DE102007042784A1 - Method and apparatus for operating a fuel cell assembly - Google Patents

Abstract

The invention relates to a method and a device for operating a fuel cell arrangement (1) with a plurality of fuel cells assembled into a stack (2) with a common cathode input (3.1) and cathode output (3.2) and anode input (4.1) and anode output (4.2) and with the first , the fuel cells with reactants supplying components and second, reaction products (RP) of the fuel cell processing components. In this case, according to the invention, a hydrogen-containing exhaust air (AL) from at least one housing (12.1 to 12.3), in which one or more of the components and / or the fuel cells are arranged, removed and fed into a cathode feed line (5) of the cathode input (3.1).

Description

The The invention relates to a method and an apparatus for operating a fuel cell assembly having a plurality, assembled into a stack Fuel cells with a common cathode input and cathode output as well as anode input and anode output and with first, the fuel cells reactants supplying components and second, reaction products the fuel cell processing components.

fuel cell assemblies Serve with multiple fuel cells or individual fuel cells a low-emission generation of electricity. there become each an anode and cathode having fuel cells on the one hand with a hydrogen-containing reactant as fuel and on the other hand with an oxygen-containing reactant acted as oxidant. As a reaction product of the oxidation processes in the fuel cell is one emerging from the fuel cell Air stream laden with water vapor and condensed water.

there is the supply of gas to the cathode as the oxidant fresh air first compressed in a compressor and then in one Intercooler cooled. Further flows the air into a humidifier module, where they expel water vapor a cathode side effluent cathode exhaust gas of the fuel cell or a fuel cell stack. Then the humidified fresh air directed into the fuel cell or fuel cell stack and participates in the electrochemical reaction there. The cathode side effluent cathode exhaust gas is then the humidifier module supplied, where it supplies water vapor to the cathode supplying Gives off air. Subsequently, the cathode exhaust gas is a Exhaust gas supplied. The anode of the fuel cell assembly becomes more than stoichiometric via a metering valve, for example Hydrogen supplied as fuel from a hydrogen storage. Unreacted hydrogen and overreached at the cathode Nitrogen and water vapor are removed by means of a blower (also Rezirkulationsgebläse called) back to the pressure level of the fresh gas and via a return fed back into the hydrogen flow.

Usually are single or multiple of the component water storage, single Fuel cells, stacked fuel cells, Humidifier, intercooler, fuel storage, coolant reservoir and / or electronic controls - from a common one or each of a separate housing for protection mechanical damage and / or environmental influences such as splashes or dirt surrounded. It is the housing surrounding the housing or with the components surrounding the housing generally ventilated. This is the case provided with a device for air exchange, the input side Fresh air feeds the housing and the output side over an exhaust duct discharges exhaust air into the environment. By operational emissions of gaseous hydrogen from exhaust pipes of the fuel cell / s during operation of the fuel cell or Fuel cell assembly may become flammable Mixtures in the vicinity of the exhaust pipe of the housing form.

About that In addition, the emerging from the fuel cell air flow with Water vapor and condensed water as the reaction product of the oxidation processes freighted in the fuel cell. The condensed water drops may be due to leakage due to damage or aging processes of the fuel cells or the piping system precipitate in the interior of the housing. This can be too an erosion of the fuel cells and / or to supply and discharge lines to lead. Furthermore, the water condensation and resulting, in the housing interior existing water also affects the conductivity of the internal atmosphere of the housing and have the insulating effect and thus the safety of the fuel cell or fuel cell arrangement with regard to specifications to be complied with, such as short circuit safety, gas and / or watertightness, affect.

From the WO 02/23657 A2 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 in a closed circulation circuit is pumped through the housing. 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, a fine filter, and is thus very complicated and expensive. In addition, frequent maintenance is required.

It is therefore an object of the invention, an improved method to indicate the operation of a fuel cell assembly in which the formation of ignitable gas mixtures in the range the housing environment is largely avoided. About that In addition, a suitable device for operating a fuel cell assembly specify.

