JP2010092836A - Fuel battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery system capable of maintaining combustion stability of a combustion section even under load following operation. <P>SOLUTION: The fuel battery system (FCS) has a control means to control under load following operation to make a fuel utilization ratio, that is a proportion of a heat volume used for power generation reaction of a fuel battery cell to a total heat volume of fuel supplied to the fuel battery cell (4), lower under a low-load zone with a small current output than that of a high-load zone with a larger current output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a fuel cell device, and more particularly to a fuel cell device that generates electric power following a required load.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, has electrodes attached to both sides thereof, supplies fuel gas on one side, and supplies the other This is a fuel cell device that generates power by supplying an oxidant (air, oxygen, etc.) to the side of the tube and generating a power generation reaction at a relatively high temperature.

  More specifically, this fuel cell apparatus (SOFC) includes a plurality of fuel cell cells that operate when fuel gas and oxidant (air, oxygen, etc.) flow from one end side to the other end side. After being supplied with reformed gas (city gas, etc.) as fuel from outside, the city gas is introduced into a reformer containing a reforming catalyst, and reformed into hydrogen-rich fuel gas Supplying to a plurality of fuel cells.

  By the way, in a fuel cell device including such a fuel cell module, the amount of fuel gas or oxidant gas (air) supplied to the fuel cell is increased or decreased according to the amount of electric power to be extracted, and so-called load following operation is performed. Are proposed in the following Patent Documents 1 to 3.

JP 2005-285433 A JP 2007-103194 A JP 2007-123139 A

However, in the above-described conventional fuel cell device, as shown in FIG. 11, when the load follows, even if the output current value changes, the fuel utilization rate (= total amount of fuel supplied to the fuel cell) The ratio of the amount of heat used for the power generation reaction of the fuel cell to the amount of heat) was constant in order to achieve energy saving by making the power generation efficiency constant and reducing the amount of fuel supplied. However, in practice, when the load is followed, when the shift is made from the high load region to the low load region, the fuel supply to the combustion chamber (combustion part) is drastically reduced, so that the combustion state in the combustion chamber becomes unstable, and As a result, the temperature in the fuel cell module rapidly decreases, which makes it difficult to maintain the temperature of the fuel cell in a narrow temperature range necessary for the power generation reaction.
Furthermore, since the reformer is placed in the combustion chamber, it is difficult to maintain the temperature required for the reforming reaction, and the reforming reaction balance (in the case of the steam reforming reaction, the balance between the heat absorption amount and the combustion heat amount) is lost. The reformed gas composition becomes non-uniform and the fuel supplied to the fuel cell also has an adverse effect.

  Accordingly, the present invention has been made to solve the problems of the prior art, and maintains the combustion stability of the combustion portion and the fuel cell when shifting from the high load region to the low load region during load following. It aims at providing the fuel cell device which can maintain the temperature of a cell in a desired temperature zone.

In order to achieve the above object, the present invention provides a fuel cell device that generates power by following a required load, a fuel cell assembly including a plurality of fuel cells arranged in a module, A reformer that is disposed in the combustion section at the top of the fuel cell assembly in the module, reforms the fuel, a fuel supply means that supplies fuel to the reformer, and supplies reforming air to the reformer Reforming air supply means, power generation air supply means for supplying power generation air to the fuel cell assembly, fuel supply means and power generation air supply means based on the current value output from the fuel cell assembly Control means for controlling the fuel, and one of the fuel and the air for power generation is supplied into the flow path of the fuel cell of the fuel cell assembly, and the fuel and the air for power generation are out of the flow path of the fuel cell. The other is supplied, and The remaining fuel and the remaining power generation air that were not used for the combustion of the fuel burned, and the control means, when following the load, controls the amount of heat used for the power generation reaction of the fuel cell with respect to the total amount of fuel supplied to the fuel cell. It is characterized by comprising a fuel utilization rate changing means for making the fuel utilization rate, which is a ratio, lower in a low load region that outputs a small current value than in a high load region that outputs a large current value.
When shifting from a high load region to a low load region during load following, the fuel supply to the combustion section suddenly decreases, so the combustion state becomes unstable, and the temperature in the module rapidly decreases accordingly. Therefore, it becomes difficult to maintain the temperature of the fuel cell in a narrow temperature range necessary for the power generation reaction.
Furthermore, since the reformer is disposed in the combustion section, it is difficult to maintain the temperature required for the reforming reaction, the balance of the reforming reaction is lost, and the fuel supplied to the fuel cells is adversely affected.
On the other hand, in the present invention, the fuel utilization rate is lower in the low load region than in the high load region, so that the amount of heat of the remaining fuel that has not been used for the power generation reaction is increased, and in the combustion part The amount of heat of the fuel is maintained almost constant. Further, since the temperature of the fuel cell is also maintained, it does not take time for reheating. Further, in the reformer, the heat quantity of the fuel in the combustion section is maintained almost constant, so that the balance of the reforming reaction is maintained and the optimum fuel can be supplied to the fuel cells. As a result, according to the present invention, when shifting from the high load region to the low load region, the temperature of the fuel cell can be maintained in a narrow temperature band, and the optimum fuel is supplied to the fuel cell, An efficient power generation reaction can be performed.

In the present invention, preferably, the fuel utilization rate changing means of the control means lowers the fuel utilization rate by increasing the amount of fuel supplied by the fuel supply means.
In the present invention configured as described above, the fuel utilization rate can be lowered without changing or drastically changing the current value, so that control that satisfies the required power is possible.

In the present invention, preferably, the fuel utilization rate changing means of the control means lowers the fuel utilization rate by reducing the current value output from the fuel cell assembly.
In the present invention configured as described above, a small amount of generated power is exhibited with respect to the required power. However, since the amount of fuel supply is reduced, the economy is improved.

In the present invention, preferably, the fuel utilization rate changing means of the control means lowers the fuel utilization rate by increasing the amount of fuel supplied by the fuel supply means and lowering the current value output from the fuel cell assembly. .
In the present invention configured as described above, since the fuel supply amount is increased and the current value is also decreased, a large increase in the fuel supply amount can be suppressed, and the economic efficiency is improved. Further, since the current value is changed to be small, the load on the fuel cell assembly is reduced, and the fuel utilization rate can be accurately reduced while improving the durability.

In the present invention, it is preferable that the control means has an air utilization rate that is a ratio of a flow rate used for a power generation reaction of the fuel battery cell with respect to a total flow rate of power generation air supplied to the fuel battery cell during load following. The power generation air supply means is controlled to be lower in the low load region than in the high load region.
In the present invention configured as described above, as described above, the air utilization rate is similarly reduced in the low load region in correspondence with the fact that the fuel utilization rate is lower in the low load region than in the high load region. It was made lower than the high load area. As a result, according to the present invention, the fuel easily burns in the combustion section even in the low load region. Furthermore, in a high load region, even if the air utilization rate is increased, there is no problem because a sufficient amount of air for power generation has already been supplied, and the inside of the module is cooled by the supply of excess air. Can be prevented.

In the present invention, preferably, the fuel utilization rate changing means of the control means decreases the rate of decrease in the fuel utilization rate as the load increases in a load region smaller than a predetermined load.
In the present invention thus configured, in a load region smaller than a predetermined load (for example, a load region having a current value of 4 A or less), the absolute amount of fuel supplied on the high load side is relatively large, and the fuel cell The cell temperature is also maintained sufficiently, and a sufficient amount of heat is also supplied to the reformer. By reducing the rate of decrease in the fuel utilization rate toward the higher load side (slowly), wasted fuel Can be prevented from being burned and consumed in the combustion section, and the power generation efficiency can be increased.

In the present invention, preferably, the control means controls the power generation air supply means so that the rate of decrease in the air utilization rate is smaller as the load is higher in a load region smaller than a predetermined load.
In the present invention configured as described above, as described above, in the load region smaller than the predetermined load, the rate of decrease in the air utilization rate corresponding to the decrease in the rate of decrease in the fuel utilization rate toward the higher load side. Similarly, the higher the load side, the smaller. As a result, according to the present invention, an amount of air necessary for fuel combustion can be secured in the fuel section.

In the present invention, preferably, in the load region smaller than the predetermined load, the control means is configured such that the rate of decrease in the fuel utilization rate decreases as the load increases, and the rate of decrease in the air utilization rate decreases as the load increases. Further, the fuel supply means and the power generation air supply means are controlled so that the rate of decrease in the air utilization rate becomes smaller than the rate of decrease in the fuel utilization rate as the load becomes lower.
In the present invention configured as described above, in a load region smaller than a predetermined load (for example, a load region having a current value of 4 A or less), the rate of decrease in the air utilization rate is made smaller than the rate of decrease in the fuel utilization rate. Therefore, in the low load region, it is possible to secure the minimum amount of air necessary for fuel to burn in the combustion section, and to prevent the inside of the module from being cooled by excessive air supply Can do.

In the present invention, preferably, the control means controls the power generation air supply means so that the rate of decrease in the air utilization rate becomes substantially zero in a load region larger than a predetermined load during load following.
In the present invention configured as described above, there is no problem because a sufficient amount of power generation air has already been supplied in a load region larger than a predetermined load, and there is no problem caused by changing the air supply amount. It is possible to prevent the balance between maintaining the temperature of the fuel battery cell from being lost due to stable combustion.

The present invention preferably further comprises fuel part temperature detecting means for detecting the temperature of the combustion part, and the control means is fuel supply means so that the temperature of the combustion part becomes equal to or higher than the self-ignition temperature of hydrogen as a fuel. To control.
In the present invention configured as described above, since the temperature of the combustion section is set to be equal to or higher than the self-ignition temperature of hydrogen as the fuel, the fuel combustibility becomes more reliable in the fuel section, and as a result, the fuel cell The temperature of the cell can also be maintained in a necessary narrow temperature range, and the reformer can maintain an optimum reforming reaction and can maintain an efficient power generation reaction.

