JP5140443B2 - FUEL CELL MODULE AND METHOD OF OPERATING FUEL CELL MODULE - Google Patents

Description

  The present invention relates to a fuel cell module including a fuel cell stack that generates power using hydrogen-rich reformed gas, and a method for operating the fuel cell module.

  A solid oxide electrolyte fuel cell (SOFC) module is a reformer for generating hydrogen-containing gas (reformed gas) obtained by reforming fuel such as kerosene and city gas. A cell stack for electrochemically generating a reaction between the reformed gas and air. The cell stack includes an anode electrode layer and a cathode electrode layer disposed with a solid electrolyte interposed therebetween. A power generation reaction occurs when a reformed gas is circulated through the anode electrode layer, air is circulated through the cathode electrode layer, and current is taken out from the cell stack.

  In this type of fuel cell module, the operating temperature of the cell stack is as high as 550 ° C. to 1000 ° C., and it is desirable to cool the cell stack to about room temperature at an early stage when the operation of the fuel cell module is stopped. Therefore, in general, for example, a large amount of air is supplied to the cathode electrode layer of the cell stack to shorten the cooling time.

  Further, when the temperature of the cell stack is lowered, if the anode electrode layer is placed in an oxidizing gas atmosphere in a state where the temperature of the anode electrode layer is equal to or higher than the oxidation deterioration point, the anode electrode layer may be oxidized and deteriorated. Therefore, in the stopping method of Patent Document 1, the reformed gas is continuously supplied to the anode electrode layer or the anode electrode layer is purged with an inert gas so as to prevent oxidative deterioration of the anode electrode layer.

In addition, when starting up an internal reforming fuel cell module, it is necessary to heat the reformer to generate reformed gas to be supplied to the cell stack. The stack is also heated. When the temperature of the anode electrode layer becomes higher than the oxidation deterioration point in an oxidizing gas atmosphere as the cell stack rises in temperature, the anode electrode layer may be oxidized and deteriorated as described above. Therefore, in the starting method described in Patent Document 2, a reducing gas or an inert gas is supplied to the anode electrode layer separately from the reformed gas for power generation.
JP 2006-294508 A JP 2005-293951 A

  However, when a large amount of air is supplied to the cathode electrode layer to cool the cell stack, the air flow path to the cathode electrode layer and the heat capacity around the air flow path are large, and the air is heated before reaching the cathode electrode layer. Therefore, it takes a long time for cooling. For this reason, there is a problem that the power consumption of the air booster such as a blower is large and the energy required for cooling the cell stack is large.

  Further, since it takes a long time to cool the cell stack at the time of stoppage, there is a problem that a large amount of reformed gas is supplied to prevent anodic oxidation deterioration and a large amount of energy is required for cooling the cell stack. In addition, there is a problem that the supply energy of the inert gas and the reducing gas supplied to prevent the oxidative deterioration of the anode electrode layer is large until the reformer is heated and the reformed gas is supplied at startup. It was.

  An object of the present invention is to solve the above problems, and to provide a fuel cell module and a method for operating the fuel cell module that can reduce energy required for cooling the fuel cell stack. .

  A fuel cell module according to the present invention includes a fuel cell stack, and a cooler that is disposed around the fuel cell stack and that cools the fuel cell stack using the heat of evaporation of a cooling medium. To do.

  In the present invention, since the fuel cell stack can be cooled using the heat of evaporation, for example, the fuel cell stack can be cooled with less power consumption than the power consumption of the blower required for cooling using sensible heat. The energy required for cooling can be reduced.

  It is preferable that the cooler is disposed with a gap between the cooler and the fuel cell stack and has a heat receiving portion that receives the radiant heat of the fuel cell stack. Since there is a gap between the cooler and the fuel cell stack, there is little need to consider the risk of electric leakage from the fuel cell stack to the cooler, and there is a heat receiving part that receives radiant heat. The energy required for cooling the fuel cell stack can be reduced as compared with the cooling using.

  Further, the fuel cell stack includes a reformer that is disposed in the casing and generates a reformed gas used for power generation of the fuel cell stack. The fuel cell stack includes a heat receiving region facing the reformer, and a region other than the heat receiving region. It is preferable that the cooler is disposed along the heat dissipation area. Since the cooler is arranged not in the heat receiving area of the fuel cell stack but in the heat dissipation area, the fuel cell stack can be selectively cooled while suppressing the cooling of the reformer in the casing.

