Alkaline electrolysis device

Abstract

The present invention relates to an alkaline electrolysis device comprising: - at least one electrolysis cell having a reactor chamber, which has a hydrogen-side reactor-chamber region, containing the aqueous electrolyte, for breaking down the aqueous electrolyte into gaseous hydrogen and has an oxygen-side reactor-chamber region, containing the aqueous electrolyte, for breaking down the aqueous electrolyte into gaseous oxygen; - a hydrogen separator, which is connected to the hydrogen-side reactor-chamber region, for separating the gaseous hydrogen from the aqueous electrolyte introduced into the hydrogen separator; and - an oxygen separator, which is connected to the oxygen-side reactor-chamber region, for separating the gaseous oxygen from the aqueous electrolyte introduced into the oxygen separator; wherein the hydrogen separator comprises a first hydrogen-separator outlet for removing the aqueous electrolyte having a first hydrogen concentration, and a second hydrogen-separator outlet for removing the aqueous electrolyte having a second hydrogen concentration that is lower than the first hydrogen concentration; and wherein the first hydrogen-separator outlet and the second hydrogen-separator outlet can be or are connected to the reactor chamber.

Description

[0001] ALKALINE ELECTROLYSIS DEVICE

[0002] The present invention relates to an alkaline electrolysis device for decomposing aqueous electrolyte into hydrogen and oxygen, comprising at least one electrolysis cell with a reactor chamber comprising a hydrogen-side reactor chamber region and an oxygen-side reactor chamber region; a hydrogen separator for separating the gaseous hydrogen from the aqueous electrolyte introduced into the hydrogen separator; and an oxygen separator for separating the gaseous oxygen from the aqueous electrolyte introduced into the oxygen separator.

[0003] In alkaline electrolysis systems, partial chemical reactions in the hydrogen-side reactor chamber and the oxygen-side reactor chamber lead to a concentration gradient of the respective aqueous electrolyte. Therefore, mixing of the two electrolyte streams is necessary, which first leave the reactor chamber before one or more mixed electrolyte streams can be recirculated to the reactor chamber.

[0004] Since a gas separation degree of 100% cannot be achieved in the hydrogen separator and the oxygen separator in practical application, gas impurities occur in the mixed electrolyte stream(s). Within the scope of the present invention, gas impurities can be understood in particular to mean that gaseous and / or dissolved hydrogen is supplied to the oxygen-side reactor chamber region above a percentage limit. Conversely, gaseous and / or dissolved oxygen is supplied to the hydrogen-side reactor chamber region above a percentage limit. As a rule, this limit must not exceed 2% on either side, as otherwise there is a risk of the formation of an explosive hydrogen-oxygen mixture.

[0005] Alkaline electrolysis devices are already known from the prior art. A generic alkaline electrolysis device is described, for example, in the non-patent literature by P. Haug, M. Koj, and T. Turek, "Influence of process conditions on gas purity in alkaline water electrolysis," International Journal of Hydrogen Energy, pp. 9406-9418, 2017. This non-patent literature describes an electrolysis device in which it is possible to switch between separate and mixed circuits in order to enable a lower partial load. Another generic alkaline electrolysis device is known from US Pat. No. 2,717,872 A. The object of the present invention is to provide an alkaline electrolysis device of the type mentioned above that has a higher level of efficiency and is safer to operate.

[0006] This object is achieved according to the invention in a generic alkaline electrolysis device in that the alkaline electrolysis device can comprise at least one electrolysis cell with a reactor chamber for decomposing aqueous electrolyte into hydrogen and oxygen.

[0007] Furthermore, it can be provided that the reactor chamber comprises a hydrogen-side reactor chamber region containing the aqueous electrolyte for decomposing the aqueous electrolyte into gaseous hydrogen.

[0008] In addition, the reactor chamber may comprise an oxygen-side reactor chamber region containing the aqueous electrolyte for decomposing the aqueous electrolyte into gaseous oxygen.

[0009] Furthermore, the alkaline electrolysis device may comprise a hydrogen separator for separating the gaseous hydrogen from the aqueous electrolyte introduced into the hydrogen separator, wherein the hydrogen separator is connected to the hydrogen-side reactor chamber region.

[0010] It is also advantageous if the alkaline electrolysis device comprises an oxygen separator for separating the gaseous oxygen from the aqueous electrolyte introduced into the oxygen separator, wherein the oxygen separator is connected to the oxygen-side reactor chamber region.

[0011] It may also prove advantageous if the hydrogen separator has a first hydrogen separator outlet for removing the aqueous electrolyte with a first hydrogen concentration and a second hydrogen separator outlet for removing the aqueous electrolyte with a second hydrogen concentration which is lower than the first hydrogen concentration.

[0012] The first hydrogen separator outlet and the second hydrogen separator outlet may also preferably be connectable or connected to the reactor chamber for returning the aqueous electrolyte with the first hydrogen concentration and with the second hydrogen concentration from the hydrogen separator into the reactor chamber.

[0013] An alkaline electrolysis device can be understood, in particular, as an electrolysis device that can be operated with an alkaline electrolyte or with a caustic soda as the electrolyte. For example, the aqueous electrolyte can be an aqueous solution of potassium hydroxide (also called potassium hydroxide solution). Additionally or alternatively, the aqueous electrolyte can be an aqueous solution of sodium hydroxide (also called caustic soda solution). Other aqueous alkaline solutions or caustic sodas based on other metal hydroxides are also conceivable in this context.

[0014] The decomposition of aqueous electrolyte into hydrogen and oxygen can preferably be understood as the basic principle of water electrolysis, according to which the decomposition of water into hydrogen and oxygen occurs with the aid of electrical current. For this purpose, the alkaline electrolysis device can comprise at least one electrolysis cell with a reactor chamber. In this context, it can be provided that the alkaline electrolysis device can have several such electrolysis cells, which in a stacked arrangement form so-called stacks. For example, the alkaline electrolysis device can have 2, 3, 4, 5, 6, 7, 8, 9 or 10, or several tens or several hundred of such electrolysis cells, which in a stacked arrangement then form the stack.

[0015] As described above, the reactor chamber can comprise the hydrogen-side reactor chamber region and the oxygen-side reactor chamber region, which are separated in a liquid-tight manner by a membrane. This membrane can preferably be designed as an ion-exchange membrane in the form of an ion-permeable polymer membrane. Particularly preferably, this membrane can be designed as an anion-exchange membrane in the form of an anion-permeable polymer membrane. This membrane can be designed to be gas-tight and only allow the transport of OH' ions from the hydrogen-side reactor chamber region to the oxygen-side reactor chamber region and vice versa, but at the same time prevents the mixing of the resulting product gases, hydrogen and oxygen, and the electrolyte. The membrane can preferably be made of a plastic composed of a perfluorinated copolymer.Alternatively or in addition to the membrane, a diaphragm can also be provided, which separates the hydrogen-side reactor chamber area from the oxygen-side reactor chamber area in a liquid-tight manner. Furthermore, the hydrogen-side reactor chamber area can have a negative electrode (also called a cathode) and the oxygen-side reactor chamber area can have a positive electrode (also called anode) to generate the cell voltage required for water electrolysis. The cell voltage can, for example, be a direct voltage of at least 1.5 volts.

[0016] The oxygen-side reactor chamber area can therefore be the area of ​​the reactor chamber in which the formation of gaseous oxygen takes place according to the following reaction equation (1):

[0017] 4OH- -> 2H2O + 4e- + O2(1).

[0018] The hydrogen-side reactor chamber area can therefore be the area of ​​the reactor chamber in which the formation of gaseous hydrogen takes place according to the following reaction equation (2):

[0019] 4H2O + 4e- -> 2H2+ 4OH' (2)

[0020] From the two reaction equations mentioned above, it follows that water is formed (along with oxygen) in the aqueous electrolyte in the oxygen-side reactor chamber, whereas water is extracted from the aqueous electrolyte in the hydrogen-side reactor chamber (forming hydrogen). This results in the concentration gradient in the aqueous electrolyte described above, so that it must be thoroughly mixed before re-entering the reactor chamber.

[0021] After the aqueous electrolyte has been decomposed or after the OH' ions have been recombined into gaseous oxygen and hydrogen in the respective oxygen-side reactor chamber region and hydrogen-side reactor chamber region, the electrolyte can be introduced into the hydrogen separator and the oxygen separator. The hydrogen separator can also be considered a hydrogen separator device or a component of such a device. Accordingly, the oxygen separator can also be considered an oxygen separator device or a component of such a device. The hydrogen separator can preferably be designed as a separator based on gravity and / or centrifugal force. Accordingly, the oxygen separator can also preferably be designed as a separator based on gravity and / or centrifugal force.The degree of separation of gaseous oxygen and hydrogen in the respective oxygen separator or hydrogen separator depends significantly on the residence time of the electrolyte in the respective oxygen separator or hydrogen separator. Accordingly, in the case of the hydrogen separator, a first hydrogen concentration can be assigned to a first residence time, and a second hydrogen concentration can be assigned to a second residence time that is longer than the first residence time. The same applies to the case of the oxygen separator, in which a first oxygen concentration can be assigned to a first residence time, and a second oxygen concentration can be assigned to a second residence time that is longer than the first residence time.

