JP2008159362A - Solid oxide fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell system from which a rated power generation output can be easily take out with a comparatively simple structure and control even if a fuel cell stack is deteriorated. <P>SOLUTION: This solid oxide fuel cell system includes a fuel reformer 6 to reform a fuel gas, and a solid oxide fuel cell stack 4 having a fuel electrode and an air electrode, and fuel cell power generation reaction is performed between the reformed gas fed to the fuel electrode side from the fuel reformer 6 and air fed to the air electrode side from a blower. In this case, an air distributing and feeding means 42 to feed air flowing toward the air electrode by distributing it is provided, the air distributing and feeding means 42 has a center feed passage part 50 and an end feed passage parts 46, 48, and if the flow of air flowing in the air passage increases, the air distributing and feeding means 42 distributes and feeds air so that the distribution ratio of a distributed air flow distributed and fed to the end feed passage part to a total air flow flowing to the air passage becomes small. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell system that performs a fuel cell reaction by reforming a fuel gas.

  Currently, as one of the fuel cells, a fuel cell system using a solid oxide fuel cell is being developed because it can generate power with high power generation efficiency (see, for example, Patent Document 1). In a solid oxide fuel cell, a solid electrolyte that conducts oxygen ions is used as an electrolyte, a fuel electrode that functions to oxidize fuel gas is provided on one side of the solid electrolyte, and oxygen in the air is reduced on the other side. An air electrode having a function to perform is provided. As the solid electrolyte, zirconia doped with yttria is generally used. For example, when a fuel gas mainly composed of methane (for example, natural gas) is used as a raw fuel gas, a reformed gas (including hydrogen, carbon monoxide, hydrocarbons, etc.) obtained by a reforming reaction of the raw fuel gas is included. Is supplied to the fuel electrode, and air (containing oxygen) is supplied to the air electrode. In such a solid oxide fuel cell, electric power is generated by electrochemical reaction of reformed gas (hydrogen, carbon monoxide, hydrocarbon) and oxygen at a high temperature of 700 to 1000 ° C. This fuel cell system using solid oxide fuel cells can be generated with higher power generation efficiency than other fuel cell systems, gas engines, etc., and is therefore developed as a promising power generation technology. ing.

  The application destinations of this type of solid oxide fuel cell system include a large size for business use and industrial use of several tens kW class or more, and a small size for household use of 1 kW class. In a small solid oxide fuel cell system with a rated power output of about 1 kW class, the power load connected to this system fluctuates greatly with time, so it exhibits high performance even during partial loads due to load fluctuations. Is required.

Japanese Patent No. 3113340

  In this solid oxide fuel cell, if the operating temperature is high, the power generation performance is improved. However, if the operating temperature exceeds the inherent degradation management temperature of the solid oxide fuel cell, the solid oxide fuel cell There is a problem that the required durability performance cannot be obtained due to an increase in the deterioration rate. Therefore, the upper limit temperature of the fuel cell stack of the solid oxide fuel cell is set, and the flow rate of air supplied to the air electrode side of the solid oxide fuel cell is controlled so as not to exceed this upper limit temperature, In this way, the progress of deterioration is suppressed.

In this solid oxide fuel cell, heat generation increases as the power generation output increases, so under operating conditions where the fuel utilization rate and air utilization rate do not change significantly, the temperature of the fuel cell stack is low at partial load, It tends to be higher at the rated output. The power output (W) of the solid oxide fuel cell is
Generated output (W) = Generated current (I) x Generated voltage (V)
When the deterioration of the fuel cell fuel cell stack progresses, the power generation voltage at the same power generation current decreases, so in order to maintain the rated power output, the power generation current is increased from the state before the deterioration. It is operated to generate electricity at a low generation voltage. When power is generated by operating in this way, the heat generation of the fuel cell stack increases with the progress of deterioration, and in order to maintain the durability of the fuel cell stack, the fuel cell stack should not be heated to a high temperature. In addition, it is necessary to increase the cooling.

  In small solid oxide fuel cell systems for home use, etc., because the power generation output is small, the heat dissipation surface area of the fuel cell stack is large, and the heat dissipated from the fuel cell stack to the outside is large. The amount of heat radiation is different between the portion and the end portion, and the center portion has less heat radiation than the end portion, and the temperature tends to be higher. When deterioration progresses at the center of the fuel cell stack where the operating temperature is high, the temperature at this center increases. Therefore, in order to suppress the progress of deterioration at the center of the fuel cell stack, this center is cooled. However, if the flow rate of air sent to the air electrode of the fuel cell stack for cooling is increased, the temperature at the center of the fuel cell stack can be lowered. The temperature also decreases at the same time. Therefore, in a state where the fuel cell stack is deteriorated, it is difficult to take out the rated power generation output without greatly impairing the power generation efficiency.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a solid oxide fuel cell system having a relatively simple configuration and control and capable of easily taking out the rated power output even if the solid oxide fuel cell stack is deteriorated. is there.

