Apparatus and method for water separation and pressure control for an electrolyzer or a fuel cell

Abstract

A device (20) for water separation and pressure control for an electrolyzer or a fuel cell, the device comprising: a gas inlet (22) for supplying gas into an interior space (24) of the device (20), a gas outlet (26) for discharging gas from the interior space (24) of the device (20), a reservoir (24) for receiving water separated from the supplied gas, a valve (30) for adjusting a gas pressure in the interior space (24), and a drain valve (32) for discharging water from the reservoir (28), the drain valve (32) being a switchable solenoid valve (32), a device (40) for monitoring a position of a piston (36) of the solenoid valve (32) and / or for monitoring an electrical characteristic of a coil (42) of the solenoid valve (32) in order to detect a change from discharged water to discharged gas during drainage.

Description

[0001] The present invention relates to a device for water separation and pressure control for an electrolyzer or a fuel cell, wherein the device comprises: a gas inlet for supplying gas into an interior of the device, a gas outlet for discharging gas from the interior of the device, a reservoir for receiving water separated from the supplied gas, a valve for adjusting a gas pressure in the interior, and a drainage valve for discharging water from the reservoir, wherein the drainage valve is a switchable solenoid valve. Furthermore, the invention relates to a method for draining a gas line of an electrolyzer or a fuel cell using such a device. In addition, the invention relates to a fuel cell and an electrolyzer using such a device.

[0002] Electrolyzers are primarily used to split water into its components, hydrogen and oxygen. The resulting gaseous hydrogen still contains residual water, e.g., up to 2500 ppm, which should be removed, if possible, before the hydrogen is stored. Furthermore, the hydrogen pressure should be adjusted to a defined value. Both of these requirements are achieved with the water separation and pressure control device mentioned above.

[0003] Such a device often includes a pressure relief valve near the gas outlet and a drain valve separate from the pressure relief valve. Such a device also often includes a level sensor to monitor the amount of water in the reservoir.

[0004] The present invention is based on the technical problem of providing an improved device and an improved method for water separation and pressure control for an electrolyzer or a fuel cell. Furthermore, a fuel cell and an electrolyzer comprising such a device are to be provided.

[0005] According to a first aspect, the invention relates to a device for water separation and pressure control for an electrolyzer or a fuel cell, the device comprising: a gas inlet for supplying gas into an interior of the device, a gas outlet for discharging gas from the interior of the device, a reservoir for receiving water separated from the supplied gas, a valve for adjusting a gas pressure in the interior, and a drainage valve for discharging water from the reservoir, wherein the drainage valve is a switchable solenoid valve. The device is characterized by a device for monitoring a position of a piston of the solenoid valve and / or for monitoring an electrical characteristic of a coil of the solenoid valve in order to detect a change from discharged water to discharged gas during drainage.

[0006] The applicant has recognized that when the reservoir is emptied, a measurable pressure change is generated at the solenoid valve when gas escapes through the solenoid valve after the water has been separated. This is because, during the transition from water separation to gas separation, a sudden pressure change and a concomitant piston movement occur, since atmospheric pressure now partially acts on the piston of the solenoid valve instead of the static water pressure. The solenoid valve can therefore be used to detect whether the water has been drained from the reservoir.

[0007] It can be provided that a drainage opening of the reservoir, which is connected to the drainage valve, is assigned to a bottom of the reservoir in order to enable essentially complete drainage of separated water via the drainage valve. In particular, the drainage opening can be arranged in the bottom of the reservoir or spaced a few millimeters from the bottom of the reservoir. In a closed position, the piston of the solenoid valve closes the drainage opening of the reservoir. In an open position, the piston releases the drainage opening of the reservoir.

[0008] According to one embodiment of the device, it can be provided that no additional water level sensor or fill level sensor is assigned to the interior of the device. The emptying of the reservoir is thus monitored exclusively by means of the drainage valve. In this way, a separate water level sensor or fill level sensor, as is frequently used in the prior art, can be omitted. In particular, the device therefore does not have a separate, additional fill level sensor; instead, the water quantity in the reservoir is monitored solely by means of the solenoid valve.

[0009] It can be provided that the drainage valve is a pressure relief valve which opens automatically when a predetermined overpressure is reached.

[0010] In particular, the drainage valve can also form the pressure relief valve, so that the drainage function and the protection against overpressure are integrated in one component, namely the drainage valve. An additional, separate pressure relief valve can be eliminated. The device can thus be provided more cost-effectively and compactly.

