Hot Module for Fuel Cells

Abstract

To provide a hot module for a fuel cell that suppresses wasteful radiation of heat of a suction flow to the outside to enhance power generation efficiency of a fuel cell.SOLUTION: A high-pressure raw fuel gas flows into a driving flow path 21 as a driving flow. A part of an exhausted fuel gas discharged from a fuel cell 11 flows into a recycling path 30 as a suction flow. An ejector 14 includes a nozzle portion 20 for ejecting the driving flow to be supplied from the driving flow path 21, a suction port 22 for sucking the suction flow flowing through the recycling flow path 30, and a mixing unit 23 and a diffuser unit 24 which mixes and pressurizes the driving flow and the suction flow. A reformer 15 reforms the mixed flow discharged from the ejector 14 into a fuel gas to be supplied to the fuel cell 11 by an endothermic reaction. A heat exchanger 13 is configured such that the suction flow flowing through the recycle flow path 30 is heat-exchanged with both the mixed flow and the driving flow.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention is applicable to fuel cell systems, and particularly to the layout of components such as heat exchangers included in a power generation module of a solid oxide fuel cell power generation system that operates at high temperatures. [Background technology]

[0002] Patent Document 1 discloses a technology in which, in a fuel cell system in which a portion of the reformed fuel discharged from the fuel cell stack is returned to the suction port of an ejector via a reuse piping, the suction flow and the driving flow are heat exchanged in a heat exchanger installed midway through the reuse piping, causing the driving flow to heat up, expand, and increase in flow rate, enabling a large amount of reformed fuel to be sucked in with less power from the fuel blower. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-72251 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology disclosed in Patent Document 1, the heat exchanger and the ejector are separate structures, and the respective gas flow paths are connected by piping. Therefore, when the heat exchanger exchanges heat between the suction flow and the driving flow, the heat of the suction flow is wasted outside the fuel cell device, which requires an increase in the supply amount of raw fuel gas to compensate for the wasted heat energy, which leads to a decrease in power generation efficiency.

[0005] In this regard, the prior art does not disclose a specific structure of the heat exchanger, does not provide any measures to address the above-mentioned problem, and moreover, does not mention the above-mentioned problem at all.

[0006] In view of the above, an object of the present invention is to provide a hot module for a fuel cell that can suppress the heat of the suction flow from being unnecessarily dissipated to the outside and increase the power generation efficiency of the fuel cell. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a hot module for a fuel cell having a configuration for supplying a fuel gas to a solid oxide fuel cell (11) that outputs electric energy by an electrochemical reaction between a fuel gas and an oxidant gas, comprising: a driving flow path (21) through which a high-pressure hydrocarbon-based raw fuel gas flows as a driving flow; a recycle flow path (30) through which a portion of exhaust fuel gas discharged from the fuel cell flows as a suction flow; an ejector (14) having a nozzle section (20) which sprays a driving flow supplied from a driving flow path, a suction port (22) through which a suction flow flowing through a recycle flow path is sucked in by the energy of the driving flow sprayed from the nozzle section, a mixer section (23) and a diffuser section (24) which mix and pressurize the driving flow and the suction flow, and which discharges a mixed flow obtained by mixing the driving flow and the suction flow; a reformer (15) that causes an endothermic reaction of the mixed flow discharged from the ejector in the presence of a catalyst to reform the mixed flow into a fuel gas to be supplied to the fuel cell; and a heat exchanger (13) configured so that the suction stream flowing through the recycle flow path is heat exchanged with both the mixed stream and the driving stream. The heat exchanger has a cylindrical first pipe portion (31) that surrounds the outside of the ejector main body portion that constitutes the mixing portion and diffuser portion of the ejector, and forms a cylindrical flow path (301) through which the suction flow flows between the ejector main body portion and the first pipe portion, so that heat exchange between the suction flow and the mixed flow is performed via the ejector main body portion.

[0008] According to this, the heat of the suction flow is transferred to both the mixed flow and the driving flow by the heat exchanger, so that the heat of the suction flow is circulated to the reformer in the hot module, and the heat is prevented from being wasted to the outside. By increasing the temperature of the mixed flow supplied to the reformer, when the hot module is equipped with a combustor that burns a part of the exhaust fuel gas, the configuration for transferring heat from the combustor to the reformer can be simplified and miniaturized, and the exhaust fuel gas to be burned in the combustor can be reduced. Therefore, the supply amount of raw fuel gas to compensate for the thermal energy can be reduced, and the power generation efficiency of the fuel cell can be improved. In addition, by increasing the temperature of the mixed flow supplied to the reformer, the reforming rate of the raw fuel gas to be reformed into fuel gas in the reformer can be improved.

[0009] In addition, by lowering the temperature of the suction flow using the heat exchanger, the volume of the suction flow is reduced and the flow rate is slowed down. As a result, a larger amount of the suction flow is sucked into the suction port of the ejector with low power. Therefore, this hot module for fuel cells can reduce the supply of raw fuel gas and increase the power generation efficiency of the fuel cell by circulating a larger amount of the suction flow, i.e., the exhaust fuel gas, with low power. Furthermore, by increasing the temperature of the driving flow using a heat exchanger, the volume of the driving flow increases and the flow rate increases, reducing the power required for the fuel pump to pressurize the driving flow (i.e., the raw fuel gas), and improving the power generation efficiency of the fuel cell.