  The present invention relates to a fuel cell device that generates power by following a required load, a fuel cell assembly including a plurality of fuel cells arranged in a module, and a fuel cell assembly in the module. A reformer disposed in the upper combustion section for reforming fuel; fuel supply means for supplying fuel to the reformer; reforming air supply means for supplying reforming air to the reformer; and fuel A fuel cell assembly comprising: a power generation air supply means for supplying power generation air to the battery cell assembly; and a control means for controlling the fuel supply means based on a current value output from the fuel cell assembly. One of the fuel and the air for power generation is supplied into the flow path of the fuel cell of the body, and the other of the fuel and the air for power generation is supplied outside the flow path of the fuel cell, and is used for the power generation reaction in the combustion section. There was no residual fuel and residual power generation air When the load follows the load, the control means outputs a small current value when the fuel utilization rate, which is the ratio of the amount of heat used for the power generation reaction of the fuel cell to the total amount of fuel supplied to the fuel cell, is low. The fuel supply means is controlled to be lower in the load region than in the high load region where a large current value is output.

  According to the fuel cell device of the present invention, when shifting from a high load region to a low load region during load following, the combustion stability of the combustion section is maintained and the temperature of the fuel cell is maintained in a desired temperature band. Can do.

1 is a perspective view showing a fuel cell module in a state in which a cover member of a fuel cell device according to a first embodiment of the present invention is removed. It is sectional drawing which looked at the fuel cell module of the fuel cell apparatus by 1st Embodiment of this invention from the A direction of FIG. It is sectional drawing which looked at the fuel cell module of the fuel cell apparatus by 1st Embodiment of this invention from the B direction of FIG. It is a front view which shows the fuel cell unit of the fuel cell apparatus by 1st Embodiment of this invention. 1 is a perspective view showing a fuel cell stack of a fuel cell device according to a first embodiment of the present invention. It is a perspective view of the fuel cell module which shows the state which removed the flow-path member from the fuel cell module shown in FIG. It is a perspective view of the fuel cell module which shows the state which removed the fuel cell unit, the reformer, etc. from the fuel cell module shown in FIG. It is the schematic which shows the fuel cell module of the fuel cell apparatus by 1st Embodiment of this invention. 1 is a block diagram showing a fuel cell device according to a first embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by 1st Embodiment of this invention. It is a diagram which shows the relationship between the electric current value at the time of the electric power generation driving | operation in the fuel cell apparatus by 1st Embodiment of this invention, and a fuel utilization factor. It is a whole block diagram which shows the fuel cell apparatus by 2nd Embodiment of this invention. It is front sectional drawing which shows the fuel cell module of the fuel cell apparatus by 2nd Embodiment of this invention. It is sectional drawing along the XIV-XIV line | wire of FIG. It is a fragmentary sectional view which shows the fuel cell unit of the fuel cell apparatus by 2nd Embodiment of this invention. It is a perspective view which shows the fuel cell stack of the fuel cell apparatus by 2nd Embodiment of this invention. It is a block diagram which shows the fuel cell apparatus by 2nd Embodiment of this invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by 2nd Embodiment of this invention. It is a time chart which shows the driving | running | working state at the time of load tracking which changes a power generation output value corresponding to the required power generation amount of the fuel cell apparatus by 2nd Embodiment of this invention. It is a figure which shows the fuel supply control characteristic (relationship between target electric power generation amount and fuel gas supply amount) in the fuel cell apparatus by 2nd Embodiment of this invention. It is a figure which shows the fuel supply control characteristic (relationship between the target electric power generation amount and the air supply amount for electric power generation) in the fuel cell apparatus by 2nd Embodiment of this invention. It is a diagram which shows the relationship between the electric current value at the time of the electric power generation driving | operation in the fuel cell apparatus by 2nd Embodiment of this invention, a fuel utilization factor, and an air utilization factor.

Hereinafter, a fuel cell device according to an embodiment of the present invention will be described with reference to the drawings.
First, a fuel cell device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a fuel cell module in a state where a cover member of the fuel cell device according to the first embodiment of the present invention is removed, and FIG. 2 is a diagram of the fuel cell device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the fuel cell module as viewed from the direction A of FIG. 1, and FIG. 3 is a cross-sectional view of the fuel cell module of the fuel cell device according to the first embodiment of the present invention as viewed from the direction B of FIG.

  The cover member (not explicitly shown in FIGS. 1 and 3, the outer shape of which is shown by a two-dot chain line in FIG. 2) includes a front side wall, a pair of longitudinal side walls, a back side wall, a ceiling, Is formed in a rectangular parallelepiped shape. A flange portion is formed at the lower end portion of each side wall, and a space sealed by the cover member and the base member 2 is formed by bringing the flange portion into contact with the base member 2. The cover member and the base member 2 are fixed by bolts (not shown), and the bolts pass through attachment holes provided in the cover member, and are fixed by passing through attachment holes 2a provided in the base member 2. ing.

  The internal space formed by the cover member and the base member 2 is separated into two spaces by the partition plate 15. Among the spaces separated by the partition plate 15, the space where the fuel cell stack 90 is disposed is the power generation chamber 16. Among the spaces separated by the partition plate 15, the other space is an exhaust gas chamber 17 (exhaust gas chamber). The inner wall surface of the cover member and the partition plate 15 are in close contact with each other directly or indirectly through some kind of contact member (for example, a flexible thin plate member).

  The partition plate 15 is placed on a support member 15 a provided on the base member 2 and is held at a predetermined distance from the base member 2. A pair of support members 15a are provided so as to support the partition plate 15 at both ends in the longitudinal direction. Accordingly, a gap 15b (inlet) is formed between the pair of support members 15a and 15a. Exhaust gas that has passed through an exhaust gas passage (not shown) provided on the wall surface of the cover member is introduced into the exhaust gas chamber 17 through the gap 15b. The exhaust gas introduced into the exhaust gas chamber 17 is exhausted from the exhaust port 11 (outlet) to the outside.

  The gas tank 3 is placed on the partition plate 15. Ten fuel cell stacks 90 are arranged side by side in the gas tank 3, and fuel gas is supplied from the gas tank 3 to the fuel cell 4 constituting each fuel cell stack 90.

  More specifically, an opening (not shown) having substantially the same shape as the lower support plate 90b of the fuel cell stack 90 is provided on the upper surface of the gas tank 3, and the lower support plate 90b is in close contact with the opening. Thus, the gas tank 3 and each fuel cell stack 90 are connected. Accordingly, the fuel cells 4 constituting the fuel cell stack 90 are erected on the gas tank 3 with their tip portions facing upward.

  Each fuel battery cell 4 has a tubular shape, and a gas flowing from one end of the fuel battery cell 4 to the other end inside the pipe of the fuel battery cell 4 and outside the pipe from the one end to the other end. It operates by the action of the gas flowing to the part. In the present embodiment, the gas flowing in the pipe of the fuel battery cell 4 is a fuel gas such as reformed gas obtained by reforming hydrogen or hydrocarbon fuel, and the gas flowing outside the pipe of the fuel battery cell 4 contains oxygen. An oxidant gas (air for power generation) such as air.

  Next, the fuel cell unit 30 including the fuel cells 4 will be described with reference to FIG. FIG. 4 is a front view showing the fuel cell unit of the fuel cell apparatus according to the first embodiment of the present invention. As shown in FIG. 4, the fuel cell unit 30 is a tubular structure formed by the fuel cells 4 and extending in the vertical direction, and includes a cylindrical fuel cell 4 and one end of the fuel cell 4. It has an inner electrode terminal 40 attached to 4a, and an outer electrode terminal 42 attached to the other end 4b.

  The fuel cell 4 includes a cylindrical inner electrode layer 44, a cylindrical outer electrode layer 48, a cylindrical electrolyte layer 46 disposed between the electrode layers 44, 48, and an inner electrode. And a through flow channel 50 configured inside the layer 44. Further, an inner electrode exposed peripheral surface 44a in which the inner electrode layer 44 is exposed to the electrolyte layer 46 and the outer electrode layer 48 at one end 4a of the fuel cell 4, and the electrolyte layer 46 is an outer electrode layer. An electrolyte exposed peripheral surface 46 a exposed to 48 is provided. The other end 4b of the fuel cell 4 is configured by an outer electrode exposed peripheral surface 48a from which the outer electrode layer 48 is exposed. The through channel 50 functions as a fuel gas channel. The inner electrode exposed peripheral surface 44 a is also an inner electrode outer peripheral surface that is in electrical communication with the inner electrode layer 44. The outer electrode exposed peripheral surface 48 a is also an outer electrode outer peripheral surface that is in electrical communication with the outer electrode layer 48.

  The inner electrode layer 44 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, ceria doped with at least one selected from Ni and rare earth elements, And a mixture of Ni and lanthanum gallate doped with at least one selected from Sr, Mg, Co, Fe, and Cu. The electrolyte layer 46 includes, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following. The outer electrode layer 48 is made of, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni, and Cu, Sr, Fe, Ni, and Cu. It is formed from at least one selected from lanthanum cobaltite doped with at least one selected from silver and silver. In this case, the inner electrode layer 44 becomes a fuel electrode, and the outer electrode layer 48 becomes an air electrode. The thickness of the inner electrode layer 44 is, for example, 1 mm, the thickness of the electrolyte layer 46 is, for example, 30 μm, the thickness of the outer electrode layer 48 is, for example, 30 μm, and the outer diameter is For example, it is 1-10 mm.

  The inner electrode terminal 40 is arranged so as to cover the inner electrode exposed peripheral surface 44a from the outside over the entire circumference and is electrically connected to the inner electrode terminal 40a, and a tubular shape extending from the main body portion 40a in the longitudinal direction of the fuel cell 4. Part 40b. The main body portion 40a and the tubular portion 40b are cylindrical and concentrically arranged, and the tube diameter of the tubular portion 40b is smaller than the tube diameter of the main body portion 40a. The tubular portion 40b has a connection channel 40c that communicates with the through channel 50 and communicates with the outside. A step portion 40 d between the main body portion 40 a and the tubular portion 40 b is in contact with the end surface 44 b of the inner electrode layer 44.

  The outer electrode terminal 42 is disposed so as to cover the outer electrode exposed peripheral surface 48a from the outside over the entire circumference and is electrically connected thereto, and a tubular shape extending from the main body portion 42a in the longitudinal direction of the fuel cell 4. Part 42b. The main body portion 42a and the tubular portion 42b are cylindrical and concentric, and the tube diameter of the tubular portion 42b is smaller than the tube diameter of the main body portion 42a. The tubular portion 42b has a connection channel 42c that communicates with the through channel 50 and communicates with the outside. A step portion 42 d between the main body portion 42 a and the tubular portion 42 b is in contact with the outer electrode layer 48, the electrolyte layer 46, and the end surface 44 c of the inner electrode layer 44 via the annular insulating member 52.

