Electrolysis system with an oxygen pre-separation function

Abstract

The invention relates to a system consisting of a plurality of electrolysis devices (10), which are accommodated in a frame or shelf (19), for generating hydrogen from water using an electric current. Each electrolysis device (10) has at least the following: a cell stack (11) consisting of a plurality of cell stack elements (12) in the form of electrolysis cells; end plates (14, 15) lying opposite each other, wherein the cell stack (11) consisting of the cell stack elements (12) is provided and compressed between the end plates (14, 15); at least one water supply connection (16) which is formed on the end plates (14, 15) and via which water can be supplied to the respective electrolysis device (10); and at least one water discharge connection (17) which is formed on the end plates (14, 15) and via which water and oxygen can be discharged from the respective electrolysis device (10). At least one pre-separator (20) for oxygen is installed on the frame or shelf (19) and / or in the frame or shelf (19) and / or in the immediate vicinity of the frame or shelf (19) in order to separate oxygen from the water discharged from the electrolysis devices (10).

Description

[0001] Electrolysis system with oxygen pre-separation

[0002] The invention relates to a system comprising several electrolysis devices with oxygen pre-separation.

[0003] DE 10 2017 108 413 A1 discloses an electrolysis device with a cell stack composed of multiple cell stack elements. Furthermore, the electrolysis device known from this prior art comprises a force application unit, via which a force can be exerted on the cell stack in order to press the cell stack elements of the cell stack together in a fluid-tight manner. The force application unit comprises opposing end plates, between which the cell stack is arranged and pressed together. Furthermore, the force application unit comprises pressing devices comprising spring elements and struts, wherein the spring force of the spring elements presses the end plates against one another, pressing the cell stack together. Connections, namely water supply connections, water discharge connections, and hydrogen connections, are formed on the end plates of the electrolysis device.Water is supplied to the electrolysis device via the water supply connections, and water and oxygen are removed from the electrolysis device via the water discharge connections. The hydrogen connections are used to remove the hydrogen produced during electrolysis.

[0004] EP 2 377 972 A1 discloses a device for generating hydrogen with an electrolyzer and a water separation device. The water separation device serves to dry the hydrogen obtained during electrolysis, i.e., to separate water from the hydrogen obtained. The water separation device has several separation stages, namely several thermal separation stages. EP 2 163 290 A1 discloses a separation vessel for operating an electrolyzer. The separation vessel disclosed therein has a cyclone separator. A mixture of water and oxygen can be supplied to the separation vessel via a first connection. The oxygen can be separated using the cyclone separator, with water leaving the separation vessel via a first line connection and oxygen leaving via a second line connection.

[0005] In systems known from practice for producing hydrogen from water, the mixture of water and oxygen leaving the system's electrolysis devices is conveyed via relatively long pipelines to an oxygen separator, where the oxygen is separated from the water. The oxygen separators known from practice are large components that require a lot of space in the hydrogen production system. The pipelines leading from the electrolysis devices to the oxygen separator are long and have a large diameter.

[0006] There is a need for a system consisting of several electrolysis devices for producing hydrogen from water, in which the effort and space requirements for oxygen separation in a process water circuit can be reduced.

[0007] Based on this, the present invention is based on the object of creating a novel system comprising several electrolysis devices.

[0008] This object is achieved by a system comprising a plurality of electrolysis devices according to claim 1. According to the invention, the system has at least one pre-separator for oxygen installed on the frame or shelf and / or in the frame or shelf and / or in the immediate vicinity of the frame or shelf in order to separate oxygen from the water discharged from the electrolysis devices.

[0009] The electrolysis device(s) according to the invention are PEM (Polymer Exchange Membrane) electrolysis devices. A PEM electrolysis device consists of a cell stack of individual electrolysis cells sandwiched between end plates, with each electrolysis cell comprising a polymer exchange membrane arranged between two half-cells. Each electrolysis device comprises a water side (first half-cells) and a hydrogen side (opposite half-cells). PEM electrolysis is characterized by the transfer of hydrogen ions, which pass through the PEM from the water side to the hydrogen side.

