Solid oxide type cell system

Abstract

To provide a solid oxide type cell system capable of satisfactorily heating a heating object by a combustor.SOLUTION: A solid oxide type cell system comprises a cell stack operating in a region generating heat as a whole, and a substantially rectangular parallelepiped combustor arranged alongside the cell stack. The combustor comprises a combustion space, an oxidant gas flow path supplying oxidant gas to the combustion space, and a case covering the combustion space and the oxidant gas flow path, and introduces fuel gas into the combustion space while introducing oxidant gas into the combustion space through the oxidant gas flow path, and heats the heating object by combusting a mixed gas of combustion gas and oxidant gas in the combustion space. An oxidant gas flow path is formed on one surface of the combustor, and the combustor is arranged alongside the cell stack in a prescribed direction with the one surface on which the oxidant gas flow path is formed facing the cell stack so as to be capable of heat transfer with the cell stack.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This specification discloses a solid oxide cell system. [Background technology]

[0002] A solid oxide fuel cell device has been proposed that includes a module case built into a housing via a heat insulating material, a power generation chamber in which fuel cell units are housed in the lower part of the module case, a combustion chamber formed above the power generation chamber, and a reformer arranged above the combustion chamber (see, for example, Patent Document 1). Fuel gas not used for power generation in the power generation chamber is burned in the fuel chamber to become exhaust gas, which rises inside the module case, passes through the reformer, and is discharged outside the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-201005 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the combustion chamber is formed as an open space above the fuel cell unit. As a result, the air injected into the power generation chamber and the exhaust gas generated by the combustion of the fuel gas in the combustion chamber dissipate in the open space, making the combustibility of the fuel gas unstable and sometimes preventing the reformer, which is the target of heating, from being heated sufficiently.

[0005] The main object of the present disclosure is to provide a solid oxide cell system including a cell stack and a combustor, in which an object to be heated is effectively heated by the combustor. [Means for solving the problem]

[0006] The present disclosure has adopted the following means to achieve the above-mentioned main object.

[0007] The solid oxide cell system of the present disclosure comprises: a cell stack that operates in a region that generates heat as a whole; a substantially rectangular parallelepiped combustor having a combustion space, an oxidant gas flow path that supplies oxidant gas to the combustion space, and a case that covers the combustion space and the oxidant gas flow path, wherein the combustor introduces a fuel gas into the combustion space and introduces the oxidant gas into the combustion space via the oxidant gas flow path, and combusts a mixed gas of the combustion gas and the oxidant gas in the combustion space to heat an object to be heated; Equipped with the oxidant gas flow path is formed on one surface of the combustor, the combustor is arranged in a predetermined direction so as to be heat transferable with the cell stack, with one surface on which the oxidant gas flow path is formed facing the cell stack. The gist of this is as follows.

[0008] In the solid oxide cell system disclosed herein, an oxidant gas flow path is formed on one side of the combustor, and the combustor is arranged in a predetermined direction so that the side with the oxidant gas flow path faces the cell stack and is heat-transferable with the cell stack. This allows the oxidant gas flowing through the oxidant gas flow path toward the combustion space to be preheated by the heat of the cell stack, thereby increasing the combustion temperature of the combustor. As a result, the object to be heated can be heated effectively. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a solid oxide cell system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of the solid oxide cell stack and the combustor. [Figure 3] FIG. 2 is a side view of a solid oxide cell stack and combustor. [Figure 4] FIG. 4 is a cross-sectional view showing the solid oxide cell stack and combustor of FIG. 3 along the line AA. [Figure 5] FIG. 2 is an external perspective view of the combustor. [Figure 6]FIG. 2 is a perspective view of the exterior of a fuel preheater and a combustor. [Figure 7] FIG. 2 is a top view of the combustor. [Figure 8] FIG. 8 is a cross-sectional view showing the cross section BB of the combustor of FIG. 7. [Figure 9] FIG. 4 is a cross-sectional view of a solid oxide cell stack and combustor according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present disclosure will be described with reference to the drawings.

