JP2006086016A - Operation method of solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the operation method of a solid oxide fuel cell capable of shortening time to restarting after power supply is stopped and suppressing useless fuel gas and electric power to the minimum. <P>SOLUTION: In the operation method of the solid oxide fuel cell generating electric power by supplying the fuel gas and oxygen-containing gas to a power generation part, after power supply to a load is stopped, restarting is conducted at higher temperature than room temperature. After the power supply to the load is stopped, restarting is conducted in a state that heat energy in the power generating part in power generation remains. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of operating a solid oxide fuel cell that generates power by supplying a fuel gas and an oxygen-containing gas to a power generation unit.

  A high-temperature fuel cell such as a solid oxide fuel cell operates at an operating temperature of 600 ° C. to 1000 ° C. Conventionally, startup takes a time of one day or more and gradually increases the temperature to the operating temperature. It was. Also, in the operation method, since the base load operation is performed, it is not necessary to stop, and it has been considered that the operation is continuously performed until the maintenance is stopped. Also, the maintenance stop method is to gradually cool down while flowing a small amount of fuel gas or purge gas such as nitrogen, and cool to room temperature. Oxygen-containing gas was sometimes used for cooling.

As a conventional method for starting and stopping a phosphoric acid fuel cell, it is known to monitor the voltage of the fuel cell while flowing a small amount of purge gas and judge the stop control. The sequence is determined by the voltage of the fuel cell (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-144334

  However, in the conventional fuel cell, the temperature inside the fuel cell is forcibly lowered to room temperature when the fuel cell is stopped. There was a problem that it took time.

  Further, in the conventional method of stopping and starting the fuel cell, it is necessary to supply useless fuel gas that does not contribute to power generation or supply oxygen-containing gas used for cooling because cooling is performed while flowing fuel gas or the like at the time of stopping. Therefore, useless energy such as a drive power source for the blower is required.

  Furthermore, since it takes time to stop, it was necessary to monitor until it stopped completely, which led to further energy loss.

  In addition, since it takes time to start and stop, it is difficult to automatically determine whether or not to start and stop, and the start and stop are determined based on human judgment. For this reason, it is necessary to determine in what state driving start / stop is determined, which is troublesome.

  It is an object of the present invention to provide a method for operating a solid oxide fuel cell that can shorten the time required to restart after power supply is stopped, and can minimize wasteful fuel gas and electric power.

  An operation method of a solid oxide fuel cell according to the present invention is an operation method of a solid oxide fuel cell that generates power by supplying a fuel gas and an oxygen-containing gas to a power generation unit, and stops supplying power to a load. Thereafter, the next start-up is performed at a temperature higher than room temperature.

  The solid oxide fuel cell operation method of the present invention is a solid oxide fuel cell operation method for generating power by supplying a fuel gas and an oxygen-containing gas to a power generation unit, and supplying power to a load. After stopping, the next start-up is performed with the thermal energy of the power generation unit remaining during power generation.

  In such a solid oxide fuel cell operation method, after the operation is stopped, restart is performed in a state in which the thermal energy of the power generation unit remains at a temperature higher than room temperature or during power generation (during steady operation). In other words, since the power generation unit is restarted before it is cooled to room temperature, it is possible to significantly reduce the energy at start-up rather than starting from room temperature, and the operation sequence at start-up also depends on this operation temperature. The start-up time can be greatly shortened by omitting the start-up sequence or stepping up quickly. Furthermore, since it is not necessary to forcibly cool to room temperature at the time of stop, it can be stopped without consuming wasteful energy to stop the gas supply system.

  In the solid oxide fuel cell operation method of the present invention, the temperature at the next start after the power supply to the load is stopped is 40% or more of the temperature of the power generation unit during power generation. It is characterized by being. Thus, since the temperature at the time of restart is 40% or more of the temperature of the power generation unit during power generation (during steady operation), the start-up sequence can be largely omitted, and the start-up time can be further shortened.

  Furthermore, the operation method of the solid oxide fuel cell according to the present invention is characterized in that the time required to reach 40% of the temperature of the power generation unit during power generation is 6 hours or more. In such a solid oxide fuel cell operation method, since the heat retention of the solid oxide fuel cell is excellent, the startup sequence can be further omitted, and the startup time can be further shortened.

  In addition, the solid oxide fuel cell operating method of the present invention is characterized in that the temperature at the next start-up is 300 ° C. or higher after the supply of power to the load is stopped. Thus, since the temperature of the power generation unit at the time of restart is 300 ° C. or higher, the start-up sequence can be largely omitted, and the start-up time can be further shortened.

  Furthermore, the solid oxide fuel cell operation method of the present invention stops the supply of the fuel gas and the oxygen-containing gas to the power generation unit after the power supply is stopped, and uses the temperature of the power generation unit as a judgment criterion when restarting. By performing the operation sequence to be performed, the startup sequence from room temperature is omitted or quick step-up is performed according to the temperature of the power generation unit. Thereby, at the time of a stop, while stopping a gas supply system, it can stop, without consuming wasteful energy, and a quick start is attained.

