Electrolytic cell partitions, partition assemblies, and electrolytic cells

Abstract

Provided is a partition wall for an electrolytic cell, the partition wall partitioning the electrolytic cell into an anode chamber and a cathode chamber and being capable of suppressing generation of gas accumulation even when recesses are formed therein. A partition wall 8 of an electrolytic cell has a first main surface 20 and a second main surface 22 positioned opposite to the first main surface 20. The first main surface 20 includes a first flat part 24 and a plurality of first recesses 36 recessed with respect to the first flat part 24. Edges 40 of the first recesses 36 are rounded. The second main surface 22 includes a second flat part 30 and a plurality of second recesses 42 recessed with respect to the second flat part 30. Edges 46 of the second recesses 42 are rounded.

Description

Technical Field

[0001] The present invention relates to a partition wall of an electrolytic cell, a partition wall assembly, and an electrolytic cell.

Background Art

[0002] As an apparatus for producing hydrogen gas and oxygen gas, a bipolar alkaline electrolytic cell is known. In a bipolar alkaline electrolytic cell, a plurality of electrolytic cell units and a plurality of diaphragms are alternately arranged. The electrolytic cell unit includes an anode disposed in the anode chamber, a cathode disposed in the cathode chamber, and a conductive partition wall that partitions the anode chamber and the cathode chamber. A plurality of ribs are provided on the first main surface of the partition wall, and the anode is fixed to the first main surface of the partition wall via the plurality of ribs. Thereby, an anode chamber is defined between the first main surface of the partition wall and the anode. Similarly, a plurality of ribs are provided on the second main surface (the surface opposite to the first main surface) of the partition wall, and the cathode is fixed to the second main surface of the partition wall via the plurality of ribs. Thereby, a cathode chamber is defined between the second main surface of the partition wall and the cathode.

[0003] In a bipolar alkaline electrolytic cell, instead of a plurality of ribs, a plurality of protrusions and depressions may be provided on each of the first and second main surfaces of the partition wall. In this case, the anode is fixed to the top of the protrusion on the first main surface, thereby defining an anode chamber between the first main surface and the anode. Further, the cathode is fixed to the top of the protrusion on the second main surface, thereby defining a cathode chamber between the second main surface and the cathode (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if multiple depressions are formed on the first and second main surfaces of the partition wall, gas generated at the electrodes may accumulate inside the depressions, potentially causing gas reservoirs. When gas reservoirs form, the flow of the electrode solution within the electrode chamber becomes uneven, resulting in concentration differences in the electrode solution within the chamber. If the concentration difference in the electrode solution becomes large, the current distribution becomes uneven, leading to a decrease in electrolysis efficiency. This problem can occur not only in alkaline water electrolytic cells used to produce hydrogen and oxygen gases, but also in other electrolytic cells such as sodium chloride electrolytic cells used to produce hydrogen, chlorine, and caustic soda.

[0006] The object of the present invention is to provide an electrolytic cell partition, a partition assembly, and an electrolytic cell that can suppress the generation of gas accumulation even if a recess is formed in the partition wall of the electrolytic cell that separates the anode chamber and the cathode chamber. [Means for solving the problem]

[0007] According to the present invention, the following electrolytic cell partition wall is provided that solves the above problems. That is, "A partition wall of an electrolytic cell that separates the anode chamber and the cathode chamber, It has a first main surface and a second main surface located on the opposite side of the first main surface, The first main surface comprises a first flat portion and a plurality of first recesses that are recessed more than the first flat portion. 、 The edges of the aforementioned first recess are rounded, The second main surface comprises a second flat portion and a plurality of second recesses that are recessed more than the second flat portion. 、 The edges of the second recess are rounded. Occasionally, Furthermore, the first main surface includes a plurality of mountain-shaped first protrusions that protrude beyond the first flat portion, and the second main surface includes a plurality of mountain-shaped second protrusions that protrude beyond the second flat portion. The entire circumference of the base of the first projection is rounded, and the entire circumference of the base of the second projection is rounded. A partition wall for the electrolytic cell is provided.

[0009] On the first main surface, a first inclined portion is provided between the first projection and the first recess, inclined with respect to the first flat portion, and on the second main surface, a second inclined portion may be provided between the second projection and the second recess, inclined with respect to the second flat portion. Preferably, the positions of the plurality of first recesses correspond to the positions of the plurality of second projections, and the positions of the plurality of second recesses correspond to the positions of the plurality of first projections.

[0010] The first projection, the second projection, the first recess, and the second recess may be hemispherical. When the radius of curvature of the edges of the first and second recesses is R3, and the radius of curvature of the bottoms of the first and second recesses is R4, the ratio of the radii of curvature, R4 / R3, is preferably between 0.1 and 19. . before When the radius of curvature of the base of the first and second projections is R1, and the radius of curvature of the top of the first and second projections is R2, the ratio of radii of curvature R2 / R1 is preferably 0.6 or more and 40 or less. When the radius of curvature of the edges of the first and second recesses is R3, and the radius of curvature of the bottoms of the first and second recesses is R4, the ratio of radii of curvature R4 / R3 is preferably 0.1 or more and 19 or less.

[0011] The first projection, the second projection, the first recess, and the second recess are conical in shape, and the tops of the first projection and the second projection, and the bottoms of the first recess and the second recess, may be rounded. When the radius of curvature of the edges of the first recess and the second recess is R7, and the radius of curvature of the bottoms of the first recess and the second recess is R8, the ratio of the radii of curvature, R8 / R7, is preferably between 0.05 and 190. . before When the radius of curvature of the base of the first and second projections is R5, and the radius of curvature of the top of the first and second projections is R6, the ratio of radii of curvature R6 / R5 is preferably between 0.6 and 400. When the radius of curvature of the edges of the first and second depressions is R7, and the radius of curvature of the bottoms of the first and second depressions is R8, the ratio of radii of curvature R8 / R7 is preferably between 0.05 and 190.

[0012] The first projection, the second projection, the first recess, and the second recess are frustoconical in shape, and the bottom periphery of the first recess and the bottom periphery of the second recess may be rounded. When the radius of curvature of the edges of the first recess and the second recess is R11, and the radius of curvature of the bottom periphery of the first recess and the second recess is R12, the ratio of the radii of curvature R12 / R11 is preferably between 0.05 and 50. The base of the first projection and the base of the second projection, as well as the top periphery of the first projection and the top periphery of the second projection, may also be rounded. When the radius of curvature of the base of the first and second projections is R9 and the radius of curvature of the top edge of the first and second projections is R10, the ratio of radii of curvature R10 / R9 is preferably between 0.1 and 100. When the radius of curvature of the edges of the first and second depressions is R11 and the radius of curvature of the bottom edge of the first and second depressions is R12, the ratio of radii of curvature R12 / R11 is preferably between 0.05 and 50.

[0013] Furthermore, the present invention provides the following bulkhead assembly that solves the above problems. That is, "a bulkhead assembly is provided which includes a bulkhead as described above and a bulkhead support frame that supports the peripheral edge of the bulkhead." The bulkhead may be circular in shape, and the bulkhead support frame may be annular. The bulkhead assembly of the present invention may include electrodes or current collectors joined to the tops of each of the plurality of first protrusions, and current collectors or electrodes joined to the tops of each of the plurality of second protrusions. Preferably, it includes electrodes or current collectors joined by welding to the tops of each of the plurality of first protrusions, and current collectors or electrodes joined to the tops of each of the plurality of second protrusions. Furthermore, the device may include electrodes or current collectors welded to the tops of each of the plurality of first protrusions, and current collectors or electrodes welded to the tops of each of the plurality of second protrusions.

[0014] Furthermore, according to the present invention, the following electrolytic cell is provided to solve the above problems. That is, "an electrolytic cell in which a plurality of partition assemblies and a plurality of membrane assemblies as described above are alternately arranged, and the membrane assembly includes a membrane and a membrane support frame that supports the peripheral edge of the membrane" is provided.