  The overall shape of the inner electrode terminal 40 and the overall shape of the outer electrode terminal 42 are the same. Further, the inner electrode terminal 40 and the fuel battery cell 4, and the outer electrode terminal 42 and the fuel battery cell 4 are sealed and fixed by a conductive sealing material 54 over the entire circumference. The sealing material 54 is various brazing materials including, for example, silver, a mixture of silver and glass, gold, nickel, copper, and titanium.

  The connection flow path 40 c of the inner electrode terminal 40, the through flow path 50 of the fuel cell 4, and the connection flow path 42 c of the outer electrode terminal 42 constitute an in-pipe flow path 30 c of the fuel cell unit 30.

  Next, the fuel cell stack 90 including the fuel cell unit 30 will be described with reference to FIG. FIG. 5 is a perspective view showing the fuel cell stack of the fuel cell device according to the first embodiment of the present invention. The fuel cell stack 90 includes 16 fuel cell units 30, an upper support plate 90a, a lower support plate 90b, a connection member 90c, and an external terminal 90d.

  The upper support plate 90a and the lower support plate 90b are rectangular, and are through holes (fitting holes) that fit into the tubular portions 40b and 42b of the fuel cell unit 30 so as to support the fuel cell unit 30 in 2 columns × 8 rows, respectively. (Not shown in the figure). The upper support plate 90a and the lower support plate 90b are formed of an electrically insulating material, for example, formed of heat resistant ceramics. Specifically, it is preferable to use alumina, zirconia, spinel, forsterite, magnesia, titania or the like.

  The 16 fuel cell units 30 are arranged so that they are electrically connected in series. Specifically, the fuel cell units 30 are arranged so that the inner electrode terminals 40 of the adjacent fuel cell units 30 are alternately arranged on the upper side and the lower side. Further, a connection member 90c for electrically connecting the 16 fuel cell units 30 in series is provided. The connection member 90 c electrically connects one adjacent inner electrode terminal 40 and one outer electrode terminal 42. Each of the inner electrode terminal 40 and the outer electrode terminal 42 at both ends of the 16 fuel cell units 30 connected in series is provided with an external terminal 90d for electrical connection with the outside. The connection member 90c and the external terminal 90d are made of, for example, a heat resistant metal such as stainless steel, a nickel base alloy, or a chromium base alloy, or a ceramic material such as lanthanum chromite. The external terminals 90d of each fuel cell stack 90 are electrically connected in series, and are connected to the electrode rods 13 and 14 at both ends thereof.

  As described with reference to FIGS. 4 and 5, in the fuel cell stack 90, the end 4 a of the fuel cell unit 30 where the inner electrode terminal 40 is provided and the end where the outer electrode terminal 42 is provided. The parts 4b are arranged so as to alternate with each other.

  Here, returning to FIGS. 1 to 3, the description of the fuel cell module FC will be continued. In the following description, reference is also made to FIGS. 6 is a perspective view of the fuel cell module showing a state in which the flow path member 7 is removed from the fuel cell module shown in FIG. 1, and FIG. 7 shows the fuel cell unit and the reformer from the fuel cell module shown in FIG. 2 is a perspective view of a fuel cell module showing a state in which a container 5, a fuel cell stack 90, and a gas tank 3 are removed. FIG. In the present embodiment, the reformer 5 is disposed so as to be positioned above the fuel cell stack 90. The reformer 5 is connected to a pipe 6C (pipe) and a pipe 6D, and the pipe 6C and the pipe 6D allow the reformer 5 to move upward with a predetermined distance from the fuel cell stack 90. Is held in place. The pipe 6 </ b> C is a pipe for supplying city gas, air (reforming air) and water vapor as reformed gas to the reformer 5, and is erected with respect to the partition plate 15. The pipe 6 </ b> D is a pipe for supplying the fuel gas reformed in the reformer 5 to the gas tank 3, and is erected with respect to the gas tank 3.

  The city gas and air supplied to the reformer 5 through the pipe 6C are introduced into the fuel cell module FC through the reformed gas supply pipe 6A. The steam supplied to the reformer 5 through the pipe 6C is introduced into the fuel cell module FC through the steam supply pipe 6B (pipe). The to-be-reformed gas supply pipe 6A and the water vapor supply pipe 6B are connected to a mixing chamber 15c provided on the opposite side of the pipe 6C with the partition plate 15 in between. The city gas and air supplied from the reformed gas supply pipe 6A and the water vapor supplied from the steam supply pipe 6B are mixed in the mixing chamber 15c and supplied to the pipe 6C.

  Although not explicitly shown in FIGS. 1 to 3, in this embodiment, electromagnetic valves are attached to the reformed gas supply pipe 6 </ b> A and the steam supply pipe 6 </ b> B, respectively, and each electromagnetic valve is output from a CPU as a control unit. The ratio of the gas to be reformed, air, and water vapor supplied to the reformer 5 can be changed by opening and closing according to the instruction signal.

  City gas (which may be mixed with steam) and air (which may be only reformed gas) as reformed gas introduced into the reformer 5 are contained in the reformer 5. The reforming catalyst is reformed. The reformed fuel gas is supplied to the gas tank 3 through the pipe 6D. The portion where the pipe 6C is connected to the reformer 5 and the portion where the pipe 6D is connected to the reformer 5 are separated from each other in the vicinity of one end and the other end in the longitudinal direction. As a result, the fuel gas and air supplied to the reformer 5 can sufficiently come into contact with the reforming catalyst.

  A reforming catalyst is enclosed in the reformer 5. As the reforming catalyst, a catalyst in which nickel is applied to the surface of the alumina sphere and a catalyst in which ruthenium is applied to the surface of the alumina sphere are appropriately used. These reforming catalysts are spheres.

  In the present embodiment, the flow path member 7 is provided so as to cover the reformer 5 and each fuel cell stack 90. The flow path member 7 has air flow path outer walls 71 and 72, an air distribution chamber 73, air collecting chambers 74 and 75, air flow path pipes 76a, 76b, 77a, and 77b, and outer walls 78 and 79. Yes. The flow path member 7 is formed such that the air flow path outer walls 71 and 72 are arranged in the longitudinal direction and the outer walls 78 and 79 are arranged in the short direction, respectively, and are formed into a box shape by these members. The flow path member 7 is erected on the partition plate 15 so as to cover the reformer 5 and each fuel cell stack 90. In the following description, the side of the flow path member 7 that is in contact with the partition plate 15 will be referred to as the lower side, and the side opposite to the lower side will be referred to as the upper side.

  The air distribution chamber 73 is attached to the upper outside of the outer wall 79. That is, the air distribution chamber 73 is attached to the outside of the box-shaped body formed by the air flow path outer walls 71 and 72 and the outer walls 78 and 79 and above the short side. An air supply pipe 7A is connected to the air distribution chamber 73, and air as an oxidant gas is supplied. Air flow passages 76a, 76b, 77a, 77b are also connected to the air distribution chamber 73.

  The air flow path pipes 76a and 76b are arranged along the air flow path outer wall 71 on the inner side of the box-shaped body formed by the air flow path outer walls 71 and 72 and the outer walls 78 and 79 and above the longitudinal side. Yes. The air channel tube 76a is disposed on the air channel outer wall 71 side, and the air channel tube 76b is disposed on the inner side of the air channel tube 76a. One end of each of the air flow path pipes 76 a and 76 b passes through the outer wall 79 and is connected to the air distribution chamber 73, and the other end is connected to the air collecting chamber 74. Therefore, the air that has flowed into the air distribution chamber 73 flows through the air flow path pipes 76a and 76b into the air collecting chamber 74 and rejoins.

  The air flow path pipes 77a and 77b are arranged along the air flow path outer wall 72 on the inner side and the upper side of the box-shaped body formed by the air flow path outer walls 71 and 72 and the outer walls 78 and 79. Yes. The air flow path pipe 77a is disposed on the air flow path outer wall 72 side, and the air flow path pipe 77b is disposed on the inner side of the air flow path pipe 77a. One end of each of the air passage pipes 77 a and 77 b passes through the outer wall 79 and is connected to the air distribution chamber 73, and the other end is connected to the air collecting chamber 75. Accordingly, the air flowing into the air distribution chamber 73 flows through the air flow path pipes 77a and 77b into the air collecting chamber 75 and rejoins.

  The air collecting chambers 74 and 75 are attached to the upper inside of the outer wall 78. That is, the air collecting chambers 74 and 75 are attached to the inside of the box-like body formed by the air flow path outer walls 71 and 72 and the outer walls 78 and 79 and above the short side. The air collecting chamber 74 is disposed so as to be in close contact with the air flow path outer wall 71, and the air that has flowed into the air collecting room 74 is configured to flow out to the air flow path outer wall 71. On the other hand, the air collecting chamber 75 is disposed so as to be in close contact with the air flow path outer wall 72, and the air flowing into the air collecting chamber 75 is configured to flow out to the air flow path outer wall 72.

  Each of the air flow path outer walls 71 and 72 has a double wall structure, and is configured so that air can flow through each of them. More specifically, the air flow path outer wall 71 has a structure divided into three chambers from above, and is formed as a first chamber 91, a second chamber 92, and a third chamber 93 in this order from above. The air that flows from the air collecting chamber 74 flows into the first chamber 91, then flows into the second chamber 92, and then flows into the third chamber 93. Similarly, the air flow path outer wall 72 is also divided into three chambers from above, and is formed as a first chamber 94, a second chamber 95, and a third chamber 96 in order from the top. The air flowing from the air collecting chamber 75 flows into the first chamber 94, then flows into the second chamber 95, and then flows into the third chamber 96.

  In the third chambers 93 and 96, a plurality of air inflow holes 93a and 96a are formed at predetermined intervals, respectively. The air inflow holes 93a and 96a are located in the direction in which the fuel cell stack 90 is connected to the gap between the fuel cells 4 and the vertical positions relative to the fuel cells 4 are substantially the same. A plurality of them are formed.

