrogen mixture.

[0257] If the electrolysis unit cannot be started, for example due to a defect, the oxygen gas separator can be shut down. In electrolysis systems where several electrolysis units are connected to a single oxygen gas separator for introducing oxygen from the electrolysis process, it should first be checked whether another electrolysis unit can be started as a replacement. The oxygen gas separator should only be shut down if no other electrolysis unit can be started as a replacement.

[0258] The restart, i.e., the end of the interruption of the electrolysis or energy supply, only occurs in all cases if the hydrogen gas content c(H2) in the oxygen gas separator is below a value CSTOP(H2) for an emergency shutdown. The value CSTOP(H2) for the emergency shutdown is greater than the critical threshold value Ckrit(H2) of the hydrogen gas content for the restart. Provided that no inert gas has been or will be introduced into the oxygen gas separator, start-up can also take place if the oxygen gas content c(Ü2) is above a value CSTOP(O2) for an emergency shutdown, the ratio of hydrogen gas content to oxygen gas content C(H2) / C(O2) in the oxygen gas separator is below a ratio TSTOP for an emergency shutdown, and / or the ratio of oxygen gas content to hydrogen gas content C(O2) / C(H2) in the oxygen gas separator is above a ratio 1 / rsTop for an emergency shutdown.The value CSTOP(O2) for emergency shutdown is less than the critical threshold value Ckrit(O2) for startup. The value TSTOP for emergency shutdown is greater than the critical value rkrit for startup. The gas concentrations or ratios of gas concentrations for emergency shutdown are each outside the range for a hydrogen / oxygen oxyhydrogen reaction in the oxygen gas separator, in particular below the lower explosive limit (LEL).

[0259] For example, a further development of the standby procedure may include the following: to ensure safe restart after the interruption of electrolysis or the power supply, i.e., when the electrolysis unit is again supplied with energy for electrolysis, the hydrogen gas content c(H2) and / or the oxygen gas content c(O2) in the oxygen gas separator are monitored, and an emergency shutdown command is triggered or generated if the hydrogen gas content c(H2) exceeds a threshold value CSTOP(H2) for the emergency shutdown, for example, CSTOP(H2) = 4 vol.%. Alternatively or additionally, if no inert gas has been or is being introduced into the oxygen gas separator, the emergency shutdown command can be triggered if the oxygen gas content c(O2) reaches a critical value CSTOP(O2). P2024.1159 WO N / P2024-20 - 57 - 5 March 2026

[0260] e.g. CSTOP(O2)=96 vol.%, falls below this value, the ratio of hydrogen gas content to oxygen gas content C(H2) / C(O2) in the oxygen gas separator exceeds a ratio TSTOP of e.g. 0.041, or the ratio of oxygen gas content to hydrogen gas content c(O2) / c(H2) in the oxygen gas separator falls below a critical ratio 1 / rsTop.

[0261] According to embodiments, after the power supply interruption, at least one electrolysis unit is started up with an increased or steep electrolysis current ramp. An increased electrolysis current ramp is a ramp that is greater than the ramp during pressureless start-up or initial commissioning of the system or electrolysis unit. For alkaline electrolysis, this ramp is typically < 0.5 I-max% / s based on the maximum electrolysis current l. max. A steep or elevated electrolysis current ramp can therefore be, for example, a ramp whose gradient > 0.6% lmax / s (percent per second) relative to the maximum electrolysis current l ma x is. Preferably, the ramp slope can also be >2% or >10% of the maximum electrolysis current, preferably even >15% of the maximum electrolysis current per second. For alkaline pressure electrolysis with a maximum electrolysis current l ma x of 10 kA, this could be, for example, an electrolysis current ramp in a range of 60 A / s to 1500 A / s or more, e.g., a ramp of >200 A / s, >500 A / s, >1000 A / s or >1500 A / s.

[0262] For example, the electrolysis current ramp starts when the initial electrolysis current Io > 0 A, for example, when the electrolysis current is >10% of the maximum electrolysis current l ma x or, for example, at >20% or >30% of the maximum electrolysis current l ma x.

[0263] In another exemplary embodiment, the at least one electrolysis unit that is started up is operated for a certain time with maximum electrolysis current l ma x operated, i.e. the electrolysis current is operated up to the maximum electrolysis current l ma x is increased. This allows the electrolysis unit and the oxygen gas separator to be supplied with oxygen gas very quickly, so that the pressure p un The oxygen production rate in the electrolysis unit and the gas separator is rapidly increased, thereby preventing further outgassing of hydrogen gas. This is achieved through the increased oxygen production rate during full-load operation at l ma In addition, oxygen is produced in at least one electrolysis unit, which has a lower proportion of hydrogen than in part-load operation, thus also quickly improving the gas quality in the oxygen gas separator.

[0264] In one exemplary further development of the process, the oxygen gas separator and the associated electrolysis unit(s) are shut down in response to a shutdown command. The shutdown command can depend on a P2024.1159 WO N / P2024-20 - 58 - 5 March 2026

[0265] The shutdown command can be triggered by user input, a time parameter, and / or at least one state parameter of the electrolysis plant, in particular a state parameter of the at least one electrolysis unit and / or the oxygen gas separator. The shutdown command can be generated internally, for example by the control device, or received externally. For example, a user request to shut down may be received, triggering a shutdown. Exceeding a threshold value for the hydrogen gas content and / or a time period after the interruption of electrolysis or the power supply, such as the fourth threshold value C4(H2) of the hydrogen gas content, the fourth time period t4 for the introduction of the intergas, and / or the time tcrit during the heating of an electrolysis unit, can also trigger the shutdown command.

[0266] For example, shutdown, in particular the cessation of inert gas injection, is only triggered if the hydrogen gas content c(H2) in the oxygen gas separator is less than a threshold value for an emergency shutdown CSTOP(H2), or if the ratio of hydrogen gas content to oxygen gas content c(H2) / c(O2) in the oxygen gas separator is below a ratio TSTOP for an emergency shutdown. This occurs, for example, when the gas quality in the oxygen gas separator is sufficiently high, allowing the shutdown to be carried out safely without an oxyhydrogen reaction. If no inert gas is introduced into the oxygen gas separator, shutdown can also occur if the oxygen gas content c(Ü2) is above a value CSTOP(O2) for an emergency shutdown, or if the ratio of oxygen gas content to hydrogen gas content c(O2) / c(H2) in the oxygen gas separator is above a ratio 1 / rsTop for an emergency shutdown. The gas contents, respectively, are determined by the following parameters:The gas concentration ratios for the emergency shutdown are in each case outside the range for a hydrogen / oxygen oxyhydrogen reaction, in particular below the lower explosive limit (LEL).

[0267] To shut down the system, any oxygen supply from all electrolysis units connected to the oxygen gas separator is stopped. This can be achieved by stopping the electrolysis process or the power supply to the respective electrolysis unit, thus preventing oxygen production in that unit, and / or by diverting the oxygen from the electrolysis unit so that no more oxygen enters the oxygen gas separator. Additionally, the operating pressure in the oxygen gas separator is reduced to ambient pressure, and any inert gas injection is stopped.

[0268] In alkaline pressure electrolysis, the pressure reduction to ambient pressure is achieved, for example, with a low pressure reduction ramp, such as a pressure reduction ramp of less than 0.4 bar per second, for example, with a pressure reduction ramp P2024.1159 WO N / P2024-20 - 59 - 5 March 2026

[0269] of less than 0.1 bar per second. The pressure reduction ramp can be set via a defined flow rate at the gas outlet valve of the oxygen gas separator.

[0270] If electrolysis or the power supply to the electrolysis unit is stopped, the electrolysis unit can also be brought to ambient pressure, for example, by keeping it connected to the oxygen gas separator while the pressure in the separator is reduced. When electrolysis or the power supply to the electrolysis unit is stopped, other functions or devices of the electrolysis unit or the electrolysis system can also be terminated or switched off. For example, temperature monitoring or voltage monitoring can also be stopped, and the electrolysis unit can be brought to ambient temperature.

[0271] Embodiments of the disclosure relate to an electrolysis plant. The electrolysis plant is suitable for carrying out the process described above. It has at least one oxygen gas separator to which at least one electrolysis unit is connected, such that during electrolysis, oxygen gas is introduced from the electrolysis unit into the oxygen gas separator. The electrolysis unit can be a cell stack or a cell sub-stack in which several electrolysis cells are electrically and hydraulically connected to one another for electrolysis. For electrolysis, the electrolysis unit is connected to a power supply device that provides energy for the electrolysis.

[0272] The electrolysis system is also designed to detect the hydrogen gas content c(H₂) and / or the oxygen gas content c(O₂) in the oxygen gas separator. Furthermore, it is designed to trigger an interruption of the power supply to at least one electrolysis unit, thereby halting the electrolysis process. For example, it can also be designed to reduce the hydrogen content g(H₂) in the oxygen gas separator before and / or after the interruption of the electrolysis or power supply. The reduction of the hydrogen content can depend on the detected hydrogen gas content C(H₂) in the oxygen gas separator, the detected oxygen gas content c(O₂) in the oxygen gas separator, and / or on a ratio of these gas contents to each other, e.g., C(H₂) / C(O₂) or C(O₂) / C(H₂).

[0273] For example, the electrolysis plant is equipped with a control device designed to trigger the interruption and / or termination of the electrolysis or energy supply to at least one electrolysis unit, depending on the hydrogen gas content c(H2) in the oxygen gas separator, the oxygen gas content c(Ü2) in the oxygen gas separator, and / or a ratio of these gas contents to each other. Furthermore, the P2024.1159 WO N / P2024-20 - 60 - 5 March 2026

[0274] The electrolysis plant, in particular the control device, comprises a timer device configured to monitor the time parameters tvo, INO, ti, IMM or tMik_i (i=1,2,3; k=1,2,3...), t2, trvii_2 or tMik_2, t3, t4, twi_on, tw2_on and / or tkrit. The control device can be configured to trigger and / or terminate the reduction of the hydrogen content in the oxygen gas separator depending on at least one of these time parameters. Additionally or alternatively, it can be configured to trigger the interruption and termination of the power supply depending on at least one of the time parameters.

[0275] The oxygen gas separator is designed to separate a stream of oxygen gas produced by electrolysis, along with electrolyte introduced into the oxygen gas separator from the electrolysis unit, into a liquid phase and a gas phase within a separation chamber of the oxygen gas separator. The hydrogen gas content c(H₂) and / or the oxygen gas content c(Ü₂) in the oxygen gas separator are determined for this gas phase. For this purpose, the electrolysis system, and in particular the oxygen gas separator, can include a gas measurement system designed to detect the hydrogen gas content c(H₂) and / or the oxygen gas content c(Ü₂) of the gas phase of the oxygen gas separator. The gas content(s) can be measured either within the oxygen gas separator itself or in a gas volume. me ss of the gas phase, which is taken from the oxygen gas separator.

[0276] Alternatively or additionally, the electrolysis plant can be configured to indirectly determine the hydrogen gas content C(H₂) and / or the oxygen gas content c(Ü₂). For example, if no inert gas is present in the oxygen gas separator, the oxygen gas content c(Ü₂) can be calculated from the hydrogen gas content c(H₂). Furthermore, the gas measurement system can be configured to detect the inert gas content c(lnert) of the gas phase in the oxygen gas separator.

[0277] In addition to the gas measuring system, the electrolysis plant, in particular the oxygen gas separator, may also have a device for level determination, which is designed to determine, in particular to measure, the level of the liquid phase, i.e. the level of separated electrolyte, in the oxygen gas separator.

[0278] The flow of oxygen gas and electrolyte is typically supplied to the oxygen gas separator from the electrolysis unit via an oxygen inlet valve located on an oxygen supply line between the electrolysis unit and the oxygen gas separator. In addition to this inlet valve, the oxygen gas separator also has an electrolyte drain valve through which the separated electrolyte can be recirculated from the oxygen gas separator into the electrolysis unit. Before the electrolyte is returned to the electrolysis unit, P2024.1159 WO N / P2024-20 - 61 - 5 March 2026

[0279] The electrolyte can be processed in an electrolyte preparation device. This device can be configured, for example, to collect the electrolyte from the oxygen gas separator, temper it, degas it, and / or adjust it to a specific electrolyte concentration, particularly an increased concentration of chlorine (Cl), e.g., by adding alkali salts and / or more concentrated electrolyte. In the electrolyte preparation device, the electrolyte from the oxygen gas separator can also be mixed with electrolyte from a hydrogen gas separator of the electrolysis plant. The mixed electrolyte can then be divided into two fractions (divided-circle process), one of which is supplied to the anode compartments and the other to the cathode compartments of the electrolysis cells in the electrolysis unit.

