JP2006032061A - Hydrogen combustion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen combustion apparatus allowing efficient combustion of a hydrogen gas by adjusting the amount of air that increases while a fuel cell system is in operation under heavy load. <P>SOLUTION: The hydrogen combustion apparatus is provided for combustion of a mixed gas composed of a mixture of a hydrogen gas and air that are discharged from a fuel cell stack 1. A hydrogen combustor 16 is provided in a main passage 18 through which air discharged from the fuel cell stack 1 flows, and a laminar flow generator 21 as an air inflow amount adjusting means for adjusting the inflow amount of air flowing through the main passage 18 is provided to surround an outer periphery of the hydrogen combustor 16. By providing the laminar flow generator 21, a large amount of air discharged while the fuel cell system is in operation under heavy load can be conveyed toward the laminar flow generator 21 while a required amount of air for combustion can be conveyed to the hydrogen combustor 16. Complete combustion of the hydrogen gas is thereby made possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen combustion apparatus that mixes and burns hydrogen gas and air discharged from a fuel cell stack of a fuel cell system, and more specifically, adjusts the amount of air that increases during high-load operation of the fuel cell system. The present invention relates to a combustion technique for efficiently burning hydrogen gas.

  For example, in a fuel cell system mounted on a fuel cell vehicle or the like, in order to prevent unburned hydrogen gas remaining without being used for power generation in the fuel cell stack from being released into the atmosphere as it is, the hydrogen gas is used. 2. Description of the Related Art Hydrogen combustion apparatuses that are mixed with air and burned are used.

In order to burn hydrogen gas, it is necessary to supply combustion air to the hydrogen combustion apparatus. As a method of introducing air, a method of forcibly sending air to the hydrogen combustion apparatus using a dedicated blower (see, for example, Patent Documents 1 and 2), or directly discharging air discharged from the fuel cell stack, There are two methods of introducing into a hydrogen combustion apparatus.
Japanese Patent Laid-Open No. 2002-12211 (see page 4, FIG. 1, etc.) Japanese Patent Laid-Open No. 2002-372208 (see page 2, FIG. 8, etc.)

  However, when a method of forcibly sending air to the hydrogen combustion apparatus using a dedicated blower is adopted, a fan, a power supply, a control unit, and the like are required, and the apparatus configuration becomes complicated.

  On the other hand, when adopting the method of directly flowing the air discharged from the fuel cell stack into the hydrogen combustion device, the hydrogen gas that has not been burned but burned by the air that increases during high-load operation of the fuel cell system May be discharged into the atmosphere as it is. In general, the combustion rate of a hydrogen combustion apparatus is proportional to the contact time between the catalyst provided in the hydrogen combustion apparatus and hydrogen gas, and therefore the contact time is shortened when the air flow rate is increased. Easily released into the atmosphere. However, in order to obtain a sufficient contact time, the catalyst must be increased in size.

  Accordingly, the present invention has been made in view of the above-described problems, and provides a hydrogen combustion apparatus that can efficiently burn hydrogen gas by adjusting the amount of air that increases during high-load operation of a fuel cell system. The purpose is to do.

  The invention according to claim 1 is a hydrogen combustion apparatus for combusting a mixed gas obtained by mixing hydrogen gas and air discharged from a fuel cell stack, respectively, in a main flow path through which air discharged from the fuel cell stack flows. A hydrogen combustor is provided, and air inflow amount adjusting means for adjusting the inflow amount of air flowing through the main flow path is provided so as to surround the outer periphery of the hydrogen combustor.

  A second aspect of the present invention is the hydrogen combustion apparatus according to the first aspect, wherein the air inflow amount adjusting means comprises a laminar flow generator that uses the air flowing through the main flow path as a laminar flow. And

  Invention of Claim 3 is a hydrogen combustion apparatus of Claim 1 or Claim 2, Comprising: The drainage channel for draining the water discharged | emitted with the said air from the said fuel cell stack is said main flow path It is characterized by being branched.

  According to the first aspect of the present invention, the hydrogen combustion apparatus is provided in the main flow path through which the air discharged from the fuel cell stack flows, and the air inflow amount adjusting means is provided so as to surround the outer periphery of the hydrogen combustion apparatus. Therefore, during high load operation of the fuel cell system, by adjusting the air inflow amount adjusting means, it is possible to introduce an air amount suitable for hydrogen combustion into the hydrogen combustion apparatus, and to the air inflow amount adjusting means, A lot of air can flow.