[0010] The system according to the invention is therefore a PEM system, i.e., a system with PEM-type electrolysis devices. The PEM system has a process water circuit in which process water is passed through the water side of the electrolysis devices. A portion of the process water is split into hydrogen and oxygen; the remaining portion of the process water, which primarily serves for cooling, is returned, treated if necessary, and passed through the electrolysis devices again.

[0011] Hydrogen produced on the hydrogen side of an electrolysis device is removed. The removed hydrogen is typically freed from residual water or moisture through one or more drying stages.

[0012] For the purposes of this document, oxygen separation means the separation of gaseous oxygen from a two-phase flow containing liquid water alongside the gaseous oxygen. This involves the separation of gas (oxygen) from a liquid phase (water).

[0013] The oxygen separation according to the invention relates exclusively to oxygen separation in the process water circuit, i.e., the removal of unwanted oxygen from the process water. The invention does not relate to hydrogen treatment. In particular, it does not relate to hydrogen separation or hydrogen drying. The invention also does not relate to other gas drying methods, in particular not to the field of oxygen drying, in which water is separated from a gas stream, e.g., by thermally induced condensation.

[0014] The invention also relates to a pre-separator for pre-separating oxygen in an electrolysis device, as well as its use in a system comprising at least one electrolysis device. The pre-separator is associated with the process water circuit, i.e., coupled to it and arranged in the process water circuit.

[0015] According to the invention, at least one pre-separator for oxygen is installed on the frame or shelf and / or in the frame or shelf and / or in the immediate vicinity of the frame or shelf which accommodates the plurality of electrolysis devices. The invention therefore proposes that oxygen separation be carried out in the frame or shelf accommodating the electrolysis devices and / or on the frame or shelf accommodating the electrolysis devices and / or in the immediate vicinity of the frame or shelf accommodating the electrolysis devices. This makes it possible to reduce the piping effort for conveying the mixture of water and oxygen compared to systems known from practice. A mixture of water and oxygen, from which a large proportion of the oxygen has already been separated, is led to a final separator (also referred to as the main separator). This allows the final separator to be designed with a smaller installation space requirement, and the space required by the frame or shelf can also be reduced.Water pipes leading to the final separator can be designed with less effort and space requirements. The final separator is preferably designed as a device that is located in a separate frame, spatially separated from the frame or shelf of the electrolysis devices.

[0016] The final separator serves to reduce the oxygen content of the process water (also referred to as water for short) conducted in a process water circuit of the system to or below a defined oxygen content. It is designed in particular to remove the (residual) oxygen present in the process water in the form of small bubbles and vesicles (microbubbles) essentially completely or at least below a predefined limit. These bubbles and vesicles, and in particular microbubbles, can have diameters of less than 1 mm. These must also be removed because they lead to cavitation in downstream pumps, heat exchangers and / or resin ion exchangers. The design effort for removing the (residual) oxygen is high. The final separator is assigned to the process water circuit, coupled to it or located within it.

[0017] In contrast to a main separator, the pre-separator(s) used according to the invention are of simple construction and serve to separate only the 'coarse' air components in the process water and are not designed or suitable to sufficiently separate bubbles and vesicles, and in particular microbubbles.

[0018] When using a main separator, the invention is characterized in that (at least) two-stage oxygen separation of the oxygen from the process water takes place in the process water circuit, wherein the first stage is realized by (one or more) pre-separators and the second stage by the main separator. The main separator is hydraulically coupled to the or each pre-separator with respect to the process water circuit. The pre-separator and main separator are arranged in the process water circuit. Preferably, for each electrolysis device, at least one individual pre-separator for oxygen is installed on the frame or shelf and / or in the frame or shelf. Alternatively, a common pre-separator for oxygen is installed on the frame or shelf and / or in the frame or shelf and / or in the immediate vicinity of the frame or shelf for all electrolysis devices.Preferably, for each cascade of series-connected electrolysis devices, a cascade-specific pre-separator for oxygen and a common pre-separator for the electrolysis devices in the cascade are installed on the rack or shelf and / or in the rack or shelf and / or in the immediate vicinity of the rack or shelf. All three variants advantageously allow oxygen to be separated from the water leaving the electrolysis devices in the immediate vicinity of the electrolysis devices. This makes it possible to reduce the piping effort between the rack or shelf and the final separator. Furthermore, the final separator can be designed with smaller dimensions. Overall, it is possible to reduce the effort required for oxygen separation.

