Method for generating hydrogen and oxygen using electrolytic apparatus

Abstract

To provide a method for generating hydrogen and oxygen in which a yield of hydrogen and oxygen can be improved as compared to the introduced electrical energy.SOLUTION: The present invention relates to a method for generating hydrogen and oxygen using an electrolytic apparatus (1) including at least one anode chamber (2) with an anode (3) and at least one cathode chamber (4) with a cathode (5). In the method, a modulation current is carried to at least the one anode (3) and at least the one cathode (5), and the hydrogen and oxygen are generated in the electrolytic apparatus (1) under the use of a prescribed pulse pattern sequence (12) formed of at least one pulse pattern (13).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing hydrogen and oxygen using an electrolyzer, and to the use of a modulated current for producing hydrogen and oxygen in an electrolyzer.

Background Art

[0002] The production of hydrogen, particularly the production of hydrogen by electrolysis of water, is becoming increasingly important in the context of the climate change debate and the efforts to achieve carbon neutrality.

[0003] To produce hydrogen or for the production of so-called eco-fuels, typically an electrolyzer, such as a PEM type electrolyzer operated using a direct current, is used, and in this case, thyristor technology is used.

[0004] The drawback in this case is the relatively low efficiency in the methods known from the state of the art.

[0005] WO98 / 42893A1 (Patent Document 1) discloses an ultra-pure gas generation system and method that uses a DC source to supply a proportional current to a cathode within an electrolytic cell.

[0006] WO2006 / 105648A1 (Patent Document 2) discloses a method of varying an effective voltage using a pulse width modulator.

[0007] WO2010 / 084358A1 (Patent Document 3) discloses an electrolysis apparatus for generating hydrogen and oxygen.

[0008] Furthermore, WO2016 / 007983A1 (Patent Document 4) discloses an electrolytic cell and method for producing hydrogen.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0010] Therefore, the present invention is based on the problem of providing a method for generating hydrogen and oxygen that can improve the yields of hydrogen and oxygen compared to the introduced electrical energy. [Means for Solving the Problems]

[0011] According to the present invention, the above problems are solved by a method having the features described in claim 1.

[0012] According to the method for generating hydrogen and oxygen using an electrolysis device including at least one anode chamber having an anode and at least one cathode chamber having a cathode, a modulated current is passed through the at least one anode and the at least one cathode, and it is contemplated that the generation of hydrogen and oxygen in the electrolysis device is carried out under the use of a defined pulse pattern sequence formed from at least one pulse pattern.

[0013] At this time, the pulse pattern sequence can be formed from a single pulse pattern and / or a combination of at least two or a plurality of different pulse patterns from a pulse pattern library.

[0014] Similarly, the present invention contemplates the use of a modulated current for generating hydrogen and oxygen in an electrolysis device under the use of a defined pulse pattern sequence formed from at least one pulse pattern.

[0015] According to the present invention, the electrolysis device operates using a modulated current. In this case, it has been found that the hydrogen yield is not necessarily greater compared to the power used than in the case of conventional direct current electrolysis. By using a defined pulse pattern sequence formed from at least one pulse pattern, the efficiency of the electrolysis device can be significantly improved.

[0016] A scientifically traceable explanation for this effect is not yet known. However, the present inventors currently hypothesize that this effect can be based on the so-called Nernst diffusion layer splitting.

[0017] The hydrogen thus produced can be converted into synthetic fuel in other process steps, for example other process steps by the Fischer-Tropsch process.

[0018] Still another advantageous form of the present invention is described in the claims in citation form. The features individually described in the claims in citation form can be combined with each other in a scientifically meaningful way and can define still another form of the present invention. Further, the features described in the claims are more specifically defined and explained in the detailed description of the invention, where still another preferred form of the present invention is described.

[0019] Advantageously, the modulated current is provided by at least one pulse rectifier, to the negative electrode of which the at least one cathode of the electrolysis device is electrically connected, and to the positive electrode of which the at least one anode is electrically connected. The use of a pulse rectifier makes it possible to define the amount and time course of each desired pulse pattern and thus the entire pulse pattern sequence, so that the production process can be optimally adapted according to given parameters.

[0020] The modulated current can advantageously be provided from a pulse rectifier implemented with switch-mode power supply technology. The pulse rectifier configured in this way is defined by the fact that the AC voltage on the electrical mains side is first rectified and smoothed. The DC voltage then generated from that, which generally has an essentially higher frequency in the range from 5 kHz to 300 kHz, is divided, converted at this high frequency, and then rectified and filtered. The applied voltage - and current regulation generally functions via pulse width modulation or pulse phase modulation.

