Hydrogen production equipment

Abstract

A hydrogen production technology is provided that improves the integration rate of a cell stack and stably applies a compressive load to the cell stack in a high-temperature environment. [Solution] The hydrogen production device 10 comprises a gas flow path 11 fixed to a frame 15 inside a heating furnace 12, a plurality of cell stacks 21 (21a, 21b, 21c, 21d) stacked so as to sandwich the gas flow path 11 from above and below, a plurality of tie rods 25 whose lower ends are fixed to the lower plate 23 of the lowest cell stack 21d and which pass through its upper plate 22 and the lower plates 23 and upper plates 22 of the other cell stacks 21 (21a, 21b, 21c), a binding plate 26 which binds the upper ends of each tie rod 25 together, and a biasing means 30 which is provided on the binding plate 26 and biases the upper plate 22 of the highest cell stack 21.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a hydrogen production technology using high-temperature steam electrolysis. [Background technology]

[0002] Solid oxide high-temperature steam electrolysis is a method of producing hydrogen by electrolyzing steam in a high-temperature atmosphere using a solid oxide electrolysis cell. By electrolyzing steam in a high-temperature atmosphere of approximately 700°C or higher, the efficiency of water electrolysis (electrolysis) is approximately 30% higher than that of conventional solid polymer electrolysis cells, and hydrogen can be produced with less power consumption.

[0003] A module that realizes high-temperature steam electrolysis is composed of an integrated number of cell stacks, each of which has approximately 100 cells stacked together, each consisting of a hydrogen electrode layer, an electrolyte layer, a reaction prevention layer, and an oxygen electrode. To ensure electrolysis performance and sealing, this module is constantly held under a compressive force of, for example, approximately 1 to 5 kN, and is heated and maintained at 700°C or higher in a heating furnace. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5007917 Summary of the Invention [Problem to be solved by the invention]

[0005] To increase the integration rate, cell stacks are stacked in multiple layers in a heating furnace, integrated with fastening members, and subjected to a compressive load. Each cell stack is made up of approximately 100 stacked cells, so stacking more than three layers will result in tilting unless dimensional accuracy and assembly precision of the cells are strictly controlled. For this reason, the practical limit for stacking cell stacks is two layers. However, when stacking two layers, there is a problem of a decrease in the integration rate of the cell stack in the heating furnace, given the need to install inlet pipes for steam and air, and outlet pipes for hydrogen and oxygen after electrolysis.

[0006] Furthermore, the fastening members of the cell stack are made of steel, such as austenitic stainless steel, due to their high-temperature strength above 700°C and their economical properties. In this case, a difference in thermal expansion occurs between the cell stack, which is mainly made of ceramics, and its fastening members. This difference in thermal expansion causes fluctuations in the compressive load applied to the cell stack, and therefore must be resolved in some way.

[0007] For this reason, consideration has been given to applying a constant compressive load using a spring mechanism or the like to cell stacks installed in high-temperature environments exceeding 700°C. However, even spring materials made of precipitation-hardened nickel alloys with high high-temperature strength, such as Alloy 718, suffer from degradation due to stress relaxation, making it impossible to maintain the compressive load.

[0008] The embodiments of the present invention have been made taking these circumstances into consideration, and aim to provide a hydrogen production technology that improves the integration rate of cell stacks and stably applies compressive loads to cell stacks in high-temperature environments. [Means for solving the problem]

[0009] The hydrogen production device according to the embodiment comprises a gas flow path fixed to a frame inside a heating furnace, a plurality of cell stacks stacked together so as to sandwich the gas flow path from above and below, a plurality of tie rods whose lower ends are fixed to the lower plate of the cell stack located at the bottom and which pass through the upper plate and the lower and upper plates of the other cell stacks, a bundling plate which bundling the upper ends of each of the tie rods, and a biasing means provided on the bundling plate which biases the upper plate of the cell stack located at the top. [Effects of the Invention]

[0010] An object of the embodiments of the present invention is to provide a hydrogen production technology that improves the integration rate of a cell stack and stably applies a compressive load to the cell stack in a high-temperature environment. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a YZ side cross-sectional view of the hydrogen production device according to the embodiment of the present invention. [Figure 2] 1 is an XZ front cross-sectional view of a hydrogen production device according to an embodiment of the present invention. [Figure 3] FIG. 2 is an XZ front cross-sectional view of the electrolysis module constituting the hydrogen production device according to the first embodiment. [Figure 4] 1 is an XY horizontal cross-sectional view of a hydrogen production device according to a first embodiment. [Figure 5] 4A and 4B are XY horizontal plane views of the biasing means applied to the hydrogen production device according to each embodiment. [Figure 6] FIG. 10 is an XZ front cross-sectional view of an electrolysis module constituting a hydrogen production device according to a second embodiment. [Figure 7] FIG. 10 is an XY horizontal cross-sectional view of the hydrogen production device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment)

