Electrolyser for alkaline hydrogen electrolysis

Abstract

The invention relates to an electrolyser for alkaline hydrogen electrolysis, comprising: a direct voltage source, in particular a rectifier (1) having an electrical positive pole (2) and an electrical negative pole (3); media inlet lines (4) for an electrolysis medium; and media outlet lines (5) for product media; wherein a plurality of electrolysis blocks (6) which are connected in series via electrical connecting lines (9) are connected between the positive pole (2) and the negative pole (3), wherein the electrolysis blocks (6) each have a number of electrolysis cells (7) which are electrically connected in series and are mechanically clamped so that they are flush with one another, wherein the media inlet lines (4) and the media outlet lines (5) each extend serially through the electrolysis blocks (6) and are distributed within each individual electrolysis block (6) to individual cell inlet lines (4', 4") and individual cell outlet lines (5', 5") of the electrolysis cells (7).

Description

[0001] Electrolyzer for alkaline hydrogen electrolysis

[0002] The invention relates to an electrolyzer for alkaline hydrogen electrolysis.

[0003] Hydrogen production through alkaline electrolysis is well known in the art. Common alkaline electrolyzers are usually systems that operate under atmospheric pressure or slight overpressure up to 1 bar. Such systems are often designed as interconnected individual cells to facilitate transport and assembly of the electrolyzer. The medium supply, often a potassium hydroxide solution (KOH) in the case of an alkaline electrolyzer, is handled separately for each individual cell. The product and excess KOH are also removed separately for each individual cell. The problem with a process under such conditions is that the hydrogen must be compressed for further processing or transport, requiring a compressor. The disadvantage of these compressors, however, is their high maintenance intensity and the resulting additional costs.

[0004] Alkaline electrolyzers can also be designed as pressurized systems. In this case, they are typically operated at a pressure of up to 30 bar. Pressurized electrolyzers are usually designed as integrated electrolysis blocks containing multiple electrolysis cells. The disadvantage of these pressurized systems is that they are difficult to transport and assemble. Such systems weigh up to 90 tons. The pressurized design also complicates series production. The object of the present invention is to overcome the problems of the prior art and to provide a pressurized electrolyzer that can be more easily transported, assembled, and maintained in a modular manner. A further object of the invention can be seen in providing the most powerful system possible with minimal material usage and enabling the simplest possible series production of the components.

[0005] These and other objects are achieved by an electrolyzer according to claim 1.

[0006] An electrolyzer according to the invention is designed for alkaline hydrogen electrolysis and comprises a direct voltage source, in particular a rectifier with a positive electrical pole and a negative electrical pole. The rectifier can be designed for connection to a powerful alternating current network and for providing a direct voltage in the range of approximately 300 V to approximately 1500 V, for example, approximately 600 V to approximately 800 V. The output direct current can be more than approximately 600 A, preferably more than approximately 2000 A.

[0007] Media supply lines for an electrolysis medium and media outlets for product media are provided. The electrolysis medium can be a lye, in particular a potassium hydroxide solution (KOH) or sodium hydroxide solution (NaOH), which is fed into the electrolyzer at a pressure of over 10 bar, preferably approximately 30 bar. The product media can be a pressurized mixture of the lye with O2 on the one hand, and H2 on the other. The gases O2 and H2 are obtained as a product of the electrolysis.

[0008] Several electrolysis blocks are connected in series via electrical connecting lines between the positive and negative poles of the rectifier, so that the output voltage of the rectifier is distributed among the individual electrolysis blocks. The electrolysis blocks each comprise a plurality of electrolysis cells that are electrically connected in series and mechanically clamped flush. Each electrolysis block can comprise up to approximately 100, and possibly even up to approximately 200 or more, individual electrolysis cells. According to the invention, the media supply lines and the media outlets each run serially through the electrolysis blocks. The media supply lines and the media outlets can be led out of the electrolysis blocks, in particular via flange connections, in order to enable a simple serial connection of the electrolysis blocks.This allows any number of electrolysis blocks to be connected in series, with the media flowing through the electrolysis blocks one after the other. Instead of flange connections, other detachable or non-detachable connections can be used. In particular, the outgoing media supply and discharge lines can also be welded.

[0009] The number of electrolysis blocks is limited by the available DC voltage and the total number of electrolysis cells, since each electrolysis cell requires a DC voltage of approximately 2 V. Within each electrolysis block, the media supply lines and the media drain lines are distributed between individual cell supply lines and individual cell drain lines of the individual electrolysis cells.

