Electrochemical system and method for rinsing such an electrochemical system

Abstract

An electrochemical system (1) has a stack (10) with a functional space (81). The functional space (81) is connected with a functional path (80). The electrochemical system (1) further has a flushing line (2) which can be connected with the functional space (81) by means of the functional path (80). Furthermore, the flushing line (2) can be connected with a liquid inlet (200) for flushing the functional space (81) and / or a functional line (3) by means of a liquid. The invention also relates to a method for flushing such an electrochemical system.

Description

Technical Field

[0001] This invention relates to an electrochemical system. Furthermore, this invention relates to a method for flushing such an electrochemical system. Background Technology

[0002] Devices for producing hydrogen are known in the prior art, for example, by the electrolysis of a liquid. For this purpose, an electrolytic cell is used, having an anode space and a cathode space. The anode space is filled with a liquid or aqueous solution, such as an electrolyte. The anode space and the cathode space are separated from each other by a membrane with electrodes on both sides. An anode electrode is located on the side facing the anode space, and a cathode electrode is located on the side facing the cathode space.

[0003] When a DC voltage is applied between the anode and cathode electrodes, catalytic decomposition of the liquid occurs on the anode side. In an example of PEM electrolysis, protons (H... + Ions diffuse through the membrane to the cathode side and react with electrons there to produce hydrogen.

[0004] Such an electrolytic single cell that operates using a so-called proton exchange membrane (PEM) is known, for example, in DE 10 2014 217462 A1.

[0005] Such a stack of electrolytic single cells is also referred to as a single-cell stack or a pile. An electrolysis system includes at least one stack, which includes at least one electrolytic single cell.

[0006] The electrolyzer has a semi-permeable membrane that is guided by specific ions but is not conductive. In a PEM electrolyzer, the membrane is permeable to protons, but other types of electrolysis exist where the membrane is permeable to anions, such as the so-called AEM electrolyzer (anion exchange membrane electrolyzer).

[0007] However, semipermeable membranes also exhibit some permeability to other substances, particularly hydrogen molecules (H2). For example, if these hydrogen molecules enter the anode space after the electrolytic cell is shut down, a mixture of oxygen and hydrogen will form there. Depending on the mixing ratio, this mixture can be explosive. This back-diffusion is particularly exacerbated during differential pressure operation. Therefore, after the electrolytic cell is shut down, the cathode space is flushed, for example, with a chemically inert gas to flush out the hydrogen.

[0008] However, rinsing with chemical inert gases leads to external contamination of the product gases, thereby reducing the hydrogen production of the entire electrolysis facility. Summary of the Invention

[0009] In contrast, the electrochemical system according to the present invention has the following advantages: when the flushing medium is replaced from a chemically inert gas to a liquid already present in the electrochemical system, a higher purity of the hydrogen produced can be achieved.

[0010] For this purpose, the electrochemical system has a stack having at least one functional space connected to a functional path. Furthermore, the electrochemical system has a flushing line that is fluidly connected to the functional space via the functional path. Additionally, the flushing line can be connected to a liquid inlet for flushing the functional space and / or the functional line with liquid.

[0011] This allows for a simpler way to improve the flexibility of the flushing process and the safety of the entire electrochemical system. Furthermore, by using a liquid as the flushing medium, the purity of the produced hydrogen is improved because no external medium (such as nitrogen) is introduced during flushing.

[0012] In a first advantageous extension, a conveying device is arranged in the flushing line at the liquid inlet, preferably with a filter placed downstream, through which the liquid can be fed for flushing the functional space. This allows for a simple way to deliver liquid along the functional path towards the functional space.

[0013] In an advantageous extension, the liquid at the liquid inlet comprises a liquid already present in the electrochemical system. Preferably, the liquid comprises DI water (deionized water).

[0014] In another configuration of the invention, it is advantageous to set the electrochemical system as an electrolysis system, preferably a PEM electrolysis system or an AEM electrolysis system.

[0015] In another configuration of the invention, the functional path is advantageously configured to include the cathode path of the electrolysis system, and the functional space includes the cathode space of the stack. This allows for a simple flushing of the cathode path of the electrolysis system and the cathode space of the stack with liquid.

[0016] In another configuration of the invention, the functional path is advantageously configured to include the anode path of the electrolysis system, and the functional space includes the anode space of the stack. This allows for a simple flushing of the anode path of the electrolysis system and the anode space of the stack with liquid.

[0017] In another configuration of the invention, the first valve, the second valve, the third valve and the fourth valve are advantageously configured to be electrically operable and switched on, thereby enabling the functional space and / or functional pipelines to be flushed by means of liquid.

