JP2018169080A - Combustion system and combustion device - Google Patents

Abstract

To provide a combustion system and a combustion device capable of suppressing lowering of concentration of a fuel gas to an oxygen-containing gas with a simple constitution.SOLUTION: A burner 50 includes a fuel pipe 52 for guiding an anode off-gas for combustion to a combustion portion, an oxygen-containing gas main pipe 54 for sending a second cathode off-gas toward the combustion portion, a combustion oxygen passage 60 for guiding a part of the second cathode off-gas flowing in the oxygen-containing gas main pipe 54 to an outlet of the fuel pipe 52, and an oxygen-containing gas separation passage 64 for guiding a part of the second cathode off-gas flowing in the oxygen-containing gas main pipe 54 from an upstream side with respect to the outlet of the fuel pipe 52 to a position separating from a fuel discharge end 58C with respect to the combustion oxygen passage 60.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a combustion system for burning fuel gas and a combustion apparatus.

  Various burners have been developed as combustion devices for burning fuel gas. And in order to improve combustibility, fuel gas and air may be mixed before combustion. For example, in Patent Document 1, combustible gas is introduced into a gas mixing chamber from a combustible gas duct, combustion air is introduced from a combustion air duct, mixed in the gas mixing chamber, and then jetted into a secondary combustion chamber for combustion. I am letting. However, in Patent Document 1, since the entire amount of air sent from the combustion air duct is supplied to the secondary combustion chamber, the concentration of the combustible gas in the secondary combustion chamber is reduced, and the combustibility is reduced. .

JP 2006-266619 A

  The present invention has been made in view of the above facts, and an object thereof is to obtain a combustion system and a combustion apparatus capable of suppressing a decrease in the concentration of fuel gas with respect to an oxygen-containing gas with a simple configuration. .

  A combustion system according to a first aspect of the present invention includes a fuel path that guides fuel gas to the combustion section, a main flow path that sends oxygen-containing gas toward the combustion section, and one of the oxygen-containing gas that flows through the main flow path. Oxygen path for leading a part to the combustion part, and oxygen-containing gas separation for leading a part of the oxygen-containing gas flowing in the main flow path from upstream to the combustion part to a position farther from the combustion part than the combustion oxygen path Road.

In the combustion system according to the first aspect, the combustion gas is guided to the combustion section by the fuel path. Moreover, oxygen-containing gas is sent out toward a combustion part by this flow path. A part of the oxygen-containing gas flowing through this flow path is guided to the combustion section through the combustion oxygen path, and the combustion gas is burned in the combustion section. On the other hand, a part of the oxygen-containing gas flowing through the main flow path is led to a position farther from the combustion section than the combustion oxygen path by the oxygen-containing gas separation path from the upstream of the combustion section. In this way, a part of the oxygen-containing gas flowing through this flow path is guided to the combustion section, and other oxygen-containing gases are guided to a position away from the combustion section, thereby suppressing a decrease in the concentration of fuel gas in the combustion section. Can do.
The fuel gas here is a gas containing a combustible substance, and is not particularly limited.

  In the combustion system according to a second aspect of the invention, the oxygen-containing gas separation path guides part of the oxygen-containing gas flowing through the main flow path to the downstream side of the combustion section.

  According to the combustion system of the second aspect of the present invention, a part of the oxygen-containing gas flowing through the main flow path is led from the oxygen-containing gas separation path to the downstream side of the combustion section, so that the oxygen-containing gas is treated with the combustion exhaust gas. can do.

  A combustion system according to a third aspect of the present invention includes a fuel cell that generates electric power using a fuel gas supplied to an anode and an oxygen-containing gas supplied to a cathode, and the fuel path converts the anode off-gas from the anode into the anode. The combustion oxygen path is configured by a cathode offgas pipe that supplies cathode offgas from the cathode to the combustion section.

According to the combustion system of the third aspect of the present invention, when the anode off-gas of the fuel cell is burned as the fuel gas, only a part of the cathode off-gas is merged with the anode off in the combustion part, so that the combustible in the anode off-gas is combusted. Combustion can be performed while suppressing a decrease in the concentration of the sex gas in the combustion section.
Here, the fuel gas is not only flammable but also a gas used for power generation in a fuel cell, for example, a gas containing hydrogen.

  According to a fourth aspect of the present invention, there is provided a combustion system wherein the fuel cell includes a first fuel cell and a second fuel cell that is supplied to the anode using the anode off-gas of the first fuel cell as a fuel gas. It is said that.

  According to the combustion system of the fourth aspect of the present invention, when the anode off gas sent from the second fuel cell in the latter stage of the multistage combustion is burned, the decrease in the concentration of the combustible gas in the anode off gas in the combustion portion is suppressed. Can be burned. Since the anode off gas delivered from the second fuel cell in the latter stage of the multi-stage type has a particularly low combustible gas concentration, the present invention can be applied effectively.

  In the combustion system according to the fifth aspect of the present invention, the anode offgas pipe is configured by a second anode offgas pipe that supplies anode offgas from the anode of the second fuel cell to the combustion section, and the cathode offgas pipe includes: A second cathode offgas pipe for supplying a cathode offgas from the cathode of the second fuel cell to the combustion section, or a first cathode offgas pipe for supplying the cathode offgas from the cathode of the first fuel cell to the combustion section; The oxygen-containing gas separation path is configured on the other side of the second cathode offgas pipe or the first cathode offgas pipe.

  In the combustion system according to the fifth aspect of the present invention, one of the second cathode offgas pipe or the first cathode offgas pipe is a combustion oxygen path, and the other that is not a combustion oxygen path is an oxygen-containing gas separation path. The cathode off gas can be easily branched without providing a branching portion.

