JPH05174858A - Manifold fastening structure for fusion carbonate type fuel cell - Google Patents

Abstract

PURPOSE:To enhance durability, improve electrical characteristics such as volt age and internal resistance, and concurrently prevent gas from leaking by deal ing with chemical, physical and structural disorders produced by operations continued for a long time at high temperatures. CONSTITUTION:A fuel gas passage is partitioned by an U-shaped anode side corrugated plate 5, so that the passage is divided into two, that is, a first and a second fuel gas passage 48 and 49. The locating position of modified medium 1 from the fuel gas inlet port and the range of a distance for arrangement in both the fuel gas passages 48 and 49 are made constant respectively.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to fuel cells, and more particularly to molten carbonate fuel cells.

[0002]

2. Description of the Related Art In an internal reforming type molten carbonate fuel cell in which a raw material fuel gas is reformed into a hydrogen-rich reformed fuel gas by a reforming catalyst, the reforming catalyst is used in a main body of the fuel cell. There are an indirect type installed in a reforming container dedicated to gas reforming provided between power generation sections and a direct type installed in a fuel cell main body section. In this case, in the former case, the reforming reaction and the anode reaction proceed separately, so that the hydrogen generated in the reforming reaction is not successively consumed, but in the latter case, since both the above reactions occur in close proximity, the hydrogen is successively consumed. The advantage is that the reforming reaction is accelerated. (Hereinafter, the "raw material fuel gas" before reforming and the "reforming fuel gas" after reforming will be simply referred to as "fuel gas" unless it is necessary to distinguish them depending on the presence or absence of a reforming reaction. FIG. 1 shows a main part of a direct internal reforming molten carbonate fuel cell according to the prior art. In the figure, 1 is a columnar reforming catalyst in which nickel is supported on alumina, 2 is a cathode whose main component is nickel oxide, 3 is an anode whose main component is nickel, 4 is lithium aluminate and an electrolyte (carbonic acid). Lithium, potassium carbonate) is an electrolyte plate,
These constitute the power generation section of the fuel cell. Under the above structure of the power generation section, further, on the back surface of the cathode, an oxidant gas (in most cases, a mixed gas of air and carbon dioxide, which is indicated by "O ₂ ". Also, the cathode gas which is the same as the illustrated method is the anode gas which is the fuel gas on the back surface of the anode (not shown in this figure, but in the following illustration, the single arrow and “C
H ₄ ”. ) Are flowing in mutually orthogonal directions. The reforming catalyst reforms the supplied raw material fuel gas such as methane to hydrogen gas, and the hydrogen gas and oxygen in the oxidant gas react with each other through the molten carbonate to generate power. Done. Incidentally, 5 is a corrugated plate for the purpose of rectifying the fuel gas on the anode side, maintaining a proper flow disturbance to keep the new fuel gas in contact with the anode, and also for supporting and mounting the reforming catalyst. Cathode frame, 7 anode frame, 8 cathode side current collector plate made of stainless steel punching plate, 9 anode side current collector plate made of nickel punching plate, 10 cathode side corrugate for rectification of stainless steel, etc. The plates are, so to speak, together with the above-mentioned components (1 to 4) directly connected to power generation, constitute the fuel cell main body.

However, since the voltage of the above-mentioned fuel cell main body is low and not practical because it is only one, it is often used by laminating a plurality of fuel cell bodies in series. In this case, the stack of unit cells, which is usually called a stack, has the same structure as the anode frame of the upper unit cell except the cathode frame 6 of the upper unit cell and the anode frame 7 of the lower unit cell. The flat surface portion 7a and the flat surface portion 6a of the sort cell frame 6 of the unit cell immediately below the flat surface portion 7a
Together form a gas separation plate, and the side wall portion 7b of the anode frame 7 and the side wall portion 6b of the cathode frame 6 serve as a part of a stack side wall (hereinafter, simply referred to as "stack side wall") and a spacer. .. Then, as a means for introducing the raw material fuel gas and the oxidant gas into each unit cell of the stack, a box-shaped member called a manifold 21 as shown in FIG. 2 is used to introduce each gas into each unit cell. Has been adopted. 2 shows the concept of the horizontal section of the manifold.

Although FIGS. 3, 8, 10 and 12 are diagrams of an embodiment described later, FIGS. 8 and 12 conceptually show the stacked state of the unit cells, and FIGS. Reference numeral 10 conceptually shows the appearance of the mounted state of the manifold. This is structurally called an external manifold, and is installed on the side surface of the stack body so as to surround the stack body. or,
As shown in FIGS. 3A and 3B, a manifold having a leaf spring mechanism called a manifold clamping plate 31 is used to install the manifold, and the manifold main body 32 is pressed against the side surface of the stack 33. In the figure, 34 is a gasket, 35 is an insulating plate, and 61 is a heater plate that stores a heater for supplying insufficient reforming reaction heat.

Further, since the fuel cell is a high-temperature chemical reaction vessel, the chemical reaction at high temperature, that is, power generation, is smoothly maintained, and the secondary chemical reaction, physicochemical reaction, thermal deformation, etc. Various measures are taken to prevent deterioration and the like. Specifically, in order to improve the reforming reaction, the porosity of the collector plate between the reforming catalyst and the anode at the feed fuel gas inlet is made smaller than at other parts, and the melt mixed in the fuel gas is melted. To prevent the carbonate from deteriorating the reforming catalyst, seal portions are formed on both sides of the cathode frame and the anode frame. To prevent sintering of the anode, C is added to the anode.
For example, a sintering inhibitor such as r is added, and a manifold clamp is used to prevent gas leakage due to thermal strain of the manifold.