  In addition, the solid oxide fuel cell operation method of the present invention is characterized by having a learning function, determining a stop time and a start time from past data of a load, and automatically performing a stop start. In addition, it has a timer function, and is stopped and started at an arbitrarily set time. Furthermore, it is characterized by stopping and starting by a stop / start switch. Furthermore, when the power supply from the solid oxide fuel cell to the external load continues for a certain period of time or longer, the solid oxide fuel cell is automatically stopped, The solid oxide fuel cell is automatically activated when power supply to the load continues for a certain period of time or longer. Further, it is characterized by performing a daily start tap (DSS) operation. The DSS operation is an operation method in which start / stop is performed once a day.

  In the present invention, after the operation is stopped, the temperature is higher than the room temperature, or in order to perform the restart with the thermal energy of the power generation unit remaining at the time of power generation (during steady operation), that is, while the power generation unit is not cooled to room temperature, Because it restarts, it is possible to significantly reduce the energy at startup compared to startup from room temperature, and the startup operation sequence can be omitted or quickly stepped up according to this operating temperature. By doing this, the startup time can be greatly reduced. Furthermore, since it is not necessary to cool to room temperature at the time of stop, it can be stopped without consuming wasteful energy to stop the gas supply system.

  Hereinafter, an example of a fuel cell assembly used in the method for operating a solid oxide fuel cell of the present invention will be described with reference to FIGS. The illustrated fuel cell assembly includes a housing 2 having a substantially rectangular parallelepiped shape. The outer surface of the six wall surfaces of the housing 2 is a heat insulating wall (heat insulating member) formed of an appropriate heat insulating material, that is, the upper heat insulating wall 4, the lower heat insulating wall 6, the right heat insulating wall 8, the left heat insulating wall 9, and the front A heat insulating wall 10 and a rear heat insulating wall 11 are provided. A power generation / combustion chamber 12 is defined in the housing 2.

  The front heat insulation wall 10 and / or the rear heat insulation wall 11 is detachably or removably attached, and the front heat insulation wall 10 and / or the rear heat insulation wall 11 is detached or opened to access the power generation / combustion chamber 12. be able to. If desired, an outer wall, which may be made of a metal plate, can be disposed on the outer surface of each heat insulating wall.

  An air chamber (gas chamber) 16 is disposed at the upper end of the housing 2. The air chamber 16 is defined in a rectangular parallelepiped case 17 having a relatively small vertical dimension. The air chamber 16 communicates with the upper end of an air introduction pipe (gas supply means) 22 for sending air (oxygen-containing gas) toward the power generation / combustion chamber. There are a plurality of air introduction pipes 22 and the shape thereof may be a cylinder or a hollow plate structure. 1 and 2, a cylindrical air introduction tube 22 is shown. The air introduction pipe 22 is disposed between the cell stacks described later, and has an opening at the lower end portion of the cell, and air is ejected from the opening portion. The air introduction tube 22 is preferably made of a material having high heat resistance such as ceramics.

  The air chamber 16 is provided with a low-temperature gas supply means including a low-temperature gas supply pipe 18. The low-temperature gas supply pipe 18 penetrates the upper heat insulating wall 4 and extends to the outside.

  The low-temperature gas supply pipe 18 supplies the same type of gas as that supplied into the air chamber 16, that is, low-temperature air, into the air chamber 16. The air supplied through the low-temperature gas supply pipe 18 is It must be cooler than the temperature of the preheated air. In particular, about room temperature is desirable.

  As shown in FIG. 2, the low temperature gas supply pipe 18 is connected to a position of the air chamber 16 that cools the power generation units 56a, 56b, 56c, and 56d, that is, the central portion of the fuel cell assembly. In other words, the air introduction pipe 22 disposed between the power generation units 56a, 56b, 56c, and 56d has a low temperature so as to open at the position of the opposing case 17 side plate with respect to the center of the opening assembly to the case 17 side plate. A gas supply pipe 18 is provided.

  A heat exchanger 24 having a flat plate shape as a whole is disposed on both sides of the housing 2, more specifically, inside the right heat insulating wall 8 and inside the left heat insulating wall 9. Each of the heat exchangers 24 is constituted by a case 26 having a hollow flat plate shape extending substantially vertically.

  A partition plate 28 located in the middle in the lateral direction is disposed in the case 26, and the inside of the case 26 is partitioned into a discharge path 30 positioned on the inner side and an inflow path 32 positioned on the outer side. Three partition walls 34 and 36 are arranged in the discharge path 30 at intervals in the vertical direction. More specifically, in the discharge passage 30, the front edge is located rearwardly away from the front wall (not shown) of the case 26, but the rear edge is the rear wall (not shown) of the case 26. And a partition wall 36 whose front edge is connected to the front wall of the case 26 but whose rear edge is spaced forward from the rear wall of the case 26. Are alternately arranged, and thus the combustion gas discharge passage 30 is zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  Similarly, the three partition walls 38 and 40, that is, the front edges thereof are also spaced apart from the front wall (not shown) of the case 26 in the inflow path 32 with a space in the vertical direction. The rear wall is connected to the rear wall (not shown) of the case 26, and the front edge of the partition wall 38 is connected to the front wall of the case 26. The partition walls 40 spaced apart from the front are alternately arranged, and thus the inflow passage 32 is also zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  A discharge opening 42 is formed at the upper end of the inner wall of the case 26, and the discharge path 30 is communicated with the power generation / combustion chamber 12 through the discharge opening 42. In the illustrated embodiment, heat storage walls (heat shielding members) made of a heat storage material are arranged on the power generation / combustion chamber 12 side of the heat exchanger 24, that is, on the fuel cell side and above and below the fuel cell. Has been. That is, the right heat storage wall 44a, the left heat storage wall 44b, the front heat storage wall 44c, the rear heat storage wall 44d, the upper heat storage wall 44e, and the lower heat storage wall 44f are disposed so as to surround the cell assembly. An opening 45 is formed in the upper part of the right heat storage wall 44 a and the left heat storage wall 44 b so as to be located at substantially the same height as the lower edge of the discharge opening 42, and the discharge opening 42 generates power through the opening 45. -It is connected to the combustion chamber 12.

