EP4061983A1

EP4061983A1 - Electrolysis device

Info

Publication number: EP4061983A1
Application number: EP20820315.8A
Authority: EP
Inventors: Martin HANDL
Original assignee: Eeg Elements Energy GmbH
Current assignee: Eeg Elements Energy GmbH
Priority date: 2019-11-21
Filing date: 2020-11-05
Publication date: 2022-09-28
Also published as: WO2021097506A1; WO2021097505A1

Abstract

The invention relates to an electrolysis device for alkaline electrolysis, comprising a first gas separator tower (1) for receiving hydrogen, a second gas separator tower (2) for receiving oxygen, and at least one electrolysis element with a hydrogen half-cell and an oxygen half-cell, wherein the hydrogen half-cell and the oxygen half-cell are separated by a diaphragm which is impermeable to electrolytes and permeable to ions, wherein the hydrogen half-cell comprises a first electrode for forming a cathode, wherein, at the first electrode, there is provided a first gas collecting chamber (21) which is connected to the first gas separator tower (1), and wherein the oxygen half-cell comprises a second electrode for forming an anode, wherein, at the second electrode, there is provided a second gas collecting chamber (33) which is connected to the second gas separator tower (2). Here, it is provided that the electrolysis device has an expansion vessel (4) for mixing the electrolytes, wherein the hydrogen half-cell and the oxygen half-cell of the at least one electrolysis element are connected to the expansion vessel (4) such that a connected fluid chamber is formed which comprises the first gas separator tower (1), the hydrogen half-cell, the expansion vessel (4), the oxygen half-cell and the second gas separator tower (2), and that the first gas separator tower (1) is reversibly closable and the second gas separator tower (2) allows an increase of a fill level of the electrolyte, in particular is open to the surroundings. The invention furthermore relates to a method for operating an electrolysis device.

Description

Electrolyzer

The invention relates to an electrolysis device according to the preamble of claim 1 and a method for operating an electrolysis device according to the preamble of claim 11.

Electrolysis devices for splitting water and for producing hydrogen and oxygen have been known for a long time. In particular, alkaline electrolysis has proven itself for use in industry.

The basic principle of operation of alkaline electrolysis can be explained as follows:

First, a container that serves as an electrolysis cell is equipped with two electrodes. The electrolytic cell is filled with a mixture of water and a lye, the electrolyte. A DC voltage of at least 1.5 volts is applied to the anode, the positive pole, or the cathode, the negative pole, of the electrolytic cell, which results in a splitting of water (H ₂ 0), with the hydrogen at the cathode -Molecules are released and the oxygen molecules at the anode. In the case of a uniformly thick electrode with a uniformly reactive surface, a uniform production of the hydrogen gas takes place on the electrode surface. When the electrode is positioned vertically, the proportion of liquid is very high in the lower part, while a proportion of gas or foam is deposited in the upper part.

The hydroxide ions (OH) produced when the water is split at the cathode are transported to the anode by the voltage difference between the electrodes. The applied voltage must be greater, the greater the distance between cathode and anode. In order to be able to reduce the distance between the electrodes without impairing the course of the reaction, an ion-permeable separating membrane is usually arranged between the cathode and the anode. The hydroxide ions are transported through this membrane or this diaphragm from the cathode to the anode and the hydroxide ions are recombined to water on the surface of the anode, with oxygen atoms being released which combine to form oxygen molecules. The oxygen formed then rises as a gas on the electrode.

Chemically, these reactions are expressed as follows:

Cathode reaction: 2 H ₂ 0 + 2e -> H ₂ + 2 OH Anode reaction: 2 OH -> 0.50 ₂ + H ₂ 0 + 2 e

Overall reaction: H ₂ + 0.50 ₂

The product gases rise on the front side facing the diaphragm. The resulting gases are diverted upwards and can be used further.

An important field of application of electrolysis devices is the storage of energy from electricity generation in the form of hydrogen. While burning fossil fuels allows electrical energy to be provided at any time when required, this is not possible with many others, especially with sustainable electricity sources. For example, the production of a solar system depends on the current solar irradiation and the production in wind turbines on the current wind strength. On the one hand, electricity is therefore produced even if it cannot be used, or electricity cannot always be generated when it is needed. Electrolysis devices enable the existing electricity to be used to carry out electrolysis. The resulting hydrogen can be stored and then used to generate electricity at a later point in time.

Since the transport of electrical energy is also associated with large losses, small, decentralized power generation systems are increasingly being used. Many companies and households produce their own electricity, for example with their own solar systems on the roof or with their own wind turbines. For these areas of application, however, there is currently no suitable option for converting or storing the electricity produced, since no suitable electrolysis devices are available.

Since oxygen and hydrogen are usually stored in pressure vessels in order to reduce the storage volume, many electrolysis devices operate at high pressures. The currently highest industrial pressure level is over 30 bar in constant operation. Such a system is shown, for example, in US 2012/0152734 A1. However, these systems require special safety devices and are therefore large and expensive.

Electrolysis devices that can be operated at normal pressure are also known. Such a device is shown, for example, in EP 3 575 442 A1. These devices are smaller because the gases are not compressed in the electrolysis device, but are usually connected downstream. However, are these devices are also unsuitable for use on a small and medium scale. On the one hand, these devices also still require a large amount of space, and on the other hand, the devices themselves have a high energy consumption and high noise emissions due to the pumps required.

