JP4584564B2 - Fuel cell exhaust system - Google Patents

Description

  The present invention relates to an exhaust system for a fuel cell, and more particularly to an exhaust system for a fuel cell suitable for processing hydrogen during purging of a fuel cell using hydrogen as a fuel mounted on a vehicle.

  Conventionally, an exhaust system has been proposed in which hydrogen at the time of purging a fuel cell using hydrogen as a fuel mounted on a vehicle is diluted to a concentration below the lower combustion limit and then exhausted outside the vehicle (see Patent Document 1).

A predetermined volume retaining region for retaining fuel discharged during purging, and a predetermined volume dilution region for allowing air discharged from the fuel cell to flow and mixing and diluting the fuel from the retaining region; Provided with a diluting device having a flow passage for allowing fuel to flow from the staying region to the diluting region, guiding the fuel to the exhausted fuel diluting device, and burning the fuel concentration over time between purges After diluting below the lower limit, it is exhausted outside the vehicle.
JP 2003-132915 A

  However, in the above conventional example, the volume of the dilution region is set to be larger than the purge amount at the maximum output of the fuel cell so as to be compatible with all purges. When mounting on equipment, securing an optimal arrangement space on the vehicle layout remains as an issue.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell exhaust system suitable for a vehicle layout.

The present invention provides a fuel cell system in which exhaust fuel discharged from a fuel cell that generates power by being supplied with fuel and air is mixed with newly supplied fuel via a circulation path and supplied to the fuel cell. An exhaust system for a fuel cell that dilutes exhaust hydrogen temporarily discharged from a circulation path of the fuel cell system by purging or the like with exhaust air exhausted from the fuel cell and discharges it to the outside air. A merging portion that dilutes the concentration of exhaust hydrogen by mixing with exhaust air, and a concentration of exhaust hydrogen mixed in the merging portion by circulating exhaust gas discharged from the merging portion through a pipe having a predetermined length. And an exhaust pipe that is disposed downstream of the exhaust pipe and has a dilution space having a cross-sectional area larger than the cross-sectional area of the exhaust pipe that is disposed downstream of the exhaust pipe and communicates with the outside air. Of exhaust hydrogen in gas Degrees were as and a diluter for discharging diluted by air.

Therefore, in the present invention, the exhaust hydrogen discharged from the confluence portion, which is obtained by diluting the concentration of the exhaust hydrogen by mixing the exhaust hydrogen exhausted from the fuel cell system by purging or the like with the exhaust air from the fuel cell. An exhaust pipe that circulates through a pipe having a predetermined length and dilutes the concentration of exhaust hydrogen mixed at the junction with air, and an exhaust pipe that is arranged downstream of the exhaust pipe and that communicates with the outside in the downstream. The fuel cell exhaust system is composed of a diluter that has a dilution space with a cross-sectional area larger than the cross-sectional area of the passage and dilutes the exhaust hydrogen concentration in the exhaust gas introduced from the exhaust pipe with air. did. For this reason, hydrogen gas discharged by purging or the like from the fuel cell system is mixed with air discharged from the fuel cell at the junction, and when the exhaust pipe, the exhaust muffler and the tail pipe are circulated, a predetermined length is obtained in the mixed state. By diluting the hydrogen gas with air, the diluter further dilutes it by passing it through a diluting space having a predetermined volume with a cross-sectional area larger than that of the exhaust pipe. Can be exhausted. In addition, since there is no large volume portion such as a staying region for retaining the exhaust hydrogen, it is possible to provide a fuel cell exhaust system suitable for a vehicle layout.

  Hereinafter, an exhaust system for a fuel cell according to the present invention will be described based on an embodiment.

  FIG. 1 is a perspective view showing a first embodiment of an exhaust system for a fuel cell to which the present invention is applied.

