Bipolar plate flow field structure of multi-stage annular proton exchange membrane electrolytic cell

Abstract

The bipolar plate flow field structure of the multi-stage annular proton exchange membrane electrolytic cell comprises a plate body, multi-stage annular flow channels are concentrically arranged at the center position of the plate body, the multi-stage annular flow channels take the center point of a bipolar plate as the circle center, and the adjacent annular flow channels are separated by channel ridges; central channels are arranged in the diameter direction, penetrate through all the annular flow channels and are communicated with each annular flow channel, and the central channels are distributed in an axial symmetry mode in the diameter direction by taking the circle center of the first-stage annular flow channel as the circle center; one end of the central channel is a water inlet, and the other end of the central channel is a water outlet; a plurality of bolt holes are formed in the peripheral edge of the plate body at intervals, and a power interface is formed in one side face of the plate body. The invention belongs to the technical field of proton exchange membrane water electrolysis hydrogen production, avoids sudden change of speed and current density at a turning position, can remarkably reduce pressure distribution in a flow field, reduces peristaltic water supply work, and improves the performance of an electrolytic cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by proton exchange membrane water electrolysis, and relates to a bipolar plate flow field structure of a multi-stage annular proton exchange membrane electrolyzer. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis hydrogen production technology offers numerous advantages, including high hydrogen purity, fast dynamic response, a wide load range, high operating current density, high hydrogen output pressure, and a compact structure. It is the most promising water electrolysis hydrogen production technology and can be coupled with distributed renewable energy generation systems to produce hydrogen, enabling peak load regulation of power systems and accommodating abandoned photovoltaic and wind power. Reducing the equipment and operating costs of PEM water electrolysis hydrogen production systems and extending their operating life are current research focuses in PEM water electrolysis technology. Bipolar plates occupy the largest volume and are the heaviest in the electrolyzer. Furthermore, they are typically made of titanium to withstand acidic environments, resulting in a relatively high price, accounting for approximately 48% of the total stack cost.

[0003] The flow fields of electrolyzers in the existing technology are mainly divided into two categories: parallel flow fields and serpentine flow fields. The advantages of parallel flow fields are simple structure and easy processing, but the pressure difference between the inlet and outlet of parallel flow fields is small, the distribution of reactants is uneven, and the speed in each channel is low, resulting in a low hydrogen production rate. The serpentine flow field has a relatively long distance between its inlet and outlet, which poses a greater resistance to the reactants, allowing the reactants to diffuse more fully, but its greater resistance increases the work done by the peristaltic pump; at the same time, the serpentine flow field cannot avoid sudden changes in speed and current density at corners, affecting the performance of the electrolyzer and posing a serious safety hazard. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure, which solves the problem in the prior art that the inlet and outlet pressure difference of the parallel flow field is small, resulting in a low hydrogen production rate; the serpentine flow field is prone to sudden changes in speed and current density at corners, which increases the work done by the peristaltic pump.

[0005] The technical solution adopted by the present invention is a multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure, including a plate body, with multiple stages of annular flow channels concentrically arranged at the center of the plate body. The multiple stages of annular flow channels are centered on the center point of the bipolar plate, and adjacent annular flow channels are separated by channel ridges; a central channel is arranged along the diameter direction, the central channel runs through all the annular flow channels and is interconnected with each annular flow channel, and the central channels are axially symmetrically distributed along the diameter direction with the center of the first-stage annular flow channel; one end of the central channel is a water inlet, and the other end of the central channel is a water outlet; a number of bolt holes are spaced apart along the four edges of the plate body, and a power interface is provided on one side of the plate body.

[0006] The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure of the present invention is further characterized by:

[0007] The channel width of the central channel gradually decreases from the water inlet to the center of the first-level annular flow channel, converges on the first-level annular flow channel at a certain angle, and then gradually increases to the water outlet, and is arranged in a symmetrical shape according to the axis of the first-level annular flow channel.

