Evaporator for fuel cell systems

Abstract

To provide a vertically placed evaporator which is mounted on a fuel cell system and has a compact form in which a height of a plate assembly is reduced.SOLUTION: An evaporator includes: a plate assembly 80 in which multiple heat transfer plates 81 are laminated; meandering passage plates 86 incorporated into low temperature fluid passages formed on one heat transfer surface side of the heat transfer plates 81; and a water distributor 90 which supplies water to the low temperature fluid passages. The plate assembly 80 has: a first header part 83a which distributes water to the low temperature fluid passages; a second header part 83b which collects steam from the low temperature fluid passages; a third header part 83c which distributes a heat source gas to the high temperature fluid passages; and a fourth header part 83d which collects the heat source gas from the high temperature fluid passages. The first header part 83a is formed at an upper part of the plate assembly 80, and the second header part 83b is formed at a lower part of the plate assembly 80.SELECTED DRAWING: Figure 23

Description

[Technical Field]

[0001] The present invention relates to an evaporator for a fuel cell system. [Background technology]

[0002] Various types of fuel cells have been developed as power generation devices that emit fewer environmentally harmful substances and have superior power generation efficiency compared to gas turbine generators and gas engine generators. In particular, solid oxide fuel cells (SOFCs) can achieve a high power generation efficiency of over 50%, and are therefore used to generate power over a wide range of outputs, from industrial to residential use.

[0003] There are two types of fuel cell systems: reforming, which uses methane-containing gases such as city gas as raw fuel, and non-reforming, which uses hydrogen as raw fuel, but the former is the mainstream in Japan because the hydrogen supply infrastructure is still in the process of being developed. Reforming fuel cell systems mainly use an endothermic external reformer that uses a steam reforming catalyst to generate reformed gas, and a thermally self-sustaining hot module is formed by packaging the cell stack, which is the core of power generation, with auxiliary equipment such as the reformer and combustor.

[0004] To carry out the steam reforming reaction, it is necessary to supply raw fuel and steam to the reformer. For this reason, as disclosed in Patent Document 1, the auxiliary equipment constituting the hot module includes an evaporator (vaporizer) for generating gaseous steam from liquid water. As an evaporator designed to be incorporated into a hot module, a configuration in which a plate heat exchanger is improved is known, as disclosed in Patent Documents 2 and 3. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Publication No. 2008 / 0311445 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-53101 [Patent Document 3] Special Publication No. 2007-506060 Summary of the Invention [Problem to be solved by the invention]

[0006] The evaporator in Patent Document 2 is a vertical-type evaporator based on a plate-fin heat exchanger, with heat transfer fins (corrugated fins) built into each of the low-temperature side flow passages and the high-temperature side flow passages. Fuel gas, such as natural gas, flows through the low-temperature side flow passages, and water is sprayed onto the heat transfer fins from an injection tube. Heating gas flows through the high-temperature side flow passages to evaporate the sprayed water. This evaporator is configured as an auxiliary device for obtaining a mixture of fuel gas and steam. In a vertical-type evaporator, water evaporation can be promoted by allowing water to flow in the form of a liquid film along the heat transfer fins between the plates. However, considering variations in water distribution across the plate width, a certain plate height is required, which makes the evaporator prone to becoming large.

[0007] The evaporator in Patent Document 3 is a horizontal evaporator based on a full-circumference plate heat exchanger using brazing or other techniques. Each low-temperature flow channel group is divided into an upstream evaporation zone with built-in heat transfer fins (offset fins) and a downstream superheat zone without heat transfer fins. Meanwhile, each high-temperature flow channel group has two overlapping turbulence-promoting plates with elongated slots arranged at a specific angle, forming an oblique flow path. High-temperature exhaust gas flows through the high-temperature flow channel group to evaporate water. A water / methanol mixture is supplied to the low-temperature flow channel group, and a mixture of fuel gas and water vapor is obtained by vaporizing the mixture. In horizontal evaporators, it is difficult to form a liquid film. A certain plate length is required to ensure a vaporization zone involving preheating and boiling of the liquid phase, making them prone to being large.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a vertically mounted evaporator to be mounted on a fuel cell system, which is a compact evaporator in which the height of the plate assembly is reduced. [Means for solving the problem]

[0009] The evaporator according to the present invention is an evaporator for generating water vapor to be mounted on a fuel cell system, and comprises a plate assembly formed by stacking a plurality of heat transfer plates, each having front and rear heat transfer surfaces that are approximately parallel to the vertical direction, between a pair of end plates arranged opposite to each other, and joining the end plates and the heat transfer plates together; a serpentine flow path plate incorporated in each of the low-temperature fluid flow paths formed on one of the heat transfer surfaces of the heat transfer plates; heat transfer fins incorporated in each of the high-temperature fluid flow paths formed on the other of the heat transfer surfaces of the heat transfer plates; and a water distributor for supplying water to each of the low-temperature fluid flow paths, The plate assembly has a first header section that distributes water to each of the low-temperature fluid flow paths, a second header section that collects water vapor from each of the low-temperature fluid flow paths, a third header section that distributes heat source gas to each of the high-temperature fluid flow paths, and a fourth header section that collects heat source gas from each of the high-temperature fluid flow paths, wherein the first header section is formed in an upper part of the plate assembly and the second header section is formed in a lower part of the plate assembly, and the serpentine flow path plate has a configuration in which multiple stages of unit flow paths are formed continuously, each stage consisting of an inclined flow path section that allows water to flow downward and a turn-back flow path section that reverses the fluid flow.

[0010] According to this configuration, a vertically-mounted evaporator to be mounted on a fuel cell system can be made compact by suppressing the height of the plate assembly. More specifically, the above configuration may be configured such that the third header section is formed in the lower part of the plate assembly, and the fourth header section is formed in the upper part of the plate assembly.

[0011] More specifically, the water distributor may include a tubular nozzle header inserted into the first header section and through which water flows, a plurality of through holes formed in a pipe wall of the nozzle header at an inserted portion of the nozzle header, and a plurality of discharge pipes provided in an outer wall of the nozzle header so as to communicate with each of the through holes. With this configuration, it is possible to distribute water to each of the cryogenic fluid flow paths using the water distributor.

[0012] More specifically, the nozzle header may be provided with a thermal insulation pipe at the protruding portion thereof, through which the nozzle header is inserted, the thermal insulation pipe having a base end closed by being joined to the end plate and an open tip end. With this configuration, the nozzle header is covered with an insulating air layer, thereby avoiding the vapor lock phenomenon caused by overheating or boiling during the supply of water.

[0013] More specifically, the heat transfer plates are made up of first and second heat transfer plates that are alternately stacked, and each of the first and second heat transfer plates has a first header portion forming hole, a second header portion forming hole, a third header portion forming hole, and a fourth header portion forming hole, the peripheral edge of the first header portion forming hole is provided with a first flange surface that protrudes toward the high-temperature fluid flow path, the peripheral edge of the second header portion forming hole is provided with a second flange surface that protrudes toward the high-temperature fluid flow path, the peripheral edge of the third header portion forming hole is provided with a third flange surface that protrudes toward the low-temperature fluid flow path, and the peripheral edge of the fourth header portion forming hole is provided with a fourth flange surface that protrudes toward the low-temperature fluid flow path. The first header portion may be formed by joining the first flange surface of the first heat transfer plate and the first flange surface of the second heat transfer plate at their protruding sides, the second header portion may be formed by joining the second flange surface of the first heat transfer plate and the second flange surface of the second heat transfer plate at their protruding sides, the third header portion may be formed by joining the third flange surface of the first heat transfer plate and the third flange surface of the second heat transfer plate at their protruding sides, and the fourth header portion may be formed by joining the fourth flange surface of the first heat transfer plate and the fourth flange surface of the second heat transfer plate at their protruding sides. This configuration is suitable for mass production of evaporators because header portions can be formed without using auxiliary parts. [Effects of the Invention]

[0014] According to the evaporator of the present invention, it is possible to provide a compact evaporator that is a vertically placed type to be mounted on a fuel cell system and that has a reduced height of the plate assembly. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram showing the configuration of a fuel cell system 100 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a hot module HM according to the present embodiment. [Figure 3]FIG. 2 is a perspective view of a hot module HM, part of which is not shown. [Figure 4] FIG. 2 is a perspective view of a hot module HM, part of which is not shown. [Figure 5] FIG. 2 is a perspective view of a hot module HM, part of which is not shown. [Figure 6] FIG. 2 is a perspective view of a hot module HM, part of which is not shown. [Figure 7] FIG. 2 is a side view of a hot module HM, with a portion not shown. [Figure 8] FIG. 2 is a side view of a hot module HM, with a portion not shown. [Figure 9] FIG. 2 is a side view of the reformed gas generation device RG according to the present embodiment. [Figure 10] FIG. 2 is a cross-sectional side view of the reformed gas generation device RG. [Figure 11] FIG. 2 is a configuration diagram of the vicinity of a burner in the reformed gas generation device RG. [Figure 12] FIG. 2 is a side view of a hot module HM, with a portion not shown. [Figure 13] FIG. 1 is a perspective view of a cell stack 1 according to the present embodiment. [Figure 14] FIG. 2 is a plan view of the cell stack 1. [Figure 15] FIG. 2 is a cross-sectional view of the vicinity of a flanged gas port of the cell stack 1 as viewed from above. [Figure 16] FIG. 2 is a perspective view of a stack assembly 61 according to the present embodiment. [Figure 17] FIG. 2 is a perspective view of a stack assembly 61. [Figure 18] FIG. 2 is an explanatory diagram of a state in which a cell stack 1 is mounted on a unit rack. [Figure 19] FIG. 2 is an explanatory diagram of a branch pipe extending from a manifold according to the embodiment. [Figure 20] FIG. 2 is an explanatory diagram relating to the connection configuration of each power terminal of the cell stack 1. [Figure 21] 1 is a configuration diagram of a plate assembly 80 according to the present embodiment. [Figure 22]10 is a perspective view of heat transfer plates 81a and 81b used in the plate assembly 80. FIG. [Figure 23] FIG. 10 is an explanatory diagram of a serpentine flow path plate. [Figure 24] FIG. 2 is an explanatory diagram of an evaporator according to the embodiment. [Figure 25] FIG. 2 is a diagram illustrating the configuration of a water distributor used in the evaporator. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] <Outline of fuel cell system configuration> First, an outline of the configuration of a fuel cell system 100 according to this embodiment will be described. Fig. 1 is an explanatory diagram showing the configuration of the fuel cell system 100. As shown in Fig. 1, the fuel cell system 100 includes a plurality of cell stacks (fuel cell stacks) 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensed water recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a power conditioner 15, and a system controller 16.

[0018] In this embodiment, a total of eight cell stacks 1 are provided, including those not shown in Fig. 1. In the following description, the fuel cell system 100 may be simply referred to as the "system."

[0019] The fuel cell system 100 also includes the following lines (pipes): a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode offgas line Ld, a cathode air line Le, a cathode offgas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reforming water line Li, a start-up air line Lj, ​​and a condensed water recovery line Lw.

[0020] The anode fuel line Lc includes a first distribution manifold Ma that serves as a main pipe for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb that serves as a main pipe for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and multiple outlets corresponding to each cell stack 1, and allow the fluid that flows into the inlet to flow out from each of the outlets.

[0021] The anode offgas line Ld includes a first collection manifold Mc that serves as a mother pipe for the anode offgas, and the cathode offgas line Lf includes a second collection manifold Md that serves as a mother pipe for the cathode offgas. These collection manifolds Mc and Md have multiple inlets and outlets corresponding to the cell stacks 1, and allow fluids that flow into each inlet to flow out from the outlet.

