Electrolysis device and method for operating electrolysis device

Abstract

The invention relates to an electrolysis plant (1) comprising an electrolysis device (3) for generating hydrogen (H2) and oxygen (O2) as product gases, which electrolysis device has a plurality of electrolysis cells, each having two half-cells separated by an ion-permeable membrane (5), thereby forming an anode chamber (7) and a cathode chamber (9). In this case, an oxygen product line (11B) is connected on the anode side on the anode chamber (7) and a hydrogen product line (11A) is connected on the cathode side on the cathode chamber (9), the hydrogen product line (11A) leading into the first gas separator (13A) and the oxygen product line (11B) leading into the second gas separator (13B). The electrolysis device (1) has a differential pressure control device (15) which comprises a differential pressure sensor (17A) which is arranged such that a differential pressure ([Delta] p) between the anode chamber (7) and the cathode chamber (9) can be determined and the value thereof can be processed in the differential pressure control device. The invention also relates to a method for operating such an electrolysis device (1).

Description

Field of the Invention

[0001] The present invention relates to an electrolysis device, which includes an electrolysis unit for generating hydrogen and oxygen as product gases. The electrolysis unit has a plurality of electrolytic cells, each of which has two half-cells separated by an ion-permeable membrane, thereby forming an anode chamber and a cathode chamber. The present invention also relates to a method for operating the electrolysis device. Background Art

[0002] Today, hydrogen is produced, for example, by proton exchange membrane (PEM) electrolysis or alkaline electrolysis. The electrolysis unit generates hydrogen and oxygen from the supplied water by means of electrical energy.

[0003] The electrolysis unit usually has a plurality of electrolytic cells arranged adjacent to each other. Through the electrolysis of water, water is decomposed into hydrogen and oxygen in the electrolytic cells. A variety of electrolysis technologies and electrolysis units are known in this regard. In a PEM electrolysis unit, distilled water is usually supplied as a reactant on the anode side, and the distilled water is decomposed into hydrogen and oxygen at a proton-permeable membrane (Proton-Exchange-Membrane; PEM). It is also possible to perform so-called anion exchange membrane water electrolysis (AEMWE) or simply AEM electrolysis, in which an aqueous solution of an alkali is used as a reactant in a manner somewhat similar to PEM electrolysis, usually an aqueous solution of potassium hydroxide KOH or potassium bicarbonate KHCO3 with a suitably selected concentration of about 1 mol / l. Water, more precisely the aqueous solution of the alkali, is oxidized to oxygen at the anode. Protons pass through the proton-permeable membrane. Hydrogen is produced on the cathode side. Here, water is usually supplied to the anode chamber and / or the cathode chamber from the bottom side. In alkaline electrolysis, a membrane is also provided, which is configured as a semi-permeable membrane or a diaphragm that selectively allows certain ions to pass through. Potassium lye (potassium hydroxide solution, KOH) with a concentration usually of 20-40% is used as the electrolyte. The airtight membrane, the so-called diaphragm, allows the transport of OH - ions, but at the same time prevents the mixing of the generated product gases.

[0004] In terms of equipment technology, the electrolysis process takes place in a so-called electrolysis stack, which consists of a plurality of electrolytic cells. In the electrolysis stack under the action of a DC voltage, water is introduced as a reactant, and after passing through the electrolytic cells, two fluid streams composed of water and bubbles (oxygen O2 or hydrogen H2) appear. Therefore, subsequent gas separation is required, that is, the phase separation of water and the corresponding gaseous product gas in the phase mixture. Here, usually, a plurality of electrolytic cells and further a plurality of electrolysis units are connected to each other through pipes, and the separated gas-water mixture is supplied to a central gas separator.

[0005] In practice, the oxygen stream contains a small amount of hydrogen here, and the hydrogen stream contains a small amount of oxygen. The amount of the corresponding impurity gas is related to the design of the electrolysis cell and also varies depending on the current density, catalyst composition, and aging, and furthermore is related to the membrane material of the electrolysis cell. Here, it is inherent to the system that a very small amount of the other product gas is present in the stream of one product gas. In a further process, usually even trace amounts of oxygen are removed from the hydrogen in subsequent gas purification steps, which can sometimes be very complex and cost-intensive, especially when a particularly high product gas quality is required, such as in the case of using hydrogen for, for example, fuel cells. In certain cases, it may be necessary here to reduce the impurity gas concentration at or after the electrolysis cell or electrolysis stack, for example, in a gas separator downstream of the electrolysis device.