Advantages of the Invention

[0015] In the present invention, since R processing is performed on the edges of the first and second depressions, the gas generated at the electrodes does not stay inside the first and second depressions, and the generation of gas accumulation can be suppressed. Therefore, since the flow of the electrode liquid in the electrode chamber is made uniform, the concentration difference in the electrode liquid in the electrode chamber does not become excessively large. As a result, the current distribution is made uniform, and a decrease in electrolysis efficiency is prevented.

Brief Description of the Drawings

[0016] [Figure 1] Schematic partial cross-sectional view of the electrolytic cell according to the present invention. [Figure 2] Schematic partial cross-sectional view of the electrolytic cell shown in FIG. 1. [Figure 3] Front view of the partition assembly shown in FIG. 1. [Figure 4] (a) Partial cross-sectional view taken along line IV-IV in FIG. 3, (b) Partial cross-sectional view of the partition wall in which an inclined portion is provided between the protrusion and the depression (cross-section corresponding to the cross-section in (a)). [Figure 5] Explanatory drawing for explaining the radius of curvature R1 of the base of the first protrusion (partial enlarged view of FIG. 4(a)). [Figure 6] Explanatory drawing for explaining the radius of curvature R2 of the top of the first protrusion (partial enlarged view of FIG. 4(a)). [Figure 7] Explanatory drawing for explaining the radius of curvature R3 of the edge of the first depression (partial enlarged view of FIG. 4(a)). [Figure 8] Explanatory drawing for explaining the radius of curvature R4 of the bottom of the first depression (partial enlarged view of FIG. 4(a)). [Figure 9] Front view of the membrane assembly shown in FIG. 1. [Figure 10](a) Partial cross-sectional view of the partition wall according to the first modified example (a cross-section corresponding to the cross-section in Figure 4(a)), (b) Partial cross-sectional view of the partition wall according to the first modified example in which an inclined portion is provided between the projection and the recess (a cross-section corresponding to the cross-section in Figure 4(a)). [Figure 11] (a) Partial cross-sectional view of the partition wall according to the second modified example (a cross-section corresponding to the cross-section in Figure 4(a)), (b) Partial cross-sectional view of the partition wall according to the second modified example in which an inclined portion is provided between the projection and the recess (a cross-section corresponding to the cross-section in Figure 4(a)). [Figure 12] An explanatory diagram illustrating the radius of curvature R10 of the apex periphery of the first projection in the second modified example (a partially enlarged view of Figure 11(a)). [Figure 13] An explanatory diagram illustrating the radius of curvature R12 of the bottom edge of the first depression in the second modified example (a partially enlarged view of Figure 11(a)). [Modes for carrying out the invention]

[0017] Hereinafter, preferred embodiments of the electrolytic cell partition, partition assembly, and electrolytic cell according to the present invention will be described with reference to the drawings.

[0018] (Electrolytic cell 2) Referring to Figures 1 and 2, the electrolytic cell, denoted by reference numeral 2, is a zero-gap type bipolar electrolytic cell in which the membrane and electrodes are in contact. The electrolytic cell 2 comprises a plurality of partition wall assemblies 4 and a plurality of membrane assemblies 6. The partition wall assemblies 4 and membrane assemblies 6 are arranged alternately in the depth direction (X direction) of the electrolytic cell 2, indicated by arrow X in Figure 1. The Y direction, indicated by arrow Y in Figure 1, is perpendicular to the X direction and is the width direction of the electrolytic cell 2. The Z direction, indicated by arrow Z in Figure 1, is the vertical direction, perpendicular to both the X and Y directions.

[0019] (Bulkhead assembly 4) The bulkhead assembly 4 includes a bulkhead 8 and a bulkhead support frame 10 that supports the peripheral edge of the bulkhead 8. The bulkhead assembly 4 of this embodiment further includes an electrode 12 disposed on one side of the bulkhead 8 in the X direction and a current collector 14 disposed on the other side of the bulkhead 8 in the X direction. In this embodiment, a cushioning material 76 and an electrode 78, described later, are further provided on the side of the current collector 14 opposite to the joint surface with the bulkhead 8. Alternatively, the current collector 14 and electrode 12 may be disposed on one side of the bulkhead 8 in the X direction, and the current collector 14, cushioning material 76, and electrode 78 may be disposed on the other side of the bulkhead 8 in the X direction.

[0020] (bulkhead 8) The partition wall 8 separates the anode chamber 16 and the cathode chamber 18 (see Figure 2). As shown in Figures 3 and 4(a), the partition wall 8 in this embodiment is a circular sheet having a first main surface 20 and a second main surface 22 located on the opposite side of the first main surface 20. However, the shape of the partition wall 8 is not limited to a circular sheet; for example, it can be a rectangular sheet. In such a case, the shape of the partition wall support frame 10, which will be described later, should correspond to the shape of the partition wall 8. For example, if the partition wall 8 is a rectangular sheet, the partition wall support frame 10 will also be rectangular. The size of the partition wall 8 can be appropriately determined considering the electrolysis capacity of the electrolytic cell 2, operating conditions, installation area, cost, etc. For example, if the partition wall 8 is a circular sheet, the diameter of the partition wall 8 can be 0.1m to 5m, and if the partition wall 8 is a rectangular sheet, one side of the partition wall 8 can be 0.1m to 5m, but it is not limited to these values. The partition wall 8 can be formed from a conductive material (for example, a metal material such as a steel plate). The surface of the partition wall 8 may be subjected to a surface treatment such as nickel plating. The thickness of the partition wall 8 can be appropriately determined by taking into consideration the shape, size and material of the partition wall 8, the number, shape and arrangement of protrusions and recesses, etc., but for example it is 0.5 mm or more and 10 mm or less, preferably 1 mm or more and 7 mm or less, and more preferably 2 mm or more and 5 mm or less.

[0021] (First main surface 20) The first main surface 20 includes a first flat portion 24 and a plurality of mountain-shaped first protrusions 26 that protrude from the first flat portion 24. The first protrusions 26 in this embodiment are hemispherical in shape, with their diameter gradually decreasing as they move away from the first flat portion 24. The radius of curvature of the first protrusions 26 may be, for example, 3 mm or more and 20 mm or less, more preferably 5 mm or more and 15 mm or less, and even more preferably 7 mm or more and 10 mm or less. The height H of the first protrusions 26 relative to the first flat portion 24 may be, for example, 3 mm or more and 20 mm or less, more preferably 5 mm or more and 15 mm or less, and even more preferably 7 mm or more and 10 mm or less.

[0022] The arrangement of the multiple first protrusions 26 is arbitrary. For example, the multiple first protrusions 26 may be aligned along the width direction (Y direction) of the electrolytic cell 2 and also aligned along the vertical direction (Z direction). Alternatively, the multiple first protrusions 26 may be arranged in a staggered pattern or in a concentric pattern. Furthermore, the number and spacing of the multiple first protrusions 26 can also be set arbitrarily.

[0023] The base portion 28 of the first projection 26 may or may not be rounded. The base portion 28 is the boundary between the first flat portion 24 and the first projection 26, or the boundary between the first inclined portion 38 (described later) and the first projection 26. If the base portion 28 of the first projection 26 on the first main surface 20 is not rounded, the electrode solution that hits the first projection 26 spreads along the first flat portion 24, improving the uniformity of the electrode solution within the electrode chamber. Furthermore, when the electrode solution hits the first projection 26, a shear force acts on the flow of the electrode solution, causing the bubbles contained in the electrode solution to become finer, which is expected to further promote the uniformity of the electrode solution and contribute to improved electrolysis efficiency. In addition, when rounding the base portion 28 of the first projection 26, it is important that the rounding is applied evenly to the base portions 28 of the multiple first projections 26. However, when forming the first projection 26 by, for example, press working, the force applied to the central part and the ends (for example, the Y-direction and Z-direction ends) of the partition wall 8 is different. Therefore, it is generally difficult to uniformly round the bottom portion 28, and the symmetry of the projection shape of the first projection 26 on the end side of the partition wall 8 tends to be disrupted. In addition, the orientation of the top portion 26a (deviation from the direction perpendicular to the first main surface 20) tends to vary among multiple first projections 26 within the first main surface 20. In such cases, there is a risk of impairing the electrode flatness when fixing the electrode to the top portion 26a of the first projection 26, which becomes a major problem in zero-gap type electrolytic cells. For these reasons, it is preferable that the bottom portion 28 of the first projection 26 is not rounded. However, for manufacturing and processing reasons of the partition wall 8, the bottom portion 28 of the first projection 26 may be rounded.