[0010] Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a fuel cell power generation system to which a fuel cell hot module according to a first embodiment is applied. [Diagram 2] FIG. 2 is a cross-sectional view showing a part of a hot module for a fuel cell. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion III in FIG. 2. [Figure 4] FIG. 6 is a cross-sectional view showing a part of a hot module for a fuel cell according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a part of a hot module for a fuel cell according to a third embodiment. [Figure 6] FIG. 11 is a cross-sectional view showing a part of a hot module for a fuel cell according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals, and the description thereof will be omitted.

[0013] (First embodiment) The first embodiment will be described with reference to Figures 1 to 3. A hot module 10 for a fuel cell (hereinafter referred to as "hot module 10") of this embodiment is applied to a fuel cell system 1. Fig. 1 is a diagram showing a schematic configuration of a fuel cell system 1. As shown in Fig. 1, the fuel cell system 1 includes a hot module 10 equipped with a fuel cell 11 and the like, an air blower 2 that supplies air as an oxidizing gas to the hot module 10, a fuel pump 3 that supplies raw fuel gas, a water pump 4 that supplies water, and the like.

[0014] 1 and 2, the hot module 10 includes a fuel cell 11, a water evaporator 12, a heat exchanger 13, an ejector 14, a reformer 15, an air preheater 16, a combustor 17, and a warm-up combustor 18 (see FIG. 2). Note that FIG. 2 shows the right half of a cross section parallel to the axis CL of the hot module 10.

[0015] The fuel cell 11 is also called a cell stack, and is an assembly of a plurality of fuel cell units (not shown). The fuel cell unit is a solid oxide fuel cell (SOFC) that operates at high temperatures, and is configured such that a fuel electrode (i.e., an anode) is formed on one side of an electrolyte, and an air electrode (i.e., a cathode) is formed on the other side. The fuel cell 11 generates electricity through an electrochemical reaction between a fuel gas supplied to the fuel electrode and air (more specifically, oxygen in the air) as an oxidant gas supplied to the air electrode.

[0016] The fuel cell 11 uses hydrogen and carbon monoxide produced by reforming city gas (i.e., gas mainly composed of methane), which is a hydrocarbon-based raw fuel, as its fuel gas. Note that the raw fuel gas used may be any gas other than city gas, so long as it is a hydrocarbon-based fuel.

[0017] The fuel cell 11 outputs electrical energy through electrochemical reactions of hydrogen and oxygen as shown in the following reaction formulas F1 and F2.

[0018] (Fuel electrode)2H2+2O 2- →2H2O+4e - …(F1) (Air electrode) O2+4e - →2O 2- …(F2)

[0019] The fuel cell 11 also outputs electrical energy through electrochemical reactions of carbon monoxide and oxygen as shown in the following reaction formulas F3 and F4.

[0020] (Fuel electrode)2CO+2O 2- →2CO2+4e - …(F3) (Air electrode) O2+4e - →2O 2- …(F4)

[0021] As shown in Fig. 1, an air blower 2 draws in air from the atmosphere and pumps it to a fuel cell 11 in a hot module 10. As shown in Figs. 1 and 2, an air preheater 16 is provided on the path from the air blower 2 to the fuel cell 11. The air preheater 16 heats the air supplied to the fuel cell 11 using the heat of the combustion gas burned in a warm-up combustor 18 or combustor 17 and the heat of the fuel cell 11. This reduces the temperature difference between the air and fuel gas supplied to the fuel cell 11, improving the power generation efficiency of the fuel cell 11.

[0022] As shown in FIG. 1, the fuel pump 3 pumps raw fuel gas containing hydrocarbons (e.g., methane) toward a heat exchanger 13 and an ejector 14 provided in a hot module 10. For example, an electric type is used as the fuel pump 3. A desulfurizer 5 is provided between the fuel pump 3 and the hot module 10. As the desulfurizer 5, a hydrodesulfurization type is used that removes sulfur content contained in the source fuel gas by using hydrogen. The raw fuel gas flowing out from the desulfurizer 5 is supplied to a nozzle portion 20 of the ejector 14 via a heat exchanger 13 provided in the hot module 10. That is, the high-pressure raw fuel gas pumped from the fuel pump 3 to the nozzle portion 20 of the ejector 14 becomes a driving flow of the ejector 14. Therefore, in this embodiment, the flow path from the fuel pump 3 to the nozzle portion 20 of the ejector 14 is called a driving flow path 21.

[0023] The water pump 4 supplies water to a water evaporator 12 in the hot module 10. The water evaporator 12 evaporates water using the heat of the combustion gas combusted in the combustor 17 to generate water steam. The water steam generated in the water evaporator 12 flows through the drive flow passage 21 together with the raw fuel gas flowing out from the desulfurizer 5, and is supplied to the nozzle portion 20 of the ejector 14 via the heat exchanger 13.

