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

Abstract

A device for water separation and pressure control for an electrolyzer (2) 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 (28) for receiving water separated from the supplied gas, a valve (30) for adjusting a gas pressure in the interior space (24), and a drainage valve (32) for discharging water from the reservoir, the drainage valve (32) being a switchable valve, the drainage valve (32) being a pressure relief valve which opens automatically when a predetermined overpressure is reached.

Description

The present invention relates to a water separation and pressure control device for an electrolyser or a fuel cell, the device having: a gas inlet for supplying gas into an interior space of the device, a gas outlet for discharging gas from the interior space of the device, a reservoir for receiving water separated from the supplied gas, a valve for setting a gas pressure in the interior space and a drainage valve for discharging water from the reservoir, wherein the drainage valve is a switchable valve. The invention further relates to a fuel cell and an electrolyser having such a device.Electrolysers are used in particular to break down water into its constituents hydrogen and oxygen. The gaseous hydrogen obtained also contains residues of gaseous water, for example up to 2500 ppm, which should be separated as far as possible before the storage of the hydrogen. Further, the pressure of the hydrogen should be set to a defined value. Both are achieved with the device mentioned at the beginning for water separation and pressure regulation.Such a device usually has a pressure relief valve in the vicinity of the gas outlet and a dewatering valve separate from the pressure relief valve.The present invention is based on the technical problem of specifying an improved device for water separation and pressure regulation for an electrolyser or a fuel cell. Furthermore, a fuel cell and an electrolyser having such a device are to be specified.The technical problem described above is solved in each case by means of the features of the independent claims. Further embodiments of the invention are evident from the dependent claims and the description below.According to a first aspect, the invention relates to a device for water separation and pressure regulation for an electrolyser or a fuel cell, wherein the device has: 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 setting a gas pressure in the interior and a dewatering valve for discharging water from the reservoir, wherein the dewatering valve is a switchable valve and wherein the dewatering valve is a pressure relief valve which opens automatically when a predetermined overpressure is reached.According to the invention, the drainage valve likewise forms the overpressure 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 omitted. The device can be provided more cost-effectively and more compactly in this way.The drain valve may be a solenoid valve.It can be provided that the drainage valve is held in a closed position in a resiliently elastically prestressed manner. In particular, it can be provided that a biasing spring defines the predefined overpressure. Thus, the overpressure function or the overpressure protection can be achieved by a cost-effective mechanical construction.The "predefined overpressure" defines the switching threshold of the overpressure valve, i.e. the pressure which causes the overpressure valve to open, so that the predefined overpressure in the interior of the device cannot be exceeded.According to one embodiment of the device, it is provided that no further pressure relief valve is assigned to the interior. The protection against overpressure is therefore preferably achieved solely by the dewatering valve.The valve for adjusting the gas pressure in the interior space may be a proportional valve. The valve for adjusting the gas pressure in the interior space may be an electromagnetically controlled proportional valve. The valve for adjusting the gas pressure in the interior can be a medium-controlled proportional valve.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 to set up up to 35 bar in the interior, further in particular to set up to 40 bar in the interior. In the aforementioned cases, the overpressure threshold of the dewatering valve is selected to be correspondingly greater than the gas pressure set by the valve for setting the gas pressure in the interior.It can be provided that the dewatering valve is configured to open automatically for an overpressure of 40 bar. Thus, the valve for adjusting the gas pressure in the interior can be configured, for example, to adjust a gas pressure of 29 bar in the interior, while the dewatering valve automatically opens at an overpressure of 40 bar.In particular, it can be provided that an overpressure threshold of the dewatering valve is more than 10 bar greater than the gas pressure set by the valve for setting 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 setting the gas pressure in the interior, the overpressure threshold can be defined, for example, at 50 bar, 55 bar or 60 bar.The device can have a pressure sensor for measuring a pressure, in particular the gas pressure, in the interior.The apparatus may have a condensation device for liquefying gaseous water of the supplied gas by condensation. According to one embodiment of the device, a plate arrangement can be arranged in the interior space in order to liquify gaseous water of the supplied gas at the plate arrangement by condensation. The condensation device can therefore comprise the plate arrangement.It can be provided that a drain opening of the reservoir, which is connected to the drain valve, is associated with a bottom of the reservoir in order to enable a substantially complete discharge of separated water via the drain valve.According to one configuration of the device, it can be provided that the dewatering valve is a switchable solenoid valve, that the device has a device for monitoring a position of a piston of the solenoid valve and / or for monitoring an electrical characteristic variable of a coil of the solenoid valve, in order to detect a change from discharged water to discharged gas during dewatering.The applicant has recognized that a pressure change measurable at the solenoid valve is generated when the reservoir is emptied, when gas escapes via the solenoid valve after the water has been separated. This is because, during the transition from water separation to gas separation, there is a sudden pressure change and a piston movement associated therewith, since the atmospheric pressure now acts partially on the piston of the solenoid valve instead of the static water pressure. It can therefore be detected by means of the solenoid valve whether the water is discharged from the reservoir.It can be provided that a drain opening of the reservoir, which is connected to the drain valve, is associated with a bottom of the reservoir in order to enable a substantially complete discharge of separated water via the drain valve. In particular, the drainage opening can be arranged in the base of the reservoir or be arranged at a distance of a few millimeters from the base 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.