[0011] The drainage valve can be held in a closed position by a resilient preload. In particular, a preload spring can define the specified overpressure. Thus, the overpressure function or overpressure protection can be achieved through a cost-effective mechanical design.

[0012] The “preset overpressure” defines the switching threshold of the pressure relief valve, i.e. the pressure that causes the pressure relief valve to open so that the preset overpressure in the interior of the device cannot be exceeded.

[0013] According to one embodiment of the device, no additional pressure relief valve is assigned to the interior. Protection against overpressure is therefore preferably achieved solely by the drainage valve.

[0014] The valve for adjusting the gas pressure in the interior can be a proportional valve. The valve for adjusting the gas pressure in the interior can be an electromagnetically controlled proportional valve. The valve for adjusting the gas pressure in the interior can be a medium-controlled proportional valve.

[0015] It can be provided that the valve is configured to set a gas pressure of 29 bar in the interior. According to further embodiments of the invention, it can be provided that the valve is configured to set a gas pressure of more than 29 bar in the interior, in particular of up to 35 bar in the interior, further in particular of up to 40 bar in the interior. In the aforementioned cases, the overpressure threshold of the drainage valve is selected to be correspondingly greater than the gas pressure set by the valve for adjusting the gas pressure in the interior.

[0016] The drain valve can be configured to open automatically at an overpressure of 40 bar. For example, the valve for adjusting the gas pressure in the interior can be configured to set a gas pressure of 29 bar in the interior, while the drain valve opens automatically at an overpressure of 40 bar.

[0017] In particular, it can be provided that an overpressure threshold of the drainage valve is more than 10 bar higher than the gas pressure set by the valve for adjusting the gas pressure in the interior. For the aforementioned examples of a set operating pressure of 35 bar, the overpressure threshold can be defined, for example, at 45 bar, 50 bar, or 55 bar, while for the example of a gas pressure of 40 bar set by the valve for adjusting the gas pressure in the interior, the overpressure threshold can be defined, for example, at 50 bar, 55 bar, or 60 bar.

[0018] The device may comprise a pressure sensor for measuring a pressure, in particular the gas pressure, in the interior.

[0019] The device may comprise a condensation device for liquefying gaseous water in the supplied gas through condensation. According to one embodiment of the device, a plate arrangement may be arranged in the interior space to liquefy gaseous water in the supplied gas through condensation on the plate arrangement. The condensation device may therefore comprise the plate arrangement.

[0020] According to a further aspect, the invention relates to a method for draining a gas line of an electrolyzer or a fuel cell, wherein the gas line has a device according to the invention, with the method steps: opening the solenoid valve, wherein the coil is supplied with electrical power in order to move the piston from a closed position to an open position; monitoring a position of the piston and / or an electrical characteristic of a coil of the solenoid valve; closing the solenoid valve if a change is detected for the position of the piston and / or the electrical characteristic, in particular a sudden change is detected.

[0021] It can be provided that the solenoid valve remains open for a predetermined period of time after the sudden change has been detected and is closed when the period of time has elapsed.

[0022] According to one embodiment of the method, it can be provided that the electrical characteristic is a current of the coil, wherein during dewatering the change from discharged water to discharged gas leads to a movement of the piston which induces a voltage in the coil, wherein a change in the current of the coil is measurable.

[0023] It can be provided that the electrical characteristic is a voltage of the coil, wherein during drainage the change from discharged water to discharged gas leads to a movement of the piston which induces a voltage in the coil, wherein a change in the voltage of the coil is measurable.

[0024] According to a further aspect, the invention relates to an electrolyzer which has a device according to the invention and / or is designed to carry out a method according to the invention.

[0025] In particular, the electrolyzer has a gas separator to separate hydrogen obtained during electrolysis from the circulating fluid (water or electrolyte).

[0026] The electrolyzer has a container for collecting the hydrogen produced, whereby a hydrogen purity of 99.9% can be achieved.

[0027] The device for water separation and pressure control according to the invention can be arranged between the gas separator and the container for collecting the hydrogen obtained in order to dry the hydrogen before it is stored in the container.

[0028] Similarly, a device for water separation and pressure control can be arranged between an oxygen-side gas separator and a container for storing the oxygen obtained.

[0029] The electrolyzer can be set up for alkaline electrolysis (AEL).

[0030] The electrolyzer can be set up as an alternative to proton exchange membrane electrolysis (PEM-EL).

[0031] The electrolyzer can be set up as an alternative to high-temperature electrolysis (HTEL) or solid oxide electrolyzer cell (SOEC).