[0022] The combustion gas line Lg includes a heat radiation tube Za and a combustion gas pipe Zb.

[0023] The raw fuel line La is a pipe connecting the fuel inlet E1 and the burner 3, and disposed in this pipe is a second raw fuel blower 13. The second raw fuel blower 13 is a device that pressurizes the raw fuel gas Gf (for example, a methane-containing gas such as city gas 13A) taken in from the fuel inlet E1 and sends it to the downstream side of the raw fuel line La, and is typically driven during start-up operation of the system.

[0024] The mixed gas line Lb is a pipe connecting the fuel inlet E2 and the reformer 2, and in this pipe, from upstream to downstream, are arranged a first raw fuel blower 10, an evaporator 4, and a first bellows-type expansion joint B1. The first raw fuel blower 10 is a device that pressurizes the raw fuel gas Ga taken in through the fuel inlet E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven when the system is operating to generate electricity.

[0025] The anode fuel line Lc is a pipe that connects the reformer 2 and the anode of each cell stack 1. More specifically, the anode fuel line Lc has, in order from the upstream side, a pipe that connects the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipes (branch pipes of the first distribution manifold Ma) that connect each outlet of the first distribution manifold Ma to the anode of each cell stack 1.

[0026] The anode offgas line Ld is a pipeline connecting the anode of each cell stack 1 to the burner 3. More specifically, the anode offgas line Ld has, from the upstream side, eight pipelines (branch pipes of the first collecting manifold Mc) connecting the anode of each cell stack 1 to each inlet of the first collecting manifold Mc, the first collecting manifold Mc, and a pipeline (hereinafter referred to as "pipe line Ld1") connecting the outlet of the first collecting manifold Mc to a first gas cylinder 31 (described later) of the burner 3. Arranged along the pipeline Ld1, from the upstream side, are a second bellows-type expansion joint B2, an anode offgas cooler 6, an anode offgas condenser 7, and an air-water separator Sa.

[0027] The cathode air line Le is a pipe connecting the air intake E3 and the cathode of each cell stack 1. More specifically, the cathode air line Le has, from the upstream side, a pipe (hereinafter referred to as "pipe Le1") connecting the air intake E3 and the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipes (branch pipes of the second distribution manifold Mb) connecting each outlet of the second distribution manifold Mb with the cathode of each cell stack 1.

[0028] Along the pipeline Le1, a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows expansion joint B3 are arranged, in that order from the upstream side. The first air blower 11 is a device that pressurizes air Aa taken in through an air inlet E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during power generation operation of the system. Furthermore, a bypass path Le2 that bypasses the anode off-gas cooler 6 and the air preheater 5 is provided in the pipeline Le1, connecting the midpoint between the air inlet E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows expansion joint B3.

[0029] The cathode offgas line Lf is a pipe connecting the cathode of each cell stack 1 to the burner 3. More specifically, the cathode offgas line Lf has, in order from the upstream side, eight pipes (branch pipes of the second collection manifold Md) connecting the cathode of each cell stack 1 to each inlet of the second collection manifold Md, the second collection manifold Md, and a pipe (hereinafter referred to as "pipe Lf1") connecting the outlet of the second collection manifold Md to a second gas cylinder 32 (described later) of the burner 3.

[0030] The combustion gas line Lg is a pipeline connecting the burner 3 and the gas exhaust port D1. More specifically, the combustion gas line Lg has, in order from the upstream side, a heat radiation tube Za, a pipeline connecting the heat radiation tube Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline connecting the combustion gas pipe Zb and the gas exhaust port D1 (hereinafter referred to as "pipe line Lg1"). In the middle of the pipeline Lg1, in order from the upstream side, a fourth bellows-type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

[0031] The burner cooling air line Lh is a pipe that connects the pipe Le1 and the startup air line Lj, ​​and is provided with a flow rate adjusting means (such as an orifice, not shown) in this pipe. More specifically, the burner cooling air line Lh branches off at the midpoint of the pipe Le1 that connects the first air blower 11 and the anode off-gas cooler 6, and merges with the startup air line Lj downstream of the second air blower 14, and is configured so that a minute flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven. Note that, as will be described in detail later, the burner cooling air line Lh may be omitted depending on the combustion temperature of the burner 3.

[0032] The reforming water line Li is a pipe that connects the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is disposed in this pipe. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 to the downstream side of the reforming water line Li as reforming water Wa.

[0033] The startup air line Lj is a pipe connecting the air intake E4 and the pipe Lf1, and is provided with a second air blower 14. The second air blower 14 is a device that pressurizes the air Ac taken in from the air intake E4 and sends it to the downstream side of the startup air line Lj, ​​and is typically driven during start-up operation of the system.

[0034] The condensed water recovery line Lw connects the water-air separator Sa, located midway along the pipeline Ld1, to the condensed water recovery tank 9. The water-air separator Sa separates the condensed water Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensed water Wb flows down the condensed water recovery line Lw. The end of the condensed water recovery line Lw is open to the gas phase without being immersed in the aqueous phase of the condensed water recovery tank 9 to prevent the amount of condensation from increasing or decreasing due to the temperature of the stored condensed water Wb. The reason for not immersing the end of the condensed water recovery line Lw in the aqueous phase is to prevent changes in the flow rate of the anode off-gas Gd sent to the burner 3. This configuration is particularly effective when the anode off-gas Gd after separation of the condensed water Wb is recycled to the primary side of the cell stack or used for power generation in a subsequent cell stack. The water-air separator Sa is, for example, a T-shaped pipe with a horizontally oriented straight pipe section and a downwardly oriented branch pipe section. Also, a small-capacity cylindrical container that is erected vertically can be used as the water-air separation section Sa.

[0035] The cell stack 1 is a power generating unit made up of solid oxide fuel cells (SOFC). A solid oxide fuel cell is a high-temperature operating fuel cell in which the solid electrolyte, anode, and cathode that make up the power generating cell are all made of ceramics, and a power generating unit in which a certain number of power generating cells are integrated via a metal interconnect material (also called a separator material) is called a cell stack. The battery output of the cell stack 1 is adjusted by a power conditioner 15 before being supplied.

[0036] The reformer 2 uses steam to reform the raw fuel gas Ga, generating reformed gas Gc, which is sent to the downstream side. The reformer 2 has a catalyst for steam reforming, and reacts methane contained in the raw fuel gas Ga with steam to generate reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, the heat supply from the burner 3 enables the reformer 2 to stably generate reformed gas Gc.

[0037] The burner 3 combusts the incoming gas to generate heat and discharges the combustion gas Gg produced by the combustion into the combustion exhaust gas line Lg. The evaporator 4 is a device that performs indirect heat exchange between the reforming water Wa and the combustion gas Gg (heat source fluid), and serves to evaporate the reforming water Wa and heat the raw fuel gas Ga through heat exchange with the combustion gas Gg.

[0038] The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that perform indirect heat exchange between a low-temperature fluid and a high-temperature fluid. The air preheater 5 serves to preheat the air Aa in the cathode air line Le by heat exchange with the combustion gas Gg, and the anode off-gas cooler 6 serves to cool the anode off-gas Gd by heat exchange with the air Aa in the cathode air line Le.

[0039] The anode off-gas condenser 7 cools the anode off-gas Gd and condenses the water vapor contained in the anode off-gas Gd. Although the anode off-gas condenser 7 in this embodiment is an air-cooled heat exchanger, a water-cooled heat exchanger may be used instead, thereby forming a cogeneration system in which heat recovery is performed.

[0040] The CO oxidizer 8 is a device that brings harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate when the oxidation reaction in the burner 3 is complete, and operates only when the oxidation reaction in the burner 3 is incomplete.

[0041] The condensed water recovery tank 9 serves to recover the condensed water Wb discharged from the air-water separation section Sa and make it reusable as reforming water Wa. The condensed water recovery tank 9 is provided with a water level detector Sb and a drain valve Sc to adjust the level of the stored reforming water Wa within a predetermined range. When the water level detector Sb detects an upper limit water level, the drain valve Sc opens, and when the water level detector Sb detects a lower limit water level, the drain valve Sc closes. In this way, the required amount of reforming water Wa is secured in the condensed water recovery tank 9. Note that to prevent anode off-gas Gd from leaking to the outside during the draining operation of the reforming water Wa, the drain position of the drain valve Sc is set near the bottom of the condensed water recovery tank 9.

[0042] The power conditioner 15 is a device for converting the power generated by the cell stack 1 into a state that can be used in business activities and social life. The power conditioner 15 has a DC / DC converter (boost circuit) that boosts the DC voltage output from the cell stack 1, a grid-connected inverter (voltage conversion circuit) that converts the DC voltage boosted by the DC / DC converter into AC voltage synchronized with the grid power supply, an output current control unit (output control circuit) that controls the output current (sweep current) of the cell stack 1, and a drive power supply unit (auxiliary circuit) that supplies drive power to auxiliary equipment.

[0043] The grid-connected inverter is electrically connected to a distribution panel of a commercial power system installed within the building. The grid-connected inverter and distribution panel can be switched between parallel and disconnection via a grid-connection switch. The distribution panel is electrically connected to the commercial power source and multiple distribution panels. The distribution panel is electrically connected to load devices such as lighting fixtures, power units, and outlets used within the building.

[0044] The drive power supply unit is connected to the blowers 10, 11, 13, and 14, the water pump 12, the spark rod (first electrode rod, described later) of the burner 3, and the like, and supplies drive power to these auxiliaries. When the auxiliaries are DC-driven, the drive power supply unit is circuit-configured to supply, for example, power obtained by AC / DC conversion of the output of the grid-connected inverter, power obtained by AC / DC conversion of the input from a commercial power source, or power obtained by DC / DC conversion of the output of the cell stack 1. On the other hand, when the auxiliaries are AC-driven, the drive power supply unit is circuit-configured to supply, for example, the output power of the grid-connected inverter or the input power from the commercial power source. Note that the above-mentioned auxiliaries are driven using the commercial power source during system startup operation and shutdown operation, and are driven using generated power during system power generation operation.

[0045] The system controller 16 is a device that controls the operation of auxiliary devices such as a blower and the power conditioner 15 (that is, the system operation) in accordance with a control program that has been created and stored in advance.

[0046] As indicated by the dashed lines in Fig. 1, the cell stacks 1, the reformer 2, the burner 3, the manifolds Ma to Md, the heat radiation tube Za, and the combustion gas pipe Zb are arranged in a first region R1 inside a first box X1 (see Fig. 3) in the hot module HM (described later). Meanwhile, the evaporator 4, the air preheater 5, the anode off-gas cooler 6, and the CO oxidizer 8 are arranged in a second region R2 outside the first box X1 and inside a second box X2 (see Fig. 3) (described later). The anode off-gas condenser 7, the condensed water recovery tank 9, the blowers 10, 11, 13, and 14, the water pump 12, the power conditioner 15, and the system controller 16 are arranged outside the hot module HM (in the room-temperature region).

[0047] <Outline of fuel cell system operation> Next, an overview of the operation of the fuel cell system 100 will be described with reference to Fig. 1. The raw fuel gas Ga supplied from the fuel inlet E2 into the mixed gas line Lb is sent to the downstream side by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reforming water Wa supplied from the condensed water recovery tank 9 into the reforming water line Li has its amount adjusted by the water pump 12 and flows into the mixed gas line Lb.

[0048] The reforming water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, and is heated by heat exchange in the evaporator 4 to become water vapor (superheated steam). The water vapor is mixed with the heated raw fuel gas Ga and flows into the reformer 2 as a mixed gas Gb.