  In the combustion system according to the sixth aspect of the invention, the anode offgas pipe includes a circulation branch pipe that re-feeds a part of the anode offgas to the anode of the fuel cell.

  In the combustion system according to the sixth aspect of the invention, when the anode off-gas sent from the circulation type fuel cell is burned, the decrease in the concentration of the combustible gas in the anode off-gas in the combustion part is suppressed and burned. Can do. Since the anode off-gas delivered from the circulation type fuel cell has a particularly low combustible gas concentration, the present invention can be applied effectively.

  According to a seventh aspect of the present invention, there is provided a combustion apparatus comprising: a fuel passage having a fuel discharge end for guiding fuel gas to a combustion section and discharging the fuel gas; and an oxygen-containing gas for sending oxygen-containing gas toward the combustion section. A main passage, a combustion oxygen passage having an oxygen discharge end for guiding a part of the oxygen-containing gas flowing through the oxygen-containing gas main passage to the fuel discharge end and releasing the oxygen-containing gas, and the oxygen-containing gas main passage And an oxygen-containing gas separation path that separates a part of the oxygen-containing gas flowing through the combustion oxygen path into a separated portion that is farther from the fuel discharge end than the combustion oxygen path.

  In the combustion apparatus according to the seventh aspect, the combustion gas is guided to the combustion section by the fuel path. The fuel gas is discharged from the fuel discharge end to the combustion section. Further, the oxygen-containing gas is sent out toward the combustion section by the oxygen-containing gas main path. Part of the oxygen-containing gas flowing through the oxygen-containing gas main path is guided to the fuel discharge end of the fuel path by the combustion oxygen path, and the oxygen-containing gas is released from the oxygen discharge end to burn the combustion gas in the combustion section. Further, a part of the oxygen-containing gas flowing through the oxygen-containing gas main path is separated by the oxygen-containing gas separation path into a separated portion that is farther from the fuel discharge end than the combustion oxygen path. In this way, a part of the oxygen-containing gas flowing through the oxygen-containing gas main path is guided to the fuel discharge end of the fuel path, and the other oxygen-containing gas is separated from the combustion oxygen path to the separation / release section farther from the fuel discharge end. Thereby, the fall of the density | concentration of the fuel gas in a fuel discharge end can be suppressed, and the fall of combustibility can be suppressed.

  A combustion apparatus according to an eighth aspect of the present invention is directed to the discharge section in which the fuel path includes a pre-release space having an enlarged cross-sectional area and a plurality of discharge holes for discharging the fuel gas at the fuel discharge end. have.

  According to the combustion apparatus of the eighth aspect, since the fuel gas is discharged from the pre-discharge space of the discharge portion through the plurality of discharge holes to the combustion portion, the combustion gas can be discharged uniformly.

  According to a ninth aspect of the present invention, the oxygen-containing gas main path and the combustion oxygen path are spaced apart from each other in the flow direction of the oxygen-containing gas so that the oxygen-containing gas can flow out. And the oxygen-containing gas separation path separates a part of the oxygen-containing gas from the separation portion.

  According to the combustion apparatus of the ninth aspect, the oxygen-containing gas main path can be separated into the combustion oxygen path and the oxygen-containing gas separation path with a simple configuration.

  In the combustion apparatus according to a tenth aspect of the present invention, a double pipe in which the oxygen-containing gas main path is disposed outside the fuel path is constituted by the fuel path and the oxygen-containing gas main path.

  According to the combustion apparatus which concerns on Claim 10, the combustion gas from a fuel path can be discharge | released toward the center part of a combustion area.

  The combustion apparatus according to claim 11, wherein the combustion oxygen passage is separated from the fuel passage and surrounds the outside of the fuel passage, and partitions the oxygen-containing gas separation passage and the combustion oxygen passage. It is comprised including.

  According to the combustion apparatus of the eleventh aspect, the combustion oxygen path can be configured with a simple configuration by the separation wall.

  A combustion apparatus according to a twelfth aspect of the present invention is surrounded by the oxygen discharge end, and a premixing space is formed between the fuel discharge end and the oxygen discharge end.

  According to the combustion apparatus of the twelfth aspect, the combustibility can be improved by mixing and burning the fuel gas and the oxygen-containing gas in the premix space.

  In the combustion apparatus according to the thirteenth aspect of the invention, the oxygen discharge end of the combustion oxygen passage is inclined inward of the premixing space.

  According to the combustion apparatus of the thirteenth aspect, the oxygen-containing gas released from the combustion oxygen passage is collected inside the premixing space by the oxygen release end, and is mixed well with the combustion gas to improve the combustibility. Can do.

  In the combustion apparatus according to the fourteenth aspect of the present invention, the combustion section and the separation / release section are disposed in a casing that forms a combustion space.

  According to the combustion apparatus of the fourteenth aspect, since the oxygen-containing gas is released from the separation / release part into the casing forming the combustion space, combustion of the remaining fuel gas without being burned in the combustion part is assisted. The oxygen-containing gas released from the separation / release part can be heated.

  A fuel cell system according to a fifteenth aspect of the invention generates power by using the combustion apparatus according to any one of the sixth to thirteenth aspects, the fuel gas supplied to the anode, and the oxygen-containing gas supplied to the cathode. A fuel cell; an anode off-gas pipe for guiding the fuel gas from the anode to the fuel path; and a cathode off-gas pipe for guiding the oxygen-containing gas from the cathode to the oxygen-containing gas main path.

