ELECTROLYSIS UNIT AND ELECTROLYZER

Description

[0001] The invention relates to an electrolysis unit with at least one electrolysis cell and a method for operating the electrolysis cell.

[0002] An electrolyzer is a device that uses electrical current to transform a substance (electrolysis). In keeping with the variety of different electrolysis processes, there are also a variety of electrolyzers, such as an electrolyzer for hydrogen electrolysis.

[0003] Current considerations are to use surplus energy from renewable energy sources during periods of abundant sun and wind, i.e., when solar or wind power generation is above average, to generate valuable materials. One such valuable material could be hydrogen, which is produced using water electrolyzers. This hydrogen can be used, for example, to produce so-called renewable gas.

[0004] A (hydrogen electrolysis) electrolyzer first generates hydrogen using electrical energy, particularly from wind or solar energy. The hydrogen is then combined with carbon dioxide in a Sabatier process to produce methane. The methane can then be fed into an existing natural gas grid, for example, enabling energy storage and transport to consumers, thus relieving the strain on the electrical grid. Alternatively, the hydrogen produced by the electrolyzer can also be used directly, for example, in a fuel cell.

[0005] DE 10 2011 053 142 A1, CH 108 697 A, and CN 101 654 787 A disclose alkaline electrolysis systems in which gas separation devices are provided, arranged above the electrolysis cell. DE 38 37 354 A1 describes a method for securing a pressurized water electrolysis system with an electrolysis cell block and oxygen and hydrogen separators arranged higher in the direction of gravity. The aim is to create a solution that reduces the security effort required for pressurized water electrolysis, achieves the necessary safety using simple means, and enables the operation of pressureless electrolysis cells. Corresponding electrolysis systems are also known from US 4 323 442 A, JP 2003 342771 A, and KR 101 769 751 B1.

[0006] In an electrolyzer for hydrogen electrolysis, water is split into hydrogen and oxygen. In a PEM electrolyzer, distilled water is typically added as the reactant on the anode side and split into hydrogen and oxygen at a proton-permeable membrane (PEM). The water is oxidized to oxygen at the anode. The protons pass through the proton-permeable membrane. Hydrogen is produced on the cathode side.

[0007] The water should be constantly pumped into the anode and / or cathode compartments to ensure even distribution of the water in these compartments and thus effective electrolytic splitting of the water. Pumping is typically achieved using pumps. The disadvantage is that pumps require regular maintenance. Furthermore, the pumping rate must be regulated depending on the pressure in the electrolysis cell to achieve a consistent reactant throughput. This requires additional control technology, which makes the electrolyzer design more complex. Furthermore, the pumps consume electrical energy, which adversely reduces the overall efficiency of the electrolysis.

[0008] The object of the present invention is therefore to provide a water electrolyzer and a method for operating a water electrolyzer which is energy-efficient and low-maintenance.

[0009] The object is achieved with an electrolysis unit according to claim 1 and a method according to claim 2.

[0010] The electrolysis device according to the invention for the electrolysis of water comprises at least one electrolysis cell, wherein the electrolysis cell comprises an anode compartment with an anode and a cathode compartment with a cathode. The anode compartment is separated from the cathode compartment by a proton exchange membrane. The anode compartment is suitable for receiving water and oxidizing it at the anode to a first product comprising oxygen. The cathode compartment is suitable for receiving water and reducing it at the cathode to a second product comprising hydrogen. The electrolysis device further comprises a first gas separation device for separating oxygen, wherein the first gas separation device is arranged above the electrolysis cell to carry out natural water circulation.

[0011] In the method according to the invention for operating an electrolysis device for the electrolysis of water, a first product comprising oxygen and a second product comprising hydrogen are produced from water as the reactant in an electrolysis cell by means of acidic electrolysis. The reactant, the first product, and / or the second product are circulated naturally.

[0012] Natural circulation refers to the circulation of water into and through the electrolysis cell, and the circulation of water and products from the electrolysis cell to the gas separation device. This circulation occurs naturally, i.e., without the use of pumps, due to the density differences between the components. The gas bubbles created in the electrolysis cell lead to a lower water density. Due to this density difference, the water and products flow through the electrolysis cell without the use of a mechanical pump.