[0011] Fig. 1 is a schematic diagram of a solid oxide cell system 1 of this embodiment, Fig. 2 is an external perspective view of a solid oxide cell stack 10 and a combustor 30, and Fig. 3 is a side view of the solid oxide cell stack 10 and a combustor 30. Fig. 4 is a cross-sectional view taken along line AA in Fig. 3. Fig. 5 is an external perspective view of the combustor 30, Fig. 6 is an external perspective view of a fuel preheater 24 and the combustor 30, Fig. 7 is a top view of the combustor 30, and Fig. 8 is a cross-sectional view taken along line BB in Fig. 7.

[0012] The solid oxide cell system 1 of this embodiment is configured as a solid oxide electrolysis cell (SOEC) system that produces hydrogen by electrolyzing high-temperature water vapor. As shown in Fig. 1, the solid oxide cell system 1 includes an electrolysis module 2 including a solid oxide cell stack 10, a fuel supply system 40 that supplies water vapor as a fuel gas to the electrolysis module 2, an air supply system 50 that supplies air as a sweep gas to the electrolysis module 2, a hydrogen recovery system 60 that recovers hydrogen produced by the electrolysis operation, and a power supply 70 that supplies the power required for steam electrolysis to the solid oxide cell stack 10.

[0013] In addition to the solid oxide cell stack 10, the electrolysis module 2 includes a combustion preheater 24, heat exchange sections 25, 26, and 27, and a combustor 30, all of which are housed in a module case 28 with thermal insulation properties.

[0014] The solid oxide cell stack 10 includes a plurality of unit cells 11, each including a solid electrolyte, a fuel electrode (cathode) disposed on one side of the solid electrolyte, and an oxidizer electrode (anode) disposed on the other side of the solid electrolyte. In this embodiment, the solid oxide cell stack 10 is installed so that the stacking direction of the plurality of unit cells 11 is horizontal. As shown in FIG. 2 , in addition to the plurality of unit cells 11, the solid oxide cell stack 10 also includes a pair of metal end plates 14 that sandwich the plurality of unit cells 11 from both ends in the stacking direction, a pair of power feed plates 12 disposed between each of the unit cells 11 disposed at both ends in the stacking direction and each of the end plates 14, and insulating plates 13 disposed between the power feed plates 12 and the end plates 14.

[0015] In the solid oxide cell stack 10, when water vapor is supplied to the anode from the fuel supply system 40 and a voltage required for electrolyzing the water vapor is applied from the power supply 70 between the anode and the oxidizer electrode (between the pair of power supply plates 12), the water vapor is decomposed into hydrogen and oxygen ions, generating hydrogen at the anode. The decomposed oxygen ions then permeate the solid electrolyte and combine with electrons at the oxidizer electrode, generating oxygen at the oxidizer electrode. The hydrogen generated at the anode, together with unreacted water vapor, is discharged from the anode outlet as anode off-gas, and the oxygen generated at the oxidizer electrode, together with sweep gas (air) supplied to the oxidizer electrode from the air supply system 50, is discharged from the oxidizer electrode outlet as anode off-gas. The power supply 70 can be a system power supply, a renewable energy device such as a solar power generation device, a storage battery, or the like. Here, the electrolysis of water vapor is an endothermic reaction, but the solid oxide cell system 1 of this embodiment adjusts the amount of power supplied from the power source 70 so that the solid oxide cell stack 10 operates in a region where it generates heat as a whole due to Joule heat generated inside the stack when power is supplied from the power source 70.

[0016] Because the solid oxide cell stack 10 operates in a high-temperature environment of approximately 650 to 800°C, the solid electrolyte, fuel electrode, and oxidizer electrode are made of ceramic materials. Furthermore, to decompose water vapor into oxygen ions and hydrogen using a catalyst, the fuel electrode uses a cermet made of ceramic and a catalytic metal such as nickel. To maintain good catalytic activity of the fuel electrode, it is necessary to keep the fuel electrode in a reducing atmosphere and prevent oxidation of the metal. For this reason, in this embodiment, hydrogen is mixed with the water vapor supplied to the fuel electrode to prevent oxidation.