  The cooler further includes a cooling passage in which a liquid phase and a gas phase of a cooling medium are formed, and a methane generation passage in which a methanation catalyst that promotes the methanation reaction is accommodated. It is preferable to have a reformed gas inflow portion to which the reformed gas from the reformer is supplied and a methane outflow portion to supply the methane-containing gas generated from the reformed gas by the methanation reaction to the fuel cell stack. . The methanation reaction with the methanation catalyst is promoted as the temperature decreases. When the fuel cell stack is cooled by the cooler, the methanation catalyst is also cooled, and methane-rich gas is supplied to the fuel cell stack by promoting the methanation reaction. As a result, a reforming reaction that is an endothermic reaction occurs on the anode electrode layer of the fuel cell stack, and the fuel cell stack can be cooled. In particular, by cooling from the inside of the fuel cell stack using the reforming reaction on the anode electrode layer, the entire fuel cell stack can be cooled more uniformly.

  Further, the cooler preferably has a cooling passage in which a liquid phase and a gas phase of the cooling medium are formed, and a preheating passage for heating the oxygen-containing gas supplied to the fuel cell stack. When the fuel cell stack is cooled by the cooler, the oxygen-containing gas passing through the preheating passage is also cooled. As a result, the cathode electrode layer can be cooled more effectively.

  The fuel cell module operating method according to the present invention includes a fuel cell stack, and a cooler that cools the fuel cell stack using the heat of evaporation of the cooling medium. When stopping, a liquid cooling medium is supplied to the cooler, and the supply amount of the cooling medium is controlled so that the cooling medium forms two phases of a liquid phase and a gas phase in the cooler. And

  According to the present invention, when the fuel cell stack is stopped, the cooling medium is maintained in the cooler so as to form two phases of a liquid phase and a gas phase. The fuel cell stack can be cooled. As a result, for example, the fuel cell stack can be cooled with less power consumption than the power consumption of the blower necessary for cooling using sensible heat, and the energy required for cooling the fuel cell stack can be reduced.

  The fuel cell module operating method according to the present invention includes a fuel cell stack, a reformer that generates reformed gas to be supplied to the fuel cell stack, and a fuel cell stack using heat of evaporation of a cooling medium. In a fuel cell module comprising a cooler for cooling, when the fuel cell stack is started, the reformer is heated and a liquid cooling medium is supplied to the cooler. When the reformed gas is generated and the generated reformed gas is supplied to the fuel cell stack, the supply of the cooling medium to the cooler is stopped.

  Even if the reformer is heated to generate the reformed gas, the fuel cell stack is cooled by using the heat of evaporation of the cooling medium in the cooler. In comparison, it is possible to prevent the temperature of the fuel cell stack from exceeding the oxidation deterioration point while suppressing power consumption. As a result, it is possible to reduce the supply energy of the inert gas or reducing gas supplied to prevent the oxidative deterioration of the anode electrode layer.

  According to the present invention, the energy required for cooling the fuel cell stack can be reduced.

  Hereinafter, preferred embodiments of a fuel cell module according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a part of a cogeneration system including a fuel cell module according to a first embodiment of the present invention. FIG. 2 is a diagram showing a fuel cell module. In FIG. 2, the vertical direction is shown on the left and right, and the left side of the drawing is the upper side and the right side is the lower side. As shown in FIG. 2, the fuel cell module 3 </ b> A includes a solid oxide fuel cell (SOFC) stack 5 that generates power using reformed gas and air, and a raw fuel for supply to the SOFC stack 5. A reformer 7 that generates a hydrogen-rich reformed gas from a gas by a steam reforming reaction and a cooler 9 for cooling the SOFC stack 5 are provided. The SOFC stack 5, the reformer 7, and the cooler 9 is accommodated in a module container (housing) 11. The module container 11 is made of a metal such as stainless steel (SUS), and for example, a heat insulating material is disposed around the module container 11.

  In the SOFC stack 5, a plurality of flat single cell stacks are stacked to form a columnar shape, and the stacked body of single cell stacks is sandwiched and fixed between a pair of end plates. The single cell stack includes an anode electrode layer (fuel electrode), a cathode electrode layer (air electrode), a solid electrolyte made of yttria-stabilized zirconia disposed between the anode electrode layer and the cathode electrode layer, and an anode electrode. And a separator disposed on the outside of the cathode electrode layer. The reformed gas from the reformer 7 is introduced into the anode electrode layer, and air is introduced into the cathode electrode layer. By taking out the current from the SOFC stack 5, an electrochemical power generation reaction is performed in each single cell stack. The operating temperature of the SOFC stack 5 is 550 ° C to 1000 ° C.

  The reformer 7 performs a steam reforming reaction of vaporized raw fuel gas such as kerosene or city gas and steam with a reforming catalyst to generate a reformed gas containing hydrogen and carbon monoxide. The steam reforming reaction is a very large endothermic reaction, and since the reaction temperature is relatively high at about 550 to 750 ° C., a high-temperature heat source is required. For this reason, the reformer 7 is disposed in the vicinity of the SOFC stack 5 as a heat source, or a heat source such as an electric heater or a burner is provided. A reformed gas supply pipe connected to the SOFC stack 5 is connected to the reformer 7.

