DE102018208987A1 - Flushing system for a housing and fuel cell system - Google Patents

Abstract

The invention relates to a flushing system (100) for a housing (7), in which enrichment of a critical substance can take place, and to a fuel cell system (1) having one. The rinsing system (100) comprises a feed path (104), a rinse path (106) connected to the feed path (104) and the housing (7) and a discharge path (108) connected to the rinse path (106). According to the invention, the supply path (104) and the discharge path (108) are fluidically connected via a bypass (110).

Description

The invention relates to a flushing system for a housing and a fuel cell system with such.

Fuel cells use the chemical transformation of a fuel with oxygen to water to generate electrical energy. For this purpose, fuel cells contain as core component the so-called membrane-electrode assembly (MEA for membrane electrode assembly), which is a microstructure of an ion-conducting (usually proton-conducting) membrane and in each case on both sides of the membrane arranged catalytic electrode (anode and cathode). The latter mostly comprise supported noble metals, in particular platinum. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode arrangement on the sides of the electrodes facing away from the membrane. As a rule, the fuel cell is formed by a large number of MEAs arranged in the stack (fuel cell stack) whose electrical powers add up. As a rule, bipolar plates (also called flow field plates or separator plates) are arranged between the individual membrane electrode assemblies, which ensure that the individual cells are supplied with the operating media, ie the reactants, and are usually also used for cooling. In addition, the bipolar plates provide an electrically conductive contact to the membrane electrode assemblies.

During operation of the fuel cell, the fuel (anode operating medium), in particular hydrogen H ₂ or a hydrogen-containing gas mixture, is supplied to the anode via an anode-side open flow field of the bipolar plate, where an electrochemical oxidation of H ₂ to protons H ⁺ takes place with release of electrons (H ₂ → 2 H ⁺ + 2 e ^- ). Via the electrolyte or the membrane, which separates the reaction spaces gas-tight from each other and electrically isolated, takes place (water-bound or anhydrous) transport of the protons from the anode compartment into the cathode compartment. The electrons provided at the anode are supplied to the cathode via an electrical line. The cathode is supplied via a cathode-side open flow field of the bipolar plate oxygen or an oxygen-containing gas mixture (for example, air) as a cathode operating medium, so that a reduction of O ₂ to O ^2- takes place with absorption of the electrons (½ O ₂ + 2 e ^- → O ^{2 -} ). At the same time, the oxygen anions in the cathode compartment react with the protons transported via the membrane to form water (O ^2- + 2 H ⁺ → H ₂ O).

Typically, one or more of the component water tanks, individual fuel cells, stacked fuel cells, humidifier, intercooler, fuel storage, coolant storage and / or electronic controls - from a common or each of a separate housing to protect against mechanical damage and / or environmental influences , such as splash water or dirt, surrounded. In this case, the housing surrounding the housing with the component or components is generally ventilated. For this purpose, the housing is provided with a device for air exchange, which feeds the housing on the input side fresh air and exhaust air on the output side via an exhaust duct discharges into the environment. Due to operational emissions of gaseous hydrogen from exhaust gas lines of the fuel cell / s during operation of the fuel cell or fuel cell assembly ignitable mixtures may form in the vicinity of the exhaust duct of the housing.

In addition, the air stream exiting the fuel cell is laden with water vapor and condensed water as the reaction product of the oxidation processes in the fuel cell. The condensed water droplets may be precipitated in the interior of the housing due to leakage due to damage or aging processes of the fuel cell or the conduit system. This can lead to erosion of the fuel cells and / or to supply and discharge lines. Furthermore, the water condensation and the resulting water present in the housing interior water can also affect the conductivity of the interior of the housing and the insulating effect and thus affect the safety of the fuel cell or fuel cell assembly with respect to be complied with requirements, such as short-circuit safety, gas and / or water resistance.