[0017] 1, one end of a fuel supply pipe 22f is connected to the anode inlet of the solid oxide cell stack 10, and the other end of the fuel supply pipe 22f is connected to a fuel supply system 40. A fuel preheater 24 and a heat exchanger 26 are provided in the fuel supply pipe 22f. One end of anode off-gas piping 23f is connected to the anode outlet of the solid oxide cell stack 10, and the other end of the anode off-gas piping 23f is connected to a hydrogen recovery system 60. Anode off-gas piping 23f is provided with a heat exchanger 25 and a heat exchanger 26.

[0018] 1, one end of an oxidant supply pipe 22a is connected to the oxidant electrode inlet of the solid oxide cell stack 10, and the other end of the oxidant supply pipe 22a is connected to an air supply system 50. A heat exchanger 25 and a heat exchanger 27 are provided in the oxidant supply pipe 22a. One end of an oxidant electrode off-gas pipe 23a is connected to the oxidant electrode outlet of the solid oxide cell stack 10, and the other end of the oxidant electrode off-gas pipe 23a is connected to a combustor 30.

[0019] 1, the fuel supply system 40 includes a water vapor supply system 41 that supplies water vapor to the fuel supply pipe 22f. Although not shown, the water vapor supply system 41 includes, for example, a water tank that stores water (raw water), a water pump that pumps the water in the water tank, and an evaporator that evaporates the water from the water pump. The water vapor introduced from the fuel supply system 40 into the electrolysis module 2 is heated to a required temperature by heat exchange with the anode off-gas in the heat exchanger 26 and by heat exchange with the combustor 30 in the fuel preheater 24, and then supplied to the anode of the solid oxide cell stack 10. The fuel supply system 40 also includes a hydrogen supply pipe 42 connected to the fuel supply pipe 22f, a hydrogen blower 43 provided in the hydrogen supply pipe 42, and a governor 44 provided in the hydrogen supply pipe 42 upstream of the hydrogen blower 43, in order to mix hydrogen with the water vapor.

[0020] 1 , the air supply system 50 includes an air supply pipe 51 having one end connected to a filter 52 and the other end connected to the oxidant supply pipe 22a, and an air blower 53 installed in the air supply pipe 51. By driving the air blower 53, air drawn into the air supply pipe 51 through the filter 52 is introduced into the oxidant supply pipe 22a and heated to a required temperature by heat exchange with the combustion exhaust gas from the combustor 30 in the heat exchanger 27 and with the anode off-gas in the heat exchanger 25.

[0021] As shown in FIG. 1 , the hydrogen recovery system 60 recovers hydrogen from the anode off-gas emitted from the anode of the solid oxide cell stack 10. The hydrogen recovery system 60 includes a hydrogen tank 61 for storing hydrogen and a condenser 62 for condensing water vapor contained in the anode off-gas to separate the gas and liquid. The condenser 62 has a heat exchange flow path capable of heat exchange with cooling water. The other end of the anode off-gas pipe 23f is connected to the inlet of the heat exchange flow path, and one end of a hydrogen recovery pipe 63 is connected to the outlet of the heat exchange flow path. The hydrogen tank 61 is connected to the other end of the hydrogen recovery pipe 63. The hydrogen recovery pipe 63 is also provided with a variable throttle valve (not shown). The anode off-gas containing hydrogen and water vapor exchanges heat with the cooling water to condense the water vapor contained in the anode off-gas, and the anode off-gas is then recovered into the hydrogen tank 61 through the hydrogen recovery pipe 63 by driving a booster pump (not shown). Furthermore, the condensed water obtained by condensing the anode off-gas in the condenser 62 is stored in a water tank (not shown). The water stored in the water tank is used as raw water for generating water vapor for electrolysis.

