JP7215032B2 - fuel cell device - Google Patents

Description

The present invention relates to a fuel cell device.

Patent Literature 1 discloses a fuel cell device that includes a fuel cell stack, a reformer, and a combustor. The reformer reforms the reformed raw material gas to generate a fuel gas to be supplied to the fuel cell stack. The reformer has a reforming catalyst inside it. When the reforming raw material gas, which has been brought to a temperature at which the reforming reaction occurs, contacts the reforming catalyst, the reforming reaction occurs and the fuel gas is generated. The combustor burns the fuel off-gas and oxidant off-gas discharged from the fuel cell stack to generate flue gas. The reforming raw material gas is heated by the flue gas to a temperature at which the reforming reaction occurs.

In the fuel cell device of Patent Document 1, the reformer is arranged around the combustor. The flue gas flowing out from the combustor flows from the inner peripheral side to the outer peripheral side of the reformer, and then flows through the flow path on the outer peripheral side of the reformer. As a result, the reforming raw material gas is heated by heat exchange between the flue gas and the reforming raw material gas via the heat transfer wall. At this time, the flow of the flue gas flowing through the flow path on the outer peripheral side of the reformer is parallel or countercurrent to the flow of the reformed raw material gas flowing through the reformer.

JP 2016-1524 A

However, as a result of investigation by the present inventor, when the flow of the combustion exhaust gas is parallel to the flow of the reformed raw material gas, the heat exchange performance is poor, so the temperature of the reformed raw material gas at the outlet of the reformer is , the reforming rate was found to be lower than the high target temperature. Therefore, it is required to ensure high heat exchange performance to bring the temperature of the reforming raw material gas closer to the target temperature.

On the other hand, when the combustion exhaust gas flows countercurrently to the reformed raw material gas flow, the heat exchange performance is excellent, so the reformed raw material gas temperature at the outlet of the reformer can be raised to the target temperature. However, in this case, the present inventor found that the temperature of the portion of the reforming catalyst in the reformer near the heat transfer wall becomes high, causing thermal deterioration of the reforming catalyst. Therefore, it is required to suppress thermal deterioration of the reforming catalyst.

In order to suppress thermal deterioration of the reforming catalyst, a flow path for supplying oxidant gas to the combustor is added, and oxidant off-gas and another oxidant gas are supplied to the combustor. can be considered. According to this, the temperature of the combustion exhaust gas can be lowered by increasing the amount of the oxidant gas supplied to the combustor and lowering the combustion temperature. However, in this case, the temperature difference between the flue gas and the raw material gas for reforming becomes small, and the heat exchange performance deteriorates, which is not preferable.

In view of the above points, the present invention aims to provide a fuel cell device capable of ensuring high heat exchange performance between the reforming raw material gas and the flue gas and suppressing thermal deterioration of the reforming catalyst. aim.

In order to achieve the above object, according to the invention of claim 1 ,
The fuel cell device
a fuel cell stack (2) that generates electricity through an electrochemical reaction using a fuel gas and an oxidant gas;
a reformer (16) that reforms the reformed raw material gas to generate a fuel gas and supplies the generated fuel gas to the fuel cell stack;
a combustor (4) that burns the fuel gas contained in the fuel off-gas discharged from the fuel cell stack and the oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack to generate flue gas;
a flue gas flow path (6) through which the flue gas flows,
The reformer has a reforming catalyst (165) for reforming the reforming raw material gas, and a catalyst placement section (S22) in which the reforming catalyst is arranged and through which the reforming raw material gas flows,
The flue gas flow path is a heating portion (S24, S25) in which the flue gas flowing through the flue gas flow path heats the reforming raw material gas flowing through the catalyst arrangement portion by heat exchange via the heat transfer walls (161, 162). has
The catalyst placement portion includes a first heat transfer wall (161) as a heat transfer wall formed in a cylindrical shape around the axis, and a heat transfer wall (161) formed in a cylindrical shape so as to cover the entire circumferential direction of the first heat transfer wall. It is formed between the second heat transfer wall (162) as a heat wall,
The heating unit includes a first heating unit (S24) and a second heating unit (S25) located downstream of the first heating unit in the flow of combustion exhaust gas,
The first heating section is formed on the opposite side of the catalyst placement section across the first heat transfer wall,
The second heating part is formed on the opposite side of the catalyst placement part with the second heat transfer wall interposed therebetween,
In the catalyst placement portion, the reforming raw material gas flows from one side to the other side in the axial direction of the first heat transfer wall,
In the first heating section, combustion exhaust gas flows from one side in the axial direction to the other side,
In the second heating section, the combustion exhaust gas flows from the other side toward the one side in the axial direction .
Further , according to the invention of claim 1 ,
The flue gas flow path has a communicating portion (S26) that communicates the first heating portion and the second heating portion on the other side in the axial direction with respect to the catalyst placement portion,
The fuel cell device
a first offgas flow path (8, S21) that guides a portion of the oxidant offgas to the combustor;
a second off-gas flow path (10) for directing another part of the oxidant off-gas to the second heating part by bypassing the combustor, the first heating part and the communicating part.

According to the first aspect of the invention, the flow of the flue gas in the first heating section is parallel to the flow of the reforming raw material gas in the catalyst placement section. The flow of the combustion exhaust gas in the second heating section is countercurrent to the flow of the reforming raw material gas in the catalyst placement section. Thereby, the temperature rise of the heat transfer wall can be suppressed as compared with the case where the flow of the combustion exhaust gas in the entire heating section is countercurrent to the flow of the reforming raw material gas. Therefore, thermal deterioration of the reforming catalyst can be suppressed. Furthermore, the temperature of the reforming raw material gas can be made higher than in the case where the combustion exhaust gas flows in parallel with the reforming raw material gas in the entire heating section.

Furthermore, according to the first aspect of the present invention, there are heat transfer walls that transfer heat from the combustion exhaust gas to the reforming raw material gas on both the inner and outer sides of the catalyst placement portion. As a result, compared to the case where the heat transfer wall is provided only on one side of the catalyst placement portion, the heat transfer area to the reforming raw material gas can be increased, and the heat transfer performance of the reformer can be improved. .

Therefore, according to the first aspect of the invention, it is possible to ensure high heat exchange performance between the reforming raw material gas and the flue gas and to suppress thermal deterioration of the reforming catalyst.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

1 is a block diagram showing components of a fuel cell system in which the fuel cell device according to the first embodiment is used; FIG. It is a cross-sectional schematic diagram which shows the internal structure of the fuel cell apparatus in 1st Embodiment. In each of the fuel cell device of the first embodiment and the fuel cell device of Comparative Example 1, the temperature of the combustion exhaust gas at each position in FIG. 4 and the temperature of the reformed raw material gas at each position in FIG. 4 were measured. It is a figure which shows a result. FIG. 3 is an enlarged view of a combustor, a reformer, and their surroundings in FIG. 2;

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
First, the fuel cell system FCS to which the fuel cell device 30 is applied will be described. As shown in FIG. 1, the fuel cell system FCS includes a fuel cell stack 2, a combustor 4, a flue gas flow path 6, a first offgas flow path 8, a second offgas flow path 10, a combustor introduction A flow path 12 , a fuel recycle flow path 14 , a reformer 16 , an evaporator 18 , a desulfurizer 20 , an ejector 22 , an air preheater 24 and an exhaust heat recovery device 26 are provided. In this embodiment, the fuel cell stack 2, the reformer 16, the combustor 4, the flue gas flow path 6, and the like are modularized and constitute a fuel cell device 30, as will be described later.