With regard to the method, the object is achieved by the angege in claim 1 Benen features solved. With regard to the device, the object is achieved by the features specified in claim 7.

advantageous Further developments of the invention are the subject of the dependent claims.

At the inventive method for operating a Fuel cell assembly with multiple, assembled into a stack Fuel cells with a common cathode input and cathode output as well as anode input and anode output and with first, the fuel cells reactants supplying components and second, reaction products the fuel cell processing components, becomes a hydrogen and water vapor-containing exhaust air from at least one housing, in which one or more of the components and / or the fuel cells are arranged, discharged and in a cathode supply line led the cathode input. Through the exhaustion the exhaust air of the housing in the cathode feed line can optionally in the exhaust air containing hydrogen by catalytic Oxidation at the cathode of the fuel cell are degraded. hereby is the formation of ignitable mixtures by Release of hydrogen-containing exhaust air (= fuel gas) from safely avoided the housing. In addition, one possible Water condensation in the housing interior largely due to leakage avoided, in which the water vapor contained in the exhaust gas by discharge and re-feeding into the cathode reliably degraded and largely completely reduced.

In a simple embodiment, the out of the housing discharged exhaust air in front of the cathode inlet with an oxygen-containing Gas, e.g. As fresh air or oxygen, mixed. Subsequently, will the mixed gas is supplied to the cathode as the oxygen-containing gas. In the following, the hydrogen contained in the exhaust air is used by catalytic oxidation at the cathode of the fuel cell largely degraded, so that on the one hand a water condensation in the housing interior and on the other hand the formation of ignitable mixtures safely avoided. Thereby instead of additional Cleaning elements, such as recombiners, components of the fuel cell assembly itself, as the cathodes for the catalytic conversion of the discharged Hydrogen used. This is a simple and secure Reduction of the discharged hydrogen while avoiding allows a complex Umwälzkreises.

In a possible embodiment, the exhaust air before or after a compressor arranged in the cathode feed line introduced into the cathode feed line. In particular, will the exhaust air in the area in front of a cathode inlet (= input port) admixed with the oxygen-containing gas. This allows a reliable and fast exhaustion and mixing of hydrogen and a reliable and fast elimination of the hydrogen in the cathode.

Conveniently, is the housing as supply air ambient air (= fresh air) and / or in a cathode circuit, in particular in the cathode feed line supplied oxygen-containing gas supplied. Especially by the use of the cathode circuit or in the Kathodenzuleitung Guided oxygen-containing gas as flushing medium for the housing interior is a simple and few feeders and / or components required construction where. Due to the reduced number of components in such a open purge cycle is the number of through the housing purge significantly reduced conditional maintenance intervals.

Preferably the supply air is after a in the cathode circuit or in the Kathodenzuleitung arranged branched air filter and fed to the housing. Thus, the housing is supplied largely purified air, whereby a formation of ignitable gas mixtures is further reduced at the exhaust outlet of the housing.

Regarding the apparatus for operating the fuel cell assembly is provided by one or more components and / or the Fuel cell assembly surrounding housing an exhaust duct for discharging hydrogen-containing exhaust air, which opens into a cathode feed line of the cathode input. Such a direct connection of exhaust duct of the housing in Kathodenzuleitung the cathode provides a reliable Reduction and elimination of the hydrogen contained in the exhaust air for sure. Preferably, the exhaust duct opens before Cathode input into the cathode feed line.

ever after embodiment of the aeration or rinsing of the housing as an open and / or closed system can in the exhaust duct an air conveyor, z. As a compressor, be arranged.

In A further embodiment provides that the Exhaust line before or after arranged in the cathode feed line Compressor opens into the cathode supply line. This will the exhaust air with the guided in the cathode supply oxygen-containing Gas mixed well fed to the cathode.

For ventilation of the housing preferably opens into this a supply air line. In this case, the supply air can be supplied directly ambient air. Alternatively, the supply air line from a Ka thodenkreislauf or branched off from the cathode feed line and opens into the housing. In this case, the oxygen-containing gas guided in the cathode circuit or in the cathode feed line is used to ventilate the housing. Furthermore, the supply air line branches off from the cathode circuit to an air filter arranged in the cathode circuit. This ensures that a purified gas or purified ambient air is used to flush or ventilate the housing.

embodiments The invention will be explained in more detail with reference to a drawing.

there shows:

1 a fuel cell assembly having a plurality of components and at least one surrounding one or more components housing which is vented.