[0006] During partial load operation or generally during load changes and during membrane aging, this problem is exacerbated and leads to restricted operating modes or even an inability to continue operating safely and an early safety shutdown. In particular, when the load gradient is positive, for example, during the start-up of the electrolysis device or when changing from partial load operation to full load operation, due to the differential pressure across the cell partition from the anode chamber to the cathode chamber and the resulting pressure gradient, the membrane is in a critical state. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an electrolysis device that can operate in an improved manner in terms of safety and device efficiency.

[0008] According to the present invention, this object is achieved by an electrolysis device comprising an electrolysis device for generating hydrogen and oxygen as product gases, the electrolysis device having a plurality of electrolysis cells, each of which has two half-cells separated by an ion-permeable membrane, thereby forming an anode chamber and a cathode chamber, wherein an oxygen product line is connected to the anode chamber on the anode side and a hydrogen product line is connected to the cathode chamber on the cathode side, wherein the hydrogen product line leads into a first gas separator and the oxygen product line leads into a second gas separator, and the electrolysis device further has a differential pressure regulating device, the differential pressure regulating device comprising a differential pressure sensor which is arranged such that the differential pressure between the anode chamber and the cathode chamber can be determined and whose value can be processed in the differential pressure regulating device.

[0009] According to the present invention, this object is also achieved by a method for operating the corresponding electrolysis device, wherein hydrogen and oxygen are generated as product gases, wherein the differential pressure between the anode chamber and the cathode chamber is measured using a differential pressure sensor, wherein the measurement signal is read into the differential pressure regulating device and compared with a reference value, and wherein, if the differential pressure is less than the reference value, the continued operation mode is maintained.

[0010] The advantages and preferred design options described below for the method can be transferred, mutatis mutandis, to the electrolysis device.

[0011] The present invention is based on the recognition that the differential pressure tolerance of the ion-permeable membrane of an electrolysis device is an important parameter for the design and operation of the electrolysis device. Therefore, it is indispensable for the monitoring, operation adjustment, and operation mode of the electrolysis device to measure the current differential pressure across the ion-conducting membrane as accurately and reliably as possible "in-situ" without distortion. Especially considering the degradation of the ion-conducting membrane due to aging, it is of great technical and economic significance to determine whether the membrane still has sufficient differential pressure tolerance and thus whether it can still operate safely. The hitherto known measurement procedures and the values determined thereby are indirect and thus inaccurate for determining the differential pressure, which particularly leads to large measurement inaccuracies in the case of higher pressure ranges. To avoid significant or irreversible membrane damage (membrane loss), due to the inaccuracies, a large safety margin has hitherto been required, which has led to these measures being taken even when the electrolysis device physically does not yet require premature safe shutdown and overhaul. This also involves monitoring the passage of hydrogen from the cathode chamber across the membrane into the anode chamber due to the current differential pressure (i.e., the impurity gas concentration of hydrogen in the oxygen side), and for safety reasons (explosion risk), the differential pressure must be limited below a maximum value. From an economic perspective, the existing solutions are inadequate and very disadvantageous. The term "ion-conducting membrane" should be understood technically in a broad sense here, particularly in the sense of an ion-permeable membrane or an ion-transporting membrane, and thus an ion-conducting membrane can be used for various types of electrolysis.

[0012] It should be noted here that from a technical-physical perspective, water electrolysis is unit-structured and has a large number of electrolysis cells. These cells are in turn constructed as two half-cells separated by a membrane. The gas evolution of the product gas occurs in each of the two half-cells. Due to the stoichiometry of the electrolysis reaction, the ratio of the gas volume flow rates H2 / O2 is 2 to 1. This asymmetry causes a differential pressure across the cell partition, i.e., across the ion-conducting membrane, especially in the case of a negative load gradient, and this differential pressure is from the hydrogen half-cell side forming the cathode chamber across the membrane to the oxygen half-cell side forming the anode chamber. The reason for this is that the additional amounts of liquid that the product gas has to displace are different. Therefore, violent gas formation leads to the formation of shock waves in the hydraulic system, resulting in local pressure peaks that exceed the target pressure by many times and hitherto cannot be reliably measured, i.e., the so-called Joukowsky shock in the hydraulic system.