[0022] The hydrogen recovery system 60 also includes a recycle pipe 64 that branches off from the hydrogen recovery pipe 63 and is connected to the hydrogen supply pipe 42 between the hydrogen blower 43 and the governor 44, and recycles a portion of the recovered hydrogen as hydrogen for anti-oxidation. The recycle pipe 64 is provided with a flow meter and a variable throttle valve, not shown. The hydrogen recovery system 60 also includes a combustion hydrogen supply pipe 65 that branches off from the hydrogen recovery pipe 63 and is connected to the combustor 30, and supplies a portion of the recovered hydrogen to the combustor 30. The combustion hydrogen supply pipe 65 is provided with a flow meter, not shown.

[0023] As shown in Figures 2 to 4, the combustor 30 is installed on the solid oxide cell stack 10. A pair of end plates 14 sandwich the multiple unit cells 11 from both ends in the stacking direction, and each end plate has a flat support portion 14a formed on its upper edge that is bent horizontally outward in the stacking direction. The combustor 30 is supported on the solid oxide cell stack 10 by having the bottom surface of the combustor 30 placed on the upper surfaces of the support portions 14a of the pair of metal end plates 14.

[0024] As shown in Figures 5 to 8, the combustor 30 includes a case 31, an inner housing 32, and a partition plate 33 that define a combustion chamber C1, a first dispersion chamber C2, and a second dispersion chamber C3, a fuel introduction pipe 34 that introduces fuel (hydrogen for combustion) into the first dispersion chamber C2, an air introduction pipe 35 that introduces air (oxidizer electrode off-gas) into the second dispersion chamber C3, and an igniter (not shown) that ignites the mixed gas of fuel and air introduced into the combustion chamber C1 via the first dispersion chamber C2 and the second dispersion chamber C3.

[0025] The case 31 is a rectangular, box-shaped member having a bottom wall 31b and side walls 31s and an open top. As shown in FIG. 6, a rectangular, flat fuel preheater 24 is joined to the top of the case 31 by heat-resistant adhesive or bolting via a gasket, etc., so as to cover the upper opening. As shown in FIG. 8, the inner housing 32 has a bottom wall 32b and side walls 31s, and is disposed within the case 31 so that the case 31 and the inner housing 32 form a hollow double wall on both sides of the short side of the case 31. A plurality of spacers SP are provided between the bottom wall 31b of the case 31 and the bottom wall 32b of the inner housing 32 to form a uniform gap. The upper edge portion of the side wall 32s of the inner housing 32 is bent and joined to the side wall 31s of the case 31 by welding or the like. The partition plate 33 is a rectangular flat plate. Both ends of the partition plate 33 in the short direction are joined to both side walls 32s of the inner housing 32 in the short direction by welding or the like. As a result, a combustion chamber C1 is defined by the fuel preheater 24, the partition plate 33, a portion of the side wall 31s of the case 31, and a portion of the side wall 32s of the inner housing 32. A first dispersion chamber C2 is defined by the partition plate 33 and a portion of the bottom wall 32b and side wall 32s of the inner housing 32. A second dispersion chamber C3 is defined by the portion of the bottom wall 31b and side wall 31s of the case 31 and the bottom wall 32b and side wall 32s of the inner housing 32. The combustion chamber C1 and the first dispersion chamber C2 are connected via a plurality (a large number) of through holes 33o (see Figures 5, 7 and 8) formed in the partition plate 33, and the combustion chamber C1 and the second dispersion chamber C3 are connected via a plurality (a large number) of through holes 32o (see Figures 5 and 7) formed in the portion of the side wall 32s of the inner housing 32 facing the combustion chamber C1 (the portion above the partition plate 33).