1 shows a fuel cell assembly 1 , The fuel cell assembly 1 includes several, to a stack 2 stacked and interconnected fuel cells. Each fuel cell comprises, as shown schematically by a block, a cathode 3 and an anode 4 as a pair of electrodes and arranged therebetween, not shown electrolyte, for example in the form of a polymer electrolyte membrane (short PEM), which together form a membrane-electrode assembly (MEA short) form.

The cathodes 3 and the anodes 4 all fuel cells of the stack 2 are doing over a common cathode input 3.1 or anode input 4.1 supplied with an oxidizing agent CM and a fuel BS. Each with an associated cathode output 3.2 or anode output 4.2 are discharged from the fuel cells exiting reaction products RP.

When Reactants become the fuel BS and the oxidant OM used. Most are gaseous reactants (in short: reaction gases) used, for. As hydrogen or a hydrogen contained gas (eg reformate gas) as fuel BS and oxygen or an oxygen-containing gas (eg, air) as the oxidizing agent OM. Reactants are all involved in the electrochemical reaction understood substances involved, including the reaction products RP, like a stream of air with water vapor and condensed water.

To supply the fuel cells with the oxidizing agent OM, in particular fresh or ambient air flows into the cathode inlet 3.1 a cathode feed line 5 , in which flow input side, an air filter 6 to clean the fresh air and a compressor 7 are arranged for compressing the fresh air.

The fuel BS becomes the respective anode 4 the fuel cell via a common anode lead 8th fed. In general, the fuel BS becomes a reservoir 9 taken. Anodenausgangside is the discharged reaction product RP, which contains hydrogen, via a return 10 and a recirculation pump disposed therein 11 the anode entrance 4.1 fed again.

Depending on the structure of the fuel cell assembly 1 are their components, like the stack 2 and / or the fuel cell supplying components, such as air filters 6 , Compressor 7 , Storage 9 , and / or the reaction products RP of the fuel cell processing components, such as recirculation pump 11 , from separate housings 12.1 to 12.3 or a common housing (not shown in detail) surrounded. As a result of leaks caused by mechanical stress or aging processes in one of the components may occur in the respective housing interior by incoming hydrogen or incoming hydrogen-containing gas to form ignitable mixtures and / or water vapor for water condensation, so that safety requirements are no longer met.

To avoid the formation of ignitable gas mixtures and / or water condensation, the respective housing 12.1 to 12.3 be ventilated. The housings are 12.1 to 12.3 on the one hand drawn around the associated component in full line representation. On the other hand, the structure of the ventilation of the housing or the 12.1 to 12.3 shown separately by a dash-dot representation for clarity. In detail, the reduction of ignitable gas mixtures in the housing (s) 12.1 to 12.3 Exhaust air AL of the or the relevant housing 12.1 to 12.3 via at least one exhaust duct 13 into the cathode feed line 5 guided and mixed there with the oxidizing agent OM and the cathode 3 fed where the hydrogen contained in the exhaust air AL by catalytic oxidation at the cathode 3 is reduced.

The exhaust air duct opens 13 after the air filter 6 and in front of the compressor 7 into the cathode feed line 5 , Alternatively, the exhaust duct 13 even after the compressor 7 and thus immediately in front of the cathode entrance 3.1 into the cathode feed line 5 lead.

As supply air ZL can the respective housing 12.1 to 12.3 the oxidizing agent OM are supplied. For this branches of the Kathodenzuleitung 5 a air supply 14 from. This branches the supply air line 14 preferably after the air filter 6 from the cathode lead 5 from. Alternatively, as a supply air ZL the respective housing 12.1 to 12.3 be supplied directly fresh air or ambient air.

To promote the exhaust air AL from the respective housing 12.1 to 12.3 can in the exhaust duct 13 an air conveyor 15 , z. As a pump can be arranged.