The fuel cell stack 2 generates electricity through an electrochemical reaction using fuel gas and oxidant gas. In this embodiment, a gas containing hydrogen gas and carbon monoxide produced by a steam reforming reaction in the reformer 16 is used as the fuel gas. Air is used as the oxidant gas. Electrical energy is generated by an electrochemical reaction between hydrogen in the fuel gas and oxygen in the oxidant gas.

The fuel cell stack 2, also called a cell stack, is an assembly of a plurality of fuel cells (not shown). Each fuel cell is a solid oxide fuel cell (Solid Oxide Fuel Cell: SOFC), in which a fuel electrode (that is, an anode) is formed on one side of a flat solid electrolyte, and the other side An air electrode (that is, a cathode) is formed on the surface of the . Both the fuel electrode and the air electrode are porous bodies made of conductive ceramics. In the fuel cell stack 2, all the fuel cells are vertically stacked and electrically connected in series.

The combustor 4 burns the fuel gas contained in the fuel off-gas and the oxidant gas contained in the oxidant off-gas to generate flue gas. The fuel off-gas is gas containing fuel gas discharged from the fuel cell stack 2 . The oxidant off-gas is gas containing oxidant gas discharged from the fuel cell stack 2 . In the present embodiment, air is used as the oxidant gas, so hereinafter the oxidant off-gas is also referred to as air off-gas.

The flue gas channel 6 is a channel through which the flue gas flows. The flue gas flow path is positioned adjacent to each of the reformer 16 , air preheater 24 and evaporator 18 . Thereby, each of the reformer 16, the air preheater 24 and the evaporator 18 is heated by the flue gas. In this embodiment, the flue gas passage 6 is arranged so that the flue gas flows through the reformer 16, the air preheater 24 and the evaporator 18 in this order. A portion of the flue gas flow path 6 downstream of the evaporator 18 is connected to an exhaust heat recovery device 26 .

The first offgas flow path 8 is a flow path that guides part of the oxidant offgas to the combustor 4 . The second offgas flow path 10 is a flow path that guides another part of the oxidant offgas to the flue gas flow path 6 while bypassing the combustor 4 . In the present embodiment, as will be described later, the second off-gas channel 10 joins the oxidant off-gas to a heating portion of the flue gas channel 6 that heats the reformer 16 .

The combustor introduction channel 12 is a channel that guides part of the fuel off-gas to the combustor 4 . The fuel recycling channel 14 is a channel for supplying another portion of the fuel off-gas to the fuel cell stack 2 . In this embodiment, the downstream end of the fuel recycle channel 14 is connected to the suction port 22 b of the ejector 22 . That is, the downstream end of the fuel recycle channel 14 is connected in the middle of the channel that supplies the reformed raw material gas to the reformer 16 . The fuel recycle channel 14 joins the fuel off-gas with the reformed raw material gas supplied to the reformer 16 .

The reformer 16 reforms the reformed raw material gas to generate a fuel gas. The reformer 16 supplies the produced fuel gas to the fuel electrode of the fuel cell stack 2 . A mixed gas of city gas and water vapor is supplied to the reformer 16 as a reforming raw material gas. Town gas is gas containing hydrocarbons (eg, methane). In the reformer 16, the town gas and steam are heated by heat exchange with the flue gas.

The evaporator 18 heats water by heat exchange with flue gas to produce steam. The evaporator 18 supplies the generated steam to the reformer 16 . The desulfurizer 20 removes sulfur components contained in the city gas. The desulfurizer 20 supplies the city gas from which sulfur components have been removed to the reformer 16 .

The ejector 22 supplies the reforming raw material gas to the reformer 16 , sucks the fuel off-gas, and supplies the sucked fuel off-gas to the reformer 16 . The ejector 22 has an inlet 22a, a suction port 22b, and a discharge port 22c. An inlet 22a of the ejector 22 is connected to a confluence section 21 where city gas and steam merge. The fuel recycling channel 14 is connected to the suction port 22b. The reformer 16 is connected to the discharge port 22c. The ejector 22 injects the fuel gas from a nozzle (not shown) inside the ejector 22 to suck the fuel off-gas from the fuel recycling passage 14 and discharge the sucked fuel off-gas together with the reforming raw material gas.

The air preheater 24 heats air by heat exchange with combustion exhaust gas. The air preheater 24 supplies preheated air to the air electrode of the fuel cell stack 2 . The exhaust heat recovery device 26 recovers the heat of the combustion exhaust gas. The exhaust heat recovery device 26 heats water by heat exchange with combustion exhaust gas to generate hot water for hot water supply.

Next, the fuel cell device 30 will be explained. As shown in FIG. 2, the fuel cell device 30 includes a casing 32, a base plate 34, a fuel cell stack 2, a reformer 16, a combustor 4, a flue gas channel 6, and the like.

The casing 32 is a substantially cylindrical housing that accommodates the fuel cell stack 2, the reformer 16, the combustor 4, the flue gas flow path 6, and the like. The side and top surfaces of the casing 32 are covered with heat insulating material (not shown).

Casing 32 has a first tubular wall 36 , a second tubular wall 38 , a third tubular wall 40 , a fourth tubular wall 42 , a fifth tubular wall 44 and a sixth tubular wall 46 . . Each of the first to sixth cylindrical walls 36 to 46 is a wall made of metal and cylindrically formed around an axis. The first to sixth cylindrical walls 36 to 46 are arranged such that their respective axes are at the same position, and their respective axes extend along the vertical direction. 2 shows a cross section of the fuel cell device 30 taken along a plane along the axes of the first to sixth cylindrical walls 36 to 46. As shown in FIG.

The base plate 34 is a metal plate horizontally arranged inside the casing 32 . The base plate 34 divides the internal space of the casing 32 into two vertically aligned spaces.

The first tubular wall 36 is positioned innermost among the first to fifth tubular walls 36-44. The first tubular wall 36 is located above the base plate 34 . The upper end of the first cylindrical wall 36 is connected to a circular first top plate 48 . The internal space S11 of the first cylindrical wall 36 is sealed by the first top plate 48, the base plate 34, and the like. The fuel cell stack 2 is accommodated in the internal space S11 of the first tubular wall 36 .

An air supply opening 361 is formed in the first cylindrical wall 36 . An air supply pipe 50 is connected to the air supply opening 361 . The air supply pipe 50 is a pipe for supplying air from the air supply opening 361 to each fuel cell of the fuel cell stack 2 .

