EP-4739816-A1 - METHOD FOR OPERATING AN ELECTROLYSIS PLANT, AND ELECTROLYSIS PLANT

EP4739816A1EP 4739816 A1EP4739816 A1EP 4739816A1EP-4739816-A1

Abstract

The invention relates to a method for operating an electrolysis plant (100) in which water is converted into oxygen and hydrogen in an electrolysis unit (110). A processed fluid flow (c) is guided from an oxygen side (114) of the electrolysis unit to a gas separator (120), 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). If necessary, ambient air (k) is supplied to the oxygen-containing fluid flow (h) at a supply point (140) before the fluid flow is supplied to the oxygen region of the electrolysis plant (100), or the oxygen-containing fluid flow (h) is replaced with ambient air (k) before the fluid flow is supplied to the oxygen region of the electrolysis plant (100). The invention also relates to a corresponding electrolysis plant (100).

Inventors

DIETZEN, MARKUS
Kunze, Eckehardt
WINKLER, FLORIAN
GAUBE, Gerald
Chromik, Karsten
MEUSEL, RONALD
STOFFREGEN, TORSTEN
WERNER, Thorsten Bernd
SCHULZE, WOLFRAM

Assignees

Linde GmbH

Dates

Publication Date: 20260513
Application Date: 20240605

Claims (14)

1 . Method for operating an electrolysis plant (100) in which water is converted into oxygen and hydrogen in an electrolysis unit (110), wherein a processed fluid stream (c) is led from an oxygen side (114) of the electrolysis unit to a gas separator (120), wherein the processed fluid stream (c) comprises water and gas, wherein an oxygen-containing fluid stream (g, h) is discharged from the gas separator (120), wherein the oxygen-containing fluid stream comprises gas, wherein the oxygen-containing fluid stream (h, d) is fed to an oxygen region of the electrolysis plant (100), and wherein, if required, ambient air (k) is fed to the oxygen-containing fluid stream (h) at a feed point (140) before being fed to the oxygen region of the electrolysis plant (100), or the oxygen-containing fluid stream (h) is passed through ambient air (k).
2. The method according to claim 1, wherein the oxygen-containing fluid stream (d) is passed through a recombination reactor (144) after the feed point (140) and before it is fed to the oxygen region of the electrolysis plant (100).
3. Method according to claim 1 or 2, wherein a part (m) of the oxygen-containing fluid stream (d) is discharged for other use after the feed point (140) 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), in particular after the feed point (140) and before the feed to the oxygen region of the electrolysis plant (100), is monitored, and wherein, if the hydrogen concentration exceeds a predetermined threshold value, in particular 2 vol %, 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 electrolysis unit (110), - Supplying the ambient air (k) into the oxygen-containing fluid stream (h), interrupting the oxygen-containing fluid stream (h) before the supply point (140) and replacing the oxygen-containing fluid stream (h) with the ambient air (k).
6. The method according to any one of the preceding claims, wherein the electrolysis plant is designed for proton exchange membrane electrolysis.
7. Method according to one of the preceding claims, wherein the oxygen-containing fluid stream (h, d) is fed to the oxygen region of the electrolysis plant (100) by feeding the oxygen-containing fluid stream (h, d) to the processed fluid stream (c) and/or the gas separator (120)
8. Electrolysis system (100) with an electrolysis unit (110) 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 generate a processed fluid flow (c) from an oxygen side (114) of the electrolysis unit 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 system (100) is set up, if required, to supply the oxygen-containing fluid flow (h) at a supply point (140) before supplying to supply ambient air (k) to the oxygen region of the electrolysis plant (100) or to replace the oxygen-containing fluid stream (h) with ambient air (k) before being supplied to the oxygen region of the electrolysis plant (100).
9. Electrolysis plant (100) according to claim 8, 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.
10. Electrolysis plant (100) according to claim 8 or 9, further comprising a recombination reactor (144), wherein the electrolysis plant (100) is arranged to guide the oxygen-containing fluid stream (g, h) through the recombination reactor before it is fed to the oxygen region of the electrolysis plant (100).
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 stream (h), in particular after the feed point (140) and before the feed to the oxygen region of the electrolysis plant (100), and, if the hydrogen concentration exceeds a predetermined threshold value, in particular 2 vol.-%, 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), - Supplying the ambient air (k) into the oxygen-containing fluid stream (h), in particular by opening a valve (146) of the electrolysis system, interrupting the processed fluid stream (c) from the oxygen side (114) of the electrolysis unit to the gas separator (120) and replacing the oxygen-containing fluid stream (h) with the ambient air (k).
13. Electrolysis plant (100) according to one of claims 8 to 12, which is designed for proton exchange membrane electrolysis.
14. Electrolysis plant (100) according to one of claims 8 to 13, which is set up to carry out a method according to one of claims 1 to 7.

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 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. At the anode (oxygen side or In contrast, during the splitting of water, 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. An explosive mixture can form, which 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 can occur. This allows In certain operating scenarios (e.g. partial load, start-up, shut-down, standstill of individual electrolysis cells or so-called stacks), hydrogen may accumulate 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 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. All of these scenarios lead to an explosion risk. The so-called lower flammability limit (LEL) of hydrogen is around 4 vol.%. From 50% of the LEL (2 vol.% hydrogen) the electrolysis plant must generally be shut down and brought into a safe state. For example, EP 3 971 324 A1 discloses an electrolysis plant in which inert gas is incorporated into the oxygen product stream in order to reduce the hydrogen concentration. 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 fluid stream to a container (which is used as a gas or oxygen se