  Therefore, according to the present invention, hydrogen gas can always be efficiently burned regardless of the operating state of the fuel cell system, and release of unburned hydrogen gas into the atmosphere can be prevented.

  In addition, since the air inflow amount adjusting means is provided so as to surround the outer periphery of the hydrogen combustion apparatus, the air inflow amount adjusting means performs a heat insulating action to absorb heat generated in the hydrogen combustion apparatus. Therefore, it is not necessary to provide a dedicated heat insulation part in the hydrogen combustion apparatus, and the hydrogen combustion apparatus can be reduced in size and weight accordingly.

  According to the second aspect of the present invention, since the laminar flow generator using the air flowing through the main flow path as a laminar flow is used as the air inflow adjustment means, the fuel cell system is discharged from the fuel cell stack during high load operation. Much of the air can flow to the laminar flow generator.

  According to the invention of claim 3, since the drainage channel for draining the water discharged together with the air from the fuel cell stack is provided so as to branch from the main channel, the pressure of the air flowing in the main channel causes the Water (water droplets) collected at the bottom of the main channel can be discharged to the drainage channel, and the water can be prevented from collecting near the hydrogen combustor in the main channel.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  The present embodiment is an example in which the hydrogen combustion apparatus of the present invention is applied to a fuel cell system mounted on a fuel cell vehicle.

"Overview of fuel cell system"
First, the fuel cell system will be briefly described. FIG. 1 is a schematic configuration diagram of a fuel cell system. In FIG. 1, a thin solid line α indicates a flow path of oxygen (air), a one-dot chain line β indicates a flow path of hydrogen, a broken line γ indicates a flow path of coolant, and a thick solid line δ indicates a flow path of pure water for humidification.

  The fuel cell stack 1 includes a fuel electrode 3 into which hydrogen gas is introduced from a compressed hydrogen tank 2 and an air electrode 4 into which air that is an oxidant gas taken from the outside is introduced. In the fuel cell stack 1, the hydrogen gas introduced into the fuel electrode 3 and the oxygen introduced into the air electrode 4 are combined with an electrolyte membrane (not shown) disposed between the fuel electrode 3 and the air electrode 4. The power is generated by reacting through (omitted).

  The hydrogen gas and oxygen supplied to the fuel cell stack 1 are humidified by the humidifier 5 to activate the power generation action and prevent the electrolyte membrane from being deteriorated. In the humidifier 5, pure water stored in the pure water tank 6 that stores pure water and collects pure water remaining in the fuel cell stack 1 when the fuel cell system is stopped is supplied to the pure water outlet pipe 7. And pure water pumping pump 8.

  The pure water tank 6 is used as a water storage tank for storing a predetermined amount of pure water to be supplied to the humidifier 5, and for example, the fuel cell system is stopped for a long time under an outside air temperature below freezing point. In order to prevent the pure water in the fuel cell stack 1 from freezing and rupturing sometimes, the pure water in the pure water path is extracted through the pure water recovery pipe 9 and stored after the system operation is completed. used.

  Further, since the fuel cell stack 1 generates heat during power generation, the coolant is circulated from the radiator 10 to the fuel cell stack 1 by the coolant pump 11 to cool the fuel cell stack 1. As the cooling liquid, for example, an antifreeze liquid (LLC liquid) is used.

  The coolant passage 12 is provided with a bypass passage 13 that bypasses the radiator 10. At the start of the fuel cell system, the radiator 10 is bypassed by the three-way valve 14 provided in the coolant path 12. The bypass passage 13 is used only when the fuel cell system is started, and is controlled so that the coolant does not flow through the bypass passage 13 during system operation.

  Furthermore, a heater 15 using electric heat or hydrogen combustion heat for heating the coolant is installed in the bypass passage 13, and the heater 15 is used to heat the coolant to promote warming of the fuel cell stack 1. The power generation system can be activated as soon as possible.

  Further, in this fuel cell system, after the hydrogen gas is burned by the hydrogen combustor 16 of the present invention, the unburned hydrogen gas that is not used for power generation in the fuel cell stack 1 is not released to the atmosphere as it is. The sound is silenced by the silencer 17 and released to the atmosphere.

"Hydrogen combustion system configuration"
Next, a hydrogen combustion apparatus to which the present invention is applied will be described. 2 is a sectional view showing a schematic configuration of the hydrogen combustion apparatus, FIG. 3A is a perspective view of a turbulent plate of a fuel ejection pipe, FIG. 3B is a sectional view of the fuel ejection pipe, and FIG. FIG. 5A is a perspective view of a laminar flow generator, and FIG. 5B is a perspective view of components of the laminar flow generator.