  The air flowing into the air flow path outer walls 71 and 72 is configured to flow into the vicinity of the fuel cell 4 in the power generation chamber 16 through the air inflow holes 93a and 96a. The air (power generation air) that flows through the air inflow holes 93 a and 96 a flows from the lower side to the upper side of each fuel cell 4 through the outside of the fuel cell 4. Air (power generation air) reaching above each fuel cell 4 is combusted together with the fuel gas that has passed through the pipe flow path of each fuel cell 4.

  Above each fuel cell stack 90 is a combustion section 18 in which air (power generation air) and fuel gas are mixed and burned. The fuel gas rises from the gas tank 3 through the in-pipe flow path 30 c of the fuel cell unit 30 toward the combustion unit 18. Further, the air flowing outside the fuel cell 4 also rises toward the combustion unit 18. An ignition device insertion hole 97 is provided in a portion of the air flow path outer wall 72 corresponding to the combustion portion 18, and an ignition device (not shown) for starting combustion of combustion gas and air burns from the ignition device insertion hole 97. Projected to the portion 18. The ignition device mixes and burns fuel gas and air. The fuel cells 4 constituting the fuel cell stack 90 are heated from above by the combustion unit 18. In addition, the air flowing through the air inflow holes 93a and 96a is also heated by the combustion in the combustion section 18 while passing through the air passage pipes 76a, 76b, 77a and 77b and the air passage outer walls 71 and 72 as described above. Is done.

  As described above, the exhaust gas generated when the fuel gas and air are mixed and burned in the combustion section 18 flows into the exhaust gas chamber 17 through the gap 15b. This inflow route will be described with reference to FIG. FIG. 8 is a schematic view showing a fuel cell module of the fuel cell device according to the first embodiment of the present invention. As shown in FIG. 8, in the combustion unit 18, exhaust gas generated by mixing and burning fuel gas and air (power generation air) passes through an exhaust gas passage 1 a formed in the cover 1. It faces downward and flows into the exhaust gas chamber 17 from the gap 15b. The exhaust gas flowing into the exhaust gas chamber 17 is exhausted from the exhaust port 11 to the outside.

  Next, the configuration of the fuel cell FCS using the fuel cell module FC will be described with reference to FIG. FIG. 9 is a block diagram showing the fuel cell device according to the first embodiment of the present invention. As shown in FIG. 9, the fuel cell FCS includes a fuel cell module FC, a fuel supply unit FP, a first air supply unit (power generation air supply unit) AP1, and a second air supply unit (reforming air supply). Part) AP2, water supply part WP, electric power extraction part EP, temperature acquisition part TD (temperature acquisition part), and control part CS (control part). The fuel supply unit FP, the first air supply unit AP1, the second air supply unit AP2, the water supply unit WP, and the power extraction unit EP constitute an auxiliary device AD of the fuel cell FCS.

  The fuel supply unit FP is a part that supplies city gas to the fuel cell module FC as reformed gas from a city gas pipe as a fuel supply source, and includes a fuel pump and an electromagnetic valve. The reformed gas supplied from the fuel supply unit FP is sent out to the reformed gas supply pipe 6A.

  The first air supply unit (power generation air supply unit) AP1 is a part that supplies air from the atmosphere as an air supply source to the fuel cell module FC, and includes an air blower and an electromagnetic valve. The air supplied from the first air supply part AP1 is sent out to the air supply pipe 7A.

  The second air supply unit (reforming air supply unit) AP2 is a part that supplies air from the atmosphere as an air supply source to the fuel cell module FC, and includes an air blower and an electromagnetic valve. The air supplied from the second air supply part AP2 is sent out to the reformed gas supply pipe 6A and mixed with the reformed gas supplied from the fuel supply part FP.

  The water supply unit WP is a part that supplies water from a water pipe as a water supply source to the fuel cell module FC, and includes a water pump and an electromagnetic valve. The water supplied from the water supply part WP becomes water vapor inside the fuel cell module FC and is sent to the water vapor supply pipe 6B.

  The power extraction unit EP is a part that extracts electric power from the fuel cell module FC, and includes a power conversion device such as an inverter. The power extraction unit EP is connected to the electrode rods 13 and 14, and the converted power is configured to be sent to a power supply destination.

The temperature acquisition unit TD is a part that acquires the temperature of the combustion unit 18 directly or indirectly. In the case of this embodiment, the temperature acquisition unit TD is configured to indirectly acquire the temperature of the combustion unit 18, detects the temperature of the reformer 5, and controls a signal indicating the temperature of the reformer 5. Output to part CS. In the control part CS, the temperature of the combustion part 18 is estimated based on this signal. The reason for estimating the temperature of the combustion section 18 is based on the correlation between the combustion section temperature measured in advance and the reformer temperature. As a mode in which the temperature acquisition unit TD detects the temperature of the reformer 5, it is preferable that the temperature sensor is in contact with the upper surface of the reformer 5. In this case, the temperature in the reformer 5 is calculated based on the correlation between the temperature inside the reformer and the temperature outside the reformer measured in advance.
In addition, when the temperature acquisition unit TD directly acquires the temperature of the combustion unit 18, a temperature sensor is disposed in the combustion unit 18. The control unit CS is a part for controlling each of the fuel supply unit FP, the first air supply unit AP1, the second air supply unit AP2, the water supply unit WP, and the power extraction unit EP, and includes a CPU and a ROM. Have. The operation of the fuel cell module FC as described above is executed based on an instruction signal from the control unit CS. The control unit CS controls the reformer 5 to supply only the gas to be reformed and the steam when at least the temperature acquisition unit TD detects that the reformer 5 has a temperature capable of steam reforming. Thereby, in the reformer 5, an autothermal reforming reaction described later proceeds.

  Next, the operation of the fuel cell system FCS (fuel cell device) including the fuel cell module FC according to the present embodiment and the operation method thereof will be described with reference to FIG. FIG. 10 is a time chart showing the operation at the start-up of the fuel cell device according to the first embodiment of the present invention.

  At the start of the fuel cell system FCS (fuel cell device), first, in order to warm the fuel cell module FC, the circuit including the fuel cell module FC is not loaded, that is, the circuit including the fuel cell module FC is opened. In this state, fuel gas and air are supplied to the fuel cell module FC. At this stage, even if fuel gas and air are present, no current flows through the circuit, so the fuel cell module FC does not generate power.

  Specifically, fuel gas is supplied. Specifically, the reformed gas is supplied from the fuel supply unit FP to the reformed gas supply pipe 6A. At this time, the control unit CS outputs a signal to the air blower and the like of the fuel pump and the fuel supply unit FP so as to supply fuel gas including city gas and air (reforming air). FIG. 10 shows the control voltage of the fuel pump and the control voltage of the air blower of the fuel supply unit FP. The reformed gas supplied from the reformed gas supply pipe 6A passes through the reformer 5 and is stored in the gas tank 3 as fuel gas. Thereby, uniform and uniform supply of fuel gas to each fuel cell unit 30 is ensured. The fuel gas accumulated in the gas tank 3 flows through the in-pipe channel 30 c of the fuel cell unit 30 and acts on the inner electrode layer 44. The fuel gas that did not act reaches the upper space of each fuel cell unit 30.

  Also, air in the atmosphere (power generation air) is supplied. Specifically, the air supply unit AP supplies the air to the air supply pipe 7A, and guides it from the air inflow holes 93a and 96a into the power generation chamber 16 through the path as described above. The air introduced into the power generation chamber 16 (power generation air) acts on the outer electrode layer 48. The air that did not act (power generation air) reaches above each fuel cell unit 30 (fuel cell 4).

  Next, fuel gas and air (power generation air) are combusted using an ignition device (not shown). The resulting exhaust gas becomes hot. The exhaust gas flows into the exhaust gas chamber 17 through the cover 1 (see FIG. 8). The exhaust gas that has flowed into the exhaust gas chamber 17 is discharged from the exhaust port 11.

  When the fuel gas and air (power generation air) are combusted, the temperature in the power generation chamber 16 is raised. Air (power generation air) introduced from the outside is heated by exchanging heat with the power generation chamber 16 while flowing through the above-described path. The hot exhaust gas flows into the exhaust gas chamber 17 and raises the temperature in the exhaust gas chamber 17.

  Subsequently, a gas obtained by mixing hydrocarbon-based city gas and air (reforming air) in advance is supplied to the reformer 5 (reforming step). In the reformer 5, the partial oxidation reforming reaction POX of the formula (1) proceeds. Since this partial oxidation reforming reaction is an exothermic reaction, the startability is good. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction continues in the combustion section 18.

_{C m H n + m / 2} O 2 → m CO + n / 2 H 2 (1)

  In the present embodiment, the partial oxidation reforming reaction POX according to the formula (1-1) is performed in two stages before the partial oxidation reforming reaction POX according to the formula (1). ing. When the temperature of the reformer 5 is lower than a predetermined temperature (for example, about 450 degrees), the amount of air supplied to the reformer 5 is reduced as shown in the formula (1-1), and methane is Suppresses excessive conversion to hydrogen.

C _m H _n + _{m / 8} O ₂ → _{m / 4} CO + _{n / 8} H ₂ +3 _{m / 4} C _m H _n (1-1)

  When the partial oxidation reforming reaction POX according to the equation (1-1) is performed and the temperature of the reformer 5 is equal to or higher than a predetermined temperature (for example, about 450 degrees), the above equation (1) is obtained. In addition, the amount of hydrogen supplied to the reformer 5 is increased to control the amount of hydrogen to be increased. The predetermined temperature used in this control is a temperature set in advance as the temperature of the reformer 5 when the temperature of the combustion unit 18 becomes the reference temperature. The reference temperature corresponds to a temperature at which the hydrogen combustion rate is higher than the hydrogen diffusion rate, and is a temperature set in advance by an experiment or the like.

  After a predetermined time has elapsed since the execution of the partial oxidation reforming reaction POX, a gas in which city gas, air and water vapor are mixed in advance is supplied to the reformer 5. At this time, the control unit CS outputs a signal to a fuel pump, an air blower of the fuel supply unit FP, a water pump, and the like so as to supply water vapor in addition to city gas and fuel gas including air. FIG. 10 shows the control voltage of the water pump. In the reformer 5, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used together proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 5 while being thermally independent. That is, heat generation by the partial oxidation reforming reaction POX is dominant when there is a large amount of oxygen, and heat absorption by the steam reforming reaction SR is dominant when there is a lot of water vapor. At this stage, the initial stage of activation has already passed, and the temperature inside the power generation chamber 16 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, the temperature does not drop significantly. Even if the autothermal reforming reaction ATR proceeds, the combustion reaction continues in the combustion section 18.