[0022] Accordingly, the aqueous electrolyte can be returned from the hydrogen separator to the reactor chamber with the first hydrogen concentration and with the second hydrogen concentration. This has the advantage that electrolytes with different hydrogen concentrations can be returned to the hydrogen-side and oxygen-side reactor chamber areas. Since gaseous hydrogen is to be generated in the hydrogen-side reactor chamber area anyway, the return of the electrolyte with the first hydrogen concentration is not critical. However, the hydrogen concentration of the aqueous electrolyte being returned to the oxygen-side reactor chamber area is critical, since gaseous hydrogen is considered a contaminant on the oxygen side and should not exceed a limit of 2% (since hydrogen and oxygen form an explosive mixture at a concentration above 4%).

[0023] Consequently, the recirculation of the electrolyte with the second hydrogen concentration (which is lower than the first hydrogen concentration) can improve the gas purity on the oxygen side, which increases the efficiency of the alkaline electrolysis device and improves its operational reliability. Furthermore, the flow rate in the reactor chamber can be advantageously controlled independently of the degree of mixing, thus further increasing efficiency. Consequently, the flow rate can be adjusted to optimize temperature and bubble detachment in the reactor chamber. Furthermore, the alkaline electrolysis device can be operated at a lower lower partial load (particularly when operating at elevated pressure) and / or at a lower alkali concentration (which improves corrosion resistance), e.g., due to the improved gas purity.The lower partial load has the advantage of increasing the overall load range, which is advantageous, for example, in the case of fluctuating electricity prices and / or fluctuating demand. In this regard, it can be provided that the first hydrogen separator outlet is connectable or connected to an inlet of the hydrogen-side reactor chamber region by means of a first hydrogen-side electrolyte return line for returning the aqueous electrolyte with the first hydrogen concentration from the hydrogen separator to the hydrogen-side reactor chamber region. Since the hydrogen-side reactor chamber region is uncritical with respect to returned electrolyte with gaseous hydrogen (in this case with the first hydrogen concentration being greater than the second hydrogen concentration), this type of return from the hydrogen separator is particularly advantageous.

[0024] Furthermore, the oxygen separator can have a first oxygen separator outlet for removing the aqueous electrolyte with a first oxygen concentration, wherein the first oxygen separator outlet can be connected or connected to an inlet of the oxygen-side reactor chamber region by means of a first oxygen-side electrolyte return line for returning the aqueous electrolyte with the first oxygen concentration from the oxygen separator to the oxygen-side reactor chamber region. Since the oxygen-side reactor chamber region is similarly uncritical with respect to returned electrolyte with gaseous oxygen (in this case with the first oxygen concentration being greater than the second oxygen concentration), this type of return from the oxygen separator is also particularly advantageous.

[0025] In addition, it may prove advantageous if the second hydrogen separator outlet is connectable or connected to the first oxygen-side electrolyte return line by means of a second hydrogen-side electrolyte return line for branching and returning the aqueous electrolyte with the second hydrogen concentration from the hydrogen separator into the first oxygen-side electrolyte return line.

[0026] From the above, it follows that the oxygen-side reactor chamber region is critical for recirculated electrolyte containing gaseous or dissolved hydrogen (in this case, with the second hydrogen concentration being lower than the first oxygen concentration). However, since the aqueous electrolyte leaving the hydrogen-side and oxygen-side reactor chamber regions exhibits concentration differences, these electrolyte flows can be balanced by mixing before re-entering these reactor chamber regions. Due to the connectivity or connection described here, electrolyte with the second hydrogen concentration can now be recirculated to the oxygen-side reactor chamber region (to balance the concentration), which has a beneficial effect on efficiency and operational reliability, as already explained above.

[0027] A first or second hydrogen-side or first oxygen-side electrolyte return line can be understood as a line whose line inlet opens into the respective outlet of the first or second hydrogen separator or into the outlet of the first oxygen separator. A connection can preferably be understood as a direct flow connection, whereas a connectability can be understood as, for example, a conditional connection (e.g., by means of a control and / or regulating valve) or an indirect connection (e.g., by means of a conveying device). The conveying device can, for example, be designed as a conveying pump or comprise such a pump.

[0028] The oxygen separator may further comprise a second oxygen separator outlet for withdrawing the aqueous electrolyte having a second oxygen concentration that is less than the first oxygen concentration.

[0029] A second oxygen-side electrolyte return line can also be understood as a line whose line inlet opens into another outlet of the second oxygen separator.

[0030] According to a further advantageous embodiment, it is conceivable that the second oxygen separator outlet is connectable or connected to the first hydrogen-side electrolyte return line by means of the second oxygen-side electrolyte return line for branching and returning the aqueous electrolyte with the second oxygen concentration from the oxygen separator into the first hydrogen-side electrolyte return line.

[0031] The hydrogen-side reactor chamber region can also be critical to recirculated electrolyte containing gaseous or dissolved oxygen (in this case, with the second oxygen concentration being lower than the first oxygen concentration). As described above, the aqueous electrolyte leaving the hydrogen-side and oxygen-side reactor chamber regions exhibits concentration differences of the metal hydroxide dissolved therein (e.g., potassium hydroxide). Consequently, these differences can be advantageously compensated by mixing before re-entering these reactor chamber regions. Due to the previously described connectivity or connection, electrolyte with the second, lower oxygen concentration can now be returned to the hydrogen-side reactor chamber region (to equalize the concentration), which also has a beneficial effect on efficiency and operational reliability.

[0032] The hydrogen separator may, for example, comprise a first hydrogen separator unit for separating gaseous hydrogen from the aqueous electrolyte introduced into the first hydrogen separator unit, and a second hydrogen separator unit for separating gaseous hydrogen from the aqueous electrolyte introduced into the second hydrogen separator unit. In other words, the hydrogen separator or hydrogen separator device may be constructed using two subunits—the first and second hydrogen separator units—which may allow for a more efficient separation of the gaseous hydrogen from the aqueous electrolyte.

[0033] Accordingly, the first hydrogen separator unit can be configured to separate gaseous hydrogen from the aqueous electrolyte in such a way that the aqueous electrolyte can have the first hydrogen concentration as a result of this separation. Furthermore, it can be provided that the second hydrogen separator unit is configured to separate gaseous hydrogen from the aqueous electrolyte in such a way that the aqueous electrolyte has the second hydrogen concentration as a result of this separation. The first and / or the second hydrogen separator unit can or can preferably operate according to the principle of gravity, according to which the heavier electrolyte in both hydrogen separator units collects below the lighter gaseous hydrogen in the direction of gravity, thus resulting in phase separation.Alternative principles for hydrogen separation such as centrifugal separation can also be used in the first and / or second hydrogen separation unit.

[0034] Furthermore, it can be provided that the first hydrogen separator unit has the first hydrogen separator outlet, and the second hydrogen separator unit has the second hydrogen separator outlet. Due to the more efficient separation of hydrogen from the aqueous electrolyte by these two separator units, the second oxygen concentration can be further reduced compared to a single oxygen separator. This can further reduce hydrogen contamination in the oxygen-side reactor chamber region, which can have an even more positive effect on efficiency and operational reliability.

[0035] Between the first hydrogen separator unit and the second

[0036] For example, a throttle can be installed in the hydrogen separator unit. This throttle can reduce the pressure in the second hydrogen separator unit, thereby achieving even better separation.

[0037] A hydrogen-side branch line can branch off from the first hydrogen-side electrolyte return line, which is connected to the second hydrogen separator unit for supplying the second hydrogen separator unit with the aqueous electrolyte having the first hydrogen concentration. A control and / or regulating valve can preferably be arranged in the branch line for controlling and / or regulating the electrolyte mass flow and / or the electrolyte volume flow that can be supplied to the second hydrogen separator unit. Thus, advantageously, the electrolyte mass flow returned to the hydrogen-side reactor chamber region, on the one hand, and the electrolyte mass flow returned to the oxygen-side reactor chamber region (for mixing), on the other hand, can be controlled and / or regulated, thereby further improving efficiency and operational reliability.Furthermore, various operating strategies for mixing can optionally be implemented depending on the recirculated and / or branched electrolyte mass flow for the operation of the alkaline electrolysis device.