[0010] Such interconnection of multiple electrolysis blocks and distribution of the media supply and discharge lines within the electrolysis blocks allows for a particularly flexible electrolyzer design. Depending on the available DC voltage and the number of electrolysis cells, a specific number of electrolysis cells can be combined into individual electrolysis blocks, and multiple electrolysis blocks can be connected in series and supplied by a single rectifier. This allows for the use of small and lightweight electrolysis blocks even at higher voltages in the range of approximately 300 V to approximately 1500 V.

[0011] Furthermore, the media supply and discharge lines do not need to be routed to each individual electrolysis cell, as the distribution to the cell supply and discharge lines takes place within the electrolysis blocks. The media supply and discharge lines are connected to the flanges of the electrolysis blocks, and the desired number of electrolysis blocks is connected in series, leaving the end flanges closed. According to the invention, the media supply and discharge lines can be grounded.

[0012] Furthermore, it can be provided that the media supply lines and media discharge lines are connected to common and preferably earthed pressure manifolds, so that the supply of the electrolysis medium and the removal of the product media can take place via the pressure manifolds.

[0013] It can be provided that the pressure manifolds are connected to a first, external electrolysis block of the series-connected electrolysis blocks, so that the electrolysis medium and the product media flow serially from this electrolysis block to all subsequent electrolysis blocks. The positive and negative poles of the rectifier are each connected to the external electrolysis blocks.

[0014] However, it can also be provided that two or more electrolysis blocks are arranged in a T-shaped arrangement around the central pressure manifolds, so that the electrolysis medium and the product media flow from these two electrolysis blocks through all other electrolysis blocks in parallel. The positive and negative poles of the rectifier are each connected to the outer electrolysis blocks. This results in a continuous voltage drop across the electrolysis blocks and, at the same time, an even distribution of the media among the electrolysis blocks. In this topology, two, four, six, eight, or more electrolysis blocks can be arranged, starting from central pressure manifolds.

[0015] According to the invention, it can be provided that the electrolysis blocks each have an identical number of electrolysis cells, so that the voltage drop across each electrolysis block is the same. However, it can also be provided that the electrolysis blocks have a different number of electrolysis cells, so that the voltage drop across the electrolysis blocks is different. According to the invention, it can be provided that the electrolysis cells each have two electrically conductive half-shells separated by a separating layer, each with a metallic outer skin. This forms an anode compartment with an anode and a cathode compartment with a cathode. The two half-shells can be connected by a circumferential, metallic and preferably annular support frame. The support frame and the outer skin can preferably be made of stainless steel.

[0016] The support frame can have recesses, in particular holes, to enable the distribution of the media supply lines and media drains to the cell supply lines and cell drains of the individual electrolysis cells. This allows for a space-saving and efficient distribution of the media from the media supply lines and media drains to the individual cell supply lines and cell drains of the electrolysis cells. The recesses or holes can have a diameter of just a few centimeters to avoid compromising the stability of the support frame.

[0017] It can also be provided that, in addition to the support frame, a separate distribution frame is provided, which has recesses, in particular bores, to enable the distribution of the media supply lines and the media outlets to the individual cell supply lines and individual cell outlets of the individual electrolysis cells. In this case, the support frame is preferably solid, metallic, and made without recesses in order to withstand the pressure of the electrolysis cells. However, the distribution frame can be made of a plastic material, as it does not have to absorb high mechanical pressure. This has the advantage that the media used do not come into contact with the metallic support frame, thus preventing corrosion of the metallic support frame.The distribution frame can preferably be alkali-resistant and can preferably be arranged within the support frame, particularly preferably in direct contact with the anode compartment and cathode compartment of the electrolysis cell. The electrolysis cells can be designed as a zero-gap system, wherein direct contact between the cathode and anode is provided with the insulating separating layer. The separating layer can be designed as a permeable membrane or as a diaphragm. The separating layer can be, for example, a polyphenylene sulfide fabric coated with a mixture of a polymer (e.g., polysulfone) and zirconium oxide (ZrCh). By applying a direct voltage of approximately 1.5 V to approximately 2.5 V to the electrolysis cell, H2 and OH' are formed in the cathode compartment and O2 and H2O are formed in the anode compartment. The OH' can subsequently diffuse through the separating layer into the anode compartment, whereby O2 and H2O can be formed again.