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 dewatering valve. In this way, a separate water level sensor or fill level sensor, as is frequently used in the prior art, can be dispensed with. In particular, the device therefore does not have a separate, additional fill level sensor, but rather the amount of water in the reservoir is monitored solely by means of the solenoid valve.According to a second aspect, the invention relates to an electrolyser which has an apparatus for water separation and pressure regulation as described above.The electrolyser has, in particular, a gas separator in order to separate hydrogen obtained during electrolysis from the circulating fluid (water or electrolyte).The electrolyser has a vessel for collecting the hydrogen obtained, it being possible to achieve a hydrogen purity of 99.9%.The water separation and pressure control device according to the invention may be arranged between the gas separator and the container for collecting the recovered hydrogen in order to dry the hydrogen before being stored in the container.Likewise, an apparatus for separating water and regulating pressure according to the invention can be arranged between an oxygen-side gas separator and a container for storing the oxygen obtained.The electrolyser may be configured for alkaline electrolysis (AEL).The electrolyser may be arranged alternatively to proton exchange membrane electrolysis (PEM-EL).The electrolyser can be configured alternatively to high-temperature electrolysis (HTEL) or solid oxide electrolyser cell (SOEC).According to a further aspect, the invention relates to a fuel cell, wherein the fuel cell has at least one device according to the invention for water separation and pressure regulation. The device for water separation and pressure regulation can be arranged between a hydrogen container and a galvanic element of the fuel cell.In each case, a device for water separation and pressure regulation can be arranged between an oxygen container and the galvanic element and between the hydrogen container and the galvanic element.A method for draining a gas line of an electrolyser or a fuel cell can be specified, wherein the gas line has a device according to the invention, having 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 into an open position; monitoring a position of the piston and / or an electrical characteristic variable 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 variable, in particular a sudden change is detected.It can be provided that the solenoid valve remains open for a predefined time period after the detection of the sudden change and is closed with the expiration of the time period.According to one embodiment of the method, it can be provided that the electrical characteristic variable 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 can be measured.It can be provided that the electrical characteristic variable is a voltage 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 voltage of the coil can be measured.The invention is described below with reference to drawings illustrating exemplary embodiments. They show in each case schematically: FIG. 1 shows an electrolyser according to the invention; FIG. 2 shows a device according to the invention; FIG. 3 shows a flow chart of a method.FIG. 1 schematically shows an electrolyser 2. the electrolyser 2 is an electrolyser for alkaline electrolysis. It goes without saying that the device according to the invention for water separation and pressure regulation, described in detail below, can equally also be used with the further electrolysis technologies, such as proton exchange membrane electrolysis or high-temperature electrolysis, already described above.The electrolyser 2 has an oxygen-side anodic gas separator 4 and a hydrogen-side cathodic gas separator 6. A diaphragm 14 is disposed between the cathode 10 and the anode 12.The diaphragm 14 is permeable to ions so that negatively charged hydroxide ions can move toward the anode 12. The diaphragm 14 is gas impervious and prevents the oxygen from mixing with the hydrogen. The cathode 10 and the anode 12 are in potassium hydroxide solution (KOH, H 2 O).Hydroxide ions and hydrogen are formed at the cathode 10 from water with electron absorption. The hydroxide ions, due to their negative charge, migrate through the diaphragm to the anode 12 where they react to form oxygen and water with electron emission.The hydrogen is supplied via the cathodic gas separator 6 to a container 16 or tank 16 and stored there.The oxygen is supplied via the anodic gas separator 4 to a container 18 or tank 18 and stored there.Between the container 16 and the cathodic gas separator 6, a device 20 according to the invention for water separation and pressure regulation is arranged. The device 20 is described in more detail below with reference to FIG. 2.The device 20 for water separation and pressure regulation has a gas inlet 22 for supplying hydrogen (H 2), which contains up to 2500 ppm of gaseous water, into an interior 24 of the device 20.The device 20 has a gas outlet 26 for discharging hydrogen from the interior 24 of the device 20.The device 20 has a reservoir 28 for receiving water separated from the supplied hydrogen and liquefied by condensation.The device 20 has a valve 30 for adjusting a gas pressure in the interior 24.The device 20 has a drain valve 32 for draining water from the reservoir 28, wherein the drain valve 32 is a switchable solenoid valve.The drainage valve 32 is also a pressure relief valve which opens automatically when a predetermined overpressure is reached. The predefined overpressure is 40 bar in the present case.The solenoid valve 32 is held elastically prestressed in a spring-loaded manner in a closed position, wherein a prestressing spring 34 defines the predefined overpressure. Thus, the overpressure at which the solenoid valve 32 overcomes the spring prestress and opens automatically can be defined by the dimensioning of the prestressing spring 34.In the present case, the spring force is set to 4 Newton, which results for a valve opening area of 1 mm 2 for the threshold pressure of 40 bar. The dewatering valve 32 is therefore configured to open automatically for an overpressure of 40 bar. That is, if a force of more than 4 Newton is exerted on a piston 36 of the solenoid valve 32, the biasing spring is compressed by a displacement of the piston 36 in the direction of the biasing spring, the valve opening 38 closed by the piston 36 is released and the water flows out of the reservoir 28.The solenoid valve 32 is also controlled and opened at regular time intervals by means of a controller 40, wherein a coil 42 displaces the piston 36 in the direction of the prestressing spring 34.No further pressure relief valve is assigned to the interior 24.The valve 30 is a proportional valve and is designed to set a gas pressure of 29 bar in the interior 24.The device 20 has a pressure sensor 44 for measuring a pressure in the interior 24.The device 20 has a plate arrangement 48 which is arranged in the interior 24 in order to liquify gaseous water of the supplied gas H 2 at the plate arrangement 48 by condensation.The supplied gas H 2 can have, for example, water fractions of up to 2500 ppm, wherein the discharged gas only has water fractions of 440 ppm as a result of the separation of the water.The valve opening 38 may also be referred to as a drain opening 38 of the reservoir 28, which is connected to the drain valve and is associated with a bottom 46 of the reservoir 28 to allow substantially complete discharge of separated water via the drain valve 32.As already explained, the one dewatering valve 32 is a switchable solenoid valve.The controller 40 is a device for monitoring an electrical characteristic variable of a coil 42 of the solenoid valve 32 in order to detect a change from discharged water to discharged gas during dewatering.According to the present example, the electrical characteristic variable 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.Next, a method for dewatering the hydrogen side gas pipe will be described with reference to FIG. 3.The method for draining the hydrogen-side gas line of the electrolyser 2, wherein the gas line has the device 20 according to the invention, has the following method steps: (A) opening the solenoid valve 32, wherein the coil 42 is supplied with electrical power in order to move the piston 36 from the closed position into the open position, wherein the coil 42 is supplied with constant voltage; (B) monitoring the current of the coil 42 of the solenoid valve 32; (C) closing the solenoid valve 32, provided that a change is detected for the current of the coil 42, in particular a sudden change is detected.The solenoid valve is immediately closed after the abrupt change is detected, in order to avoid an outflow of hydrogen.Reference numerals denote reference numerals2 Electrolyser 4 Gas separator 6 Gas separator 8 Current source 10 Cathode 12 Anode 14 Diaphragm 16 Container / tank 18 Container / tank 20 Device 22 Gas inlet 24 Interior 26 Gas outlet 28 Reservoir 30 Valve 32 Dewatering valve 34 Prestressing spring 36 Piston 38 Valve opening 40 Controller 42 Coil 44 Pressure sensor 46 Base 48 Plate arrangement