[0049] The reformer 2 reforms the raw fuel gas Ga using the steam in the mixed gas Gb to generate the reformed gas Gc, which is then sent to the downstream side. The reformed gas Gc sent from the reformer 2 passes through the anode fuel line Lc and is distributed to the anodes of each cell stack 1.

[0050] Meanwhile, in parallel with the supply of the raw fuel gas Ga described above, air Aa is supplied from the air intake E3 into the cathode air line Le. The air Aa in the cathode air line Le is sent to the downstream side by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6, and is further heated by heat exchange in the air preheater 5, and then distributed to the cathodes of each cell stack 1. Note that, in order to adjust the temperature of the air Aa, it is also possible to flow a portion of the air Aa, that is, air Aa1, into the cathodes of each cell stack 1 via a bypass path Le2.

[0051] Furthermore, air Ab is supplied into the cooling air line Lh in synchronization with the supply of air Aa to the cathode. The air Ab in the cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant that lowers the combustion temperature of the burner 3 and prevents overheating and burning of the flame stabilizer 33 (described below). Note that if the flame temperature is maintained at a level that does not cause overheating or burning of the flame stabilizer 33 without supplying air Ab, the burner cooling air line Lh may be omitted.

[0052] Each cell stack 1 generates electricity using the reformed gas Gc that flows into the anode and the air Aa that flows into the cathode, and discharges anode offgas Gd from the anode to an anode offgas line Ld and cathode offgas Ge from the cathode to a cathode offgas line Lf. The anode offgas Gd contains fuel components that did not react at the anode, and the cathode offgas Ge contains oxygen that did not react at the cathode.

[0053] The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to a temperature below the dew point temperature, and the water vapor contained in the anode off-gas Gd is condensed.

[0054] The anode off-gas Gd that has passed through the anode off-gas condenser 7 is sent to the water-vapor separation section Sa where it is separated into water and vapor, and the condensed water Wb is collected in the condensed water recovery tank 9. The condensed water Wb collected in the condensed water recovery tank 9 is reused as reforming water Wa, as described above. The uncondensed portion of the anode off-gas Gd (anode off-gas Gd after water-vapor separation) is sent to the burner 3.

[0055] The cathode offgas Ge discharged from each cell stack 1 to the cathode offgas line Lf is collected in the second collection manifold Md, then mixed in a pipe Lf1 with air Ab that flows in via the burner cooling air line Lh, and sent to the burner 3. Depending on the operating state of the system, raw fuel gas Gf supplied from a fuel inlet E1 is sent to the burner 3 via the raw fuel line La, and air Ac supplied from an air inlet E4 is sent to the burner 3 via the startup air line Lj.

[0056] The burner 3 receives the first burner gas Gx, which is raw fuel gas Gf and / or anode offgas Gd, and the second burner gas Gy, which is air Ac and / or cathode offgas Ge, and combusts them to generate heat. Specifically, the first burner gas Gx is either a mixture of raw fuel gas Gf and anode offgas Gd, or either raw fuel gas Gf or anode offgas Gd, which state can vary depending on the operating state of the system, etc. The second burner gas Gy is either a mixture of air Ac and cathode offgas Ge, or either air Ac and cathode offgas Ge, which state can vary depending on the operating state of the system, etc. Specifically, the state of the gas supplied to the burner 3 changes appropriately depending on the system's startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc.

[0057] The raw fuel gas Gf is a type of hydrocarbon-containing gas, while the air Ac is a type of oxidant-containing gas. During combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh to adjust the combustion temperature.

[0058] The combustion gas Gg generated by combustion in the burner 3 is sent to the combustion gas line Lg, passes through the heat radiation tube Za, the combustion gas pipe Zb, the evaporator 5, the CO oxidizer 8, and the evaporator 4 in that order, and is then discharged from the hot module HM through the gas outlet D1. As will be described in more detail below, the heat radiation tube Za and the combustion gas pipe Zb are positioned so that the combustion gas Gg can be used to effectively heat the reformer 2. Furthermore, the combustion gas Gg in the combustion gas line Lg is used for heat exchange as it passes through the evaporator 5 and the evaporator 4, and if it contains carbon monoxide, the carbon monoxide is converted to carbon dioxide as it passes through the CO oxidizer 8.

[0059] <Hot Module> Next, the configuration of the hot module HM will be described in more detail. Fig. 2 is a perspective view of the hot module HM. Fig. 3 is a perspective view of the hot module HM, in which the first box X1, the second box X2, and part of the plate-shaped insulating material 53 are not shown to facilitate understanding of the internal structure of the hot module HM. Note that the front-rear, left-right, and up-down directions (directions that are perpendicular to each other) in the following description are defined merely for convenience, as shown in Fig. 2 and other figures. In the example of this embodiment, the up-down direction coincides with the vertical direction.

[0060] As shown in Figures 2 and 3, the hot module HM includes a first base X1a, a second base X2a, a first box X1 formed on the first base X1a, a second box X2 formed on the second base X2a, a plurality of first pillars 51 (four in this embodiment) supporting the first base X1a, and a plurality of second pillars 52 (four in this embodiment) supporting the second base X2a.

[0061] The first box X1 is housed inside the second box X2, and in this state, multiple first support columns 51 support the first pedestal X1a at a predetermined height from the second pedestal X2a. The first box X1 is set in a first region R1 (see FIG. 1), whose internal region is a high-temperature operating region, and houses a first equipment group GP1, which undergoes chemical reactions inside when the system is operating to generate electricity. This first equipment group GP1 includes a cell stack 1, a reformer 2, and a burner 3.

[0062] The area inside the second box X2 but outside the first box X1 (below the first pedestal X1a) is set as a second area R2 (see FIG. 1), which is a low-temperature operating area, and houses a second equipment group GP2, which does not involve chemical reactions inside during power generation operation of the system. The second equipment group GP2 includes an evaporator 4 and heat exchangers (air preheater 5 and anode off-gas cooler 6).

[0063] The second region R2 also houses a third equipment group GP3, which undergoes a chemical reaction inside only when certain conditions are met during power generation operation of the system. The third equipment group GP3 includes a CO oxidizer 8, which does not operate when the oxidation reaction in the burner 3 is complete, but operates only when the oxidation reaction in the burner 3 is incomplete. Because the heat generated by the catalytic reaction of the CO oxidizer 8 is slight, there is almost no problem in placing the CO oxidizer 8 in the second region R2 (low-temperature operation region), which makes it possible to reduce the capacity of the first box X1.

[0064] Plate-shaped insulating materials 53 are attached to the front, rear, left, and right sides and the top (upper side) of the first box X1. The plate-shaped insulating materials 53 cover almost the entire outer surface of the front, rear, left, right, and upper sides of the first box X1. This provides a strong insulating effect, making it easy to maintain a high temperature inside the first box X1.

[0065] The space of the second region R2 (the arrangement space of the second equipment group GP2) is filled with granular insulating material (not shown). Heat is conducted from the first box X1, which is the high-temperature operating region, to the second region R2 through the first pedestal X1a, but filling the space with the granular insulating material provides sufficient insulation. Therefore, the second equipment group GP2 and its connecting piping can be constructed without using expensive high-temperature resistant materials.

[0066] Furthermore, the first pedestal X1a is provided with a pipe insertion hole (through hole), and each line (pipe) extending across the boundary between the first region R1 and the second region R2 is arranged to pass through this through hole. As a result, fluid is transferred between the first device group GP1 and the second device group GP2 via a pipe that passes through the first pedestal X1a in the vertical direction. As such, in this embodiment, the piping for transferring fluid between the device groups GP1 and GP2 is simply a structure in which the pipe is attached to a pipe insertion hole drilled in the first pedestal X1a, and therefore no special seals or the like are required.

[0067] Furthermore, bellows-type expansion joints may be provided in the fluid pipelines passing through the second equipment group GP2. The pipes connecting the pipelines passing through the first pedestal X1a to the heat exchangers, and the pipes connecting the heat exchangers to each other, expand and contract due to temperature changes between when the system is cold and when it is operating. The thermal stress generated by this expansion and contraction can cause cracks or breaks in the pipe body and joints, which can sometimes cause serious problems such as flammable gas leaks. By including bellows-type expansion joints in the piping equipment used for fluid connections in the second equipment group GP2, the generation of thermal stress can be minimized, making it possible to avoid such problems.

[0068] 1, at least in each fluid pipeline passing through the second equipment group GP2 that extends across the boundary between the first region R1 and the second region R2, a vertically expandable bellows-type expansion joint is installed near the boundary of the second region R2. More specifically, a first bellows-type expansion joint B1 is installed near the boundary of the mixed gas line Lb, a second bellows-type expansion joint B2 is installed near the boundary of the anode off-gas line Ld, a third bellows-type expansion joint B3 is installed near the boundary of the cathode air line Le, and a fourth bellows-type expansion joint B4 is installed near the boundary of the combustion gas line Lg. Bellows-type expansion joints may also be installed in each pipe connecting heat exchangers in the second region R2.

[0069] The hot module HM is assembled, for example, by the following process. First, the second equipment group GP2 is placed on the second pedestal X2a, and the necessary piping materials are used to install the piping between the equipment. Next, multiple first supports 51 are attached to the second pedestal X2a, and the first pedestal X1a is placed and fixed on the tips of the first supports 51. Next, a pipe is attached to a pipe insertion hole drilled in the first pedestal X1a, and piping is installed between this pipe and the second equipment group GP2. Next, a casing that surrounds the second equipment group GP2 is attached to the second pedestal X2a to form a semi-open second box X2, and granular insulation material is filled inside the second box X2.

[0070] Next, the first equipment group GP1 is placed on the first pedestal X1a, and piping is installed between the conduit attached to the first pedestal X1a and the first equipment group GP1, and piping between the equipment is installed using the required piping materials. Next, a casing that surrounds the first equipment group GP1 is attached to the first pedestal X1a to form a sealed first box X1, and plate-shaped insulation material 53 is attached to the sides and top of the first box X1. A casing that surrounds the plate-shaped insulation material 53 attached to the first box X1 is attached to the semi-open second box X2 to form a sealed second box X2. By going through the above steps, the hot module HM can be easily assembled.

[0071] 4 to 6 are perspective views of the hot module HM from different viewpoints. Also, FIGS. 7 and 8 are side views of the hot module HM from different viewpoints. Note that in these figures, the first box X1, the second box X2, and the plate-shaped insulator 53 are not shown to facilitate understanding of the internal structure of the hot module HM. Also, the outline arrows in FIGS. 5 to 8 schematically indicate the flow direction of each fluid.

[0072] As shown in these figures, a cylindrical reformer 2 standing upright (vertically) is disposed on the upper side of the first pedestal X1a in a generally central position when viewed from above, and a burner 3 is disposed above the reformer 2. As will be described in more detail later, the reformer 2, burner 3, and heat radiation cylinder Za are integrally configured as a reformed gas generating device.

[0073] Cell stack assemblies 61, each consisting of a plurality of cell stacks 1 (four in this embodiment) stacked vertically, are disposed on both the left and right sides of the reformer 2. In the area sandwiched between the left and right cell stack assemblies 61 on the front side of the reformer 2, a first distribution manifold Ma and a second distribution manifold Mb are disposed so as to extend vertically, as shown in Fig. 4. The first distribution manifold Ma and the second distribution manifold Mb are disposed adjacent to each other and in the vicinity of the cell stack assemblies 61.