[0032] According to a further aspect, the invention relates to a fuel cell which has a device according to the invention and / or is designed to carry out a method according to the invention.

[0033] The invention is described below with reference to drawings illustrating exemplary embodiments. They show schematically: Fig. 1 an electrolyzer according to the invention; Fig. 2 a device according to the invention; Fig. 3 a flow chart of a method according to the invention.

[0034] Fig. Figure 1 schematically shows an electrolyzer 2. The electrolyzer 2 is an electrolyzer for alkaline electrolysis. It is understood that the device according to the invention for water separation and pressure control, described in detail below, can also be used with the other electrolysis technologies described above, such as proton exchange membrane electrolysis or high-temperature electrolysis.

[0035] The electrolyzer 2 has an oxygen-side, anodic gas separator 4 and a hydrogen-side, cathodic gas separator 6. The electrolyzer 2 has a power source 8 connected to a cathode 10 and an anode 12 of the electrolyzer 2. A diaphragm 14 is arranged between the cathode 10 and the anode 12.

[0036] Diaphragm 14 is permeable to ions, allowing negatively charged hydroxide ions to move to anode 12. Diaphragm 14 is gas-tight and prevents the oxygen from mixing with the hydrogen. Cathode 10 and anode 12 are immersed in potassium hydroxide solution (KOH, H2O).

[0037] At the cathode 10, water absorbs electrons to form hydroxide ions and hydrogen. As already mentioned, the hydroxide ions, due to their negative charge, migrate through the diaphragm 14 to the anode 12, where they react to form oxygen and water by releasing electrons.

[0038] The hydrogen is fed via the cathodic gas separator 6 to a container 16 or tank 16 and stored there.

[0039] The oxygen is fed via the anodic gas separator 4 to a container 18 or tank 18 and stored there.

[0040] A device 20 according to the invention for water separation and pressure control is arranged between the container 16 and the cathodic gas separator 6. The device 20 is described below with reference to Fig. 2 described in more detail.

[0041] The water separation and pressure control device 20 has a gas inlet 22 for supplying gas, namely hydrogen (H2), containing up to 2500 ppm water, into an interior space 24 of the device 20.

[0042] The device 20 has a gas outlet 26 for removing hydrogen from the interior 24 of the device 20.

[0043] The device 20 has a reservoir 28 for receiving water separated from the supplied hydrogen and liquefied by condensation.

[0044] The device 20 has a valve 30 for adjusting a gas pressure in the interior space 24.

[0045] The device 20 has a drain valve 32 for draining liquid water from the reservoir 28, wherein the drain valve 32 is a switchable solenoid valve.

[0046] The drain valve 32 is also a pressure relief valve that opens automatically when a predetermined overpressure is reached. In this case, the predetermined overpressure is 40 bar.

[0047] The solenoid valve 32 is held in a closed position by a resilient preload, with a preload spring 34 defining the specified overpressure. Thus, the overpressure at which the solenoid valve 32 overcomes the spring preload and opens automatically can be defined by the dimensioning of the preload spring 34.

[0048] In this case, the spring force is set to 4 Newton, which is suitable for a valve opening area of ​​1 mm 2for the threshold pressure of 40 bar. The drainage valve 32 is therefore designed to open automatically for an overpressure of 40 bar. This means that if a force of more than 4 Newtons is exerted on a piston 36 of the solenoid valve 32, the preload spring 34 is compressed by a displacement of the piston 36 in the direction of the preload spring 34, the valve opening 38 closed by the piston 36 is released, and the water flows out of the reservoir 28.

[0049] The solenoid valve 32 is also controlled and opened at regular intervals by means of a controller 40, whereby a coil 42 moves the piston 36 in the direction of the biasing spring 34.

[0050] No further pressure relief valve is assigned to the interior 24.

[0051] The valve 30 is a proportional valve and is designed to set a gas pressure of 29 bar in the interior space 24.

[0052] The device 20 has a pressure sensor 44 for measuring a pressure in the interior space 24.

[0053] The device 20 has a plate arrangement 48 arranged in the interior space 24 in order to liquefy gaseous water of the supplied hydrogen on the plate arrangement 48 by condensation.

[0054] The supplied hydrogen can, for example, contain gaseous water contents of up to 2500 ppm (parts per million), whereas the discharged gas only contains water contents of 440 ppm due to the separation of the water.