[0018] According to the invention, the half-shells of the electrolysis cells can be electrically insulated from one another at their edges, wherein the half-shells each comprise at least one individual cell supply line and at least one individual cell discharge line for a medium. In an electrolysis block, the outer skin of the cathode compartment of each electrolysis cell is arranged flush with the outer skin of the anode compartment of another electrolysis cell and is arranged in an electrically conductive manner. This forms a stack-like arrangement of the electrolysis cells in the electrolysis block.

[0019] All components of the electrolysis cell can essentially be alkali-resistant, hydrogen-resistant, oxygen-resistant and water-resistant.

[0020] If necessary, the half-shells are connected exclusively via the support frames, so that the two outer skins of the half-shells do not touch each other. A circumferential plastic seal can be provided for electrical insulation and to seal the support frames. Preferably, several screw connections can be provided to connect the support frames.

[0021] Optionally, it is provided that the support frame is thicker than the outer skin by a factor of approximately 100 to approximately 200 and preferably has a thickness of approximately 1 cm to approximately 2 cm. The depth of the support frame can be approximately 5 cm to approximately 20 cm. This forms a stable support frame that is suitable for absorbing radial compressive forces prevailing inside the half-shells. Optionally, it is provided that the half-shells have a diameter of approximately 1 m to approximately 3 m and a thickness of approximately 1 cm to approximately 3 cm, so that the electrolysis cell has a thickness of approximately 2 cm to approximately 6 cm. This ensures the stability of the electrolysis cell, while the material expenditure is low and a relatively low weight of approximately 150 kg to 250 kg can be achieved for a single electrolysis cell with an active area of ​​several m2.

[0022] According to the invention, the electrolysis cells of an electrolysis block can be held together by connecting means, in particular screw connections, wherein the connecting means preferably extend entirely through the support frames and press them together. The connecting means can be designed to hold together the support frames of several, preferably up to approximately 100, serially arranged electrolysis cells per electrolysis block.

[0023] According to the invention, it can be provided that the electrolysis cells of an electrolysis block are arranged between end plates, wherein the end plates are firmly clamped by preferably several tie rods, and wherein the end plates are arranged on insulating elements.

[0024] Further features of the invention emerge from the claims, the description of the embodiments, and the figures. The invention is explained below with reference to figures showing exemplary embodiments:

[0025] Fig. 1a shows a first embodiment of an electrolyzer according to the invention; Fig. 1b shows a sectional view of an electrolysis block of an electrolyzer according to the invention;

[0026] Fig. 1c shows a sectional view of an electrolysis cell of an electrolyzer according to the invention.

[0027] Fig. 1a shows a schematic, not-to-scale representation of a first embodiment of an electrolyzer according to the invention for alkaline hydrogen electrolysis. The electrolyzer comprises a rectifier 1 with an electrical positive pole 2 and an electrical negative pole 3, as well as media supply lines 4 for potassium hydroxide solution KOH and media outlet lines 5 for the product media KOH + H2 and KOH + O2. Four electrolysis blocks 6, connected in series via electrical connecting lines 9 and electrodes 10, are connected between the positive pole 2 and the negative pole 3. In this embodiment, the electrical direct voltage is distributed essentially identically among the four electrolysis blocks 6.

[0028] The electrolysis blocks 6 each contain approximately 80 electrolysis cells 7 electrically connected in series and mechanically clamped flush, with the media supply lines 4 and the media outlet lines 5 each running serially through the electrolysis blocks 6 and being distributed within each individual electrolysis block 6 to individual cell supply lines 4', 4" and cell outlet lines 5', 5" of the electrolysis cells 7. The electrolysis blocks 6 each have electrodes 10 (shown in bold) as positive and negative poles, via which an electrical voltage is applied to the closely spaced electrolysis cells 7.

[0029] The media supply lines 4 and the media outlet lines 5 are led out of the electrolysis blocks 6 via flange connections 8, 8' and are each connected to the next electrolysis block 6. The two outer electrolysis blocks 6 are designed as end blocks and have closed end flanges. In this exemplary embodiment, the electrolysis medium is supplied and the product media is removed via grounded central pressure manifolds 17, 18. Specifically, four electrolysis blocks 6 are arranged in a T-shaped arrangement around the central pressure manifolds 17, 18, so that the electrolysis medium and the product media, starting from the two inner electrolysis blocks 6, pass through the two outer electrolysis blocks 6 in parallel.