[0013] As aging progresses and due to defects in the membranes that conduct ions in each battery, the battery may lose its differential pressure tolerance characteristic necessary for operation. If this occurs, then the electrolysis system must be repaired at a cost of money and time, even though it can still be used for stable operation.

[0014] The present invention recognizes here that the currently known simple and indirect differential pressure monitoring cannot particularly reliably determine the increase in the concentration of hydrogen in oxygen and maintain it below the still permitted limit for future requirements. This is especially true for future electrolysis equipment with a high system pressure of > 30 bar required for its electrolysis device. In the case of usually having two independent absolute pressure sensors, the sensitivity of the sensors is not sufficient to determine and precisely resolve the differential pressure typically in the range of ± 50 mbar by subtraction: for example, an absolute pressure sensor with a measuring range of 1 bar provides a scaling ratio of 10 mV / mbar in the voltage range of 0 - 10 V. In contrast, an absolute pressure sensor with a measuring range of 50 bar, for example, provides a scaling ratio of 0.2 mV / mbar. Just from this simple consideration, the typical 0.1% relative measurement accuracy of the measured value corresponds to a measurement accuracy of ± 1 mbar or ± 50 mbar, which is not sufficient.

[0015] In contrast, with the present invention, it is possible for the first time to directly determine a very precise "in-situ" differential pressure even in the case of a high system pressure. As an in-situ status indicator, direct differential pressure measurement is achieved at a selected and representative measurement site in the electrolysis equipment. For this purpose, a differential pressure regulating device is provided, which includes a differential pressure sensor that is arranged such that the differential pressure between the anode chamber and the cathode chamber can be determined and its value can be processed in the differential pressure regulating device. Therefore, the differential pressure sensor is connected across two selected sensing sites respectively representing the anode chamber and the cathode chamber, and its differential pressure measurement signal can be processed in the differential pressure regulating device. The direct differential pressure measurement enables a very precise and almost delay-free status diagnosis and thus ensures the safe operation of the electrolysis equipment. To determine and evaluate the differential pressure, the differential pressure regulating device has a differential pressure sensor that directly measures the differential pressure between the half-cells. This measurement can be carried out at different sensing sites as required.

[0016] Therefore, it is particularly advantageous that the electrolysis equipment can continue to operate because the current differential pressure can be reliably monitored and adjusted relative to the permitted maximum differential pressure. The maximum permitted differential pressure can also be predetermined and set or adjusted in the differential pressure regulating device.

[0017] Here, the present invention can be advantageously and flexibly applied to various types of electrolysis devices, such as alkaline water electrolysis, PEM electrolysis, or anion exchange membrane water electrolysis (AEMWE), in which a differential pressure regulating device with a differential pressure sensor is implemented in the electrolysis device. Thereby, in particular, the risk that gas undesirably enters from one side of the electrolysis half-cell into the other side due to the differential pressure is minimized and monitored. Especially for PEM electrolysis, even if the separating membrane develops cracks, holes, or similar damage due to aging, the present invention can ensure safe continued operation. Measurements taken directly across the half-cell chambers (anode chamber and cathode chamber), more precisely in the vicinity thereof, best reflect the differential pressure situation during dynamic processes, such as the power consumption when the electrolysis device is started up or when the operating mode changes between partial load operation and full load operation.

[0018] In a particularly preferred design of the electrolysis device, the differential pressure regulating device is designed to limit the differential pressure, wherein a maximum value of the differential pressure is set.

[0019] Thereby, it is possible to particularly simply and at the same time effectively limit the differential pressure between the anode chamber and the cathode chamber, and thus limit the differential pressure load across the membrane according to the set maximum differential pressure value, while at the same time monitoring the passage of gas. Generally, the differential pressure during operation is preferably as low as possible.

[0020] Preferably, in the electrolysis device, the differential pressure sensor is connected to corresponding sensing sites on the first gas separator and the second gas separator, wherein the sensing sites are arranged in the upper region of the gas separator, so that the differential pressure in the gas phase of the gas separator can be determined. Thereby, the differential pressure between the gas phases of the gas separators can be determined.