[0024] As shown in Figure 4(a), the base portion 28 of the first projection 26 in the partition wall 8 may be rounded. If rounded, it is preferable that it is applied around the entire circumference of the base portion 28. By rounding the base portion 28, the gas generated at the electrode flows smoothly near the first projection 26 without stagnation. As a result, the formation of gas accumulation near the first projection 26 can be suppressed.

[0025] When the radius of curvature of the base portion 28 of the first projection 26 is R1 and the radius of curvature of the top portion 26a of the first projection 26 is R2, the ratio of the radii of curvature R2 / R1 is preferably between 0.6 and 40. This enhances the effect of the gas generated at the electrode flowing smoothly near the first projection 26. The radius of curvature R1 of the base portion 28 may be, for example, between 0.5 mm and 5 mm. If the radius of curvature R1 of the base portion 28 is between 0.5 mm and 5 mm, the effects of the electrode liquid spreading within the electrode chamber along the first flat portion 24 and the effects of the shear force acting on the flow of the electrode liquid can be obtained simultaneously.

[0026] The radius of curvature R1 of the base portion 28 of the first projection 26 will be explained with reference to Figure 5. Let P1 be the intersection point of a straight line L1 extending along the first flat portion 24 and a tangent line L2 of the first projection 26 passing through the base portion 28. Define an auxiliary line L3 that passes through the intersection point P1 and bisects the angle θ1 between the straight line L1 and the tangent line L2. Assume a virtual circle C1 with center O1 on the auxiliary line L3. Then, the radius of the virtual circle C1 when its circumference passes through the intersection point Q1 of the base portion 28 of the first projection 26 and the auxiliary line L3, and when the circumference of the virtual circle C1 is tangent to both the straight line L1 and the tangent line L2, is defined as the radius of curvature R1 in this invention.

[0027] The radius of curvature R2 of the top 26a of the first projection 26 will be explained with reference to Figure 6. Define a straight line L1 extending along the first flat portion 24 and a straight line L4 passing through the top 26a of the first projection 26 and intersecting the straight line L1 perpendicularly. Assume a virtual circle C2 having center O2 on the straight line L4. The radius of virtual circle C2 such that the circumference of virtual circle C2 passes through the top 26a of the first projection 26 and the overlap between the circumference of virtual circle C2 and the contour of the first projection 26 is maximized is defined as the radius of curvature R2 in this invention.

[0028] To determine the radii of curvature R1 and R2, for example, the partition wall 8 can be cut by a plane perpendicular to the first main surface 20 of the partition wall 8, passing through the top 26a of the first projection 26, to expose the cross section corresponding to Figure 4, and the radii of curvature R1 and R2 can be directly measured at the cross section of the partition wall 8 (the cross section corresponding to Figure 4). Alternatively, the cross section of the partition wall 8 (the cross section corresponding to Figure 4) can be photographed to obtain a cross-sectional image of the partition wall 8, and the radii of curvature R1 and R2 can be determined by performing image analysis on the obtained cross-sectional image.

[0029] As described above, the radii of curvature R1 and R2 may be determined by cutting the partition wall 8, but it is preferable to determine the radii of curvature R1 and R2 without cutting the partition wall 8. For example, resin, clay, plaster, impression material, etc., is pressed against the first main surface 20 of the partition wall 8 to form a mold that replicates the shape of the first main surface 20 of the partition wall 8. Next, the mold is cut by a plane that passes through the point corresponding to the top 26a of the first projection 26 in the mold and is perpendicular to the surface corresponding to the first main surface 20 of the partition wall 8. Then, the cut surface of the mold is photographed to obtain a cross-sectional image of the mold, and the radii of curvature R1 and R2 can be determined without cutting the partition wall 8 by performing image analysis on the obtained cross-sectional image.

[0030] (Second main surface 22) Continuing the explanation with reference to Figures 3 and 4(a), the second main surface 22 includes a second flat portion 30 and a plurality of mountain-shaped second protrusions 32 that project from the second flat portion 30. The second protrusions 32 in this embodiment are hemispherical in shape, similar to the first protrusions 26, with their diameter gradually decreasing as they move away from the second flat portion 30. The dimensions of the second protrusions 32 may be the same as or different from those of the first protrusions 26.

[0031] The arrangement of the multiple second protrusions 32 is arbitrary. For example, the multiple second protrusions 32 may be aligned along the width direction (Y direction) of the electrolytic cell 2 and also aligned along the vertical direction (Z direction). Alternatively, the multiple second protrusions 32 may be arranged in a staggered pattern or in a concentric pattern. Furthermore, the number and spacing of the multiple second protrusions 32 can also be set arbitrarily.

[0032] The base portion 34 of the second projection 32 may or may not be rounded. The base portion 34 is the boundary between the second flat portion 30 and the second projection 32, or the boundary between the second inclined portion 44 (described later) and the second projection 32. If the base portion 34 of the second projection 32 on the second main surface 22 is not rounded, the electrode solution that hits the second projection 32 spreads along the second flat portion 30, improving the uniformity of the electrode solution within the electrode chamber. Furthermore, when the electrode solution hits the second projection 32, a shear force acts on the flow of the electrode solution, causing the bubbles contained in the electrode solution to become finer, which is expected to further promote the uniformity of the electrode solution and contribute to improved electrolysis efficiency. In addition, when rounding the base portion 34 of the second projection 32, it is important that the rounding is applied evenly to the base portions 34 of the multiple second projections 32. However, when forming the second projection 32 by, for example, press working, the force applied to the central part and the ends (for example, the Y-direction and Z-direction ends) of the partition wall 8 is different. Therefore, it is generally difficult to uniformly round the bottom portion 34, and the symmetry of the projection shape of the second projection 32 on the end side of the partition wall 8 tends to be disrupted. In addition, the orientation of the top portion 32a (deviation from the direction perpendicular to the second main surface 22) tends to vary among multiple second projections 32 within the second main surface 22. In such cases, there is a risk of impairing electrode flatness when fixing electrodes to the top portion 32a of the second projection 32, which becomes a major problem in zero-gap type electrolytic cells. For these reasons, it is preferable that the bottom portion 34 of the second projection 32 is not rounded. However, for manufacturing and processing reasons of the partition wall 8, it is acceptable for the bottom portion 34 of the second projection 32 to be rounded.

[0033] As shown in Figure 4(a), the base portion 34 of the second projection 32 may also be given a rounded edge (R-shaping) in the partition wall 8. If R-shaping is applied, it is preferable that it is applied around the entire circumference of the base portion 34. By applying R-shaping to the base portion 34, the gas generated at the electrode flows smoothly near the second projection 32, thus suppressing the formation of gas accumulation near the second projection 32. The radius of curvature of the base portion 34 of the second projection 32 may be the same as or different from the radius of curvature of the base portion 28 of the first projection 26.

[0034] (First depression 36) The first main surface 20 of this embodiment includes a plurality of first recesses 36 that are recessed from the first flat portion 24. As shown in Figure 4(a), the positions of the plurality of first recesses 36 correspond to the positions of the plurality of second protrusions 32. That is, the arrangement, number, and spacing of the first recesses 36 correspond to the arrangement, number, and spacing of the second protrusions 32. Furthermore, the first recesses 36 are hemispherical in shape, with their diameter gradually decreasing as they move away from the first flat portion 24. The radius of curvature of the first recesses 36 may be, for example, 2 mm to 19 mm, more preferably 3 mm to 15 mm, and even more preferably 4 mm to 10 mm. The depth D of the first recesses 36 relative to the first flat portion 24 may be, for example, 3 mm to 20 mm, more preferably 5 mm to 15 mm, and even more preferably 7 mm to 10 mm. The greater the depth D of the first recess 36, that is, the deeper the first recess 36, the greater the risk of gas accumulating within the first recess 36 and forming a gas reservoir. However, as described later, by applying a rounded edge 40 to the edge 40 of the first recess 36, gas that enters the first recess 36 is quickly discharged from the first recess 36 and does not accumulate within the first recess 36.