[0280] However, systems are also possible in which the electrolyte streams from the gas separators are not mixed. The electrolyte from the oxygen gas separator is fed exclusively to the anode compartments of the electrolysis cells, and the electrolyte from the hydrogen gas separator is fed exclusively to the cathode compartments of the electrolysis cells. The electrolyte streams thus circulate in separate circuits ("separate circuits" process) within the electrolysis system, without mixing. Before being introduced into the electrolysis cells of the electrolysis unit, the electrolyte streams can be treated separately. For this purpose, for example, two separate electrolyte treatment devices can be provided: one for the electrolyte from the oxygen gas separator and a second for the electrolyte from the hydrogen gas separator.

[0281] Alternatively, cross-flow electrolysis plants are also possible, as known, for example, from EP 4004259 A1. In this system, the electrolyte streams are circulated in separate circuits without mixing within the electrolysis plant, similar to the separated-circuit process. However, the electrolyte from the oxygen gas separator is fed to the cathode compartments of the electrolysis cells, and the electrolyte from the hydrogen gas separator is fed to the anode compartments of the electrolysis cells. The electrolyte streams can be treated in electrolyte conditioning devices before being introduced into the electrolysis unit.

[0282] Alternatively or additionally to degassing and / or temperature control in an electrolyte preparation device, the electrolysis plant may also include a separate degassing unit for degassing the electrolyte and / or a separate temperature control unit for maintaining the electrolyte temperature, particularly for heating during temperature and / or stress monitoring. Furthermore, the oxygen gas separator and / or the hydrogen gas separator may also be configured to adjust the electrolyte concentration, particularly an increased concentration of chlorine chloride (Cl), in the separated electrolyte. P2024.1159 WO N / P2024-20 - 62 - 5 March 2026

[0283] In some configurations, the oxygen gas separator can be designed as a gravity separator, for example, as a gas bubble separator, in which oxygen gas bubbles rise due to the density difference between the electrolyte and the oxygen gas and are thus separated from the electrolyte. The hydrogen gas separator of the electrolysis plant can also be designed as a gravity separator, in particular as a gas bubble separator. The hydrogen gas separator can be connected to the electrolysis unit via a hydrogen supply line. A hydrogen inlet valve can be arranged on the hydrogen supply line, which can be used to control, in particular to interrupt, the introduction of hydrogen from the electrolysis unit into the hydrogen gas separator.In some configurations, the oxygen gas separator and the hydrogen gas separator can be hydraulically coupled to each other, for example via at least one pendulum line at the bottom of their separation chambers, where the separated electrolyte collects.

[0284] In one example, the electrolysis plant is equipped with an inert gas supply device designed to introduce inert gas into the oxygen gas separator. The inert gas supply device can have an inert gas inlet line connected to an inert gas source, such as an inert gas tank. It can also have an inert gas inlet valve designed to supply the inert gas from the inert gas inlet line to the oxygen gas separator. The inert gas can be introduced directly into the separation chamber of the gas separator. Alternatively, the inert gas can be supplied to the oxygen gas separator via the oxygen inlet line, which carries the oxygen from the electrolysis unit to the oxygen gas separator. In this case, the inert gas inlet valve is located on an inert gas inlet line leading to the oxygen inlet line.In both cases, the inert gas can be introduced by introducing it into the gas volume of the gas phase in the oxygen gas separator. Alternatively or additionally, it is also possible to introduce the inert gas into the liquid phase in the oxygen gas separator, so that the liquid phase is permeated and degassed by the inert gas.

[0285] In addition to the inert gas inlet valve, the inert gas supply device also has a gas outlet valve designed to discharge the gas mixture from the oxygen gas separator. The gas outlet valve can, for example, be positioned on a discharge line on the oxygen gas separator. The inert gas inlet valve and gas outlet valve can be controlled by the control device. The control device can be configured, in particular, to control the opening and closing of the inert gas inlet valve and the gas outlet valve for the stepwise or continuous flow process, depending on the hydrogen gas content C(H₂), oxygen gas content c(O₂), a ratio of these gas contents, a minimum time period IMM, tMi_2 and / or t3, U, and a flow rate q. f in by the inert gas-P2024.1159 WO N / P2024-20 - 63 - March 5, 2026

[0286] inlet valve and / or a flow rate q out is controlled by the gas outlet valve, an electrolyte level or volume in the oxygen gas separator and / or a pressure in the gas phase in the oxygen gas separator.

[0287] In addition to sensors for measuring these state parameters, the electrolysis plant may also have other measuring systems or control devices, in particular a measuring system for determining the operating pressure p. un it and the operating temperature T un with at least one electrolysis unit, a measuring system for determining the electrolyte concentration, a measuring and control system for determining and controlling the electrolysis current I and / or a measuring system for determining the voltage o unThe electrolysis unit, in particular a tensile stress on at least one tie rod and / or tie rod of a tensioning device of the electrolysis unit, must be present. The state parameters measured by the respective system can be stored in the control device, i.e., transmitted to it from the systems, for example continuously.

[0288] In some embodiments, the control device may have several control units, e.g.:

[0289] a gas control device for regulating the electrolysis gas flows (H2, O2), the pressure and temperature of the electrolysis gases, and the distribution of inert gas (e.g., N2) into the oxygen gas separator and / or hydrogen gas separator, in particular the flow rate and pressure of inert gas into the oxygen gas separator and / or hydrogen gas separator and the gas mixture from the oxygen gas separator and / or hydrogen gas separator.

[0290] a liquid control device for regulating the flow rate and distribution of cooling water and deionized water for electrolyte preparation at the at least one cell stack and, if applicable, other units of the electrolysis plant,

[0291] an electrolyte control device for regulating the temperature, concentration, flow rate and distribution as well as monitoring the pressure of the electrolyte to the at least one electrolysis unit,

[0292] an operating control device for regulating the operating temperature and operating pressure in the electrolysis unit and / or

[0293] a control device for controlling the energy supply of the at least one electrolysis unit, in particular the electrolysis current and / or the electrolysis voltage, and if applicable, the distribution of the energy to several electrolysis units.

[0294] In one embodiment, the electrolysis system is equipped with a user interface via which a user can trigger the signal to interrupt standby, start from standby, or shut down from standby with a user input, and / or a P2024.1159 WO N / P2024-20 - 64 - 5 March 2026

[0295] The system can request a specific quantity of hydrogen gas and / or oxygen gas. The command can be received by the control device. The user interface can also be configured to allow a user to select the procedure for reducing the hydrogen content in the oxygen gas separator from at least one list displayed on the interface and send it to the control device. The list can include at least one measure (Mj) for reducing the hydrogen content in the oxygen gas separator.

[0296] Further advantages, features, and developments will emerge from the following examples, which are explained in conjunction with the figures. Identical, similar, and similarly effective elements can be marked with the same reference symbols across different figures.

[0297] Fig. 1 shows an electrolysis plant with a schematically depicted electrolysis unit and its tensioning device,

[0298] Fig. 2 shows an electrolysis plant with several schematically represented electrolysis units,

[0299] Fig. 3 shows the values ​​for a lower explosion limit depending on the content of hydrogen gas in mol% in a hydrogen / oxygen gas mixture.

[0300] Fig. 4 Explosion ranges and limits for hydrogen / oxygen / nitrogen gas mixtures,

[0301] Fig. 5 in a flowchart shows an example of a sequence for a standby procedure before the interruption of electrolysis or the power supply for standby.

[0302] Fig. 6 in a flowchart shows another example of a process for a standby procedure before the interruption of electrolysis or the power supply for standby.

[0303] Fig. 7 in a flowchart shows another example of a process for a standby procedure before the interruption of electrolysis or the standby power supply.

[0304] Fig. 8 in a flowchart shows an example of a process for temperature monitoring and / or stress monitoring, P2024.1159 WO N / P2024-20 - 65 - 5 March 2026

[0305] Fig. 8 shows the continuation of the standby process from Figure 5, 6 or 7 after the interruption of electrolysis or the power supply,

[0306] Fig. 10 shows the continuation of the standby process from Figure 9 after the interruption of electrolysis or the power supply, and

[0307] Fig. 11 shows an overview of the control of several electrolysis units for standby.

[0308] Figure 1 shows a schematic view of an electrolysis plant 400. The electrolysis plant 400 comprises at least one electrolysis unit 1 with a clamping device shown schematically in Figure 1. The electrolysis unit 1 is connected to an oxygen gas separator 2, which is equipped with a gas measuring system. The gas measuring system detects the hydrogen gas content c(H₂) and / or oxygen gas content c(Ü₂) of the gas phase of the oxygen gas separator. It can also measure an inert gas content c(lnert) of the gas phase.

[0309] The connection between electrolysis unit 1 and oxygen gas separator 2 is made via an oxygen supply line with an oxygen inlet valve 9A, through which the flow of oxygen and electrolyte from electrolysis unit 1 to oxygen gas separator 2 can be adjusted, in particular interrupted. The oxygen is typically taken from the anode side of the electrolysis cells of electrolysis unit 1 and contains both oxygen and electrolyte.

[0310] The electrolysis unit 1 can consist of a single unit comprising all the cells of a cell stack 1, or it can consist of cell sub-stacks, each of which can operate independently of the others. The cell sub-stacks of a cell stack can, for example, be electrically isolated from one another and connected in parallel. Furthermore, the electrolysis system can have several electrolysis units 1, as illustrated by example in Figure 2. These can be connected individually or as a group to the oxygen gas separator 2.

[0311] The oxygen gas separator 2 is designed to separate the oxygen gas and the electrolyte from each other and has a gas outlet valve 11A through which the separated oxygen can be withdrawn from the oxygen gas separator 2. The oxygen gas separator 2 is further connected to an electrolyte recovery arrangement 200 via an electrolyte drain line and an electrolyte drain valve 12A. This arrangement includes an electrolyte recovery device 7, anP2024.1159 WO N / P2024-20 - 66 - 5 March 2026

[0312] the separated liquid electrolyte can be discharged. From the electrolyte preparation device 7, electrolyte is fed back to the electrolysis unit 1 along with water from a water supply 8, i.e., recirculated. The water supply 8 can provide distilled / deionized water for electrolyte preparation. By reducing the amount of water supplied, a higher electrolyte concentration (CL) can be achieved in the electrolyte preparation device 7. The electrolyte concentration can also be adjusted by adding electrolyte with a higher concentration. If an electrolysis plant does not have an electrolyte preparation device 7, it can also be provided to prepare the electrolyte in a gas separator, the oxygen and / or hydrogen gas separator, as in the example shown in Figure 2, i.e., by adding water and, if necessary, lye or its salt.

[0313] In the electrolyte preparation device 7 of Figure 1, the electrolyte is also heated to provide it for heating the electrolysis unit 1 to a specific temperature. If the electrolysis plant does not have an electrolyte preparation device 7, a separate temperature control unit can be provided in which the electrolyte is heated, as shown, for example, in Figure 2. The temperature control unit can be, for example, a plate heat exchanger or a tube heater.

[0314] In the electrolyte preparation device 7, of Figure 1, the electrolyte can also be degassed and brought to a specific pressure in a pressure-controlled container of the electrolyte preparation device 7, in particular to an operating pressure p. unwith the electrolysis unit 1. For this purpose, an inert gas supply line 22 can be provided. Excess gas can be discharged from a pressure-controlled container of the electrolyte preparation device 7 via a blow-off valve 20C. Alternatively, the electrolyte can be degassed via blow-off valves 20A, 20B in the bypass lines, which are arranged at a highest point of the respective bypass line. As an alternative to degassing, a degassed electrolyte can also be supplied to the recirculating electrolyte, or the recirculated electrolyte can be replaced by a degassed electrolyte, which is then supplied to the electrolysis unit 1.