[0021] Thereby, during the operation of the electrolysis device, as a reliable and representative measure of the differential pressure, the pressure difference between the gas chambers of the two gas separators is measured. Through the sensing sites of the differential pressure sensor, the differential pressure can be directly and largely undistorted sensed here. The gas phase is located in the upper container region of the gas separator, above the liquid phase, while the liquid phase is located in the lower container region. Due to the phase separation of the liquid phase and the gas phase in the corresponding product gas, hydrogen or oxygen in the phase mixture can be spatially separated. The present invention recognizes that by positioning and implementing the differential pressure sensor at the particularly selected sensing sites of the gas separator, a particularly reliable and representative differential pressure value is provided in the gas phase, which allows conclusions to be drawn "on-site" regarding the state of the membrane in the half-cell and the transport of gas across the membrane.

[0022] In a particularly preferred design of the electrolysis device, the differential pressure sensor is connected to the corresponding sensing sites of the anode half-cell and the cathode half-cell, so that the differential pressure across the half-cell can be determined.

[0023] With this configuration, differential pressure measurements can be made directly across representative half-cells, making the differential pressure between the anode and cathode chambers particularly precise and at the same time flexible. Here, the selected half-cells do not necessarily belong to the same electrolytic cell. It is sufficient if two sensing sites measure the differential pressure between the anode and cathode chambers across the respective representative half-cells. Instantaneous local differential pressure information is provided. Such measurements made directly across or in the vicinity of the half-cells represent the local differential pressure situation during dynamic processes, such as during the start-up of an electrolysis device, in a particularly reliable manner. Redundancy can also be provided by implementing multiple differential pressure sensors in the electrolysis device, which allows representative in-situ differential pressure measurements to be made across half-cells, across electrolysis stacks or segments. The accuracy is improved by the redundancy, and in addition, dynamic changes in the electrolysis device can be located in time and space. Thus, local state information about the membrane conducting ions in the electrolysis device can also be detected by the number and arrangement of the differential pressure sensors, and these local state information are about the current pressure-bearing capacity of the membrane due to aging and gas passage.

[0024] Preferably, in the electrolysis device, an electrolytic cell is formed by an anode half-cell and a cathode half-cell, so that the differential pressure across the electrolytic cell can be determined specifically for the cell.

[0025] Here, the selected half-cells in the electrolysis assembly of the electrolysis device are considered, which are separated by a membrane and have sensing sites through which the differential pressure sensor measures the differential pressure. Thereby, differential pressure measurements specific to the cell are achieved, and the cell state can be located particularly precisely in space and time.

[0026] Compared with simply measuring the differential pressure in the gas phase between the gas separators, especially in the case of a positive load gradient, the differential pressure signal may be strongly attenuated and delayed in time because the pressure must first be built up in the usually very large-sized gas separators. Here, introducing the differential pressure sensor into the half-cell provides additional advantages in these special operating modes. Thus, differential pressure measurements across the gas separator and locally across the selected half-cells can be advantageously combined and complement each other.

[0027] In a particularly preferred design of the electrolysis device, the sensing sites are arranged at the reactant inlets of the anode half-cell and the cathode half-cell.

[0028] Accordingly, a corresponding sensing site is implemented on the battery inlet side in the electrolysis device, so that the differential pressure between the anode chamber and the cathode chamber can be directly and accurately determined, because dynamic effects can be detected locally together. For PEM electrolysis, for example, sensing sites can be arranged at the battery inlet for the reactant water or near the battery inlet, respectively, at the reactant inlets of the differential pressure sensors on the oxygen side and the hydrogen side, which advantageously facilitates the particularly accurate measurement and monitoring of the differential pressure between the anode chamber and the cathode chamber. Here, in a preferred design of the electrolysis device, a first reactant pipeline is connected to the cathode chamber on the cathode side, and a second reactant pipeline is connected to the anode chamber on the anode side.

[0029] Here, water, especially fully desalinated water, is considered as the reactant for PEM electrolysis, and this water can be supplied through two reactant pipelines on the anode side and the cathode side. Thus, two reactant circuits are formed as water circuits in PEM electrolysis. In an alternative design of PEM electrolysis, the reactant water can also preferably be supplied only on the anode side through the reactant pipeline. In this case, the cathode remains dry and the reactant water is not applied through the reactant pipeline, so only one reactant circuit is used. It is also called dry cathode operation. Alternatively, the electrolysis device can be designed for alkaline electrolysis, where the electrolyte (such as potassium hydroxide solution with a concentration of 20%-40%) can be supplied as a reactant to the electrolysis cell through the reactant pipeline.