[0024] 3, the ejector 14 has a nozzle section 20, a suction port 22, a mixing section 23, a diffuser section 24, and a discharge port 25. The nozzle section 20 of the ejector 14 injects the driving flow supplied from the driving flow passage 21 from an injection hole 26 at the tip of the nozzle section 20 toward the mixing section 23 and the diffuser section 24.

[0025] The mixing section 23 of the ejector 14 houses the nozzle section 20 and is a flow path formed so that the flow path area gradually decreases from the nozzle section 20 toward the discharge port 25. A suction port 22 is provided on the inner wall of the mixing section 23, radially outside the nozzle section 20.

[0026] As shown in FIGS. 1 to 3, the suction port 22 of the ejector 14 is connected to a recycle flow path 30 through which a part of the exhaust fuel gas (hereinafter referred to as "offgas") discharged from the fuel cell 11 flows. The offgas discharged from the fuel cell 11 contains fuel gas that was not used in the chemical reaction of the fuel cell 11. The offgas flowing through the recycle flow path 30 becomes an intake flow that is drawn into the suction port 22 of the ejector 14. The intake flow drawn into the ejector 14 from the suction port 22 is mixed with a driving flow injected from the injection hole 26, and the mixed flow is discharged from the discharge port 25 of the ejector 14 to the reformer 15. That is, the fuel cell system 1 is configured to mix the offgas discharged from the fuel cell 11 with raw fuel gas and steam, and supply it again to the fuel cell 11 through the reformer 15, thereby repeatedly using it for power generation.

[0027] Incidentally, the off-gas discharged from the fuel cell 11 that does not flow into the recycle flow path 30 is combusted in the combustor 17 together with the off-air discharged from the fuel cell 11. The heat of the combustion gas combusted in the combustor 17 is used to raise the temperatures of the reformer 15, the water evaporator 12, the air preheater 16, etc.

[0028] The mixing section 23 and the diffuser section 24 of the ejector 14 are in communication with each other. The diffuser section 24 is a flow path formed so that the flow path area on the discharge port 25 side is gradually larger than the flow path area on the mixing section 23 side. The diffuser section 24 may have a throat section 27 formed so that the flow path area is almost constant or slightly larger toward the discharge port 25 side, at the mixing section 23 side. The diffuser section 24 decelerates the mixed flow and increases the pressure. That is, the diffuser section 24 converts the kinetic energy of the mixed flow into pressure energy to increase the pressure of the mixed flow.

[0029] In this way, the ejector 14 sucks in the suction flow through the recycle flow passage 30 from the suction port 22 by the energy of the driving flow injected from the injection hole 26 at the tip of the nozzle portion 20. The ejector 14 mixes the driving flow and the suction flow in the mixing portion 23, and pressurizes the mixed flow in the diffuser portion 24 and discharges it from the discharge port 25. In the following description, the cylindrical member that constitutes the mixing portion 23 and the diffuser portion 24 of the ejector 14 is referred to as the ejector main body portion 28.

[0030] The mixed flow discharged from the discharge port 25 of the ejector 14 flows into the reformer 15. The mixed flow contains raw fuel gas, off-gas, and steam. The reformer 15 is configured to contain a steam reforming catalyst containing nickel, for example. The reformer 15 heats the mixed flow by exchanging heat between the combustion gas burned in the combustor 17 and the mixed flow, and reforms the mixed flow into a fuel gas to be supplied to the fuel cell 11 by a steam reforming reaction in the presence of a catalyst. In FIG. 2, the heat transfer from the combustion gas burned in the combustor 17 to the reformer 15 is indicated by a hollow arrow HT. The fuel gas generated in the reformer 15 is supplied to the fuel electrode of the fuel cell 11 through a pipe 150.

[0031] The reformer 15 generates a fuel gas containing hydrogen and carbon monoxide through a reforming reaction shown in the following reaction formula F5 and a shift reaction shown in the following reaction formula F6.

[0032] CH4+H2O→CO+H2…(F5) CO+H2O→CO2+H2…(F6)

[0033] Here, the steam reforming in the reformer 15 is an endothermic reaction, and the reforming rate improves under high temperature conditions. Therefore, by increasing the temperature of the mixed flow discharged from the ejector 14 to the reformer 15, it is possible to improve the reforming rate in the reformer 15. In addition, by increasing the temperature of the mixed flow, it is possible to simplify and miniaturize the configuration for transferring heat from the combustor 17 to the reformer 15, and it is also possible to reduce the flow rate of the off-gas combusted in the combustor 17.

[0034] Therefore, in this embodiment, the suction flow through the recycle flow passage 30 is heat-exchanged with both the mixed flow through the ejector 14 and the driving flow through the driving flow passage 21 by the heat exchanger 13 provided to surround the outside of the ejector 14. Regarding the temperatures of the suction flow, the driving flow, and the mixed flow (hereinafter referred to as "three fluids"), the suction flow, which is a part of the off-gas discharged from the fuel cell 11, has the highest temperature among the three fluids. Also, the driving flow, which includes the raw fuel gas pumped from the fuel pump 3 outside the hot module 10, has the lowest temperature among the three fluids. And the mixed flow, which is a mixture of the suction flow and the driving flow, has an intermediate temperature among the three fluids. Therefore, in the heat exchanger 13, the heat of the suction flow is transferred to both the mixed flow and the driving flow.