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a YZ side cross-sectional view of a hydrogen production device 10 (10A, 10B) according to an embodiment of the present invention. Fig. 2 is an XZ front cross-sectional view thereof. As described above, the hydrogen production device 10 has a gas flow path 11 fixed to a stand 15 inside a heating furnace 12, and multiple cell stacks 21 (21a, 21b, 21c, 21d) integrated so as to sandwich this gas flow path 11 from above and below.

[0014] The hydrogen production device 10 uses a solid oxide electrolysis cell (SOEC) to decompose water introduced as a raw material and generate hydrogen and oxygen. This SOEC utilizes the property that the higher the temperature, the less energy is required to decompose water, and is composed of a cell stack 21 (21a, 21b, 21c, 21d) that operates efficiently at approximately 700°C. This cell stack 21 is made up of a stack of ceramic single cells, and several of these are further integrated in series to form the electrolysis module 20.

[0015] As shown in Fig. 1, the hydrogen production device 10 is composed of a plurality of electrolysis modules 20 (six in the figure) arranged along a gas flow path 11. Furthermore, as shown in Fig. 2, the hydrogen production device 10 has a combination of a plurality of (four in the figure) gas flow paths 11 (11a, 11b, 11c, 11d) (see also Fig. 4) arranged in a plurality of rows (two in the figure). The gas flow paths 11 (11a, 11b, 11c, 11d) that flow the same type of gas 19 (19a, 19b, 19c, 19d) (four types in the figure) are integrated inside the heating furnace 12, and open ends 16 (16a, 16b, 16c, 16d) are formed on the outside.

[0016] In this embodiment, the four gas flow paths 11 are composed of a water vapor inlet pipe, an air inlet pipe, a hydrogen output pipe, and an oxygen output pipe, and each of these is connected to an external open end 16 (16a, 16b, 16c, 16d). The combined set of gas flow paths 11 is sandwiched from above and below by a pair of clamping plates 18 (18a, 18b) and supported by the upper ends of legs 17 erected from a base 15, thereby being fixed to the heating furnace 12. The base 15 supports the entire weight of the gas flow paths 11 and the electrolysis module 20.

[0017] 3 is an XZ front cross-sectional view of the electrolysis module 20A (20) constituting the hydrogen production device 10 according to the first embodiment. As described above, the electrolysis module 20 of the hydrogen production device 10 includes a gas flow path 11 (11a, 11b, 11c, 11d) fixed to a frame inside the heating furnace 12, a plurality of cell stacks 21 (21a, 21b, 21c, 21d) integrated so as to sandwich the gas flow path 11 from above and below, a plurality of tie rods 25 whose lower ends are fixed to the lower plate 23 of the lowermost cell stack 21d and which penetrate the upper plate 22 of the lowermost cell stack 21d and which penetrate the lower plates 23 and upper plates 22 of the other cell stacks 21 (21a, 21b, 21c), a bundling plate 26 that bundling the upper ends of the tie rods 25 together, and biasing means 30 that is attached to the bundling plate 26 and biases the upper plate 22 of the uppermost cell stack 21a.

[0018] The electrolysis module 20 is configured by electrically connecting in series a plurality of cell stacks 21 (21a, 21b, 21c, 21d) that are integrated with a set of gas flow paths 11 (11a, 11b, 11c, 11d) in between. A pair of power terminals (not shown) that supply power to the electrolysis modules 20 is provided on the uppermost cell stack 21a and the lowermost cell stack 21d. A unit made up of a plurality of electrolysis modules 20 arranged side by side on a set of gas flow paths 11 has power terminals of the same polarity connected in parallel by power supply wiring, and this power supply wiring is drawn from the inside to the outside of the heating furnace 12. The power supply wiring drawn from each unit is coupled in parallel and connected to a power supply system (not shown).