[0315] During electrolysis, the electrolyte is circulated in a closed loop. It is drawn from electrolysis unit 1 along with the produced oxygen gas, fed into the oxygen gas separator, separated from the oxygen gas there, processed, and returned to electrolysis unit 1. However, if no oxygen is produced, it is also possible to circulate the electrolyte without passing it through the oxygen gas separator 2. For this purpose, the electrolyte drain line and oxygen supply line are connected via a bypass line and a bypass valve 19A. The electrolyte drain valve 12A and the oxygen inlet valve 9AP2024.1159 WO N / P2024-20 - 67 - March 5, 2026

[0316] These are located between bypass valve 19A and oxygen gas separator 2. The electrolysis unit 1 can be isolated from oxygen gas separator 2 via oxygen inlet valve 9A and bypass valve 19A by closing these valves. If bypass valve 19A is opened and electrolyte drain valve 12A is closed, the electrolyte can be circulated through the bypass line without passing through oxygen gas separator 2.

[0317] The electrolyte supply to the electrolysis unit 1 can be controlled via an electrolyte inlet valve 18, which is arranged between the electrolyte preparation device 7 and the electrolysis unit 1. By closing the electrolyte inlet valve 18, the electrolysis unit 1 can be isolated from the electrolyte preparation device 7. If no electrolyte preparation device 7 with an electrolyte inlet valve 18 is provided, the electrolyte supply from the oxygen gas separator 2 to the electrolysis unit 1 can also be controlled via the electrolyte drain valve 12A and the bypass valve 19A.

[0318] The electrolysis unit 1 is also connected to a hydrogen gas separator 3 via a hydrogen supply line. A hydrogen inlet valve 9B is arranged on the hydrogen supply line, allowing the flow rate of hydrogen and electrolyte into the hydrogen gas separator 3 to be adjusted. The hydrogen is typically drawn from the cathode side of the electrolysis cells of the electrolysis unit 1 and contains both hydrogen and electrolyte. In the hydrogen gas separator 3, the hydrogen is separated from the electrolyte and withdrawn from the system via a gas outlet valve 11B. Electrolyte is withdrawn from the hydrogen gas separator 3 via an electrolyte drain valve 12B and fed back to the electrolyte preparation device 7 and then to the electrolysis unit 1. Similar to the oxygen gas separator, a bypass valve 19B can also be provided on a bypass line between the hydrogen inlet valve 9B and the electrolyte drain valve 12B.The bypass line connects the hydrogen supply line and the electrolyte drain line of the hydrogen gas separator. Closing the hydrogen inlet valve 9B and electrolyte drain valve 12B isolates the electrolysis unit 1 from the hydrogen gas separator 3. If no electrolyte conditioning device 7 and electrolyte inlet valve 18 are provided, the electrolyte supply from the hydrogen gas separator 3 to the electrolysis unit 1 can also be controlled via the electrolyte drain valve 12B on the hydrogen gas separator 3.

[0319] In the embodiment shown in Figure 1, the electrolyte is supplied to and removed from the cathode and anode compartments of the electrolysis cells in separate electrolyte fractions. The removed electrolyte fractions are separated from the electrolysis gases in the gas separators 2 and 3 and subsequently, for example, in a common tank of the electrolyte recovery unit 7, P2024.1159 WO N / P2024-20 - 68 - March 5, 2026

[0320] mixed together before two fractions are formed again from the mixed electrolyte, one of which is fed back to the anode compartments and the other to the cathode compartments (also known as the "divided circles" process).

[0321] Alternatively, arrangements are also possible in which the electrolyte preparation takes place without mixing, and the electrolyte streams from the oxygen gas separator 2 and the hydrogen gas separator 3 are circulated in separate circuits within the electrolysis system (also known as "separate circuits" or "separate circuits"). In this case, the electrolyte from the oxygen gas separator 2 is fed unmixed to the anode compartments of the electrolysis cells, and the electrolyte from the hydrogen gas separator 3 is fed unmixed to the cathode compartments of the electrolysis cells. The electrolysis system can also be designed for cross-flow electrolyte circulation. In this case, the electrolyte from the oxygen gas separator 2 is fed unmixed to the cathode compartments of the electrolysis cells, and the electrolyte from the hydrogen gas separator 3 is fed unmixed to the anode compartments of the electrolysis cells.

[0322] The gas separators 2, 3 can be single- or multi-stage gravity separators, in particular gas bubble separators. They can be hydraulically coupled to each other, for example via at least one shuttle line. The gas separators 2, 3 are connected to each other via a liquid column according to the principle of communicating vessels or tubes, allowing an exchange of the separated electrolyte between the gas separators 2, 3. However, it is also possible for the gas separators 2, 3 to be independent, i.e., not hydraulically connected to each other.

[0323] A power connection 4 for a power supply E is shown schematically in Figure 1. Here, the electrical power input to the electrolysis system can be monitored. The entire electrolysis system is controlled by a control unit 5, which is shown schematically. The control unit 5 is specifically designed to control the electrical supply to the electrolysis unit 1, such as the start and end of the electrolysis or power supply interruption, as well as all inlet and outlet valves. The measurement data from the gas measurement system, the fill level measurement, and other state parameters are also available to the control unit 5 for processing. Other state parameters can include the concentration of dissolved hydrogen gas in the circulating electrolyte, the electrolyte temperature, the electrolysis current, and the operating pressure p. unit and / or the operating temperature Tunit of the at least one electrolysis unit 1 , the concentration of the electrolyte for electrolysis, the mechanical stress o un with at least one electrolysis unit 1, the flow rate q f through the inert gas inlet valve (10A to oxygen gas separator 2 and 10B to hydrogen gas separator 3), the flow rate q ou t through the gas-P2024.1159 WO N / P2024-20 - 69 - 5 March 2026

[0324] outlet valve (11 A from oxygen gas separator 2 and 11 B from hydrogen gas separator 3), the pressure in the oxygen gas separator 2 and / or in the hydrogen gas separator 3, and / or the gas composition in the electrolysis unit 1, in particular the anode and / or cathode side content of hydrogen gas and / or oxygen gas.

[0325] The recording of the temperature T unThe temperature of electrolysis unit 1 can be measured using a surface thermometer on a pipe of the electrolysis unit or with a weld-in thermometer in the pipe close to the electrolysis unit. For direct measurement of the electrolysis unit's temperature, infrared sensors can be used to measure the temperature of the individual cells of the electrolysis unit, or a thermometer can be inserted in the cell frame or directly inside the cell. Temperature monitoring and other parameters can be controlled, for example, using a PID controller.

[0326] The gas contents in electrolysis unit 1 can be determined using simulations based on the operating conditions and the geometry of the respective cell stack or cell substack that forms the electrolysis unit. Measurement is also possible by connecting a gas analysis system, similar to the gas measurement system for the hydrogen and / or oxygen gas content of the oxygen gas separator. The tension o un The electrolysis unit 1 can, for example, be used to measure with a measuring system 15 at the clamping device, for example at at least one tie rod or tie rod 14 of the clamping device. The tie rods or tie rods 14 are typically guided through end plates 13 at the ends of a cell stack, so that the stack is compressed between the end plates 13 and the cells in the cell stack are sealed against each other.

[0327] The control device 5 of the electrolysis plant can have or be connected to at least one user interface 16. This user interface 16 can be configured, in particular, to receive user input for standby, starting from standby, or shutting down and forward it as a command to the control device 5. The user interface can also be configured to allow a user to request a specific quantity of hydrogen gas and / or oxygen gas via the user interface 16 and / or to select the procedure for reducing the hydrogen content in the oxygen gas separator 2 from at least one list displayed via the user interface 16 and send it to the control device 5. The control device 5 can be subdivided into several control units in various embodiments.

[0328] Figure 2 schematically shows another embodiment of an electrolysis plant 600. The electrolysis plant 600 is constructed like the plant 400 from the example in Figure 1. P2024.1159 WO N / P2024-20 - 70 - March 5, 2026

[0329] However, it comprises several electrolysis units 1. The electrolysis units 1 can be clamped together by a common clamping device. It is also possible for each electrolysis unit 1 to be equipped with its own clamping device. The electrolysis units 1 are supplied with energy for electrolysis via a power supply. Electrolysis can be carried out independently in each electrolysis unit 1, in particular, it can be interrupted and resumed. For electrolysis, the electrolysis units 1 can also be supplied independently with electrolyte, which can be fed to the respective electrolysis unit 1 via an electrolyte inlet valve 18. The electrolyte can be pumped around in an electrolyte preparation arrangement 200 by a pump 21 and heated to a specific temperature by a temperature control unit 17.The electrolyte preparation arrangement 200 can also optionally include a pressure-controlled container 25 with an inert gas supply line 22.

[0330] The electrolysis units 1 are connected to the oxygen gas separator 2 via oxygen supply lines, so that oxygen produced in the anode compartments of the electrolysis units 1 during electrolysis is introduced into the oxygen gas separator. The oxygen supply lines are equipped with oxygen inlet valves 9A1 and 9A2, which can be controlled independently of each other by the control device 5. The electrolysis units 1 are also connected to the hydrogen gas separator 3 via hydrogen supply lines, so that hydrogen produced in the cathode compartments of the electrolysis units 1 during electrolysis is introduced into the hydrogen gas separator 3 along with electrolyte. The hydrogen inlet valves 9B1 and 9B2 are located on the hydrogen supply lines and can be controlled independently of each other by the control device 5.

[0331] The oxygen supply lines and electrolyte drain lines are each connected to each other via bypass lines. Bypass valves 19A1 and 19A2 are attached to the bypass lines. The electrolyte from the electrolyte drain line of the oxygen gas separator and the hydrogen gas separator is combined and then recirculated to the electrolysis units 1. Valves 24A and 24B control which of the electrolysis units 1 receives the electrolyte. Before the electrolyte is introduced into the electrolysis units 1, it can be degassed via vent valves 20A and 20B and / or heated in the electrolyte conditioning units 200 using heaters 17.

[0332] In the electrolysis plant 600 of Figure 2, a potassium hydroxide solution with an increased concentration of CL in the range of 25 wt% to 30 wt%, for example in the range of 27 wt% to 30 wt%, for example 30 wt%, is used for electrolysis. The water for electrolysis is supplied to the electrolyte in the oxygen gas separator 2. P2024.1159 WO N / P2024-20 - 71 - 5 March 2026

[0333] The concentration is adjusted such that the electrolyte introduced into electrolysis unit 1 has a concentration of CL.

[0334] Figure 3 shows a diagram illustrating the explosion limits of hydrogen / oxygen gas mixtures. The diagram is taken from the publication by Volkmar Schröder, "Explosion Limits of Hydrogen and Hydrogen / Methane Mixtures," Research Report 253, published by the Federal Institute for Materials Research and Testing (BAM 2002). The diagram shows the pressure dependence of the explosion limits at 20°C and 80°C in the range of 1 bar to 200 bar.

[0335] The lower explosive limit (LEL) allows the determination of the respective gas concentrations for hydrogen and oxygen gas, which must be below (in the case of hydrogen gas) or above (in the case of oxygen gas) to prevent a hydrogen / oxygen reaction. For electrolysis with an operating temperature above 80°C, the values ​​can be extrapolated, or, for safety, the values ​​for 80°C can be used. Schröder's publication also describes the measurement method for determining the explosive limits at specific pressures and temperatures.

[0336] Fig. 4 shows the explosion range and explosion limits for a hydrogen / oxygen / nitrogen gas mixture according to Schröder, "Explosion Limits of Hydrogen and Hydrogen / Methane Mixtures", Research Report 253, published by the Federal Institute for Materials Research and Testing (BAM 2002). The lower explosion limit (LEL) is the limit with a lower hydrogen gas content than oxygen gas content.

[0337] Figure 5 shows a flowchart for the standby procedure. The oxygen gas separator is referred to as the "O2 gas separator" in this and subsequent figures. The procedure begins with the reception of a signal to interrupt the electrolysis of electrolysis unit 1, e.g., a standby command, in procedure step 100 at time tvo = 0. In the subsequent step 102, the hydrogen gas content c(H2) and / or the oxygen gas content c(Ü2) in the oxygen gas separator is measured, which is then carried out essentially continuously or at discrete time intervals. In step 104, the measured values ​​for the hydrogen gas content c(H2) and / or oxygen gas content c(Ü2) are compared with initial threshold values ​​c(H2) and / or c(O2).In particular, it is determined whether the current hydrogen gas content c(H2) exceeds the first threshold CI(H2) and / or the current oxygen gas content c(Ü2) exceeds the first threshold C(O2). Instead of the gas contents C(H2), C(Ü2), a ratio of the gas contents, e.g. c(H2) / c(O2) or c(O2) / c(H2), can also be compared with a first threshold n or 1 / n for the ratio, in particular obP2024.1159 WO N / P2024-20 - 72 - 5 March 2026.