[0030] Preferably, in the electrolysis device, the ion-permeable membrane is designed as a proton-permeable membrane, so that PEM electrolysis can be carried out.

[0031] In the case of PEM electrolysis, the proton-permeable membrane is preferably designed based on a gas-tight and liquid-tight fluoropolymer. Therefore, the membrane can be designed to selectively perform ion transport for protons.

[0032] In an acidic electrolysis device or a proton exchange membrane electrolysis device (PEM electrolysis), distilled or fully desalinated water is decomposed into hydrogen and oxygen by an electric current. The electrolysis device includes a proton-permeable polymer membrane (English: proton exchange membrane or polymer electrolyte membrane, abbreviated as PEM). The membrane is coated with a porous electrode made of platinum supported on carbon on the cathode side, and a noble metal in metallic form or in oxide form (mainly iridium and ruthenium) on the anode side. An external voltage is applied at these electrodes. Usually, water is supplied as a reactant on the anode side of the electrolysis device. Both half-cells can also be filled with water, or only the cathode side is filled with water, which is related to the purpose of use. The catalytic action of the noble metal electrode causes water to be decomposed on the anode side: oxygen, free electrons and positively charged H are generated.+ Ions. Hydrogen ions diffuse through the proton-conducting membrane to the cathode side, where the hydrogen ions combine with electrons to form hydrogen gas as the product gas.

[0033] In the case of an alternatively particularly preferred anion exchange membrane (AEM), the membrane is designed to selectively perform ion transport for hydroxide anions to transport hydroxide ions OH - from the anode chamber through the ion-transporting membrane to the cathode chamber. Thus, the electrolysis device is equipped with an electrolysis device based on anion exchange membrane water electrolysis (AEMWE).

[0034] In a further preferred design of the electrolysis device, the ion-permeable membrane is designed as a diaphragm that selectively allows hydroxide ions to pass through, enabling alkaline electrolysis to be carried out.

[0035] For an alkaline electrolysis device, hydrogen is formed at the cathode and oxygen is formed at the anode under the action of a DC voltage of at least 1.5 volts. Potassium hydroxide solution (KOH), usually with a concentration of 20%-40%, is used as the electrolyte. An airtight membrane, i.e., a so-called diaphragm, is used as the ion-permeable membrane. This allows the transport of OH - ions, but at the same time prevents the mixing of the generated product gases. So-called "DSA electrodes" (dimensionally stable anodes) are used as the electrodes, which are usually titanium electrodes coated with ruthenium oxide. These are metal plate meshes coated with noble metal catalyst oxides (such as ruthenium oxide or iridium oxide). However, there are also systems with Raney nickel catalysts in gas diffusion electrodes. Alkaline electrolysis devices are widely used worldwide.

[0036] The present invention can be advantageously implemented and used in PEM electrolysis devices, AEM water electrolysis devices, and alkaline electrolysis devices, so that regardless of the technology used, the differential pressure regulating device can be used in the electrolysis device. The separation of the half-cells depends on the technology. Alkaline electrolysis uses a so-called diaphragm, a semi-permeable membrane that is permeable to alkaline liquids and at the same time has low gas permeability below a certain differential pressure. PEM electrolysis and AEM electrolysis use airtight and liquid-tight fluoropolymers as described above. Therefore, PEM technology is generally significantly less sensitive to higher differential pressures or differential pressure changes.

[0037] Here, with the present invention, even a slight change in the pressure difference or a fluctuation of <50 mbar can now be determined and monitored very precisely and directly. This allows for reliable diagnosis and conclusions to be drawn, especially regarding the aging state of the membrane and the unwanted passage of gases through the ion-conducting membrane.

[0038] Thus, in a method for operating such an electrolysis device, hydrogen and oxygen can be produced as product gases, wherein the differential pressure between the anode chamber and the cathode chamber is measured using a differential pressure sensor, wherein the measurement signal is read into a differential pressure regulating device and compared with a reference value, and wherein, if the differential pressure is less than the reference value, a continuous operation mode is maintained.

[0039] A predetermined and adjustable reference value is stored in the differential pressure regulating device as the maximum value of the permitted pressure difference. Due to the improved accuracy of differential pressure measurement and differential pressure limitation, the continuous operation of the electrolysis device can be planned and advantageously made feasible. Here, the continuous operation can include various operation modes, such as normal operation at full load or partial load, or load changes or even start-up. Even in the continuous operation mode, the differential pressure is continuously monitored. Compared with previous measurement schemes using inaccurate absolute pressure sensors, premature shutdown operation due to maintained safety margins is avoided, and economical continuous utilization and hydrogen production are achieved.

[0040] Preferably, if the differential pressure is greater than the reference value, a shutdown operation mode is initiated by the differential pressure regulating device.

[0041] By measuring the differential pressure and thus the higher measurement accuracy, the adjustment parameters for initiating the shutdown operation mode in the differential pressure regulating device can be determined more precisely, especially at high system pressures, and the safety margin can be smaller. Premature shutdown operation is avoided because continuous operation advantageously most likely has priority.

[0042] Here, in the method, pressure electrolysis with a system pressure of at least 5 bar is preferably carried out. Particularly preferably, a high system pressure greater than 30 bar is used as the nominal pressure for carrying out the method using a pressure electrolysis device. The system pressure is preferably at least 10 bar to 35 bar. Thus, the method of the present invention can be particularly advantageously applied to pressure electrolysis because the direct measurement of the differential pressure by at least two differential pressure sensors implemented improves the measurement accuracy, and reliable differential pressure determination and differential pressure limitation are achieved even at high pressures. Generally, the differential pressure across the membrane for transporting ions between the anode chamber and the cathode chamber is preferably as low as possible and in any case should not often exceed the maximum value of the differential pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Embodiments of the present invention are explained in more detail with reference to the accompanying drawings. The drawings schematically and extremely simplifiedly show here:

[0044] An electrolysis device having a differential pressure regulating device according to the present invention. DETAILED DESCRIPTION

[0045] In the sole drawing, the electrolysis device 1 is shown in a highly simplified schematic illustration of the device parts and components. The electrolysis device 1 has an electrolysis unit 3, which is optionally designed as a PEM electrolysis unit or an alkaline electrolysis unit.

[0046] The electrolysis unit 3 includes a cathode chamber 9 and an anode chamber 7 separated by an ion-permeable membrane 5. The anode chamber 9 and the cathode chamber 7 are each formed by a plurality of anode half-cells and cathode half-cells stacked axially, not shown in detail in the figure, which are separated by the ion-conducting membrane 5. Thus, the vertically oriented electrolysis unit 3 shown in the figure is designed to electrochemically decompose water H2O or an electrolyte as a reactant into hydrogen H2 and oxygen O2 as product gases by means of an electric current. In the case of acidic electrolysis, fully desalinated water H2O is used as the reactant. In the case of alkaline electrolysis, an alkaline solution, for example an aqueous potassium hydroxide KOH solution with a concentration usually of 20% to 40%, is used. A plurality of such electrolysis cells can be connected in series successively to form a so-called electrolysis stack stacked horizontally.

[0047] In the illustrated embodiment, the electrolysis unit in the electrolysis device 1 is designed as a PEM electrolysis unit. Each electrolysis cell here has a proton-permeable membrane 5 based on a fluoropolymer, with the corresponding electrodes (anode and cathode) placed on both sides thereof, and an external voltage is applied through these electrodes during operation. On the cathode side, there is a first reactant pipeline 21A for supplying water H2O to the cathode chamber 9. On the anode side, a second reactant pipeline 21B for supplying water H2O is connected to the anode chamber 7. Thus, two circuits are realized in the electrolysis unit 3 designed as a PEM electrolysis unit. Therefore, water H2O circulates not only through the anode chamber 7 but also through the cathode chamber 5. However, it is also possible to realize an electrolysis unit 3 with only one anode-side circuit.

[0048] During the operation of the electrolysis device 1, the oxygen O2 generated in the anode chamber 7 in the electrolysis cell is discharged through the oxygen product pipeline 11B. On the cathode side, there is a hydrogen product pipeline 11A for discharging the generated hydrogen from the cathode chamber 5.

[0049] In order to perform a corresponding phase separation of the product gas and the water phase mixture, a first gas separator 13A is connected downstream of the hydrogen product pipeline 11A. Correspondingly, a second gas separator 13B is connected downstream of the oxygen product pipeline 11B. Thus, phase separation is achieved, so that in the upper regions of the gas separators 11A, 11B there are gas chambers with a gas phase, while the liquid phase is located at the bottom of the gas separators 11A, 11B, i.e., the water level.

[0050] The electrolysis device 1 is equipped with a differential pressure regulating device 15, which includes differential pressure sensors 17A and 17B. Therefore, the differential pressure sensor 17A is connected across the gas chamber, and this differential pressure sensor is led out at the corresponding sensing parts 19A and 19B on the first gas separator 13A and the second gas separator 13B, so that the differential pressure Δp related to the gas phase of the gas separators 13A and 13B can be directly determined. In addition, corresponding pressure measuring devices for determining the absolute pressure value are connected to the gas separators 13A and 13B, so that in addition to the differential pressure Δp, the absolute pressure p in the gas phase of the first gas separator 13A can also be determined A and the absolute pressure p in the gas phase of the second gas separator 13B B . The differential pressure Δp between the cathode chamber 9 and the anode chamber 7 can be determined by the differential pressure sensor 17A. The pressure values p A and p B in the gas separators 13A and 13B and the measurement signal of the differential pressure are processed in the differential pressure regulating device 15. As the input variables of the differential pressure regulating device, the maximum differential pressure Δp max is stored or can be set max . This value of the maximum differential pressure Δp max can be adjusted if necessary to adapt to the corresponding selected or typical operating conditions of the electrolysis device 3 and the aging state of the ion-permeable membrane 5. The differential pressure regulating device is arranged to output control signals S1 and S2, and these control signals can be transferred to a higher-level control system (not shown in detail) of the electrolysis device 1. Thereby, the physical operating parameters of the electrolysis device 1, such as electrolysis current, electrolysis current density, reaction object volume flow rate, system pressure or differential pressure Δp < Δp max .

[0051] The differential pressure regulating device 15 can also be designed as a part of the higher-level control system and integrated into it here. Therefore, the control system is designed to control the operation of the electrolysis stack. With the help of the control system, for example, a predetermined absolute pressure p a can be set as the target value in the anode chamber 7 and a predetermined absolute pressure p b can be set as the target value in the cathode chamber 9, where, for example, it is also possible to achieve the operation that the pressure p a on the anode side is set higher than the pressure p k in the cathode chamber 9. In this way, the negative consequences that may be caused by membrane damage during the operation of the electrolysis device 3 are minimized, because when the ion-permeable membrane 5 ruptures, less hydrogen gas migrates from the cathode chamber 9 through the membrane to the anode chamber 7. Thereby, the emergency operation characteristics are achieved

[0052] To further improve the accuracy of differential pressure measurement and differential pressure monitoring, as an alternative to or in addition to the differential pressure sensor 17A, another differential pressure sensor 17B is connected to the respective sensing parts 19A, 19B of the anode half-cell and the cathode half-cell, so that the differential pressure Δp can be locally determined through the selected and representative half-cells. Here, the selected half-cells can form one and the same electrolytic cell. By locally introducing the differential pressure sensor 17B at the half-cell level, the measurement signal of the differential pressure Δp is not distorted by hydrodynamic processes, which especially occurs during load changes or startup. In particular, through local measurement, the dynamic effects of the water columns above the anode chamber 7 and the cathode chamber 9 and the phase mixture composed of product gas and water are further minimized, and good measurement quality can be ensured even at high system pressures, such as in pressure electrolysis.

[0053] During the operation of the electrolysis device 1, the reactant water H2O is supplied to the electrolysis unit 3 through the reactant pipelines 21A, 21B, and hydrogen H2 and oxygen O2 are generated as product gases. The differential pressure Δp between the anode chamber 7 and the cathode chamber 9 is measured by the differential pressure sensors 17A, 17B. The measurement signal is read into the differential pressure regulating device 15 and compared with the reference value Δp max . If the differential pressure Δp is less than the reference value Δp max , the continuous operation mode is maintained.

[0054] If the differential pressure Δp is greater than the reference value Δp max , the shutdown operation mode is started through the differential pressure regulating device 15. This can also be carried out in the upper-level control unit by transferring the corresponding control signals S1, S2 from the differential pressure regulating device 15 to the upper-level control unit. Due to the more accurate differential pressure measurement, pressure electrolysis with a high system pressure of at least 30 bar can also be carried out reliably. Overall, the continuous operation mode and the emergency operation characteristics enable the electrolysis device to continue operating safely and avoid premature shutdown, which brings economic advantages and increases the operating time. In addition, through continuous and accurate "on-site" differential pressure diagnosis, maintenance and overhaul work can be planned more prospectively, and maintenance measures can be arranged and adjusted according to the aging state.