[0008] The annular width of the multi-stage annular flow channel satisfies Murray's bifurcation law:

[0009] D2 3 =2D1 3 , D3 3 =2D2 3 ,···,D R 3 =2D R-1 3 ,

[0010] In the above formula, D1 is the width of the first-stage annular flow channel, D2 is the width of the second-stage annular flow channel, D3 is the width of the third-stage annular flow channel, ..., D R is the width of the n-stage annular flow channel.

[0011] The length of the straight line connecting the two intersection points of the central channel and the outer ring of the first-level annular flow channel is equal to the ring width of the second-level annular flow channel, the length of the straight line connecting the two intersection points of the central channel and the outer ring of the second-level annular flow channel is equal to the ring width of the third-level annular flow channel, and so on. The length of the straight line connecting the two intersection points of the central channel and the outer ring of the n-1-level annular flow channel is equal to the ring width of the n-level annular flow channel.

[0012] The depth of the central channel is 0.2 to 3 mm.

[0013] The width of the first-stage annular flow channel is 0.5 to 3 mm, and the widths of the remaining annular flow channels are obtained by recursion through Murray's law, and the depths are all 0.2 to 3 mm.

[0014] The width of the channel ridge is 0.5 to 3 mm, and the depth is 0.2 to 3 mm.

[0015] The beneficial effects of the present invention are that the annular flow channels are distributed in concentric rings, and the width of the annular flow channels at each level gradually increases from the inside to the outside; the center line of the central channel is parallel to the upper and lower edges of the electrode plate, and the width of the central channel gradually decreases from the outer ring to the inner ring. After reaching the inner ring, the channel gradually increases again, converges at a certain angle, and connects all the annular flow channels. The reaction water enters the flow field from the water inlet, and is distributed through the central channel and the annular flow channel, so that the reaction water is evenly distributed in the entire flow field. The annular flow field design of the present invention conforms to Murray's law. The design of the flow field structure with multi-stage annular flow channel width changes can effectively avoid the water from turning in the flow channel and avoid sudden changes in speed and current density at the turning point. It can significantly reduce the pressure distribution in the flow field, reduce the peristaltic water delivery work, and improve the performance of the electrolytic cell. The structure of the present invention can be used as an anode and / or cathode flow field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a top view of a four-stage annular flow field bipolar plate according to Example 1 of the present invention;

[0017] Figure 2 This is an oblique view of a four-stage annular flow field bipolar plate according to Example 1 of the present invention;

[0018] Figure 3 1. A top view of a five-stage annular flow field bipolar plate according to Example 2 of the present invention;

[0019] Figure 4 A top view of a conventional multi-channel parallel flow field bipolar plate based on a circular plane;

[0020] Figure 5 Schematic diagram of the straight line connecting the two intersection points of the central channel and the annular flow channels at each stage in Example 1 of the present invention;

[0021] Figure 6 A pressure distribution cloud diagram of a proton exchange membrane electrolyzer flow field under the same current density and other identical conditions is provided for comparison between Example 1 of the present invention and a conventional multi-channel parallel flow field.

[0022] In the figure, 1. Water inlet, 2. Water outlet, 3. Central channel, 4. First-level annular flow channel, 5. Second-level annular flow channel, 6. Third-level annular flow channel, 7. Fourth-level annular flow channel, 8. Bolt hole, 9. Power interface, 10. Channel ridge, 11. Plate body, 12. Fifth-level annular flow channel. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The terms "primary, secondary, tertiary, quaternary, and fifth level" in the following text are used only for distinguishing descriptive purposes and should not be understood as indicating or implying relative importance.