[0338] C(H2) / C(O2) exceeds the first threshold n and / or c(O2) / c(H2) falls below the first threshold 1 / ri. Alternatively or additionally, the time started in step 100 with tvo = 0 is also compared with a first time threshold ti, in particular whether it has reached or exceeded the first time threshold or the first time duration ti since tvo=0.

[0339] If one or more of these queries are answered in the affirmative, the process continues to step 106. In step 106, the hydrogen content g(H2), in particular the hydrogen gas content c(H2), in the oxygen gas separator is reduced. As a measure to reduce the hydrogen content, a degassed electrolyte may be used for electrolysis, or the electrolysis current I may be increased, in particular to the maximum electrolysis current l. ma x, the operating pressure of the electrolysis unit p U nit and / or the operating temperature of the electrolysis unit T unThe hydrogen content can be reduced by using an electrolyte with an increased electrolyte concentration CL and / or by lowering the electrolyte level in the oxygen gas separator. Alternatively or additionally, in step 106, the hydrogen content in the oxygen gas separator can also be reduced by introducing inert gas, in particular nitrogen and / or air, into the oxygen gas separator.

[0340] The reduction of the hydrogen content in step 106 continues until, in process step 108, the value recorded for the hydrogen gas content c(H2) is less than a second threshold value C2(H2) and / or the value determined for the oxygen gas content c(O2) is greater than a second threshold value c2(O2). Alternatively or additionally, the reduction of the hydrogen content can also be carried out until a ratio of the gas contents falls below or is below a second threshold value, e.g., c(H2) / c(O2) is less than a second threshold value r2ist and / or C(O2) / C(H2) is greater than 1 / r2ist.

[0341] In the procedure shown in Figure 5, it can also be checked whether the time t started at the beginning of the standby is now equal to or greater than a second time limit t2 (step 108) and / or whether a command to terminate the standby has been issued (step 110). If neither of these conditions is met, the procedure continues with the reduction of the hydrogen content in process step 106. If the optional query 110 indicates that the standby should be terminated, the end of the standby procedure is initiated in process step 112. If it turns out that the standby should not be terminated, an interruption of the electrolysis is initiated in step 114. The electric current I for the electrolysis in electrolysis unit 1 is reduced to such an extent that no more electrolysis gas is produced in electrolysis unit 1, or the energy supply for the electrolysis in electrolysis unit 1 is completely interrupted (I = 0 A).1159 WO N / P2024-20 - 73 - March 5, 2026.

[0342] If several electrolysis units 1 are connected to the oxygen gas separator 2, the electrolysis of all these electrolysis units is interrupted. Optionally, a temperature and / or voltage monitoring can also be initiated in step 114. An example of the sequence of such monitoring is shown schematically in Figure 7. Furthermore, the gas volume can be... me ss and / or the sampling frequency f me The pressure in the gas separator is reduced before taking a sample for gas content determination in order to maintain the pressure for as long as possible. This is particularly useful when no inert gas is introduced into the gas separator.

[0343] The measures for reducing the hydrogen content, in particular the hydrogen gas content C(H2), in the oxygen gas separator in process step 106 are explained in more detail below:

[0344] 1. Degassed Electrolyte: The use of a degassed electrolyte can be achieved, for example, via fresh electrolyte, i.e., an electrolyte that is supplied to the electrolysis unit in addition to or instead of the electrolyte recirculated from the gas separator for electrolysis, for example, from a separate storage tank. Alternatively, it is also possible to use the electrolyte recirculated during operation and reduce the concentration of dissolved gases in this electrolyte in a degassing unit, which can, for example, be part of the electrolyte conditioning arrangement 200, without affecting the operating pressure in the electrolysis unit. In this case, the electrolysis unit 1 is isolated from the gas separators 2 and 3, valves 11A, 12A, 9A, 11B, 9B, and 12B are closed, and valves 19A and 19B are open. The electrolyte pressure is reduced via valves 19A and 19B.Degassing takes place either via a pressureless pressure-controlled container 7, 25 of the electrolyte preparation arrangement 200 or via the degassing valves 20A, 20B (which are connected, for example, at the highest point of a siphon). Subsequently, the electrolyte is brought back to the operating pressure of the electrolysis unit 1 via a dedicated pump in the pressure-controlled container or via an external pump 17 (Figure 2) and flows back into it.

[0345] Alternatively, degassing can also occur only on the anolyte side. For this, valves 11A, 9A, 12A, 9B, 12B, 11B, and 19B are closed, while valve 19A is open. The electrolyte pressure is reduced via valve 19A. Degassing takes place either via the unpressurized pressure-controlled container or the degassing valve 20A (which is connected to a siphon, for example). Subsequently, the electrolyte is pressurized back to the pressure of the respective electrolysis unit 1 via a dedicated pump in the pressure-controlled container or via pump 17 and flows back into it. P2024.1159 WO N / P2024-20 - 74 - 5 March 2026

[0346] In systems with separate electrolyte circuits for the anode and cathode sides, there is inherently less electrolyte contamination by unwanted gases. In these systems, the pressure in the oxygen gas separator can be controlled independently of the operating pressure p. unThe pressure in the electrolysis unit and the hydrogen gas separator are lowered to degas the anode-side electrolyte (anolyte). For example, the membranes of the electrolysis cells in the electrolysis unit can be separated from the electrolyte circuit to protect them from damage caused by increased pressure differences between the anode and cathode sides. While the use of additional separate components, such as a storage tank, separate degassing device, or separate electrolyte circuits, is more complex in design, it ensures that the operating parameters in the electrolysis unit are not affected and thus hydrogen production remains constant.

[0347] Degassed means, in particular for the dissolved hydrogen content, for alkaline electrolysis with potassium hydroxide (KOH) as the electrolyte:

[0348] < 6.579x10 -6kg H2 / per kilogram at 85°C, 25 wt.% KOH, 35 bar (absolute), for example < 6.579x10' 6 kg(H2) / kg at 85°C, 25 wt.% KOH, 35 bar (absolute), further examples < 4.745xio -6 kg(H2) / kg at 85°C, 30 wt.% KOH, 35 bar(a), for example < 3.707x10' 6 kg(H2) / kg at 60°C, 25 wt.% KOH, 26 bar (absolute), whole for example < 2.532xio -6 kg(H2) / kg at 60°C, 30 wt.% KOH, 26 bar (absolute).

[0349] 2. Increasing the electric current for electrolysis: Another way to reduce the hydrogen content is to use an increased electrolysis current I or even the maximum electrolysis current l. max, i.e., operation of the respective electrolysis unit at full load. The resulting increased gas production leads to improved gas quality with a higher oxygen content before standby, which also reduces the hydrogen content in the oxygen gas separator. The electrolysis current I is typically increased relative to the electrolysis current l(tvo) at time tvo=0, when the signal to interrupt is received or generated, or at the start of gas content measurement. If the electrolysis system comprises several electrolysis units connected to the oxygen gas separator, all of these electrolysis units can be operated with an increased electrolysis current I, particularly lmax, before the electrolysis or standby power supply is interrupted. In alkaline pressure electrolysis, the maximum electrolysis current l ma x, for example, lies in a range of 5 kA to 15 kA.

[0350] 3. Reduction of operating pressure and / or operating temperature: In process step 106, the operating pressure p can also be reduced to lower the hydrogen content. un with the electrolysis unit and / or the operating temperature T un The electrolysis unit will be lowered. This is P2024.1159 WO N / P2024-20 - 75 - March 5, 2026

[0351] This concerns operating parameters that lead to outgassing of the electrolyte. Lowering the operating temperature (typically to a temperature >70% of the maximum operating temperature for alkaline electrolysis) can generally be achieved by increased cooling, for example by increasing the cooling water flow through heat exchangers, which reduces the process temperature of the electrolysis process.

[0352] A reduction in operating pressure can be achieved by changing a threshold value of the pressure control. For alkaline pressure electrolysis, the pressure can be reduced, for example, within a range of 25 to 34 bar gauge, e.g., to 32.5 bar gauge, 28 bar gauge, or 25 bar gauge. The oxygen can be vented from the oxygen gas separator via a blower while gas is still being produced in the electrolysis process. This is necessary because otherwise, the pressure reduction would contaminate the oxygen gas separator with outgassing hydrogen.

[0353] In electrolysis plants where several electrolysis units are connected to the oxygen gas separator, the operating pressure p unThe pressure in all electrolysis units that are in electrolysis operation, i.e., whose power supply is not interrupted, is reduced to the same pressure. Electrolysis units that are not in electrolysis operation, i.e., whose power supply or electrolysis is interrupted, are each shut off from the oxygen gas separator, and in the case of hydraulically coupled gas separators, also from the hydrogen gas separator. For this purpose, the oxygen inlet valve 9A and, for example, the hydrogen inlet valve 9B are closed.

[0354] 4. Increasing the electrolyte concentration Ci_: An increased concentration of the electrolyte (Cl) can be set before the electrolysis unit is started up, for example, in alkaline electrolysis with KOH as the electrolyte in a concentration range of 25 to 30 wt%, e.g., 27 wt%, e.g., 30 wt%, so that when the power supply is switched off, regardless of any standby demand, the electrolyte concentration is already increased. This can be achieved by filling the electrolysis unit and the associated system with an electrolyte of the selected concentration (Cl) before starting up.

[0355] Alternatively or additionally, for standby operation, the electrolyte concentration can be increased before the electrolysis is switched off or interrupted by adding less or no distilled / deionized water to the recirculated electrolyte during electrolyte preparation. This water normally replaces the water consumed during electrolysis. Alternatively, an alkali salt or an electrolyte with a higher concentration can be added, thus increasing the concentration to Cl. When using degassed electrolyte, see P2024.1159 WO N / P2024-20 - 76 - 5 March 2026

[0356] For example, the degassed electrolyte from the storage tank may have an increased concentration, or the concentration of the electrolyte may also be increased during degassing in a degassing unit.

[0357] 5. Level Reduction in the Oxygen Gas Separator: As a measure in process step 106, the electrolyte level in the oxygen gas separator can also be reduced. This reduction is relative to the level of the oxygen gas separator during normal operation, particularly at time tvo=0. For hydraulically coupled gas separators, the shuttle lines should be connected as low as possible to the respective separator vessel, for example, at the lowest point of the separation chamber between the oxygen and hydrogen gas separators. This allows for very large level differences between the oxygen and hydrogen gas separators by controlling the withdrawal rates from the gas separators, thus generating the largest possible gas volumes in the oxygen gas separator and preventing the electrolysis gases from mixing due to insufficient levels.

[0358] If the oxygen gas separator 2 is hydraulically connected to the hydrogen gas separator 3, the fill level can be lowered, for example, by reducing the flow rate of oxygen gas from the oxygen gas separator 2. The flow rate can be controlled via the gas outlet valve 11A on the oxygen gas separator. Alternatively or additionally, more hydrogen gas can be drawn from the hydrogen gas separator 3. The flow rate can be controlled via a gas outlet valve 11B on the hydrogen gas separator. If the oxygen gas separator 2 and the hydrogen gas separator 3 are not hydraulically coupled, the fill levels can be adjusted by controlling the flow rate of electrolyte from the gas separators 2 and 3.To lower the fill level in the oxygen gas separator 2, for example, more electrolyte can be removed from the oxygen gas separator 2 than in normal operation, so that there is a larger gas volume than electrolyte volume in the oxygen gas separator 2.

[0359] 6. Introducing inert gas: As an alternative or in addition to one or more of the described measures Mi (i=1, 2, 3... ), inert gas can also be introduced into the oxygen gas separator in step 106 to reduce the hydrogen content, for example, using a stepwise or continuous flow process. Once inert gas is introduced into the oxygen gas separator to reduce the hydrogen content, the previously described measures are only carried out depending on the threshold values ​​for the hydrogen gas content C(H2), since the oxygen gas content in the gas separator decreases instead of increasing. P2024.1159 WO N / P2024-20 - 77 - 5 March 2026

[0360] rise. A hydrogen-free gas, such as nitrogen or air, can be used as an inert gas.