[0006]

However, the fuel cell according to the prior art, particularly the molten carbonate fuel cell, has the following problems. (1) In the direct internal reforming type, most of the reforming reaction of the raw material fuel gas is carried out at the inlet side of the fuel gas, so that the deterioration of the reforming catalyst in this part is more remarkable than in other parts. Become. For this reason, the cell voltage drops despite the fact that the reforming catalysts at the center and the fuel gas outlet side function. In addition, the reforming reaction is an endothermic reaction, so that the temperature drop on the fuel gas inlet side becomes significant, and the effect extends to the power generation section. For these reasons, the battery voltage is lowered, and the battery life is shortened due to deterioration of the reforming catalyst.

Further, as a countermeasure against this, if the porosity of the collector plate between the reforming catalyst and the anode is made smaller at the fuel gas inlet portion than at other portions, the anode reaction at the inlet portion is suppressed. Therefore, the H ₂ O gas generated by the anode reaction becomes insufficient, carbon easily breaks out, and it becomes difficult to supply the fuel gas to the anode, and the cell characteristics deteriorate. (2) Similarly, in the direct internal reforming fuel cell, even if the seal portions are provided on both side surfaces of the anode frame and the cathode frame,
It is not possible to completely prevent the mixture of molten carbonate into the fuel gas,
For this reason, the electrolyte oozing out from the sealing surface of the anode electrode or the like or mixed in the fuel gas adheres to the reforming catalyst, resulting in significant deterioration of the reforming catalyst.

As a result, the battery voltage drops and the battery life shortens. (3) Since the surface of the anode is a nickel particle sintered body, which is the main component, in a fuel gas atmosphere of high temperature and high pressure, sintering agglomeration proceeds and the thickness decreases. This decrease is remarkable on the outlet side where the amount of H ₂ O gas is large, and therefore the thickness of the anode becomes non-uniform, and the electrical contact between the anode and the electrolyte plate or current collector plate becomes poor, so that the internal resistance increases. As a result, the battery performance will not be fully exhibited. However, if the sintering inhibitor is excessively mixed, the production itself by sintering the anode becomes difficult. (4) In the stack of the external manifold type fuel cell in which the electrode area is large (2000 cm ² or more), and the number of stacked layers is about 20 cells, the manifold itself is also large. As a result, the dimensional strain cannot be completely absorbed by the conventional fastening method using the manifold fastening plate. Under a continuous operation for a long time, the manifold tightening pressure becomes uneven, which causes a problem such as gas leakage.

Of course, as a countermeasure against this, there may be adopted a structure in which the rear surface of the manifold is pressed by a separate tightening tool, and the tightening pressure is efficiently transmitted to the manifold flange section, but in the case of a metal tightening tool. The rear part of the manifold is close to the battery body, causing corrosion due to the scattering and adhesion of electrolyte, and in the case of highly corrosion-resistant ceramic fasteners, the current ceramic has small thermal expansion and is vulnerable to thermal shock, so it is not suitable for practical use. There are difficulties.

The present invention has been made for the purpose of solving the above-mentioned series of problems resulting from the fate that a molten carbonate fuel cell is physically, structurally, and chemically complicated and is operated at high temperature for a long time. Is.

[0011]

In order to achieve the above object, and particularly to solve the problem (1), in the internal reforming molten carbonate fuel cell according to the invention of claim 1, an anode and a cathode are provided. Are disposed with an electrolyte plate in between, and a fuel gas passage for supplying the anode is provided on the back side of the anode, while an oxidant gas passage for supplying an oxidant gas to the cathode is provided on the back side of the cathode. In the provided internal reforming molten carbonate fuel cell, the fuel gas passage is provided on the anode side, and Lo is transformed into the reforming fuel gas from the raw material fuel gas inlet in the raw material fuel gas inlet side passage. When the distance to the outlet is defined as the first fuel gas passage in which the reforming catalyst is arranged in the passage at a distance from the inlet of the raw material fuel gas to 0.7Lo, The reforming catalyst is provided in the direction opposite to the anode (on the back side) and is free to move in and out of the first fuel gas passage, and the reforming catalyst is arranged within the range of 0.3 Lo or more and Lo or less from the raw material fuel gas inlet in the fuel gas outlet passage It is characterized by having a second gas passage.

In particular, in order to solve the above problem (1), in the internal reforming molten carbonate fuel cell according to the invention of claim 2, the anode and the cathode are arranged with the electrolyte plate sandwiched therebetween, and A molten carbonate fuel cell in which a fuel gas passage for supplying a fuel gas to the anode is provided on the back side of the anode and an oxidant gas passage for supplying an oxidant gas to the cathode is provided on the back side of the cathode. The reformed fuel gas exiting the first fuel gas passage located on the oxidant gas outlet side on the anode side and the reforming catalyst located on the oxidant gas inlet side on the anode side Has a second fuel gas passage having a width in the range of 2 to 5 times the width of the first fuel gas passage.

In particular, in order to solve the above-mentioned problem (2), in the direct internal reforming molten carbonate fuel cell according to the invention of claim 3, the anode and the cathode are arranged so as to sandwich the electrolyte plate, and A fuel gas passage provided with a reforming catalyst for reforming the fuel gas and a gas separation plate for separating the fuel gas and the oxidant gas are sequentially provided on the back side of the anode, and the gas separation is performed. In a direct internal reforming molten carbonate fuel cell in which sealing surfaces are formed on both sides of the plate, a protective plate for protecting the reforming catalyst is provided between the fuel gas passage and the gas separation plate. It is characterized by

In order to solve the above-mentioned problem (3), in the molten carbonate fuel cell anode according to the invention of claim 4, an electrolyte plate holding a carbonate is sandwiched between the anode and the cathode and held. In a molten carbonate fuel cell in which fuel gas is supplied to the anode and oxidant gas is supplied to the cathode to generate power, the content of the second component metal or metal oxide, which is the sintering inhibitor of the anode, is determined by the flow direction of the fuel gas. It is characterized by changing along.

