Multi-string electrolysis plant and operation thereof

Abstract

The invention relates to a multi-string electrolysis plant (1) for splitting water into hydrogen and oxygen, the plant comprising: a plurality of electrolysis strings (2) connected in parallel, each having a plurality of electrolysis stacks (3) connected in series; a first separator (4) which is connected to first inlets (7) of a first electrode side (8) of the electrolysis strings (2) via a first main supply line (5) and first branch lines (6) branching therefrom, wherein first outlets (9) of the first electrode side (8) of the electrolysis strings (2) are connected to the first separator (4) via first collection lines (10) which open into a first main discharge line (12); and a second separator (12) which is connected to second inlets (15) of a second electrode side (16) of the electrolysis strings (2) via a second main supply line (13) and second branch lines (14) branching therefrom, wherein second outlets (17) of the second electrode side (16) of the electrolysis strings (2) are connected to the second separator (12) via second collection lines (18) which open into a second main discharge line (19), wherein valves (20) are arranged in the first and second main supply lines (5, 13), the first and second branch lines (6, 14), the first and second collection lines (10, 18), and the first and second main discharge lines (11, 19). The invention also relates to a method for operating a multi-string electrolysis plant (1).

Description

2024PF00107 1 Description TITLE Multi-strand electrolysis plant and its operation TECHNICAL AREA

[0001] The invention relates to a multi-strand electrolysis plant for the decomposition of water into hydrogen and oxygen and to a method for operating a multi-strand electrolysis plant. BACKGROUND

[0002] Electrolyzers produce a gas-water 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] In the event of a defect in the electrolysis stack, e.g., frame breakage, loss of the seal between the cells, 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 or at least minimized. SUMMARY OF THE INVENTION

[0004] The object of the invention is to provide a multi-strand electrolysis system for safe operation in the event of a fault. Furthermore, it is an object of the invention to provide a 2024PF00107 2 To specify a procedure for the safe operation of a multi-strand electrolysis plant.

[0095] The problem directed towards a multi-strand electrolysis plant is solved by a multi-strand electrolysis plant for the decomposition of water into hydrogen and oxygen, comprising several hydraulically parallel electrolysis strands, each with several hydraulically parallel electrolysis stacks, wherein first outputs of the first electrode side of each electrolysis strand lead via first collecting lines into a first main discharge line, further comprising a second separator, which is connected via a second main supply line and second branch lines leading from it to second inputs of a second electrode side of each electrolysis strand, wherein second outputs of the second electrode side of each electrolysis strand are connected to the second separator via second collecting lines leading into a second main discharge line, wherein in the second main supply line, the second branch lines,Valves are arranged in the first and second collecting pipes and the first and second main discharge pipes.

[0006] If a safety-relevant situation involving media leakage occurs in an electrolysis line, the other electrolysis lines do not need to be isolated from the process equipment and, primarily, from the separator. Instead, only the affected electrolysis line in its respective branch line needs to be isolated using safety valves. This isolates not only the affected process side but also the adjacent process side (H₂ / O₂ or O₂ / H₂), as otherwise, a high differential pressure within the stack could lead to a membrane / diaphragm rupture with gas mixing and backflow. An advantageous embodiment of the multi-line electrolysis plant further comprises a first separator connected via a first main supply line and first branch lines leading from it to the first inlets of each electrode side of the electrolysis lines, wherein the first separator is smaller than the second separator. 2024PF00107 3 The separators can have significantly different volumes; especially in the case of electrolysis with only one circulation system, e.g., an anode-side system, gas-liquid separation on the cathode side is only required to a very limited extent, so that piping with liquid separation alone may suffice. This configuration also carries considerable risks.

[0009] In an advantageous embodiment of the invention, the electrolysis system comprises pressure relief lines branching off from the first and second manifolds between the electrolysis strings and the valves in these manifolds, with pressure relief valves being arranged in the pressure relief lines. This prevents undesirable pressure build-up in the electrolysis system. The safety of the electrolysis system is increased by the ability to release excess pressure via the pressure relief lines. In the case of alkaline electrolysis technology (AEL, AEM), the media outlet at the line end is designed to prevent or minimize uncontrolled release of alkali into the environment. Typical technical solutions such as cyclone separators, droplet separators, or scrubbers with and without neutralization are used for this purpose.

[0010] For the same reasons, it is advantageous to have main pressure relief lines branching off from the main discharge lines between the valves in the manifold lines and the valves in the main discharge lines, with main pressure relief valves being arranged in the main pressure relief lines. As at the level of the individual electrolysis strings, it is also important at the overall plant level to avoid a safety-critical pressure increase.

[0011] The safety of the electrolysis plant can be further increased if at least some of the valves are redundantly designed by means of additional valves, with an additional pressure relief line branching off between the valve and the additional valve and an additional pressure relief valve in the additional pressure relief line. 2024PF00107 4 is arranged. This approach further increases the safety of the electrolysis plant, as it first provides for replacements in the event of a valve failure at particularly critical points by increasing the number of valves, while also ensuring that excess pressure does not build up in the first place by means of appropriately positioned additional valves in the pressure relief lines. This minimizes the risk of pressure build-up and potential safety problems.

[0012] Integrating a control unit into the electrolysis plant offers several advantages. Through centralized control and monitoring, the control unit enables the automatic control and monitoring of all valves, optimizing the plant's operation and ensuring proper valve function. Furthermore, the control unit contributes to optimizing energy consumption and the early detection of potential problems, thus enhancing the efficiency, safety, and reliability of the electrolysis plant.

[0013] The problem directed towards a method is solved by a method for operating a multi-strand electrolysis plant, comprising several electrolysis strands, each with a first electrode side and a second electrode side, and with a product side and optionally a reactant side, wherein in the event of a fault on the first electrode side of an electrolysis strand, the product side and optionally the reactant side of the faulty electrolysis strand is separated from the other electrolysis strands, characterized in that the product side and optionally the reactant side of the second electrode side of the faulty electrolysis strand are also separated from the other electrolysis strands.

[0014] This ensures that the faulty electrolysis string is isolated without affecting the functionality of the other electrolysis strings. This contributes to the reliable and uninterrupted operation of the electrolysis plant. 2024PF00107 5

[0015] Under these conditions, it is advisable to continue operating the remaining electrolysis lines. By isolating the faulty electrolysis line, the remaining lines can continue to operate efficiently and achieve the desired production targets. This contributes to the economic viability and continuity of operation of the electrolysis plant.

[0016] Simultaneously interrupting the reactant and product connections ensures that no further materials or reagents enter the faulty electrolysis line, which could potentially lead to unwanted reactions or damage. This simultaneous interruption maintains control over the material flows in the electrolysis plant and minimizes the risk of adverse effects resulting from the fault. However, it can also be advantageous to interrupt the reactant connections after the product connections. In other words, the closing sequence for the liquid inlet to the electrolysis lines and for the gas-liquid outlet from the electrolysis lines can be sequentially delayed by a few seconds, with the gas-liquid outlet being closed first. This maintains an adequate water supply for cooling.No delay occurs with AEL stacks due to the risk of caustic soda leakage. In any case, if a fault is detected, the corresponding electrolysis line is immediately disconnected from the DC power supply.

[0018] Advantageously, pressure relief is implemented for the faulty electrolysis line to ensure the safety and efficiency of the electrolysis plant. This pressure relief ensures that any gases or pressure drops remaining in the faulty electrolysis line are safely discharged to prevent potential overload or damage to the system. This helps to increase operational reliability and minimize potential risks such as the build-up of differential pressures. 2024PF00107 6

[0019] If all electrolysis lines are affected by faults, it is advisable to disconnect the reactant and product connections between all electrolysis lines and the first and second separators. This comprehensive disconnection ensures that no further faults or damage from the faulty lines are transmitted to other parts of the electrolysis plant. Furthermore, it facilitates maintenance and repair, as isolating all electrolysis lines generally allows for more efficient and comprehensive troubleshooting.

[0020] It is advantageous to implement pressure relief on the electrolysis side when the valves (safety valves) are closed. As already explained for the individual electrolysis line, such pressure relief ensures that any gases or pressure drops that may occur in the electrolysis plant are safely discharged to prevent potential overload or damage to the system.

[0021] It is advantageous for a control unit to control the multi-strand electrolysis system.

[0022] The present invention increases safety in the event of a cell frame failure or loss of the seal between the individual cells of an electrolysis plant. It prevents the escape of large quantities of gas and process fluid from the gas separators, which would each have serious safety consequences. This makes it significantly safer to operate large plants with many electrolysis stacks and correspondingly large process technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG 1 shows a multi-strand electrolysis system according to the invention in normal operation without a fault,

[0024] FIG2 shows an alternative form of a multi-strand electrolysis plant according to the invention in normal operation without fault conditions using only one separator, 2024PF00107 7

[0025] FIG 3 shows a multi-strand electrolysis plant according to the invention in operation with a fault in the upper electrolysis strand,

[0026] FIG 4 shows a multi-strand electrolysis plant according to the invention in operation with a fault in the lower electrolysis strand,

[0027] FIG 5 shows a multi-strand electrolysis plant according to the invention in operation with fault cases in both electrolysis strands and

[0028] FIG 6 shows a section for a redundant valve with pressure relief. DESCRIPTION OF THE EXECUTION FORMS

[0029] FIG. 1 shows an exemplary multi-strand electrolysis plant 1 according to the invention, which serves to split water into hydrogen and oxygen. The embodiment shown in FIG. 1 comprises two electrolysis strands 2 connected hydraulically in parallel, each electrolysis strand 2 comprising three electrolysis stacks 3 connected hydraulically in parallel, containing electrolysis cells that are not shown in FIG. 1. It should be noted that the invention is not limited to this specific configuration and is also applicable to electrolysis plants 1 with a different number of electrolysis strands 2 or electrolysis stacks 3. The hydraulically connected electrolysis stacks are typically connected electrically in series. In the event of a fault, the corresponding electrolysis section is disconnected from the DC power supply before the valves are activated.

[0030] A first separator 4 is connected on the reactant side 35 via a first main feed line 5 and first branch lines 6 leading from it to first inputs 7 of each first electrode side 8 of the electrolysis strings 2. These first inputs 7 are in turn connected via first distributors 31 to the electrolysis stacks 3. Similarly, the electrolysis stacks 3 on the product side 36 are connected via first collectors 32 to first outputs 9 of each first electrode side 8 of the electrolysis strings 2, which are also connected to the first separator 4 via first collector lines 10 that lead into a first main discharge line 11. The first electrode side 8 is in 2024PF00107 8 In the embodiment of FIG. 1, the cathode side is shown. Consequently, in the first separator 8, hydrogen is separated from water and transported away via the hydrogen line 29. Similarly, a second separator 12 is connected via a second main supply line 13 and second branch lines 14 leading from it to second inputs 15 of a second electrode side 16 of the electrolysis strings 2, to which second distributors 33 are connected. Second collectors 34 open from the individual electrolysis stacks 3 into second outputs 17 of the second electrode side 16 of the electrolysis strings 2, which in turn are connected to the second separator 12 via second collector lines 18, which open into a second main discharge line 19. In the embodiment of FIG. 1, the second electrode side 16 is the anode side. Consequently, in the second separator 12, oxygen is separated from water and transported away via the oxygen line 30.

[0032] According to the invention, valves 20 are arranged in the first and second main supply lines 5, 13, in the first and second branch lines 6, 14, in the first and second collecting lines 10, 18 and in the first and second main discharge lines 11, 19. Open valves 20 are shown in white, closed valves 20 are shown in black.

[0033] The separators can have considerably different volumes; especially in the case of electrolysis with only one circulation system, e.g., an anode-side system, gas-liquid separation on the cathode side is only required to a very limited extent, so that only one pipeline with liquid separation may be sufficient, as shown in FIG 2.

[0034] The embodiment of FIG 1 further comprises pressure relief lines 21 branching off from the first and second collector lines 10, 18 between the electrolysis strings 2 and the valves 20 in the collector lines 10, 18, wherein pressure relief valves 22 are arranged in the pressure relief lines 21. 2024PF00107 9 The same principle can be applied to the entire electrolysis plant 1 by providing main pressure relief lines 23 branching off from the main discharge lines 11, 19 between the valves 20 in the collecting lines 10, 18 and the valves 20 in the main discharge lines 11, 19, as shown in FIG 1, wherein main pressure relief valves 24 are arranged in the main pressure relief lines 23.

[0036] The electrolysis plant 1 is controlled by a control unit 28. This control unit 28 controls, among other things, the valves 20, the pressure relief valves 22 and the main pressure relief valves 24.

[0037] In the example shown in FIG. 1, the multi-strand electrolysis plant 1 is operating without fault, which is why all valves 20 are open and all pressure relief valves 22 and main pressure relief valves 24 are closed. The embodiment shown in FIG. 2 also shows a multi-strand electrolysis plant 1 without faults.

[0038] In the following exemplary embodiments shown in Figures 3, 4, and 5, an electrolysis plant 1 with two circulations, as depicted in Figure 1, is presented in various operating modes. Although the electrolysis plant 1 with only one circulation from Figure 2 is not explicitly shown in different operating modes, the invention is nevertheless also applicable to it.

[0039] FIG. 3 shows the multi-strand electrolysis plant 1, as already known from FIG. 1, but in a different operating mode. In the example of FIG. 3, a safety-critical situation exists in the upper electrolysis strand 2. In order to continue operating the rest of the electrolysis plant 1 and to safely isolate the faulty electrolysis strand 2, the valves 20 in the first branch line 6 and the first manifold 10 in the upper electrolysis strand 2 are closed. At the same time, the valves 20 in the second branch line 14 and the second manifold 18 in the upper electrolysis strand 2 are closed. Furthermore, the pressure relief valves 22 in the upper electrolysis strand 2 are closed. 2024PF00107 10 Pressure relief lines 21 are opened to prevent dangerous overpressure from forming in the isolated electrolysis string 2.

[0040] FIG 4 shows the analogous scenario to FIG 3, this time with a functioning upper electrolysis string 2 and a safety-critical situation in the lower electrolysis string 2.

[0041] FIG. 5 shows the case in which all electrolysis strings 2 have failed. In this scenario, the valve positions are exactly the opposite of those in FIG. 1: The pressure relief valves 22 and the main pressure relief valves 24 are open to prevent pressure build-up in the electrolysis plant 1, while all other valves 20 are closed.

[0042] At least some of the valves 20 are redundantly configured by means of further valves 25. FIG 6 shows how, in such a case, an additional pressure relief line 26 branches off between the valve 20 and the further valve 25, and an additional pressure relief valve 27 is arranged in the additional pressure relief line 26. This principle is applicable to all valves 20 in the electrolysis plant 1 according to the invention. REFERENCE MARK LIST 1 multi-strand electrolysis plant 2 Electrolysis train 3 Electrolysis stacks 4 first separator 5 first main supply line 6 first branch lines 7 first entrances 8 first electrode side 9 first exits 10 first collection lines 11 first main drainage line 12 second separator 2024PF00107 11 13 second main supply line 14 second branch lines 15 second entrances 16 second electrode side 17 second exits 18 second collector lines 19 second main drainage line 20 valves 21 Pressure relief line 22 Pressure relief valve 23 Main pressure relief line 24 Main pressure relief valve 25 more valve 26 Additional pressure relief line 27 Additional pressure relief valve 28 Control unit 29 Hydrogen pipeline 30 Oxygen line 31 first distributor 32 first collector 33 second distributor 34 second collector 35 Educ side 36 Product page

Claims

2024PF00107 12 Claims 1. Multi-strand electrolysis plant (1) for the decomposition of water into hydrogen and oxygen, comprising several hydraulically parallel electrolysis strands (2) each with several hydraulically parallel electrolysis stacks (3), wherein first outputs (9) of the first electrode side (8) of the electrolysis strands (2) open via first collecting lines (10) into a first main discharge line (11), further comprising a second separator (12) which is connected via a second main supply line (13) and second branch lines (14) leading from it to second inputs (15) of a second electrode side (16) of the electrolysis strands (2), wherein second outputs (17) of the second electrode side (16) of the electrolysis strands (2) are connected to the second separator (12) via second collecting lines (18) which open into a second main discharge line (19), characterized in that in the second main supply line (13),Valves (20) are arranged in the second branch lines (14), the first and second collecting lines (10, 18) and the first and second main discharge lines (11, 19).

2. Multi-strand electrolysis system (1) according to claim 1, further comprising a first separator (4) which is connected via a first main supply line (5) and first branch lines (6) leading from it to first inputs (7) of a first electrode side (8) of the electrolysis strands (2), wherein the first separator (4) is smaller than the second separator (12).

3. Multi-strand electrolysis plant (1 ) according to one of claims 1 or 2, further comprising pressure relief lines (21) branching off from the first and second manifolds (10, 18) between the electrolysis strands (2) and the valves (20), wherein pressure relief valves (22) are arranged in the pressure relief lines (21 ). 2024PF00107 13 4. Multi-strand electrolysis plant (1 ) according to one of the preceding claims, further comprising main pressure relief lines (23) branching off from the main discharge lines (11 , 19) between the valves (20) in the collecting lines (10, 18) and the valves (20) in the main discharge lines (11 , 19), wherein main pressure relief valves (24) are arranged in the main pressure relief lines (23).

5. Multi-strand electrolysis system (1) according to one of the preceding claims, wherein at least part of the valves (20) are redundantly designed by means of further valves (25), wherein an additional pressure relief line (26) branches off between the valve (20) and the further valve (25) and an additional pressure relief valve (27) is arranged in the additional pressure relief line (26).

6. Multi-strand electrolysis system (1) according to one of the preceding claims, further comprising a control unit (28) for controlling the electrolysis system (1).

7. Method for operating a multi-strand electrolysis plant (1), comprising several electrolysis strands (2) each with a first electrode side (8) and a second electrode side (16) and with a product side (36) and optionally a reactant side (35), wherein in the event of a fault on the first electrode side (8) of an electrolysis strand (2) the product side (36) and optionally the reactant side (35) of the faulty electrolysis strand (2) is separated from the other electrolysis strands (2), characterized in that the product side (36) and optionally the reactant side (35) of the second electrode side (16) of the faulty electrolysis strand (2) are also separated from the other electrolysis strands (2).

8. Method according to claim 7, wherein the remaining electrolysis strands (2) continue to be operated. 2024PF00107 14 9. Method according to one of claims 7 or 8, wherein the reactant-side connections are interrupted simultaneously with the product-side connections.

10. Method according to one of claims 7 or 8, wherein the reactant-side connections are interrupted after the product-side connections.

11. Method according to any one of claims 7 to 10, wherein pressure relief is provided for the faulty electrolysis string (2).

12. Method according to one of claims 7 to 11, wherein, in the event that all electrolysis strands (2) are affected by faults, reactant-side and product-side connections between an entirety of the electrolysis strands (2) and the first and second separators (4, 12) are interrupted.

13. Method according to claim 12, wherein pressure relief is brought about on the electrolysis side.

14. Method according to any one of claims 7 to 13, wherein a control unit (28) controls the multi-strand electrolysis system (1).

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