  When the temperature acquisition unit TD detects that the reformer 5 has a temperature capable of steam reforming after a predetermined time has elapsed from the start of the execution of the autothermal reforming reaction, the gas previously mixed with city gas and steam is modified. Supply to the mass device 5. At this time, the control unit CS outputs a signal to the fuel pump and the water pump so as to supply water vapor in addition to the fuel gas containing only the city gas, and stops the air blower of the second air supply unit AP2. Output a signal.

  In the reformer 5, the steam reforming reaction SR of the formula (2) proceeds. Since this steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance by the combustion heat from the combustion section 18. At this stage, since the power generation chamber 16 has already been heated to a sufficiently high temperature since it is already the final stage of start-up, there is no significant temperature drop even if the endothermic reaction is the main component. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion section 18.

_{C m H n + m H 2} O → m CO + (n / 2 + m) H 2 (2)

  As described above, the temperature in the power generation chamber 16 is gradually increased by switching the reforming process in accordance with the progress of the combustion process from the ignition process. When the temperature in the power generation chamber 16 and the fuel cell 4 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module FC is stably operated, the circuit including the fuel cell module FC is closed. Thereby, the fuel cell module FC starts power generation, and a current flows through the circuit. Due to the power generation of the fuel cell, the fuel cell 4 itself also generates heat, and the temperature of the fuel cell 4 rises. As a result, the temperature reaches a rated temperature at which the fuel cell module FC is operated, for example, 600 to 800 ° C.

  Thereafter, in order to maintain the rated temperature, fuel gas and air in an amount larger than the amount of fuel gas and air consumed by the fuel battery cell 4 are supplied, and combustion in the power generation chamber 16 is continued. Let During power generation, power generation proceeds with a steam reforming reaction SR with high reforming efficiency. The steam reforming reaction SR itself (strictly speaking) is performed at about 400 ° C. to 800 ° C., but is operated at about 500 ° C. to 700 ° C. in combination with a fuel cell.

  During this power generation, load following operation is executed. In the case of this embodiment, since the rated current is 7 A, when the required current value is smaller than the rated current value, the operation for suppressing the generated current value is set as the load following operation. In the case of the present embodiment, the control unit CS sets the amount of reformed gas (city gas amount) supplied when the current value is 7A to 2.7 L / min, and supplies the reformed gas when the current value is 2A. The gas amount (city gas amount) is 1.5 L / min. When compared with the fuel utilization rate, the fuel utilization rate is about 68% when the current value is 7A, and the fuel utilization rate is about 35% when the current value is 2A.

  FIG. 11 is a graph showing the relationship between the current value and the fuel utilization rate. Here, as described above, the fuel utilization rate is the ratio of the amount of heat used for the power generation reaction of the fuel cell to the total amount of heat of the fuel supplied to the fuel cell. As shown in FIG. 11, conventionally, since the fuel utilization rate was controlled to be constant as described above, the amount of reformed gas to be supplied is reduced when the generated current value is small. Therefore, the amount of fuel gas supplied to the fuel battery cell 4 is reduced, and as a result, the amount of fuel gas reaching the combustion unit 18 as the remaining fuel gas is insufficient. Therefore, in the present embodiment, when the current value to be generated is small, control is performed to lower the fuel utilization rate, thereby increasing the amount of the reformed gas to be supplied and the fuel gas supplied to the fuel cell 4 also. As a result, the amount of fuel gas reaching the combustion section 18 as the remaining fuel gas is ensured. For this reason, in the combustion part 18 of the fuel cell module FC of this embodiment, generation | occurrence | production of malfunctions, such as defective combustion, can be suppressed.

  In addition, the control unit CS of the present embodiment acquires the temperature of the combustion unit 18 and adjusts the amount of reformed gas to be supplied so that the acquired temperature does not fall below the ignition temperature of hydrogen. . Therefore, in addition to the control described above, the combustion stability of the combustion unit 18 can be further ensured.

Next, a fuel cell device according to a second embodiment of the present invention will be described with reference to FIGS.
FIG. 12 is an overall configuration diagram showing a fuel cell device according to a second embodiment of the present invention. As shown in FIG. 12, a fuel cell device 101 that is a solid oxide fuel cell (SOFC) according to an embodiment of the present invention includes a fuel cell module 102 and an auxiliary unit 104.

  The fuel cell module 102 includes a housing 106, and a sealed space 108 is formed inside the housing 106 via a heat insulating material (not shown, but the heat insulating material is not an essential component and may not be necessary). Is formed. A fuel cell assembly 112 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 110 that is a lower portion of the sealed space 108. The fuel cell assembly 112 includes ten fuel cell stacks 114 (see FIG. 16), and the fuel cell stack 114 is composed of 16 fuel cell units 116 (see FIG. 15). Yes. Thus, the fuel cell assembly 112 has 160 fuel cell units 116, and all of these fuel cell units 116 are connected in series.

A combustion chamber 118 is formed above the above-described power generation chamber 110 in the sealed space 108 of the fuel cell module 102. In this combustion chamber 118, residual fuel gas and residual oxidant (air) that have not been used for the power generation reaction are formed. ) And combusted to generate exhaust gas.
Further, a reformer 120 for reforming the fuel gas is disposed above the combustion chamber 118, and the reformer 120 is heated to a temperature at which the reforming reaction can be performed by the combustion heat of the residual gas described above. is doing. Further, an air heat exchanger 122 for receiving combustion heat and heating air is disposed above the reformer 120.

  Next, the auxiliary unit 104 stores a water from a water supply source 124 such as a water supply and uses a filter to obtain a pure water tank 126, and a water flow rate for adjusting the flow rate of the water supplied from the water storage tank. An adjustment unit 128 (such as a “water pump” driven by a motor) is provided. The auxiliary unit 104 also includes a gas shut-off valve 132 that shuts off the fuel gas supplied from the fuel supply source 130 such as city gas, a desulfurizer 136 that removes sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 138 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 104 includes an electromagnetic valve 142 that shuts off air that is an oxidant supplied from the air supply source 140 and a reforming air flow rate adjustment unit 144 that adjusts the flow rate of air (driven by a motor “ An air blower ”) and a power generation air flow rate adjustment unit 145 (such as an“ air blower ”driven by a motor), a first heater 146 for heating the reforming air supplied to the reformer 120, and a power generation chamber And a second heater 148 that heats the power generation air supplied to the. The first heater 146 and the second heater 148 are provided in order to efficiently raise the temperature at startup, but may be omitted.

Next, a hot water production apparatus 150 to which exhaust gas is supplied is connected to the fuel cell module 102. The hot water production apparatus 150 is supplied with tap water from a water supply source 124, and the tap water is heated by the heat of the exhaust gas to be supplied to a hot water storage tank of an external water heater (not shown).
The fuel cell module 102 is provided with a control box 152 for controlling the amount of fuel gas supplied and the like.
Further, the fuel cell module 102 is connected to an inverter 154 which is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module to the outside.

Next, the internal structure of the fuel cell module of the fuel cell device according to the embodiment of the present invention will be described with reference to FIGS. 13 and 14. FIG. 13 is a side sectional view showing a fuel cell module of a fuel cell device according to a second embodiment of the present invention, and FIG. 14 is a sectional view taken along line XIV-XIV in FIG.
As shown in FIGS. 13 and 14, in the sealed space 108 in the housing 106 of the fuel cell module 102, as described above, the fuel cell assembly 112, the reformer 120, and the air heat exchange are sequentially arranged from below. A device 122 is arranged.

  The reformer 120 is provided with a pure water introduction pipe 160 for introducing pure water and a to-be-reformed gas introduction pipe 162 for introducing reformed fuel gas and reforming air on the upstream end side thereof. In the reformer 120, an evaporator 120a and a reformer 120b are formed in this order from the upstream side, and the reformer 120b is filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 120 are reformed by the reforming catalyst filled in the reformer 120. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

  A fuel gas supply pipe 164 is connected to the downstream end side of the reformer 120, and the fuel gas supply pipe 164 extends downward and further in a manifold 166 formed below the fuel cell assembly 112. It extends horizontally. A plurality of fuel supply holes 164b are formed in the lower surface of the horizontal portion 164a of the fuel gas supply pipe 164, and the reformed fuel gas is supplied into the manifold 166 from the fuel supply holes 164b.

  A lower support plate 168 having a through hole for supporting the above-described fuel cell stack 114 is attached above the manifold 166, and the fuel gas in the manifold 166 enters the fuel cell unit 116. Supplied.

  Next, an air heat exchanger 122 is provided above the reformer 120. The air heat exchanger 122 includes an air aggregation chamber 170 on the upstream side and two air distribution chambers 172 on the downstream side. The air aggregation chamber 170 and the air distribution chamber 172 include six air flow channel tubes 174. Connected by. Here, as shown in FIG. 14, the three air flow path pipes 174 form a set (174a, 174b, 174c, 174d, 174e, 174f), and the air in the air collecting chamber 170 is in each set. The air flows from the air flow pipes 174 to the respective air distribution chambers 172.

The air flowing through the six air flow path tubes 174 of the air heat exchanger 122 is preheated by the exhaust gas that burns and rises in the combustion chamber 118.
An air introduction pipe 176 is connected to each of the air distribution chambers 172, and the air introduction pipe 176 extends downward, and its lower end side communicates with the lower space of the power generation chamber 110, and the air that has been preheated in the power generation chamber 110. Is introduced.

Next, an exhaust gas chamber 178 is formed below the manifold 166. Further, as shown in FIG. 14, an exhaust gas passage 180 extending in the vertical direction is formed inside the front surface 106 a and the rear surface 106 b which are surfaces along the longitudinal direction of the housing 106, and the upper end side of the exhaust gas passage 180 is formed. Is in communication with the space in which the air heat exchanger 122 is disposed, and the lower end side is in communication with the exhaust gas chamber 178. Further, an exhaust gas discharge pipe 182 is connected to substantially the center of the lower surface of the exhaust gas chamber 178, and the downstream end of the exhaust gas discharge pipe 182 is connected to the above-described hot water producing apparatus 150 shown in FIG.
As shown in FIG. 13, an ignition device 183 for starting combustion of fuel gas and air is provided in the combustion chamber 118.

