Gas detection device for an electrolyzer, test bench device and method for operating the test bench device

Abstract

The invention relates to a gas detection device (10) for an electrolyzer (1), having a supply line (41) for supplying gas to a gas analysis device (50), wherein the gas can be supplied into the supply line (41) via a separator (14, 22) connectable to a cathode side (5) or anode side (4) of the electrolyzer (1), wherein the pressure of the gas prevailing in the supply line (41) can be adjusted between an atmospheric pressure and a pressure higher than atmospheric pressure via a pressure reducer (30, 32) which is operatively connected to the supply line (41) and arranged in an outlet line (26, 28).

Description

Technical area

[0001] The invention relates to a gas detection device for an electrolyzer, which, particularly in connection with the use of the gas detection device in a test bench, enables the detection of leakage gases occurring due to damage to a membrane of the electrolyzer at different operating pressures. Furthermore, the invention relates to a test bench device with an electrolyzer designed according to the invention and a method for operating the test bench device. State of the art

[0002] Test bench facilities are used, among other things, to examine electrolyzers used to generate hydrogen and oxygen for damage to the membranes within the electrolyzer. Such membranes, which are often Nafion® membranes made of perfluorinated copolymer with sulfonic acid groups, are characterized by the fact that they are not diffusion-tight. Various mechanisms can lead to damage to the relatively thin membrane and thus to the formation of so-called pinholes. These pinholes connect the reaction sides of the electrolyzer, which are normally hydraulically separated by the membrane, and can lead to gas transfer through the membrane. For this reason, gas detectors are installed behind separators on both the anode and cathode sides of electrolyzers in order to shut down the system before critical conditions are reached.However, such gas detectors available on the market can only operate under atmospheric conditions. Therefore, the pressure on the anode or cathode in the gas phase is reduced via a bypass, using a pressure reducer, and then fed to the gas detector. This has the disadvantage that gas monitoring is only effective when the electrolyzer is operating at overpressure. In addition, so-called sample gas pumps are known, which also operate under atmospheric conditions but are only suitable for pressureless operation. Disclosure of the invention

[0003] Particularly in the context of a test bench facility for testing new electrolyzers or prototypes, it is necessary that the test bench facility be suitable for testing electrolyzers under various possible operating conditions, i.e., not only under overpressure operation, but also under atmospheric conditions. In the latter operating condition, however, gas monitoring would not be effective, as the gas flow would not be able to pass through the conventional gas warning or gas analysis device. Furthermore, gas analysis is only effective once a sufficient pressure has built up in the separators, through which the gas is fed to the gas analysis device. This may take several minutes. During this period, the test bench facility would be without adequate explosion protection monitoring.

[0004] In light of the above explanations, a gas detection device for an electrolyzer according to the invention has the advantage that the gas analyzer used to detect (harmful) gases can be operated both under atmospheric conditions and under overpressure conditions. This enables safe operation across all conceivable test scenarios and pressures.

[0005] The gas detection device according to the invention for an electrolyzer with the features of claim 1 has a supply line for supplying gas to a gas analyzer. The gas can be supplied to the supply line via a separator connectable to a cathode side or anode side of the electrolyzer, wherein the gas pressure prevailing in the supply line can be adjusted between atmospheric pressure and a pressure higher than atmospheric pressure via a pressure reducer operatively connected to the supply line and arranged in an outlet line. Furthermore, the pressure of the gas to which the gas analyzer is subjected can be adjusted to an operating pressure of the gas analyzer at least approximately constant by means of a pressure adjustment device arranged in the supply line.

[0006] Such an inventive design of the gas detection device makes it possible to operate the gas analyzer, for example, at a typical operating pressure of a few hundred millibars, independent of the pressure prevailing in the supply line upstream of the pressure adjustment device, which on the cathode side can range from atmospheric pressure to, for example, up to 40 or 50 bar. On the anode side, in contrast, the gas pressure is between atmospheric pressure and typically up to 5 bar.

[0007] Advantageous further developments of the gas detection device according to the invention for an electrolyzer are listed in the subclaims.

[0008] In a preferred design embodiment of the pressure adjustment device, it has an absolute pressure reducer which is coupled on the inlet side to the side of the supply line facing the electrolyzer and which is coupled on the outlet side to a vacuum pump, the pressure side of which is in turn connected to the gas analysis device.