[0035] As shown in FIG. 3, the heat exchanger 13 has a cylindrical first pipe section 31 provided to surround the outside of the ejector body section 28, and a cylindrical second pipe section 40 provided to surround the outside of the first pipe section 31. Between the ejector body section 28 and the first pipe section 31, a cylindrical flow path 301 is formed as a part of the recycle flow path 30 through which the suction flow flows. The cylindrical flow path 301 is formed in a cylindrical shape so as to surround the outside of the ejector body section 28. With this configuration, heat exchange between the suction flow and the mixed flow is performed through the ejector body section 28. In addition, between the first pipe section 31 and the second pipe section 40, an outer cylindrical flow path 201 is formed as a part of the driving flow path 21 through which the driving flow flows. The outer cylindrical flow path 201 is formed in a cylindrical shape so as to surround the outside of the first pipe section 31. With this configuration, heat exchange between the suction flow and the driving flow is performed through the first pipe section 31.

[0036] The cylindrical flow passage 301 formed between the ejector body 28 and the first pipe 31 communicates with the suction port 22 of the ejector 14. The outer cylindrical flow passage 201 formed between the first pipe 31 and the second pipe 40 communicates with the inlet 29 of the nozzle 20 of the ejector 14.

[0037] 2, the hot module 10 houses the water evaporator 12, the reformer 15, the air preheater 16, the combustor 17, the fuel cell 11, etc. inside a housing 19. The housing 19 of the hot module 10 may be composed of outer walls of the air preheater 16, the reformer 15, the water evaporator 12, etc.

[0038] In Fig. 2 and Fig. 3, for convenience of explanation, one end side and the other end side of the axial direction of the ejector body 28, the first pipe section 31, and the second pipe section 40 are indicated by double-headed arrows DR. As shown in Fig. 3, one axial end of the ejector body 28, the first pipe section 31, and the second pipe section 40 is connected to the housing 19 of the hot module 10 or a component member inside the housing 19. Specifically, one axial end of the ejector body 28 is connected to a component member 151 on the inlet side of the reformer 15 inside the housing 19. One axial end of the first pipe section 31 is connected to a member 311 that constitutes the recycle flow passage 30 inside the housing 19. One axial end of the second pipe section 40 is connected to an outer wall 121 of the water evaporator 12. The outer wall 121 of the water evaporator 12 constitutes a part of the housing 19 of the hot module 10.

[0039] Meanwhile, the other axial end of the ejector body 28, the other axial end of the first pipe 31, and the other axial end of the second pipe 40 extend outward from the housing 19 of the hot module 10. The ejector body 28, the first pipe 31, and the second pipe 40 all have a "one-side free structure" in which the other axial end extends outward from the housing 19, making them freely deformable in response to thermal expansion and reducing thermal distortion. The other axial end of the first pipe 31 is closed, and the other axial end of the second pipe 40 is also closed.

[0040] In the ejector 14, the nozzle portion 20 is disposed on the other axial end side of the ejector body portion 28, and the discharge port 25 is disposed on one axial end side of the ejector body portion 28. Therefore, the mixed flow flows inside the ejector body portion 28 from the other end side to the one end side. Also, as described above, one axial end of the first pipe portion 31 is connected to the member 311 constituting the recycle flow path 30 inside the housing 19, and the suction port 22 of the ejector 14 is provided on the other end side of the ejector body portion 28. Therefore, the suction flow flows through the cylindrical flow path 301 from one end side to the other end side. In this way, the mixed flow flowing inside the ejector body portion 28 and the suction flow flowing through the cylindrical flow path 301 are counterflows flowing in opposite directions. Therefore, it is possible to increase the heat exchange efficiency between the mixed flow and the suction flow.

[0041] As described above, one axial end of the second pipe section 40 is connected to the outer wall 121 of the water evaporator 12. Therefore, the driving flow flows through the outer cylindrical passage 201 from one end to the other end. In this way, the suction flow flowing through the cylindrical passage 301 and the driving flow flowing through the outer cylindrical passage 201 are parallel flows that flow in parallel to each other. This makes it possible to prevent the driving flow from being overheated and to prevent the temperature of the driving flow from entering the carbon deposition region. In addition, by arranging the outer cylindrical passage 201, through which the driving flow with the lowest temperature of the three fluids flows, at the outermost position, the amount of heat dissipated from the second pipe section 40 to the outside can be reduced. That is, this configuration of the heat exchanger 13 makes it possible to reduce the amount of heat dissipated from the three fluids to the outside.