From the WO 02/23657 A2 and the WO 2007/004020 A1 a fuel cell assembly is known in which to avoid water condensation and / or the formation of ignitable mixtures, the housing is purged by fuel cells, in which a flushing medium, in particular air is pumped through the housing in a closed circulation. The flushing medium is passed through a recombiner, in which the emerging from the exhaust gas flow of the fuel cell hydrogen is catalytically converted to water with oxygen. In this case, the circulating circuit comprises a plurality of gas purification elements, such as a catalytic reactor (= recombiner), a condenser and a fine filter and is thus very complicated and expensive. In addition, frequent maintenance is required.

Out US 2004/0219399 A1 and WO 2007/004020 A1 Housing flushes are known for fuel cell systems. The rinse Air introduced into the housing absorbs unreacted hydrogen during flushing. Since unreacted hydrogen can be prone to explode, it must be ensured that a maximum value for the hydrogen concentration, in particular that specified by law, is not exceeded during discharge. For this purpose, fuel cell downstream components are used, either dilute the gas mixture to be discharged or chemically react the hydrogen contained. In particular, when the fuel cell is operated with a hydrogen-containing anode gas, it may be necessary to remove hydrogen from selected areas of the fuel cell device. For example, when the fuel cell device is turned off, it may be necessary to purge the hydrogen from the anode gas path to remove hydrogen residues. Such a fuel cell device is in the DE 11 2008 000 254 T5 disclosed. Furthermore, it may be necessary to flush the housing surrounding the membrane-electrode assembly in order to be able to remove hydrogen leaked from the anode gas path from the housing. Such a fuel cell device is in the US 2007/0231628 A1 disclosed.

In order to be able to conduct the purge gas to the housing and away from the housing, it is known from the prior art to provide conduits for conducting the purge gas and other components, for example for filtering the purge gas. However, these additional lines or other additional components of the purge gas path complicate the structure of the fuel cell device and require additional space. However, even if the fuel cell device is intended for mobile use, for example in an automobile, the installation space is limited.

Due to the reduced installation space, additional components and guide lines, in particular for fuel cell systems, are contraindicated. Such problems occur in addition to fuel cell systems in other systems that have enclosed by a housing, a critical substance producing or recycling device.

The object of the invention is now to provide a flushing system which eliminates or at least reduces the problems of the prior art. In particular, the flushing system provided should make it possible to comply with legal requirements regarding maximum values when gaseous critical substances are discharged.

This object is achieved by a flushing system and a fuel cell system with the features of the independent claims. Thus, a first aspect of the invention relates to a flushing system for a housing, comprising the housing and a device enclosed by the housing, which is capable of releasing a combustible or explosion-prone gas. For flushing and discharging a potentially present in the housing critical substance, the housing is connected to a ventilation system for flushing the housing with a fluid. The ventilation system has a feed path fluidly connected to an inlet of the housing and a purge path extending within the housing and fluidly connected to the feed path, and a discharge path fluidly connected to an outlet and to the purge path. According to the invention, it is provided that the supply path and the discharge path are fluid-conductively connected to one another by a bypass bypassing the rinse path.

The advantage of the invention is, in particular, that a critical substance is led out of the housing via the discharge path and in the meantime diluted with supply air. Thus, a dilution of the critical substance takes place without additional components have to be connected downstream of the housing. This saves installation space and offers production advantages. In addition, the flushing system according to the invention compared to conventional systems is low maintenance, since less complex, maintenance-intensive components are included.

In addition, the dilution is carried out promptly or locally close to the place of origin. In other words, the critical substance is conducted over a very short, minimized distance in undesired or critically high concentration. Long derivation paths with a high concentration of the substance are eliminated.

In the flushing system according to the invention, a flushing fluid, in particular air, is supplied to a housing via a feed path in order to pass into a flushing path, which circumscribes or partially flushes through the device. In the rinse path, the rinse fluid is enriched with critical material. The purge path goes downstream of the device into the discharge path through which the critical fluid-enriched fluid is removed from the housing.

Upstream of the device, the supply stream is dispensed according to the invention and passed through a bypass, bypassing the device directly into the discharge path. In this case, the bypass (further also the bypass path or bypass line) opens downstream of the device into the discharge path.

Thus, downstream of the confluence in the discharge path, the rinse fluid enriched with the critical mass is mixed with fresh rinse fluid from the bypass. Since the fresh flushing fluid no enrichment with the critical substance, dilution of the effluent stream based on the concentration of the critical substance takes place.