[0038] The oxygen separator can further comprise an oxygen outlet for removing gaseous oxygen from the oxygen separator, wherein the oxygen outlet is connectable or connected to the hydrogen separator by means of an oxygen feed line for feeding the gaseous oxygen into the hydrogen separator. By feeding gaseous oxygen into the hydrogen separator, the partial pressure of the gaseous hydrogen can be reduced, thereby reducing its solubility on the one hand and increasing its tendency to outgassing on the other. The hydrogen, which is more difficult to separate from the aqueous electrolyte due to its decreasing bubble size (the smaller the bubble size, the more difficult it is to separate from the electrolyte) as a result of an increasing electrolyte mass flow, can consequently outgas in greater quantities from the aqueous electrolyte within the hydrogen separator.This further improves the separation efficiency between gaseous hydrogen and the electrolyte, resulting in a lower level of hydrogen contamination in the electrolyte used for mixing. This translates, among other things, into improved efficiency and increased safety of the alkaline electrolysis system. Furthermore, the hydrogen concentration in oxygen is more critical, as more hydrogen is produced than oxygen (molar ratio 2 to 1). Consequently, more hydrogen is dissolved in the aqueous electrolyte, which is enhanced by the diffusion of hydrogen (due to the smaller molecular size) through the membrane.

[0039] In this case, it may be advantageous if the oxygen outlet is connected to the second hydrogen separator unit via the oxygen feed line for feeding gaseous oxygen into the second hydrogen separator unit. As already explained above, the aqueous electrolyte with the second hydrogen concentration serves for recirculation and branching into the first oxygen-side electrolyte return line to equalize the electrolyte concentration. Since the hydrogen obtained primarily originates from the first hydrogen separator unit, feeding oxygen into this first hydrogen separator unit would be counterproductive or safety-critical, as it would then result in an explosive mixture.In this respect, feeding into the second hydrogen separator unit is particularly advantageous, as the hydrogen content here may not exceed 2%, for example, so that the oxygen content in the gas phase is always at least 98%, preventing the formation of an explosive mixture. This means that the separation efficiency in a two-stage separation of the hydrogen from the aqueous electrolyte can be further increased by the oxygen feed (in addition to the effect of the improved separation by the first and second hydrogen separator units themselves). Only in the version in which the second hydrogen separator unit is connected to the oxygen feed line does it apply that it may contain a maximum of 2% hydrogen. However, the fed-in oxygen should be separated from the contaminated hydrogen on the oxygen side by means of an oxygen purification unit (as described below).Without such purification, the additional separation of hydrogen in the second hydrogen separation unit would not justify the expense of feeding oxygen. If no oxygen is fed into the second hydrogen separation unit, the gas phase would have to contain at least 98% hydrogen to prevent an explosive mixture from forming.

[0040] An oxygen purification unit can be arranged in the oxygen feed line for removing gaseous hydrogen from the gaseous oxygen. The oxygen purification unit can comprise a polymer membrane with high hydrogen permeability. Additionally or alternatively, the oxygen purification unit can comprise a microchannel palladium membrane oxygen purification unit. Additionally or alternatively, the oxygen purification unit can comprise a pressure swing adsorption oxygen purification unit. Additionally or alternatively, the oxygen purification unit can also be operated as a catalytic reaction unit for the catalytic reaction of hydrogen and oxygen to form water.Using the oxygen purification unit, the hydrogen content in the oxygen can be minimized, allowing even purer oxygen to be fed to the second hydrogen separation unit, resulting in an even better separation of gaseous hydrogen from the aqueous electrolyte in the second hydrogen separation unit. Finally, the partial pressure of hydrogen can be further reduced by the even purer oxygen.

[0041] Additionally or alternatively, it can be provided that the oxygen outlet is connectable or connected to an oxygen feed inlet of the oxygen separator by means of the oxygen feed line for feeding the gaseous oxygen back into the oxygen separator. In this case, a portion of the oxygen (contaminated with hydrogen) downstream of the oxygen outlet is purified as described above and returned to the oxygen separator via the oxygen feed inlet, thereby further improving oxygen separation in the electrolyte. This improvement has the further advantage that the electrolysis device can be operated at even lower partial load, which increases the overall load range (which is advantageous, for example, in the case of fluctuating electricity prices and / or demand).

[0042] Preferably, an oxygen reservoir can be arranged in the oxygen feed line, which can be arranged between the oxygen purification unit and the second hydrogen separator unit. The oxygen reservoir can preferably be designed as an oxygen buffer reservoir. An oxygen feed valve can also be arranged between the oxygen reservoir and the second hydrogen separator unit for controlling and / or regulating the incoming oxygen. By means of the oxygen reservoir and / or the oxygen feed valve, the incoming oxygen mass flow can be dampened so that it can be supplied more evenly to the second hydrogen separator unit, which can result in further improved hydrogen separation from the aqueous electrolyte.

[0043] Furthermore, the oxygen separator may comprise a first oxygen separation unit for separating gaseous oxygen from the aqueous electrolyte introduced into the first oxygen separation unit, and a second oxygen separation unit for separating gaseous oxygen from the aqueous electrolyte introduced into the second oxygen separation unit. In other words, the oxygen separator or the oxygen separation device may be constructed using two subunits—the first and second oxygen separation units—which may allow for more efficient separation of the gaseous oxygen from the aqueous electrolyte.

[0044] In this regard, it can be provided that the first oxygen separator unit is configured to separate gaseous oxygen from the aqueous electrolyte in such a way that the aqueous electrolyte has the first oxygen concentration as a result of this separation. Furthermore, the second oxygen separator unit can be configured to separate gaseous oxygen from the aqueous electrolyte in such a way that the aqueous electrolyte has the second oxygen concentration as a result of this separation. The first and / or the second oxygen separator unit can preferably operate according to the principle of gravity, according to which the heavier electrolyte in both oxygen separator units collects below the lighter gaseous oxygen in the direction of gravity, thus resulting in phase separation.Alternative principles for oxygen separation, such as centrifugal separation, can also be applied in the first and / or second hydrogen separation unit. The first and / or second oxygen separation unit can be designed as vertical or horizontal oxygen separation units.

[0045] Furthermore, it is conceivable for the first oxygen separator unit to have the first oxygen separator outlet and the second oxygen separator unit to have the second oxygen separator outlet. Due to the more efficient separation of oxygen from the aqueous electrolyte by these two separator units, the second oxygen concentration can be further reduced compared to a single oxygen separator used. This can further reduce oxygen contamination in the hydrogen-side reactor chamber region, which can have a positive effect on efficiency and operational reliability. A throttle can be arranged between the first oxygen separator unit and the second oxygen separator unit. This throttle can reduce the pressure in the second oxygen separator unit, thereby achieving even better separation.

[0046] An oxygen-side branch line can branch off from the first oxygen-side electrolyte return line and be connected to the second oxygen separator unit for supplying the second oxygen separator unit with the aqueous electrolyte having the first oxygen concentration. A further control and / or regulating valve can preferably be arranged in the branch line for controlling and / or regulating the electrolyte mass flow that can be supplied to the second oxygen separator unit. Thus, advantageously, the electrolyte mass flow returned to the oxygen-side reactor chamber region, on the one hand, and the electrolyte mass flow returned to the hydrogen-side reactor chamber region (for mixing), on the other hand, can be controlled and / or regulated, which can further improve efficiency and operational reliability.Furthermore, various operating strategies for mixing can optionally be implemented depending on the recirculated and / or branched electrolyte mass flow for the operation of the alkaline electrolysis device.

[0047] According to a further preferred embodiment of the alkaline electrolysis device, it may be advantageous if only the hydrogen separator comprises the first hydrogen separator unit and the second hydrogen separator unit for the two-stage separation of gaseous hydrogen from the aqueous electrolyte, so that the oxygen separator is configured for the single-stage separation of gaseous oxygen from the aqueous electrolyte. This design results in a simplified and thus more cost-effective alkaline electrolysis device, since hydrogen contamination on the oxygen side is significantly more critical than, conversely, oxygen contamination on the hydrogen side.In order to address this circumstance and to provide a more cost-effective and simpler alkaline electrolysis device, it may prove advantageous to provide the two-stage separation by means of the first hydrogen separator unit and the second hydrogen separator unit only on the hydrogen side.

[0048] The following description of preferred embodiments of the invention, taken in conjunction with the drawings, serves to explain the invention in more detail. A preferred embodiment of an alkaline electrolysis device according to the invention is described.