The heat insulating walls 4, 6, 8, 9, 10, and 11 formed on the outer surface of the six wall surfaces of the housing 2 are formed of an alumina / silica general-purpose heat insulating material so as to surround the cell assembly. The heat storage walls 44 a, 44 b, 44 c, 44 d, 44 e, 44 f are formed from a heat insulating material having a higher alumina purity than the heat insulating materials 4, 6, 8, 9, 10. The heat insulating walls 4, 6, 8, 9, 10, 11 and the heat storage walls 44a, 44b, 44c, 44d, 44e, 44f may be formed of the same material, but the density of the heat storage material is larger than that of the heat insulating material. Is desirable. The heat insulating walls 4, 6, 8, 9, 10, 11 have a density of 0.26 g / cm ³ or less, and the heat storage walls 44a, 44b, 44c, 44d, 44e, 44f have a density of 0.32 g / cm ³ or less. The thermal conductivity of is preferably 0.1 to 0.4 W / (m · K).

  An inflow opening 48 is formed on the outer side of the upper wall of the case 26, and the inflow path 32 is communicated with the air chamber 16 through the inflow opening 48. The heat exchanger 24 and the inflow opening 48 constitute a gas supply channel. A double cylinder 50 (only the upper end portion is shown in FIG. 1) extending in the vertical direction is disposed behind each of the inflow passages 32. The double cylinder 50 is an outer cylinder member. 52 and an inner cylindrical member 54. The lower end of the discharge path 30 is connected to the lower end of the discharge path defined between the outer cylinder member 52 and the inner cylinder member 54, and the lower end of the inflow path 32 is defined in the inner cylinder member 54. Connected to the inflow channel.

  Thus, the configuration of the fuel cell assembly shown in the drawing is substantially the same as the fuel cell assembly disclosed in the specification and drawings of Japanese Patent Application No. 2003-295790 filed by the present applicant. Therefore, the details of the configuration described above are left to the specification and drawings of Japanese Patent Application No. 2003-295790, and the description thereof is omitted in this specification.

  Four power generation units 56a, 56b, 56c and 56d are arranged in the lower part of the above-described power generation / combustion chamber. The power generation units 56a, 56b, 56c, and 56d are respectively positioned between the air introduction pipes 22 described above. In other words, the air introduction pipe 22 is disposed between the power generation units 56a, 56b, 56c and 56d. 3 and 4 together with FIGS. 1 and 2, the power generation unit 56a includes a rectangular parallelepiped fuel gas case 58a extending in the front-rear direction (direction perpendicular to the paper surface in FIG. 1). .

  A cell stack 60a is mounted on the upper surface of the fuel gas case 58a that defines the fuel gas chamber. The cell stack 60a is configured by arranging a plurality of upright cells 62 extending in the vertical direction in the longitudinal direction of the fuel gas case 58a (that is, in the front-rear direction). As clearly shown in FIG. 5, each cell 62 includes an electrode support substrate 64, a fuel electrode layer 66 that is an inner electrode layer, a solid electrolyte layer 68, an oxygen electrode layer 70 that is an outer electrode layer, and an interconnector 72. Has been.

  The electrode support substrate 64 is a columnar plate-like piece that is elongated in the vertical direction, and the cross-sectional shape thereof has both flat surfaces and both sides of a semicircular shape. The electrode support substrate 64 is formed with a plurality (six in the illustrated example) of fuel gas passages 74 penetrating therethrough in the vertical direction. Each of the electrode support substrates 64 is bonded to the upper wall of the fuel gas case 58a by, for example, a ceramic adhesive having excellent heat resistance.

  On the upper wall of the fuel gas case 58a, a plurality of slits (not shown) extending in the left-right direction are formed at intervals in a direction perpendicular to the paper surface in FIG. A fuel gas passage 74 is communicated with the fuel gas chamber according to each of the slits.

  The interconnector 72 is disposed on one side of the electrode support substrate 64 (upper surface in the cell stack 60a in FIG. 5). The fuel electrode layer 66 is disposed on the other surface (the lower surface in the cell stack 60a of FIG. 5) and both side surfaces of the electrode support substrate 64, and both ends thereof are joined to both ends of the interconnector 72. The solid electrolyte layer 68 is disposed so as to cover the entire fuel electrode layer 66, and both ends thereof are joined to both ends of the interconnector 72. The oxygen electrode layer 70 is disposed on the main part of the solid electrolyte layer 68, that is, on the portion covering the other surface of the electrode support substrate 64, and is positioned to face the interconnector 72 with the electrode support substrate plate 64 interposed therebetween. Yes.