In particular, in order to solve the above-mentioned problem (4), the fastener for molten carbonate fuel cell according to the invention of claim 5 has a structure for directly pressing the rear face of the manifold and its own thermal expansion. Is characterized by having a structure capable of converting into a manifold tightening pressure and being made of high thermal expansion ceramic.

[0016]

With the above construction, in the invention of claim 1, the anode side is filled with the reforming catalyst at the inlet side of the raw fuel gas, and the reforming catalyst is filled at the outlet side of the reforming fuel gas. Since the second fuel gas passage is provided, the raw fuel gas is distributed to both passages, most of the fuel gas is supplied to the inlet portion of the fuel gas from the first fuel gas passage, and the fuel gas is provided to the center portion of both fuel gas passages. The fuel is supplied from the passage, and most of the outlet is supplied from the second fuel gas passage.

According to the second aspect of the present invention, the fuel gas supplied from the inlet of the first fuel gas passage is reformed by the endotherm from the high temperature oxidant waste gas without being significantly lowered in temperature, and then the other stack surface. A closed manifold attached to the second fuel gas passage reversely supplies the second fuel gas passage. According to the third aspect of the invention, the protective plate provided between the fuel gas passage and the gas separation plate prevents penetration of the molten carbonate from the sealing surface or the like. In the invention of claim 4, the sintering inhibitor having a large content along the fuel gas flow direction prevents the progress of uneven sintering along the fuel gas flow direction of the anode. In the invention of claim 5, the fastener made of high thermal expansion ceramic directly presses the rear surface of the manifold by the pressure obtained by converting its thermal expansion.

[0018]

【Example】

(First Embodiment) The invention according to claim 1 will be described below based on an embodiment. FIG. 4 is a vertical cross-sectional view orthogonal to the flow direction of the raw fuel gas near the inlet of the raw fuel gas of the unit cell of the direct internal reforming molten carbonate fuel cell stack according to the present invention. In the figure, reference numeral 4 is an electrolyte plate, on the lower surface of which an anode 3 is provided, and on the upper surface thereof, a cathode 2 made of a sintered body of nickel oxide is provided. On the upper surface side of the cathode 2, a cathode side current collector plate 8
A cathode-side corrugated plate 10 which has a corrugated plate shape and constitutes a passage for an oxidant gas (a mixed gas of air and carbon dioxide gas in this embodiment), and a cathode frame 6 are sequentially provided. That is, the above configuration is the same as that of the conventional technique shown in FIG. Next, the configuration of the portion according to the present invention will be described.

On the lower surface side of the anode 3, an anode side current collector plate 9 and an anode side corrugated plate 5 which has a corrugated plate shape and forms a fuel gas passage in a direction perpendicular to the cathode side corrugated plate 10. The anode frame 7 is sequentially stacked. Therefore, the first fuel gas passage 48 is formed by the anode-side corrugated plate 5, the anode-side collector plate 9 and the anode 3.
Similarly, the anode-side corrugated plate 5 and the anode frame flat surface portion 7a constitute a second fuel gas passage 49. Further, both of the fuel passages enable the passage of fuel gas through the holes of the corrugated plate (not shown). Furthermore,
As shown in FIG. 5, the reforming catalyst 1 includes the first fuel gas passage 48.
Is filled in the fuel gas inlet side, that is, in the range where the distance from the raw material fuel gas inlet is 0 or more and 0.6 Lo or less,
On the other hand, in the second fuel gas passage 49, the distance from the fuel gas outlet side, that is, the raw material gas inlet is 0.4 Lo or more L
It is filled in the following range.

For this reason, the reforming catalyst in the second fuel gas passage 49 is not shown in FIG. On this occasion,
0.6L from the gas inlet tip in the passage of the first fuel gas
In the fuel cell according to the prior art, the reforming reaction is almost completed from the inlet tip of the fuel gas passage to 30% of the whole in the fuel cell according to the prior art. In consideration of the fact that the fuel gas passage is divided into two in this embodiment, the fuel gas passage is divided by 30% so as to appropriately share the reforming reaction in both passages. is there. However, in reality, since the fuel gas flows between the first fuel gas passage and the second fuel gas passage, the value of 0.6 Lo is another condition such as the degree of the passage of fuel gas in both passages. There may be some increase or decrease depending on the first fuel gas passage and the second fuel gas passage.
Of course, the reforming catalyst filling portions of the fuel gas passage may overlap. Then, the electrolyte plate 4, the anode 3,
Cathode 2, both collector plates 8 and 9, corrugated plates 5 and 1
0, the cathode frame 6 and the anode frame 7 constitute a unit cell P, and a large number of the unit cells P are laminated and fastened in the stacking direction by upper and lower end plates (not shown) to form a battery stack.

Further, a fuel gas supply manifold is connected to the fuel gas suction portion, and an oxidant gas supply manifold is connected to the oxidant gas suction portion (not shown in FIG. 4). The stacking and reinforcing structure, the uniform flow of the fuel gas into each unit cell, and the like are the same as those of the molten carbonate fuel cell according to the related art, and thus the description thereof will be omitted.