Next, the fuel cell unit 116 will be described with reference to FIG. FIG. 15 is a partial cross-sectional view showing a fuel cell unit of a fuel cell device according to a second embodiment of the present invention.
As shown in FIG. 15, the fuel cell unit 116 includes a fuel cell 184 and inner electrode terminals 186 respectively connected to the vertical ends of the fuel cell 184.
The fuel cell 184 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 190 that forms a fuel gas flow path 188 therein, a cylindrical outer electrode layer 192, an inner electrode layer 190, and an outer side. An electrolyte layer 194 is provided between the electrode layer 192 and the electrode layer 192. The inner electrode layer 190 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 192 is an air electrode that comes into contact with air and becomes a (+) electrode.

  Since the inner electrode terminal 186 attached to the upper end side and the lower end side of the fuel cell 116 has the same structure, the inner electrode terminal 186 attached to the upper end side will be specifically described here. The upper portion 190 a of the inner electrode layer 190 includes an outer peripheral surface 190 b and an upper end surface 190 c that are exposed to the electrolyte layer 194 and the outer electrode layer 192. The inner electrode terminal 186 is connected to the outer peripheral surface 190b of the inner electrode layer 190 through a conductive sealing material 196, and is further in direct contact with the upper end surface 190c of the inner electrode layer 190. Electrically connected. A fuel gas channel 198 communicating with the fuel gas channel 188 of the inner electrode layer 190 is formed at the center of the inner electrode terminal 186.

  The inner electrode layer 190 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 194 includes, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 192 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni, and Cu, Sr, Fe, Ni, Cu It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 16 is a perspective view showing a fuel cell stack of a fuel cell device according to a second embodiment of the present invention.
As shown in FIG. 16, the fuel cell stack 114 includes 16 fuel cell units 116, and the lower end side and the upper end side of these fuel cell units 116 are respectively a ceramic lower support plate 168 and an upper support plate 168. It is supported by the support plate 200. The lower support plate 18 and the upper support plate 200 are formed with through holes 168a and 200a through which the inner electrode terminal 186 can pass.

  Further, a current collector 202 and an external terminal 204 are attached to the fuel cell unit 116. The current collector 202 includes a fuel electrode connection portion 202a that is electrically connected to an inner electrode terminal 186 attached to the inner electrode layer 190 that is a fuel electrode, and an entire outer peripheral surface of the outer electrode layer 192 that is an air electrode. And an air electrode connecting portion 202b electrically connected to each other. The air electrode connecting portion 202b is formed by a vertical portion 202c extending in the vertical direction on the surface of the outer electrode layer 192 and a large number of horizontal portions 202d extending in the horizontal direction along the surface of the outer electrode layer 192 from the vertical portion 202c. Has been. Further, the fuel electrode connecting portion 202a is linearly directed obliquely upward or obliquely downward from the vertical portion 202c of the air electrode connecting portion 202b toward the inner electrode terminal 186 positioned in the vertical direction of the fuel cell unit 116. It extends.

  Furthermore, the inner electrode terminals 186 at the upper end and the lower end of the two fuel cell units 116 located at the ends of the fuel cell stack 114 (the far left side and the near side in FIG. 16) are external terminals, respectively. 204 is connected. These external terminals 204 are connected to the external terminals 204 (not shown) of the fuel cell unit 16 at the end of the adjacent fuel cell stack 114, and as described above, the 160 fuel cell units 116 are connected to each other. Everything is connected in series.

Next, sensors and the like attached to the fuel cell device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 17 is a block diagram showing a fuel cell device according to the second embodiment of the present invention.
As shown in FIG. 17, the fuel cell apparatus (SOFC) 101 includes a control unit 210. The control unit 210 includes operation buttons such as “ON” and “OFF” for operation by the user. An operation device 212, a display device 214 for displaying various data such as a power generation output value (wattage), and a notification device 216 that issues an alarm (warning) in an abnormal state are connected. The notification device 216 may be connected to a remote management center and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 210.
First, the combustible gas detection sensor 220 is for detecting a gas leak, and is attached to the fuel cell module 102 and the auxiliary unit 104.
The CO detection sensor 222 detects whether or not CO in the exhaust gas originally discharged to the outside through the exhaust gas passage 180 or the like leaks to an external housing (not shown) that covers the fuel cell module 102 and the auxiliary unit 104. Is to do.
The hot water storage state detection sensor 224 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 226 is for detecting the current, voltage, and the like of the inverter 154 and a distribution board (not shown).
The power generation air flow rate detection sensor 228 is for detecting the flow rate of the power generation air supplied to the power generation chamber 110.
The reforming air flow rate sensor 230 is for detecting the flow rate of the reforming air supplied to the reformer 120.
The fuel flow rate sensor 232 is for detecting the flow rate of the fuel gas supplied to the reformer 120.

The water flow sensor 234 is for detecting the flow rate of pure water (steam) supplied to the reformer 120.
The water level sensor 236 is for detecting the water level of the pure water tank 126.
The pressure sensor 238 is for detecting the pressure on the upstream side outside the reformer 120.
The exhaust temperature sensor 240 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 150.

As shown in FIG. 14, the power generation chamber temperature sensor 242 is provided on the front side and the back side in the vicinity of the fuel cell assembly 112, detects the temperature in the vicinity of the fuel cell stack 114, and detects the fuel cell stack. This is for estimating the temperature of 114 (that is, the fuel cell 184 itself).
The combustion chamber temperature sensor 244 is for detecting the temperature of the combustion chamber 118.
The exhaust gas chamber temperature sensor 246 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 178.
The reformer temperature sensor 248 is for detecting the temperature of the reformer 120 and calculates the temperature of the reformer 120 from the inlet temperature and the outlet temperature of the reformer 120.
The outside air temperature sensor 250 is for detecting the temperature of the outside air when the fuel cell device (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

Signals from these sensors are sent to the control unit 210, which controls the water flow rate adjustment unit 128, the fuel flow rate adjustment unit 138, the reforming air flow rate adjustment unit 144, based on data from these signals. A control signal is sent to the power generation air flow rate adjustment unit 145 to control each flow rate in these units.
Further, the control unit 210 sends a control signal to the inverter 154 to control the power supply amount.

Next, the operation at the time of start-up by the fuel cell apparatus (SOFC) according to the second embodiment of the present invention will be described with reference to FIG. FIG. 18 is a time chart showing the operation at the start-up of the fuel cell device according to the second embodiment of the present invention.
Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

First, reforming air is supplied from the reforming air flow rate adjustment unit 144 to the reformer 120 of the fuel cell module 102 via the first heater 146. At the same time, power generation air is supplied from the power generation air flow rate adjustment unit 145 via the second heater 148 to the air heat exchanger 122 of the fuel cell module 102, and this power generation air is generated by the power generation chamber 110 and the combustion chamber. Reach chamber 118.
Immediately after this, the fuel gas is also supplied from the fuel flow rate adjustment unit 138, and the fuel gas mixed with the reforming air passes through the reformer 120, the fuel cell stack 114, and the fuel cell unit 116, It reaches the combustion chamber 118.

  Next, ignition is performed by the ignition device 183, and the fuel gas and air (reforming air and power generation air) in the combustion chamber 118 are combusted. Exhaust gas is generated by the combustion of the fuel gas and air, the power generation chamber 110 is warmed by the exhaust gas, and when the exhaust gas rises in the sealed space 108 of the fuel cell module 102, The fuel gas containing the reforming air is warmed, and the power generation air in the air heat exchanger 122 is also warmed.

  At this time, the fuel gas mixed with the reforming air is supplied to the reformer 120 by the fuel flow rate adjusting unit 138 and the reforming air flow rate adjusting unit 144. The partial oxidation reforming reaction POX shown in FIG. Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. Further, the heated fuel gas is supplied to the lower part of the fuel cell stack 114 through the fuel gas supply pipe 164, whereby the fuel battery cell stack 114 is heated from below, and the combustion chamber 118 is also supplied with fuel gas and air. The fuel cell stack 114 is also heated from above, and as a result, the fuel cell stack 114 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 118.

_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (3)

  After the partial oxidation reforming reaction POX starts, when the reformer temperature sensor 248 detects that the reformer 120 has reached a predetermined temperature (for example, 600 ° C.), the water flow rate adjustment unit 128 and the fuel flow rate adjustment unit 138 are detected. In addition, the reforming air flow rate adjusting unit 144 supplies the reformer 120 with a gas in which fuel gas, reforming air, and steam are mixed in advance. At this time, in the reformer 120, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used together proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 120 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

  When the reformer temperature sensor 246 detects that the reformer 120 has reached a predetermined temperature (for example, 700 ° C.) after the start of the autothermal reforming reaction ATR shown in Formula (4), the reforming air flow rate The supply of reforming air by the adjustment unit 144 is stopped, and the supply of water vapor by the water flow rate adjustment unit 128 is increased. As a result, the reformer 120 is supplied with a gas that does not contain air but contains only fuel gas and water vapor, and the steam reforming reaction SR of the formula (5) proceeds in the reformer 120.

_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (4)
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (5)

  Since the steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 118. At this stage, since the fuel cell module 102 is in the final stage of startup, the power generation chamber 110 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 110 significantly decreases in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 118.

  In this way, after the fuel cell module 102 is ignited by the igniter 183, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed sequentially, so that the inside of the power generation chamber 110 The temperature gradually increases. Next, when the temperature in the power generation chamber 110 and the fuel cell 184 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module 102 is stably operated, the circuit including the fuel cell module 102 is closed, and the fuel cell Power generation by the module 102 is started, thereby causing a current to flow through the circuit. Due to the power generation of the fuel cell module 102, the fuel cell 184 itself also generates heat, and the temperature of the fuel cell 184 also rises. As a result, the rated rated temperature at which the fuel cell module 102 is operated becomes, for example, 600 ° C. to 800 ° C.