  A current collecting member 76 is disposed between adjacent cells 62 in the cell stack 60a, and connects the interconnector 72 of one cell 62 and the oxygen electrode layer 70 of the other cell 62. Current collecting members 76 are disposed on both ends of the cell stack 60a, that is, on one side and the other side of the cell 62 positioned at the upper end and the lower end in FIG. Electric power extraction means (not shown) is connected to the current collecting members 76 located at both ends of the cell stack 60a, and the electric power extraction means is the front heat insulation wall 10, the rear heat insulation wall 11 or the lower heat insulation wall of the housing 2. The material 6 extends outside the housing 2. If desired, the cell stacks 60a, 60b, 60c and 60d are connected in series with each other by appropriate connection means instead of disposing the power extraction means in each of the cell stacks 60a, 60b, 60c and 60d. Common power extraction means may be provided for the cell stacks 60a, 60b, 60c and 60d.

  More specifically about the cell 62, the electrode support substrate 64 is gas permeable to allow fuel gas to permeate to the anode layer 66, and is also conductive to collect current through the interconnector 72. Can be formed from a porous conductive ceramic (or cermet) that satisfies such requirements.

  In order to manufacture the cell 62 by co-firing with the fuel electrode layer 66 and / or the solid electrolyte layer 68, it is preferable to form the electrode support substrate 64 from the iron group metal component and the specific rare earth oxide. In order to provide the required gas permeability, it is preferred that the open porosity is in the range of 30% or more, in particular 35 to 50%, and the conductivity is also 300 S / cm or more, in particular 440 S / cm or more. Is preferred.

The fuel electrode layer 66 can be formed of a porous conductive ceramic, for example, ZrO ₂ (referred to as stabilized zirconia) in which a rare earth element is dissolved and Ni and / or NiO.

The solid electrolyte layer 68 has a function as an electrolyte for bridging electrons between electrodes, and at the same time needs to have a gas barrier property in order to prevent leakage between fuel gas and air. In general, it is formed from ZrO ₂ in which ₃ to 15 mol% of a rare earth element is dissolved.

The oxygen electrode layer 70 can be formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. The oxygen electrode layer 70 needs to have gas permeability, and the open porosity is preferably 20% or more, particularly preferably in the range of 30 to 50%.

Although the interconnector 72 can be formed from a conductive ceramic, it needs to have a reduction resistance and an oxidation resistance in order to come into contact with a fuel gas and air that may be hydrogen gas. A perovskite oxide (LaCrO ₃ oxide) is preferably used. The interconnector 72 must be dense in order to prevent leakage of fuel gas passing through the fuel gas passage 74 formed in the electrode support substrate 64 and air flowing outside the electrode support substrate 64, and is 93% or more. In particular, it is desired to have a relative density of 95% or more.

  The current collecting member 76 can be composed of a member having an appropriate shape formed of a metal or alloy having elasticity, or a member obtained by adding a required surface treatment to a felt made of metal fiber or alloy fiber.

  Continuing the description with reference to FIG. 4, the power generation unit 56 a also includes a reforming case 78 a that is preferably a rectangular parallelepiped shape (or a cylindrical shape) extending in the front-rear direction above the cell stack 60 a. . One end, that is, the upper end of the fuel gas supply pipe 80a is connected to the front surface of the reforming case 78a.

  The fuel gas supply pipe 80a extends downward, then curves and extends rearward, and the other end of the fuel gas supply pipe 80a is connected to the front surface of the fuel gas case 58a. One end of a reformed gas supply pipe 82a is connected to the rear surface of the reforming case 78a. The to-be-reformed gas supply pipe 82 a extends downward from the reforming case, and extends under the housing 2 and out of the housing 2.

  The to-be-reformed gas supply pipe 82a is connected to a to-be-reformed gas supply source (not shown) which may be a hydrocarbon gas such as city gas, and is connected to the reforming case 78a through the to-be-reformed gas supply pipe 82a. A gas to be reformed is supplied. An appropriate reforming catalyst for reforming the fuel gas into a hydrogen-rich fuel gas is accommodated in the reforming case 78a.

  In the illustrated embodiment, the reforming case 78a is connected to the fuel gas case 58a via the fuel gas supply pipe 80a and is held in a required position by this, but if necessary, the two-dot chain line in FIG. For example, an appropriate support member 84a can be provided between the lower surface of the reformed gas supply pipe 82a and the lower surface or rear surface of the rear end portion of the fuel gas case 58a.

  Referring to FIG. 3, the power generation unit 56c is substantially the same as the power generation unit 56a described above, and the power generation units 56b and 56d are disposed in the front-rear direction opposite to the power generation units 56a and 56c. Fuel gas supply pipes (not shown) connecting the quality cases 78b and 78d and the fuel gas cases 58b and 58d are arranged on the rear side, and the reformed gas supply pipes 82b and 82d are located downward from the reforming case. It extends under the housing 2 and extends out of the housing 2.