Now, under the above gas flow path configuration, the raw material fuel gas supplied from the gas supply manifold to the rear side raw material fuel gas inlet of each anode 3 is the first fuel gas passage 48 and the second fuel gas. After being introduced into the gas passage 49, it is reformed into reformed fuel gas by the reforming catalyst 1 and then supplied to the anode 3 to cause a cell reaction. At this time, in the present embodiment, on the anode side, the first fuel gas passage 48 filled with the reforming catalyst 1 at the fuel gas inlet side and the second fuel gas filled with the reforming catalyst 1 at the fuel gas outlet side are provided. Passage 49
Further, since the ratio of the gas passing through both gas passages is appropriate, the raw fuel gas is distributed to both passages, and then the reformed fuel gas necessary for power generation is first supplied to the fuel gas inlet portion. It is supplied from the fuel gas passage 48, is supplied from both fuel gas passages 48 and 49 at the central portion, and is largely supplied from the second fuel gas passage 49 at the outlet portion. Therefore, the suppression of the anode reaction in the vicinity of the inlet is eliminated, and eventually the H ₂ O gas does not run short in the vicinity of the fuel gas inlet. As a result, it is possible to prevent the carbon from leaking into the fuel gas passage and clogging of the fuel gas passage.

Further, since the raw material fuel gas is distributed to both passages, the reforming reaction becomes uniform on both the inlet side and the outlet side of the fuel gas. Therefore, it is possible to suppress deterioration of the reforming catalyst and uneven temperature distribution in the vicinity of the reforming reaction portion, which in turn suppresses a decrease in battery voltage, a decrease in temperature at the fuel gas inlet side, and a decrease in battery life. It will be possible. The invention according to claim 1 has been described above based on the embodiments, but it goes without saying that the invention is not limited to the above embodiments. That is, for example, the raw material fuel gas is the first fuel gas because the reforming catalyst at the inlet of the first fuel gas passage changes the flow passage cross-sectional areas of the first fuel gas passage and the second fuel gas passage to some extent instead of 1: 1. When it is difficult to flow into the passage, a passage-resistant material similar in shape to the reforming catalyst is provided in the second fuel gas passage, and conversely, a passage-resistant material is provided at the outlet of the first fuel gas passage. Means such as suppressing the outflow of the reformed gas may be taken.

However, since the fuel cell has a high temperature and the shape thereof is complicated, a method of finding the optimum one by experiments in individual plants is adopted for the setting of the passage holes for the fuel gas in both gas passages. (Experiment 11) In the above-mentioned embodiment, the outlet of the second fuel gas passage 49 is open as shown in FIG. 5, but in the performance experiment of the present invention, it is blocked by nickel wool or the above-mentioned stack side wall. Of the structure that prevents the fuel gas from being directly discharged from the second fuel gas passage 49 by finally flowing into the first fuel gas passage from the vicinity of the outlet (such a stack (cell), Hereinafter, this is performed in (A) stack. As a comparative example, a stack (cell) having the same structure as the above (A) stack except that the second fuel gas passage was not provided (hereinafter referred to as (X) stack) was used.

FIG. 6 shows the measurement results of the relationship between the ratio of the distance L from the fuel gas inlet of the (A) stack and the (X) stack to the Lo and the temperature. The above L is the distance from the fuel gas inlet to the measurement position. The experimental conditions are
The ratio of water vapor to methane in the raw fuel gas is 3: 1, the current density is 150 mA / cm ² , and the set temperature of the battery is 650.
A ° C., also the electrode effective area 250 cm ^2, was used a stack of laminated number 4 cells.

As is apparent from FIG. 6, (X) of the comparative example.
It can be seen that in the stack, the temperature drastically decreases near the inlet of the fuel gas and rises with increasing distance from the inlet, whereas in the stack (A), the temperature is substantially uniform. Now, considering that the reforming reaction is an endothermic reaction and the temperature decreases in the portion where the reforming reaction is progressing, it can be seen that the reforming reaction is uniformized in the stack (A).

(Experiment 12) FIG. 7 shows the results of measurement of changes with time in the average voltage of the (A) stack of the present invention and the (X) stack of the comparative example. The experimental conditions are as described above (Experiment 1
Same as 1). As is clear from this figure, the initial voltage of the (X) stack of the comparative example is maintained only for about 700 hours, while the initial voltage of the (A) stack is maintained for about 1300 hours. ..

In addition, it is also recognized that the voltage drop of the (A) stack is slower than that of the (X) stack. (Second Embodiment) The invention according to claim 2 will be described below based on an embodiment. FIG. 8 is an exploded perspective view of a unit cell of an internal reforming molten carbonate fuel cell which is an embodiment of the present invention.

In the figure, 2 is a cathode, 3 is an anode, 4 is an electrolyte plate, 5 is an anode-side corrugated plate, and 7c.
Is a gas separation plate, 8 is a cathode side current collecting plate, 9 is an anode side current collecting plate, 12 and 13 are stack side walls and spacers,
Their basic structure is the same as in the prior art. Therefore, their description is omitted. Next, the part relating to the present invention will be described.

The anode side corrugated plate 5 is the anode 3,
Together with the gas separation plate 7C, the first fuel gas passage 51 and the second fuel gas passage 51
The fuel gas passage 52 is formed, and the chip-shaped reforming catalyst 1 is filled and held in both passages above and below the corrugated plate 9. Further, a carbonate absorbing material 53 containing lithium aluminate as a main component is filled and held in a boundary portion separating the first fuel gas passage 51 and the second fuel gas passage 52.
The ratio of the widths of the gas passages is preferably 1/5 to 1/2 of the first fuel gas passage / the second fuel gas passage, and is 1/3 in this embodiment.
I am trying. In addition, a preferable ratio of the widths of both gas passages is 2 to
The reason for No. 5 is that in the fuel cell according to the prior art, the reforming reaction is almost completed within a distance of 30% from the tip of the fuel gas passage. This is because the gas is located in a portion where the heat of the gas is not high, and the uniform flow of the fuel gas in both gas passages, and particularly in the first fuel gas passage is taken into consideration. The first fuel gas passage 51 is located on the oxidant gas outlet side, and the second fuel gas passage 52 is located on the oxidant gas inlet side.