[0019] Preferably, the respective pre-separator and the lines leading to and from the respective pre-separator are made of plastic. If the pre-separator and preferably also the lines leading to and from the respective pre-separator for conveying the water are made of plastic, there is no risk of, for example, metal ions being introduced into the water and thus contaminating the process water. The water can therefore be reused after the oxygen has been separated and fed back into the electrolysis devices to generate hydrogen.

[0020] Preferably, the respective pre-separator is designed such that the oxygen separation rate therein is between 30% and 95%, preferably between 50% and 95%, particularly preferably between 80% and 95%. To this end, it is preferably provided that the residence time of the water introduced into the pre-separator is approximately 40% to 60% of the time required for oxygen bubbles to rise within the respective pre-separator. This drastically reduces the proportion of oxygen that must be piped from the rack or shelf housing the electrolysis devices to a final separator. Ultimately, this reduces the effort required to separate oxygen from the water.

[0021] Preferably, the respective pre-separator has a flow area for water and, above the same, a collection area for oxygen, wherein oxygen can be discharged from the collection area via an oxygen outlet in such a way that a water pressure loss is limited. The oxygen outlet is assigned a throttle or a valve which opens or closes further depending on a measured variable, e.g. a water pressure or oxygen pressure, a water level in the pre-separator, mechanical vibrations or another air sensor (air sensor) which directly or indirectly detects the presence of air to be separated. This allows particularly efficient separation of oxygen from the water, without the risk of too much water being entrained during the oxygen separation and without the risk of the water pressure being reduced too much.

[0022] The throttle or valve can be controlled via an active or passive actuator. A suitable passive actuator is, among other things, a float positioned in the pre-separator, which opens or closes the throttle or valve depending on the changing water level in the pre-separator or the air above it. The valve is then a float valve, whose float acts as an indirect air sensor.

[0023] An electromagnet, preferably integrated into the throttle or valve, can be used as an active actuator. This solenoid is controlled depending on a measurement signal and opens or closes the throttle or valve. Any air sensor that directly or indirectly detects the presence of air is suitable for generating the measurement signal. These include optical sensors such as distance sensors for determining the water level, electromagnetic sensors for detecting the presence of air vs. water, e.g., using the phenomenon of light refraction at media transitions, or vibration sensors calibrated to different vibration patterns of air or water flow. As mentioned above, water or air can also be detected via pressure fluctuations.

[0024] Other types of throttle or valve control are possible.

[0025] Preferably, the respective pre-separator has an inlet for the mixture of water and oxygen on a first vertical wall, an outlet for water below the inlet, and an outlet for oxygen above the inlet. A partition wall extends from the first vertical wall towards an opposite second vertical wall, is directed downwards towards the second wall, and ends at a distance from the second wall. Preferably, the outlet for oxygen is formed adjacent to the second vertical wall in the region of an upper wall of the respective pre-separator, said upper wall extending obliquely upwards from the first vertical wall towards the second vertical wall. This design of a pre-separator allows particularly efficient and advantageous separation of oxygen from the water.

[0026] In an advantageous development, two or more of the electrolysis devices of the system according to the invention are hydraulically connected in series, so that the water exiting the water discharge connection from one electrolysis device is introduced into the water inlet connection of the or a subsequent electrolysis device. An oxygen pre-separator is arranged between each of the electrolysis devices hydraulically connected in series. Only because the oxygen released during electrolysis is removed from the water circuit immediately after release via the oxygen pre-separator does it become technically feasible to feed the thus treated water directly into a subsequent electrolysis device.Without the oxygen pre-separation, a hydraulic series connection would not be possible without disproportionate performance losses, since the oxygen-enriched process water would negatively influence the electrolysis efficiency.

[0027] By connecting electrolysis devices in series, significantly smaller process water volume flows (with all the associated advantages) can be operated in the process water circuit at the same hydrogen production rate compared to connecting them in parallel.