[0030] The electrolysis cells 7 each comprise two electrically conductive half-shells separated by a separating layer 14, each having a metallic outer skin. The half-shells are connected by a surrounding, metallic, and preferably annular support frame 11. The support frames 11 have recesses (not shown in Fig. 1a) to enable the distribution of the media supply lines 4 and the media outlet lines 5 to the individual cell supply lines 4', 4" and individual cell outlet lines 5', 5" (not shown) of the individual electrolysis cells 7.

[0031] Furthermore, the solid end plates 15 are visible in this illustration, which press the electrolysis cells 7 of each electrolysis block 6 together, wherein the end plates are firmly clamped by tension rods (not shown), and wherein the end plates 15 are arranged on insulating elements 16.

[0032] Fig. 1b shows a sectional view of an electrolysis block 6 of an electrolyzer according to the invention, with a single electrolysis cell 7 visible. In this exemplary embodiment, the electrolysis cell 7 is essentially circular, with the media supply lines 4 located in the lower region and the media outlet lines 5 located in the upper region. The support frame 11 surrounds the circular half-shells 12, 14 of the electrolysis cell 7 around their entire circumference and is electrically insulated from them. The outer surfaces of adjacent electrolysis cells 7 are arranged flush and electrically conductively, ensuring good, full-surface electrical contact.

[0033] KOH solution is introduced into the electrolysis cell 7 through the pressure collection line 17 and subsequently the media supply lines 4, building up a pressure of up to 30 bar and more. The support frame 11 is designed to absorb any radial compressive forces that arise. Electrolysis is initiated in the electrolysis cell 7 by the applied direct voltage of approximately 1.5 to 2.5 volts per cell. The product gases H2 and O2 are introduced from the electrolysis cell 7 through the media outlets 5 in the upper region of the support frame 11 into the pressure collection line 18 and subsequently fed to external separators for separating the lye and H2 or O2. Fig. 1c shows a schematic, not to scale, sectional view of an electrolysis cell 7 of an electrolyzer according to the invention.The electrolysis cell 7 comprises two electrically conductive half-shells separated by a separating layer 14, each with a metallic outer skin, so that an anode chamber 12 with an anode (not shown) and a cathode chamber 13 with a cathode (not shown) are formed.

[0034] Between the two electrodes, an electrically insulating separating layer 14 in the form of a membrane is arranged, which is, however, ion-permeable, allowing OH' ions to diffuse through the separating layer 14 and forming a closed circuit. In this embodiment, the separating layer 14 consists of a polyphenylene sulfide fabric containing a mixture of polysulfone and zirconium oxide (ZrO2), as well as optionally polytetrafluoroethylene and inorganic additives. It is 0.5 mm thick and has a porosity of, for example, 55%. The anode, the separating layer 14, and the cathode are arranged directly adjacent to one another, creating a zero-gap arrangement.

[0035] The half-shells are connected by a circumferential, metallic and annular support frame 11, which has bores to enable distribution of the media supply lines 4 and the media outlets 5 to the internal individual cell supply lines 4', 4" and individual cell outlets 5', 5" of the individual electrolysis cells 7, which open radially into the anode chamber 12 and the cathode chamber 13.

[0036] However, the invention is not limited to the described

[0037] Embodiments, but encompasses all devices within the scope of the following patent claims. List of reference symbols