[0042] The hot module 10 of the present embodiment described above provides the following advantages. (1) The heat exchanger 13 provided in the hot module 10 of this embodiment is configured so that the suction flow through the recycle flow path 30 exchanges heat with both the mixed flow flowing in the ejector 14 and the driving flow flowing through the driving flow path 21. According to this, the heat of the suction flow is transferred to both the mixed flow and the driving flow by the heat exchanger 13, so that the heat of the suction flow is circulated to the reformer 15 in the hot module 10, and the heat is prevented from being wasted to the outside. By increasing the temperature of the mixed flow supplied to the reformer 15, the configuration for transferring heat from the combustor 17 to the reformer 15 can be simplified and miniaturized, and the amount of off-gas burned in the combustor 17 can be reduced. Therefore, the amount of raw fuel gas supplied to compensate for the thermal energy can be reduced, and the power generation efficiency of the fuel cell 11 can be improved. In addition, by increasing the temperature of the mixed flow supplied to the reformer 15, it is also possible to improve the reforming rate at which the raw fuel gas is reformed into fuel gas in the reformer 15. Therefore, the amount of raw fuel gas supplied can be reduced, and the power generation efficiency of the fuel cell 11 can be improved.

[0043] Furthermore, by lowering the temperature of the suction flow using the heat exchanger 13, the volume of the suction flow is reduced and the flow rate is slowed down. Therefore, a larger amount of the suction flow is sucked into the suction port 22 of the ejector 14 with low power. Therefore, this hot module 10 can reduce the supply amount of raw fuel gas and increase the power generation efficiency of the fuel cell 11 by circulating a larger amount of the suction flow, i.e., off-gas, with low power.

[0044] Furthermore, by increasing the temperature of the driving flow using heat exchanger 13, the volume of the driving flow increases and the flow rate increases, thereby reducing the power required by fuel pump 3 to pressurize the driving flow, i.e., the raw fuel gas, and improving the power generation efficiency of fuel cell 11.

[0045] (2) In this embodiment, the heat exchanger 13 has a cylindrical first pipe portion 31 that surrounds the outside of the ejector main body portion 28, and forms a cylindrical flow path 301 through which the suction flow flows between the ejector main body portion 28 and the first pipe portion 31, so that heat exchange between the suction flow and the mixed flow is performed via the ejector main body portion 28. According to this, in this embodiment, the ejector 14 and the heat exchanger 13 can be seen as a compact double-pipe structure when focusing on the ejector body 28 and the first pipe portion 31. As a result, the ejector 14 and the heat exchanger 13 are integrally configured, which allows the number of parts to be reduced and the size to be reduced.

[0046] In addition, in this embodiment, by surrounding the outside of the ejector main body 28 with the first pipe 31, it is possible to ensure a wide flow passage cross-sectional area of ​​the cylindrical flow passage 301 inside the first pipe 31, and it is possible to reduce the pressure loss of the suction flow. Although not shown, a conventional type ejector is generally configured so that the suction flow flows in from a direction perpendicular to the axis of the ejector, and a tank for reducing the pressure loss is sometimes provided around the suction port. In contrast, the ejector 14 of this embodiment is configured so that the pressure loss of the suction flow can be reduced, and therefore it is possible to eliminate the tank as in the conventional type ejector.

[0047] Furthermore, in this embodiment, by reducing the pressure loss of the suction flow, a larger amount of the suction flow can be sucked into the suction port 22 of the ejector 14 with less power, so that the power of the fuel pump 3 for pressurizing the driving flow, i.e., the raw fuel gas, can be reduced.

[0048] Incidentally, in the hot module 10 described in the above Patent Document 1, the heat exchanger 13 and the ejector 14 are configured separately, which causes a problem in that a large amount of heat is radiated to the outside from the surface of the piping through which the suction flow and the driving flow flow from the heat exchanger 13 to the ejector 14 and from the surface of the heat exchanger 13. In addition, there is also a problem in that the number of parts is increased due to the piping through which the suction flow and the driving flow flow from the heat exchanger 13 to the ejector 14.

[0049] In contrast, in this embodiment, the heat exchanger 13 and the ejector 14 are integrally configured by the first pipe portion 31 that surrounds the outside of the ejector body 28, which enables heat transfer from the suction flow to the mixed flow and reduces the amount of heat dissipated to the outside from the surface of the heat exchanger 13. In addition, since the heat exchanger 13 and the ejector 14 are integrally configured, the number of parts can be reduced and the size can be reduced.

[0050] (3) In this embodiment, the mixed flow flowing inside the ejector body 28 and the suction flow flowing through the cylindrical flow passage 301 between the first pipe portion 31 and the ejector body 28 flow in a counter direction. Thus, by configuring the counterflow type heat exchanger 13 by the ejector body 28 and the first pipe 31, it is possible to improve the heat transfer performance and increase the heat exchange efficiency between the mixed flow and the suction flow.

[0051] (4) In this embodiment, the heat exchanger 13 has a cylindrical second pipe section 40 that surrounds the outside of the first pipe section 31, and forms an outer cylindrical flow path 201 between the first pipe section 31 and the second pipe section 40, through which the driving flow flows, so that heat exchange between the suction flow and the driving flow is performed via the first pipe section 31. According to this, in this embodiment, when focusing on the ejector body 28, the first pipe 31, and the second pipe 40, they can be seen as a compact triple pipe structure. As a result, the ejector 14 and the heat exchanger 13 are integrally configured, so that the number of parts can be reduced and the size can be reduced.