A solid oxide fuel cell system according to claim 1 of the present invention is a solid oxide fuel cell system having a fuel reformer for generating a reformed gas by reforming a fuel gas, and a fuel electrode and an air electrode. A fuel cell stack, a reformed gas feed passage for feeding reformed gas from the fuel reformer to the fuel electrode side of the solid oxide fuel cell stack, and air from a blower for the solid oxidation An air flow path for feeding to the air electrode side of the physical fuel cell stack, and the solid oxide fuel cell stack is fed to the reformed gas to be fed to the fuel electrode side and to the air electrode side. A solid oxide fuel cell system that performs a fuel cell power generation reaction with supplied air,
The air flow path is provided with an air content delivery means for distributing and feeding the air flowing toward the air electrode, and the air content delivery means is provided on the solid oxide fuel cell stack. A central feed channel for feeding to the center and an end feed channel for feeding to the end of the solid oxide fuel cell stack;
When the flow rate of the air flowing through the air flow path is small, the air delivery / feed means is connected to the end feed flow with respect to the total air flow rate flowing through the air flow path in connection with the small dynamic pressure of the air flow. When the air is distributed and supplied so that the distribution ratio of the distributed air flow to be distributed to the passage is increased, and the flow rate of the air flowing through the air flow path increases, the dynamic pressure of the air flow increases. The air distribution delivery means distributes the air so that a distribution ratio of a distribution air flow rate distributed to the end feed flow path portion with respect to a total air flow rate flowing through the air flow path is small. It is characterized by delivery.

  Further, in the solid oxide fuel cell system according to claim 2 of the present invention, the opening of the central supply flow path part and the opening of the end supply flow path part of the air content delivery and supply means are When the flow rate of air flowing through the air flow path is changed at different angles with respect to the air flow line of the air flow flowing through the air flow path, the end feeding flow with respect to the total air flow rate flowing through the air flow path The distribution ratio of the distribution air flow rate distributed and supplied to the road portion is changed.

  In the solid oxide fuel cell system according to claim 3 of the present invention, the air content delivery / supply means is provided adjacent to the solid oxide fuel cell stack, and the air content delivery / supply means is provided. Heat exchange is performed between flowing air and heat of the solid oxide fuel cell stack.

  In the solid oxide fuel cell system according to claim 4 of the present invention, the fuel reformed gas discharged from the fuel electrode side and the air electrode are disposed downstream of the solid oxide fuel cell stack. A combustion chamber for reacting with the air discharged from the side and burning it, and the air content delivery and supply means is provided from the combustion chamber to the solid oxide fuel cell stack, and the air content delivery and supply Heat exchange is performed between the air flowing through the means and the heat of the combustion chamber and the solid oxide fuel cell stack.

  Furthermore, in the solid oxide fuel cell system according to claim 5 of the present invention, temperature detection means for detecting the temperature of the central portion of the solid oxide fuel cell stack is provided, and the temperature detection means The number of rotations of the blower is controlled based on the detected temperature, and the flow rate of air supplied from the blower increases when the detected temperature rises.

  According to the solid oxide fuel cell system of the first aspect of the present invention, air is distributed and supplied to the air flow path for supplying air to the air electrode side of the solid oxide fuel cell stack. An air content delivery and supply means is provided, the air content delivery and supply means comprising: a central feed channel for feeding to the central portion of the solid oxide fuel cell stack; and a solid oxide fuel cell And an end feeding flow path section for feeding to the end of the stack. When the air flow rate flowing through the air flow path is small, the air content delivery and supply means is connected to the end feed flow path portion for the total air flow rate flowing through the air flow path in relation to the small dynamic pressure of the air flow. Since the distribution is performed so that the distribution ratio of the distribution air flow to be distributed is increased, the entire solid oxide fuel cell stack is cooled almost uniformly in such a supply state, and this fuel is supplied. The entire battery stack can be kept at approximately the same temperature. In addition, when the air flow rate flowing through the air flow path is large, this air component delivery and supply means is connected to the end feed flow path portion for the total air flow rate flowing through the air flow path in connection with the large dynamic pressure of the air flow. Therefore, when the air flow rate is increased, a large amount of air flow rate is applied to the central portion of the fuel cell stack, i.e., the part that becomes hot. While it can be delivered, the air flow rate at the end of the fuel cell stack, that is, the portion where the temperature does not become high does not increase so much, and thus the temperature rise in the central portion of the fuel cell stack (ie, the high temperature portion) is suppressed The temperature of the end portion (that is, the low temperature portion) can be maintained, whereby the average temperature of the fuel cell stack can be kept high. As a result, it is possible to effectively cool the central portion of the fuel cell stack, which has been prone to temperature rise due to deterioration, to suppress the temperature rise, and thus to take out the rated power output without significantly impairing power generation efficiency. It becomes possible. Further, in this solid oxide fuel cell system, the distribution ratio of the air flow rate is changed by utilizing the dynamic pressure fluctuation of the air flow. The above-described effects can be achieved with a relatively simple and inexpensive configuration without requiring a special configuration and control for distributing and controlling the flow path portion.