  The SOFC stack 5 is columnar. The reformer 7 is disposed adjacent to one end face 5 a of the SOFC stack 5. The end surface 5 a of the SOFC stack 5 faces the reformer 7 and forms a heat receiving region 13 that receives heat from the reformer 7. The SOFC stack 5 is heated by the radiant heat from the reformer 7. A region other than the end surface 5 a of the SOFC stack 5, that is, the side surface 5 b and the other end surface 5 c of the SOFC stack 5 form a heat dissipation region 15.

  FIG. 3 is a side sectional view of the cooler 9. In FIG. 3, the left side is shown as being up and the right side is shown as being down. As shown in FIG. 3, the cooler 9 includes a casing portion 17 that is adjacent to the side surface 5b of the SOFC stack 5 with a gap S1 and extends along the side surface 5b. The casing part 17 is made of a metal such as stainless steel (SUS), and is a cylindrical body having a rectangular cross section whose left and right ends are closed. An inflow portion 19 to which water serving as a cooling medium is supplied is provided at the lower left end of the casing portion 17, and an outflow portion 21 through which water vapor evaporated in the casing portion 17 flows out is provided at the upper right end. The inflow portion 19 is provided at an edge far from the SOFC stack 5, and the outflow portion 21 is provided at an edge near the SOFC stack 5.

  The casing portion 17 constitutes a cooling passage, and passage walls 23 are provided on the left and right in order to form a meandering flow path 24 of water. The water flowing in from the inflow portion 19 moves along the passage wall 23 while meandering left and right. The casing portion 17 receives the radiant heat of the SOFC stack 5 at the outer peripheral surface (heat receiving portion) 18, and receives the most radiant heat at the peripheral surface 18 a on the side facing the SOFC stack 5 in the outer peripheral surface 18. Of the meandering flow path 24 of water formed in the casing part 17, the most downstream region 24a communicating with the outflow part 21 is in contact with the outer wall forming the peripheral surface 18a. The state of the water flowing in from the inflow part 19 forms a liquid single-phase DP, a gas-liquid mixed phase (a state where steam is generated), and a gas single-phase GP in order from the upstream side, and the water vapor in the most downstream region 24a is The water is discharged from the water vapor pipe 22 connected to the outflow portion 21. The cooler 9 cools the SOFC stack 5 using the heat of evaporation of water supplied into the casing portion 17. In order to perform the cooling using the heat of evaporation, it is sufficient to form a gas-liquid mixed phase, that is, a state where steam is generated in the casing portion 17, so that the water in the gas-liquid mixed phase is supplied to the steam pipe. 22 may be discharged.

  The temperature near the outflow portion 21 in the casing portion 17 is high because it is close to the SOFC stack 5, while the temperature near the inflow portion 19 is relatively low because it is far from the SOFC stack 5. Therefore, bumping due to rapid heating of the water supplied to the inflow portion 19 can be suppressed, and evaporation vibration can be suppressed.

  The SOFC stack 5 is provided with a first temperature sensor 25 (see FIG. 2), and a second temperature sensor 27 is provided in the vicinity of the outflow portion 21 of the cooler 9. Further, a water supply pipe 29 for supplying water is connected to the inflow portion 19 of the cooler 9, and a pump 31 for boosting the water is provided on the water supply pipe 29. The first temperature sensor 25, the second temperature sensor 27, and the pump 31 are connected to the control unit 33 so that signals can be transmitted and received.

  Specifically, the control unit 33 corresponds to a PLC (Programmable Logic Controller) or the like, and is configured by hardware such as a CPU (Central Processing Unit) or a memory. The control unit 33 controls the flow of the water supplied to the cooler 9 by controlling the driving of the pump 31 based on the temperatures detected by the first temperature sensor 25 and the second temperature sensor 27. Further, the control unit 33 monitors the output current extracted from the SOFC stack 5, and appropriately controls the output current from the SOFC stack 5. Further, the control unit 33 controls the flow rate of the raw fuel gas supplied to the reformer 7 and the flow rate control of the oxygen-containing gas supplied to the cathode electrode layer of the SOFC stack.

  As shown in FIG. 1, the fuel cell module 3 </ b> A is incorporated in the cogeneration system 1. The cogeneration system 1 includes an inverter 35 that converts DC power output from the fuel cell module 3A into AC power. The cogeneration system 1 also includes a hot water tank 37 connected to the cooler 9 of the fuel cell module 3A.

  The hot water storage tank 37 is connected to a water supply pipe 29 for supplying water to the cooler 9 and a water vapor pipe 22 through which water vapor from the cooler 9 passes. The water vapor passing through the water vapor pipe 22 is cooled outside the fuel cell module 3A to become a liquid, and flows into the hot water storage tank 37 as hot water as it is. A hot water heater (not shown) or the like is connected to the hot water storage tank 37, and the heat recovered by the cooler 9 is effectively used via the hot water storage tank 37.