[0018] In a favorable extension, the functional path is configured to have a functional pipeline that can be connected to a flushing pipeline by means of a first valve, wherein a check valve is arranged in the functional pipeline to prevent gas from flowing from the functional pipeline into the flushing pipeline.

[0019] In another configuration of the invention, the functional space of the stack is advantageously configured to have a first functional space outlet and a second functional space outlet, the first functional space outlet connecting to the functional pipeline at a first bypass node, and the second functional space outlet connecting to the functional pipeline at a second bypass node. Preferably, the functional pipeline has a bypass passage between the first and second bypass nodes, in which the second valve is arranged.

[0020] In another advantageous extension of the invention, the functional pipeline is configured to have a third bypass node downstream, which connects to a first liquid outlet channel for low pressure and a second liquid outlet channel for high pressure. This allows flushing at both low and high pressures in a structurally simple manner. Furthermore, by leading to two different pressure levels, connections to peripheral system equipment are simplified.

[0021] In another configuration of the invention, a third valve is advantageously arranged in the first liquid outlet channel for opening and closing the connection between the functional line and the first liquid outlet channel.

[0022] In a favorable extension configuration, a fourth valve is arranged in the second liquid outlet channel for opening and closing the connection between the functional pipeline and the second liquid outlet channel.

[0023] Furthermore, the present invention relates to a method for rinsing such an electrochemical system, comprising the following steps: a. Close the second and fourth valves, and open the first and third valves; b. Liquid at a pressure lower than the operating pressure is introduced from the flushing line into the functional line, such that the liquid passes through the functional space of the flow stack through the first functional space outlet, and then exits through the second functional space outlet, and flows towards the first liquid outlet channel through the third valve.

[0024] In this way, the gas is flushed out of the functional lines and functional spaces using a liquid. This improves the efficiency and purity of hydrogen production and, for example, prevents hydrogen from diffusing from the cathode space through the membrane into the anode space. It also prevents the diffused hydrogen from reacting with oxygen in the anode space to form a potentially detonating gas mixture.

[0025] Flushing improves the safety of electrochemical systems and increases the flexibility of the flushing process using liquids. This leads to an improvement in the overall usability of the electrochemical system. Attached Figure Description

[0026] The invention will now be described in more detail with reference to the accompanying drawings.

[0027] It shows: Figure 1 This is a schematic view of a feasible embodiment of the electrochemical system according to the present invention. Figure 2 This is a schematic view of a feasible embodiment of a group consisting of x electrochemical system modules. Detailed Implementation

[0028] Figure 1 A schematic view of a feasible embodiment of an electrochemical system 1 according to the present invention is shown. The electrochemical system 1 has a stack 10 with a functional space 81. The functional space 81 is connected to a functional path 80. The stack 10 includes at least one electrolytic cell, wherein, typically, a stack of multiple electrolytic cells is referred to as a stack. Furthermore, the stack 10 may be, for example, a PEM stack or an AEM stack. In this embodiment, it is a PEM stack.

[0029] The stack 10 has an anode space 102 and a cathode space 101, which are separated from each other by a semi-permeable membrane 103. The membrane 103 has an anode electrode 106 on the anode side and a cathode electrode 105 on the cathode side.

[0030] The functional path 80 is configured, for example, as a cathode path 300 or an anode path 1020.

[0031] In this embodiment, the functional path 80 corresponds to the cathode path 300 of the electrolysis system 1, and the functional space 81 corresponds to the cathode space 101 of the stack 10.

[0032] In an alternative embodiment, the functional path 80 corresponds to the anode path 1020 of the electrolysis system 1, and the functional space 81 corresponds to the anode space 102 of the stack 10.

[0033] Functional path 80 (here, cathode path 300) has a functional line 3, which can be connected to a flushing line 2 via a first valve 23. The flushing line 2 is connected to a liquid inlet 200. Furthermore, a delivery device 21 (e.g., configured as a pump) and a filter 22 located downstream are arranged in the flushing line 2, thereby allowing liquid to be fed into the functional line 3 for flushing the functional space 81. The liquid inlet 200 is fluidly connected to a liquid reservoir 20 (preferably under pressure), wherein the liquid in the liquid reservoir 20 is a deionized liquid.

[0034] A check valve 24 is also arranged in the functional line 3, which prevents gas from flowing from the functional line 3 into the flushing line 2.

[0035] The first valve 23 in the flushing line 2 is electrically controllable and opens when power is off.

[0036] The functional space 81 of the stack 10 has a first functional space outlet 7 and a second functional space outlet 8. The first functional space outlet 7 leads to the functional pipeline 3 at a first bypass node 82, and the second functional space outlet 8 leads to the functional pipeline at a second bypass node 83.