[0028] Preferably, no more than four, and particularly preferably exactly three, electrolysis devices are hydraulically connected in series. Limiting the number of electrolysis devices to four or three in series has the advantage that the process-related heating (waste heat) of the process water can be kept within controlled limits. Since the temperature of the process water increases by a temperature delta AT each time it flows through an electrolysis device, the total delta of the temperature increase can be limited to a multiple of AT corresponding to the number of electrolysis devices, for example, to 3x AT for three electrolysis devices hydraulically connected in series. Thus, each electrolysis device experiences an essentially identical AT, starting from a respective increasing initial temperature level.

[0029] By limiting the temperature range in each electrolysis device, degradation effects of the cells of the electrolysis device can be kept small even at higher temperatures compared to a series connection.

[0030] Advantageously, the system is operated with electrolysis devices in such a way that process water is pumped successively from a first electrolysis device to a second—and optionally to a third, fourth, fifth, etc.—subsequent electrolysis device, with oxygen being separated from the process water between each of the successive electrolysis devices. Other hydraulic connections of individual electrolysis devices are possible.

[0031] The system of electrolysis devices is expediently arranged in a housing, such as in particular a container, whereby the oxygen separated via the individual pre-separators is directly

[0032] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein:

[0033] Fig. 1 is a schematic representation of a first system according to the invention comprising several electrolysis devices for producing hydrogen from water by means of electric current,

[0034] Fig. 2 is a schematic representation of a second system according to the invention comprising several electrolysis devices for producing hydrogen from water by means of electric current,

[0035] Fig. 3 is a schematic representation of a third system according to the invention comprising several electrolysis devices for producing hydrogen from water by means of electric current,

[0036] Fig. 4 is a schematic representation of a pre-separator for oxygen of a system according to the invention comprising several electrolysis devices.

[0037] Fig. 1 shows a schematic view of a first system according to the invention comprising a plurality of electrolysis devices 10. In the electrolysis devices 10, hydrogen H2 and oxygen O2 are obtained from the water H2O by electrolysis of water H2O using electrical energy. The electrolysis devices 10 each have a cell stack 11 made up of a plurality of cell stack elements 12, namely a plurality of electrolysis cells. The cell stack 11 of the respective electrolysis device 10 made up of the plurality of cell stack elements 12 is pressed together in a fluid-tight manner by a force application unit 13 of the respective electrolysis device 10, wherein the force application unit 13 of the respective electrolysis device 10 has end plates 14, 15, between which the cell stack 11 of the respective electrolysis device 10 is arranged and pressed together.In order to press the cell stack 11 between the end plates 14, 15, the force application unit 13 of the respective electrolysis device 10 further comprises a pressing device (not shown).

[0038] As already explained, each electrolysis device 10, and thus the system comprising several electrolysis devices 10, serves to produce hydrogen H2 from water H2O. Oxygen O2 is also produced in the process. Each electrolysis device 10 has water connections through which, on the one hand, water H2O can be supplied to the electrolysis device 10 and, on the other hand, from which water H2O and preferably also oxygen O2 can be discharged from the electrolysis device 10. Furthermore, each electrolysis device 10 has hydrogen connections that serve to discharge the hydrogen H2 from the electrolysis device 10. In Fig.2, a water supply connection 16 and a water discharge connection 17 are shown for each electrolysis device 10, wherein the respective water supply connection 16 serves to supply water H2O to the respective electrolysis device 10 and the respective water discharge connection 17 serves to discharge water H2O and oxygen O2 from the respective electrolysis device 10.

[0039] The electrolysis devices 10 shown in Fig. 1 are connected in series and thus combined to form a cascade 18 of electrolysis devices 10. A mixture of water and oxygen leaving the left electrolysis device 11 shown in Fig. 1 via the water discharge connection 17 thereof can be fed in the direction of the water supply connection 16 of the electrolysis device 11 connected downstream of this electrolysis device 11 in the cascade 18. The electrolysis devices 10 are accommodated in a frame or shelf 19. According to the invention, the system comprising the electrolysis devices 10 accommodated in the frame or shelf 19 comprises at least one pre-separator 20 for oxygen, which is installed on the frame or shelf 19 and / or in the frame or shelf 19 and / or in the immediate vicinity of the frame or shelf 19 and which serves to separate oxygen from the water discharged by the electrolysis devices 10.

