Electrolyser and method of separating an electrolysis stack from the separator

Abstract

The invention relates to an electrolysis system (1) for the dividing of water into hydrogen and oxygen, comprising an electrolysis stack (2) having a first electrode side (3) and a second electrode side (4), a first separator (5), a first collecting conduit (6) that branches off from the first electrode side (3) of the electrolysis stack (2) and opens into the first separator (5), and a first liquid circulation conduit (7) that has a first liquid circulation valve (8), branches off from the first separator (5) and opens into the first electrode side (3) of the electrolysis stack (2), further comprising a second separator (9), a second collecting conduit (10) that branches off from the second electrode side (4) of the electrolysis stack (2) and opens into the second separator (9), and a second liquid circulation conduit (11) that has a second liquid circulation valve (12), branches off from the second separator (9) and opens into the second electrode side (4) of the electrolysis stack (2), wherein a first safety valve (13) is positioned in the first collecting conduit (6) and a second safety valve (14) is positioned in the second collecting conduit (10). The invention further relates to a method of separating an electrolysis stack () from a first separator (5) in an electrolysis system (1).

Description

2024PF00103 1 Description TITLE Electrolyzer and method for separating an electrolysis stack from the separator TECHNICAL AREA

[0001] The invention relates to an electrolyzer and a method for separating an electrolysis stack from the separator. BACKGROUND

[0002] Electrolyzers produce a gas-liquid mixture on the anode side, and depending on the design, also on the cathode side, when water and electricity are supplied. This mixture is fed through manifolds to a gas-liquid separator, where the gas and liquid are separated by gravity. The gas and liquid are then discharged via different paths to further processes. The separator can have a considerable volume of several cubic meters.

[0003] There are various types of electrolysis cells used to produce hydrogen. Alkaline electrolysis (AEL) uses an aqueous solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH) as the electrolyte. Anion exchange membrane electrolysis (AEM) is a method for producing hydrogen from water using a special membrane that allows the transport of anions. AEM technology offers the advantage of operating in a wider pH range and does not require corrosive electrolytes like alkaline electrolysis. Finally, polymer electrolyte membrane electrolysis (PEM) is a method for producing hydrogen from water using a special polymer membrane. PEM technology is characterized by its efficiency, low operating temperature, and fast reaction times. 2024PF00103 2

[0004] In the event of a defect in the electrolysis stack, e.g., a frame break, or in the piping system, pressure relief occurs at the point of the defect, reversing the natural flow direction (electrolysis => gas-liquid separator), with gas preferentially flowing backward. This release poses significant hazards (fire, pressure, strong oxidizing effect, entrainment of foreign matter, etc.) and must be prevented. SUMMARY OF THE INVENTION

[0005] The object of the invention is therefore to provide an electrolysis plant for the decomposition of water into hydrogen and oxygen, in which an electrolysis stack can be reliably separated from the separator. Furthermore, it is an object of the invention to provide a method for separating an electrolysis stack from a separator in an electrolysis plant.

[0006] The problem directed towards an electrolysis plant is solved by an electrolysis plant for the decomposition of water into hydrogen and oxygen comprising an electrolysis stack with a first electrode side and a second electrode side, a first separator, a first collecting line branching off from the first electrode side of the electrolysis stack and opening into the first separator, and a first liquid circulation line branching off from the first separator and opening into the first electrode side of the electrolysis stack with a first liquid circulation valve, further comprising a second separator, a second collecting line branching off from the second electrode side of the electrolysis stack and opening into the second separator, characterized in that a first safety valve is arranged in the first collecting line and a second safety valve is arranged in the second collecting line.

[0007] The solution according to the invention increases safety in the event of a cell frame failure in an electrolysis plant. Closed safety valves in the respective manifolds prevent the escape of large quantities of gas and process liquid from the gas separators, which would otherwise cause serious damage. 2024PF00103 3 would have safety-related consequences. Especially large plants with many electrolysis stacks and correspondingly large process technologies can be operated much more safely as a result. It is advantageous for the electrolysis plant to have a primary circulation pump in the first liquid circulation line. Besides natural circulation, this technical solution is also relevant for forced circulation systems with a circulation pump. A forced circulation system in electrolysis offers several advantages. It ensures a uniform distribution of the electrolyte around the electrodes, which can lead to a more homogeneous reaction and thus higher product quality. Effective electrolyte recirculation can improve electrolysis efficiency by optimizing transport processes and maintaining reaction conditions. Furthermore, the forced circulation system can help reduce the formation of gas deposits at the electrodes, improving the performance and safety of the electrolysis plant.

[0009] In an advantageous embodiment of the invention, the electrolysis system further comprises a second liquid circulation line branching off from the second separator and opening into the second electrode side of the electrolysis stack, with a second liquid circulation valve. This contributes to improving the efficiency, homogeneity, and operational stability of the electrolysis.

[0010] It is also advantageous to have a second circulation pump in the second fluid circulation line.

[0011] In an advantageous embodiment of the invention, the electrolysis system comprises a first pressure relief line branching off from the first manifold upstream of the first safety valve at a first branch, with a first pressure relief valve, and a second pressure relief line branching off from the second manifold upstream of the second safety valve at a second branch. 2024PF00103 4 a second pressure relief valve. This arrangement serves to prevent unwanted pressure build-up in the electrolysis system. The ability to release excess pressure via the pressure relief lines increases the safety of the electrolysis system.

[0012] In a further advantageous embodiment of the invention, the electrolysis system further comprises a first auxiliary valve arranged between the first safety valve and the first branch, a first additional pressure relief line branching off from the first manifold between the first safety valve and the first auxiliary valve, with a first additional pressure relief valve, a second auxiliary valve arranged between the second safety valve and the second branch, and a second additional pressure relief line branching off from the second manifold between the second safety valve and the second auxiliary valve, with a second additional pressure relief valve. The advantage of this arrangement is that additional safety precautions are taken to ensure even greater safety in the event of a pressure increase in the electrolysis system.The additional valves and pressure relief lines provide redundancy and increase the operational reliability of the system. Should a valve or line fail, other safety mechanisms remain in place to prevent uncontrolled pressure build-up and protect the electrolysis system.

[0013] Integrating a control unit into the electrolysis plant is particularly advantageous because it enables centralized control and monitoring of the entire system. The control unit allows for the automatic control and monitoring of all valves, optimizing the plant's operation and ensuring proper valve function. Furthermore, the control unit can also help optimize energy consumption and monitor plant operation to identify and resolve potential problems early on. Thus, the control unit contributes to the efficiency, safety, and reliable operation of the electrolysis plant. 2024PF00103 5

[0014] The problem, which concerns a method for separating an electrolysis stack from a separator in an electrolysis plant, is solved by a method for separating an electrolysis stack from a first separator, wherein a first safety valve is closed in a first manifold branching off from a first side of the electrolysis stack and leading into the first separator, and a second safety valve is closed in a second manifold branching off from a second side of the electrolysis stack and leading into a second separator. This contributes to ensuring the safety of the electrolysis plant. Closing the safety valves prevents backflow, which could potentially lead to operational malfunctions or safety hazards. The separation of the electrolysis stack from the separators using the safety valves thus serves to protect the electrolysis plant and the safety of the operating personnel.

[0015] It is advantageous to open a first pressure relief valve in a first pressure relief line, which branches off from the first manifold upstream of the first safety valve at a first branch, and a second pressure relief valve in a second pressure relief line, which branches off from the second manifold upstream of the second safety valve at a second branch, is also opened. This serves to release excess pressure in the electrolysis plant in a controlled manner. If the pressure in the plant exceeds a certain level, the pressure relief valves can be opened to reduce the pressure in a controlled manner, thus ensuring the safety of the electrolysis plant and preventing potential damage or safety risks. This controlled pressure release increases the stability and reliability of the electrolysis plant.

[0016] It is further advantageous if, in an electrolysis plant, comprising a first auxiliary valve arranged between the first safety valve and the first branch, as well as a pressure relief line branching off from the first manifold between the first safety valve and the first auxiliary valve, with a first further pressure relief valve, the 2024PF00103 6 The electrolysis system further comprises a second auxiliary valve arranged between the second safety valve and the second branch, as well as a pressure relief line branching off from the second manifold between the second safety valve and the second auxiliary valve, with a second additional pressure relief valve. When the first and second auxiliary valves are closed, the first additional pressure relief valve and the second additional pressure relief valve are opened. Opening the first and second additional pressure relief valves in conjunction with closing the auxiliary valves provides greater protection for the electrolysis system due to the redundancy of the safety valves, and allows excess pressure in the electrolysis system to be released in a controlled manner to protect the system from uncontrolled pressure build-up.These additional safety precautions increase the operational reliability of the plant and help to minimize potential risks. The redundancy of the safety mechanisms ensures reliable operation of the electrolysis plant and protects it from undesirable pressure conditions.

[0017] The power supply to the electrolysis stack is advantageously interrupted. This can help stop the damage from spreading and minimize potential risks. Furthermore, it can help preserve the integrity of the system and allow repairs or maintenance to be carried out safely without causing further damage. Interrupting the power supply thus serves to protect the system, ensure the safety of personnel, and prevent consequential damage.

[0018] Simultaneously, and with the same advantages, it is also expedient to close the first and second liquid circulation valves to interrupt the liquid supply to the electrolysis stack. Due to the risk of alkali leakage, it is advantageous for alkaline electrolysis (AEL) if the first safety valve and the first liquid circulation valve are closed simultaneously. The same applies to the second safety valve and the second liquid circulation valve. 2024PF00103 7

[0019] The situation is different with anion exchange membrane (AEM) and polymer electrolyte membrane (PEM) electrolysis. In these systems, it is advantageous for the first and second liquid recirculation valves to close after the first and second safety valves, respectively. The closing sequence can occur with a slight time difference of a few seconds, so that the first and second safety valves close earlier than the first and second liquid recirculation valves. This maintains a certain liquid supply for cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG 1 shows a state-of-the-art electrolyzer,

[0021] FIG 1a shows a state-of-the-art electrolyzer with only one recirculation,

[0022] FIG 2 shows a first embodiment of an electrolyzer according to the invention and

[0023] FIG 3 shows a second embodiment of an electrolyzer according to the invention. DESCRIPTION OF THE EXECUTION FORMS

[0024] Figure 1 shows a prior art electrolysis plant 1 for the decomposition of water into hydrogen and oxygen. It comprises one or more electrolysis stacks 2 with a first electrode side 3 (e.g. the anode side) and a second electrode side 4 (e.g. the cathode side) with circuits for the reactants and products of the electrolysis.

[0025] The circuit on the first electrode side 3 comprises, starting from the electrolysis stack 2 and arranged in series, a first collecting line 6, a first separator 5, which separates a generated gas (oxygen on the anode side) from the liquid, and a first liquid circulation line 7. The first collecting line 6 connects the electrolysis stack 2 to the first separator 5. 2024PF00103 8 The first liquid circulation line 7 connects the first separator 5 to the electrolysis stack 2 and closes the circuit. A first liquid circulation valve 8 arranged in the first liquid circulation line 7 regulates the amount of liquid supplied to the first electrode side 3.

[0026] Analogous to the circuit on the first electrode side 3, a second collecting line 10, a second separator 9 and a second liquid circulation line 11 with a second liquid circulation valve 12 are arranged in the same way on the second electrode side 4.

[0027] The product lines are shown in FIG. 1 with 28 for oxygen and 29 for hydrogen. Furthermore, a first circulation pump 30 and a second circulation pump 31 are arranged in each of the first liquid circulation line 7 and the second liquid circulation line 11.

[0028] The electrolysis plant 1 is controlled via a control unit 27.

[0029] The electrolysis system 1 in FIG. 1a is largely identical to the electrolysis system 1 of FIG. 1, with the exception of the recirculation in the right-hand part, which can be omitted depending on the type of electrolysis. The second separator 9 can be smaller, as shown; in extreme cases, the pipe volume is sufficient. It should also be noted that the presence of recirculation has no influence on the invention. Although the invention is illustrated with embodiments featuring two recirculations, it is also applicable to embodiments with only one recirculation.

[0030] FIG. 2 shows a first embodiment according to the invention with a first safety valve 13 in the first manifold 6 and a second safety valve 14 in the second manifold 10. In the event of a safety-critical situation, the first separator 5 is separated from the electrolysis stack 2 by the first safety valve 13, thereby preventing backflow of the electrolysis products from the first separator 5. Even if the technical problem has only occurred on one side, it is important to have a separation between separator 5 and electrolysis stack 2 on both electrode sides. 2024PF00103 9, as otherwise a high differential pressure within the electrolysis stack could lead to a diaphragm rupture with the corresponding consequence (gas backflow). The embodiment shown in FIG. 2 further shows a first pressure relief line 16 branching off from the first manifold 6 at a first branch 15 upstream of the first safety valve 13, with a first pressure relief valve 17, and a second pressure relief line 19 branching off from the second manifold 10 at a second branch 18 upstream of the second safety valve 14, with a second pressure relief valve 20. This prevents pressure build-up on the electrolysis side.

[0032] Typically, in the event of a fault, further process engineering measures are taken, such as interrupting the power supply or stopping the liquid circulation by closing the first liquid circulation valve 8 and the second liquid circulation valve 12. Depending on the electrolysis system 1, the first and the second liquid circulation valve 8, 12 can be closed simultaneously or at different times.

[0033] The embodiment shown in FIG. 3 shows a possible addition compared to the embodiment shown in FIG. 2, which leads to increased safety of the electrolysis plant 1. This addition essentially consists of doubling the structural measures already shown. Specifically, a first auxiliary valve 21 is arranged between the first safety valve 13 and the first branch 15, as well as a first additional pressure relief line 22 branching off from the first manifold 6 between the first safety valve 13 and the first auxiliary valve 21, with a first additional pressure relief valve 23, and a second auxiliary valve 24 arranged between the second safety valve 14 and the second branch 18, as well as a second additional pressure relief line 25 branching off from the second manifold 10 between the second safety valve 14 and the second auxiliary valve 24, with a second additional pressure relief valve 26. 2024PF00103 10 REFERENCE MARK LIST 1 Electrolysis plant 2 Electrolysis stacks 3 first electrode side 4 second electrode side 5 first separator 6 first collection line 7 first fluid circulation line 8 first liquid circulation valve 9 second separator 10 second collection line 11 second fluid circulation line 12 second liquid circulation valve 13 first safety valve 14 second safety valve 15 first turn 16 first pressure relief line 17 first pressure relief valve 18 second branch 19 second pressure relief line 20 second pressure relief valve 21 first auxiliary valve 22 first further pressure relief line 23 first further pressure relief valve 24 second auxiliary valve 25 second further pressure relief line 26 second further pressure relief valve 27 Control unit 28 Oxygen conduit 29 Hydrogen pipeline 30 first circulation pump 2024PF00103 11 31 second circulation pump

Claims

2024PF00103 12 Claims What is claimed:

1. Electrolysis plant (1) for the splitting of water into hydrogen and oxygen comprising an electrolysis stack (2) with a first electrode side (3) and a second electrode side (4), a first separator (5), a first collecting line (6) branching off from the first electrode side (3) of the electrolysis stack (2) and opening into the first separator (5), and a first liquid circulation line (7) branching off from the first separator (5) and opening into the first electrode side (3) of the electrolysis stack (2) with a first liquid circulation valve (8), further comprising a second separator (9), a second collecting line (10) branching off from the second electrode side (4) of the electrolysis stack (2) and opening into the second separator (9), characterized in that a first safety valve (13) is arranged in the first collecting line (6) and a second safety valve (14) is arranged in the second collecting line (10).

2. Electrolysis system (1) according to claim 1, further comprising a first circulation pump (30) in the first liquid circulation line (7).

3. Electrolysis system (1) according to claim 1, further comprising a second liquid circulation line (11) branching off from the second separator (9) and opening into the second electrode side (4) of the electrolysis stack (2) with a second liquid circulation valve (12).

4. Electrolysis system (1 ) according to claim 3, further comprising a second circulation pump (31) in the second liquid circulation line (11). 2024PF00103 13 5. Electrolysis system (1) according to one of the preceding claims, further comprising a first pressure relief line (16) branching off in the direction of flow upstream of the first safety valve (13) at a first branch (15) from the first manifold (6) with a first pressure relief valve (17) and a second pressure relief line (19) branching off in the direction of flow upstream of the second safety valve (14) at a second branch (18) from the second manifold (10) with a second pressure relief valve (20).

6. Electrolysis system (1) according to claim 5, further comprising a first auxiliary valve (21) arranged between the first safety valve (13) and the first branch (15) and a first further pressure relief line (22) branching off from the first manifold (6) between the first safety valve (13) and the first auxiliary valve (21) with a first further pressure relief valve (23) and a second auxiliary valve (24) arranged between the second safety valve (14) and the second branch (18) and a second further pressure relief line (25) branching off from the second manifold (10) between the second safety valve (14) and the second auxiliary valve (24) with a second further pressure relief valve (26).

7. Electrolysis system (1) according to one of the preceding claims, further comprising a control unit (27).

8. Method for separating an electrolysis stack (2) from a first separator (5) in an electrolysis plant (1), wherein a first safety valve (13) is closed in a first collecting line (6) branching off from a first electrode side (3) of the electrolysis stack (2) and opening into the first separator (5), and a second safety valve (14) is closed in a second collecting line (10) branching off from a second side (4) of the electrolysis stack (2) and opening into a second separator (9). 2024PF00103 14 9. Method according to claim 8, wherein a first pressure relief valve (17) is opened in a first pressure relief line (16) which branches off in the flow direction upstream of the first safety valve (13) at a first branch (15) from the first collecting line (6), wherein furthermore a second pressure relief valve (20) is opened in a second pressure relief line (19) which branches off in the flow direction upstream of the second safety valve (14) at a second branch (18) from the second collecting line (10).

10. A method according to claim 8 or 9, the electrolysis system (1) further comprising a first auxiliary valve (21) arranged between the first safety valve (13) and the first branch (15) and a pressure relief line (22) branching off from the first manifold (6) between the first safety valve (13) and the first auxiliary valve (21) with a first further pressure relief valve (23), wherein the first auxiliary valve (21) is closed and the first further pressure relief valve (23) is opened, the electrolysis system (1) further comprising a second auxiliary valve (24) arranged between the second safety valve (14) and the second branch (18) and a pressure relief line (25) branching off from the second manifold (10) between the second safety valve (14) and the second auxiliary valve (24) with a second further pressure relief valve (26),wherein the second auxiliary valve (24) is closed and the second further pressure relief valve (26) is opened.

11. Method according to one of claims 8 to 10, wherein a current supply to the electrolysis stack (2) is interrupted.

12. Method according to one of claims 8 to 11, wherein a first and a second liquid circulation valve (8, 12) are closed to interrupt a liquid supply to the electrolysis stack (2).

13. Method according to claim 12, wherein the first safety valve (13) and the first liquid circulation valve (8) are closed simultaneously. 2024PF00103 15 14. Method according to claim 12, wherein the first liquid circulation valve (13) is closed downstream of the first safety valve (8).

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