  According to the fuel cell system of the fifteenth aspect of the present invention, the ratio of the fuel gas and the oxygen-containing gas when the part of the oxygen-containing gas discharged from the cathode is separated by the oxygen-containing gas separation path and burned is determined. It can be adjusted easily.

  According to the combustion system and the combustion apparatus according to the present invention, it is possible to suppress a decrease in the concentration of the fuel gas with respect to the oxygen-containing gas with a simple configuration.

1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. It is a schematic block diagram of the fuel cell system which concerns on 2nd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on 3rd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on 4th Embodiment. It is a perspective view of the burner used for the fuel cell system concerning a 4th embodiment. It is sectional drawing of the burner used for the fuel cell system concerning 4th Embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a fuel cell system 10A according to the first embodiment of the present invention. The fuel cell system 10A includes, as main components, a vaporizer 12, a reformer 14, a first fuel cell stack 16, a second fuel cell stack 18, an air supply unit 46, a separation unit 20, a first heat exchange unit 30, A second heat exchange unit 32, a third heat exchange unit 34, a combustor 40, and a tank 42 are provided.

  One end of the source gas pipe P1 is connected to the vaporizer 12, and the other end of the source gas pipe P1 is connected to a gas source (not shown). From the gas source, methane is sent to the vaporizer 12 by the blower B. A water supply pipe P2 from a tank 42 for storing water is connected to an intermediate portion of the source gas pipe P1. Water (liquid phase) is sent from the tank 42 to the vaporizer 12 by the pump P. In the vaporizer 12, water is vaporized. For the vaporization, the heat of the combustor 40 described later is used. In this embodiment, methane is used as the raw material gas, but it is not particularly limited as long as it can be reformed, and a hydrocarbon fuel can be used. Examples of the hydrocarbon fuel include natural gas, LP gas (liquefied petroleum gas), coal reformed gas, lower hydrocarbon gas, biogas, and the like. Examples of the lower hydrocarbon gas include lower hydrocarbons having 4 or less carbon atoms such as methane, ethane, ethylene, propane, and butane, and methane used in the present embodiment is preferable. The hydrocarbon fuel may be a mixture of the above-described lower hydrocarbon gas, and the above-described lower hydrocarbon gas may be a gas such as natural gas, city gas, or LP gas.

  Methane and water vapor are sent from the vaporizer 12 to the reformer 14 via the pipe P3. The reformer 14 is adjacent to the combustor 40, the first fuel cell stack 16, and the second fuel cell stack 18, and is heated by exchanging heat with them.

  In the reformer 14, methane is reformed to generate fuel gas containing hydrogen and having a temperature of about 600 ° C. The reformer 14 is connected to the anode (fuel electrode) 16 </ b> A of the first fuel cell stack 16. The fuel gas generated by the reformer 14 is supplied to the anode 16A of the first fuel cell stack 16 via the fuel gas pipe P4.

  The first fuel cell stack 16 is a solid oxide fuel cell stack, and has a plurality of stacked fuel cells. The first fuel cell stack 16 is an example of a fuel cell (first fuel cell) in the present invention. In the present embodiment, the operating temperature is about 650 ° C. Each fuel cell has an electrolyte layer, and an anode 16A and a cathode (air electrode) 16B that are respectively laminated on the front and back surfaces of the electrolyte layer. In FIG. 1, individual anodes and cathodes of a plurality of fuel cells are collectively shown as “anode 16A” and “cathode 16B”, respectively.

  The basic configuration of the second fuel cell stack 18 is the same as that of the first fuel cell stack 16, and has an anode 18A corresponding to the anode 16A and a cathode 18B corresponding to the cathode 16B.

Air is supplied to the cathode 16B of the first fuel cell stack 16 via an air supply pipe P8 described later. In the cathode 16B, as shown in the following formula (1), oxygen in the air and electrons react to generate oxygen ions. The generated oxygen ions reach the anode 16A of the first fuel cell stack 16 through the electrolyte layer.

(Air electrode reaction)
1 / 2O ₂ + 2e ⁻ → O ²⁻ (1)

The cathode 16B is connected to a first cathode offgas pipe P6 that guides the cathode offgas discharged from the cathode 16B to the cathode 18B of the second fuel cell stack 18.

  On the other hand, in the anode 16A of the first fuel cell stack 16, as shown in the following formulas (2) and (3), oxygen ions that have passed through the electrolyte layer react with hydrogen and carbon monoxide in the fuel gas, Water (water vapor), carbon dioxide and electrons are generated. Electrons generated at the anode 16A move from the anode 16A through the external circuit to the cathode 16B, and are thus generated in each fuel cell. Each fuel cell generates heat during power generation.

(Fuel electrode reaction)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (2)
CO + O ²⁻ → CO ₂ + 2e ⁻ (3)

  One end of an anode offgas pipe P7 is connected to the anode 16A of the first fuel cell stack 16, and the anode offgas is discharged from the anode 16A to the anode offgas pipe P7. The anode off gas contains unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, water vapor, and the like.

The fuel cell of the present invention is not limited to a solid oxide fuel cell (SOFC), and other fuel cells in which at least one of carbon dioxide and hydrogen is contained in the anode off-gas, For example, a molten carbonate fuel cell (MCFC) may be used.

The other end of the anode off-gas pipe P7 is connected to the separation unit 20 via a second heat exchange unit 32 and a first heat exchange unit 30 described later. The separation unit 20 separates water vapor from the anode off gas by condensation.

  The anode off-gas becomes a regenerated fuel gas having a reduced water vapor concentration by separating the water vapor in the separation unit 20, and is sent to the regenerated fuel gas pipe P9. The regenerated fuel gas pipe P9 is connected to the anode 18A of the second fuel cell stack 18, and the regenerated fuel gas is supplied to the anode 18A of the second fuel cell stack 18 via the regenerated fuel gas pipe P9.

