JP2005155997A - Catalyst combuster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly burn anode offgas exhausted from a fuel cell, inside a catalyst combuster. <P>SOLUTION: Anode offgas supply piping 120 for leading in anode offgas is formed in approximately L-shaped piping structure comprising a gas supply piping horizontal part 121, a gas supply piping bent part 122 and a gas supply piping lead-in part 123 in a housing 19. The gas supply piping horizontal part 121 is horizontally disposed in the housing 19, and the gas supply piping lead-in part 123 is disposed in a direction orthogonal to the longitudinal direction of the housing 19 and in a range of 0<θ<90° from a horizontal plane on the two-dimensional horizontal plane orthogonal to a gravity direction from the front face view of the housing 19. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a catalytic combustor that burns a mixed gas of an anode off gas and a cathode off gas discharged from a fuel cell using a catalyst.

  As a fuel cell system that can be mounted on a combustion cell vehicle, for example, hydrogen serving as a fuel gas is supplied to the fuel electrode of the fuel cell, and air is supplied as an oxidant gas to the oxidant electrode, and these are reacted in the electrolyte membrane The generated power is obtained.

In such a fuel cell system, when a gas discharged from the fuel electrode of the fuel cell (hereinafter referred to as anode off gas) is discharged to the outside, the one that is burned by a catalytic combustor is known (for example, Patent Document 1). reference). As a related art, a hydrogen rich gas taken out from a reformer is supplied to a combustor together with heated compressed air (see, for example, Patent Document 2).
JP 2002-231294 A JP 2002-339766 A

  The anode off gas is discharged intermittently (or continuously) from the fuel electrode of the fuel cell. In the case where the fuel cell is a solid polymer type, since it is operated in a wet state (substantially saturated humidity), the anode off-gas discharged from the fuel electrode is also saturated. The reaction of the combustion cell is an exothermic reaction, and the high efficiency range is also a temperature range above room temperature, so when the anode off gas is exhausted from the fuel cell (unless the pipe is specially heated), it is cooled inside the pipe. Moisture becomes supersaturated. That is, the anode off gas becomes a mixed fluid of hydrogen gas and liquid water.

  Since such an anode off-gas discharge pipe (hereinafter referred to as anode off-gas discharge pipe) has a bent portion, turbulent flow is likely to occur at the bent portion, and liquid water accumulates at the bent portion of the pipe, and the flow of the anode off gas is reduced. There was an obstacle. In particular, when liquid water accumulates at a bent portion in the combustor of the anode off-gas discharge pipe, the flow of the gas is obstructed and the concentration of the anode off-gas is biased, making it difficult to burn uniformly in the combustor. there were.

  A catalytic combustor according to the present invention is a catalytic combustor in which a secondary fuel gas containing hydrogen discharged from a fuel electrode of a combustion cell and combustion air are mixed in a housing, and the mixed gas is combusted using a catalyst. The gas supply pipe for introducing the secondary fuel gas has a substantially L-shaped pipe structure comprising a gas supply pipe horizontal portion, a gas supply pipe bent portion, and a gas supply pipe introduction portion in the housing, and the gas supply A two-dimensional arrangement in which a horizontal pipe portion is disposed horizontally in the housing, and the gas supply pipe introduction portion is perpendicular to the longitudinal direction of the housing and perpendicular to the direction of gravity when the housing is viewed from the front. It is arranged on the horizontal plane in a range of 0 <θ <90 ° from the horizontal plane.

  According to the present invention, since turbulent flow is less likely to occur at the bent portion of the gas supply pipe, liquid water contained in the secondary fuel gas does not accumulate in the bent portion of the gas supply pipe, and the gas flow in the pipe is prevented. There is no hindrance. Therefore, there is no bias in the gas concentration in the pipe, and the gas can be uniformly burned in the combustor.

  Hereinafter, as the best mode for carrying out the catalytic combustor according to the present invention, an embodiment in which the present invention is applied to a vehicle combustion cell system will be described.

  FIG. 3 is a block diagram showing a schematic configuration of the fuel cell system according to the present embodiment.