[0009] In the event that the desired or required operating pressure of the gas analyzer is already present in the flow direction downstream of the absolute pressure reducer due to the operating mode of the electrolyzer, it can also be provided that the vacuum pump is equipped with a bypass that can be activated at a pressure in the supply line corresponding to the operating pressure of the gas analyzer in order to connect the absolute pressure reducer (bypassing the vacuum pump) directly to the gas analyzer.

[0010] In order to prevent a negative pressure from being created in the separator due to the operation of the gas detection device, it is further provided that an output line of the gas analysis device can be connected to the separator via a first check valve with a return line.

[0011] In a preferred development of the last proposal, the outlet line is connected to the outlet line via a second check valve arranged in parallel with the first check valve, which opens into the outlet line downstream of the absolute pressure reducer in the direction of gas flow. In particular, the opening pressure of the first check valve is lower than the opening pressure of the second check valve.

[0012] The vacuum pump can be designed as a diaphragm pump. This has the advantage that the gas is shielded from the remaining components of the diaphragm pump.

[0013] In a preferred design, the vacuum pump is configured as a continuously operating pump in which the medium to be pumped, in this case the gas, is continuously moved. In particular, the continuously operating pump can be configured as a jet pump, preferably as a gas injector pump. The pumping action is generated by a propellant gas, which draws in the medium to be pumped—here the gas—through a momentum exchange. The propellant gas is stored in a propellant gas supply tank, which is connected to the gas injector pump by a propellant gas line. In addition to supplying the vacuum pump, the propellant gas in the propellant gas supply tank can also be used for other purposes.

[0014] A pressure regulator can be provided in the propellant gas line, which is designed to regulate the pressure of the propellant gas and thus adjust the delivery rate of the vacuum pump. The pressure regulator can be provided in addition to the absolute pressure reducer. An inert gas, in particular nitrogen, is preferably provided as the propellant gas. As a propellant gas, nitrogen has the advantage over air that the formation of an explosive gas mixture is avoided, which can be formed in particular on the cathode side through contact of the propellant gas with hydrogen formed at the cathode. In particular, a propellant gas valve is provided in the propellant gas line, which in a predefined position prevents the supply of the propellant gas, with the result that the vacuum pump is switched into a non-functional state. Additionally or alternatively, a propellant gas check valve can be provided in the propellant gas line, which prevents, for example,Hydrogen or an explosive gas mixture flows into the propellant gas supply container.

[0015] The vacuum pump designed in this way can be operated continuously, ensuring constant delivery conditions within the gas analyzer without any pulsation. Furthermore, such a vacuum pump is inexpensive, compact, and can be easily integrated into the gas analyzer, for example, via a compression fitting. Unlike diaphragm pumps, where the delivery diaphragm and seals must be replaced regularly, the vacuum pump designed as a gas injector pump is also largely wear-free and maintenance-free. The gas injector pump is a purely mechanical device with no moving components. Documentation or testing, which might otherwise be necessary to comply with any operational safety guidelines, are not required for its operation, making its use particularly simple and cost-effective.

[0016] Furthermore, the invention comprises a test bench device for an electrolyzer which is provided with a gas detection device designed according to the invention as described so far.

[0017] It is particularly preferred for such a test bench device to have two gas detection devices, with a first gas detection device connected to an anode side of the electrolyzer and a second gas detection device connected to a cathode side of the electrolyzer. In particular, the first gas detection device is designed to detect hydrogen, and the second gas detection device is designed to detect oxygen.

[0018] Finally, the invention also encompasses a method for operating such a test bench device, wherein the method is characterized in that the electrolyzer is operated in such a way that different gas pressures prevail in the supply line during operation of the electrolyzer. This allows all possible operating states of the electrolyzer to be checked or tested.

[0019] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. Short description of the description of the drawings Fig. 1 shows a schematic representation of a test bench device for monitoring an electrolyzer to detect damage to a membrane of the electrolyzer and Fig. 2 a detail of the Fig. 1 of the test bench facility in the area of ​​a gas detection device with, if provided, a bypass in the area of ​​a vacuum pump, also in schematic representation. Embodiments of the invention

[0020] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0021] In the Fig. Figure 1 shows a highly simplified test bench device 100 for testing or checking an electrolyzer 1. The test bench device 100 can be used, for example, to test prototypes of electrolyzers 1 with regard to their functionality, or to test electrolyzers 1 in series production as part of quality control.