  On the other hand, air is supplied from the air supply unit 46 and supplied to the cathode 16B through the first heat exchange unit 30 and the third heat exchange unit 34 described later.

  The anode 18A and the cathode 18B of the second fuel cell stack 18 generate power by the same reaction as that of the first fuel cell stack 16. The used gas discharged from the anode 18A is sent to the combustor 40 through the pipe P11. The used gas (hereinafter referred to as “combustion anode off-gas”) contains a combustible gas such as methane or carbon monoxide, and is used for incineration in the combustor 40.

  The second cathode offgas discharged from the cathode 18B is sent to the second cathode offgas pipe P12. The second cathode off gas contains oxygen. The second cathode offgas pipe P12 is branched into two. One of the branches is a second cathode-off combustion introduction pipe P12-1 connected to the combustor 40, and the other is a second cathode-off connected to the combustion exhaust pipe P10 from which the combustion exhaust gas of the combustor 40 is discharged. It is set as the separation pipe P12-2. The branch portion is provided with a flow divider V1, and the flow rate of the second cathode off gas sent to the second cathode off combustion introduction pipe P12-1 and the second cathode sent to the second cathode off separation pipe P12-2. The off-gas flow rate can be adjusted. When the ratio of the gas to be separated is determined in advance, the separation may be performed using an orifice or the like without using the flow divider V1. From the second cathode off-combustion introduction pipe P <b> 12-1, used gas containing oxygen (hereinafter referred to as “combustion cathode off-gas”) is sent to the combustor 40 and used for incineration in the combustor 40.

  In the fuel cell system 10A of the present embodiment, the anode off-gas that is the fuel used in the first fuel cell stack 16 is regenerated and reused as the fuel gas in the second fuel cell stack 18. It has become.

  Combustion exhaust gas is sent from the combustor 40. The combustion exhaust gas merges with the spent gas (hereinafter referred to as “detour cathode off gas”) from the second cathode off separation pipe P12-2, circulates in the combustion exhaust pipe P10, the third heat exchange unit 34, and the vaporization It flows into the tank 42 through the vessel 12. Note that the second cathode off separation pipe P12-2 does not necessarily have to be joined with the combustion exhaust gas pipe P10 between the combustor 40 and the third heat exchange section 34, and also on the downstream side of the third heat exchange section 34, It may be merged at other positions.

  The first heat exchange unit 30 is provided downstream of the anode 16 </ b> A of the first fuel cell stack 16, upstream of the separation unit 20, and downstream of the air supply unit 46. In the first heat exchanging unit 30, heat exchange is performed between the anode off gas flowing through the anode off gas pipe P7 and the air flowing through the air supply pipe P8.

  The second heat exchanging unit 32 includes a second fuel on the downstream side of the anode 16A of the first fuel cell stack 16 on the upstream side of the first heat exchanging unit 30 (for the anode offgas pipe P7) and on the downstream side of the separation unit 20. It is provided on the upstream side of the anode 18A of the battery stack 18 (about the regenerated fuel gas pipe P9). In the second heat exchanging section 32, heat exchange is performed between the anode off gas flowing through the anode off gas pipe P7 and the regenerated fuel gas flowing through the regenerated fuel gas pipe P9.

  The third heat exchanging section 34 is downstream of the first heat exchanging section 30 and upstream of the cathode 16B of the first fuel cell stack 16, and downstream of the combustor 40 and upstream of the carburetor 12 (combustion exhaust gas pipe). P10). In the 3rd heat exchange part 34, heat exchange is performed between the air A which flows through the air supply pipe P8, and the combustion exhaust gas which flows through the combustion exhaust gas pipe P10.

  Next, the operation of the fuel cell system 10A of the present embodiment will be described.

  In the fuel cell system 10 </ b> A, methane, which is fuel from a gas source, and water from the tank 42 are supplied to the vaporizer 12. In the vaporizer 12, the supplied methane and water are mixed, and heat is obtained from the combustion exhaust gas flowing through the combustion exhaust pipe P <b> 10, and the water is vaporized to become steam.

  Methane and water vapor are sent from the vaporizer 12 to the reformer 14 via the pipe P3. In the reformer 14, a fuel gas containing about 600 ° C. containing hydrogen is generated by the reforming reaction. The fuel gas is supplied to the anode 16A of the first fuel cell stack 16 through the fuel gas pipe P4.

Air heated by the first heat exchange unit 30 and the third heat exchange unit 34 is supplied from the air supply unit 46 to the cathode 16B of the first fuel cell stack 16. Thereby, in the 1st fuel cell stack 16, electric power generation is performed by the above-mentioned reaction. Along with this power generation, anode off-gas is discharged from the anode 16A of the fuel cell stack 16. Further, the cathode off gas is discharged from the cathode 16B. The cathode off gas is supplied to the cathode 18B of the second fuel cell stack 18 through the first cathode off gas pipe P6.

  The anode off gas discharged from the anode 16A is guided to the anode off gas pipe P7, and flows into the separation unit 20 through the second heat exchange unit 32 and the first heat exchange unit 30. The water vapor in the anode off-gas is condensed and separated by the separation unit 20, and the regenerated fuel gas whose water vapor concentration is reduced is supplied to the anode 18 </ b> A of the second fuel cell stack 18 through the regenerated fuel gas pipe P <b> 9.