[0035] The diameter d of the first recess 36 may be, for example, 5 mm or more and 50 mm or less. As shown in Figure 4(a), the diameter d is the diameter at the edge 40 of the first recess 36, that is, the maximum diameter of the portion that is recessed in the X-axis direction from the first flat portion 24 of the first main surface 20. When the diameter d of the first recess 36 is 5 mm or more and 50 mm or less, as described later, by applying R-shaping to the edge 40 of the first recess 36, gas that has entered the first recess 36 can be quickly discharged from the first recess 36.

[0036] As shown in Figure 4(a), the first recess 36 and the first projection 26 can be connected via the first flat portion 24. Alternatively, as shown in Figure 4(b), a first inclined portion 38, which is inclined with respect to the first flat portion 24, may be provided between the first recess 36 and the first projection 26. When the first inclined portion 38 is provided, gas generated at the electrode can flow more easily between the first recess 36 and the first projection 26.

[0037] The edge 40 of the first recess 36 of the first main surface 20 is rounded (R-shaped). The edge 40 is the boundary between the first flat portion 24 and the first recess 36, or the boundary between the first inclined portion 38 and the first recess 36. It is desirable that the rounded edge 40 be applied around its entire circumference. By rounding the edge 40, the gas generated at the electrode flows smoothly through the first recess 36, thereby suppressing the formation of gas accumulation in the first recess 36.

[0038] When the radius of curvature of the edge 40 of the first recess 36 is R3 and the radius of curvature of the bottom 36a of the first recess 36 is R4, the ratio of the radii of curvature R4 / R3 is preferably 0.1 or more and 19 or less, and more preferably 0.3 or more and 5 or less. This enhances the effect of the gas generated at the electrode flowing smoothly through the first recess 36. The radius of curvature R3 of the edge 40 may be, for example, 1 mm or more and 20 mm or less, and more preferably 3 mm or more and 10 mm or less.

[0039] The radius of curvature R3 of the edge 40 of the first recess 36 will be explained with reference to Figure 7. Let P2 be the intersection point of the straight line L1 extending along the first flat portion 24 and the tangent line L5 of the first recess 36 passing through the edge 40. Define an auxiliary line L6 that passes through the intersection point P2 and bisects the angle θ2 between the straight line L1 and the tangent line L5. Assume a virtual circle C3 with center O3 on the auxiliary line L6. Then, the radius of the virtual circle C3 when the circumference of the virtual circle C3 passes through the intersection point Q2 of the edge 40 of the first recess 36 and the auxiliary line L6, and when the circumference of the virtual circle C3 is tangent to both the straight line L1 and the tangent line L5, is defined as the radius of curvature R3 in this invention.

[0040] The radius of curvature R4 of the bottom 36a of the first depression 36 will be explained with reference to Figure 8. Define a straight line L1 extending along the first flat portion 24 and a straight line L7 passing through the bottom 36a of the first depression 36 and intersecting the straight line L1 perpendicularly. Assume a virtual circle C4 with center O4 on the straight line L7. The radius of virtual circle C4 such that its circumference passes through the bottom 36a of the first depression 36 and the overlap between its circumference and the contour of the first depression 36 is maximized is defined as the radius of curvature R4 in this invention.

[0041] The radii of curvature R3 and R4 can be determined using the same method as described above for determining the radii of curvature R1 and R2.

[0042] When a first inclined portion 38 is provided between the first recess 36 and the first projection 26, inclined with respect to the first flat portion 24 (see Figure 4(b)), the radius of curvature R1 of the base portion 28 of the first projection 26 is defined in the same way as the radius of curvature R1 described above, with P1 being the intersection point of a straight line extending along the first inclined portion 38 and a tangent line L2 of the first projection 26 passing through the base portion 28. Furthermore, when the first inclined portion 38 is provided, the radius of curvature R3 of the edge 40 of the first recess 36 is defined in the same way as the radius of curvature R3 described above, with P2 being the intersection point of a straight line extending along the first inclined portion 38 and a tangent line L5 of the first recess 36 passing through the edge 40.

[0043] (Second depression 42) The second main surface 22 of this embodiment includes a plurality of second recesses 42 that are recessed more deeply than the second flat portion 30. The positions of the plurality of second recesses 42 correspond to the positions of the plurality of first protrusions 26, and the arrangement, number, and spacing of the second recesses 42 correspond to the arrangement, number, and spacing of the first protrusions 26. Furthermore, the second recesses 42 are hemispherical in shape, with their diameter gradually decreasing as they move away from the second flat portion 30. The dimensions of the second recesses 42 may be the same as or different from the dimensions of the first recesses 36. The greater the depth of the second recesses 42, that is, the deeper the second recesses 42, the greater the risk of gas accumulating in the second recesses 42 and forming gas pockets. However, as described later, by rounding the edges 46 of the second recesses 42, gas that enters the second recesses 42 is quickly discharged from the second recesses 42 and does not accumulate in the second recesses 42.

[0044] The diameter of the second recess 42 may be, for example, 5 mm to 50 mm, similar to the diameter d of the first recess 36. The diameter of the second recess 42 is the diameter at the edge 46 of the second recess 42, that is, the maximum diameter of the portion that is recessed in the X-axis direction compared to the second flat portion 30 of the second main surface 22. When the diameter of the second recess 42 is 5 mm to 50 mm, as described later, by applying a rounded edge 46 to the edge 46 of the second recess 42, gas that has entered the second recess 42 can be quickly discharged from the second recess 42.

[0045] As shown in Figure 4(a), the second recess 42 and the second projection 32 can be connected via the second flat portion 30. Alternatively, as shown in Figure 4(b), a second inclined portion 44, which is inclined with respect to the second flat portion 30, may be provided between the second recess 42 and the second projection 32. When the second inclined portion 44 is provided, gas generated at the electrode can flow more easily between the second recess 42 and the second projection 32.

[0046] The edge 46 of the second recess 42 of the second main surface 22 is also rounded (R-shaped). The edge 46 is the boundary between the second flat portion 30 and the second recess 42, or the boundary between the second inclined portion 44 and the second recess 42. It is desirable that the rounded edge 46 be rounded all around. By rounding the edge 46, the gas generated at the electrode can flow smoothly through the second recess 42, thereby suppressing the formation of gas accumulation in the second recess 42. The radius of curvature of the edge 46 of the second recess 42 may be the same as or different from the radius of curvature of the edge 40 of the first recess 36.

[0047] As described above, the first and second projections 26, 32 and the first and second recesses 36, 42 can be formed by embossing. Similarly, the rounded edges 28, 34 and 40, 46, as well as the first and second inclined portions 38, 44, can also be formed by embossing.

[0048] The radius of curvature R1 of the base 34 of the second projection 32, the radius of curvature R2 of the top 32a of the second projection 32, the radius of curvature R3 of the edge 46 of the second recess 42, and the radius of curvature R4 of the bottom 42a of the second recess 42 are defined in the same way as the radii of curvature R1 to R4 on the first main surface 20, and can be determined in the same way as the radii of curvature R1 to R4 on the first main surface 20.