[0361] In the stepwise process, inert gas is first introduced into the oxygen gas separator 2 via the inert gas inlet valve 10A. The gas outlet valve 11A and the oxygen inlet valve 9A are closed during this step. With hydraulically coupled gas separators, e.g., via a shuttle line, the liquid level in the oxygen gas separator decreases and the liquid level in the hydrogen gas separator increases. With a hydraulically decoupled (self-contained) oxygen gas separator, the electrolyte level remains constant, and the pressure in the oxygen gas separator increases, but not beyond the pressure limit of the separator vessel.In the second step, the gas outlet valve 11A of the oxygen gas separator is opened, allowing the inert gas / oxygen mixture to flow towards the discharge line until the fill level in the oxygen gas separator has risen to a defined limit or a defined pressure in the oxygen gas separator has been reached, in particular a pressure not less than 70% of the operating pressure, for example, not less than 85% or not less than 90% of the operating pressure. The process is then repeated until, depending on the pressure and volume in the gas separator, a specific threshold value C2(H2) for the hydrogen gas content, for example, 2 vol%, is reached. For the second step, the inert gas inflow rate can be reduced or, for example, the inert gas inflow can be interrupted. In contrast to the stepwise method, the gas outlet valve 11A remains continuously open in the flow-through method.

[0362] For both processes, the fill level in the oxygen gas separator 2 can be raised before the inert gas is introduced in order to reduce inert gas consumption. In hydraulically coupled gas separators 2, 3, this can be achieved, for example, by increasing the oxygen gas outflow rate q. ou The fill level can be increased by removing oxygen gas from separator 2 and / or by reducing the hydrogen gas outflow rate from hydrogen gas separator 3. In the flow-through method, the fill level can also be increased during the introduction process by reducing the gas outflow rate q. ou The flow rate t from the oxygen gas separator 2 is reduced relative to the inert gas flow rate qni. In self-contained gas separators, the fill level in the oxygen gas separator 2 can be raised by adding electrolyte or water from outside into the oxygen gas separator.

[0363] In the example shown in Figure 5, one or more of the described measures are carried out simultaneously in process step 106 to reduce the hydrogen content. This means that the threshold values ​​CI(H2), C2(H2), Ci(O2), O2(O2), H, r2 and / or the time parameters ti, t2 are the threshold values ​​or time parameters for all of the measures to be carried out. For example, only those measures are carried out in which no inert gas enters the oxygen-P2024.1159 WO N / P2024-20 - 78 - 5 March 2026

[0364] Gas separator is initiated. For example, the only measures that can be taken simultaneously are electrolysis operation with an increased electrolysis current I and an increased electrolyte concentration CL, as well as an increase in the fill level.

[0365] Which measure is implemented and whether an inert gas injection takes place is already determined in step 100, for example, due to user or system requirements, or is determined in step 105 after a threshold value is exceeded or fallen below, depending on at least one currently determined state parameter of the electrolysis plant, in particular a state parameter of electrolysis unit 1. Due to the limited parameter set of threshold values ​​CI(H2), C2(H2), CI(Ü2), C2(Ü2), H, r2 and / or time parameters ti, t2, the standby procedure can react quickly to changes in the hydrogen content in the oxygen gas separator.

[0366] Figure 6 shows an embodiment in which, in process step 106, one or more measures Mj for reducing the hydrogen content can be carried out sequentially and / or at least partially simultaneously. For this purpose, each measure Mj (i=1, 2, 3...) is assigned sets (k=1, 2, 3...) of its own first and second threshold values ​​and / or first and second time parameters. The index i denotes the same measure, and the index k denotes the k-th execution of measure Mj.

[0367] In step 104, the currently recorded values ​​of the gas contents c(H2) and c(Ü2) are compared with the first threshold values ​​CMik_i(H2) and / or CMik_i(Ü2) of a set k for the respective measure Mj. In step 108, the currently determined values ​​of the gas contents are compared with the second threshold values ​​CMik_2(H2) and / or CMik_2(Ü2) of the set k for the respective measure Mj. Alternatively, in steps 104 and / or 108, ratios of the gas contents, e.g., C(H2) / C(O2) or C(O2) / C(H2), can also be compared with the first and second threshold values ​​for the ratios rMik_i, rMik_2, and 1 / r, respectively. M ik_i, 1 / r Mik_2 can be compared. In steps 106 and / or 108, first time parameters tMik_i for a measure Mj and second time parameters tMik_2 for a measure Mj can be provided as an alternative or in addition to the threshold values ​​for the gas contents or their ratios.

[0368] The respective measures Mj can be implemented depending on the threshold values ​​of the gas concentrations, their ratio, and / or the time parameters. For example, they can be implemented if values ​​for the gas concentrations c(H2) and / or c(Ü2) are recorded that lie within the interval [CMH (H2), CMik_2(H2)] or [CMik_i(O2), CMik_2(O2)]. Alternatively, the measures Mj can be implemented within the time interval [tMik_i(H2), tMik_2(H2)]. The duration of the time interval is chosen such that the respective threshold value CMik_2(H2) and / or CMik_2(Ü2) is reached when time tMik_2(H2) is reached. In a further alternative, the P2024.1159 WO N / P2024-20 - 79 - 5 March 2026

[0369] Measures Mj are initiated when the first threshold CMik_i(H2) for the hydrogen gas content C(H2) is exceeded within the time interval [tMik_i(H2), tMik_2(H2)] and / or the first threshold CMik_i(O2) for the oxygen gas content c(O2) is undershot. The measures are carried out until their second time parameter or point tMik_2 is reached and the hydrogen gas content c(H2) has fallen below the second threshold CMik_2(H2) and / or the oxygen gas content c(O2) has exceeded the first threshold CMik_2(O2).

[0370] The threshold values ​​for gas concentrations and / or time parameters define a sequence and thus a prioritization of the measures Mj. This sequence, along with the selection of measures to be implemented, allows for the optimized operation of the electrolysis plant for specific operating modes. The selection and sequence of measures Mj can be determined by the control device and / or user input. For example, one or more measures can be implemented exclusively or with priority, ensuring that the hydrogen production rate does not decrease and / or that no inert gas injection is necessary. E.g.:

[0371] Use of degassed electrolyte

[0372] Increasing the electrolysis current I, in particular to the maximum electrolysis current l ma x Use of an electrolyte with increased concentration of CL and / or increasing the electrolyte concentration to CL

[0373] Level reduction in the oxygen gas separator.

[0374] Figure 7 shows an embodiment of the standby procedure, in which the procedure is carried out with particular time efficiency. A measure Mj is initiated each time the first threshold CMik_i(H2) is exceeded within the time interval [tMik_i(H2), tMik_2(H2)] and / or the first threshold CMik_i(O2) is undershot. The measure is carried out until the hydrogen gas content c(H2) falls below the second threshold CMik_2(H2) and / or the oxygen gas content c(O2) exceeds the first threshold CMik_2(O2). If this occurs before the second time parameter or point tMik_2 is reached, the procedure continues with recalculated time parameters (step 116) without waiting for the time to elapse until the second time parameter tMik_2 is reached.If the second threshold values ​​for gas content are not reached by the second time point, an error message can be issued and / or another / further measure can be initiated as a support measure.

[0375] Figure 8 shows a section of the process described in Figures 5 to 7, in which temperature and / or stress monitoring is performed. During or after the interruption, an operating temperature T is measured. un it and / or a mechanical stress o un with the P2024.1159 WO N / P2024-20 - 80 - March 5, 2026

[0376] At least one electrolysis unit is detected. When a critical temperature Tknt and / or voltage Okrit is reached or falls below a critical value, the electrolysis unit is heated until the detected temperature Tknt is reached. un it is greater than the critical temperature Tknt and / or the detected mechanical stress o unIt is greater than the critical stress Okrit. The critical stress Okrit can, in particular, correspond to a stress at the critical temperature Tknt. The stress can be detected at the tensioning device of the electrolysis unit. It can be measured, for example, with stress sensors on tension rods or anchors of the tensioning device, for example, in the longitudinal direction of a cell stack or cell sub-stack of the electrolysis unit.

[0377] When the critical temperature Tknt and / or stress Okrit of the electrolysis unit is reached or falls below the critical temperature Tcrit, heating of the electrolysis unit is initiated. For this heating, electrolyte with a temperature Ti > Tcrit is circulated through the electrolysis unit. The electrolyte is circulated through the bypass line of the respective electrolysis unit with the bypass valve 19A open. The oxygen supply valve 12A and the electrolyte drain valves 9A are closed. The temperature TL of the circulated electrolyte can be set in an electrolyte conditioning device 7 or a temperature control unit 17.

[0378] Figure 9 shows the continuation of the standby process after the interruption of electrolysis or the power supply.

[0379] By choosing the threshold values ​​C3(H2) and 03(02) in comparison to the critical threshold values ​​CMik_2(H2) and CMik_2(Ü2), two different scenarios can be created for gas exchange with inert gas after the interruption of electrolysis or energy supply:

[0380] Scenario 1: The third thresholds C3(H2), O3(O2) are chosen to be equal to or less stringent than the second thresholds CMik_2(H2), CMik_2(Ü2), in particular C3(H2) s |CMik_2(H2)|max and / or O3(O2) s |CMik_2(O2)|min. In this scenario, the gas quality is improved before the interruption of electrolysis or the power supply to such an extent that inert gas is only introduced into the oxygen gas separator during standby if the gas quality deteriorates during standby, after the interruption of electrolysis or the power supply, to such an extent that the gas concentrations c(H2) > C3(H2) or c(Ü2) < Cs(O2). It is therefore possible for standby to occur even without inert gas introduction. Example values ​​are |CMik_2(H2)|max < 1 vol.% and |c M ik_2(H2)|max < C3(H2) < 2 Vol.-%.P2024.1159 WO N / P2024-20 - 81 - March 5, 2026

[0381] Scenario 2: In the second scenario, the third thresholds C3(H2), O3(O2) are chosen to be stricter than the second thresholds CMik_2(H2), CMik_2(O2), i.e., Cs(H2) < |CMik_2(H2)|min and / or O3(O2) > |CMik_2(O2)|max. The gas quality is improved by the measures already explained above, but gas exchange with inert gas still occurs after the electrolysis or energy supply is shut down. However, the measures can improve the gas quality to such an extent that less inert gas is consumed.

[0382] The two procedures described above are also evident from the flowchart in Figure 9. In step 120, the electrolysis or energy supply is interrupted at time t = INO = 0. Simultaneously, temperature and / or voltage monitoring is started. In query 122, the measured hydrogen gas content c(H2) and / or oxygen gas content c(Ü2) are compared with the third threshold values ​​C3(H2) and O3(O2), and / or the elapsed time is compared with a specific duration ts.If the hydrogen gas content exceeds the third threshold value C3(H2) and / or the oxygen gas content falls below the corresponding third threshold value 03(02), inert gas is continuously or stepwise introduced into the oxygen gas separator until the detected hydrogen gas content C(H2) is less than a fourth threshold value C4(H2), the detected oxygen gas content c(Ü2) is less than a fourth threshold value 04(02), and / or a fourth time parameter t4 is reached. Alternatively, instead of the threshold values ​​C4(H2), 04(02), and / or the time parameter t4, the inert gas content can also be detected, and inert gas can be introduced until a threshold value for the inert gas content C4(lnert) in the oxygen gas separator is reached or exceeded.

[0383] Depending on the choice of the second threshold values ​​CMik_2(H2) and CMik_2(Ü2) of the measures Mivor before the interruption of electrolysis or energy supply, the following sequence of steps can result in Figure 5:

[0384] Scenario 1: 122, 128

[0385] Scenario 2: 122, 124, 126, 128.

[0386] Whether or not an inert gas purge takes place in step 124 also depends on the absolute values ​​of the threshold values ​​CMik_2(H2) and CMik_2(Ü2).

[0387] Step 128 checks whether a request to end standby has been made. If so, a procedure to end standby is initiated in step 130. P2024.1159 WO N / P2024-20 - 82 - March 5, 2026

[0388] The end of standby operation in process step 130 is initiated by receiving a command to terminate standby operation. This command can be, for example, a command to start up at least one electrolysis unit, a command to shut down the electrolysis plant, or a command for an emergency shutdown. The commands can be triggered by the operator or user of the electrolysis plant and / or dependent on an external power / voltage supply (wind turbine, solar park, electricity provider, etc.) and / or generated by the control device 5 based on measured and / or calculated state parameters of the electrolysis plant or by time parameters.

[0389] In a system where multiple electrolysis units are connected to the oxygen gas separator, restarting from standby mode can be performed for individual electrolysis units or for groups of electrolysis units. A restart can be initiated for various reasons. At least one electrolysis unit can be restarted when a critical state is reached within that electrolysis unit, when a critical state of the oxygen gas separator is reached, and / or when a specific time period has elapsed. This time period can be, in particular, the shortest time within which an electrolysis unit reaches a critical state. In normal operation, it can be determined from the interruption of electrolysis or the interruption of the power supply to the electrolysis unit; in standby mode, from the beginning of standby, e.g., from the receipt of the signal to interrupt operation or from the start of gas content measurement in the oxygen gas separator for standby.