  In the second fuel cell stack 18, power generation is performed by the above-described reaction. From the anode 18A, the combustion anode off-gas is sent to the combustor 40 through the pipe P11. Cathode off-gas is sent from the cathode 18B to the second cathode off-gas pipe P12 and divided into the second cathode off combustion introduction pipe P12-1 and the second cathode off separation pipe P12-2. One of the divided flows (the second cathode off combustion introduction pipe P12-1 side) is sent to the combustor 40 through the second cathode off combustion introduction pipe P12-1. The other of the divided flows (the second cathode off separation pipe P12-2 side) is sent to the combustion exhaust gas pipe P10.

  The combustion exhaust gas is discharged from the combustor 40 to the combustion exhaust gas pipe P10. The combustion exhaust gas is sent to the tank 42 through the third heat exchange unit 34 and the vaporizer 12. The water vapor contained in the combustion exhaust gas is cooled in the path from the vaporizer 12 to the tank 42 or in the tank 42, condensed, and stored in the tank 42. Other combustion exhaust gas is discharged from the tank 42. The second cathode off separation pipe P12-2 is joined to the combustion exhaust gas pipe P10 on the upstream side of the third heat exchanging section 34, and the bypass cathode off gas is sent to the tank 42 together with the combustion exhaust gas.

  According to the fuel cell system 10A of this embodiment, since the second cathode offgas pipe P12 is branched into two, the flow rate of the second cathode offgas supplied to the combustor 40 is reduced. Therefore, the fall of the combustibility of the combustor 40 can be suppressed by suppressing the fall of the density | concentration of the combustible gas in a combustion space.

  Further, since the second cathode off separation pipe P12-2 joins with the combustion exhaust gas pipe P10 on the downstream side of the combustor 40, the bypass cathode off gas is used for heat exchange in the third heat exchanging section 34 together with the combustion exhaust gas. be able to.

  The fuel cell system 10A of the present embodiment is a multistage fuel cell system in which anode gas flows are connected in series with respect to the anodes of the first fuel cell stack 16 and the second fuel cell stack 18. Further, since fuel regeneration is performed by water condensation, the fuel gas utilization rate in the entire fuel cell system can be set high, and therefore the anode off-gas sent from the anode 18A of the second fuel cell stack 18 at the subsequent stage is particularly The concentration of combustible gas may be low. Therefore, the present invention can be applied effectively.

  In the present embodiment, the fuel cell system 10A has been described as an example, but the present invention can also be applied to other combustion systems. In particular, in the fuel cell system, the anodes 16A and 18A, and the cathodes 16B and 18B each receive fuel gas and air in amounts that take into account the power generation in the fuel cells (the first fuel cell stack 16 and the second fuel cell stack 18). Supplied. Therefore, the ratio of anode off gas to cathode off gas tends to be unbalanced for combustion. Therefore, according to the present invention, the excess ratio of oxygen and nitrogen to combustible gas (hydrogen, carbon monoxide, etc.) can be effectively reduced.

  In the present embodiment, an example in which air is connected in series so that air is supplied from the cathode 16B of the first fuel cell stack 16 to the cathode 18B of the second fuel cell stack 18 has been described. May be connected in parallel so as to be supplied to both the cathode 16B and the cathode 18B. In that case, either the cathode off gas from the cathode 16B or the cathode off gas from the cathode 18B can be supplied to the combustor 40, and the other can be connected to the combustion exhaust pipe P10 on the downstream side of the combustor 40. Alternatively, the cathode off gas from the cathode 16B and the cathode off gas from the cathode 18B may be merged once and branched downstream thereof.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the part same as 1st Embodiment, and description is abbreviate | omitted.

  FIG. 2 shows a fuel cell system 10B according to the second embodiment of the present invention. The fuel cell system 10B is different from the fuel cell system 10A described in the first embodiment in that it does not have the second fuel cell stack 18 and is a circulation type.

  One end of the first cathode offgas pipe P6 is connected to the cathode 16B of the first fuel cell stack 16, and the other end of the first cathode offgas pipe P6 is connected to the combustor 40. 1 and a first cathode off separation pipe P6-2 connected to the combustion exhaust gas pipe P10 are branched by a flow divider V2. The first cathode off separation pipe P6-2 does not necessarily need to be joined with the combustion exhaust gas pipe P10 between the combustor 40 and the third heat exchange section 34, and even on the downstream side of the third heat exchange section 34, It may be merged at other positions. Further, instead of the flow divider V2, the flow may be divided by an orifice.

  Further, one end of the regenerated fuel gas pipe P9 is connected to the separation unit 20, and the other end of the regenerated fuel gas pipe P9 is connected to a pipe P11 connected to the combustor 40 and a circulation pipe P9-2 connected to the pipe P3. It is branched by the shunt V3. In the present embodiment, the flow divider V <b> 3 is provided on the upstream side of the second heat exchanger 32, but may be provided on the downstream side of the second heat exchanger 32. The downstream end of the circulation pipe P9-2 is joined on the upstream side of the pipe P3 and the reformer 14. Note that the downstream end of the circulation pipe P9-2 may be joined on the downstream side of the pipe P3 and the reformer 14.

  Also in this embodiment, the same effects as those of the first embodiment can be obtained except for the effect of being a multistage type. Further, since the fuel cell system 10B of the present embodiment is a circulation type, the combustible gas concentration in the anode off-gas is low as compared with the case where the fuel gas is not reused. Therefore, the present invention can be applied effectively.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the part same as 1st, 2 embodiment, and description is abbreviate | omitted.

  FIG. 3 shows a fuel cell system 10C according to a third embodiment of the present invention. The fuel cell system 10C is different from the fuel cell system 10A described in the first embodiment in that it includes a third fuel cell stack 17 arranged in parallel with the first fuel cell stack 16. .