With currently available electrolysis devices, the costs per kilowatt of power for alkaline electrolysis are more than EUR 800 / kW. In order to enable decentralized, economical storage, however, much more efficient and cost-effective devices are necessary.

There is thus a need for small and quiet electrolysers for use in small and medium-sized businesses and households.

The object of the invention is therefore to provide an electrolysis device which requires little space and enables operation that is as energy-efficient and quiet as possible.

This object is achieved by an electrolysis device with the characterizing features of claim 1.

According to the invention it is provided that the electrolysis device has an equalizing tank for mixing the electrolyte, the hydrogen half-cell and the oxygen half-cell of the at least one electrolysis element being connected to the equalizing tank so that it encompasses the first gas separator tower, the hydrogen half-cell, the equalizing tank, the oxygen half-cell and the second gas separator tower connected fluid space is formed. The first gas separator tower can be closed reversibly and the second gas separator tower enables the level of the electrolyte to rise.

The arrangement according to the invention enables thorough mixing of the electrolyte without the need for a pump system. The electrolysis device is therefore small and the noise emission is reduced. Furthermore, the efficiency of hydrogen production is increased. The gas separator tower, which enables the level of the electrolyte to rise, can be open to the environment, so that the electrolysis can be carried out at normal pressure. This has the advantage that a complex printing system can be dispensed with. The electrolysis device thus enables economical operation even with lower electricity production, as is the case, for example, in small solar systems on roofs or by small wind turbines. This electrolysis device can thus also enable economical storage of energy for private households and small businesses.

To operate the electrolysis device, a direct voltage is first applied to the electrodes. The product gases form on the electrodes. Both gases rise and are separated from the electrolyte liquid in the gas separator towers. When the reversibly closable gas separator tower is closed, the gas rises in the gas separator tower and the level of the electrolyte in this gas separator tower drops. The rising gas pushes the electrolyte downwards and the electrolysis element into the expansion tank. At the same time, the level in the other gas separator tower rises because the electrolyte is pressed from the expansion tank through the electrolysis element into the other gas separator tower. As soon as the reversibly closable gas separator tower is opened, the gas flows out of this gas separator tower and the level of the electrolyte rises in the closable gas separator tower, with the electrolyte flowing through the half-cells connected to the other gas separator tower, the expansion tank and the half-cells connected to the closable gas separator tower. The electrolyte is thus sufficiently mixed to enable permanent, economical operation of the electrolysis device.

The gases can be discharged or sucked out of the gas separator towers for further use.

Advantageous features are listed below:

In order to be able to use the electrolysis device particularly efficiently, a suction device can be connected downstream of the electrolysis device. For this purpose, a compressor can be provided on the outlet side of the first gas separator tower, in particular following a valve that reversibly closes the first gas separator tower in the direction of flow, for sucking off the hydrogen produced.

It is possible, for example, to connect to a compressor as disclosed in the international application PCT / AT2020 / 060388 "Compressor" by the same applicant from November 5, 2020, the compressor shown there being hereby incorporated as part of the present application. A system comprising an electrolysis device described here and such a compressor allows particularly efficient operation, since the cyclic suction provides a optimal mixing of the electrolyte and at the same time an effective compression of the resulting gas, in particular hydrogen, is made possible.

If particularly pure gases are to be produced, a corresponding filter can be attached to the electrolysis device in the direction of flow downstream of a valve that reversibly closes the first gas separator tower for further purification.

In order to enable particularly safe and efficient operation, it can be provided that the first gas separator tower can be closed as a function of the fill level.

In order to enable a simple measurement of the fill level, it can be provided in particular that a first sensor for detecting a first fill level of the electrolyte is provided in the first gas separator tower. In order to further increase safety, it can preferably be provided that at least a first maximum and / or a first minimum operating level can be detected. The maximum operating level is set in the upper area of the gas separator tower, the minimum operating level in the lower area of the gas separator tower. On the basis of these operating levels, the point in time for closing or opening the closable gas separator tower can be controlled particularly easily and efficiently. The same effects can be achieved if it is provided that a second sensor for detecting a second fill level of the electrolyte is provided in the second gas separator tower, whereby it is preferably provided that at least a second maximum and / or a second minimum operating fill level can be detected. If the level of the electrolyte is measured in both gas separator towers, redundant level measurement is made possible, which avoids many sources of error and enables reliable operation of the electrolysis device. The sensors can each be arranged either directly in the gas separator tower or, for example, in a parallel bypass or a level measuring chamber.

The safety of the electrolysis device can be improved if a sensor is designed to detect the total fill level of the electrolyte in the device. This makes it possible to determine whether the amount of electrolyte in the electrolysis device is sufficient to enable safe operation, in particular to avoid overheating of the device. In this case, the first and / or second sensor can be designed to measure the total fill level, with the second sensor preferably being able to detect the total fill level. The operation of the electrolysis device is particularly safe if it is provided that a minimum total fill level can be detected. As a result, when it is reached, the operation of the device can be stopped automatically in order to avoid overheating of the device. In order to enable simple maintenance, it can be provided that a maintenance indicator is provided which is connected to the sensor in such a way that a total fill level measured by the sensor is displayed. This makes it particularly easy to determine the point in time when it is necessary to top up with water.