Also, the air off-gas from the fuel cell stack 2 is discharged into the internal space S11 of the first cylindrical wall 36 . The internal space S11 of the first cylindrical wall 36 constitutes part of the flow path through which the air off-gas discharged from the fuel cell stack 2 flows.

The fuel cell stack 2 is supported by support members 52 . The support member 52 forms a space between the fuel cell stack 2 and the base plate 34 and lifts the fuel cell stack 2 so that this space communicates with a space on the side of the fuel cell stack 2 .

The second cylindrical wall 38 extends vertically from a position above the base plate 34 to a position below the base plate 34 . The inner diameter of the second tubular wall 38 is equal to the outer diameter of the base plate 34 . The second tubular wall 38 and the base plate 34 are fixed with the base plate 34 arranged inside the second tubular wall 38 .

An upper portion 38 a of the second tubular wall 38 above the base plate 34 is located outside the first tubular wall 36 and covers the entire circumferential direction of the first tubular wall 36 . A first space S<b>12 is formed between the first tubular wall 36 and the upper portion 38 a of the second tubular wall 38 over the entire circumference of the first tubular wall 36 .

The third tubular wall 40 is arranged outside the second tubular wall 38 and covers the entire circumferential direction of the second tubular wall 38 . A second space S<b>13 is formed between the second tubular wall 38 and the third tubular wall 40 over the entire circumference of the second tubular wall 38 .

The fourth tubular wall 42 is arranged outside the third tubular wall 40 and covers the entire circumference of the third tubular wall 40 . A third space S<b>14 is formed between the third tubular wall 40 and the fourth tubular wall 42 over the entire circumference of the third tubular wall 40 .

The upper end of the second tubular wall 38 and the upper end of the fourth tubular wall 42 are at the same position in the vertical direction. The upper end of the second cylindrical wall 38 is connected to the inner peripheral end of the annular second top plate 54 . The upper end of the fourth tubular wall 42 is connected to the outer peripheral end of the second top plate 54 .

The position of the upper end of the third tubular wall 40 is lower than the upper ends of the second tubular wall 38 and the upper ends of the fourth tubular wall 42 . Therefore, the second space S<b>13 and the third space S<b>14 communicate with each other on the upper end side of the third cylindrical wall 40 . The second space S<b>13 and the third space S<b>14 constitute part of the flue gas flow path 6 .

The fifth tubular wall 44 is arranged outside the fourth tubular wall 42 and covers the entire circumferential direction of the fourth tubular wall 42 . A fourth space S<b>15 is formed between the fourth tubular wall 42 and the fifth tubular wall 44 over the entire circumference of the fourth tubular wall 42 .

The upper end of the fifth tubular wall 44 is located above the upper end of the first tubular wall 36 . The upper end of the fifth cylindrical wall 44 is connected to a circular third top plate 56 . That is, the upper side of the fifth cylindrical wall 44 is closed with the third top plate 56 . An upper space S<b>16 is formed between the third top plate 56 and the second top plate 54 . An upper space S<b>17 is formed between the third top plate 56 and the first top plate 48 . The first space S12 and the fourth space S15 communicate with each other through these upper spaces S16 and S17. In this embodiment, at least the first space S<b>12 and the fourth space S<b>15 constitute an air flow path through which heated air flows toward the fuel cell stack 2 , that is, the air preheater 24 .

A circular first bottom plate 58 is arranged inside the fourth tubular wall 42 on the lower end side. The first bottom plate 58 is fixed to the fourth tubular wall 42 . A lower end of the third cylindrical wall 40 is connected to the first bottom plate 58 . Therefore, the second space S<b>13 and the third space S<b>14 are not communicated with each other on the lower end side of the third cylindrical wall 40 .

One end of a flue gas pipe 60 forming part of the flue gas flow path is connected to a portion of the fourth cylindrical wall 42 on the side of the first bottom plate 58 . A lower end portion of the third space S14 communicates with the internal space of the flue gas pipe 60 . The other end of the flue gas pipe 60 is connected to the exhaust heat recovery device 26 shown in FIG. Therefore, the lower end of the third space S14 communicates with the exhaust heat recovery device 26 via the flue gas pipe 60 .

A lower end of the fifth cylindrical wall 44 is located above the first bottom plate 58 . The lower end of the fifth cylindrical wall 44 is connected to the annular second bottom plate 62 . The second bottom plate 62 closes the lower end of the fourth space S15. One end of an air pipe 64 is connected to the lower end side of the fifth cylindrical wall 44 . The air pipe 64 constitutes part of an air flow path through which air supplied to the fuel cell stack 2 flows. A lower end portion of the fourth space S15 communicates with the internal space of the air pipe 64 .

A lower end of the second cylindrical wall 38 is located above the first bottom plate 58 . Therefore, the second space S<b>13 and the fifth space S<b>18 described later communicate with each other on the lower end side of the second cylindrical wall 38 .

The sixth tubular wall 46 is arranged inside the lower portion 38 b of the second tubular wall 38 below the base plate 34 . The sixth tubular wall 46 extends downward from the bottom surface of the base plate 34 .

The combustor 4 is arranged in the internal space S<b>20 of the sixth tubular wall 46 . The combustor 4 has a cylindrical shape and extends downward from the lower surface of the base plate 34 . The lower end of the combustor 4 is located above the lower end of the sixth tubular wall 46 . A first communication space S<b>21 is formed in the base plate 34 to allow communication between the internal space S<b>11 of the first cylindrical wall 36 and the combustor 4 . A portion of the oxidant off-gas discharged from the fuel cell stack 2 is supplied to the combustor 4 via this first communication space S21. Therefore, in this embodiment, the first communication space S21 constitutes the first offgas flow path 8 .

Although not shown, the fuel cell stack 2 is connected to a pipe (not shown) through which the fuel off-gas flows. A portion of this pipe on the downstream side is connected to the combustor 4 . Another part of this pipe on the downstream side is connected to the suction port 22 b of the ejector 22 .

In the combustor 4, a mixed gas of fuel off-gas and oxidant off-gas is ignited by an igniter (not shown). As a result, the fuel gas contained in the fuel off-gas and the oxidant gas contained in the oxidant off-gas are combusted. This combustion produces hot flue gas.

A lower portion 38b of the second tubular wall 38 is located outside the sixth tubular wall 46 and covers the entire circumferential direction of the sixth tubular wall 46 . A fifth space S<b>18 is formed between the sixth tubular wall 46 and the lower portion 38 b of the second tubular wall 38 over the entire circumference of the sixth tubular wall 46 . The fifth space S18 communicates with the internal space S20 of the sixth tubular wall 46 at a position below the lower end of the sixth tubular wall 46 .

A reformer 16 is arranged in the fifth space S18. The reformer 16 has a reformer inner peripheral wall 161 , a reformer outer peripheral wall 162 , a reformer top plate 163 , a partition wall 164 and a reforming catalyst 165 .