The basic configuration of the third fuel cell stack 17 is the same as that of the first fuel cell stack 16, and includes an anode 17A corresponding to the anode 16A and a cathode 17B corresponding to the cathode 16B. The fuel gas pipe P4 connected to the reformer 14 is branched from the fuel gas pipe P4-2 at the branching section B4. The fuel gas pipe P4 is connected to the anode 16A and supplies fuel gas from the reformer 14 to the anode 16A. The fuel gas pipe P4-2 is connected to the anode 17A and supplies fuel gas from the reformer 14 to the anode 17A. An anode offgas pipe P7 is connected to the anode 17A, and the anode offgas pipe P7-2 is joined at the junction B5 upstream of the anode offgas pipe P7 and the second heat exchange section 32. From the anode 17A, the used anode off gas is sent out and flows into the separation unit 20 through the anode off gas pipes P7-2 and P7.

  An air supply pipe P8-2 branched from the air supply pipe P8 at the branch part B6 is connected to the cathode 17B on the downstream side of the third heat exchange part 34. Air is supplied to the cathode 17B via the oxidizing gas pipe P8-2. The cathode offgas discharged from the cathode 17B is sent to the combustion cathode offgas pipe P6-3 and merged with the combustion exhaust pipe P10.

  Even in the fuel cell system 10C of the present embodiment, the same effects as those of the first embodiment can be obtained.

  Further, in the present embodiment, the cathode off gas discharged from the cathode 17B is directly sent to the combustion exhaust gas pipe P10. Therefore, the flow rate of the second cathode off gas can be reduced with a simple configuration without providing a branch path in the cathode off gas path. Can do.

  In the present embodiment, an example in which air is connected in series so that air is supplied from the cathode 16B of the first fuel cell stack 16 to the cathode 18B of the second fuel cell stack 18 has been described. May be connected in parallel so that air is supplied to each of the cathodes 16B, 17B, and 18B. In that case, at least one of the cathode off-gas pipes from each of the cathode 16B, the cathode 17B, and the cathode 18B is connected to the combustor 40, and the other is connected to the combustion exhaust pipe P10 on the downstream side of the combustor 40. it can. As an example, the cathode offgas pipes from the cathodes 16B and 17B can be connected to the combustion exhaust gas pipe P10, and the cathode offgas pipes from the cathode 18B can be connected to the combustor 40. As another example, the cathode offgas pipes from the cathodes 16B and 17B can be connected to the combustor 40, and the cathode offgas pipe from the cathode 18B can be connected to the combustion exhaust pipe P10.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the part same as 1-3 embodiment, and description is abbreviate | omitted.

  FIG. 4 shows a fuel cell system 10D according to a fourth embodiment of the present invention. Compared to the fuel cell system 10A described in the first embodiment, the fuel cell system 10D has the second cathode off-gas pipe P12 that is not branched into two and has a second cathode off-separation pipe P12-2. Not different.

  The combustor 40 of this embodiment includes a burner 50. As shown in FIG. 4, the burner 50 includes a fuel path pipe 52 and an oxygen-containing gas main path pipe 54. The burner 50 is disposed in the housing 56. The casing 56 is in the shape of a rectangular parallelepiped box that constitutes the outer plate of the combustor 40, is made of a steel plate, and has a combustion space 40R formed therein.

  The upstream side of the fuel path pipe 52 is tubular and is connected to the pipe P <b> 11. The fuel path pipe 52 passes through the casing 56 and is inserted into the casing 56. A discharge portion 58 is formed at the downstream end of the fuel passage tube 52. The discharge portion 58 has a rectangular parallelepiped box shape, and a pre-discharge space 58A having a cross-section enlarged from the upstream side of the fuel path pipe 52 is formed inside the box. The combustion anode off-gas sent from the pipe P11 flows into the discharge portion 58. A plurality of discharge holes 58B are formed at the downstream end of the discharge portion 58, that is, at the discharge end of the combustion anode off gas (hereinafter referred to as “fuel discharge end 58C”). The combustion anode off-gas is discharged from the discharge hole 58B.

  The oxygen-containing gas main pipe 54 is connected to the second cathode off-gas pipe P <b> 12 and is formed on the outer periphery of the fuel path pipe 52. The fuel path pipe 52 and the oxygen-containing gas main path pipe 54 constitute a double pipe 53 in which the fuel path pipe 52 is disposed inside. The oxygen-containing gas main pipe 54 communicates with the inside of the housing 56.

  The oxygen-containing gas main pipe 54 is terminated upstream of the discharge part 58. In this embodiment, it terminates at the entrance to the housing 56, and the fuel path pipe 52 opens into the housing 56. A combustion oxygen passage 60 is formed on the outer periphery of the discharge portion 58. The combustion oxygen passage 60 is formed between the separation wall 60 </ b> A and the discharge portion 58 disposed so as to be separated from the discharge portion 58 and surround the discharge portion 58. A separation portion 59 is formed between the upstream end of the separation wall 60 </ b> A and the end of the oxygen-containing gas main pipe 54. The separation portion 59 is open to the combustion space 40R, and the flow path in the oxygen-containing gas main pipe 54 and the combustion oxygen path 60 are discontinuous.

