WO2022258394A1

WO2022258394A1 - Electrolysis cell and electrolyzer

Info

Publication number: WO2022258394A1
Application number: PCT/EP2022/064384
Authority: WO
Inventors: Sebastian Austenfeld; Peter Toros; Aleksander STACHNIK
Original assignee: thyssenkrupp nucera AG & Co. KGaA
Priority date: 2021-06-07
Filing date: 2022-05-27
Publication date: 2022-12-15

Abstract

The invention relates to an electrolysis cell (1) comprising a cell casing (2) with two semi-shells (3, 4) made of an electrically conducting material, a separator (5) interposed between the semi-shells (3, 4), and an electrode (6, 7) disposed within each of the semi-shells (3, 4), wherein the semi-shells (3, 4) comprise a pan (8) with a rear wall (9) and circumferential side walls (10) attached to the rear wall (9), and a circumferential flange portion (11) with an inner edge portion (12) being attached to the side walls (10) of the pan (8), and wherein the side walls (10) of the pan (8) connecting the flange portion (11) with the rear wall (9) are shaped in the form of an arch (15) and tension means (13, 14) are provided, which are attached to the inner edge portion (12) of the flange portion (11) and extend across the pan (8).

Description

Electrolysis Cell and Electrolyzer

Background of the invention

The invention relates to an electrolysis cell according to the preamble of claim 1 and an elec trolyzer according to the preamble of claim 13.

From US 6282 774 B1 an electrolyzer for producing halogen gases from aqueous alkali halogenide solution with several plate-like electrolysis cells arranged side-by-side in a stack is known. Each cell is encased in to semi-shells made from electroconductive material with contact strips on the outer side of the casing’s rear wall. The anode and the cathode are sep arated from one another by a partition, are arranged parallel to one another and are electri cally connected to the rear wall of the respective casing via metal reinforcements in the form of solid plates.

An electrolyzer having a similar cell design is known from US 4664770 A.

The known electrolyzers are typically configured to provide their product gases at ambient pressure. For the use of these gases in downstream chemical facilities or in a private or pub lic gas grid the gases must be provided at a predefined overpressure. For this reason addi tional gas compressors with high compression ratios are needed that require additional en ergy supply and therefore reduce the overall degree of efficiency of the gas production pro cess. Operating the known electrolysis cells at an internal fluid overpressure even of only 0.5 bar (g) results in a high bending strain in the bent wall/flange structure of the semi-shells that can only be absorbed if the thickness of the sheet metal forming the semi-shells is in creased significantly at high material costs.

Brief Summary of Invention

The object of the invention is to provide an electrolysis cell and an electrolyzer that is able to provide the product gases at an elevated pressure at low costs, thereby increasing the over all degree of efficiency of the gas production process. This object is achieved by an electrolysis cell with the features of claim 1 and an electrolyzer with the features of claim 13.

Hereby, an electrolysis cell is provided that comprises a cell casing with two semi-shells made of an electrically conducting material, a separator interposed between the semi-shells, and an electrode disposed within each of the semi-shells. The semi-shells each comprise a pan with a rear wall and circumferential side walls attached to the rear wall, as well as a cir cumferential flange portion with an inner edge portion being attached to the side walls of the pan. According to the invention, the side walls of the pan connecting the flange portion with the rear wall are shaped in the form of an arch. Further, tension means are provided, which are attached to the inner edge portion of the flange portion and extend across the pan.