  The fuel cell 1 is a fuel cell stack that generates DC power by being supplied with a fuel gas and an oxidant gas, and has a fuel cell structure in which a fuel electrode 3 and an oxidant electrode 4 are disposed on both sides of an electrolyte membrane 2. The body is sandwiched between separators (not shown), and a plurality of these are stacked. Hydrogen as a fuel gas is supplied to the inlet 3a of the fuel electrode 3 from the hydrogen supply device 5 via the fuel gas supply pipe 7, and air as the oxidant gas is supplied to the inlet 4a of the oxidant electrode 4 as air. The gas is supplied from the device 6 through the oxidant gas supply pipe 8.

  On the other hand, the anode offgas (secondary fuel gas) as exhausted hydrogen remaining without being consumed during power generation is discharged from the outlet 3 b of the fuel electrode 3 of the fuel cell 1, and from the outlet 4 b of the oxidizer electrode 4. Similarly, cathode off gas (combustion air) as exhaust air remaining without being consumed during power generation is discharged.

  The outlet 3 b of the fuel electrode 3 is connected to the anode offgas circulation device 10, and part of the anode offgas discharged from the outlet 3 b of the fuel electrode 3 is supplied from the anode offgas circulation device 10 through the anode offgas circulation pipe 9 to supply fuel gas. It is configured to recirculate to the pipe 7. The anode off-gas circulation device 10 is connected to a catalytic combustor via an anode off-gas supply pipe (gas supply pipe) 12 provided with an on-off valve 11. The catalyst combustor 13 and the outlet 4 b of the oxidant electrode 4 are connected by a cathode offgas supply pipe 14. The catalyst combustor 13 is provided with a catalyst 15 for burning a mixed gas of anode off-gas and cathode off-gas, and at the outlet side, exhaust for exhausting combustion exhaust gas generated when the mixed gas is burned by the catalyst 15. A pipe 16 is connected. For example, a heat exchanger may be connected to the downstream side of the exhaust pipe 16.

  In the present embodiment, the cathode off gas discharged from the oxidant electrode 4 of the fuel cell 1 is introduced into the catalytic combustor 13 as combustion air. However, the air taken in from another air supply line is used for combustion. It may be introduced as air.

  Further, the fuel cell 1 is provided with a voltage detection means 17. When the voltage detection means 17 detects a voltage lower than a predetermined voltage value, the on / off valve 11 is controlled by a purge signal output from the system controller 18. The anode off-gas of a predetermined flow rate is supplied from the anode off-gas circulation device 10 to the catalytic combustor 13. The control by the system controller 18 is executed intermittently or continuously according to the power generation status of the fuel cell 1.

  Next, the configuration of the catalytic combustor 13 will be described with reference to FIGS. 1 and 2.

  FIG. 1 is an explanatory view showing the internal structure of the catalytic combustor 13, FIG. 1 (a) is a side sectional view, and FIG. 1 (b) is a front view when viewed from an arrow A in FIG. . 2A and 2B are explanatory views showing the structure of the anode off-gas supply pipe 12 in the housing. FIG. 2A is a side view and FIG. 2B is a cross-sectional view taken along line BB in FIG.

  The catalytic combustor 13 includes a cylindrical housing 19 in which a catalyst 15 for burning a mixed gas of an anode off gas and a cathode off gas is accommodated. A cathode offgas supply pipe 14 (see FIG. 3) (not shown) is connected to one end 19a of the housing 19, and an exhaust pipe 16 (see FIG. 3) (not shown) is connected to the other end 19b. . Further, an outlet end portion 120 of the anode off gas supply pipe 12 is attached to one side surface of the housing 19 so as to penetrate the housing body. In the figure, the arrow 12a indicates the anode off gas, the arrow 14a indicates the cathode off gas, and the arrow 16a indicates the flow of the combustion exhaust gas.

  As shown in FIG. 2A, the outlet end 120 of the anode off-gas supply pipe 12 inserted into the housing includes a gas supply pipe horizontal part 121, a gas supply pipe bent part 122, and a gas supply pipe introduction part 123. It is configured as a substantially L-shaped pipe.

  Among these, the gas supply pipe horizontal portion 121 is horizontally disposed on the center line of the housing 19, and the discharge end 121 a of the gas supply pipe horizontal portion 121 faces the upstream side (arrow 14 a) of the cathode off gas introduction side. Has been placed. The discharge end 121a of the gas supply pipe horizontal portion 121 is sealed by a stopper plate 124, and anode off-gas discharge ports 125a, 125b, 125c, and 125d are radially formed around the discharge end 121a as shown in FIG. It is formed at equal intervals. In addition, the number of holes and the hole shape of the discharge port can be selected as appropriate. However, at least one discharge port needs to be formed in the direction of gravity.

