JP2698481B2 - Power generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generator for generating power using a cylindrical solid oxide fuel cell device.

[0002]

2. Description of the Related Art Recently, fuel cells have attracted attention as power generation devices. This is a device that can directly convert the chemical energy of fuel into electrical energy. It is not restricted by the Carnot cycle, so it has essentially high energy conversion efficiency and can diversify the fuel (naphtha, natural gas). ,
(Methanol, coal reformed gas, heavy oil, etc.), low pollution, and power generation efficiency is not affected by the scale of equipment, and is a very promising technology. In particular, solid oxide fuel cells (SOFC)
The electrode reaction is extremely active because it operates at a high temperature of 1000 ° C.
Since no expensive noble metal catalyst such as platinum is required, the polarization is small, and the output voltage is relatively high, the energy conversion efficiency is significantly higher than other fuel cells. Further, since all the structural materials are composed of solids, they have a stable and long life.

FIG. 4 shows a power generator using a bottomed cylindrical SOFC element. In FIG. 4, an air electrode 17, a solid electrolyte 18, and a fuel electrode 19 are sequentially formed on the surface of a bottomed cylindrical porous support 16 to form a bottomed cylindrical SOFC.
The element 8 is constituted. This SOFC element 8 is fixed at a predetermined position in the power generation chamber 5. However, usually, a large number of SOFC elements 8 are connected in series and in parallel to form an assembled battery.
1 shows only one SOFC element 8 for convenience. A fuel gas chamber 23 is provided below the power generation chamber 5, and the fuel gas chamber 23 and the power generation chamber 5 are separated by a bottomed partition wall 20. A heat insulating partition 21 is provided below the fuel gas chamber 23. An exhaust gas chamber 15 is provided above the power generation chamber 5, and the exhaust gas chamber 15 and the power generation chamber 5 are separated by an open end partition 13. A through hole 13a is formed in the opening end partition wall 13, and the opening end of the SOFC element 8 is inserted into the through hole 13a. A heat insulating partition 22 is provided above the exhaust gas chamber 15, and the oxidizing gas supply pipe 14 is inserted through the through hole and held. The tip opening of the oxidizing gas supply pipe 14 opens in the inner space 12 of the SOFC element 8 toward the bottomed part of the SOFC element 8.

When the oxidizing gas is supplied from the oxidizing gas chamber to the oxidizing gas supply pipe 14 as shown by an arrow F during the operation of the power generating apparatus, the oxidizing gas flowing out of the oxidizing gas supply port is inverted at the bottomed portion, and the porosity is reduced. It flows in the interior space 12 of the quality support 16 and flows out into the exhaust gas chamber 15 as shown by the arrow G. On the other hand, when the fuel gas is supplied from the fuel gas supply hole 21a of the heat insulating partition 21 at the bottom as shown by the arrow A, the pressure in the fuel gas chamber 23 increases, and the fuel is supplied through the fuel gas supply port 20a of the bottomed partition 20. The gas is supplied into the power generation chamber 5 as shown by the arrow B. When this fuel gas flows along the surface of the fuel electrode 19, the fuel gas and oxygen ions diffused in the solid electrolyte react on the surface of the fuel electrode 19, and as a result, the air electrode 17 and the fuel electrode 19 Current flows during The fuel gas used for power generation passes through the gap between the opening end side partition 13 and the opening end of the SOFC element 8 and flows into the exhaust gas chamber 15 as shown by an arrow E.
Since the SOFC element 8 is used at a high temperature of about 1000 ° C., the embodiment shown in FIG. 4 which can be configured without a seal portion is a preferable embodiment.

[0005]

In order to put SOFCs to practical use, it is necessary to reduce costs and improve power density. For this reason, it is required that the length of the SOFC element 8 be increased to increase the power generation output per one. However, the SOFC having the configuration as shown in FIG. 4 has a problem that a remarkable temperature gradient is generated particularly due to the concentration gradient of the fuel gas flow. That is, since the fuel content is still large near the fuel gas supply port 20a, a large amount of fuel is consumed in the electrochemical reaction in the vicinity of the fuel gas supply port 20a, and the temperature rises. This temperature increase further activates the electrochemical reaction between oxygen ions and fuel at the fuel electrode 19.