  As shown in FIG. 2, the hydrogen combustion apparatus is provided so as to surround a hydrogen combustor 16 provided in a main flow path 18 through which air discharged from the fuel cell stack 1 flows, and an outer periphery of the hydrogen combustor 16. And a laminar flow generator 21 which is an air flow rate adjusting means.

  The hydrogen combustor 16 includes a fuel injection unit 23 that injects hydrogen gas into a cylindrical combustor 22, a mixing unit 24 that mixes inflowing oxygen and the injected hydrogen gas, and a mixing unit 24. And a temperature measuring element 26 for measuring the temperature of the combustion unit 25.

  The combustor 22 is formed of a material that can withstand the combustion temperature and pressure, such as stainless steel (SUS304), and is formed in a cylindrical shape having a predetermined size. The combustor 22 may have other shapes and materials as long as the combustor 22 is designed to satisfy requirements such as a gas flow rate and a calorific value required for the combustion system.

  The fuel injection part 23 is a part for injecting unburned hydrogen gas discharged from the fuel cell stack 1 into the combustor 22, and includes a fuel injection pipe 27 connected to an anode off-gas pipe. In the fuel ejection portion 23, the front end side portion of the fuel ejection pipe 27 is projected into the combustor 22, and hydrogen gas is ejected from a plurality of fuel ejection holes 28 formed in the front end side portion.

  As shown in FIGS. 3A and 3B, the fuel ejection pipe 27 is a pipe made of, for example, a stainless steel pipe, and a plurality of fuel ejection holes 28 for ejecting hydrogen gas are formed on the peripheral surface of the pipe tip side. is doing. This fuel ejection hole 28 may be provided at one location in the center of the pipe circumferential surface, or may be provided at a plurality of locations in the circumferential direction. A disc-shaped turbulent flow plate 30 is attached to the tip of the fuel ejection pipe 27.

  The mixing unit 24 is a part that forms an air-fuel mixture (mixed gas) by mixing hydrogen gas and oxygen, and is provided at the downstream side of the fuel ejection unit 23 in the exhaust direction. The mixing unit 24 is configured, for example, by arranging and fixing a plurality of mixing plates 31 and 32 in the combustor 22 at a predetermined interval. As shown in FIG. 4, the mixing plate 31 disposed on the fuel ejection portion 23 side is formed as a disk having a large circular hole 33 formed in the center. On the other hand, the other plurality of mixing plates 32 are formed as a disk in which a plurality of small circular holes 34 are formed. After the hydrogen gas and oxygen form a turbulent flow through the circular holes 33 and 34 formed in the two kinds of mixing plates 31 and 32 and these are mixed, the mixed gas mixture is It is sent to the combustion section 25 on the rear side of the combustor.

  The combustion unit 25 is a part that burns an air-fuel mixture composed of hydrogen gas and oxygen mixed in the mixing unit 24, and is provided behind the mixing unit 24 (on the exhaust downstream side). A catalyst 35 that burns the air-fuel mixture by being in contact with the air-fuel mixture is disposed in the combustion unit 25. As the catalyst 35, a conventionally known catalyst technique in which a noble metal such as platinum (Pt) is supported on a carrier such as a metal honeycomb or a ceramic honeycomb can be used.

  The temperature measuring element 26 measures heat generated in the combustion unit 25 and is inserted into the combustor 22.

  The laminar flow generator 21 is arranged so as to surround the outer periphery of the combustor 22, and as shown in FIGS. 5A and 5B, a flat plate 36 made of, for example, stainless steel and a corrugated plate 37 are provided. Overlapping and forming a cylindrical body having a combustor insertion hole 29 in the center. The laminar flow generator 21 thus formed has a so-called honeycomb shape. If this laminar flow generator 21 is attached to the outer periphery of the hydrogen combustor 16 provided in the main flow path 18, the air flow flowing through the laminar flow generator 21 becomes a laminar flow.

  In addition to this configuration, the main flow path 18 is connected to the front and rear of the hydrogen combustor 16, and the drainage path 20 branched from the main flow path 18 is bypassed so as to be parallel to the main flow path 18. Yes. The drainage channel 20 discharges water (water droplets) discharged together with air from the fuel cell stack 1 by the pressure of the air flowing in the main flow path 18.

"Action / Effect"
Next, operations and effects of the hydrogen combustion apparatus in which the laminar flow generator 21 is provided in the main flow path 18 in which the hydrogen combustor 16 is disposed will be described.