The reformer inner peripheral wall 161 is a wall formed in a cylindrical shape around the axis and is located on the inner peripheral side of the reformer 16 . The axis corresponds to the centerline when the wall is in the shape of a body of revolution. The reformer outer peripheral wall 162 is a wall formed in a cylindrical shape around the axis and is positioned on the outer peripheral side of the reformer 16 . The inner peripheral wall 161 of the reformer and the outer peripheral wall 162 of the reformer may have a cylindrical shape such as a polygonal shape instead of a cylindrical shape. That is, the shape of the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 in the cross section perpendicular to the axial direction may be other shapes such as a polygon instead of a circle.

The reformer outer peripheral wall 162 is arranged so as to cover the entire circumferential region of the reformer inner peripheral wall 161 . More specifically, the axis of the reformer outer peripheral wall 162 is at the same position as the axis of the reformer inner peripheral wall 161, and the reformer inner peripheral wall 161 and the reformer outer periphery extend over the entire circumferential direction of the reformer inner peripheral wall 161. The reformer outer peripheral wall 162 is arranged with respect to the reformer inner peripheral wall 161 so that a catalyst arrangement space S22 is formed between the wall 162 and the reformer outer peripheral wall 162 . The catalyst placement space S22 is a space in which the reforming catalyst 165 is placed and the reforming raw material gas flows, and corresponds to a catalyst placement portion.

The reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 are arranged such that the axial direction of the reformer inner peripheral wall 161 and the axial direction of the reformer outer peripheral wall 162 are along the vertical direction. The axial direction of the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 has the same meaning as the height direction of the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 . In other words, the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 extend in one direction. This one direction is the vertical direction.

The reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 extend from the first bottom plate 58 toward the base plate 34 . The lower end of the reformer inner peripheral wall 161 is located above the first bottom plate 58 . A lower end of the reformer outer peripheral wall 162 is fixed to the first bottom plate 58 . The upper end of the inner peripheral wall 161 of the reformer and the upper end of the outer peripheral wall 162 of the reformer are at the same position in the vertical direction and are located below the base plate 34 .

The reformer top plate 163 has an annular shape and extends in the horizontal direction. The reformer top plate 163 is connected to the upper end of the reformer inner peripheral wall 161 and the upper end of the reformer outer peripheral wall 162 . The reformer top plate 163 closes the upper end of the catalyst placement space S22.

The partition wall 164 is circular and extends in the horizontal direction. The partition wall 164 is connected to the lower end of the inner peripheral wall 161 of the reformer. The partition wall 164 is positioned above the first bottom plate 58 . The partition wall 164 partitions the internal space S20 of the sixth tubular wall 46 and the entrance space S23 formed between the partition wall 164 and the first bottom plate 58 . The inlet space S23 is a space into which the reforming raw material gas flows.

The inlet space S23 communicates with the catalyst placement space S22. A reforming catalyst 165 is arranged from the upper surface of the first bottom plate 58 to the lower surface of the reformer top plate 163 in the catalyst arrangement space S22. The reforming catalyst 165 is a catalyst that reforms the reforming raw material gas. As the reforming catalyst 165, for example, a catalyst metal such as nickel supported on the surface of alumina spheres is used.

Although not shown, one end of a fuel gas supply pipe is connected to the top plate 163 of the reformer. The other end of the fuel gas supply pipe is connected to the fuel cell stack 2 . The fuel gas supply pipe is a pipe for supplying the fuel gas reformed by the reformer 16 to each fuel cell of the fuel cell stack 2 .

The fifth space S18 is divided into an inner peripheral space S24, an outer peripheral space S25, and a top board space S26 by arranging the reformer 16 therein. The inner peripheral space S24 is formed between the reformer inner peripheral wall 161 and the sixth cylindrical wall 46 . That is, the inner peripheral space S24 is formed on the opposite side of the catalyst placement space S22 with the inner peripheral wall 161 of the reformer interposed therebetween. The outer space S<b>25 is formed between the reformer outer wall 162 and the lower portion 38 b of the second cylindrical wall 38 . That is, the outer space S25 is formed on the opposite side of the catalyst arrangement space S22 with the reformer outer peripheral wall 162 interposed therebetween. The top plate-side space S26 is formed between the reformer top plate 163 and the base plate 34 . The inner peripheral space S24 and the outer peripheral space S25 communicate with each other through a top plate space S26. In this embodiment, the internal space S20, the inner peripheral space S24, the outer peripheral space S25, and the top plate-side space S26 of the sixth cylindrical wall 46 constitute part of the flue gas flow path 6. As shown in FIG.

The base plate 34 is formed with a second communication space S27 that allows the top plate side space S26 and the internal space S11 of the first cylindrical wall 36 to communicate with each other. Another part of the oxidant off-gas discharged from the fuel cell stack 2 is supplied to the top plate side space S26 via the second communication space S27. Therefore, in this embodiment, the second communication space S27 constitutes the second offgas flow path 10 .

Although not shown in FIG. 2, the fuel cell device 30 includes the evaporator 18 and the ejector 22 shown in FIG. The evaporator 18 is arranged inside the casing 32 . The ejector 22 is arranged inside the casing 32 .

Next, gas flows such as air and fuel gas during operation of the fuel cell system FCS will be described with reference to FIGS.

Air is supplied to the air electrode of the fuel cell stack 2 after being heated by the air preheater 24, as shown in FIG. Specifically, as shown in FIG. 2, air flows into the casing 32 from the air pipe 64 . The air flowing in from the air pipe 64 is supplied to the air electrode of the fuel cell stack 2 after flowing through the fourth space S15, the first space S12, and the air supply pipe 50 in order. The air flowing through the fourth space S15 and the first space S12 is heated by heat exchange with the flue gas flowing through the second space S13 and the third space S14.

The city gas is desulfurized by the desulfurizer 20 and then flows toward the confluence section 21 as shown in FIG. As shown in FIG. 1, the water is evaporated in the evaporator 18 to become steam. Although not shown in FIG. 2, the water is heated inside the casing 32 by heat exchange with the flue gas to become steam. The water vapor generated by the evaporator 18 flows toward the confluence section 21 . In the confluence section 21, the city gas and water vapor merge to form a mixed gas. A mixed gas of city gas and water vapor flows into the ejector 22 from the inlet 22a and is discharged from the discharge port 22c.

The mixed gas discharged from the discharge port 22 c flows into the reformer 16 . The mixed gas that has flowed into the reformer 16 is reformed in the reformer 16 to become fuel gas. The fuel gas reformed by the reformer 16 is supplied to the fuel electrode of the fuel cell stack 2 .