[0049] They show:

[0050] Fig. 1 : a schematic view of an alkaline electrolysis device from the

[0051] State of the art;

[0052] Fig. 2: a diagram showing the ascent velocity of gas bubbles over a

[0053] bubble size is plotted;

[0054] Fig. 3: a schematic view of a first embodiment of an alkaline electrolysis device according to the invention;

[0055] Fig. 4: a schematic view of a second embodiment of an alkaline electrolysis device according to the invention; Fig. 5: a schematic view of a third embodiment of an alkaline electrolysis device according to the invention;

[0056] Fig. 6: a schematic view of a fourth embodiment of an alkaline electrolysis device according to the invention; and

[0057] Fig. 7 is a schematic view of a fifth embodiment of an alkaline electrolysis device according to the invention.

[0058] Fig. 1 shows a schematic view of an alkaline electrolysis device 100 from the prior art.

[0059] The alkaline electrolysis device 100 for decomposing aqueous electrolyte E into hydrogen H2 and oxygen O2 comprises an electrolysis cell 102 with a reactor chamber 104.

[0060] This reactor chamber 104 comprises a hydrogen-side reactor chamber region 106 (containing the aqueous electrolyte E) for decomposing the aqueous electrolyte E into gaseous hydrogen H2. Furthermore, the reactor chamber 104 comprises an oxygen-side reactor chamber region 108 (containing the aqueous electrolyte E) for decomposing the aqueous electrolyte E into gaseous oxygen O2. The reactor chamber 104 is a reactor chamber known in the prior art, which functions on the basis of the likewise known water electrolysis.

[0061] Furthermore, the alkaline electrolysis device 100 comprises a hydrogen separator 110, which is connected to the hydrogen-side reactor chamber region 106, for separating the gaseous hydrogen H2 from the aqueous electrolyte E introduced into the hydrogen separator 110. In addition, the alkaline electrolysis device 100 comprises an oxygen separator 112, which is connected to the oxygen-side reactor chamber region 108, for separating the gaseous oxygen O2 from the aqueous electrolyte E introduced into the oxygen separator 112.

[0062] The hydrogen separator 110 further comprises a hydrogen separator outlet 114 for removing the aqueous electrolyte E with a hydrogen concentration. This hydrogen concentration is to be understood as remaining in the aqueous electrolyte E as a residual hydrogen concentration due to the incomplete separation of hydrogen from the aqueous electrolyte E. In addition, the hydrogen separator 110 comprises a hydrogen outlet 142 for removing the separated gaseous hydrogen, which is then fed to an external storage device (not shown in Fig.

[0063] 1) or can be fed into a pipeline system for further industrial processing.

[0064] The hydrogen separator outlet 114 is connectable to the reactor chamber 104 via a hydrogen-side return line 118, a hydrogen-side return conveying device 134, and a mixing unit 136. This return conveying device 134 can be designed, for example, as a return conveying pump. These serve to return the aqueous electrolyte E with the hydrogen concentration explained above from the hydrogen separator 110 to the reactor chamber 104.

[0065] Accordingly, the oxygen separator 112 also has an oxygen separator outlet 122 for removing the aqueous electrolyte E with an oxygen concentration. This oxygen concentration is to be understood analogously as remaining in the aqueous electrolyte E as a residual oxygen concentration due to the incomplete separation or removal of oxygen from the aqueous electrolyte E.

[0066] The oxygen separator outlet 122 is connectable to the reactor chamber 104 via an oxygen-side return line 124, an oxygen-side return conveying device 138 and via the mixing unit 136 for returning the aqueous electrolyte E with the above-described oxygen concentration from the oxygen separator 112 into the reactor chamber 104. This return conveying device 138 can, for example, be designed as a return conveying pump or comprise such a pump.

[0067] In the alkaline electrolysis device 100 according to Fig. 1, the partial chemical reactions in the hydrogen-side reactor chamber region 106 and in the oxygen-side reactor chamber region 108 lead to a concentration gradient in the aqueous electrolyte E.

[0068] Mixing of both electrolyte streams (with the previously explained hydrogen and oxygen concentrations) by means of the mixing unit 136 is therefore necessary to compensate for the resulting concentration gradient. Only after this gradient has been compensated can one or more mixed electrolyte streams be fed back to the reactor chamber 104. On the oxygen side, the mixing unit 136 can be bridged by a bypass line 140, whereby the aqueous electrolyte E having the oxygen concentration can be fed or mixed with the aqueous electrolyte E having the hydrogen concentration between the mixing unit 136 and the oxygen-side reactor chamber region 108. Fig. 2 shows a diagram in which the ascent rate of gas bubbles is plotted against a bubble size.

[0069] It can be seen that there is an essentially exponential or polynomial relationship between the rising speed of gas bubbles in a liquid as a function of their bubble size.

[0070] This relationship is therefore important in the context of the present invention because the electrolyte E entering the hydrogen separator 110 (cf. Fig. 3) contains the separated hydrogen H2 in the form of hydrogen gas bubbles before they rise in the electrolyte E in the hydrogen separator 110 and leave it.

[0071] From Fig. 2, it can therefore be seen that the largest possible bubble size should be aimed for when the electrolyte E enters the hydrogen separator in order, firstly, to minimize the residence time of the electrolyte within the hydrogen separator 110. Secondly, this maximizes the degree of deposition or separation of hydrogen H2 from the electrolyte E. The greater the degree of deposition, the fewer gas impurities in the form of hydrogen H2 are fed to the oxygen-side reactor chamber region 108 by recirculation of the electrolyte E, which is reflected, among other things, in improved efficiency and increased operational reliability of the alkaline electrolysis device 100.

[0072] Fig. 3 shows a schematic view of a first embodiment of an alkaline electrolysis device 100 according to the invention.

[0073] The alkaline electrolysis device 100 for decomposing aqueous electrolyte E into hydrogen H2 and oxygen O2 comprises at least one electrolysis cell 102. The aqueous electrolyte E preferably contains an aqueous solution of 20 wt.% - 40 wt.% potassium hydroxide (also called potassium hydroxide solution). Additionally or alternatively, the aqueous electrolyte E can contain a corresponding aqueous solution of sodium hydroxide (also called caustic soda solution). Other alkaline aqueous solutions or alkalis based on other metal hydroxides are also conceivable in this context.

[0074] In Fig. 3, the alkaline electrolysis device 100 is shown by way of example with an electrolysis cell 102. It is understood that the alkaline electrolysis device 100 can also have a plurality of such electrolysis cells 102, which can form stacks in a stacked arrangement. For example, the alkaline electrolysis device can have 2, 3, 4, 5, 6, 7, 8, 9, or 10, or several 10, or several 100 such electrolysis cells 102, which form the stack in a stacked arrangement.

[0075] The electrolysis cell 102 comprises a reactor chamber 104, which comprises a hydrogen-side reactor chamber region 106 containing the aqueous electrolyte E for decomposing the aqueous electrolyte E into gaseous hydrogen H2.

[0076] Accordingly, the reactor chamber 104 comprises an oxygen-side reactor chamber region 108 containing the aqueous electrolyte E for decomposing the aqueous electrolyte E into gaseous oxygen O2.

[0077] The hydrogen-side and oxygen-side reactor chamber regions 106, 108 are separated from each other in a liquid-tight manner by an ion-permeable membrane 144. The ion-permeable membrane 144 can preferably be designed as an anion-permeable membrane. This membrane 144 can also be designed to be gas-tight and only allow the transport of OH ions from the hydrogen-side reactor chamber region 106 to the oxygen-side reactor chamber region 108 and vice versa. At the same time, it prevents the mixing of the resulting product gases, hydrogen H2 and oxygen O2, and the electrolyte E. The membrane 144 can preferably be made of a plastic containing a perfluorinated copolymer.

[0078] On both sides of the ion-permeable membrane 144, a negative electrode in the form of a cathode 146 is arranged in the hydrogen-side reactor chamber region 106, and a positive electrode in the form of an anode 148 is arranged in the oxygen-side reactor chamber region 108. The cathode 146 and the anode 148 are preferably in direct contact with the ion-permeable membrane 144 and generate the necessary cell DC voltage of at least 1.5 volts.

[0079] The oxygen-side reactor chamber area 108 is a closed area of ​​the reactor chamber 104 in which the formation of gaseous oxygen O2 takes place according to the following reaction equation (1):

[0080] 4OH- -> 2H2O + 4e- + O2(1). The hydrogen-side reactor chamber region 106 is therefore a closed region of the reactor chamber 104, in which the formation of gaseous hydrogen occurs according to the following reaction equation (2):

[0081] 4H2O + 4e- -> 2H2+ 4O1+ (2).

[0082] The hydrogen-side reactor chamber region 106 further has an inlet 120 and an outlet 150 for supplying and discharging the aqueous electrolyte E, and correspondingly, the oxygen-side reactor chamber region 108 also has an inlet 126 and an outlet 152 for supplying and discharging the aqueous electrolyte E.