[0021] For the high frequencies in the transmitter, the transformer is configured much smaller, and as a result, the energy losses are much lower. Therefore, depending on the system, an essentially higher power efficiency of the DC supply is brought about.

[0022] Depending on the design, the pulse rectifier can be provided modularly. This results in an essentially higher availability, since the power to be provided by a defective module can be borne by other modules, and it can be quickly replaced when the defective module is repaired.

[0023] Yet another advantage is that the quality of the DC, especially its low residual ripple, is essentially better with lower losses than in the case of conventional thyristor-based DC electrolysis, the repair of defective devices is essentially more quickly and easily achievable, and the existing DC current / DC voltage supply system can be extended by further modules later using the appropriate regulation technology that can enhance the performance of the DC current / DC voltage supply system.

[0024] Furthermore, the pulse rectifier or other suitable voltage source used, such as an IGBT (Insulated Gate Bipolar Transistor), unlike the thyristor device connected to the electrical mains, offers the possibility of preheating the electrolysis device in a suitable structure (especially when it is connected to a battery), and of providing correspondingly good efficiency at rectifier operating points of less than 100% during stationary operation. This results in an increase in the efficiency of the overall hydrogen production system when the DC voltage supply has the same efficiency.

[0025] In one advantageous embodiment, it is contemplated that the at least one pulse rectifier is connected to a central control unit via which the production process is controlled and / or regulated. In this case, particularly preferably, it is contemplated that the at least one pulse pattern of the pulse pattern sequence is sent from the central control unit to the at least one pulse rectifier.

[0026] For this purpose, in the present invention, it is contemplated that the production process is carried out under the use of a defined pulse pattern sequence formed from individual pulse patterns. Here, the pulse pattern sequence can be formed from at least two or a plurality of the same and / or different pulse patterns from a single pulse pattern and / or a collection of pulse patterns.

[0027] Normally, the pulse patterns of the pulse pattern sequence include at least one cathode pulse defined by the pulse duration and at least one pulse pause time, where the cathode pulse is defined via the pulse duration and its respective shape, for example, in the shape of a rectangle.

[0028] The pulse duration of the cathode pulse can advantageously be from 200 μs to 500 ms. The shortest pulse duration is limited to 200 μs for technical reasons. Therefore, among other things, the shortest pulse duration is contemplated to be 200 μs, preferably 500 μs, more preferably 1000 μs, even more preferably 2000 μs, and most preferably 5000 μs.

[0029] However, the pulse duration may also not exceed a time of 500 ms. Therefore, the maximum pulse duration is, among other things, 500 ms, preferably 250 ms, more preferably 100 ms, even more preferably 50 ms, and most preferably 10 ms.

[0030] A particularly preferred range of the pulse duration is from 200 μs to 1000 μs, very particularly preferably from 200 μs to 700 μs.

[0031] The pulse pause time, i.e., the time between two consecutive cathode pulses, can be, among other things, in the range from 0.01 times to 10 times the cathode pulse, preferably in the range from 0.1 times to 5 times the cathode pulse, more preferably in the range from 1 time to 4 times the cathode pulse, even more preferably in the range from 2 times to 3.50 times the cathode pulse, and most preferably 5 times the cathode pulse.

[0032] The pulse pause time can be carried out in the present invention without current or under a holding current. In other words, in a first advantageous embodiment variant, the electrolysis device is not supplied with current for a short time, and as a result, the current intensity I has a value of zero (I A = 0). In yet another variant of an embodiment, the pulse pause time can be carried out under a holding current. In this case, the current between two cathode pulses is reduced to a specific value. This value can advantageously be up to 5 / 6 of the current of the preceding cathode pulse, preferably up to 4 / 5, more preferably up to 3 / 4, even more preferably up to 2 / 3.

[0033] The electrolysis device can be configured as a membrane-type electrolysis device such as, for example, a proton exchange membrane electrolysis device, a Nafion membrane electrolysis device, a polymer electrolyte membrane electrolysis device, or a proton exchange membrane fuel cell electrolysis device.