  Further, according to the solid oxide fuel cell system according to claim 2 of the present invention, the opening of the central feed flow path part and the opening of the end feed flow path part of the air content delivery means are: Since it is arranged at a different angle with respect to the air flow line of the air flow flowing through the air flow path, when the flow rate of the air flowing through the air flow path changes, the end feed flow path section for the total air flow rate flowing through the air flow path Thus, the distribution ratio of the distribution air flow rate to be distributed is changed, and thus the distribution ratio of the air flow rate can be changed by utilizing the dynamic pressure fluctuation of the air flow. For example, the opening of the central feed flow path section is arranged in the direction of the air flow line of the air flowing through the air flow path, and the opening of the end feed flow path section is in a direction perpendicular to the air flow line. Be placed.

  In the solid oxide fuel cell system according to claim 3 of the present invention, the air content delivery / supply means is provided adjacent to the solid oxide fuel cell stack. Heat exchange is performed between the flowing air and the heat of the solid oxide fuel cell stack, and the fuel cell stack can be cooled by this heat exchange. In particular, when the flow rate of air flowing through the air flow path is large, the flow rate of air flowing through the central supply flow path of the air distribution delivery means increases, so the air flowing through the central distribution supply and the center of the fuel cell stack The heat exchange with the part (that is, the high-temperature part) is promoted and the cooling effect is enhanced, whereby the center portion of the fuel cell stack can be cooled more effectively and the temperature rise can be suppressed.

  In the solid oxide fuel cell system according to claim 4 of the present invention, since the air content delivery / supply means is provided from the combustion chamber to the solid oxide fuel cell stack, the air content delivery / supply means is provided. Heat exchange is performed between the flowing air and the heat of the combustion chamber and the solid oxide fuel cell stack. By this heat exchange, the fuel cell stack can be cooled as described above.

  Furthermore, according to the solid oxide fuel cell system according to claim 5 of the present invention, the blower fan is based on the detected temperature of the temperature detecting means for detecting the temperature of the central portion of the solid oxide fuel cell stack. When the rotational speed is controlled and the detected temperature rises, the air flow rate supplied from the blower increases, so that the fuel cell stack can be prevented from rising to a high temperature.

  Embodiments of a solid oxide fuel cell system according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view schematically showing an embodiment of a solid oxide fuel cell system, and FIG. 2 is a simplified cross-sectional view showing air content delivery and supply means in the solid oxide fuel cell system of FIG. FIG. 3 is a diagram for explaining air distribution when the air flow rate is small when the air content delivery / supply means of FIG. 2 is used, and FIG. 4 is an air content delivery / supply means of FIG. It is a figure for demonstrating distribution of air when there are many air flow rates in the case of using.

  In FIG. 1, a solid oxide fuel cell system 2 of the illustrated embodiment includes a solid oxide fuel cell stack 4, a fuel reformer 6, and an air preheater 8. The battery stack 4, the fuel reformer 6, and the air preheater 8 are accommodated in a high-temperature accommodation chamber 12 defined by a heat insulating wall 10 that is insulated. The solid oxide fuel cell stack 4 is disposed at substantially the center of the high-temperature housing chamber 12 and includes a plurality of fuel cells 14 that are spaced apart in the left-right direction in FIG. The part is connected to the communication connecting member 16.

  Although not shown, each fuel battery cell 14 includes a solid electrolyte that conducts oxygen ions, a fuel electrode disposed on one side of the solid electrolyte, and an air electrode disposed on the other side. The electrolyte is made of zirconia doped with yttria, for example. The reformed gas reformed as described later is oxidized at the fuel electrode, and oxygen in the air is reduced at the air electrode, and these oxygen ions pass through and move through the solid electrolyte to cause an electrochemical reaction with the reformed gas. By doing so, power generation is performed. The electrochemical reaction in the solid oxide fuel cell stack 4 is performed at a high temperature of 700 to 1000 ° C. In addition, since the solid oxide fuel cell stack 4 is accommodated in the high temperature accommodation chamber 1 surrounded by the heat shield wall 10, the high temperature of the solid oxide fuel cell stack 4 is maintained.