[0040] In the embodiment shown in Fig. 1, each electrolysis device 10 is assigned an individual pre-separator 20, which is installed in and / or on the frame or shelf 19 in the immediate vicinity of the respective electrolysis device 10. The pre-separators 20 are assigned to the water side of each electrolysis device, i.e. are hydraulically arranged in the process water circuit. The mixture of water and oxygen, which leaves the respective electrolysis device 10 via the respective water discharge connection 17, is passed through the pre-separator 20 operatively connected to the respective electrolysis device 10 in order to individually separate oxygen in the immediate vicinity of the respective electrolysis device 10 from the water discharged from the respective electrolysis device 10. Within the space shown in Fig.In the cascade 18 of electrolysis devices 10 shown in Figure 1, a portion of the oxygen is separated from the mixture of water and oxygen leaving the respective electrolysis device 10 immediately after each electrolysis device 10, so that a mixture of water and oxygen with a reduced oxygen content is supplied to the respective electrolysis device 10 following in the cascade. This can increase the efficiency of the electrolysis.

[0041] Downstream of the right-hand, last electrolysis device of the cascade 18 shown in Fig. 1 and the individual pre-separator 20 assigned to this electrolysis device 10, the mixture of water and oxygen is fed to a final separator 21 in order to separate as much residual oxygen as possible from the water in the final separator 21. The final separator 21 is assigned to the process water circuit, i.e., it is hydraulically arranged in the process water circuit. The water obtained in this way, which is largely free of oxygen, is fed via a pump 22 back towards the electrolysis devices 10 of the cascade 18 shown there in order to use the water again for electrolysis. In this context, it is particularly advantageous if all water-carrying pipes, the pre-separator 20 and also the final separator 21 are made of plastic. This is advantageous because it prevents metal ions from contaminating the water.This is also advantageous in order to enable efficient electrolysis of water and thus efficient production of hydrogen.

[0042] In the embodiment shown in Fig. 1, the electrolysis devices 11 accommodated in the rack or frame 19 are arranged together with the pre-separators 20 and together with the final separator 21 in an enclosed space or a container 23 which delimits an explosion-hazardous area of ​​the system.

[0043] In the embodiment of Fig. 1, each pre-separator 20 is assigned an individual vent line 24 for the oxygen separated in the respective pre-separator 20, via which the separated oxygen can be removed from the potentially explosive area of ​​the container 23. Thus, the vent lines 24 lead from the potentially explosive area of ​​the container 23 into the environment of the container 23. The individual vent lines 24 of the respective pre-separators 20, which interact with the pre-separators 20, open into a common collecting line 25, which leads to a vent line 26 of the final oxygen separator 21. From this vent line 26, the oxygen is ultimately released into the environment in a controlled manner or can be collected in a container.

[0044] A siphon 27 can be installed in the area of ​​each of the blow-off lines 24 of the pre-separator 20 and in the area of ​​the blow-off line 26 of the final separator 21 to separate water from the oxygen being blown off. The water separated from the oxygen being blown off in the area of ​​the respective siphon 27 of the respective pre-separator 20 is returned via respective drip lines 28, namely directly downstream of the respective pre-separator 20 into the water leaving the respective pre-separator 20.

[0045] The water separated from the oxygen in the area of ​​the siphon 27 of the blow-off line 26 of the final separator 21 can be fed to a waste water line 31 via a line 29, which is preferably assigned a valve 30.

[0046] Fig. 2 shows a system for producing water from hydrogen with three cascades 18, each consisting of several electrolysis devices 10 connected in series, all of which are mounted on a common rack or frame 19. In the embodiment of Fig. 2, each cascade 18 is assigned an individual pre-separator 20 for oxygen, which is mounted in and / or on the rack or frame 19.