[0074] By arranging the first distribution manifold Ma and the second distribution manifold Mb adjacent to each other, heat exchange occurs between the surfaces of these two distribution manifolds by radiation heat transfer and convection heat transfer. Furthermore, by arranging each distribution manifold Ma, Mb near the cell stack assembly 61, heat exchange occurs between the surfaces of the equipment by radiation heat transfer and convection heat transfer. This makes it possible to equalize the temperatures of the anode fuel (reformed gas Gc) and cathode air (air Aa) supplied to the cell stack 1 and to raise the temperature close to the operating temperature of the cell stack 1, thereby enabling an efficient power generation reaction to occur throughout the entire power generation cell.

[0075] 6, in the area sandwiched between the left and right cell stack assemblies 61 on the rear side of the reformer 2, a first collection manifold Mc and a second collection manifold Md are arranged to extend vertically. That is, the cell stack assembly 61, the first collection manifold Mc, and the second collection manifold Md are arranged to surround the outer casing 21 of the reformer 2.

[0076] In this way, each cell stack 1, the first collecting manifold Mc, and the second collecting manifold Md are arranged near the reformer 2, making it possible to efficiently provide the reformer 2 with waste heat associated with the power generation reaction. In particular, the first collecting manifold Mc has the role of actively providing the reformer 2 with the waste heat contained in the anode off-gas Gd. In addition, the second collecting manifold Md has the role of actively providing the reformer 2 with the waste heat contained in the cathode off-gas Ge. This significantly increases the amount of heat absorbed in the catalyst layer in the reformer 2, improving the efficiency of the steam reforming reaction, reducing the amount of catalyst used, and enabling the reformer 2 to be made more compact.

[0077] <Reformer, burner, heat radiation tube> Next, the configurations of the reformer 2, the burner 3, and the heat radiation cylinder Za will be described in more detail. In this embodiment, the reformer 2, the burner 3, and the heat radiation cylinder Za are integrally configured as a reformed gas generator RG.

[0078] Fig. 9 shows a side view of the reformed gas generator RG, and Fig. 10 shows a cross-sectional view of the reformed gas generator RG as seen from the side. Fig. 11 shows a detailed configuration of the reformed gas generator RG near the burner 3. Fig. 11 also shows a schematic configuration example of the ignition / flame detection circuit 40.

[0079] In the reformed gas generator RG, the reformer 2 has an outer cylinder 21 , an inner cylinder 22 , a catalyst packed layer 23 , a base end side cover plate 24 , and a terminal end side cover plate 25 .

[0080] The outer cylinder 21 and the inner cylinder 22 are formed in a cylindrical shape with a common axis extending vertically, and although their lengths in the vertical direction are roughly the same, the diameter of the outer cylinder 21 is larger than the diameter of the inner cylinder 22. The outer cylinder 21 and the inner cylinder 22 form a reaction vessel 2a with a double-cylinder structure, in which the inner cylinder 22 is disposed inside the outer cylinder 21. Between the outer cylinder 21 and the inner cylinder 22, i.e., inside the reaction vessel 2a, a catalyst-packed layer 23 packed with a catalyst for steam reforming is provided.

[0081] The base end cover plate 24 connects the base ends (upper ends) of the outer tube 21 and the inner tube 22 to seal the top of the reaction vessel 2a, and the terminal end cover plate 25 connects the terminal ends (lower ends) of the outer tube 21 and the inner tube 22 to seal the bottom of the reaction vessel 2a.

[0082] The base end cover plate 24 and the distal end cover plate 25 are annular head plates, and the cross-sectional shape of the annular head plates is dish-shaped, regular semi-elliptical, or approximately semi-elliptical. By using annular head plates as the cover plates of the reaction vessel 2a, radial expansion and contraction due to temperature changes can be absorbed. Therefore, damage or breakage of the reaction vessel 2a due to thermal stress can be more effectively prevented. The cross-sectional shapes of the head plates are those specified in JIS B 8247 "Head Plates for Pressure Vessels," excluding flat head plates.

[0083] Furthermore, a bellows-structured expansion absorbing section 21c is formed in the outer casing 21 slightly above the intake port 21a. By providing the expansion absorbing section 21c, expansion and contraction of the outer casing 21 due to temperature changes over time and temperature distribution over position are absorbed. Therefore, damage or breakage of the reaction vessel 2a containing the catalyst due to thermal stress can be avoided, and the reaction vessel 2a can be used for a long period of time. Note that a commercially available bellows-type expansion joint is preferably used as the expansion absorbing section 21c, and the outer casing 21 can be manufactured inexpensively by joining this joint to a straight pipe.

[0084] In the reformed gas generator RG, the burner 3 has a first gas cylinder 31, a second gas cylinder 32, a flame stabilizer 33, and a heat radiation cylinder Za.

[0085] The first gas cylinder 31 and the second gas cylinder 32 are formed in a cylindrical shape with a common axis extending vertically, and the diameter of the second gas cylinder 32 is larger than the diameter of the first gas cylinder 31. The upper part of the first gas cylinder 31 protrudes upward beyond the upper end of the second gas cylinder 32, and the lower part of the first gas cylinder 31 is disposed inside the second gas cylinder 32. The upper end of the first gas cylinder 31 is sealed, and the gap between the first gas cylinder 31 and the second gas cylinder 32 is sealed at the upper end of the second gas cylinder 32.

[0086] The second gas cylinder 32 and the heat radiation cylinder Za are formed from a single tube, and the lower end of the second gas cylinder 32 is connected to the upper end of the heat radiation cylinder Za. By forming the second gas cylinder 32 and the heat radiation cylinder Za from a single tube in this way, work such as aligning and joining the two components is not required, and the burner 3 can be manufactured at low cost. Also, as shown in Figure 10, the first burner gas Gx described above flows into the upper part of the first gas cylinder 31, and the second burner gas Gy described above flows into the upper part of the second gas cylinder 32.

[0087] The flame stabilizer 33 is connected to the lower end of the first gas cylinder 31 and is formed in a truncated cone shape with its tip widening downward (toward the downstream side of the flow of the gas to be combusted). The flame stabilizer 33 has multiple rows of through holes 33a spaced apart in the widening direction. The outer diameter of the flame stabilizer 33 and the inner diameter of the second gas cylinder 32 are formed to be approximately the same diameter, which allows the burner 3 to combust the first burner gas Gx and the second burner gas Gy and form a stable flame over the entire radial cross section of the inner diameter of the second gas cylinder 32.

[0088] 11, the burner 3 is provided with an electrode pair 40x consisting of a first electrode rod 41 and a second electrode rod 42, and the tip of the electrode pair 40x is disposed inside the flame stabilizer 33. The first electrode rod 41 is electrically insulated from the first gas cylinder 31, and the second electrode rod 42 is electrically connected to the first gas cylinder 31.

[0089] Electrode pair 40x is connected to ignition / flame detection circuit 40, which controls gas ignition operation and detects flames, and can be used for both gas ignition and flame detection. Ignition / flame detection circuit 40 includes gas ignition unit 40a, current detection unit 40b, first switch 40c1, and second switch 40c2. When igniting gas, ignition / flame detection circuit 40 closes first switch 40c1 and opens second switch 40c2, connecting electrode pair 40x to gas ignition unit 40a. A high current from gas ignition unit 40a flows between the electrodes, generating a spark and achieving gas ignition.

[0090] On the other hand, when detecting a flame, the ignition / flame detection circuit 40 connects the electrode pair 40x to the current detection unit 40b by opening the first switch 40c1 and closing the second switch 40c2, and determines whether or not a flame is present by having the current detection unit 40b detect the current generated by applying a voltage between the electrodes. This makes it possible to detect the presence or absence of a flame by utilizing the conductivity of the flame when a voltage is applied between the electrodes.

[0091] In this way, during gas ignition, the burner 3 causes the first electrode rod 41 to function as a spark rod and the second electrode rod 42 to function as a ground rod. On the other hand, during flame detection, the burner 3 causes the first electrode rod 41 to function as a flame rod and the second electrode rod 42 to function as a ground rod. Therefore, the burner 3 can perform reliable and safe combustion operation by using the electrode pair 40x consisting of the first electrode rod 41 and the second electrode rod 42 to switch between the gas ignition mechanism and the flame detection mechanism.

[0092] The heat radiation cylinder Za is formed in a cylindrical shape with a common axis with the inner cylinder 22, and the outer diameter of the heat radiation cylinder Za is smaller than the inner diameter of the inner cylinder 22. In addition, the upper end of the heat radiation cylinder Za is connected to the lower end of the second gas cylinder 32 inside the inner cylinder 22, and the lower end of the heat radiation cylinder Za protrudes downward below the lower end of the inner cylinder 22. The heat radiation cylinder Za can also be seen as one element of the burner 3.

[0093] The heat radiation tube Za functions as a combustion chamber and a flow path for combustion gas in the burner 3, and its surface serves as a combustion heat radiating section. Because the combustion flame of the burner 3 is located inside the heat radiation tube Za, the thermal energy of this combustion flame can be efficiently radiated from the outer surface of the heat radiation tube Za. In this embodiment, because the heat radiation tube Za functions as a combustion chamber tube, damage or breakage of the heat radiation tube Za due to thermal stress can be avoided even if combustion heat is continuously applied from the inside to the reaction vessel 2a containing the catalyst.

[0094] The heat radiation cylinder Za is inserted into the inner cylinder 22 so that the surfaces of the heat radiation cylinder Za and the inner cylinder 22 are separated from each other throughout the entire circumferential direction. In this way, a gap is provided between the outer surface of the heat radiation cylinder Za and the inner surface of the inner cylinder 22. Therefore, when thermal energy is applied from the inner cylinder 22 to the catalyst packed layer 23 for the steam reforming reaction, heat is transferred by radiation from the heat radiation cylinder Za, without heat conduction. This makes it possible to use the reaction vessel 2a containing the catalyst for a long period of time while avoiding damage or breakage due to thermal stress of the reaction vessel 2a.

[0095] Furthermore, in the reformer 2, an inlet 21a for the mixed gas Gb (a mixed gas of raw fuel gas Ga and steam) is provided near the lower end of the outer cylinder 21, and an outlet 21b for the reformed gas Gc is provided near the upper end of the outer cylinder 21. The mixed gas Gb taken in between the outer cylinder 21 and the inner cylinder 22 from the inlet 21a is reformed as it passes through the catalyst packed layer 23, and is taken out from the outlet 21b as the reformed gas Gc. Thus, in this embodiment, the inlet 21a is provided on the side corresponding to the tip side of the heat radiation cylinder Za, and the outlet 21b is provided on the side corresponding to the base end side of the heat radiation cylinder Za.

[0096] Here, the thermal energy of the combustion gas Gg is utilized for heat absorption accompanying the steam reforming reaction, so the temperature of the combustion gas Gg decreases from the base end side to the tip end side of the heat radiation tube Za. Taking this into consideration, in this embodiment, the intake port 21a and the outlet port 21b are arranged as described above, so that the mixed gas Gb flowing in from the intake port 21a is preheated by the combustion gas Gg whose temperature has been reduced, and then reformed using the thermal energy of the higher-temperature combustion gas Gg.

[0097] The generated reformed gas Gc (gas containing hydrogen and carbon monoxide) is continuously discharged from the outlet 21b and used as the anode fuel gas for each cell stack 1. In this manner, in this embodiment, the flow of the mixed gas Gb and the reformed gas Gc and the flow of the combustion gas are counter-flowing, so that an efficient steam reforming reaction can be carried out.