On the other hand, as the distance from the fuel gas supply port 20a increases, the fuel concentration in the fuel gas decreases, and as a result, the amount of fuel consumed in the electrochemical reaction decreases. For this reason, the temperature of the fuel electrode 19 does not increase so much, and the electrochemical reaction becomes more inactive. Moreover, the fuel gas having a reduced concentration contains a considerable amount of CO ₂ and water vapor as a result of the electrochemical reaction, and these adhere to the surface of the fuel electrode 19 and hinder the reaction. The reaction becomes inactive. For this reason, a large temperature gradient is generated between the upstream side and the downstream side of the fuel gas flow, which can cause cracks when the power generation device is operated for a long period of time, and has a bad influence on the power generation efficiency itself. This tendency becomes more severe and remarkable as the length of the SOFC element 8 increases.

Further, as described above, due to the temperature difference between the parts of the unit cell, the dimensions of the unit cell change during power generation, and the relative positions of the unit cells are shifted, which may cause a connection failure or the like. there were. An object of the present invention is to reduce the gradient of the fuel concentration in the fuel gas flowing through the power generation chamber in a power generator that generates an electric power by installing an assembled battery to which a bottomed tubular SOFC element is connected in the power generation chamber. The purpose is to reduce the resulting temperature difference. It is another object of the present invention to prevent displacement of the unit cells during power generation, thereby preventing problems such as poor connection.

[0008]

SUMMARY OF THE INVENTION The present invention is a power generating apparatus having a plurality of bottomed cylindrical solid oxide fuel cell elements, wherein the plurality of elements are arranged substantially in parallel in a power generating chamber. A collective battery is configured by the elements connected in series and in parallel, and the positive electrode and the negative electrode of the collective battery are respectively connected to the current collector, and the power generation chamber is formed by a partition provided on the bottomed side of the element. The fuel gas supply chamber is divided, and a non-conductive fuel gas supply pipe extending in a direction intersecting the length direction of the element is interposed between the elements connected in parallel. The gas supply pipe is installed at a position away from the partition, a flexible metal material is fixed to the outer peripheral surface of the fuel gas supply pipe, and the flexible metal material is in contact with the fuel electrode of the element, The flexible metal material allows the elements to be aligned with each other. A power generation device, wherein the power generation device is connected to supply an oxidizing gas to the inner space of the element and to supply the fuel gas from a side peripheral surface of the fuel gas supply pipe to the power generation chamber. Things.

The fuel gas refers to a gas containing a fuel such as hydrogen, reformed hydrogen, carbon monoxide and the like. “Oxidizing gas” refers to a gas containing an oxidizing agent such as oxygen or hydrogen peroxide. The fuel gas supply pipe interposed between adjacent elements is formed of a non-conductive material.

Since the fuel gas supply pipe is made of a non-conductive material, the electrical connection between adjacent elements is made of a conductive material,
For example, by metal felt. The fuel gas supply pipe is interposed between the elements connected in parallel.

[0011]

FIG. 1 shows a power generator according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of the same power generator cut along a direction perpendicular to the length direction of the SOFC element. FIG. FIG. 2 is a partially enlarged view of FIG. The same reference numerals are given to the same functional members as the members in FIG. 4, and the description thereof will be omitted.

First, a bottomed cylindrical SOFC element 8 is connected in series and in parallel to form an assembled battery. At this time, in FIG. 1, four columns are shown in series and three columns are shown in parallel, but the number of columns may be changed. An air electrode 17 is provided on the outer periphery of the bottomed cylindrical porous support 16, and a solid electrolyte 18 and a fuel electrode 19 are provided along the outer periphery of the air electrode 17. In FIG. The interconnector 9 is provided on the electrode 17, and the connection terminal 10 is attached thereon. In order to connect the SOFC elements 8 in series, the air electrode 17 of the SOFC element 8 and the fuel electrode 19 of the adjacent SOFC element are connected via the interconnector 9, the connection terminal 10, and the metal felt 11.

In this way, the SOFC elements 8 are connected in series, for example, in four rows. On the other hand, in FIG.
The fuel gas supply pipes 6 are interposed between the SOFC elements 8, respectively. In this embodiment, as shown in FIG. 2, the number of the fuel gas supply pipes 6 is two in a row as viewed in the longitudinal direction of the SOFC element 8. Metal felts 7 are attached to the outer periphery of each fuel gas supply pipe 6 at predetermined intervals at a total of four locations. Each metal felt 7 is in contact with the fuel electrode 19 of the SOFC element 8 adjacent in the left-right direction in FIG.
The fuel supply pipe 6 is made of a porous non-conductive material.
In FIG. 3, the SOFC elements 8 adjacent to each other in the left-right direction are electrically connected by the metal felt 7.