Critical substance in the present case is to be understood as meaning a chemical substance which tends to explode and / or is combustible or inflammable. This is produced or implemented by the device in the interior of the housing and passes through leaks in the device and the associated with these lines in the housing. Concentration of the critical substance beyond a certain level must be avoided for safety reasons. For this purpose, the flushing of the housing.

In a preferred embodiment of the invention, it is provided that the ratio of fluid guided in the flushing path to fluid guided in the bypass is adjustable in the range of 0-100% by volume. Thus, all the fluid can be passed through the bypass or the purge path in parallel either through the bypass or through the purge path or in any proportions. The adjustment of the ratio is preferably carried out by a ratio of the channel diameter of the feed path and the bypass to each other and / or by an actuating means which is arranged in the bypass or at a branch from the feed path to the bypass or from the bypass to the discharge path. The adjusting means is designed for example as a throttle, pressure reducer or as a control valve, in particular as a three-way valve.

The adjustability of the fluid streams in the feed path and bypass allows control of the degree of dilution. This can be adapted to the device once or dynamically (via an adjusting means). The latter has the advantage that the dilution in the discharge path can be adapted to the release of the critical substance.

For this purpose, it is advantageous if the concentration of the critical substance in the rinse path and / or in the discharge path is measurable. Thus, in a further preferred embodiment of the invention, it is provided that upstream of and / or downstream of the mouth of the bypass in the discharge path, a sensor is arranged, which is adapted to measure a concentration of the critical substance.

Advantageously, the ratio of fluid conducted in the flushing path to fluid guided in the bypass is thus adjustable as a function of a quantity of the critical substance, in particular dynamically. This makes it possible to avoid concentration peaks and, in particular, if the adjustment takes place automatically via a control unit, a permanent undershooting of a maximum concentration value of the critical substance in the discharge path.

For this purpose, a control unit is advantageously arranged in the flushing system or connected to this, which is tax-technically connected to the sensor and the actuating means. Preferably, an algorithm is stored in the control unit, which controls an opening degree and thus a volume flow through the actuating means as a function of a measured value of the sensor, so that a desired value or a desired interval for a concentration of the critical substance in the discharge path is maintained. This is preferably done via an if-then query or loop.

Advantageously, the bypass is arranged within the housing. This leads to an optimal space utilization and avoids the need to provide additional space. In addition, the safety of the system is increased because critical material that leaks through any leaks occurring in the bypass and / or the actuating means, remains in the housing and can be led out of this by the flushing system.

Alternatively, the bypass outside of the housing, in particular arranged parallel to a housing side longitudinally. This offers the advantage of better maintenance of the bypass line and offers the possibility of retrofitting existing systems.

The flushing system according to the invention is arranged with particular advantage in a fuel cell system, wherein the device is a fuel cell, or a fuel cell stack. As stated above, fuel cells convert hydrogen with oxygen into water chemically. Hydrogen is volatile and within the meaning of the invention is a critical substance. In addition, high demands are placed on fuel cell systems in terms of space and weight, which are both possible to reduce. Therefore, the flushing system according to the invention is particularly suitable for use in a fuel cell system.

In the case of a fuel cell arranged in the housing, the critical substance detected by the sensor is the fuel gas of the fuel cell, in particular hydrogen.

Thus, another aspect of the invention relates to a fuel cell system having a purge system according to the invention.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 eine schematische Darstellung eines bevorzugten Ausführungsbeispiels des erfindungsgemäßen Brennstoffzellensystems,
• 2 eine schematische Darstellung eines Spülsystems in einer bevorzugten Ausgestaltung der Erfindung, und
• 3 eine schematische Darstellung eines Spülsystems in einer weiteren bevorzugten Ausgestaltung der Erfindung.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

• 1 a schematic representation of a preferred embodiment of the fuel cell system according to the invention,
• 2 a schematic representation of a flushing system in a preferred embodiment of the invention, and
• 3 a schematic representation of a flushing system in a further preferred embodiment of the invention.