[0019] 4 is an XY horizontal cross-sectional view of the hydrogen production device 10A according to the first embodiment. The gas flow path 11 is a set of gas flow path 11a that supplies high-temperature steam to the cell stack 21, gas flow path 11b that similarly supplies high-temperature air, gas flow path 11c that extracts electrolyzed hydrogen, and gas flow path 11d that extracts electrolyzed oxygen, and is fixed to a stand 15 inside the heating furnace 12 via legs 17. Note that, although the embodiment illustrates an example in which four gas flow paths 11 are included in one set, there is no particular limitation on the number of gas flow paths 11.

[0020] The sandwiching plates 18 (18a, 18b) that sandwich the set of gas flow paths 11 (11a, 11b, 11c, 11d) from above and below are provided with through holes (not shown) through which tie rods 25 pass and screw holes (not shown) for fixing the cell stacks 21. Furthermore, one of the sandwiching plates 18 (18a, 18b) is provided with perforations 14 that connect to passages 27 (27a, 27b) that are linked to each of the multiple cell stacks 21.

[0021] The gas flow path 11 vertically sandwiches multiple cell stacks 21 and accumulates them. This configuration allows each cell stack 21 to share the gas flow path 11 and its peripheral components, reducing the number of parts and saving space, thereby improving the integration rate of cell stacks 21 within the heating furnace 12. Furthermore, the downsizing of the heating furnace 12 itself contributes to reducing the plant site area and costs.

[0022] The lower ends of the tie rods 25 are provided with male threads that screw into female threads that are provided in the lower plate 23 of the cell stack 21d located at the bottom. The upper ends of the tie rods 25 are also provided with male threads that are inserted into holes in the bundling plate 26 and fastened with nuts. This restricts displacement of the bundling plate 26 along the tie rods 25 and also binds the upper ends of the tie rods 25 together.

[0023] Furthermore, the tie rod 25 not only penetrates the sandwiching plates 18 (18a, 18b) of the gas flow path 11, but also penetrates the lower plate 23 and upper plate 22 of the cell stack 21 (21a, 21b, 21c). As a result, when the uppermost cell stack 21a is urged toward the gas flow path 11 by the urging means 30, the reaction force acts via the tie rod 25 and urges the lowermost cell stack 21d toward the gas flow path 11. In this way, the same compressive force is applied uniformly to all of the cell stacks 21 (21a, 21b, 21c, 21d).

[0024] The cell stack 21 is mainly made of ceramics, while the tie rods 25 and other structural materials are made of austenitic stainless steel. Therefore, when the electrolysis module 20 is heated to a high temperature in the heating furnace 12, the relative positional relationship between the cell stack 21 and surrounding structures changes slightly due to differences in thermal expansion. However, the compressive force acting on the cell stack 21 (21a, 21b, 21c, 21d) is maintained constant because it is applied from the biasing means 30 only via the tie rods 25.

[0025] The biasing means 30 has a stick 33 that comes into contact with the upper plate 22 of the cell stack 21a under the action of a spring member 35, and a sleeve 34 that houses the spring member 35 and the stick 33 and has an opening 37 at its lower end that engages with the binding plate 26.

[0026] A disc spring is preferably used as the spring member 35. The elastic force generated by the elastic deformation of this spring member 35 becomes the compressive force applied to the cell stack 21 (21a, 21b, 21c, 21d). The spring member 35 is initially set so that this compressive force does not exceed the maximum allowable load (approximately 5 kN) of the cell stack 21. Note that this compressive force can also be adjusted by the number of disc springs installed as the spring member 35.

[0027] In the biasing means 30, a push screw 36 that adjusts the amount of compression of the spring member 35 is threaded into the sleeve 34. This push screw 36 is provided at the top of the sleeve 34 and abuts against the opposite end of the spring member 35, one end of which is in contact with the top of the stick 33. By screwing in this push screw 36, the spring member 35 expands and contracts, making it possible to adjust the compressive force applied to the cell stack 21 (21a, 21b, 21c, 21d).

[0028] The tip of stick 33 protruding from opening 37 of sleeve 34 is formed into a spherical surface. This allows the elastic force generated by spring member 35 to be stably transmitted as a compressive force to upper plate 22 even if stick 33 abuts against upper plate 22 at a slight angle.

[0029] The upper end of the sleeve 34 that houses the spring member 35 inside is exposed to the outside of the heating furnace 12. The heating furnace 12 is provided with a hole 13 large enough to allow the sleeve 34 of the urging means 30 to pass through, and a cover 38 is provided to cover the upper end of the urging means 30 exposed through the hole 13 and seal the inside and outside of the heating furnace 12.