[0049] (Partition support frame 10) As shown in Figures 1 and 3, the annular partition support frame 10 has a first main surface 48 and a second main surface 50 opposite to the first main surface 48. The partition support frame 10 is positioned radially outside the circular partition wall 8, and the inner peripheral edge of the partition support frame 10 and the outer peripheral edge of the partition wall 8 are mechanically joined using fasteners such as screws, bolts, and rivets, or joined by welding. It is preferable that the inner peripheral edge of the partition support frame 10 and the outer peripheral edge of the partition wall 8 are joined by welding, as this eliminates the risk of fasteners falling off and provides sufficient joint strength for long-term use. The material of the partition support frame 10 may be a conductive material (for example, a metal material such as steel plate) or an insulating material (for example, a resin). When a metal material is used for the partition support frame 10, the surface of the partition support frame 10 may be subjected to a surface treatment such as nickel plating. The bulkhead support frame 10 may also be fitted with brackets (not shown) that extend radially outward from the outer peripheral edge of the bulkhead support frame 10.

[0050] (Supply route for the bulkhead support frame 10) The partition support frame 10 has supply passages for supplying electrode liquid to the electrode chamber. Specifically, as shown in Figure 3, the partition support frame 10 has a first supply passage 52 for supplying anodic liquid to the anode chamber 16 and a second supply passage 54 for supplying cathode liquid to the cathode chamber 18. The first supply passage 52 includes a first supply opening 56 that penetrates the lower part of the partition support frame 10 and a first supply recess 58 that extends radially inward from the first supply opening 56 on the first main surface 48 of the partition support frame 10. The second supply passage 54 includes a second supply opening 60 that penetrates the lower part of the partition support frame 10 and a second supply recess 62 that extends radially inward from the second supply opening 60 on the second main surface 50 of the partition support frame 10.

[0051] (Discharge passage of the bulkhead support frame 10) Furthermore, the partition support frame 10 has an outlet passage for discharging electrode liquid and gas from the electrode chamber. Specifically, as shown in Figure 3, the partition support frame 10 has a first outlet passage 64 for discharging anosolite and gas from the anode chamber 16 and a second outlet passage 66 for discharging cathode liquid and gas from the cathode chamber 18. The first outlet passage 64 includes a first outlet opening 68 that penetrates the upper part of the partition support frame 10 and a first outlet recess 70 that extends radially inward from the first outlet opening 68 on the first main surface 48 of the partition support frame 10. The second outlet passage 66 includes a second outlet opening 72 that penetrates the upper part of the partition support frame 10 and a second outlet recess 74 that extends radially inward from the second outlet opening 72 on the second main surface 50 of the partition support frame 10.

[0052] (electrode 12) In this embodiment, electrode 12 is configured as an anode. As shown in Figures 1 and 2, electrode 12 is joined by welding to the top 26a of the first projection 26 on the first main surface 20 of partition wall 8. This defines an anode chamber 16 between the first main surface 20 of partition wall 8 and electrode 12 (anode). Electrode 12 is formed as a circular sheet from a perforated plate such as expanded metal or perforated metal, or from a plain weave wire mesh. The material of electrode 12 may be a conductive material (for example, a metallic material such as nickel, or a metallic material such as steel plate with nickel plating). Catalysts known as catalysts for water electrolysis, such as nickel oxide or precious metal oxides, may be appropriately attached to electrode 12.

[0053] (Current collector 14) The current collector 14 is joined by welding to the top 32a of the second projection 32 on the second main surface 22 of the bulkhead 8. The current collector 14 is formed as a circular sheet from a perforated plate such as expanded metal or perforated metal. The material of the current collector 14 may be a conductive material (for example, a metal material such as steel plate). The surface of the current collector 14 may be subjected to a surface treatment such as nickel plating.

[0054] In the present invention, the method of joining electrodes or current collectors to the tops of the first or second projections is not limited to the welding described above, but any method that can ensure electrical conductivity between the partition wall and the electrodes or current collectors is acceptable, such as screw fastening or crimping with a press. From the viewpoint of reducing electrical resistance and providing excellent long-term stability, it is preferable that electrodes or current collectors are joined by welding to the tops of at least one of the first or second projections, and it is more preferable that electrodes or current collectors are joined by welding to the tops of both the first and second projections.

[0055] (Cushioning material 76) As shown in Figures 1 and 2, a cushioning material 76 is provided on the side of the current collector 14 opposite to the joint surface with the partition wall 8, for pressing the electrodes 12 and 78 against the film 80 to ensure close contact. The cushioning material 76 is an elastic mat woven from wires and is formed as a circular sheet. The material of the cushioning material 76 may be a conductive material (for example, a metallic material such as nickel).

[0056] (electrode 78) An electrode 78 is provided on the surface of the cushioning material 76 opposite to the surface in contact with the current collector 14. In this embodiment, the electrode 78 is configured as a cathode. As described above, the current collector 14 is joined to the top 32a of the second projection 32, and the electrode 78 (cathode) is in contact with the current collector 14 via the cushioning material 76, thus defining a cathode chamber 18 between the second main surface 22 of the partition wall 8 and the electrode 78. The electrode 78 is formed in the same way as the electrode 12 above, from a perforated plate such as expanded metal or perforated metal, or from a plain woven wire mesh, in the shape of a circular sheet. The material of the electrode 78 may be a conductive material (for example, a metallic material such as nickel, or a metallic material such as steel plate with nickel plating). A catalyst known as a catalyst for water electrolysis, such as nickel oxide or a noble metal oxide, may be appropriately attached to the electrode 78.

[0057] In this embodiment, electrode 12 is the anode and electrode 78 is the cathode, but the opposite may also be true, with electrode 12 being the cathode and electrode 78 being the anode. In this case, the electrode chamber indicated by reference numeral 16 becomes the cathode chamber, and the electrode chamber indicated by reference numeral 18 becomes the anode chamber.

[0058] (Membrane assembly 6) Referring to Figures 1, 2, and 9, the membrane assembly 6 includes a membrane 80, a membrane support frame 82 that supports the peripheral edge of the membrane 80, and a gasket 84 that seals the anode chamber 16 and the cathode chamber 18. Note that in Figure 9, the gasket 84 is omitted for convenience.

[0059] (membrane 80) In the case of electrolysis of an alkali metal hydroxide aqueous solution, the membrane 80 is configured as an ion-permeable membrane (for example, a diaphragm or an ion exchange membrane), and in the case of electrolysis of an alkali metal chloride aqueous solution, it is configured as an ion exchange membrane. As shown in Figure 9, the membrane 80 is formed in a circular shape, similar to the diaphragm 8.

[0060] (Membrane support frame 82) The membrane support frame 82 is formed in an annular shape corresponding to the partition support frame 10. The membrane support frame 82 is positioned radially outside the circular membrane 80, and supports the outer peripheral edge of the membrane 80 by sandwiching it with the inner peripheral edge of the membrane support frame 82. The material of the membrane support frame 82 may be a conductive material (for example, a metal material such as steel plate) or an insulating material (for example, a resin or elastomer). If the membrane support frame 82 is made of a conductive material, the surface of the membrane support frame 82 may be subjected to a surface treatment such as nickel plating. The membrane support frame 82 may also be fitted with a bracket (not shown) that extends radially outward from the outer peripheral edge of the membrane support frame 82.

[0061] As shown in Figure 9, the lower part of the membrane support frame 82 has first and second supply openings 86 and 88 that penetrate the membrane support frame 82. The upper part of the membrane support frame 82 also has first and second discharge openings 90 and 92 that penetrate the membrane support frame 82. The position of the first supply opening 86 of the membrane support frame 82 corresponds to the position of the first supply opening 56 of the partition support frame 10, and the position of the second supply opening 88 of the membrane support frame 82 corresponds to the position of the second supply opening 60 of the partition support frame 10. Furthermore, the position of the first discharge opening 90 of the membrane support frame 82 corresponds to the position of the first discharge opening 68 of the partition support frame 10, and the position of the second discharge opening 92 of the membrane support frame 82 corresponds to the position of the second discharge opening 72 of the partition support frame 10.