(Stop processing)
Next, stop processing of the SOFC stack 5 in the operation method of the fuel cell module 3A will be described. FIG. 4 is a flowchart showing the operation procedure of the stop process of the SOFC stack 5.

  When the stop process of the SOFC stack 5 is started, the control unit 33 decreases the output current taken out from the SOFC stack 5 (step S1), and decreases the supply amount of the raw fuel gas supplied to the reformer 7 (step S2).

  The SOFC stack 5 operates at a very high temperature of 550 ° C. to 1000 ° C., and when it stops, it needs to be lowered to about room temperature as soon as possible. Therefore, the control unit 33 monitors the output current taken out from the SOFC stack 5 (step S3). When the output current becomes “0”, the control unit 33 starts driving the pump 31 and stores water as a cooling medium in the hot water storage tank. It supplies to the cooler 9 from 37 (step S4).

  When the water supplied to the cooler 9 evaporates at, for example, 100 ° C., it vaporizes by taking a heat amount of 40.8 kJ / mol as the heat of evaporation. The water vaporized in the cooler 9 is discharged through the steam pipe 22 and returned to the hot water storage tank 37. As a result, the SOFC stack 5 can be cooled using the heat of water evaporation, and the heat recovered from the SOFC stack 5 can be effectively used.

  The control unit 33 controls the driving of the pump 31 so that a liquid phase and a gas phase are formed in the cooler 9 in order to enable continuous cooling. For example, the control unit 33 monitors the temperature detected by the second temperature sensor 27. The second temperature sensor 27 is disposed in the vicinity of the outflow portion 21 of the cooler 9, and if the temperature detected by the second temperature sensor 27 is less than 100 ° C., the cooler 9 supplies a liquid phase cooling medium. Will be discharged. In this case, the control unit 33 controls the drive of the pump 31 so that the amount of water supplied by the pump 31 is reduced, the temperature detected by the second temperature sensor 27 is 100 ° C. or higher, and the cooling of the gas phase Allow the media to be ejected.

  The control unit 33 also monitors the first temperature sensor 25 arranged in the SOFC stack 5. When the oxidative deterioration point of the anode electrode layer is, for example, 400 ° C., when the temperature detected by the first temperature sensor 25 is reduced to, for example, “390 ° C.” (step S5), the raw fuel gas Is stopped (step S6). Thereafter, when the temperature detected by the first temperature sensor 25 has decreased to, for example, “110 ° C.” (step S7), the driving of the pump 31 is stopped (step S8), and the cooler from the hot water storage tank 37 is cooled. The supply of water to 9 is stopped and the stop process is terminated.

(Start process)
Next, the startup process of the SOFC stack 5 in the operation method of the fuel cell module 3A will be described. FIG. 5 is a flowchart showing the operation procedure of the startup process of the SOFC stack 5.

  When starting the fuel cell module 3A, the control unit 33 drives the pump 31 to supply water as a cooling medium from the hot water storage tank 37 to the cooler 9 (step S11). Further, the control unit 33 starts heating the reformer 7 (step S12). When the temperature of the reformer 7 rises, the SOFC stack 5 is also heated by the radiant heat from the reformer 7.

  When the temperature of the SOFC stack 5 rises, the temperature of the anode electrode layer rises above the oxidation deterioration point, and when the anode electrode layer is in an oxidizing gas atmosphere such as air or water vapor, the anode is oxidized. May deteriorate. However, since the SOFC stack 5 is cooled by the cooler 9, the temperature of the SOFC stack 5 can be prevented from becoming higher than the oxidation deterioration point.

  In particular, since the cooler 9 is disposed along the heat radiation area 15 of the SOFC stack 5 so as not to face the reformer 7, the SOFC stack 5 can be selectively cooled while suppressing the cooling of the reformer 7. .

  The control unit 33 monitors the temperature of the reformer 7 (step S13), and when the reformer 7 reaches a temperature at which steam reforming is possible, the raw fuel gas is supplied to the reformer 7 (step S14). ). Then, reformed gas is generated from the reformer 7 and the reformed gas is supplied to the anode electrode layer of the SOFC stack 5. Then, since the oxidative deterioration of the anode electrode layer is prevented by the reducing action of the reformed gas, the control unit 33 stops driving the pump 31 (step S15), and supplies water from the hot water storage tank 37 to the cooler 9. To stop the startup process.

  As described above, in the fuel cell module 3 </ b> A according to the present embodiment, the SOFC stack 5 is cooled using the evaporation heat of water. That is, the water evaporation part in the cooler 9 is kept at the boiling point, a large temperature difference is obtained from the SOFC stack 5, and heat can be quickly taken from the SOFC stack 5. The power consumption of the pump 31 required for cooling using the evaporation heat of water is smaller than the power consumption of the blower required for cooling using sensible heat, for example. Therefore, energy required for cooling the SOFC stack 5 can be reduced as compared with cooling using sensible heat. Furthermore, the cooler 9 is not disposed so as to be sandwiched between the single cell stacks constituting the SOFC stack 5, but is disposed around the SOFC stack 5, for example. If the cooler 9 is disposed between the single cell stacks, the temperature difference in the SOFC stack 5 increases, and the cell may be damaged by thermal stress. However, the cooler 9 is disposed around the SOFC stack 5. Thus, the risk of breakage due to thermal stress can be reduced.