[0025] Reference Figure 1 、 Figure 2 、 Figure 3 The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure of the present invention includes a plate body 11, and a multi-stage annular flow channel (at least three stages) is concentrically arranged at the center position of the plate body 11. The multi-stage annular flow channel is centered at the center point of the bipolar plate, and adjacent annular flow channels are separated by channel ridges 10; a central channel 3 is provided along the diameter direction, and the central channel 3 runs through all the annular flow channels and communicates with each annular flow channel. The central channels 3 are symmetrically distributed along the diameter direction with the center of the first-stage annular flow channel 4. One end of the central channel 3 is a water inlet 1, and the other end of the central channel 3 is a water outlet 2; a plurality of bolt holes 8 are spaced apart along the four edges of the plate body 11 for connecting bolts and fixing them to other components of the PEM electrolyzer; a power interface 9 is provided on one side of the plate body 11, and an external power supply is connected through this interface.

[0026] The width of central channel 3 gradually decreases from water inlet 1 to the center of primary annular channel 4, converging onto primary annular channel 4 at a certain angle before gradually increasing to water outlet 2, arranged symmetrically about the axis of primary annular channel 4. After the reaction water enters central channel 3, due to its own narrowing width and the resistance of the columnar channel ridge 10 at the axis of primary annular channel 4, it flows into the diversion ports of each level of annular channel (on the right side). Multiple streams of water flow forward around each annular channel, finally flowing out (on the left side) and converging back to water outlet 2 of central channel 3 for discharge.

[0027] The number of rings in the annular flow field can be selected according to actual needs until the entire reaction area is covered. The width of the primary annular flow channel 4 can also be selected according to actual needs; the width of the channel ridge 10 can also be adaptively changed according to the width of the primary annular flow channel 4.

[0028] Generally speaking, the intervals of the annular flow channels at each level are uniform and distributed in concentric rings, and the width of the annular flow channels at each level satisfies Murray's bifurcation law:

[0029] D2 3 =2D1 3 , D3 3 =2D2 3 ,···,D R 3 =2D R-1 3 ,

[0030] In the above formula, D1 is the width of the primary annular flow channel 4, D2 is the width of the secondary annular flow channel 5, D3 is the width of the tertiary annular flow channel 6, ..., D R is the width of the n-stage annular flow channel.

[0031] The length of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the first-level annular flow channel 4 is equal to the ring width of the second-level annular flow channel 5, and the length of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the second-level annular flow channel 5 is equal to the ring width of the third-level annular flow channel 6. Similarly, the length of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the n-1-level annular flow channel is equal to the ring width of the n-level annular flow channel.

[0032] The depth of the central channel 3 is 0.2 to 3 mm, which is the same as the depth of the annular flow channels at each level. The width of the first-level annular flow channel 4 is 0.5 to 3 mm, and the widths of the remaining annular flow channels are obtained by recursion through Murray's law, and the depths are all 0.2 to 3 mm. The width of the channel ridge 10 is 0.5 to 3 mm, and the depth is 0.2 to 3 mm, which should be the same as the depth of the annular flow channels at each level. As the scale of the electrolytic cell increases, the reaction area loaded with the structure of the present invention also increases accordingly, and the number of annular flow channels also needs to be increased accordingly until the annular flow field fully covers the reaction area.

[0033] Example 1

[0034] See Figure 1 、 Figure 2 , is the structure of Example 1 of the present invention, wherein the annular flow channel is set to four levels, namely, the first-level annular flow channel 4, the second-level annular flow channel 5, the third-level annular flow channel 6, and the fourth-level annular flow channel 7, and each annular flow channel is distributed in a concentric ring shape; the width of each annular flow channel satisfies the following relationship: D2 3 =2D1 3 , D3 3 =2D2 3 , D4 3 =2D3 3 ,

[0035] Among them, D1 is the ring width of the primary annular flow channel 4, D2 is the ring width of the secondary annular flow channel 5, D3 is the ring width of the tertiary annular flow channel 6, and D4 is the ring width of the quaternary annular flow channel 7.

[0036] like Figure 5 As shown, the length L1 of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the first-level annular flow channel 4 is equal to the ring width W1 of the second-level annular flow channel 5, the length L2 of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the second-level annular flow channel 5 is equal to the ring width W2 of the tertiary annular flow channel 6, and the length L3 of the straight line connecting the two intersection points of the central channel 3 and the outer ring of the tertiary annular flow channel 6 is equal to the ring width W3 of the fourth-level annular flow channel 7, and the same applies to the dimensions L4 and W4.