In this way, the SOFC elements 8 are connected in series and in parallel to form an assembled battery in which the SOFC elements 8 are arranged as shown in FIG. However, in FIGS. 1 and 2, for the sake of convenience, the detailed structure and the like of each SOFC element 8 are not shown, and the interconnector 9 and the connection terminal 10 are shown integrally. The positive electrode and the negative electrode of the assembled battery thus configured are electrically connected to the current collecting plate 4 via the metal felt 11, respectively. The current collectors 4 serve as a pair of current collectors of the battery pack, and each current collector 4 is connected to a lead wire (not shown). The assembled battery and the current collector plate 4 are housed in the power generation chamber 5 in an integrated state.

Among the partitions forming the power generation chamber 5, an open-end partition 13 is provided on the open end side of the bottomed cylindrical SOFC element 8, and the position of the SOFC element 8 is located on the open-end partition 13. A circular through-hole 13a is provided corresponding to the above, and the opening end of the SOFC element 8 is inserted into each circular through-hole 13a. Each SOFC
An oxidizing gas supply pipe 14 is inserted into each of the inner spaces 12 of the elements 8.

Among the partitions forming the power generation chamber 5, the bottomed partition 20 provided on the bottomed side of the SOFC element 8 is substantially perpendicular to the length direction of the SOFC element 8. In this embodiment, the bottomed portion of the SOFC element 8 is placed on the bottomed partition 20. Further, among the partition walls forming the power generation chamber 5, SO
A pair of side partition walls 3 are provided so as to sandwich the assembled battery including the FC elements 8 and the two current collector plates 4. These side partition walls 3 are substantially parallel to the length direction of the SOFC element 8, and a pair of side partition walls 3 are arranged substantially parallel to each other. The side partition wall 3 and the current collector plate 4 face each other with a slight space therebetween. A can body 1 made of a heat insulating material so as to surround the bottomed side partition 20 and the pair of side partitions 3.
Is formed, and a fuel gas chamber 2 is provided between the can body 1 and the bottomed side wall 20 and the side wall 3. At the bottom of the can 1, a fuel gas supply port 1a is provided.

A plurality of fuel gas supply ports 20a are regularly provided in the bottomed partition wall 20 at predetermined intervals. Further, the side partition walls 3 and the current collector plate 4 have circular through holes 3a, 4a corresponding to the positions of the fuel gas supply pipes 6, respectively.
Are formed, and the fuel gas supply pipe 6 is inserted into and held by these circular through holes 3a and 4a. Each fuel gas supply pipe 6
Are slightly projecting into the fuel gas chamber 2 respectively.

When the power generator is operated, an oxidizing gas is supplied to the oxidizing gas supply pipe 14 as shown by an arrow F.
This oxidizing gas blows out from an opening at the tip of the oxidizing gas supply pipe 14, collides with the bottom of the SOFC element 8, changes its direction, rises in the inner space 12, and flows into the exhaust gas chamber 15 as shown by an arrow G. Is discharged. On the other hand, the fuel gas is supplied from the fuel gas supply port 1a to the fuel gas chamber 2 as shown by an arrow A. As a result, the pressure of the fuel gas chamber 2 increases, so that the fuel gas is supplied from each fuel gas supply port 20a into the power generation chamber 5 as shown by the arrow B.

Since the inner space 6a of each fuel gas supply pipe 6 communicates with the fuel gas chamber 2, the fuel gas flows from the fuel gas chamber 2 to the inner space 6a as shown by the arrow C. Since each fuel gas supply pipe 6 is formed from a heat-resistant porous material, the fuel gas flowing into the inner space 6a flows from the side peripheral surface of each fuel gas supply pipe 6 to the power generation chamber as shown by the arrow D. Blow out to 5. Here, the interconnector 9 of each SOFC element 8,
The metal felt 11 for connecting the SOFC element 8 in series with the SOFC element 8 has a strip shape and extends along the length direction of the SOFC element 8. For this reason, SOFCs that are adjacent in series
The space between the elements 8 is considerably closed by the strip-shaped interconnector 9 and the metal felt 11, so that the flow of the fuel gas is difficult. Therefore, the fuel gas radially blown out from the side peripheral surface of each fuel gas supply pipe 6 in the radial direction of the fuel gas supply pipe 6 eventually rises as shown by the arrow H in FIG. Used.