Specifically, as shown in FIG. 2, the mixed gas discharged from the discharge port 22c, that is, the reforming raw material gas, flows into the inlet space S23 from below. The mixed gas that has flowed into the inlet space S23 flows radially from the central portion of the inlet space S23 along the horizontal direction. Then, the mixed gas flows horizontally into the lower part of the catalyst placement space S22. In the catalyst placement space S22, the mixed gas flows from the lower side to the upper side in the vertical direction. At this time, the mixed gas is heated by heat exchange with the flue gas. When the mixed gas is brought into contact with the reforming catalyst 165 while the mixed gas is brought to a temperature at which the hydrogen reforming reaction occurs, a steam reforming reaction occurs, and hydrogen gas and carbon monoxide are generated by this steam reforming reaction. The steam reforming reaction is an endothermic reaction. The heat required for the steam reforming reaction is supplied from the flue gas. The fuel gas thus reformed is supplied to the fuel cell stack 2 via a fuel gas supply pipe (not shown) connected to the upper portion of the catalyst placement space S22.

By supplying air and fuel gas to the fuel cell stack 2 in this way, the fuel cell stack 2 generates electricity. At this time, fuel off-gas containing fuel gas not used for power generation is discharged from the fuel cell stack 2 , and air off-gas containing air not used for power generation is discharged from the fuel cell stack 2 .

As shown in FIG. 1 , part of the air off-gas discharged from the air electrode of the fuel cell stack 2 is supplied to the combustor 4 via the first off-gas flow path 8 . Specifically, as shown in FIG. 2, the air off-gas is discharged from the air electrode of the fuel cell stack 2 into the internal space S11 of the first cylindrical wall 36 . A part of the air off-gas delivered to the internal space S11 is supplied to the combustor 4 via the first communication space S21 as the first off-gas flow path 8 .

Further, as shown in FIG. 1 , another part of the air off-gas discharged from the air electrode of the fuel cell stack 2 is supplied to the flue gas flow path 6 via the second off-gas flow path 10 . Specifically, as shown in FIG. 2, another part of the air off-gas delivered to the internal space S11 passes through the second communicating space S27 as the second off-gas flow path 10 to the top plate side space. It is supplied to S26.

As shown in FIG. 1 , part of the fuel off-gas discharged from the fuel electrode of the fuel cell stack 2 is supplied to the combustor 4 via the combustor introduction channel 12 . Specifically, part of the fuel off-gas is supplied to the combustor 4 via a pipe (not shown) that connects the fuel outlet side of the fuel electrode and the combustor 4 as indicated by arrows in FIG.

Further, as shown in FIG. 1 , another part of the fuel gas discharged from the fuel electrode of the fuel cell stack 2 is sucked into the ejector 22 through the fuel recycling channel 14 . Specifically, as indicated by arrows in FIG. is attracted to The fuel off-gas sucked into the ejector 22 joins the mixed gas flowing toward the inlet space S23. As a result, another part of the fuel off-gas is supplied to the fuel electrode.

In the combustor 4, combustion exhaust gas is generated by combustion of the fuel gas contained in the fuel off-gas and the oxidant gas contained in the oxidant off-gas. The generated flue gas flows through the flue gas passage 6 in the order of the reformer 16, the air preheater 24, and the evaporator 18, as shown in FIG.

Specifically, as shown in FIG. 2, inside the fuel cell device 30, the combustion exhaust gas flows from the internal space S20 of the sixth cylindrical wall 46 to the inner peripheral space S24, the top plate space S26, and the outer peripheral space. It flows in order of S25. In the inner peripheral space S24, combustion exhaust gas flows from the lower side to the upper side in the vertical direction. In the top plate side space S26, combustion exhaust gas flows from the inside toward the outside. In the outer peripheral space S25, combustion exhaust gas flows from the upper side to the lower side in the vertical direction. In this embodiment, the lower side in the vertical direction corresponds to one side of the reformer inner peripheral wall 161 in the axial direction, and the upper side in the vertical direction corresponds to the other side in the axial direction of the inner peripheral wall 161 of the reformer.

At this time, the flue gas flowing through the inner peripheral space S24 heats the reforming raw material gas flowing through the catalyst placement space S22 by heat exchange via the reformer inner peripheral wall 161 . The flue gas flowing through the outer space S25 heats the reforming raw material gas flowing through the catalyst arrangement space S22 by heat exchange via the reformer outer peripheral wall 162 .

In the present embodiment, the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 function as heat transfer walls that transfer heat from the flue gas to the reforming raw material gas by thermal conduction. The reformer inner peripheral wall 161 corresponds to a first heat transfer wall. The reformer outer peripheral wall 162 corresponds to a second heat transfer wall. The inner peripheral space S24 and the outer peripheral space S25 correspond to a heating section in which the flue gas flowing through the flue gas flow path heats the reforming raw material gas flowing through the catalyst placement section by heat exchange via the heat transfer wall. The outer space S25 is located downstream of the inner space S24 in the flow of the combustion exhaust gas. Therefore, the inner peripheral space S24 corresponds to the first heating section, and the outer peripheral space S25 corresponds to the second heating section located downstream of the first heating section in the flow of the combustion exhaust gas.

The flue gas that has flowed out from the outer peripheral space S25 flows through the second space S13 and the third space S14 in this order. In the second space S13, combustion exhaust gas flows from the lower side to the upper side in the vertical direction. In the third space S14, combustion exhaust gas flows from the upper side to the lower side in the vertical direction. At this time, the flue gas flowing through the second space S13 heats the air flowing through the first space S12 by heat exchange via the first cylindrical wall 36 . The flue gas flowing through the third space S14 heats the air flowing through the fourth space S15 by heat exchange via the fourth cylindrical wall 42 . After that, the flue gas is supplied to the exhaust heat recovery device 26 via the flue gas pipe 60 .

As described above, the fuel cell device 30 of this embodiment includes the fuel cell stack 2 , the reformer 16 , the combustor 4 , and the flue gas flow path 6 . The reformer 16 has a reforming catalyst 165 and a catalyst placement space S22. The catalyst placement space S22 is an annular space formed between the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162 . The flue gas flow path 6 includes an inner space S24 and an outer space S25 through which the flue gas flows. The outer peripheral space S25 is located downstream of the inner peripheral space S24 in the flow of the combustion exhaust gas. The inner peripheral space S24 is formed on the opposite side of the catalyst placement space S22 with the reformer inner peripheral wall 161 interposed therebetween. The outer peripheral space S25 is formed on the opposite side of the catalyst arrangement space S22 with the reformer outer peripheral wall 162 interposed therebetween. In the catalyst placement space S22, the reforming raw material gas flows from the lower side to the upper side in the vertical direction. In the inner peripheral space S24, combustion exhaust gas flows from the lower side to the upper side in the vertical direction. In the outer peripheral space S25, combustion exhaust gas flows from the upper side to the lower side in the vertical direction.

According to this, the flow of the combustion exhaust gas in the inner peripheral space S24 is parallel to the flow of the reforming raw material gas in the catalyst placement space S22. The flow of combustion exhaust gas in the outer space S25 is countercurrent to the flow of the reforming material gas in the catalyst placement space S22. As a result, unlike the present embodiment, the flow of the flue gas in the entire heating portion for heating the reforming raw material gas in the flue gas channel is in a countercurrent direction to the flow of the reforming raw material gas. , the temperature rise of the reformer inner peripheral wall 161 and the reformer outer peripheral wall 162, which are heat transfer walls, can be suppressed. Therefore, thermal deterioration of the reforming catalyst 165 can be suppressed. Furthermore, the temperature of the reforming raw material gas can be made higher than in the case where the combustion exhaust gas flows in parallel with the reforming raw material gas in the entire heating section.