  In FIG. 1, an exhaust system 1 for a fuel cell includes a merging portion 2 for mixing exhaust air, which is cathode exhaust gas discharged from a fuel cell system (not shown), and exhaust hydrogen discharged at the time of purge, Exhaust pipe 3 comprising exhaust pipe 7, exhaust muffler 8 and tail pipe 9 provided to have a predetermined length so as to dilute the exhaust hydrogen with air, and a dilution space having a predetermined volume due to a larger cross-sectional area than exhaust pipes 7 and 9. The diluter 4 is provided, and through these, the hydrogen concentration in the exhaust gas is diluted below the lower combustion limit and then exhausted outside the vehicle. Further, in the middle of the path from the junction 2 to the diluter 4, a catalytic combustor 5 that reduces the hydrogen gas concentration by causing a combustion reaction between the mixed exhaust hydrogen and exhaust air when the concentration of exhaust hydrogen is high; A heat exchanger 6 capable of cooling the exhaust gas and diluting the exhaust hydrogen with the exhaust air when passing through the exhaust gas can be added as necessary.

The merging section 2 is introduced with exhaust air that is cathode exhaust gas discharged from a fuel cell system (not shown) and exhaust hydrogen discharged during purge. The fuel cell system uses pure hydrogen (hereinafter referred to as “hydrogen”) as fuel, and in order to improve its utilization efficiency, a circulation system that supplies exhaust hydrogen from the fuel cell to the fuel cell again using an ejector or a hydrogen pump Is provided. In this circulation system, nitrogen (N ₂ ) permeated from the cathode side, condensed water and condensed water in the generated water accumulate in the circulating hydrogen gas in the circulation system and the anode gas flow path in the fuel cell, thereby inhibiting the power generation reaction. Therefore, a purge process for temporarily releasing the hydrogen of the circulation system to the outside when the cell voltage is lowered is provided. The discharge of the exhausted hydrogen by the purge process is executed intermittently at regular intervals. The amount of hydrogen purge discharged is proportional to the output when purging the fuel cell. Further, exhaust air discharged from the fuel cell system is introduced into the merging portion 2 of the exhaust system 1 via a pressure control valve (not shown) that controls the cathode gas pressure. In the merging section 2, the exhausted hydrogen that is discharged at the time of the purge is joined to the exhaust air that is always introduced, and the two are mixed to dilute the concentration of the hydrogen gas.

  The catalyst-type combustor 5 incorporates a catalyst, introduces exhaust gas mixed in the merging section 2, causes exhaust hydrogen in the exhaust gas to undergo a combustion reaction with exhaust air and the catalyst, and generates hydrogen in the exhaust gas. The gas concentration is reduced and supplied to the downstream heat exchanger 6. When the purge amount of hydrogen discharged from the fuel cell system is large, the hydrogen concentration in the exhaust gas becomes high, the combustion reaction is promoted, and the hydrogen gas concentration can be effectively reduced. When the concentration of hydrogen contained in the exhaust gas is low, the combustion reaction becomes slow.

  The heat exchanger 6 introduces and cools the exhaust gas whose temperature has been increased by the combustion heat generated by the combustion reaction in the catalytic combustor 5. The exhaust gas is cooled while passing through the heat exchange passage, and the exhaust hydrogen contained in the exhaust gas is mixed with the exhaust air and diluted to flow to the downstream exhaust pipe 3. If the heat exchanger 6 and the upstream catalytic combustor 5 are disposed in the upstream portion where the hydrogen concentration in the exhaust gas is relatively high, the hydrogen concentration can be effectively reduced, and the downstream exhaust pipe 3 and the dilution can be reduced. The reduction rate of the hydrogen concentration in the vessel 4 can be reduced.

  The exhaust pipe line 3 includes a front exhaust pipe 7A connected to the merging portion 2 and a rear exhaust pipe 7B having a flexible tube 7C in the middle, and an exhaust muffler 8 disposed from the position below the floor in the center of the vehicle to the rear of the vehicle. An exhaust passage having a predetermined length is formed. The exhaust gas mixed in the merging portion 2 flows while diluting the hydrogen gas concentration contained in the exhaust gas with the exhaust air as it flows through the front exhaust pipe 7A and the rear exhaust pipe 7B. For this reason, hydrogen is diluted as it flows from upstream to downstream, and the hydrogen gas concentration is lowered. Exhaust gas that has reached the exhaust muffler 8 is expanded and contracted every time it passes through a plurality of chambers (not shown) that are expanded for noise reduction, thereby further reducing the concentration of exhaust hydrogen, thereby promoting the rear part of the vehicle. Is introduced into the tail pipe 9 and reaches the diluter 4.