  Further, in the present embodiment, the cooler 9 is disposed with a gap S1 between the SOFC stack 5 and therefore there is little need to consider the possibility of electric leakage from the SOFC battery stack 5 to the cooler 9. Furthermore, since the cooler 9 has an outer surface (heat receiving portion) 18 that receives the radiant heat of the SOFC stack 5, it is possible to reduce energy required for cooling the SOFC stack 5 at a higher temperature than cooling using sensible heat. Become.

  Further, in the operation method of the fuel cell module according to the present embodiment, when the SOFC stack 5 is stopped, liquid water is supplied to the cooler 9, and the water is converted into a liquid phase and a gas phase in the cooler 9. The supply amount of water is controlled so as to form two phases. When the SOFC stack 5 is stopped, the water in the cooler 9 is maintained so as to form two phases of a liquid phase and a gas phase, thereby enabling cooling using the heat of evaporation of water. The power consumption of the pump 31 necessary for cooling using the heat of evaporation of water is, for example, less than the power consumption of the blower necessary for cooling using sensible heat, and energy can be reduced. In addition, the cooling time can be shortened by cooling using the evaporation heat of water. If the cooling time can be shortened, the supply amount of the reformed gas for preventing the oxidative deterioration of the anode electrode layer can be reduced. As a result, energy required for cooling the fuel cell stack can be reduced.

  In the fuel cell module operating method according to the present embodiment, when the SOFC stack 5 is started, the reformer 7 is heated and liquid water is supplied to the cooler 9. When hydrogen-rich reformed gas is generated, the supply of water to the cooler 9 is stopped.

  Even if the reformer 7 is heated to generate the reformed gas, the SOFC stack 5 is deprived of heat by the evaporation heat of the water in the cooler 9, so that, for example, compared with cooling using sensible heat. Further, it is possible to prevent the temperature of the fuel cell stack from becoming higher than the oxidation deterioration point while suppressing power consumption. As a result, it is possible to reduce the supply energy of the inert gas or reducing gas supplied to prevent the oxidative deterioration of the anode electrode layer.

(Second Embodiment)
A fuel cell module 3B according to the second embodiment will be described with reference to FIG. FIG. 6 is a view showing a fuel cell module according to the second embodiment. The fuel cell module 3B will be described with a focus on differences from the fuel cell system 3A according to the first embodiment, and the same or equivalent elements and members will be described with the same reference numerals as the fuel cell system 3A in the drawings. Is omitted.

  The cooler 41 includes a spiral pipe part (cooling passage) 43 arranged so as to spirally wind the side surface 5b along the side surface 5b of the SOFC stack 5. There is a gap S <b> 2 between the spiral piping portion 43 and the side surface 5 b, and the radiant heat from the SOFC stack 5 is received by the surface 43 a of the spiral piping portion 43. The lower end of the spiral pipe 43 is connected to the water supply pipe 29, and the upper end of the spiral pipe 43 is connected to the water vapor pipe 22. The first temperature sensor 45 is disposed in the SOFC stack 5, and the second temperature sensor 47 is disposed in the vicinity of the upper end of the spiral piping unit 43.

  The control unit 33 monitors the detected temperatures of the first temperature sensor 45 and the second temperature sensor 47. When the SOFC stack 5 is cooled when the SOFC stack 5 is stopped or started, the spiral piping section 43 is used. The pump 31 is driven and controlled so that two phases of a liquid phase and a gas phase of water are formed.

  According to the fuel cell module 3B according to the present embodiment, the SOFC stack 5 can be cooled using the evaporation heat of water as in the case of the fuel cell module 3A, and therefore, compared with the case where cooling is performed using sensible heat or the like. Energy required for cooling the SOFC stack 5 can be reduced.

(Third embodiment)
A fuel cell module according to a third embodiment will be described with reference to FIG. FIG. 7 is a view showing a fuel cell module according to the third embodiment. The fuel cell module 3C will be described with a focus on differences from the fuel cell system 3A according to the first embodiment, and the same or equivalent elements and members will be described with the same reference numerals as the fuel cell system 3A in the drawings. Is omitted.

  The cooler 51 includes a casing portion 57 having a first chamber 53 and a second chamber 55. The casing part 57 consists of metals, such as stainless steel (SUS), for example. The casing portion 57 is disposed along the side surface 5b of the SOFC stack 5 with a gap S1 therebetween.

