Electrolyzer and method for separating an electrolysis stack from the separator

Abstract

The invention relates to an 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), and 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), wherein 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). The invention further relates to a method for separating an electrolysis stack () from a first separator (5) in an electrolysis plant (1).

Description

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 (AEM) electrolysis 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 (PEM) electrolysis 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.

[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 have serious safety consequences. Large plants with many electrolysis stacks and correspondingly large process technologies can therefore be operated much more safely.

[0008] 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 at a first branch point upstream of the first safety valve, and a second pressure relief line branching off from the second manifold at a second branch point upstream of the second safety valve, and a second pressure relief line with a second pressure relief valve. This arrangement serves to prevent an undesirable 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.

[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, further 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 electrolysis plant further comprising 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 further pressure relief valve, the first and the second auxiliary valve are closed and the first further pressure relief valve and the second further pressure relief valve are opened.Opening the first and second pressure relief valves in conjunction with closing the auxiliary valves provides greater protection for the electrolysis plant due to the redundancy of the safety valves. Excess pressure in the electrolysis plant can be released in a controlled manner, protecting it from uncontrolled pressure build-up. These additional safety measures increase the operational reliability of the plant and help 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.

[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 Fig. Figure 1 shows a state-of-the-art electrolyzer. Fig. Figure 1a shows a state-of-the-art electrolyzer with only one recirculation. Fig. Figure 2 shows a first embodiment of an electrolyzer according to the invention and Fig. Figure 3 shows a second embodiment of an electrolyzer according to the invention. DESCRIPTION OF THE EXECUTION FORMS

[0020] Fig. Figure 1 shows a state-of-the-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.

[0021] 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. 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.

[0022] 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.

[0023] The product lines are labeled 28 for oxygen and 29 for hydrogen in Fig. Figure 1 shows. In addition, 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.

[0024] The electrolysis plant 1 is controlled via a control unit 27.

[0025] Electrolysis plant 1 in Fig. 1a is largely identical to electrolysis plant 1 of Fig. 1, with the exception of the recirculation in the right-hand part, which may be omitted depending on the type of electrolysis. The second separator 9 can be smaller, as shown; in the extreme case, the tube volume is sufficient. It should also be noted that the presence of recirculation has no influence on the invention. Although the invention is presented with embodiments featuring two recirculations, it is also applicable to embodiments with only one recirculation.

[0026] Fig. Figure 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 provide separation between separator 5, 9 and electrolysis stack 2 on both electrode sides, since otherwise a high differential pressure within the electrolysis stack could lead to a membrane / diaphragm rupture with the corresponding consequence (gas backflow).

[0027] The exemplary embodiment of Fig. Figure 2 further shows 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. This prevents pressure build-up on the electrolysis side.

[0028] 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.

[0029] The exemplary embodiment of Fig. 3 shows in comparison to the embodiment of Fig. 2. A possible addition that leads to increased safety of the electrolysis plant 1. The 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, as well as a second auxiliary valve 24 arranged between the second safety valve 14 and the second branch 18, and 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. 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 31 second circulation pump

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