Furthermore, according to this, the inner peripheral space S24 is formed on the opposite side of the catalyst placement space S22 with the inner peripheral wall 161 of the reformer interposed therebetween. The outer peripheral space S25 is formed on the opposite side of the catalyst arrangement space S22 with the reformer outer peripheral wall 162 interposed therebetween. For this reason, there are heat transfer walls that transfer heat from the flue gas to the reforming raw material gas on both the inner and outer sides of the catalyst placement space S22. As a result, compared to the case where the heat transfer wall is provided only on one side of the catalyst placement space S22, the heat transfer area to the reforming raw material gas can be increased, and the heat transfer performance can be improved.

Therefore, according to the present embodiment, it is possible to ensure high heat exchange performance between the reforming raw material gas and the flue gas and to suppress thermal deterioration of the reforming catalyst.

Here, the fuel cell device 30 of this embodiment includes a fuel recycling channel 14 in addition to the combustor introduction channel 12 . In the fuel cell device 30 of this embodiment, the fuel off-gas supplied to the combustor 4 is reduced as compared with the case where the fuel cell device 30 does not include the fuel recycling channel 14 . For example, if half of the fuel off-gas discharged from the fuel cell stack 2 flows through the fuel recycling channel 14, the amount of fuel off-gas supplied to the combustor 4 is halved. Therefore, in the fuel cell device 30 of the present embodiment, the amount of heat generated by the combustion exhaust gas generated by the combustor 4 is smaller than when the fuel cell device 30 does not include the fuel recycling channel 14 .

Therefore, unlike the fuel cell device 30 of the present embodiment, the flow of the flue gas in the entire heating portion for heating the reformed gas in the flue gas passage 6 is parallel to the flow of the reformed raw gas. In this case, the problem that the heat exchange performance is poor and the temperature of the raw material gas to be reformed is lower than the target temperature becomes conspicuous. On the other hand, according to the present embodiment, even if the fuel recycling passage 14 is provided, high heat exchange performance between the reforming raw material gas and the combustion exhaust gas can be ensured, and the temperature of the reforming raw material gas can be achieved as a target. temperature can be approached.

Further, when the fuel cell device 30 does not have the fuel recycle channel 14, the mixture ratio of the fuel gas to the air supplied to the combustor 4 is the fuel gas and air (more specifically, oxygen in the air). A case is assumed in which the fuel recycle channel 14 is added to the case where the reaction is set to be just right. This mixing ratio is a mass ratio. In this case, the amount of fuel gas supplied to the combustor 4 is less than the amount of fuel gas required to react with all of the air contained in the air off-gas discharged from the fuel cell stack 2 without excess or deficiency. As a result, combustion in the combustor 4 becomes unstable. In other words, the fuel gas contained in the mixed gas of the air and the fuel gas supplied to the combustor 4 becomes lean, causing the problem that the flame blows out.

Therefore, in the fuel cell device 30 of the present embodiment, in addition to the first offgas flow path 8 that guides part of the air offgas to the combustor 4, another part of the air offgas bypasses the combustor 4, A second offgas channel 10 leading to the flue gas channel 6 is provided. According to this, the air off-gas supplied to the combustor 4 can be reduced compared to the case where the second off-gas flow path 10 is not provided. Therefore, by increasing the mixture ratio of fuel gas to air in the combustor 4, combustion in the combustor 4 can be stabilized.

Furthermore, according to this, the combustion temperature in the combustor 4 can be increased by increasing the mixture ratio of the fuel gas to the air in the combustor 4 . Therefore, the temperature difference between the combustion exhaust gas and the reforming raw material gas can be increased, and the heat transfer performance of the reformer 16 can be improved.

In addition, in the fuel cell device 30 of the present embodiment, the flue gas flow path 6 has the top plate side space S26 that allows the inner peripheral side space S24 and the outer peripheral side space S25 to communicate with each other. The second offgas flow path 10 guides another part of the air offgas to the top plate side space S26 by bypassing the combustor 4 and the inner peripheral side space S24.

According to this, by joining the air off-gas with the flue gas radiated in the inner peripheral space S24, the heat capacity of the flue gas after joining can be increased. Therefore, as shown in FIG. 3, compared to the case where the second off-gas flow path 10 is not provided, it is possible to suppress the decrease in the temperature of the combustion exhaust gas in the outer space S25. can raise the temperature of the reforming raw material gas. As a result, according to the present embodiment, it is possible to bring the temperature of the reforming source gas close to the target temperature at which the reforming rate is high.

FIG. 3 shows the temperature of the flue gas at each position in FIG. 4 and the temperature of the reformed raw material gas at each position in FIG. is a diagram showing the measurement results of the temperature of . The fuel cell device of Comparative Example 1 is different from the fuel cell device 30 of the present embodiment in that the second offgas channel 10 is not provided. Other configurations of the fuel cell device of Comparative Example 1 are the same as those of the fuel cell device 30 of the present embodiment.

As shown in FIG. 4 , the temperature of flue gas at position H1 is the temperature of the flue gas generated in combustor 4 . The temperature of the flue gas at the position H2 is the temperature of the flue gas near the outlet of the inner space S24. The temperature of the combustion exhaust gas at the position H3 is the temperature of the combustion gas near the entrance of the outer space S25. The temperature of the combustion exhaust gas at the position H4 is the temperature of the combustion gas near the exit of the outer space S25. The temperature of the reforming raw material gas at the position L1 is the temperature of the reforming raw material gas before flowing into the catalyst placement space S22. The temperature of the reforming raw material gas at the position L2 is the temperature of the reforming raw material gas near the exit of the catalyst placement space S22.

In the fuel cell device of Comparative Example 1, the temperature of the flue gas and the temperature of the reforming raw material gas change as indicated by the dashed lines in FIG. When the temperature of the flue gas at the position H1 was 900°C, the temperature of the flue gas at the positions H2 and H3 was 750°C, and the temperature of the flue gas at the position H4 was 600°C. In this case, the temperature drop width, which is the difference between the temperature near the outlet and the temperature near the inlet of the combustion exhaust gas flowing through the outer space S25, was 150°C. Also, when the temperature of the reforming raw material gas at the position L1 was 500.degree. C., the temperature of the reforming raw material gas at the position L2 was 575.degree.

On the other hand, in the fuel cell device 30 of the present embodiment, the temperature of the flue gas and the temperature of the reforming raw material gas change as indicated by the solid line in FIG. When the temperature of the flue gas at the position H1 was 900°C, the temperature of the flue gas at the position H2 was 750°C. When the temperature of the air off-gas flowing into the top plate-side space S26 from the second off-gas channel 10 is 700°C, the temperature of the flue gas at the position H3 is 725°C, and the temperature of the flue gas at the position H4 is 650°C. Met. In this case, the temperature drop width of the combustion exhaust gas flowing through the outer peripheral space S25 was 75°C. Further, when the temperature of the reforming raw material gas at the position L1 was 500° C., the temperature of the reforming raw material gas at the position L2 was 600° C., which is higher than that in Comparative Example 1.