[0034] The present invention and the technical environment will be described in more detail below with reference to the drawings. It should be noted that the present invention is not limited to the illustrated embodiments. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the drawings and combine them with other components and findings from this specification and / or the drawings. In particular, it should be noted that the drawings and especially the indicated dimensional ratios are only approximate. The same reference signs denote the same objects, and therefore, in some cases, the descriptions from other figures can also be complementarily incorporated.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0036] FIG. 1 shows a structure known from the state of the art of an electrolysis device 1 for generating hydrogen and oxygen, which is capable of electrolytically decomposing water into both products. The electrolysis device 1 shown here is configured as a PEM type electrolysis device and includes an anode chamber 2 having an anode 3 and a cathode chamber 4 having a cathode 5. A semi-permeable membrane 6 is disposed between the two electrodes 3, 5, which is proton-permeable as symbolized based on arrow 7.

[0037] The anode chamber 2 includes a hydrogen inflow 8 through which water or electrolyte is preferably continuously introduced into the anode chamber 2, and an outlet opening 9 through which the generated oxygen can be withdrawn. As can be further seen from the depiction of FIG. 1, the cathode chamber 4 also includes an outlet opening 10 through which the hydrogen generated in the electrolysis device 1 can then be withdrawn.

[0038] To carry out the production process, a modulated current is applied to the anode 3 and the cathode 5, which is provided from a pulse rectifier 11 that can be implemented with switch-mode power supply technology. The pulse rectifier 11 is electrically connected to the cathode 5 via its negative pole and to the anode 3 via its positive pole. Both electrodes 5, 5 can supply current via the modulated current so that the process can be carried out under the use of a defined pulse pattern sequence 12 formed from individual pulse patterns 13.

[0039] Advantageously, the pulse rectifier 11 is electrically connected to a central control unit 14 via which each desired pulse pattern 13 of the pulse pattern sequence 12 can be sent to it.

[0040] In FIGS. 2-5, different implementation variations of the pulse pattern 13 are shown, which form part of the pulse pattern sequence 12 that enables the present production process to be carried out.

[0041] Figure 2 shows an embodiment variation of the pulse pattern 12, which shows a repetitive pulse pattern 12 that is uniformly configured with respect to the current value (I) and time (t). The pulse pattern 12 shows a plurality of continuously arranged rectangular cathode pulses, each having the same current intensity (I) and a pulse duration (t1). The individual pulses are arranged separated from each other within the pulse pattern 12 via a pulse pause time (t2), where t2 = t1.

[0042] In contrast, as shown by the dashed lines in FIGS. 2 to 5, a constant cathode current over time is shown as used in conventional direct current electrolysis (DC electrolysis).

[0043] Figure 3 shows an embodiment variation of the pulse pattern 12, which also shows a repetitive pulse pattern 12 that is uniformly configured with respect to the current value and time. The pulse pattern 12 shows a plurality of continuously arranged crown-shaped cathode pulses that are separated from each other by a pulse pause time (t4) and have a pulse duration (t3), where t4 = 1 / 2t1. Each of these crown-shaped pulses has three sub-pulses each having the same pulse duration (t1) and the same current intensity (I). As can be seen based on the pulse pattern 12, the individual sub-pulses are separated from each other by a pulse pause time (t2) having a holding current at a level of 2 / 3 of the current intensity of the sub-pulse. In this case, the pulse duration (t1) and the pulse pause time (t2) are of the same length (t2 = t1).

[0044] Figure 4 shows yet another pulse pattern 12, which shows a repeating pulse pattern 12 that is uniformly configured with respect to current value and time. The pulse pattern 12 shows a plurality of rectangular cathode pulses arranged in succession, each having the same current intensity (I) and a pulse duration (t1). The individual pulses are arranged within the pulse pattern 12 in a separated state from each other via a pulse pause time (t2), where t2 = t1. The holding current during the pulse pause time (t2) is here 1 / 4 of the current intensity of the pulse.

[0045] Figure 5 shows yet another implementation variant of the pulse pattern 12. The pulse pattern 12 shows an alternating sequence of rectangular cathode pulses of different current intensities. The first two pulses each have the same pulse duration (t1) and the same current intensity (I). The subsequent two pulses have their current value reduced by half (I2 = 1 / 2I1). All the pulses are separated from each other by a pulse pause time (t2), and for these, t2 = 2t1.

Example

[0046] In principle, a PEM type electrolysis device as shown in Figure 1 was used. An aqueous NaOH solution was used as the electrolyte. The electrolysis device was operated at a current intensity of 0.5 A / cm 2 and a cell voltage of about 2 V.