Due to the arched side walls in combination with the tension means, the inventive electrolysis cell is able to withstand internal fluid pressures, in particular internal fluid pressures of sev eral bar (g), and is producible with the cost-saving techniques of metal sheet manufacturing at the same time. In case of an internal fluid pressure exceeding the ambient pressure, the walls of the pans are exposed to internal pressure forces acting in a normal direction from the inside to the outside on the respective wall. In the region of the rear walls of the pans in creasing pressure forces of neighboring cells within a cell stack compensate for each other, since the rear walls of the neighboring cell are in direct contact with each other and the pres sure forces act in opposite directions. In the region of the side walls the arched shape of the side walls allows to absorb the pressure forces in form of tensile or compressive stresses. The arched shape is configured to deflect the absorbed pressure forces at its ends to the rear wall and to the tension means extending across the pan, respectively. Thus, the pres sure forces acting on the arched side walls are advantageously dissipated into tensile stresses of the rear wall and the tension means. Thereby, deformations of the electrolysis cell casing at its circumference can be reduced, even without needing to increase the mate rial thickness.

In preferred embodiments of the invention the arch has an arch height and an arch span, wherein a ratio of the arch height to the arch span is at least 0.1. For an effective dissipation of the forces to the rear wall and to the tension means a larger arch height is advantageous. However, the cell volume enclosed in the arched region cannot effectively take part in the electrolysis process. Thus, even more preferred the ratio is within the range of 0.4 to 0.8. Generally, for force dissipation purposes, the arch shape of the side walls may be arched outwards or inwards. An outward arch, i.e. concave arch when viewed from the inside of the cell, results in tensile stresses in the arch and larger installation space requirements. In pre ferred embodiments the side walls are arched inwards, i.e. providing a convex arch when viewed from the inside of the cell. In this case the arch is exposed to compressive stresses and no additional installation space is needed. However, it is even conceivable to have a combination of inwardly and outwardly arched side walls within the same semi-shell.

Preferably, the arch has a circular, elliptical or polygonal shape in cross section. The circular cross-section is preferred as the theoretically most stable configuration. However, an ellipti cal shape may allow for larger attachment surfaces to the rear wall and/or the flange portion, and thus may be preferred for practical reasons. A polygonal cross section may result in manufacturing advantages as it can be produced by segmented bending of a metal sheet.

In further preferred embodiments the arch has a closed geometry cross section. Thus, it is conceivable that the side walls are made of tubes, in particular round or flattened tubes, or D- shaped profiles. Using a closed geometry has the advantages that prefabricated components may be used as side walls of the electrolysis cell. Moreover, it is conceivable that the closed geometry of the arch can be used to conduct electrolysis educts and/or products to/away from the cell.

In further preferred embodiments, the tension means form a mechanical support for the elec trode within the semi-shell. Thus, the pressure forces deflected to the tension means as ten sile stresses are advantageously made use of by increasing the support of the electrode. In particular, the electrode may be pressed to the separator by the additional supporting forces exerted by the tension means.

Preferably, the inner edge portion of the flange portion is provided with inwardly protruding anchoring portions to which the tension means are attached. The pressure forces acting on the side walls of the pan are transferred to the tension means via the flange portion. The in wardly protruding anchoring portions of the flange portion help to reduce the strain intro duced to the flange portion. Particularly preferably, the anchoring portions widen at the junc tion to the flange portion. Thereby, a larger radius of curvature at the junction is achieved that helps to reduce stress peaks in the flange portion. Preferably, the tension means comprise a plurality of tension stripes traversing the pan in at least two crossing directions. Thereby it is ensured that tension stripes are attached to every side wall of the pan. Every pressure force dissipated into the tension stripes is counteracted by a corresponding counterforce introduced to the other end of the tension stripe. Preferably, the two crossing directions correspond to a width and a height direction of the pan.

Preferably, at least part of the tension stripes have a T-shaped, L-shaped or l-shaped cross section. By and L- or T-shaped cross section the second moment of area of the tension stripes is enhanced. Thereby the function to support the electrode is improved.

The tension means preferably comprise a wire mesh at least partly covering the pan. This wire mesh can be used as a mechanical support for the electrode or form itself the electrode within the respective semi-shell.

In preferred embodiments the electrolysis cell is suitable for chlor-alkali electrolysis or alka line water electrolysis. Thus, the materials of the electrolysis cell are chosen as to withstand alkaline conditions. In particular, parts or all of the semi-shells may be made of nickel or nickel alloys.