The maintenance of the electrolyzer is also simplified when to

Level measurement, in particular as a first and / or second sensor, a measuring element for inductive measurement is provided. As a result, the sensor can be arranged outside the gas separator towers and can thus be serviced or replaced in a particularly simple manner. For this purpose, it can be provided in particular that an inductively detectable float, preferably made of graphite, is arranged. The float can either be arranged directly in the gas separator tower or in a filling level measuring chamber which is in fluid connection with the gas separator tower. This enables a particularly reliable measurement.

The mixing of the electrolyte is improved when the volume of the

Expansion tank corresponds to at least the volume of the first gas separator tower. In order to avoid overheating and to increase the safety of the electrolysis device, it can in particular be provided that the volume of the expansion tank corresponds to 120-200%, preferably 150%, of the volume of the first gas separator tower. The electrolysis device is particularly safe if the volume of the expansion tank corresponds to 110-130%, in particular 115%, of the volume in all of the electrolysis elements connected to the expansion tank. The device is particularly efficient if the expansion tank has a partition for partial

Separation of a first equalization area connected to the hydrogen half-cells and a second equalization area connected to the oxygen half-cells, the first and second equalization areas being connected to one another, in particular in the lower area of the equalization tank, preferably at the bottom of the equalization tank. If the expansion tank has a partition, it is particularly advantageous if the first compensation area has a volume which is at least 15% larger than the volume of the hydrogen half-cells and / or if the second compensation area has a volume which is at least 15% larger, than the volume of the oxygen half-cells. This can improve the purity of the gases. The mixing of the electrolyte is also improved if the volume of the first gas separator tower corresponds to 115-150%, in particular 140%, of the volume of all hydrogen half-cells. In order to improve the safety of the operation of the electrolysis device, it can be provided that the second gas separator tower has a volume that is greater than or equal to the volume of the first gas separator tower.

In order to further increase the safety of the electrolysis device, it can be provided that a cooling chamber is provided for throughflow cooling. The electrolysis device can be cooled particularly efficiently if the cooling chamber is arranged between the gas separator towers, the expansion tank and the at least one electrolysis element. If the connection between the connecting spaces and the gas separator towers is cooled and / or cooling of the gas separator towers is provided, cooled hydrogen or cooled oxygen is released from the electrolysis device. The cooled gases can be further processed particularly easily. If necessary, the cooling water heated by the electrolysis device can be reused, for example for a heating system. In this case, the electrolysis device can also be used for warm water preparation, whereby the energy efficiency can be further improved.

The structure of the electrolysis device can be simplified if a base unit is provided, the expansion tank being arranged in the lower area of the base unit, a first connection channel for connection to the hydrogen half-cell and a second connection channel for connection to the oxygen half-cell being provided on the top of the expansion tank , and wherein the gas separator towers are arranged in the upper region of the base unit, with a first connection space for connection to the first gas collecting space of the hydrogen half-cell being arranged on the underside of the first gas separating tower and a second connection space for connection with the second gas collecting space of the Oxygen half-cell. The electrolysis device can be designed to be particularly small and space-saving if it is provided that the base unit is designed in the form of a plate, whereby it is preferably provided that the base unit has a thickness of 2-100 mm, in particular 20-60 mm, preferably 40 mm . Particularly efficient cooling is possible if the cooling chamber is arranged in the base unit, in particular in the central area, the expansion tank preferably being arranged below the cooling chamber and the gas separator towers being arranged above the cooling chamber.

The electrolysis device can be designed to be particularly small and space-saving if the electrolysis element or the electrolysis elements are plate-shaped. The electrolysis element then comprises a first plate-shaped nickel electrode, a spacing which can be produced, for example, by a first element frame, a plate-shaped membrane, a further spacing which can be produced, for example, by a second element frame, and a second plate-shaped nickel electrode. The electrolysis device can be designed to be particularly space-saving if, in particular, it is provided that the electrolysis element has a thickness of 5-50 mm, in particular 8-14 mm. The hydrogen half-cells, the electrodes and the diaphragm are plate-shaped. The distance between the electrodes is 1–30 mm, in particular 6–8 mm, the diaphragm preferably being arranged in the middle. The distance from the diaphragm to the electrodes is then preferably 2 to 8 mm in each case.

The electrolysis device can also be designed to be small and space-saving if the at least one electrolysis element between the first electrode and the diaphragm has a first element frame for receiving the electrolyte, the first element frame having an open first gas collecting space for a connection to the first gas separator tower and an open first Having a connecting channel for a connection to the expansion tank and wherein the first element frame has a separate first flow space for a connection to the second gas separator tower and a separate first flow channel for a connection to the expansion tank.

The electrolysis element has a second element frame for receiving the electrolyte between the diaphragm and the second electrode, the second element frame having an open second gas collecting space for a connection to the second gas separator tower and an open second connection channel for a connection to the expansion tank. The second element frame has a separated second flow space for a connection to the first gas separator tower and a separated second flow channel for a connection to the expansion tank. The electrolysis device can be manufactured particularly efficiently if the first and second element frames are constructed identically.