[0047] In contrast to Fig. 1, in Fig. 2 there is not a pre-separator 20 operatively connected to each of the electrolysis devices 10, but rather a pre-separator 20 is operatively connected to each cascade 18 of series-connected electrolysis devices 18, which pre-separator 20 is installed in and / or on the rack or frame 19 and thus carries out a pre-separation of oxygen from the mixture of water and oxygen leaving the cascade 18 in the immediate vicinity of the electrolysis devices 10 or cascades 18. With regard to all other details, the embodiment of Fig. 2 corresponds to the embodiment of Fig. 1, so that to avoid unnecessary repetition, the same reference numerals are used for the same components and reference is made to the above explanations regarding the embodiment of Fig. 1. Fig. 3 shows a modification of the system of Fig. 2, whereby in the system of Fig.3 For all electrolysis devices 10 of all cascades 18 shown, a common pre-separator 20 is installed on the frame or shelf 19 in the immediate vicinity of the frame or shelf 19. This pre-separator 20 can also be installed in the frame 19. This also makes it possible to separate oxygen from the water leaving the electrolysis devices 10 in the immediate vicinity of the frame 19 and thus in the immediate vicinity of the electrolysis devices 10 accommodated by the frame 19, so that the final separator 21 can be dimensioned smaller, as can the pipes leading to the final separator 21 for conveying the water.

[0048] The respective pre-separator 20 of the embodiments of Figs. 1, 2 and 3 is preferably designed such that the oxygen separation rate therein is between 30% and 95%, preferably between 50% and 95%, particularly preferably between 80% and 95%.

[0049] Then, if the separation rate refers to the mixture of water and oxygen entering the respective pre-separator 20, the mixture of water and oxygen leaving the respective pre-separator 20 has 30% to 95%, preferably 50% to 95%, particularly preferably 80% to 95%, less oxygen than the mixture of water and oxygen entering the respective pre-separator 20.

[0050] It can be provided that the separation rate of the respective pre-separator 20 also relates to the narrow separator 21. In this case, the respective pre-separator 20 is designed such that the relative separation rate of oxygen from water therein is at least 30%, preferably at least 50%, particularly preferably at least 80% relative to the separation rate of the main separator 21. If, as shown in Fig. 1, each electrolysis device 10 is assigned an individual pre-separator 20, the respective pre-separator 20 is in particular designed such that the water leaving the respective pre-separator 20 contains a maximum of 15% to 30% or a maximum of 20% to 25% more oxygen than the water entering the respective electrolysis device 10 assigned to this pre-separator 20.This ensures that effective electrolysis of water and thus effective production of hydrogen is also possible in the electrolysis devices 10 following in a cascade.

[0051] Fig. 4 shows a preferred embodiment of a pre-separator 20. The pre-separator 20 has a housing 32, wherein in Fig. 4 a first, vertically running housing wall 33 and a second, vertically running housing wall 34 opposite this first, vertically running housing wall 33 are shown. Between these vertically running housing walls 33, 34 extend a lower wall 35 and an upper wall 36 of the housing 33, wherein the lower wall 35 can also be referred to as the bottom wall and the upper wall 36 can also be referred to as the roof wall. An inlet 37 for the mixture of water and oxygen entering the pre-separator 20 is formed on the housing 32. This inlet 37 is formed on the first housing wall 33 at an upper section thereof.

[0052] Also on the first housing wall 33, below the inlet 37 for the mixture of water and oxygen, there is an outlet 38 for water. In the area of ​​the upper wall 36, adjacent to the second wall 37 opposite the first wall 33, there is an outlet 39 for blowing off oxygen. The housing 32 of the pre-separator 20 defines a flow area 40 for the water and a collection area 41 for the separated oxygen. Starting from this collection area 41 for the oxygen, the separated oxygen can be blown off via the outlet 39. The pre-separator 20 is preferably designed such that the residence time of water introduced into the pre-separator 20 via the inlet 37 is 40% to 60% of the time required for oxygen bubbles to rise within the pre-separator 20. For this purpose, in the embodiment of Fig.4, the flow area 40 of the pre-separator 20 is divided into two sub-areas by a partition wall 42, which are connected to one another in the region of the second vertically extending wall 34. The partition wall 42 extends downward from the first vertically extending wall 33 of the pre-separator 20 from a region formed between the two connections 37, 38 in the direction of the second vertically extending wall 34 of the housing 32 opposite the first vertically extending wall 33, and ends at a distance from the second, vertically extending housing wall 34.

[0053] The upper wall 36 of the housing 32 extends upwards from the first vertical wall 33 towards the opposite second vertical wall 34 of the housing 32.