[0098] However, the arrangement of the intake 21a and outlet 21b may be reversed from that of this embodiment, with the intake 21a located on the side corresponding to the base end of the heat radiation tube Za and the outlet 21b located on the side corresponding to the tip end of the heat radiation tube Za. In this case, the mixed gas Gb flowing in from the intake 21a is instantly preheated by the high-temperature combustion gas Gg and then reformed using the thermal energy of the combustion gas Gg, which has slightly cooled. In this way, by making the flow of the mixed gas Gb and the reformed gas Gc parallel to the flow of the combustion gas Gg, the preheating effect of the mixed gas Gb is enhanced, and it is possible to design the evaporator 4, which prepares the mixed gas Gb, with a reduced heating capacity (heat exchange capacity), which is expected to reduce the cost of the evaporator 4.

[0099] <Combustion gas pipe> Next, the configuration of the combustion gas pipe Zb will be described in more detail. Fig. 12 is a side view of the hot module HM in which the boxes X1, X2, the plate-shaped heat insulator 53, and the manifolds Ma to Md are not shown in order to make the arrangement of the combustion gas pipe Zb easier to understand.

[0100] As shown in this figure, the combustion gas pipe Zb is composed of a folded pipe path that makes a U-turn at the top so that two straight pipes extending vertically are lined up on the left and right (i.e., parallel), and is arranged behind the reformer 2. The left and right straight pipes that are connected at the top extend from near the bottom end to near the top end of the reformer 2 and are arranged directly opposite each other near the outer casing 21 of the reformer 2. As indicated by the dashed arrows in Figure 12, the combustion gas Gg flows upward through the straight pipe on the right and downward through the straight pipe on the left.

[0101] As a result, the combustion gas Gg generated when the burner 3 is activated flows sequentially through the heat radiation tube Za and the combustion gas pipe Zb, and can provide combustion heat from both the inside and outside of the reformer 2. As a result, the amount of heat absorbed in the catalyst layer increases, significantly lowering the temperature of the combustion gas Gg, making it possible to supply the cooled combustion gas Gg to the preheating heat exchanger, and the heat exchanger can be made from inexpensive materials (e.g., SUS321, SUS316L, SUS310S, etc.).

[0102] Furthermore, since the amount of heat absorbed in the catalyst layer increases significantly, the efficiency of the steam reforming reaction increases, allowing the amount of catalyst used to be reduced, and making it possible to downsize the reformer 2. In this embodiment, most of the energy required for the steam reforming reaction in the reformer 2 is provided by combustion heat. Therefore, the reformer 2 can stably generate reformed gas Gc without depending on the operating temperature of the cell stack 1.

[0103] 12, the left combustion gas pipe Zb is disposed directly opposite the right side of the left cell stack assembly 61, and the right combustion gas pipe Zb is disposed directly opposite the left side of the right cell stack assembly 61. This enables the fuel cell system 100 to shorten its startup operation time.

[0104] In other words, in a reforming fuel cell system that uses steam reforming, steam (superheated steam) may be used to heat the reformer and cell stack during startup operation of the fuel cell system. In this case, combustion gas generated by burner combustion is used as the heat source for the evaporator, and water is heated inside the evaporator to generate steam. However, using only steam to heat the evaporator requires a very long startup operation time, typically over eight hours. In this embodiment, the combustion gas pipe Zb is located near the reformer 2 and cell stack assembly 61, so that the cold reformer 2 and cell stack assembly 61 are indirectly heated by heat radiation during burner combustion. As a result, the startup operation time can be shortened to, for example, around four hours.

[0105] In this embodiment, the reformer 2 is disposed near the cell stack assembly 61, and waste heat generated by the power generation reaction in the cell stack 1 is also used as an auxiliary for the steam reforming reaction in the reformer 2. Therefore, even if energy loss increases due to deterioration of the power generation cells, the cell stack 1 can be cooled, and the cell stack 1 can be maintained at an appropriate operating temperature.

[0106] Furthermore, in this embodiment, by making the combustion gas pipe Zb a turn-back pipe, combustion heat can be repeatedly applied from outside the reformer 2, further increasing the amount of heat absorbed in the catalyst layer. Therefore, by reducing the amount of catalyst used and downsizing the reformer 2, the material costs of the hot module HM can be effectively reduced. Note that the turn-back pipe may be laid so that the straight portion of the pipe is aligned along the axial direction of the reformer 2, or may be laid perpendicular to the axial direction of the reformer 2. Furthermore, although the turn-back pipe has one turn in this embodiment, the turn-back pipe may have multiple turns.

[0107] <Cell stack> Next, a more detailed description will be given of the configuration of the cell stack 1. Figures 13 and 14 are perspective views of the cell stack 1, and Figure 14 is a plan view of the cell stack 1.

[0108] 13 to 15, the cell stack 1 includes a stacking section 75 in which a predetermined number of flat-plate type power generating cells are stacked on the left and right, a first end plate 76a provided at the left end of the stacking section 75, and a second end plate 76b provided at the right end of the stacking section 75. The first end plate 76a and the second end plate 76b are provided as a pair of end plates facing each other on the left and right sides of the stacking section 75, and are generally rectangular when viewed from the left.

[0109] Flanged gas ports 72 are disposed near each of the four corners of the first end plate 76a. Specifically, as shown in Fig. 14, a total of four flanged gas ports 72 are provided, including an anode fuel inlet port 72a, a cathode air inlet port 72b, an anode off-gas outlet port 72c, and a cathode off-gas outlet port 72d. Each flanged gas port 72 has a flange portion 72x that extends radially from the entire circumference of the left (outer) edge.

[0110] The cell stack 1 is also provided with a support plate 71 that is fixed to the edge of the flange portion 72x of each flanged gas port 72. The support plate 71 has through holes formed in it that correspond to the position and size of each flange 72x of each flanged gas port 72, and the outer circumferential surface of each flange portion 72x is in close contact with the inner circumferential surface of each through hole.

[0111] A plate-shaped first power terminal 74a and a second power terminal 74b with the top and bottom in the width direction are arranged on the front side of the stacked unit 75 as terminals for outputting power generated by the power generation cells of the stacked unit 75. The first power terminal 74a and the second power terminal 74b are power terminals with opposite polarities. The first power terminal 74a protrudes forward from the front side of the stacked unit 75, with an end 74a1 bent to the left. The second power terminal 74b protrudes forward from a position on the front side of the stacked unit 75 that is lower and to the left of the first power terminal 74a, with an end 74b1 bent to the right.

[0112] In this way, the first power terminal 74a and the second power terminal 74b protrude in the same direction (forward in this embodiment) and approximately parallel to the stacking surface (plane perpendicular to the left-right direction) of the flat-plate type power generating cells in the stacking portion 75. The end portions 74a1, 74b1 of the power terminals both form a plane facing forward, and are positioned in the same position in the front-rear and left-right directions.

[0113] <Cell stack assembly> Next, the configuration of the cell stack assembly 61 will be described in more detail. Figures 16 and 17 are perspective views of the left stack assembly 61 as seen from different viewpoints. In this embodiment, the cell stack 1 in the right cell stack assembly 61 is arranged upside down compared to the cell stack 1 in the left cell stack assembly 61. As a result, the cell stack assemblies 61 provided on either side of the reformer 2 are configured so that the power terminals 74a, 74b are located in front and the flanged gas port 72 is located inside in the left-right direction.

[0114] The stack assembly 61 is configured by stacking a plurality of cell stacks 1 vertically on an open rack 62. This makes it possible to minimize the installation area of ​​the cell stack assembly 61, and therefore the installation area of ​​the hot module HM. Therefore, according to this embodiment, it is possible to construct a fuel cell system 100 that can be easily installed in a narrow space, such as an empty space in an existing facility. Furthermore, by mounting a plurality of cell stack assemblies 61 on a hot module HM, it is easy to increase the power generation output capacity of the fuel cell system 100.

[0115] The open rack 62 has vertically extending pillars 64 at each of its four corners when viewed from above, and multiple stage boards 63 are arranged at approximately equal intervals in the vertical direction so as to be fixed and supported by these four pillars 64. The size of the space between the stage boards 63 is set to match the size of the cell stack 1.

[0116] Each cell stack 1 is placed on the stage board 63, and the support plate 71 is fixed to the right-side column 64, for example, by screws, and then housed in the open rack 62. Therefore, to assemble the cell stack assembly 61, it is sufficient to simply repeat the process of placing the cell stack 1 on the stage board 63 and fixing the support plate 71 to the column 64. This makes it easy to assemble the cell stack assembly 61. Furthermore, the stage board 63 stably supports the weight of each individual cell stack 1, keeping them in the correct position in the vertical direction and preventing them from falling off during operation.

[0117] Furthermore, the above-described open rack 62 is designed to be capable of mounting a specified number of cell stacks 1 (four in this embodiment), but instead of this open rack, it is also possible to use an open rack assembled from a plurality of unit racks each corresponding to one cell stack 1. Figure 18 shows an example of a state in which cell stacks 1 are mounted on a unit rack 62a that can form such an open rack.

[0118] The unit rack 61a has a stage base 63a having a configuration equivalent to one stage of the stage base 63 in the open rack 62, and four pillars 64a having a configuration equivalent to one stage of the four pillars 64 in the open rack 62, and it is possible to stack and fix the unit racks 61a one on top of another in the vertical direction. As a result, in the same way as in the case of the open rack 62, a required number of cell stacks 1 can be accommodated in each unit rack 61a, and by stacking and fixing the accommodated unit racks 61a (stack holders), it is possible to obtain something equivalent to the stack assembly 61 described above.

[0119] In this case, the open rack is formed by unit racks 61a divided into individual cell stacks 1. When using unit racks 61a in this way, the number of cell stacks 1 mounted can be easily adjusted according to the power generation output of the hot module HM, for example. Furthermore, since there are no empty spaces in the open rack where no cell stacks 1 are mounted, the material costs of the rack can be reduced.

[0120] <Manifold branch pipe> Each flanged gas port 72 in all cell stacks 1 is connected to a branch pipe extending from a corresponding manifold. Specifically, the anode fuel inlet port 72a is connected to a branch pipe extending from the first distribution manifold Ma, the cathode air inlet port 72b is connected to a branch pipe extending from the second distribution manifold Mb, the anode off-gas outlet port 72c is connected to a branch pipe extending from the first collection manifold Mc, and the cathode off-gas outlet port 72d is connected to a branch pipe extending from the second collection manifold Md. In this embodiment, since eight cell stacks 1 are provided, eight branch pipes extend from each manifold.

[0121] The branch pipes extending from each of the manifolds Ma to Md have a pipe length longer than the shortest distance connecting the corresponding flanged gas port 72 and the manifold, and are configured to include a curved portion. Each branch pipe has a flange at its tip, and the flange can be connected to the flange portion 72x of the corresponding flanged gas port 72.

[0122] 19 shows an example of the configuration of branch pipes extending from each of the manifolds Ma to Md (collectively referred to as "manifold Mx" for convenience). Each branch pipe BP shown in this figure extends from the manifold Mx and has a flange Fg at its tip.

[0123] 19(A) partially illustrates two branch pipes BP extending from a manifold Mx to two cell stacks 1, with one branch pipe BP including a curved portion CV1 and the other branch pipe BP including a curved portion CV2. These curved portions CV1 and CV2 both have planar (i.e., two-dimensional) pipe structures. That is, throughout the entire area of ​​curved portion CV1, the cross-sectional center of the branch pipe BP (the cross-sectional center when cut along a plane perpendicular to the direction in which the branch pipe BP extends) is contained within the same plane (a plane perpendicular to the axial direction of the manifold Mx), and throughout the entire area of ​​curved portion CV2, the cross-sectional center of the branch pipe BP is contained within the same plane (a plane perpendicular to the axial direction of the manifold Mx).