  The first chamber 53 is disposed on the inner side near the SOFC stack 5, and the second chamber 55 is disposed on the outer side far from the SOFC stack 5. An inflow portion 53a to which water as a cooling medium is supplied is formed at one end of the first chamber (cooling passage) 53, and an outflow portion 53b from which water vapor flows out is formed at the other end. Yes. The inflow portion 53 a is connected to the water supply pipe 29, and the outflow portion 53 b is connected to the water vapor pipe 22. Radiant heat from the SOFC stack 5 is received by the outer peripheral surface (heat receiving portion) 57a of the casing portion 57, and the heat is taken away by the evaporation heat of the water supplied into the first chamber 53 to cool the SOFC stack 5. ing.

  The second chamber (methane generation passage) 55 contains a methanation catalyst Ca that promotes the methanation reaction. As the methanation catalyst Ca, a catalyst similar to the steam reforming catalyst can be used, and group VII metals such as ruthenium, nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum can be used. Further, a reformed gas inflow portion 55a to which the reformed gas from the reformer 7 is supplied is formed at one end of the second chamber 55, and methane-rich by the methanation reaction is formed at the other end. A gas outflow portion (methane outflow portion) 55b for supplying the reformed gas (methane-containing gas) changed in composition to the anode electrode layer of the SOFC stack 5 is formed. Hereinafter, the reforming reaction including the methanation reaction will be described.

When kerosene as the raw fuel is steam reformed, a reformed gas containing hydrogen is obtained. If the reforming raw material is C _n H _{2n + 2} (n is a natural number), the steam reforming reaction is represented by the formula (I). If the reforming reaction is a partial oxidation reforming reaction, it is represented by the formula (II).

  When a catalyst is used for reforming, a shift reaction represented by the formula (III) may occur during reforming. The shift reaction is an equilibrium reaction that can proceed in the reverse direction.

  In addition, when a catalyst is used for reforming, a methanation reaction may occur during the reforming. The methanation reaction is a reaction for generating methane from hydrogen and carbon monoxide or carbon dioxide, and is represented by formula (IV) or formula (V). Both reactions of formula (IV) and formula (V) are exothermic reactions, and the lower the temperature, the more methane. In addition, any reaction is an equilibrium reaction that can proceed in the reverse direction. For example, if the steam / carbon ratio is 3.0, the reforming temperature (reforming catalyst layer outlet temperature) is 700 ° C. or higher and the reaction pressure is approximately atmospheric pressure, methane in the reformed gas at the catalyst outlet wet The concentration is as low as about 0.3 mol% or less. The methanation reaction temperature is adjusted depending on how much cooling is performed by methane reforming inside the cell. For example, if the methanation reaction temperature (the methanation catalyst layer outlet temperature) is about 500 ° C., the methane concentration in the reformed gas with increased methane may be about 10 mol% when the pressure is about atmospheric pressure. it can.

C _n H _{2n + 2} + nH ₂ O → CO + (2n + 1) H ₂ (I)
_{C n H 2n + 2 + (} n / 2) O 2 → nCO + (n + 1) H 2 ... (II)
CO + H ₂ O → CO ₂ + H ₂ (III)
CO + 3H ₂ → CH ₄ + H ₂ O (IV)
CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O (V)

  When the SOFC stack 5 is operated, the reformed gas generated by the reformer 7 is supplied into the second chamber 55 from the reformed gas inflow portion 55a. In this case, water is not supplied into the first chamber 53, and the entire cooler 51 is maintained at a high temperature by the radiant heat from the SOFC stack 5. Therefore, even when the reformed gas is supplied to the second chamber 55, the methanation reaction is not promoted, and the reformed gas is supplied to the SOFC stack 5 in a hydrogen-rich state.

  On the other hand, when water is supplied into the first chamber 53 in order to cool the SOFC stack 5, the heat of the second chamber 55 is taken away by the evaporation heat of the water, and the methanation catalyst Ca is cooled. Then, the methanation reaction is promoted, and methane-rich reformed gas (methane-containing gas) is supplied to the anode electrode layer of the SOFC stack 5. Then, a reforming reaction that is an endothermic reaction occurs in the anode electrode layer, which contributes to cooling of the SOFC stack 5.

  In this embodiment, when the SOFC stack 5 is cooled by the cooler 51, the methanation catalyst Ca is also cooled, and methane-rich reformed gas is supplied to the SOFC stack 5 by promoting the methanation reaction. As a result, a reforming reaction that is an endothermic reaction occurs on the anode electrode layer of the SOFC stack 5, and the SOFC stack 5 can be cooled. In particular, by cooling from the inside of the SOFC stack 5 using a reforming reaction on the anode electrode layer, the entire SOFC stack 5 can be cooled more uniformly.