[0054] By this design of the pre-separator 20, on the one hand, the residence time of the water is advantageously adjusted in relation to the rising time of the oxygen bubbles, and on the other hand, a desired separation rate for oxygen of at least 30% to 95%, preferably of at least 50% to 95%, particularly preferably of between 80% and 95%, is made possible by simple means.

[0055] In the area of ​​the oxygen outlet 39, through which the separated oxygen can be blown off from the pre-separator 20, a throttle or valve 43 is assigned, which can be opened and closed passively or actively. This serves in particular to maintain the water pressure, i.e., to prevent excessive pressure loss of the water as it flows through the pre-separator 20. When the throttle or valve 43 is passively opened or closed, it is particularly provided that a control or regulating device opens or closes the throttle or valve 43 depending on the water pressure in the pre-separator 20 or depending on the water pressure immediately upstream of the pre-separator 20.

[0056] Fig. 4 shows an active control for the throttle or valve 43 using a control device 44, which further opens or closes the throttle or valve 43 depending on the measurement signal from an air sensor 45. The air sensor 45 can, for example, be a pressure sensor, which then further opens or closes the throttle or valve 43 depending on the oxygen pressure in the pre-separator 20.

[0057] Alternatively, it is also possible to influence a backpressure in the outlet 39 by having the outlet 39 with a relatively small diameter. However, the above-mentioned passive or active control of the opening position of the throttle or valve 43 is preferably dependent on the water pressure in or upstream of the pre-separator 20 or dependent on the oxygen pressure in the pre-separator 20.

[0058] The valve 43, which is installed in the area of ​​the outlet 39 of the respective pre-separator 20, is not a float valve. It should also be noted that the pre-separator 20 does not have a sponge structure for separating the oxygen. Therefore, the mixture of water and oxygen can flow freely through the pre-separator 20. Only the partition wall 42 directs the flow and divides the flow area of ​​the pre-separator 20 for the water into interconnected sub-areas.

[0059] The partition wall 41 of the respective pre-separator 20 forms a collection area for oxygen bubbles, which then, from the partition wall 42, enter the collection area 41 of the respective pre-separator 20. The partition wall 41 of the respective pre-separator 20 ensures a angular flow of the water through the flow area 40 of the respective pre-separator 20.

[0060] Particularly in the embodiment of Fig. 1, the pre-separators 20 have a base area that approximately corresponds to the base area of ​​an end plate 14, 15 of the respective electrolysis device 10. The base area refers to the horizontal dimension of the respective pre-separator. The height and thus vertical dimension of the pre-separators 20 shown in Fig. 1 is preferably a maximum of 60 cm, preferably a maximum of 50 cm. The respective pre-separator 20 can be an integral component of the respective electrolysis device 10 and can be mounted together with the respective electrolysis device 10 in and / or on the frame or frame 19.

[0061] The invention enables the provision of an efficient system of electrolysis devices 10, which serves to produce hydrogen through the electrolysis of water. Oxygen produced during electrolysis can be efficiently separated.