  In the solid oxide fuel cell system 2, an air flow path 26 is disposed on the air electrode side of the fuel cell stack 4, and a blower 28 as an air supply means and air / exhaust are provided in the air flow path 26. An air preheater 8 as a heat exchanger is provided, air from the blower 28 flows through the air flow path 26 and the air preheater 8, and is preheated in the air preheater 8 as described later, and the preheated air is described later. In this way, it is fed to the air electrode side of the solid oxide fuel cell stack 4.

  A communication connecting member 16 is connected to the fuel electrode side of the solid oxide fuel cell stack 4 (that is, the fuel electrode side of each fuel cell 14), and the communication connecting member 16 is a reformed gas feed channel. The fuel reformer 6 is connected to a desulfurizer 34 via a fuel gas supply passage 32, and the desulfurizer 34 is connected via a fuel gas supply passage 36. A fuel supply source (not shown) such as a fuel tank (or a buried supply pipe) is connected, and a booster fan 38 is disposed in the fuel gas supply flow path 36.

  In the solid oxide fuel cell system 2, for example, a fuel gas based on liquefied natural gas, that is, a fuel gas mainly composed of methane (for example, city gas) is used as the fuel gas. The raw fuel gas is supplied through the fuel gas supply passage 36, and the supplied fuel gas is boosted by the booster fan 38 and then fed to the desulfurizer 34. In the desulfurizer 34, the sulfur component contained in the fuel gas is removed, and the desulfurized fuel gas is supplied to the fuel reformer 6 through the fuel gas supply passage 32. The fuel reformer 6 has a built-in reforming catalyst. For example, the reforming reaction of the fuel gas is performed at a high temperature of about 700 to 800 ° C., and the reformed reformed gas is supplied to the reformed gas supply passage. 30 is supplied to the communication connecting member 16, and the reformed gas is supplied to the fuel electrode side of each fuel cell 14 of the solid oxide fuel cell stack 4 through the communication connecting member 16.

  In this solid oxide fuel cell system 2, a combustion chamber 40 is provided on the discharge side, that is, the downstream side of the fuel cell stack 4, and the combustion exhaust gas from the combustion chamber 40 passes through the air preheater 8 and flows into the exhaust stream. It is configured to be discharged to the outside through the path 62. Reacted fuel gas from the fuel electrode side of the fuel cell stack 4 and air from the air electrode side of the fuel cell stack 4 are discharged to the combustion unit 40, and the reaction fuel gas is burned using oxygen in the air. A fuel reformer 6 is disposed in the combustion chamber 40, and the fuel qualifier 6 performs a fuel gas reforming reaction process using the combustion heat of the combustion chamber 40.

  Referring to FIG. 1 and FIG. 2, in this solid oxide fuel cell system 2, air distribution delivery means 42 is provided in the air flow path 26, and the air delivery delivery means 42 is a solid oxide fuel. The air supplied to the air electrode side of the battery stack 4 is distributed and supplied as required. In the form shown in the figure, the air content delivery / supply means 42 is connected to the air preheater 8, and from this connection 44 to one end side of the solid oxide fuel cell stack 4 (left end side in FIG. 1). From the first end feed flow path section 46 that branches off, the second end feed flow path section 48 that branches from the connection section 44 to the other end side of the fuel cell stack 4 (right end side in FIG. 1), and the connection section 44 The fuel cell stack 4 has a central supply flow path portion 50 that branches into the central portion. The openings 52 and 54 of the first and second end feed flow channel portions 46 and 48 and the opening 56 of the central feed flow channel portion 50 are defined by the air flow channel 26 (specifically, the connection portion 44). Are arranged at different angles with respect to the air flow line 58 (in other words, the axis of the air flow direction) of the air flow flowing through the flow path), and in this form, the opening 56 of the central feed flow path section 50 is Are arranged in the direction of the air flow line 58, that is, so as to coincide with the flow path of the connecting portion 44, and the openings 52 and 54 of the first and second end feed flow path portions 46 and 48 are provided with this air flow line. If the flow rate of the air flowing through the air flow path 26 fluctuates due to this arrangement, the first and second end feeds with respect to the total flow rate of the air flowing through the air flow path 26 are arranged. The distribution ratio of the distribution air flow rate distributed and supplied to the supply passage portions 46 and 48 changes.