[0083] The alkaline electrolysis device 100 further comprises a hydrogen separator 110, which is connected to the hydrogen-side reactor chamber region 106 via the outlet 150, for separating the gaseous hydrogen H2 from the aqueous electrolyte E introduced into the hydrogen separator 110. This connection is made by means of a hydrogen-side electrolyte feed line 164.

[0084] According to Fig. 3, the hydrogen separator 110 is preferably designed as a gravity separator for two-stage gas separation that is horizontally oriented in the assembled state. The liquid aqueous electrolyte E collects at the bottom, thus forming a bottom-side electrolyte volume. A gas volume of hydrogen H2, initially contained in the liquid electrolyte E in the form of bubbles and released from the liquid electrolyte E, collects above the liquid electrolyte E in the direction of gravity. Due to the greater density of the liquid aqueous electrolyte E compared to gaseous hydrogen H2, a separation occurs between the liquid electrolyte phase and the gaseous hydrogen phase.

[0085] The hydrogen separator 110 further has a first hydrogen separator outlet 114 for removing the aqueous electrolyte E having a first hydrogen concentration. The aqueous electrolyte E having the first hydrogen concentration is formed by an incomplete separation of hydrogen H2 and aqueous electrolyte E as a result of its removal after a first residence time h from the hydrogen separator 110 by means of the first hydrogen separator outlet 114.

[0086] As can be seen in Fig. 3, the hydrogen separator 110 has a second hydrogen separator outlet 116 for removing the aqueous electrolyte E with a second hydrogen concentration that is lower than the first hydrogen concentration. The aqueous electrolyte E with the second hydrogen concentration is created analogously by an incomplete separation of hydrogen H2 and aqueous electrolyte E as a result of its removal after a second residence time t2 from the hydrogen separator 110 by means of the second hydrogen separator outlet 116. Due to the longer residence time t2 compared to h, a larger amount of bubbles can outgas from the aqueous electrolyte E according to the relationship explained in Fig. 2, so that the second hydrogen concentration is lower than the first hydrogen concentration.

[0087] The hydrogen separator 110 further comprises separating elements 154, 156 for additional mechanical separation of the liquid electrolyte phase and the gaseous hydrogen phase. These separating elements can be inserted into the hydrogen separator 110 in the form of perforated plates or other, preferably porous, packing elements.

[0088] As an alternative to the horizontal separator design, the hydrogen separator 110 can be configured as a gravity separator that is vertically oriented in the assembled state. Furthermore, it is alternatively possible for the hydrogen separator 110 to be configured as a centrifugal separator.

[0089] The first hydrogen separator outlet 114 and the second hydrogen separator outlet 116 are connectable to the reactor chamber 104 for returning the aqueous electrolyte E with the first hydrogen concentration and with the second hydrogen concentration from the hydrogen separator 110 into the reactor chamber 104.

[0090] For this purpose, the alkaline electrolysis device 100 comprises a first hydrogen-side electrolyte return line 118, by means of which the first hydrogen separator outlet 114 can be connected to the inlet 120 of the hydrogen-side reactor chamber region 106 for returning the aqueous electrolyte E with the first hydrogen concentration from the hydrogen separator 110 into the hydrogen-side reactor chamber region 106.

[0091] A hydrogen-side recirculation pump 134 is arranged in the first hydrogen-side electrolyte recirculation line 118, which supplies the aqueous electrolyte E with the first hydrogen concentration to the inlet 120 of the hydrogen-side reactor chamber region 106. Since the decomposition of the aqueous electrolyte E into oxygen H2 already takes place in the hydrogen-side reactor chamber region 106, recirculation of the electrolyte E with the first, higher hydrogen concentration is uncritical. Furthermore, the hydrogen separator 110 has a hydrogen outlet 142 for removing the separated gaseous hydrogen, which can then be supplied to an external storage device (not shown in Fig. 1) or a pipeline system for further industrial processing.

[0092] In addition, the alkaline electrolysis device 100 comprises an oxygen separator 112, which is connected to the oxygen-side reactor chamber region 108, for separating the gaseous oxygen O2 from the aqueous electrolyte E introduced into the oxygen separator 112. This connection is made by means of an oxygen-side electrolyte feed line 166.

[0093] According to Fig. 3, the oxygen separator 112 is preferably designed as a gravity separator for two-stage separation that is horizontally oriented in the assembled state. The liquid aqueous electrolyte E collects at the bottom, thus forming a bottom-side electrolyte volume. In the direction of gravity above the liquid electrolyte E, a gas volume of oxygen O2, initially contained in the liquid electrolyte E in the form of bubbles and released, collects. Due to the greater density of the liquid aqueous electrolyte E compared to the gaseous oxygen O2, a separation occurs between the liquid electrolyte phase and the gaseous oxygen phase.

[0094] The oxygen separator 112 further has a first oxygen separator outlet 122 for removing the aqueous electrolyte E having a first oxygen concentration. The aqueous electrolyte E having the first oxygen concentration is produced by an incomplete separation of oxygen O2 and aqueous electrolyte E as a result of the latter being removed from the oxygen separator 112 by means of the first oxygen separator outlet 122 after a first residence time h.

[0095] As can further be seen in Fig. 3, the oxygen separator 112 has a second oxygen separator outlet 130 for removing the aqueous electrolyte E with a second oxygen concentration that is lower than the first oxygen concentration. The aqueous electrolyte E with the second oxygen concentration is analogously created by an incomplete separation of oxygen O2 from the aqueous electrolyte E as a result of its removal after a second residence time t2 from the oxygen separator 112 by means of the second oxygen separator outlet 130. Due to the longer residence time t2 compared to h, a larger amount of bubbles can outgas from the aqueous electrolyte E according to the relationship explained in Fig. 2, so that the second oxygen concentration is lower than the first oxygen concentration.

[0096] The oxygen separator 112 further comprises separating elements 158, 160 for additional mechanical separation of the liquid electrolyte phase and the gaseous oxygen phase. These separating elements can be inserted into the oxygen separator 112 in the form of perforated plates or other, preferably porous, filler materials.

[0097] As an alternative to the horizontal separator design, the oxygen separator 112 can be configured as a gravity separator that is vertically oriented in the assembled state. Alternatively, the oxygen separator 112 can be configured as a centrifugal separator.

[0098] The first oxygen separator outlet 122 and the second oxygen separator outlet 130 are connectable to the reactor chamber 104 for returning the aqueous electrolyte E with the first oxygen concentration and with the second oxygen concentration from the oxygen separator 112 to the reactor chamber 104.

[0099] For this purpose, the alkaline electrolysis device 100 comprises a first oxygen-side electrolyte return line 124, by means of which the first oxygen separator outlet 122 can be connected to the inlet 126 of the oxygen-side reactor chamber region 108 for returning the aqueous electrolyte E with the first oxygen concentration from the oxygen separator 112 into the oxygen-side reactor chamber region 108.

[0100] An oxygen-side recirculation pump 138 is arranged in the first oxygen-side electrolyte recirculation line 124, which supplies the aqueous electrolyte E with the first oxygen concentration to the inlet 126 of the oxygen-side reactor chamber region 108. Since the decomposition of the aqueous electrolyte E into oxygen O2 already takes place in the oxygen-side reactor chamber region 108, recirculation of the electrolyte E with the first, higher oxygen concentration is uncritical. More critical, however, is the hydrogen concentration contained in the aqueous electrolyte E supplied to the oxygen-side reactor chamber region 108 due to the necessary mixing (see the above discussion on this).

[0101] In addition, the oxygen separator 112 has an oxygen outlet 162 for removing the separated gaseous oxygen, which can then usually be supplied to the atmosphere. According to Fig. 3, the alkaline electrolysis device 100 further has a second hydrogen-side electrolyte return line 128, by means of which the second hydrogen separator outlet 116 is connected to the first oxygen-side electrolyte return line 124 for branching and returning the aqueous electrolyte E with the second hydrogen concentration from the hydrogen separator 110 into the first oxygen-side electrolyte return line 124. Consequently, a mixed electrolyte E is supplied (through the branch) to the oxygen-side reactor chamber region 108, which has only the lower, second hydrogen concentration (in addition to the non-critical first oxygen concentration).Thus, the gas contamination in the oxygen-side reactor chamber region 108 by the hydrogen H2 can be reduced, so that the efficiency is increased and operational reliability is improved.

[0102] In the opposite case, the oxygen concentration is critical, which is contained in the electrolyte E supplied to the hydrogen-side reactor chamber area due to the necessary mixing (see the above discussion on this).