[0052] Furthermore, by surrounding the outside of the first pipe section 31 with the second pipe section 40, it is possible to ensure a wide flow path cross-sectional area of ​​the outer cylindrical flow path 201 between the first pipe section 31 and the second pipe section 40, thereby reducing the pressure loss of the driving flow.

[0053] Furthermore, in this embodiment, by arranging the outer cylindrical flow path 201, through which the driving flow, which is the fluid with the lowest temperature among the suction flow, the mixed flow, and the driving flow, flows, at the outermost position, it is possible to reduce the amount of heat dissipation from the second pipe section 40 to the outside. That is, with this configuration of the heat exchanger 13, it is possible to reduce the amount of heat dissipation from the three fluids to the outside.

[0054] (5) In this embodiment, the suction flow flowing through the tubular flow path 301 and the driving flow flowing through the outer tubular flow path 201 are parallel flows. According to this, by forming a parallel flow type heat exchanger 13 using the first pipe section 31 and the second pipe section 40, the upper limit temperature of the driving flow can be controlled and excessive temperature rise can be prevented, thereby preventing carbon deposition.

[0055] (6) In this embodiment, the ejector 14, the first pipe portion 31, and the second pipe portion 40 have one ends connected to the housing 19 or a component inside the housing 19, and the other ends extending outward from the housing 19. According to this, the ejector 14, the first pipe portion 31 and the second pipe portion 40 are made to have a one-side free structure, so that they can freely deform in response to thermal expansion, thereby making it possible to prevent damage due to thermal distortion.

[0056] (7) In this embodiment, the other end of the second pipe portion 40 is connected to the water evaporator 12, and the outer cylindrical flow path 201 is configured so that a driving flow containing raw fuel gas and water vapor flows through it. According to this, by increasing the temperature of the driving flow by heat exchanger 13, condensation of water vapor in outer cylindrical channel 201 can be prevented.

[0057] Furthermore, it is possible to ensure a wide flow passage cross-sectional area of ​​the outer cylindrical flow passage 201, thereby reducing the pressure loss of the driving flow flowing therethrough. As a result, the power of the fuel pump 3 for pressurizing the driving flow, i.e., the raw fuel gas, can be reduced, and power generation efficiency can be improved.

[0058] (8) In this embodiment, the discharge port 25 of the ejector 14, which discharges the mixed flow, is connected to the reformer 15. This makes it possible to ensure a wide cross-sectional area of ​​the flow passage from the discharge port 25 of the ejector 14 to the reformer 15, thereby reducing the pressure loss of the mixed flow passing therethrough. As a result, the power of the fuel pump 3 can be reduced.

[0059] Second embodiment The second embodiment will be described. The second embodiment is different from the first embodiment in that a part of the configuration of the heat exchanger 13 is changed, and other parts are the same as those of the first embodiment, so only the parts that are different from the first embodiment will be described.

[0060] 4, like the first embodiment, the heat exchanger 13 included in the hot module 10 of the second embodiment also has a cylindrical first pipe portion 31 surrounding the outside of the ejector main body portion 28 and a cylindrical second pipe portion 40 surrounding the outside of the first pipe portion 31. A cylindrical flow path 301 through which the suction flow flows is formed between the ejector main body portion 28 and the first pipe portion 31, and an outer cylindrical flow path 201 through which the driving flow flows is formed between the first pipe portion 31 and the second pipe portion 40.

[0061] In the second embodiment, a cover member 41 is removably provided on the other axial end of the second pipe section 40. Specifically, a tubular member 42 for attaching the cover member 41 is fixed to an end portion on the other axial end side of the second pipe section 40. A female thread 43 is provided on the radially inner side of the tubular member 42. Meanwhile, a male thread 44 is provided on the outer wall of the cover member 41. Therefore, by screwing the male thread 44 of the cover member 41 into the female thread 43 of the tubular member 42, the cover member 41 is removably provided on the other axial end of the second pipe section 40.

[0062] The cover member 41 is provided with a temperature monitoring sensor 45. The temperature monitoring sensor 45 has a temperature detection portion disposed inside the nozzle portion 20 of the ejector 14 from the outer cylindrical flow path 201. This makes it possible to monitor the temperature of the driving flow flowing from the outer cylindrical flow path 201 to the nozzle portion 20. Note that the temperature monitoring sensor 45 may be, for example, a thermocouple.

[0063] The second embodiment explained above can also achieve the same effects as the first embodiment described above. Furthermore, in the second embodiment, the hot module 10 monitors the temperature of the driving flow using a temperature monitoring sensor 45 arranged inside the nozzle portion 20 of the ejector 14, thereby preventing the driving flow from overheating and monitoring the temperature of the driving flow to prevent it from entering the carbon deposition region.

[0064] In the second embodiment, a lid member 41 is detachably provided on the other end of the second pipe portion 40 constituting the heat exchanger 13. Therefore, it is possible to remove the lid member 41 and perform maintenance work on the nozzle portion 20. Therefore, it is possible to prevent clogging of the flow path of the nozzle portion 20 due to adhesion of foreign matter to the nozzle portion 20 or carbon deposition.