Under the above structure, the raw material fuel gas is introduced from the inlet of the first fuel gas passage 51. Next, the flow of fuel gas will be described. FIG. 9 is a schematic plan view showing the flow of fuel gas according to the present embodiment. In the figure, a first fuel gas passage 51 and a second fuel gas passage 52, which are arranged parallel to each other in the vertical direction of the gas flow, are provided on one circumferential surface of the cell stack.
Are opened, and on the inlet side of the first fuel gas passage 51,
A raw fuel gas supply manifold 21a is attached, and for supplying reformed fuel gas to the other peripheral surface of the stack so that the outlet side of the first fuel gas passage 51 and the inlet side of the second fuel gas passage 52 communicate with each other. The closed manifolds 21b are attached respectively. Further, a fuel waste gas discharge manifold 21c is attached to the outlet side of the second fuel gas passage 52 in parallel with the raw fuel gas supply manifold 21a.

Further, manifolds 22a and 22b for supplying and discharging the oxidant gas are attached to the other opposing peripheral surfaces, respectively. Note that FIG. 10 is an external perspective view of this embodiment. However, the manifold fasteners, heaters, etc., which are not directly related to the invention of this claim, are omitted because the drawings are complicated.

Next, the operation of this embodiment will be described. The raw fuel gas is supplied from the manifold 21a to the first fuel gas passage 51.
Reforming is performed under the heat of the cathode exhaust gas at a high temperature in addition to the reaction heat (about 650 ° C.) that is supplied to the reactor and is supplied from a battery (not shown). Then, the reformed fuel gas generated in the first fuel gas passage 51 is inverted by the closed manifold 21b and introduced into the second fuel gas passage 52, supplied to each cathode, and then reacted with the cathode gas to generate electric power. .. After that, the reacted anode waste gas is discharged into the manifold 2
It is discharged from the battery 1c to the outside of the battery.

At this time, in the first fuel gas passage 51,
Receiving heat from the oxidant exhaust (waste) gas that has become high temperature due to power generation, almost all of the raw material fuel gas is reformed without a drastic temperature decrease due to the reforming reaction which is an endothermic reaction. However, in consideration of the presence of unreformed raw fuel gas due to deterioration of the reforming catalyst 1 or the presence of raw fuel gas leaking from the boundary of the first / second fuel gas passage, the second fuel gas The passage 52 is also filled with the reforming catalyst 1.

In this embodiment, from the standpoint of preventing carbonate poisoning of the catalyst, the carbonate absorbent is filled and held above and below the corrugated plate, which is the boundary between the first fuel gas passage and the second fuel gas passage. Inconel or N
It goes without saying that a metal spacer made of a material such as i-plated reduction corrosion resistant material may be provided.

As a matter of course, the ratio of the widths of the two gas passages can be determined to be an optimum value within the range of 2 to 5 by experiments in individual fuel cells. (Third Embodiment) The invention according to claim 3 will be described based on an embodiment. 11 and 12 show an embodiment of a direct internal reforming molten carbonate fuel cell according to the present invention. FIG. 11 is a schematic sectional view of a unit cell, and FIG. 12 is an exploded perspective view of a main part of a stack. It is a figure.

In FIGS. 11 and 12, 1 is a reforming catalyst, 2 is a cathode, 3 is an anode, 4 is an electrolyte plate, 5 is an anode side corrugated plate, 6 is a cathode frame, 7 is an anode frame, and 8 is a cathode side. Collector plate, 9 is a collector plate on the anode side,
Reference numeral 10 is a cathode side corrugated plate, 12 and 13 in FIG. 12 are fuel gas side and oxidant gas side stack side walls and spacers, each of which has a rectangular parallelepiped shape, and 7c is a flat portion of the cathode frame and the anode frame integrated with each other. Gas separation plates, which are the same as those of the related art,
The description is omitted.

Reference numeral 24 denotes a protective plate made of a nickel thin plate having a plate thickness of 0.1 to 0.2 mm and having a sufficient water (liquid) tightness, which constitutes an essential part of the present invention. Next, the fuel cell stack sealing mechanism closely related to the present invention will be described. The fuel cell stack is constructed by stacking a large number of the unit cells shown in FIG. 11 as shown in FIG. 12 and tightening them in the stacking direction with upper and lower end plates (not shown). However, as described in the prior art, the cathode frame 6 and the anode frame 7 integrally form the gas separation plate 7c and the stack side walls and spacers 12 and 13 in the unit cell in the middle of stacking. In this embodiment, a rectangular parallelepiped stack sidewall / spacer 12 is fixed to both sides of the upper surface of the gas separating plate 7c along the flow direction of the fuel gas, while oxidizer gas is attached to both sides of the lower surface. A rectangular parallelepiped stack side wall / spacer 13 is fixed along the flow direction (orthogonal to the fuel gas flow direction). The stack side walls and spacers 12 and 13 also serve as flow path side walls for forming the flow paths of the fuel gas and the oxidant gas. As a result, the gas separation plate 7c is formed by pressing the separator portion 7c for separating the fuel gas and the oxidant gas and the stack side walls and spacers 12, 13 against the electrolyte plate 14, 15. And will have.