[0390] A critical state of an electrolysis unit can occur, for example, when the pressure (Punit) or the temperature (T) exceeds a certain threshold. un IT and / or tension o un A critical condition can also occur if the concentration in the electrolysis unit decreases faster than a critical rate and / or reaches or falls below a critical value pcrit, Tcrit, or Okrit. A critical condition can also be a gas composition with an increased risk of hydrogen explosion in the electrolysis unit. A critical gas composition can be present, for example, if the hydrogen gas content on the anode side c ano(H2) in an electrolysis unit reaches or exceeds a certain value Ckrit_ano(H2), if the anode-side oxygen gas content Cano(O2) in an electrolysis unit reaches or falls below a certain value Ckrit_ano(O2), if the cathode-side hydrogen gas content Ckato(H2) in an electrolysis unit reaches or falls below a certain value Ckrit_kato(H2) and / or if the cathode-side oxygen gas content Ckato(O2) in an electrolysis unit reaches or exceeds a certain value Ckrit_kato(O2).

[0391] A critical condition of the oxygen gas separator can occur, for example, when a critical hydrogen gas content Ccrit(H2) in the oxygen gas separator is exceeded, or a critical temperature Tcskrit and / or the critical pressure p is exceeded. kr it in the oxygen gas separator reached P2024.1159 WO N / P2024-20 - 83 - 5 March 2026

[0392] or falls below a certain threshold. If no inert gas is or has been introduced into the oxygen gas separator, a critical state can also occur when the oxygen gas content Ccrit(O2) in the oxygen gas separator falls below a certain threshold. In electrolysis plants with multiple electrolysis units, it may be sufficient to start up one of the electrolysis units to resolve the critical state. The selection of which electrolysis unit should be started up can be carried out, for example, as in the alternating operation shown in Figure 11 (setpoint x=1 at n=0). However, several of the electrolysis units can also be started up (setpoint x>1 at n=0) if, for example, an overproduction of electrolysis gases is acceptable or to end the critical state of the oxygen gas separator as quickly and reliably as possible.

[0393] Another reason for starting up a system could be an increase in the number of electrolysis units required. Such a change can occur, for example, when hydrogen production is needed again and / or when electrical power is available for electrolysis. The setpoint for the number of electrolysis units to be started up can be determined by or stored within the control device. The selection of which electrolysis unit(s) to start up can be performed, for example, as in the alternating operation shown in Figure 11 (setpoint x>0 when n=0).

[0394] In any case, it is important that the respective electrolysis unit is started up quickly and safely.

[0395] Figure 10 schematically illustrates a start-up process. For safe start-up, at least one electrolysis unit is started with an increased electrolysis current ramp. The increased electrolysis current ramp means that the electrolysis current is higher compared to a pressureless start-up, which typically has a ramp gradient of <0.5 l. ma exhibits x% / s. A rapid start with a steeper ramp, e.g., >0.6% hax / s, >2% Uax / s, >10% l ma x / s or >15% l ma x / s enables a rapid improvement in gas quality in the oxygen gas separator.

[0396] The steep electrolysis current ramp can be maintained until a specific electrolysis current is reached. This electrolysis current can be for operating the electrolysis unit at partial load, particularly when insufficient power is available for full-load operation, or it can be a different electrolysis current. max for operation at full load. Preferably, the at least one electrolysis unit is operated at maximum electrolysis current l for at least a certain period of time after start-up. ma x operated to produce as much oxygen as possible and introduce it into the oxygen gas separator, thus improving the gas quality as quickly as possible. P2024.1159 WO N / P2024-20 - 84 - 5 March 2026

[0397] to improve the electrolysis unit and the oxygen gas separator. Alternatively or additionally, a faster improvement in gas quality can also be achieved by starting the electrolysis current not with an initial current of 0 A, but with an initial electrolysis current Io > 0 A, for example, 10%, 20%, or 30% of the maximum electrolysis current Lax. The initial electrolysis current Io can, for example, be an electrolysis current at which electrolysis takes place, i.e., electrolysis gas is formed.

[0398] Furthermore, the safety of the start-up process can be improved by lowering the electrolyte level in the oxygen gas separator. This reduces the risk of an oxyhydrogen reaction because, firstly, there is a smaller volume of liquid from which hydrogen can escape, and secondly, there is a larger volume of gas in which the escaping hydrogen is diluted. The electrolyte level can be lowered to such an extent that, during start-up, there is a smaller volume of liquid than gas in the oxygen gas separator. This is particularly useful when starting up a large number of electrolysis units or all of the electrolysis units connected to the oxygen gas separator.

[0399] As a further measure for rapid start-up, the emergency shutdown thresholds can be adjusted so that they are less stringent than during normal operation and / or during interruptions of electrolysis or the power supply. This means that the hydrogen gas content threshold CSTOP(H2) for start-up is higher than during normal operation and / or during interruptions of electrolysis or the power supply, and the oxygen gas content threshold CSTOP(O2) is correspondingly lower, provided no inert gas has been introduced into the gas separator. For example, in pressure alkaline electrolysis at 30 bar, a value >4 vol.% for CSTOP(H2) and / or <96 vol.% for CSTOP(O2) can be selected. However, the thresholds are set below the lower explosive limit (see Figure 2). These adjusted thresholds help avoid unnecessary emergency shutdowns.

[0400] If the gas volume V is used for standby me ss and / or the sampling frequency f me If the values ​​for gas content c(H2), c(Ü2) and / or c(lnert) were reduced during sampling from the oxygen gas separator for determining the gas content, these values ​​can now be increased again during start-up.

[0401] Figure 11 schematically illustrates how, when the number of electrolysis units required for operation changes, it can be selected for which electrolysis unit the electrolysis or energy supply is interrupted, and for which electrolysis unit this P2024.1159 WO N / P2024-20 - 85 - 5 March 2026

[0402] The interruption ends, meaning a restart takes place. This alternating operation (alternating operation 2) can be performed before standby in normal operation to keep the electrolysis units in such good condition that standby can be carried out safely for a certain period of time.

[0403] The first step is to determine whether standby mode should be initiated. This involves checking whether any electrolysis units are still operating (actual value n>0) and whether the number of electrolysis units to be operated is zero (target value x=0). If these conditions are met, standby mode is initiated, for example, in response to receiving the interrupt signal, and the standby procedure is executed.

[0404] Otherwise, in a second step, it is determined whether the requested number x of electrolysis units is less than the number n of electrolysis units currently operating. This can be done, for example, in the control device. If more electrolysis units n are operating than the requested x, the electrolysis or power supply is interrupted for the difference (nx) of electrolysis units; otherwise, a command to start is issued for the difference of (xn) electrolysis units. The electrolysis or power supply is then interrupted in those electrolysis units operating with a high or the highest electrolysis current I, or at a high or the highest temperature T. un it, a high or the highest pressure p un it, a high or the highest tension o un it, a high or the highest anode-side oxygen gas content c ano(O2), a high or the highest cathode-side hydrogen gas content; Ckato(H2), a low or the lowest anode-side hydrogen gas content; c ano (H2) and / or a low or the lowest cathode-side oxygen gas content Ck a to(O2). High or low values ​​can be values ​​that meet at least a threshold, such as Pw2_off, Tw2_off, Ow2_off, Cw2ano_off(O2), Cw2kato_off(H2) and / or Cw2ano_off(H2) and Cw2kato_off(O2).

[0405] Conversely, during startup, only those electrolysis units in an unfavorable condition can be started up. These could be electrolysis units with, for example, a low or the lowest temperature (Tunit), a low or the lowest pressure (Punit), or a low or the lowest voltage. unit, a low or the lowest anode-side oxygen gas content c ano (O2), a low or the lowest cathode-side hydrogen gas content; Ckato(H2), a high or the highest anode-side hydrogen gas content; c ano (H2) and / or have a high or the highest cathode-side oxygen gas content Ckato(O2). High or low values ​​can be values ​​that meet at least one threshold, e.g., pw2. _on, Tw2_orb Ow2_orb CW2ano_on(O2), CW2kato_on(H2) ölTöiChön OdöTP2024.1159 WO N / P2024-20 - 86 - 5 March 2026

[0406] The threshold values ​​for interrupting electrolysis or the energy supply may fall below the specified threshold and / or reach or exceed the values ​​for Cw2ano_on(H2) and Cw2kato_on(O2). Instead of the threshold values, a time period may also be reached, which is determined such that the respective threshold value in the electrolysis unit is reached, exceeded, or fallen below.

[0407] By performing the changeover with only a number of electrolysis units corresponding to the difference (nx) or (xn) between the n requested electrolysis units and the x electrolysis units currently operating, the changeover can be carried out very quickly. Alternatively, the changeover can be performed by identifying, from the total number of electrolysis units connected to the oxygen gas separator, n electrolysis units that are in an unfavorable state and then switching to those electrolysis units whose electrolysis is still interrupted.

[0408] The selection procedure for starting up described in Figure 11 can also be used when an electrolysis unit reaches a critical state and needs to be started up. This can be a start-up from standby (n=0) or a start-up in normal operation (n>0), in which, instead of the electrolysis unit switching to electrolysis operation, the electrolysis or energy supply of another electrolysis unit is interrupted. In this alternating operation, in which one electrolysis unit is started up and the electrolysis or energy supply of another electrolysis unit is interrupted (alternating operation 1), the number of electrolysis units in electrolysis operation remains constant. Furthermore, the electrolysis gas production can also remain constant, as the electrolysis unit being started up produces electrolysis gas with the same electrolysis gas flow rate as the electrolysis unit whose electrolysis or energy supply is interrupted.The power supply is interrupted.

[0409] For alternating operation 1, the same threshold values ​​of the state parameters can be chosen as for alternating operation 2, or separate threshold values ​​can be set, in particular stricter threshold values:

[0410] Pwi_on>PW2_on, Twi_on>Tw2_on, Cwiano_on(O2)>Cw2ano_on(O2), Cwikato_on(H2)>Cw2kato_on(H2), Cwiano_on(H2) < 'Cw2ano_on(H2) And / OdeT Cw2kato_on(O2) < 'Cw2kato_on(O2).

[0411] The threshold values ​​can also be chosen to be stricter than a critical threshold for starting up the electrolysis unit during standby.

[0412]

[0413] P2024.1159 WO N / P2024-20 - 87 - 5 March 2026

[0414] PW2_on > Pkrit, Tw2_on > Tkrit, Cw2an o_on (H2)<Cknt_ _ano (H2), Cwßan o_on (02)> Ckrit_ _ano (O2), Cw2kato_on(H2)>Ckrit _ kato(H2) And / OdST Cw2kato_on(O2) < 'Ckrit _ kato(O2).

[0415] This ensures that the electrolysis units are kept in such good condition during normal operation that they do not need to be started up immediately when in standby mode, but can instead be safely operated in standby for a certain period. This is particularly beneficial for electrolysis plants with multiple electrolysis units, where the electrolysis or power supply to individual units may be interrupted during normal operation (partial load operation). For electrolysis plants with only a single electrolysis unit connected to the oxygen gas separator, alternating operation is not possible. In these cases, standby can be safely maintained primarily due to measures taken to reduce the hydrogen content (g(H2)).

[0416] For example, the electrolysis system includes electrolysis unit 1 and oxygen gas separator 2 for separating oxygen gas and electrolyte. For example, electrolysis unit 1 is connected to power supply terminal 4 for the energy supply E for electrolysis in electrolysis unit 1.

[0417] The procedure for a standby of an electrolysis plant 400, 600 includes, for example: - Determining a hydrogen gas content c(H2) in the oxygen gas separator and / or an oxygen gas content c(O2) in the oxygen gas separator2,

[0418] - Receiving a signal to interrupt the electrolysis of electrolysis unit 1 for standby mode,

[0419] - Lowering the hydrogen content g(H2) in the oxygen gas separator 2 in response to the signal to interrupt, depending on the hydrogen gas content c(H2) in the oxygen gas separator 2 and / or depending on the oxygen gas content c(O2) in the oxygen gas separator 2.