[0030] By removing this cover 38, the compressive force applied to the cell stack 21 (21a, 21b, 21c, 21d) can be adjusted by operating the set screws 36 even when the hydrogen production device 10 is in operation. Furthermore, by exposing the spring member 35 to the outside of the heating furnace 12, the thermal influence can be reduced and the stress relaxation phenomenon, in which the elastic force decreases over time, can be avoided. Note that, if the stress relaxation phenomenon of the spring member 35 can be avoided (as long as the temperature does not exceed 425°C in the case of austenitic stainless steel), the upper end of the sleeve 34 does not need to be exposed to the outside of the heating furnace 12.

[0031] In the electrolysis module 20A of the hydrogen production device 10A of the first embodiment, the passages 27 (27a, 27b) connecting the gas flow passage 11 and the cell stacks 21 are connected via an external connection. That is, the gas (water vapor) flowing through the gas flow passage 11a first flows through the passage 27a arranged externally and is then supplied to each of the cell stacks 21 (21a, 21b, 21c, 21d). The gas (oxygen) produced by an electrochemical reaction while passing through each cell stack 21 is then first output to the passage 27b arranged externally and then flows through the gas flow passage 11d.

[0032] Although not shown in the figure, gas (air) flowing through gas flow path 11b is similarly supplied to cell stack 21. Gas (hydrogen) generated in cell stack 21 is also similarly output and then flows through gas flow path 11c. By making the lengths of the passages 27 connecting gas flow path 11 to cell stack 21 equal, pressure losses can be matched and gas (water vapor, air) can be supplied evenly to each of cell stacks 21 (21a, 21b, 21c, 21d).

[0033] 5(A) and 5(B) are XY horizontal plan views of the biasing means 30 applied to the hydrogen production device 10 according to each embodiment. As described above, the opening 37 of the sleeve 34 is provided with a first locking piece 31 that protrudes in the radial direction. The hole in the binding plate 26 is also provided with a second locking piece 32 that abuts against the first locking piece 31 when the inserted sleeve 34 is angled in the axial rotation direction.

[0034] The biasing means 30 is installed after the gas flow paths 11 (11a, 11b, 11c, 11d), the cell stacks 21 (21a, 21b, 21c, 21d), the binding plate 26, and the tie rods 25 are assembled in the heating furnace 12. That is, as shown in FIG. 5(A) (see FIG. 3 as appropriate), the biasing means 30 is inserted into the hole 13 of the heating furnace 12 and the hole of the binding plate 26 so that the first locking piece 31 and the second locking piece 32 do not interfere with each other.

[0035] 5(B), the sleeve 34 is rotated 90° so that the first locking piece 31 and the second locking piece 32 overlap. As a result, even if the sleeve 34 receives a reaction force from the urging force of the stick 33, it remains connected to the binding plate 26 and is prevented from coming off. Then, a cover 38 is installed in the hole 13 to prevent heat from escaping upward from the heating furnace 12.

[0036] Configuring the electrolysis module 20 in this manner not only makes it easier to assemble the cell stack 21, but also makes it easier to disassemble and remove it from the heating furnace 12 for periodic inspections or in the unlikely event of a malfunction, thereby improving maintainability.

[0037] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is an XZ front cross-sectional view of an electrolysis module 20B constituting a hydrogen production device 10B according to the second embodiment. Fig. 7 is an XY horizontal cross-sectional view of the hydrogen production device 10B according to the second embodiment.

[0038] The hydrogen production device 10B of the second embodiment differs from the first embodiment in the following respects: The passages 29 (29a, 29b) connecting the gas flow path 11 and the cell stack 21 are connected through the interior, and airtight seals 28 are provided around the passages 29 on the contact surfaces of the upper plate 22 and the lower plate 23 of the cell stack 21.

[0039] Furthermore, in the first embodiment, the perforations 14 connected to the passages 29 (29a, 29b) were provided in a position adjacent to the cell stack 21, but in the second embodiment, they are provided in a position overlapping the cell stack 21. In Figures 6 and 7, parts having the same configuration or function as those in Figures 3 and 4 are indicated by the same reference numerals, and duplicated explanations will be omitted.

[0040] As shown in FIG. 6, the passage 29 is formed in a straight line so as to penetrate the gas flow path 11, the sandwiching plate 18, the upper plate 22, the lower plate 23, and the cell stack 21 located between the uppermost upper plate 22 and the lowermost lower plate 23.