Under the above structure, the protective plate 2 according to the present invention
The width of 4 is made narrower than the separation portion of the gas separation plate 7c, so that a gap is created between the bent portion 24a of the protection plate 24 and the reinforcing member 12. A chip-shaped carbonate absorbent 53 made of lithium aluminate is filled and held in this gap. Next, this operation will be described. The protective plate prevents the molten carbonate impregnated in the electrolyte plate 4 from penetrating into the anode-side corrugated plate 5, and thus suppresses the deterioration of the reforming catalyst 1 filled and held in the anode-side corrugated plate 5. it can. Furthermore, since the protective plate 24 is made of nickel, which has poor (low) wettability with respect to carbonate, deterioration due to carbonate adhering to the nickel surface of the reforming catalyst can be further suppressed. In addition, as described above, the bent portion 24 of the protective plate 24
Since the molten salt absorbent is filled and held in the gap between a and 12, even if the molten carbonate would otherwise permeate into the anode side corrugated plate 5 through the seal, the molten carbonate would melt. It will be absorbed by the salt absorbent. Therefore, the deterioration of the reforming catalyst 1 can be further suppressed. At this time, since it is a thin plate, it is not only easy to bend,
It can absorb heat contraction reasonably, and because it is lightweight, no load due to weight is generated.

The molten salt absorbent is not limited to lithium aluminate, and any other porous absorbent that is stable with respect to molten carbonate may be used. Further, in the above embodiment, the gap between the bent portion 24a of the protection plate 24 and the fuel gas side stack side wall / spacer 12 is provided on both sides, but one end is fixed to the fuel gas side stack side wall / spacer. Of course, the structure may be such that the gap is formed only on one side.

(Fourth Embodiment) The invention according to claim 4 will be described based on an embodiment. FIG. 13 is a schematic sectional view of an internal reforming molten carbonate fuel cell according to the present invention. In the figure, 1 is a reforming catalyst, 2 is a cathode, 4 is an electrolyte plate, 5 is an anode side corrugated plate, 6 is a cathode frame, 7 is an anode frame, 8 is a cathode side current collecting plate, and 9 is an anode side current collecting plate. Board,
Reference numeral 10 denotes a cathode side corrugated plate, which are the same as those in the related art. Therefore, the description thereof is omitted.

Reference numeral 3 is an anode which is a main part of the present invention. In this embodiment, the content of the sintering inhibitor is changed by dividing the anode 3 into two parts, an upstream part and a downstream part of the fuel gas flow indicated by a single arrow. The upstream anode 3a is Ni / 5.
Ni produced by forming Cr alloy powder by a doctor blade method and sintering at 1000 ° C. for 1-2 hours in a hydrogen atmosphere.
A / 5Cr porous plate is used. On the other hand, the downstream side anode 3b uses a Ni / 10Cr porous plate made of Ni / 10Cr alloy powder by the same method.

This anode, a cathode obtained by sintering carbonyl nickel powder in an inert atmosphere, and a eutectic salt (L
i ₂ CO ₃ / K ₂ CO ₃ = 62/38 mol%) is used to prepare a fuel cell unit cell using an electrolyte plate made of a lithium aluminate matrix. (Experiment 41) Experimental results of the operation of the battery having the above configuration are shown below.

[0044]

[Table 1]

The anode is H ₂ / CO ₂ / H ₂ O (= 7
2/18/10%) fuel gas is supplied, operating temperature 65
At 0 ° C, fuel gas utilization rate is 75%, current density is 150 mA /
It is a gas composition at the anode inlet and outlet when operated under the condition of cm ² . Since H ₂ O is produced by the cell reaction, the amount of H ₂ O is 10% at the fuel gas inlet but 45% at the outlet.

Since the amount of H ₂ O in the downstream portion of the fuel gas flow is larger than that in the upstream portion, the atmosphere is apt to promote the reduction of the thickness of the anode, but the downstream portion contains Cr as a sintering inhibitor. Since a large amount of anode is used, the mechanical strength is high and the reduction in thickness due to the progress of sintering is suppressed. As a result, H ₂ generated along the fuel gas flow direction
The deterioration of the cell characteristics due to the non-uniformity of the thickness reduction in the upstream and downstream portions of the fuel gas flow due to the difference in O amount was improved.

Although the invention of claim 4 has been described based on the embodiments and the like, it goes without saying that the present invention is not limited to the above embodiments. That is, in the present embodiment, the anode was divided into two parts, the upstream part and the downstream part of the fuel gas flow. However, if the content of the sintering inhibitor is changed sequentially along the fuel gas flow direction,
Corresponding mechanical strength can be obtained by the amount of H ₂ O in the fuel gas, resulting in better results.

In this embodiment, Ni was used as the main component of the anode and Cr was used as the second component, but Cu or an alloy or mixture of Ni and Cu was used as the main component, and C was used as the second component.
Similar results are obtained when using a metal or metal oxide of o, Al, Zr, or a mixture thereof. In short, the optimum material, division, etc. are selected for each fuel cell in consideration of ensuring appropriate sinterability in manufacturing the anode, compensation for sintering during fuel cell operation, and the like.

(Fifth Embodiment) A fastener for a molten carbonate fuel cell according to the invention of claim 5 will be described with reference to an embodiment. FIG. 14 is a perspective view of the attached state,
FIG. 15 is a side view. In both figures, 61 is a heater plate surrounding a heater that supplies the heat of reforming reaction which is insufficient for only the battery, 21 is a manifold, 21d is a manifold rear part, 34 is a gasket, and 35 is an insulating plate. The description is omitted because it is the same as the technology.