  As shown in FIG. 2, the diluter 4 includes a diluting space 11 that is connected to the outlet end of the tail pipe 9 and has a cross-sectional area gradually enlarged, and prevents backfire in the middle or downstream of the diluting space 11. A filter 12 is provided. Reference numeral 13 denotes a cover that protects the dilution space. The dilution space 11 whose cross-sectional area is gradually enlarged from the end of the tail pipe 9 suppresses the passing speed of the passing exhaust gas, further promotes the mixing of exhaust hydrogen and exhaust air contained in the exhaust gas, and increases the hydrogen gas concentration. Is further reduced. A backfire prevention filter 12 composed of a metal mesh, punching metal, or the like is disposed at the end of the dilution space 11 as an air opening, and exhaust gas that has passed through the dilution space 11 passes through the backfire prevention filter 12. And discharged to the outside air. The backfire prevention filter 12 can be provided not only downstream of the dilution space 11 but also in the middle.

  In this backfire prevention filter 12, even if exhaust hydrogen discharged from the dilution space 11 to the outside air has some kind of fire (open flame), for example, on the road outside the vehicle, it burns in the filter 12 even if it should burn. Since the heat is taken away and the flame is extinguished, combustion does not propagate to the dilution space 11. The backfire prevention filter 12 has a shape that swells to the outside air side, for example, a shape that increases the contact area with the exhaust gas in the flow direction of the exhaust gas, such as a hemispherical type. For this reason, the pressure loss at the time of exhaust gas passage can be reduced, and a flameproof performance and a silencing performance are improved.

  In the present embodiment, the following effects can be achieved.

  (A) Circulation of a fuel cell system in which exhaust fuel discharged from a fuel cell that generates power by supplying fuel and air is mixed with newly supplied fuel via a circulation path and supplied to the fuel cell. An exhaust system 1 for a fuel cell that dilutes exhaust hydrogen temporarily discharged by purging or the like from a path with exhaust air exhausted from a fuel cell and exhausts it to outside air, and mixes the exhaust hydrogen with exhaust air And the concentration of exhaust hydrogen mixed in the merging portion 2 is diluted with air by passing the exhaust gas discharged from the merging portion 2 through a pipe having a predetermined length. An exhaust pipe 3 and a dilution space 11 disposed downstream of the exhaust pipe 3 and having a cross-sectional area larger than the cross-sectional area of the exhaust pipe 3, and exhaust hydrogen in exhaust gas introduced from the exhaust pipe 3 Diluted with air and discharged And interpretation unit 4, and the like comprising a. For this reason, in the junction 2, the hydrogen gas discharged from the fuel cell system by purging or the like is mixed with the air discharged from the fuel cell, and when the exhaust pipe 7, the exhaust muffler 8 and the tail pipe 9 pass, the mixed state Then, the hydrogen gas is diluted with air by flowing through a predetermined length in the diluter 4, and in the diluter 4, the cross-sectional area is larger than the cross-sectional area of the exhaust pipes 7 and 9, and passes through the dilution space 11 having a predetermined volume. By flowing, it can be further diluted and exhausted to the outside air. In addition, since there is no large volume portion such as a staying region for retaining the exhaust hydrogen, it is possible to provide a fuel cell exhaust system suitable for a vehicle layout.

  (A) Since the diluter 4 includes a backfire prevention filter 12 as a dilution promoting means for diluting the exhaust hydrogen in the exhaust gas with air in the downstream area of the dilution space 11 or in the dilution space 11, the diluter 4 is located near the exhaust outlet ) Even if there is some kind of fire (open flame) and the discharged exhaust gas should burn, it is possible to prevent the flame from entering the exhaust pipe 9 or the dilution space 11.