[0103] In this regard, the alkaline electrolysis device 100 has a second oxygen-side electrolyte return line 132, by means of which the second oxygen separator outlet 130 is connected to the first hydrogen-side electrolyte return line 118 for branching and returning the aqueous electrolyte E with the second oxygen concentration from the oxygen separator 112 into the first hydrogen-side electrolyte return line 118. Thus, a mixed electrolyte E (through the branch) is supplied to the hydrogen-side reactor chamber region 106, which has only the lower, second oxygen concentration (in addition to the non-critical first hydrogen concentration). Consequently, the gas contamination in the hydrogen-side reactor chamber region 106 can be reduced by the lower proportion of oxygen O2, thus increasing efficiency and resulting in improved operational reliability.

[0104] In each of the lines 118, 124, 128, 132, 164, and 166 shown in Fig. 3, a control and / or regulating valve 168 is arranged, by means of which the electrolyte flows in these lines 118, 124, 128, 132, 164, and 166 can be controlled and / or regulated. For this purpose, the control and / or regulating valves 168 are connected to a control and / or regulating unit 172 via signal lines 170. The signal lines 170 and the control and / or regulating unit 172 are not shown in the following Figs. 4 to 6, but are nevertheless included in these exemplary embodiments of the alkaline electrolysis devices 200, 300, and 400 according to the invention.

[0105] Fig. 4 shows a schematic view of a second embodiment of an alkaline electrolysis device 200 according to the invention.

[0106] The second embodiment of the alkaline electrolysis device 200 according to the invention is structurally and functionally based on the first embodiment of the alkaline electrolysis device 100 according to the invention according to Fig. 3, the structural and functional differences being explained below:

[0107] The hydrogen separator 210 is not designed as a single piece as in Fig. 3, which has a two-stage hydrogen separation process, but rather has a separate unit for each separation stage. Accordingly, the hydrogen separator 210 comprises a first hydrogen separator unit 214 for separating gaseous hydrogen H2 from the aqueous electrolyte E introduced into the first hydrogen separator unit 214, and a second hydrogen separator unit 216 for separating gaseous hydrogen H2 from the aqueous electrolyte E introduced into the second hydrogen separator unit 216.

[0108] The first hydrogen separator unit 214, as shown in Fig. 4, is preferably designed as a gravity separator unit for single-stage separation that is horizontally oriented in the assembled state. The liquid aqueous electrolyte E collects at the bottom, thus forming a bottom-side electrolyte volume. A gas volume of hydrogen H2, initially contained in the liquid electrolyte E in the form of bubbles and then outgassing, collects above the liquid electrolyte E in the direction of gravity. Due to the greater density of the liquid aqueous electrolyte E compared to the gaseous hydrogen H2, a separation occurs between the liquid electrolyte phase and the gaseous hydrogen phase.

[0109] The first hydrogen separator unit 214 further comprises one or more separating elements 154, 156 for additional mechanical separation of the liquid electrolyte phase and the gaseous hydrogen phase. These separating elements can be inserted into the first hydrogen separator unit 214 in the form of perforated plates or other, preferably porous, filler bodies.

[0110] As an alternative to the design as a horizontal separator unit, the first hydrogen separator unit 214 can be designed as a gravity separator unit that is vertically oriented in the assembled state. Alternatively, the first hydrogen separator unit 214 can be designed as a centrifugal separator unit.

[0111] The second hydrogen separator unit 216 is structurally and functionally designed to correspond to the first hydrogen separator unit 214.

[0112] The first hydrogen separator unit 214 has the first hydrogen separator outlet 114 according to Fig. 4 and the second hydrogen separator unit 216 has the second hydrogen separator outlet 116 accordingly.

[0113] A hydrogen-side branch line 218 is branched off from the first hydrogen-side electrolyte return line 118, which is connected or connectable to the second hydrogen separator unit 216 for feeding the second hydrogen separator unit 216 with the aqueous electrolyte E having the first hydrogen concentration.

[0114] The first hydrogen separator unit 214 is thus configured to separate gaseous hydrogen H2 from the aqueous electrolyte E such that the aqueous electrolyte E has the first hydrogen concentration as a result of this separation. Accordingly, the second hydrogen separator unit 216 is configured to separate gaseous hydrogen H2 from the aqueous electrolyte E such that the aqueous electrolyte E has the second hydrogen concentration as a result of this separation.

[0115] The oxygen separator 212, on the other hand, is designed as a single-stage oxygen separator and accordingly has only a first oxygen separator outlet 122, which is connectable to the inlet 126 of the oxygen-side reactor chamber region 108 via the first oxygen-side electrolyte return line 124. This enables the return of the aqueous electrolyte E with the first oxygen concentration from the oxygen separator 212 to the oxygen-side reactor chamber region 108.

[0116] The oxygen separator 212 may alternatively (not shown in Fig. 4) be designed in two stages, so that it can have a separate oxygen separation unit for each separation stage.

[0117] The first oxygen separator unit may have the first oxygen separator outlet 122, wherein the first oxygen-side electrolyte return line 124 may open with its inlet into the first oxygen separator outlet 122. Furthermore, the second oxygen separator unit may have a second oxygen separator outlet 130 (see Fig. 6), wherein the second oxygen-side electrolyte return line 132 may open with its inlet into the second oxygen separator outlet 130.

[0118] The first oxygen separator unit is thus configured to separate gaseous oxygen O2 from the aqueous electrolyte E in such a way that the aqueous electrolyte E has the first oxygen concentration as a result of this separation and is returned to the oxygen-side reactor chamber region 108. Accordingly, the second oxygen separator unit can be configured to separate gaseous oxygen O2 from the aqueous electrolyte E in such a way that the aqueous electrolyte E has the second oxygen concentration as a result of this separation and is accordingly returned to the hydrogen-side reactor chamber region 106.

[0119] Additionally, a connecting line 220 with an integrated control and / or regulating valve 168 can extend between the first oxygen-side electrolyte return line 124 and the first hydrogen-side electrolyte return line 118. This line 220 serves to branch the electrolyte E with the first oxygen concentration into the first hydrogen-side electrolyte return line 118, by means of which the electrolyte E with the first hydrogen concentration is returned. Since the oxygen concentration on the hydrogen side is less critical than vice versa, such mixing can occur with the first (i.e., higher) water and oxygen concentration on the hydrogen side.

[0120] Accordingly, only the hydrogen separator 210 comprises the first hydrogen separator unit 214 and the second hydrogen separator unit 216 for the two-stage separation of the gaseous hydrogen H2 from the aqueous electrolyte E, whereas the oxygen separator 212 is configured for the single-stage separation of gaseous oxygen O2 from the aqueous electrolyte E.

[0121] Fig. 5 shows a schematic view of a third embodiment of an alkaline electrolysis device 300 according to the invention.

[0122] The third embodiment of the alkaline electrolysis device 300 according to the invention is structurally and functionally based on the second embodiment of the alkaline electrolysis device 200 according to the invention according to Fig. 4, the structural and functional differences being explained below: The oxygen separator 212 is designed as a single-stage oxygen separator and has an oxygen outlet 302 for removing gaseous oxygen O2 from the oxygen separator 212.

[0123] The oxygen separator 212 may alternatively (not shown in Fig. 5) be designed in two stages, so that it can have a separate oxygen separation unit for each separation stage.

[0124] The first oxygen separator unit may have the first oxygen separator outlet 122, wherein the first oxygen-side electrolyte return line 124 may open with its inlet into the first oxygen separator outlet 122.

[0125] Furthermore, the second oxygen separator unit may have a second oxygen separator outlet 130 (see Fig. 6), wherein the second oxygen-side electrolyte return line 132 opens with its inlet into the second oxygen separator outlet 130.

[0126] The first oxygen separator unit is thus configured to separate gaseous oxygen O2 from the aqueous electrolyte E in such a way that the aqueous electrolyte E has the first oxygen concentration as a result of this separation and is returned to the oxygen-side reactor chamber region 108. Accordingly, the second oxygen separator unit can be configured to separate gaseous oxygen O2 from the aqueous electrolyte E in such a way that the aqueous electrolyte E has the second oxygen concentration as a result of this separation and is accordingly returned to the hydrogen-side reactor chamber region 106.