  For example, when the flow rate of the air flowing through the air flow path 26 is small, the dynamic pressure of the air flow is small. At this time, the air is distributed and supplied as shown in FIG. That is, the air from the connecting portion 44 flows as shown by an arrow in FIG. 3A because the dynamic pressure is small, and as shown in FIG. 3B, the opening of the central feed channel portion 50 The unit area flow rate (flow rate per unit area) flowing through 56 and the unit area flow rate flowing through the openings 52, 54 of the first and second end feed flow channel portions 46, 48 are distributed in a distributed manner. The Further, for example, when the flow rate of air flowing through the air flow path 26 is large, the dynamic pressure of the air flow is large. At this time, air is distributed and supplied as shown in FIG. That is, since the dynamic pressure of the air from the connecting portion 44 is large, most of the air flows in the direction of the air flow line as shown by arrows in FIG. 4A, and as shown in FIG. Partial delivery so that the unit area flow rate flowing through the opening 56 of the central feed flow channel portion 50 is larger than the unit area flow rate flowing through the openings 52, 54 of the first and second end feed flow channel portions 46, 48. Be paid. As described above, by arranging the openings 52 and 54 of the first and second end supply flow passage portions 46 and 48 and the opening portion 56 of the central supply flow passage portion 50, along with the fluctuation of the flow rate of the air flow, The distribution ratio of the air flow rate supplied to the first and second end supply flow path portions 46 and 48 with respect to the total flow rate of the air flowing through the air flow rate 26 can be changed. In this embodiment, the openings 52 and 54 of the first and second end feed flow passages 46 and 48 are arranged in a direction perpendicular to the air flow line 58. The angle with respect to can be set to an appropriate angle, and by setting this angle small, the flow rate of air flowing through the first and second end feed flow path portions 46 and 48 with respect to the central feed flow path portion 56 can be reduced. It can be increased relatively.

  In this embodiment, the air content delivery / supply means 42 is provided from the combustion chamber 40 to the solid oxide fuel cell stack 4, and the central feed channel portion 50 communicates with the central portion of the fuel cell stack 4 downward. 16, the first and second end supply flow path portions 46 extend downward from both ends of the fuel cell stack 4 to the vicinity of the communication connection member 16, and the air flowing through the central supply flow path portion 50. Is mainly supplied to the air electrode side of the fuel cell 14 arranged at the center of the fuel cell stack 4, and the air flowing through the first and second end supply flow path portions 46 and 48 is mainly the fuel cell stack 4. Are supplied to the air electrode side of the fuel cells 14 arranged at both ends of the fuel cell.

  In this embodiment, the central supply flow channel portion 50 and the first and second end supply flow channel portions 46 and 48 of the air content delivery and supply means 42 are provided on one side of the solid oxide fuel cell stack 4 (FIG. 1). The ratio of the width W1 of the first end feed channel portion 46, the width W2 of the central feed channel portion 50, and the width W3 of the second end feed channel portion 48 is For example, W1: W2: W3 = (1.5 to 2.5) :( 7.0 to 5) so that the central feeding flow path portion 50 is positioned at a high temperature portion of the solid oxide fuel cell stack 4. .0): (1.5 to 2.5).

  In this embodiment, temperature detecting means 64 for detecting the temperature of the central portion (that is, a high temperature portion) of the solid oxide fuel cell stack 4 is further provided, and the temperature detecting means 64 is composed of, for example, a thermocouple. Is done. The detected temperature of the temperature detecting means 64 is used to control the rotational speed of the blower 28. When the detected temperature rises, the rotational speed of the blower increases and the air flow rate supplied from the blower to the air flow path 26 is increased. The rotation of the blower 28 is controlled so that the temperature of the solid oxide fuel cell stack 4 does not exceed the set upper limit temperature.

  Next, the operation of the solid oxide fuel cell system 2 described above will be described mainly with reference to FIGS. 1 and 2. A fuel gas (for example, city gas) containing methane as a main fuel gas as a main component is supplied through the fuel gas supply flow path 36, and the supplied fuel gas is pressurized by a booster 38 and then desulfurizer 34. The sulfur component contained in the fuel gas is removed by the desulfurizer 34. The fuel gas desulfurized in the desulfurizer 34 is fed to the fuel reformer 6, the reforming process is performed in the fuel reformer 6, and the reformed reformed gas is supplied to the reformed gas. The fuel is fed to the fuel electrode 18 side of each fuel cell 14 of the solid oxide fuel cell stack 4 through the path 30 and the communication connecting member 16.

  Further, air from the blower 28 is supplied to the air electrode of each fuel cell 14 of the solid oxide fuel cell stack 4 through the air flow path 26 as described later, and this solid oxide fuel cell stack 4. In each of the fuel cells 14, the reformed gas and oxygen in the air react with each other in the fuel cell power generation to generate power.

  The reaction fuel gas from the fuel electrode side of the fuel cell 14 of the solid oxide fuel cell stack 4 and the air from the air electrode side are supplied to the combustion chamber 40 and remain in the reaction fuel gas in the combustion chamber 40. The hydrogen gas that burns is burned. Combustion exhaust gas from the combustion chamber 40 flows through the air preheater 8 and is discharged to the outside through the exhaust passage 62, and in this air preheater 8, the combustion exhaust gas flowing into the discharge passage 62 and Heat exchange is performed with the air flowing through the air flow path 26 to preheat the air, and the preheated air is supplied to the air electrode side of the solid oxide fuel cell stack 4.