The electrolysis device is particularly efficient if 1-100, in particular 10, electrolysis elements are provided. As a result, the electrical energy can be used to a large extent, since a large area is available for electrolysis. At the same time, thorough mixing of the electrolyte and efficient cooling of the electrolysis device can take place. In particular, the electrolysis elements are connected to form a stack, whereby it is preferably provided that the anodes of the electrolysis elements connected to the stack are connected in series and the cathodes of the electrolysis elements connected to the stack are connected in series. In this case, all hydrogen half-cells are preferably connected to one another and have a common connection, in particular a common first gas collecting space, to the first gas separator tower and a common connection, in particular a common first connecting channel, to the expansion tank. Likewise, all oxygen half-cells are preferably connected to one another and have a common connection, in particular a common second gas collecting space, to the second gas separator tower and a common connection, in particular a common second connecting channel, to the expansion tank. The individual gas collection spaces are connected by the individual flow spaces to form a common gas collection space. The individual connection channels are connected by the individual flow channels to form a common connection channel.

According to the invention, there is also a method for operating an electrolysis device, the electrolysis device having at least one electrolysis element for carrying out the electrolysis, the electrolysis element having a first reversibly closable gas separator tower for collecting hydrogen, and a second gas separating tower for collection, which enables the level of the electrolyte to rise is connected by oxygen, so that a fluid space connecting the at least one electrolysis element and the gas separator towers is formed, the electrolysis device being put into operation by applying a voltage to the electrolysis element, characterized in that

- the first gas separator tower is closed so that the hydrogen that forms is collected in the first gas separator tower, which leads to a drop in the level of the electrolyte in the first gas separator tower and, due to the connected fluid space, the level in the second gas separator tower increases at the same time, - while waiting for gas production,

- wherein the first gas separator tower is opened and the hydrogen produced is removed, so that the level in the first gas separator tower increases and the level in the second gas separator tower drops,

- wherein the opening and closing of the first gas separator tower is repeated.

This makes the operation of an electrolysis device particularly energy-efficient, since no pump is required to mix the electrolyte. At the same time, the noise emission is reduced and operation can be particularly quiet.

This method is particularly advantageous when operating a previously described electrolysis device.

Advantageous embodiments of the method are described below:

The method can be carried out particularly efficiently if the first gas separator tower is opened as a function of the fill level, with a measurement of an operating fill level of the electrolyte in the first and / or in the second gas separator tower. In particular, it can be provided that the first gas separator tower is closed when a predetermined first maximum operating level is reached in the first gas separator tower and / or a predetermined second minimum operating level is reached in the second gas separator tower. It can also be provided that the first gas separator tower is opened when a predetermined first minimum operating level is reached in the first gas separator tower and / or a predetermined second maximum operating level is reached in the second gas separator tower. As a result, particularly efficient mixing of the electrolyte can be achieved and the level-dependent opening can reduce the number of cycles and the noise emissions associated with opening and closing.

The reliability of the method can be improved if a volume of the electrolyte in the device is measured, with provision being made in particular that the fill level in the second gas separator tower is determined for this purpose, the electrolysis device being automatically stopped when a maintenance fill level below the minimum operating fill level is reached becomes. In order to be able to carry out the method in a particularly simple and cost-effective manner, it can be provided that the electrolysis is carried out at ambient pressure, it being provided in particular that the oxygen produced in the second gas separator tower is discharged into the environment.

In order to increase the efficiency of the method, it can be provided that the gas produced, in particular the hydrogen produced in the first gas separator tower, is sucked off. The mixing of the electrolyte is improved by the suction.

The same effect can be achieved if the first gas separator tower is opened and closed 2 to 50 times per minute, in particular 3 to 4 times per minute.

A particularly advantageous embodiment of a device according to the invention and a method according to the invention is shown below by way of example:

1a shows an exemplary base unit for an electrolysis device.

FIG. 1b shows the base unit from FIG. 1a from a first side.

FIG. 1c shows the base unit from FIG. 1a from a second side.

2a shows an exemplary first element frame for an electrolysis device from a first side.

2b shows an exemplary second element frame for an electrolysis device from a first side.

FIG. 2c shows the first or second element frame from FIGS. 2a and 2b from a second side.

3 shows an exemplary electrolysis device.

FIG. 4 shows the electrolysis device from FIG. 3 in a side view.

FIG. 5 shows the electrolysis device from FIG. 3 from below.

FIG. 6 shows the electrolysis device from FIG. 3 from a side view.

FIG. 7 shows the electrolysis device from FIG. 3 from a front side.

FIG. 8 shows the electrolysis device from FIG. 3 from a rear side.

3 shows an exemplary electrolysis device. The electrolysis device has a base unit 10. In the upper area of the electrolysis device, a first gas separator tower 1 is provided for receiving the hydrogen produced during the electrolysis. The first gas separator tower 1 can be closed reversibly by a valve. Furthermore, a second gas separator tower 2, which enables the level of the electrolyte to rise, is provided for receiving the oxygen produced during the electrolysis, which in the embodiment shown is open to the environment or to the atmosphere. A compensation tank 4 is arranged in the lower area. In the central area, at least one electrolysis element is provided for carrying out the electrolysis, a stack 3 with 10 connected electrolysis elements being arranged in the embodiment shown.

In the embodiment shown, each electrolysis element is plate-shaped and has a thickness of 10 mm. The electrolysis elements each comprise a hydrogen half-cell and an oxygen half-cell, the hydrogen half-cell and the oxygen half-cell being separated by an ion-permeable diaphragm which is impermeable to the electrolyte. The hydrogen half cell comprises a first electrode to form a cathode, the oxygen half cell comprises a second electrode to form an anode. In the embodiment shown, the electrodes are spaced 5 mm apart. In the embodiment shown, the electrodes are nickel electrodes.