The invention further relates to an electrolyzer for alkaline water electrolysis or chlor-alkali electrolysis comprising a plurality of electrolysis cells arranged side-by-side in a stack whilst being electrically connected via their rear walls, wherein the electrolysis cells are configured as described above.

Further advantages of the invention are described in the following with regard to the embodi ments shown in the attached drawings.

Brief Description of Drawings

Fig. 1 shows schematically a cross-sectional view of two electrolysis cells accord ing to a first embodiment of the invention in a side-by-side arrangement of an inventive electrolyzer,

Fig. 2A shows schematically a perspective view of one corner of a semi-shell of the electrolysis cells of Fig. 1,

Fig. 2B shows schematically a second perspective, partly sectional view of the cor ner of the semi-shell shown in Fig. 2A from a different perspective, Fig. 3A to 3D show schematically a cross-sectional view of four different alternative de signs for the side walls the electrolysis cell according to the invention,

Fig. 4 shows schematically a plan view of a semi-shell of an electrolysis cell ac cording to a second embodiment of the invention having a wire-mesh form ing the tension means.

Detailed Description of Invention

In the drawings same parts are consistently identified by the same reference signs and are therefore generally described and referred to only once.

In Fig. 1 an electrolyzer 100 for alkaline water electrolysis or chlor-alkali electrolysis is shown. The electrolyzer 100 comprises a plurality of electrolysis cells 1 - two of which are depicted in Fig. 1 - arranged side-by-side in a stack. Neighboring electrolysis cells 1 are electrically connected via their rear walls 9. Thus, during operation of the electrolyzer 100, a supply voltage is provided to the rear walls 9 of the leftmost and the rightmost electrolysis cell 1 in the stack resulting in an electrolysis current through the complete stack of electroly sis cells 1 connected in series.

The electrolysis cells 1 of the electrolyzer 100 comprise a cell casing 2 with two semi-shells 3, 4 made of an electrically conducting material, a separator 5 interposed between the semi shells 3, 4, and an electrode 6, 7 disposed within each of the semi-shells 3, 4.

The semi-shells 3, 4 comprise a pan 8 with a rear wall 9 and circumferential side walls 10 at tached to the rear wall 9, and a circumferential flange portion 11 with an inner edge portion 12 being attached to the side walls 10 of the pan 8.

The flange portions 11 of the semi-shells 3, 4 of each cell casing 2 are fixed to one another by fixation means 16 with the separator 5 interposed between them. The separator 5 and/or an additional seal interposed between the flange portions 11 of the semi-shells 3, 4 for elec trically isolating the semi-shells 3, 4 from one-another. The electrodes 6, 7 are electrically connected to the rear wall 9 of the respective semi-shell 3, 4. As shown in Fig. 1 this electri cal connection can be established by substantially vertical ribs 19 that may form a mechani cal support for the electrodes 6, 7 at the same time. The fixation means 16 shown in Fig. 1 are formed by a plurality of bolts arranged circumfer entially around the cell and fixing the cell casing 2 to metal frames in which the electrolysis cells 1 are mounted. However, additional or alternative fixation means, in particular clamping means are conceivable to hold the semi-shells 3, 4 together.

The educts of the electrolysis are fed to the electrolysis cells 1 via external supply tubes 17 connected to internal feed pipes 18 that distribute the educts homogeneously at the bottom of the cell. The electrolysis products are withdrawn at the top of the cell 1 via outlet channels (not shown).

According to the invention the side walls 10 of the pan 8 that connect the flange portion 11 with the rear wall 9 and are shaped in the form of an arch 15. Further, tension means 13 are provided, which are attached to the inner edge portion 12 of the flange portion 11 and extend across the pan 8. Internal pressure forces acting on the side walls 10 are absorbed by the arch 15 and transferred to the rear wall 9 and the tension means 13 on both sides of the arch 15. For an effectively transferring the forces it is preferred that the arch 15 has an arch height H and an arch span S, wherein the ratio of the arch height H to the arch span S is at least 0.1, and, more preferred, lies in the range of 0.4 to 0.8.