[0124] 19(B) partially illustrates one branch pipe BP extending from the manifold Mx to one cell stack 1, and this branch pipe BP includes a curved section CV3. This curved section CV3 also has a planar pipe structure. That is, the center of the cross section of the branch pipe BP throughout the entire area of ​​the curved section CV3 is included in the same plane (a plane perpendicular to the axial direction of the manifold Mx). A bellows-type expansion joint Bp1 is provided midway along the branch pipe BP, enabling it to absorb expansion and contraction of the branch pipe BP.

[0125] 19(C) partially illustrates two branch pipes BP extending from a manifold Mx to two cell stacks 1, with one branch pipe BP including a curved portion CV4 and the other branch pipe BP including a curved portion CV5. These curved portions CV4 and CV5 each have a three-dimensional pipe structure. That is, in neither curved portion CV4 nor CV5 is the cross-sectional center of the branch pipe BP included in the same plane throughout the entire area.

[0126] 19(D) partially illustrates two branch pipes BP extending from a manifold Mx to two cell stacks 1, with one branch pipe BP including a curved portion CV6 and the other branch pipe BP including a curved portion CV7. Both of these curved portions CV6 and CV7 have a three-dimensional pipe structure. That is, in neither of the curved portions CV6 and CV7, the cross-sectional center of the branch pipe BP is located on the same plane throughout the entire area.

[0127] 19(A) or 19(B), by providing a curved section with a flat pipe structure in the branch pipe BP of the manifold Mx, it is possible to effectively absorb the expansion and contraction of the pipe that occurs mainly in the horizontal direction of the branch pipe BP (the direction perpendicular to the up-down direction of the hot module HM), thereby eliminating the problem of gas leaks caused by stress acting on the joint with the flanged gas port 72.

[0128] 19(C) or 19(D), if a curved section having a three-dimensional pipe structure is provided in the branch pipe BP of the manifold Mx, expansion and contraction of the pipe that occurs in the vertical direction (up and down direction of the hot module HM) as well as the horizontal direction of the branch pipe BP can be effectively absorbed. This solves the problem of gas leaks caused by stress acting on the joint with the flanged gas port 72. The type of pipe structure to provide a curved section in the branch pipe of each manifold Ma to Md can be determined depending on, for example, the specifications of the hot module HM.

[0129] <Power terminals and their connection configuration> In addition, in both the left and right stack assemblies 61, the power terminals 74a, 74b of each cell stack 1 protrude forward, and the ends 74a1, 74b1 of these power terminals are aligned so that they are positioned identically in the front-to-rear and left-to-right directions. Furthermore, the vertical positional relationship of the first power terminal 74a and the second power terminal 74b is aligned between the cell stacks 1 in the same stack assembly 61. That is, in the right-side stack assembly 61, the first power terminal 74a is located above the second power terminal 74b in each cell stack 1, and in the left-side stack assembly 61, the first power terminal 74a is located below the second power terminal 74b in each cell stack 1.

[0130] 5, 7, etc., the power terminals 74a, 74b of adjacent cell stacks 1 are electrically connected using a main bus bar 78a and a sub-bus bar 78b, making it possible to collectively output to the outside the power generated by each cell stack 1. Note that the bus bars 78a, 78b are connected and fixed to the ends 74a1, 74b1 of the power terminals, for example, by screws or the like.

[0131] 20 shows a schematic diagram of the connection of the power terminals 74a, 74b. As shown in the figure, in each cell stack 1 of the cell stack assembly 61 on the right side, the first power terminal 74a is provided above the second power terminal 74b, and in each cell stack 1 of the cell stack assembly 61 on the left side, the first power terminal 74a is provided below the second power terminal 74b.

[0132] In the cell stack assembly 61 on the right side, the connection between the second power terminal 74b of the topmost cell stack 1 and the first power terminal 74a of the second-highest cell stack 1, the connection between the second power terminal 74b of the second-highest cell stack 1 and the first power terminal 74a of the third-highest cell stack 1, and the connection between the second power terminal 74b of the third-highest cell stack 1 and the first power terminal 74a of the bottommost cell stack 1 are each realized by the main bus bar 78a.

[0133] In the cell stack assembly 61 on the left side, the connection between the first power terminal 74a of the topmost cell stack 1 and the second power terminal 74b of the second-highest cell stack 1, the connection between the first power terminal 74a of the second-highest cell stack 1 and the second power terminal 74b of the third-highest cell stack 1, and the connection between the first power terminal 74a of the third-highest cell stack 1 and the second power terminal 74b of the bottommost cell stack 1 are each realized by the main bus bar 78a.

[0134] Furthermore, the second power terminal 74b of the lowermost cell stack 1 in the right-side cell stack assembly 61 and the first power terminal 74a of the lowermost cell stack 1 in the left-side cell stack assembly 61 are realized by a sub-bus bar 78b. The first power terminal 74a of the uppermost cell stack 1 in the right-side cell stack assembly 61 and the second power terminal 74b of the uppermost cell stack 1 in the left-side cell stack assembly 61 are each connected to separate power lines 79. These power lines 79 are each protected by separate power line protection pipes 79a and extend to the outside of the hot module HM.

[0135] The main bus bar 78a is made of a metal plate having an expansion / contraction absorbing portion 78a1 to prevent malfunctions caused by vertical expansion / contraction due to the temperature difference between when the hot module HM is in a cold state and when it is in power generation operation. In the example of this embodiment, the expansion / contraction absorbing portion 78a1 is a U-shaped curved portion when viewed from the left and right, as shown in FIG. 8, etc., but it may also be a V-shaped bent portion or the like. By employing the main bus bar 78a having the expansion / contraction absorbing portion 78a1, thermal stress is alleviated, enabling stable power generation operation and preventing excessive force from acting on the cell stack 1 of each stage.

[0136] The sub-busbar 78b is made of a metal plate having an expansion / contraction absorbing portion 78b1 to prevent malfunctions caused by horizontal expansion / contraction due to the temperature difference between when the hot module HM is in a cold state and when it is in power generation operation. In the example of this embodiment, the expansion / contraction absorbing portion 78b1 is a U-shaped curved portion when viewed from the top / bottom direction, as shown in FIG. 5 etc., but it may also be a V-shaped bent portion or the like. By employing the sub-busbar 78b having the expansion / contraction absorbing portion 78b1, thermal stress is alleviated, enabling stable power generation operation and preventing excessive force from acting on the uppermost cell stack 1.

[0137] <Evaporator> Next, the configuration of the evaporator 4 will be described in more detail. Figure 21 is a configuration diagram of a plate assembly 80 that functions as the evaporator 4, with a left side view shown on the left, a front view shown in the center, and a right side view shown on the right.

[0138] The plate assembly 80 is formed by stacking a plurality of heat transfer plates 81 in the front-to-rear direction between a first end plate 82a and a second end plate 82b arranged opposite each other in the front-to-rear direction, and joining together the end plates 82a, 82b and the heat transfer plates 81. As will be described later, each of these heat transfer plates 81 is formed with either a low-temperature fluid flow path through which the low-temperature fluid (raw fuel gas Ga and reforming water Wa) in the evaporator 4 flows, or a high-temperature fluid flow path through which the high-temperature fluid (combustion gas Gg) in the evaporator 4 flows.

[0139] 22 is a perspective view of the first heat transfer plate 81a and the second heat transfer plate 81b. As shown in this figure, the first heat transfer plate 81a and the second heat transfer plate 81b each have a substantially rectangular flat plate portion 81x (heat transfer surface portion) with the longitudinal direction in the up-down direction, and a frame portion 81y that protrudes rearward from the entire peripheral edge of the flat plate portion 81x to a substantially uniform height. Each of the flat surfaces on the front and back of the flat plate portion 81x functions as a heat transfer surface parallel to the vertical direction.

[0140] A first header portion forming hole 83a1 is provided in a position near the upper right of the flat plate portion 81x. Furthermore, a second header portion forming hole 83b1 is provided in a position near the lower left of the flat plate portion 81x, a third header portion forming hole 83c1 is provided in a position near the lower right of the flat plate portion 81x, and a fourth header portion forming hole 83d1 is provided in a position near the upper left of the flat plate portion 81x.

[0141] In the first heat transfer plate 81a, a first flange surface 84a protruding rearward is provided on the periphery of the first header portion forming hole 83a1, a second flange surface 84b protruding rearward is provided on the periphery of the second header portion forming hole 83b1, a third flange surface 84c protruding forward is provided on the periphery of the third header portion forming hole 83c1, and a fourth flange surface 84d protruding forward is provided on the periphery of the fourth header portion forming hole 83d1. The height of each of the flange surfaces 84a to 84d is approximately half the height of the frame portion 81y.

[0142] On the other hand, in the second heat transfer plate 81b, a first flange surface 85a protruding forward is provided on the periphery of the first header portion forming hole 83a1, a second flange surface 85b protruding forward is provided on the periphery of the second header portion forming hole 83b1, a third flange surface 85c protruding rearward is provided on the periphery of the third header portion forming hole 83c1, and a fourth flange surface 85d protruding rearward is provided on the periphery of the fourth header portion forming hole 83d1. The height of each of the flange surfaces 85a to 85d is approximately half the height of the frame portion 81y.

[0143] In this way, in each heat transfer plate 81a, 81b, the periphery of the first header portion forming hole 83a1 is provided with first flange surfaces 84a, 85a that protrude toward the high-temperature fluid flow path, the periphery of the second header portion forming hole 83b1 is provided with second flange surfaces 84b, 85b that protrude toward the high-temperature fluid flow path, the periphery of the third header portion forming hole 83c1 is provided with third flange surfaces 84c, 85c that protrude toward the low-temperature fluid flow path, and the periphery of the fourth header portion forming hole 83d1 is provided with fourth flange surfaces 84d, 85d that protrude toward the low-temperature fluid flow path. Note that the flange surfaces 84a-84d, 85a-85d can be formed by pressing the heat transfer plates 81a, 81b, and the header portion forming holes 83a1-83d1 can be formed by trimming the heat transfer plates 81a, 81b.

[0144] In the plate assembly 80, second heat transfer plates 81b having low-temperature fluid flow paths formed therein and first heat transfer plates 81a having high-temperature fluid flow paths formed therein are alternately stacked and integrated between the end plates 82a, 82b. In the plate assembly 80 formed in this manner, it can also be seen that a low-temperature fluid flow path is formed on one heat transfer surface side of each of the heat transfer plates 81a, 81b (flat plate portions 81x), and a high-temperature fluid flow path is formed on the other heat transfer surface side.

[0145] Each end plate 82a, 82b is formed in a generally plate-like shape whose outer edge roughly coincides with that of each heat transfer plate 81a, 81b when viewed from the front, and the first end plate 82a is provided with a fluid port that communicates with the first header portion forming hole 83a1, while the second end plate 82b is provided with fluid ports that correspond to the second, third, and fourth header portion forming holes 83b1, 83c1, 83d1, respectively. The fluid ports that communicate with the first header portion forming hole 83a1 consist of two ports: a water port 82a1 and a gas port 82a2.

[0146] In the plate assembly 80, the first flange surfaces 84a, 85a of the adjacent first and second heat transfer plates 81a, 81b are joined together on their protruding sides to form a first header portion 83a in which the first header portion-forming holes 83a1 are connected in the front-to-rear direction, and this first header portion opens forward in the first end plate 82a. Furthermore, the second flange surfaces 84b, 85b of the adjacent first and second heat transfer plates 81a, 81b are joined together on their protruding sides to form a second header portion in which the second header portion-forming holes 83b1 are connected in the front-to-rear direction. This second header portion opens rearward in the second end plate 82b.