1a shows an exemplary base unit 10. The base unit 10 is designed in the form of a plate. In the embodiment shown, the base unit 10 has a height of 150 cm, a width of 30 cm and a thickness of 4 cm. The expansion tank 4 is arranged in the lower region of the base unit 10, the first gas separator tower 1 and the second gas separator tower 2 are arranged in the upper region. The first gas separator tower 1 and the second gas separator tower 2 are separated in the base unit 10 by a web 18 in a fluid-tight manner, that is to say in a liquid-tight and gas-tight manner. A cooling chamber 5 for throughflow cooling is provided between the expansion tank 4 and the gas separator towers 1, 2. The stack 3 can be arranged in front of the cooling chamber 5. The base unit 10 and the electrolysis elements of the stack 3 are connected to one another at bores 15.

On the top of the expansion tank 4 there is a first connection channel 12 for the connection to the hydrogen half-cells of the electrolysis elements and a second connection channel 14 for connection with the oxygen half-cells of the electrolysis elements. On the underside of the first gas separator tower 1 there is a first connection space 11 for connection to the first gas collecting space 21 of the hydrogen half-cell and on the underside of the second Gas separator space 2, a second connection space 13 is provided for connection to the second gas collection space 33 of the oxygen half-cell.

In the electrolysis device, a continuous, connected fluid space for the electrolyte or the gases formed is formed, which extends from the first gas separator tower 1, through the hydrogen half-cells of the electrolysis elements of the stack 3, via the expansion tank 4, the oxygen half-cells of the electrolysis elements of the stack 3 and the second Gas separator tower 2 extends.

A first fill level measuring space 8, which corresponds to the first gas separator tower 1, and a second fill level measuring space 9, which corresponds to the second gas separator tower 2, are provided for filling level measurement. The level measuring spaces 8, 9 are attached to the gas separator towers 1, 2 in such a way that electrolyte can flow in on the underside and gas can flow in on the upper side. As a result, foam formation in the fill level measuring spaces 8, 9 is avoided and a particularly precise fill level measurement is made possible.

In the embodiment shown, a sensor for inductive level measurement is provided. An inductively detectable float can be arranged in the fill level measuring spaces 8, 9, which float rises and falls with the fill level of the electrolyte in the fill level measuring space 8, 9 or in the gas separator tower 1, 2. In the embodiment shown, the float made of graphite is provided, which can be easily detected and is particularly stable in the environment of the electrolyte.

Any other suitable method for measuring the fill levels can also be used, it being possible for example to provide a capacitive measurement.

In the embodiment shown, a first sensor for detecting a first fill level is provided on the outside of the first fill level measuring space 8. The first sensor can detect at least a first maximum and a first minimum operating level. The first maximum operating level is arranged in the upper region of the first gas separator tower 1. When the first maximum operating level is reached, the first gas separator tower can be closed so that the electrolyte from the first gas separator tower 1 can be prevented from overflowing. The first minimum operating level is arranged in the lower area of the gas separator tower 1. When the first minimum operating level is reached, the first gas separator tower 1 can be opened so that hydrogen can flow out of the first gas separator tower 1 and the electrolyte into the first Gas separator tower 1 can flow in, so that the hydrogen half-cells connected to the first gas separator tower 1 remain filled with electrolyte.

A second sensor for detecting a second fill level in the second gas separator tower 2 is provided on the outside of the second fill level measuring space 9. The sensor detects at least a second maximum and a second minimum operating level. The second maximum operating level is specified in the upper area of the second gas separator tower 2. When the second maximum operating level is reached, the first gas separator tower 1 is opened so that the hydrogen is removed and the electrolyte rises in the first gas separator tower 1 and falls in the second gas separator tower 2. This can prevent the second gas separator tower 2 from overflowing. The second minimum operating level is specified in the lower area of the second gas separator tower 2. This can prevent the fill level in the second gas separator tower 2 from dropping too far and the oxygen half-cells can be prevented from running dry.

Furthermore, the second sensor can detect the total fill level of the electrolyte in the device, the difference between the fill levels being used in the embodiment shown. At least a minimum total fill level can be detected by the sensor. When the minimum total level is reached, the electrolysis is automatically stopped.

In an embodiment not shown, a maintenance indicator, for example a scale, can be provided which shows the fill level of the electrolyte in the device. This makes it particularly easy to determine when water has to be topped up in the device in order to avoid reaching the minimum total fill level and stopping the electrolysis.

1b shows the base unit 10 from the side facing away from the stack 3.

1c shows the side of the base unit 10 facing the stack 3. The first and second gas separator towers 1, 2 have the same volume of 5 l in the embodiment shown.

The volume of the expansion tank 4 in the embodiment shown comprises 7.5 I and in the embodiment shown corresponds to 150% of the volume of the first gas separator tower 1. The volume of the expansion tank 4 thus corresponds to 115% of the volume in all of the electrolysis elements connected to the expansion tank 4 Stacks 3. The expansion tank 4 has a partition 17. This partition wall 17 protrudes from the upper end of the expansion tank 4 downwards, where it is in lower area of the expansion tank 4 ends. The partition 17 partially separates a first compensation area connected to the hydrogen half-cells and a second compensation area connected to the oxygen half-cells from one another. This prevents the gases formed from reaching the other half-cells, which in turn leads to the gases formed being mixed. The two compensation areas are connected at the lower end, in the embodiment shown, at the bottom of the compensation tank 4. In the embodiment shown, the two compensation areas are of the same size. The volume of the compensation areas is each 15% greater than the volume of the electrolysis half-cells connected to the compensation area.

