EP-4739817-A1 - METHOD FOR OPERATING AN ELECTROLYSIS PLANT, AND ELECTROLYSIS PLANT

Abstract

The invention relates to a method for operating an electrolysis plant (100) in which water is converted into oxygen and hydrogen in a plurality of electrolysis cells (110.1a, 110.2a, 110.1b, 110.2b). Fluid flows from an oxygen side (114) of the plurality of electrolysis cells (110.1a, 110.2a, 110.1b, 110.2b) are combined and supplied to a gas separator (120) as a processed fluid flow (c), and the processed fluid flow (c) has water and gas. An oxygen-containing fluid flow (g, h) is discharged from the gas separator (120), said oxygen-containing fluid flow having gas, and the oxygen-containing fluid flow (h, d) is supplied to an oxygen region of the electrolysis plant (100). Before being supplied to the oxygen region of the electrolysis plant (100), the oxygen-containing fluid flow (d) is guided through a device (148) for removing hydrogen, in particular a recombination reactor.

Inventors

• DIETZEN, MARKUS
• WINKLER, FLORIAN

Assignees

• Linde GmbH

Dates

Publication Date

20260513

Application Date

20240605

Claims (1)

1. patent claims 1 . Method for operating an electrolysis plant (100) in which water is converted into oxygen and hydrogen in a plurality of electrolysis cells (110.1 a, 110.2a, 110.1 b, 110.2b), wherein fluid flows from an oxygen side (114) of the plurality (110.1 a, 110.2a, 110.1 b, 110.2b) are combined and fed as a processed fluid flow (c) to a gas separator (120), wherein the processed fluid flow (c) comprises water and gas, wherein an oxygen-containing fluid flow (g, h) is discharged from the gas separator (120), wherein the oxygen-containing fluid flow comprises gas, wherein the oxygen-containing fluid flow (h, d) is fed to an oxygen region of the electrolysis plant (100), and wherein the oxygen-containing fluid flow (d) is fed to an oxygen region of the electrolysis plant (100) before it is fed to the Oxygen region of the electrolysis plant (100) is passed through a device (148) for hydrogen removal, in particular a recombination reactor. 2. The method according to claim 1, wherein the oxygen-containing fluid stream (d), after the device (148) for hydrogen removal and before it is fed to the oxygen region of the electrolysis plant (100), is passed through a device (150) for cleaning. 3. The method according to claim 2, wherein a portion (m) of the oxygen-containing fluid stream (d) is discharged for other use after the cleaning device (150) and before it is fed to the oxygen region of the electrolysis plant (100). 4. Method according to one of the preceding claims, wherein a hydrogen concentration in the oxygen-containing fluid stream (h, k), in particular before and/or after the device (144) for hydrogen removal, is monitored, and wherein an amount of the oxygen-containing fluid stream (h, k, d) supplied to the oxygen region of the electrolysis plant (100) is set or adjusted such that the hydrogen concentration does not exceed a predetermined threshold value, in particular 2 vol.%, and/or wherein, if the hydrogen concentration exceeds the predetermined threshold, at least one safety measure is initiated. 5. The method of claim 4, wherein the at least one security measure comprises at least one of the following security measures: Switching off the several electrolysis cells (110.1a, 110.2a, 110.1b, 110.2b), Interrupting the processed fluid flow (c) from the oxygen side (114) of the plurality of electrolysis cells (110.1a, 110.2a, 110.1b, 110.2b) to the gas separator (120), Interrupting the oxygen-containing fluid flow (h). 6. Method according to one of the preceding claims, wherein the electrolysis plant (100) is set up for proton exchange membrane electrolysis. 7. Method according to one of the preceding claims, wherein the oxygen-containing fluid stream (d) is fed to the oxygen region of the electrolysis plant (100) by feeding the oxygen-containing fluid stream (d) to the processed fluid stream (c) and/or the gas separator (120) 8. Electrolysis plant (100) with several electrolysis cells (110.1 a, 110.2a, 110.1b, 110.2b), in which water can be converted into oxygen and hydrogen, and with a gas separator (120), wherein the electrolysis system (100) is set up to combine fluid flows from an oxygen side (114) of the plurality of electrolysis cells (110.1 a, 110.2a, 110.1b, 110.2b) and to generate a processed fluid flow (c) to the gas separator (120), wherein the processed fluid flow comprises water and gas, wherein the electrolysis system (100) is set up to discharge an oxygen-containing fluid flow (g, h) from the gas separator (120) and to supply it to an oxygen region of the electrolysis system (100), in particular the processed fluid flow (c) and/or the gas separator (120), wherein the oxygen-containing fluid flow comprises gas, and wherein the electrolysis plant (100) has a device (148) for hydrogen removal, in particular a recombination reactor, and is designed to guide the oxygen-containing fluid stream (h) through the device (150) for hydrogen removal before it is fed to the oxygen region of the electrolysis plant (100). 9. Electrolysis plant (100) according to claim 8, further comprising a device (150) for cleaning, wherein the electrolysis plant (100) is arranged to guide the oxygen-containing fluid stream (g, h) through the device (150) for cleaning after the device (148) for hydrogen removal and before it is fed to the oxygen region of the electrolysis plant (100). 10. Electrolysis plant (100) according to claim 8 or 9, further comprising a blower (142), wherein the electrolysis plant (100) is configured to supply the oxygen-containing fluid stream (g, h) to the oxygen region of the electrolysis plant (100) by means of the blower. 11. Electrolysis plant (100) according to one of claims 8 to 10, further comprising a monitoring device (160) which is set up to monitor a hydrogen concentration in the oxygen-containing fluid flow (h, k), in particular before and/or after the device (148) for hydrogen removal, and to set or adapt an amount of the oxygen-containing fluid flow (h, d) which is supplied to the oxygen region of the electrolysis plant (100) in such a way that the hydrogen concentration does not exceed a predetermined threshold value, in particular 2 vol.%, and/or if the hydrogen concentration exceeds the predetermined threshold value, to initiate at least one safety measure. 12. Electrolysis plant (100) according to claim 11, wherein the at least one safety measure comprises at least one of the following safety measures: Switching off the electrolysis unit (110), interrupting the processed fluid flow (c) from the oxygen side (114) of the electrolysis unit to the gas separator (120), Interrupting the oxygen-containing fluid flow (h). 13. Electrolysis system (100) according to one of claims 8 to 12, which is set up for proton exchange membrane electrolysis.