  In the hydrogen combustion apparatus of the present embodiment, when the pressure on the inlet side in the vicinity of the hydrogen combustor 16 in the main flow path 18 is low (during low load operation of the fuel cell system), the air flow rate V1 flowing to the hydrogen combustor 16 side and The air flow rate V2 flowing through the laminar flow generator 21 is substantially the same. However, when the pressure on the inlet side is high (during high-load operation of the fuel cell system), a space is simply provided between the hydrogen combustor 16 and the main flow path 18 (the hydrogen combustor 16 and the main flow path 18). When the laminar flow generator 21 is not installed between the two, a large amount of air flows to the space side, and unburned hydrogen gas is released to the atmosphere as it is.

In general, the pressure loss [Delta] P of the fluid, the [Delta] P = K1v when laminar flow, when the turbulence is expressed by [Delta] P = K2V _2. However, K is a constant and V is a flow rate. As can be seen from these equations, if the flow rate of fluid (air in this embodiment) increases, the pressure loss in the case of turbulent flow increases as the square of the flow rate, and the pressure loss in the case of laminar flow increases by the flow rate. The amount of increase in pressure loss is small compared to the case of turbulent flow. That is, in the case of laminar flow, the pressure loss does not increase so much even if the air flow rate increases.

  Further, when the pressure on the inlet side in the vicinity of the hydrogen combustor 16 in the main flow path 18 increases and the air flow rate increases, the air flow rate on the space side where the laminar flow generator 21 that is a laminar flow with low pressure loss is arranged increases. Will do. Therefore, the amount of air flowing through the hydrogen combustor 16 does not increase as much as the pressure increases. However, an amount of air necessary for combustion flows through the hydrogen combustor 16. That is, the total amount of air can be increased without greatly increasing the amount of air in the hydrogen combustor 16 even during high load operation of the fuel cell system.

  FIG. 6 is a diagram showing the relationship between the inlet pressure on the inlet side of the main flow path 18 near the hydrogen combustor 16 and the air flow rate (for each of the hydrogen combustor 16 side and the laminar flow generator 21 side), and FIG. 7 shows hydrogen combustion. It is a figure which shows the air flow rate which flows through the container 16 side and the laminar flow generator 21 side, respectively.

  From FIG. 6, it can be seen that the inlet pressure on the inlet side and the air flow rate are substantially proportional to each other, and that the air flow rate increases in proportion to the increase in the inlet pressure. Further, as described above, it can be seen that the air flow rate tends to increase on the honeycomb-shaped laminar flow generator 21 side as compared with the hydrogen combustor 16 side.

  7 that the air flow rate on the hydrogen combustor 16 side is much lower than the air flow rate on the laminar flow generator 21 side. For example, when the flow rate of air flowing through the laminar flow generator 21 is 2000 [L / min], the flow rate of air flowing through the hydrogen combustor 16 is only about 600 [L / min]. That is, a large amount of air flows to the laminar flow generator 21 side with respect to the hydrogen combustor 16 side.

  Actually, when the mixed gas was combusted using the hydrogen combustion apparatus of the present embodiment, the fuel cell system was operated at a low load (air flow rate 1200 [L / min], hydrogen gas flow rate 20 [L / min]. ) And during high load operation (air flow rate 2000 [L / min], hydrogen gas flow rate 30 [L / min]), the mixed gas could be burned safely and completely.

Further, for example, in the existing hydrogen combustion apparatus as shown in FIG. 8 in which the same reference numerals are assigned to the corresponding parts as in FIG. 2 and the hydrogen combustion apparatus of the present embodiment, the mixed gas is burned under the same conditions as described above. Table 1 shows the results of comparison. As can be seen from the table, the catalyst capacity of the conventional (existing) hydrogen combustor 40 is about 295 [mL], whereas the catalyst capacity of the hydrogen combustor 16 of the present embodiment is about 75 [mL]. It was found that the concentration of discharged hydrogen was about 0.3% in the former and 0.1% or less in the latter. The pressure loss at that time was about 3.1 [kPa] for the former and only about 1.3 [kPa] for the latter. The pressure loss is determined by the diameter and length of the laminar flow generator 21, but in this embodiment, the one having an outer diameter of 76 [mm], an inner diameter of 49 [mm], and a length of 80 [mm] was used. .