The invention is explained below by way of example with reference to embodiments with reference to the drawings. The different features of the embodiments can be combined independently of each other, as has already been explained in the individual advantageous embodiments. First, the structure and function of a fuel cell device according to the invention with reference to the embodiment of 1 described.

1 shows the fuel cell device 1 schematically with a fuel cell 2 a cathode gas path 3 , a section of an anode gas path 4 and a purge gas path 5 , Transport directions of gas through the cathode gas path 3 , the anode gas path 4 and the purge gas path 5 are represented by arrows. The fuel cell 2 is with a membrane electrode assembly 6 and a housing 7 formed, wherein the membrane electrode assembly 6 in the case 7 is arranged.

The cathode gas path 3 has an entrance 8th on, for example, as an input of a cathode gas filter 9 can be trained. Along the cathode gas path 3 is the entrance 8th preferably a compressor 10 downstream, by means of which the cathode gas through the cathode gas path 3 can be transported. The compressor 10 can along the cathode gas path 3 other elements for the preparation of the cathode gas, for example between the compressor 10 and the fuel cell 2 , be downstream. For example, the cathode gas path 3 a heat exchanger 11 have for tempering the cathode gas. Alternatively or additionally, the cathode gas path 3 a moisture regulator 12 have, with which the water content of the cathode gas is adjustable. The heat exchanger 11 and / or the moisture regulator 12 can be bridged by bypasses. In the embodiment of 1 is just the moisture regulator 12 using a bypass of the cathode gas path 3 bridged shown.

Between the entrance 8th and the fuel cell 2 extends an input-side section 13 the cathode gas path 3 , The cathode gas path 3 extends through the membrane-electrode assembly on the cathode side 6 and transports the cathode gas to the cathode of the membrane-electrode assembly 6 , In the transport direction of the cathode gas path 3 behind the fuel cell 2 extends an output-side section 14 the cathode gas path 3 , The output section 14 flows into an exit 15 the cathode gas path 3 and may pass through another moisture regulator or even through the existing moisture regulator 12 extend. An entrance 16 the separate section of the purge gas path 5 is in the embodiment of 1 , separated and spaced from the entrance 8th the cathode gas path 3 trained, represented.

The entrance 16 the separate section of the purge gas path 5 is for example as an input of a purge gas filter 17 designed. In the transport direction of the purge gas path 5 behind the entrance 16 is an optional blower 18 for transporting the purge gas through the purge gas path 5 intended. The fan 18 can in particular along the purge gas path 5 between its entrance 16 and the housing 7 the fuel cell 2 be arranged.

The purge gas path 5 extends through the fuel cell 2 and in particular along the membrane-electrode assembly 6 through the housing 7 , A membrane electrode assembly 6 surrounding volume within the housing 7 can be flushed out using the purge gas. Between the entrance 16 and the fuel cell 2 extends an input-side section 19 the separate section of the purge gas path 5 ,

In the transport direction of the purge gas path 5 downstream of the fuel cell 2 extends an output-side section 20 the separate section of the purge gas path 5 , The purge gas path 5 also has a bypass that controls the purge gas path 5 upstream or fuel cell 2 with the purge gas path 5 downstream of the fuel cell 2 fluidically connects. At one of the fuel cell 2 downstream output 21 the separately formed portion of the purge gas path 5 The fresh purge gas mixes with a fuel cell 2 Passed purge gas, which may be enriched with hydrogen.

The section of the cathode gas path 3 between the exit 21 and the exit 15 may be a manifold conducting the purge gas and the cathode gas.

The 2 and 3 each show a schematic representation of a section of the flushing system according to the invention in a preferred embodiment. It is shown that the purge gas path 5 in an upstream of the fuel cell 2 disposed feed path 104 , a fuel cell 2 passing and / or flushing rinse path 106 and one downstream of the fuel cell 2 arranged derivation path 108 is divisible. Here is the purge path 106 only inside the case 7 arranged while the feed path 104 and the derivation path 108 the housing 7 fluidically with an outside of the housing 7 arranged purge gas source (not shown) connect.