[0037] Between the first bypass node 82 and the second bypass node 83, the functional pipeline 3 has a bypass pipeline 3a, in which a second valve 25 is arranged. The second valve 25 is electrically operable and closes when power is off.

[0038] Furthermore, the functional pipeline 3 has a third bypass node 300 downstream, which connects to a first liquid outlet channel 5 for low pressure and a second liquid outlet channel 6 for high pressure. Here, the operating pressure of the reactor 10 is considered high pressure, which includes, for example, a range of 0.5 bar to 100 bar. Pressures close to atmospheric pressure are considered low pressure, or alternatively, the pressure level of the anode space 102 (i.e., low pressure) corresponds to the pressure release of the cathode space 101.

[0039] A third valve 27 is arranged in the first liquid outlet channel 5 for opening and closing the connection between the functional pipeline 3 and the first liquid outlet channel 5. The first liquid outlet channel 5 also leads to the discharge port 30. The third valve 27 is electrically operable and opens when power is off.

[0040] A fourth valve 26 is arranged in the second liquid outlet channel 6 for opening and closing the connection between the functional line 3 and the second liquid outlet channel 6. The second liquid outlet channel 6 leads downstream to the gas-liquid separator 54. The fourth valve 26 is electrically operated and closes when power is off.

[0041] In addition, Figure 1 The diagram shows an electrochemical system module 100 comprising n stacks 10, 10', 10'' of the aforementioned electrochemical system 1. These stacks are hydraulically connected in parallel such that for the electrochemical system module 100, liquid is guided through a flushing line 2 by means of a delivery device 21 arranged in the flushing line 2 into the functional spaces 81 of the n stacks 10, 10', 10'' and flushed. Here, preferably, a regulating valve (not shown) can be arranged at each inlet of the n stacks 10, 10', 10'' to ensure a uniform liquid volumetric flow rate for the n stacks 10, 10', 10'' within the electrochemical system module 100.

[0042] In an alternative embodiment, each stack 10, 10', 10'' may also have one conveyor 21.

[0043] During operation, the first valve 23 is closed, preventing any liquid from flowing from the flushing line 2 toward the functional path 80 and the functional spaces 81 or 10, 10', 10'' of the stack 10. Furthermore, the check valve 24 prevents backflow into the flushing line 2 and toward the liquid inlet 200 and toward the parallel-connected stacks 10, 10', 10'' of the electrolysis system module 100 during hydrogen production. The second valve 25 in the bypass line 3a is electrically operated and held in the open position during hydrogen production in operation. Thus, the generated hydrogen flows from the first functional space outlet 7 via the first bypass node 82 and from the second functional space outlet 8 via the second bypass node 83 into the functional line 3, and through the open fourth valve 26 into the second liquid outlet channel 6 toward the gas-liquid separator 54. The gas-liquid separator 54 typically separates the generated hydrogen from the entrained DI water.

[0044] Under specific operating conditions, such as system shutdown, emergency shutdown, or standby, the electrochemical system 1 or the electrochemical system module 100, particularly the functional pipelines 3 and the functional spaces 81 of the stacks 10, 10', 10'', are flushed with liquid to ensure the removal of gases (especially hydrogen or oxygen). This is also referred to as liquid-based inerting or flushing. The liquid in the liquid inlet 200 includes liquids already present in the electrochemical system. In this embodiment, it is a PEM electrolysis system, therefore the liquid includes DI water.

[0045] In alternative embodiments, such as in an AEM electrolysis system, KOH alkaline solution or liquid alkaline electrolyte solution or any dilution of electrolyte solution is used as the liquid.

[0046] For flushing, the control strategy of electrochemical system 1 or electrochemical system module 100 is used, thereby closing the second valve 25 and the fourth valve 26, while opening the first valve 23 and the third valve 27. By means of the delivery device 21, liquid now flows from the liquid reservoir 20 (preferably under pressure) toward the functional lines 3 of the n stacks 10, 10', 10''. Due to the closed second valve 25, bypass line 3a is impassable, so liquid flows through the first functional space outlet 7 into the functional spaces 81 of stacks 10, 10', 10'', and then returns from stacks 10, 10', 10'' to the functional lines 3 via the second functional space outlet 8. Liquid is discharged through the third bypass node 300 into the first liquid outlet channel 5 toward the discharge port 30 by means of the third valve 27.

[0047] Thus, in this embodiment, hydrogen is flushed out of the functional space 81 (i.e., cathode space 101) by liquid and separated from the liquid again by means of gas-liquid separator 54. This improves the efficiency of hydrogen production on the one hand, and minimizes the possibility of hydrogen diffusing from cathode space 101 to anode space 102 through membrane 103 and combining with oxygen there, resulting in a detonating gas reaction.