  In the fuel cell assembly as described above, the gas to be reformed is supplied to the reforming cases 78a, 78b, 78c and 78d via the gas to be reformed supply pipes 82a, 82b, 82c and 82d, and the reforming case 78a. , 78b, 78c and 78d, the fuel defined in the fuel gas cases 58a, 58b, 58c and 58d through the fuel gas supply pipes 80a, 80b, 80c and 80d after being reformed into hydrogen-rich fuel gas. It is supplied to the gas chamber and then supplied to the cell stacks 60a, 60b, 60c and 60d.

In each of the cell stacks 60a, 60b, 60c and 60d, at the oxygen electrode,
1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte)
The electrode reaction of
O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻
The electrode reaction is generated and power is generated.

  Fuel gas and air that have flown upward from the cell stacks 60a, 60b, 60c and 60d without being used for power generation are ignited by an ignition means (not shown) disposed in the power generation / combustion chamber 12 at the time of startup. It is ignited and burned. As is well known, the power generation / combustion chamber 12 has a high temperature of, for example, about 1000 ° C. due to power generation in the cell stacks 60a, 60b, 60c and 60d, and also due to combustion of fuel gas and air. The reforming cases 78a, 78b, 78c and 78d are disposed in the power generation / combustion chamber 12, and are positioned immediately above the cell stacks 60a, 60b, 60c and 60d, and are directly heated by the combustion flame. Thus, the high temperature generated in the power generation / combustion chamber 12 is effectively used for reforming the reformed gas.

  The combustion gas generated in the power generation / combustion chamber 12 flows into the discharge passage 30 from the discharge opening 42 formed in the heat exchanger 24, and flows through the discharge passage 30 extending in a zigzag shape. 50 is discharged through a discharge passage defined between the outer cylinder member 52 and the inner cylinder member 54. When the combustion gas flows through the discharge path in the double cylinder 50, air flows through the inflow path in the double cylinder 50, and heat exchange is performed between the combustion gas and air.

  Further, when the combustion gas is caused to flow in the exhaust passage 30 of the heat exchanger 24 in a zigzag manner, the air is caused to flow so as to face the inflow passage 32 of the heat exchanger 24 in a zigzag manner. Thus, heat is effectively exchanged between the combustion gas and air to preheat the air.

  When part or all of the cell stacks 60a, 60b, 60c and 60d deteriorates due to power generation over a long period of time, the front heat insulation wall 10 or the rear heat insulation wall 11 of the housing 2 is detached or opened. Part or all of the power generation units 56 a, 56 b, 56 c and 56 d are taken out from the housing 2.

  Then, replace some or all of the power generation units 56a, 56b, 56c and 56d with new ones, or only the cell stacks 60a, 60b, 60c and 60d in some or all of the power generation units 56a, 56b, 56c and 56d. May be replaced with a new one and mounted again at a required position in the housing 2. Even when it is necessary to replace the reforming catalyst accommodated in the reforming cases 78a, 78b, 78c and 78d in some or all of the power generation units 56a, 56b, 56c and 56d, the power generation units 56a, 56b , 56c and 56d are removed from the housing 2, and the reforming cases 78a, 78b, 78c and 78d themselves in the power generation units 56a, 56b, 56c and 56d are replaced with new ones or reforming cases. Only the reforming catalyst in 78a, 78b, 78c and 78d may be replaced with a new one.

  In order to be able to perform the replacement of the reforming catalyst in the reforming cases 78a, 78b, 78c and 78d sufficiently easily, a part of the reforming cases 78a, 78b, 78c and 78d can be opened and closed if desired. It can be put on the door.

  On the other hand, air is supplied to the inflow path 32 of the heat exchanger 24 through the inflow path defined in the inner cylinder member 54 of the double cylinder 50, and is preheated (heated) through the heat exchanger 24. Is temporarily stored in the air chamber 16 and supplied between the cell stacks of the combustion / power generation chamber 12 through the air introduction pipe 22. At this time, the air introduction pipe 22 passes through the combustion gas atmosphere that burns in the vicinity of the fuel gas passage 74 at the upper end of the fuel cell 62 of the cell stack 60. Accordingly, the preheated air in the air chamber 16 is further heated in the combustion region above the cell stack 60, and the air heated to a high temperature is supplied to the cell.

  During normal operation, air preheated by the heat exchanger 24 is introduced into the air chamber 16, and air is introduced from the air chamber 16 into the combustion / power generation chamber 12 using the air introduction pipe 22. When the temperature rises more than expected, the low-temperature air that has passed through the low-temperature gas supply pipe 18 that does not pass through the heat exchanger 24 is introduced into the air chamber 16 and preheated through the heat exchanger 24. And the air temperature of the air chamber 16 is reduced to some extent. By supplying this air between the power generation chambers 12, that is, between the cell stacks, air having a lower temperature than that during normal operation is introduced between the cell stacks. Therefore, a good fuel cell assembly that can appropriately control the temperature in the power generation chamber is provided.