  Thereafter, in order to maintain the rated temperature, more fuel gas and air than the amount of fuel gas and air consumed in the fuel cell 184 are supplied, and combustion in the combustion chamber 118 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

Next, with reference to FIG. 19 to FIG. 21, an operation state when changing the power generation output value corresponding to the required power generation amount of the fuel cell apparatus (SOFC) according to the second embodiment of the present invention to follow the load will be described.
FIG. 19 is a time chart showing an operation state at the time of load following in which the power generation output value is changed corresponding to the required power generation amount of the fuel cell device according to the second embodiment of the present invention, and FIG. 20 is a fuel according to the second embodiment. FIG. 21 is a diagram showing fuel supply control characteristics (relationship between required power generation amount and fuel gas supply amount) in the battery device, and FIG. 21 is a fuel supply control characteristic (required power generation amount and power generation air) in the fuel cell device according to the second embodiment. It is a figure which shows (relation with supply amount).

First, in FIG. 19, the vertical axis represents the power generation chamber temperature (T1), the fuel gas supply amount, and the power generation air supply amount, and the horizontal axis represents time (t).
The fuel cell apparatus (SOFC) 101 according to the second embodiment is a fuel cell having a required power generation amount of 100 W to 700 W, and can follow the load by changing the power generation output value with respect to the required power generation amount within this range. It is like that.

  Next, the fuel battery cell 184 needs to be kept in a temperature band because it can generate a power generation reaction well when generating a rated power generation output value of 100 W to 700 W. This temperature band is a standard when designing without any solid difference. This corresponds to a rated power generation output value of 100 W to 700 W under the condition that the fuel cell is operated in a predetermined reference operation state.

  Next, a lower limit temperature value (Ta) that is a predetermined temperature lower than the temperature of the fuel battery cell 84 corresponding to the lower limit rated power generation amount 100 W is set to 690 ° C., and the fuel battery cell 84 corresponding to the upper limit rated power generation amount 700 W is set. An upper limit temperature value (Tb) that is a predetermined temperature higher than the above temperature is set to 710 ° C., and a temperature range between the lower limit temperature value (Ta) and the upper limit temperature value (Tb) is defined as a temperature monitoring band W. The temperature of the fuel cell 84 corresponding to the lower limit rated power generation amount 100W is set as the lower limit temperature value, the temperature of the fuel cell 84 corresponding to the upper limit rated power generation amount 700W is set as the upper limit temperature value, and these lower limit temperature value and upper limit temperature are set. The temperature range of the value may be the temperature monitoring band W.

  In this way, the lower limit temperature value and the lower limit temperature value are determined in consideration of the lower limit rated power generation amount and the upper limit rated power generation amount, and as will be described later, the monitoring room temperature has the lower limit temperature value and the upper limit temperature value. Since the supply amount of fuel gas and power generation air is corrected when out of the band W, the fuel supply control characteristic is changed when changing the fuel supply amount corresponding to the required power generation amount to follow the load. It is not necessary to perform such complicated control, and simple and sufficient control is possible.

  In the second embodiment, the rated operation is performed when the fuel cell apparatus (SOFC) is installed, and the power generation chamber temperature of the fuel cell at this time is set as the rated reference temperature (T0), and the rated reference temperature is the center. Thus, a lower limit temperature value and an upper limit temperature value separated by 10 ° C. in the vertical direction may be set. Thereby, the solid difference of the fuel cell 84 can be absorbed in the initial stage of operation.

Next, in the second embodiment, as shown in FIG. 20, the “relationship between required power generation amount and fuel gas supply amount”, which is a fuel supply control characteristic, is determined in advance, and as shown in FIG. The fuel supply control characteristic “relation between required power generation amount and power generation air supply amount” is determined in advance.
In the second embodiment, after the fuel cell module 2 shifts to steady operation, when changing the power generation output value corresponding to the required power generation amount to follow the load, the fuel gas supply amount and the power generation air supply amount are set as follows. Based on the fuel supply control characteristics shown in FIG. 20 and FIG. 21, it is possible to follow the requested load by increasing or decreasing.

  When following this load, the fuel cell 184 of the fuel cell module 102 is a fuel cell due to individual differences of the fuel cell 184 and the outside air environment (temperature, humidity, etc.) in which the fuel cell module 2 is installed. The temperature (T1) of the cell 84 may be outside the temperature monitoring band W. Therefore, in the second embodiment, when the power generation chamber temperature (T1) of the fuel battery cell 184 is lower than the lower limit temperature value (Ta), the supply amounts of the fuel gas and power generation air are respectively set to predetermined amounts ( In the case where the power generation chamber temperature (T1) of the fuel cell 84 exceeds the upper limit temperature value (Tb), the fuel gas and The power generation chamber temperature (T1) of the fuel cell 84 is set within the temperature monitoring band W by performing a decrease correction that decreases the supply amount of the power generation air by a predetermined amount (10% of the supply amount in the fuel supply control characteristic). Adaptive control is executed.

  In the second embodiment, by this adaptive control, a predetermined prohibition period (for example, 5 hours) elapses after correction by increasing or decreasing the supply amount of fuel gas and the supply amount of power generation air during load following. Until next time, the next correction is not executed. Thus, after the fuel supply amount is corrected to decrease or increase, the supply amount of fuel gas and power generation air is corrected until a period during which the temperature of the fuel cell 84 is stabilized (generally, several hours are required for SOFC). Is not executed, the adverse effect of the fuel cell 184 due to overcorrection can be prevented, and it can be adapted to the influence on the fuel supply control characteristics caused by the individual difference of the fuel cell 184 and the change in the outside air environment.

  Next, as shown in FIG. 19, in the second embodiment, 720 ° C., which is higher than the upper limit temperature value (Tb) of the temperature monitoring band W, is set as the cooling temperature (Tc), and the power generation of the fuel battery cell 184 is performed. When the chamber temperature (T1) exceeds the cooling temperature (Tc), a large amount of power generation air is introduced into the power generation chamber 110 of the fuel cell module 102 by the air flow rate adjustment unit 144, and this air causes the fuel cell. The cell assembly 112 is forcibly cooled.

  Further, as shown in FIG. 19, in the second embodiment, a temperature range (800 ° C. or higher) higher than the upper limit temperature value (Tb) and the cooling temperature (Tc) of the temperature monitoring zone W, and the temperature monitoring zone When a band of temperature (500 ° C. or lower) lower than the lower limit temperature value (Ta) of W is set as an abnormal temperature band, and the power generation chamber temperature (T1) of the fuel cell 184 becomes this abnormal temperature band, the fuel cell I am trying to regulate driving. Specifically, the operation of the fuel cell itself is stopped, the power generation operation of the fuel cell is stopped, the amount of fuel gas supplied is reduced, an alarm (warning) is issued, and the like. Thereby, according to the second embodiment, even when the fuel supply control characteristic is in an abnormal state that cannot be adapted to changes in the outside air environment (temperature, humidity, etc.) or the solid difference of the fuel cell 84, It is possible to reliably prevent the fuel cell 84 from being in an abnormal state.

  Next, the relationship between the current value, the fuel usage rate, and the air usage rate during load following in the fuel cell device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 22 is a diagram showing the relationship between the current value, the fuel utilization rate, and the air utilization rate during the power generation operation in the fuel cell device according to the second embodiment of the present invention.

  Here, as described above, the fuel utilization rate is the ratio of the amount of heat used for the power generation reaction of the fuel cell to the total amount of heat of the fuel supplied to the fuel cell. The air utilization rate is a ratio of the flow rate used for the power generation reaction of the fuel cell to the total flow rate of power generation air supplied to the fuel cell.

  In the second embodiment of the present invention, the fuel utilization rate can be lowered by the following three modes (first to third examples). That is, as in the first embodiment described above, when the current value output from the fuel cell assembly is constant, the flow rate of the reformed gas (fuel supply amount) is increased (first example), Lowering the fuel utilization rate by lowering the current value when the flow rate of the reformed gas is constant (second example) and increasing the flow rate of the reformed gas and lowering the current value (third example) be able to.

  The first example described above will be specifically described. For example, when the current value flowing through the fuel cell assembly is 7A, 5A, 3A, the amount of reformed gas (fuel amount) used for the power generation reaction is 70 cc / min, 50 cc / min, 30 cc / min. When the fuel utilization rate is set to 70% (constant), the total fuel supply amount is controlled to be 100 cc / min, about 71 cc / min, and about 43 cc / min, respectively. On the other hand, the amount of reformed gas (fuel amount) used for combustion in the combustion section corresponds to the amount obtained by subtracting the amount used for power generation reaction from the total amount of fuel supply, so 30 cc / min, 21 cc / min, 13 cc / Min. In this case, when the current value is 3 A (low load region), the amount of fuel used for combustion (= 13 cc / min) is too small, so that the amount of fuel used for fuel is further increased by 10 cc / min. When controlled, the amount of fuel used for combustion becomes 23 cc / min, and the fuel utilization rate decreases to 57%.

  The 2nd example mentioned above is demonstrated similarly to the above. For example, when the value of the current flowing through the fuel cell assembly is 5 A and the fuel utilization rate is set to 70%, the total fuel supply amount is controlled to be about 71 cc / min. If the total amount of fuel supplied at this time is fixed (= about 71 cc / min) and the current value is changed to 3 A, the amount of reformed gas (fuel amount) used for the power generation reaction becomes 30 cc / min. Therefore, the amount of reformed gas (fuel amount) used for combustion in the combustion section is 41 cc / min, and the fuel utilization rate at that time decreases to 41%. By reducing the current value, the amount of reformed gas (fuel amount) used for the power generation reaction decreases, and as a result, the amount of reformed gas (fuel amount) used for combustion in the combustion section increases.

Hereinafter, the fuel cell apparatus according to the second embodiment using the first example will be described. First, the fuel utilization rate and the air utilization rate are determined by the fuel flow rate adjustment unit 138 and the power generation air flow rate adjustment unit 145 based on the output current value during the load following operation. It is changed by being controlled.
Here, in FIG. 22, for the sake of convenience, the region where the output current value of the fuel utilization rate is 4 A or more is called the A1 region, the region less than this is called the A2 region, and the region where the output current value of the air utilization rate is 4 A or more. The area B1 and the area less than this are called the area B2.