Each electrolysis element is composed of a first electrode, a first element frame 20 for the hydrogen half cells, a diaphragm, a second element frame 30 for the oxygen half cells and a second electrode.

2a shows the first element frame 20 for the hydrogen half-cell of an electrolysis element of the stack 3.

The element frame 20 is plate-shaped and has a square outline. In the embodiment shown, the first element frame 20 is approximately 5 mm thick. In the corner areas, on a first side at the top, the first gas collecting space 21 for connecting to the first connecting space 11 of the base unit 10 and to the first gas separator tower 1 and, at the bottom, the connecting channel 22 for connecting to the first connecting channel 12 to the expansion tank 4. The gas collecting space 21 and the connecting channel 22 are open to the interior of the first element frame 20, so that the interior is filled with the electrolyte during operation and the electrolyte is in contact with the cathode. In the corner areas on the other, second side of the first element frame 20, a first throughflow space 23 and at the bottom a first throughflow channel 24 are formed, which are separated from the interior of the first element frame 20 and which are connected to the oxygen half-cells, the second gas separator tower 2 and the expansion tank 4 are.

FIG. 2b shows the second element frame 30 for the oxygen half-cell of the electrolysis element 3. The second element frame 30 is structurally identical to the first element frame 20 from FIG. 2a. The second element frame 30 is rotated by 180 ° so that in the corner areas on the first side a second flow space 31 is formed at the top and a second flow channel 32 is formed at the bottom, each of which is separated from the interior of the second element frame 30, which is filled with the electrolyte during operation and with the hydrogen cells, the first gas separator tower 1 and the surge tank 4 are connected. On the second side, the second gas collecting space 33 for connecting to the second connecting space 13 and for connecting to the second gas separator tower 2 is formed at the top. At the bottom, the connecting channel 34 is designed for connecting to the second connecting channel 14 for connecting to the expansion tank 4. The gas collecting space 33 and the connecting channel 34 are open to the interior of the second element frame 30, so that the electrolyte can flow past the anode during operation.

2c shows the rear side of the element frames 20, 30.

In the embodiment shown, the base unit 10 and the element frame 20, 30 are made of PTFE (polytetrafluoroethylene), since this is particularly resistant and durable. In the embodiment shown, the seals are made of EPDM (ethylene propylene diene rubber), as this has particularly good sealing properties. In the embodiment shown, nickel electrodes are provided as electrodes.

3 shows the first gas separator tower 1, the second gas separator tower 2, the expansion tank 4 and the stack 3. In the stack 3, the electrolysis elements are arranged one behind the other and connected in series. The first connection point 6 is connected to the anodes of the electrolysis elements, the second connection point 7 is connected to the cathodes of the electrolysis elements. In the embodiment shown, a cooling system 5 is also provided, which is arranged between the gas separator towers 1, 2, the stack 3 and the expansion tank 4.

4 and 6 each show a side view of the electrolysis device. In the embodiment shown, the base unit 10 is designed to be particularly flat and therefore particularly space-saving. The stack 3 has a side surface of 300 ^* 400 mm.

Fig. 5 shows the electrolysis device from below. The base area of the stack 3 is 300 ^* 400 mm in the embodiment shown.

7 shows the electrolysis device in a view of the stack 3. In the embodiment shown, the front surface of the stack 3 is 300 ^* 300 mm. In the embodiment shown, the stack 3 is cuboid and therefore has a particularly small volume and at the same time provides a large surface for carrying out the electrolysis.

The electrolysis device shown has a height of 150 cm, a width of 33 cm and a depth of 45 cm. In the illustrated embodiment

1 sqm electrolysis area provided. When the electrolysis device is operated at normal pressure, with a power consumption of 8 kWh, 1800-2200 l hydrogen / hour can be generated with the embodiment shown.

An exemplary method for operating an electrolytic device can be guided by the following steps:

At the beginning of the electrolysis operation, both gas separator towers 1, 2 are approximately half full. The first gas separator tower 1 is closed by a valve, the second gas separator tower 2 is open to the environment. In the embodiment described, a suction device is provided on the first gas separator tower 1 or the first gas separator tower 1 is connected to a compressor.

First, a voltage is applied to the electrolysis elements of the electrolysis device in order to start the electrolysis. In the embodiment described, a DC voltage of at least 1.5 volts is used for each electrolysis element.