The force transfer mechanism of the arch 15 depends on the direction of its curvature. In the embodiment shown in Fig. 1 the side walls 10 are arched inwards. In this case the forces are transferred within the arch 15 as compressive stresses. As can be seen in Fig. 1 the inwardly arched side walls 10 have the additional advantage to save installation space for the fixation means 16 holding the semi-shells 3, 4 together. If the side walls 10 are arched outwards, the forces are transferred as tensile stresses within the arch 15.

As depicted in Fig. 1 , the tension means 13 preferably form a support for the electrode 6, 7 within the respective semi-shell 3, 4. Thus, the electrodes 6, 7 may be - directly or indirectly - in mechanical connection with the tension means 13.

In Fig. 2A and 2B parts of the semi-shells 3, 4 are shown in more detail. To the sheet-like rear wall 9 arched side-walls 10 are attached, thereby forming the pan 8. To the other side of the arch 15 a sheet-like flange portion 11 is attached with its inner edge portion 12. The flange portion has circumferentially distributed mounting borings for the passage of fixation means 16. Within the semi shells 3, 4 metal ribs 19 are arranged in a height direction of the cell as a support and electrically conducting connection for the electrodes (not shown) with the rear wall 9.

The tension means 13 in the embodiment of Fig. 2A and 2B comprise a plurality of tension stripes 13.1, 13.2 that traverse the pan 8 in two crossing directions. Preferably, the tension stripes 13.1, 13.2 connect opposing inner edges of the circumferential flange portion 11. In the shown example, the tension stripes 13.1 extend in a width direction and the tension stripes 13.2 extend in a height direction of the cell.

The inner edge portion 12 of the flange portion 11 is preferably provided with inwardly pro truding anchoring portions 22 to which the tension means 13, 14 are attached. Thereby the stress introduced into the flange portion 11 at the joint with the tension means 13, 14 is ho mogenized in order to minimize strain. For enhancing the support of the electrodes, it is pre ferred if at least part of the tension stripes 13.2 have a T-shaped, L-shaped or l-shaped cross section.

In Fig. 3A to 3D several alternative geometries for the arched side-walls 10 are shown. Fig. 3A shows a side wall 10 between the rear wall 9 and the tension means 13, that has a polyg onal shape cross sections. The pressure forces p are transferred to the rear wall 9 and the tension means 13 and act there as tensile forces Ft. Although the edges of the polygonal shape result in an inhomogeneous stress distribution within the arch 15, such a shape may be preferred for practical reasons as it can be manufactured by segmented bending of a sheet metal.

Figs. 3B and 3C show side walls 10 with a closed geometry cross section. In Fig. 3B a side wall 10 made from a tube 20 is shown. The tube 20 is flattened in the region of its attachment to the rear wall 9 and the tension means 13, which facilitates the attachment. However, also the use of round tubes is conceivable. Fig. 3C shows a side wall 10 made from a D-shaped profile 21.

In Fig. 3D an embodiment of a side wall 10 is shown that is arched outwards, such that the pressure forces p are transferred as tensile stresses in the arch 15.

In the Figs. 3A to 3D the ratio of the arch height H to the arch span S of the arch 15 is larger than 0.3 and below 0.8. Fig. 4 shows one semi-shell 3 according to a second embodiment of the inventive electroly sis cell 1. The second embodiment differs from the first embodiment shown in Fig. 1 and 2 only in that instead of tension stripes 13.1, 13.2 a wire mesh 14 is used as tension means 13. The wire mesh 14 covers the area of the pan 8 and is fixed to the circumferential flange por tion 11 at its inner edge portion 12. As shown in Fig. 4 the wire mesh 14 preferably forms the electrode 6 of the semi-shell 3. In this case it is advantageous that no additional tension means in form of tension stripes are needed.