The depleted fuel gas that has been sufficiently used for power generation finally passes through the gap between each SOFC element 8 and the partition 13 on the open end side, flows into the exhaust gas chamber 15 as shown by the arrow E, and is depleted in the oxidized gas. Mixed with.

Air electrode 17 may be doped or undoped LaMnO ₃ , CaMnO _3, LaNiO ₃ , La
LaMnO ₃ , which can be produced from a conductive perovskite oxide such as CoO _{3 or} LaCrO ₃ and is doped with strontium, is preferred. The solid electrolyte 18 is made of yttria-stabilized zirconia,
It is preferable to manufacture with yttria partially stabilized zirconia or the like. In general, the fuel electrode 19 is preferably made of nickel-zirconia cermet or cobalt-zirconia cermet. The interconnector 9 may be a doped or undoped perovskite LaCr
O ₃ and LaMnO ₃ are preferred.

According to this embodiment, since the fuel gas is supplied from the side peripheral surface of the fuel gas supply pipe 6 formed of a porous material, the fuel gas supply pipe 6 is provided separately from the bottomed side partition wall 20. Also, fresh and less depleted fuel gas can always be supplied to the side near the open end of the SOFC element 8. Therefore, the gradient of the fuel concentration in the power generation chamber 5 is reduced and made uniform, so that the temperature gradient in the length direction of the SOFC element 8 can be reduced. As a result, even if the power generator is operated for a long time, the SO
Since cracks and the like hardly occur in the FC element 8 and unevenness of the electrochemical reaction can be reduced, the power generation efficiency of each SOFC element 8 can be improved as compared with the conventional case.

Further, a metal felt 7 is adhered to the side peripheral surface of the fuel gas supply pipe 6, and the fuel electrode of each SOFC element 8 does not directly contact the fuel gas supply pipe 6, but the metal felt 7 abuts. I have. Therefore, even if the SOFC element 8 expands and contracts due to a change in temperature, the displacement caused by the expansion and contraction is absorbed by the deformation of the metal felt 7, so that the SOFC element 8 is less likely to crack. In addition, since the temperature difference between the respective parts of the elements is reduced as described above, the degree of shrinkage is reduced, and the respective elements are positioned in the parallel connection direction by the fuel gas supply pipe 6, so that each element is displaced due to misalignment. No connection failure occurs.

As described above, the fuel gas supply pipe 6 is formed of a porous non-conductive material. As the porous non-conductive material, non-conductive ceramics such as porous zirconia and alumina are preferable.

The open porosity of the fuel gas supply pipe 6 is 10
It is preferably set to ~ 90%. If the open porosity exceeds 90%, the strength of the fuel gas supply pipe 6 decreases, and the open porosity becomes 10%.
If it is less than the above value, the permeation amount of the fuel gas decreases. Further, the open porosity of the fuel gas supply pipe 6 is given an appropriate gradient so that the fuel can be uniformly distributed in the power generation chamber 5.

The following method can be used to provide a gradient in the open porosity of the fuel gas supply pipe 6. (1) When the fuel gas supply pipe 6 made of porous ceramics is manufactured by firing, one end of the powder compact having the shape of the fuel gas supply pipe is held, and a weight is attached to the other end of the powder compact. To suspend the powder compact. This allows
A relatively large load is applied to a side near one end of the powder compact, and the powder compact is slightly elongated, and the open porosity increases. In addition, since a load is not so much applied to the side near the other end of the powder compact, the open porosity is relatively small. (2) Prepare a tubular sintered body made of porous ceramics. Next, the filler is impregnated into the open pores of the sintered body to fill the open pores to some extent, and then the sintered body is dried or heated to fix the filler. At this time, by changing the impregnation amount of the filler in each part of the tubular sintered body, a gradient can be provided in the open porosity of the sintered body.

In the above example, the fuel gas supply pipe 6 is formed of a porous material, but may be formed of a dense heat-resistant and reduction-resistant material.

In this case, several fuel gas supply ports are provided through the wall of the fuel gas supply pipe, and the fuel gas is blown out from these fuel gas supply ports. The size, position, and number of these fuel gas supply ports are optimized so that the fuel is evenly distributed to each SOFC element 8.