[0037] In this embodiment 1, the width of the first-level annular flow channel 4 is 1 mm; the widths of the remaining annular flow channels are recursively derived from the width of the first-level annular flow channel 4 through Murray's bifurcation law, and the depths are all 1 mm; the depth of the central channel 3 is 1 mm; the width of the channel ridge 10 is 1 mm and the depth is 1 mm.

[0038] Example 2

[0039] See Figure 3 , which is the structure of Example 2 of the present invention. The difference from Example 1 is that the annular flow channel is set to five levels, namely, the first-level annular flow channel 4, the second-level annular flow channel 5, the third-level annular flow channel 6, the fourth-level annular flow channel 7, and the fifth-level annular flow channel 12, and the annular flow channels are distributed in concentric rings.

[0040] In this embodiment 2, the width of the first-level annular flow channel 4 is 1 mm; the widths of the remaining annular flow channels are recursively deduced from the width of the first-level annular flow channel 4 through Murray's bifurcation law, and the depths are all 1.2 mm; the depth of the central channel 3 is 1.2 mm; the width of the channel ridge 10 is 2 mm and the depth is 1.2 mm.

[0041] Example 3

[0042] The structure of Example 3 is similar to the aforementioned structure, except that the annular flow channel is arranged in six levels, namely, the first-level annular flow channel 4, the second-level annular flow channel 5, the third-level annular flow channel 6, the fourth-level annular flow channel 7, the fifth-level annular flow channel 12, and the sixth-level annular flow channel, and each annular flow channel is distributed in a concentric ring shape.

[0043] In this embodiment 3, the width of the first-level annular flow channel 4 is 1.5 mm; the widths of the remaining levels of annular flow channels are recursively deduced from the width of the first-level annular flow channel 4 through Murray's branch law, and the depth is 1.5 mm; the depth of the central channel 3 is 1.5 mm; the width of the channel ridge 10 is 1.5 mm and the depth is 1.5 mm.

[0044] Experimental verification

[0045] like Figure 4 As shown, existing proton exchange membrane electrolyzers mostly use multi-channel parallel flow fields. Due to the small pressure difference between the inlet and outlet of the parallel channels, the reactants are unevenly distributed, and the speed in each channel is low, resulting in a low hydrogen production rate. Based on the above problems, the present invention is based on the principle that the branched structure that conforms to Murray's law is the lowest energy consumption structure selected by natural selection. This principle is applied to the flow field structure of the bipolar plate of the proton exchange membrane electrolyzer to solve the problem of excessive pressure and high energy consumption in the electrolysis process. At the same time, starting from the circular reaction plane, the annular flow field structure also avoids the design of corners, making the velocity and current density distribution more uniform.

[0046] The following describes the effect of the design of the flow field structure of the bipolar plate of the multi-stage annular proton exchange membrane electrolyzer through Example 1. Based on the structure of Example 1, after the reaction water enters the flow field from the water inlet 1, it is evenly distributed by the four-stage annular flow channel. The reaction water does not turn in the electrolyzer, ensuring the uniform distribution of water and improving the stability of the electrolyzer performance; water flows in and out from the central channel 3. The branching structure designed based on Murray's law ensures that the energy consumption of water consumption is reduced, reduces the energy consumption of the electrolysis process, and improves the performance of the electrolyzer. Figure 6 , are two flow fields under the same conditions and the same current density of 2A / cm 2 Under such circumstances, fluid mechanics simulation shows that the structure of Example 1 greatly reduces the pressure in the flow field, reduces the work done by the peristaltic pump to deliver water, and reduces the energy consumption during the electrolysis process.