[0026] As shown in FIGS. 5, 7, and 8, the fuel introduction pipe 34 is disposed so as to penetrate one side wall 31s of the case 31 in the longitudinal direction and extend to the center of the first dispersion chamber C2 in the longitudinal direction. A combustion hydrogen supply pipe 65 is connected to an inlet of the fuel introduction pipe 34. An outlet pipe 34o is connected to an outlet of the fuel introduction pipe 34, and the outlet pipe 34o is disposed so that an open end of the outlet pipe 34o is slightly spaced from the bottom wall 31b of the case 31 and the fuel (combustion hydrogen) is discharged toward the bottom wall 32b of the inner housing 32. The fuel (combustion hydrogen) discharged from the outlet pipe 34o of the fuel introduction pipe 34 collides with the bottom wall 32b of the inner housing 32, diffuses to the surrounding area, and is supplied to the combustion chamber C1 through a plurality of through holes 33o formed in the partition plate 33. This allows the fuel (hydrogen for combustion) supplied to the combustion chamber C1 via the first dispersion chamber C2 to be distributed throughout the entire combustion chamber C1.

[0027] As shown in FIGS. 5, 7, and 8, the air introduction pipe 35 is disposed so as to penetrate one side wall 31s of the case 31 in the longitudinal direction and extend parallel to the fuel introduction pipe 34 within the first dispersion chamber C2 to the center in the longitudinal direction. The oxidizer electrode off-gas pipe 23a is connected to the inlet of the air introduction pipe 35. The outlet of the air introduction pipe 35 is connected to the outlet pipe 35o, and the open end of the outlet pipe 35o is connected to a through-hole 32h formed in the bottom wall 32b of the inner housing 32. The air (oxidizer electrode off-gas) discharged from the outlet pipe 35o of the air introduction pipe 35 collides with the bottom wall 31b of the case 31 and diffuses to the surroundings. The air passes through the gap between the case 31 and the inner housing 32 and is supplied to the combustion chamber C1 via a plurality of through-holes 32o formed in the side wall 32s of the inner housing 32, which is a side portion between the fuel preheater 24 and the partition plate 33. By narrowing the gap between the case 31 and the inner housing 32 (second dispersion chamber C3), it is possible to suppress the uneven flow of air (oxidizer electrode off-gas) due to pressure loss, and to distribute the air (oxidizer electrode off-gas) supplied to the combustion chamber C1 via the second dispersion chamber C3 throughout the entire combustion chamber C1.

[0028] As a result, in the combustor 30 of this embodiment, the fuel (hydrogen for combustion) and air (oxidizer electrode off-gas) can be uniformly dispersed within the combustion chamber C1, thereby further improving combustibility.

[0029] The fuel preheater 24 is disposed directly above the combustion chamber C1 of the combustor 30. As shown in FIG. 6, the fuel preheater 24 has a fuel flow path that includes a straight section 24s and a turning section 24t, and that allows the fuel (steam) supplied from the fuel supply system 40 to flow in a serpentine manner. This allows the fuel (steam) flowing through the fuel flow path of the fuel preheater 24 to be directly heated by the combustion heat generated by the fuel mixture of fuel (hydrogen for combustion) and air (oxidizer electrode off-gas) in the combustion chamber C1, and the combustion heat can be transferred to the solid oxide cell stack 10. As a result, the fuel (steam) and the solid oxide cell stack 10 can be efficiently heated to the required temperature using less energy (hydrogen for combustion), thereby further improving the efficiency of the solid oxide cell system 1.

[0030] The combustor 30 of this embodiment has a substantially rectangular parallelepiped case 31, and is supported on the solid oxide cell stack 10 with the bottom wall 31b of the case 31, in which the second dispersion chamber C3 is formed, in contact with the support portion 14a of the metal end plate 14. In this embodiment, as described above, the solid oxide cell stack 10 operates in a region in which heat is generated as a whole, and therefore, the air (oxidizer electrode off-gas) passing through the second dispersion chamber C3 is heated by the heat of the solid oxide cell stack 10 transferred via the end plate 14 before being supplied to the combustion chamber C1. The bottom wall 31b of the substantially rectangular parallelepiped case 31 is the widest surface of the rectangular parallelepiped, and the bottom wall 31b of the case 31 is in direct contact with the metal end plate 14, so that the heat of the solid oxide cell stack 10 can be efficiently transferred to the combustor 30. This increases the combustion temperature in the combustion chamber C1, thereby effectively heating the fuel preheater 24, which is the heating target, and more reliably increases the temperature of the water vapor in the fuel preheater 24 to the temperature required for electrolysis.