(Second embodiment)
In the first embodiment, the second offgas flow path 10 guides another portion of the air offgas to the top plate side space S26 by bypassing the combustor 4 and the inner peripheral space S24. On the other hand, in the present embodiment, although not shown, the second offgas flow path 10 causes another part of the air offgas to bypass the combustor 4, the inner peripheral space S24, and the top plate side space S26. , to the outer space S25. This also provides the same effects as in the first embodiment.

(Other embodiments)
(1) The second offgas flow path 10 may lead another portion of the air offgas to the inner peripheral space S24 by bypassing the combustor 4 . This also provides the same effects as in the first embodiment. As in the first, second and this embodiment, the second offgas flow path 10 bypasses the combustor 4 for another portion of the air offgas to the reforming feedstock in the flue gas flow path 6 . Any device may be used as long as it leads to a heating unit that heats the gas. In this case, the heat of the air off-gas can be used to heat the reformed feed gas.

(2) The second off-gas flow path 10 allows another part of the air off-gas to bypass the combustor 4, the inner peripheral space S24, the top plate-side space S26, and the outer peripheral space S25, and It may lead to a portion downstream of the outer peripheral space S25. As a result, among the effects of the first embodiment, the effect of stabilizing the combustion in the combustor 4 by increasing the mixture ratio of the fuel gas to the air in the combustor 4 can be obtained.

(3) In each of the above-described embodiments, the ejector 22 is provided in order to form the flow of the fuel off-gas in the fuel recycle channel 14, but the present invention is not limited to this. A pump may be provided in the fuel recycle channel 14 instead of the ejector 22 .

(4) In each of the embodiments described above, the fuel cell device 30 includes the fuel recycling channel 14 . However, the fuel cell device 30 may not have the fuel recycling channel 14 . In the fuel cell device 30, the amount of fuel gas contained in the fuel off-gas supplied to the combustor 4 should be reacted with all of the oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack 2 in just the right amount. is less than the amount of fuel gas required for In this case, for example, the utilization rate of the fuel gas in the fuel cell stack 2 is improved. In this case, if all of the oxidant off-gas discharged from the fuel cell stack 2 is supplied to the combustor 4, the fuel gas becomes lean and combustion in the combustor 4 becomes unstable. Therefore, in such a case, by adopting the configuration of each of the above embodiments (excluding the fuel recycling channel 14), the same effects as those of each of the above embodiments can be obtained.

(5) In addition, according to the present invention, the amount of fuel gas contained in the fuel off-gas supplied to the combustor 4 is equal to the total amount of oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack 2. It is not limited to the case where the amount is less than the amount of fuel gas required for reaction. Even without this case, effects similar to those of the first embodiment can be obtained, except for the effect of stabilizing combustion in the combustor.

(6) In each of the above embodiments, the reforming raw material gas flows from the bottom to the top in the vertical direction through the catalyst placement space S22, and the combustion exhaust gas flows from the bottom to the top in the vertical direction through the inner circumferential space S24. The combustion exhaust gas flows from the upper side to the lower side in the vertical direction in the outer peripheral space S25. However, because the fuel cell device 30 is arranged upside down or the like, the reforming raw material gas flows from the upper side to the lower side in the catalyst arrangement space S22, and the inner peripheral side space S24 flows from the upper side to the lower side in the vertical direction. The combustion exhaust gas may flow toward the side, and the combustion exhaust gas may flow in the outer peripheral space S25 from the bottom to the top in the vertical direction. In this case, the upper side in the vertical direction corresponds to one side of the reformer inner peripheral wall 161 in the axial direction, and the lower side in the vertical direction corresponds to the other side in the axial direction of the inner peripheral wall 161 of the reformer.

(7) In each of the above-described embodiments, the fuel cell stack 2 has a structure in which a plurality of fuel cells using a flat plate-shaped fixed electrolyte are stacked, but other structures may be used. Further, in each of the above embodiments, solid oxide fuel cells were used as the fuel cells, but other fuel cells may be used as long as they use the same reformed raw material gas as in each of the above embodiments. may For example, a molten carbonate fuel cell (MCFC) cell may be used.

(8) The present invention is not limited to the above-described embodiments, but can be modified as appropriate within the scope of the claims, including various modifications and modifications within the equivalent range. Moreover, the above-described embodiments are not unrelated to each other, and can be appropriately combined unless the combination is clearly impossible. Further, in each of the above-described embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential, unless it is explicitly stated that they are essential, or they are clearly considered essential in principle. stomach. In addition, in each of the above-described embodiments, when numerical values such as the number, numerical value, amount, range, etc. of the constituent elements of the embodiment are mentioned, when it is explicitly stated that they are particularly essential, and when they are clearly limited to a specific number in principle It is not limited to that specific number, except when In addition, in each of the above-described embodiments, when referring to the material, shape, positional relationship, etc. of the constituent elements, unless otherwise specified or in principle limited to a specific material, shape, positional relationship, etc. , its material, shape, positional relationship, and the like.

(summary)
According to a first aspect shown in part or all of the above embodiments, the fuel cell device includes a fuel cell stack (2), a reformer (16), a combustor (4), a combustion and an exhaust gas flow path (6). The reformer has a reforming catalyst (165) and a catalyst placement section (S22). The flue gas flow path is a heating portion (S24, S25) in which the flue gas flowing through the flue gas flow path heats the reforming raw material gas flowing through the catalyst arrangement portion by heat exchange via the heat transfer walls (161, 162). have The catalyst placement portion includes a first heat transfer wall (161) as a heat transfer wall formed in a cylindrical shape around the axis, and a heat transfer wall (161) formed in a cylindrical shape so as to cover the entire circumferential direction of the first heat transfer wall. It is formed between the second heat transfer wall (162) as a heat wall. The heating section includes a first heating section (S24) and a second heating section (S25) located downstream of the first heating section in the flow of combustion exhaust gas. The first heating section is formed on the opposite side of the catalyst placement section with the first heat transfer wall interposed therebetween. The second heating section is formed on the opposite side of the catalyst placement section with the second heat transfer wall interposed therebetween. In the catalyst placement portion, the reforming raw material gas flows from one side of the first heat transfer wall to the other side in the axial direction. In the first heating section, combustion exhaust gas flows from one side to the other side in the axial direction. In the second heating section, the combustion exhaust gas flows from the other side toward the one side in the axial direction.