Reference numeral 36 is a lateral tightening tool according to the present invention, 37 is a bolt, and 38 is a nut, both of which function as a unit with the lateral tightening tool. The material of the tightening tool used in this example is ZrO ₂ 50 vol% and MgF ₂
It is a highly thermal expansive ceramic obtained by mixing and sintering 50 vol%, and is processed into a substantially L shape as shown in FIGS. 14 and 15. However, only the topmost portion has a wall thickness because it is necessary to provide a hole for the bolt 37 to pass through.

The installation method is the same as that of the conventional one, that is, the nut 3 is inserted through the bolt 37 standing on the side surface of the heater plate 61.
This is done by tightening 8 with the specified torque. When the temperature rises, the heater plate 61 expands outward, that is, expands in the direction of the tightening tool 36, and the tightening tool 36 attached to the manifold 21 via the bolts 37 also moves outward, that is, in the direction of the anti-heater plate 61. Therefore, the tightening tool 36
Moves in the direction in which the tightening pressure loosens, but the tightening tool 36
Because of the shape of the arm 36a, the arm 36a (a part of the lower part of the L shape) of the tightening tool 36 expands toward the heater plate 61. Therefore, the manifold tightening pressure is reduced only slightly.

When the temperature is lowered, the opposite effect is exerted. Therefore, excessive thermal stress is not generated, and damage of the tightening tool can be prevented. In addition, although the tightening tool is approximately L-shaped in the present embodiment, it is not limited to this as long as it can compensate for thermal expansion and contraction of the bolt. Of course, for example, the "one" part under "L" may be much longer.

(Experiment 51) A performance test of the fastener according to the present invention was conducted by operating a molten carbonate fuel cell having an electrode area of 3000 cm ² and a stack number of 20 cells in the same manner as in the prior art. During the operation for about 1000 hours, the gas leakage from the manifold did not increase, and there was no slack in the manifold and no damage to the manifold clamp when observed after cooling.

From the above, it was confirmed that it is possible to maintain a stable and efficient tightening pressure during long-term operation. It was also confirmed that a high temperature resistant elastic body such as a spring washer made of high temperature resistant nickel alloy was inserted between the nut and the tightening tool to maintain the tightening pressure more appropriately. Was done.

In addition to the above-mentioned embodiment, this high thermal expansion ceramic contains CaF ₂ , MgF ₂ , AlF ₃ , ScF ₃ , Y in any one of Al ₂ O ₃ , ZrO ₂ and BaTiO _3.
It may be obtained by mixing and sintering any one of F ₃ and LaF ₃ .

[0056]

As described above, according to the invention of claim 1, the raw material fuel gas is distributed to both passages, so that the reforming reaction becomes uniform regardless of the inlet side and the outlet side of the fuel gas.
Therefore, it is possible to eliminate the ubiquity of the cell temperature, which is a temperature drop on the fuel gas inlet side. Further, the distribution of the fuel gas within the cell surface can be made uniform, the reforming reaction can be carried out uniformly on the cell surface, and the uneven distribution of catalyst deterioration can be eliminated. Further, the pressure loss on the inlet side and the outlet side of the fuel gas can be small. Furthermore, since the anode reaction is not suppressed at the inlet portion, there is no shortage of water vapor at the inlet portion. As a result, it is possible to suppress carbon from protruding and to prevent clogging of the fuel gas passage. Therefore, the cell life and cell characteristics of the internal reforming fuel cell can be dramatically improved.

According to the invention of claim 2, the fuel gas passage on the anode side is divided into two, and the raw material fuel gas supplied from the inlet of the first fuel gas passage is reformed and then attached to the other stack surface. Since it is reversely supplied to the second fuel gas passage by the closed manifold, a portion having a large endotherm due to the reforming reaction is located on the high temperature oxidant gas discharge side, and the reforming reaction is smoothly performed.

As a result, it is possible to prevent the temperature distribution on the surface of the battery from becoming uneven and to improve the battery characteristics. According to the invention of claim 3, since permeation of the molten salt in the vicinity of the seal surface where permeation is likely to occur can be suppressed, the reforming catalyst is less likely to deteriorate. As a result, the catalytic ability of the reforming catalyst is maintained for a long time, so that the cell characteristics of the fuel cell can be improved and the life of the cell can be extended.

According to the fourth aspect of the present invention, it is possible to prevent a non-uniform thickness reduction of the anode along the fuel gas flow direction, and thus, the anode and the electrolyte plate or the current collector plate due to the non-uniform thickness of the anode. It is possible to prevent contact failure of the battery, increase of electric resistance due to the contact failure, and deterioration of battery performance. According to the invention of claim 5, a more stable manifold tightening pressure is supplied, the tightening pressure is not reduced and thermal stress is not generated even during operation at high temperature, and chemical deterioration, physical damage, and mechanical damage are prevented. By providing a non-fastening tool, it is possible to prevent gas leakage and the like over a long period of high temperature operation.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a vertical cross section of a unit cell of a direct internal reforming molten carbonate fuel cell according to a conventional technique.

FIG. 2 is a conceptual diagram of an external manifold of a direct internal reforming molten carbonate fuel cell according to the related art.

FIG. 3 is a mounting view of a manifold fastener of a direct internal reforming molten carbonate fuel cell according to the prior art.

FIG. 4 is an exploded perspective view of an embodiment of a direct internal reforming molten carbonate fuel cell according to the invention of claim 1.

FIG. 5 is a diagram showing an arrangement of reforming catalysts in the above embodiment.

