Electrochemical system and method for the continuous purging of such an electrochemical system

Abstract

An electrochemical system (1) with a stack (10), which stack (10) has a functional chamber (81). The functional chamber (81) is connected to a functional path (80). Furthermore, the electrochemical system (1) has a flushing line (2), which flushing line (2) can be fluidically connected to the functional chamber (81) via the functional path (80). In addition, the flushing line (2) can be connected to a liquid inlet (200) for the continuous flushing of the functional chamber (81) and / or the functional line (3) with liquid. Furthermore, the invention relates to a method for the continuous rinsing of such an electrochemical system.

Description

[0001] The present invention relates to an electrochemical system. Furthermore, the invention relates to a method for permanently flushing such an electrochemical system. State of the art

[0002] Devices for generating hydrogen, for example, by electrolysis of liquid, are known from the prior art. An electrolytic cell is used for this purpose, which has an anode compartment and a cathode compartment. The anode compartment is filled with liquid or an aqueous solution, for example, an electrolyte. The anode compartment and the cathode compartment are separated from each other by a membrane, which is provided with electrodes on both sides. The side facing the anode compartment has an anode electrode, and the side facing the cathode compartment has a cathode electrode.

[0003] If a direct current is applied between the anode and cathode electrodes, a catalytic splitting of the liquid occurs on the anode side. In the example of PEM electrolysis, the protons, H + -ions pass through the membrane to the cathode side and react there with electrons to form hydrogen.

[0004] Such electrolytic cells, which work with a so-called proton exchange membrane (PEM), are known, for example, from DE 10 2014 217 462 A1.

[0005] A stack of such electrolytic cells is also referred to as a cell stack. An electrolysis system comprises at least one stack, which contains at least one electrolytic cell.

[0006] Electrolyzers have a semipermeable membrane that is conductive to certain ions but electrically non-conductive. In PEM electrolyzers, the membrane is permeable to protons, whereas other types of electrolysis exist in which the membrane is permeable to anions, for example, the so-called AEM electrolyzers (anion exchange membrane electrolyzers).

[0007] However, a semipermeable membrane also exhibits a certain permeability to other substances, particularly hydrogen molecules (H2). If these enter the anode compartment, for example, after the electrolytic cell has been shut down, a mixture of oxygen and hydrogen forms there. Depending on the mixture, this can become explosive. This back diffusion occurs particularly frequently during differential pressure operation. Therefore, after the electrolytic cell has been shut down, the cathode compartment is purged with, for example, a chemically inert gas to flush the hydrogen out of the cathode compartment.

[0008] However, purging with chemically inert gas leads to foreign contamination of the product gas and thus reduces the hydrogen yield of the entire electrolysis plant. Advantages of the invention

[0009] In contrast, the electrochemical system according to the invention has the advantage that by flushing with a liquid which is already present in the electrochemical system, a higher purity of the hydrogen produced and an effective discharge of hydrogen is achieved.

[0010] For this purpose, the electrochemical system comprises a stack, which stack has at least one functional chamber connected to a functional path. Furthermore, the electrochemical system comprises a flushing line that can be fluidically connected to the functional chamber via the functional path. Furthermore, the flushing line can be connected to a liquid inlet for continuously flushing the functional chamber and / or the functional line with liquid.

[0011] In this way, the flexibility of the purging process and the safety of the entire electrochemical system can be increased in a simple manner. Furthermore, the use of liquid as the purging medium increases the purity of the hydrogen produced, since no foreign medium (e.g. nitrogen) is introduced during purging. In this way, effective removal of hydrogen from the electrochemical system can be achieved in a simple manner. Continuous purging ensures a safe condition in the stack, as well as in the functional line and the entire functional path, at all times. The solution according to the invention also makes it possible to purge at high pressure (i.e. at operating pressure), making pressure relief on the cathode side obsolete. This enables rapid start-up and reaching of the operating pressure, for example after a standby period, which in turn results in improved availability of the electrochemical system.Furthermore, the minimized pressure change reduces the mechanical stress on the membrane and thus increases the service life of the stack and thus of the entire electrochemical system.