[0420] For example, the process includes lowering the hydrogen content g(H2) in the oxygen gas separator 2, such that the hydrogen gas content c(H2) in the oxygen gas separator 2 and / or the oxygen gas content c(O2) in the oxygen gas separator 2 are outside a range for an oxyhydrogen reaction.

[0421] For example, the procedure includes interrupting electrolysis in electrolysis unit 1 in response to the signal to interrupt electrolysis. P2024.1159 WO N / P2024-20 - 88 - 5 March 2026

[0422] For example, the procedure includes blocking a fluid connection between the electrolysis unit 1 and the oxygen gas separator 2 in response to the signal to interrupt electrolysis.

[0423] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 involves introducing a degassed electrolyte into the electrolysis unit 1.

[0424] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 before interrupting electrolysis in the electrolysis unit 1 involves reducing an operating temperature T. un it in electrolysis unit 1.

[0425] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 before interrupting electrolysis in the electrolysis unit 1 involves reducing an operating pressure p. un it in electrolysis unit 1.

[0426] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 before interrupting electrolysis in the electrolysis unit 1 includes operating the electrolysis in the electrolysis unit 1 with an electrolyte having a concentration CL of dissolved alkali salt of at least 25 wt.%.

[0427] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 before interrupting electrolysis in the electrolysis unit 1 involves reducing a volume of the electrolyte in the oxygen gas separator 2.

[0428] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 before interrupting electrolysis in the electrolysis unit 1 includes increasing an electric electrolysis current I for the electrolysis in the electrolysis unit 1 and / or operating the electrolysis in the electrolysis unit 1 with a maximum electrolysis current l ma x.

[0429] For example, lowering the hydrogen content g(H2) in the oxygen gas separator 2 involves introducing an inert gas into the oxygen gas separator 2.

[0430] For example, the introduction of the inert gas is carried out in a step-by-step process.

[0431] For example, the introduction of the inert gas is carried out using a flow-through process. P2024.1159 WO N / P2024-20 - 89 - 5 March 2026

[0432] For example, the procedure includes increasing the electrolyte level in the oxygen gas separator 2.

[0433] For example, the procedure includes:

[0434] - Providing a temperature threshold TM for electrolysis unit 1,

[0435] After interrupting electrolysis in electrolysis unit 1, determine an operating temperature of electrolysis unit 1.

[0436] - Comparing the determined operating temperature T un it with the temperature threshold TM, and - if the determined operating temperature T un If the temperature threshold Tcrit is equal to or less than the temperature threshold Tcrit: Increasing the operating temperature of the electrolysis unit Tunit-

[0437] For example, the procedure includes:

[0438] - Providing a stress threshold value Okrit for electrolysis unit 1,

[0439] After interrupting electrolysis in electrolysis unit 1, determine if there is a mechanical stress. un with the electrolysis unit 1,

[0440] - Comparing the determined tension o un it with the stress threshold value Okrit, and - if the determined stress o un if it is equal to or less than the stress threshold value Okrit: Increasing the operating temperature Tunit of the electrolysis unit 1.

[0441] For example, the procedure includes:

[0442] - Providing a pressure threshold for electrolysis unit 1,

[0443] - After interrupting electrolysis in electrolysis unit 1, determine a pressure p un it in electrolysis unit 1,

[0444] - Comparing the measured pressure p un it with the pressure threshold, and

[0445] - if the determined pressure p un it is less than or equal to the stress threshold value Okrit: Increasing the pressure p un it in electrolysis unit 1.

[0446] For example, the method for operating the electrolysis plant 400, 600 includes receiving a control signal to terminate an interruption of the electrolysis of electrolysis unit 1 while the electrolysis in electrolysis unit 1 is interrupted.

[0447] For example, the procedure includes:

[0448] - Providing a pressure threshold value pcrit for electrolysis unit 1,

[0449] - Determining a pressure p un it in electrolysis unit 1 ,

[0450] - Comparing the measured pressure p un it with the pressure threshold pcrit, and

[0451] - if the determined pressure p un it is less than or equal to the pressure threshold p kr It is: Sending the control signal. P2024.1159 WO N / P2024-20 - 90 - March 5, 2026

[0452] For example, the procedure includes:

[0453] - Providing a temperature threshold TM for electrolysis unit 1,

[0454] - Determining an operating temperature T un with the electrolysis unit 1,

[0455] - Comparing the determined operating temperature T un it with the temperature threshold TM, and - if the determined operating temperature T unIf the temperature threshold Tkrit is equal to or less than the temperature threshold value, the control signal is sent.

[0456] For example, the procedure includes:

[0457] - Providing a stress threshold value Okrit for electrolysis unit 1,

[0458] - Determining mechanical stress o un with the electrolysis unit 1,

[0459] - Comparing the determined tension o un it with the stress threshold value Okrit, and - if the determined stress o un If the stress threshold value Okrit is equal to or less than the stress threshold value, the control signal is sent.

[0460] For example, the procedure includes:

[0461] - Providing one or more thresholds from: an anode hydrogen threshold Ckrit_ano(H2), an anode oxygen threshold Ckrit_ano(O2), a cathode hydrogen threshold Ckrit_kato(H2) and a cathode oxygen threshold Okrit_kato(O2),

[0462] - Sending the control signal when an anode-side hydrogen gas content c ano (H2) in electrolysis unit 1 is equal to or greater than the anode hydrogen threshold Ccrit_ano(H2) when an anode-side oxygen gas content c ano (O2) in electrolysis unit 1 is equal to or less than the anode oxygen threshold Ckrit_ano(O2) when a cathode-side hydrogen gas content Ck a t0(H2) in the electrolysis unit (1) is equal to or less than the cathode hydrogen threshold Ckrit_kato(H2), and / or if a cathode-side oxygen gas content Ck ato(O2) in electrolysis unit 1 is equal to or greater than the cathode oxygen threshold Ckrit_kato(O2).

[0463] For example, the procedure includes:

[0464] - Sending the control signal after a time period that is predetermined such that an anode-side hydrogen gas content c ano (H2) in electrolysis unit 1 is equal to or greater than an anode hydrogen threshold value Ccrit_ano(H2) when an anode-side oxygen gas content c ano(O2) in electrolysis unit 1 is equal to or less than an anode oxygen threshold Ckrit_ano(O2) if a cathode-side hydrogen gas content Ckato(H2) in electrolysis unit 1 is equal to or less than a cathode hydrogen threshold Ckrit_kato(H2) if a cathode-side oxygen gas content Ckato(O2) in electrolysis unit 1 is equal to or greater than a cathode oxygen threshold Ckrit_kato(O2) and / or a critical P2024.1159 WO N / P2024-20 - 91 - 5 March 2026

[0465] Temperature Tcrit and / or a critical pressure pcrit in electrolysis unit 1 is reached or falls below the set point.

[0466] For example, the procedure includes:

[0467] - Providing one or more threshold values ​​from: a hydrogen threshold Ccrit(H2), a ratio threshold Tcrit and an oxygen threshold Ccrit(O2) for the gas content in oxygen gas separator 2,

[0468] - Sending the control signal when a hydrogen gas content c(H2) in the oxygen gas separator 2 is greater than the hydrogen threshold Ccrit(H2), a ratio of hydrogen gas content C(H2) to oxygen gas content c(Ü2) in the oxygen gas separator 2 is greater than the ratio threshold Tcrit, an oxygen gas content c(Ü2) in the oxygen gas separator 2 is less than the oxygen threshold Ccrit(O2), and / or a ratio of an oxygen gas content c(Ü2) to a hydrogen gas content c(H2) in the oxygen gas separator 2 is less than the reciprocal of the ratio threshold Tcrit-

[0469] For example, the method includes providing the threshold or several thresholds for the gas content such that the gas content is outside a range for an oxyhydrogen reaction.

[0470] For example, the procedure includes:

[0471] - Sending the control signal after a predetermined time period, which is specified in such a way that

[0472] - a hydrogen gas content c(H2) in which oxygen gas separator 2 is not greater than the hydrogen threshold Ccrit(H2), a ratio of hydrogen gas content c(H2) to oxygen gas content c(Ü2) in which oxygen gas separator 2 is not greater than the ratio threshold Tcrit, an oxygen gas content c(Ü2) in which oxygen gas separator 2 is not less than the oxygen threshold Ccrit(O2), and / or a ratio of an oxygen gas content c(Ü2) to a hydrogen gas content c(H2) in which oxygen gas separator 2 is not less than the reciprocal of the ratio threshold Tcrit.

[0473] For example, the method includes operating electrolysis unit 1 with an electric current I in response to receiving the control signal, wherein the electric current I has a greater increase per unit of time than during the initial commissioning of electrolysis unit 1. P2024.1159 WO N / P2024-20 - 92 - 5 March 2026

[0474] For example, the method includes operating the electrolysis unit 1 with an electric current I in response to receiving the control signal, wherein the electric current I is subject to a maximum electrolysis current l ma x corresponds.

[0475] For example, the method includes operating the electrolysis unit 1 with an electric current I in response to receiving the control signal, wherein the electric current I is increased from a starting value Io, where the starting value Io is greater than zero amperes.

[0476] For example, a procedure for a standby of the electrolysis system includes 400, 600:

[0477] - Receiving a signal to interrupt the electrolysis of electrolysis unit 1 for standby mode,

[0478] - Lowering the hydrogen content g(H2) in the oxygen gas separator 2 in response to the interrupt signal when a first threshold CI(H2), CMM(H2) for a hydrogen gas content in the oxygen gas separator 2 is exceeded, when a first threshold for an oxygen gas content Ci(O2), CMI_I(O2) in the oxygen gas separator 2 is undershot, when a predetermined first time (h) is reached, when a first threshold n, TMM for a ratio c(H2) / c(O2) of hydrogen gas content to oxygen gas content in the oxygen gas separator 2 is exceeded, and / or when a first threshold 1 / ri , 1 / rMi_i for a ratio c(O2) / c(H2) of oxygen gas content to hydrogen gas content in the oxygen gas separator 2 is undershot, and thereafter

[0479] - Interrupting the electrolysis of electrolysis unit 1.

[0480] For example, the procedure includes:

[0481] - Lowering the hydrogen content g(H2) in the oxygen gas separator 2 in response to the signal to interrupt until a second threshold value C2(H2), CMI_2(H2) for the hydrogen content in the oxygen gas separator 2 is undershot, until a second threshold value C2(Ü2), CMi_2(Ü2) for the oxygen gas content in the oxygen gas separator 2 is exceeded, until a predetermined second time t2 is reached, until a second threshold value r2, rMi_2 for the ratio C(H2) / C(O2) of hydrogen gas content to oxygen gas content in the oxygen gas separator 2 is undershot, and / or until a second threshold value 1 / r2, 1 / rMi_2 for the ratio C(O2) / C(H2) of oxygen gas content to hydrogen gas content in the oxygen gas separator 2 is exceeded.

[0482] For example, the second threshold C2(H2), CMI_2(H2) for the hydrogen gas content is set such that the second threshold C2(H2), CMI_2(H2) for the hydrogen gas content is outside a range for a hydrogen / oxygen oxyhydrogen reaction, and / or the second threshold O2(O2), CMI_2(O2) for the oxygen gas content is set such that P2024.1159 WO N / P2024-20 - 93 - 5 March 2026

[0483] It is specified that the second threshold value 02(02), CMI_2(O2) for the oxygen gas content is outside a range for a hydrogen / oxygen oxyhydrogen reaction and / or the second time t2 is chosen such that in the time period between the first time ti and the second time t2 in the oxygen gas separator 2 a hydrogen gas content c(H2) and / or an oxygen gas content c(Ü2) is reached which is outside a range for a hydrogen / oxygen oxyhydrogen reaction.

[0484] For example, the procedure includes blocking the interruption of the electrolysis if the second threshold C2(H2), CMI_2(H2) for the hydrogen content in the oxygen gas separator is exceeded, if the second threshold 02(02), CMI_2(O2) for the oxygen gas content in the oxygen gas separator is not reached, if the time interval between the first time h and the second time t2 has not yet elapsed, if the second threshold r2 , rMi_2 for the ratio c(H2) / c(O2) is exceeded, and / or if the second threshold 1 / r2, 1 / rMi_2 for the ratio c(O2) / c(H2) is not reached.