Description

Description Method for operating an electrolysis plant and electrolysis plant The invention relates to a method for operating an electrolysis plant for water electrolysis, as well as to such an electrolysis plant which is used, for example, for the production of hydrogen. State of the art So-called electrolysis can be used to produce hydrogen, in which, for example, water is split or converted into oxygen and hydrogen using electrical energy. This is also referred to as water electrolysis. One example of this is the so-called proton exchange membrane electrolysis (PEM electrolysis). In this context, PEM electrolysis systems or PEM electrolyzers are also mentioned. During PEM electrolysis, a large part of the water usually remains on the oxygen side of the membrane. While the hydrogen is generated and removed on the other side of the membrane, the oxygen initially remains in the water and is then typically separated from the water in a container. The pressure at the cathode (hydrogen side or hydrogen formation) is typically over 20 barg or even over 30 barg. At the anode (oxygen side or water splitting), however, the pressure of the oxygen product is below the pressure on the cathode side, e.g. slightly above atmospheric pressure. However, it can happen that a certain amount of hydrogen diffuses back to the oxygen side or gets there in other ways, e.g. due to defects or cracks in the membrane. It can form an explosive mixture that can ignite under certain circumstances and damage the electrolysis system due to the resulting explosion. Against this background, the task is to make an electrolysis system and its operation safer. The pressure difference between the electrodes can lead to a constant hydrogen transfer (so-called "cross over") through the membrane. In certain operating scenarios (e.g. partial load, start-up, shut-down, standstill of individual electrolysis cells or so-called stacks), this can lead to a hydrogen accumulation on the oxygen side of the electrolysis while the electrolysis units are in operation. A hydrogen leakage through membrane perforation from the cathode side with, for example, more than 20 or 30 barg to the anode side can also occur as a result of undetected membrane defects while the electrolysis cells are in operation. A membrane tear can lead to a sudden transfer of large amounts of hydrogen from the cathode side to the anode side. For example, EP 3 971 324 A1 describes an electrolysis plant in which inert gas is incorporated into the oxygen product stream in order to reduce the hydrogen concentration. However, the measures described in EP 3 971 324 A1 do not guarantee inherently safe operation, since the measures are only taken when a certain hydrogen concentration has been detected to be exceeded. However, the response times of analysis equipment are usually too long to guarantee safe operation. Against this background, the task is to provide a better way to reduce the risk of explosion in water electrolysis, e.g. PEM electrolysis, and thus improve the operation of the electrolysis plant. disclosure of the invention This object is achieved by a method for operating an electrolysis system and an electrolysis system with the features of the independent patent claims. Embodiments are the subject of the dependent patent claims and the following description. Advantages of the invention The invention concerns water electrolysis and electrolysis systems or their operation for this purpose. Such electrolysis systems are typically used to produce or obtain hydrogen by means of electrolysis. In so-called water electrolysis, water is converted (split) into hydrogen and oxygen, i.e. in addition to hydrogen, oxygen is always obtained or produced at the same time. In water electrolysis, there is, for example, so-called alkaline water electrolysis (AEL, "Alkaline Electrolysis") or so-called proton exchange membrane electrolysis (PEM electrolysis, "Proton Exchange Membrane" electrolysis). The basics of this are known per se, e.g. from "Bessarabov et al: PEM electrolysis for Hydrogen production. CRC Press." There are also so-called solid oxide electrolysis cells (SOEC) and anion exchange membrane electrolysis (AEM). In particular, those electrolysis technologies that take place at low temperatures, such as PEM, AEL and AEM electrolysis, are suitable for supporting the transition of energy generation to renewable energies due to the possibilities of flexible operation. In PEM electrolysis, for example, water, particularly demineralized water, is fed as the feed medium into an electrolysis unit with a proton exchange membrane (PEM), in which the feed medium, i.e. the water, is converted (split) into hydrogen and oxygen. As mentioned, a large part of the water in PEM electrolysis usually remains on the oxygen side of the membrane. While the hydrogen is generated and removed on the other side of the membrane, the oxygen initially remains in the water and is then typically fed as a processed fl