[0127] The oxygen outlet 302 explained above is, according to Fig. 5, connectable to the hydrogen separator 210 by means of an oxygen feed line 304 for feeding the gaseous oxygen O2 into the hydrogen separator 210. More precisely, the oxygen outlet 302 is connected to the second hydrogen separator unit 216 by means of the oxygen feed line 304 for feeding gaseous oxygen O2 into the second hydrogen separator unit 216. For this purpose, the second hydrogen separator unit 216 has an oxygen feed inlet 310 into which the oxygen feed line 304 opens. As explained above, the aqueous electrolyte E having the second hydrogen concentration is used for recirculation and branching into the first oxygen-side electrolyte return line 124 for mixing the electrolyte E.Since the hydrogen obtained primarily originates from the first hydrogen separator unit 214, feeding it into this first hydrogen separator unit 214 would be counterproductive or safety-critical, as an explosive mixture would then be present. In this respect, feeding it into the second hydrogen separator unit 216 is particularly advantageous, since the hydrogen content here may not exceed 2%, so that the oxygen content in the gas phase is always at least 98%. Consequently, no explosive mixture can form. Thus, the degree of separation in a two-stage separation of hydrogen H2 from the aqueous electrolyte E can be further increased by the oxygen feed (in addition to the effect of the improved separation by the first and second hydrogen separator units 214, 216).Finally, the hydrogen partial pressure can be further reduced by the presence of oxygen O2, which leads to an even better hydrogen separation in the second hydrogen separator unit 216.

[0128] According to Fig. 5, an oxygen purification unit 306 is arranged in the oxygen feed line 304 for removing gaseous hydrogen H2 from the gaseous oxygen O2.

[0129] The oxygen purification unit 304 may comprise a polymer membrane with high hydrogen permeability. Additionally or alternatively, the oxygen purification unit 304 may comprise a microchannel palladium membrane oxygen purification unit. Additionally or alternatively, the oxygen purification unit 304 may comprise a pressure swing adsorption oxygen purification unit. Additionally or alternatively, the oxygen purification unit 304 may comprise a catalytic reaction unit for the catalytic reaction of hydrogen and oxygen to form water.

[0130] Optionally, an oxygen storage device 308 in the form of an oxygen buffer storage device can be arranged in the oxygen supply line 304, which is arranged between the oxygen purification unit 306 and the second hydrogen separator unit 216. By means of the oxygen storage device 308, the oxygen mass flow entering the second hydrogen separator unit 216 can be dampened so that it can be supplied more evenly, which results in further improved hydrogen separation from the aqueous electrolyte E. Fig. 6 shows a schematic view of a fourth embodiment of an alkaline electrolysis device 400 according to the invention.

[0131] The fourth embodiment of the alkaline electrolysis device 400 according to the invention is structurally and functionally based on the first embodiment of the alkaline electrolysis device 100 according to the invention according to Fig. 3, the structural and functional differences being explained below:

[0132] The hydrogen separator 210 is structurally and functionally constructed as in the second embodiment of the alkaline electrolysis device 200 according to the invention according to Fig. 4.

[0133] The oxygen separator 402, however, is not designed as a single piece as in Fig. 3, with a two-stage oxygen separation taking place therein, but rather has a separate unit for each separation stage. Accordingly, the oxygen separator 402 comprises a first oxygen separator unit 404 for separating gaseous oxygen O2 from the aqueous electrolyte E introduced into the first oxygen separator unit 404, and a second oxygen separator unit 406 for separating gaseous oxygen O2 from the aqueous electrolyte E introduced into the second oxygen separator unit 406.

[0134] The first oxygen separator unit 404, as shown in Fig. 6, is preferably designed as a gravity separator unit for single-stage separation that is horizontally oriented in the assembled state. The liquid aqueous electrolyte E collects at the bottom, thus forming a bottom-side electrolyte volume. A gas volume of oxygen O2, initially contained in the liquid electrolyte E in the form of bubbles and then released as gas, collects above the liquid electrolyte E in the direction of gravity. Due to the greater density of the liquid aqueous electrolyte E compared to the gaseous oxygen O2, a separation occurs between the liquid electrolyte phase and the gaseous oxygen phase.

[0135] The first oxygen separator unit 404 further comprises one or more separating elements 154, 156 for additional mechanical separation of the liquid electrolyte phase and the gaseous oxygen phase. These separating elements can be inserted into the first oxygen separator unit 404 in the form of perforated plates or other, preferably porous, fillers. As an alternative to the design as a horizontal separator unit, the first oxygen separator unit 404 can be designed as a gravity separator unit that is vertically oriented in the assembled state. Furthermore, it is alternatively possible for the first oxygen separator unit 404 to be designed as a centrifugal separator unit.

[0136] The second oxygen separator unit 406 is structurally and functionally designed to correspond to the first oxygen separator unit 404.

[0137] According to Fig. 6, the first oxygen separator unit 404 further comprises the first oxygen separator outlet 122 and the second oxygen separator unit 406 correspondingly comprises the second oxygen separator outlet 130.

[0138] An oxygen-side branch line 408 is branched off from the first oxygen-side electrolyte return line 124, which is connected or connectable to the second oxygen separator unit 406 for feeding the second oxygen separator unit 406 with the aqueous electrolyte E having the first oxygen concentration.

[0139] The first oxygen separator unit 404 is thus configured to separate gaseous oxygen O2 from the aqueous electrolyte E such that the aqueous electrolyte E has the first oxygen concentration as a result of this separation. Accordingly, the second oxygen separator unit 406 is configured to separate gaseous oxygen O2 from the aqueous electrolyte E such that the aqueous electrolyte E has the second oxygen concentration as a result of this separation.

[0140] Fig. 7 shows a schematic view of a fifth embodiment of an alkaline electrolysis device 500 according to the invention.

[0141] The fifth embodiment of the alkaline electrolysis device 500 according to the invention is structurally and functionally based on the third embodiment of the alkaline electrolysis device 300 according to the invention according to Fig. 5, the structural and functional differences being explained below:

[0142] In contrast to the third exemplary embodiment of the alkaline electrolysis device 300 according to the invention shown in Fig. 5, it is not the second hydrogen separator unit 216 that has the oxygen feed inlet 310, but rather the oxygen separator 212 itself. The oxygen outlet 302 can therefore be connected to the oxygen feed inlet 310 by means of an oxygen feed line 304 for feeding a portion of the gaseous oxygen O2 back into the oxygen separator 212.

[0143] According to Fig. 7, an oxygen purification unit 306 is arranged in the oxygen feed line 304 for removing gaseous hydrogen H2 from the gaseous oxygen O2.

[0144] The oxygen purification unit 304 may comprise a polymer membrane with high hydrogen permeability. Additionally or alternatively, the oxygen purification unit 304 may comprise a microchannel palladium membrane oxygen purification unit. Additionally or alternatively, the oxygen purification unit 304 may comprise a pressure swing adsorption oxygen purification unit. Additionally or alternatively, the oxygen purification unit 304 may comprise a catalytic reaction unit for the catalytic reaction of hydrogen and oxygen to form water.

[0145] The purified oxygen O2 can further improve the separation efficiency in the oxygen separator 212. Finally, the oxygen partial pressure can be further reduced by the absence or near absence of hydrogen H2, which leads to even better oxygen separation in the oxygen separator 212.

[0146] Furthermore, an oxygen delivery device 312 is arranged in the oxygen feed line 304 between the oxygen purification unit 306 and the oxygen outlet 302. The oxygen delivery device 312 can, for example, be an oxygen feed compressor. Optionally, a control and / or regulating valve 168 can also be arranged in the oxygen feed line 304 between the oxygen purification unit 306 and the oxygen feed inlet 310.

[0147] By means of the oxygen delivery device 312 and the control and / or regulating valve 168, in particular the partial mass flow and / or partial volume flow of the purified oxygen returned from the oxygen outlet 302 can be controlled or regulated. List of reference symbols

[0148] Electrolysis device

[0149] Electrolysis cell

[0150] Reactor chamber hydrogen-side reactor chamber area oxygen-side reactor chamber area

[0151] Hydrogen separator

[0152] Oxygen separator first hydrogen separator outlet second hydrogen separator outlet first hydrogen-side electrolyte return line

[0153] Inlet of the hydrogen-side reactor chamber area first oxygen separator outlet first oxygen-side electrolyte return line

[0154] Inlet of the oxygen-side reactor chamber area, second hydrogen-side electrolyte return line, second oxygen separator outlet, second oxygen-side electrolyte return line, hydrogen-side return conveyor

[0155] Mixing unit oxygen-side return conveyor

[0156] Bypass line

[0157] Hydrogen outlet ion-permeable membrane

[0158] cathode

[0159] anode

[0160] Outlet of the hydrogen-side reactor chamber area

[0161] Outlet of the oxygen-side reactor chamber area

[0162] Separating element

[0163] Separating element

[0164] Separating element

[0165] Separating element

[0166] Oxygen outlet hydrogen-side electrolyte feed line oxygen-side electrolyte feed line

[0167] Control and / or regulating valve 170 signal lines

[0168] 172 Control and / or regulating device 00 Electrolysis device 10 Hydrogen separator 12 Oxygen separator 14 First hydrogen separator unit 16 Second hydrogen separator unit 18 Hydrogen-side branch line 20 Connecting line 00 Electrolysis device 02 Oxygen outlet 04 Oxygen feed line 06 Oxygen purification unit 08 Oxygen storage