[0013] Advantageously, both the water supply and the heat management of the electrolysis system are achieved through natural circulation on both the oxygen and hydrogen sides, or exclusively on the oxygen side. This advantageously avoids the use of a mechanical circulation device to circulate the water and products. This advantageously reduces the system's maintenance intervals and thus also its downtime. Advantageously, the physical principle of natural circulation, based on density differences, regulates the water flow rate automatically, i.e., without the intervention of controllers. With a suitable process design, the water flow rate adapts to the system's heat loss. In other words, this means that with increased heat production, the water flow rate increases.Furthermore, the higher the gas separator is positioned above the electrolysis cell, the higher the production rate is achieved, provided the gas-water mixture contains a constant amount of gas.

[0014] The electrolysis device comprises a first line connected to an upper portion of the anode chamber and the first gas separation device. The electrolysis device further comprises a second line connected to the first gas separator and a lower portion of the anode chamber.

[0015] The first line serves as the riser pipe, the second as the downpipe. Advantageously, the water and the products rise through the first line into the gas separation device. In the gas separation device, the gas, i.e., the product—in this case, oxygen—is separated from the water. The water, which now has a higher density than the product-water mixture, is returned to the anode chamber of the electrolysis cell via the second line, the downpipe. Oxygen is produced there, which reduces the density, causing the water-product mixture to rise again in the riser pipe.

[0016] The electrolysis device comprises a second gas separation device for separating hydrogen, a third line connected to an upper portion of the cathode chamber and the second gas separation device, and a fourth line connected to the second gas separation device and a lower portion of the cathode chamber, wherein the second gas separation device is arranged above the electrolysis cell to carry out a natural water circulation.

[0017] The third line serves as the riser pipe, the fourth as the downpipe. These lines connect the second gas separation device to the cathode side of the electrolysis cell. The water-hydrogen mixture, which has a lower density than pure water, advantageously rises in the riser pipe. It then reaches the second gas separation device, where the hydrogen is separated from the water. The water, which now has a higher density than the product-water mixture, is returned to the cathode chamber via the downpipe, i.e., the fourth line.

[0018] In a further advantageous embodiment and development of the invention, a first diameter of the first line is smaller than a second diameter of the third line.

[0019] The water splitting takes place in simplified form according to equation 1: H2O ( l ) → H 2 ( g ) + 1< / 2 O 2 ( g)     (1)

[0020] Equation (1) shows that approximately twice the volume of hydrogen is produced as that of oxygen. If the electrolyzer cells and piping are designed identically for the hydrogen and oxygen sides, the hydrogen side therefore has a higher water production rate than the oxygen side. If the electrolysis unit is designed such that the production rate is limited by the riser pipe, i.e. the first and / or third line, the production rate can be optimized by adjusting the riser pipe diameter. Due to the lower gas volume flow on the oxygen side, it is possible that a lower water production rate is present there. If the diameter of the riser pipe on the oxygen side, i.e. the first line, is dimensioned smaller than the third line, a higher water production rate can advantageously be achieved.It is particularly advantageous if the first line on the oxygen side has approximately half the cross-sectional area compared to the cross-sectional area of ​​the third line on the hydrogen side.

[0021] A first heat exchanger is located in the second line, and a second heat exchanger is located in the fourth line. The first and second heat exchangers are thermally coupled.

[0022] In a non-claimed embodiment and development of the invention, the first and second heat exchangers are materially coupled to one another. In other words, this means that there is only one common heat exchanger. This can, in particular, comprise two inlet openings, one for the oxygen-side water and one for the hydrogen-side water, and a common outlet opening.

[0023] Within the electrolysis cell, due to the process involved in splitting water, both protons and water are transported from the oxygen side, i.e., the anode compartment, to the hydrogen side, i.e., the cathode compartment. If the anode-side water and the cathode-side water are separated from each other, this disadvantageously leads to a level shift in the gas separation devices. Mixing the materials in the heat exchanger advantageously prevents a level shift in the gas separation devices. This advantageously prevents the cathode compartment or the anode compartment from being completely emptied, which would result in a gas mixing of the hydrogen and oxygen. A slight increase in the hydrogen concentration on the oxygen side does not impair the safe operation of the electrolysis system, since only the dissolved gases are mixed, not the gas phase.For this reason in particular, it is also advantageous if this mixing takes place at the lowest point of the system in order to achieve the greatest possible distance between the two gas phases comprising oxygen and hydrogen.