  Moreover, since the air temperature in the air chamber 16 is mixed with the outside air supplied from the low temperature gas supply pipe 18 and the air preheated through the heat exchanger 24, the air temperature is not as low as room temperature. Even if the fuel cell 60 is supplied to the hot fuel cell 60, it is possible to avoid problems such as cracks and thermal shock destruction of the fuel cell 60, and to suppress the deterioration of the function of the entire fuel cell power generation system and to extend the life.

  Furthermore, by supplying the supply of the low temperature gas from the low temperature gas supply pipe 18 toward the center of the opening of the air supply pipe 22, the air heated from the heat exchangers on both sides is further directed to the center of the opening. The air supplied through the air supply pipe 22 to the center of the cell assembly that is most easily heated can be at the lowest temperature, and the temperature can be increased as the distance from the center increases. can do.

  In the fuel cell assembly of the present invention, the heat storage wall 44a, the left heat storage wall 44b, the front heat storage wall 44c and the rear heat storage wall 44d, the lower heat storage wall 44e, the upper heat storage wall are provided in the housing 2 and around the cell assembly. By disposing the wall 44f on the outer surface of the housing 2, the upper heat insulating wall 4, the lower heat insulating wall 6, the right heat insulating wall 8, the left heat insulating wall 9, the front heat insulating wall 10, and the rear heat insulating wall 11 are arranged. Can be effectively stored together with the heat storage wall and the heat insulating material, and in the fuel cell assembly for distributed power generation, during partial load operation with less heat generation In this case, the power generation temperature can be effectively maintained.

  In other words, fuel cell assemblies for distributed power generation such as home use are small in size because they generate little power, and they are self-sustaining and effectively generate power during steady operation, but the amount of power generated is reduced by reducing the amount of fuel gas. However, in the present invention, heat is effectively confined in the housing by the heat insulating wall, and the heat storage wall absorbs the high-temperature heat in the steady operation, so that the partial load is reduced. When operation is performed and the amount of heat generated is reduced, heat can be dissipated and the temperature inside the housing can be effectively maintained.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and various modifications and corrections can be made without departing from the scope of the present invention. It goes without saying that this is possible.

  For example, the present invention has been described in relation to a fuel cell assembly having a specific reforming case above the cell stack. However, the present invention can be applied even when the reforming case is not located above the cell stack. I can do it. Moreover, the case where a reforming case is not provided in a housing may be sufficient.

  Further, in the above embodiment, a case has been described in which low temperature gas supply means is provided in the air chamber and air is supplied to the outer surface of the fuel cell by the air supply pipe. However, the present invention provides the inside of the fuel cell by the air supply pipe. Of course, air may be supplied to the air. In this case, it goes without saying that an air electrode is formed inside the fuel cell and a fuel electrode is formed outside.

  Further, in the above embodiment, an example in which the low temperature gas supply means is provided in the air chamber has been described. However, it is of course possible to provide the low temperature gas supply means in the fuel gas chamber and cool the fuel cell with the fuel gas. It is.

  Furthermore, although the case where fuel gas and air react and burn above the fuel battery cell has been described in the above embodiment, the present invention may of course not burn.

  Hereinafter, the operation method of the solid oxide fuel cell of the present invention will be described based on the flowchart of FIG.

  First, the system is initialized (n-1) and the presence or absence of an initial abnormality is confirmed (n-2). When there is an abnormality, the emergency stop is performed (n-3).

  When there is no initial abnormality of the system components, the blower is started (n-4), and a predetermined flow rate of air is supplied into the storage container 2 through the air introduction pipe 22 while monitoring the flow rate with the flow rate monitor.

  Thereafter, the ignition (ignition) heater is turned on to start the heater (n-5). By this operation, preparation for ignition of surplus fuel gas discharged from above the fuel cell is performed.

  Since the temperature does not rise immediately even when the ignition heater is turned on, it is confirmed whether or not one minute or more has elapsed until ignition (n-6). After 1 minute or more has elapsed, power is turned on to the gas solenoid valve of the reformed gas (city gas) supply pipe, and the valve is opened to prepare for flowing city gas (n-7). A flow rate setting signal is sent to the city gas flow control device to supply city gas (n-8). Thereafter, the power of the air solenoid valve is turned on, the valve is opened, and preparations are made to flow air through the reforming case (n-9). The power of the air pump is turned on, the pump is driven, and preparations for flowing air are made (n-10). The flow rate of air is set (n-11), and air is supplied to the reforming case.

  Confirm the ignition confirmation (n-12). After the gas flow is finished, the temperature of the thermocouple temperature (combustion temperature) is checked after a lapse of 10 seconds, and if it is 100 ° C. or higher, it is assumed that ignition has occurred. If it is not ignited, return to startup.

  Thereafter, the ignition heater is turned off and the heater is stopped (n-13).

  It is confirmed whether it is possible to proceed from partial oxidation reforming (fuel and air) to ATR (autothermal reforming) (fuel, air and water) (n-14). When the measured temperature of the thermocouple, for example, the module temperature (power generation unit temperature) and the reforming inlet temperature are 200 ° C. and 650 ° C. or higher, the process proceeds to the next step.

  Thereafter, the ignition heater is started (n-15). Turn on the ignition heater and start the heater. Re-ignite again because the gas flow rate is changed. The ignition heater is operated for 5 minutes and then stopped.