  (C) The backfire prevention filter 12 as dilution promoting means has a dome shape projecting in the downstream direction so as to increase the contact area with the passing exhaust gas, and is formed by a plate material or net having a large number of holes. Therefore, the contact area with the exhaust gas is increased in the exhaust flow direction as in the hemispherical type, and the pressure loss can be reduced, and the flameproof performance and the sound deadening performance can be improved.

  (D) When a catalytic combustor 5 having a catalyst for burning exhaust hydrogen in exhaust gas with air is provided between the junction 2 and the diluter 4, purging of hydrogen discharged from the fuel cell system When the amount is large, the hydrogen concentration in the exhaust gas becomes high, the combustion reaction is promoted, and the hydrogen gas concentration can be effectively reduced. Since the combustion reaction generated by the catalytic combustor 5 is more effectively promoted as the hydrogen concentration is higher, the catalytic combustor 5 is arranged in the upstream portion where the hydrogen concentration in the exhaust gas is relatively high. The hydrogen concentration can be effectively reduced, and the reduction rate of the hydrogen concentration in the downstream exhaust pipe 3 and the diluter 4 can be reduced.

  (E) If the catalytic combustor 5 is provided with a heat exchanger 6 that cools the exhaust gas from the catalytic combustor 5 downstream thereof, the temperature of the exhaust gas that has risen in temperature due to the combustion reaction of the catalytic combustor 5 is increased. In addition to being able to reduce, dilution of the hydrogen concentration can be promoted when the exhaust gas passes through the heat exchanger 6.

  In the above-described embodiment, the exhaust air exhausted from the fuel cell is used as the air for diluting the exhaust hydrogen contained in the exhaust gas. However, although not shown, air is newly added to the exhaust system from the outside. May be provided.

The perspective view of the exhaust system of the fuel cell which shows one Embodiment of this invention. Similarly sectional drawing of a diluter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell exhaust system 2 Merge part 3 Exhaust pipe 4 Diluter 5 Catalytic combustor 6 Heat exchanger 7 Exhaust pipe 8 Exhaust muffler 9 Tail pipe 11 Dilution space 12 Backfire prevention filter

Claims (5)

A fuel cell system comprising a fuel cell system for supplying exhaust fuel discharged from a fuel cell that is supplied with fuel and air to a fuel cell through a circulation path and supplying the fuel to a fuel cell In a fuel cell exhaust system that exhausts exhausted hydrogen temporarily discharged from a circulation path of the system by purging or the like with exhaust air exhausted from the fuel cell and exhausts it to the outside air,
A merging section for diluting the concentration of exhaust hydrogen by mixing the exhaust hydrogen with exhaust air;
An exhaust pipe for circulating the exhaust gas discharged from the joining section through a pipe having a predetermined length and diluting the concentration of exhaust hydrogen mixed in the joining section with air;
A dilution space that is arranged downstream of the exhaust pipe and communicates with the outside air to have a cross-sectional area that is larger than the cross-sectional area of the exhaust pipe, and has a concentration of exhaust hydrogen in the exhaust gas introduced from the exhaust pipe. An exhaust system for a fuel cell, comprising: a diluter that dilutes and discharges with air.   2. The fuel cell according to claim 1, wherein the diluter includes a backfire prevention filter as a dilution promoting means for diluting the exhaust hydrogen in the exhaust gas with air in a downstream area of the dilution space or in the dilution space. Exhaust system.   The backfire prevention filter as the dilution accelerating means has a dome shape protruding in the downstream direction so as to increase the contact area with the passing exhaust gas, and is formed of a plate material or a net having a large number of holes. The exhaust system for a fuel cell according to claim 2, wherein the exhaust system is a fuel cell.   The exhaust system of the fuel cell includes a catalytic combustor having a catalyst for burning exhaust hydrogen in exhaust gas with air between the junction and the diluter. 4. The fuel cell exhaust system according to any one of 3 above.   5. The exhaust system for a fuel cell according to claim 4, wherein the catalytic combustor includes a heat exchanger for cooling exhaust gas from the catalytic combustor downstream thereof.

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