  The downstream end of the separation wall 60A extends downstream from the downstream end of the discharge portion 58, and the separation wall 60A has an opening narrowed from a portion corresponding to the downstream end of the discharge portion 58, that is, combustion oxygen. When viewed from the extending direction of the channel 60, an oxygen release end 60B is formed which is inclined inside the premixing space 62 surrounded by the separation wall 60A. An opening 60C is formed by the edge of the oxygen release end 60B. A premix space 62 is formed between the oxygen discharge end 60B and the fuel discharge end 58C. Combustion anode off-gas released from the discharge hole 58B flows into the premix space 62, and combustion cathode off-gas released from the combustion oxygen passage 60 flows into the premix space 62. The combustion anode off-gas and the combustion cathode off-gas are mixed in the premixing space 62 and discharged from the opening 60C to the combustion space 40R.

  An ignition unit 70 is provided on the downstream side of the opening 60 </ b> C, and the combustion anode off-gas is combusted in the vicinity of the downstream side of the opening 60 </ b> C by ignition by the ignition unit 70. A portion where this combustion occurs is a combustion portion.

  Between the separation wall 60A and the housing 56, an oxygen-containing gas separation path 64 is formed in a part of the combustion space 40R. The oxygen-containing gas separation path 64 allows the separated cathode off-gas that has flowed from the oxygen-containing gas main pipe 54 to the oxygen-containing gas separation path 64 side at the separation portion 59 downstream of the oxygen discharge end 60B, that is, the fuel discharge end. Guide from 58C to a position further away from the oxygen release end 60B. A downstream side adjacent to the oxygen release end 60 </ b> B is referred to as a separation release unit 66. The separation / release part 66 is further away from the fuel discharge end 58 </ b> C than the combustion oxygen path 60.

  Next, operation | movement of the burner 50 of this embodiment is demonstrated.

  The combustion anode off-gas from the anode 18A is introduced into the fuel path pipe 52, then guided to the pre-discharge space 58A, and discharged from the discharge hole 58B to the premixing space 62. The cathode off gas introduced into the oxygen-containing gas main pipe 54 is sent to the combustion space 40R, and part of the cathode off gas flows into the combustion oxygen passage 60 as the combustion cathode off gas and is sent to the premixing space 62. In the premix space 62, the combustion anode off gas and the combustion cathode off gas are mixed, discharged from the opening 60C to the combustion space 40R, and burned while forming a combustion point near the downstream side of the opening 60C.

  On the other hand, a part of the cathode off-gas introduced into the oxygen-containing gas main pipe 54 flows into the oxygen-containing gas separation path 64 from the separation portion 59 as a separation cathode off-gas, passes through the separation discharge portion 66, and is downstream of the combustion space 40R. Sent to. The separated cathode off-gas assists combustion of the combustion anode off-gas that has not been burned near the downstream side of the opening 60C in the combustion space 40R.

  Further, in the burner 50 of the present embodiment, the second cathode off gas is branched into two, and only a part for the second cathode off gas combustion introduced into the combustion space 40R is mixed with the combustion anode off gas. Therefore, the flow rate of the combustion cathode off gas supplied to the premixing space 62 is reduced. Accordingly, it is possible to suppress a decrease in the concentration of the combustible gas in the premix space 62 and to suppress a decrease in the combustibility of the combustion anode off-gas in the combustor 40.

  Further, by mixing and burning the combustion anode off-gas and the combustion cathode off-gas in the premixing space 62, the combustibility can be improved.

  Further, the separation of the second cathode off-gas can be easily performed with a simple configuration by flowing into the oxygen-containing gas separation path 64 from the separation portion 59.

  In addition, since the burner 50 is provided with the discharge portion 58, the combustion anode off-gas can be discharged uniformly into the premixing space 62.

  Further, since the fuel pipe 52 and the oxygen-containing gas main pipe 54 constitute a double pipe 53 having the fuel path pipe 52 disposed inside, the combustion anode off-gas is discharged from the center of the combustion area. Can do.

  In the present embodiment, the combustion oxygen path 60 and the oxygen-containing gas separation path 64 can be configured with a simple configuration by providing the separation wall 60A on the outer periphery of the discharge portion 58.

  In the present embodiment, the oxygen release end 60B is formed at the downstream end of the separation wall 60A, and the oxygen release end 60B is inclined inward so as to narrow the opening. Therefore, the combustion cathode off-gas released from the combustion oxygen passage 60 is collected inside the premixed spinning space by the oxygen release end 60B, and is well mixed with the combustion anode off-gas, thereby improving the combustibility.

  In the present embodiment, a separation / release part 66 is formed in the combustion space 40 </ b> R inside the housing 56. Therefore, it is possible to assist the combustion of the combustible gas (such as methane contained in the combustion anode off-gas) that is sent to the downstream side of the opening 60C without being burned.

  In the present embodiment, the box-shaped housing 56 has been described as an example, but the housing may have other shapes. As an example, the housing can be cylindrical. When the casing is cylindrical, the pre-release space 58A, the separation wall 60A, and the like are also cylindrical.

  In the present embodiment, the burner 50 is used for combustion in the combustor 40 of the fuel cell system 10D. However, the burner 50 may be used for the fuel cell systems 10A-10C of the first to third embodiments. . Further, the burner 50 of the present embodiment may be used for combustion other than the fuel cell system.

Furthermore, the present invention is not limited to the above-described first to fourth embodiments, and is implemented by a person skilled in the art in combination with the above-described embodiments within the technical idea of the present invention. Moreover, in this invention, the installation position of a heat exchanger, a combination, etc. are not limited to these embodiment, for example. Moreover, you may use means other than a heat exchanger for the heating and cooling of various fluids, such as gas and water.

Further, in the fuel cell systems 10A, 10B, and 10C, the example provided with the reformer 14 has been described as an example. . The number of fuel cell stacks to which the anodes are connected in series is not limited to two or three, but four or more may be connected.