  In the solid oxide fuel cell system 4, the air supplied to the solid oxide fuel cell stack 4 is further delivered by the air delivery delivery means 42. For example, when the temperature of the fuel cell stack 4 is low (that is, the detection temperature of the temperature detection means 64 is low) when the solid oxide fuel cell system 2 is in a partial load operation state, the rotational speed of the blower 28 is low. The amount of air supplied from the blower 28 is small, and in this case, the air flowing through the air flow path 26 is delivered and supplied by the air delivery / supply means 42 as shown in FIG. That is, the air from the air blower 28 is caused by the small dynamic pressure of the air flow, so that the first and second end feed flow path portions 46 and 48 of the air content delivery and supply means 42 and the central feed flow path portion. 50 (ie, distributed so that the flow rate per unit area is substantially uniform), and the air flowing through the first and second end feeding flow path portions 46 and 48 is a solid oxide. Heat exchanged with the heat at the end of the fuel cell stack 4 is heated, and is mainly supplied to the air electrode side of the fuel cell 14 at this end, and also flows through the central feed flow path 50. Is exchanged with the heat at the center of the solid oxide fuel cell stack 4 and is mainly supplied to the air electrode side of the fuel cell 14 at the center. At this time, since the flow rate of the air flowing through the first and second end feed flow channel portions 46 and 48 and the central feed flow channel portion 50 is small, the solid oxide fuel cell stack 4 is not excessively cooled. The solid oxide fuel cell system 2 can be partially loaded as required.

  Further, for example, when the deterioration of the solid oxide fuel cell system 2 progresses and the temperature of the fuel cell stack 4 rises (that is, the detected temperature of the temperature detecting means 64 reaches the set upper limit temperature), the blower 28 rotates. The number increases, and the amount of air supplied from the blower 28 increases. In this case, the air flowing through the air flow passage 26 is distributed and supplied by the air distribution and supply means 42 as shown in FIG. . In other words, the distribution ratio of the air from the blower 28 to the central supply flow path portion 50 of the air distribution delivery means 42 is the first and second end supply due to the large dynamic pressure of the air flow. It distributes so that it may become larger than flow-path parts 46 and 48 (namely, the flow volume per unit area of central supply flow-path part 50 distributes more than the 1st and 2nd end supply flow-path parts 46 and 48. ) Therefore, as described above, the air flowing through the central supply flow path section 50 is heat-exchanged with the heat of the central section of the solid oxide fuel cell stack 4, but the heat exchange is performed because the flow rate is large. The cooling effect at the central portion of the fuel cell stack 4 is enhanced, and the central portion (that is, the high temperature portion of the fuel cell stack 4) can be effectively cooled. At this time, the flow rate of the air flowing through the first and second end feeding flow path portions 46 and 48 hardly increases, and therefore the end portion of the solid oxide fuel cell stack 4 may be excessively cooled. However, the solid oxide fuel cell stack 4 as a whole can be maintained at an appropriate temperature state.

  In the embodiment described above, the air content delivery / supply means 42 is provided from the combustion chamber 40 to the solid oxide fuel cell stack 4, but is not limited to such a configuration, and may be provided as shown in FIG. 5. . In FIG. 5, in this embodiment, the air content delivery / supply means 42A is provided adjacent to the solid oxide fuel cell stack 4, and the first and second end feed passages downstream from the connecting portion 44A. The portions 46A, 48A and the central feed channel 50A are arranged to face the side surface of the fuel cell stack 4, and the first end feed channel 46A extends downward at one end of the fuel cell stack 4. The second end feed channel 48A extends downward at the other side of the fuel cell stack 4, and the center feed channel 50A extends downward through the center of the fuel cell stack 4. The other structure of this form is substantially the same as embodiment shown in FIGS.

  Also in this form, the air flowing through the first and second end supply flow path portions 46A, 48A is subjected to heat exchange with the heat generated at both ends of the solid oxide fuel cell stack 4, In addition, the air flowing through the central feed channel 50A is exchanged with the heat generated in the central portion (that is, the high temperature portion) of the fuel cell stack 4, and thus configured as described above. The same effects as described above can be achieved.

  As mentioned above, although the embodiment of the solid oxide fuel cell system according to the present invention has been described, the present invention is not limited to such an embodiment, and various variations and modifications can be made without departing from the scope of the present invention. It is.

  For example, in the above-described embodiment, the air content delivery and supply means 42 (42A) is connected to the first and second end supply flow path portions 46 (46A) and 48 (48A) and the central supply flow path portion 50 (50A). Provided, and the air flowing through the air flow path 26 is divided into three. However, four or five feeding flow path portions are provided, and four or five air from the air flow path 26 are provided. You may make it distribute and supply to two or more.