(Fourth embodiment)
A fuel cell module according to the fourth embodiment will be described with reference to FIG. FIG. 8 is a view showing a fuel cell module according to the fourth embodiment. The fuel cell module 3D will be described with a focus on differences from the fuel cell system 3A according to the first embodiment, and the same or equivalent elements and members will be described with the same reference numerals as the fuel cell system 3A in the drawings. Is omitted.

  The cooler 61 includes a casing portion 67 having a first chamber 63 and a second chamber 65. The casing part 67 consists of metals, such as stainless steel (SUS), for example. The casing portion 67 is disposed along the side surface 5b of the SOFC stack 5 with a gap S1 therebetween.

  The first chamber 63 is disposed on the inner side near the SOFC stack 5, and the second chamber 65 is disposed on the outer side far from the SOFC stack 5. An inflow portion 63a to which water as a cooling medium is supplied is formed at one end of the first chamber (cooling passage) 63, and an outflow portion 63b from which water vapor flows out is formed at the other end. Yes. The inflow part 63 a is connected to the water supply pipe 29, and the outflow part 63 b is connected to the water vapor pipe 22. Radiant heat from the SOFC stack 5 is received by the outer peripheral surface (heat receiving portion) 67 a of the casing portion 67, and the heat is taken away by the evaporation heat of the water supplied into the first chamber 63 to cool the SOFC stack 5. ing.

  The first chamber 63 is filled with particles 69 made of a material having high thermal conductivity. The material of the particles 69 can be appropriately selected from materials that can withstand the temperature and atmosphere, and examples thereof include ceramics such as alumina and silica, and metals such as stainless steel. Further, as the shape of the particle 69, an appropriate shape such as a sphere, a cylinder, a wedge, a rectangular parallelepiped, or the like can be adopted.

  By filling the first chamber 63 with the particles 69, the locations of bumping that are likely to occur when water is vaporized are dispersed, and the probability of multiple bumping occurring at the same time is reduced, greatly increasing the evaporation vibration due to bumping. Can be small. When bumping is reduced, the liquid phase and the gas phase can be stably formed in the first chamber 63, and the possibility of breakage of the cooler, piping, etc. due to the evaporation shock can be reduced.

  An air inflow portion 65 a into which air supplied to the cathode electrode layer of the SOFC stack 5 flows is formed at one end of the second chamber (preheating passage) 65, and the second chamber 65 is formed at the other end. An air outflow portion 65b for supplying preheated air to the cathode electrode layer of the SOFC stack 5 is formed. The preheating of the air in the second chamber 65 is performed by receiving the radiant heat of the SOFC stack 5.

  In the present embodiment, when the SOFC stack 5 is cooled by the cooler 61, the air passing through the second chamber 65 is also cooled. As a result, the cathode electrode layer of the SOFC stack 5 can be cooled more effectively.

(Fifth embodiment)
A fuel cell module according to a fifth embodiment will be described with reference to FIG. FIG. 9 is a view showing a fuel cell module according to the fourth embodiment. The fuel cell module 3E will be described mainly with respect to differences from the fuel cell system 3A according to the first embodiment, and the same or equivalent elements and members will be described with the same reference numerals as the fuel cell system 3A in the drawings. Is omitted.

  The cooler 71 includes a casing portion 77 having a first chamber 73 and a second chamber 75. The casing portion 77 is made of a metal having high thermal conductivity, for example, stainless steel (SUS). The casing portion 77 is disposed along the side surface 5b of the SOFC stack 5 with a gap S1 therebetween.

  The first chamber 73 is disposed inside the SOFC stack 5, and the second chamber 75 is disposed outside the SOFC stack 5. An inflow portion 75a to which water as a cooling medium is supplied is formed at one end of the second chamber (cooling passage) 75, and an outflow portion 75b from which water vapor flows out is formed at the other end. Yes. The inflow part 75 a is connected to the water supply pipe 29, and the outflow part 75 b is connected to the water vapor pipe 22. Radiation heat from the SOFC stack 5 is received by the outer peripheral surface (heat receiving portion) 77a of the casing portion 77, and the heat is taken away by the evaporation heat of the water supplied into the second chamber 75 to cool the SOFC stack 5. ing.

  An air inflow portion 73 a into which air supplied to the cathode electrode layer of the SOFC stack 5 flows is formed at one end of the first chamber (preheating passage) 73, and the first chamber 73 is formed at the other end. An air outflow portion 73b for supplying the preheated air to the cathode electrode layer of the SOFC stack 5 is formed. The preheating of the air in the first chamber 73 is performed by receiving the radiant heat of the SOFC stack 5.

  The first chamber 73 is filled with particles 81 made of a material having high thermal conductivity. The material of the particles 81 can be appropriately selected from materials that can withstand the temperature and atmosphere, and examples thereof include ceramics such as alumina and silica, and metals such as stainless steel. As the shape of the particle 81, an appropriate shape such as a sphere, a cylinder, a wedge, a rectangular parallelepiped, or the like can be adopted.