[0485] For example, the procedure includes:

[0486] - Selecting two or more measures Mj to reduce the hydrogen content g(H2) in the oxygen gas separator 2,

[0487] - Specify for each measure Mj of the measures Mj a second threshold value CMI_2(H2) for the hydrogen gas content, a second threshold value CMI_2(O2) for the oxygen gas content, a second threshold value rMi_2 for the ratio of hydrogen gas content and oxygen gas content and / or a second threshold value 1 / rMi_2 for the ratio for the ratio of oxygen gas content and hydrogen gas content in the oxygen gas separator 2.

[0488] For example, the procedure includes

[0489] - Selecting two or more measures Mj, Mj to reduce the hydrogen content g(H2) in the oxygen gas separator 2,

[0490] - Specify for each measure Mj of the measures Mj, Mj a first time point tMi_i and a second time point twi_2, between which the measure Mj, Mj is carried out.

[0491] For example, the procedure includes specifying the respective first time point tMi_i and the respective second time point tMi_2 depending on one or more further measures Mj, Mj, which are carried out simultaneously with the respective measure Mj, Mj.

[0492] For example, the procedure includes specifying the respective first time point tMi_i depending on a specified sequence of measures Mj, Mj.P2024.1159 WO N / P2024-20 - 94 - 5 March 2026

[0493] For example, the procedure includes specifying the same first threshold values ​​CMM(H2) and second threshold values ​​CMi_2(H2) for the hydrogen gas content c(H2) in oxygen gas separator 2, the same first threshold values ​​CMM(O2) and second threshold values ​​CMI_2(O2) for the oxygen gas content c(Ü2) in oxygen gas separator 2, and / or the same first and second time points IMM , tMi_2 for the two or more measures Mi, Mj.

[0494] For example, the procedure includes interrupting the electrolysis if the hydrogen gas content C(H2) in the oxygen gas separator 2 falls below the minimum of the second threshold values ​​|CMi_2(H2)|min of the two or more measures Mj, the oxygen gas content c(Ü2) in the oxygen gas separator exceeds the maximum of the second threshold values ​​|CMi_2(O2)|max of two or more measures Mj, and / or the minimum of the threshold values ​​|rMi_2|min of the two or more measures Mj for the ratio is not reached.

[0495] For example, the procedure includes interrupting the electrolysis when the maximum of the second time points |tMi_2|max of the two or more measures Mj is reached.

[0496] For example, the procedure includes determining a new first time point tMi_i(tvnew) and / or a new second time point tMi_2(tvnew) if the second threshold CMI_2(H2) for the hydrogen gas content is not reached, the second threshold rMi_2 for the ratio of hydrogen gas content to oxygen gas content is not reached, the second threshold CMi_2(Ü2) for the oxygen gas content is exceeded, and / or the second threshold 1 / rMi_2 for the ratio of oxygen gas content to hydrogen gas content is exceeded before the second time point tMi_2 is reached.

[0497] For example, the procedure includes:

[0498] - Specifying two or more sets of first and second thresholds CMik_i(H2), CMik_2(H2), CMik_i(O2), CMik_2(O2), rMik_i , rMik_2, 1 / rMik_i, 1 / rMik_2 and / or time points tMik_i , tMik_2, - Repeating the execution of one measure Mj or two or more measures Mj, Mj, applying the thresholds of a common set for each execution.

[0499] For example, the procedure includes specifying a sequence for carrying out the two or more measures Mj, Mj.

[0500] For example, the procedure after interrupting electrolysis includes:

[0501] - Introduction of inert gas into oxygen gas separator 2 if at least one of the following is fulfilled: P2024.1159 WO N / P2024-20 - 95 - 5 March 2026

[0502] - the hydrogen gas content c(H2) in the oxygen gas separator 2 is greater than a third threshold value Ca(H2) for the hydrogen gas content c(H2),

[0503] - an oxygen gas content c(Ü2) in the oxygen gas separator 2 is less than a third threshold 03(02) for the oxygen gas content c(O2), and

[0504] - a predetermined third time period t3 has expired.

[0505] For example, the procedure includes:

[0506] - Specifying the third threshold Ca(H2) for the hydrogen gas content c(H2) equal to or greater than the second threshold C2(H2), CMI_2(H2) of the hydrogen content, and / or - Specifying the third threshold 03(02) for the oxygen gas content c(Ü2) equal to or less than the second threshold 02(02), CMI_2(O2) of the oxygen gas content.

[0507] For example, the procedure includes:

[0508] - Specifying the third threshold Ca(H2) for the hydrogen gas content c(H2) as less than the second threshold C2(H2), CMI_2(H2) of the hydrogen content, and / or

[0509] - Specifying the third threshold 03(02) for the oxygen gas content c(Ü2) greater than the second threshold 02(02), CMI_2(O2) of the oxygen gas content.

[0510] For example, the procedure includes:

[0511] - Selection of two or more measures Mi, Mj to reduce the hydrogen content g(H2) in the oxygen gas separator 2,

[0512] - Specify for each measure Mj, Mj of measures Mj, Mj a first threshold CMM(H2) for the hydrogen gas content, a first threshold CMI_I(O2) for the oxygen gas content, a first threshold TMU for the ratio of hydrogen gas content to oxygen gas content, and / or a first threshold 1 / rMi_i for the ratio of oxygen gas content to hydrogen gas content.

[0513] For example, a control device is adapted to carry out a procedure according to one or more of the preceding examples.

[0514] The electrolysis plant 400, 600, for example, comprises the control device and the electrolysis unit 1, which is coupled to the control device 5 via a signal connection, as well as the oxygen gas separator 2 for separating oxygen gas and electrolyte, which is fluidly coupled to the electrolysis unit 1 and is also coupled to the control device 5 via a signal connection. P2024, 1159 WO N / P2024-20 - 96 - 5 March 2026

[0515] The electrolysis plant 400, 600, for example, has the electrolyte preparation arrangement 200, wherein the electrolyte preparation arrangement 200 comprises at least one of: an electrolyte preparation device 7, a heater 17, a pump 21 and a pressure-controlled container.

Claims

P2024.1159 WO N / P2024-20 - 97 - 5 March 2026 Claims 1. Method for operating an electrolysis plant (400, 600), wherein the electrolysis plant comprises an electrolysis unit (1) and an oxygen gas separator (2) for separating oxygen gas and electrolyte, and the electrolysis unit (1) is connected to a power connection (4) for an energy supply (E) for electrolysis in the electrolysis unit (1), the method comprising: - Receiving a control signal to terminate an interruption of the electrolysis of the electrolysis unit (1) while the electrolysis in the electrolysis unit (1) is interrupted.

2. The method according to the preceding claim, comprising: - Providing a pressure threshold (Pcrit) for the electrolysis unit (1), - Determining a pressure (p un it) in the electrolysis unit (1), - Comparing the measured pressure (p unit) with the pressure threshold (pcrit), and - if the determined pressure (p un if the pressure threshold (Pcrit) is less than or equal to the pressure threshold value (Pcrit): send the control signal.

3. A method according to any one of the preceding claims, comprising: - Providing a temperature threshold (Tknt) for the electrolysis unit (1), - Determining an operating temperature (Tunit) of the electrolysis unit (1), - Comparing the determined operating temperature (Tunit) with the temperature threshold (Tknt), and -if the determined operating temperature (Tunit) is equal to or less than the temperature threshold (Tkrit): Send the control signal.

4. A method according to any one of the preceding claims, comprising: - Providing a voltage threshold (oct) for the electrolysis unit (1), - Determining mechanical stress (o un it) of the electrolysis unit (1), - Comparing the determined tension (o un it) with the stress threshold (oct), and - if the determined stress (o un if the voltage threshold (oct) is equal to or less than the voltage threshold (oct): send the control signal.

5. A method according to any one of the preceding claims, comprising: - Providing one or more thresholds from: an anode hydrogen threshold (Ckrit_ano(H2)), an anode oxygen threshold (Ckrit_ano(O2)), a cathode hydrogen threshold (Ckrit_kato(H2)) and a cathode oxygen threshold (Ckrit_kato(O2)) ,P2024.1159 WO N / P2024-20 - 98 - 5 March 2026 - Sending the control signal when an anode-side hydrogen gas content (c an o(H2)) in the electrolysis unit (1) is equal to or greater than the anode hydrogen threshold (Ccrit_ano(H2)) when an anode-side oxygen gas content (c ano(O2)) in the electrolysis unit (1) is equal to or less than the anode oxygen threshold (Ckrit_ano(O2)) if a cathode-side hydrogen gas content (Ckato(H2)) in the electrolysis unit (1) is equal to or less than the cathode hydrogen threshold (Ckrit_kato(H2)), and / or if a cathode-side oxygen gas content (Ckato(O2)) in the electrolysis unit (1) is equal to or greater than the cathode oxygen threshold (Ckrit_kato(O2)).

6. A method according to any one of the preceding claims, comprising: - Sending the control signal after a time period that is predetermined such that an anode-side hydrogen gas content (c ano (H2)) in the electrolysis unit (1) is equal to or greater than an anode hydrogen threshold (Ccrit_ano(H2)) when an anode-side oxygen gas content (c ano(O2)) in the electrolysis unit (1) is equal to or less than an anode oxygen threshold (Ckrit_ano(O2)) when a cathode-side hydrogen gas content (Ck a t0(H2)) in the electrolysis unit (1) is equal to or less than a cathode hydrogen threshold (Ckrit_kato(H2)) if a cathode-side oxygen gas content (Ckato(O2)) in the electrolysis unit (1) is equal to or greater than a cathode oxygen threshold (Ckrit_kato(O2)) and / or a critical temperature (Tknt) and / or a critical pressure (pknt) in the electrolysis unit (1) is reached or fallen below.

7. A method according to any one of the preceding claims, comprising: - Providing one or more threshold values ​​from: a hydrogen threshold (Ccrit(H2)), a ratio threshold (rknt) and an oxygen threshold (Ccrit(O2)) for the gas content in the oxygen gas separator (2), - Sending the control signal when a hydrogen gas content (c(H2)) in the oxygen gas separator (2) is greater than the hydrogen threshold (Ccrit(H2)), a ratio of hydrogen gas content (C(H2)) TO oxygen gas content (c(Ü2)) in the oxygen gas separator (2) is greater than the ratio threshold (rknt), an oxygen gas content (c(Ü2)) in the oxygen gas separator (2) is less than the oxygen threshold (Ccrit(O2)), and / or a ratio of an oxygen gas content (c(Ü2)) to a hydrogen gas content (c(H2)) in the oxygen gas separator (2) is less than the reciprocal of the ratio threshold (rknt).

8. The method according to the preceding claim, in its entirety. - Provide the threshold or thresholds for the gas content such that the gas content is outside a range for an oxyhydrogen reaction. P2024.1159 WO N / P2024-20 - 99 - 5 March 2026 9. A method according to any one of the preceding claims, comprising: - Sending the control signal after a predetermined time period, which is specified in such a way that - a hydrogen gas content (c(H2)) in the oxygen gas separator (2) is not greater than the hydrogen threshold (Ccrit(H2)), a ratio of hydrogen gas content (c(H2)) to oxygen gas content (c(H2)) in the oxygen gas separator (2) is not greater than the ratio threshold (rkcrit), an oxygen gas content (c(H2)) in the oxygen gas separator (2) is not less than the oxygen threshold (Ccrit(H2)), and / or a ratio of an oxygen gas content (c(H2)) to a hydrogen gas content (c(H2)) in the oxygen gas separator (2) is not less than the reciprocal of the ratio threshold (rkcrit).

10. A method according to any one of the preceding claims, comprising: - Operating the electrolysis unit (1) with an electric current (I) in response to receiving the control signal, wherein the electric current (I) has a greater increase per time than during the initial start-up of the electrolysis unit (1).

11. A method according to any one of the preceding claims comprising: - Operating the electrolysis unit (1) with an electric current (I) in response to receiving the control signal, wherein the electric current (I) corresponds to a maximum electrolysis current (Imax).

12. A method according to any one of the preceding claims comprising: - Operating the electrolysis unit (1) with an electric current (I) in response to receiving the control signal, wherein the electric current (I) is increased from a starting value (Io), where the starting value (Io) is greater than zero amperes.

13. Control device (5) for an electrolysis plant (1), wherein the control device (5) is adapted to carry out a method according to one of the preceding claims.

14. Electrolysis plant (400, 600), comprising: - a control device (5) according to claim 13, - an electrolysis unit (1) which is coupled to the control device (5) via signal technology, - an oxygen gas separator (2) for separating oxygen gas and electrolyte, which is coupled to the electrolysis unit (1) via a fluid conductor and which is coupled to the control device (5) via signal technology.

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