[0147] Furthermore, by joining the third flange surfaces 84c, 85c of the adjacent first heat transfer plate 81a and second heat transfer plate 81b on their protruding sides, a third header portion is formed in which the third header portion-forming holes 83c1 are connected in the front-to-rear direction, and this third header portion opens rearward in the second end plate 82b. Furthermore, by joining the fourth flange surfaces 84d, 85d of the adjacent first heat transfer plate 81a and second heat transfer plate 81b on their protruding sides, a fourth header portion is formed in which the fourth header portion-forming holes 83d1 are connected in the front-to-rear direction, and this fourth header portion opens rearward in the second end plate 82b.

[0148] In the plate assembly 80, when the heat transfer plates 81a, 81b are stacked, the opposing flange surfaces of the fluid flow paths that do not require fluid distribution / collection are joined by brazing or the like to prevent unwanted fluid from entering, and an appropriate header section is easily formed. In this configuration, the heat transfer plates must be manufactured using two types of press dies, but because no auxiliary parts are used to form the header section, it is suitable for mass production of the evaporator 4.

[0149] Each of the heat transfer plates 81a and 81b has a predetermined member disposed inside the frame portion 81y to form one of a low-temperature fluid flow path and a high-temperature fluid flow path.

[0150] A serpentine flow path plate 86 shown in Fig. 23 is used as a component that constitutes the low-temperature fluid flow path. Heat transfer fins (not shown) are used as components that constitute the high-temperature fluid flow path. In this embodiment, the heat transfer fins are corrugated fins with a large number of flow paths that extend in the vertical direction, and are widely arranged in the central regions of the heat transfer plates 81a and 81b.

[0151] The serpentine flow path plate 86, which is widely disposed in the central region of the heat transfer plates 81a and 81b, has a serpentine flow path 86a formed therein, which extends in a serpentine pattern from top to bottom. The serpentine flow path 86a can be formed, for example, by punching using laser processing. Fabricating the serpentine flow path plate 86 in this manner enables mass production with fewer steps and reduces processing costs. The serpentine flow path 86a generally comprises multiple stages of unit flow paths Ch formed continuously in the vertical direction. The stages include an inclined flow path section Ch1 that slopes obliquely downward so that fluid flows from one end near the left end to the other near the right end, and a return flow path section Ch2 that reverses the flow of fluid at the end of the inclined flow path section Ch1.

[0152] The lower region of serpentine flow path plate 86 has cutouts 87c at positions corresponding to third flange surfaces 84c and 85c, and has second header portion-accommodating holes 83b2 at positions corresponding to second header portion-forming holes 83b1. Second header portion-accommodating holes 83b2 are connected to the lower end of serpentine flow path 86a.

[0153] The upper region of serpentine flow path plate 86 has cutouts 87d at positions corresponding to fourth flange surfaces 84d and 85d, and has a first header portion-accommodating hole 83a2 at a position corresponding to first header portion-forming hole 83a1. First header portion-accommodating hole 83a2 is connected to the upper end of serpentine flow path 86a.

[0154] The evaporator 4 according to this embodiment includes a water distributor 90 attached to the plate assembly 80. As shown in FIG. 24, the water distributor 90 includes a nozzle header 91 (inner pipe) and a thermal insulation pipe 92 (outer pipe). The thermal insulation pipe 92 is formed in a tubular shape extending forward and backward, and its rear end (base end) is joined to the front surface of the first end plate 82a and closed. On the other hand, the front end (tip end) of the thermal insulation pipe 92 protrudes outside the hot module HM and is open to the atmosphere. In other words, an air insulation layer is formed between the nozzle header 91 and the thermal insulation pipe 92.

[0155] The nozzle header 91 has a tubular portion 91a that extends in the front-to-rear direction. As shown in Fig. 24, the rearward portion of the tubular portion 91a is inserted into the first header portion 83a via the water port 82a1, and the portion further forward is disposed inside the thermal insulation pipe 92. As shown in Fig. 25, the portion of the tubular portion 91a that is inserted into the first header portion 83a has a plurality of through-holes 91c formed in the lower pipe wall of the tubular portion 91a.

[0156] A plurality of discharge pipes 91b are provided corresponding to the plurality of through holes 91c so as to protrude downward from the pipe wall. The discharge pipes 91b can be integrated with the tubular portion 91a, for example, by fitting them into the through holes 91c and then brazing them. The interior of each discharge pipe 91b is in communication with the interior of the tubular portion 91a, and the cross section of the pipe wall of each discharge pipe 91b is rectangular with front, rear, left, and right sides.

[0157] As described above, the water distributor 90 has a double-pipe structure for the external pipe leading to the plate assembly 80, and only the nozzle header 91 protrudes into the first header portion 83a. That is, inside the first header portion 83a, the nozzle header 91 extends in the stacking direction of the heat transfer plates 81a, 81b. Each of the multiple discharge pipes 91b is arranged to correspond to the position of each cryogenic fluid flow path in the plate assembly 80 (inside the frame portion 81y of the second heat transfer plate 81b).

[0158] The water distributor 90 configured as described above functions as a fluid supply mechanism that evenly distributes the reforming water Wa to each of the low-temperature fluid flow paths in the plate assembly 80. The portion of the tubular portion 91a protruding from the first end plate 92a is covered with an air insulation layer made of a thermal insulation pipe 92 inside the second box X2, and this thermal insulation pipe 92 is also covered with granular insulation material. Therefore, vapor lock caused by overheating or boiling during the supply of the reforming water Wa is avoided, and the reforming water Wa continues to be smoothly discharged from the discharge pipe 91b.

[0159] The raw fuel gas Ga supplied to the gas port 82a2 flows directly into the first header section 83a and is distributed evenly to each of the cryogenic fluid flow paths. The reforming water Wa supplied from the water port 82a1 using the water distributor 90 travels through the tubular section 91a to the depths of the first header section 83a, where it drips equally from each discharge pipe 91b as shown by the dotted arrows in Figure 25 and is distributed evenly to each of the cryogenic fluid flow paths. Each discharge pipe 91b prevents adjacent water droplets from coalescing and acts to guide the water droplets to fall independently.

[0160] The reforming water Wa dripping from each discharge pipe 91b flows down to the uppermost stage of the serpentine flow path 86a. This reforming water Wa is heated as it travels through the serpentine flow path 86a, becoming steam and reaching the second header section 83b. The raw fuel gas Ga is also heated as it travels through the serpentine flow path 86a together with the reforming water Wa, and reaches the second header section 83b. In this way, the plate assembly 80 is configured to cause water evaporation in the raw fuel gas Ga, and a mixed gas Gb of raw fuel gas Ga and steam is continuously obtained in a superheated state in the second header section 83b. This mixed gas Gb can be supplied as is to the reformer 2.

[0161] On the other hand, combustion gas Gg is supplied to the third header section 83c as heat source gas. The combustion gas Gg supplied to the third header section 83c is evenly distributed to each high-temperature fluid flow path, flows upward through each flow path in the heat transfer fins, and is collected in the fourth header section 83d and discharged to the pipe line Lg1.

[0162] At this time, the serpentine path 86a of each low-temperature fluid flow path faces the heat transfer fins of the adjacent high-temperature fluid flow path in the front-to-back direction via the heat transfer plates 81a, 81b, so that the reforming water Wa and raw fuel gas Ga are efficiently heated using the heat of the combustion gas Gg.

[0163] Furthermore, the reforming water Wa and raw fuel gas Ga flow downward through the serpentine path 86a, while the combustion gas Gg flows upward through the heat transfer fins, resulting in a counterflow heat exchange between them. As a result, in the lower region of the plate assembly 80, steam (reforming water Wa) is heated by the high-temperature heat source gas (combustion gas Gg) immediately after being introduced from the third header section 83c, and superheated steam can be extracted from the second header section 83b. This superheated steam is useful in the steam reforming reaction of hydrocarbon fuel in the reformer 2.

[0164] <Effects of the present invention and other modifications> As described above, the evaporator 4 for generating water vapor mounted in the fuel cell system 100 comprises a plate assembly 80 in which a plurality of heat transfer plates 81, each having front and rear heat transfer surfaces that are approximately parallel to the vertical direction, are stacked between a pair of oppositely arranged end plates 82a, 82b, and the end plates 82a, 82b and the heat transfer plates 81 are joined together to form an integrated unit; serpentine flow path plates 86 incorporated into each of the low-temperature fluid flow paths formed on one heat transfer surface side of the heat transfer plates 81; and heat transfer fins incorporated into each of the high-temperature fluid flow paths formed on the other heat transfer surface side of the heat transfer plates 81.

[0165] The plate assembly 80 also has a first header section 83a that distributes water (reforming water Wa) to each of the low-temperature fluid flow paths, a second header section 83b that collects water vapor from each of the low-temperature fluid flow paths, a third header section 83c that distributes heat source gas (combustion gas Gg) to each of the high-temperature fluid flow paths, and a fourth header section 83d that collects the heat source gas from each of the high-temperature fluid flow paths. The first header section 83a is formed in the upper part of the plate assembly 80, and the second header section 83b is formed in the lower part of the plate assembly 80. The serpentine flow path plate 86 has multiple stages of unit flow paths Ch formed continuously, each stage consisting of an inclined flow path section Ch1 that allows water to flow downward and a return flow path section Ch2 that reverses the fluid flow.

[0166] Therefore, even if the height of the plate assembly 80 is restricted, the serpentine flow path ensures sufficient contact time between the heating surface and the water film, resulting in a compact evaporator 4 with good evaporation efficiency. In addition, the water film flowing down the serpentine flow path can be gradually heated, which slows the evaporation rate and produces steam at a stable pressure.

[0167] Among heat transfer fins, corrugated fins can be manufactured simply by bending a metal plate, whereas offset fins require at least three processes (bending → cutting → bending). Therefore, in a configuration in which heat transfer fins with many processes are incorporated into the low-temperature fluid flow path and the high-temperature fluid flow path, the processing costs for the auxiliary parts can become high in some cases. In this embodiment, a serpentine flow path plate 86 is incorporated into the low-temperature fluid flow path, while relatively inexpensive corrugated fins are incorporated into the high-temperature fluid flow path as heat transfer fins. In particular, the serpentine flow path plate 86 can be manufactured by blanking using laser processing or the like, which allows for mass production with few steps and low processing costs.

[0168] In the evaporator 4, the third header section 83c is formed in the lower part of the plate assembly 80, and the fourth header section 83d is formed in the upper part of the plate assembly 80. Therefore, water distributed from the first header section 83a evaporates while flowing downward through each of the low-temperature fluid flow paths and is collected in the second header section 83b, while the heat-source gas distributed from the third header section 83c flows upward through each of the high-temperature fluid flow paths and is collected in the fourth header section 83d. In other words, the evaporator 4 is configured to perform heat exchange between water and heat-source gas in a counterflow manner. In the lower region of the plate assembly 80, steam is heated by the high-temperature heat-source gas immediately after being introduced from the third header section 83c, and superheated steam can be extracted from the second header section 83b. This superheated steam is useful for the steam reforming reaction of hydrocarbon fuels.

[0169] The plate assembly 80 consists of a first heat transfer plate 81a and a second heat transfer plate 81b stacked alternately, and these heat transfer plates 81a, 81b each have a first header portion forming hole 83a1, a second header portion forming hole 83b1, a third header portion forming hole 83c1, and a fourth header portion forming hole 83d1. In addition, in these heat transfer plates 81a, 81b, the peripheral portion of the first header portion forming hole 83a1 is provided with a first flange surface 84a (or first flange surface 85a) protruding toward the high-temperature fluid flow path, the peripheral portion of the second header portion forming hole 83b1 is provided with a second flange surface 84b (or second flange surface 85b) protruding toward the high-temperature fluid flow path, the peripheral portion of the third header portion forming hole 83c1 is provided with a third flange surface 84c (or third flange surface 85c) protruding toward the low-temperature fluid flow path, and the peripheral portion of the fourth header portion forming hole 83d1 is provided with a fourth flange surface 84d (or fourth flange surface 85d) protruding toward the low-temperature fluid flow path.