[0024] According to the invention, the second line and the fourth line are connected via a connecting line for water equalization. This connecting line, also called a bypass line, is arranged such that the water from the anode side and the water from the cathode side are mixed shortly before entering the electrolysis cell, particularly at the lowest point of the system. The natural water circulation occurs naturally due to the density differences between the water and the products, without the use of pumps.

[0025] Within the electrolysis cell, during the water splitting process, a certain amount of water is transported from the oxygen side to the hydrogen side, along with protons. If the anode-side water and the cathode-side water are separated from each other, this disadvantageously leads to a level shift in the gas separation devices. This level shift is advantageously avoided due to the process-related water transport from the oxygen side to the hydrogen side in the electrolysis cell. This advantageously avoids the need to pump additional water into one of the gas separation devices. By mixing the two water streams shortly before entering the electrolysis cell, only a small amount of dissolved hydrogen is transported to the oxygen side of the electrolysis cell, which does not endanger the safe operation of the system.

[0026] In a further advantageous embodiment, the electrolysis device comprises at least two electrolysis cells and at least two first gas separation devices, wherein the first gas separation devices are connected via a siphon-like fifth line suitable for conducting the water.

[0027] In a further advantageous embodiment and development of the invention, the electrolysis device comprises at least two electrolysis cells and at least two second gas separation devices. The second gas separation devices are connected via a siphon-like sixth line suitable for conducting the water.

[0028] Advantageously, these connecting lines simplify the construction of an electrolysis stack, i.e. an electrolysis unit comprising at least two electrolysis cells, since the number of lines is reduced.

[0029] In a further advantageous embodiment and development of the invention, the electrolysis device comprises a closable opening in the cathode chamber, which is suitable for partially accommodating a seventh line, in other words a second riser line, which connects the cathode chamber to the second gas separation device. This seventh line is arranged opposite the third line in the cathode chamber. If it becomes necessary to increase the hydrogen delivery rate, which the third line can no longer ensure as a riser pipe, the hydrogen-water mixture can additionally rise via the seventh line into the second gas separation device. The effective cross-section of the riser pipe is thus achieved by the hydrogen-water mixture flowing out of the electrolysis cell on both sides, which advantageously prevents the limitation of the water delivery.Experiments have shown that the operating point of the electrolysis plant can thus be brought back to an optimal operating point with regard to the production characteristics.

[0030] In a further advantageous embodiment and development of the invention, the electrolysis device comprises a supply device for fresh water. This is arranged such that the fresh water can be added to the fifth and / or sixth line. Particularly preferably, the amount of water consumed during the reaction is fed into the fifth line, i.e., the connecting line of the first gas separation devices for oxygen. Particularly advantageously, the water then replaces the water consumed on the anode side. This advantageously avoids the need for additional piping to the individual gas separation devices, simplifying the construction of the electrolysis unit. Connecting the first and / or second gas separation devices equalizes the fill levels of the first and / or second gas separation devices via the water return line.By connecting the hydrogen and oxygen gas separators via the water circuit before entering the cell stacks, they balance each other out.

[0031] Due to the leveling effect on each gas side or the equalization of the gas sides via the heat exchanger circuit, the electrolysis cells, or several connected electrolysis stacks, advantageously have a balanced filling level in the respective gas separation devices.

[0032] In a further advantageous embodiment and development of the invention, the operating pressure in the electrolysis device is in a range from 0.5 bar to 2 bar, particularly preferably at 1 bar, i.e., atmospheric pressure. At this atmospheric pressure, the density differences caused by gas production in the electrolysis cell are so great that natural circulation is reliably ensured, thus allowing the electrolysis unit to be operated without the use of pumps. In other words, the operating pressure of the electrolysis device is a maximum of 0.5 bar above or below the operating pressure of the first and / or second gas separation device.

[0033] In a further advantageous embodiment and development of the invention, the oxygen-water mixture is fed from the first line into the first gas separation device at the level of the liquid fill level in the first gas separation device. In other words, the feed opening in the first gas separation device is located at the level of the phase boundary between gas and liquid in the first gas separation device. Advantageously, the hydrogen-water mixture is also added from the third line to the second gas separation device at the level of a second liquid fill level, which designates the phase boundary in the second gas separation device. In other words, this also means that the feed opening in the second gas separation device is located at the level of the phase boundary between gas and liquid.Advantageously, the flow rate is higher if the distance between the return line from the first and / or second gas separation device is designed to be minimal.