[0012] In a first advantageous embodiment, a conveying device, preferably with a downstream filter, is arranged at the fluid inlet in the flushing line, through which the fluid for flushing the functional space can be fed. This allows the fluid to be easily conveyed into the functional path toward the functional space.

[0013] In an advantageous development, the liquid in the liquid inlet comprises a liquid that is already present in the electrochemical system. Advantageously, the liquid comprises DI water (deionized water).

[0014] In an advantageous development, the electrochemical system includes a heat exchanger and / or ion exchanger. This allows the membrane to be cooled, for example, via the anode circuit in addition to temperature control via the cathode circuit. By using the ion exchanger, a low water conductivity on the cathode side can be achieved.

[0015] In a further embodiment of the invention, it is advantageously provided that the electrochemical system is an electrolysis system, preferably a PEM electrolysis system or an AEM electrolysis system.

[0016] In a further embodiment of the invention, it is advantageously provided that the functional path comprises a cathode path of the electrolysis system, and the functional space comprises a cathode space of the stack. This allows the cathode path of the electrolysis system and the cathode space of the stack to be easily flushed with liquid.

[0017] In a further embodiment of the invention, it is advantageously provided that the functional path comprises an anode path of the electrolysis system, and the functional space comprises an anode space of the stack. Thus, the anode path of the electrolysis system and the anode space of the stack can be easily flushed with liquid.

[0018] In a further embodiment of the invention, it is advantageously provided that a first valve, a second valve, a third valve and a fourth valve are each electrically controllable and switchable in such a way that a permanent flushing of the functional space and / or the functional line with liquid is possible.

[0019] In an advantageous further development, it is provided that the functional path has a functional line which can be connected to the purge line by means of the first valve, wherein a check valve is arranged in the functional line which prevents the inflow of gas from the functional line into the purge line.

[0020] In a further embodiment of the invention, it is advantageously provided that the functional space of the stack has a first functional space outlet and a second functional space outlet, which first functional space outlet opens into the functional line at a first bypass node and which second functional space outlet opens into the functional line at a second bypass node. Advantageously, the functional line has a bypass channel between the first bypass node and the second bypass node, in which bypass channel the second valve is arranged.

[0021] In an advantageous further development, it is provided that the first bypass node and / or the second bypass node are designed as a Y-pipe section.

[0022] Furthermore, the invention relates to a method for permanently flushing such an electrochemical system, comprising the following steps: a. Holding the first valve, the second valve and the fourth valve in an open position and holding the third valve in a closed position; b. Continuous introduction of fluid from the flushing line into the functional line, which fluid flows via the second valve towards the second fluid outlet channel.

[0023] In this way, the liquid continuously flushes the gas from the functional line and the functional chamber. This not only increases the efficiency and purity of hydrogen production, but also prevents, for example, the diffusion of hydrogen from the cathode chamber through the membrane into the anode chamber. This also prevents the diffused hydrogen from reacting with the oxygen in the anode chamber to form a potentially explosive gas mixture.

[0024] The ability to continuously flush at different pressure levels, particularly at high pressure, increases the safety of the electrochemical system and increases the flexibility of the liquid flushing process. Furthermore, when flushing at high pressure, which corresponds to the operating pressure when flushing the cathode path, the pressure in the cathode chamber does not necessarily have to be reduced, allowing for faster startup and reaching of the operating pressure after a standby or shutdown of the electrochemical system. Furthermore, the mechanical stress on the membrane caused by pressure changes is reduced. Furthermore, during a standby of the electrochemical system, for example, the continued operation of the pumping system for a predefined period of time ensures that hydrogen is continuously and safely transported out of the electrochemical system. This also directly renders the electrochemical system inert for restart.Ultimately, this leads to improved availability and safety of the entire electrochemical system. Short description of the drawing

[0025] The invention is described in more detail below with reference to the drawing.