  As described above, according to the hydrogen combustion apparatus of the present embodiment, the hydrogen combustor 16 is provided in the main flow path 18 through which the air discharged from the fuel cell stack 1 flows, and the outer periphery of the hydrogen combustor 16 is provided. Since the laminar flow generator 21 for adjusting the inflow amount of the air flowing through the main flow path 18 is provided so as to surround, the flow rate of air discharged from the fuel cell stack 1 during high load operation of the fuel cell system increases. However, a large amount of air can flow to the laminar flow generator 21 while sending the amount of air necessary for combustion to the hydrogen combustor 16. As a result, the hydrogen gas can be completely burned, and the hydrogen gas can be prevented from being released to the atmosphere without being burned.

  Therefore, according to this hydrogen combustion apparatus, hydrogen gas can always be efficiently burned regardless of the operating state of the fuel cell system, and release of unburned hydrogen gas into the atmosphere can be prevented.

  In addition, since the laminar flow generator 21 is provided so as to surround the outer periphery of the hydrogen combustor 16, the laminar flow generator 21 performs a heat insulating action to absorb heat generated in the hydrogen combustor 16. Therefore, it is not necessary to provide a dedicated heat insulating portion in the hydrogen combustor 16, and the hydrogen combustion apparatus can be reduced in size and weight accordingly.

  Moreover, according to the hydrogen combustion apparatus of the present embodiment, a large pressure loss is not generated. On the other hand, when the air discharged from the fuel cell stack 1 is directly flown into the hydrogen combustor 16 as in the prior art, defective hydrogen combustion occurs or pressure loss increases during high load operation of the fuel cell system. To do.

  Furthermore, according to the hydrogen combustion apparatus of the present embodiment, the laminar flow generator 21 that uses the air flowing through the main flow path 18 as a laminar flow is used as the air inflow amount adjusting means. Sometimes, the air discharged from the fuel cell stack 1 can be actively flowed to the laminar flow generator 21.

  Furthermore, according to the hydrogen combustion apparatus of the present embodiment, the drainage channel 20 for draining the water discharged together with the air from the fuel cell stack 1 is provided so as to be branched from the main channel 18. The water (water droplets) accumulated at the bottom of the main channel 18 can be discharged to the drainage channel 20 by the pressure of the air flowing inside, and the water accumulates in the vicinity of the hydrogen combustor 16 in the main channel 18. Can be prevented.

  As mentioned above, although embodiment of this invention was described, it should not be understood that description and drawing which make a part of indication of embodiment mentioned above limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

It is a schematic block diagram of a fuel cell system. It is sectional drawing which shows schematic structure of the hydrogen combustion apparatus of this Embodiment. FIG. 3A is a perspective view of the turbulent flow plate of the fuel ejection pipe, and FIG. 3B is a cross-sectional view of the fuel ejection pipe. It is a perspective view which shows the mixing plate of the mixing part in a hydrogen combustor. 5A is a perspective view of a laminar flow generator, and FIG. 5B is a perspective view of components of the laminar flow generator. It is a figure which shows the relationship between the inlet pressure and the air flow rate in the inlet side in which a main flow path and a branch flow path cross | intersect. It is a figure which shows the air flow rate which each flows through the hydrogen combustor side and laminar flow generator side in a main flow path. It is sectional drawing which shows schematic structure of the existing hydrogen combustion apparatus which provided the heat insulation layer in the outer periphery of a hydrogen combustor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 16 ... Hydrogen combustor 18 ... Main flow path 20 ... Drainage channel 21 ... Laminar flow generator 22 ... Combustor 23 ... Fuel injection part 24 ... Mixing part 25 ... Combustion part 26 ... Temperature measuring element

Claims (3)

In a hydrogen combustion apparatus for burning a mixed gas in which hydrogen gas and air discharged from the fuel cell stack (1) are mixed,
A hydrogen combustor (16) is provided in a main channel (18) through which air discharged from the fuel cell stack (1) flows, and the main channel (18) is surrounded by an outer periphery of the hydrogen combustor (16). 18) A hydrogen combustion apparatus comprising an air inflow amount adjusting means (21) for adjusting an inflow amount of air flowing through 18). The hydrogen combustion apparatus according to claim 1,
The hydrogen inflow apparatus characterized in that the air inflow amount adjusting means includes a laminar flow generator (21) that uses air flowing through the main flow path (18) as a laminar flow. The hydrogen combustion apparatus according to claim 1 or 2,
A hydrogen combustion apparatus characterized in that a drainage channel (20) for draining water discharged together with the air from the fuel cell stack (1) is branched from the main channel (18).

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