Examples and Comparative Examples In order to confirm the effect of the solid oxide fuel cell system of the present invention, the following experiment was conducted. As an example, a solid oxide fuel cell system shown in FIGS. 1 and 2 was used, and a power generator with a rated DC power generation end output of 1000 W was generated under a constant rated infusion output condition. A city gas containing 90% methane was used as the fuel gas. The fuel utilization rate was fixed at 73%, and the DC power generation end power was fixed. The air flow rate is controlled so that the air utilization rate is 33 to 37%. When the temperature of the central portion (high temperature portion) of the solid oxide fuel cell stack exceeds 800 ° C., the rotation of the blower is performed. The air flow was increased by increasing the number, and the blower was controlled so that the temperature at the center did not exceed 800 ° C. As the air content delivery and supply means, the one shown in FIG. 2 is used, and the width W1 of the first end feed flow path section, the width W2 of the central feed flow path section, and the width of the second end feed flow path section. The ratio with W3 was W1: W2: W3 = 2.0: 6.0: 2.0. The temperature in the air delivery and supply means was 400 to 600 ° C., the operating pressure was normal pressure, and the exhaust pressure from the solid oxide fuel cell stack to the exhaust of the solid oxide fuel cell system was about 1 kPa. The first temperature detecting means (first thermocouple) is disposed at the center of the solid oxide fuel cell stack, and the second temperature detecting means (second thermocouple) is disposed at the end of the solid oxide fuel cell stack. The temperature state of the fuel cell system was detected.

  The solid oxide fuel cell system was continuously operated and the results shown in Table 1 were obtained. In this embodiment, at the initial stage of power generation, the detected temperature of the first temperature detecting means is 790 ° C., the detected temperature of the second temperature detecting means is 762 ° C., and the detected temperature of the first temperature detecting means as the power generation time elapses. The detected temperature reached 800 ° C. when the operation was continued for about 300 hours, and then the operation was continued for 5000 hours to obtain the results shown in Table 1.

また、比較例として、実施例と同様の定格直流発電端出願１０００Ｗの固体酸化物形燃料電池システムを用い、実施例と同様の条件で定格直流出力一定条件で発電させた。また、実施例の空気分配送給手段に代えて、第１及び第２端送給流路部並びに中央送給流路部が共通の一つの流路部を構成する空気送給手段を用いた。固体酸化物燃料電池スタックの特性、発電条件などは実施例と同一であった。

In addition, as a comparative example, a solid oxide fuel cell system with a rated DC power generation end application 1000 W similar to that of the example was used, and power was generated under a constant DC output constant condition under the same conditions as in the example. Moreover, it replaced with the air content delivery supply means of the Example, and used the air supply means in which the 1st and 2nd end supply flow path part and the central supply flow path part comprised one common flow path part. . The characteristics of the solid oxide fuel cell stack, power generation conditions, etc. were the same as in the examples.

  Also in the comparative example, the solid oxide fuel cell system was continuously operated and the results shown in Table 2 were obtained. In this embodiment, at the initial stage of power generation, the detected temperature of the first temperature detecting means is 790 ° C., the detected temperature of the second temperature detecting means is 760 ° C., and the detected temperature of the first temperature detecting means as the power generation time elapses. When the operation was continued for about 300 hours as in the example, the detected temperature reached 800 ° C., and the operation was continued for 5000 hours to obtain the results shown in Table 2.

表１及び表２から明らかなように、所定の発電条件の下で５０００時間継続して稼動運転した時点における発電効率を対比すると、実施例の固体酸化物形燃料電池システムの方が高い発電効率を維持することができたことが確認できた。比較例の燃料電池システムでは、燃料電池スタックの劣化に伴ってその中央部の温度が上昇し、この温度上昇に伴って空気流量も増大したが、この空気流量の増大は、燃料電池スタックの中央部とその端部とにほぼ同等に増えたために、燃料電池スタックの端部の温度が抑制されて低い温度状態となり、燃料電池スタックの端部における燃料電池セルの発電電圧が低くなる。

As is clear from Tables 1 and 2, when comparing the power generation efficiency at the time of continuous operation for 5000 hours under a predetermined power generation condition, the power generation efficiency of the solid oxide fuel cell system of the example is higher. We were able to confirm that we were able to maintain. In the fuel cell system of the comparative example, the temperature at the center of the fuel cell stack increased with the deterioration of the fuel cell stack, and the air flow rate increased with the temperature increase. Therefore, the temperature at the end of the fuel cell stack is suppressed to a low temperature state, and the power generation voltage of the fuel cell at the end of the fuel cell stack is lowered.