[0047] In the comparative example, first, water was decomposed into oxygen and hydrogen using conventional direct current electrolysis. At this time, a hydrogen volume of 50 mL / min could be detected.

[0048] In the example according to the present invention, a modulated current was passed through the electrolysis device, and in this case, a pulse pattern sequence consisting of the pulse pattern shown in Figure 2 was used. In this case, a hydrogen volume of 60 mL / min could be detected at the same power consumption. This application relates to the invention described in the claims, but the disclosure of this application also includes the following: 1. A method for generating hydrogen and oxygen using an electrolysis apparatus (1) including at least one anode chamber (2) equipped with an anode (3) and at least one cathode chamber (4) equipped with a cathode (5), wherein a modulated current is applied to the at least one anode (3) and the at least one cathode (5), and hydrogen and oxygen are generated within the electrolysis apparatus (1) under the use of a specified pulse pattern sequence (12) formed from at least one pulse pattern (13). 2. The method according to 1., wherein the modulated current is provided by at least one pulse rectifier (11), and the at least one cathode (5) is electrically connected to the negative electrode of the at least one pulse rectifier (11), and the at least one anode (3) is electrically connected to the positive electrode. 3. The method according to 2., wherein the at least one pulse rectifier (11) is electrically connected to a central control unit (14), and the generation process is controlled and / or adjusted via the central control unit (14). 4. The method according to 3., wherein the at least one pulse pattern (13) of the pulse pattern sequence (12) is transmitted from the central control unit (14) to the at least one pulse rectifier (11). 5. The method according to any one of 1. to 4., wherein the at least one pulse pattern (13) of the pulse pattern sequence (12) includes at least one cathode pulse defined via a pulse duration and at least one pulse pause time. 6. The method according to 5., wherein the pulse duration of the cathode pulse is from 200 μs to 500 ms. 7. The method according to 5. or 6., wherein the pulse pause time between two consecutive cathode pulses ranges from 0.01 times to 10 times that of the cathode pulse. 8. The method according to any one of 1. to 7., wherein the electrolysis device (1) is configured as a membrane electrolysis device. 9. Use of a modulated current for generating hydrogen and oxygen in an electrolysis device (1) using a defined pulse pattern sequence (12) formed from at least one pulse pattern (13).

Explanation of Symbols

[0049] 1. Electrolysis device 2. Anode chamber 3. Anode 4. Cathode chamber 5. Cathode 6. Membrane 7. Arrow / Proton transport direction 8. Hydrogen inflow 9. Outlet opening Oxygen 10. Outlet opening Hydrogen 11. Pulse rectifier 12. Pulse pattern sequence 13. Pulse pattern 14. Control unit

Claims

1. A method for the production of hydrogen and oxygen using an electrolysis device (1) comprising at least one anode chamber (2) provided with an anode (3) and at least one cathode chamber (4) provided with a cathode (5), wherein a modulated current is passed through said at least one anode (3) and said at least one cathode (5), and the production of hydrogen and oxygen in the electrolysis device (1) is carried out using a defined pulse pattern sequence (12) formed from at least one pulse pattern (13).

2. The method according to claim 1, wherein the modulated current is provided by at least one pulse rectifier (11), and said at least one cathode (5) is electrically connected to the negative pole of said at least one pulse rectifier (11), and said at least one anode (3) is electrically connected to the positive pole.

3. The method according to claim 2, wherein said at least one pulse rectifier (11) is electrically connected to a central control unit (14), and the production process is controlled and / or regulated via said central control unit (14).

4. The method according to claim 3, wherein said at least one pulse pattern (13) of the pulse pattern sequence (12) is transmitted from said central control unit (14) to said at least one pulse rectifier (11).

5. The method according to any one of claims 1 to 4, wherein said at least one pulse pattern (13) of the pulse pattern sequence (12) comprises at least one cathode pulse defined via a pulse duration and at least one pulse pause time.

6. The method according to claim 5, wherein the pulse duration of the cathode pulse is from 200 μs to 500 ms.

7. The method according to claim 5 or 6, wherein the pulse pause time between two consecutive cathode pulses ranges from 0.01 times to 10 times the cathode pulse.

8. The method according to any one of claims 1 to 7, wherein the electrolysis device (1) is configured as a membrane electrolysis device.

9. Use of a modulated current for producing hydrogen and oxygen in an electrolysis device (1) using a defined pulse pattern sequence (12) formed from at least one pulse pattern (13).

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