[0065] Third embodiment A third embodiment will be described. The third embodiment is also different from the first embodiment, etc. in that a part of the configuration of the heat exchanger 13 is changed, and other parts are similar to the first embodiment, etc., so only the parts different from the first embodiment, etc. will be described.

[0066] 5, the heat exchanger 13 included in the hot module 10 of the third embodiment is composed of a cylindrical first pipe section 31 surrounding the outside of the ejector main body section 28, and a spiral pipe 46 spirally provided on the outside of the first pipe section 31. The spiral pipe 46 is provided so as to spiral around the first pipe section 31. A driving flow flows through the driving flow path 21 inside the spiral pipe 46. With this configuration, it is possible to perform heat exchange between the suction flow and the driving flow via the first pipe section 31 and the spiral pipe 46.

[0067] In the third embodiment described above, the heat exchanger 13 has a configuration in which the spiral pipe 46 is added to the double-pipe structure of the ejector body 28 and the first pipe 31. That is, the heat exchanger 13 is not limited to the triple-pipe structure described in the first embodiment, and may have a double-pipe structure as exemplified in the third embodiment. In the configuration of the third embodiment, too, by increasing the temperature of the mixed flow supplied to the reformer 15, it is possible to simplify and miniaturize the configuration for transferring heat from the combustor 17 to the reformer 15, and it is possible to reduce the amount of off-gas combusted in the combustor 17. In addition, by increasing the temperature of the mixed flow supplied to the reformer 15, it is possible to improve the reforming rate at which the raw fuel gas is reformed into fuel gas in the reformer 15.

[0068] In addition, by lowering the temperature of the suction flow by the heat exchanger 13, the volume of the suction flow is reduced and the flow rate is slowed down. Therefore, a larger amount of the suction flow is sucked into the suction port 22 of the ejector 14 with low power. Therefore, this hot module 10 can circulate a larger amount of the suction flow, i.e., off-gas, with low power.

[0069] Furthermore, by increasing the temperature of the driving flow using heat exchanger 13, the volume of the driving flow increases and the flow rate increases, thereby reducing the power required by fuel pump 3 to pressurize the driving flow, i.e., the raw fuel gas, and improving the power generation efficiency of fuel cell 11.

[0070] (Fourth embodiment) The fourth embodiment will be described. The fourth embodiment is also the same as the first embodiment, etc., except that a part of the configuration of the heat exchanger 13 is changed, and therefore only the parts different from the first embodiment, etc. will be described.

[0071] 6, like the first embodiment, the heat exchanger 13 included in the hot module 10 of the fourth embodiment also has a cylindrical first pipe portion 31 surrounding the outside of the ejector main body portion 28 and a cylindrical second pipe portion 40 surrounding the outside of the first pipe portion 31. A cylindrical flow path 301 through which the suction flow flows is formed between the ejector main body portion 28 and the first pipe portion 31, and an outer cylindrical flow path 201 through which the driving flow flows is formed between the first pipe portion 31 and the second pipe portion 40.

[0072] In the fourth embodiment, a plurality of dimples 48 are provided in the second pipe portion 40. The plurality of dimples 48 protrude radially inward from the second pipe portion 40, and their tips contact the outer wall of the first pipe portion 31. This makes it possible to keep the width of the outer cylindrical flow path 201 constant.

[0073] The fourth embodiment described above can also achieve the same effects as the first embodiment described above.

[0074] As a first modified example of the fourth embodiment, although not shown in the drawings, a plurality of dimples may be provided in the first pipe section 31. In that case, the plurality of dimples protrude radially outward from the first pipe section 31, with their tips contacting the inner wall of the second pipe section 40. Even in this case, it is possible to maintain the width of the outer cylindrical flow path 201 constant.

[0075] Furthermore, as a second modified example of the fourth embodiment, although not shown in the drawings, a plurality of dimples may be provided protruding radially inward from the first pipe portion 31, and the tips of the dimples may be configured to contact the outer wall of the ejector body portion 28. This makes it possible to keep the width of the cylindrical flow path 301 constant.

[0076] Fifth embodiment A fifth embodiment will be described. In the above-described first embodiment and the like, the suction flow is caused to flow around the ejector body 28, thereby exchanging heat between the mixed flow and the suction flow. In contrast, in the fifth embodiment, heat exchange may be performed between the mixed flow discharged from the discharge port 25 and the suction flow in the middle of the flow path downstream of the discharge port 25 of the ejector body 28.

[0077] (Other embodiments) (1) In each of the above embodiments, the first pipe portion 31 and the second pipe portion 40 are described as being cylindrical, but this is not limited thereto, and the shapes of the first pipe portion 31 and the second pipe portion 40 can be various shapes, such as a cross section relative to the axis that is circular, elliptical, polygonal, or a combination of a polygonal and a circular shape.

[0078] (2) In each of the above embodiments, the ejector 14, the first pipe section 31, and the second pipe section 40 are arranged to extend outward from the housing 19 of the hot module 10. However, this is not limited to this. For example, the ejector 14, the first pipe section 31, and the second pipe section 40 may be arranged inside the housing 19 of the hot module 10.