[0026] It shows: Fig. 1 a possible embodiment of an electrochemical system according to the invention in a schematic view, Fig. 2 shows a further possible embodiment of an electrochemical system according to the invention in a schematic view. Description of the embodiments

[0027] Fig. Figure 1 shows a schematic view of a possible embodiment of an electrochemical system 1 according to the invention. The electrochemical system 1 comprises a stack 10 with a functional space 81. The functional space 81 is connected to a functional path 80. The stack 10 comprises at least one electrochemical cell, whereby a stack of several electrochemical cells is typically referred to as a stack. Furthermore, the stack 10 can be, for example, a PEM stack or an AEM stack. In this embodiment, it is a PEM stack.

[0028] The stack 10 has an anode compartment 102 and a cathode compartment 101, which are separated from each other by a semipermeable membrane 103. The membrane 103 is provided with an anode electrode 106 on the anode side and a cathode electrode 105 on the cathode side.

[0029] The functional path 80 is designed, for example, as a cathode path 300 or anode path 1020.

[0030] 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.

[0031] 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.

[0032] The functional path 80, here cathode path 300, has a functional line 3, which can be connected to a flushing line 2 by means of a first valve 23. The flushing line 2 is connected to a liquid inlet 200. Furthermore, a conveying device 21, e.g., designed as a pump, and a downstream filter 22 are arranged in the flushing line 2, through which liquid for flushing the functional space 81 can be fed into the functional line 3. The liquid inlet 200 is fluidly connected, preferably under pressure, to a liquid reservoir 20, wherein the liquid in the liquid reservoir 20 is deionized liquid.

[0033] In the functional line 3 there is also a check valve 24 which prevents the flow of gas from the functional line 3 into the purge line 2.

[0034] The functional chamber 81 of the stack 10 has a first functional chamber outlet 7 and a second functional chamber outlet 8. The first functional chamber outlet 7 opens into the functional line 3 at a first bypass node 82, and the second functional chamber outlet 8 opens into the functional line 3 at a second bypass node 83.

[0035] Between the first bypass node 82 and the second bypass node 83, the functional line 3 has a bypass line 3a in which a second valve 25 is arranged.

[0036] Furthermore, the functional line 3 has a third bypass node 300 downstream, which opens into a first liquid outlet channel 5 for low pressure and a second liquid outlet channel 6 for high pressure. The high pressure is assumed here to be the operating pressure of the stack 10, which, for example, covers a range from 0.5 bar to 100 bar. A pressure close to atmospheric pressure is assumed to be the pressure level of the anode chamber 102, i.e., low pressure corresponds to a pressure relief of the cathode chamber 101.

[0037] A third valve 27 is arranged in the first fluid outlet channel 5 for opening and closing a connection between the functional line 3 and the first fluid outlet channel 5. The first fluid outlet channel 5 also opens into a drain 30.

[0038] A fourth valve 26 is arranged in the second liquid outlet channel 6 for opening and closing a connection between the functional line 3 and the second liquid outlet channel 6. The second liquid outlet channel 6 leads downstream to a gas-liquid separator 54.

[0039] The first valve 23, the second valve 25, the third valve 27 and the fourth valve 26 are each electrically controllable and switchable in such a way that a permanent flushing of the functional space 81 and / or the functional line 3 with liquid is possible.

[0040] Furthermore, Fig. 1 shows an electrochemical system module 100 with a number n of stacks 10, 10', 10'' of the electrochemical system 1 described above. These are hydraulically connected in parallel, so that for an electrochemical system module 100, liquid is conveyed via the flushing line 2 by means of this one conveying device 21 arranged in the flushing line 2 into the functional space 81 of the n stacks 10, 10', 10'', and these are flushed. In this case, a control valve (not shown here) can advantageously be arranged at each inlet of the n stacks 10, 10', 10'' in order to ensure a uniform liquid volume flow to the n stacks 10, 10', 10'' in the electrochemical system module 100.

[0041] In an alternative design, one conveyor device 21 per stack 10, 10', 10'' is also possible.