Furthermore, in the fuel cell systems 10A, 10B, and 10C, the separation unit 20 has been described as separating the water vapor from the anode off gas by condensation, but the water vapor may be separated by other means such as a separation membrane. Moreover, gas other than water vapor, for example, carbon dioxide may be removed.

The present invention can also be applied to a combustion part in an engine system other than the fuel cell system.

10A, 10B, 10C Fuel cell system (combustion system)
16 First fuel cell stack (fuel cell, first fuel cell)
16A, 17A, 18A Anode 16B, 17B, 18B Cathode 17 Third fuel cell stack (fuel cell, first fuel cell)
18 Second fuel cell stack (fuel cell, second fuel cell)
20 separation unit, 40 combustor (combustion unit)
50 burner (combustion device), 52 fuel path pipe (fuel path), 53 double pipe 54 oxygen-containing gas main pipe (oxygen-containing gas main path)
56 housing, 58 discharge section, 58A space before discharge, 58C fuel discharge end 59 separation section, 60 combustion oxygen path, 60A separation wall 60B oxygen discharge end, 60C opening, 62 premix space 64 oxygen-containing gas separation path, 66 separation Release part, P11 piping (fuel path)
P12 Cathode off-gas pipe (main flow path)
P12-1 Second cathode off combustion introduction pipe (combustion oxygen path)
P12-2 Second cathode off separator (Oxygen-containing gas separator)

Claims (15)

A fuel path for guiding the fuel gas to the combustion section;
A main flow path for sending oxygen-containing gas toward the combustion section, a combustion oxygen path for guiding a part of the oxygen-containing gas flowing through the main flow path to the combustion section, and the main flow path from the upstream side of the combustion section An oxygen-containing gas separation path for leading a part of the flowing oxygen-containing gas to a position farther from the combustion section than the combustion oxygen path;
With combustion system.   The combustion system according to claim 1, wherein the oxygen-containing gas separation path guides a part of the oxygen-containing gas flowing through the main flow path to a downstream side of the combustion unit. Comprising a fuel cell that generates electric power from a fuel gas supplied to the anode and an oxygen-containing gas supplied to the cathode;
The fuel path is configured by an anode offgas pipe that supplies anode offgas from the anode to the combustion section, and the combustion oxygen path is configured by a cathode offgas pipe that supplies cathode offgas from the cathode to the combustion section. The combustion system according to claim 1 or 2, wherein   4. The combustion according to claim 3, wherein the fuel cell is a multistage type including a first fuel cell and a second fuel cell that is supplied to the anode using the anode off-gas of the first fuel cell as a fuel gas. 5. system. The anode offgas pipe is composed of a second anode offgas pipe that supplies anode offgas from the anode of the second fuel cell to the combustion section;
The cathode offgas pipe supplies the cathode offgas from the cathode of the second fuel cell to the combustion section, or supplies the cathode offgas from the cathode of the first fuel cell to the combustion section. One cathode off-gas pipe,
The oxygen-containing gas separation path is constituted by the other of the second cathode offgas pipe or the first cathode offgas pipe.
The combustion system according to claim 4.   The combustion system according to claim 3, wherein the anode offgas pipe includes a circulation branch pipe that re-feeds a part of the anode offgas to the anode of the fuel cell. A fuel path having a fuel discharge end for guiding the fuel gas to the combustion section and releasing the fuel gas;
An oxygen-containing gas main path for sending an oxygen-containing gas toward the combustion section;
A combustion oxygen path having an oxygen discharge end for guiding a part of the oxygen-containing gas flowing through the oxygen-containing gas main path to the fuel discharge end and releasing the oxygen-containing gas;
An oxygen-containing gas separation path that separates a part of the oxygen-containing gas flowing through the oxygen-containing gas main path into a separation and discharge portion that is farther from the fuel discharge end than the combustion oxygen path;
Combustion device equipped with.   8. The fuel path according to claim 7, wherein the fuel passage has a pre-release space with an enlarged cross-sectional area and a discharge portion formed with a plurality of discharge holes for discharging the fuel gas at the fuel discharge end. Combustion device.   The oxygen-containing gas main path and the combustion oxygen path are spaced apart from each other in the flow direction of the oxygen-containing gas so that the oxygen-containing gas can flow out, and the oxygen-containing gas separation path includes the The combustion apparatus according to claim 7 or 8, wherein a part of the oxygen-containing gas is separated from the separation portion.   10. The double pipe in which the oxygen-containing gas main path is disposed outside the fuel path is constituted by the fuel path and the oxygen-containing gas main path. The combustion apparatus as described in.   The combustion oxygen path includes a separation wall that separates the oxygen-containing gas separation path and the combustion oxygen path from the fuel path and surrounds the outside of the fuel path. The combustion device according to claim 10.   The combustion apparatus according to any one of claims 7 to 11, wherein a premix space is formed between the fuel discharge end and the oxygen discharge end, surrounded by the oxygen discharge end.   The combustion apparatus according to claim 12, wherein the oxygen discharge end of the combustion oxygen passage is inclined inward of the premixing space.   The combustion apparatus according to any one of claims 7 to 13, wherein the combustion section and the separation / release section are disposed in a casing that forms a combustion space. The combustion apparatus according to any one of claims 7 to 14,
A fuel cell that generates electricity using a fuel gas supplied to the anode and an oxygen-containing gas supplied to the cathode;
An anode offgas pipe for guiding the fuel gas from the anode to the fuel path;
A cathode offgas pipe for guiding the oxygen-containing gas from the cathode to the oxygen-containing gas main line;
A fuel cell system comprising: