Electrolysis device and method with turbine coupled to compressor

Abstract

The invention relates to an electrolysis device (10) having at least one electrolysis unit (12) for reducing a medium provided for the electrolysis, in particular water, an air supply line (20) for supplying air to the electrolysis unit (12), and an exhaust gas line (24) for discharging anode exhaust gases of the electrolysis unit (12). According to the invention, the air supply line (20) has a compressor (66) for increasing the pressure of the air, and the exhaust gas line (24) has a turbine (74) mechanically coupled to the compressor (66).

Description

[0001] R. 406383

[0002] - 1 -

[0003] Description

[0004] title

[0005] Electrolysis device, process

[0006] The invention relates to an electrolysis device according to the preamble of the independent claim. The invention further relates to a method for operating such an electrolysis device.

[0007] State of the art

[0008] Conventional SOEC systems for hydrogen production require an external hydrogen compressor to bring the produced hydrogen to the necessary pressure. This results in high electrical energy consumption and reduces the overall efficiency of the system.

[0009] Disclosure of the invention

[0010] Advantages

[0011] The present invention describes an electrolysis device with at least one electrolysis unit for reducing a medium intended for electrolysis, in particular water, with an air supply line for supplying air to the electrolysis unit, and with an exhaust line for removing anode exhaust gases from the electrolysis unit. According to the invention, the electrolysis device has an air supply line with a compressor for increasing the air pressure, wherein the exhaust line has a turbine which is mechanically coupled to the compressor.

[0012] With the present invention, the electrolysis unit can be operated under pressure, so that the produced reduced medium, advantageously hydrogen, can be manufactured or supplied under pressure. Through the mechanical coupling of R. 406383

[0013] - 2 -

[0014] The energy required to increase the air pressure in the compressor and turbine can be at least partially obtained from the exhaust gas stream of the electrolysis process. This increases the energy efficiency of the electrolysis device.

[0015] An electrolysis device is understood to be, in particular, a device designed for the production of fuel from at least one base substance and electricity—especially hydrogen from electricity and water—by electrolysis. The electrolysis device comprises an electrolysis unit, which is supplied with a medium as the base substance—for example, water—and advantageously with an auxiliary medium. In the electrolysis unit, the medium is reduced in a redox reaction under the input of electrical energy, producing oxygen. Specifically, the electrolysis unit generates a product gas containing the reduced medium and an exhaust gas containing oxygen. The reduced medium is discharged from the electrolysis unit and constitutes the fuel, for example, hydrogen.Accordingly, the electrolysis device includes components and lines to supply the electrolysis unit with the medium and fuel, to provide electrical energy, and to remove and, if necessary, store the reduced medium and exhaust gas from the electrolysis unit. Furthermore, the electrolysis device includes components and lines to bring the respective fluids to the temperatures required for electrolysis and / or to process the waste heat generated in the electrolysis unit. An auxiliary medium is understood to be, in particular, a sufficiently inert gas intended to drive the oxygen out of the electrolysis unit. Advantageously, the auxiliary medium is also intended to heat or cool the electrolysis unit. Possible auxiliary media include, for example, air, CO2, or N2; air is typically used.

[0016] In the context of the present invention, "conduits" are understood to mean conduits designed to carry a fluid. A fluid can be, in particular, liquid or gaseous. A fluid is understood to be, in particular, the medium, the reduced medium, or a product gas generated in the electrolysis unit, and / or the auxiliary medium. For example, an air supply line is provided to carry air as the auxiliary medium. A conduit connects R. 406383

[0017] - 3 - From a fluid dynamics perspective, a line typically connects two components of the electrolysis device. It is also conceivable that a line connects several components of the electrolysis device in series. For example, the air supply line can connect an air source to an air blower, and the air blower to the electrolysis unit. It is conceivable that a line is designed for different fluids depending on the operating state and / or the line section. For example, it is conceivable that the reduced medium is injected into a supply line for the medium at an inlet gas section, so that a mixture of the medium and the reduced medium flows downstream of the inlet gas section. For example, a line can have one or more pipes. In particular, a line can have several line sections, which, for example, connect different components from a fluid dynamics perspective.

[0018] An electrolysis unit is understood to be, in particular, a component comprising at least one electrolysis cell. Typically, an electrolysis unit comprises a plurality of electrolysis cells connected electrically in series, with the electrolysis cells advantageously being stacked. A stack of electrolysis cells is also referred to as an electrolysis stack. The electrolysis unit can also be designed as a stack module. A stack module is understood to be a plurality of electrolysis stacks, which can be connected electrically individually, in parallel, or in series, and are arranged, for example, on a common chassis or support, or in a common housing.

[0019] The electrolysis cell is an electrochemical cell designed for the chemical production or conversion of substances through chemical reactions initiated by applying an electrical voltage. The electrolysis cell comprises at least two electrode layers and a separating layer or electrolyte layer, which in particular functions as an ion conductor. Preferably, the electrolysis cell includes an electrode layer configured as an oxidation electrode or air electrode, which is specifically designed to contact the oxidant and / or a decomposition product. Preferably, at least one [R. 406383]

[0020] - 4 -

[0021] The electrode layer is configured as a fuel electrode, specifically for contact with the fuel and / or another fission product. The air electrode defines the anode side of the electrolysis cell, and the fuel electrode defines the cathode side.

[0022] The electrolysis cell is preferably a solid oxide electrolysis cell (SOEC), particularly a high-temperature SOEC. Alternatively, the electrolysis cell can also be designed as a proton-conducting ceramic electrolysis cell (PCEC) based on a proton-conducting oxide (PCO). However, the present invention is independent of the type of electrolysis cell; the electrolysis device also works for other types of electrolysis cells, for example, an electrolysis unit based on proton-permeable polymer membranes (proton exchange membranes or polymer electrolyte membranes - PEM) is also conceivable.

[0023] A compressor is understood to be, in particular, a mechanical compressor for the auxiliary medium, preferably air.

[0024] A turbine is understood to be, in particular, a device designed to convert the flow energy of a fluid into mechanical rotational energy. Typically, the turbine has an impeller or turbine wheel with a plurality of blades arranged so that the fluid flows over them and converts some of the fluid's kinetic or pressure energy into a torque that sets the impeller or turbine wheel in rotation. The rotational energy of the impeller or turbine wheel is then used to generate a torque.

[0025] The turbine wheel can be transmitted to another device via a shaft.

[0026] The phrase "the exhaust pipe includes the turbine" is understood to mean, in particular, that the turbine is fluidically connected to the exhaust pipe in such a way that the flow energy of the exhaust gases or anode gases, which flow through the exhaust pipe during operation of the electrolysis device, can be converted into rotational energy by the turbine. R. 406383

[0027] - 5 -

[0028] The phrase "the turbine is mechanically coupled to the compressor" means, in particular, that the turbine is mechanically coupled to the compressor in such a way that rotational energy generated by the turbine can be transferred to the compressor. Specifically, it is possible that the compressor is coupled to the turbine via a shaft. Such a system consisting of a compressor and a turbine, which are mechanically coupled to each other, is also called a turbocharger or exhaust gas turbocharger.

[0029] Advantageously, the electrolysis device includes a media metering pump, which is designed to pump the medium to be reduced and which is designed to pressurize the medium to be reduced, preferably water.

[0030] Advantageous further developments of the electrolysis device are possible due to the features listed in the dependent claims.

[0031] The electrolysis device is further improved by a turbine with a controllable exhaust valve. This controllable exhaust valve allows for regulation of the turbine pressure and thus the rotational speed of the turbine and the mechanically coupled compressor. This enables precise control of the exhaust gas pressure and the anode pressure in the electrolysis unit. Furthermore, the pressure of the air compressed by the compressor can also be regulated in this way.

[0032] The exhaust valve can, for example, be designed as a needle valve. The phrase "the turbine has an exhaust valve" means, in particular, that the exhaust valve is arranged on and / or in the turbine in such a way that an adjustable portion of the exhaust gas flow can be diverted around the turbine or the turbine wheel. Such an exhaust valve is also called a wastegate. An exhaust valve or...

[0033] A wastegate is typically used to limit the speed of the turbine and thus the boost pressure of the compressor.

[0034] It is also advantageous to have an adjustable medium valve on a discharge line for a reduced medium or on a filling line for the reduced medium. The adjustable medium valve allows precise control of the R. 406383

[0035] - 6 -

[0036] The pressure of the reduced medium or the cathode pressure further increases the efficiency and safety of the electrolysis device. In particular, this makes it possible to control or regulate the ratio of the reduced medium pressure to atmospheric pressure.

[0037] A discharge line for the reduced medium is understood to be, in particular, a line designed to discharge the reduced medium flowing from the electrolysis unit. A filling line is understood to be, in particular, a discharge line that is fluidically connected to a storage unit for the reduced medium—for example, a gas cylinder—and / or to a connection for venting the reduced medium from the electrolysis device.

[0038] The medium valve can, for example, be designed as a needle valve. The phrase "the medium valve is arranged on a line" means, in particular, that the medium valve is arranged on and / or in the line in such a way that an adjustable gas flow can be directed through the line.

[0039] It is also advantageous if the air supply line includes an adjustable air blower. The adjustable air blower provides an additional control option for the air supply and air pressure, especially at low compressor speeds. If the pressure generated from the anode exhaust gases by the turbine and compressor is insufficient, the adjustable air blower can provide the missing pressure. This can be particularly relevant during startup.

[0040] The electrolysis device is further improved by an electrolysis unit arranged in a pressure tank, in particular by the arrangement of a hot component within the pressure tank. The arrangement of the electrolysis unit or the hot component within a pressure tank enables pressurized operation when the electrolysis unit used is not suitable or designed for the pressure differential between the desired pressure and the environment. The suitability of the electrolysis unit for pressurization depends on the type of [R. 406383]

[0041] - 7 - installed electrolysis cells as well as the technical details of the electrolysis unit itself.

[0042] A hot section of the plant is understood to be, in particular, a subgroup of components of the electrolysis device. The hot section comprises the electrolysis unit and other components that are in close thermal contact with the electrolysis unit, typically heat exchangers designed for the direct return of waste heat from the electrolysis unit to the electrolysis unit. The hot section is also referred to as the hot Balance of Plant (hot BoP) or hotbox. In particular, the hot section may include stack heat exchangers.

[0043] A stack heat exchanger is a heat exchanger designed to transfer the waste heat from the product gas and / or exhaust gas of the electrolysis unit to the auxiliary medium and / or the medium supplied to the electrolysis unit. Such a stack heat exchanger is often also referred to as a recuperative heat exchanger. Typically, the stack heat exchanger is the first heat exchanger located downstream of the electrolysis unit with respect to the flow of the product gas and / or exhaust gas. Conversely, it is typically the last heat exchanger located upstream of the electrolysis unit with respect to the flow of the medium and / or auxiliary medium. For the purposes of this text, the terms heat exchanger and heat transfer medium are used synonymously.

[0044] A cold plant section refers specifically to a subgroup of components of the electrolysis device. The cold plant section typically includes components that supply the hot plant section, or the electrolysis unit, with the medium and / or auxiliary medium, and that discharge the exhaust gas and the reduced medium. The cold plant section is also referred to as the cold Balance of Plants (cold BoP). The components of the cold plant section operate at a lower temperature than the components of the hot plant section. The components of the hot plant section are advantageously located within the framework of R. 406383.

[0045] - 8 -

[0046] The electrolysis device is advantageously arranged in a spatially grouped manner. The components of the cold section of the system are advantageously arranged in a spatially grouped manner within the electrolysis device. It is particularly advantageous for the electrolysis device to have thermal insulation between the components of the cold section and the components of the hot section. For example, it is conceivable that the components of the hot section, or at least some of the components of the hot section, are arranged in a housing that spatially separates the components of the hot section, at least partially, from the components of the cold section.

[0047] The electrolysis device is further improved by a recirculation line, which is designed to return a portion of the reduced medium to the electrolysis unit.

[0048] The recirculation line allows a portion of the already reduced medium, e.g., hydrogen, to be returned to the electrolysis unit. This has the advantage that, in some types of electrolysis units, damage caused by operation with the pure medium can be avoided. For example, with SOEC electrolysis units, it is advantageous to add a mole fraction of hydrogen between 1% and 15% to the supplied water, advantageously between 2% and 10%, and particularly advantageously between 5% and 8%.

[0049] For example, the product gas or treated product gas, in particular the reduced medium, discharged from the electrolysis unit can be split into two partial flows at a flow divider on the discharge line. One partial flow is intended for storing the product gas or reduced medium, and the other partial flow is returned to the electrolysis unit via the recirculation line. Advantageously, the portion of the reduced medium carried through the recirculation line is mixed with the medium supplied to the electrolysis unit. For example, the supply line for the medium can have a gas inlet section which is fluidly connected to the recirculation line and where the reduced medium—preferably gaseous—is mixed with the medium—preferably gaseous. R. 406383

[0050] - 9 -

[0051] The electrolysis device is further improved by a compression unit designed to compress a portion of the reduced medium, particularly for storage of the reduced medium.

[0052] The integrated compression unit enables the storage of the produced reduced medium, e.g., hydrogen, under increased pressure. This is particularly advantageous for the further use and transport of the reduced medium. In the electrolysis device according to the invention, the possibility of operating under pressure means that the compression unit does not require such a high compression ratio as in the prior art. In addition to higher efficiency, this also enables safer and more reliable operation.

[0053] The present invention further describes a method for pressurized operation or for starting the pressurized operation of an electrolysis device according to the present invention, wherein, according to the invention, an anode pressure at an exhaust line and / or cathode pressure at a discharge line for the reduced medium is determined, and the exhaust valve is controlled depending on the anode pressure and / or cathode pressure. By measuring and controlling the pressure at the anode and / or cathode side, the pressure in the electrolysis unit can be precisely controlled, and safe and efficient operation of the electrolysis process can be ensured.

[0054] The electrolysis device includes a control unit configured to execute the method according to the invention. In particular, the control unit includes a processing unit and a memory and is equipped via appropriate interfaces to receive information, especially measurement data, and to send control commands to functional components of the control unit. The control unit is optionally configured to receive external signals, for example, from an input device for inputting control commands by an operator or from a higher-level control unit—for example, a higher-level overall system consisting of several fuel cell devices or a cloud. The control unit is configured to process received measurement signals and / or control commands. R. 406383

[0055] - 10 - and, if necessary, convert it into control commands. The control unit is specifically designed to supply the electrolysis unit with electricity, in particular to apply a voltage to the electrolysis unit, in order to enable the electrochemical reaction. For this purpose, the control unit may, for example, have power electronics electrically connected to the electrolysis unit or control a power electronic component electrically connected to the electrolysis unit accordingly. The power electronics may, for example, include an AC-DC rectifier.

[0056] The process is further improved by determining the anode and cathode pressures and controlling the medium valve based on the ratio of these pressures. Regulating the medium valve according to this ratio allows for even more precise pressure control within the electrolysis unit.

[0057] In particular, controlling the ratio of anode pressure to cathode pressure allows for further efficiency gains. The electrical power consumption of the electrolysis device can be further reduced if the anode pressure is chosen to be lower than the cathode pressure. A high anode pressure is advantageous for a high pressure of the reduced medium, while a lower cathode pressure necessitates less power consumption for the additional compression of the air or auxiliary medium.

[0058] To start a pressurized operation from a pressureless operation, the anode pressure and / or cathode pressure are advantageously increased until a desired anode and cathode pressure is reached for starting a pressurized operation from a pressureless operation, whereby the start of the pressurized operation is aborted and a pressureless operation is initiated if the difference between anode pressure and cathode pressure exceeds a critical value.

[0059] By monitoring the pressure difference between the anode and cathode sides during a start-up process, safe operation of the electrolysis device can be ensured. If the pressure difference exceeds a critical value, the R. 406383

[0060] - 11 -

[0061] The start-up process was aborted and a pressureless operation was initiated to prevent damage to the electrolysis device. A higher cathode pressure than the anode pressure can be advantageous, but this depends on the pressure resistance of the electrolysis unit and the electrolysis cells it contains. Depending on the specific technical and design details of the electrolysis unit, there is a critical value for the difference between cathode and anode pressure up to which the electrolysis unit can be operated safely. This critical value can be determined experimentally and / or through simulations and is advantageously stored in the control unit.

[0062] In advantageous variants, the difference between anode pressure and cathode pressure is also monitored in pressurized operation, and a pressureless operation is initiated if the difference between anode pressure and cathode pressure exceeds the critical value.

[0063] Drawings

[0064] The drawings depict exemplary embodiments of the electrolysis device and the method for operating the electrolysis device, which are explained in more detail in the following description. They show

[0065] Figure 1 shows a schematic circuit diagram of an exemplary embodiment of an electrolysis device.

[0066] Figure 2 shows a schematic circuit diagram of a variant of the electrolysis device and

[0067] Figure 3 shows a schematic flowchart of a method for operating the electrolysis device.

[0068] Description

[0069] In the various versions, identical parts are assigned the same reference numbers. R. 406383

[0070] - 12 -

[0071] Figure 1 shows a schematic representation of an embodiment of an electrolysis device 10. The electrolysis device 10 comprises at least one electrolysis unit 12. The electrolysis unit 12 is a unit that includes at least one electrolysis cell. Accordingly, the electrolysis unit 12 can also be understood as an electrolysis cell unit. Similarly, the electrolysis device 10 can also be understood as an electrolysis cell unit. For the sake of clarity, the shorter terms electrolysis device 10 and electrolysis unit 12 will be used in the following.

[0072] In the illustrated embodiment, the electrolysis unit 12 comprises a plurality of electrolysis cells, which in this case are arranged in an electrolysis cell stack. The electrolysis cells of the electrolysis unit 12 are designed as solid oxide electrolyzer cells (SOECs).

[0073] From a media source 14, the medium intended for electrolysis, in this case water, is supplied to the electrolysis unit 12 via a supply line 16. More precisely, the medium is supplied to a cathode side 12b of the electrolysis unit 12. Air is supplied to the electrolysis unit 12 from an air source 18 via an air supply line 20. More precisely, the air is supplied to an anode side 12a of the electrolysis unit 12. In the present embodiment and the following variants, air is the auxiliary medium. The air supply line 20 is an auxiliary medium supply line 20.

[0074] The medium is then subjected to a chemical redox reaction with the supply of electrical energy and is accordingly reduced, in this case to hydrogen. The electrical energy is provided, for example, by an AC-DC rectifier 22 connected to the electrolysis unit 12, which converts the alternating voltage from an external power supply into direct current for the electrolysis unit. R. 406383

[0075] - 13 -

[0076] Following the chemical redox reaction in the electrolysis unit 12, i.e., the reduction of water to hydrogen, the resulting exhaust gas, in this case oxygen or oxygen-rich air, is discharged from the electrolysis unit 12 via an exhaust line 24, and the produced product gas, containing the reduced medium, in this case hydrogen or moist hydrogen, is discharged via a discharge line 26. The exhaust line 24 carries away the exhaust gases or anode exhaust gases from the anode side 12a of the electrolysis unit 12. The discharge line 26 carries away the produced product gas or reduced medium or cathode exhaust gas from the cathode side 12b of the electrolysis unit 12.

[0077] The redox reaction occurring during electrolysis is endothermic. More efficient electrolysis can be achieved if the media used for electrolysis are thermally pretreated or heated. Ideally, the thermal energy in the medium used for electrolysis is completely utilized for the endothermic redox reaction. However, it can happen that after electrolysis, thermal energy remains in the discharged media, in this case the exhaust gas or oxygen, and / or in the product gas produced from the electrolysis, which contains the reduced medium or, in this case, hydrogen. This residual thermal energy can be considered waste heat from the electrolysis unit 12.

[0078] Advantageously, the waste heat from the electrolysis unit 12 is at least partially returned to the electrolysis unit 12. In the exemplary embodiment, the electrolysis device 10 has a first stack heat exchanger 28a, which is designed to transfer heat from the exhaust gas or anode exhaust gas, in this case oxygen exhaust gas, flowing from the electrolysis unit 12 or its anode side 12a, to the air that is supplied to the electrolysis unit 12 or its anode side 12a via the air supply line 20. In this way, the efficiency of the electrolysis device 10 can be increased. In the exemplary embodiment, the first stack heat exchanger 28a is located upstream of the electrolysis unit at the air supply line 20 with respect to the airflow direction. R. 406383

[0079] - 14 -

[0080] 12. In the exemplary embodiment, the first stack heat exchanger 28a is arranged on the exhaust gas line 24 after the electrolysis unit 12 with respect to the flow direction of the exhaust gas or the anode exhaust gas.

[0081] In the exemplary embodiment, the electrolysis device 10 has a second stack heat exchanger 28b, which is designed to transfer heat from the reduced medium or cathode exhaust gas, in this case hydrogen or moist hydrogen, flowing from the electrolysis unit 12 or its cathode side 12b, to the medium supplied to the electrolysis unit 12 or its cathode side 12b via the supply line 16. In this way, the efficiency of the electrolysis device 10 can be increased. In the exemplary embodiment, the second stack heat exchanger 28b is arranged upstream of the electrolysis unit 12 on the supply line 16 with respect to the flow direction of the medium. In the exemplary embodiment, the second stack heat exchanger 28b is arranged downstream of the electrolysis unit 12 on the discharge line 26 with respect to the flow direction of the product gas or reduced medium or cathode exhaust gas.

[0082] In the exemplary embodiment, the electrolysis device 10 has a first preheater 30a, which is designed to heat the air supplied to the electrolysis unit 12, or rather its anode side 12a, via the air supply line 20. The first preheater 30a is arranged on the air supply line 20 and, for illustrative purposes, is positioned between the first stack heat exchanger 28a and the electrolysis unit 12. In this way, the air supplied to the electrolysis unit 12 is first heated by the first stack heat exchanger 28a and then flows into the first preheater 30a. The first preheater 30a only needs to heat the already preheated air to the minimum temperature required for electrolysis, if necessary. This enables efficient operation of the electrolysis device 10.

[0083] In the exemplary embodiment, the electrolysis device 10 has a second preheater 30b, which is provided for heating the medium which is supplied via the R. 406383

[0084] - 15 -

[0085] The feed line 16, which supplies the electrolysis unit 12 or its cathode side 12b, is heated. The second preheater 30b is arranged on the feed line 16 and, for illustrative purposes, is positioned between the second stack heat exchanger 28b and the electrolysis unit 12. In this way, the medium supplied to the electrolysis unit 12 is first heated by the second stack heat exchanger 28b and then flows into the second preheater 30b. The second preheater 30b only needs to heat the already preheated medium to the minimum temperature required for electrolysis, if necessary. This enables efficient operation of the electrolysis device 10.

[0086] The electrolysis unit 12, the two stack heat exchangers 28a, 28b and the two preheaters 30a, 30b are, by way of example, part of a hot plant section 32.

[0087] During electrolysis, the medium intended for electrolysis in the electrolysis unit 12, i.e., the water, is typically not completely reduced to hydrogen. In addition to the reduced medium, the product gas typically also contains a proportion of unreduced medium, such as moist hydrogen in this embodiment. In the illustrated embodiment, the product gas is first routed via the discharge line 26 to the second stack heat exchanger 28b and from there via the discharge line 26 to a first heat exchanger 34a. The first heat exchanger 34a is designed to transfer the heat from the product gas in the discharge line 26 to the medium transported from the media source 14 via the supply line 16 to the electrolysis unit 12. From a fluid dynamics perspective, the first heat exchanger 34a is arranged on the supply line 16 between the media source 14 and the electrolysis unit 12.As an example, the first heat exchanger 34a is arranged fluidically on the supply line 16 between the media source 14 and the second stack heat exchanger 28b. The first heat exchanger 34a is designed to cool the product gas returned from electrolysis unit 12 in such a way that the unreduced portion of the medium at least partially condenses out of the reduced medium. (See R. 406383.)

[0088] - 16 -

[0089] In this embodiment, moist hydrogen is discharged via the discharge line 26 and directed into the first heat exchanger 34a, whereby at least some of the water from the moist hydrogen condenses out in the heat exchanger 34a. By way of example, the electrolysis device 10 has a first condensate line 36a, which is designed to return the condensed medium from the first heat exchanger 34a back into the supply line 16.

[0090] In this exemplary embodiment, the media source 14 is a source of liquid tap water. Other media sources 14 are also conceivable in variations, for example, sources of liquid rainwater, liquid seawater, or water vapor, and the like. The medium, i.e., tap water, is conveyed via the supply line 16 to a purification unit 38. The purification unit 38 is designed to process the medium supplied to the electrolysis device 10 from the media source 14—in this case, tap water—into the medium intended for electrolysis in the electrolysis unit 12—in this exemplary embodiment, pure water (H₂O). In the illustrated case, the purification unit 38 is designed to remove impurities from the tap water and to deionize and demineralize the tap water so that pure water (H₂O) can be provided for electrolysis in the electrolysis unit 12.

[0091] In the exemplary embodiment, the first heat exchanger 34a is connected to the cleaning unit 38 via the first condensate line 36a. In this way, the condensed medium from the first heat exchanger 34a is supplied to the cleaning unit 38 via the first condensate line 36a.

[0092] In the direction of flow of the medium in the supply line 16, a controllable media metering pump 40 is arranged downstream of the cleaning unit 38. The media metering pump 40 is designed to deliver the medium in the desired dosage or to adjust the desired flow rate of the medium. In particular, the media metering pump 40 is designed to... R. 406383

[0093] - 17 -

[0094] The medium is pressurized, for example for pressure operation of the electrolysis device 10. The medium is fed by the media metering pump 40 via the supply line 16 into the first heat exchanger 34a. The first heat exchanger 34a is located downstream of the media metering pump 40 in the supply line 16 in the direction of flow of the medium.

[0095] In the illustrated case, the cleaning unit 38 and the media dosing pump 40 are part of the electrolysis device 10, while the media source 14 is not part of the electrolysis device 10 and is merely connected to it. However, it is also possible that in other configurations the cleaning unit 38 and / or the media dosing pump 40 and / or the media source 14 may or may not be part of the electrolysis device 10.

[0096] In the exemplary embodiment, an evaporator 42 is connected downstream of the first heat exchanger 34a in the feed line 16 in the direction of flow of the medium. The evaporator 42 is designed to convert the liquid medium into a gaseous state so that a gaseous medium can be supplied to the electrolysis unit 12. In the exemplary embodiment, the evaporator 42 is designed to evaporate the liquid water. It is particularly advantageous that the first heat exchanger 34a heats the medium to a temperature close to its boiling point.

[0097] In the direction of flow of the medium in the feed line 16, the electrolysis unit 12 is connected downstream of the evaporator 42; in particular, the hot part of the system 32 is connected downstream of the evaporator 42. In the exemplary embodiment, the second stack heat exchanger 28b is connected downstream of the evaporator 42 in the direction of flow of the medium in the feed line 16.

[0098] In some variants, it is conceivable that a gaseous medium is already supplied to the electrolysis device 10; for example, the medium source 14 can be a water vapor source, such as water vapor from an industrial process. In such variants, an evaporator 42 and / or a cleaning unit 38 are not necessary. If the water vapor source is the medium R. 406383

[0099] - 18 - already provides sufficient pressure, a media metering pump 40 is not necessary in such variants. In such variants, the media source 14 can be directly connected to the hot part of the system 32 via the supply line 16, in particular to the electrolysis unit 12 and / or to the second stack heat exchanger 28b. It is conceivable that, from a flow engineering perspective, a media control valve and / or a pressure control valve is arranged between the media source 14 and the hot part of the system 32 - in particular to the electrolysis unit 12 and / or the second stack heat exchanger 28b - which is intended to regulate the quantity and / or pressure of the medium supplied to the electrolysis unit 12.

[0100] In the embodiment shown in Figure 1, a compression unit 48 is connected downstream of the first heat exchanger 34a in the flow direction of the reduced medium through the discharge line 26. The first heat exchanger 34a is fluidically connected to the compression unit 48 via a filling line 46. The filling line 46 is designed to carry the reduced medium. The compression unit 48 is designed to compress the gaseous reduced medium. In the illustrated embodiment, a controllable medium valve 70 is arranged fluidically between the first heat exchanger 34a and the compression unit 48 on the filling line 46. The medium valve 70 is designed as a needle valve. The medium valve 70 is specifically designed to control a pressure differential between an anode pressure at the exhaust line 24 and a cathode pressure at the discharge line 26.For example, the electrolysis device 10 has a differential pressure sensor 68 for determining the pressure difference between the anode pressure at the exhaust line 24 and the cathode pressure from the discharge line 26.

[0101] Advantageously, the compression unit 48 is also designed to clean and / or dehumidify the reduced medium. For example, the compression unit 48 can have a first section for compression and a second section for cleaning. Advantageously, the R. 406383

[0102] - 19 -

[0103] Cleaning followed by compression. In the exemplary embodiment, the compression unit 48 is also designed to further dehumidify the at least partially dehumidified hydrogen. In this embodiment, the compression unit 48 is connected to the supply line 16 via a second condensate line 36b. The second condensate line 36b is designed to return the unreduced medium – in this case, water – extracted from the medium back to the supply line 16. By way of example, the compression unit 48 is fluidically connected to the cleaning unit 38 via the second condensate line 36b.

[0104] In the direction of flow of the first partial flow of the reduced medium through the filling line 46, a gas pressure vessel 50 is arranged downstream of the compression unit 48. It is intended that the hydrogen, dehumidified, purified, and compressed by the compression unit 48, is filled into the gas pressure vessel 50. For example, the hydrogen is stored in the gas pressure vessel 50 at a pressure of 30 bar. Advantageously, the gas pressure vessel 50 has a gas extraction port 52, which allows the hydrogen stored in the gas pressure vessel 50 to be withdrawn.

[0105] The gas pressure vessel 50 is connected via a return line 72 to a single-gas section 56 on the supply line 16. The return line 72 is designed to return a portion of the reduced medium back to the electrolysis unit 12 or its cathode side 12b.

[0106] In particular, the return line 72 fluidically connects the gas pressure vessel 50 to the in-gas section 56. The return line 72 includes, for example, an emergency shut-off valve and an adjustable metering valve, which is intended to meter the reduced medium returned to the supply line 16.

[0107] The inlet gas section 56 is arranged on the supply line 16, in a fluid-technical example, between the evaporator 42 and the second stack heat exchanger 28b. In this way, the gaseous medium R, transported by the supply line 16 to the hot part of the system 32 or to the electrolysis unit 12, is supplied with a gaseous gas section. 406383

[0108] - 20 -

[0109] - In this case, water vapor - a portion of the reduced medium - in this case, at least partially dehumidified hydrogen - is added to the inlet gas section 56. The addition of hydrogen is particularly advantageous in a SOEC stack to prevent damage to SOEC cells. Typically, a hydrogen mole fraction of approximately 5% to approximately 10% is beneficial.

[0110] As an example, an air blower 64 is arranged in the air supply line 20 between the air source 18 and the first stack heat exchanger 28a. The air blower 64 is designed to supply air to the electrolysis unit 12 or its anode side 12a. Advantageously, the air blower 64 is controllable, i.e., the airflow strength can be adjusted.

[0111] Airflow is adjustable. In this way, the airflow required for the operation of the electrolysis unit 12 can be adjusted. In the exemplary embodiment, the air source 18 is designed as an opening for outside air, which has an air filter. The air filter is intended to filter pollutants and / or impurities out of the air.

[0112] Furthermore, a compressor 66 is arranged on the air supply line 20. The compressor 66 is designed to pressurize the air supplied to the electrolysis unit 12. By way of example, the compressor 66 is designed as a mechanical compressor. By way of example, the compressor 66 is arranged fluidically between the air blower 64 and the first stack heat exchanger 28a.

[0113] A turbine 74 is arranged at the exhaust gas outlet 24. The turbine 74 is designed to recover kinetic energy from the exhaust gases of the electrolysis unit. For example, the turbine 74 is arranged fluidically between the first stack heat exchanger 28a and an exhaust gas outlet 60. The turbine 74 and the compressor 66 are mechanically coupled, for example via a common shaft. In this way, the incoming R. 406383 can be powered from the kinetic energy recovered from the exhaust gas.

[0114] - 21 -

[0115] Air is compressed. If the recovered mechanical energy is insufficient to bring the air to the desired pressure level, the missing pressure can advantageously be provided by the air blower 64, preferably an electrically driven, controllable air blower 64.

[0116] For example, turbine 74 has a controllable exhaust valve 76. The exhaust valve 76 is designed to divert an adjustable portion of the exhaust gas flow driving turbine 74 around the turbine. This limits the turbine speed and the pressure generated by the compressor 66. The exhaust valve 76 is also designed, for example, to control the anode pressure at the exhaust line 24. For example, electrolysis device 10 has an absolute pressure sensor 78 for determining the anode pressure at the exhaust line 24.

[0117] The electrolysis device 10 has a cold system section comprising at least the air blower 64 and at least one heat exchanger 34 for transferring the waste heat from the electrolysis unit to the medium and / or the air. Advantageously, the cold system section includes the compressor 66 and the turbine 74. In the exemplary embodiment, the cold system section 66 additionally includes, by way of example, the air source 18, the first heat exchanger 34, the media supply – comprising the cleaning unit 38, the media metering pump 40, and the evaporator 42 – as well as the filling section for the reduced medium – comprising the compression unit 48 and the gas pressure vessel 50. In variants, it is conceivable that the compression unit 48 and / or the gas pressure vessel 50 are not part of the electrolysis device 10 but part of an external overall system that includes the electrolysis device 10 or to which one or more electrolysis devices 10 are connected.Typically, the AC-DC rectifier 22 can also be assigned to the cold part of the system 66.

[0118] Figure 2 illustrates a variant of the electrolysis device. The variant shown in Figure 2 largely corresponds to the embodiment shown in Figure 1 and differs essentially in that no reduced medium from R. 406383 is used.

[0119] - 22 - is returned to the gas pressure vessel 50 in the supply line 16.

[0120] Accordingly, the variant in Figure 2 does not have a return line 72. Instead, the variant in Figure 2 has a recirculation line 54 for a more direct return of the reduced medium. The variants in Figure 1 and Figure 2 are identical in all other features; therefore, only the recirculation line 54 and the necessary additional components and features will be explained below.

[0121] In the embodiment shown in Figure 2, a flow divider 44 is connected downstream of the first heat exchanger 34a in the direction of flow of the reduced medium through the discharge line 26. Typically, the reduced medium may still contain a residual proportion of non-reduced medium. For the sake of clarity, the term "reduced medium" is also used within the scope of the present invention to refer to a mixture of reduced and non-reduced medium. For the same reason, the term "reduced medium" is used synonymously with the product gas or cathode exhaust gas. The flow divider 44 is fluidically connected to the first heat exchanger 34a via the discharge line 26. The flow divider 44 is designed, by way of example, to divide the flow of the reduced medium—in this case, hydrogen at least partially dehumidified by the first heat exchanger 34a—flowing through the discharge line 26 into two partial flows.A first partial flow of the reduced medium is intended to be stored. A second partial flow of the reduced medium is intended to be used further in the electrolysis device 10.

[0122] The flow divider 44 is connected to a compression unit 48 via a filling line 46. The filling line 46 is designed to carry the first partial flow of the reduced medium. The compression unit 48 is specifically designed to compress the gaseous reduced medium. In the embodiment shown in Figure 2, as in the variant from Figure 2, the controllable medium R is flowed between the first heat exchanger 34a and the compression unit 48 in the filling line 46. 406383

[0123] - 23 -

[0124] Valve 70 is arranged, which is advantageously also designed to regulate the pressure difference between the anode pressure at the exhaust line 24 and the cathode pressure from the discharge line 26.

[0125] In the illustrated variant, the compression unit 48 is connected to the supply line 16 via the second condensate line 36b. The second condensate line 36b is designed to return the unreduced medium – in this case, water – extracted from the process to the supply line 16. As an example, the compression unit 48 is also connected to the cleaning unit 38 via the second condensate line 36b.

[0126] In the direction of flow of the first partial flow of the reduced medium through the filling line 46, a gas pressure vessel 50 is arranged downstream of the compression unit 48. It is intended that the hydrogen, dehumidified, purified, and compressed by the compression unit 48, is filled into the gas pressure vessel 50. For example, the hydrogen is stored in the gas pressure vessel 50 at a pressure of 30 bar. Advantageously, the gas pressure vessel 50 has a gas extraction port 52, which allows the hydrogen stored in the gas pressure vessel 50 to be withdrawn.

[0127] The flow divider 44 is connected to the inlet gas section 56 on the supply line 16 via the recirculation line 54. The recirculation line 54 is designed to carry the second partial flow of the reduced medium and, in particular, to return it to the electrolysis unit 12 or its cathode side 12b. Specifically, the recirculation line 54 fluidically connects the flow divider 44 to the inlet gas section 56. The inlet gas section 56 is fluidically arranged on the supply line 16 between the evaporator 42 and the second stack heat exchanger 28b. In this way, a portion of the reduced medium—in this case, at least partially dehumidified hydrogen—is mixed at the inlet gas section 56 with the gaseous medium—in this case, water vapor—transported by the supply line 16 to the hot part of the system 32 or to the electrolysis unit 12. R. 406383

[0128] - 24 -

[0129] In the flow direction of the second partial flow of the reduced medium through the recirculation line 54, a recirculation blower 58 is advantageously arranged downstream of the flow divider 44 and upstream of the inlet gas section 56. The recirculation blower 58 is designed to convey the partial flow of the reduced medium to the inlet gas section 56. Advantageously, the recirculation blower 58 is controllable or its delivery rate is adjustable. In this way, the flow rate and / or the pressure of the reduced medium can be adjusted.

[0130] Advantageously, a second heat exchanger 34b is arranged in the recirculation line 54 between the flow divider 44 and the inlet gas section 56. The second heat exchanger 34b is designed to transfer the heat from the exhaust gases or anode exhaust gases in the exhaust line 24 – in this case, oxygen-enriched air – to the second partial flow of the reduced medium. With respect to the exhaust line 24, the second heat exchanger 34b is arranged, by way of example, between the first stack heat exchanger 28a and the turbine 76. With respect to the recirculation line 54, the second heat exchanger 34b is arranged, by way of example, between the recirculation fan 58 and the inlet gas section 56.

[0131] As an example, a shut-off valve 62 is arranged in the recirculation line 54 between the recirculation fan 58 and the second heat exchanger 34b. The shut-off valve 62 allows the recirculation line 54 to be shut off.

[0132] The second heat exchanger 34b, as well as the recirculation circuit - comprising the recirculation blower 58 and the shut-off valve 62 - are exemplary components of the cold system part of the variant of the electrolysis device 10 shown in Figure 2.

[0133] Figure 3 illustrates a method 100 for pressurizing or starting a pressurized operation of the electrolysis device 10. First, in step S1, the electrolysis device 10 is operated without pressure. R. 406383

[0134] - 25 -

[0135] If pressurized operation is desired, the anode and cathode pressures are increased from the unpressurized operation in step S2 until the desired anode and cathode pressures are reached. In the exemplary embodiment, the anode pressure is periodically determined by the absolute pressure sensor 78, and the pressure difference between the anode and cathode pressures is determined by the differential pressure sensor 68. Depending on the anode and cathode pressures, the air blower 64 and / or the media metering pump 40 are ramped up and controlled. In the exemplary embodiment, the media valve 70 and exhaust valve 76 are used to control the anode and cathode pressures, in particular for fine control and the control of the pressure difference between the anode and cathode pressures.

[0136] Furthermore, in the exemplary embodiment, the start of the pressure operation is aborted in step S2 and a pressureless operation is initiated after step S1 if the difference between anode pressure and cathode pressure exceeds a previously defined, critical value.

[0137] Once the desired anode and cathode pressures are reached in step S2, the electrolysis device is operated under pressure in step S3. For example, the air blower 64 and / or the media metering pump 40 continue to operate in the state or performance state established in step S2. The anode pressure and the pressure differential between the anode and cathode pressures are monitored, for example, by the differential pressure sensor 68 and the absolute pressure sensor 78. If there is a deviation from the desired anode and / or cathode pressure, these are regulated by the media valve 70 and / or the exhaust valve 76.

[0138] Furthermore, in the exemplary embodiment, the start of the pressure operation is aborted in step S3 and a pressureless operation is initiated after step S1 if the difference between anode pressure and cathode pressure exceeds a previously defined, critical value.

Claims

R. 406383 - 26 - Claims 1. Electrolysis device (10) with at least one electrolysis unit (12) for reducing a medium intended for electrolysis, in particular water, with an air supply line (20) for supplying air to the electrolysis unit (12), with an exhaust gas line (24) for discharging anode exhaust gases from the electrolysis unit (12), characterized in that the air supply line (20) has a compressor (66) for increasing the pressure of the air, the exhaust gas line (24) has a turbine (74) which is mechanically coupled to the compressor (66).

2. Electrolysis device (10) according to claim 1 , characterized in that the turbine (74) has a controllable exhaust valve (76).

3. Electrolysis device (10) according to one of the preceding claims, characterized in that a controllable medium valve (70) is arranged on a discharge line (26) for a reduced medium or on a filling line (46) for the reduced medium.

4. Electrolysis device (10) according to one of the preceding claims, characterized in that the air supply line (20) has a controllable air blower (64).

5. Electrolysis device (10) according to one of the preceding claims, characterized in that the electrolysis unit (12) is arranged in a pressure tank, in particular that the hot part of the system (32) is arranged in the pressure tank.

6. Electrolysis device (10) according to one of the preceding claims, characterized in that the electrolysis device (10) has a recirculation line (54) which is designed to return a portion of the reduced medium to the electrolysis unit (12).

7. Electrolysis device (10) according to one of the preceding claims, characterized in that the electrolysis device (10) includes a compression unit R. 406383 - 27 - (48) features which is designed to compress a portion of the reduced medium, in particular for storing the reduced medium.

8. Method (100) for pressure operation or for starting the pressure operation of an electrolysis device (10) according to one of the preceding claims, characterized in that an anode pressure at an exhaust line (24) and / or cathode pressure at a discharge line (26) for the reduced medium is determined and the exhaust valve (76) is controlled depending on the anode pressure and / or cathode pressure.

9. Method (100) according to claim 8, characterized in that the anode pressure and cathode pressure are determined and the medium valve (70) is controlled depending on a ratio of anode pressure to cathode pressure.

10. Method (100) according to claim 8 or 9, wherein, to start a pressure operation from a pressureless operation, the anode pressure and / or cathode pressure is increased until a desired anode pressure and cathode pressure is reached, wherein the start of the pressure operation is aborted and a pressureless operation is initiated if the difference between anode pressure and cathode pressure exceeds a critical value.

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