Claims

1. An electrolysis device (1), the electrolysis device comprising an electrolysis unit (3) for generating hydrogen (H2) and oxygen (O2) as product gases, the electrolysis unit having a plurality of electrolysis cells, each of the electrolysis cells having two half-cells separated by an ion-permeable membrane (5), thereby forming an anode chamber (7) and a cathode chamber (9), wherein, On the anode side, an oxygen product pipeline (11B) is connected to the anode chamber (7), and on the cathode side, a hydrogen product pipeline (11A) is connected to the cathode chamber (9). The hydrogen product pipeline (11A) leads into a first gas separator (13A), and the oxygen product pipeline (11B) leads into a second gas separator (13B). The electrolysis device further has a differential pressure regulating device (15), which includes differential pressure sensors (17A, 17B). The differential pressure sensors are arranged such that the differential pressure (Δp) between the anode chamber (7) and the cathode chamber (9) can be determined, and its value can be processed in the differential pressure regulating device (15).

2. The electrolysis device (1) according to claim 1, wherein, The differential pressure regulating device (15) is designed to limit the differential pressure, wherein a maximum value (Δp max ) of the differential pressure is set.

3. The electrolysis device (1) according to claim 1 or 2, wherein, The differential pressure sensors (17A, 17B) are connected to corresponding sensing parts (19A, 19B) on the first gas separator (13A) and the second gas separator (13B). The sensing parts (19A, 19B) are arranged in the upper regions of the gas separators (13A, 13B) so that the differential pressure (Δp) in the gas phases of the gas separators (13A, 13B) can be determined.

4. The electrolysis device (1) according to any one of the preceding claims, wherein, The differential pressure sensors (17A, 17B) are connected to the corresponding sensing parts (19A, 19B) of the anode half-cell and the cathode half-cell, so that the differential pressure (Δp) across the half-cells can be determined.

5. The electrolysis device (1) according to claim 4, wherein, An electrolytic cell is formed by the anode half-cell and the cathode half-cell, so that the differential pressure (Δp) across the electrolytic cell can be determined specifically for the cell.

6. The electrolysis device (1) according to claim 4 or 5, wherein, The sensing parts (19A, 19B) are arranged at the reaction medium inlets of the anode half-cell and the cathode half-cell.

7. The electrolysis device (1) according to any one of the preceding claims, wherein, On the anode side, a reactant pipeline (21B) is connected to the anode chamber (7).

8. The electrolysis device (1) according to any one of claims 1 to 6, wherein, On the cathode side, a first reactant pipeline (21A) is connected to the cathode chamber (9), and on the anode side, a second reactant pipeline (21B) is connected to the anode chamber (7).

9. The electrolysis device (1) according to any one of the preceding claims, wherein, The ion-permeable membrane (5) is designed as a proton-permeable membrane, so that PEM electrolysis can be carried out.

10. The electrolysis device (1) according to any one of claims 1 to 8, wherein, The ion-permeable membrane (5) is designed as an anion-transporting membrane, so that anion exchange membrane water electrolysis (AEMWE) can be carried out.

11. The electrolysis device () according to any one of claims 1 to 8, wherein, The ion-permeable membrane (5) is designed as a diaphragm that selectively allows hydroxide ions to pass through, so that alkaline electrolysis can be carried out.

12. A method for operating an electrolysis device (1) according to any one of the preceding claims, wherein, Hydrogen (H2) and oxygen (O2) are produced as product gases, wherein a differential pressure sensor (17A, 17B) is used to measure the differential pressure (Δp) between the anode chamber (7) and the cathode chamber (9), wherein the measurement signal is read into a differential pressure regulating device (15) and compared with a reference value (Δp max ), and wherein, if the differential pressure (Δp) is less than the reference value (Δp max ), a continuous operation mode is maintained.

13. The method according to claim 12, wherein, If the differential pressure (Δp) is greater than the reference value (Δp max ), the shutdown operation mode is started by means of the differential pressure regulating device (15).

14. The method according to claim 12 or 13, wherein, Pressure electrolysis is carried out with a system pressure of at least 5 bar, in particular at least 10 bar to 35 bar.

Images