As in the first embodiment, the electrolysis cell 1 according to the second embodiment is suit able for chlor-alkali electrolysis or alkaline water electrolysis.

In all other respects, the description of the first embodiment is applicable to the second em bodiment shown in Fig. 4, accordingly.

List of Reference Signs

1 Electrolysis cell

2 Cell Casing

3, 4 Semi-Shell

5 Separator

6, 7 Electrode

8 Pan

9 Rear Wall

10 Side Wall 11 Flange Portion 12 Inner Edge Portion

13 Tension Means

13.1, 13.2 Tension Stripes

14 Tension Means; Wire Mesh

15 Arch

16 Fixation Means

17 External Supply Tube

18 Internal Feed Pipe

19 Rib

20 Tube 21 D-shaped Profile 22 Anchoring Portion 100 Electrolyzer

H Height of Arch

S Span of Arch

Ft Tension Force p Pressure Force

Claims

1. Electrolysis cell comprising a cell casing (2) with two semi-shells (3, 4) made of an electrically conducting material, a separator (5) interposed between the semi-shells (3, 4), and an electrode (6, 7) disposed within each of the semi-shells (3, 4), wherein the semi-shells (3, 4) comprise a pan (8) with a rear wall (9) and circumferential side walls (10) attached to the rear wall (9) , and a circumferential flange portion (11) with an inner edge portion (12) being at tached to the side walls (10) of the pan (8), characterized in that the side walls (10) of the pan (8) connecting the flange por tion (11) with the rear wall (9) are shaped in the form of an arch (15) and tension means (13, 14) are provided, which are attached to the inner edge portion (12) of the flange portion (11) and extend across the pan (8).

2. Electrolysis cell according to claim 1, characterized in that the arch (15) has an arch height (H) and an arch span (S), wherein a ratio of the arch height (H) to the arch span (S) is at least 0.1.

3. Electrolysis cell according to claim 1 or 2, characterized in that the side walls (10) are arched inwards.

4. Electrolysis cell according to any one of the claims 1 to 3, characterized in that the arch (15) has closed geometry cross section.

5. Electrolysis cell according to any one of the claims 1 to 4, characterized in that the side walls (10) are made of tubes (20), in particular round or flattened tubes, or D- shaped profiles (21).

6. Electrolysis cell according to any one of the claims 1 to 5, characterized in that the tension means (13, 14) form a mechanical support for the electrode (6, 7) within the semi-shell (3, 4).

7. Electrolysis cell according to any one of the claims 1 to 6, characterized in that the inner edge portion (12) of the flange portion (11) is provided with inwardly protruding anchoring portions (22) to which the tension means (13, 14) are attached.

8. Electrolysis cell according to any one of the claims 1 to 7, characterized in that the tension means (13, 14) comprise a plurality of tension stripes (13.1, 13.2) traversing the pan (8) in at least two crossing directions.

9. Electrolysis cell according to claim 8, characterized in that at least part of the ten sion stripes (13.2) have a T-shaped, L-shaped or l-shaped cross section.

10. Electrolysis cell according to any one of the claims 1 to 9, characterized in that the tension means (13, 14) comprise a wire mesh (14) at least partly covering the pan (8).

11. Electrolysis cell according to claim 10, characterized in that the wire mesh (14) forms the electrode or the support for the electrode (6, 7) within the respective semi shell (3, 4).

12. Electrolysis cell according to any one of the claims 1 to 11, characterized in that the electrolysis cell (1) is suitable for chlor-alkali electrolysis or alkaline water electrolysis.

13. Electrolyzer for alkaline water electrolysis or chlor-alkali electrolysis comprising a plu rality of electrolysis cells (1) arranged side by side in a stack whilst being electrically connected via their rear walls (9), characterized in that the electrolysis cells (1) are configured according to any one of the claims 1 to 12.