  Further, the gas supply pipe introduction portion 123 is in a direction 101 orthogonal to the longitudinal direction of the housing 19 as shown in FIG. 1B, and as viewed from the arrow A as shown in FIG. On the two-dimensional horizontal plane 103 orthogonal to the gravitational direction 102 at this time, it is inserted into the housing 19 at an angle of θ (0 <θ <90 °) from this horizontal plane. However, the gas supply pipe introduction part 123 assumes the angle θ described above at least in the housing 19. Further, the insertion direction into the housing 19 may be a direction from the upper right to the center as shown in FIG.

  Further, as shown in FIG. 2A, the gas supply pipe bent part 122 has a pipe shape that connects the gas supply pipe horizontal part 121 and the gas supply pipe introduction part 123 with a curve.

  In the above configuration, the anode off gas introduced into the housing 19 through the anode off gas supply pipe 12 is guided from the gas supply pipe introduction section 123 to the gas supply pipe horizontal section 121 via the gas supply pipe bent section 122 and discharged. It is discharged into the housing 19 from the discharge ports 125a to 125d formed around the end 121a. On the other hand, the cathode offgas (arrow 14a) introduced into the catalytic combustor 13 via the cathode offgas supply pipe 14 (not shown) is sent toward the gas supply pipe horizontal portion 121, where the anode offgas and the cathode offgas are separated. A mixed gas is formed by mixing. This mixed gas is further combusted by the catalyst 15 at the subsequent stage, and the combustion exhaust gas (arrow 16a) generated at this time is exhausted to the outside through an exhaust pipe 16 (not shown).

  In this embodiment, the gas supply pipe introduction portion 123 of the anode off-gas supply pipe 12 is inserted into the housing 19 at an angle θ from the horizontal plane as shown in FIG. 122, the turbulent flow is less likely to occur, and the liquid water contained in the anode off-gas is conveyed to the discharge end 121a of the gas supply pipe horizontal part 121 without collecting in the gas supply pipe bent part 122 or the gas supply pipe horizontal part 121, The gas is discharged together with the anode off gas from discharge ports 125 a to 125 d formed at the discharge end 121 a of the gas supply pipe horizontal portion 121. Therefore, the flow of the anode off-gas is not obstructed by the gas supply pipe bent part 122 or the gas supply pipe horizontal part 121 and the concentration of the anode off-gas is not biased, so that the catalyst 15 can be uniformly burned. it can.

  Further, since the liquid water contained in the anode off gas does not accumulate in the gas supply pipe bent part 122 or the gas supply pipe horizontal part 121 which is the pipe of the housing 19, even when the system is left in a low temperature environment below freezing point, Freezing and blockage of condensed water in the piping can be prevented.

  Next, the operation when the angle of the gas supply pipe introduction part 123 is set to θ (0 <θ <90 °) from the horizontal plane will be described.

Normally, when only hydrogen is circulated, the Reynolds number Re does not increase so as to affect the flow because the density is small even if turbulent flow occurs in the bent or horizontal portion of the pipe. However, when turbulent flow is generated in a bent part or a horizontal part of the pipe such as an anode off gas, the Reynolds number Re becomes very large and the fluid does not flow easily. Therefore, when used as the internal piping of the catalytic combustor 13 as in the present embodiment, it is required to reduce the Reynolds number Re. The Reynolds number Re is
Re = U · L / ν (where U: flow velocity, L: pipe length, ν: kinematic viscosity)
It is represented by In this case, the pipe length L is determined by the outer diameter of the housing 19 as shown in FIG. The kinematic viscosity ν is constant as a physical property value. Therefore, in order to reduce the Reynolds number Re, it is important to reduce the flow velocity U. Here, if the angle θ of the gas supply pipe introduction part 123 is 90 ° from the horizontal plane, that is, arranged vertically, the flow velocity U increases by the amount of gravitational acceleration. In FIG. 1B, the flow velocity U and the pipe length L have a relationship of U∝L · sin θ. Therefore, in order to improve the fluid flow, it is preferable that the angle θ is not in the range of 90 ° but in the range of 0 <θ <90 °. Incidentally, when the angle θ is increased, the Reynolds number Re is increased, and when the angle θ is decreased, the Reynolds number Re is decreased. However, θ = 0 ° is not preferable because liquid water accumulates inside the pipe.