[0062] (Gasket 84) As shown in Figures 1 and 2, the gasket 84 is attached to both sides of the membrane support frame 82 in the X direction. The gasket 84 may be bonded to the membrane support frame 82 by adhesive or double-sided adhesive tape. The gasket 84 is formed in an annular shape that extends along the entire circumference of the membrane support frame 82. However, although not shown in detail, the gasket 84 is not present at the positions corresponding to the first and second supply openings 86, 88 and the first and second discharge openings 90, 92 of the membrane support frame 82. The material of the gasket 84 may be any suitable known material such as an elastomer.

[0063] Alternatively, the gasket 84 can also serve as a membrane support frame 82. That is, the outer edge of the membrane 80 can be supported by sandwiching it between the inner circumference of the annular gasket 84, which is formed in correspondence with the partition support frame 10. In this case, the gasket 84 functions as a membrane support frame 82, and, similar to the membrane support frame 82, it is provided with first and second supply openings 86, 88 and first and second discharge openings 90, 92.

[0064] When assembling the electrolytic cell 2 as described above, multiple partition wall assemblies 4 and membrane assemblies 6 are prepared and arranged alternately. At this time, the first and second supply openings 56 and 60 of the partition wall support frame 10 are aligned with the first and second supply openings 86 and 88 of the membrane support frame 82. Also, the first and second discharge openings 68 and 72 of the partition wall support frame 10 are aligned with the first and second discharge openings 90 and 92 of the membrane support frame 82. Furthermore, the electrodes 78 are placed on the side of the current collector 14 opposite to the joint surface with the partition wall 8, via a cushioning material 76.

[0065] Next, the alternately arranged partition wall assemblies 4 and membrane assemblies 6 are clamped and pressed by a fixed head (not shown) and a movable head (not shown). Specifically, the fixed head and the movable head are connected by multiple tie rods (not shown) to clamp and press the alternately arranged partition wall assemblies 4 and membrane assemblies 6 between the fixed head and the movable head.

[0066] Although not shown in the diagram, the movable head and the fixed head are connected to a flow channel member for supplying anodic acid that communicates with the first supply opening 56 of the partition support frame 10 and the first supply opening 86 of the membrane support frame 82, a flow channel member for supplying cathode liquid that communicates with the second supply opening 60 of the partition support frame 10 and the second supply opening 88 of the membrane support frame 82, a flow channel member for discharging anodic acid that communicates with the first discharge opening 68 of the partition support frame 10 and the first discharge opening 90 of the membrane support frame 82, and a flow channel member for discharging cathode liquid that communicates with the second discharge opening 72 of the partition support frame 10 and the second discharge opening 92 of the membrane support frame 82.

[0067] (electrolytic) When electrolysis is performed in electrolytic cell 2, first, anosol is supplied from an anosol pump (not shown) to a flow channel member for supplying anosol, and simultaneously, cathode liquid is supplied from a cathode pump (not shown) to a flow channel member for supplying cathode liquid. The pressure inside electrolytic cell 2 during electrolysis can be set to any pressure value within the range of approximately 10 kPa to 10 MPa. It is more preferable that the pressure inside electrolytic cell 2 during electrolysis be in the range of 300 kPa to 5 MPa, as this allows for miniaturization of the electrolytic cell 2 and improves electrolysis efficiency.

[0068] The anodic acid supplied to the flow channel member for supplying anodic acid passes through the first supply opening 56 of the partition support frame 10 and the first supply opening 86 of the membrane support frame 82, and also passes through the first supply recess 58 of the partition support frame 10 before being supplied to the anode chamber 16. The cathode acid supplied to the flow channel member for supplying cathode acid passes through the second supply opening 60 of the partition support frame 10 and the second supply opening 88 of the membrane support frame 82, and also passes through the second supply recess 62 of the partition support frame 10 before being supplied to the cathode chamber 18.

[0069] After supplying anolyte to the anode chamber 16 and cathode liquid to the cathode chamber 18, the required voltage is applied to the electrode 12 (anode in this embodiment) and electrode 78 (cathode in this embodiment). As a result, gas is generated from both electrodes 12 and 78. The gas generated at electrode 12, along with the anolyte, is discharged from the anode chamber 16 via the first discharge recess 70 of the partition support frame 10, and then passes through the first discharge opening 68 of the partition support frame 10 and the first discharge opening 90 of the membrane support frame 82 to be sent to the flow channel member for anolyte discharge. The gas generated at electrode 78, along with the cathode liquid, is discharged from the cathode chamber 18 via the second discharge recess 74 of the partition support frame 10, and then passes through the second discharge opening 72 of the partition support frame 10 and the second discharge opening 92 of the membrane support frame 82 to be sent to the flow channel member for cathode liquid discharge.

[0070] As described above, in this embodiment, the edges 40 and 46 of the first and second recesses 36 and 42 are rounded, so that the gas generated at electrode 12 flows without accumulating inside the first recess 36, and the gas generated at electrode 78 flows without accumulating inside the second recess 42. As a result, the formation of gas accumulation inside the first and second recesses 36 and 42 can be suppressed. Therefore, the flow of the electrode solution inside the electrode chambers (anode chamber 16 and cathode chamber 18) is made uniform, and the concentration difference in the electrode solution inside the electrode chambers does not become excessively large. As a result, the current distribution is made uniform, and a decrease in electrolysis efficiency is prevented.

[0071] Furthermore, as in this embodiment, if the base portions 28 and 34 of the first and second protrusions 26 and 32 are also rounded, the formation of gas accumulation near the first and second protrusions 26 and 32 is suppressed. Therefore, the flow of the electrode solution within the electrode chamber can be made even more uniform.

[0072] Incidentally, when the operation of electrolytic cell 2 is stopped, gases dissolved in the electrode solution are released from the electrode solution, which may reduce the purity of the gas produced by electrolysis. For this reason, it is preferable to quickly replace or discharge the electrode solution in the electrode chamber when the operation of electrolytic cell 2 is stopped. In particular, in high-pressure electrolytic cells where the operating pressure of electrolytic cell 2 is relatively high (for example, electrolytic cells operated in the range of 300 kPa to 5 MPa), the amount of dissolved gas in the electrode solution is large, so it is necessary to quickly replace or discharge the electrode solution in the electrode chamber. In this regard, in the electrolytic cell 2 of this embodiment, the edges 40 and 46 of the first and second recesses 36 and 42 are rounded, so that the accumulation of electrode solution in the first and second recesses 36 and 42 is reduced. Therefore, it becomes possible to quickly replace or discharge the electrode solution in the electrode chamber, and the reduction in the purity of the gas produced by electrolysis is suppressed.

[0073] (First variation) With respect to the first and second projections 26, 32 and the first and second recesses 36, 42, although an example of a hemispherical shape was described in the above embodiment, the shape is not limited to a hemispherical shape and may be other shapes. For example, as shown in Figures 10(a) and 10(b), the first and second projections 26, 32 and the first and second recesses 36, 42 may be conical. The tops 26a and 32a of the first and second projections 26, 32 are rounded. The bottoms 36a and 42a of the first and second recesses 36, 42 are also rounded. The diameter of the first projection 26 and the first recess 36 gradually decreases as they move away from the first flat portion 24. Similarly, the diameter of the second projection 32 and the second recess 42 gradually decreases as they move away from the second flat portion 30.

[0074] In the first modified example, the radius of curvature of the tops 26a and 32a of the first and second protrusions 26 and 32 may be, for example, about 3 mm to 200 mm, but more preferably 3 mm to 200 mm, and more preferably 5 mm to 50 mm. The radius of curvature of the bottoms 36a and 42a of the first and second recesses 36 and 42 may be, for example, about 1 mm to 190 mm, but more preferably 1 mm to 190 mm, more preferably 2 mm to 50 mm, and even more preferably 3 mm to 20 mm. In the first modified example, the height H of the first and second protrusions 26 and 32 and the depth D of the first and second recesses 36 and 42 may be, for example, about 3 mm to 20 mm, more preferably 5 mm to 15 mm, and even more preferably 7 mm to 10 mm.