  By filling the particles 81 in the first chamber 73, heat transfer to the air can be promoted. In addition, heat is easily transferred to the second chamber 75 via the particles 81, and the SOFC stack 5 can be cooled more effectively using the heat of evaporation of water in the second chamber 75.

  In the present embodiment, when the SOFC stack 5 is cooled by the cooler 71, the air passing through the first chamber 73 is also cooled. As a result, the cathode electrode layer of the SOFC stack 5 can be cooled more effectively.

  Although the fuel cell modules 3A to 3E according to the first to fifth embodiments have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, the SOFC stack 5 has been described as an example. However, for example, a molten carbonate type (MCFC) stack or the like may be used. In the above embodiment, the SOFC stack 5 has a flat plate structure, but the present invention can also be applied to a fuel cell system including a cylindrical SOFC bundle (stack).

  In addition, the cooler can appropriately select a shape such as a rectangular or circular cross section, and a single or a plurality of coolers may be provided in the housing. Furthermore, a single or a plurality of cooling passages formed in the cooler can be provided. In the third embodiment, an example in which a cooling passage and a methane generation passage are formed in the cooler is shown. In the fourth or fifth embodiment, a cooling passage and a preheating passage are formed in the cooler. Although an example has been shown, it is possible to form the cooler by combining all of the cooling passage, the methane generation passage, and the preheating passage, and particles having high thermal conductivity such as metal particles in the cooling passage and the preheating passage. May be filled.

It is a figure which shows a part of cogeneration system provided with the fuel cell module which concerns on 1st Embodiment of this invention. It is a figure which shows the fuel cell module which concerns on 1st Embodiment. It is a sectional side view of a cooler. It is a flowchart which shows the operation | movement procedure of the stop process of a SOFC stack. It is a flowchart which shows the operation | movement procedure of the starting process of a SOFC stack. It is a figure which shows the fuel cell module which concerns on 2nd Embodiment. It is a figure which shows the fuel cell module which concerns on 3rd Embodiment. It is a figure which shows the fuel cell module which concerns on 4th Embodiment. It is a figure which shows the fuel cell module which concerns on 5th Embodiment.

Explanation of symbols

  3A, 3B, 3C, 3D, 3E ... fuel cell module, 5 ... SOFC stack (fuel cell stack), 7 ... reformer, 11 ... module container (housing), 13 ... heat receiving area, 15 ... heat dissipation area, 17 ... casing portion (cooling passage), 18, 57a, 67a, 77a ... outer peripheral surface of casing portion (heat receiving portion), 43 ... spiral pipe portion (cooling passage), 53, 63 ... first chamber (cooling passage) ), 55 ... second chamber (methane generation passage), 55a ... reformed gas inflow portion, 55b ... gas outflow portion (methane outflow portion), 65 ... second chamber (preheating passage), 73 ... first chamber (Preheating passage), 75 ... second chamber (cooling passage), Ca ... methanation catalyst.

Claims (6)

A fuel cell stack;
A cooler disposed around the fuel cell stack and cooling the fuel cell stack using heat of evaporation of a cooling medium;
A reformer that generates a reformed gas used for power generation of the fuel cell stack;
In the housing ,
The fuel cell stack has a heat receiving region facing the reformer, and a heat radiating region other than the heat receiving region,
The cooler is disposed along the heat dissipation area with a gap between the cooler and the fuel cell stack, and a heat receiving unit that receives radiant heat of the fuel cell stack, and a liquid phase and a gas phase of the cooling medium. A cooling passage in which a phase is formed and a methanation passage containing a methanation catalyst that promotes the methanation reaction,
The methane generation passage supplies a reformed gas inflow portion to which the reformed gas from the reformer is supplied and a methane-containing gas generated from the reformed gas by the methanation reaction to the fuel cell stack. And a methane effluent section that
The cooling passage has an inflow portion to which the cooling medium is supplied at one end and an outflow portion from which the vaporized cooling medium flows out at the other end, and the inflow portion is more fuel than the outflow portion. A fuel cell module, wherein the fuel cell module is provided at a position far from the battery stack . 2. The fuel cell module according to claim 1, wherein the cooler is disposed so as not to face the reformer. 3. The fuel cell module according to claim 1, wherein the cooling passage forms a meandering channel so as to approach the fuel cell stack stepwise from an upstream region toward a downstream region. The cooler includes a cooling passage in which a liquid phase and a gas phase of the cooling medium are formed, and a preheating passage for heating an oxygen-containing gas supplied to the fuel cell stack. 1-3 any one SL placing the fuel cell module of the. 5. The fuel cell module according to claim 4, wherein the preheating passage is filled with particles having higher thermal conductivity than the oxygen-containing gas. The fuel cell module according to any one of claims 1 to 5, wherein the cooling passage is filled with particles having higher thermal conductivity than the cooling medium.

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