[0022] The electrolyzer 1 has, in a known manner, a membrane 2 in the form of a proton-permeable polymer membrane (PEM). The membrane 2 serves to split the distilled water in the electrolyzer 1 into hydrogen and oxygen using electrical current. For this purpose, the membrane 2 is coated on the cathode side with a porous electrode made of carbon-supported platinum, and on the anode side with metallic or oxide noble metals. An external electrical voltage is applied to these electrodes (not shown). Water is supplied to the anode side 4 of the electrolyzer 1; it is also conceivable to supply water to the cathode side 5 as well, depending on the intended use and as is known per se. The catalytic effect of the noble metal electrode on the anode side leads to the decomposition of the water. This produces hydrogen, free electrodes, and positively charged hydrogen ions.The hydrogen ions diffuse through the proton-conducting membrane 2 to the cathode side, where they combine with the electrons to form hydrogen. The functioning of the (PEM) electrolyzer 1 described so far is well known.

[0023] In order to check, among other things, the condition of the membrane 2 for any damage (so-called "pinholes"), the electrolyzer 1 is operated on the test bench device 100. The anode side 4 of the electrolyzer 1 to be tested is connected via a first line 12 to a separator 14, which serves in a known manner to separate the oxygen formed on the anode side 4 from the (distilled) water. The separator 14 is connected to the electrolyzer 1 via a return line 16 with a feed pump 18 arranged therein in order to feed the water 1 back to the electrolyzer 1.

[0024] The cathode side 5 is also connected to a separator 22 for generating hydrogen via a second line 20. The water formed in the separator 22 is discharged via an outlet 24 in the exemplary embodiment.

[0025] The gases (oxygen and hydrogen) obtained in the two separators 14, 22 are each discharged via an outlet line 26, 28 with an interposed pressure reducer 30, 32, for example, into a storage tank 34, 36. The pressure reducers 30, 32 serve to adjust the pressure in the outlet lines 26, 28. Depending on the setting on the cathode side 5 (hydrogen), this pressure in the outlet line 28 can typically be between 40 bar and 50 bar, or, with the pressure reducer 32 open, atmospheric pressure. In contrast, the oxygen pressure prevailing in the outlet line 26 is typically (depending on the position of the pressure reducer 30) between atmospheric pressure and approximately 5 bar.

[0026] An (identically designed) gas detection device 10 is arranged in each bypass of the outlet line 26, 28. The gas detection device 10 has a supply line 41 branching off from the respective outlet line 26, 28. With the interposition of a gas drying device 42, the gas is then fed to an absolute pressure reducer 44. By means of the absolute pressure reducer 44, which is part of a pressure adjustment device 45, the pressure of the gas (hydrogen or oxygen) prevailing in the supply line 41 on the outlet side of the absolute pressure reducer 44 can be adjusted to an operating pressure of less than 1 bar absolute, typically, for example, 0.95 bar. For this purpose, a vacuum pump 46 is provided downstream of the absolute pressure reducer 44 in the direction of gas flow, which builds up a slight negative pressure downstream of the absolute pressure reducer 44.The vacuum pump 46 compresses the gas again slightly above atmospheric pressure and feeds it to a gas analyzer 50.

[0027] The gas analyzer 50 is designed to be subjected to a specific (relatively low) overpressure, for example, an overpressure of a few hundred millibars as the operating pressure, in order to detect any oxygen that may have formed on the cathode side 5 (in the event of damage to the membrane 2). In contrast, the gas analyzer 50 arranged on the anode side 4 serves to detect any hydrogen that may have formed on the anode side 4 in the event of damage to the membrane 2.

[0028] The two gas analysis devices 50 are each at least indirectly connected to a warning or control device (not shown) of the test bench device 100 in order to, for example, stop the operation of the electrolyzer 1 or to output corresponding information to an operator when leaks in the membrane 2 are detected.

[0029] Depending on the pressure of the gas in the supply line 41 on the inlet side of the absolute pressure reducer 44, it may also happen that a (slight) overpressure already exists on the outlet side of the absolute pressure reducer 44, which allows immediate operation of the respective gas analysis device 50, bypassing the respective vacuum pump 46. In this case, it may be possible according to the Fig.2, it can be provided that a bypass 52 is arranged in the respective supply line 41, which bypass supplies the gas directly (i.e. bypassing the vacuum pump 46) to the gas analysis device 50 via a 2-way valve 54 at a corresponding pressure in the supply line 41.