[0031] In the above-described embodiment, the combustor 30 is installed so that the bottom surface of the combustor 30 is in direct contact with the support portion 14a of the end plate 14. However, as shown in Fig. 9, a flat metal heat transfer plate 15 having approximately the same size as the bottom wall 31b of the case 31 may be interposed between the bottom wall 31b of the case 31 and the support portion 14a of the end plate 14. This allows the heat of the solid oxide cell stack 10 to be transferred uniformly to the bottom surface of the combustor 30.

[0032] In the above-described embodiment, the combustor 30 is installed above the solid oxide cell stack 10, but it need only be installed so as to be capable of transferring heat to the solid oxide cell stack 10. For example, the combustor 30 may be installed below the solid oxide cell stack 10, or may be installed so as to be aligned horizontally with the solid oxide cell stack 10. In the latter case, the combustor 30 may be installed so that the side wall of the case 31 is in contact with the solid oxide cell stack 10 (end plate 14 or heat transfer plate 15).

[0033] In the above-described embodiment, the combustor 30 heated the fuel preheater 24 as the heating target, but an air preheater that preheats the air supplied from the air supply system 50 may be provided, and the air preheater may be the heating target.

[0034] In the above-described embodiment, the solid oxide cell system 1 is configured as an electrolysis system that performs electrolysis to produce hydrogen by high-temperature steam electrolysis. However, the solid oxide cell system 1 may also be configured to use the solid oxide cell stack 10 as a reversible solid oxide cell stack, so that it can switch between the above-described electrolysis operation and power generation operation that generates power by reacting hydrogen as fuel gas with oxygen contained in the air.

[0035] In the above-described embodiment, the solid oxide cell system 1 is configured as an electrolysis system having a solid oxide electrolysis cell (SOEC) stack as the solid oxide cell stack, but it may also be configured as a fuel cell system having a solid oxide fuel cell (SOFC) stack.

[0036] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0037] The present disclosure is applicable to the solid oxide cell system manufacturing industry and the like. [Explanation of symbols]

[0038] 1 solid oxide cell system, 10 electrolysis cell stack (solid oxide cell stack), 14a flat portion (support member), 15 heat transfer plate (heat transfer member), 24 fuel preheater (heating object), 30 combustor, 31 case, 31b bottom wall (bottom surface), C1 combustion chamber (combustion space), C3 second dispersion chamber (oxidizer gas flow path).

Claims

1. a cell stack that operates in a region that generates heat as a whole; a substantially rectangular parallelepiped combustor having a combustion space, an oxidant gas flow path that supplies oxidant gas to the combustion space, and a case that covers the combustion space and the oxidant gas flow path, wherein the combustor introduces a fuel gas into the combustion space and introduces the oxidant gas into the combustion space via the oxidant gas flow path, and combusts a mixed gas of the combustion gas and the oxidant gas in the combustion space to heat an object to be heated; Equipped with the oxidant gas flow path is formed on one surface of the combustor, the combustor is arranged in a predetermined direction so as to be heat transferable with the cell stack, with one surface on which the oxidant gas flow path is formed facing the cell stack. Solid oxide cell system.

2. 10. The solid oxide cell system of claim 1, the surface of the combustor on which the oxidant gas flow path is formed is the widest surface of a substantially rectangular parallelepiped; Solid oxide cell system.

3. 3. The solid oxide cell system according to claim 1 or 2, the predetermined direction is the up-down direction, The cell stack has a metal support member extending horizontally at an upper portion thereof, the oxidant gas flow path is formed in a bottom surface of the combustor, the support member abuts against a bottom surface of the combustor to support the combustor. Solid oxide cell system.

4. 3. The solid oxide cell system according to claim 1 or 2, the predetermined direction is the up-down direction, the oxidant gas flow path is formed in a bottom surface of the combustor, a plate-shaped metal heat transfer member is disposed between the bottom surface of the combustor and the upper portion of the cell stack so as to abut against the bottom surface of the combustor; Solid oxide cell system.

Images