First, as shown in FIG. 22, in the fuel cell device according to the second embodiment, as in the first embodiment described above, the fuel utilization rate is a low load region (A2) that outputs a small current value during load following. In the region), the fuel gas supply amount is controlled by the fuel flow rate adjusting unit 138 so as to be lower than the high load region (A1 region) in which a large current value is output.
As described above, in the fuel cell device of the second embodiment, the fuel utilization rate is lower in the low load region than in the high load region. Therefore, the residual that is not used for the power generation reaction in the low load region. The amount of heat of the fuel increases, and the amount of heat of the fuel in the combustion chamber (combustion unit) 118 is maintained substantially constant. Further, since the temperature of the fuel cell 184 is also maintained, it does not take time for reheating. Further, in the reformer 120 as well, the amount of heat of the fuel in the combustion chamber 118 is maintained almost constant, so that the balance of the reforming reaction is maintained and the optimum fuel can be supplied to the fuel cell 184. As a result, according to the fuel cell device according to the second embodiment, when shifting from the high load region to the low load region, the temperature of the fuel cell 118 can be maintained in a narrow temperature band, and the optimum fuel can be obtained. It is supplied to the fuel battery cell, and an efficient power generation reaction can be performed.

Next, as shown in FIG. 22, in the fuel cell device according to the second embodiment, as with the fuel usage rate, the air usage rate is high in the low load region (B1 region) when the load follows. The supply amount of power generation air is controlled by the power generation air flow rate adjustment unit 145 so as to be lower than (region).
As described above, in the fuel cell device of the second embodiment, the air utilization rate is similarly reduced in the low load region in correspondence with the fuel utilization rate being lower than that in the high load region in the low load region. Lower than the high load area. As a result, according to the fuel cell device according to the second embodiment, the fuel easily burns in the combustion chamber 118 even in the low load region. Further, in a high load region, even if the air utilization rate is increased, there is no problem because a sufficient amount of power generation air has already been supplied, and the fuel cell module 2 is cooled by excessive air supply. Can be prevented.

Next, as shown in FIG. 22, in the fuel cell device according to the second embodiment, the rate of decrease in the fuel utilization rate is smaller in the load region where the output current value is smaller than 4A (A2 region) as the load increases. Thus, the fuel gas supply amount is controlled by the fuel flow rate adjustment unit 138.
Thus, in the fuel cell device according to the second embodiment, in the load region where the output current value is smaller than 4A, the absolute amount of fuel supplied on the high load side is relatively large, and the temperature of the fuel cell 184 is also high. Since it is considered that sufficient heat quantity is supplied to the reformer, the waste rate of the fuel utilization rate is reduced (slowly) toward the high load side, so that waste fuel is discharged from the combustion chamber 118. It can be prevented from being burned and consumed and the power generation efficiency can be increased.

Next, as shown in FIG. 22, in the fuel cell device according to the second embodiment, the rate of decrease in the air utilization rate is smaller in the load region (B2 region) where the output current value is smaller than 4A as the load becomes higher. Thus, the supply amount of power generation air is controlled by the power generation air supply unit 145.
As described above, in the fuel cell device according to the second embodiment, in the load region where the output current value is smaller than 4A, the reduction rate of the fuel utilization rate is made smaller toward the higher load side, and the air utilization rate is reduced. Similarly, the rate of decrease was made smaller as the load increased. As a result, according to the fuel cell device of the second embodiment, it is possible to secure an amount of air necessary for fuel combustion in the fuel chamber 118.

Next, as shown in FIG. 22, in the fuel cell device according to the second embodiment, in the load region (A2 region and B2 region) where the output current value is smaller than 4A, the above-described rate of decrease in the fuel utilization rate is high. In addition to the smaller the load side, the smaller the rate of decrease in the air utilization rate, the smaller the higher the load side, the lower the load side, the lower the rate of air utilization rate, the lower the rate of fuel utilization rate. The fuel flow rate and the power generation air flow rate are controlled by the fuel flow rate adjustment unit 138 and the power generation air flow rate adjustment unit 145 so as to be smaller.
Thus, in the fuel cell device according to the second embodiment, in the load region where the output current value is smaller than 4A, the rate of decrease in the air utilization rate is made smaller than the rate of decrease in the fuel utilization rate. In the region, it is possible to secure a minimum amount of air necessary for the fuel to burn in the combustion section, and it is possible to prevent the inside of the module from being cooled due to excessive supply of air.

Next, as shown in FIG. 22, in the fuel cell device according to the second embodiment, in the load region (B1 region) where the output current value is larger than 4A, the rate of decrease in the air utilization rate is almost zero. The amount of power generation air supplied is controlled by the power generation air flow rate adjustment unit 145.
As described above, in the fuel cell device according to the second embodiment, there is no problem because a sufficient amount of power generation air is already supplied in the load region where the output current value is larger than 4 A. It is possible to prevent the balance with the temperature maintenance of the fuel cell from being lost due to unstable combustion caused by the fluctuation.

Next, as shown in FIG. 22, the fuel cell apparatus according to the second embodiment also includes a fuel chamber temperature sensor 244 that detects the temperature of the combustion chamber 118, as in the first embodiment described above. The fuel supply amount is controlled by the fuel flow rate adjustment unit 138 so that the temperature of the fuel becomes equal to or higher than the self-ignition temperature of hydrogen as the fuel.
As described above, also in the fuel cell device according to the second embodiment, the temperature of the combustion chamber 118 is set to be equal to or higher than the self-ignition temperature of hydrogen, which is the fuel. As a result, the temperature of the fuel battery cell 184 can also be maintained in a necessary narrow temperature range, and the reformer 120 can maintain an optimal reforming reaction and maintain an efficient power generation reaction. it can.

DESCRIPTION OF SYMBOLS 4 Fuel cell 5 Reformer 16 Power generation chamber 18 Combustion part 30 Fuel cell unit 90 Fuel cell stack FC Fuel cell module FCS Fuel cell FP Fuel supply part AP1 1st air supply part (Power generation air supply part)
AP1 Second air supply unit (reforming air supply unit)
WP water supply unit 101 fuel cell device 102 fuel cell module 110 power generation chamber 112 fuel cell assembly 114 fuel cell stack 116 fuel cell unit 118 combustion chamber (combustion unit)
120 reformer 128 water flow rate adjustment unit 130 fuel flow rate adjustment unit 144 reformed air flow rate adjustment unit 145 power generation air flow rate adjustment unit 184 fuel cell 244 combustion chamber temperature sensor

Claims (11)

In a fuel cell device that generates power following the required load,
A fuel cell assembly comprising a plurality of fuel cells arranged in a module;
A reformer that is disposed in the combustion section at the top of the fuel cell assembly in the module and reforms the fuel;
Fuel supply means for supplying fuel to the reformer;
Reforming air supply means for supplying reforming air to the reformer;
Power generation air supply means for supplying power generation air to the fuel cell assembly;
Control means for controlling the fuel supply means and the power generation air supply means based on the current value output from the fuel cell assembly,
One of the fuel and the air for power generation is supplied into the flow path of the fuel battery cell of the fuel cell assembly, and the other of the fuel and the air for power generation is supplied outside the flow path of the fuel battery cell,
In the combustion section, the remaining fuel and the remaining power generation air that were not used in the power generation reaction burned,
The control means is a low load region that outputs a small current value as a fuel utilization rate, which is a ratio of a heat amount used for a power generation reaction of the fuel cell to a total heat amount of the fuel supplied to the fuel cell at the time of load following. Then, the fuel cell device is characterized by comprising a fuel utilization rate changing means for lowering than a high load region that outputs a large current value.   2. The fuel cell device according to claim 1, wherein the fuel utilization rate changing means of the control means lowers the fuel utilization rate by increasing the amount of fuel supplied by the fuel supply means.   2. The fuel cell apparatus according to claim 1, wherein the fuel utilization rate changing means of the control means lowers the fuel utilization rate by lowering the current value output from the fuel cell assembly.   The fuel utilization rate changing means of the control means lowers the fuel utilization rate by increasing the amount of fuel supplied by the fuel supply means and decreasing the current value output from the fuel cell assembly. Fuel cell device.   The control means has an air utilization ratio, which is a ratio of a flow rate used for a power generation reaction of the fuel cell to a total flow rate of the power generation air supplied to the fuel cell at the time of load following, in the low load region. The fuel cell device according to claim 1, wherein the power generation air supply unit is controlled to be lower than a load region.   The fuel cell apparatus according to any one of claims 1 to 4, wherein the fuel utilization rate changing means of the control means reduces the rate of decrease in the fuel utilization rate in a load region smaller than a predetermined load as the load increases. .   6. The fuel cell device according to claim 5, wherein the control means controls the power generation air supply means so that the rate of decrease in the air utilization rate becomes smaller as the load increases in a load region smaller than a predetermined load.   In the load region smaller than the predetermined load, the control means is further configured so that the rate of decrease in the fuel utilization rate decreases as the load increases, and the rate of decrease in the air utilization rate decreases as the load increases. 6. The fuel cell device according to claim 5, wherein the fuel supply unit and the power generation air supply unit are controlled so that the rate of decrease in the air utilization rate is smaller than the rate of decrease in the fuel utilization rate as the load decreases.   8. The fuel according to claim 7, wherein the control means controls the power generation air supply means so that the rate of decrease in the air utilization rate becomes substantially zero in a load region larger than the predetermined load during load following. Battery device. Furthermore, a fuel part temperature detecting means for detecting the temperature of the combustion part is provided,
The fuel cell device according to any one of claims 1 to 9, wherein the control means controls the fuel supply means so that a temperature of the combustion section is equal to or higher than a self-ignition temperature of hydrogen as a fuel. In a fuel cell device that generates power following the required load,
A fuel cell assembly comprising a plurality of fuel cells arranged in a module;
A reformer that is disposed in the combustion section at the top of the fuel cell assembly in the module and reforms the fuel;
Fuel supply means for supplying fuel to the reformer;
Reforming air supply means for supplying reforming air to the reformer;
Power generation air supply means for supplying power generation air to the fuel cell assembly;
Control means for controlling the fuel supply means based on the current value output from the fuel cell assembly,
One of the fuel and the air for power generation is supplied into the flow path of the fuel battery cell of the fuel cell assembly, and the other of the fuel and the air for power generation is supplied outside the flow path of the fuel battery cell,
In the combustion section, the remaining fuel and the remaining power generation air that were not used in the power generation reaction burned,
The control means is a low load region in which the fuel utilization rate, which is the ratio of the amount of heat used for the power generation reaction of the fuel cell to the total amount of fuel supplied to the fuel cell when the load follows, outputs a small current value. Then, the fuel supply device is characterized in that the fuel supply means is controlled to be lower than a high load region where a large current value is output.

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