1

A fuel cell assembly

2

stack

3

cathode

3.1

cathode input

3.2

cathode output

4

anode

4.1

anode input

4.2

anode output

5

cathode lead

6

air filter

7

compressor

8th

anode lead

9

Storage

10

return

11

recirculation pump

12.1 until 12.3

casing

13

exhaust duct

14

air supply

15

Air conveyor

AL

exhaust

BS

fuel

OM

oxidant

RP

reaction product

ZL

supply air

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 02/23657 A2 [0006]

Claims (14)

Method for operating a fuel cell assembly ( 1 ) with several, to a stack ( 2 ) assembled fuel cells with a common cathode input ( 3.1 ) and cathode output ( 3.2 ) as well as anode entrance ( 4.1 ) and anode output ( 4.2 ) and with first, the fuel cells with reactants supplying components and second reaction products (RP) of the fuel cell processing components, characterized in that a hydrogen-containing exhaust air (AL) from at least one housing ( 12.1 to 12.3 ), in which one or more of the components and / or the fuel cells are arranged, dissipated and into a cathode feed line ( 5 ) of the cathode input ( 3.1 ) to be led. A method according to claim 1, characterized in that the exhaust air (AL) in front of the cathode entrance ( 3.1 ) is mixed with an oxidizing agent (OM), in particular an oxygen-containing gas. A method according to claim 1 or 2, characterized in that the hydrogen of the exhaust air (AL) by catalytic oxidation of cathodes ( 3 ) of the fuel cell is degraded. Method according to one of claims 1 to 3, characterized in that the exhaust air (AL) before or after a in the Kathodenzuleitung ( 5 ) arranged compressors ( 7 ) into the cathode feed line ( 5 ) is introduced. Method according to one of claims 1 to 4, characterized in that the housing ( 12.1 to 12.3 ) is supplied as supply air (ZL) ambient air and / or guided in a cathode circuit oxidant (OM). Process according to Claim 5, characterized in that the supply air (ZL) is cooled in accordance with a charge in the cathode feed line (ZL). 5 ) or arranged in the cathode circuit air filter ( 6 ) and the housing ( 12.1 to 12.3 ) is supplied. Device for operating a fuel cell arrangement ( 1 ) with several, to a stack ( 2 ) assembled fuel cells with a common cathode input ( 3.1 ) and cathode output ( 3.2 ) as well as anode entrance ( 4.1 ) and anode output ( 4.2 ) and with the first components supplying the fuel cells with reactants and second components issuing from the fuel cell (RP), characterized in that one or more components and / or the fuel cells in at least one housing ( 12.1 to 12.3 ) are arranged and from the housing ( 12.1 to 12.3 ) an exhaust duct ( 13 ) for discharging hydrogen-containing exhaust air (AL), which in a cathode feed line ( 5 ) of the cathode input ( 3.1 ) opens. Apparatus according to claim 7, characterized in that the exhaust duct ( 13 ) in front of the cathode entrance ( 3.1 ) into the cathode feed line ( 5 ) opens. Apparatus according to claim 7 or 8, characterized in that in the exhaust duct ( 13 ) an air conveying device ( 15 ) is arranged. Device according to one of claims 7 to 9, characterized in that the exhaust air duct ( 13 ) before or after one in the cathode feed line ( 5 ) arranged compressors ( 7 ) into the cathode feed line ( 5 ) opens. Device according to one of claims 7 to 9, characterized in that in the housing ( 12.1 to 12.3 ) an air supply line ( 14 ) opens. Apparatus according to claim 10, characterized in that the supply air line ( 14 ) Ambient air can be supplied. Apparatus according to claim 10, characterized in that the supply air line ( 14 ) from a cathode circuit and / or the cathode feed line ( 5 ) branches off and into the housing ( 12.1 to 12.3 ) opens. Apparatus according to claim 10 or 12, characterized in that the supply air line ( 14 ) after a in the cathode circuit or in the cathode feed line ( 5 ) arranged air filter ( 6 ) branches off.