[0075] In the first modified example, the edges 40 and 46 of the first and second recesses 36 and 42 are also given a rounded radius (R-shape). When the radius of curvature of the edge 40 of the first recess 36 is R7 and the radius of curvature of the bottom 36a of the first recess 36 is R8, the ratio of the radii of curvature R8 / R7 is preferably between 0.05 and 190, more preferably between 0.2 and 17, and even more preferably between 0.3 and 7. Furthermore, the base 28 of the first projection 26 may also be given a rounded radius (R-shape). For example, when the radius of curvature of the base 28 of the first projection 26 is R5 and the radius of curvature of the top 26a of the first projection 26 is R6, the ratio of the radii of curvature R6 / R5 is preferably between 0.6 and 400.

[0076] The radius of curvature R5 of the base portion 28 of the first projection 26 may be, for example, 0.5 mm or more and 5 mm or less, but is preferably 0.7 mm or more and 3 mm or less. Also, the radius of curvature R7 of the edge 40 of the first recess 36 may be, for example, 1 mm or more and 20 mm or less, but is preferably 3 mm or more and 10 mm or less. In the example shown in Figure 10, the dimensions of the second projection 32 (including the radius of curvature of the top portion 32a and the base portion 34) are the same as the dimensions of the first projection 26, and the dimensions of the second recess 42 (including the radius of curvature of the bottom portion 42a and the edge 46) are the same as the dimensions of the first recess 36, but they may be different.

[0077] In the first modified example, the radii of curvature R5 to R8 correspond to the radii of curvature R1 to R4 described above, and are defined in the same way as the radii of curvature R1 to R4. They can be determined using the same method as for determining the radii of curvature R1 to R4.

[0078] In the first modified example described above, the gas generated at electrode 12 flows without accumulating inside the first recess 36, and the gas generated at electrode 78 flows without accumulating inside the second recess 42, thus suppressing the formation of gas pockets inside the first and second recesses 36 and 42. Furthermore, if the base portions 28 and 34 of the first and second protrusions 26 and 32 are also rounded, the gas generated at electrode 12 flows without accumulating near the first protrusion 26, and the gas generated at electrode 78 flows without accumulating near the second protrusion 32, thus further suppressing the formation of gas pockets near the first and second protrusions 26 and 32.

[0079] In the first modified example, the first recess 36 and the first projection 26 are connected via the first flat portion 24, and the second recess 42 and the second projection 32 can be connected via the second flat portion 30 (see Figure 10(a)). Alternatively, as shown in Figure 10(b), a first inclined portion 38 may be provided between the first recess 36 and the first projection 26, and a second inclined portion 44 may be provided between the second recess 42 and the second projection 32.

[0080] (Second variation) As shown in Figures 11(a) and 11(b), the first and second projections 26, 32 and the first and second recesses 36, 42 may be frustoconical in shape. The diameter of the first projection 26 and the first recess 36 gradually decreases as they move away from the first flat portion 24. The diameter of the second projection 32 and the second recess 42 gradually decreases as they move away from the second flat portion 30. In the second modified example, the height H of the first and second projections 26, 32 and the depth D of the first and second recesses 36, 42 may be, for example, 3 mm to 20 mm, more preferably 5 mm to 15 mm, and even more preferably 7 mm to 10 mm.

[0081] In the second modified example, the tops 26a and 32a of the first and second projections 26 and 32 are circular or substantially circular when viewed from a direction perpendicular to the first main surface 20 and the second main surface 22, respectively. The diameter d1 of the tops 26a and 32a of the first and second projections 26 and 32 is the diameter of the portion parallel or substantially parallel to the first flat portion 24 of the first main surface 20 (excluding the portion with R processing), as shown in Figure 11, and is smaller than the diameter d of the first and second recesses 36 and 42. In the second modified example as well, electrodes or current collectors are joined to the tops 26a and 32a of the first and second projections 26 and 32 by welding, and current passes through during electrolysis. From the viewpoint of reducing electrical resistance during electrolysis and improving electrolysis efficiency, the diameter d1 of the tops 26a and 32a of the first and second projections 26 and 32 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. In the second modified example, the electrodes or current collectors may be joined to the tops 26a and 32a of the first and second projections 26 and 32 by methods other than welding.

[0082] In the second modified example, the edges 40 and 46 of the first and second recesses 36 and 42 are also rounded. Furthermore, the base portions 28 and 34 of the first and second projections 26 and 32 may also be rounded. In addition, in the second modified example, it is preferable that the top edges 26b and 32b of the first and second projections 26 and 32 are also rounded, and the bottom edges 36b and 42b of the first and second recesses 36 and 42 are also rounded.

[0083] When the radius of curvature of the base portion 28 of the first projection 26 is R9 and the radius of curvature of the top peripheral edge 26b of the first projection 26 is R10, the ratio of radii of curvature R10 / R9 is preferably 0.1 or more and 100 or less, and more preferably 0.4 or more and 40 or less. Also, when the radius of curvature of the edge 40 of the first recess 36 is R11 and the radius of curvature of the bottom peripheral edge 36b of the first recess 36 is R12, the ratio of radii of curvature R12 / R11 is preferably 0.05 or more and 50 or less, more preferably 0.1 or more and 10 or less, and even more preferably 0.2 or more and 5 or less.

[0084] The radius of curvature R9 of the base portion 28 of the first projection 26 may be, for example, 0.5 mm or more and 5 mm or less, and the radius of curvature R11 of the edge 40 of the first recess 36 may be, for example, 1 mm or more and 20 mm or less, but is preferably 3 mm or more and 15 mm or less. Also, the radius of curvature R10 of the top peripheral edge 26b of the first projection 26 may be, for example, 0.5 mm or more and 50 mm or less, but is preferably 2 mm or more and 20 mm or less. The radius of curvature R12 of the bottom peripheral edge 36b of the first recess 36 may be, for example, 1 mm or more and 50 mm or less, but is preferably 2 mm or more and 20 mm or less, and is even more preferably 3 mm or more and 10 mm or less. In the example shown in Figure 11, the dimensions of the second projection 32 (including the radius of curvature of the top edge 32b and the base 34) are the same as those of the first projection 26, and the dimensions of the second recess 42 (including the radius of curvature of the bottom edge 42b and the edge 46) are the same as those of the first recess 36, although they may be different.

[0085] In the second modified example, the radius of curvature R9 of the base 28 of the first projection 26 and the radius of curvature R9 of the base 34 of the second projection 32 are defined in the same way as the radius of curvature R1 described above and can be determined in the same way as the method for determining the radius of curvature R1. Furthermore, in the second modified example, the radius of curvature R11 of the edge 40 of the first recess 36 and the radius of curvature R11 of the edge 46 of the second recess 42 are defined in the same way as the radius of curvature R3 described above and can be determined in the same way as the method for determining the radius of curvature R3.

[0086] The radius of curvature R10 of the top edge 26b of the first projection 26 in the second modified example will be explained with reference to Figure 12. Let P3 be the intersection point of a straight line L8 extending along the top 26a of the first projection 26 and a tangent line L9 of the first projection 26 passing through the top edge 26b. Define an auxiliary line L10 that passes through intersection point P3 and bisects the angle θ3 between the straight line L8 and the tangent line L9. Assume a virtual circle C5 with center O5 on the auxiliary line L10. The radius of the virtual circle C5 when the circumference of the virtual circle C5 passes through the intersection point Q3 of the top edge 26b of the first projection 26 and the auxiliary line L10, and when the circumference of the virtual circle C5 is tangent to both the straight line L8 and the tangent line L9, is defined as the radius of curvature R10 in this invention.

[0087] The radius of curvature R12 of the bottom edge 36b of the first depression 36 in the second modified example will be explained with reference to Figure 13. Let P4 be the intersection point of the straight line L11 extending along the bottom 36a of the first depression 36 and the tangent line L12 of the first depression 36 passing through the bottom edge 36b. Define an auxiliary line L13 that passes through intersection point P4 and bisects the angle θ4 between the straight line L11 and the tangent line L12. Assume a virtual circle C6 with center O6 on the auxiliary line 13. Then, the radius of the virtual circle C6 when it passes through the intersection point Q4 of the bottom edge 36b of the first depression 36 and the auxiliary line L13, and when the circumference of the virtual circle C6 is tangent to both the straight line L11 and the tangent line L12, is defined as the radius of curvature R12 in this invention.