[0034] In a further advantageous embodiment and development of the invention, the fifth and / or sixth line comprises at least one pressure control valve. The pressure control valves are located at the end of the pipeline connecting the gas separation devices on each gas side. If, for example, the first and second gas separation devices are mechanically identical, it is crucial that no level shift occurs. This means that if one gas side has a higher pressure, the water shifts to the corresponding other gas side. The use of a pressure control valve advantageously prevents this.

[0035] Further features, characteristics, and advantages of the present invention will become apparent from the following description with reference to the accompanying figures, which schematically show: Figure 1 shows an electrolysis unit with a first and a second gas separation device; Figure 2 shows an electrolysis cell with a proton exchange membrane; Figure 3 shows an electrolysis unit with a first and a second gas separation device and a water bypass; Figure 4 shows an electrolysis unit comprising two electrolysis cells and interconnected first gas separation devices.

[0036] Figure 1shows a first embodiment of an electrolysis unit 1 with an electrolysis cell 2. The electrolysis cell 2 comprises a proton exchange membrane 3, which separates the anode compartment 4 from the cathode compartment 5. The anode compartment 4 comprises an anode 7. The cathode compartment 5 comprises a cathode 8. In the anode compartment 4, water H 2 O is oxidized to oxygen O 2 at the anode. The oxygen-water mixture produced in the anode compartment 4 during electrolysis has a lower density than pure water. As a result, it rises in the first line 9, also called a riser pipe, into a first gas separation device 20. The first gas separation device 20 is located above the anode compartment 4. In the first gas separation device 20, the oxygen is separated from the water. The oxygen O 2 can be led out of the electrolysis unit 1. The water is led via a second line 10 into a heat exchanger 6.In the cathode compartment, water is reduced to hydrogen H2 at the cathode 8 during electrolysis. Due to its lower density compared to water, the hydrogen-water mixture rises via a third line 11 into a second gas separation device 21. In the second gas separation device 21, the hydrogen is separated from the water. The hydrogen leaves the electrolysis unit 1. The water can be led into the heat exchanger via a fourth line 12. The water is then led from the heat exchanger 6 back into the anode compartment 4 and the cathode compartment 5. The heat exchanger is operated with a coolant, in particular water. No mass transfer takes place between this coolant and the water from the electrolysis. The coolant inflow and outflow from the heat exchanger 6 is not shown for the sake of clarity. Figure 1 , 3 , and 4 shown.

[0037] Advantageously, the electrolysis unit 1 can be operated dynamically, i.e. depending on the load input, the electrolysis unit 1 can be operated with an energy density of more than 0 A / cm 2< up to 4 A / cm 2< , particularly preferably of more than 1 A / cm 2< up to 3 A / cm 2< .

[0038] The first and second gas separation devices 20, 21 are located at a height h 2 . The maximum height of the electrolysis cell is h 1 . The height h 2 is above the height h 1 . This ensures natural circulation of the reactants and products in the electrolyzer solely due to the density differences that arise in the electrolyzer. However, both heights must be above the height h 1 of the electrolysis cell. Additional pumps or other conveying devices are advantageously not necessary. As an alternative to the design shown here, it is also possible to carry out natural circulation exclusively on the oxygen side, i.e. in the anode chamber 4. The principle of natural circulation, which is based on the physical parameter of density, regulates the water flow rate itself. This means that with a suitable process design, the water flow rate increases with an increased gas production rate, which in turn advantageously dissipates the heat.

[0039] The operation of natural circulation at atmospheric pressure is particularly advantageous, since the gas bubble size of the hydrogen and / or oxygen and thus the resulting transport capacity with regard to the gases and water is sufficiently large so that pumps can be completely dispensed with.

[0040] The water circuits of the hydrogen and oxygen sides, i.e. the water in the anode chamber 4 and the cathode chamber 5, are connected to each other via the heat exchanger 6.

[0041] Based on the reaction equation for water splitting, it is clear that approximately twice the volume of hydrogen gas is produced as oxygen gas when the water is split. Thus, if the hydrogen side and the oxygen side have the same pipe diameter, the hydrogen side would have a higher water delivery rate than the oxygen side, as long as the delivery rate is not limited by the pipe diameter. If the water delivery rate is limited by the riser pipe, the delivery rate can be optimized by adjusting the riser pipe diameter. In order to optimize the water flow on both sides, the first diameter 13 of the first line 9 is dimensioned smaller than the second diameter 14 of the third line 11. Particularly advantageously, the first line 9 has a cross-sectional area of ​​approximately half the cross-sectional area of ​​the third line 11.Advantageously, a higher water delivery rate can be achieved, especially on the anode side, compared to a conventional, similar pipe diameter distribution.