[0042] In the operating case, that is, when the electrochemical system 1 is in operation and hydrogen is produced, the first valve 23, the second valve 25 and the fourth valve 26 are kept in an open position and the third valve 27 is kept in a closed position. The check valve 24 ensures, during the production of hydrogen, a backflow into the purge line 2 and in the direction of the liquid inlet 200 as well as in the direction of the parallel-connected stacks 10, 10', 10'' of the electrolysis system module 100. Thus, produced 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 via the open fourth valve 26 into the second liquid outlet channel 6 in the direction of the gas-liquid separator 54. The gas-liquid separator 54 typically separates the produced hydrogen from entrained DI water.At the same time, the functional path 80 is continuously flushed with liquid from the liquid inlet 200 to ensure the removal of gases, particularly hydrogen or oxygen. This is also referred to as liquid-based inerting or flushing. The liquid in the liquid inlet 200 comprises a liquid that is already present in the electrochemical system. In this embodiment, it is a PEM electrolysis system, so the liquid comprises DI water.

[0043] In alternative designs, for example in an AEM electrolysis system, KOH lye or a liquid alkaline electrolyte solution or any dilution of the electrolyte solution is used as the liquid.

[0044] By means of the conveying device 21, the liquid flows from the liquid reservoir 20, preferably under pressure, toward the functional line 3 of the n stacks 10, 10', 10''. Via the bypass line 3a, the liquid flows through the fourth valve 26 into the second liquid outlet channel 6 toward the gas-liquid separator 54.

[0045] As the liquid flows past the first functional space outlet 7 and the second functional space outlet 8 of the stack 10 or the stacks 10', 10'', the hydrogen is discharged from the functional space 81 by negative pressure and directed towards the gas-liquid separator 54.

[0046] In the case of standby or shutdown of the electrochemical system 1, i.e. when no hydrogen is being produced, the second valve 25 can be closed so that the flushed liquid no longer flows via the bypass line 3a, but via the first functional space outlet 7 into the functional space 81 of the stack 10 or the stacks 10', 10'' and via the second functional space outlet 8 back into the functional line 3 in the direction of the second liquid outlet channel 6 and thus in the direction of the gas-liquid separator 54. Thus, when the conveyor device 21 continues to operate and the electrochemical system 1 is continuously flushed, the functional space 81 can also be actively flowed through.

[0047] Fig. Figure 2 shows a further possible embodiment of an electrochemical system 1 according to the invention in a schematic view. It essentially corresponds in function and structure to the embodiment from Fig. 1. It differs in that the first bypass node 82 and the second bypass node 83 are designed as Y-shaped pipe sections in this embodiment. This arrangement creates a suction effect as the liquid flows past the bypass line 3a, so that the produced hydrogen and, if applicable, the liquid used for flushing are sucked out of the functional chamber 81 and the first functional chamber outlet 7 and the second functional chamber outlet 8 and directed toward the gas-liquid separator 54.

[0048] In an alternative embodiment, it is possible for only the first bypass node 82 or the second bypass node 83 to be designed as a Y-shaped pipe section. For example, when the electrochemical system 1 is not in operation and the second valve 25 is closed, the fluid can be directed into the functional chamber 81 via the first bypass node 82 and the first fluid chamber outlet 7 and out again via the second fluid chamber outlet 8 and the second bypass node 83. If the second bypass node 83 is designed as a Y-shaped pipe section, a better flow can be achieved.

[0049] In this embodiment, the hydrogen can be easily flushed through the liquid from the functional chamber 81, the cathode chamber 101, and separated from the liquid again by the gas-liquid separator 54. This increases the efficiency of hydrogen production and minimizes the possibility of hydrogen diffusing from the cathode chamber 101 into the anode chamber 102 via the membrane 103, where this, in combination with the oxygen, leads to an oxyhydrogen reaction.

[0050] In an alternative embodiment, the liquid does not flush the hydrogen from the functional space 81, cathode space 101, but rather the oxygen from the anode space 102.

[0051] In an alternative embodiment, the bypass line 3a and the second valve 25 are omitted, so that a permanent flushing takes place via the first liquid space outlet and the second liquid space outlet 8.