The hydrogen formed rises, but cannot escape through the closed first gas separator tower 1. This creates a pressure that the

Pushes the electrolyte column down so that the first level of the electrolyte drops. The electrolyte is pressed into the expansion tank 4 through the hydrogen half-cells of the stack 3. The hydrogen half-cells are connected to the oxygen half-cells via the expansion tank 4. The electrolyte is therefore pressed out of the expansion tank 4, through the oxygen half-cells and out of the oxygen half-cells into the second gas separator tower 2. As a result, the second level in the second gas separator tower 2 rises to the same extent as the level in the first

Gas separator tower 1 sinks. The volume of the hydrogen formed thus displaces the electrolyte from the first gas separator tower 1 and leads to an increase in the fill level in the second gas separator tower 2. If in the second gas separator tower

2 the second level has reached a maximum operating level, a minimum operating level is reached in the first gas separator tower 1 at the same time. When these fill levels are reached, the first gas separator tower 1 is opened. This results in a level equalization between the first and second gas separator towers 1, 2. In the embodiment shown, the cyclic suction switches on, which is arranged following the valve of the first gas separator tower in the direction of flow. By opening the first gas separator tower 1, the collected gas can escape. The electrolyte is sucked through the electrolysis elements of the stack 3 in the direction of the first gas separator tower 1. The rise and fall of the fill level result in excellent mixing of the electrolyte and even heat distribution. At the same time, a pump for mixing the electrolyte can be dispensed with, so that the process can be carried out in a more energy-efficient manner and the device works particularly quietly.

When the electrolyte in the first gas separator tower 1 reaches a maximum operating level, a minimum operating level is simultaneously reached in the second gas separator tower 2. The first gas separator tower 1 is then closed. The process starts all over again. In the exemplary method described, the first gas separator tower 1 is opened and closed approximately 3-4 times per minute.

The combination of filling level measurement on both sides enables the filling amount of the electrolyte in the device to be determined particularly precisely. As a result, the method can run particularly reliably and trouble-free. Furthermore, the amount of water to be topped up during maintenance can be precisely determined. If the total level of the electrolyte reaches a minimum maintenance level, the electrolysis is automatically stopped to prevent the device from overheating.

The alkaline electrolysis can be carried out at a temperature of 40 to 90 ° C. Flow cooling can be provided to dissipate the resulting heat. The warmed-up cooling water can, for example, be used for heating water.

The device shown and the method shown create a safe, inexpensive, space-saving and noise emission-reduced possibility of efficiently converting electrical energy into hydrogen and thus storing it.

Claims

Patent claims:

1. Electrolysis device for alkaline electrolysis comprising a first gas separator tower (1) for the absorption of hydrogen, a second gas separator tower (2) for the absorption of oxygen, and at least one electrolysis element with a hydrogen half-cell and an oxygen half-cell, the hydrogen half-cell and the oxygen half-cell by a for an electrolyte impermeable and ion-permeable diaphragm are separated, wherein the hydrogen half-cell comprises a first electrode for forming a cathode, wherein a first gas collecting space (21) is provided on the first electrode, which is connected to the first gas separator tower (1), and wherein the Oxygen half-cell comprises a second electrode for forming an anode, with a second gas collecting chamber (33) being provided on the second electrode, which is connected to the second gas separator tower (2), characterized in that the electrolysis device has an expansion tank (4) for Durc The mixture of the electrolyte, the hydrogen half-cell and the oxygen half-cell of the at least one electrolysis element being connected to the expansion tank (4) so that the first gas separator tower (1), the hydrogen half-cell, the expansion tank (4), the oxygen half-cell and the second gas separator tower (2 ) is formed with a comprehensive connected fluid space, and that the first gas separator tower (1) can be closed reversibly and the second gas separator tower (2) enables the level of the electrolyte to rise, in particular is open to the environment.

2. Electrolysis device according to claim 1, wherein the first gas separator tower (1) can be closed reversibly depending on the fill level, it being provided in particular that a first sensor is provided for detecting a first fill level in the first gas separator tower (1), it is preferably provided that at least one first maximum and / or a first minimum operating fill level can be detected, and / or it is provided in particular that a second sensor is provided for detecting a second fill level in the second gas separator tower (2), whereby it is preferably provided that at least a second maximum and / or or a second minimum operating level can be detected.

3. Electrolysis device according to claim 1 or 2, wherein a sensor, in particular the first and / or second sensor, is designed to detect the total level of the electrolyte in the device, it being provided in particular that a minimum total level can be detected, preferably one Maintenance indicator is provided, which is connected to the sensor in such a way that a total fill level measured by the sensor can be displayed.

4. Electrolysis device according to one of claims 2 or 3, wherein a measuring element for inductive measurement is provided for level measurement, in particular as a first and / or second sensor, it is provided in particular that an inductively detectable float, preferably made of graphite, is provided.

5. Electrolysis device according to one of claims 1 to 4, wherein the volume of the expansion tank (4) corresponds at least to the volume of the first gas separator tower (1), it being provided in particular that the volume of the expansion tank (4) 120 to 200%, preferably 150 %, of the volume of the first gas separator tower (1) and / or where the volume of the expansion tank (4) corresponds to 110 to 130%, in particular 115%, of the volume in all of the electrolysis elements connected to the expansion tank (4).

6. Electrolysis device according to one of claims 1 to 5, wherein the volume of the first gas separator tower (1) corresponds to 115 to 150%, in particular 140%, of the volume of all hydrogen half-cells and / or that the second gas separator tower (2) has a volume that is greater or equal to the volume of the first gas separator tower (1).

7. Electrolysis device according to one of claims 1 to 6, wherein a cooling chamber (5) is provided for throughflow cooling, it being provided in particular that the cooling chamber (5) between the gas separator towers (1, 2), the expansion tank (4) and the at least an electrolysis element is arranged.