[0079] (3) In each of the above embodiments, the heat exchanger 13 is configured so that the mixed flow and the suction flow are counter flows. However, this is not limited to this, and the heat exchanger 13 may be configured so that the mixed flow and the suction flow are parallel flows.

[0080] (4) In each of the above embodiments, the heat exchanger 13 is configured so that the suction flow and the driving flow are parallel flows. However, the present invention is not limited to this, and the suction flow and the driving flow may be configured so that they are counter flows.

[0081] (5) In each of the above embodiments, a cylindrical flow path 301 is formed between the ejector main body 28 and the first pipe section 31, and an outer cylindrical flow path 201 is formed between the first pipe section 31 and the second pipe section 40. However, the cylindrical flow path 301 and the outer cylindrical flow path 201 are not limited to being circumferentially continuous flow paths, and may be flow paths having portions thereof that are discontinuous in the circumferential direction.

[0082] The present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims. Moreover, the above-described embodiments are not unrelated to each other, and can be appropriately combined, except when the combination is clearly impossible. Moreover, in each of the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except when they are specifically stated to be essential or when they are clearly considered to be essential in principle. Moreover, in each of the above-described embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiments are mentioned, they are not limited to the specific numbers, except when they are specifically stated to be essential or when they are clearly limited to a specific number in principle. Moreover, in each of the above-described embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., except when they are specifically stated to be essential or when they are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0083] 11 Fuel Cell 13 Heat exchanger 14 Ejector 15 Reformer 20 Nozzle section 21 Driving Channel 22 Suction port 23 Mixing section 24 Diffuser section 30 Recycle Channel

Claims

1. A hot module for a fuel cell is provided with a configuration for supplying a fuel gas to a solid oxide fuel cell (11) that outputs electric energy by an electrochemical reaction between a fuel gas and an oxidant gas, a driving flow path (21) through which a high-pressure hydrocarbon-based raw fuel gas flows as a driving flow; a recycle flow path (30) through which a part of the exhaust fuel gas discharged from the fuel cell flows as a suction flow; an ejector (14) having a nozzle section (20) for spraying the driving flow supplied from the driving flow path, a suction port (22) for sucking in the suction flow flowing through the recycle flow path by the energy of the driving flow sprayed from the nozzle section, a mixer section (23) for mixing the driving flow and the suction flow and increasing the pressure of the mixed flow and a diffuser section (24), and discharging a mixed flow obtained by mixing the driving flow and the suction flow; a reformer (15) that causes an endothermic reaction of the mixed flow discharged from the ejector in the presence of a catalyst to reform the mixed flow into a fuel gas to be supplied to the fuel cell; a heat exchanger (13) configured to exchange heat between the suction stream flowing through the recycle flow path and both the mixed stream and the driving stream; The heat exchanger has a cylindrical first pipe portion (31) that surrounds the outside of an ejector main body portion that constitutes the mixing portion and the diffuser portion of the ejector, and forms a cylindrical flow path (301) through which the suction flow flows between the ejector main body portion and the first pipe portion, thereby enabling heat exchange between the suction flow and the mixed flow to be performed via the ejector main body portion.

2. 2. The hot module for a fuel cell according to claim 1, wherein the mixed flow flowing inside the ejector body and the suction flow flowing through the cylindrical flow passage are counter flows flowing in opposite directions to each other.

3. 3. The hot module for a fuel cell according to claim 1, wherein the heat exchanger has a cylindrical second pipe portion (40) surrounding the outside of the first pipe portion, and an outer cylindrical flow path (201) through which the driving flow flows is formed between the first pipe portion and the second pipe portion, so that heat exchange between the suction flow and the driving flow is performed via the first pipe portion.

4. 4. The hot module for a fuel cell according to claim 3, wherein the suction flow flowing through the cylindrical flow passage and the driving flow flowing through the outer cylindrical flow passage are parallel flows that flow in parallel to each other.

5. 5. The hot module for a fuel cell according to claim 3, further comprising a temperature monitoring sensor (45) provided from the outer cylindrical flow path to the inside of the nozzle portion.

6. The hot module includes a housing (19) that houses the fuel cell and the reformer; 6. A hot module for a fuel cell as described in any one of claims 3 to 5, wherein one end of the ejector, the first pipe portion and the second pipe portion are connected to the housing or a component inside the housing, and the other ends extend outward from the housing.

7. The nozzle portion of the ejector is disposed on the other end side of the ejector, 7. The hot module for a fuel cell according to claim 6, wherein a cover member (41) is detachably provided on the other end of the second pipe portion.

8. The hot module includes a water evaporator (12) for evaporating water to generate water vapor; 8. A hot module for a fuel cell as described in any one of claims 3 to 7, wherein the other end of the second pipe portion is connected to the water evaporator, and the driving flow containing the raw fuel gas and the water vapor flows through the outer cylindrical flow path.

9. 9. The hot module for a fuel cell according to claim 1, wherein the ejector has a discharge port for discharging the mixed flow, the discharge port being connected to the reformer.

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