[0030] The output side of the respective gas analyzer 50 is connected to an output line 56, in which a first check valve 58 and a second check valve 60 are arranged in parallel. The first check valve 58 is connected to the respective separator 14, 22 via a return line 62. The second check valve 60, in contrast, leads to the respective outlet line 26, 28 and opens into an area downstream of the respective pressure reducer 30, 32. The first check valve 58 opens at a pressure that is lower than the opening pressure of the second check valve 60. The respective first check valves 58 serve to prevent a negative pressure in the respective separator 14, 22 by recirculating the gas escaping from the gas analyzer 50 via the output line 56 to the respective separator 14, 22.

[0031] During operation or testing of the electrolyzer 1, a different pressure can prevail in the outlet line 26, 28 for testing possible operating states, depending on the setting of the respective pressure reducer 30, 32. The pressure can be changed or adjusted using test programs or manually over the test time. However, the gas analyzer 50 can always be operated regardless of the pressure currently prevailing in the outlet line 26, 28 and thus also in the supply line 41 to the respective gas analyzer 50.

[0032] The gas detection device 10 or test bench device 100 described so far can be modified or altered in many different ways without deviating from the inventive concept.

Claims

[1] Gas detection device (10) for an electrolyzer (1), comprising a supply line (41) for supplying gas to a gas analysis device (50), wherein the gas can be supplied into the supply line (41) via a separator (14, 22) connectable to a cathode side (5) or anode side (4) of the electrolyzer (1), wherein the pressure of the gas prevailing in the supply line (41) can be adjusted between an atmospheric pressure and a pressure higher than atmospheric pressure via a pressure reducer (30, 32) operatively connected to the supply line (41) and arranged in an outlet line (26, 28), and wherein the pressure of the gas with which the gas analysis device (50) is acted upon can be kept at least approximately constant at an operating pressure of the gas analysis device (50) by means of a pressure adjustment device (45) arranged in the supply line (41). is adjustable. [2] Gas detection device according to claim 1, characterized bythat the pressure adjustment device (45) comprises an absolute pressure reducer (44) which is connected on the inlet side to the side of the feed line (41) facing the electrolyzer (1) and on the outlet side to a vacuum pump (46), the pressure side of which is connected to the gas analysis device (50). [3] Gas detection device according to claim 2, characterized by that in the area of ​​the vacuum pump (46) a bypass (52) is provided which can be activated at a pressure in the supply line (41) corresponding to the operating pressure of the gas analysis device (50) in order to connect the absolute pressure reducer (44) directly to the gas analysis device (50). [4] Gas detection device according to one of claims 1 to 3, characterized by that an output line (56) of the gas analysis device (50) can be connected to the separator (14, 22) via a first check valve (58) and a return line (62). [5] Gas detection device according to claim 4, characterized bythat the output line (56) is connected to the outlet line (26, 28) via a second check valve (60) arranged in parallel with the first check valve (58), which second check valve opens into the outlet line (26, 28) downstream of the pressure reducer (30, 32) in the flow direction of the gas. [6] Gas detection device according to claim 5, characterized by that the opening pressure of the first check valve (58) is lower than the opening pressure of the second check valve (60). [7] Gas detection device according to one of the preceding claims, characterized by that the vacuum pump (46) is designed as a continuously operating pump, in particular as a gas injector pump. [8] Test bench device (100) for an electrolyzer (1), comprising at least one gas detection device (10) designed according to one of claims 1 to 7. [9] Test bench device according to claim 8, characterized bythat two gas detection devices (10) are present, wherein a first gas detection device (10) is connected to an anode side (4) of the electrolyzer (1) and a second gas detection device (10) is connected to a cathode side (5) of the electrolyzer (1). [10] Test bench device according to claim 9, characterized by that the first gas detection device (10) is designed to detect hydrogen, and the second gas detection device (10) is designed to detect oxygen. [11] Method for operating a test bench device (100) which is designed according to one of claims 8 to 10, characterized by that the electrolyser (1) is operated in such a way that during operation of the electrolyser (1) in the supply line (41) different pressures of the gas prevail in succession.

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