[0042] Figure 2shows an electrolysis cell with a proton exchange membrane. The electrolysis cell comprises an anode 7 and a cathode 8. Bipolar plates 30, 31 border the two electrodes 7, 8, respectively. The bipolar plates each border a porous support structure 32. The reactant water flows through this support structure 32 through the electrolysis cell 2. The porous support structure 32, in turn, borders an electrocatalytic layer 33. An electrocatalytic layer 33 is arranged in the anode compartment 4, and an electrocatalytic layer 33 is arranged in the cathode compartment 5. The electrocatalytic layer 33 on the anode side typically comprises iridium, and the electrocatalytic layer 33 on the cathode side typically comprises platinum. The proton exchange membrane (PEM) is located between these two catalytic layers 33.

[0043] This comprises, in particular, a sulfonated fluoropolymer, particularly preferably comprising perfluorosulfonic acid. One advantage of the PEM electrolysis cell is that pure water can be used as the reactant. It is advantageous not to use lye or other liquid components as a carrier component for the water.

[0044] In a further embodiment of an electrolysis unit 1 with an electrolysis cell 2, not shown in the figures, an alternative arrangement of the riser pipes 11 from the cathode chamber 5 is used. All components are arranged in the same way as in the first embodiment in Figure 1Only an additional riser pipe connects the cathode chamber 5 to the second gas separation device 21. If the delivery rate is insufficient due to the existing operating conditions despite the different cross-sectional areas of the riser pipes 10 and 11, an additional second riser line 15 can be provided on the hydrogen side. This second riser line, in other words the seventh line, advantageously guarantees a sufficiently high delivery rate of the water and hydrogen into the second gas separation device 21. It is also conceivable that the first embodiment and the second embodiment can be combined. In other words, this means that a second riser line is provided, but it is only opened via the use of valves when necessary due to the delivery rate on the hydrogen side.

[0045] Figure 3shows a third embodiment of an electrolysis unit 1 with an electrolysis cell 2 with a first gas separation device 20 and a second gas separation device 21. The gas separation devices 20, 21 are each connected to the anode chamber 4 and cathode chamber 5 via riser pipes 9, 11. The gas separation devices 20, 21 are each connected to the heat exchanger 6 via a second line 10 and a fourth line 12. The second line 10, in turn, connects the heat exchanger 6 to the anode chamber 4. The fourth line 12 connects the heat exchanger 6. In other words, the heat exchanger 6 is arranged in the second line 10, and the heat exchanger 6' is also arranged in the fourth line 12. No mass transfer takes place in the heat exchangers 6 and 6', so that the returned water from the anode side is separated from the returned water from the cathode side.The disadvantage of completely separating the water circuits in this way would be a level shift in the gas separators, since during the water splitting reaction, not only protons but also water is transported from the oxygen side to the hydrogen side. The water circuits are connected to one another by the piping layout shown in this third exemplary embodiment, which provides a bypass line 16 between the second line 10, i.e., the anode chamber 4, and the fourth line 12, i.e., the cathode chamber 5. Advantageously, the returning water streams are not mixed with one another in the heat exchanger 6, but only immediately before entering the electrolysis cell 2. By connecting the cathode chamber to the anode side, a communicating system is formed, which advantageously ensures that the water flow from the hydrogen side to the oxygen side is balanced.A slight increase in the hydrogen concentration on the oxygen side does not impair the safe operation of the system. If the water streams are already mixed in heat exchanger 6, the residence time of the mixed water streams is significantly longer. This can lead to an increase in the respective foreign gas concentration in the gas separator. If only a directed water flow is directed from the hydrogen to the oxygen side via the bypass connection 16, this potentially only increases the hydrogen concentration in the oxygen in the gas separator. The safety of the system is thus further enhanced.