[0170] The first header portion 83a is formed by joining the first flange surface 84a of the first heat transfer plate 81a and the first flange surface 85a of the second heat transfer plate 81b on the protruding side, the second header portion 83b is formed by joining the second flange surface 84b of the first heat transfer plate 81a and the second flange surface 85b of the second heat transfer plate 81b on the protruding side, the third header portion 83c is formed by joining the third flange surface 84c of the first heat transfer plate 81a and the third flange surface 85c of the second heat transfer plate 81b on the protruding side, and the fourth header portion 83d is formed by joining the fourth flange surface 84d of the first heat transfer plate 81a and the fourth flange surface 85d of the second heat transfer plate 81b on the protruding side.

[0171] In this way, each of the heat transfer plates 81a, 81b that form the plate assembly 80 is provided with flange surfaces 84a-84d (or flange surfaces 85a-85d) that protrude beyond the heat transfer surface by trimming in advance, and each of the header portion-forming holes 83a1-83d1 is provided by laser processing. When stacking the heat transfer plates 81a, 81b, for fluid flow paths that do not require fluid distribution / collection, each header portion is easily formed by joining the opposing flange surfaces together by brazing or the like. When manufacturing a plate assembly 80 configured in this way, the heat transfer plates must be manufactured using two types of press molds, but this is suitable for mass production of the evaporator 4 in that no auxiliary parts such as auxiliary plates are required to form each header portion.

[0172] The evaporator 4 also includes a water distributor 90 attached to the plate assembly 80. The water distributor 90 includes a tubular nozzle header 91 inserted into the first header portion 83a and through which the reforming water Wa flows, a plurality of through holes 91c formed in the pipe wall of the nozzle header 91 at the insertion portion of the nozzle header 91, and a plurality of discharge pipes 91b provided on the outer wall of the nozzle header 91 so as to communicate with each of the through holes 91c. The water distributor 90 also includes a thermal insulation pipe 92 at the protruding portion of the nozzle header 91, through which the nozzle header 91 is inserted, the thermal insulation pipe 92 having a base end closed by being joined to the first end plate 82a and an open tip end.

[0173] The water distributor 90 is a fluid supply mechanism that evenly distributes the reforming water Wa to each of the low-temperature fluid flow paths. The water distributor 90 has a double-pipe structure consisting of a nozzle header 91 and a thermal insulation pipe 92 in the external pipe leading to the plate assembly 90a, with only the nozzle header 91 protruding into the first header section 83a. In other words, inside the first header section 83a, the nozzle header 91 extends in the stacking direction of the heat transfer plates 81a, 81b.

[0174] In the evaporator 4 having this configuration, water is evaporated in the raw fuel gas Ga by dripping water from a plurality of through-holes 91c formed in the nozzle header 91 while the raw fuel gas Ga flows into the first header section 83a through the gas port 82a2. A discharge pipe 91b, which is provided on the outer wall of the nozzle header 91 and communicates with the through-holes 91c, prevents adjacent water droplets from coalescing and guides the water droplets to fall independently. This allows a superheated mixture Gb of raw fuel gas Ga and steam to be continuously obtained from the second header section 83b of the plate assembly 80. This superheated mixture Gb can be supplied directly to the reformer 2.

[0175] The evaporator 4 of this embodiment is configured to supply raw fuel gas Ga together with reforming water Wa to the low-temperature fluid flow path, and generate a mixed gas Gb of raw fuel gas Ga and steam. However, the present invention is not limited to this, and the evaporator 4 may generate only superheated steam, and the mixed gas Gb may be generated by mixing the steam and raw fuel gas Ga downstream of the evaporator 4. In this case, it is preferable to preheat the raw fuel gas Ga to a temperature higher than the steam using a fuel preheater or the like before mixing.

[0176] Although the system of this embodiment is a single-stage fuel cell system, the present invention can also be applied to multi-stage fuel cell systems. As an example, in a two-stage fuel cell system, a front-stage cell stack and a rear-stage cell stack are provided, and the rear-stage cell stack is configured to generate power using anode off-gas (containing unreacted fuel components) discharged from the front-stage cell stack.

[0177] Although the embodiments of the present invention have been described above, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. In other words, the above embodiments are illustrative in all respects and should be considered not to be limiting. The technical scope of the present invention is defined by the claims, not by the description of the above embodiments, and should be understood to include all modifications that fall within the meaning and scope of the claims.

[0178] The present invention can be used in a solid oxide fuel cell system. [Explanation of symbols]

[0179] 1 Cell stack 2 Reformer 2a Reaction vessel 3 Burner 4. Evaporator 5. Air preheater 6 Anode off-gas cooler 7. Anode off-gas condenser 8 CO oxidation reactor 9 Condensate recovery tank 10. First raw fuel blower 11 No. 1 air blower 12 Water pump 13 Second raw fuel blower 14 Second air blower 15 Power conditioner 16 System Controller 21 Outer cylinder 21a Inlet 21b Outlet 21c Elastic absorbent part 22 Inner cylinder 23 Catalyst packed bed 24 Proximal cover plate 25 Distal cover plate 31 First gas cylinder 32 Second gas cylinder 33 Flame holder 40 Ignition / Flame Detection Circuit 40a Gas ignition unit 40b Current detection unit 40c1 First switch 40c2 Second switch 40x electrode pairs 51 1st pillar 52 Second pillar 53 Plate-shaped insulation material 61 Cell stack assembly 62 Open Rack 62a Unit Rack 63 Stage Edition 63a Stage Edition 64 Column section 64a Pillar 71 Support plate 72 flanged gas port 72a Anode fuel inlet port 72b Cathode air inlet port 72c Anode off-gas outlet port 72d Cathode off-gas outlet port 72x flange 74a 1st power terminal 74a1 End of first power terminal 74b Second power terminal 74b1 End of second power terminal 75 Laminated section 76a 1st end plate 76b 2nd end plate 78a Main Busbar 78a1 Elastic absorption part 78b Sub-bass bar 78b1 Elastic absorption part 79 Power Lines 79a Power line protection tube 80 Plate assembly 81a First heat transfer plate 81b Second heat transfer plate 81x flat plate part 81y frame 82a First end plate 82b Second end plate 82a1 Water port 82a2 gas port 83a First header section 83b Second header section 83c Third Header 83d 4th Header 83a1 First header forming hole 83a2 First header corresponding hole 83b1 Second header forming hole 83b2 Second header corresponding hole 83c1 Third header forming hole 83d1 4th header forming hole 84a, 85a First flange surface 84b, 85b Second flange surface 84c, 85c 3rd flange surface 84d, 85d 4th flange surface 86 Serpentine flow path plate 86a Serpentine channel 87c, 87d Notch 90 Water distributor 91 Nozzle Header 91a Tubular part 91b Discharge pipe 91c through hole 92 Insulated pipe 100 Fuel Cell System Aa~Ac Air B1 First bellows type expansion joint B2 Second bellows type expansion joint B3 Third bellows type expansion joint B4 No. 4 Bellows Expansion Joint BP branch pipe Bp1 Bellows type expansion joint CV curved section Ch unit flow channel Ch1 Inclined channel section Ch2 Turning flow path section D1 Gas outlet E1, E2 fuel intake E3, E4 air intakes Fg flange Ga raw fuel gas Gb mixed gas Gc reformed gas Gd anode off-gas Ge cathode offgas Gf raw fuel gas Gg Combustion gas La raw fuel line Lb mixed gas line Lc anode fuel line Ld Anode off-gas line Ld1 conduit Le cathode air line Le1 conduit Le2 bypass route Lf Cathode off-gas line Lf1 conduit Lg combustion gas line Lg1 conduit Lh Burner cooling air line Li reformed water line Lj Starting air line Lw Condensate recovery line Ma 1st distribution manifold Mb Second distribution manifold Mc 1st Collection Manifold Md Second collection manifold RG Reformed Gas Generator Sa air / water separation section Sb Water Level Detector Sc drain valve Wa modified water Wb Condensed water X1 Box 1 X1a 1st base X2 2nd Box X2a 2nd base Za Heat Radiator Zb Combustion gas pipe

Claims

1. An evaporator for generating water vapor to be mounted on a fuel cell system, a plate assembly in which a plurality of heat transfer plates, each having front and rear heat transfer surfaces that are substantially parallel to the vertical direction, are stacked between a pair of end plates arranged opposite to each other, and the end plates and the heat transfer plates are joined together to form an integrated assembly; a serpentine flow path plate incorporated into each of the cryogenic fluid flow paths formed on one of the heat transfer surfaces of the heat transfer plate; heat transfer fins incorporated in each of the high-temperature fluid flow paths formed on the other heat transfer surface side of the heat transfer plate; a water distributor that supplies water to each of the cryogenic fluid flow paths; the plate assembly includes a first header section that distributes water to each of the low-temperature fluid flow paths, a second header section that collects water vapor from each of the low-temperature fluid flow paths, a third header section that distributes heat source gas to each of the high-temperature fluid flow paths, and a fourth header section that collects heat source gas from each of the high-temperature fluid flow paths; The first header portion is formed on an upper portion of the plate assembly, The second header portion is formed on a lower portion of the plate assembly, An evaporator for a fuel cell system, characterized in that the serpentine flow path plate has multiple stages of unit flow paths formed continuously, each stage consisting of an inclined flow path section that allows water to flow downward and a turn-back flow path section that reverses the fluid flow.

2. the third header portion is formed at a lower portion of the plate assembly, 2. The evaporator of claim 1, wherein the fourth header portion is formed on an upper portion of the plate assembly.

3. The water distributor comprises: a tubular nozzle header inserted into the first header portion and through which water flows; a plurality of through holes formed in a pipe wall of the nozzle header at an insertion portion of the nozzle header; 3. The evaporator according to claim 1, further comprising: a plurality of discharge pipes provided on the outer wall of the nozzle header so as to communicate with the through holes, respectively.

4. a thermal insulation pipe, into which the nozzle header is inserted, at a protruding portion of the nozzle header; 4. The evaporator according to claim 3, wherein the thermal insulation pipe has a base end closed by joining to the end plate and a tip end open.

5. The heat transfer plate includes first and second heat transfer plates that are alternately stacked, the first heat transfer plate and the second heat transfer plate each have a first header portion forming hole, a second header portion forming hole, a third header portion forming hole, and a fourth header portion forming hole; a first flange surface protruding toward the high-temperature fluid flow path is provided on a peripheral edge of the first header portion forming hole, a second flange surface protruding toward the high-temperature fluid flow path is provided on a peripheral edge of the second header portion forming hole, a third flange surface protruding toward the low-temperature fluid flow path is provided on a peripheral edge of the third header portion forming hole, a fourth flange surface protruding toward the low-temperature fluid flow path is provided on a peripheral edge of the fourth header portion forming hole, the first header portion is formed by joining the first flange surface of the first heat transfer plate and the first flange surface of the second heat transfer plate at their protruding sides, the second header portion is formed by joining the second flange surface of the first heat transfer plate and the second flange surface of the second heat transfer plate at their protruding sides, the third header portion is formed by joining the third flange surface of the first heat transfer plate and the third flange surface of the second heat transfer plate at their protruding sides, The evaporator according to any one of claims 1 to 4, characterized in that the fourth header portion is formed by joining the fourth flange surface of the first heat transfer plate and the fourth flange surface of the second heat transfer plate on their protruding sides.

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