Further, according to the second aspect, in the first aspect, the fuel cell device comprises a first offgas flow path (8) that guides part of the oxidant offgas to the combustor and another part of the oxidant offgas. and a second offgas flow path (10) bypassing the combustor and leading to the flue gas flow path. According to this, it is possible to reduce the amount of oxidant off-gas supplied to the combustor compared to the case where the second off-gas flow path is not provided. As a result, the mixture ratio of the fuel gas to the oxidant gas in the combustor is increased, so that the combustion temperature in the combustor can be increased. Therefore, the temperature difference between the combustion exhaust gas and the reforming raw material gas can be increased, and the heat transfer performance of the reformer can be improved.

According to a third aspect, in the first aspect, the combustion exhaust gas flow path is a communicating portion that communicates the first heating portion and the second heating portion on the other side in the axial direction with respect to the catalyst placement portion. (S26). The fuel cell device includes a first offgas flow path (8, S21) that guides part of the oxidant offgas to the combustor, and another part of the oxidant offgas that bypasses the combustor and the first heating unit, and a second offgas flow path (10, S27) leading to the communication portion.

According to this, the same effect as the second aspect can be obtained. Furthermore, according to this, the heat capacity of the combined combustion exhaust gas can be increased by joining the oxidant off-gas with the combustion exhaust gas radiated by the first heating section. Therefore, compared to the case where the second offgas flow path is not provided, it is possible to suppress the extent of the temperature decrease of the combustion exhaust gas in the second heating section, and it is possible to increase the temperature of the reforming raw material gas after heat exchange. .

According to a fourth aspect, in the first aspect, the flue gas flow path is a communicating portion that communicates the first heating portion and the second heating portion on the other side in the axial direction with respect to the catalyst placement portion. (S26). The fuel cell device includes a first offgas flow path (8, S21) that guides part of the oxidant offgas to the combustor, and another part of the oxidant offgas bypassing the combustor, the first heating section and the communicating section. and a second off-gas flow path (10) leading to a second heating unit.

According to this, the same effect as the second aspect can be obtained. Furthermore, according to this, the heat capacity of the combined combustion exhaust gas can be increased by joining the oxidant off-gas with the combustion exhaust gas radiated by the first heating section. Therefore, compared to the case where the second offgas flow path is not provided, it is possible to suppress the extent of the temperature decrease of the combustion exhaust gas in the second heating section, and it is possible to increase the temperature of the reforming raw material gas after heat exchange. .

Further, according to the fifth aspect, in the first to fourth aspects, the amount of fuel gas contained in the fuel off-gas supplied to the combustor is the amount of oxidant contained in the oxidant off-gas discharged from the fuel cell stack. It is less than the amount of fuel gas required to react with all of the agent gas in just the right amount.

In the case of the configuration of the fifth aspect, it is particularly effective to employ the configurations of the first to fourth aspects. That is, in the case of the configuration of the fifth aspect, the amount of fuel gas contained in the fuel off-gas supplied to the combustor is equal to all of the oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack. The amount of heat in the flue gas produced in the combustor is less than the same amount of fuel gas required for reaction. For this reason, if the flow of the flue gas is parallel to the flow of the reforming raw material gas in the entire heating section that heats the reforming raw material gas in the flue gas passage, the heat exchange performance is said to be low. problem becomes noticeable. Therefore, by adopting the configuration of the first aspect in the case of the configuration of the fifth aspect, the effect obtained by the first aspect becomes remarkable.

Further, in the case of the configuration of the fifth aspect, if all of the oxidant off-gas discharged from the fuel cell stack is supplied to the combustor, the fuel gas becomes lean and combustion in the combustor becomes unstable. Become. Therefore, by adopting the configurations of the second to fourth aspects in the case of the configuration of the fifth aspect, the oxidizer off-gas supplied to the combustor is reduced compared to the case where the second off-gas flow path is not provided. can be reduced. Therefore, by increasing the mixture ratio of the fuel gas to the oxidant gas in the combustor, combustion in the combustor can be stabilized.

Further, according to the sixth aspect, the fuel cell device includes a combustor introduction passage (12) that guides part of the fuel off-gas to the combustor and another part of the fuel off-gas discharged from the fuel cell stack. , and a fuel recycling channel (14) for feeding the fuel cell stack. A case of adopting the configuration of the sixth aspect can be cited as a case of adopting the configuration of the fifth aspect.

2 fuel cell stack 4 combustor 6 flue gas flow path 16 reformer 165 reforming catalyst S22 catalyst placement space 161 reformer inner wall 162 reformer outer wall S24 inner peripheral space S25 outer peripheral space

Claims (3)

A fuel cell device,
a fuel cell stack (2) that generates electricity through an electrochemical reaction using a fuel gas and an oxidant gas;
a reformer (16) that reforms a reformed raw material gas to generate the fuel gas and supplies the generated fuel gas to the fuel cell stack;
A combustor (4) for burning the fuel gas contained in the fuel off-gas discharged from the fuel cell stack and the oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack to generate flue gas. and,
and a flue gas flow path (6) through which the flue gas flows,
The reformer has a reforming catalyst (165) for reforming the reforming raw material gas, and a catalyst arrangement part (S22) in which the reforming catalyst is arranged and through which the reforming raw material gas flows. death,
The flue gas flow path is a heating section in which the flue gas flowing through the flue gas flow path heats the reforming raw material gas flowing through the catalyst placement section by heat exchange via heat transfer walls (161, 162). (S24, S25),
The catalyst placement portion includes a first heat transfer wall (161) as the heat transfer wall, which is cylindrically formed around the axis, and a cylindrical shape covering the entire circumferential direction of the first heat transfer wall. is formed between the second heat transfer wall (162) as the heat transfer wall,
The heating unit includes a first heating unit (S24) and a second heating unit (S25) located downstream of the first heating unit in the flow of the combustion exhaust gas,
The first heating part is formed on the opposite side of the catalyst placement part across the first heat transfer wall,
The second heating part is formed on the opposite side of the catalyst placement part across the second heat transfer wall,
In the catalyst placement portion, the reforming raw material gas flows from one side to the other side in the axial direction of the first heat transfer wall,
in the first heating unit, the combustion exhaust gas flows from the one side toward the other side in the axial direction;
in the second heating unit, the combustion exhaust gas flows from the other side in the axial direction toward the one side;
The combustion exhaust gas flow path has a communicating portion (S26) that communicates the first heating portion and the second heating portion on the other side in the axial direction with respect to the catalyst placement portion,
The fuel cell device
a first offgas flow path (8, S21) that guides part of the oxidant offgas to the combustor;
a second off-gas flow path (10) for guiding another part of the oxidant off-gas to the second heating part by bypassing the combustor, the first heating part and the communication part. battery device. The amount of the fuel gas contained in the fuel off-gas supplied to the combustor is necessary to react with all of the oxidant gas contained in the oxidant off-gas discharged from the fuel cell stack. 2. The fuel cell apparatus according to claim 1 , wherein the amount of said fuel gas is less than the amount of said fuel gas. The fuel cell device
a combustor introduction passageway (12) for guiding part of the fuel off-gas to the combustor;
2. The fuel cell device according to claim 1 , further comprising a fuel recycling channel (14) for supplying another part of said fuel off-gas discharged from said fuel cell stack to said fuel cell stack.

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