[0052] In an alternative embodiment, flushing at low pressure is also possible, in which case the liquid flushed through the electrochemical system 1 is drained via the third valve 27 into the first liquid outlet channel 5 in the direction of the drain 30.

[0053] In alternative embodiments, a heat exchanger 500 and / or an ion exchanger 500' may be arranged in the electrochemical system 1. The heat exchanger 500 and / or the ion exchanger 500' are arranged between the gas-liquid separator 54 and the liquid reservoir 20, as shown in Fig. 1 is shown with a dashed line. This allows the membrane of stack 10 to be additionally cooled and the conductivity of the DI water in electrochemical system 1 to be kept consistently low. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 217 462 A1

[0004]

Claims

[1] Electrochemical system (1) with a stack (10), which stack (10) has at least one functional space (81), which functional space (81) is connected to a functional path (80), and with a flushing line (2), which flushing line (2) is fluidically connectable to the functional space (81) by means of the functional path (80), characterized by that the flushing line (2) can be connected to a liquid inlet (200) for permanently flushing the functional space (81) and / or the functional line (3) with liquid. [2] Electrochemical system (1) according to claim 1, characterized by that a conveying device (21), preferably with a downstream filter (22), is arranged at the liquid inlet (200) in the flushing line (2), through which conveying device (21) the liquid for permanently flushing the functional space (81) and / or the functional line (3) can be fed. [3] Electrochemical system (1) according to claim 1 or 2, characterized bythat the liquid in the liquid inlet (200) comprises a liquid which is already present in the electrochemical system (1). [4] Electrochemical system (1) according to the preceding claim, characterized by that the liquid includes DI water (deionized water). [5] Electrochemical system (1) according to one of the preceding claims, characterized by that the electrochemical system (1) comprises a heat exchanger (500) and / or ion exchanger (500'). [6] Electrochemical system (1) according to one of the preceding claims, characterized by that the electrochemical system (1) is an electrolysis system, preferably a PEM electrolysis system or an AEM electrolysis system. [7] Electrochemical system (1) according to the preceding claim, characterized by that the functional path (80) comprises a cathode path (300) of the electrolysis system and the functional space (81) comprises a cathode space (101) of the stack (10). [8] Electrochemical system (1) according to claim 6, characterized by that the functional path (80) comprises an anode path (1020) of the electrolysis system and the functional space (81) comprises an anode space (102) of the stack (10). [9] Electrochemical system (1) according to one of the preceding claims, characterized by that a first valve (23), a second valve (25), a third valve (27) and a fourth valve (26) are each electrically controllable and switchable in such a way that a permanent flushing of the functional space (81) and / or the functional line (3) with liquid is possible. [10] Electrochemical system (1) according to the preceding claim, characterized by in that the functional path (80) has a functional line (3) which can be connected to the purge line (2) by means of the first valve (23), wherein a check valve (24) is arranged in the functional line (3) which prevents the inflow of gas from the functional line (3) into the purge line (2). [11] Electrochemical system (1) according to claim 9, characterized by that the functional space (81) of the stack (10) has a first functional space outlet (7) and a second functional space outlet (8), which first functional space outlet (7) opens into the functional line (3) at a first bypass node (82) and which second functional space outlet (8) opens into the functional line (3) at a second bypass node (83). [12] Electrochemical system (1) according to the preceding claim, characterized by that the functional line (3) has a bypass channel (3a) between the first bypass node (82) and the second bypass node (83), in which bypass channel (3a) the second valve (25) is arranged. [13] Electrochemical system (1) according to claim 11 or 12, characterized by that the first bypass node (82) and / or the second bypass node (83) are designed as a Y-pipe section. [14] Method for permanently flushing an electrochemical system (1) according to one of claims 1 to 13, comprising the following steps: a. Holding the first valve (23), the second valve (25) and the fourth valve (26) in an open position and holding the third valve (27) in a closed position; b. Continuous introduction of liquid from the flushing line (2) into the functional line (3), which liquid flows via the second valve (25) in the direction of the second liquid outlet channel (6).

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