FIG. 6 is a comparison experimental result of temperature distributions of the above-described example and the related art.

FIG. 7 is a result of comparison experiment of voltage-time curves of the above-described example and the related art.

FIG. 8 is an exploded perspective view of an embodiment of an internal reforming molten carbonate fuel cell according to the invention of claim 2;

FIG. 9 is a plan conceptual diagram showing a flow of fuel gas in the above-mentioned embodiment.

FIG. 10 is an external perspective view of the above embodiment.

FIG. 11 is a schematic cross-sectional view of an embodiment of a direct internal reforming molten carbonate fuel cell according to the invention of claim 3.

FIG. 12 is a divided perspective view of the above embodiment.

FIG. 13 is a schematic cross-sectional view of an internal reforming molten carbonate fuel cell according to the invention of claim 4.

FIG. 14 is an external perspective view of a molten carbonate fuel cell manifold fastening device according to the fifth aspect of the present invention in a mounted state.

FIG. 15 is a side view of the above embodiment.

[Explanation of symbols]

 1 Reforming Catalyst 2 Cathode 3 Anode 3a Upstream Anode 3b Downstream Anode 4 Electrolyte Plate 5 Anode Side Corrugated Plate 6 Cathode Frame 6a Cathode Frame Plane 6b Cathode Frame Sidewall 7 Anode Frame 7a Anode Frame Plane 7b Anode Frame Sidewall 7c Gas separation plate 8 Cathode side current collector plate 9 Anode side current collector plate 10 Cathode side corrugated plate 12 Fuel gas side stack side wall (also spacer) 13 Oxidant gas side stack side wall (also spacer) 14 Cathode side wet seal surface 15 Anode Side wet seal surface 21 Manifold 21a Raw material fuel gas manifold 21b Closed manifold 21c Anode waste gas manifold 21d Manifold rear surface 22a Oxidizing gas supply manifold 22b Oxidizing gas discharge manifold 24 Plate 24a Protective Plate Bent Part 31 Manifold Tightening Plate 32 Manifold Main Body 33 Stack Side Surface 34 Gasket 35 Insulating Plate 36 Ceramic Manifold Tightening Tool 36a Ceramic Manifold Tightening Arm 37 Bolt 38 Nut 48 First Fuel Gas Passage 49 Second Fuel Gas Passage 51 First fuel gas passage 52 Second fuel gas passage 53 Carbonate absorbent 61 Heater plate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshihiko Saito 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd. (72) Inventor Nobuhiro Furukawa 2-18 Keiyo Hondori, Moriguchi Sanyo Electric Co., Ltd. (72) Inventor Yasuhiko Ito 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd. (72) Inventor Kimihiko Okuchi 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. An anode and a cathode are arranged so as to sandwich an electrolyte plate, and a fuel gas passage for supplying the anode is provided on the back side of the assault, while an oxidizer is added to the cathode on the back side of the cathode. In an internal reforming molten carbonate fuel cell provided with an oxidant gas passage for supplying gas, the fuel gas passage is provided on the anode side, and Lo is an inlet of a raw material fuel gas in a fuel gas inlet side passage. The first fuel gas passage in which the reforming catalyst is arranged in the passage in the range of 0.7 Lo from the inlet of the raw material fuel gas, when the distance from the outlet to the reformed fuel gas is It is provided in the direction opposite to the anode (on the back side) from the first fuel gas passage, and the gas can freely move in and out of the first fuel gas passage, and 0.3 L from the raw fuel gas inlet in the fuel gas outlet passage.
An internal reforming molten carbonate fuel cell, characterized in that it has a second gas passage in which a reforming catalyst is arranged in a range of a distance from o to Lo. 2. An anode and a cathode are arranged with an electrolyte plate in between, and a fuel gas passage for supplying a fuel gas to the anode is provided on the back side of the anode, while a cathode is provided on the back side of the cathode. In the internal reforming molten carbonate fuel cell in which an oxidant gas passage for supplying the oxidant gas is provided in the first fuel, the anode side is the first fuel located on the oxidant gas outlet side and the reforming catalyst is disposed. The width of the gas passage and the passage through which the reformed fuel gas exits from the first fuel gas passage, which is also located on the oxidant gas inlet side, is 2 to 5 times the width of the first fuel gas passage. An internal reforming molten carbonate fuel cell having a second fuel gas passage. 3. An anode and a cathode are arranged with an electrolyte plate sandwiched between them, and a fuel gas passage provided with a reforming catalyst for reforming the fuel gas on the back side of the anode, a fuel gas and an oxidant gas. In the direct internal reforming molten carbonate fuel cell in which a gas separation plate for separating the gas separation plate is provided in sequence, and seal surfaces are formed on both side surfaces of the gas separation plate, the fuel gas passage and the gas A direct internal reforming molten carbonate fuel cell, characterized in that a protective plate for protecting the reforming catalyst is provided between the separating plate and the separating plate. 4. An anode and a cathode are arranged with an electrolyte plate in between, and a fuel gas passage for supplying a fuel gas to the anode is provided on the back side of the anode, while a cathode is provided on the back side of the cathode. In the internal reforming molten carbonate fuel cell in which the oxidant gas passage for supplying the oxidant gas is provided, the content of the second component metal or metal oxide, which is the sintering inhibitor of the anode, is changed to the fuel gas flow. An internal reforming molten carbonate fuel cell anode characterized by being changed along the direction. 5. A molten carbon dioxide characterized by having a structure for directly pressing the rear surface of the manifold, having a structure capable of converting its own thermal expansion into a pressure for tightening the manifold, and being made of a highly thermally expansive ceramic. Fasteners for salt fuel cells.