[0062] List of reference symbols

[0063] 10 Electrolysis device

[0064] 11 cell stacks

[0065] 12 cell stack element

[0066] 13 Force application unit

[0067] 14 End plate

[0068] 15 End plate

[0069] 16 Water supply connection

[0070] 17 Water drainage connection

[0071] 18 Cascade

[0072] 19 frame, shelf

[0073] 20 pre-separators

[0074] 21 final separators

[0075] 22 Pump

[0076] 23 containers

[0077] 24 Blow-off line

[0078] 25 Collective line

[0079] 26 Blow-off line

[0080] 27 Siphon

[0081] 28 Drip line

[0082] 29 Line

[0083] 30 valve

[0084] 31 sewer line

[0085] 32 housings

[0086] 33 Housing wall

[0087] 34 Housing wall

[0088] 35 lower wall

[0089] 36 upper wall

[0090] 37 Inlet

[0091] 38 Outlet

[0092] 39 Outlet

[0093] 40 Flow area 41 Collection area

[0094] 42 Partition wall

[0095] 43 Valve

[0096] 44 Control unit 45 Air sensor

Claims

Claims 1. A system comprising a plurality of electrolysis devices (10) accommodated in a frame or shelf (19) for generating hydrogen from water using electrical current, wherein each electrolysis device (10) has at least the following: a cell stack (11) comprising a plurality of cell stack elements (12) designed as electrolysis cells, opposing end plates (14, 15), wherein the cell stack (11) comprising the cell stack elements (12) is arranged and pressed between the end plates (14, 15), at least one water supply connection (16) formed on the end plates (14, 15), via which water can be supplied to the respective electrolysis device (10), and at least one water discharge connection (17) formed on the end plates (14, 15), via which water and oxygen can be discharged from the respective electrolysis device (10),characterized by at least one pre-separator (20) for oxygen installed on the frame or shelf (19) and / or in the frame or shelf (19) and / or in the immediate vicinity of the frame or shelf (19) in order to separate oxygen from the water discharged from the electrolysis devices (10).

2. System according to claim 1, characterized by a main separator (21) coupled to the or each pre-separator (20).

3. System according to claim 1 or 2, characterized by at least one cascade (13) of several electrolysis devices connected in series 4. System according to one of the preceding claims, characterized in that several cascades (19) are connected in parallel.

5. System according to one of the preceding claims, characterized in that for each electrolysis device (10) at least one individual pre-separator (20) for oxygen is installed on the frame or shelf (19) and / or in the frame or shelf (19).

6. System according to one of the preceding claims, characterized in that for all electrolysis devices (10) a common pre-separator (20) for oxygen is installed on the frame or shelf (19) and / or in the frame or shelf (19) and / or in the immediate vicinity of the frame or shelf (19).

7. System according to one of the preceding claims 3 or 4, characterized in that for each cascade (13) of electrolysis devices (10) a cascade-specific pre-separator (20) for oxygen, which is common to the electrolysis devices (10) of the cascade (19), is installed in the frame or shelf (19) and / or in the frame or shelf (19) and / or in the immediate vicinity of the frame or shelf (19).

8. System according to one of the preceding claims, characterized in that the respective pre-separator (20) and preferably lines leading to the respective pre-separator (20) and lines leading away from the respective pre-separator (20) are made of plastic.

9. System according to one of the preceding claims, characterized in that the respective pre-separator (20) is designed such that the oxygen separation rate therein is between 30% and 95%, preferably between 50% and 95%, particularly preferably between 80% and 95%.

10. System according to one of the preceding claims, characterized in that the respective pre-separator (20) is designed such that a residence time of water introduced into the pre-separator (20) is approximately 40% to 60% of the time which oxygen bubbles require to rise within the respective pre-separator.

11. System according to one of the preceding claims, characterized in that the respective pre-separator (20) has a flow area (40) for water and, above the same, a collection area (41) for oxygen, wherein oxygen can be discharged from the collection area (41) via an outlet (39) for oxygen in such a way that a water pressure loss is limited.

12. System according to claim 11, characterized in that the outlet (39) for oxygen is assigned a throttle or a valve (43) which opens or closes depending on air detection by means of an air sensor.

13. System according to claim 11 or 12, characterized in that the respective pre-separator (20) has an inlet (37) for the mixture of water and oxygen on a first vertically extending wall (33), an outlet (38) for water below the inlet (37) and the outlet (39) for oxygen above the inlet (37), wherein starting from the first vertically extending wall (33) in the direction of an opposite second vertically extending wall (34) extends a partition wall (42) directed downwards in the direction of the second vertically extending wall (34) and ends at a distance from the second wall (34).

14. System according to claim 13, characterized in that the outlet (39) for oxygen is formed adjacent to the second vertically extending wall (34) in the region of an upper wall (36) of the respective pre-separator (20), said upper wall (36) extending obliquely upwards from the first vertically extending wall (33) in the direction of the second vertically extending wall (34).

15. System according to one of the preceding claims, characterized in that two or more of the electrolysis devices (10) are hydraulically connected in series such that water from a water discharge connection (17) of one electrolysis device (10) is connected to the water supply connection (16) of a subsequent electrolysis device (10), wherein the or a pre-separator (20) for oxygen is arranged between the water discharge connection of one electrolysis device (10) and the water supply connection (16) of the subsequent electrolysis device (10).

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