[0047] It should be noted that the flow channel design of the above-mentioned bipolar plate is based on the results of fluid dynamics simulation. The simulation model establishment process is as follows: establish a simulation model that corresponds to the flow channel configuration on the bipolar plate; set water inlet 1 and water outlet 2; and set water parameters, including flow rate, conductivity, etc.; perform fluid dynamics simulation, mainly observing the pressure distribution in the channel; set the two models to 2A / cm 2 The simulation was performed with the same current density, and it was observed that the pressure distribution of the annular flow field of the present invention was greatly reduced compared with the pressure distribution of the parallel flow field, which effectively reduced the energy consumption during the electrolysis process.

[0048] In summary, there are many ways to change the area of the annular flow field. Any approach that achieves the above-mentioned technical effect by simple modification to reduce the flow channel pressure is within the scope of protection of the present invention, for example, changing the ring width of the first-level annular flow channel 4, increasing the ring width of each level of annular flow channel from the inside to the outside, changing the width of the channel ridge 10, etc. The present invention cleverly applies the branching structure that satisfies Murray's law, which is the best combination of minimum energy consumption produced by natural selection, to the flow field design of the bipolar plate, which can achieve uniform distribution of reaction water in the flow field channel and effectively reduce energy consumption during the electrolysis process; the flow field structure of the annular proton exchange membrane electrolyzer bipolar plate is an annular design, which effectively avoids the problem of sudden changes in velocity and current density at the corners in the serpentine flow field, thereby posing a safety hazard.

Claims

1. A multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure, characterized by: The invention comprises a plate body (11), wherein a multi-stage annular flow channel is concentrically arranged at the center of the plate body (11), wherein the multi-stage annular flow channel is centered at the center point of the bipolar plate, and adjacent annular flow channels are separated by channel ridges (10); a central channel (3) is arranged along the diameter direction, wherein the central channel (3) passes through all the annular flow channels and is interconnected with each annular flow channel, and the central channels (3) are axially symmetrically distributed along the diameter direction with the center of the first-stage annular flow channel (4); one end of the central channel (3) is a water inlet (1), and the other end of the central channel (3) is a water outlet (2); a plurality of bolt holes (8) are spaced apart along the four edges of the plate body (11), and a power supply interface (9) is provided on one side of the plate body (11).

2. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The width of the central channel (3) gradually decreases from the water inlet (1) to the center of the primary annular flow channel (4), converges on the primary annular flow channel (4) at a certain angle, and then gradually increases to the water outlet (2), and is arranged in a symmetrical shape according to the axis of the primary annular flow channel (4).

3. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The annular width of the multi-stage annular flow channel satisfies Murray's bifurcation law: <h2 style=";text-align:left;direction:ltr">D2<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> =2D1<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> D3<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> =2D2<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> ,···,D<h2 style=";text-align:left;direction:ltr"> R <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> =2D<h2 style=";text-align:left;direction:ltr"> R-1 <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> , In the above formula, D1 is the width of the first-stage annular channel (4), D2 is the width of the second-stage annular channel (5), D3 is the width of the third-stage annular channel (6), ..., D R is the width of the n-stage annular flow channel.

4. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The length of the straight line connecting the two intersection points of the central channel (3) and the outer ring of the first-level annular flow channel (4) is equal to the ring width of the second-level annular flow channel (5), the length of the straight line connecting the two intersection points of the central channel (3) and the outer ring of the second-level annular flow channel (5) is equal to the ring width of the third-level annular flow channel (6), and so on. The length of the straight line connecting the two intersection points of the central channel (3) and the outer ring of the n-1-level annular flow channel is equal to the ring width of the n-level annular flow channel.

5. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The depth of the central channel (3) is 0.2-3 mm.

6. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The width of the first-stage annular flow channel (4) is 0.5-3 mm, and the widths of the remaining annular flow channels are obtained by recursive deduction of Murray's law, and the depths are all 0.2-3 mm.

7. The multi-stage annular proton exchange membrane electrolyzer bipolar plate flow field structure according to claim 1, characterized in that: The channel ridge (10) has a width of 0.5 to 3 mm and a depth of 0.2 to 3 mm.

Images