[0055] The valve opening 38 may also be referred to as a drainage opening 38 of the reservoir 28, which is connected to the drainage valve 32e and is associated with a bottom 46 of the reservoir 28 to enable substantially complete drainage of separated water via the drainage valve 32.

[0056] As already explained, the drain valve 32 is a switchable solenoid valve.

[0057] The controller 40 is a device for monitoring an electrical characteristic of a coil 42 of the solenoid valve 32 in order to detect a change from discharged water to discharged gas during drainage.

[0058] According to the present example, the electrical characteristic is a current of the coil, wherein during dewatering the change from discharged water to discharged gas leads to a movement of the piston 36 which induces a voltage in the coil 42, wherein a change in the current of the coil 42 is measurable.

[0059] The method according to the invention is described below with reference to Fig. 3 described.

[0060] The method for dewatering the hydrogen-side gas line of the electrolyzer 2, wherein the gas line comprises the device 20 according to the invention, has the following method steps: (A) opening the solenoid valve 32, supplying electrical power to the coil 42 to move the piston 36 from the closed position to the open position, supplying a constant voltage to the coil 42; (B) monitoring the current of the coil 42 of the solenoid valve 32; (C) Closing the solenoid valve 32 if a change is detected for the current of the coil 42, in particular a sudden change is detected.

[0061] The solenoid valve is immediately closed after detecting the sudden change to prevent hydrogen from escaping. Reference symbol 2 electrolyzer 4 gas separators 6 gas separators 8 Power source 10 Cathode 12 Anode 14 Diaphragm 16 containers / tanks 18 containers / tanks 20 Device 22 Gas inlet 24 Interior 26 Gas outlet 28 Reservoir 30 valve 32 Drain valve 34 Preload spring 36 pistons 38 Valve opening 40 Control 42 coil 44 Pressure sensor 46 Floor 48 plate arrangement

Claims

[1] A device for water separation and pressure control for an electrolyzer or a fuel cell, the device comprising: - a gas inlet (22) for supplying gas into an interior (24) of the device (20), - a gas outlet (26) for discharging gas from the interior (24) of the device (20), - a reservoir (24) for receiving water separated from the supplied gas, - a valve (30) for adjusting a gas pressure in the interior (24) and - a drainage valve (32) for draining water from the reservoir (28), wherein the drainage valve (32) is a switchable solenoid valve (32), characterized by - a device (40) for monitoring a position of a piston (36) of the solenoid valve (32) and / or for monitoring an electrical characteristic of a coil (42) of the solenoid valve (32), - to detect a change from discharged water to discharged gas during drainage. [2] Device according to claim 1, characterized by that a drainage opening (38) of the reservoir (28), which is connected to the drainage valve (32), is associated with a bottom (46) of the reservoir (28) in order to enable a substantially complete discharge of separated water via the drainage valve (32). [3] Device according to one of the preceding claims, characterized by that no additional level sensor is assigned to the interior (24). [4] Device according to one of the preceding claims, characterized by that the drainage valve (32) is a pressure relief valve which opens automatically when a predetermined overpressure is reached. [5] Method for draining a gas line of an electrolyzer or a fuel cell, wherein the gas line comprises a device (20) according to one of the preceding claims, comprising the method steps: - opening the solenoid valve (32), wherein the coil (42) is supplied with electrical power to move the piston (36) from a closed position to an open position; - monitoring a position of the piston (36) and / or an electrical characteristic of a coil (42) of the solenoid valve (32); - closing the solenoid valve (32) if a change is detected in the position of the piston (36) and / or the electrical characteristic, in particular a sudden change is detected. [6] Method according to claim 5, characterized by that the solenoid valve (32) remains open for a predetermined period of time after the sudden change has been detected and is closed when the period of time has elapsed. [7] Method according to claim 5 or claim 6, characterized by that the electrical characteristic is a current of the coil (42), wherein during dewatering the change from discharged water to discharged gas leads to a movement of the piston which induces a voltage in the coil (42), wherein a change in the current of the coil is measurable, wherein the coil (42) is operated in particular with a constant voltage. [8] Method according to claim 7, characterized by that the electrical characteristic is a voltage of the coil (42), wherein during drainage the change from discharged water to discharged gas leads to a movement of the piston which induces a voltage in the coil (42), wherein a change in the voltage of the coil (42) is measurable. [9] Electrolyzer, characterized by a device (20) according to one of the preceding claims and / or configured to carry out a method according to one of the claims. [10] Fuel cell, characterized bya device (20) according to one of the preceding claims and / or configured to carry out a method according to one of the claims.

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