In the above embodiment, the metal felt 7 is brought into contact with the SOFC elements 8 adjacent to each other in the left-right direction in FIG.
The position, number, inner diameter, and outer diameter of the fuel gas supply pipe 6 can be changed as appropriate. At the present time, in order to effectively supply fuel gas into the power generation chamber 5 and prevent the size of the battery pack from increasing,
It is preferable that the outer diameter of the fuel gas supply pipe 6 be 1 to 8 mm.

In each of the above embodiments, each SOFC element 8
Was held up and down. That is, the length direction of each SOFC element 8 was vertical. However, it is also possible to hold each SOFC element 8 in the horizontal direction and make the length direction of each SOFC element 8 coincide with the horizontal direction to manufacture the power generation device.

Further, the temperature gradient in the longitudinal direction of the SOFC element was measured using each of the power generators shown in FIGS. However, measurement points a, b, c, d, and e as shown in FIG. 2 were selected as the measurement points, and the distance between the measurement points was 100 mm. The fuel gas used was 96% hydrogen and 4% water vapor, and the oxidizing gas used was air. A thermocouple was used to measure the temperature of the SOFC element.
Further, the output per SOFC element shown in FIGS. 1 to 3 and 4 was also compared. The results are shown below. The power generator of FIG. 4 abcde 1036 ° C 1020 ° C 1005 ° C 944 ° C 870 ° C output 7.8 W The power generator of FIGS. As can be seen from the results, according to the power generators of FIGS. 1 to 3, the temperature gradient between the measurement points a to e can be reduced, thereby increasing the overall output.

[0032]

According to the present invention, fresh and less depleted fuel gas can always be supplied to the side near the open end of each element. Therefore, the gradient of the fuel concentration in the power generation chamber is reduced and made uniform, so that the temperature gradient in the length direction of the element can be reduced. As a result, even if the power generator is operated for a long time, cracks and the like are less likely to occur in the SOFC element, and unevenness of the electrochemical reaction can be reduced. In addition, since the temperature difference between the respective parts of the elements is reduced as described above, the degree of shrinkage is reduced, and the respective elements are positioned in the parallel connection direction by the fuel gas supply pipe. No defect occurs. In addition, a flexible metal material is adhered to the outer peripheral surface of the fuel gas supply pipe, and the flexible metal material is in contact with the fuel electrode of each element without directly contacting the fuel gas supply pipe. Therefore, even if the element expands and contracts due to a change in temperature, the displacement caused by the expansion and contraction is absorbed by the deformation of the flexible metal material, so that the element is less likely to crack.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a power generation device according to an embodiment of the present invention, taken along a direction perpendicular to the length direction of a SOFC element.

FIG. 2 is a schematic cross-sectional view of the power generator according to the embodiment of the present invention, which is cut horizontally with respect to the length direction of the SOFC element.

FIG. 3 is a cross-sectional view showing a part of the power generation device of FIG. 1 in an enlarged manner.

FIG. 4 is a cross-sectional view showing a conventional power generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Can body 2, 23 Fuel gas chamber 3 Side partition 4 Current collector 5 Power generation chamber 6 Fuel gas supply pipe 7 Metal felt 8 Bottom cylindrical SOFC element 11 Strip shaped metal felt 12 Inner space of SOFC element 15 Exhaust gas chamber A, B, C, D, E, H Fuel gas flow F, G Oxidizing gas flow

Claims (2)

(57) [Claims] 1. A power generation device comprising a plurality of bottomed cylindrical solid oxide fuel cell elements, wherein the plurality of elements are arranged substantially in parallel in a power generation chamber.
An assembled battery is configured by the elements connected in series and in parallel, and the positive electrode and the negative electrode of the assembled battery are connected to a current collector, respectively, and the partition is provided on the bottomed side of the element. A power generation chamber and a fuel gas supply chamber are partitioned, and a non-conductive fuel gas supply pipe extending in a direction intersecting the length direction of the element is interposed between the elements connected in parallel. The fuel gas supply pipe is installed at a position distant from the partition wall, and a flexible metal material is fixed to an outer peripheral surface of the fuel gas supply pipe. Metal elements are in contact with each other, and the elements are connected in parallel with each other by the flexible metal material. The element supplies an oxidizing gas to the inner space of the element, and from the side peripheral surface of the fuel gas supply pipe to the power generation chamber. And supply fuel gas Characterized in that it is configured to so that power generation apparatus. 2. The power generator according to claim 1, wherein the fuel gas supply pipe is porous.