[0041] That is, the gas (water vapor) flowing through the gas flow path 11a flows through the passage 29a disposed inside and is then supplied to each of the cell stacks 21 (21a, 21b, 21c, 21d).The gas (oxygen) generated by an electrochemical reaction while passing through each cell stack 21 is output to the passage 29b disposed inside and then flows through the gas flow path 11d.

[0042] Although not shown in the figure, the gas (air) flowing through the gas flow path 11b is similarly supplied to the cell stack 21. Furthermore, the gas (hydrogen) generated in the cell stack 21 is similarly output and then flows through the gas flow path 11c. Thus, in the second embodiment, unlike the first embodiment, no piping is provided that branches out to the outside, thereby reducing the number of parts and facilitating assembly work.

[0043] According to at least one embodiment of the hydrogen production device described above, by stacking multiple cell stacks so that they sandwich the gas flow path from above and below and biasing them with a biasing means, it is possible to improve the integration rate of cell stacks within the heating furnace and to stably apply a compressive load to the cell stacks in a high-temperature environment.

[0044] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents. [Explanation of symbols]

[0045] 10 (10A, 10B)...hydrogen production device, 11 (11a, 11b, 11c, 11d)...gas flow path, 12...heating furnace, 13...hole, 14...perforation, 15...frame, 16...opening end, 17...leg, 18...clamping plate, 19...gas, 20 (20A, 20B)...electrolysis module, 21 (21a, 21b, 21c, 21d)...cell stack, 22...upper plate, 23...lower plate, 25...tie rod, 26...binding plate, 27 (27a, 27b)...passage, 28...airtight seal, 29 (29a, 29b)...passage, 30...biasing means, 31...first locking piece, 32...second locking piece, 33...stick, 34...sleeve, 35...spring member, 36...press screw, 37...opening, 38...cover.

Claims

1. a gas flow path fixed to a frame inside the heating furnace; a plurality of cell stacks integrated so as to sandwich the gas flow path from above and below; a plurality of tie rods whose lower ends are fixed to the lower plate of the cell stack located at the bottom and which penetrate the upper plate thereof, and which also penetrate the lower plates and upper plates of the other cell stacks; a binding plate for binding the upper end of each of the tie rods; and a biasing means provided on the bundling plate for biasing the upper plate of the uppermost cell stack.

2. The hydrogen production device according to claim 1, The biasing means is a stick that is acted upon by a spring member and abuts against an upper plate of the cell stack; a sleeve that accommodates the spring member and the stick therein and has an opening at its lower end that is engaged with the binding plate.

3. The hydrogen production device according to claim 2, A set screw for adjusting the amount of compression of the spring member is threaded into the sleeve.

4. The hydrogen production device according to claim 2, The tip of the stick protruding from the opening is formed into a spherical surface.

5. The hydrogen production device according to claim 2 or 3. The hydrogen generating device, wherein the upper end of the sleeve that houses the spring member therein is exposed to the outside of the heating furnace.

6. The hydrogen production device according to claim 2 or 3. The opening of the sleeve is provided with a first locking piece that protrudes in a radial direction, The opening of the binding plate is provided with a second locking piece that abuts against the first locking piece when the inserted sleeve is angled in the axial rotation direction.

7. The hydrogen production device according to claim 1 or 2, the gas flow path comprises a water vapor inlet pipe, an air inlet pipe, a hydrogen output pipe, and an oxygen output pipe; The combination of gas flow paths is sandwiched from above and below by a pair of sandwiching plates, and is fixed to the heating furnace by connecting them to the upper ends of legs that stand upright from the base.

8. The hydrogen production device according to claim 1 or 2, A hydrogen generating device in which a passage connecting the gas flow path and the cell stack is connected via an external source.

9. The hydrogen production device according to claim 1 or 2, a passage connecting the gas flow channel and the cell stack penetrates the interior and is connected; The hydrogen generating device has an airtight seal provided around the passage on each contact surface of the upper plate and the lower plate of the cell stack.

10. The hydrogen production device according to claim 1 or 2, a plurality of electrolysis modules each comprising the cell stack, the binding plate, and the biasing means are arranged along the gas flow path; Furthermore, the arrays of the electrolysis modules are arranged in a plurality of rows, The hydrogen generating apparatus has the gas flow passages, each of which allows the same type of gas to flow, integrated inside the heating furnace and having an open end outside the furnace.

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