  As described above, since the angle θ of the gas supply pipe introduction portion 123 is in the range of 0 <θ <90 °, it is possible to suppress the occurrence of turbulent flow at the bent portion or the horizontal portion of the pipe. Effects such as pressure loss reduction, shortening of the pipe length of the gas supply pipe horizontal portion (rectifying portion described later) 121, and reduction of uneven hydrogen concentration in the catalytic combustor 13 can be obtained. Thereby, the liquid water contained in the anode off gas can be completely vaporized in the catalytic combustor.

  The angle θ of the gas supply pipe introduction part 123 is appropriately set according to the liquid water ratio, humidity, etc. contained in the anode off gas.

  In this embodiment, the horizontal portion 121 of the gas supply pipe disposed horizontally inside the housing 19 serves as a rectifying unit. Therefore, the two-phase mixed phase fluid of the anode off gas is rectified at this portion, and two phases of gas and liquid water are rectified. Can be separated. Further, since the anode off gas can be discharged from the discharge ports 125a to 125d in the rectifying unit, the unevenness of the hydrogen concentration in the subsequent catalyst 15 can be reduced. Further, since the gas supply pipe horizontal portion 121 is disposed on the center line of the housing 19, the anode off gas can be discharged evenly in the direction 101 (FIG. 1) orthogonal to the longitudinal direction of the housing 19. Furthermore, since the discharge ports 125a to 125d are formed radially at equal intervals at the discharge end 121a of the gas supply pipe horizontal portion 121, the anode off gas can be discharged radially and uniformly.

  Further, since the discharge end 121a of the gas supply pipe horizontal portion 121 is arranged toward the upstream side of the cathode offgas introduction side, the mixing path of the anode offgas and the cathode offgas can be lengthened, and a more uniform mixed gas can be obtained. Can be obtained.

  Further, in this embodiment, as shown in FIG. 2A, the gas supply piping bent portion 122 has a curved piping structure. Generation of turbulence can be further reduced.

Explanatory drawing which shows the internal structure of a catalyst combustor. (A) is side sectional drawing. (B) is a front view when it sees from the arrow A of (a). Explanatory drawing which shows the structure in the housing of anode off gas supply piping. (A) is a side view. (B) is BB sectional drawing of (a). The block diagram which shows schematic structure of the fuel cell system concerning an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Electrolyte membrane 3 ... Fuel electrode 4 ... Oxidant electrode 5 ... Hydrogen supply device 6 ... Air supply device 7 ... Fuel gas supply piping 8 ... Oxidant gas supply piping 12 ... Anode off-gas supply piping 13 ... Catalytic combustion 14 ... Cathode off-gas supply pipe 15 ... Catalyst 19 ... Housing 120 ... Outlet end 121 ... Gas supply pipe horizontal part 122 ... Gas supply pipe bent part 123 ... Gas supply pipe introduction part 125a-125d ... Discharge port

Claims (5)

In a catalytic combustor in which a secondary fuel gas discharged from a fuel electrode of a combustion cell and combustion air are mixed in a housing, and the mixed gas is burned using a catalyst.
In the housing, the gas supply pipe for introducing the secondary fuel gas has a substantially L-shaped pipe structure including a gas supply pipe horizontal part, a gas supply pipe bent part, and a gas supply pipe introduction part,
The gas supply pipe horizontal portion is disposed horizontally in the housing, and the gas supply pipe introduction portion is perpendicular to the longitudinal direction of the housing, and perpendicular to the direction of gravity when the housing is viewed from the front. A catalytic combustor which is disposed in a range of 0 <θ <90 ° from a horizontal plane on a two-dimensional horizontal plane.   The catalytic combustor according to claim 1, wherein a discharge end of the horizontal portion of the gas supply pipe is directed upstream of the combustion air introduction side.   The catalytic combustor according to claim 1 or 2, wherein a plurality of discharge ports for discharging the secondary fuel gas are radially formed at a discharge end of the horizontal portion of the gas supply pipe.   The catalytic combustor according to any one of claims 1 to 3, wherein the horizontal portion of the gas supply pipe is disposed on a center line of the housing. 5. The catalytic combustor according to claim 1, wherein the bent portion of the gas supply pipe has a curved pipe structure.

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