[0048] In an alternative embodiment, instead of flushing hydrogen from functional space 81 (i.e., cathode space 101), the liquid flushes oxygen from anode space 102.

[0049] Figure 2 A schematic view of a feasible embodiment of a group 1000 consisting of x electrochemical system modules 100, 100', 100'' is shown. The electrochemical system modules 100, 100', 100'' each have discharge ports 30, 30', 30'', whereby a liquid aggregate can be guided from the electrochemical system modules 100, 100', 100'' via first liquid outlet channels 5, 5', 5''.

[0050] In addition, the electrochemical system modules 100, 100', and 100'' each have second liquid outlet channels 6, 6', and 6'', which lead to a common gas-liquid separator 54. Each electrochemical system module 100, 100', and 100'' includes a separate and independent liquid inlet, not shown here.

Claims

1. An electrochemical system (1) having a stack (10) and a flushing line (2), the stack (10) having at least one functional space (81) connected to a functional path (80), the flushing line (2) being fluidly connected to the functional space (81) via the functional path (80), characterized in that, The flushing line (2) can be connected to a liquid inlet (200) for flushing the functional space (81) and / or the functional line (3) with liquid.

2. The electrochemical system (1) according to claim 1, characterized in that, A conveying device (21) is arranged in the flushing line (2) at the liquid inlet (200), the conveying device preferably having a filter (22) placed downstream, the liquid being fed through the conveying device (21) for flushing the functional space (81).

3. The electrochemical system (1) according to claim 1 or 2, characterized in that, The liquid in the liquid inlet (200) includes the liquid that is already present in the electrochemical system (1).

4. The electrochemical system (1) according to the preceding claim, characterized in that, The liquid includes DI water (deionized water).

5. The electrochemical system (1) according to any one of the preceding claims, characterized in that, The electrochemical system is an electrolysis system, preferably a PEM electrolysis system or an AEM electrolysis system.

6. The electrochemical system (1) according to the preceding claim, characterized in that, The functional path (80) includes the cathode path (300) of the electrolysis system, and the functional space (81) includes the cathode space (101) of the stack (10).

7. The electrochemical system (1) according to claim 5, characterized in that, The functional path (80) includes the anode path (1020) of the electrolysis system, and the functional space (81) includes the anode space (102) of the stack (10).

8. The electrochemical system (1) according to any one of the preceding claims, characterized in that, The first valve (23), the second valve (25), the third valve (27) and the fourth valve (26) are electrically operable and can be switched on to enable the functional space (81) and / or functional pipeline (3) to be flushed by means of liquid.

9. The electrochemical system (1) according to the preceding claim, characterized in that, The functional path (80) has a functional pipeline (3) that can be connected to the flushing pipeline (2) by means of the first valve (23), wherein a check valve (24) is arranged in the functional pipeline (3) to prevent gas from flowing from the functional pipeline (3) into the flushing pipeline (2).

10. The electrochemical system (1) according to claim 8, characterized in that, The functional space (81) of the stack (10) has a first functional space outlet (7) and a second functional space outlet (8), the first functional space outlet (7) leading to the functional pipeline (3) at a first bypass node (82), and the second functional space outlet (8) leading to the functional pipeline at a second bypass node (83).

11. The electrochemical system (1) according to the preceding claim, characterized in that, The functional pipeline (3) has a bypass channel (3a) between the first bypass node (82) and the second bypass node (83), in which the second valve (25) is arranged.

12. The electrochemical system (1) according to claim 8, characterized in that, The functional pipeline (3) has a third bypass node (300) downstream, which connects to a first liquid outlet channel (5) for low pressure and to a second liquid outlet channel (6) for high pressure.

13. The electrochemical system (1) according to the preceding claim, characterized in that, The third valve (27) is arranged in the first liquid outlet channel (5) for opening and closing the connection between the functional pipeline (3) and the first liquid outlet channel (5).

14. The electrochemical system (1) according to claim 12 or 13, characterized in that, The fourth valve (26) is arranged in the second liquid outlet channel (6) for opening and closing the connection between the functional pipeline (3) and the second liquid outlet channel (6).

15. A method for rinsing an electrochemical system (1) according to any one of claims 1 to 14, comprising the following steps: a. Close the second valve (25) and the fourth valve (26), and open the first valve (23) and the third valve (27); b. The liquid is introduced from the flushing line (2) into the functional line (3) such that the liquid flows through the functional space (81) of the stack (10) through the first functional space outlet (7), and the liquid leaves through the second functional space outlet (8) and flows through the third valve (27) toward the first liquid outlet channel (5).

Images