[0038] 1 rectifier

[0039] 2 positive pole

[0040] 3 Negative pole

[0041] 4 media supply lines

[0042] 5 media derivatives

[0043] 6 Electrolysis block

[0044] 7 electrolysis cells

[0045] 8, 8' flange connection

[0046] 9 Electrical connecting cable

[0047] 4', 4" Individual cell lead

[0048] 5', 5" Individual cell derivation

[0049] 10 Electrode

[0050] 11 support frames

[0051] 12 Anode compartment

[0052] 13 Cathode compartment

[0053] 14 Separating layer

[0054] 15 end plates

[0055] 16 Insulating element

[0056] 17 Pressure manifold for media supply line

[0057] 18 Pressure manifold for media discharge

Claims

Patent claims 1. Electrolyzer for alkaline hydrogen electrolysis, comprising - a direct voltage source, in particular a rectifier (1) with an electrical positive pole (2) and an electrical negative pole (3), and - media supply lines (4) for an electrolysis medium and media outlets (5) for product media, characterized in that - between the positive pole (2) and the negative pole (3) several electrolysis blocks (6) connected in series via electrical connecting lines (9) are connected, whereby - the electrolysis blocks (6) each have a plurality of electrolysis cells (7) electrically connected in series and mechanically clamped flush, wherein - the media supply lines (4) and the media outlets (5) each run serially through the electrolysis blocks (6) and are distributed within each individual electrolysis block (6) to individual cell supply lines (4', 4") and cell outlets (5', 5") of the electrolysis cells (7).

2. Electrolyzer according to claim 1, characterized in that the media supply lines (4) and the media outlets (5) are led out of the electrolysis blocks (6) via flange connections (8, 8').

3. Electrolyzer according to claim 1 or 2, characterized in that the media supply lines (4) and the media outlet lines (5) are earthed.

4. Electrolyzer according to one of claims 1 to 3, characterized in that the supply of the electrolysis medium and the removal of the product media takes place via preferably earthed, central pressure collecting lines (17, 18).

5. Electrolyzer according to claim 4, characterized in that the pressure collecting lines (17, 18) are connected to a first, external electrolysis block (6) of the series-connected electrolysis blocks (6), so that the electrolysis medium and the product media, starting from this electrolysis block (6), pass through all further electrolysis blocks (6) in series.

6. Electrolyzer according to claim 4, characterized in that two, four, six, eight or more electrolysis blocks (6) are arranged in a T-shaped arrangement around the central pressure manifolds (17, 18), so that the electrolysis medium and the product media, starting from these two electrolysis blocks (6), pass through all the other electrolysis blocks (6) in parallel.

7. Electrolyzer according to one of claims 1 to 6, characterized in that the electrolysis blocks (6) each have an identical number of electrolysis cells (7), so that the voltage drop across each electrolysis block (6) is substantially identical.

8. Electrolyzer according to one of claims 1 to 6, characterized in that the electrolysis blocks (6) have a different number of electrolysis cells (7), so that the voltage drop across the electrolysis blocks (6) is different.

9. Electrolyzer according to one of claims 1 to 8, characterized in that - the electrolysis cells (7) each have two electrically conductive half-shells separated by a separating layer (14), each with a metallic outer skin, so that an anode chamber (12) with an anode and a cathode chamber (13) with a cathode are formed, wherein - the half-shells are connected by a circumferential, metallic and preferably annular support frame (11), and wherein - the support frame (11) has recesses, in particular bores, to enable the distribution of the media supply lines (4) and the media outlets (5) to the individual cell supply lines (4', 4") and individual cell outlets (5', 5") of the individual electrolysis cells (7).

10. Electrolyzer according to claim 9, characterized in that - the half-shells are electrically insulated at their edges, whereby - the half-shells each comprise at least one individual cell supply line (4') and at least one individual cell discharge line (5') for a medium, and wherein an outer skin of the cathode chamber (13) of each electrolysis cell (7) is arranged flush and electrically conductively with an outer skin of the anode chamber (12) of a further electrolysis cell (7).

11. Electrolyzer according to claim 10, characterized in that the half-shells of the electrolysis cells (7) are connected only via the support frames (11), a circumferential plastic seal being provided between the support frames (11) for electrical insulation.

12. Electrolyzer according to one of claims 1 to 11, characterized in that the electrolysis medium is a potassium hydroxide solution (KOH) or sodium hydroxide solution (NaOH) which is under a pressure of more than 10 bar, preferably about 30 bar.

13. Electrolyzer according to one of claims 1 to 12, characterized in that the electrolysis cells (7) of an electrolysis block (6) are held together by connecting means, in particular screw connections, wherein the connecting means preferably extend entirely through the support frames (11) and press them together.

14. Electrolyzer according to claim 13, characterized in that the connecting means are designed to hold together the support frames (11) of several, preferably up to about 100, serially arranged electrolysis cells (7) per electrolysis block (6).

15. Electrolyzer according to one of claims 1 to 14, characterized in that the electrolysis cells (7) of an electrolysis block (6) are arranged between end plates (15), wherein the end plates (15) are firmly clamped by preferably several tie rods, and wherein the end plates (15) are arranged on insulating elements (16).

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