[0088] In the second modified example described above, the gas generated at electrode 12 flows without accumulating inside the first recess 36, and the gas generated at electrode 78 flows without accumulating inside the second recess 42, thus suppressing the formation of gas pockets inside the first and second recesses 36 and 42. Furthermore, if the base portions 28 and 34 of the first and second protrusions 26 and 32 are also rounded, the gas generated at electrode 12 flows without accumulating near the first protrusion 26, and the gas generated at electrode 78 flows without accumulating near the second protrusion 32, thus further suppressing the formation of gas pockets near the first and second protrusions 26 and 32.

[0089] Furthermore, in the second modified example, since the first and second protrusions 26 and 32 are frustoconical in shape, the contact area between the first protrusion 26 and the electrode 12 and the contact area between the second protrusion 32 and the current collector 14 are larger compared to the above-described embodiment and the first modified example. Therefore, the electrical resistance during electrolysis is reduced, and the electrolysis efficiency is improved.

[0090] In the second modified example, the first recess 36 and the first projection 26 are connected via the first flat portion 24, and the second recess 42 and the second projection 32 can be connected via the second flat portion 30 (see Figure 11(a)). Alternatively, as shown in Figure 11(b), a first inclined portion 38 may be provided between the first recess 36 and the first projection 26, and a second inclined portion 44 may be provided between the second recess 42 and the second projection 32. [Explanation of Symbols]

[0091] 2: Electrolytic cell 4: Bulkhead assembly 6: Membrane assembly 8: Bulkhead 10: Partition support frame 12: Electrode 14: Current collector 16:Anode chamber 18: Cathode chamber 20: First main surface of the partition wall 22: Second main surface of the partition wall 24: 1st flat part 26:1st protrusion 26a: Top of the first projection 26b: Periphery of the apex of the first projection (second modified form) 28: Base of the first projection 30: 2nd flat part 32:Second protrusion 32a: Top of the second projection 32b: Periphery of the apex of the second projection (second modified form) 34: Base of the second projection 36: First depression 36a: Bottom of the first depression 36b: Bottom edge of the first depression (second modified form) 40: Edge of the first depression 42: Second depression 42a: Bottom of the second depression 42b: Bottom edge of the second depression (second modified example) 46: Edge of the second depression 76: Cushioning material 78: Electrode 80: Membrane 82: Membrane support frame 84: Gasket

Claims

1. A partition wall of an electrolytic cell that separates the anode chamber and the cathode chamber, It has a first main surface and a second main surface located on the opposite side of the first main surface, The first main surface includes a first flat portion and a plurality of first recesses that are recessed more than the first flat portion, and the edges of the first recesses are rounded. The second main surface includes a second flat portion and a plurality of second recesses that are recessed more than the second flat portion, and the edges of the second recesses are rounded. Furthermore, the first main surface includes a plurality of mountain-shaped first protrusions that protrude beyond the first flat portion, and the second main surface includes a plurality of mountain-shaped second protrusions that protrude beyond the second flat portion. A partition wall for an electrolytic cell, wherein the entire circumference of the base of the first projection is rounded, and the entire circumference of the base of the second projection is rounded.

2. A first inclined portion is provided between the first projection and the first recess on the first main surface, which is inclined with respect to the first flat portion. The partition wall of an electrolytic cell according to claim 1, wherein a second inclined portion is provided between the second projection and the second recess on the second main surface, and is inclined with respect to the second flat portion.

3. The positions of the plurality of first recesses correspond to the positions of the plurality of second protrusions, The partition wall of an electrolytic cell according to claim 1, wherein the positions of the plurality of second recesses correspond to the positions of the plurality of first protrusions.

4. The partition wall of the electrolytic cell according to claim 1, wherein the first projection, the second projection, the first recess, and the second recess are hemispherical.

5. The partition wall of an electrolytic cell according to Claim 4, wherein when the radius of curvature of the edges of the first recess and the second recess is R3, and the radius of curvature of the bottoms of the first recess and the second recess is R4, the ratio of radii of curvature R4 / R3 is 0.1 or more and 19 or less.

6. When the radius of curvature of the base of the first projection and the second projection is R1, and the radius of curvature of the top of the first projection and the second projection is R2, the ratio of the radii of curvature R2 / R1 is 0.6 or more and 40 or less, The partition wall for an electrolytic cell according to claim 4, wherein, when the radius of curvature of the edges of the first and second recesses is R3, and the radius of curvature of the bottoms of the first and second recesses is R4, the ratio of radii of curvature R4 / R3 is 0.1 or more and 19 or less.

7. The partition wall of an electrolytic cell according to claim 1, wherein the first projection, the second projection, the first recess, and the second recess are conical in shape, and the tops of the first projection and the second projection and the bottoms of the first recess and the second recess are rounded.

8. The partition wall for an electrolytic cell according to claim 7, wherein when the radius of curvature of the edges of the first recess and the second recess is R7, and the radius of curvature of the bottoms of the first recess and the second recess is R8, the ratio of radii of curvature R8 / R7 is 0.05 or more and 190 or less.

9. When the radius of curvature of the base of the first projection and the second projection is R5, and the radius of curvature of the top of the first projection and the second projection is R6, the ratio of the radii of curvature R6 / R5 is 0.6 or more and 400 or less. The partition wall for an electrolytic cell according to claim 7, wherein, when the radius of curvature of the edges of the first and second recesses is R7, and the radius of curvature of the bottoms of the first and second recesses is R8, the ratio of the radii of curvature R8 / R7 is 0.05 or more and 190 or less.

10. The first projection, the second projection, the first recess, and the second recess are frustoconical in shape, The partition wall of the electrolytic cell according to claim 1, wherein the bottom edge of the first recess and the bottom edge of the second recess are rounded.

11. The partition wall of an electrolytic cell according to claim 10, wherein when the radius of curvature of the edges of the first recess and the second recess is R11, and the radius of curvature of the bottom periphery of the first recess and the second recess is R12, the ratio of radii of curvature R12 / R11 is 0.05 or more and 50 or less.

12. The partition wall of the electrolytic cell according to claim 10, wherein the base of the first projection, the base of the second projection, and the periphery of the top of the first projection and the periphery of the top of the second projection are rounded.

13. When the radius of curvature of the base of the first projection and the second projection is R9, and the radius of curvature of the apex periphery of the first projection and the second projection is R10, the ratio of the radii of curvature R10 / R9 is 0.1 or more and 100 or less. The partition wall for an electrolytic cell according to claim 12, wherein, when the radius of curvature of the edges of the first and second recesses is R11, and the radius of curvature of the bottom edges of the first and second recesses is R12, the ratio of radii of curvature R12 / R11 is 0.05 or more and 50 or less.

14. A partition wall assembly comprising a partition wall according to any one of claims 1 to 13 and a partition wall support frame for supporting the peripheral edge of the partition wall.

15. The partition wall assembly according to claim 14, wherein the partition wall is circular in shape and the partition wall support frame is annular.

16. The partition assembly according to claim 14, further comprising an electrode or current collector joined to the top of each of the plurality of first protrusions, and a current collector or electrode joined to the top of each of the plurality of second protrusions.

17. The partition assembly according to claim 14, further comprising an electrode or current collector joined by welding to the top of each of the plurality of first protrusions, and a current collector or electrode joined to the top of each of the plurality of second protrusions.

18. The partition assembly according to claim 14, further comprising an electrode or current collector welded to the top of each of the plurality of first protrusions, and a current collector or electrode welded to the top of each of the plurality of second protrusions.

19. An electrolytic cell in which a plurality of partition assemblies and a plurality of membrane assemblies are alternately arranged as described in Claim 16, The aforementioned membrane assembly includes an electrolytic cell comprising a membrane and a membrane support frame that supports the peripheral edge of the membrane.

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