  During the operation of the ignition heater, the flow rate of the water supplied to the reforming case is changed, and the water is flowed by the water pump (n-16). It is confirmed whether or not it is possible to proceed from ATR (autothermal reforming) (fuel, air, and water) to the transition zone (n-17). When the measured temperature of the thermocouple, for example, the module temperature and the reforming outlet temperature are 300 ° C. and 550 ° C. or higher, the process proceeds to the next step.

  The ignition heater is turned on to start the heater (n-18). Re-ignite again because the gas flow rate is changed. The ignition heater is operated for 5 minutes and then stopped. Change the flow rate of water and air while the ignition heater is operating. That is, the flow rate of the water pump is set to be constant, and water is supplied (n-19). The air flow rate is controlled and air is supplied (n-20).

  It is confirmed whether it is allowed to proceed from the transition section to SR (steam reform) (n-21). When the measured temperature of the thermocouple, for example, the module temperature and the reforming outlet temperature become 400 or 550 ° C. or more, the next step is started.

  Next, turn on the ignition heater and start the heater (n-22). Re-ignite again because the gas flow rate is changed. The ignition heater is operated for 5 minutes and then stopped.

During the operation of the ignition heater, the flow rate of water is changed at (n-23) to (n-26) to stop the air. That is, the water pump is set so that the flow rate of water becomes a predetermined amount, and water is allowed to flow (n-23).

  Set the air flow rate control to 0 and turn off the power (n-24). Thereafter, the power of the air pump is turned off and the pump is stopped (n-25). The power of the air solenoid valve is turned off and the valve is closed (n-26).

  Confirm whether it is OK to proceed to SR (Steam Reform) from the transition section. When the measured temperature of the thermocouple, for example, the module temperature (power generation unit temperature: temperature between the power generation units 56b and 56c) and the reforming outlet temperature are 650 and 550 ° C. or more, the next step is performed.

  In this way, the solid oxide fuel cell is started and is steadily operated. When the operation is stopped, first, output from the fuel cell to the load is stopped, and then supply of the reformed gas and oxygen-containing gas to the fuel cell is stopped. Safety devices and sensors may remain active. The start of the stop is shifted by the determination of the stop switch or the control unit. For stopping, a very small amount of fuel gas and water vapor are supplied from the operating temperature to the temperature at which the gas supply is stopped. Thereafter, shutdown may be performed. Since the oxygen-containing gas also serves as a gas purge for the fuel cell, it may be stopped after being supplied for several minutes. This makes it possible to reduce wasteful fuel gas and power consumption during operation. At this time, a shutdown may be performed to stop everything.

  After that, start-up is started. For example, this is a case where power generation is stopped at night and power generation is stopped and started in the morning. Thus, when restarting after a stop, it is desirable that the temperature of the power generation unit at the time of restarting is higher than room temperature, for example, 300 ° C. or higher. In other words, the temperature is preferably 40% or more of the temperature of the power generation unit during power generation. This is a state in which the thermal energy of the power generation unit remains at the time of power generation. At the time of restart, the higher the temperature of the power generation unit, that is, the more heat energy remaining in the power generation unit. It is desirable to start. In this case, activation can be performed quickly.

  In the solid oxide fuel cell described above, heat can be effectively confined in the housing by the heat insulating wall and the heat storage wall, and the time until the temperature reaches 40% of the temperature of the power generation unit during power generation is 6 hours or more. Can be long. In other words, since heat energy can remain in the power generation unit for a long time, the system of the present invention can be used to quickly restart after stopping.

  That is, in the operation method of the solid oxide fuel cell of the present invention, after the output is stopped, the heat can be effectively confined in the housing by the heat insulating wall and the heat storage wall, so that the temperature in the housing is not easily lowered. Using this property, it is characterized in that it is not forced to cool to room temperature. Conventionally, cooling is performed by a blower or the like, but the present invention is characterized by not cooling. Thus, since the cooling to room temperature is not performed, the temperature of the fuel cell or the temperature of the reforming portion remains sufficiently high at the next start-up. For this reason, in the operation at the time of starting operation, a part of the starting sequence from room temperature is omitted or rapidly stepped up according to the temperature of the power generation unit and / or the temperature of the reforming unit.

  In other words, the temperature of the power generation unit and / or the temperature of the reforming unit may be determined, and may be advanced from the middle of the startup sequence, or may be performed according to the procedure from room temperature. Thus, it is possible to proceed to the next step one after another. For this reason, a battery output can be performed in a short time with respect to the conventional starting from room temperature.

  By doing in this way, it became possible to cope with various start and stop methods. For example, it has become possible to cope with DSS operation, which has been impossible in the past, without losing energy. Here, the daily start tap (DSS operation) is an operation method of starting and stopping once a day, for example, starting in the morning, driving (power generation) during the day and night, and stopping at midnight. is there.

  In addition, the solid oxide fuel cell operation method of the present invention has a learning function, calculates a stop activation time from past data of the load, automatically performs a stop activation, has a timer function, and is optional. Stop and start at the set time, stop and start by the stop and start switch, and automatically when the power supply from the solid oxide fuel cell to the external load continues for a certain time or more The solid oxide fuel cell is automatically stopped when the power supply from the system power to the external load continues for a certain period of time or longer. An operation can also be performed.