Generally, the power generation output (P) is
Power generation output (P) = Power generation current (I) × Fuel cell stack voltage (V)
And the calorific value (H) is
Calorific value (H) = [Generating current (I)] ² x Internal resistance of fuel cell stack (R)
It is represented by When a constant power generation output is taken out, if the power generation voltage (V) is low, the power generation current (I) increases, thereby increasing the heat generation in the solid oxide fuel cell stack. The air flow rate supplied to the air electrode side of the stack also increases. As a result, the temperature difference between the central portion and the end portion of the solid oxide fuel cell stack in the comparative example was increased as compared with the embodiment, and the direct current power generation end efficiency of the fuel cell stack was reduced. On the other hand, in the embodiment, when the temperature of the central portion of the solid oxide fuel cell stack rises, the distribution ratio of the flow rate of the air flowing through the central feeding flow path portion of the air content delivery and supply means is the first and first. This is larger than the distribution ratio of the flow rate of the air flowing through the two-end supply flow path portion, and the cooling efficiency of the central portion of the fuel cell stack is enhanced, while the cooling of the end portion is suppressed. As a result, the temperature difference between the central portion and the end portion of the solid oxide fuel cell stack in the embodiment becomes small, and the rated power output is not greatly impaired even if the solid oxide fuel cell stack deteriorates. Can be easily taken out.

1 is a cross-sectional view schematically showing an embodiment of a solid oxide fuel cell system. FIG. 2 is a simplified cross-sectional view showing air content delivery / supply means in the solid oxide fuel cell system of FIG. 1. The figure for demonstrating distribution of air when the air flow rate is small at the time of using the air part delivery and supply means of FIG. The figure for demonstrating distribution of air when there are many air flow rates in the case of using the air part delivery supply means of FIG. Sectional drawing which shows other embodiment of a solid oxide fuel cell system simply.

Explanation of symbols

2, 2A Solid oxide fuel cell system 4 Solid oxide fuel cell stack 6 Fuel reformer 8 Air preheater 14 Fuel cell 26 Air channel 28 Blower 40 Combustion chamber 42, 42A Air content delivery and supply means 46, 46A First end feed channel 48, 48A Second end feed channel 50, 50A Central feed channel 58 Air flow line 64 Temperature detection means

Claims (5)

A fuel reformer for reforming a fuel gas to generate a reformed gas, a solid oxide fuel cell stack having a fuel electrode and an air electrode, and the reformed gas from the fuel reformer as the solid A reformed gas feed passage for feeding the fuel electrode side of the oxide fuel cell stack, and an air passage for feeding air from a blower to the air electrode side of the solid oxide fuel cell stack; The solid oxide fuel cell stack includes a solid oxide type that performs a fuel cell power generation reaction between the reformed gas supplied to the fuel electrode side and the air supplied to the air electrode side. A fuel cell system,
The air flow path is provided with an air content delivery means for distributing and feeding the air flowing toward the air electrode, and the air content delivery means is provided on the solid oxide fuel cell stack. A central feed channel for feeding to the center and an end feed channel for feeding to the end of the solid oxide fuel cell stack;
When the flow rate of the air flowing through the air flow path is small, the air delivery / feed means is connected to the end feed flow with respect to the total air flow rate flowing through the air flow path in connection with the small dynamic pressure of the air flow. When the air is distributed and supplied so that the distribution ratio of the distributed air flow to be distributed to the passage is increased, and the flow rate of the air flowing through the air flow path increases, the dynamic pressure of the air flow increases. The air distribution delivery means distributes the air so that a distribution ratio of a distribution air flow rate distributed to the end feed flow path portion with respect to a total air flow rate flowing through the air flow path is small. A solid oxide fuel cell system, characterized by being delivered.   The opening of the central feed channel and the opening of the end feed channel are arranged at different angles with respect to the air flow line of the air flow flowing through the air channel. When the flow rate of the air flowing through the air flow path is changed, the distribution ratio of the distributed air flow distributed to the end feeding flow path section with respect to the total air flow flowing through the air flow path is changed. The solid oxide fuel cell system according to claim 1.   The air content delivery and supply means is provided adjacent to the solid oxide fuel cell stack, and heat exchange is performed between the air flowing through the air content delivery and supply means and the heat of the solid oxide fuel cell stack. The solid oxide fuel cell system according to claim 1, wherein the solid oxide fuel cell system is performed.   A combustion chamber for reacting and burning the fuel reformed gas discharged from the fuel electrode side and the air discharged from the air electrode side is provided on the downstream side of the solid oxide fuel cell stack. The air content delivery / supply means is provided from the combustion chamber to the solid oxide fuel cell stack, and air flowing through the air content delivery / supply means and heat of the combustion chamber and the solid oxide fuel cell stack. The solid oxide fuel cell system according to claim 1, wherein heat exchange is performed between the two.   When temperature detection means for detecting the temperature of the central portion of the solid oxide fuel cell stack is provided, the rotational speed of the blower is controlled based on the detected temperature of the temperature detection means, and the detected temperature rises The solid oxide fuel cell system according to claim 1, wherein an air flow rate supplied from the blower is increased.

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