The purge gas path 5 also has a fuel cell 2 immediate bypass 110 on. The bypass 110 connects the feed path 104 fluidically with the discharge path 108 , The bypass 110 can, as in 2 shown outside the case 7 or else, as in 3 shown inside the case 7 be arranged.

In the feeding path 104 and / or in the bypass 110 can be an adjusting agent 114 be provided, which is the distribution of the volume flow on supply path 104 and bypass 110 controls. These are, for example, a throttle, a pressure reducer or a 2- or 3-way valve, the latter being arranged at the branch point at which a part of the feed path 104 in the bypass 110 branches.

Upstream or downstream of the junction 112 can in the derivation path 108 a sensor 116 for determining the hydrogen concentration in the purge gas path 5 be arranged. The sensor 116 is preferably control technology with the actuating means 114 connected.

The flushing system according to the invention has the functioning, a part of the over the feed path 104 guided fresh flushing fluid upstream of the fuel cell 2 in a fuel cell 2 immediate bypass 110 divert. Downstream of the fuel cell 2 opens the bypass 110 over a junction 112 in the derivation path 108 and mixes fresh flushing fluid with flushing fluid, which is when flowing through or flowing past the fuel cell 2 or the fuel cell stack 2 enriched with hydrogen. This leads to dilution of the flushing fluid and a decrease in the concentration of hydrogen in the discharge path 108 guided fluid.

LIST OF REFERENCE NUMBERS

1

fuel cell device

2

Device, fuel cell

3

Cathode gas path

4

Anode gas path

5

Spülgaspfad

6

Membrane electrode assembly

7

casing

8th

Entrance of the cathode gas path

9

Cathode gas filter

10

compressor

11

heat exchangers

12

moisture regulator

13

input-side section of the cathode gas path

14

output side portion of the cathode gas path

15

Exit of the cathode gas path

16

Entrance of the separate section of the purge gas path

17

Spülgasfilter

18

fan

19

Input side portion of the separate portion of the purge gas path

20

output side portion of the separate portion of the purge gas path

21

Output of the separately formed portion of the purge gas path

23

Output of the separate section of the purge gas path

24

continuous section of the cathode gas path

100

flushing system

104

feed path

106

Spülpfad

108

dissipation path

110

Bypass, bypass path

112

junction

114

actuating means

116

sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO0223657 A2 [0006]
• WO 2007/004020 A1 [0006, 0007]
• US 2004/0219399 A1 [0007]
• DE 112008000254 T5 [0007]
• US 2007/0231628 A1 [0007]

Claims (8)

A flushing system (100) for a housing (7) comprising - a housing (7), - a device (2) enclosed by the housing (7) capable of releasing a combustible or explosion-prone gas, - a housing (7 A ventilation system for flushing the housing (7) with a fluid, comprising a feed path (104) connected in fluid-conducting manner to an inlet of the housing (7), a purge path (14) running within the housing (7) and fluidically connected to the feed path (104). 106) and a discharge path (108) fluidly connected to an outlet and to the purge path (106), characterized in that the supply path (104) and the discharge path (108) are fluid-conducting through a bypass (110) bypassing the purge path (106) are connected. Rinsing system (100) after Claim 1 , characterized in that the ratio of in the flushing path (106) guided fluid in the bypass (110) guided fluid, in particular in the range of 0-100% by volume, is adjustable. Flushing system (100) according to one of the preceding claims, characterized in that upstream of and / or downstream of a junction (112) of the bypass (110) in the discharge path (108) a sensor (116) is arranged, which is arranged, a concentration of to measure critical substance. Rinsing system (100) after Claim 3 , characterized in that the ratio of fluid guided in the flushing path (106) to fluid guided in the bypass (110) is adjustable as a function of the concentration of the critical substance measured by the sensor (116). Flushing system (100) according to any one of the preceding claims, characterized in that the bypass (110) within the housing (7) is arranged. Flushing system (100) according to one of the preceding claims, characterized in that the device is a fuel cell (2). Rinsing system (100) after Claim 3 and 6 , characterized in that the critical substance is a fuel gas of the fuel cell (2). Fuel cell system (1) comprising a flushing system (100) according to one of the preceding claims.

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