  Using a fuel cell as shown in FIG. 1, the start switch is pushed, and the fuel cell is started according to the flowchart shown in FIG. 6, and the power generation units 56b, 56c that are the center of the four power generation units 56a, 56b, 56c, and 56d of the fuel cell. The gas to be reformed is controlled so that the temperature of the thermocouple placed in between is 750 ° C, and the temperature of the thermocouple placed on the outlet side of the reformer is 500-600 ° C, and steady operation is performed. It was. It took 2 hours from pressing the start switch to steady operation.

  Thereafter, the stop switch was pressed to stop the output from the fuel cell to the load, and the supply of the reformed gas and the oxygen-containing gas to the fuel cell was stopped. A small amount of fuel gas and water vapor were supplied from the operating temperature to the temperature at which the gas supply was stopped.

  6 hours after the power supply to the load was stopped, the start switch was pushed to restart. The temperature at the center of the power generation unit at the time of restart was 450 ° C. (60% of the temperature of the power generation unit), and the outlet side temperature of the reformer was 400 ° C.

  In the start-up, since the operation at 450 ° C. or lower in the flowchart of FIG. 6 is omitted or stepped up in a short time, the time required for the steady operation is 48 minutes.

  When restarting is started 8 hours after the stop, the temperature at the center of the power generation unit at the time of restart is 380 ° C. (50% of the temperature of the power generation unit), and the time required for steady operation is 72. For minutes.

  Furthermore, when restarting is started 4 hours after stopping, the temperature at the center of the power generation unit at the time of restart is 560 ° C. (74% of the temperature of the power generation unit), and the time required for steady operation is 32. For minutes.

  From these experiments, it can be seen that steady operation can be achieved in a shorter time than when starting from room temperature. Moreover, since it is not necessary to cool a power generation part to room temperature, it turns out that the gas required for cooling is unnecessary and waste can minimize the amount of gas used.

Sectional drawing which shows the suitable form of the solid oxide form fuel cell used for this invention. The top view of the fuel cell of FIG. The perspective view which shows the electric power generation unit of the fuel cell of FIG. The perspective view which shows the cell stack of the fuel cell of FIG. Sectional drawing which shows a cell stack. The flowchart which shows the operating method of the solid oxide fuel cell of this invention.

Explanation of symbols

2: Housing 12: Power generation / combustion chamber 16: Air chamber (gas chamber)
18: Low temperature gas supply pipe 22: Air introduction pipe (gas supply pipe)
24: Heat exchangers 56a, 56b, 56c and 56d: Power generation units 58a, 58b, 58c and 58d: Fuel gas cases 60a, 60b, 60c and 60d: Cell stack 62: Fuel cell 78a, 78b, 78c and 78d: Modified Quality case

Claims (11)

An operation method of a solid oxide fuel cell that generates power by supplying fuel gas and oxygen-containing gas to a power generation unit, and after the power supply to a load is stopped, the next start-up is performed at a temperature higher than room temperature. A method for operating a solid oxide fuel cell. A method of operating a solid oxide fuel cell that generates power by supplying a fuel gas and an oxygen-containing gas to a power generation unit, and after the power supply to a load is stopped, the thermal energy of the power generation unit during power generation is allowed to remain A method for operating a solid oxide fuel cell, characterized in that the next start-up is performed in a state. 3. The solid oxide according to claim 1, wherein the temperature at the next start after the power supply to the load is stopped is 40% or more of the temperature of the power generation unit during power generation. Fuel cell operation method. The method for operating a solid oxide fuel cell according to any one of claims 1 to 3, wherein the time until the temperature of the power generation unit reaches 40% of the temperature during power generation is 6 hours or more. The method for operating a solid oxide fuel cell according to any one of claims 1 to 4, wherein the temperature at the next start after the power supply to the load is stopped is 300 ° C or higher. . After the power supply is stopped, supply of fuel gas and oxygen-containing gas to the power generation unit is stopped, and at the time of restart, an operation sequence is performed based on the temperature of the power generation unit as a criterion. 6. The method for operating a solid oxide fuel cell according to claim 1, wherein a part of a startup sequence from room temperature is omitted or rapid step-up is performed. 7. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell has a learning function, calculates a stop time and a start time from past load data, and automatically performs a stop start. Driving method. The solid oxide fuel cell operating method according to any one of claims 1 to 6, further comprising a timer function, wherein the operation is stopped and started at an arbitrarily set time. The solid oxide fuel cell operating method according to any one of claims 1 to 6, wherein the operation is stopped and started by a stop / start switch. When the power supply from the solid oxide fuel cell to the external load continues for a certain time or longer, the solid oxide fuel cell is automatically stopped and the power from the system power to the external load is The solid oxide according to any one of claims 1 to 6, wherein the solid oxide fuel cell is automatically activated when power supply continues for a certain period of time or longer. Fuel cell operation method. The method for operating a solid oxide fuel cell according to any one of claims 1 to 6, wherein a daily start stick (DSS) operation is performed.

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