8. Electrolysis device according to one of claims 1 to 7, wherein a base unit (10) is provided, wherein the expansion tank (4) is arranged in the lower region of the base unit (10), with a first connection channel (4) on the top of the expansion tank (4). 12) is provided for the connection to the hydrogen half-cell and a second connection channel (14) for connection to the oxygen half-cell, and wherein the gas separator towers (1, 2) are arranged in the upper region of the base unit (10) are, with a first connection space (11) for connection to the first gas collecting space (21) of the hydrogen half-cell being arranged on the underside of the first gas separator tower (1) and a second connection space (21) for connection with the underside of the second gas separator tower (2) the second gas collecting space (33) of the oxygen half-cell, it being provided in particular that the base unit (10) is plate-shaped, it is preferably provided that the base unit (10) has a thickness of 2 to 100 mm.

9. Electrolysis device according to claim 8, wherein a cooling chamber for flow cooling is arranged in the base unit (10).

10. Electrolysis device according to claim 9, wherein the expansion tank (4) is arranged below the cooling chamber (5) and the gas separator towers (1, 2) are arranged above the cooling chamber (5).

11. Electrolysis device according to one of claims 1 to 10, wherein the electrolysis element is plate-shaped, it being provided in particular that the electrolysis element has a thickness of 5 to 50 mm, preferably 8-14 mm.

12. Electrolysis device according to one of claims 1 to 11, wherein the at least one electrolysis element between the first electrode and the diaphragm has a first element frame (20) for receiving the electrolyte, wherein the first element frame (20) has an open first gas collecting space (21) for a connection to the first gas separator tower (1) and an open first connection channel (22) for a connection to the expansion tank (4) and wherein the first element frame (20) has a separate first flow space (23) for a connection to the second gas separator tower (2) and a separate first flow channel (24) for connection to the expansion tank (4), and wherein the electrolysis element has a second element frame (30) between the diaphragm and the second electrode, the second element frame (30) having an open second gas collecting space ( 33) for a connection to the second gas separator tower (2) and an open second Ver Binding channel (34) for a connection to the expansion tank (4) and wherein the second element frame (30) has a separate second flow space (32) for a Connection to the first gas separator tower (1) and a separated second flow channel (34) for connection to the expansion tank (4), whereby it is preferably provided that the first and second element frames (16, 26) are constructed identically.

13. Electrolysis device according to one of claims 1 to 12, wherein 1 to 100, in particular 10, electrolysis elements are provided, wherein it is provided in particular that the electrolysis elements are connected to a stack (3), it is preferably provided that the anodes of the stack (3) connected electrolysis elements are connected in series and the cathodes of the electrolysis elements connected to the stack (3) are connected in series.

14. Electrolysis device according to one of claims 1 to 13, wherein on the output side of the first gas separator tower (1), in particular a valve reversibly closing the first gas separator tower (1) in the direction of flow, a compressor is provided for sucking off the hydrogen produced.

15. A method for operating an electrolysis device, in particular according to one of claims 1 to 14, wherein the electrolysis device has at least one electrolysis element for performing the electrolysis, the electrolysis element with a first reversibly closable gas separator tower (1) for collecting hydrogen, and with a second a gas separator tower (2) allowing a fill level increase of the electrolyte is connected for the collection of oxygen, so that a fluid space connecting the at least one electrolysis element and the gas separator towers (1, 2) is formed, the electrolysis device being put into operation by applying a voltage to the electrolysis element, characterized that

- The first gas separator tower (1) is closed so that the hydrogen that forms is collected in the first gas separator tower (1), which leads to a drop in the level of the electrolyte in the first gas separator tower (1) and, due to the connected fluid space, an increase in the level at the same time takes place in the second gas separator tower (2),

- while waiting for gas production,

- The first gas separator tower (1) is opened and the hydrogen produced is removed, so that the level in the first gas separator tower (1) increases and the level in the second gas separator tower (2) falls at the same time,

- The opening and closing of the first gas separator tower (2) being repeated.

16. The method according to claim 15, wherein the first gas separator tower (1) is opened depending on the fill level, the operating level of the electrolyte being measured in the first gas separator tower (1) and / or in the second gas separator tower (2), it being provided in particular

- That the first gas separator tower (1) is closed when a predetermined first maximum operating level is reached in the first gas separator tower (1) and / or a predetermined second minimum operating level is reached in the second gas separator tower (2) and / or

- That the first gas separator tower (1) is opened when a predetermined first minimum operating level is reached in the first gas separator tower (1) and / or a predetermined second maximum operating level is reached in the second gas separator tower (2).

17. The method according to any one of claims 15 or 16, wherein a measurement of the volume of the electrolyte located in the device is carried out, wherein it is provided in particular that the level in the second gas separator tower (2) is determined for this purpose, with one below the minimum operating level being reached when the maintenance level is lying, the electrolysis device is automatically stopped.

18. The method according to any one of claims 15 to 17, wherein the electrolysis is carried out at ambient pressure, it being provided in particular that the oxygen produced in the second gas separator tower (2) is discharged into the environment.

19. The method according to any one of claims 15 to 18, wherein the gas formed, in particular the hydrogen formed in the first gas separator tower (1), is sucked off.

20. The method according to any one of claims 15 to 19, wherein the first gas separator tower (1) is opened and closed 2 to 50 times per minute, in particular 3-4 times per minute.