[0046] In all three examples of the Figure 1 , 3 and 4It becomes clear that the water-gas mixture is fed into the gas separation devices 20, 21 close to the phase boundary in the gas separation devices 21 and 22. This is ensured by regulating pressure valves connected to the gas separation devices 20, 21 (not shown in the figures). Since both containers are hydraulically connected, almost the same fill level is achieved in both gas separation devices 21 and 20. The prerequisite for this is that the pressure losses caused by the gas flow in the pipes connecting to the gas separation devices 20, 21 do not generate any significant pressure losses in the gas separation device 20, 21. In other words, the pipe diameters of the pipes are large enough that there is no limitation of the material flow and thus no level shift occurs in the gas separation devices 20, 21.

[0047] Figure 4shows an electrolysis unit 1 with two electrolysis cells 2. Both electrolysis cells each have a first gas separation device 20, 20' on the oxygen side and a second gas separation device 21, 21' on the hydrogen side. The water recirculation is designed analogously to the first exemplary embodiment such that the returning water streams mix in the heat exchanger and are then fed back to the oxygen side into the electrolysis cell. Alternatively, it is also conceivable to implement a bypass according to the third exemplary embodiment. The oxygen-side gas separation devices 20, 20 are connected to one another via a siphon-like fifth line 17. Furthermore, the fifth line 17 comprises a supply device 18 for fresh water. In this exemplary embodiment, there is a one-sided circulation operation on the oxygen side.Connecting several electrolysis cells via the siphon-like fifth line 17 advantageously ensures the replenishment of water, which advantageously prevents the liquid level in the gas separation devices 20, 21 from dropping below the set level. The fresh water used during the reaction is advantageously supplied to the fifth line 17, which connects the first gas separation devices 20. This advantageously avoids the need for additional piping to the gas separation devices.

[0048] To minimize the likelihood of gas leakage and thus avoid a malfunction, the first gas separation devices 20, 20' on the oxygen side are connected to one another and, separately, the second gas separation devices 21, 21' on the hydrogen side are connected to one another. In other words, the gas separation devices are only connected to one another in such a way that the oxygen side remains separated from the hydrogen side. In addition to the embodiment shown in Figure 5, it is also possible to connect the second gas separation devices 21 on the hydrogen side via a siphon-like line. This advantageously equalizes the fill levels between the second gas separation devices 21.

Claims

1. Electrolysis device (1) for the electrolysis of water, having: - at least one electrolysis cell (2), wherein the electrolysis cell (2) comprises an anode space (4) having an anode (7) and a cathode space (5) having a cathode (8), wherein the anode space (4) is separated from the cathode space (5) by means of a proton exchange membrane (3), and the anode space (4) is suitable for receiving water and oxidizing it at the anode (7) to give a first product comprising oxygen and the cathode space (5) is suitable for receiving water and reducing it at the cathode (8) to give a second product comprising hydrogen; - a first gas separating apparatus (20) for the separation of oxygen; wherein the first gas separating apparatus (20) is arranged above the electrolysis cell (2) for the purposes of performing a natural circulation of water, - a first line (9) which is connected to an upper section of the anode space (4) and to the first gas separating apparatus (20) and - a second line (10) which is connected to the first gas separating apparatus (20) and to a lower section of the anode space (4), - a second gas separating apparatus (21) for the separation of hydrogen; - a third line (11) which is connected to an upper section of the cathode space (5) and to the second gas separating apparatus (21) ; - a fourth line (12) which is connected to the second gas separating apparatus (21) and to a lower section of the anode space (4) and / or cathode space (5), wherein the second gas separating apparatus (21) is arranged above the electrolysis cell (2) for the purposes of performing a natural circulation of water, wherein a first heat exchanger (6) is arranged in the second line (10) and a second heat exchanger is arranged in the fourth line (12) and the first heat exchanger (6) and the second heat exchanger are thermally coupled, and - the second line (10) and the fourth line (12) are connected via a connection line (16) for the purposes of water equalization, wherein the natural circulations of water take place naturally due to the density differences of the water and the products, without the use of pumps.

2. Method for operating an electrolysis device (1) according to Claim 1 for the electrolysis of water, wherein in the electrolysis cell (2) the oxygen-comprising first product and the hydrogen-comprising second product are produced by means of electrolysis at the proton-exchange membrane (3) from water as starting material, wherein circulation of the starting material, the first product and the second product takes place in the form of natural circulation of water which takes place naturally due to the density differences of the water and the products, without the use of pumps.

3. Method according to Claim 2, wherein the prevailing operating pressure is atmospheric pressure.