Claims

A device for water separation and pressure control for an electrolyser (2) or a fuel cell, the device having: - 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 (28) for receiving water separated from the supplied gas, - a valve (30) for setting a gas pressure in the interior space (24), and - a dewatering valve (32) for discharging water from the reservoir, wherein the dewatering valve (32) is a switchable valve, characterized in that - the dewatering valve (32) is a pressure relief valve which opens automatically when a predetermined overpressure is reached.Device according to claim 1, characterised in that the dewatering valve (32) is a solenoid valve.Device according to one of the preceding claims, characterized in that the dewatering valve (32) is held in a closed position in a resiliently pretensioned manner, in particular in that a pretensioning spring (34) defines the predefined overpressure.Device according to one of the preceding claims, characterized in that no further overpressure valve is assigned to the interior (24).Device according to one of the preceding claims, characterized in that the valve (30) is a proportional valve.Device according to one of the preceding claims, characterized in that - the valve (30) is configured to set a gas pressure of 29 bar in the interior space and / or - the dewatering valve (32) is configured to open automatically for an overpressure of 40 bar and / or - a pressure sensor (44) is provided for measuring a pressure in the interior space.Device according to one of the preceding claims, characterized in that a plate arrangement (48) is arranged (24) in the interior space in order to liquify gaseous water of the supplied gas at the plate arrangement (48) by condensation.Device according to one of the preceding claims, characterized in that a drainage opening (38) of the reservoir (28), which is connected to the drainage valve (32), is assigned to a base (46) of the reservoir (28) in order to enable substantially complete discharge of separated water via the drainage valve (32).Electrolyser, characterized bya device (20) according to one of the preceding claims.Fuel cell, characterized bya device (20)g according to one of the preceding claims.

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