[0169] 310 Oxygen feed inlet

[0170] 312 Oxygen supply device 00 Electrolysis device 02 Oxygen separator

[0171] 404 first oxygen separator unit

[0172] 406 second oxygen separator unit

[0173] 408 oxygen-side branch line

[0174] 500 electrolysis facility

[0175] E aqueous electrolyte

[0176] H2hydrogen

[0177] O2Oxygen

Claims

PATENT CLAIMS 1. Alkaline electrolysis device (100; 200; 300; 400; 500) for decomposing aqueous electrolyte (E) into hydrogen (H2) and oxygen (O2), comprising: - at least one electrolysis cell (102) comprising a reactor chamber (104) which comprises a hydrogen-side reactor chamber region (106) containing the aqueous electrolyte (E) for decomposing the aqueous electrolyte (E) into gaseous hydrogen (H2) and an oxygen-side reactor chamber region (108) containing the aqueous electrolyte (E) for decomposing the aqueous electrolyte (E) into gaseous oxygen (O2); - a hydrogen separator (110; 210) for separating the gaseous hydrogen (H2) from the aqueous electrolyte (E) introduced into the hydrogen separator (110; 210), wherein the hydrogen separator (110; 210) is connected to the hydrogen-side reactor chamber region (106); and - an oxygen separator (112; 212; 402) for separating the gaseous oxygen (O2) from the aqueous electrolyte (E) introduced into the oxygen separator (112; 212, 402), wherein the oxygen separator (112; 212; 402) is connected to the oxygen-side reactor chamber region (108); wherein the hydrogen separator (110; 210) has a first hydrogen separator outlet (114) for removing the aqueous electrolyte (E) with a first hydrogen concentration and a second hydrogen separator outlet (116) for removing the aqueous electrolyte (E) with a second hydrogen concentration which is lower than the first hydrogen concentration;and wherein the first hydrogen separator outlet (114) and the second hydrogen separator outlet (116) are connectable or connected to the reactor chamber (104) for returning the aqueous electrolyte (E) with the first hydrogen concentration and with the second hydrogen concentration from the hydrogen separator (110; 210) to the reactor chamber (104).; 2. Alkaline electrolysis device (100; 200; 300; 400; 500) according to claim 1, characterized in that the first hydrogen separator outlet (114) is connectable or connected by means of a first hydrogen-side electrolyte return line (118) to an inlet (120) of the hydrogen-side reactor chamber region (106) for returning the aqueous electrolyte (E) with the first hydrogen concentration from the Hydrogen separator (110; 210) into the hydrogen-side reactor chamber region (106); the oxygen separator (112; 212; 402) has a first oxygen separator outlet (122) for removing the aqueous electrolyte (E) having a first oxygen concentration, wherein the first oxygen separator outlet (122) is connectable or connected to an inlet (126) of the oxygen-side reactor chamber region (108) by means of a first oxygen-side electrolyte return line (124) for returning the aqueous electrolyte (E) having the first oxygen concentration from the oxygen separator (112; 212, 402) into the oxygen-side reactor chamber region (108);and the second hydrogen separator outlet (116) is connectable or connected to the first oxygen-side electrolyte return line (124) by means of a second hydrogen-side electrolyte return line (128) for branching off and returning the aqueous electrolyte (E) with the second hydrogen concentration from the hydrogen separator (110; 210) into the first oxygen-side electrolyte return line (124).

3. Alkaline electrolysis device (100; 200; 300; 400; 500) according to claim 2, characterized in that the oxygen separator (112; 402) has a second oxygen separator outlet (130) for removing the aqueous electrolyte (E) with a second oxygen concentration which is lower than the first oxygen concentration, wherein the second oxygen separator outlet (130) is connectable or connected to the first hydrogen-side electrolyte return line (118) by means of a second oxygen-side electrolyte return line (132) for branching off and returning the aqueous electrolyte (E) with the second oxygen concentration from the oxygen separator (112; 402) into the first hydrogen-side electrolyte return line (118).

4. Alkaline electrolysis device (200; 300; 400; 500) according to one of the preceding claims, characterized in that the hydrogen separator (210) comprises a first hydrogen separator unit (214) for separating gaseous hydrogen (H2) from the aqueous electrolyte (E) introduced into the first hydrogen separator unit (214) and a second hydrogen separator unit (216) for separating gaseous Hydrogen (H2) from the aqueous electrolyte (E) introduced into the second hydrogen separator unit (216).

5. Alkaline electrolysis device (200; 300; 400; 500) according to claim 4, characterized in that the first hydrogen separator unit (214) is configured to separate gaseous hydrogen (H2) from the aqueous electrolyte (E) such that the aqueous electrolyte (E) has the first hydrogen concentration as a result of this separation; and the second hydrogen separator unit (216) is configured to separate gaseous hydrogen (H2) from the aqueous electrolyte (E) such that the aqueous electrolyte (E) has the second hydrogen concentration as a result of this separation.

6. Alkaline electrolysis device (200; 300; 400; 500) according to claim 4 or claim 5, characterized in that the first hydrogen separator unit (214) has the first hydrogen separator outlet (114) and the second hydrogen separator unit (216) has the second hydrogen separator outlet (116).

7. Alkaline electrolysis device (200; 300; 400; 500) according to one of claims 4 to 6, characterized in that a hydrogen-side branch line (218) is branched off from the first hydrogen-side electrolyte return line (118), which is connected to the second hydrogen separator unit (216) for feeding the second hydrogen separator unit (216) with the aqueous electrolyte (E) having the first hydrogen concentration.

8. Alkaline electrolysis device (300; 500) according to one of the preceding claims, characterized in that the oxygen separator (212) has an oxygen outlet (302) for removing gaseous oxygen (O2) from the oxygen separator (212), wherein the oxygen outlet (302) is connected by means of an oxygen feed line (304) with: - connectable or connected to the hydrogen separator (210) for feeding the gaseous oxygen (O2) into the hydrogen separator (210) and / or - is connectable or connected to an oxygen feed inlet (310) of the oxygen separator (212) for feeding the gaseous oxygen (O2) back into the oxygen separator (212).

9. Alkaline electrolysis device (300) according to claim 8, characterized in that the oxygen outlet (302) is connected to the second hydrogen separator unit (216) by means of the oxygen feed line (304) for feeding gaseous oxygen (O2) into the second hydrogen separator unit (216).

10. Alkaline electrolysis device (300) according to claim 8 or claim 9, characterized in that an oxygen purification unit (306) is arranged in the oxygen feed line (304) for removing gaseous hydrogen (H2) from the gaseous oxygen, wherein an oxygen storage device (308), preferably an oxygen buffer storage device, is preferably arranged in the oxygen feed line (304), which is arranged between the oxygen purification unit (306) and the second hydrogen separator unit (216).

11. Alkaline electrolysis device (400) according to one of the preceding claims, characterized in that the oxygen separator (402) comprises a first oxygen separator unit (404) for separating gaseous oxygen (O2) from the aqueous electrolyte (E) introduced into the first oxygen separator unit (404) and a second oxygen separator unit (406) for separating gaseous oxygen (O2) from the aqueous electrolyte (E) introduced into the second oxygen separator unit (406).

12. Alkaline electrolysis device (400) according to claim 11, characterized in that the first oxygen separator unit (404) is configured to separate gaseous oxygen (O2) from the aqueous electrolyte (E) such that the aqueous electrolyte (E) has the first oxygen concentration as a result of this separation, and the second oxygen separator unit (406) is configured to separate gaseous oxygen (O2) from the aqueous electrolyte (E) such that the aqueous electrolyte (E) has the second oxygen concentration as a result of this separation.

13. Alkaline electrolysis device (400) according to claim 11 or claim 12, characterized in that the first oxygen separator unit (404) has the first oxygen separator outlet (122) and the second Oxygen separator unit (406) has the second oxygen separator outlet (130).

14. Alkaline electrolysis device (400) according to one of claims 11 to 13, characterized in that an oxygen-side branch line (408) is branched off from the first oxygen-side electrolyte return line (124) and is connected to the second oxygen separator unit (406) for feeding the second oxygen separator unit (406) with the aqueous electrolyte (E) having the first oxygen concentration.

15. Alkaline electrolysis device (200; 300; 500) according to one of claims 1 to 10, characterized in that exclusively the hydrogen separator (210) comprises the first hydrogen separator unit (214) and the second hydrogen separator unit (216) for the two-stage separation of the gaseous hydrogen (H2) from the aqueous electrolyte (E), so that the oxygen separator (212) is configured for the single-stage separation of gaseous oxygen (O2) from the aqueous electrolyte (E).

Images